Language：English   Publishing type：Research paper (scientific journal)  

An unstructured mesh Reynolds-averaged Navier-Stokes (RANS) solver has been developed for numerical simulation of violent sloshing flows inside a tank with complicated inner structures. The numerical solver employs the unstructured multi-dimensional tangent hyperbolic interface capturing method (UMTHINC) for free-surface capturing combined with various turbulence models. The sloshing motion is numerically modeled using the body-force method which introduces a source term into the momentum equation corresponding to the tank motion profile. Numerical simulations of the tank sloshing problems are performed for different test cases with various oscillation frequencies. The performance of the interface capturing method has been discussed and the effect of turbulence model choice on loading predictions is highlighted by studying several RANS models and analyzing its effect on fluid motion and impact pressure. Numerical simulations of the sloshing inside the tank with a vertical baffle has also been conducted and a discussion is provided on different numerical treatment of the baffle.

DOI： 10.1007/s42241-020-0019-z

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents an implementation of the adaptive hybrid WENO (weighted essentially non-oscillatory) scheme based on our previous investigations for compressible multi-medium flows (Liu and Hu, J. Comput. Phys., 342 (2017), 43-65). In this study a simple and efficient method is developed for Euler equations and Navier-Stokes equations arising from the conservation laws. A class of high order weighted essentially non-oscillatory (WENO) schemes are applied to resolve the complicated flow structures and shock waves. Classical WENO schemes are computationally expensive in calculating the non-linear weight and smoothness indicators. We propose a block-structured adaptive mesh method together with a modified hybrid-WENO scheme to reduce the cost, the reconstruction is only performed at non-smooth region. Comparisons of WENO scheme with various smoothness indicators and different Lax-Friedrich flux vector splitting methods are performed on block structured adaptive mesh. Benchmark tests show present adaptive hybrid WENO method is low-dissipative and highly robust. The 2-D/3-D shock wave boundary layer interaction are simulated to verify the efficiency of present AMR (adaptive mesh refinement) solver in predicting turbulent flow.

DOI： 10.4208/cicp.OA-2018-0059

Language：English   Publishing type：Research paper (scientific journal)  

This work proposes an efficient actuator line – immersed boundary (AL-IB) method to predict the wake of multiple horizontal-axis tidal turbines (HATTs). A sharp IB method with a simple adaptive mesh refinement strategy is used to improve the computational efficiency. The velocity and other scalar fields adjacent to the solid surface are reconstructed by a moving least square (MLS) interpolation. A computationally efficient AL model is applied to represent the rotors by adding source term to the governing equation rather than resolving the fully geometry of the blade. To predict the turbulent wake, the AL-IB method is implemented with an unsteady Reynolds-averaged Navier–Stokes (URANS) solver. Performance of three types of turbulence models, k−ω−SST model, standard and corrected k−ω model are evaluated. An efficient wall function model is proposed for the MLS-IB approach. The accuracy of the present AL-IB method is validated by numerical tests of a single rotor and multiple tandem arranged IFREMER rotors [1,2]. Wake interference of Manchester rotors [3] with side by side arrangement is also investigated numerically. The predicted wake velocity and turbulence intensity (TI) are in reasonably good agreement with the experimental results.

DOI： 10.1016/j.renene.2019.01.019

Language：English   Publishing type：Research paper (scientific journal)  

In this study, an immersed boundary (IB) approach on the basis of moving least squares (MLS) interpolation is proposed for analyzing the dynamic response of a rigid body immersed in incompressible flows. An improved mapping strategy is proposed for a quick update of the signed distance field. A CIP-CSL (constraint interpolation profile - semi-Lagrangian) scheme with a compact stencil is adopted for the convective term in momentum equation. Fluid–structure interaction problems can be solved by either the weak or the strong coupling schemes according to the density ratio of the solid and fluid. This research is based on our previous studies on block-structured adaptive mesh refinement (AMR) method for incompressible flows (Liu & Hu, 2018). Present AMR-FSI solver is proved to be accurate and robust in predicting dynamics of VIV (vortex induced vibration) problems. The efficiency of the adaptive method is demonstrated by the 2D simulation of a freely falling plate with the comparison to other numerical methods. Finally, the freely falling and rising 3D sphere are computed and compared with corresponding experimental measurement.

DOI： 10.1016/j.cpc.2018.05.015

Language：English   Publishing type：Research paper (scientific journal)  

A novel CFD approach based on adaptive mesh refinement (AMR) technique is being developed for numerical simulation of violent free surface flows. CIP method is applied to the flow solver and tangent of hyperbola for interface capturing with slope weighting (THINC/SW) scheme is implemented as the free surface capturing scheme. The PETSc library is adopted to solve the linear system. The linear solver is redesigned and modified to satisfy the requirement of the AMR mesh topology. In this paper, our CFD method is outlined and newly obtained results on numerical simulation of violent free surface flows are presented.

DOI： 10.1007/s42241-018-0043-4

Language：English   Publishing type：Research paper (scientific journal)  

In this study, a multi-moment finite volume method (FVM) based on block-structured adaptive Cartesian mesh is proposed for simulating incompressible flows. A conservative interpolation scheme following the idea of the constrained interpolation profile (CIP) method is proposed for the prolongation operation of the newly created mesh. A sharp immersed boundary (IB) method is used to model the immersed rigid body. A moving least squares (MLS) interpolation approach is applied for reconstruction of the velocity field around the solid surface. An efficient method for discretization of Laplacian operators on adaptive meshes is proposed. Numerical simulations on several test cases are carried out for validation of the proposed method. For the case of viscous flow past an impulsively started cylinder (Re=3000,9500), the computed surface vorticity coincides with the result of the body-fitted method. For the case of a fast pitching NACA 0015 airfoil at moderate Reynolds numbers (Re=10000,45000), the predicted drag coefficient (C_D) and lift coefficient (C_L) agree well with other numerical or experimental results. For 2D and 3D simulations of viscous flow past a pitching plate with prescribed motions (Re=5000,40000), the predicted C_D, C_L and C_M (moment coefficient) are in good agreement with those obtained by other numerical methods.

DOI： 10.1016/j.jcp.2018.01.006

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, a simple and efficient immersed boundary (IB) method is developed for the numerical simulation of inviscid compressible Euler equations. We propose a method based on coordinate transformation to calculate the unknowns of ghost points. In the present study, the body-grid intercept points are used to build a complete bilinear (2-D)/trilinear (3-D) interpolation. A third-order weighted essentially nonoscillation scheme with a new reference smoothness indicator is proposed to improve the accuracy at the extrema and discontinuity region. The dynamic blocked structured adaptive mesh is used to enhance the computational efficiency. The parallel computation with loading balance is applied to save the computational cost for 3-D problems. Numerical tests show that the present method has second-order overall spatial accuracy. The double Mach reflection test indicates that the present IB method gives almost identical solution as that of the boundary-fitted method. The accuracy of the solver is further validated by subsonic and transonic flow past NACA2012 airfoil. Finally, the present IB method with adaptive mesh is validated by simulation of transonic flow past 3-D ONERA M6 Wing. Global agreement with experimental and other numerical results are obtained.

DOI： 10.1002/fld.4399

Language：English   Publishing type：Research paper (scientific journal)  

A second order Ghost Fluid method is proposed for the treatment of interface problems of elliptic equations with discontinuous coefficients. By appropriate use of auxiliary virtual points, physical jump conditions are enforced at the interface. The signed distance function is used for the implicit description of irregular domain. With the additional unknowns, high order approximation considering the discontinuity can be built. To avoid the ill-conditioned matrix, the interpolation stencils are selected adaptively to balance the accuracy and the numerical stability. Additional equations containing the jump restrictions are assembled with the original discretized algebraic equations to form a new sparse linear system. Several Krylov iterative solvers are tested for the newly derived linear system. The results of a series of 1-D, 2-D tests show that the proposed method possesses second order accuracy in L ^∞ norm. Besides, the method can be extended to the 3-D problems straightforwardly. Numerical results reveal the present method is highly efficient and robust in dealing with the interface problems of elliptic equations.

DOI： 10.4208/cicp.OA-2016-0155

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, a THINC (tangent of hyperbola for interface capturing) (Xiao F. et al., 2005) [26] coupled with GFM (Ghost Fluid Method) is proposed for numerical simulation of compressible multi-medium flows. The THINC scheme, which was first developed for incompressible flows, is applied for capturing the distorted material interface of compressible flows. The hybrid WENO (weighted essentially non-oscillatory) scheme with the blocked structured adaptive mesh refinement (AMR) method is implemented. Load balancing is considered in the parallel computing. Several well documented numerical tests are performed and the results show that the THINC scheme behaviors better in mass conservation. It is the first endeavor to implement THINC scheme with adaptive mesh for computing the compressible multiphase problems. The shock wave–helium bubble interaction test reveals that the present method is efficient in prediction of the deformed interface. The solver is further validated by shock wave impact SF6 interface with square, rectangle, forward and backward triangle shapes in which the wave positions and intersecting angles are compared quantitatively. Finally, the collapse of an air bubble under shock in water is simulated, global agreement with experimental and other numerical results are obtained.

DOI： 10.1016/j.jcp.2017.04.032

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/S1001-6058(16)60702-3

Language：English   Publishing type：Research paper (scientific journal)  

Investigations have been conducted to analyze the accuracy of the ghost fluid immersed boundary lattice Boltzmann method and the conventional interpolation/extrapolation bounce-back schemes. The intrinsic sources of pressure oscillation for numerical simulation of moving boundary flows have also been inves- tigated. An existing bilinear ghost fluid immersed boundary lattice Boltzmann method (BGFM) (Tiwari and Vanka, 2012) and a proposed quadratic ghost fluid immersed boundary lattice Boltzmann method (QGFM) have been compared with Guo’s second-order extrapolation bounce-back scheme (Guo et al.) and the linear and quadratic interpolation bounce-back scheme (LIBB, QIBB) (Bouzidi et al., 2001; Lalle- mand and Luo, 2003). To study the numerical pressure oscillations in the moving boundary problem, (i) three existing refilling techniques and one proposed refilling technique are compared; (ii) three col- lision models, including the single-relaxation-time model, the multiple-relaxation-time model and the two-relaxation-time model, are investigated; (iii) two force evaluation schemes, a Galilean invariant mo- mentum exchange method Wen et al. and a stress integration method Inamuro et al., are considered. The accuracy and the performance in pressure oscillation suppression for the studied numerical approaches are compared and discussed by five numerical examples: an eccentric cylinder flow, a Cylindrical Couette flow, an impulsively started cylinder in a channel, an oscillation cylinder in calm water and a particle suspension problem. The numerical results indicate that the accuracy of QGFM scheme is comparable to Guo’s scheme while the accuracy of BGFM is worse than both of them. The QIBB scheme shows the best performance in the space convergence accuracy among all the schemes. Selection of the collision model, refilling technique and force evaluation scheme affect the pressure oscillation phenomenon in moving boundary simulations remarkably.

DOI： 10.1016/j.compfluid.2016.01.015

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.jcp.2014.06.042

Language：English   Publishing type：Research paper (scientific journal)  

A multi-phase flow model which applies lattice Boltzmann method (LBM) is developed for numerical simulation
of the initial accelerating stage of a rising CO 2 droplet in the deep ocean. In the present LBM model, a
multiple-relaxation time (MRT) collision operator is adopted to increase the numerical stability, and a color
model is used to treat the two-phase fluid. A domain shift scheme is proposed to make the long distance
calculation available. The computation is accelerated by using the GPU computing and correspondent parallel
implementation techniques are developed. The proposed numerical model is first validated against several
benchmark problems: Laplace law test, binary Poiseuille flow problem and rise of a toluene droplet. Then
numerical simulation of a liquid CO 2 droplet rising from quiescence to its steady state is carried out and the
results are compared to a laboratory experiment. Excellent agreement is obtained on both terminal velocity
and variation of droplet shape.

DOI： 10.1016/j.apor.2013.06.005

Language：English   Publishing type：Research paper (scientific journal)  

A partitioned approach by the coupling finite difference method (FDM) and the finite element method
(FEM) is developed for simulating the interaction between free surface flow and a thin elastic plate. The FDM, in
which the constraint interpolation profile method is applied, is used for solving the flow field in a regular fixed
Cartesian grid, and the tangent of the hyperbola for interface capturing with the slope weighting scheme is used for
capturing free surface. The FEM is used for solving structural deformation of the thin plate. A conservative
momentum-exchange method, based on the immersed boundary method, is adopted to couple the FDM and the
FEM. Background grid resolution of the thin plate in a regular fixed Cartesian grid is important to the computational
accuracy by using this method. A virtual structure method is proposed to improve the background grid resolution
of the thin plate. Both of the flow solver and the structural solver are carefully tested and extensive validations
of the coupled FDM–FEM method are carried out on a benchmark experiment, a rolling tank sloshing with a thin
elastic plate.

DOI： 10.1007/s00773-012-0191-0

Language：English   Publishing type：Research paper (scientific journal)  

A numerical approach is proposed to study the behavior of a natural carbon dioxide (CO2) droplet leaked from the
seafloor. Motion and deformation of the droplet at the initial stage are simulated by a lattice Boltzmann multi-phase
method to obtain the terminal velocity. The whole process of droplet rise and dissolution is modeled by a simplified
analytical method. The in-situ experiment case on a natural CO2 droplet at the Okinawa Trough (Shitashima, et al.1))
is studied by using the proposed numerical model. Numerical experiments show strong dependency between the
terminal velocity and the droplet density. The phenomena obtained in the on-sea observation are discussed by the
present numerical study.

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents further developments of a constrained interpolation profile (CIP)-based Cartesian grid method (Hu et al. [29]) to model nonlinear interactions between extreme waves and a floating body, which is validated against to a newly performed experiment. In the experiment, three kinds of waves (regular wave, focused wave and combined regular and focused wave) are generated and a box-shaped floating body with a superstructure is used. Validation computations on the experiment are performed by the improved CIP-based Cartesian grid method, in which the THINC/WLIC scheme (THINC: tangent of hyperbola for interface capturing; WLIC: Weighed line interface calculation), is used for interface capturing. The highly nonlinear wave-body interactions, including large amplitude body motions and water-on-deck are numerically investigated through implementation of focused wave input to the CIP-based method. Computations are compared with experimental results and good agreement is achieved. The effects of the water-on-deck phenomena and different input focus positions on the body response are also dealt with in the research.

DOI： 10.1016/j.apor.2012.01.001

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00773-008-0031-4

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00773-004-0180-z

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Publisher：Journal of Computational Physics  

We propose a numerical framework for simulating two-phase flow considering gravity and surface tension, and implement it with adaptive mesh. The framework employs a pressure compensation method and a jump model, ensuring accurate modeling of gravity and surface tension when the interface crosses between adaptive meshes of different refinement levels. Additional treatments have been developed to accommodate existing interface capturing and curvature estimation approaches for the adaptive mesh. The method is straightforward to implement and significantly reduces the unnecessary refinement around the free surface. Numerical validations demonstrate the robustness of the treatment for coarse/fine interfaces, with overall accuracy converging and comparable to results obtained with a uniform mesh. Furthermore, the numerical approach accurately reproduces the physics of bubble rising and jet capillary breakup.

DOI： 10.1016/j.jcp.2024.113485

Scopus

Publisher：Ocean Engineering  

In the marine environment, the interaction between wind and waves plays a crucial role in the transfer of wind-wave energy and the shaping of the ocean surface. Our research employs a two-phase flow solver with adaptive mesh technology to simulate the dynamics of wind-driven wave breaking, exploring the evolution of wave fields and the mechanisms of energy transfer throughout wave growth and breaking. We validated the reliability of our simulations through comparisons with theoretical and experimental results, including wave energy dissipation, wind velocity distribution, and wind-wave growth rates. We investigated the effects of dimensionless parameters such as initial wave steepness, wind Reynolds numbers, and Bond numbers on wave profile, energy evolution, and the maximum slope of wave. Furthermore, we developed an equation to predict the onset of wave breaking based on the ratio of wind-wave speed, Bond numbers, and initial wave steepness. This equation was substantiated through several 2D and 3D simulations. We find that, due to airflow separation, wind force tend to delay wave breaking but still enhance the intensity of breaking. Surface tension can restrain wave from plunging breaking, but still cause intense energy decrease by enhancing capillary effect.

DOI： 10.1016/j.oceaneng.2024.118913

Web of Science

Scopus

Publisher：Journal of Marine Science and Engineering  

In this paper, an experimental study is conducted to investigate the effectiveness of vibration dampers in suppressing vortex-induced vibration in a long, flexible catenary cable with a low mass ratio. The dampers, consisting of two small, symmetric, lightweight pipes clamped to the cable, are sparsely deployed along the cable to shape the vibration characteristics. The experimental results demonstrate that dampers significantly reduce the vibration amplitude by up to 60% and axial tension by up to 61% at high flow velocities, effectively suppressing the cable vibration in perpendicular flow. In addition, it is observed that the in-line and cross-flow vibration frequencies are approximately equal when the dampers are applied. This behavior contrasts with the conventional undamped catenary cable, where the in-line vibration frequencies are double those of the cross-flow frequencies.

DOI： 10.3390/jmse12111995

Scopus

Publisher：Renewable Energy  

In the paper, a CFD method that employs the flux reconstruction (FR) method and the actuator line method (ALM) is proposed, to develop a novel numerical framework to improve the efficiency and accuracy of turbulent wake predictions of horizontal axis wind turbines (HAWT). The PyFR solver, which is an open-source program that uses the FR method is applied. The ALM is for the first time implemented in the FR solver to simulate HAWTs. To increase the fidelity of the wake prediction, the nacelle and tower of the HAWT are also modeled, and the proposed numerical simulation method is named as AL-PyFR(N&T) model. The NTNU “Blind Test 1” wind turbine is used to validate the proposed model. First, the mesh and time step dependence of the AL-PyFR(N&T) model are verified. Second, the accuracy of the proposed model is verified by comparing the velocity deficits and turbulent kinetic energy results at different downstream locations with the measured values and the results from other CFD studies. By comparison of the results with and without the effect of the nacelle and tower, it is found that tower wake plays a significant role in wake asymmetry. Crucially, the AL-PyFR(N&T) model demonstrates a capacity for accurate wake predictions with fewer mesh requirements compared to conventional CFD models. This efficiency marks a significant advancement for high-fidelity numerical simulations of offshore wind farms.

DOI： 10.1016/j.renene.2024.121092

Web of Science

Scopus

Publisher：Ocean Engineering  

In this paper, a numerical model based on Euler-Bernoulli beam theory and a single van der Pol wake oscillator model is proposed to study the vortex-induced vibration of a long flexible catenary cable with a low mass ratio. The wake model uses only one oscillator to describe the in-line and cross-flow vibration with consideration of their nonlinear coupling. An experiment on a flexible cable model in perpendicular flow is carried out to validate the proposed numerical model. Numerical results and experimental measurements are compared on the vortex-induced vibration responses including the maximum amplitude, axial tension, and vibration frequency. A sensitivity analysis of the parameters used in the numerical model has been carried out. Numerical simulations by the proposed numerical model with properly selected parameters have demonstrated that the vibration frequency and the axial tension can be well predicted, and the variation of the vibration amplitudes can also be properly captured. The lock-in phenomena and the axial tension variation of the long flexible catenary cable in perpendicular flow have been carefully studied both numerically and experimentally.

DOI： 10.1016/j.oceaneng.2024.117937

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Scopus

Language：English   Publisher：Physical Review E  

When bubbles collapse near a wall, they typically experience an asymmetric deformation. This collapse leads to the creation of a jet that strikes the bubble interface, causing the formation of a toroidal bubble and the subsequent release of a water-hammer shock. In this study, we present a systematic analysis of the collapse of a toroidal bubble in an open field or adjacent to a flat wall using high-fidelity numerical simulation. To maintain the sharpness of the interface, we employ the interface compression technique and the boundary variation diminishing approach within the two-phase model. Our findings demonstrate that shock waves emitted from the toroidal bubble consistently propagate toward the central axis of the torus, resulting in significant pressure shocks along the axis, similar to the water-hammer shock formed during the collapse of a spherical bubble. In contrast, weak pressure waves are generated in the transverse directions, leading to relatively weaker pressure peaks. Furthermore, the wall-pressure peak induced by the toroidal bubble is approximately three times higher than that induced by the spherical bubble. Based on the directional characteristics of pressure wave propagation from collapsing toroidal bubbles, toroidal-shaped pressure vessels can be designed as buoyancy materials for deep submersibles. This design enables the focused release of energy in a specific direction, effectively minimizing the destructive chain reaction caused by the implosion.

DOI： 10.1103/PhysRevE.110.015103

Web of Science

Scopus

PubMed

Publisher：Ocean Engineering  

Plunging breakers are frequently observed in the ocean, where the energetic interaction between air and water generates bubbles and droplets of various sizes. In this study, we conducted high-fidelity simulations of plunging breaking waves considering different initial wave slopes. To accurately capture the dynamics of high-density-ratio flows, we employed a mass-momentum consistent scheme along with a reliable surface tension model. Our simulations successfully reproduced essential breaking events such as jet overturning, droplet splashing, and the formation of liquid sheets. We also conducted a comprehensive analysis, taking into account factors such as grid resolution and spanwise scale to verify the convergence of bubble and droplet characteristics. Our investigation focused on the mechanisms of spray droplet formation during plunging breakers, leading us to identify four primary mechanisms of spray droplet formation. Additionally, we explored the influence of surface tension and wave slopes on the formation of the principal air cavity. To support our findings, we performed extensive statistical analyses, including the size, velocity, and spatial distribution of bubbles and droplets, using a specially developed bubble-droplet detection program. These analyses revealed that both droplet and bubble size distributions follow a power-law scaling, consistent with previous studies. The volume evolution of the droplets displays multiple peaks, and two main peaks are observed in the number density. The cascade process is a significant factor contributing to the overall increase in number density. Additionally, the velocity distribution of droplets exhibites a normal distribution pattern, where larger droplets tend to possess higher velocities.

DOI： 10.1016/j.oceaneng.2024.117635

Web of Science

Scopus

Publisher：Physics of Fluids  

The present study investigates the dynamics of the interface in the presence of a decaying Lamb-Oseen vortex, and four distinct wave patterns are observed: non-breaking waves with small periodic oscillations, plunging breakers, depression breakers, and gravity-capillary waves. The deformation of the interface is induced by a two-dimensional Lamb-Oseen vortex, and the study examines the influence of vortex strength and surface tension on the resulting flow. The wave dynamics are characterized as a function of the Reynolds and Weber numbers, and a phase diagram is presented in terms of ( Re , We ) to distinguish the different wave patterns. To ensure accurate reconstruction of the interface, the numerical methods used in this study feature a mass and momentum consistent advection method, high-order interpolation schemes, and a block-structured adaptive mesh refinement strategy. The study presents the characteristics of the air cavity entrained at the moment of wave impact for each wave pattern. Furthermore, the results provide insight into the nature of bubble entrainment within a vortex and reveals the bubble entrainment process via a breakup cascade. Meanwhile, it is also shown that the entrainment of bubble results in significant vortex distortion. Overall, this research contributes to enhance our understanding of wave dynamics and the intricate interaction between vortices and interfaces.

DOI： 10.1063/5.0218087

Web of Science

Scopus

Publisher：Ocean Engineering  

The phenomenon of bubble collapse is ubiquitous in both natural and industrial settings, often manifesting in the form of bubble clusters. Despite its prevalence, there has been limited research on the dynamics of bubble clusters. In order to gain a better understanding of shock wave emission, liquid jet propagation, and the resulting pressure loads during bubble cluster collapse, we have developed a high-fidelity numerical approach aimed at accurately capturing shock waves and phase interfaces. The interface compression technique is introduced into the compressible two-phase model to improve the sharpness of the phase interface. We solve the physical model using the BVD (Boundary Variation Diminishing) principle. Both the 5th order WENO (Weighted Essentially Non-Oscillatory) scheme and the interface capturing function THINC (Tangent of Hyperbola for INterface Capturing) are utilized to reconstruct primary variables at cell boundaries, effectively minimizing numerical dissipation. For further resolution improvement, we implement these numerical methods on the AMR (Adaptive Mesh Refinement) mesh. Our numerical results demonstrate that the distance between the wall and the bubble cluster, as well as the nearest bubble to the wall, significantly influence the wall peak pressure. However, they have a minimal impact on the overall evolution of the bubble cluster and the peak pressure induced in the flow field. Remarkably, the spatial distribution of bubbles and the total number of bubbles play a crucial role in shaping the dynamic behavior of the bubble cluster and the pressure loads exerted both on the solid wall and in the flow field. The crucial findings offer profound insights into a range of applications, including cavitation erosion, underwater explosions, and drug delivery.

DOI： 10.1016/j.oceaneng.2024.117362

Web of Science

Scopus

Publisher：Physics of Fluids  

During the occurrence of plunging wave breaking, a substantial number of multi-scale bubbles are generated. These submerged bubbles persist for extended periods and contribute to the distinct acoustic and optical characteristics of the wake. In this study, we utilize high-fidelity simulations, combined with the adaptive refinement strategy to accurately track bubbles of multi-scales during the entire rising stage. Unlike previous studies, our emphasis is specifically on investigating the process of bubble rising during plunging wave breaking. Comprehensive statistical analyses are performed and characteristics of bubbles across various scales are also provided. Our findings reveal that most bubbles are concentrated in small scales, while larger bubbles rapidly ascend to the surface or undergo fragmentation into smaller bubbles through breaking cascades eventually. A distinct stratification of bubble size distribution along the depth direction is observed. Bubble velocity distributions are also important characteristics that are frequently neglected in studies of plunging wave breaking. Bubbles primarily spread along the spanwise direction, with a uniform distribution of velocity in this dimension. The velocity distribution of bubbles displays asymmetric tails that extend to higher velocities, and within this high-velocity regime, a power law behavior is observed, similar to the size distributions. Ultimately, the flow field is left with only a few small bubbles, moving at an exceedingly low speed. Furthermore, dynamical evolution of bubble rise in plunging wave breaking is described in detail and we analyze the intricate interactions between bubbles and turbulent flows. We observe that vortices are predominantly generated in close proximity to the bubbles, and bubble motion plays a crucial role in initiating turbulent flows. Simultaneously, these vortices contribute to the fragmentation of large-scale bubbles, transforming them into smaller counterparts due to turbulent fluctuations.

DOI： 10.1063/5.0206434

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Scopus

Publisher：International Journal of Multiphase Flow  

In this study, numerical simulations of bubbly flows in an infinitely long vertical channel were performed. Generally, the upper and lower boundaries of such channels are simplified as periodic boundary conditions. Unlike horizontal channel flows, the presence of gravity in the streamwise direction complicates the establishment of periodic boundary conditions. Therefore, a specialized treatment is required to prevent fluid acceleration. Here, we developed a novel treatment for the imposition of periodic boundaries and proposed a new microbubble model to consider the surface tension effect of microbubbles. To detect each bubble in the flow field, we implemented a bubble identification algorithm, which facilitates a thorough statistical analysis of bubble number, size, and spatial distribution. Validation tests were conducted, and good agreement was achieved between our results and reference data. We also confirmed that the results obtained with periodic boundaries are consistent with those achieved without them. Finally, we simulated the evolution of rising bubble swarms in a quiescent liquid. The method presented here contributes to the numerical simulations of bubbly flows in industrial systems, including oil-gas transportation, bubble columns, and nuclear reactors.

DOI： 10.1016/j.ijmultiphaseflow.2024.104816

Web of Science

Scopus

Publisher：Physics of Fluids  

This article introduces a novel method for computing consistent fluxes, which enables highly robust simulations of two-phase flow problems characterized by large-density ratios. The approach is based on the geometric reconstruction volume of fluid method and utilizes a staggered grid implementation. This allows for accurate and robust simulation of phenomena like droplet bag breakup in flows with intense velocity shear and significant density differences. Through numerical experiments, it has been demonstrated that this method can reliably simulate two-phase flows with large-density ratios while preserving excellent energy conservation properties. Expanding on these findings, the researchers have developed a solver that leverages block-structured adaptive mesh to perform high-fidelity simulations of droplet bag breakup scenarios. Remarkably, this solver accurately reproduces three distinct breakup patterns: bag mode, stamen mode, and sheet-stripping mode. A comprehensive analysis has also been conducted by comparing the dimensionless maximum cross-stream radius with experimental test results. Furthermore, the study investigates the kinetic energy spectrum of fully developed two-phase turbulence under different droplet generation mechanisms and examines the distribution of droplet sizes. The numerical results validate the efficacy and reliability of this method in accurately simulating two-phase flows characterized by significant density disparities and interface momentum exchange.

DOI： 10.1063/5.0182113

Web of Science

Scopus

Publisher：China Ocean Engineering  

To obtain the interaction characteristics between Internal solitary waves (ISWs) and submerged bodies, a three-dimensional numerical model for simulating ISWs was established in the present study based on the RANS equation. The velocity entrance method was adopted to generate the ISWs. First, the reliability of this numerical model was validated by comparing it with theoretical and literature results. Then, the influence of environmental and navigation parameters on interactions between ISWs and a fixed SUBOFF-submerged body was studied. According to research, the hydrodynamic performance of the submerged body has been significantly impacted by the ISWs when the body is nearing the central region of the wave. Besides, the pitching moment (y′) will predominate when the body encounters the ISWs at a certain angle between 0° and 180°, and the lateral force is larger than the horizontal force. Additionally, the magnitude of the force acting on the body is mostly affected by the wave amplitude. The variation of the vertical force is the main way that ISWs affect the hydrodynamic performance of the bodies. The investigations and findings discussed above can serve as a guide to forecast how ISWs will interact with submerged bodies.

DOI： 10.1007/s13344-023-0078-3

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Scopus

Language：Japanese   Publisher：The Japan Society of Naval Architects and Ocean Engineers  

DOI： 10.14856/conf.37.0_459

CiNii Research

Language：Japanese   Publisher：The Japan Society of Naval Architects and Ocean Engineers  

DOI： 10.14856/conf.37.0_793

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Journal of Multiphase Flow  

The shock waves and high-speed jets induced by the violent collapse of bubbles can cause serious damage to nearby structures. To fully understand the shock wave and jet characteristics induced by bubble-bubble interaction, we developed a diffuse-interface method for the simulation of compressible two-phase flow, which combined interface compression technique with interface sharpening technique to keep the sharpness of the shock wave and phase interface. The thermodynamically consistent five-equation model was improved using interface compression technique to maintain a constant thickness of the phase interface. To further suppress numerical dissipation, the high-order scheme WENO (Weighted Essentially Non-Oscillatory) and interface sharpening function THINC (Tangent of Hyperbola for INterface Capturing) were used for the flux reconstruction at the grid boundary to ensure that the total variation at the cell boundary was minimized (Boundary Variation Diminishing, BVD), thus the spatial reconstruction scheme, named WENO-THINC-BVD, was developed. Moreover, we extended the present method to a block-structured adaptive mesh refinement framework to improve grid resolution and save computing resources. Numerical results of several benchmark tests fully demonstrated the advantages of the present method in simulating complex compressible flows containing shock-shock and shock-interface interactions. Based on the present high-fidelity numerical methods, we investigated the shock wave and liquid jet induced by the two-bubble interaction in an open space. A phase diagram of the liquid jet propagation direction as a function of the initial bubble pressure and the inter-bubble distance was summarized. Finally, according to the bubble-bubble interaction process, an empirical formula for the collapse strength and another for the attenuation of shock waves were developed.

DOI： 10.1016/j.ijmultiphaseflow.2023.104584

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Environmental Science and Pollution Research  

A new fractional non-Fourier (Cattaneo) photovoltaic (PV) model is presented to enhance the thermal performance of a PV system combined with a heat spreader (HS). The fractional Cattaneo model is shown to be effective in examining transient processes across the entirety of a PV system, in contrast to the conventional Fourier model’s inability to predict system performance. Consequently, a comparison is conducted between the classical Fourier model with the fractional Fourier and fractional Cattaneo models for the PV system. The impact of using an aluminum heat spreader, with rectangular and trapezoidal shapes, has been developed under hot and cold climate conditions. The findings show that adding a trapezoidal heat spreader reduced the cell temperature by 20 K in summer and 12 K in winter. The reduction in the PV temperature led to an enhancement in daily average power by approximately 28% and 37% in hot and cold weather, respectively. Moreover, economic, exergoeconomic, and enviroeconomic assessment is introduced. The outcomes revealed that the electrical production costs of the rectangular and trapezoidal HS systems are 0.272 and 0.214 $/kWh, respectively, while about 0.286 $/kWh for the conventional PV panel. Based on the environmental study, the estimated CO2 reduction for PV, PV with rectangular HS, and PV with trapezoidal spreader is 0.5504, 0.7704, and 0.8012 tons, respectively. Finally, real experimental data are used to validate the fractional Cattaneo model. The results demonstrate that there is a great fitting with the measured data, with errors in PV power and exergy efficiency of just 0.628% and 3.84%, respectively, whereas their corresponding values for the classical model are 5.72 and 13.13%.

DOI： 10.1007/s11356-023-29654-8

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Fusion Energy  

Harsh heat load conditions on plasma-facing components (PFCs) in steady-state and transient phenomena (e.g., disruptions and ELMs) in DEMO fusion reactors question the feasibility of current approaches based on solid targets made of tungsten. This issue calls for the development of innovative plasma-facing components. Liquid metal PFCs with strong convection enhance heat removal capability and resilience after the transient phenomena. However, transporting liquid metal across magnetic fields gives rise to MHD drag. MHD drag for the case of uniform B, estimated analytically, is acceptable. Grad-B MHD drags with straight ducts could seriously drag the LM flow across non-uniform B. Expanding the duct along B and shrinking the duct in a perpendicular direction could make electromotive force |vBh| approximately constant along the duct and significantly reduces the grad-B MHD drag. Here v denotes the flow velocity along the duct, B is the magnetic field strength, and h is the vertical duct size. Three-dimensional simulations for internal and free surface thermo-MHD phenomena have demonstrated that the proposed duct design reduces the total pressure drop along the duct.

DOI： 10.1007/s10894-023-00388-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Plasma Science and Nuclear Fusion Research  

<p>Liquid metal divertors are expected to have higher thermal load tolerance compared with solid divertors. Precise prediction of liquid metal behavior using magnetohydrodynamic (MHD) simulation enables the practical designing of a liquid metal divertor. The aim of this study is to confirm the accuracy of an MHD simulation that is developed for liquid metal flow prediction. As a benchmark test of the MHD simulation, a comparison of the Galinstan flowing through a vertical magnetic field and the simulated results was performed, and qualitative reproduction using the MHD simulation was confirmed. In addition, the source of wave creation and the causes of failure of the quantitative reproduction were investigated, which is may caused by the variations of the Galinstan surface tension.</p>

DOI： 10.1585/pfr.18.2405083

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CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1142/S0129183123501164

Publisher：IOP Publishing  

Evaluating ice loads acting on ships is essential for the safety of ships navigating in ice-covered seas. In this study, we develop a CFD method to handle ship, ice, and fluid interaction. The lattice Boltzmann method, capable of large-scale calculations, is applied to the simulation of free-surface fluids. The ice motion is computed by solving the equations of motion of a rigid body, and the discrete element method models the ice-ice and ice-ship contact interactions. A momentum exchange scheme couples the lattice Boltzmann method and particle-based rigid body simulation. We introduce tree-based adaptive mesh refinement and multiple GPU computing to improve grid resolution and computational time. The proposed method is applied to model scale simulations of ship navigation in a brash ice channel. Simulations were performed for various conditions with different ice concentrations and ship velocities, and we observed that ice resistance increased with the ice concentration and the ship velocity increased. The ice motions and resistances obtained from our simulations are reasonable compared to model equations of Finnish-Swedish ice class rules (FSICR) and numerical analyses of a previous study.

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1757-899X/1288/1/012015

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nuclear Fusion  

Divertor systems of fusion devices are exposed to intense heat loads from plasmas, which degrade solid plasma-facing components. Fast liquid metal (LM) flow divertors may be more advantageous for this purpose but have risk of piling due to intense magnetohydrodynamic (MHD) drag. However, severe deceleration of the flow could be countered with the injection of currents that are transverse to external magnetic fields, allowing to thrust the flow with j × B (Lorentz) forces. Given that the injection of currents as an approach to propel LM-divertor flows has remained experimentally understudied, this article focuses on the evaluation of j × B -thrust and finding its drawbacks. j × B -thrust was experimentally tested with free-surface-LM flows, a vertical magnetic field and an externally applied current. Experiments were reviewed with a theoretical model, showing agreement in the trends of theory and experiments. Full 3D-MHD-free-surface-flow simulations were also performed with FreeMHD and confirmed the sensitivity to unstable flow behavior in LM systems when applying external currents. Furthermore, excessive power requirements are expected for the implementation of j × B -thrust at the reactor scale, making these systems inefficient for commercial devices. This paper evidences that the simple operation of a LM-flow divertor with j × B -thrust, without any of the instabilities caused from reactor plasmas or parasitic currents, already presents intrinsic challenges.

DOI： 10.1088/1741-4326/ace9e9

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1757-899X/1288/1/012033

Language：English   Publishing type：Research paper (scientific journal)  

Publisher：Acta Mechanica Sinica/Lixue Xuebao  

In this paper, we present a modified tangent of hyperbola for interface capturing (THINC) scheme for freestream and vortex preservation on the general curvilinear grids, in which the symmetric conservative metric method is employed to eliminate the geometrical errors in the discretization of Jacobian and the metrics. As the original THINC with a fixed jump steepness may lose accuracy and result in instability problem on non-uniform grids, a new algorithm is introduced to reduce the numerical dissipation, in which the jump steepness is scaled adaptively according to varying mesh intervals. Numerical tests show the new THINC scheme can hold freestream and vortex preservation and is capable of resolving discontinuities and small-scale smooth flow structures with less dissipation on general curvilinear grids, compared with the original THINC. By using the boundary variation diminishing (BVD) principle, the modified THINC is implemented in combination with a finite-difference weighted essentially non-oscillatory (WENO) scheme. Comprehensive numerical validations are performed to evaluate the performance of the improved THINC and WENO combined with the modified THINC in the framework of both the FDM and FVM, with twisting and even randomly spaced curvilinear meshes. Numerical results of the double Mach reflection also demonstrate the improved THINC can alleviate non-physical oscillations with less numerical dissipation. [Figure not available: see fulltext.].

DOI： 10.1007/s10409-022-22422-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physics of Fluids  

In the present study, high-fidelity simulations of the wake behind a transom stern are performed with a block-based adaptive mesh refinement technology. By transom stern, we mean a square-ended stern of a ship, which is a favorable design for the high-speed ship. The sharp volume of fluid method is adopted to capture the gas-liquid interface, and the immersed boundary method is applied to simulate the boundaries of ship hull. Simulation results show that the V-like diverging wave along with air entrainment constitute the main characteristics of the wake. Air cavity of various scales is captured and tracked by the cavity-detection algorithm. Thus, the spatial and temporal distribution of the number and volume of air cavity is obtained in the simulation. Different draft Froude numbers are considered to analyze their influence on the wake. The wave profile, distribution of air cavity, turbulence kinetic energy, and the air entrainment features of the wakes behind dry and wetted stern are compared quantitatively. Numerical results demonstrate the present solver is capable of reproducing the main characteristics of wake behind a high-speed transom stern.

DOI： 10.1063/5.0151170

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nuclear Fusion  

While flowing Liquid Metal (LM) Plasma-Facing Components (PFCs) represent a potentially transformative technology to enable long-pulse operation with high-power exhaust for fusion reactors, Magnetohydrodynamic (MHD) drag in the conducting LM will reduce the flow speed. Experiments have been completed in the linear open-channel LMX-U device [Hvasta et al 2018 Nucl. Fusion 58 01602] for validation of MHD drag calculations with either insulating or conducting walls, with codes similar to those used to design flowing LM PFCs for a Fusion Nuclear Science Facility [Kessel et al 2019 Fusion Sci. Technol. 75 886]. We observe that the average channel flow speed decreased with the use of conducting walls and the strength of the applied transverse magnetic field. The MHD drag from the retarding Lorentz force resulted in an increase of the LM depth in the channel that ‘piled up’ near the inlet, but not the outlet. As reproduced by OpenFOAM and ANSYS CFX calculations, the magnitude and characteristics of the pileup in the flow direction increased with the applied traverse magnetic field by up to 120%, as compared to the case without an applied magnetic field, corresponding to an average velocity reduction of ∼45%. Particle tracking measurements confirmed a predicted shear in the flow speed, with the surface velocity increasing by 300%, despite the 45% drop in the average bulk speed. The MHD effect makes the bulk flow laminarized but keeps surface waves aligned along the magnetic field lines due to the anisotropy of MHD drag. The 3D fringe field and high surface velocity generate ripples around the outlet region. It was also confirmed that the MHD drag strongly depends on the conductivity of the channel walls, magnetic field, and volumetric flow rate, in agreement with the simulations and a developed analytical model. These validated models are now available to begin to determine the conditions under which the ideal LM channel design of a constant flow speed and fluid depth could be attained.

DOI： 10.1088/1741-4326/acd864

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Ocean Engineering  

The oscillating hydrofoil has been widely used in ocean engineering applications such as ships, underwater vehicles and ocean energy devices. However, Reynolds number of existing research are lower than real ocean applications.This study reports our recent numerical effort in studying a sinusoidally oscillating hydrofoil under unsteady conditions by solving the Reynolds-averaged Navier–Stokes equations. By using experimental test data, the numerical method is well validated. Three wake patterns are identified to fundamentally affect the propulsive performance of the oscillating hydrofoil. Only the wake in the reverse von Kármán vortex street pattern is found to generate thrust for purely oscillating motion. The leading-edge vortex is demonstrated todirectly influence the pressure distribution over the foil's surface but not the thrust.Furthermore, impact of 3D effect on vortex shedding on the hydrodynamic performance of the hydrofoil is presented. This study is expected to provide guidance on both academics and industries in relevant fields.

DOI： 10.1016/j.oceaneng.2023.114097

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Review Fluids  

A bluff body advancing through the water surface at high Froude number produces intricate two-phase flow patterns. One intuitive feature is an entrapped air cavity which subsequently breaks apart into a mass of droplets and bubbles. The bluff-induced cavity partially accounts for the appearance of bubble clouds in the wake. However, few experimental or numerical studies have been devoted to this phenomenon. To clarify this mechanism, high-fidelity simulations are performed to emphasize the evolution of the aerated cavity generated by a surface-piercing rectangular plate. First, the mesh independency study is performed to validate the trend of the convergence of the time-averaged wave profile, the bubble size distribution, the bubble number density, and the entrapped bubble volume. Then the formation and development of the aerated cavity induced by a surface-piercing plate with various yaw angles (αE∈[10∘,50∘]) are investigated. Numerical simulations show that the air pocket is entrapped and develops with stabilized rotational motion, and the subsequent breakup of the air pocket constitutes the leading cause of the bubbly wake. The geometrical characteristics of the aerated rotation cavity are summarized as a function of yaw angles. Moreover, with the adaptive mesh strategy and high-resolution schemes, all the bubbles of equivalent radius r≥2mm are captured and tracked, so the spatial and size distribution laws of the varying-sized bubbles pinching off from the air cavity in the wake are summed up. In addition, large-scale coherent structures wrapped around the cavity and the effects on air entrainment are discussed.

DOI： 10.1103/PhysRevFluids.8.044003

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1142/S0129183123501164

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Transdisciplinary Research and Education Center for Green Technologies, Kyushu University  

The numerical study of vortex-induced vibration (VIV) of a near-wall cylinder, as well as the impacts of the wall on VIV response, is presented. The Reynolds number for a cylinder near a wall is lower than that of an isolated cylinder when the max vibration amplitude occurs. The max vibration amplitude of the cylinder near a wall is less than that of an isolated cylinder. Moreover, the vortex shedding observed from a wall interacts with the vortex shedding emanating from a cylinder, weakening it. As a near-wall cylinder enters the lock-in region, the vortex shedding from a wall interact with that from the cylinder, which promote separation of the wall boundary layer and alter the wake vortex structure.

DOI： 10.5109/6781072

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Review Fluids  

The accidental implosions of pressure vessels in the deep ocean may cause severe damage to the surrounding structures, and the induced liquid jet and shock wave can even lead to a chain reaction of nearby pressure vessels. Since the whole physical process can be approximately reproduced by the inertial collapse of air bubbles, in this study, the collapse of two adjacent bubbles near a solid wall is considered as an analog to assess the implosions of pressure vessels. An adaptive mesh refinement solver is developed for the high-fidelity simulation of the compressible multiphase flows. First, the implosion of a single bubble and the explosion of two bubbles are simulated for numerical validation. Then the collapsing process of two equal-sized bubbles with a different arrangement is simulated. By the advantage of the present numerical technique, the sharp shock fronts emitted from the collapse are captured with high resolution, and the high wall pressure induced by the shock wave is investigated in detail. Numerical results reveal that the wall-bubble distance and the bubble-bubble distance are crucial for the shock-impacting wall pressure and the jet flow direction. It is found that the maximum wall pressure occurs
when the two bubbles are horizontally arranged in relation to the solid wall, while the perpendicular arrangement leads to the lowest wall pressure. The present findings of the two-bubble collapse are significant in determining the arrangement of pressure vessels inside submersible structures.

DOI： 10.1103/PhysRevFluids.8.023602

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Marine Science and Technology (Japan)  

The development of tidal turbine farms desires an understanding of the effects of free-surface waves and turbine interactions. The objective of this paper is to investigate surface wave effects on the performance of two tidal turbines axially aligned with current flows. Scale model experiments with and without regular waves are conducted on two horizontal-axis tidal turbines in a towing tank. Regular waves have no effect on time-averaged performance but induce periodic fluctuations in rotor torque for the upstream turbine that is not impacted by the wake of other turbines. Waves improve downstream turbine performance marginally, and the amplitude of torque fluctuations is frequently lower than that of the upstream turbine. A comparison of five wave situations with varying wave heights and periods is also explored. It is demonstrated that as the wave height and period increased, so did the range of torque variation.

DOI： 10.1007/s00773-023-00929-6

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Publisher：Proceedings of the International Offshore and Polar Engineering Conference  

Wind resource assessment is essential for the development of offshore wind energy. In this study, we propose a design of tension-leg platform (TLP) based met mast for wind measurements. To evaluate the design, a time-domain numerical model is developed for the dynamic analysis of the TLP under wave, wind, current or earthquake excitations. Based on this model, the performance of the TLP under extremely harsh environmental conditions is numerically examined. The results show that (1) the developed numerical model is capable of predicting TLP motion responses and tendon tensions under various environmental conditions; (2) the performance of the present TLP design is satisfactory in the considered extreme sea state and seismic situation.

Scopus

Language：English   Publisher：The Japan Society of Naval Architects and Ocean Engineers  

DOI： 10.14856/conf.35.0_523

CiNii Research

Language：English   Publisher：The Japan Society of Naval Architects and Ocean Engineers  

DOI： 10.14856/conf.35.0_495

CiNii Research

Publisher：International Journal of Multiphase Flow  

In present study, a simple and robust method is proposed to calculate the mass and momentum flux in the simulation of large-density-ratio interfacial flows. An auxiliary continuity equation is introduced and solved in a consistent manner with the momentum equations. This method ensures the consistency of the mass and momentum transportation in both phases. The erroneous interfacial momentum transfer often arising in traditional two-phase flow simulations can be suppressed. Moreover, this method can be extended straightforwardly to work with any of the VOF (Volume of Fluid) - type interface capturing methods. Present algorithm is implemented on an in-house code with block-structured adaptive mesh refinement (BAMR) (Liu and Hu, 2018) technologies, and is highly applicable for the massively parallel computations. We demonstrate the numerical stability and accuracy through a series of typical two-phase flow tests with high density ratios. Finally, the simulation of atomization of liquid sheet is considered to further demonstrate the capability in simulating surface tension driven flows. Numerical results show the spurious air velocity and unphysical interface fragmentation are completely avoided. Present consistent method exhibits much better performance in suppressing the excessive kinetic energy introduced by the two-phases co-existing cells. Moreover, the method is simple for implementation and is robust for the violent two-phase flow problems, even with strong shear velocity around the interface.

DOI： 10.1016/j.ijmultiphaseflow.2022.104192

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Transdisciplinary Research and Education Center for Green Technologies, Kyushu University  

An improved numerical model is proposed to investigate the dynamics of an offshore overhead power transmission system. The hydrodynamic performance of the TLP type tower is evaluated by a potential flow theory method, and the aerodynamic performance of the electric wire is analyzed by lumped parameter method. The numerical model has been validated by comparison to water tank tests. The TLP type tower and the weight control system to reduce the body-wire interaction are newly designed for better performance in the condition of wind and wave. We found that the wire dynamics are significantly affected by the wave direction and wind direction through the numerical simulation, so the wind-wave misalignment conditions should be considered in the system safety assessment. Additionally, the safety situation of conductor wires under different environments can be studied by time-domain simulations, which can be used in system designs and feasibility discussions.

DOI： 10.5109/4842521

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Advances  

Surface tension in two-phase flow problems plays a dominant role in many micro-flow phenomena and has an important influence on the development of flow instability phenomena that contain free surfaces. In this study, the multi-moment finite volume method is extended for direct numerical simulation of two-phase flow problems. A constraint interpolation profile-CSL (semi-Lagrangian) scheme is used for discretization of the advection part in the momentum equation. A compact volume of fluid method-approximated piecewise linear calculation method without flux limiter is proposed for capturing the moving interface. For modeling the surface tension accurately, the logic in curvature estimation is redesigned based on the height function (HF) method. The isolated volumetric fractions that may reduce accuracy in HF integration are excluded, and the numerical solution shows that the accuracy in the curvature estimation is improved for a coarse mesh. The present method is implemented with a parallel block-structured adaptive mesh refinement (BAMR) strategy; thus, the computational cost can be reduced significantly. Numerical tests show that the present BAMR solver is capable of reproducing the theoretical predictions of capillary wave instability problems with high accuracy. The simulation of droplet collisions further demonstrates the accuracy of the surface tension model. Finally, we extend it to the liquid jet atomization. The wavy disturbance, film breakup, liquid filament pinch-off, and droplet generation are well reproduced. The droplet size distribution satisfies the experimental measurement and theoretical predictions power-law. BAMR shows a huge advantage in computational efficiency than the traditional Cartesian grid. The findings of this study can help for a better understanding of the micro-mechanism of surface tension driven flows.

DOI： 10.1063/5.0098717

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE  

Wave drift forces on two barges in side-by-side arrangement are of engineering significance for control of the distance between the vessels. Hence the influence of resonant behaviors between the two barges on drift forces is worthy to investigating. In this paper, a two-dimensional numerical model is developed to evaluate the time-averaged drift forces on two floating bodies. The near-field and far-field methods have been implemented in an in-house program code for computations. First, numerical validations were conducted against published data in literatures. Then, the influence of the gap width and edge shapes of two fixed floating boxes were investigated numerically. It is found that the total mean surge drift force in wave direction was substantially reduced by the piston mode resonance in the gap, whereas considerable drift forces were observed on two respective boxes in opposite directions. Further examinations indicate that the effect of resonant wave behaviors on drift force is dependent on viscous damping of gap resonance.

DOI： 10.1115/OMAE2022-79910

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Hydrodynamics  

In numerical simulations of tidal current farms, large-scale computational fluid dynamic (CFD) simulations with a high-resolution grid are required to calculate the interactions between tidal turbines. In this study, we develop a numerical simulation method for tidal current turbines using the lattice Boltzmann method (LBM), which is suitable for large-scale CFD simulations. Tidal turbines are modeled by using the actuator line (ACL) model, which represents each blade as a group of actuator points in a line. In order to validate our LBM-ACL model, we perform simulations for two interacting tidal turbines, and results of turbine performance are compared with a water tank experiment. The proposed model successfully reproduces the variation of the torque due to wave effects and mean turbine performance. We have demonstrated a large-scale simulation for ten tidal turbines using 8.55×108 grid points and 16 GPUs of Tesla P100 and the simulation has been completed within 9 hours with the LBM performance of 392 MLUPS per GPU.

DOI： 10.1007/s42241-022-0037-0

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Language：English   Publisher：The Japan Society of Naval Architects and Ocean Engineers  

DOI： 10.14856/conf.34.0_571

CiNii Research

Language：Japanese   Publisher：The Japan Society of Naval Architects and Ocean Engineers  

DOI： 10.14856/conf.34.0_567

CiNii Research

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： https://doi.org/10.1145/3492805.3492811

Language：English   Publisher：ACM International Conference Proceeding Series  

The lattice Boltzmann method has recently become popular as an alternative to Navier-Stokes solvers for large-scale fluid simulations. We conduct a performance study of the lattice Boltzmann method on the A64FX Arm-based processor of the supercomputer Fugaku. We compared four types of data layouts: SoA, AoS, Clusterd SoA (CSoA), and CSoA2, and three algorithms for the LBM streaming step: Pull, Push, and Swap schemes. The performance measurement on a single CMG (Core Memory Group) shows that the combination of the CSoA2 layout and the Swap scheme has the highest performance of 176 GFLOP, which corresponds to 11.5% of the single-precision peak performance. Our simulations have demonstrated good weak scaling up to 16,384 nodes and achieved high performance 10.9 PFLOPS in single precision. The strong scalability is also a good result, with parallel efficiencies of 63.9%, 68.3% and 72.7 % for the D3Q15, D3Q19 and D3Q27 velocity model, respectively when scaling from 512 to 16,384 nodes.

DOI： 10.1145/3492805.3492811

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DOI： 10.1201/9781003320289-37

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>This study developed a large-eddy simulation code for offshore wind farms based on the lattice Boltzmann method. We present simulation results for a mesh convergence study for a single wind turbine performance and turbine wake and simulation results for a portion of the wind farm (8 wind turbines) under different inflow turbulence conditions. For Vestas V80 wind turbine with a rotor diameter of 80 m, the actuator line model shows the mesh convergence on a 2 m grid. The mesh dependence was significant for the uniform inflow condition for the wind turbine wake. In contrast, the resolution dependence on the mean velocity was significantly smaller for the turbulence inflow winds. The wind farm calculations captured trends in the observed wind turbine performance. Still, the following wind turbine performances were smaller than the observation data, suggesting the need to introduce rotational speed and pitch control into the simulations.</p>

DOI： 10.1299/jsmecmd.2022.35.23-02

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/5.0074943

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/5.0077348

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： https://doi.org/10.1115/OMAE2021-65524

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.oceaneng.2021.109078

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/5.0055727

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s42241-021-0028-6

Language：English   Publishing type：Research paper (scientific journal)  

Three-legged triangular tension leg platforms (TLPs), which are a kind of compliant-type floating structure, are drawing attention from industrial society. To reduce the transportation cost, a multiple linked ship towing system that the platform and anchor are linked and wet towed is studied. A unified seakeeping and maneuvering method which can take account of the hydrodynamic interaction between the bodies and utilize the experimental results for tuning the damping coefficients is proposed to model the towing system. In the method, a low-pass filter is applied to separate the slowly and fast motion components for the maneuvering and seakeeping calculations. The maneuvering and seakeeping problems can thus be solved simultaneously with a same time scale. SimMechanics™, which provides multi-body simulation environment for mechanical systems, is applied to implement the numerical model for studying the fully coupled six degrees-of-freedom (DOFs) motion of the towing system. Besides, experiments are carried out to demonstrate the feasibility of the system and the effectiveness of the numerical model. A circular motion in irregular waves is studied at the end and the issues of the system are discussed accordingly.

DOI： 10.1016/j.oceaneng.2021.108577

Language：English   Publishing type：Research paper (international conference proceedings)  

A time-domain method is developed for modeling the dynamics of a floating truss-structure wind turbine with multiple rotors mounted on the deck of the platform. In its hydrodynamic aspect, a hybrid panel-stick model is built up incorporating the potential flow theory to evaluate the wave inertia force and a Morison strip method to evaluate the wave drag force. The proposed analysis model is validated against a 1/50 scale test of a semi-submersible floating wind turbine, which was carried out in Kyushu University. Good agreement between the simulation results and the experimental data confirms the validity of the developed method. Further numerical simulations are performed in a set of wind and wave conditions to investigate the effect of wave drag force on the dynamics of the floating wind turbine. The results show that applying a hybrid panel-stick model is fairly effective to reduce the unphysical large resonant responses.

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (international conference proceedings)  

In present study, the interaction between internal solitary waves (ISWs) and a uniform slope is numerically studied based on the moving particles semi-implicit (MPS) method. Aiming at the stratified flows, a multiphase MPS method is firstly developed on the basis of the original single-phase MPS method, by introducing a series of special interface treatments. These treatments include the density smoothing scheme, inter-particle viscosity model and surface tension model. Then, the multiphase MPS method is validated through the numerical simulation of the ISWs generation and propagation. The results obtained by present method achieve good agreement with the experimental data and other numerical methods on the interfacial displacements and wave profiles. Moreover, the calculated pressure and velocity fields are smooth and reflect the actual physical features. Finally, the multiphase MPS method is applied to investigate the ISWs interaction with the submarine slopes with different inclinations, and a qualitatively analysis of the different breaking mechanisms is performed.

Language：English   Publishing type：Research paper (international conference proceedings)  

A trimaran usually consists of a main hull and two side hulls which has already been an important type of high-performance vessels. In order to reduce its total drag at different speeds for the need of saving energy and reducing pollution, the hull form optimization solver OPTShip-SJTU is used, and the spacing of side hulls and the shape parameters of the main hull can be changed and regarded as optimization design variables. Furthermore, the total drag of the trimaran is evaluated based on the potential flow theory after verifying the reliability of the potential-flow-based NMShip-SJTU solver. After evaluations of new sample hulls created by Optimal Latin Hypercube Sampling method, Kriging surrogate models are then constructed and validated to save the computational cost. Finally, a multi-objective optimization program is implemented to obtain the optimal hulls, and the selected typical optimal trimarans are further analyzed to ensure the optimization effects.

Language：English   Publishing type：Research paper (international conference proceedings)  

In this paper, numerical simulation of a flexible riser is carried out at first. Results are compared with the model test to verify the validity of the solver. Then, cases with different KC number with the same motion amplitudes are simulated to explain the effect of KC number in the VIV of the riser in the oscillatory flow. Typical characteristics of the vibration are observed including the modal transition and the “build-up-lock-in-die-out” process. Finally, through wavelet analysis, it was found that the main control modes at different positions were in three states when KC number was 84 and 168.

Language：English   Publishing type：Research paper (international conference proceedings)  

In this paper, the tip-vortex cavitation of NACA0009 hydrofoil is simulated at three tip clearances and one foil incidence angle. Two RANS turbulence models and LES sub-grid model are used in simulations. The key characteristics, including cavity trajectory, cavity shape, velocity and pressure fields in different downstream positions, are in good agreement with experimental results. It is found that the RANS simulations have a good prediction of the averaged cavity trajectory and the LES simulation can capture the rotation motion of tip-vortex cavity very well.

Language：English   Publishing type：Research paper (international conference proceedings)  

In this work, computational fluid dynamics (CFD) simulations have been conducted on leaked LNG vapor diffusion in which the gas is discharged from the vent post of a LNG powered RORO ship. A numerical model is proposed based on an open source Computational Fluid Dynamics (CFD) tool called OpenFOAM® for numerical simulation of the turbulent gas diffusion. The numerical method is first validated against a benchmark case and an experimental case. Two turbulence models, k-ε and LES, are applied and the numerical results are compared and discussed. By using the proposed numerical model, a series of LES simulations have been conducted on the LNG vapor diffusion of the RORO ship under several wind speeds and air temperatures.

Language：English   Publishing type：Research paper (scientific journal)  

The integration of wave energy converters and a floating wind turbine has the potential to reduce the cost of energy, since they can share the mooring system and the infrastructure of the power grid. In this study, oscillating-water-column-type wave energy converters mounted on a semisubmersible-type floating wind turbine are presented. Water tank tests are carried out to illustrate that the wave energy converters can not only capture the wave energy but also help in reducing the motion of the floating platform when active control is applied. This study provides a new perspective on hybrid renewable energy application to widen renewable energy penetration by enhancing system reliability.

DOI： 10.1007/s00773-019-00671-y

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

In order to address the problem of heat and particle removal in tokamak-type, magnetic confinement nuclear fusion reactors, a divertor that utilizes liquid metal is suggested to replace solid tungsten divertors due to concerns regarding their structural integrity at high energy fluxes. The operation of such a device gives rise to phenomena spanning multiple disciplines of physics such as fluid dynamics, electromagnetics, thermodynamics and plasma physics. Smoothed Particle Hydrodynamics (SPH) is a Lagrangian, mesh-free numerical method that has been proven effective in a variety of disciplines. In this work, the hydrodynamic aspect of the liquid metal divertor is simulated using SPH, paving the way to implement additional physics in future work.

Language：English   Publishing type：Research paper (scientific journal)  

This paper addresses a fundamental study of a floating type shrouded wind turbine on the design, mathematical model and motion analysis. Several novel concepts are introduced to the system for cost reduction: a revolute hinge is applied between the tower and the nacelle to maintain the orientation of the nacelle even in a large tower inclination, a swashplate mechanism with cyclic control is employed for blade pitch regulation to improve the system controllability, a novel mooring system with a slewing bearing is utilized to build the passive yawing system, and an advanced spar-type floater is used to obtain high restoring performance with a short spar. Firstly, the design aspects of the main components of the system are given. Then, the numerical model including the structural model, hydrodynamic/aerodynamic model, and the control system is presented. The static and dynamic responses under both the operational situation and survival conditions are finally studied. The paper illustrates the probability of the shrouded wind turbine on floating offshore application, and can provide critical information for the optimization design in next stage.

DOI： 10.1016/j.renene.2018.09.028

Language：English   Publishing type：Research paper (scientific journal)  

The aim of this research has been to conduct experimental measurements of the dam break impact on a vertical cylinder placed over a dry horizontal bed. The work aims to emphasize the effect of cylinder cross-section on the nature of impact as well as provide accurate and comprehensive data for the validation of computational fluid dynamics(CFD) codes. The experimental setup is based on a series of experiments conducted in the Research Institute for Applied Mechanics (RIAM) between the years 2010 and 2017. The gate motion is thoroughly studied and a novel gate motion formula is proposed based on the recent experimental data. The effect of gate obstruction on the time of impact with the cylindrical obstacle is presented and correlated to the parameters of the proposed motion profile thus emphasizing its significance in the numerical modeling of dam break flow. The effect of the cross-section of the cylinder is studied by examining the pressure signal on the cylinder as well as the vertical wall downstream of the cylinder. The pressure on the wall is compared with the no-obstacle case to highlight its effect on the pressure of the downstream conditions. The square cylinder is found to experience fairly similar pressure impulse as the circular cylinder. However, the square cylinder seems to impede the flow momentum in the x-direction more than the circular case. The data-set presented in this article is provided as Supplementary Materials including gate motion measurement, pressure measurements, and high-resolution videos.

DOI： 10.1016/j.jfluidstructs.2019.01.015

Language：English   Publishing type：Research paper (scientific journal)  

In this study, an efficient numerical method for predicting the wake interference of multiple turbines is presented. The actuator line (AL) model instead of the geometry-resolved method is adopted to represent the rotor. The Large-eddy simulation (LES) is performed to predict wakes of multiple turbines operated in turbulent flows. An efficient immersed boundary (IB) method with moving least square reconstruction (MLS) is developed to model the nacelle and support structure of the tidal turbine. A simple wall function based on the MLS-IB method and boundary-layer equations is employed to compute the instantaneous wall shear stress. Laminar flow simulations of unsteady flows past a cylinder illustrate the accuracy of the wall function IB method. Finally, the proposed method is extended to study turbulent flow past tandem tidal rotors, in which the wake profile behind rotors is analyzed. The results are found to be in reasonable agreement with published data.

DOI： 10.1007/s42241-019-0010-8

Language：English   Publishing type：Research paper (other academic)  

The bow wave depending on the bow shape can be determined by relatively simple geometric parameters due to little influence of the downstream wave. Accurate prediction of the bow wave is essential for ship resistance and motion responses. In this paper, the benchmark ship model, the Blunt modified Wigley, is used for all the simulations. The bow wave generated by the Blunt modified Wigley hull at a constant speed in incident waves is considered. The bow wave and the ship hydrodynamics are investigated by using Reynolds-averaged Navier-Stokes (RANS) method with Volume of Fluid (VOF) method to capture the free surface. In-house computational fluid dynamics solver, naoe-FOAM-SJTU, is applied to predict the hydrodynamics. The added resistance and motion responses of the Blunt modified Wigley in incident waves are studied to help understand the effect of the wave length on motion responses. The 1^st harmonic amplitude and corresponding phase for heave and pitch motions are analyzed in detail. Furthermore, the wave patterns are visualized to discuss the evolution of the bow wave.

Language：English   Publishing type：Research paper (other academic)  

The Wigley hull is considered as the initial ship, which can be globally deformed by shifting method and locally deformed by RBF (Radial Basis Function) method to generate a bulbous bow. Two optimization cases are given. In case 1, only shifting method is used, while in case 2, shifting and RBF methods are both used. The genetic algorithm is taken to obtain two optimal ships with minimum wave drag. Further validation by CFD solver naoe-FOAM-SJTU turns out that for the hull without bulbous bow, through combination of the two methods, a hull that has a much fewer wave drag can be obtained.

Language：English   Publishing type：Research paper (other academic)  

Wake interaction normally occurs in all wind farms and impacts significantly the flow field and performance of downstream wind turbines. The present work aims to study the wind turbine wake interaction phenomenon through the CFD method using LES and actuator line model. The solver used in the present work is developed based on the open source C++ class library OpenFOAM, in which the PISO algorithm is applied to deal with the velocity pressure coupling problem. The simulations which consider uniform inflow condition and six different layouts are implemented to study the evolving process of the interacting wakes. From the numerical result, the interacting region of wakes contains higher level turbulent flow than the single wake. The fully developed turbulence appears the earliest in the case of tandem layout, leading to serious wake meandering in the end of computational domain. The diffusion of turbulence causes the merging of wakes, and thus the velocity is redistributed among the whole wake region. Velocity deficit caused by the wake decreases the convertible wind energy. The turbulent flow and meandering of the wake result in the multi-scale fluctuation of the aero-power curves of wind turbines downstream.

Language：English   Publishing type：Research paper (scientific journal)  

The booming developments of coastal/offshore renewable energies in recent years call for a powerful numerical code, ideally open-source packaged, to accelerate the researches in the spotlight. This paper presents such an efficient software package for evaluating the performance of floating renewable energy systems in the coastal and offshore regions. It aims to contribute an open-source effort in numerical simulations for ocean energy converters. Though computation of the free-surface effect in moderate depth region is extremely troublesome due to the singularities, the software package proposed in the present paper gives a satisfactory solution to keep the balance of accuracy and efficiency. In the present paper, the interface and structure of the package are introduced in detail so as to be well understood by the reader. Benchmark tests for various types of converters have confirmed the accuracy and efficiency of the package which can be incorporated easily with a frequency domain solver for efficient analysis. By contributing as one of the pioneer works in the open-source effort of evaluating the moderate-depth free-surface Green's function, with its advantages of a reliable accuracy and a relatively low cost, the authors are hoping that the publication of the present software package will promote the continuous researches in developing robust and reliable coastal and offshore renewable energy systems.

DOI： 10.1016/j.enconman.2018.08.012

Language：English   Publishing type：Research paper (scientific journal)  

The three-dimensionality extent of the dam break flow over a vertical wall is investigated numerically and experimentally in this paper. The numerical method is based on Reynolds averaged Navier-Stokes (RANS) equation that describes the three-dimensional incompressible turbulent flow. The free surface is captured by using the unstructured multi-dimensional interface capturing (UMTHINC) scheme. The equations are discretized on 2-D and 3-D unstructured grids using finite volume method. The numerical simulations are compared with newly conducted experiment with emphasis on the effect of three-dimensionality on both free surface and impact pressure. The comparison between the numerical and experimental results shows good agreement. Furthermore, the results also show that 3-D motion of the flow originates at the moment of impact at the lower corners of the impact wall and propagates to the inner region as time advances. The origin of the three-dimensionality is found to be the turbulence development as well as the relative velocity between the side wall region and the inner region of the wave front at the moment of impact.

DOI： 10.1007/s42241-018-0074-x

Language：English   Publishing type：Research paper (international conference proceedings)  

The fully-coupled aero-hydrodynamic simulations of a floating offshore wind turbine consisting of a NREL-5MW baseline wind turbine and a semi-submersible floating platform are conducted. The three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations are solved for the coupled aero-hydrodynamic numerical simulation. The in-house code naoe-FOAM-SJTU, which is based on OpenFOAM and overset grid technology and developed for ship and ocean engineering, is employed. Aerodynamic loads on wind turbine are predicted. With the directly viscous simulations, detailed flow information around the turbine blades is available. The coupling effect on the aerodynamics of wind turbine from the platform motion is investigated.

Language：English   Publishing type：Research paper (international conference proceedings)  

The interaction of waves with fixed or floating structures involves complex wave radiation, wave diffraction and free surface deformation. In this work, the interaction of waves with a pair of cylinders in tandem arrangement is investigated using a numerical wave tank. The numerical simulation is first validated by comparing numerical results and experimental data for regular wave interaction with a single cylinder. Wave interaction with tandem cylinders is investigated for different center-to-center distances between the cylinders. All the numerical simulations are carried out by the in-house CFD solver naoe-FOAM-SJTU which is developed on the open source platform OpenFOAM. The incompressible unsteady Reynolds averaged Navier-Stokes (URANS) equations are adopted as the governing equations. The volume of fluid (VOF) method is applied to capture the free surface. The surface elevation around the cylinders is probed by a series of wave gauges and analyzed using transfer function. The wave forces of upstream and downstream cylinder are discussed in detail. The wave forces experienced by the tandem cylinders is highly influenced by the distance between the cylinders. The local surface elevation and the scattered wave field around the cylinders are also investigated. The results show that the present CFD solver can be an alternative tool to deal with wave-structure interactions.

DOI： 10.1115/OMAE201878373

Language：English   Publishing type：Research paper (international conference proceedings)  

The wake interaction between floating offshore wind turbines (FOWTs) has a significant effect on the FOWT's power output, system dynamics responses and structural loadings. To better understand the wake interaction phenomenon in floating wind farms, fully coupled simulations considering the coupling effects between the wind turbine, floating platform and mooring system for FOWTs are necessary. In the present paper, the unsteady actuator line model (UALM) is embedded into in-house CFD solver naoe-FOAM-SJTU to establish a fully coupled CFD analysis tool named FOWT-UALM-SJTU for numerical simulations of FOWTs. Coupled aero-hydrodynamic simulations of two OC3 Hywindspar FOWT models in tandem layout under shear wind and regular wave conditions are performed using this tool. The unsteady aerodynamics of wind turbines are given by the UALM, and the hydrodynamic responses of floating platforms and mooring tensions are predicted by naoe-FOAM-SJTU. From the simulations, unsteady aerodynamic characteristics can be extracted including the rotor power and thrust as well as detailed wake flow information, and hydrodynamic responses such as the six-degree-of-freedom motions and mooring tensions are also available. Moreover, the influence of wake interaction on the performance of FOWTs is studied. It can be found that strong wake interaction phenomenon is observed and the unsteady aero-hydrodynamic responses of downstream FOWT system are greatly affected by the wake interaction.

Language：English   Publishing type：Research paper (international conference proceedings)  

The wake interaction phenomenon among wind turbines has a great influence on aerodynamic power output, wind speed deficit turbulence stress and wake vortex structure, which indicates that more attention should be placed on the wake interaction for the optimal arrangement of wind farm. In this present study, firstly a numerical validation of aerodynamics for the two offset model wind turbines using actuator line model and CFD technique. The results obtained from the present simulations are compared to the data from the experiment “Blind Test 3” and other simulation models. Based on the simulations results, the present study shows good agreement with the experimental results. Then considering the uniform inflow condition, the complex phenomenon of wake interaction in wind farm containing fourteen wind turbines is simulated using a numerical method. Large eddy simulations combined with an actuator line model are conducted in the in-house CFD code FOWT-UALM-SJTU Solver. The motivation for this work is to create a sound methodology for performing the simulation of large wind farms. To better understand the wake interaction phenomenon, the aerodynamic power coefficients and basic features of both the near and far wake, including the distribution characteristics of the mean wake velocity and vortex structures are studied in detail.

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper addresses the modeling and attitude control of a novel shrouded floating wind turbine with hinged structure in harsh environmental conditions. Firstly, SimMechanics™ is applied to model the mechanical components of the wind turbine system. Secondly, the wave- and wind- loads acting on the system are respectively calculated based on Morison's equation and blade element momentum theory. Controllers of the elevator and the rudder located at the upwind side are designed based on linearized models to enhance the stability of the system. Numerical examples with three extreme weather conditions are finally performed to verify the effectiveness of the controllers. The results demonstrate that the pitching motion of the nacelle can be regulated to be within 3 degrees in the examples. In addition, the wind turbine could yaw itself stably toward the wind direction.

DOI： 10.1109/DISTRA.2017.8191162

Language：English   Publishing type：Research paper (scientific journal)  

The purpose of the present research is to study three-dimensional lattice Boltzmann method (LBM) simulation on free surface impact phenomena with the validation on a newly performed dam breaking experiment. Large eddy simulation (LES) is implemented in the LBM to enhance the computational efficiency and to relax the restriction of the computational stability. The LBM method involves a surface-tracking technique with free surface algorithm. In this study, the present numerical simulation is validated by comparing wave front propagation and water level elevation with the experimental measurements. A three dimensional numerical simulation on dam breaking with vertical cylinder obstacles are performed and qualitative comparison with the experimental measurement has been made. Good qualitative agreement between numerical simulations and the experiments has been obtained in terms of free surface development, splash pattern and splash distance. For the square cross section cylinder, the water impacts on the cylinder violently and the flow is directed to the sides of the tank. For the circular cross section cylinder, the water flows smoothly around the cylinder and impacts tank wall violently. The results show that the free surface lattice Boltzmann method is efficient for dealing with complex geometrical problems.

Language：English   Publishing type：Research paper (scientific journal)  

The purpose of the present research is to study three-dimensional lattice Boltzmann method (LBM) simulation on free surface impact phenomena with the validation on a newly performed dam breaking experiment. Large eddy simulation (LES) is implemented in the LBM to enhance the computational efficiency and to relax the restriction of the computational stability. The LBM method involves a surface-tracking technique with free surface algorithm. In this study, the present numerical simulation is validated by comparing wave front propagation and water level elevation with the experimental measurements. A three dimensional numerical simulation on dam breaking with vertical cylinder obstacles are performed and qualitative comparison with the experimental measurement has been made. Good qualitative agreement between numerical simulations and the experiments has been obtained in terms of free surface development, splash pattern and splash distance. For the square cross section cylinder, the water impacts on the cylinder violently and the flow is directed to the sides of the tank. For the circular cross section cylinder, the water flows smoothly around the cylinder and impacts tank wall violently. The results show that the free surface lattice Boltzmann method is efficient for dealing with complex geometrical problems.

Language：English   Publishing type：Research paper (international conference proceedings)  

To develop renewable energy, the offshore wind energy technology has become an attractive research field. Considering the coupling effect of the platform motions and aerodynamic loads, how to accurately simulate the aero-hydrodynamics of floating offshore wind turbine is important. In this paper, an unsteady actuator line model (UALM) coupled with a two-phase CFD solver called naoe-FOAM-SJTU is applied to solve the three-dimensional Navier-Stokes equations to focus on the coupled dynamic responses of an aerodynamics-hydrodynamics-mooring system for a floating offshore wind turbine named OC3-HywindSpar under extreme sea conditions. Response characteristics including the thrust and the rotor power of the wind turbine, the motions of the platform and the mooring loads under different extreme sea states are carefully compared to study the influence of the wind speed and the wave height on the floating offshore wind turbine. Furthermore, several conclusions are drawn based on the comparison results.

Language：English   Publishing type：Research paper (scientific journal)  

In the original publication of this paper, Fig. 4 was incorrectly published. The corrected version is given in this erratum. (Figure Presented.).

DOI： 10.1007/s00773-016-0427-5

Language：English   Publishing type：Research paper (international conference proceedings)  

When considering flows with multiple fluids such as free surface flow and multiphase flow, an interface tracking scheme or an interface capturing scheme is required for treatment of the interfaces. The latter is more popular with CFD community due to its adaptability to different flow structures and different kinds of grids as well as its good computational efficiency. The THINC scheme is an interface capturing scheme which was originally developed for use with Cartesian grid flow solvers. Since the method provides an algebraic model for the transition between different fluids it becomes relatively easy to compute the convective fluxes which is the target of advection schemes. In this work, we apply an unstructured grid extension of the THINC scheme, UMTHINC scheme, to our newly developed unstructured grid flow solver for free surface impact problems. The efficiency and accuracy of the proposed method is investigated by applying it to some standard benchmark cases on dam break problem with an obstacle. Both two and three dimensional simulations are carried out and the results are compared to experimental data wherever possible.

Language：English   Publishing type：Research paper (other academic)  

In rough sea conditions, semi-submersible platform often suffers from extreme wave impact loads, which can result in structural damage. It is important to predict the wave impact loads on semi-submersible platform. Therefore, the purpose of this study is to investigate the wave impact loads on semisubmersible platform with numerical methods. A numerical method, based on a fixed regular Cartesian grid system, has been developed by the authors. In the method, the FDM (Finite Difference Method) is applied for solving flow field, and the THINC/SW (Tangent of Hyperbola for INterface Capturing with Slope Weighting) model, which is kind of VOF (Volumeof- Fluid) model, is adopted to capture the free surface. Some selected model test cases, form Exwave JIP project, will be used to validate the present numerical method and to analyze the wave impact loads on semi-submersible platform.

DOI： 10.1115/OMAE2017-62464

Language：English   Publishing type：Research paper (international conference proceedings)  

Among several wind farm layout design parameters, the inter-turbine spacing, which has a great influence on aerodynamic power output, wind speed deficit, lifetime, wake vortex structure, is one of the most critical factors. Therefore, the effects of inter-turbine spacing on aerodynamics for wind farms must be carefully studied. In this study, Considering the uniform inflow conditions, the effects of inter-turbine spacing changing from three to nine times of rotor diameter on aerodynamics for wind farms containing two NREL 5MW baseline wind turbines in tandem layout are analyzed using actuator line model and CFD method, and the RANS equation with k-ω SST turbulence model was solved in the simulations conducted in the OpenFOAM. From the study, it is concluded that the inter-turbine spacing has significant effects on the aerodynamic power and wake characteristics. The aerodynamic power output of the downstream wind turbine exits sharp fluctuation before power output of the downstream wind turbine is becoming steady. Furthermore, periodic oscillation whose period is about the one-third of rotor rotating period can be also concluded from the study. Moreover, there is strong wake interaction which will impact the aerodynamics for wind farms seriously.

Language：English   Publishing type：Research paper (scientific journal)  

Three-dimensional numerical simulations of strongly nonlinear free surface flows are performed by lattice Boltzmann method (LBM), which features a number of performance-related advantages, particularly concerning data locality and parallel computing. A Multi-Passage-Interface (MPI) multicore processors parallelized free surface LBM solver is applied for the present three-dimensional numerical simulations. A Smagorinsky LES turbulent model serves to capture the small-scale turbulent structures of the flow. Experiments on dam breaking from previous articles are used to compare and verify two-dimensional (2D) and three-dimensional (3D) LBM model. A new experimental setup is also developed in order to observe the three-dimensionality effect. The findings demonstrated that the free surface LBM simulation agrees well with the experiments.

Language：English   Publishing type：Research paper (scientific journal)  

This work presents an application of the Unstructured Multi-dimensional Tangent Hyperbolic Interface Capturing (UMTHINC), volume of fluid, scheme for the multi-phase solution of free surface flows on unstructured mesh. The applicability of the UMTHINC to practical engineering problems with interfacial multiphase flow is investigated and the accuracy of the results are reported. The UMTHINC is integrated into an in-house unstructured incompressible flow solver and used as an engine to capture the moving interface. The well-known dam break problems with and without an obstacle are used to evaluate the accuracy and performance of the scheme. This work is limited to two dimensional cases with no turbulence modeling. The relationship between the sharpness parameter β, and CFL number is examined and reported. The results are well analyzed and compared to experimental data wherever possible. The results show that the UMTHINC interface capturing method is able to accurately capture the interface without the complexity and computation cost of the geometrical reconstruction method.

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00773-016-0390-1

Language：English   Publishing type：Research paper (scientific journal)  

In this study, we established non-linear time-domain coupled dynamic equations and aero/hydro-dynamical models to study the interaction between wind waves and floating offshore turbine systems (FOWTs). We used Fortran code, time-frequency domain transformation, and the Runge-Kutta iteration method to solve nonlinear equations. We analyzed the 5DOF motion response characteristics of Spar FOWTs, except yawing, under steady wind wave, regular wave, and random wind-wave conditions. The results show that constant wind affects the average and peak-to-peak values of surge, pitch, heave, sway, and roll at the rated wind speeds, while it does not affect the peak-to-peak values of sway at other wind speeds. In addition, regular waves have only marginal effect on the average values of surge, pitch, heave, sway, and roll, but enlarge their peak-to-peak values. Under random wind and wave conditions, we characterized the system's sway and pitch motions for low and high wave frequencies, depending on the wind speed. The results of this study provide references for the design and hydrodynamic analysis of offshore floating wind turbine systems.

DOI： 10.11990/jheu.201510073

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1115/1.4033948

Language：English   Publishing type：Research paper (international conference proceedings)  

The aerodynamic performance of the floating offshore wind turbine has an extra level of complexity than that of bottom-fixed wind turbines because of the motions of the supporting platform. In this paper, the unsteady aerodynamic performance of the NREL-5MW Baseline wind turbine with periodical surge and pitch motions of its supporting platform are investigated. The three-dimensional Reynolds Averaged Navier-Stokes equations are solved for the aerodynamic numerical simulation. The naoe-FOAM-os-SJTU solver, which is based on OpenFOAM and overset grid technology and developed for ship and ocean engineering problems, is employed. From the simulation, the time series of the unsteady torque and thrust are obtained, together with the detailed information of the wake flow field, and the pressure coefficient distribution in different cross-section are also available to clarity the detailed flow filed information. The simulation results are compared both with those obtained from aerodynamic simulation of wind turbine without effects of platform motions, and with other approaches in previous studies. The simulation results show that the pitch motion has more significant effects on the aerodynamic forces and moments of the rotor than the surge motion does. And the motion of the platform especially the pitch motion may bring very bad influence on the turbine forces and wake flow, even on the power generation in case of very severe pitch motion.

Language：English   Publishing type：Research paper (international conference proceedings)  

With the development of ocean energy exploration, reliable and low cost semi-submersible platforms are expected to develop. The maximum pitching amplitude of a floater for floating offshore wind turbine should be less than a few degrees to avoid fatigue failure. In this paper, a novel conceptual design of a new type semi-submersible with suspensions for suppressing the pitch motion is presented. Many wave energy dissipation devices, such as add-onwave energy converters to a floating platform, could be regarded as the suspension system in our design. Firstly, linear models are applied to approximate the radiation forces and wave exciting forces so that the whole motion system is represented by a state-space model. Then, we show that design of suspensions leads to synthesize a controller via solving a constrained H∞ optimization problem. Finally, numerical examples are performed to verify the design and it can be shown that the pitch motion of the semi-submersible platform is remarkably reduced.

DOI： 10.1115/OMAE2016-54347

Language：English   Publishing type：Research paper (scientific journal)  

With the development of ocean energy exploration, reliable floating platforms with very small motion are expected to develop. For instance, the maximum pitching amplitude of a floater for floating offshore wind turbine is required to be less than a few degrees. On the other hand, ocean waves contain abundance of untapped renewable energy with very high power density. Integration of floating platform with wave energy converters while reducing the structure interaction becomes significant for offshore development. In this paper, control of wave energy converters on reducing the pitch motion of a floating platform is studied. Firstly, mathematical model of the whole system is proposed. The control of wave energy converters leads to solve a constrained optimization problem. Secondly, hybrid model predictive control is presented to synthesize the controller. Finally, numerical examples are given to verify the effectiveness of the proposed controller. It is shown that the reduction of pitch motion of the platform and the wave energy extraction are compatible.

DOI： 10.1016/j.ifacol.2016.10.434

Language：English   Publishing type：Research paper (other academic)  

An Unsteady Actuator Line Model (UALM) is developed in this paper and applied to a 5MW floating offshore wind turbine (FOWT). This model is implemented into two-phase fluid CFD solver, naoeFOAMSJTU. The goal of the approach presented here is to investigate the interaction of the aerodynamic loads with the platform motion within acceptable time cost. A semi-submerged floating platform conceptualized in the Offshore Code Comparison Collaboration (OC4) is considered in this paper. Initially the UALM is verified by comparison with the results of a previous study. Next, two kind of fullsystem simulations with different complexity are performed: first, the wind forces are simplified into a constant thrust; second, the fully coupled dynamic analysis with wind and wave excitation is conducted by utilizing UALM. Based on the results, the aerodynamic loads and coupled responses for cases of different complexity are discussed.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00773-015-0326-1

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.apor.2015.02.002

Language：English   Publishing type：Research paper (scientific journal)  

An improved boundary element method is presented for numerical analysis of hydrodynamic behavior of marine structures. A new algorithm for numerical solution of the finite depth free-surface Green function in three dimensions is developed based on multiple series representations. The whole range of the key parameter R/h is divided into four regions, within which different representation is used to achieve fast convergence. The well-known epsilon algorithm is also adopted to accelerate the convergence. The critical convergence criteria for each representation are investigated and provided. The proposed method is validated by several well-documented benchmark problems.

DOI： 10.1515/ijnaoe-2015-0026

Language：English   Publishing type：Research paper (other academic)  

A diffraction-radiation analysis is usually required when the hydrodynamic interactions between structural members occur in short waves. For bracings or small cylinder members, which play important roles in the vicinity of the natural frequency of a floating platform, special care should be taken into account for the effect of viscous damping. Two hybrid panel-stick models are therefore developed, through the combination of the standard diffraction-radiation method and the Morison's formulae, while considering the effect of small members differently. The fluid velocity is obtained directly by the panel model. The viscous fluid force is calculated for individual members by the stick model. A semi-submersible type platform with a number of fine cylindrical structures, which is designed as a floating foundation for multiple wind turbines, is analysed as a numerical example. The results show that viscous force has large influence on the behaviour of the floating body and can successfully be considered by the proposed hybrid models.

Language：Japanese   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00773-013-0252-z

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s11242-014-0329-0

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.4028/www.scientific.net/AMM.543-547.434

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s12650-013-0194-x

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s12650-013-0194-x

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Hydroelastic behavior of an elastic wedge impacting on calm water surface was investigated. A partitioned approach by coupling finite difference method (FDM) and finite element method (FEM) was developed to analyze the fluid structure interaction (FSI) problem. The FDM, in which the Constraint Interpolation Profile (CIP) method was applied, was used for solving the flow field in a fixed regular Cartesian grid system. Free surface was captured by the Tangent of Hyperbola for Interface Capturing with Slope Weighting (THINC/SW) scheme. The FEM was applied for calculating the structural deformation. A volume weighted method, which was based on the immersed boundary (IB) method, was adopted for coupling the FDM and the FEM together. An elastic wedge water entry problem was calculated by the coupled FDM-FEM method. Also a comparison between the current numerical results and the published results indicate that the coupled FDM-FEM method has reasonably good accuracy in predicting the impact force.

DOI： 10.1007/s11804-013-1181-2

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (other academic)  

Numerical Simulation of Water Wave by THINC Scheme

Language：Japanese   Publishing type：Research paper (other academic)  

Numerical Simulation of Ship Motion in Oblique Waves by CIP based Cartesian Grid Method

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1115/1.2199558

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (other academic)  

3D numerical simulation of strongly nonlinear ship-wave interactions by CIP method
Changhong Hu, Masashi Kashiwagi
Proc. 15th Computational Mechanics Conference

Language：Japanese   Publishing type：Research paper (other academic)  

3D numerical simulation of strongly nonlinear ship-wave interactions by CIP method
Changhong Hu, Masashi Kashiwagi
Proc. 15th Computational Mechanics Conference

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00773-003-0171-5

Language：Japanese   Publishing type：Research paper (other academic)  

Numerical Study on Interaction of Waves with Structures by CIP Method
Changhong Hu, Masashi Kashiwagi and Tsutomu Momoki
Proc. 15th Computational Mechanics Conference
pp. 433-434

Language：Japanese   Publishing type：Research paper (scientific journal)  

A Study on the Ventilation System of Metallic Fume and the Working Environment
in a Fabrication Shop　(Part 1) The Analysis of Fume Transportation in Turbulent flow
Changhong Hu and Nobuyoshi Fukuchi
Journal of the Society of Naval Architects of Japan
Vol. 191, pp. 159-168

Language：Japanese   Publishing type：Research paper (scientific journal)  

A Study on Numerical Simulation of Turbulent Natural Convection by LES
Changhong Hu and Nobuyoshi Fukuchi
Transactions of the West-Japan Society of Naval Architects
Vol. 102, pp. 209-217

Language：Japanese   Publishing type：Research paper (scientific journal)  

The Characteristic Analysis of Turbulent Diffusion on the Functional Design of Marine Systems (Part 2) The Effect of Heat Radiation on Turbulent Natural Convection in an Enclosure
Changhong Hu, Nobuyoshi Fukuchi and Tohru Nakashima
Journal of the Society of Naval Architects of Japan
Vol 189, pp.127-135

Language：Japanese   Publishing type：Research paper (scientific journal)  

Three Dimensional Numerical Simulation of the Turbulent Thermal Convection in an Open Compartment
Changhong Hu, Nobuyoshi Fukuchi and Koichi Yoshida
Transactions of the West-Japan Society of Naval Architects
Vol. 100, pp. 189-198

Language：Japanese   Publishing type：Research paper (scientific journal)  

Computation of Turbulent Thermal Convection with Large Temperature Variation (Part 1) Numerical Simulation of Compressible Flow Using Low Mach-Number Approximation
Changhong Hu and Nobuyoshi Fukuchi
Journal of the Society of Naval Architects of Japan
Vol. 186, pp. 663-671

Language：Japanese   Publishing type：Research paper (scientific journal)  

The Threshold Conditions and Characteristic Analysis of the Marine Fire Spread Phenomena (Part 2) Heat Transfer in Multi-Compartments by Field Mathematical Model
Nobuyoshi Fukuchi, Changhong Hu, Hiromasa Ohishi and Hisahiro Fujii
Journal of the Society of Naval Architects of Japan
Vol 185, pp. 151-162

Language：Japanese   Publishing type：Research paper (scientific journal)  

A Numerical Analysis on Instability os Stratified Shear Flow
Changhong Hu and Nobuyoshi Fukuchi
Journal of the Society of Naval Architects of Japan
Vol 183, pp. 19-26

Event date： 2019.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Qingdao   Country：China  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nantes   Country：France  

Event date： 2012.9

Presentation type：Oral presentation (invited, special)  

Venue：Nantes   Country：France  

Development of CIP Based Cartesian Grid Method and Its Application to Strongly Nonlinear Wave-Body Interactions

Presentation type：Oral presentation (general)  

Venue：Trondheim   Country：Norway  

Presentation type：Oral presentation (invited, special)  

Venue：京都大学   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Hamburg   Country：Germany  

Event date： 2023.11 - 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：東京   Country：Japan  

Event date： 2023.11 - 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：東京   Country：Japan  

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：長崎   Country：Japan  

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：長崎   Country：Japan  

Event date： 2022.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Online   Country：Japan  

Event date： 2022.5

Language：English  

Venue：Online   Country：Japan  

researchmap

Event date： 2021.5 - 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Online   Country：Japan  

Event date： 2021.5 - 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Online   Country：Japan  

Event date： 2021.5 - 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Online   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Online   Country：Japan  

Event date： 2019.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Shanghai   Country：China  

Event date： 2019.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Hiroshima   Country：Japan  

Event date： 2019.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Toki   Country：Japan  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Hamburg   Country：Germany  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Napoli   Country：Italy  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎   Country：Japan  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎   Country：Japan  

Event date： 2019.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Harbin   Country：China  

Event date： 2018.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Taipei   Country：Taiwan, Province of China  

Event date： 2018.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Taipei   Country：Taiwan, Province of China  

Event date： 2018.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Shanghai   Country：China  

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪   Country：Japan  

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪   Country：Japan  

Event date： 2018.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Guidel-Plages   Country：France  

Event date： 2017.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Keelung   Country：Taiwan, Province of China  

Event date： 2017.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Trondheim   Country：Norway  

Event date： 2017.6

Language：English   Presentation type：Oral presentation (general)  

Venue：San Francisco   Country：United States  

Event date： 2017.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Dalian   Country：China  

Event date： 2016.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Event date： 2016.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Trondheim   Country：Norway  

Event date： 2016.6 - 2016.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Rhodes   Country：Greece  

Event date： 2016.6 - 2016.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Rhodes   Country：Greece  

Event date： 2016.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Busan   Country：Korea, Republic of  

Event date： 2016.5

Language：English   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Event date： 2016.5

Language：English   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Event date： 2016.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Michigan   Country：United States  

Event date： 2015.12 - 2014.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Fukuoka   Country：Japan  

Event date： 2015.12 - 2014.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Fukuoka   Country：Japan  

Event date： 2015.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Nantes   Country：France  

Event date： 2015.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Hawaii   Country：United States  

Event date： 2015.5 - 2015.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Newfoundland   Country：Canada  

Event date： 2015.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2014.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Tokyo   Country：Japan  

Event date： 2014.11

Language：English   Presentation type：Oral presentation (general)  

Venue：長崎   Country：Japan  

Event date： 2014.11

Language：English   Presentation type：Oral presentation (general)  

Venue：長崎   Country：Japan  

Event date： 2014.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Shanghai   Country：China  

Event date： 2014.7 - 2014.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Tokyo   Country：Japan  

Event date： 2014.7 - 2014.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Tokyo   Country：Japan  

Event date： 2014.7 - 2014.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Tokyo   Country：Japan  

Event date： 2014.7 - 2014.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Tokyo   Country：Japan  

Event date： 2014.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Busan   Country：Korea, Republic of  

Event date： 2014.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Busan   Country：Korea, Republic of  

Event date： 2014.4

Language：English   Presentation type：Oral presentation (general)  

Venue：仙台   Country：Japan  

Event date： 2013.12

Language：English   Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nantes   Country：France  

Event date： 2013.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島   Country：Japan  

CFD Simulation of a Floating Wind Turbine Foundation in Waves

Event date： 2013.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島   Country：Japan  

Experimental Study of a Triangular Semi-submergible Floating Body for Wind Turbines

Event date： 2012.9

Presentation type：Oral presentation (general)  

Venue：Nantes   Country：France  

Large-Scale Simulation of Violent Flow Impacting on an Obstacle

Event date： 2012.9

Presentation type：Oral presentation (general)  

Venue：Nantes   Country：France  

Parallel Simulation of RIAM-CMEN for Strongly Nonlinear Wave-Ship Interaction

Event date： 2012.7

Presentation type：Oral presentation (general)  

Venue：Rio de Janeiro   Country：Brazil  

VIV Simulation of 2-D Deformable Cylinder Using Coupled FDM/FEM Method

Event date： 2012.5

Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Development of a Hybrid LBM/FVM Approach for Numerical Simulation of CO2

Event date： 2012.5

Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Demonstration Experiment of Offshore Wind Power Generation on a Floating Platform in Hakata Bay

Event date： 2012.5

Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

2-D Numerical Simulation of Elastic Floating Structure Response to Regular Waves

Event date： 2012.5

Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

2-D Numerical Simulation of Elastic Floating Structure Response to Regular Waves

Event date： 2011.12

Presentation type：Oral presentation (general)  

Venue：大阪   Country：Japan  

Event date： 2011.9

Presentation type：Oral presentation (general)  

Venue：Shanghai   Country：China  

Event date： 2011.5

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Numerical Simulation of Floating Wind Turbine Platform in Large Waves

Event date： 2011.4

Presentation type：Oral presentation (general)  

Venue：Athens, Greece   Country：Japan  

Event date： 2010.12

Presentation type：Oral presentation (general)  

Venue：Gothenburg   Country：Sweden  

Event date： 2010.11 - 2010.10

Presentation type：Oral presentation (general)  

Venue：Portsmouth   Country：United Kingdom  

Event date： 2010.10

Presentation type：Oral presentation (general)  

Venue：Shanghai   Country：China  

Event date： 2010.7

Presentation type：Oral presentation (general)  

Venue：Sydney   Country：Australia  

Event date： 2010.6

Presentation type：Oral presentation (general)  

Venue：Shanghai   Country：China  

Event date： 2010.5

Presentation type：Oral presentation (general)  

Venue：Harbin   Country：China  

Event date： 2010.1

Presentation type：Oral presentation (general)  

Venue：Harbin   Country：China  

Event date： 2009.11

Presentation type：Oral presentation (general)  

Venue：熊本県荒尾市   Country：Japan  

Numerical Simulation of Ship Motion in Oblique Waves by CIP based Cartesian Grid Method

Event date： 2009.10

Presentation type：Oral presentation (general)  

Venue：金沢   Country：Japan  

Numerical Simulation of Water Wave by THINC Scheme

Event date： 2009.6

Presentation type：Oral presentation (general)  

Venue：Osaka   Country：Japan  

Event date： 2009.4

Presentation type：Oral presentation (general)  

Venue：Tokyo   Country：Japan  

Event date： 2008.11

Presentation type：Oral presentation (general)  

Venue：沖縄   Country：Japan  

Event date： 2008.10

Presentation type：Oral presentation (general)  

Venue：Chiba   Country：Japan  

Event date： 2008.10

Venue：Soeul   Country：Korea, Republic of  

Event date： 2008.7

Presentation type：Oral presentation (general)  

Venue：Vancouver   Country：Canada  

Event date： 2008.4

Presentation type：Oral presentation (general)  

Venue：Jeju   Country：Korea, Republic of  

Event date： 2008.2

Presentation type：Oral presentation (general)  

Venue：Osaka   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Busan   Country：Korea, Republic of  

Development of CFD Simulation Method for Extreme Wave-Body Interactions
Changhong Hu and Masashi Kashiwagi
8th International Conference on Numerical Ship Hydrodynamics
Busan, Korea, Sep. 2003

Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Three Dimensional Numerical Simulation of Water on Deck by CIP Method
Changhong Hu, Masashi Kashiwagi and Zdravko
The autumn conference of the Society of Naval Architects of Japan
Kobe, Nov. 2003

Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

On the Precision of Numerical Simulation of Wave Impact Phenomenon by CIP Method
Changhong Hu and Masashi Kashiwagi
The 16th Computational Mechanics Conference
Kobe, Nov. 2003

Presentation type：Oral presentation (general)  

Venue：広島大学   Country：Japan  

Application of CIP-CSL3 Scheme for Capturing Extremely Nonlinear Free Surface
Changhong Hu and Masashi Kashiwagi
9th Symposium on Nonlinear and Free-Surface Flows
Hiroshima University, Dec. 2003

Presentation type：Oral presentation (general)  

Venue：Cortona   Country：Italy  

Numerical Simulation of Violent Sloshing by CIP Method
Changhong Hu, Masashi Kashiwagi and Zdravko Kishev
19th International Workshop on Water Waves and Floating Bodies
Cortona, Italy, 28-31 March, 2004

Presentation type：Oral presentation (general)  

Venue：Hamburg   Country：Germany  

Development and Validation of CIP based Cartesian Grid Method for Nonlinear Wave-Body Interactions
Changhong Hu, Odd Faltinsen and Masashi Kashiwagi
7th Numerical Towing Tank Symposium
Hamburg, Germany, 3-5 Oct. 2004.

Presentation type：Oral presentation (general)  

Venue：Longyearbyen   Country：Norway  

3-D Numerical Simulation of Water-Entry Problem by CIP based Cartesian Grid Method
Changhong Hu, Odd Faltinsen and Masashi Kashiwagi
20th International Workshop on Water Waves and Floating Bodies
Longyearbyen, Norway, 29 May-1 June, 2005

Presentation type：Oral presentation (general)  

Venue：Seoul   Country：Korea, Republic of  

3-D Numerical Simulation of Freely Moving Floating Body by CIP Method
Changhong Hu, Odd Faltinsen and Masashi Kashiwagi
15th International Offshore and Polar Engineering Conference
Seoul, Korea, 19-24 June 2005

Presentation type：Oral presentation (general)  

Venue：Shanghai   Country：China  

Recent Progress in CIP Method for Strongly Nonlinear Ship-Wave Interactions
Changhong Hu, Masashi Kashiwagi and Odd Faltinsen
4th Interactional Workshop on Ship Hydrodynamics
Shanghai, China, 24-27 Sept., 2005

Presentation type：Oral presentation (general)  

Venue：Varna   Country：Bulgaria  

3-D Computation of Ship-Wave Interaction by CIP / Cartesian Grid Method
Changhong Hu, Masashi Kashiwagi and Odd Faltinsen
8th Numerical Towing Tank Symposium
Varna, Bulgaria, 2-4 Oct., 2005

Presentation type：Oral presentation (general)  

Venue：筑波大学   Country：Japan  

3D numerical simulation of strongly nonlinear ship-wave interactions by CIP method
Changhong Hu, Masashi Kashiwagi
The 15th Computational Mechanics Conference
Tsukuba University, Japan, 19-21 Nov., 2005

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

On the NTNU Center for Ships and Ocean Structures
Changhong Hu
The autumn conference of the Japan Society of Naval Architects and Ocean Engineers
Fukuoka, Japan, 24-25 Nov., 2005

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Validation of CIP based Method for Strongly Nonlinear Wave-Body Interactions
Changhong Hu, Akihiko Kitadai and Masashi Kashiwagi
The autumn conference of the Japan Society of Naval Architects and Ocean Engineers
Fukuoka, Japan, 24-25 Nov., 2005

Presentation type：Oral presentation (general)  

Venue：京都大学   Country：Japan  

Numerical Simulation of Strongly Nonlinear Free Surface Problems by CIP Method
Changhong Hu and Masashi Kashiwagi
55th National Congress of Theoretical & Applied Mechanics
Kyoto, Japan, 24-26 Jan., 2006

Presentation type：Oral presentation (general)  

Venue：Loughborough   Country：United Kingdom  

Presentation type：Oral presentation (general)  

Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Shanghai   Country：China  

Presentation type：Oral presentation (general)  

Venue：金沢   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Andorra  

Presentation type：Oral presentation (general)  

Venue：熊本大学   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Le Croisic   Country：France  

Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：東京大学   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Michigan   Country：United States  

Presentation type：Oral presentation (general)  

Venue：Houston, Texas   Country：United States  

Presentation type：Oral presentation (general)  

Venue：今治   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：今治   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Fukuoka   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Kyoto   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：東京   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：徳島大学   Country：Japan  

Numerical Simulation of Extreme Wave-Body Interaction by CIP Method
Changhong Hu and Masashi Kashiwagi
Mechanical Engineering Congress, 2003 Japan
Tokushima University, Aug. 2003

Presentation type：Oral presentation (general)  

Venue：中央大学(東京都）   Country：Japan  

A Basic Study on Instability of Stratified Shear Flow
Changhong Hu and Nobuyoshi Fukuchi
The spring conference of the Society of Naval Architects of Japan
Tokyo, May 1998

Presentation type：Oral presentation (general)  

Venue：Atlanta   Country：United States  

A Numerical Analysis in Instability of Stratified Shear Flow
Nobuyoshi Fukuchi and Changhong Hu
ICES'98
Atlanta, USA, Oct. 1998

Presentation type：Oral presentation (general)  

Venue：中央大学(東京都）   Country：Japan  

Impact Pressure on a Horizontal Platform by a Solitary Wave
Yusaku Kyozuka, Susumu Sugiyama, Changhong Hu
No. 97 conference of the West-Japan Society of Naval Architects
Tokyo, Nov. 1998

Presentation type：Oral presentation (general)  

Venue：中央大学(東京都）   Country：Japan  

The Effect of Richardson Number and Reynolds Number on Stability of a ShearedDensity Interface
Nobuyoshi Fukuchi, Changhong Hu, Takeshi Shinoda, Yousuke Nakamura and Junichi Mori
Tokyo, Nov. 1998

Presentation type：Oral presentation (general)  

Venue：中央大学(東京都）   Country：Japan  

The Threshold Conditions and Characteristic Analysis of the Marine Fire Spread Phenomena (Part 2) Heat Transfer in Multi-Compartments by Field Mathematical Model
Nobuyoshi Fukuchi, Changhong Hu, Hiromasa Ohishi and Hisahiro Fujii
The spring conference of the Society of Naval Architects of Japan
Tokyo, May 1999

Presentation type：Oral presentation (general)  

Venue：長崎市   Country：Japan  

Computation of Turbulent Thermal Convection with Large Temperature Variation (Part 1) Numerical Simulation of Compressible Flow Using Low Mach-Number Approximation
Changhong Hu and Nobuyoshi Fukuchi
The autumn conference of the Society of Naval Architects of Japan
Nagasaki, Nov. 1999

Presentation type：Oral presentation (general)  

Venue：佐世保市   Country：Japan  

Three Dimensional Numerical Simulation of the Turbulent Thermal Convection in an Open Compartment
Changhong Hu, Nobuyoshi Fukuchi and Koichi Yoshida
No. 100 conference of the West-Japan Society of Naval Architects
Sasebo, May 2000