Language：English   Publisher：Computational Particle Mechanics  

This work shows the extension of a corrected Arbitrary Lagrangian Eulerian Incompressible Smoothed Particle Hydrodynamics (ALE-ISPH) method to surface tension simulations. In this context, the term “corrected” refers to the fact that all derivative operators are modified to enable first-order accuracy. Moreover, particles move according to a transport velocity, which is the summation of the material velocity and a small shifting of particle location to promote a smooth particle distribution at every step; hence, it is based on an ALE formulation. Using this method as a basis, we propose some small empirical modifications to the conventional curvature-based calculation of surface tension forces to simulate this phenomenon. Furthermore, we propose a special wall boundary treatment including ghost particles to reproduce the desired contact angles. Validation and verification tests include the obtaining of the theoretical Laplace pressure in a water droplet, the analysis of the frequency of an oscillating 3D droplet, the comparison of the capillary rise with the theoretical value and the collision of water droplets compared to physical experiments. All numerical simulations were successful, so we consider this to be a reasonable method to simulate the phenomena of surface tension under a wide range of conditions.

DOI： 10.1007/s40571-023-00666-y

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Language：Japanese   Publisher：JAPAN SOCIETY FOR COMPUTATIONAL ENGINEERING AND SCIENCE  

<p>While the particle method is suitable for representation of large and discontinuous deformations, it is prone to accuracy degradation and numerical instability due to issues with particle distribution. To solve this problem, SPH(2) has been proposed, which can perform highly accurate calculations even when there are disturbances in the particle distribution. But is still limited in overcoming numerical instability. From previous studies, it is found that more stable and accurate calculations can be achieved by using SPH(2) in combination with the particle shifting technique. However, the existing particle shifting technique tends to expand the volume in the long term smulations. Therefore, we propose a new particle rearrangement method that can simultaneously improve particle homogeneous distribution and volume conservation. For this purpose, it is also important to use the proposed method in combination with other stabilization techniques, and our policy is to sort out the roles of various stabilization techniques and eliminate unnecessary terms. In addition, the numerical stability and accuracy improvement of the proposed method are demonstrated by Rotating square patch fluid simulations and Dam break simulations.</p>

DOI： 10.11421/jsces.2024.20241007

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CiNii Research

Language：Japanese   Publisher：JAPAN SOCIETY FOR COMPUTATIONAL ENGINEERING AND SCIENCE  

<p>The discontinuous Galerkin (DG) method is effective and promising tool for the hyperbolic equations with discontinuities. In recent years, the DG method has been applied and shown to be effective in the analysis of shallow water equations (SWEs), which are widely used for river flooding, storm surge, tsunami, and other natural disaster simulations. In this study, the DG method is applied to the governing equations for riverbed variation, which are coupling of the SWEs and equilibrium sediment transport equation, and wetting-drying treatment and numerical flux are discussed for our purpose. The proposed method has been verified with numerical analysis such as erodible dam-break flow and sandbar migration simulation. The numerical results have shown that the proposed method is effective for riverbed variation analysis.</p>

DOI： 10.11421/jsces.2024.20241006

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CiNii Research

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

粒状体からなる斜面安定性を数値解析で評価し、また流動後の構造物に作用する力までを連続体力学モデルとして定量的に評価するための新しい技術を提案した。レオロジーモデル自身は、すでに発表されたモデルではあるが、それを粒子法で実装し、また高速化までを実現するためにGPU計算機上で陰的な時間積分法を採用した。これにより、従来モデルには実現できなかった高速化を達成することができた。

DOI： https://doi.org/10.2208/jscejj.23-15018

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

DOI： https://doi.org/10.2208/jscejj.22-15019

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.tafmec.2024.104599

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1007/s40571-024-00856-2

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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

Accurate simulations of cracks remain a challenging task in the computational mechanics community. The main purpose of this work is to develop a nodal-based Lagrange multiplier/cohesive zone (LM/CZ) method for arbitrary three-dimensional (3D) crack simulations in the finite element (FE) models of quasi-brittle materials. The main idea of the developed method is to fulfill the displacement compatibility condition before crack onset via LMs enforced at nodes and describe crack behaviors with the aid of the cohesive zone model (CZM). The main appeal of our method lies in effectively addressing the so-called artificial compliance numerical issue arising in the conventional intrinsic CZMs, thereby yielding more accurate numerical results than intrinsic CZMs. Node-pair groups are generated via a robust data structure. In each group, the LM forces for all nodal pairs are calculated in a predictor–corrector form, which can achieve convergence within a limited number of iterations using the Gauss–Seidel method. Two loop types for nodal pairs are compared to find a more efficient scheme with fewer iterations. The nodal constraints are smoothly switched from LMs to cohesive forces after a defined fracture criterion is satisfied. The developed method is implemented in conjunction with tetrahedral elements. Several quasi-static numerical examples, including modes I and I/II cracks, are performed to demonstrate the numerical accuracy of our developed method. Finally, this work simulates a Kolthoff plate impact problem, where the computational accuracy and efficiency are further investigated and discussed by comparing our results with those calculated via the intrinsic CZMs.

DOI： 10.1016/j.engfracmech.2023.109637

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Computer Methods in Applied Mechanics and Engineering  

In this paper, we propose a class of decoupled first- and second-derivatives models for the Smoothed Particle Hydrodynamics (SPH) method, which were inspired by the Lagrangian Differencing Dynamics (LDD) (Bašić et al., 2018) and (Bašić et al., 2022) and arranged to the SPH framework. Being extensions of existing gradient and Laplacian SPH models, the proposed decoupled models include the cross-derivatives, which are crucial to ensure 2nd-order accuracy. Under the framework of the proposed class of decoupled models, we defined five second-derivative models, here termed, Naïve (NI), Block Diagonal (BD), SUM, Part Inverse (PI), and Full Inverse (FI). Among these models, only the NI and BD have equivalences in existing models, while the other three are completely original. Therefore, we believe that, besides the development of new models, this work may provide a standard classification for second-derivative models in SPH. In addition, applying the FI model into the first-derivative model, we propose the first instance of a 2nd-order accurate gradient model in SPH. Then, we demonstrated that the convergence rate of the truncation error decreases the higher the order of the model, and the results were investigated for different particle disorder levels. After that, we applied the proposed derivative models to incompressible fluid flow simulations for validation. The validation includes four famous benchmark tests: the lid-driven cavity, the Kármán vortex behind a cylinder, the rotating square patch, and the dam break problem. The first two tests are used to discuss the accuracy of the spatial derivative models without a free surface, while the third test already includes the effects of the free surface, where particle disorder is more severe. All examples demonstrate the robustness and accuracy of our proposed spatial derivatives at 2nd-order accuracy. Since the combination of the FI Laplacian model and the 2nd-order gradient model can satisfy 2nd-order accuracy, we expect this to be the second generation of SPH formulations, which we call SPH(2).

DOI： 10.1016/j.cma.2023.116203

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DOI： https://doi.org/10.1007/s40571-023-00666-y

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

DOI： https://doi.org/10.1016/j.cma.2023.116203

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

DOI： https://doi.org/10.1016/j.engfracmech.2023.109637

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

粉体工学の分野において、ビーズミルの摩耗予測をすることは、機械のメンテナンス上重要なことであり、これを数値解析を通して簡易的に評価する方法を提案した。特に羽根の形状により、その摩耗特性は異なり、実験との比較検証をして十分に実用的であることを示した。

DOI： 10.4164/sptj.60.470

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

Physics-Informed Neural Networks (PINNs) have been a promising machine learning model for evaluating various physical problems. Despite their success in solving many types of partial differential equations (PDEs), some problems have been found to be difficult to learn, implying that the baseline PINNs is biased towards learning the governing PDEs while relatively neglecting given initial or boundary conditions. In this work, we propose Dynamically Normalized Physics-Informed Neural Networks (DN-PINNs), a method to train PINNs while evenly distributing multiple back-propagated gradient components. DN-PINNs determine the relative weights assigned to initial or boundary condition losses based on gradient norms, and the weights are updated dynamically during training. Through several numerical experiments, we demonstrate that DN-PINNs effectively avoids the imbalance in multiple gradients and improves the inference accuracy while keeping the additional computational cost within a reasonable range. Furthermore, we compare DN-PINNs with other PINNs variants and empirically show that DN-PINNs is competitive with or outperforms them. In addition, since DN-PINN uses exponential decay to update the relative weight, the weights obtained are biased toward the initial values. We study this initialization bias and show that a simple bias correction technique can alleviate this problem.

DOI： 10.1088/2399-6528/ace416

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DOI： https://doi.org/10.1016/j.jcpx.2023.100125

Language：English   Publisher：Journal of Computational Physics: X  

It is well-known in the Smoothed Particle Hydrodynamics (SPH) community that correction in the gradient and Laplacian operators have the potential to drastically increase the accuracy of the method at the expense of computational stability. This paper proposes a stable implementation of such corrections in all derivative operators to the Arbitrary Lagrangian Eulerian incompressible SPH (ALE-ISPH) method, in addition to a novel Neumann boundary condition (BC) applied directly on the velocity (as opposed to traditional BCs where the constraint is applied on the acceleration). In this way, the pressure is solved for both water and wall particles simultaneously, leading to a pressure field that obeys non-penetration BC and divergence-free at the same time. Furthermore, to stabilize the method, we have developed a novel density-based particle shifting technique (PST), specifically designed to deal with incompressible fluids. In this formulation, the numerical density is given as one of the most critical constraint variables. As a result, the proposed density-based PST can maintain the fluid's overall volume for the whole simulation. In addition, it also provides numerical stability as it prevents particle clustering and leads the fluid domain to an isotropic composition. First, we verified the proposed corrected formulation with the novel Neumann BC for both non-penetration and non-slip conditions with the simulation of hydrostatic pressure and Poisenuille flow, respectively. Then, we tested the proposed density-based PST with the rotating square patch problem with results comparable to previous studies. Lastly, we verified the proposed method for the dam break with an obstacle test, a highly dynamic problem.

DOI： 10.1016/j.jcpx.2023.100125

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

<p>SPH methods discretize a continuum with particles and update their position based on the Lagrangian description. Therefore, deformation of the domain can be represented by the movement of the particles. Besides, SPH methods generally use interpolation approximations with a fixed kernel depending on the distance from the target particle to the neighboring particles. Hence, its computational accuracy is guaranteed only when the particles are distributed regularly. Several methods to support its accuracy are proposed such as particle shifting methods, which re-arrange the particle configuration to a regular state, and the correction of differential models in response to particle disorder. In this context, we present a high accuracy second-order derivative model and demonstrate the performance improvement with several examples. In addition, we find that particle shifting methods provides higher-order approximation and simulation stability.</p>

DOI： 10.2208/jscejj.22-15019

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

<p>With the rapid increase in torrential rainfall disasters and associated landslides, the demand for predictive numerical simulations has been growing. Due to computational limits, one needs to introduce approximations, however, the parameters to link detailed and approximated simulations (e.g. drag / bed friction coefficients) are determined empirically, and their applicability remains vague. In this context, this paper presents the application of a deep learning model, PINN (Physics-Informed Neural Network) to inverse analysis. This work assumes a scenario where one has an access to limited data (which is the case for real-site observation), and proposes utilizing data’s spatial features extracted from POD (Proper Orthogonal Decomposition) instead of conventional random number-based method. We found that proposed method supports PINN for faster training convergence and efficient parameter identification.</p>

DOI： 10.2208/jscejj.22-15011

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

<p>In recent years, a number of bridges have been washed out due to torrential rains. When analyzing scour around piers, one of the causes of damage to bridges, using particle methods such as the SPH(Smoothed Particle Hydrodynamics) methods, the non-uniform distribution of particles and tensile instability caused by negative pressure occur. We especially focus on the pressure gradient model, which has been conventionally and frequently used for stable analysis, and discuss pressure gradient calculations suitable for negative pressure regions. Moreover we introduce a modified gradient model that satisfies first-order consistency as well as PS (Particle Shifting) scheme to maintain the particle distribution regularity. The modified SPH method reproduces von Karman vortex, and its validity is quantitatively examined by comparing the twin vortex size, drag coefficient, lift coefficient and Strouhal number with experimental data.</p>

DOI： 10.2208/jscejj.22-15023

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Language：English   Publisher：Advanced Modeling and Simulation in Engineering Sciences  

This study develops a new numerical simulation model for rubble mound failure prediction caused by piping destruction under seepage flows. The piping has been pointed out as a significant cause of breakwater failure during tsunamis. Once boiling and heaving occur on the mound surface, the piping suddenly propagates in the opposite direction of seepage flow. For the seepage failure prediction, a coupled fluid-soil-structure simulator is developed by combining the ISPH for fluid and the DEM for rubble mounds and caisson blocks. The ISPH, a Lagrangian particle method for incompressible fluids, can simulate seepage and violent flows such as tsunamis. The DEM has been applied for discrete particle and rigid body simulations that include discontinuous deformation, as in the rubble mounds failure and large displacement of the caisson block. ISPH-DEM coupling simulations have already been proposed as a technique for multi-phase flows. Still, the technique cannot reproduce the sudden onset of piping from a stable mound. Two simple assumptions are applied to reduce the numerical cost for the fluid-soil-structure simulators of a breakwater structure composed of a rubble mound and the caisson block. Firstly, each rubble is modeled as an idealized spherical DEM particle with the mean diameter of the rubble. The ISPH particle size is assumed to be the same size as the DEM particle. Under these assumptions, the unresolved coupling model between rubble mound particles and fluid, which obtains the interaction through empirical drag force, should be applied. At the same time, the interaction between the fluid and the caisson block is fully resolved with the spatial resolution with the ISPH and DEM particle size. Our new contribution in this paper is how to model the interaction as an unresolved coupling between seepage flow simulated by ISPH and rubble mound particle modeled with DEM. Our original seepage failure experiment is simulated using the proposed ISPH-DEM coupling simulator. We identified the conventional drag force models as the unresolved coupling model are insufficient to initiate the boiling and piping observed in the experiment. It may be due in one part to excessive averaging of flow velocities caused by unresolved coupling. Therefore, Terzaghi’s critical hydraulic gradient is introduced to initiate the boiling and heaving. Unstable DEM particles, judged by Terzaghi’s critical hydraulic gradient, gradually lose their mass to represent unresolved suspended fine rubble mound particles. Our models qualitatively reproduce the sand boiling and backward erosion in the opposite direction of the seepage flow, as shown in the experiment.

DOI： 10.1186/s40323-022-00239-3

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DOI： https://doi.org/10.1186/s40323-022-00239-3

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

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The present work shows a novel phase-change concept for simulating landslides using the smoothed particles hydrodynamics (SPH) method. The idea is to initiate the simulation of a slope stability problem with a Solid Mechanics-based SPH, modeling the soil as an elastoplastic material at finite strain. Next, if a particle exceeds a certain level of plastic strain, such particle changes its phase to a fluid state with non-Newtonian rheology, which is then solved with a Fluid Dynamics-based SPH method. We use the total Lagrangian SPH (TLSPH) method to solve the Solid Mechanics phase to avoid problems related to particle distribution (such as the tensile instability), while the implicit incompressible SPH (IISPH) to solve the Fluid Dynamics part to avoid the restriction on time increment in relation to high values of viscosity. The coupling between the two phases is treated as a conventional fluid-solid interaction (FSI) problem. We verified the proposed TLSPH method with the triaxial compression problem and demonstrated the robustness of the proposed phase-change TLSPH-IISPH coupled method in the simulation of the Aso landslide. Specifically, it may be the first time to simulate the Aso landslide from its initiation to its propagation in a single numerical simulation.

DOI： 10.1016/j.compgeo.2022.104815

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DOI： 10.4164/sptj.60.470

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

豪雨時の斜面崩壊など、地盤における水と土の連成問題の予測が求められている。粒子法の一つであるISPH法は、これまで主に水のみを対象とした解析技術として発展してきたが、この解析手法の拡張し、水と土の連成現象を強連成の定式化で解析できる手法を構築した。

DOI： https://doi.org/10.1016/j.compgeo.2021.104570

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

This paper is dedicated to the introduction of a strong coupled soil-water interaction formulation based on an incompressible smoothed particle hydrodynamics (ISPH) framework. The method is based on the u-w-p Biot's formulation and adapted to a semi-implicit projection method for incompressibility condition of pore water and soil grains. The SPH Lagrangian particles move according to the soil velocity, while water variables are embedded into such soil particles. This allows to solve the pressure Poisson equation in a strong coupling way, in addition to enable to update the Darcy's drag force implicitly. A simple boundary treatment on natural boundary conditions for soil particle is proposed to take into account both non-penetration and friction effects. The proposed method was verified and validated through a series of numerical tests resulting in good agreements with both theoretical and experimental results. Finally, we show the applicability of the proposed method in the famous Selborne experiment, a full-scale slope failure problem.

DOI： 10.1016/j.compgeo.2021.104570

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

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

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

粒子法による流体構造連成解析をする際，特に構造解析の大変形解析が不安定になり，ロバストに解析が実施することが困難であった。そこで、超弾性体モデルの範囲内であれば、初期配置と現配置の間に1対1の関係があることを利用し、固体のつり合い問題を初期配置で解くTotalラグランジュ記述によるSPH粒子法を利用した新しい流体構造連成解析法を提案した。

DOI： https://doi.org/10.1016/j.cma.2021.113832

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

In this work, we propose a two-way coupling technique between a total Lagrangian smoothed particle hydrodynamics (SPH) method for Solid Mechanics and the explicit incompressible SPH (EISPH) to simulate fluid-structure interaction problems. In the solid part, the total Lagrangian framework guarantees that the particle distribution keep stable to correctly calculate the deformation gradient and thus the elastic forces. The constitutive model follows hyperelastic formulations, and the stability of the method is enforced by a Jameson-Schmidt-Turkel (JST) stabilization procedure. For the fluid part, we applied an EISPH formulation, which is a fully explicit incompressible scheme based on a projection method capable of providing accurate pressure distributions for free-surface flows, while avoiding costly linear equations. The coupling scheme follows the same manner as the fixed wall ghost particle (FWGP) approach, which was here adapted to include moving walls. In addition, the non-penetration condition is rigorously reinforced through a numerical algorithm to avoid penetration of every fluid particle, including free-surface particles. Our method for solid is then verified through a large deformed tension plate numerical test, and our coupling forces through a series floating tests and hydrostatic water column over a thin infinite plate. Then, the method is validated comparing it with experimental data of a dam break test in which the water column attacks a thin rubber plate. (C) 2021 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cma.2021.113832

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

© 2020, OWZ. We present an explicit incompressible smoothed particle hydrodynamics formulation with stabilized pressure distribution and its implementation in a multiple graphics processing unit environment. The pressure Poisson equation is stabilized via both pressure invariance and divergence-free conditions, and its explicit formulation is derived using the first step of the Jacobi iterative solver. Also, we show how to adapt the fixed wall ghost particle for the boundary condition into our explicit approach. Verification and validation of the method include hydrostatic and dam break numerical tests. The computational performance in the multi-GPU environment was notably high with reasonable speedup values compared to our single-GPU implementation. In particular, our code allows simulations with very large number of particles reaching up to 200 million per GPU card. Finally, to illustrate the potential of our formulation in simulating natural disasters, we present a simulation of the famous Fukushima Dai-ichi Power Plant inundation by the tsunami from The Great East Japan Earthquake in 2011, in Japan.

DOI： 10.1007/s40571-020-00347-0

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

© 2021 The Author(s) In this paper, a new particle-based fluid–rigid-body interaction simulator for violent free-surface flow problems is developed. The incompressible Smoothed Particle Hydrodynamics (ISPH) method has been proven to produce a smooth and accurate pressure distribution of free-surface fluid flow with breaking and fragmentation. Computed hydrodynamic forces can be applied onto rigid bodies, which may simultaneously experience contact or impact with the surrounding wall boundaries or another rigid body. Modeled by using the discrete element method (DEM), the contact force between rigid bodies is traditionally calculated employing the penalty approach, where a spring-based repulsive force is approximated at the vicinity of contact points depending on the deepest penetration depth. However, for high-speed collision problems involving a system of many rigid bodies, the values of approximated repulsive forces may be highly overestimated, and thus, a much smaller time step and an excessive damping parameter are often required to stabilize the approximated forces. This problem is highly inefficient for the computational resources of the fluid–rigid body interaction simulation since the computational cost at each time step is mostly dominated by the incompressible fluid simulation. The capability to increase the time increment following the critical time step of the fluid solver is, therefore, strongly demanded to increase the simulation efficiency. The current paper incorporates the usage of the energy-tracking impulse (ETI) method as an alternative approach to handle contact accurately. To achieve better energy conservation and enhance stability, Stronge's hypothesis is considered instead of the generally assumed Newton's contact law. The current work also covers three experimental validation tests, which were conducted to assure the quality and robustness of the coupled ISPH–DEM implementation.

DOI： 10.1016/j.cma.2021.113681

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

© 2020, OWZ. Simulations of multi-body dynamics for computer graphics, 3D game engines, or engineering simulations often involve contact and articulated connections to produce plausible results. Multi-body dynamics simulations generally require accurate contact detection and induce high computational costs because of tiny time increments. As higher accuracy and robustness are continually being sought for engineering purposes, we propose an improved multi-body dynamics simulator based on an impulse method, specifically an energy-tracking impulse (ETI) algorithm that has been modified to handle particle-discretized rigid-body simulations. In order to decrease the computational costs of the simulations, in the current work, we assume a fixed moderate time increment, allowing multiple-point contacts within a single time increment. In addition to that, we distinguish the treatment between point-to-point and multiple-point contacts, which include edge-to-surface and surface-to-surface contacts, through an additional sub-cycling iterations. The improved ETI method was verified with analytical solutions of examples with single-body contact, a frictional slip, and a rolling contact. Moreover, the method was also validated with an experimental test of a line of dominoes with multiple-point contacts. Finally, a demonstration simulation with bodies of complicated shape subjected to a large number of constraints is given to show the optimum performance of the formulation.

DOI： 10.1007/s40571-020-00326-5

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

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

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

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

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

剛体接触解析を行う常套手段としては、バネとダッシュポットで簡易的に表現するペナルティ法が良く採用されるが、時間増分が小さくなる、また人工パラメータの設定方法が曖昧であるなどの、問題点があった。そこで、適切な力（撃力：インパルス）で接触を表現するインパルス法に着目し、特にエネルギー保存性を担保できるEnergy-tracking impulse法をベースとし、これをDEMなどの粒子離散化された剛体の解析へと適用した。

DOI： https://doi.org/10.1007/s40571-020-00326-5

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

Language：Japanese  

Estimation on collapse mechanism of Aso-bridge during the 2016 Kumamoto earthquakes using ASI-Gauss code
<p>Many bridges and infrastrucutures were damaged by the seismic waves in the 2016 Kumamoto Earthquakes, and in this research, we focused on the Aso-bridge which collapsed immediately after the main shock. A huge landslide happened after the earthquakes and Aso-bridge, which was constructed in the same location of the landslide, totally collapsed. There are a couple of reports that four main factors might have contributed to this collapse; (1) seismic wave, (2) ground deformation, (3) landslide material load increase on the bridge, (4) basement ground collapse. In this paper, a numerical analysis of the Aso-Bridge collapse was conducted using the ASI-Gauss code, which is one of the finite element method utilizing beam elements. Then, we have discussed the main factor of the Aso-bridge collapse.</p>

DOI： 10.11532/structcivil.66A.59

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

Language：Japanese  

SPH-DEM COUPLING SIMULATION WITH A LIQUID BRIDGE FORCE FOR THE REPRESENTATION OF GROUND COLLAPSE PHENOMENON
<p>Recently, the ground collapse caused by deterioration of sewer pipes, which is constructed during the period of high economic growth, has occurred frequently. In this study, 3-dimensional numerical analysis is conducted to understand the mechanism of ground collapse. As an analysis method, we developed a fluidsoil multi-phase flow analysis method based on particle method that can follow large deformation and discontinuous motion. By introducing the liquid bridging force, which has been studied in the field of powder engineering, the apparent cohesion due to water content was taken into consideration and improvements were made to adapt to unsaturated ground. We succeeded in reproducing the qualitative collapse phenomenon by the analysis of the depression phenomenon using this method.</p>

DOI： 10.2208/jscejam.75.2_I_203

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

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

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

© 2019, OWZ. This study describes the application of two main improvements in highly viscous fluid simulations using the smoothed particle hydrodynamics (SPH) method: an implicit time integration scheme to overcome the problem of impractically small time step restriction and the introduction of air ghost particles to fix problems regarding the free surface treatment. This study adopts the incompressible SPH as a basis for the implementation of these improvements, which guarantees a stable and accurate pressure distribution. We verified the proposed implicit time integration scheme with simulations of pipe flow and the free surface treatment with a simple hydrostatic problem. As a result, the free surface of the hydrostatic problem became very smooth and stable. In addition, we conducted a variety of dam-break simulations to validate this proposed SPH method, as well as to analyze the density and divergence error. Finally, we demonstrate the potential of this method with the highly viscous vertical jet flow over a horizontal plate test, which features a complex viscous coiling behavior.

DOI： 10.1007/s40571-019-00231-6

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

土石流あるいは火砕流などの災害シミュレーションへ向けた高粘性流体のシミュレーションのために、独自に開発してきた粒子法（ISPH法）を改良し、
安定かつ高精度に解析可能な手法を開発した。

DOI： 10.1007/s40571-019-00231-6

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

Improvements in highly viscous fluid simulation using a fully implicit SPH method
This study describes the application of two main improvements in highly viscous fluid simulations using the smoothed particle hydrodynamics (SPH) method: an implicit time integration scheme to overcome the problem of impractically small time step restriction and the introduction of air ghost particles to fix problems regarding the free surface treatment.

DOI： 10.1007/s40571-019-00231-6

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DOI： https://doi.org/10.11421/jsces.2018.20182010

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

DOI： https://doi.org/10.11421/jsces.2018.20182010

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

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

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

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

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

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

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

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

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

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

In 2011, the example that breakwaters collapsed because of the basic ground's destabilization was reported by Tohoku-Kanto earthquake tsunami. Fluid-Structure-Soil coupling simulation is desired for a systematic comprehension of the breakwater collapse mechanism, and it may help to develop next disaster prevention method. In this study, A particle simulation tool based on the SPH has been modified and improved to analyze seepage flow and soil scouring. In seepage flow analysis, as a first step, this simulation treat the surface flow and seepage flow interactions by using governing equation. In the scouring analysis, soil scour is judged by an empirical criteria based on quicksand quantity formula.

DOI： 10.1051/matecconf/20164703019

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

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

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

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

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

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

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

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

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

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

Language：Japanese   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 (scientific journal)  

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

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：Japanese   Publishing type：Research paper (scientific journal)  

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

Publishing type：Research paper (scientific journal)  

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

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

<p>Particle methods such as the SPH and MPS methods have problems in that the approximation accuracy decreases due to disorder in particle arrangements and it is difficult to treat accurately curved bottom surfaces such as seabed surface. Regarding the first problem, we proposed the SPH(2), which satisfy the second order convergence in space and maintain its accuracy against for particle disorders. In this study, the second problem, the treatments of the curved bottom surfaces, has been improved using a coordinate transformation with the SPH(2)'s second derivative model Although the theory for the coordinate transformation was established in the MPS method, its accuracy did not give the desired accuracy because of the numerical errors of the second derivative models. Therefore, the numerical errors in these coordinate transformations were overcome by applying the second derivative model of SPH(2) to the coordinate transformation formulas. The superiority and validity of the proposed coordinate transformation using SPH(2) are demonstrated through validation examples such as hydrostatic pressure problems and dam breakage problems.</p>

DOI： 10.2208/jscejj.23-15017

CiNii Research

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p>For simulating the fluidized ground during landslides, a new ISPH using the fully implicit time integration has been developed to decrease total simulation costs for highly viscous fluid simulation in non-Newtonian fluids. With the help of the proposed fully implicit ISPH, <i>μ</i>(<i>I</i>) rheology model, which is one of the reliable non-Newtonian fluids for dense granular materials, can be implemented with lower numerical costs than the semi-implicit ISPH keeping the same accuracy. The fully implicit ISPH method was implemented on a GPU computer to speed up their heavy computations and achieve stable and fast analysis by combining hardware speed-up and software improvement. Finally, comparing numerical and experimental results for sand flow supports the usefulness of the <i>μ</i>(<i>I</i>) rheology model and fully implicit ISPH method for granular flow.</p>

DOI： 10.2208/jscejj.23-15018

CiNii Research

Language：English  

DOI： 10.1038/s41598-023-44098-3

Web of Science

PubMed

Publishing type：Research paper (scientific journal)   Publisher：Numerical Heat Transfer; Part A: Applications  

The ISPH method is adopted to simulate the diffusion of solid particles through a nanofluid flow during the dual rotation of two circular cylinders inside a cavity. Half of the solid particles are carrying (Formula presented.) and the others carry (Formula presented.). The novelty of this work is in simulating the dual rotation of circular cylinders with the dispersion of solid particles below the influences of Soret-Dufour numbers. The major outcomes revealed that the interactions between solid particles and nanofluid flow are enhanced according to an increase in Soret/Dufour numbers. Increasing the Hartmann number declines the interaction process between solid particles and nanofluid flow. The radius of a circular cylinder is working well in changing the transport of heat/mass within a cavity due to the variations in the total number of solid particles. The values of Nusselt and Sherwood numbers are influenced by physical factors.

DOI： 10.1080/10407782.2022.2156413

Web of Science

Scopus

researchmap

Publisher：Journal of Advanced Research in Fluid Mechanics and Thermal Sciences  

Incompressible Smoothed Particle Hydrodynamic (ISPH), one of the particle methods, is frequently employed to address a variety of challenging physical issues, such as those involving free surface flow. For measuring the precise and reliable pressure close to the boundary, the study of boundary treatment has lately been an active research field in the mesh-free or particle approach. If the solid barrier's appropriate pressure boundary condition is not met, fluid particles may penetrate it. This study proposes a straightforward boundary treatment that can satisfy the non-homogenous Neumann boundary condition on the solid boundary and the Dirichlet condition on the water surface. The main idea behind our suggested approach is that by solving a modified pressure Poisson equation, these boundary conditions are automatically satisfied. This technique can be improved such that it can be applied to any shape having a concave-convex boundary in addition to basic solid boundaries. The suggested method was tested using the hydrostatic case, followed by a numerical analysis validated using a 3D dam break flow with an opening gate and a Stanford rabbit demonstration. The outcome of the numerical modelling simulation was then contrasted with the findings of the theoretical and experimental studies. The obtained findings support the suggested technique by providing a good tendency and similarity output that enhances the boundary treatment on solid boundaries

DOI： 10.37934/arfmts.103.1.211222

Scopus

Language：Japanese   Publisher：The Society of Powder Technology, Japan  

<p>While the Discrete Element Method (DEM) is expected to evaluate wet grinding performance of bead mills, the conventional DEM requires high computational cost because it has the limitation of the time step size for stable computation. In addition, the simulation of wet grinding process requires additional cost to consider the interaction between beads and fluids by using such as CFD-DEM coupling techniques. This study proposes an analysis system for evaluating wet grinding performance of bead mills with less computational cost. Our proposed system adopts the Impulse-Based DEM (IB-DEM) which can use large time step size, the wall model by using the Sign Distance Function (SDF) which flexibly represents complicated shape walls, and the simple modeling of fluid force which can reduce computational cost. We verify our proposed system by comparing the numerical results with experimental results of bead mills with different shapes of rotors.</p>

DOI： 10.4164/sptj.59.488

Scopus

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Numerous tsunami numerical models have been proposed, but their prediction accuracies have not been directly compared. For quantifying the modeling uncertainties, the authors statistically analyzed the prediction results submitted by participants in the tsunami blind contest held at the 17th World Conference on Earthquake Engineering. The reproducibility of offshore water level generated due to the tsunami with soliton fission significantly decreased when the nonlinear shallow water equation models (NSWE) was used compared to three-dimensional (3D) models. The inundation depth was reproduced well in 3D models. However, the reproducibility of wave forces acting on the structure and velocities over land was lower in 3D models than that in NSWE models. For cases where the impulsive tsunami wave pressure generated could not be calculated based on the hydrostatic assumption, the prediction accuracy of the NSWE models was higher than that of the 3D models. The prediction accuracies of both models were not improved at small grid-cell sizes. The NSWE model cannot simulate the short-wave component and vertical pressure distribution. Therefore, further developments in 3D models and smoothed particle hydrodynamics methods (SPH) are needed. The presented results contribute to the future development of tsunami numerical simulation tools.

DOI： 10.1080/21664250.2022.2072611

Web of Science

Scopus

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p>There has been a growing demand to strengthen existing disaster prevention education tobe prepared for the huge tsunami expected to occur in the near future. Virtual reality, which allows people to virtually experience natural disasters, has a strong potential in fostering disaster awareness among citizens. However, it requires enormous human and time resources to map the texture of structures to urban area-imitating virtual space. On the other hand, pix2pixHD proposed by Wang et al. can generate high-resolution synthetic images by learning from reference images, label data, and object boundary data. In this study, we applied pix2pixHD and transfer learning, which diverts networks trained on other similar domains, to verify texture mapping of urban areas in Japan from a limited set of image data.</p>

DOI： 10.11532/jsceiii.3.j2_551

CiNii Research

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

© 2020, Emerald Publishing Limited. Purpose: The purpose of this study is to apply the incompressible smoothed particle hydrodynamics (ISPH) method to simulate the natural convection flow from an inner heated Y-fin inside Y-shaped enclosure filled with nanofluid. Design/methodology/approach: The dimensionless governing partial differential equations are described in the Lagrangian form and solved by an implicit scheme of the ISPH method. The embedded Y-fin is kept at a high temperature Th with variable heights during the simulations. The lower area of Y-shaped enclosure is squared with width L = 1 m and its side-walls are kept at a low temperature Tc. The upper area of the Y-shaped enclosure is V-shaped with width 0.5 L for each side and its walls are adiabatic. Findings: The performed simulations revealed that the height of the inner heated Y-fin plays an important role in the heat transfer and fluid flow inside the Y-shaped enclosure, where it enhances the heat transfer. Rayleigh number augments the buoyancy force inside the Y-shaped enclosure and, consequently, it has a strong impact on temperature distributions and strength of the fluid flow inside Y-shaped enclosure. Adding more concentration of the nanofluid until 10&#37; has a slight effect on the temperature distributions and it reduces the strength of the fluid flow inside Y-shaped enclosure. In addition, the average Nusselt number is measured along the inner heated Y-fin and it grows as the Rayleigh number increases. The average Nusselt number is decreasing by adding more concentrations of the nanofluid. Originality/value: An improved ISPH method is used to simulate the natural convection flow of Y-fin embedded in the Y-shaped enclosure filled with a nanofluid.

DOI： 10.1108/HFF-02-2020-0094

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

© 2020 Tech Science Press. All rights reserved. In the present work, an incompressible smoothed particle hydrodynamic (SPH) method is introduced to simulate water-soil-structure interactions. In the current calculation, the water is modelled as a Newtonian fluid. The soil is modelled in two different cases. In the first case, the granular material is considered as a fluid where a Bingham type constitutive model is proposed based on Mohr-Coulomb yield-stress criterion, and the viscosity is derived from the cohesion and friction angle. In addition, the fictitious suspension layers between water and soil depending on the concentration of soil are introduced. In the second case, Hooke's law introduces elastic soil. In ISPH, the pressure is evaluated by solving the pressure Poisson equation using a semi-implicit algorithm based on the projection method and an eddy viscosity for water is modelled by a large eddy simulation with the Smagorinsky model. In the proposed ISPH method, the pressure is stabilized to simulate the multiphase flow between soil and water. Numerical experiments for water-soil suspension flow of Louvain erosional dam break with flat soil foundation, is simulated and validated using 3D-ISPH method. Coupling between water-soil interactions with different solid structures are simulated. The results revealed that, the suspension layers with the Bingham model of soil gives more accurate results in the experiment as compared to the case of the Bingham model without suspension layers. In addition, the elastic soil model by the Hooke's law can simulate soil hump accurately as compared to the Bingham model. From the simulations, avoiding erosion behind the structure for preventing the structure break during flood are investigated by using an extended structure or a wedge structure.

DOI： 10.32604/cmc.2020.09227

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

Purpose: The purpose of this study is to apply the incompressible smoothed particle hydrodynamics (ISPH) method to simulate the natural convection flow from an inner heated Y-fin inside Y-shaped enclosure filled with nanofluid. Design/methodology/approach: The dimensionless governing partial differential equations are described in the Lagrangian form and solved by an implicit scheme of the ISPH method. The embedded Y-fin is kept at a high temperature with variable heights during the simulations. The lower area of Y-shaped enclosure is squared with width L = 1 m and its side-walls are kept at a low temperature . The upper area of the Y-shaped enclosure is V-shaped with width 0.5 L for each side and its walls are adiabatic. Findings: The performed simulations revealed that the height of the inner heated Y-fin plays an important role in the heat transfer and fluid flow inside the Y-shaped enclosure, where it enhances the heat transfer. Rayleigh number augments the buoyancy force inside the Y-shaped enclosure and, consequently, it has a strong impact on temperature distributions and strength of the fluid flow inside Y-shaped enclosure. Adding more concentration of the nanofluid until 10% has a slight effect on the temperature distributions and it reduces the strength of the fluid flow inside Y-shaped enclosure. In addition, the average Nusselt number is measured along the inner heated Y-fin and it grows as the Rayleigh number increases. The average Nusselt number is decreasing by adding more concentrations of the nanofluid. Originality/value: An improved ISPH method is used to simulate the natural convection flow of Y-fin embedded in the Y-shaped enclosure filled with a nanofluid.

DOI： 10.1108/HFF-02-2020-0094

Language：Japanese  

A VALIDATION FOR SOIL SCOURING SIMULATION BASED ON AN ISPH-DEM COUPLING METHOD
<p>The mechanisms of the seawall destruction have been studied and the following three causes have been investigated in general; 1) horizontal force due to the water level difference, 2) soil scour and erosion behind the seawall during overflow, 3) seepage failure associated with the reduction of the bearing capacity. Whereas, the collapse predictions by complex destruction factors have not ever been realized.</p><p>Hence, to predict various destruction due to interaction between water and soil, a multiphase flow simulator utilizing the Incompressible Smoothed Particle Hydrodynamics method (ISPH method) for water and Discrete Element method (DEM) for soil is developed in our research group. In this research, we simulated scouring phenomena due to vertical jet experiment for a validation test. In our SPH model, a turbulence model is adopted, and the velocity in the vicinity of the gravel DEM particles may decrease because of the eddy viscosity effect of the turbulent model. Then, we propose a modification to take into account the influence of unresolved turbulent flow. The modified drag force model shows a better performance to represent the gravel movement during this vertical jet simulation. Consequently, the result in this research indicate possibility that the gravel movement force needs to be supplemented energy.</p>

DOI： 10.2208/jscejam.75.2_I_249

Language：Japanese  

A RATIONALE OF THE STABILIZED ISPH METHOD II -AN OPTIMIZATION OF RELAXATION COEFFICIENT BASED ON ERROR ESTIMATES-
<p>The stabilized ISPH method is a particle method for the incompressible Navier–Stokes equations and has a characteristic of adding a relaxation term with respect to a particle density in the pressure Poisson equation. The relaxation term contributes to keeping uniformness of particle distribution, then, enhancements of stability, volume conservation, and accuracy are confirmed by numerical results. For the stabilized ISPH method, it was shown by our previous study that the stabilization term is theoretically derived as an approximate solution of an energy minimization problem with respect to errors of incompressibility of fluid and uniformness of particle distributions weighted by a relaxation coefficient. However, a theoretical derivation of the optimal value of the relaxation coefficient remained unsolved. Then, this paper derives an optimal relaxation coefficient in the sense that minimizing an upper bound of errors derived by error analysis. Moreover, it is shown that the value and tendency of the optimal relaxation coefficient coincide with experimental results.</p>

DOI： 10.2208/jscejam.75.2_I_187

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

Purpose: This study aims to focus on the numerical simulation of natural convection from heated novel fin shapes in a cavity filled with nanofluid and saturated with a partial layer of porous medium using improved incompressible smoothed particle hydrodynamics (ISPH) method. Design/methodology/approach: The dimensionless of Lagrangian description for the governing equations were numerically solved using improved ISPH method. The current ISPH method was improved in term of wall boundary treatment by using renormalization kernel function. The effects of different novel heated (Tree, T, H, V, and Z) fin shapes, Rayleigh number Ra, porous height H (0.2-0.6), Darcy parameter and solid volume fraction ϕ(0.0-0.05) on the heat transfer of nanofluid have been investigated. Findings: The results showed that the variation on the heated novel fin shapes gives a suitable choice for enhancement heat transfer inside multi-layer porous cavity. Among all fin shapes, the H-fin shape causes the maximum stream function and Z-fin shape causes the highest value of average Nusselt number. The concentrations of the fluid flows in the nanofluid region depend on the Rayleigh and Darcy parameters. In addition, the penetrations of the fluid flows through porous layers are affected by porous heights and Darcy parameter. Originality/value: Natural convection from novel heated fins in a cavity filled with nanofluid and saturated with a partial layer of porous medium have been investigated numerically using improved ISPH method.

DOI： 10.1108/HFF-03-2019-0270

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

© 2019, Emerald Publishing Limited. Purpose: This study aims to focus on the numerical simulation of natural convection from heated novel fin shapes in a cavity filled with nanofluid and saturated with a partial layer of porous medium using improved incompressible smoothed particle hydrodynamics (ISPH) method. Design/methodology/approach: The dimensionless of Lagrangian description for the governing equations were numerically solved using improved ISPH method. The current ISPH method was improved in term of wall boundary treatment by using renormalization kernel function. The effects of different novel heated (Tree, T, H, V, and Z) fin shapes, Rayleigh number Ra(103 – 106), porous height Hp (0.2-0.6), Darcy parameter Da(10−5 − 10−1) and solid volume fraction ϕ(0.0-0.05) on the heat transfer of nanofluid have been investigated. Findings: The results showed that the variation on the heated novel fin shapes gives a suitable choice for enhancement heat transfer inside multi-layer porous cavity. Among all fin shapes, the H-fin shape causes the maximum stream function and Z-fin shape causes the highest value of average Nusselt number. The concentrations of the fluid flows in the nanofluid region depend on the Rayleigh and Darcy parameters. In addition, the penetrations of the fluid flows through porous layers are affected by porous heights and Darcy parameter. Originality/value: Natural convection from novel heated fins in a cavity filled with nanofluid and saturated with a partial layer of porous medium have been investigated numerically using improved ISPH method.

DOI： 10.1108/HFF-03-2019-0270

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

© 2019 World Scientific Publishing Company. In this paper, a partitioned coupling analysis system is developed for a numerical simulation of 3-dimensional fluid-structure interaction (FSI) problems, adopting an incompressible smoothed particle hydrodynamics (SPH) method for fluid dynamics involving free surface flow and the finite element method (FEM) for structural dynamics. A coupling analysis of a particle-based method and a grid-based method has been investigated. However, most of these are developed as a function-specific application software, and therefore lack versatility. Hence, to save cost in software development and maintenance, the open source software is utilized. Especially, a general-purpose finite element analysis system, named ADVENTURE, and a general-purpose coupling analysis platform, named REVOCAP-Coupler, are employed. Moreover, techniques of an interface marker on fluid-structure boundaries and a dummy mesh for fluid analysis domain are adopted to solve the problem that the REVOCAP-Coupler performs to unify two or more grid-based method codes. To verify a developed system, the dam break problem with an elastic obstacle is demonstrated, and the result is compared with the results calculated by the other methods.

DOI： 10.1142/S0219876218430090

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

Bingham flow model by fully implicit SPH and its application to reinforce underground caves
© 2019 Taylor & Francis Group, London. The present work shows the application of the Smoothed Particle Hydrodynamics (SPH) on non-Newtonian fluids for simulating the injection of a cementitious material into underground caves to reinforce the soil. In special, it presents two main improvements over the already established SPH formulation: an implicit time integration scheme to overcome the problem of impracticable small time step restriction in highly viscous fluid simulation, and the introduction of air ghost particles (AGP) to fix problems on the free-surface treatment. This project utilizes the Incompressible SPH (ISPH) as a basis for the implementation of such improvements, which guarantees a stable and accurate pressure distribution. We validate the proposed implicit time integration scheme with pipe flow simulations and the free-surface treatment with a simple hydrostatic problem. Also, dam break numerical simulations using the proposed method resulted in very good agreement with experimental data. At last, we demonstrate the potential of this method with the highly viscous vertical jet flow over a horizontal plate validation test, which shows a complex viscous coiling behavior.

DOI： 10.1201/9780429327933-48

Language：Japanese  

A RATIONALE OF THE STABILIZED ISPH METHOD-A DERIVATION OF A STABILIZATION TERM FROM AN ENERGY MINIMIZATION PROBLEM-

DOI： 10.2208/jscejam.74.I_159

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

© 2018, China Ship Scientific Research Center. In this paper, we simulated the vertical impact of spheres on a water surface using three-dimensional incompressible smoothed particle hydrodynamics (3-D ISPH) method. The sphere motion is taken to be a rigid body motion and it is modeled by ISPH method. The governing equations are discretized and solved numerically using ISPH method. A stabilized incompressible SPH method by relaxing the density invariance condition is adopted. Here, we computed the motions of a rigid body by direct integration of the fluid pressure at the position of each particle on the body surface. The equations of translational and rotational motions were integrated in time domain to update the position of the rigid body at each time step. In this study, we improved the boundary treatment between fluid and fixed solid boundary by using virtual marker technique. In addition, an improved algorithm based on the virtual marker technique for the boundary particles is proposed to treat the moving boundary of the rigid body motion. The force exerted on the moving rigid boundary particles by the surrounding particles, is calculated by the SPH approximation at the virtual marker points. The applicability and efficiency of the current ISPH method are tested by comparison with reference experimental results.

DOI： 10.1007/s42241-018-0133-3

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

© 2018 Wiley Periodicals, Inc. After the Great East Japan Earthquake Tsunami, new Tsunami disaster-prevention and mitigation methods for the next millennium Tsunami are actively being discussed. Consequently, the methods have highlighted the importance of both hard disaster-prevention method, which means direct prevention using infrastructure such as breakwater, and soft disaster-prevention method, including disaster-prevention education. In this paper, a visualization and polygonization system that can be effectively utilized for Tsunami disaster prevention is proposed for large-scale particle simulation. The system includes two important features, such as engineering-purposed visualization and polygonization for hard and soft tsunami disaster-prevention methods, respectively. Moreover, the system can handle the large-scale particle simulation data that are computed by a high-performance computer via an offline on-demand tool without data transfer.

DOI： 10.1002/ecj.12050

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

Language：Japanese  

DIFFERENCES ON DIFFERENT FIDELITY LEVEL IN MODELING OF BUILDING AND EMBANKMENT HEIGHT ON TSUNAMI RUN UP SIMULATION BY 2D FINITE DIFFERENCE METHOD

DOI： 10.2208/jscejseee.74.I_1052

Language：Others  

Fluid-rigid body interaction simulation based on a stabilized ISPH method incorporated with the impulse-based rigid body dynamics
© 2018 by the Japan Society for Computational Engineering and Science. In fluid-rigid body interaction simulation based on the particle method, incompressible Smoothed Particle Hydrodynamic (ISPH) method is used to resolve the problem of fluid particles’ motion and impact load on the structure in the meanwhile DEM based on the penalty method is commonly applied to deal with the contact problem of rigid bodies. However, the accuracy of penalty method relies on a relatively small time increment. In this paper, the impulse-based rigid body dynamics is applied to deal with the collision contact problem instead of the conventional penalty method for robust and faster computation.

DOI： 10.11421/jsces.2018.20182010

Language：Others  

Validation of a fluid-solid multiphase flow simulation by a SPH-DEM coupled method and soil foundation scour simulation with a coarse graining particle model
© 2013 by the Japan Society for Computational Engineering and Science.. Disasters, such as sediment disaster caused by heavy rain and Tsunami disaster caused by an earthquake, are multiphase flow phenomena of fluid (water) and solid (soil). For damage prediction and countermeasure, fluid-solid analysis method is necessary since there is a scale limitation for an experiment. In this study, we develop multiphase simulator utilizing the Incompressible Smoothed Particle Hydrodynamics method (ISPH method) for fluid and Discrete Element Method (DEM) for solid. The interaction between ISPH method and DEM is implemented by considering an interaction force between fluid and solid. Free surface judgement is an important factor to obtain a good fluid analysis result. We utilize a method proposed by Marrone et al. to improve the free surface detection in a solid domain. In a simple validation test, dam break flow of water and glass beads, we validate and verify our method. At last, the method is applied to scouring analysis with a coarse graining particle model.

DOI： 10.11421/jsces.2018.20182001

Language：Others  

An offline based on-demand visualization system of large-scale particle simulation for tsunami disaster prevention
© 2017 The Institute of Electrical Engineers of Japan. After the Great East Japan Earthquake Tsunami, new Tsunami disaster-prevention and mitigation methods for the next millennium Tsunami are actively being discussed. Consequently, the methods have highlighted the importance of both hard disaster-prevention method, which means direct prevention using infrastructure such as breakwater, and soft disaster-prevention method, including disaster-prevention education. In this paper, a visualization and polygonization system that can be effectively utilized for Tsunami disaster-prevention is proposed for large-scale particle simulation. The system includes two important features, such as engineering-purposed visualization and polygonization for hard and soft tsunami disaster-prevention methods, respectively. Moreover, the system can handle the large-scale particle-simulation data that is computed by a high-performance computer via an offline on-demand tool without data transfer.

DOI： 10.1541/ieejeiss.137.1422

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

This paper focuses on a weak coupling analysis system of 3-dimensional fluid structure interaction problems. As the numerical discretization scheme, the stabilized incompressible smoothed particle hydrodynamics (ISPH) method is adopted for fluid dynamics involving free surface flow and the finite element method (FEM) is used for structural dynamics. To save cost in software developments maintenance, the open source software is utilized. Especially, a general-purpose finite element analysis system, named ADVENTURE Solid, and a general-purpose coupling analysis platform, named REVOCAP Coupler, are employed. Moreover, techniques of an interface marker on the fluid-structure boundary and a dummy mesh for a fluid analysis domain is adopted to solve the problem that the REVOCAP Coupler performs to unify two or more grid-based method codes. To verify a developed system, the dam break problem with an elastic obstacle is demonstrated. Moreover, the effect of a relaxation parameter in the ISPH method is studied.

DOI： 10.11345/nctam.64.143

Language：Japanese  

3次元離散型有限要素モデルによる石造アーチ橋の静的・動的強度解析

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

The tsunami run-up simulation by the particle method at city level needs to huge number of particle at least 1 billion particles. The conventional particle simulation method is not easy to solve these huge problem even on the premise of using super-computer. Then, a new particle method 'fully explicit Incompressible SPH' is developed that takes into consideration both calculation efficiency and accuracy. Finally, we demonstrate the future plan how to use our simulation resultes for a practical 'Soft' disaster mitigation method through the evacuation education with the Virtual Reality(VR) system.

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

In 2011, Tohoku-Kanto earthquake tsunami caused serious damage to the port and coastal structures such as breakwaters and seawalls. The damage mechanism of these structures has been studied in the past, and it is found that there are some causes. In this study, a new simulation tool taking account of the soil scouring and seepage flow phenomena is developed to represent and predict the collapse of the breakwater with SPH-DEM coupled method.

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

The 2011 off the Pacific coast of Tohoku Earthquake was one of the most powerful earthquakes on record in Japan and the huge tsunami caused by the earthquake inflicted extensive damage to the coastal areas of the Tohoku region. To form safe coastal areas, countermeasures against disaster should be developed considering not only tangible infrastructures including breakwater and bridges but also intangible measures including education on disaster prevention and the development of hazard maps. The tsunami run-up analysis is expected to play a role as one of the countermeasures against tsunami. In this research, we aim to establish a tool to effectively analyze the tsunami run-up in urban areas based on the Smoothed particle hydrodynamics (SPH) method. And then, we propose a series of pre-process procedures to develop a detailed geography analysis model that reflects the geography, elevation, and exterior shapes of buildings by referring to 3D location information and digital elevation model data obtained from a geographical information system. Finally, we established a photorealistic visualization method so that citizen can understand the tsunami phenomenon intuitively.

DOI： 10.1142/S1793431116400200

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

In 2011, the tsunami generated by the Great East Japan Earthquake devastated infrastructure along the Pacific coast of northeastern Japan. In particular, the collapse of bridges resulted in much disruption to traffic, which led to delays in recovery after the disaster. We are developing a multi-scale and multi-physics tsunami disaster simulation tool to evaluate the safety and damage of infrastructure from huge tsunami. Multistage zooming tsunami analysis is one of the possible methods for implementing a high-resolution three-dimensional (3D) tsunami inundation simulation for a city. In this research, a virtual wave source that includes transition layers is proposed for a coupled simulation based on 3D particle simulation. The zooming analysis has been undertaken using the same particle method and a two-dimensional (2D) finite difference simulation. The 3D particle coupled simulation has been examined and validated.

DOI： 10.1142/S1793431116400194

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

© Owned by the authors, published by EDP Sciences, 2016. In 2011, the huge tsunami caused by the great east Japan earthquake devastated many infrastructures in pacific coast of north eastern Japan. Particularly, collapse of bridges caused a traffic disorder and these collapse behaviors led to delay of recovery after the disaster. In this study, the bridge wash away accident is selected as a target issue, and it is represented by a numerical simulation. For this purpose, Smoothed Particle Hydrodynamics (SPH) Method, which is one of the pure mesh free methods, is utilized for the rigid body motion simulation. In this study, rigid body motion is introduced for the fluid-rigid interaction behavior during bridge wash away simulation. In the numerical analysis, the upper bridge structure is washed away by receiving an impact fluid force. The wash away simulation of two types of the bridge girder showed good agreement with the real accident on the great east Japan earthquake tsunami.

DOI： 10.1051/matecconf/20164702019

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

© Emerald Group Publishing Limited. Purpose - The purpose of this paper is to model mixed convection in a square cavity included circular cylinders motion using an incompressible smoothed particle hydrodynamics (ISPH) technique. Design/methodology/approach - The problem is solved numerically by using the ISPH method. Findings - The SPH tool shows robust performance to simulate the rigid body motion in the mixed convective flow with heat transfer, and it may apply easily to complicated problems in 2D and 3D problem without difficulties. Originality/value - The application of the SPH method to mixed convective flow with heat transfer and its potential application easily to complicated 3D problems is original.

DOI： 10.1108/HFF-10-2014-0305

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

© 2015, Springer Science+Business Media Dordrecht. In this paper, a stabilized incompressible smoothed particle hydrodynamics (ISPH) method is presented in three dimensions for simulating fluid flows through porous structures. In the ISPH algorithm, a semi-implicit velocity correction procedure is utilized and the pressure is implicitly evaluated by solving pressure Poisson equation. Evaluated pressure has been improved by relaxing the density invariance condition to formulate a modified pressure Poisson equation. The effect of eddy viscosity by using a sub-particle scale turbulence model is introduced to the entire computational domain. The key point for the application to the non-Darcy flows is to include porosity and drag forces of the medium into ISPH method. Modified density of particles according to their porosity is introduced to satisfy continuity criteria in ISPH method. Tracking free surface with Dirichlet boundary condition is modified for the free surface flows in the porous structure. In this study, different numerical tests for fluid flows through porous structures have been simulated. Also, the results from this investigation are well validated and have favorable comparisons with the experimental results.

DOI： 10.1007/s11242-015-0568-8

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

© 2015, Springer Science+Business Media Dordrecht. In this paper, a stabilized incompressible smoothed particle hydrodynamics (ISPH) method is presented in three dimensions for simulating fluid flows through porous structures. In the ISPH algorithm, a semi-implicit velocity correction procedure is utilized and the pressure is implicitly evaluated by solving pressure Poisson equation. Evaluated pressure has been improved by relaxing the density invariance condition to formulate a modified pressure Poisson equation. The effect of eddy viscosity by using a sub-particle scale turbulence model is introduced to the entire computational domain. The key point for the application to the non-Darcy flows is to include porosity and drag forces of the medium into ISPH method. Modified density of particles according to their porosity is introduced to satisfy continuity criteria in ISPH method. Tracking free surface with Dirichlet boundary condition is modified for the free surface flows in the porous structure. In this study, different numerical tests for fluid flows through porous structures have been simulated. Also, the results from this investigation are well validated and have favorable comparisons with the experimental results.

DOI： 10.1007/s11242-015-0568-8

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

© 2015, Springer Science+Business Media Dordrecht. In this paper, a stabilized incompressible smoothed particle hydrodynamics (ISPH) method is presented in three dimensions for simulating fluid flows through porous structures. In the ISPH algorithm, a semi-implicit velocity correction procedure is utilized and the pressure is implicitly evaluated by solving pressure Poisson equation. Evaluated pressure has been improved by relaxing the density invariance condition to formulate a modified pressure Poisson equation. The effect of eddy viscosity by using a sub-particle scale turbulence model is introduced to the entire computational domain. The key point for the application to the non-Darcy flows is to include porosity and drag forces of the medium into ISPH method. Modified density of particles according to their porosity is introduced to satisfy continuity criteria in ISPH method. Tracking free surface with Dirichlet boundary condition is modified for the free surface flows in the porous structure. In this study, different numerical tests for fluid flows through porous structures have been simulated. Also, the results from this investigation are well validated and have favorable comparisons with the experimental results.

DOI： 10.1007/s11242-015-0568-8

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

Copyright © 2015 Taylor & Francis Group, LLC. In this article, a novel numerical method is presented for the simulation of non-Darcy flows through porous media by the incompressible smooth particle hydrodynamics (ISPH) method with a predictor-corrector scheme. In the ISPH algorithm, a semi-implicit velocity-correction procedure is used and the pressure is obtained by solving the pressure Poisson equation. The key point for the application to non-Darcy flows is to include porosity and drag forces of the medium (the Darcy term and the Forcheimer term) in the ISPH method. Unsteady lid-driven flow, natural convection in non-Darcy porous cavities, and natural convection at a porous medium-fluid interface are examined separately by our extended ISPH method. The results are presented with flow configurations, isotherms, and average Nusselt numbers for different Darcy numbers from 10-4 to 10-2, porosity values from 0.4 to 0.9, and Reynolds/Rayleigh numbers. The flow pattern and rate of heat transfer inside the cavity are affected by these parameters. The results demonstrate the important effect of the Darcy number on both the heat transfer rate and the flow regime. The results from this investigation are well validated and compare favorably with previously published results.

DOI： 10.1080/10407790.2014.955772

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

Language：Japanese  

3次元粒子法による橋桁に作用する津波外力評価とその精度検証
On March 11, 2011, the huge tsunami caused by the great east Japan earthquake devastated the Pacific coast of north-eastern Japan. Many infrastructures including bridges were collapsed by the tsunami. New generation of tsunami disaster prevention and mitigation method should be reconsidered toward the next millennium Tsunami. In this study, a new boundary treatment using a virtual marker and the fixed boundary particle is developed to control the slip and no-slip boundary condition for the velocity field and to satisfy the pressure Neumann condition at the same time. Finally, the accuracy and efficiencies of our proposed method are validated by comparison between a numerical solution and experimental results.

DOI： 10.11532/structcivil.60A.293

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

In this paper, fluid-structure interaction (FSI) on free surface flows has been simulated using ISPH method. The governing equations are discretized and solved with respect to Lagrangian moving particles filled within the mesh-free computational domain and the pressure was evaluated by solving pressure Poisson equation using a semi-implicit algorithm based on the projection scheme to ensure divergence free velocity field and density invariance conditions. In this study, the structure is taken as a rigid body and it modeled using ISPH method by two different techniques. In the first technique, the solid particles are treated initially as fluid particles and after corrector step in projection method, the solid constraint is applied to get the rigid body motion. In the second technique, we computed the motions of a rigid body by direct integration of fluid pressure at the position of each particle on the body surface. Then, the equations of translational and rotational motions were integrated in time to update the position of the rigid body at each time step. The applicability and efficiency of current ISPH method with the two different treatment of rigid body are tested by comparison with reference experimental results.

DOI： 10.1615/InterJFluidMechRes.v41.i6.10

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

Purpose - The purpose of this paper is to show how a surface tension model and an eddy viscosity based on the Smagorinsky sub-grid scale model, which belongs to the Large-Eddy Simulation (LES) theory for turbulent flow, have been introduced into ISPH (Incompressible smoothed particle hydrodynamics) method. In addition, a small modification in the source term of pressure Poisson equation has been introduced as a stabilizer for robust simulations. This stabilization generates a smoothed pressure distribution and keeps the total volume of fluid, and it is analogous to the recent modification in MPS. Design/methodology/ approach - The surface tension force in free surface flow is evaluated without a direct modeling of surrounding air for decreasing computational costs. The proposed model was validated by calculating the surface tension force in the free surface interface for a cubic-droplet under null-gravity and the milk crown problem with different resolution models. Finally, effects of the eddy viscosity have been discussed with a fluid-fluid interaction simulation. Findings - From the numerical tests, the surface tension model can handle free surface tension problems including high curvature without special treatments. The eddy viscosity has clear effects in adjusting the splashes and reduces the deformation of free surface in the interaction. Finally, the proposed stabilization appeared in the source term of pressure Poisson equation has an important role in the simulation to keep the total volume of fluid. Originality/value - An incompressible smoothed particle hydrodynamics is developed to simulate milk crown problem using a surface tension model and the eddy viscosity.

DOI： 10.1108/09615531311301263

Language：Others  

Coupling simulator between chemical diffusion and crack propagation by a Voxel FEM incorporated with the Damage Mechanics
Alkali Silica Reaction (ASR), chloride damage of reinforced steel and other aging degradations in concrete structures are strongly dependent on both of chemical phenomena and mechanical behavior including fracture. In this study, a coupling simulator has been developed in order to investigate the degradation mechanism of these concrete aging damages. In the coupling simulator, non-stationary diffusion analysis for Alkali ion is solved firstly, and then the expansion force act on the aggregate is evaluated by referring consistency of the alkali ion. In the second step, nonlinear damage analysis is conducted. The nonlinear damage analysis evaluates cracking region with the damage parameter. The following diffusion analysis changes diffusion coefficient in the cracking region by referring the damage parameter. The above procedures are coupled at each time step. © 2013 by the Japan Society for Computational Engineering and Science.

Language：Japanese  

Slip and no-slip boundary treatment for particle simulation model with incompatible step-shaped boundaries by using a virtual maker
Particle method such as Smoothed Particle Hydrodynamics (SPH) and Moving Particle Semi-implicit method (MPS) can handle quite complicated physical problems involving dynamic changes of free surface and crack propagation, and it is wildly expanding its applications not only in the fluid dynamics but also in the solid mechanics. Beside of these advantages, particle methods are not so easy to treat boundary conditions, like pressure Neumann condition and slip or no-slip condition in fluid dynamics. This is one of the typical difficulties in mesh-less type method. In addition, particle simulation model may include an incompatible step-shaped boundary line, which is made by using a simple pre-processing of particle model. Although the simple and robust pre-processing is one of the advantage of particle simulation, the step-shaped boundary may generate un-realistic numerical solution across the real boundary line especially in the fluid dynamics. Recently, pressure Neumann condition in SPH is re-focused with fixed ghost boundary method using virtual makers. In this paper, the fixed ghost boundary method is modified to treat the incompatible step-shaped boundary particles by referring the real physical boundary line. The accuracy and efficiencies of proposed method are validated by comparison between a numerical solution and experimental results. © 2013 by the Japan Society for Computational Engineering and Science.

DOI： 10.11421/jsces.2013.20130011

Language：Others  

Coupling simulator between chemical diffusion and crack propagation by a Voxel FEM incorporated with the Damage Mechanics
Alkali Silica Reaction (ASR), chloride damage of reinforced steel and other aging degradations in concrete structures are strongly dependent on both of chemical phenomena and mechanical behavior including fracture. In this study, a coupling simulator has been developed in order to investigate the degradation mechanism of these concrete aging damages. In the coupling simulator, non-stationary diffusion analysis for Alkali ion is solved firstly, and then the expansion force act on the aggregate is evaluated by referring consistency of the alkali ion. In the second step, nonlinear damage analysis is conducted. The nonlinear damage analysis evaluates cracking region with the damage parameter. The following diffusion analysis changes diffusion coefficient in the cracking region by referring the damage parameter. The above procedures are coupled at each time step. © 2013 by the Japan Society for Computational Engineering and Science.

Language：Others  

Slip and no-slip boundary treatment for particle simulation model with incompatible step-shaped boundaries by using a virtual maker
Particle method such as Smoothed Particle Hydrodynamics (SPH) and Moving Particle Semi-implicit method (MPS) can handle quite complicated physical problems involving dynamic changes of free surface and crack propagation, and it is wildly expanding its applications not only in the fluid dynamics but also in the solid mechanics. Beside of these advantages, particle methods are not so easy to treat boundary conditions, like pressure Neumann condition and slip or no-slip condition in fluid dynamics. This is one of the typical difficulties in mesh-less type method. In addition, particle simulation model may include an incompatible step-shaped boundary line, which is made by using a simple pre-processing of particle model. Although the simple and robust pre-processing is one of the advantage of particle simulation, the step-shaped boundary may generate un-realistic numerical solution across the real boundary line especially in the fluid dynamics. Recently, pressure Neumann condition in SPH is re-focused with fixed ghost boundary method using virtual makers. In this paper, the fixed ghost boundary method is modified to treat the incompatible step-shaped boundary particles by referring the real physical boundary line. The accuracy and efficiencies of proposed method are validated by comparison between a numerical solution and experimental results. © 2013 by the Japan Society for Computational Engineering and Science.

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：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)  

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：Others  

Constitutive modeling for texture reinforced rubber by using an anisotropic visco-hyperelastic model
Fabric reinforced rubber shows an anisotropy and viscosity in wide strain range. In this paper, an anisotropic visco-elastic model based on Mooney-Rivlin model is developed for fabric reinforced rubber. Anisotropy is introduced, in this constitutive model, by using a structure tensor that shows direction of reinforced fiber. A new strain energy density function for anisotropic elasticity is proposed to improve accuracy associated with shear behaviors. After developing an elastic model, an anisotropic viscosity is modeled by a kind of Maxwell viscosity model at large strains. In addition to the development of constitutive model, a simple fracture prediction method, which refers to the finite element solution incorpolated with our proposed constitutive model, is proposed. Finally, our proposed constitutive model and fracture prediction method are validated with comparisons of uni-axial tension tests with fabric reinforced rubber.

DOI： 10.2208/jsceja.66.194

Language：Japanese  

Constitutive modeling for texture reinforced rubber by using an anisotropic visco-hyperelastic model
Fabric reinforced rubber shows an anisotropy and viscosity in wide strain range. In this paper, an anisotropic visco-elastic model based on Mooney-Rivlin model is developed for fabric reinforced rubber. Anisotropy is introduced, in this constitutive model, by using a structure tensor that shows direction of reinforced fiber. A new strain energy density function for anisotropic elasticity is proposed to improve accuracy associated with shear behaviors. After developing an elastic model, an anisotropic viscosity is modeled by a kind of Maxwell viscosity model at large strains. In addition to the development of constitutive model, a simple fracture prediction method, which refers to the finite element solution incorpolated with our proposed constitutive model, is proposed. Finally, our proposed constitutive model and fracture prediction method are validated with comparisons of uni-axial tension tests with fabric reinforced rubber.

DOI： 10.2208/jsceja.66.194

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

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

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

Publishing type：Research paper (scientific journal)  

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

Reduction of Finite Element Mesh and Model Order for Fast Dynamic Analysis of Global/Local Problem
MEMS structures and machines fabricated by photolithography and/or etching have often repeated unit microstructure. We need to design not only the global parameters but also microscopic and local parameters. In pursuit of this, a dynamic analysis of global/local problem is essential, and especially fast computational method and convenient modeling technique are both required for the MEMS design. Hence, this paper presents the application of model order reduction (MOR) for fast dynamic analysis combined with the finite element mesh superposition (FEMS) technique for practical and convenient modeling of the above-mentioned microstructures. Through two examples, the accuracy is carefully investigated for both global and local responses associated with the base vectors in MOR algorithm. The first example is analyzed by a kind of homogenization technique and MOR. The number of DOFs was finally reduced by a factor of approximately 1/6 (47,362/296,268). In addition, MOR enabled us to reduce the coefficient matrix size to only 300. The second example is analyzed by both FEMS and MOR, and it was found that MOR is also applicable to an unusual matrices generated by FEMS.

DOI： 10.1299/jmmp.3.572

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

Reduction of Finite Element Mesh and Model Order for Fast Dynamic Analysis of Global/Local Problem

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

Language：English  

Language：Japanese  

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

A new preconditioned iterative solver based on the Kryrov subspace method is developed for solving large-scale finite element (FE) models of piezoelectric problems. The system matrix of piezoelectric FE analysis has negative eigenvalues because of coupling terms between mechanical and electrical fields. A general preconditioned iterative solver is ineffective for large-scale piezoelectric FE analysis due to the indefinite system matrix. A block diagonal preconditioner for the piezoelectric finite element method (FEM) is proposed by grouping nodal values as a block. Then the proposed solver is applied to the homogenization method, which can evaluate the effective macroscopic material properties by using FEM. In the FE modelling of complex microstructures, a semi-automatic technique with nondestructive observation provides reasonable 3D micrographs of porous Pb(Zr, Ti)O-3 (PZT). The efficiency of the proposed solver is investigated through the homogenization analysis of real porous PZT samples.

DOI： 10.1088/0965-0393/15/6/002

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

A new preconditioned iterative solver based on the Kryrov subspace method is developed for solving large-scale finite element (FE) models of piezoelectric problems. The system matrix of piezoelectric FE analysis has negative eigenvalues because of coupling terms between mechanical and electrical fields. A general preconditioned iterative solver is ineffective for large-scale piezoelectric FE analysis due to the indefinite system matrix. A block diagonal preconditioner for the piezoelectric finite element method (FEM) is proposed by grouping nodal values as a block. Then the proposed solver is applied to the homogenization method, which can evaluate the effective macroscopic material properties by using FEM. In the FE modelling of complex microstructures, a semi-automatic technique with nondestructive observation provides reasonable 3D micrographs of porous Pb(Zr, Ti)O-3 (PZT). The efficiency of the proposed solver is investigated through the homogenization analysis of real porous PZT samples.

DOI： 10.1088/0965-0393/15/6/002

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

A dual-time-scale finite element model is developed in this paper for simulating cyclic deformation in polycrystalline alloys. The material is characterized by crystal plasticity constitutive relations. The finite element formulation of the initial boundary-value problems with cyclic loading involves decoupling the governing equations into two sets of problems corresponding to two different time-scales. One is a long-time-scale (low-frequency) problem characterizing a cycle-averaged solution, while the other is a short-time-scale (high-frequency) problem for a remaining oscillatory portion. Cyclic averaging together with asymptotic expansion of the variables in the time domain forms the basis of the multitime-scaling. The crystal plasticity equations at the two scales are used to study cyclic deformation of a titanium alloy Ti-6Al. This model is intended to study the fatigue response of a material by simulating a large number of cycles to initiation.

DOI： 10.1243/03093247JSA233

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

A dual-time-scale finite element model is developed in this paper for simulating cyclic deformation in polycrystalline alloys. The material is characterized by crystal plasticity constitutive relations. The finite element formulation of the initial boundary-value problems with cyclic loading involves decoupling the governing equations into two sets of problems corresponding to two different time-scales. One is a long-time-scale (low-frequency) problem characterizing a cycle-averaged solution, while the other is a short-time -scale (high-frequency) problem for a remaining oscillatory portion. Cyclic averaging together with asymptotic expansion of the variables in the time domain forms the basis of the multitime- scaling. The crystal plasticity equations at the two scales are used to study cyclic deformation of a titanium alloy Ti-6Al. This model is intended to study the fatigue response of a material by simulating a large number of cycles to initiation.

DOI： 10.1243/03093247JSA233

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

A dual-time-scale finite element model is developed in this paper for simulating cyclic deformation in polycrystalline alloys. The material is characterized by crystal plasticity constitutive relations. The finite element formulation of the initial boundary-value problems with cyclic loading involves decoupling the governing equations into two sets of problems corresponding to two different time-scales. One is a long-time-scale (low-frequency) problem characterizing a cycle-averaged solution, while the other is a short-time -scale (high-frequency) problem for a remaining oscillatory portion. Cyclic averaging together with asymptotic expansion of the variables in the time domain forms the basis of the multitime- scaling. The crystal plasticity equations at the two scales are used to study cyclic deformation of a titanium alloy Ti-6Al. This model is intended to study the fatigue response of a material by simulating a large number of cycles to initiation.

DOI： 10.1243/03093247JSA233

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

Language：Japanese  

Image-Based Multi-Scale Analysis for Porous Piezoelectric Materials Based on the Homogenization Method
This paper presents an image-based multi-scale analysis in order to evaluate macroscopic properties of heterogeneous porous piezoelectric materials by finite element calculations. The multi-scale analysis is based on the mathematical homogenization theory. Material heterogeneity is represented as a micro structure FE model that is automatically generated from the cross-sectioned images by high resolution X-ray CT. The high resolution X-ray measurement for porous PZT is compared with the digital image of SEM. Radius of pore is quantified from their images to compare these images. Nodal blocking preconditioned iterative solver is developed for piezoelectric FEM with high degree of freedom. In the numerical examples, material properties of porous PZT materials with different porosity are evaluated by the image-based multi-scale analysis to show the applicability and efficiency. Image-based multi-scale analysis with one million elements can be conducted by conventional PC with help of the proposed iterative solver.

DOI： 10.2472/jsms.55.1111

Language：Japanese  

Image-Based Multi-Scale Analysis for Porous Piezoelectric Materials Based on the Homogenization Method
This paper presents an image-based multi-scale analysis in order to evaluate macroscopic properties of heterogeneous porous piezoelectric materials by finite element calculations. The multi-scale analysis is based on the mathematical homogenization theory. Material heterogeneity is represented as a micro structure FE model that is automatically generated from the cross-sectioned images by high resolution X-ray CT. The high resolution X-ray measurement for porous PZT is compared with the digital image of SEM. Radius of pore is quantified from their images to compare these images. Nodal blocking preconditioned iterative solver is developed for piezoelectric FEM with high degree of freedom. In the numerical examples, material properties of porous PZT materials with different porosity are evaluated by the image-based multi-scale analysis to show the applicability and efficiency. Image-based multi-scale analysis with one million elements can be conducted by conventional PC with help of the proposed iterative solver.

DOI： 10.2472/jsms.55.1111

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

Language：Japanese  

Multi-Scale Stress Analysis of Trabecular Bone Considering Trabeculae Morphology and Biological Apatite Crystallite Orientation
This paper presents the multi-scale stress analysis of trabecular bone by the homogenization method bridging nano-micro-macro scales. Three-dimensional microstructure of trabeculae is obtained by the X-ray CT and the image-based modeling technique. Biological apatite (BAp) crystallite orientation is considered in the microstructure model by means of the anisotropic mechanical properties. The c-axis of BAp is set up as the maximum principal stress direction under the long term macroscopic stress condition. These properties are automatically assigned to each voxel element. To determine appropriately the microstructure model, the trabeculae morphology is analyzed and quantified as the trabecular density distribution. The proposed method is applied to pig's femur. It was revealed by the morphology analysis and homogenized macroscopic properties that the trabecular bone has plate-like characteristics. The predicted anisotropic level of the macroscopic properties was quantitatively coincident with the measured value by the X-ray diffraction analysis.

DOI： 10.2472/jsms.55.874

Language：Japanese  

Multi-Scale Stress Analysis of Trabecular Bone Considering Trabeculae Morphology and Biological Apatite Crystallite Orientation
This paper presents the multi-scale stress analysis of trabecular bone by the homogenization method bridging nano-micro-macro scales. Three-dimensional microstructure of trabeculae is obtained by the X-ray CT and the image-based modeling technique. Biological apatite (BAp) crystallite orientation is considered in the microstructure model by means of the anisotropic mechanical properties. The c-axis of BAp is set up as the maximum principal stress direction under the long term macroscopic stress condition. These properties are automatically assigned to each voxel element. To determine appropriately the microstructure model, the trabeculae morphology is analyzed and quantified as the trabecular density distribution. The proposed method is applied to pig's femur. It was revealed by the morphology analysis and homogenized macroscopic properties that the trabecular bone has plate-like characteristics. The predicted anisotropic level of the macroscopic properties was quantitatively coincident with the measured value by the X-ray diffraction analysis.

DOI： 10.2472/jsms.55.874

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

Language：Japanese  

Composites Science/Technology and New Challenges for Tomorrow's Applications : II : Simulation-Based Design of Composite Materials and Structures

DOI： 10.2472/jsms.55.237

Language：Japanese  

Composites Science/Technology and New Challenges for Tomorrow's Applications : II : Simulation-Based Design of Composite Materials and Structures

DOI： 10.2472/jsms.55.237

Language：Others  

Finite cover method for physically and geometrically nonlinear problems

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

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

Language：Japanese  

A NON-LOCAL VOXEL FINITE ELEMENT METHOD AND ITS APPLICATION TO FAILURE ANALYSES
A non-local voxel FEM is developed for simulating the failure phenomena of heterogeneous brittle materials. The micro-scale or meso-scale morphology of heterogeneous materials is realized by the image-based modeling technique, whereas the cracking is simulated by the element vanish technique. Also, the nonlocal technique of integral-averaging type is effectively utilized to avoid both the stress oscillation errors on the material interfaces and the spurious dependency on the voxel size for crack propagation problems. The three-dimensional numerical simulations successfully demonstrate the cracking phenomena induced by the micro-scale heterogeneities and the so-called biaxial effect that is typical in the strength characteristics of concrete.

DOI： 10.2208/jscej.2004.759_233

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

We introduce the finite cover method (FCM) as a generalization of the finite element method (FEM) and extend it to analyse the linear and non-linear mechanical behaviour of heterogeneous solids and structures. The name 'FCM' is actually an alias for the manifold method (MM) and the basic idea of the method has already been established for linear analyses of structures with homogeneous materials. After reviewing the concept of physical and mathematical covers for approximating functions in the FCM, we present the formulation for the static equilibrium state of a structure with arbitrary physical boundaries including material interfaces. The problem essentially involves the discontinuities in strains, and possibly has the discontinuities in displacement caused by interfacial debonding or rupture of material interfaces. We simulate such non-linear mechanical behaviour after presenting simple numerical examples that demonstrate the equivalence between the approximation capabilities of the FCM and those of the FEM. Copyright (C) 2003 John Wiley Sons, Ltd.

DOI： 10.1002/nme.820

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

We introduce the finite cover method (FCM) as a generalization of the finite element method (FEM) and extend it to analyse the linear and non-linear mechanical behaviour of heterogeneous solids and structures. The name 'FCM' is actually an alias for the manifold method (MM) and the basic idea of the method has already been established for linear analyses of structures with homogeneous materials. After reviewing the concept of physical and mathematical covers for approximating functions in the FCM, we present the formulation for the static equilibrium state of a structure with arbitrary physical boundaries including material interfaces. The problem essentially involves the discontinuities in strains, and possibly has the discontinuities in displacement caused by interfacial debonding or rupture of material interfaces. We simulate such non-linear mechanical behaviour after presenting simple numerical examples that demonstrate the equivalence between the approximation capabilities of the FCM and those of the FEM. Copyright (C) 2003 John Wiley Sons, Ltd.

DOI： 10.1002/nme.820

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

Language：English  

Meso-scopic numerical analysis of concrete structures by a modified lattice model
Realistic simulation of the mechanical behavior of concrete and reinforced concrete structures is performed by using a lattice type numerical model. Five different types of lattice members with simple constitutive models are introduced for mortar, coarse aggregate, steel, aggregate-mortar interface and steel-concrete interface. The meso-scopic morphology of concrete, which can be realized by the image-based geometry modeling technique, is taken into account. By the incorporation of the accurate meso-scopic morphology into the lattice type numerical modeling, the cracking behavior induced by the meso-scopic heterogeneities has been successfully captured.

DOI： 10.2208/jsceseee.20.43s

Language：English  

Meso-Scopic Numerical Analysis of Concrete Structures by a Modified Lattice Model

DOI： 10.2208/jscej.2003.731_19

Language：English  

Meso-scopic numerical analysis of concrete structures by a modified lattice model
Realistic simulation of the mechanical behavior of concrete and reinforced concrete structures is performed by using a lattice type numerical model. Five different types of lattice members with simple constitutive models are introduced for mortar, coarse aggregate, steel, aggregate-mortar interface and steel-concrete interface. The meso-scopic morphology of concrete, which can be realized by the image-based geometry modeling technique, is taken into account. By the incorporation of the accurate meso-scopic morphology into the lattice type numerical modeling, the cracking behavior induced by the meso-scopic heterogeneities has been successfully captured.

DOI： 10.2208/jsceseee.20.43s

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

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

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

Language：English  

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

Publishing type：Research paper (scientific journal)  

Language：Japanese   Book type：Scholarly book

Language：Japanese   Book type：Scholarly book

Language：Japanese   Book type：General book, introductory book for general audience

Language：Japanese   Book type：Scholarly book

Language：English  

CiNii Books

Language：Japanese  

CiNii Books

Responsible for pages：総ページ数：v, 225p   Language：Japanese  

Event date： 2025.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：埼玉   Country：Japan  

Event date： 2025.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：埼玉   Country：Japan  

Event date： 2025.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：埼玉   Country：Japan  

Event date： 2025.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：埼玉   Country：Japan  

Event date： 2025.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：埼玉   Country：Japan  

Event date： 2025.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山   Country：Japan  

Event date： 2025.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都   Country：Japan  

Event date： 2025.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都   Country：Japan  

Event date： 2025.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山   Country：Japan  

Event date： 2025.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山   Country：Japan  

Event date： 2025.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山   Country：Japan  

Event date： 2025.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山   Country：Japan  

Event date： 2025.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山   Country：Japan  

Event date： 2025.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都   Country：Japan  

Event date： 2024.9

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Kita-Kyushu   Country：Japan  

Event date： 2024.9

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Kita-Kyushu   Country：Japan  

Event date： 2024.9

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Kita-Kyushu   Country：Japan  

Event date： 2024.9

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Kita-Kyushu   Country：Japan  

Event date： 2024.9

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Kita-Kyushu   Country：Japan  

Event date： 2024.9

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Kita-Kyushu   Country：Japan  

Event date： 2024.8

Language：Japanese   Presentation type：Oral presentation (keynote)  

Venue：福岡   Country：Japan  

Event date： 2024.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Vancouver   Country：Canada  

Event date： 2024.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Vancouver   Country：Canada  

Event date： 2024.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Vancouver   Country：Canada  

Event date： 2024.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Vancouver   Country：Canada  

Event date： 2024.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Vancouver   Country：Canada  

Event date： 2024.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Vancouver   Country：Canada  

Event date： 2024.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Vancouver   Country：Canada  

Event date： 2024.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Vancouver   Country：Canada  

Event date： 2024.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Vancouver   Country：Canada  

Event date： 2024.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：神戸   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：神戸   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2024.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神戸   Country：Japan  

Event date： 2024.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山   Country：Japan  

Event date： 2024.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山   Country：Japan  

Event date： 2024.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山   Country：Japan  

Event date： 2024.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山   Country：Japan  

Event date： 2022.11

Language：English   Presentation type：Oral presentation (general)  

Venue：山梨   Country：Japan  

Event date： 2022.11

Language：English   Presentation type：Oral presentation (general)  

Venue：山梨   Country：Japan  

Event date： 2022.11

Language：English   Presentation type：Oral presentation (general)  

Venue：山梨   Country：Japan  

Event date： 2022.11

Language：English   Presentation type：Oral presentation (general)  

Venue：山梨   Country：Japan  

Event date： 2022.11

Language：English   Presentation type：Oral presentation (general)  

Venue：山梨   Country：Japan  

Event date： 2022.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Austin, Texas   Country：United States  

Event date： 2022.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Austin, Texas   Country：United States  

Event date： 2022.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Austin, Texas   Country：United States  

Event date： 2022.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Austin, Texas   Country：United States  

Event date： 2022.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Milan   Country：Italy  

Event date： 2022.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Milan   Country：Italy  

Event date： 2022.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Milan   Country：Italy  

Event date： 2022.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Milan   Country：Italy  

Event date： 2022.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Milan   Country：Italy  

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Berkeley   Country：United States  

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Berkeley   Country：United States  

Event date： 2022.9

Language：English  

Venue：Berkeley   Country：Japan  

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Event date： 2022.9

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：北九州（オンライン）   Country：Japan  

Event date： 2022.9

Language：English  

Venue：北九州（オンライン）   Country：Japan  

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Event date： 2022.7 - 2022.8

Language：English   Presentation type：Oral presentation (general)  

Venue：横浜（オンライン）   Country：Japan  

Event date： 2022.7 - 2022.8

Language：English   Presentation type：Oral presentation (general)  

Venue：横浜（オンライン）   Country：Japan  

Event date： 2022.7 - 2022.8

Language：English   Presentation type：Oral presentation (general)  

Venue：横浜（オンライン）   Country：Japan  

Event date： 2022.7 - 2022.8

Language：English  

Venue：横浜（オンライン）   Country：Japan  

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Event date： 2021.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Hamburg   Country：Germany  

Event date： 2021.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Hamburg   Country：Germany  

Event date： 2021.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto   Country：Japan  

Event date： 2021.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto   Country：Japan  

Event date： 2021.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Sardinia   Country：Italy  

Event date： 2021.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Sardinia   Country：Italy  

Event date： 2021.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Paris   Country：France  

Event date： 2021.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Paris   Country：France  

Event date： 2020.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Kobe   Country：Japan  

Event date： 2020.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Kobe   Country：Japan  

Event date： 2020.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Kobe   Country：Japan  

Event date： 2020.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Kobe   Country：Japan  

Event date： 2019.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Taipei   Country：Taiwan, Province of China  

Event date： 2019.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Taipei   Country：Taiwan, Province of China  

Event date： 2019.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Taipei   Country：Taiwan, Province of China  

Event date： 2019.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Taipei   Country：Taiwan, Province of China  

Event date： 2019.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Taipei   Country：Taiwan, Province of China  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：バルセロナ   Country：Spain  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：バルセロナ   Country：Spain  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：バルセロナ   Country：Spain  

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：バルセロナ   Country：Spain  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Whistler   Country：Canada  

Event date： 2019.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Chicago   Country：United States  

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎   Country：Japan  

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Event date： 2018.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Hanoi   Country：Viet Nam  

Event date： 2018.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Hanoi   Country：Viet Nam  

Event date： 2018.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Hanoi   Country：Viet Nam  

Event date： 2018.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Hanoi   Country：Viet Nam  

Event date： 2018.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道   Country：Japan  

Event date： 2018.7

Language：English   Presentation type：Oral presentation (general)  

Venue：New York   Country：United States  

Event date： 2018.7

Language：English   Presentation type：Oral presentation (general)  

Venue：New York   Country：United States  

Event date： 2018.7

Language：English   Presentation type：Oral presentation (general)  

Venue：New York   Country：United States  

Event date： 2018.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Event date： 2018.4

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Changwon   Country：Korea, Republic of  

独自に開発を進めている粒子法によるマルチフィジックス解析ツールによる災害被害予測シミュレーションに関する招待講演（セミプレナリー）を実施した。

Event date： 2018.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Changwon   Country：Korea, Republic of  

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宮崎大学   Country：Japan  

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宮崎大学   Country：Japan  

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宮崎大学   Country：Japan  

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宮崎   Country：Japan  

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宮崎   Country：Japan  

Event date： 2017.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Chengdu   Country：China  

Event date： 2017.10

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Chengdu   Country：China  

Event date： 2017.10

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Chengdu   Country：China  

Event date： 2017.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Chengdu   Country：China  

Event date： 2017.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Chengdu   Country：China  

Event date： 2017.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Chengdu   Country：China  

Event date： 2017.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Hannover   Country：Germany  

Event date： 2017.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Hannover   Country：Germany  

Event date： 2017.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Hannover   Country：Germany  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：関西大学   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：関西大学   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州大学   Country：Japan  

Event date： 2016.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北九州   Country：Japan  

Event date： 2016.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：久留米   Country：Japan  

Event date： 2013.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：佐賀   Country：Japan  

Event date： 2013.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Stuttgart   Country：Germany  

Event date： 2013.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Raleigh (North Carolina)   Country：United States  

Event date： 2012.11

Language：Others   Presentation type：Oral presentation (general)  

Venue：Jeju   Country：Korea, Republic of  

Event date： 2012.5

Language：Others   Presentation type：Oral presentation (general)  

Venue：京都   Country：Japan  

Event date： 2011.4

Language：Others   Presentation type：Oral presentation (general)  

Venue：pusan   Country：Korea, Republic of  

Event date： 2010.9

Language：Others   Presentation type：Oral presentation (general)  

Venue：札幌   Country：Japan  

Event date： 2009.9

Language：Others  

Venue：福岡大学，福岡   Country：Japan  

Event date： 2025

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台   Country：Japan  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台   Country：Japan  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台   Country：Japan  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台   Country：Japan  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台   Country：Japan  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台   Country：Japan  

Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島   Country：Japan  

Event date： 2023.9

Language：Japanese  

Venue：広島   Country：Japan  

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Event date： 2023.9

Language：Japanese  

Venue：広島   Country：Japan  

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Event date： 2023.9

Language：Japanese  

Venue：広島   Country：Japan  

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Event date： 2023.9

Language：Japanese  

Venue：広島   Country：Japan  

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Event date： 2023.9

Language：Japanese  

Venue：広島   Country：Japan  

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Event date： 2023.9

Language：Japanese  

Venue：広島   Country：Japan  

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Event date： 2023.5 - 2023.6

Language：English   Presentation type：Oral presentation (general)  

Venue：筑波   Country：Japan  

Event date： 2023.5 - 2023.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：筑波   Country：Japan  

Event date： 2023.5 - 2023.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：筑波   Country：Japan  

Event date： 2023.5 - 2023.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：筑波   Country：Japan  

Event date： 2023.5 - 2023.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：筑波   Country：Japan  

Event date： 2023.5 - 2023.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：筑波   Country：Japan  

Event date： 2023.5 - 2023.6

Language：English   Presentation type：Oral presentation (general)  

Venue：筑波   Country：Japan  

Event date： 2023.5 - 2023.6

Language：English   Presentation type：Oral presentation (general)  

Venue：筑波   Country：Japan  

Event date： 2023.5 - 2023.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：筑波   Country：Japan  

Event date： 2023.5 - 2023.6

Language：English  

Venue：筑波   Country：Japan  

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Event date： 2023.5 - 2023.6

Language：English  

Venue：筑波   Country：Japan  

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Event date： 2023.5 - 2023.6

Language：Japanese  

Venue：筑波   Country：Japan  

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Event date： 2023.5 - 2023.6

Language：Japanese  

Venue：筑波   Country：Japan  

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Event date： 2023.5 - 2023.6

Language：Japanese  

Venue：筑波   Country：Japan  

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Event date： 2023.5 - 2023.6

Language：Japanese  

Venue：筑波   Country：Japan  

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Event date： 2023.5 - 2023.6

Language：Japanese  

Venue：筑波   Country：Japan  

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Event date： 2023.5 - 2023.6

Language：Japanese  

Venue：筑波   Country：Japan  

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Event date： 2023.5 - 2023.6

Language：English  

Venue：筑波   Country：Japan  

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Event date： 2023.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京   Country：Japan  

Event date： 2023.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京   Country：Japan  

Event date： 2023.5