Authorship：Corresponding author   Publisher：Journal of Computational Physics  

This study theoretically proves that the properties of kinetic energy preservation and product rule discretely hold in a non-dissipative numerical scheme based on a compact scheme. A previous work developed a kinetic energy and entropy preserving (KEEP) compact scheme and showed superior numerical stability compared to the standard compact scheme. However, the reason for the improved numerical stability in the KEEP-compact scheme was not clearly discussed in the previous work. This study reviews the construction of the compact scheme using the Padé approximation and shows that the important discrete properties of kinetic energy preservation and product rule, which play major roles in improving numerical stability in the existing explicit KEEP schemes, hold in the KEEP-compact scheme.

DOI： 10.1016/j.jcp.2025.113829

Web of Science

Scopus

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

This study examines the similarity between directed percolation (DP) and boundary layer transition on a flat plate, performing large eddy simulation (LES).A flat-plate boundary-layer flow is one of the well-studied fundamental flows and is widely used in developing turbulence and transition models.In this study, laminar-turbulent transition is enforced on a flat plate by a blowing-suction wall-normal velocity given at the upper computational boundary.Since the separated shear layer plays a major role in causing laminar-turbulent transition in the flow field studied in this study, the relation between the transition and DP is investigated on a constant plane along the separated shear layer.The DP universality class is characterized by some critical exponents, and two of the three critical exponents obtained by the present LES are in good agreement with the one-dimensional DP universality class.

DOI： 10.7566/JPSJ.93.114003

Web of Science

Scopus

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Computers and Fluids  

This study proposes a quantum annealing-based algorithm for flow computation based on lattice-gas automata (LGA). Since the state of the lattice gas is determined by Boolean variables, 0 (absence) or 1 (presence), in LGA, it is well suited for implementation in quantum annealing and simulated annealing computers. The quantum annealing-based algorithm proposed in this study is constructed so that conservation of mass and momentum is satisfied at the particle collision process. Verification tests performed with various quantum annealing and simulated annealing computers confirm that the proposed algorithm well replicates a conventional LGA collision model.

DOI： 10.1016/j.compfluid.2024.106238

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Scopus

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Journal of Computational Physics  

A kinetic energy and entropy preserving (KEEP) finite-volume scheme on unstructured meshes is proposed for non-dissipative and stable compressible flow computations. The KEEP finite volume scheme proposed in the present study is based on the existing KEEP schemes developed for finite difference methods. The KEEP schemes have shown superior numerical robustness without numerical dissipation in previous studies. The KEEP schemes are discretized such that the numerical fluxes discretely replicate the key analytical relations that the governing equations hold, leading to preservation of kinetic energy and a superior entropy preservation property in the incompressible and inviscid limits. This study proposes using cell-vertex discretization for the proposed KEEP finite volume scheme in order to maintain this characteristic property of the KEEP scheme and achieve second-order accuracy in space on simplex meshes and arbitrary meshes that are not highly irregular. In the numerical tests performed in this study, the proposed KEEP finite volume scheme successfully performs long-time stable computations on various unstructured meshes. Also, the proposed KEEP scheme shows much better numerical stability and spatial accuracy than the KEEP scheme with cell-centered discretization.

DOI： 10.1016/j.jcp.2023.112521

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

<p>A numerical study on the flow around a full-scale train subjected to crosswind has been conducted on the basis of detached-eddy simulation (DES). Finite-volume method is applied to unstructured mesh generated around a three-car-train model whose running speed is fixed to 120 km/h while the crosswind speed is set to 5 m/s,15 m/s, and 25 m/s. A clear longitudinal vortex structure is recognized in the case of the crosswind speed of 25 m/s, where two longitudinal vortices are evolved respectively from the roof and floor of the head car (roof-edge and floor-edge vortices), forming a characteristic vortex pair. This longitudinal vortex structure around the head car is discussed with a focus on its non-trivial role in the side-force mechanism. Our simulation suggests a causal association between these two vortices, which implies an importance of optimum designing of the underfloor equipment in addition to the roof and head shapes of the head car.</p>

DOI： 10.1299/mel.22-00464

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