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Ohashi, Kunihide*; Hino, Takanori*; Kobayashi, Hiroshi*; Onodera, Naoyuki; Sakamoto, Nobuaki*
Journal of Marine Science and Technology, 24(3), p.884 - 901, 2019/09
Times Cited Count：17 Percentile：75.85(Engineering, Marine)An unsteady Reynolds averaged Navier-Stokes solver with a structured overset grid method has been developed. Velocity pressure coupling is achieved using an artificial compressibility approach, spatial discretization is based on a FVM. Body motions are considered using the grid deformation technique and grid velocities in the convective term. The full multigrid (FMG) method is applied to obtain fast convergence. The cell flag on a coarse grid level is determined using the cell flag on a fine grid level. In the coarse and fine grid level calculations at the FMG stage, the data are interpolated until the finest grid level is achieved at an overset update interval. Then, the data are updated based on the overset relations at the finest grid level and then transferred to a coarser grid level. The computations for flows around a hull form, including an unsteady simulation with regular waves, are demonstrated.
Onodera, Naoyuki; Ohashi, Kunihide*
no journal, ,
Ship maneuverability under heavy weather is one of important themes for safety. In order to understand the detail of ship motion, it is necessary to carry out large scale gas-liquid-solid multiphase simulations. We have developed a CFD code based on LBM (Lattice Boltzmann Method) with a two-phase free-surface model. LBM accesses memory with a simple algorithm and is suitable for large-scale computations. The code is written in CUDA and tuned to achieve high performance on TSUBAME 2.5. The proposed two-phase model is based on a free-surface model, and both liquid and gas phases are independently time-integrated. We demonstrate a fluid-structure interaction problem by using a bulk carrier data. The simulation is executed with 700 
120 400 mesh, and numerical stabilities are confirmed with high density ratio.
Ohashi, Kunihide*; Onodera, Naoyuki
no journal, ,
The applicability of shared memory type computing with Xeon Phi Knights Landing processor is examined with the flow solver which is dedicated to the flow computation around a ship hull. The computations at the high Reynolds number with the one- or two-equation turbulence models and the free surface model, additionally, the over-set grid method are selected as the test cases. The processing speeds of the Xeon Broadwell and the Skylake processors show better results than the speed of the Xeon Phi processors. The speed up ratio is smoothly increasing until the maximum number of the core with using the Xeon Phi processor.
