Seiya Watanabe

In tsunami inundations or slope disasters of heavy rain, a lot of floating debris or driftwood logs are included in the flows. The damage to structures from solid body impacts is more severe than the damage from the water pressure. In order to study free-surface flows that include floating debris, developing a high-accurate simulation code of free-surface flows with high performance for large-scale computations is desired. We propose the single-phase free-surface flow model based on the cumulant

The lattice Boltzmann method has recently become popular as an alternative to Navier-Stokes solvers for large-scale fluid simulations. We conduct a performance study of the lattice Boltzmann method on the A64FX Arm-based processor of the supercomputer Fugaku. We compared four types of data layouts: SoA, AoS, Clusterd SoA (CSoA), and CSoA2, and three algorithms for the LBM streaming step: Pull, Push, and Swap schemes. The performance measurement on a single CMG (Core Memory Group) shows that the

Abstract A wind turbine wake causes a decrease in wind speed and an increase in turbulence intensity. The wind turbine wake interaction is essential for predicting the power output of a wind farm consisting of many wind turbines. This research proposes a CFD method able to reproduce wake interactions and power outputs of multiple wind turbines with high speed and accuracy. Large eddy simulations with the lattice Boltzmann method are used for fluid calculations, specifically for large-scale CFD s

Abstract Evaluating ice loads acting on ships is essential for the safety of ships navigating in ice-covered seas. In this study, we develop a CFD method to handle ship, ice, and fluid interaction. The lattice Boltzmann method, capable of large-scale calculations, is applied to the simulation of free-surface fluids. The ice motion is computed by solving the equations of motion of a rigid body, and the discrete element method models the ice-ice and ice-ship contact interactions. A momentum exchan

Abstract A diffuser-augmented wind turbine (DAWT) achieves greater power generation efficiency by increasing wind speed through the diffuser. Nevertheless, scaling up this technology is difficult because of the considerable amount of wind drag on the diffusers. To overcome this difficulty, a multi-rotor system with two or more wind turbines on the same structure is one approach to increasing wind turbine power output. This research proposes a computational fluid dynamics (CFD) method to evaluate

Numerical simulations are powerful tools to study tsunami impacts on building structures. We have developed a CFD code for free-surface flows interacting with floating debris by using Lattice Boltzmann Method (LBM) and Discrete Element Method (DEM). Both methods are suitable for GPU computing and large-scale simulations because they are explicit time-integration schemes. In order to improve the accuracy and the stability of flow computation, the cumulant LBM model has been employed and coupled w

Nos primeiros anos do século XXI, foi desenvolvida uma plataforma para a programação de GPUs para uso geral, o que alavancou o estudo da dinâmica de fluidos computacional por meio da computação paralela. Neste trabalho, sumarizamos dois métodos que podem ser aplicados a tal computação. Primeiramente, descrevemos o método do escoamento fracamente compressível, que negligencia variações de densidade em curtos intervalos de tempo; bem como demonstramos uma aplicação deste método em um problema bidi