渡邉 智昭 (Tomoaki Watanabe)

Y. Tai, T. Watanabe, K. Nagata Multi-particle models of molecular diffusion for Lagrangian simulation coupled with LES for passive scalar mixing in compressible turbulence Computers and Fluids, 221 104886 2021 Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  This article may be found at  https://doi.org/10.1016/j.compfluid.2021.104886 . Abstract Lagrangian simulation coupled with large eddy simulation (LES) is studied for turbulent scalar mixing in compressible flows, where Lagrangian simulation solves advection-diffusion equations with computational particles. In Lagrangian simulation, a molecular diffusion term needs to be modeled with a so-called mixing model, which also requires modeling the dissipation rate of scalar fluctuations. The present study extends a particle-based subgrid-scale model for the scalar dissipation rate to compressible flows, and its validity in compressible turbulence ...

R. Nagata, T. Watanabe, K. Nagata, C. B. da Silva Triple decomposition of velocity gradient tensor in homogeneous isotropic turbulence Computer & Fluids, 198 104389 2020 Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  This article may be found at  https://doi.org/10.1016/j.compfluid.2019.104389 . Abstract The triple decomposition of a velocity gradient tensor is studied with direct numerical simulations of homogeneous isotropic turbulence, where the velocity gradient tensor $\nabla {\bd{u}}$ is decomposed into three components representing an irrotational straining motion $(\nabla\bd{u})_{\rm EL}$, a rigid-body rotation $(\nabla\bd{u})_{\rm RR}$, and a shearing motion  $(\nabla\bd{u})_{\rm SH}$. Strength of these motions can be quantified with the decomposed components. A procedure of the triple decomposition is proposed for three-dimensional flows, where the decomposition is applied i...

T. Watanabe, X. Zhang, K. Nagata Direct numerical simulation of incompressible turbulent boundary layers and planar jets at high Reynolds numbers initialized with implicit large eddy simulation Computer & Fluids, 194 104314 2019 Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  This article may be found at  https://doi.org/10.1016/j.compfluid.2019.104314 . Abstract A direct numerical simulation (DNS) initialized with an implicit large eddy simulation (ILES) is performed for temporally evolving planar jets and turbulent boundary layers. In the ILES, an initial laminar flow develops into a fully developed state of the planar jet or the boundary layer. Subsequently, the DNS is started from the flow field obtained by the ILES. This hybrid ILES/DNS methodology is tested for the planar jet and boundary layer by comparing the results with full DNS started from the initial laminar flow. The ILES re...