Locally mesh-refined lattice Boltzmann method for fuel debris air cooling analysis on GPU supercomputer

Onodera, Naoyuki   ; Idomura, Yasuhiro   ; Uesawa, Shinichiro  ; Yamashita, Susumu   ; Yoshida, Hiroyuki  

A dry method is one of practical methods for decommissioning the TEPCO's Fukushima Daiichi Nuclear Power Station. Japan Atomic Energy Agency (JAEA) has been evaluating the air cooling performance of the fuel debris by using the JUPITER code based on an incompressible fluid model and the CityLBM code based on the lattice Boltzmann method (LBM). However, these codes were based on a uniform Cartesian grid system, and required large computational time and cost to capture complicated debris structures. We develop an adaptive mesh refinement (AMR) version of the CityLBM code on GPU based supercomputers and apply it to thermal-hydrodynamics problems. The proposed method is validated against free convective heat transfer experiments at JAEA. It is also shown that the AMR based CityLBM code on 4 NVIDIA TESLA V100GPUs gives 6.7x speedup of the time to solution compared with the JUPITER code on 36 Intel Xeon E5-2680v3 CPUs.