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Onodera, Naoyuki; Idomura, Yasuhiro
Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 7 Pages, 2018/07
A large-scale simulation of the environmental dynamics of radioactive substances is very important from the viewpoint of nuclear security. Recently, GPU has been emerging as one of high performance devices to realize a large-scale simulation with less power consumption. We design a plume dispersion simulation based on the AMR-based LBM. We measure the performance of the LBM code on the GPU-rich supercomputer TSUBAME 3.0 at Tokyo Tech. We achieved good weak scaling from 4 GPUs to 144 GPUs, and 30 times higher node performance with CPUs. The code is validated against a wind tunnel test which was released from the National Institute of Advanced Industrial Science and Technology (AIST). The computational grids are subdivided by the AMR method, and the total number of grid points is reduced to less than 10% compared to the finest meshes. In spite of the fewer grid points, the turbulent statistics and plume dispersion are in good agreement with the experiment data.
Onodera, Naoyuki
no journal, ,
The SPEEDI and its world version (WSPEEDI) were developed to predict the off-site diffusion behavior of radioactive substances covering wide areas at ~100km scale based on a mesoscale metrological model. In this work, we apply two new ingredients, GPUs and an adaptive mesh refinement (AMR) method to the lattice Boltzmann method (LBM). In this report, we confirmed the good scalability on the GPU-rich supercomputer, and our code can reproduce the wind tunnel experiment. We conclude that the present LBM is one of most promising approaches to realize a real-time simulation.
Onodera, Naoyuki; Idomura, Yasuhiro; Ali, Y.*; Shimokawabe, Takashi*
no journal, ,
We have developed a communication reduced multi-time-step (CRMT) algorithm for the Post-K supercomputer, and measured the performance on the GPU-based supercomputers. This algorithm is based on the temporal blocking method, and can improve computational efficiency by replacing a communication bottleneck with additional computation. The proposed method is easily applied to the explicit time integration scheme, and is implemented on an extreme scale airflow simulation code CityLBM. We evaluate the performance of the CRMT algorithm on GPU based supercomputers, TSUBAME and Reedbush. Thanks to the CRMT algorithm, the communication cost is reduced by 64%, and weak and strong scaling are improved up to 200 GPUs. The obtained performance indicates that real time airflow simulations for about 2 km square area with the wind speed of 5m/s is feasible using 1m resolution. We conclude that the CRMT algorithm is indispensable for the AMR-LBM to realize a real time simulation on future exascale systems.
Onodera, Naoyuki
no journal, ,
The simulation for dissipation of radioactive substances attract high social interest, and it is required to satisfy both the rapidity and the accuracy. To perform a real-time simulation with high resolution mesh for the scale of human living area such as alleyways and buildings, it is required to develop simulation schemes which can fully utilize high computational performance. In this study, we introduced a nudging-based data assimilation method into the lattice Boltzmann method (LBM), so that we can performe plume dissipation simulations for urban area.
Onodera, Naoyuki; Idomura, Yasuhiro; Kawamura, Takuma; Nakayama, Hiromasa; Shimokawabe, Takashi*; Aoki, Takayuki*
no journal, ,
The simulation for dispersion of radioactive substances attract high social interest, and it is required to satisfy both the speed and the accuracy. To perform a real-time simulation with high resolution mesh for the scale of human living area involving alleyways and buildings, it is required to develop simulation schemes which can fully utilize high computational performance. In this study, we introduced a nudging-based data assimilation method and a plant canopy model into the lattice Boltzmann method (LBM), and confirmed the accuracy of plume dispersion simulations for urban areas is improved.
Hasegawa, Yuta
no journal, ,
To realize the large-scale LES simulation for the aerodynamics of complex shape bodies and the local wind analysis of urban areas, multiple GPU computation of the lattice Boltzmann method (LBM) with adaptive mesh refinement has been implemented. In this presentation, we will explain optimization techniques for the developed code such as single GPU optimization, an optimization of MPI communication, and a spacial parallel implementation for intra-node multiple GPU computation on the latest GPU platforms.