Large-Scale Simulations for Free-Surface Flows with Objects by Lattice Boltzmann Method
Large-Scale Simulations for Free-Surface Flows with Objects by Lattice Boltzmann Method
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DOI：
10.3811/jjmf.2019.003
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发表时间：
2019-03
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影响因子：
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通讯作者：
Seiya Watanabe;T. Aoki;Yuta Hasegawa;Jun Kawahara;H. Hashimoto
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文献类型：
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作者：
Seiya Watanabe;T. Aoki;Yuta Hasegawa;Jun Kawahara;H. Hashimoto
数值模拟是研究海啸对建筑物结构影响的有力工具。利用格子玻尔兹曼法（LBM）和离散元法（DEM）开发了自由表面流与浮物相互作用的CFD程序。这两种方法都是显式的时间积分方案，适用于GPU计算和大规模仿真。为了提高流动计算的精度和稳定性，采用了累积量LBM模型，并结合保守的Allen-Cahn方程进行自由表面捕获。在液固界面处采用了一种基于内插反弹格式的移动边界方法。利用DEM计算浮物的刚体动力学。由多个小球体构成的模型代表了复杂形状的碎片。我们测试了TSUBAME3.0超级计算机在多个gpu上的弱可扩展性，当扩展到16到256个gpu时，代码的并行效率达到83.4%。作为测试用例，我们使用200×600×3000晶格节点和24个gpu Tesla P100演示了带有浮木的海啸流，模拟在24小时内完成。浮木作用在壁上的冲击力大约是水的15倍。结果表明，浮木效应对评价海啸对建筑物的破坏具有重要意义
Hirotada Abstract 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 with the conservative Allen-Cahn equation for the purpose of free-surface capturing. A moving boundary approach based on the interpolated bounce-back scheme is utilized at liquid-solid interfaces. Rigid body dynamics of floating debris is computed by using DEM. A model constructed by multiple small spheres represents complex shapes of debris. We measure the weak scalability on multiple GPUs of the TSUBAME3.0 supercomputer, and the code achieved 83.4% parallel efficiency when scaled 16 to 256 GPUs. As a test case, we demonstrate a tsunami flow with driftwoods using 200×600×3000 lattice nodes and 24 GPUs Tesla P100, and the simulation has completed within 24 hours. The impact force of the driftwoods acting on the wall is about 15 times larger than only water. It shows that effects of driftwoods are important to evaluate the tsunami damage on building