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Modeling a mechanism of MHD turbulent diffusion in Earth and Planetary fluid cores

模拟地球和行星流体核心 MHD 湍流扩散机制

基本信息

批准号：
15540405
负责人：
MATSUSHIMA Masaki
金额：
$ 2.37万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540405/
关键词：
MHD turbulence Earth and planetary fluid core turbulent diffusion parallel computation subgrid-scale scale similarity

项目摘要

Aiming at modeling an eddy diffusivity tensor, we have performed direct numerical simulations of MHD turbulence in a rapidly rotating system. To carry out computation using molecular diffusivity in a realistic planetary core, required is high resolution even for a very small region in the core. In the present research, the computational region is divided into several segments, which are allocated to respective CPUs on a parallel computer with large size of memory. Using results of direct numerical simulations thus obtained, we have examined scale similarity in MHD turbulence to model subgrid-scale physical processes, and we have found that scale similarity holds. On the basis of scale similarity law as well as spatial-filter width dependence, we have estimated the effect of subgrid-scales on grid-scales. We have then carried out large eddy simulations of MHD turbulence with the model of subgrid-scales. We have compared their results with those of direct numerical simulations, and confirmed that the present subgrid-scale model holds valid. That is, heat flux, kinetic energy, and magnetic energy averaged over computational time and computational region for large eddy simulation with the subgrid-scale model are closer to those for direct numerical simulations than those for numerical simulations without the model. It should be noted, however, that there is no significant difference among power spectra for velocity field, magnetic field, and temperature.

针对涡扩散系数张量模型，我们对快速旋转系统中的MHD湍流进行了直接数值模拟。为了在一个现实的行星核中使用分子扩散率进行计算，即使对于核中非常小的区域，也需要高分辨率。在本研究中，计算区域被划分为几个部分，这是分配给各自的CPU上的并行计算机与大容量的内存。利用直接数值模拟的结果，从而获得，我们已经检查了MHD湍流模型亚网格尺度的物理过程的尺度相似性，我们已经发现，尺度相似性持有。基于尺度相似律和空间滤波器宽度依赖性，我们估计了子网格尺度对网格尺度的影响。然后，我们进行了大涡模拟的MHD湍流的亚网格尺度模型。我们将它们的结果与直接数值模拟的结果进行了比较，证实了本亚网格模型的有效性。也就是说，在计算时间和计算区域上平均的热通量，动能和磁能的大涡模拟与亚网格尺度模型更接近直接数值模拟比那些没有模型的数值模拟。然而，应该注意的是，速度场、磁场和温度的功率谱之间没有显著差异。