Effect of flow topology on the kinetic energy flux in compressible isotropic turbulence
Effect of flow topology on the kinetic energy flux in compressible isotropic turbulence
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流动拓扑对可压缩各向同性湍流动能通量的影响
DOI：
10.1017/jfm.2019.867
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发表时间：
2020
影响因子：
3.7
通讯作者：
Chen Shiyi
中科院分区：
文献类型：
--
作者：
Wang Jianchun;Wan Minping;Chen Song;Xie Chenyue;Zheng Qinmin;Wang Lian-Ping;Chen Shiyi
研究了流动拓扑结构对可压缩各向同性湍流中亚网格尺度动能通量的影响。基于过滤后速度梯度张量的三个不变量，在不同的尺度上分析了8种流动拓扑类型，以及它们在动能传递的大小和方向上的作用。不稳定焦点/压缩(UFC)、不稳定节点/鞍点(UN/S/S)和稳定焦点/拉伸(SFS)是所有尺度上的三种主要拓扑类型，它们至少占流动区域的75%。UN/S/S型和SFS型对惯性范围内从大尺度到小尺度的SGS平均动能通量有较大贡献。不稳定的聚焦/伸展(UFS)拓扑对从小尺度到大尺度的反SGS动能通量有贡献。在强压缩区域，稳定的节点/鞍形(SN/S/S)结构对SGS动能通量的平均贡献为正，且优于其他流动结构。在强膨胀区，UFS拓扑对反SGS动能通量有很大贡献。随着湍流马赫数的增加，UFS拓扑区体积分数的增加导致动能的SGS背向散射增加。SN/S/S拓扑对可压缩动能分量的正SGS通量贡献最大，而UFS拓扑对可压缩动能分量的反向SGS通量贡献最大。
The effects of flow topology on the subgrid-scale (SGS) kinetic energy flux in compressible isotropic turbulence is studied. The eight flow topological types based on the three invariants of the filtered velocity gradient tensor are analysed at different scales, along with their roles in the magnitude and direction of kinetic energy transfer. The unstable focus/compressing (UFC), unstable node/saddle/saddle (UN/S/S) and stable focus/stretching (SFS), are the three predominant topological types at all scales; they account for at least 75 % of the flow domain. The UN/S/S and SFS types make major contributions to the average SGS flux of the kinetic energy from large scales to small scales in the inertial range. The unstable focus/stretching (UFS) topology makes a contribution to the reverse SGS flux of kinetic energy from small scales to large scales. In strong compression regions, the average contribution of the stable node/saddle/saddle (SN/S/S) topology to the SGS kinetic energy flux is positive and is predominant over those of other flow topologies. In strong expansion regions, the UFS topology makes a major contribution to the reverse SGS flux of the kinetic energy. As the turbulent Mach number increases, the increase of volume fraction of the UFS topological regions leads to the increase of the SGS backscatter of kinetic energy. The SN/S/S topology makes a dominant contribution to the direct SGS flux of the compressible component of the kinetic energy, while the UFS topology makes a dominant contribution to the reverse SGS flux of the compressible component of the kinetic energy.