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中国物理学会期刊

横向磁场作用下Taylor-Couette湍流流动的大涡模拟

CSTR: 32037.14.aps.70.20210389

Large eddy simulation of Taylor-Couette turbulent flow under transverse magnetic field

CSTR: 32037.14.aps.70.20210389
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  • 采用大涡模拟方法对横向磁场作用下导电流体Taylor-Couette湍流流动进行数值模拟, 以研究其运动规律. 计算模型为无限长度, 半径比为1/2. 雷诺数分别选取为3000和5000, 磁场加载方式为全局磁场, 哈特曼数取值0—50. 对磁场作用下泰勒涡的演化过程、速度分布和湍动能分布进行分析, 并与轴向磁场作用下泰勒涡演化过程进行对比. 结果表明: 磁场对流场有显著的抑制作用, 扭曲的泰勒涡在横向磁场的作用下破裂成小尺度涡结构, 并沿磁场方向排列; 在外圆筒和垂直于磁场方向的区域, 磁场抑制效果较强; 随着雷诺数的增加, 磁场抑制效果减弱, 在流场不同区域, 流动呈现出不同的特点. 与轴向磁场相比, 横向磁场对流场的抑制效果较弱, 流场分布呈现出明显的各向异性.

     

    By the large eddy simulation method, the turbulent Taylor-Couette flow of conducting fluid under a homogenous transverse magnetic field is investigated through using the computational fluid dynamic software ANSYS Fluent 17.0. The flow is confined between two infinitely long cylinders, thus a periodic boundary condition is imposed in the axial direction. The inner cylinder rotates while the outer one is at rest, and their radius ratio is 1/2. Two Reynolds numbers of 3000 and 5000 are considered in the simulations, and the Hartmann number is varied from 0 to 50. In the present study, we assume a lower magnetic Reynolds number Re_\rm m \ll 1, i.e., the influence of the induced magnetic field on the flow is negligible in comparison with the imposed magnetic field. The evolution of Taylor vortices, velocity profile of mean flow, and turbulent kinetic energy distribution under the transverse magnetic field are analyzed and compared with the results of the axial magnetic field counterpart. It shows that the imposed magnetic field has a significant damping effect on the Taylor-Couette flow. The twisted Taylor vortices break into small-scale vortex structures under the transverse magnetic field and they arrange themselves along the magnetic field. The fluctuations which are perpendicular to the magnetic field are suppressed effectively, while the one which is parallel to the magnetic field is nearly uninfluenced, resulting in quasi-two-dimensional elongated structure in the flow field. As anticipated, in a sufficiently strong magnetic field, the turbulent Taylor-Couette flow may eventually decay to a Couette laminar flow. In the outer cylinder and the area perpendicular to the direction of the magnetic field, the suppression effect is even stronger than those in any other places and fewer vortices are observed in the simulations. The turbulent kinetic energy is transferred firstly from large eddies to intermediate eddies, then to small eddies, and finally dissipated due to the viscous and Joule effect. As the Reynolds number increases, the suppression effect of the magnetic field weakens, and the flow behaves divergently in different areas of the apparatus. Compared with the axial magnetic field, the transverse magnetic field has a weak suppression effect on the flow field, and the profiles of related variables are obviously anisotropic.

     

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