Numerical study of magnetohydrodynamic duct flow at high Reynolds and Hartmann numbers
Numerical study of magnetohydrodynamic duct flow at high Reynolds and Hartmann numbers
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DOI：
10.1017/jfm.2012.256
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发表时间：
2012-07
影响因子：
3.7
通讯作者：
D. Krasnov;O. Zikanov;T. Boeck
中科院分区：
文献类型：
--
作者：
D. Krasnov;O. Zikanov;T. Boeck
摘要采用高分辨率直接数值模拟方法，分析了导电流体在具有电绝缘壁和施加横向磁场的方形截面管道中的湍流状态。流的雷诺数为$1{0}^{5}$，哈特曼数在$0$到$400$之间变化。研究发现，在很宽的哈特曼数范围内，流动既不是层流，也不是完全湍流，而是具有层流核心、哈特曼边界层和平行于磁场的壁面附近的湍流区。对湍流波动的分析表明，每个区都由两层组成：以壁面附近的边界层为特征的小尺度湍流和以磁场方向上强烈拉长的大尺度涡旋结构为主的外层。我们还发现了一种特殊的平均速度尺度，根据这种尺度，von Kármán系数的倒数随着到壁面的距离几乎线性增长。
Abstract High-resolution direct numerical simulations are conducted to analyse turbulent states of the flow of an electrically conducting fluid in a duct of square cross-section with electrically insulating walls and imposed transverse magnetic field. The Reynolds number of the flow is $1{0}^{5} $ and the Hartmann number varies from $0$ to $400$ . It is found that there is a broad range of Hartmann numbers in which the flow is neither laminar nor fully turbulent, but has laminar core, Hartmann boundary layers and turbulent zones near the walls parallel to the magnetic field. Analysis of turbulent fluctuations shows that each zone consists of two layers: the boundary layer near the wall characterized by small-scale turbulence and the outer layer dominated by large-scale vortical structures strongly elongated in the direction of the magnetic field. We also find a peculiar scaling of the mean velocity, according to which the reciprocal von Kármán coefficient grows nearly linearly with the distance to the wall.