Numerical simulations of a cylinder wake under a strong axial magnetic field
Numerical simulations of a cylinder wake under a strong axial magnetic field
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DOI：
10.1063/1.2831153
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发表时间：
2008-01
影响因子：
4.6
通讯作者：
V. Dousset;A. Pothérat
中科院分区：
文献类型：
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作者：
V. Dousset;A. Pothérat
我们研究了方管中液态金属在强外加磁场中流经圆柱体的流动。在这些条件下，流动是准二维的，这使得我们可以使用二维(2D)模型对其进行建模。我们通过在[0…]范围内改变两个控制参数Re和Ha(Ha2是洛伦兹与粘性力的比率)来执行参数研究6000]和[0…2160]。发现这一流动呈现出四个区域的序列。前三个区域与非磁流体力学(Non-MHD)二维圆形尾迹相似，其相变由摩擦参数Re/Ha控制。第四个特征是通道侧壁边界层分离产生的涡旋，对卡门涡街产生强烈的扰动。这第一次解释了由Frank，Barleon和Muller[Phys]首先通过实验观察到的2D卡门涡街的破裂。流体13,2287(2001)]。我们还表明，对于高的Ha(Ha⩾1120)，Re∝0.56Ha发生了向第四区的转变，并且伴随着Strouhal数的突然下降。在前三个区域，我们发现阻力系数和定常回流区的长度由参数Re/HA4/5控制。同时，将回流区与自由流分开的自由剪切层类似于自由磁流体平行层，其厚度为Ha−1/2量级，与非磁流体情况有很大的不同，因此对该区域的动力学有很大的影响。在Re=3×104，Ha=1120的情况下，该层经历了Kelvin-Helmholtz类型的不稳定性.我们研究了方管中液态金属在强外加磁场中通过圆柱的流动.在这些条件下，流动是准二维的，这使得我们可以使用二维(2D)模型对其进行建模。我们通过在[0…]范围内改变两个控制参数Re和Ha(Ha2是洛伦兹与粘性力的比率)来执行参数研究6000]和[0…2160]。发现这一流动呈现出四个区域的序列。前三个区域与非磁流体力学(Non-MHD)二维圆形尾迹相似，其相变由摩擦参数Re/Ha控制。第四个特征是通道侧壁边界层分离产生的涡旋，对卡门涡街产生强烈的扰动。这第一次解释了由Frank，Barleon和Muller[Phys]首先通过实验观察到的2D卡门涡街的破裂。流体13,2287(2001)]。我们还表明，对于较高的Ha(H…
We study the flow of a liquid metal in a square duct past a circular cylinder in a strong externally imposed magnetic field. In these conditions, the flow is quasi-two-dimensional, which allows us to model it using a two-dimensional (2D) model. We perform a parametric study by varying the two control parameters Re and Ha (Ha2 is the ratio of Lorentz to viscous forces) in the ranges [0…6000] and [0…2160], respectively. The flow is found to exhibit a sequence of four regimes. The first three regimes are similar to those of the non-magnetohydrodynamic (non-MHD) 2D circular wake, with transitions controlled by the friction parameter Re∕Ha. The fourth one is characterized by vortices raising from boundary layer separations at the duct side walls, which strongly disturbs the Karman vortex street. This provides the first explanation for the breakup of the 2D Karman vortex street first observed experimentally by Frank, Barleon, and Muller [Phys. Fluids 13, 2287 (2001)]. We also show that, for high values of Ha (Ha⩾1120), the transition to the fourth regime occurs for Re∝0.56Ha, and that it is accompanied by a sudden drop in the Strouhal number. In the first three regimes, we show that the drag coefficient and the length of the steady recirculation regions located behind the cylinder are controlled by the parameter Re∕Ha4∕5. Also, the free shear layer that separates the recirculation region from the free stream is similar to a free MHD parallel layer, with a thickness of the order of Ha−1∕2 that is quite different to that of the non-MHD case, and therefore strongly influences the dynamics of this region. We also present one case at Re=3×104 and Ha=1120, where this layer undergoes an instability of the Kelvin–Helmholtz-type.We study the flow of a liquid metal in a square duct past a circular cylinder in a strong externally imposed magnetic field. In these conditions, the flow is quasi-two-dimensional, which allows us to model it using a two-dimensional (2D) model. We perform a parametric study by varying the two control parameters Re and Ha (Ha2 is the ratio of Lorentz to viscous forces) in the ranges [0…6000] and [0…2160], respectively. The flow is found to exhibit a sequence of four regimes. The first three regimes are similar to those of the non-magnetohydrodynamic (non-MHD) 2D circular wake, with transitions controlled by the friction parameter Re∕Ha. The fourth one is characterized by vortices raising from boundary layer separations at the duct side walls, which strongly disturbs the Karman vortex street. This provides the first explanation for the breakup of the 2D Karman vortex street first observed experimentally by Frank, Barleon, and Muller [Phys. Fluids 13, 2287 (2001)]. We also show that, for high values of Ha (H...