磁化球库埃特流实验中的带剪切和超旋转
Zonal shear and super-rotation in a magnetized spherical Couette flow experiment
摘要：
我们目前的测量在一个充满液体钠的球壳中进行，其中半径为74 mm的内球旋转，而半径为210 mm的外球处于静止状态。内球体拥有一个偶极磁场，旋转时就像一个磁力推进器。在这个实验装置中，速度的直接测量是通过超声多普勒测速仪进行的。还测量了电势和感应磁场的差异以表征磁流体动力学流。内球的旋转频率在-30 Hz和+30 Hz之间变化，基于测量的钠速度和壳半径的磁雷诺数达到约33。我们已经研究了平均轴对称部分的流动，其中包括微分旋转。直接测量流体相对于旋转内球的强超旋转。它被发现，组织的平均流量并没有改变太多的整个范围内的参数覆盖我们的实验。在磁力主导惯性力的内球附近，纬向速度的直接测量很好地说明了费拉罗等旋定律。从内部的费拉罗状态到外部区域的地转状态的转变，其中惯性力占主导地位，已经得到了很好的证明。它发生在当地埃尔萨瑟数约为1的地方。当保持相同的Elsasser数时，与非线性数值模拟的定量协议。实验还揭示了一个违反费拉罗定律的区域，就在内球上方。
英文摘要：
We present measurements performed in a spherical shell filled with liquid sodium, where a 74 mm-radius inner sphere is rotated while a 210 mm-radius outer sphere is at rest. The inner sphere holds a dipolar magnetic field and acts as a magnetic propeller when rotated. In this experimental set-up called DTS, direct measurements of the velocity are performed by ultrasonic Doppler velocimetry. Differences in electric potential and the induced magnetic field are also measured to characterize the magnetohydrodynamic flow. Rotation frequencies of the inner sphere are varied between -30 Hz and +30 Hz, the magnetic Reynolds number based on measured sodium velocities and on the shell radius reaching to about 33. We have investigated the mean axisymmetric part of the flow, which consists of differential rotation. Strong super-rotation of the fluid with respect to the rotating inner sphere is directly measured. It is found that the organization of the mean flow does not change much throughout the entire range of parameters covered by our experiment. The direct measurements of zonal velocity give a nice illustration of Ferraro's law of isorotation in the vicinity of the inner sphere where magnetic forces dominate inertial ones. The transition from a Ferraro regime in the interior to a geostrophic regime, where inertial forces predominate, in the outer regions has been well documented. It takes place where the local Elsasser number is about 1. A quantitative agreement with non-linear numerical simulations is obtained when keeping the same Elsasser number. The experiments also reveal a region that violates Ferraro's law just above the inner sphere.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
