Inverse and Direct Energy Cascades in Three-Dimensional Magnetohydrodynamic Turbulence at Low Magnetic Reynolds Number.
Inverse and Direct Energy Cascades in Three-Dimensional Magnetohydrodynamic Turbulence at Low Magnetic Reynolds Number.
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DOI：
10.1103/physrevlett.120.224502
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发表时间：
2017-08
影响因子：
8.6
通讯作者：
N. T. Baker;A. Pothérat;L. Davoust;F. Debray
中科院分区：
文献类型：
--
作者：
N. T. Baker;A. Pothérat;L. Davoust;F. Debray
这项实验研究分析了湍流的维度与其能量传递的高尺度或低尺度性质之间的关系。我们这样做，迫使低Rm磁流体动力学湍流在一个封闭的通道，同时精确地控制其维数通过外部施加的磁场。我们首先确定一个特定的长度尺度l[over ^]_{c}，它将较小的3D结构与较大的准2D结构分开。然后，我们表明，逆能量级联的水平动能沿着水平尺度总是可以观察到在大尺度上，它延伸到该地区的三维结构。与此同时，直接的能量级联局限于最小的和强烈的三维尺度观察。因此，这些动态似乎不是简单地由单个尺度的维度，也不是由强迫尺度，不像在其他研究。事实上，我们的研究结果表明，运动学和动力学之间的关系是不普遍的，可能强烈依赖于在发挥作用的强迫和耗散机制。
This experimental study analyzes the relationship between the dimensionality of turbulence and the upscale or downscale nature of its energy transfers. We do so by forcing low-Rm magnetohydrodynamic turbulence in a confined channel, while precisely controlling its dimensionality by means of an externally applied magnetic field. We first identify a specific length scale l[over ^]_{⊥}^{c} that separates smaller 3D structures from larger quasi-2D ones. We then show that an inverse energy cascade of horizontal kinetic energy along horizontal scales is always observable at large scales, and that it extends well into the region of 3D structures. At the same time, a direct energy cascade confined to the smallest and strongly 3D scales is observed. These dynamics therefore appear not to be simply determined by the dimensionality of individual scales, nor by the forcing scale, unlike in other studies. In fact, our findings suggest that the relationship between kinematics and dynamics is not universal and may strongly depend on the forcing and dissipating mechanisms at play.