论文标题
MHD湍流中的局部通量
Local fluxes in MHD Turbulence
论文作者
论文摘要
使用高度分辨的直接数值模拟，我们检查了局部能量通量速率$π_\ ell（x）$的统计特性，用于三种各向同性湍流磁性流动力流的小尺度，这在磁场的强度和结构上有所不同。我们分析了动力学和磁能中的级联进程，从而分解了对整体能量动力学的不同助焊剂贡献。结果表明，局部能量通量的概率分布会形成与极端事件相关的长尾巴，类似于流体动力学病例。能量通量的不同术语表现出不同的特性，并对所检查的流动类型表现出灵敏度。我们进一步研究了局部能量通量与所涉及场梯度之间的关节PDF。结果指出了与磁场梯度的相关性，但是分散剂比流体动力流中观察到的分散剂要强得多。最后，还表明，局部能量通量显示出对磁场的局部幅度的一定依赖性。目前的结果对我们讨论的子网格量表模型具有影响。
Using highly resolved direct numerical simulations we examine the statistical properties of the local energy flux rate $Π_\ell(x)$ towards small scales for three isotropic turbulent magnetohydrodynamic flows, which differ in strength and structure of the magnetic field. We analyse the cascade process both in the kinetic and magnetic energy, disentangling the different flux contributions to the overall energy dynamics. The results show that the probability distribution of the local energy flux develops long tails related to extreme events, similar to the hydrodynamic case. The different terms of the energy flux display different properties and show sensitivity on the type of the flow examined. We further examine the joint pdf between the local energy flux and the gradients of the involved fields. The results point out a correlation with the magnetic field gradients, showing however a dispersion much stronger than what is observed in hydrodynamic flows. Finally, it is also shown that the local energy flux shows some dependence on the local amplitude of the magnetic field. The present results have implications for subgrid scale models that we discuss.
