Statistics of passive tracers in three-dimensional magnetohydrodynamic turbulence
Statistics of passive tracers in three-dimensional magnetohydrodynamic turbulence
复制标题
三维磁流体动力湍流中被动示踪剂的统计
DOI：
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发表时间：
2007
期刊：
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通讯作者：
R. Grauer
中科院分区：
文献类型：
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作者：
A. Busse;W. Müller;H. Homann;R. Grauer
采用高分辨率直接数值模拟方法，从拉格朗日的观点出发，通过跟踪流体粒子示踪剂，研究了磁流体动力学（MHD）湍流。关于湍流扩散和色散以及拉格朗日结构函数的结果。尽管湍流单粒子扩散在Navier-Stokes和MHD湍流中表现出基本相同的行为，但在MHD情况下的两粒子相对弥散与Navier-Stokes行为明显不同。这一观察结果与MHD湍流的局部各向异性有关，这一点在拉格朗日参考系中的测量量中得到了清楚的反映。在MHD的情况下，拉格朗日结构函数显示出较低的水平相比，Navier-Stokes的情况下，对比欧拉的结果。这不仅适用于短时间增量[H。霍曼河Grauer，A. Busse和W.- C. Muller，J. Plasma Phys.73，821（2007）]，但也适用于高达积分时标量级的增量。这种明显的差异可以用在大多数奇异耗散结构附近的流体粒子轨迹的特征形状的差异来解释。
Magnetohydrodynamic(MHD)turbulence is studied from the Lagrangian viewpoint by following fluid particle tracers in high resolution direct numerical simulations. Results regarding turbulent diffusion and dispersion as well as Lagrangian structure functions are presented. Whereas turbulent single-particle diffusion exhibits essentially the same behavior in Navier-Stokes and MHDturbulence, two-particle relative dispersion in the MHD case differs significantly from the Navier-Stokes behavior. This observation is linked to the local anisotropy of MHDturbulence which is clearly reflected by quantities measured in a Lagrangian frame of reference. In the MHD case the Lagrangian structure functions display a lower level of intermittency as compared to the Navier-Stokes case contrasting Eulerian results. This is not only true for short time increments [H. Homann, R. Grauer, A. Busse, and W.-C. Muller, J. Plasma Phys.73, 821 (2007)] but also holds for increments up to the order of the integral time scale. The apparent discrepancy can be explained by the difference in the characteristic shapes of fluid particle trajectories in the vicinity of most singular dissipative structures.