论文标题
在周期盒中，在不可压缩的磁流体动力湍流中检查四分之一法律的纵向三阶矩
Examination of the four-fifths law for longitudinal third-order moments in incompressible magnetohydrodynamic turbulence in a periodic box
论文作者
论文摘要
通过使用直接数值模拟数据来检查三维强制不可压缩的磁性水力动力学（MHD）湍流，而没有均匀强加的磁场在周期性盒中，使用了直接数值模拟数据来检查三分之二的定律。磁性prandtl编号设置为一个，网格点的数量为$ 512^3 $。在各向同性MHD湍流中用于二阶速度矩的广义Kármán-Howarth-Kolmogorov方程扩展到各向异性MHD MHD湍流，而不是$ \ \ \\ textbf {r} $。在这里，$ \ textbf {r} $是一个分离向量。量化了广义方程中的粘性，强迫，各向异性和非平稳项。发现与粘性期相比，各向异性术语对四分之一定律的影响在小尺度上可以忽略不计。但是，定向各向异性的影响是通过从球形平均$ \ textbf {r} $的特定方向上偏离特定方向来衡量的。
The four-fifths law for third-order longitudinal moments is examined, by the use of direct numerical simulation data on three-dimensional forced incompressible magnetohydrodynamic (MHD) turbulence without a uniformly imposed magnetic field in a periodic box. The magnetic Prandtl number is set to one, and the number of grid points is $512^3$. A generalized Kármán-Howarth-Kolmogorov equation for second-order velocity moments in isotropic MHD turbulence is extended to anisotropic MHD turbulence by means of a spherical average over the direction of $\textbf{r}$. Here, $\textbf{r}$ is a separation vector. The viscous, forcing, anisotropy and nonstationary terms in the generalized equation are quantified. It is found that the influence of the anisotropic terms on the four-fifths law is negligible at small scales, compared to that of the viscous term. However, the influence of the directional anisotropy, which is measured by the departure of the third-order moments in a particular direction of $\textbf{r}$ from the spherically averaged ones, on the four-fifths law is suggested to be substantial, at least in the case studied here.
