论文标题
低磁性剪切场景的相移周期平行边界条件
A phase-shift-periodic parallel boundary condition for low-magnetic-shear scenarios
论文作者
论文摘要
我们将广义的周期性边界条件制定为标准扭转和平行边界条件的极限，该条件适用于模拟具有低磁性剪切的等离子体。这是通过在越过平行边界时在双向方向上应用相移来完成的。尽管使用扭转边界条件时，可以将这种相移设置为零，而不会在局部通量管限制中损失一般性，但我们表明，在采用周期性平行边界时，这不是最一般的情况，甚至可能不是最可取的。非零相移可用于避免对流型细胞，这些对流模拟了三维的谷川 - 瓦卡塔尼系统，并显示出在周期性的低磁性剪切旋转模拟模拟中具有可测量的效果。我们提出了一个数值程序，其中使用随机伪辐射表面进行周期性模拟的采样来确定统计意义上的物理可观察物。这种方法可以作为将扭转边界条件应用于低磁性剪切场景的替代方案，尽管更直接地可以计算，虽然更直接地进行了要求。
We formulate a generalized periodic boundary condition as a limit of the standard twist-and-shift parallel boundary condition that is suitable for simulations of plasmas with low magnetic shear. This is done by applying a phase shift in the binormal direction when crossing the parallel boundary. While this phase shift can be set to zero without loss of generality in the local flux-tube limit when employing the twist-and-shift boundary condition, we show that this is not the most general case when employing periodic parallel boundaries, and may not even be the most desirable. A non-zero phase shift can be used to avoid the convective cells that plague simulations of the three-dimensional Hasegawa-Wakatani system, and is shown to have measurable effects in periodic low-magnetic-shear gyrokinetic simulations. We propose a numerical program where a sampling of periodic simulations at random pseudo-irrational flux surfaces are used to determine physical observables in a statistical sense. This approach can serve as an alternative to applying the twist-and-shift boundary condition to low-magnetic-shear scenarios which, while more straightforward, can be computationally demanding.
