比较SPH人工粘度及其对开普勒圆盘的影响
A comparison of SPH artificial viscosities and their impact on the Keplerian disk
摘要：
旋转圆盘的流体动力学模拟在天体物理和行星科学领域具有重要的意义。光滑粒子流体动力学（SPH）已被广泛用于这种模拟。然而，人们已经知道，在SPH中，由于不必要的角动量转移，冷而薄的开普勒盘会破裂。已经提出了两个可能的原因，这种破裂的磁盘;人工粘度（AV）和SPH中的压力梯度的评估中的数值误差。哪一个占主导地位，目前还不清楚。在本文中，我们调查的原因，这种快速破碎的磁盘。我们实现了大多数流行的AV和开关的配方，并测量了角动量传递由于AV和SPH估计的压力梯度的误差。我们发现，角动量转移，由于AV的内边缘触发的磁盘的破碎。我们还发现，经典的von-Neumann-Richtmyer-Landshoff型AV与高阶估计的$\nabla \cdot \vec{v}$可以保持磁盘的$\sim 100$轨道，即使在使用的SPH的标准制定。
英文摘要：
Hydrodynamical simulations of rotating disk play important roles in the field of astrophysical and planetary science. Smoothed Particle Hydrodynamics (SPH) has been widely used for such simulations. It, however, has been known that with SPH, a cold and thin Kepler disk breaks up due to the unwanted angular momentum transfer. Two possible reasons have been suggested for this breaking up of the disk; the artificial viscosity (AV) and the numerical error in the evaluation of pressure gradient in SPH. Which one is dominant has been still unclear. In this paper, we investigate the reason for this rapid breaking up of the disk. We implemented most of popular formulations of AV and switches and measured the angular momentum transfer due to both AV and the error of SPH estimate of pressure gradient. We found that the angular momentum transfer due to AV at the inner edge triggers the breaking up of the disk. We also found that the classical von-Neumann-Richtmyer-Landshoff type AV with a high order estimate for $\nabla \cdot \vec{v}$ can maintain the disk for $\sim 100$ orbits even when used with the standard formulation of SPH.
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