在星系盘模拟中检验流体力学方案
Testing Hydrodynamics Schemes in Galaxy Disc Simulations
摘要：
我们研究如何从根本上不同的数值流体动力学代码遵循一个等温星系盘的演化与外部螺旋势。我们比较了自适应网格细化代码（RAMSES），光滑粒子流体动力学代码（MANNG），和体积离散无网格代码（GIZMO）。使用标准的细化标准，我们发现，RAMSES产生的光盘，是垂直集中，并没有达到这样的高密度，如BARNNG或GIZMO运行。与其他代码相比，RAMSES模拟的螺旋臂中的气体表面密度以较低的速率增加。此外，在BARNG和GIZMO运行中也有更大程度的亚结构，次级旋臂更明显。通过解决牛仔裤的长度与更大数量的网格单元，我们实现了更相似的结果，在这项研究中使用的拉格朗日代码。对细化方案的其他修改（添加额外的细化级别和基于局部密度梯度的细化）在减少RAMSES和RAMNG/GIZMO之间的差异方面不太成功。虽然更相似，但GISNG显示了与GIZMO所有模式（包括平滑粒子流体动力学版本）不同的密度分布和垂直质量剖面。这表明也会出现差异，这些差异不是特定方法所固有的，而是由于其实施。代码之间的差异（特别是螺旋臂中达到的密度）可能会导致引力坍缩的位置和时间尺度的差异，从而影响更复杂的星系盘模拟中的恒星形成活动。
英文摘要：
We examine how three fundamentally different numerical hydrodynamics codes follow the evolution of an isothermal galactic disc with an external spiral potential. We compare an adaptive mesh refinement code (RAMSES), a smoothed particle hydrodynamics code (sphNG), and a volume-discretised meshless code (GIZMO). Using standard refinement criteria, we find that RAMSES produces a disc that is less vertically concentrated and does not reach such high densities as the sphNG or GIZMO runs. The gas surface density in the spiral arms increases at a lower rate for the RAMSES simulations compared to the other codes. There is also a greater degree of substructure in the sphNG and GIZMO runs and secondary spiral arms are more pronounced. By resolving the Jeans' length with a greater number of grid cells we achieve more similar results to the Lagrangian codes used in this study. Other alterations to the refinement scheme (adding extra levels of refinement and refining based on local density gradients) are less successful in reducing the disparity between RAMSES and sphNG/GIZMO. Although more similar, sphNG displays different density distributions and vertical mass profiles to all modes of GIZMO (including the smoothed particle hydrodynamics version). This suggests differences also arise which are not intrinsic to the particular method but rather due to its implementation. The discrepancies between codes (in particular, the densities reached in the spiral arms) could potentially result in differences in the locations and timescales for gravitational collapse, and therefore impact star formation activity in more complex galaxy disc simulations.
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