激波中的数值过冷
Numerical overcooling in shocks
摘要：
本文采用光滑粒子流体动力学（SPH）和自适应网格加密技术对辐射激波冷却进行了研究。我们获得了一个相似的解决方案，在辐射冷却的存在下的激波管问题，并测试如何以及该解决方案是重现在小工具和Flash。激波增宽的数值方案的细节（人工粘度或黎曼解）导致潜在的显着过冷在这两个代码。我们解释我们的研究结果的分辨率标准，并将其应用到现实的模拟宇宙吸积冲击星系晕，冷吸积和热反馈超新星或活动星系核。为了避免吸积冲击在晕上的数值过冷，从而发展出热日冕，需要粒子或细胞质量分辨率为10^6 M_sun，这是目前最先进的模拟所能达到的。在这样的质量分辨率下，星系星际介质中的热反馈要求超新星或活动星系核驱动的气泡的温度在n_H=1.0 cm^-3时超过10^7 K，以避免数值过冷对反馈的虚假抑制。
英文摘要：
We present a study of cooling in radiative shocks simulated with smoothed particle hydrodynamics (SPH) and adaptive mesh refinement codes. We obtain a similarity solution for a shock-tube problem in the presence of radiative cooling, and test how well the solution is reproduced in Gadget and Flash. Shock broadening governed by the details of the numerical scheme (artificial viscosity or Riemann solvers) leads to potentially significant overcooling in both codes. We interpret our findings in terms of a resolution criterion, and apply it to realistic simulations of cosmological accretion shocks onto galaxy haloes, cold accretion and thermal feedback from supernovae or active galactic nuclei. To avoid numerical overcooling of accretion shocks onto haloes that should develop a hot corona requires a particle or cell mass resolution of 10^6 M_sun, which is within reach of current state-of-the-art simulations. At this mass resolution, thermal feedback in the interstellar medium of a galaxy requires temperatures of supernova or AGN driven bubbles to be in excess of 10^7 K at densities of n_H=1.0 cm^-3, in order to avoid spurious suppression of the feedback by numerical overcooling.
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