Thermal condensation in a turbulent atomic hydrogen flow
Thermal condensation in a turbulent atomic hydrogen flow
复制标题
湍流原子氢流中的热凝结
DOI：
10.1051/0004-6361:20041474
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发表时间：
2004
影响因子：
6.5
通讯作者：
E. Audit
中科院分区：
文献类型：
--
作者：
P. Hennebelle;E. Audit
我们提出了一个数值和分析研究的热碎裂的湍流星际氢。我们首先提出了不同的动力学过程和大范围的空间（和时间）尺度，需要在数值模拟中充分表示。接下来，我们提出了二维模拟的湍流收敛流，诱导的动态冷凝的温暖的中性相到冷相。然后，我们分析了冷结构和不稳定气体在每个模拟的分数，特别注意湍流度的影响。当流动非常湍流时，大部分气体保持在热不稳定区域中。这种不稳定的气体形成一个网状结构。我们表明，热不稳定气体的分数是强烈相关的湍流的流动水平。然后，我们开发了一个半解析模型来解释这种不稳定气体的起源。这个简单的模型能够定量地再现模拟中观察到的不稳定气体的比例及其与湍流的相关性。最后，我们强调的事实是，即使当流动是非常湍流，尽管事实上，大部分的气体保持动态的热不稳定域，经典的图片2相介质与刚性的热锋和局部压力平衡原来仍然是相关的附近的冷结构。
We present a numerical and analytical study of the thermal fragmentation of a turbulent flow of interstellar hydrogen. We first present the different dynamical processes and the large range of spatial (and temporal) scales that need to be adequately represented in numerical simulations. Next, we present bidimensional simulations of turbulent converging flows which induce the dynamical condensation of the warm neutral phase into the cold phase. We then analyse the cold structures and the fraction of unstable gas in each simulation, paying particular attention to the influence of the degree of turbulence. When the flow is very turbulent a large fraction of the gas remains in the thermally unstable domain. This unstable gas forms a filamentary network. We show that the fraction of thermally unstable gas is strongly correlated with the level of turbulence of the flow. We then develop a semi-analytical model to explain the origin of this unstable gas. This simple model is able to quantitatively reproduce the fraction of unstable gas observed in the simulations and its correlation with turbulence. Finally, we stress the fact that even when the flow is very turbulent and in spite of the fact that a large fraction of the gas is maintained dynamically in the thermally unstable domain, the classical picture of a 2-phase medium with stiff thermal fronts and local pressure equilibrium turns out to be still relevant in the vicinity of the cold structures.