The Field Condition: A New Constraint on Spatial Resolution in Simulations of the Nonlinear Development of Thermal Instability
The Field Condition: A New Constraint on Spatial Resolution in Simulations of the Nonlinear Development of Thermal Instability
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DOI：
10.1086/382478
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发表时间：
2003-02
期刊：
影响因子：
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通讯作者：
H. Koyama;S. Inutsuka
中科院分区：
文献类型：
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作者：
H. Koyama;S. Inutsuka
我们提出了一个热膨胀介质的动力学使用一维数值计算，包括冷却，加热，热传导，和物理粘度。我们从热不稳定的单相介质中建立了一个两相介质，并跟踪其长期演化。为了阐明热传导的作用，我们比较了两种模型的结果，有和没有热传导。计算表明，热传导有助于产生云平移运动的动能。接下来，我们关注空间分辨率，因为我们必须解决场长度λF，这是热传导的特征长度尺度。只有当考虑热传导并且使用足够大的单元数时，结果才显示收敛性。我们发现在两相介质中要实现收敛运动，必须保持胞元尺寸小于λF/3。我们把λF/3的约束条件称为“场条件”。“包含热传导以满足场条件对于热不稳定性（TI）的数值研究至关重要，并且对于湍流星际两相介质的研究可能很重要：没有热传导的TI计算可能容易受到人为现象的污染，这些现象不会随着分辨率的增加而收敛。
We present the dynamics of a thermally bistable medium using one-dimensional numerical calculations, including cooling, heating, thermal conduction, and physical viscosity. We set up a two-phase medium from a thermally unstable one-phase medium and follow its long-term evolution. To clarify the role of thermal conduction, we compare the results of the two models, with and without thermal conduction. The calculations show that the thermal conduction helps to generate the kinetic energy of translational motions of the clouds. Next, we focus on spatial resolution because we have to resolve the Field length λF, which is the characteristic length scale of the thermal conduction. The results show convergence only when thermal conduction is included and a large enough cell number is used. We find it necessary to maintain a cell size of less than λF/3 to achieve a converged motion in the two-phase medium. We refer to the constraint that λF/3 be resolved as the "Field condition." The inclusion of thermal conduction to satisfy the Field condition is crucial to numerical studies of thermal instability (TI) and may be important for studies of the turbulent interstellar two-phase medium: the calculations of TI without thermal conduction may be susceptible to contamination by artificial phenomena that do not converge with increasing resolutions.