Ceci n'est pas une Couche de Mélange: 解析湍流辐射混合层的意义
Ceci n'est pas une Couche de Mélange: The Meaning of Resolved Turbulent Radiative Mixing
AI总结：
通过高分辨率AthenaK模拟研究湍流辐射混合层的微观和宏观性质，发现总冷却率的分辨率无关性源于数值耗散与数值粘度的抵消效应，并指出正确解析相结构需分辨湍流场长度尺度λ_F,turb。
摘要：
湍流辐射混合层（TRMLs）对多相天体物理流体中能量和动量的输运具有根本重要性。我们利用高分辨率\texttt{AthenaK}模拟中这些层的“微观”和“宏观”性质测量，来研究其性质何时可以被认为是\textit{良好}分辨的。特别地，我们证明了这些模拟中先前注意到的总冷却率$\dot{E}_{\rm cool}$的分辨率无关性是由于数值耗散和数值粘度的相反效应的显著（或许是偶然的）抵消。这质疑了我们在多大程度上可以信任这些实验的结果，因为没有物理图像可以解释这种抵消。我们还证明，为了正确分辨这些层中的相结构（这对于准确预测其可观测性质至关重要），必须分辨湍流扩散在时间尺度与冷却时间相当的作用尺度。这个“湍流场长度”$λ_{\rm F,turb}$是涡旋周转时间等于冷却时间（$t_{\rm eddy}(λ_{\rm F,turb}) = t_{\rm cool}$）的尺度。我们证明，分辨该尺度会导致收敛的相结构和气体相中空间分辨的转变。
英文摘要：
Turbulent Radiative Mixing Layers (TRMLs) are of fundamental importance to the transport of energy and momentum in multi-phase, astrophysical fluids. We use measurements of the "micro" and "macro" properties of these layers in high-resolution \texttt{AthenaK} simulations to investigate when their properties can be considered \textit{well}-resolved. In particular, we demonstrate that the previously noticed resolution independence of total cooling, $\dot{E}_{\rm cool}$, in these simulations is due to a remarkable, and perhaps fortuitous, cancellation of the countervailing effects of numerical dissipation and numerical viscosity. This calls into question the degree to which we can trust the results of these experiments, as there is no physical picture that explains this cancellation. We also demonstrate that in order to correctly resolve the phase structure in these layers, important for accurate predictions of their observable properties, one must resolve the scale on which turbulent diffusion acts on time-scales comparable to the cooling time. This "turbulent Field length", $λ_{\rm F,turb}$, is where the eddy turnover time is equal to the cooling time ($t_{\rm eddy}(λ_{\rm F,turb}) = t_{\rm cool}$). We demonstrate that resolving this scale results in converged phase-structure and spatially resolved transitions in the gas phases.
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