论文标题

VETTAM:使用可变的Eddington Tensor方法进行自适应网状细化的辐射流体动力学方案

VETTAM: A scheme for radiation hydrodynamics with adaptive mesh refinement using the variable Eddington tensor method

论文作者

Menon, Shyam H., Federrath, Christoph, Krumholz, Mark R., Kuiper, Rolf, Wibking, Benjamin D., Jung, Manuel

论文摘要

我们提出了自适应网格(\ texttt {vettam})上的Eddington张量封闭的转运,这是一种新算法,用于求解辐射流体动力学方程(RHD),并支持自适应网格细化(AMR)在频率融合的频率融合,两位数的配方中。该方法基于非本地变量Eddington Tensor(VET)闭合,该闭合是使用用于射线跟踪的混合特性方案计算的。我们使用戈杜诺夫方法将辐射的双曲线运输和隐式向后的时间更新,以避免光线涂抹时间施加的明确时间段限制,以及一个固定点的PICARD迭代方案,以处理非线性气体放射交换术语,并具有两个隐式更新阶段,共同进行了共同的更新阶段。我们还为AMR开发了一种修改的波速校正方法,我们认为这对于在扩散状态中获得准确的结果至关重要。我们通过一系列纯辐射和RHD测试来证明我们的方案的鲁棒性,并表明它成功捕获了流,静态扩散和动态扩散状态以及它们之间的空间过渡,施放尖锐的阴影,并产生辐射和气体之间动量和能量交换速率的准确结果。辐射矩方程的不同闭合之间的比较与爱丁顿的近似(0段闭合)和$ m_1 $近似值(第一矩闭合),这表明了兽医方法(第二阶段的闭合)的优势在简单的闭合方案上。 \ texttt {vettam}已与AMR \ texttt {flash}(磁通 - )水力动力学代码耦合,我们通过报告实现的性能功能和瓶颈来总结。

We present Variable Eddington Tensor-closed Transport on Adaptive Meshes (\texttt{VETTAM}), a new algorithm to solve the equations of radiation hydrodynamics (RHD) with support for adaptive mesh refinement (AMR) in a frequency-integrated, two-moment formulation. The method is based on a non-local Variable Eddington Tensor (VET) closure computed with a hybrid characteristics scheme for ray tracing. We use a Godunov method for the hyperbolic transport of radiation with an implicit backwards-Euler temporal update to avoid the explicit timestep constraint imposed by the light-crossing time, and a fixed-point Picard iteration scheme to handle the nonlinear gas-radiation exchange term, with the two implicit update stages jointly iterated to convergence. We also develop a modified wave-speed correction method for AMR, which we find to be crucial for obtaining accurate results in the diffusion regime. We demonstrate the robustness of our scheme with a suite of pure radiation and RHD tests, and show that it successfully captures the streaming, static diffusion, and dynamic diffusion regimes and the spatial transitions between them, casts sharp shadows, and yields accurate results for rates of momentum and energy exchange between radiation and gas. A comparison between different closures for the radiation moment equations, with the Eddington approximation (0th-moment closure) and the $M_1$ approximation (1st-moment closure), demonstrates the advantages of the VET method (2nd-moment closure) over the simpler closure schemes. \texttt{VETTAM} has been coupled to the AMR \texttt{FLASH} (magneto-)hydrodynamics code and we summarize by reporting performance features and bottlenecks of our implementation.

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