一个高性能和可移植的具有M1模型的渐近保持辐射流体动力学程序
A high-performance and portable asymptotic preserving radiation hydrodynamics code with the M1 model
摘要：
目标。我们提出了一个新的辐射流体动力学程序，称为“ARK-RT”，它使用一个两个时刻的模型与M1封闭关系的辐射转移。此代码旨在为exascale架构上的高性能计算做好准备。方法.采用有限体积法求解双矩模型。该方案是渐近保持准确地捕捉光学厚和薄制度。我们还提出了一个平衡的离散化的辐射通量源项能够捕获恒定通量的不透明的不连续稳态。我们使用Trilinos库进行线性代数，而Kokkos包使我们能够在不同的架构（例如多核、众核和GP-GPU）上实现高性能计算和可移植性。结果ARK-RT能够在自由流动和扩散极限下再现标准测试，包括纯辐射测试和辐射流体力学测试。使用时间隐式求解器是有利的，只要由流体动力学给出的时间步长比辐射转移的显式时间步长大50-100倍，这取决于预处理器和架构。尽管还需要做更多的工作来确保所有情况下的稳定。利用ARK-RT研究了对流致密核中电离锋的传播。我们表明，电离前是强稳定的扰动，即使不稳定的对流运动。因此，不稳定性的存在应谨慎解释。总的来说，ARK-RT非常适合研究许多涉及对流和辐射转移的天体物理问题，例如大质量星前致密核中H ii区域的动力学，未来的应用可能包括行星大气。
英文摘要：
Aims. We present a new radiation hydrodynamics code, called "ARK-RT" which uses a two-moment model with the M1 closure relation for radiative transfer. This code aims at being ready for high-performance computing, on exascale architectures. Methods. The two-moment model is solved using a finite volume scheme. The scheme is asymptotic preserving to capture accurately both optically thick and thin regimes. We also propose a well-balanced discretization of the radiative flux source term able to capture constant flux steady states with discontinuities in opacity. We use the library Trilinos for linear algebra and the package Kokkos allows us to reach high-performance computing and portability across different architectures, such as multi-core, many-core, and GP-GPU. Results. ARK-RT is able to reproduce standard tests in both free-streaming and diffusive limits, including purely radiative tests and radiation hydrodynamics ones. Using a time-implicit solver is profitable as soon as the time step given by the hydrodynamics is 50-100 times larger than the explicit time step for radiative transfer, depending on the preconditioner and the architecture. Albeit more work is needed to ensure stability in all circumstances. Using ARK-RT, we study the propagation of an ionization front in convective dense cores. We show that the ionization front is strongly stable against perturbations even with destabilizing convective motions. As a result, the presence of instabilities should be interpreted with caution. Overall, ARK-RT is well-suited to study many astrophysical problems involving convection and radiative transfer such as the dynamics of H ii regions in massive pre-stellar dense cores and future applications could include planetary atmospheres.
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