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arXiv 2008.10593math.NAcs.NAphysics.comp-ph
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自引力气体动力学的纯双曲间断Galerkin方法

A purely hyperbolic discontinuous Galerkin approach for self-gravitating gas dynamics

Michael Schlottke-Lakemper, Andrew R. Winters, Hendrik Ranocha, Gregor J. Gassner

摘要:

利用自引力模拟天体物理流动的挑战之一是计算引力。与双曲型流体动力学方程不同,重力场由椭圆型泊松方程描述。我们提出了一个纯双曲的方法,通过重新制定的椭圆问题成双曲扩散问题,这是解决在伪时间使用相同的显式高阶间断Galerkin方法,我们使用的流量解决方案。流动和重力求解器在联合层次笛卡尔网格上操作,并且通过源项双向耦合。我们的方法的一个关键好处是,它允许重用现有的显式双曲型求解器,而无需修改,同时保留其先进的功能,如非一致性和解决方案自适应网格。通过在流体动力学求解器的每个龙格-库塔阶段更新重力场,即使在耦合的多物理场模拟中也实现了高阶收敛。在验证了单物理和多物理设置的预期收敛顺序后,我们通过模拟Jeans引力不稳定性来验证我们的方法。此外,我们证明了我们的数值框架的全部功能,通过计算一个自引力Sedov爆炸与冲击波捕获在流动求解器和自适应网格细化整个耦合系统。

英文摘要:

One of the challenges when simulating astrophysical flows with self-gravity is to compute the gravitational forces. In contrast to the hyperbolic hydrodynamic equations, the gravity field is described by an elliptic Poisson equation. We present a purely hyperbolic approach by reformulating the elliptic problem into a hyperbolic diffusion problem, which is solved in pseudotime using the same explicit high-order discontinuous Galerkin method we use for the flow solution. The flow and the gravity solvers operate on a joint hierarchical Cartesian mesh and are two-way coupled via the source terms. A key benefit of our approach is that it allows the reuse of existing explicit hyperbolic solvers without modifications, while retaining their advanced features such as non-conforming and solution-adaptive grids. By updating the gravitational field in each Runge-Kutta stage of the hydrodynamics solver, high-order convergence is achieved even in coupled multi-physics simulations. After verifying the expected order of convergence for single-physics and multi-physics setups, we validate our approach by a simulation of the Jeans gravitational instability. Furthermore, we demonstrate the full capabilities of our numerical framework by computing a self-gravitating Sedov blast with shock capturing in the flow solver and adaptive mesh refinement for the entire coupled system.

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