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arXiv 2402.15437math.NAastro-ph.IMcs.NAphysics.comp-phphysics.plasm-ph
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基于GQL的保界且局部无散度的中心间断伽辽金方法用于相对论磁流体力学

GQL-Based Bound-Preserving and Locally Divergence-Free Central Discontinuous Galerkin Schemes for Relativistic Magnetohydrodynamics

Shengrong Ding, Kailiang Wu

AI总结:

本文针对特殊相对论磁流体力学,提出基于GQL框架的任意高阶中心间断伽辽金格式,通过修正方程源项离散和新型二维单元平均分解,实现可证明的保界与局部无散性质,并在多种状态方程下验证了其鲁棒性和有效性。

摘要:

本文针对具有一般状态方程(EOS)的特殊相对论磁流体力学(RMHD),发展了新颖且鲁棒的任意高阶精度中心间断伽辽金(CDG)格式。这些格式可证明具有保界(BP)性质,即一致地保持亚光速流体速度的上界以及密度和压强的正性,同时(局部地)维持磁场的无散(DF)约束。对于一维RMHD,标准CDG方法精确满足无散条件,并且其保界性质在可由保界限幅器实现的条件得到证明。对于二维RMHD,我们基于对修正RMHD系统的适当离散,设计了可证明保界且局部无散的CDG格式。我们格式的一个关键创新在于对修正RMHD方程中附加源项的离散,从而精确抵消重叠网格上散度误差对保界性质的影响。我们为所提出的CDG格式提供了保界性质的严格证明,并首次建立了RMHD中重叠网格上保界性质与离散无散性质之间的理论联系。由于原始变量无法用守恒变量显式表达,物理界约束是强非线性的,这使得保界证明极具挑战性。我们通过在几何拟线性化(GQL)框架内进行技术性估计来克服这些困难,该框架将非线性约束转化为线性约束。此外,我们引入了一种新的二维重叠网格单元平均分解方法,该方法放宽了理论上的保界CFL约束并减少了内部节点数量,从而提高了二维保界CDG方法的效率。我们将所提出的CDG格式应用于具有各种状态方程的广泛RMHD问题,展示了其在具有挑战性的场景中的鲁棒性和有效性。

英文摘要:

This paper develops novel and robust central discontinuous Galerkin (CDG) schemes of arbitrarily high-order accuracy for special relativistic magnetohydrodynamics (RMHD) with a general equation of state (EOS). These schemes are provably bound-preserving (BP), i.e., consistently preserve the upper bound for subluminal fluid velocity and the positivity of density and pressure, while also (locally) maintaining the divergence-free (DF) constraint for the magnetic field. For 1D RMHD, the standard CDG method is exactly DF, and its BP property is proven under a condition achievable by BP limiter. For 2D RMHD, we design provably BP and locally DF CDG schemes based on the suitable discretization of a modified RMHD system. A key novelty in our schemes is the discretization of additional source terms in the modified RMHD equations, so as to precisely counteract the influence of divergence errors on the BP property across overlapping meshes. We provide rigorous proofs of the BP property for our CDG schemes and first establish the theoretical connection between BP and discrete DF properties on overlapping meshes for RMHD. Owing to the absence of explicit expressions for primitive variables in terms of conserved variables, the constraints of physical bounds are strongly nonlinear, making the BP proofs highly nontrivial. We overcome these challenges through technical estimates within the geometric quasilinearization (GQL) framework, which converts the nonlinear constraints into linear ones. Furthermore, we introduce a new 2D cell average decomposition on overlapping meshes, which relaxes the theoretical BP CFL constraint and reduces the number of internal nodes, thereby enhancing the efficiency of the 2D BP CDG method. We implement the proposed CDG schemes for extensive RMHD problems with various EOSs, demonstrating their robustness and effectiveness in challenging scenarios.

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