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arXiv 0905.1378math.NAcs.NA
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一类用于动力学方程及相关含刚性源问题的渐近保持格式

A class of asymptotic preserving schemes for kinetic equations and related problems with stiff sources

Francis Filbet, S. Jin

AI总结:

本文提出一种通用框架,通过BGK型松弛项惩罚非线性碰撞项,设计出在欧拉极限下渐近保持、均匀稳定且无需非线性迭代的格式,适用于玻尔兹曼方程及相关问题。

摘要:

本文提出了一种通用框架,用于设计玻尔兹曼动力学方程及相关方程的渐近保持格式。由于小平均自由程或松弛时间引起的非线性刚性碰撞(源)项,数值求解这些方程具有挑战性。我们提出用BGK型松弛项来惩罚非线性碰撞项,即使时间上隐式离散,该松弛项也可以显式求解。此外,BGK型松弛算子有助于将密度分布驱动到局部麦克斯韦分布,从而在欧拉极限下自然实现渐近保持格式。所设计的格式不需要任何非线性迭代求解器或使用Wild Sum。它在(可能很小的)克努森数方面是均匀稳定的,并且即使克努森数决定的小尺度未被数值分辨,也能捕捉宏观流体动力学(欧拉)极限。如果粘性和热传导被数值分辨,该格式也与可压缩纳维-斯托克斯方程一致。该方法适用于许多其他相关问题,例如具有刚性松弛的双曲系统和高阶抛物型方程。

英文摘要:

In this paper, we propose a general framework to design asymptotic preserving schemes for the Boltzmann kinetic kinetic and related equations. Numerically solving these equations are challenging due to the nonlinear stiff collision (source) terms induced by small mean free or relaxation time. We propose to penalize the nonlinear collision term by a BGK-type relaxation term, which can be solved explicitly even if discretized implicitly in time. Moreover, the BGK-type relaxation operator helps to drive the density distribution toward the local Maxwellian, thus natually imposes an asymptotic-preserving scheme in the Euler limit. The scheme so designed does not need any nonlinear iterative solver or the use of Wild Sum. It is uniformly stable in terms of the (possibly small) Knudsen number, and can capture the macroscopic fluid dynamic (Euler) limit even if the small scale determined by the Knudsen number is not numerically resolved. It is also consistent to the compressible Navier-Stokes equations if the viscosity and heat conductivity are numerically resolved. The method is applicable to many other related problems, such as hyperbolic systems with stiff relaxation, and high order parabilic equations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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