arXivDaily arXiv每日学术速递 周一至周五更新
北美退伍军人节(Veterans Day),12 日无更新
arXiv 1406.4429math.NAcs.NA
收藏

高阶渐近保持节点不连续伽辽金IMEX方案用于BGK方程

High Order Asymptotic Preserving Nodal Discontinuous Galerkin IMEX Schemes for the BGK Equation

University of Houston(休斯顿大学);University of California Riverside(加州大学河滨分校);Rensselaer Polytechnic Institute(伦斯勒理工学院)

Tao Xiong, Juhi Jang, Fengyan Li, Jing-Mei Qiu

AI总结:

本文提出高阶渐近保持方案用于超声学尺度下的BGK方程,通过微-宏观分解和高阶IMEX时间离散化方法,实现高精度计算。

摘要:

本文开发了高阶渐近保持(AP)方案用于超声学尺度下的BGK方程,该方案在渐近极限下可得到宏观模型如欧拉方程和可压缩纳维-斯托克斯方程。方法基于动能方程的微-宏观公式,将问题分解为平衡和非平衡部分。所提方法适用于常数或空间变化的Knudsen数。新方法包括任意阶精度的不连续伽辽金(DG)空间离散化和高阶全局刚性准确隐-显Runge-Kutta(RK)时间离散化。提出了两种方案:方案I基于BGK方程的微-宏观分解,方案II则利用连续问题的渐近分析特性。与方案I相比,方案II计算效率更高,且能建立形式渐近分析。具体而言,当0<ε<<1时,方案II在O(ε²)范围内成为局部DG离散化,使用显式RK方法求解可压缩纳维-斯托克斯方程。数值结果展示了方法在广泛Knudsen数下的有效性及高阶精度。

英文摘要:

In this paper, we develop high-order asymptotic preserving (AP) schemes for the BGK equation in a hyperbolic scaling, which leads to the macroscopic models such as the Euler and compressible Navier-Stokes equations in the asymptotic limit. Our approaches are based on the so-called micro-macro formulation of the kinetic equation which involves a natural decomposition of the problem to the equilibrium and the non-equilibrium parts. The proposed methods are formulated for the BGK equation with constant or spatially variant Knudsen number. The new ingredients for the proposed methods to achieve high order accuracy are the following: we introduce discontinuous Galerkin (DG) discretization of arbitrary order of accuracy with nodal Lagrangian basis functions in space; we employ a high order globally stiffly accurate implicit-explicit (IMEX) Runge-Kutta (RK) scheme as time discretization. Two versions of the schemes are proposed: Scheme I is a direct formulation based on the micro-macro decomposition of the BGK equation, while Scheme II, motivated by the asymptotic analysis for the continuous problem, utilizes certain properties of the projection operator. Compared with Scheme I, Scheme II not only has better computational efficiency (the computational cost is reduced by half roughly), but also allows the establishment of a formal asymptotic analysis. Specifically, it is demonstrated that when $0<ε\ll 1$, Scheme II, up to $\mathcal{O}(ε^2)$, becomes a local DG discretization with an explicit RK method for the macroscopic compressible Navier-Stokes equations, a method in a similar spirit to the ones in [Bassi \& Rabey 1997, Cockburn \& Shu 1998]. Numerical results are presented for a wide range of Knudsen number to illustrate the effectiveness and high order accuracy of the methods.

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。

↑