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arXiv 2104.14217physics.flu-dynphysics.comp-ph
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等温格子Boltzmann格式的流体力学极限和数值误差

Hydrodynamic limits and numerical errors of isothermal lattice Boltzmann schemes

Gauthier Wissocq, Pierre Sagaut

摘要:

为了更好地理解格子玻尔兹曼方法(LBM)的数值特性,提出了一种在离散条件下推导其流体力学极限的一般方法。它依赖于低Knudsen数极限下的泰勒展开。用一个单一的渐近分析,Navier-Stokes(NS)方程的两种偏差被明确证明:一致性错误,继承从动力学描述的LBM,和数值误差归因于其空间和时间离散。该方法适用于Bhatnagar-Gross-Krook(BGK),正则化和多重弛豫时间(MRT)碰撞模型中的等温框架。偏差项系统地面对线性分析,以验证其表达式,解释它们,并提供解释其数值特性。BGK模型的低耗散与泰勒展开式中的误差项的特定模式有关。同样地,正则化和MRT模型的耗散特性可以用一种称为超粘性简并的现象来解释。后者包括在一个意想不到的复苏高阶努森效应引起的一个大的数值前因子。它是在低粘度制度的过度耗散和严重的不稳定性的起源。

英文摘要:

With the aim of better understanding the numerical properties of the lattice Boltzmann method (LBM), a general methodology is proposed to derive its hydrodynamic limits in the discrete setting. It relies on a Taylor expansion in the limit of low Knudsen numbers. With a single asymptotic analysis, two kinds of deviations with the Navier-Stokes (NS) equations are explicitly evidenced: consistency errors, inherited from the kinetic description of the LBM, and numerical errors attributed to its space and time discretization. The methodology is applied to the Bhatnagar-Gross-Krook (BGK), the regularized and the multiple relaxation time (MRT) collision models in the isothermal framework. Deviation terms are systematically confronted to linear analyses in order to validate their expressions, interpret them and provide explanations for their numerical properties. The low dissipation of the BGK model is then related to a particular pattern of its error terms in the Taylor expansion. Similarly, dissipation properties of the regularized and MRT models are explained by a phenomenon referred to as hyperviscous degeneracy. The latter consists in an unexpected resurgence of high-order Knudsen effects induced by a large numerical pre-factor. It is at the origin of over-dissipation and severe instabilities in the low-viscosity regime.

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