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arXiv 1809.08683physics.comp-ph
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自校正状态方程的格子Boltzmann模型及其在热-流体动力耦合流动中的应用

Lattice Boltzmann model with self-tuning equation of state for coupled thermo-hydrodynamic flows

Rongzong Huang, Huiying Wu, Nikolaus A. Adams

摘要:

提出了一种新的格子Boltzmann(LB)模型和自校正状态方程(EOS),用于模拟热-流体动力耦合流动。速度场由最近发展的密度分布函数的多重弛豫时间LB方程求解,由此可以恢复自调谐状态方程。对于温度场,直接在离散水平上建立了一个新的MRT LB方程。通过在LB方程中引入密度DF相关项,设计总能量DF的平衡矩函数,统一考虑了粘性耗散和压缩功,并通过修正碰撞矩阵,得到了无偏差项的能量守恒方程.通过自校正状态方程和粘性耗散及压缩功实现了热流体动力效应的完全耦合。目前的LB模型是在标准格的基础上发展起来的,在实际应用中可以采用各种EOS。此外,普朗特数和比热比都可以任意调节。此外,边界条件的处理也提出了明智的基础上分解成平衡,力(源),和非平衡部分的DF。质量、动量和能量的局部守恒在边界节点处严格满足。采用三种不同的EOS对热Poiffille流和Couette流进行了数值模拟,数值结果与解析解吻合较好。然后,模拟了瑞利数从$10^3$到$10^8$的大温差方腔内的自然对流。数值计算结果与前人的计算结果吻合较好,进一步验证了本文提出的热-流体动力耦合流动LB模型的正确性。

英文摘要:

A novel lattice Boltzmann (LB) model with self-tuning equation of state (EOS) is developed in this work for simulating coupled thermo-hydrodynamic flows. The velocity field is solved by the recently developed multiple-relaxation-time (MRT) LB equation for density distribution function (DF), by which a self-tuning EOS can be recovered. As to the temperature field, a novel MRT LB equation for total energy DF is directly developed at the discrete level. By introducing a density-DF-related term into this LB equation and devising the equilibrium moment function for total energy DF, the viscous dissipation and compression work are consistently considered, and by modifying the collision matrix, the targeted energy conservation equation is recovered without deviation term. The full coupling of thermo-hydrodynamic effects is achieved via the self-tuning EOS and the viscous dissipation and compression work. The present LB model is developed on the basis of the standard lattice, and various EOSs can be adopted in real applications. Moreover, both the Prandtl number and specific heat ratio can be arbitrarily adjusted. Furthermore, boundary condition treatment is also proposed on the basis of the judicious decomposition of DF into its equilibrium, force (source), and nonequilibrium parts. The local conservation of mass, momentum, and energy can be strictly satisfied at the boundary node. Numerical simulations of thermal Poiseuille and Couette flows are carried out with three different EOSs, and the numerical results are in good agreement with the analytical solutions. Then, natural convection in a square cavity with a large temperature difference is simulated for the Rayleigh number from $10^3$ up to $10^8$. Good agreement between the present and previous numerical results is observed, which further validates the present LB model for coupled thermo-hydrodynamic flows.

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