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基于对流扩散系统的不可压Navier-Stokes方程的多分布正则化格子Boltzmann方法

MULTI-DISTRIBUTION REGULARIZED LATTICE BOLTZMANN METHOD FOR CONVECTION-DIFFUSION-SYSTEM-BASED INCOMPRESSIBLE NAVIER-STOKES EQUATION

  • 摘要: 不可压Navier-Stokes方程组在环境科学、生物医学和流体力学等众多科学领域都扮演着十分重要的角色. 发展求解不可压Navier-Stokes方程组的稳定高效数值模拟方法具有重要的科学价值和实际意义. 为此, 提出了一种求解不可压Navier-Stokes方程组的多分布正则化格子Boltzmann (MDF-RLB)模型. 该模型的核心思想是将不可压Navier-Stokes方程组转换为一个耦合的对流扩散系统, 并针对该系统进行正则化格子Boltzmann方法的建模, 即为系统中的每一个对流扩散方程(CDE)构造一个分布函数的演化方程. 接着, 通过Chapman-Enskog分析证明了该模型能够准确恢复基于对流扩散系统的不可压Navier-Stokes方程组. 此外, 本文推导了利用分布函数的零阶矩和一阶矩直接计算速度和压力和利用非平衡态分布函数的一阶矩来局部计算速度梯度、速度散度、应变率张量、切应力和涡度的公式. 最后, 我们通过一系列的基准解算例: 二维泊肃叶流、简化二维四辊轧机问题以及二维顶盖驱动方腔流验证了本模型和这些物理量的局部计算格式的有效性和准确性. 通过数值测试我们发现本模型和我们所提出的一些物理量的局部格式在空间上具有二阶收敛速率. 同时, 与多分布多松弛的格子Boltzmann (MDF-MRTLB)模型相比, MDF-RLB模型在某些情况下模拟结果更精确, 且MDF-RLB模型具有更高的计算效率, 计算时间减少了7%以上.

     

    Abstract: The incompressible Navier-Stokes equations play a pivotal role across diverse scientific disciplines including environmental science, biomedical engineering, and fluid mechanics. Given the profound scientific significance and practical implications associated with developing robust and efficient numerical methodologies for solving the incompressible Navier-Stokes equations. To address this need, this study proposes a multiple-distribution-function regularized lattice Boltzmann (MDF-RLB) model for simulating the incompressible Navier-Stokes equations. At the heart of this approach lies a transformation of the incompressible Navier-Stokes equations into a coupled convection-diffusion system and then apply the regularized lattice Boltzmann method to model this system. Specifically, an evolution equation for the distribution function is constructed for each convection-diffusion equation (CDE) within the system. Subsequently, through rigorous Chapman-Enskog analysis, we have conclusively demonstrated that the proposed model can accurately recover the incompressible Navier-Stokes equations based on the convection-diffusion system. Furthermore, this research has yielded important theoretical derivations, including formulations for direct computation of velocity and pressure fields through zeroth and first moments of the distribution functions, as well as local computational schemes based on first moments of non-equilibrium distribution functions for calculating velocity gradients, velocity divergence, strain rate tensor, shear stress, and vorticity. Finally, to comprehensively validate the effectiveness and accuracy of the proposed model and the local computational formulations for these physical quantities, we conducted a series of benchmark numerical simulations, including two-dimensional Poiseuille flow, a simplified two-dimensional four-roll mill problem, and two-dimensional lid-driven cavity flow. The numerical tests reveal that the MDF-RLB model and the local formulations for physical quantities have a second-order convergence rate in space. Furthermore, compared to the multiple-distribution multiple-relaxation-time lattice Boltzmann (MDF-MRTLB) model, the MDF-RLB model demonstrates higher accuracy in certain cases and exhibits superior computational efficiency, achieving a reduction in computational time exceeding 7%.

     

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