基于格子Boltzmann方法的液力

Flow Field Simulation of Stator Cascade in Automotive Torque Converters based on Lattice Boltzmann Method

摘要:

研究了基于格子Boltzmann方法（LBM）的液力变矩器导轮内流场数值计算理论与方法.首先，提出了LBM中处理旋转周期性边界条件的方法.然后，分析了LBM中各项参数对于计算稳定性以及计算效率之间的影响.为了保证粒子迁移与碰撞计算的稳定进行，必须合理选定弛豫时间τ，从而避免在计算过程中平衡态分布函数feq出现负值的情形.此外，在LBM中运用大涡模拟（LES）可以降低计算稳定性对于弛豫时间τ选取的限制，在一定程度上提高计算效率.最后，在开源代码Palabos的基础上进行功能拓展，实现导轮内流场的仿真计算，得到了导轮尾迹区域瞬时非定常流动分布特征.结果表明，LBM与传统计算流体力学（CFD）方法相比，液流对导轮作用力的计算结果在数值上较为接近.然而，使用LBM可以获得详细流场形成过程的时间历程以及局部复杂的流动细节.

Abstract:

Theory and application of the lattice Boltzmann method (LBM) for flow field simulation in the torque converter stator cascade is studied. Firstly, treatment for rotational periodic boundary is proposed. Then, influence of different parameters on computational stability and efficiency is analyzed. In order to ensure stable calculation of migration and collision process of particles, it is essential to choose appropriate value of the relaxation time, τ to avoid occurrence of negative value of the equilibrium distribution function, feq. Furthermore, the large eddy simulation (LES) is adopted in the LBM to lessen the restriction of computational stability on the relaxation time, τ and to improve computational efficiency. Finally, flow field simulation of the stator cascade is realized by extending function of an open source code named ‘Palabos’, and instantaneous structure of unsteady wake flow behind the stator blade is obtained. The computational result shows that calculated force applied by fluid on the stator blade is nearly the same for the LBM to that of the tradition computational fluid dynamics (CFD) method. However, the LBM has advantage in calculating the forming history of flow filed and complex details of instantaneous flow structure.