用lattice Boltzmann方法模拟矩形竖腔内混合对流

Simulation of mixed convection in slender rectangular cavities using lattice Boltzmann method

用lattice Boltzmann方法(LBM)模拟了纵横比(高度与宽度之比)大于1的矩形竖腔内同时存在自然对流和强制对流的混合流动时流场与温度场分布.比较了不同雷诺数(Re)、瑞利数(Ra)下矩形腔的流场分布在不同纵横比时的特点,研究了这些参数值对混合对流换热的影响,提出混合对流存在时Re和Ra对流动和换热的影响可由Richardson数(Ri)综合反映,并得到在不同纵横比时平均Nusselt数(Nu)随Ra和Re的变化关系式.与常用的LBGK模型不同,用了LB力矩模型.

The lattice Boltzmann method is applied to simulate the mixed flow, which combines natural convection for temperature difference and forced convection for lid driven in a two-dimensional rectangular cavity with aspect ratio above 1. For different aspect ratios, the features of the isotherms and streamlines are presented at different Reynolds number （Re）and Rayleigh number （Ra）. The effects of Re and Ra on the flow and heat transfer are discussed, which can be reflected synthetically by Richardson number （Ri） under complex convection. An experiential formula is obtained to describe the relationship between the average Nusselt number （Nu） and Ra and Re for different aspect ratios. Differing from the LBGK approximation, an LB moment model is applied.