不同冷热壁面对方腔内对流换热影响的格子Boltzmann模拟

Lattice Boltzmann simulation of convection heat transfer in a cubic cavity with different local cold and hot wall conditions

基于格子Boltzmann方法,选取多弛豫时间(MRT)模型对具有局部冷热壁面立体方腔中的三维自然对流换热进行模拟研究。分别采用三维D3Q19模型描述速度场,D3Q7模型描述温度场,研究不同瑞利数Ra(103≤Ra≤105)和局部冷热壁面位置变化对三维方腔内自然对流的影响。结果表明:冷热壁面的布置方式对流动换热有显著影响,且瑞利数Ra越大,其影响效果越明显。其中,冷热壁面均处于中间位置(工况5)的自然对流换热能力最强,并且随着Ra逐渐增大,自然对流能力增强,流线逐渐复杂。在相同工况条件下,随着Ra增大,平均努塞尔数Nuav也逐渐增加,换热能力增强。在相同Ra条件下,工况5的Nuav最大,表明其自然对流换热能力最强。

Based on the lattice Boltzmann method,the multiple-relaxation-time(MRT)model was selected to simulate the three-dimensional natural convection heat transfer in a cubic cavity with local hot and cold walls.The D3Q19 model and the D3Q7 model were used to describe the velocity field and temperature field,respectively.The effects of different Rayleigh numbers Ra(103≤Ra≤105)and local hot and cold wall position on the natural convection in the three-dimensional cubic cavity were studied.The results reveal that the arrangement of the hot and cold walls has a significant effect on the flow heat transfer,and the larger the Ra,the more obvious the effect.The strongest natural convection heat transfer capacity is obtained by Case 5 with the hot and cold walls in the middle position.As the Ra increases gradually,the natural convection ability increases and the streamline becomes more complicated.Under the same working case,with the increase of Ra,the average Nusselt number Nuav also increases gradually,and the heat transfer capacity is stronger.The Nuav value of Case 5 is the largest at the same Ra,indicating that its natural convection heat transfer capability is the strongest.