倾斜角对方腔内非稳态自然对流影响的格子Boltzmann方法模拟

Effects of Inclination Angles on Unsteady Natural Convection Flow in Closed Cavity based on Lattice Boltzmann Method

采用格子Boltzmann方法构建非稳态方腔自然对流的数学模型,并进行模型验证,分析流场和温度场随时间的变化,重点讨论瑞利数 Ra、倾斜角度θ对方腔内非稳态流动特性和传热特性的影响.结果表明:随着瑞利数Ra增大,平均努塞尔数Nu a 变大.瑞利数Ra=10 4、Ra=10 5和Ra=10 6工况的平均努塞尔数Nu a 曲线发生波动,瑞利数Ra=10 3工况的平均努塞尔数Nu a 曲线未产生波动.瑞利数Ra=10 6工况的稳定时间最短,瑞利数Ra=10 4工况的稳定时间最长.倾斜角度θ=0 °和θ=30 °工况的平均努塞尔数最优,且稳定时间最短;倾斜角度θ=90 °和θ=270 °工况的平均努塞尔数最差.

The lattice Boltzmann method is used to construct the mathematical model of the unsteady natural convection flow in a closed cavity. The developed code is validated against published works by numerical simulation for natural convection flow. The change of stream function and temperature distribution with time is analyzed. The effects of Rayleigh number( Ra ) and inclination angle(θ) on the fliud flow and heat transfer are emphatically investigated in this study. Results showed that, with the increase of Rayleigh number, the average Nusselt number increased. The average Nusselt number curves of Ra =10 4, Ra =10 5 and Ra =10 6 fluctuated, while the average Nusselt number curves of Ra =10 3 did not fluctuate. The stability time of condition for Ra =10 6 was the shortest, on the contrary, the stability time of condition for Ra =10 4 was the longest. The average Nusselt number of conditions for the inclination angle θ=0° and θ=30° was the best, and the stable time was the shortest;conversely, the average Nusselt number of conditions for the inclination angle θ= 90° and θ=270° was the worst.