圆内开缝圆环形空间自然对流的格子Boltzmann模拟

采用耦合热格子Boltzmann模型,对圆内开缝圆环形空间自然对流进行了数值模拟,分析了瑞利数Ra(10~4≤Ra≤10~6)和开缝度S(0.1≤S≤0.4)对环形空间内流动与换热的影响。模拟结果表明:随着瑞利数增加,环形空间内自然对流换热会出现较强的不稳定性,流型转化也较丰富,存在4种流型,稳定的二涡流、四涡流、二涡流和四涡流之间振荡的交变流以及振荡的二涡流;此外,开缝度的改变对环形空间内自然对流换热影响是显著的。随着开缝度的增大,流体更易形成多涡流型,进而增强流体扰动,流动不稳定性增强;另外,增大开缝度虽能增强环形空间内自流换热,但不是开缝度越大越好,而是存在一个最佳临界开缝度。

Lattice Boltzmann Simulation of Natural Convection in an Annulus Space with an Internal Slotted Circle

A coupled thermal lattice Boltzmann model was adopted to simulate the natural convection in an annulus space with an internal slotted circle. The influences of the Rayleigh number and slotted degree on the flow and heat transfer in the annulus space were discussed. The results show that, with the increase of Rayleigh number, the natural convection in the annulus space will appear strongly instable and the flow regime transition is also multiple. There are four kinds of flow patterns:steady two-eddy flow, four-eddy flow, oscillation between two-eddy and four-eddy flow and oscillatory two-eddy flow. In addition, the influence of the variation of slotted degree on the natural convective heat transfer in the annulus space is significant. With the increase of the slotted degree, the fluid is more likely to form a multi-eddy pattern''s flow, which in turn increases the fluid disturbance and enhances the flow instability. The results also indicate that increasing the slotted degree can enhance the natural convective heat transfer. But the slotted degree is not the larger the better, there is a critical value.