论文标题
二维圆形对流电池中大规模循环的可转移流状态和逆转
Tristable flow states and reversal of the large-scale circulation in two-dimensional circular convection cells
论文作者
论文摘要
我们介绍了在二维圆形雷利 - 贝纳德细胞中大规模循环（LSC）的流量和逆转的数值研究。长时间直接数值模拟在雷利号（$ ra $）范围$ 10^{7} \ le ra \ le 10^{8} $和prandtl号码（$ pr $）范围$ 2.0 \ le pr \ le pr \ le 20.0 $中进行。我们发现，除了通常观察到的循环态（顺时针和逆时针方向的LSC）外，还有一个新的，长期的混乱状态。循环状态由中间的一个主要卷和顶部和底部圆形壁附近的两个二次卷组成。主要卷变得越来越强大，而两个次要卷会减少，随着$ ra $的增加。我们的结果表明，LSC的逆转伴随着次要卷，打破了主要卷，然后连接以形成一个带有反向方向的新主要卷。我们绘制了LSC存在的相位图和在$ ra $ -pr $空间中的逆转，该空间表明，当$ ra $大，$ pr $很小时，流量在流通状态。 LSC的逆转只能发生在有限的$ PR $范围内。相图可以从热扩散和粘性扩散之间的竞争来理解。我们还发现，内流状态表现为努塞尔特和雷诺数等全球性能。
We present a numerical study of the flow states and reversals of the large-scale circulation (LSC) in a two-dimensional circular Rayleigh-Bénard cell. Long-time direct numerical simulations are carried out in the Rayleigh number ($Ra$) range $10^{7} \le Ra \le 10^{8}$ and Prandtl number ($Pr$) range $2.0 \le Pr \le 20.0$. We found that a new, long-lived, chaotic flow state exists, in addition to the commonly observed circulation states (the LSC in the clockwise and counterclockwise directions). The circulation states consist of one primary roll in the middle and two secondary rolls near the top and bottom circular walls. The primary roll becomes stronger and larger, while the two secondary rolls diminish, with increasing $Ra$. Our results suggest that the reversal of the LSC is accompanied by the secondary rolls growing, breaking the primary roll and then connecting to form a new primary roll with reversed direction. We mapped out the phase diagram of the existence of the LSC and the reversal in the $Ra$-$Pr$ space, which reveals that the flow is in the circulation states when $Ra$ is large and $Pr$ is small. The reversal of the LSC can only occur in a limited $Pr$ range. The phase diagram can be understood in terms of competition between the thermal and viscous diffusions. We also found that the internal flow states manifested themselves into global properties such as Nusselt and Reynolds numbers.
