Physics of Fluids Group, Faculty of Science and Technology, Impact and MESAþ Institutes & Burgers Center for Fluid Dynamics,University of Twente, 7500AE Enschede, The Netherlands.
Phys Rev Lett. 2010 Jul 16;105(3):034503. doi: 10.1103/PhysRevLett.105.034503.
We analyze the reversals of the large-scale flow in Rayleigh-Bénard convection both through particle image velocimetry flow visualization and direct numerical simulations of the underlying Boussinesq equations in a (quasi-) two-dimensional, rectangular geometry of aspect ratio 1. For medium Prandtl number there is a diagonal large-scale convection roll and two smaller secondary rolls in the two remaining corners diagonally opposing each other. These corner-flow rolls play a crucial role for the large-scale wind reversal: They grow in kinetic energy and thus also in size thanks to plume detachments from the boundary layers up to the time that they take over the main, large-scale diagonal flow, thus leading to reversal. The Rayleigh vs Prandtl number space is mapped out. The occurrence of reversals sensitively depends on these parameters.
我们通过粒子图像测速流可视化和在（准）二维、长宽比为 1 的矩形几何形状下的基础 Boussinesq 方程的直接数值模拟来分析瑞利-贝纳德对流的大规模流动反转。对于中等普朗特数，存在对角线大尺度对流卷和另外两个较小的二次卷，它们在对角相对的两个剩余角中。这些角流卷对于大尺度风的反转起着至关重要的作用：它们的动能增长，因此也随着羽流从边界层脱离而增长，直到它们接管主要的对角线大尺度流，从而导致反转。瑞利与普朗特数的空间被映射出来。反转的发生敏感地取决于这些参数。
