We report a comparative experimental study of the reversal of the large-scale circulation in turbulent Rayleigh–Benard convection in a quasi-two-dimensional corner-less cell where the corner vortices are absent and in a quasi-two-dimensional normal cell where the corner vortices are present. It is found that in the corner-less cell the reversal frequency exhibits a slow decrease followed by a fast decrease with increasing Rayleigh number $Ra$ , separated by a transitional $Ra$ ( $Ra_{t,r}$ ). The transition is similar to that in the normal cell, and $Ra_{t,r}$ is almost the same for both cells. Despite the similarities, the reversal frequency is greatly reduced in the corner-less cell. The reduction of the reversal frequency is more significant, in terms of both the amplitude and the scaling exponent, in the high- $Ra$ regime. In addition, we classified the reversals into main-vortex-led and corner-vortex-led, and found that both types exist in the normal cell while only the former exists in the corner-less cell. The frequency of main-vortex-led reversal in the normal cell is found to be in excellent agreement with the frequency of reversals in the corner-less cell. Our results reveal for the first time the quantitative role of the corner vortices in the occurrence of the reversals of the large-scale circulation.

中文翻译：

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在没有角涡的情况下减少湍流对流中的流动逆转

我们报告了在没有角涡的准二维无角单元和准二维正常单元中湍流瑞利-贝纳德对流中大规模环流逆转的比较实验研究存在角涡。发现在无角单元中，反转频率随着瑞利数 $Ra$ 的增加呈现缓慢下降，然后快速下降，由过渡 $Ra$ ( $Ra_{t,r}$ ) 隔开。转换与正常单元格中的转换相似，并且两个单元格的 $Ra_{t,r}$ 几乎相同。尽管有相似之处，但无角单元中的反转频率大大降低。就振幅和标度指数而言，在高 $Ra$ 区域，反转频率的降低更为显着。此外，我们将反转分为 main-vortex-led 和corner-vortex-led，发现两种类型都存在于正常单元中，而只有前者存在于无角单元中。发现正常单元中主涡流导致的反转频率与无角单元中的反转频率非常一致。我们的结果首次揭示了角涡在大规模环流逆转发生中的定量作用。