通过横向限制实现低普朗特数对流中的流动反转
Flow Reversal in Low-Prandtl-Number Convection via Lateral Confinement
AI总结：
研究低普朗特数流体中LSC流动反转问题，通过直接数值模拟液态金属对流，发现强横向限制能引发“羽流凝聚”转变，减少热损失，为角涡提供浮力驱动反转，绘制出“反转岛”，确立横向限制为控制参数。
AI中文摘要：
一种普遍的共识认为，在低普朗特数（Pr）流体中，大尺度环流（LSC）的流动反转受到抑制，因为高热扩散率会迅速耗散为角涡机制提供能量所需的能量。在此，我们报告了液态金属对流（Pr = 0.029）的直接数值模拟，结果表明强横向限制违背了这一共识，能够实现持续的LSC反转。我们表明，限制引发了“羽流凝聚”转变，将混沌热羽流重组为高度相干的准线性结构。热耗散分析表明，这种相干性极大地减少了传输过程中的热损失，使羽流能够为角涡提供足够的浮力以驱动反转。我们在参数空间中绘制了一个独特的“反转岛”，确立了横向限制作为能够克服高热扩散率稳定作用的控制参数。
英文摘要：
A prevailing consensus holds that flow reversals of the large-scale circulation (LSC) are suppressed in low-Prandtl-number (Pr) fluids, as high thermal diffusivity rapidly dissipates the energy required to fuel the corner-vortex mechanisms. Here, we report Direct Numerical Simulations of liquid metal convection (Pr=0.029) revealing that strong lateral confinement defies this consensus, enabling sustained LSC reversals. We show that confinement triggers a ``plume condensation" transition, reorganizing chaotic thermal plumes into highly coherent, quasi-linear structures. A thermal dissipation analysis demonstrates that this coherence drastically reduces heat loss during transport, allowing plumes to deliver sufficient buoyancy to corner vortices to drive reversals. We map a distinct ``island of reversal" in the parameter space, establishing lateral confinement as a control parameter capable of overcoming the stabilizing effects of high thermal diffusivity.
