湍流热对流中的动力学和传热研究

Flow dynamics and heat transport in turbulent thermal convection

文章介绍了湍流热对流中流动结构和动力学的实验研究.本文作者通过流动示标和粒子成像测速系统(PIV)的测量,清晰地揭示了对流系统的三维流动结构,发现大尺度环流的角向运动在不同的时间尺度上有不同的表现.通过统计分析,本文作者进一步发现大尺度环流方位角的变化具有布朗棘齿的特性,并且从实验上证明在湍流热对流系统中不同的流动模式的确可以得到不同的传热效率.

An experimental study of flow structure and dynamics and their relationship with the heat transport in turbulent thermal convection is reported. It is shown that the instantaneous large-scale flow structure in a cylindrical convection cell consists of an elliptical circulatory roll and two smaller counter-rotating roils. As the quasi-2D instantaneous flow structure rotates azimuthally, it generates a time-averaged 3D flow pattern featuring two toroidal tings near the top and bottom plates respectively. It is found that the apparently stochastic azimuthal motion of the flow structure, which generates a net rotation on average, has the characters of a Brownian ratchet. We also provide convincing evidence that a particular value of the heat transport efficiency Nu can be associated with a specific internal flow mode of the system.