Center for Combustion Energy, Department of Energy and Power Engineering and Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, 100084 Beijing, China.
Physics of Fluids Group and Max Planck Center for Complex Fluid Dynamics, MESA+Institute and J. M. Burgers Centre for Fluid Dynamics, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands.
Phys Rev Lett. 2018 Jan 26;120(4):044501. doi: 10.1103/PhysRevLett.120.044501.
In this combined experimental and numerical study on thermally driven turbulence in a rectangular cell, the global heat transport and the coherent flow structures are controlled with an asymmetric ratchetlike roughness on the top and bottom plates. We show that, by means of symmetry breaking due to the presence of the ratchet structures on the conducting plates, the orientation of the large scale circulation roll (LSCR) can be locked to a preferred direction even when the cell is perfectly leveled out. By introducing a small tilt to the system, we show that the LSCR orientation can be tuned and controlled. The two different orientations of LSCR give two quite different heat transport efficiencies, indicating that heat transport is sensitive to the LSCR direction over the asymmetric roughness structure. Through a quantitative analysis of the dynamics of thermal plume emissions and the orientation of the LSCR over the asymmetric structure, we provide a physical explanation for these findings. The current work has important implications for passive and active flow control in engineering, biofluid dynamics, and geophysical flows.
在这项关于矩形腔内热驱动湍流的实验与数值联合研究中，通过在上、下壁面设置不对称的棘齿状粗糙结构来控制整体热输运和相干流动结构。研究表明，由于在导热壁面上存在棘齿结构，打破了对称，可以将大尺度环流卷（LSCR）的方向锁定在一个优选方向，即使当腔室完全水平时也是如此。通过对系统引入一个小的倾斜，我们发现 LSCR 的方向可以被调节和控制。LSCR 的两个不同方向产生了两种截然不同的热输运效率，这表明热输运对 LSCR 方向在非对称粗糙结构上非常敏感。通过对热羽流排放的动力学和 LSCR 在非对称结构上的方向的定量分析，我们对这些发现提供了物理解释。当前的工作对于工程、生物流体动力学和地球物理流中的被动和主动流动控制具有重要意义。
