The generation and evolution of turbulent mimetic structures significantly affect the transport of heat in turbulent flows. Under the same buoyancy drive, thermoturbulent systems may exhibit different large-scale order-fitting structures (Xi & Xia, 2008, Phys. Fluids). In addition, there is a transient correlation between flow modes and heat transfer efficiency, and multiple states of turbulent structure can lead to different overall heat transport (Xi et al., 2016, J. Fluid Mech.). Recently, Xu Ao et al., a young faculty member in Prof. Hengdong Xi's team at the School of Aeronautics and Astronautics/Institute of Extreme Mechanics of XUT, have achieved a predetermined active control of heat transfer efficiency enhancement by controlling the flow structure through wall shear. Based on the team's previous results (Xu et al., 2020, Phys. Fluids), the researchers designed three wall shear approaches aiming to achieve a single vortex structure, a horizontally stacked double vortex structure and a vertically stacked double vortex structure, respectively, to regulate the heat transfer efficiency of the convective system. Direct numerical simulations show that the horizontal superimposed double vortex structure has the highest heat transfer efficiency among the three sheared thermoturbulent systems, due to the fact that the horizontal superimposed double vortex structure creates a more efficient heat transfer channel in the flow field.
In addition, the researchers identified anomalies in the laminarisation characteristics of thermal turbulence as the shear intensity increases. By analysing the kinetic evolution of the plume within the cavity, the researchers confirmed that wall shear inhibits the self-organising behaviour of the plume, resulting in a weakening of the generation of turbulent kinetic energy and thus a new laminar state of thermal turbulence.
The research results were published in the top journal of fluid mechanics "Journal of Fluid Mechanics" under the title "Wall-sheared thermal convection: heat transfer enhancement and turbulence relaminarization". Journal of Fluid Mechanics. The first author is Associate Professor Xu Ao and co-authors are Master's student Xu Benrui and Professor Xi Hengdong (corresponding author). Northwestern Polytechnic University is the sole signatory of the paper. The research was supported by the National Natural Science Foundation of China and the 111th Intellectual Research Base for Complex Flow and Control of Aircraft.
Link to the paper: https://doi.org/10.1017/jfm.2023.173
