Exploring the plume and shear effects in turbulent Rayleigh–Bénard convection with effective horizontal buoyancy under streamwise and spanwise geometrical confinements. (10th June 2022)

• Record Type: Journal Article
• Authors: Zhang, Lu; Dong, Jing; Xia, Ke-Qing
• Is Part Of: Journal of fluid mechanics. Volume 940(2022)
• Publication Date: 2022-06-10
• Subjects: Bénard convection -- plumes/thermals -- turbulence control; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2022.187
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract: Abstract : We present an experimental and numerical study of turbulent thermal convection in the presence of an effective horizontal buoyancy that generates extra shear at the boundary. Geometrical confinements are also applied by varying the streamwise and spanwise aspect ratios of the convection cell to condense the plumes. With these, we systematically explore the effects of plume and shear on heat transfer. It is found that a streamwise confinement results in increased plume coverage but decreased shear compared with spanwise confinement. The fact that streamwise confinement leads to a higher vertical heat transfer efficiency than the spanwise confined case suggests that the increase of plume coverage is the dominant effect responsible for the enhanced heat transfer. Our results highlight the potential applications of coherent structure manipulation in efficient passive heat transfer control and thermal engineering. We also analyse the energetics of the present system and derive the expression of mixing efficiency accordingly. The mixing efficiency is found to increase with both the buoyancy ratio and streamwise dimension.