Numerical study of flow and thermal behaviour of lid-driven flows in cavities of small aspect ratios

Numerical study has been performed to investigate the effects of cavity shape on flow and heat transfer characteristics of the lid-driven cavity flows. Dependence of flow and thermal behaviour on the aspect ratio of the cavities is also evaluated. Three types of the cross-sectional shape, namely, circular, triangular, and rectangular, and four aspect ratios, 0.133,0.207,0.288, and 0.5, are taken into account to construct twelve possible combinations; however, attention is focused on the small-aspect-ratio situations. Value of the Reynolds number considered in this study is varied between 100 and 1800. For the cases considered in this study a major clockwise vortex driven by the moving lid prevailing in the cavity is always observed. When the Reynolds number is fixed, the rectangular cavity produces strongest lid-driven flow, and the triangular cavity weakest. For the cases at small aspect ratio and low Reynolds number, the streamlines appear symmetric fore-and-aft with respect to the central line at x/L=0.5. Data for the local and average Nusselt numbers are also provided. For rectangular cavities, it is observed that case 1/5R produces the highest average Nusselt number at any Reynolds number. Among the twelve possible geometric cases considered herein, the highest and lowest average Nusselt numbers are found with cases 1/6T and 1/2C, respectively.