Flow Over Flat and Curved Plates: A Flow Visualization Study

Visualization experiments are conducted in a water channel to investigate the wake vortex characteristics of a flat plate and convex and concave curved plates. Three parameters—vortex size ($S_v$), vortex length ($L_v$), and Strouhal number ($St$)—are investigated in this study to deduce the effect of plate curvature and orientation. These parameters are estimated for both the upper and lower vortices by keeping the chord length ($L_c$) fixed and changing the plate diameter (D). Various plate configurations are demonstrated by altering the $L_c/\mathrm{D}$ ratio from 0 to 1; $L_c/\mathrm{D}=0$, 6/13, 3/4, and 1. The Reynolds number (Re) based on chord length remains unchanged at 5,878 throughout the analysis. For each case of the $L_c/\mathrm{D}$ ratio, the angle of flow incidence of the plate ($\alpha$) is varied from 0° to 30° in steps of 5°. For the convex plate, the combined effect of curvature and orientation is found to enhance the vortex shedding frequency by 70.7%, whereas vortices shrink by 26.71%, and the vortex length is reduced by 25.38%. The manipulations achieved for concave plates reveal comparatively lesser enhancement in shedding frequency; however, concave surfaces are observed to be more suitable for stretching the vortices toward the downstream. The modifications thus achieved have significant practical relevance in various applications. A shedding mechanism that partially interrupts Gerrard’s mechanism is also found to operate with concave plate configurations.