Experimental investigations on the effect of upstream-edge rounding on the BARC configuration

Abstract

We experimentally investigate the influence of upstream-edge roundness on the flow around a 5:1 rectangular cylinder. We examine various values of edge curvature radius, ranging from nearly sharp edges to r/D=0.1104 at Reynolds number Re=40000, based on the freestream velocity and the crossflow dimension of the cylinder. Additionally, we explore the combined effects of edge roundness and (i) Reynolds number (Re=20000−80000) and (ii) angle of attack (|α|≤2deg). For all examined Re and α, limited sensitivity to upstream-edge rounding is observed up to r/D=0.0360, with results close to those obtained for nominally sharp edges. For r/D≥0.0781, and fixed Re and α=0deg, a noticeable decrease in the size of the mean recirculation region alongside the rectangular cylinder, lr, is observed with increasing r/D. For r/D≥0.0781, the flow features are also sensitive to Re, with a reduction in the length of the mean recirculation with increasing Re. The reduction of lr with increasing r/D and Re is due to the detached shear layer becoming more tilted towards the cylinder. Finally, for r/D≥0.0781, the effect of α, that is the increase of lr on the leeward side surface and the opposite on the windward side, is more important than for small r/D values.