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 R e = 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 ( R e = 20000 − 80000 ) and (ii) angle of attack ( | α | ≤ 2 deg ). For all examined R e 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 R e and α = 0 deg , a noticeable decrease in the size of the mean recirculation region alongside the rectangular cylinder, l r , is observed with increasing r / D . For r / D ≥ 0 . 0781 , the flow features are also sensitive to R e , with a reduction in the length of the mean recirculation with increasing R e . The reduction of l r with increasing r / D and R e 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 l r on the leeward side surface and the opposite on the windward side, is more important than for small r / D values. • Experiments have been carried out for a 5:1 rectangular cylinder (BARC benchmark). • Investigation on combined effects of edge curvature radius, Reynolds, and angle of attack. • For curvature radii below r / D = 0 . 0360 , the flow features are similar to those of ‘sharp’ edges. • For r / D ≥ 0 . 0781 , the mean lateral recirculation region decreases as r/D increases. • For r / D ≥ 0 . 0781 , the sensitivity to Reynolds and angle of attack is larger.

Topics & Concepts