Effect of corner rounding and angle of attack on the dynamics of the shear layers detaching from the upstream corners of a 5:1 rectangular cylinder

The high Reynolds number flow around a rectangular cylinder, having a chord-to-depth ratio equal to 5, is the object of the international benchmark BARC. This configuration is characterized by shear layer separation at the upstream corners and mean-flow reattachment on the cylinder side. In Rocchio et al. (J Wind Eng. Ind. Aerod., 2020), highly-resolved LES showed that even very small values of the corner curvature radius have a dramatic impact on the numerical solution on the cylinder sides, leading to a better agreement with available experiments. In this work, we experimentally investigate the sensitivity of the flow pattern to the degree of rounding of the upstream corners and, also, to small angles of attack of the free-stream flow. A small value of the corner roundings does not produce significant differences in the shear-layer dynamics and the mean-flow reattachment point. On the contrary, for large values of the roundings the reattachment point moves upstream. Small angle of attacks produces a significative variance of the length of the two recirculation regions. As an example, for an angle of 2 degrees, the distance between the mean reattachment points on the windward and leeward sides of the cylinder is about 0.2 times the length of the side.