Flow around a 5:1 rectangular cylinder: effects of corner roundings

This work aims at shedding some light on this counter-intuitive behavior of the numerical simulations on a 5:1 rectangular cylinder at high Reynolds number. In particular, it has been shown that the length of the mean recirculation bubble on the cylinder side is strictly connected with the location at which the shear layers separating from the upstream corners lose coherence and roll-up in vortical structures. Simulations with low SGS dissipation and highly refined grids were characterized by early roll-up and by small vortical structures. Following this result, additional simulations are carried out to investigate the effect of a small rounding in the upstream corners of the rectangular cylinder. We want to investigate whether the presence of perfectly sharp corners can generate some disturbances which are not damped in numerical simulations characterized by low numerical and SGS dissipation as the present ones, which may in turn lead to a premature instability of the shear layers.