Effect of the Lateral Mean Recirculation Characteristics on Near-Wake and Bulk Quantities of a 5:1 Rectangular Cylinder

A database of several LES carried out for the high-Reynolds number flow around a 5:1 rectangular cylinder is analyzed to highlight the effects of the characteristics of the mean flow over the cylinder side on the near-wake features and on some bulk quantities. Different simulation set-ups are considered by varying the grid refinement in the spanwise direction and the amount of SGS dissipation for sharp upstream edges and with different values of the upstream-edge rounding. These simulations may be considered as possible instances of this kind of flow with different mean flow features on the cylinder side. Among the different characteristic lengths defining the mean recirculation, the streamwise length is the most important parameter. The wake width increases linearly with this parameter, while the vortex-shedding non-dimensional frequency shows a linear decrease. The drag coefficient also linearly decreases with increasing the recirculation length and this is due to a reduction of the suctions on the cylinder base. However, the overall variation of CD is small. Finally, a significant, and once again linear, increase of the fluctuations of the lift coefficient is found for increasing the mean recirculation streamwise length.