Shear effects on flows past a square cylinder with rounded corners at Re=2.2x10(4)

摘要

The effects of planar shear inflows are investigated on flows past a rounded-corner square cylinder at Re = 2.2 x 10(4). The dimensionless shear parameter K ranges from 0.0 to 1.0. Strong dependency on K is found when K = 0-0.4. At K = 0.1, the flow fully separates on the high- and low-velocity sides despite asymmetry; the shear effects on aerodynamic characteristics have an overall similarity with those of sharp-corner square cylinders. At K = 0.4, the flow topology is changed significantly. Flow reattachment occurs on the high-velocity side, inducing a separation bubble. The low-velocity side is featured by a completely separated shear layer that is farther from the cylinder than at lower K, and by much weaker Kaman vortices. This flow pattern results in very small mean pressures near the upper frontal corner, low r.m.s pressures on the bottom wall and a higher Strouhal number. When the local and extreme shear inflow at K = 1.0 is imposed with a high blockage ratio, the alternative vortex shedding is suppressed in the absence of interaction between two shear layers. The wake appears like a turbulent mixing layer which emanates from the trailing corner and rolls up to a series of large-scale coherent structures. However, the lower shear layer stays nearly stationary.