The effect of turbulence on aerodynamic forces on a square cylinder with various corner shapes

To comprehensively investigate the effect of corner modification on aerodynamic forces, we set up an experimental model of a two- and three-dimensional square cylinder in several types of oncoming flow, a smooth and homogeneous turbulent flow. We carried out wind tunnel tests for measurements of aerodynamic quantities, such as averaged and fluctuating statistics of lift and drag forces, acting on a square sectioned cylinder with sharp, chamfered or rounded corners. The principal results are as follows: (1) Chamfered and rounded corners decrease drag forces, as a result of reduction in wake width. (2) For a round-cornered cylinder in turbulent flow, it is found that the shear layer that separate from the windward edge reattaches to the side surface even at angle of attack a=0°. (3) The values of C LRMS for three-dimensional cylinders are reduced to about 10% (in uniform flow) of the values for two-dimensional cylinders. This means that the effect of Karman vortices and the resulting lift force are not so large for three-dimensional cylinders.