NUMERICAL PREDICTION OF UNSTEADY PRESSURES ON A SQUARE CYLINDER WITH VARIOUS CORNER SHAPES

Three-dimensional incompressible flows around a square cylinder with v arious corner shapes are numerically simulated by the direct finite di fference scheme without any turbulence model. In order to overcome num erical instability for the high Reynolds number flows, third-order upw ind scheme is incorporated for the convection terms. Experiment is als o performed for the same model under same conditions. It is demonstrat ed that, as the corner shape is slightly changed, the aerodynamic char acteristics result in drastic modification. For example, the modified drag has a possibility to decrease up to approximately 60% of the orig inal value due to an appropriate shape. So this kind of passive techni que for reduction of the aerodynamic forces is very promising. Especia lly we focus on the unsteady pressures acting on the surface of the cy linder and compare the computational results with the experimental one s. The spatial correlation of pressures is also investigated, in order to understand the detailed structures of the separated shear layers w hich mainly decide the aerodynamic characteristics. On the basis of th e numerical results, the mechanism far reducing the aerodynamic forces is clarified. (C) 1998 Elsevier Science Ltd. All rights reserved.