Large Eddy Simulation of Blockage Effect on Flow Past a Two Dimensional Square Cylinder

Abstract:

The uniform flow past two dimensional square cylinders with blockage ratios 4.2%, 10%, 16.7%, 20% and 25% were numerically investigated by largeeddy simulation (LES). The aerodynamic forces and pressure distributions of the cylinders with these blockage ratios were discussed. The blockage effects on flow field characteristics and instantaneous vorticity were investigated. The results show that when the blockage ratio increases from 4.2% to 25%, the average drag coefficient， fluctuating lift coefficient and Strouhal number increase by 27.6%, 43.6% and 31%, respectively. The mean suction pressure coefficients and fluctuating pressure coefficients on the side and leeward surfaces of the cylinder both increase with the blockage ratios. The blockage effects on the flow characteristics around the cylinders are significant. Furthermore, for high blockage ratios, periodic and alternating vortices are observed in the vicinity of the walls and mix with the vortices shedding from the cylinders.

Key words:wind tunnel test; blockage ratio; large eddy simulation; aerodynamic forces; instantaneous vorticity