Numerical study on wake control of square cylinder based on vertical axis wind turbines

A large eddy simulation is used in this study to explore wake control for a square cylinder based on vertical axis wind turbines. These vertical axis wind turbines are installed around a chamfered square cylinder, and the effects of the wind turbine diameter and the spacing between the wind turbine and the chamfered square cylinder on the aerodynamic forces and wake characteristics of the chamfered square cylinder are investigated. The analysis results indicate that wind turbines continuously transport high-speed fluid to the wake and the negative pressure value in the square cylinder wake decreases, which leads to a reduction in the downwind drag. Further, the time-averaged main vortex in the chamfered square cylinder wake is elongated and the center of the main vortex is farther away from the square cylinder; this considerably reduces the surface pressure and lift coefficient fluctuation. The optimal control effect for the square cylinder wake is obtained when h is 1/8d and the ratio of d to D (the side length of square cylinder) is 0.25. Compared with the results of flow around an uncontrolled chamfered square cylinder, the root mean square value of the lift coefficient and the mean value of the drag coefficient are reduced by 80.5% and 19.8%, respectively. Thus, the aerodynamic control method based on the vertical axis wind turbines can effectively suppress the vortex shedding mode of a square-cylinder wake, so as to reduce the aerodynamic forces and vortex-induced vibration.