Supression of vortex shedding in the wake of a bluff body by active control

Abstract

An active control method with blowing and suction is used to suppress the vortex shedding in the wake of a vehicular shaped body. We use active control by continuous supply of fluid velocity on the rear side of the body. We have performed two dimensional numerical simulations for a range of Reynolds number and velocity ratios (VR) to reduce the vorticity in the wake. Velocity ratio is defined as the ratio between the suction/blowing velocities to the free stream velocity. These simulations are performed using RANS turbulence model at three different Reynold's no. i.e. Re = 10000, 25000 & 50000 for different VRs. Three dimensional simulations are also performed at Re = 10000 for two different VRs. It is found that at a particular value of VR, there is a great reduction in magnitude of vortices at different downstream locations behind the body. This velocity ratio is referred to as optimum velocity ratio. The corresponding condition is referred as optimal condition. Average vorticity at different downstream locations are calculated and a comparison in these values is made between the two cases of without control and optimum control. Vortex shedding almost suppresses at this optimal condition. Coefficient of lift and strouhal number almost become close to zero although there is an increase in coefficient of drag. Overall, this method gives us several advantages in terms of greatly reducing the strength of vortices and stabilizing the body by suppressing vortex shedding.