In order to suppress vortex shedding and reduce drag

an active control is implemented by two symmetrical affiliated cylinders with fixed rotation

which are located right behind the main cylinder. Numerical study on this active control is employed for the two-dimensional unsteady flow around the cylinder.Numerical simulations are performed in a range of rotation speed α and different directions of rotation at Reynolds number of 200.The numerical simulation result indicates that when the upper small cylinder spins clockwise and the bottom cylinder spins counterclockwise

the purpose can be achieved. When α equals to 2.4

vortex shedding of wake fluid of the main cylinder is suppressed completely. When the rotation directions of two affiliated cylinders are different

the vorticity is reinforced and the drag and lift coefficients are increased.