Flow control using rotating cylinders: effect of gap

Abstract

The flow past a bluff body can be controlled significantly by placing small rotating cylinders at appropriate locations. Computational results for control of Re = 10 flow past a circular cylinder are presented. Two control cylinders of one-twentieth the diameter of the main cylinder rotate at a rate such that their tip speed is five times the free-stream speed of the flow. Computations are carried out for various values of the gap between the main and control cylinders. A stabilized finite element method is utilized to solve the incompressible Navier-Stokes equations in the primitive variables formulation. A gap value of one-tenth the diameter of the main cylinder is found to be close to the optimal value. Compared to the flow past an isolated cylinder a very significant reduction in the drag and unsteady forces is observed for the flow with control.