Suppression of Vortex Shedding for Flow Around a Circular Cylinder Using Optimal Control

Chris Homescu, I.M.Navon, Zhijin Li

Adjoint formulation is employed for the optimal control of flow around a rotating cylinder, governed by the unsteady Navier-Stokes equations.The main objective consists of suppressing Karman vortex shedding in the wake of the cylinder by controlling the angular velocity of the rotating body, which can be constant in time or time-dependent. Since the numerical control problem is ill-posed, regularization is employed. An empirical logarithmic law relating the regularization coefficient to the Reynolds number was derived for Re between 60 and 140. Optimal values of the angular velocity of the cylinder are obtained for Reynolds numbers ranging from Re =60 to Re =1000.The results obtained by computational optimal control method agree with previously obtained experimental and numerical observations. A significant reduction of the amplitude of the variation of the drag coefficient is obtained or the optimized values of the rotation rate.