Simulations of three dimensional feedback control of a circular cylinder wake

*† ‡ + § Three-dimensional feedback controlled simulations of the wake behind a circular cylinder were performed. Feedback control was achieved by using a low dimensional model based on Proper Orthogonal Decomposition (POD) in conjunction with least square sensor based estimation to estimate the flow state. At a Reynolds numbers of 100, experimental and computational investigations have shown that although the vortex shedding is weakened by the introduction of closedloop control, spanwise phase variations eventually lead to an instability which results in the loss of control. In the current simulations, a three-dimensional sensor array was placed in the wake to estimate the flow state based on two dimensional POD Modes, which were applied at multiple spanwise locations. A linear stochastic estimator was used to map sensor readings to the temporal coefficients of the POD modes. The simulations were aimed at investigating the efficacy of threedimensional flow sensing to improve feedback control. Because the control input had only one degree of freedom (1 DOF), the mode amplitudes had to be combined into one actuator signal. The effect of selecting various spanwise sensing locations for feedback flow control was investigated.