MIMO Feedback Control of Flow Separation

A multiple-input/multiple-output (MIMO) generalized predictive control (GPC) algorithm is applied to the flow separation control problem on a NACA 0025 airfoil model using zero-net mass-flux actuators and unsteady pressure sensors. The results are compared with previous results obtained using an adaptive feedback disturbance rejection algorithm. The goal of the GPC control scheme is to suppress the pressure fluctuations at multiple locations on the upper surface of the airfoil model, which results in reduced flow separation as well as increased lift-to-drag ratio. A recursive MIMO system identification (ID) algorithm is used to model the flow dynamics. The MIMO GPC algorithm is able to reduce the broadband power of the pressure/velocity fluctuations. In addition, the lift-to-drag ratio is increased by a factor of ~7 at 12° at Rec=120,000, where the baseline flow is massively stalled. The adaptive feedback controller is able to keep the flow partially attached up to ~20°.