Nonlinear system identification for the interaction of synthetic jets with a boundary layer

Considered in this paper is the development of a dynamic model based on system identification for a specific problem of active control of flow separation using synthetic jets. A feedback control loop is very crucial for the efficient operation of synthetic jets. Constructing the dynamic model of the jets is of fundamental importance to accomplish such feedback control. We apply a polynomial NARMAX (nonlinear autoregressive moving average model with exogenous inputs) method to the results derived from numerical simulation, where the interaction of synthetic jets with a laminar boundary layer is examined. Since the pressure distribution across a control surface including the jet slot is a good measure of flow separation, a dynamic nonlinear model is identified for the downstream pressure response with respect to the synthetic jet actuation. The model is verified using a set of CFD simulation results with different actuation frequencies. The identified dynamic model with uncertainty caused by variation of free stream velocity is proposed for control system design for mitigating flow separation.