Parametrized reduced-order modeling of nonlinear separated flows

Flight and renewable energy systems, ranging from micro air vehicles to wind turbines, encounter large operating regimes. Efficient reduced-order unsteady aerodynamic models that accurately capture the dynamics over large operating regimes are essential for prediction and control. In this work, we consider viscous, separated flows over a rigid flat plate and identify interpretable models that accurately capture the transient and post-transient lift and drag dynamics over large nonlinear flow regimes. The identified models are based on data gathered from Reynolds number 100 direct numerical simulations. We use a variant of the sparse identification of nonlinear dynamics (SINDy) algorithm to find a parametrized, low-order model that is valid over a wide range of angles of attack including the critical angle of attack at which a bifurcation occurs. We show that the parametrized model can accurately capture the bifurcation location, limit cycle amplitudes and phases, and transient decay rates of the rigid flat plate flow over a range of operating conditions.