Parameter-varying aerodynamics models for aggressive pitching-response prediction

Current low-dimensional aerodynamic-modeling capabilities are greatly challenged in the face of aggressive flight maneuvers, such as rapid pitching motions that lead to aerodynamic stall. Nonlinearities associated with leading-edge vortex development and flow separation push existing real-time-capable aerodynamics models beyond their predictive limits, which puts reliable real-time flight simulation and control out of reach. In the present development, a push toward realizing real-time-capable models with enhanced predictive performance for flight operations has been made by considering the simpler problem of modeling an aggressively pitching airfoil in a low-dimensional manner.A parameter-varying model, composed of three coupled quasi-linear sub-models, is proposed to approximate the lift, drag, and pitching-moment response of an airfoil to arbitrarily prescribed aggressiveramp-hold pitching kinematics. An output-error-minimization strategy is used to identify the low-dimensional quasi-linear parameter-varying submodels from input-output data gathered from low-Reynolds-number (Re = 100) direct numerical fluid dynamics simulations. The resulting models have noteworthy predictive capabilities for arbitrary ramp-hold pitching maneuvers spanning a broad range of operating points, thus making the models especially useful for aerodynamic optimization and real-time control and simulation.