Closed-Loop Control of Separation in Subsonic and Transonic Flows

Clear Science Corp. and Syracuse University propose to demonstrate the feedback control technologies they developed during Phase I in a series of coordinated Phase II computational and experimental tests. The Phase II objective is validated software thatintegrates reduced-model simulations, CFD simulations, and experimental data into a package for designing fixed-wing aircraft flow control systems. In Phase I, we developed a low-order dynamical model, a system-state estimator, and two feedback algorithmsfor predicting and controlling aerodynamic forces in two configurations: the ActiveWing Facility (a backward facing ramp) and Syracuse University's NACA 4412 airfoil test rig. The Phase II control system consists of an array of modular pressure sensors andpulsed jets, surface mounted on the NACA 4412 airfoil and communicating through a digital signal processor and controller. The controllers use a set of basis functions, computed off-line, to track and maintain prescribed coefficients of lift and drag.One controller computes gains based on errors between target output and output from the reduced model. The second is an output regulator that computes gains based on a linearized model. Phase II demonstrations will benchmark the model, estimator, andcontrollers in a series of hardware-in-the-loop computational simulations and wind tunnel tests. The commercial product to be developed is experimentally validated software for designing active flow control systems. Increased performance requirements andtighter constraints on volume and weight force aerospace systems closer to their design limits. Airframe and propulsion system designers need new tools for these new challenges and all stand to gain from a computational environment for designing robustand scalable active flow control systems. The corresponding market niche is designers of aerospace, automotive, and industrial systems for which flow control is critical. Potential applications of the software include control system designs for low-dragwings on commercial aircraft, low-drag bodies in high-performance automobiles, high-lift blades in rotorcraft, low-distortion jet engine inlets, and high-mixing combustors.