Publisher's Synopsis
Design and implementation of a digital feedback controller for a flow control experiment was performed. The experiment was conducted in a cryogenic pressurized wind tunnel on a generic separated configuration at a chord Reynolds number of 16 million and a Mach number of 0.25. The model simulates the upper surface of a 20% thick airfoil at zero angle-of-attack. A moderate favorable pressure gradient, up to 55% of the chord, is followed by a severe adverse pressure gradient which is relaxed towards the trailing edge. The turbulent separation bubble, behind the adverse pressure gradient, is then reduced by introducing oscillatory flow excitation just upstream of the point of flow separation. The degree of reduction in the separation region can be controlled by the amplitude of the oscillatory excitation. A feedback controller was designed to track a given trajectory for the desired degree of flow reattachment and to improve the transient behavior of the flow system. Closed-loop experiments demonstrated that the feedback controller was able to track step input commands and improve the transient behavior of the open-loop response.Allan, Brian G. and Juang, Jer-Nan and Raney, David L. and Seifert, Avi and Pack, latunia G. and Brown, Donald E.Langley Research CenterFEEDBACK CONTROL; BOUNDARY LAYER SEPARATION; BOUNDARY LAYER CONTROL; WIND TUNNEL TESTS; CONTROLLERS; SEPARATED FLOW; OSCILLATING FLOW; AIRFOILS; EXCITATION; CRYOGENIC WIND TUNNELS; ANGLE OF ATTACK; DIGITAL SYSTEMS; LOW REYNOLDS NUMBER; PRESSURE GRADIENTS; SHEAR LAYERS; TRAILING EDGES; VORTICES...
