Flow-Interactive Control of a Flexible Wing Using Aerodynamic Distributed Bleed Actuation
Controlled interactions between a 3-D flexible wing model and the embedding cross flow were explored in wind tunnel investigations for effecting tunable structural and aeroelastic characteristics by exploiting regulation of the aerodynamic loads that are effected by fluidic actuation. The aerodynamic loads are regulated using distributed autonomous air bleed that is driven through surface ports by pressure differences between its pressure and suction surfaces and is regulated by surface louvers. Assessment of the control authority of time invariant bleed showed that prescribed decrements of the aerodynamic loads could be varied bi-directionally relative to a prescribed operating point by regulating the surface porosity of the actuation. The physical mechanism by which distributed bleed affects the aerodynamic loads was investigated using planar and stereo PIV measurements and it was demonstrated that time-invariant bleed affects the balance of streamwise vorticity in the near wake leading to variation in the sectional circulation and spanwise loading. Furthermore, the characteristic response time of the circulation to temporal bleed actuation points to reasonably broad band control. The utility of regulated bleed-induced spanwise load distributions for aerodynamic structural control was demonstrated by the suppression of deliberate planform vibrations using real time feedback control. Up to 70% reduction in RMS wing tip oscillation was achieved along with comparable reductions in associated oscillations of the aerodynamic loads and moment with minimal penalties in lift and drag, indicating the bleed potential for controlling its aeroelastic characteristics for flutter or gust alleviation.