Control of Unsteady Aerodynamic Loads Using Pulsed Bleed Actuation

The aerodynamic loads of a static and pitching wind tunnel model (Re_c = 6.3∙10^5) are varied spatially and temporally without conventional moving control surfaces using direct lift control. Actuation is effected using Aerodynamic Distributed Bleed (ADB), a form of active flow control in which inherent pressure differences in flight across the pressure and suction surfaces drive a flow through ports on the surface near the leading edge or near midchord. The bleed flow is regulated using integrated low-power louvers located beneath the surface, enabling temporal variation of the aerodynamic loads on the convective timescale of the flow without an auxiliary air supply. Steady bleed actuation leads to a lift increase of over 11%, with minimal change in pitching moment, while transitory pulsed bleed actuation applied at different instances of a time-periodic pitch cycle leads to significant variation in the unsteady aerodynamic loads with up to 25% increase in maximum lift.