Temporal Control of the Aerodynamic Loads on a Cylinder at High Incidence using an Active Bleed Forebody

Dynamic variation of the aerodynamic loads on a slender cylinder at high angles of incidence (up to 60o) is investigated in wind tunnel experiments. The loads on the wire-mounted model are effected using azimuthally-segmented aerodynamic bleed actuation that is driven by the pressure distribution over the surface of the ogive forebody (20% porosity) and is regulated by a computer-controlled internal louver shell. Time-resolved measurements of the flow field about the cylinder and the aerodynamic loads show that the azimuthally segmented bleed can effectively alter the formation and evolution of the forebody vortices and their subsequent coupling and interactions with the cylinder’s near wake. Prescribed azimuthal actuation induces wake asymmetries along the cylinder that modify the aerodynamic loads and yields bi-directional control of the side force and yawing moment. This attribute enables direct control of the nominally-random formation of the forebody vortices and thereby override natural, unpredictable side forces and yawing moments in the absence of actuation. The temporally-varying bleed actuation enables attitude control on time scales that are commensurate with the characteristic convective time scale of the flow over the cylinder.