Modification of the Aerodynamic Characteristics of Bluff Bodies Using Fluidic Actuators

The apparent aerodynamic shape (and thus lift and drag) of a 2-D cylinder is modified in wind tunnel experiments using a spanwise pair of fluidic actuators based on synthetic jet technology. Because the jet actuators do not dispense new fluid into the flow (but allow for momentum transfer), their interaction with an embedding flow leads to the formation of closed recirculation regions and thus to an apparent modification of the flow boundary on scales that are one to two orders of magnitude larger than the characteristic length scale of the jets themselves. The cylinder can be rotated about its centerline so that the angle between the actuator jets and the direction of the free stream can be continuously varied. Smoke visualization experiments at low Reynolds numbers (ReD =4000) demonstrate that the closed recirculating flow regimes near the surface scale with the momentum coefficient and can displace local streamlines well outside the surface boundary layer. Azimuthal distributions of surface pressure measured at higher Reynolds numbers(ReD =75,500,C^ = 6-10"4) over a range of jet angles demonstrate that the jets effect substantial concomitant increase in lift (up to CL = 0.55) and reduction in drag (up to 30%).