NASA Langley Research Center has invented three serial high-performance, piezoelectric, hybrid synthetic jet actuators to provide active flow control for current and future wing-borne vehicles in subsonic, transonic, and supersonic flow. Effective active flow control results in reduced vehicle drag and the prevention of events that can lead to catastrophic loss.
Synthetic jet actuators produce a jet flow using the surrounding air rather than relying on a secondary fluid. The interaction of synthetic jets with an external crossflow over the surface on which they are mounted can displace the local streamlines and induce an apparent or virtual change in the shape of the surface, thereby effecting flow changes on length scales that are one to two orders of magnitude larger than the characteristic scale of the jets.
Active flow control will be an inherent input to the conceptual design of the next generation of commercial and military flight vehicles. Retrofitted to current fixed-wing aircraft, active flow control can clean up complex three-dimensional external flow separations on the wing top surface, particularly severe under maneuvering conditions. The outcome is a reduction in overall drag of the vehicle, alleviation of unsteady loads, and prevention of the expulsion of the inlet shock system (that may lead to catastrophic loss of the airframe).
In these piezoelectric actuators, all the walls of the chamber are electrically controlled synergistically to reduce or enlarge the volume of the synthetic jet actuator chamber in three dimensions simultaneously. The jet velocity and mass flow rate for the actuators is from several times up to a couple of orders magnitude higher than conventional piezoelectric actuators.