Distributed hingeless flow control and rotary synthetic jet actuation

In this paper, a continuing research effort is detailed aimed at effecting practical hinge-less closed-loop flow control of wings. The systematic evolution of synthetic/pneumatic actuators suitable for this purpose, via distributed actuation, is described as is their effectiveness as flow control tools. The synthetic jet mechanisms are based on automotive technology; piston to Wankel-rotary, with the piston or rotor acting as the compressor. Control methodologies, for both controlling the DC motors, driving the synthetic jet actuators (SJA) as well as controlling the wing in free-to-pitch motions were developed. Methods of implementing and distributing the actuation, so as to allow pitch control at both low and high angles of attack are presented. High angle of attack control facilitated through upper surface separation control (with the SJA located close to the leading edge and ejecting its jet tangential to the surface) was shown to be effective and controllable. However, at low incidence, this geometric implementation is ineffective. For these conditions, a wind tunnel investigation was undertaken to examine the possibility of using a jet flap for hinge-less control. Tests encompassed jet momentum coefficient variation and comparison with a Gurney flap located at the same location. The data showed that the jet flap generates lift and moment coefficient increments similar to a 0.75% of chord Gurney flap for moderate jet momentum coefficients.