Delta wing stall and roll control using segmented piezoelectric fluidic actuators

The separated flow around a balance-mounted, 60-deg sweptback, semispan delta wing with a sharp leading edge was controlled using zero-mass-flux periodic excitation from a segmented leading-edge slot. Excitation was generated by cavity-installed piezoelectric actuators operating at resonance with amplitude modulation (AM) and burst mode (BM) signals being used to achieve reduced frequencies (scaled with the freestream velocity and the root chord) in the range from script O sign (1) to script O sign (10). Results of a parametric investigation, studying the effects of AM frequency, BM duty cycle and frequency, excitation amplitude, location of the actuation along the leading edge, and optimal phase difference between the actuators, as well as the Reynolds number, are reported and discussed. Balance data were supplemented by upper surface static pressure measurements and particle image velocimetry (PIV) data. Order unity reduced-frequency modulation of the high-frequency carrier wave increased the normal force generated by the delta wing most effectively. BM with a duty cycle that was as low as 5% was more effective than the amplitude-modulated signal with larger peak excitation velocity and an order of magnitude larger momentum input. PIV data suggest that excitation enhances the momentum transfer across the shear layer, downstream of the original vortex breakdown location, generating a streamwise vortex the size of which is commensurate with the local wing span.