High Angle of Attack Flight Control of Delta Wings Using Vortex Actuators

Abstract

The objective of this work was to develop an active fluidic control system that can effectively manipulate the vortex breakdown location over a highly swept delta wing. By moving the vortex breakdown fore or aft, a pitching moment can be induced on the delta wing without the use of any conventional control surfaces. The active control system can be incorporated into a feedback loop to input a desired pitching moment based on the real-time measured surface pressure. The type of active fluidic control system shown to be the most effective at delaying vortex breakdown was the along-core injection technique. The present study describes an open loop control system, that is, the flow field was observed and measured and then injection conditions were changed manually. The process was repeated until optimal conditions were observed. Initial closed loop feedback control tests were performed to test the response of the system. A 60° delta wing model with a maximum span of 15.5 inches and a root chord of 13.5 inches was mounted in a subsonic wind tunnel. The wing was equipped with six control jets with variable azimuthal and pitch angles on the top surface approximately beneath the vortex core. A thorough optimization process was completed measuring static pressure to determine vortex breakdown location. Other variables in addition to azimuthal and pitch angles were injection momentum, frequency, and duty cycle. Measuring dynamic pressure, that is pressure fluctuation due to vortex shedding and pulsed injection, was also necessary to the development of a control algorithm. Dynamic pressure was measured at four chord-wise locations with uniform and randomly modulated duty cycles in order to ascertain duty cycle sensitivity on the system’s overall effectiveness.