Vortex Breakdown on Pitching Delta Wing: Control by Intermittent Trailing-Edge Blowing

To retard the onset of vortex breakdown on a half-delta wing subjected to periodic, large-amplitude maneuvers to high angle of attack, controls were applied in the form of a deflectable flap at the leading edge and variable blowing at the trailing edge of the wing. Intermittent blowing, applied during the upstroke part of the pitching cycle, appears to be the most energetically efficient means of retarding the onset of breakdown. Corresponding values of a dimensionless blowing coefficient are an order of magnitude smaller than those traditionally employed. Particle image velocimetry measurements of the velocity field in the plane of the leading-edge vortex show that blowing-induced changes of the velocity field propagate upstream along the lower surface of the wing. Intermittent blowing produces a radical change in the velocity distribution near the surface of the delta wing that persists throughout the entire pitching cycle. The phase lag of the blowing-induced velocity appears to be central to maintaining retardation of the onset of breakdown