Laser-scanning particle image velocimetry applied to a delta wing in transient maneuver

Abstract

A laser scanning technique, which utilizes a galvanometer scanner to produce particle-image photographs, is employed to investigate the flow over a delta wing undergoing pitching maneuvers at a high angle of attack. Use of a unique forcing system and a large-scale prism arrangement allow characterization of the instantaneous velocity field over the entire crossflow plane at a desired angle of attack.Contours of constant streamwise vorticity are calculated from the crossflow velocity field at various pitching rates. The vorticity distribution occurring during the pitch-up motion differs substantially from that on the stationary wing at the same angle of attack. During the pitch-up motion, the leading-edge vortex is remarkably coherent, in contrast to the disordered structure on the stationary wing. During the corresponding pitch-down motion, the vorticity distribution is quite similar to that on the stationary wing at the same angle of attack. This behavior is evident for a range of pitching rates.

Effects of Unsteady Trailing-Edge Blowing on Delta Wing Aerodynamics

“…Hence, characteristic response times for accelerating and decelerating jets appear to be different. It is interesting that this behavior is similar to the different flow structures reported at the same angle of attack during the pitch-up and pitchdown motions of a delta wing [30]. Also, different time constants for the upstream and downstream motion of the breakdowns were reported in response to an oscillating fin over a delta wing [31].…”