Evolution of Vortical Structure over Delta-Wing with Transient Along-Core Blowing

Abstract

Over delta-wing with a 75-deg sweep angle and 40-deg of the angle of attack, the vortex core subject to transient along-core blowing is investigated experimentally. In response to the transient along-core blowing,the vortex core, before breakdown, serves as a transmitting vessel that steadily delivers the supplied momentum to overcome the strong adverse along-core pressure gradient, especially near the onset location of the vortex breakdown. The central region of the vortex core is found to be more sensitive to the external perturbation than the outer region. This key characteristic of the vortex core is the reason for transformation of the along-core velocity distribution from the velocity excess (or jet-like) profile to the velocity deficit (or wake-like) profile as the onset of vortex breakdown is encountered. The magnitude of suction peak coefficient measured on the wing surface along the vortex core direction increases in response to the transient along-core blowing. Then it recovers to the unperturbed value as the vortex breakdown recovers to its long-time averaged location. Variation of pressure gradient along the vortex center differs from the gradient of the suction peak coefficient measured on the wing surface along the vortex core direction.