Primary and Secondary Vortex Structures Over Accelerated-Decelerated Airfoils at High Angles of Attack

An experimental study is conducted to investigate the vortex developments over high angles of attack flat plate airfoils in an accelerated-decelerated flow. To preform the required experiments, a new experimental system was developed and incorporated into an open return subsonic wind tunnel. The system was employed to visualize the details of vortex structures and processes over and downstream of the airfoils for an angle of attack range between 30° and 90°. While flow acceleration encouraged flow separation and vortex convection, flow deceleration delayed the convection of the primary vortex structures as well as the reverse flow reattachment and shredding. The details provided in the article may help in developing control possibilities of vortical flow over vehicles or structures subjected to accelerating-decelerating motions. Further, the study presents guidelines to develop unsteady flow experimental arrangements suitable for incorporation into steady flow subsonic wind tunnels.