WIND TUNNEL INVESTIGATION ON UNSTEADY VORTEX FLOW OVER A HYPERSONIC DELTA GLIDER IN SUBSONIC REGIME

Abstract

ABSTRACT

In this wind-tunnel investigation, unsteady 3-D velocity components over a hypersonic delta glider have been measured in subsonic wind tunnel using a constant temperature hot-wire probe at different angles of attack. The effect of the intrusive hot-wire probe on the vortex core and the vortex structure has been predicted at angles of attack over 25 degree and x/Cr=0.9 resulting in an early vortex breakdown. Stream wise, vertical and lateral root-mean-square velocity components over the wing have been presented. The acquired data are correlated to the surface-pressure data and the laser-light-sheet results published by the author. The lateral location of the vortex subcore has been predicted using the data of the hot-wire measurements, the surface pressure measurements, and the flow visualization, while the vertical location of the vortex subcore axis over the wing upper surface is predicted using the data of hot-wire measurements and the flow visualization. The predicted experimental data using the intrusive hot-wire probe reflects obvious interferences and deviations from those obtained using surface pressure transducers. These differences increase by increasing the angle of attack and by moving downstream close to the trailing edge due to the upstream movement of the adverse pressure region and to the kinking of the vortex axis over the rear part of the wing. Based on these results, it is advised to avoid using intrusive probes to investigate vortex flow because of its distortion effect on the vortex structures and the early vortex breakdown, and using instead nonintrusive methods as Laser Doppler Velocimetry (LDV).