An Experimental Study of Wing Tip Vortex in the Near Wake of a Rectangular Wing

Abstract

Abstract : An experimental study of the tip vortex behind a NACA 0015 rectangular wing of aspect ratio 4 was carried out to understand the structure and evolution of the vortex in the near-wake region. The results of these experimental studies are presented in this report. These measurements were made nonintrusively using three-component laser-Doppler velocimetry (LDV). The experiments were carried out at a Reynolds number of about 180,000 in a low- speed wind tunnel. Two cases were studied, namely, (1) stationary wing and (2) wing oscillating in pitch sinusoidally about its quarter-chord axis. The flow properties measured were the three components of the instantaneous velocity. These data were processed to obtain time-mean and phase-locked flow properties such as velocity, vorticity and turbulence. The data were obtained at several locations at 0.15 - 3.0 chord lengths downstream from the trailing edge. The typical distributions of mean velocity, vorticity, circulation and turbulent intensity in the near wake are presented and discussed for the stationary wing. In the case of the oscillating wing, the phase-locked velocity, vorticity and turbulence data show details of the evolution of the unsteady tip vortex downstream from the trailing edge. The results also show that the flow is strongly non-quasi-steady at the oscillation frequency studied. The results are fully archived on tape and are available to any interested reader. These can be used as database in the development of wake models for the finite wing, and in studies of three-dimensional wing aerodynamics.