Flow over a flat surface behind delta winglets of varying aspect ratios

Abstract

The effect of winglet aspect ratio on the generated vortical flow over a flat surface was experimentally scrutinized in a wind tunnel using a triple sensor hot-wire. Aspect ratios of 1, 2 and 4 were considered at a Reynolds number based on winglet height of 6000 and an angle of attack of 30 degrees. A large longitudinal vortex structure was observed in the cross-stream plane. The streamwise velocity deficit at the main vortex core lessened, while that at the Upwash Region remained unaltered, with increasing aspect ratio. Moreover, the vortex moved downward and inward and its intensity decreased. The turbulence level decreased with a corresponding increase in Taylor microscale. The integral length was found to be independent of the aspect ratio but scaled with the winglet height.