Angle of Attack and Planform Effects on Flat Plate Vortices at Low Reynolds Numbers

Tip vortices of low aspect ratio wings were studied in a water tunnel at Reynolds numbers of 8,000 and 24,000, with dye injection and digital particle image velocimetry in crossflow planes in the near wake, for rectangular, semi-elliptical and delta-wing planforms. The velocity data were used to calculate lift via circulation, and the results were compared with direct force measurements. The objectives of the study were to assess how low vortex circulation, how well the measurement of lift coefficient from tip-vortex circulation, how well the measurements, fit the slender wing theory lift curve slope, and the extent to which planform shape affects lift coefficient while aspect ratio and area are kept constant. All models were thin flat plates with square edges. For the range of streamwise locations and angles of attack studied, apparent viscous effects on vorticity in the wake were small, resulting in good agreement between lift coefficient values inferred from the measurements, the force balance data, and the classical inviscid formulas