Effect of wing planform on leading-edge vortex structures

Flow visualization experiments are conducted in water tunnel for low aspect ratio cropped wings at low Reynolds number. The experimental results show that the model sweep angle A influences the formation and development of the leading-edge vortex. For wings with Lambda =0 degrees, the dominant flow structure is transverse vortex. When Lambda >= 26 degrees, the dual vortex structure can be observed at some angles of attack, and it is confirmed that the dual vortex is a special structure for flow over low aspect ratio wing at low Reynolds number. For Lambda >= 56 degrees wings, the dual vortex structure can be observed in a large range of attack angles. Moreover, in comparison with the outer vortex, the breakdown position of the primary vortex is delayed, and the larger the A, the later the breakdown location at the same angle of attack.