Edge vortices of a double element wing in ground effect

The influence of edge vortices generated by a generic double-element wing on force behaviors are discussed. The wing is equipped with end plates and operates in ground effect. The downforce-vs-height curve is divided into three distinct regions according to ground proximity and flap setting. As the wing is moved from a height in freestream to the ground plane, the downforce first experiences a rapid enhancement (region A). This process is accompanied by the presence of a concentrated vortex off the edge of the side plate and diffuser effect of the wing. At a critical height, the vortex breaks down and its contribution to the downforce is lost. This creates a change in the gradient of the downforce slope. The force enhancement process continues as the height of the wing is reduced (region B); the main diffuser effect is still present. The downforce is lost below a height where the maximum downforce is reached, due to large separation on the wing (region C). The importance of the edge vortices in defining the characteristics of the downforce curve is established