Robustness of point vortex equilibria in the vicinity of a Kasper Wing

The concept of the Kapser Wing was introduced by Witold Kasper in the early 1970's. His design proposed to add additional ``flaps'' or auxiliary aerofoils close to the main aerofoil to control the feeding and shedding of vortices in the vicinity of the wing - the aim being to ``trap'' a vortex above the main aerofoil thus resulting in an increased lift being experienced. In this study, equilibira consisting of a single point vortex in the presence of an idealised Kapser Wing (modelled as three thin plates) are computed. A background potential flow at an angle attack $\chi$ to to the main plate is also present. A range of auxiliary plate configurations is considered and the lift of the system computed. It is seen that the lift experienced by the main plate is ``sensitive'' to the placement of the auxiliary plates and can be enhanced in comparison to the single plate case (previously considered by Saffman and Sheffield, 1977). The linear stability and non-linear time evolution of the Kasper Wing system is then compared to that of the single plate system. It is seen that the presence of the auxiliary plates, in general, result in a larger range of ``useful' neutrally stable equilibria (according to linear theory) and and can increase the non-linear robustness of the system.