For conical bodies, at moderate angles of attack, the flow separates from the lee side, forming two vortices. Although the vortex lift contribution is highly desirable, as the angle of attack increases, the vortex system becomes asymmetric, and eventually the vortices breakdown. Thus, some control of the separation process is necessary if the vortex lift is to be exploited at higher angles of attack.

The theoretical model which is used in this analysis has three parts. First, the ‘single line-vortex’ model is used within the framework of ‘slender-body theory’ to compute the outer inviscid field for specified separation lines. Second, the 3-D boundary layer is represented by a momentum equation for the cross-flow, analogous to that for a plane boundary layer and a von Karman/Pohlhausen approximation is applied to solve this equation. The cross-flow separation for both laminar and turbulent layers is determined by matching the pressure at the upper and lower separation points. This iterative procedure yields a unique solution for the separation lines and consequently for the positions of the vortices and the vortex lift on the body. Third, control of separation is achieved by blowing tangentially from slots located symmetrically along cone generators.