An Attached Flow Design of a Noninterferring Leading Edge Extension to a Thick Delta Wing

An analytical procedure for the determination of the shape of a Leading-Edge Extension (LEE) which satisfies design criteria, including especially noninterference at the wing design point, has been developed for thick delta wings. The LEE device best satisfying all criteria is designed to be mounted on a wing along a dividing stream surface associated with an attached flow design lift coefficient (CL,d) of greater than zero. This device is intended to improve the aerodynamic performance of transonic aircraft at CL greater than CL,d system emanating from the LEE leading edge. In order to quantify this process a twisted and cambered thick delta wing was chosen for the initial application of this design procedure. Appropriate computer codes representing potential and vortex flows were employed to determine the dividing stream surface at CL,d and an optimized LEE planform shape at CL greater than CL,d, respectively. To aid in the LEE selection, the aerodynamic effectiveness of 36 planforms was investigated at CL greater than CL,d. This study showed that reducing the span of the candidate LEEs has the most detrimental effect on overall aerodynamic efficiency, regardless of the shape or area. Furthermore, for a fixed area, constant-chord LEE candidates were relatively more efficient than those with sweep less than the wing. At CL,d, the presence of the LEE planform best satisfying the design criteria was found to have no effect on the wing alone aerodynamic performance.