Circulation controlled STOL wing optimization

By replacing the sharp trailing edge of an airfoil with a rounded Coanda surface, one can generate high lift at a moderate blowing rate. In such a circulation controlled (CC) airfoil, a two-dimensional wall jet is used to force the rear stagnation point down and increase the circulation and lift. The CC airfoil performance and blowing power requirements depend on both the wall jet momentum and the wall jet to freestream velocity ratio because a significant portion of the wall jet momentum is lost to shear over the Coanda surface. When using highpressure jet engine bleed air, an internal wall jet ejector can be used to optimize the wall jet velocity. This will reduce the required bleed airflow rate and cool the wing structure, in addition to providing boundary-layer control by suction. The applicability of CC high lift generation for short takeoff and landing aircraft was first demonstrated at West Virginia University in April 1974 with the WVU CC Technology Demonstrator STOL Aircraft. A second such CC technology demonstrator, a modified Navy A-6A was test flown five years later. The importance of optimizing the wall jet velocity is analyzed in this paper.