Abstract: A system for controlling fluid turbulence inside and just outside of a cay adjacent to an opening in a wall, the wall having a forward lip which defines the leading edge of the opening and an aft lip having a leading edge which defines the trailing edge of the opening, the forward lip terminating in a sharp edge lying generally in the plane of the outer surface of the wall. The aft lip has a length of 10 to 50% of the length of the opening and extends into the opening at an angle of 30 to 60 degrees to terminate in an arcuate portion having a radius of 2 to 6% of the length of the opening.

Abstract: To enhance the flow of air into a flush-type, air inlet on the fuselage of an aircraft, a wing-like deflector is mounted on a pedestal attached to the aircraft and is positioned outwardly from the fuselage and forwardly of the inlet so as to deflect free stream air flowing past slower-moving boundary layer air adjacent the fuselage, into the inlet. The deflector has an ogee shaped planform and is pitched at a predetermined angle of attack with respect to the direction of free stream flow to generate counterrotating flow vortices that trail the deflector and produce a strong downwash behind the deflector. The vortices entrain high energy air from the free stream and direct it down into the inlet. In one disclosed embodiment, the inlet is equipped with a door that swings between a closed position, flush with the exterior of the fuselage to block air flow from entering the inlet, and an open position, recessed within the inlet duct.