Low-speed wind-tunnel tests on the characteristics of leading-edge air intakes in swept wings

Abstract

Low-speed wind-tunnel tests have been made to determine the external and internal characteristics of leading-edge air intakes in swept wings, under flight conditions. Tests on a delta model show that leading-edge intakes in the wing root give an advantage in effective sweepback and critical Mach number (estimated from the low-speed pressure distribution) compared with nacelle-type intakes adjacent to the body. The internal loss in level flight for a 52° sweptback entry is 4~/o ram worse than when the entry is square to the direction of flight. The explanation of this loss is found in the nature of the pre-entry retardation for level-flight velocity ratios. A boundary-layer bypass leading from a slot inside the intake removes most of the additional loss. Tests on a swept-wing model with a simplified intake give the effects of duct diffusion, of boundary layer from an adjacent body, and of boundary-layer removal through a slot or porous wall. A general formula for intake loss is applied to show the dependence of the loss on entry shape and on the value of the design velocity ratio.