Boundary layer bleed drag at supersonic speeds

Abstract

Four types of flow in boundary-layer bleeds are discussed. Expressions are given for calculating the bleed internal drag for the various types using two alternative definitions of drag. Some general curves are plotted which show the dependence of bleed drag on bleed pressure recovery and free stream Mach number. A number of calculated and measured bleed pressure recoveries are compared. Calculations have been made which show under what conditions there is no longer a performance advantage in 'burying' engines within the adjacent body or wing. Other calculations compare the drag obtained by ejecting the bleed air slowly (base bleed) with no boattailing on the nacelle and ejecting the air as a high speed flow combined with the concomitant boat-tailing.