The influence of permeable boundaries on transonic flow past an airfoil

The relation between the parameters of transonic flow past an airfoil in a channel with permeable walls and the height of the channel is studied. The gas is assumed to be viscous and the Reynolds numbers are large. The method of asymptotic expansions is used. The results are compared with the solution of the Navier-Stokes equations in the approximation of viscous-inviscid interaction. In this theory the influence of viscosity is neglected everywhere outside the boundary layer on the airfoil and outside the wake. On the walls of the test length the conditions are taken from the usual simplified model of a porous or longitudinal-slit perforation. Outside the boundary layer and the wake the flow is assumed to be vortex-free and isoenergetic. The WINTUN program [1], specially written for the computer simulation of flow past an airfoil in a channel with permeable walls, is used. (C) 1997 Elsevier Science Ltd. All rights reserved.