Measurements of the boundary layer and wake of two aerofoil sections at high Reynolds numbers and high-subsonic Mach numbers

Abstract

Boundary layer and wake surveys have been made on two cambered lifting aerofoils and integral parameters and skin-friction data have been extracted from the measurements. Skin-friction results obtained, using four integral laws and results from a 'Clauser' analysis of profile data, are consistent but values obtained, using Preston tubes, are 8 per cent higher than these, probably due to uncertainties in the compressibility corrections required, and results from razor-blade measurements are 5 per cent lower. Momentum thickness, shape parameter and skin friction (using an integral law) are compared with boundary-layer estimates made, using (i) Green's extension to compressible flow of Head's entrainment method and (ii) Bradshaw's turbulent-energy method. Agreement is generally good, though both methods under-estimate momentum thickness at the trailing edge on the upper surface, where the boundary layer is close to separation. Wake estimates were made, using Green's entrainment method, and agreement is again generally good. However, there are discrepancies between measurements and Green's method regarding the entrainment parameter used in the boundary layer.