Free-flight measurements of the zero-lift drag of a slender ogee wing at transonic and supersonic speeds

The zero-lift drag of a slender-wing model has been measured using the free-flight technique and the wing wave drag has been deduced by subtracting the non-wave-drag components. The results are presented without correction for the drag increment caused by the transition strip and show a smooth variation of the wave drag factor Ko with Mach number with a maximum occurring near M=1.1. The overall level of Ko is some 10% higher than that predicted by linear theory, but this result is very dependent on the accuracy of the skin-friction estimates as well as on the transition strip drag increment. Attempts to estimate the latter suggest that 4% of the total drag may arise from this source which would reduce Ko by some 12% bringing it well in line with theory.