Photographs of shock wave movement

Abstract

Consecutive photographs were taken at millisecond intervals of the flow past a low-drag aerofoil at compressibility speeds. At a Mach number 0.1 above the 'pressure critical' the shock wave was found to oscillate rapidly but aperiodically, whereas the edge of the associated boundary layer remained quite steady, at least for periods of 1/50 sec. At the critical Mach number and just below it a series of small shock waves was observed, apparently moving against the direction of flow. Note. The photographs reproduced in this paper were taken in January, 1944. Their issue was postponed in view of possible improvement in technique.