An experimental investigation of the stability of plane shock waves

Abstract

The stability of plane shock waves was measured in a shock tube by perturbing the primary shock wave, formed on rupturing the diaphragm, by means of thin wedges. A time-record of the shape of the shock wave after it passed the wedges and travelled along a channel of constant cross-section was obtained by Schlieren photography. Analysis of the photographs enabled the rate at which the shock wave recovered its plane shape to be determined and this, together with the detailed shape of the wave at various instants, was compared with the first-order theory of Freeman (although all the conditions assumed in the theory could not be faithfully reproduced in the experiments).For shock-wave Mach numbers of 1·165, 1·41 and 1·60, the time-rate of decay of the perturbations was found to agree quite well with the theoretical value, but the amplitudes of the perturbations were much larger than those given by the theory.The experiments failed to give reliable information about the decay of the perturbations after a large time, owing, it is believed, to flow separation from the sharp corners of the wedges which constituted an additional source of disturbance to the shock waves.