Investigation of the distortion of shock-fronts in real gases

In view of experimental investigations of conditions under which nonplanar shock fronts and nonuniform test slugs occur in shock tubes, suggesting that a Rayleigh-Taylor instability at the contact surface is related to real gas effects of the test gas, an extension is made of the Levine (1970) analysis considering contact surface leakage when it is embedded in the relaxation region. In order to take account of Levine-type mixing across the contact surface, the effect of the post shock boundary layer on possible contact surface instability is elucidated by a discussion of a modification of Mirel's (1963) boundary layer entrainment theory. Time-resolved differential interferometry and streak shadowgraphs are used for AR/SF6 test gas mixtures in order to determine shock shape, test sample uniformity and test slug length, and results suggest that flow nonuniformities depend strongly on test slug conditions.