The Thickness of Shock Fronts in Argon and Nitrogen and Rotational Heat Capacity Lags

Abstract

Shock front thicknesses in argon and nitrogen have been measured at Mach numbers of approximately 1.12, 1.28, and 1.40 by the reflectivity method. These thicknesses are significantly greater than predicted by Thomas and demonstrate the need for an improved theory which will cover the whole range of shock strengths. Reflectivity measurements have also been used to detect distortions of shock fronts in nitrogen owing to the lag of the rotational heat capacity. About 20 collisions are required for the rotational relaxation of nitrogen at room temperature.