Radiation Gas Dynamics in the Shock Tube

Abstract

An assessment of the shock tube as an instrument for research in radiation gas dynamics is presented. Principal results obtained since Kantrowitz and Laporte first observed luminous fronts are described and the roles of impurity and nonequilibrium radiation, spectral intensities, rate processes, and continuum radiation are discussed. Spectroscopy was originally used as an aid to understanding problems in gas dynamics at moderate temperatures. More recently the shock tube has been used as a tool for spectroscopic research. The present trend is toward a fusion of these two interests in studying radiation-coupled flows where radiant energy transport affects the flow field. Present day shock tubes with arc-heated drivers attain thermodynamic conditions typical of superorbital speeds—the regime where radiant energy transfer becomes important. The current interest is in determining the radiative properties of gases at these high temperatures (10 000-20 000°K). Here the presence of significant amounts of vacuum ultraviolet radiation causes instrumentation problems which hamper investigations at present. However, solutions have been devised. Shock-tube results are compared to current theoretical predictions for the spectrally integrated total radiant intensity of high-temperature air. These reveal differences on the order of a factor of 2 and also clarify certain important areas of future endeavor. These include thermodynamic state measurements of gases shocked to temperatures above 10 000°K, additional measurements of the total intensity, and measurements of the spectral radiant intensity of high-temperature gases. An extensive bibliography is included.