Characteristics of Nonequilibrium Radiation behind Strong Shock Waves in Low-Density Air

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Nonequilibrium radiation characteristics behind strong shock waves in low-density air is experimentally investigated by the ultraviolet diagnostic system for simultaneous observation of the total radiation and its spectral radiation of the air behind the hypervelocity shock wave of up to 12km/s by using the free-piston, double-diaphragm shock tube.1. The characteristics of the free-piston, double-diaphragm shock tube flows and tube operation is investigated numerically and experimentally. From the results obtained it is elucidated that there exist the effects of compression process and diaphragm rapture duration on the total tube characteristics. Total reproducibility of the tube data has been increased by these results.2. Simultaneous measurements of total radiation and the spectral radiation in the nonequilibrium, chemically reacting air behind the strong shock waves in low-density air are performed. Among the results the total radiation profiles of one-peak to two-peaks in strength are elucidated to reflect the possibility of radiation from the chemical reactions by contaminants in test gas.3. Doing the improved experiments by purified conditions of the test section and the test gas by new instruments of shock tube and gas monitoring system, the more precise data of ultraviolet spectral and total radiation are obtained. The obtained radiation profiles are discussed in view of test gas composition effects.4. Numerical analysis for radiation phenomena in the strong shock induced flow along a flat plate is investigated by Navier-Stokes equation coupled with thermochemical nonequilibrium. The results indicates the existence of intense nonequilibrium radiation in shock induced boundary layer.