Possible uses of optical methods for determining the structure of nonequilibrium hypersonic flows

Results are given of the investigation of self-luminosity of flow in hypersonic wind tunnels with electric-arc heaters, and the possibilities of using this luminosity for the visualization of flow past bodies are analyzed. It is demonstrated that the luminosity is caused by nonequilibrium physicochemical processes in nozzles and is defined by the excitation of low-potential electron-vibrational levels of molecules and atoms of impurities in the flow. It follows from comparison of flow patterns obtained by the shadow method with photographs of flow in the vicinity of bodies that the use of luminosity for determining the structure of flow past models is not always justified. Results are given of applying the method of induced resonance fluorescence for the visualization of flow past bodies.