EXPERIMENTAL MEASUREMENTS OF TEMPERATURE AND RELAXATION TIMES BEHIND SHOCK WAVES
ADVISORY GROUP FOR AERONAUTICAL RESEARCH AND DEVELOPMENT PARIS (FRANCE)
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By using a photomultiplier and cathode-ray oscillograph responsive only to changes in light signal, the sodium-line reversal technique has been adapted for time-resolved studies of temperature behind shock waves produced by a bursting diaphragm. A double-beam system has also been developed, which eliminates changes due to varying concentration of added metal, and interference filters can be used instead of a spectrograph. General agreement between calculated and observed temperatures is obtained, but both air and oxygen show a high-temperature region due to burning at the interface with the hydrogen driver gas. In nitrogen around 2400 K, a low temperature region close to the shock front may be attributed to a vibrational energy lag of the order of 100 microseconds, the sodium excitation following the effective vibrational temperature rather than the translational temperature of the nitrogen. In oxygen, evidence for a dissociation relaxation effect is obtained for shocks, giving temperatures of around 2500 K this produces an abnormally high temperature near the front.
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