Ministry of Technology

Temperatures and pressures have been measured in the shock-heated gas upstream of the nozzle of a reflected-shock hypersonic tunnel. Temperatures were measured by spectrum-line reversal, using sodium D lines for some measurements and the blue resonance lines of chromium for others. The temperature and pressure measurements immediately behind the first reflected-shock wave agreed well with theory but subsequent variations in temperature and pressure did not agree very well with theory. These differences between theory and experiment are attributed to boundary-layer development and contact region behaviour. In particular, the duration of the shock-heated gas at the higher shock Mach numbers was much less than theory predicts and much less than pressure measurements alone indicated. This appears to be due to encroachment of the contact region into the shock-heated gas at the closed end of the tube, and presents a limitation to the running time of a shock tunnel at high enthalpies.