Experimental investigation of pressure characteristics behind the reflected shock waves in a metrological shock tube

Abstract

The pressure behind the reflected shock wave in real shock tubes deviates from the ideal behavior. This results in lower measurement accuracy and thus affects experiments and interpretations. The deviations depend on several factors, such as the pressure magnitude, shock tube geometry, and working gas. This study investigated it quantitatively and attempted to accurately describe its characteristics via the introduction of two parameters: pressure gain and pressure rise. To improve the accuracy of the pressure gain measurement, a model of the incident shock wave attenuation was proposed and the influence of the shock tube geometry was explored. The experimental results showed that the measurement accuracy was significantly improved: in the cases of 0.07, 0.14, 0.25, and 0.30 mm thick aluminum diaphragms, it was improved by approximately 4, 7, 12, and 22 times, respectively. In addition, a model of the pressure rise dependence on the Mach number of the incident shock wave was constructed through a linear fit of the pressure rise data. Further, the effects of the working gas on the reflected shock wave were examined: the results demonstrate that by working with the air the pressure behind the reflected shock wave exhibited good stability and amplitude.