Production and Propagation of Spherical Shock Waves at Low Ambient Pressures

摘要

An experimental investigation was made of the spherical shock waves produced when 2-cm-diameter thin-walled glass spheres, which were filled with air at a pressure of about 760 torrs, are burst in an ambient environment of dry air at pressures ranging from 0.015 to 5.0 torrs. Piezoelectric pressure transducers were used to measure the rate of decay of the spherical-shock Mach number with increasing radius. A comparison of the experimentally observed shock Mach numbers with those predicted from calculations based on an approximate theory by Friedman and Whithman shows that the two are in good agreement. Shock overpressures and shock thickness determined from impact pressure records are in fair agreement with existing approximate theories. The effect of glass particles on the flow field was found to be important when the initial pressure ratio across the glass diaphragm is below 500. At low pressures, viscous and rarefied flow phenomena tend to cause the measured impact pressure to depart radically from the theoretical value for continuum flow. (Author)