An Experimental Study on Shock Waves in Liquid : The Generation of Shock Waves by an Impinging Piston and their Behavior

Abstract

Onedimensional pressure waves (shock waves) were generated in a liquid (water) column contained in a vertical pipe by the impingement of a piston accelerated by compressed air. The waveforms obtained were sawtooth waves with peak pressures of 100-500kg/cm2 and widths of 1 to 2 msec. While waves in this pressure range were found to behave essentially as sound waves, the steepening of the wave front with originally a rise time of tens of micro-seconds to a discontinuity over a propagation distance of around 2 meters was observed, which was explainable in terms of the compressibility of the liquid. The density change across the wave front measured with the integrated schlieren technique was found to be proportional to the pressure change in accordance with the relation of adiabatic change of he medium. The motion of the piston following the impingement was observed by means of instantaneous photography, and a fine correspondence of the deceleration process with the generated waveform was evidenced. The displacement velocity of the liquid behind the wave front was also measured with a simple technique.