Measurement of tensile strength of liquids by an explosion technique

Abstract

A WIDE variety of methods has been used in the estimation of the static tensile strength of water1,2. Recently, a dynamic method, using an impulse-generated pressure wave, has been described which uses a measurement of the negative pressure produced by the wave reflected from a free surface3. Wilson et al.4 had previously shown how estimates of the negative-pressure wave reflecting from a free surface could be used to measure liquid tensile strength in underwater-explosion research, and an adaption of that technique has been used to estimate the tensile strength of water and glycerine. The basic idea is to make high speed motion picture photographs of the spray plume rising from an explosive charge detonated a small distance underwater. In a one-dimensional analysis the particle velocity of the explosive shock wave propagates as P/ρU, and hence water at the free surface detaches with an initial velocity 2P/ρU, less the contribution of the tension exerted by the reflected shock wave T/ρU. So the initial spray dome velocity is: where P is the maximum pressure of the explosion, T is the negative pressure in the reflected shock wave, ρ is the water density, and U is the shock wave velocity. By observing the value of V0 at various explosive charge depths and extrapolating to zero velocity where T = 2P, an estimate of the water tensile strength can be made.