Experimental investigation of converging shocks in water with various confinement materials

Fluid-solid coupling typically plays a negligible role in confined converging shocks in gases because of the rigidity of the surroundingmaterial and large acoustic impedance mismatch of wave propagation between it and the gas. However, this is not true for converging shocks in a liquid. In the latter case, the coupling can not be ignored and properties of the surrounding material have a direct influence on wave propagation. In shock focusing in water confined in a solid convergent geometry, the shock in the liquid transmits to the solid and both transverse and longitudinal waves propagate in the solid. Shock focusing in water for three types of confinement materials has been studied experimentally with schlieren and photoelasticity optical techniques. A projectile from a gas gun impacts a liquid contained in a solid convergent geometry. The impact produces a shock wave in water that develops even higher pressure when focused in the vicinity of the apex. Depending on the confining material, the shock speed in the water can be slower, faster, or in between wave speeds in the solid. For solid materials with higher wave speeds than the shock in water, regions in the water is put in tension and cavitation occurs. Materials with slower wave speeds will deform easily.