Formation mechanism of cavitating spalls

The dynamics of formation of cavitation zones in a liquid upon reflection of a shock pulse from the free surface is studied numerically in a one-dimensional formulation using the Iordanskii–Kogarko–van Wijngaarden two-phase model. It is shown that the formation of a system of cavitation zones (clusters) with a dynamically increasing volume concentration of the gas phase near the free surface is due to oscillations of the structure of the rarefaction wave profile. The fast relaxation of tensile stresses in the cavitation zone ends in the formation of a quasistationary mass-velocity field, which provides for almost unbounded growth of cavitation bubbles in subsurface clusters and explains the occurrence of the spall layers observed in experiments.