Evaporation-capillary instability in a deep vapour-gas cavity

A theoretical investigation is made of an instability of a molten metal surface on the walls of a deep vapour–gas cavity or crater when this surface absorbs a uniform flux of the energy of laser radiation. The instability is due to the growth of perturbations on the free surface of the melt. This growth is maintained by an associated space–time modulation of the evaporation pressure. The dispersion equation for weak hydrodynamic perturbations is derived and investigated. This equation allows for the dependence of the instability increment on the laser radiation and phase transition parameters, and also on the material constants of the medium. Quantitative estimates are obtained of the conditions for the realisation of the investigated instability mechanism.