Diffusive and convective evaporation of irradiated droplets

Abstract

The evaporation of a spherically symmetric liquid droplet subject to a high-irradiance laser flux is investigated on the basis of a hydrodynamic description of the system composed of the ejected vapor and ambient gas. For low irradiance beams, diffusive mass transport and conductive energy transport are the dominant interactions between the droplet and its environment.1 In this isobaric case, changes in the state of the ambient medium are small. For higher-flux beams, convective mass transport becomes significant, and droplet vaporization is accompanied by the production of strong shock waves in the surrounding gas. Following Knight,2jump conditions at the droplet boundary aid us in solving the hydrodynamic boundary value problem. An extension of Knight’s analysis to include both diffusive and convective mass flux allows the transition regime between the low-flux isobaric case and the high-flux shock-wave dominated case to be investigated. Numerical solutions illustrating droplet vaporization and ambient-medium hydrodynamic effects are presented for selected droplet-beam configurations.