A Look into the bubble interior by molecular dynamics simulation

Abstract

The interior dynamics of a collapsing and rebounding cavitation bubble is investigated by means of molecular dynamics (MD) simulations. A hard sphere model for the species inside the bubble is adopted. The dynamics of the surrounding liquid (water) is modeled by a Rayleigh-Plesset (RP) type equation coupled to the bubble interior by the gas pressure at the wall obtained from the MD calculations. Water vapor and vapor chemistry are included in the hybrid RP-MD model as well as mass and energy transfer through the bubble wall. Calculations are done for bubbles at conditions typical for single bubble sonoluminescence and for small bubbles driven atMHz frequencies to determine the evolution of temperature, density and pressure within a bubble and to predict how the particle numbers and densities of different vapor dissociation and reaction products in the bubble develop in space and time. Among the parameters varied are the bubble size, the sound pressure amplitude of the driving sound field, the frequency of the sound field and the noble gas mixture in the bubble.