A study of cavitation nucleation in pure water using molecular dynamics simulation

Abstract

To discover the microcosmic mechanism of cavitation nucleation in pure water, the nucleation processes in pure water are simulated using the molecular dynamics method. Cavitation nucleation is generated by uniformly stretching of the system under isothermal conditions, and the formation and development of cavitation nuclei are simulated and discussed at the molecular level. The process of energy, pressure, and density are analyzed, and the tensile strength of the pure water and the critical volume of the bubble nuclei are investigated. The results show that critical states exist in the process of cavitation nucleation. In the critical state, the energy, density, and pressure of the system would change abruptly, and the steady cavitation nucleus would be produced if the energy barrier and critical volume has been broken through. System pressure and water density are the key factors in generating cavitation nuclei. When the critical state is broken through, the liquid is completely ruptured, and the volume of the cavitation nucleus increases rapidly to more than 100 nm3 and then the surface tension of the bubble dominates the cavitation nucleus instead of intermolecular forces. The negative critical pressure of bubble nucleation is -198.6MPa, the corresponding critical volume is 13.84nm3 and the nucleation rate is 2.42×1032 m-3 s-1 in pure water at 300K. Temperature has a significant effect on nucleation, as temperature rises, nucleation thresholds decrease, and cavitation nucleation occurs earlier.