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

Abstract

To discover the microscopic mechanism responsible for cavitation nucleation in pure water, nucleation processes in pure water are simulated using the molecular dynamics method. Cavitation nucleation is generated by uniformly stretching the system under isothermal conditions, and the formation and development of cavitation nuclei are simulated and discussed at the molecular level. The processes 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 change abruptly, and a stable cavitation nucleus is produced if the energy barrier is broken and the critical volume is exceeded. System pressure and water density are the key factors in the generation of cavitation nuclei. When the critical state is surpassed, the liquid is completely ruptured, and the volume of the cavitation nucleus rapidly increases to larger than 100 nm3; at this point, the surface tension of the bubble dominates the cavitation nucleus, instead of intermolecular forces. The negative critical pressure for bubble nucleation is –198.6 MPa, the corresponding critical volume is 13.84 nm3, and the nucleation rate is 2.42 × 1032 m−3⋅s−1 in pure water at 300 K. Temperature has a significant effect on nucleation: as the temperature rises, nucleation thresholds decrease, and cavitation nucleation occurs earlier.