Abstract: Cavitation in water generally takes place at much lower negative pressure than predicted from theories. In this work, we try to stress the discrepancy from the influence of the dissolved gas on cavitation nucleation. By combining molecular dynamics simulation and thermodynamic analysis, we evaluated the lowering of surface tension as a function of density of gas molecules in gas clusters formed in aqueous solution. We found that the obtained surface tension of small gas clusters is much more substantially reduced than expected. The surface tension lowering and the non-ideality of gas molecules in the clusters are then taken into account in determining the nucleation of cavitation, and as a consequence, the required negative pressure for cavitation becomes comparable to experimental values. Thus, we give an alternative explanation for the discrepancy of cavitation pressure between experiment and theory, i.e., it is the substantially reduced surface tension for small gas nuclei, which have not been taken into account in theory, along with the ideal gas approxiamtion that induce its deviation from the experimental values.

Key words: Cavitation, Dissolved gas, Thermodynamics, Molecular simulation, Surface tension

摘要： Cavitation in water generally takes place at much lower negative pressure than predicted from theories. In this work, we try to stress the discrepancy from the influence of the dissolved gas on cavitation nucleation. By combining molecular dynamics simulation and thermodynamic analysis, we evaluated the lowering of surface tension as a function of density of gas molecules in gas clusters formed in aqueous solution. We found that the obtained surface tension of small gas clusters is much more substantially reduced than expected. The surface tension lowering and the non-ideality of gas molecules in the clusters are then taken into account in determining the nucleation of cavitation, and as a consequence, the required negative pressure for cavitation becomes comparable to experimental values. Thus, we give an alternative explanation for the discrepancy of cavitation pressure between experiment and theory, i.e., it is the substantially reduced surface tension for small gas nuclei, which have not been taken into account in theory, along with the ideal gas approxiamtion that induce its deviation from the experimental values.

关键词: Cavitation, Dissolved gas, Thermodynamics, Molecular simulation, Surface tension