Effect of dissolved gas on the tensile strength of water

While theoretical estimates suggest that cavitation of water should occur when the pressure falls much below $-25$ MPa at room temperature, in experiments we commonly observe conversion to vapor at pressures of the order of $3$ kPa. The commonly accepted explanation for this discrepancy is that water usually contains nanometer-sized cavitation nuclei. When the pressure decreases, these nuclei expand and become visible to the naked eye. However, the origin of these cavitation nuclei is not well understood. Earlier work in this field has mainly focused on the inception of nuclei which are purely composed of water vapor, whereas experimental data suggests that these nuclei are mainly composed of air. In this letter, we develop a theoretical approach to study the inception of cavitation nuclei in water with uniformly dissolved air, using the diffuse interface approach. We derive equations which govern the transition of water with uniformly dissolved air to the critical state. Our results show that dissolved air decreases the free energy barrier from the initial to the critical state, thereby aiding the formation of cavitation nuclei. This study opens up possibilities to explore cavitation inception in fluids containing dissolved gases.