A capillary-induced negative pressure is able to initiate heterogeneous cavitation.

Abstract

A capillarity-induced negative pressure is of general importance for understanding the phase behaviors of liquids in small pores and cracks. A unique example is the embolism in the xylem of plants and the cavitation at the limiting negative pressure generated by evaporation of water from nanocapillaries in the cell walls of leaves. In this work, by combining the effect of a capillary and cavitation together, we demonstrate with molecular dynamics (MD) simulations that capillarity is able to induce spontaneous cavitation in the presence of hydrophobic heterogeneities. Our simulation results reveal separately how the capillary generates a negative pressure and how the generated negative pressure affects the onset of cavitation. We then interpret the cavitation mechanism and determine the occurrence of cavitation as a function of the hydrophobicity of the nucleating substrates where the cavitation initiates and as a function of the hydrophilicity of the capillary tube from which the negative pressure generates. Our results reveal that the capillary-induced cavitation can be described well with a heterogeneous nucleation mechanism, within the framework of classical nucleation theory.