关键词: elastic confinement, liquid cavities, cavitation nucleation

Abstract: According to classical nucleation theory, gas nuclei can generate and grow into a cavitation bubble when the liquid pressure exceeds a threshold. However, classical nucleation theory does not include boundary effects. An enclosed spherical liquid cavity surrounded by elastic medium is introduced to model the nucleation process in tissue. Based on the equilibrium pressure relationship of a quasi-static process, the expressions of the threshold and the modified nucleation rate are derived by considering the tissue elasticity. It is shown that the constraint plays an important role in the nucleation process. There is a positive correlation between nucleation threshold pressure and constraint, which can be enhanced by an increasing tissue elasticity and reducing the size of the cavity. Meanwhile, temperature is found to be a key parameter of nucleation process, and cavitation is more likely to occur in confined liquids at temperature T >100 ℃. In contrast, less influences are induced by these factors, such as bulk modulus, liquid cavity size, and acoustic frequency. Although these theoretical predictions of the thresholds have been demonstrated by many previous researches, much lower thresholds can be obtained in liquids containing dissolved gases, e.g., the nucleation threshold is about -21 MPa in a liquid of 0.8-nm gas nuclei at room temperature. Moreover, when there is a gas nucleus of 20 nm, the theoretical threshold pressure might be less than 1 MPa.

Key words: elastic confinement, liquid cavities, cavitation nucleation