Three-dimensional simulation of an orifice flow with cavitation-induced air release

A model for the approximation of cavitation-induced air release in three-dimensional flow simulations is proposed. A cavitating orifice flow is investigated. It is assumed that vapor vanishes yet in the proximity of the orifice and bubbles further downstream consist essentially of air. The model is based on a homogeneous mixture assumption and comprises one main parameter, which needs to be adjusted to the experimentally measured degassing fraction. Experimental validation is based on transmission light images downstream of the orifice. In the proximity of the orifice, the inclusion of air release in the CFD simulation yields a better agreement to experimentally measured cavitation intensity than the consideration of pure vapor only. It is concluded that a considerably larger amount of air than is dissolved in the evaporated amount of liquid, is released. The simulation results suggest that the released air mass corresponds to about 1% of the evaporated liquid mass. These observations may be a good basis for purposeful future experiments, which are indispensable for the development of a more predictive approach of cavitation-induced air release in 3D CFD methods.