A simple cavitation model for unsteady simulation and its application to cavitating flow in two-dimensional convergent-divergent nozzle

Abstract

In this paper, a simple cavitation model is developed under the framework of homogeneousone-fluid model, in which the perfect mixture of liquid and vapor phases is assumed. In most of conventional models, the vapor phase is considered as a dispersed phase against the liquid phase as a continuous phase, while in the present model, two extreme conditions are considered: for low void fraction, dispersed vapor bubbles in continuous liquid phase, while for high void fraction, dispersed droplets in continuous vapor phase. The growth of bubbles and droplets are taken into account in the mass transfer between vapor and liquid phases, and are switched according to the local void fraction. The model is applied for the simulation of cavitating flow in a two-dimensional convergent-divergent nozzle, and the result is compared with that using a conventional model. To enhance the unsteadiness of cavitation due to the instability at the cavity interphase, the turbulent shear stress is modified depending upon the continuous phases in combination with the proposed cavitation model, which drastically reduces the turbulent viscosity for high void fraction region. As a result, the unsteadiness of cavitation observed in experiments is well reproduced.