Modeling for isothermal and cryogenic cavitation

Cavitation typically occurs when the fluid pressure is lower than the vapor pressure at a local thermodynamic state. The goal of our overall efforts is to establish a predictive tool for turbulent cavitating flows, including those under cryogenic conditions with noticeable thermal effect associated with the phase change. The modeling framework consists of a transport-based cavitation model with ensemble-averaged fluid dynamics equations and turbulence closures. To date, the reported experimental investigations contain little information about the turbulent characteristics in the flow field. It is noted that the exchange between static and dynamic pressures has a dominant impact on the cavitation dynamics, and the viscous effect can modify the effective shape of a solid object to cause noticeable variations in the predicted multiphase flow structures. The uncertainty of the inlet turbulent flow variables at the inlet can affect the prediction outcome. A filter-based approach is utilized along with two-equation turbulence closures so that one can assess the local numerical resolution with the computed turbulence length scale, and reduce the impact of the inlet boundary conditions of the eddy viscosity. Experimental information covering both isothermal and cryogenic cavitation with different geometries is utilized to aid the model validation. Furthermore, it is shown that for cryogenic cavitation, the thermal effect on the evaporation and condensation dynamics appears via modifying the local cavitation number and the liquid/vapor density ratio.