MULTI-DIMENSIONAL SIMULATION OF CAVITATING FLOWS USING A PDF MODEL FOR PHASE CHANGE

摘要

A new cavitation model is described for multidimensional computation of cavitating flows. The model employs a transport equation for vapor mass fraction in conjunction with the full Navier-Stokes equations. The phase change rates are postulated to depend upon the local time-mean pressure as well as turbulent pressure fluctuations. A Probability Function (PDF) approach is employed to calculate the local time-mean phase change rates from instantaneous pressures. The influence of pressure fluctuations on phase change rates is an important factor that has not been accounted for in past models. Its inclusion improves both the physical realism and numerical stability of the solutions. The PDF cavitation model has been incorporated into an advanced finite-volume, pressure-based CFD code, and has enabled solutions for a wide range of flow conditions. The predicted solutions have been validated with experimental data available for orifices and hydrofoils. The model is extendable to include additional physical phenomena such as bubble dynamics, velocity slip, thermal non-equilibrium, and presence of impurities and non-condensable gases.