Atomization and Sprays, Vol.7, No.6, 603-616, 1997
Analytical prediction of the exit flow of cavitating orifices
When studying sprays, a is often desirable to have a simple model of the nozzle exit Typically, the cavitating nozzle exit velocity profile is assumed to be slug flow. In order to provide a simple yet more accurate model, an analytical description of cavitating nozzle exit flow is constructed. First, an existing model for the mass flow rate through the nozzle is rederived and compared with experimental data. Then, using a momentum balance and neglecting momentum transfer to the wails, the momentum flux through the orifice exit is calculated. An expression for the effective cross-sectional area of this exit flow and for its effective velocity is presented The predictions of this zero wad shear model are compared to experimental velocity and drop size data and to predictions from a multidimensional CFD code. The agreement between the predictions and data suggests that this model can be used as a simple representation of the connection between the cavitating nozzle and the downstream spray. The zero wall shear model is considerably more accurate than modeling the cavitating nozzle exit condition as slug flow.