Numerical Study of Cavitating Flow in Asymmetrical Nozzles of Injectors/Atomizers. Part I. Assessment of Calibrated Eddy Viscosity Models in Developing Cavitation Cases

Abstract

Cavitating flow is related to turbulent and multiphase flows with mass transfer between the liquid and its gaseous phase. Cavitation in pressure injectors/atomizers strongly affects the liquid/spray jet behavior at its outlet. The type of atomization induced by cavitation allows developing more efficient devices if this cavitation state is controlled. Experiments show that an improvement in the quality of the spray is reached when a fully developed cavitation state is present at the nozzle, being this state clearly unsteady due to the presence of the re-entrant jet and the vortex shedding downstream of the cavity. Previous works showed that it is possible to capture several of the incipient cavitating or quasi- steady cavitating flow characteristics performing a careful calibration of the available Eddy Viscosity Models in nozzles with several inlet and outlet geometries. A careful calibration of the selected Eddy Viscosity Model becomes an important task to obtain accurate predictions of the flow both in quasi- steady and unsteady cavitation states. The numerical results discussed in this first part show that it is possible to capture the main cavity features by a steady state cavitation simulation despite the incipient unsteady state of the slightly developed cavitation state. It is demonstrated that the obtained results become competitive when they are compared against ones computed by Large Eddy Simulations which need a lot of computational resources and an appropriate initial solution for running. The possibility to perform unsteady simulations using Eddy Viscosity Models is explored. As a first step, a discussion of the experimental data available for fully developed cavitation cases and the developed simulation strategies to carry out these cases are presented.