Numerical modeling and simulation of laminar and transitional submerged cavitating jets

Numerical investigations on the effect of cavitation and bubble dynamics on fluid flow with applications to hydraulic valves are carried out. First, the parameter space of a previously developed quasi-one-dimensional model accounting for the coupling between the fluid flow and bubble dynamics is explored. Several flow and geometric parameters are shown to have a considerable effect on the stability of the flow. Second, the commercially available CFD code, FLUENT, which features a recently added cavitation model, is tested for predictions of flashing onset in a converging-diverging axisymmetric nozzle and for cavitation in both a model and industrial spool valve. The results highlight the limitations of such a model for cavitating turbulent flows. Third, a research computer code is developed and tested to study cavitation inception in a planar submerged laminar jet. A direct numerical simulation (DNS) of the Navier-Stokes equations is coupled to a previously published cavitation model which accounts for various aspects of bubble dynamics. The results highlight the effect of cavitation on vortex dynamics in submerged jets and are in qualitative agreement with recent experimental investigations. Finally, DNS of low Reynolds number transitional cavitating submerged jets is conducted. Simulation results are first presented for a round jet under non-cavitating and cavitating conditions to study the effect of cavitation on vortex dynamics in three-dimensions. Cavitation tends to distort the vortical structures and intensify local vorticity and break up the vortex ring into several sections. The influence of non-circular nozzles and swirl on jet vortical structure and its influence on cavitation inception control is also studied