Gas Transport Into Vortex Cavities

The research presented in this thesis aims at understanding how gases influence the cavitating vortex generated by a wing tip in a stationary flow. Gases in the flow occur as non-condensible microbubbles as well as gases dissolved in the liquid. They are typically abundant in surface flows. For studying how dissolved gases influence a cavitating vortex, a set of diffusion models are developed that predict how gases dissolved in water are transported into a vortex cavity. The predictions of the growth rate of a cavitating vortex using these models is then compared with the growth and development of a cavitating wingtip vortex generated by a NACA 662 −(415) foil. The cavitating vortex is measured using single-view shadowgraph imaging in a cavitation tunnel. Some experimental practices on how the flow conditions are prepared prior to a measurement are also investigated, which is instructive in guiding experimental practices that promote repeatability of the results. A good agreement is achieved between the measured growth rate of the cavity, and that predicted by the diffusion models. The results also explain previously observed behavior of the development of a cavitating vortex from literature.