| Tip vortex cavitation is of critical importance due to its impact on the performance and noise production of a propeller. In order to avoid or control cavitation, engineers are required to understand what mechanisms lead to cavitation inception of the tip vortex. From previous studies, it was found that the underlying liquid flow plays the most important role on the cavitation inception. Although the tip vortex cavitation has been investigated for decades, the details of the underlying liquid flow near the tip region, especially the unsteadiness of the tip vortex, still remain unclear.;In the present study, the INS3D computer code developed by Rogers et al. (1991) is adapted and modified. To implement the numerical scheme in generalized coordinates, a three-dimensional H-H grid generation scheme with two blocks is developed for the present geometry of the finite-span hydrofoil. Both steady-state and unsteady finite-span hydrofoil flows were numerically studied. For the steady-state case, the Reynolds-Averaged Navier-Stokes equations with turbulence models were solved. The influence of different Reynolds numbers, angles of attack, foil cross sections, and hydrofoil planforms on the tip vortex was qualitatively and quantitatively investigated.;For the unsteady case, the computations were directly numerical simulations of all resolvable structures without adding the turbulence model. The topological structure of unsteady separated flow and the influence of the unsteady laminar separated flow on the tip vortex for both swept and unswept hydrofoils was qualitatively investigated. It was found that the secondary flow induced by the swept planform played an important role on the unsteadiness of the tip vortex.;The present study was concluded by applying a bubble dynamics model to study the real flow effects on the prediction of cavitation inception in the single phase flow. The results obtained in the steady-state case was used as a prescribed flow field through which the bubble is passively convected. A "window of opportunity" through which a candidate nucleus must pass in order to be drawn into the tip-vortex core and cavitate was determined for different initial nucleus sizes. |
