Flow feature identification for capture of propeller tip vortex evolution

The application of a regional based mesh adaptation scheme is applied to a ship propeller. The meshing strategy adopted aims to capture the downstream tip vortex track while maintaining the flow quality within its Rankine vortex structure. A prescribed mesh density is used across the viscous vortex core and an outer annulus of lower density cells around the high tangential velocity zone immediately outside the viscous core. An initially coarse mesh provides enough information to identify the initially diffused vortex. A semi-automated system of progressive mesh refinement allows the vortex to be tracked as far downstream as required. The limitation on this tracking process arises from the total mesh size available on a given computer system. A detailed validation study has been carried out using the DTMB P4119 propeller. The influence, on the propeller forces developed, of the tip vortex refinement process is shown to be significant. Overall, good comparisons are achieved with force data and LDV measurements. The work has demonstrated the effectiveness of the VORTFIND identification scheme when used to control a regional mesh refinement scheme for prolonged resolution of propeller tip vortices. Such schemes become even more essential when analyzing unsteady propeller performance or the behaviour of the propeller subject to the influence of a downstream appendage