Propeller Wake Analysis Behind a Ship by Stereo PIV

An experimental investigation of a five blade MAU propeller wake behind a Series 60 Cb=0.6 ship model has been performed using Stereo Particle Image Velocimetry (Stereo-PIV) in a large free surface cavitation tunnel. The investigation of the wake at different longitudinal stations and its evolution in phase with the propeller has pointed out the capability of Stereo-PIV in resolving the complexity of the flow field. The blade viscous wake, which develops from the blade surface boundary layers, the trailing vortex sheets that are due to the radial gradient of the bound circulation, and the velocity fluctuation distributions are identified and discussed. The complex interaction between the hull wake and propeller is described through the evolution of the mean velocity components and the vorticity fields. In the near field the effects of turbulent diffusion and viscous dissipation, which cause a rapid decay of the velocity gradients in the trailing edge wake, are also examined.