Investigation of the near wake of a propeller using particle image velocimetry

The investigation of a propeller wake is carried out in a cavitation tunnel using particle image velocimetry. To achieve high spatial resolution, a mu ltigrid adaptive cross-correlation algorithm is used for image analysis. Th e contributions of the viscous wake, originated by the boundary layer on th e blades of the trailing vortex sheets, as well as of the vorticity distrib ution are resolved and discussed for different angular positions of the bla de. The near wake flow is characterised by strong deformations, due to the bending of the blade wake sheets, to the contraction of the slipstream and to the trajectory of the tip vortex. The turbulent diffusion and the viscou s dissipation rapidly lead to broadening and decay of the trailing edge wak e. Furthermore, secondary tip vortex structures are also pointed out.