Propeller Wake Analysis by Means of PIV

An experimental investigation of the propeller wake in a cavitation tunnel has been performed using Particle Image Velocimetry (PIV). The hydrodynamic and geometrical investigation of the wake and its evolution has been pointed out. The blade viscous wake, developing from the blade surface boundary layers, the trailing vortex sheets, due to the radial gradient of the bound circulation, and the velocity fluctuation distributions are identified and discussed. The near wake geometry is described through the bending of the blade wake sheets, the slipstream contraction and the tip vortex trajectory and viscous interactions. In the near field the effects of turbulent diffusion and viscous dissipation, which cause a rapid space-broadening of the velocity gradients in the trailing edge wake, are also examined. In the far wake the development of the slipstream instability and the breakdown of the hub and tip vortices are outlined.