Effect of Propeller Tip Clearance on Hull Pressure Pulses

Paper in proceeding, 2017

The objective of this study was to investigate how hull forces and pressure are influenced by small propeller tip clearance by creating a setup where systematic variation of tip clearance could be achieved at similar propeller conditions ; in this study, clearances between the propeller tip and a generic hull with tunnel configuration were 0.7%D P , 5%D P , and 20%D P. Simulations were performed using a scale resolved PANS approach, combined with cavitation modelling considering the fluid as a mixture and incorporating mass transfer source terms. The predicted impact on hull pressure is very large, with the maximum amplitude differing an order of magnitude between the small clearance case and the one with normal clearance. More important, however, is probably the forces exerted on the hull plate, and here the difference is much less; the standard deviation of pressure variation differs by a factor that does not exceed two. However, the higher order blade passing frequencies are much more prominent in the case with small clearance, presumably due to a complex behaviour of the tip vortex along the hull plate.