Analysis on the mechanisms of propeller-hull vortex cavitation induced in ice block environments

  Objectives  The propeller-hull vortex cavitation (PHVC) can lead to a sharp rise in propeller induced exciting forces. For ships in ice fields, the load on propellers is always high, and with the ice block effect taken into account, there are risks of PHVC occurrences. So, a preliminary analysis of the mechanism of the PHVC is deemed necessary.

  Methods  A test was specially setup and carried out in the large cavitation tunnel. Through simulation, a Pirouette effect was introduced and a detailed analysis was done through the hydrodynamic aspect.

  Results  When the distance H from lower edge of the ice model to centerline of the propeller shaft is 0.25 times of the propeller diameter D, the PHVC occurred by adjusting the relative axial position of the ice model and propeller, but at H=0.5D, the PHVC did not occur from beginning to the end.

  Conclusions  Analyses show that, the common mechanism of the propeller hull being conducted at high hydrodynamic interactions will cause vortex cavitation and the continual action of a Pirouette effect.