Investigation Of The Scale Effect On Sheet Cavitation And Tip Vortex Cavitation Around A Three-Dimension Hydrofoil

Cavitation on propeller plays an important role in stealth performance of a ship.The sheet cavitation and tip vortex cavitation are two main types of cavitation on propeller.Due to the complexity of cavitation phenomenon,so far to predict propeller cavitation for practical purpose is mainly based on model experiments.Because not all the similarity parameters can be simulated,the scale effect is an important obstacle for predicting full scale case and some correction methods are necessary.Present research,model tests of a three dimensional hydrofoil were carried out in cavitation mechanism tunnel and large cavitation channel to investigate the Reynolds number effect.Meanwhile numerical simulation was performed as well in order to get some influence rules of the scale effects of the sheet cavitation and tip vortex cavitation.The background of this research is for a propeller and therefore a three dimensional hydrofoil which has the same spanwise load distribution and foil contour as the propeller,is investigated with three sizes tested in large cavitation channel with different flow speed and another small size foil tested in the cavitation mechanism tunnel with various flow speed and air content.The investigation is focused on the Reynolds number effect on the inception of sheet cavitation and tip vortex cavitation.Based on the test results,analysis has been done,which may be as a reference for the laboratories.Based on numerical simulation,the flow field around hydrofoil was studied under different Reynolds number and angle of attack.Some comparisons between the calculated and test results have been made,which are:? calculated region of low pressure and the cavitation region from model tests,? the calculated location of minimum pressure and the location of cavitation inception from test,? the calculated minimum pressure coefficient and the tested incipient cavitation number.It indicates that numerical simulation can provide some reference to model tests.Finally a scale effect correction formula for tip vortex cavitation inception in large cavitation tunnel is proposed.