Bursting Phenomenon of Propeller Tip Vortex Cavitation and its Relationship with the Result of Numerical Simulation of Propeller in Unsteady Condition

Bursting phenomenon of tip vortex cavitation causes severe high-frequency vibration, but estimation of it by numerical computation is not yet realized. In this study the authors made model experiments to observe the bursting phenomena and measured the pressure fluctuations caused by that, changing two propellers, wake distributions, thrust coefficients and cavitation numbers parametrically. After analyzing frequency of it we found that there would be two methods to suppress the bursting phenomenon : stabilizing the tip vortex cavitation or reducing the volume of cavitation. We also did numerical fluid simulations around a propeller in non-cavitating, unsteady condition and compared the strength of tip vortex along the circumference and its derivatives. As a result the phenomena were parameterized by the time derivative of the strength of tip vortex, and if it was higher than a certain value, tip vortex cavitation bursted. Therefore there is the possibility to predict the occurrence of bursting phenomenon by numerical analysis.