Efficient and multi-objective cavitating propeller optimization: An application to a high-speed craft

The design of a propeller for a high-speed craft is addressed by using a multi-objective numerical opti-mization approach. By combining a fast and reliable Boundary Elements Method (BEM), a viscous flowsolver based on the RANSE approximation, a parametric 3D description of the blade and a genetic algo-rithm, the new propeller shape is designed to improve the propulsive efficiency, reduce the cavitationextension, increase the cavitation inception speed and maximize, at the same time, the ship speed. Ratherthan by constraining the propeller delivered thrust, indeed, the proposed procedure works together withan engine-propeller matching algorithm that, each time a new propeller is defined, identifies the achiev-able maximum ship speed and the resulting engine functioning point that turn in additional goals for themulti-objective optimization. A set of optimal propellers, obtained through the design by optimizationbased on potential flow calculations (via the Boundary Elements Method), are selected for additionalviscous analyses (RANSE calculations) in order to further validate the results of the BEM calculationsand provide a deeper insight into the complex flow fields of high speed propellers. Among this subsetof optimal configurations, a final geometry is selected to verify the reliability of the design procedure bymeans of dedicated cavitation tunnel tests and full-scale measurements on a high-speed craft providedby Azimut|Benetti.