Kaijia Han

A Procedure for Optimizing Cavitating Propeller Blades in a Given Wake

Abstract The blade geometry of a cavitating propeller in a given wake is optimized to maximize propeller efficiency and minimize propeller induced pressure fluctuations. The Keller criterion, the cavity volume and other constraints are considered in the optimization process. Such constraints are cavity area, cavity length and face side pressure. These are switched on separately or simultaneously to investigate their influence on cavitation and efficiency. The optimization starts from a near optimum propeller as well as from an off-design propeller. Results indicate that the present optimization technique can yield higher efficiency and lower pressure amplitude with tolerable cavitation for a cavitating propeller in a given wake.

Numerical optimisation of propeller-hull configurations at full scale

Optimisation of propeller/hull configurations based on the Reynolds-Averaged Navier-Stokes (RANS) equations has been very rare so far due to the large computational effort required. Virtually no such optimisation has been carried out at full scale, where only a few RANS methods are at all applicable due to stability problems. The present paper introduces a newly developed RANS solver especially designed for stability and this solver is shown to work well at full scale. Through a link to a commonly used propeller analysis code, predictions of the viscous flow around the full scale ship with an operating propeller may be made. This is utilised in the work reported here, where the flow codes are introduced into a system for automatic optimisation. It is shown that even well designed propellers may be further improved, both in a fixed wake and in the wake behind a fixed hull.