Propeller design by means of multiobjective optimization: CP propeller test case

Validatipon of the results by means of an experimental campaign carried out at Genoa University Cavitation Tunnel

1. Introduction

Propeller design has evolved significantly in the last few years, with the introduction of numerical methods which can provide an ever improving assessment of propeller characteristics, considering propeller non stationary functioning and cavitating behavior, not only in correspondence to the usual design conditions, but also to off-design conditions. This assessment has become widely adopted, with numerical methods being able to predict propeller characteristic curves (and cavitating behavior) in correspondence to a wide range of advance coefficients. Modern propeller requirements involve many different characteristics, not limiting only to maximum efficiency, but considering also propeller cavitating behavior and, more and more, its side effects, in terms of radiated noise and pressure pulses. This is evident with the ever-increasing demand for improvement of comfort onboard and discussions about radiated noise problems, especially in proximity of protected areas.
In recent years, the interest towards the problem of radiated noise has led the EU to fund some cooperative projects, i.e. SILENV, AQUO and SONIC, whose activities were concluded at the end of 2015. In the context of the first project, UNIGE was involved in the analysis of different ways to reduce underwater radiated noise; since the marine propeller, when cavitating, may become the most significant noise source of a ship, a large part of the work was devoted to the application of a design procedure in which in-house panel codes are coupled with the modeFRONTIER, a multiobjective optimization software. This procedure had already been proposed in (Gaggero, S. and Brizzolara, S. 2009. Parametric CFD Optimization of Fast Marine Propellers FAST 2009), however in the context of this project it was also possible to test it against a real case study and, most important, to validate the results by means of an experimental campaign carried out at Genoa University Cavitation Tunnel.