Propeller design requirements are nowadays more and more demanding, demanding not only to provide high efficiency and to avoid cavitation, but including also requirements in terms of low induced vibrations and radiated noise. Ducted propellers, consisting of a propeller located inside a foil shaped nozzle, may provide the opportunity to reduce these negative effects. Moreover use of this kind of propulsion may also increase the efficiency of heavily loaded propellers. These different effects can be obtained using different shapes of the duct.

This paper presents the development of a measuring device adopted to evaluate the forces on the duct and the results achieved during the tests on two ducted propellers at the cavitation tunnel of the University of Genoa. The measurement tool was designed and realized in house in the framework of a research project partially funded by the University of Genova and it is at the same time the support of the duct to be placed in the cavitation tunnel and the device measuring the acting forces. It basically consists of a light alloy tube where strain gauges were suitably located.

By means of the developed measuring device, two ducted propellers with different characteristics (namely with accelerating and decelerating duct), whose design was carried out in cooperation with Fincantieri Naval Vessel Business unit in the framework of the European Project BESST, were tested at cavitation tunnel. The results of these two test series were compared with data acquired at the SVA towing tank showing a good agreement.

Moreover, in order to investigate the cavitation behaviour of the two ducted propellers, cavitation test were also carried out, focusing the attention on the phenomena on the duct and on other interesting characteristics, such as thrust breakdown, providing useful data for future validations of numerical propeller design and analysis tool.