Cavitation Tunnel Tests on Ducted Propellers

Propeller design requirements are nowadays more and more stringent, 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 may provide the opportunity to reduce these negative effects or to increase the efficiency of heavily loaded propellers. This paper presents the development of a measuring device for the cavitation tunnel, in order to evaluate the forces on the duct. The measurement tool was designed and realized in house 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. By means of the developed measuring device, two ducted propellers with different characteristics (namely with accelerating and decelerating duct) have been tested at cavitation tunnel. The results of these two test series were compared with towing tank open water test data, showing a good agreement. Moreover, cavitation tests 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.