Design, analysis and experimental characterization of a propeller in decelerating duct

Despite having been applied since a long time, ducted propellers design still represents a challenge for the designer, especially when dealing with the less widespread decelerating duct, due to the complex evaluation of the duct effects and to the limited amount of available experimental information. In the paper an hybrid design approach is described. Moreover, a series of experimental results at towing tank and, especially, at cavitation tunnel are presented, in order to provide an insight into the particular functioning of this propulsor including cavitation behavior and a validation of the proposed design procedure. Particular attention is given to the development of the cavitating tip leakage vortex, which characterizes this propulsor functioning. To this aim, experimental observations are compared with numerical results obtained by means of a commercial RANSE solver, in order to check its applicability for the prediction of cavitation inception and extent.