Abstract
In this paper the design process of ducted propeller configurations for high powered large ships is discussed, particular emphasis is placed upon the selection of concept, i.e. the general layout of propeller, nozzle, rudder(s) and struts and their location with respect to the ship’s afterbody. A new concept, characterized by two rudders of high aspect ratio placed behind a relatively short nozzle is investigated for a 425 000 t.d.w. restricted draft tanker, and the optimization of the basic design parameters by means of systematic computer calculations is discussed for this case. Based on this concept, a twin rudder-short nozzle was designed and compared with the conventional single rudder configuration, both with and without a nozzle, on the basis of model tests. The results show that the new concept offers significant gains in efficiency, cavitation properties and manoeuvering characteristics.
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