Influence of wake on propeller loading and cavitation

Article type: Research Article

Authors: van Gent, W. | van Oossanen, P.

Affiliations: Propulsion Hydrodynamics Department, Netherlands Ship Model Basin, Wageningen, The Netherlands

Abstract: In this paper an attempt is made to determine some aspects of the interrelationship between wakefield, adapted propeller design, cavitation and dynamic load. This is performed by means of theoretical procedures for propeller design, for the determination of the dynamic propeller load and for the determination of cavitation performance. The use and need for such theoretically based calculation methods in addition to experimental methods is discussed. A number of five-hole pitottube measurements, performed at the N.S.M.B., are analysed to determine whether or not it is possible to derive properties of wakefields which are typical for certain types of ships. This is done for a group of large tankers and some container ships. For these two ships two propeller series are designed. For the tanker a series of which the blade number is varied and for the container vessel a series having a varying margin against cavitation. The merits of the conventional design procedure, typical of procedures in present use, are critically reviewed. The combinations of nominal wakefields and designed propellers are analysed with respect to the dynamic load due.to the inhomogenity of the wakefield and the occurrence and extent of cavitation. Use is made of calculation programmes based on unsteady lifting surface theory for the dynamic load and based on quasi-steady propeller theory combined with two-dimensional wing theory for the cavitation prediction. The main conclusions are that in order to calculate accurately the dynamic load distributions very detailed knowledge of the wake structure is required and that it is necessary to incorporate cavitation minimisation criteria in propellers design procedures.

DOI: 10.3233/ISP-1973-2022801

Journal: International Shipbuilding Progress, vol. 20, no. 228, pp. 279-321, 1973