MODEL TESTS ON CONTRAROTATING 

 PROPELLERS 



J. D. van Manen and M. W. C. Oosterveld 



Netherlands Ship Model Basin 



Wageningen, The Netherlands 



ABSTRACT 



This paper presents the results of open-water tests with a systematic 

 series of contrarotating propellers, consisting of a four-bladed forward 

 screw and a five-bladed aft screw. 



Based on the open-water test results, contrarotating propeller systems 

 were designed for a tanker and a cargo liner. Comparative tests have 

 been carried out with the tanker and the cargo liner both equipped with 

 contrarotating propellers and with a conventional screw. The propul- 

 sive efficiencies, the cavitation characteristics, the propeller induced 

 vibratory forces, and the stopping abilities are dealt with. 



INTRODUCTION * 



During the past years the trend of most ship designs has been toward higher 

 speeds (cargo liners) and/or larger displacement (tankers or carriers) and 

 therefore toward high-powered ships. As a result the problems of propeller 

 cavitation and propeller induced vibration became matters of great concern. 



In an attempt to provide merchant ships with propulsion devices with supe- 

 rior cavitation and propeller induced vibration characteristics in addition to a 

 high propulsive efficiency, the application of contrarotating propellers have been 

 the subject of several investigations [1-3]. This paper presents the results of 

 investigations on contrarotating propellers performed at the Netherlands Ship 

 Model Basin during the past five years. 



These investigations covered the following details. A systematic series of 

 contrarotating propeller systems was designed and manufactured. These sys- 

 tems, consisting of a four-bladed forward screw and a five-bladed aft screw, 

 were designed for equal power absorption by the forward and the aft screw. 

 Tests were carried out in the towing tank to determine the open-water charac- 

 teristics of this series of contrarotating propellers. 



Based on these open-water test results, contrarotating propellers were de- 

 signed for a tanker and a cargo liner. Comparative tests have been carried out 

 with both ships equipped with a contrarotating propeller system and with a con- 

 ventional single screw arrangement. In Fig. 1 the contrarotating propeller ar- 

 rangement on the stern of the tanker model is shown. The propulsive efficiencies, 



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