Propulsive Efficiency and Cavitation Characteristics of Contrarotating Propellers designed for a low speed ship

Contrarotating propellers (CRP) became one of the most hopeful propulsion systems from a energy saving point of view owing to the development of reliable shafting systems. The efficiency of CRP in open water is superior to a conventional propeller. However, it is very important to investigate other properties such as propulsive efficiency, cavitation characteristics and propeller induced pressure fluctuations.Although several experimental studies concerned with these items were conducted in these twenty years, there was a lack of hydrodynamic considerations in this area. The author intends to describe the essential differences between CRP and conventional propellers on the basis of previous studies which were pursued by the author et al.. As a result of experimental and theoretical studies on contrarotating propellers, advantages of contrarotating propellers over a conventional propeller in propulsive efficiency, propeller cavitation and pressure fluctuations are revealed.