Experimental study of air layer drag reduction on a flat plate and bottom hull of a ship with cavity

Abstract In an effort to cope with the global warming environment and oil prices, the development of energy-saving ships is greatly anticipated by the shipping industry. Air lubrication is one of the promising techniques for reducing the frictional resistance of a ship and improving the fuel efficiency. In this study, air layer drag reduction in the frictional resistance under a flat plate was investigated experimentally in the towing tank. The shape of air layers was observed, and the changes of resistance were measured. The results show that air layer drag reduction with bottom cavity is useful in reducing the frictional resistance at specific conditions of air injection. Then, resistance and self-propulsion test of a model ship based on a 95,000 DWT bulk carrier was conducted in the towing tank using method of air layer drag reduction with bottom cavity. Bottom air layer were observed and the expected power savings were estimated, the results indicated that the delivered power can be reach 15% at the full-scale ship without considering the consumption of air injection.