Air Lubrication Reduces Underwater Radiated Noise (URN)

Professor John Carlton – a fellow of the Royal Academy of Engineering, and Professor of Marine Engineering and Director of Maritime Studies at City, University of London – has published a new whitepaper analysing the impact of hull air lubrication on underwater radiated noise (URN), propulsion and cavitation.

Focusing on URN, which has been, and continues to be, a key sustainability issue for the International Maritime Organization (IMO), the whitepaper finds that “the presence of air in the form of an air bubble- mixture around the hull, for example as generated by an air lubrication system, will significantly attenuate the transmission of noise from the ship into the sea environment.” Furthermore, the paper formulates that “the presence of air in the propeller disc as introduced by an air lubrication system, rather than negatively affecting performance, attenuates higher harmonics of radiated pressure spectrum emitted by cavitating propeller (as well as helps in attenuating cavitation erosion).”

It is our interpretation, based on the whitepaper’s findings, that the Silverstream^® System reduces URN emissions both from the hull and the propeller. From the hull, noise emitted through the flat of bottom will be masked by the bubble carpet, while more importantly, the noise levels generated by the propeller can be significantly reduced through the cushioning effect of emitted pressure pulses by air introduced through the air lubrication system.

Head to our academic resources page to read more.