GREENWAVE - DRACS - Drag Reducing Aerodynamic Components for Shipping

While the greatest source of drag on large vessels is between the hull and the water, the way that the air travels around the ships superstructures does affect the ship's speed and fuel efficiency. As a single ships fuel costs are over US $3m a year, any saving has an economic as well as an environmental benefit.

Today’s global fleet of cargo vessels was built when fuel was more plentiful and less costly than today. Aerodynamic drag was not a prime consideration. Consequently it is little surprise to find that bulk carriers, supertankers and container vessels might be described as being about as aerodynamic as a concrete block.

The DRACS program set out to identify where the main sources of wind resistance were.

Using scale models, from an actual fleet of bulk cargo carriers, the Greenwave Project Team commenced wind tunnel tests in the University of Auckland’s Twisted Flow Wind Tunnel to identify precisely those aspects of the ships structures that created wind turbulence – the factor that has the most negative aerodynamic impact. Once the key trouble spots had been both identified and quantified (typically the main accommodation superstructure and the cranes) the team began creating solutions that would guide the wind round the points of greatest resistance.

These designs, which can be easily fitted to existing ships, were again tested on large scale models in a wind tunnel. Computer linked sensors measured ‘before and after’ improvements.

The results were fed into our specially designed analysis system. Using extensive records from actual ships’ logs (apparent wind angles and speeds) the program can accurately predict just how much positive impact the aerodynamic improvements are having.

These easy-to-fit aerodynamic improvements, unveiled at the Posidonia International Maritime Exhibition in Piraeus, Athens in June 2008, will have an immediate impact on fuel reduction.

All wind tunnel photographs were taken at the University of Auckland’s Twisted Flow Wind Tunnel

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Special thanks to the team at the University of Auckland’s Twisted Flow Wind Tunnel.

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