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Ship designers at Rolls-Royce have been working on a project that incorporates a wave-piercing bow design with low resistance in order to improve fuel efficiency.

The designers have focused their efforts on a vessel's behaviour under real sea conditions and have been looking at ways to optimise performance and minimise the power requirement within a vessel's normal operating profile.

For ships that operate on fixed routes it is important to maintain a given speed to arrive at the scheduled destination on time. Like other vessels, they must often cut speed to avoid bow damage and unacceptable acceleration levels when seas are too great to ensure acceptable comfort for the passengers on board. This means they often have to drive harder when the sea state permits to make up lost time. This in turn leads to an uneconomical operating mode, increased fuel consumption and greater emissions.

To meet these challenges, Rolls-Royce's design team incorporated the patented wave-piercing bow and hull form developed for the award-winning Environship, and used the experience gained from operating vessels that went into service from 2013. The wave-piercing hull, with its vertical stem, has a slender, progressive entry to the water. When a wave is encountered, the cutting edge hull shape pierces through the water rather than riding over the top. This gives less resistance, less acceleration, less bow impact and therefore a smoother ride for passengers and crew.

Compared to a conventional curved bow, the flare has been replaced with straight-lined sections to allow the water to flow along the shipsides, rather than be thrown out and forward. By stretching the waterline to the front of the bow, the waterline's angle of entrance is reduced. Buoyancy is moved slightly forward and the shoulder can be reduced. This results in significantly reduced resistance.

Computer simulations were used extensively in developing the design, based on realistic weather conditions in the typical operating areas. The bow is said to have demonstrated a reduction in resistance of between five and eight percent compared with an optimised conventional raked bow with bulb, the precise figure depending on the wave period. At the same time, accelerations in the forward part of the vessel are reduced by five to 10 percent, again dependent on wave period.

Computational fluid dynamics (CFD) analysis was used to optimise the reduction in hull resistance. Following the computer-based work, the findings were verified by tank testing. Propulsion tests in still water showed that the new bow produced three percent lower hull resistance than the optimised conventional bow.

Rolls-Royce has applied this bow design to a wide range of vessel types, such as passenger, ro-pax and ro-ro ships, chemical and product tankers, LNG and LPG tankers, bulk carriers, LNG bunkering vessels and superyachts, as well as the new design for Hurtigruten's future explorer vessels.

In addition to the gain in fuel efficiency and improved seakeeping, the bow form is said to be easier to build, requiring fewer double-curvature plates.