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Offshore Support Journal

Offshore Support Journal

Asymmetric stern enhances icebreaking capability

Fri 25 Nov 2016

Asymmetric stern enhances icebreaking capability

Ice-class vessel specialist Aker Arctic has developed a new, asymmetric stern design for icebreaking vessels, which it believes will outperform conventional designs. It notes that icebreakers and ice management vessels typically have azimuth pulling type thrusters, with the propellers located very close to each other when they are turned inwards for ice flushing

operations. However, if the amount of water they need in order to create the maximum flushing effect is limited, this can cause them to cavitate, vibrate and create noise. In this circumstance, flushing operations are not very efficient if the thrusters cannot be used at full power.

“We have invented a solution to this,” said Aker Arctic’s project manager Riku Kiili. “By changing the stern design to an asymmetrical form, the thrusters can be installed lengthwise, well away from each other. There is more space in between the pods, and when turning them sideways for ice flushing, they get enough water and can blow the ice away using full power.”

Extensive model testing seems to have vindicated the new design. Two stern designs were tested in conditions simulating level icebreaking capability with two different thicknesses of ice, breaking out from an ice channel stern first, breaking through an ice ridge and clearing brash ice. The results from the tests showed that the level icebreaking capability and the ability to break out from an ice channel remained the same but the asymmetric stern enhanced brash ice and ridge-clearing capability. In addition to ice management advantages and improved flushing capabilities, the new design showed improved dynamic positioning potential in some situations.

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