Numerical prediction of propeller loading due to sea ice


As part of the Cooperative Research Ships (CRS) consortium, MARIN has undertaken a project to better understand and predict loads on propellers when they are in ice. Adam Peddle, a.peddle@marin.nl


Interaction zones in ice


Vessels and crews operating in Arctic con- ditions have a lot to worry about: extreme cold, polar nights, total isolation and perhaps most importantly of all, sea ice. Operating in sea ice and safely navigating through an ice field is a serious challenge for any vessel. As with any ship design, powering is vital. In the Arctic, however, the propeller must be strong enough to withstand severe loads due to the impact from ice pieces.


A tool has now been developed to deter- mine the loading on a propeller due to interaction with ice. By using this tool, propeller designers will be able to deter- mine the loads without having to resort


Coefficient of pressure due to ice


to costly model tests. This means that safer and more efficient designs can be developed from the comfort and safety of the office.


As an ice piece approaches a propeller, the flow field is disturbed and the propeller experiences heightened hydrodynamic loading as a result of the blockage effects. Upon impact, the blade will mill through the ice piece, resulting in very high structural loads, which can lead to propeller failure if it has not been sufficiently strengthened. Determining the total load in a propeller blade due to ice is a highly complex prob- lem, which must consider the interplay of the blade, ice and water.


PROCAL In order to arrive at a solution, a model that considers ice milling and block- age has been implemented in PROCAL, MARIN’s proprietary code for determining propeller loading based on a Boundary Element Method (BEM). Model tests carried out at Aker Arctic in Finland have been used to validate the final predictions.


Operating in harsh Arctic environments remains a serious challenge for ship design- ers and operators. With the ability to predict the conditions the propeller will have to handle and strengthen it accordingly, crews can now sleep a little more soundly knowing that whatever happens, they’ll be able to keep steaming.


report 13


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