JEMS Maritime Sci. Ahead of Print: JEMS-50480

Astern running of heavy-tonnage vessels in ice channel

Aleksei Dobrodeev, Kirill Sazonov
Krylov State Research Centre, St. Petersburg, Russia

One of the most important tasks in raising the efficiency of marine transport systems is to make heavy-tonnage vessels move at faster speeds in channels laid by icebreakers. Studies carried out in the KSRC Ice Basin have shown that broken ice is a significant factor restricting vessels’ speed through ice channels. Wide breadths of heavy-tonnage vessels make it difficult to push ice pieces aside resulting in their accumulation ahead of the bow. Ice blocks can be removed from the bow area only if they are immersed and passed along the hull underwater. With a speed increase this processes require more and more energy.
Potentially, easy ice passage along the underwater hull and speed improvements can be achieved if large-size vessels go stern-first in ice channels. In this mode of operation we have a number of factors contributing to a more efficient passage of ice provided by a small angle of the sternpost making it easier for ice floes to dive under the hull, as well as suction produced by propellers. Moreover, propeller slipstreams wash away submerged ice outside the channel edges and reduce ice friction of the underwater hull.
The paper gives some theoretical assessments regarding the efficiency of running a large-size vessel astern in ice channel. Model studies have been undertaken in the KSRC Ice Basin to confirm that the suggested mode of operation is effective. During these experiments the models of large-size vessels were run through ice channel to determine ice resistance and speed. Theoretical estimates were compared with the model test results obtained in the Ice Basin. Analysis of all results proves that the described mode of operation promises faster speeds of vessels through ice channels.

Keywords: Heavy-tonnage vessel, Propulsion in ice, Hull form, Ice basin, Model tests

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