Squat of ships sailing in a non centered track in a canal
De Koning Gans, H.J. (2011). Squat of ships sailing in a non centered track in a canal, in: Pettersen, B. et al. (Ed.) 2nd International Conference on Ship Manoeuvring in Shallow and Confined Water: Ship to Ship Interaction, May 18 - 20, 2011, Trondheim, Norway. pp. 97-106
In: Pettersen, B. et al. (2011). 2nd International Conference on Ship Manoeuvring in Shallow and Confined Water: Ship to Ship Interaction, May 18 - 20, 2011, Trondheim, Norway. Flanders Hydraulics Research/Ghent University/Norwegian Marine Technology Research Institute/Norwegian University of Science and Technology (NTNU)/The Royal Institute of Naval Architects: London. ISBN 978-1-905040-83-4. X, 422 pp., more
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Document type: Conference paper
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| Abstract |
Squat is a serious problem when very large container ships are entering harbours with small underkeel margins. The squat effects are that the ship acquires sinkage and trim. Due to this sinkage and trim the keel clearance decreases drastically. The distance between bottom and ship becomes very small and measures must be taken to avoid contact between the ship and the bottom.
Also when the ships are not sailing in the centre of the canal, the squat effects become more serious. The flow around the ship is not symmetrical anymore, and also the gap between the wall and the ship becomes smaller and higher return flows are expected. This will cause extra forces to act on the ship and as a result, the ship will suffer extra squateffects.
This study looks at several sailing tracks at the centre and parallel of the centre line of the port. The flow calculations are carried out with a three-dimensional potential flow model. For this model the wetted hull geometry has only to be determined of the underwater body (wetted hull) in still water conditions. From these calculations the pressures on the wetted hull are determined and by integrating the pressures, the forces are determined. From each track the forces are determined and the trim and sinkage are calculated. From these results, it appears that, when the ship sails more closely to the wall the forces will increase drastically. |
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