A prediction method for squat in restricted and unrestricted rectangular fairways

Abstract The hydrodynamic behaviour of a vessel changes when sailing in shallow and/or confined water. The restricted space underneath and alongside a vessel has a noticeable influence on both the sinkage and trim of a vessel, also known as squat. To assess these influences an extensive model test program has been carried out in the Towing Tank for Manoeuvres in Shallow Water (cooperation Flanders Hydraulics Research — Ghent University) in Antwerp, Belgium with a scale model of the KVLCC2 Moeri tanker. This benchmark vessel was selected for its full hull form, to maximize the effects of the blockage. To thoroughly investigate the influences of the blockage on the squat of the vessel, tests have been carried out at different water depths, widths of the canal section and forward speeds (2 up to 16 knots full scale whenever possible). The squat observed during the model tests is compared with the squat predicted with a mathematical model based on mass conservation and the Bernoulli principle. The correlation between measured and modelled squat for each canal width for all tested speeds and water depths is very good, but shows a constant slope deviation. An improved model for the squat is proposed and takes into account the forward speed, propeller action, lateral position in the fairway, total width of the fairway and water depth.

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