Afdeling Maritieme Techniek Universiteit Gent
Shallow Water

Ship Motion Measurement

Measurements at full scale

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Since the beginning of 2010 Flanders Hydraulics Research possesses an accurate measurement equipment that can be installed in a short time on almost any vessel. The main purpose of this equipment is to validate the mathematical manoeuvring models which drive ship manoeuvring simulators. The advantage of measuring at full scale is that it reveals differences, such as environmental effects, which may not be picked up by mathematical models because they were derived from tests carried out at model scale. Several surveys using the equipment have already been carried out.

Measurement equipment

The equipment uses a combination of RTK GPS antennas, accelerometers and inclinometers to measure the position and orientation of the vessel in three dimensions with an accuracy upto respectively 2 cm and 0.01°. It consists of a precalibrated housing carrying two GPS antennas with seperation distance two metre, sending the measured data wireless to a laptop standing in the bridge house. Furthermore AIS-data from the ship's pilot plug are supplied to the laptop using a pilot plug splitter. During the survey the time evolution of rudder angles and machine orders are registrated manually.

Selected surveys

Survey of a bulk carrier in the Port of Dunkirk

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On request of the Port Authority of Dunkirk, the motions of the capesize bulk carrier MV Cape Aster (292 m x 45 m x 14.2 m) were measured on a trip departing from the Western port of Dunkirk at 11:00 am and mooring at the Arcelor Mittal plant in the Eastern port of Dunkirk at 08:30pm.

The survey was carried out with support of the Dunkirk Pilotage and the main objective was to study the behaviour of a ship during the passing of the Charles de Gaulle Lock in the Eastern port of Dunkirk. The hydrodynamic effects while entering the lock with a ship of maximum dimensions with respect to the actual regulations were studied in detail.

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The motions of the vessel were recorded in 6 dimensions (3 translational and 3 rotational) at high frequency. During the survey, the rudder angle, propeller rate of turn and the forces applied by tugboats were also captured. A survey carried out at full scale is always interesting because it reveals differences which cannot be predicted from model scale. For example, effects from wind and forces exerted by tugs may be quite different in reality.

The data from the full-scale measurements were used for the validation of an improved mathematical model. Details can be found in the paper entitled Hydrodynamics of a ship while entering a lock, which was presented at the Third International Conference on Ship Manoeuvring in Shallow and Confined Water. Details of the behaviour of the ship while entering the Charles de Gaulle Lock can be found in the paper entitled Lock manoeuvres: practical cases in Europe and Panama.

Survey to validate the mathematical manoeuvring model of a CEMT Class IV inland vessel

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In order to validate the mathematical manoeuvring model of a CEMT Class IV inland vessel which was derived from comprehensive model experiments, full-scale measurements of the inland vessel MT Elise (105 m x 9.5 m x 2.6 m) have been carried out on the Lys Diversion Canal. The ship positions were measured with an accuracy of up to 2 cm and the application of rudder and propeller during the passage of the bend of Nevele were registered. In post-processing, the bottom profile and the water level were taken into account so that the effect of under keel clearance and the proximity of banks can be studied in detail.

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During the lock passage at Sint-Baafs-Vijve, the water level variation in the lock was logged at six locations in order to analyse the slope of the water level during the filling of the lock. The measured slope of the water level was compared with the trim angle of the MT Elise in order to validate the numerical calculations of lock filling which are in use at Flanders Hydraulics Research. Particular attention was paid to comparing the longitudinal forces on a ship during this procedure.

Survey of the entry of a bulk carrier in the Westlock of Terneuzen

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A Kamsarmax bulk carrier with a breadth of 37 m was followed entering the Westlock in Terneuzen characterised by a total breadth of 40 m and an available breadth of 38 m (due to the fendering system). As one can imagine this manoeuvre results in large lock effects when the ship presses the water out of the lock between the small gaps between the ship and the lock structure.

The entrance of Kansarmax bulkcarriers to the West lock in Terneuzen was simulated at FHR in 2007 for determining the maximum ship dimensions to whom the West lock is limited. The survey supplies FHR with validation data for the mathematical model of lock effects present in the ship manoeuvring simulators.