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Captive model testing for ship to ship operations

Abstract

Applications of ship-to-ship operations for liquid cargo transfer, in particular for crude oil and LNG, will to be increasing in the future. Moreover, such operations are expected to take place in more severe environmental conditions. In order to have a better understanding of the hydrodynamic phenomena that are of importance for this kind of manoeuvres, a research project entitled “Investigating hydrodynamic aspects and control strategies for ship-to-ship operations” has been initiated, co-ordinated by MARINTEK (Trondheim, Norway) and supported financially by the Research Council of Norway. The main objective is to improve existing simulator based training activities for personnel involved in complex ship-to-ship operations in open seas through increased knowledge and understanding of the complex water flow between two ships operating in close proximity. As a final goal, a new generation simulation tools for ship-to-ship operations incorporating up-to-date knowledge of fluid dynamics has to be established. The project consists of four work packages: (1) Computational Fluid Dynamics; (2) Particle Image Velocimetry; (3) Mathematical models for simulators; (4) Nautical safety and control aspects. In the frame of the third work package, captive model tests are being carried out at the Towing tank for manoeuvres in shallow water (co-operation Flanders Hydraulics Research – Ghent University) in Antwerp, Belgium. While the model of an Aframax tanker is attached to the computer controlled planar motion carriage, a VLCC model is attached to the towing carriage as well. Two types of tests are considered: steady state tests, during which the main tests parameters (ships’ speed, relative longitudinal and lateral position, propeller rates, drift angle of the Aframax tanker, rudder angle) are kept constant, and dynamic tests, characterised by a varying lateral distance and/or heading. Horizontal forces and moments, propeller thrust and torque, and vertical motions are measured on both ship models, while the vertical motions of the free surface are monitored in three fixed points of the towing tank. The paper intends to give a summary of the test results, that will be used for validation of mathematical manoeuvring simulation models and CFD calculations

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