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Escort tugs operate at high yaw angles in order to produce forces to steer and stop the vessel they are escorting in an emergency. In this paper, RANS predictions of forces and flow patterns around the hull of an escort tug model are compared with experimental data. Two alternative meshing strategies were used, one using tetrahedral elements with triangular faces and one using hexahedral elements with quadrilateral faces. Experiments were carried out with and without the low aspect ratio tin that is typical of many escort tugs. Lift and drag forces were measured experimentally for yaw angles from 15 to 45 degrees. Flow measurements around the tug at 45 degrees yaw were obtained using a stereoscopic particle image velocimetry (PIV) system. The results from each CFD simulation were compared to the measured flow patterns using a numerical procedure that led to a quantitative measure of the accuracy of the predicted results. The analysis of the flow patterns indicated that the main features of the flow were predicted, and that on average, the predicted velocity magnitudes were within 10% of the measured values. Neither mesh approach had a significant effect on the accuracy of the flow pattern predictions. The hexahedral mesh gave more accurate force predictions that the tetrahedral mesh. Forces were predicted by the CFD code with this mesh to within 5 % of the experimentally obtained values.

Item Type:	Refereed Article
Research Division:	Engineering
Research Group:	Maritime engineering
Research Field:	Naval architecture
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in engineering
UTAS Author:	Bose, N (Professor Neil Bose)
ID Code:	54641
Year Published:	2008
Deposited By:	NC Maritime Engineering and Hydrodynamics
Deposited On:	2009-02-26
Last Modified:	2015-01-27
Downloads:	7 View Download Statistics