Figure 3: Side force and yawing moment from stationary (red) and instationary (green) tests.
The third figure gives the unconventional maneuvers. Figure 3 shows how in one run through the Seakeeping and Maneuvering Basin four radii are tested and hence, information is obtained on four steady states. A photograph is shown with the trajectory of the naval combatant in the Seakeeping and Manoeuvring basin. The captive connection between the towing carriage and the model can be seen. A yoke is mounted which allows the model to trim and sink during the tests. But the motions in all other directions are restricted, so that forces and moments can be measured.
Does it work?
So to the million-dollar question, do these results give the same answers as a traditional approach? Figure 3 shows a sample of the results. It compares the results of a test with a continuously changing drift angle, with results obtained using traditional captive drift tests. The right hand figure shows the typical trajectory, while the left hand figure is showing the correspondence of the results. A near perfect match is achieved!
And the future?
The range of applications goes further. Not only a continuously changing drift angle or rate of turn is possible, also a continuously changing combination of rate of turn and drift angle can be done. The results of these measurements are displayed and indeed, using fewer model tests, they provide a complete description of forces and moments for the creation of a mathematical model.
Cable & Pipe Transits Will Never Be the Same A Revolution of Epic Proportions... ...Coming January 2009 www.csd.us.com
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About the Author Frans Quadvlieg is senior project manager Manoeuvring & Seakeeping at MARIN, the Maritime Research Institute Netherlands. MARIN offers simulation, model testing, full-scale measurements and training programmes, to the shipbuilding and offshore industry and governments. Email: f.quadvlieg@marin.nl � www.marin.nl February 2009