Damping effect of bilge keels with different aspect ratios

The main goal of this research project was to improve the accuracy of numerical seakeeping analysis. Better estimation methods make the evaluation procedures for new vessels more useful. All ship responses are non-linear to some extent, but in many cases when non linearities are small a linear theory yields good predictions. Linear potential theory estimates of motion damping are generally adequate, and reasonable motion predictions are usually obtained. Rolling is an exception to this general rule: roll motions are large, and viscous damping is important. The bilge keel produces additional damping due to normal force on the keel plus pressure variation on the hull surface caused by the presence of the bilge keel. The additional damping caused by bilge keels seemed to be directly proportional to the area of the appendages. A bilge keel of higher aspect ratio was more effective than one with a lower aspect ratio