Experimental and numerical investigation of the effects of bilge keel geometry on damping characteristics

Large roll amplitudes due to roll motion are undesirable. For this reason, it is important to analyze the roll motion and the roll damping directly related to it in detail. In this thesis, the roll and damping characteristics of bilge keels with different types of geometric shapes on the ship model are investigated experimentally and numerically under different roll amplitudes. From the comparison of the dimensionless roll damping coefficients obtained by experiments and numerical analyses, it is seen that geometrically shaped bilge keels other than the usual plate bilge keel shape have different roll damping coefficients. It has been observed that the shape features of the bilge keels are effective on roll damping. Roll keels with sharper tip ends are found to have higher roll damping coefficients. Based on these results, it has been suggested that the corners and tip ends of the plate should be sharpened in roll keel designs in order to increase the roll damping coefficient. Also, comparisons are made with the Ikeda method, and suggestions are made to improve it.