On Eddy Making Component of Roll Damping Force on Naked Hull

From the results of the forced roll tests of two-dimensional cylinders having various cross sections, it is found that the eddy making component of roll damping force is proportional to the square of the frequency and the amplitude of roll motion. In other words, the damping coefficient CR of this component for ship-like sections can be regarded to be independent of the period parameter for practical use.An empirical formula for the eddy making component of the roll damping force for two-dimensional sections is deduced from the theoretical considerations on the basis of these experimental results. For three-dimensional ship forms without bilge keels at zero Froude number, the estimated results of the roll damping force which consist of the eddy making, the wave making and the frictional component, are in fairly good agreement with experimental results of ship models.