Vol 76 No 4 76406

Abstract

In this paper, the scale effects on a container ship’s roll motion are investigated by numerical approach. The accuracy of the numerical method is verified by comparing numerical results with experimental data through a grid sensitivity study. The roll decay tests of the vessel at full-scale and model-scale at various forward speeds are simulated, and it is noticed that scale effects on roll motion occur when forward speed is nil or low. To further understand the impacts of scale on damping components, forced roll tests with different forward speeds are simulated, roll damping coefficients are determined, the flow field created by roll motion and forward speed near bilge keels is observed. It is found that the scale effects affect both the frictional and bilge keel damping components. At low Froude number, the difference of the relative velocity distributions for the height (or breadth) of bilge keels between model (model-scale) and ship (full-scale) is proved as the cause of the scale effects on the bilge keel component.