Frequency Dependence of Bilge Keels

Abstract

The goal of this master's thesis is to inspect the damping generated by bilge keels. Two dimensional cross sections have been modeled both with and without bilge keels and simulated using the computational fluid dynamics software STAR-CCM+. The results have been post-processed in order to identify the damping forces using both a linearized approach and a composite model that divides the damping into wave-making and quadratic components. Simulations without bilge keels was compared with results from existing model experiments. Different bilge keel length and tip shapes was simulated and the difference in generated damping is compared.

The motivation for this study is to get a better understanding of the fluid flow around bilge keels in order to achieve better future designs. The due to the accuracy of the simulations, the results are inconclusive. But the results indicate that bilge keel has a very limited impact on wave-damping and that the accuracy of damping is highly time-step sensitive and bilge keel length has a large impact on the damping provided.