Estimation of Roll Damping Coefficients for Non-conventional Mid-ship Sections

A correct estimation for roll motion is needed to evaluate the stability and operational efficiency of offshore vessels like FPSO, shuttle tanker and drill ship. The prediction of roll motion is directly affected by roll damping coefficients. In this work, the roll-damping coefficient for non-conventional cross sections is investigated experimentally. Tank tests are carried out for box-type sections with step. In order to validate the present approach, a typical bilge section is considered and our result is compared with published data. The comparison shows a good agreement. For convenience, the roll damping is divided into wave-making component and viscous component. The wave component is determined experimentally by far-field momentum method and compared with numerical results obtained from potential theory. The viscous component is estimated by extracting the wave component from the total damping. It is found that the roll damping of the box-type section with step increases significantly due to the enhanced vortex shedding and that the roll arm is an important parameter for the magnitude of the roll damping