Study on the estimation methods of roll damping coefficients using designed excitation device for harmonic roll motion

Abstract

In general, the motions of floating structure are evaluated based on linear potential theory. However, because viscous effects are ignored in the linear potential theory, roll motion through potential theory may be significantly different with actual roll motion, especially at the adjacent of resonance. In this study, the estimation techniques of roll damping using free decay and harmonic excited roll motion were studied. To design roll motion excitation device (RMED), numerical simulations are conducted for the design variables such as moving weight, moving distance and period. The test conditions are also chosen considering the results of numerical simulations. To study the roll damping of 30k LNG-BS(Bunkering Shuttle), experiments using RMED are carried out and results are analyzed by three different analysis methods for determining equivalent roll damping moment studied by Handschel et al.(2015). In addition, free decay model tests were performed, and the roll damping results were compared with the results of RMED. Copyright ？ 2018 by the International Society of Offshore and Polar Engineers (ISOPE)