Study On Prediction Of Roll Damping Of Container Ship And Its Influence On Motion Amplitude

Since the advent of the container ship,its development has become increasingly large-scale,but in order to ensure the seakeeping and load capacity at the same time,it is necessary to increase the length and shape width of the container ship in the design process,it may affect the stability of the ship,such as bow flare and square stern.Therefore,it is of great significance to study how to avoid large roll and accurately predict the amplitude of roll motion.At present,one of the difficulties in the prediction of ship rolling amplitude is how to obtain accurate roll damping,but the roll damping calculated by traditional potential flow theory can not keep precision.At present,the most widely used calculation methods of roll damping coefficient are empirical formula,tank testing and numerical simulation.First of all,a numerical towing tank is established based on the CFD method,and the free roll decay numerical simulation of the C11 container ship is carried out.The roll decay time history plot and rolling elimination curve obtained are in good agreement with the tank testing results,which verifies the accuracy of the numerical simulation of ship model free decay by CFD method.And the free roll decay numerical simulation of 20000 TEU container ship with or without bilge keel is carried out,which provides conditions for predicting the amplitude of its roll motion.Secondly,the roll damping coefficients obtained by Ikeda formula,Nikolayev formula,CFD and tank testing are used to predict the roll motion amplitude of C11 container ship in regular waves.The numerical calculation software is AQWA and the self-made ship three-degrees-of-freedom Matlab program.Compared with the tank testing,it is proved that the roll damping coefficient obtained by the CFD method and the tank testing is more reliable for the prediction of rolling amplitude.Then,the roll motion amplitude of the 20000 TEU container ship in the regular wave is predicted,and the anti-rolling effect after installing the bilge keel is verified.At the same time,the comparison shows that the empirical formula method is no longer suitable for the prediction of roll damping of container ships because of its limitations.Finally,the amplitude of roll motion of C11 container ship in irregular wave is predicted,and compared with tank testing,it is proved that the roll damping coefficient obtained by CFD method and tank testing method is also suitable for the prediction of roll motion amplitude in irregular wave.The prediction of the roll motion amplitude of the 20000 TEU container ship in the irregular wave verifies the anti-rolling effect after installing the bilge keel.