| The ship crane system is widely used and has been installed on many ships and platforms.The ship crane system is always working on water,and under the combined action of wind,wave,flow and hanger,so the six degree of freedom motion of the ship will generally appear.Therefore,the ship crane system design not only consider dynamic load and structural safety suspender mechanism and sling,but also consider the coupled motion of ship crane system.It is necessary to analyze the law of the coupling motion of the ship crane system in the wave,and provide the method and basis for the optimum design of the ship lifting system and the anti pendulum mechanism.For ship crane system,the traditional analysis methods are mostly solved within the framework of linear theory,which is difficult to deal with the large coupling motion of ship crane system in waves,and it is often unidirectional decoupling,ignoring the influence of Hoists on ship motion.The purpose of this paper is to overcome the limitations of the traditional methods and to establish a nonlinear analysis method for the large coupling motion of a ship crane system in the wave.The work of this article mainly includes the following aspects:(1)the multibody dynamics theory is introduced to establish the universal processingmethod for the dynamic coupling of the ship crane multibody system.The methodregards hull and crane as objects that can move six degrees of freedom in space,thuscancelling the linear motion limitation of ship and hoist,and introducing the constraintequation with explicit time constraints,so as to achieve the coupled motion solution andexternal control of ship crane system.(2)the marine hydrodynamic calculation method based on the Green function in the deepwater time domain is optimized.This paper focuses on improving the calculationstrategy of three-dimensional deep water time Green function,and proposes a moregeneral idea of dealing with the skew wall singularity at the free surface,and deducesthe relevant calculation formula.(3)According to the multibody dynamic model of ship crane system and the method ofmarine hydrodynamic calculation based on Green’s function in the deep water timedomain.Combined with the correction method for breach of contract and the differentialstep iteration technique,the calculation process,program frame and program code of thecoupling motion of the ship crane system in the wave are compiled.The code ofthe program is verified by two examples of the vertical harmonic oscillations of thesubmersible ball and the coupling motion of the ship hoist in the hydrostatic water.(4)By using the numerical method and program developed in this paper,the large couplingmotion characteristics of the ship crane system in the plane traveling wave arecalculated.Focus on the analysis of the effect from suspension mass,hull width(displacement),hanging point and sling releasing to hull roll.The coupled motion model of ship crane system established in this paper does not have the limitation of linear assumption,so it is easy to implement constraint default control.Therefore,it is more universal and easy to expand to other multi-body dynamic systems in the future.The model considers the hydrodynamic force as the external force,which ensures the independence of the multi-body coupling calculation module,the hydrodynamic and other external force calculation modules,so the numerical accuracy is higher. |
