Time Domain Coupling Motion Analysis Of S-lay Crane Vessel

With the increasing demands for oil and gas driven by the large amout of consumption from both industry and human life,the importance of exploiting oil and gas under ocean is gaining ever more attention nowadays,especially when the resource inland is becoming barely available year after year.Therefore,in order to meet the increasing demands,the offshore industry steps from shallow water to deep water which means that the crane-lay vessel plays a more significant role in offshore engineering as the main tool for offshore pipe-lay and offshore lifting operation.However,the horrible ocean environment raises the requirements for offshore pipe-lay and lifting opreration to a higher level.The lack of design and operation experience of offshore pipe-lay and lifting in deep ocean has been dramatically slowing down the development of offshore industry in China.As a result,in order to provide reference for design and operation,it is necessary to conduct analysis on the motion and loads of the crane-lay vessel in deep water.Among all kinds of pipe installation menthods,the S-lay method stands out as the most widely used and common one because of its availability for varieties of water depths and relatively fast installation speed.In this thesis,a deep water S-lay Crane Vessel is chosen as the object.Model tests,frequency domain analysis and time domain coupling analysis was conducted on both the 3000 m S-lay installation and 4000 t lifting operation.The researches in this thesis can be categorized into the following parts: motion performance comparison between model tests and numerical simulation,motion performance comparison between coupling model and uncoupling model,pipe's and lifting module's influence on vessel motin,and the newly designed vessel's improvement over the prototype.Model tests on the crane-lay vessel.The model was made according to the figure of hull lines and and the talbe of offsets.Model tests of both 3000 m S-lay installation and 4000 t lifrting operation were conducted at the multi-functional deep-water basin in Harbin Engineering University.As soon as the wave was generated in the basin,a Non-contact Optical 6 DOF Tracking System,manufactured by Qualisys,was used to measure the 6 DOF motions of the model.The Response Amplitude Operator(RAO)can be gotten after post-process.Frequency domain analysis on the crane-lay vessel.Based on the 3-D diffraction-radiation potential flow theory,the hydrodynamic coefficients,such as added mass,damping,and RAO,of the vessel during both 3000 m S-lay installation and 4000 t lifrting operation can be calculated.On on hand,these hydrodynamic coefficients can be used as input parameters for the time domain analysis.For another,the calculated RAO was compared with that obtained from model tests to verify the validity of the numerical models.The second order wave exciting forces for the two conditions mentioned above were calculated using the far-field equation to provide reference for the dynamic positioning system in time domain simulation.Time domain analysis on the crane-lay vessel.During the reallife operation of a crance-lay vessel,the installation system or the lifting system can be seen as a complex system which is comprised of multiple interactive components.A comparison between coupling model and uncoupling model was carried out.The results showed that the simulation of coupling model provide better accuracy.Based on the coupling method,analysis on the pipe's and the lifring module's influence on the vessel is conducted.Futhermore,the newly designed vessel's improvement over the prototype is analyzed based on the coupling model.