| The ocean contains rich oil and gas resources.The lazy-wave riser is an important equipment for the development of the offshore oil and gas exploration.The laying and installation of the lazy-wave riser is the crucial aspect in the construction of the riser system.Due to the influence of complex and changeable marine environment and laying parameters,the mechanical properties of lazy-wave riser are changed in the process of laying and installation.Therefore,the mechanical analysis of lazy-wave riser installation process has important theoretical significance and practical applications.The main research contents of this thesis include:(1)The mechanical model of lazy-wave riser installation process is established based on the principle of virtual work.The finite difference and Newton-Raphson are used to discretize and iteratively solve the mechanical model respectively,and the mechanical model solution and data processing program are written in MATLAB.The accuracy and rationality of the program are verified by comparing the calculation results of the program with Orcaflex.(2)The influence of key parameters of lazy-wave riser on its mechanical response during installation is analyzed.The key parameters include buoyancy factor,buoyancy length,buoyancy starting position,current velocity and current direction.The mechanical response of riser mainly includes the shape,bending moment,shear force and tension of riser.The results show that the increase of buoyancy factor and buoyancy length can reduce the top tension,and the change of buoyancy starting position has little effect on the bending moment of riser,However,it will affect the top tension.Downstream installation has little effect on the change of riser shape,but it will increase the top tension of riser.During countercurrent installation,the shape of riser changes greatly,but the top tension will decrease.(3)The finite element software Orcaflex is used to analyze the dynamic response of lazy-wave riser installation process.The mechanical response of lazy-wave riser under level I to level V waves and the combination of waves and currents are studied respectively.The installation strength analysis and strength check of lazy-wave risers are carried out based on riser specifications API RP 2RD and DNV OS F101.The results show that when there is no current and only the wave acts alone,when the wave angle is 90°,the effective tension,maximum bending stress and maximum equivalent stress of the riser are the largest,and the location of maximum bending stress and maximum equivalent stress is located at the float section.When the combination of wave and current is that the wave angle is 90°and the current direction is 0°,the top tension of the riser is the largest.When the wave angle is 90°and the current direction is 180°,the maximum bending stress and maximum equivalent stress of the riser are the largest.(4)The mechanical model is combined with virtual reality technology,the marine riser mechanical analysis software and interactive virtual simulation system are developed based on Unity 3D platform,the system realizes the data interactive transmission function between Unity 3D and MATLAB,and visually displays the calculation results of MATLAB in the system.The system includes three functional modules: model base,mechanical analysis,scene layout and roaming.The system realizes the marine riser mechanical analysis,rapid construction of marine oil and gas production layout scene and visual roaming. |
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