New Type FDPSO Anti-motion Structure Development And Motion Response Analysis

The roll and pitch motion of the cylinder FDPSO is significantly better than the traditional ship type FPSO,and its advantages in wave resistance and cost are increasingly favored by countries all over the world.However,there are also technical problems that are difficult to control due to the heave motion on the wave,which has become a technical bottleneck for the application and development of the cylinder FDPSO.Therefore,it is of great engineering significance to study the way to increase the heave motion damping of such equipment in order to suppress the large heave motion of the structure.In this paper,a new concept cylinder FDPSO with extended cylinder and antimotion structure is developed for cylinder FDPSO,and three different types of antimotion structures are designed.Using the ratio of 1:77.8 and considering the similarity rate between prototype and model,the FDPSO test model with anti-motion structure was designed and tested in the Ocean Engineering Pool of Tianjin University.The natural motion characteristics and dimensionless damping coefficient of different antimotion structures are tested and compared.The damping characteristics and mechanisms is analyzed and compared.Numerical analysis is done using computational fluid dynamics software FLUENT and damping characteristics is obtained by simulating pool test.The influence of different structural parameters on damping characteristics is analyzed.The numerical simulation and pool test results are verified mutually.The comparison shows that the model test results are consistent with the trend of damping characteristics obtained by numerical simulation.The experimental results and CFD numerical simulation results show that the developed FDPSO anti-motion structure can increase the natural period and heave damping.Heave motion of FDPSO is controlled effectively.Wherein,the gap between the anti-motion structure and the cylinder and the outer edge of the damper structure can significantly increase the structural damping.This finding has guiding significance for FDPSO anti-motion structure design.The outer edge anti-motion structure is selected as the FDPSO anti-motion structure to analyze the hydrodynamic characteristics.Analysis of hydrodynamic characteristics and numerical simulation of motion response in frequency domain and time domain is done.Computational analysis of hydrodynamic loads in different marine environments is carried out,as well as frequency domain and time domain motion response.and compared with cylindrical FDPSO with traditional anti-motion structure.The results show that the anti-motion structure and the extended cylinder of the new cylindrical FDPSO can significantly increase the additional mass/additional moment of inertia of the structure.Thereby the natural period of the structural heave motion is increased,avoiding the concentrated area of the wave energy,and improving the motion response performance.The heave motion of the structure is reduced by about 50%,which indicates that the anti-motion structure developed in this paper has important engineering application value and prospects.