The Research Of Extreme Response Of Ocean Riser Subjected To Nonlinear Wave Loads

In recent years, with technological advancement and the persistent raise of crude oil price human naturally turn their steps to ocean area in deep water. It has been the inevitable trends to make exploiture of oil /gas from offing to blue water. Riser system is the main constituent of ocean infrastructure. The riser is the emphases of petroleum and natural gas industry in independent project of deep water.The first part of this paper clearly introduces wave theory in structure hydrodynamics as foundation and discusses the fundamental equation and derivation in linear wave theory and Stokes' wave theory and finally introduces calculation means of wave force of small and large members in ocean engineering structure. When calculating the small volume wave loads, Morison formulation, the selection of wave theory and the confirmation of drag coefficient and mass coefficient is introduced. When calculating the large volume wave loads, the basic idea and clue of solution in numerical method is mainly introduced.The second part of this paper makes a simplified modeling analysis and ascertains the basic parameter of ABS system, In addition the condition and the environmental loads of the riser are given. The fluid software FLUENT is used to simulate and calculate fluid loads of ABS in the paper. Dynamic response is studied using finite element software ABAQUS/AQUA subjected to the coupling of wave and current. Nonlinear Stokes 5 wave theory is selected to study dynamic time-domain analysis of the riser and get more accurate results .The third part of this paper mainly makes a statistical analysis of extreme value. Probability paper of different distribution types is formed using the chart function in Microsoft Excel. Through comparison and certification, distribution style and function which is better suited for extreme value of bending moment is ascertained. It is very valuable in engineering design.