Dynamic Analysis Of Riser Considering Seabed-outflow-floating Body Effect

The main research work of this paper are as follows:(1)Based on the nonlinear seabed riser interaction mechanism,the four processes of the interaction are discussed in detail,and the sensitivity of nonlinear seabed parameters is analyzed;At the same time,the lateral motion and buckling analysis of riser under nonlinear seabed constraints are studied.The buckling problem of riser under high temperature is analyzed by ABAQUS using small parameter perturbation method,and the buckling mode of riser is obtained.Based on the eigenvalue buckling analysis,the analysis step is changed to implicit dynamics,and the lateral buckling shape is obtained by applying temperature load to the opposite tube;At the same time,the overall nonlinear buckling analysis of riser under ocean current is studied.(2)The effects of initial trench and irregular seabed on the mechanical properties of opposite pipes are studied.Orcaflex is used to construct initial trenches with different depths and seabed with extremely irregular profile.The results show that the maximum bending moment and maximum shear force at the contact point of the riser are reduced when there is an initial trench on the seabed of the comparison platform.(3)Study on mechanical characteristics of catenary riser with different external flow patterns.The external flow pattern is: real ocean current,different velocity,shear flow,internal wave flow and different incident angles of incoming current load.The mechanical characteristics include the overall change form,tension,shear and bending moment of SCR.The change trend of bending moment is consistent with that of shear force;Different flow velocity has little effect on the mechanical response of the opposite pipe;Different inflow angles have a great influence on the overall shape of the opposite tube,and the bending moment and maximum tension show a decreasing trend.(4)According to the environmental parameters of a target oilfield,the raos data of the upper floating platform under extreme working conditions are calculated as the boundary conditions to study the influence of the upper floating body excitation on the opposite pipe.The research shows that when the raos of the floating body is loaded,the horizontal direction and lateral direction of the riser show the law of simple harmonic motion.The motion amplitudes of all six degrees of freedom of the floating body are the sum of the amplitudes generated by separately loading surge and heavy.