Investigation On Hydrodynamics Of Spar Platform In Deep Water

The motion response of the Spar platform is investigated in this paper. A spar platform is such a compliant floating structure used for deep water for the drilling, production, processing and storage of ocean deposits. The structural character and recently development of Spar platform is presented in detail in this paper. Facing the urgent requirement of deep ocean exploitation, Spar platform has become one of most popular platforms for world deepwater oil and gas exploitation.In this paper, based on the 3 dimensional diffraction and radiation theory of potential flow, the author proposes the mathematical model of platform, establishes the boundary integral equation, and uses the suitable frequency-domain oscillating source Green function to calculate the hydrodynamics coefficients of a floating-body. This article adopts the new model based on the finite element method to analyze the mooring system. In the static analysis, wave forces, current forces and gravity are taken into account and distributed to the nodes through certain rules. The non-linear equations are solved by the Newton iteration methods, thus the displacement and the tension vectors are obtained. In the dynamic analysis, the inertia forces and the added water mass are considered in calculating the forces on the elements of mooring line. Considering that on each moment the forces on element are on balance, the author establishes the motion equation of mooring line. Through the couple analysis of the mooring line and the floating body motion systems, motion equations of moored buoy are solved.The calculation is carried out on the real sea state. The motion response of surge, pitch and heave of the platform in first order motions and the results of spectrum analysis are obtained. The numerical results are in good agreement with the experiment values, which shows that the precision is allowable in the engineering practices. Finally, the motion responses are further analyzed with the variation of the radius of the spar and the position of mooring point.