On the non-linear forces acting on a floating spar platform in ocean waves

Abstract The exploitation of hydrocarbon reservoirs under the seabed in very deep water requires the use of innovative floating platform configurations. The hydrodynamic interaction of such platforms with ocean waves and the understanding and quantification of the non-linear components of these interactions have been a subject of continuing research. This paper examines these non-linear interaction components for a specific very deep draft spar platform type that is increasingly being used in the oceans. It investigates a formulation for two non-linear force components — called the axial divergence force and the centrifugal force. The latter is invariably neglected in conventional analyses but is shown in this paper to actually be of significant importance. Non-linear equations for wave loading and motion are developed and solved, and the results are used to demonstrate the significance of the above terms. A limited comparison with experimental data is also presented.