ANALYTICAL SOLUTION ON THE DRAGGED SURGE VIBRATION OF TENSION LEG PLATFORMS (TLPS) WITH WAVE LARGE BODY AND SMALL BODY MULTI-INTERACTIONS

This paper presents a complete analytical solution for the dynamic behavior of both the platform and tethers in the tension-leg platform system when the platform system is subjected to the wave-induced surge motion and the flow-induced drag motion. Along with the analysis the coupling problem of a two-dimensional tension leg platform interacting with a monochromatic linear wave train in an inviscid and incompressible fluid is considered. Both the scattering problem and the radiation problem are combined together with the equation of motion for the platform and the one for the tether to solve for all unknowns in the flow field and for the response of the platform system. The dynamic behavior of the platform and tethers is realized from these solutions. The material property of the tether and the dimensional effect for the platform and the tether are both taken into account in the analytical analysis. The convergence of the solution is verified and the results are further compared with the case without considering the drag effect. It is found that the non-linear drag effect is significant when the draft or the dimension of the platform structure is small and furthermore, the variation of material properties and dimension of tether also affect the dynamic behavior of both the tether and the platform itself.