The absolute nodal coordinate formulation in the analysis of offshore floating operations Part I: Theory and modeling

Abstract

The analysis of flexible structures is essential to the design and safety in various offshore floating operations. It is challenging to take full considerations of the flexibility and large motion generated by the coupled floating systems under dynamic loads. In this paper series, the absolute nodal coordinate formulation (ANCF) is introduced to model and study the flexible cable in various types of floating operations. ANCF employs coordinate slope instead of angle to enable arbitrary large deformation in flexible cable without considering centrifugal and Coriolis effects. Linear expression of inertial force is derived and the hydrodynamic-structure and soil–structure interactions are also fully considered in dynamic analysis. The theory and modeling of dynamic flexible cable, multibody hydrodynamics and dynamics of floating systems, as well as the numerical calculation process in time domain are derived. The in-house code MiNos dedicated for flexible cable dynamics and program KraKen for multibody floating operation analysis were developed. Dynamic analysis of flexible cable in several floating operation scenarios by ANCF is performed and the in-house code MiNos is validated. The results show the advantage of ANCF for solving flexible structures with fewer elements and good accuracy as well as the robustness, which makes this method feasible and suitable for dynamic cable problems in most situations of floating offshore operations. Part I of this paper series contains the detailed theory and modeling of ANCF and a short review on methodology of hydrodynamics and dynamics of floating systems. Part II focus on the in-house code validation and analysis of flexible cable and mooring line in actual floating operation scenarios.