Planar multibody dynamics of floating Y-method installation system and the lowering of subsea equipment based on finite element modeling

The subsea equipment installation is a complex operation that demands a precise and reliable approach to avoid the accidental losses of lives and equipment damage. The multibody installation system is overwhelmed with the dynamic behavior and responses of the system, which signifies the importance of analysis of the Multibody Dynamic System (MBDS). The modeling of MBDS is challenging and complicated due to the interconnectivity and nonlinearity assigned to them. In this paper, the planar dynamics of a floating multibody system are attained by employing two tugboats and a payload with a contextual offshore installation scenario to be applied in a water depth of over 1500 m. The lifting operation is nine degrees of freedom (9-DOF) multibody model done with the help of two strands and three bodies having 3-DOF each. The coupled equations of motion are established by deploying the Velocity Transformation Technique. The hydrodynamic and two-strand forces are simplified as linear, while the hydrostatic and mooring forces are treated as nonlinear external loads. The numerical solution to the equations for the MBDS is obtained from the Runge Kutta Method of Fourth-Order. Furthermore, the Finite Element Modeling approach discusses the installation operation using Y-method. The results of the proposed numerical model are validated by comparing it with the numerical simulation from OrcaFlex, and the results from both models are found to be in good agreement. The findings of this study will help improve the safe and stable installation of deep-water multibody structures.