A mathematical model for the dynamic analysis of multi-body floating platforms with complex mechanical constraints

The new methodology based on generalised coordinates for the analysis of floating multi-body systems with nonlinear geometric constraints is developed, and it is demonstrated through numerical application for a hybrid floating wind-wave platform consisting of a floating offshore wind turbine and an articulated wave energy converter that moves a hydraulic piston. The formulation is applied to achieve explicit formulae regarding the dynamic response in a low-dimensional scenario used to verify a post-processing code. The verification considers the nonlinear geometric constraints, hydrodynamic interaction, the dynamics of articulated arms, and the dynamics of hydraulic power take-off systems. An analytical expression for the system's natural frequencies is attained and verified likewise. The results presented in this paper indicate significant improvement in the simulation and analysis of multi-degrees-of-freedom nonlinear hydrodynamic systems, which will ultimately be necessary for designing efficient hybrid floating wind-wave platforms. • A new formulation based on generalised degrees of freedom to simulate floating multi-body systems ispresented. • The model may handle hybrid platforms, aquaculture systems, WEC arrays, etc. • The multi-degrees of freedom coupled dynamics of a hybrid platform is presented in detail. • Results include RAOs, RPOs, natural frequencies, wave power absorption, among others. • The system's natural frequencies are obtained analytically and numerically and are verified by comparing the responses.