A fully coupled time domain model capturing nonlinear dynamics of float-over deck installation

This study develops an efficient constant parameter time-domain model (CPTDM) to investigate the nonlinear dynamics associated with float-over installations that are comprised of rigid body motions, impact-absorbing systems, and mooring dynamics. The Cummins equation is used to deal with the wave-induced floating body's motions. To improve the calculation efficiency in time domain, state-space models are adopted. Bilinear spring-damper systems are introduced in the model to consider the limited load capacities of impact-absorbing systems. An open-sourced mooring system dynamics modeler, MoorDyn, is coupled to the CPTDM in a coupling approach. The developed CPTDM is validated against a standard hydrodynamic analysis package, AQWA, showing satisfactory agreements in general. The most striking advance of the CPTDM developed here is that it could appropriately capture the nonlinear physics relevant to float-over operations. Further applications of the CPTDM could include walk-to-work operations for offshore wind maintenance.