Finite element method for wet-towing transportation of suction pile-based offshore wind turbines

With the increasing demand for sustainable energy, offshore wind turbines (OWTs) have emerged as a critical solution. However, their transportation and installation still pose environmental and logistical challenges, especially for the structural analysis and design that ensures this phase of safety. This study investigates the feasibility of using a wet-towing method, leveraging the inherent buoyancy of suction pile-based foundations, to transport OWT support structures. Then, a nonlinear finite-element method (FEM) was developed to unify trapped-air compressibility with hydrostatic restoring in a single equilibrium path-tracking framework, embedding a consistent linearization of the air-spring stiffness directly in the solver. The method is validated against analytical benchmarks and quasi-static basin tests, showing close agreement in load–submergence response. A case study on the wet-towing of a 15-MW OWT with triple-suction piles demonstrates the practical application of the method that safe transportation is achievable under moderate sea states. By enabling early identification of tow-ready configurations and reducing reliance on heavy-lift operations, the approach can shorten weather windows and vessel days, thereby lowering transport and installation costs. The proposed FEM provides a reliable tool for assessing and optimizing the wet-towing of large OWT structures, reducing offshore construction risks and costs.