A Benchmark of BEM Solvers for Predicting 2nd-Order Hydrodynamic Loads on FOWTs

Floating offshore wind turbines require accurate prediction of low‑frequency second‑order hydrodynamic loads, which strongly influence platform motions and mooring‑system forces. This paper benchmarks four Boundary Element Method solvers: WAMIT, HydroStar, OrcaWave, and Nemoh. The benchmark is performed using the 5 MW DeepCwind and 15 MW VolturnUS‑S semisubmersibles. Input files and meshes are kept the same between solvers to ensure comparability. First‑order added mass, radiation damping, excitation forces and second‑order Quadratic Transfer Funtions are evaluated. Since free‑surface discretization is omitted and only the VolturnUS‑S WAMIT data include free‑surface panels, results are compared mainly at low frequencies. The first‑order results show good agreement. At second-order, the near‑field method either under- or overestimates forces.