Unsteady Aerodynamics of Large-Scale Floating Offshore Wind Turbines in Surge Motion

Journal Article · Mon Dec 15 00:00:00 EST 2025 · Renewable Energy

DOI:https://doi.org/10.1016/j.renene.2025.124977· OSTI ID:3015696

Schulz, Christian ^[1]; Bergua, Roger ^[2]; Branlard, Emmanuel ^[3]; Netzband, Stefan ^[1]; Jonkman, Jason ^[2]; Robertson, Amy ^[2]

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1. Hamburg University of Technology
2. National Laboratory of the Rockies, Golden, CO (United States)
3. University of Massachusetts Amherst

Unsteady aerodynamic loads significantly influence the design and wake flow field of floating offshore wind turbines, especially due to wave- or vibration-induced tower top motions triggering various unsteady phenomena. Recent studies show that increasing turbine sizes amplify unsteady aerodynamic effects, as their impact typically grows with rotor diameter. This work combines recent findings from experiments and simulations on model-scale FOWT aerodynamics with new numerical analyses of large-scale rotors, providing a comprehensive understanding of unsteady phenomena occurrence and impact. Numerical analyses of the IEA 15-MW and 22-MW rotors undergoing surge motions characterise the combined influence of motion-induced unsteady phenomena on rotor thrust. Results indicate that unsteady effects can reduce thrust force variations by up to 40% at realistic surge periods. These findings contrast with prior model-scale rotor investigations, attributed to the specialised design of the model rotors. Comparisons between numerical methods - the dynamic blade element momentum method in OpenFAST and free vortex wake modules in panMARE and OpenFAST - reveal persistent differences in thrust predictions under both idealised and realistic conditions. This highlights that classical blade element momentum approaches require enhancement to accurately capture unsteady loads on large-scale floating offshore wind turbines at low wind speeds.

• Research Organization: National Laboratory of the Rockies (NLR), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Wind Energy Technologies Office
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 3015696
• Report Number(s): NLR/JA-5000-95618
• Journal Information: Renewable Energy, Journal Name: Renewable Energy Vol. 260
• Country of Publication: United States
• Language: English

Related Subjects

16 TIDAL AND WAVE POWER
17 WIND ENERGY
floating wind
FOWT
IEA 15-MW
returning wake
surge motion
unsteady aerodynamics