Wireless

WHY

The offshore wind industry is rapidly evolving, driven by larger turbines and expansion into deeper, more energetic marine environments. Modern turbines have grown from a few megawatts to 15 MW and beyond, increasing their size, mass, and flexibility. This significantly affects the dynamic behaviour of monopile-based support structures and their interaction with waves. As turbine size increases, the first natural period increases, bringing it closer to the energy range of storm waves in regions such as the North Sea. Under these conditions, wave groups can excite the structure and induce resonance, especially in idling conditions when aerodynamic damping is low. Although resonance is not new in offshore engineering, its occurrence in high-energy storm conditions is becoming more critical and may increasingly govern turbine design.

This marks a fundamental shift in design conditions. Earlier turbines experienced resonance mainly outside energetic sea states, whereas modern turbines are exposed to resonance both during operation and storms. Consequently, wave-induced loads, particularly from wave groups containing energy near the resonant period, can significantly amplify structural responses and contribute to fatigue loading. Steep and breaking waves also still need to be taken into account for their contribution to ultimate loads. This increases complexity and uncertainty in the design process.

Current design standards are not fully adapted to this regime. They provide limited guidance for handling resonance under realistic sea states and operational conditions, leading engineers to rely on simplified assumptions or conservative margins. This can increase costs or leave uncertainties insufficiently addressed, highlighting the need for improved modelling approaches. Previous initiatives, such as the WIFI and Runwave projects, have improved the understanding of wave-induced loads, including those from steep and breaking waves. However, they did not fully address larger turbines and more complex sea states, which are now relevant to the industry.

Therefore, innovation is essential. Future offshore wind development requires advanced experiments, better numerical models, and more representative datasets to ensure reliable and cost-effective turbine design.

WHAT

The Wireless project is designed to extend and build upon the work carried out in the Runwave Project by addressing key limitations associated with the use of idealised conditions. In Runwave, laboratory experiments and numerical simulations were performed to validate existing methodologies for quantifying the impact of resonant waves on offshore wind turbine generators. However, the use of simplified wave conditions and limited turbine configurations restricts the direct applicability of these findings to real design scenarios.

To overcome this limitation, Wireless significantly broadens the experimental and numerical scope by considering a more representative range of environmental and operational conditions. The project focuses on generating a comprehensive dataset that captures the behaviour of large-scale monopile-based wind turbines under realistic sea states and turbine operating modes. This dataset will serve as a basis for validating numerical models and improving confidence in their ability to predict resonant responses under practical design conditions.

The project is structured into four main work packages. In the first phase (WP1), a detailed test matrix will be defined through collaboration between project partners. This matrix will include a wide variety of conditions, such as short-crested seas, bimodal wave systems combining wind-sea and swell, and multiple realisations of individual sea states to quantify variability. In addition, variations in turbine operation, including damping effects related to wind speed and turbine orientation, will be accounted for. The existing 15 MW and 22 MW scale models from Runwave will be reused and adapted where necessary.

In WP2, an extensive series of high-fidelity laboratory experiments will be conducted at MARIN. These tests will expose the scale models to the defined wave and operating conditions, with a focus on capturing fatigue-relevant loads and response mechanisms. Particular attention will be given to accurately modelling wind-induced effects using either physical wind-generation systems or controlled damping devices.WP3 focuses on validating numerical models using experimental data. Both high-fidelity and efficient low-fidelity models will be assessed for their ability to reproduce the observed resonant behaviour. At the same time, additional simulations will extend the analysis beyond the tested conditions.

Finally, WP4 will synthesise the findings into guidance for industry, outlining the capabilities and limitations of current modelling approaches and identifying priorities for future development.

EXPECTED RESULTS

The Wireless project is expected to provide a better understanding of wave-induced resonance effects on monopile-based offshore wind turbines under realistic operating conditions. Extending the Runwave Project will produce an expanded experimental dataset capturing structural responses across a wider range of wave climates and turbine states, representative of practical design conditions.

Key results will include high-quality laboratory measurements combined with validated numerical simulations, enabling a reliable assessment of how well existing models predict resonant responses in realistic seas. The project will identify the strengths and limitations of current modelling approaches under complex conditions, including short-crested and bimodal waves, as well as varying turbine operation modes.

Another outcome will be a validated framework for analysing fatigue loading due to wave-induced resonance, supporting improved estimates of accumulated fatigue damage over a turbine’s lifetime using more representative environmental data. Although the project does not aim to develop new design methods, it will provide a strong foundation for future improvements by highlighting key uncertainties and modelling gaps. Finally, a summary report and guidance note will be delivered to support industry stakeholders in selecting suitable modelling approaches and defining next steps for engineering practice and research.