TURBINIA: Turbulent Inflow Innovative Aerodynamics

Objectives

The IEA Wind TCP Task 47 TURBINIA Phase II builds on Phase I, which established international collaboration on detailed aerodynamic wind turbine measurements and analyses of the IEA 15 MW Reference Wind Turbine (RWT). These activities revealed several aerodynamic modelling limitations that become more pronounced for larger turbines. Although Phase I indicated possible improvement paths, the issues could not be fully resolved.

Phase II advances this work by systematically addressing these limitations using the larger IEA 22 MW RWT as designed in the IEA Wind TCP Task 55, REFWIND [4]. A broad range of aerodynamic models will be applied—ranging from industry standard BEM engineering tools to high fidelity computational approaches—to identify the most critical sources of modelling inaccuracies. Studying a turbine of this scale will further clarify how model deficiencies grow with rotor size. The resulting insights will support targeted refinements of existing models and strengthen the aerodynamic tools used in wind turbine design codes, enabling more reliable and efficient turbine designs at the 22 MW scale.

Phase I also demonstrated the value of international collaboration in specialized aerodynamic experiments, but progress was constrained by restrictions on sharing detailed turbine model data. Phase II will explore strategies to make full use of detailed aerodynamic measurements even under such restrictions, with the aim of generating high quality validation data for the community.

The overarching research objective of Phase II is therefore to systematically, understand, and reduce aerodynamic model limitations for next generation large wind turbines—ultimately improving the reliability of design tools for turbines up to 22 MW using the best possible validation data

Participation

Progress, Results, and Impact in 2025

In 2025, the final reporting for Phase I was completed and approved by the ExCo, including publication of the final technical report [1]. In addition, practical lessons learned from conducting aerodynamic experiments were compiled into a publicly available recommendations document [2], intended to support future experimentalists and help prevent unnecessary duplication of effort.

Phase II officially commenced with a kick off meeting in March 2025. During this meeting, representatives from the IEA Wind TCP Task 55 REFWIND kindly provided design information for the 22 MW RWT. Following this, the first simulations of the 22 MW RWT were initiated using a preliminary reference case to ensure consistent input data across participants.

This case considered steady, uniform inflow under both rigid and flexible turbine configurations. The results were processed and showed overall good agreement. Figure 1 illustrates an example: blade torsion caused by flexibility. Even at a low wind speed of 6 m/s, the torsion angle reaches approximately 2°, which in turn affects the aerodynamic performance of the turbine significantly.

The original plan for the 22 MW RWT simulations was to increase model complexity gradually while studying scaling effects by comparing the full-scale turbine to a scaled down version. However, designing a representative scaled model is difficult and therefore an alternative innovative strategy was proposed: instead of scaling the turbine, the wind field and its non-uniformities are scaled. This approach is expected to replicate the modelling challenges that arise due to increasing flow nonuniformity with rotor size, and it remains feasible as long as turbulence is excluded.

This approach led to defining two gust cases with different characteristic diameters: a coherent 284 m gust (matching the rotor size) and an incoherent 142 m gust. Several simulations of these cases have already been completed, and analysis is ongoing. So far, mainly lifting-line results could be provided because there was noComputational Fluid Dynamics input for the 22 MW RWT yet. Since then DTU has invested considerable effort in generating a suitable CAD blade model, after which DLR will create CFD meshes in multiple formats for distribution to partners

In parallel, attention has focused on enabling high quality aerodynamic measurements on large turbines. During Phase I, extensive measurements were carried out, but restrictions on sharing machine data—especially blade geometry—limited collaborative analysis. Since this is a persistent issue in wind energy which exists for a long time already, TURBINIA has defined a long term goal to perform a full scale aerodynamic measurement campaign on a large turbine with fully accessible machine data. The first step was to identify a suitable turbine, which was found in the Catapult Samsung 7 MW turbine in Scotland, for which blade data may be shared—an exceptional allowance. Moreover, some TURBINIA participants already have experience with these blade data through national projects, strengthening confidence in the model information. The cover photo shows a nice example of Infrared flow visualization measurements on this turbine. These measurements were collected during a MEECE project (UK), and the lead scientist has since moved to the TURBINIA participant NTUA.

A preliminary measurement program for the Samsung 7 MW turbine has been drafted. It outlines the desired operating conditions to be tested—including special cases such as extreme yaw misalignment and measurements during turbine vibrations—and the aerodynamic measurement techniques to be deployed, including torsion angle measurements.

Next Steps

• Finalise CFD model input data for the 22 MW RWT
• Run simulations with scaled wind inflow to evaluate how scaling influences aerodynamic deficiencies. Simulations are done with a wide variety of models, including engineering and CFD methods
• Perform an aero elastic benchmark on the 22 MW RWT to assess the various aero elastic modelling approaches.
• Conduct calculations for standstill storm conditions, focusing on potential instabilities for very large rotors—an urgent and difficult industry wide modelling challenge.
• Develop a detailed experimental program for the Samsung 7 MW turbine and seek collaboration with other IEA Wind TCP Tasks for a joint experiment.

References

1. Schepers, J. G., Boorsma, K., Boisard, R., Bangga, G., Jonkman, J., Kelley, C., Branlard, E., Goncalves Pinto, W., Imiela, M., Hach, O., Greco, L., Testa, C., Aryan, N., Madsen, H. A., Croce, A., Cacciola, S., Pirrung, G. R., Sorensen, N., Grinderslev, C., Bernardini, C., Cherubini S., Bianchini A., Papi, F., Pagomonici, L., Braud, C., Honig, L., Theron, J.N., Mohan, K. (2025). Task 47, TURBINIA, Turbulent Inflow Innovative Aerodynamics, Final Technical Report, Phase I, Zenodo. https://doi.org/10.5281/zenodo.17897185
2. Schepers, J. G., Boorsma, K., Deparday, J., Kelley, C., Braud, C., Schaffarczyk,, A. P., Gomez Gonzales, A., Madsen, H. A., & Fritz, E. (2025). Recommendations for performing aerodynamic field measurements on wind turbine rotors. Zenodo. https://doi.org/10.5281/zenodo.19068333
3. K. Boorsma and J.G. Schepers and C. Grinderslev and M. Imiela and H.A. Madsen and G.R. Pirrung and N.N. Sørensen, Differences in Modeling Blade- and Inflow-induced Rotor Aerodynamic non-Uniformities, presented at Wind Energy Science Conference, 24-27 June 2025, Nantes, France
4. F. Zahle et al, Definition of the IEA Wind 22-Megawatt Offshore Reference Wind Turbine, DTU Wind E-0243, 2024