Results

The NOSTRUM project has been completed. On 13 February 2026, the final workshop was held at Sapienza University of Rome, bringing together the full research team to present the outcomes of two years of work on the design and optimization of floating offshore wind turbines for the Mediterranean Sea. The project was funded under the Italian PNRR programme (MUR/NextGenerationEU, PRIN) and delivered a comprehensive set of scientific and technical results.

Technical Summary of Results

Metocean characterization and design conditions

Mediterranean wind and wave conditions were characterized to define design-relevant environments for floating wind turbines. Drawing on ERA5 reanalysis data from 2001 to 2022, the team established the complete set of design environmental conditions prescribed by IEC 61400-3 – namely the Normal, Severe, and Extreme Sea States – for both fatigue and ultimate load cases. IEC 61400-1 Class III was identified as the reference condition, and three representative sites (Gulf of Lion, Montalto di Castro, Sicily) were selected. The semi-closed morphology of the Mediterranean, together with its limited fetch and shorter wave periods, gives rise to conditions markedly different from those of the North Sea. Joint wind–wave statistics were derived and translated into probabilistic design load cases (DLCs).

Resources available at: https://doi.org/10.5281/zenodo.18195507

Rotor and system design optimization

A Mediterranean-adapted turbine design was developed starting from a large-scale reference model. A solver-independent, surrogate-based optimization framework was built, coupling high-fidelity CFD (ANSYS Fluent and OpenFOAM, 2D RANS) with a Stochastic Radial Basis Function (SRBF) surrogate and adaptive sampling, while keeping surrogate errors below 1–2%. Rotor geometries (chord and twist) and a dedicated airfoil database were optimized for low-to-moderate wind regimes, achieving AEP increases up to ~20%. Optimization of the thick inboard airfoils (FFA-W3-211 and FFA-W3-241) yielded lift-to-drag improvements of up to 6% across the relevant range of Reynolds numbers. The impact on structural loads was quantified within a fully coupled aero-hydro-servo-elastic simulation framework.

Resources available at: https://doi.org/10.5281/zenodo.18620593

CFD airfoil dataset: https://doi.org/10.5281/zenodo.18960850

Software tool: https://github.com/DIMA-SEAFM-Lab/NOSTRUM-SurrogateModel4BladeDesign.git

Aerodynamic enhancement at low wind speeds

Fixed slotted trailing-edge flap configurations were investigated to improve blade performance at low wind speeds. High-fidelity CFD analyses showed increased lift in thick airfoil regions, improved efficiency in the pre-stall regime, and a shift of optimal performance toward lower angles of attack, with clearly identified aerodynamic trade-offs. A parametric CFD database showed that the optimal flap geometry increases the lift coefficient by up to 36% at moderate angles of attack, with acceptable drag penalties – highlighting strong potential for enhanced energy capture during partial-load operation.

Mediterranean reference wind turbine (NOSTRUM-270)

A new open-access reference turbine (NOSTRUM-270) was developed for Mediterranean offshore applications – a 15 MW-class floating offshore turbine with a 270 m rotor, designed specifically for Mediterranean conditions. It integrates aerodynamic optimization, structural adaptation, and system-level validation, incorporating the custom NOSTRUM-W-21 and NOSTRUM-W-24 airfoils, CFD-validated polars, and a fully coupled OpenFAST model featuring the UMaine VolturnUS-S spar platform, MoorDyn mooring, and site-representative irregular wave loading. The design shows consistent AEP improvements (≈7–10%) while maintaining stable aeroelastic response under DLC conditions.

Model available at: https://github.com/DIMA-SEAFM-Lab/NOSTRUM-270-RWT.git

Performance results from DLC 1.1 aeroelastic simulations are summarized below:

List of Produced Scientific Papers

The project's findings have been disseminated through high-impact, open-access conference and journal papers. In particular, the most significant journal ones are reported below:

1. Cardamone, R., Broglia, R., Papi, F., Rispoli, F., Corsini, A., Bianchini, B., Castorrini, A. Aerodynamic design of wind turbine blades using multi-fidelity analysis and surrogate models, Proceedings of the 16th European Turbomachinery Conference, Turbomachinery Fluid Dynamics and Thermodynamics, ETC16 – 24–28 March 2025 – Hannover, Germany.
2. Cardamone, R., Broglia, R., Papi, F., Rispoli, F., Corsini, A., Bianchini, A., & Castorrini, A. (2025). Aerodynamic design of wind turbine blades using multi-fidelity analysis and surrogate models. International Journal of Turbomachinery, Propulsion and Power, 10(3), 16.
3. Cardamone, R., Morici, V., Broglia, R., Corsini, A., Bianchini, A., Castorrini, A. (2026). Aerodynamic Improvements of Thick Offshore Wind Turbine Airfoils Using Slotted Trailing Edge Flap: A Parametric CFD Study, ASME 2026 Turbomachinery Technical Conference & Exposition (GT2026).

Open-Access Resources

All models, codes, datasets, and design tools produced by the NOSTRUM project are freely available to the scientific community:

• GitHub (source code, optimization tools, OpenFAST models): https://github.com/DIMA-SEAFM-Lab
• Zenodo (turbine definition files, datasets, DLC results): https://zenodo.org/communities/nostrum-project
• LinkedIn: linkedin.com/in/nostrum-project