Intercomparison between URANS and LES simulations of the turbulent flow around the NTNU T1 wind turbine, using OpenFOAM with the Actuator Disc Model

Reliable open-source computational fluid dynamics (CFD) tools are essential for optimizing wind turbine aerodynamics and understanding complex wake interactions. This study presents a comparative analysis between Unsteady Reynolds-Averaged Navier–Stokes (URANS) and Large Eddy Simulation (LES) for predicting the turbulent wake of the NTNU T1 reference turbine. To address editorial requirements for high-fidelity quantitative validation, this research adopts the NTNU Blind Test 1 experimental benchmark Re»10^5.

The numerical framework, implemented in OpenFOAM, utilizes the Actuator Disc Model (ADM). To ensure physical consistency, the model explicitly incorporates the nacelle’s drag and employs experimental blade polars (S826) to accurately capture laminar separation bubble effects. Preliminary validation results demonstrate excellent agreement with experimental data, yielding a power coefficient CP of 0.45 and a thrust coefficient CT of 0.82.

Qualitative results contrast the ability of LES to resolve helical vortex structures and wake meandering against the numerical diffusion characteristic of the URANS approach. Quantitatively, the intercomparison focuses on velocity deficits and turbulence intensity recovery at 3D and 5D downstream locations. This study provides a validated workflow that balances physical fidelity and computational efficiency for offshore wind applications.

References

1- Krogstad, Per-Åge., Eriksen, P. E., & Melheim and J. A. (2011). “Blind test” workshop calculations for a model wind turbine (Technical report). Norwegian University of Science and Technology (NTNU), Department of Energy and Process Engineering.