Numerical simulation of transitional flow on a wind turbine airfoil with RANS-based transition model

ABSTRACT

This paper presents a numerical investigation of transitional flow on the wind turbine airfoil DU91-W2-250 with chord-based Reynolds number Re_c = 1.0 × 10⁶. The Reynolds-averaged Navier–Stokes based transition model using laminar kinetic energy concept, namely the k − k_L − ω model, is employed to resolve the boundary layer transition. Some ambiguities for this model are discussed and it is further implemented into OpenFOAM-2.1.1. The k − k_L − ω model is first validated through the chosen wind turbine airfoil at the angle of attack (AoA) of 6.24° against wind tunnel measurement, where lift and drag coefficients, surface pressure distribution and transition location are compared. In order to reveal the transitional flow on the airfoil, the mean boundary layer profiles in three zones, namely the laminar, transitional and fully turbulent regimes, are investigated. Observation of flow at the transition location identifies the laminar separation bubble. The AoA effect on boundary layer transition over wind turbine airfoil is also studied. Increasing the AoA from −3° to 10°, the laminar separation bubble moves upstream and reduces in size, which is in close agreement with wind tunnel measurement.

KEYWORDS:

• Boundary layer transition
• laminar separation bubble
• wind turbine aerodynamics
• RANS modelling
• laminar kinetic energy

Acknowledgements

The authors would like to acknowledge Ir. Nando Timmers from TU Delft for the discussion on the experiment. Meanwhile, the financial support of China Scholarship Council is also gratefully acknowledged. Finally, we acknowledge the OpenFOAM community and code developers.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. ω = sqrt(k)/l

Additional information

Funding

China Scholarship Council