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. Modern wind-turbine airfoil design requires robust performance predictions forvarying thicknesses, shapes, and appropriate Reynolds numbers. The airfoils ofcurrent large offshore wind turbines operate with chord-based Reynolds numbersin the range of 3–15 million. Turbulence transition in the airfoil boundarylayer is known to play an important role in the aerodynamics of these airfoilsnear the design operating point. While the lack of prediction of lift stallthrough Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics(CFD) is well known, airfoil design using CFD requires the accurate predictionof the glide ratio (L/D) in the linear portion of the lift polar. Theprediction of the drag bucket and the glide ratio is greatly affected by thechoice of the transition model in RANS CFD of airfoils. We present theperformance of two existing local correlation-based transitionmodels – one-equation model (γ− SA) and two-equation model(γ-Reθt‾- SA) coupled with the Spalart–Allmaras (SA)RANS turbulence model – for offshore wind-turbine airfoils operatingat a high Reynolds number. We compare the predictions of the two transitionmodels with available experimental and CFD data in the literature in theReynolds number range of 3–15 million including the AVATAR projectmeasurements of the DU00-W-212 airfoil. Both transition models predict alarger L/D compared to fully turbulent results at all Reynolds numbers. Thetwo models exhibit similar behavior at Reynolds numbers around 3 million. However, at higher Reynolds numbers, the one-equation model fails topredict the natural transition behavior due to early transition onset. Thetwo-equation transition model predicts the aerodynamic coefficients forairfoils of various thickness at higher Reynolds numbers up to 15 millionmore accurately compared to the one-equation model. As a result, thetwo-equation model predictions are more comparable to the predictions fromeN transition model.However, a limitation of this model is observed at very high Reynolds numbersof around 12–15 million where the predictions are very sensitive to theinflow turbulent intensity. The combination of the two-equation transitionmodel coupled with the Spalart–Allmaras (SA) RANS turbulence model is agood method for performance prediction of modern wind-turbine airfoilsusing CFD.

Local correlation-based transition models for high-Reynolds-number wind-turbine airfoils