simulation of transitional flow on a wind turbine airfoil with RANS-based transition model. This is the accepted version of the paper. This version of the publication may differ from the final published version. Permanent repository link: http://openaccess.city.ac.uk/18490/ Link to published version: http://dx.Abstract 7 This paper presents a numerical investigation of transitional flow on the 8 wind turbine airfoil DU91-W2-250 with chord-based Reynolds number Re c = 9 1.0 × 10 6 . The RANS-based transition model using laminar kinetic energy 10 concept, namely the k − k L − ω model, is employed to resolve the boundary 11 layer transition. Some ambiguities for this model are discussed and it is 12 further implemented into OpenFOAM-2.1.1. The k − k L − ω model is first 13 validated through the chosen wind turbine airfoil at the angle of attack (AoA) 14 of 6.24 • against wind tunnel measurement, where lift and drag coefficients, 15 surface pressure distribution and transition location are compared. In order 16 to reveal the transitional flow on the airfoil, the mean boundary layer profiles 17 in three zones, namely the laminar, transitional and fully turbulent regimes, 18 are investigated. Observation of flow at the transition location identifies the 19 laminar separation bubble. The AoA effect on boundary layer transition over 20 wind turbine airfoil is also studied. Increasing the AoA from −3 • to 10 • , the 21 laminar separation bubble moves upstream and reduces in size, which is in 22 close agreement with wind tunnel measurement. 23 particular phenomenon that plays a key role in blade performance is the 31 laminar-turbulence transition (LTT). The LTT is not only crucial in aero-32 dynamic characteristics of wind turbine airfoil, but also in forming laminar 33 separation bubble (LSB). The LSB is very sensitive to flow perturbation and 34 it may burst during the blade rotation. Consequently, it could cause the 35 double-stall phenomenon, which decreases the wind turbine performance sig-36 nificantly [1]. As a result, accurate LTT prediction is of great importance for 37 the aerodynamic design and analysis of wind turbine blade, and it is aimed 38 as the first objective in the present work. 39 Benefiting from the rapid development of flow simulation methodology, 40 transition has been extensively investigated by Computational Fluid Dynam-41 ics (CFD) methods. The Direct Numerical Simulation (DNS) and the Large 42 Eddy Simulation (LES) have delivered promising results in transition simu-43 lations [2][3]. However, the expensive computational hours due to high grid 44 resolution and unsteady simulation are still deterring their widespread appli-45 cation. On the other hand, the Reynolds Averaged Naiver-Stokes (RANS)-46 based turbulent flow modeling is still the workhorse in the aerodynamic re-47 lated simulations, as it is able to provide reasonably good results for attached 48 flow and flow with minor separation under small or moderate requirements of 49 computation resources. Therefore, it would be very useful to a...
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