Abstract
Abstract. As wind turbines grow larger, the use of flatback airfoils has become standard practice for the root region of the blades. Flatback profiles provide higher lift and reduced sensitivity to soiling at significantly higher drag values. A number of flow control devices have been proposed to improve the performance of flatback profiles. In the present study, the flow past a flatback airfoil at a chord Reynolds number of 1.5×106 with and without trailing edge flow control devices is considered. Two different numerical approaches are applied, unsteady Reynolds-Averaged Navier Stokes (RANS) simulations and detached eddy simulations (DES). The computational predictions are compared against wind tunnel measurements to assess the suitability of each method. The effect of each flow control device on the flow is examined based on the DES results on the finer mesh. Results agree well with the experimental findings and show that a newly proposed flap device outperforms traditional solutions for flatback airfoils. In terms of numerical modelling, the more expensive DES approach is more suitable if the wake frequencies are of interest, but the simplest 2D RANS simulations can provide acceptable load predictions.
Highlights
Wind turbine blade design is dominated by structural and transportation requirements in the root region, which results in compromised aerodynamic design
The coarse and fine URANS and improved delayed detached eddy simulation (IDDES) results are included in these comparisons to assess which method is the most suitable for the analysis of the flow under investigation
A computational investigation of the flow past a flatback airfoil with and without trailing edge (TE) control devices has been presented, and the results have been compared with wind tunnel measurements
Summary
Wind turbine blade design is dominated by structural and transportation requirements in the root region, which results in compromised aerodynamic design This leads to the use of thicker airfoils with a blunt trailing edge (TE), i.e. flatback (FB) airfoils, in the inner part of the blade. FB airfoils provide a number of aerodynamic, structural and aeroelastic benefits compared to traditional airfoils of the same thickness They provide higher lift values due to the reduced adverse pressure gradient over the aft part of the suction side. Their performance is insensitive to surface roughness compared to traditional airfoils of similar thickness (Baker et al, 2006). Blades that utilise FB profiles have improved aeroelastic behaviour, as the blunt TE offers increased flap-wise stiffness
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