ECN publication
Improving Airfoil Drag Prediction
Ramanujam, G.; Ozdemir, H.; Hoeijmakers, H.W.M.
Published by: Publication date:
ECN Wind Energy 29-2-2016
ECN report number: Document type:
ECN-M--16-022 Conference Paper
Number of pages: Full text:
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An improved formulation of drag estimation for thick airfoils is presented. Drag under-prediction in XFOIL like viscous-inviscid interaction methods can be quite signi cant for thick airfoils used in wind turbine applications (up to 30% as seen in the present study). The improved drag formulation predicts the drag accurately for airfoils with reasonably small trailing edge thickness. The erivation of drag correction is based on the difference between the actual momentum loss thickness based on free stream velocity and the one based on the velocity at the edge of the boundary layer. The improved formulation is implemented in the most recent version of XFOIL and RFOIL (an aerodynamic design and analysis method based on XFOIL, developed by a consortium of ECN, NLR and TU Delft after ECN acquired the XFOIL code. After 1996, ECN maintained and improved the tool.) and the results are compared with experimental data, results from commercial CFD methods like ANSYS CFX and other methods like DTU-AED EllipSys2D and CENER WMB. The improved version of RFOIL shows good agreement with experimental data.

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