Computational Fluid Dynamics of Flatback Airfoils for Wind Turbine Applications

Abstract

This paper presents results from a computational study of the aerodynamic performance of various atbac k airfoils designed for wind turbines. Multiple turbulence modelings methods are used for the aerodynamic modeling: Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations, Detached-Eddy Simulations (DES) and a Hybrid RANS/Large-Eddy Simulations (HRLES) method based on the k{! RANS model and k{equation sub-grid LES model. All simulations make use of overset structured grids. Turbulence modeling and grid resolution studies show that both DES and HRLES methods capture the expected qualitative turbulent behavior such as cross o w in the separated wake regions of the o w. Quantitative results include the predicted lift and drag over a range of angles-of-attack using URANS. It is shown that the atbac k airfoil design results in a substantially increased lift compared to traditional thin trailing edge airfoils. Flow-eld results from the two advanced modeling methods, DES and HRLES, are qualitatively compared and analyzed. It is observed that the DES method does not predict the transition and separation along the airfoil while the HRLES method does. This limitation is explained and the eects on the aerodynamic forces is also given.