The cross-sectional geometry of a diffuser-augmented wind turbine (DAWT) is often that of a cambered airfoil oriented at an angle of attack such that the lift coefficient of the airfoil is maximal. Beyond this angle separation occurs, and the performance decreases. Thus, predicting this transition is important for creating an optimally designed diffuser. The focus of this work is to validate two numerical methods for predicting the onset of separation for highly cambered airfoils. The numerical models investigated are a Reynolds-averaged-Navier-Stokes (RANS) k–ε model and XFOIL. The results were compared to each other and to experimental data. Overall the most accurate model was the k–ε model. Using this model, an optimization of a 2D DAWT was performed which determined the optimal placement of the diffuser. This optimization showed that the optimal angle of attack for the diffuser is much greater than what one would expect based on the maximum lift angle of an airfoil in a free-stream.

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