Verification of computational simulations of the NREL 5 MW rotor with a focus on inboard flow separation

Abstract

ABSTRACTThe aerodynamic characteristics of the NREL 5 MW rotor have been examined using a Reynolds‐averaged Navier–Stokes method, OVERFLOW2. A comprehensive off‐body grid independence study has been performed. A strong dependence on the size of the near‐body wake grid has been found. Rapid diffusion of the wake appears to generate an overprediction of power and thrust. A large, continuous near‐wake grid at a minimum of two rotor diameters downstream of the rotor appears to be necessary for accurate predictions of near‐body forces. The NREL 5 MW rotor demonstrates significant inboard flow separation up to 30% of span. This separation appears to be highly three dimensional, with a significant amount of radial flow increasing the size of the separated region outboard. A simple, continuous full‐chord fence was applied at the maximum chord location of the blade, within the region of separation. This non‐optimized device reduced the boundary‐layer cross‐flow and resulting separation. The fence increased energy capture by nearly 1% at a wind speed of 8 m s−1 and slightly increased blade loading over the length of the span. Copyright © 2011 John Wiley & Sons, Ltd.