Application of a 'parallelized coupled Navier-Stokes/Vortex-Panel solver' to the NREL phase VI rotor

A commercially available Navier-Stokes solver, CFX V5.6, is coupled with an in-house developed Vortex-Panel method for the numerical analysis of wind turbines. The Navier-Stokes zone is confined to the near-field around one wind turbine blade, the Vortex-Panel method models the entire vortex sheet of a two-bladed rotor and accounts for the far-field. This coupling methodology reduces both numerical diffusion and computational cost. The coupled solver is parallelized on a cluster of 4 processors. The parallelized coupled solver (PCS) is applied to some distinctive cases of the NREL Phase VI rotor configuration with and without flow separation under steady and no-yaw conditions. Fully turbulent flow is assumed using the k-ε and k-ω turbulence models. Calculations performed with the coupled solver show very good agreement with experiments for fully attached flow. For separated and partially stalled flow, the k-ε model overpredicts rotor power while the k-ω model still shows better agreement with experiments. Discrepancies between the two turbulence models are related to different prediction of the onset of separation. This is revealed by 2D airfoil data of the S809 profile.