Full rotor modelling and generalized actuator disc for wind turbine wake investigation

Abstract

This paper purpose a numerical study of the flow downstream a wind turbine erected in the neutral atmospheric boundary layer. A first part consists of unsteady wind flow simulations through a full moving rotor, which lets identifying the vortex generated in the wind turbine wake. The governed equations were solved in two sub-domains (Rotor/Stator) and the moved fluid flow continuity at the domain interface was managed by the Sliding Mesh technique of Turbo-machinery implemented in an open-source ‘Code _Saturne’. However, the unsteady full rotor calculations proved to be extensive and inadequate for optimizing the wind farm layout. Therefore, to achieve a more accessible wake model, the second part consists of the design of a generalized hybrid wake model in which, contrary to the full simulation, an actuator disc ‘with non-zero thicknesses’ has substituted the rotor and was coupled to the Reynolds averaged Navier Stokes equations (RANS) through additional source terms. The modified k-ε was used to model the turbulence developed downstream the rotor. The ability of the proposed model to represent the wake was demonstrated by a series of validations with experimental data and results were in good agreement. Keywords: U-RANS, Sliding Mesh, Generalized actuator volume, CFD