Numerical Modeling Framework for Wind Turbine Analysis & Atmospheric Boundary Layer Interaction

Abstract

Prevailing atmospheric conditions can have a significant impact on the performance of large mega-watt wind turbines. A purely experimental evaluation of this impact is currently not possible and hence numerical techniques have been employed in this work. With the focus on aerodynamic performance of wind turbine, an attempt is made to realize the following objectives: (a) To evaluate the predictive capabilities of fully resolved Sliding Mesh Interface (SMI) transient simulations around the wind turbine against the steady state Multiple Reference Frame (MRF) simulations (b) To investigate the performance of the wind turbine subjected to uniform inlet profiles against atmospheric boundary layer profiles. (c) To study the effect of atmospheric stability on wind turbine performance. The methods are validated first and then implemented on a national renewable energy laboratory 5 MW reference wind turbine model for the aerodynamic study. Highly uneven and irregular wake profiles are seen with variation in input conditions(TKE). Uneven distribution of flow velocity in the lateral direction enhances the momentum transfer with in the shear layers and contributes positively towards the wake recovery. It is also found that in unstable stratified conditions, the positive buoyancy flux at the surface creates thermal instabilities which enhances the turbulent kinetic energy and the turbulent mixing, and helps the wake to recover faster.