CFD modeling of wind flows in complex terrain taking into account the atmospheric stability

Computational Fluid Dynamics (CFD) models are more and more frequently used for wind resource assessment, especially in complex terrain. One of the problems is still to take into account properly the thermal stability. In this study, CFD simulations have been compared with in-situ measurements on a complex site, with and without taking into account stability. A detailed analysis is provided on a stable situation. The measurement has been obtained during a campaign organized by EDF-R&D and EDF-Energies Nouvelles which took place in the south of France and lasted about one year. Three masts (one 80 m height and two 50 m height) were equipped with cup anemometers and vanes. The 80 m mast was also equipped with 4 sonic anemometers and 4 temperature sensors. One sodar provided measurements up to about 600 m. The open source CFD model Code-Saturne was used to solve numerically the 3D Reynolds Averaged Navier Stokes equations (RANS) using the turbulence model "standard k-ϵ". The used mesh had 3.3 million cells. A mesoscale model prediction of wind regime provided the boundary conditions to the CFD model. The thermal stability is accounted for using potential temperature. The first results show an improvement in the numerical simulation if the thermal stratification is taken into account. The atmospheric stability should be taken into account to assess accurately wind resource. However, it can be difficult to define an appropriate methodology to impose the initial and boundary conditions for the thermal variable in complex terrain.