CFD wind turbines wake assessment in complex topography

•The improved Hybrid method (CFD- actuator disk) is used in the wake study.•The proposed model is applied to define the wake evolution in wind farm.•The topographies effects on the wind flow are thoroughly evaluated.•The soil effects on the near wake and the far wake are assessed.•The results obtained can serve in the optimisation of a wind farm layout. The purpose of this work is to numerically study the wind turbine wake evolution in farm over both complex and flat terrain. The nonlinear, aerodynamic interaction between the rotor wake and the wind farm terrain is modeled using the Hybrid method combining CFD (Computational Fluid dynamics) with the actuator disk model. The rotor defined as a function of the wind speed and the thrust coefficient is applied through a source term added in Navier-Stokes equations within (RANS) decomposition. The framework is structured and resolved via an Open Source Computational fluid dynamics program based on the finite volume method. The interactions between atmospheric upwind boundary layer, downwind wake and ground effects are evaluated considering different wind farm configurations: First, simulations are conducted for flat terrain by varying the wind turbine hub height. The soil effects on the wake evolution are estimated by means of the size length of the eddy areas of low speed recorded behind the rotor. In the second configuration concerning the complex terrain, the proposed hybrid method is adapted to the local wind field significantly disturbed by the topography singularities. The flow field obtained at the hub level is then analyzed and used to define the corresponding actuator disk model. This approach is applied to a small region located in north of Algeria. However, the accuracy and performance of the proposed model to predict the near wake and the far wake are demonstrated by a comparison with wake measurement over flat terrain and are in good agreement with experimental data. Results obtained in all cases gives interesting information involved in wind farm layout.