In the present thesis the wake flow behind wind turbines is analyzed numerically using large-eddy simulations. The wind turbine rotors are modeled by using either the actuator disc method or the actuator line method in which the blades are represented by body forces computed with airfoil data. Using these models, the boundary layers of the turbine blades are not resolved and most of the computa...

The actuator disc-RANS model has widely been used in wind and tidal energy to predict the wake of a horizontal axis turbine. The model is appropriate where large-scale effects of the turbine on a flow are of interest, for example, when considering environmental impacts, or arrays of devices. The accuracy of the model for modelling the wake of tidal stream turbines has not been demonstrated, and...

If the effects of fluid rotation are neglected, one-dimensional theory for a single actuator disc gives a maximum power coefficient of 16/27. This is the usual Betz limit for the power of horizontal-axis wind turbines. Tandem discs are a more appropriate representation for a vertical-axis, Darrieum, wind turbine and give more accurate predictions of turbine performance when used in conjunction ...

The aerodynamic performance of freely flying birds is inherently difficult to measure directly without interfering with their natural flight. Many current methods thus combine kinematic parameters derived from high-speed video with theoretical force and power models. However, these methods often require manual tracking of points in each frame of a video to obtain kinematic data. This project ut...

This work aims at introducing model methodology and numerical studies related to a Lagrangian stochastic approach applied to the computation of the wind circulation around mills. We adapt the Lagrangian stochastic downscaling method that we have introduced in [3] and [4] to the atmospheric boundary layer and we introduce here a Lagrangian version of the actuator disc methods to take account of ...

The Betz theory expresses that no horizontal axis wind turbine can extract more than 16/27 (59.3%) of the kinetic energy of the wind. The factor 16/27 (0.593) is known as the Betz limit. Horizontal Axis wind turbine designers try to improve the power performance to reach the Betz limit. Modern operational wind turbines achieve at peak 75% to 80% of the Betz limit. In 1919, Albert Betz used an a...