Analyse de l'interaction rotor/nacelle a l'aide du disque actuateur et de la ligne actuatrice.

摘要

This PhD project concerns a numerical simulation of the very near wake of wind turbines.;The analysis is focused on the interaction of the very near wake with the nacelle at the anemometer location. The anemometer located on wind turbine nacelle, essential for production control and the safety of the machine is increasingly used for performance assessment and site calibration. However, in order to construct the power curve, undisturbed wind speed is required. Thus, in order to be able to make use of nacelle anemometry, one needs to know the NTF, the relationship linking free stream wind speed and nacelle wind speed. This relationship must take into consideration all the perturbations that can have a significant impact on the flow near the nacelle. The shape of the nacelle, the turbulence, the tip vortex and the terrain are among the most significant.;The main objective of this work is to develop a CFD method to investigate the rotor/nacelle interaction. The methodology used consists to solve 2D-axisymmetric and 3D Navier-Stokes equations, averaged according to Reynolds decomposition. The flow is considered fully turbulent and two turbulence equations models are used to close the system of equations. The governing equations are solved using finite volume technique implemented in the commercial solver Fluent. Given the proximity of the anemometer to the nacelle wall, the geometry of the nacelle is reproduced as faithfully as possible in the mesh.;First, the shape of the nacelle and its impact on the NTF is investigated. For 3D simulations, special attention is accorded to boundary conditions to reproduce a neutral atmospheric boundary layer and rough ground through an adequate wall law. The rotor is modeled by the actuator disk concept where the average effects of the blades are reported uniformly on a porous surface. Only axial effects are considered from experimental values of the thrust coefficient of the simulated turbine. The use of a 3D approach, when the geometry of the nacelle is complex, and a k-&ohgr; sst turbulence model instead of k-epsilon model, with a standard wall law at the nacelle, improve the prediction of the NTF.;Second, the ground roughness, the hub height variation and the phenomena of speed-up and flow inclination due to escarpments, are analyzed and their impacts on the NTF quantified. The sensitivity of the NTF to the terrain slope is reduced by displacing the position of the anemometer upward the nacelle body.;Finally, the analysis is focused on the representation of the blades effects on the flow. Three various rotor models are used and compared in a turbulent flow where the terrain is neglected. The approach of the actuator disk with uniform loading of the first part is used and compared to a generalized actuator disk where the wake rotation is considered by using the blade element theory. The third approach is the actuator line which is implemented and validated. This technique considers each blade separately as a line where axial and tangential forces are injected in the flow. The rotation of the blades is taken into account by considering the governing equations of the flow in a non-inertial reference frame. The actuator line improves the capture of the vortical structure of the wake and thus allows an enhanced prediction of the NTF compared to the actuator disk approach.