Numerical study of the aerodynamics and wakes of VAWTs in complex situations : double-rotor and offshore single rotor

The present work concerns a complete numerical study of the vertical-axis wind turbines in two complex configurations: the double-rotor and the floating offshore single rotor. Two numerical tools are used for this purpose: an aerodynamic solver, being a lifting-line enabled vortex particle-mesh (VPM) method, and a symbolic generator of the equations of motion to solve multibody systems. The two main objectives for this Master's thesis are : 1) Elucidating the gains offered by closely-spaced vertical-axis wind turbines through the analysis of their aerodynamics and wakes. 2) Clarifying the influence of the hydrodynamic loads of a semi-submersible platform on the performances of a vertical-axis wind turbine. This document is hence articulated as follows. First, the underlying equations and methodology of the used numerical tools are presented. Secondly, a two-dimensional study of the aerodynamics and wakes of the different double-rotor configurations is performed. The effect of turbines spacing and wind direction is assessed with an emphasis on the counter-up configuration. Then, the aforementioned study is extended to the three-dimensions. An analysis on the performances and wakes is achieved while focusing on 3D effects. Besides, the influence of the number of blades and the aspect ratio is investigated. Finally, a full floating platform and its VAWT are implemented in the symbolic software. An hydrodynamic loads model, an anchor model and a statistical description of ocean waves are incorporated in the solvers to study the influence of the wave's motion and loads on the performances and wakes of a full-scale turbine. Conclusions as well as perspectives for possible further research are discussed in the very last part.