Computational Modelling Of Wind Turbine Wakes Using an Actuator Disc Coupled With Reynolds Averaged Navier-Stokes Models

Abstract

Wind energy is one of the fastest growing sources of renewable energy. Because of the increasing growth of the wind energy sector, advanced computational modelling of wind turbine aerodynamics and wake interactions is required. Experiments on wind turbines can be costly and sometimes impractical. Often, a computational model can be an easier and less expensive solution. Computational fluid dynamics (CFD) uses numerical methods to solve complex flow models. For wind turbine applications, several models have been implemented in CFD. The actuator disc model (ADM) is considered the simplest model. It treats the rotor as an actuator disc with a small thickness. Other computational models are the actuator line model (ALM) and a fully resolved turbine geometry. The main objectives of this thesis are to use CFD to study the wake of a wind turbine and the interaction between two turbines in tandem. This research uses the ADM coupled with the RANS equations and explores a series of turbulence models. The first study covers the wake analysis of a standalone wind turbine, where the k-ω SST with the corrections of Cao et al. (2018) is shown to be the best model. The second study covers the wake interaction between two in-line turbines. Finally, a study using neutral atmospheric boundary conditions was also performed. The actuator disc Reynolds-Averaged Navier-Stokes (AD/RANS) method was not able to fully capture the wake profile downstream of a rotor, especially in the region nearest to the rotor. The model did not match the spread rate and decay of the experimental data. The model was able to reproduce the disc edge effects to some extent, but not the hub effects. The AD/RANS model results begin to agree better with the experimental data in the region farther downstream of the rotor. All simulations in this thesis work were performed using four parallel processors, in contrast to the large supercomputer simulations reported in the literature. This was realized by assumptions that were meant to maintain the essential physics while reducing the problem’s complexity. The AD/RANS study demonstrates the potential of simplified models for exploring wind farm simulations, in particular turbine wake interaction.