The Aerodynamics of Fixed and Variable Pitch Vertical Axis Wind Turbines

Due to the challenging wind potential and the increasing energy demand, it is important to design the future wind turbines to operate efficiently at low wind speeds. The focus of this thesis is about the small scale straight-bladed Vertical Axis Wind Turbine (VAWT) due to its competitive advantages and promising market. This thesis aims to provide an in-depth understanding of the aerodynamics of small VAWTs and the effect of blade pitch in the turbine performance at low wind speed conditions. Moreover, this thesis proposes a novel procedure for the analysis of turbine performance and the estimation of the Angle of Attack (AOA). This enables the design of the most appropriate fixed pitch and variable pitch configurations. Based on the unsteady Reynolds-Averaged Navier-Stokes (uRANS), the state-of-the-art Computational Fluid Dynamics (CFD) simulation is utilised as a modelling approach and this enables high fidelity analysis with a reasonable computational cost. In order to find the most appropriate CFD methodology for the modelling of a VAWT, detailed verification and validation studies are carried out and this includes the comparisons of the CFD predictions against detailed instantaneous experimental data.