Aerodynamic investigations of H-type vertical axis wind turbines

Abstract

Vertical Axis Wind Turbines (VAWTs), especially the Darrieus type, have gained significant attention in recent years as a viable alternative for energy production. However, the aerodynamic complexities of these devices, particularly at low tip speed ratios where dynamic stall has a notable impact on performance, present ongoing challenges. This thesis contributes to the field through a combination of numerical and experimental investigations focused on an H-type VAWT. The research is organized into three main studies, each targeting a distinct aspect of VAWT aerodynamics. The first study aims to identify the most suitable Unsteady Reynolds-Averaged Navier-Stokes (URANS) turbulence model within the OpenFOAM Framework, involving a comparative analysis of three turbulence models under conditions of deep dynamic stall. The second study focuses on estimating the angle of attack (AoA) and relative velocity of VAWT blades using computational fluid dynamics data, implementing two methods within OpenFOAM, and applied in 2D URANS simulations coupled with Κ-ω SST and the four-equation transition models. The third study examines the wake of a small H-type VAWT, combining numerical simulations using various turbulence models in OpenFOAM with experimental Particle Image Velocimetry (PIV) to investigate the velocity deficit in the turbine's wake. Overall, this thesis aims to improve the understanding and aerodynamic performance of VAWTs through detailed numerical analysis and experimental approach, addressing critical issues in their operation.