The prediction of wind turbine performance with passive flow control solutions

Wind turbines are dependent on blade technology for the conversion of wind energy into electrical power. There are several Horizontal Axis Wind Turbine (HAWT) studies that have investigated the aerodynamic performance of the turbine blade under steady conditions. These studies have been beneficial for the development of blade technology; however, they do not reflect the real operating conditions of HAWTs and therefore are of limited applicability. This thesis makes an original contribution to the wind engineering corpus by addressing a clear gap in existing numerical studies, in which HAWT aerodynamics are predominantly modelled under steady inflow assumptions. In contrast, the present work presents a consistent and robust numerical framework to model the blade efficiency of the NREL Phase VI turbine using Computational Fluid Dynamics (CFD) under unsteady inflow conditions. Furthermore, the numerical study analyses the performance of PFC devices under unsteady conditions and evaluates their effectiveness across different flow regimes.

This thesis demonstrates that passive devices are useful technological solutions for the optimization of the NREL Phase VI. The microtab, Gurney flap and riblet configurations are utilized to enhance power output across a range of TSRs. The Gurney flap was found to be most effective at λ = 3.79 and λ = 2.92 where overall power efficiency is improved by 3.5% and 2.23%. The microtab also yielded comparable improvements in the aerodynamic performance by modifying the pressure distribution near the trailing edge and increasing the effective camber of the blade. This configuration enhanced lift and improved power efficiency across the investigated power range. The slip length model is used to represent the riblet configurations which are investigated in the parametric study. The optimal configuration for the riblet geometry is shown to be Riblet Geometry III where the h+ =8-15, demonstrating a significant reduction in viscous drag and cross flow fluctuations.