Vertical-Axis Wind Turbine Aerodynamics

Abstract

Horizontal-axis wind turbines (HAWTs) are widely studied and have proven their technological capabilities. However, wind turbines are moving into new environments, such as floating far-offshore or urban applications, where the operational conditions are significantly different. Vertical-axis wind turbines (VAWTs) could be more suitable and compatible in these environments, hence, the interest in VAWTs is rekindling. Although vertical-axis wind turbines have a long history, the behavior of these turbines and their complex flow field is still not fully understood. The lack of understanding the complex unsteady aerodynamics of VAWTs and the challenge to predict the loads and performance of this kind of turbines accurately, has led to systematic failures and as such variable interest in VAWTs throughout history. Advancing the understanding and modeling of VAWT’s aerodynamics will be crucial to advance the technology further. This chapter highlights the main aerodynamic phenomena and challenges of vertical-axis wind turbines. First, an introduction is provided on the VAWT history and (dis-)advantages. The basics of VAWT aerodynamics and the various rotor simplifications/representations are presented. Further, the state-of-the art aerodynamic modeling techniques, specifically for VAWTs, are discussed. Since VAWTs are inherently unsteady, the main unsteady phenomena that play a crucial role in VAWT aerodynamics are summarized. Finally, wake aerodynamics and the importance of airfoil design for VAWTs are highlighted.