A review on the wake aerodynamics of H-rotor vertical axis wind turbines

Vertical axis wind turbines (VAWTs) have distinctive attributes, for example, exceptional performance in built environments and high packing density in wind farms. This study reviews recent research in the wake aerodynamics of H-rotor VAWTs. The general mathematical expressions for the analysis of the rotor aerodynamics of VAWTs are presented, followed by a classic aerodynamic model. Velocity deficit and turbulence increase are common features of wind turbine wakes, and the deep dynamic stall of operational VAWTs further complicates their wakes. This study systematically compiles the investigations of the wake flow fields and vortical structures of VAWTs. In these investigations, a wide range of research methods have been used, for instance, wind tunnel testing, particle image velocimetry (PIV) tests, field tests, computational fluid dynamics (CFD) simulations, and theoretical development. The results of these studies suggest that the wakes of VAWTs are characterized by distinctive features, such as strong asymmetry and counter-rotating vortical motion. Based on these characteristics, researchers have developed various wake models. The proposed wake models can be used to design standalone VAWTs or layouts for multiple VAWTs. Finally, this paper provides discussions and suggestions pertaining to the investigations of the wakes of VAWTs.