Numerical Investigations on the Transient Aerodynamic Performance Characterization of a Multibladed Vertical Axis Wind Turbine

The use of vertical axis wind turbines (VAWTs) in urban environments is on the rise due to their relatively smaller size, simpler design, lower manufacturing and maintenance costs, and above all, due to their omnidirectionality. The multibladed drag-based VAWT has been identified as a design configuration with superior aerodynamic performance. Numerous studies have been carried out in order to better understand the complex aerodynamic performance of multibladed VAWTs employing steady-state or quasi-steady numerical methods. The transient aerodynamics associated with a multibladed VAWT, especially the time-history of the power coefficient of each blade, has not been reported in the published literature. This information is important for the identification of individual blade's orientation when producing negative torque. The current study aims to bridge this gap in the literature through real-time tracking of the rotor blade's aerodynamic performance characteristics during one complete revolution. Numerical investigations were carried out using advanced computational fluid dynamics (CFD)-based techniques for a tip speed ratio of 0 to 1. The results indicate that transient aerodynamic characterization is 13% more accurate in predicting the power generation from the VAWT. While steady-state performance characterization indicates a negative power coefficient (Cp) at lambda = 0.65, transient analysis suggests that this happens at lambda = 0.75.