Numerical Investigation of an Optimum Leading-Edge Slat Positioning for an Urban-Scale Vertical Axis Wind Turbine (VAWT) /

Abstract

Due to its omnidirectional operation and comparatively simple installation and maintenance, vertical axis wind turbines (VAWTs) provide a practical choice for small-scale applications. However, due to the existence of dynamic stall (DS) and related blade-wake interaction induced vibrations, the VAWTs characterize reduced power coefficient (Cp) in distinct tip-speed ratio (TSR) activities compared to the horizontal axis wind turbines (HAWTs). Due to a large and periodic variation in the angle of attack during rotation, a DS happens. In this respect, an advance VAWT rotor with leading-edge (LE) slat for an H-Darrieus VAWT was built and the prospective enhancement of DS features was investigated. A 2D transient CFD assessment was conducted on a VAWT rotor baseline and slatted airfoils. For performance simulation, ANSYS ICEM CFD and Fluent software were widely used. In this research, the model k-ω Shear Stress Transport (SST) was used to accurately capture the near-wall region of the airfoil. The efficiency of the turbine rotor in terms of Cp vs. TSR was investigated in detail along with the flow separation over the rotor blades in the form of downstream wind and vorticity structures. Analysis of the DS was also carried out. For the slatted blade, a noticeable improvement in vortex shedding was noted. The findings indicate a rise in the peak lifting value and a 4º delay in the stall angle. Also, the enhanced advance rotor performance ultimately leads to a rise in the overall CP vs. TSR curve, with a rise of 15 percent in the CP at the TSR design stage. The rise in rotor efficiency and power production is significant progress with better opportunities for urban scale installation in an H-Darrieus type VAWT technology.