Double-Multiple Streamtube Analysis of a Flexible Vertical Axis Wind Turbine

Vertical-axis wind turbines (VAWTs) have drawn increased attention for off-grid and off-shore power generation due to inherent advantages over the more popular horizontal-axis (HAWTs). Among these are generator locale, omni-directionality simplistic design. However, one major disadvantage is lower efficiency, which can be alleviated through blade pitching. Since each must transit both up- down-stream revolution, VAWT pitching techniques not yet commonplace complexity cost. Utilizing passively-morphing flexible blades offer similar results as active pitching, requiring no sensors or actuators, has shown promise in increasing performance select cases. In this study, tunnel tests been conducted with rigid-bladed NACA 0012 airfoils, order provide necessary input data a Double-Multiple Stream-Tube (DMST) model. The from study indicate that achieve maximum coefficient (Cp) far exceeding CP (18.9% vs. 10%) reduced normal force fluctuations much 6.9%. Operational range of tip-speed ratio also observed increase by 40.3%.