Performance Enhancement of Vertical Axis Wind Turbine Using Riblets

Recently, vertical axis wind turbines (VAWTs) have gained the interest of numerous researchers across the globe to harness wind power. However, they have lower power efficiencies than Horizontal Axis Wind Turbines (HAWTs). VAWTs blade experiences post-stall angles of attack that cause flow separation on the blade surface. One solution to improve the power coefficient of vertical axis wind turbines is to delay the dynamic stall and reduce the drag of its blade. This study investigates the efficacy of riblets on turbine blades to improve their performance. Riblets are small streamwise grooves that generate turbulent vortices on the surface. The riblets reduce drag when their spacing is small enough to fit one vortex in its groove. Turbine blades with various riblet geometries are analyzed using 2.5D CFD and compared to a smooth-bladed turbine. It is observed that the best-performing riblet geometry increases the power coefficient of the turbine by 9% at the optimum tip speed ratio.