Numerical study on the effect of vortex generator geometry and placement on single-blade performance in vertical axis current turbines

This study investigates the effect of adding vortex generators (VGs) to a single NACA 0021 blade applied in vertical axis current turbines (VACTs). The focus is on rectangular and trapezoidal VG shapes and their placement between 10 and 30 % of the chord length on the hydrofoil surface. CFD analyses were carried out under steady state conditions using the Reynolds-Averaged Navier–Stokes (RANS) approach, coupled with the k-ω SST turbulence model. The results demonstrate performance improvements of the hydrofoil with the inclusion of VGs. Specifically, rectangular VGs positioned at 10 % of the chord length increased the average lift coefficient (CL) by 31.5 % and reduced the average drag coefficient (CD) by 8 %. Similarly, trapezoidal VGs placed at 15 % of the chord length increased CL by 29.5 % and decreased CD by 7.1 %. Optimizing the geometry and placement of VGs can significantly enhance turbine efficiency by improving boundary layer control and delaying flow separation.