An investigation into the use of vortex generators on the blade of vertical axis current turbine in correlation with delaying stall and increasing energy efficiency

Abstract

The common phenomena in vertical-axis turbines arise from the continuously changing angle of attack (AoA), which results in; flow separation, dynamic stall, unsteady hydrodynamics, complex wake and vortex structures, and Cyclic structural loading. Devices such as vortex generators (VGs) are used to mitigate flow separation and dynamic stall, thereby significantly improving turbine performance. Numerical simulations investigate the effect of VG addition on turbine performance in general, specifically the NACA 0021 blades in the H-type Darrieus turbine. The single-blade model was equipped with rectangular VGs of specific dimensions, arranged in a single row and contra rotating. Computational Fluid Dynamics (CFD) simulation using ANSYS-FLUENT was employed as the numerical approach to compare the performance of an NACA 0021 blade with and without rectangular VGs. The VGs were placed at chordwise positions of 20%c, 25%C, and 30%c. The simulation results show that the most effective VG placement is at 25%c, where the drag coefficient is reduced by up to 38.0% at an AoA of 15°, and by 17.3% at AoA = 20°, compared to the clean airfoil without VGs. This study shows that the addition of VGs reduces drag and enhances turbine performance. The reduction in drag influences the flow separation behavior, thereby delaying stall.