Enhancing performance of gravitational water vortex turbines through airfoil design and basin parameters

Gravitational water vortex turbines (GWVTs) have emerged as promising hydrokinetic technology for energy extraction in riverine systems characterized by low flow velocity and ultra-low head, where conventional hydropower solutions are not feasible. In this study, a three-dimensional computational fluid dynamics (CFD) model is developed to investigate turbine performance within a conical basin configuration. The numerical framework, validated against published reference data, is used to systematically evaluate the influence of airfoil axial spacing, chord sizing, and airfoil profile, on vortex structure and power coefficient. The results demonstrate that basin-induced flow control plays a critical role in enhancing tangential momentum transfer to the rotor. Among the investigated cases, a configuration employing a NACA0024 ducted airfoil with a chord size of 35 mm and an axial spacing of 50 mm yielded the highest power coefficient of 0.419 compared to the baseline basin power coefficient of 0.313 and reached a maximum value of 0.736 at higher inlet velocities. Performance analysis based on tip speed ratio (TSR) further identified an optimal low-TSR operating range consistent with gravitational water vortex turbine characteristics. Compared with previous GWVT studies that focus on turbine geometry, the present work highlights the effectiveness of basin wall airfoil design as an impactful strategy for performance enhancement in low-head hydrokinetic applications.