Numerical comparison of an H-Darrieus rotor with two tank configurations for a gravitational vortex turbine

The gravitational vortex turbine (GVT) is an increasingly popular alternative for energy generation and consumption due to its easy manufacturing and low maintenance requirements. This study focuses on key aspects of the GVT, including the design of the rotor, the tank geometry, and the formation of the vortex. The tank geometry and vortex formation were also considered in this study. Different tank geometries, such as conical and cylindrical tanks, were evaluated, with experimental and numerical analyses conducted to compare their efficiencies. The conical tank demonstrated superior performance compared to the cylindrical tank, as evidenced by outlet velocity values. Moreover, the BSL RSM turbulence model was found to best represent the vortex geometry and tangential velocity inside the tank. Regarding the rotor design, a three-blade H-Darrieus rotor was proposed and investigated. The analysis revealed significant variations in water pressure across the rotor blades, with differences of up to 47%. This confirms that the fluid accelerates as it approaches the center and bottom of the tank, highlighting the importance of rotor design in optimizing GVT performance. The study also identified an optimal angular velocity range for the rotor between 50 and 75 rpm, exhibiting higher performance with minimal performance differences. However, at rotor speeds of 100 rpm or higher, the performance differences become more pronounced, reaching up to 28%.