The effect of the blade rotation velocity and the freestream velocity of gravitational vortex hydro turbine

Data from the Central Statistics Agency in 2020 states that 2.9 million Indonesians do not have access to electrical energy. Most of the areas that do not have electricity are remote areas in eastern Indonesia. An independent power source is needed to solve this problem. Therefore, a vortex hydro turbine is used as an option to be built as an off-grid power plant in available water resources. To generate a high efficiency of water vortex turbine, one of the most important problems to be solved is the rotation of the turbine shaft. This study aims to determine the optimum rotation using a non-dimensional number called Coefficient of Velocity is determined. The coefficient of velocity is the ratio of the blade rotation velocity to the freestream inlet velocity. The methodology used in this study is the numerical method using Computational Fluid Dynamics software named Ansys Fluent. In this study, freestream inlet velocity is divided into 3 cases which are 0.225 m/s, 0.5 m/s, and 0.75 m/s. The rotational velocity of all cases is varied from 10-300 Rpm. Based on the results of this study, it can be concluded that the optimum Coefficient of Velocity of the vortex turbine is 21. The maximum efficiency obtained is 25.4%, with an inlet velocity of 0.5 m/s. In addition, based on this study, it can be seen that the high value of CV explains that the Vortex turbine is a type of hydro turbine that requires a low head.