Numerical investigation of the effects of immersion on the efficiency of a tidal helical turbine

In the current study, a two-phase simulation of a tidal helical turbine was performed that contrasts with previous studies in two ways. First, the current research simulated the turbine in different states of immersion in water, whereas previous studies simulated turbines mostly in single-phase conditions and full immersion in water. Second, the present study used a horizontal-axis turbine, whereas previous research employed a vertical-axis helical turbine or Darrius turbine. In this study, a simulation was conducted using the volume of fluid method in ANSYS Fluent 18. Results indicated that the complete immersion of the turbine in water generated a high torque, thereby reducing the efficiency of the device. To determine the conditions with the highest efficiency, immersion rates of 100%, 75%, 50%, and 25% in water were examined, and a configuration with best power coefficient (C p = 0.175 in TSR = 0.47) was found in 25% immersion. In immersion rate of 25%, resistant pressure on blades was minimum.