Numerical evaluation of helical hydrokinetic turbines with different solidities under different flow conditions

In the present study, the effect of the turbine solidity on the performance of helical cross-flow hydrokinetic turbines is numerically investigated under different flow conditions. Four turbines, with different solidities of 0.15, 0.2, 0.25 and 0.3, were investigated in five dissimilar flow conditions with Froude numbers of 0.0714, 0.143, 0.214, 0.286 and 0.357. The devices employed in the analyses were three-bladed with the diameter of 1 m and length of 1.5 m. They were positioned horizontally in a rectangular-shaped channel with a perpendicular alignment to the flow direction. Symmetrical NACA0018 hydrofoils, which are twisted with an angle of 120°, were used in the blade design. The investigation results have shown that the turbines with the solidity values 0.15 and 0.2 are more efficient than the other two cases. Considering all five flow conditions, the models have displayed the worst performance at a tip speed ratio of 4.0.