Numerical Modeling of a Darrieus Horizontal Axis Shallow-Water Turbine

Abstract

For decades, Darrieus turbines have shown their advantage over other turbines for providing hydropower. Most studies tend to be conducted with the turbine in its vertical axis configuration, while few have examined the horizontal axis configuration. In this paper, we undertake a computational fluid dynamics (CFD) analysis that investigates blade profile alternatives to improve the efficiency of a horizontal axis Darrieus turbine under more natural flow conditions. An inlet boundary layer profile and a confined domain are imposed to represent river conditions. Four blade profiles are tested under various tip-speed ratios using a three-bladed turbine. The developed model is based on an unsteady k-ω shear stress transport (SST) turbulence closure associated with a very-fine-grid mesh. The model methods are first validated against open-channel experimental results published in the literature and show less than 13% discrepancy. The S1046 blade profile is shown to improve the power coefficient Cp by 14% compared to the NACA0018 blade profile. The S809 blade profile exhibits the lowest performance in the dynamic stall and transition regions. For high tip-speed ratios, the FXLV152 profile produces the highest local efficiency power coefficient. The influence of the blade number is also quantified. The four- and two-bladed S1046 configurations achieve the highest power coefficients in the low and high tip-speed ratio regions, respectively.