Numerical analysis on hydrodynamic performance and wake recovery of helical-bladed hydrokinetic turbine: Impact of section inclination angle

Abstract

In the context of exploiting renewable sources, cross-flow helical hydrokinetic turbine is conceded as one of the promising choices to unlock the potential in free-flowing water bodies. This study examines the impact of blade section inclination angle (−10° to +8°) and operational parameters, namely, tip speed ratio (0.6–1.4) and inflow velocity (1.0–2.5 m/s) on the performance as well as wake recovery of a 4-bladed rotor. The coefficients of power and section-averaged mean streamwise velocity deficit values are computed by solving the unsteady Reynolds-Averaged Navier-Stokes equations coupled with k-ε RNG turbulence model using numerical simulations to assess the performance and velocity recovery, respectively. The power coefficients are seen to be improved with an increase in negative section inclination angle and are found optimum in the range from −6° to −10° at a tip speed ratio of 1.0. The simulation results also reveal that the section inclination angle and tip speed ratio parameters significantly influence the velocity recovery. Furthermore, the performance decreases as the inflow velocity increases; however, the wake recovery is unaffected, with an identical wake length of 13 times the rotor diameter along the streamwise direction at a tip speed ratio of 1.0.