Parametric study of H-Darrieus vertical-axis turbines using CFD simulations

Abstract

A parametric study of vertical axis turbines of the H-Darrieus type is conducted using state-of-the-art Computational Fluid Dynamics (CFD) and the k-ω Shear Stress Transport RANS model in its unsteady form. Although most parameters have previously been investigated individually, the effect of solidity, number of blades, tip speed ratio, Reynolds number, fixed blade pitch angle, and blade thickness on the aerodynamic efficiency of the turbine is evaluated using the same performance evaluation set-up in order to determine what would be the best aerodynamic configuration and operation parameter in a given application. The quantitative impact of 3D effects associated with the blade aspect ratio and the use of end-plates is also investigated. For high-Reynolds applications, optimal radius-based solidity is found to be around σ=0.2, while higher solidities show a lower maximum efficiency than what was previously published using simpler streamtube based methods. In 3D, a small blade aspect ratio (AR=7) leads to a relative efficiency drop of nearly 60% compared to the 2D prediction. Longer blades improve the 3D efficiency greatly. End-plates are found to have a positive effect on power extraction performances, as long as their size and thus their drag are limited.

Vortex Dynamics in the Wake of Three Generic Types of Freestream Turbines

“…The spatial and temporal resolutions of the simulations in this study have already been proven to be adequate in previous investigations on turbines [22,23,38]. Nonetheless, two more simulations for each turbine concept have been carried out in order to confirm the resolution adequacy.…”

“…The rotating shaft and connecting arms are not included in this study. More precisely, the CFT investigated corresponds to one of the single-bladed turbines studied by Gosselin et al [22], which is characterized by a NACA0015 profile, a blade's aspect ratio (b/c) of 15, a diameter to chord length ratio of 7 and a tip speed ratio of 4.25. As shown in Fig.…”

Design and numerical analysis of an efficient H-Darrieus vertical-axis hydrokinetic turbine

“…In turn, Gosselin et al [25] performed a detailed 2D and 3D CFD analyses of a Darrieus wind turbine to study all the major factors affecting the turbine performance; i.e., TSR, Reynolds number, σ, N, AR, pitch angle (θ) and blade thickness. They also mentioned that for high-Reynolds applications, optimal radius-based σ is found to be around σ =0.2, while higher solidities show a lower maximum efficiency than what was previously published using simpler streamtube based methods [25].…”

Aerodynamic performance and characteristic of vortex structures for Darrieus wind turbine. I. Numerical method and aerodynamic performance

“…According to Sabaeifard (2012), a 3-bladed Darrieus turbine with 35% solidity has the best efficiency among all geometries that were numerically studied in his work. 8 Gosselin (2013) simulated an H-type Darrieus wind turbine using the Fluent commercial code and found that the maximum power coefficient of turbine decreases when solidity increases. 9 Roh (2013), however, suggested that the maximum power coefficient increases with the increase of the solidity at first, beyond a certain solidity, the maximum power coefficient then decreases with further increasing solidity.…”

“…8 Gosselin (2013) simulated an H-type Darrieus wind turbine using the Fluent commercial code and found that the maximum power coefficient of turbine decreases when solidity increases. 9 Roh (2013), however, suggested that the maximum power coefficient increases with the increase of the solidity at first, beyond a certain solidity, the maximum power coefficient then decreases with further increasing solidity. 10 Numerical analysis of blade-vortex interaction in a Darrieus wind turbine was conducted by Amet (2009), 11 but the effect of the observed physical phenomena on the aerodynamic performance of the Darrieus wind turbine was not explained in his work.…”