Computational Fluid Dynamics Analysis of a Hydrokinetic Turbine Based on Oscillating Hydrofoils

Abstract

The performance of a new concept of hydrokinetic turbine using oscillating hydrofoils to extract energy from water currents (tidal or gravitational) is investigated using URANS numerical simulations. The numerical predictions are compared with experimental data from a 2 kW prototype, composed of two rectangular oscillating hydrofoils of aspect ratio 7 in a tandem spatial configuration. 3D computational fluid dynamics (CFD) predictions are found to compare favorably with experimental data especially for the case of a single-hydrofoil turbine. The validity of approximating the actual arc-circle trajectory of each hydrofoil by an idealized vertical plunging motion is also addressed by numerical simulations. Furthermore, a sensitivity study of the turbine’s performance in relation to fluctuating operating conditions is performed by feeding the simulations with the actual time-varying experimentally recorded conditions. It is found that cycle-averaged values, as the power-extraction efficiency, are little sensitive to perturbations in the foil kinematics and upstream velocity.

Effect of wake interaction on the response of two tandem oscillating hydrofoils

“…33 The S-A (Spalart-Allmaras) has lower requirement for the quality of meshing. 33 The S-A (Spalart-Allmaras) has lower requirement for the quality of meshing.…”

Effects of time-varying camber deformation on flapping foil propulsion and power extraction

“…CFD is useful due to the ease of computing a variety of different flow regimes and Reynolds numbers, altering the airfoil shape, and implementing a variety of airfoil motions that would be difficult to recreate in an experimental setting. However, limitations exist to the computational approach, particularly relating to accurate computation of transitional and turbulent flows at moderate Reynolds numbers and the extreme computational cost of 3-dimensional solutions (Visbal, 2009;Ashraf et al, 2012;Kinsey and Dumas, 2012). Due to these limitations, much of the computational work has been performed at low Reynolds numbers, thus precluding the possibility of transitional flow and reducing the effect of that 3D flow structures would have in a higher Re 3D simulation.…”

Design, implementation, and power estimation of a lab-scale flapping-type turbine

“…The companies in this industry include Engineering Business Ltd. (UK), who developed the ''Stingray'' [3]; Pulse Generation Ltd. (UK), who developed the ''Pulse-Stream'' [4]; BioPowerSystem (Australia) with their ''BioSTREAM'' [5]; Aniprop, which stands for Animal Propulsion (Germany), who developed the ''StrokeWing-Engine'' [6]; and FESTO (Germany), who very recently developed a compact plunging-type turbine called the ''DualWingGenerator'' [7]. The interest from industry is driven by the continually increasing number of studies, starting with McKinney and DeLaurier [8] in 1981 to more recent studies by Young et al [9], Le et al [10], and Kinsey and Dumas [11][12][13]. Most of the aforementioned studies are devoted to plunging-type foils, either with experimental or numerical analysis approaches.…”