Optimal Tandem Configuration for Oscillating-Foils Hydrokinetic Turbine

Kinsey, Thomas; Dumas, Guy

doi:10.1115/1.4005423

Cited by 126 publications

(63 citation statements)

References 11 publications

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“…In addition, multiple foils in either tandem arrangement or parallel arrangement have also been investigated for the efficiency improvement. 14 It is known that the studies on flapping foils are inspired by bird/insect flight and fish swimming in nature. Currently, there exists a lot of work on the flapping foils for the purpose of locomotion, which contains some important issues that are utilized to enhance the thrust and/or lift force generation.…”

Section: Introductionmentioning

confidence: 99%

Numerical study on the power extraction performance of a flapping foil with a flexible tail

Chen

Zhao

et al. 2015

Physics of Fluids

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The numerical study on the power extraction performance of a flapping foil with a flexible tail is performed in this work. A NACA0015 airfoil is arranged in a two-dimensional laminar flow and imposed with a synchronous harmonic plunge and pitch rotary motion. A flat plate that is attached to the trailing edge of the foil is utilized to model a tail, and so they are viewed as a whole for the purpose of power extraction. In addition, the tail either is rigid or can deform due to the exerted hydrodynamic forces. To implement numerical simulations, an immersed boundary-lattice Boltzmann method is employed. At a Reynolds number of 1100 and the position of the pitching axis at third chord, the influences of the mass and flexibility of the tail as well as the frequency of motion on the power extraction are systematically examined. It is found that compared to the foil with a rigid tail, the efficiency of power extraction for the foil with a deformable tail can be improved. Based on the numerical analysis, it is indicated that the enhanced plunging component of the power extraction, which is caused by the increased lift force, directly contributes to the efficiency improvement. Since a flexible tail with medium and high masses is not beneficial to the efficiency improvement, a flexible tail with low mass together with high flexibility is recommended in the flapping foil based power extraction system.

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Section: Introductionmentioning

confidence: 99%

Numerical study on the power extraction performance of a flapping foil with a flexible tail

Chen

Zhao

et al. 2015

Physics of Fluids

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“…Work has focussed on the effects of phase alone (Rival et al 2011;Lian et al 2014), or the effect of phase and frequency , or spacing and frequency (or Strouhal number, St) (Kinsey & Dumas 2012). Many studies have investigated both the phase and spacing, but at only one flapping frequency Kumar & Hu 2011;Boschitsch et al 2014;Gong et al 2015Gong et al , 2016.…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies have shown that the force production on the hind foil of a tandemfoil configuration is affected by the phase difference in the kinematics between the fore and hind foils (ϕ) and the inter-foil spacing (S) Rival et al 2011;Kumar & Hu 2011;Broering & Lian 2010;Kinsey & Dumas 2012;Lian et al 2014;Boschitsch et al 2014;Gong et al 2015Gong et al , 2016. This effect has been addressed as "wake recapture", "wing/wake interaction", or "thrust augmentation For the purposes of this work, "performance augmentation" is deemed the most suitable description, as this term accounts for the augmentation of both thrust and efficiency.…”

Section: Introductionmentioning

confidence: 99%

Performance augmentation mechanism of in-line tandem flapping foils

2017

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The propulsive performance of a pair of tandem flapping foils is sensitively dependent on the spacing and phasing between them. Large increases in thrust and efficiency of the hind foil are possible, but the mechanisms governing these enhancements remain largely unresolved. Two-dimensional numerical simulations of tandem and single foils oscillating in heave and pitch at a Reynolds number of 7,000 are performed over a broad and dense parameter space, allowing the effects of inter-foil spacing (S) and phasing (ϕ) to be investigated over a range of non-dimensional frequencies (or Strouhal number, St). Results indicate that the hind foil can produce from no thrust, to twice the thrust of a single foil depending on its spacing and phasing with respect to the fore foil, which is consistent with previous studies that were carried out over a limited parameter space. Examination of instantaneous flowfields indicate that high thrust occurs when the hind foil weaves in between the vortices that have been shed by the fore foil, and low thrust occurs when the hind foil intercepts these vortices. Contours of high thrust and minimal thrust appear as inclined bands in the S − ϕ parameter space and this behaviour is apparent over the entire range of Strouhal numbers considered (0.2 St 0.5). A novel quasi-steady model that utilises kinematics of a virtual hind foil together with data obtained from simulations of a single flapping foil shows that performance augmentation is primarily determined through modification of the instantaneous angle of attack of the hind foil by the vortex street established by the fore foil. This simple model provides estimates of thrust and efficiency for the hind foil, which is consistent with data obtained through full simulations. The limitations of the virtual hind foil method and its physical significance is also discussed.

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“…Moreover, an auxiliary foil is arranged below the flapping foil, which consequently induces the vortex interaction between two foils. Different from the previous work (Lefrancois, 2008;Kinsey and Dumas, 2012), only the flapping foil is employed to implement the power extraction in this work. As the rotating motion consumes relatively less extra energy, such motion is adopted to drive the auxiliary foil.…”

Section: Introductionmentioning

confidence: 96%

“…For example, Lefrancois (2008) indicated that the overall efficiencies of two oscillating flat plates in parallel and tandem configurations could reach 31% and 41% respectively. Kinsey and Dumas (2012) recently reported that both the upstream foil and the downstream foil could achieve a higher efficiency than a single one as they are arranged within a specific parameter range. On the other hand, it is found that both foils are employed to harvest energy in the multiple foils system, but the underlying mechanism of efficiency improvement is still required to be explored.…”

Section: Introductionmentioning

confidence: 99%