On Optimal Oscillating-Foil Power Generation in Free and Constrained Flow

Karakaş, Ferhat; Zaloğlu, Berk; Fenercioglu, Idil; Hoke, Charles M.; Young, John; Lai, Joseph H.K.; Platzer, Max F.

doi:10.2514/6.2016-2070

Cited by 5 publications

(3 citation statements)

References 27 publications

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“…Figure 9 shows the mean power coefficient values for the sinusoidal case in constrained and free flow with the three-dimensional and finite test models, where the free flow side-wall distance is denoted with dw = 4 considering the water channel dimensions. The maximum mean power coefficient of ̅ = 0.43 is obtained in two dimensional cases for the finite flat plate with nonsinusoidal pitch stroke reversal of TR = 0.4 and phase angle of  = 90° in free flow (Karakas et al, 2016). However, 17.02% decrease in mean power coefficient is observed when the same motion parameters are used in the three dimensional setup.…”

Section: Resultsmentioning

confidence: 87%

“…The side wall effect enhances the power output for the sinusoidal (TR = 0.5) and nearsinusoidal (TR = 0.4) cases. In a previous study for 2D flow (Karakas et al 2016), it was observed that a 29.57% increase in efficiency can be achieved when the side walls are placed at dw = 0.5 for the sinusoidal flapping flat plate as compared with the free flow. In this study for the 3D cases, a 27.86% increase in efficiency is achieved with the same side wall distance (dw = 0.5) in sinusoidal case compared with the free flow.…”

Section: Resultsmentioning

confidence: 94%

“…In their numerical study using a sinusoidally flapping airfoil, Wu et al (2104) defines an elongated high pressure region on the upper surface of the airfoil as it gets closer to an upper wall causing a negative lift force that they attribute to the shear-induced effect (Saffman, 1965). The flat plate also experiences higher added mass as the pitch reversal rate is increased by decreasing TR and this high added mass possibly increases the power consumption and lowers the power production as also pointed out by Karakas et al (2016), which might result in sinusoidal cases to perform better than non-sinusoidal cases in constrained flow. show the time histories of the contributions of the plunging and pitching motions to the total power coefficient respectively for the same case.…”

Section: Resultsmentioning

confidence: 97%

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Effect of Side-Walls on Flapping-Wing Power-Generation: an Experimental Study

Karakaş

Fenercioglu

2016

JAFM

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Effect of constrained flow is investigated experimentally for a flapping foil power-generator. The flow structures around and in the near wake of a flat plate placed between two side walls are captured via PIV technique with simultaneous direct force measurements in uniform flow at Re = 10 000. The rectangular flat plate oscillates with periodic non-sinusoidal pitching and plunging motions about its 0.44 chord position with stroke reversal times (TR) of 0.1 (rapid reversal) to 0.5 (sinusoidal reversal), phase angles of  = 90° and 110°, plunge amplitude of 1.05 chords and pitch amplitude of 73° at a constant reduced frequency of k = 0.8. The non-dimensional distances between the side walls and the oscillating flat plate are dw = 0.1, 0.5 and 1.0. Airfoil rotation speed dictates the strength, evolution and timing of shedding of leading and trailing edge vortices; as the stroke reversal time is decreased, earlier shedding of stronger vortices are observed. Increasing the phase angle between the pitching and plunging motions decreases the power generation efficiency for all cases. The highest power extraction coefficient is acquired for the non-sinusoidal case of TR = 0.4 in free flow. Optimum choice of side-wall distance improves power generation of flapping foils compared to free flow performance, up to 6.52% increase in efficiency is observed for the non-sinusoidal case TR = 0.4 with dw = 0.5, with remarkable enhancements for the sinusoidal case; 27.85% increase is observed with dw = 0.5 and 43.50% increase with dw = 1.0 where both cases outperform the highest power generation efficiency of the finite flat plate with non-sinusoidal flapping motion.

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Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 94%