Abstract
The present paper proposes an oscillating Gurney flap to enhance the power extraction efficiency of a flapping airfoil system. Two-dimensional Navier–Stokes resolutions by the flow solver fluent are performed. To alter the flap position during the flapping cycle, a dynamic mesh technique is used. The flow regime is considered fully laminar, with a free stream Reynolds number of Re = 1100. Results show that, the synchronization of the Gurney flap motion with the central flapping airfoil motion generates a virtual camber which corrects the pressure distribution and ultimately enhances the lift force during both, the up-stroke and down-stroke stages. The lift enhancement is interpreted to an improvement in the output power as compared to a clean flapping extractor.
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Abbreviations
- c :
-
Chord length
- CD:
-
Airfoil drag coefficient, \(\frac{D}{1/2\rho U_\infty ^2 C}\)
- CL:
-
Airfoil lift coefficient, \(\frac{L}{1/2\rho U_\infty ^2 C}\)
- \(C_M \) :
-
Airfoil pitching moment coefficient, \(\frac{M}{1/2\rho U_\infty ^2 C^{2}}\)
- L(t):
-
Lift force
- M(t):
-
Pitching moment on the airfoil
- h(t):
-
Plunge amplitude of the airfoil pivot point
- \(\theta (t)\) :
-
Airfoil instantaneous angle
- \(\theta _0\) :
-
Pitching amplitude
- \(\theta _1 \) :
-
Flap pitching amplitude relative to trailing edge tip
- \(\dot{\theta }\) :
-
Angular velocity of the airfoil
- \(\phi _{{\text {flap}}} \) :
-
Phase angle between airfoil pitching and flap pitching
- \(f^{*}\) :
-
Non-dimensional frequency
- f :
-
Flapping frequency
- \(\phi \) :
-
Phase angle between the pitching and plunging motions
- \(P_\theta (t)\) :
-
Power extracted by pitching motion
- \(P_h (t)\) :
-
Power extracted by plunging motion
- Re:
-
Reynolds number based on chord, \(\frac{\rho U_\infty c}{\mu }\)
- \(\bar{C}_{{p_{{\text {total}}} }}\) :
-
Aerodynamic power coefficient, \(\frac{P}{1/2\rho U_\infty ^3 C}\)
- \(\bar{C}_{{p_{{\text {flag}}}}}\) :
-
Flap aerodynamic power coefficient, \(\frac{P_{{\text {flap}}} }{1/2\rho U_\infty ^3 C}\)
- \(\bar{C}_{{P_{{h}}}}\) :
-
Power coefficient due to plunging, \(\frac{P_h }{1/2\rho U_\infty ^3 C}\)
- \(\bar{C}_{{p_{{\theta }} }}\) :
-
Power coefficient due to pitching, \(\frac{P_\theta }{1/2\rho U_\infty ^3 C}\)
- \(\eta _{\mathrm{{total}}}\) :
-
Total energy extraction efficiency
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Bouzaher, M.T., Drias, N. & Guerira, B. Improvement of Energy Extraction Efficiency for Flapping Airfoils by Using Oscillating Gurney Flaps. Arab J Sci Eng 44, 809–819 (2019). https://doi.org/10.1007/s13369-018-3270-7
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DOI: https://doi.org/10.1007/s13369-018-3270-7