Arabian Journal for Science and Engineering

, Volume 44, Issue 2, pp 809–819 | Cite as

Improvement of Energy Extraction Efficiency for Flapping Airfoils by Using Oscillating Gurney Flaps

  • Mohamed Taher BouzaherEmail author
  • Nouredine Drias
  • Belhi Guerira
Research Article - Mechanical Engineering


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.


Gurney flap Power extraction efficiency Flapping airfoil system Lift force 

List of symbols


Chord length


Airfoil drag coefficient, \(\frac{D}{1/2\rho U_\infty ^2 C}\)


Airfoil lift coefficient, \(\frac{L}{1/2\rho U_\infty ^2 C}\)

\(C_M \)

Airfoil pitching moment coefficient, \(\frac{M}{1/2\rho U_\infty ^2 C^{2}}\)


Lift force


Pitching moment on the airfoil


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


Non-dimensional frequency


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


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, \(\frac{P_{{\text {flap}}} }{1/2\rho U_\infty ^3 C}\)


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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Copyright information

© King Fahd University of Petroleum & Minerals 2018

Authors and Affiliations

  • Mohamed Taher Bouzaher
    • 2
    Email author
  • Nouredine Drias
    • 1
  • Belhi Guerira
    • 1
  1. 1.Département de Génie MécaniqueUniversité de BiskraBiskraAlgeria
  2. 2.Unité de Recherche Appliquée en Energies Renouvelables, URAERCentre de Développement des Energies Renouvelables, CDERGhardaïaAlgeria

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