Effects of the hinge position and suction on flow separation and aerodynamic performance of the NACA 0012 airfoil

  • Esmaeel Fatahian
  • Ali Lohrasbi NichkoohiEmail author
  • Hesamoddin Salarian
  • Jahanfar Khaleghinia
Technical Paper


In the present study, the effect of hinge position (H) has been numerically investigated to find the appropriate position for improving the aerodynamic performance of the NACA 0012 flapped airfoil. In addition, perpendicular and tangential suctions have been applied to control the flow separation and enhance the aerodynamic performance over the NACA 0012 flapped airfoil at each different hinge positions. The simulations were carried out at a Reynolds number of 5 × 105 (Ma = 0.021) based on two-dimensional incompressible unsteady Reynolds-averaged Navier–Stokes calculations to determine the adequate hinge position. The turbulence was modeled using the shear stress transport kω turbulence model. The effect of perpendicular suction (θjet = − 90°) and tangential suction (θjet = − 30°) was computationally studied over NACA 0012 flapped airfoil for five different hinge positions (H = 0.7c, 0.75c, 0.8c, 0.85c and 0.9c) and a flap deflection (δf) of 15°. Based on the results, the hinge position significantly affects the aerodynamic performance of the airfoil. The lift coefficient increased clearly as the hinge position moved to the trailing edge of the airfoil. Using perpendicular suction caused to increase the lift coefficient and decrease the drag coefficient. Consequently, the maximum value of the lift-to-drag ratio (CL/CD) for perpendicular and tangential suctions was achieved about 35.8% and 25.1% higher than that of the case without suction at an angle of attack of 12° and H = 0.9c. Also, the effect of perpendicular suction was more considerable compared to the tangential suction. This caused a reduction in the size of the recirculation zone from 0.5 to 0.09 of the airfoil chord length and also transferred it from 1.13 to 1.18 of the airfoil chord length.


Flow separation Suction Lift coefficient Drag coefficient NACA 0012 Hinge position 

List of symbols


Angle of attack


The angle between the free-stream velocity direction and the local jet surface


Airfoil chord length


Pressure coefficient


Lift coefficient


Drag coefficient


Skin friction coefficient

ω (ε/k)

Specific dissipation rate


Turbulent kinetic energy






Shear stress


Flap deflection




Hinge position

\( \rho_{\infty } \)

Free-stream density


Hinge moment


Reference area of the control surface


Control surface reference chord


Free-stream dynamic pressure


Hinge moment coefficient


Reynolds number


Mach number


Free-stream velocity


Dimensionless wall distance


Jet angle


Jet location


Jet velocity


Jet velocity ratio



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Copyright information

© The Brazilian Society of Mechanical Sciences and Engineering 2020

Authors and Affiliations

  • Esmaeel Fatahian
    • 1
  • Ali Lohrasbi Nichkoohi
    • 2
    Email author
  • Hesamoddin Salarian
    • 1
  • Jahanfar Khaleghinia
    • 1
  1. 1.Department of Mechanical Engineering, Nour BranchIslamic Azad UniversityNourIran
  2. 2.Department of Mechanical Engineering, Nowshahr BranchIslamic Azad UniversityNowshahrIran

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