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Research Papers: Flows in Complex Systems

Active Control of a Stalled Airfoil Through Steady or Unsteady Actuation Jets

[+] Author and Article Information
V. G. Chapin

Associate Professor
Department of Aerodynamic Energetic
and Propulsion,
Institut Supérieur de l'Aéronautique
et de l'Espace (ISAE),
Université de Toulouse,
Toulouse 31000, France
e-mail: vincent.chapin@isae.fr

E. Benard

Associate Professor
Department of Aerodynamic Energetic
and Propulsion,
Institut Supérieur de l'Aéronautique
et de l'Espace (ISAE),
Université de Toulouse,
Toulouse 31000, France
e-mail: emmanuel.benard@isae.fr

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 19, 2014; final manuscript received February 17, 2015; published online June 9, 2015. Assoc. Editor: Feng Liu.

J. Fluids Eng 137(9), 091103 (Sep 01, 2015) (10 pages) Paper No: FE-14-1082; doi: 10.1115/1.4030483 History: Received February 19, 2014; Revised February 17, 2015; Online June 09, 2015

The active control of the leading-edge (LE) separation on the suction surface of a stalled airfoil (NACA 0012) at a Reynolds number of 106 based on the chord length is investigated through a computational study. The actuator is a steady or unsteady jet located on the suction surface of the airfoil. Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations are solved on hybrid meshes with the Spalart–Allmaras turbulence model. Simulations are used to characterize the effects of the steady and unsteady actuation on the separated flows for a large range of angle of attack (0 < α < 28 deg). Parametric studies are carried out in the actuator design-space to investigate the control effectiveness and robustness. An optimal actuator position, angle, and frequency for the stalled angle of attack α = 19 deg are found. A significant increase of the lift coefficient is obtained (+ 84% with respect to the uncontrolled reference flow), and the stall is delayed from angle of attack of 18 deg to more than 25 deg. The physical nonlinear coupling between the actuator position, velocity angle, and frequency is investigated. The critical influence of the actuator location relative to the separation location is emphasized.

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References

Figures

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Fig. 1

Mesh topology with structured blocks around the airfoil

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Fig. 2

(a) A typical hybrid mesh around the airfoil with a jet located at xj/c = 12% and (b) zoom on the boundary layer mesh along the airfoil surface

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Fig. 3

Grid dependence of the mean lift coefficient versus angle of attack, Re = 106

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Fig. 4

Mesh refinement convergence study at various angles of attack for mean lift coefficient

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Fig. 5

Lift versus angle of attack experimental results on NACA 0012

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Fig. 6

(a) Comparison of experimental and numerical results on lift coefficient versus angle of attack on NACA 0012 and (b) velocity magnitude at angle of attack (AoA) = 10 deg, 14 deg, 16 deg, and 19 deg

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Fig. 7

Periodic function of time f(fj, t) of the actuator for synthetic and pulsed jet

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Fig. 8

Airfoil and the actuator design-space (xj/c, dj/c, Vj, and θj)

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Fig. 9

Lift coefficient versus angle of attack, Re = 106. (ref.) reference case without control, (tj) tangential continuous jet, with Vj/V0 = 2, θj = 30 deg and xj/c = 12% (tsj) tangential synthetic jet, with Vj/V0 = 2, θj = 30 deg and xj/c = 12%, fj = 15 (tpj) tangential pulsed jet. with Vj/V0 = 2, θj = 30 deg and xj/c = 12%, fj = 15, DC = 0.5.

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Fig. 10

Mean flow separation location versus angle of attack for tangential synthetic jet

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Fig. 11

Actuator effect on mean lift coefficient versus angle of attack

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Fig. 12

Effects of the four synthetic jet actuator parameters (xj/c, Vj, θj, and fj) on the lift coefficient, α = 19 deg: (a) actuator location xj/c effect with Vj/V0 = 2, θj = 30 deg, and fj = 15; (b) Actuator velocity magnitude Vj/V0 effect with xj/c = 12%, θj = 30 deg, and fj = 15; (c) actuator velocity angle θj effect with Vj/V0 = 2, xj/c = 12%, and fj = 15; and (d) actuator frequency fj effect with Vj/V0 = 2, θj = 30 deg, and xj/c = 12%

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Fig. 13

Instantaneous streamlines with various actuator locations for α = 19 deg: (a) control OFF, (b) control ON Xj/c = 12%, (c) control ON Xj/c = 40%, and (d) control ON Xj/c = 45%

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Fig. 14

Lift coefficient history with various actuator locations for α = 19 deg

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Fig. 15

Response surface of the lift coefficient Cl(θj, xj/c)

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Fig. 16

Response surface of the lift coefficient Cl(F+j, xj/c)

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Fig. 17

Response surface of the lift coefficient Cl(Vj/V0, xj/c)

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Fig. 18

Synthetic jet velocity and lift coefficient on one period of actuation

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Fig. 19

Skin friction coefficient during one period of actuation of the synthetic jet: (a) skin friction along the airfoil suction surface and (b) zoom in the actuator region

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