Delay of airfoil stall by periodic excitation

Seifert, Avi; Darabi, Ahmad; Wygnanski, I.

doi:10.2514/3.47003

Cited by 564 publications

(284 citation statements)

References 6 publications

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“…Using the simple scaling for the vortex shedding time scale discussed in §2a, St = 0.15 = fc sin d f /U , where d f is the flap deflection angle, we conclude that a typical vortex shedding frequency would have f + > 1 when d f > 8 • ; one can infer that wake and/or separation bubble instabilities may equally have played a role. Seifert et al [24] used oscillatory blowing at the leading edge of a NACA0015 aerofoil at Re = 10 6 , and found lift enhancement and drag reduction over range 0 < f + < 2, with a broad maximum around f + = 0.75, which, for the range of 16…”

Section: (B) Actuated Flowsmentioning

confidence: 99%

Control of vortex shedding on two- and three-dimensional aerofoils

Colonius

Williams

2011

Phil. Trans. R. Soc. A.

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We review and expand on the control of separated flows over flat plates and aerofoils at low Reynolds numbers associated with micro air vehicles. Experimental observations of the steady-state and transient lift response to actuation, and its dependence on the actuator, aerofoil geometry and flow conditions, are discussed and an attempt is made to unify them in terms of their excitation of periodic and transient vortex shedding. We also examine strategies for closed-loop flow and flight control using actuation of leading-edge vortices.

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Section: (B) Actuated Flowsmentioning

confidence: 99%

Control of vortex shedding on two- and three-dimensional aerofoils

Colonius

Williams

2011

Phil. Trans. R. Soc. A.

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“…Therefore, active flow control may produce interesting approaches for a large variety of problems, e.g. changing lift for rotary wing aircraft [1], designing minimum radar cross-section aircraft or delaying aerodynamic stall to enhance maximum lift [2]. However, most of the flow control techniques based on steady jet suction or blowing are difficult to implement into airfoils in practice, since they require large amount of power and room for air supply.…”

Section: Introductionmentioning

confidence: 99%

“…It was reported that a high momentum coefficient was required to obtain a significant lift increase. Steady blowing as well as oscillatory jet actuations were simulated by Donovan et al [9] and compared to experimental measurements performed by Seifert et al [2]. The same configuration was also studied by Ekaterinaris [10], who tested some different jet parameters.…”

Section: Introductionmentioning

confidence: 99%

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Optimization of a synthetic jet actuator for aerodynamic stall control

Duvigneau

Visonneau

2006

Computers & Fluids

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The numerical simulation of aerodynamic stall control using a synthetic jet actuator is presented and the automatic optimization of the control parameters is investigated. Unsteady Reynolds-averaged NavierStokes equations are solved on unstructured grids using a near-wall low-Reynolds number turbulence closure to simulate the effects of a synthetic jet, located at 12% of the chord from the leading edge of a NACA 0015 airfoil, for a Reynolds number Re = 8.96 10 5 and incidences between 12 to 24 degrees. Then, an automatic optimization procedure coupled with the flow solver is employed to optimize the parameters of the actuator (momentum coefficient, frequency, angle with respect to the wall) at each incidence in order to increase the time-averaged lift. A significant increase of the maximum lift is obtained (+52% with respect to the baseline airfoil) and the stall delayed from 16 • to 22 • for optimal parameters. The flow characteristics and the influence of the respective control parameters are analysed.

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“…Indeed, several experiments have successfully suppressed large separation bubble on an airfoil. [3][4][5][6][7] In the case of weak external disturbances, it is expected that the most amplified wave for the linear instability is effective in controlling separation when the separation bubble is not very large. However, when strong forcing is applied to suppress the large separation bubble, the scale of the most effective disturbance is larger than that of the most amplified disturbance and is comparable to the height of the separation bubble.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Separation Control of Turbulent Boundary Layers by Vortex Excitation

Asai¹,

Shimada²,

Imai³

2005

Trans. Japan Soc. Aero. S Sci.

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Artificial disturbances are introduced to a turbulent boundary layer separating at a convex corner to see how excited vortices control the turbulent separation. The results clearly show that excitation of vortices with appropriate scale can effectively suppress the separation of turbulent boundary layer, not unlike the case of laminar separation. However, strong disturbance growth due to Kelvin-Helmholtz instability, which decisively dominates development of separation bubble for laminar separation, does not occur for turbulent separation. Therefore direct excitation of energetic vortices around the separation point is required for suppression of turbulent separation.

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Delay of airfoil stall by periodic excitation

Cited by 564 publications

References 6 publications

Control of vortex shedding on two- and three-dimensional aerofoils

Control of vortex shedding on two- and three-dimensional aerofoils

Optimization of a synthetic jet actuator for aerodynamic stall control

Experimental Study on the Separation Control of Turbulent Boundary Layers by Vortex Excitation

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