Dynamic Stall Control by Periodic Excitation, Part 2: Mechanisms

Greenblatt, David; Nishri, B.; Darabi, Ahmad; Wygnanski, I.

doi:10.2514/2.2811

Cited by 65 publications

(26 citation statements)

References 25 publications

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“…A multitude of passive and active means to control flow separation have been proposed and investigated. Some of the most common approaches involve vortex generators [2,3] , miniature trailing edge devices [4] , continuous and oscillatory blowing and suction [5][6][7][8][9] , microjets [10][11][12][13] , and zero-net-mass-flux actuation (e.g., plasma actuators [14] and synthetic jets [15][16][17][18][19][20][21][22][23] ). These methods and their feasibility for full-scale applications have been reviewed and evaluated by numerous authors [24][25][26][27][28][29][30] .…”

Section: Introductionmentioning

confidence: 99%

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Parameters Governing Separation Control with Sweeping Jet Actuators

Woszidlo

2011

29th AIAA Applied Aerodynamics Conference

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Section: Introductionmentioning

confidence: 99%

“…The combination of C  and C Q may also be expressed only in terms of C Q (Equation (18)) or C  (Equation (19)). Equation (18) indicates that the actuation intensity may be increased more effectively by increasing C Q and not by…”

Section:  Ts =20mentioning

confidence: 99%

Parameters Governing Separation Control with Sweeping Jet Actuators

Woszidlo

2011

29th AIAA Applied Aerodynamics Conference

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“…The turbine consists of two NACA 0015 blades (chord length c ¼ 0. 15 blades were connected symmetrically to a central hollow vertical shaft of diameter 50.8 mm, running on self-aligning bearings that were located above and below the tunnel walls. The turbine dimensions were diameter D ¼ 0.5 m, projected area A ¼ HD ¼ 0.3 m 2 and a photograph of the turbine, mounted in the wind tunnel, is shown in Fig.…”

Section: Wind Turbine Configurationmentioning

confidence: 99%

Inboard/outboard plasma actuation on a vertical-axis wind turbine

Greenblatt

Lautman

2015

Renewable Energy

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a b s t r a c tVertical axis wind turbine (VAWT) blades can experience large positive and large negative angles-ofattack that produce both inboard and outboard dynamic stall. Dielectric barrier discharge (DBD) plasma actuators can control dynamic stall and hence an inboard/outboard switching control technique was developed where encapsulated electrodes were deployed on either side of the blades of an H-rotor turbine. An electromechanical system, including a shaft-mounted micro-switch and high-voltage relays, was developed for the purpose of earthing the inboard encapsulated electrode of the upwind blade with the outboard encapsulated electrode of the downwind blade. The actuators were connected to a highvoltage source via slip-rings and were pulse-modulated to exploit flow instabilities in an on/off feedforward configuration. Turbine performance measurements showed that switching produced slightly larger improvements than either inboard or outboard actuation alone. The modest differences were traced to weak plasma being generated over the floating encapsulated electrodes, whose source was unavoidable slip-ring conductor proximity. Elimination of the floating electrode plasma resulted in larger performance increments for inboard versus outboard actuation due to the larger dynamic pressure relative to the blades in the upwind swept area of the turbine compared to that in the the downwind swept area.

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“…On a NACA 0015 airfoil (e.g. [11,12]), the fundamental perturbation phase velocity can be quantified to first approximation by the relationship:…”

Section: Sweep Relations Applied To Controlmentioning

confidence: 99%

Influence of Finite Span and Sweep on Active Flow Control Efficacy

Greenblatt

Washburn

2008

AIAA Journal

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Active flow control efficacy was investigated by means of leading-edge and flap-shoulder zero mass-flux blowing slots on a semispan wing model that was tested in unswept (standard) and swept configurations. On the standard configuration, stall commenced inboard, but with sweep the wing stalled initially near the tip. On both configurations, leading-edge perturbations increased C L,max and post stall lift, both with and without deflected flaps. Without sweep, the effect of control was approximately uniform across the wing span but remained effective to high angles of attack near the tip; when sweep was introduced a significant effect was noted inboard, but this effect degraded along the span and produced virtually no meaningful lift enhancement near the tip, irrespective of the tip configuration. In the former case, control strengthened the wingtip vortex; in the latter case, a simple semi-empirical model, based on the trajectory or "streamline" of the evolving perturbation, served to explain the observations. Control on finite-span flaps did not differ significantly from their two-dimensional counterpart, while control over a tip flap produced significant variations to all three moments in the presence of large deflection and these variations were linear with input slot momentum. Control from the flap produced expected lift enhancement and C L,max improvements in the absence of sweep, but these improvements degraded with the introduction of sweep. Nomenclature AR= wing model aspect ratio c = model chord-length C dp = sectional form-drag coefficient

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Dynamic Stall Control by Periodic Excitation, Part 2: Mechanisms

Cited by 65 publications

References 25 publications

Parameters Governing Separation Control with Sweeping Jet Actuators

Parameters Governing Separation Control with Sweeping Jet Actuators

Inboard/outboard plasma actuation on a vertical-axis wind turbine

Influence of Finite Span and Sweep on Active Flow Control Efficacy

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