Active Flow Control of a Delta Wing at High Incidence Using Segmented Piezoelectric Actuators

Margalit, Sapir; Greenblatt, David; Seifert, Avi; Wygnanski, I.

doi:10.2514/6.2002-3270

Cited by 25 publications

(10 citation statements)

References 13 publications

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“…( Bar-Sever 1989;Seifert et al 1993;Ravindran 1999;Wygnanski 2000;Darabi & Wygnanski 2002;Funk et al 2002;Margalit et al 2002). Among studies that define F + J = f x T E /U ∞ , where x T E is streamwise distance between the actuator and the trailing edge, optimal values of F + J range from 0.5 to 2.0 (Greenblatt & Wygnanski 1999;Seifert & Pack 1999;Gilarranz & Rediniotis 2001).…”

Section: Scaling Of Characteristic Frequenciesmentioning

confidence: 97%

Nonlinear dynamics and synthetic-jet-based control of a canonical separated flow

et al. 2010

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A novel flow configuration devised for investigation of active control of separated airfoil flows using synthetic jets is presented. The configuration consists of a flat plate, with an elliptic leading edge and a blunt trailing edge, at zero incidence in a free stream. Flow separation is induced on the upper surface of the airfoil at the aft-chord location by applying suction and blowing on the top boundary of the computational domain. Typical separated airfoil flows are generally characterized by at least three distinct frequency scales corresponding to the shear layer instability, the unsteadiness of the separated region and the vortex shedding in the wake, and all these features are present in the current flow. Two-dimensional Navier-Stokes simulations of this flow at a chord Reynolds number of 6 104 have been carried out to examine the nonlinear dynamics in this flow and its implications for synthetic-jet-based separation control. The results show that there is a strong nonlinear coupling between the various features of the flow, and that the uncontrolled as well as the forced flow is characterized by a variety of lock-on states that result from this nonlinear coupling. The most effective separation control is found to occur at the highest forcing frequency for which both the shear layer and the separated region lock on to the forcing frequency. The effects of the Reynolds number on the scaling of the characteristic frequencies of the separated flow and its subsequent control are studied by repeating some of the simulations at a higher Reynolds number of 1 105. © 2010 Cambridge University Press

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Section: Scaling Of Characteristic Frequenciesmentioning

confidence: 97%

Nonlinear dynamics and synthetic-jet-based control of a canonical separated flow

et al. 2010

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“…III.C), but not studied in detail. 28 Figures 3a-3c show examples of the three modes, where the function generator (input voltage) signal is shown together with the derectified hotwire measured velocities. Mode (1) is self-explanatory.…”

Section: B Modes Of Excitation: Definitionsmentioning

confidence: 99%

Delta Wing Stall and Roll Control Using Segmented Piezoelectric Fluidic Actuators

Margalit

Greenblatt

Seifert

et al. 2005

Journal of Aircraft

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The separated flow around a balance-mounted, 60-deg sweptback, semispan delta wing with a sharp leading edge was controlled using zero-mass-flux periodic excitation from a segmented leading-edge slot. Excitation was generated by cavity-installed piezoelectric actuators operating at resonance with amplitude modulation (AM) and burst mode (BM) signals being used to achieve reduced frequencies (scaled with the freestream velocity and the root chord) in the range from O(1) to O(10). Results of a parametric investigation, studying the effects of AM frequency, BM duty cycle and frequency, excitation amplitude, location of the actuation along the leading edge, and optimal phase difference between the actuators, as well as the Reynolds number, are reported and discussed. Balance data were supplemented by upper surface static pressure measurements and particle image velocimetry (PIV) data. Order unity reduced-frequency modulation of the high-frequency carrier wave increased the normal force generated by the delta wing most effectively. BM with a duty cycle that was as low as 5% was more effective than the amplitude-modulated signal with larger peak excitation velocity and an order of magnitude larger momentum input. PIV data suggest that excitation enhances the momentum transfer across the shear layer, downstream of the original vortex breakdown location, generating a streamwise vortex the size of which is commensurate with the local wing span. Nomenclatureleading-edge length D = drag force DCy = duty cycle, n f m / f r FM = figure of merit, η/(C L /C D ) baseline F + = nondimensional excitation frequency, ( f c/U ∞ ) f = excitation frequency; either f m or f r , depends on excitation type f m = modulating frequency f r = actuators resonance frequency K = number of active actuator elements L = length of separated region n = number of excitation cycles p = local pressure Q = in-plane velocity, √ (w 2 + v 2 ) q = freestream dynamic pressure, ρU 2 ∞ /2 Re = root chord Reynolds number, U ∞ c/ν T m = input signal modulation period T r = period of actuators' sine wave U p = slot exit peak velocity U ∞ = freestream velocity u f = fast Fourier transform amplitude results at f = f m u = rms of velocity fluctuations u s = u at the slot's exit V rms = rms excitation voltage v, w = velocity components of the flow in the y, z directions W= actuator input power, W X R = distance from actuator to reattachment area X TE = distance from actuator to trailing edge x, y, z = Cartesian coordinates, (Fig. 1) x , y = rotated coordinates, (Fig. 1) α = angle of attack α s = stall α η = aerodynamic efficiency, C L /(C D + C E ) η R = spanwise location of the center of pressure, origin at tunnel wall, C R /C N ν = kinematic viscosity ρ = air density = phase angle between input signals to each actuator χ M = streamwise location of the center of pressure, origin at midchord, C M /C N = dimensionless vorticity, (∂v/∂x − ∂u/∂ y)/U ∞ c

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“…11,3,12,13,14,15,16 Other studies that scale F + by the length of the separation bubble observe optimal values between 0.75 and 2.0. Each of these scales by a different length associated with the separation and a characteristic speed, although freestream velocity U ∞ is often used for the latter.…”

Section: Introductionmentioning

confidence: 97%

Control of a canonical separated flow

Griffin

Oyarzun

Cattafesta³

et al. 2013

43rd Fluid Dynamics Conference

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A stalled airfoil can exhibit up to three natural frequencies associated with the separated flow: that of the shear layer, the separation bubble, and the wake. This work investigates these flow phenomena using a simplified canonical setup and targets their frequencies with zero-net mass-flux (ZNMF) actuation in order to effectively and efficiently reduce the extent of the separation. First, boundary layer separation is created on a flat plate model, devoid of curvature that would otherwise include effects particular to the type of aerodynamic body, by imposing an adverse pressure gradient via a ZNMF suction/blowing boundary condition on the tunnel ceiling. At a chord Reynolds number of 10 5 , the nominal two-dimensional characteristics of the flow are verified. The uncontrolled flow is characterized, including identification of the key flow frequency content, prior to strategically targeting this content with unsteady actuation. The identified natural frequencies of the shear layer and wake are then targeted via open-loop ZNMF sinusoidal and burst-modulated (BM) forcing. The results clearly indicate the ability to reattach the separated flow using significantly reduced Cµ values via BM forcing compared to sinusoidal forcing at the actuator resonance frequency.

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Active Flow Control of a Delta Wing at High Incidence Using Segmented Piezoelectric Actuators

Cited by 25 publications

References 13 publications

Nonlinear dynamics and synthetic-jet-based control of a canonical separated flow

Nonlinear dynamics and synthetic-jet-based control of a canonical separated flow

Delta Wing Stall and Roll Control Using Segmented Piezoelectric Fluidic Actuators

Control of a canonical separated flow

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