Vortical Interactions Behind Deployable Vortex Generator for Airfoil Static Stall Control

Joubert, G. D.; Pape, Arnaud Le; Heine, Benjamin; Huberson, S.

doi:10.2514/1.j051767

Cited by 10 publications

(7 citation statements)

References 25 publications

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“…A midpoint between active and passive flow control is a passive flow control which is deployed only during the pitching period of the airfoil or wing. This includes vortex generators which are retracted at low angle of attack [18,19], dynamically drooping leading edge geometries [20,21], dynamically actuated trailing edge flaps [22][23][24][25] or dynamically actuated gurney flaps [26,27]. In each of these cases, the dynamic stall alleviation is via a passive alteration of the airfoil contour, but actuators are required to vary the contour, so that the power requirements and complexity of the control devices is a function of the engineering design of the actuators.…”

Section: Introductionmentioning

confidence: 99%

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Reduction of dynamic stall using a back-flow flap

Gardner¹,

Opitz²,

Wolf³

et al. 2017

CEAS Aeronaut J

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A back-flow flap attached to the suction side of an airfoil is investigated in both passively and actively actuated modes for the control of dynamic stall. This method of dynamic stall control has low power requirements and no parasitic drag when not actuated. Experiments in a low-speed wind tunnel at 50 m/s were used to characterize the reduction in dynamic stall hysteresis using pressure measurements on the midline airfoil section. It was found that the pitching moment peak is reduced by an average of 25% for all deep stall test cases for active actuation of the flap, while for passive actuation the pitching moment peak is reduced by 19%. In each case the maximum lift remained the same, while the peak drag increased by an average of 2.5% for the active flap, and by 0.9% for the passive flap. With the flap closed at low angles of attack, the reference values of the airfoil are retained. KeywordsHelicopter blade Á Wind tunnel Á Flow control Á Dynamic stall Á Back-flow flap Á Experiment List of symbols a; a max Angle of attack; maximum ( ) c Airfoil model chord (m) C D ; C D max Drag coefficient; peak C L ; C L max Lift coefficient; peak C M ; C M min Pitching moment coefficient; peak C P Pressure coefficient f Frequency of pitching (Hz) M Mach number k Reduced frequency: k ¼ pfc=v 1 Re Reynolds number based on c t Time (s) T Period (s) u, v Velocity: in x direction, in z direction (m/s) v 1Freestream velocity (m/s) x, zCoordinates: chord, upward (m)This paper is based on a presentation at the AHS 72nd Annual Forum,

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Section: Introductionmentioning

confidence: 99%

“…The best known early experiments are from McCroskey [39], but the method has been used at least since the 1950s [10]. Dynamic pitching airfoil rigs are used by a large number of universities [40][41][42][43] and research institutions [13,14,19,[44][45][46]. Good overviews of dynamic stall are given by [47][48][49].…”

Section: Introductionmentioning

confidence: 99%

Reduction of dynamic stall using a back-flow flap

Gardner¹,

Opitz²,

Wolf³

et al. 2017

CEAS Aeronaut J

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“…Several attempts at optimizing the vortex generator shape and placement for static operation point can be found in the literature (Godard and Stanislas (2006); Mueller-Vahl et al 2012; Fouatih et al (2016)). Vortex generators are not limited to static stall control but have also been used for dynamic stall control (Pape et al (2012); Heine et al (2013); Joubert et al (2013a, b); Choudhry et al (2016)). For dynamic stall control, the devices have to be located close to the leading edge such that the formation of the dynamics stall vortex is suppressed or at least delayed to higher angles of attack.…”

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confidence: 99%

Parametric slat design study for thick base airfoils at high Reynolds numbers

Steiner¹,

Viré²,

Benetti³

et al. 2019

Preprint

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Abstract. Standard passive aerodynamic flow control devices such as vortex generators and gurney flaps have a working principle that is well understood. They increase the stall angle and the lift below stall and are mainly applied at the inboard part of wind turbine blades. However, the potential of applying a rigidly fixed leading edge slat element at inboard blade stations is less well understood but has received some attention in the past decade. This solution may offer advantages not only under steady conditions but also under unsteady inflow conditions such as yaw. This article aims at further clarifying what an optimal two-element configuration with a thick main element would look like, and what kind of performance characteristics can be expected from a purely aerodynamic point of view. To accomplish this an aerodynamic shape optimization procedure is used to derive optimal profile designs for different optimization boundary conditions including the optimization of both the slat and the main element. The performance of the optimized designs shows several positive characteristics as compared to single element airfoils, such as a high stall angle, high lift below stall, low roughness sensitivity and higher aerodynamic efficiency. Furthermore, the results highlight the benefits of an integral design procedure, where both slat and main element are optimized, over an auxiliary one. Nevertheless, the designs also have two caveats, namely a steep drop in lift post-stall and high positive pitching moments.

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“…Jira´sek found that the jBAY model captured the VG arrays effect under internal and external flows [24]. Joubert investigated an OA209 airfoil with a deployable VG device through numerical simulations [25]. Yan used simulations to investigate the flow over a compression ramp, with and without a micro-ramp VG upstream [26].…”

Section: Introductionmentioning

confidence: 99%

Suppression of the Hydrodynamic Noise Induced by the Horseshoe Vortex through Mechanical Vortex Generators

Liu

Hongxu

et al. 2019

Applied Sciences

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The hydrodynamic noise from the horseshoe vortex can greatly destroy the acoustic stealth of underwater vehicles at low frequency. We investigated the flow-induced noise suppression mechanism by mechanical vortex generators (VGs) on a SUBOFF model. Based on the numerical simulation, we calculated the flow field and the sound field of the three shapes of mechanical VGs: triangular, semi-circular, and trapezoidal. The triangular VGs with an angle of 30° to the flow direction achieved a better noise reduction. The optimum noise suppression is 8.93 dB, when the distance from the triangular VGs to the sail hull’s leading edge is 0.1c, where c is the chord length. The noise reduction mechanism is such that the mechanical VGs can destroy the formation of the horseshoe vortex at the origin and produce counter-rotation vortices to weaken its intensity. We created two steel models according to the simulation, and the experimental measurement was carried out in a gravity water tunnel. The measured results showed that the formation of the horseshoe vortex could be effectively inhibited by the triangular VGs. The results in our study can provide a new method for hydrodynamic noise suppression by flow control.

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Vortical Interactions Behind Deployable Vortex Generator for Airfoil Static Stall Control

Cited by 10 publications

References 25 publications

Reduction of dynamic stall using a back-flow flap

Reduction of dynamic stall using a back-flow flap

Parametric slat design study for thick base airfoils at high Reynolds numbers

Suppression of the Hydrodynamic Noise Induced by the Horseshoe Vortex through Mechanical Vortex Generators

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