Control of VR-7 Dynamic Stall by Strong Steady Blowing

Weaver, David; Mcalister, K. W.; Tso, Jin

doi:10.2514/1.4413

Cited by 28 publications

(14 citation statements)

References 13 publications

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“…It appears that positioning the control slot at 5% chord rather than further downstream increases the effectiveness of constant blowing. In contrast to the tests by Weaver et al [54,55], where constant blowing was applied at quarter chord and C μ > 16% was required for effective control, blowing fully suppressed the formation of the DSV at a comparatively low-momentum input in the present case. However, the validity of this comparison is limited because of the different airfoil geometries, Reynolds numbers, and angle-of-attack ranges.…”

Section: E Dynamic Stall Controlcontrasting

confidence: 82%

“…McCloud et al found that blowing from a slot near the leading edge (x∕c 8.5%) was capable of delaying retreating-blade stall [53]. More recently, Weaver et al reported a reduction in lift hysteresis and a decrease in unsteady load fluctuations produced by constant blowing on a VR-7 airfoil [54,55]. Somewhat similar observations were made by Singh et al [56], who used air-jet vortex generators to control dynamic stall on an RAE 9645 airfoil.…”

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confidence: 99%

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Control of Thick Airfoil, Deep Dynamic Stall Using Steady Blowing

et al. 2015

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The utility of constant blowing as an aerodynamic load control concept for wind turbine blades was explored experimentally. A NACA 0018 airfoil model equipped with control slots near the leading edge and at mid-chord was investigated initially under quasi-static conditions at Reynolds numbers ranging from 1.25 · 10 5 to 3.75 · 10 5 . Blowing from the leading-edge slot showed a significant potential for load control applications. Leading-edge stall was either promoted or inhibited depending on the momentum coefficient, and a corresponding reduction or increase in lift on the order of Δc l ≈ 0.5 was obtained. Control from the mid-chord slot counteracted trailing-edge stall but was ineffective at preventing leading-edge separation. The impact of blowing from the leading-edge slot on dynamic stall was explored by means of unsteady surface pressure measurements and simultaneous particle image velocimetry above the suction surface. At a sufficiently high momentum coefficient, the formation and shedding of the dynamic stall vortex were fully suppressed. This led to a significant reduction in lift hysteresis and form drag while simultaneously mitigating moment coefficient excursions.airfoil pitching frequency, Hz h = control slot height (1.2 mm) k = reduced pitching frequency; πfc∕U ∞ M = Mach number N = number of samples Re = Reynolds number; U ∞ c∕ν s = airfoil span (610 mm) u = streamwise velocity component (wind-tunnel frame of reference), m∕s U e = local boundary-layer edge velocity, m∕s U j = blowing jet velocity, m∕s U ∞ = wind-tunnel speed, m∕s _ V = volumetric blowing flow rate, m 3 ∕s x, y = chordwise and chord-normal positions (airfoil frame of reference), m x 0 , y 0 = streamwise and normal positions (wind-tunnel frame of reference), m y m = distance of the point of maximum jet velocity from the wall, m α = angle of attack, deg α s = static stall angle, deg Δc l = relative change in lift coefficient produced by control η = angle of the control slots relative to the airfoil surface (20 deg) ν = kinematic viscosity, m 2 ∕s σ c l = standard deviation of the lift coefficient σ c m = standard deviation of the moment coefficient ϕ= phase angle of the sinusoidal pitching motion, deg ω = airfoil pitching angular frequency; 2πf ω z = nondimensional vorticity; ∂v∕∂x − ∂u∕∂y · c∕U ∞

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Section: E Dynamic Stall Controlcontrasting

confidence: 82%

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confidence: 99%

Control of Thick Airfoil, Deep Dynamic Stall Using Steady Blowing

et al. 2015

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“…34 More recently, Weaver et al reported a reduction in lift hysteresis and a decrease in unsteady load fluctuations produced by constant blowing on a VR-7 airfoil. 35,36 Steady blowing has been studied since the early 1920s as a tool to overcome boundary layer separation. 37,38 The application at the shoulder of deflected flaps for the purpose of increasing lift, typically for landing, has been investigated extensively and reached the stage of serial-production on several aircraft 39,40 This is the classical application of constant blowing where the excess momentum near the wall offsets the adverse pressure gradient that would otherwise promote separation (e.g.…”

Section: Introductionmentioning

confidence: 99%

Control of Unsteady Aerodynamic Loads Using Adaptive Blowing

Mueller-Vahl

Nayeri

Paschereit

et al. 2014

32nd AIAA Applied Aerodynamics Conference

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Adaptive slot blowing was experimentally investigated on a NACA 0018 airfoil model as a method to minimize unsteady aerodynamic loads. Tests were conducted in a wind tunnel facility specifically designed to facilitate high amplitude wind speed fluctuations. Initially, the effect of steady blowing from a control slot located near the leading-edge was investigated under quasistatic conditions. At Reynolds numbers ranging from 1.5·10 5 to 5·10 5 , a relative change in lift of ∆cl ≈ 0.5 was obtained over a wide range of angles of attack. Various dynamic test cases including a pitching motion, a sinusoidal variation of the wind tunnel speed and a combination of both were considered. The formation of the dynamic stall vortex was suppressed with blowing at moderate momentum coefficients. Dynamically adapting the momentum coefficient effectively counteracted the lift fluctuations resulting from the unsteady inflow conditions and virtually constant lift was obtained in all test cases. Furthermore, control significantly reduced the moment excursions in all dynamic pitching experiments.

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“…Stall suppression with an active flow control technique is of interest in this study. Various active flow control techniques using fluidic actuators have been studied to mitigate flow separation [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Among numerous methods, steady-blowing jet would be the simplest fluidic actuation, ejecting a jet flow continuously into the surrounding.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Jet Angle Effect on Airfoil Stall Control

et al. 2019

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Numerical study on flow separation control is conducted for a stalled airfoil with steady-blowing jet. Stall conditions relevant to a rotorcraft are of interest here. Both static and dynamic stalls are simulated with solving compressible Reynolds-averaged Navier-Stokes equations. It is expected that a jet flow, if it is applied properly, provides additional momentum in the boundary layer which is susceptible to flow separation at high angles of attack. The jet angle can influence on the augmentation of the flow momentum in the boundary layer which helps to delay or suppress the stall. Two distinct jet angles are selected to investigate the impact of the jet angle on the control authority. A tangential jet with a shallow jet angle to the surface is able to provide the additional momentum to the flow, whereas a chord-normal jet with a large jet angle simply averts the external flow. The tangential jet reduces the shape factor of the boundary layer, lowering the susceptibility to the flow separation and delaying both the static and dynamic stalls.

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Control of VR-7 Dynamic Stall by Strong Steady Blowing

Cited by 28 publications

References 13 publications

Control of Thick Airfoil, Deep Dynamic Stall Using Steady Blowing

Control of Thick Airfoil, Deep Dynamic Stall Using Steady Blowing

Control of Unsteady Aerodynamic Loads Using Adaptive Blowing

Numerical Investigation of Jet Angle Effect on Airfoil Stall Control

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