Vortex breakdown on slender sharp-edged wings

Kohlman, D. L.; Wentz, W. H.

doi:10.2514/3.44247

Cited by 233 publications

(40 citation statements)

References 3 publications

(2 reference statements)

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“…Constant-height flaps with height/chord ratios of 1, 2, 3, and 5% were tested at a Reynolds number based on root chord of 8:6 10 5 . However, when the results presented in [9] were compared with previous data for 60 delta wings (e.g., [15]), it became clear that the basic wing lift-curve slope was far too high, by a factor of around 30%. An analysis of the entire data set [16] showed that dividing all lift, drag, and pitching-moment measurements by 1.3 gave a more reasonable agreement with published 60 wing data and with the effects of flap height reported later in this paper.…”

Section: Gurney Flaps Applied To Delta Wingsmentioning

confidence: 92%

“…4Comparison of basic 60 wing with theory and results from Torlund[28] and Wentz and Kohlman[15].Fig. 5Effect of flap height on lift increment at zero incidence.…”

mentioning

confidence: 89%

“…The FFA wing had a very similar geometry (a strut-mounted flat-plate model with an underbody fairing) and was tested at the same Reynolds number of 0:71 10 6 . Figure 4 also shows normal force data from the seminal study of delta-wing aerodynamics by Wentz and Kohlman [15] and the theoretical normal force given by the leading-edge suction analogy (LESA) [29]. Angle of attack is given relative to the zero-lift incidence 0L , to allow for the effect of different leading-edge chamfer angles [30] and support interference.…”

Section: Experimental Arrangementmentioning

confidence: 99%

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Gurney Flaps on Slender and Nonslender Delta Wings

Greenwell

2010

Journal of Aircraft

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A parametric low-speed wind-tunnel study has been undertaken of the effects of Gurney flap height on the aerodynamic characteristics of delta wings with sweep angles of 40, 60, and 70 . Flap effects on lift and drag are consistent with previous two-dimensional data when wing geometry is accounted for by using the change in zero-lift incidence rather than lift and using the relative flap area rather than flap height. Flap deployment primarily affects the attached-flow potential lift on delta wings, with vortex lift being almost unchanged. Induced-drag factors are considerably reduced as flap height is increased, but this is due to the use of flat-plate models with near-zero leadingedge suction. For control applications, pitch/lift ratios are similar to those for delta wings with conventional trailingedge flaps, but the trim-drag penalties are much higher. An aft shift in loading associated with Gurney flap deployment leads to large aft movements of the aerodynamic center, which significantly reduces control capability.pitching-moment coefficient at zero lift C N = normal force coefficient, N=qS C NP = potential flow component of normal force C NV = vortex lift component of normal force D = drag h = projected flap height (measured from lower surface) K P = potential lift factor, C L K V = vortex lift factor k = induced-drag factor, C D C D min AR=C 2 L L = lift q = dynamic pressure, 1 2 V 2 q = lift increase factor on flap height S = wing area S f = flap frontal area, hb t = wing thickness = angle of attack 0L = zero-lift angle of attack 0P = zero-lift angle of attack for potential lift component 0V = zero-lift angle of attack for vortex lift component = leading-edge sweep angle

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Section: Gurney Flaps Applied To Delta Wingsmentioning

confidence: 92%

“…4Comparison of basic 60 wing with theory and results from Torlund[28] and Wentz and Kohlman[15].Fig. 5Effect of flap height on lift increment at zero incidence.…”

mentioning

confidence: 89%

Section: Experimental Arrangementmentioning

confidence: 99%

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Gurney Flaps on Slender and Nonslender Delta Wings

Greenwell

2010

Journal of Aircraft

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“…1 The phenomenon is of interest for various disciplines due to its occurrence in geophysical as well as in industrial swirling flows. Vortex breakdown was first observed over the delta wings of aircraft [2][3][4] where it creates a sudden drop in the lift and an increase in the drag, possibly leading to a loss of aircraft control. 5 By contrast, it can be advantageous in geophysical applications since it largely decreases the swirl of the vortex and thus limits the destructive power of tornadoes.…”

Section: Introductionmentioning

confidence: 98%

Experimental control of vortex breakdown by density effects

Ismadi¹,

Meunier²,

Fouras³

et al. 2011

Physics of Fluids

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International audienceThe vortex breakdown inside a cylinder with a rotating top lid is controlled experimentally by injecting at the bottom a fluid with a small density difference. The density difference is obtained by mixing a heavy dye or alcohol with water in order to create a jet denser or lighter than water. The injection of a heavy fluid creates a buoyancy force downward, which counteracts the meridional recirculation in the cylinder and thus enhances the formation of a vortex breakdown bubble. The stability diagram shows that even a very small density difference of 0.02% is able to decrease by a factor of 2 the critical Reynolds number of appearance of the breakdown. On the other hand, the injection of a lighter fluid does not destroy the vortex breakdown. However, for large enough density differences (larger than 0.03%), the lighter fluid is able to pierce through the bubble and leads to a new structure of the vortex breakdown. Finally, a parallel is drawn between a light jet and a vortex ring generated at the bottom of the cylinder: strong vortex rings are able to pierce through the bubble, whereas weak vortex rings are simply advected around the bubble

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“…A T HIGH angles of attack, delta wings can generate high lift, with better stability and control characteristics [1][2][3]. For this reason, current and future unmanned combat air vehicle (UCAV) designs have blended delta wing-body configurations.…”

Section: Introductionmentioning

confidence: 99%

Effects of Unsteady Trailing-Edge Blowing on Delta Wing Aerodynamics

Jiang

Wang

Gursul

2010

Journal of Aircraft

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The effects of unsteady trailing-edge blowing on delta wing aerodynamics were investigated experimentally to understand the aerodynamics-propulsion interaction for dynamic thrust vectoring. Two models with sweep angles of 50 and 65 deg, representing nonslender and slender delta wings, respectively, were tested in a water tunnel. Flow visualization and velocity and force measurements were conducted at stall and poststall incidences. For the periodic blowing, it was found that the dynamic response of leading-edge vortex breakdown and wing normal force coefficient exhibit phase lags for both nonslender and slender delta wings. The estimated time constants are larger than those reported in the literature for unsteady wings undergoing pitching or plunging. In the case of transient blowing, the time delay for the decelerating jet is significantly larger than that for the accelerating jet. The variation of the circulation and the reattachment process near the wing surface were studied by means of velocity measurements. The range of the estimated time constants is similar at the stall and poststall incidences for both the slender and nonslender wings.= dimensionless frequency, fc=U 1 q = freestream dynamic pressure Re = Reynolds number S w = wing surface area s = local semispan T = period t = wing thickness or time U jet = jet velocity U 1 = freestream velocity u = velocity X bd = distance from wing apex to leading-edge vortex breakdown location y jet = spanwise location of jet = wing incidence = jet pitch angle = circulation X bd = peak-to-peak amplitude of the variation of the vortex breakdown location = leading-edge sweep angle = fluid kinematic viscosity = air density = time constant = phase lag ! = angular frequency ! x = streamwise vorticity

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Vortex breakdown on slender sharp-edged wings

Cited by 233 publications

References 3 publications

Gurney Flaps on Slender and Nonslender Delta Wings

Gurney Flaps on Slender and Nonslender Delta Wings

Experimental control of vortex breakdown by density effects

Effects of Unsteady Trailing-Edge Blowing on Delta Wing Aerodynamics

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