Flow Survey of the Vortex Wake behind Wings

El-Ramly, Z.; Rainbird, W. J.

doi:10.2514/3.58897

Cited by 26 publications

(8 citation statements)

References 15 publications

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“…This phenomenon is typically observed within a vortex that is decaying, 14 ' 16 expanding, 17 or subjected to breakdown. 3 Conversely, during vortex roll-up, 9 the tangential velocity increases with x/c, creating a negative axial pressure gradient and, consequently, an increase in the axial velocity. Thus, the boundary layer on the wing and vortex roll-up have opposite effects.…”

Section: Axial Velocitymentioning

confidence: 96%

“…9 ' 11 This profile was first predicted by Hoffmann and Joubert, who developed a model for turbulent line vortices that ineluded diffusion of angular momentum. 12 However, viscous diffusion within the near field is insignificant because of the associated long time scales.…”

Section: Introductionmentioning

confidence: 93%

“…Results of previous experimental studies range between a minimum of 45% 4 ' n to a maximum of 80%. 9 Thus, the tip vortex circulation, determined from the instantaneous velocity distribution, is still much lower than the wing circulation, as estimated from the lift coefficient.…”

Section: Circulationmentioning

confidence: 99%

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Near-field behavior of a tip vortex

Shekarriz

Katz

et al. 1993

AIAA Journal

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The near-field behavior of a tip vortex trailing behind a low aspect ratio wing, attached to an axisymmetric body, is investigated in this paper. This study was performed in a tow tank and involved the use of particle displacement velocimetry. Evolution of the tip vortex was studied by mapping its instantaneous lateral velocity at several consecutive axial locations. The axial velocity distribution was also measured. Experiments were repeated at various Reynolds numbers and incidence angles. Repeatability was also examined at the same conditions. The results indicate that roll-up is almost complete at the trailing edge and that less than 66% of the root circulation is entrained into the vortex. At Re c = 2.2 x 10 s , the results are steady, and the spatially averaged tangential velocity agrees well with the existing models. At Re c

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Section: Axial Velocitymentioning

confidence: 96%

Section: Introductionmentioning

confidence: 93%

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Near-field behavior of a tip vortex

Shekarriz

Katz

et al. 1993

AIAA Journal

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“…First, for the wing loading distribution of interest, evaluate the left-hand side of Eq. (23) analytically. This^term appears in Eqs.…”

Section: Resultsmentioning

confidence: 97%

“…Note that the piecewise continuous definitions of axial and swirl velocity in the core necessitate that the right-hand-side integral be evaluated over two ranges, from 0 to r x and from r, to r t . For the present model, this equation becomes m + fi, r 2 F 2 (\ mj\ (23) where two new functions, F[ and F 2 , are functions only of the quantity r s /r t and m. Because r s /r t appears frequently, it is convenient to define a new solution parameter, R = r s /r t , which replaces r v as the fourth solution parameter. Physically, R represents the proportion of the viscous core that is strictly solid body rotation and is guaranteed to lie between 0 and 1.…”

Section: Viscous Core Conservation Lawsmentioning

confidence: 98%

Prediction of Viscous Trailing Vortex Structure from Basic Loading Parameters

Rule

Bliss

1998

AIAA Journal

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An analytical method has been developed to predict the structure of a fully developed trailing vortex with a viscous core. Vortex structure is calculated from the load distribution on the generating wing and fundamental conservation laws are satisfied. The present rollup model implicitly addresses viscous effects in the vortex core region by assuming a turbulent mixing process in the core during formation. Mixing theory suggests the appropriate functional form of the solution velocity profiles within this region, with constants that are determined uniquely by the method for arbitrary wing loading distributions. Important structural properties such as vortex strength, core size, and peak swirl velocity are calculated directly from these solution constants. The viscous core model was validated against two recent experimental studies, which provided new insight into vortex growth. NomenclatureAI = shooting parameter C L = coefficient of lift i, ^2, G\, GI -auxiliary functions m = core axial velocity power law p = pressure Poo = freestream pressure R = core radius ratio, r s /r t r = vortex radius r c = vortex outer radius: complete inviscid rollup r in = streamtube inlet radius r p -vortex outer radius: partial inviscid rollup r s = solid body region outer radius r t = turbulent core radius s = span of rollup region (wing semispan) UQQ = freestream velocity u = vortex axial velocity v = vortex swirl velocity a = wing geometric angle of attack F = bound circulation F max = maximum bound circulation f = vortex circulation 6 = dimensionless wing loading strength £ = spanwise coordinate (from tip) f = centroid of vorticity Subscripts and Superscript i = initial condition t = value on turbulent core boundary = dimensionless quantity

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The aerodynamic interference between a flapped tanker aircraft and a receiver aircraft during air-to-air refuelling

Bloy¹,

Trochalidis²,

West³

1991

Aeronaut. j.

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SummaryWind tunnel data have been obtained from a flapped tanker wing and receiver aircraft model at varying vertical separation and the results compared with theory. In the aerodynamic model, the tanker wing is represented by a pair of horseshoe vortices from the wing and flap tips and an allowance is made for the self-induced vertical displacement of the trailing vortices at the receiver aircraft position. The aerodynamic loads on the receiver are determined by the vortex-lattice method and lifting-line theory, although an approximate method is used to determine the side force on the fin. Data were obtained from open and closed test sections in order to estimate the wind tunnel boundary interference effect. In the longitudinal case, significant differences were obtained between theory and experiment. Two reasons for the differences are the assumption that the trailing vortices are fully rolled up and the neglect of viscous decay of the vortices. The lateral aerodynamic interference was determined by banking the tanker wing and displacing it sideways and by yawing the receiver aircraft model. In the case of the rolling moment due to sideways displacement, which is the most significant lateral aerodynamic interference term, the wind tunnel boundary interference is highly significant and the difference between theory and experiment is large due to incomplete roll up of the trailing vortices. The theoretical and experimental trends are similar although the theory overpredicts the rolling moment due to bank and sideways displacement while the corresponding side force and yawing moment are underpredicted. As in previous tests using an unflapped tanker wing, the effect of the sidewash due to the tanker wing on the receiver in yaw is found to be relatively insignificant.

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Flow Survey of the Vortex Wake behind Wings

Cited by 26 publications

References 15 publications

Near-field behavior of a tip vortex

Near-field behavior of a tip vortex

Prediction of Viscous Trailing Vortex Structure from Basic Loading Parameters

The aerodynamic interference between a flapped tanker aircraft and a receiver aircraft during air-to-air refuelling

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