Abstract
The near-field flow structure of a tip vortex behind a sweptback and tapered NACA 0015 wing was investigated and compared with a rectangular wing at the same lift force and Re=1.81×105. The tangential velocity decreased with the downstream distance while increased with the airfoil incidence. The core radius was about 3% of the root chord c r, regardless of the downstream distance and α for α<8°. The core axial velocity was always wake-like. The core Γc and total Γo circulation of the tip vortex remained nearly constant up to x/c r=3.5 and had a Γc/Γo ratio of 0.63. The total circulation of the tip vortex accounted for only about 40% of the bound root circulation Γb. For a rectangular wing, the axial flow exhibited islands of wake- and jet-like velocity distributions with Γc/Γo=0.75 and Γo/Γb=0.70. For the sweptback and tapered wing tested, the inner region of the tip vortex flow exhibited a self-similar behavior for x/c r≥1.0. The lift force computed from the spanwise circulation distributions agreed well with the force-balance data. A large difference in the lift-induced drag was, however, observed between the wake integral method and the inviscid lifting-line theory.
Similar content being viewed by others
Abbreviations
- AR:
-
Aspect ratio (b 2/S)
- b :
-
(Semi-)wing span
- c :
-
Chord of rectangular wing
- c r :
-
Root chord
- c t :
-
Tip chord
- C D :
-
Drag coefficient without wing tip effects
- C Di :
-
Lift-induced drag coefficient (D i /0.5ρu 2∞ S)
- C D,3-D :
-
Drag coefficient of a 3-D wing configuration
- C L :
-
Lift coefficient without wing tip effects (L/0.5ρu 2∞ S)
- C L,3-D :
-
Lift coefficient of a 3-D wing configuration
- D :
-
Drag without wing tip effects
- D 3-D :
-
Drag of a 3-D wing configuration
- D i :
-
Lift-induced drag
- L :
-
Lift
- p :
-
Local static pressure
- p ∞ :
-
Free-stream static pressure
- r :
-
Radial position
- r o :
-
Vortex outer radius
- r c :
-
Vortex core radius
- Re :
-
Reynolds number (u ∞ c r/ν or u ∞ c/ν)
- S :
-
Wing area
- u :
-
Axial mean velocity
- u c :
-
Core axial velocity
- u ∞ :
-
Free-stream velocity
- v :
-
Transverse mean velocity
- v θ :
-
Tangential velocity
- w :
-
Spanwise mean velocity
- x :
-
Streamwise or axial direction
- y :
-
Normal direction
- z :
-
Spanwise direction
- ρ:
-
Fluid density
- ν:
-
Fluid kinematic viscosity
- ζ:
-
Streamwise vorticity (∂w/∂y - ∂v/∂z)
- Γ:
-
Circulation or vortex strength
- Γb :
-
Bound root circulation
- Γc :
-
Core circulation
- Γo :
-
Total circulation
- α:
-
Angle of attack
- αss :
-
Static-stall angle
- λ:
-
Taper ratio (c t/c r)
- ψ:
-
Stream function
- φ:
-
Velocity potential
- σ:
-
A source term in Eq. 6 (∂v/∂y + ∂w/∂z)
References
Batchelor GK (1964) Axial flow in trailing line vortices. J Fluid Mech 20:645–658
Birch D, Lee T (2004) Structure and induced drag of a tip vortex. J Aircr 41(5):1138–1145
Brune GW (1994) Quantitative low-speed wake surveys. J Aircr 31(2):249–255
Chow JS, Zilliac GG, Bradshaw P (1997) Mean and turbulence measurements in the near field of a wingtip vortex. AIAA J 35(10):1561–1567
Devenport WJ, Rife MC, Liapis SI, Follin GJ (1996) The structure and development of a wing-tip vortex. J Fluid Mech 312:67–106
El-Ramly Z, Rainbird WJ, Earl DG (1976) Wind tunnel measurement of rolling moment in a swept-wing vortex wake. J Aircr 13(12):962–967
Francis MS, Kennedy DA (1979) Formation of a trailing vortex. J Aircr 16(3):148–154
Francis TB, Katz J (1988) Observations on the development of a tip vortex on a rectangular hydrofoil. J Fluids Eng 110:208–215
Glauert TH (1926) The elements of airfoil and airscrew theory. Cambridge University Press, London
Green SI, Acosta AJ (1991) Unsteady flow in trailing vortices. J Fluid Mech 227:107–134
Hoffmann ER, Joubert PN (1963) Turbulent line vortices. J Fluid Mech 16:395–411
Kusunose K (1997) Development of a universal wake survey data analysis code. AIAA 2294
Lamb H (1945) Hydrodynamics, 6th edn. Dover, New York, p 592
Maskell E (1973) Progress towards a method for the measurement of the components of the drag of a wing of finite span. RAE Technical Report 72232
McAlister KW, Takahashi RK (1991) NACA 0015 wing pressure and trailing vortex measurements. NASA TP-3151
Moore DW, Saffman PG (1973) Axial flow in laminar vortices. Proc R Soc Lond A 333:491–508
Naik DA, Ostowari C (1990) Effects of nonplanar wing forms on a wing. J Aircr 27(2):117–122
Orloff KL, Ciffone DL (1974) Vortex measurements behind a swept wing transport model. J Aircr 11(6):362–364
Ozger E, Schell I, Jacob D (2001) On the structure and attenuation of an aircraft wake. J Aircr 38(5):878–887
Phillips WRC (1981) The turbulent trailing vortex during roll-up. J Fluid Mech 105:451–467
Ramaprian BR, Zheng Y (1997) Measurements in rollup region of the tip vortex from a rectangular wing. AIAA J 35(12):1837–1843
Shekarriz A, Fu TC, Katz J, Huang TT (1993) Near-field behavior of a tip vortex. AIAA J 31(1):112–118
Spalart PR (1998) Airplane trailing vortices. Ann Rev Fluid Mech 30:107–138
Wenger CW, Devenport WJ (1999) Seven-hole pressure probe calibration utilizing look-up error tables. AIAA J 37(6):675–679
Williams GM (1974) Viscous modeling of wing-generated trailing vortices. Aeronaut Q 25:143–154
Zeman O (1995) The persistence of trailing vortices: a modeling study. Phys Fluids 7(1):135–143
Acknowledgments
This work was supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Gerontakos, P., Lee, T. Near-field tip vortex behind a swept wing model. Exp Fluids 40, 141–155 (2006). https://doi.org/10.1007/s00348-005-0056-y
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00348-005-0056-y