Advertisement

Experiments in Fluids

, 60:24 | Cite as

Effect of vane sweep angle on vortex generator wake

  • Sen Wang
  • Sina GhaemiEmail author
Research Article
  • 206 Downloads

Abstract

The effect of varying the vane sweep angle of different vortex generators (VGs) on the statistics of the wake flow and the coherent structures was investigated. Pairs of rectangular, trapezoid, and delta vanes with sweep angle varying in ascending order were arranged at an equal but opposite angle with respect to the flow. A single rectangular vane was also investigated to identify the effect of vane pairing. The VGs were installed in the thin laminar boundary layer of a flat plate at Reynolds number of 930, based on VG height and free-stream velocity. Time-resolved tomographic particle image velocimetry (tomo-PIV) was carried out in a volume covering the wake, and stereo-PIV was applied to two cross-flow planes of the wake. The measurements showed two counter-rotating streamwise vortices, which induce a strong upward motion along the centerline of the wake. A pair of secondary counter-rotating streamwise vortices were also observed. The single rectangular vane showed a primary streamwise vortex and a weaker secondary streamwise vortex with opposite rotation. The evaluation of wall-normal momentum transport along the wake centerline showed that the paired configuration enhanced flow mixing. The investigation of the instantaneous coherent structures and proper-orthogonal-decomposition of the three-dimensional velocity fluctuations indicated that the coherence and strength of the vortices were inversely proportional to the sweep angle of the VG. The delta vane VG, with the largest sweep angle, produced more small-scale turbulence while the rectangular VG, with an upswept vane, produced the most coherent streamwise vortices. The investigation of wall-normal momentum transport showed that the rectangular VG had the best performance in improving flow mixing, followed by the trapezoidal, single rectangular, and delta VG. When evaluating the performance of VG using the ratio of mixing enhancement over drag, the trapezoidal VG was the most efficient one. The investigation confirmed the possibility of lowering the device drag while maintaining the effectiveness of VG using an optimum sweep angle. The performance of delta VG was about 60% of the trapezoidal VG, which suggests a large sweep angle can adversely affect the VG performance.

Graphical abstract

Abbreviations

c

Vortex generator chord (mm)

h

Vortex generator height (mm)

f

Focal length of camera lens

u

Streamwise fluctuating velocity (m/s)

v

Wall-normal fluctuating velocity (m/s)

x

Streamwise direction

y

Wall-normal direction

z

Spanwise direction

CD

Coefficient of drag

P

Turbulence production (m2/s3)

Q

Q-criterion (s−2)

U

Instantaneous streamwise velocity (m/s)

U

Free-stream velocity (m/s)

V

Instantaneous wall-normal velocity (m/s)

W

Instantaneous spanwise velocity (m/s)

β

Incidence angle of the vane (°)

γ

Leading-edge sweep angle (°)

δ

Boundary layer thickness (mm)

\({\omega _x}\)

Streamwise vorticity fluctuation (s−1)

\({\omega _z}\)

Spanwise vorticity fluctuation (s−1)

\({\Omega _x}\)

Streamwise mean vorticity (s−1)

Notes

Supplementary material

Supplementary material 1 (AVI 56171 KB)

Supplementary material 2 (AVI 65751 KB)

Supplementary material 3 (AVI 69963 KB)

Supplementary material 4 (AVI 48925 KB)

References

  1. Betterton J, Hackett K, Ashill P, Wilson M, Woodcock I (2000) Laser doppler anemometry investigation on sub boundary layer vortex generators for flow control. In: 10th International symposium on applications of laser techniques to fluid mechanics, pp 10–13Google Scholar
  2. Bohl DG, Koochesfahani MM (2009) MTV measurements of the vortical field in the wake of an airfoil oscillating at high reduced frequency. J Fluid Mech 620:63–88CrossRefGoogle Scholar
  3. Elsinga GE, Scarano F, Wieneke B, van Oudheusden BW (2006) Tomographic particle image velocimetry. Exp Fluids 41(6):933–947CrossRefGoogle Scholar
  4. Forster KJ, White TR (2014) Numerical investigation into vortex generators on heavily cambered wings. AIAA J 52(5):1059–1071CrossRefGoogle Scholar
  5. Godard G, Stanislas M (2006) Control of a decelerating boundary layer. Part 1: optimization of passive vortex generators. Aerosp Sci Technol 10(3):181–191CrossRefGoogle Scholar
  6. Holmes AE, Hickey PK, Murphy WR, Hilton DA (1987) The application of sub-boundary layer vortex generators to reduce canopy Mach rumble interior noise on the Gulf-stream III. In: AIAA 25th aerospace sciences meeting, Reno, NL, January 12–15Google Scholar
  7. Hunt JCR, Wray AA, Moin P (1998) Eddies, stream, and convergence zones in turbulent flows. Center for Turbulence, research report CTR-S88, pp 193–208Google Scholar
  8. Ku HH (1966) Notes on the use of propagation of error formulas. J Res Natl Bur Stand 70(4):263–273Google Scholar
  9. Kuethe AM (1972) Effect of streamwise vortices on wake properties associated with sound generation. J Aircr 9(10):715–719CrossRefGoogle Scholar
  10. Lin JC (1999) Control of turbulent boundary-layer separation using micro-vortex generators. In: 30th fluid dynamics conference, AIAA 99-3404Google Scholar
  11. Lin JC, Howard FG, Selby GV (1990) Investigation of several passive and active methods for turbulent flow separation control. In: 21st fluid dynamics, plasma dynamics and lasers conferenceGoogle Scholar
  12. Lin JC, Howard FG, Selby GV (1991) Exploratory study of vortex-generating devices for turbulent flow separation control. In: 29th aerospace sciences meeting, JanuaryGoogle Scholar
  13. Lin JC, Robinson SK, McGhee RJ, Valarezo WO (1994) Separation control on high-lift airfoils via micro-vortex generators. J Aircr 31(6):1317–1323CrossRefGoogle Scholar
  14. Lumley JL (1967) The structure of inhomogeneous turbulent flows. Atmos Turbul Radio Wave Propag 166–178Google Scholar
  15. Pauley WR, Eaton JK (1994) The effect of embedded longitudinal vortex arrays on turbulent boundary layer heat transfer. J Heat Transf 116(4):871–879CrossRefGoogle Scholar
  16. Prasad AK, Adrian RJ (1993) Stereoscopic particle image velocimetry applied to liquid flows. Exp Fluids 15(1):49–60CrossRefGoogle Scholar
  17. Raffel M, Willert CE, Scarano F, Kähler CJ, Wereley ST, Kompenhans J (2018) Particle image velocimetry: a practical guide. Springer, BerlinCrossRefGoogle Scholar
  18. Rao D, Kariya T (1988) Boundary-layer submerged vortex generators for separation control—an exploratory study. In: 1st national fluid dynamics conference, Reston, Virigina: American Institute of Aeronautics and AstronauticsGoogle Scholar
  19. Scarano F, Poelma C (2009) Three-dimensional vorticity patterns of cylinder wakes. Exp Fluids 47(1):69CrossRefGoogle Scholar
  20. Schubauer GB, Spangenberg WG (1960) Forced mixing in boundary layers. J Fluid Mech 8(1):10–32CrossRefGoogle Scholar
  21. Sirovich L (1987) Turbulence and the dynamics of coherent structures. I. Coherent structures. Q Appl Math 45(3):561–571MathSciNetCrossRefGoogle Scholar
  22. Sun Z (2015) Micro-vortex generators for boundary layer control: principles and applications. Int J Flow Control 7(1–2)Google Scholar
  23. Taylor HD (1947) The elimination of diffuser separation by vortex generators. United Aircraft Corporation, East Hartford, CT, Technical report no 4012: 3Google Scholar
  24. Westerweel J, Scarano F (2005) Universal outlier detection for PIV data. Exp Fluids 39(6):1096–1100CrossRefGoogle Scholar
  25. Wieneke B (2005) Stereo-PIV using self-calibration on particle images. Exp Fluids 39(2):267–280CrossRefGoogle Scholar
  26. Wieneke B (2008) Volume self-calibration for 3D particle image velocimetry. Exp Fluids 45(4):549–556CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringUniversity of AlbertaEdmontonCanada

Personalised recommendations