Hostname: page-component-cd9895bd7-q99xh Total loading time: 0 Render date: 2024-12-28T06:33:20.808Z Has data issue: false hasContentIssue false
  • English
  • Français

Boundary condition effects on the evolution of a train of vortex pairs in still air

Published online by Cambridge University Press:  03 February 2016

T. Yehoshua  and
A. Seifert
T. Yehoshua
Affiliation:
Dept of Fluid Mechanics and Heat Transfer, Tel-Aviv University, Ramat-Aviv, Israel
A. Seifert
Affiliation:
Dept of Fluid Mechanics and Heat Transfer, Tel-Aviv University, Ramat-Aviv, Israel
Get access Rights & Permissions [Opens in a new window]

Abstract

Effects of boundary conditions on the performance of compact oscillatory momentum and vorticity generators, commonly known as ‘synthetic jet’, ejecting a train of vortex-pairs into still air, were studied experimentally. The different boundary conditions altered the near-device entrainment process of the zero-net-mass-flux actuator. The measurements included hot-wire and Particle Image Velocimetry, cavity pressures and temperatures.

When the actuator operates in still air, a quasi-2D vortex pair is generated due to the extreme shear at the edges of the fluid slug ejected during the blowing stage of each excitation cycle. The vorticity flux exiting the slot determines the resulting vortex-pair circulation. The threshold slot exit velocity, for the current configuration and operating conditions, determines if the vortices will be sucked into the actuator’s cavity or be released. Once released, the vortex convection speed approximately scales with the peak velocity at the slot exit. However, the normalised convection velocity increases with the slot Reynolds number.

When even a very short extension is attached to one ‘lip’ of the actuator exit, the jet is deflected in the direction opposite the extended lip, due to the restriction on the entrainment process. When long, one ‘lip’ extension is attached, such that the vortex pair is ejected parallel to a plate, the coherence of the vortices improve, their phase speed and magnitude decrease.

The effects of high-frequency excitation, ejected perpendicular to a wall into still air, were also investigated. It was found that the presence of the plate does not have a measurable effect on the wall normal excitation, indicating that the majority of the entrainment is taking place from the forward 180° of the actuator exit plane. When the slot is inclined to the surface at a shallow angle of 30 degrees, an unsteady wall jet is formed, transferring momentum along the wall. This is a direct result of the symmetry break, altering the relative magnitudes of the vortex pair.

Type
Research Article
Information
The Aeronautical Journal , Volume 110 , Issue 1109 , July 2006 , pp. 397 - 417
Copyright
Copyright © Royal Aeronautical Society 2006 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1. Seifert, A., Darabi, A., Wygnanski, I., Delay of airfoil stall by periodic excitation, J Aircr, 33, (4), July-August 1996, pp 691–698.Google Scholar
2. Gutmark, E.J., Schadow, K.C., and Yu, K.H., Mixing enhancement in supersonic free shear flows, Annu Rev Fluid Mech, 1995, 27, pp 375–417.Google Scholar
3. Seifert, A. and Pack, L.G. Oscillatory control of separation at high Reynolds numbers, AIAA J, September 1999, 37, (9), pp 1062–1071.Google Scholar
4. Smith, B. L. and Glezer, A., The formation and evolution of synthetic jets, Phys Fluids, 1998, 31:2281–97.Google Scholar
5. Pack, L.G. and Seifert, A., Periodic excitation for jet vectoring and enhanced spreading, (AIAA paper 99-0672), J Aircr, May-June 2001, 38, (3), pp 486–495.Google Scholar
6. Amitay, M., Smith, D.R., Kibens, V., Parekh, D.E. and Glezer, A. 2001. Aerodynamic flow control over an unconventional airfoil using synthetic jet actuators. AIAA J, 39, pp 361–370.Google Scholar
7. Smith, B.L. and Glezer, A., Jet vectoring using synthetic jets, J Fluid Mech, 2002, 458, pp 1–34.Google Scholar
8. Crow, S.C. and Champagne, F.H., Orderly structure in jet turbulence, J Fluid Mechanics, 1971, 48, (3), pp 547–591.Google Scholar
9. Collis, S.S., Joslin, R.D., Seifert, A. and Theofilis, V., Issues in active flow control: theory, simulation and experiment, Prog Aero Sci, May-July 2004, 40, (4-5), (previously AIAA paper 2002-3277).Google Scholar
10. Gallas, Q., Mathew, J., Kaysap, A., Holman, R., Nishida, T., Carroll, B., Sheplak, M. and Cattafesta, L., Lumped element modeling of piezoelectric-driven synthetic jet actuators, AIAA paper 2002-0125, January 2002.Google Scholar
11. Margalit, S., Greenbaltt, D., Seifert, A. and Wygnanski, I., Active flow control of a delta wing at high incidence using segmented piezoelectric actuators, AIAA 2002-3270, June 2002, In Press, J Aircr.Google Scholar
12. Ingard, U. and Ising, H., Acustic nonlinearity of an orifice, J Acoustical Soc America, February 1967, 42, (1), pp 6–17.Google Scholar
13. Lee, C.Y. and Goldstein, D.B., Two-dimensional synthetic jet Simulation, AIAA J, 40, (3).Google Scholar
14. Mittal, R., Rampunggoon, P. and Udaykumar, H. S., Interaction of a synthetic jet with a flat plate boundary layer, AIAA 2001-2773, June 2001.Google Scholar
15. Mittal, R. and Rampunggoon, , On the virtual aeroshaping effect of synthetic jets, Phys Fluids, 14, (4), pp 1533–1536.Google Scholar
16. Park, S-H., Lee, I., and Sung, H.J., Effect of local forcing on a turbulent boundary layer, Experiments in Fluids, 2001, 31, (4), pp 384–393, 2001.Google Scholar
17. , H, T., MSc thesis, Tel Aviv University, April 2004.Google Scholar
18. Adrian, R.J., Meinhart, C.D. and Tomkins, C.D., Vortex organization in the outer region of the turbulent boundary layer, J Fluid Mech, 2000, (422), pp 1–54.Google Scholar
19. Grosjeany, N., Graftieauxy, L., Michard, M., Y, Hubner, W., Tropeaz, C. and Volkert, J., Combining LDA and PIV for turbulence measurements in unsteady swirling flows, Meas Sci Technol, 8, 1997, pp 1523–1532.Google Scholar
20. Bera, J.C., Michard, M., Grosjean, G. and Comte-Bellot, G., Flow analysis of two-dimensional pulsed jets by particle image velocimetry, Experiments in Fluids, 2001, 31, pp 519–532.Google Scholar
21. Im, T.T and Nickels, T.B., Vortex rings, in Fluid Vortices, Green, S.I (Ed), Kluwer, 1995, pp 95–147.Google Scholar
22. Naim, A., Greenblatt, D., Seifert, A. and Wygnanski, I., Active control of cylinder flow with and without a splitter plate using piezoelectric actuators, AIAA 2002-3070.Google Scholar
23. Shusser, M. and Gharib, M., Energy and velocity of a forming vortex ring, Physics Fluids, March 2000, 12, (3), pp 618–621.Google Scholar
24. Luton, A., Ragab, S., and Telionis, D., Interaction of spanwise vortices with a boundary layer, Phys of Fluids, 7, (11), 1995, p 2757.Google Scholar
25. Yehoshua, T. and Seifert, A., Boundary condition effects on oscillatory momentum generator, AIAA Paper 2003-3710, June 2003.Google Scholar
26. Utturkar, Y., Holman, R., Mittal, R., Carrol, M., Sheplak, M. and Cattafesta, L., A Jet formation criterion for synthetic jet actuators, AIAA paper 2003-0636, January, 2003.Google Scholar
27. Holman, R., Utturkar, Y., Mittal, R., Smith, B.L. and Cattafesta, L., A jet formation criterion for synthetic jet actuators, AIAA J, 2005, 43, (10), pp 2110-2116.Google Scholar
28. Faber, T.E., Fluid Dynamics for Physicists, Cambridge University Press, 1995.Google Scholar
29. Rizzetta, D.P., Visbal, M.R. and Stanek, M.J., Numerical investigation of synthetic-jet flowfields, AIAA J, 1999, 37, (8), pp 919–927.Google Scholar
30. Yehoshua, T. and Seifert, A., Active boundary layer tripping using oscillatory vorticity generator, Aerospace Science and Technology, 10, 2006, pp 175–180.Google Scholar
31. Yehoshua, T. and Seifert, A., On the evolution of amplitude modulated train of vortex pairs in still air, Submitted to Journal publication, October 2005.Google Scholar