Advertisement

Closed-loop bluff-body wake stabilization via fluidic excitation

  • O. Stalnov
  • I. Fono
  • A. SeifertEmail author
Original Article

Abstract

This article describes an experimental study aimed at stabilizing the wake of a shedding bluff-body by means of closed-loop active flow control at low Reynolds numbers. A D-shaped (6.5 mm thick) cylinder was used to allow a direct wake interaction rather than mixed wake-boundary-layer separation control. The fluidic actuators, installed inside the thin body, were ideally located at the separation locations, i.e., the trailing edges’ upper and lower corners. The wake unsteadiness was monitored by a pair of hot wires (HWs), while a single surface-mounted hot-film (HF) sensor was used as a frequency and phase reference for closed-loop control. The HF signal was contaminated by noise. Hence, a technique for real-time tracking of a low signal-to-noise ratio (SNR) signal was necessary. This was achieved by means of a Phase-Locked Loop (PLL), common in communications systems. The closed-loop scheme was based on real-time measurement of the wake-state, using the surface-mounted HF sensor, and control authority imposed by the fluidic actuators. By using opposition control at frequencies close to the natural vortex shedding frequency (VSF), it was possible to significantly reduce the wake unsteadiness. Applying the same approach, but sensing the wake HW signal, rather than the surface-mounted HF signal, as the controller input did not result in wake stabilization. On the contrary, the unsteadiness increased at all the tested conditions. It is expected that a similar approach would work at much higher Reynolds numbers as well, as long as a clearly identifiable and nominally 2D vortex shedding occurs, even when the background flow is fully turbulent.

Keywords

Bluff body Vortex shedding Oscillatory vorticity generators Actuators Flow control Closed-loop flow control 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Adrian, R.J.: On the role of conditional averages in turbulence theory. In: Proceedings of the Fourth Biennial Symposium, Rolla, MO, September 22–24, 1975 (A77-40426 18-34), pp. 323–332. Science Press, Princeton, NJ (1977)Google Scholar
  2. 2.
    Allan, B.G., Juang, J.N., Raney, D.L., Seifert, A., Pack, L.G., Brown, D.E.: Closed loop separation control using oscillatory flow excitation. In ICASE Report 2000-32 (2000)Google Scholar
  3. 3.
    Blevins R.: Flow-Induced Vibrations. 2nd edn. Van Nostrand Reinhold, New York (1990)Google Scholar
  4. 4.
    Cattafesta L., Song Q., Williams D., Rowley C., Alvi F.: Active control of flow-induced cavity resonance. Prog. Aerospace Sci. 44, 479–502 (2008)CrossRefGoogle Scholar
  5. 5.
    De Bellescize H.: La reception synchrone. Onde Electr. 11, 230–240 (1932)Google Scholar
  6. 6.
    Gerrard J.H.: The mechanism of the formation region of vortices behind bluff bodies. J. Fluid Mech. 25, 401–413 (1966)CrossRefGoogle Scholar
  7. 7.
    Gharib M.: Response of the cavity shear layer oscillations to external forcing. AIAA J. 25(1), 43–47 (1987)CrossRefGoogle Scholar
  8. 8.
    Gillies E.A.: Low-dimensional Control of the Circular Cylinder Wake. J. Fluid Mech. 371, 157–178 (1998)MathSciNetzbMATHCrossRefGoogle Scholar
  9. 9.
    Henning L., Pastoor, M., King R., Noack, B.R.: Feedback control applied to bluff body wake. In: Active Flow Control Conference, Berlin, Germany (2006)Google Scholar
  10. 10.
    Holmes P., Lumley J., Berkooz G.: Turbulence, Coherent Structures, Dynamical Systems and Symmetry. Cambridge University press, Cambridge, UK (1998)zbMATHGoogle Scholar
  11. 11.
    Klapper J., Frankle J.T.: Phase-Locked and Frequency-Feedback Systems; Principles and Techniques. Academic Press, New York (1972)Google Scholar
  12. 12.
    Lehmann, O., Luchtenburg, M., Noack, B.R., King, R., Morzynski, M., Tadmor, G.: Wake stabilization using POD Galerkin models with interpolated modes. In: European Control Conference ECC (2005)Google Scholar
  13. 13.
    Moes, T.R., Sarma, G.R., Mangalm, S.M.: Flight Demonstration of Shock Location Sensor Using Constant Voltage Hot-Film Anemometry. NASA Technical Memorandum 4806 (1997)Google Scholar
  14. 14.
    Naim, A., Greenblatt, D., Seifert, A., Wygnanski, I.: Active Control of a Circular Cylinder Flow at Transitional Reynolds Numbers (part of AIAA Paper 2002-3070), Special Issue of Flow, Turbulence and Combustion on “Air-jet actuators and their use for flow control”, vol. 78, pp. 383–407 (2007)Google Scholar
  15. 15.
    Pastoor, M., King, R., Noack, B.R., Dillmann, A., Tadmor, G.: Model-based coherent-structure control of turbulent shear flows using low-dimensional vortex models. AIAA Paper 2003-4261 (2003)Google Scholar
  16. 16.
    Rapoport D., Fono I., Cohen K., Seifert A.: Closed-loop vectoring control of a turbulent jet using periodic excitation. J. Propuls. Power 19(4), 646–654 (2003)CrossRefGoogle Scholar
  17. 17.
    Roshko, A.: On the drag and shedding frequency of two-dimensional bluff bodies. NACA TM 3169 (1954)Google Scholar
  18. 18.
    Roussopoulos K., Monkewitz P.A.: Nonlinear modeling of vortex shedding control in cylinder wakes. Physica D 97, 264–273 (1996)CrossRefGoogle Scholar
  19. 19.
    Samimy, M., Debias, M., Caraballo, E., Ozbay, H., Efe, M., Yuan, X., Debonis, J., Myatt, J.: Development of closed loop flow control for cavity flows. AIAA Paper 2003-4258 (2003)Google Scholar
  20. 20.
    Seigel, S., Cohen, K., McLaughlin, T.: Experimental variable gain feedback control of a cylinder wake. AIAA Paper 2004-2611 (2004)Google Scholar
  21. 21.
    Stalnov, O., Palei, V., Fono, I., Cohen, K., Seifert, A.: Experimental validation of sensor placement for control of a D-shaped cylinder wake. AIAA Paper 2005-5260 (2005)Google Scholar
  22. 22.
    Stalnov O., Palei V., Fono I., Cohen K., Seifert A.: Experimental estimation of a D-shape cylinder wake using body-mounted sensors. Exp. Fluids 45, 531–542 (2007)CrossRefGoogle Scholar
  23. 23.
    Tadmor, G., Noack, B.R.: Dynamic estimation for reduced Galerkin Models of fluid flows. In: The 2004 APC Meeting, pp. 746–751 (2004)Google Scholar
  24. 24.
    Tadmor, G., Noack, B.R., Morzynski, M., Siegel, S.: Low-dimensional models for feedback flow control. Part II. Observer and controller design. AIAA Paper 2004-2409 (2004)Google Scholar
  25. 25.
    von Kàrmàn, Th.: Über den Mechanismus des Widerstands, den ein bewegter Körper ineiner Flüssigkeit erfährt. Nachr. Wiss. Ges. Göttingen. Math. Phys. Kl., pp. 509–517 (1911)Google Scholar
  26. 26.
    Williamson C.H.K.: Vortex dynamics in the cylinder wake. Annu. Rev. Fluid Mech. 28, 477–539 (1996)CrossRefGoogle Scholar
  27. 27.
    Yehoshua T., Seifert A.: Boundary condition effects on the evolution of a train of vortex pairs in still air. Aeronaut. J. 110(1109), 397–417 (2006)Google Scholar

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.School of Mechanical EngineeringTel-Aviv UniversityTel-AvivIsrael

Personalised recommendations