Hostname: page-component-78c5997874-8bhkd Total loading time: 0 Render date: 2024-11-13T01:29:00.079Z Has data issue: false hasContentIssue false
  • English
  • Français

The interaction of round synthetic jets with a turbulent boundary layer separating from a rounded ramp

Published online by Cambridge University Press:  15 September 2011

S. Lardeau  and
M. A. Leschziner
S. Lardeau*
Affiliation:
Department of Aeronautics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
M. A. Leschziner
Affiliation:
Department of Aeronautics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
*
†Email address for correspondence: s.lardeau@imperial.ac.uk
Get access Rights & Permissions [Opens in a new window]

Abstract

A computational large eddy simulation (LES) study is presented of the interaction between a turbulent boundary layer separating from a rounded ramp in a duct and a pair of spanwise-periodic, round synthetic jets, actuated upstream of the nominal separation line. Several scenarios are considered, for different injection angles and velocity ratios. In all cases, the actuation frequency corresponds to the shedding-instability mode of the separated shear layer. Experimental data, available for both the baseline flow and one actuated configuration, are used to verify the validity of the computational solutions. The analysis includes a separation of coherent and stochastic contributions to the time-averaged statistics of the auto- and cross-correlations of the fluctuations. The control authority is examined by reference to the effects of the actuation on the size of the separated zone, the momentum thickness of the boundary layer, the velocity field, various turbulence quantities and phase-averaged properties. The study demonstrates that the principal aspect of the interaction, at mean-flow level, is an increase in mixing provoked by the formation of strong streamwise vortices away from the wall, the induction of much weaker streamwise vortices close to the wall, and the extra production of stochastic turbulence caused by unsteady straining. The coherent stresses arising from the periodic perturbations are high – typically 5 times the levels of the unperturbed flow – but only within about 5–7 diameters of the jet orifice, and 2 orifice diameters on each side of the jet, and these are dominant primarily in the outer parts of the boundary layer. Stochastic turbulence is also elevated, but more modestly. The global effect of the actuation is a reduction of 10–20 % in the length of the separated region and 20–40 % in the thickness of the reverse-flow layer, depending on the actuation scheme, counter-flow actuation being the most effective. This reduction is mainly associated with a delay in separation. These results highlight the need for synthetic jets to be placed close to the separation zone and for the inter-jet distance to be of order 5 or lower to achieve a high level of separation-control authority.

JFM classification

Boundary Layers: Boundary layer separation Flow Control: Drag reduction Turbulent Flows: Turbulence control
Type
Papers
Information
Journal of Fluid Mechanics , Volume 683 , 25 September 2011 , pp. 172 - 211
Copyright
Copyright © Cambridge University Press 2011

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. Aram, E., Mittal, R. & Cattafesta, L. 2010 Simple representations of zero-net mass-flux jets in grazing flow for flow-control simulations. Intl J. Flow Control 2 (2), 109–125.CrossRefGoogle Scholar
2. Avdis, A., Lardeau, S. & Leschziner, M. 2009 Large eddy simulation of separated flow over a two-dimensional hump with and without control by means of a synthetic slot-jet. Flow Turbul. Combust. 83 (3), 343–370.CrossRefGoogle Scholar
3. Cater, J. E. & Soria, J. 2002 The evolution of round zero-net-mass-flux jets. J. Fluid Mech. 472, 167–200.CrossRefGoogle Scholar
4. Dandois, J., Garnier, E. & Sagaut, P. 2006 Unsteady simulation of a synthetic jet in a crossflow. AIAA J. 44 (2), 225.CrossRefGoogle Scholar
5. Dandois, J., Garnier, E. & Sagaut, P. 2007 Numerical simulation of active separation control by a synthetic jet. J. Fluid Mech. 574, 25–58.CrossRefGoogle Scholar
6. Dejoan, A. & Leschziner, M. A. 2004 Large eddy simulation of periodically perturbed separated flow over a backward-facing step. Intl J. Heat Fluid Flow 25 (4), 581–592.CrossRefGoogle Scholar
7. Fishpool, G. M. & Leschziner, M. A. 2009 Stability bounds for explicit fractional-step schemes for the Navier–Stokes equations at high Reynolds number. Comput. Fluids 38 (6), 1289–1298.CrossRefGoogle Scholar
8. Fröhlich, J., Mellen, C., Rodi, W., Temmerman, L. & Leschziner, M. A. 2005 Highly resolved large-eddy simulation of separated flow in a channel with streamwise periodic constrictions. J. Fluid Mech. 526 (-1), 19–66.CrossRefGoogle Scholar
9. Garcia-Villalba, M., Li, N., Rodi, W. & Leschziner, M. A. 2009 Large-eddy simulation of separated flow over a three-dimensional axisymmetric hill. J. Fluid Mech. 627, 55–96.CrossRefGoogle Scholar
10. Garcillan, L., Liddle, S., Sunneechurra, K., Crowther, B., Zhong, S. & Wood, N. 2006 PIV measurements of the effect of pitch and skew on a circular orifice synthetic jet in a turbulent boundary layer. AIAA Paper 318, 2006.Google Scholar
11. Germano, M., Piomelli, U., Moin, P. & Cabot, W. H. 1991 A dynamic subgrid-scale eddy viscosity model. Phys. Fluids A 3, 1760.CrossRefGoogle Scholar
12. Gharib, M., Rambod, E. & Shariff, K. 1998 A universal time scale for vortex ring formation. J. Fluid Mech. 360, 121–140.CrossRefGoogle Scholar
13. Glezer, A. 1981 An experimental study of a turbulent vortex ring. PhD thesis, California Institute of Technology.Google Scholar
14. Glezer, A. & Amitay, M. 2002 Synthetic jets. Annu. Rev. Fluid Mech. 34 (1), 503–529.CrossRefGoogle Scholar
15. Gordon, M. & Soria, J. 2002 PIV measurements of a zero-net-mass-flux jet in cross flow. Exp. Fluids 33 (6), 863–872.CrossRefGoogle Scholar
16. Greenblatt, D., Paschal, K. B., Yao, C., Harris, J., Schaeffler, N. W. & Washburn, A. E. 2006 Experimental investigation of separation control. Part 1. Baseline and steady suction. AIAA J. 44 (12), 2855.Google Scholar
17. Hasan, M. A. Z. & Khan, A. S. 1992 On the instability characteristics of a reattaching shear layer with nonlaminar separation. Intl J. Heat Fluid Flow 13 (3), 224–231.CrossRefGoogle Scholar
18. Hussain, A. 1983 Coherent structures: reality and myth. Phys. Fluids 26, 2816.CrossRefGoogle Scholar
19. Inagaki, M., Kondoh, T. & Nagano, Y. 2005 A mixed-time-scale SGS model with fixed model-parameters for practical LES. Trans. ASME: J. Fluids Engng 127, 1.Google Scholar
20. Jabbal, M. & Zhong, S. 2008 The near wall effect of synthetic jets in a boundary layer. Intl J. Heat Fluid Flow 29 (1), 119–130.CrossRefGoogle Scholar
21. Jiménez, J., Hoyas, S., Simens, M. P., Mizuno, & Y., 2010 Turbulent boundary layers and channels at moderate Reynolds numbers. J. Fluid Mech. 1–26.Google Scholar
22. Krishnan, V., Squires, K. D. & Forsythe, J. R. 2006 Prediction of separated flow characteristics over a hump. AIAA J. 44 (2), 252.CrossRefGoogle Scholar
23. Leschziner, M. A. & Lardeau, S. 2011 Simulation of slot and round synthetic jets in the context of boundary-layer separation control. Philos. Trans. Royal Soc. A: Math. Phys. Engng Sci. 369, 1495–1512.CrossRefGoogle ScholarPubMed
24. Lilly, D. K. 1992 A proposed modification of the Germano subgrid-scale closure method. Phys. Fluids A 4, 633.CrossRefGoogle Scholar
25. Lund, T. S., Wu, X. & Squires, K. D. 1998 Generation of turbulent inflow data for spatially-developing boundary layer simulations. J. Comput. Phys. 140 (2), 233–258.CrossRefGoogle Scholar
26. Mittal, R. & Rampunggoon, P. 2002 On the virtual aeroshaping effect of synthetic jets. Phys. Fluids 14, 1533.CrossRefGoogle Scholar
27. Neumann, J. & Wengle, H. 2004 Coherent structures in controlled separated flow over sharp-edged and rounded steps. J. Turbul. 5 (22), 1–24.CrossRefGoogle Scholar
28. Oppenheim, A. V. & Schafer, R. W. 2007 Discrete-time signal processing. Pearson Education; 3 edition (31 Dec 2007), ISBN-13:978-0132067096.Google Scholar
29. Ozawa, T., Lesbros, S. & Hong, G. 2010 LES of synthetic jets in boundary layer with laminar separation caused by adverse pressure gradient. Comput. Fluids 39, 845–858.CrossRefGoogle Scholar
30. Pamart, P. Y., Dandois, J., Garnier, E. & Sagaut, P. 2010 Large Eddy Simulation Study of Synthetic Jet Frequency and Amplitude Effects on a Rounded Step Separated Flow, 5th AIAA Shear Flow Control Conference, Chicago, Illinois, 28/06 to 01/07 2010 .Google Scholar
31. Raju, R., Aram, E., Mittal, R. & Cattafesta, L. 2009 Simple models of zero-net mass-flux jets for flow control simulations. Intl J. Flow Control 1 (3), 179–197.CrossRefGoogle Scholar
32. Ravi, B. R., Mittal, R. & Najjar, F. M. 2004 Study of three-dimensional synthetic jet flow fields using direct numerical simulation. AIAA Paper 51, 61801.Google Scholar
33. Rhie, C. M. & Chow, W. L. 1983 Numerical study of the turbulent flow past an aerofoil with trailing edge separation. AIAA J. 21 (11), 1525–1532.CrossRefGoogle Scholar
34. Rizzetta, D. P., Visbal, M. R. & Stanek, M. J. 1999 Numerical investigation of synthetic-jet flow fields. AIAA J. 37 (8).CrossRefGoogle Scholar
35. Rumsey, C. L., Gatski, T. B., Sellers, W. L., Vatsa, V. N. & Viken, S. A. 2006 Summary of the 2004 computational fluid dynamics validation workshop on synthetic jets. AIAA J. 44 (2), 194.CrossRefGoogle Scholar
36. Saffman, P. G. 1981 Dynamics of vorticity. J. Fluid Mech. 106, 49–58.CrossRefGoogle Scholar
37. Sau, R. & Mahesh, K. 2008 Dynamics and mixing of vortex rings in crossflow. J. Fluid Mech. 604, 389–409.CrossRefGoogle Scholar
38. Schaeffler, N. W. & Jenkins, L. N. 2006 Isolated synthetic jet in crossflow: experimental protocols for a validation dataset. AIAA J. 44 (12), 2835.CrossRefGoogle Scholar
39. Smith, B. L. & Glezer, A. 1998 The formation and evolution of synthetic jets. Phys. Fluids 10, 2281.CrossRefGoogle Scholar
40. Smith, B. L. & Swift, G. W. 2003 A comparison between synthetic jets and continuous jets. Exp. Fluids 34 (4), 467–472.CrossRefGoogle Scholar
41. Song, S. & Eaton, J. K. 2004 Reynolds number effects on a turbulent boundary layer with separation, reattachment, and recovery. Exp. Fluids 36 (2), 246–258.CrossRefGoogle Scholar
42. Udaykumar, H. S., Mittal, R., Rampunggoon, P. & Khanna, A. 2001 A sharp interface Cartesian grid method for simulating flows with complex moving boundaries. J. Comput. Phys. 174 (1), 345–380.CrossRefGoogle Scholar
43. Wu, D. K. L. & Leschziner, M. A. 2009 Large-eddy simulations of circular synthetic jets in quiescent surroundings and in turbulent cross-flow. Intl J. Heat Fluid Flow 30 (3), 421–434.CrossRefGoogle Scholar
44. You, D., Ham, F. & Moin, P. 2008 Discrete conservation principles in large-eddy simulation with application to separation control over an airfoil. Phys. Fluids 20, 101515.CrossRefGoogle Scholar
45. Zaman, K. & Milanovic, I. 2002 Synthetic jets in cross-flow. Part II. Jets from orifices of different geometry. In 33rd AIAA Fluid Dynamics Conference and Exhibit AIAA Paper 2002-3715, Orlando, FL, 23–26 June.CrossRefGoogle Scholar
46. Zhang, S. & Zhong, S. 2010 An experimental investigation of turbulent flow separation control by an array of synthetic jets. AIAA Paper 2010–4582.Google Scholar
47. Zhong, S., Jabbal, M., Tang, H., Garcillan, L., Guo, F., Wood, N. & Warsop, C. 2007 Towards the design of synthetic-jet actuators for full-scale flight conditions. Flow Turbul. Combust. 78 (3), 283–307.CrossRefGoogle Scholar
48. Zhou, J. & Zhong, S. 2009 Numerical simulation of the interaction of a circular synthetic jet with a boundary layer. Comput. Fluids 38 (2), 393–405.CrossRefGoogle Scholar