Hostname: page-component-848d4c4894-mwx4w Total loading time: 0 Render date: 2024-07-04T21:39:45.485Z Has data issue: false hasContentIssue false
  • English
  • Français

Measurements of velocities in the near field of a lobed forced mixer trailing edge

Published online by Cambridge University Press:  04 July 2016

S. C. M. Yu  and
T. H. Yip
S. C. M. Yu
Affiliation:
Thermal and Fluids Engineering Division, School of Mechanical and Production Engineering, Nanyang Technological University, Singapore
T. H. Yip
Affiliation:
Thermal and Fluids Engineering Division, School of Mechanical and Production Engineering, Nanyang Technological University, Singapore
Get access Rights & Permissions [Opens in a new window]

Abstract

Previous experimental studies have shown that the development of flow behind the trailing edge of a lobed forced mixer is greatly influenced by the formation of large-scale streamwise vortices. The main objective of the present study is to establish quantitatively the presence and role of the streamwise vortices in the mixing layer in the near field of a lobed forced mixer trailing edge. The near field was defined as the region within five wavelengths (of the trailing edge profile) from the trailing edge. A two-stream mixing layer with a velocity ratio of 0.6 was generated with initially turbulent boundary layers and nominally two-dimensional flow. Mean flow and turbulence measurements were made on fine cross-plane grids across the wake region and at several streamwise locations using a two-component laser-doppler anemometer. Production of turbulent kinetic energy existed in most parts of the near field enhancing the overall mixing process. The streamwise vortex development underwent a three-step process by which it was formed, intensified and quickly dissipated towards the end of the near field. The distance between two rows of streamwise vortices of alternate signs within a lobe reduced with downstream distance causing the amalgamation and annihilation of the vortices. Analysing this movement of vortices, based on inviscid vortex dynamics, suggested that the normal vortices shed at the trailing edge had actually provided a squeezing (pinched off) effect to two adjacent rows of streamwise vortices within a lobe, forcing them to interact with each other.

Type
Research Article
Information
The Aeronautical Journal , Volume 101 , Issue 1003 , March 1997 , pp. 121 - 129
Copyright
Copyright © Royal Aeronautical Society 1997 

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. Bell, J.H. and Mehta, R.D. Measurements of the streamwise vortical structures in a plane mixing layer, J Fluid Mech, 1992, 239, pp 213–248.Google Scholar
2. Bell, J.H. and Mehta, R.D. Effects of imposed spanwise perturbations on plane mixing-layer structure, J Fluid Mech, 1993, 257, pp 33–63.Google Scholar
3. Presz, W.M., Blinn, R.F. and Morin, B. Short efficient ejector systems, AIAA Paper 87-1837, January 1987.Google Scholar
4. Presz, W.M., Gousy, R. and Morin, B. Forced mixer lobes in ejector design, AIAA J of Prop Power, July 1988, 4, (4), p 350.Google Scholar
5. Koutmos, P. and McGuirk, J.J. Isothermal velocity and turbulence measurements downstream of a model multilobed turbofan mixer, Exp in Fluids, 1989, 9, pp 183–191.Google Scholar
6. Malecki, R., Mityas, S. and Lord, W. Navier-Stokes analysis of an ejector and mixer ejector operating at pressure ratio in the range 2-4, AIAA Paper 90-2730, July 1990.Google Scholar
7. Presz, W.M., Reynolds, G. and McCormick, D. Thrust augmentation using mixer-ejector-diffuser systems, AIAA Paper 94-0020, January 1994.Google Scholar
8. Kozlowski, H. and Kraft, G. Experimental evaluation of exhaust mixers for an energy efficient engine, AIAA Paper 80-0188, June 1980.Google Scholar
9. Paterson, R.W. Turbofan forced-mixer nozzle internal flow field Vol 1: A benchmark experimental study, NASA CR-3492, 1982.Google Scholar
10. Paterson, R.W. Turbofan mixer nozzle flowfield — a benchmark experimental study, ASME J Eng for Gas Turb Power, July 1984, 106, pp 692–698.Google Scholar
11. Barber, T., Paterson, R.W. and Skebe, S.A. Turbofan forced mixer lobe flow modeling Vol 1: Experimental and analytical assessment, NASA CR-4147, 1988.Google Scholar
12. O'sullivan, M.N., Kransnodebski, I.A., Waitz, I.A., Greitzer, E.M. and Tan, C.S. Computational study of viscous effects on lobed mixer flow features and performance, AIAA J Prop Power, May 1996, 12, (3), pp 449–456.Google Scholar
13. Werle, M.J., Paterson, R.W. and Presz, W.M. Flow structure in a periodic axial vortex array, AIAA Paper 87-0610, January 1987.Google Scholar
14. Manning, T.A. Experimental Studies of Mixing Flows with Streamwise Vorticity, MS thesis, MIT, September 1991.Google Scholar
15. EcKerle, W.A., Sheibani, H. and Awad, J. Experimental measurement of the vortex development downstream of a lobed forced mixer, ASME J Eng for Gas Turb Power, January 1992, 114, pp 63–71.Google Scholar
16. Tsui, Y.Y. and Wu, P.W. Investigation of the mixing flow structure in multilobe mixers, AIAA J, July 1996, 34, (7), pp 1386–1391.Google Scholar
17. McCormick, D.C. and Bennett, J.C. Vortical and turbulent structure of a lobed forced mixer free-shear layer, AIAA J, 1994, 32, (9), pp 1852–1859.Google Scholar
18. Yu, S.C.M., Yeo, J.H. and Teh, J.K.L. Velocity measurements downstream of lobed forced mixers with different convoluted trailing edge configurations, AIAA J Prop Power, January 1995, 13, (1), pp 87–97.Google Scholar
19. Ukeiley, L., Glauser, M. and Wick, D. Downstream evolution of proper orthogonal decomposition eigenfunctions in a lobed mixer, AIAA J, 1993, 31, (8), pp 1392–1397.Google Scholar
20. Ukeiley, L., Varghese, M., Glauser, M. and Valentine, D. Multifracial analysis of a lobed mixer flowfield utilizing the proper orthogonal decompostion, AIAA J, 1992, 30, (5), pp 1260–1267.Google Scholar
21. Durst, F., Melling, A. and Whitelaw, J.H. Principles and Practice of Laser-Doppler Anemometry, Academic Press, London, 1981.Google Scholar
22. Yanta, W.J. and Smith, R.A. Measurements of turbulence transport properties with a laser-Doppler velocimeter, AIAA Paper 73-169, 1973.Google Scholar
23. Bell, J.H., Plesniak, M.W. and Mehta, R.D. Spanwise averaging of plane mixing layer properties, AIAA J, 1993, 30, (3), pp 835–837.Google Scholar
24. Yu, S.C.M., Xu, X.G. and Yip, T.H. Effects of initial boundary layer thicknesses to the lobed forced mixer trailing streamwise vorticity, AIAA J Prop Power, March 1996, 14, (2), pp 440–442.Google Scholar
25. Weygandt, J.H. and Mehta, R.D. Effects of streamwise vorticity injection on a plane turbulent wake, AIAA J, 1995, 33, (1), pp 86–93.Google Scholar
26. Bradshaw, P., Cebeci, T. and Whitelaw, J.H. Engineering Calculation Methods for Turbulent Flow, Academic Press, London, 1981, p 28.Google Scholar
27. Tew, D.E., Waitz, L.A., Hermanson, J.C., Greitzer, E.M. and Tan, C.S. Streamwise vorticity enhanced compressible mixing downstream mixing downstream of lobed mixers, AIAA Paper 95-2746, July 1995.Google Scholar
28. Yu, S.C.M., Yip, T.H. and Liu, C.Y. The mixing characteristics of forced mixers with scalloped lobes, to appear in AIAA J Prop Power, March 1997, 15, (2).Google Scholar