Hostname: page-component-cd9895bd7-jn8rn Total loading time: 0 Render date: 2024-12-22T15:10:12.003Z Has data issue: false hasContentIssue false
  • English
  • Français

Effects of sweep on the dynamics of active separation control

Published online by Cambridge University Press:  04 July 2016

L. G. Pack  and
A. Seifert
L. G. Pack
Affiliation:
NASA Langley Research Center, Hampton, VA, USA
A. Seifert
Affiliation:
Faculty of Engineering, Tel-Aviv University, Israel
Get access Rights & Permissions [Opens in a new window]

Abstract

A series of active flow control experiments were recently conducted at high Reynolds numbers on a wall mounted ‘Hump’. The model simulates the upper surface of a 20% thick Glauert-Goldschmied type airfoil at zero incidence. The flow over the model is turbulent since the tunnel sidewall boundary-layer flows over it, eliminating laminar-turbulent transition from the problem. The main motivation for the experiments was to generate a comprehensive data base for validation of unsteady numerical simulation as a first step in the development of a design tool, without which it would not be possible to effectively utilise the great potential of unsteady flow control. This paper focuses on the dynamics of several key features of the baseline as well as the controlled two- and three-dimensional flows.

It was found that the two-dimensional separated flow contains unsteady waves centered on a reduced frequency (Strouhal number based on the length of the separated region and free-stream velocity) of 0·8, while in the three-dimensional separated flow, reduced frequencies of 0·3 and 1·0 are active. Several scenarios of resonant wave interaction take place over the separated shear-layer and in the pressure recovery regions. The unstable reduced frequency bands for periodic excitation are centered on 1·5 and 5, but these reduced frequencies are based on the length of the baseline bubble that shortens due to the excitation. The conventional swept wing-scaling works well for the coherent wave features. Reproduction of these dynamic effects by a numerical simulation would provide benchmark validation.

Type
Research Article
Information
The Aeronautical Journal , Volume 107 , Issue 1076 , October 2003 , pp. 617 - 629
Copyright
Copyright © Royal Aeronautical Society 2003 

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. and Pack, L.G. Active flow separation control on wall-mounted hump at high Reynolds numbers, AIAA J, July 2002, 40, (7), pp 1363–1372, previously AIAA paper 99-3403, 30th AIAA Fluid Dynamics Conference, Norfolk, VA, June 1999.Google Scholar
2. Seifert, A. and Pack, L.G. Effects of compressibility and excitation slot location on active separation control at high Reynolds numbers, J Aircr, Jan-Feb 2003, 40, (1), pp 110–119, part of AIAA Paper 00-0410, January 2000.Google Scholar
3. Seifert, A. and Pack, L.G. Effects of sweep on active separation control at high Reynolds numbers, J Aircr, Jan-Feb 2003, 40, (1), pp 120–126, Part of AIAA Paper 00-0410, January 2000.Google Scholar
4. Mabey, D.G. Analysis and correlation of data on pressure fluctuations in separated flow, J Aircr, September 1972, 9, pp 642–645.Google Scholar
5. Rockwell, D. Oscillations of impinging shear layers, AIAA J, May 1983, 21, (5), pp 645–664.Google Scholar
6. Le, H., Moin, P. and Kim, J. Direct numerical simulation of turbulent flow over a backward-facing step, J Fluid Mech, 1997, 330, pp 349–374.Google Scholar
7. Na, Y. and Moin, P. Direct numerical simulation of a separated turbulent boundary-layer, J Fluid Mech, 374, 1998, pp 379–405.Google Scholar
8. Seifert, A. and Pack, L.G. Sweep and compressibility effects on separation control at high Re numbers, January 2000, AIAA paper 2000–0410.Google Scholar
9. Glauert, M.B. The design of suction aerofoils with a very large CL-Range, November 1945, Aeronautical Research Council, R&M 2111.Google Scholar
10. Seifert, A. and Pack, L.G. Oscillatory control of separation at high Reynolds numbers, AIAA J, September 1999, 37, (9), pp 1063–1071.Google Scholar
11. Naveh, T., Seifert, A., Tumin, A. and Wygnanski, I. Sweep effect on parameters governing control of separation by periodic excitation, J Aircr, 1998, 35, (3), pp 510–512.Google Scholar
12. Greenblatt, D., Nishri, B., Darabi, A. and Wygnanski, I. Some factors affecting stall control with particular emphasis on dynamic stall, 1999, AIAA paper 99-3504, Norfolk, VA, 28 June - 1 July, 1999.Google Scholar