Hostname: page-component-5c6d5d7d68-wpx84 Total loading time: 0 Render date: 2024-08-19T14:19:36.411Z Has data issue: false hasContentIssue false
  • English
  • Français

Visualisation of flow separation with shear-sensitive liquid crystals

Published online by Cambridge University Press:  04 July 2016

S. O’Brien  and
S. Zhong
S. O’Brien
Affiliation:
School of Engineering, University of Manchester, Manchester, UK
S. Zhong
Affiliation:
School of Engineering, University of Manchester, Manchester, UK
Get access Rights & Permissions [Opens in a new window]

Abstract

Coatings of chiral-nematic liquid crystals are known to change colour under different levels of surface shear stress. In this study, the liquid crystal coating was used to provide information about flow separation and reattachment on a backward facing step and a delta wing respectively. The tests were carried out at a free-stream velocity of 25ms-1. The Reynolds number based on the step height of the backward facing step is 16,000 and based on the chord length of the delta wing is 270,000. The study revealed that the locations of boundary-layer separation and reattachment can be identified from spatial variations in the surface colour. Agreement was obtained between the results acquired from liquid crystal and surface oil flow technique. The variation in hue was used to improve the determination on the location of flow characteristics. This study showed that the liquid crystal coating is an effective method for the qualitative study of separated flow characteristics.

Type
Research Article
Information
The Aeronautical Journal , Volume 105 , Issue 1052 , October 2001 , pp. 597 - 602
Copyright
Copyright © Royal Aeronautical Society 2001 

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. Klein, E.J. and Margozzi, A.P. Exploratory investigation on the measurement of skin friction by means of liquid crystals, 1969, NASA TM-X-1774.Google Scholar
2. Smith, S.C. Use of shear-sensitive liquid crystals for surface flow visu-alisation, J Aircr, 1992, 29, (2), pp 289–293.Google Scholar
3. D.C., Reda and Wilder, M.C. Simultaneous, full-surface visualisations of transition and separation using liquid crystal coatings, AIAA J, 1997, 35, (4), pp 615–616.Google Scholar
4. Reda, D., Wilder, M.C, Farina, D.J. and Zilliac, G. New methodology for the measurement of surface shear stress vector distributions, AIAA J, 1997, 35, (4), pp 608–614.Google Scholar
5. Parmar, D.S. A novel technique for response function determination of shear sensitive cholesteric liquid crystal for boundary-layer investigations, Rev Sci lnstrums, 1991, 62, (6), pp 1596–1608.Google Scholar
6. Toy, N., Savory, E., Hoang, Q.H. and Gaudet, L. Calibration and use of shear-sensitive liquid crystals, 1993, International congress on instrumentation in aerospace simulation facilities, 1993.Google Scholar
7. Zhonc, S. and Chew, W.W.C. Visualisation of flow separation on aero foil with shear-sensitive liquid crystals, 2000, Paper No 438, Proceedings of the ninth International symposium on flow visualisation, August 2000, Edinburgh.Google Scholar
8. Ireland, P.T., Wang, Z. and Jones, T.V. Liquid crystal heat transfer measurements. Von Karman Institute for Fluid Dynamics 1992-1993 lecture series.Google Scholar
9. Papadopoulos, G. and Otugen, M.V. Separating and reattaching flow structure in a suddenly expanding rectangular duct, J Fluids Eng, 1995, 117, pp 17–23.Google Scholar
10. Eaton, J.K. and Johnston, J.P. A review of research on subsonic turbulent flow reattachment, AIAA J, 1981, 19, pp 1093–1200.Google Scholar
11. Yehna Narayan, K. and Seshadri, S.N. Types of flow on the lee side of delta wings, Progress in Aerospace Sci, 1997, 33.Google Scholar