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The distortion of a jet by tabs

Published online by Cambridge University Press:  29 March 2006

L. J. S. Bradbury  and
A. H. Khadem
L. J. S. Bradbury
Affiliation:
Mechanical Engineering Department, University of Surrey, Guildford, England
A. H. Khadem
Affiliation:
Mechanical Engineering Department, University of Surrey, Guildford, England
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Abstract

In an attempt to explain the discrepancies that have been observed in the spread of nominally axisymmetric jets, an experimental investigation has been carried out in which the effects of a number of factors which it was thought might be important to jet development have been studied. These factors included the nozzle boundary-layer thickness, turbulence level and convergence. However, over the limited range of the tests, it was found that none of these factors had a very strong influence on the jet development. By contrast, the insertion of small rectangular tabs into the jet flow on the nozzle perimeter was found to have a very profound effect on the jet development. In particular, it was found that just two tabs produced gross distortions in the jet development resulting in the jet almost splitting in two with high velocity regions on either side of the diameter joining the tabs. Some explanations for this effect based on further tests with wedges are put forward.

In addition to the measurements of the mean flow field, a few spectrum and correlation measurements are reported for jets both from a clean nozzle and also from a nozzle with two tabs. In the former tests, evidence additional to the results of other experimenters was found for the existence of flow structures which have some coherence around the entire circumference of the jet. It has been suggested that these ‘vortex rings’ or ‘puffs’ may be of some importance in producing jet noise and it seems that the effect of inserting tabs is to prevent the occurrence of these structures.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 70 , Issue 4 , 26 August 1975 , pp. 801 - 813
Copyright
© 1975 Cambridge University Press

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References

Bradbury, L. J. S. 1972 The impact of an axi-symmetric jet onto a normal ground. Aero. Quart. 23, 141.Google Scholar
Bradshaw, P., Ferriss, D. H. & Johnson, R. F. 1964 Turbulence in the noise-producing region of a turbulent jet. J. Fluid Mech. 19, 591.Google Scholar
Crow, S. C. & Champagne, F. H. 1971 Orderly structures in jet turbulence. J. Fluid Mech. 48, 547.Google Scholar
Davies, P. O. A. L. & Yule, A. J. 1975 Coherent structures in turbulence. J. Fluid Mech. 69, 513.Google Scholar
Gentry, G. L. & Margarson, R. J. 1966 Jet induced lift losses on VTOL configurations hovering in and out of ground effect. N.A.S.A. Tech. Note, D-3166.Google Scholar
Kuhn, R. E. 1959 An investigation to determine conditions under which downwash from VTOL aircraft will start surface erosion from various types of terrain. N.A.S.A. Tech. Note, D-56.Google Scholar
Lau, J. C. 1971 The coherent structure of jets. Ph.D. thesis, University of Southampton.
Taylor, G. I. 1960 Formation of thin flat sheets of water. Proc. Roy. Soc. A 259, 1.Google Scholar