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Characteristics of a supersonic elliptic jet

Published online by Cambridge University Press:  23 March 2016

S.M. Aravindh Kumar  and
E. Rathakrishnan
S.M. Aravindh Kumar*
Affiliation:
Department of Aerospace Engineering, Indian Institute of Technology Kanpur, India
E. Rathakrishnan
Affiliation:
Department of Aerospace Engineering, Indian Institute of Technology Kanpur, India
*
[email protected]
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Abstract

Comparative mixing of a Mach 2 elliptical free jet from a convergent-divergent elliptic nozzle with an aspect ratio of 2:1 in the presence of adverse and marginally favourable pressure gradients has been studied experimentally. It is found that the mixing of the elliptical jet is higher than that for the equivalent circular jet at all the levels of expansion. The decay of elliptic jet is significantly higher than the equivalent circular jet in all three zones of the jet field – the core, characteristic decay and fully developed regions. The reason for the faster decay of the elliptic jet is found to be the continuous variation in the size of the mixing-promoting vortices shed from the nozzle exit owing to its azimuthal asymmetry. The evolution of the jet and its axis-switching phenomenon has been studied using iso-pitot pressure contours taken at different axial locations in the plane normal to the jet axis. As expected, the elliptic jet spreads faster along the minor axis plane than the major axis plane, leading to axis-switching at all the levels of expansion studied. The axis-switching of the elliptic jet shifts upstream with increase in nozzle pressure ratio (NPR) from 4 to 5; from 5 to 7, it shifts downstream. But at marginally under-expanded condition of NPR 8, the axis-switching is found to shift slightly upstream. The occurrence of axis-switching in the elliptic jet indicates enhanced near-field mixing, compared to the equivalent circular jet. The shadowgraph pictures of the jet reveal that the waves prevailing in the elliptic jet are significantly weaker than those in the circular jet.

Keywords

Elliptic jetaxis-switchingsupersonic core lengthazimuthal asymmetry
Type
Research Article
Information
The Aeronautical Journal , Volume 120 , Issue 1225 , March 2016 , pp. 495 - 519
Copyright
Copyright © Royal Aeronautical Society 2016 

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References

REFERENCES

1.Ho, C.M. and Gutmark, E.J.Vortex induction and mass entrainment in a small-aspect ratio elliptic jet, J Fluid Mech, 1987, 179, pp 383–405.Google Scholar
2.Hussain, A.K.M.F. and Husain, H.S.Elliptic jets. Part I. Characteristics of unexcited and excited jets, J Fluid Mech, 1989, 208, pp 257–320.Google Scholar
3.Hussain, A.K.M. F. and Husain, H.S.Elliptic jets. Part 2. Dynamics of coherent structures: pairing, J Fluid Mech, 1991, 233, pp 439–482.Google Scholar
4.Quinn, W.R.On mixing in an elliptic turbulent free jet, Phys Fluids A, 1989, 1, (10), pp 1716–1722.Google Scholar
5.Schadow, K.C., Gutmark, E.J., Koshigoe, S. and Wilson, K.J.Combustion-related shear-flow dynamics in elliptic supersonic jets, AIAA J, 1989, 27, (10), pp 1347–1353.CrossRefGoogle Scholar
6.Gutmark, E.J., Schadow, K. C. and Wilson, K.J.Noncircular jet dynamics in supersonic combustion, Journal of Propulsion, 1989, 5, (5), pp 529–533.CrossRefGoogle Scholar
7.Verma, S.B., Rathakrishnan, E.Effect of mach number and aspect-ratio on the acoustic properties of underexpanded elliptic-slot jets, Int J Turbo Jet Engines, 2002, 19, pp 179–194.Google Scholar
8.Yoon, J., and Lee, S.Investigation of the near-field structure of an elliptic jet using stereoscopic particle image velocimetry, Meas Sci Technol, 2013, 14, pp 2034–2046.Google Scholar
9.Baty, R.S., Seiner, J.M. and Ponton, M.K. Instability of a supersonic shock free elliptic jet, 13th AIAA Aeroacoustic Conference, Tallahassee, Florida, US, 2010, pp AIAA-90-3959.Google Scholar
10.Menon, N. and Skews, B.Shock wave configurations and flow structures in non-axisymmetric underexpanded sonic jets, Shock Waves, 2010, 20, pp 175–190.Google Scholar
11.Mitchell, D., Honnery, D. and Soria, J.Near-field structure of underexpanded elliptic jets, Exp Fluids, 2013, 54, pp 1578.Google Scholar
12.Zaman, K.B.M.Q.Axis switching and spreading of an asymmetric jet: the role of coherent structure dynamics, Journal of Fluid Mech. 1996, 316, pp 1–27.CrossRefGoogle Scholar
13.Arun Kumar, P. and Rathakrishnan, E.Truncated triangular tabs for supersonic jet control, J Propul Power, 2013, 29, (1), pp 50–65.Google Scholar
14.Rathakrishnan, E, Applied Gas Dynamics, 2010, John Wiley & Sons Inc., Hoboken, New Jersey, US.Google Scholar
15.Phanindra, B.C. and Rathakrishnan, E.Corrugated tabs for supersonic jet control, AIAA J, 2010, 48, (2), pp 453–465.Google Scholar
16.Tam, C.K.W.Supersonic jet noise, Ann Rev Fluid Mech, 1995, 27, pp 17–43.Google Scholar
17.Arun Kumar, P. and Rathakrishnan, E.Corrugated truncated triangular tabs for supersonic jet control, J Fluids Eng, 2013, 135, (9), pp 091104–1 to 091104-11.Google Scholar
18.Rathakrishnan, E.Experimental studies on the limiting tab, AIAA J, 2009, 47, (10), pp 2475–2485.Google Scholar