THERMAL SCIENCE

International Scientific Journal

Authors of this Paper

External Links

Amina Meslem

,

Ilinca Nastase

CROSS AND CLOVER SHAPED ORIFICE JETS ANALYSIS AT LOW REYNOLDS NUMBER

ABSTRACT
The jet coming from a cross-shaped orifice with an open center has been shown in the past, to provide substantial increase in the near field convective transport-mixing, in comparison to a classical round orifice jet. Detailed information has been reported in previous works on the role played in the jet mixing enhancement by the crow of vortices composed of counter-rotating pairs of secondary streamwise structures which are developing in orifice’s troughs. A trough in the cross-shaped jet generates a local shear like the one generated by a triangular tab in a square jet. In the present study we are interested by the modification of local shears in the troughs of the cross-shaped jet, when orifice geometry is modified, such as the center of the orifice becomes closed, leading to a clover-shaped orifice. The general motivation is to understand the effect of using a set of combination of longitudinal structures, themselves produced by the superposition of local shear regions, in mixing performance of a cross jet. It is shown that lower entrainment rates in the clover jet is a results of a additional internal crown of vortices which opposes the external one due to inner shears generated by closing the center of the orifice.
KEYWORDS
clover jet, cross jet, switching-over, entrainment, jet throw
PAPER SUBMITTED: 2013-07-24
PAPER REVISED: 2013-11-28
PAPER ACCEPTED: 2013-12-02
PUBLISHED ONLINE: 2013-12-22
DOI REFERENCE: https://doi.org/10.2298/TSCI130724166M
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2015, VOLUME 19, ISSUE Issue 6, PAGES [2139 - 2150]
REFERENCES
  1. Suprayan, R. and H.E. Fiedler, On streamwise vortical structures in the near-field of axisymmetric shear layers. Meccanica, 1994. 29(4): p. 403-410.
  2. Liepmann, D. and M. Gharib, The role of streamwise vorticty in the near field entrainement of round jets. Journal of Fluid Mechanics, 1992. 245: p. 642-668.
  3. Husain, Z.D. and A.K.M.F. Hussain, Natural Instability of Free Shear Layers. AIAA Journal, 1983. 21(11): p. 1512-1517.
  4. Brown, G.L. and A. Roshko, On density effects and large structures in turbulent mixing layers. Journal of Fluid Mechanics, 1974. 64(4): p. 775-816.
  5. Becker, H.A. and T.A. Massaro, Vortex evolution in a round jet. Journal of Fluid Mechanics, 1968. 31(3): p. 435-448.
  6. Crow, S.C. and F.H. Champagne, Orderly structure in jet turbulence. Journal of Fluid Mechanics, 1971. 48(3): p. 547-591.
  7. Toyoda, K. and R. Hiramoto, Effect of streamwise vortices on characteristics of jets. 2006.
  8. Todde, V., P.G. Spazzini, and M. Sandberg, Experimental analysis of low-Reynolds number free jets. Evolution along the jet centerline and Reynolds number effects. Experiments in Fluids, 2009. 47: p. 279-294.
  9. Mathew, J. and A.J. Basu, Some characteristcs of entrainment at a cylindrical turbulence boundary. Physics of Fluids, 2002. 14(7): p. 2065-2072.
  10. Liepmann, D., Streamwise vorticity and entrainement in the near field of a round jet. Physics of Fluids, 1991. 3(5): p. 1179-1185.
  11. Gutmark, E.J. and C.M. Ho, Preferred modes and the spreading rates of jets. Physics of Fluids, 1983. 26(10): p. 2932-2938.
  12. Zaman, K.B.M.Q. Streamwise vorticity generation and mixing enhancement in free jets by delta tabs. in AIAA paper. 1993.
  13. Gutmark, E.J. and F.F. Grinstein, Flow Control with Noncircular Jets. Annual Reviews of Fluid Mechanics, 1999. 31: p. 239-272.
  14. New, T.H., An experimental study on jets issuing from elliptic inclined nozzles. Experiments in Fluids, 2009. 46(6): p. 1139-1157.
  15. Husain, H.S. and A.K.M.F. Hussain, The elliptic whistler jet. Journal of Fluid Mechanics, 1999. 397: p. 23-44.
  16. Nastase, I. and A. Meslem, Vortex dynamics and mass entrainment in turbulent lobed jets with and without lobe deflection angles. Experiments in Fluids, 2010. 48(4): p. 693-714.
  17. Hussain, F. and H.S. Husain, Elliptic jets. Part1. Characteristics of unexcited and excited jets. Journal of Fluid Mechanics, 1989. 208: p. 257-320.
  18. Hu, H., et al., A Study on a Lobed Jet Mixing Flow by Using Stereoscopic Particle Image Velocimetry Technique. Physics of Fluids, 2001. 13(11): p. 3425-3441.
  19. El-Hassan, M., A. Meslem, and K. Abed-Meraïm, Experimental investigation of the flow in the near-field of a cross-shaped orifice jet. Phys. Fluids, 2011. 23(045101): p. 16 p.
  20. El-Hassan, M. and A. Meslem, Time-resolved stereoscopic PIV investigation of the entrainement in the near-field of circular and daisy-shaped orifice jets. Physics of Fluids, 2010. 22(035107): p. 26 p.
  21. Nastase, I., A. Meslem, and P. Gervais, Primary and secondary vortical structures contribution in the entrainement of low Reynolds number jet flows. Experiments in Fluids, 2008. 44(6): p. 1027-1033.
  22. Meslem, A., M. El-Hassan, and I. Nastase, Analysis of jet entrainment mechanism in the transitional regime by time-resolved PIV. Journal of Visualization, 2011. 14(1): p. 41-52.
  23. Wang, X.K., L.P. Chua, and S.C.M. Yu, On the near-field of a square jet with vortex-generating tabs. Fluid Dynamics Research, 2003. 32: p. 99-117.
  24. Mishra, D.P. and P. Kumar, Experimental study of bluff-body stabilized LPG-H2 jet diffusion flame with preheated reactant. Fuel, 2010. 89: p. 212-218.
  25. Jeong, J. and F. Hussain, On the identification of a vortex. Journal of Fluid Mechanics, 1995. 285: p. 69-94.
  26. Dubief, Y. and F. Delcayre, On coherent-vortex identification in turbulence. Journal of Turbulence, 2000. 1(11): p. 1-22.
PDF VERSION [DOWNLOAD]
Cross and clover shaped orifice jets analysis at low Reynolds number

© 2024 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence