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Effect of background turbulence on an axisymmetric turbulent jet

Published online by Cambridge University Press:  04 November 2013

B. Khorsandi ,
S. Gaskin  and
L. Mydlarski
B. Khorsandi
Affiliation:
Department of Civil Engineering and Applied Mechanics, McGill University, 817 Sherbrooke Street West, Montréal, QC, H3A 0C3, Canada
S. Gaskin
Affiliation:
Department of Civil Engineering and Applied Mechanics, McGill University, 817 Sherbrooke Street West, Montréal, QC, H3A 0C3, Canada
L. Mydlarski*
Affiliation:
Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montréal, QC, H3A 0C3, Canada
*
†Email address for correspondence: [email protected]
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Abstract

The effect of different levels of background turbulence on the dynamics and mixing of an axisymmetric turbulent jet at different Reynolds numbers has been investigated. Approximately homogeneous and isotropic background turbulence was generated by a random jet array and had a negligible mean flow (${\langle {U}_{\alpha } \rangle }/ {u}_{\alpha \mathit{rms}} \ll 1$). Velocity measurements of a jet issuing into two different levels of background turbulence were conducted for three different jet Reynolds numbers. The results showed that the mean axial velocities decay faster with increasing level of background turbulence (compared with a jet in quiescent surroundings), while the mean radial velocities increase, especially close to the edges of the jet. Furthermore, the axial root-mean-square velocities of the jet increased in the presence of background turbulence, as did the jet’s width. However, the mass flow rate of the jet decreased, from which it can be inferred that the entrainment into the jet is reduced in a turbulent background. The effect of background turbulence on the entrainment mechanisms is discussed.

JFM classification

Wakes/Jets: Jets Turbulent Flows: Turbulent Flows Wakes/Jets: Wakes/Jets
Type
Papers
Information
Journal of Fluid Mechanics , Volume 736 , 10 December 2013 , pp. 250 - 286
Copyright
©2013 Cambridge University Press 

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