Effect of background turbulence on an axisymmetric turbulent jet

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 (...

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Veröffentlicht in:Journal of fluid mechanics Jg. 736; S. 250 - 286
Hauptverfasser: Khorsandi, B., Gaskin, S., Mydlarski, L.
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Cambridge, UK Cambridge University Press 10.12.2013
Schlagworte:
Computational fluid dynamics
Decay rate
Dimensional analysis
Dynamics
Entrainment
Exact sciences and technology
Flow rates
Fluid dynamics
Fundamental areas of phenomenology (including applications)
Instrumentation for fluid dynamics
Jets
Mass flow rate
Physics
Pollutants
Reynolds number
Turbulence
Turbulent flows, convection, and heat transfer
Velocity
wakes/jets
turbulent flows
jets
Hot film anemometer
Turbulent flow
Acoustic Doppler velocimeter
Circular jet
Experimental study
Velocity measurement
Turbulence structure
Mixing layer
ISSN:0022-1120, 1469-7645
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Zusammenfassung: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.
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ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2013.465