Mixing enhancement in axisymmetric turbulent isothermal and buoyant jets

E. Mastorakos, M. Shibasaki, Koichi Hishida

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Measurements of the velocity and concentration in axisymmetric, turbulent, isothermal and buoyant jets have been performed with laser-Doppler velocimetry and planar and point laser-induced fluorescence to quantify the mixing enhancement achieved by periodic forcing when the jet exit has a fully-developed turbulent pipe flow, a situation less well-studied than the case of laminar initial conditions. It was found that forcing at Strouhal numbers around 0.6 enhances mixing in the developing region of the jet and this enhancement increased with increasing amplitude of excitation, consistent with results of initially-laminar jets. The initial turbulence intensity did not have any effect, but an increase in the initial lengthscale of the turbulence, controlled by a perforated plate inside the nozzle, caused faster mixing. In agreement with previous experiments, the initial conditions of the jet did not affect the far-field rate of decay, but the jet-fluid concentration there was significantly reduced by forcing due to the increased mixing during the early stages of development, an effect that can be described by a smaller virtual origin in decay laws of jet decay. These results are independent of the Froude number because the initial conditions have an influence only in the early stages where the flow is still momentum dominated.

Original languageEnglish
Pages (from-to)279-290
Number of pages12
JournalExperiments in Fluids
Volume20
Issue number4
DOIs
Publication statusPublished - 1996 Feb

Fingerprint

augmentation
Turbulence
decay
turbulence
laminar jets
fluid jets
perforated plates
Perforated plates
Strouhal number
Froude number
turbulent jets
pipe flow
Lasers
Pipe flow
Velocity measurement
laser induced fluorescence
nozzles
far fields
Nozzles
Momentum

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Computational Mechanics
  • Fluid Flow and Transfer Processes

Cite this

Mixing enhancement in axisymmetric turbulent isothermal and buoyant jets. / Mastorakos, E.; Shibasaki, M.; Hishida, Koichi.

In: Experiments in Fluids, Vol. 20, No. 4, 02.1996, p. 279-290.

Research output: Contribution to journalArticle

Mastorakos, E. ; Shibasaki, M. ; Hishida, Koichi. / Mixing enhancement in axisymmetric turbulent isothermal and buoyant jets. In: Experiments in Fluids. 1996 ; Vol. 20, No. 4. pp. 279-290.
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