Characteristics of the turbulent/non-turbulent interface of a non-isothermal jet

The turbulent/non-turbulent interface of a jet is characterized by sharp jumps ('discontinuities') in the conditional flow statistics relative to the interface. Experiments were carried out to measure the conditional flow statistics for a non-isothermal jet, i.e. a cooled jet. These experi...

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Bibliographic Details
Published in:Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences physical, and engineering sciences, 2011-02, Vol.369 (1937), p.723-737
Main Authors: Westerweel, Jerry, Petracci, Alberto, Delfos, René, Hunt, Julian C. R.
Format: Article
Language:English
Subjects:
Buoyancy
Entrainment
Fluid jets
Fluorescence
Free-Shear Turbulence
Mixing
Momentum
Nozzles
Temperature distribution
Temperature gradients
Temperature measurement
Turbulent jets
Velocity
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Summary:The turbulent/non-turbulent interface of a jet is characterized by sharp jumps ('discontinuities') in the conditional flow statistics relative to the interface. Experiments were carried out to measure the conditional flow statistics for a non-isothermal jet, i.e. a cooled jet. These experiments are complementary to previous experiments on an isothermal Re = 2000 jet, where, in the present experiments on a non-isothermal jet, the thermal diffusivity is intermediate to the diffusivity of momentum and the diffusivity of mass. The experimental method is a combined laser-induced fluorescence/particle image velocimetry method, where a temperature-sensitive fluorescent dye (rhodamine 6G) is used to measure the instantaneous temperature fluctuations. The results show that the cooled jet can be considered to behave like a self-similar jet without any significant buoyancy effects. The detection of the interface is based on the instantaneous temperature, and provides a reliable means to detect the interface. Conditional flow statistics reveal the superlayer jump in the conditional vorticity and in the temperature.
ISSN:1364-503X
1471-2962
1471-2962
DOI:10.1098/rsta.2010.0308