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Conditionally sampled measurements in a heated turbulent jet

Published online by Cambridge University Press:  29 March 2006

R. A. Antonia ,
A. Prabhu  and
S. E. Stephenson
R. A. Antonia
Affiliation:
Department of Mechanical Engineering, University of Sydney, New South Wales 2006, Australia
A. Prabhu
Affiliation:
Department of Mechanical Engineering, University of Sydney, New South Wales 2006, Australia
S. E. Stephenson
Affiliation:
Department of Mechanical Engineering, University of Sydney, New South Wales 2006, Australia
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Abstract

Measurements of velocity fluctuations u (axial) and v (radial) and temperature fluctuations θ averaged over the turbulent zone have been made in a turbulent heated jet with a co-flowing stream and compared with the conventionally averaged results. The zone-averaged mean temperature and temperature fluctuation intensity appear to be nearly homogeneously distributed in the outer, intermittent region of the jet. This homogeneity does not apply to the u and v fluctuations. The flatness factor of the temperature within the turbulent part of the flow is remarkably constant throughout the intermittent region. Although the skewness of the turbulent θ fluctuations is non-zero, it is smaller than the skewness of the turbulent u and v fluctuations. The average $\overline{\theta v}$ of the heat flux over the turbulent zone increases in the intermittent region whereas the zone-averaged momentum flux $\overline{uv}$ and zone-averaged heat flux $\overline{\theta u}$ continuously decrease. This leads to the Prandtl number of the turbulent fluid being smaller than the conventional Prandtl number in the outer part of the flow. A budget for the square of the temperature fluctuations within the turbulent part of the flow indicates a constant distribution of temperature dissipation. The transport of heat by the large-scale structure of the flow is briefly discussed in the light of available experimental information on other turbulent shear flows.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 72 , Issue 3 , 9 December 1975 , pp. 455 - 480
Copyright
© 1975 Cambridge University Press

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