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Influence of jet exit conditions on the passive scalar field of an axisymmetric free jet

Published online by Cambridge University Press:  22 June 2001

J. MI ,
D. S. NOBES  and
G. J. NATHAN
J. MI
Affiliation:
Department of Mechanical Engineering, University of Adelaide, SA 5005, Australia
D. S. NOBES
Affiliation:
Department of Mechanical Engineering, University of Adelaide, SA 5005, Australia Current address: Optical Sensors Group, Department of Power Engineering and Propulsion, School of Mechanical Engineering, Cranfield University, Cranfield, Bedfordshire MK43 0AL, UK.
G. J. NATHAN
Affiliation:
Department of Mechanical Engineering, University of Adelaide, SA 5005, Australia
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Abstract

The influence of initial flow conditions on the passive scalar field of a turbulent free jet issuing from the round nozzle is investigated in this paper by a review of the literature and a detailed experimental study. Two sets of distinctly different initial conditions are generated using two nozzle types: a smooth contraction and a long straight pipe. The present measurements of the passive scalar (temperature) field were conducted in a slightly heated air jet from each nozzle at a Reynolds number of 16 000 using identical experimental facilities and a single measurement technique. Significant differences between the flows from the two nozzles are revealed throughout the measured flow region which covers the axial range from 0 to 70 jet exit diameters. The study suggests that the differences observed in the statistics of the scalar field may be related to differences in the underlying turbulence structure of the jet in the near field. The present findings support the analytical result of George (1989) that the entire flow is influenced by the initial conditions, resulting in a variety of self-similar states in the far field.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 432 , 10 April 2001 , pp. 91 - 125
Copyright
© 2001 Cambridge University Press

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