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Effects of heat release in a turbulent, reacting shear layer

Hermanson, J. C. and Dimotakis, P. E. (1989) Effects of heat release in a turbulent, reacting shear layer. Journal of Fluid Mechanics, 199 . pp. 333-375. ISSN 0022-1120. doi:10.1017/S0022112089000406.

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Experiments were conducted to study the effects of heat release in a planar, gas-phase, reacting mixing layer formed between two free streams, one containing hydrogen in an inert diluent, the other, fluorine in an inert diluent. Sufficiently high concentrations of reactants were utilized to produce adiabatic flame temperature rises of up to 940 K (corresponding to 1240 K absolute). The temperature field was measured at eight fixed points across the layer. Flow visualization was accomplished by schlieren spark and motion picture photography. Mean velocity information was extracted from Pitot-probe dynamic pressure measurements. The results showed that the growth rate of the layer, for conditions of zero streamwise pressure gradient, decreased slightly with increasing heat release. The overall entrainment into the layer was substantially reduced as a consequence of heat release. A posteriori calculations suggest that the decrease in layer growth rate is consistent with a corresponding reduction in turbulent shear stress. Large-scale coherent structures were observed at all levels of heat release in this investigation. The mean structure spacing decreased with increasing temperature. This decrease was more than the corresponding decrease in shear-layer growth rate, and suggests that the mechanisms of vortex amalgamation are, in some manner, inhibited by heat release. The mean temperature rise profiles; normalized by the adiabatic flame temperature rise, were not greatly changed in shape over the range of heat release of this investigation. A small decrease in normalized mean temperature rise with heat release was however observed. Imposition of a favourable pressure gradient in a mixing layer with heat release resulted in an additional decrease in layer growth rate, and caused only a very slight increase in the mixing and amount of chemical product formation. The additional decrease in layer growth rate is shown to be accounted for in terms of the change in free-stream velocity ratio induced by the pressure gradient.

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Additional Information:© 1989 Cambridge University Press. Received 24 July 1987 and in revised form 21 April 1988. The authors gratefully acknowledge the expert advice and assistance of Dr M. G. Mungal as well as the help of C. E. Frieler, Dr R. C. Miake-Lye, and Mr Earl Dahl in running the experiments reported here. We are also thankful for the helpful input and ideas of Drs J. E. Broadwell and M. M. Koochesfahani. This work was sponsored by the Air Force Office of Scientific Research (AFOSR) Contract No. F49620-79-C-0159 and Grant No. 83-0213.
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Air Force Office of Scientific Research (AFOSR)F49620-79-C-0159
Air Force Office of Scientific Research (AFOSR)83-0213
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Official Citation:J. C. Hermanson and P. E. Dimotakis (1989). Effects of heat release in a turbulent, reacting shear layer. Journal of Fluid Mechanics, 199, pp 333-375 doi:10.1017/S0022112089000406
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67615
Deposited By: Paul Dimotakis
Deposited On:06 Jun 2016 21:21
Last Modified:11 Nov 2021 03:51

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