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Mixing and chemical reactions in a turbulent liquid mixing layer

Koochesfahani, M. M. and Dimotakis, P. E. (1986) Mixing and chemical reactions in a turbulent liquid mixing layer. Journal of Fluid Mechanics, 170 . pp. 83-112. ISSN 0022-1120.

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An experimental investigation of entrainment and mixing in reacting and non-reacting turbulent mixing layers at large Schmidt number is presented. In non-reacting cases, a passive scalar is used to measure the probability density function (p.d.f.) of the composition field. Chemically reacting experiments employ a diffusion-limited acid–base reaction to directly measure the extent of molecular mixing. The measurements make use of laser-induced fluorescence diagnostics and high-speed, real-time digital image-acquisition techniques. Our results show that the vortical structures in the mixing layer initially roll-up with a large excess of fluid from the high-speed stream entrapped in the cores. During the mixing transition, not only does the amount of mixed fluid increase, but its composition also changes. It is found that the range of compositions of the mixed fluid, above the mixing transition and also throughout the transition region, is essentially uniform across the entire transverse extent of the layer. Our measurements indicate that the probability of finding unmixed fluid in the centre of the layer, above the mixing transition, can be as high as 0.45. In addition, the mean concentration of mixed fluid across the layer is found to be approximately constant at a value corresponding to the entrainment ratio. Comparisons with gas-phase data show that the normalized amount of chemical product formed in the liquid layer, at high Reynolds number, is 50% less than the corresponding quantity measured in the gas-phase case. We therefore conclude that Schmidt number plays a role in turbulent mixing of high-Reynolds-number flows.

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Additional Information:© 1986 Cambridge University Press. Received 13 August 1985 and in revised form 11 February 1986. Published online: 21 April 2006. We would like to acknowledge the valuable contributions of Drs D. B. Lang and F. A. Roberts during the course of this research. The many illuminating discussions with Drs R. E. Breidenthal, J. E. Broadwell and M.G. Mungal are very much appreciated. This work was sponsored by the Air Force Office of Scientific Research Contract Nos F44620-76-C-0046, F49620-79-C-0159 and Grant No. AFOSR-83-0213.
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Air Force Office of Scientific Research (AFORS) F44620-76-C-0046
Air Force Office of Scientific Research (AFOSR)F49620-79-C-0159
Air Force Office of Scientific Research (AFOSR)AFOSR-83-0213
Record Number:CaltechAUTHORS:20120627-085420456
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Official Citation: M. M. Koochesfahani and P. E. Dimotakis (1986). Mixing and chemical reactions in a turbulent liquid mixing layer. Journal of Fluid Mechanics, 170 , pp 83-112 doi:10.1017/S0022112086000812
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32126
Deposited By: Ruth Sustaita
Deposited On:27 Jun 2012 17:14
Last Modified:21 Sep 2016 23:05

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