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Direct numerical simulation of a confined three-dimensional gas mixing layer with one evaporating hydrocarbon-droplet-laden stream

Miller, R. S. and Bellan, J. (1999) Direct numerical simulation of a confined three-dimensional gas mixing layer with one evaporating hydrocarbon-droplet-laden stream. Journal of Fluid Mechanics, 384 . pp. 293-338. ISSN 0022-1120. http://resolver.caltech.edu/CaltechAUTHORS:20171024-080217729

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Abstract

Direct numerical simulations are performed of a confined three-dimensional, temporally developing, initially isothermal gas mixing layer with one stream laden with as many as 7.3×10^5 evaporating hydrocarbon droplets, at moderate gas temperature and subsonic Mach number. Complete two-way phase couplings of mass, momentum and energy are incorporated which are based on a thermodynamically self-consistent specification of the vapour enthalpy, internal energy and latent heat of vaporization. Effects of the initial liquid mass loading ratio (ML), initial Stokes number (St0), initial droplet temperature and flow three-dimensionality on the mixing layer growth and development are discussed. The dominant parameter governing flow modulation is found to be the liquid mass loading ratio. Variations in the initial Stokes number over the range 0.5 ⩽ St_0 ⩽ 2.0 do not cause significant modulations of either first- or second-order gas phase statistics. The mixing layer growth rate and kinetic energy are increasingly attenuated for increasing liquid loadings in the range 0 ⩽ ML ⩽ 0.35. The laden stream becomes saturated before evaporation is completed for all but the smallest liquid loadings owing to: (i) latent heat effects which reduce the gas temperature, and (ii) build up of the evaporated vapour mass fraction. However, droplets continue to be entrained into the layer where they evaporate owing to contact with the relatively higher-temperature vapour-free gas stream. The droplets within the layer are observed to be centrifuged out of high-vorticity regions and to migrate towards high-strain regions of the flow. This results in the formation of concentration streaks in spanwise braid regions which are wrapped around the periphery of secondary streamwise vortices. Persistent regions of positive and negative slip velocity and slip temperature are identified. The velocity component variances in both the streamwise and spanwise directions are found to be larger for the droplets than for the gas phase on the unladen stream side of the layer; however, the cross-stream velocity and temperature variances are larger for the gas. Finally, both the mean streamwise gas velocity and droplet number density profiles are observed to coincide for all ML when the cross-stream coordinate is normalized by the instantaneous vorticity thickness; however, first-order thermodynamic profiles do not coincide.


Item Type:Article
Related URLs:
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https://doi.org/10.1017/S0022112098004042 DOIArticle
https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/direct-numerical-simulation-of-a-confined-threedimensional-gas-mixing-layer-with-one-evaporating-hydrocarbondropletladen-stream/DAFA9DACA31FF2B51DC1C4C75F264C0FPublisherArticle
Additional Information:© 1999 Cambridge University Press. Received 14 January 1998 and in revised form 23 October 1998. Published online: 10 April 1999. This research was conducted at the California Institute of Technology's Jet Propulsion Laboratory (JPL) and sponsored by General Electric (GE) through the Air Force Office of Scientific Research (AFOSR) Focused Research Initiative program with Dr Hukam Mongia from GE serving as contract monitor. The authors would like to thank Dr Kenneth Harstad of JPL and Dr Farzad Mashayek of the University of Hawaii for helpful discussions. Computational resources were provided by the supercomputing facility at JPL.
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Funding AgencyGrant Number
JPL/CaltechUNSPECIFIED
General ElectricUNSPECIFIED
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Record Number:CaltechAUTHORS:20171024-080217729
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20171024-080217729
Official Citation:MILLER, R., & BELLAN, J. (1999). Direct numerical simulation of a confined three-dimensional gas mixing layer with one evaporating hydrocarbon-droplet-laden stream. Journal of Fluid Mechanics, 384, 293-338. doi:10.1017/S0022112098004042
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82608
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Oct 2017 20:24
Last Modified:24 Oct 2017 20:24

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