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Characteristics of transitional multicomponent gaseous and drop-laden mixing layers from direct numerical simulation: Composition effects

Selle, L. C. and Bellan, J. (2007) Characteristics of transitional multicomponent gaseous and drop-laden mixing layers from direct numerical simulation: Composition effects. Physics of Fluids, 19 (6). Art. No. 063301. ISSN 1070-6631. http://resolver.caltech.edu/CaltechAUTHORS:SELpof07

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Abstract

Transitional states are obtained by exercising a model of multicomponent-liquid (MC-liquid) drop evaporation in a three-dimensional mixing layer at larger Reynolds numbers, Re, than in a previous study. The gas phase is followed in an Eulerian frame and the multitude of drops is described in a Lagrangian frame. Complete dynamic and thermodynamic coupling between phases is included. The liquid composition, initially specified as a single-Gamma (SG) probability distribution function (PDF) depending on the molar mass, is allowed to evolve into a linear combination of two SGPDFs, called the double-Gamma PDF (DGPDF). The compositions of liquid and vapor emanating from the drops are calculated through four moments of their PDFs, which are drop-specific and location-specific, respectively. The mixing layer is initially excited to promote the double pairing of its four initial spanwise vortices, resulting into an ultimate vortex in which small scales proliferate. Simulations are performed for four liquids of different compositions, and the effects of the initial mass loading and initial free-stream gas temperature are explored. For reference, simulations are also performed for gaseous multicomponent mixing layers for which the effect of Re is investigated in the direct-numerical-simulation–accessible regime. The results encompass examination of the global layer characteristics, flow visualizations, and homogeneous-plane statistics at transition. Comparisons are performed with previous pretransitional MC-liquid simulations and with transitional single-component (SC) liquid-drop-laden mixing layer studies. Contrasting to pretransitional MC flows, the vorticity and drop organization depend on the initial gas temperature, this being due to drop/turbulence coupling. The vapor-composition mean molar mass and standard deviation distributions strongly correlate with the initial liquid-composition PDF. Unlike in pretransitional situations, regions of large composition standard deviation no longer necessarily coincide with those of large mean molar mass. The rotational and composition characteristics are all liquid-specific and the variation among liquids is amplified with increasing free-stream gas temperature. The classical energy cascade is found to be of similar strength, but the smallest scales contain orders of magnitude less energy than SC flows, which is confirmed by the larger viscous dissipation for MC flows. The kinetic energy and dissipation are liquid-specific and the variation among liquids is amplified with increasing free-stream gas temperature. The gas composition, of which the first four moments are calculated, is shown to be close to, but distinct from, a SGPDF. Eulerian and Lagrangian statistics of gas-phase quantities show that the different observation framework may affect the perception of the flow.


Item Type:Article
Additional Information:©2007 American Institute of Physics (Received 13 November 2006; accepted 23 March 2007; published online 22 June 2007) This study was conducted at the Jet Propulsion Laboratory, JPL, California Institute of Technology (Caltech), under the partial sponsorship of the Donors of The Petroleum Research Fund administered by the American Chemical Society through a grant (to J.B.) for Caltech Post Doctoral Fellow support and the U.S. Department of Energy under an agreement with the National Aeronautics and Space Administration. The authors wish to thank Dr. Kenneth G. Harstad of JPL for useful discussions. Computational resources were provided by the supercomputing facility at JPL.
Subject Keywords:flow simulation; two-phase flow; drops; evaporation; vortices; turbulence
Issue or Number:6
Record Number:CaltechAUTHORS:SELpof07
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:SELpof07
Alternative URL:http://dx.doi.org/10.1063/1.2734997
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8498
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:16 Aug 2007
Last Modified:26 Dec 2012 09:39

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