Large eddy simulations of turbulent mixing and reactions in the ISU planar jet reactor

PurposeThe purpose of this numerical work is to present and test a new approach for large-scale scalar advection (splicing) in large eddy simulations (LES) that use the linear eddy sub-grid mixing model (LEM) called the LES-LEM.Design/methodology/approachThe new splicing strategy is based on an ordered flux of spliced LEM segments. The principle is that low-flux segments have less momentum than high-flux segments and, therefore, are displaced less than high-flux segments. This strategy affects the order of both inflowing and outflowing LEM segments of an LES cell. The new splicing approach is implemented in a pressure-based fluid solver and tested by simulation of passive scalar transport in a co-flowing turbulent rectangular jet, instead of combustion simulation, to perform an isolated investigation of splicing. Comparison of the new splicing with a previous splicing approach is also done.FindingsThe simulation results show that the velocity statistics and passive scalar mixing are correctly predicted using the new splicing approach for the LES-LEM. It is argued that modeling of large-scale advection in the LES-LEM via splicing is reasonable, and the new splicing approach potentially captures the physics better than the old approach. The standard LES sub-grid mixing models do not represent turbulent mixing in a proper way because they do not adequately represent molecular diffusion processes and counter gradient effects. Scalar mixing in turbulent flow consists of two different processes, i.e. turbulent mixing that increases the interface between unmixed species and molecular diffusion. It is crucial to model these two processes individually at their respective time scales. The LEM explicitly includes both of these processes and has been used successfully as a sub-grid scalar mixing model (McMurtry et al., 1992; Sone and Menon, 2003). Here, the turbulent mixing capabilities of the LES-LEM with a modified splicing treatment are examined.Originality/valueThe splicing strategy proposed for the LES-LEM is original and has not been investigated before. Also, it is the first LES-LEM implementation using unstructured grids.

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Large Eddy Simulations of Turbulent Mixing Layers Excited with Two Frequencies

Flow Turbulence and Combustion ◽

10.1007/s10494-013-9507-3 ◽

2013 ◽

Vol 92 (3) ◽

pp. 651-671 ◽

Cited By ~ 6

Author(s):

Abhishek Sarkar ◽

Jörg Schlüter

Keyword(s):

Turbulent Mixing ◽

Large Eddy Simulations ◽

Mixing Layers ◽

Large Eddy

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Large Eddy Simulations of scaled HTGR lower plenum for assessment of turbulent mixing

Nuclear Engineering and Design ◽

10.1016/j.nucengdes.2018.04.016 ◽

2018 ◽

Vol 334 ◽

pp. 24-41 ◽

Cited By ~ 6

Author(s):

Sasan Salkhordeh ◽

Corey Clifford ◽

Anirban Jana ◽

Mark L. Kimber

Keyword(s):

Turbulent Mixing ◽

Large Eddy Simulations ◽

Large Eddy

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Large-Eddy Simulations of Baroclinic Instability and Turbulent Mixing

10.21236/ada590579 ◽

2012 ◽

Author(s):

Eric D. Skyllingstad ◽

Roger M. Samelson

Keyword(s):

Turbulent Mixing ◽

Baroclinic Instability ◽

Large Eddy Simulations ◽

Large Eddy

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A priorianda posterioriinvestigations for developing large eddy simulations of multi-species turbulent mixing under high-pressure conditions

Physics of Fluids ◽

10.1063/1.4916284 ◽

2015 ◽

Vol 27 (3) ◽

pp. 035117 ◽

Cited By ~ 22

Author(s):

Giulio Borghesi ◽

Josette Bellan

Keyword(s):

High Pressure ◽

Turbulent Mixing ◽

Large Eddy Simulations ◽

Large Eddy

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Hybrid Reynolds-Averaged Navier-Stokes/Large-Eddy Simulations of Supersonic Turbulent Mixing

AIAA Journal ◽

10.2514/2.1934 ◽

2003 ◽

Vol 41 (2) ◽

pp. 218-229 ◽

Cited By ~ 43

Author(s):

Nicholas J. Georgiadis ◽

J. Iwan D. Alexander ◽

Eli Reshotko

Keyword(s):

Turbulent Mixing ◽

Large Eddy Simulations ◽

Navier Stokes ◽

Large Eddy ◽

Reynolds Averaged Navier Stokes

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Computational Studies of Two-Dimensional Rayleigh-Taylor Driven Mixing for a Tilted-Rig

Journal of Fluids Engineering ◽

10.1115/1.4027587 ◽

2014 ◽

Vol 136 (9) ◽

Cited By ~ 12

Author(s):

Malcolm J. Andrews ◽

David L. Youngs ◽

Daniel Livescu ◽

Tie Wei

Keyword(s):

Turbulent Mixing ◽

Large Scale ◽

Large Eddy Simulations ◽

Two Dimensional ◽

Complex Flows ◽

Molecular Mixing ◽

One Dimensional ◽

Large Eddy ◽

Mixing Problem ◽

Good Agreement

A time-dependent, incompressible, turbulent mixing problem, referred here to as the “tilted-rig,” is defined, based results from an experiment that involved the introduction of a large-scale overturning motion, with a superposed localized Rayleigh-Taylor (RT) driven mixing. The problem serves to examine the development of RT turbulent mixing while being strained by a large-scale two-dimensional confined motion. Care is taken to define the problem in detail so others might use the definition, and the results, to help develop advanced models of buoyancy driven mixing in complex flows. Aside from a careful definition, the problem has been solved using two different implicit-large-Eddy-simulations (ILES) based codes, and with a direct numerical simulations (DNS) code. Two-dimensional and one-dimensional mix metrics are defined, and then used to examine the development of the mixing region, and the overall evolution of the flow. Comparison of simulations with experiment reveals that large-scale overturning can be well captured in all the simulations, similarly central mix widths, and spike/bubble sidewall penetrations are also in good agreement. A comparison between the different simulation methodologies, ILES and DNS, reveals an overall good agreement between mix metrics such as the amount of molecular mixing. The DNS simulations reveal a dependency on Reynolds number that merits further experimental work.

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