Mixing and combustion with low heat release in a turbulent shear layer

Mungal, M. G.; Dimotakis, Paul E.

doi:10.1017/s002211208400238x

Cited by 189 publications

(127 citation statements)

References 34 publications

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“…It is presumably this rotation of the average scalar contours in the central part of the core that is responsible for the 'non-marching' peak in the probability density function of the fluid composition reported in several experimental studies of post-transition mixing layers (Konrad 1976;Mungal & Dimotakis 1984;Koochesfahani & Dimotakis 1986). …”

Section: Topography Of Post-transition Structuresmentioning

confidence: 97%

Organised large structure in the post-transition mixing layer. Part 2. Large-eddy simulation

McMullan¹,

Gao²,

Coats³

2014

J. Fluid Mech.

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Three-dimensional large-eddy simulations of two-stream mixing layers developing spatially from laminar boundary layers are presented, replicating wind-tunnel experiments carried out in Part 1 of this study. These simulations have been continued through the mixing transition and into the fully turbulent self-similar flow beyond. In agreement with the experiments, the simulations show that the familiar mechanism of growth by vortex amalgamation is replaced at the mixing transition by a previously unrecognised mechanism in which the spanwise-coherent large structures individually undergo continuous linear growth. In the post-transition flow it is this continuous linear growth of the individual structures that produces the self-similar growth of the mixing-layer thickness, the large-structure interactions occurring as a consequence of the growth, not its cause. New information is also presented on the topography of the organised post-transition flow and on its cyclical evolution through the lifetimes of the individual large structures. The dynamic and kinematic implications of these findings are discussed and shown to define quantitatively the growth rate of the homogeneous post-transition mixing layer in its organised state. _______________________________________________________________

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Section: Topography Of Post-transition Structuresmentioning

confidence: 97%

Organised large structure in the post-transition mixing layer. Part 2. Large-eddy simulation

McMullan¹,

Gao²,

Coats³

2014

J. Fluid Mech.

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“…Comparisons are presented here with chemical-reaction results of Mungal & Dimotakis (1984) and passive-scalar measurements of Konrad (1976), both of which were performed in gas-phase mixing layers.…”

Section: Comparisonsmentioning

confidence: 99%

“…Note that the only distinguishing feature between cases (a) and (b) is the exchange of the chemical composition of the free streams between the two sets ('flip' experiments), see also and Mungal & Dimotakis (1984).…”

Section: Laser-induced Fluorescence (Lif)mentioning

confidence: 99%

“…In the second type of experiment, the extent of molecular mixing is directly measured using an isothermal, constant-density acid-base chemical reaction. These measurements are the liquid counterpart to the gas-phase experiment of Mungal & Dimotakis (1984).…”

Section: Introductionmentioning

confidence: 99%

“…Much of this knowledge has come from investigations in gas-phase flows both in non-reacting cases, such as those of Brown & Roshko (1971, 1974, Fiedler (1974) and Konrad (1976), and also inchemicallyreactingflows (Ganji & Sawyer 1980;Wallace 1981;Pitz & Daily 1983;Mungal & Dimotakis 1984). Studies of mixing in liquid layers, by contrast, are very few.…”

Section: Introductionmentioning

confidence: 99%

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Mixing and chemical reactions in a turbulent liquid mixing layer

1986

Self Cite

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An experimental investigation of entrainment and mixing in reacting and nonreacting turbulent mixing layers at large Schmidt number is presented. In nonreacting cases, a passive scalar is used to measure the probability density function (p.d.f.) ofthe composition field. Chemically reacting experiments employ a diffusionlimited 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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Recent Advances in Turbulent Mixing

Dimotakis

2001

Mechanics for a New Mellennium

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Mixing and combustion with low heat release in a turbulent shear layer

Cited by 189 publications

References 34 publications

Organised large structure in the post-transition mixing layer. Part 2. Large-eddy simulation

Organised large structure in the post-transition mixing layer. Part 2. Large-eddy simulation

Mixing and chemical reactions in a turbulent liquid mixing layer

Recent Advances in Turbulent Mixing

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