A simple model of mixing and chemical reaction in a turbulent shear layer

Broadwell, James E.; Breidenthal, Robert E.

doi:10.1017/s0022112082003401

Cited by 304 publications

(121 citation statements)

References 17 publications

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“…In the context of LES, a subgrid model for filamentation has been developed by Grabowski (2007) and Jarecka et al (2009) drawing on developments in combustion modelling. Grabowski (2007) proposed an advection-diffusion equation for the length scale, λ, of a filament based on the similarity arguments of Broadwell and Breidenthal (1982), who suggested that filaments of a conserved scalar field should obey…”

Section: Mechanisms For Entrainment In Cloudsmentioning

confidence: 99%

Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

245

281

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In this survey we consider the impact of turbulence on cloud formation from the cloud scale to the droplet scale. We assess progress in understanding the effect of turbulence on the condensational and collisional growth of droplets and the effect of entrainment and mixing on the droplet spectrum. The increasing power of computers and better experimental and observational techniques allow for a much more detailed study of these processes than was hitherto possible. However, much of the research necessarily remains idealized and we argue that it is those studies which include such fundamental characteristics of clouds as droplet sedimentation and latent heating that are most relevant to clouds. Nevertheless, the large body of research over the last decade is beginning to allow tentative conclusions to be made. For example, it is unlikely that small-scale turbulent eddies (i.e. not the energy-containing eddies) alone are responsible for broadening the droplet size spectrum during the initial stage of droplet growth due to condensation. It is likely, though, that small-scale turbulence plays a significant role in the growth of droplets through collisions and coalescence. Moreover, it has been possible through detailed numerical simulations to assess the relative importance of different processes to the turbulent collision kernel and how this varies in the parameter space that is important to clouds. The focus of research on the role of turbulence in condensational and collisional growth has tended to ignore the effect of entrainment and mixing and it is arguable that they play at least as important a role in the evolution of the droplet spectrum. We consider the role of turbulence in the mixing of dry and cloudy air, methods of quantifying this mixing and the effect that it has on the droplet spectrum. Copyright

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Section: Mechanisms For Entrainment In Cloudsmentioning

confidence: 99%

Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

245

281

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“…This section contains a brief description of the recent Broadwell-Breidenthal ( 1982) model for mixing and chemical reaction in a turbulent shear layer. It is discussed at this point since some of the results to be presented are interpreted in terms of the model.…”

Section: Broadwell-breidenthal Modelmentioning

confidence: 99%

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

1984

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Turbulent mixing and combustion are investigated in a gaseous shear layer formed between two streams: one containing a low concentration of hydrogen in nitrogen and the other containing a low concentration of fluorine in nitrogen. The resulting temperature field is measured simultaneously at eight points across the width of the layer using fast-response cold-wire thermometry. The results show the presence of large, hot structures separated by tongues of cool fluid that enter the layer from either side. The usual bell-shaped mean-temperature profiles therefore result from a duty cycle whereby a fixed probe sees alternating hot and cool fluid, which results in the local mean. The adiabatic flame temperature is not achieved in the mean, at any location across the layer. For fixed velocities, it is found that, in general, two different mean-temperature profiles result from a given pair of reactant compositions if the sides of the layer on which they are carried are exchanged ('flipped'). This finding is a direct consequence of the asymmetric entrainment of fluid into the layer. Results are compared with the predictions of Konrad and discussed in the context of the Broadwell-Breidenthal model. By comparison with the liquid result of Breidenthal, the amount of product formed in the layer at high Reynolds number is found to be dependent upon the Schmidt number. Results for a helium-nitrogen layer are discussed briefly.

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“…The scaling arguments of Ref. [3] give the time for the interfacial area increase as comparable to the integral scale time τ I ∼ L=U. But in the time τ I diffusion produces a layer width…”

mentioning

confidence: 93%

“…The turbulent shear layer of neutral fluids provides a simplified paradigm for how the mix models of high density fusion are supposed to work. A model [3] for these shear layers computes the growth in time of the interfacial area, using scaling and similarity arguments that extend the homogeneous turbulence picture of Kolmogorov. The model [3] predicts that the interfacial area grows by a factor comparable to the ratio of the integral scale to the dissipation scale, or L=λ K ∼ R 3=4 e .…”

mentioning

confidence: 99%

“…Subsequent increase of mix comes entirely from growth of the stirred volume, which does not depend on diffusion. Reference [3] has this limit as always satisfied for high Reynolds number flows provided turbulence is fully developed. It is an open question, however, whether ICF capsule implosions are of sufficient duration or steadiness to allow turbulence to fully develop and to grow the interfacial area to the size required in Ref.…”

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confidence: 99%

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Nonlinear Structure of the Diffusing Gas-Metal Interface in a Thermonuclear Plasma

et al. 2014

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This Letter describes the theoretical structure of the plasma diffusion layer that develops from an initially sharp gas-metal interface. The layer dynamics under isothermal and isobaric conditions is considered so that only mass diffusion (mixing) processes can occur. The layer develops a distinctive structure with asymmetric and highly nonlinear features. On the gas side of the layer the diffusion coefficient goes nearly to zero, causing a sharp "front," or well defined boundary between mix layer and clean gas with similarities to the Marshak thermal waves. Similarity solutions for the nonlinear profiles are found and verified with full ion kinetic code simulations. A criterion for plasma diffusion to significantly affect burn is given.

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A simple model of mixing and chemical reaction in a turbulent shear layer

Cited by 304 publications

References 17 publications

Droplet growth in warm turbulent clouds

Droplet growth in warm turbulent clouds

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

Nonlinear Structure of the Diffusing Gas-Metal Interface in a Thermonuclear Plasma

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