A Second-order Closure Analysis of Turbulent Diffusion Flames

A Second-order Closure Analysis of Turbulent Diffusion Flames PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 92

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A Second-order Closure Analysis of Turbulent Diffusion Flames

A Second-order Closure Analysis of Turbulent Diffusion Flames PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 92

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Evaluation of Closure Models of Turbulent Diffusion Flames

Evaluation of Closure Models of Turbulent Diffusion Flames PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Modeling methods applied in the field of turbulent combustion were investigated via Direct Numerical Simulations (DNS) and theoretical analysis with an emphasis on subgrid-scale modeling to be applied in Large Eddy Simulations (LES). The DNS results supported the conditional moment closure approximation, refuted the common modeling of differential diffusion effects, raised a suggestion for valid modeling of differential diffusion, resolved outstanding theoretical issues regarding mixing layers, and demonstrated the need for including flamelet/flamelet interactions in the modeling of extinction/reignition events. The DNS methodology was reconfirmed by comparison to the classical laboratory results of Comte-Bellot and Corrsin. A new subgrid-scale model (Large Eddy Laminar Flamelet; LELFM, a quasi-steady model) was established and applied to the prediction of laboratory results in a simulated mixing layer with nitric oxide/ozone reaction. The results support the modeling. New results were derived and confirmed via DNS regarding the subgrid-scale modeling of the filtered mixture fraction, its second moment and dissipation rate.

Turbulent Mixing in Nonreactive and Reactive Flows

Turbulent Mixing in Nonreactive and Reactive Flows PDF Author: S. Murthy
Publisher: Springer Science & Business Media
ISBN: 1461587387
Category : Science
Languages : en
Pages : 469

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Turbulence, mixing and the mutual interaction of turbulence and chemistry continue to remain perplexing and impregnable in the fron tiers of fluid mechanics. The past ten years have brought enormous advances in computers and computational techniques on the one hand and in measurements and data processing on the other. The impact of such capabilities has led to a revolution both in the understanding of the structure of turbulence as well as in the predictive methods for application in technology. The early ideas on turbulence being an array of complicated phenomena and having some form of reasonably strong coherent struc ture have become well substantiated in recent experimental work. We are still at the very beginning of understanding all of the aspects of such coherence and of the possibilities of incorporating such structure into the analytical models for even those cases where the thin shear layer approximation may be valid. Nevertheless a distinguished body of "eddy chasers" has come into existence. The structure of mixing layers which has been studied for some years in terms of correlations and spectral analysis is also getting better understood. Both probability concepts such as intermittency and conditional sampling as well as the concept of large scale structure and the associated strain seem to indicate possibilities of distinguishing and synthesizing 'engulfment' and molecular mixing.

Evaluation of Closure Models of Turbulent Diffusion Flames

Evaluation of Closure Models of Turbulent Diffusion Flames PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
Modeling methods applied in the field of turbulent combustion were investigated via Direct Numerical Simulations (DNS) and theoretical analysis with an emphasis on subgrid-scale modeling to be applied in Large Eddy Simulations (LES). The DNS results supported the conditional moment closure approximation, refuted the common modeling of differential diffusion effects, raised a suggestion for valid modeling of differential diffusion, resolved outstanding theoretical issues regarding mixing layers, and demonstrated the need for including flamelet/flamelet interactions in the modeling of extinction/reignition events. The DNS methodology was reconfirmed by comparison to the classical laboratory results of Comte-Bellot and Corrsin. A new subgrid-scale model (Large Eddy Laminar Flamelet; LELFM, a quasi-steady model) was established and applied to the prediction of laboratory results in a simulated mixing layer with nitric oxide/ozone reaction. The results support the modeling. New results were derived and confirmed via DNS regarding the subgrid-scale modeling of the filtered mixture fraction, its second moment and dissipation rate.

Evaluation of Closure Models of Turbulent Diffusion Flames

Evaluation of Closure Models of Turbulent Diffusion Flames PDF Author: G. Kosaly
Publisher:
ISBN:
Category : Flame
Languages : en
Pages : 10

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Gasdynamics of Explosions and Reactive Systems

Gasdynamics of Explosions and Reactive Systems PDF Author: A. K. Oppenheim
Publisher: Elsevier
ISBN: 1483150054
Category : Science
Languages : en
Pages : 787

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Book Description
Gas Dynamics of Explosions and Reactive Systems documents the proceedings of the 6th Colloquium held at the Royal Institute of Technology in Stockholm, Sweden, 22-26 August 1977. The meeting was held under the auspices of the Royal Swedish Academy of Sciences and the International Academy of Astronautics. The scientific program included over one hundred papers. The contributions in this volume are organized into four parts. Part I contains papers on gaseous detonations. It covers topics such as theoretical model of a detonation cell; spherical detonations in hydrocarbon-air mixtures; and shock wave propagation in tubes filled with water foams. Part II presents studies on explosions, such as the detonation of hydrogen azide and propagation of a laser-supported detonation wave. Part III examines condensed phase detonations. It includes papers on the mechanism of the divergent and convergent dark waves originating at the charge boundary in detonating liquid homogeneous explosives with unstable detonation front; and initiation studies in sensitized nitromethane. Part IV presents discussions on turbulent detonations, covering topics such as the computational aspects of turbulent combustion and problems and techniques in turbulent reactive systems.

Scientific and Technical Aerospace Reports

Scientific and Technical Aerospace Reports PDF Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 704

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Turbulent Combustion

Turbulent Combustion PDF Author: Norbert Peters
Publisher: Cambridge University Press
ISBN: 1139428063
Category : Science
Languages : en
Pages : 322

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Book Description
The combustion of fossil fuels remains a key technology for the foreseeable future. It is therefore important that we understand the mechanisms of combustion and, in particular, the role of turbulence within this process. Combustion always takes place within a turbulent flow field for two reasons: turbulence increases the mixing process and enhances combustion, but at the same time combustion releases heat which generates flow instability through buoyancy, thus enhancing the transition to turbulence. The four chapters of this book present a thorough introduction to the field of turbulent combustion. After an overview of modeling approaches, the three remaining chapters consider the three distinct cases of premixed, non-premixed, and partially premixed combustion, respectively. This book will be of value to researchers and students of engineering and applied mathematics by demonstrating the current theories of turbulent combustion within a unified presentation of the field.

Turbulent Premixed Flames

Turbulent Premixed Flames PDF Author: Nedunchezhian Swaminathan
Publisher: Cambridge University Press
ISBN: 1139498584
Category : Technology & Engineering
Languages : en
Pages : 447

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Book Description
A work on turbulent premixed combustion is important because of increased concern about the environmental impact of combustion and the search for new combustion concepts and technologies. An improved understanding of lean fuel turbulent premixed flames must play a central role in the fundamental science of these new concepts. Lean premixed flames have the potential to offer ultra-low emission levels, but they are notoriously susceptible to combustion oscillations. Thus, sophisticated control measures are inevitably required. The editors' intent is to set out the modeling aspects in the field of turbulent premixed combustion. Good progress has been made on this topic, and this cohesive volume contains contributions from international experts on various subtopics of the lean premixed flame problem.

NASA Technical Paper

NASA Technical Paper PDF Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 64

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