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Author: Robert P. Gilbert
Publisher:
ISBN:
Category :
Languages : en
Pages : 30
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Book Description
The report is intended to provide Institute members with a concise discussion on the computation of the flow behind a shock leading to detonation in a one-dimensional system. The computation would be performed using the method of characteristics, and this reduction would also be used later for our investigation of the stochastic initiation of detonations. Stochastic effects might be introduced either as white noise or as variations in material properties such as so-called 'hot spots'. Mathematically these effects would appear as part of the 'driving terms' in the characteristic formulation. Consequently the purpose of the present report is to be viewed primarily as a supportive document for our research effort on the stochastic initiation of detonation.
Author: Robert P. Gilbert
Publisher:
ISBN:
Category :
Languages : en
Pages : 30
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Book Description
The report is intended to provide Institute members with a concise discussion on the computation of the flow behind a shock leading to detonation in a one-dimensional system. The computation would be performed using the method of characteristics, and this reduction would also be used later for our investigation of the stochastic initiation of detonations. Stochastic effects might be introduced either as white noise or as variations in material properties such as so-called 'hot spots'. Mathematically these effects would appear as part of the 'driving terms' in the characteristic formulation. Consequently the purpose of the present report is to be viewed primarily as a supportive document for our research effort on the stochastic initiation of detonation.
Author: Bao Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 273
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Book Description
Abstract: This dissertation is focused on the numerical simulation of the detonation initiation process. The space-time Conservation Element and Solution Element (CESE) method, a novel numerical method for time-accurate solutions of nonlinear hyperbolic equations, is extended to model conservation laws with stiff source terms for the detonation initiation process with multiple-step, finite-rate chemistry. The first part of the dissertation illustrates the numerical framework for unsteady chemically reacting flows by incorporating multiple-step, finite-rate chemical mechanisms using the CESE method. One- and two-dimensional solvers have been developed. Extensive code validation and verification are provided for the one- and two-dimensional CESE solvers. The second part focuses on the numerical investigation of the detonation initiation process. The numerical framework is first applied to the direct initiation of gaseous detonations by a blast wave. One-dimensional cylindrical and spherical direct initiation processes in a hydrogen-oxygen mixture are studied with a twenty-four step chemical reaction model. Structures of unsteady reaction zone are clearly resolved. The competition between heat release rate, front curvature, and unsteadiness is investigated. Detailed wave movements in the detonation wave front show that nonlinear waves play an important role in the reacceleration process and are the key to understanding the detonation failure mechanism. The detonation initiation process by implosion shock is then investigated. Shock focusing and shock interactions in the detonation initiation process are examined. Results show a two-shock implosion system due to the interaction between the reflected primary shock and the imploding contact discontinuity. Oblique detonation is studied for the code verification and validation of the two-dimensional CESE solvers. Stabilized detonation structures are resolved and the length of the induction zone is compared with point ignition test data. Implosion with polygonal shock fronts is then explored. Similar to the findings in the one-dimensional results, pressure histories in the focal region show multiple implosions. This Ph. D. study work applies the very accurate and efficient CESE method to study detonation initiation processes. The resultant solvers are state-of-the-art numerical codes that are ready to be applied to time-accurate solutions of detonation initiation processes. This approach provides a new numerical framework for high-fidelity simulations of detonation initiation.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 376
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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: John H. S. Lee
Publisher: Cambridge University Press
ISBN: 1139473204
Category : Technology & Engineering
Languages : en
Pages : 389
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Book Description
This book introduces the detonation phenomenon in explosives. It is ideal for engineers and graduate students with a background in thermodynamics and fluid mechanics. The material is mostly qualitative, aiming to illustrate the physical aspects of the phenomenon. Classical idealized theories of detonation waves are presented first. These permit detonation speed, gas properties ahead of and behind the detonation wave, and the distribution of fluid properties within the detonation wave itself to be determined. Subsequent chapters describe in detail the real unstable structure of a detonation wave. One-, two-, and three-dimensional computer simulations are presented along with experimental results using various experimental techniques. The important effects of confinement and boundary conditions and their influence on the propagation of a detonation are also discussed. The final chapters cover the various ways detonation waves can be formed and provide a review of the outstanding problems and future directions in detonation research.
Author: Anatoly N. Dremin
Publisher: Springer Science & Business Media
ISBN: 9780387986722
Category : Technology & Engineering
Languages : en
Pages : 172
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Book Description
It is known that the Chapman-Jouguet theory of detonation is based on the assumption of an instantaneous and complete transformation of explosives into detonation products in the wave front. Therefore, one should not expect from the theory any interpretations of the detonation limits, such as shock initiation of det onation and kinetic instability and propagation (failure diameter). The Zeldovich-Von Neuman-Doring (ZND) theory of detonation appeared, in fact, as a response to the need for a theory capable of interpreting such limits, and the ZND detonation theory gave qualitative interpretations to the detonation limits. These interpretations were based essentially on the theoretical notion that the mechanism of explosives transformation at detonation is a combustion of a layer of finite thickness of shock-compressed explosive behind the wave shock front with the velocity of the front. However, some experimental findings turned out to be inconsistent with the the ory. A very small change of homogeneous (liquid) explosives detonation velocity with explosive charge diameter near the rather sizable failure diameter is one of the findings. The elucidation of the nature of this finding has led to the discovery of a new phenomenon. This phenomenon has come to be known as the breakdown (BD) of the explosive self-ignition behind the front of shock waves under the effect of rarefaction waves.
Author: Zonglin Jiang
Publisher: Springer Nature
ISBN: 9811970025
Category : Science
Languages : en
Pages : 281
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Book Description
This book highlights the theories and research progress in gaseous detonation research, and proposes a universal framework theory that overcomes the current research limitations. Gaseous detonation is an extremely fast type of combustion that propagates at supersonic speed in premixed combustible gas. Being self-sustaining and self-organizing with the unique nature of pressure gaining, gaseous detonation and its gas dynamics has been an interdisciplinary frontier for decades. The research of detonation enjoyed its early success from the development of the CJ theory and ZND modeling, but phenomenon is far from being understood quantitatively, and the development of theories to predict the three-dimensional cellular structure remains a formidable task, being essentially a problem in high-speed compressible reacting flow. This theory proposed by the authors’ research group breaks down the limitation of the one-dimensional steady flow hypothesis of the early theories, successfully correlating the propagation and initiation processes of gaseous detonation, and realizing the unified expression of the three-dimensional structure of cell detonation. The book and the proposed open framework is of high value for researchers in conventional applications such as coal mine explosions and chemical plant accidents, and state-of-the-art research fields such as supernova explosion, new aerospace propulsion engines, and detonation-driven hypersonic testing facilities. It is also a driving force for future research of detonation.
Author:
Publisher:
ISBN:
Category : Explosions
Languages : en
Pages : 42
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Book Description
Detailed numerical simulations of supersonic reactive flow and gas phase detonation problems are very expensive due to their computer time and memory requirements. The bulk of this cost is in integrating the ordinary differential equations describing chemical reactions. A global induction parameter model has thus been developed which describes the chemical induction time of a mixture and allows for release of energy over a finite time period. The specific gases for which it has been calibrated are stoichiometric mixtures of hydrogen and methane in air. The relatively inexpensive induction parameter model is then used in time-dependent one- and two-dimensional simulations of supersonic reactive flows. (Author).
Author: Wildon Fickett
Publisher: Courier Corporation
ISBN: 0486140709
Category : Science
Languages : en
Pages : 420
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Book Description
Comprehensive review of detonation explores the "simple theory" and experimental tests of the theory; flow in a reactive medium; steady detonation; the nonsteady solution; and the structure of the detonation front. 1979 edition.
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.
Author: Charles L. Mader
Publisher:
ISBN:
Category : Explosions
Languages : en
Pages : 17
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Book Description
