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  • 1
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    Mixing and mixing enhancement in supersonic reacting flowfields (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Propulsion systems planned for use late in this century and beyond will require appropriate physical models for describing supersonic combustion and numerical techniques for solving the model governing equations. A computer program to study these flows is reported which considers the multicomponent diffusion and convection of important chemical species, the finite-rate reaction of these species, and the resulting interaction of the field mechanics and the chemistry. The application of the program to a spatially developing and reacting mixing layer, which serves an an excellent physical model for the mixing and reaction processes that take place in a scramjet combustor, is reported. Several techniques to enhance the fuel-air mixing and growth of that layer and improve its overall combustion efficiency are considered.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 2
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    A numerical model for supersonic reacting mixing layers (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A current research effort is underway at the NASA Langley Research Center to achieve a detailed understanding of important phenomena present when a supersonic flow undergoes a chemical reaction. A computer program has been developed to study the details of such flows. The program has been constructed to consider the multicomponent diffusion and convection of important species, the finite-rate reaction of these species, and the resulting interaction between the fluid mechanics and chemistry. Code results from the analysis of a spatially developing and reacting mixing layer are presented, and conclusions are drawn regarding the structure of the evolving layer and its associated flame.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 64; 39-60
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  • 3
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    Supersonic reacting internal flowfields (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The national program to develop a trans-atmospheric vehicle has kindled a renewed interest in the modeling of supersonic reacting flows. A supersonic combustion ramjet, or scramjet, has been proposed to provide the propulsion system for this vehicle. The development of computational techniques for modeling supersonic reacting flowfields, and the application of these techniques to an increasingly difficult set of combustion problems are studied. Since the scramjet problem has been largely responsible for motivating this computational work, a brief history is given of hypersonic vehicles and their propulsion systems. A discussion is also given of some early modeling efforts applied to high speed reacting flows. Current activities to develop accurate and efficient algorithms and improved physical models for modeling supersonic combustion is then discussed. Some new problems where computer codes based on these algorithms and models are being applied are described.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 4
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    Investigation of radiative interactions in chemically reacting supersonic internal flows (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Analyses and numerical procedures are presented to investigate the radiative interactions of absorbing-emitting species in chemically reacting supersonic flow in various ducts. Specific attention is directed in investigating the radiative contributions of H2O, OH, and NO under realistic physical and flow conditions. The radiative interactions in reacting flows are investigated by considering the supersonic flow of premixed hydrogen and air in a channel with a compression corner at the lower boundary. The results indicate that radiation can have significant influence on the flowfield and species production depending on the chemistry model employed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 91-0572
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  • 5
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    Modeling turbulent/chemistry interactions using assumed pdf methods (1992)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Two assumed probability density functions (pdfs) are employed for computing the effect of temperature fluctuations on chemical reaction. The pdfs assumed for this purpose are the Gaussian and the beta densities of the first kind. The pdfs are first used in a parametric study to determine the influence of temperature fluctuations on the mean reaction-rate coefficients. Results indicate that temperature fluctuations significantly affect the magnitude of the mean reaction-rate coefficients of some reactions depending on the mean temperature and the intensity of the fluctuations. The pdfs are then tested on a high-speed turbulent reacting mixing layer. Results clearly show a decrease in the ignition delay time due to increases in the magnitude of most of the mean reaction rate coefficients.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 92-3638
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  • 6
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    Development of an algebraic turbulence model for analysis of propulsion flows (1992)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A simple turbulence model that will be applicable to propulsion flows having both wall bounded and unbounded regions was developed and installed within the PARC Navier-Stokes code by linking two existing algebraic turbulence models. The first is the Modified Mixing Length (MML) model which is optimized for wall bounded flows. The second is the Thomas model, the standard algebraic turbulence model in PARC which has been used to calculate both bounded and unbounded turbulent flows but was optimized for the latter. This paper discusses both models and the method employed to link them into one model (referred to as the MMLT model). The PARC code with the MMLT model was applied to two dimensional turbulent flows over a flat plate and over a backward facing step to validate and optimize the model and to compare its predictions to those obtained with the three turbulence models already available in PARC.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 92-3861
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  • 7
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    A detailed numerical model of a supersonic reacting mixing layer (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A current research effort is underway at the NASA Langley Research Center to achieve a detailed understanding of important phenomena present when a supersonic flow undergoes chemical reaction. A computer program has been developed to study the details of such flows. The program has been constructed to consider the multicomponent diffusion and convection of important species, the finite-rate reaction of these species, and the resulting interaction between the fluid mechanics and chemistry. Code results from the analysis of a spatially developing and reacting mixing layer are presented, and conclusions are drawn regarding the structure of the evolving layer and its associated flame.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 86-1427
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  • 8
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    The efficient calculation of chemically reacting flow (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A semi-implicit finite volume formulation is used to study flows with chemical reactions. In this formulation the source terms resulting from the chemical reactions are treated implicitly and the resulting system of partial differential equations is solved using two time-stepping schemes. The first is based on the Runge-Kutta method while the second is based on an Adams predictor-corrector method. Results show that improvements in computational efficiency depend to a large extent on the manner in which the source term is treated. Further, analysis and computation indicate that the Runge-Kutta method is more efficient than the Adams methods. Finally, an adaptive time stepping scheme is developed to study problems involving shock ignition. Calculations for a hydrogen-air system agree well with other methods.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 86-0563
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  • 9
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    Evolution and status of CFD techniques for scramjet applications (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Computational Fluid Dynamics (CFD) methods are presently applied to the design and analysis of scramjet propulsion systems for missiles and aircraft operating at speeds in excess of Mach 5, in forms ranging from simple inviscid codes for parametric studies of inlet geometries to Navier-Stokes codes incorporating chemistry models which address complex scramjet combustion phenomena. Attention is given to the development history of CFD for the hypersonic regime, as well as to scramjet flowfield modeling in inlets, combustors and nozzles, and prospective development trends.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 86-0160
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  • 10
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    A numerical study of mixing enhancement in a supersonic combustor (1990)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This investigation describes an application of the Langley Research Center (LaRC) SPARK family of computer codes to swept and unswept ramp fuel injectors in a reacting highly vortical flow. Both mixing and reacting studies are performed. They show substantially higher mixing as well as flow losses for the swept ramp case. Computational results are compared both qualitatively and quantitatively with experimental results.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 90-0203
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