Compressibility Effects in Free Turbulent Shear Flows
Compressibility Effects in Free Turbulent Shear Flows

Author: S. Dash

Publisher:

Published: 1975

Total Pages: 38

ISBN-13:

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A heuristic model of compressibility effects stipulates that the fluctuating pressure-strain correlation acts to reduce the effective turbulent viscosity at the general axial station x in a compressible free shear flow by an amount uniquely dependent upon the rms Mach number fluctuation. Accordingly, the turbulent viscosity is related to the turbulent kinetic energy and the turbulent energy dissipation rate. Numerical predictions are generated for a number of standard test cases involving heterogeneous and non-equilibrium flows. Comparisons between these predictions and the experimental data are made.

Direct and Large-Eddy Simulation IV
Direct and Large-Eddy Simulation IV

Author: Bernard Geurts

Publisher: Springer Science & Business Media

Published: 2001-11-30

Total Pages: 554

ISBN-13: 9781402001772

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This volume contains the proceedings of the 2001 DLES4 workshop. It describes and discusses state-of-the-art modeling and simulation approaches for complex flows. Fundamental turbulence and modeling issues but also elements from modern numerical analysis are at the heart of this field of interest.

Compressibility, Turbulence and High Speed Flow
Compressibility, Turbulence and High Speed Flow

Author: Thomas B. Gatski

Publisher: Academic Press

Published: 2013-03-05

Total Pages: 343

ISBN-13: 012397318X

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Compressibility, Turbulence and High Speed Flow introduces the reader to the field of compressible turbulence and compressible turbulent flows across a broad speed range, through a unique complimentary treatment of both the theoretical foundations and the measurement and analysis tools currently used. The book provides the reader with the necessary background and current trends in the theoretical and experimental aspects of compressible turbulent flows and compressible turbulence. Detailed derivations of the pertinent equations describing the motion of such turbulent flows is provided and an extensive discussion of the various approaches used in predicting both free shear and wall bounded flows is presented. Experimental measurement techniques common to the compressible flow regime are introduced with particular emphasis on the unique challenges presented by high speed flows. Both experimental and numerical simulation work is supplied throughout to provide the reader with an overall perspective of current trends. - An introduction to current techniques in compressible turbulent flow analysis - An approach that enables engineers to identify and solve complex compressible flow challenges - Prediction methodologies, including the Reynolds-averaged Navier Stokes (RANS) method, scale filtered methods and direct numerical simulation (DNS) - Current strategies focusing on compressible flow control

Chemical Reactions in Turbulent Mixing Flows
Chemical Reactions in Turbulent Mixing Flows

Author: Paul E. Dimotakis

Publisher:

Published: 1998

Total Pages: 72

ISBN-13:

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This program focused on fundamental investigations of mixing, chemical-reaction, and combustion processes, in turbulent, subsonic, and supersonic free-shear flows. The program was comprised of an experimental effort; an analytical, modeling, and computational effort; and a diagnostics, instrumentation, and data-acquisition-development effort, with significant progress in each. With regard to gas-phase shear-layer mixing and combustion, effects of inflow/initial conditions, compressibility, and Reynolds number were experimentally investigated and, to a large extent, clarified. New measures to characterize level sets in turbulence were developed and successfully employed to characterize experimental data of liquid-phase turbulent-jet flows as well as three-dimensional direct-numerical-simulation data of Rayleigh-Taylor-instability flows. The computational effort has added to our understanding of the (H2+NO)/F2 chemical system employed in the shear-layer-mixing investigations as well as mixing in high-speed flows, along with further developments in Riemann-Invariant-Manifold gasdynamic simulation techniques and their application to unsteady detonation phenomena. On the diagnostic front, developments in digital imaging and Image Correlation Velocimetry have continued, and been used to investigate turbulent-jet mixing, the unsteady flow over an accelerating airfoil, to mitigate aliasing problems in the computer reconstruction of (2+1)-dimensional isosurface data, and in other applications.

Direct Simulation of Compressible Turbulence in a Shear Flow
Direct Simulation of Compressible Turbulence in a Shear Flow

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-07-02

Total Pages: 46

ISBN-13: 9781722173715

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Compressibility effects on the turbulence in homogeneous shear flow are investigated. The growth of the turbulent kinetic energy was found to decrease with increasing Mach number: a phenomenon which is similar to the reduction of turbulent velocity intensities observed in experiments on supersonic free shear layers. An examination of the turbulent energy budget shows that both the compressible dissipation and the pressure-dilatation contribute to the decrease in the growth of kinetic energy. The pressure-dilatation is predominantly negative in homogeneous shear flow, in contrast to its predominantly positive behavior in isotropic turbulence. The different signs of the pressure-dilatation are explained by theoretical consideration of the equations for the pressure variance and density variance. Previously, the following results were obtained for isotropic turbulence: (1) the normalized compressible dissipation is of O(M(sub t)(exp 2)); and (2) there is approximate equipartition between the kinetic and potential energies associated with the fluctuating compressible mode. Both of these results were substantiated in the case of homogeneous shear. The dilatation field is significantly more skewed and intermittent than the vorticity field. Strong compressions seem to be more likely than strong expansions. Sarkar, S. and Erlebacher, G. and Hussaini, M. Y. Unspecified Center NAS1-18605; RTOP 505-90-52-01...

Combustion in High-Speed Flows
Combustion in High-Speed Flows

Author: John Buckmaster

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 639

ISBN-13: 9401110506

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This volume contains the proceedings of the Workshop on Com bustion, sponsored by the Institute for Computer Applications in Science and Engineering (ICASE) and the NASA Langley Research Center (LaRC). It was held on October 12-14, 1992, and was the sec ond workshop in the series on the subject. The first was held in 1989, and its proceedings were published by Springer-Verlag under the title "Major Research Topics in Combustion," edited by M. Y. Hussaini, A. Kumar, and R. G. Voigt. The focus of the second workshop was directed towards the development, analysis, and application of basic models in high speed propulsion of particular interest to NASA. The exploration of a dual approach combining asymptotic and numerical methods for the analysis of the models was particularly encouraged. The objectives of this workshop were i) the genesis of models that would capture or reflect the basic pllysical phenomena in SCRAMJETs and/or oblique detonation-wave engines (ODWE), and ii) the stimulation of a greater interaction between NASA exper imental research community and the academic community. The lead paper by D. Bushnell on the status and issues of high speed propulsion relevant to both the SCRAMJET and the ODWE parallels his keynote address which set the stage of the workshop. Following the lead paper were five technical sessions with titles and chairs: Experiments (C. Rogers), Reacting Free Shear Layers (C. E. Grosch), Detonations (A. K. Kapila), Ignition and Struc ture (J. Buckmaster), and Unsteady Behaviour ('1'. L. Jackson).