Download or read book Compressibility Effects in Turbulent Nonpremixed Reacting Shear Flows written by Carlos Pantano-Rubino and published by . This book was released on 2000 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Compressibility Effects in Free Turbulent Shear Flows written by S. Dash and published by . This book was released on 1975 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book The Stabilizing Effect of Compressibility in Turbulent Shear Flow written by S. Sarkar and published by . This book was released on 1994 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Compressible Turbulent Reacting Flows written by Forman Arthur Williams and published by . This book was released on 2000 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aspects of Turbulent Shear Layer Dynamics and Mixing written by Michael David Slessor and published by . This book was released on 1998 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments have been conducted in the GALCIT Supersonic Shear Layer Facility to investigate some aspects of high Reynolds number, turbulent, shear layer flows in both incompressible and compressible flow regimes. Experiments designed to address several issues were performed; effects of inflow conditions, freestream conditions (supersonic/subsonic flow), and compressibility, on both large scale dynamics and small scale mixing, are described. Chemically reacting and non reacting flows were investigated, the former relying on the (H2+NO)/F2 chemical system, in the fast-kinetic regime, to infer the structure and amount of molecular scale mixing through use of "flip" experiments. Both inflow conditions and compressibility are found to have significant effects on the flow. In particular, inflow conditions are "remembered" for long distances downstream, a sensitivity similar to that observed in low-dimensionality, nonlinear (chaotic) systems. A previously proposed mode selection rule for turbulent structure convection speeds, based on the presence of a lab frame subsonic freestream, was demonstrated to be incorrect. Compressibility, when decoupled from other parameters, e.g., Reynolds number, velocity and density ratios, reduces large scale entrainment and growth, but slightly enhances mixing, and changes the molecularly mixed fluid structure. This reduction in shear layer growth rate is examined and a new parameter that interprets compressibility as an energy exchange mechanism is proposed. The parameter reconciles and collapses experimentally observed growth rates.
Download or read book Direct and Large Eddy Simulation IV written by Bernard Geurts and published by Springer Science & Business Media. This book was released on 2001-11-30 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Compressibility Turbulence and High Speed Flow written by Thomas B. Gatski and published by Elsevier. This book was released on 2009-02-27 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book 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. For the computation of turbulent compressible flows, current methods of averaging and filtering are presented so that the reader is exposed to a consistent development of applicable equation sets for both the mean or resolved fields as well as the transport equations for the turbulent stress field. For the measurement of turbulent compressible flows, current techniques ranging from hot-wire anemometry to PIV are evaluated and limitations assessed. Characterizing dynamic features of free shear flows, including jets, mixing layers and wakes, and wall-bounded flows, including shock-turbulence and shock boundary-layer interactions, obtained from computations, experiments and simulations are discussed. - Describes prediction methodologies including the Reynolds-averaged Navier Stokes (RANS) method, scale filtered methods and direct numerical simulation (DNS) - Presents current measurement and data analysis techniques - Discusses the linkage between experimental and computational results necessary for validation of numerical predictions - Meshes the varied results of computational and experimental studies in both free and wall-bounded flows to provide an overall current view of the field
Download or read book Chemical Reactions in Turbulent Mixing Flows written by Paul E. Dimotakis and published by . This book was released on 1998 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Combustion in High Speed Flows written by John Buckmaster and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 639 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulence Modeling for Compressible Shear Flows written by Carlos Arturo Gomez Elizondo and published by . This book was released on 2013 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressibility profoundly affects many aspects of turbulence in high-speed flows - most notably stability characteristics, anisotropy, kinetic-potential energy interchange and spectral cascade rate. Many of the features observed in compressible flows are due to the changing nature of pressure. Whereas for incompressible flows pressure merely serves to enforce incompressibility, in compressible flows pressure becomes a thermodynamic variable that introduces a strong coupling between energy, state, and momentum equations. Closure models that attempt to address compressibility effects must begin their development from sound first-principles related to the changing nature of pressure as a flow goes from incompressible to compressible regime. In this thesis, a unified framework is developed for modeling pressure-related compressibility effects by characterizing the role and action of pressure at different speed regimes. Rapid distortion theory is used to examine the physical connection between the various compressibility effects leading to model form suggestions for the pressure-strain correlation, pressure-dilatation and dissipation evolution equation. The pressure-strain correlation closure coefficients are established using fixed point analysis by requiring consistency between model and direct numerical simulation asymptotic behavior in compressible homogeneous shear flow. The closure models are employed to compute high-speed mixing-layers and boundary layers in a differential Reynolds stress modeling solver. The self-similar mixing-layer profile, increased Reynolds stress anisotropy and diminished mixing-layer growth rates with increasing relative Mach number are all well captured. High-speed boundary layer results are also adequately replicated even without the use of advanced thermal-flux models or low Reynolds number corrections. To reduce the computational burden required for differential Reynolds stress calculations, the present compressible pressure-strain correlation model is incorporated into the algebraic modeling framework. The resulting closure is fully explicit, physically realizable, and is a function of mean flow strain rate, rotation rate, turbulent kinetic energy, dissipation rate, and gradient Mach number. The new algebraic model is validated with direct numerical simulations of homogeneous shear flow and experimental data of high-speed mixing-layers. Homogeneous shear flow calculations show that the model captures the asymptotic behavior of direct numerical simulations quite well. Calculations of plane supersonic mixing-layers are performed and comparison with experimental data shows good agreement. Therefore the algebraic model may serve as a surrogate for the more computationally expensive differential Reynolds stress model for flows that permit the weak-equilibrium simplification. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148160
Download or read book IUTAM Symposium on Turbulent Mixing and Combustion written by Andrew Pollard and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goals of the Symposium were to draw together researchers in turbulence and combustion so as to highlight advances and challenge the boundaries to our understanding of turbulent mixing and combus tion from both experimental and simulation perspectives; to facilitate cross-fertilization between leaders in these two fields. These goals were noted to be important given that turbulence itself is viewed as the last great problem in classical physics and the addition of chemical reaction amplifies the difficulties enormously. The papers that have been included here reflect the richness of our subject. Turbulence is rich and complex in its own right. And, its inner structure, hidden in the morass of scales, large and small, can dominate transport. Earlier IUTAM Symposia have considered this field, Eddy Structure Identification in Free Turbulent Flows, Bonnet and Glauser (eds) 1992 and Simulation and Identification of Organized Structures in Flows, Sorensen, Hopfinger and Aubry (eds) 1997. The combustion community is well served by its specialized events, most notable is the bi annual International Combustion Symposium, held under the auspices of the Combustion Institute. Mixing is often considered somewhere in between these two. This broad landscape was addressed in this Sym posium in a somewhat temporal linear fashion of increasing complexity. The lectures considered the many challenges posed by adding one ele ment to the base formed by others: turbulence and turbulent mixing in the absence of combustion through to turbulent mixing dominated by chemistry and combustion.
Download or read book Symposium on Turbulent Shear Flows written by and published by . This book was released on with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Compressibility Variable Density and Curvature Effects on Turbulent Shear Layers written by Kristen Matsuno and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent mixing layers occur between two streams of fluids with different kinematic and/or thermodynamic properties, and are fundamental flow features which influence the dynamics of a wide variety of applications, ranging from the mixing efficiency of fuel injection in internal combustion to vehicle loads in external aerodynamics. Two motivating applications behind this research include the study of high-speed jets in cross-flow and supersonic retro-propulsion, which occurs as aerospace vehicles use jet plumes to decelerate during entry, descent, and landing. Both these applications are highly influenced by hot jet plumes under highly compressible conditions which exhibit significant streamwise curvature. Simulating the entire flow field associated with such applications is extremely computationally expensive; capturing all important flow features at full resolution is exorbitant for the purposes of engineering design. Thus, grasping the full behavior of turbulent mixing layers in a representative parameter space enables the development of models which can reliably and accurately predict the complex flow fields present in these engineering applications. This work enriches the present understanding of mixing in turbulent shear layers via the systematic inclusion of compressibility, variable density, and streamwise curvature effects. The spreading, or growth rate, of turbulent shear layers is known to decrease with increasing compressibility. Dilatational velocities and pressure-dilatation magnitudes show little contribution to shear layer growth rates, even under highly compressible conditions. A new turbulent length and velocity scale is introduced and shown to scale key turbulent quantities. Inclusion of freestream density variations are also known to decreasing mixing layer growth rates. Trends with increasing compressibility and the importance of mixing layer asymmetry are identified--shear layer centerlines and turbulent stresses in variable density shear layers are biased towards the less-dense freestream, which reduces the turbulent mixing of the mean momentum profile and corresponding growth rates. The combined effects of compressibility and streamwise curvature are demonstrated to be comparable for the selected parameter space. Shear layer growth rates are dominated by the freestream density ratio when streamwise curvature is significant. Changes to model predictions of turbulent growth rates and turbulent kinetic energy levels resulting from various model modifications are evaluated. Reduced accuracy in model predictions of turbulent kinetic energy magnitudes under curved conditions, even with the inclusion of compressibility and curvature modifications, is demonstrated.
Download or read book Effect of Turbulence chemistry Interactions in Compressible Reacting Flows written by J. R. Narayan and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
