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Probability Density Function Method For Variable Density Pressure Gradient Driven Turbulence And Mixing
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Book Synopsis Probability Density Function Method for Variable-density Pressure-gradient-driven Turbulence and Mixing by :
Download or read book Probability Density Function Method for Variable-density Pressure-gradient-driven Turbulence and Mixing written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Probability density function (PDF) methods are extended to variable-density pressure-gradient-driven turbulence. We apply the new method to compute the joint PDF of density and velocity in a non-premixed binary mixture of different-density molecularly mixing fluids under gravity. The full time-evolution of the joint PDF is captured in the highly non-equilibrium flow: starting from a quiescent state, transitioning to fully developed turbulence and finally dissipated by molecular diffusion. High-Atwood-number effects (as distinguished from the Boussinesq case) are accounted for: both hydrodynamic turbulence and material mixing are treated at arbitrary density ratios, with the specific volume, mass flux and all their correlations in closed form. An extension of the generalized Langevin model, originally developed for the Lagrangian fluid particle velocity in constant-density shear-driven turbulence, is constructed for variable-density pressure-gradient-driven flows. The persistent small-scale anisotropy, a fundamentally 'non-Kolmogorovian' feature of flows under external acceleration forces, is captured by a tensorial diffusion term based on the external body force. The material mixing model for the fluid density, an active scalar, is developed based on the beta distribution. The beta-PDF is shown to be capable of capturing the mixing asymmetry and that it can accurately represent the density through transition, in fully developed turbulence and in the decay process. The joint model for hydrodynamics and active material mixing yields a time-accurate evolution of the turbulent kinetic energy and Reynolds stress anisotropy without resorting to gradient diffusion hypotheses, and represents the mixing state by the density PDF itself, eliminating the need for dubious mixing measures. Direct numerical simulations of the homogeneous Rayleigh-Taylor instability are used for model validation.
Book Synopsis A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows by : László Könözsy
Download or read book A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows written by László Könözsy and published by Springer. This book was released on 2019-02-26 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gives a mathematical insight--including intermediate derivation steps--into engineering physics and turbulence modeling related to an anisotropic modification to the Boussinesq hypothesis (deformation theory) coupled with the similarity theory of velocity fluctuations. Through mathematical derivations and their explanations, the reader will be able to understand new theoretical concepts quickly, including how to put a new hypothesis on the anisotropic Reynolds stress tensor into engineering practice. The anisotropic modification to the eddy viscosity hypothesis is in the center of research interest, however, the unification of the deformation theory and the anisotropic similarity theory of turbulent velocity fluctuations is still missing from the literature. This book brings a mathematically challenging subject closer to graduate students and researchers who are developing the next generation of anisotropic turbulence models. Indispensable for graduate students, researchers and scientists in fluid mechanics and mechanical engineering.
Book Synopsis Velocity/wave-vector Probability Density Function Models for Inhomogeneous Turbulent Flows by : Paul Richard Van Slooten
Download or read book Velocity/wave-vector Probability Density Function Models for Inhomogeneous Turbulent Flows written by Paul Richard Van Slooten and published by . This book was released on 1998 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt: Constructs and implements turbulence models for probability density function (PDF) methods for the computation of turbulent reacting flows. Treats the processes of convection and reaction without further assumptions at this level of closure, while the effects of the fluctuation pressure gradient and the diffusion of the fluctuating velocity by molecular viscosity require modeling. Effects correspond to the pressure-rate-of-strain correlations, the pressure transport, and the dissipation tensor in the Reynolds stress equation. Investigates models for each of these variables.
Book Synopsis Developments in the Probability Density Function Method for Turbulent Flows by : Daniel Connell Haworth
Download or read book Developments in the Probability Density Function Method for Turbulent Flows written by Daniel Connell Haworth and published by . This book was released on 1986 with total page 614 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Analysis of the Modeling of Variable Density Turbulence by : Jordan M. MacInnes
Download or read book An Analysis of the Modeling of Variable Density Turbulence written by Jordan M. MacInnes and published by . This book was released on 1980 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Modeling of Turbulent Mixing at Density Discontinuities in Nonsteady Compressible Flows by : R. I. Issa
Download or read book Modeling of Turbulent Mixing at Density Discontinuities in Nonsteady Compressible Flows written by R. I. Issa and published by . This book was released on 1981 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document describes a theoretical modeling of turbulent mixing at density discontinuities in nonsteady compressible flows. It is shown that when density and pressure gradients are large and have opposite signs (e.g., near the combustion products/air contact surface in blast waves driven by high-explosive sources), flow perturbations will be amplified, leading to local turbulent mixing. The applicability of using a turbulence model to simulate this process is examined. The conservation laws (for mass, momentum, energy and species) are presented in mass-averaged form, the k-epsilon model of turbulence is applied. The relevant term for the generation of turbulent kinetic energy, the term of dominant importance in this problem, is derived by two independent approaches. This generation term is driven by gradients of pressure and density normal to the interface between the high-explosive products of combustion and the shocked air, and not by shear. The present work is thought to represent the first description of a turbulence model for flows driven by such normal gradients. (Author).
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1974 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Buoyancy-Driven Flows by : Eric P. Chassignet
Download or read book Buoyancy-Driven Flows written by Eric P. Chassignet and published by Cambridge University Press. This book was released on 2012-03-05 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: Buoyancy is one of the main forces driving flows on our planet, especially in the oceans and atmosphere. These flows range from buoyant coastal currents to dense overflows in the ocean, and from avalanches to volcanic pyroclastic flows on the Earth's surface. This book brings together contributions by leading world scientists to summarize our present theoretical, observational, experimental and modeling understanding of buoyancy-driven flows. Buoyancy-driven currents play a key role in the global ocean circulation and in climate variability through their impact on deep-water formation. Buoyancy-driven currents are also primarily responsible for the redistribution of fresh water throughout the world's oceans. This book is an invaluable resource for advanced students and researchers in oceanography, geophysical fluid dynamics, atmospheric science and the wider Earth sciences who need a state-of-the-art reference on buoyancy-driven flows.
Book Synopsis Modeling of Scalar Probability Density Functions in Turbulent Flows by : Ashok Kumara Varma
Download or read book Modeling of Scalar Probability Density Functions in Turbulent Flows written by Ashok Kumara Varma and published by . This book was released on 1978 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent flows involving chemical reactions are a basic feature of many combustion and propulsion systems. The development of calculation procedures for turbulent reacting flows requires the understanding and modeling of the coupling between turbulence and combustion. Second-order closure modeling of turbulent flows provides a convenient framework for studying these interactions between turbulence and chemical reactions. Models for the scalar probability density function (pdf) have to be developed to achieve closure of turbulent transport equations for mixing and reacting flows. A delta function 'typical eddy' model has been developed for the joint pdf of the scalar variables. It has been demonstrated that delta functions are a necessary part of pdf's in order to attain the extremums of the statistical constraints on the moments. The statistical bounds on a number of moments of interest have been derived. It has been proven that a rational pdf composed of a set of delta functions alone can always be constructed at any point within the statistically valid moment space. The model provides a good representation of actual pdf's in two-species, variable-density mixing flows. The model has been directly compared to experimental pdf measurements and good agreement for higher-order moments has been demonstrated. It can be shown that the delta function pdf model is significantly simpler than other proposed pdf models and is more than adequate for the closure of the transport equations. (Author).
Book Synopsis Advances in Modeling Mixing and Molecular Transport in Probability Density Function Methods of Turbulent Reacting Flows by : Sharadha Viswanathan
Download or read book Advances in Modeling Mixing and Molecular Transport in Probability Density Function Methods of Turbulent Reacting Flows written by Sharadha Viswanathan and published by . This book was released on 2011 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modeling of turbulent reacting flow problems using Probability Density Function (PDF) methods yields transport and reaction in closed form while the processes related to the conditional dissipation of species compositions need to be closed using mixing models. First, we study the dispersion from line sources in decaying grid turbulence using a modified form of the Interaction by Exchange with the Conditional Mean (IECM) mixing model. These flows pose a significant challenge to statistical models, because the scalar length scale (of the initial plume) is much smaller than the turbulence integral scale. Consequently, this necessitates incorporating the effects of molecular diffusion in order to model laboratory experiments. The effects of molecular diffusion are modeled by adding a conditional mean scalar drift term and a laminar wake model is used to obtain an analytic expression for the mixing timescale at small times which is subsequently used as part of a general specification of the mixing timescale. Based on this modeling, PDF calculations are performed, and comparison is made primarily with existing experimental and numerical data on single and multiple line sources. A heated mandoline is also considered. This establishes the validity of the proposed model and the significant effect of molecular diffusion on the decay of scalar fluctuations. Next, various numerical implementations of mixing and molecular transport in LES/PDF studies of turbulent reacting flows are evaluated for accuracy using the Method of Manufactured Solutions (MMS). Mixing is modeled using the Interaction by Exchange with the Mean (IEM) model and the effects of molecular transport are incorporated as a mean drift term in the mixing step. This methodology avoids spurious production of scalar variance and also allows direct incorporation of differential diffusion effects. The implementation of the mixing model is shown to be successful in capturing the effects of differential diffusion accurately with the additional property of satisfying detailed conservation and realizability of species mass fractions. Additionally, we present a new variance reduction technique by way of an implicit smoothing methodology. This smoothing scheme is shown to satisfy conservation, boundedness and regularity criteria. Moreover, for an appropriate choice of the smoothing length scale, significant improvements in accuracy can be achieved for an incremental increase in computational cost. Also, it is shown that with smoothing, the bias and statistical errors due to finite number of particles in the Lagrangian Monte Carlo simulations now scale as N[-]1 and tot N[-]1/2 respectively, where Ntot is the total number of particles in the computatot tional domain. Finally, the numerical implementations described are applied to the study of a turbulent reacting jet flame (Sandia Flame D). It is shown that this implementation yields a consistent formulation between the LES and the PDF methods. Further, cross-validation is presented as a numerical technique to assist in the automatic choice of the smoothing length scale and the application of crossvalidation to smoothing of PDF fields is shown to improve the consistency between the LES and PDF fields.
Book Synopsis Turbulent Reactive Flows by : R. Borghi
Download or read book Turbulent Reactive Flows written by R. Borghi and published by Springer. This book was released on 2012-10-20 with total page 950 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent reactive flows are of common occurrance in combustion engineering, chemical reactor technology and various types of engines producing power and thrust utilizing chemical and nuclear fuels. Pollutant formation and dispersion in the atmospheric environment and in rivers, lakes and ocean also involve interactions between turbulence, chemical reactivity and heat and mass transfer processes. Considerable advances have occurred over the past twenty years in the understanding, analysis, measurement, prediction and control of turbulent reactive flows. Two main contributors to such advances are improvements in instrumentation and spectacular growth in computation: hardware, sciences and skills and data processing software, each leading to developments in others. Turbulence presents several features that are situation-specific. Both for that reason and a number of others, it is yet difficult to visualize a so-called solution of the turbulence problem or even a generalized approach to the problem. It appears that recognition of patterns and structures in turbulent flow and their study based on considerations of stability, interactions, chaos and fractal character may be opening up an avenue of research that may be leading to a generalized approach to classification and analysis and, possibly, prediction of specific processes in the flowfield. Predictions for engineering use, on the other hand, can be foreseen for sometime to come to depend upon modeling of selected features of turbulence at various levels of sophistication dictated by perceived need and available capability.
Book Synopsis Direct Numerical Simulations of Variable-density, Instability Driven Turbulence by :
Download or read book Direct Numerical Simulations of Variable-density, Instability Driven Turbulence written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Provisional Analysis of Two-Dimensional Turbulent Mixing with Variable Density by : Paul A. Libby
Download or read book A Provisional Analysis of Two-Dimensional Turbulent Mixing with Variable Density written by Paul A. Libby and published by . This book was released on 1972 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: A predictive method for the titled flows based on the Prandtl energy method is developed and assessed by comparing prediction with experimental results. For constant density flows both gross properties such as spreading rate and maximum turbulent kinetic energy and detailed properties such as mean shear stress distribution are shown to be well predicted. For variable density flows considerable attention is devoted to the inclusion in the analysis of the added effect of pressure fluctuations and of the variation in the several extant empirical parameters on the turbulent kinetic energy. (Author).
Book Synopsis Treatise on Estuarine and Coastal Science by :
Download or read book Treatise on Estuarine and Coastal Science written by and published by Academic Press. This book was released on 2012-03-06 with total page 4604 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of estuaries and coasts has seen enormous growth in recent years, since changes in these areas have a large effect on the food chain, as well as on the physics and chemistry of the ocean. As the coasts and river banks around the world become more densely populated, the pressure on these ecosystems intensifies, putting a new focus on environmental, socio-economic and policy issues. Written by a team of international expert scientists, under the guidance of Chief Editors Eric Wolanski and Donald McClusky, the Treatise on Estuarine and Coastal Science, Ten Volume Set examines topics in depth, and aims to provide a comprehensive scientific resource for all professionals and students in the area of estuarine and coastal science Most up-to-date reference for system-based coastal and estuarine science and management, from the inland watershed to the ocean shelf Chief editors have assembled a world-class team of volume editors and contributing authors Approach focuses on the physical, biological, chemistry, ecosystem, human, ecological and economics processes, to show how to best use multidisciplinary science to ensure earth's sustainability Provides a comprehensive scientific resource for all professionals and students in the area of estuarine and coastal science Features up-to-date chapters covering a full range of topics
Download or read book Physics Briefs written by and published by . This book was released on 1991 with total page 1132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Presumed and Synthesized Probability Density Function Method for Nonpremixed Turbulent Reacting Flow Calculations by : Ziqin Hu
Download or read book A Presumed and Synthesized Probability Density Function Method for Nonpremixed Turbulent Reacting Flow Calculations written by Ziqin Hu and published by . This book was released on 1994 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
