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Theoretical And Numerical Study Of Collision And Coalescence Statistical Modeling Approaches In Gas Droplet Turbulent Flows
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Book Synopsis Theoretical and Numerical Study of Collision and Coalescence - Statistical Modeling Approaches in Gas-droplet Turbulent Flows by : Dirk Wunsch
Download or read book Theoretical and Numerical Study of Collision and Coalescence - Statistical Modeling Approaches in Gas-droplet Turbulent Flows written by Dirk Wunsch and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coalescence in a droplet cloud is studied in this work by means of direct numerical simulation of the turbulent gas flow, which is coupled with a Lagrangian tracking of the disperse phase. In a first step, a collision detection algorithm is developed and validated, which can account for a polydisperse phase. This algorithm is then implemented into an existing code for direct numerical simulations coupled with a Lagrangian tracking scheme. Second, simulations are performed for the configuration of homogeneous isotropic turbulence of the fluid phase and a disperse phase in local equilibrium with the fluid. The influence of both droplet inertia and turbulence intensity on the coalescence rate of droplets is discussed in a pure permanent coalescence regime. First results are given, if other droplet collision outcomes than permanent coalescence (i.e. stretching and reflexive separation) are considered. These results show a strong dependence on the droplet inertia via the relative velocity of the colliding droplets at the moment of collision. The performed simulations serve also as reference data base for the development and validation of statistical modeling approaches, which can be used for simulations of industrial problems. In particular, the simulation results are compared to predictions from a Lagrangian Monte-Carlo type approach and the Eulerian 'Direct Quadrature Method of Moments' (DQMOM) approach. Different closures are validated for the coalescence terms in these approaches, which are based either on the assumption of molecular-chaos, or based on a formulation, which allows to account for the correlation of droplet velocities before collision by the fluid turbulence. It is shown that the latter predicts much better the coalescence rates in comparison with results obtained by the performed deterministic simulations.
Book Synopsis Statistical Theory and Modeling for Turbulent Flows by : P. A. Durbin
Download or read book Statistical Theory and Modeling for Turbulent Flows written by P. A. Durbin and published by John Wiley & Sons. This book was released on 2011-06-28 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: Providing a comprehensive grounding in the subject of turbulence, Statistical Theory and Modeling for Turbulent Flows develops both the physical insight and the mathematical framework needed to understand turbulent flow. Its scope enables the reader to become a knowledgeable user of turbulence models; it develops analytical tools for developers of predictive tools. Thoroughly revised and updated, this second edition includes a new fourth section covering DNS (direct numerical simulation), LES (large eddy simulation), DES (detached eddy simulation) and numerical aspects of eddy resolving simulation. In addition to its role as a guide for students, Statistical Theory and Modeling for Turbulent Flows also is a valuable reference for practicing engineers and scientists in computational and experimental fluid dynamics, who would like to broaden their understanding of fundamental issues in turbulence and how they relate to turbulence model implementation. Provides an excellent foundation to the fundamental theoretical concepts in turbulence. Features new and heavily revised material, including an entire new section on eddy resolving simulation. Includes new material on modeling laminar to turbulent transition. Written for students and practitioners in aeronautical and mechanical engineering, applied mathematics and the physical sciences. Accompanied by a website housing solutions to the problems within the book.
Book Synopsis Modeling Approaches and Computational Methods for Particle-laden Turbulent Flows by : Shankar Subramaniam
Download or read book Modeling Approaches and Computational Methods for Particle-laden Turbulent Flows written by Shankar Subramaniam and published by Academic Press. This book was released on 2022-10-20 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modelling Approaches and Computational Methods for Particle-laden Turbulent Flows introduces the principal phenomena observed in applications where turbulence in particle-laden flow is encountered while also analyzing the main methods for analyzing numerically. The book takes a practical approach, providing advice on how to select and apply the correct model or tool by drawing on the latest research. Sections provide scales of particle-laden turbulence and the principal analytical frameworks and computational approaches used to simulate particles in turbulent flow. Each chapter opens with a section on fundamental concepts and theory before describing the applications of the modelling approach or numerical method. Featuring explanations of key concepts, definitions, and fundamental physics and equations, as well as recent research advances and detailed simulation methods, this book is the ideal starting point for students new to this subject, as well as an essential reference for experienced researchers. - Provides a comprehensive introduction to the phenomena of particle laden turbulent flow - Explains a wide range of numerical methods, including Eulerian-Eulerian, Eulerian-Lagrange, and volume-filtered computation - Describes a wide range of innovative applications of these models
Book Synopsis Turbulent Collision Statistics of Cloud Droplets at Low Dissipation Rates by : Sandipan Banerjee
Download or read book Turbulent Collision Statistics of Cloud Droplets at Low Dissipation Rates written by Sandipan Banerjee and published by . This book was released on 2016 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: Collisions of sedimenting droplets in a turbulent flow is of great importance in cloud physics. Collision efficiency and collision enhancement over gravitational collision by air turbulence govern the growth of the cloud droplets leading to warm rain initiation and precipitation dynamics. In this thesis we present direct numerical simulation (DNS) results for collision statistics of droplets in turbulent flows of low dissipation rates (in the range of 3 cm2/s3--100 cm2/s3) relevant to strato-cumulus clouds. First, we revisit the case of gravitational collision in still fluid to validate the details of the collision detection algorithm used in our code. We compare the collision statistics with either new analytical predictions regarding the percentages of different collision types, or results from published papers. The effect of initial conditions on the collision statistics and statistical uncertainties are analyzed both analytically and through the simulation data. Second, we consider the case of weak turbulence (as in strato-cumulus clouds). In this case the particle motion is mainly driven by gravity. The standard deviation (or the uncertainty) of the average collision statistics is examined analytically in terms of time correlation function of the data. We then report new DNS results of collision statistics in a turbulent flow, showing how air turbulence increases the geometric colli- sion statistics and the collision efficiency. We find that the collision-rate enhancement due to turbulence depends nonlinearly on the flow dissipation rate. This result calls for a more careful parameterization of the collision statistics in strato-cumulus clouds. Due to the low flow dissipation rate in stratocumulus clouds, a related challenge is low droplet Stokes number. Here the Stokes number is the ratio of droplet inertial response time to the flow Kolmogorov time. A very low Stokes number implies that the numerical integration time step is now governed by the droplet inertial response time, rather than the time step necessary for the flow simulation. This situation makes the simulations very expensive to perform. With the motivation to speed up the simulations, we implement the asymptotic expansion approach (as in Maxey, 1987) for particle tracking as this method is suitable for low particle Stokes number and avoids the numerical integration of the stiff equation of motion of droplets. We first validate our implementation using the simpler 2-D cellular flow. Next, we compare the collision statistics of the newly implemented asymptotic approach with our existing approach of particle tracking as well as with published results from journal papers. Finally, we provide the run time comparison for both methods.
Book Synopsis Statistical Theories and Computational Approaches to Turbulence by : Y. Kaneda
Download or read book Statistical Theories and Computational Approaches to Turbulence written by Y. Kaneda and published by Springer. This book was released on 2002-10-14 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the papers presented at the workshop on Statistical The ories and Computational Approaches to Turbulence: Modern Perspectives and Applications to Global-Scale Flows, held October 10-13, 2001, at Nagoya Uni versity, Nagoya, Japan. Because of recent developments in computational capabilities, the compu tational approach is showing the potential to resolve a much wider range of length and time scales in turbulent physical systems. Nevertheless, even with the largest supercomputers of the foreseeable future, development of adequate modeling techniques for at least some scales of motion will be necessary for practical computations of important problems such as weather forecasting and the prediction and control of global pollution. The more powerful the available machines become, the more demand there will be for precise prediction of the systems. This means that more precise and reliable knowledge of the underlying dynamics will become important, and that more efficient and precise numerical methods best adapted to the new generation of computers will be necessary. The understanding of the nature of unresolved scales then will playa key role in the modeling of turbulent motion. The challenge to turbulence theory here is to elucidate the physics or dynamics of those scales, in particular their sta tistical aspects, and thereby develop models on sound bases to reduce modeling ambiguity. The challenge to the computational method is to develop efficient algorithms suitable for the problems, the machines, and the developed models.
Book Synopsis Mathematical and Numerical Foundations of Turbulence Models and Applications by : Tomás Chacón Rebollo
Download or read book Mathematical and Numerical Foundations of Turbulence Models and Applications written by Tomás Chacón Rebollo and published by Springer. This book was released on 2014-06-17 with total page 530 pages. Available in PDF, EPUB and Kindle. Book excerpt: With applications to climate, technology, and industry, the modeling and numerical simulation of turbulent flows are rich with history and modern relevance. The complexity of the problems that arise in the study of turbulence requires tools from various scientific disciplines, including mathematics, physics, engineering and computer science. Authored by two experts in the area with a long history of collaboration, this monograph provides a current, detailed look at several turbulence models from both the theoretical and numerical perspectives. The k-epsilon, large-eddy simulation and other models are rigorously derived and their performance is analyzed using benchmark simulations for real-world turbulent flows. Mathematical and Numerical Foundations of Turbulence Models and Applications is an ideal reference for students in applied mathematics and engineering, as well as researchers in mathematical and numerical fluid dynamics. It is also a valuable resource for advanced graduate students in fluid dynamics, engineers, physical oceanographers, meteorologists and climatologists.
Book Synopsis The Statistical Dynamics of Turbulence by : Jovan Jovanovic
Download or read book The Statistical Dynamics of Turbulence written by Jovan Jovanovic and published by Springer Science & Business Media. This book was released on 2004-02-09 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: This short but complicated book is very demanding of any reader. The scope and style employed preserve the nature of its subject: the turbulence phe nomena in gas and liquid flows which are believed to occur at sufficiently high Reynolds numbers. Since at first glance the field of interest is chaotic, time-dependent and three-dimensional, spread over a wide range of scales, sta tistical treatment is convenient rather than a description of fine details which are not of importance in the first place. When coupled to the basic conserva tion laws of fluid flow, such treatment, however, leads to an unclosed system of equations: a consequence termed, in the scientific community, the closure problem. This is the central and still unresolved issue of turbulence which emphasizes its chief peculiarity: our inability to do reliable predictions even on the global flow behavior. The book attempts to cope with this difficult task by introducing promising mathematical tools which permit an insight into the basic mechanisms involved. The prime objective is to shed enough light, but not necessarily the entire truth, on the turbulence closure problem. For many applications it is sufficient to know the direction in which to go and what to do in order to arrive at a fast and practical solution at minimum cost. The book is not written for easy and attractive reading.
Book Synopsis New Approaches in Modeling Multiphase Flows and Dispersion in Turbulence, Fractal Methods and Synthetic Turbulence by : F.C.G.A. Nicolleau
Download or read book New Approaches in Modeling Multiphase Flows and Dispersion in Turbulence, Fractal Methods and Synthetic Turbulence written by F.C.G.A. Nicolleau and published by Springer Science & Business Media. This book was released on 2011-10-29 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains a collection of the main contributions from the first five workshops held by Ercoftac Special Interest Group on Synthetic Turbulence Models (SIG42. It is intended as an illustration of the sig’s activities and of the latest developments in the field. This volume investigates the use of Kinematic Simulation (KS) and other synthetic turbulence models for the particular application to environmental flows. This volume offers the best syntheses on the research status in KS, which is widely used in various domains, including Lagrangian aspects in turbulence mixing/stirring, particle dispersion/clustering, and last but not least, aeroacoustics. Flow realizations with complete spatial, and sometime spatio-temporal, dependency, are generated via superposition of random modes (mostly spatial, and sometime spatial and temporal, Fourier modes), with prescribed constraints such as: strict incompressibility (divergence-free velocity field at each point), high Reynolds energy spectrum. Recent improvements consisted in incorporating linear dynamics, for instance in rotating and/or stably-stratified flows, with possible easy generalization to MHD flows, and perhaps to plasmas. KS for channel flows have also been validated. However, the absence of "sweeping effects" in present conventional KS versions is identified as a major drawback in very different applications: inertial particle clustering as well as in aeroacoustics. Nevertheless, this issue was addressed in some reference papers, and merits to be revisited in the light of new studies in progress.
Book Synopsis Particles in Turbulent Flows by : Leonid I. Zaichik
Download or read book Particles in Turbulent Flows written by Leonid I. Zaichik and published by John Wiley & Sons. This book was released on 2008-12-04 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: The only work available to treat the theory of turbulent flow with suspended particles, this book also includes a section on simulation methods, comparing the model results obtained with the PDF method to those obtained with other techniques, such as DNS, LES and RANS. Written by experienced scientists with background in oil and gas processing, this book is applicable to a wide range of industries -- from the petrol industry and industrial chemistry to food and water processing.
Book Synopsis Impacts of Turbulence on Cloud Microphysics and Warm-rain Initiation by : Sisi Chen
Download or read book Impacts of Turbulence on Cloud Microphysics and Warm-rain Initiation written by Sisi Chen and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In shallow cloud systems, such as cumulus or stratocumulus clouds, broad droplet size spectra and fast rain formation times are frequently observed using radar and in-situ measurements. However, these observations cannot be represented by classical condensational growth theory. Turbulence has been hypothesized to accelerate the formation of raindrops by enhancing the cloud droplet collision-coalescence process. In this thesis, the direct numerical simulation (DNS) approach is used to investigate the role of turbulence in cloud microphysics processes during warm-rain initiation and to quantify the effect of turbulence on the collision rate between droplets. We developed an accurate and sophisticated modeling framework that couples dynamics and thermodynamics, thus allowing the incorporation of droplet growth by simultaneous condensational and collisional processes under various turbulent conditions. Throughout the thesis, three sets of numerical experiments are conducted to study the turbulence impact on various droplet growth processes: 1) the droplet geometric collision, i.e., collisions without considering the disturbance flow induced by the presence of droplets, 2) the droplet hydrodynamic collisions, by including the disturbance flow, and 3) the interactions between condensational growth and collisional growth by further including the thermodynamic fields. The results of the first two sets of experiments demonstrate that for droplet pairs with different sizes (r1/r20.8), turbulence plays a dominant role in modifying the droplet hydrodynamic response to the local disturbance flow, weakly increasing the droplet relative velocity and creating the clustering of droplets in space. Consequentially, a significant enhancement of the collision efficiency and a mild enhancement of geometric collision kernel resulted. On the other hand, for droplet pairs with similar sizes (r1/r20.8), the turbulence enhancement in geometric collision and droplet hydrodynamic interactions is strong. Since droplet condensational growth produces a narrow droplet size distribution (DSD), we hypothesize that turbulence effectively widens the narrow spectrum by boosting similar-sized collisions. This hypothesis is further verified by conducting simulations of DSD evolution through collision-coalescence at various flow conditions. It is found that turbulence significantly broadens the DSD, and similar-sized collisions contribute to 21-24% of the total collisions compared to only 9% in the still-air experiments. Finally, we study the interaction of thermodynamics and dynamics and its impact on droplet growth by allowing droplets to simultaneously grow by condensation and collision in turbulent and non-turbulent environments. The results show that the condensational process promotes collisions in a turbulent environment while it reduces the collisions when in still air, indicating a positive impact of dynamics (turbulence) on the interaction of condensation and collision.In addition, we investigate the relative importance of different scales of turbulent flow on the collision statistics by varying the computational domain size. It is found that for small droplets (r
Book Synopsis Modeling Complex Turbulent Flows by : Manuel D. Salas
Download or read book Modeling Complex Turbulent Flows written by Manuel D. Salas and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence modeling both addresses a fundamental problem in physics, 'the last great unsolved problem of classical physics,' and has far-reaching importance in the solution of difficult practical problems from aeronautical engineering to dynamic meteorology. However, the growth of supercom puter facilities has recently caused an apparent shift in the focus of tur bulence research from modeling to direct numerical simulation (DNS) and large eddy simulation (LES). This shift in emphasis comes at a time when claims are being made in the world around us that scientific analysis itself will shortly be transformed or replaced by a more powerful 'paradigm' based on massive computations and sophisticated visualization. Although this viewpoint has not lacked ar ticulate and influential advocates, these claims can at best only be judged premature. After all, as one computational researcher lamented, 'the com puter only does what I tell it to do, and not what I want it to do. ' In turbulence research, the initial speculation that computational meth ods would replace not only model-based computations but even experimen tal measurements, have not come close to fulfillment. It is becoming clear that computational methods and model development are equal partners in turbulence research: DNS and LES remain valuable tools for suggesting and validating models, while turbulence models continue to be the preferred tool for practical computations. We believed that a symposium which would reaffirm the practical and scientific importance of turbulence modeling was both necessary and timely.
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1989 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Coarse Grained Simulation and Turbulent Mixing by : Fenando F. Grinstein
Download or read book Coarse Grained Simulation and Turbulent Mixing written by Fenando F. Grinstein and published by Cambridge University Press. This book was released on 2016-06-30 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reviews our current understanding of the subject. For graduate students and researchers in computational fluid dynamics and turbulence.
Book Synopsis Statistical Theories and Computational Approaches to Turbulence by : Y. Kaneda
Download or read book Statistical Theories and Computational Approaches to Turbulence written by Y. Kaneda and published by . This book was released on 2014-01-15 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Turbulent Particle-Laden Gas Flows by : Aleksei Y. Varaksin
Download or read book Turbulent Particle-Laden Gas Flows written by Aleksei Y. Varaksin and published by Springer Science & Business Media. This book was released on 2007-07-05 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents results of experimental and theoretical studies of "gas-solid particles" turbulent two-phase flows. It analyzes the characteristics of heterogeneous flows in channels (pipes), as well as those in the vicinity of the critical points of bodies subjected to flow and in the boundary layer developing on their surface. Coverage also treats in detail problems of physical simulation of turbulent gas flows which carry solid particles.
Book Synopsis Physics and Chemistry of Clouds by : Dennis Lamb
Download or read book Physics and Chemistry of Clouds written by Dennis Lamb and published by Cambridge University Press. This book was released on 2011-04-28 with total page 599 pages. Available in PDF, EPUB and Kindle. Book excerpt: Clouds affect our daily weather and play key roles in the global climate. Through their ability to precipitate, clouds provide virtually all of the fresh water on Earth and are a crucial link in the hydrologic cycle. With ever-increasing importance being placed on quantifiable predictions - from forecasting the local weather to anticipating climate change - we must understand how clouds operate in the real atmosphere, where interactions with natural and anthropogenic pollutants are common. This textbook provides students - whether seasoned or new to the atmospheric sciences - with a quantitative yet approachable path to learning the inner workings of clouds. Developed over many years of the authors' teaching at Pennsylvania State University, Physics and Chemistry of Clouds is an invaluable textbook for advanced students in atmospheric science, meteorology, environmental sciences/engineering and atmospheric chemistry. It is also a very useful reference text for researchers and professionals.
Book Synopsis Lecture Notes on Turbulence and Coherent Structures in Fluids, Plasmas and Nonlinear Media by : Michael Shats
Download or read book Lecture Notes on Turbulence and Coherent Structures in Fluids, Plasmas and Nonlinear Media written by Michael Shats and published by World Scientific Publishing Company Incorporated. This book was released on 2006-01-01 with total page 387 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book combines lecture notes from the 19th Canberra Intentional Summer School on Turbulence and Coherent Structures in Fluids, Plasma and Granular Flows as well as selected papers from the accompanying workshop on the same topic. Modern concepts, tools and approaches to studying turbulence and coherent structures are introduced by world-class experts in several fields. The book covers theoretical approaches, numerical modeling and experimental methods in quasi-two-dimensional geophysical flows (such as oceans and atmospheres), turbulence and structures in ionized gases (such as magnetized plasma), three-dimensional flows (such as turbulent boundary layers), and also vortices and solutions in nonlinear optical medium. Many of the methodologies presented may also be applicable to other complex systems. One of the main objectives of this book is to introduce modern studies of turbulence as a cross-disciplinary domain and to give the reader exposure to some of the most vital theoretical and experimental areas of turbulence research.
