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Sirignano, , W. Fluids Eng.
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Start by pressing the button below! Fluid Dynamics and Transport of Droplets and Sprays The study of droplets and sprays has developed rapidly over the past Fluid Dynamics and Transport of Droplets and Sprays The study of droplets and sprays has developed rapidly over the past two decades because of their many important applications, from automobile engine combustion to drug aerosols.
This book addresses the complex subject of the interactions of droplets and sprays. It describes the behavior of an individual droplet in a spray, the behavior of a spray, and the criticial relationships between the two.
In particular, it discusses the fluid mechanics and transport phenomena that govern the behavior of droplets and sprays in many important applications. Along with a strong theoretical foundation, the book presents results in a way that will be useful for engineering practice, with summaries of key formulas and examples of various spray computations. Among topics covered are transient heating or cooling and vaporization or condensation , multicomponent liquid droplet vaporization, near-critical and supercritical ambient conditions, interaction of droplets with turbulent or vortical structures, distortion of the spherical shape and secondary atomization of the droplets, and computational issues.
As an authoritative review of the science and technology of droplets and sprays, this book will be useful for graduate students, researchers, and practicing engineers. William A. Sirignano This publication is in copyright.
Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press.
First published Reprinted This digitally printed first paperback version A catalogue recordfor this publication is available from the British Library Library of Congress Cataloguing in Publication data Sirignano, W.
Includes bibliographical references and index. ISBN 1. S6S57 '. There are many interesting applications of spray theory related to power, propulsion, heat exchange, and materials processing. Spray phenomena also have natural occurrences. Spray and droplet behaviors have a strong impact on vital economic and military issues.
Examples include the diesel engine and gas-turbine engine for automotive, power-generation, and aerospace applications. Manufacturing technologies including droplet-based net form processing, coating, and painting are important applications. Applications involving medication, pesticides and insecticides, and other consumer uses add to the impressive list of important industries that use spray and droplet technologies. These industries involve annual production certainly measured in tens of billions of dollars and possibly higher.
The potentials for improved performance, improved market shares, reduced costs, and new products and applications are immense. An effort is needed to optimize the designs of spray and droplet applications and to develop strategies and technologies for active control of sprays in order to achieve the huge potential in this answer.
In this book, I have attempted to provide some scientific foundation for movement toward the goals of optimal design and effective application of active controls. The book, however, will not focus on design and controls. Rather, I discuss the fluid mechanics and transport phenomena that govern the behavior of sprays and droplets in the many important applications.
Various theoretical and computational aspects of the fluid dynamics and transport of sprays and droplets are reviewed in detail. I undertook this writing because no previous treatise exists that broadly addresses theoretical and computational issues related to both spray and droplet behavior. There are other books that address either sprays on a global scale or individual isolated droplets on the fine scale.
However, no other book has attempted a true integration of these two critically related topics. My research interests have focused on the theoretical and computational aspects of the spray problem. Therefore this monograph will emphasize those aspects. Major but not total attention will be given to the works of my research team since we have many research publications and review papers on this subject. On the basis of these research studies over the years, a decent comprehensive portrayal of the field is achievable.
I have given emphasis to liquid-fuel droplets and to combustion applications since my experience is centered in that domain and, more importantly, since the high temperatures and rapid vaporization makes the dynamics of the phenomenon much more interesting and general. Rapidly vaporizing sprays have a richness of the scientific phenomena and several, often disparate, time scales. The discussions are Preface often also relevant to other important applications including materials processing, heat exchange, and coatings.
Since the field of droplet and spray studies is still developing in terms of both science and technology, a critical review is undertaken here. This monograph was developed largely on the basis of my lecture notes generated during several offerings of a graduate course. This treatise can serve both as a graduatelevel text and as a reference book for scientists and engineers. Attention is given to the behavior of individual droplets including the effects of forced convection due to relative droplet-gas motion, Stefan convection due to the vaporization or condensation of the liquid, multicomponent liquids and slurries , and internal circulation of the liquid.
Flow-field details in the gas boundary layer and wake and in the liquid-droplet interior are examined. Also, the determinations of droplet lift and drag coefficients and Nusselt and Sherwood numbers and their relationships with Reynolds number, transfer number, Prandtl and Schmidt numbers, and spacing between neighboring droplets are extensively discussed. Results from droplet analyses are presented in a manner that makes them useful as subgrid models in spray computations.
Several examples of spray computations for which these models are used are presented. The two-phase flow equations governing spray behavior are presented in various forms and thoroughly discussed. Attention is given to issues of computational accuracy and efficiency. Various configurations for spray flows are studied. Droplet interactions with vortical and turbulent fields are analyzed. Droplet behavior at near-critical and supercritical conditions is discussed.
My interactions over the past two decades with twelve postdoctoral associates and sixteen graduate students on the subject of sprays have been very productive, stimulating, and instructive. These junior at the time collaborators are well represented in the references. They are Boris Abramzon, Suresh K. Exciting interactions with senior collaborators are also recognized: H.
Dwyer, S. Elghobashi, G. Fix, B. Sanders, E. Suuberg, and S. Yao are identified here. Special appreciation is extended to Sue Kanda for her role in proofreading and indexing. Edwards is thanked for the comments and proofreading that improved the second printing of this book.
See Eqs. The heat flux at the droplet interface then equals the heat flux instantaneously at the edge of the liquid core. From Eqs. Using Eqs. This boundary condition is used to discard any singular solution, keeping the first term on the right-hand side of Eq. The boundary condition on the finite-difference computation is that 3r b O,x d lL 30 2.
Certain interesting observations can be made even before the solution of the equation: i Eq. With no vaporization, the coefficients depend on only 0, but in general they vary with both r and 0. Other nonlinearities due to the temperature dependence of transport and thermodynamic properties could appear in a more exact analysis. This implies that there is no such phenomenon as a rapid-mixing limit.
The diffusion equation 2. The direction of the convection here is normal to the droplet surface. This boundary layer in this limit would amount to a relaxation zone that regresses into the interior of the droplet as rapid vaporization occurs; the core temperature would remain intact at the initial temperature until the relaxation zone arrives.
This limit can occur only when the droplet lifetime is much shorter than the droplet-heating time and 43 Theory of Isolated Droplet Vaporization, Heating, and Acceleration has not been observed in practical situations at typical combustor temperatures and with typical fuels. The analog of this situation will be possible in the case of liquid-phase mass diffusion in which a characteristic diffusion time can be much larger than the droplet lifetime.
This point is discussed in Chapter 3. We would expect this relaxation zone appearing in this limit to overlay and to incorporate the boundary layer discussed above as the relaxation zone between the two-dimensional gas-phase solution and the one-dimensional core solution. When droplet slip is present, the droplet Nusselt number increases with the square root of the Reynolds number so that heat flux increases and droplet lifetime decreases. As mentioned in point iv above, the characteristic heating time is less than that value for the nonslipping case but the heating time is independent of vortex strength and implicitly Reynolds number for a fixed viscosity at large vortex strength or large Reynolds number.
We already know that in the nonslipping, noncirculating case in a typical combustor environment with typical fuels, the droplet-heating time and droplet lifetime are comparable. Note that here both scale with initial droplet radius squared.
Coincidentally, for Reynolds numbers of the order of , both times are again comparable, although reduced from their values at zero Reynolds number.
The heating time still scales with initial radius squared but the lifetime no longer does; in a quasi-steady situation, the lifetime can be shown to be proportional to initial radius squared divided by the square root of Reynolds number effectively a radius to the threehalves power dependence. At lower Reynolds number, we may expect heating time to be shorter than lifetime so that a uniform temperature approximation could become reasonable.
At higher Reynolds numbers, lifetimes would become shorter and the rapid regression limit of point v above would be approached; however, in practice, the Weber number tends to become large at high Reynolds number and droplets disintegrate into smaller droplets with decreased Reynolds numbers.
Then Eq. Temperature is a monotonically increasing function of 0 with the gradient diminishing with time. The limit of uniform but time-varying temperature results as the liquid thermal diffusivity goes to infinity. Contrary to earlier beliefs by some investigators, the uniform temperature limit does not result from infinitely rapid internal circulation. As shown above, infinitely fast circulation or an infinite liquid Peclet number results in the finite temperature gradients' becoming oriented normal to the stream surfaces.
Note that the averaging of the temperature over the stream surface eliminated the convection term from Eq. The effect of the regressing interface appears in the coefficient of that diffusion equation. Under that assumption, the nonlinearities introduced by the coefficients in Eq.
The study of droplets and sprays has developed rapidly over the past two decades because of their many important applications, from automobile engine combustion to drug aerosols. This book addresses the complex subject of the interactions of droplets and sprays. It describes the behavior of an individual droplet in a spray, the behavior of a spray, and the critical relationships between the two. Along with a strong theoretical foundation, the book presents results in a way that will be useful for engineering practice, with summaries of key formulae and examples of various spray computations. Among topics covered are transient heating or cooling and vaporization or condensation , multicomponent liquid droplet vaporization, near critical and supercritical ambient conditions, interaction of droplets with turbulent or vortical structures, distortion of the spherical shape and secondary atomization of the droplets, and computational issues. As an authoritative review of the science and technology of droplets and sprays, this book will be useful for graduate students, researchers, and practicing engineers.
The system can't perform the operation now. Try again later. Citations per year. Duplicate citations. The following articles are merged in Scholar. Their combined citations are counted only for the first article. Merged citations.
Sirignano, , W. Fluids Eng. March ; 1 : It is easy to make the case for a book on the behavior and properties of sprays. Considerable part of the energy need of mankind is met by burning liquid fuels—almost always by atomizing it first—and other applications are in abundance.
It discusses how droplet level transport is central to a multitude of applications and how droplet level manipulation and control can enhance the efficiency and design of multiphase systems. Droplets and sprays are ubiquitous in a variety of multiphase and multiscale applications in surface patterning, oil recovery, combustion, atomization, spray drying, thermal barrier coating, renewable energy, and electronic cooling, to name but a few. This book provides two levels of details pertaining to such applications. Each chapter delves into a specific application and provides not only an overview but also detailed physical insights into the application mechanism from the point of view of droplets and sprays.
Haynes ManualsThe Haynes Author : William A. Sirignano Description:This book serves as both a graduate text and a reference for engineers and scientists exploring the theoretical and computational aspects of the fluid dynamics and transport of sprays and droplets. Attention is given to the behavior of individual droplets, including the effects of forced convection due to relative droplet-gas motion, Stefan convection due to the vaporization or condensation of the liquid, multicomponent liquids and slurries , and internal circulation of the liquid.
Дэвид на экране застыл в глубокой задумчивости. - Разница, - бормотал он себе под нос. - Разница между U235 и U238.
Прошло еще несколько минут. Она пыталась не думать о Дэвиде, но безуспешно. С каждым завыванием сирены слова Хейла эхом отдавались в ее мозгу: Я сожалею о Дэвиде Беккере. Сьюзан казалось, что она сходит с ума.
Джабба нередко прибегал к ВР, что в компьютерных кругах означало виртуальная реальность, но в АНБ это сокращение имело несколько иной смысл - визуальная репрезентация. В мире технических служащих и политиков, имеющих чрезвычайно разные уровни понимания, визуальная репрезентация нередко была единственным способом что-либо доказать: взмывающая вверх кривая производит куда более сильное впечатление, чем целые тома рассуждений. Джабба понимал, что ВР текущего кризиса со всей наглядностью объяснит то, что он хотел сказать. - ВР! - крикнула Соши, усаживаясь за компьютер в задней части комнаты.
Короче, он отдаст ключ публике.
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