A systems approach to theoretical fluid mechanics: Fundamentals
Anyiwo, J. C.
1978-01-01
A preliminary application of the underlying principles of the investigator's general system theory to the description and analyses of the fluid flow system is presented. An attempt is made to establish practical models, or elements of the general fluid flow system from the point of view of the general system theory fundamental principles. Results obtained are applied to a simple experimental fluid flow system, as test case, with particular emphasis on the understanding of fluid flow instability, transition and turbulence.
International Nuclear Information System (INIS)
Granger, R.A.
1985-01-01
This text offers the most comprehensive approach available to fluid mechanics. The author takes great care to insure a physical understanding of concepts grounded in applied mathematics. The presentation of theory is followed by engineering applications, helping students develop problem-solving skills from the perspective of a professional engineer. Extensive use of detailed examples reinforces the understanding of theoretical concepts
International Nuclear Information System (INIS)
Paraschivoiu, I.; Prud'homme, M.; Robillard, L.; Vasseur, P.
2003-01-01
This book constitutes at the same time theoretical and practical base relating to the phenomena associated with fluid mechanics. The concept of continuum is at the base of the approach developed in this work. The general advance proceeds of simple balances of forces as into hydrostatic to more complex situations or inertias, the internal stresses and the constraints of Reynolds are taken into account. This advance is not only theoretical but contains many applications in the form of solved problems, each chapter ending in a series of suggested problems. The major part of the applications relates to the incompressible flows
Shivamoggi, Bhimsen K
1998-01-01
"Although there are many texts and monographs on fluid dynamics, I do not know of any which is as comprehensive as the present book. It surveys nearly the entire field of classical fluid dynamics in an advanced, compact, and clear manner, and discusses the various conceptual and analytical models of fluid flow." - Foundations of Physics on the first edition. Theoretical Fluid Dynamics functions equally well as a graduate-level text and a professional reference. Steering a middle course between the empiricism of engineering and the abstractions of pure mathematics, the author focuses
Drazin, Philip
1987-01-01
Outlines the contents of Volume II of "Principia" by Sir Isaac Newton. Reviews the contributions of subsequent scientists to the physics of fluid dynamics. Discusses the treatment of fluid mechanics in physics curricula. Highlights a few of the problems of modern research in fluid dynamics. Shows that problems still remain. (CW)
Left ventricular fluid mechanics: the long way from theoretical models to clinical applications.
Pedrizzetti, Gianni; Domenichini, Federico
2015-01-01
The flow inside the left ventricle is characterized by the formation of vortices that smoothly accompany blood from the mitral inlet to the aortic outlet. Computational fluid dynamics permitted to shed some light on the fundamental processes involved with vortex motion. More recently, patient-specific numerical simulations are becoming an increasingly feasible tool that can be integrated with the developing imaging technologies. The existing computational methods are reviewed in the perspective of their potential role as a novel aid for advanced clinical analysis. The current results obtained by simulation methods either alone or in combination with medical imaging are summarized. Open problems are highlighted and perspective clinical applications are discussed.
Theoretical Physics 1. Theoretical Mechanics
International Nuclear Information System (INIS)
Dreizler, Reiner M.; Luedde, Cora S.
2010-01-01
After an introduction to basic concepts of mechanics more advanced topics build the major part of this book. Interspersed is a discussion of selected problems of motion. This is followed by a concise treatment of the Lagrangian and the Hamiltonian formulation of mechanics, as well as a brief excursion on chaotic motion. The last chapter deals with applications of the Lagrangian formulation to specific systems (coupled oscillators, rotating coordinate systems, rigid bodies). The level of this textbook is advanced undergraduate. The authors combine teaching experience of more than 40 years in all fields of Theoretical Physics and related mathematical disciplines and thorough knowledge in creating advanced eLearning content. The text is accompanied by an extensive collection of online material, in which the possibilities of the electronic medium are fully exploited, e.g. in the form of applets, 2D- and 3D-animations. (orig.)
Theoretical Physics 1. Theoretical Mechanics
Energy Technology Data Exchange (ETDEWEB)
Dreizler, Reiner M.; Luedde, Cora S. [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik
2010-07-01
After an introduction to basic concepts of mechanics more advanced topics build the major part of this book. Interspersed is a discussion of selected problems of motion. This is followed by a concise treatment of the Lagrangian and the Hamiltonian formulation of mechanics, as well as a brief excursion on chaotic motion. The last chapter deals with applications of the Lagrangian formulation to specific systems (coupled oscillators, rotating coordinate systems, rigid bodies). The level of this textbook is advanced undergraduate. The authors combine teaching experience of more than 40 years in all fields of Theoretical Physics and related mathematical disciplines and thorough knowledge in creating advanced eLearning content. The text is accompanied by an extensive collection of online material, in which the possibilities of the electronic medium are fully exploited, e.g. in the form of applets, 2D- and 3D-animations. (orig.)
Theoretical Mechanics Theoretical Physics 1
Dreizler, Reiner M
2011-01-01
After an introduction to basic concepts of mechanics more advanced topics build the major part of this book. Interspersed is a discussion of selected problems of motion. This is followed by a concise treatment of the Lagrangian and the Hamiltonian formulation of mechanics, as well as a brief excursion on chaotic motion. The last chapter deals with applications of the Lagrangian formulation to specific systems (coupled oscillators, rotating coordinate systems, rigid bodies). The level of this textbook is advanced undergraduate. The authors combine teaching experience of more than 40 years in all fields of Theoretical Physics and related mathematical disciplines and thorough knowledge in creating advanced eLearning content. The text is accompanied by an extensive collection of online material, in which the possibilities of the electronic medium are fully exploited, e.g. in the form of applets, 2D- and 3D-animations. - A collection of 74 problems with detailed step-by-step guidance towards the solutions. - A col...
International Nuclear Information System (INIS)
Kreider, J.F.
1985-01-01
This book is an introduction on fluid mechanics incorporating computer applications. Topics covered are as follows: brief history; what is a fluid; two classes of fluids: liquids and gases; the continuum model of a fluid; methods of analyzing fluid flows; important characteristics of fluids; fundamentals and equations of motion; fluid statics; dimensional analysis and the similarity principle; laminar internal flows; ideal flow; external laminar and channel flows; turbulent flow; compressible flow; fluid flow measurements
Shinbrot, Marvin
2012-01-01
Readable and user-friendly, this high-level introduction explores the derivation of the equations of fluid motion from statistical mechanics, classical theory, and a portion of the modern mathematical theory of viscous, incompressible fluids. 1973 edition.
Editorial Special Issue on Fluid Mechanics and Fluid Power (FMFP ...
Indian Academy of Sciences (India)
This special issue of Sadhana contains selected papers from two conferences related to fluid mechanics held in India recently, Fluid Mechanics and Fluid Power conference at NIT, Hamirpur, and an International Union of Theoretical ... A simple, well thought out, flow visualization experiment or a computation can sometimes ...
Michell, S J
2013-01-01
Fluid and Particle Mechanics provides information pertinent to hydraulics or fluid mechanics. This book discusses the properties and behavior of liquids and gases in motion and at rest. Organized into nine chapters, this book begins with an overview of the science of fluid mechanics that is subdivided accordingly into two main branches, namely, fluid statics and fluid dynamics. This text then examines the flowmeter devices used for the measurement of flow of liquids and gases. Other chapters consider the principle of resistance in open channel flow, which is based on improper application of th
Theoretical models for supercritical fluid extraction.
Huang, Zhen; Shi, Xiao-Han; Jiang, Wei-Juan
2012-08-10
For the proper design of supercritical fluid extraction processes, it is essential to have a sound knowledge of the mass transfer mechanism of the extraction process and the appropriate mathematical representation. In this paper, the advances and applications of kinetic models for describing supercritical fluid extraction from various solid matrices have been presented. The theoretical models overviewed here include the hot ball diffusion, broken and intact cell, shrinking core and some relatively simple models. Mathematical representations of these models have been in detail interpreted as well as their assumptions, parameter identifications and application examples. Extraction process of the analyte solute from the solid matrix by means of supercritical fluid includes the dissolution of the analyte from the solid, the analyte diffusion in the matrix and its transport to the bulk supercritical fluid. Mechanisms involved in a mass transfer model are discussed in terms of external mass transfer resistance, internal mass transfer resistance, solute-solid interactions and axial dispersion. The correlations of the external mass transfer coefficient and axial dispersion coefficient with certain dimensionless numbers are also discussed. Among these models, the broken and intact cell model seems to be the most relevant mathematical model as it is able to provide realistic description of the plant material structure for better understanding the mass-transfer kinetics and thus it has been widely employed for modeling supercritical fluid extraction of natural matters. Copyright © 2012 Elsevier B.V. All rights reserved.
Advances in Environmental Fluid Mechanics
Mihailovic, Dragutin T
2010-01-01
Environmental fluid mechanics (EFM) is the scientific study of transport, dispersion and transformation processes in natural fluid flows on our planet Earth, from the microscale to the planetary scale. This book brings together scientists and engineers working in research institutions, universities and academia, who engage in the study of theoretical, modeling, measuring and software aspects in environmental fluid mechanics. It provides a forum for the participants, and exchanges new ideas and expertise through the presentations of up-to-date and recent overall achievements in this field.
Theoretical physics. Quantum mechanics
International Nuclear Information System (INIS)
Rebhan, Eckhard
2008-01-01
From the first in two comprehensive volumes appeared Theoretical Physics of the author by this after Mechanics and Electrodynamics also Quantum mechanics appears as thinner single volume. First the illustrative approach via wave mechanics is reproduced. The more abstract Hilbert-space formulation introduces the author later by postulates, which are because of the preceding wave mechanics sufficiently plausible. All concepts of quantum mechanics, which contradict often to the intuitive understanding formed by macroscopic experiences, are extensively discussed and made by means of many examples as well as problems - in the largest part provided with solutions - understandable. To the interpretation of quantum mechanics an extensive special chapter is dedicated. this book arose from courses on theoretical physics, which the author has held at the Heinrich-Heine University in Duesseldorf, and was in numerous repetitions fitted to the requirement of the studyings. it is so designed that it is also after the study suited as reference book or for the renewing. All problems are very thoroughly and such extensively studied that each step is separately reproducible. About motivation and good understandability is cared much
Basniev, Kaplan S; Chilingar, George V 0
2012-01-01
The mechanics of fluid flow is a fundamental engineering discipline explaining both natural phenomena and human-induced processes, and a thorough understanding of it is central to the operations of the oil and gas industry. This book, written by some of the world's best-known and respected petroleum engineers, covers the concepts, theories, and applications of the mechanics of fluid flow for the veteran engineer working in the field and the student, alike. It is a must-have for any engineer working in the oil and gas industry.
International Nuclear Information System (INIS)
Truckenbrodt, E.
1980-01-01
The second volume contains the chapter 4 to 6. Whereas chapter 1 deals with the introduction into the mechanics of fluids and chapter 2 with the fundamental laws of fluid and thermal fluid dynamics, in chapter 3 elementary flow phenomena in fluids with constant density are treated. Chapter 4 directly continues chapter 3 and describes elementary flow phenomena in fluids with varying density. Fluid statics again is treated as a special case. If compared with the first edition the treatment of unsteady laminar flow and of pipe flow for a fluid with varying density were subject to a substantial extension. In chapter 5 rotation-free and rotating potential flows are presented together. By this means it is achieved to explain the behaviour of the multidimensional fictionless flow in closed form. A subchapter describes some related problems of potential theory like the flow along a free streamline and seepage flow through a porous medium. The boundary layer flows in chapter 6 are concerned with the flow and temperature boundary layer in laminar and turbulent flows at a fired wall. In it differential and integral methods are applied of subchapter reports on boundary layer flows without a fixed boundary, occurring e.g. in an open jet and in a wake flow. The problems of intermittence and of the Coanda effect are briefly mentioned. (orig./MH)
Relativistic viscoelastic fluid mechanics
International Nuclear Information System (INIS)
Fukuma, Masafumi; Sakatani, Yuho
2011-01-01
A detailed study is carried out for the relativistic theory of viscoelasticity which was recently constructed on the basis of Onsager's linear nonequilibrium thermodynamics. After rederiving the theory using a local argument with the entropy current, we show that this theory universally reduces to the standard relativistic Navier-Stokes fluid mechanics in the long time limit. Since effects of elasticity are taken into account, the dynamics at short time scales is modified from that given by the Navier-Stokes equations, so that acausal problems intrinsic to relativistic Navier-Stokes fluids are significantly remedied. We in particular show that the wave equations for the propagation of disturbance around a hydrostatic equilibrium in Minkowski space-time become symmetric hyperbolic for some range of parameters, so that the model is free of acausality problems. This observation suggests that the relativistic viscoelastic model with such parameters can be regarded as a causal completion of relativistic Navier-Stokes fluid mechanics. By adjusting parameters to various values, this theory can treat a wide variety of materials including elastic materials, Maxwell materials, Kelvin-Voigt materials, and (a nonlinearly generalized version of) simplified Israel-Stewart fluids, and thus we expect the theory to be the most universal description of single-component relativistic continuum materials. We also show that the presence of strains and the corresponding change in temperature are naturally unified through the Tolman law in a generally covariant description of continuum mechanics.
Relativistic viscoelastic fluid mechanics.
Fukuma, Masafumi; Sakatani, Yuho
2011-08-01
A detailed study is carried out for the relativistic theory of viscoelasticity which was recently constructed on the basis of Onsager's linear nonequilibrium thermodynamics. After rederiving the theory using a local argument with the entropy current, we show that this theory universally reduces to the standard relativistic Navier-Stokes fluid mechanics in the long time limit. Since effects of elasticity are taken into account, the dynamics at short time scales is modified from that given by the Navier-Stokes equations, so that acausal problems intrinsic to relativistic Navier-Stokes fluids are significantly remedied. We in particular show that the wave equations for the propagation of disturbance around a hydrostatic equilibrium in Minkowski space-time become symmetric hyperbolic for some range of parameters, so that the model is free of acausality problems. This observation suggests that the relativistic viscoelastic model with such parameters can be regarded as a causal completion of relativistic Navier-Stokes fluid mechanics. By adjusting parameters to various values, this theory can treat a wide variety of materials including elastic materials, Maxwell materials, Kelvin-Voigt materials, and (a nonlinearly generalized version of) simplified Israel-Stewart fluids, and thus we expect the theory to be the most universal description of single-component relativistic continuum materials. We also show that the presence of strains and the corresponding change in temperature are naturally unified through the Tolman law in a generally covariant description of continuum mechanics.
Experimental and theoretical advances in fluid dynamics
Klapp, Jaime; Fuentes, Oscar Velasco
2011-01-01
The book is comprised of lectures and selected contributions presented at the Enzo Levi and XVI Annual Meeting of the Fluid Dynamic Division of the Mexican Physical Society in 2010. It is aimed at fourth year undergraduate and graduate students, as well as scientists in the fields of physics, engineering and chemistry with an interest in fluid dynamics from the experimental and theoretical point of view. The lectures are introductory and avoid the use of complicated mathematics. The other selected contributions are also geared to fourth year undergraduate and graduate students. The fluid dynam
Mechanics of solids and fluids
International Nuclear Information System (INIS)
Ziegler, F.
1991-01-01
This book is a comprehensive treatise on the mechanics of solids and fluids, with a significant application to structural mechanics. In reading through the text, I can not help being impressed with Dr. Ziegler's command of both historical and contemporary developments of theoretical and applied mechanics. The book is a unique volume which contains information not easily found throughout the related literature. The book opens with a fundamental consideration of the kinematics of particle motion, followed by those of rigid body and deformable medium .In the latter case, both small and finite deformation have been presented concisely, paving the way for the constitutive description given later in the book. In both chapters one and two, the author has provided sufficient applications of the theoretical principles introduced. Such a connection between theory and appication is a common theme throughout every chapter, and is quite an attractive feature of the book
Fluid mechanics in fluids at rest.
Brenner, Howard
2012-07-01
Using readily available experimental thermophoretic particle-velocity data it is shown, contrary to current teachings, that for the case of compressible flows independent dye- and particle-tracer velocity measurements of the local fluid velocity at a point in a flowing fluid do not generally result in the same fluid velocity measure. Rather, tracer-velocity equality holds only for incompressible flows. For compressible fluids, each type of tracer is shown to monitor a fundamentally different fluid velocity, with (i) a dye (or any other such molecular-tagging scheme) measuring the fluid's mass velocity v appearing in the continuity equation and (ii) a small, physicochemically and thermally inert, macroscopic (i.e., non-Brownian), solid particle measuring the fluid's volume velocity v(v). The term "compressibility" as used here includes not only pressure effects on density, but also temperature effects thereon. (For example, owing to a liquid's generally nonzero isobaric coefficient of thermal expansion, nonisothermal liquid flows are to be regarded as compressible despite the general perception of liquids as being incompressible.) Recognition of the fact that two independent fluid velocities, mass- and volume-based, are formally required to model continuum fluid behavior impacts on the foundations of contemporary (monovelocity) fluid mechanics. Included therein are the Navier-Stokes-Fourier equations, which are now seen to apply only to incompressible fluids (a fact well-known, empirically, to experimental gas kineticists). The findings of a difference in tracer velocities heralds the introduction into fluid mechanics of a general bipartite theory of fluid mechanics, bivelocity hydrodynamics [Brenner, Int. J. Eng. Sci. 54, 67 (2012)], differing from conventional hydrodynamics in situations entailing compressible flows and reducing to conventional hydrodynamics when the flow is incompressible, while being applicable to both liquids and gases.
FOREWORD Fluid Mechanics and Fluid Power (FMFP)
Indian Academy of Sciences (India)
This section of the Special Issue carries selected articles from the Fluid Mechanics and Fluid. Power Conference held during 12–14 December 2013 at the National Institute of Technology,. Hamirpur (HP). The section includes three review articles and nine original research articles. These were selected on the basis of their ...
Fay, James A.; Sonwalkar, Nishikant
1996-05-01
This CD-ROM is designed to accompany James Fay's Introduction to Fluid Mechanics. An enhanced hypermedia version of the textbook, it offers a number of ways to explore the fluid mechanics domain. These include a complete hypertext version of the original book, physical-experiment video clips, excerpts from external references, audio annotations, colored graphics, review questions, and progressive hints for solving problems. Throughout, the authors provide expert guidance in navigating the typed links so that students do not get lost in the learning process. System requirements: Macintosh with 68030 or greater processor and with at least 16 Mb of RAM. Operating System 6.0.4 or later for 680x0 processor and System 7.1.2 or later for Power-PC. CD-ROM drive with 256- color capability. Preferred display 14 inches or above (SuperVGA with 1 megabyte of VRAM). Additional system font software: Computer Modern postscript fonts (CM/PS Screen Fonts, CMBSY10, and CMTT10) and Adobe Type Manager (ATM 3.0 or later). James A. Fay is Professor Emeritus and Senior Lecturer in the Department of Mechanical Engineering at MIT.
The Janus fluid a theoretical perspective
Fantoni, Riccardo
2013-01-01
The state-of-the-art in the theoretical statistical physics treatment of the Janus fluid is reported with a bridge between new research results published in journal articles and a contextual literature review. Recent Monte Carlo simulations on the Kern and Frenkel model of the Janus fluid have revealed that in the vapor phase, below the critical point, there is the formation of preferred inert clusters made up of a well-defined number of particles: the micelles and the vesicles. This is responsible for a re-entrant gas branch of the gas-liquid binodal. Detailed account of this findings are given in the first chapter where the Janus fluid is introduced as a product of new sophisticated synthesis laboratory techniques. In the second chapter a cluster theory is developed to approximate the exact clustering properties stemming from the simulations. It is shown that the theory is able to reproduce semi-quantitatively the micellization phenomenon.
Multidomain multiphase fluid mechanics
International Nuclear Information System (INIS)
Sha, W.T.; Soo, S.L.
1976-10-01
A set of multiphase field equations--conversion of mass, momentum and energy--based on multiphase mechanics is developed. Multiphase mechanics applies to mixtures of phases which are separated by interfaces and are mutually exclusive. Based on the multiphase mechanics formulation, additional terms appear in the field equations when the physical size of the dispersed phase (bubble or droplet) is many times larger than the inter-molecular spacing. These terms are the inertial coupling due to virtual mass and the additional viscous coupling due to unsteadiness of the flow field. The multiphase formulation given here takes into account the discreteness of particles of dispersed phases and, at the same time, the necessity of the distributive representation of field variables via space-time averaging when handling a large number of particles. The provision for multidomain transition further permits us to treat dispersed phases which are large compared to the characteristic dimension of the flow system via interdomain relations. The multidomain multiphase approach provides a framework for us to model the various flow regimes. Because some of the transport parameters associated with the system equations are not well known at the present time, an idealized two-domain two-phase solution approach is proposed as a first step. Finally, comparisons are made between the field equations formulated based on the multidomain-multiphase fluid mechanics and the pertinent existing models, and their relative significances are discussed. The desirability of consistent approximation and simplifications possible for dilute suspensions are discussed
Mechanics lectures on theoretical physics
Sommerfeld, Arnold Johannes Wilhelm
1952-01-01
Mechanics: Lectures on Theoretical Physics, Volume I covers a general course on theoretical physics. The book discusses the mechanics of a particle; the mechanics of systems; the principle of virtual work; and d'alembert's principle. The text also describes oscillation problems; the kinematics, statics, and dynamics of a rigid body; the theory of relative motion; and the integral variational principles of mechanics. Lagrange's equations for generalized coordinates and the theory of Hamilton are also considered. Physicists, mathematicians, and students taking Physics courses will find the book
Barati Farimani, Amir; Gomes, Joseph; Pande, Vijay
2017-11-01
We have developed a new data-driven model paradigm for the rapid inference and solution of the constitutive equations of fluid mechanic by deep learning models. Using generative adversarial networks (GAN), we train models for the direct generation of solutions to steady state heat conduction and incompressible fluid flow without knowledge of the underlying governing equations. Rather than using artificial neural networks to approximate the solution of the constitutive equations, GANs can directly generate the solutions to these equations conditional upon an arbitrary set of boundary conditions. Both models predict temperature, velocity and pressure fields with great test accuracy (>99.5%). The application of our framework for inferring and generating the solutions of partial differential equations can be applied to any physical phenomena and can be used to learn directly from experiments where the underlying physical model is complex or unknown. We also have shown that our framework can be used to couple multiple physics simultaneously, making it amenable to tackle multi-physics problems.
Fluid mechanics a geometrical point of view
Rajeev, S G
2018-01-01
Fluid Mechanics: A Geometrical Point of View emphasizes general principles of physics illustrated by simple examples in fluid mechanics. Advanced mathematics (e.g., Riemannian geometry and Lie groups) commonly used in other parts of theoretical physics (e.g. General Relativity or High Energy Physics) are explained and applied to fluid mechanics. This follows on from the author's book Advanced Mechanics (Oxford University Press, 2013). After introducing the fundamental equations (Euler and Navier-Stokes), the book provides particular cases: ideal and viscous flows, shocks, boundary layers, instabilities, and transients. A restrained look at integrable systems (KdV) leads into a formulation of an ideal fluid as a hamiltonian system. Arnold's deep idea, that the instability of a fluid can be understood using the curvature of the diffeomorphism group, will be explained. Leray's work on regularity of Navier-Stokes solutions, and the modern developments arising from it, will be explained in language for physicists...
Fluid mechanics fundamentals and applications
Cengel, Yunus
2013-01-01
Cengel and Cimbala's Fluid Mechanics Fundamentals and Applications, communicates directly with tomorrow's engineers in a simple yet precise manner. The text covers the basic principles and equations of fluid mechanics in the context of numerous and diverse real-world engineering examples. The text helps students develop an intuitive understanding of fluid mechanics by emphasizing the physics, using figures, numerous photographs and visual aids to reinforce the physics. The highly visual approach enhances the learning of Fluid mechanics by students. This text distinguishes itself from others by the way the material is presented - in a progressive order from simple to more difficult, building each chapter upon foundations laid down in previous chapters. In this way, even the traditionally challenging aspects of fluid mechanics can be learned effectively. McGraw-Hill is also proud to offer ConnectPlus powered by Maple with the third edition of Cengel/Cimbabla, Fluid Mechanics. This innovative and powerful new sy...
Quantum mechanics the theoretical minimum
Susskind, Leonard
2014-01-01
From the bestselling author of The Theoretical Minimum, an accessible introduction to the math and science of quantum mechanicsQuantum Mechanics is a (second) book for anyone who wants to learn how to think like a physicist. In this follow-up to the bestselling The Theoretical Minimum, physicist Leonard Susskind and data engineer Art Friedman offer a first course in the theory and associated mathematics of the strange world of quantum mechanics. Quantum Mechanics presents Susskind and Friedman’s crystal-clear explanations of the principles of quantum states, uncertainty and time dependence, entanglement, and particle and wave states, among other topics. An accessible but rigorous introduction to a famously difficult topic, Quantum Mechanics provides a tool kit for amateur scientists to learn physics at their own pace.
Theoretical mechanics for sixth forms
Plumpton, C
1971-01-01
Theoretical Mechanics for Sixth Forms, Second Edition is a 14-chapter book that begins by elucidating the nature of theoretical mechanics. The book then describes the statics of a particle in illustration of the techniques of handling vector quantities. Subsequent chapters focus on the principle of moments, parallel forces and centers of gravity; and the application of Newton's second law to the dynamics of a particle and the ideas of work and energy, impulse and momentum, and power. The concept of friction is also explained. This volume concludes with chapters concerning motion in a circle an
Fluid mechanics of Windkessel effect.
Mei, C C; Zhang, J; Jing, H X
2018-01-08
We describe a mechanistic model of Windkessel phenomenon based on the linear dynamics of fluid-structure interactions. The phenomenon has its origin in an old-fashioned fire-fighting equipment where an air chamber serves to transform the intermittent influx from a pump to a more steady stream out of the hose. A similar mechanism exists in the cardiovascular system where blood injected intermittantly from the heart becomes rather smooth after passing through an elastic aorta. In existing haeodynamics literature, this mechanism is explained on the basis of electric circuit analogy with empirical impedances. We present a mechanistic theory based on the principles of fluid/structure interactions. Using a simple one-dimensional model, wave motion in the elastic aorta is coupled to the viscous flow in the rigid peripheral artery. Explicit formulas are derived that exhibit the role of material properties such as the blood density, viscosity, wall elasticity, and radii and lengths of the vessels. The current two-element model in haemodynamics is shown to be the limit of short aorta and low injection frequency and the impedance coefficients are derived theoretically. Numerical results for different aorta lengths and radii are discussed to demonstrate their effects on the time variations of blood pressure, wall shear stress, and discharge. Graphical Abstract A mechanistic analysis of Windkessel Effect is described which confirms theoretically the well-known feature that intermittent influx becomes continuous outflow. The theory depends only on the density and viscosity of the blood, the elasticity and dimensions of the vessel. Empirical impedence parameters are avoided.
Annual review of fluid mechanics. Volume 23
International Nuclear Information System (INIS)
Lumley, J.L.; Van Dyke, M.; Reed, H.L.
1991-01-01
Recent advances in theoretical, experimental, and computational fluid mechanics are discussed in a collection of annual review essays. Topics addressed include Lagrangian ocean studies, drag reduction in nature, the hydraulics of rotating strait and sill flow, analytical methods for the development of Reynolds-stress closures in turbulence, and exact solutions of the Navier-Stokes equations. Consideration is given to the theory of hurricanes, flow phenomena in CVD of thin films, particle-imaging techniques for experimental fluid mechanics, symmetry and symmetry-breaking bifurcations in fluid dynamics, turbulent mixing in stratified fluids, numerical simulation of transition in wall-bounded shear flows, fractals and multifractals in fluid turbulence, and coherent motions in the turbulent boundary layer
Theoretical physics 1 classical mechanics
Nolting, Wolfgang
2016-01-01
This textbook offers a clear and comprehensive introduction to classical mechanics, one of the core components of undergraduate physics courses. The book starts with a thorough introduction to the mathematical tools needed, to make this textbook self-contained for learning. The second part of the book introduces the mechanics of the free mass point and details conservation principles. The third part expands the previous to mechanics of many particle systems. Finally the mechanics of the rigid body is illustrated with rotational forces, inertia and gyroscope movement. Ideally suited to undergraduate students in their first year, the book is enhanced throughout with learning features such as boxed inserts and chapter summaries, with key mathematical derivations highlighted to aid understanding. The text is supported by numerous worked examples and end of chapter problem sets. About the Theoretical Physics series Translated from the renowned and highly successful German editions, the eight volumes of this series...
Fluid mechanics in the perivascular space.
Wang, Peng; Olbricht, William L
2011-04-07
Perivascular space (PVS) within the brain is an important pathway for interstitial fluid (ISF) and solute transport. Fluid flowing in the PVS can affect these transport processes and has significant impacts on physiology. In this paper, we carry out a theoretical analysis to investigate the fluid mechanics in the PVS. With certain assumptions and approximations, we are able to find an analytical solution to the problem. We discuss the physical meanings of the solution and particularly examine the consequences of the induced fluid flow in the context of convection-enhanced delivery (CED). We conclude that peristaltic motions of the blood vessel walls can facilitate fluid and solute transport in the PVS. Copyright © 2011 Elsevier Ltd. All rights reserved.
Fractional vector calculus and fluid mechanics
Lazopoulos, Konstantinos A.; Lazopoulos, Anastasios K.
2017-04-01
Basic fluid mechanics equations are studied and revised under the prism of fractional continuum mechanics (FCM), a very promising research field that satisfies both experimental and theoretical demands. The geometry of the fractional differential has been clarified corrected and the geometry of the fractional tangent spaces of a manifold has been studied in Lazopoulos and Lazopoulos (Lazopoulos KA, Lazopoulos AK. Progr. Fract. Differ. Appl. 2016, 2, 85-104), providing the bases of the missing fractional differential geometry. Therefore, a lot can be contributed to fractional hydrodynamics: the basic fractional fluid equations (Navier Stokes, Euler and Bernoulli) are derived and fractional Darcy's flow in porous media is studied.
State of the Art Review on Theoretical Tribology of Fluid Power Displacement Machines
DEFF Research Database (Denmark)
Cerimagic, Remzija; Johansen, Per; Andersen, Torben O.
2016-01-01
machines, and also the work done to validate the theoretical models. This review is not a complete historical account, but aim to describe current trends in fluid power displacement machine tribology. The review considers the rheological models used in the theoretical approaches, the modeling...... and wear mechanisms in the lubricating gaps in fluid power machines is confined to simulation models, as experimental treatments of these mechanisms are very difficult. The aim of this paper is a state of the art review on the theoretical work for the design and optimization of fluid power displacement...... of elastohydrodynamic effects, the modeling of thermal effects, and finally the experimental validation of the theoretical models....
Blanks, Robert F.
1979-01-01
A humanistic approach to teaching fluid mechanics is described which minimizes lecturing, increases professor-student interaction, uses group and individual problem solving sessions, and allows for student response. (BB)
Fluid dynamics theoretical and computational approaches
Warsi, ZUA
2005-01-01
Important Nomenclature Kinematics of Fluid Motion Introduction to Continuum Motion Fluid Particles Inertial Coordinate Frames Motion of a Continuum The Time Derivatives Velocity and Acceleration Steady and Nonsteady Flow Trajectories of Fluid Particles and Streamlines Material Volume and Surface Relation between Elemental Volumes Kinematic Formulas of Euler and Reynolds Control Volume and Surface Kinematics of Deformation Kinematics of Vorticity and Circulation References Problems The Conservation Laws and the Kinetics of Flow Fluid Density and the Conservation of Mass Prin
Fluid mechanics of heart valves.
Yoganathan, Ajit P; He, Zhaoming; Casey Jones, S
2004-01-01
Valvular heart disease is a life-threatening disease that afflicts millions of people worldwide and leads to approximately 250,000 valve repairs and/or replacements each year. Malfunction of a native valve impairs its efficient fluid mechanic/hemodynamic performance. Artificial heart valves have been used since 1960 to replace diseased native valves and have saved millions of lives. Unfortunately, despite four decades of use, these devices are less than ideal and lead to many complications. Many of these complications/problems are directly related to the fluid mechanics associated with the various mechanical and bioprosthetic valve designs. This review focuses on the state-of-the-art experimental and computational fluid mechanics of native and prosthetic heart valves in current clinical use. The fluid dynamic performance characteristics of caged-ball, tilting-disc, bileaflet mechanical valves and porcine and pericardial stented and nonstented bioprostheic valves are reviewed. Other issues related to heart valve performance, such as biomaterials, solid mechanics, tissue mechanics, and durability, are not addressed in this review.
Fluid mechanics problems and solutions
Spurk, Joseph H
1997-01-01
his collection of over 200 detailed worked exercises adds to and complements the textbook Fluid Mechanics by the same author, and illustrates the teaching material through examples. In the exercises the fundamental concepts of Fluid Mechanics are applied to obtaining the solution of diverse concrete problems, and in doing this the student's skill in the mathematical modeling of practical problems is developed. In addition, 30 challenging questions without detailed solutions have been included, and while lecturers will find these questions suitable for examinations and tests, the student himself can use them to check his understanding of the subject.
International Nuclear Information System (INIS)
Jain, Anuj; Paul, Akshoy Ranjan
2016-01-01
Fluid Mechanics and Fluid Power (FMFP) Conference is an important meeting to promote all activities in the field of Fluid Mechanics and Fluid Power in India. FMFP-2016 offers great opportunity to scientists, researchers, engineers and business executives from all parts of the world to share the recent advancements and future trends in all aspects of fluid mechanics and fluid power- be it theoretical, experimental, applied and computational, and build network. It covers theoretical and experimental fluid dynamics, flow instability, transition, turbulence and control, fluid machinery, turbomachinery and fluid power, IC engines and gas turbines, multiphase flows, fluid-structure interaction and flow-induced noise, micro and nano fluid mechanics, bio-inspired fluid mechanics, energy and environment, specialized topics (transport phenomena in materials processing and manufacturing, MHD and EHD flows, granular flows, nuclear reactor, thermal hydraulics, defence and space engineering, sustainable habitat. Papers relevant to INIS are indexed separately
Development of a theoretical framework for analyzing cerebrospinal fluid dynamics
Directory of Open Access Journals (Sweden)
Vedel Søren
2009-09-01
Full Text Available Abstract Background To date hydrocephalus researchers acknowledge the need for rigorous but utilitarian fluid mechanics understanding and methodologies in studying normal and hydrocephalic intracranial dynamics. Pressure volume models and electric circuit analogs introduced pressure into volume conservation; but control volume analysis enforces independent conditions on pressure and volume. Previously, utilization of clinical measurements has been limited to understanding of the relative amplitude and timing of flow, volume and pressure waveforms; qualitative approaches without a clear framework for meaningful quantitative comparison. Methods Control volume analysis is presented to introduce the reader to the theoretical background of this foundational fluid mechanics technique for application to general control volumes. This approach is able to directly incorporate the diverse measurements obtained by clinicians to better elucidate intracranial dynamics and progression to disorder. Results Several examples of meaningful intracranial control volumes and the particular measurement sets needed for the analysis are discussed. Conclusion Control volume analysis provides a framework to guide the type and location of measurements and also a way to interpret the resulting data within a fundamental fluid physics analysis.
Fluid Mechanics of Fish Swimming
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 14; Issue 1. Fluid Mechanics of Fish Swimming - Lift-based Propulsion. Jaywant H Arakeri. General Article Volume 14 Issue 1 January 2009 pp 32-46. Fulltext. Click here to view fulltext PDF. Permanent link:
Theoretical aspects of fracture mechanics
Atkinson, C.; Craster, R. V.
1995-03-01
In this review we try to cover various topics in fracture mechanics in which mathematical analysis can be used both to aid numerical methods and cast light on key features of the stress field. The dominant singular near crack tip stress field can often be parametrized in terms of three parameters K(sub I), K(sub II) and K(sub III) designating three fracture modes each having an angular variation entirely specified for the stress tensor and displacement vector. These results and contact zone models for removing the interpenetration anomaly are described. Generalizations of the above results to viscoelastic media are described. For homogeneous media with constant Poisson's ratio the angular variation of singular crack tip stresses and displacements are shown to be the same for all time and the same inverse square root singularity as occurs in the elastic medium case is found (this being true for a time varying Poisson ratio too). Only the stress intensity factor varies through time dependence of loads and relaxation properties of the medium. For cracks against bimaterial interfaces both the stress singularity and angular form evolve with time as a function of the time dependent properties of the bimaterial. Similar behavior is identified for sharp notches in viscoelastic plates. The near crack tip behavior in material with non-linear stress strain laws is also identified and stress singularities classified in terms of the hardening exponent for power law hardening materials. Again for interface cracks the near crack tip behavior requires careful analysis and it is shown that more than one singular term may be present in the near crack tip stress field. A variety of theory and applications is presented for inhomogeneous elastic media, coupled thermoelasticity etc. Methods based on reciprocal theorems and dual functions which can also aid in getting awkward singular stress behavior from numerical solutions are also reviewed. Finally theoretical calculations of fiber
Finite element computational fluid mechanics
International Nuclear Information System (INIS)
Baker, A.J.
1983-01-01
This book analyzes finite element theory as applied to computational fluid mechanics. It includes a chapter on using the heat conduction equation to expose the essence of finite element theory, including higher-order accuracy and convergence in a common knowledge framework. Another chapter generalizes the algorithm to extend application to the nonlinearity of the Navier-Stokes equations. Other chapters are concerned with the analysis of a specific fluids mechanics problem class, including theory and applications. Some of the topics covered include finite element theory for linear mechanics; potential flow; weighted residuals/galerkin finite element theory; inviscid and convection dominated flows; boundary layers; parabolic three-dimensional flows; and viscous and rotational flows
Fluid Mechanics and Homeland Security
Settles, Gary S.
2006-01-01
Homeland security involves many applications of fluid mechanics and offers many opportunities for research and development. This review explores a wide selection of fluids topics in counterterrorism and suggests future directions. Broad topics range from preparedness and deterrence of impending terrorist attacks to detection, response, and recovery. Specific topics include aircraft hardening, blast mitigation, sensors and sampling, explosive detection, microfluidics and labs-on-a-chip, chemical plume dispersal in urban settings, and building ventilation. Also discussed are vapor plumes and standoff detection, nonlethal weapons, airborne disease spread, personal protective equipment, and decontamination. Involvement in these applications requires fluid dynamicists to think across the traditional boundaries of the field and to work with related disciplines, especially chemistry, biology, aerosol science, and atmospheric science.
Fluid Mechanics and Fluid Power (FMFP)
Indian Academy of Sciences (India)
Amitabh Bhattacharya
of renewable energy (e.g., via wind, hydrokinetic generators), creating low-cost healthcare ... multiphase flow, turbulence, bio-fluid dynamics, atmospheric flows, microfluidic flows, and ... study the challenging problem of entry of solids in water.
Computational modelling in fluid mechanics
International Nuclear Information System (INIS)
Hauguel, A.
1985-01-01
The modelling of the greatest part of environmental or industrial flow problems gives very similar types of equations. The considerable increase in computing capacity over the last ten years consequently allowed numerical models of growing complexity to be processed. The varied group of computer codes presented are now a complementary tool of experimental facilities to achieve studies in the field of fluid mechanics. Several codes applied in the nuclear field (reactors, cooling towers, exchangers, plumes...) are presented among others [fr
Fluid mechanics of environmental interfaces
Gualtieri, Carlo
2008-01-01
Fluid Mechanics of Environmental Interfaces describes the concept of the environmental interface, defined as a surface between two either abiotic or biotic systems. These are in relative motion and exchange mass, heat and momentum through biophysical and/or chemical processes. These processes are fluctuating temporally and spatially.The book will be of interest to graduate students, PhD students as well as researchers in environmental sciences, civil engineering and environmental engineering, (geo)physics and applied mathematics.
Finite approximations in fluid mechanics
International Nuclear Information System (INIS)
Hirschel, E.H.
1986-01-01
This book contains twenty papers on work which was conducted between 1983 and 1985 in the Priority Research Program ''Finite Approximations in Fluid Mechanics'' of the German Research Society (Deutsche Forschungsgemeinschaft). Scientists from numerical mathematics, fluid mechanics, and aerodynamics present their research on boundary-element methods, factorization methods, higher-order panel methods, multigrid methods for elliptical and parabolic problems, two-step schemes for the Euler equations, etc. Applications are made to channel flows, gas dynamical problems, large eddy simulation of turbulence, non-Newtonian flow, turbomachine flow, zonal solutions for viscous flow problems, etc. The contents include: multigrid methods for problems from fluid dynamics, development of a 2D-Transonic Potential Flow Solver; a boundary element spectral method for nonstationary viscous flows in 3 dimensions; navier-stokes computations of two-dimensional laminar flows in a channel with a backward facing step; calculations and experimental investigations of the laminar unsteady flow in a pipe expansion; calculation of the flow-field caused by shock wave and deflagration interaction; a multi-level discretization and solution method for potential flow problems in three dimensions; solutions of the conservation equations with the approximate factorization method; inviscid and viscous flow through rotating meridional contours; zonal solutions for viscous flow problems
Theoretical physics 2 analytical mechanics
Nolting, Wolfgang
2016-01-01
This textbook offers a clear and comprehensive introduction to analytical mechanics, one of the core components of undergraduate physics courses.It follows on naturally from the previous volumes in this series, thus expanding the knowledge in classical mechanics. The book starts with a thorough introduction into Lagrangian mechanics, detailing the d’Alembert principle, Hamilton’s principle and conservation laws. It continues with an in-depth explanation of Hamiltonian mechanics, illustrated by canonical and Legendre transformation, the generalization to quantum mechanics through Poisson brackets and all relevant variational principles. Finally, the Hamilton-Jacobi theory and the transition to wave mechanics are presented in detail. Ideally suited to undergraduate students with some grounding in classical mechanics, the book is enhanced throughout with learning features such as boxed inserts and chapter summaries, with key mathematical derivations highlighted to aid understanding. The text is supported by ...
Selected topics of fluid mechanics
Kindsvater, Carl E.
1958-01-01
The fundamental equations of fluid mechanics are specific expressions of the principles of motion which are ascribed to Isaac Newton. Thus, the equations which form the framework of applied fluid mechanics or hydraulics are, in addition to the equation of continuity, the Newtonian equations of energy and momentum. These basic relationships are also the foundations of river hydraulics. The fundamental equations are developed in this report with sufficient rigor to support critical examinations of their applicability to most problems met by hydraulic engineers of the Water Resources Division of the United States Geological Survey. Physical concepts are emphasized, and mathematical procedures are the simplest consistent with the specific requirements of the derivations. In lieu of numerical examples, analogies, and alternative procedures, this treatment stresses a brief methodical exposition of the essential principles. An important objective of this report is to prepare the user to read the literature of the science. Thus, it begins With a basic vocabulary of technical symbols, terms, and concepts. Throughout, emphasis is placed on the language of modern fluid mechanics as it pertains to hydraulic engineering. The basic differential and integral equations of simple fluid motion are derived, and these equations are, in turn, used to describe the essential characteristics of hydrostatics and piezometry. The one-dimensional equations of continuity and motion are defined and are used to derive the general discharge equation. The flow net is described as a means of demonstrating significant characteristics of two-dimensional irrotational flow patterns. A typical flow net is examined in detail. The influence of fluid viscosity is described as an obstacle to the derivation of general, integral equations of motion. It is observed that the part played by viscosity is one which is usually dependent on experimental evaluation. It follows that the dimensionless ratios known as
Theoretical investigation of the extinction coefficient of magnetic fluid
Energy Technology Data Exchange (ETDEWEB)
Fang Xiaopeng; Xuan Yimin, E-mail: ymxuan@mail.njust.edu.cn; Li Qiang [Nanjing University of Science and Technology, School of Energy and Power Engineering (China)
2013-05-15
A new theoretical approach for calculating the extinction coefficient of magnetic fluid is proposed, which is based on molecular dynamics (MD) simulation and T-matrix method. By means of this approach, the influence of particle diameter, particle volume fraction, and external magnetic filed on the extinction coefficient of magnetic fluid is investigated. The results show that the extinction coefficient of the magnetic fluid linearly increases with increase in the particle volume fraction. For a given particle volume fraction, the extinction coefficient increases with increase in the particle diameter which varies from 5 to 20 nm. When a uniform external magnetic filed is applied to the magnetic fluid, the extinction coefficient of the magnetic fluid presents an anisotropic feature. These results agree well with the reported experimental results. The proposed approach is applicable to investigating the optical properties of magnetic fluids.
Annual review of fluid mechanics. Volume 15
International Nuclear Information System (INIS)
Van Dyke, M.; Wehausen, J.V.; Lumley, J.L.
1983-01-01
A survey of experimental results and analytical techniques for modelling various flows and the behavior of flows around flown-driven machinery is presented. Attention is given to analytical models for wind flows and power extraction by horizontal axis wind turbines. The phenomena occurring in the impact of compressible fluids with a solid body are described, as are the instabilities, pattern formation, and turbulence in flames. Homogeneous turbulence is explored, theories for autorotation by falling bodies are discussed, and attention is devoted to theoretical models for magneto-atmospheric waves and their presence in solar activity. The design characteristics of low Reynolds number airfoils are explored, and numerical and fluid mechanics formulations for integrable, chaotic, and turbulent vortex motion in two-dimensional flows are reviewed. Finally, measurements and models of turbulent wall jets for engineering purposes are examined
Fluid mechanics. 5. enlarged ed.
International Nuclear Information System (INIS)
Kalide, W.
1980-01-01
Originally written for students in the field of engineering, this book may also be of use in the engineering practice. The subject is presented with a view to practice. Fundamental theorems of fluid mechanics are presented without going too much into theory. The chapter on supersonic flow has been extended in the fifth edition as this is a field of great importance in engineering. The new chapter on gas dynamics takes account of these processes in turbine and compressure construction and aeronautical engineering. There is an appendix with material data, characteristic values, flow resistance coefficients, diagrams and two tables with rated pressure loss values for pipeline flow. (orig./GL)
Nonlinear mechanics a supplement to theoretical mechanics of particles and continua
Fetter, Alexander L
2006-01-01
In their prior Dover book, Theoretical Mechanics of Particles and Continua, Alexander L. Fetter and John Dirk Walecka provided a lucid and self-contained account of classical mechanics, together with appropriate mathematical methods. This supplement-an update of that volume-offers a bridge to contemporary mechanics.The original book's focus on continuum mechanics-with chapters on sound waves in fluids, surface waves on fluids, heat conduction, and viscous fluids-forms the basis for this supplement's discussion of nonlinear continuous systems. Topics include linearized stability analysis; a det
Solving problems in fluid mechanics. Vol. 1
International Nuclear Information System (INIS)
Douglas, J.F.
1986-01-01
Fluid mechanics is that part of applied mechanics concerned with the statics and dynamics of liquids and gases. The presentation is in a pedagogically sound question-and-answer format, which includes many worked examples preceding the exercises. This book which assumes only an elementary knowledge of mathematics and mechanics, offers a clear exposition of topics including hydrostatics, fluid pressure and the stability of floating bodies, fluid motion, flow measurement, pipelines, open channel flow, and fluid friction
FOREWORD Fluid Mechanics and Fluid Power (FMFP)
Indian Academy of Sciences (India)
journal for their enthusiastic help. The articles contained in this section of the Special Issue represent diversity and content. We hope that the readers are stimulated by the choice of the articles and their presentation. May 2015. AMIT AGRAWAL. Department of Mechanical Engineering,. Indian Institute of Technology Bombay ...
Development of a theoretical framework for analyzing cerebrospinal fluid dynamics
DEFF Research Database (Denmark)
Cohen, Benjamin; Voorhees, Abram; Vedel, Søren
2009-01-01
Background: To date hydrocephalus researchers acknowledge the need for rigorous but utilitarian fluid mechanics understanding and methodologies in studying normal and hydrocephalic intracranial dynamics. Pressure volume models and electric circuit analogs introduced pressure into volume conservat...
Fluid mechanics of environmental interfaces
Gualtieri, Carlo
2012-01-01
Preface Preface of the first editionBiographies of the authors Part one - Preliminaries1. Environmental fluid mechanics: Current issues and future outlook B. Cushman-Roisin, C. Gualtieri & D.T. MihailovicPart two - Processes at atmospheric interfaces2. Point source atmospheric diffusionB. Rajkovic, I. Arsenic & Z. Grsic3. Air-sea interaction V. Djurdjevic & B. Rajkovic4. Modelling of flux exchanges between heterogeneous surfaces and atmosphere D.T. Mihailovic & D. Kapor5. Desert dust uptake-transport and deposition mechanisms - impacts of dust on radiation, clouds and precipitation G. Kallos, P. Katsafados & C. SpyrouPart three - Processes at water interfaces6. Gas-transfer at unsheared free-surfaces C. Gualtieri & G. Pulci Doria7. Advective diffusion of air bubbles in turbulent water flows H. Chanson8. Exchanges at the bed sediments-water column interface F.A. Bombardelli & P.A. Moreno9. Surface water and streambed sediment interaction: The hyporheic exchange D. Tonina10. Environm...
Problems in Microgravity Fluid Mechanics: G-Jitter Convection
Homsy, G. M.
2005-01-01
This is the final report on our NASA grant, Problems in Microgravity Fluid Mechanics NAG3-2513: 12/14/2000 - 11/30/2003, extended through 11/30/2004. This grant was made to Stanford University and then transferred to the University of California at Santa Barbara when the PI relocated there in January 2001. Our main activity has been to conduct both experimental and theoretical studies of instabilities in fluids that are relevant to the microgravity environment, i.e. those that do not involve the action of buoyancy due to a steady gravitational field. Full details of the work accomplished under this grant are given below. Our work has focused on: (i) Theoretical and computational studies of the effect of g-jitter on instabilities of convective states where the convection is driven by forces other than buoyancy (ii) Experimental studies of instabilities during displacements of miscible fluid pairs in tubes, with a focus on the degree to which these mimic those found in immiscible fluids. (iii) Theoretical and experimental studies of the effect of time dependent electrohydrodynamic forces on chaotic advection in drops immersed in a second dielectric liquid. Our objectives are to acquire insight and understanding into microgravity fluid mechanics problems that bear on either fundamental issues or applications in fluid physics. We are interested in the response of fluids to either a fluctuating acceleration environment or to forces other than gravity that cause fluid mixing and convection. We have been active in several general areas.
Theoretical and quantum mechanics fundamentals for chemists
Ivanov, Stefan
2006-01-01
Provides the basics of theoretical and quantum mechanics in one place and emphasizes the continuity between themUniquely presented to be used for self-taught courses covering theoretical and quantum mechanicsEach chapter includes a detailed outline, a summary, self-assessment questions for which answers can be found in the textInvaluable for chemistry undergraduate and graduate students, chemists, other non-physical scientists, engineering students of modern techniques and technology, specialists who need a better understanding of quantum mechanics.
Proceedings of industrial applications of fluid mechanics
International Nuclear Information System (INIS)
Sherif, S.A.; Morrow, T.B.; Marshall, L.R.; Dalton, C.
1990-01-01
The is the fourth Forum on Industrial Applications of Fluid Mechanics sponsored by the Fluid Mechanics Committee of the ASME Fluids Engineering Division. The Forum objective is to promote the discussion and interchange of current information on developing and state-of-the-art applications of fluid mechanics technology. The program is organized as a technical forum to encourage the presentation of new ideas, especially those which may be so innovative that a conservative review process might delay their dissemination to the fluids engineering community. Four sessions and a total of 17 papers are scheduled for this program. Three of the four sessions were devoted to contributed papers, while the fourth is a panel discussion with three invited presentations. All papers were reviewed editorially to assure that they are related to the forum theme The papers were not evaluated technically, and therefore carry no endorsement from the Fluid Mechanics Committee or the Fluids Engineering Division with regard to peer evaluation. The forum presentations will focus on specific applications of fluid mechanics technology. Lively discussion of the papers is encouraged at the forum. The Fluid Mechanics Committee plans to sponsor a forum with an industrial applications theme each year at the ASME Winter Annual Meeting. In 1991, the scope of the forum will be enlarged to include the topic of textile applications of fluid mechanics, and another panel session featuring speakers with industrial experience in different areas of fluid mechanics applications. In future years, it is anticipated that the forum will solicit papers from other areas where fluid mechanics technology is applied
NASA Ames Fluid Mechanics Laboratory research briefs
Davis, Sanford (Editor)
1994-01-01
The Ames Fluid Mechanics Laboratory research program is presented in a series of research briefs. Nineteen projects covering aeronautical fluid mechanics and related areas are discussed and augmented with the publication and presentation output of the Branch for the period 1990-1993.
Elements of theoretical mechanics for electronic engineers
Bultot, Franz
1965-01-01
Elements of Theoretical Mechanics for Electronic Engineers deals with theoretical mechanics, which is considered one of the fundamental branches of instruction essential to training an engineer. This book discusses the oscillatory motions and their counterparts in electrical circuits and radio, and provides an introduction to differential operators of vector field theory. Other topics covered include systems and functions of vectors; dynamics of a free point; vibrations and waves; and statics. Worked examples and many notes on the application of most sections of the theories to electrical deve
On the fluid mechanics of bilabial plosives
Pelorson, X.; Hofmans, G.C.J.; Ranucci, M.; Bosch, R.C.M.
1997-01-01
In this paper we present a review of some fluid mechanical phenomena involved in bilabial plosive sound production. As a basis for further discussion, firstly an in vivo experimental set-up is described. The order of magnitude of some important geometrical and fluid dynamical quantities is
XXII Fluid Mechanics Conference (KKMP2016)
International Nuclear Information System (INIS)
2016-01-01
This Journal of Physics: Conference Series contains papers that have been presented at XXII Fluid Mechanics Conference (XXII FMC) held in Słok near Bełchatów in Poland during llth-14th September of 2016. The Conference is organized by Wrocław University of Science and Technology, Polish Academy of Sciences - Committee of Mechanics and Foun-dation for Development of Wroclaw University of Science and Technology. Let us recall some historical facts: Fluid Mechanics Conferences have been taking place every two years since 1974, which makes a total of forty-two years. The goal of this conference is to provide a forum for exposure and exchange of ideas, methods and results in fluid mechanics. We have already met in Bełchatów 10 years ago (XVII KKMP). It was a successful meeting. Since then the National Conference on Fluid Mechanics has changed title and has started to be named Fluid Mechanics Conference in the hopes that it will attract more participants from other countries. English became the Conference's first language and we started to invite world leading scientists - working in the field of fluid mechanics. At the 2006 conference we hosted for the first time prof. Keith Moffatt from the Cambridge University. In this year prof. Moffatt once again promised us to arrive to Bełchatów. The whole fluid mechanics community celebrates 9 2 anniversary of his birthday. So let us also wish happy anniversary to prof. Moffatt. In the mean time we had to pay last respects to our collages. Prof. Prosnak who is regarded as a founder of the Notational Conference on Fluid Mechanics and is well known through his books. Prof. Puzyrewski who was present at all conferences so far. He was providing via his discussions a special value to these conferences, and our colleague prof. Konrad Bajer who was intended to be the organizer and host of the present conference. Short memories to them will be given during the opening ceremony. Conference topics include, but are not limited
Fluid mechanics for engineers. A graduate textbook
Energy Technology Data Exchange (ETDEWEB)
Schobeiri, Meinhard T. [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering
2010-07-01
The contents of this book covers the material required in the Fluid Mechanics Graduate Core Course (MEEN-621) and in Advanced Fluid Mechanics, a Ph.D-level elective course (MEEN-622), both of which I have been teaching at Texas A and M University for the past two decades. While there are numerous undergraduate fluid mechanics texts on the market for engineering students and instructors to choose from, there are only limited texts that comprehensively address the particular needs of graduate engineering fluid mechanics courses. To complement the lecture materials, the instructors more often recommend several texts, each of which treats special topics of fluid mechanics. This circumstance and the need to have a textbook that covers the materials needed in the above courses gave the impetus to provide the graduate engineering community with a coherent textbook that comprehensively addresses their needs for an advanced fluid mechanics text. Although this text book is primarily aimed at mechanical engineering students, it is equally suitable for aerospace engineering, civil engineering, other engineering disciplines, and especially those practicing professionals who perform CFD-simulation on a routine basis and would like to know more about the underlying physics of the commercial codes they use. Furthermore, it is suitable for self study, provided that the reader has a sufficient knowledge of calculus and differential equations. (orig.)
Shocks, singularities and oscillations in nonlinear optics and fluid mechanics
Santo, Daniele; Lannes, David
2017-01-01
The book collects the most relevant results from the INdAM Workshop "Shocks, Singularities and Oscillations in Nonlinear Optics and Fluid Mechanics" held in Rome, September 14-18, 2015. The contributions discuss recent major advances in the study of nonlinear hyperbolic systems, addressing general theoretical issues such as symmetrizability, singularities, low regularity or dispersive perturbations. It also investigates several physical phenomena where such systems are relevant, such as nonlinear optics, shock theory (stability, relaxation) and fluid mechanics (boundary layers, water waves, Euler equations, geophysical flows, etc.). It is a valuable resource for researchers in these fields. .
Fluid Mechanics An Introduction to the Theory of Fluid Flows
Durst, Franz
2008-01-01
Advancements of fluid flow measuring techniques and of computational methods have led to new ways to treat laminar and turbulent flows. These methods are extensively used these days in research and engineering practise. This also requires new ways to teach the subject to students at higher educational institutions in an introductory manner. The book provides the knowledge to students in engineering and natural science needed to enter fluid mechanics applications in various fields. Analytical treatments are provided, based on the Navier-Stokes equations. Introductions are also given into numerical and experimental methods applied to flows. The main benefit the reader will derive from the book is a sound introduction into all aspects of fluid mechanics covering all relevant subfields.
Mechanics of couple-stress fluid coatings
Waxman, A. M.
1982-01-01
The formal development of a theory of viscoelastic surface fluids with bending resistance - their kinematics, dynamics, and rheology are discussed. It is relevant to the mechanics of fluid drops and jets coated by a thin layer of immiscible fluid with rather general rheology. This approach unifies the hydrodynamics of two-dimensional fluids with the mechanics of an elastic shell in the spirit of a Cosserat continuum. There are three distinct facets to the formulation of surface continuum mechanics. Outlined are the important ideas and results associated with each: the kinematics of evolving surface geometries, the conservation laws governing the mechanics of surface continua, and the rheological equations of state governing the surface stress and moment tensors.
A Course in Fluid Mechanics of Suspensions.
Davis, Robert H.
1989-01-01
Discusses a course focusing on fluid mechanics and physical chemistry of suspensions. Describes the main themes of the lectures and includes a list of course outlines. Possible textbooks and many journal articles are listed. (YP)
Semiclassical statistical mechanics of fluids
International Nuclear Information System (INIS)
Singh, Y.; Sinha, S.K.
1981-01-01
The problem of calculating the equilibrium properties of fluids in the semiclassical limit when the quantum effects are small is studied. Particle distribution functions and thermodynamic quantities are defined in terms of the Slater sum and methods for evaluating the Slater sum are discussed. It is shown that the expansion method employing the usual Wigner-Kirkwood or Hemmer-Jancovici series is not suitable to treat the properties of the condensed state. Using the grand canonical ensemble and functional differentiation technique we develop cluster expansion series of the Helmholtz free energy and pair correlation functions. Using topological reduction we transform these series to more compact form involving a renormalized potential or a renormalized Mayer function. Then the convergence of the two series is improved by an optimal choice of the renormalized potential or the Mayer function. Integral equation theories are derived and used to devise perturbation methods. An application of these methods to the calculation of the virial coefficients, thermodynamic properties and the pair correlation function for model fluids is discussed. (orig.)
Dissipative fluid mechanics of nuclei
International Nuclear Information System (INIS)
Morgenstern, B.
1987-11-01
With the aim to describe nucleus-nucleus collisions at low energies in the present thesis for the first time dissipative fluid dynamics for large-amplitude nuclear motion have been formulated. Thereby the collective dynamics are described in a scaling approximation in which the wave function of the system is distorted by a vortex-free velocity field. For infintely extended nuclear matter this scaling of the wave functions leads to a deformation of the Fermi sphere. Two-body collisions destroy the collective deformation of the Fermi sphere and yield so the dissipative contribution of the motion. Equations of motion for a finite set of collective variables and a field equation for the collective velocity potential in the limit of infinitely many degrees of freedom were developed. In the elastic limit oscillations around the equilibrium position are described. For small collective amplitudes and vortex-free velocity fields the integrodifferential equation for the velocity potential in the elastic limit could be transformed to the divergence of the field equation of fluid dynamics. In the dissipative limit an equation results which is similar to the Navier-Stokes equation and transforms to the divergence of the Navier-Stokes equation for vortex-free fields. It was shown that generally the dynamics of the many-body system is described by non-Markovian equations. (orig./HSI) [de
On the fluid mechanics of fires
Energy Technology Data Exchange (ETDEWEB)
TIESZEN,SHELDON R.
2000-02-29
Fluid mechanics research related to fire is reviewed with focus on canonical flows, multiphysics coupling aspects, experimental and numerical techniques. Fire is a low-speed, chemically-reacting, flow in which buoyancy plans an important role. Fire research has focused on two canonical flows, the reacting boundary-layer and the reacting free plume. There is rich, multi-lateral, bi-directional, coupling among fluid mechanics and scalar transport, combustion, and radiation. There is only a limited experimental fluid-mechanics database for fire due to measurement difficulties in the harsh environment, and the focus within the fire community on thermal/chemical consequences. Increasingly, computational fluid dynamics techniques are being used to provide engineering guidance on thermal/chemical consequences and to study fire phenomenology.
Fluid Mechanics of Urban Environments
Fernando, Harindra J.
2008-11-01
The rapid urbanization of the Earth has led to highly populated cities that act as concentrated centers of anthropogenic stressors on the natural environment. The degradation of environmental quality due to such stressors, in turn, greatly impacts human behavior. Anthropogenic stressors largely originate as a result of coupling between man-made urban elements (i.e., networks of engineering and socio-economic infrastructures) and the environment, for which surrounding fluid motions play a key role. In recent years, research efforts have been directed at the understanding and modeling of fluid motions in urban areas, infrastructure dynamics and interactions thereof, with the hope of identifying environmental impacts of urbanization and complex outcomes (or ``emergent properties'') of nominally simple interactions between infrastructures and environment. Such consequences play an important role in determining the ``resilience'' of cities under anthropogenic stressors, defined as maintaining the structure and essential functions of an urbanity without regime shifts. Holistic integrated models that meld the dynamics of infrastructures and environment as well as ``quality of life'' attributes are becoming powerful decision-making tools with regard to sustainability of urban areas (continuance or even enhancement of socio-economic activities in harmony with the environment). The rudimentary forms of integrated models are beginning to take shape, augmented by comprehensive field studies and advanced measurement platforms to validate them. This presentation deals with the challenges of modeling urban atmosphere, subject to anthropogenic forcing. An important emergent property, the Urban Heat Island, and its role in determining resilience and sustainability of cities will be discussed based on the prediction of a coupled model.
The fluid mechanics of natural ventilation
Linden, Paul
1999-11-01
Natural ventilation of buildings is the flow generated by temperature differences and by the wind. Modern buildings have extreme designs with large, tall open plan spaces and large cooling requirements. Natural ventilation offers a means of cooling these buildings and providing good indoor air quality. The essential feature of ventilation is an exchange between an interior space and the external ambient. Recent work shows that in many circumstances temperature variations play a controlling feature on the ventilation since the directional buoyancy force has a large influence on the flow patterns within the space and on the nature of the exchange with the outside. Two forms of buoyancy-driven ventilation are discussed: mixing ventilation in which the interior is at approximately uniform temperature and displacement ventilation where there is strong internal stratification. The dynamics of these flows are considered and the effects of wind on them are examined both experimentally and theoretically. The aim behind this work is to give designers rules and intuition on how air moves within a building and the research shows a fascinating branch of fluid mechanics.
[Research advances of fluid bio-mechanics in bone].
Chen, Zebin; Huo, Bo
2017-04-01
It has been found for more than one century that when experiencing mechanical loading, the structure of bone will adapt to the changing mechanical environment, which is called bone remodeling. Bone remodeling is charaterized as two processes of bone formation and bone resorption. A large number of studies have confirmed that the shear stress is resulted from interstitial fluid flow within bone cavities under mechanical loading and it is the key factor of stimulating the biological responses of bone cells. This review summarizes the major research progress during the past years, including the biological response of bone cells under fluid flow, the pressure within bone cavities, the theoretical modeling, numerical simulation and experiments about fluid flow within bone, and finally analyzes and predicts the possible tendency in this field in the future.
Theoretical physics 6 quantum mechanics : basics
Nolting, Wolfgang
2017-01-01
This textbook offers a clear and comprehensive introduction to the basics of quantum mechanics, one of the core components of undergraduate physics courses. It follows on naturally from the previous volumes in this series, thus developing the physical understanding further on to quantized states. The first part of the book introduces wave equations while exploring the Schrödinger equation and the hydrogen atom. More complex themes are covered in the second part of the book, which describes the Dirac formulism of quantum mechanics. Ideally suited to undergraduate students with some grounding in classical mechanics and electrodynamics, the book is enhanced throughout with learning features such as boxed inserts and chapter summaries, with key mathematical derivations highlighted to aid understanding. The text is supported by numerous worked examples and end of chapter problem sets. About the Theoretical Physics series Translated from the renowned and highly successful German editions, the eight volumes of this...
Topology optimization of fluid mechanics problems
DEFF Research Database (Denmark)
Gersborg-Hansen, Allan
While topology optimization for solid continuum structures have been studied for about 20 years and for the special case of trusses for many more years, topology optimization of fluid mechanics problems is more recent. Borrvall and Petersson [1] is the seminal reference for topology optimization......D Navier-Stokes equation as well as an example with convection dominated transport in 2D Stokes flow. Using Stokes flow limits the range of applications; nonetheless, the present work gives a proof-of-concept for the application of the method within fluid mechanics problems and it remains...... processing tool. Prior to design manufacturing this allows the engineer to quantify the performance of the computed topology design using standard, credible analysis tools with a body-fitted mesh. [1] Borrvall and Petersson (2003) "Topology optimization of fluids in Stokes flow", Int. J. Num. Meth. Fluids...
Fluid Mechanics of Blood Clot Formation.
Fogelson, Aaron L; Neeves, Keith B
2015-01-01
Intravascular blood clots form in an environment in which hydrodynamic forces dominate and in which fluid-mediated transport is the primary means of moving material. The clotting system has evolved to exploit fluid dynamic mechanisms and to overcome fluid dynamic challenges to ensure that clots that preserve vascular integrity can form over the wide range of flow conditions found in the circulation. Fluid-mediated interactions between the many large deformable red blood cells and the few small rigid platelets lead to high platelet concentrations near vessel walls where platelets contribute to clotting. Receptor-ligand pairs with diverse kinetic and mechanical characteristics work synergistically to arrest rapidly flowing cells on an injured vessel. Variations in hydrodynamic stresses switch on and off the function of key clotting polymers. Protein transport to, from, and within a developing clot determines whether and how fast it grows. We review ongoing experimental and modeling research to understand these and related phenomena.
An introduction to the mechanics of fluids
Truesdell, C
2000-01-01
The authors have backgrounds which are ideally suited for writing this book. The late C. Truesdell is well known for his monumental treatises on continuum thermomechanics. K.R. Rajagopal has made many important contributions to the mechanics of continua in general, and to nonlinear fluids in particular. They have produced a compact, moderately general book which encompasses many fluid models of current interest…The book is written very clearly and contains a large number of exercises and their solutions. The level of mathematics is that commonly taught to undergraduates in mathematics departments. This is an excellent book which is highly recommended to students and researchers in fluid mechanics. —Mathematical Reviews The writing style is quintessential Truesdellania: purely mathematical, breathtaking, irrepressible, irreverent, uncompromising, taking no prisoners...The book is filled with historical nuggets…Its pure, exact mathematics will baptize, enlighten and exhilarate. —Applied Mechanics Review...
Topological fluid mechanics of Axisymmetric Flow
DEFF Research Database (Denmark)
Brøns, Morten
1998-01-01
Topological fluid mechanics in the sense of the present paper is the study and classification of flow patterns close to a critical point. Here we discuss the topology of steady viscous incompressible axisymmetric flows in the vicinity of the axis. Following previous studies the velocity field v...... to the authors knowledge has not been used systematically to high orders in topological fluid mechanics. We compare the general results with experimental and computational results on the Vogel-Ronneberg flow. We show that the topology changes observed when recirculating bubbles on the vortex axis are created...
Theoretical mechanics an introduction to mathematical physics
Sweetman Ames, Joseph
1958-01-01
In this book Professors Ames and Murnaghan undertake a mathematically rigorous development of theoretical mechanics from the point of view of modern physics. It gives an intensive survey of this basis field with extensive and extremely thorough discussions of vector and tensor methods, the displacement and motion of a rigid body, dynamics of inertial and non-inertial reference frames, dynamics of a particle, harmonic vibrations, nonrectilinear motion of a particle, central forces and universal gravitation, dynamics of a systems of material particle,impulsive forces, motion of a rigid body about a fixed point, gyroscopic and barygyroscopic theory, general dynamical theorems, vibrations about a point of equilibrium, the principle of least action, holonomic and nonholonomic systems, the principle of least constraint, general methods of integration and the three body problem, the potential function (including simple-layer and double-layer potentials), wave motion, the Lorentz-Einstein transformation and an illumi...
Introductory fluid mechanics for physicists and mathematicians
Pert, Geoffrey J
2013-01-01
This textbook presents essential methodology for physicists of the theory and applications of fluid mechanics within a single volume. Building steadily through a syllabus, it will be relevant to almost all undergraduate physics degrees which include an option on hydrodynamics, or a course in which hydrodynamics figures prominently.
Isogeometric shape optimization in fluid mechanics
DEFF Research Database (Denmark)
Nørtoft, Peter; Gravesen, Jens
2013-01-01
The subject of this work is numerical shape optimization in fluid mechanics, based on isogeometric analysis. The generic goal is to design the shape of a 2-dimensional flow domain to minimize some prescribed objective while satisfying given geometric constraints. As part of the design problem...
Neural Control Mechanisms and Body Fluid Homeostasis
Johnson, Alan Kim
1998-01-01
The goal of the proposed research was to study the nature of afferent signals to the brain that reflect the status of body fluid balance and to investigate the central neural mechanisms that process this information for the activation of response systems which restore body fluid homeostasis. That is, in the face of loss of fluids from intracellular or extracellular fluid compartments, animals seek and ingest water and ionic solutions (particularly Na(+) solutions) to restore the intracellular and extracellular spaces. Over recent years, our laboratory has generated a substantial body of information indicating that: (1) a fall in systemic arterial pressure facilitates the ingestion of rehydrating solutions and (2) that the actions of brain amine systems (e.g., norepinephrine; serotonin) are critical for precise correction of fluid losses. Because both acute and chronic dehydration are associated with physiological stresses, such as exercise and sustained exposure to microgravity, the present research will aid in achieving a better understanding of how vital information is handled by the nervous system for maintenance of the body's fluid matrix which is critical for health and well-being.
Annual review of fluid mechanics. Volume 22
International Nuclear Information System (INIS)
Lumley, J.L.; Van Dyke, M.; Reed, H.L.
1990-01-01
Topics presented include rapid granular flows, issues in viscoelastic fluid mechanics, wave loads on offshore structures, boundary layers in the general ocean circulation, parametrically forced surface waves, wave-mean flow interactions in the equatorial ocean, and local and global instabilities in spatially developing flows. Also presented are aerodynamics of human-powered flight, aerothermodynamics and transition in high-speed wind tunnels at NASA-Langley, wakes behind blunt bodies, and mixing, chaotic advection, and turbulence. Also addressed are the history of the Reynolds number, panel methods in computational fluid dynamics, numerical multipole and boundary integral equation techniques in Stokes flow, plasma turbulence, optical rheometry, and viscous-flow paradoxes
Computational fluid mechanics and heat transfer
Pletcher, Richard H; Anderson, Dale
2012-01-01
""I have always considered this book the best gift from one generation to the next in computational fluid dynamics. I earnestly recommend this book to graduate students and practicing engineers for the pleasure of learning and a handy reference. The description of the basic concepts and fundamentals is thorough and is crystal clear for understanding. And since 1984, two newer editions have kept abreast to the new, relevant, and fully verified advancements in CFD.""-Joseph J.S. Shang, Wright State University""Computational Fluid Mechanics and Heat Transfer is very well written to be used as a t
Handbook of mathematical analysis in mechanics of viscous fluids
Novotný, Antonín
2018-01-01
Mathematics has always played a key role for researches in fluid mechanics. The purpose of this handbook is to give an overview of items that are key to handling problems in fluid mechanics. Since the field of fluid mechanics is huge, it is almost impossible to cover many topics. In this handbook, we focus on mathematical analysis on viscous Newtonian fluid. The first part is devoted to mathematical analysis on incompressible fluids while part 2 is devoted to compressible fluids.
Interfacial Fluid Mechanics A Mathematical Modeling Approach
Ajaev, Vladimir S
2012-01-01
Interfacial Fluid Mechanics: A Mathematical Modeling Approach provides an introduction to mathematical models of viscous flow used in rapidly developing fields of microfluidics and microscale heat transfer. The basic physical effects are first introduced in the context of simple configurations and their relative importance in typical microscale applications is discussed. Then,several configurations of importance to microfluidics, most notably thin films/droplets on substrates and confined bubbles, are discussed in detail. Topics from current research on electrokinetic phenomena, liquid flow near structured solid surfaces, evaporation/condensation, and surfactant phenomena are discussed in the later chapters. This book also: Discusses mathematical models in the context of actual applications such as electrowetting Includes unique material on fluid flow near structured surfaces and phase change phenomena Shows readers how to solve modeling problems related to microscale multiphase flows Interfacial Fluid Me...
2014-01-01
This collection of 23 articles is the output of lectures in special sessions on “The History of Theoretical, Material and Computational Mechanics” within the yearly conferences of the GAMM in the years 2010 in Karlsruhe, Germany, 2011 in Graz, Austria, and in 2012 in Darmstadt, Germany; GAMM is the “Association for Applied Mathematics and Mechanics”, founded in 1922 by Ludwig Prandtl and Richard von Mises. The contributions in this volume discuss different aspects of mechanics. They are related to solid and fluid mechanics in general and to specific problems in these areas including the development of numerical solution techniques. In the first part the origins and developments of conservation principles in mechanics and related variational methods are treated together with challenging applications from the 17th to the 20th century. Part II treats general and more specific aspects of material theories of deforming solid continua and porous soils. and Part III presents important theoretical and enginee...
Salomone, Horacio D.; Olivieri, Néstor A.; Véliz, Maximiliano E.; Raviola, Lisandro A.
2018-05-01
In the context of fluid mechanics courses, it is customary to consider the problem of a sphere falling under the action of gravity inside a viscous fluid. Under suitable assumptions, this phenomenon can be modelled using Stokes’ law and is routinely reproduced in teaching laboratories to determine terminal velocities and fluid viscosities. In many cases, however, the measured physical quantities show important deviations with respect to the predictions deduced from the simple Stokes’ model, and the causes of these apparent ‘anomalies’ (for example, whether the flow is laminar or turbulent) are seldom discussed in the classroom. On the other hand, there are various variable-mass problems that students tackle during elementary mechanics courses and which are discussed in many textbooks. In this work, we combine both kinds of problems and analyse—both theoretically and experimentally—the evolution of a system composed of a sphere pulled by a chain of variable length inside a tube filled with water. We investigate the effects of different forces acting on the system such as weight, buoyancy, viscous friction and drag force. By means of a sequence of mathematical models of increasing complexity, we obtain a progressive fit that accounts for the experimental data. The contrast between the various models exposes the strengths and weaknessess of each one. The proposed experience can be useful for integrating concepts of elementary mechanics and fluids, and is suitable as laboratory practice, stressing the importance of the experimental validation of theoretical models and showing the model-building processes in a didactic framework.
New Directions in Mathematical Fluid Mechanics
Fursikov, Andrei V
2010-01-01
The scientific interests of Professor A.V. Kazhikhov were fundamentally devoted to Mathematical Fluid Mechanics, where he achieved outstanding results that had, and still have, a significant influence on this field. This volume, dedicated to the memory of A.V. Kazhikhov, presents the latest contributions from renowned world specialists in a number of new important directions of Mathematical Physics, mostly of Mathematical Fluid Mechanics, and, more generally, in the field of nonlinear partial differential equations. These results are mostly related to boundary value problems and to control problems for the Navier-Stokes equations, and for equations of heat convection. Other important topics include non-equilibrium processes, Poisson-Boltzmann equations, dynamics of elastic body, and related problems of function theory and nonlinear analysis.
22nd International Congress of Theoretical and Applied Mechanics
Finn, Matthew
2013-01-01
The 22nd International Congress of Theoretical and Applied Mechanics (ICTAM) of the International Union of Theoretical and Applied Mechanics was hosted by the Australasian mechanics community in the city of Adelaide during the last week of August 2008. Over 1200 delegates met to discuss the latest development in the fields of theoretical and applied mechanics. This volume records the events of the congress and contains selected papers from the sectional lectures and invited lectures presented at the congresses six mini-symposia.
Revisiting Newtonian and Non-Newtonian Fluid Mechanics Using Computer Algebra
Knight, D. G.
2006-01-01
This article illustrates how a computer algebra system, such as Maple[R], can assist in the study of theoretical fluid mechanics, for both Newtonian and non-Newtonian fluids. The continuity equation, the stress equations of motion, the Navier-Stokes equations, and various constitutive equations are treated, using a full, but straightforward,…
Experimental and theoretical studies of levitated quantum fluids
International Nuclear Information System (INIS)
Schmidt, J.; Halley, J.W.; Giese, C.F.
1998-01-01
We describe the opportunities for improved scientific understanding and technical manipulation of cryogenic fields, particularly molecular hydrogen, by the use of carefully designed magnetic field configurations produced with assemblies of permanent magnets. We discuss the levitation of hydrogen in order to perfect technical means for handling this and other cryogenic fluids. The development of the techniques to be explored here provide extraordinary opportunities for improved methods for handling rocket fuels and cryogenic fluids in low gravity environments
Theoretical aspects concerning working fluids in hydraulic systems
Directory of Open Access Journals (Sweden)
Tița Irina
2017-01-01
Full Text Available Among the properties of working fluid, viscosity is the most important as it regards especially to pumps. In order to study the behavior of hydrostatic transmission it is important to create a reliable research instrument for dynamic simulation. Our research expertise being in SimHydraulics consequently this instrument is the suitable block diagram. The purpose of this paper is to present the possible ways to customize the properties of the working fluid in the block diagram.
Basic Coandă MAV Fluid Dynamics and Flight Mechanics
Djojodihardjo, H.; Ahmed, RI
2017-04-01
Capitalizing on the basic fundamental principles, the Fluid Dynamics and Flight Mechanics of a semi-spherical Coandă MAV configurations are revisited and analyzed as a baseline. A mathematical model for a spherical Coandă MAV in hover and translatory motion is developed and analyzed from first physical principles. To gain further insight into the prevailing flow field around a Coandă MAV, as well as to verify the theoretical prediction presented in the work, a computational fluid dynamic CFD simulations for a Coandă MAV generic model are elaborated. The mathematical model and derived performance measures are shown to be capable in describing the physical phenomena of the flow field of the semi-spherical Coandă MAV. The relationships between the relevant parameters of the mathematical model of the Coandă MAV to the forces acting on it are elaborated subsequently.
Recent developments of mathematical fluid mechanics
Giga, Yoshikazu; Kozono, Hideo; Okamoto, Hisashi; Yamazaki, Masao
2016-01-01
The book addresses recent developments of the mathematical research on the Navier-Stokes and Euler equations as well as on related problems. In particular, there are covered: 1) existence, uniqueness, and the regularity of weak solutions; 2) stability of the motion in rest and the asymptotic behavior of solutions; 3) singularity and blow-up of weak and strong solutions; 4) vorticity and energy conservation; 5) motions of rotating fluids, or of fluids surrounding a rotating body; 6) free boundary problems; 7) maximal regularity theory and other abstract results for mathematical fluid mechanics. For this quarter century, these topics have been playing a central role in both pure and applied mathematics and having a great influence to the developm ent of the functional analysis, harmonic analysis and numerical analysis whose tools make a a substantial contribution to the investigation of nonlinear partial differential equations, particularly the Navier-Stokes and the Euler equations. There are 24...
Mechanical metamaterials at the theoretical limit of isotropic elastic stiffness
Berger, J. B.; Wadley, H. N. G.; McMeeking, R. M.
2017-02-01
A wide variety of high-performance applications require materials for which shape control is maintained under substantial stress, and that have minimal density. Bio-inspired hexagonal and square honeycomb structures and lattice materials based on repeating unit cells composed of webs or trusses, when made from materials of high elastic stiffness and low density, represent some of the lightest, stiffest and strongest materials available today. Recent advances in 3D printing and automated assembly have enabled such complicated material geometries to be fabricated at low (and declining) cost. These mechanical metamaterials have properties that are a function of their mesoscale geometry as well as their constituents, leading to combinations of properties that are unobtainable in solid materials; however, a material geometry that achieves the theoretical upper bounds for isotropic elasticity and strain energy storage (the Hashin-Shtrikman upper bounds) has yet to be identified. Here we evaluate the manner in which strain energy distributes under load in a representative selection of material geometries, to identify the morphological features associated with high elastic performance. Using finite-element models, supported by analytical methods, and a heuristic optimization scheme, we identify a material geometry that achieves the Hashin-Shtrikman upper bounds on isotropic elastic stiffness. Previous work has focused on truss networks and anisotropic honeycombs, neither of which can achieve this theoretical limit. We find that stiff but well distributed networks of plates are required to transfer loads efficiently between neighbouring members. The resulting low-density mechanical metamaterials have many advantageous properties: their mesoscale geometry can facilitate large crushing strains with high energy absorption, optical bandgaps and mechanically tunable acoustic bandgaps, high thermal insulation, buoyancy, and fluid storage and transport. Our relatively simple
Editorial Special Issue on Fluid Mechanics and Fluid Power (FMFP ...
Indian Academy of Sciences (India)
a shark is more efficient than a propeller; the notoriously complicated and nonlinear Navier–. Stokes equations governing fluid motion provide fertile ground for research to both applied and pure mathematicians. There is the phenomenon of turbulence in fluid flows. A statement in 1932, attributed to Horace Lamb, author of ...
Statistical mechanics and the physics of fluids
Tosi, Mario
This volume collects the lecture notes of a course on statistical mechanics, held at Scuola Normale Superiore di Pisa for third-to-fifth year students in physics and chemistry. Three main themes are covered in the book. The first part gives a compact presentation of the foundations of statistical mechanics and their connections with thermodynamics. Applications to ideal gases of material particles and of excitation quanta are followed by a brief introduction to a real classical gas and to a weakly coupled classical plasma, and by a broad overview on the three states of matter.The second part is devoted to fluctuations around equilibrium and their correlations. Coverage of liquid structure and critical phenomena is followed by a discussion of irreversible processes as exemplified by diffusive motions and by the dynamics of density and heat fluctuations. Finally, the third part is an introduction to some advanced themes: supercooling and the glassy state, non-Newtonian fluids including polymers and liquid cryst...
Potential fluid mechanic pathways of platelet activation.
Shadden, Shawn C; Hendabadi, Sahar
2013-06-01
Platelet activation is a precursor for blood clotting, which plays leading roles in many vascular complications and causes of death. Platelets can be activated by chemical or mechanical stimuli. Mechanically, platelet activation has been shown to be a function of elevated shear stress and exposure time. These contributions can be combined by considering the cumulative stress or strain on a platelet as it is transported. Here, we develop a framework for computing a hemodynamic-based activation potential that is derived from a Lagrangian integral of strain rate magnitude. We demonstrate that such a measure is generally maximized along, and near to, distinguished material surfaces in the flow. The connections between activation potential and these structures are illustrated through stenotic flow computations. We uncover two distinct structures that may explain observed thrombus formation at the apex and downstream of stenoses. More broadly, these findings suggest fundamental relationships may exist between potential fluid mechanic pathways for mechanical platelet activation and the mechanisms governing their transport.
Game Theoretic Problems in Network Economics and Mechanism Design Solutions
Narahari, Y; Narayanam, Ramasuri; Prakash, Hastagiri
2009-01-01
Explores game theoretic modeling and mechanism design for problem solving in Internet and network economics. This monograph contains an exposition of representative game theoretic problems in three different network economics situations and a systematic exploration of mechanism design solutions to these problems.
Supercritical Fluid Chromatography--Theoretical Background and Applications on Natural Products.
Hartmann, Anja; Ganzera, Markus
2015-11-01
The use of supercritical fluid chromatography for natural product analysis as well as underlying theoretical mechanisms and instrumental requirements are summarized in this review. A short introduction focusing on the historical development of this interesting separation technique is followed by remarks on the current instrumental design, also describing possible detection modes and useable stationary phases. The overview on relevant applications is grouped based on their basic intention, may it be (semi)preparative or purely analytical. They indicate that supercritical fluid chromatography is still primarily considered for the analysis of nonpolar analytes like carotenoids, fatty acids, or terpenes. The low polarity of supercritical carbon dioxide, which is used with modifiers almost exclusively as a mobile phase today, combined with high efficiency and fast separations might explain the popularity of supercritical fluid chromatography for the analysis of these compounds. Yet, it has been shown that more polar natural products (e.g., xanthones, flavonoids, alkaloids) are separable too, with the same (if not superior) selectivity and reproducibility than established approaches like HPLC or GC. Georg Thieme Verlag KG Stuttgart · New York.
Fluid mechanics aspects of magnetic drug targeting.
Odenbach, Stefan
2015-10-01
Experiments and numerical simulations using a flow phantom for magnetic drug targeting have been undertaken. The flow phantom is a half y-branched tube configuration where the main tube represents an artery from which a tumour-supplying artery, which is simulated by the side branch of the flow phantom, branches off. In the experiments a quantification of the amount of magnetic particles targeted towards the branch by a magnetic field applied via a permanent magnet is achieved by impedance measurement using sensor coils. Measuring the targeting efficiency, i.e. the relative amount of particles targeted to the side branch, for different field configurations one obtains targeting maps which combine the targeting efficiency with the magnetic force densities in characteristic points in the flow phantom. It could be shown that targeting efficiency depends strongly on the magnetic field configuration. A corresponding numerical model has been set up, which allows the simulation of targeting efficiency for variable field configuration. With this simulation good agreement of targeting efficiency with experimental data has been found. Thus, the basis has been laid for future calculations of optimal field configurations in clinical applications of magnetic drug targeting. Moreover, the numerical model allows the variation of additional parameters of the drug targeting process and thus an estimation of the influence, e.g. of the fluid properties on the targeting efficiency. Corresponding calculations have shown that the non-Newtonian behaviour of the fluid will significantly influence the targeting process, an aspect which has to be taken into account, especially recalling the fact that the viscosity of magnetic suspensions depends strongly on the magnetic field strength and the mechanical load.
Planar articulated mechanism design by graph theoretical enumeration
DEFF Research Database (Denmark)
Kawamoto, A; Bendsøe, Martin P.; Sigmund, Ole
2004-01-01
This paper deals with design of articulated mechanisms using a truss-based ground-structure representation. By applying a graph theoretical enumeration approach we can perform an exhaustive analysis of all possible topologies for a test example for which we seek a symmetric mechanism. This guaran....... This guarantees that one can identify the global optimum solution. The result underlines the importance of mechanism topology and gives insight into the issues specific to articulated mechanism designs compared to compliant mechanism designs....
The Status of Fluid Mechanics in Bioengineering Curricula.
Miller, Gerald E.; Hyman, William A.
1981-01-01
Describes the status of fluid mechanics courses in bioengineering curricula. A survey of institutions offering bioengineering degrees indicates that over half do not require fluid mechanics courses. Suggests increasing number of mechanics courses to increase the quality of bioengineering students and to prepare students for graduate work and more…
Ahlers, Marieke; Koch, Marcus; Lägel, Bert; Klingel, Steffen; Schlehuber, Dennis; Gehrke, Ilka; Eloo, Christina; Bart, Hans-Jörg
2017-01-01
The manipulation of the water wetting properties of heat exchangers into dropwise condensation by the use of microstructured surfaces promises an enhanced heat transfer. In order to design a hydrophobic surface geometry, different theoretical models have been introduced in the past. While these models describe the surface-drop-interaction of sessile drops reasonably well, nucleation and droplet growth in dropwise condensation are not considered. Modifications of roughness based models have be...
Collective fluid mechanics of honeybee nest ventilation
Gravish, Nick; Combes, Stacey; Wood, Robert J.; Peters, Jacob
2014-11-01
Honeybees thermoregulate their brood in the warm summer months by collectively fanning their wings and creating air flow through the nest. During nest ventilation workers flap their wings in close proximity in which wings continuously operate in unsteady oncoming flows (i.e. the wake of neighboring worker bees) and near the ground. The fluid mechanics of this collective aerodynamic phenomena are unstudied and may play an important role in the physiology of colony life. We have performed field and laboratory observations of the nest ventilation wing kinematics and air flow generated by individuals and groups of honeybee workers. Inspired from these field observations we describe here a robotic model system to study collective flapping wing aerodynamics. We microfabricate arrays of 1.4 cm long flapping wings and observe the air flow generated by arrays of two or more fanning robotic wings. We vary phase, frequency, and separation distance among wings and find that net output flow is enhanced when wings operate at the appropriate phase-distance relationship to catch shed vortices from neighboring wings. These results suggest that by varying position within the fanning array honeybee workers may benefit from collective aerodynamic interactions during nest ventilation.
Theoretical study on flow-induced vibration of a cylindrical weir due to fluid discharge
International Nuclear Information System (INIS)
Fujita, Katsuhisa; Ito, Tomohiro; Hirota, Kazuo; Kodama, Tetsuhiko
1994-01-01
In a FBR, the inside of the reactor vessel is cooled by liquid sodium. Liquid sodium is supplied to the upper plenum from its bottom and discharges over the top of the cylindrical weir down to the lower plenum. The weir is so thin in order to decrease the thermal stress on it that the fluid--structure interaction becomes predominant. A fluidelastic vibration of the weir due to fluid discharge was discovered in a French FBR. In this study, a theoretical model was developed on the ''fluid--elastic mode'' instability of a cylindrical weir due to fluid discharge from the upper plenum to the lower plenum. In the analysis, the fluctuation of both the discharge flow rate over a weir due to the vibration of the cylindrical shell and the pressure in the lower plenum due to fluid discharge were formulated. Instability criteria was derived from the added damping ratio due to fluid discharge using modal analysis. The natural modes and modal mass of the weir were obtained by the analysis using the FEM code taking the fluid - structure interaction into consideration. The theoretical instability range in terms of the fall height and the flow rate is compared with the experimental results. The theoretical values showed a good agreement with the experimental ones
Mathematica for Theoretical Physics Classical Mechanics and Nonlinear Dynamics
Baumann, Gerd
2005-01-01
Mathematica for Theoretical Physics: Classical Mechanics and Nonlinear Dynamics This second edition of Baumann's Mathematica® in Theoretical Physics shows readers how to solve physical problems and deal with their underlying theoretical concepts while using Mathematica® to derive numeric and symbolic solutions. Each example and calculation can be evaluated by the reader, and the reader can change the example calculations and adopt the given code to related or similar problems. The second edition has been completely revised and expanded into two volumes: The first volume covers classical mechanics and nonlinear dynamics. Both topics are the basis of a regular mechanics course. The second volume covers electrodynamics, quantum mechanics, relativity, and fractals and fractional calculus. New examples have been added and the representation has been reworked to provide a more interactive problem-solving presentation. This book can be used as a textbook or as a reference work, by students and researchers alike. A...
Quantitative image processing in fluid mechanics
Hesselink, Lambertus; Helman, James; Ning, Paul
1992-01-01
The current status of digital image processing in fluid flow research is reviewed. In particular, attention is given to a comprehensive approach to the extraction of quantitative data from multivariate databases and examples of recent developments. The discussion covers numerical simulations and experiments, data processing, generation and dissemination of knowledge, traditional image processing, hybrid processing, fluid flow vector field topology, and isosurface analysis using Marching Cubes.
Nambu brackets in fluid mechanics and magnetohydrodynamics
International Nuclear Information System (INIS)
Salazar, Roberto; Kurgansky, Michael V
2010-01-01
Concrete examples of the construction of Nambu brackets for equations of motion (both 3D and 2D) of Boussinesq stratified fluids and also for magnetohydrodynamical equations are given. It serves a generalization of Hamiltonian formulation for the considered equations of motion. Two alternative Nambu formulations are proposed, first by using fluid dynamical (kinetic) helicity and/or enstrophy as constitutive elements and second, by using the existing conservation laws of the governing equation.
"Audacity or Precision": The Paradoxes of Henri Villat's Fluid Mechanics in Interwar France
Aubin , David
2010-01-01
In Interwar France, Henri Villat became the true leader of theoretical researches on fluid mechanics. Most of his original work was done before the First World War; it was highly theoretical and its applicability was questioned. After having organized the first post-WWI International Congress of Mathematicians in 1920, Villat became the editor of the famous Journal de math\\'ematiques pure et appliqu\\'es and the director of the influential book series "M\\'emorial des sciences math\\'ematiques."...
Theoretical equation of state for classical fluids. I. Test by perturbation theory
International Nuclear Information System (INIS)
Gil-Villegas, A.; Chavez, M.; Del Rio, F.
1993-01-01
This paper shows how to construct the theoretical equation of state (TEOS) of a classical simple fluid. The theory relies on the mean collisional diameter and range, and maps the thermodynamical properties of the fluid into those of an equivalent square-well (ESW) fluid of appropriate depth ε , diameter σ and range R. It is shown that the ESW has the same pressure as the fluid of interest. Hence the THEOS of any simple fluid takes the form of a SW EOS of the given ε , σ and R. The theory is applied to a Lennard-Jones (LJ) system in a first-order perturbation. The mapping equation have a physical solution for densities where the SW EOS is accurate; the resulting LJ TEOS agrees very well with the results of computer simulations, and compares favorably with the recent TEOS developed by Song and Mason. (Author). 17 refs, 7 figs, 1 tab
Statistical mechanics of homogeneous partly pinned fluid systems.
Krakoviack, Vincent
2010-12-01
The homogeneous partly pinned fluid systems are simple models of a fluid confined in a disordered porous matrix obtained by arresting randomly chosen particles in a one-component bulk fluid or one of the two components of a binary mixture. In this paper, their configurational properties are investigated. It is shown that a peculiar complementarity exists between the mobile and immobile phases, which originates from the fact that the solid is prepared in presence of and in equilibrium with the adsorbed fluid. Simple identities follow, which connect different types of configurational averages, either relative to the fluid-matrix system or to the bulk fluid from which it is prepared. Crucial simplifications result for the computation of important structural quantities, both in computer simulations and in theoretical approaches. Finally, possible applications of the model in the field of dynamics in confinement or in strongly asymmetric mixtures are suggested.
Theoretical Modeling of Rock Breakage by Hydraulic and Mechanical Tool
Directory of Open Access Journals (Sweden)
Hongxiang Jiang
2014-01-01
Full Text Available Rock breakage by coupled mechanical and hydraulic action has been developed over the past several decades, but theoretical study on rock fragmentation by mechanical tool with water pressure assistance was still lacking. The theoretical model of rock breakage by mechanical tool was developed based on the rock fracture mechanics and the solution of Boussinesq’s problem, and it could explain the process of rock fragmentation as well as predicating the peak reacting force. The theoretical model of rock breakage by coupled mechanical and hydraulic action was developed according to the superposition principle of intensity factors at the crack tip, and the reacting force of mechanical tool assisted by hydraulic action could be reduced obviously if the crack with a critical length could be produced by mechanical or hydraulic impact. The experimental results indicated that the peak reacting force could be reduced about 15% assisted by medium water pressure, and quick reduction of reacting force after peak value decreased the specific energy consumption of rock fragmentation by mechanical tool. The crack formation by mechanical or hydraulic impact was the prerequisite to improvement of the ability of combined breakage.
Application of the principle of similarity fluid mechanics
International Nuclear Information System (INIS)
Hendricks, R.C.; Sengers, J.V.
1979-01-01
Possible applications of the principle of similarity to fluid mechanics is described and illustrated. In correlating thermophysical properties of fluids, the similarity principle transcends the traditional corresponding states principle. In fluid mechanics the similarity principle is useful in correlating flow processes that can be modeled adequately with one independent variable (i.e., one-dimensional flows). In this paper we explore the concept of transforming the conservation equations by combining similarity principles for thermophysical properties with those for fluid flow. We illustrate the usefulness of the procedure by applying such a transformation to calculate two phase critical mass flow through a nozzle
Employing the Mathcad program within the course of Theoretical Mechanics
Directory of Open Access Journals (Sweden)
Kurilin Alexander V.
2016-01-01
Full Text Available The author shares his experience in using the «Mathcad» software for conducting classes on «Theoretical Mechanics» in the University course. The program «Mathcad» combines a simple user interface and powerful mathematical tools which can be employed for different mechanical problems. It gives invaluable help in evaluating analytically and numerically many difficult integrals, in solving differential equations, in picturing graphics and can also simulate different mechanical phenomena with the computer. This allows significantly to expand the range of topics that can be considered in the standard University course of «Theoretical Mechanics» and gives students an opportunity to concentrate on practical problems, avoiding unnecessary routine of mathematical calculations. As an example the author considers one famous problem of the Lagrange analytical mechanics associated with the body motion in the field of gravity in the presence of stationary holonomic constraints.
Diffuse-Interface Methods in Fluid Mechanics
Anderson, D. M.; McFadden, G. B.; Wheeler, A. A.
1997-01-01
The authors review the development of diffuse-interface models of hydrodynamics and their application to a wide variety of interfacial phenomena. The authors discuss the issues involved in formulating diffuse-interface models for single-component and binary fluids. Recent applications and computations using these models are discussed in each case. Further, the authors address issues including sharp-interface analyses that relate these models to the classical free-boundary problem, related computational approaches to describe interfacial phenomena, and related approaches describing fully-miscible fluids.
Czech Academy of Sciences Publication Activity Database
Bogdanić, Grozdana; Pavlíček, Jan; Wichterle, Ivan
2012-01-01
Roč. 42, SI (2012), s. 1873-1878 E-ISSN 1877-7058. [International Congress of Chemical and Process Engineering CHISA 2012 and 15th Conference PRES 2012 /20./. Prague, 25.08.2012-29.08.2012] Institutional support: RVO:67985858 Keywords : petroleum fluids * prediction * physico-chemical properties Subject RIV: CF - Physical ; Theoretical Chemistry
Fluid catalytic cracking : Feedstocks and reaction mechanism
Dupain, X.
2006-01-01
The Fluid Catalytic Cracking (FCC) process is one of the key units in a modern refinery. Traditionally, its design is primarily aimed for the production of gasoline from heavy oil fractions, but as co-products also diesel blends and valuable gasses (e.g. propene and butenes) are formed in
Generalised fluid dynamics and quantum mechanics
Broer, L.J.F.
1974-01-01
A generalised theory of irrotational fluid flow is developed in hamiltonian form. This allows a systematic derivation of equations for momentum, energy and the rate of work. It is shown that a nonlinear field equation for weakly interacting condensed bosons as given by Gross1) and the one-electron
Theoretical physics IV. Quantum mechanics with problems in MAPLE
International Nuclear Information System (INIS)
Reinecker, Peter; Schulz, Michael; Schulz, Beatrix M.
2008-01-01
Quantum mechanics 2 is the fourth volume of the new and unique series for theoretical physics with Maple applications. This from basics newly concipated series mediates theoretical physics from contemporary view and in a way referring to a comprehensive lecture experience. Extensively and completely in five consecutively appearing volumes classical mechanics, electrodynamics, quantum mechanics 1 and 2, as well as statistical physics and thermodynamics are presented. Additionally for the elegant and extensive presentation on an each added CP applications for MAPLE trademark are contained, the software, which at more and more university is already applied in the lecture. They allow the experimenting with theory - and facilitate the understanding essentially. The present volume mediates extending, more complex contents of quantum mechanics, which are based on volume III of the series
Isogeometric Analysis and Shape Optimization in Fluid Mechanics
DEFF Research Database (Denmark)
Nielsen, Peter Nørtoft
This thesis brings together the fields of fluid mechanics, as the study of fluids and flows, isogeometric analysis, as a numerical method to solve engineering problems using computers, and shape optimization, as the art of finding "best" shapes of objects based on some notion of goodness. The flow...... approximations, and for shape optimization purposes also due to its tight connection between the analysis and geometry models. The thesis is initiated by short introductions to fluid mechanics, and to the building blocks of isogeometric analysis. As the first contribution of the thesis, a detailed description...... isogeometric analysis may serve as a natural framework for shape optimization within fluid mechanics. We construct an efficient regularization measure for avoiding inappropriate parametrizations during optimization, and various numerical examples of shape optimization for fluids are considered, serving...
Fluid Mechanics, Arterial Disease, and Gene Expression.
Tarbell, John M; Shi, Zhong-Dong; Dunn, Jessilyn; Jo, Hanjoong
2014-01-01
This review places modern research developments in vascular mechanobiology in the context of hemodynamic phenomena in the cardiovascular system and the discrete localization of vascular disease. The modern origins of this field are traced, beginning in the 1960s when associations between flow characteristics, particularly blood flow-induced wall shear stress, and the localization of atherosclerotic plaques were uncovered, and continuing to fluid shear stress effects on the vascular lining endothelial) cells (ECs), including their effects on EC morphology, biochemical production, and gene expression. The earliest single-gene studies and genome-wide analyses are considered. The final section moves from the ECs lining the vessel wall to the smooth muscle cells and fibroblasts within the wall that are fluid me chanically activated by interstitial flow that imposes shear stresses on their surfaces comparable with those of flowing blood on EC surfaces. Interstitial flow stimulates biochemical production and gene expression, much like blood flow on ECs.
Software for principles of fluid mechanics
International Nuclear Information System (INIS)
Kreider, J.F.
1985-01-01
This book is intended as a software supplement and provides a means for solving problems rapidly to determine the relative importance of flow and environmental parameters. Topics covered include the following: momentum equation: rocket trajectory; Bernoulli's equation: pipe plug-flow or Bernoulli's equation: tank drawing; fluid statics: submerged gate, or fluid statics: manometry; laminar flow: pipe fittings plus straight pipe, or laminar external flow: between parallel planes; ideal flow: plot of pressure distribution on a cylinder with circulation; laminar external flow: drag force and friction coefficient; turbulent external flow: drag force and friction coefficient on flat plate; turbulent external flow: drag force and friction coefficient on sphere; turbulent pipe flow: fittings plus straight sections (moody diagram); turbulent channel flow; isentropic compressible flow; normal shocks: property changes errors; choked nozzle flow; pump curve and system curve simultaneous solution; and fan affinity laws
Rotating fluid models in classical and quantum mechanics
International Nuclear Information System (INIS)
Arvieu, R.; Troudet, T.
1979-01-01
To describe the behavior of high-spin nuclei it is necessary to refer back to the classical mechanics of fluids in rotation where some results are general enough to apply to the rotational nuclear fluid. It is then shown that the quantum model of rotational oscillator gives a simple classification of rotating configurations [fr
Mechanical stimulation of bone cells using fluid flow
Huesa, C.; Bakker, A.D.
2012-01-01
This chapter describes several methods suitable for mechanically stimulating monolayers of bone cells by fluid shear stress (FSS) in vitro. Fluid flow is generated by pumping culture medium through two parallel plates, one of which contains a monolayer of cells. Methods for measuring nitric oxide
1994-01-01
This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science during the period October 1, 1993 through March 31, 1994. The major categories of the current ICASE research program are: (1) applied and numerical mathematics, including numerical analysis and algorithm development; (2) theoretical and computational research in fluid mechanics in selected areas of interest to LaRC, including acoustics and combustion; (3) experimental research in transition and turbulence and aerodynamics involving LaRC facilities and scientists; and (4) computer science.
Research in Applied Mathematics, Fluid Mechanics and Computer Science
1999-01-01
This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science during the period October 1, 1998 through March 31, 1999.
[Research activities in applied mathematics, fluid mechanics, and computer science
1995-01-01
This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science during the period April 1, 1995 through September 30, 1995.
Vectors, tensors and the basic equations of fluid mechanics
Aris, Rutherford
1962-01-01
Introductory text, geared toward advanced undergraduate and graduate students, applies mathematics of Cartesian and general tensors to physical field theories and demonstrates them in terms of the theory of fluid mechanics. 1962 edition.
A statistical mechanics approach to mixing in stratified fluids
Venaille , Antoine; Gostiaux , Louis; Sommeria , Joël
2016-01-01
Accepted for the Journal of Fluid Mechanics; Predicting how much mixing occurs when a given amount of energy is injected into a Boussinesq fluid is a longstanding problem in stratified turbulence. The huge number of degrees of freedom involved in these processes renders extremely difficult a deterministic approach to the problem. Here we present a statistical mechanics approach yielding a prediction for a cumulative, global mixing efficiency as a function of a global Richard-son number and th...
Application of a two fluid theoretical plasma transport model on current tokamak reactor designs
International Nuclear Information System (INIS)
Ibrahim, E.; Fowler, T.K.
1987-06-01
In this work, the new theoretical transport models to TIBER II design calculations are described and the results are compared with recent experimental data in large tokamaks (TFTR, JET). Tang's method is extended to a two-fluid model treating ions and electrons separately. This allows for different ion and electron temperatures, as in recent low-density experiments in TFTR, and in the TIBER II design itself. The discussion is divided into two parts: (1) Development of the theoretical transport model and (2) calibration against experiments and application to TIBER II
The fluid mechanics of root canal irrigation.
Gulabivala, K; Ng, Y-L; Gilbertson, M; Eames, I
2010-12-01
Root canal treatment is a common dental operation aimed at removing the contents of the geometrically complex canal chambers within teeth; its purpose is to remove diseased or infected tissue. The complex chamber is first enlarged and shaped by instruments to a size sufficient to deliver antibacterial fluids. These irrigants help to dissolve dying tissue, disinfect the canal walls and space and flush out debris. The effectiveness of the procedure is limited by access to the canal terminus. Endodontic research is focused on finding the instruments and clinical procedures that might improve success rates by more effectively reaching the apical anatomy. The individual factors affecting treatment outcome have not been unequivocally deciphered, partly because of the difficulty in isolating them and in making the link between simplified, general experimental models and the complex biological objects that are teeth. Explicitly considering the physical processes within the root canal can contribute to the resolution of these problems. The central problem is one of fluid motion in a confined geometry, which makes the dispersion and mixing of irrigant more difficult because of the absence of turbulence over much of the canal volume. The effects of treatments can be understood through the use of scale models, mathematical modelling and numerical computations. A particular concern in treatment is that caustic irrigant may penetrate beyond the root canal, causing chemical damage to the jawbone. In fact, a stagnation plane exists beyond the needle tip, which the irrigant cannot penetrate. The goal is therefore to shift the stagnation plane apically to be coincident with the canal terminus without extending beyond it. Needle design may solve some of the problems but the best design for irrigant penetration conflicts with that for optimal removal of the bacterial biofilm from the canal wall. Both irrigant penetration and biofilm removal may be improved through canal fluid
The fluid mechanics of root canal irrigation
International Nuclear Information System (INIS)
Gulabivala, K; Ng, Y-L; Gilbertson, M; Eames, I
2010-01-01
Root canal treatment is a common dental operation aimed at removing the contents of the geometrically complex canal chambers within teeth; its purpose is to remove diseased or infected tissue. The complex chamber is first enlarged and shaped by instruments to a size sufficient to deliver antibacterial fluids. These irrigants help to dissolve dying tissue, disinfect the canal walls and space and flush out debris. The effectiveness of the procedure is limited by access to the canal terminus. Endodontic research is focused on finding the instruments and clinical procedures that might improve success rates by more effectively reaching the apical anatomy. The individual factors affecting treatment outcome have not been unequivocally deciphered, partly because of the difficulty in isolating them and in making the link between simplified, general experimental models and the complex biological objects that are teeth. Explicitly considering the physical processes within the root canal can contribute to the resolution of these problems. The central problem is one of fluid motion in a confined geometry, which makes the dispersion and mixing of irrigant more difficult because of the absence of turbulence over much of the canal volume. The effects of treatments can be understood through the use of scale models, mathematical modelling and numerical computations. A particular concern in treatment is that caustic irrigant may penetrate beyond the root canal, causing chemical damage to the jawbone. In fact, a stagnation plane exists beyond the needle tip, which the irrigant cannot penetrate. The goal is therefore to shift the stagnation plane apically to be coincident with the canal terminus without extending beyond it. Needle design may solve some of the problems but the best design for irrigant penetration conflicts with that for optimal removal of the bacterial biofilm from the canal wall. Both irrigant penetration and biofilm removal may be improved through canal fluid
Potential fluid mechanic pathways of platelet activation
Shadden, Shawn C.; Hendabadi, Sahar
2012-01-01
Platelet activation is a precursor for blood clotting, which plays leading roles in many vascular complications and causes of death. Platelets can be activated by chemical or mechanical stimuli. Mechanically, platelet activation has been shown to be a function of elevated shear stress and exposure time. These contributions can be combined by considering the cumulative stress or strain on a platelet as it is transported. Here we develop a framework for computing a hemodynamic-based activation ...
Theoretical methods and models for mechanical properties of soft biomaterials
Directory of Open Access Journals (Sweden)
Zhonggang Feng
2017-06-01
Full Text Available We review the most commonly used theoretical methods and models for the mechanical properties of soft biomaterials, which include phenomenological hyperelastic and viscoelastic models, structural biphasic and network models, and the structural alteration theory. We emphasize basic concepts and recent developments. In consideration of the current progress and needs of mechanobiology, we introduce methods and models for tackling micromechanical problems and their applications to cell biology. Finally, the challenges and perspectives in this field are discussed.
Molecular mechanics and structure of the fluid-solid interface in simple fluids
Wang, Gerald J.; Hadjiconstantinou, Nicolas G.
2017-09-01
Near a fluid-solid interface, the fluid spatial density profile is highly nonuniform at the molecular scale. This nonuniformity can have profound effects on the dynamical behavior of the fluid and has been shown to play an especially important role when modeling a wide variety of nanoscale heat and momentum transfer phenomena. We use molecular-mechanics arguments and molecular-dynamics (MD) simulations to develop a better understanding of the structure of the first fluid layer directly adjacent to the solid in the layering regime, as delineated by a nondimensional number that compares the effects of wall-fluid interaction to thermal energy. Using asymptotic analysis of the Nernst-Planck equation, we show that features of the fluid density profile close to the wall, such as the areal density of the first layer ΣFL (defined as the number of atoms in this layer per unit of fluid-solid interfacial area), can be expressed as polynomial functions of the fluid average density ρave. This is found to be in agreement with MD simulations, which also show that the width of the first layer hFL is a linear function of the average density and only a weak function of the temperature T . These results can be combined to show that, for system average densities corresponding to a dense fluid (ρave≥0.7 ), the ratio C ≡ΣFLρavehFL, representing a density enhancement with respect to the bulk fluid, depends only weakly on temperature and is essentially independent of density. Further MD simulations suggest that the above results, nominally valid for large systems (solid in contact with semi-infinite fluid), also describe fluid-solid interfaces under considerable nanoconfinement, provided ρave is appropriately defined.
Predicting Athletes’ Pre-Exercise Fluid Intake: A Theoretical Integration Approach
Directory of Open Access Journals (Sweden)
Chunxiao Li
2018-05-01
Full Text Available Pre-exercise fluid intake is an important healthy behavior for maintaining athletes’ sports performances and health. However, athletes’ behavioral adherence to fluid intake and its underlying psychological mechanisms have not been investigated. This prospective study aimed to use a health psychology model that integrates the self-determination theory and the theory of planned behavior for understanding pre-exercise fluid intake among athletes. Participants (n = 179 were athletes from college sport teams who completed surveys at two time points. Baseline (Time 1 assessment comprised psychological variables of the integrated model (i.e., autonomous and controlled motivation, attitude, subjective norm, perceived behavioral control, and intention and fluid intake (i.e., behavior was measured prospectively at one month (Time 2. Path analysis showed that the positive association between autonomous motivation and intention was mediated by subjective norm and perceived behavioral control. Controlled motivation positively predicted the subjective norm. Intentions positively predicted pre-exercise fluid intake behavior. Overall, the pattern of results was generally consistent with the integrated model, and it was suggested that athletes’ pre-exercise fluid intake behaviors were associated with the motivational and social cognitive factors of the model. The research findings could be informative for coaches and sport scientists to promote athletes’ pre-exercise fluid intake behaviors.
Active Learning in Fluid Mechanics: Youtube Tube Flow and Puzzling Fluids Questions
Hrenya, Christine M.
2011-01-01
Active-learning exercises appropriate for a course in undergraduate fluid mechanics are presented. The first exercise involves an experiment in gravity-driven tube flow, with small groups of students partaking in a contest to predict the experimental flow rates using the mechanical energy balance. The second exercise takes the form of an…
Mechanical collapse of confined fluid membrane vesicles.
Rim, Jee E; Purohit, Prashant K; Klug, William S
2014-11-01
Compact cylindrical and spherical invaginations are common structural motifs found in cellular and developmental biology. To understand the basic physical mechanisms that produce and maintain such structures, we present here a simple model of vesicles in confinement, in which mechanical equilibrium configurations are computed by energy minimization, balancing the effects of curvature elasticity, contact of the membrane with itself and the confining geometry, and adhesion. For cylindrical confinement, the shape equations are solved both analytically and numerically by finite element analysis. For spherical confinement, axisymmetric configurations are obtained numerically. We find that the geometry of invaginations is controlled by a dimensionless ratio of the adhesion strength to the bending energy of an equal area spherical vesicle. Larger adhesion produces more concentrated curvatures, which are mainly localized to the "neck" region where the invagination breaks away from its confining container. Under spherical confinement, axisymmetric invaginations are approximately spherical. For extreme confinement, multiple invaginations may form, bifurcating along multiple equilibrium branches. The results of the model are useful for understanding the physical mechanisms controlling the structure of lipid membranes of cells and their organelles, and developing tissue membranes.
Mechanism of chain formation in nanofluid based MR fluids
International Nuclear Information System (INIS)
Patel, Rajesh
2011-01-01
Mechanism of structure formation in bidispersed colloids is important for its physical and optical properties. It is microscopically observed that the mechanism of chain formation in magnetic nanofluid based magnetorheological (MR) fluid is quite different from that in the conventional MR fluid. Under the application of magnetic field the magnetic nanoparticles are filled inside the structural microcavities formed due to the association of large magnetic particles, and some of the magnetic nanoparticles are attached at the end of the chains formed by the large particles. The dipolar energy of the large particles in a magnetic nanofluid matrix becomes effective magnetic permeability (μ eff ) times smaller than that of the neutral medium. Inclusion of magnetic nanoparticles (∼10 nm) with large magnetic particles (∼3-5 μm) restricts the aggregation of large particles, which causes the field induced phase separation in MR fluids. Hence, nanofluid based MR fluids are more stable than conventional MR fluids, which subsequently increase their application potentiality. - Research highlights: → In bidispersed magnetic colloids nanoparticles are attached at the end of the chains formed by the large particles. → Inclusion of magnetic nanoparticles (∼10 nm) with large magnetic particles (∼3-5 m) restricts the aggregation of large particles. → Nanofluid based MR fluids are more stable than conventional MR fluids.
The fluid mechanics of continuous flow electrophoresis
Saville, D. A.
1990-01-01
The overall objective is to establish theoretically and confirm experimentally the ultimate capabilities of continuous flow electrophoresis chambers operating in an environment essentially free of particle sedimentation and buoyancy. The efforts are devoted to: (1) studying the effects of particle concentration on sample conductivity and dielectric constant. The dielectric constant and conductivity were identified as playing crucial roles in the behavior of the sample and on the resolving power and throughput of continuous flow devices; and (2) improving the extant mathematical models to predict flow fields and particle trajectories in continuous flow electrophoresis. A dielectric spectrometer was designed and built to measure the complex dielectric constant of a colloidal dispersion as a function of frequency between 500 Hz and 200 kHz. The real part of the signal can be related to the sample's conductivity and the imaginary part to its dielectric constant. Measurements of the dielectric constants of several different dispersions disclosed that the dielectric constants of dilute systems of the sort encountered in particle electrophoresis are much larger than would be expected based on the extant theory. Experiments were carried out to show that, in many cases, this behavior is due to the presence of a filamentary structure of small hairs on the particle surface. A technique for producing electrokinetically ideal synthetic latex particles by heat treating was developed. Given the ubiquitous nature of hairy surfaces with both cells and synthetic particles, it was deemed necessary to develop a theory to explain their behavior. A theory for electrophoretic mobility of hairy particles was developed. Finally, the extant computer programs for predicting the structure of electro-osmotically driven flows were extended to encompass flow channels with variable wall mobilities.
Fluid transportation mechanisms by a coupled system of elastic membranes and magnetic fluids
International Nuclear Information System (INIS)
Ido, Y.; Tanaka, K.; Sugiura, Y.
2002-01-01
The basic properties of the fluid transportation mechanism that is produced by the coupled waves propagating along a thin elastic membrane covering a magnetic fluid layer in a shallow and long rectangular vessel are investigated. It is shown that the progressive magnetic field induced by the rectangular pulses generates sinusoidal vibration of the displacement of elastic membrane and makes the system work more efficiently than the magnetic field induced by the pulse-width-modulation method
Elucidating Grinding Mechanism by Theoretical and Experimental Investigations
Directory of Open Access Journals (Sweden)
AMM Sharif Ullah
2018-02-01
Full Text Available Grinding is one of the essential manufacturing processes for producing brittle or hard materials-based precision parts (e.g., optical lenses. In grinding, a grinding wheel removes the desired amount of material by passing the same area on the workpiece surface multiple times. How the topography of a workpiece surface evolves with these passes is thus an important research issue, which has not yet been addressed elaborately. The present paper tackles this issue from both the theoretical and the experimental points of view. In particular, this paper presents the results of experimental and theoretical investigations on the multi-pass surface grinding operations where the workpiece surface is made of glass and the grinding wheel consists of cBN abrasive grains. Both investigations confirm that a great deal of stochasticity is involved in the grinding mechanism, and the complexity of the workpiece surface gradually increases along with the number of passes.
Elucidating Grinding Mechanism by Theoretical and Experimental Investigations.
Ullah, Amm Sharif; Caggiano, Alessandra; Kubo, Akihiko; Chowdhury, M A K
2018-02-09
Grinding is one of the essential manufacturing processes for producing brittle or hard materials-based precision parts (e.g., optical lenses). In grinding, a grinding wheel removes the desired amount of material by passing the same area on the workpiece surface multiple times. How the topography of a workpiece surface evolves with these passes is thus an important research issue, which has not yet been addressed elaborately. The present paper tackles this issue from both the theoretical and the experimental points of view. In particular, this paper presents the results of experimental and theoretical investigations on the multi-pass surface grinding operations where the workpiece surface is made of glass and the grinding wheel consists of cBN abrasive grains. Both investigations confirm that a great deal of stochasticity is involved in the grinding mechanism, and the complexity of the workpiece surface gradually increases along with the number of passes.
Fluid-mechanic model for fabrication of nanoporous fibers by electrospinning
Directory of Open Access Journals (Sweden)
Fan Chengxu
2017-01-01
Full Text Available A charged jet in the electrospinning process for fabrication of nanoporous fibers is studied theoretically. A fluid-mechanic model considering solvent evaporation is established to research the effect of solvent evaporation on nanopore structure formation. The model gives a powerful tool to offering in-depth physical under-standing and controlling over electrospinning parameters such as voltage, flow rate, and solvent evaporation rate.
Fluid-mechanic model for fabrication of nanoporous fibers by electrospinning
Fan Chengxu; Sun Zhaoyang; Xu Lan
2017-01-01
A charged jet in the electrospinning process for fabrication of nanoporous fibers is studied theoretically. A fluid-mechanic model considering solvent evaporation is established to research the effect of solvent evaporation on nanopore structure formation. The model gives a powerful tool to offering in-depth physical under-standing and controlling over electrospinning parameters such as voltage, flow rate, and solvent evaporation rate.
A blended learning approach to teach fluid mechanics in engineering
Rahman, Ataur
2017-05-01
This paper presents a case study on the teaching and learning of fluid mechanics at the University of Western Sydney (UWS), Australia, by applying a blended learning approach (BLA). In the adopted BLA, various flexible learning materials have been made available to the students such as online recorded lectures, online recorded tutorials, hand written tutorial solutions, discussion board and online practice quizzes. The lecture and tutorial class times have been primarily utilised to discuss confusing topics and engage students with practical issues in applying the theories learnt in fluid mechanics. Based on the data of over 734 students over a 4-year period, it has been shown that a BLA has improved the learning experience of the fluid mechanics students in UWS. The overall percentage of student satisfaction in this subject has increased by 18% in the BLA case compared with the traditional one.
Second GAMM-conference on numerical methods in fluid mechanics
International Nuclear Information System (INIS)
Hirschel, E.H.; Geller, W.
1977-01-01
Proceedings of the Second GAMM-Conference on Numerical Methods in Fluid Mechanics held at the DFVLR, Koeln, October 11 to 13, 1977. The conference was attended by approximately 100 participants from 13 European countries representing quite different fields ranging from Aerodynamics to Nuclear Energy. At the meeting 34 papers were presented, many of them concerned with basic problems in the field. It was well demonstrated that Numerical Methods in Fluid Mechanics do not only serve as means for the computation of flow fields but also as tools in the analysis of fluid mechanical phenomena, a role of large future importance if one considers the complexity especially of three-dimensional flows. (orig./RW) [de
Fluids and the evolution of rock mechanical properties
International Nuclear Information System (INIS)
Reuschle, Thierry
1989-01-01
This research thesis reports the study of the various phenomena of fluid-solid interaction (mechanical or chemical interaction with fracturing by fluid overpressure, slow crack propagation, and pore deformation by transfer in solution) which may occur in the interaction of fluids with rocks. The author first presents the formalism of slow crack propagation based on the generalisation of the Griffith criterion. The model results are compared with experimental results obtained on four materials (glass, quartz, sandstone, and micrite) by using the double-torsion test. In the second part, the author addresses the issue of pore deformation by transfer in solution: dissolution and crystallisation under stress. The Gibbs chemical potential equation is firstly generalised to the case of a circular pore, and a formalism combining mechanics and thermodynamics is then proposed. A set of simulations highlights important parameters. In the third part, the author addresses the problem of fluid-rock mechanical interaction by studying the mechanical role of fluid pressure in crack initiation and propagation [fr
Quantum mechanics. Textbook on theoretical physics III. 4. rev. ed.
International Nuclear Information System (INIS)
Fliessbach, T.
2005-01-01
This textbook present an intoduction to quantum mechanics, as it is offerred at the university in the cycle ''Theoretical Physics''. Special value has the author put on a well readable, understandable, and surveyable representation, so that the reader it can reproduce without larger difficulties. By the partition into chapters, which form separated course units, and the kind of the representation the book is also suited for bachelor curricula. The quantum mechanics are first introduced in the form of Schroedinge's wave mechanics. The fundamental relations of quantum mechanics and their interpretation are thereby explained by means of examples and first applications. In the following chapters the most important applications of the Schroedinger equation are studied, like the alpha decay, the scattering of a particle on a potential, and the hydrogen atom. Thereafter the abstract formulation of quantum mechanics (Hilbert space) is introduced in analogy to the known structure of the vector space. This formulation is then applied to concrete problems like the oscillator, tha angular momentum, and the spin. The most important approximation methods of quantum mechanics are then summarized. In the concluding part about many-particle systems the ideal Fermi gas is treated; simple applications of this model in atomic, solid-state, nuclear, ans astrophysics are discussed
An Introduction to Computational Fluid Mechanics by Example
Biringen, Sedat
2011-01-01
This new book builds on the original classic textbook entitled: An Introduction to Computational Fluid Mechanics by C. Y. Chow which was originally published in 1979. In the decades that have passed since this book was published the field of computational fluid dynamics has seen a number of changes in both the sophistication of the algorithms used but also advances in the computer hardware and software available. This new book incorporates the latest algorithms in the solution techniques and supports this by using numerous examples of applications to a broad range of industries from mechanical
Directory of Open Access Journals (Sweden)
Bogdanov Alexander
2016-01-01
Full Text Available The architecture of a digital computing system determines the technical foundation of a unified mathematical language for exact arithmetic-logical description of phenomena and laws of continuum mechanics for applications in fluid mechanics and theoretical physics. The deep parallelization of the computing processes results in functional programming at a new technological level, providing traceability of the computing processes with automatic application of multiscale hybrid circuits and adaptive mathematical models for the true reproduction of the fundamental laws of physics and continuum mechanics.
Fluid mechanics and heat transfer advances in nonlinear dynamics modeling
Asli, Kaveh Hariri
2015-01-01
This valuable new book focuses on new methods and techniques in fluid mechanics and heat transfer in mechanical engineering. The book includes the research of the authors on the development of optimal mathematical models and also uses modern computer technology and mathematical methods for the analysis of nonlinear dynamic processes. It covers technologies applicable to both fluid mechanics and heat transfer problems, which include a combination of physical, mechanical, and thermal techniques. The authors develop a new method for the calculation of mathematical models by computer technology, using parametric modeling techniques and multiple analyses for mechanical system. The information in this book is intended to help reduce the risk of system damage or failure. Included are sidebar discussions, which contain information and facts about each subject area that help to emphasize important points to remember.
Yielding to Stress: Recent Developments in Viscoplastic Fluid Mechanics
Balmforth, Neil J.; Frigaard, Ian A.; Ovarlez, Guillaume
2014-01-01
The archetypal feature of a viscoplastic fluid is its yield stress: If the material is not sufficiently stressed, it behaves like a solid, but once the yield stress is exceeded, the material flows like a fluid. Such behavior characterizes materials common in industries such as petroleum and chemical processing, cosmetics, and food processing and in geophysical fluid dynamics. The most common idealization of a viscoplastic fluid is the Bingham model, which has been widely used to rationalize experimental data, even though it is a crude oversimplification of true rheological behavior. The popularity of the model is in its apparent simplicity. Despite this, the sudden transition between solid-like behavior and flow introduces significant complications into the dynamics, which, as a result, has resisted much analysis. Over recent decades, theoretical developments, both analytical and computational, have provided a better understanding of the effect of the yield stress. Simultaneously, greater insight into the material behavior of real fluids has been afforded by advances in rheometry. These developments have primed us for a better understanding of the various applications in the natural and engineering sciences.
Quantum mechanics. Textbook on Theoretical Physics III. 5. ed.
International Nuclear Information System (INIS)
Fliessbach, Torsten
2008-01-01
This textbook gives an introduction to quantum mechanics, as it is presented at the university in the cycle ''Theoretical Physics''. Special care has the author put om a well readable, understandable, and clearly arranged presentation, so that the reader can it reproduce without greater difficulties. By the partition into chapters, which form self-contained teaching units, and the kind of presentation the book is also very well suited for bachelor courses. Quantum mechanics is first introduced in form of Schroedinger's wave mechanics. The fundamental relations and their interpretation are thereby explained hand in hand with examples and first applications. In the following parts the most important applications of the Schroedinger equation are studied, as the alpha decay, the scattering of particles on a potential, and the hydrogen atom. Thereafter the abstract formulation of quantum mechanics (Hilbert space) is introduced in analogy to the known structure of the vector space. This formulation is applied to concrete problems, as the oscillator, the angular momentum, and the spin. The most important approximation methods of quantum mechanics are then summarized. In the final part about many-particle systems the ideal Fermi gas is treated; simple application of this model in atomic, solid-state,and astrophysics are discussed
Mechanical properties of jennite: A theoretical and experimental study
Energy Technology Data Exchange (ETDEWEB)
Moon, Juhyuk, E-mail: juhyuk.moon@stonybrook.edu [Civil Engineering Program, Department of Mechanical Engineering, Stony Brook University, NY 11794 (United States); Yoon, Seyoon [School of Engineering, Kings College, University of Aberdeen, Aberdeen AB24 3UE (United Kingdom); Monteiro, Paulo J.M. [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States)
2015-05-15
The objective of this study is to determine the mechanical properties of jennite. To date, several hypotheses have been proposed to predict the structural properties of jennite. For the first time as reported herein, the isothermal bulk modulus of jennite was measured experimentally. Synchrotron-based high-pressure x-ray diffraction experiments were performed to observe the variation of lattice parameters under pressure. First-principles calculations were applied to compare with the experimental results and predict additional structural properties. Accurately measured isothermal bulk modulus herein (K{sub 0} = 64(2) GPa) and the statistical assessment on experimental and theoretical results suggest reliable mechanical properties of shear and Young's modulus, Poisson's ratio, and elastic tensor coefficients. Determination of these fundamental structural properties is the first step toward greater understanding of calcium–silicate–hydrate, as well as provides a sound foundation for forthcoming atomic level simulations.
Theoretical physics 7 quantum mechanics : methods and applications
Nolting, Wolfgang
2017-01-01
This textbook offers a clear and comprehensive introduction to methods and applications in quantum mechanics, one of the core components of undergraduate physics courses. It follows on naturally from the previous volumes in this series, thus developing the understanding of quantized states further on. The first part of the book introduces the quantum theory of angular momentum and approximation methods. More complex themes are covered in the second part of the book, which describes multiple particle systems and scattering theory. Ideally suited to undergraduate students with some grounding in the basics of quantum mechanics, the book is enhanced throughout with learning features such as boxed inserts and chapter summaries, with key mathematical derivations highlighted to aid understanding. The text is supported by numerous worked examples and end of chapter problem sets. About the Theoretical Physics series Translated from the renowned and highly successful German editions, the eight volumes of this seri...
Elvira, Luis; Resa, Pablo; Castro, Pedro
2013-03-01
In this paper, the principles of Thickness-Expansion Mode (TEM) resonators for the characterization of fluids are described. From the measurement of the resonance parameters of a TEM piezoelectric transducer, the compressional acoustic impedance of gases and liquids can be determined. Since the propagation of mechanical waves into the fluid is not necessary, information in a wide range of frequencies can be obtained. Alternatively, these sensors can be driven in combination with other ultrasonic techniques to simultaneously determine the density, speed of sound and viscosity of samples. Some potential applications include the probe monitoring of processes and the characterization of fluids under harsh conditions. The main experimental criteria for the design and construction of high-resolution impedance meters (such as piezoelectric material, protective coating or thermal response) have been studied using equivalent electrical circuit modeling and finite element analysis. Copyright © 2012 Elsevier B.V. All rights reserved.
Gao, Yan; Liu, Yuyou
2017-06-01
Vibrational energy is transmitted in buried fluid-filled pipes in a variety of wave types. Axisymmetric (n = 0) waves are of practical interest in the application of acoustic techniques for the detection of leaks in underground pipelines. At low frequencies n = 0 waves propagate longitudinally as fluid-dominated (s = 1) and shell-dominated (s = 2) waves. Whilst sensors such as hydrophones and accelerometers are commonly used to detect leaks in water distribution pipes, the mechanism governing the structural and fluid motions is not well documented. In this paper, the low-frequency behaviour of the pipe wall and the contained fluid is investigated. For most practical pipework systems, these two waves are strongly coupled; in this circumstance the ratios of the radial pipe wall displacements along with the internal pressures associated with these two wave types are obtained. Numerical examples show the relative insensitivity of the structural and fluid motions to the s = 2 wave for both metallic and plastic pipes buried in two typical soils. It is also demonstrated that although both acoustic and vibration sensors at the same location provide the identical phase information of the transmitted signals, pressure responses have significantly higher levels than acceleration responses, and thus hydrophones are better suited in a low signal-to-noise ratio (SNR) environment. This is supported by experimental work carried out at a leak detection facility. Additional pressure measurements involved excitation of the fluid and the pipe fitting (hydrant) on a dedicated water pipe. This work demonstrates that the s = 1 wave is mainly responsible for the structural and fluid motions at low frequencies in water distribution pipes as a result of water leakage and direct pipe excitation.
Fracturing Fluid Leak-off for Deep Volcanic Rock in Zhungeer Basin: Mechanism and Control Method
Directory of Open Access Journals (Sweden)
Huang Bo
2017-01-01
Full Text Available The deep volcanic reservoir in Zhungeer Basin is buried in over 4000m depth, which is characterized by complex lithology (breccia, andesite, basalt, etc., high elastic modulus and massive natural fractures. During hydraulic fracturing, hydraulic fracture will propagate and natural fractures will be triggered by the increasing net pressure. However, the extension of fractures, especially natural fractures, would aggravate the leak-off effect of fracturing fluid, and consequently decrease the fracturing success rate. 4 out of 12 fracturing wells in the field have failed to add enough proppants due to fluid loss. In order to increase the success rate and efficiency of hydraulic fracturing for deep volcanic reservoir, based on theoretical and experimental method, the mechanism of fracturing fluid leak-off is deeply studied. We propose a dualistic proppant scheme and employ the fluid loss reducer to control the fluid leak-off in macro-fractures and micro-fractures respectively. The proposed technique remarkably improved the success rate in deep volcanic rock fracturing. It bears important theoretical value and practical significance to improve the hydraulic fracturing design for deep volcanic reservoir.
A Blended Learning Approach to Teach Fluid Mechanics in Engineering
Rahman, Ataur
2017-01-01
This paper presents a case study on the teaching and learning of fluid mechanics at the University of Western Sydney (UWS), Australia, by applying a blended learning approach (BLA). In the adopted BLA, various flexible learning materials have been made available to the students such as online recorded lectures, online recorded tutorials, hand…
Flippin' Fluid Mechanics--Comparison Using Two Groups
Webster, Donald R.; Majerich, David M.; Madden, Amanda G.
2016-01-01
A flipped classroom approach was implemented in an undergraduate fluid mechanics course. Students watched short, online video lectures before class, participated in active in-class problem solving sessions (in pairs), and completed individualized online quizzes weekly. In-class activities were designed to develop problem-solving skills and teach…
Fluid Mechanics of Wing Adaptation for Separation Control
Chandrasekhara, M. S.; Wilder, M. C.; Carr, L. W.; Davis, Sanford S. (Technical Monitor)
1997-01-01
The unsteady fluid mechanics associated with use of a dynamically deforming leading edge airfoil for achieving compressible flow separation control has been experimentally studied. Changing the leading edge curvature at rapid rates dramatically alters the flow vorticity dynamics which is responsible for the many effects observed in the flow.
Instructor's Guide for Fluid Mechanics: A Modular Approach.
Cox, John S.
This guide is designed to assist engineering teachers in developing an understanding of fluid mechanics in their students. The course is designed around a set of nine self-paced learning modules, each of which contains a discussion of the subject matter; incremental objectives; problem index, set and answers; resource materials; and a quiz with…
Multiscale methods in computational fluid and solid mechanics
Borst, de R.; Hulshoff, S.J.; Lenz, S.; Munts, E.A.; Brummelen, van E.H.; Wall, W.; Wesseling, P.; Onate, E.; Periaux, J.
2006-01-01
First, an attempt is made towards gaining a more systematic understanding of recent progress in multiscale modelling in computational solid and fluid mechanics. Sub- sequently, the discussion is focused on variational multiscale methods for the compressible and incompressible Navier-Stokes
The fluid mechanics of channel fracturing flows: experiment
Rashedi, Ahmadreza; Tucker, Zachery; Ovarlez, Guillaume; Hormozi, Sarah
2017-11-01
We show our preliminary experimental results on the role of fluid mechanics in channel fracturing flows, particularly yield stress fracturing fluids. Recent trends in the oil industry have included the use of cyclic pumping of a proppant slurry interspersed with a yield stress fracturing fluid, which is found to increase wells productivity, if particles disperse in a certain fashion. Our experimental study aims to investigate the physical mechanisms responsible for dispersing the particles (proppant) within a yield stress carrier fluid, and to measure the dispersion of proppant slugs in various fracturing regimes. To this end we have designed and built a unique experimental setup that resembles a fracture configuration coupled with a particle image/tracking velocimetry setup operating at micro to macro dimensions. Moreover, we have designed optically engineered suspensions of complex fluids with tunable yield stress and consistency, well controlled density match-mismatch properties and refractive indices for both X-rays and visible lights. We present our experimental system and preliminary results. NSF (Grant No. CBET-1554044- CAREER), ACS PRF (Grant No. 55661-DNI9).
Fluid and solid mechanics in a poroelastic network induced by ultrasound.
Wang, Peng; Olbricht, William L
2011-01-04
We made a theoretical analysis on the fluid and solid mechanics in a poroelastic medium induced by low-power ultrasound. Using a perturbative approach, we were able to linearize the governing equations and obtain analytical solutions. We found that ultrasound could propagate in the medium as a mechanical wave, but would dissipate due to frictional forces between the fluid and the solid phase. The amplitude of the wave depends on the ultrasonic power input. We applied this model to the problem of drug delivery to soft biological tissues by low-power ultrasound and proposed a mechanism for enhanced drug penetration. We have also found the coexistence of two acoustic waves under certain circumstances and pointed out the importance of very accurate experimental determination of the high-frequency properties of brain tissue. Copyright © 2010 Elsevier Ltd. All rights reserved.
Application of computational fluid mechanics to atmospheric pollution problems
Hung, R. J.; Liaw, G. S.; Smith, R. E.
1986-01-01
One of the most noticeable effects of air pollution on the properties of the atmosphere is the reduction in visibility. This paper reports the results of investigations of the fluid dynamical and microphysical processes involved in the formation of advection fog on aerosols from combustion-related pollutants, as condensation nuclei. The effects of a polydisperse aerosol distribution, on the condensation/nucleation processes which cause the reduction in visibility are studied. This study demonstrates how computational fluid mechanics and heat transfer modeling can be applied to simulate the life cycle of the atmosphereic pollution problems.
CISM course on stochastic methods in fluid mechanics
Chibbaro, Sergio
2013-01-01
Since their first introduction in natural sciences through the work of Einstein on Brownian motion in 1905 and further works, in particular by Langevin, Smoluchowski and others, stochastic processes have been used in several areas of science and technology. For example, they have been applied in chemical studies, or in fluid turbulence and for combustion and reactive flows. The articles in this book provide a general and unified framework in which stochastic processes are presented as modeling tools for various issues in engineering, physics and chemistry, with particular focus on fluid mechan
Bilateral patching in retinal detachment: fluid mechanics and retinal "settling".
Foster, William J
2011-07-20
When a patient suffers a retinal detachment and surgery is delayed, it is known clinically that bilaterally patching the patient may allow the retina to partially reattach or "settle." Although this procedure has been performed since the 1860s, there is still debate as to how such a maneuver facilitates the reattachment of the retina. Finite element calculations using commercially available analysis software are used to elucidate the influence of reduction in eye movement caused by bilateral patching on the flow of subretinal fluid in a physical model of retinal detachment. It was found that by coupling fluid mechanics with structural mechanics, a physically consistent explanation of increased retinal detachment with eye movements can be found in the case of traction on the retinal hole. Large eye movements increase vitreous traction and detachment forces on the edge of the retinal hole, creating a subretinal vacuum and facilitating increased subretinal fluid. Alternative models, in which intraocular fluid flow is redirected into the subretinal space, are not consistent with these simulations. The results of these simulations explain the physical principles behind bilateral patching and provide insight that can be used clinically. In particular, as is known clinically, bilateral patching may facilitate a decrease in the height of a retinal detachment. The results described here provide a description of a physical mechanism underlying this technique. The findings of this study may aid in deciding whether to bilaterally patch patients and in counseling patients on pre- and postoperative care.
The genesis of fluid mechanics, 1640-1780
Calero, Julián Simón
2008-01-01
Fluid Mechanics, as a scientific discipline in a modern sense, was established between the last third of the 17th century and the first half of the 18th one. This book analyses its genesis, following its evolution along two basic lines of research, which have been named the "problem of resistance" and the "problem of discharge". This approach highlights the existence of a remarkable experimental aspect in the aforementioned research lines, together with their link with problems of a practical nature, such as ballistics, hydraulics, fluid-using machines or naval theory. On the other hand, although previous studies usually present fluid mechanics from the point of view of mathematics, this is complemented here by an engineering viewpoint; gathering attempts made in the beginnings of fluid mechanics to see if the theory was capable of productive application in practical terms. This is nothing unusual in a time where the quality of knowledge and skill is measured largely by its usefulness. (c) Universidad Naciona...
Mechanics of magnetic fluid column in strong magnetic fields
Energy Technology Data Exchange (ETDEWEB)
Polunin, V.M.; Ryapolov, P.A., E-mail: r-piter@yandex.ru; Platonov, V.B.
2017-06-01
Elastic-and magnetic properties of magnetic fluid confined by ponderomotive force in a tube fixed in horizontal position are considered. The system is placed in a strong magnetic field under the influence of external static and dynamic perturbations. An experimental setup has been developed. A theoretical basis of the processes of magnetic colloid elastic deformation has been proposed. The values of the static ponderomotive elasticity coefficient and the elasticity coefficient under dynamic action are experimentally determined. The calculations of the saturation magnetization for two magnetic fluid samples, carried out according to the equation containing the dynamic elasticity coefficient, are in good agreement with the experimental magnetization curve. The described method is of interest when studying magnetophoresis and aggregation of nanoparticles in magnetic colloids.
Experimental study on the fluid stratification mechanism in the density lock
International Nuclear Information System (INIS)
Gu Haifeng; Yan Changqi; Sun Licheng
2009-01-01
Visualized experiments were conducted on the forming process of stratification between hot and cold fluids in three tubes with different diameters. The results show that the working fluids were divided into three layers from top to bottom: convective, interfacial, and constant temperature layers. The working fluid in the convective layer always retains the property of a high rate of temperature increase. The rate of temperature increase in the interfacial layer gradually decreased from top to bottom and was less than that in the convective layer. The working fluid temperature in the constant-temperature layer remained stable. Based on the experimental study, we built a simplified theoretical model and analyzed the stratification mechanism. The results indicate the following stratification mechanism: because of the existence of the transition points in the heat transfer modes, the differences in the rates of temperature increase appear. These differences result in the appearance of fluid stratification. In addition, research on the process of stratification under different conditions tells us that the structure of the density lock influences the position of the transition point. The density lock with a structure of variable cross-sectional grids can effectively control the position of the transition points of the heat transfer modes. (author)
Vieira, Sheila Lopes; de Arruda, Antonio Celso Fonseca
In the majority of published articles on the topic, ER fluids have been studied as if they were viscous liquids. In this work, electrorheological fluids were characterized as solids and their mechanical properties were determined. The results infer that ER materials are controllably resistant to compression, tensile and shear stress, in this order of magnitude. More precisely, fluids made of starch have elasticity modulus similar to that of rubber, they have tensile strength 103 to 5×104 times lower than that of low density polyethylene (LDPE), static yield stress 4×104 to 8×105 times lower than that of acrylonitrile-butadiene-styrene terpolymer (ABS) and fatigue life similar to some polymers like polyethylene(PE) and polypropylene (PP).
Fluid coupling in a discrete model of cochlear mechanics.
Elliott, Stephen J; Lineton, Ben; Ni, Guangjian
2011-09-01
A discrete model of cochlear mechanics is introduced that includes a full, three-dimensional, description of fluid coupling. This formulation allows the fluid coupling and basilar membrane dynamics to be analyzed separately and then coupled together with a simple piece of linear algebra. The fluid coupling is initially analyzed using a wavenumber formulation and is separated into one component due to one-dimensional fluid coupling and one comprising all the other contributions. Using the theory of acoustic waves in a duct, however, these two components of the pressure can also be associated with a far field, due to the plane wave, and a near field, due to the evanescent, higher order, modes. The near field components are then seen as one of a number of sources of additional longitudinal coupling in the cochlea. The effects of non-uniformity and asymmetry in the fluid chamber areas can also be taken into account, to predict both the pressure difference between the chambers and the mean pressure. This allows the calculation, for example, of the effect of a short cochlear implant on the coupled response of the cochlea. © 2011 Acoustical Society of America
Stanley Corrsin Award Talk: Fluid Mechanics of Fungi and Slime
Brenner, Michael
2013-11-01
There are interesting fluid mechanics problems everywhere, even in the most lowly and hidden corners of forest floors. Here I discuss some questions we have been working on in recent years involving fungi and slime. A critical issue for the ecology of fungi and slime is nutrient availability: nutrient sources are highly heterogeneous, and strategies are necessary to find food when it runs out. In the fungal phylum Ascomycota, spore dispersal is the primary mechanism for finding new food sources. The defining feature of this phylum is the ascus, a fluid filled sac from which spores are ejected, through a build up in osmotic pressure. We outline the (largely fluid mechanical) design constraints on this ejection strategy, and demonstrate how it provides strong constraints for the diverse morphologies of spores and asci found in nature. The core of the argument revisits a classical problem in elastohydrodynamic lubrication from a different perspective. A completely different strategy for finding new nutrient is found by slime molds and fungi that stretch out - as a single organism- over enormous areas (up to hectares) over forest floors. As a model problem we study the slime mold Physarum polycephalum, which forages with a large network of connected tubes on the forest floors. Localized regions in the network find nutrient sources and then pump the nutrients throughout the entire organism. We discuss fluid mechanical mechanisms for coordinating this transport, which generalize peristalsis to pumping in a heterogeneous network. We give a preliminary discussion to how physarum can detect a nutrient source and pump the nutrient throughout the organism.
Fluid mechanics as a driver of tissue-scale mechanical signaling in organogenesis.
Gilbert, Rachel M; Morgan, Joshua T; Marcin, Elizabeth S; Gleghorn, Jason P
2016-12-01
Organogenesis is the process during development by which cells self-assemble into complex, multi-scale tissues. Whereas significant focus and research effort has demonstrated the importance of solid mechanics in organogenesis, less attention has been given to the fluid forces that provide mechanical cues over tissue length scales. Fluid motion and pressure is capable of creating spatial gradients of forces acting on cells, thus eliciting distinct and localized signaling patterns essential for proper organ formation. Understanding the multi-scale nature of the mechanics is critically important to decipher how mechanical signals sculpt developing organs. This review outlines various mechanisms by which tissues generate, regulate, and sense fluid forces and highlights the impact of these forces and mechanisms in case studies of normal and pathological development.
Effect of Chamber Backpressure on Swirl Injector Fluid Mechanics
Kenny, R. Jeremy; Hulka, James R.; Moser, Marlow D.; Rhys, Noah O.
2008-01-01
A common propellant combination used for high thrust generation is GH2/LOX. Historical GH2/LOX injection elements have been of the shear-coaxial type. Element type has a large heritage of research work to aid in element design. The swirl-coaxial element, despite its many performance benefits, has a relatively small amount of historical, LRE-oriented work to draw from. Design features of interest are grounded in the fluid mechanics of the liquid swirl process itself, are based on data from low-pressure, low mass flow rate experiments. There is a need to investigate how high ambient pressures and mass flow rates influence internal and external swirl features. The objective of this research is to determine influence of varying liquid mass flow rate and ambient chamber pressure on the intact-length fluid mechanics of a liquid swirl element.
Friction mechanisms and interfacial slip at fluid-solid interfaces
Leger, L
2003-01-01
We present series of experiments based on near field laser velocimetry, developed to characterize the friction mechanisms at fluid-solid interfaces. For polymers, entangled polymer melts are sheared against smooth solid surfaces, covered by surface attached polymer chains of the same chemical species, having a controlled surface density. Direct measurements of the interfacial velocity and of the shear force allow identification of the molecular mechanisms of friction. Depending on the value of the inverse of the shear rate experienced by the polymer compared to the reptation time, the transition between a regime of high and a regime of low friction observed when increasing the shear rate can be related to disentanglement or to the extraction of the surface chains from the bulk polymer. Surfaces with adjusted friction properties can thus be designed by choosing chain anchored length and surface density. For simple fluids, the direct measurements of the interfacial velocity show that, contrary to the usual hypo...
A cyber-physical approach to experimental fluid mechanics
Mackowski, Andrew Williams
This Thesis documents the design, implementation, and use of a novel type of experimental apparatus, termed Cyber-Physical Fluid Dynamics (CPFD). Unlike traditional fluid mechanics experiments, CPFD is a general-purpose technique that allows one to impose arbitrary forces on an object submerged in a fluid. By combining fluid mechanics with robotics, we can perform experiments that would otherwise be incredibly difficult or time-consuming. More generally, CPFD allows a high degree of automation and control of the experimental process, allowing for much more efficient use of experimental facilities. Examples of CPFD's capabilites include imposing a gravitational force in the horizontal direction (allowing a test object to "fall" sideways in a water channel), simulating nonlinear springs for a vibrating fluid-structure system, or allowing a self-propelled body to move forward under its own force. Because experimental parameters (including forces and even the mass of the test object) are defined in software, one can define entire ensembles of experiments to run autonomously. CPFD additionally integrates related systems such as water channel speed control, LDV flow speed measurements, and PIV flowfield measurements. The end result is a general-purpose experimental system that opens the door to a vast array of fluid-structure interaction problems. We begin by describing the design and implementation of CPFD, the heart of which is a high-performance force-feedback control system. Precise measurement of time-varying forces (including removing effects of the test object's inertia) is more critical here than in typical robotic force-feedback applications. CPFD is based on an integration of ideas from control theory, fluid dynamics, computer science, electrical engineering, and solid mechanics. We also describe experiments using the CPFD experimental apparatus to study vortex-induced vibration (VIV) and oscillating-airfoil propulsion. We show how CPFD can be used to simulate
Fluid mechanics of fusion lasers. Final technical report
International Nuclear Information System (INIS)
Shwartx, J.; Golik, R.J.; Merkle, C.L.; Ausherman, D.R.; Fishman, E.
1978-04-01
The primary objective of this study is to define the fluid mechanical requirements for a repetitively-pulsed high energy laser that may be used as a driver in an inertial confinement fusion system designed for electric power generation. Emphasis was placed on defining conceptual designs of efficient laser flow systems that are capable of conserving gas and minimizing operating power requirements. The development of effective pressure wave suppression concepts to produce acceptable beam quality for fusion applications was also considered
Fluid Mechanics of Aquatic Locomotion at Large Reynolds Numbers
Govardhan, RN; Arakeri, JH
2011-01-01
Abstract | There exist a huge range of fish species besides other aquatic organisms like squids and salps that locomote in water at large Reynolds numbers, a regime of flow where inertial forces dominate viscous forces. In the present review, we discuss the fluid mechanics governing the locomotion of such organisms. Most fishes propel themselves by periodic undulatory motions of the body and tail, and the typical classification of their swimming modes is based on the fraction of their body...
Fluid Mechanics of the Vascular Basement Membrane in the Brain
Coloma, Mikhail; Hui, Jonathan; Chiarot, Paul; Huang, Peter; Carare, Roxana; McLeod, Kenneth; Schaffer, David
2013-11-01
Beta-amyloid is a normal product of brain metabolic function and is found within the interstitial fluid of the brain. Failure of the clearance of beta-amyloid from the aging brain leads to its accumulation within the walls of arteries and to Alzheimer's disease. The vascular basement membrane (VBM) within the walls of cerebral arteries surrounds the spirally arranged smooth muscle cells and represents an essential pathway for removal of beta-amyloid from the brain. This process fails with the stiffening of arterial walls associated with aging. In this study we hypothesize that the deformation of the VBM associated with arterial pulsations drives the interstitial fluid to drain in the direction opposite of the arterial blood flow. This hypothesis is theoretically investigated by modeling the VBM as a thin, coaxial, fluid-filled porous medium surrounding a periodically deforming cylindrical tube. Flow and boundary conditions required to achieve such a backward clearance are derived through a control volume analysis of mass, momentum, and energy.
Theoretical prediction of crystallization kinetics of a supercooled Lennard-Jones fluid
Gunawardana, K. G. S. H.; Song, Xueyu
2018-05-01
The first order curvature correction to the crystal-liquid interfacial free energy is calculated using a theoretical model based on the interfacial excess thermodynamic properties. The correction parameter (δ), which is analogous to the Tolman length at a liquid-vapor interface, is found to be 0.48 ± 0.05 for a Lennard-Jones (LJ) fluid. We show that this curvature correction is crucial in predicting the nucleation barrier when the size of the crystal nucleus is small. The thermodynamic driving force (Δμ) corresponding to available simulated nucleation conditions is also calculated by combining the simulated data with a classical density functional theory. In this paper, we show that the classical nucleation theory is capable of predicting the nucleation barrier with excellent agreement to the simulated results when the curvature correction to the interfacial free energy is accounted for.
Teaching fluid mechanics to high schoolers: methods, challenges, and outcome
Manikantan, Harishankar
2017-11-01
This talk will summarize the goals, methods, and both short- and long-term feedback from two high-school-level courses in fluid mechanics involving 43 students and cumulatively spanning over 100 hours of instruction. The goals of these courses were twofold: (a) to spark an interest in science and engineering and attract a more diverse demographic into college-level STEM programs; and (b) to train students in a `college-like' method of approaching the physics of common phenomena, with fluid mechanics as the context. The methods of instruction included classes revolving around the idea of dispelling misconceptions, group activities, `challenge' rounds and mock design projects to use fluid mechanics phenomena to achieve a specified goal, and simple hands-on experiments. The feedback during instruction was overwhelmingly positive, particularly in terms of a changing and favorable attitude towards math and engineering. Long after the program, a visible impact lies in a diverse group of students acknowledging that the course had a positive effect in their decision to choose an engineering or science major in a four-year college.
Fluid mechanical responses to nutrient depletion in fungi and biofilmsa)
Brenner, Michael P.
2014-10-01
In both fungi and bacterial biofilms, when nutrients are depleted, the organisms cannot physically migrate to find a new source, but instead must develop adaptations that allow them to survive. This paper reviews our work attempting to discover design principles for these adaptations. We develop fluid mechanical models, and aim to understand whether these suggest organizing principles for the observed morphological diversity. Determining whether a proposed organizing principle explains extant biological designs is fraught with difficulty: simply because a design principle predicts characteristics similar to an organism's morphology could just as well be accidental as revealing. In each of the two sets of examples, we adopt different strategies to develop understanding in spite of this difficulty. Within the fungal phylum Ascomycota, we use the large observed diversity of different morphological solutions to the fundamental fluid mechanical problem to measure how far each solution is from a design optimum, thereby measuring how far the extant designs deviate from the hypothesized optimum. This allows comparing different design principles to each other. For biofilms, we use engineering principles to make qualitative predictions of what types of adaptations might exist given the physicochemical properties of the repertoire of proteins that bacteria can create, and then find evidence for these adaptations in experiments. While on the surface this paper addresses the particular adaptations used by the fungal phylum Ascomycota and bacterial biofilms, we also aim to motivate discussion of different approaches to using design principles, fluid mechanical or otherwise, to rationalize observed engineering solutions in biology.
Oscillatory fluid flow influences primary cilia and microtubule mechanics.
Espinha, Lina C; Hoey, David A; Fernandes, Paulo R; Rodrigues, Hélder C; Jacobs, Christopher R
2014-07-01
Many tissues are sensitive to mechanical stimuli; however, the mechanotransduction mechanism used by cells remains unknown in many cases. The primary cilium is a solitary, immotile microtubule-based extension present on nearly every mammalian cell which extends from the basal body. The cilium is a mechanosensitive organelle and has been shown to transduce fluid flow-induced shear stress in tissues, such as the kidney and bone. The majority of microtubules assemble from the mother centriole (basal body), contributing significantly to the anchoring of the primary cilium. Several studies have attempted to quantify the number of microtubules emanating from the basal body and the results vary depending on the cell type. It has also been shown that cellular response to shear stress depends on microtubular integrity. This study hypothesizes that changing the microtubule attachment of primary cilia in response to a mechanical stimulus could change primary cilia mechanics and, possibly, mechanosensitivity. Oscillatory fluid flow was applied to two different cell types and the microtubule attachment to the ciliary base was quantified. For the first time, an increase in microtubules around primary cilia both with time and shear rate in response to oscillatory fluid flow stimulation was demonstrated. Moreover, it is presented that the primary cilium is required for this loading-induced cellular response. This study has demonstrated a new role for the cilium in regulating alterations in the cytoplasmic microtubule network in response to mechanical stimulation, and therefore provides a new insight into how cilia may regulate its mechanics and thus the cells mechanosensitivity. Copyright © 2014 Wiley Periodicals, Inc.
Advances in cardiovascular fluid mechanics: bench to bedside.
Dasi, Lakshmi P; Sucosky, Philippe; de Zelicourt, Diane; Sundareswaran, Kartik; Jimenez, Jorge; Yoganathan, Ajit P
2009-04-01
This paper presents recent advances in cardiovascular fluid mechanics that define the current state of the art. These studies include complex multimodal investigations with advanced measurement and simulation techniques. We first discuss the complex flows within the total cavopulmonary connection in Fontan patients. We emphasize the quantification of energy losses by studying the importance of caval offsets as well as the differences among various Fontan surgical protocols. In our studies of the fluid mechanics of prosthetic heart valves, we reveal for the first time the full three-dimensional complexity of flow fields in the vicinity of bileaflet and trileaflet valves and the microscopic hinge flow dynamics. We also present results of these valves functioning in a patient-specific native aorta geometry. Our in vitro mitral valve studies show the complex mechanism of the native mitral valve apparatus. We demonstrate that the different components of the mitral valve have independent and synergistically complex functions that allow the valve to operate efficiently. We also show how valve mechanics change under pathological and repair conditions associated with enlarged ventricles. Finally, our ex vivo studies on the interactions between the aortic valve and its surrounding hemodynamic environment are aimed at providing insights into normal valve function and valve pathology. We describe the development of organ- and tissue-culture systems and the biological response of the tissue subjected to their respective simulated mechanical environment. The studies noted above have enhanced our understanding of the complex fluid mechanics associated with the cardiovascular system and have led to new translational technologies.
Fluid mechanics of eating, swallowing and digestion - overview and perspectives.
Engmann, Jan; Burbidge, Adam S
2013-02-26
From a very simplistic viewpoint, the human digestive system can be regarded as a long tube (with dramatic variations in diameter, cross-section, wall properties, pumping mechanisms, regulating valves and in-line sensors). We single out a few fluid mechanical phenomena along the trajectory of a food bolus from the mouth to the small intestine and discuss how they influence sensorial perception, safe transport, and nutrient absorption from a bolus. The focus is on lubrication flows between the tongue and palate, the oropharyngeal stage of swallowing and effects of flow on absorption in the small intestine. Specific challenges and opportunities in this research area are highlighted.
Theoretical and numerical investigations of inverse patchy colloids in the fluid phase
International Nuclear Information System (INIS)
Kalyuzhnyi, Yurij V.; Bianchi, Emanuela; Ferrari, Silvano; Kahl, Gerhard
2015-01-01
We investigate the structural and thermodynamic properties of a new class of patchy colloids, referred to as inverse patchy colloids (IPCs) in their fluid phase via both theoretical methods and simulations. IPCs are nano- or micro- meter sized particles with differently charged surface regions. We extend conventional integral equation schemes to this particular class of systems: our approach is based on the so-called multi-density Ornstein-Zernike equation, supplemented with the associative Percus-Yevick approximation (APY). To validate the accuracy of our framework, we compare the obtained results with data extracted from NpT and NVT Monte Carlo simulations. In addition, other theoretical approaches are used to calculate the properties of the system: the reference hypernetted-chain (RHNC) method and the Barker-Henderson thermodynamic perturbation theory. Both APY and RHNC frameworks provide accurate predictions for the pair distribution functions: APY results are in slightly better agreement with MC data, in particular at lower temperatures where the RHNC solution does not converge
Topological Fluid Mechanics with Applications to Free Surfaces and Axisymmetric Flows
DEFF Research Database (Denmark)
Brøns, Morten
1996-01-01
Topological fluid mechanics is the study of qualitative features of fluid patterns. We discuss applications to the flow beneath a stagnant surface film, and to patterns in axisymmetric flow.......Topological fluid mechanics is the study of qualitative features of fluid patterns. We discuss applications to the flow beneath a stagnant surface film, and to patterns in axisymmetric flow....
Interpreting Students’ Perceptions in Fluid Mechanics Learning Outcomes
Directory of Open Access Journals (Sweden)
Filomena SOARES
2015-11-01
Full Text Available The objective of this study is to analyse the impact of introducing a practical work in the learning process of the Fluid Transport Systems course in Chemical Engineering degree. The students, in groups of two or three elements, were free to choose the application case in order to develop the practical work proposed by the responsible teachers. The students selected a centrifugal pump to supply water to houses or buildings and designed the piping system. The practical work was evaluated through the written report. The students’ perceptions were analysed through a questionnaire. The learning outcomes were also considered in order to understand how the fluid mechanics concepts were acquired. In the teachers’ point of view the teamwork should enable the development of students’ soft skills and competencies, promoting the ability to integrate and work in teams. The students changed their learning processing and perception becoming more reflective and less accommodative, forcing them to think critically and share opinions. Regarding the Fluid Mechanics assessment, the practical work increased, in average, the final grade at least one value.
Mechanical design problems associated with turbopump fluid film bearings
Evces, Charles R.
1990-01-01
Most high speed cryogenic turbopumps for liquid propulsion rocket engines currently use ball or roller contact bearings for rotor support. The operating speeds, loads, clearances, and environments of these pumps combine to make bearing wear a limiting factor on turbopump life. An example is the high pressure oxygen turbopump (HPOTP) used in the Space Shuttle Main Engine (SSME). Although the HPOTP design life is 27,000 seconds at 30,000 rpms, or approximately 50 missions, bearings must currently be replaced after 2 missions. One solution to the bearing wear problem in the HPOTP, as well as in future turbopump designs, is the utilization of fluid film bearings in lieu of continuous contact bearings. Hydrostatic, hydrodynamic, and damping seal bearings are all replacement candidates for contact bearings in rocket engine high speed turbomachinery. These three types of fluid film bearings have different operating characteristics, but they share a common set of mechanical design opportunities and difficulties. Results of research to define some of the mechanical design issues are given. Problems considered include transient strat/stop rub, non-operational rotor support, bearing wear inspection and measurement, and bearing fluid supply route. Emphasis is given to the HPOTP preburner pump (PBP) bearing, but the results are pertinent to high-speed cryogenic turbomachinery in general.
Fluid mechanics and heat transfer spirally fluted tubing
Larue, J. C.; Libby, P. A.; Yampolsky, J. S.
1981-08-01
The objective of this program is to develop both a qualitative and a quantitative understanding of the fluid mechanics and heat transfer mechanisms that underlie the measured performance of the spirally fluted tubes under development at General Atomic. The reason for the interest in the spirally fluted tubes is that results to date have indicated three advantages to this tubing concept: The fabrication technique of rolling flutes on strip and subsequently spiralling and simultaneously welding the strip to form tubing results in low fabrication costs, approximately equal to those of commercially welded tubing. The heat transfer coefficient is increased without a concomitant increase of the friction coefficient on the inside of the tube. In single-phase axial flow of water, the helical flutes continuously induce rotation of the flow both within and without the tube as a result of the effect of curvature. An increase in condensation heat transfer on the outside of the tube is achieved. In a vertical orientation with fluid condensing on the outside of the helically fluted tube, the flutes provide a channel for draining the condensed fluid.
On the Use of Computers for Teaching Fluid Mechanics
Benson, Thomas J.
1994-01-01
Several approaches for improving the teaching of basic fluid mechanics using computers are presented. There are two objectives to these approaches: to increase the involvement of the student in the learning process and to present information to the student in a variety of forms. Items discussed include: the preparation of educational videos using the results of computational fluid dynamics (CFD) calculations, the analysis of CFD flow solutions using workstation based post-processing graphics packages, and the development of workstation or personal computer based simulators which behave like desk top wind tunnels. Examples of these approaches are presented along with observations from working with undergraduate co-ops. Possible problems in the implementation of these approaches as well as solutions to these problems are also discussed.
Fluid Mechanics, Drag Reduction and Advanced Configuration Aeronautics
Bushnell, Dennis M.
2000-01-01
This paper discusses Advanced Aircraft configurational approaches across the speed range, which are either enabled, or greatly enhanced, by clever Flow Control. Configurations considered include Channel Wings with circulation control for VTOL (but non-hovering) operation with high cruise speed, strut-braced CTOL transports with wingtip engines and extensive ('natural') laminar flow control, a midwing double fuselage CTOL approach utilizing several synergistic methods for drag-due-to-lift reduction, a supersonic strut-braced configuration with order of twice the L/D of current approaches and a very advanced, highly engine flow-path-integrated hypersonic cruise machine. This paper indicates both the promise of synergistic flow control approaches as enablers for 'Revolutions' in aircraft performance and fluid mechanic 'areas of ignorance' which impede their realization and provide 'target-rich' opportunities for Fluids Research.
A consideration on pipe-wall thinning mechanisms from an aspect of fluid-mechanics
International Nuclear Information System (INIS)
Inada, Fumio; Yoneda, Kimitoshi; Morita, Ryo; Fujiwara, Kazutoshi; Furuya, Masahiro
2008-01-01
The contribution of the fluid mechanics to the piping wall thinning phenomena was investigated. It was shown that the fluid force to the wall was quite different between flow accelerated corrosion (FAC) and erosion. The turbulent mass transfer, which is one of the primary factors of FAC, was analogous to the turbulent heat transfer. The model that the molecular transport in the viscous sublayer nearby soon of wall was predominant was practicable. In addition, the mass transport was predicted using commercial codes of computational fluid dynamics. Some prediction results of the mass transfer in orifice and the elbow using above techniques were explained. (author)
Study of a few problems concerning plasma physics and fluid mechanics
International Nuclear Information System (INIS)
Colin, M.
2011-01-01
The works presented in this thesis deal with solving partial differential equations concerning the laser-plasma interaction and some issues in fluid mechanics. All these works involve significant research in the modelization field: the approximation of oscillating hyperbolic systems, the simulation of Zakharov-type systems involving the Raman effect, Hele-Shaw models and gigantic micelles models. They also tackles theoretical issues like the existence and the uniqueness of solutions, the stability or instability of solitary waves, the optimal control, error estimation and model convergency
Spectral methods and their implementation to solution of aerodynamic and fluid mechanic problems
Streett, C. L.
1987-01-01
Fundamental concepts underlying spectral collocation methods, especially pertaining to their use in the solution of partial differential equations, are outlined. Theoretical accuracy results are reviewed and compared with results from test problems. A number of practical aspects of the construction and use of spectral methods are detailed, along with several solution schemes which have found utility in applications of spectral methods to practical problems. Results from a few of the successful applications of spectral methods to problems of aerodynamic and fluid mechanic interest are then outlined, followed by a discussion of the problem areas in spectral methods and the current research under way to overcome these difficulties.
Analytical and Numerical Studies of Several Fluid Mechanical Problems
Kong, D. L.
2014-03-01
In this thesis, three parts, each with several chapters, are respectively devoted to hydrostatic, viscous, and inertial fluids theories and applications. Involved topics include planetary, biological fluid systems, and high performance computing technology. In the hydrostatics part, the classical Maclaurin spheroids theory is generalized, for the first time, to a more realistic multi-layer model, establishing geometries of both the outer surface and the interfaces. For one of its astrophysical applications, the theory explicitly predicts physical shapes of surface and core-mantle-boundary for layered terrestrial planets, which enables the studies of some gravity problems, and the direct numerical simulations of dynamo flows in rotating planetary cores. As another application of the figure theory, the zonal flow in the deep atmosphere of Jupiter is investigated for a better understanding of the Jovian gravity field. An upper bound of gravity field distortions, especially in higher-order zonal gravitational coefficients, induced by deep zonal winds is estimated firstly. The oblate spheroidal shape of an undistorted Jupiter resulting from its fast solid body rotation is fully taken into account, which marks the most significant improvement from previous approximation based Jovian wind theories. High viscosity flows, for example Stokes flows, occur in a lot of processes involving low-speed motions in fluids. Microorganism swimming is such a typical case. A fully three dimensional analytic solution of incompressible Stokes equation is derived in the exterior domain of an arbitrarily translating and rotating prolate spheroid, which models a large family of microorganisms such as cocci bacteria. The solution is then applied to the magnetotactic bacteria swimming problem, and good consistency has been found between theoretical predictions and laboratory observations of the moving patterns of such bacteria under magnetic fields. In the analysis of dynamics of planetary
Fluid mechanics. An introduction. Technische Stroemungslehre. Eine Einfuehrung
Energy Technology Data Exchange (ETDEWEB)
Kalide, W
1980-01-01
Originally written for students in the field of engineering, this book may also be of use in the engineering practice. The subject is presented with a view to practice. Fundamental theorems of fluid mechanics are presented without going too much into theory. The chapter on supersonic flow has been extended in the fifth edition as this is a field of great importance in engineering. The new chapter on gas dynamics takes account of these processes in turbine and compressor construction and aeronautical engineering. There is an appendix with material data, characteristic values, flow resistance coefficients, diagrams and two tables with rated pressure loss values for pipeline flow.
Review of coaxial flow gas core nuclear rocket fluid mechanics
International Nuclear Information System (INIS)
Weinstein, H.
1976-01-01
In a prematurely aborted attempt to demonstrate the feasibility of using a gas core nuclear reactor as a rocket engine, NASA initiated a number of studies on the relevant fluid mechanics problems. These studies were carried out at NASA laboratories, universities and industrial research laboratories. Because of the relatively sudden termination of most of this work, a unified overview was never presented which demonstrated the accomplishments of the program and pointed out the areas where additional work was required for a full understanding of the cavity flow. This review attempts to fulfill a part of this need in two important areas
Laser metrology in fluid mechanics granulometry, temperature and concentration measurements
Boutier, Alain
2013-01-01
In fluid mechanics, non-intrusive measurements are fundamental in order to improve knowledge of the behavior and main physical phenomena of flows in order to further validate codes.The principles and characteristics of the different techniques available in laser metrology are described in detail in this book.Velocity, temperature and concentration measurements by spectroscopic techniques based on light scattered by molecules are achieved by different techniques: laser-induced fluorescence, coherent anti-Stokes Raman scattering using lasers and parametric sources, and absorption sp
McNair, James N; Newbold, J Denis
2012-05-07
Most ecological studies of particle transport in streams that focus on fine particulate organic matter or benthic invertebrates use the Exponential Settling Model (ESM) to characterize the longitudinal pattern of particle settling on the bed. The ESM predicts that if particles are released into a stream, the proportion that have not yet settled will decline exponentially with transport time or distance and will be independent of the release elevation above the bed. To date, no credible basis in fluid mechanics has been established for this model, nor has it been rigorously tested against more-mechanistic alternative models. One alternative is the Local Exchange Model (LEM), which is a stochastic advection-diffusion model that includes both longitudinal and vertical spatial dimensions and is based on classical fluid mechanics. The LEM predicts that particle settling will be non-exponential in the near field but will become exponential in the far field, providing a new theoretical justification for far-field exponential settling that is based on plausible fluid mechanics. We review properties of the ESM and LEM and compare these with available empirical evidence. Most evidence supports the prediction of both models that settling will be exponential in the far field but contradicts the ESM's prediction that a single exponential distribution will hold for all transport times and distances. Copyright Â© 2012 Elsevier Ltd. All rights reserved.
Dynamics of polymeric liquids. Vol. 1, 2nd Ed.: Fluid mechanics
International Nuclear Information System (INIS)
Bird, R.B.; Armstrong, R.C.; Hassager, O.
1987-01-01
This book examines Newtonian liquids and polymer fluid mechanics. It begins with a review of the main ideas of fluid dynamics as well as key points of Newtonian fluids. Major revisions include extensive updating of all material and a greater emphasis on fluid dynamics problem solving. It presents summaries of experiments describing the difference between polymeric and simple fluids. In addition, it traces, roughly in historical order, various methods for solving polymer fluid dynamics problems
Directory of Open Access Journals (Sweden)
Guan Heng Yeoh
2016-12-01
Full Text Available The main focus in the analysis of pool or flow boiling in saturated or subcooled conditions is the basic understanding of the phase change process through the heat transfer and wall heat flux partitioning at the heated wall and the two-phase bubble behaviours in the bulk liquid as they migrate away from the heated wall. This paper reviews the work in this rapid developing area with special reference to modelling nucleate boiling of cryogenic liquids in the context of computational fluid dynamics and associated theoretical developments. The partitioning of the wall heat flux at the heated wall into three components – single-phase convection, transient conduction and evaporation – remains the most popular mechanistic approach in predicting the heat transfer process during boiling. Nevertheless, the respective wall heat flux components generally require the determination of the active nucleation site density, bubble departure diameter and nucleation frequency, which are crucial to the proper prediction of the heat transfer process. Numerous empirical correlations presented in this paper have been developed to ascertain these three important parameters with some degree of success. Albeit the simplicity of empirical correlations, they remain applicable to only a narrow range of flow conditions. In order to extend the wall heat flux partitioning approach to a wider range of flow conditions, the fractal model proposed for the active nucleation site density, force balance model for bubble departing from the cavity and bubble lifting off from the heated wall and evaluation of nucleation frequency based on fundamental theory depict the many enhancements that can improve the mechanistic model predictions. The macroscopic consideration of the two-phase boiling in the bulk liquid via the two-fluid model represents the most effective continuum approach in predicting the volume fraction and velocity distributions of each phase. Nevertheless, the
Theoretical physics 3. Quantum mechanics 1 with problems in MAPLE
International Nuclear Information System (INIS)
Reineker, P.; Schulz, M.; Schulz, B.M.
2007-01-01
The following topics are dealt with: Historically heuristic introduction to quantum mechanics, the Schroedinger equation, foundations of quantum mechanics, the linear harmonic oscillator, quantum-mechanical motion in the central field, approximation methods for the solution of quantum mechanical problems, motion of particles in the electromagnetic field, spin and magnetic moment of the electron, many-particle systems, conceptional problems of quantum mechanics
Partitioned fluid-solid coupling for cardiovascular blood flow: left-ventricular fluid mechanics.
Krittian, Sebastian; Janoske, Uwe; Oertel, Herbert; Böhlke, Thomas
2010-04-01
We present a 3D code-coupling approach which has been specialized towards cardiovascular blood flow. For the first time, the prescribed geometry movement of the cardiovascular flow model KaHMo (Karlsruhe Heart Model) has been replaced by a myocardial composite model. Deformation is driven by fluid forces and myocardial response, i.e., both its contractile and constitutive behavior. Whereas the arbitrary Lagrangian-Eulerian formulation (ALE) of the Navier-Stokes equations is discretized by finite volumes (FVM), the solid mechanical finite elasticity equations are discretized by a finite element (FEM) approach. Taking advantage of specialized numerical solution strategies for non-matching fluid and solid domain meshes, an iterative data-exchange guarantees the interface equilibrium of the underlying governing equations. The focus of this work is on left-ventricular fluid-structure interaction based on patient-specific magnetic resonance imaging datasets. Multi-physical phenomena are described by temporal visualization and characteristic FSI numbers. The results gained show flow patterns that are in good agreement with previous observations. A deeper understanding of cavity deformation, blood flow, and their vital interaction can help to improve surgical treatment and clinical therapy planning.
Respiratory mechanics and fluid dynamics after lung resection surgery.
Miserocchi, Giuseppe; Beretta, Egidio; Rivolta, Ilaria
2010-08-01
Thoracic surgery that requires resection of a portion of lung or of a whole lung profoundly alters the mechanical and fluid dynamic setting of the lung-chest wall coupling, as well as the water balance in the pleural space and in the remaining lung. The most frequent postoperative complications are of a respiratory nature, and their incidence increases the more the preoperative respiratory condition seems compromised. There is an obvious need to identify risk factors concerning mainly the respiratory function, without neglecting the importance of other comorbidities, such as coronary disease. At present, however, a satisfactory predictor of postoperative cardiopulmonary complications is lacking; postoperative morbidity and mortality have remained unchanged in the last 10 years. The aim of this review is to provide a pathophysiologic interpretation of the main respiratory complications of a respiratory nature by relying on new concepts relating to lung fluid dynamics and mechanics. New parameters are proposed to improve evaluation of respiratory function from pre- to the early postoperative period when most of the complications occur. Published by Elsevier Inc.
Fluid mechanics experiments in oscillatory flow. Volume 2: Tabulated data
Seume, J.; Friedman, G.; Simon, T. W.
1992-01-01
Results of a fluid mechanics measurement program in oscillating flow within a circular duct are presented. The program began with a survey of transition behavior over a range of oscillation frequency and magnitude and continued with a detailed study at a single operating point. Such measurements were made in support of Stirling engine development. Values of three dimensionless parameters, Re sub max, Re sub w, and A sub R, embody the velocity amplitude, frequency of oscillation, and mean fluid displacement of the cycle, respectively. Measurements were first made over a range of these parameters that are representative of the heat exchanger tubes in the heater section of NASA's Stirling cycle Space Power Research Engine (SPRE). Measurements were taken of the axial and radial components of ensemble-averaged velocity and rms velocity fluctuation and the dominant Reynolds shear stress, at various radial positions for each of four axial stations. In each run, transition from laminar to turbulent flow, and its reverse, were identified and sufficient data was gathered to propose the transition mechanism. Volume 2 contains data reduction program listings and tabulated data (including its graphics).
[Present status and trend of heart fluid mechanics research based on medical image analysis].
Gan, Jianhong; Yin, Lixue; Xie, Shenghua; Li, Wenhua; Lu, Jing; Luo, Anguo
2014-06-01
With introduction of current main methods for heart fluid mechanics researches, we studied the characteristics and weakness for three primary analysis methods based on magnetic resonance imaging, color Doppler ultrasound and grayscale ultrasound image, respectively. It is pointed out that particle image velocity (PIV), speckle tracking and block match have the same nature, and three algorithms all adopt block correlation. The further analysis shows that, with the development of information technology and sensor, the research for cardiac function and fluid mechanics will focus on energy transfer process of heart fluid, characteristics of Chamber wall related to blood fluid and Fluid-structure interaction in the future heart fluid mechanics fields.
Serious Fun: Using Toys to Demonstrate Fluid Mechanics Principles
Saviz, Camilla M.; Shakerin, Said
2014-01-01
Many students have owned or seen fluids toys in which two immiscible fluids within a closed container can be tilted to generate waves. These types of inexpensive and readily available toys are fun to play with, but they are also useful for provoking student learning about fluid properties or complex fluid behavior, including drop formation and…
Links between fluid mechanics and quantum mechanics: a model for information in economics?
Haven, Emmanuel
2016-05-28
This paper tallies the links between fluid mechanics and quantum mechanics, and attempts to show whether those links can aid in beginning to build a formal template which is usable in economics models where time is (a)symmetric and memory is absent or present. An objective of this paper is to contemplate whether those formalisms can allow us to model information in economics in a novel way. © 2016 The Author(s).
Computational thermal, chemical, fluid, and solid mechanics for geosystems management.
Energy Technology Data Exchange (ETDEWEB)
Davison, Scott; Alger, Nicholas; Turner, Daniel Zack; Subia, Samuel Ramirez; Carnes, Brian; Martinez, Mario J.; Notz, Patrick K.; Klise, Katherine A.; Stone, Charles Michael; Field, Richard V., Jr.; Newell, Pania; Jove-Colon, Carlos F.; Red-Horse, John Robert; Bishop, Joseph E.; Dewers, Thomas A.; Hopkins, Polly L.; Mesh, Mikhail; Bean, James E.; Moffat, Harry K.; Yoon, Hongkyu
2011-09-01
This document summarizes research performed under the SNL LDRD entitled - Computational Mechanics for Geosystems Management to Support the Energy and Natural Resources Mission. The main accomplishment was development of a foundational SNL capability for computational thermal, chemical, fluid, and solid mechanics analysis of geosystems. The code was developed within the SNL Sierra software system. This report summarizes the capabilities of the simulation code and the supporting research and development conducted under this LDRD. The main goal of this project was the development of a foundational capability for coupled thermal, hydrological, mechanical, chemical (THMC) simulation of heterogeneous geosystems utilizing massively parallel processing. To solve these complex issues, this project integrated research in numerical mathematics and algorithms for chemically reactive multiphase systems with computer science research in adaptive coupled solution control and framework architecture. This report summarizes and demonstrates the capabilities that were developed together with the supporting research underlying the models. Key accomplishments are: (1) General capability for modeling nonisothermal, multiphase, multicomponent flow in heterogeneous porous geologic materials; (2) General capability to model multiphase reactive transport of species in heterogeneous porous media; (3) Constitutive models for describing real, general geomaterials under multiphase conditions utilizing laboratory data; (4) General capability to couple nonisothermal reactive flow with geomechanics (THMC); (5) Phase behavior thermodynamics for the CO2-H2O-NaCl system. General implementation enables modeling of other fluid mixtures. Adaptive look-up tables enable thermodynamic capability to other simulators; (6) Capability for statistical modeling of heterogeneity in geologic materials; and (7) Simulator utilizes unstructured grids on parallel processing computers.
Directory of Open Access Journals (Sweden)
Romero EL
2013-08-01
Full Text Available Eder Lilia Romero, Maria Jose Morilla Nanomedicine Research Program, Department of Science and Technology, National University of Quilmes, Bernal, Buenos Aires, Argentina Abstract: Vesicles that are specifically designed to overcome the stratum corneum barrier in intact skin provide an efficient transdermal (systemic or local drug delivery system. They can be classified into two main groups according to the mechanisms underlying their skin interaction. The first group comprises those possessing highly deformable bilayers, achieved by incorporating edge activators to the bilayers or by mixing with certain hydrophilic solutes. The vesicles of this group act as drug carriers that penetrate across hydrophilic pathways of the intact skin. The second group comprises those possessing highly fluid bilayers, owing to the presence of permeation enhancers. The vesicles of this group can act as carriers of drugs that permeate the skin after the barrier of the stratum corneum is altered because of synergistic action with the permeation enhancers contained in the vesicle structure. We have included a detailed overview of the different mechanisms of skin interaction and discussed the most promising preclinical applications of the last five years of Transfersomes® (IDEA AG, Munich, Germany, ethosomes, and invasomes as carriers of antitumoral and anti-inflammatory drugs applied by the topical route. Keywords: Transfersomes, ethosomes, antitumoral, anti-inflammatory, topical delivery
Blocken, B.J.E.; Gualtieri, C.
2012-01-01
Computational Fluid Dynamics (CFD) is increasingly used to study a wide variety of complex Environmental Fluid Mechanics (EFM) processes, such as water flow and turbulent mixing of contaminants in rivers and estuaries and wind flow and air pollution dispersion in urban areas. However, the accuracy
The Pi-Theorem Applications to Fluid Mechanics and Heat and Mass Transfer
Yarin, L P
2012-01-01
This volume presents applications of the Pi-Theorem to fluid mechanics and heat and mass transfer. The Pi-theorem yields a physical motivation behind many flow processes and therefore it constitutes a valuable tool for the intelligent planning of experiments in fluids. After a short introduction to the underlying differential equations and their treatments, the author presents many novel approaches how to use the Pi-theorem to understand fluid mechanical issues. The book is a great value to the fluid mechanics community, as it cuts across many subdisciplines of experimental fluid mechanics.
Computational fluid mechanics in R and D on uranium enrichment
International Nuclear Information System (INIS)
Soubbaramayer, O.
1988-01-01
Uranium enrichment represents an essential link in the cycle of nuclear fuels for power production. There are many processes of uranium enrichment, but three of them dominate the nuclear history as well in the past (Gaseous diffusion and centrifugation) as in the present (Laser process). The important role played by the Numerical Fluid Mechanics in the three processes is pointed out. The type of problem raised by Gaseous Diffusion is Channel Flow with wall suction, by Centrifugation, flow of a Compressible gas in a strongly rotating cylinder (Stewartson and Ekman layers) and by Laser process, Thermocapillary-buoyancy flow of a molten metal in an evaporation crucible. The methods and results in these problems are reviewed. 18 refs, 11 figs
Application of ICT supported learning in fluid mechanics
DEFF Research Database (Denmark)
Brohus, Henrik; Svidt, Kjeld
2004-01-01
of tools for knowledge transfer facilitates deep understanding and increases learning efficiency. Air flow is by nature invisible and represents a further challenge in the effort of providing sufficient understanding of typical flow patterns and behaviour of room air flow. An example of visualisation......This paper focuses on the application of ICT, Information & Communication Technology, supported learning in the area of fluid mechanics education. Taking a starting point in a course in Ventilation Technology, including room air flow and contaminant distribution, it explains how ICT may be used...... actively in the learning environment to increase efficiency in the learning process. The paper comprises past experiences and lessons learnt as well as prospect for future development in the area. A model is presented that describes a high efficiency learning environment where ICT plays an important role...
Fluid mechanics relevant to flow through pretreatment of cellulosic biomass.
Archambault-Léger, Véronique; Lynd, Lee R
2014-04-01
The present study investigates fluid mechanical properties of cellulosic feedstocks relevant to flow through (FT) pretreatment for biological conversion of cellulosic biomass. The results inform identifying conditions for which FT pretreatment can be implemented in a practical context. Measurements of pressure drop across packed beds, viscous compaction and water absorption are reported for milled and not milled sugarcane bagasse, switchgrass and poplar, and important factors impacting viscous flow are deduced. Using biomass knife-milled to pass through a 2mm sieve, the observed pressure drop was highest for bagasse, intermediate for switchgrass and lowest for poplar. The highest pressure drop was associated with the presence of more fine particles, greater viscous compaction and the degree of water absorption. Using bagasse without particle size reduction, the instability of the reactor during pretreatment above 140kg/m(3) sets an upper bound on the allowable concentration for continuous stable flow. Copyright © 2014. Published by Elsevier Ltd.
Fluid-Structure Interaction Mechanisms for Close-In Explosions
Directory of Open Access Journals (Sweden)
Andrew B. Wardlaw Jr.
2000-01-01
Full Text Available This paper examines fluid-structure interaction for close-in internal and external underwater explosions. The resulting flow field is impacted by the interaction between the reflected explosion shock and the explosion bubble. This shock reflects off the bubble as an expansion that reduces the pressure level between the bubble and the target, inducing cavitation and its subsequent collapse that reloads the target. Computational examples of several close-in interaction cases are presented to document the occurrence of these mechanisms. By comparing deformable and rigid body simulations, it is shown that cavitation collapse can occur solely from the shock-bubble interaction without the benefit of target deformation. Addition of a deforming target lowers the flow field pressure, facilitates cavitation and cavitation collapse, as well as reducing the impulse of the initial shock loading.
An intelligent data acquisition system for fluid mechanics research
Cantwell, E. R.; Zilliac, G.; Fukunishi, Y.
1989-01-01
This paper describes a novel data acquisition system for use with wind-tunnel probe-based measurements, which incorporates a degree of specific fluid dynamics knowledge into a simple expert system-like control program. The concept was developed with a rudimentary expert system coupled to a probe positioning mechanism operating in a small-scale research wind tunnel. The software consisted of two basic elements, a general-purpose data acquisition system and the rulebased control element to take and analyze data and supplying decisions as to where to measure, how many data points to take, and when to stop. The system was validated in an experiment involving a vortical flow field, showing that it was possible to increase the resolution of the experiment or, alternatively, reduce the total number of data points required, to achieve parity with the results of most conventional data acquisition approaches.
Escape response of planktonic protists to fluid mechanical signals
DEFF Research Database (Denmark)
Jakobsen, Hans Henrik
2001-01-01
The escape response to fluid mechanical signals was examined in 6 protists, 4 ciliates and 2 dinoflagellates. When exposed to a siphon flow. 3 species of ciliates, Balanion comatum, Strobilidium sp., and Mesodinium pulex, responded with escape jumps. The threshold deformation rates required...... times lower than that of a non-jumping similar sized protist when the predator was Temora longicornis, which captures prey entrained in a feeding current. However, when the predator was the ambush- feeding copepod Acartia tonsa, the predation mortalities of jumping and non-jumping protists were...... of similar magnitude. Escape responses may thus be advantageous in some situations. However, jumping behaviour may also enhance susceptibility to some predators, explaining the different predator avoidance strategies (jumping or not) that have evolved in planktonic protists....
Flippin' Fluid Mechanics - Comparison of Blended Classroom vs. Traditional Lecture
Webster, D. R.; Kadel, R. S.; Newstetter, W. C.
2017-11-01
We conducted a study of student performance in and perceptions of a blended classroom delivery of a junior-level fluid mechanics course. In the blended pedagogy, students watch short on-line videos before class, participate in interactive in-class problem solving (in dyads), and complete individualized on-line quizzes weekly. Comparisons are made among four sections of the blended classroom delivery in the period of 2013-2017 to eleven sections delivered in a traditional lecture-style format by the same instructor in 2002-2012. The results reveal dramatic improvement in student engagement, perceptions, and achievement in the blended pedagogy. For instance, the withdrawal/fail/barely-passing (WFD) rate is significantly lower for the blended classroom (8.6% vs. 16.3%; p self-perception of how-much-learned, perception of the value of the course activities, and the overall effectiveness of the course and instructor in the blended classroom.
Fluid Mechanics of a High Performance Racing Bicycle Wheel
Mercat, Jean-Pierre; Cretoux, Brieuc; Huat, Francois-Xavier; Nordey, Benoit; Renaud, Maxime; Noca, Flavio
2013-11-01
In 2012, MAVIC released the most aerodynamic bicycle wheel on the market, the CXR 80. The french company MAVIC has been a world leader for many decades in the manufacturing of bicycle wheels for competitive events such as the Olympic Games and the Tour de France. Since 2010, MAVIC has been in a research partnership with the University of Applied Sciences in Geneva, Switzerland, for the aerodynamic development of bicycle wheels. While most of the development up to date has been performed in a classical wind tunnel, recent work has been conducted in an unusual setting, a hydrodynamic towing tank, in order to achieve low levels of turbulence and facilitate quantitative flow visualization (PIV). After a short introduction on the aerodynamics of bicycle wheels, preliminary fluid mechanics results based on this novel setup will be presented.
Introduction to the internal fluid mechanics research session
Miller, Brent A.; Povinelli, Louis A.
1990-01-01
Internal fluid mechanics research at LeRC is directed toward an improved understanding of the important flow physics affecting aerospace propulsion systems, and applying this improved understanding to formulate accurate predictive codes. To this end, research is conducted involving detailed experimentation and analysis. The following three papers summarize ongoing work and indicate future emphasis in three major research thrusts: inlets, ducts, and nozzles; turbomachinery; and chemical reacting flows. The underlying goal of the research in each of these areas is to bring internal computational fluid mechanic to a state of practical application for aerospace propulsion systems. Achievement of this goal requires that carefully planned and executed experiments be conducted in order to develop and validate useful codes. It is critical that numerical code development work and experimental work be closely coupled. The insights gained are represented by mathematical models that form the basis for code development. The resultant codes are then tested by comparing them with appropriate experiments in order to ensure their validity and determine their applicable range. The ultimate user community must be a part of this process to assure relevancy of the work and to hasten its practical application. Propulsion systems are characterized by highly complex and dynamic internal flows. Many complex, 3-D flow phenomena may be present, including unsteadiness, shocks, and chemical reactions. By focusing on specific portions of a propulsion system, it is often possible to identify the dominant phenomena that must be understood and modeled for obtaining accurate predictive capability. The three major research thrusts serve as a focus leading to greater understanding of the relevant physics and to an improvement in analytic tools. This in turn will hasten continued advancements in propulsion system performance and capability.
Fluid mechanics experiments in oscillatory flow. Volume 1: Report
Seume, J.; Friedman, G.; Simon, T. W.
1992-01-01
Results of a fluid mechanics measurement program in oscillating flow within a circular duct are presented. The program began with a survey of transition behavior over a range of oscillation frequency and magnitude and continued with a detailed study at a single operating point. Such measurements were made in support of Stirling engine development. Values of three dimensionless parameters, Re(sub max), Re(sub w), and A(sub R), embody the velocity amplitude, frequency of oscillation and mean fluid displacement of the cycle, respectively. Measurements were first made over a range of these parameters which included operating points of all Stirling engines. Next, a case was studied with values of these parameters that are representative of the heat exchanger tubes in the heater section of NASA's Stirling cycle Space Power Research Engine (SPRE). Measurements were taken of the axial and radial components of ensemble-averaged velocity and rms-velocity fluctuation and the dominant Reynolds shear stress, at various radial positions for each of four axial stations. In each run, transition from laminar to turbulent flow, and its reverse, were identified and sufficient data was gathered to propose the transition mechanism. Models of laminar and turbulent boundary layers were used to process the data into wall coordinates and to evaluate skin friction coefficients. Such data aids in validating computational models and is useful in comparing oscillatory flow characteristics to those of fully-developed steady flow. Data were taken with a contoured entry to each end of the test section and with flush square inlets so that the effects of test section inlet geometry on transition and turbulence are documented. Volume 1 contains the text of the report including figures and supporting appendices. Volume 2 contains data reduction program listings and tabulated data (including its graphical presentation).
Fluid mechanics experiments in oscillatory flow. Volume 1
International Nuclear Information System (INIS)
Seume, J.; Friedman, G.; Simon, T.W.
1992-03-01
Results of a fluid mechanics measurement program is oscillating flow within a circular duct are present. The program began with a survey of transition behavior over a range of oscillation frequency and magnitude and continued with a detailed study at a single operating point. Such measurements were made in support of Stirling engine development. Values of three dimensionless parameters, Re max , Re W , and A R , embody the velocity amplitude, frequency of oscillation and mean fluid displacement of the cycle, respectively. Measurements were first made over a range of these parameters which included operating points of all Stirling engines. Next, a case was studied with values of these parameters that are representative of the heat exchanger tubes in the heater section of NASA's Stirling cycle Space Power Research Engine (SPRE). Measurements were taken of the axial and radical components of ensemble-averaged velocity and rms-velocity fluctuation and the dominant Reynolds shear stress, at various radial positions for each of four axial stations. In each run, transition from laminar to turbulent flow, and in reverse, were identified and sufficient data was gathered to propose the transition mechanism. Models of laminar and turbulent boundary layers were used to process the data into wall coordinates and to evaluate skin friction coefficients. Such data aids in validating computational models and is useful in comparing oscillatory flow characteristics to those of fully-developed steady flow. Data were taken with a contoured entry to each end of the test section and with flush square inlets so that the effects of test section inlet geometry on transition and turbulence are documented. The following is presented in two-volumes. Volume I contains the text of the report including figures and supporting appendices. Volume II contains data reduction program listings and tabulated data (including its graphical presentation)
Yielding to stress: Recent developments in viscoplastic fluid mechanics
BALMFORTH, Neil; FRIGAARD, Ian A.; OVARLEZ, Guillaume
2014-01-01
The archetypal feature of a viscoplastic fluid is its yield stress: If the material is not sufficiently stressed, it behaves like a solid, but once the yield stress is exceeded, the material flows like a fluid. Such behavior characterizes materials common in industries such as petroleum and chemical processing, cosmetics, and food processing and in geophysical fluid dynamics. The most common idealization of a viscoplastic fluid is the Bingham model, which has been widely used to rationalize e...
Wei, Wei; Gu, Zhaolin
2015-10-01
distribution and mechanical behaviors of liquid surface can be predicted by using this method. The methodology combining particle charging model with Computational Fluid Dynamics (CFD) and Discrete element method (DEM) is applicable to study the particle charging/charged processes in gas-solid two phase flows, the influence factors of particle charging, such as gas-particle interaction, contact force, contact area, and various velocities, are described systematically. This review would explore a clear understanding of the particulate charging and provide theoretical references to control and utilize the charging/charged particulate entrained fluid system.
International Nuclear Information System (INIS)
Wei, Wei; Gu, Zhaolin
2015-01-01
charge distribution and mechanical behaviors of liquid surface can be predicted by using this method. The methodology combining particle charging model with Computational Fluid Dynamics (CFD) and Discrete element method (DEM) is applicable to study the particle charging/charged processes in gas–solid two phase flows, the influence factors of particle charging, such as gas–particle interaction, contact force, contact area, and various velocities, are described systematically. This review would explore a clear understanding of the particulate charging and provide theoretical references to control and utilize the charging/charged particulate entrained fluid system.
Energy Technology Data Exchange (ETDEWEB)
Wei, Wei [School of Energy and Power Engineering, Wuhan University of Technology, Wuhan, Hubei, 430063 (China); School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi, 710049 (China); Gu, Zhaolin, E-mail: guzhaoln@mail.xjtu.edu.cn [School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi, 710049 (China)
2015-10-28
charge distribution and mechanical behaviors of liquid surface can be predicted by using this method. The methodology combining particle charging model with Computational Fluid Dynamics (CFD) and Discrete element method (DEM) is applicable to study the particle charging/charged processes in gas–solid two phase flows, the influence factors of particle charging, such as gas–particle interaction, contact force, contact area, and various velocities, are described systematically. This review would explore a clear understanding of the particulate charging and provide theoretical references to control and utilize the charging/charged particulate entrained fluid system.
Group Theoretical Approach for Controlled Quantum Mechanical Systems
National Research Council Canada - National Science Library
Tarn, Tzyh-Jong
2007-01-01
The aim of this research is the study of controllability of quantum mechanical systems and feedback control of de-coherence in order to gain an insight on the structure of control of quantum systems...
Elastic contact mechanics: percolation of the contact area and fluid squeeze-out.
Persson, B N J; Prodanov, N; Krick, B A; Rodriguez, N; Mulakaluri, N; Sawyer, W G; Mangiagalli, P
2012-01-01
The dynamics of fluid flow at the interface between elastic solids with rough surfaces depends sensitively on the area of real contact, in particular close to the percolation threshold, where an irregular network of narrow flow channels prevails. In this paper, numerical simulation and experimental results for the contact between elastic solids with isotropic and anisotropic surface roughness are compared with the predictions of a theory based on the Persson contact mechanics theory and the Bruggeman effective medium theory. The theory predictions are in good agreement with the experimental and numerical simulation results and the (small) deviation can be understood as a finite-size effect. The fluid squeeze-out at the interface between elastic solids with randomly rough surfaces is studied. We present results for such high contact pressures that the area of real contact percolates, giving rise to sealed-off domains with pressurized fluid at the interface. The theoretical predictions are compared to experimental data for a simple model system (a rubber block squeezed against a flat glass plate), and for prefilled syringes, where the rubber plunger stopper is lubricated by a high-viscosity silicon oil to ensure functionality of the delivery device. For the latter system we compare the breakloose (or static) friction, as a function of the time of stationary contact, to the theory prediction.
Theoretical and experimental study on the magnetic fluid seal of reciprocating shaft
Li, Decai; Xu, Haiping; He, Xinzhi; Lan, Huiqing
2005-03-01
The authors obtain anti-pressure formula of reciprocating shaft magnetic fluid seal from general Navier-Stokes equation. In order to verify the correctness of the anti-pressure formula, the authors set up a magnetic fluid anti-pressure experiment rig for a reciprocating seal. Finally, the authors have verified influence of speed and stroke on the seal anti-pressure.
Relation between boundary slip mechanisms and waterlike fluid behavior
Ternes, Patricia; Salcedo, Evy; Barbosa, Marcia C.
2018-03-01
The slip of a fluid layer in contact with a solid confining surface is investigated for different temperatures and densities using molecular dynamic simulations. We show that for an anomalous waterlike fluid the slip goes as follows: for low levels of shear, defect slip appears and is related to the particle exchange between the fluid layers; at high levels of shear, global slip occurs and is related to the homogeneous distribution of the fluid in the confining surfaces. The oscillations in the transition velocity from defect to global slip are shown to be associated with changes in the layering distribution in the anomalous fluid.
Magnetic particle translation as a surrogate measure for synovial fluid mechanics.
Shah, Yash Y; Maldonado-Camargo, Lorena; Patel, Neal S; Biedrzycki, Adam H; Yarmola, Elena G; Dobson, Jon; Rinaldi, Carlos; Allen, Kyle D
2017-07-26
The mechanics of synovial fluid vary with disease progression, but are difficult to quantify quickly in a clinical setting due to small sample volumes. In this study, a novel technique to measure synovial fluid mechanics using magnetic nanoparticles is introduced. Briefly, microspheres embedded with superparamagnetic iron oxide nanoparticles, termed magnetic particles, are distributed through a 100μL synovial fluid sample. Then, a permanent magnet inside a protective sheath is inserted into the synovial fluid sample. Magnetic particles translate toward the permanent magnet and the percentage of magnetic particles collected by the magnet in a given time can be related to synovial fluid viscosity. To validate this relationship, magnetic particle translation was demonstrated in three phases. First, magnetic particle translation was assessed in glycerol solutions with known viscosities, demonstrating that as fluid viscosity increased, magnetic particle translation decreased. Next, the relationship between magnetic particle translation and synovial fluid viscosity was assessed using bovine synovial fluid that was progressively degenerated via ultrasonication. Here, particle collection in a given amount of time increased as fluid degenerated, demonstrating that the relationship between particle collection and fluid mechanics holds in non-Newtonian synovial fluid. Finally, magnetic particle translation was used to assess differences between healthy and OA affected joints in equine synovial fluid. Here, particle collection in a given time was higher in OA joints relative to healthy horses (pfluid mechanics in limited volumes of synovial fluid sample. Copyright © 2017 Elsevier Ltd. All rights reserved.
Bayesian inverse problems for functions and applications to fluid mechanics
International Nuclear Information System (INIS)
Cotter, S L; Dashti, M; Robinson, J C; Stuart, A M
2009-01-01
In this paper we establish a mathematical framework for a range of inverse problems for functions, given a finite set of noisy observations. The problems are hence underdetermined and are often ill-posed. We study these problems from the viewpoint of Bayesian statistics, with the resulting posterior probability measure being defined on a space of functions. We develop an abstract framework for such problems which facilitates application of an infinite-dimensional version of Bayes theorem, leads to a well-posedness result for the posterior measure (continuity in a suitable probability metric with respect to changes in data), and also leads to a theory for the existence of maximizing the posterior probability (MAP) estimators for such Bayesian inverse problems on function space. A central idea underlying these results is that continuity properties and bounds on the forward model guide the choice of the prior measure for the inverse problem, leading to the desired results on well-posedness and MAP estimators; the PDE analysis and probability theory required are thus clearly dileneated, allowing a straightforward derivation of results. We show that the abstract theory applies to some concrete applications of interest by studying problems arising from data assimilation in fluid mechanics. The objective is to make inference about the underlying velocity field, on the basis of either Eulerian or Lagrangian observations. We study problems without model error, in which case the inference is on the initial condition, and problems with model error in which case the inference is on the initial condition and on the driving noise process or, equivalently, on the entire time-dependent velocity field. In order to undertake a relatively uncluttered mathematical analysis we consider the two-dimensional Navier–Stokes equation on a torus. The case of Eulerian observations—direct observations of the velocity field itself—is then a model for weather forecasting. The case of
Choi, Eunsong
Computer simulations are an integral part of research in modern condensed matter physics; they serve as a direct bridge between theory and experiment by systemactically applying a microscopic model to a collection of particles that effectively imitate a macroscopic system. In this thesis, we study two very differnt condensed systems, namely complex fluids and frustrated magnets, primarily by simulating classical dynamics of each system. In the first part of the thesis, we focus on ionic liquids (ILs) and polymers--the two complementary classes of materials that can be combined to provide various unique properties. The properties of polymers/ILs systems, such as conductivity, viscosity, and miscibility, can be fine tuned by choosing an appropriate combination of cations, anions, and polymers. However, designing a system that meets a specific need requires a concrete understanding of physics and chemistry that dictates a complex interplay between polymers and ionic liquids. In this regard, molecular dynamics (MD) simulation is an efficient tool that provides a molecular level picture of such complex systems. We study the behavior of Poly (ethylene oxide) (PEO) and the imidazolium based ionic liquids, using MD simulations and statistical mechanics. We also discuss our efforts to develop reliable and efficient classical force-fields for PEO and the ionic liquids. The second part is devoted to studies on geometrically frustrated magnets. In particular, a microscopic model, which gives rise to an incommensurate spiral magnetic ordering observed in a pyrochlore antiferromagnet is investigated. The validation of the model is made via a comparison of the spin-wave spectra with the neutron scattering data. Since the standard Holstein-Primakoff method is difficult to employ in such a complex ground state structure with a large unit cell, we carry out classical spin dynamics simulations to compute spin-wave spectra directly from the Fourier transform of spin trajectories. We
The approval mechanism solves the prisoner's dilemma theoretically and experimentally
Tatsuyoshi Saijo; Yoshitaka Okano; Takafumi Yamakawa
2015-01-01
Consider a situation where players in a prisoner's dilemma game can approve or reject the other's choice such as cooperation or defection. If both players approve the other's choice, the outcome is the one they chose, whereas if either one rejects the other's choice, the outcome is the one when both defect, which we name the approval mechanism herein (this is inspired by the Cold War doctrine of mutually assured destruction). Experimentally, we find that the cooperation rate with the approval...
Directory of Open Access Journals (Sweden)
Song Haiyan
2017-01-01
Full Text Available It is important to study the properties and mechanics of egg drop impacts in order to reduce egg loss during processing and logistics and to provide a basis for the protective packaging of egg products. In this paper, we present the results of our study of the effects of the structural parameters on the mechanical properties of an egg using a finite element model of the egg. Based on Fluid-Solid coupling theory, a finite element model of an egg was constructed using ADINA, a finite element calculation and analysis software package. To simplify the model, the internal fluid of the egg was considered to be a homogeneous substance. The egg drop impact was simulated by the coupling solution, and the feasibility of the model was verified by comparison with the experimental results of a drop test. In summary, the modeling scheme was shown to be feasible and the simulation results provide a theoretical basis for the optimum design of egg packaging and egg processing equipment.
Binous, Housam
2007-01-01
We study four non-Newtonian fluid mechanics problems using Mathematica[R]. Constitutive equations describing the behavior of power-law, Bingham and Carreau models are recalled. The velocity profile is obtained for the horizontal flow of power-law fluids in pipes and annuli. For the vertical laminar film flow of a Bingham fluid we determine the…
Secondary degradation mechanisms - A theoretical approach to remedial actions
International Nuclear Information System (INIS)
Rudling, P.
2001-04-01
A failed BWR fuel rod may degrade either by developing long axial cracks and/or transversal breaks. The tendency of failed BWR rods to degrade depends on the fuel design and reactor operation of the failed rod. The knowledge of the degradation mechanisms may be used to develop secondary degradation resistant fuel and/or to mitigate the degradation tendencies during operation of failed fuel. Literature data from three different categories has been analysed: Open literature data on failed BWR rods that have and have not degraded; Data generated in experimental reactors where primary failures have been simulated either by drilling a hole in the intact cladding before the test or by letting water/steam into the rod from a capsule connected to the otherwise intact rod. In addition data related to hydrogen production in the pellet-cladding gap in a failed rod and the subsequent hydrogen ingress and finally the hydride formation in zirconium alloys; Open literature data out-of-pile material tests to improve the knowledge of the secondary degradation mechanisms. To get an idea of the degradation mechanisms one may first characterise the failed fuel rods in commercial BWRs that form axial splits, transversal breaks and also failed rods that do not degrade at all. Considering axial splits in BWRs, they seem to occur mostly for failed fuel rods with intermediate and high burnups, i.e., in rods with small pellet-cladding gaps, that have been subjected to a power ramp. Such data indicate that the axial crack propagation rate is larger than 0.16 mm/h. It is also clear that the axial cracks formed in commercial reactors show mostly brittle cleavage features at reactor operating temperature even though the hydrogen content in the fuel cladding is low, 150-300 wtppm. Macroscopically the brittle cleavage fractures are characterised by: a fracture surface that is perpendicular to the main tensile stress direction i.e., in the cladding circumferential direction, no or very little clad
A fluid-mechanical model of elastocapillary coalescence
Singh, Kiran
2014-03-25
© 2014 Cambridge University Press. We present a fluid-mechanical model of the coalescence of a number of elastic objects due to surface tension. We consider an array of spring-block elements separated by thin liquid films, whose dynamics are modelled using lubrication theory. With this simplified model of elastocapillary coalescence, we present the results of numerical simulations for a large number of elements, N = O(10^{4}). A linear stability analysis shows that pairwise coalescence is always the most unstable mode of deformation. However, the numerical simulations show that the cluster sizes actually produced by coalescence from a small white-noise perturbation have a distribution that depends on the relative strength of surface tension and elasticity, as measured by an elastocapillary number K. Both the maximum cluster size and the mean cluster size scale like K^{-1/2} for small K. An analytical solution for the response of the system to a localized perturbation shows that such perturbations generate propagating disturbance fronts, which leave behind \\'frozen-in\\' clusters of a predictable size that also depends on K. A good quantitative comparison between the cluster-size statistics from noisy perturbations and this \\'frozen-in\\' cluster size suggests that propagating fronts may play a crucial role in the dynamics of coalescence.
Nodal methods for problems in fluid mechanics and neutron transport
International Nuclear Information System (INIS)
Azmy, Y.Y.
1985-01-01
A new high-accuracy, coarse-mesh, nodal integral approach is developed for the efficient numerical solution of linear partial differential equations. It is shown that various special cases of this general nodal integral approach correspond to several high efficiency nodal methods developed recently for the numerical solution of neutron diffusion and neutron transport problems. The new approach is extended to the nonlinear Navier-Stokes equations of fluid mechanics; its extension to these equations leads to a new computational method, the nodal integral method which is implemented for the numerical solution of these equations. Application to several test problems demonstrates the superior computational efficiency of this new method over previously developed methods. The solutions obtained for several driven cavity problems are compared with the available experimental data and are shown to be in very good agreement with experiment. Additional comparisons also show that the coarse-mesh, nodal integral method results agree very well with the results of definitive ultra-fine-mesh, finite-difference calculations for the driven cavity problem up to fairly high Reynolds numbers
Fluid Mechanics of Lean Blowout Precursors in Gas Turbine Combustors
Directory of Open Access Journals (Sweden)
T. M. Muruganandam
2012-03-01
Full Text Available Understanding of lean blowout (LBO phenomenon, along with the sensing and control strategies could enable the gas turbine combustor designers to design combustors with wider operability regimes. Sensing of precursor events (temporary extinction-reignition events based on chemiluminescence emissions from the combustor, assessing the proximity to LBO and using that data for control of LBO has already been achieved. This work describes the fluid mechanic details of the precursor dynamics and the blowout process based on detailed analysis of near blowout flame behavior, using simultaneous chemiluminescence and droplet scatter observations. The droplet scatter method represents the regions of cold reactants and thus help track unburnt mixtures. During a precursor event, it was observed that the flow pattern changes significantly with a large region of unburnt mixture in the combustor, which subsequently vanishes when a double/single helical vortex structure brings back the hot products back to the inlet of the combustor. This helical pattern is shown to be the characteristic of the next stable mode of flame in the longer combustor, stabilized by double helical vortex breakdown (VBD mode. It is proposed that random heat release fluctuations near blowout causes VBD based stabilization to shift VBD modes, causing the observed precursor dynamics in the combustor. A complete description of the evolution of flame near the blowout limit is presented. The description is consistent with all the earlier observations by the authors about precursor and blowout events.
Secondary degradation mechanisms - A theoretical approach to remedial actions
Energy Technology Data Exchange (ETDEWEB)
Rudling, P. [Advanced Nuclear Technology, Uppsala (Sweden)
2001-04-01
A failed BWR fuel rod may degrade either by developing long axial cracks and/or transversal breaks. The tendency of failed BWR rods to degrade depends on the fuel design and reactor operation of the failed rod. The knowledge of the degradation mechanisms may be used to develop secondary degradation resistant fuel and/or to mitigate the degradation tendencies during operation of failed fuel. Literature data from three different categories has been analysed: Open literature data on failed BWR rods that have and have not degraded; Data generated in experimental reactors where primary failures have been simulated either by drilling a hole in the intact cladding before the test or by letting water/steam into the rod from a capsule connected to the otherwise intact rod. In addition data related to hydrogen production in the pellet-cladding gap in a failed rod and the subsequent hydrogen ingress and finally the hydride formation in zirconium alloys; Open literature data out-of-pile material tests to improve the knowledge of the secondary degradation mechanisms. To get an idea of the degradation mechanisms one may first characterise the failed fuel rods in commercial BWRs that form axial splits, transversal breaks and also failed rods that do not degrade at all. Considering axial splits in BWRs, they seem to occur mostly for failed fuel rods with intermediate and high burnups, i.e., in rods with small pellet-cladding gaps, that have been subjected to a power ramp. Such data indicate that the axial crack propagation rate is larger than 0.16 mm/h. It is also clear that the axial cracks formed in commercial reactors show mostly brittle cleavage features at reactor operating temperature even though the hydrogen content in the fuel cladding is low, 150-300 wtppm. Macroscopically the brittle cleavage fractures are characterised by: a fracture surface that is perpendicular to the main tensile stress direction i.e., in the cladding circumferential direction, no or very little clad
Zhang, Ou; Zou, Xuan; Li, Qi-Hong; Sun, Zhi; Liu, Yong Dong; Zhong, Ru Gang
2016-07-07
N-nitrosodimethylamine (NDMA), as a representative of endogenously formed N-nitroso compounds (NOCs), has become the focus of considerable research interest due to its unusually high carcinogenicity. In this study, effects of ethanol and acetic acid on the formation of NDMA from dimethylamine (DMA) and nitrite in simulated gastric fluid (SGF) were investigated. Experimental results showed that ethanol in the concentrations of 1-8% (v/v) and acetic acid in the concentrations of 0.01-8% (v/v) exhibit inhibitory and promotion effects on the formation of NDMA, respectively. Moreover, they are both in a dose-dependent manner with the largest inhibition/promotion rate reaching ∼70%. Further experimental investigations indicate that ethanol and acetic acid are both able to scavenge nitrite in SGF. It implies that there are interactions of ethanol and acetic acid with nitrite or nitrite-related nitrosating agents rather than DMA. Theoretical calculations confirm the above experimental results and demonstrate that ethanol and acetic acid can both react with nitrite-related nitrosating agents to produce ethyl nitrite (EtONO) and acetyl nitrite (AcONO), respectively. Furthermore, the reactivities of ethyl nitrite, acetyl nitrite, and dinitrogen trioxide reacting with DMA were found in the order of AcONO > N2O3 ≫ EtONO. This is probably the main reason why there are completely different effects of ethanol and acetic acid on NDMA formation. On the basis of the above results, two requirements for a potential inhibitor of NOCs formation in SGF were provided. The results obtained in this study will be helpful in better understanding the inhibition/promotion mechanisms of compounds on NDMA formation in SGF and searching for protective substances to prevent carcinogenic NOCs formation.
Cavo, Marta; Scaglione, Silvia
2016-11-01
The really nontrivial goal of tissue engineering is combining all scaffold micro-architectural features, affecting both fluid-dynamical and mechanical performance, to obtain a fully functional implant. In this work we identified an optimal geometrical pattern for bone tissue engineering applications, best balancing several graft needs which correspond to competing design goals. In particular, we investigated the occurred changes in graft behavior by varying pore size (300μm, 600μm, 900μm), interpore distance (equal to pore size or 300μm fixed) and pores interconnection (absent, 45°-oriented, 90°-oriented). Mathematical considerations and Computational Fluid Dynamics (CFD) tools, here combined in a complete theoretical model, were carried out to this aim. Poly-lactic acid (PLA) based samples were realized by 3D printing, basing on the modeled architectures. A collagen (COL) coating was also realized on grafts surface and the interaction between PLA and COL, besides the protein contribution to graft bioactivity, was evaluated. Scaffolds were extensively characterized; human articular cells were used to test their biocompatibility and to evaluate the theoretical model predictions. Grafts fulfilled both the chemical and physical requirements. Finally, a good agreement was found between the theoretical model predictions and the experimental data, making these prototypes good candidates for bone graft replacements. Copyright © 2016 Elsevier B.V. All rights reserved.
Effects of mechanical layering on hydrofracture emplacement and fluid transport in reservoirs
Directory of Open Access Journals (Sweden)
Sonja Leonie Philipp
2013-12-01
Full Text Available Fractures generated by internal fluid pressure, for example, dykes, mineral veins, many joints and man-made hydraulic fractures, are referred to as hydrofractures. Together with shear fractures, they contribute significantly to the permeability of fluid reservoirs such as those of petroleum, geothermal water, and groundwater. Analytical and numerical models show that – in homogeneous host rocks – any significant overpressure in hydrofractures theoretically generates very high crack tip tensile stresses. Consequently, overpressured hydrofractures should propagate and help to form interconnected fracture systems that would then contribute to the permeability of fluid reservoirs. Field observations, however, show that in heterogeneous and anisotropic, e.g., layered, rocks many hydrofractures become arrested or offset at layer contacts and do not form vertically interconnected networks. The most important factors that contribute to hydrofracture arrest are discontinuities (including contacts, stiffness changes between layers, and stress barriers, where the local stress field is unfavourable to hydrofracture propagation. A necessary condition for a hydrofracture to propagate to the surface is that the stress field along its potential path is everywhere favourable to extension-fracture formation so that the probability of hydrofracture arrest is minimised. Mechanical layering and the resulting heterogeneous stress field largely control whether evolving hydrofractures become confined to single layers (strata¬bound frac¬tures or not (non-stratabound fractures and, there¬fore, if a vertically intercon¬nec¬ted fracture system forms. Non-stratabound hydrofractures may propagate through many layers and generate interconnected fracture systems. Such systems commonly reach the percolation threshold and largely control the overall permeability of the fluid reservoirs within which they develop.
THEORETICAL CONSIDERATIONS REGARDING THE AUTOMATIC FISCAL STABILIZERS OPERATING MECHANISM
Directory of Open Access Journals (Sweden)
Gondor Mihaela
2012-07-01
Full Text Available This paper examines the role of Automatic Fiscal Stabilizers (AFS for stabilizing the cyclical fluctuations of macroeconomic output as an alternative to discretionary fiscal policy, admitting its huge potential of being an anti crisis solution. The objectives of the study are the identification of the general features of the concept of automatic fiscal stabilizers and the logical assessment of them from economic perspectives. Based on the literature in the field, this paper points out the disadvantages of fiscal discretionary policy and argue the need of using Automatic Fiscal Stabilizers in order to provide a faster decision making process, shielded from political interference, and reduced uncertainty for households and business environment. The paper conclude about the need of using fiscal policy for smoothing the economic cycle, but in a way which includes among its features transparency, responsibility and clear operating mechanisms. Based on the research results the present paper assumes that pro-cyclicality reduces de effectiveness of the Automatic Fiscal Stabilizer and as a result concludes that it is very important to avoid the pro-cyclicality in fiscal rule design. Moreover, by committing in advance to specific fiscal policy action contingent on economic developments, uncertainty about the fiscal policy framework during a recession should be reduced. Being based on logical analysis and not focused on empirical, contextualized one, the paper presents some features of AFS operating mechanism and also identifies and systematizes the factors which provide its importance and national individuality. Reaching common understanding on the Automatic Fiscal Stabilizer concept as a institutional device for smoothing the gap of the economic cycles across different countries, particularly for the European Union Member States, will facilitate efforts to coordinate fiscal policy responses during a crisis, especially in the context of the fiscal
Mechanisms of Neurofeedback: A Computation-theoretic Approach.
Davelaar, Eddy J
2018-05-15
Neurofeedback training is a form of brain training in which information about a neural measure is fed back to the trainee who is instructed to increase or decrease the value of that particular measure. This paper focuses on electroencephalography (EEG) neurofeedback in which the neural measures of interest are the brain oscillations. To date, the neural mechanisms that underlie successful neurofeedback training are still unexplained. Such an understanding would benefit researchers, funding agencies, clinicians, regulatory bodies, and insurance firms. Based on recent empirical work, an emerging theory couched firmly within computational neuroscience is proposed that advocates a critical role of the striatum in modulating EEG frequencies. The theory is implemented as a computer simulation of peak alpha upregulation, but in principle any frequency band at one or more electrode sites could be addressed. The simulation successfully learns to increase its peak alpha frequency and demonstrates the influence of threshold setting - the threshold that determines whether positive or negative feedback is provided. Analyses of the model suggest that neurofeedback can be likened to a search process that uses importance sampling to estimate the posterior probability distribution over striatal representational space, with each representation being associated with a distribution of values of the target EEG band. The model provides an important proof of concept to address pertinent methodological questions about how to understand and improve EEG neurofeedback success. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.
Taketomi, Susamu; Takahashi, Hiromasa; Inaba, Nobuyuki; Miyajima, Hideki
1991-05-01
Macro-clusters formation of the magnetic colloidal particles in magnetic fluids is investigated. Experiments of an optical microscope observation of the macro-clusters formation and of anomalous light scattering by the magnetic fluid are reported. Looking upon the anomalous light scattering of the magnetic fluid as a kind of critical opalescence and using Debye’s opalescence theory, we derive a thermodynamical instability theory of the colloidal particles’ dispersion. Relations among the instability theory of Cebers, that of Sano and Doi, and ours are discussed. An interaction energy among the colloidal particles is evaluated from the light scattering experiment. Similarities among the macro-cluster formation, spinodal decomposition of precipitation-type magnetic alloys, and flux-line lattice formation in type-II superconductors are discussed.
Theoretical analysis of hydrogen spillover mechanism on carbon nanotubes
Directory of Open Access Journals (Sweden)
Rosalba eJuarez Mosqueda
2015-02-01
Full Text Available The spillover mechanism of molecular hydrogen on carbon nanotubes in the presence of catalytically active platinum clusters was critically and systematically investigated by using density-functional theory. Our simulation model includes a Pt4 cluster for the catalyst nanoparticle and curved and planar circumcoronene for two exemplary single-walled carbon nanotubes (CNT, the (10,10 CNT and one of large diameter, respectively. Our results show that the H2 molecule dissociates spontaneously on the Pt4 cluster. However, the dissociated H atoms have to overcome a barrier of more than 2 eV to migrate from the catalyst to the CNT, even if the Pt4 cluster is at full saturation with six adsorbed and dissociated hydrogen molecules. Previous investigations have shown that the mobility of hydrogen atoms on the CNT surface is hindered by a barrier. We find that instead the Pt4 catalyst may move along the outer surface of the CNT with activation energy of only 0.16 eV, and that this effect offers the possibility of full hydrogenation of the CNT. Thus, although we have not found a low-energy pathway to spillover onto the CNT, we suggest, based on our calculations and calculated data reported in the literature, that in the hydrogen-spillover process the observed saturation of the CNT at hydrogen background pressure occurs through mobile Pt nanoclusters, which move on the substrate more easily than the substrate-chemisorbed hydrogens, and deposit or reattach hydrogens in the process. Initial hydrogenation of the carbon substrate, however, is thermodynamically unfavoured, suggesting that defects should play a significant role.
Analysis of sponge zones for computational fluid mechanics
International Nuclear Information System (INIS)
Bodony, Daniel J.
2006-01-01
The use of sponge regions, or sponge zones, which add the forcing term -σ(q - q ref ) to the right-hand-side of the governing equations in computational fluid mechanics as an ad hoc boundary treatment is widespread. They are used to absorb and minimize reflections from computational boundaries and as forcing sponges to introduce prescribed disturbances into a calculation. A less common usage is as a means of extending a calculation from a smaller domain into a larger one, such as in computing the far-field sound generated in a localized region. By analogy to the penalty method of finite elements, the method is placed on a solid foundation, complete with estimates of convergence. The analysis generalizes the work of Israeli and Orszag [M. Israeli, S.A. Orszag, Approximation of radiation boundary conditions, J. Comp. Phys. 41 (1981) 115-135] and confirms their findings when applied as a special case to one-dimensional wave propagation in an absorbing sponge. It is found that the rate of convergence of the actual solution to the target solution, with an appropriate norm, is inversely proportional to the sponge strength. A detailed analysis for acoustic wave propagation in one-dimension verifies the convergence rate given by the general theory. The exponential point-wise convergence derived by Israeli and Orszag in the high-frequency limit is recovered and found to hold over all frequencies. A weakly nonlinear analysis of the method when applied to Burgers' equation shows similar convergence properties. Three numerical examples are given to confirm the analysis: the acoustic extension of a two-dimensional time-harmonic point source, the acoustic extension of a three-dimensional initial-value problem of a sound pulse, and the introduction of unstable eigenmodes from linear stability theory into a two-dimensional shear layer
Mechanics of undulatory swimming in a frictional fluid.
Ding, Yang; Sharpe, Sarah S; Masse, Andrew; Goldman, Daniel I
2012-01-01
The sandfish lizard (Scincus scincus) swims within granular media (sand) using axial body undulations to propel itself without the use of limbs. In previous work we predicted average swimming speed by developing a numerical simulation that incorporated experimentally measured biological kinematics into a multibody sandfish model. The model was coupled to an experimentally validated soft sphere discrete element method simulation of the granular medium. In this paper, we use the simulation to study the detailed mechanics of undulatory swimming in a "granular frictional fluid" and compare the predictions to our previously developed resistive force theory (RFT) which models sand-swimming using empirically determined granular drag laws. The simulation reveals that the forward speed of the center of mass (CoM) oscillates about its average speed in antiphase with head drag. The coupling between overall body motion and body deformation results in a non-trivial pattern in the magnitude of lateral displacement of the segments along the body. The actuator torque and segment power are maximal near the center of the body and decrease to zero toward the head and the tail. Approximately 30% of the net swimming power is dissipated in head drag. The power consumption is proportional to the frequency in the biologically relevant range, which confirms that frictional forces dominate during sand-swimming by the sandfish. Comparison of the segmental forces measured in simulation with the force on a laterally oscillating rod reveals that a granular hysteresis effect causes the overestimation of the body thrust forces in the RFT. Our models provide detailed testable predictions for biological locomotion in a granular environment.
Intrauterine Defensive Mechanism of Amniotic Fluid and Fetal Membranes
金山, 尚裕
1994-01-01
To determine the intrauterine defensive role of urinary trypsin inhibitor (UTI), we studied the effects of UTI in amniotic fluid, fetal membranes and myometrium. The level of UTI was 94±34U/ml in neonatal urine (compared to adult urine 8.0±6.0U/ml) and 88±37U/ml in amniotic fluid. This may indicate that the main source of UTI in the amniotic fluid is the fetal urine. UTI was found to be concentrated in vernix, fetal intestine, amniotic membranes and uterine myometrium. Immunostaining of term ...
International Nuclear Information System (INIS)
Wang Han; Yang Yongming; Hu Yüe; Zhang Huisheng; Zhang Zhenyu
2008-01-01
A numerical method for simulating the motion and deformation of an axisymmetric bubble or drop rising or falling in another infinite and initially stationary fluid is developed based on the volume of fluid (VOF) method in the frame of two incompressible and immiscible viscous fluids under the action of gravity, taking into consideration of surface tension effects. A comparison of the numerical results by this method with those by other works indicates the validity of the method. In the frame of inviscid and incompressible fluids without taking into consideration of surface tension effects, the mechanisms of the generation of the liquid jet and the transition from spherical shape to toroidal shape during the bubble or drop deformation, the increase of the ring diameter of the toroidal bubble or drop and the decrease of its cross-section area during its motion, and the effects of the density ratio of the two fluids on the deformation of the bubble or drop are analysed both theoretically and numerically. (condensed matter: structure, thermal and mechanical properties)
Teaching Fluid Mechanics to the Beginning Graduate Student--An Objective-Oriented Approach.
Liu, Henry
A premature embarkation in specialized areas of fluid mechanics by the beginning graduate student, without having first thoroughly learned the basics, leads to learning difficulties and destroys zeal for learning. To avoid these problems, many schools in the U.S. offer beginning graduate courses in fluid mechanics (BGCFM). Because the success or…
Evans, Cherice; Findley, Gary L.
The quasi-free electron energy V0 (ρ) is important in understanding electron transport through a fluid, as well as for modeling electron attachment reactions in fluids. Our group has developed an isotropic local Wigner-Seitz model that allows one to successfully calculate the quasi-free electron energy for a variety of atomic and molecular fluids from low density to the density of the triple point liquid with only a single adjustable parameter. This model, when coupled with the quasi-free electron energy data and the thermodynamic data for the fluids, also can yield optimized intermolecular potential parameters and the zero kinetic energy electron scattering length. In this poster, we give a review of the isotropic local Wigner-Seitz model in comparison to previous theoretical models for the quasi-free electron energy. All measurements were performed at the University of Wisconsin Synchrotron Radiation Center. This work was supported by a Grants from the National Science Foundation (NSF CHE-0956719), the Petroleum Research Fund (45728-B6 and 5-24880), the Louisiana Board of Regents Support Fund (LEQSF(2006-09)-RD-A33), and the Professional Staff Congress City University of New York.
Introduction to the concept of added mass in fluid mechanics
International Nuclear Information System (INIS)
Pham Dan Tam.
1977-07-01
The physical phenomenum which leads to the concept of added mass for an inviscid fluid is recalled. The added-mass tensor for a solid body moving through an unbounded fluid is defined and some of its properties are presented. The Taylor theorem is exposed, which enables some of the tensor components to be analytically derived in particular cases. Added-mass values are provided for bodies of particular shape. Applications of the added-mass concept to different problems are given [fr
Evidence of nonuniqueness and oscillatory solutions in computational fluid mechanics
International Nuclear Information System (INIS)
Nunziato, J.W.; Gartling, D.K.; Kipp, M.E.
1985-01-01
We will review some of our recent experiences in computing solutions for nonlinear fluids in relatively simple, two-dimensional geometries. The purpose of this discussion will be to display by example some of the interesting but difficult questions that arise when ill-behaved solutions are obtained numerically. We will consider two examples. As the first example, we will consider a nonlinear elastic (compressible) fluid with chemical reactions and discuss solutions for detonation and detonation failure in a two-dimensional cylinder. In this case, the numerical algorithm utilizes a finite-difference method with artificial viscosity (von Neumann-Richtmyer method) and leads to two, distinctly different, stable solutions depending on the time step criterion used. The second example to be considered involves the convection of a viscous fluid in a rectangular container as a result of an exothermic polymerization reaction. A solidification front develops near the top of the container and propagates down through the fluid, changing the aspect ratio of the region ahead of the front. Using a Galerkin-based finite element method, a numerical solution of the partial differential equations is obtained which tracks the front and correctly predicts the fluid temperatures near the walls. However, the solution also exhibits oscillatory behavior with regard to the number of cells in the fluid ahead of the front and in the strength of the cells. More definitive experiments and analysis are required to determine whether this oscillatory phenomena is a numerical artifact or a physical reality. 20 refs., 14 figs
Symbolic manipulation methods in general relativity and fluid mechanics
International Nuclear Information System (INIS)
Cohen, I.
1976-03-01
Algebraic manipulation by computer, or automatic symbol manipulation (ASM) has not been used much in theoretical physics, especially if one compares it with numerical methods. Three examples of the use of ASM as a tool in theoretical physics are discussed. (Auth.)
Computational fluid mechanics qualification calculations for the code TEACH
International Nuclear Information System (INIS)
DeGrazia, M.C.; Fitzsimmons, L.B.; Reynolds, J.T.
1979-11-01
KAPL is developing a predictive method for three-dimensional (3-D) turbulent fluid flow configurations typically encountered in the thermal-hydraulic design of a nuclear reactor. A series of experiments has been selected for analysis to investigate the adequacy of the two-equation turbulence model developed at Imperial College, London, England for predicting the flow patterns in simple geometries. The analysis of these experiments is described with the two-dimensional (2-D) turbulent fluid flow code TEACH. This work qualifies TEACH for a variety of geometries and flow conditions
DEFF Research Database (Denmark)
Fristrup, Peter; Kreis, Michael; Palmelund, Anders
2008-01-01
that similar mechanisms are operating. A DFT (B3LYP) study of the catalytic cycle indicated a rapid oxidative addition into the C(O)-H bond followed by a rate-limiting extrusion of CO and reductive elimination. The theoretical kinetic isotope effects based on this mechanism were in excellent agreement...
International Nuclear Information System (INIS)
Gray, W.H.; Sun, C.T.
1976-07-01
The mechanical properties of a composite superconducting (NbTi/Cu) wire are characterized in terms of the mechanical properties of each constituent material. For a particular composite superconducting wire, five elastic material constants were experimentally determined and theoretically calculated. Since the Poisson's ratios for the fiber and the matrix material were very close, there was essentially no (less than 1 percent) difference among all the theoretical predictions for any individual mechanical constant. Because of the expense and difficulty of producing elastic constant data of 0.1 percent accuracy, and therefore conclusively determining which theory is best, no further experiments were performed
Baumann, Gerd
2005-01-01
Mathematica for Theoretical Physics: Electrodynamics, Quantum Mechanics, General Relativity, and Fractals This second edition of Baumann's Mathematica® in Theoretical Physics shows readers how to solve physical problems and deal with their underlying theoretical concepts while using Mathematica® to derive numeric and symbolic solutions. Each example and calculation can be evaluated by the reader, and the reader can change the example calculations and adopt the given code to related or similar problems. The second edition has been completely revised and expanded into two volumes: The first volume covers classical mechanics and nonlinear dynamics. Both topics are the basis of a regular mechanics course. The second volume covers electrodynamics, quantum mechanics, relativity, and fractals and fractional calculus. New examples have been added and the representation has been reworked to provide a more interactive problem-solving presentation. This book can be used as a textbook or as a reference work, by student...
Fluid Mechanics Of Molten Metal Droplets In Additive Manufacturing
Czech Academy of Sciences Publication Activity Database
Tesař, Václav; Šonský, Jiří
2016-01-01
Roč. 4, č. 4 (2016), s. 403-412 ISSN 2046-0546 R&D Projects: GA ČR GA13-23046S Institutional support: RVO:61388998 Keywords : additive manufacturing * droplets * molten metal Subject RIV: BK - Fluid Dynamics http://www.witpress.com/elibrary/cmem-volumes/4/4/1545
Book review: Partial Differential Equations and Fluid Mechanics
Muntean, A.
2011-01-01
The baak is the result of the workshop Partial Differential Equations and Fluid Dynamics that look place at the Mathematics Institute of the University of Warwick. May 21st - 23rd, 2007. It contains ten review and research papers which provide an accessible summary of a wide range of active research
International Nuclear Information System (INIS)
Corti, D.S.; Debenedetti, P.G.
1998-01-01
The rigorous statistical mechanics of metastability requires the imposition of internal constraints that prevent access to regions of phase space corresponding to inhomogeneous states. We derive exactly the Helmholtz energy and equation of state of the one-dimensional hard rod fluid under the influence of an internal constraint that places an upper bound on the distance between nearest-neighbor rods. This type of constraint is relevant to the suppression of boiling in a superheated liquid. We determine the effects of this constraint upon the thermophysical properties and internal structure of the hard rod fluid. By adding an infinitely weak and infinitely long-ranged attractive potential to the hard core, the fluid exhibits a first-order vapor-liquid transition. We determine exactly the equation of state of the one-dimensional superheated liquid and show that it exhibits metastable phase equilibrium. We also derive statistical mechanical relations for the equation of state of a fluid under the action of arbitrary constraints, and show the connection between the statistical mechanics of constrained and unconstrained ensembles. copyright 1998 The American Physical Society
Some applications of magnetic resonance imaging in fluid mechanics: Complex flows and complex fluids
Bonn, Daniel; Rodts, Stephane; Groenink, Maarten; Rafai, Salima; Shahidzadeh-Bonn, Noushine; Coussot, Philippe
2008-01-01
The review deals with applications of magnetic resonance imaging (MRI) techniques to study flow. We first briefly discuss the principles of flow measurement by MRI and give examples of some applications, such as multiphase flows, the MRI rheology of complex fluid flows, and blood flows in the human
Lin, Min; Luo, Zheng Yuan; Bai, Bo Feng; Xu, Feng; Lu, Tian Jian
2011-03-23
Dental thermal pain is a significant health problem in daily life and dentistry. There is a long-standing question regarding the phenomenon that cold stimulation evokes sharper and more shooting pain sensations than hot stimulation. This phenomenon, however, outlives the well-known hydrodynamic theory used to explain dental thermal pain mechanism. Here, we present a mathematical model based on the hypothesis that hot or cold stimulation-induced different directions of dentinal fluid flow and the corresponding odontoblast movements in dentinal microtubules contribute to different dental pain responses. We coupled a computational fluid dynamics model, describing the fluid mechanics in dentinal microtubules, with a modified Hodgkin-Huxley model, describing the discharge behavior of intradental neuron. The simulated results agreed well with existing experimental measurements. We thence demonstrated theoretically that intradental mechano-sensitive nociceptors are not "equally sensitive" to inward (into the pulp) and outward (away from the pulp) fluid flows, providing mechanistic insights into the difference between hot and cold dental pain. The model developed here could enable better diagnosis in endodontics which requires an understanding of pulpal histology, neurology and physiology, as well as their dynamic response to the thermal stimulation used in dental practices.
Formulation of the Chip Cleanability Mechanics from Fluid Transport
Garg, Saurabh; Dornfeld, David; Klaus Berger
2009-01-01
The presence of solid particle contaminant chips in high performance and complex automotive components like cylinder heads of internal combustion engines is a source of major concern for the automotive industry. Current industrial cleaning technologies, simply relying on the fluid transport energy of high pressure or intermittent high impulse jets discharged at the water jacket inlets of the cylinder head, fail to capture the dynamics of interaction between the chip morphology and the complex...
Fluid mechanics phenomena in microgravity; ASME Winter Annual Meeting, Anaheim, CA, Nov. 8-13, 1992
Siginer, Dennis A. (Editor); Weislogel, Mark M. (Editor)
1992-01-01
This paper is the first in a series of symposia presenting research activity in microgravity fluid mechanics. General topics addressed include two-phase flow and transport phenomena, thermo-capillary flow, and interfacial stability. Papers present mathmatical models of fluid dynamics in the microgravity environment. Applications suggested include space manufacturing and storage of liquids in low gravity.
National Research Council Canada - National Science Library
Dyakonov, M
1997-01-01
The purpose of this work is to develop further the theory of novel mechanisms for generation and detection of electromagnetic radiation in the terahertz range using the plasma oscillations of the two...
Basic course theoretical physics. Vol. 5/1. Quantum mechanics - foundations. 7. upd. ed.
International Nuclear Information System (INIS)
Nolting, Wolfgang
2009-01-01
The favoured basic course theoretical physics covers in seven volumes all fields relevant for the diploma. Each volume mediates well thought the in each semester necessary theoretically-physical tools. Numerous exercise problem with extensive solutions serve for the deepening of the matter. The first part of the fifth volume begins with an inductive foundation of quantum mechanics in order to illustrate after a study and summary of the formal foundations of quantum mechanics on simple model systems the concepts and term formations. The present new edition was fundamentally worked out and supplemented. The meanwhile proved two-color presentation allows a very understandable and fast approach to the matter [de
Contact mechanics for poroelastic, fluid-filled media, with application to cartilage.
Persson, B N J
2016-12-21
I study a simple contact mechanics model for a poroelastic, fluid-filled solid squeezed against a rigid, randomly rough substrate. I study how the fluid is squeezed out from the interface, and how the area of contact, and the average interfacial separation, change with time. I present numerical results relevant for a human cartilage. I show that for a fluid filled poroelastic solid the probability of cavitation (and the related wear as the cavities implode), and dynamical scraping (defined below and in Hutt and Persson, J. Chem. Phys. 144, 124903 (2016)), may be suppressed by fluid flow from the poroelastic solid into the (roughness induced) interfacial gap between the solids.
International Nuclear Information System (INIS)
Chen, S.H.H.
1984-01-01
Analytical models are developed to predict the hydrodynamical transients resulting from the energetic interactions between a high temperature molten material and a low temperature liquid coolant. Initially, the molten material at high temperature and pressure is separated from the low temperature fluid by a solid metal barrier. Upon contact between the molten material and solid barrier, thermal attack occurs eventually resulting in a loss of barrier integrity. Subsequently, the molten material is injected into the liquid pool resulting in energetic interactions. The analytical models integrate a wide variety of potentially mutually-interacting transport phenomena which dominate the transient process into a deterministic scheme to predict the hydrodynamic transient process into a deterministic scheme to predict the hydrodynamic transient process. The model calculations are compared with the existing experimental results to show its engineering accuracy and adequacy in predicting such energetic interactions. Two models are formulated to bracket the transport of molten material to the rupture site for the reactor system. The stratified model minimized the rate of transport of material to the break location while the dispersed model maximized such transport. These two models are applied to a reference pressure tube reactor to evaluate the pressure transients and the potential structural damages as a result of a postulated severe primary coolant blockage in a power channel
Gamez-Montero, P. Javier; Raush, Gustavo; Domènech, Lluis; Castilla, Robert; García-Vílchez, Mercedes; Moreno, Hipòlit; Carbó, Albert
2015-01-01
"Mechanics" and "Fluids" are familiar concepts for any newly-registered engineering student. However, when combined into the term "Fluid Mechanics", students are thrust into the great unknown. The present article demonstrates the process of adaptation employed by the Fluid Mechanics course in the undergraduate…
Use of piezoelectric multicomponent force measuring devices in fluid mechanics
Richter, A.; Stefan, K.
1979-01-01
The characterisitics of piezoelectric multicomponent transducers are discussed, giving attention to the advantages of quartz over other materials. The main advantage of piezoelectric devices in aerodynamic studies is their ability to indicate rapid changes in the values of physical parameters. Problems in the accuracy of measurments by piezoelectric devices can be overcome by suitable design approaches. A practical example is given of how such can be utilized to measure rapid fluctuations of fluid forces exerted on a circular cylinder mounted in a water channel.
Crystal Growth and Fluid Mechanics Problems in Directional Solidification
Tanveer, Saleh A.; Baker, Gregory R.; Foster, Michael R.
2001-01-01
Our work in directional solidification has been in the following areas: (1) Dynamics of dendrites including rigorous mathematical analysis of the resulting equations; (2) Examination of the near-structurally unstable features of the mathematically related Hele-Shaw dynamics; (3) Numerical studies of steady temperature distribution in a vertical Bridgman device; (4) Numerical study of transient effects in a vertical Bridgman device; (5) Asymptotic treatment of quasi-steady operation of a vertical Bridgman furnace for large Rayleigh numbers and small Biot number in 3D; and (6) Understanding of Mullins-Sererka transition in a Bridgman device with fluid dynamics is accounted for.
The instanton method and its numerical implementation in fluid mechanics
Grafke, Tobias; Grauer, Rainer; Schäfer, Tobias
2015-08-01
A precise characterization of structures occurring in turbulent fluid flows at high Reynolds numbers is one of the last open problems of classical physics. In this review we discuss recent developments related to the application of instanton methods to turbulence. Instantons are saddle point configurations of the underlying path integrals. They are equivalent to minimizers of the related Freidlin-Wentzell action and known to be able to characterize rare events in such systems. While there is an impressive body of work concerning their analytical description, this review focuses on the question on how to compute these minimizers numerically. In a short introduction we present the relevant mathematical and physical background before we discuss the stochastic Burgers equation in detail. We present algorithms to compute instantons numerically by an efficient solution of the corresponding Euler-Lagrange equations. A second focus is the discussion of a recently developed numerical filtering technique that allows to extract instantons from direct numerical simulations. In the following we present modifications of the algorithms to make them efficient when applied to two- or three-dimensional (2D or 3D) fluid dynamical problems. We illustrate these ideas using the 2D Burgers equation and the 3D Navier-Stokes equations.
The instanton method and its numerical implementation in fluid mechanics
International Nuclear Information System (INIS)
Grafke, Tobias; Grauer, Rainer; Schäfer, Tobias
2015-01-01
A precise characterization of structures occurring in turbulent fluid flows at high Reynolds numbers is one of the last open problems of classical physics. In this review we discuss recent developments related to the application of instanton methods to turbulence. Instantons are saddle point configurations of the underlying path integrals. They are equivalent to minimizers of the related Freidlin–Wentzell action and known to be able to characterize rare events in such systems. While there is an impressive body of work concerning their analytical description, this review focuses on the question on how to compute these minimizers numerically. In a short introduction we present the relevant mathematical and physical background before we discuss the stochastic Burgers equation in detail. We present algorithms to compute instantons numerically by an efficient solution of the corresponding Euler–Lagrange equations. A second focus is the discussion of a recently developed numerical filtering technique that allows to extract instantons from direct numerical simulations. In the following we present modifications of the algorithms to make them efficient when applied to two- or three-dimensional (2D or 3D) fluid dynamical problems. We illustrate these ideas using the 2D Burgers equation and the 3D Navier–Stokes equations. (topical review)
Experiments and Modeling of G-Jitter Fluid Mechanics
Leslie, F. W.; Ramachandran, N.; Whitaker, Ann F. (Technical Monitor)
2002-01-01
While there is a general understanding of the acceleration environment onboard an orbiting spacecraft, past research efforts in the modeling and analysis area have still not produced a general theory that predicts the effects of multi-spectral periodic accelerations on a general class of experiments nor have they produced scaling laws that a prospective experimenter can use to assess how an experiment might be affected by this acceleration environment. Furthermore, there are no actual flight experimental data that correlates heat or mass transport with measurements of the periodic acceleration environment. The present investigation approaches this problem with carefully conducted terrestrial experiments and rigorous numerical modeling for better understanding the effect of residual gravity and gentler on experiments. The approach is to use magnetic fluids that respond to an imposed magnetic field gradient in much the same way as fluid density responds to a gravitational field. By utilizing a programmable power source in conjunction with an electromagnet, both static and dynamic body forces can be simulated in lab experiments. The paper provides an overview of the technique and includes recent results from the experiments.
Electroresponsive Aqueous Silk Protein As “Smart” Mechanical Damping Fluid
2015-01-01
Here we demonstrate the effectiveness of an electroresponsive aqueous silk protein polymer as a smart mechanical damping fluid. The aqueous polymer solution is liquid under ambient conditions, but is reversibly converted into a gel once subjected to an electric current, thereby increasing or decreasing in viscosity. This nontoxic, biodegradable, reversible, edible fluid also bonds to device surfaces and is demonstrated to reduce friction and provide striking wear protection. The friction and mechanical damping coefficients are shown to modulate with electric field exposure time and/or intensity. Damping coefficient can be modulated electrically, and then preserved without continued power for longer time scales than conventional “smart” fluid dampers. PMID:24750065
STAFAN, Fluid Flow, Mechanical Stress in Fractured Rock of Nuclear Waste Repository
International Nuclear Information System (INIS)
Huyakorn, P.; Golis, M.J.
1989-01-01
1 - Description of program or function: STAFAN (Stress And Flow Analysis) is a two-dimensional, finite-element code designed to model fluid flow and the interaction of fluid pressure and mechanical stresses in a fractured rock surrounding a nuclear waste repository. STAFAN considers flow behavior of a deformable fractured system with fracture-porous matrix interactions, the coupling effects of fluid pressure and mechanical stresses in a medium containing discrete joints, and the inelastic response of the individual joints of the rock mass subject to the combined fluid pressure and mechanical loading. 2 - Restrictions on the complexity of the problem: STAFAN does not presently contain thermal coupling, and it is unable to simulate inelastic deformation of the rock mass and variably saturated or two-phase flow in the fractured porous medium system
Personal Computer (PC) based image processing applied to fluid mechanics
Cho, Y.-C.; Mclachlan, B. G.
1987-01-01
A PC based image processing system was employed to determine the instantaneous velocity field of a two-dimensional unsteady flow. The flow was visualized using a suspension of seeding particles in water, and a laser sheet for illumination. With a finite time exposure, the particle motion was captured on a photograph as a pattern of streaks. The streak pattern was digitized and processed using various imaging operations, including contrast manipulation, noise cleaning, filtering, statistical differencing, and thresholding. Information concerning the velocity was extracted from the enhanced image by measuring the length and orientation of the individual streaks. The fluid velocities deduced from the randomly distributed particle streaks were interpolated to obtain velocities at uniform grid points. For the interpolation a simple convolution technique with an adaptive Gaussian window was used. The results are compared with a numerical prediction by a Navier-Stokes computation.
Schaum’s outline of fluid mechanics and hydraulics
Giles, Ranald V; Liu, Cheng
2014-01-01
Tough Test Questions? Missed Lectures? Not Enough Time? Fortunately, there's Schaum's. More than 40 million students have trusted Schaum's to help them succeed in the classroom and on exams. Schaum's is the key to faster learning and higher grades in every subject. Each Outline presents all the essential course information in an easy-to-follow, topic-by-topic format. You also get hundreds of examples, solved problems, and practice exercises to test your skills. This Schaum's Outline gives you: 622 fully solved problems; extra practice on topics such as buoyancy and flotation, complex pipeline systems, fluid machinery, flow in open channels, and more; and support for all the major textbooks for fluidmechanics and hydraulics courses. Fully compatible with your classroom text, Schaum's highlights all the important facts you need to know. Use Schaum's to shorten your study time - and get your best test scores! Schaum's Outlines - Problem Solved.
The NASA Lewis Research Center Internal Fluid Mechanics Facility
Porro, A. R.; Hingst, W. R.; Wasserbauer, C. A.; Andrews, T. B.
1991-01-01
An experimental facility specifically designed to investigate internal fluid duct flows is described. It is built in a modular fashion so that a variety of internal flow test hardware can be installed in the facility with minimal facility reconfiguration. The facility and test hardware interfaces are discussed along with design constraints of future test hardware. The plenum flow conditioning approach is also detailed. Available instrumentation and data acquisition capabilities are discussed. The incoming flow quality was documented over the current facility operating range. The incoming flow produces well behaved turbulent boundary layers with a uniform core. For the calibration duct used, the boundary layers approached 10 percent of the duct radius. Freestream turbulence levels at the various operating conditions varied from 0.64 to 0.69 percent of the average freestream velocity.
Analysis of Skylab IV fluid mechanic science demonstration
Klett, M. G.; Bourgeois, S. V.
1975-01-01
Several science demonstrations performed on Skylab III and IV were concerned with the behavior of fluid drops free floating in microgravity. These demonstrations, with large liquid drops, included the oscillation, rotation, impact and coalescence, and air injection into the drops. Rayleigh's analysis of the oscillation of spherical drops of a liquid predicts accurately the effect of size and surface tension on the frequency of vibrated water globules in the Skylab demonstration. However, damping occurred much faster than predicted by Lamb's or Scriven's analyses of the damping time for spherical drops. The impact demonstrations indicated that a minimum velocity is necessary to overcome surface forces and effect a coalescence, but a precise criterion for the coalescence of liquids in low g could not be determined.
Mechanisms of sampling interstitial fluid from skin using a microneedle patch.
Samant, Pradnya P; Prausnitz, Mark R
2018-05-01
Although interstitial fluid (ISF) contains biomarkers of physiological significance and medical interest, sampling of ISF for clinical applications has made limited impact due to a lack of simple, clinically useful techniques that collect more than nanoliter volumes of ISF. This study describes experimental and theoretical analysis of ISF transport from skin using microneedle (MN) patches and demonstrates collection of >1 µL of ISF within 20 min in pig cadaver skin and living human subjects using an optimized system. MN patches containing arrays of submillimeter solid, porous, or hollow needles were used to penetrate superficial skin layers and access ISF through micropores (µpores) formed upon insertion. Experimental studies in pig skin found that ISF collection depended on transport mechanism according to the rank order diffusion sampling is transport through the dermis. Based on these studies and other considerations like safety and convenience for future clinical use, we designed an MN patch prototype to sample ISF using suction as the driving force. Using this approach, we collected ISF from human volunteers and identified the presence of biomarkers in the collected ISF. In this way, sampling ISF from skin using an MN patch could enable collection of ISF for use in research and medicine.
Theoretical analysis of material removal mechanisms in pulsed laser fusion cutting of ceramics
Energy Technology Data Exchange (ETDEWEB)
Quintero, F [Dpto FIsica Aplicada, Universidad de Vigo, ETS Ingenieros Industriales, Lagoas-Marcosende 9, 36310 Vigo (Spain); Varas, F [Dpto Matematica Aplicada II, Universidad de Vigo, ETS Ingenieros Industriales, Lagoas-Marcosende 9, 36310 Vigo (Spain); Pou, J [Dpto FIsica Aplicada, Universidad de Vigo, ETS Ingenieros Industriales, Lagoas-Marcosende 9, 36310 Vigo (Spain); Lusquinos, F [Dpto FIsica Aplicada, Universidad de Vigo, ETS Ingenieros Industriales, Lagoas-Marcosende 9, 36310 Vigo (Spain); Boutinguiza, M [Dpto FIsica Aplicada, Universidad de Vigo, ETS Ingenieros Industriales, Lagoas-Marcosende 9, 36310 Vigo (Spain); Soto, R [Dpto FIsica Aplicada, Universidad de Vigo, ETS Ingenieros Industriales, Lagoas-Marcosende 9, 36310 Vigo (Spain); Perez-Amor, M [Dpto FIsica Aplicada, Universidad de Vigo, ETS Ingenieros Industriales, Lagoas-Marcosende 9, 36310 Vigo (Spain)
2005-02-21
It is well known that the efficiency of material removal mechanisms has a crucial influence on the performance and quality of the laser cutting process. However, they are very difficult to study since the physical processes and parameters which govern them are quite complicated to observe and measure experimentally. For this reason, the development of theoretical models to analyse the material removal mechanisms is very important for understanding the characteristics and influence of these processes. In this paper, a theoretical model of the pulsed laser fusion cutting of ceramics is presented. The material removal mechanisms from the cutting front are modelled under the assumption that the ceramic material may be, simultaneously, melted and evaporated by the laser radiation. Therefore, three ejection mechanisms are investigated together: ejection of molten material by the assist gas, evaporation of the liquid and ejection of molten material due to the recoil pressure generated by the evaporation from the cutting front. The temporal evolution of the material removal mechanisms and the thickness of the molten layer are solved for several laser pulse modes. Theoretical results are compared with experimental observations to validate the conclusions regarding the influence of frequency and pulse length on the cutting process.
DEFF Research Database (Denmark)
Jabbari, Masoud; Sarlak Chivaee, Hamid; Hattel, Jesper Henri
2017-01-01
We are pleased to introduce this special issue of the Applied Mathematical Modelling journal with highlights from theTheoretical, Experimental, and Computational Mechanics Symposium (TECM-2015). This special issue consists of four rigorouslyselected papers originally presented at TECM-2015...... as a part of the 13th International Conference of Numerical Analysisand Applied Mathematics 2015 (ICNAAM 2015), which was held on 23-29 September 2015 in Rhodes, Greece.The symposium attracted a broad range of international and local leaders in theoretical, experimental, and computational mechanics across...... various fields and application. The symposium did an excellent job of outlining the current landscape of computational mechanics and its capabilities in solving complex industrial problems in the process industries, and we agree with the editor-in-chief of the journal that it is certainly worthwhile...
Study of network resource allocation based on market and game theoretic mechanism
Liu, Yingmei; Wang, Hongwei; Wang, Gang
2004-04-01
We work on the network resource allocation issue concerning network management system function based on market-oriented mechanism. The scheme is to model the telecommunication network resources as trading goods in which the various network components could be owned by different competitive, real-world entities. This is a multidisciplinary framework concentrating on the similarity between resource allocation in network environment and the market mechanism in economic theory. By taking an economic (market-based and game theoretic) approach in routing of communication network, we study the dynamic behavior under game-theoretic framework in allocating network resources. Based on the prior work of Gibney and Jennings, we apply concepts of utility and fitness to the market mechanism with an intention to close the gap between experiment environment and real world situation.
20th International Congress of Theoretical and Applied Mechanics, ICTAM2000
Energy Technology Data Exchange (ETDEWEB)
Hassan, Aref
2000-08-27
The 20th International Congress of Theoretical and Applied Mechanics, ICTAM2000, was held in Chicago, IL, from August 27 - September 2, 2000. It was 32 years since the last of these congresses had been held in USA. A record number of researchers in the mechanical engineering sciences attended and presented their work. The Congress provided an opportunity for the US mechanics community to act as international hosts. Several universities, professional societies, private foundations and individuals, and Federal agencies provided financial support for the Congress.
Combustion research in the Internal Fluid Mechanics Division
Mularz, Edward J.
1986-01-01
The goal of this research is to bring computational fluid dynamics to a state of practical application for the aircraft engine industry. The approach is to have a strongly integrated computational and experimental program for all the disciplines associated with the gas turbine and other aeropropulsion systems by advancing the understanding of flow physics, heat transfer, and combustion processes. The computational and experimental research is integrated in the following way: the experiments that are performed provide an empirical data set so that physical models can be formulated to describe the processes that are occurring - for example, turbulence or chemical reaction. These experiments also form a data base for those who are doing code development by providing experimental data against which the codes can be verified and assesed. Models are generated as closure to some of the numerical codes, and they also provide physical insight for experiments. At the same time, codes which solve the complete Navier-Stokes equations can be used as a kind of numerical experiment from which far more extensive data can be obtained than ever could be obtained experimentally. This could provide physical insight into the complex processes that are taking place. These codes are also exercised against experimental data to assess the accuracy and applicability of models.
Mechanics of fluid flow over compliant wrinkled polymeric surfaces
Raayai, Shabnam; McKinley, Gareth; Boyce, Mary
2014-03-01
Skin friction coefficients (based on frontal area) of sharks and dolphins are lower than birds, fish and swimming beetles. By either exploiting flow-induced changes in their flexible skin or microscale textures, dolphins and sharks can change the structure of the fluid flow around them and thus reduce viscous drag forces on their bodies. Inspired by this ability, investigators have tried using compliant walls and riblet-like textures as drag reduction methods in aircraft and marine industries and have been able to achieve reductions up to 19%. Here we investigate flow-structure interaction and wrinkling of soft polymer surfaces that can emulate shark riblets and dolphin's flexible skin. Wrinkling arises spontaneously as the result of mismatched deformation of a thin stiff coating bound to a thick soft elastic substrate. Wrinkles can be fabricated by controlling the ratio of the stiffness of the coating and substrate, the applied displacement and the thickness of the coating. In this work we will examine the evolution in the kinematic structures associated with steady viscous flow over the polymer wrinkled surfaces and in particular compare the skin friction with corresponding results for flow over non-textured and rigid surfaces.
Mechanical testing of hydraulic fluids II; Mechanische Pruefung von Hydraulikfluessigkeiten II
Energy Technology Data Exchange (ETDEWEB)
Kessler, M.; Feldmann, D.G.; Laukart, V.
2001-09-01
Since May 1996 the Institute for Mechanical Engineering Design 1 of Technical University of Hamburg-Harburg is working on the topic of ''Mechanical Testing of Hydraulic fluids''. The first project lasting 2 1/2 years was completed in 1999, the results are published as the DGMK report 514. Within these project a testing principle for the ''mechanical testing'' of hydraulic fluids has been derived, a prototype of a test rig was designed and set in operation at the authors' institute. This DGMK-report 514-1 describes the results of the second project, which investigates the operating behaviour of the test-rig more in detail. Several test-runs with a total number of 11 different hydraulic fluids show the dependence of the different lubricating behaviour of the tested fluids and their friction and wear behaviour during the tests in a reproducible way. The aim of the project was to derive a testing principle including the design of a suitable test-rig for the mechanical testing of hydraulic fluids. Based on the described results it can be stated that with the developed test it is possible to test the lubricity of hydraulic fluids reproducible and in correlation to field experiences within a relatively short time, so the target was reached. (orig.)
A computational analysis on homogeneous-heterogeneous mechanism in Carreau fluid flow
Khan, Imad; Rehman, Khalil Ur; Malik, M. Y.; Shafquatullah
2018-03-01
In this article magnetohydrodynamic Carreau fluid flow towards stretching cylinder is considered in the presence of homogeneous-heterogeneous reactions effect. The flow model is structured by utilizing theoretical grounds. For the numerical solution a shooting method along with Runge-Kutta algorithm is executed. The outcomes are provided through graphs. It is observed that the Carreau fluid concentration shows decline values via positive iterations of homogeneous-heterogeneous reaction parameters towards both shear thinning and thickening case. The present work is certified through comparison with already existing literature in a limiting sense.
Use of Facebook in Teaching: A Case Study of a Fluid Mechanics Course
Mandavgane, Sachin A.
2016-01-01
Fluid mechanics (FM) is a core course of the chemical, mechanical, civil, and aerospace engineering programs. Students have both theory and practical classes in FM. The general expectation is that students should be able to demonstrate the fundamentals learnt in theory and get hands-on experience during the lab course. In this regard, students…
Finite element procedures for coupled linear analysis of heat transfer, fluid and solid mechanics
Sutjahjo, Edhi; Chamis, Christos C.
1993-01-01
Coupled finite element formulations for fluid mechanics, heat transfer, and solid mechanics are derived from the conservation laws for energy, mass, and momentum. To model the physics of interactions among the participating disciplines, the linearized equations are coupled by combining domain and boundary coupling procedures. Iterative numerical solution strategy is presented to solve the equations, with the partitioning of temporal discretization implemented.
Energy Technology Data Exchange (ETDEWEB)
Berryman, J.G.
2010-06-01
The mechanics of vertically layered porous media has some similarities to and some differences from the more typical layered analysis for purely elastic media. Assuming welded solid contact at the solid-solid interfaces implies the usual continuity conditions, which are continuity of the vertical (layering direction) stress components and the horizontal strain components. These conditions are valid for both elastic and poroelastic media. Differences arise through the conditions for the pore pressure and the increment of fluid content in the context of fluid-saturated porous media. The two distinct conditions most often considered between any pair of contiguous layers are: (1) an undrained fluid condition at the interface, meaning that the increment of fluid content is zero (i.e., {delta}{zeta} = 0), or (2) fluid pressure continuity at the interface, implying that the change in fluid pressure is zero across the interface (i.e., {delta}p{sub f} = 0). Depending on the types of measurements being made on the system and the pertinent boundary conditions for these measurements, either (or neither) of these two conditions might be directly pertinent. But these conditions are sufficient nevertheless to be used as thought experiments to determine the expected values of all the poroelastic coefficients. For quasi-static mechanical changes over long time periods, we expect drained conditions to hold, so the pressure must then be continuous. For high frequency wave propagation, the pore-fluid typically acts as if it were undrained (or very nearly so), with vanishing of the fluid increment at the boundaries being appropriate. Poroelastic analysis of both these end-member cases is discussed, and the general equations for a variety of applications to heterogeneous porous media are developed. In particular, effective stress for the fluid permeability of such poroelastic systems is considered; fluid permeabilities characteristic of granular media or tubular pore shapes are treated
The chemo-mechanical effect of cutting fluid on material removal in diamond scribing of silicon
Kumar, Arkadeep; Melkote, Shreyes N.
2017-07-01
The mechanical integrity of silicon wafers cut by diamond wire sawing depends on the damage (e.g., micro-cracks) caused by the cutting process. The damage type and extent depends on the material removal mode, i.e., ductile or brittle. This paper investigates the effect of cutting fluid on the mode of material removal in diamond scribing of single crystal silicon, which simulates the material removal process in diamond wire sawing of silicon wafers. We conducted scribing experiments with a diamond tipped indenter in the absence (dry) and in the presence of a water-based cutting fluid. We found that the cutting mode is more ductile when scribing in the presence of cutting fluid compared to dry scribing. We explain the experimental observations by the chemo-mechanical effect of the cutting fluid on silicon, which lowers its hardness and promotes ductile mode material removal.
The fluid mechanics of scleral buckling surgery for the repair of retinal detachment.
Foster, William Joseph; Dowla, Nadia; Joshi, Saurabh Y; Nikolaou, Michael
2010-01-01
Scleral buckling is a common surgical technique used to treat retinal detachments that involves suturing a radial or circumferential silicone element on the sclera. Although this procedure has been performed since the 1960s, and there is a reasonable experimental model of retinal detachment, there is still debate as to how this surgery facilitates the re-attachment of the retina. Finite element calculations using the COMSOL Multiphysics system are utilized to explain the influence of the scleral buckle on the flow of sub-retinal fluid in a physical model of retinal detachment. We found that, by coupling fluid mechanics with structural mechanics, laminar fluid flow and the Bernoulli effect are necessary for a physically consistent explanation of retinal reattachment. Improved fluid outflow and retinal reattachment are found with low fluid viscosity and rapid eye movements. A simulation of saccadic eye movements was more effective in removing sub-retinal fluid than slower, reading speed, eye movements in removing subretinal fluid. The results of our simulations allow us to explain the physical principles behind scleral buckling surgery and provide insight that can be utilized clinically. In particular, we find that rapid eye movements facilitate more rapid retinal reattachment. This is contradictory to the conventional wisdom of attempting to minimize eye movements.
1992-01-01
Research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, numerical analysis, fluid mechanics including fluid dynamics, acoustics, and combustion, aerodynamics, and computer science during the period 1 Apr. 1992 - 30 Sep. 1992 is summarized.
Gritti, Fabrice; Fogwill, Michael
2017-06-09
The potential advantage of turbulent supercritical fluid chromatography (TSFC) in open tubular columns (OTC) was evaluated on both theoretical and practical viewpoints. First, the dispersion model derived by Golay in 1958 and recently extended from laminar to turbulent flow regime is used for the predictions of the speed-resolution performance in TSFC. The average dispersion coefficient of matter in the turbulent flow regime was taken from the available experimental data over a range of Reynolds number from 2000 to 6000. Kinetic plots are built at constant pressure drop (ΔP=4500psi) and Schmidt number (Sc=15) for four inner diameters (10, 30, 100, and 300μm) of the OTC and for three retention factors (0, 1, and 10). Accordingly, in turbulent flow regime, for a Reynolds number of 4000 and a retention factor of 1 (the stationary film thickness is assumed to be negligible with respect to the OTC diameter), the theory projects that a 300μm i.d. OTC has the same speed-resolution power (200,000 theoretical plates; 2.4min hold-up time) as that of a 10μm i.d. OTC operated in laminar flow regime. Secondly, the experimental plate heights of n-butylbenzene are measured in laminar and turbulent flow regimes for a 180μm×4.8m fused silica capillary column using pure carbon dioxide as the mobile phase. The back pressure regulator was set at 1500psi, the temperature was uniform at 297K, and the flow rate was increased step-wise from 0.50 to 3.60mL/min so that the experimental Reynolds number increases from 700 to 5400. The experiments are in good agreement with the plate heights projected in TSFC at high flow rates and with those expected at low flow rates in a laminar flow regime. Copyright © 2017 Elsevier B.V. All rights reserved.
Anisotropic mechanical properties and Stone-Wales defects in graphene monolayer: A theoretical study
International Nuclear Information System (INIS)
Fan, B.B.; Yang, X.B.; Zhang, R.
2010-01-01
We investigate the mechanical properties of graphene monolayer via the density functional theoretical (DFT) method. We find that the strain energies are anisotropic for the graphene under large strain. We attribute the anisotropic feature to the anisotropic sp 2 hybridization in the hexagonal lattice. We further identify that the formation energies of Stone-Wales (SW) defects in the graphene monolayer are determined by the defect concentration and also the direction of applied tensile strain, correlating with the anisotropic feature.
Fluid mechanics of directional solidification at reduced gravity
Chen, C. F.
1992-01-01
The primary objective of the proposed research is to provide additional groundbased support for the flight experiment 'Casting and Solidification Technology' (CAST). This experiment is to be performed in the International Microgravity Laboratory-1 (IML-1) scheduled to be flown on a space shuttle mission scheduled for 1992. In particular, we will provide data on the convective motion and freckle formation during directional solidification of NH4Cl from its aqueous solution at simulated parameter ranges equivalent to reducing the gravity from the sea-level value down to 0.1 g or lower. The secondary objectives of the proposed research are to examine the stability phenomena associated with the onset of freckles and the mechanisms for their subsequent growth and decline (to eventual demise of some) by state-of-the-art imaging techniques and to formulate mathematical models for the prediction of the observed phenomena.
A novel coarsening mechanism of droplets in immiscible fluid mixtures
Shimizu, Ryotaro; Tanaka, Hajime
2015-06-01
In our daily lives, after shaking a salad dressing, we see the coarsening of oil droplets suspended in vinegar. Such a demixing process is observed everywhere in nature and also of technological importance. For a case of high droplet density, domain coarsening proceeds with inter-droplet collisions and the resulting coalescence. This phenomenon has been explained primarily by the so-called Brownian-coagulation mechanism: stochastic thermal forces exerted by molecules induce random motion of individual droplets, causing accidental collisions and subsequent interface-tension-driven coalescence. Contrary to this, here we demonstrate that the droplet motion is not random, but hydrodynamically driven by the composition Marangoni force due to an interfacial tension gradient produced in each droplet as a consequence of composition correlation among droplets. This alters our physical understanding of droplet coarsening in immiscible liquid mixtures on a fundamental level.
Obstructive renal injury: from fluid mechanics to molecular cell biology.
Ucero, Alvaro C; Gonçalves, Sara; Benito-Martin, Alberto; Santamaría, Beatriz; Ramos, Adrian M; Berzal, Sergio; Ruiz-Ortega, Marta; Egido, Jesus; Ortiz, Alberto
2010-04-22
Urinary tract obstruction is a frequent cause of renal impairment. The physiopathology of obstructive nephropathy has long been viewed as a mere mechanical problem. However, recent advances in cell and systems biology have disclosed a complex physiopathology involving a high number of molecular mediators of injury that lead to cellular processes of apoptotic cell death, cell injury leading to inflammation and resultant fibrosis. Functional studies in animal models of ureteral obstruction using a variety of techniques that include genetically modified animals have disclosed an important role for the renin-angiotensin system, transforming growth factor-β1 (TGF-β1) and other mediators of inflammation in this process. In addition, high throughput techniques such as proteomics and transcriptomics have identified potential biomarkers that may guide clinical decision-making.
Fluid Mechanics of Capillary-Elastic Instabilities in Microgravity Environment
Grotberg, James B.
2002-01-01
The aim of this project is to investigate the closure and reopening of lung airways due to surface tension forces, coupled with airway elasticity. Airways are liquid-lined, flexible tubes and closure of airways can occur by a Rayleigh instability of the liquid lining, or an instability of the elastic support for the airway as the surface tension of the air-liquid interface pulls the tube shut, or both. Regardless of the mechanism, the airway is closed because the liquid lining has created a plug that prevents axial gas exchange. In the microgravity environment, surface tension forces dominate lung mechanics and would lead to more prevalent, and more uniformly distributed air-way closure, thereby creating a potential for respiratory problems for astronauts. Once closed the primary option for reopening an airway is by deep inspiration. This maneuver will pull the flexible airways open and force the liquid plug to flow distally by the incoming air stream. Airway reopening depends to a large extent on this plug flow and how it may lead to plug rupture to regain the continuity of gas between the environment and the alveoli. In addition to mathematical modeling of plug flows in liquid-lined, flexible tubes, this work has involved benchtop studies of propagating liquid plugs down tube networks that mimic the human airway tree. We have extended the work to involve animal models of liquid plug propagation in rat lungs. The liquid is radio-opaque and x-ray video imaging is used to ascertain the movement and distribution of the liquid plugs so that comparisons to theory may be made. This research has other uses, such as the delivery of liquids or drugs into the lung that may be used for surfactant replacement therapy or for liquid ventilation.
Deng, Jian; Zhou, Guangming; Ji, Le; Wang, Xiaopei
2017-12-01
Mechanical properties and failure mechanisms of a newly designed 3D multi-layer braided composites are evaluated by experimental, numerical and theoretical studies. The microstructure of the composites is introduced. The unit cell technique is employed to address the periodic arrangement of the structure. The volume averaging method is used in theoretical solutions while FEM with reasonable periodic boundary conditions and meshing technique in numerical simulations. Experimental studies are also conducted to verify the feasibility of the proposed models. Predicted elastic properties agree well with the experimental data, indicating the feasibility of the proposed models. Numerical evaluation is more accurate than theoretical assessment. Deformations and stress distributions of the unit cell under tension shows displacement and traction continuity, guaranteeing the rationality of the applied periodic boundary conditions. Although compression and tension modulus are close, the compressive strength only reaches 70% of the tension strength. This indicates that the composites can be weakened in compressive loading. Additionally, by analysing the micrograph of fracture faces and strain-stress curves, a brittle failure mechanism is observed both in composites under tension and compression.
Vandre, Eric
2014-11-01
Dynamic wetting is crucial to processes where a liquid displaces another fluid along a solid surface, such as the deposition of a coating liquid onto a moving substrate. Dynamic wetting fails when process speed exceeds some critical value, leading to incomplete fluid displacement and transient phenomena that impact a variety of applications, such as microfluidic devices, oil-recovery systems, and splashing droplets. Liquid coating processes are particularly sensitive to wetting failure, which can induce air entrainment and other catastrophic coating defects. Despite the industrial incentives for careful control of wetting behavior, the hydrodynamic factors that influence the transition to wetting failure remain poorly understood from empirical and theoretical perspectives. This work investigates the fundamentals of wetting failure in a variety of systems that are relevant to industrial coating flows. A hydrodynamic model is developed where an advancing fluid displaces a receding fluid along a smooth, moving substrate. Numerical solutions predict the onset of wetting failure at a critical substrate speed, which coincides with a turning point in the steady-state solution path for a given set of system parameters. Flow-field analysis reveals a physical mechanism where wetting failure results when capillary forces can no longer support the pressure gradients necessary to steadily displace the receding fluid. Novel experimental systems are used to measure the substrate speeds and meniscus shapes associated with the onset of air entrainment during wetting failure. Using high-speed visualization techniques, air entrainment is identified by the elongation of triangular air films with system-dependent size. Air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Meniscus confinement in a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a variety of
International Nuclear Information System (INIS)
Rojas-Trigos, J.B.; Marín, E.; Mansanares, A.M.; Cedeño, E.; Juárez-Gracia, G.; Calderón, A.
2014-01-01
Highlights: • A model for photopyroelectric thermal characterization of fluids is presented. • A slanted detector configuration is considered with a finite measurement cell. • The mean temperature distribution in the photopyroelectric detector, as function of the beam spot position, is calculated. • The influence of the excitation beam spot size, the thermal diffusion length and size of the sample is discussed. • The high lateral resolution of the method observed in experiments is explain. - Abstract: This work presents an extended description about the theoretical aspects related to the generation of the photopyroelectric signal in a recently proposed wedge-like heat transmission detection configuration, which recreates the well-known Angstrom method (widely used for solid samples) for accurate thermal diffusivity measurement in gases and liquids. The presented model allows for the calculation of the temperature profile detected by the pyroelectric sensor as a function of the excitation beam position, and the study of the influence on it of several parameters, such as spot size, thermal properties of the absorber layer, and geometrical parameters of the measurement cell. Through computer simulations, it has been demonstrated that a narrow temperature distribution is created at the sensor surface, independently of the lateral diffusion of heat taking place at the sample's surface
Shape matters: Near-field fluid mechanics dominate the collective motions of ellipsoidal squirmers.
Kyoya, K; Matsunaga, D; Imai, Y; Omori, T; Ishikawa, T
2015-12-01
Microswimmers show a variety of collective motions. Despite extensive study, questions remain regarding the role of near-field fluid mechanics in collective motion. In this paper, we describe precisely the Stokes flow around hydrodynamically interacting ellipsoidal squirmers in a monolayer suspension. The results showed that various collective motions, such as ordering, aggregation, and whirls, are dominated by the swimming mode and the aspect ratio. The collective motions are mainly induced by near-field fluid mechanics, despite Stokes flow propagation over a long range. These results emphasize the importance of particle shape in collective motion.
Fluid-injection and the mechanics of frictional stability of shale-bearing faults
Scuderi, Marco Maria; Collettini, Cristiano; Marone, Chris
2017-04-01
Fluid overpressure is one of the primary mechanisms for triggering tectonic fault slip and human-induced seismicity. This mechanism is appealing because fluids lubricate the fault and reduce the effective normal stress that holds the fault in place. However, current models of earthquake nucleation, based on rate- and state- friction, imply that stable sliding is favored by the increase of pore fluid pressure. Despite this apparent dilemma, there are a few studies on the role of fluid pressure in frictional stability under controlled, laboratory conditions. Here, we describe laboratory experiments on shale fault gouge, conducted in the double direct shear configuration in a true-triaxial machine. To characterize frictional stability and hydrological properties we performed three types of experiments: 1) stable sliding shear experiment to determine the material failure envelope resulting in fault strength of µ=0.28 and fault zone permeability (k 10-19m2); 2) velocity step experiments to determine the rate- and state- frictional properties, characterized by a velocity strengthening behavior with a negative rate parameter b, indicative of stable aseismic creep; 3) creep experiment to study fault slip evolution with increasing pore-fluid pressure. In these creep experiments fault slip history can be divided in three main stages: a) for low fluid pressure the fault is locked and undergoes compaction; b) with increasing fluid pressurization, we observe aseismic creep (i.e. v=0.0001 µm/s) associated with fault dilation, with maintained low permeability; c) As fluid pressure is further increased and we approach the failure criteria fault begins to accelerate, the dilation rate increases causing an increase in permeability. Following the first acceleration we document complex fault slip behavior characterized by periodic accelerations and decelerations with slip velocity that remains slow (i.e. v 200 µm/s), never approaching dynamic slip rates. Surprisingly, this complex
A Finite-Volume computational mechanics framework for multi-physics coupled fluid-stress problems
International Nuclear Information System (INIS)
Bailey, C; Cross, M.; Pericleous, K.
1998-01-01
Where there is a strong interaction between fluid flow, heat transfer and stress induced deformation, it may not be sufficient to solve each problem separately (i.e. fluid vs. stress, using different techniques or even different computer codes). This may be acceptable where the interaction is static, but less so, if it is dynamic. It is desirable for this reason to develop software that can accommodate both requirements (i.e. that of fluid flow and that of solid mechanics) in a seamless environment. This is accomplished in the University of Greenwich code PHYSICA, which solves both the fluid flow problem and the stress-strain equations in a unified Finite-Volume environment, using an unstructured computational mesh that can deform dynamically. Example applications are given of the work of the group in the metals casting process (where thermal stresses cause elasto- visco-plastic distortion)
The Fast and Non-capillary Fluid Filling Mechanism in the Hummingbird's Tongue
Rico-Guevara, Alejandro; Fan, Tai-Hsi; Rubega, Margaret
2014-03-01
Hummingbirds gather nectar by inserting their beaks inside flowers and cycling their tongues at a frequency of up to 20 Hz. It is unclear how they achieve efficiency at this high licking rate. Ever since proposed in 1833, it has been believed that hummingbird tongues are a pair of tiny straws filled with nectar by capillary rise. Our discoveries are very different from this general consensus. The tongue does not draw up floral nectar via capillary action under experimental conditions that resemble natural ones. Theoretical models based on capillary rise were mistaken and unsuitable for estimating the fluid intake rate and to support foraging theories. We filmed (up to 1265 frames/s) the fluid uptake in 20 species of hummingbirds that belong to 7 out of the 9 main hummingbird clades. We found that the fluid filling within the portions of the tongue that remain outside the nectar is about five times faster than capillary filling. We present strong evidence to rule out the capillarity model. We introduce a new fluid-structure interaction and hydrodynamic model and compare the results with field experimental data to explain how hummingbirds actually extract fluid from flowers at the lick level.
International Nuclear Information System (INIS)
Wang, Ji-Xiang; Li, Yun-Ze; Zhang, Hong-Sheng; Wang, Sheng-Nan; Liang, Yi-Hao; Guo, Wei; Liu, Yang; Tian, Shao-Ping
2016-01-01
Highlights: • A highly self-adaptive cold plate integrated with paraffin-based actuator is proposed. • Higher operating economy is attained due to an energy-efficient strategy. • A greater compatibility of the current space control system is obtained. • Model was entrenched theoretically to design the system efficiently. • A strong self-adaptability of the cold plate is observed experimentally. - Abstract: Aiming to improve the conventional single-phase mechanically pumped fluid loop applied in spacecraft thermal control system, a novel actively-pumped loop using distributed thermal control strategy was proposed. The flow control system for each branch consists primarily of a thermal control valve integrated with a paraffin-based actuator residing in the front part of each corresponding cold plate, where both coolant’s flow rate and the cold plate’s heat removal capability are well controlled sensitively according to the heat loaded upon the cold plate due to a conversion between thermal and mechanical energies. The operating economy enhances remarkably owing to no energy consumption in flow control process. Additionally, realizing the integration of the sensor, controller and actuator systems, it simplifies structure of the traditional mechanically pumped fluid loop as well. Revolving this novel scheme, mathematical model regarding design process of the highly specialized cold plate was entrenched theoretically. A validating system as a prototype was established on the basis of the design method and the scheduled objective of the controlled temperature (43 °C). Then temperature control performances of the highly self-adaptive cold plate under various operating conditions were tested experimentally. During almost all experiments, the controlled temperature remains within a range of ±2 °C around the set-point. Conclusions can be drawn that this self-driven control system is stable with sufficient fast transient responses and sufficient small steady
David, C.; Dautriat, J. D.; Sarout, J.; Macault, R.; Bertauld, D.
2014-12-01
Water weakening is a well-known phenomenon which can lead to subsidence during the production of hydrocarbon reservoirs. The example of the Ekofisk oil field in the North Sea has been well documented for years. In order to assess water weakening effects in reservoir rocks, previous studies have focused on changes in the failure envelopes derived from mechanical tests conducted on rocks saturated either with water or with inert fluids. However, little attention has been paid so far on the mechanical behaviour during the fluid injection stage, like in enhanced oil recovery operations. We studied the effect of fluid injection on the mechanical behaviour of Sherwood sandstone, a weakly-consolidated sandstone sampled at Ladram Bay in UK. In order to highlight possible weakening effects, water and inert oil have been injected into critically-loaded samples to assess their effect on strength and elastic properties and to derive the acoustic signature of the saturation front for each fluid. The specimens were instrumented with 16 ultrasonic P-wave transducers for both passive and active acoustic monitoring during fluid injection and loading. After conducting standard triaxial tests on three samples saturated with air, water and oil respectively, mechanical creep tests were conducted on dry samples loaded at 80% of the compressive strength of the dry rock. While these conditions are kept constant, a fluid is injected at the bottom end of the sample with a low back pressure (0.5 MPa) to minimize effective stress variations during injection. Both water and oil were used as the injected pore fluid in two experiments. As soon as the fluids start to flow into the samples, creep is taking place with a much higher strain rate for water injection compared to oil injection. A transition from secondary creep to tertiary creep is observed in the water injection test whereas in the oil injection test no significant creep acceleration is observed after one pore volume of oil was
The Theoretical Basis of Modeling the Economic Mechanism of Intellectual Security of Enterprise
Directory of Open Access Journals (Sweden)
Puyda Halia V.
2017-11-01
Full Text Available The article is aimed at studying the existing scientific approaches to the process of modeling the economic mechanism of intellectual security of enterprise. The author has allocated three approaches: process; based on IDFE0 methodology; system, considering the entities of economic activity as complex systems; and the so-called «information», based on the theory of economic mechanisms. The main features of each of the studied approaches have been disclosed, suggesting to consolidate them to obtain a synergistic effect in the construction of the economic mechanism of intellectual security of enterprises. The basic principles of creation of mechanisms of intellectual security of enterprise have been developed. Also, on the basis of the main postulate of the theory of economic mechanisms – reverse design, the cyclic passes process of designing the economic mechanism of intellectual security of enterprise has been illustrated. That, certainly, does not exhaust the theoretical problematics in the field of modeling the economic mechanisms of intellectual security of enterprise, raising new challenges for further researches.
10th International Symposium on Applications of Laser Techniques to Fluid Mechanics
Adrian, R J; Heitor, M V; Maeda, M; Tropea, C; Whitelaw, J H
2002-01-01
This volume includes revised and extended versions of selected papers presented at the Tenth International Symposium on Applications of Laser Techniques to Fluid Mechanics held at the Calouste Gulbenkian Foundation in Lisbon, during the period of July 10 to 13, 2000. The papers describe instrumentation developments for Velocity, Scalar and Multi-Phase Flows and results of measurements of Turbulent Flows, and Combustion and Engines. The papers demonstrate the continuing and healthy interest in the development of understanding of new methodologies and implementation in terms of new instrumentation. The prime objective of the Tenth Symposium was to provide a forum for the presentation of the most advanced research on laser techniques for flow measurements, and communicate significant results to fluid mechanics. The application of laser techniques to scientific and engineering fluid flow research was emphasized, but contributions to the theory and practice of laser methods were also considered where they facilita...
Anti-collapse mechanism of CBM fuzzy-ball drilling fluid
Directory of Open Access Journals (Sweden)
Lihui Zheng
2016-03-01
Full Text Available Although fuzzy-ball drilling fluid has been successfully applied in CBM well drilling, it is necessary to study its anti-collapse mechanism so that adjustable coalbed sealing effects, controllable sealing strength, rational sealing cost and controllable reservoir damage degree can be realized. In this paper, laboratory measurement was performed on the uniaxial compressive strength of the plungers of No. 3 coalbed in the Qinshui Basin and the inlet pressure of Ø38 mm coal plunger displacement. The strengths of coal plungers were tested and compared after 2% potassium chloride solution, low-solids polymer drilling fluid and fuzzy-ball drilling fluid were injected into the coal plungers respectively. It is shown that coal strength rises by 38.46% after the fuzzy-ball drilling fluid is injected (in three groups; and that no fuzzy-ball drilling fluid is lost at the displacement pressures of 20.73 and 21.46 MPa, nor 2% potassium chloride solution is leaked at such pressures of 24.79 and 25.64 MPa after the plunger was sealed by the fuzzy-ball drilling fluid. This indicates that the fuzzy-ball drilling fluid can increase the formation resistance to fluid. Indoor microscopic observation was conducted on the sealing process of the fuzzy-ball drilling fluid in sand packs with coal cuttings of three grain sizes (60–80, 80–100 and 100–120 mesh. It is shown that the leakage pathways of different sizes are sealed by the vesicles in the form of accumulation, stretch and blockage. And there are vesicles at the inlet ends of the flowing pathways in the shape of beaded blanket. The impact force of drilling tools on the sidewalls is absorbed by the vesicles due to their elasticity and tenacity, so the sidewall instability caused by drilling tools is relieved. It is concluded that the main anti-collapse mechanisms of the CBM fuzzy-ball drilling fluid are to raise the coal strength, increase the formation resistance to fluid, and buffer the impact of
Fluid Mechanics and Complex Variable Theory: Getting Past the 19th Century
Newton, Paul K.
2017-01-01
The subject of fluid mechanics is a rich, vibrant, and rapidly developing branch of applied mathematics. Historically, it has developed hand-in-hand with the elegant subject of complex variable theory. The Westmont College NSF-sponsored workshop on the revitalization of complex variable theory in the undergraduate curriculum focused partly on…
Introducing Innovative Approaches to Learning in Fluid Mechanics: A Case Study
Gynnild, Vidar; Myrhaug, Dag; Pettersen, Bjornar
2007-01-01
The purpose of the current article is to examine the impact of laboratory demonstrations and computer visualizations on learning in a third-year fluid mechanics course at Norwegian University of Science and Technology (NTNU). As a first step, on entering the course, students were exposed to a laboratory demonstration focusing on the nature of…
Mechanisms underlying the volume regulation of interstitial fluid by capillaries: a simulation study
Directory of Open Access Journals (Sweden)
Yukiko Himeno
2016-03-01
Conclusion: Mathematical analyses revealed that the system of the capillary is stable near the equilibrium point at steady state and normal physiological capillary pressure. The time course of the tissue-volume change was determined by two kinetic mechanisms: rapid fluid exchange and slow protein fluxes.
Houben, R.J.; Leclercq, P.A.; Cramers, C.A.M.G.
1991-01-01
Ionization mechanisms have been studied for supercritical fluid chromatography (SFC) with mass spectrometric (MS) detection. One of the problems associated with SFC-MS is the interference of mobile phase constituents in the ionization process, which complicates the interpretation of the resulting
Mechanical stretching of proteins-a theoretical survey of the Protein Data Bank
International Nuclear Information System (INIS)
Sulkowska, Joanna I; Cieplak, Marek
2007-01-01
The mechanical stretching of single proteins has been studied experimentally for about 50 proteins, yielding a variety of force patterns and peak forces. Here we perform a theoretical survey of proteins of known native structure and map out the landscape of possible dynamical behaviours under stretching at constant speed. We consider 7510 proteins comprising not more than 150 amino acids and 239 longer proteins. The model used is constructed based on the native geometry. It is solved by methods of molecular dynamics and validated by comparing the theoretical predictions to experimental results. We characterize the distribution of peak forces and investigate correlations with the system size and with the structure classification as characterized by the CATH scheme. Despite the presence of such correlations, proteins with the same CATH index may belong to different classes of dynamical behaviour. We identify proteins with the biggest forces and show that they belong to few topology classes. We determine which protein segments act as mechanical clamps and show that, in most cases, they correspond to long stretches of parallel β-strands, but other mechanisms are also possible. (topical review)
Schuman-Olivier, Zev; Britton, Willoughby B.; Fresco, David M.; Desbordes, Gaelle; Brewer, Judson A.; Fulwiler, Carl
2016-01-01
The purpose of this review is to provide (1) a synopsis on relations of mindfulness with cardiovascular disease (CVD) and major CVD risk factors, and (2) an initial consensus-based overview of mechanisms and theoretical framework by which mindfulness might influence CVD. Initial evidence, often of limited methodological quality, suggests possible impacts of mindfulness on CVD risk factors including physical activity, smoking, diet, obesity, blood pressure, and diabetes regulation. Plausible mechanisms include (1) improved attention control (e.g., ability to hold attention on experiences related to CVD risk, such as smoking, diet, physical activity, and medication adherence), (2) emotion regulation (e.g., improved stress response, self-efficacy, and skills to manage craving for cigarettes, palatable foods, and sedentary activities), and (3) self-awareness (e.g., self-referential processing and awareness of physical sensations due to CVD risk factors). Understanding mechanisms and theoretical framework should improve etiologic knowledge, providing customized mindfulness intervention targets that could enable greater mindfulness intervention efficacy. PMID:26482755
International Nuclear Information System (INIS)
Allen, R.R. Jr.
1987-01-01
The Lin constraint has been utilized by a number of authors who have sought to develop Eulerian variational principles in both fluid mechanics and electromagnetics (or plasmadynamics). This dissertation first reviews the work of earlier authors concerning the development of variational principles in both the Eulerian and Lagrangian nomenclatures. In the process, it is shown whether or not the Euler-Lagrange equations that result from the variational principles are equivalent to the generally accepted equations of motion. In particular, it is shown in the case of several Eulerian variational principles that imposition of the Lin constraint results in Euler-Lagrange equations equivalent to the generally accepted equations of motion, whereas neglect of the Lin constraint results in restrictive Euler-Lagrange equations. In an effort to improve the physical motivation behind introduction of the Lin constraint, a new variational constraint is developed based on teh concept of surface forces within a fluid. Additionally, it is shown that a quantity often referred to as the canonical momentum of a charged fluid is not always a constant of the motion of the fluid; and it is demonstrated that there does not exist an unconstrained Eulerian variational principle giving rise to the generally accepted equations of motion for both a perfect fluid and a cold, electromagnetic fluid
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-03-01
The general purpose of the program is the development of efficient algorithms, their implementation in codes of Computational Fluid Mechanics (CFD), and the experimental verification of these codes. Flows of both fundamental and applied nature will be investigated, including flows in industrial process equipment, about aerodynamics structures and ships, and flows over bed forms of importance for sediment transport. The experimental work will include the development of improved techniques, emphasizing optical methods. The objectives will be met through a coordinated experimental and theoretical/computational research program, organized in 7 specific projects: 1. CFD-methods and algorithms. 2. Spectral element simulation of ultrafiltration. 3. Turbulent swirling flows. 4. Near-wall models of turbulence. 5. Flow over bed forms. 6. Flow past ship hull. 7. Development of experimental techniques. (EG) 10 refs.
Directory of Open Access Journals (Sweden)
Saverio Maietta
2018-02-01
Full Text Available Experimental/theoretical analyses have already been performed on poly(ε-caprolactone (PCL loaded with organic–inorganic fillers (PCL/TiO2 and PCL/ZrO2 to find a correlation between the results from the small punch test and Young’s modulus of the materials. PCL loaded with Ti2 (PCL = 12, TiO2 = 88 wt % and Zr2 (PCL = 12, ZrO2 = 88 wt % hybrid fillers showed better performances than those obtained for the other particle composition. In this context, the aim of current research is to provide further insight into the mechanical properties of PCL loaded with sol–gel-synthesized organic–inorganic hybrid fillers for bone tissue engineering. For this reason, theoretical analyses were performed by the finite element method. The results from the small punch test and Young’s modulus of the materials were newly correlated. The obtained values of Young’s modulus (193 MPa for PCL, 378 MPa for PCL/Ti2 and 415 MPa for PCL/Zr2 were higher than those obtained from a previous theoretical modelling (144 MPa for PCL, 282 MPa for PCL/Ti2 and 310 MPa for PCL/Zr2. This correlation will be an important step for the evaluation of Young’s modulus, starting from the small punch test data.
Annual review of numerical fluid mechanics and heat transfer. Volume 1
International Nuclear Information System (INIS)
Chawla, T.C.
1987-01-01
Numerical techniqes for the analysis of problems in fluid mechanics and heat transfer are discussed, reviewing the results of recent investigations. Topics addressed include thermal radiation in particulate media with dependent and independent scattering, pressure-velocity coupling in incompressiblefluid flow, new explicit methods for diffusion problems, and one-dimensional reaction-diffusion equations in combustion theory. Consideration is given to buckling flows, multidimensional radiative-transfer analysis in participating media, freezing and melting problems, and complex heat-transfer processes in heat-generating horizontal fluid layers
Dependence of fracture mechanical and fluid flow properties on fracture roughness and sample size
International Nuclear Information System (INIS)
Tsang, Y.W.; Witherspoon, P.A.
1983-01-01
A parameter study has been carried out to investigate the interdependence of mechanical and fluid flow properties of fractures with fracture roughness and sample size. A rough fracture can be defined mathematically in terms of its aperture density distribution. Correlations were found between the shapes of the aperture density distribution function and the specific fractures of the stress-strain behavior and fluid flow characteristics. Well-matched fractures had peaked aperture distributions that resulted in very nonlinear stress-strain behavior. With an increasing degree of mismatching between the top and bottom of a fracture, the aperture density distribution broadened and the nonlinearity of the stress-strain behavior became less accentuated. The different aperture density distributions also gave rise to qualitatively different fluid flow behavior. Findings from this investigation make it possible to estimate the stress-strain and fluid flow behavior when the roughness characteristics of the fracture are known and, conversely, to estimate the fracture roughness from an examination of the hydraulic and mechanical data. Results from this study showed that both the mechanical and hydraulic properties of the fracture are controlled by the large-scale roughness of the joint surface. This suggests that when the stress-flow behavior of a fracture is being investigated, the size of the rock sample should be larger than the typical wave length of the roughness undulations
Fully coupled thermal-mechanical-fluid flow model for nonliner geologic systems
International Nuclear Information System (INIS)
Hart, R.D.
1981-01-01
A single model is presented which describes fully coupled thermal-mechanical-fluid flow behavior of highly nonlinear, dynamic or quasistatic, porous geologic systems. The mathematical formulation for the model utilizes the continuum theory of mixtures to describe the multiphase nature of the system, and incremental linear constitutive theory to describe the path dependency of nonlinear material behavior. The model, incorporated in an explicit finite difference numerical procedure, was implemented in two different computer codes. A special-purpose one-dimensional code, SNEAKY, was written for initial validation of the coupling mechanisms and testing of the coupled model logic. A general purpose commercially available code, STEALTH, developed for modeling dynamic nonlinear thermomechanical processes, was modified to include fluid flow behavior and the coupling constitutive model. The fully explicit approach in the coupled calculation facilitated the inclusion of the coupling mechanisms and complex constitutive behavior. Analytical solutions pertaining to consolidation theory for soils, thermoelasticity for solids, and hydrothermal convection theory provided verification of stress and fluid flow, stress and conductive heat transfer, and heat transfer and fluid flow couplings, respectively, in the coupled model. A limited validation of the adequacy of the coupling constitutive assumptions was also performed by comparison with the physical response from two laboratory tests. Finally, the full potential of the coupled model is illustrated for geotechnical applications in energy-resource related areas. Examples in the areas of nuclear waste isolation and cut-and-fill mining are cited
Analysis of theoretical security level of PDF Encryption mechanism based on X.509 certificates
Directory of Open Access Journals (Sweden)
Joanna Dmitruk
2017-12-01
Full Text Available PDF Encryption is a content security mechanism developed and used by Adobe in their products. In this paper, we have checked a theoretical security level of a variant that uses public key infrastructure and X.509 certificates. We have described a basis of this mechanism and we have performed a simple security analysis. Then, we have showed possible tweaks and security improvements. At the end, we have given some recommendations that can improve security of a content secured with PDF Encryption based on X.509 certificates. Keywords: DRM, cryptography, security level, PDF Encryption, Adobe, X.509
International Nuclear Information System (INIS)
Zhong, Haijian; Liu, Zhenghui; Xu, Gengzhao; Shi, Lin; Fan, Yingmin; Yang, Hui; Xu, Ke; Wang, Jianfeng; Ren, Guoqiang
2014-01-01
Graphene has been proposed as a material for semiconductor electronic and optoelectronic devices. Understanding the charge transport mechanisms of graphene/semiconductor Schottky barriers will be crucial for future applications. Here, we report a theoretical model to describe the transport mechanisms at the interface of graphene and semiconductors based on conventional semiconductor Schottky theory and a floating Fermi level of graphene. The contact barrier heights can be estimated through this model and be close to the values obtained from the experiments, which are lower than those of the metal/semiconductor contacts. A detailed analysis reveals that the barrier heights are as the function of the interface separations and dielectric constants, and are influenced by the interfacial states of semiconductors. Our calculations show how this behavior of lowering barrier heights arises from the Fermi level shift of graphene induced by the charge transfer owing to the unique linear electronic structure
The mechanism of reequilibration of solids in the presence of a fluid phase
International Nuclear Information System (INIS)
Putnis, Andrew; Putnis, Christine V.
2007-01-01
The preservation of morphology (pseudomorphism) and crystal structure during the transformation of one solid phase to another is regularly used as a criterion for a solid-state mechanism, even when there is a fluid phase present. However, a coupled dissolution-reprecipitation mechanism also preserves the morphology and transfers crystallographic information from parent to product by epitaxial nucleation. The generation of porosity in the product phase is a necessary condition for such a mechanism as it allows fluid to maintain contact with a reaction interface which moves through the parent phase from the original surface. We propose that interface-coupled dissolution-reprecipitation is a general mechanism for reequilibration of solids in the presence of a fluid phase. - Graphical abstract: A single crystal of KBr is transformed to a porous single crystal of KCl by immersion in saturated KCl solution. The image shows partial transformation of a crystal of KBr (core) to KCl (porous, milky rim) by an interface coupled dissolution-reprecipitation mechanism. The external dimensions and crystallographic orientation of the original crystal are preserved, while a reaction interface moves through the crystal
Directory of Open Access Journals (Sweden)
Farnaz Fekri
Full Text Available Drug delivery to tumors is limited by several factors, including drug permeability of the target cell plasma membrane. Ultrasound in combination with microbubbles (USMB is a promising strategy to overcome these limitations. USMB treatment elicits enhanced cellular uptake of materials such as drugs, in part as a result of sheer stress and formation of transient membrane pores. Pores formed upon USMB treatment are rapidly resealed, suggesting that other processes such as enhanced endocytosis may contribute to the enhanced material uptake by cells upon USMB treatment. How USMB regulates endocytic processes remains incompletely understood. Cells constitutively utilize several distinct mechanisms of endocytosis, including clathrin-mediated endocytosis (CME for the internalization of receptor-bound macromolecules such as Transferrin Receptor (TfR, and distinct mechanism(s that mediate the majority of fluid-phase endocytosis. Tracking the abundance of TfR on the cell surface and the internalization of its ligand transferrin revealed that USMB acutely enhances the rate of CME. Total internal reflection fluorescence microscopy experiments revealed that USMB treatment altered the assembly of clathrin-coated pits, the basic structural units of CME. In addition, the rate of fluid-phase endocytosis was enhanced, but with delayed onset upon USMB treatment relative to the enhancement of CME, suggesting that the two processes are distinctly regulated by USMB. Indeed, vacuolin-1 or desipramine treatment prevented the enhancement of CME but not of fluid phase endocytosis upon USMB, suggesting that lysosome exocytosis and acid sphingomyelinase, respectively, are required for the regulation of CME but not fluid phase endocytosis upon USMB treatment. These results indicate that USMB enhances both CME and fluid phase endocytosis through distinct signaling mechanisms, and suggest that strategies for potentiating the enhancement of endocytosis upon USMB treatment may
An experimental and theoretical study of reaction mechanisms between nitriles and hydroxylamine.
Vörös, Attila; Mucsi, Zoltán; Baán, Zoltán; Timári, Géza; Hermecz, István; Mizsey, Péter; Finta, Zoltán
2014-10-28
The industrially relevant reaction between nitriles and hydroxylamine yielding amidoximes was studied in different molecular solvents and in ionic liquids. In industry, this procedure is carried out on the ton scale in alcohol solutions and the above transformation produces a significant amount of unexpected amide by-product, depending on the nature of the nitrile, which can cause further analytical and purification issues. Although there were earlier attempts to propose mechanisms for this transformation, the real reaction pathway is still under discussion. A new detailed reaction mechanistic explanation, based on theoretical and experimental proof, is given to augment the former mechanisms, which allowed us to find a more efficient, side-product free procedure. Interpreting the theoretical results obtained, it was shown that the application of specific imidazolium, phosphonium and quaternary ammonium based ionic liquids could decrease simultaneously the reaction time while eliminating the amide side-product, leading to the targeted product selectively. This robust and economic procedure now affords a fast, selective amide free synthesis of amidoximes.
Theoretical models to predict the mechanical behavior of thick composite tubes
Directory of Open Access Journals (Sweden)
Volnei Tita
2012-02-01
Full Text Available This paper shows theoretical models (analytical formulations to predict the mechanical behavior of thick composite tubes and how some parameters can influence this behavior. Thus, firstly, it was developed the analytical formulations for a pressurized tube made of composite material with a single thick ply and only one lamination angle. For this case, the stress distribution and the displacement fields are investigated as function of different lamination angles and reinforcement volume fractions. The results obtained by the theoretical model are physic consistent and coherent with the literature information. After that, the previous formulations are extended in order to predict the mechanical behavior of a thick laminated tube. Both analytical formulations are implemented as a computational tool via Matlab code. The results obtained by the computational tool are compared to the finite element analyses, and the stress distribution is considered coherent. Moreover, the engineering computational tool is used to perform failure analysis, using different types of failure criteria, which identifies the damaged ply and the mode of failure.
Fluid and electrolyte homeostasis during spaceflight: Elucidation of mechanisms in a primate
Churchill, Susanne
1990-01-01
Although it is now well accepted that exposure to the hypogravic environment of space induces a shift of fluid from the lower extremities toward the upper body, the actual physiological responses to this central volume expansion have not been well characterized. Because it is likely that the fluid and electrolyte response to hypogravity plays a critical role in the development of Cardiovascular Deconditioning, elucidation of these mechanisms is of critical importance. The goal of flight experiment 223, scheduled to fly on SLS-2, is the definition of the basic renal, fluid and electrolyte response to spaceflight in four instrumented squirrel monkeys. The studies were those required to support the development of flight hardware and optimal inflight procedures, and to evaluate a ground-based model for weightlessness, lower body positive pressure (LBPP).
International Nuclear Information System (INIS)
Zhou Jianfeng; Gu Boqin
2007-01-01
The heat transfer model of the rotating ring and the stationary ring of mechanical seal was built. The method to calculate the frictional heat that transferred by the rings was given. the coupling analysis of the frictional heat of fluid film and thermal deformation of end faces was carried out by using FEA and BP ANN, and the relationship among the rotational speed ω, the fluid film thickness h i on the inner diameter of sealing face and the radial separation angle β of deformed end faces was obtained. Corresponding to a given ω, h i and β can be obtained by the equilibrium condition between the closing force and the bearing force of fluid film. The relationship between the leakage rate and the closing force was analyzed, and the fundamental of controlling the leakage rate by regulating the closing force was also discussed. (authors)
Theoretical and experimental insights into the ·OH-mediated mineralization mechanism of flutriafol
International Nuclear Information System (INIS)
Liu, Siqi; Zhou, Xiezhen; Han, Weiqing; Li, Jiansheng; Sun, Xiuyun; Shen, Jinyou; Wang, Lianjun
2017-01-01
Highlights: • A complete ·OH-mediated degradation pathway of flutriafol is proposed. • Computational approach is effective to reveal the favorable transformation process. • The electrochemical experiments well verify the theoretical results. - Abstract: Flutriafol is one of the widely used triazole fungicides in global pesticides market, and its degradation mechanisms are important to develop powerful technologies to remove it. Insight into the kinetics and mechanisms of ·OH-mediated mineralization of flutriafol have been obtained using quantum chemical calculation and electrochemical experiment methods. The complete ·OH-mediated degradation pathway of flutriafol was proposed by density functional theory (DFT) simulation and the potential energy surface was mapped out for possible reactions. On the basis of DFT calculations, the optimal ·OH-mediated mineralization mechanism of flutriafol was revealed, and a series of intermediates were observed accumulated in the degradation process, most significance among which were (2-fluorophenyl) (4-fluorophenyl)-Methanone, phenol, dihydroxybenzenes, benzoquinones, muconic acids, maleic acids, oxalic acids and formic acid. To give deeper insight into the ·OH-mediated reaction mechanism, the electrostatic potential (ESP) and average local ionization energy (ALIE) analysis were conducted for o-benzoquinone and p-benzoquinone. The proposed mechanism was further validated by electrochemical experiments at TiO_2-NTs/SnO_2-Sb/PbO_2 anode. The main intermediates were identified and quantified by experimental method, indicating that the proposed ·OH-mediated degradation mechanism derived from DFT calculations was feasible. These detailed findings could be instrumental for a comprehensive understanding of the ·OH-mediated mineralization mechanism of flutriafol and the similar contaminants.
[Improving myocardial mechanics parameters of severe burn rabbits with oral fluid resuscitation].
Ruan, Jing; Zhang, Bing-qian; Wang, Guang; Luo, Zhong-hua; Zheng, Qing-yi; Zheng, Jian-sheng; Huang, Yue-sheng; Xiao, Rong
2008-08-01
To investigate the protective effect of oral fluid resuscitation on cardiac function in severe burn rabbits. One hundred and fifty rabbits were randomly divided into normal control group (NC group, n = 6, without treatment), burn group (B group, n = 42, without fluid therapy), immediate oral fluid resuscitation group (C group, n = 42), delayed oral fluid resuscitation group (D group, n = 30) and delayed and rapid oral fluid resuscitation group (E group, n = 30). The rabbits in B, C, D, E groups were subjected to 40% TBSA full-thickness burn, then were treated with fluid therapy immediately after burn (C group), at 6 hour after burn (D, E groups). The myocardial mechanics parameters including mean arterial pressure (MAP), left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), LV +/- dp/dt max were observed at 2, 6, 8, 12, 24, 36 and 48 post burn hour (PBH). Urine output was also examined. The level of LVSP, LV +/- dp/dt max in B roup were significantly lower than those in NC group. The level of LVSP, LV +/- dp/dt max in the C and E group were singnificantly increased during 24 hour after burn. The level of LV + dp/dt max and LV-dp/dt max in C group peaked at 8 PBH (892 +/- 116 kPa/s) and at 6PBH (724 +/- 149 kPa/s) respectively. The levels of LV +/- dp/dt max, LVSP in D group at each time point were similar to B group (P > 0.05). Both the levels of LV +/- dp/dt max in E group peaked at 8 PBH. The level of LVEDP was no obvious difference between B and other groups at each time point (P > 0.05). The changes of MAP and urine output on 24 PBH in each group were similar to above indices. Effective oral fluid therapy in severe burn rabbits during 24 hours after burn can ameliorate myocardial mechanics parameters. The amount of fluid resuscitation can be estimated according to relevant formula for delayed fluid resuscitation in burn rabbits.
DEFF Research Database (Denmark)
Kiørboe, Thomas
2013-01-01
, and mechanisms for mobility of the parties involved. Here, I describe the mechanisms of sensing, escaping predators, and capturing prey in marine pelagic copepods. I demonstrate that feeding tradeoffs vary with feeding mode, and I describe simple fluid mechanical models that are used to quantify these tradeoffs......Many animals are predator and prey at the same time. This dual position represents a fundamental dilemma because gathering food often leads to increased exposure to predators. The optimization of the tradeoff between eating and not being eaten depends strongly on the sensing, feeding...
Fluid load support and contact mechanics of hemiarthroplasty in the natural hip joint.
Pawaskar, Sainath Shrikant; Ingham, Eileen; Fisher, John; Jin, Zhongmin
2011-01-01
The articular cartilage covering the ends of the bones of diarthrodial synovial joints is thought to have evolved so that the loads are transferred under different and complex conditions, with a very high degree of efficiency and without compromising the structural integrity of the tissue for the life of an individual. These loading conditions stem from different activities such as walking, and standing. The integrity of cartilage may however become compromised due to congenital disease, arthritis or trauma. Hemiarthroplasty is a potentially conservative treatment when only the femoral cartilage is affected as in case of femoral neck fractures. In hemiarthroplasty, a metallic femoral prosthesis is used to articulate against the natural acetabular cartilage. It has also been hypothesized that biphasic lubrication is the predominant mechanism protecting the cartilage through a very high fluid load support which lowers friction. This may be altered due to hemiarthroplasty and have a direct effect on the frictional shear stresses and potentially cartilage degradation and wear. This study modelled nine activities of daily living and investigated the contact mechanics of a hip joint with a hemiarthroplasty, focussing particularly on the role of the fluid phase. It was shown that in most of the activities studied the peak contact stresses and peak fluid pressures were in the superior dome or lateral roof of the acetabulum. Total fluid load support was very high (~90%) in most of the activities which would shield the solid phase from being subjected to very high contact stresses. This was dependent not only on the load magnitude but also the direction and hence on the location of the contact area with respect to the cartilage coverage. Lower fluid load support was found when the contact area was nearer the edges where the fluid drained easily. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.
Todd, Jocelyn N; Maak, Travis G; Ateshian, Gerard A; Maas, Steve A; Weiss, Jeffrey A
2018-03-01
Osteoarthritis of the hip can result from mechanical factors, which can be studied using finite element (FE) analysis. FE studies of the hip often assume there is no significant loss of fluid pressurization in the articular cartilage during simulated activities and approximate the material as incompressible and elastic. This study examined the conditions under which interstitial fluid load support remains sustained during physiological motions, as well as the role of the labrum in maintaining fluid load support and the effect of its presence on the solid phase of the surrounding cartilage. We found that dynamic motions of gait and squatting maintained consistent fluid load support between cycles, while static single-leg stance experienced slight fluid depressurization with significant reduction of solid phase stress and strain. Presence of the labrum did not significantly influence fluid load support within the articular cartilage, but prevented deformation at the cartilage edge, leading to lower stress and strain conditions in the cartilage. A morphologically accurate representation of collagen fibril orientation through the thickness of the articular cartilage was not necessary to predict fluid load support. However, comparison with simplified fibril reinforcement underscored the physiological importance. The results of this study demonstrate that an elastic incompressible material approximation is reasonable for modeling a limited number of cyclic motions of gait and squatting without significant loss of accuracy, but is not appropriate for static motions or numerous repeated motions. Additionally, effects seen from removal of the labrum motivate evaluation of labral reattachment strategies in the context of labral repair. Copyright © 2018 Elsevier Ltd. All rights reserved.
Wei, Tie; Ford, Julie
2015-01-01
This article provides information about the integration of innovative hands-on activities within a sophomore-level Fluid Mechanics course at New Mexico Tech. The course introduces students to the fundamentals of fluid mechanics with emphasis on teaching key equations and methods of analysis for solving real-world problems. Strategies and examples…
Wiputra, Hadi; Lai, Chang Quan; Lim, Guat Ling; Heng, Joel Jia Wei; Guo, Lan; Soomar, Sanah Merchant; Leo, Hwa Liang; Biwas, Arijit; Mattar, Citra Nurfarah Zaini; Yap, Choon Hwai
2016-12-01
There are 0.6-1.9% of US children who were born with congenital heart malformations. Clinical and animal studies suggest that abnormal blood flow forces might play a role in causing these malformation, highlighting the importance of understanding the fetal cardiovascular fluid mechanics. We performed computational fluid dynamics simulations of the right ventricles, based on four-dimensional ultrasound scans of three 20-wk-old normal human fetuses, to characterize their flow and energy dynamics. Peak intraventricular pressure gradients were found to be 0.2-0.9 mmHg during systole, and 0.1-0.2 mmHg during diastole. Diastolic wall shear stresses were found to be around 1 Pa, which could elevate to 2-4 Pa during systole in the outflow tract. Fetal right ventricles have complex flow patterns featuring two interacting diastolic vortex rings, formed during diastolic E wave and A wave. These rings persisted through the end of systole and elevated wall shear stresses in their proximity. They were observed to conserve ∼25.0% of peak diastolic kinetic energy to be carried over into the subsequent systole. However, this carried-over kinetic energy did not significantly alter the work done by the heart for ejection. Thus, while diastolic vortexes played a significant role in determining spatial patterns and magnitudes of diastolic wall shear stresses, they did not have significant influence on systolic ejection. Our results can serve as a baseline for future comparison with diseased hearts. Copyright © 2016 the American Physiological Society.
Han, X; Critser, J K
BACKGROUND: Rodent sperm cryopreservation is of critical importance for the maintenance of lines or strains of genetically engineered mice and rats. However, rodent sperm are extremely mechanically sensitive due to their unusual morphology, and are severely damaged using current methods of cryopreservation. Those methods result in poor post thaw motility (PTM) for mouse. To investigate the mechanism of mechanical damage introduced to rodent sperm during freezing, a micro-mechanical model was established to analyze the sperm radial and axial thermal stresses generated by microscale extracellular ice formation. PTM of mouse sperm cryopreserved in capillaries of different radii (100, 200, 344, 526, 775µm) was measured using a standard computer-assisted sperm analysis system. The model predicts that when one of the inner dimensions of the containers (the inner diameter of plastic straws or straw capillaries) is on the same order of magnitude of sperm length, axial stress is significantly increased. The experimental results showed that the value of PTM was decreased from 38 ± 8 % in the larger (775µm) capillaries to 0 ± 0 % in the smaller (100 µm) ones. Theoretical analysis based on the established model were experimentally validated and can be used to guide the design of novel devices to improve the efficiency of rodent sperm cryopreservation.
Marasulov, Akhmat; Saipov, Amangeldi; ?rymbayeva, Kulimkhan; Zhiyentayeva, Begaim; Demeuov, Akhan; Konakbaeva, Ulzhamal; Bekbolatova, Akbota
2016-01-01
The aim of the study is to examine the methodological-theoretical construction bases for development mechanism of an integrated model for a specialist's training and teacher's conceptual-theoretical activity. Using the methods of generalization of teaching experience, pedagogical modeling and forecasting, the authors determine the urgent problems…
Huang, Weifeng; Liao, Chuanjun; Liu, Xiangfeng; Suo, Shuangfu; Liu, Ying; Wang, Yuming
2014-09-01
Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants. More accurate models on the operating mechanism of the seals are needed to help improve their performance. The thermal fluid-solid interaction (TFSI) mechanism of the hydrostatic seal is investigated in this study. Numerical models of the flow field and seal assembly are developed. Based on the mechanism for the continuity condition of the physical quantities at the fluid-solid interface, an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method. Dynamic mesh technology is adopted to adapt to the changing boundary shape. Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure. The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data. Using the TFSI model, the behavior of the seal is presented, including mechanical and thermal deformation, and the temperature field. The influences of the rotating speed and differential pressure of the sealing device on the temperature field, which occur widely in the actual use of the seal, are studied. This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals, and the model is validated by full-sized experiments.
Thesken, John C.; Murthy, Pappu L. N.; Phoenix, S. L.; Greene, N.; Palko, Joseph L.; Eldridge, Jeffrey; Sutter, James; Saulsberry, R.; Beeson, H.
2009-01-01
A theoretical investigation of the factors controlling the stress rupture life of the National Aeronautics and Space Administration's (NASA) composite overwrapped pressure vessels (COPVs) continues. Kevlar (DuPont) fiber overwrapped tanks are of particular concern due to their long usage and the poorly understood stress rupture process in Kevlar filaments. Existing long term data show that the rupture process is a function of stress, temperature and time. However due to the presence of a load sharing liner, the manufacturing induced residual stresses and the complex mechanical response, the state of actual fiber stress in flight hardware and test articles is not clearly known. This paper is a companion to a previously reported experimental investigation and develops a theoretical framework necessary to design full-scale pathfinder experiments and accurately interpret the experimentally observed deformation and failure mechanisms leading up to static burst in COPVs. The fundamental mechanical response of COPVs is described using linear elasticity and thin shell theory and discussed in comparison to existing experimental observations. These comparisons reveal discrepancies between physical data and the current analytical results and suggest that the vessel s residual stress state and the spatial stress distribution as a function of pressure may be completely different from predictions based upon existing linear elastic analyses. The 3D elasticity of transversely isotropic spherical shells demonstrates that an overly compliant transverse stiffness relative to membrane stiffness can account for some of this by shifting a thin shell problem well into the realm of thick shell response. The use of calibration procedures are demonstrated as calibrated thin shell model results and finite element results are shown to be in good agreement with the experimental results. The successes reported here have lead to continuing work with full scale testing of larger NASA COPV
Jiang, Houshuo; Meneveau, Charles; Osborn, Thomas R.
2003-11-01
Copepods are small crustaceans living in oceans and fresh waters and play an important role in the marine and freshwater food webs. As they are the biggest biomass in the oceans some call them "the insects of the sea". Previous laboratory observations have shown that the fluid mechanical phenomena occurring at copepod body scale are crucial for the survival of copepods. One of the interesting phenomena is that many calanoid copepods display various behaviors to create the feeding currents for the purpose of capturing food particles. We have developed a fluid mechanical model to study the feeding currents. The model is a self-propelled body model in that the Navier-Stokes equations are properly coupled with the dynamic equations for the copepod's body. The model has been solved both analytically using the Stokes approximation with a spherical body shape and numerically using CFD with a realistic body shape.
International Nuclear Information System (INIS)
Dorning, J.
1981-01-01
The research and development over the past eight years on local Green's function methods for the high-accuracy, high-efficiency numerical solution of nuclear engineering problems is reviewed. The basic concepts and key ideas are presented by starting with an expository review of the original fully two-dimensional local Green's function methods developed for neutron diffusion and heat conduction, and continuing through the progressively more complicated and more efficient nodal Green's function methods for neutron diffusion, heat conduction and neutron transport to establish the background for the recent development of Green's function methods in computational fluid mechanics. Some of the impressive numerical results obtained via these classes of methods for nuclear engineering problems are briefly summarized. Finally, speculations are proffered on future directions in which the development of these types of methods in fluid mechanics and other areas might lead. (orig.) [de
Experimental and theoretical fracture mechanics applied to volcanic conduits and domes
Sammonds, P.; Matthews, C.; Kilburn, C.; Smith, R.; Tuffen, H.; Meredith, P.
2008-12-01
We present an integrated modelling and experimental approach to magma deformation and fracture, which we attempt to validate against field observations of seismicity. The importance of fracture processes in magma ascent dynamics and lava dome growth and collapse are apparent from the associated seismicity. Our laboratory experiments have shown that brittle fracture of magma can occur at high temperature and stress conditions prevalent in the shallow volcanic system. Here, we use a fracture mechanics approach to model seismicity preceding volcanic eruptions. Starting with the fracture mechanics concept of a crack in an elastic body, we model crack growth around the volcanic conduit through the processes of crack interactions, leading either to the propagation and linkage of cracks, or crack avoidance and the inhibition of crack propagation. The nature of that interaction is governed by the temperature and plasticity of the magma. We find that fracture mechanics rules can account for the style of seismicity preceding eruptions. We have derived the changes in seismic b-value predicted by the model and interpret these in terms of the style of fracturing, fluid flow and heat transport. We compare our model with results from our laboratory experiments where we have deformed lava at high temperatures under triaxial stresses. These experiments were conducted in dry and water saturated conditions at effective pressures up to 10 MPa, temperatures up to 1000°C and strain rates from 10-4 s-1 to 10-6 s-1. The behaviour of these magmas was largely brittle under these conditions. We monitored the acoustic emission emitted and calculate the change in micro-seismic b-value with deformation. These we find are in accord with volcano seismicity and our fracture mechanics model.
Energy Technology Data Exchange (ETDEWEB)
Staub, Isabelle; Fredriksson, Anders; Outters, Nils [Golder Associates AB, Uppsala (Sweden)
2002-05-01
In the purpose of studying the possibilities of a Deep Repository for spent fuel, the Swedish Nuclear and Fuel Management Company (SKB) is currently planning for Site Investigations. Data collected from these Site Investigations are interpreted and analysed to achieve the full Site Description, which is built up of models from all the disciplines that are considered of importance for the Site Description. One of these models is the Rock Mechanical Descriptive Model,which would be developed for any site in hard crystalline rock, and is a combination and evaluation of the characterisation of rock mass by means of empirical relationships and a theoretical approach based on numerical modelling. The present report describes the theoretical approach. The characterisation of the mechanical properties of the rock mass, viewed as a unit consisting of intact rock and fractures, is achieved by numerical simulations with following input parameters: initial stresses, fracture geometry, distribution of rock mechanical properties, such as deformation and strength parameters, for the intact rock and for the fractures. The numerical modelling was performed with the two-dimensional code UDEC, and the rock block models were generated from 2D trace sections extracted from the 3D Discrete Fracture Network (DFN) model. Assumptions and uncertainties related to the set-up of the model are considered. The numerical model was set-up to simulate a plain strain-loading test. Different boundary conditions were applied on the model for simulating stress conditions (I) in the undisturbed rock mass, and (II) at the proximity of a tunnel. In order to assess the reliability of the model sensitivity analyses have been conducted on some rock block models for defining the dependency of mechanical properties to in situ stresses, the influence of boundary conditions, rock material and joint constitutive models used to simulate the behaviour of intact rock and fractures, domain size and anisotropy. To
International Nuclear Information System (INIS)
Staub, Isabelle; Fredriksson, Anders; Outters, Nils
2002-05-01
In the purpose of studying the possibilities of a Deep Repository for spent fuel, the Swedish Nuclear and Fuel Management Company (SKB) is currently planning for Site Investigations. Data collected from these Site Investigations are interpreted and analysed to achieve the full Site Description, which is built up of models from all the disciplines that are considered of importance for the Site Description. One of these models is the Rock Mechanical Descriptive Model,which would be developed for any site in hard crystalline rock, and is a combination and evaluation of the characterisation of rock mass by means of empirical relationships and a theoretical approach based on numerical modelling. The present report describes the theoretical approach. The characterisation of the mechanical properties of the rock mass, viewed as a unit consisting of intact rock and fractures, is achieved by numerical simulations with following input parameters: initial stresses, fracture geometry, distribution of rock mechanical properties, such as deformation and strength parameters, for the intact rock and for the fractures. The numerical modelling was performed with the two-dimensional code UDEC, and the rock block models were generated from 2D trace sections extracted from the 3D Discrete Fracture Network (DFN) model. Assumptions and uncertainties related to the set-up of the model are considered. The numerical model was set-up to simulate a plain strain-loading test. Different boundary conditions were applied on the model for simulating stress conditions (I) in the undisturbed rock mass, and (II) at the proximity of a tunnel. In order to assess the reliability of the model sensitivity analyses have been conducted on some rock block models for defining the dependency of mechanical properties to in situ stresses, the influence of boundary conditions, rock material and joint constitutive models used to simulate the behaviour of intact rock and fractures, domain size and anisotropy. To
Bazile , Alban; Hachem , Elie; Larroya-Huguet , Juan-Carlos; Mesri , Youssef
2018-01-01
International audience; In this work, we present a new a posteriori error estimator based on the Variational Multiscale method for anisotropic adaptive fluid mechanics problems. The general idea is to combine the large scale error based on the solved part of the solution with the sub-mesh scale error based on the unresolved part of the solution. We compute the latter with two different methods: one using the stabilizing parameters and the other using bubble functions. We propose two different...
Travelling wave solutions for a surface wave equation in fluid mechanics
Directory of Open Access Journals (Sweden)
Tian Yi
2016-01-01
Full Text Available This paper considers a non-linear wave equation arising in fluid mechanics. The exact traveling wave solutions of this equation are given by using G'/G-expansion method. This process can be reduced to solve a system of determining equations, which is large and difficult. To reduce this process, we used Wu elimination method. Example shows that this method is effective.
Neurocognitive mechanisms of perception-action coordination: a review and theoretical integration.
Ridderinkhof, K Richard
2014-10-01
The present analysis aims at a theoretical integration of, and a systems-neuroscience perspective on, a variety of historical and contemporary views on perception-action coordination (PAC). We set out to determine the common principles or lawful linkages between sensory and motor systems that explain how perception is action-oriented and how action is perceptually guided. To this end, we analyze the key ingredients to such an integrated framework, examine the architecture of dual-system conjectures of PAC, and endeavor in an historical analysis of the key characteristics, mechanisms, and phenomena of PACs. This analysis will reveal that dual-systems views are in need of fundamental re-thinking, and its elements will be amalgamated with current views on action-oriented predictive processing into a novel integrative theoretical framework (IMPPACT: Impetus, Motivation, and Prediction in Perception-Action Coordination theory). From this framework and its neurocognitive architecture we derive a number of non-trivial predictions regarding conative, motive-driven PAC. We end by presenting a brief outlook on how IMPPACT might present novel insights into certain pathologies and into action expertise. Copyright © 2014 Elsevier Ltd. All rights reserved.
Mazzuca, James W.; Haut, Nathaniel K.
2018-06-01
It has been recently shown that in the presence of an applied voltage, hydrogen and deuterium nuclei can be separated from one another using graphene membranes as a nuclear sieve, resulting in a 10-fold enhancement in the concentration of the lighter isotope. While previous studies, both experimental and theoretical, have attributed this effect mostly to differences in vibrational zero point energy (ZPE) of the various isotopes near the membrane surface, we propose that multi-dimensional quantum mechanical tunneling of nuclei through the graphene membrane influences this proton permeation process in a fundamental way. We perform ring polymer molecular dynamics calculations in which we include both ZPE and tunneling effects of various hydrogen isotopes as they permeate the graphene membrane and compute rate constants across a range of temperatures near 300 K. While capturing the experimentally observed separation factor, our calculations indicate that the transverse motion of the various isotopes across the surface of the graphene membrane is an essential part of this sieving mechanism. An understanding of the multi-dimensional quantum mechanical nature of this process could serve to guide the design of other such isotopic enrichment processes for a variety of atomic and molecular species of interest.
Mazzuca, James W; Haut, Nathaniel K
2018-06-14
It has been recently shown that in the presence of an applied voltage, hydrogen and deuterium nuclei can be separated from one another using graphene membranes as a nuclear sieve, resulting in a 10-fold enhancement in the concentration of the lighter isotope. While previous studies, both experimental and theoretical, have attributed this effect mostly to differences in vibrational zero point energy (ZPE) of the various isotopes near the membrane surface, we propose that multi-dimensional quantum mechanical tunneling of nuclei through the graphene membrane influences this proton permeation process in a fundamental way. We perform ring polymer molecular dynamics calculations in which we include both ZPE and tunneling effects of various hydrogen isotopes as they permeate the graphene membrane and compute rate constants across a range of temperatures near 300 K. While capturing the experimentally observed separation factor, our calculations indicate that the transverse motion of the various isotopes across the surface of the graphene membrane is an essential part of this sieving mechanism. An understanding of the multi-dimensional quantum mechanical nature of this process could serve to guide the design of other such isotopic enrichment processes for a variety of atomic and molecular species of interest.
Theoretical modeling of mechanical homeostasis of a mammalian cell under gravity-directed vector.
Zhou, Lüwen; Zhang, Chen; Zhang, Fan; Lü, Shouqin; Sun, Shujin; Lü, Dongyuan; Long, Mian
2018-02-01
Translocation of dense nucleus along gravity vector initiates mechanical remodeling of a eukaryotic cell. In our previous experiments, we quantified the impact of gravity vector on cell remodeling by placing an MC3T3-E1 cell onto upward (U)-, downward (D)-, or edge-on (E)- orientated substrate. Our experimental data demonstrate that orientation dependence of nucleus longitudinal translocation is positively correlated with cytoskeletal (CSK) remodeling of their expressions and structures and also is associated with rearrangement of focal adhesion complex (FAC). However, the underlying mechanism how CSK network and FACs are reorganized in a mammalian cell remains unclear. In this paper, we developed a theoretical biomechanical model to integrate the mechanosensing of nucleus translocation with CSK remodeling and FAC reorganization induced by a gravity vector. The cell was simplified as a nucleated tensegrity structure in the model. The cell and CSK filaments were considered to be symmetrical. All elements of CSK filaments and cytomembrane that support the nucleus were simplified as springs. FACs were simplified as an adhesion cluster of parallel bonds with shared force. Our model proposed that gravity vector-directed translocation of the cell nucleus is mechanically balanced by CSK remodeling and FAC reorganization induced by a gravitational force. Under gravity, dense nucleus tends to translocate and exert additional compressive or stretching force on the cytoskeleton. Finally, changes of the tension force acting on talin by microfilament alter the size of FACs. Results from our model are in qualitative agreement with those from experiments.
Johan, Wiklund; Reinhardt, Kotze; Beat, Birkhofer; Stefano, Ricci; Valentino, Meacci; Mats, Stading; Rainer, Haldenwang; SP-Technical Research Institute of Sweden; FPRC, Cape Peninsula University of Technology; Sika Services AG; Information Engineering Department - University of Florence; Information Engineering Department - University of Florence; SP-Technical Research Institute of Sweden; FPRC, Cape Peninsula University of Technology
2015-01-01
In this work we have presented the world's first commercially available embedded in-line fluids characterization system, "Flow-Viz". It has been specifically designed for the non-invasive, in-line, continuous, real-time velocity profile and rheological assessment of opaque, non-Newtonian industrial fluids. The Flow-Viz system has been successfully installed in pilot plants of international companies and used also for academic research. The technology has been applied to a wide range of fluids...
Hangx, Suzanne; Spiers, Christopher
2014-05-01
Subsurface exploitation of the Earth's natural resources removes the natural system from its chemical and physical equilibrium. As such, groundwater extraction and hydrocarbon production from subsurface reservoirs frequently causes surface subsidence and induces (micro)seismicity. These effects are not only a problem in onshore (e.g. Groningen, the Netherlands) and offshore hydrocarbon fields (e.g. Ekofisk, Norway), but also in urban areas with extensive groundwater pumping (e.g. Venice, Italy). It is known that fluid extraction inevitably leads to (poro)elastic compaction of reservoirs, hence subsidence and occasional fault reactivation, and causes significant technical, economic and ecological impact. However, such effects often exceed what is expected from purely elastic reservoir behaviour and may continue long after exploitation has ceased. This is most likely due to time-dependent compaction, or 'creep deformation', of such reservoirs, driven by the reduction in pore fluid pressure compared with the rock overburden. Given the societal and ecological impact of surface subsidence, as well as the current interest in developing geothermal energy and unconventional gas resources in densely populated areas, there is much need for obtaining better quantitative understanding of creep in sediments to improve the predictability of the impact of geo-energy and groundwater production. The key problem in developing a reliable, quantitative description of the creep behaviour of sediments, such as sands and sandstones, is that the operative deformation mechanisms are poorly known and poorly quantified. While grain-scale brittle fracturing plus intergranular sliding play an important role in the early stages of compaction, these time-independent, brittle-frictional processes give way to compaction creep on longer time-scales. Thermally-activated mass transfer processes, like pressure solution, can cause creep via dissolution of material at stressed grain contacts, grain
International Nuclear Information System (INIS)
Pradhan, V.H.
2011-01-01
The fifty sixth congress of Indian Society of Theoretical and Applied Mechanics had been organized from December 19-21, 2011. Mathematics has been playing a key role in the development of society right from the use of geometry in land measurement to satellite launching. The appropriate mathematical tools are right answers to real world problems which has increase many fold because of the advancement in various branches of applied sciences, engineering and technologies with the advanced development of high speed super digital computers. The topics such as wireless communication, health systems, financing, budgeting, planning, management and decision making which plays important role in day to day lives have been covered in this meet. Papers relevant to INIS have been indexed separately
Theoretical evaluation of a mechanism of precipitate-enhanced cavity swelling during irradiation
International Nuclear Information System (INIS)
Mansur, L.K.
1981-03-01
It is often observed experimentally in complex alloys such as the austenitic stainless steels that the largest cavities produced during irradiation are attached to second phase precipitate particles. One hypothesis that such observations suggest is that the precipitate-matrix interface may assist in the collection of irradiation-produced point defects which are channelled to the attached cavities. A theoretical analysis is developed to evaluate this mechanism. It is found that the growth of cavities attached to precipitates is increased compared to the growth of cavities in the matrix. The relative growth rates of the two types of cavities are also affected by differences in bias and differences in sink strength. The relationships required to evaluate these effects are developed and the consequences of enhanced point defect collection are explored in some detail
A game-theoretical pricing mechanism for multiuser rate allocation for video over WiMAX
Chen, Chao-An; Lo, Chi-Wen; Lin, Chia-Wen; Chen, Yung-Chang
2010-07-01
In multiuser rate allocation in a wireless network, strategic users can bias the rate allocation by misrepresenting their bandwidth demands to a base station, leading to an unfair allocation. Game-theoretical approaches have been proposed to address the unfair allocation problems caused by the strategic users. However, existing approaches rely on a timeconsuming iterative negotiation process. Besides, they cannot completely prevent unfair allocations caused by inconsistent strategic behaviors. To address these problems, we propose a Search Based Pricing Mechanism to reduce the communication time and to capture a user's strategic behavior. Our simulation results show that the proposed method significantly reduce the communication time as well as converges stably to an optimal allocation.
Theoretical and numerical study of thermo-hydro-mechanical damage in unsaturated porous media
International Nuclear Information System (INIS)
Arson, Ch.
2009-09-01
Nuclear waste disposals are designed in multi-phase porous media. A new damage model, formulated in independent state variables (net stress, suction and thermal stress), is proposed for such geo-materials. The damage variable is a second-order tensor, which principal values grow with tensile strains. The stress/strain relations are derived from a postulated expression of the free energy. The degraded rigidities are computed by applying the Principle of Equivalent Elastic Energy for each stress state variable. Cracking effects are taken into account in transfers by introducing internal length parameters in the expressions of moisture conductivities. The damage model has been implemented in Θ-Stock Finite Element code. The mechanical model has been validated by comparing numerical results to experimental data and theoretical predictions. The qualitative evolutions given by the model in the parametric studies performed on realistic complex configurations show good trends. (author)
Iseki, Ryuta
2004-12-01
This article reviewed research on construction of situation models during reading. To position variety of research in overall process appropriately, an unitary framework was devised in terms of three theories for on-line processing: resonance process, event-indexing model, and constructionist theory. Resonance process was treated as a basic activation mechanism in the framework. Event-indexing model was regarded as a screening system which selected and encoded activated information in situation models along with situational dimensions. Constructionist theory was considered to have a supervisory role based on coherence and explanation. From a view of the unitary framework, some problems concerning each theory were examined and possible interpretations were given. Finally, it was pointed out that there were little theoretical arguments on associative processing at global level and encoding text- and inference-information into long-term memory.
Birmingham, E; Grogan, J A; Niebur, G L; McNamara, L M; McHugh, P E
2013-04-01
Bone marrow found within the porous structure of trabecular bone provides a specialized environment for numerous cell types, including mesenchymal stem cells (MSCs). Studies have sought to characterize the mechanical environment imposed on MSCs, however, a particular challenge is that marrow displays the characteristics of a fluid, while surrounded by bone that is subject to deformation, and previous experimental and computational studies have been unable to fully capture the resulting complex mechanical environment. The objective of this study was to develop a fluid structure interaction (FSI) model of trabecular bone and marrow to predict the mechanical environment of MSCs in vivo and to examine how this environment changes during osteoporosis. An idealized repeating unit was used to compare FSI techniques to a computational fluid dynamics only approach. These techniques were used to determine the effect of lower bone mass and different marrow viscosities, representative of osteoporosis, on the shear stress generated within bone marrow. Results report that shear stresses generated within bone marrow under physiological loading conditions are within the range known to stimulate a mechanobiological response in MSCs in vitro. Additionally, lower bone mass leads to an increase in the shear stress generated within the marrow, while a decrease in bone marrow viscosity reduces this generated shear stress.
Effective Hydro-Mechanical Properties of Fluid-Saturated Fracture Networks
Pollmann, N.; Vinci, C.; Renner, J.; Steeb, H.
2015-12-01
Consideration of hydro-mechanical processes is essential for the characterization of liquid-resources as well as for many engineering applications. Furthermore, the modeling of seismic waves in fractured porous media finds application not only in geophysical exploration but also reservoir management. Fractures exhibit high-aspect-ratio geometries, i.e. they constitute thin and long hydraulic conduits. Motivated by this peculiar geometry, the investigation of the hydro-mechanically coupled processes is performed by means of a hybrid-dimensional modeling approach. The effective material behavior of domains including complex fracture patterns in a porous rock is assessed by investigating the fluid pressure and the solid displacement of the skeleton saturated by compressible fluids. Classical balance equations are combined with a Poiseuille-type flow in the dimensionally reduced fracture. In the porous surrounding rock, the classical Biot-theory is applied. For simple geometries, our findings show that two main fluid-flow processes occur, leak-off from fractures to the surrounding rock and fracture flow within and between the connected fractures. The separation of critical frequencies of the two flow processes is not straightforward, in particular for systems containing a large number of fractures. Our aim is to model three dimensional hydro-mechanically coupled processes within complex fracture patterns and in particular determine the frequency-dependent attenuation characteristics. Furthermore, the effect of asperities of the fracture surfaces on the fracture stiffness and on the hydraulic conductivity will be added to the approach.
International Nuclear Information System (INIS)
Rebhan, E.
2005-01-01
The present second volume treats quantum mechanics, relativistic quantum mechanics, the foundations of quantum-field and elementary-particle theory as well as thermodynamics and statistics. Both volumes comprehend all fields, which are usually offered in a course about theoretical physics. In all treated fields a very careful introduction to the basic natural laws forms the starting point, whereby it is thoroughly analysed, which of them is based on empirics, which is logically deducible, and which role play basic definitions. Extendingly the matter extend of the corresponding courses starting from the relativistic quantum theory an introduction to the elementary particles is developed. All problems are very thoroughly and such extensively studied, that each step is singularly reproducible. On motivation and good understandability is cared much about. The mixing of mathematical difficulties with problems of physical nature often obstructive in the learning is so circumvented, that important mathematical methods are presented in own chapters (for instance Hilbert spaces, Lie groups). By means of many examples and problems (for a large part with solutions) the matter worked out is deepened and exercised. Developments, which are indeed important, but seem for the first approach abandonable, are pursued in excurses. This book starts from courses, which the author has held at the Heinrich-Heine university in Duesseldorf, and was in many repetitions fitted to the requirements of the students. It is conceived in such a way, that it is also after the study suited as dictionary or for the regeneration
Theoretical study of effect of working fluid on the performance of 77–100 K adsorption cryocooler
International Nuclear Information System (INIS)
Luo, B.J.; Wang, Z.L.; Yan, T.; Hong, G.T.; Li, Y.L.; Liang, J.T.
2015-01-01
Highlights: • Investigate the effects of nitrogen, argon and oxygen on the performance of adsorption cryocooler in the range 77–100 K. • A model of adsorption compressor with a two-stage adsorption compressor is constructed and optimized with genetic algorithm. • Working fluid has larger effects on the adsorption compressor than on the cold stage. • The best selection of working fluid depends on the operating parameters. - Abstract: The aim of this study is to investigate the effects of working fluid (nitrogen, argon and oxygen) on the performance of adsorption cryocooler in the range 77–100 K. A thermodynamic model of adsorption cryocooler with two-stage compressor has been constructed. The model is based on quasi-static conditions without considering the temperature profiles and pressure drops across the compressor. It is then analyzed with an optimization toolbox to determine the optimum operating conditions to obtain the optimum performance of adsorption cryocooler. The Coefficient of Performance (COP) for each working fluid in the range 77–100 K is obtained and compared. It is found that working fluid has larger effects on adsorption compressor than on cold stage, and the optimum selection of working fluid depends on the operating parameters
Ghosal, Sandip
2004-01-01
Electroosmotic flow (EOF) usually accompanies electrophoretic migration of charged species in capillary electrophoresis unless special precautions are taken to suppress it. The presence of the EOF provides certain advantages in separations. It is an alternative to mechanical pumps, which are inefficient and difficult to build at small scales, for transporting reagents and analytes on microfluidic chips. The downside is that any imperfection that distorts the EOF profile reduces the separation efficiency. In this paper, the basic facts about EOF are reviewed from the perspective of fluid mechanics and its effect on separations in free solution capillary zone electrophoresis is discussed in the light of recent advances.
The effect of the pore-fluid factor on strength and failure mechanism of Wilkeson sandstone
Kätker, A. K.; Rempe, M.; Renner, J.
2016-12-01
The effective stress law, σn,eff = σn - αpf, is a central tool in analysing phenomena related to hydromechanical coupling, such as fluid-induced seismicity or aftershock activity. The effective-stress coefficient α assumes different values for specific physical properties and may deviate from 1. The limited number of studies suggest that brittle compressive strength obeys an effective-stress law when effective drainage is achieved. Yet, open questions remain regarding, e.g., the role of the loading path. We performed suites of triaxial compression tests on samples of Wilkeson sandstone at a range of pore-fluid pressures but identical effective confining pressure (60, 100, and 120 MPa) maintaining the pore-fluid factor λ = pf / pc constant (0.05, 0.2, 0.4, 0.55) during the isostatic loading stage to ensure uniform loading paths. Samples were shortened with a strain rate of 4×10-7 s-1 yielding drained conditions. All tests were terminated at a total axial strain of 4.5% for comparability of microstructures. The tests also included continuous permeability determination and ultrasonic p-wave-velocity measurements to monitor microstructural evolution. Results from experiments conducted at peff = 100 MPa show that dry samples exhibit a higher peak strength and brittle failure while water-saturated samples tend to deform at lower stress by cataclastic flow indicating physico-chemical weakening. Regardless of pore-fluid factor, the saturated experiments exhibit similar peak and residual strength. Differences in failure mechanism (degree of macroscopic localization) and volumetric strain evolution are however noticed, albeit without systematic relation to pore-fluid factor. Microstructure analyses by optical and scanning electron microscopy revealed an evolution from localized shear zones in dry experiments and experiments with a low pore-fluid factor to rather distributed cataclastic flow for experiments with high pore fluid factors. Yet, mechanical and structural
Gas-phase thermolysis reaction of formaldehyde diperoxide. Kinetic study and theoretical mechanisms
Energy Technology Data Exchange (ETDEWEB)
Jorge, Nelly Lidia [Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Av. Las Palmeras 4, 18100 Armilla, Granada (Spain); Area de Quimica Fisica Facultad de Ciencias Exactas y Naturales y Agrimensura, UNNE, Avda. Libertad 5460, 3400 Corrientes (Argentina); Romero, Jorge Marcelo [Area de Quimica Fisica Facultad de Ciencias Exactas y Naturales y Agrimensura, UNNE, Avda. Libertad 5460, 3400 Corrientes (Argentina); Grand, Andre [INAC, SCIB, Laboratoire ' Lesions des Acides Nucleiques' , UMR CEA-UJF E3, CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble cedex 9 (France); Hernandez-Laguna, Alfonso, E-mail: ahlaguna@ugr.es [Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Av. Las Palmeras 4, 18100 Armilla, Granada (Spain)
2012-01-17
Highlights: Black-Right-Pointing-Pointer Kinetic and mechanism of the gas-phase thermolysis of tetroxane were determined. Black-Right-Pointing-Pointer Gas chromatography and computational potential energy surfaces were performed. Black-Right-Pointing-Pointer A mechanism in steps looked like the most probable mechanism. Black-Right-Pointing-Pointer A spin-orbit coupling appeared at the singlet and triple diradical open structures. Black-Right-Pointing-Pointer A non-adiabatic crossing from the singlet to the triplet state occurred. - Abstract: Gas-phase thermolysis reaction of formaldehyde diperoxide (1,2,4,5-tetroxane) was performed in an injection chamber of a gas chromatograph at a range of 463-503 K. The average Arrhenius activation energy and pre-exponential factor were 29.3 {+-} 0.8 kcal/mol and 5.2 Multiplication-Sign 10{sup 13} s{sup -1}, respectively. Critical points and reaction paths of the ground singlet and first triplet potential energy surfaces (PES) were calculated, using DFT method at BHANDHLYP/6-311+G{sup Asterisk-Operator Asterisk-Operator} level of the theory. Also, G3 calculations were performed on the reactant and products. Reaction by the ground-singlet and first-triplet states turned out to be endothermic and exothermic, respectively. The mechanism in three steps seemed to be the most probable one. An electronically non-adiabatic process appeared, in which a crossing, at an open diradical structure, from the singlet to the triplet state PES occurred, due to a spin-orbit coupling, yielding an exothermic reaction. Theoretical kinetic constant coming from the non- adiabatic transition from the singlet to the triplet state agrees with the experimental values.
Gas-phase thermolysis reaction of formaldehyde diperoxide. Kinetic study and theoretical mechanisms
International Nuclear Information System (INIS)
Jorge, Nelly Lidia; Romero, Jorge Marcelo; Grand, André; Hernández-Laguna, Alfonso
2012-01-01
Highlights: ► Kinetic and mechanism of the gas-phase thermolysis of tetroxane were determined. ► Gas chromatography and computational potential energy surfaces were performed. ► A mechanism in steps looked like the most probable mechanism. ► A spin–orbit coupling appeared at the singlet and triple diradical open structures. ► A non-adiabatic crossing from the singlet to the triplet state occurred. - Abstract: Gas-phase thermolysis reaction of formaldehyde diperoxide (1,2,4,5-tetroxane) was performed in an injection chamber of a gas chromatograph at a range of 463–503 K. The average Arrhenius activation energy and pre-exponential factor were 29.3 ± 0.8 kcal/mol and 5.2 × 10 13 s −1 , respectively. Critical points and reaction paths of the ground singlet and first triplet potential energy surfaces (PES) were calculated, using DFT method at BHANDHLYP/6-311+G ∗∗ level of the theory. Also, G3 calculations were performed on the reactant and products. Reaction by the ground-singlet and first-triplet states turned out to be endothermic and exothermic, respectively. The mechanism in three steps seemed to be the most probable one. An electronically non-adiabatic process appeared, in which a crossing, at an open diradical structure, from the singlet to the triplet state PES occurred, due to a spin–orbit coupling, yielding an exothermic reaction. Theoretical kinetic constant coming from the non- adiabatic transition from the singlet to the triplet state agrees with the experimental values.
Mechanical properties and theoretical modeling of self-centering shape memory alloy pseudo-rubber
International Nuclear Information System (INIS)
Li, Suchao; Mao, Chenxi; Li, Hui; Zhao, Yagebai
2011-01-01
Pounding between adjacent components and structures has become an important cause of structural damage or even collapse under large excitations such as earthquakes and ship collisions. Shock absorber devices (SAD) are often used to connect the separation gap to reduce the pounding force. However, some shock absorber devices may have residual deformation and need to be repaired or replaced after strong impact. A novel energy absorbing material with residual deformation self-recovery ability, martensitic nickel titanium (NiTi) shape memory alloy pseudo-rubber (SMAPR), is fabricated using three methods in this study. The mechanical properties of SMAPR at room temperature and deformation self-recovery ability of SMAPR material are investigated. After that, the deformation recovery ability of SMAPR specimens even with residual deformation is further tested through heating the specimens in a thermo-control stove. The subsequent mechanical properties after deformation recovery are further investigated to investigate whether degradation in mechanical properties occurs for all kinds of specimens. The experimental results indicate that SMAPR is a kind of material with good potential to develop novel shock absorber devices for engineering applications. Furthermore, theoretical modeling of SMAPR is conducted. Micro-variable-pitch springs in parallel and series, in parallel with a friction component, are employed to model the mechanical behavior of SMAPR. The hysteretic rules are presented and the parameters of this model are derived and identified. Finally, based on micro-variable-pitch springs (MVPS) in parallel and series, a parametric analysis is carried out and the effects of nominal densities, diameters of metal wires, diameters of micro-springs and generalized coefficients of friction of SMAPR are analyzed and discussed
Brims, Fraser J H; Davies, Michael G; Elia, Andy; Griffiths, Mark J D
2015-01-01
Pleural effusions occur commonly after cardiac surgery and the effects of drainage on gas exchange in this population are not well established. We examined pulmonary function indices following drainage of pleural effusions in cardiac surgery patients. We performed a retrospective study examining the effects of pleural fluid drainage on the lung function indices of patients recovering from cardiac surgery requiring mechanical ventilation for more than 7 days. We specifically analysed patients who had pleural fluid removed via an intercostal tube (ICT: drain group) compared with those of a control group (no effusion, no ICT). In the drain group, 52 ICTs were sited in 45 patients. The mean (SD) volume of fluid drained was 1180 (634) mL. Indices of oxygenation were significantly worse in the drain group compared with controls prior to drainage. The arterial oxygen tension (PaO2)/fractional inspired oxygen (FiO2) (P/F) ratio improved on day 1 after ICT placement (mean (SD), day 0: 31.01 (8.92) vs 37.18 (10.7); pdrain group patients were more likely to have an improved mode of ventilation on day 1 compared with controls (p=0.028). Pleural effusion after cardiac surgery may impair oxygenation. Drainage of pleural fluid is associated with a rapid and sustained improvement in oxygenation.
Leak Mitigation in Mechanically Pumped Fluid Loops for Long Duration Space Missions
Miller, Jennifer R.; Birur, Gajanana; Bame, David; Mastropietro, A. J.; Bhandari, Pradeep; Lee, Darlene; Karlmann, Paul; Liu, Yuanming
2013-01-01
Mechanically pumped fluid loops (MPFLs) are increasingly considered for spacecraft thermal control. A concern for long duration space missions is the leak of fluid leading to performance degradation or potential loop failure. An understanding of leak rate through analysis, as well as destructive and non-destructive testing, provides a verifiable means to quantify leak rates. The system can be appropriately designed to maintain safe operating pressures and temperatures throughout the mission. Two MPFLs on the Mars Science Laboratory Spacecraft, launched November 26, 2011, maintain the temperature of sensitive electronics and science instruments within a -40 deg C to 50 deg C range during launch, cruise, and Mars surface operations. With over 100 meters of complex tubing, fittings, joints, flex lines, and pumps, the system must maintain a minimum pressure through all phases of the mission to provide appropriate performance. This paper describes the process of design, qualification, test, verification, and validation of the components and assemblies employed to minimize risks associated with excessive fluid leaks from pumped fluid loop systems.
The mechanism of fluid secretion in the rabbit pancreas studied by means of various inhibitors.
Kuijpers, G A; Van Nooy, I G; De Pont, J J; Bonting, S L
1984-12-05
In order to increase our understanding of the mechanism of pancreatic fluid secretion we have studied the effects of various transport inhibitors on this process in the isolated rabbit pancreas. In this preparation, a high rate of unstimulated fluid secretion occurs, which probably originates from the ductular cells. Inhibitory are ouabain, furosemide, bumetanide, piretanide, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) and acetazolamide, with their half-inhibitory concentrations: 2 X 10(-6) M (ouabain), 1.3 X 10(-3) M (furosemide), 2.2 X 10(-3) M (bumetanide and piretanide) and 1.4 X 10(-4) M (SITS). With acetazolamide a maximal inhibition of only 20% is found at 10(-3) M. Amiloride (10(-3) M) has no effect on pancreatic fluid secretion. The inhibitory effects on HCO-3 output are always larger and those on Cl- output lower than those on fluid secretion. The results suggest that the ouabain-sensitive (Na+ + K+)-ATPase system provides the energy for a Na+-gradient-driven Cl--HCO-3-exchange transport system, sensitive to the loop diuretics furosemide, bumetanide and piretanide and to SITS. This system would drive the transcellular transport of HCO-3 and secondarily that of cations, Cl- and water.
Brims, Fraser J H; Davies, Michael G; Elia, Andy; Griffiths, Mark J D
2015-01-01
Background Pleural effusions occur commonly after cardiac surgery and the effects of drainage on gas exchange in this population are not well established. We examined pulmonary function indices following drainage of pleural effusions in cardiac surgery patients. Methods We performed a retrospective study examining the effects of pleural fluid drainage on the lung function indices of patients recovering from cardiac surgery requiring mechanical ventilation for more than 7 days. We specifically analysed patients who had pleural fluid removed via an intercostal tube (ICT: drain group) compared with those of a control group (no effusion, no ICT). Results In the drain group, 52 ICTs were sited in 45 patients. The mean (SD) volume of fluid drained was 1180 (634) mL. Indices of oxygenation were significantly worse in the drain group compared with controls prior to drainage. The arterial oxygen tension (PaO2)/fractional inspired oxygen (FiO2) (P/F) ratio improved on day 1 after ICT placement (mean (SD), day 0: 31.01 (8.92) vs 37.18 (10.7); pdrain group patients were more likely to have an improved mode of ventilation on day 1 compared with controls (p=0.028). Conclusions Pleural effusion after cardiac surgery may impair oxygenation. Drainage of pleural fluid is associated with a rapid and sustained improvement in oxygenation. PMID:26339492
Interstitial Fluid Flow: The Mechanical Environment of Cells and Foundation of Meridians
Directory of Open Access Journals (Sweden)
Wei Yao
2012-01-01
Full Text Available Using information from the deep dissection, microobservation, and measurement of acupoints in the upper and lower limbs of the human body, we developed a three-dimensional porous medium model to simulate the flow field using FLUENT software and to study the shear stress on the surface of interstitial cells (mast cells caused by interstitial fluid flow. The numerical simulation results show the following: (i the parallel nature of capillaries will lead to directional interstitial fluid flow, which may explain the long interstitial tissue channels or meridians observed in some experiments; (ii when the distribution of capillaries is staggered, increases in the velocity alternate, and the velocity tends to be uniform, which is beneficial for substance exchange; (iii interstitial fluid flow induces a shear stress, with magnitude of several Pa, on interstitial cell membranes, which will activate cells and lead to a biological response; (iv capillary and interstitial parameters, such as capillary density, blood pressure, capillary permeability, interstitial pressure, and interstitial porosity, affect the shear stress on cell surfaces. The numerical simulation results suggest that in vivo interstitial fluid flow constitutes the mechanical environment of cells and plays a key role in guiding cell activities, which may explain the meridian phenomena and the acupuncture effects observed in experiments.
Theoretical study of elastic, mechanical and thermodynamic properties of MgRh intermetallic compound
Directory of Open Access Journals (Sweden)
S. Boucetta
2014-03-01
Full Text Available In the last years, Magnesium alloys are known to be of great technological importance and high scientific interest. In this work, density functional theory plane-wave pseudo potential method, with local density approximation (LDA and generalized gradient approximation (GGA are used to perform first-principles quantum mechanics calculations in order to investigate the structural, elastic and mechanical properties of the intermetallic compound MgRh with a CsCl-type structure. Comparison of the calculated equilibrium lattice constant and experimental data shows good agreement. The elastic constants were determined from a linear fit of the calculated stress–strain function according to Hooke's law. From the elastic constants, the bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio σ, anisotropy factor A and the ratio B/G for MgRh compound are obtained. The sound velocities and Debye temperature are also predicted from elastic constants. Finally, the linear response method has been used to calculate the thermodynamic properties. The temperature dependence of the enthalpy H, free energy F, entropy S, and heat capacity at constant volume Cv of MgRh crystal in a quasi-harmonic approximation have been obtained from phonon density of states and discussed for the first report. This is the first quantitative theoretical prediction of these properties.
Ma, Zhenyang; Liu, Xuhong; Yu, Xinhai; Shi, Chunlei; Wang, Dayun
2017-08-08
The structural, mechanical, elastic anisotropic, and electronic properties of Pbca -XN (X = C, Si, Ge) are investigated in this work using the Perdew-Burke-Ernzerhof (PBE) functional, Perdew-Burke-Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA-PZ) functional in the framework of density functional theory. The achieved results for the lattice parameters and band gap of Pbca -CN with the PBE functional in this research are in good accordance with other theoretical results. The band structures of Pbca -XN (X = C, Si, Ge) show that Pbca -SiN and Pbca -GeN are both direct band gap semiconductor materials with a band gap of 3.39 eV and 2.22 eV, respectively. Pbca -XN (X = C, Si, Ge) exhibits varying degrees of mechanical anisotropic properties with respect to the Poisson's ratio, bulk modulus, shear modulus, Young's modulus, and universal anisotropic index. The (001) plane and (010) plane of Pbca -CN/SiN/GeN both exhibit greater elastic anisotropy in the bulk modulus and Young's modulus than the (100) plane.
Zhao, Jinfeng; Dong, Hao; Zheng, Yujun
2018-02-08
As the most important component of deep red pigments, alkannin is investigated theoretically in detail based on time-dependent density functional theory (TDDFT) method. Exploring the dual intramolecular hydrogen bonds (O1-H2···O3 and O4-H5···O6) of alkannin, we confirm the O1-H2···O3 may play a more important role in the first excited state than the O4-H5···O6 one. Infrared (IR) vibrational analyses and subsequent charge redistribution also support this viewpoint. Via constructing the S 1 -state potential energy surface (PES) and searching transition state (TS) structures, we illuminate the excited state double proton transfer (ESDPT) mechanism of alkannin is the stepwise process that can be first launched by the O1-H2···O3 hydrogen bond wire in gas state, acetonitrile (CH 3 CN) and cyclohexane (CYH) solvents. We present a novel mechanism that polar aprotic solvents can contribute to the first-step proton transfer (PT) process in the S 1 state, and nonpolar solvents play important roles in lowering the potential energy barrier of the second-step PT reaction.
Theoretical studies on the inactivation mechanism of γ-aminobutyric acid aminotransferase.
Durak, A T; Gökcan, H; Konuklar, F A S
2011-07-21
The inactivation mechanism of γ-aminobutyric acid aminotransferase (GABA-AT) in the presence of γ-vinyl-aminobutyric acid, an anti-epilepsy drug, has been studied by means of theoretical calculations. Density functional theory methods have been applied to compare the three experimentally proposed inactivation mechanisms (Silverman et al., J. Biol. Chem., 2004, 279, 363). All the calculations were performed at the B3LYP/6-31+G(d,p) level of theory. Single point solvent calculations were carried out in water, by means of an integral equation formalism-polarizable continuum model (IEFPCM) at the B3LYP/6-31+G(d,p) level of theory. The present calculations provide an insight into the mechanistic preferences of the inactivation reaction of GABA-AT. The results also allow us to elucidate the key factors behind the mechanistic preferences. The computations also confirm the importance of explicit water molecules around the reacting center in the proton transfer steps.
Mechanical, Anisotropic, and Electronic Properties of XN (X = C, Si, Ge): Theoretical Investigations
Ma, Zhenyang; Liu, Xuhong; Yu, Xinhai; Shi, Chunlei; Wang, Dayun
2017-01-01
The structural, mechanical, elastic anisotropic, and electronic properties of Pbca-XN (X = C, Si, Ge) are investigated in this work using the Perdew–Burke–Ernzerhof (PBE) functional, Perdew–Burke–Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA–PZ) functional in the framework of density functional theory. The achieved results for the lattice parameters and band gap of Pbca-CN with the PBE functional in this research are in good accordance with other theoretical results. The band structures of Pbca-XN (X = C, Si, Ge) show that Pbca-SiN and Pbca-GeN are both direct band gap semiconductor materials with a band gap of 3.39 eV and 2.22 eV, respectively. Pbca-XN (X = C, Si, Ge) exhibits varying degrees of mechanical anisotropic properties with respect to the Poisson’s ratio, bulk modulus, shear modulus, Young’s modulus, and universal anisotropic index. The (001) plane and (010) plane of Pbca-CN/SiN/GeN both exhibit greater elastic anisotropy in the bulk modulus and Young’s modulus than the (100) plane. PMID:28786960
Hartlieb, Philipp; Bock, Stefan
2018-03-01
This study presents a theoretical analysis of the influence of the rock mass rating on the cutting performance of roadheaders. Existing performance prediction models are assessed for their suitability for forecasting the influence of pre-damaging the rock mass with alternative methods like lasers or microwaves, prior to the mechanical excavation process. Finally, the RMCR model was chosen because it is the only reported model incorporating a range of rock mass properties into its calculations. The results show that even very tough rocks could be mechanically excavated if the occurrence, orientation and condition of joints are favourable for the cutting process. The calculated improvements in the cutting rate (m3/h) are up to 350% for the most favourable cases. In case of microwave irradiation of hard rocks with an UCS of 200 MPa, a reasonable improvement in the performance by 120% can be achieved with as little as an extra 0.7 kWh/m3 (= 1% more energy) compared to cutting only.
Yoshihara, Lena; Roth, Christian J; Wall, Wolfgang A
2017-04-01
In this article, a novel approach is presented for combining standard fluid-structure interaction with additional volumetric constraints to model fluid flow into and from homogenised solid domains. The proposed algorithm is particularly interesting for investigations in the field of respiratory mechanics as it enables the mutual coupling of airflow in the conducting part and local tissue deformation in the respiratory part of the lung by means of a volume constraint. In combination with a classical monolithic fluid-structure interaction approach, a comprehensive model of the human lung can be established that will be useful to gain new insights into respiratory mechanics in health and disease. To illustrate the validity and versatility of the novel approach, three numerical examples including a patient-specific lung model are presented. The proposed algorithm proves its capability of computing clinically relevant airflow distribution and tissue strain data at a level of detail that is not yet achievable, neither with current imaging techniques nor with existing computational models. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Wang, Jie; Zhao, Shougen; Wu, Dafang; Jing, Xingjian
2016-01-01
Micro-vibration isolation is a hot topic in spacecraft vibration control, and fluid based vibration isolators alternatively provide a good and reliable solution to this challenging issue. In this paper, a novel fluid based micro-vibration isolator (FBMVI) is investigated. According to its inherent working principle and deformation pattern, the generation mechanisms of the damping and stiffness characteristics are derived, which are nonlinear functions of the environmental temperature. Then a lumped parameter model which is expressed by the physical design parameters (PDPs) is constructed, and the corresponding performance objective indices (POIs) are also obtained by applying the equivalence of mechanical impedance. Based on the finite element analysis of the internal damping component, a single variable method is further adopted to carry out the parametric study, and the influences of each PDP on the POIs are analyzed in details. Finally, experiments are conducted to identify the variation of fluid bulk modulus with the outside environmental temperature, and to validate the performance of the isolator under different temperature environments. The tested results show great consistence compared with the predicted tendencies of the parametric study. The results of this study can provide a very useful insight into and/or an important guidance for the design and application of this type of FBMVIs in engineering practice.
Tian, Shan; Zhu, Fengping; Hu, Ruiping; Tian, Song; Chen, Xingxing; Lou, Dan; Cao, Bing; Chen, Qiulei; Li, Bai; Li, Fang; Bai, Yulong; Wu, Yi; Zhu, Yulian
2018-01-01
Exercise preconditioning is a simple and effective way to prevent ischemia. This paper further provided the mechanism in hemodynamic aspects at the cellular level. To study the anti-apoptotic effects of fluid mechanics preconditioning, Cultured rats brain microvascular endothelial cells were given fluid intervention in a parallel plate flow chamber before oxygen glucose deprivation. It showed that fluid mechanics preconditioning could inhibit the apoptosis of endothelial cells, and this process might be mediated by the shear stress activation of Tie-2 on cells membrane surface and Bcl-2 on the mitochondria surface. Copyright © 2017 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Irina A Buhimschi
2008-04-01
Full Text Available Though recent advancement in proteomics has provided a novel perspective on several distinct pathogenetic mechanisms leading to preterm birth (inflammation, bleeding, the etiology of most preterm births still remains elusive. We conducted a multidimensional proteomic analysis of the amniotic fluid to identify pathways related to preterm birth in the absence of inflammation or bleeding.A proteomic fingerprint was generated from fresh amniotic fluid using surface-enhanced laser desorbtion ionization time of flight (SELDI-TOF mass spectrometry in a total of 286 consecutive samples retrieved from women who presented with signs or symptoms of preterm labor or preterm premature rupture of the membranes. Inflammation and/or bleeding proteomic patterns were detected in 32% (92/286 of the SELDI tracings. In the remaining tracings, a hierarchical algorithm was applied based on descriptors quantifying similarity/dissimilarity among proteomic fingerprints. This allowed identification of a novel profile (Q-profile based on the presence of 5 SELDI peaks in the 10-12.5 kDa mass area. Women displaying the Q-profile (mean+/-SD, gestational age: 25+/-4 weeks, n = 40 were more likely to deliver preterm despite expectant management in the context of intact membranes and normal amniotic fluid clinical results. Utilizing identification-centered proteomics techniques (fluorescence two-dimensional differential gel electrophoresis, robotic tryptic digestion and mass spectrometry coupled with Protein ANalysis THrough Evolutionary Relationships (PANTHER ontological classifications, we determined that in amniotic fluids with Q-profile the differentially expressed proteins are primarily involved in non-inflammatory biological processes such as protein metabolism, signal transduction and transport.Proteomic profiling of amniotic fluid coupled with non-hierarchical bioinformatics algorithms identified a subgroup of patients at risk for preterm birth in the absence of intra
Zamir, Mair; Moore, James E; Fujioka, Hideki; Gaver, Donald P
2010-03-01
In the field of fluid flow within the human body, focus has been placed on the transportation of blood in the systemic circulation since the discovery of that system; but, other fluids and fluid flow phenomena pervade the body. Some of the most fascinating fluid flow phenomena within the human body involve fluids other than blood and a service other than transport--the lymphatic and pulmonary systems are two striking examples. While transport is still involved in both cases, this is not the only service which they provide and blood is not the only fluid involved. In both systems, filtration, extraction, enrichment, and in general some "treatment" of the fluid itself is the primary function. The study of the systemic circulation has also been conventionally limited to treating the system as if it were an open-loop system governed by the laws of fluid mechanics alone, independent of physiological controls and regulations. This implies that system failures can be explained fully in terms of the laws of fluid mechanics, which of course is not the case. In this paper we examine the clinical implications of these issues and of the special biofluid mechanics issues involved in the lymphatic and pulmonary systems.
Extrema principles of entrophy production and energy dissipation in fluid mechanics
Horne, W. Clifton; Karamcheti, Krishnamurty
1988-01-01
A survey is presented of several extrema principles of energy dissipation as applied to problems in fluid mechanics. An exact equation is derived for the dissipation function of a homogeneous, isotropic, Newtonian fluid, with terms associated with irreversible compression or expansion, wave radiation, and the square of the vorticity. By using entropy extrema principles, simple flows such as the incompressible channel flow and the cylindrical vortex are identified as minimal dissipative distributions. The principal notions of stability of parallel shear flows appears to be associated with a maximum dissipation condition. These different conditions are consistent with Prigogine's classification of thermodynamic states into categories of equilibrium, linear nonequilibrium, and nonlinear nonequilibrium thermodynamics; vortices and acoustic waves appear as examples of dissipative structures. The measurements of a typical periodic shear flow, the rectangular wall jet, show that direct measurements of the dissipative terms are possible.
Effect of fluid balance on alveolar-arterial oxygen gradient in mechanically ventilated patients.
Aliyali, Masoud; Sharifpour, Ali; Tavakoli, Abdolrasol
2011-01-01
Fluid balance affects outcome in critically ill patients. We studied the effect of fluid balance on oxygen exchange by assessing alveolar-arterial oxygen gradient (PA-a O2) in mechanically ventilated patients. Our primary objective was to evaluate the difference in PA-aO2 and the secondary goal was to evaluate the differences in age and mortality rate. This retrospective observational study was performed on patients who were admitted to medical and surgical ICUs of Sari Imam Hospital, Mazandaran University of Medical Sciences, from 2003 to 2009. Daily fluid balance was calculated by input minus output. Thirty patients with continuous positive fluid balance (PFB) and 30 subjects with continuous negative fluid balance (NFB) during 4 consecutive days were enrolled in this study. PA-a O2 was calculated in these two groups. The mean (±SD) age was 48.9±21.2 yrs. in PFB group (19 males and 11 females) and 37.1±15.7 yrs. in NFB group (25 males and 5 females) which showed a statistically significant difference in age between the two groups (p = 0.017). The 24h, 48h, and 96h fluid balances were 1226(cc)±881, 1311(cc)±751, and 957(cc)±661 in PFB group and -1122(cc)±692, -920(cc)±394, and -1164(cc)±695 in NFB group, respectively. The mean differences (±SD) of PA-a O2 in 24h, 48h, and 96h versus the same value in the admission day were 11.3±39.2, 1.69±51.1, and -1.50±64 in PFB subjects and -21.8±60.8, -27.8±84.9, and -19.3±68.7 in NFB patients. The difference was statistically significant only in the first day of admission (p = 0.015). However, no difference was detected in overall mean oxygen gradient during 96h among the two groups. Mortality rate was significantly higher in PFB patients (P < 0.0001). Positive fluid balance had no significant effect on PA-a O2 but can be used as a predictor of mortality.
Zhang, Han-Wei; Zheng, Yong; Du, Lan; Pan, Guan-Song
The tidal variation in Earth's rotation rate is a periodical response to solar-lunar tide generating potential (TGP). In this article, the factor of the fluid core, which is related with the variation in the polar moment of inertia of the Earth, is considered and introduced distinctly into the theoretical formula of the variation in the Earth's rotational rate caused by lunar-solar tide-producing force based on the dynamics principle of the fluid core Earth. Different from previously work, some Doodson developments are given including the variation formulae of the Earth's rotational rate, LOD and UT1. The reasons are pointed why the moment of inertia for the scale should be the effective polar rotational moment of inertia of the mantle and the Love number should be the effective Love number of the mantle. It is also indicated that the factor of the fluid core is consistent with the effect of the effective Love number of the mantle due to fluid core.
Syrakos, Alexandros; Dimakopoulos, Yannis; Tsamopoulos, John
2018-03-01
The flow inside a fluid damper where a piston reciprocates sinusoidally inside an outer casing containing high-viscosity silicone oil is simulated using a finite volume method, at various excitation frequencies. The oil is modeled by the Carreau-Yasuda (CY) and Phan-Thien and Tanner (PTT) constitutive equations. Both models account for shear-thinning, but only the PTT model accounts for elasticity. The CY and other generalised Newtonian models have been previously used in theoretical studies of fluid dampers, but the present study is the first to perform full two-dimensional (axisymmetric) simulations employing a viscoelastic constitutive equation. It is found that the CY and PTT predictions are similar when the excitation frequency is low, but at medium and higher frequencies, the CY model fails to describe important phenomena that are predicted by the PTT model and observed in experimental studies found in the literature, such as the hysteresis of the force-displacement and force-velocity loops. Elastic effects are quantified by applying a decomposition of the damper force into elastic and viscous components, inspired from large amplitude oscillatory shear theory. The CY model also overestimates the damper force relative to the PTT model because it underpredicts the flow development length inside the piston-cylinder gap. It is thus concluded that (a) fluid elasticity must be accounted for and (b) theoretical approaches that rely on the assumption of one-dimensional flow in the piston-cylinder gap are of limited accuracy, even if they account for fluid viscoelasticity. The consequences of using lower-viscosity silicone oil are also briefly examined.
The Fluid Mechanics of the Bible: Miracles Explainable by Christian Science?
Lang, Amy
2015-11-01
The Bible is full of accounts clearly in violation of our scientific understanding of fluid mechanics. Examples include the floating axe head, Jesus walking on the water and immediately calming a storm. ``Jesus of Nazareth was the most scientific man that ever trod the globe. He plunged beneath the material surface of things, and found the spiritual cause,'' wrote Mary Baker Eddy (1821-1910), the founder of a now well-established religion known as Christian Science, in her seminal work Science & Health with Key to the Scriptures. She asserted that Jesus' miracles were in accord with the, ``Science of God's unchangeable law.'' She also proclaimed that matter is a derivative of consciousness. Independently with the discovery of quantum mechanics, physicists such as Max Planck and Sir James Jeans began to make similar statements (``The Mental Universe'', Nature, 2005). More recently, Max Tegmark (MIT) theorized that consciousness is a state of matter (New Scientist, April 2014). Using a paradigm shift from matter to consciousness as the primary substance, one can scientifically explain how a mental activity (i.e. prayer) could influence the physical. Since this conference is next door to the original church of Christian Science (Const. 1894), this talk will discuss various fluid-mechanic miracles in the Bible and provide an explanation based on divine metaphysics while providing an overview of scientific Christianity and its unifying influence to the fields of science, theology and medicine.
Special requirements for the fluid mechanical design of hard coal-fired SCR retrofit units
Energy Technology Data Exchange (ETDEWEB)
NONE
2006-07-01
The system design of high-dust SCR units for retrofits is a challenge that is to be mastered in order to meet the fluid mechanical requirements. Retrofitting power plants with NOx control technologies is a cost-intensive adventure that many utilities are undertaking. Except for a few recent new boiler installations, SCR installations must be considered as retrofit projects. In most cases the limitation of space on site entails unfavorable conditions that do not allow appropriate upstream conditions for SCR catalysts. To comply with the requirements of high performance DeNOx systems and to lower the investment costs for retrofit units, several technical solutions and concepts for the reactor layout, for NOx and dust distribution, for flow stabilization in diffusers, and advanced ammonia injection systems are explained in this paper. Balcke-Duerr offers customer-tailored solutions for flow optimization, which are evaluated by model studies. Physical flow and dust model tests in an appropriate scale provide flexibility to test various engineering concepts. The experience of Balcke-Duerr is based on continuous research and development activities over the last 25 years and more than 350 executed projects for gas flow optimization applications. The success of these installations is a direct result of the key decisions based on the improved fluid mechanical design and proper system integration. This paper also identifies the sensible design particularities and solutions that have two be considered in the fluid mechanical design of high-dust SCR retrofit units. This article demonstrates that the layout of SCR units must be carefully reviewed in order to meet the performance requirements and to avoid problems, i.e. wear, catalyst plugging and ammonia slip. 9 refs., 18 figs.
International Nuclear Information System (INIS)
Praveena, R.; Sadasivam, K.
2016-01-01
Synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are found to be toxic, hence non-carcinogenic naturally occurring radical scavengers especially flavonoids have gained considerable importance in the past two decades. In the present investigation, the radical scavenging activity of C-glycosyl flavonoids is evaluated using theoretical approach which could broaden its scope in therapeutic applications. Gas and solvent phase studies of structural and molecular characteristics of C-glycosyl flavonoid, isovitexin is investigated through hydrogen atom transfer mechanism (HAT), Electron transfer-proton transfer (ET–PT) and Sequential proton loss electron transfer (SPLET) by Density functional theory (DFT) using hybrid parameters. The computed values of the adiabatic ionization potential, electron affinity, hardness, softness, electronegativity and electrophilic index indicate that isovitexin possess good radical scavenging activity. The behavior of different –OH groups in polyphenolic compounds is assessed by considering electronic effects of the neighbouring groups and the overall geometry of molecule which in turn helps in analyzing the antioxidant capacity of the polyphenolic molecule. The studies indicate that the H–atom abstraction from 4’–OH site is preferred during the radical scavenging process. From Mulliken spin density analysis and FMOs, B–ring is found to be more delocalized center and capable of electron donation. Comparison of antioxidant activity of vitexin and isovitexin leads to the conclusion that isovitexin acts as a better radical scavenger. This is an evidence for the importance of position of glucose unit in the flavonoid.
THEORETICAL RESEARCH ON THE MULTI-CHANNEL REACTION MECHANISM AND KINETICS OF HNCS WITH OH-
Directory of Open Access Journals (Sweden)
Li-Jie Hou
Full Text Available We presented a theoretical study on the detailed reaction mechanism and kinetics of the HNCS molecule with the OH-. The barrierless minimum energy path and the most favorable entrance channel have been determined by study the thermodynamic and kinetic characters of the channel with low energy barrier. The B3LYP/6-311++G** method was employed for all the geometrical optimizations and a multi-level extrapolation method based on the G3 energies was employed for further energy refinements. In addition, the analysis of the combining interaction between hydroxide ion and HNCS was performed by natural bond orbitals (NBO analysis. The calculation results indicated that the reaction of OH- with HNCS had four channels, and the channel of H-atom in HNCS direct extraction to OH- (OH-+HNCS→IM1→TS3→IM4→P2(SCN- +H2O in singlet state was the main channel with the low potential energy and high equilibrium constant and reaction rate constant. SCN- and H2O were main products.
Energy Technology Data Exchange (ETDEWEB)
Praveena, R. [Department of Chemistry, Bannari Amman Institute of Technology, Sathyamangalam, Erode, Tamil Nadu (India); Sadasivam, K. [Department of Physics, Bannari Amman Institute of Technology, Sathyamangalam, Erode, Tamil Nadu (India)
2016-05-06
Synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are found to be toxic, hence non-carcinogenic naturally occurring radical scavengers especially flavonoids have gained considerable importance in the past two decades. In the present investigation, the radical scavenging activity of C-glycosyl flavonoids is evaluated using theoretical approach which could broaden its scope in therapeutic applications. Gas and solvent phase studies of structural and molecular characteristics of C-glycosyl flavonoid, isovitexin is investigated through hydrogen atom transfer mechanism (HAT), Electron transfer-proton transfer (ET–PT) and Sequential proton loss electron transfer (SPLET) by Density functional theory (DFT) using hybrid parameters. The computed values of the adiabatic ionization potential, electron affinity, hardness, softness, electronegativity and electrophilic index indicate that isovitexin possess good radical scavenging activity. The behavior of different –OH groups in polyphenolic compounds is assessed by considering electronic effects of the neighbouring groups and the overall geometry of molecule which in turn helps in analyzing the antioxidant capacity of the polyphenolic molecule. The studies indicate that the H–atom abstraction from 4’–OH site is preferred during the radical scavenging process. From Mulliken spin density analysis and FMOs, B–ring is found to be more delocalized center and capable of electron donation. Comparison of antioxidant activity of vitexin and isovitexin leads to the conclusion that isovitexin acts as a better radical scavenger. This is an evidence for the importance of position of glucose unit in the flavonoid.
Experimental and theoretical study of breakdown mechanisms in a gas in an uniform electric field
International Nuclear Information System (INIS)
Bayle, Pierre.
1975-01-01
The theoretical study of breakdown mechanisms in a gas with an applied electric field has been made on the basis of a deterministic model built on continuity equations governing the evolution of electronic and ionic densities. With this purpose, the breakdown formation has been simulated in electronegative gases (air, oxygen) taking into account the space charge effects on initial applied electric field, the electronic emission on the cathode by photonic or ionic impact, the delayed electrons processes (attachment, detachment) and charge exchange processes. Without space charge, the influence of photoionization in the gas on the electronic and ionic population has been pointed out in a discharge in nitrogen. Then the problem of external electrode discharges has been approached for the study of plasma visualization pannel cells, and the fundamental role of the charges deposed on dielectrics has been manifested. In the experimental study, the discharge formation has been analysed in rare gases and nitrogen for high over voltages (more than 100%) and for pressures of about hundred torrs. Using high-speed cinematographic techniques, the discharge propagation has been studied with a one nanosecond time resolution. The ultra-fast propagation zone of anode-directed streamer has been linked with the intervention of distance ionization process. The arrival of the streamers on the anode induces the beginning of an ionization front propagating towards the cathode [fr
Experimental and theoretical study of breakdown mechanisms in a gas in an uniform electric field
Energy Technology Data Exchange (ETDEWEB)
Bayle, P
1975-01-01
The theoretical study of breakdown mechanisms in a gas with an applied electric field has been made on the basis of a deterministic model built on continuity equations governing the evolution of electronic and ionic densities. With this purpose, the breakdown formation has been simulated in electronegative gases (air, oxygen) taking into account the space charge effects on initial applied electric field, the electronic emission on the cathode by photonic or ionic impact, the delayed electrons processes (attachment, detachment) and charge exchange processes. Without space charge, the influence of photoionization in the gas on the electronic and ionic population has been pointed out in a discharge in nitrogen. Then the problem of external electrode discharges has been approached for the study of plasma visualization pannel cells, and the fundamental role of the charges deposed on dielectrics has been manifested. In the experimental study, the discharge formation has been analysed in rare gases and nitrogen for high over voltages (more than 100%) and for pressures of about hundred torrs. Using high-speed cinematographic techniques, the discharge propagation has been studied with a one nanosecond time resolution. The ultra-fast propagation zone of anode-directed streamer has been linked with the intervention of distance ionization process. The arrival of the streamers on the anode induces the beginning of an ionization front propagating towards the cathode.
Wolbring, Tobias; Riordan, Patrick
2016-05-01
Plenty of studies show that the physical appearance of a person affects a variety of outcomes in everyday life. However, due to an incomplete theoretical explication and empirical problems in disentangling different beauty effects, it is unclear which mechanisms are at work. To clarify how beauty works we present explanations from evolutionary theory and expectation states theory and show where both perspectives differ and where interlinkage appears promising. Using students' evaluations of teaching we find observational and experimental evidence for the different causal pathways of physical attractiveness. First, independent raters strongly agree over the physical attractiveness of a person. Second, attractive instructors receive better student ratings. Third, students attend classes of attractive instructors more frequently - even after controlling for teaching quality. Fourth, we find no evidence that attractiveness effects become stronger if rater and ratee are of the opposite sex. Finally, the beauty premium turns into a penalty if an attractive instructor falls short of students' expectations. Copyright © 2016 Elsevier Inc. All rights reserved.
Fluid mechanics of additive manufacturing of metal objects by accretion of droplets – a survey
Directory of Open Access Journals (Sweden)
Tesař Václav
2016-01-01
Full Text Available Paper presents a survey of principles of additive manufacturing of metal objects by accretion of molten metal droplets, focusing on fluid-mechanical problems that deserve being investigated. The main problem is slowness of manufacturing due to necessarily small size of added droplets. Increase of droplet repetition rate calls for basic research of the phenomena that take place inside and around the droplets: ballistics of their flight, internal flowfield with heat and mass transfer, oscillation of surfaces, and the ways to elimination of satellite droplets.
Fluid mechanics of additive manufacturing of metal objects by accretion of droplets - a survey
Tesař, Václav
2016-03-01
Paper presents a survey of principles of additive manufacturing of metal objects by accretion of molten metal droplets, focusing on fluid-mechanical problems that deserve being investigated. The main problem is slowness of manufacturing due to necessarily small size of added droplets. Increase of droplet repetition rate calls for basic research of the phenomena that take place inside and around the droplets: ballistics of their flight, internal flowfield with heat and mass transfer, oscillation of surfaces, and the ways to elimination of satellite droplets.
Mass sensors with mechanical traps for weighing single cells in different fluids.
Weng, Yaochung; Delgado, Francisco Feijó; Son, Sungmin; Burg, Thomas P; Wasserman, Steven C; Manalis, Scott R
2011-12-21
We present two methods by which single cells can be mechanically trapped and continuously monitored within the suspended microchannel resonator (SMR) mass sensor. Since the fluid surrounding the trapped cell can be quickly and completely replaced on demand, our methods are well suited for measuring changes in cell size and growth in response to drugs or other chemical stimuli. We validate our methods by measuring the density of single polystyrene beads and Saccharomyces cerevisiae yeast cells with a precision of approximately 10(-3) g cm(-3), and by monitoring the growth of single mouse lymphoblast cells before and after drug treatment.
Dong, Guanyu
2018-03-01
In order to analyze the microscopic stress field acting on residual oil droplets in micro pores, calculate its deformation, and explore the hydrodynamic mechanism of viscous-elastic fluids displacing oil droplets, the viscous-elastic fluid flow equations in micro pores are established by choosing the Upper Convected Maxwell constitutive equation; the numerical solutions of the flow field are obtained by volume control and Alternate Direction Implicit methods. From the above, the velocity field and microscopic stress field; the forces acting on residual oil droplets; the deformations of residual oil droplets by various viscous-elastic displacing fluids and at various Wiesenberg numbers are calculated and analyzed. The result demonstrated that both the normal stress and horizontal force acting on the residual oil droplets by viscous-elastic fluids are much larger compared to that of inelastic fluid; the distribution of normal stress changes abruptly; under the condition of the same pressure gradient in the system under investigation, the ratio of the horizontal forces acting on the residual oil droplets by different displacing fluids is about 1:8:20, which means that under the above conditions, the driving force on a oil droplet is 20 times higher for a viscous-elastic fluid compared to that of a Newtonian Fluid. The conclusions are supportive of the mechanism that viscous-elastic driving fluids can increase the Displacement Efficiency. This should be of help in designing new chemicals and selecting Enhanced Oil Recovery systems.
A diffusion tensor imaging tractography algorithm based on Navier-Stokes fluid mechanics.
Hageman, Nathan S; Toga, Arthur W; Narr, Katherine L; Shattuck, David W
2009-03-01
We introduce a fluid mechanics based tractography method for estimating the most likely connection paths between points in diffusion tensor imaging (DTI) volumes. We customize the Navier-Stokes equations to include information from the diffusion tensor and simulate an artificial fluid flow through the DTI image volume. We then estimate the most likely connection paths between points in the DTI volume using a metric derived from the fluid velocity vector field. We validate our algorithm using digital DTI phantoms based on a helical shape. Our method segmented the structure of the phantom with less distortion than was produced using implementations of heat-based partial differential equation (PDE) and streamline based methods. In addition, our method was able to successfully segment divergent and crossing fiber geometries, closely following the ideal path through a digital helical phantom in the presence of multiple crossing tracts. To assess the performance of our algorithm on anatomical data, we applied our method to DTI volumes from normal human subjects. Our method produced paths that were consistent with both known anatomy and directionally encoded color images of the DTI dataset.
Fluid Mechanics of Taylor Bubbles and Slug Flows in Vertical Channels
International Nuclear Information System (INIS)
Anglart, Henryk; Podowski, Michael Z.
2002-01-01
Fluid mechanics of Taylor bubbles and slug flows is investigated in vertical, circular channels using detailed, three-dimensional computational fluid dynamics simulations. The Volume of Fluid model with the interface-sharpening algorithm, implemented in the commercial CFX4 code, is used to predict the shape and velocity of Taylor bubbles moving along a vertical channel. Several cases are investigated, including both a single Taylor bubble and a train of bubbles rising in water. It is shown that the potential flow solution underpredicts the water film thickness around Taylor bubbles. Furthermore, the computer simulations that are performed reveal the importance of properly modeling the three-dimensional nature of phenomena governing the motion of Taylor bubbles. Based on the present results, a new formula for the evaluation of bubble shape is derived. Both the shape of Taylor bubbles and the bubble rise velocity predicted by the proposed model agree well with experimental observations. Furthermore, the present model shows good promise in predicting the coalescence of Taylor bubbles
Ups and downs of using ``kitchen sink'' experiments in an introductory fluid mechanics class
Kaye, Nigel
2015-11-01
Both positive and negative experiences from two semesters of using take home ``kitchen sink'' experiments in an introductory civil engineering fluid mechanics class are reported. Four different experimental assignments were given each semester to groups of four students. The students were tasked with using common household equipment to measure various properties of fluids or fluid flows. These included the density of cooking oil, the exit velocity from a garden hose, and the mass flux of air from a compressed air can. Students were given minimal guidance on how to do the measurements and each measurement had to be done in at least two different ways. The labs were used to relate their course work to everyday situations and was also used as a platform for discussing experimental uncertainty and error propagation in calculations. In general the students successfully completed each task using at least one method. Finding a second method sometimes proved problematic. The presentation will discuss the logistics of running the program and the positive and negative aspects from the instructor viewpoint. A summary of student feedback on the labs will also be presented. Links to resources for those interested in implementing such a program will be provided.
International Nuclear Information System (INIS)
Tian, Hua; Liu, Lina; Shu, Gequn; Wei, Haiqiao; Liang, Xingyu
2014-01-01
Highlights: • Among all examined working fluids, toluene possesses the maximum W net , highest η e and η ec . • The increase of T 3 worsens system performance, decreasing W net , η e and η ec . • Condenser C LT and turbine T LT possesses the least system irreversibility. • Turbines and exhaust evaporators are optimization components. - Abstract: In this paper, a regenerative transcritical dual-loop organic Rankine cycle is proposed to recover the waste heat of the exhaust, engine coolant and all the residual heat of the HT loop. Double regenerators are adopted in this system. Transcritical cycles are used in both loops. Hexamethyldisiloxane (MM), octamethyl cyclotetrasiloxane (D 4 ), octamethyltrisiloxane (MDM), cyclohexane, toluene and n-decane are chosen as the candidate working fluids of the HT loop and R143a is chosen as the working fluid of the LT loop. Influences of inlet temperature of turbine T HT (T 3 ) on mass flow rates (m f,HT and m f,LT ), net output power (W net ), energy conversion efficiency (η ec ), volumetric expansion ratio (VER), ratio of power consumed to power output (COR) and component irreversibility are analyzed and performance comparison of these working fluids is also evaluated. Results show that toluene possesses the maximum W net (42.46 kW), highest η e (51.92%) and η ec (12.77%). The increase of T 3 worsens system performance, decreasing W net , η e and η ec . Condenser C LT and turbine T LT possess the least system irreversibility. In addition, turbines and exhaust evaporators are optimized components
Experimental and Theoretical Investigations of a Mechanical Lever System Driven by a DC Motor
Nana, B.; Fautso Kuiate, G.; Yamgoué, S. B.
This paper presents theoretical and experimental results on the investigation of the dynamics of a nonlinear electromechanical system made of a lever arm actuated by a DC motor and controlled through a repulsive magnetic force. We use the method of harmonic balance to derive oscillatory solutions. Theoretical tools such as, bifurcation diagrams, Lyapunov exponents, phase portraits, are used to unveil the rich nonlinear behavior of the system including chaos and hysteresis. The experimental results are in close accordance with the theoretical predictions.
Monteith, Corey E; Brunner, Matthew E; Djagaeva, Inna; Bielecki, Anthony M; Deutsch, Joshua M; Saxton, William M
2016-05-10
The transport of cytoplasmic components can be profoundly affected by hydrodynamics. Cytoplasmic streaming in Drosophila oocytes offers a striking example. Forces on fluid from kinesin-1 are initially directed by a disordered meshwork of microtubules, generating minor slow cytoplasmic flows. Subsequently, to mix incoming nurse cell cytoplasm with ooplasm, a subcortical layer of microtubules forms parallel arrays that support long-range, fast flows. To analyze the streaming mechanism, we combined observations of microtubule and organelle motions with detailed mathematical modeling. In the fast state, microtubules tethered to the cortex form a thin subcortical layer and undergo correlated sinusoidal bending. Organelles moving in flows along the arrays show velocities that are slow near the cortex and fast on the inward side of the subcortical microtubule layer. Starting with fundamental physical principles suggested by qualitative hypotheses, and with published values for microtubule stiffness, kinesin velocity, and cytoplasmic viscosity, we developed a quantitative coupled hydrodynamic model for streaming. The fully detailed mathematical model and its simulations identify key variables that can shift the system between disordered (slow) and ordered (fast) states. Measurements of array curvature, wave period, and the effects of diminished kinesin velocity on flow rates, as well as prior observations on f-actin perturbation, support the model. This establishes a concrete mechanistic framework for the ooplasmic streaming process. The self-organizing fast phase is a result of viscous drag on kinesin-driven cargoes that mediates equal and opposite forces on cytoplasmic fluid and on microtubules whose minus ends are tethered to the cortex. Fluid moves toward plus ends and microtubules are forced backward toward their minus ends, resulting in buckling. Under certain conditions, the buckling microtubules self-organize into parallel bending arrays, guiding varying directions
Directory of Open Access Journals (Sweden)
Jian Zhou
2016-09-01
Full Text Available Hydraulic fracturing is a useful tool for enhancing rock mass permeability for shale gas development, enhanced geothermal systems, and geological carbon sequestration by the high-pressure injection of a fracturing fluid into tight reservoir rocks. Although significant advances have been made in hydraulic fracturing theory, experiments, and numerical modeling, when it comes to the complexity of geological conditions knowledge is still limited. Mechanisms of fluid injection-induced fracture initiation and propagation should be better understood to take full advantage of hydraulic fracturing. This paper presents the development and application of discrete particle modeling based on two-dimensional particle flow code (PFC2D. Firstly, it is shown that the modeled value of the breakdown pressure for the hydraulic fracturing process is approximately equal to analytically calculated values under varied in situ stress conditions. Furthermore, a series of simulations for hydraulic fracturing in competent rock was performed to examine the influence of the in situ stress ratio, fluid injection rate, and fluid viscosity on the borehole pressure history, the geometry of hydraulic fractures, and the pore-pressure field, respectively. It was found that the hydraulic fractures in an isotropic medium always propagate parallel to the orientation of the maximum principal stress. When a high fluid injection rate is used, higher breakdown pressure is needed for fracture propagation and complex geometries of fractures can develop. When a low viscosity fluid is used, fluid can more easily penetrate from the borehole into the surrounding rock, which causes a reduction of the effective stress and leads to a lower breakdown pressure. Moreover, the geometry of the fractures is not particularly sensitive to the fluid viscosity in the approximate isotropic model.
International Symposium on Boundary Element Methods : Advances in Solid and Fluid Mechanics
Tseng, Kadin
1990-01-01
The Boundary Element Method (BEM) has become established as an effective tool for the solutions of problems in engineering science. The salient features of the BEM have been well documented in the open literature and therefore will not be elaborated here. The BEM research has progressed rapidly, especially in the past decade and continues to evolve worldwide. This Symposium was organized to provide an international forum for presentation of current research in BEM for linear and nonlinear problems in solid and fluid mechanics and related areas. To this end, papers on the following topics were included: rotary wing aerodynamics, unsteady aerodynamics, design and optimization, elasticity, elasto dynamics and elastoplasticity, fracture mechanics, acoustics, diffusion and wave motion, thermal analysis, mathematical aspects and boundary/finite element coupled methods. A special session was devoted to parallel/vector supercomputing with emphasis on mas sive parallelism. This Symposium was sponsored by United ...
Appplication of a general fluid mechanics program to NTP system modeling
International Nuclear Information System (INIS)
Lee, S.K.
1993-01-01
An effort is currently underway at NASA and the Department of Energy (DOE) to develop an accurate model for predicting nuclear thermal propulsion (NTP) system performance. The objective of the effort is to develop several levels of computer programs which vary in detail and complexity according to user's needs. The current focus is on the Level 1 steady-state, parametric system model. This system model will combine a general fluid mechanics program, SAFSIM, with the ability to analyze turbines, pumps, nozzles, and reactor physics. SAFSIM (System Analysis Flow SIMulator) is a FORTRAN computer program that simulates integrated performance of systems involving fluid mechanics, heat transfer, and reactor dynamics. SAFSIM has the versatility to allow simulation of almost any system, including a nuclear reactor system. The focus of this paper is the validation of SAFSIM's capabilities as a base computational engine for a nuclear thermal propulsion system model. Validation is being accomplished by modeling of a nuclear engine test using SAFSIM and comparing the results to known experimental data
Farassat, Fereidoun; Myers, Michael K.
2011-01-01
This paper is the first part of a three part tutorial on multidimensional generalized functions (GFs) and their applications in aeroacoustics and fluid mechanics. The subject is highly fascinating and essential in many areas of science and, in particular, wave propagation problems. In this tutorial, we strive to present rigorously and clearly the basic concepts and the tools that are needed to use GFs in applications effectively and with ease. We give many examples to help the readers in understanding the mathematical ideas presented here. The first part of the tutorial is on the basic concepts of GFs. Here we define GFs, their properties and some common operations on them. We define the important concept of generalized differentiation and then give some interesting elementary and advanced examples on Green's functions and wave propagation problems. Here, the analytic power of GFs in applications is demonstrated with ease and elegance. Part 2 of this tutorial is on the diverse applications of generalized derivatives (GDs). Part 3 is on generalized Fourier transformations and some more advanced topics. One goal of writing this tutorial is to convince readers that, because of their powerful operational properties, GFs are absolutely essential and useful in engineering and physics, particularly in aeroacoustics and fluid mechanics.
Changes to the geometry and fluid mechanics of the carotid siphon in the pediatric Moyamoya disease.
Jamil, Muhammad; Tan, Germaine Xin Yi; Huq, Mehnaz; Kang, Heidi; Lee, Zhi Rui; Tang, Phua Hwee; Hu, Xi Hong; Yap, Choon Hwai
2016-12-01
The Moyamoya disease is a cerebrovascular disease that causes occlusion of the distal end of the internal carotid artery, leading to the formation of multiple tiny collateral arteries. To date, the pathogenesis of Moyamoya is unknown. Improved understanding of the changes to vascular geometry and fluid mechanics of the carotid siphon during disease may improve understanding of the pathogenesis, prognosis techniques and disease management. A retrospective analysis of Magnetic Resonance Angiography (MRA) images was performed for Moyamoya pediatric patients (MMD) (n = 23) and control (Ctrl) pediatric patients (n = 20). The Ctrl group was composed of patients who complained of headache and had normal MRA. We performed segmentation of MRA images to quantify geometric parameters of the artery. Computational fluid dynamics (CFD) was performed to quantify the hemodynamic parameters. MMD internal carotid and carotid siphons were smaller in cross-sectional areas, and shorter in curved vascular length. Vascular curvature remained constant over age and vascular size and did not change between Ctrl and MMD, but MMD carotid siphon had lower tortuosity in the posterior bend, and higher torsion in the anterior bend. Wall shear stress and secondary flows were significantly lower in MMD, but the ratio of secondary flow kinetic energy to primary flow kinetic energy were similar between MMD and Ctrl. There were alterations to both the geometry and the flow mechanics of the carotid siphons of Moyamoya patients but it is unclear whether hemodynamics is the cause or the effect of morphological changes observed.
D'Auria, L; Pimpinelli, F; Ferraro, C; D'Ambrogio, G; Giacalone, B; Bellocci, M; Ameglio, F
1998-01-01
Bullous pemphigoid (BP) blisters contain several molecules, some of which spread into the blisters from the interstitial fluid, while others are produced locally and migrate into the circulation. The calculation of the ratios between blister/serum concentrations may help to distinguish between these two types of molecules. The rules regulating the diffusion of the molecules have been described only in suction blisters, where the theoretical molecular weight (MW) represents one of the principal influencing factors. The aim of the present study was to analyse the relationship between theoretical MWs and the ratios of concentrations of several molecules evaluated both in sera and in blister fluids. Eight cytokines (interleukin-2, interleukin-3, interleukin-4, interleukin-5, interleukin-10, tumor necrosis factor-alpha, oncostatin-M and vascular endothelial growth factor), two acute phase reactants (alpha-1 acid glycoprotein, haptoglobin), albumin, one soluble membrane molecule with adhesion functions (sICAM-1) and the eosinophil cathionic protein (ECP) were measured in samples from 15 patients affected with BP by means of commercially available tests. The data suggest that the MW may influence the rate of diffusion throughout the blister, both in input and output directions, despite the discontinuity observed at the basement membrane level on the BP blister floor.
Gehne, Stephan; Benson, Philip; Koor, Nick; Enfield, Mark
2017-04-01
The finding of considerable volumes of hydrocarbon resources within tight sedimentary rock formations in the UK led to focused attention on the fundamental fracture properties of low permeability rock types and hydraulic fracturing. Despite much research in these fields, there remains a scarcity of available experimental data concerning the fracture mechanics of fluid driven fracturing and the fracture properties of anisotropic, low permeability rock types. In this study, hydraulic fracturing is simulated in a controlled laboratory environment to track fracture nucleation (location) and propagation (velocity) in space and time and assess how environmental factors and rock properties influence the fracture process and the developing fracture network. Here we report data on employing fluid overpressure to generate a permeable network of micro tensile fractures in a highly anisotropic shale ( 50% P-wave velocity anisotropy). Experiments are carried out in a triaxial deformation apparatus using cylindrical samples. The bedding planes are orientated either parallel or normal to the major principal stress direction (σ1). A newly developed technique, using a steel guide arrangement to direct pressurised fluid into a sealed section of an axially drilled conduit, allows the pore fluid to contact the rock directly and to initiate tensile fractures from the pre-defined zone inside the sample. Acoustic Emission location is used to record and map the nucleation and development of the micro-fracture network. Indirect tensile strength measurements at atmospheric pressure show a high tensile strength anisotropy ( 60%) of the shale. Depending on the relative bedding orientation within the stress field, we find that fluid induced fractures in the sample propagate in two of the three principal fracture orientations: Divider and Short-Transverse. The fracture progresses parallel to the bedding plane (Short-Transverse orientation) if the bedding plane is aligned (parallel) with the
Scaling options for integral experiments for molten salt fluid mechanics and heat transfer
International Nuclear Information System (INIS)
Philippe Bardet; Per F Peterson
2005-01-01
Full text of publication follows: Molten fluoride salts have potentially large benefits for use in high-temperature heat transport in fission and fusion energy systems, due to their very very low vapor pressures at high temperatures. Molten salts have high volumetric heat capacity compared to high-pressure helium and liquid metals, and have desirable safety characteristics due to their chemical inertness and low pressure. Therefore molten salts have been studied extensively for use in fusion blankets, as an intermediate heat transfer fluid for thermochemical hydrogen production in the Next Generation Nuclear Plant, as a primary coolant for the Advanced High Temperature Reactor, and as a solvent for fuel in the Molten Salt Reactor. This paper presents recent progress in the design and analysis of scaled thermal hydraulics experiments for molten salt systems. We have identified a category of light mineral oils that can be used for scaled experiments. By adjusting the length, velocity, average temperature, and temperature difference scales of the experiment, we show that it is possible to simultaneously match the Reynolds (Re), Froude (Fr), Prandtl (Pr) and Rayleigh (Ra) numbers in the scaled experiments. For example, the light mineral oil Penreco Drakesol 260 AT can be used to simulate the molten salt flibe (Li 2 BeF 4 ). At 110 deg. C, the oil Pr matches 600 deg. C flibe, and at 165 deg. C, the oil Pr matches 900 deg. C flibe. Re, Fr, and Ra can then be matched at a length scale of Ls/Lp = 0.40, velocity scale of U s /U p = 0.63, and temperature difference scale of ΔT s /ΔT p = 0.29. The Weber number is then matched within a factor of two, We s /We p = 0.7. Mechanical pumping power scales as Qp s /Qp p = 0.016, while heat inputs scale as Qh s /Qh p = 0.010, showing that power inputs to scaled experiments are very small compared to the prototype system. The scaled system has accelerated time, t s /t p = 0.64. When Re, Fr, Pr and Ra are matched, geometrically scaled
Theoretical analysis of selectivity mechanisms in molecular transport through channels and nanopores
International Nuclear Information System (INIS)
Agah, Shaghayegh; Pasquali, Matteo; Kolomeisky, Anatoly B.
2015-01-01
Selectivity is one of the most fundamental concepts in natural sciences, and it is also critically important in various technological, industrial, and medical applications. Although there are many experimental methods that allow to separate molecules, frequently they are expensive and not efficient. Recently, a new method of separation of chemical mixtures based on utilization of channels and nanopores has been proposed and successfully tested in several systems. However, mechanisms of selectivity in the molecular transport during the translocation are still not well understood. Here, we develop a simple theoretical approach to explain the origin of selectivity in molecular fluxes through channels. Our method utilizes discrete-state stochastic models that take into account all relevant chemical transitions and can be solved analytically. More specifically, we analyze channels with one and two binding sites employed for separating mixtures of two types of molecules. The effects of the symmetry and the strength of the molecular-pore interactions are examined. It is found that for one-site binding channels, the differences in the strength of interactions for two species drive the separation. At the same time, in more realistic two-site systems, the symmetry of interaction potential becomes also important. The most efficient separation is predicted when the specific binding site is located near the entrance to the nanopore. In addition, the selectivity is higher for large entrance rates into the channel. It is also found that the molecular transport is more selective for repulsive interactions than for attractive interactions. The physical-chemical origin of the observed phenomena is discussed
International Nuclear Information System (INIS)
Heusler, Stefan
2006-01-01
The main focus of the second, enlarged edition of the book Mathematica for Theoretical Physics is on computational examples using the computer program Mathematica in various areas in physics. It is a notebook rather than a textbook. Indeed, the book is just a printout of the Mathematica notebooks included on the CD. The second edition is divided into two volumes, the first covering classical mechanics and nonlinear dynamics, the second dealing with examples in electrodynamics, quantum mechanics, general relativity and fractal geometry. The second volume is not suited for newcomers because basic and simple physical ideas which lead to complex formulas are not explained in detail. Instead, the computer technology makes it possible to write down and manipulate formulas of practically any length. For researchers with experience in computing, the book contains a lot of interesting and non-trivial examples. Most of the examples discussed are standard textbook problems, but the power of Mathematica opens the path to more sophisticated solutions. For example, the exact solution for the perihelion shift of Mercury within general relativity is worked out in detail using elliptic functions. The virial equation of state for molecules' interaction with Lennard-Jones-like potentials is discussed, including both classical and quantum corrections to the second virial coefficient. Interestingly, closed solutions become available using sophisticated computing methods within Mathematica. In my opinion, the textbook should not show formulas in detail which cover three or more pages-these technical data should just be contained on the CD. Instead, the textbook should focus on more detailed explanation of the physical concepts behind the technicalities. The discussion of the virial equation would benefit much from replacing 15 pages of Mathematica output with 15 pages of further explanation and motivation. In this combination, the power of computing merged with physical intuition would
Competition between Bending and Internal Pressure Governs the Mechanics of Fluid Nanovesicles.
Vorselen, Daan; MacKintosh, Fred C; Roos, Wouter H; Wuite, Gijs J L
2017-03-28
Nanovesicles (∼100 nm) are ubiquitous in cell biology and an important vector for drug delivery. Mechanical properties of vesicles are known to influence cellular uptake, but the mechanism by which deformation dynamics affect internalization is poorly understood. This is partly due to the fact that experimental studies of the mechanics of such vesicles remain challenging, particularly at the nanometer scale where appropriate theoretical models have also been lacking. Here, we probe the mechanical properties of nanoscale liposomes using atomic force microscopy (AFM) indentation. The mechanical response of the nanovesicles shows initial linear behavior and subsequent flattening corresponding to inward tether formation. We derive a quantitative model, including the competing effects of internal pressure and membrane bending, that corresponds well to these experimental observations. Our results are consistent with a bending modulus of the lipid bilayer of ∼14k b T. Surprisingly, we find that vesicle stiffness is pressure dominated for adherent vesicles under physiological conditions. Our experimental method and quantitative theory represents a robust approach to study the mechanics of nanoscale vesicles, which are abundant in biology, as well as being of interest for the rational design of liposomal vectors for drug delivery.
International Nuclear Information System (INIS)
Patel, Vipul M.; Gaurav; Mehta, Hemantkumar B.
2017-01-01
Highlights: • Startup mechanism and thermal performance of a CLPHP is reported. • Influence of pure fluids, water-based binary fluids and surfactant solutions are investigated. • Startup heat flux is observed lower for acetone and higher for water compared to all other working fluids. • Thermal resistance is observed to decrease with increase in heat input irrespective of working fluids. • CLPHP is observed to perform better with acetone, water-acetone, water-45 PPM and water-60 PPM surfactant solutions. - Abstract: Development of efficient cooling system is a tricky and challenging task in the field of electronics. Pulsating heat pipe has a great prospect in the upcoming days for an effective cooling solution due to its excellent heat transfer characteristics. Experimental investigations are reported on a Closed Loop Pulsating Heat Pipe (CLPHP). The influence of working fluids on startup mechanism and thermal performance of a CLPHP are carried out on 2 mm, nine turn copper capillary. Total eleven (11) working fluids are prepared and investigated. Deionized (DI) Water (H_2O), ethanol (C_2H_6O), methanol (CH_3OH) and acetone (C_3H_6O) are used as pure fluids. The water-based mixture (1:1) of acetone, methanol and ethanol are used as binary fluids. Sodium Dodecyl Sulphate (SDS, NaC_1_2H_2_5SO_4) is used as a surfactant to prepare the water-based surfactant solutions of 30 PPM, 45 PPM, 60 PPM and 100 PPM. The filling ratio is kept as 50%. The vertical bottom heating position of a CLPHP is considered. Heat input is varied in the range of 10–110 W. Significant influence is observed for water-based binary fluids and surfactant solutions on startup mechanism and thermal performance of a CLPHP compared to DI water used as the pure working fluid.
Directory of Open Access Journals (Sweden)
Yonghui Xie
2014-01-01
Full Text Available A three-dimensional fluid-thermal-structural coupled analysis for a radial inflow micro gas turbine is conducted. First, a fluid-thermal coupled analysis of the flow and temperature fields of the nozzle passage and the blade passage is performed by using computational fluid dynamics (CFD. The flow and heat transfer characteristics of different sections are analyzed in detail. The thermal load and the aerodynamic load are then obtained from the temperature field and the pressure distribution. The stress distributions of the blade are finally studied by using computational solid mechanics (CSM considering three cases of loads: thermal load, aerodynamics load combined with centrifugal load, and all the three types of loads. The detailed parameters of the flow, temperature, and the stress are obtained and analyzed. The numerical results obtained provide a useful knowledge base for further exploration of radial gas turbine design.
Chen, Guobao; Lv, Yonggang; Guo, Pan; Lin, Chongwen; Zhang, Xiaomei; Yang, Li; Xu, Zhiling
2013-07-01
Stem cells have the ability to self-renew and to differentiate into multiple mature cell types during early life and growth. Stem cells adhesion, proliferation, migration and differentiation are affected by biochemical, mechanical and physical surface properties of the surrounding matrix in which stem cells reside and stem cells can sensitively feel and respond to the microenvironment of this matrix. More and more researches have proven that three dimensional (3D) culture can reduce the gap between cell culture and physiological environment where cells always live in vivo. This review summarized recent findings on the studies of matrix mechanics that control stem cells (primarily mesenchymal stem cells (MSCs)) fate in 3D environment, including matrix stiffness and extracellular matrix (ECM) stiffness. Considering the exchange of oxygen and nutrients in 3D culture, the effect of fluid shear stress (FSS) on fate decision of stem cells was also discussed in detail. Further, the difference of MSCs response to matrix stiffness between two dimensional (2D) and 3D conditions was compared. Finally, the mechanism of mechanotransduction of stem cells activated by matrix mechanics and FSS in 3D culture was briefly pointed out.
High-performance coupled poro-hydro-mechanical models to resolve fluid escape pipes
Räss, Ludovic; Makhnenko, Roman; Podladchikov, Yury
2017-04-01
Field observations and laboratory experiments exhibit inelastic deformation features arising in many coupled settings relevant to geo-applications. These irreversible deformations and their specific patterns suggest a rather ductile or brittle mechanism, such as viscous creep or micro cracks, taking place on both geological (long) and human (short) timescales. In order to understand the underlying mechanisms responsible for these deformation features, there is a current need to accurately resolve the non-linearities inherent to strongly coupled physical processes. Among the large variety of modelling tools and softwares available nowadays in the community, very few are capable to efficiently solve coupled systems with high accuracy in both space and time and run efficiently on modern hardware. Here, we propose a robust framework to solve coupled multi-physics hydro-mechanical processes on very high spatial and temporal resolution in both two and three dimensions. Our software relies on the Finite-Difference Method and a pseudo-transient scheme is used to converge to the implicit solution of the system of poro-visco-elasto-plastic equations at each physical time step. The rheology including viscosity estimates for major reservoir rock types is inferred from novel lab experiments and confirms the ease of flow of sedimentary rocks. Our results propose a physical mechanism responsible for the generation of high permeability pathways in fluid saturated porous media and predict their propagation in rates observable on operational timescales. Finally, our software scales linearly on more than 5000 GPUs.
International Nuclear Information System (INIS)
Chao Yan; Martire, D.E.
1992-01-01
A mean-field lattice model is used to describe the partitioning of blocklike molecules between an isotropic mobile phase and an anisotropic stationary phase in chromatography by applying it to supercritical fluid retention of polycyclic aromatic hydrocarbons in a polymeric smectic phase. This concludes that the logarithm of the capacity factor (1) increases linearly with increasing reciprocal temperature, (2) decreases with increasing mobile phase density more rapidly for solute molecules with a relatively larger contact area with the mobile phase, and (3) is a linear function of the minimum area. The van't Hoff plot slope is also determined to be more negative for solute molecules with a relatively larger ratio of contact area with the stationary phase versus the mobile phase. 18 refs., 9 figs., 5 tabs
Effects of walking in deep venous thrombosis: a new integrated solid and fluid mechanics model.
López, Josep M; Fortuny, Gerard; Puigjaner, Dolors; Herrero, Joan; Marimon, Francesc; Garcia-Bennett, Josep
2017-05-01
Deep venous thrombosis (DVT) is a common disease. Large thrombi in venous vessels cause bad blood circulation and pain; and when a blood clot detaches from a vein wall, it causes an embolism whose consequences range from mild to fatal. Walking is recommended to DVT patients as a therapeutical complement. In this study the mechanical effects of walking on a specific patient of DVT were simulated by means of an unprecedented integration of 3 elements: a real geometry, a biomechanical model of body tissues, and a computational fluid dynamics study. A set of computed tomography images of a patient's leg with a thrombus in the popliteal vein was employed to reconstruct a geometry model. Then a biomechanical model was used to compute the new deformed geometry of the vein as a function of the fiber stretch level of the semimembranosus muscle. Finally, a computational fluid dynamics study was performed to compute the blood flow and the wall shear stress (WSS) at the vein and thrombus walls. Calculations showed that either a lengthening or shortening of the semimembranosus muscle led to a decrease of WSS levels up to 10%. Notwithstanding, changes in blood viscosity properties or blood flow rate may easily have a greater impact in WSS. Copyright © 2016 John Wiley & Sons, Ltd.
Cooling Systems Design in Hot Stamping Tools by a Thermal-Fluid-Mechanical Coupled Approach
Directory of Open Access Journals (Sweden)
Tao Lin
2014-06-01
Full Text Available Hot stamping tools with cooling systems are the key facilities for hot stamping process of Ultrahigh strength steels (UHSS in automotive industry. Hot stamping tools have significant influence on the final microstructure and properties of the hot stamped parts. In serials production, the tools should be rapidly cooled by cooling water. Hence, design of hot stamping tools with cooling systems is important not only for workpieces of good quality but also for the tools with good cooling performance and long life. In this paper, a new multifield simulation method was proposed for the design of hot stamping tools with cooling system. The deformation of the tools was also analyzed by this method. Based on MpCCI (Mesh-based parallel Code Coupling Interface, thermal-fluid simulation and thermal-fluid-mechanical coupled simulation were performed. Subsequently, the geometrical parameters of the cooling system are investigated for the design. The results show that, both the distance between the ducts and the distance between the ducts and the tools loaded contour have significant influence on the quenching effect. And better quenching effect can be achieved with the shorter distance from the tool surface and with smaller distance between ducts. It is also shown that, thermal expansion is the main reason for deformation of the hot forming tools, which causes the distortion of the cooling ducts, and the stress concentration at corner of the ducts.
International Nuclear Information System (INIS)
Gulaboski, Rubin; Kokoškarova, Pavlinka; Mitrev, Saša
2012-01-01
Highlights: ► Theoretical models for 2e− successive mechanisms are considered. ► The models are compatible for various metal-containing redox proteins. ► Diagnostic criteria are provided to recognize the particular redox mechanism. - Abstract: Protein-film voltammetry (PFV) is a versatile tool designed to provide insight into the enzymes physiological functions by studying the redox properties of various oxido-reductases with suitable voltammetric technique. The determination of the thermodynamic and kinetic parameters relevant to protein's physiological properties is achieved via methodologies established from theoretical considerations of various mechanisms in PFV. So far, the majority of the mathematical models in PFV have been developed for redox proteins undergoing a single-step electron transfer reactions. However, there are many oxido-reductases containing quinone moieties or polyvalent ions of transition metals like Mo, Mn, W, Fe or Co as redox centers, whose redox chemistry can be described only via mathematical models considering successive two-step electron transformation. In this work we consider theoretically the protein-film redox mechanisms of the EE (Electrochemical–Electrochemical), ECE (Electrochemical–Chemical–Electrochemical), and EECat (Electrochemical–Electrochemical–Catalytic) systems under conditions of cyclic staircase voltammetry. We also propose methodologies to determine the kinetics of electron transfer steps by all considered mechanisms. The experimentalists working with PFV can get large benefits from the simulated voltammograms given in this work.
A theoretical study on the mechanism of electronic to vibrational energy transfer in Hg/3P/ + CO
Kato, S.; Jaffe, R. L.; Komornicki, A.; Morokuma, K.
1983-01-01
The mechanism of electronic-to-vibrational (E-V) energy transfer in Hg(3P) + CO collisions has been studied theoretically. The configuration interaction (CI) method was employed to calculate potential energy surfaces of the collision system. A simplified theoretical model, based on the reaction coordinate concept and the calculated potential energy characteristics, was used to discuss the mechanism of the singlet-triplet transition and the energy disposal in the collision. The results obtained were that: (a) the quenching process processed via a collision complex mechanism; and that (b) the triplet-singlet transition occurs near the collinear geometry. A model classical trajectory calculation gives a product CO vibrational distribution in good agreement with the experimental result.
Bleckmann, Horst
2012-01-01
This book is the closing report of the national priority program Nature-Inspired Fluid Mechanics (Schwerpunktprogramm SPP 1207: Strömungsbeeinflussung in der Natur und Technik). Nature-inspired fluid mechanics is one subset of biomimetics, a discipline which has received increased attention over the last decade, with numerous faculties and degree courses devoted solely to exploring ‘nature as a model’ for engineering applications. To save locomotion energy, evolution has optimized the design of animals such that friction loss is minimized. In addition to many morphological adaptations, animals that are often exposed to water or air currents have developed special behaviors that allow them to use the energy contained in air or water fluctuations for energy savings. Such flow manipulation and control is not only important for many animals, but also for many engineering applications. Since living beings have been optimized by several million years of evolution it is very likely that many engineering discipl...
Vaughan, O. H., Jr.; Hung, R. J.
1975-01-01
Skylab 4 crew members performed a series of demonstrations showing the oscillations, rotations, as well as collision coalescence of water droplets which simulate various physical models of fluids under low gravity environment. The results from Skylab demonstrations provide information and illustrate the potential of an orbiting space-oriented research laboratory for the study of more sophisticated fluid mechanic experiments. Experiments and results are discussed.
Directory of Open Access Journals (Sweden)
Pedro Javier Gamez-Montero
2015-03-01
Full Text Available “Mechanics” and “Fluids” are familiar concepts for any newly-registered engineering student. However, when combined into the term “Fluid Mechanics”, students are thrust into the great unknown. The present article demonstrates the process of adaptation employed by the Fluid Mechanics course in the undergraduate engineering program, along with the teaching methodology, teaching materials and results obtained, evaluating the final objective in terms of student satsfaction and level of learning.
Transport equations, Level Set and Eulerian mechanics. Application to fluid-structure coupling
International Nuclear Information System (INIS)
Maitre, E.
2008-11-01
My works were devoted to numerical analysis of non-linear elliptic-parabolic equations, to neutron transport equation and to the simulation of fabrics draping. More recently I developed an Eulerian method based on a level set formulation of the immersed boundary method to deal with fluid-structure coupling problems arising in bio-mechanics. Some of the more efficient algorithms to solve the neutron transport equation make use of the splitting of the transport operator taking into account its characteristics. In the present work we introduced a new algorithm based on this splitting and an adaptation of minimal residual methods to infinite dimensional case. We present the case where the velocity space is of dimension 1 (slab geometry) and 2 (plane geometry) because the splitting is simpler in the former
Analytical approach to linear fractional partial differential equations arising in fluid mechanics
International Nuclear Information System (INIS)
Momani, Shaher; Odibat, Zaid
2006-01-01
In this Letter, we implement relatively new analytical techniques, the variational iteration method and the Adomian decomposition method, for solving linear fractional partial differential equations arising in fluid mechanics. The fractional derivatives are described in the Caputo sense. The two methods in applied mathematics can be used as alternative methods for obtaining analytic and approximate solutions for different types of fractional differential equations. In these methods, the solution takes the form of a convergent series with easily computable components. The corresponding solutions of the integer order equations are found to follow as special cases of those of fractional order equations. Some numerical examples are presented to illustrate the efficiency and reliability of the two methods
Mosquitoes drink with a burst in reserve: explaining pumping behavior with a fluid mechanics model
Chatterjee, Souvick; Socha, Jake; Stremler, Mark
2014-11-01
Mosquitoes drink using a pair of in-line pumps in the head that draw liquid food through the proboscis. Experimental observations with synchrotron x-ray imaging indicate two modes of drinking: a predominantly occurring continuous mode, in which the cibarial and pharyngeal pumps expand cyclically at a constant phase difference, and an occasional, isolated burst mode, in which the pharyngeal pump expansion is 10 to 30 times larger than in the continuous mode. We have used a reduced order model of the fluid mechanics to hypothesize an explanation of this variation in drinking behavior. Our model results show that the continuous mode is more energetically efficient, whereas the burst mode creates a large pressure drop across the proboscis, which could potentially be used to clear blockages. Comparisons with pump knock-out configurations demonstrate different functional roles of the pumps in mosquito feeding. This material is based upon work supported by the NSF under Grant No. #0938047.
Thermal and Fluid Mechanical Investigation of an Internally Cooled Piston Rod
Klotsche, K.; Thomas, C.; Hesse, U.
2017-08-01
The Internal Cooling of Reciprocating Compressor Parts (ICRC) is a promising technology to reduce the temperature of the thermally stressed piston and piston rod of process gas compressors. The underlying heat transport is based on the flow of a two-phase cooling medium that is contained in the hollow reciprocating assembly. The reciprocating motion forces the phases to mix, enabling an enhanced heat transfer. In order to investigate this heat transfer, experimental results from a vertically reciprocating hollow rod are presented that show the influence of different liquid charges for different working temperatures. In addition, pressure sensors are used for a crank angle dependent analysis of the fluid mechanical processes inside the rod. The results serve to investigate the two-phase flow in terms of the velocity and distribution of the liquid and vapour phase for different liquid fractions.
Energy Technology Data Exchange (ETDEWEB)
NONE
1996-10-01
The Engineering Research Program is charged with the identification, initiation, and management of fundamental research on broad, generic topics addressing energy-related engineering problems. Its stated goals are: (1) to improve and extend the body of knowledge underlying current engineering practice so as to create new options for enhancing energy savings and production, for prolonging useful life of energy-related structures and equipment and for developing advanced manufacturing technologies and materials processing with emphasis on reducing costs with improved industrial production and performance quality; (2) to expand the store of fundamental concepts for solving anticipated and unforeseen engineering problems in the energy technologies. The 26 papers in this proceedings are arranged in the following topical sections: superconductors (4 papers); materials (7); controls (4); fluid mechanics (7); and thin films (4). Papers have been processed separately for inclusion on the data base.
Energy Technology Data Exchange (ETDEWEB)
Watson, R.
1995-07-01
Waterflooding is the most commonly used secondary oil recovery technique. One of the requirements for understanding waterflood performance is a good knowledge of the basic properties of the reservoir rocks. This study is aimed at correlating rock-pore characteristics to oil recovery from various reservoir rock types and incorporating these properties into empirical models for Predicting oil recovery. For that reason, this report deals with the analyses and interpretation of experimental data collected from core floods and correlated against measurements of absolute permeability, porosity. wettability index, mercury porosimetry properties and irreducible water saturation. The results of the radial-core the radial-core and linear-core flow investigations and the other associated experimental analyses are presented and incorporated into empirical models to improve the predictions of oil recovery resulting from waterflooding, for sandstone and limestone reservoirs. For the radial-core case, the standardized regression model selected, based on a subset of the variables, predicted oil recovery by waterflooding with a standard deviation of 7%. For the linear-core case, separate models are developed using common, uncommon and combination of both types of rock properties. It was observed that residual oil saturation and oil recovery are better predicted with the inclusion of both common and uncommon rock/fluid properties into the predictive models.
Directory of Open Access Journals (Sweden)
Randa Aly Soliman
2015-04-01
Conclusions: Baseline stroke volume variation ⩾8.15% predicted fluid responsiveness in mechanically ventilated patients with acute circulatory failure. The study also confirmed the ability of pulse pressure variation to predict fluid responsiveness.
International Nuclear Information System (INIS)
Laval, H.
1981-01-01
This report describes the theoretical and numerical aspects of the finite element computer code CONVEC designed for the transient analysis of two-dimensional plane or three-dimensional axisymmetric incompressible flows including the effects of heat transfer. The governing equations for the above class of problems are the time-dependent incompressible Navier-Stokes equations and the thermal energy equation. The general class of flow problems analysed by CONVEC is discussed and the equations for the initial-boundary value problem are represented. A brief description of the finite element method and the weighted residual formulation is presented. The numerical solution of the incompressible equations is achieved by using a fractional step method. The mass lumping process associated with an explicit time integration scheme is described. The time integration is analysed and the stability conditions are derived. Numerical applications are presented. Standard problems of natural and forced convection are solved and the solutions obtained are compared with other numerical solutions published in the literature
International Nuclear Information System (INIS)
Minkin, V.I.; Minyaev, R.M.
1975-01-01
The energy characteristics and electron distributions were calculated for the fundamental and transitional states in topomerization of configuration of sulfo-, selenium and tellurium-uranium compounds of the AX 4 type. Also mapping of the potential energies was made for the predominant topomerization mechanisms. The mechanisms were classified into rearrangement types according to exchange-responsible apical and equatorial ligands. The physical mechanisms of the topomerization were determined on the basis of symmetry requirements for transitional configuration with respect to non-interchanging ligands. The lowest activation barrier was characteristic for the Berry mechanism of pseudorotation; however, other mechanism (the lever and pyramidal type) can compete with the Berry mechanisms. The expanded method of Hukkel does not give correct values for the relative energy of the fundamental and transitional configurations for sulfouranium molecules and their analogs for two of the three exchange mechanisms examined. Tunnel ligand-exchange mechanism cannot compete with the kinetic path of psudorotation reaction even at very low temperatures
International Nuclear Information System (INIS)
Esquivel, R.O.; Flores-Gallegos, N.; Iuga, C.; Carrera, E.M.; Angulo, J.C.; Antolin, J.
2010-01-01
The information-theoretic description of the course of two elementary chemical reactions allows a phenomenological description of the chemical course of the hydrogenic abstraction and the S N 2 identity reactions by use of Shannon entropic measures in position and momentum spaces. The analyses reveal their synchronous/asynchronous mechanistic behavior.
Receptor-mediated mechanism for the transport of prolactin from blood to cerebrospinal fluid
International Nuclear Information System (INIS)
Walsh, R.J.; Slaby, F.J.; Posner, B.I.
1987-01-01
Prolactin (PRL) interacts with areas of the central nervous system which reside behind the blood-brain barrier. While vascular PRL does not cross this barrier, it is readily accessible to the cerebrospinal fluid (CSF) from which it may gain access to the PRL-responsive areas of the brain. Studies were undertaken to characterize the mechanism responsible for the translocation of PRL from blood to CSF. Rats were given external jugular vein injections of [ 125 -I]iodo-PRL in the presence or absence of an excess of unlabeled ovine PRL (oPRL), human GH, bovine GH, or porcine insulin. CSF and choroid plexus were removed 60 min later. CSF samples were electrophoresed on sodium dodecyl sulfate-polyacrylamide slab gels and resultant autoradiographs were analyzed with quantitative microdensitometry. The data revealed that unlabeled lactogenic hormones, viz. oPRL and human GH, caused a statistically significant inhibition of [ 125 I]iodo-PRL transport from blood to CSF. In contrast, nonlactogenic hormones, viz bovine GH and insulin, had no effect on [ 125 I]iodo-PRL transport into the CSF. An identical pattern of competition was observed in the binding of hormone to the choroid plexus. Furthermore, vascular injections of [ 125 I]iodo-PRL administered with a range of concentrations of unlabeled oPRL revealed a dose-response inhibition in the transport of [ 125 I]iodo-PRL from blood to CSF. The study demonstrates that PRL enters the CSF by a specific, PRL receptor-mediated transport mechanism. The data is consistent with the hypothesis that the transport mechanism resides at the choroid plexus. The existence of this transport mechanism reflects the importance of the cerebroventricular system in PRL-brain interactions
Directory of Open Access Journals (Sweden)
Gregory C Burgess
2010-09-01
Full Text Available A critical aspect of executive control is the ability to limit the adverse effects of interference. Previous studies have shown activation of left ventrolateral prefrontal cortex after the onset of interference, suggesting that interference may be resolved in a reactive manner. However, we suggest that interference control may also operate in a proactive manner to prevent effects of interference. The current study investigated the temporal dynamics of interference control by varying two factors - interference expectancy and fluid intelligence (gF - that could influence whether interference control operates proactively versus reactively.A modified version of the recent negatives task was utilized. Interference expectancy was manipulated across task blocks by changing the proportion of recent negative (interference trials versus recent positive (facilitation trials. Furthermore, we explored whether gF affected the tendency to utilize specific interference control mechanisms. When interference expectancy was low, activity in lateral prefrontal cortex replicated prior results showing a reactive control pattern (i.e., interference-sensitivity during probe period. In contrast, when interference expectancy was high, bilateral prefrontal cortex activation was more indicative of proactive control mechanisms (interference-related effects prior to the probe period. Additional results suggested that the proactive control pattern was more evident in high gF individuals, whereas the reactive control pattern was more evident in low gF individuals.The results suggest the presence of two neural mechanisms of interference control, with the differential expression of these mechanisms modulated by both experimental (e.g., expectancy effects and individual difference (e.g., gF factors.
Directory of Open Access Journals (Sweden)
Chivukula VK
2015-01-01
Full Text Available Venkat Keshav Chivukula,1 Benjamin L Krog,1,2 Jones T Nauseef,2 Michael D Henry,2 Sarah C Vigmostad1 1Department of Biomedical Engineering, 2Department of Molecular Physiology and Biophysics, Holden Comprehensive Cancer Center, University of Iowa, Seamans Center for the Engineering Arts and Sciences, Iowa City, IA, USA Abstract: Over 90% of cancer deaths result not from primary tumor development, but from metastatic tumors that arise after cancer cells circulate to distal sites via the circulatory system. While it is known that metastasis is an inefficient process, the effect of hemodynamic parameters such as fluid shear stress (FSS on the viability and efficacy of metastasis is not well understood. Recent work has shown that select cancer cells may be able to survive and possibly even adapt to FSS in vitro. The current research seeks to characterize the effect of FSS on the mechanical properties of suspended cancer cells in vitro. Nontransformed prostate epithelial cells (PrEC LH and transformed prostate cancer cells (PC-3 were used in this study. The Young's modulus was determined using micropipette aspiration. We examined cells in suspension but not exposed to FSS (unsheared and immediately after exposure to high (6,400 dyn/cm2 and low (510 dyn/cm2 FSS. The PrEC LH cells were ~140% stiffer than the PC-3 cells not exposed to FSS. Post-FSS exposure, there was an increase of ~77% in Young's modulus after exposure to high FSS and a ~47% increase in Young's modulus after exposure to low FSS for the PC-3 cells. There was no significant change in the Young's modulus of PrEC LH cells post-FSS exposure. Our findings indicate that cancer cells adapt to FSS, with an increased Young's modulus being one of the adaptive responses, and that this adaptation is specific only to PC-3 cells and is not seen in PrEC LH cells. Moreover, this adaptation appears to be graded in response to the magnitude of FSS experienced by the cancer cells. This is the first study
Thermal, mechanical and fluid flow aspects of the high power beam dump for FRIB
Energy Technology Data Exchange (ETDEWEB)
Avilov, Mikhail [Facility for Rare Isotope Beams, Michigan State University, East Lansing, MI 48824 (United States); Aaron, Adam [Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831 (United States); Amroussia, Aida [Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824 (United States); Bergez, Wladimir [Institut de Mecanique des Fluides de Toulouse, Toulouse University, CNRS, Allée Camille Soula, 31400 Toulouse (France); Boehlert, Carl [Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824 (United States); Burgess, Thomas; Carroll, Adam [Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831 (United States); Colin, Catherine [Institut de Mecanique des Fluides de Toulouse, Toulouse University, CNRS, Allée Camille Soula, 31400 Toulouse (France); Durantel, Florent [Centre des recherches sur les Ions, les Materiaux et la Photonique (CIMAP) CEA-CNRS-ENSICAEN-UCN, BP 5133, 14070 CAEN CEDEX 5 (France); Ferrante, Paride; Fourmeau, Tiffany [Facility for Rare Isotope Beams, Michigan State University, East Lansing, MI 48824 (United States); Graves, Van [Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831 (United States); Grygiel, Clara [Centre des recherches sur les Ions, les Materiaux et la Photonique (CIMAP) CEA-CNRS-ENSICAEN-UCN, BP 5133, 14070 CAEN CEDEX 5 (France); Kramer, Jacob [Facility for Rare Isotope Beams, Michigan State University, East Lansing, MI 48824 (United States); Mittig, Wolfgang [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Monnet, Isabelle [Centre des recherches sur les Ions, les Materiaux et la Photonique (CIMAP) CEA-CNRS-ENSICAEN-UCN, BP 5133, 14070 CAEN CEDEX 5 (France); Patel, Harsh [Facility for Rare Isotope Beams, Michigan State University, East Lansing, MI 48824 (United States); and others
2016-06-01
The Facility for Rare Isotope Beams (FRIB) under construction at Michigan State University is based on a 400 kW heavy ion accelerator and uses in-flight production and separation to generate rare isotope beams. The first section of the fragment separator houses the rare isotope production target, and the primary beam dump to stop the unreacted primary beam. The experimental program will use 400 kW ion beams from {sup 16}O to {sup 238}U. After interaction with the production target, over 300 kW in remaining beam power must be absorbed by the beam dump. A rotating water-cooled thin-shell metal drum was chosen as the basic concept for the beam dump. Extensive thermal, mechanical and fluid flow analyses were performed to evaluate the effects of the high power density in the beam dump shell and in the water. Many properties were optimized simultaneously, such as shell temperature, mechanical strength, fatigue strength, and radiation resistance. Results of the analyses of the beam dump performance with different design options will be discussed. For example, it was found that a design modification to the initial water flow pattern resulted in a substantial increase in the wall heat transfer coefficient. A detailed evaluation of materials for the shell is in progress. The widely used titanium alloy, Ti–6Al–4V (wt%), is presently considered as the best candidate, and is the subject of specific tests, such as studies of performance under heavy ion irradiation.
Sedov, L
1968-01-01
At its meeting on April 23, 1965 in Paris the Bureau of IUTAM decided to have a Symposium on the Irreversible Aspects of Continaum Mechanics held in June 1966 in Vienna. In addition, a Symposium on the Transfer of Physical Characteristics in Moving Fluids which, orig inally, had been scheduled to take place in Stockholm was rescheduled to be held in Vienna immediately following the Symposium on the Irre versible Aspects of Continuum Mechanics. It was felt that the subjects of the two symposia were so closely related that participants should be given an opportunity to attend both. Both decisions were unanimously approved by the members of the General Assembly of IUTAM. Prof. H. PARKUS, Vienna, was appointed Chairman of the Symposium on the Irreversible Aspects, and Prof. L. I. SEDOV, Moscow, was appointed Chairman of the Symposium on the Transfer of Physical Characteristics, with Prof. P ARKUS being re sponsible for the local organization of both symposia. In accordance with the policy set forth by IUTAM...
An in-pipe mobile micromachine using fluid power. A mechanism adaptable to pipe diameters
International Nuclear Information System (INIS)
Yoshida, Kazuhiro; Yokota, Shinichi; Takahashi, Ken
2000-01-01
To realize micro maintenance robots for small diameter pipes of nuclear reactors and so on, high power in-pipe mobile micromachines have been required. The authors have proposed the bellows microactuator using fluid power and have tried to apply the actuators to in-pipe mobile micromachines. In the previous papers, some inchworm mobile machine prototypes with 25 mm in diameter are fabricated and the traveling performances are experimentally investigated. In this paper, to miniaturize the in-pipe mobile machine and to make it adaptable to pipe diameters, firstly, a simple rubber-tube actuator constrained with a coil-spring is proposed and the static characteristics are investigated. Secondly, a supporting mechanism which utilizes a toggle mechanism and is adaptable to pipe diameters is proposed and the supporting forces are investigated. Finally, an in-pipe mobile micromachine for pipe with 4 - 5 mm in diameter is fabricated and the maximum traveling velocity of 7 mm/s in both ahead and astern movements is experimentally verified. (author)
Influence of Reduced Mass Flow Rate and Chamber Backpressure on Swirl Injector Fluid Mechanics
Kenny, R Jeremy; Hulka, James R.
2008-01-01
Industry interest in variable-thrust liquid rocket engines places a demand on engine injector technology to operate over a wide range of liquid mass flow rates and chamber backpressures. One injection technology of current interest for variable thrust applications is an injector design with swirled fluids. Current swirl injector design methodologies do not take into account how swirl injector design parameters respond to elevated chamber backpressures at less than design mass flow rates. The current work was created to improve state-of-the-art swirl injector design methods in this area. The specific objective was to study the effects of elevated chamber backpressure and off-design mass flow rates on swirl injector fluid mechanics. Using a backpressure chamber with optical access, water was flowed through a swirl injector at various combinations of chamber backpressure and mass flow rates. The film thickness profile down the swirl injector nozzle section was measured through a transparent nozzle section of the injector. High speed video showed measurable increases in the film thickness profile with application of chamber backpressure and mass flow rates less than design. At prescribed combinations of chamber backpressure and injected mass flow rate, a discrete change in the film thickness profile was observed. Measured injector discharge coefficient values showed different trends with increasing chamber backpressure at low mass flow rates as opposed to near-design mass flow rates. Downstream spray angles showed classic changes in morphology as the mass flow rate was decreased below the design value. Increasing chamber backpressure decreased the spray angle at any injection mass flow rate. Experimental measurements and discussion of these results are reported in this paper.
Studies on the mechanism of action of enterotoxin-induced fluid secretion in the gut
International Nuclear Information System (INIS)
Schirgi-Degen, A.
1992-12-01
The mechanism of action of Clostridium difficile enterotoxin A (CA), of Escherichia coli enterotoxin (STa) and of cholera toxin (CT), which are known to cause severe diarrhea, were studied in a preparation of ligated jejunal loops of anesthetized rats in vivo. The toxins were administered intraluminally. Pharmacological agents, which were tested for their potency to influence toxin-related effects, were administered subcutaneously. Net fluid transport was determined gravimetrically, prostaglandin (PG) E 2 -output into the lumen, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) contents in the mucosa were measured by radioimmunoassay, serotonin-(5-HT)-output into the lumen was determined by high performance liquid chromatography. The histopathological effects of CA and CT were examined by light- and scanning electron microscopy. All three toxins caused net fluid secretion (FS). 5-HT 2 -(ketanserin) and 5-HT 3 -receptor antagonists (tropisetron, ondansetron, granisetron) dose-dependently reduced or abolished CT- and STa-induced net FS, CA-induced net FS was not influenced. Indomethacin reduced CA-, CT- and STa-induced net FS. Elevation of PGE 2 -output occurred after exposure to CA and CT and was reduced by indomethacin. CA caused severe histopathological lesions and also CT time-dependently caused morphological changes, which may take part in the secretory response. It is concluded that 5-HT, using both 5-HT 2 - and 5-HT 3 -receptors, mediates CT- and STa, but not CA-induced FS. PGE 2 is involved in FS caused by all three toxins. CAMP and cGMP are presumedly no causative mediators of toxin-induced FS
Theoretical model for the mechanical behavior of prestressed beams under torsion
Directory of Open Access Journals (Sweden)
Sérgio M.R. Lopes
2014-12-01
Full Text Available In this article, a global theoretical model previously developed and validated by the authors for reinforced concrete beams under torsion is reviewed and corrected in order to predict the global behavior of beams under torsion with uniform longitudinal prestress. These corrections are based on the introduction of prestress factors and on the modification of the equilibrium equations in order to incorporate the contribution of the prestressing reinforcement. The theoretical results obtained with the new model are compared with some available results of prestressed concrete (PC beams under torsion found in the literature. The results obtained in this study validate the proposed computing procedure to predict the overall behavior of PC beams under torsion.
International Nuclear Information System (INIS)
Creton, N.; Optasanu, V.; Montesin, T.; Garruchet, S.
2008-01-01
This paper offers a study of oxygen dissolution into a solid, and its consequences on the mechanical behaviour of the material. In fact, mechanical strains strongly influence the oxidation processes and may be, in some materials, responsible for cracking. To realize this study, mechanical considerations are introduced into the classical diffusion laws. Simulations were made for the particular case of uranium dioxide, which undergoes the chemical fragmentation. According to our simulations, the hypothesis of a compression stress field into the oxidised UO 2 compound near the internal interface is consistent with some oxidation mechanisms of oxidation experimentally observed. More generally, this work will be extended to the simulation to an oxide layer growth on a metallic substrate. (authors)
Directory of Open Access Journals (Sweden)
Cho Nam Ng
Full Text Available Common-pool resource (CPR dilemmas distinguish themselves from general public good problems by encompassing both social and physical features. This paper examines how a physical mechanism, namely asymmetric payoff; and a social mechanism, reciprocity; simultaneously affect collective cooperation in theoretical water sharing interactions. We present an iterative N-person game theoretic model to investigate the joint effects of these two mechanisms in a linear fully connected river system under three information assumptions. From a simple evolutionary perspective, this paper quantitatively addresses the conditions for Nash Equilibrium in which collective cooperation might be established. The results suggest that direct reciprocity increases every actor's motivation to contribute to the collective good of the river system. Meanwhile, various upstream and downstream actors manifest individual disparities as a result of the direct reciprocity and asymmetric payoff mechanisms. More specifically, the downstream actors are less willing to cooperate unless there is a high probability that long-term interactions are ensured; however, a greater level of asymmetries is likely to increase upstream actors' incentives to cooperate even though the interactions could quickly end. The upstream actors also display weak sensitivity to an increase in the total number of actors, which generally results in a reduction in the other actors' motivation for cooperation. It is also shown that the indirect reciprocity mechanism relaxes the overall conditions for cooperative Nash Equilibrium.
The physical vulnerability of elements at risk: a methodology based on fluid and classical mechanics
Mazzorana, B.; Fuchs, S.; Levaggi, L.
2012-04-01
The impacts of the flood events occurred in autumn 2011 in the Italian regions Liguria and Tuscany revived the engagement of the public decision makers to enhance in synergy flood control and land use planning. In this context, the design of efficient flood risk mitigation strategies and their subsequent implementation critically relies on a careful vulnerability analysis of both, the immobile and mobile elements at risk potentially exposed to flood hazards. Based on fluid and classical mechanics notions we developed computation schemes enabling for a dynamic vulnerability and risk analysis facing a broad typological variety of elements at risk. The methodological skeleton consists of (1) hydrodynamic computation of the time-varying flood intensities resulting for each element at risk in a succession of loading configurations; (2) modelling the mechanical response of the impacted elements through static, elasto-static and dynamic analyses; (3) characterising the mechanical response through proper structural damage variables and (4) economic valuation of the expected losses as a function of the quantified damage variables. From a computational perspective we coupled the description of the hydrodynamic flow behaviour and the induced structural modifications of the elements at risk exposed. Valuation methods, suitable to support a correct mapping from the value domains of the physical damage variables to the economic loss values are discussed. In such a way we target to complement from a methodological perspective the existing, mainly empirical, vulnerability and risk assessment approaches to refine the conceptual framework of the cost-benefit analysis. Moreover, we aim to support the design of effective flood risk mitigation strategies by diminishing the main criticalities within the systems prone to flood risk.
Schertzer, D.; Falgarone, E.
1 Facts about the Workshop This workshop was convened on November 13-15 1995 by E. Falgarone and D. Schertzer within the framework of the Groupe de Recherche Mecanique des Fluides Geophysiques et Astrophysiques (GdR MFGA, Research Group of Geophysical and Astrophysical Fluid Mechanics) of Centre National de la Recherche Scientifique (CNRS, (French) National Center for Scientific Research). This Research Group is chaired by A. Babiano and the meeting was held at Ecole Normale Superieure, Paris, by courtesy of its Director E. Guyon. More than sixty attendees participated to this workshop, they came from a large number of institutions and countries from Europe, Canada and USA. There were twenty-five oral presentations as well as a dozen posters. A copy of the corresponding book of abstracts can be requested to the conveners. The theme of this meeting is somewhat related to the series of Nonlinear Variability in Geophysics conferences (NVAG1, Montreal, Aug. 1986; NVAG2, Paris, June 1988; NVAG3, Cargese (Corsica), September, 1993), as well as seven consecutive annual sessions at EGS general assemblies and two consecutive spring AGU meeting sessions devoted to similar topics. One may note that NVAG3 was a joint American Geophysical Union Chapman and European Geophysical Society Richardson Memorial conference, the first topical conference jointly sponsored by the two organizations. The corresponding proceedings were published in a special NPG issue (Nonlinear Processes in Geophysics 1, 2/3, 1994). In comparison with these previous meetings, MFGA-IDT2 is at the same time specialized to fluid turbulence and its intermittency, and an extension to the fields of astrophysics. Let us add that Nonlinear Processes in Geophysics was readily chosen as the appropriate journal for publication of these proceedings since this journal was founded in order to develop interdisciplinary fundamental research and corresponding innovative nonlinear methodologies in Geophysics. It had an
Directory of Open Access Journals (Sweden)
D. Schertzer
1996-01-01
Full Text Available 1 Facts about the Workshop This workshop was convened on November 13-15 1995 by E. Falgarone and D. Schertzer within the framework of the Groupe de Recherche Mecanique des Fluides Geophysiques et Astrophysiques (GdR MFGA, Research Group of Geophysical and Astrophysical Fluid Mechanics of Centre National de la Recherche Scientifique (CNRS, (French National Center for Scientific Research. This Research Group is chaired by A. Babiano and the meeting was held at Ecole Normale Superieure, Paris, by courtesy of its Director E. Guyon. More than sixty attendees participated to this workshop, they came from a large number of institutions and countries from Europe, Canada and USA. There were twenty-five oral presentations as well as a dozen posters. A copy of the corresponding book of abstracts can be requested to the conveners. The theme of this meeting is somewhat related to the series of Nonlinear Variability in Geophysics conferences (NVAG1, Montreal, Aug. 1986; NVAG2, Paris, June 1988; NVAG3, Cargese (Corsica, September, 1993, as well as seven consecutive annual sessions at EGS general assemblies and two consecutive spring AGU meeting sessions devoted to similar topics. One may note that NVAG3 was a joint American Geophysical Union Chapman and European Geophysical Society Richardson Memorial conference, the first topical conference jointly sponsored by the two organizations. The corresponding proceedings were published in a special NPG issue (Nonlinear Processes in Geophysics 1, 2/3, 1994. In comparison with these previous meetings, MFGA-IDT2 is at the same time specialized to fluid turbulence and its intermittency, and an extension to the fields of astrophysics. Let us add that Nonlinear Processes in Geophysics was readily chosen as the appropriate journal for publication of these proceedings since this journal was founded in order to develop interdisciplinary fundamental research and corresponding innovative nonlinear methodologies in Geophysics
[Application of fluid mechanics and simulation: urinary tract and ureteral catheters.
Gómez-Blanco, J C; Martínez-Reina, J; Cruz, D; Blas Pagador, J; Sánchez-Margallo, F M; Soria, F
2016-10-01
The mechanics of urine during its transport from the renal pelvis to the bladder is of great interest for urologists. The knowledge of the different physical variables and their interrelationship, both in physiologic movements and pathologies, will help a better diagnosis and treatment. The objective of this chapter is to show the physics principles and their most relevant basic relations in urine transport, and to bring them over the clinical world. For that, we explain the movement of urine during peristalsis, ureteral obstruction and in a ureter with a stent. This explanation is based in two tools used in bioengineering: the theoretical analysis through the Theory of concontinuous media and Ffluid mechanics and computational simulation that offers a practical solution for each scenario. Moreover, we review other contributions of bioengineering to the field of Urology, such as physical simulation or additive and subtractive manufacturing techniques. Finally, we list the current limitations for these tools and the technological development lines with more future projection. In this chapter we aim to help urologists to understand some important concepts of bioengineering, promoting multidisciplinary cooperation to offer complementary tools that help in diagnosis and treatment of diseases.
International Nuclear Information System (INIS)
Frisone, F.
2007-01-01
In this paper are illustrated the main features of tunneling traveling between two deuterons within a lattice. Considering the screening effect due lattice electrons we compare the d-d fusion rate evaluated from different authors assuming different screening efficiency and different d-d potentials. Then, we propose a effective potential which describe very well the attractive contribute due to plasmon exchange between two deuterons and by means of it we will compute the d-d fusion rates for different energy values. Finally the good agreement between theoretical and experimental results proves the reality of cold fusion phenomena and the reliability of our model
International Nuclear Information System (INIS)
Iwasa, Y.; Bobrov, E.S.; Tsukamoto, O.; Takaghi, T.; Fujita, H.; Massachusetts Inst. of Tech., Cambridge
1985-01-01
The theoretical correlation between shear stress and epoxy resin fracture developed in an earlier paper was verified experimentally using a series of epoxy-impregnated, thin-walled superconducting test coils. In test coils with both ends rigidly clamped, cracks occurred as transport current was increased; during a training sequence the test was terminated by a premature quench. Using acoustic emission and voltage signals, each premature quench was linked directly to a crack occurring near one of the ends. Test coils which had both ends unsupported, giving the winding freedom to expand radially, did not experience epoxy fracture and showed no premature quenches. (author)
Mechanics of granular-frictional-visco-plastic fluids in civil and mining engineering
Alehossein, H.; Qin, Z.
2013-10-01
The shear stress generated in mine backfill slurries and fresh concrete contains both velocity gradient dependent and frictional terms, categorised as frictional viscous plastic fluids. This paper discusses application of the developed analytical solution for flow rate as a function of pressure and pressure gradient in discs, pipes and cones for such frictional Bingham-Herschel-Bulkley fluids. This paper discusses application of this continuum fluid model to industrial materials like mine and mineral slurries, backfills and fresh concrete tests.
Elliott, Morgan; Martin, David
2015-01-01
For my summer internship project, I organized a pilot study to analyze the effects of a cephalic fluid shift on venous return and right ventricular mechanics to increase right ventricular and venous knowledge. To accomplish this pilot study, I wrote a testing protocol, obtained Institutional Review Board (IRB) approval, completed subject payment forms, lead testing sessions, and analyzed the data. This experiment used -20deg head down tilt (20 HDT) as the ground based simulation for the fluid shift that occurs during spaceflight and compared it to data obtained from the seated and supine positions. Using echocardiography, data was collected for the right ventricle, hepatic vein, internal jugular vein, external jugular vein, and inferior vena cava. Additionally, non-invasive venous pressure measurements, similar to those soon to be done in-orbit, were collected. It was determined that the venous return from below the heard is increased during 20 HDT, which was supported by increased hepatic vein velocities, increased right ventricular inflow, and increased right ventricular strain at 20 HDT relative to seated values. Jugular veins in the neck undergo an increase in pressure and area, but no significant increase in flow, relative to seated values when a subject is tilted 20 HDT. Contrary to the initial expectations based on this jugular flow, there was no significant increase in central venous pressure, as evidenced by no change in Doppler indices for right arterial pressure or inferior vena cava diameter. It is suspected that these differences in pressure are due to the hydrostatic pressure indifference point shifting during tilt; there is a potential for a similar phenomenon with microgravity. This data will hopefully lead to a more in-depth understanding of the response of the body to microgravity and how those relate to the previously mentioned cardiovascular risk of fluid shift that is associated with spaceflight. These results were presented in greater detail
Burgher, J. K.; Finkel, D.; Adesope, O. O.; Van Wie, B. J.
2015-01-01
This study used a within-subjects experimental design to compare the effects of learning with lecture and hands-on desktop learning modules (DLMs) in a fluid mechanics and heat transfer class. The hands-on DLM implementation included the use of worksheets and one of two heat exchangers: an evaporative cooling device and a shell and tube heat…
Han, Duanduan; Ugaz, Victor
2017-01-01
Three self-contained mini-labs were integrated into a core undergraduate fluid mechanics course, with the goal of delivering hands-on content in a manner scalable to large class sizes. These mini-labs supported learning objectives involving friction loss in pipes, flow measurement, and centrifugal pump analysis. The hands-on experiments were…
Energy Technology Data Exchange (ETDEWEB)
Fredriksson, Anders; Olofsson, Isabelle [Golder Associates AB, Uppsala (Sweden)
2005-12-15
The present report summarises the theoretical approach to estimate the mechanical properties of the rock mass in relation to the Preliminary Site Descriptive Modelling, version 1.2 Forsmark. The theoretical approach is based on a discrete fracture network (DFN) description of the fracture system in the rock mass and on the results of mechanical testing of intact rock and on rock fractures. To estimate the mechanical properties of the rock mass a load test on a rock block with fractures is simulated with the numerical code 3DEC. The location and size of the fractures are given by DFN-realisations. The rock block was loaded in plain strain condition. From the calculated relationship between stresses and deformations the mechanical properties of the rock mass were determined. The influence of the geometrical properties of the fracture system on the mechanical properties of the rock mass was analysed by loading 20 blocks based on different DFN-realisations. The material properties of the intact rock and the fractures were kept constant. The properties are set equal to the mean value of each measured material property. The influence of the variation of the properties of the intact rock and variation of the mechanical properties of the fractures are estimated by analysing numerical load tests on one specific block (one DFN-realisation) with combinations of properties for intact rock and fractures. Each parameter varies from its lowest values to its highest values while the rest of the parameters are held constant, equal to the mean value. The resulting distribution was expressed as a variation around the value determined with mean values on all parameters. To estimate the resulting distribution of the mechanical properties of the rock mass a Monte-Carlo simulation was performed by generating values from the two distributions independent of each other. The two values were added and the statistical properties of the resulting distribution were determined.
International Nuclear Information System (INIS)
Fredriksson, Anders; Olofsson, Isabelle
2005-12-01
The present report summarises the theoretical approach to estimate the mechanical properties of the rock mass in relation to the Preliminary Site Descriptive Modelling, version 1.2 Forsmark. The theoretical approach is based on a discrete fracture network (DFN) description of the fracture system in the rock mass and on the results of mechanical testing of intact rock and on rock fractures. To estimate the mechanical properties of the rock mass a load test on a rock block with fractures is simulated with the numerical code 3DEC. The location and size of the fractures are given by DFN-realisations. The rock block was loaded in plain strain condition. From the calculated relationship between stresses and deformations the mechanical properties of the rock mass were determined. The influence of the geometrical properties of the fracture system on the mechanical properties of the rock mass was analysed by loading 20 blocks based on different DFN-realisations. The material properties of the intact rock and the fractures were kept constant. The properties are set equal to the mean value of each measured material property. The influence of the variation of the properties of the intact rock and variation of the mechanical properties of the fractures are estimated by analysing numerical load tests on one specific block (one DFN-realisation) with combinations of properties for intact rock and fractures. Each parameter varies from its lowest values to its highest values while the rest of the parameters are held constant, equal to the mean value. The resulting distribution was expressed as a variation around the value determined with mean values on all parameters. To estimate the resulting distribution of the mechanical properties of the rock mass a Monte-Carlo simulation was performed by generating values from the two distributions independent of each other. The two values were added and the statistical properties of the resulting distribution were determined
Theoretical study on the mechanism of CH3NH2 and O3 ...
Indian Academy of Sciences (India)
CH3NH + OH + O2 adducts with one transition state is the most favoured path. Keywords. Ozone; calculation; reaction mechanism; potential energy profile; transition state. 1. Introduction ..... University of. Applied Science, Bielefeld, Germany.
Mechanisms of plasma-assisted catalyzed growth of carbon nanofibres: a theoretical modeling
Gupta, R.; Sharma, S. C.; Sharma, R.
2017-02-01
A theoretical model is developed to study the nucleation and catalytic growth of carbon nanofibers (CNFs) in a plasma environment. The model includes the charging of CNFs, the kinetics of the plasma species (neutrals, ions and electrons), plasma pretreatment of the catalyst film, and various processes unique to a plasma-exposed catalyst surface such as adsorption of neutrals, thermal dissociation of neutrals, ion induced dissociation, interaction between neutral species, stress exerted by the growing graphene layers and the growth of CNFs. Numerical calculations are carried out for typical glow discharge plasma parameters. It is found that the growth rate of CNFs decreases with the catalyst nanoparticle size. In addition, the effect of hydrogen on the catalyst nanoparticle size, CNF tip diameter, CNF growth rate, and the tilt angle of the graphene layers to the fiber axis are investigated. Moreover, it is also found that the length of CNFs increases with hydrocarbon number density. Our theoretical findings are in good agreement with experimental observations and can be extended to enhance the field emission characteristics of CNFs.
Analysis of fluid lubrication mechanisms in metal forming at mesoscopic scale
DEFF Research Database (Denmark)
Dubar, L.; Hubert, C.; Christiansen, Peter
2012-01-01
The lubricant entrapment and escape phenomena in metal forming are studied experimentally as well as numerically. Experiments are carried out in strip reduction of aluminium sheet applying a transparent die to study the fluid flow between mesoscopic cavities. The numerical analysis involves two...... computation steps. The first one is a fully coupled fluid-structure Finite Element computation, where pockets in the surface are plastically deformed leading to the pressurization of the entrapped fluid. The second step computes the fluid exchange between cavities through the plateaus of asperity contacts...
Balancing Venturi and Laissez-Faire Management Styles: Insights from Fluid Mechanical Analogs
Directory of Open Access Journals (Sweden)
Ruud Weijermars
2007-12-01
Full Text Available Mobilizing distributed Organizational Intelligence involves managerial efforts whereby the generation of new tacit knowledge requires dissemination of newly codified externalized knowledge. The managerial role in the early stage of knowledge creation is to support and stimulate the process of knowledge generation and to aid the diffusion of knowledge across organizational boundaries. In contrast, the subsequent 'harvesting' and goal-oriented application of knowledge requires convergence of human actors (H as carriers of distributed intelligence (DI. Optimization of the organizational performance and improved workflow efficiency is best effectuated by applying insights from fluid mechanical analogs. Several such analogs are introduced here and these provide insight that helps to funnel tacit and explicit knowledge into tangible asset value. Three sets of managerial lessons are inferred from the analogs: (1 Social bonding between professionals needs to be stimulated because professionals with strong social bonds (S can sustain effective workflows under relatively high pressures, while weak social bonds lead to turbulence and disruption; (2 Effective vision sharing is essential for goal-oriented and accelerated knowledge development in DI systems, and; (3 Managerial pressure may not overheat the critical limit that can be handled by resilient and strongly bonded DI networks, as this would result in disruptive turbulence even in experienced neural networks.
Directory of Open Access Journals (Sweden)
ROZGA, P.
2014-08-01
Full Text Available This article describes the measurement techniques used for the study of mechanisms of electrical discharge development in ester fluids under lightning impulse voltage. These techniques were applied in a laboratory experimental system which enabled the acquisition of a wide range of experimental data. An analysis of the data gives the possibility of assessing the processes responsible for electrical discharge propagation in different types of dielectric liquids. The photographic registration system provides photographs of developing discharges. This uses the shadowgraph method with an impulse laser as a flash lamp. The system of light emission registration enables collection of the time courses of light emitted by the developing discharge. Both systems operating together are synchronized using light guide communication. They are also unaffected by external disturbances such as network overvoltages and high electrical field stress. Preliminary results obtained on the basis of the described techniques, in the field of electrical discharge development in synthetic and natural esters, are presented in the article. These results confirm suitability of the methods used and give the possibility to formulate first conclusions.
Modelling the fluid mechanics of cilia and flagella in reproduction and development.
Montenegro-Johnson, Thomas D; Smith, Andrew A; Smith, David J; Loghin, Daniel; Blake, John R
2012-10-01
Cilia and flagella are actively bending slender organelles, performing functions such as motility, feeding and embryonic symmetry breaking. We review the mechanics of viscous-dominated microscale flow, including time-reversal symmetry, drag anisotropy of slender bodies, and wall effects. We focus on the fundamental force singularity, higher-order multipoles, and the method of images, providing physical insight and forming a basis for computational approaches. Two biological problems are then considered in more detail: 1) left-right symmetry breaking flow in the node, a microscopic structure in developing vertebrate embryos, and 2) motility of microswimmers through non-Newtonian fluids. Our model of the embryonic node reveals how particle transport associated with morphogenesis is modulated by the gradual emergence of cilium posterior tilt. Our model of swimming makes use of force distributions within a body-conforming finite-element framework, allowing the solution of nonlinear inertialess Carreau flow. We find that a three-sphere model swimmer and a model sperm are similarly affected by shear-thinning; in both cases swimming due to a prescribed beat is enhanced by shear-thinning, with optimal Deborah number around 0.8. The sperm exhibits an almost perfect linear relationship between velocity and the logarithm of the ratio of zero to infinite shear viscosity, with shear-thickening hindering cell progress.
Directory of Open Access Journals (Sweden)
A. A. Hemeda
2013-01-01
Full Text Available An extension of the so-called new iterative method (NIM has been used to handle linear and nonlinear fractional partial differential equations. The main property of the method lies in its flexibility and ability to solve nonlinear equations accurately and conveniently. Therefore, a general framework of the NIM is presented for analytical treatment of fractional partial differential equations in fluid mechanics. The fractional derivatives are described in the Caputo sense. Numerical illustrations that include the fractional wave equation, fractional Burgers equation, fractional KdV equation, fractional Klein-Gordon equation, and fractional Boussinesq-like equation are investigated to show the pertinent features of the technique. Comparison of the results obtained by the NIM with those obtained by both Adomian decomposition method (ADM and the variational iteration method (VIM reveals that the NIM is very effective and convenient. The basic idea described in this paper is expected to be further employed to solve other similar linear and nonlinear problems in fractional calculus.
Mosquito drinking with a burst in reserve: explaining behavior with a fluid mechanics model
Chatterjee, Souvick; Socha, Jake; Stremler, Mark
2014-03-01
Mosquitoes drink using a pair of in-line pumps in the head that draw liquid food through a long drinking channel, or proboscis. Experimental observations indicate two modes of drinking: a predominantly occurring continuous mode, in which the cibarial and pharyngeal pumps expand cyclically at a constant phase difference, and an isolated burst mode, in which the pharyngeal pump expansion is several orders of magnitude larger than in the continuous mode. We use a reduced order model of the fluid mechanics to hypothesize an explanation of this naturally occurring drinking behavior. Our model results show that the continuous mode is the more efficient mode in terms of energy expenditure, and the burst mode creates a large pressure difference across the proboscis. We speculate that the mosquito uses this pressure drop to clear blockages in the proboscis. We compared the two-pump system with one-pump configurations, as found in some other insects like butterflies, and show that the two pumps have unique roles in mosquito feeding.
Mechanics of Fluid-Filled Interstitial Gaps. II. Gap Characteristics in Xenopus Embryonic Ectoderm.
Barua, Debanjan; Parent, Serge E; Winklbauer, Rudolf
2017-08-22
The ectoderm of the Xenopus embryo is permeated by a network of channels that appear in histological sections as interstitial gaps. We characterized this interstitial space by measuring gap sizes, angles formed between adjacent cells, and curvatures of cell surfaces at gaps. From these parameters, and from surface-tension values measured previously, we estimated the values of critical mechanical variables that determine gap sizes and shapes in the ectoderm, using a general model of interstitial gap mechanics. We concluded that gaps of 1-4 μm side length can be formed by the insertion of extracellular matrix fluid at three-cell junctions such that cell adhesion is locally disrupted and a tension difference between cell-cell contacts and the free cell surface at gaps of 0.003 mJ/m 2 is generated. Furthermore, a cell hydrostatic pressure of 16.8 ± 1.7 Pa and an interstitial pressure of 3.9 ± 3.6 Pa, relative to the central blastocoel cavity of the embryo, was found to be consistent with the observed gap size and shape distribution. Reduction of cell adhesion by the knockdown of C-cadherin increased gap volume while leaving intracellular and interstitial pressures essentially unchanged. In both normal and adhesion-reduced ectoderm, cortical tension of the free cell surfaces at gaps does not return to the high values characteristic of the free surface of the whole tissue. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-10-01
The general purpose of the program has been the development of efficient algorithms, their implementation in codes of Computational Fluid Mechanics (CFD), and the experimental verification of these codes. Flows of both fundamental and applied nature has been investigated, including flows in industrial process equipment, about aerodynamics structures and ships, and flows over bed forms of importance for sediment transport. The experimental work has included the development of improved techniques, emphasizing optical methods. The objectives were realized through a coordinated experimental and theoretical/computation research program, organized in 6 specific projects: 1. CFD-methods and algorithms. 2. Special element simulation of ultrafiltration. 3. Turbulent swirling flows; 4. Near-wall models of turbulence and development of experimental techniques. 5. Flow over bed forms. 6. Flow past ship hull. (au)
Energy Technology Data Exchange (ETDEWEB)
Takada, Toshikazu [Research Program for Computational Science, RIKEN 2-1, Hirosawa, Wako, Saitama 351-0198 (Japan)
2007-07-15
The goal of this project is to understand the charge separation mechanisms in biological systems using the molecular orbital theories. Specially, the charge separation in the photosynthetic reaction center is focused on, since the efficiency in use of the solar energy is extraordinary and the reason for it is still kept unknown. Here, a QM/MM theoretical scheme is employed to take the effects of the surrounding proteins onto the pigments into account. To describe such excited electronic structures, a unified theory by MRSCI and DFT is newly invented. For atoms in the MM space, a new sampling method has also been created, based on the statistical physics. By using these theoretical framework, the excited and positively charged states of the special pair, that is, chlorophyll dimmer are planning to be calculated this year.
International Nuclear Information System (INIS)
Takada, Toshikazu
2007-01-01
The goal of this project is to understand the charge separation mechanisms in biological systems using the molecular orbital theories. Specially, the charge separation in the photosynthetic reaction center is focused on, since the efficiency in use of the solar energy is extraordinary and the reason for it is still kept unknown. Here, a QM/MM theoretical scheme is employed to take the effects of the surrounding proteins onto the pigments into account. To describe such excited electronic structures, a unified theory by MRSCI and DFT is newly invented. For atoms in the MM space, a new sampling method has also been created, based on the statistical physics. By using these theoretical framework, the excited and positively charged states of the special pair, that is, chlorophyll dimmer are planning to be calculated this year
Theoretical prediction of the mechanical properties of zeolitic imidazolate frameworks (ZIFs)
Zheng, Bin
2017-08-25
A good resistance against mechanical stress is essential for the utilization of metal-organic frameworks (MOFs) in practical applications such as gas sorption, separation, catalysis or energy conversion. Here, we report on the successful modification of the mechanical properties of zeolitic imidazolate frameworks (ZIFs) achieved through a substitution of the terminal group. The mechanical modulus of SALEM-2 was found to significantly improve when the -H groups at position 2 of the imidazole linkers were replaced with electron withdrawing groups (-CHO, -Cl, or -Br). The charge distribution and electron density were analyzed to reveal the mechanism behind the observed variation of the elastic stiffness. Furthermore, ZIF-I with a -I group at position 2 of the imidazole linkers was predicted to exhibit an excellent mechanical strength in our study and then prepared experimentally. The results indicate that an inconspicuous change of the structure of ZIFs, i.e., additional groups strengthening the ZnN4 tetrahedron, will lead to a stiffer framework.
Theoretical prediction of the mechanical properties of zeolitic imidazolate frameworks (ZIFs)
Zheng, Bin; Zhu, Yihan; Fu, Fang; Wang, Lian Li; Wang, Jinlei; Du, Huiling
2017-01-01
A good resistance against mechanical stress is essential for the utilization of metal-organic frameworks (MOFs) in practical applications such as gas sorption, separation, catalysis or energy conversion. Here, we report on the successful modification of the mechanical properties of zeolitic imidazolate frameworks (ZIFs) achieved through a substitution of the terminal group. The mechanical modulus of SALEM-2 was found to significantly improve when the -H groups at position 2 of the imidazole linkers were replaced with electron withdrawing groups (-CHO, -Cl, or -Br). The charge distribution and electron density were analyzed to reveal the mechanism behind the observed variation of the elastic stiffness. Furthermore, ZIF-I with a -I group at position 2 of the imidazole linkers was predicted to exhibit an excellent mechanical strength in our study and then prepared experimentally. The results indicate that an inconspicuous change of the structure of ZIFs, i.e., additional groups strengthening the ZnN4 tetrahedron, will lead to a stiffer framework.
Zhang, Weichao; Zhang, Dongju
2012-08-01
The potential energy surfaces for the OH + divinyl sulfoxide reaction in the presence of O2/NO are theoretically characterized at the CCSD(T)/6-311+G(d,p)//BH&HLYP/6-311++G(d,p)+ZPE level of theory. Various possible pathways including the direct hydrogen abstraction channels and the addition-elimination channels are considered. The calculations show that the exclusive feasible entrance channel is the formation of adduct CH2(OH)CHS(O)CHdbnd CH2 (IM1) in the initial reaction pathways. In the atmosphere, the newly formed adduct IM1 can further react with O2/NO to form the dominant products HCHO + C(O)HS(O)CHdbnd CH2 (P9). The calculated results confirm the experimental studies.
The non-equilibrium statistical mechanics of a simple geophysical fluid dynamics model
Verkley, Wim; Severijns, Camiel
2014-05-01
Lorenz [1] has devised a dynamical system that has proved to be very useful as a benchmark system in geophysical fluid dynamics. The system in its simplest form consists of a periodic array of variables that can be associated with an atmospheric field on a latitude circle. The system is driven by a constant forcing, is damped by linear friction and has a simple advection term that causes the model to behave chaotically if the forcing is large enough. Our aim is to predict the statistics of Lorenz' model on the basis of a given average value of its total energy - obtained from a numerical integration - and the assumption of statistical stationarity. Our method is the principle of maximum entropy [2] which in this case reads: the information entropy of the system's probability density function shall be maximal under the constraints of normalization, a given value of the average total energy and statistical stationarity. Statistical stationarity is incorporated approximately by using `stationarity constraints', i.e., by requiring that the average first and possibly higher-order time-derivatives of the energy are zero in the maximization of entropy. The analysis [3] reveals that, if the first stationarity constraint is used, the resulting probability density function rather accurately reproduces the statistics of the individual variables. If the second stationarity constraint is used as well, the correlations between the variables are also reproduced quite adequately. The method can be generalized straightforwardly and holds the promise of a viable non-equilibrium statistical mechanics of the forced-dissipative systems of geophysical fluid dynamics. [1] E.N. Lorenz, 1996: Predictability - A problem partly solved, in Proc. Seminar on Predictability (ECMWF, Reading, Berkshire, UK), Vol. 1, pp. 1-18. [2] E.T. Jaynes, 2003: Probability Theory - The Logic of Science (Cambridge University Press, Cambridge). [3] W.T.M. Verkley and C.A. Severijns, 2014: The maximum entropy