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)
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
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.
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
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.
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.
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
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 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...
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)
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.
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.
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:
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.
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 ...
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
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
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. 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)
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 ...
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.
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...
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.
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...
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.)
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)
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
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.
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.
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...
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.
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...
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...
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.
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
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...
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.
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.
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…
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.
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.
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.
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
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.
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
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...
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
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
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...
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 ...
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.
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.
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.
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
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
[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.
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
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
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 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.
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).
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...
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...
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.
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.
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.
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)
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
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
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.
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)
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.
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...
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
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.
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…
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.
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 ...
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…
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
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.
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
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
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.
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...
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,…
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.
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.
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
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.
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.
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.)
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.
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.
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.
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)
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
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
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
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)
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
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.
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
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)
[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.
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.
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.
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.
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.
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
"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."...
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.
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.
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...
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.
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.
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
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.
Wei, Wei; Gu, Zhaolin
2015-10-01
Particulates in natural and industrial flows have two basic forms: liquid (droplet) and solid (particle). Droplets would be charged in the presence of the applied electric field (e.g. electrospray). Similar to the droplet charging, particles can also be charged under the external electric field (e.g. electrostatic precipitator), while in the absence of external electric field, tribo-electrostatic charging is almost unavoidable in gas-solid two-phase flows due to the consecutive particle contacts (e.g. electrostatic in fluidized bed or wind-blown sand). The particle charging may be beneficial, or detrimental. Although electrostatics in particulate entrained fluid flow systems have been so widely used and concerned, the mechanisms of particulate charging are still lack of a thorough understanding. The motivation of this review is to explore a clear understanding of particulate charging and movement of charged particulate in two-phase flows, by summarizing the electrification mechanisms, physical models of particulate charging, and methods of charging/charged particulate entrained fluid flow simulations. Two effective methods can make droplets charged in industrial applications: corona charging and induction charging. The droplet charge to mass ratio by corona charging is more than induction discharge. The particle charging through collisions could be attributed to electron transfer, ion transfer, material transfer, and/or aqueous ion shift on particle surfaces. The charges on charged particulate surface can be measured, nevertheless, the charging process in nature or industry is difficult to monitor. The simulation method might build a bridge of investigating from the charging process to finally charged state on particulate surface in particulate entrained fluid flows. The methodology combining the interface tracking under the action of the applied electric with the fluid flow governing equations is applicable to the study of electrohydrodynamics problems. The charge
International Nuclear Information System (INIS)
Wei, Wei; Gu, Zhaolin
2015-01-01
Particulates in natural and industrial flows have two basic forms: liquid (droplet) and solid (particle). Droplets would be charged in the presence of the applied electric field (e.g. electrospray). Similar to the droplet charging, particles can also be charged under the external electric field (e.g. electrostatic precipitator), while in the absence of external electric field, tribo-electrostatic charging is almost unavoidable in gas–solid two-phase flows due to the consecutive particle contacts (e.g. electrostatic in fluidized bed or wind-blown sand). The particle charging may be beneficial, or detrimental. Although electrostatics in particulate entrained fluid flow systems have been so widely used and concerned, the mechanisms of particulate charging are still lack of a thorough understanding. The motivation of this review is to explore a clear understanding of particulate charging and movement of charged particulate in two-phase flows, by summarizing the electrification mechanisms, physical models of particulate charging, and methods of charging/charged particulate entrained fluid flow simulations. Two effective methods can make droplets charged in industrial applications: corona charging and induction charging. The droplet charge to mass ratio by corona charging is more than induction discharge. The particle charging through collisions could be attributed to electron transfer, ion transfer, material transfer, and/or aqueous ion shift on particle surfaces. The charges on charged particulate surface can be measured, nevertheless, the charging process in nature or industry is difficult to monitor. The simulation method might build a bridge of investigating from the charging process to finally charged state on particulate surface in particulate entrained fluid flows. The methodology combining the interface tracking under the action of the applied electric with the fluid flow governing equations is applicable to the study of electrohydrodynamics problems. The
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
Particulates in natural and industrial flows have two basic forms: liquid (droplet) and solid (particle). Droplets would be charged in the presence of the applied electric field (e.g. electrospray). Similar to the droplet charging, particles can also be charged under the external electric field (e.g. electrostatic precipitator), while in the absence of external electric field, tribo-electrostatic charging is almost unavoidable in gas–solid two-phase flows due to the consecutive particle contacts (e.g. electrostatic in fluidized bed or wind-blown sand). The particle charging may be beneficial, or detrimental. Although electrostatics in particulate entrained fluid flow systems have been so widely used and concerned, the mechanisms of particulate charging are still lack of a thorough understanding. The motivation of this review is to explore a clear understanding of particulate charging and movement of charged particulate in two-phase flows, by summarizing the electrification mechanisms, physical models of particulate charging, and methods of charging/charged particulate entrained fluid flow simulations. Two effective methods can make droplets charged in industrial applications: corona charging and induction charging. The droplet charge to mass ratio by corona charging is more than induction discharge. The particle charging through collisions could be attributed to electron transfer, ion transfer, material transfer, and/or aqueous ion shift on particle surfaces. The charges on charged particulate surface can be measured, nevertheless, the charging process in nature or industry is difficult to monitor. The simulation method might build a bridge of investigating from the charging process to finally charged state on particulate surface in particulate entrained fluid flows. The methodology combining the interface tracking under the action of the applied electric with the fluid flow governing equations is applicable to the study of electrohydrodynamics problems. The
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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
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.
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.
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.
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.
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
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.
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…
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.
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.
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.
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)
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
An experimental study of the fluid mechanics associated with porous walls
Ramachandran, N.; Heaman, J.; Smith, A.
1992-01-01
The fluid mechanics of air exiting from a porous material is investigated. The experiments are filter rating dependent, as porous walls with filter ratings differing by about three orders of magnitude are studied. The flow behavior is investigated for its spatial and temporal stability. The results from the investigation are related to jet behavior in at least one of the following categories: (1) jet coalescence effects with increasing flow rate; (2) jet field decay with increasing distance from the porous wall; (3) jet field temporal turbulence characteristics; and (4) single jet turbulence characteristics. The measurements show that coalescence effects cause jet development, and this development stage can be traced by measuring the pseudoturbulence (spatial velocity variations) at any flow rate. The pseudoturbulence variation with increasing mass flow reveals an initial increasing trend followed by a leveling trend, both of which are directly proportional to the filter rating. A critical velocity begins this leveling trend and represents the onset of fully developed jetting action in the flow field. A correlation is developed to predict the onset of fully developed jets in the flow emerging from a porous wall. The data further show that the fully developed jet dimensions are independent of the filter rating, thus providing a length scale for this type of flow field (1 mm). Individual jet characteristics provide another unifying trend with similar velocity decay behavior with distance; however, the respective turbulence magnitudes show vast differences between jets from the same sample. Measurements of the flow decay with distance from the porous wall show that the higher spatial frequency components of the jet field dissipate faster than the lower frequency components. Flow turbulence intensity measurements show an out of phase behavior with the velocity field and are generally found to increase as the distance from the wall is increased.
Pacheco, Ana P; Bedenice, Daniela; Mazan, Melissa R; Hoffman, Andrew M
2012-01-01
To evaluate respiratory mechanical function and bronchoalveolar lavage (BAL) cytologic results in healthy alpacas. 16 client-owned adult alpacas. Measurements of pulmonary function were performed, including functional residual capacity (FRC) via helium dilution, respiratory system resistance via forced oscillatory technique (FOT), and assessment of breathing pattern by use of respiratory inductive plethysmography (RIP) in standing and sternally recumbent alpacas. Bronchoalveolar lavage was performed orotracheally during short-term anesthesia. Mean ± SD measurements of respiratory function were obtained in standing alpacas for FRC (3.19 ± 0.53 L), tidal volume (0.8 ± 0.13 L), and respiratory system resistance at 1 Hz (2.70 ± 0.88 cm H(2)O/L/s), 2 Hz (2.98 ± 0.70 cm H(2)O/L/s), 3 Hz (3.14 ± 0.77 cm H(2)O/L/s), 5 Hz (3.45 ± 0.91 cm H(2)O/L/s), and 7 Hz (3.84 ± 0.93 cm H(2)O/L/s). Mean phase angle, as a measurement of thoracoabdominal asynchrony, was 19.59 ± 10.06°, and mean difference between nasal and plethysmographic flow measurements was 0.18 ± 0.07 L/s. Tidal volume, peak inspiratory flow, and peak expiratory flow were significantly higher in sternally recumbent alpacas than in standing alpacas. Cytologic examination of BAL fluid revealed 58.52 ± 12.36% alveolar macrophages, 30.53 ± 13.78% lymphocytes, 10.95 ± 9.29% neutrophils, 0% mast cells, and several ciliated epithelial cells. Pulmonary function testing was tolerated well in nonsedated untrained alpacas. Bronchoalveolar lavage in alpacas yielded samples with adequate cellularity that had a greater abundance of neutrophils than has been reported in horses.
Smoothed particle hydrodynamics modelling in continuum mechanics: fluid-structure interaction
Directory of Open Access Journals (Sweden)
Groenenboom P. H. L.
2009-06-01
Full Text Available Within this study, the implementation of the smoothed particle hydrodynamics (SPH method solving the complex problem of interaction between a quasi-incompressible fluid involving a free surface and an elastic structure is outlined. A brief description of the SPH model for both the quasi-incompressible fluid and the isotropic elastic solid is presented. The interaction between the fluid and the elastic structure is realised through the contact algorithm. The results of numerical computations are confronted with the experimental as well as computational data published in the literature.
Vapour loss (``boiling'') as a mechanism for fluid evolution in metamorphic rocks
Trommsdorff, Volkmar; Skippen, George
1986-11-01
The calculation of fluid evolution paths during reaction progress is considered for multicomponent systems and the results applied to the ternary system, CO2-H2O-NaCl. Fluid evolution paths are considered for systems in which a CO2-rich phase of lesser density (vapour) is preferentially removed from the system leaving behind a saline aqueous phase (liquid). Such “boiling” leads to enrichment of the residual aqueous phase in dissolved components and, for certain reaction stoichiometries, to eventual saturation of the fluids in salt components. Distinctive textures, particularly radiating growths of prismatic minerals such as tremolite or diopside, are associated with saline fluid inclusions and solid syngenetic salt inclusions at a number of field localities. The most thoroughly studied of these localities is Campolungo, Switzerland, where metasomatic rocks have developed in association with fractures and veins at 500° C and 2,000 bars of pressure. The petrography of these rocks suggests that fluid phase separation into liquid and vapour has been an important process during metasomatism. Fracture systems with fluids at pressure less than lithostatic may facilitate the loss of the less dense vapour phase to conditions of the amphibolite facies.
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.
Directory of Open Access Journals (Sweden)
Limei Tian
2015-11-01
Full Text Available Studies have shown that the structure of dolphin skin controls fluid media dynamically. Gaining inspiration from this phenomenon, a kind of bionic structural heterogeneous composite material was designed. The bionic structural heterogeneous composite material is composed of two materials: a rigid metal base layer with bionic structures and an elastic polymer surface layer with the corresponding mirror structures. The fluid control mechanism of the bionic structural heterogeneous composite material was investigated using a fluid–solid interaction method in ANSYS Workbench. The results indicated that the bionic structural heterogeneous composite material’s fluid control mechanism is its elastic deformation, which is caused by the coupling action between the elastic surface material and the bionic structure. This deformation can decrease the velocity gradient of the fluid boundary layer through changing the fluid–solid actual contact surface and reduce the frictional force. The bionic structural heterogeneous composite material can also absorb some energy through elastic deformation and avoid energy loss. The bionic structural heterogeneous composite material was applied to the impeller of a centrifugal pump in a contrast experiment, increasing the pump efficiency by 5% without changing the hydraulic model of the impeller. The development of this bionic structural heterogeneous composite material will be straightforward from an engineering point of view, and it will have valuable practical applications.
On the mechanical interaction between a fluid-filled fracture and the earth's surface
Pollard, D.D.; Holzhausen, G.
1979-01-01
The mechanical interaction between a fluid-filled fracture (e.g., hydraulic fracture joint, or igneous dike) and the earth's surface is analyzed using a two-dimensional elastic solution for a slit of arbitrary inclination buried beneath a horizontal free surface and subjected to an arbitrary pressure distribution. The solution is obtained by iteratively superimposing two fundamental sets of analytical solutions. For uniform internal pressure the slit behaves essentially as if it were in an infinite region if the depth-to-center is three times greater than the half-length. For shallower slits interaction with the free surface is pronounced: stresses and displacements near the slit differ by more than 10% from values for the deeply buried slit. The following changes are noted as the depth-to-center decreases: 1. (1) the mode I stress intensity factor increases for both ends of the slit, but more rapidly at the upper end; 2. (2) the mode II stress-intensity factor is significantly different from zero (except for vertical slits) suggesting propagation out of the original plane of the slit; 3. (3) displacements of the slit wall are asymmetric such that the slit gaps open more widely near the upper end. Similar changes are noted if fluid density creates a linear pressure gradient that is smaller than the lithostatic gradient. Under such conditions natural fractures should propagate preferentially upward toward the earth's surface requiring less pressure as they grow in length. If deformation near the surface is of interest, the model should account explicitly for the free surface. Stresses and displacements at the free surface are not approximated very well by values calculated along a line in an infinite region, even when the slit is far from the line. As depth-to-center of a shallow pressurized slit decreases, the following changes are noted: 1. (1) displacements of the free surface increase to the same order of magnitude as the displacements of the slit walls, 2. (2
Brom, Sarah Susanne; Schnitzspahn, Katharina Marlene; Melzer, Marlen; Hagner, Franziska; Bernhard, Anka; Kliegel, Matthias
2014-03-01
The aim of the present study was to test if a cognitive strategy improves older adults' prospective memory performance in a naturalistic health task. Moreover, it was tested if a possible strategy effect is moderated by individual differences. Therefore, a group of older adults was asked to perform a task taken from the medication adherence literature (i.e., blood pressure monitoring). Half of them were asked to form implementation intentions. Additionally, crystallized pragmatics and fluid mechanics, conscientiousness, self-efficacy, and lifestyle factors were assessed as possible moderators. Results showed a strong positive strategy effect on prospective memory. Moreover, the effect was qualified by a significant interaction and only emerged for participants with low levels in fluid mechanics. No other moderator showed an effect. In conclusion, an enhancing effect of implementation intentions on prospective memory seems to be dependent on individual differences in cognitive capacity and less related to key motivational or personality variables.
Mechanisms controlling the volume of pleural fluid and extravascular lung water
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G. Miserocchi
2009-12-01
Full Text Available Pleural and interstitial lung fluid volumes are strictly controlled and maintained at the minimum thanks to the ability of lymphatics to match the increase in filtration rate. In the pleural cavity, fluid accumulation is easily accommodated by retraction of lung and chest wall (high compliance of the pleural space; the increase of lymph flow per unit increase in pleural fluid volume is high due to the great extension of the parietal lymphatic. However, for the lung interstitium, the increase in lymph flow to match increased filtration does not need to be so great. In fact, increased filtration only causes a minor increase in extravascular water volume (<10% due to a marked increase in interstitial pulmonary pressure (low compliance of the extracellular matrix which, in turn, buffers further filtration. Accordingly, a less extended lymphatic network is needed. The efficiency of lymphatic control is achieved through a high lymphatic conductance in the pleural fluid and through a low interstitial compliance for the lung interstitium. Fluid volume in both compartments is so strictly controlled that it is difficult to detect initial deviations from the physiological state; thus, a great physiological advantage turns to be a disadvantage on a clinical basis as it prevents an early diagnosis of developing disease.
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.
Thermodynamic and fluid mechanic analysis of rapid pressurization in a dead-end tube
Leslie, Ian H.
1989-01-01
Three models have been applied to very rapid compression of oxygen in a dead-ended tube. Pressures as high as 41 MPa (6000 psi) leading to peak temperatures of 1400 K are predicted. These temperatures are well in excess of the autoignition temperature (750 K) of teflon, a frequently used material for lining hoses employed in oxygen service. These findings are in accord with experiments that have resulted in ignition and combustion of the teflon, leading to the combustion of the stainless steel braiding and catastrophic failure. The system analyzed was representative of a capped off-high-pressure oxygen line, which could be part of a larger system. Pressurization of the larger system would lead to compression in the dead-end line, and possible ignition of the teflon liner. The model consists of a large plenum containing oxygen at the desired pressure (500 to 6000 psi). The plenum is connected via a fast acting valve to a stainless steel tube 2 cm inside diameter. Opening times are on the order of 15 ms. Downstream of the valve is an orifice sized to increase filling times to around 100 ms. The total length from the valve to the dead-end is 150 cm. The distance from the valve to the orifice is 95 cm. The models describe the fluid mechanics and thermodynamics of the flow, and do not include any combustion phenomena. A purely thermodynamic model assumes filling to be complete upstream of the orifice before any gas passes through the orifice. This simplification is reasonable based on experiment and computer modeling. Results show that peak temperatures as high as 4800 K can result from recompression of the gas after expanding through the orifice. An approximate transient model without an orifice was developed assuming an isentropic compression process. An analytical solution was obtained. Results indicated that fill times can be considerably shorter than valve opening times. The third model was a finite difference, 1-D transient compressible flow model. Results from
Flippin' Fluid Mechanics - Quasi-experimental Pre-test and Post-test Comparison Using Two Groups
Webster, D. R.; Majerich, D. M.; Luo, J.
2014-11-01
A flipped classroom approach has been implemented in an undergraduate fluid mechanics course. Students watch short on-line videos before class, participate in active in-class problem solving (in dyads), and complete individualized on-line quizzes weekly. In-class activities are designed to achieve a trifecta of: 1. developing problem solving skills, 2. learning subject content, and 3. developing inquiry skills. The instructor and assistants provide critical ``just-in-time tutoring'' during the in-class problem solving sessions. Comparisons are made with a simultaneous section offered in a traditional mode by a different instructor. Regression analysis was used to control for differences among students and to quantify the effect of the flipped fluid mechanics course. The dependent variable was the students' combined final examination and post-concept inventory scores and the independent variables were pre-concept inventory score, gender, major, course section, and (incoming) GPA. The R-square equaled 0.45 indicating that the included variables explain 45% of the variation in the dependent variable. The regression results indicated that if the student took the flipped fluid mechanics course, the dependent variable (i.e., combined final exam and post-concept inventory scores) was raised by 7.25 points. Interestingly, the comparison group reported significantly more often that their course emphasized memorization than did the flipped classroom group.
Sheldon, Claire A; Kwon, Young Joon; Liu, Grant T; McCormack, Shana E
2015-02-01
Pseudotumor cerebri syndrome (PTCS) is defined by the presence of elevated intracranial pressure (ICP) in the setting of normal brain parenchyma and cerebrospinal fluid (CSF). Headache, vision changes, and papilledema are common presenting features. Up to 10% of appropriately treated patients may experience permanent visual loss. The mechanism(s) underlying PTCS is unknown. PTCS occurs in association with a variety of conditions, including kidney disease, obesity, and adrenal insufficiency, suggesting endocrine and/or metabolic derangements may occur. Recent studies suggest that fluid and electrolyte balance in renal epithelia is regulated by a complex interaction of metabolic and hormonal factors; these cells share many of the same features as the choroid plexus cells in the central nervous system (CNS) responsible for regulation of CSF dynamics. Thus, we posit that similar factors may influence CSF dynamics in both types of fluid-sensitive tissues. Specifically, we hypothesize that, in patients with PTCS, mitochondrial metabolites (glutamate, succinate) and steroid hormones (cortisol, aldosterone) regulate CSF production and/or absorption. In this integrated mechanism review, we consider the clinical and molecular evidence for each metabolite and hormone in turn. We illustrate how related intracellular signaling cascades may converge in the choroid plexus, drawing on evidence from functionally similar tissues.
International Nuclear Information System (INIS)
Prymak, O.; Klocke, A.; Kahl-Nieke, B.; Epple, M.
2003-01-01
The aim of this study was to analyze in vitro the fatigue resistance of nickel-titanium (NiTi) and CuNiTi orthodontic wires when subjected to forces and fluids which are present intraorally. The wires were subjected to dynamic mechanical analysis (DMA) while they were immersed into different fluids with mechanical loading parameters similar to those that are subjected in the mouth. The characteristic temperatures of transitions and a rough surface structure on the perimeter of the wires were determined by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively, before and after the DMA experiments. Stainless steel wires were used for comparison. In general, NiTi wires fractured earlier than the stainless steel specimens. Survival times were lower for the NiTi wires when immersed in fluids (water, citric acid, NaCl solution, artificial saliva, and fluoridated artificial saliva) than in air. SEM surface analysis showed that the NiTi and CuNiTi wires had a rougher surface than steel wires. The fracture occurred within a short number of loading cycles. Until fracture occurred, the mechanical properties remained mostly constant
Energy Technology Data Exchange (ETDEWEB)
Prymak, O.; Klocke, A.; Kahl-Nieke, B.; Epple, M
2003-07-25
The aim of this study was to analyze in vitro the fatigue resistance of nickel-titanium (NiTi) and CuNiTi orthodontic wires when subjected to forces and fluids which are present intraorally. The wires were subjected to dynamic mechanical analysis (DMA) while they were immersed into different fluids with mechanical loading parameters similar to those that are subjected in the mouth. The characteristic temperatures of transitions and a rough surface structure on the perimeter of the wires were determined by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively, before and after the DMA experiments. Stainless steel wires were used for comparison. In general, NiTi wires fractured earlier than the stainless steel specimens. Survival times were lower for the NiTi wires when immersed in fluids (water, citric acid, NaCl solution, artificial saliva, and fluoridated artificial saliva) than in air. SEM surface analysis showed that the NiTi and CuNiTi wires had a rougher surface than steel wires. The fracture occurred within a short number of loading cycles. Until fracture occurred, the mechanical properties remained mostly constant.
Pawaskar, Sainath Shrikant; Fisher, John; Jin, Zhongmin
2010-03-01
Contact detection in cartilage contact mechanics is an important feature of any analytical or computational modeling investigation when the biphasic nature of cartilage and the corresponding tribology are taken into account. The fluid flow boundary conditions will change based on whether the surface is in contact or not, which will affect the interstitial fluid pressurization. This in turn will increase or decrease the load sustained by the fluid phase, with a direct effect on friction, wear, and lubrication. In laboratory experiments or clinical hemiarthroplasty, when a rigid indenter or metallic prosthesis is used to apply load to the cartilage, there will not be any fluid flow normal to the surface in the contact region due to the impermeable nature of the indenter/prosthesis. In the natural joint, on the other hand, where two cartilage surfaces interact, flow will depend on the pressure difference across the interface. Furthermore, in both these cases, the fluid would flow freely in non-contacting regions. However, it should be pointed out that the contact area is generally unknown in advance in both cases and can only be determined as part of the solution. In the present finite element study, a general and robust algorithm was proposed to decide nodes in contact on the cartilage surface and, accordingly, impose the fluid flow boundary conditions. The algorithm was first tested for a rigid indenter against cartilage model. The algorithm worked well for two-dimensional four-noded and eight-noded axisymmetric element models as well as three-dimensional models. It was then extended to include two cartilages in contact. The results were in excellent agreement with the previous studies reported in the literature.
Bhandari, Pradeep; Dudik, Brenda; Birur, Gajanana; Karlmann, Paul; Bame, David; Mastropietro, A. J.
2012-01-01
For single phase mechanically pumped fluid loops used for thermal control of spacecraft, a gas charged accumulator is typically used to modulate pressures within the loop. This is needed to accommodate changes in the working fluid volume due to changes in the operating temperatures as the spacecraft encounters varying thermal environments during its mission. Overall, the three key requirements on the accumulator to maintain an appropriate pressure range throughout the mission are: accommodation of the volume change of the fluid due to temperature changes, avoidance of pump cavitation and prevention of boiling in the liquid. The sizing and design of such an accumulator requires very careful and accurate accounting of temperature distribution within each element of the working fluid for the entire range of conditions expected, accurate knowledge of volume of each fluid element, assessment of corresponding pressures needed to avoid boiling in the liquid, as well as the pressures needed to avoid cavitation in the pump. The appropriate liquid and accumulator strokes required to accommodate the liquid volume change, as well as the appropriate gas volumes, require proper sizing to ensure that the correct pressure range is maintained during the mission. Additionally, a very careful assessment of the process for charging both the gas side and the liquid side of the accumulator is required to properly position the bellows and pressurize the system to a level commensurate with requirements. To achieve the accurate sizing of the accumulator and the charging of the system, sophisticated EXCEL based spreadsheets were developed to rapidly come up with an accumulator design and the corresponding charging parameters. These spreadsheets have proven to be computationally fast and accurate tools for this purpose. This paper will describe the entire process of designing and charging the system, using a case study of the Mars Science Laboratory (MSL) fluid loops, which is en route to
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.
Siewert, S; Sämann, M; Schmidt, W; Stiehm, M; Falke, K; Grabow, N; Guthoff, R; Schmitz, K-P
2015-12-01
Glaucoma is the leading cause of irreversible blindness worldwide. In therapeutically refractory cases, alloplastic glaucoma drainage devices (GDD) are being increasingly used to decrease intraocular pressure. Current devices are mainly limited by fibrotic encapsulation and postoperative hypotension. Preliminary studies have described the development of a glaucoma microstent to control aqueous humour drainage from the anterior chamber into the suprachoroidal space. One focus of these studies was on the design of a micro-mechanical valve placed in the anterior chamber to inhibit postoperative hypotension. The present report describes the coupled analysis of fluid-structure interaction (FSI) as basis for future improvements in the design micro-mechanical valves. FSI analysis was carried out with ANSYS 14.5 software. Solid and fluid geometry were combined in a model, and the corresponding material properties of silicone (Silastic Rx-50) and water at room temperature were assigned. The meshing of the solid and fluid domains was carried out in accordance with the results of a convergence study with tetrahedron elements. Structural and fluid mechanical boundary conditions completed the model. The FSI analysis takes into account geometric non-linearity and adaptive remeshing to consider changing geometry. A valve opening pressure of 3.26 mmHg was derived from the FSI analysis and correlates well with the results of preliminary experimental fluid mechanical studies. Flow resistance was calculated from non-linear pressure-flow characteristics as 8.5 × 10(-3) mmHg/µl · min(-1) and 2.7 × 10(-3) mmHg/µl · min(-1), respectively before and after valve opening pressure is exceeded. FSI analysis indicated leakage flow before valve opening, which is due to the simplified model geometry. The presented bidirectional coupled FSI analysis is a powerful tool for the development of new designs of micro-mechanical valves for GDD and may help to minimise the time and cost
Kaminsky, R; Morbiducci, U; Rossi, M; Scalise, L; Verdonck, P; Grigioni, M
2007-02-01
Prosthetic heart valves (PHVs) have been used to replace diseased native valves for more than five decades. Among these, mechanical PHVs are the most frequently implanted. Unfortunately, these devices still do not achieve ideal behavior and lead to many complications, many of which are related to fluid mechanics. The fluid dynamics of mechanical PHVs are particularly complex and the fine-scale characteristics of such flows call for very accurate experimental techniques. Adequate temporal resolution can be reached by applying time-resolved PIV, a high-resolution dynamic technique which is able to capture detailed chronological changes in the velocity field. The aim of this experimental study is to investigate the evolution of the flow field in a detailed time domain of a commercial bileaflet PHV in a mock-loop mimicking unsteady conditions, by means of time-resolved 2D Particle Image Velocimetry (PIV). The investigated flow field corresponded to the region immediately downstream of the valve plane. Spatial resolution as in "standard" PIV analysis of prosthetic valve fluid dynamics was used. The combination of a Nd:YLF high-repetition-rate double-cavity laser with a high frame rate CMOS camera allowed a detailed, highly temporally resolved acquisition (up to 10000 fps depending on the resolution) of the flow downstream of the PHV. Features that were observed include the non-homogeneity and unsteadiness of the phenomenon and the presence of large-scale vortices within the field, especially in the wake of the valve leaflets. Furthermore, we observed that highly temporally cycle-resolved analysis allowed the different behaviors exhibited by the bileaflet valve at closure to be captured in different acquired cardiac cycles. By accurately capturing hemodynamically relevant time scales of motion, time-resolved PIV characterization can realistically be expected to help designers in improving PHV performance and in furnishing comprehensive validation with experimental data
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
Mechanisms underlying rhythmic locomotion: body–fluid interaction in undulatory swimming
Chen, J.; Friesen, W. O.; Iwasaki, T.
2011-01-01
Swimming of fish and other animals results from interactions of rhythmic body movements with the surrounding fluid. This paper develops a model for the body–fluid interaction in undulatory swimming of leeches, where the body is represented by a chain of rigid links and the hydrodynamic force model is based on resistive and reactive force theories. The drag and added-mass coefficients for the fluid force model were determined from experimental data of kinematic variables during intact swimming, measured through video recording and image processing. Parameter optimizations to minimize errors in simulated model behaviors revealed that the resistive force is dominant, and a simple static function of relative velocity captures the essence of hydrodynamic forces acting on the body. The model thus developed, together with the experimental kinematic data, allows us to investigate temporal and spatial (along the body) distributions of muscle actuation, body curvature, hydrodynamic thrust and drag, muscle power supply and energy dissipation into the fluid. We have found that: (1) thrust is generated continuously along the body with increasing magnitude toward the tail, (2) drag is nearly constant along the body, (3) muscle actuation waves travel two or three times faster than the body curvature waves and (4) energy for swimming is supplied primarily by the mid-body muscles, transmitted through the body in the form of elastic energy, and dissipated into the water near the tail. PMID:21270304
Effect of lung resection on pleuro-pulmonary mechanics and fluid balance.
Salito, C; Bovio, D; Orsetti, G; Salati, M; Brunelli, A; Aliverti, A; Miserocchi, G
2016-01-15
The aim of the study was to determine in human patients the effect of lung resection on lung compliance and on pleuro-pulmonary fluid balance. Pre and post-operative values of compliance were measured in anesthetized patients undergoing resection for lung cancer (N=11) through double-lumen bronchial intubation. Lung compliance was measured for 10-12 cm H2O increase in alveolar pressure from 5 cm H2O PEEP in control and repeated after resection. No air leak was assessed and pleural fluid was collected during hospital stay. A significant negative correlation (r(2)=0.68) was found between compliance at 10 min and resected mass. Based on the pre-operative estimated lung weight, the decrease in compliance following lung resection exceeded by 10-15% that expected from resected mass. Significant negative relationships were found by relating pleural fluid drainage flow to the remaining lung mass and to post-operative lung compliance. Following lung re-expansion, data suggest a causative relationship between the decrease in compliance and the perturbation in pleuro-pulmonary fluid balance. Copyright © 2015 Elsevier B.V. All rights reserved.
Fluid mechanics of needle valves with rounded components Part III: Pressure distributions on walls
Czech Academy of Sciences Publication Activity Database
Tesař, Václav
2016-01-01
Roč. 248, September (2016), s. 138-147 ISSN 0924-4247 R&D Projects: GA ČR GA13-23046S Institutional support: RVO:61388998 Keywords : needle valves * pressure measurements * valves Subject RIV: BK - Fluid Dynamics Impact factor: 2.499, year: 2016 http://www.sciencedirect.com/science/article/pii/S0924424716303417
In fascination of fluid mechanics : a symposium in honour of Leen van Wijngaarden
Biesheuvel, A.; Heijst, van G.J.F.
1998-01-01
In Fascination of Fluid Dynamics contains a collection of papers by international experts in hydrodynamics, based on oral presentations at a symposium held in honour of Professor Leen van Wijngaarden on his 65th birthday. The book begins with a personal sketch of his life and scientific career. It
2017-07-05
SECURITY CLASSIFICATION OF: We use multiscale modeling and computational fluid dynamics to examine the stability of a swimming organism in the face of...information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and
Directory of Open Access Journals (Sweden)
Hameed Shihab
2012-06-01
Full Text Available Abstract Background/Aims Infants with diabetes insipidus (DI, especially those with impaired thirst mechanism or hypothalamic hyperphagia, are prone to severe sodium fluctuations, often requiring hospitalization. We aimed to avoid dangerous fluctuations in serum sodium and improve parental independence. Methods A 16-month old girl with central DI, absent thirst mechanism and hyperphagia following surgery for hypothalamic astrocytoma had erratic absorption of oral DDAVP during chemotherapy cycles. She required prolonged hospitalizations for hypernatremia and hyponatremic seizure. Intensive monitoring of fluid balance, weight and clinical assessment of hydration were not helpful in predicting serum sodium. Discharge home was deemed unsafe. Oral DDAVP was switched to subcutaneous (twice-daily injections, starting with 0.01mcg/dose, increasing to 0.024mcg/dose. The parents adjusted daily fluid allocation by sliding-scale, according to the blood sodium level (measured by handheld i-STAT analyser, Abbott. We adjusted the DDAVP dose if fluid allocation differed from maintenance requirements for 3 consecutive days. Results After 2.5 months, sodium was better controlled, with 84% of levels within reference range (135-145 mmol/L vs. only 51% on the old regimen (p = 0.0001. The sodium ranged from 132-154 mmol/L, compared to 120–156 on the old regimen. She was discharged home. Conclusion This practical regimen improved sodium control, parental independence, and allowed discharge home.
Hameed, Shihab; Mendoza-Cruz, Abel C; Neville, Kristen A; Woodhead, Helen J; Walker, Jan L; Verge, Charles F
2012-06-09
Infants with diabetes insipidus (DI), especially those with impaired thirst mechanism or hypothalamic hyperphagia, are prone to severe sodium fluctuations, often requiring hospitalization. We aimed to avoid dangerous fluctuations in serum sodium and improve parental independence. A 16-month old girl with central DI, absent thirst mechanism and hyperphagia following surgery for hypothalamic astrocytoma had erratic absorption of oral DDAVP during chemotherapy cycles. She required prolonged hospitalizations for hypernatremia and hyponatremic seizure. Intensive monitoring of fluid balance, weight and clinical assessment of hydration were not helpful in predicting serum sodium. Discharge home was deemed unsafe. Oral DDAVP was switched to subcutaneous (twice-daily injections, starting with 0.01mcg/dose, increasing to 0.024mcg/dose). The parents adjusted daily fluid allocation by sliding-scale, according to the blood sodium level (measured by handheld i-STAT analyser, Abbott). We adjusted the DDAVP dose if fluid allocation differed from maintenance requirements for 3 consecutive days. After 2.5 months, sodium was better controlled, with 84% of levels within reference range (135-145 mmol/L) vs. only 51% on the old regimen (p = 0.0001). The sodium ranged from 132-154 mmol/L, compared to 120-156 on the old regimen. She was discharged home. This practical regimen improved sodium control, parental independence, and allowed discharge home.
Mckillop, A. A.; Baughn, J. W.; Dwyer, H. A.
1976-01-01
Major research advances in heat transfer and fluid dynamics are outlined, with particular reference to relevant energy problems. Of significant importance are such topics as synthetic fuels in combustion, turbulence models, combustion modeling, numerical methods for interacting boundary layers, and light-scattering diagnostics for gases. The discussion covers thermal convection, two-phase flow and boiling heat transfer, turbulent flows, combustion, and aerospace heat transfer problems. Other areas discussed include compressible flows, fluid mechanics and drag, and heat exchangers. Featured topics comprise heat and salt transfer in double-diffusive systems, limits of boiling heat transfer in a liquid-filled enclosure, investigation of buoyancy-induced flow stratification in a cylindrical plenum, and digital algorithms for dynamic analysis of a heat exchanger. Individual items are announced in this issue.
DEFF Research Database (Denmark)
Liddelow, S A; Dziegielewska, K M; Møllgård, K
2011-01-01
Specialized populations of choroid plexus epithelial cells have previously been shown to be responsible for the transfer of individual plasma proteins from blood to the cerebrospinal fluid (CSF), contributing to their characteristically high concentrations in CSF of the developing brain. The mech......Specialized populations of choroid plexus epithelial cells have previously been shown to be responsible for the transfer of individual plasma proteins from blood to the cerebrospinal fluid (CSF), contributing to their characteristically high concentrations in CSF of the developing brain....... The mechanism of this protein transfer remains elusive. Using a marsupial, Monodelphis domestica, we demonstrate that the albumin-binding protein SPARC (osteonectin/BM-40/culture-shock protein) is present in a subset of choroid plexus epithelial cells from its first appearance, throughout development...
Fluid mechanics of needle valves with rounded components Part I: Configurations and models
Czech Academy of Sciences Publication Activity Database
Tesař, Václav
2017-01-01
Roč. 254, February (2017), s. 101-108 ISSN 0924-4247 R&D Projects: GA ČR GA13-23046S Institutional support: RVO:61388998 Keywords : needle valves * valve with rounded inlet * valve Subject RIV: BK - Fluid Dynamics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.499, year: 2016 http://ac.els-cdn.com/S0924424716310226/1-s2.0-S0924424716310226-main.pdf?_tid=f1570ee0-2f46-11e7-b057-00000aab0f26&acdnat=1493736920_595bfaae6a6922d4213225a968d5d74c
Directory of Open Access Journals (Sweden)
Waqar Azeem Khan
Full Text Available The present paper deals with the analysis of melting heat and mass transfer characteristics in the stagnation point flow of an incompressible generalized Burgers fluid over a stretching sheet in the presence of non-linear radiative heat flux. A uniform magnetic field is applied normal to the flow direction. The governing equations in dimensional form are reduced to a system of dimensionless expressions by implementation of suitable similarity transformations. The resulting dimensionless problem governing the generalized Burgers is solved analytically by using the homotopy analysis method (HAM. The effects of different flow parameters like the ratio parameter, magnetic parameter, Prandtl number, melting parameter, radiation parameter, temperature ratio parameter and Schmidt number on the velocity, heat and mass transfer characteristics are computed and presented graphically. Moreover, useful discussions in detail are carried out with the help of plotted graphs and tables. Keywords: Generalized Burgers fluid, Non-linear radiative flow, Magnetic field, Melting heat transfer
Fracturing Fluid Leak-off for Deep Volcanic Rock in Zhungeer Basin: Mechanism and Control Method
Huang Bo; Cheng Hao; He Yidong; Fu Yanming
2017-01-01
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 ...
Dirac mechanics and Landau two-fluid model in /sup 4/HeII
Energy Technology Data Exchange (ETDEWEB)
Rodriguez-Gomez, J [Instituto Universitario Pedagogico de Caracas (Venezuela). Dept. de Matematica y Fisica
1980-07-01
This paper is devoted to the development of the Dirac formalism for singular systems when applied to the Landau two-fluid model in superfluid helium. Notably, the Hamiltonian density is weakly zero (in the sense of Dirac). We obtain the physical and gauge variables and show that all the constraints are of first class and hence that the Dirac bracket coincides with the Poisson bracket. The quantization of this system is left for a future paper.
Fakir, Rachid; Barka, Noureddine; Brousseau, Jean
2018-03-01
This paper proposes a statistical approach to analyze the mechanical properties of a standard test specimen, of cylindrical geometry and in steel 4340, with a diameter of 6 mm, heat-treated and quenched in three different fluids. Samples were evaluated in standard tensile test to access their characteristic quantities: hardness, modulus of elasticity, yield strength, tensile strength and ultimate deformation. The proposed approach is gradually being built (a) by a presentation of the experimental device, (b) a presentation of the experimental plan and the results of the mechanical tests, (c) anova analysis of variance and a representation of the output responses using the RSM response surface method, and (d) an analysis of the results and discussion. The feasibility and effectiveness of the proposed approach leads to a precise and reliable model capable of predicting the variation of mechanical properties, depending on the tempering temperature, the tempering time and the cooling capacity of the quenching medium.
Energy Technology Data Exchange (ETDEWEB)
Kang, Seok Hoon; Park, Sang Hu; Son, Chang Min; Ha, Man Young; Min, June Kee; Jeong, Ho Sung [Pusan Nat' l Univ., Busan (Korea, Republic of); Cho, Jongrae [Korea Maritime Univ., Busan (Korea, Republic of); Kim, Hyun Jun [Donghwa Entec Co., Ltd., Busan (Korea, Republic of)
2013-01-15
Recent years have witnessed a strong need for eco friendly and energy efficient systems owing to global environmental problems. A heat exchanger is a well known mechanical rig that has long been used in many energy systems. The use of a heat exchanger in an airplane engine has been attempted. In this case, the heat exchanger should be redesigned to be compact, lightweight, and highly reliable, and the issue of mechanical integrity gains importance. Therefore, in this study, we proposed a method for evaluating the mechanical integrity of a tube type heat exchanger. A U shaped single tube was used as an example, and its behavior and stress distribution were studied using fluid structure interaction (FSI) analysis.
Maitland, Kathryn; George, Elizabeth C; Evans, Jennifer A; Kiguli, Sarah; Olupot-Olupot, Peter; Akech, Samuel O; Opoka, Robert O; Engoru, Charles; Nyeko, Richard; Mtove, George; Reyburn, Hugh; Brent, Bernadette; Nteziyaremye, Julius; Mpoya, Ayub; Prevatt, Natalie; Dambisya, Cornelius M; Semakula, Daniel; Ddungu, Ahmed; Okuuny, Vicent; Wokulira, Ronald; Timbwa, Molline; Otii, Benedict; Levin, Michael; Crawley, Jane; Babiker, Abdel G; Gibb, Diana M
2013-03-14
Early rapid fluid resuscitation (boluses) in African children with severe febrile illnesses increases the 48-hour mortality by 3.3% compared with controls (no bolus). We explored the effect of boluses on 48-hour all-cause mortality by clinical presentation at enrolment, hemodynamic changes over the first hour, and on different modes of death, according to terminal clinical events. We hypothesize that boluses may cause excess deaths from neurological or respiratory events relating to fluid overload. Pre-defined presentation syndromes (PS; severe acidosis or severe shock, respiratory, neurological) and predominant terminal clinical events (cardiovascular collapse, respiratory, neurological) were described by randomized arm (bolus versus control) in 3,141 severely ill febrile children with shock enrolled in the Fluid Expansion as Supportive Therapy (FEAST) trial. Landmark analyses were used to compare early mortality in treatment groups, conditional on changes in shock and hypoxia parameters. Competing risks methods were used to estimate cumulative incidence curves and sub-hazard ratios to compare treatment groups in terms of terminal clinical events. Of 2,396 out of 3,141 (76%) classifiable participants, 1,647 (69%) had a severe metabolic acidosis or severe shock PS, 625 (26%) had a respiratory PS and 976 (41%) had a neurological PS, either alone or in combination. Mortality was greatest among children fulfilling criteria for all three PS (28% bolus, 21% control) and lowest for lone respiratory (2% bolus, 5% control) or neurological (3% bolus, 0% control) presentations. Excess mortality in bolus arms versus control was apparent for all three PS, including all their component features. By one hour, shock had resolved (responders) more frequently in bolus versus control groups (43% versus 32%, P <0.001), but excess mortality with boluses was evident in responders (relative risk 1.98, 95% confidence interval 0.94 to 4.17, P = 0.06) and 'non-responders' (relative risk 1
Mechanics of Fluid-Filled Interstitial Gaps. I. Modeling Gaps in a Compact Tissue.
Parent, Serge E; Barua, Debanjan; Winklbauer, Rudolf
2017-08-22
Fluid-filled interstitial gaps are a common feature of compact tissues held together by cell-cell adhesion. Although such gaps can in principle be the result of weak, incomplete cell attachment, adhesion is usually too strong for this to occur. Using a mechanical model of tissue cohesion, we show that, instead, a combination of local prevention of cell adhesion at three-cell junctions by fluidlike extracellular material and a reduction of cortical tension at the gap surface are sufficient to generate stable gaps. The size and shape of these interstitial gaps depends on the mechanical tensions between cells and at gap surfaces, and on the difference between intracellular and interstitial pressures that is related to the volume of the interstitial fluid. As a consequence of the dependence on tension/tension ratios, the presence of gaps does not depend on the absolute strength of cell adhesion, and similar gaps are predicted to occur in tissues of widely differing cohesion. Tissue mechanical parameters can also vary within and between cells of a given tissue, generating asymmetrical gaps. Within limits, these can be approximated by symmetrical gaps. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.
Directory of Open Access Journals (Sweden)
Panayotounakos D. E.
1996-01-01
Full Text Available We develop a new unique technique in constructing closed-form solutions for several nonlinear partial differential systems appearing in fluid mechanics and gas dynamics. The obtained solutions include fewer arbitrary functions than needed for general solutions, fact that permits us to specify them according to the initial state, or the geometry, of each specific problem under consideration. In order to apply the before mentioned technique we construct closed-form solutions concerning the gas-dynamic equations with constant pressure, the dynamic equations of an ideal gas in isentropic flow, and the two-dimensional incompressible boundary layer flow.
International Nuclear Information System (INIS)
Wang, J.S.Y.; Narasimhan, T.N.
1984-10-01
In contrast to the saturated zone where fluid moves rapidly along fractures, the fractures (with apertures large relative to the size of matrix pores) will desaturate first during drainage process and the bulk of fluid flow would be through interconnected pores in the matrix. Within a partially drained fracture, the presence of a relatively continuous air phase will produce practically an infinite resistance to liquid flow in the direction parallel to the fracture. The residual liquid will be held by capillary force in regions around fracture contact areas where the apertures are small. Normal to the fracture surfaces, the drained portion of the fractures will reduce the effective area for liquid flow from one matrix block to another matrix block. A general statistical theory is constructed for flow along the fracture and for flow between the matrix blocks to the fractures under partially saturated conditions. Results are obtained from an aperture distribution model for fracture saturation, hydraulic conductivity, and effective matrix-fracture flow areas as functions of pressure. Drainage from a fractured tuff column is simulated. The parameters for the simulations are deduced from fracture surface characteristics, spacings and orientations based on core analyses, and from matrix characteristics curve based on laboratory measurements. From the cases simulated for the fractured, porous column with discrete vertical and horizontal fractures and porous matrix blocks explicitly taken into account, it is observed that the highly transient changes from fully saturated conditions to partially saturated conditions are extremely sensitive to the fracture properties. However, the quasi-steady changes of the fluid flow of a partially saturated, fractured, porous system could be approximately simulated without taking the fractures into account. 22 references, 16 figures
1989-01-01
IJ-1_1 - from which we deduce: H U 1/ f II Hu A//- + 2M AtAr , and indeed the expected estimate : // un+l //_ lluo/ + (2MT) Ax since nAt _9 T...the propa- gation of a planar premixed flame with one-step chemistry . In this case, diffusive and reactive terms are added to the energy and species...to use exceedingly fine computational scales, to resolve the chemistry and internal fluid layers fully (which would normally be prohibitive in a large
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.
Fluid mechanics of needle valves with rounded components. Part II: Preliminary measurements
Czech Academy of Sciences Publication Activity Database
Tesař, Václav
2016-01-01
Roč. 251, November (2016), s. 52-58 ISSN 0924-4247 R&D Projects: GA ČR GA13-23046S Institutional support: RVO:61388998 Keywords : needle valves * pressure measurements * valves Subject RIV: BK - Fluid Dynamics Impact factor: 2.499, year: 2016 http://ac.els-cdn.com/S092442471630440X/1-s2.0-S092442471630440X-main.pdf?_tid=45acccf4-951f-11e6-a831-00000aab0f02&acdnat=1476787402_bf349ff3cfc7a824c1a01397a9a5b8b3
Damodara, Vijaya; Chen, Daniel H; Lou, Helen H; Rasel, Kader M A; Richmond, Peyton; Wang, Anan; Li, Xianchang
2017-05-01
Emissions from flares constitute unburned hydrocarbons, carbon monoxide (CO), soot, and other partially burned and altered hydrocarbons along with carbon dioxide (CO 2 ) and water. Soot or visible smoke is of particular concern for flare operators/regulatory agencies. The goal of the study is to develop a computational fluid dynamics (CFD) model capable of predicting flare combustion efficiency (CE) and soot emission. Since detailed combustion mechanisms are too complicated for (CFD) application, a 50-species reduced mechanism, LU 3.0.1, was developed. LU 3.0.1 is capable of handling C 4 hydrocarbons and soot precursor species (C 2 H 2 , C 2 H 4 , C 6 H 6 ). The new reduced mechanism LU 3.0.1 was first validated against experimental performance indicators: laminar flame speed, adiabatic flame temperature, and ignition delay. Further, CFD simulations using LU 3.0.1 were run to predict soot emission and CE of air-assisted flare tests conducted in 2010 in Tulsa, Oklahoma, using ANSYS Fluent software. Results of non-premixed probability density function (PDF) model and eddy dissipation concept (EDC) model are discussed. It is also noteworthy that when used in conjunction with the EDC turbulence-chemistry model, LU 3.0.1 can reasonably predict volatile organic compound (VOC) emissions as well. A reduced combustion mechanism containing 50 C 1 -C 4 species and soot precursors has been developed and validated against experimental data. The combustion mechanism is then employed in the computational fluid dynamics (CFD) of modeling of soot emission and combustion efficiency (CE) of controlled flares for which experimental soot and CE data are available. The validated CFD modeling tools are useful for oil, gas, and chemical industries to comply with U.S. Environmental Protection Agency's (EPA) mandate to achieve smokeless flaring with a high CE.
Danso, E K; Mäkelä, J T A; Tanska, P; Mononen, M E; Honkanen, J T J; Jurvelin, J S; Töyräs, J; Julkunen, P; Korhonen, R K
2015-06-01
Meniscus adapts to joint loads by depth- and site-specific variations in its composition and structure. However, site-specific mechanical characteristics of intact meniscus under compression are poorly known. In particular, mechanical nonlinearities caused by different meniscal constituents (collagen and fluid) are not known. In the current study, in situ indentation testing was conducted to determine site-specific elastic, viscoelastic and poroelastic properties of intact human menisci. Lateral and medial menisci (n=26) were harvested from the left knee joint of 13 human cadavers. Indentation tests, using stress-relaxation and dynamic (sinusoidal) loading protocols, were conducted for menisci at different sites (anterior, middle, posterior, n=78). Sample- and site-specific axisymmetric finite element models with fibril-reinforced poroelastic properties were fitted to the corresponding stress-relaxation curves to determine the mechanical parameters. Elastic moduli, especially the instantaneous and dynamic moduli, showed site-specific variation only in the medial meniscus (pmeniscus. The phase angle showed no statistically significant variation between the sites (p>0.05). The values for the strain-dependent fibril network modulus (nonlinear behaviour of collagen) were significantly different (pmeniscus only between the middle and posterior sites. For the strain-dependent permeability coefficient, only anterior and middle sites showed a significant difference (pmeniscus. This parameter demonstrated a significant difference (pmeniscus shows more site-dependent variation in the mechanical properties as compared to lateral meniscus. In particular, anterior horn of medial meniscus was the stiffest and showed the most nonlinear mechanical behaviour. The nonlinearity was related to both collagen fibrils and fluid. Copyright © 2015 Elsevier Ltd. All rights reserved.
Modeling mechanical properties of a shear thickening fluid damper based on phase transition theory
Wei, Minghai; Lin, Kun; Guo, Qian
2018-03-01
Shear thickening fluids (STFs) are highly concentrated colloidal suspensions consisting of monodisperse nano-particles suspended in a carrying fluid, and have the capacity to display both flowable and rigid behaviors, when subjected to sudden stimuli. In that process, the external energy that acts on an STF can be dissipated quickly. The aim of this study is to present a dynamic model of a damper filled with STF that can be directly used in control engineering fields. To this end, shear stress during phase transition of the STF material is chosen as an internal variable. A non-convex function with bifurcation behavior is used to describe the phase transitioning of STF by determining the relationship between the behavioral characteristics of the microscopic phase and macroscopic damping force. This model is able to predict force-velocity and force-displacement relationships as functions of the loading frequency. Efficacy of the model is demonstrated via comparison with experimental results from previous studies. In addition, the results confirm the hypothesis regarding the occurrence of STF phase transitioning when subject to shear stress.
Ding, Fang; Meng, Huan-xin; Li, Qi-qiang; Zhao, Yi-bing; Feng, Xiang-hui; Zhang, Li
2010-04-18
To evaluate the subgingival prevalent rates of 6 periodontal pathogenic bacteria in gingival crevicular fluids of CP patients before and after treatment, to analyze the relationship between the prevalent variance and periodontal clinical parameters, and to provide a microbiologic method of evaluating curative effect and estimating the prognosis. Gingival crevicular fluids of 13 CP patients were collected at baseline, 2 weeks, 2 months and 4 months after periodontal mechanical treatment. Also, gingival crevicular fluids were collected from 11 healthy subjects. Six periodontal pathogenic bacteria including Actinobacillus actinomycetemcomitans (Aa), Porphyromonas gingivalis(Pg), Tannerella forsythensis (Tf), Prevotella intermedia (Pi), Fusobacterium nucleatum(Fn), Prevotella nigrescens (Pn) were detected by 16S rRNA based PCR. The PLI, PD, BI of the CP patients 2 months and 4 months after periodontal mechanical treatment were evidently less than those before treatment. These 4 months after treatment were a little more than those 2 months after. The six bacteria were more frequently detected in the CP patients at baseline than in healthy controls. The prevalent rates of Tf (42.1%, 73.7%, 70.2%), Pg (47.4%, 68.4%, 77.2%), Aa (15.8%, 22.8%, 7.0%), Pn (38.6%, 57.9%, 64.9%), Pi(15.8%, 38.6%, 42.1%) 2 weeks, 2 months and 4 months following treatment were significantly lower than those at baseline (Tf 96.5%, Pg 93.0%, Aa 36.8%, Pn 86.0%, Pi 84.2%), but the prevalent rates of all the detected bacteria 2 months after treatment were higher than those at 2 weeks after. Tf, Pg, Aa, Pn and Pi may cooperate in the development of CP. The changes of periodontal pathogenic bacteria could be detected before the changes of clinical parameters and the patients should be re-evaluated and re-treated regularly within 2 months after treatment.
Tresoldi, Claudia; Bianchi, Elena; Pellegata, Alessandro Filippo; Dubini, Gabriele; Mantero, Sara
2017-08-01
The in vitro replication of physiological mechanical conditioning through bioreactors plays a crucial role in the development of functional Small-Caliber Tissue-Engineered Blood Vessels. An in silico scaffold-specific model under pulsatile perfusion provided by a bioreactor was implemented using a fluid-structure interaction (FSI) approach for viscoelastic tubular scaffolds (e.g. decellularized swine arteries, DSA). Results of working pressures, circumferential deformations, and wall shear stress on DSA fell within the desired physiological range and indicated the ability of this model to correctly predict the mechanical conditioning acting on the cells-scaffold system. Consequently, the FSI model allowed us to a priori define the stimulation pattern, driving in vitro physiological maturation of scaffolds, especially with viscoelastic properties.
DEFF Research Database (Denmark)
Damsgaard, Anders; Egholm, David Lundbek; Beem, Lucas H.
The macroscopic behavior of granular materials is the result of the self-organizing complexity of the constituent grains. Granular materials are known for their ability to change phase, where each phase is characterized by distinct mechanical properties. This rich generic phenomenology has made...... it difficult to constrain generalized and adequate mathematical models for their mechanical behavior. Glaciers and ice streams often move by deformation of underlying melt-water saturated sediments. Glacier flow models including subglacial sediment deformation use simplified a priori assumptions for sediment......, the method imposes intense computational requirements on the computational time step. The majority of steps in the granular dynamics algorithm are massively parallel, which makes the DEM an obvious candidate for exploiting the capabilities of modern GPUs. The granular computations are coupled to a fluid...
Burazin, Andrijana; Drapaca, Corina S; Tenti, Giuseppe; Sivaloganathan, Siv
2018-05-01
Although the mechanisms responsible for elevated interstitial fluid pressure (IFP) in tumours remain obscure, it seems clear that high IFP represents a barrier to drug delivery (since the resulting adverse pressure gradient implies a reduction in the driving force for transvascular exchange of both fluid and macromolecules). R. Jain and co-workers studied this problem, and although the conclusions drawn from their idealized mathematical models offered useful insights into the causes of elevated IFP, they by no means gave a definitive explanation for this phenomenon. In this paper, we use poroelasticity theory to also develop a macroscopic mathematical model to describe the time evolution of a solid tumour, but focus our attention on the mechanisms responsible for the rise of the IFP, from that for a healthy interstitium to that measured in malignant tumours. In particular, we discuss a number of possible time scales suggested by our mathematical model and propose a tumour-dependent time scale that leads to results in agreement with experimental observations. We apply our mathematical model to simulate the effect of "vascular normalization" (as proposed by Jain in Nat Med 7:987-989, 2001) on the IFP profile and discuss and contrast our conclusions with those of previous work in the literature.
International Nuclear Information System (INIS)
Liu, Yan; Xu, Lining; Lu, Minxu; Meng, Yao; Zhu, Jinyang; Zhang, Lei
2014-01-01
Highlights: • The corrosion behavior of 13Cr steel exposed to bromine salt completion fluid containing high concentration bromine ions was investigated. • There are passive circles around pits on the 13Cr steel surface after 7 d of exposure. • Macroscopic galvanic corrosion formed between the passive halo and the pit. • The mechanism of pitting corrosion on 13Cr stainless steel exposed to heavy bromine brine was established. - Abstract: A series of corrosion tests of 13Cr stainless steel were conducted in a simulated completion fluid environment of high temperature and high concentration bromine salt. Corrosion behavior of specimens and the component of corrosion products were investigated by means of scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS). The results indicate that 13Cr steel suffers from severe local corrosion and there is always a passive halo around every pit. The formation mechanism of the passive halo is established. OH − ligand generates and adsorbs in a certain scale because of abundant OH − on the surface around the pits. Passive film forms around each pit, which leads to the occurrence of passivation in a certain region. Finally, the dissimilarities in properties and morphologies of regions, namely the pit and its corresponding passive halo, can result in different corrosion sensitivities and may promote the formation of macroscopic galvanic pairs
Physics of continuous media problems and solutions in electromagnetism, fluid mechanics and MHD
Vekstein, Grigory
2013-01-01
This book presents an excellent and exemplary collection of up-to-date exercises and their solutions on continuous media, covering a wide range of topics from electro-, magnetohydro- and fluid dynamics, and from the theory of elasticity. The author is an international expert with many years of research and teaching experience in the field. Each chapter begins with a comprehensive summary of definitions and the mathematical description of the physical laws necessary to understand and solve the series of problems that follow. The problems and exercises are a gradual built up in each of the topics and they introduce the reader step by step into the principles of the subject. The solutions are well explained and detailed with additional readings when necessary. This exercise book is written in a true scholarly manner that allows the reader to understand the basic principles and physical laws of continuous media. This problem-solving book is highly recommended to graduate and postgraduate students, postdoctoral re...
Experimental studies in fluid mechanics and materials science using acoustic levitation
Trinh, E. H.; Robey, J.; Arce, A.; Gaspar, M.
1987-01-01
Ground-based and short-duration low gravity experiments have been carried out with the use of ultrasonic levitators to study the dynamics of freely suspended liquid drops under the influence of predominantly capillary and acoustic radiation forces. Some of the effects of the levitating field on the shape as well as the fluid flow fields within the drop have been determined. The development and refinement of measurement techniques using levitated drops with size on the order of 2 mm in diameter have yielded methods having direct application to experiments in microgravity. In addition, containerless melting, undercooling, and freezing of organic materials as well as low melting metals have provided experimental data and observations on the application of acoustic positioning techniques to materials studies.
Personal computer (PC) based image processing applied to fluid mechanics research
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 processsed 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 commputation.
International Nuclear Information System (INIS)
McEligot, Donald M.; Becker, Stefan; McIlroy, Hugh M. Jr.
2010-01-01
In recent international collaboration, INL and Uni. Erlangen have developed large MIR flow systems which can be ideal for joint graduate student education and research. The benefit of the MIR technique is that it permits optical measurements to determine flow characteristics in complex passages and around objects to be obtained without locating a disturbing transducer in the flow field and without distortion of the optical paths. The MIR technique is not new itself; others employed it earlier. The innovation of these MIR systems is their large size relative to previous experiments, yielding improved spatial and temporal resolution. This report will discuss the benefits of the technique, characteristics of the systems and some examples of their applications to complex situations. Typically their experiments have provided new fundamental understanding plus benchmark data for assessment and possible validation of computational thermal fluid dynamic codes.
Rančić, Milica
2016-01-01
This book highlights the latest advances in engineering mathematics with a main focus on the mathematical models, structures, concepts, problems and computational methods and algorithms most relevant for applications in modern technologies and engineering. In particular, it features mathematical methods and models of applied analysis, probability theory, differential equations, tensor analysis and computational modelling used in applications to important problems concerning electromagnetics, antenna technologies, fluid dynamics, material and continuum physics and financial engineering. The individual chapters cover both theory and applications, and include a wealth of figures, schemes, algorithms, tables and results of data analysis and simulation. Presenting new methods and results, reviews of cutting-edge research, and open problems for future research, they equip readers to develop new mathematical methods and concepts of their own, and to further compare and analyse the methods and results discussed. The ...
Energy Technology Data Exchange (ETDEWEB)
Donald M. McEligot; Stefan Becker; Hugh M. McIlroy, Jr.
2010-07-01
In recent international collaboration, INL and Uni. Erlangen have developed large MIR flow systems which can be ideal for joint graduate student education and research. The benefit of the MIR technique is that it permits optical measurements to determine flow characteristics in complex passages and around objects to be obtained without locating a disturbing transducer in the flow field and without distortion of the optical paths. The MIR technique is not new itself; others employed it earlier. The innovation of these MIR systems is their large size relative to previous experiments, yielding improved spatial and temporal resolution. This report will discuss the benefits of the technique, characteristics of the systems and some examples of their applications to complex situations. Typically their experiments have provided new fundamental understanding plus benchmark data for assessment and possible validation of computational thermal fluid dynamic codes.
Quantification of ventilated facade efficiency by using computational fluid mechanics techniques
International Nuclear Information System (INIS)
Mora Perez, M.; Lopez Patino, G.; Bengochea Escribano, M. A.; Lopez Jimenez, P. A.
2011-01-01
In some countries, summer over-heating is a big problem in a buildings energy balance. Ventilated facades are a useful tool when applied to building design, especially in bio climatic building design. A ventilated facade is a complex, multi-layer structural solution that enables dry installation of the covering elements. The objective of this paper is to quantify the efficiency improvement in the building thermal when this sort of facade is installed. These improvements are due to convection produced in the air gap of the facade. This convection depends on the air movement inside the gap and the heat transmission in this motion. These quantities are mathematically modelled by Computational Fluid Dynamics (CFD) techniques using a commercial code: STAR CCM+. The proposed method allows an assessment of the energy potential of the ventilated facade and its capacity for cooling. (Author) 23 refs.
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.
Yoon, Jeoung Seok; Zang, Arno; Zimmermann, Günter; Stephansson, Ove
2016-04-01
Operation of fluid injection into and withdrawal from the subsurface for various purposes has been known to induce earthquakes. Such operations include hydraulic fracturing for shale gas extraction, hydraulic stimulation for Enhanced Geothermal System development and waste water disposal. Among these, several damaging earthquakes have been reported in the USA in particular in the areas of high-rate massive amount of wastewater injection [1] mostly with natural fault systems. Oil and gas production have been known to induce earthquake where pore fluid pressure decreases in some cases by several tens of Mega Pascal. One recent seismic event occurred in November 2013 near Azle, Texas where a series of earthquakes began along a mapped ancient fault system [2]. It was studied that a combination of brine production and waste water injection near the fault generated subsurface pressures sufficient to induced earthquakes on near-critically stressed faults. This numerical study aims at investigating the occurrence mechanisms of such earthquakes induced by fluid injection [3] and withdrawal by using hydro-geomechanical coupled dynamic simulator (Itasca's Particle Flow Code 2D). Generic models are setup to investigate the sensitivity of several parameters which include fault orientation, frictional properties, distance from the injection well to the fault, amount of fluid withdrawal around the injection well, to the response of the fault systems and the activation magnitude. Fault slip movement over time in relation to the diffusion of pore pressure is analyzed in detail. Moreover, correlations between the spatial distribution of pore pressure change and the locations of induced seismic events and fault slip rate are investigated. References [1] Keranen KM, Weingarten M, Albers GA, Bekins BA, Ge S, 2014. Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection, Science 345, 448, DOI: 10.1126/science.1255802. [2] Hornbach MJ, DeShon HR
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
International Nuclear Information System (INIS)
Lee, Jae Han; Joo, Young Sang; Lee, Hueong Yeon and others
2005-03-01
The key research items during the fiscal years of Phase 3 of the mechanical design technology development for liquid metal reactor are described. The objective of this project is to develop the design technology for the mechanical system of 600MWe, pool type liquid metal reactor with sodium coolant, and the structural integrity evaluation technology for mechanical system of the reactor system, structures and equipments. In the design technology development for mechanical structures, the reactor internal structures, reactor head and piping system, reactor containment structures have been studied, and new structural concepts compatible with the new reactor have been proposed. The thermal protection devices of reactor vessel and the refueling system have been conceptually established and the feasibility study for 3-D seismic isolation of reactor building was performed. The structural damage detection technology for reactor internal structures has been studied and its application has been confirmed. In the structural integrity evaluation technology development, the sensitivities of material constants for inelastic analysis codes have been studied and the applicabilities of the developed codes are enhanced. The high temperature creep-fatigue structural behavior test has been conducted so that high temperature structural damage test and evaluation technology were ensured at first in domestic. The high temperature seismic buckling analysis method to evaluate the buckling of thin reactor shell structure under the transient thermal load was established. In addition, the core seismic response analysis code reflected the fluid effect of core was developed and its accuracy was confirmed with a scale-down model test
Fluid Mechanics Experiments as a Unifying Theme in the Physics Instrumentation Laboratory Course
Borrero-Echeverry, Daniel
2017-11-01
We discuss the transformation of a junior-level instrumentation laboratory course from a sequence of cookbook lab exercises to a semester-long, project-based course. In the original course, students conducted a series of activities covering the usual electronics topics (amplifiers, filters, oscillators, logic gates, etc.) and learned basic LabVIEW programming for data acquisition and analysis. Students complained that these topics seemed disconnected and not immediately applicable to ``real'' laboratory work. To provide a unifying theme, we restructured the course around the design, construction, instrumentation of a low-cost Taylor-Couette cell where fluid is sheared between rotating coaxial cylinders. The electronics labs were reworked to guide students from fundamental electronics through the design and construction of a stepper motor driver, which was used to actuate the cylinders. Some of the legacy labs were replaced with a module on computer-aided design (CAD) in which students designed parts for the apparatus, which they then built in the departmental machine shop. Signal processing topics like spectral analysis were introduced in the context of time-series analysis of video data acquired from flow visualization. The course culminated with a capstone project in which students conducted experiments of their own design on a variety of topics in rheology and nonlinear dynamics.
Topological fluid mechanics of the formation of the Kármán-vortex street
DEFF Research Database (Denmark)
Heil, Matthias; Rosso, Jordan; Hazel, Andrew L.
2017-01-01
consider to be feature points for vortices. The basic vortex creation mechanism is shown to be a topological cusp bifurcation in the vorticity field, where a saddle and an extremum of the vorticity are created simultaneously. We demonstrate that vortices are first created approximately 100 diameters...
Ciliary and mucus-net filter feeding, with special reference to fluid mechanical characteristics
DEFF Research Database (Denmark)
Jørgensen, C.B.; Kiørboe, Thomas; Møhlenberg, F.
1984-01-01
feeding characterized by processing of water at low pressures (.ltoreq. 1 mm H2O). Mechanisms of water processing and particle retention in brachiopods and bivalves are compared. Laminar flow of through-currents and surface-currents in brachiopods is consistent with the hypothesis of capture of suspended...
Rabbah, Jean-Pierre; Saikrishnan, Neelakantan; Yoganathan, Ajit P
2013-02-01
Numerical models of the mitral valve have been used to elucidate mitral valve function and mechanics. These models have evolved from simple two-dimensional approximations to complex three-dimensional fully coupled fluid structure interaction models. However, to date these models lack direct one-to-one experimental validation. As computational solvers vary considerably, experimental benchmark data are critically important to ensure model accuracy. In this study, a novel left heart simulator was designed specifically for the validation of numerical mitral valve models. Several distinct experimental techniques were collectively performed to resolve mitral valve geometry and hemodynamics. In particular, micro-computed tomography was used to obtain accurate and high-resolution (39 μm voxel) native valvular anatomy, which included the mitral leaflets, chordae tendinae, and papillary muscles. Three-dimensional echocardiography was used to obtain systolic leaflet geometry. Stereoscopic digital particle image velocimetry provided all three components of fluid velocity through the mitral valve, resolved every 25 ms in the cardiac cycle. A strong central filling jet (V ~ 0.6 m/s) was observed during peak systole with minimal out-of-plane velocities. In addition, physiologic hemodynamic boundary conditions were defined and all data were synchronously acquired through a central trigger. Finally, the simulator is a precisely controlled environment, in which flow conditions and geometry can be systematically prescribed and resultant valvular function and hemodynamics assessed. Thus, this work represents the first comprehensive database of high fidelity experimental data, critical for extensive validation of mitral valve fluid structure interaction simulations.
Prodanov, L; Semeins, C M; van Loon, J J W A; te Riet, J; Jansen, J A; Klein-Nulend, J; Walboomers, X F
2013-05-01
Introducing nanoroughness on various biomaterials has been shown to profoundly effect cell-material interactions. Similarly, physical forces act on a diverse array of cells and tissues. Particularly in bone, the tissue experiences compressive or tensile forces resulting in fluid shear stress. The current study aimed to develop an experimental setup for bone cell behavior, combining a nanometrically grooved substrate (200 nm wide, 50 nm deep) mimicking the collagen fibrils of the extracellular matrix, with mechanical stimulation by pulsatile fluid flow (PFF). MC3T3-E1 osteoblast-like cells were assessed for morphology, expression of genes involved in cell attachment and osteoblastogenesis and nitric oxide (NO) release. The results showed that both nanotexture and PFF did affect cellular morphology. Cells aligned on nanotexture substrate in a direction parallel to the groove orientation. PFF at a magnitude of 0.7 Pa was sufficient to induce alignment of cells on a smooth surface in a direction perpendicular to the applied flow. When environmental cues texture and flow were interacting, PFF of 1.4 Pa applied parallel to the nanogrooves initiated significant cellular realignment. PFF increased NO synthesis 15-fold in cells attached to both smooth and nanotextured substrates. Increased collagen and alkaline phosphatase mRNA expression was observed on the nanotextured substrate, but not on the smooth substrate. Furthermore, vinculin and bone sialoprotein were up-regulated after 1 h of PFF stimulation. In conclusion, the data show that interstitial fluid forces and structural cues mimicking extracellular matrix contribute to the final bone cell morphology and behavior, which might have potential application in tissue engineering. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Dynamic Fluid Flow Mechanical Stimulation Modulates Bone Marrow Mesenchymal Stem Cells.
Hu, Minyi; Yeh, Robbin; Lien, Michelle; Teeratananon, Morgan; Agarwal, Kunal; Qin, Yi-Xian
2013-03-01
Osteoblasts are derived from mesenchymal stem cells (MSCs), which initiate and regulate bone formation. New strategies for osteoporosis treatments have aimed to control the fate of MSCs. While functional disuse decreases MSC growth and osteogenic potentials, mechanical signals enhance MSC quantity and bias their differentiation toward osteoblastogenesis. Through a non-invasive dynamic hydraulic stimulation (DHS), we have found that DHS can mitigate trabecular bone loss in a functional disuse model via rat hindlimb suspension (HLS). To further elucidate the downstream cellular effect of DHS and its potential mechanism underlying the bone quality enhancement, a longitudinal in vivo study was designed to evaluate the MSC populations in response to DHS over 3, 7, 14, and 21 days. Five-month old female Sprague Dawley rats were divided into three groups for each time point: age-matched control, HLS, and HLS+DHS. DHS was delivered to the right mid-tibiae with a daily "10 min on-5 min off-10 min on" loading regime for five days/week. At each sacrifice time point, bone marrow MSCs of the stimulated and control tibiae were isolated through specific cell surface markers and quantified by flow cytometry analysis. A strong time-dependent manner of bone marrow MSC induction was observed in response to DHS, which peaked on day 14. After 21 days, this effect of DHS was diminished. This study indicates that the MSC pool is positively influenced by the mechanical signals driven by DHS. Coinciding with our previous findings of mitigation of disuse bone loss, DHS induced changes in MSC number may bias the differentiation of the MSC population towards osteoblastogenesis, thereby promoting bone formation under disuse conditions. This study provides insights into the mechanism of time-sensitive MSC induction in response to mechanical loading, and for the optimal design of osteoporosis treatments.
The Use of Fluid Mechanics to Predict Regions of Microscopic Thrombus Formation in Pulsatile VADs.
Topper, Stephen R; Navitsky, Michael A; Medvitz, Richard B; Paterson, Eric G; Siedlecki, Christopher A; Slattery, Margaret J; Deutsch, Steven; Rosenberg, Gerson; Manning, Keefe B
2014-03-01
We compare the velocity and shear obtained from particle image velocimetry (PIV) and computational fluid dynamics (CFD) in a pulsatile ventricular assist device (VAD) to further test our thrombus predictive methodology using microscopy data from an explanted VAD. To mimic physiological conditions in vitro , a mock circulatory loop is used with a blood analog that matched blood's viscoelastic behavior at 40% hematocrit. Under normal physiologic pressures and for a heart rate of 75 bpm, PIV data is acquired and wall shear maps are produced. The resolution of the PIV shear rate calculations are tested using the CFD and found to be in the same range. A bovine study, using a model of the 50 cc Penn State V-2 VAD, for 30 days at a constant beat rate of 75 beats per minute (bpm) provides the microscopic data whereby after the 30 days, the device is explanted and the sac surface analyzed using scanning electron microscopy (SEM) and, after immunofluorescent labeling for platelets and fibrin, confocal microscopy. Areas are examined based on PIV measurements and CFD, with special attention to low shear regions where platelet and fibrin deposition are most likely to occur. Data collected within the outlet port in a direction normal to the front wall of the VAD shows that some regions experience wall shear rates less than 500 s -1 , which increases the likelihood of platelet and fibrin deposition. Despite only one animal study, correlations between PIV, CFD, and in vivo data show promise. Deposition probability is quantified by the thrombus susceptibility potential, a calculation to correlate low shear and time of shear with deposition.
Apiwan, Suttinee; Puttharugsa, Chokchai; Khemmani, Supitch
2018-01-01
The purposes of this research were to help students to perform Physics laboratory by themselves and to provide guidelines for high school teacher to develop active learning on fluid mechanics by using Torricelli's tank experiment. The research was conducted as follows: 1) constructed an appropriate Torricelli's tank experiment for high school teaching and investigated the condition for maximum water falling distance. As a consequence, it was found that the distance of the falling water measured from the experiment was shorter than that obtained from the theory of ideal fluid because of the energy loss during a flow, 2) developed instructional manual for high school teaching that encourages active learning by using problem based learning (PBL) approach, which is consistent with the trend of teaching and learning in 21st century. The content validity of our instructional manual using Index of Item-objective Congruence (IOC) as evaluated by three experts was over 0.67. The manual developed was therefore qualified for classroom practice.
Delvigne, Frank; Takors, Ralf; Mudde, Rob; van Gulik, Walter; Noorman, Henk
2017-09-01
Efficient optimization of microbial processes is a critical issue for achieving a number of sustainable development goals, considering the impact of microbial biotechnology in agrofood, environment, biopharmaceutical and chemical industries. Many of these applications require scale-up after proof of concept. However, the behaviour of microbial systems remains unpredictable (at least partially) when shifting from laboratory-scale to industrial conditions. The need for robust microbial systems is thus highly needed in this context, as well as a better understanding of the interactions between fluid mechanics and cell physiology. For that purpose, a full scale-up/down computational framework is already available. This framework links computational fluid dynamics (CFD), metabolic flux analysis and agent-based modelling (ABM) for a better understanding of the cell lifelines in a heterogeneous environment. Ultimately, this framework can be used for the design of scale-down simulators and/or metabolically engineered cells able to cope with environmental fluctuations typically found in large-scale bioreactors. However, this framework still needs some refinements, such as a better integration of gas-liquid flows in CFD, and taking into account intrinsic biological noise in ABM. © 2017 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.
"Shape function + memory mechanism"-based hysteresis modeling of magnetorheological fluid actuators
Qian, Li-Jun; Chen, Peng; Cai, Fei-Long; Bai, Xian-Xu
2018-03-01
A hysteresis model based on "shape function + memory mechanism" is presented and its feasibility is verified through modeling the hysteresis behavior of a magnetorheological (MR) damper. A hysteresis phenomenon in resistor-capacitor (RC) circuit is first presented and analyzed. In the hysteresis model, the "memory mechanism" originating from the charging and discharging processes of the RC circuit is constructed by adopting a virtual displacement variable and updating laws for the reference points. The "shape function" is achieved and generalized from analytical solutions of the simple semi-linear Duhem model. Using the approach, the memory mechanism reveals the essence of specific Duhem model and the general shape function provides a direct and clear means to fit the hysteresis loop. In the frame of the structure of a "Restructured phenomenological model", the original hysteresis operator, i.e., the Bouc-Wen operator, is replaced with the new hysteresis operator. The comparative work with the Bouc-Wen operator based model demonstrates superior performances of high computational efficiency and comparable accuracy of the new hysteresis operator-based model.
The physics of hearing: fluid mechanics and the active process of the inner ear.
Reichenbach, Tobias; Hudspeth, A J
2014-07-01
Most sounds of interest consist of complex, time-dependent admixtures of tones of diverse frequencies and variable amplitudes. To detect and process these signals, the ear employs a highly nonlinear, adaptive, real-time spectral analyzer: the cochlea. Sound excites vibration of the eardrum and the three miniscule bones of the middle ear, the last of which acts as a piston to initiate oscillatory pressure changes within the liquid-filled chambers of the cochlea. The basilar membrane, an elastic band spiraling along the cochlea between two of these chambers, responds to these pressures by conducting a largely independent traveling wave for each frequency component of the input. Because the basilar membrane is graded in mass and stiffness along its length, however, each traveling wave grows in magnitude and decreases in wavelength until it peaks at a specific, frequency-dependent position: low frequencies propagate to the cochlear apex, whereas high frequencies culminate at the base. The oscillations of the basilar membrane deflect hair bundles, the mechanically sensitive organelles of the ear's sensory receptors, the hair cells. As mechanically sensitive ion channels open and close, each hair cell responds with an electrical signal that is chemically transmitted to an afferent nerve fiber and thence into the brain. In addition to transducing mechanical inputs, hair cells amplify them by two means. Channel gating endows a hair bundle with negative stiffness, an instability that interacts with the motor protein myosin-1c to produce a mechanical amplifier and oscillator. Acting through the piezoelectric membrane protein prestin, electrical responses also cause outer hair cells to elongate and shorten, thus pumping energy into the basilar membrane's movements. The two forms of motility constitute an active process that amplifies mechanical inputs, sharpens frequency discrimination, and confers a compressive nonlinearity on responsiveness. These features arise because the
The physics of hearing: fluid mechanics and the active process of the inner ear
International Nuclear Information System (INIS)
Reichenbach, Tobias; Hudspeth, A J
2014-01-01
Most sounds of interest consist of complex, time-dependent admixtures of tones of diverse frequencies and variable amplitudes. To detect and process these signals, the ear employs a highly nonlinear, adaptive, real-time spectral analyzer: the cochlea. Sound excites vibration of the eardrum and the three miniscule bones of the middle ear, the last of which acts as a piston to initiate oscillatory pressure changes within the liquid-filled chambers of the cochlea. The basilar membrane, an elastic band spiraling along the cochlea between two of these chambers, responds to these pressures by conducting a largely independent traveling wave for each frequency component of the input. Because the basilar membrane is graded in mass and stiffness along its length, however, each traveling wave grows in magnitude and decreases in wavelength until it peaks at a specific, frequency-dependent position: low frequencies propagate to the cochlear apex, whereas high frequencies culminate at the base. The oscillations of the basilar membrane deflect hair bundles, the mechanically sensitive organelles of the ear's sensory receptors, the hair cells. As mechanically sensitive ion channels open and close, each hair cell responds with an electrical signal that is chemically transmitted to an afferent nerve fiber and thence into the brain. In addition to transducing mechanical inputs, hair cells amplify them by two means. Channel gating endows a hair bundle with negative stiffness, an instability that interacts with the motor protein myosin-1c to produce a mechanical amplifier and oscillator. Acting through the piezoelectric membrane protein prestin, electrical responses also cause outer hair cells to elongate and shorten, thus pumping energy into the basilar membrane's movements. The two forms of motility constitute an active process that amplifies mechanical inputs, sharpens frequency discrimination, and confers a compressive nonlinearity on responsiveness. These features arise
Energy Technology Data Exchange (ETDEWEB)
Gu Yanhong, E-mail: ygu2@alaska.edu [Department of Mechanical Engineering, University of Alaska Fairbanks, Fairbanks, AK 99775 (United States); Chen Chengfu [Department of Mechanical Engineering, University of Alaska Fairbanks, Fairbanks, AK 99775 (United States); Bandopadhyay, Sukumar [Department of Mining Engineering, University of Alaska Fairbanks, Fairbanks, AK 99775 (United States); Ning Chengyun [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Zhang Yongjun [Department of Mining Engineering, University of Alaska Fairbanks, Fairbanks, AK 99775 (United States); Guo Yuanjun [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China)
2012-06-01
This paper addresses the effect of pulse frequency on the corrosion behavior of microarc oxidation (MAO) coatings on AZ31 Mg alloys in simulated body fluid (SBF). The MAO coatings were deposited by a pulsed DC mode at four different pulse frequencies of 300 Hz, 500 Hz, 1000 Hz and 3000 Hz with a constant pulse ratio. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were used for corrosion rate and electrochemical impedance evaluation. The corroded surfaces were examined by X-ray diffraction (XRD), X-ray fluorescence (XRF) and optical microscopy. All the results exhibited that the corrosion resistance of MAO coating produced at 3000 Hz is superior among the four frequencies used. The XRD spectra showed that the corrosion products contain hydroxyapatite, brucite and quintinite. A model for corrosion mechanism and corrosion process of the MAO coating on AZ31 Mg alloy in the SBF is proposed.
Brown, Alan
2018-01-01
Much learning takes place outside of formal class settings, yet students starting in higher education are not always well equipped with independent learning skills, appropriate self-knowledge or the required levels of intrinsic motivation This project used students as partners to develop resources that could be used by first-year undergraduates in fluid mechanics, using activities and receiving feedback through the virtual learning environment (VLE), in order to build these three attributes of independent learners. While there were significant benefits to the students who developed the resources, the target students saw much lower benefits as a result of poorer than expected engagement. The challenge this research presents is to develop activities that maximise engagement in large classes, as well as develop appropriate independent learning skills.
Du, Dongxing; Jiang, Song; Wang, Ze; Hu, Yingying; He, Zhaoming
2014-01-01
Mitral valve (MV) edge-to-edge repair (ETER) is a surgical procedure for the correction of mitral valve regurgitation by suturing the free edge of the leaflets. The leaflets are often sutured at three different positions: central, lateral and commissural portions. To study the effects of position of suture on left ventricular (LV) fluid mechanics under mitral valve ETER, a parametric model of MV-LV system during diastole was developed. The distribution and development of vortex and atrio-ventricular pressure under different suture position were investigated. Results show that the MV sutured at central and lateral in ETER creates two vortex rings around two jets, compared with single vortex ring around one jet of the MV sutured at commissure. Smaller total orifices lead to a higher pressure difference across the atrio-ventricular leaflets in diastole. The central suture generates smaller wall shear stresses than the lateral suture, while the commissural suture generated the minimum wall shear stresses in ETER.
International Nuclear Information System (INIS)
Gu Yanhong; Chen Chengfu; Bandopadhyay, Sukumar; Ning Chengyun; Zhang Yongjun; Guo Yuanjun
2012-01-01
This paper addresses the effect of pulse frequency on the corrosion behavior of microarc oxidation (MAO) coatings on AZ31 Mg alloys in simulated body fluid (SBF). The MAO coatings were deposited by a pulsed DC mode at four different pulse frequencies of 300 Hz, 500 Hz, 1000 Hz and 3000 Hz with a constant pulse ratio. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were used for corrosion rate and electrochemical impedance evaluation. The corroded surfaces were examined by X-ray diffraction (XRD), X-ray fluorescence (XRF) and optical microscopy. All the results exhibited that the corrosion resistance of MAO coating produced at 3000 Hz is superior among the four frequencies used. The XRD spectra showed that the corrosion products contain hydroxyapatite, brucite and quintinite. A model for corrosion mechanism and corrosion process of the MAO coating on AZ31 Mg alloy in the SBF is proposed.
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.
Quantum mechanical description of the two fluid model of liquid /sup 4/He solving the Bloch equation
International Nuclear Information System (INIS)
Fung, P.C.W.; Lam, C.C.
1986-01-01
The authors apply the U-matrix theory recently developed (Lam and Fung, Phys. Rev. A, vol.27, p.1760, 1983) to study certain physical properties of liquid /sup 4/He across a range of temperatures including the lambda -point. They propose a model for the chemical potential mu which is constant above T/sub lambda / but is a function of T below T/sub lambda /. They have discovered that the super-particles 'emerge' mathematically due to the uncommutability of the Hamiltonians at different temperatures, leading to a quantum mechanical description of the two-fluid model. Using the two-particle potential function deduced from scattering data, they have calculated numerically the approximate values of the number density for a range of temperatures starting from T/sub lambda /, taking the hard-core diameter Delta , 'effective chemical potential' mu ' as parameters
Li, Juan; Suo, Jinping; Zou, Peng; Jia, Lintao; Wang, Shifang
2010-01-01
The data for long-term drug-delivery systems are scarce compared to the short-term systems because the required research efforts are more time-consuming. In this study, we report a novel cross-linked composite based on poly(vinyl alcohol) (PVA) containing cupric ions for long-term delivery, which is helpful for contraception and trace element balance in the human body. The composition, corrosion products, crystal structure, chemical structure and mechanical stability of the composite, after being immersed in simulated body fluid (SBF) for one year, were studied by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR) and mechanical testing. The results show that no other new elements, such as P, Cl and Ca, appear on the surface of the composite and no Cu(2)O was formed after immersion in SBF for one year. The effectiveness of copper can be greatly improved and the side-effects caused by these compounds might also be eliminated. Furthermore, this novel composite exhibits long-term mechanical stability in SBF. The present in vitro long-term data suggest that this novel copper-containing composite may serve as a substitute for conventional materials of copper-containing intrauterine devices (Cu-IUDs) and as a carrier for controlled-release material in a variety of other applications.
Defining the best parallelization strategy for a diphasic compressible fluid mechanics code
International Nuclear Information System (INIS)
Berthou, Jean-Yves; Fayolle, Eric; Faucher, Eric; Scliffet, Laurent
2000-01-01
Nuclear plants use steam generator safety valves in order to regulate possible large pressure variations of fluids. In case of an incident these valves may be fed with pressurized liquid water (for instance a pressure of 9 MPa at a temperature of 300degC). When a pressurized liquid is submitted to a strong pressure drop, it will start evaporating. This phenomena is called flashing. Z. Bilicki and co-authors proposed the homogeneous relaxation model (HRM) to compute critical flashing water flows. Its computation in the case of non stationary one-dimensional flashing flows has been carried out with the development of a dedicated time dependent Finite Volume scheme based on a simplified version of the Godunov approach. Electricite De France Research and Development division have developed a monodimensional implementation of the HRM model: ECOSS, a 11000 lines FORTRAN 90. Applied to a shock tube test case with a 20000 elements monodimensional mesh, the simulation of the physical phenomenon during 2.5 seconds requires at least 100 days of computation on a SUN Sparc-Ultra60. This execution time justifies the ECOSS parallelization. Furthermore, we plan a modeling on 2D meshes for the next few years. Knowing that multiplying the mesh dimension by a factor 10 multiplies the execution time by a factor 100, ECOSS would take years of computation with small 2D meshes (1000 x 1000) on a conventional workstation. This paper describes the parallelization analysis we have conducted and we presents the experimental results we have obtained applying different programming model (MPI, OpenMP, HPF) on various platforms (a Compaq Proliant 6000 4 processors, a Cray T3E-750 300 processors, a HP class V 16 processors, a SGI Origin2000 32 processors, a cluster of PCs and a COMPAQ SC 232 processors). These experimental results will be discussed according to the following criteria: efficiency, salability, maintainability, developing costs and portability. As a conclusion, we will present the
Defining the best parallelization strategy for a diphasic compressible fluid mechanics code
Energy Technology Data Exchange (ETDEWEB)
Berthou, Jean-Yves; Fayolle, Eric [Electricite de France, Research and Development division, Modeling and Information Technologies Department, CLAMART CEDEX (France); Faucher, Eric; Scliffet, Laurent [Electricite de France, Research and Development Division, Mechanics and Component Technology Branch Department, Moret sur Loing (France)
2000-09-01
Nuclear plants use steam generator safety valves in order to regulate possible large pressure variations of fluids. In case of an incident these valves may be fed with pressurized liquid water (for instance a pressure of 9 MPa at a temperature of 300degC). When a pressurized liquid is submitted to a strong pressure drop, it will start evaporating. This phenomena is called flashing. Z. Bilicki and co-authors proposed the homogeneous relaxation model (HRM) to compute critical flashing water flows. Its computation in the case of non stationary one-dimensional flashing flows has been carried out with the development of a dedicated time dependent Finite Volume scheme based on a simplified version of the Godunov approach. Electricite De France Research and Development division have developed a monodimensional implementation of the HRM model: ECOSS, a 11000 lines FORTRAN 90. Applied to a shock tube test case with a 20000 elements monodimensional mesh, the simulation of the physical phenomenon during 2.5 seconds requires at least 100 days of computation on a SUN Sparc-Ultra60. This execution time justifies the ECOSS parallelization. Furthermore, we plan a modeling on 2D meshes for the next few years. Knowing that multiplying the mesh dimension by a factor 10 multiplies the execution time by a factor 100, ECOSS would take years of computation with small 2D meshes (1000 x 1000) on a conventional workstation. This paper describes the parallelization analysis we have conducted and we presents the experimental results we have obtained applying different programming model (MPI, OpenMP, HPF) on various platforms (a Compaq Proliant 6000 4 processors, a Cray T3E-750 300 processors, a HP class V 16 processors, a SGI Origin2000 32 processors, a cluster of PCs and a COMPAQ SC 232 processors). These experimental results will be discussed according to the following criteria: efficiency, salability, maintainability, developing costs and portability. As a conclusion, we will present the
Statistical mechanics of a one-component fluid of charged hard rods in 1D
International Nuclear Information System (INIS)
Vericat, F.; Blum, L.
1986-09-01
The statistical mechanics of a classical one component system of charged hard rods in a neutralizing background is investigated in 1D stressing on the effects of the hard core interactions over the thermodynamic and the structure of the system. The crystalline status of the system at all temperatures and densities and the absence of phase transitions is shown by extending previous results of Baxter and Kunz on the one-component plasma of point particles. Explicit expressions for the thermodynamic functions and the one-particle correlation function are given in the limits of small and strong couplings. (author)
Zhang, Yuan; Li, Jianxing; Li, Jingyuan
2018-04-01
Magnesium and its alloys have unique advantages to act as resorbable bone fixation materials, due to their moderate mechanical properties and biocompatibility, which are similar to those of human tissue. However, early resorption and insufficient mechanical strength are the main problems that hinder their application. Herein, the effects of microstructure transformation on the mechanical properties and corrosion performance of Mg-Zn-Mn-Ca were investigated with electrochemical and immersion measurements at 37 °C in a simulated body fluid (SBF). The results showed that the number density of Ca 2 Mg 6 Zn 3 /Mg 2 Ca precipitates was remarkably reduced and grain sizes were gradually increased as the temperature increased. The alloy that received the 420 °C/24 h treatment demonstrated the best mechanical properties and lowest corrosion rate (5.94 mm/a) as well as presented a compact and denser film than the others. The improvement in mechanical properties could be explained by the eutectic compounds and phases (Mg 2 Ca/Ca 2 Mg 6 Zn 3 ) gradually dissolving into a matrix, which caused severely lattice distortion and facilitated structural re-arrangement of the increased Ca solute. Moreover, the difference in potential between the precipitates and the matrix is the main essence for micro-galvanic corrosion formation as well as accelerated the dissolution activity and current exchange density at the Mg/electrolyte interface. As a result, the best Mg alloys corrosion resistance must be matched with a moderate grain size and phase volume fractions. Copyright © 2018 Elsevier Ltd. All rights reserved.
[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.
Structural determinants of hydration, mechanics and fluid flow in freeze-dried collagen scaffolds.
Offeddu, G S; Ashworth, J C; Cameron, R E; Oyen, M L
2016-09-01
Freeze-dried scaffolds provide regeneration templates for a wide range of tissues, due to their flexibility in physical and biological properties. Control of structure is crucial for tuning such properties, and therefore scaffold functionality. However, the common approach of modeling these scaffolds as open-cell foams does not fully account for their structural complexity. Here, the validity of the open-cell model is examined across a range of physical characteristics, rigorously linking morphology to hydration and mechanical properties. Collagen scaffolds with systematic changes in relative density were characterized using Scanning Electron Microscopy, X-ray Micro-Computed Tomography and spherical indentation analyzed in a time-dependent poroelastic framework. Morphologically, all scaffolds were mid-way between the open- and closed-cell models, approaching the closed-cell model as relative density increased. Although pore size remained constant, transport pathway diameter decreased. Larger collagen fractions also produced greater volume swelling on hydration, although the change in pore diameter was constant, and relatively small at ∼6%. Mechanically, the dry and hydrated scaffold moduli varied quadratically with relative density, as expected of open-cell materials. However, the increasing pore wall closure was found to determine the time-dependent nature of the hydrated scaffold response, with a decrease in permeability producing increasingly elastic rather than viscoelastic behavior. These results demonstrate that characterizing the deviation from the open-cell model is vital to gain a full understanding of scaffold biophysical properties, and provide a template for structural studies of other freeze-dried biomaterials. Freeze-dried collagen sponges are three-dimensional microporous scaffolds that have been used for a number of exploratory tissue engineering applications. The characterization of the structure-properties relationships of these scaffolds is
Computational Fluid Dynamic Investigation of Loss Mechanisms in a Pulse-Tube Refrigerator
International Nuclear Information System (INIS)
Martin, K; Esguerra, J; Dodson, C; Razani, A
2015-01-01
In predicting Pulse-Tube Cryocooler (PTC) performance, One-Dimensional (1-D) PTR design and analysis tools such as Gedeon Associates SAGE® typically include models for performance degradation due to thermodynamically irreversible processes. SAGE®, in particular, accounts for convective loss, turbulent conductive loss and numerical diffusion “loss” via correlation functions based on analysis and empirical testing.In this study, we compare CFD and SAGE® estimates of PTR refrigeration performance for four distinct pulse-tube lengths. Performance predictions from PTR CFD models are compared to SAGE® predictions for all four cases. Then, to further demonstrate the benefits of higher-fidelity and multidimensional CFD simulation, the PTR loss mechanisms are characterized in terms of their spatial and temporal locations. (paper)
Hubert, Antoine; Dadonau, Maksim; Dembele, Siaka; Denissenko, Petr; Wen, Jennifer
2017-11-01
Growing demand for the LNG fosters growth of the number of production sites with varying composition and density. Combining different sources of LNG may result in a stably stratified system, in which heat and mass transfer between the layers is limited. Heating of the LNG due to wall thermal conductivity leads to formation of convection cells confined within the layers. While the upper layer can release the extra energy via preferential methane boil-off, the bottom layer cannot and hence becomes superheated. Gradual density equilibration reduces stratification and may eventually lead to a sudden mixing event called ``rollover'', accompanied by violent evaporation of the superheated LNG. Three phenomena are potentially responsible for density equilibration. The first is the growing difference in thermal expansion of the layers due to the reduced ability of the bottom layer to reject heat. The second is the penetration of the heated near-wall boundary layer into the upper layer. The third is the ``entrainment mixing'' occurring at the contact surface between the two layers. The present study uses CFD to compare these mechanisms. Boussinesq approximation and an extended version of the k- ɛ model is used. The code is validated by comparison with a large-scale LNG rollover experiment.
Del Gaudio, Costantino; Gasbarroni, Pier Luca; Romano, Giovanni Paolo
2016-12-01
End-stage failing heart valves are currently replaced by mechanical or biological prostheses. Both types positively contribute to restore the physiological function of native valves, but a number of drawbacks limits the expected performances. In order to improve the outcome, tissue engineering can offer an alternative approach to design and fabricate innovative heart valves capable to support the requested function and to promote the formation of a novel, viable and correctly operating physiological structure. This potential result is particularly critical if referred to the aortic valve, being the one mainly exposed to structural and functional degeneration. In this regard, the here proposed study presents the fabrication and in vitro characterization of a bioresorbable electrospun heart valve prosthesis using the particle image velocimetry technique either in physiological and pathological fluid dynamic conditions. The scaffold was designed to reproduce the aortic valve geometry, also mimicking the fibrous structure of the natural extracellular matrix. To evaluate its performances for possible implantation, the flow fields downstream the valve were accurately investigated and compared. The experimental results showed a correct functionality of the device, supported by the formation of vortex structures at the edge of the three cusps, with Reynolds stress values below the threshold for the risk of hemolysis (which can be comprised in the range 400-4000N/m(2) depending on the exposure period), and a good structural resistance to the mechanical loads generated by the driving pressure difference. Copyright © 2016 Elsevier Ltd. All rights reserved.
Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio
2016-04-21
We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.
Kannan, M Bobby; Raman, R K Singh
2008-05-01
The successful applications of magnesium-based alloys as degradable orthopaedic implants are mainly inhibited due to their high degradation rates in physiological environment and consequent loss in the mechanical integrity. This study examines the degradation behaviour and the mechanical integrity of calcium-containing magnesium alloys using electrochemical techniques and slow strain rate test (SSRT) method, respectively, in modified-simulated body fluid (m-SBF). Potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) results showed that calcium addition enhances the general and pitting corrosion resistances of magnesium alloys significantly. The corrosion current was significantly lower in AZ91Ca alloy than that in AZ91 alloy. Furthermore, AZ91Ca alloy exhibited a five-fold increase in the surface film resistance than AZ91 alloy. The SSRT results showed that the ultimate tensile strength and elongation to fracture of AZ91Ca alloy in m-SBF decreased only marginally (approximately 15% and 20%, respectively) in comparison with these properties in air. The fracture morphologies of the failed samples are discussed in the paper. The in vitro study suggests that calcium-containing magnesium alloys to be a promising candidate for their applications in degradable orthopaedic implants, and it is worthwhile to further investigate the in vivo corrosion behaviour of these alloys.
Schulze, Waltraud X.; Sanggaard, Kristian W.; Kreuzer, Ines; Knudsen, Anders D.; Bemm, Felix; Thøgersen, Ida B.; Bräutigam, Andrea; Thomsen, Line R.; Schliesky, Simon; Dyrlund, Thomas F.; Escalante-Perez, Maria; Becker, Dirk; Schultz, Jörg; Karring, Henrik; Weber, Andreas; Højrup, Peter; Hedrich, Rainer; Enghild, Jan J.
2012-01-01
The Venus flytrap (Dionaea muscipula) is one of the most well-known carnivorous plants because of its unique ability to capture small animals, usually insects or spiders, through a unique snap-trapping mechanism. The animals are subsequently killed and digested so that the plants can assimilate nutrients, as they grow in mineral-deficient soils. We deep sequenced the cDNA from Dionaea traps to obtain transcript libraries, which were used in the mass spectrometry-based identification of the proteins secreted during digestion. The identified proteins consisted of peroxidases, nucleases, phosphatases, phospholipases, a glucanase, chitinases, and proteolytic enzymes, including four cysteine proteases, two aspartic proteases, and a serine carboxypeptidase. The majority of the most abundant proteins were categorized as pathogenesis-related proteins, suggesting that the plant's digestive system evolved from defense-related processes. This in-depth characterization of a highly specialized secreted fluid from a carnivorous plant provides new information about the plant's prey digestion mechanism and the evolutionary processes driving its defense pathways and nutrient acquisition. PMID:22891002
Directory of Open Access Journals (Sweden)
Peter M Mourani
Full Text Available BACKGROUND: Despite strong evidence linking infections to the pathogenesis of bronchopulmonary dysplasia (BPD, limitations of bacterial culture methods have precluded systematic studies of airway organisms relative to disease outcomes. Application of molecular bacterial identification strategies may provide new insight into the role of bacterial acquisition in the airways of preterm infants at risk for BPD. METHODS: Serial (within 72 hours, 7, 14, and 21 days of life tracheal aspirate samples were collected from 10 preterm infants with gestational age ≤34 weeks at birth, and birth weight of 500-1250 g who required mechanical ventilation for at least 21 days. Samples were analyzed by quantitative real time PCR assays for total bacterial load and by pyrosequencing for bacterial identification. RESULTS: Subjects were diagnosed with mild (1, moderate (3, or severe (5 BPD. One patient died prior to determination of disease severity. 107,487 sequences were analyzed, with mean of 3,359 (range 1,724-4,915 per sample. 2 of 10 samples collected 70copies/reaction. 72 organisms were observed in total. Seven organisms represented the dominant organism (>50% of total sequences in 31/32 samples with positive sequences. A dominant organism represented>90% of total sequences in 13 samples. Staphylococcus, Ureaplasmaparvum, and Ureaplasmaurealyticum were the most frequently identified dominant organisms, but Pseudomonas, Enterococcus, and Escherichia were also identified. CONCLUSIONS: Early bacterial colonization with diverse species occursafter the first 3 days of life in the airways of intubated preterm infants, and can be characterized by bacterial load and marked species diversity. Molecular identification of bacteria in the lower airways of preterm infants has the potential to yield further insight into the pathogenesis of BPD.
International Nuclear Information System (INIS)
Le Guen, Y.
2006-10-01
CO 2 injection into geological repositories will induce chemical and mechanical instabilities. The study of these instabilities is based on experimental deformation of natural rock samples under stress, in the presence of fluids containing, or not, dissolved CO 2 . Triaxial cells used for the experiments permitted an independent control and measurement of stress, temperature, fluid pressure and composition. Vertical strains were measured during several months, with a resolution of 1.10 -12 s -1 on the strain rate. Simultaneously, fluids were analysed in order to quantify fluid-rock interactions. For limestone samples, percolation of CO 2 -rich fluids increases strain rate by a factor 1.7 up to 5; on the other hand, sandstone deformation remained almost the same. Increase in strain rate with limestone samples was explained by injected water acidification by the CO 2 which increases rock solubility and reaction kinetics. On the opposite, small effect of CO 2 on quartz explains the absence of deformation. X-ray observations confirmed the importance of rock composition and structure on the porosity evolution. Numerical simulations of rock elastic properties showed increasing shear stress into the sample. Measured deformation showed an evolution of reservoir rocks mechanical properties. It was interpreted as the consequence of pressure solution mechanisms both at grains contacts and on grain free surfaces. (author)
Directory of Open Access Journals (Sweden)
Kempka Thomas
2015-04-01
Full Text Available We assessed the synergetic benefits of simultaneous formation fluid extraction during CO2 injection for reservoir pressure management by coupled hydro-mechanical simulations at the prospective Vedsted storage site located in northern Denmark. Effectiveness of reservoir pressure management was investigated by simulation of CO2 storage without any fluid extraction as well as with 66% and 100% equivalent volume formation fluid extraction from four wells positioned for geothermal heat recovery. Simulation results demonstrate that a total pressure reduction of up to about 1.1 MPa can be achieved at the injection well. Furthermore, the areal pressure perturbation in the storage reservoir can be significantly decreased compared to the simulation scenario without any formation fluid extraction. Following a stress regime analysis, two stress regimes were considered in the coupled hydro-mechanical simulations indicating that the maximum ground surface uplift is about 0.24 m in the absence of any reservoir pressure management. However, a ground uplift mitigation of up to 37.3% (from 0.24 m to 0.15 m can be achieved at the injection well by 100% equivalent volume formation fluid extraction. Well-based adaptation of fluid extraction rates can support achieving zero displacements at the proposed formation fluid extraction wells located close to urban infrastructure. Since shear and tensile failure do not occur under both stress regimes for all investigated scenarios, it is concluded that a safe operation of CO2 injection with simultaneous formation fluid extraction for geothermal heat recovery can be implemented at the Vedsted site.
Azarov, Alexey V; Woodward, Donald J
2014-01-17
The goal of this study was to clarify similar and distinctly different parameters of fluid intake during early phases of ethanol and water choice drinking in alcohol preferring P-rat vs. non-selected Wistar and Sprague Dawley (SD) rats. Precision information on the drinking amounts and timing is needed to analyze micro-behavioral components of the acquisition of ethanol intake and to enable a search for its causal activity patterns within individual CNS circuits. The experiment followed the standard ethanol-drinking test used in P-rat selective breeding, with access to water, then 10% ethanol (10E) as sole fluids, and next to ethanol/water choice. The novelty of the present approach was to eliminate confounding prandial elevations of fluid intake, by time-separating daily food from fluid access. P-rat higher initial intakes of water and 10E as sole fluids suggest adaptations to ethanol-induced dehydration in P vs. Wistar and SD rats. P-rat starting and overall ethanol intake during the choice period were the highest. The absolute extent of ethanol intake elevation during choice period was greatest in Wistar and their final intake levels approached those of P-rat, contrary to the hypothesis that selection would produce the strongest elevation of ethanol intake. The total daily fluid during ethanol/water choice period was strikingly similar between P, Wistar and SD rats. This supports the hypothesis for a universal system that gauges the overall intake volume by titrating and integrating ethanol and water drinking fluctuations, and indicates a stable daily level of total fluid as a main regulated parameter of fluid intake across the three lines in choice conditions. The present findings indicate that a stable daily level of total fluid comprises an independent physiological limit for daily ethanol intake. Ethanol drinking, in turn, stays under the ceiling of this limit, driven by a parallel mechanism of ethanol/water choice. © 2013 Elsevier Inc. All rights reserved.
International Nuclear Information System (INIS)
Ishii, Takemasa; Marui, Atsunao; Takahashi, Manabu; Tsukamoto, Hitoshi
1999-01-01
Aim of this study are to elucidate transfer and diffusion mechanism of fluid under an environment of deep geological environment by each two geological media such as fractured and porous media, to establish a precise evaluation method on hydrogeological features, to develop a new researching method on transfer and diffusion mechanism of fluid at field, and to conduct model construction and effect evaluation of fluid at deep underground based on measuring values. As a result, on cracking medium, it was found that a value relating to storage rate could be evaluated simultaneously, that both water permeability coefficient and storage rate decreased as sealing pressure of specimen increased, and that change of hydrologic features in specimen could be evaluated more accurately. And, on porous medium, it was conducted to compare mutually two water permeability coefficients obtained by using three kinds of sedimentation rock with different interstitial ratio and two testing methods of transient pulse method and changing water level method. (G.K.)
International Nuclear Information System (INIS)
Toda, Saburo; Yuki, Kazuhisa; Muramatsu, Toshiharu
2002-03-01
In a region where two fluids with different temperatures are mixed together, unsteady temperature fluctuation, i.e. thermal striping, occurs in going through the unstable mixing process of the fluids, and structural materials in the surrounding area may be damaged by high-cycle thermal fatigue. In this report, in order to clarify the relation between the thermal striping and temperature fluctuation of structural wall, PIV measuring system is applied to visualize the fluid mixing state in a T-junction area in which important parameters for the fluid mixing are the flow velocity and aperture ratios of a main pipe to a small pipe and an incidence angle of the small pipe to the main pipe as well as temperature difference of the two flows. As a result of visualization experiments in a isothermal field, it is confirmed that a jet-axis, which is a stream line flowing out from the center of the small pipe, vibrates unsteadily and that its behavior is strongly affected by circulating flow, Karman vortex formed behind the jet axis, and especially flow-fluctuation which exists as a background-flow in the main pipe. Especially, the frequency band of the flow-fluctuation in the main pipe almost corresponds to that of the vibration of the jet-axis where the ratio of flow rate is low. Furthermore, in order to estimate the vibration state of the jet-axis and to find out the conditions for preventing the thermal fatigue, the penetration depth of the jet-axis is generalized. From measurements of temperature fluctuation of wall, it is shown that a high power fluctuation area exists universally behind the junction point of the small pipe where the flow rate of the small pipe flow is relatively lower than that of the main pipe flow. The band of dominant frequency of the temperature fluctuation is almost the same as the flow-fluctuation and the jet-axis vibration mentioned above. In addition, visualization experiments of secondary flow formed in a 90-degree bend, which is installed
Nayfeh, A. H.; Mobarak, A.; Rayan, M. Abou
This conference presents papers in the fields of flow separation, unsteady aerodynamics, fluid machinery, boundary-layer control and stability, grid generation, vorticity dominated flows, and turbomachinery. Also considered are propulsion, waves and sound, rotor aerodynamics, computational fluid dynamics, Euler and Navier-Stokes equations, cavitation, mixing and shear layers, mixing layers and turbulent flows, and fluid machinery and two-phase flows. Also addressed are supersonic and reacting flows, turbulent flows, and thermofluids.
Energy Technology Data Exchange (ETDEWEB)
Nayfeh, A.H.; Mobarak, A.; Rayan, M.A.
1990-01-01
This conference presents papers in the fields of flow separation, unsteady aerodynamics, fluid machinery, boundary-layer control and stability, grid generation, vorticity dominated flows, and turbomachinery. Also considered are propulsion, waves and sound, rotor aerodynamics, computational fluid dynamics, Euler and Navier-Stokes equations, cavitation, mixing and shear layers, mixing layers and turbulent flows, and fluid machinery and two-phase flows. Also addressed are supersonic and reacting flows, turbulent flows, and thermofluids.
Energy Technology Data Exchange (ETDEWEB)
Muller, J [IRSID, Institut de Recherches Siderurgie, 57 - Maizieres-les-Metz (France)
1997-12-31
Radiant heat transfer is the main solution retained in many iron and steel metallurgy installations (re-heating and annealing furnaces etc..). Today, it has become important to dispose of performing radiant heat transfer models in heat transfer and fluid mechanics simulation softwares, and well adapted to multidimensional industrial problems. This work presents the discrete ordinate radiant heat transfer model developed at the IRSID (the French institute of research in iron and steel metallurgy) and coupled with the PHOENICS heat transfer-fluid mechanics software. Three modeling approaches are presented concerning the radiative properties of gases (H{sub 2}O-CO{sub 2}). A ``weighted grey gases sum`` model gives satisfactory results for several 1-D validation cases. (J.S.) 20 refs.
Energy Technology Data Exchange (ETDEWEB)
Muller, J. [IRSID, Institut de Recherches Siderurgie, 57 - Maizieres-les-Metz (France)
1996-12-31
Radiant heat transfer is the main solution retained in many iron and steel metallurgy installations (re-heating and annealing furnaces etc..). Today, it has become important to dispose of performing radiant heat transfer models in heat transfer and fluid mechanics simulation softwares, and well adapted to multidimensional industrial problems. This work presents the discrete ordinate radiant heat transfer model developed at the IRSID (the French institute of research in iron and steel metallurgy) and coupled with the PHOENICS heat transfer-fluid mechanics software. Three modeling approaches are presented concerning the radiative properties of gases (H{sub 2}O-CO{sub 2}). A ``weighted grey gases sum`` model gives satisfactory results for several 1-D validation cases. (J.S.) 20 refs.
Harrison, David J.; Saito, Laurel; Markee, Nancy; Herzog, Serge
2017-01-01
To examine the impact of a hybrid-flipped model utilising active learning techniques, the researchers inverted one section of an undergraduate fluid mechanics course, reduced seat time, and engaged in active learning sessions in the classroom. We compared this model to the traditional section on four performance measures. We employed a propensity…
Kasagi, Nobuhide
2000-01-01
The Nusselt Reynolds Prize has been established by the Assembly of World Conferences to commemorate outstanding contributions by Wilhelm Nusselt and Osborne Reynolds as experimentalists, researchers, educators, and authors. As many as three prizes may be bestowed at every World Conference, one in each of the areas of heat transfer, fluid mechanics, thermodynamics, or any combination of these.
Eijkel, Jan C.T.
2014-01-01
The authors of the paper “Nanoscale Fluid Mechanics and Energy Conversion” have presented an overview of recent applications of nanofluidic phenomena for energy conversion and storage. The discussion given here aims to place this paper in a broader context of literature and theory.
Directory of Open Access Journals (Sweden)
Zhigang Xu
2016-12-01
Full Text Available Fe–Mn-based degradable biomaterials (DBMs are promising candidates for temporary implants such as cardiovascular stents and bone fixation devices. Identifying their mechanical properties and biocompatibility is essential to determine the feasibility of Fe–Mn-based alloys as DBMs. This study presents the tensile properties of two powder metallurgical processed Fe–Mn-based alloys (Fe–28Mn and Fe–28Mn-3Si, in mass percent as a function of immersion time in simulated body fluid (SBF. In addition, short-term cytotoxicity testing was performed to evaluate the in vitro biocompatibility of the sintered Fe–Mn-based alloys. The results reveal that an increase in immersion duration deteriorated the tensile properties of both the binary and ternary alloys. The tensile properties of the immersed alloys were severely degraded after being soaked in SBF for ≥45 days. The ion concentration in SBF released from the Fe–28Mn-3Si samples was higher than their Fe–28Mn counterparts after 7 days immersion. The preliminary cytotoxicity testing based on the immersed SBF medium after 7 days immersion suggested that both the Fe–28Mn-3Si and Fe–28Mn alloys presented a good biocompatibility in Murine fibroblast cells.
Lai, Chang Quan; Lim, Guat Ling; Jamil, Muhammad; Mattar, Citra Nurfarah Zaini; Biswas, Arijit; Yap, Choon Hwai
2016-10-01
The mechanics of intracardiac blood flow and the epigenetic influence it exerts over the heart function have been the subjects of intense research lately. Fetal intracardiac flows are especially useful for gaining insights into the development of congenital heart diseases, but have not received due attention thus far, most likely because of technical difficulties in collecting sufficient intracardiac flow data in a safe manner. Here, we circumvent such obstacles by employing 4D STIC ultrasound scans to quantify the fetal heart motion in three normal 20-week fetuses, subsequently performing 3D computational fluid dynamics simulations on the left ventricles based on these patient-specific heart movements. Analysis of the simulation results shows that there are significant differences between fetal and adult ventricular blood flows which arise because of dissimilar heart morphology, E/A ratio, diastolic-systolic duration ratio, and heart rate. The formations of ventricular vortex rings were observed for both E- and A-wave in the flow simulations. These vortices had sufficient momentum to last until the end of diastole and were responsible for generating significant wall shear stresses on the myocardial endothelium, as well as helicity in systolic outflow. Based on findings from previous studies, we hypothesized that these vortex-induced flow properties play an important role in sustaining the efficiency of diastolic filling, systolic pumping, and cardiovascular flow in normal fetal hearts.
Indian Academy of Sciences (India)
It would also have been useful to demonstrate the application of unsteady Bernoulli equation with simple examples. There is a large. On the whole, I strongly recommend these as text books for undergraduate engineering students at the beginner's level. ______ ,AA~AAA __ ------. 88 ..., V V V V"". RESONANCE I Augustl996 ...
Bioengineering fluid mechanics
Hung, Tin-kan
2013-01-01
This book highlights the basic concepts and equations for bioengineering flow processes. Physical concepts and meanings are emphasized while rigorous derivations are simplified, making it easier for self learning on some biological and medical flow processes. The well known Bernoulli equation in hydraulics is extended for pulsating flows, peristaltic flows and cardiac pumping. The dimensional analysis, model law and dimensionless equations can be related to computational models and experimental observations. The velocity vector imaging stored in echocardiograms can be used to analyze the pumping characteristics of the ventricular contraction. New topics included oxygen transport in membrane oxygenator and micro mixing of blood flow in capillary channels.
Hassan, H. A.
1993-01-01
Two papers are included in this progress report. In the first, the compressible Navier-Stokes equations have been used to compute leading edge receptivity of boundary layers over parabolic cylinders. Natural receptivity at the leading edge was simulated and Tollmien-Schlichting waves were observed to develop in response to an acoustic disturbance, applied through the farfield boundary conditions. To facilitate comparison with previous work, all computations were carried out at a free stream Mach number of 0.3. The spatial and temporal behavior of the flowfields are calculated through the use of finite volume algorithms and Runge-Kutta integration. The results are dominated by strong decay of the Tollmien-Schlichting wave due to the presence of the mean flow favorable pressure gradient. The effects of numerical dissipation, forcing frequency, and nose radius are studied. The Strouhal number is shown to have the greatest effect on the unsteady results. In the second paper, a transition model for low-speed flows, previously developed by Young et al., which incorporates first-mode (Tollmien-Schlichting) disturbance information from linear stability theory has been extended to high-speed flow by incorporating the effects of second mode disturbances. The transition model is incorporated into a Reynolds-averaged Navier-Stokes solver with a one-equation turbulence model. Results using a variable turbulent Prandtl number approach demonstrate that the current model accurately reproduces available experimental data for first and second-mode dominated transitional flows. The performance of the present model shows significant improvement over previous transition modeling attempts.
Monin, A S
2007-01-01
""If ever a field needed a definitive book, it is the study of turbulence; if ever a book on turbulence could be called definitive, it is this book."" - ScienceWritten by two of Russia's most eminent and productive scientists in turbulence, oceanography, and atmospheric physics, this two-volume survey is renowned for its clarity as well as its comprehensive treatment. The first volume begins with an outline of laminar and turbulent flow. The remainder of the book treats a variety of aspects of turbulence: its statistical and Lagrangian descriptions, shear flows near surfaces and free turbulenc
Zhao, Feihu; Vaughan, Ted J; Mc Garrigle, Myles J; McNamara, Laoise M
2017-10-01
Tissue formation within tissue engineering (TE) scaffolds is preceded by growth of the cells throughout the scaffold volume and attachment of cells to the scaffold substrate. It is known that mechanical stimulation, in the form of fluid perfusion or mechanical strain, enhances cell differentiation and overall tissue formation. However, due to the complex multi-physics environment of cells within TE scaffolds, cell transport under mechanical stimulation is not fully understood. Therefore, in this study, we have developed a coupled multiphysics model to predict cell density distribution in a TE scaffold. In this model, cell transport is modelled as a thermal conduction process, which is driven by the pore fluid pressure under applied loading. As a case study, the model is investigated to predict the cell density patterns of pre-osteoblasts MC3T3-e1 cells under a range of different loading regimes, to obtain an understanding of desirable mechanical stimulation that will enhance cell density distribution within TE scaffolds. The results of this study have demonstrated that fluid perfusion can result in a higher cell density in the scaffold region closed to the outlet, while cell density distribution under mechanical compression was similar with static condition. More importantly, the study provides a novel computational approach to predict cell distribution in TE scaffolds under mechanical loading. Copyright © 2017 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Irwan Iskandar
2018-03-01
Full Text Available The Tampomas Volcano is a Quaternary volcano located on Java Island and controlled by a west-northwest–east-southeast (WNW-ESE regional fault trend. This regional structure acts as conduits for the hydrothermal fluids to ascend from a deeper system toward the surface and, in the end, mix with groundwater. In this research, water geochemistry, gas chemistry and isotopes 2H, 18O and 13C were used to explore the subsurface fluid characteristics and mixing mechanisms of the hydrothermal fluids with groundwater. In addition to those geochemical methods, soil-gas and dissolved 222Rn observations were performed to understand the geological control of fluid chemistry. Based on the analytical results, the hydrothermal system of Tampomas is only developed at the northeastern flank of the volcano, which is mainly controlled by NE-SW structures as deep fluid conduits, while the Cimalaka Caldera Rim around Sekarwangi act as the boundary flow of the system. This system is also categorized as an “intermediate temperature system” wherein fluid is derived from the interaction between the volcanic host-rock at 170 ± 10 °C mixed with trace organic gas input from sedimentary formation; afterwards, the fluid flows laterally and is diluted with groundwater near the surface. Soil-gas and dissolved 222Rn confirm that these permeable zones are effective conduits for the ascending thermal fluids. It is found that NE faults carry higher trace elements from the deeper system, while the circular feature of the Caldera Rim acts as the boundary of the hydrothermal system.
Three-dimensional fluid mechanics of particulate two-phase flows in U-bend and helical conduits
Tiwari, Prashant; Antal, Steven P.; Podowski, Michael Z.
2006-04-01
The results of numerous studies performed to date have shown that the performance of various hydraulic systems can be significantly improved by using curved conduit geometries instead of straight tubes. In particular, the formation of Dean vortices, which enhance the development of centrifugal instabilities, has been identified as a factor behind reducing the near-wall concentration buildup in particulate flow devices (e.g., in membrane filtration modules). Still, several issues regarding the effect of conduit curvature on local multidimensional phenomena governing fluid flow still remain open. A related issue is concerned with the impact that conduit geometry makes on the concentration distribution of a dispersed phase in two-phase flows in general, and in particulate flows (solid/liquid or solid/gas suspensions) in particular. It turns out that only very limited efforts have been made in the past to understand the fluid mechanics of such flows via advanced computer simulations. The purpose of this paper is to present the results of full three-dimensional (3D) theoretical and numerical analyses of single- and two-phase dilute particle/liquid flows in U-bend and helical curved conduits. The numerical analysis is based on computational fluid dynamics (CFD) simulations performed using a state-of-the-art multiphase flow computer code, NPHASE. The major issues discussed in the first part of the paper are concerned with the effect of curved/coiled geometry on the evolution of flow field and the associated wall shear. It has been demonstrated that the primary curvature (a common factor for both the U-bend and helix geometries) may cause a substantial asymmetry in the radial distribution of the main flow velocity. This, in turn, leads to a significant, albeit highly nonuniform, increase in the wall shear stress. Specifically, the wall shear around the outer half of tube circumference may become twice the corresponding value for a straight tube, and gradually decrease to
International Nuclear Information System (INIS)
Schneider, B.; Aly, K.
2012-01-01
Much analysis, research and inspection has gone into the understanding of deposition within steam generators. All of that work notwithstanding, it still remains a mystery in many respects - particularly regarding the fluid mechanics of deposition. This presentation tracks corrosion product transport (CPT) ingress to an SG and the approximate distribution of the resultant deposition. It also investigates deposition of the small but highly problematic amount of CPT which ends up on the tube-supports (TSPs). CPT ingress during full-power operation of modern well-run steam generators (SGs) represents as reported elsewhere at this conference, a very small amount of material. Unfortunately operation has not always achieved such standards. Plants with a few decades operation may have significant deposition – a condition which may well be accompanied by severe tube and tube-support deposition and the consequent blockage of the TSPs. CPT ingress to a steam generator may, in very rough numbers, distribute as follows; i) removal by blow-down ~ 15% (i.e. - most of what comes in stays in the SG); ii) deposition to the SG tube surface ~ 50% (plated out thinly over the 1 to 2 acres of SG tube surface); iii) tube-sheet sludge pile ~ 25% (bad news for tube life, but easy to inspect and water-lance); iv) TSP deposition <~5% (a small but highly problematic amount of material). Deposition as it turns out is exacerbated by the fluid-mechanics at square-cornered contractions which may exist at the entrance to flow passages of some types of tube-supports. High local velocities will occur at such corners – resulting in a significant local static-pressure depression – which causes flash-evaporation – which can leave behind CPT materials particularly in areas of moderately high bulk quality. All of that results counter-intuitively, in the initiation of deposition right at the -corner of the tube support. This type of inlet-corner deposition was first seen about three decades ago at
International Nuclear Information System (INIS)
Drew, D.A.; Flaherty, J.E.
1986-01-01
The mathematical analysis of fluid mechanics and stability and its applications in science and engineering are examined in reviews and reports. Topics addressed include Taylor-vortex flow, isothermal fluid-film lubrication theories, the morphology of spiral galaxies, rotating-fluid problems in ballistics, coupled Lorenz oscillators, the connection between chaos and turbulence, plane-front alloy solidification versus free-surface Benard convection, and the nonlinear stability of spiral flow between rotating cylinders with a small gap. Consideration is given to resonance conditions for forced two-dimensional channel flows, the secondary bifurcation of standing surface waves in rectangular basins, instability in the flow of granular materials, and the supercritical dynamics of baroclinic disturbances
White, Samuel G.; Gilinsky, Mikhail M.
1997-01-01
In accordance with the project plan for the report period in the proposal titled above, HU and FML teams investigated two sets of concepts for reduction of noise and improvement in efficiency for jet exhaust nozzles of aircraft engines and screws for mixers, fans, propellers and boats. The main achievements in the report period are: (a) Publication of the paper in the AIAA Journal, which described our concepts and some results. (b) The Award in the Civil Research and Development Foundation (CRDF) competition. This 2 year grant for Hampton University (HU) and Central AeroHydrodynamic Institute (TSAGI, Moscow, Russia) supports the research implementation under the current NASA FAR grant. (c) Selection for funding by NASA HQ review panel of the Partnership Awards Concept Paper. This two year grant also will support our current FAR grant. (d) Publication of a Mobius Strip concept in NASA Technical Briefs, June, 1996, and a great interest of many industrial companies in this invention. Successful experimental results with the Mobius shaped screw for mixers, which save more than 30% of the electric power by comparison with the standard screws. Creation of the scientific-popular video-film which can be used for commercial and educational purposes. (e) Organization work, joint meetings and discussions of the NASA LARC JNL Team and HU professors and administration for the solution of actual problems and effective work of the Fluid Mechanics Laboratory at Hampton University. In this report the main designs are enumerated. It also contains for both concept sets: (1) the statement of the problem for each design, some results, publications, inventions, patents, our vision for continuation of this research, and (2) present and expected problems in the future.
Vala, A. K.; Desai, R.; Upadhyay, R. V.; Mehta, R. V.
2008-12-01
Interaction of facultative marine fungus Aspergillus niger with a Mn-Zn ferrite magnetic fluid (MF) has been studied. The fungus exhibited a luxuriant growth in the presence of magnetic fluid at test concentrations. Though the biomass accumulation was found to be almost similar, mycelial spread was found to be rapid in the presence of MF if compared to the control one. The MF also exhibited a positive effect on the biomass accumulation during prolonged incubation. These preliminary observations provide a baseline information for possible exploitation of the magnetic fluid-facultative marine fungal interaction for bioremediation purposes. Figs 5, Refs 13.
International Nuclear Information System (INIS)
Dutrow, Barbara
2008-01-01
Our research evaluates the hypothesis that feedback amongst thermal-chemical-mechanical processes operative in fluid-rock systems alters the fluid flow dynamics of the system which, in turn, affects chemical transport and temporal and spatial scales of equilibria, thus impacting the resultant mineral textural development of rocks. Our methods include computational experimentation and detailed analyses of fluid-infiltrated rocks from well-characterized terranes. This work focuses on metamorphic rocks and hydrothermal systems where minerals and their textures are utilized to evaluate pressure (P), temperature (T), and time (t) paths in the evolution of mountain belts and ore deposits, and to interpret tectonic events and the timing of these events. Our work on coupled processes also extends to other areas where subsurface flow and transport in porous media have consequences such as oil and gas movement, geothermal system development, transport of contaminants, nuclear waste disposal, and other systems rich in fluid-rock reactions. Fluid-rock systems are widespread in the geologic record. Correctly deciphering the products resulting from such systems is important to interpreting a number of geologic phenomena. These systems are characterized by complex interactions involving time-dependent, non-linear processes in heterogeneous materials. While many of these interactions have been studied in isolation, they are more appropriately analyzed in the context of a system with feedback. When one process impacts another process, time and space scales as well as the overall outcome of the interaction can be dramatically altered. Our goals to test this hypothesis are: to develop and incorporate algorithms into our 3D heat and mass transport code to allow the effects of feedback to be investigated numerically, to analyze fluid infiltrated rocks from a variety of terranes at differing P-T conditions, to identify subtle features of the infiltration of fluids and/or feedback, and
Mithraratne, K; Ho, H; Hunter, P J; Fernandez, J W
2012-10-01
A coupled computational model of the foot consisting of a three-dimensional soft tissue continuum and a one-dimensional (1D) transient blood flow network is presented in this article. The primary aim of the model is to investigate the blood flow in major arteries of the pathologic foot where the soft tissue stiffening occurs. It has been reported in the literature that there could be up to about five-fold increase in the mechanical stiffness of the plantar soft tissues in pathologic (e.g. diabetic) feet compared with healthy ones. The increased stiffness results in higher tissue hydrostatic pressure within the plantar area of the foot when loaded. The hydrostatic pressure acts on the external surface of blood vessels and tend to reduce the flow cross-section area and hence the blood supply. The soft tissue continuum model of the foot was modelled as a tricubic Hermite finite element mesh representing all the muscles, skin and fat of the foot and treated as incompressible with transversely isotropic properties. The details of the mechanical model of soft tissue are presented in the companion paper, Part 1. The deformed state of the soft tissue continuum because of the applied ground reaction force at three foot positions (heel-strike, midstance and toe-off) was obtained by solving the Cauchy equations based on the theory of finite elasticity using the Galerkin finite element method. The geometry of the main arterial network in the foot was represented using a 1D Hermite cubic finite element mesh. The flow model consists of 1D Navier-Stokes equations and a nonlinear constitutive equation to describe vessel radius-transmural pressure relation. The latter was defined as the difference between the fluid and soft tissue hydrostatic pressure. Transient flow governing equations were numerically solved using the two-step Lax-Wendroff finite difference method. The geometry of both the soft tissue continuum and arterial network is anatomically-based and was developed using
Berthelon, Josselin; Sassi, William; Burov, Evgueni
2016-04-01
Many source-rocks are shale and constitute potential detachment levels in Fold-and-Thrust Belts (FTB): the toarcian Schistes-Cartons in the French Chartreuse FTB for example. Their mechanical properties can change during their burial and thermal maturation, as for example when large amount of hydrocarbon fluids are generated. A structural reconstruction of the Chartreuse FTB geo-history places the Toarcian Formation as the major decollement horizon. In this work, a mechanical analysis integrating the fluids overpressuring development is proposed to discuss on the validity of the structural interpretation. At first, an analogue of the Chartreuse Toarcian Fm, the albanian Posidonia Schist, is documented as it can provide insights on its initial properties and composition of its kerogen content. Laboratory characterisation documents the vertical evolution of the mineralogical, geochemical and mechanical parameters of this potential decollement layer. These physical parameters (i.e. Total Organic Carbon (TOC), porosity/permeability relationship, friction coefficient) are used to address overpressure buildup in the frontal part of the Chartreuse FTB with TEMISFlow Arctem Basin modelling approach (Faille et al, 2014) and the structural emplacement of the Chartreuse thrust units using the FLAMAR thermo-mechanical model (Burov et al, 2014). The hydro-mechanical modeling results highlight the calendar, distribution and magnitude of the overpressure that developed within the source-rock in the footwall of a simple fault-bend fold structure localized in the frontal part of the Chartreuse FTB. Several key geological conditions are required to create an overpressure able to fracture the shale-rocks and induce a significant change in the rheological behaviour: high TOC, low permeability, favourable structural evolution. These models highlight the importance of modeling the impact of a diffuse natural hydraulic fracturing to explain fluids propagation toward the foreland within
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
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-09-01
The title describes the two tasks summarized in this report. The remainder of the report contains information on meetings held or to be held on the subjects. The US National Committee for Rock Mechanics (USNC/RM) provides for US participation in international activities in rock mechanics, principally through adherence to the International Society for Rock Mechanics (ISRM). It also keeps the US rock mechanics community informed about new programs directed toward major areas of national concern in which rock mechanics problems represent critical or limiting factors, such as energy resources, excavation, underground storage and waste disposal, and reactor siting. The committee also guides or produces advisory studies and reports on problem areas in rock mechanics. A new panel under the auspices of the US National Committee for Rock Mechanics has been appointed to conduct a study on Conceptual Models of Fluid Infiltration in Fractured Media. The study has health and environmental applications related to the underground flow of pollutants through fractured rock in and around mines and waste repositories. Support of the study has been received from the US Nuclear Regulatory Commission and the Department of Energy`s Yucca Mountain Project Office. The new study builds on the success of a recent USNC/RM report entitled Rock Fractures and Fluid Flow: Contemporary Understanding and Applications (National Academy Press, 1996, 551 pp.). A summary of the new study is provided.
International Nuclear Information System (INIS)
1998-01-01
The title describes the two tasks summarized in this report. The remainder of the report contains information on meetings held or to be held on the subjects. The US National Committee for Rock Mechanics (USNC/RM) provides for US participation in international activities in rock mechanics, principally through adherence to the International Society for Rock Mechanics (ISRM). It also keeps the US rock mechanics community informed about new programs directed toward major areas of national concern in which rock mechanics problems represent critical or limiting factors, such as energy resources, excavation, underground storage and waste disposal, and reactor siting. The committee also guides or produces advisory studies and reports on problem areas in rock mechanics. A new panel under the auspices of the US National Committee for Rock Mechanics has been appointed to conduct a study on Conceptual Models of Fluid Infiltration in Fractured Media. The study has health and environmental applications related to the underground flow of pollutants through fractured rock in and around mines and waste repositories. Support of the study has been received from the US Nuclear Regulatory Commission and the Department of Energy's Yucca Mountain Project Office. The new study builds on the success of a recent USNC/RM report entitled Rock Fractures and Fluid Flow: Contemporary Understanding and Applications (National Academy Press, 1996, 551 pp.). A summary of the new study is provided
Peng, Yan; Grassl, Julia; Millar, A Harvey; Baer, Boris
2016-01-27
The societies of ants, bees and wasps are genetically closed systems where queens only mate during a brief mating episode prior to their eusocial life and males therefore provide queens with a lifetime supply of high-quality sperm. These ejaculates also contain a number of defence proteins that have been detected in the seminal fluid but their function and efficiency have never been investigated in great detail. Here, we used the honeybee Apis mellifera and quantified whether seminal fluid is able to combat infections of the fungal pathogen Nosema apis, a widespread honeybee parasite that is also sexually transmitted. We provide the first empirical evidence that seminal fluid has a remarkable antimicrobial activity against N. apis spores and that antimicrobial seminal fluid components kill spores in multiple ways. The protein fraction of seminal fluid induces extracellular spore germination, which disrupts the life cycle of N. apis, whereas the non-protein fraction of seminal fluid induces a direct viability loss of intact spores. We conclude that males provide their ejaculates with efficient antimicrobial molecules that are able to kill N. apis spores and thereby reduce the risk of disease transmission during mating. Our findings could be of broader significance to master honeybee diseases in managed honeybee stock in the future. © 2016 The Author(s).
International Nuclear Information System (INIS)
Lue Xing; Zhu Hongwu; Yao Zhenzhi; Meng Xianghua; Zhang Cheng; Zhang Chunyi; Tian Bo
2008-01-01
In this paper, the multisoliton solutions in terms of double Wronskian determinant are presented for a generalized variable-coefficient nonlinear Schroedinger equation, which appears in space and laboratory plasmas, arterial mechanics, fluid dynamics, optical communications and so on. By means of the particularly nice properties of Wronskian determinant, the solutions are testified through direct substitution into the bilinear equations. Furthermore, it can be proved that the bilinear Baecklund transformation transforms between (N - 1)- and N-soliton solutions
Dostál, P; Senkeřík, M; Pařízková, R; Bareš, D; Zivný, P; Zivná, H; Cerný, V
2010-01-01
Hypothermia was shown to attenuate ventilator-induced lung injury due to large tidal volumes. It is unclear if the protective effect of hypothermia is maintained under less injurious mechanical ventilation in animals without previous lung injury. Tracheostomized rats were randomly allocated to non-ventilated group (group C) or ventilated groups of normothermia (group N) and mild hypothermia (group H). After two hours of mechanical ventilation with inspiratory fraction of oxygen 1.0, respiratory rate 60 min(-1), tidal volume 10 ml x kg(-1), positive end-expiratory pressure (PEEP) 2 cm H2O or immediately after tracheostomy in non-ventilated animals inspiratory pressures were recorded, rats were sacrificed, pressure-volume (PV) curve of respiratory system constructed, bronchoalveolar lavage (BAL) fluid and aortic blood samples obtained. Group N animals exhibited a higher rise in peak inspiratory pressures in comparison to group H animals. Shift of the PV curve to right, higher total protein and interleukin-6 levels in BAL fluid were observed in normothermia animals in comparison with hypothermia animals and non-ventilated controls. Tumor necrosis factor-alpha was lower in the hypothermia group in comparison with normothermia and non-ventilated groups. Mild hypothermia attenuated changes in respiratory system mechanics and modified cytokine concentration in bronchoalveolar lavage fluid during low lung volume ventilation in animals without previous lung injury.
International Nuclear Information System (INIS)
Coulon, Fanny
2010-09-01
A validation of Code-Saturne, a computational fluids dynamics model developed by EDF, is proposed for stable conditions. The goal is to guarantee the performance of the model in order to use it for impacts study. A comparison with the Prairie Grass data field experiment and with two Gaussian plume models will be done [fr
Taoka, Toshiaki; Naganawa, Shinji
2018-04-10
After Kanda's first report in 2014 on gadolinium (Gd) deposition in brain tissue, a considerable number of studies have investigated the explanation for the observation. Gd deposition in brain tissue after repeated administration of gadolinium-based contrast medium (GBCM) has been histologically proven, and chelate stability has been shown to affect the deposition. However, the mechanism for this deposition has not been fully elucidated. Recently, a hypothesis was introduced that involves the 'glymphatic system', which is a coined word that combines 'gl' for glia cell and 'lymphatic' system. According to this hypothesis, the perivascular space functions as a conduit for cerebrospinal fluid to flow into the brain parenchyma. The perivascular space around the arteries allows cerebrospinal fluid to enter the interstitial space of the brain tissue through water channels controlled by aquaporin 4. The cerebrospinal fluid entering the interstitial space clears waste proteins from the tissue. It then flows into the perivascular space around the vein and is discharged outside the brain. In addition to the hypothesis regarding the glymphatic system, some reports have described that after GBCM administration, some of the GBCM distributes through systemic blood circulation and remains in other compartments including the cerebrospinal fluid. It is thought that the GBCM distributed into the cerebrospinal fluid cavity via the glymphatic system may remain in brain tissue for a longer duration compared to the GBCM in systemic circulation. Glymphatic system may of course act as a clearance system for GBCM from brain tissue. Based on these findings, the mechanism for Gd deposition in the brain will be discussed in this review. The authors speculate that the glymphatic system may be the major contributory factor to the deposition and clearance of gadolinium in brain tissue.
International Nuclear Information System (INIS)
Reardon, F.H.; Thinh, N.D.
1987-01-01
Experimental and analytical techniques in heat transfer and fluid dynamics and state-of-the-art applications are examined in reviews and reports. Topics discussed include the recirculation characteristics of a vortex pump, simulation of radial-flow impellers using the Navier-Stokes equations, the transient effect in composite-medium conduction or diffusion, flow in a tube with a porous obstruction, the measurement of the physical heat-transfer coefficient, and a penalty FEM for combined forced and free convection in a rectangular enclosure. Consideration is given to heat transfer in the entrance region of multiply connected ducts, working-fluid selection for low-temperature Rankine cycles, a computational-experimental method for monitoring particulate flux in fluid streams, medical applications of a vortex aerosol generator, and the interaction of unlike propellant droplets in various reactive environments
International Nuclear Information System (INIS)
Sargentini, Lucia
2014-01-01
The purpose of this study is to improve the knowledge about the core behavior of a sodium fast breeder reactor (Na-FBR) during vibrations through the fluid-structure interaction analysis. Namely, we investigate the flowering of the Phenix core during the SCRAM for negative reactivity (AURN) and the seismic behavior of the core of Astrid project. Three approaches are followed: experimental campaign, performing of analytical solution and development of numerical model. We create a flow regime map to identify the flow regimes in the fluid gap for very short times scales (as AURN) as well as longer time scales (as seismic oscillations). The most suitable equation system (Navier-Stokes, Euler or linearized Euler) is chosen to model the fluid flow in the numerical code. To our knowledge, for the first time, an analytical solution for free vibration and very narrow gaps is proposed. We designed two experimental apparatus (PISE-1a and PISE-2c) composed respectively by 1 and 19 hexagonal assemblies (two crowns) of Poly-methyl methacrylate (PMMA). Every PMMA assembly is fixed to a stainless steel twin-blades support allowing only orthogonal oscillations with respect to generating line of assembly. The twin-blades supports are designed to give the same range frequency of Phenix assembly in liquid sodium. The experimental equipment PISE-1a is used to determine the dynamic characteristics of PISE-2c assembly, to calibrate instrumentation and for validating our numerical model. Free vibration tests in air are performed to evaluate the dynamic characteristics of the body. Free vibration experiments in water allow to assess the added mass and added damping effect on the frequency. Even though the fluid flow during vibration should be completely bidimensional, the fluid flow is affected by a 3D effect - named 'jambage' - at the top and the basis of the assembly. This effect produces a lower frequency than the theoretical value. Tests are modeled with a bidimensional
Li, Xuesong; Van Wie, Bernard J.
2016-01-01
The difficulty in covering chemical engineering concepts using traditional lectures and whiteboard teaching approaches means today's students' learning demands are unfulfilled, so alternate methods are needed. Desktop learning modules (DLMs) are designed to show industrial fluid flow and heat transfer concepts in a standard classroom so students…
Bark, David L; Dasi, Lakshmi P
2016-05-01
We examine the influence of the added mass effect (fluid inertia) on mitral valve leaflet stress during isovolumetric phases. To study this effect, oscillating flow is applied to a flexible membrane at various frequencies to control inertia. Resulting membrane strain is calculated through a three-dimensional reconstruction of markers from stereo images. To investigate the effect in vivo, the analysis is repeated on a published dataset for an ovine mitral valve (Journal of Biomechanics 42(16): 2697-2701). The membrane experiment demonstrates that the relationship between pressure and strain must be corrected with a fluid inertia term if the ratio of inertia to pressure differential approaches 1. In the mitral valve, this ratio reaches 0.7 during isovolumetric contraction for an acceleration of 6 m/s(2). Acceleration is reduced by 72% during isovolumetric relaxation. Fluid acceleration also varies along the leaflet during isovolumetric phases, resulting in spatial variations in stress. These results demonstrate that fluid inertia may be the source of the temporally and spatially varying stiffness measurements previously seen through inverse finite element analysis of in vivo data during isovolumetric phases. This study demonstrates that there is a need to account for added mass effects when analyzing in vivo constitutive relationships of heart valves.
Whale, MacMurray D.; Cravalho, Ernest G.
This paper describes two parallel efforts that attempt to implement a new approach to the teaching of thermal fluids engineering. In one setting, at the Massachusetts Institute of Technology (MIT), the subject matter is integrated into a single year-long subject at the introductory level. In the second setting, at Victoria (British Columbia,…
Energy Technology Data Exchange (ETDEWEB)
Jones, H.D.; Kesler, S.E. (Univ. of Michigan, Ann Arbor (United States))
1992-01-01
Analyses of fluid inclusion gases from Mississippi Valley-type districts in east Tennessee reveal the presence of several distinct aqueous solutions and vapors that were part of the mineralizing process. Inclusion contents were released by crushing 5 to 25 mg mineral samples and by decrepitating individual inclusions; all analyses were obtained by quadrupole mass spectrometry. Most analyzed inclusion fluids consist of H{sub 2}O with significant amounts of CH{sub 4} (0.3 to 2.9 mol%), CO{sub 2} (0.1 to 4.7 mol%), and smaller amounts of C{sub 2}H{sub 6}, C{sub 3}H{sub 8}, H{sub 2}S, SO{sub 2}, N{sub 2}, and Ar. Compositional similarities in the inclusion fluids from three districts imply that mineralization probably formed from fluids that permeated the entire region. Saturation pressures calculated for these fluid compositions range from 300 to 2,200 bars. Burial depths for the host unit have been estimated to be about 2 to 3 km during Devonian time, the age of mineralization indicated by recent isotopic ages. Exsolution of a vapor phase from the mineralizing brines should cause precipitation of carbonate and sulfide minerals, but reaction path modeling indicates that the resulting sparry dolomite:sphalerite ratios would be too high to form an ore-grade deposit. If the vapor phase was from a preexisting sour gas cap that was intercepted by a Zn-rich brine, large amounts of spalerite would precipitate in a fairly small region. Preliminary mass balance calculations suggest that a gas cap of dimensions similar to the individual districts in east Tennessee could have contained enough H{sub 2}S to account for the total amount of sphalerite precipitated.
International Nuclear Information System (INIS)
Huet, Y.; Perichon, C.
1985-01-01
The control system comprises two hydraulic cylinders of which rods are integral with the mechanical organs. The piston of the first cylinder separates the chamber of this one in two parts. The piston of the second cylinder separates its chamber in three parts. The inlet chamber of the two cylinders are connected to pressurized fluid feed pipes, and the outlet chambers to a depressurization pipe. According to the position of the piston depending itself on the state of locking or unlocking of the rods, an interconnection pipe and a feed pipe of the pressurized fluid hydraulic circuit communicate with a chamber or another one. The feed of the hydraulic circuit is possible only the two rods are unlocked. The invention applies more particularly to the feed of the control circuit of an emergency seal of the primary pump of a pressurized water nuclear reactor [fr
Digital Repository Service at National Institute of Oceanography (India)
Jacob, N.; Ansari, M.A.; Revichandran, C.
the sea (Mallik et al., 1988). Fluidmud has high socio-economic importance as it is considered responsible for the enormous fish catch during monsoon. Fluid mud is associated with high biological productivity as it is rich in organic matter, phytoplankton... tritium (3H), sourced from the fallout of thermo nuclear weapons testing, carried out in the atmosphere during 1950e1963, could be effectively used to identify the recent recharge (estimate residence time) from precipitation or surface water bodies...
Bobby Kannan, M; Singh Raman, R K; Witte, F; Blawert, C; Dietzel, W
2011-02-01
Applications of magnesium alloys as biodegradable orthopaedic implants are critically dependent on the mechanical integrity of the implant during service. In this study, the mechanical integrity of an AZ91 magnesium alloy was studied using a constant extension rate tensile (CERT) method. The samples in two different geometries that is, circumferentially notched (CN), and circumferentially notched and fatigue cracked (CNFC), were tested in air and in simulated body fluid (SBF). The test results show that the mechanical integrity of the AZ91 magnesium alloy decreased substantially (∼50%) in both the CN and CNFC samples exposed to SBF. Fracture surface analysis revealed secondary cracks suggesting stress corrosion cracking susceptibility of the alloy in SBF. Copyright © 2010 Wiley Periodicals, Inc.
Zhou, Jihan; Liang, Dehai; Contera, Sonia
2015-10-01
Penetration and partition of C60 to the lipid bilayer core are both relevant to C60 toxicity, and useful to realise C60 biomedical potential. A key aspect is the effect of C60 on bilayer mechanical properties. Here, we present an experimental study on the mechanical effect of the incorporation of C60 into the hydrophobic core of fluid and gel phase zwitterionic phosphatidylcholine (PC) lipid bilayers. We demonstrate its incorporation inside the hydrophobic lipid core and the effect on the packing of the lipids and the vesicle size using a combination of infrared (IR) spectroscopy, atomic force microscopy (AFM) and laser light scattering. Using AFM we measured the Young's modulus of elasticity (E) of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) in the absence (presence) of intra-membranous C60 at 24.5 °C. E of fluid phase supported bilayers is not altered by C60, but E increases with incorporation of C60 in gel phase bilayers. The increase is higher for longer hydrocarbon chains: 1.6 times for DPPC and 2 times for DSPC. However the mechanical resistance of gel phase bilayers of curved bilayered structures decreases with the incorporation of C60. Our combined results indicate that C60 causes a decrease in gel phase lipid mobility, i.e. an increase in membrane viscosity.
International Nuclear Information System (INIS)
Wei, Guang-Mei
2006-01-01
Generalized two-dimensional variable-coefficient Burgers model is of current value in fluid mechanics, acoustics and cosmic-ray astrophysics. In this paper, Painleve analysis leads to the constraints on the variable coefficients for such a model to pass the Painleve test and to an auto-Baecklund transformation. Moreover, four transformations from this model are constructed, to the standard two-dimensional and one-dimensional Burgers models with the relevant constraints on the variable coefficients via symbolic computation. By virtue of the given transformations the properties and solutions of this model can be obtained from those of the standard two-dimensional and one-dimensional ones
de Loubens, Clément; Lentle, Roger G; Love, Richard J; Hulls, Corrin; Janssen, Patrick W M
2013-06-06
We conducted numerical experiments to study the influence of non-propagating longitudinal and circular contractions, i.e. pendular activity and segmentation, respectively, on flow and mixing in the proximal duodenum. A lattice-Boltzmann numerical method was developed to simulate the fluid mechanical consequences for each of 22 randomly selected sequences of high-definition video of real longitudinal and radial contractile activity in the isolated proximal duodenum of the rat and guinea pig. During pendular activity in the rat duodenum, the flow was characterized by regions of high shear rate. Mixing was so governed by shearing deformation of the fluid that increased the interface between adjacent domains and accelerated their inter-diffusion (for diffusion coefficients approx. less than 10(-8) m² s(-1)). When pendular activity was associated with a slow gastric outflow characteristic of post-prandial period, the dispersion was also improved, especially near the walls. Mixing was not promoted by isolated segmentative contractions in the guinea pig duodenum and not notably influenced by pylorus outflow. We concluded that pendular activity generates mixing of viscous fluids 'in situ' and accelerates the diffusive mass transfer, whereas segmentation may be more important in mixing particulate suspensions with high solid volume ratios.
de Loubens, Clément; Lentle, Roger G.; Love, Richard J.; Hulls, Corrin; Janssen, Patrick W. M.
2013-01-01
We conducted numerical experiments to study the influence of non-propagating longitudinal and circular contractions, i.e. pendular activity and segmentation, respectively, on flow and mixing in the proximal duodenum. A lattice-Boltzmann numerical method was developed to simulate the fluid mechanical consequences for each of 22 randomly selected sequences of high-definition video of real longitudinal and radial contractile activity in the isolated proximal duodenum of the rat and guinea pig. During pendular activity in the rat duodenum, the flow was characterized by regions of high shear rate. Mixing was so governed by shearing deformation of the fluid that increased the interface between adjacent domains and accelerated their inter-diffusion (for diffusion coefficients approx. less than 10−8 m² s−1). When pendular activity was associated with a slow gastric outflow characteristic of post-prandial period, the dispersion was also improved, especially near the walls. Mixing was not promoted by isolated segmentative contractions in the guinea pig duodenum and not notably influenced by pylorus outflow. We concluded that pendular activity generates mixing of viscous fluids ‘in situ’ and accelerates the diffusive mass transfer, whereas segmentation may be more important in mixing particulate suspensions with high solid volume ratios. PMID:23536539
International Nuclear Information System (INIS)
Dumbser, Michael; Peshkov, Ilya; Romenski, Evgeniy; Zanotti, Olindo
2016-01-01
Highlights: • High order schemes for a unified first order hyperbolic formulation of continuum mechanics. • The mathematical model applies simultaneously to fluid mechanics and solid mechanics. • Viscous fluids are treated in the frame of hyper-elasticity as generalized visco-plastic solids. • Formal asymptotic analysis reveals the connection with the Navier–Stokes equations. • The distortion tensor A in the model appears to be well-suited for flow visualization. - Abstract: This paper is concerned with the numerical solution of the unified first order hyperbolic formulation of continuum mechanics recently proposed by Peshkov and Romenski [110], further denoted as HPR model. In that framework, the viscous stresses are computed from the so-called distortion tensor A, which is one of the primary state variables in the proposed first order system. A very important key feature of the HPR model is its ability to describe at the same time the behavior of inviscid and viscous compressible Newtonian and non-Newtonian fluids with heat conduction, as well as the behavior of elastic and visco-plastic solids. Actually, the model treats viscous and inviscid fluids as generalized visco-plastic solids. This is achieved via a stiff source term that accounts for strain relaxation in the evolution equations of A. Also heat conduction is included via a first order hyperbolic system for the thermal impulse, from which the heat flux is computed. The governing PDE system is hyperbolic and fully consistent with the first and the second principle of thermodynamics. It is also fundamentally different from first order Maxwell–Cattaneo-type relaxation models based on extended irreversible thermodynamics. The HPR model represents therefore a novel and unified description of continuum mechanics, which applies at the same time to fluid mechanics and solid mechanics. In this paper, the direct connection between the HPR model and the classical hyperbolic–parabolic Navier
Energy Technology Data Exchange (ETDEWEB)
Dumbser, Michael, E-mail: michael.dumbser@unitn.it [Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento (Italy); Peshkov, Ilya, E-mail: peshkov@math.nsc.ru [Open and Experimental Center for Heavy Oil, Université de Pau et des Pays de l' Adour, Avenue de l' Université, 64012 Pau (France); Romenski, Evgeniy, E-mail: evrom@math.nsc.ru [Sobolev Institute of Mathematics, 4 Acad. Koptyug Avenue, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 2 Pirogova Str., 630090 Novosibirsk (Russian Federation); Zanotti, Olindo, E-mail: olindo.zanotti@unitn.it [Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento (Italy)
2016-06-01
Highlights: • High order schemes for a unified first order hyperbolic formulation of continuum mechanics. • The mathematical model applies simultaneously to fluid mechanics and solid mechanics. • Viscous fluids are treated in the frame of hyper-elasticity as generalized visco-plastic solids. • Formal asymptotic analysis reveals the connection with the Navier–Stokes equations. • The distortion tensor A in the model appears to be well-suited for flow visualization. - Abstract: This paper is concerned with the numerical solution of the unified first order hyperbolic formulation of continuum mechanics recently proposed by Peshkov and Romenski [110], further denoted as HPR model. In that framework, the viscous stresses are computed from the so-called distortion tensor A, which is one of the primary state variables in the proposed first order system. A very important key feature of the HPR model is its ability to describe at the same time the behavior of inviscid and viscous compressible Newtonian and non-Newtonian fluids with heat conduction, as well as the behavior of elastic and visco-plastic solids. Actually, the model treats viscous and inviscid fluids as generalized visco-plastic solids. This is achieved via a stiff source term that accounts for strain relaxation in the evolution equations of A. Also heat conduction is included via a first order hyperbolic system for the thermal impulse, from which the heat flux is computed. The governing PDE system is hyperbolic and fully consistent with the first and the second principle of thermodynamics. It is also fundamentally different from first order Maxwell–Cattaneo-type relaxation models based on extended irreversible thermodynamics. The HPR model represents therefore a novel and unified description of continuum mechanics, which applies at the same time to fluid mechanics and solid mechanics. In this paper, the direct connection between the HPR model and the classical hyperbolic–parabolic Navier
Juffer, P.; Bakker, A.D.; Klein-Nulend, J.; Jaspers, R.T.
2014-01-01
Skeletal muscle fibers have the ability to increase their size in response to a mechanical overload. Finite element modeling data suggest that mechanically loaded muscles in vivo may experience not only tensile strain but also shear stress. However, whether shear stress affects biological pathways
DEFF Research Database (Denmark)
Gromov, Pavel; Gromova, Irina; Olsen, Charlotta J.
2013-01-01
Tumor interstitial fluid (TIF) is a proximal fluid that, in addition to the set of blood soluble phase-borne proteins, holds a subset of aberrantly externalized components, mainly proteins, released by tumor cells and tumor microenvironment through various mechanisms, which include classical...
Collyer, A. A.
1973-01-01
Discusses theories underlying Newtonian and non-Newtonian fluids by explaining flow curves exhibited by plastic, shear-thining, and shear-thickening fluids and Bingham plastic materials. Indicates that the exact mechanism governing shear-thickening behaviors is a problem of further study. (CC)
Directory of Open Access Journals (Sweden)
Paweł H. Malinowski
2018-04-01
Full Text Available Composite materials are commonly used in many branches of industry. One of the effective methods to join the carbon fibre reinforced polymer (CFRP parts includes the use of adhesives. There is a search on effective methods for quality assurance of bonded parts. In the research here reported the influence of surface pre-bond modification on the adhesive bonds of CFRP plates has been analyzed. Adherends surface modifications, to include defects affecting the bonding quality, were obtained through surface thermal treatment, surface contamination with de-icing fluid and a combination of both the previously described treatments. Characterization of bonded joints was performed by means of mechanical testing, ultrasounds and electromechanical impedance (EMI measurements. The study here proposed has also the aim to evaluate the ability of different destructive and non-destructive techniques to assess the quality of the bonds. While mechanical tests were strongly affected by the surface modifications, results obtained ultrasound and EMI test have demonstrate only a limited ability of these techniques to differentiate between the different samples. In fact, ultrasounds did not show any changes in the bondline, due to pre-bond modifications. However, this technique was able to detect delamination in CFRP for one of the samples thermally treated at 280 °C. Electromechanical impedance (EMI measurements showed similar behavior as mechanical tests for samples thermally treated at 260 °C and 280 °C, and for the sample whose surface modification was made with a combination of thermally and de-icing fluid treatments.
Carlos Varas, Álvaro E; Peters, E A J F; Kuipers, J A M
2017-05-17
We report a computational fluid dynamics-discrete element method (CFD-DEM) simulation study on the interplay between mass transfer and a heterogeneous catalyzed chemical reaction in cocurrent gas-particle flows as encountered in risers. Slip velocity, axial gas dispersion, gas bypassing, and particle mixing phenomena have been evaluated under riser flow conditions to study the complex system behavior in detail. The most important factors are found to be directly related to particle cluster formation. Low air-to-solids flux ratios lead to more heterogeneous systems, where the cluster formation is more pronounced and mass transfer more influenced. Falling clusters can be partially circumvented by the gas phase, which therefore does not fully interact with the cluster particles, leading to poor gas-solid contact efficiencies. Cluster gas-solid contact efficiencies are quantified at several gas superficial velocities, reaction rates, and dilution factors in order to gain more insight regarding the influence of clustering phenomena on the performance of riser reactors.
Fiszdon, W
1965-01-01
Fluid Dynamics Transactions, Volume 2 compiles 46 papers on fluid dynamics, a subdiscipline of fluid mechanics that deals with fluid flow. The topics discussed in this book include developments in interference theory for aeronautical applications; diffusion from sources in a turbulent boundary layer; unsteady motion of a finite wing span in a compressible medium; and wall pressure covariance and comparison with experiment. The certain classes of non-stationary axially symmetric flows in magneto-gas-dynamics; description of the phenomenon of secondary flows in curved channels by means of co
Global oscillations of a fluid torus as a modulation mechanism for black-hole high-frequency QPOs
Czech Academy of Sciences Publication Activity Database
Bursa, Michal
2005-01-01
Roč. 9, č. 326 (2005), s. 849-855 ISSN 0004-6337 Institutional research plan: CEZ:AV0Z1003909 Keywords : black hole physics * gravitation * X-rays Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.871, year: 2005
International Nuclear Information System (INIS)
Caffrey, M.
1987-01-01
A study of the dynamics and mechanism of the various thermotropic phase transitions undergone by the hydrated monoacylglycerides monoolein and monoelaidin, in the temperature range of 20-120 0 C and from 0 to 5 M NaCl, has been undertaken. Measurements were made by using time-resolved X-ray diffraction at the Cornell High-Energy Synchrotron Source. The lamellar chain order/disorder, lamellar/cubic (body centered, space group No.8), cubic (body centered, No.8)/cubic (primitive No.4), cubic (body centered, No.12)/cubic (primitive, No.4), cubic (primitive, No.4)/fluid isotropic, cubic (body centered, No.12)/inverted hexagonal, cubic (primitive, No.4)/inverted hexagonal, and hexagonal/fluid isotropic transitions were examined under active heating and passive cooling by using a jump in temperature to effect phase transformation. All of the transitions with the exception of the cubic (body centered, No.8)/cubic (primitive, No.4) and the cubic (body centered, No.12)/cubic (primitive, No.4) cooling transitions were found (1) to be repeatable, (2) to be reversible, and (3) to have an upper bound on the transit time (time required to complete the transition) of ≤ 3s. In addition to the time-resolved measurements, data were obtained on the stability of the various phases in the temperature range of 20-120 0 C and from 0 to 5 M NaCl. In the case of fully hydrated monoolein, high salt strongly favors the hexagonal over the cubic (body centered, No.8) phase and slightly elevates the hexagonal/fluid isotropic transition temperature. With fully hydrated monoelaidin, the hexagonal phase which is not observed in the absence of salt becomes the dominant phase at high salt concentration
Microgravity Fluids for Biology, Workshop
Griffin, DeVon; Kohl, Fred; Massa, Gioia D.; Motil, Brian; Parsons-Wingerter, Patricia; Quincy, Charles; Sato, Kevin; Singh, Bhim; Smith, Jeffrey D.; Wheeler, Raymond M.
2013-01-01
Microgravity Fluids for Biology represents an intersection of biology and fluid physics that present exciting research challenges to the Space Life and Physical Sciences Division. Solving and managing the transport processes and fluid mechanics in physiological and biological systems and processes are essential for future space exploration and colonization of space by humans. Adequate understanding of the underlying fluid physics and transport mechanisms will provide new, necessary insights and technologies for analyzing and designing biological systems critical to NASAs mission. To enable this mission, the fluid physics discipline needs to work to enhance the understanding of the influence of gravity on the scales and types of fluids (i.e., non-Newtonian) important to biology and life sciences. In turn, biomimetic, bio-inspired and synthetic biology applications based on physiology and biology can enrich the fluid mechanics and transport phenomena capabilities of the microgravity fluid physics community.
Maximilian Korges; Philipp Weis; Volker Lüders; Oscar Laurent
2018-01-01
Tin (Sn) and tungsten (W) mineralization are commonly associated with each other in relation to highly evolved granites, but economical ore grades are restricted to rare global occurrences and mineralization styles are highly variable, indicating different mechanisms for ore formation. The Sn-W Zinnwald deposit in the Erzgebirge (Germany and the Czech Republic) in the roof zone of a Variscan Li-F granite hosts two contrasting styles of mineralization: (1) cassiterite (Sn) in greisen bodies, a...
Mei, Yuan; Liu, Weihua; Brugger, Joël; Sherman, David M.; Gale, Julian D.
2018-04-01
HCl is one of the most significant volatiles in the Earth's crust. It is well established that chloride activity and acidity (pH) play important roles in controlling the solubility of metals in aqueous hydrothermal fluids. Thus, quantifying the dissociation of HCl in aqueous solutions over a wide range of temperature and pressure is crucial for the understanding and numerical modeling of element mobility in hydrothermal fluids. Here we have conducted ab initio molecular dynamics (MD) simulations to investigate the mechanism of HCl(aq) dissociation and to calculate the thermodynamic properties for the dissociation reaction at 25-700 °C, 1 bar to 60 kbar, i.e. including high temperature and pressure conditions that are geologically important, but difficult to investigate via experiments. Our results predict that HCl(aq) tends to associate with increasing temperature, and dissociate with increasing pressure. In particular, HCl(aq) is highly dissociated at extremely high pressures, even at high temperatures (e.g., 60 kbar, 600-700 °C). At 25 °C, the calculated logKd values (6.79 ± 0.81) are close to the value (7.0) recommended by IUPAC (International Union of Pure and Applied Chemistry) and some previous experimental and theoretical studies (Simonson et al.., 1990; Sulpizi and Sprik, 2008, 2010). The MD simulations indicate full dissociation of HCl at low temperature; in contrast, some experiments were interpreted assuming significant association at high HCl concentrations (≥1 m HCltot) even at room T (logKd ∼0.7; e.g., Ruaya and Seward, 1987; Sretenskaya, 1992; review in Tagirov et al., 1997). This discrepancy is most likely the result of difficulties in the experimental determination of minor (if any) concentration of associated HCl(aq) under ambient conditions, and thus reflects differences in the activity models used for the interpretation of the experiments. With increasing temperature, the discrepancy between our MD results and previous experimental
International Nuclear Information System (INIS)
Guo, Shimin; Mei, Liquan; Li, Ying; Sun, Youfa
2012-01-01
By introducing a new general ansätz, the improved fractional sub-equation method is proposed to construct analytical solutions of nonlinear evolution equations involving Jumarie's modified Riemann–Liouville derivative. By means of this method, the space–time fractional Whitham–Broer–Kaup and generalized Hirota–Satsuma coupled KdV equations are successfully solved. The obtained results show that the proposed method is quite effective, promising and convenient for solving nonlinear fractional differential equations. -- Highlights: ► We propose a novel method for nonlinear fractional differential equations. ► Two important fractional differential equations in fluid mechanics are solved successfully. ► Some new exact solutions of the fractional differential equations are obtained. ► These solutions will advance the understanding of nonlinear physical phenomena.
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)
Harrison, David J.; Saito, Laurel; Markee, Nancy; Herzog, Serge
2017-11-01
To examine the impact of a hybrid-flipped model utilising active learning techniques, the researchers inverted one section of an undergraduate fluid mechanics course, reduced seat time, and engaged in active learning sessions in the classroom. We compared this model to the traditional section on four performance measures. We employed a propensity score method entailing a two-stage regression analysis that considered eight covariates to address the potential bias of treatment selection. First, we estimated the probability score based on the eight covariates, and second, we used the inverse of the probability score as a regression weight on the performance of learners who did not select into the hybrid course. Results suggest that enrolment in the hybrid-flipped section had a marginally significant negative impact on the total course score and a significant negative impact on homework performance, possibly because of poor video usage by the hybrid-flipped learners. Suggested considerations are also discussed.
Rahmani, L.; Seghier, O.; Benmoussa, A.; Draoui, B.
2018-06-01
The most of operations of chemical, biochemical or petrochemical industries are carried out in tanks or in reactors which are mechanically-controlled. The optimum mode of operation of these devices requires a finalized knowledge of the thermo-hydrodynamic behavior induced by the agitator. In the present work, the characterization of the incompressible hydrodynamic and thermal fields of a non-Newtonian fluid (Bingham) in a flat, non-baffled cylindrical vessel fitted with anchor agitator was undertaken by numerical simulation, using the CFD code Fluent (6.3.26) based on the finite volume discretization method of the energy equation and the Navier-Stokes equations which are formulated in (U.V.P) variables. We have summarized this simulated system by comparing of the consumed power and the Nusselt number for this type of mobile (Anchor agitator).
Directory of Open Access Journals (Sweden)
Gbeminiyi Sobamowo
2017-04-01
Full Text Available The development of mathematical models for describing the dynamic behaviours of fluid conveying pipes, micro-pipes and nanotubes under the influence of some thermo-mechanical parameters results into nonlinear equations that are very difficult to solve analytically. In cases where the exact analytical solutions are presented either in implicit or explicit forms, high skills and rigorous mathematical analyses were employed. It is noted that such solutions do not provide general exact solutions. Inevitably, comparatively simple, flexible yet accurate and practicable solutions are required for the analyses of these structures. Therefore, in this study, approximate analytical solutions are provided to the nonlinear equations arising in flow-induced vibration of pipes, micro-pipes and nanotubes using Galerkin-Newton-Harmonic Method (GNHM. The developed approximate analytical solutions are shown to be valid for both small and large amplitude oscillations. The accuracies and explicitness of these solutions were examined in limiting cases to establish the suitability of the method.
Directory of Open Access Journals (Sweden)
Antonio Hospitaler
2013-05-01
Full Text Available Broiler production in modern poultry farms commonly uses mechanical ventilation systems. This mechanical ventilation requires an amount of electric energy and a high level of investment in technology. Nevertheless, broiler production is affected by periodic problems of mortality because of thermal stress, thus being crucial to explore the ventilation efficiency. In this article, we analyze a cross-mechanical ventilation system focusing on air velocity distribution. In this way, two methodologies were used to explore indoor environment in livestock buildings: Computational Fluid Dynamics (CFD simulations and direct measurements for verification and validation (V&V of CFD. In this study, a validation model using a Generalized Linear Model (GLM was conducted to compare these methodologies. The results showed that both methodologies were similar in results: the average of air velocities values were 0.60 ± 0.56 m s−1 for CFD and 0.64 ± 0.54 m s−1 for direct measurements. In conclusion, the air velocity was not affected by the methodology (CFD or direct measurements, and the CFD simulations were therefore validated to analyze indoor environment of poultry farms and its operations. A better knowledge of the indoor environment may contribute to reduce the demand of electric energy, increasing benefits and improving the thermal comfort of broilers.
Kolan, Krishna C R; Leu, Ming C; Hilmas, Gregory E; Velez, Mariano
2012-09-01
The effect of particle size distribution, binder content, processing parameters, and sintering schedule on the microstructure and mechanical properties of porous constructs was investigated. The porous constructs were produced by indirect selective laser sintering (SLS) of 13-93 bioactive glass using stearic acid as a polymeric binder. The binder content and d(50) particle size in the feedstock powders were simultaneously reduced from 22 to 12 wt% and from 20 to 11 μm, respectively, to identify the minimum binder content required for the SLS fabrication. An average particle size of ∼16 μm with a binder content of 15 wt% significantly reduced post-processing time and improved mechanical properties. Increasing the laser power and scan speed at the energy density of 1 cal/cm² maintained the feature sharpness of the parts during the fabrication of green parts and could almost double the mechanical properties of the sintered parts. Changes in the heating rates, ranging from 0.1 to 2 °C/min, during the post-processing of the fabricated "green" scaffolds showed that the heating rate significantly affects the densification and mechanical properties of the sintered scaffolds. The compressive strength of the scaffolds manufactured with the optimized parameters varied from 41 MPa, for a scaffold with a porosity of ∼50%, to 157 MPa, for a dense part. The bioactive scaffolds soaked in simulated body fluids for durations up to 6 weeks were used to evaluate the change in mechanical properties in vitro. Copyright © 2012 Elsevier Ltd. All rights reserved.
Noncommuting fields and non-Abelian fluids
International Nuclear Information System (INIS)
Jackiw, R.
2004-01-01
The original ideas about noncommuting coordinates are recalled. The connection between U(1) gauge fields defined on noncommuting coordinates and fluid mechanics is explained. Non-Abelian fluid mechanics is described
Boeker, Peter; Leppert, Jan; Mysliwietz, Bodo; Lammers, Peter Schulze
2013-10-01
The Deans' switch is an effluent switching device based on controlling flows of carrier gas instead of mechanical valves in the analytical flow path. This technique offers high inertness and a wear-free operation. Recently new monolithic microfluidic devices have become available. In these devices the whole flow system is integrated into a small metal device with low thermal mass and leak-tight connections. In contrast to a mechanical valve-based system, a flow-controlled system is more difficult to calculate. Usually the Deans' switch is used to switch one inlet to one of two outlets, by means of two auxiliary flows. However, the Deans' switch can also be used to deliver the GC effluent with a specific split ratio to both outlets. The calculation of the split ratio of the inlet flow to the two outlets is challenging because of the asymmetries of the flow resistances. This is especially the case, if one of the outlets is a vacuum device, such as a mass spectrometer, and the other an atmospheric detector, e.g. a flame ionization detector (FID) or an olfactory (sniffing) port. The capillary flows in gas chromatography are calculated with the Hagen-Poiseuille equation of the laminar, isothermal and compressible flow in circular tubes. The flow resistances in the new microfluidic devices have to be calculated with the corresponding equation for rectangular cross-section microchannels. The Hagen-Poiseuille equation underestimates the flow to a vacuum outlet. A corrected equation originating from the theory of rarefied flows is presented. The calculation of pressures and flows of a Deans' switch based chromatographic system is done by the solution of mass balances. A specific challenge is the consideration of the antidiffusion resistor between the two auxiliary gas lines of the Deans' switch. A full solution for the calculation of the Deans' switch including this restrictor is presented. Results from validation measurements are in good accordance with the developed
Directory of Open Access Journals (Sweden)
Limei Tian
2014-01-01
Full Text Available The surface topography (surface morphology and structure of the left Scapharca subcrenata shell differs from that of its right shell. This phenomenon is closely related to antiwear capabilities. The objective of this study is to investigate the effects and mechanisms of surface topography on the antiwear properties of Scapharca subcrenata shells. Two models are constructed—a rib morphology model (RMM and a coupled structure model (CSM—to mimic the topographies of the right and left shells. The antiwear performance and mechanisms of the two models are studied using the fluid-solid interaction (FSI method. The simulation results show that the antiwear capabilities of the CSM are superior to those of the RMM. The CSM is also more conducive to decreasing the impact velocity and energy of abrasive particles, reducing the probability of microcrack generation, extension, and desquamation. It can be deduced that in the real-world environment, Scapharca subcrenata’s left shell sustains more friction than its right shell. Thus, the coupled structure of the left shell is the result of extensive evolution.
Energy Technology Data Exchange (ETDEWEB)
Hecker, Simon
2011-06-22
This work presents design guidelines for two categorically different concepts of a power plant turbine inlet duct; a ring-type inlet chamber and an inlet scroll. Subjects of the analysis are aerodynamic considerations of the flow field in the ducts as well as the impact of the chamber topology on the radial clearances influencing casing deformations in stationary and transient load cases. To show the reliability of the CFD-program used, calculated results are compared with measured data. The numerical method catches the main physical effects observed in the reference cases with high accuracy. The flow field in the ring-type inlet chamber strongly depends on the Reynolds number Re; according to Re a symmetrical or swirling flow field can be observed. The calculations indicate that measured values in test stands of inlet ducts with a Reynolds number that is not comparable to the full-size model should be examined carefully. The optimization of the ring-type inlet chamber leads to a geometry with minimum losses from an aerodynamic and mechanical point of view. The greatest benefit can be realized by an optimized flow into the downstream following stator blades. The analysis of the inlet scroll unveils a negative influence of eccentrically arranged pipe ends on the leakage losses. For the casings investigated a very compact design leads to minimum total losses. When choosing the scroll topology, the leakage losses should be minded, as the link between scroll size and casing deformation is not negligible. A comparison of both optimized inlet chambers shows that they have the same loss level. The selection of one concept should take into account stress distributions and the offsets of casing flanges including their consequences.