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Sample records for fluid mechanics natural

  1. Fluid Mechanics.

    Science.gov (United States)

    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)

  2. Fluid Mechanics

    Science.gov (United States)

    Pnueli, David; Gutfinger, Chaim

    1997-01-01

    This text is intended for the study of fluid mechanics at an intermediate level. The presentation starts with basic concepts, in order to form a sound conceptual structure that can support engineering applications and encourage further learning. The presentation is exact, incorporating both the mathematics involved and the physics needed to understand the various phenomena in fluid mechanics. Where a didactical choice must be made between the two, the physics prevails. Throughout the book the authors have tried to reach a balance between exact presentation, intuitive grasp of new ideas, and creative applications of concepts. This approach is reflected in the examples presented in the text and in the exercises given at the end of each chapter. Subjects treated are hydrostatics, viscous flow, similitude and order of magnitude, creeping flow, potential flow, boundary layer flow, turbulent flow, compressible flow, and non-Newtonian flows. This book is ideal for advanced undergraduate students in mechanical, chemical, aerospace, and civil engineering. Solutions manual available.

  3. Fluid mechanics

    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

  4. Nature-Inspired Fluid Mechanics Results of the DFG Priority Programme 1207 ”Nature-inspired Fluid Mechanics” 2006-2012

    CERN Document Server

    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...

  5. 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 (e.g., via point-of-care medical testing) and improvement of energy efficiency of fluid power systems, depends on improving our understanding of Fluid. Mechanics. Fluids are ubiquitous in both nature and technological applications, ...

  6. Mechanics of fluid flow

    CERN Document Server

    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.

  7. Principles of fluid mechanics

    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

  8. Fundamental Fluid Mechanics

    Indian Academy of Sciences (India)

    BOOK I REVIEW. Fundamental Fluid. Mechanics. Good Text Book Material. V H Arakeri. Fluid Mechanics for Engineers. P N Chatterjee. MacMillan India Limited. Vol. 1, pp. 367. RS.143. Vo1.2, pp.306. RS.130. Fluid Mechanics for Engineers in two vol- umes by P N Chatterjee contains standard material for a first level ...

  9. Relativistic viscoelastic fluid mechanics.

    Science.gov (United States)

    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.

  10. 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.

  11. Lectures on fluid mechanics

    CERN Document Server

    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.

  12. Fluid and particle mechanics

    CERN Document Server

    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

  13. Advances in Environmental Fluid Mechanics

    CERN Document Server

    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.

  14. Fluid Mechanics and Fluid Power (FMFP)

    Indian Academy of Sciences (India)

    Amitabh Bhattacharya

    decades, mainly due to the rapid improvement in computational efficiency, cameras, optics and instrumentation, both computational and experimental techniques have improved significantly, allowing researchers in Fluid Mechanics to build better mechanistic and analytical models for processes involving dynamics of fluids.

  15. Fundamental Fluid Mechanics

    Indian Academy of Sciences (India)

    umes by P N Chatterjee contains standard material for a first level course in fluid me- chanics for Civil, Mechanical, Aeronautical and Chemical Engineering students. It is however not suitable for Applied Science students like those majoring in Physics or. Mathematics and is not a good reference book for practising ...

  16. Comparison of the key mechanisms leading to rollovers in Liquefied Natural Gas using Computational Fluid Dynamics

    Science.gov (United States)

    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.

  17. Fluid mechanics in fluids at rest.

    Science.gov (United States)

    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.

  18. 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 ...

  19. Fluid mechanics fundamentals and applications

    CERN Document Server

    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...

  20. Editorial Special Issue on Fluid Mechanics and Fluid Power (FMFP ...

    Indian Academy of Sciences (India)

    Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore. Fluid mechanics touches almost all aspects of the natural and engineering ... lence which distorts electromagnetic waves; an earth scientist may simulate convection in the earth's mantle to understand plate tectonics or convection in the atmosphere to ...

  1. Fluid Mechanics Can Be Fun.

    Science.gov (United States)

    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)

  2. 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

  3. Fluid Mechanics of Taste

    Science.gov (United States)

    Noel, Alexis; Bhatia, Nitesh; Carter, Taren; Hu, David

    2015-11-01

    Saliva plays a key role in digestion, speech and tactile sensation. Lack of saliva, also known as dry mouth syndrome, increases risk of tooth decay and alters sense of taste; nearly 10% of the general population suffer from this syndrome. In this experimental study, we investigate the spreading of water drops on wet and dry tongues of pigs and cows. We find that drops spread faster on a wet tongue than a dry tongue. We rationalize the spreading rate by consideration of the tongue microstructure, such as as papillae, in promoting wicking. By investigating how tongue microstructure affects spreading of fluids, we may begin to how understand taste receptors are activated by eating and drinking.

  4. Fluid Mechanics An Introduction to the Theory of Fluid Flows

    CERN Document Server

    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.

  5. Fluid mechanics problems and solutions

    CERN Document Server

    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.

  6. Computational fluid mechanics

    Science.gov (United States)

    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.

  7. Respiratory Fluid Mechanics

    Science.gov (United States)

    Grotberg, James

    2005-11-01

    This brief overview of our groups activities includes liquid plug propagation in single and bifurcating tubes, a subject which pertains to surfactant delivery, liquid ventilation, pulmonary edema, and drowning. As the plug propagates, a variety of flow patterns may emerge depending on the parameters. It splits unevenly at airway bifurcations and can rupture, which reopens the airway to gas flow. Both propagation and rupture may damage the underlying airway wall cells. Another topic is surfactant dynamics and flow in a model of an oscillating alveolus. The analysis shows a nontrivial cycle-averaged surfactant concentration gradient along the interface that generates steady streaming. The steady streaming patterns particularly depend on the ratio of inspiration to expiration time periods and the sorption parameter. Vortices, single and multiple, may be achieved, as well as a saddle point configuration. Potential applications are pulmonary drug administration, cell-cell signaling pathways, and gene therapy. Finally, capillary instabilities which cause airway closure, and strategies for stabilization, will be presented. This involves the core-annular flow of a liquid-lined tube, where the core (air) is forced to oscillate axially. The stabilization mechanism is similar to that of a reversing butter knife, where the core shear wipes the growing liquid bulge, from the Rayleigh instability, back on to the tube wall during the main tidal volume stroke, but allows it to grow back as the stroke and shear turn around.

  8. Fluid Mechanics in Sommerfeld's School

    Science.gov (United States)

    Eckert, Michael

    2015-01-01

    Sommerfeld's affiliation with fluid mechanics started when he began his career as an assistant of the mathematician Felix Klein at Göttingen. He always regarded fluid mechanics as a particular challenge. In 1904, he published a theory of hydrodynamic lubrication. Four years later, he conceived an approach for the analysis of flow instability (the Orr-Sommerfeld approach) as an attempt to account for the transition from laminar to turbulent flow. The onset of turbulence also became a major challenge for some of his pupils, in particular Ludwig Hopf and Fritz Noether. Both contributed considerably to elaborate the Orr-Sommerfeld theory. Heisenberg's doctoral work was another attempt in this quest. When Sommerfeld published his lectures on theoretical physics during World War II, he dedicated one of the six volumes to the mechanics of continuous media. With chapters on boundary layer theory and turbulence, it exceeded the scope of contemporary theoretical physics—revealing Sommerfeld's persistent appreciation of fluid mechanics. He resorted to Prandtl's Göttingen school of fluid mechanics in order to stay abreast of the rapid development of these specialties.

  9. 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:

  10. 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 and Applied Mechanics (IUTAM) symposium held at. Jawaharlal Nehru Centre for ...

  11. 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

  12. Fluid mechanics of environmental interfaces

    CERN Document Server

    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.

  13. Shooting mechanisms in nature

    NARCIS (Netherlands)

    Sakes, Aimée; Wiel, van der Marleen; Henselmans, Paul W.J.; Leeuwen, van Johan L.; Dodou, Dimitra; Breedveld, Paul

    2016-01-01

    Background In nature, shooting mechanisms are used for a variety of purposes, including prey capture, defense, and reproduction. This review offers insight into the working principles of shooting mechanisms in fungi, plants, and animals in the light of the specific functional demands that these

  14. Neural Control Mechanisms and Body Fluid Homeostasis

    Science.gov (United States)

    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.

  15. Selected topics of fluid mechanics

    Science.gov (United States)

    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

  16. 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

  17. Fundamental fluid mechanics and magnetohydrodynamics

    CERN Document Server

    Hosking, Roger J

    2016-01-01

    This book is primarily intended to enable postgraduate research students to enhance their understanding and expertise in Fluid Mechanics and Magnetohydrodynamics (MHD), subjects no longer treated in isolation. The exercises throughout the book often serve to provide additional and quite significant knowledge or to develop selected mathematical skills, and may also fill in certain details or enhance readers’ understanding of essential concepts. A previous background or some preliminary reading in either of the two core subjects would be advantageous, and prior knowledge of multivariate calculus and differential equations is expected.

  18. 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)

  19. Black holes from fluid mechanics

    Science.gov (United States)

    Lahiri, Subhaneil

    2009-12-01

    We use the AdS/CFT correspondence in a regime where the field theory is well described by fluid mechanics to study large black holes in asymptotically locally anti de Sitter spaces. In particular, we use the fluid description to study the thermodynamics of the black holes and the existence of exotic horizon topologies in higher dimensions. First we test this method by comparing large rotating black holes in global AdSD spaces to stationary solutions of the relativistic Navier-Stokes equations on SD-2. Reading off the equation of state of this fluid from the thermodynamics of non-rotating black holes, we proceed to construct the nonlinear spinning solutions of fluid mechanics that are dual to rotating black holes. In all known examples, the thermodynamics and the local stress tensor of our solutions are in precise agreement with the thermodynamics and boundary stress tensor of the spinning black holes. Our results yield predictions for the thermodynamics of all large black holes in all theories of gravity on AdS spaces, for example, IIB string theory on AdS5 x S 5 and M theory on AdS4 x S7 and AdS7 x S 4. We then construct solutions to the relativistic Navier-Stokes equations that describe the long wavelength collective dynamics of the deconfined plasma phase of N = 4 Yang Mills theory compactified down to d = 3 on a Scherk-Schwarz circle. Our solutions are stationary, axially symmetric spinning balls and rings of plasma. These solutions, which are dual to (yet to be constructed) rotating black holes and black rings in Scherk-Schwarz compactified AdS 5, and have properties that are qualitatively similar to those of black holes and black rings in flat five dimensional gravity. We also study the stability of these solutions to small fluctuations, which provides an indirect method for studying Gregory-Laflamme instabilities. We also extend the construction to higher dimensions, allowing one to study the existence of new black hole topologies and their phase diagram.

  20. 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 ...

  1. Fluid Mechanics Optimising Organic Synthesis

    Science.gov (United States)

    Leivadarou, Evgenia; Dalziel, Stuart

    2015-11-01

    The Vortex Fluidic Device (VFD) is a new ``green'' approach in the synthesis of organic chemicals with many industrial applications in biodiesel generation, cosmetics, protein folding and pharmaceutical production. The VFD is a rapidly rotating tube that can operate with a jet feeding drops of liquid reactants to the base of the tube. The aim of this project is to explain the fluid mechanics of the VFD that influence the rate of reactions. The reaction rate is intimately related to the intense shearing that promotes collision between reactant molecules. In the VFD, the highest shears are found at the bottom of the tube in the Rayleigh and the Ekman layer and at the walls in the Stewardson layers. As a step towards optimising the performance of the VFD we present experiments conducted in order to establish the minimum drop volume and maximum rotation rate for maximum axisymmetric spreading without fingering instability. PhD candidate, Department of Applied Mathematics and Theoretical Physics.

  2. Fluid mechanics of environmental interfaces

    CERN Document Server

    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...

  3. Applied Fluid Mechanics. Lecture Notes.

    Science.gov (United States)

    Gregg, Newton D.

    This set of lecture notes is used as a supplemental text for the teaching of fluid dynamics, as one component of a thermodynamics course for engineering technologists. The major text for the course covered basic fluids concepts such as pressure, mass flow, and specific weight. The objective of this document was to present additional fluids…

  4. The mechanization of natural philosophy

    CERN Document Server

    Garber, Daniel

    2014-01-01

    This book reviews the transformation of natural philosophy in the 16th and 17th centuries: description of nature in mathematical terms; comparison of natural phenomena to existing or imaginary machines and the use of mechanical analogies in natural philosophy.

  5. NASA Ames Fluid Mechanics Laboratory research briefs

    Science.gov (United States)

    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.

  6. 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

  7. A Course in Fluid Mechanics of Suspensions.

    Science.gov (United States)

    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)

  8. 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.)

  9. 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.

  10. Fluid Mechanics of Fish Swimming

    Indian Academy of Sciences (India)

    user

    forces generated by their °apping tails. A nguilliform sw im m .... In natural systems, like a human walking or a ¯sh swimming, there is always unsteadiness. ... (L) mainly from the wings balances the weight (W). b) For the fish shown here the thrust is mainly from the flapping tail. Lift from fins and buoyancy (FB ) bal- ance the ...

  11. Topology optimization of fluid mechanics problems

    DEFF Research Database (Denmark)

    Gersborg-Hansen, Allan

    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...

  12. An introduction to the mechanics of fluids

    CERN Document Server

    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...

  13. 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...

  14. Introductory fluid mechanics for physicists and mathematicians

    CERN Document Server

    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.

  15. Handbook of mathematical analysis in mechanics of viscous fluids

    CERN Document Server

    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.

  16. Interfacial Fluid Mechanics A Mathematical Modeling Approach

    CERN Document Server

    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...

  17. Fluid mechanics as a driver of tissue-scale mechanical signaling in organogenesis.

    Science.gov (United States)

    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.

  18. CISM course on stochastic methods in fluid mechanics

    CERN Document Server

    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

  19. New Directions in Mathematical Fluid Mechanics

    CERN Document Server

    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.

  20. Attracting Students to Fluid Mechanics with Coffee

    Science.gov (United States)

    Ristenpart, William

    2016-11-01

    We describe a new class developed at U.C. Davis titled "The Design of Coffee," which serves as a nonmathematical introduction to chemical engineering as illustrated by the process of roasting and brewing coffee. Hands-on coffee experiments demonstrate key engineering principles, including material balances, chemical kinetics, mass transfer, conservation of energy, and fluid mechanics. The experiments lead to an engineering design competition where students strive to make the best tasting coffee using the least amount of energy - a classic engineering optimization problem, but one that is both fun and tasty. "The Design of Coffee" started as a freshmen seminar in 2013, and it has exploded in popularity: it now serves 1,533 students per year, and is the largest and most popular elective course at U.C. Davis. In this talk we focus on the class pedagogy as applied to fluid mechanics, with an emphasis on how coffee serves as an engaging and exciting topic for teaching students about fluid mechanics in an approachable, hands-on manner.

  1. Statistical mechanical theory of fluid mixtures

    Science.gov (United States)

    Zhao, Yueqiang; Wu, Zhengming; Liu, Weiwei

    2014-01-01

    A general statistical mechanical theory of fluid mixtures (liquid mixtures and gas mixtures) is developed based on the statistical mechanical expression of chemical potential of components in the grand canonical ensemble, which gives some new relationships between thermodynamic quantities (equilibrium ratio Ki, separation factor α and activity coefficient γi) and ensemble average potential energy u for one molecule. The statistical mechanical expressions of separation factor α and activity coefficient γi derived in this work make the fluid phase equilibrium calculations can be performed by molecular simulation simply and efficiently, or by the statistical thermodynamic approach (based on the saturated-vapor pressure of pure substance) that does not need microscopic intermolecular pair potential functions. The physical meaning of activity coefficient γi in the liquid phase is discussed in detail from a viewpoint of molecular thermodynamics. The calculated Vapor-Liquid Equilibrium (VLE) properties of argon-methane, methanol-water and n-hexane-benzene systems by this model fit well with experimental data in references, which indicates that this model is accurate and reliable in the prediction of VLE properties for small, large and strongly associating molecules; furthermore the statistical mechanical expressions of separation factor α and activity coefficient γi have good compatibility with classical thermodynamic equations and quantum mechanical COSMO-SAC approach.

  2. 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

  3. Mechanism of Wettability Hysteresis in Natural Soils

    Science.gov (United States)

    Ryder, J. L.; Demond, A. H.

    2006-12-01

    Because models of subsurface flow and transport depend on the contact angles made by the air/water and waste liquid/water interfaces with soil and rock surfaces, accurate knowledge of the wettability of subsurface systems is necessary. Sessile drop contact angles were measured on dry rock surfaces and on the same rock surfaces immersed in a second fluid. Quartz slides and cut rock faces that had been leveled and polished served as representative surfaces for silica sand, talc, kerogen containing shales, bituminous coal, and mineralized carbon. For several carbon-containing materials, contact angles are reversed from near 170 degrees when water is the receding fluid to less than 70 degrees if water is the advancing fluid. However, some mineral soils do not display wetting reversal. This work seeks to explain the mechanisms of the wetting order hysteresis. Utilizing an aqueous 0.01 M NaCl solution, glycerol, 1-bromonapthalene, and diidomethane as probe fluids, contact angle values are assessed with the method of van Oss et al. (1988) to determine the surface energy components of each type of soil. The quartz mineral surface energy has a large polar component and the calculated quartz surface energy does not depend on the wetting history of the slide. However, the magnitudes of the surface energy components of the carbon-containing materials change depending on the wetting history, indicating that the nature of the surface is altered by the surrounding fluid. The presence of wetting order hysteresis may contribute to the heterogeneous fluid distributions found at many waste liquid sites. When soil is known to contain carbon, some knowledge of the wetting history is necessary to predict the contact angle and thus the transport behavior.

  4. Recent developments of mathematical fluid mechanics

    CERN Document Server

    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...

  5. The genesis of fluid mechanics, 1640-1780

    CERN Document Server

    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...

  6. Statistical mechanics and the physics of fluids

    CERN Document Server

    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...

  7. Stanley Corrsin Award Talk: Fluid Mechanics of Fungi and Slime

    Science.gov (United States)

    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.

  8. Fluid mechanics of mathematics testing in Texas

    Science.gov (United States)

    Marder, Michael

    2010-03-01

    The performance of Texas high school students on mathematics exams is tightly connected to the level of poverty in the school. I will employ the coarse-graining techniques that lead from molecular motions to fluid mechanics in order to find how student scores evolve over time. I will show that the points of divergence between well-off and low-income kids are particularly clear when viewed as streamlines of a flow in the space of grade-level and score. The results can also be cast in the form of a Fokker-Planck equation, which highlights the separate roles of convection and diffusion. I will use the results the assess the plausibility of using charter schools, highly qualified teachers, and accountability systems as primary agents of school reform.

  9. Natural convection in horizontal fluid layers

    International Nuclear Information System (INIS)

    Suo-Antilla, A.J.

    1977-02-01

    The experimental work includes developing and using a thermal convection cell to obtain measurements of the heat flux and turbulent core temperature of a horizontal layer of fluid heated internally and subject to both stabilizing and destabilizing temperature differences. The ranges of Rayleigh numbers tested were 10 7 equal to or less than R/sub I/ equal to or less than 10 13 and -10 10 equal to or less than R/sub E/ equal to or less than 10 10 . Power integral methods were found to be adequate for interpolating and extrapolating the data. The theoretical work consists of the derivation, solution and use of the mean field equations for study of thermally driven convection in horizontal layers of infinite extent. The equations were derived by a separation of variables technique where the horizontal directions were described by periodic structures and the vertical being some function of z. The derivation resulted in a coupled set of momentum and energy equations. The equations were simplified by using the infinite Prandtl number limit and neglecting direct intermodal interaction. Solutions to these equations are used to predict the existence of multi-wavenumber flows at all supercritical Rayleigh numbers. Subsequent inspection of existing experimental photographs of convecting fluids confirms their existence. The onset of time dependence is found to coincide with the onset of the second convective mode. Each mode is found to consist of two wavenumbers and typically the velocity and temperature fields of the right modal branch are found to be out of phase

  10. Natural convection in superposed fluid-porous layers

    CERN Document Server

    Bagchi, Aniruddha

    2013-01-01

    Natural Convection in Composite Fluid-Porous Domains provides a timely overview of the current state of understanding on the phenomenon of convection in composite fluid-porous layers. Natural convection in horizontal fluid-porous layers has received renewed attention because of engineering problems such as post-accident cooling of nuclear reactors, contaminant transport in groundwater, and convection in fibrous insulation systems. Because applications of the problem span many scientific domains, the book serves as a valuable resource for a wide audience.

  11. CEE3500 - Fluid Mechanics, Spring 2006

    OpenAIRE

    Urroz, Gilberto E.

    2006-01-01

    Explores fluid properties, hydrostatics, fluid dynamics, similitude, energy and momentum principles, closed conduit flow, open channel flow, and flow measurement. Includes laboratory exercises in flow measurement, open channel flow, pipe friction, physical modeling, and data collection.

  12. Fluid Mechanics, Drag Reduction and Advanced Configuration Aeronautics

    Science.gov (United States)

    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.

  13. The Status of Fluid Mechanics in Bioengineering Curricula.

    Science.gov (United States)

    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…

  14. Fluid Mechanics of Cricket and Tennis Balls

    Science.gov (United States)

    Mehta, Rabindra D.

    2009-11-01

    Aerodynamics plays a prominent role in defining the flight of a ball that is struck or thrown through the air in almost all ball sports. The main interest is in the fact that the ball can often deviate from its initial straight path, resulting in a curved, or sometimes an unpredictable, flight path. It is particularly fascinating that that not all the parameters that affect the flight of a ball are always under human influence. Lateral deflection in flight, commonly known as swing, swerve or curve, is well recognized in cricket and tennis. In tennis, the lateral deflection is produced by spinning the ball about an axis perpendicular to the line of flight, which gives rise to what is commonly known as the Magnus effect. It is now well recognized that the aerodynamics of sports balls are strongly dependent on the detailed development and behavior of the boundary layer on the ball's surface. A side force, which makes a ball curve through the air, can also be generated in the absence of the Magnus effect. In one of the cricket deliveries, the ball is released with the seam angled, which trips the laminar boundary layer into a turbulent state on that side. The turbulent boundary layer separates relatively late compared to the laminar layer on the other side, thereby creating a pressure difference and hence side force. The fluid mechanics of a cricket ball become very interesting at the higher Reynolds numbers and this will be discussed in detail. Of all the round sports balls, a tennis ball has the highest drag coefficient. This will be explained in terms of the contribution of the ``fuzz" drag and how that changes with Reynolds number and ball surface wear. It is particularly fascinating that, purely through historical accidents, small disturbances on the ball surface, such as the stitching on cricket balls and the felt cover on tennis balls are all about the right size to affect boundary layer transition and development in the Reynolds numbers of interest. The fluid

  15. Intracellular Fluid Mechanics: Coupling Cytoplasmic Flow with Active Cytoskeletal Gel

    Science.gov (United States)

    Mogilner, Alex; Manhart, Angelika

    2018-01-01

    The cell is a mechanical machine, and continuum mechanics of the fluid cytoplasm and the viscoelastic deforming cytoskeleton play key roles in cell physiology. We review mathematical models of intracellular fluid mechanics, from cytoplasmic fluid flows, to the flow of a viscous active cytoskeletal gel, to models of two-phase poroviscous flows, to poroelastic models. We discuss application of these models to cell biological phenomena, such as organelle positioning, blebbing, and cell motility. We also discuss challenges of understanding fluid mechanics on the cellular scale.

  16. Collective fluid mechanics of honeybee nest ventilation

    Science.gov (United States)

    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.

  17. Quantitative image processing in fluid mechanics

    Science.gov (United States)

    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.

  18. 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.

  19. 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

  20. Diffuse-Interface Methods in Fluid Mechanics

    Science.gov (United States)

    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.

  1. Fluid catalytic cracking : Feedstocks and reaction mechanism

    NARCIS (Netherlands)

    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

  2. Proceedings of the sixth international and forty third national conference on fluid mechanics and fluid power: book of abstracts

    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

  3. Mechanical stimulation of bone cells using fluid flow

    NARCIS (Netherlands)

    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

  4. 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

  5. Vectors, tensors and the basic equations of fluid mechanics

    CERN Document Server

    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.

  6. [Research activities in applied mathematics, fluid mechanics, and computer science

    Science.gov (United States)

    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.

  7. Research in Applied Mathematics, Fluid Mechanics and Computer Science

    Science.gov (United States)

    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.

  8. 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.

  9. 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

  10. The fluid mechanics of root canal irrigation.

    Science.gov (United States)

    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

  11. Problems in Microgravity Fluid Mechanics: G-Jitter Convection

    Science.gov (United States)

    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.

  12. Analysis of the fluid mechanical sewing machine

    Science.gov (United States)

    Brun, Pierre-Thomas; Audoly, Basile; Ribe, Neil

    2012-02-01

    A thin thread of viscous fluid falling onto a moving belt generates a surprising variety of patterns, similar to the stitch patterns produced by a traditional sewing machine. By simulating the dynamics of the viscous thread numerically, we can reproduce these patterns and their bifurcations. The results lead us to propose a new classification of the stitch patterns within a unified framework, based on the Fourier spectra of the motion of the point of contact of the thread with the belt. The frequencies of the longitudinal and transverse components of the contact point motion are locked in most cases to simple ratios of the frequency φc of steady coiling on a surface at rest (i.e., the limit of zero belt speed). In particular, the ``alternating loops'' pattern involves the first five multiples of φc/3. The dynamics of the patterns can be described by matching the upper (linear) and the lower (non-linear) portions of the thread. Following this path we propose a toy model that successfully reproduces the observed transitions from the steady dragged configuration to sinusoidal meanders, alternating loops, and the translated coiling pattern as the belt speed is varied.

  13. Fluid Mechanics of Inhalant Siphon Flows

    Science.gov (United States)

    True, A. C.; Crimaldi, J. P.

    2016-02-01

    Inhalant siphon and suction flows are ubiquitous in marine ecosystems. From biological flows in filter-feeding benthic bivalves and predation by planktivorous fishes, to engineered flows in water samplers and production of hydrodynamic stimuli for laboratory assays, inhalant siphon flows span much of the laminar range (Reynolds number 0.01 - 2,000) and fundamentally influence many transport and exchange processes. Direct numerical simulations (DNS) of inhalant siphon flows with varying Reynolds numbers and geometries have informed design and construction of an index of refraction-matched flow facility (mineral oil, borosilicate glass tubing) in which we are employing particle image velocimetry (PIV) to quantify transient and steady-state flow fields outside and inside the siphon tube. Varying siphon diameter, flow rate, and extraction height allows us to evaluate effects of Reynolds number and siphon geometry on local hydrodynamics. This complementary experimental and numerical modeling investigation of siphon flow hydrodynamics was motivated recently by a colleague whose biologically inspired numerical modeling of inhalant siphons using a boundary condition of constant volumetric outflow (as opposed to the classically assumed uniform inlet velocity profile) revealed nontrivial departures from idealized flows: inviscid potential flows (i.e. point sink) and pipe flows (the classical pipe entry problem), particularly in the low Reynolds number regime. Reduced entrance lengths, larger radial inflows, and modifications to fluid capture zones seen numerically at low Reynolds number are being tested experimentally and may have important implications for both biological and engineered siphons.

  14. Active Learning in Fluid Mechanics: Youtube Tube Flow and Puzzling Fluids Questions

    Science.gov (United States)

    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…

  15. 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.

  16. FLUID MECHANICS OF ARTIFICIAL HEART VALVES

    OpenAIRE

    Dasi, Lakshmi P; Simon, Helene A; Sucosky, Philippe; Yoganathan, Ajit P

    2009-01-01

    1. Artificial heart valves have been in use for over five decades to replace diseased heart valves. Since the first heart valve replacement performed with a caged-ball valve, more than 50 valve designs have been developed, differing principally in valve geometry, number of leaflets and material. To date, all artificial heart valves are plagued with complications associated with haemolysis, coagulation for mechanical heart valves and leaflet tearing for tissue-based valve prosthesis. For mecha...

  17. 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

  18. Introducing Innovative Approaches to Learning in Fluid Mechanics: A Case Study

    Science.gov (United States)

    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…

  19. 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

  20. 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

  1. Heat Transfer and Fluid Flow in Naturally Ventilated Greenhouses

    Directory of Open Access Journals (Sweden)

    M. Elashmawy

    2017-08-01

    Full Text Available In this paper, heat transfer and fluid flow in naturally ventilated greenhouses are studied numerically for tow configuration according to the number and positions of the opening. The equations governing the phenomenon are developed using the stream function-vorticity formalism and solved using the finite volume method. The aim of the study is to investigate how buoyancy forces influence airflow and temperature patterns inside the greenhouse. Rayleigh number is the main parameter which changes from 103 to 106 and Prandtl number is fixed at Pr=0.71. Results are reported in terms of stream function, isotherms and average Nusselt number. It is found that the flow structure is sensitive to the value of Rayleigh number and the number of openings. Also, that using asymmetric opening positions improve the natural ventilation and facilitate the occurrence of buoyancy induced upward cross-airflow inside the greenhouse.

  2. Shocks, singularities and oscillations in nonlinear optics and fluid mechanics

    CERN Document Server

    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. .

  3. An Introduction to Computational Fluid Mechanics by Example

    CERN Document Server

    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

  4. The fluid mechanics of continuous flow electrophoresis

    Science.gov (United States)

    Saville, D. A.

    1990-01-01

    The overall objective is to establish theoretically and confirm experimentally the ultimate capabilities of continuous flow electrophoresis chambers operating in an environment essentially free of particle sedimentation and buoyancy. The efforts are devoted to: (1) studying the effects of particle concentration on sample conductivity and dielectric constant. The dielectric constant and conductivity were identified as playing crucial roles in the behavior of the sample and on the resolving power and throughput of continuous flow devices; and (2) improving the extant mathematical models to predict flow fields and particle trajectories in continuous flow electrophoresis. A dielectric spectrometer was designed and built to measure the complex dielectric constant of a colloidal dispersion as a function of frequency between 500 Hz and 200 kHz. The real part of the signal can be related to the sample's conductivity and the imaginary part to its dielectric constant. Measurements of the dielectric constants of several different dispersions disclosed that the dielectric constants of dilute systems of the sort encountered in particle electrophoresis are much larger than would be expected based on the extant theory. Experiments were carried out to show that, in many cases, this behavior is due to the presence of a filamentary structure of small hairs on the particle surface. A technique for producing electrokinetically ideal synthetic latex particles by heat treating was developed. Given the ubiquitous nature of hairy surfaces with both cells and synthetic particles, it was deemed necessary to develop a theory to explain their behavior. A theory for electrophoretic mobility of hairy particles was developed. Finally, the extant computer programs for predicting the structure of electro-osmotically driven flows were extended to encompass flow channels with variable wall mobilities.

  5. Fluid Mechanical Properties of Silkworm Fibroin Solutions

    Science.gov (United States)

    Matsumoto, Akira

    2005-11-01

    The aqueous solution behavior of silk fibroin is of interest due to the assembly and processing of this protein related to the spinning of protein fibers that exhibit remarkable mechanical properties. To gain insight into the origins of this functional feature, it is desired to determine how the protein behaves under a range of solution conditions. Pure fibroin at different concentrations in water was studied for surface tension, as a measure of surfactancy. In addition, shear induced changes on these solutions in terms of structure and morphology was also determined. Fibroin solutions exhibited shear rate-sensitive viscosity changes and precipitated at a critical shear rate where a dramatic increase of 75-150% of the initial value was observed along with a decrease in viscosity. In surface tension measurements, critical micelle concentrations were in the range of 3-4% w/v. The influence of additional factors, such as sericin protein, divalent and monovalent cations, and pH on the solution behavior in relation to structural and morphological features will also be described.

  6. Shooting mechanisms in Nature : A systematic review

    NARCIS (Netherlands)

    Sakes, A.; van der Wiel, M.; Henselmans, P.W.J.; van Leeuwen, J.L.; Dodou, D.; Breedveld, P.

    2016-01-01

    Background
    In nature, shooting mechanisms are used for a variety of purposes, including prey capture, defense, and reproduction. This review offers insight into the working principles of shooting mechanisms in fungi, plants, and animals in the light of the specific functional demands that these

  7. Fluid mechanics and heat transfer advances in nonlinear dynamics modeling

    CERN Document Server

    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.

  8. Mechanics and mathematics of fluids of the differential type

    CERN Document Server

    Cioranescu, D; Rajagopal, K R

    2016-01-01

    This text is the first of its kind to bring together both the thermomechanics and mathematical analysis of Reiner-Rivlin fluids and fluids of grades 2 and 3 in a single book. Each part of the book can be considered as being self-contained. The first part of the book is devoted to a description of the mechanics, thermodynamics, and stability of flows of fluids of grade 2 and grade 3. The second part of the book is dedicated to the development of rigorous mathematical results concerning the equations governing the motion of a family of fluids of the differential type. Finally, the proofs of a number of useful results are collected in an appendix.

  9. Space-time fluid mechanics computation of heart valve models

    Science.gov (United States)

    Takizawa, Kenji; Tezduyar, Tayfun E.; Buscher, Austin; Asada, Shohei

    2014-10-01

    Fluid mechanics computation of heart valves with an interface-tracking (moving-mesh) method was one of the classes of computations targeted in introducing the space-time (ST) interface tracking method with topology change (ST-TC). The ST-TC method is a new version of the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) method. It can deal with an actual contact between solid surfaces in flow problems with moving interfaces, while still possessing the desirable features of interface-tracking methods, such as better resolution of the boundary layers. The DSD/SST method with effective mesh update can already handle moving-interface problems when the solid surfaces are in near contact or create near TC, if the "nearness" is sufficiently "near" for the purpose of solving the problem. That, however, is not the case in fluid mechanics of heart valves, as the solid surfaces need to be brought into an actual contact when the flow has to be completely blocked. Here we extend the ST-TC method to 3D fluid mechanics computation of heart valve models. We present computations for two models: an aortic valve with coronary arteries and a mechanical aortic valve. These computations demonstrate that the ST-TC method can bring interface-tracking accuracy to fluid mechanics of heart valves, and can do that with computational practicality.

  10. 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...... unites the power to solve complex engineering problems from finite element analysis (FEA) with the ability to effectively represent complex shapes from computer aided design (CAD). The methodology is appealing for flow modeling purposes also due to the inherent high regularity of velocity and pressure...... 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...

  11. Quantum mechanics as a natural generalization of classical statistical mechanics

    International Nuclear Information System (INIS)

    Xu Laizi; Qian Shangwu

    1994-01-01

    By comparison between equations of motion of geometrical optics (GO) and that of classical statistical mechanics (CSM), it is found that there should be an analogy between GO and CSM instead of GO and classical mechanics (CM). Furthermore, by comparison between the classical limit (CL) of quantum mechanics (QM) and CSM, the authors find that CL of QM is CSM not CM, hence they demonstrated that QM is a natural generalization of CSM instead of CM

  12. A Blended Learning Approach to Teach Fluid Mechanics in Engineering

    Science.gov (United States)

    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…

  13. Fluid Mechanics of Wing Adaptation for Separation Control

    Science.gov (United States)

    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.

  14. Instructor's Guide for Fluid Mechanics: A Modular Approach.

    Science.gov (United States)

    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…

  15. The No-Slip Boundary Condition in Fluid Mechanics

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 9; Issue 5. The No-Slip Boundary Condition in Fluid Mechanics - Solution of the Sticky Problem. Sandeep Prabhakara M D Deshpande. General Article Volume 9 Issue 5 May 2004 pp 61-71 ...

  16. Flippin' Fluid Mechanics--Comparison Using Two Groups

    Science.gov (United States)

    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…

  17. The fluid mechanics of channel fracturing flows: experiment

    Science.gov (United States)

    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).

  18. Application of computational fluid mechanics to atmospheric pollution problems

    Science.gov (United States)

    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.

  19. Mechanical energy dissipation in natural ceramic composites.

    Science.gov (United States)

    Mayer, George

    2017-12-01

    Ceramics and glasses, in their monolithic forms, typically exhibit low fracture toughness values, but rigid natural marine ceramic and glass composites have shown remarkable resistance to mechanical failure. This has been observed in load-extension behavior by recognizing that the total area under the curve, notably the part beyond the yield point, often conveys substantial capacity to carry mechanical load. The mechanisms underlying the latter observations are proposed as defining factors for toughness that provide resistance to failure, or capability to dissipate energy, rather than fracture toughness. Such behavior is exhibited in the spicules of glass sponges and in mollusk shells. There are a number of similarities in the manner in which energy dissipation takes place in both sponges and mollusks. It was observed that crack diversion, a new form of crack bridging, creation of new surface area, and other important energy-dissipating mechanisms occur and aid in "toughening". Crack tolerance, key to energy dissipation in these natural composite materials, is assisted by promoting energy distribution over large volumes of loaded specimens by minor components of organic constituents that also serve important roles as adhesives. Viscoelastic deformation was a notable characteristic of the organic component. Some of these energy-dissipating modes and characteristics were found to be quite different from the toughening mechanisms that are utilized for more conventional structural composites. Complementary to those mechanisms found in rigid natural ceramic/organic composites, layered architectures and very thin organic layers played major roles in energy dissipation in these structures. It has been demonstrated in rigid natural marine composites that not only architecture, but also the mechanical behavior of the individual constituents, the nature of the interfaces, and interfacial bonding play important roles in energy dissipation. Additionally, the controlling

  20. Characterization of the Mechanical Properties of Electrorheological Fluids Made of Starch and Silicone Fluid

    Science.gov (United States)

    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).

  1. Fluid coupling in a discrete model of cochlear mechanics.

    Science.gov (United States)

    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

  2. Mechanisms of natural ventilation in livestock buildings

    DEFF Research Database (Denmark)

    Rong, Li; Bjerg, Bjarne Schmidt; Batzanas, Thomas

    2016-01-01

    Studies on the mechanisms of natural ventilation in livestock buildings are reviewed and influences on discharge and pressure coefficients are discussed. Compared to studies conducted on buildings for human occupation and industrial buildings which focus on thermal comfort, ventilation systems......, indoor air quality, building physics and energy etc., our understanding of the mechanisms involved in natural ventilation of livestock buildings are still limited to the application of the orifice equation. It has been observed that the assumptions made for application of the orifice equation...... are not valid for wind-induced cross ventilation through large openings. This review identifies that the power balance model, the concept of stream tube and the local dynamic similarity model has helped in the fundamental understanding of wind-induced natural ventilation in buildings for human occupation...

  3. Effect of Chamber Backpressure on Swirl Injector Fluid Mechanics

    Science.gov (United States)

    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.

  4. Friction mechanisms and interfacial slip at fluid-solid interfaces

    CERN Document Server

    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...

  5. The Fluid Mechanics of Cancer and Its Therapy

    OpenAIRE

    Koumoutsakos Petros; Pivkin Igor; Milde Florian

    2012-01-01

    Fluid mechanics is involved in the growth progression metastasis and therapy of cancer. Blood vessels transport oxygen and nutrients to cancerous tissues provide a route for metastasizing cancer cells to distant organs and deliver drugs to tumors. The irregular and leaky tumor vasculature is responsible for increased interstitial pressure in the tumor microenvironment whereas multiscale flow structure interaction processes control tumor growth metastasis and nanoparticle mediated drug deliver...

  6. Fluid mechanical responses to nutrient depletion in fungi and biofilmsa)

    Science.gov (United States)

    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.

  7. Teaching fluid mechanics to high schoolers: methods, challenges, and outcome

    Science.gov (United States)

    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.

  8. Fluid mechanics of eating, swallowing and digestion - overview and perspectives.

    Science.gov (United States)

    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.

  9. The fluid mechanics of the inner-ear disorder BPPV

    Science.gov (United States)

    Weidman, Michael; Squires, Todd; Stone, Howard

    2001-11-01

    The inner ear of mammals contains fluid-filled semi-circular canals with a flexible sensory membrane (called a cupula) which detects rotational acceleration. Benign Paroxysmal Positional Vertigo (BPPV) is one of the most common disorders of this system diagnosed today, and is characterized by symptoms of dizziness and nausea brought on by sudden changes in head orientation. BPPV is believed to have a mechanical (rather than nervous) origin, in which dense particles called otoconia settle into the canals and trigger false sensations of rotational acceleration. Several qualitative mechanisms have been proposed by the medical community, which we examine from a fluid mechanical standpoint. Traditionally, the semicircular canal and the cupula are modeled as an over-damped torsional pendulum with a driving force provided by rotational acceleration. We extend this model to include the time-dependent mechanical response owing to sedimentation of the otoconia. We make qualitative and quantitative predictions associated with the proposed mechanisms, with an eye towards differentiating between them and perhaps towards more effective diagnostic and therapeutic methods.

  10. 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....

  11. Dynamical density functional theory for molecular and colloidal fluids: a microscopic approach to fluid mechanics.

    Science.gov (United States)

    Archer, A J

    2009-01-07

    In recent years, a number of dynamical density functional theories (DDFTs) have been developed for describing the dynamics of the one-body density of both colloidal and atomic fluids. In the colloidal case, the particles are assumed to have stochastic equations of motion and theories exist for both the case when the particle motion is overdamped and also in the regime where inertial effects are relevant. In this paper, we extend the theory and explore the connections between the microscopic DDFT and the equations of motion from continuum fluid mechanics. In particular, starting from the Kramers equation, which governs the dynamics of the phase space probability distribution function for the system, we show that one may obtain an approximate DDFT that is a generalization of the Euler equation. This DDFT is capable of describing the dynamics of the fluid density profile down to the scale of the individual particles. As with previous DDFTs, the dynamical equations require as input the Helmholtz free energy functional from equilibrium density functional theory (DFT). For an equilibrium system, the theory predicts the same fluid one-body density profile as one would obtain from DFT. Making further approximations, we show that the theory may be used to obtain the mode coupling theory that is widely used for describing the transition from a liquid to a glassy state.

  12. Renal and Vascular Mechanisms of Thiazolidinedione-Induced Fluid Retention

    Directory of Open Access Journals (Sweden)

    Tianxin Yang

    2008-01-01

    Full Text Available Thiazolidinediones (TZDs are peroxisome proliferator-activated receptor subtype γ (PPARγ activators that are clinically used as an insulin sensitizer for glycemic control in patients with type 2 diabetes. Additionally, TZDs exhibit novel anti-inflammatory, antioxidant, and antiproliferative properties, indicating therapeutic potential for a wide variety of diseases associated with diabetes and other conditions. The clinical applications of TZDs are limited by the common major side effect of fluid retention. A better understanding of the molecular mechanism of TZD-induced fluid retention is essential for the development of novel therapies with improved safety profiles. An important breakthrough in the field is the finding that the renal collecting duct is a major site for increased fluid reabsorption in response to rosiglitazone or pioglitazone. New evidence also indicates that increased vascular permeability in adipose tissues may contribute to edema formation and body weight gain. Future research should therefore be directed at achieving a better understanding of the detailed mechanisms of TZD-induced increases in renal sodium transport and in vascular permeability.

  13. Mechanical design problems associated with turbopump fluid film bearings

    Science.gov (United States)

    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.

  14. 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.

  15. A fully coupled thermal-mechanical-fluid flow model for nonlinear geologic systems

    Science.gov (United States)

    Hart, R. D.

    1981-02-01

    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.

  16. On the Use of Computers for Teaching Fluid Mechanics

    Science.gov (United States)

    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.

  17. Basic Coandă MAV Fluid Dynamics and Flight Mechanics

    Science.gov (United States)

    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.

  18. 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

  19. 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...... to elicit an escape ranged between 1.8 and 3 s(-1). Escape speeds varied between 100 to 150 body length s(-1). Jump directions were non- random in all jumping species and had a negative geotactic component. In a grazing experiment with copepods, the predation mortality of a jumping ciliate was about 15...

  20. 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

  1. Laser metrology in fluid mechanics granulometry, temperature and concentration measurements

    CERN Document Server

    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

  2. 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

  3. Shooting Mechanisms in Nature: A Systematic Review

    Science.gov (United States)

    Sakes, Aimée; van der Wiel, Marleen; Henselmans, Paul W. J.; van Leeuwen, Johan L.; Dodou, Dimitra; Breedveld, Paul

    2016-01-01

    Background In nature, shooting mechanisms are used for a variety of purposes, including prey capture, defense, and reproduction. This review offers insight into the working principles of shooting mechanisms in fungi, plants, and animals in the light of the specific functional demands that these mechanisms fulfill. Methods We systematically searched the literature using Scopus and Web of Knowledge to retrieve articles about solid projectiles that either are produced in the body of the organism or belong to the body and undergo a ballistic phase. The shooting mechanisms were categorized based on the energy management prior to and during shooting. Results Shooting mechanisms were identified with projectile masses ranging from 1·10−9 mg in spores of the fungal phyla Ascomycota and Zygomycota to approximately 10,300 mg for the ballistic tongue of the toad Bufo alvarius. The energy for shooting is generated through osmosis in fungi, plants, and animals or muscle contraction in animals. Osmosis can be induced by water condensation on the system (in fungi), or water absorption in the system (reaching critical pressures up to 15.4 atmospheres; observed in fungi, plants, and animals), or water evaporation from the system (reaching up to −197 atmospheres; observed in plants and fungi). The generated energy is stored as elastic (potential) energy in cell walls in fungi and plants and in elastic structures in animals, with two exceptions: (1) in the momentum catapult of Basidiomycota the energy is stored in a stalk (hilum) by compression of the spore and droplets and (2) in Sphagnum energy is mainly stored in compressed air. Finally, the stored energy is transformed into kinetic energy of the projectile using a catapult mechanism delivering up to 4,137 J/kg in the osmotic shooting mechanism in cnidarians and 1,269 J/kg in the muscle-powered appendage strike of the mantis shrimp Odontodactylus scyllarus. The launch accelerations range from 6.6g in the frog Rana pipiens to 5

  4. Shooting Mechanisms in Nature: A Systematic Review.

    Directory of Open Access Journals (Sweden)

    Aimée Sakes

    Full Text Available In nature, shooting mechanisms are used for a variety of purposes, including prey capture, defense, and reproduction. This review offers insight into the working principles of shooting mechanisms in fungi, plants, and animals in the light of the specific functional demands that these mechanisms fulfill.We systematically searched the literature using Scopus and Web of Knowledge to retrieve articles about solid projectiles that either are produced in the body of the organism or belong to the body and undergo a ballistic phase. The shooting mechanisms were categorized based on the energy management prior to and during shooting.Shooting mechanisms were identified with projectile masses ranging from 1·10-9 mg in spores of the fungal phyla Ascomycota and Zygomycota to approximately 10,300 mg for the ballistic tongue of the toad Bufo alvarius. The energy for shooting is generated through osmosis in fungi, plants, and animals or muscle contraction in animals. Osmosis can be induced by water condensation on the system (in fungi, or water absorption in the system (reaching critical pressures up to 15.4 atmospheres; observed in fungi, plants, and animals, or water evaporation from the system (reaching up to -197 atmospheres; observed in plants and fungi. The generated energy is stored as elastic (potential energy in cell walls in fungi and plants and in elastic structures in animals, with two exceptions: (1 in the momentum catapult of Basidiomycota the energy is stored in a stalk (hilum by compression of the spore and droplets and (2 in Sphagnum energy is mainly stored in compressed air. Finally, the stored energy is transformed into kinetic energy of the projectile using a catapult mechanism delivering up to 4,137 J/kg in the osmotic shooting mechanism in cnidarians and 1,269 J/kg in the muscle-powered appendage strike of the mantis shrimp Odontodactylus scyllarus. The launch accelerations range from 6.6g in the frog Rana pipiens to 5,413,000g in

  5. Shooting Mechanisms in Nature: A Systematic Review.

    Science.gov (United States)

    Sakes, Aimée; van der Wiel, Marleen; Henselmans, Paul W J; van Leeuwen, Johan L; Dodou, Dimitra; Breedveld, Paul

    2016-01-01

    In nature, shooting mechanisms are used for a variety of purposes, including prey capture, defense, and reproduction. This review offers insight into the working principles of shooting mechanisms in fungi, plants, and animals in the light of the specific functional demands that these mechanisms fulfill. We systematically searched the literature using Scopus and Web of Knowledge to retrieve articles about solid projectiles that either are produced in the body of the organism or belong to the body and undergo a ballistic phase. The shooting mechanisms were categorized based on the energy management prior to and during shooting. Shooting mechanisms were identified with projectile masses ranging from 1·10-9 mg in spores of the fungal phyla Ascomycota and Zygomycota to approximately 10,300 mg for the ballistic tongue of the toad Bufo alvarius. The energy for shooting is generated through osmosis in fungi, plants, and animals or muscle contraction in animals. Osmosis can be induced by water condensation on the system (in fungi), or water absorption in the system (reaching critical pressures up to 15.4 atmospheres; observed in fungi, plants, and animals), or water evaporation from the system (reaching up to -197 atmospheres; observed in plants and fungi). The generated energy is stored as elastic (potential) energy in cell walls in fungi and plants and in elastic structures in animals, with two exceptions: (1) in the momentum catapult of Basidiomycota the energy is stored in a stalk (hilum) by compression of the spore and droplets and (2) in Sphagnum energy is mainly stored in compressed air. Finally, the stored energy is transformed into kinetic energy of the projectile using a catapult mechanism delivering up to 4,137 J/kg in the osmotic shooting mechanism in cnidarians and 1,269 J/kg in the muscle-powered appendage strike of the mantis shrimp Odontodactylus scyllarus. The launch accelerations range from 6.6g in the frog Rana pipiens to 5,413,000g in cnidarians, the

  6. Fluid mechanics experiments in oscillatory flow. Volume 2: Tabulated data

    Science.gov (United States)

    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).

  7. Mechanisms of self-cleaning in fluid-based smooth adhesive pads of insects

    International Nuclear Information System (INIS)

    Clemente, Christofer J; Federle, Walter

    2012-01-01

    Pressure-sensitive adhesives such as tapes become easily contaminated by dust particles. By contrast, animal adhesive pads are able to self-clean and can be reused millions of times over a lifetime with little reduction in adhesion. However, the detailed mechanisms underlying this ability are still unclear. Here we test in adhesive pads of stick insects (Carausius morosus) (1) whether self-cleaning is enhanced by the liquid pad secretion, and (2) whether alternating push–pull movements aid the removal of particles. We measured attachment forces of insect pads on glass after contamination with 10 µm polystyrene beads. While the amount of fluid present on the pad showed no effect on the pads' susceptibility to contamination, the recovery of adhesive forces after contamination was faster when higher fluid levels were present. However, this effect does not appear to be based on a faster rate of self-cleaning since the number of spheres deposited with each step did not increase with fluid level. Instead, the fluid may aid the recovery of adhesive forces by filling in the gaps between contaminating particles, similar to the fluid's function on rough surfaces. Further, we found no evidence that an alternation of pushing and pulling movements, as found in natural steps, leads to a more efficient recovery of adhesion than repeated pulling slides. (paper)

  8. Mechanisms of self-cleaning in fluid-based smooth adhesive pads of insects.

    Science.gov (United States)

    Clemente, Christofer J; Federle, Walter

    2012-12-01

    Pressure-sensitive adhesives such as tapes become easily contaminated by dust particles. By contrast, animal adhesive pads are able to self-clean and can be reused millions of times over a lifetime with little reduction in adhesion. However, the detailed mechanisms underlying this ability are still unclear. Here we test in adhesive pads of stick insects (Carausius morosus) (1) whether self-cleaning is enhanced by the liquid pad secretion, and (2) whether alternating push-pull movements aid the removal of particles. We measured attachment forces of insect pads on glass after contamination with 10 µm polystyrene beads. While the amount of fluid present on the pad showed no effect on the pads' susceptibility to contamination, the recovery of adhesive forces after contamination was faster when higher fluid levels were present. However, this effect does not appear to be based on a faster rate of self-cleaning since the number of spheres deposited with each step did not increase with fluid level. Instead, the fluid may aid the recovery of adhesive forces by filling in the gaps between contaminating particles, similar to the fluid's function on rough surfaces. Further, we found no evidence that an alternation of pushing and pulling movements, as found in natural steps, leads to a more efficient recovery of adhesion than repeated pulling slides.

  9. Serious Fun: Using Toys to Demonstrate Fluid Mechanics Principles

    Science.gov (United States)

    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…

  10. Links between fluid mechanics and quantum mechanics: a model for information in economics?

    Science.gov (United States)

    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).

  11. Nature and source of the ore-forming fluids associated with orogenic gold deposits in the Dharwar Craton

    Directory of Open Access Journals (Sweden)

    Biswajit Mishra

    2018-05-01

    , pyrite and arsenopyrite point toward operation of fault-valves that caused pressure fluctuation-induced fluid phase separation, which acted as the dominant process of gold precipitation, apart from fluid-rock sulfidation reactions. Therefore, results from geochemistry of hydrothermal minerals and those from fluid inclusion microthermometry corroborate in constraining source of ore fluid, nature of gold transport (by Au-bisulfide complex and mechanism of gold ore formation in the Dharwar Craton. Keywords: Dharwar, Gold, Fluid inclusions, Isotopes, Fluid composition, Greenstone metamorphism

  12. The Pi-Theorem Applications to Fluid Mechanics and Heat and Mass Transfer

    CERN Document Server

    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.

  13. Fluid Mechanics of Biological Surfaces and their Technological Application

    Science.gov (United States)

    Bechert, D. W.; Bruse, M.; Hage, W.; Meyer, R.

    A survey is given on fluid-dynamic effects caused by the structure and properties of biological surfaces. It is demonstrated that the results of investigations aiming at technological applications can also provide insights into biophysical phenomena. Techniques are described both for reducing wall shear stresses and for controlling boundary-layer separation. (a) Wall shear stress reduction was investigated experimentally for various riblet surfaces including a shark skin replica. The latter consists of 800 plastic model scales with compliant anchoring. Hairy surfaces are also considered, and surfaces in which the no-slip condition is modified. Self-cleaning surfaces such as that of lotus leaves represent an interesting option to avoid fluid-dynamic deterioration by the agglomeration of dirt. An example of technological implementation is discussed for riblets in long-range commercial aircraft. (b) Separation control is also an important issue in biology. After a few brief comments on vortex generators, the mechanism of separation control by bird feathers is described in detail. Self-activated movable flaps (=artificial bird feathers) represent a high-lift system enhancing the maximum lift of airfoils by about 20%. This is achieved without perceivable deleterious effects under cruise conditions. Finally, flight experiments on an aircraft with laminar wing and movable flaps are presented.

  14. An intelligent data acquisition system for fluid mechanics research

    Science.gov (United States)

    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.

  15. A cubic spline approximation for problems in fluid mechanics

    Science.gov (United States)

    Rubin, S. G.; Graves, R. A., Jr.

    1975-01-01

    A cubic spline approximation is presented which is suited for many fluid-mechanics problems. This procedure provides a high degree of accuracy, even with a nonuniform mesh, and leads to an accurate treatment of derivative boundary conditions. The truncation errors and stability limitations of several implicit and explicit integration schemes are presented. For two-dimensional flows, a spline-alternating-direction-implicit method is evaluated. The spline procedure is assessed, and results are presented for the one-dimensional nonlinear Burgers' equation, as well as the two-dimensional diffusion equation and the vorticity-stream function system describing the viscous flow in a driven cavity. Comparisons are made with analytic solutions for the first two problems and with finite-difference calculations for the cavity flow.

  16. 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.

  17. Introduction to the internal fluid mechanics research session

    Science.gov (United States)

    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.

  18. Fluid mechanics experiments in oscillatory flow. Volume 1: Report

    Science.gov (United States)

    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).

  19. 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)

  20. That is Cool: the Nature Of Aesthetics in Fluid Physics

    Science.gov (United States)

    Hertzberg, Jean

    2013-11-01

    Aesthetics has historically been defined as the study of beauty and thus as a metric of art. More recently, psychologists are using the term to describe a spectrum of responses from ``I hate it'' to ``I love it.'' In the context of fluid physics, what is beautiful? What elicits a ``Wow! Awesome! Cool!'' response versus a snore? Can we use aesthetics to deepen or change students' or the public's perceptions of physics and/or the world around them? For example, students seem to appreciate the aesthetics of destruction: environmental fluid dynamics such as storms, tornadoes, floods and wildfires are often responsible for massive destruction, yet humans draw pleasure from watching such physics and the attendant destruction from a safe distance. Can this voyeurism be turned to our advantage in communicating science? Observations of student and Facebook Flow Visualization group choices for fluid physics that draw a positive aesthetic response are sorted into empirical categories; the aesthetics of beauty, power, destruction, and oddness. Each aesthetic will be illustrated with examples drawn from flow visualizations from both the Flow Visualization course (MCEN 4151) taught at the University of Colorado, Boulder, and sources on the web. This work is supported by NSF: EEC 1240294.

  1. Electrification of particulate entrained fluid flows—Mechanisms, applications, and numerical methodology

    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

  2. Obstructive renal injury: from fluid mechanics to molecular cell biology

    Directory of Open Access Journals (Sweden)

    Alvaro C Ucero

    2010-04-01

    Full Text Available Alvaro C Ucero1,*, Sara Gonçalves2,*, Alberto Benito-Martin1, Beatriz Santamaría1, Adrian M Ramos1, Sergio Berzal1, Marta Ruiz-Ortega1, Jesus Egido1, Alberto Ortiz11Fundación Jiménez Díaz, Universidad Autónoma de Madrid, Fundación Renal Iñigo Alvarez de Toledo, Madrid, Spain; 2Nefrologia e Transplantação Renal, Hospital de Santa Maria EPE, Lisbon, Portugal *Both authors contributed equally to the manuscriptAbstract: 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.Keywords: urinary tract obstruction, renal injury, fluid mechanics, molecular cell biology

  3. Relation between boundary slip mechanisms and waterlike fluid behavior

    Science.gov (United States)

    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.

  4. 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.

  5. Towards a statistical mechanical theory of active fluids.

    Science.gov (United States)

    Marini Bettolo Marconi, Umberto; Maggi, Claudio

    2015-12-07

    We present a stochastic description of a model of N mutually interacting active particles in the presence of external fields and characterize its steady state behavior in the absence of currents. To reproduce the effects of the experimentally observed persistence of the trajectories of the active particles we consider a Gaussian force having a non-vanishing correlation time τ, whose finiteness is a measure of the activity of the system. With these ingredients we show that it is possible to develop a statistical mechanical approach similar to the one employed in the study of equilibrium liquids and to obtain the explicit form of the many-particle distribution function by means of the multidimensional unified colored noise approximation. Such a distribution plays a role analogous to the Gibbs distribution in equilibrium statistical mechanics and provides complete information about the microscopic state of the system. From here we develop a method to determine the one- and two-particle distribution functions in the spirit of the Born-Green-Yvon (BGY) equations of equilibrium statistical mechanics. The resulting equations which contain extra-correlations induced by the activity allow us to determine the stationary density profiles in the presence of external fields, the pair correlations and the pressure of active fluids. In the low density regime we obtained the effective pair potential ϕ(r) acting between two isolated particles separated by a distance, r, showing the existence of an effective attraction between them induced by activity. Based on these results, in the second half of the paper we propose a mean field theory as an approach simpler than the BGY hierarchy and use it to derive a van der Waals expression of the equation of state.

  6. Partitioning of naturally-occurring radionuclides (NORM) in Marcellus Shale produced fluids influenced by chemical matrix.

    Science.gov (United States)

    Nelson, Andrew W; Johns, Adam J; Eitrheim, Eric S; Knight, Andrew W; Basile, Madeline; Bettis, E Arthur; Schultz, Michael K; Forbes, Tori Z

    2016-04-01

    Naturally-occurring radioactive materials (NORM) associated with unconventional drilling produced fluids from the Marcellus Shale have raised environmental concerns. However, few investigations into the fundamental chemistry of NORM in Marcellus Shale produced fluids have been performed. Thus, we performed radiochemical experiments with Marcellus Shale produced fluids to understand the partitioning behavior of major radioelements of environmental health concern (uranium (U), thorium (Th), radium (Ra), lead (Pb), and polonium (Po)). We applied a novel radiotracer, (203)Pb, to understand the behavior of trace-levels of (210)Pb in these fluids. Ultrafiltration experiments indicated U, Th, and Po are particle reactive in Marcellus Shale produced fluids and Ra and Pb are soluble. Sediment partitioning experiments revealed that >99% of Ra does not adsorb to sediments in the presence of Marcellus Shale produced fluids. Further experiments indicated that although Ra adsorption is related to ionic strength, the concentrations of heavier alkaline earth metals (Ba, Sr) are stronger predictors of Ra solubility.

  7. 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

  8. Natural Frequencies of a Cracked Beam Coupled with a Compressible Sloshing Fluid

    Directory of Open Access Journals (Sweden)

    Michele Di Sciuva

    2004-01-01

    Full Text Available This article describes studies into the flexural vibration of a cracked cantilevered beam in contact with a non-viscous fluid. The crack has been represented by a mass-less rotational spring, the flexibility of which has been calculated using linear fracture mechanics. The coupled system is subject to undisturbed boundary condition at infinity in the fluid domain. A range of different boundary conditions have been analysed such as both incompressible and compressible fluid, with and without sloshing. Various crack sizes and positions have been considered in order to assess the effect of damage in the fluid-structure interaction problem.

  9. Introducing Non-Newtonian Fluid Mechanics Computations with Mathematica in the Undergraduate Curriculum

    Science.gov (United States)

    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…

  10. Development of drilling fluids based on polysaccharides and natural minerals

    Directory of Open Access Journals (Sweden)

    Zhanar Nurakhmetova

    2016-03-01

    Full Text Available The technology of oil well drilling in complex geological conditions by applying the drilling muds based on the polysaccharides – gellan, xanthan and their mixture which potentially possess a good flocculation properties and the ability to reversible sol-gel transition in dependence of temperature and concentration of low molecular weight cations in water has been justified in this work. For the preparation of drilling muds, gellan and xanthan were used, these polymers were obtained from biomass by an aerobic fermentation using microorganisms Sphingomonas elodea and Xanthomonas campestris. Bentonite was used as a natural mineral. Physical and chemical characteristics of aqueous and aqueous-salt solutions of natural polysaccharide gellan including: density, intrinsic and effective viscosity, static shear stress, dynamic shear stress, sedimentation stability and other parameters were determined while varying polymer compositions and concentrations, ionic strength of the solution, nature of low molecular weight salts, concentration of dispersion phase, pH of the medium and temperature.

  11. Mechanical Properties of Gels; Stress from Confined Fluids

    Energy Technology Data Exchange (ETDEWEB)

    George W. Scherer

    2009-12-01

    Abstract for Grant DE-FG02-97ER45642 Period: 1997-2002 Mechanical Properties of Gels 2002-2008 Stress from Confined Fluids Principal investigator: Prof. George W. Scherer Dept. Civil & Env. Eng./PRISM Eng. Quad. E-319 Princeton, NJ 08544 USA Recipient organization: Trustees of Princeton University 4 New South Princeton, NJ 08544 USA Abstract: The initial stage of this project, entitled Mechanical Properties of Gels, was dedicated to characterizing and explaining the properties of inorganic gels. Such materials, made by sol-gel processing, are of interest for fabrication of films, fibers, optical devices, advanced insulation and other uses. However, their poor mechanical properties are an impediment in some applications, so understanding the origin of these properties could lead to enhanced performance. Novel experimental methods were developed and applied to measure the stiffness and permeability of gels and aerogels. Numerical simulations were developed to reproduce the growth process of the gels, resulting in structures whose mechanical properties matched the measurements. The models showed that the gels are formed by the growth of relatively robust clusters of molecules that are joined by tenuous links whose compliance compromises the stiffness of the structure. Therefore, synthetic methods that enhance the links could significantly increase the rigidity of such gels. The next stage of the project focused on Stress from Confined Fluids. The first problem of interest was the enhanced thermal expansion coefficient of water that we measured in the nanometric pores of cement paste. This could have a deleterious effect on the resistance of concrete to rapid heating in fires, because the excessive thermal expansion of water in the pores of the concrete could lead to spalling and collapse. A series of experiments demonstrated that the expansion of water increases as the pore size decreases. To explain this behavior, we undertook a collaboration with Prof. Stephen

  12. 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.

  13. A fluid-mechanical model of elastocapillary coalescence

    KAUST Repository

    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(104). 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.

  14. Flippin' Fluid Mechanics - Comparison of Blended Classroom vs. Traditional Lecture

    Science.gov (United States)

    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 average course total (i.e., aggregate of exam and assignment scores) is significantly greater in the blended classes (p grade with an R-squared of 0.563, and the blended class variable is significant (p point scale). Regarding student perceptions, surveys reveal significantly greater enthusiasm, stimulation, 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.

  15. Fluid Shearing for Accelerated Chemical Reactions - Fluid Mechanics in the VFD

    Science.gov (United States)

    Leivadarou, Evgenia; Dalziel, Stuart; G. K. Batchelor Laboratory, Department of Applied Mathematics; Theoretical Physics Team

    2016-11-01

    The Vortex Fluidic Device (VFD) is a rapidly rotating tube that can operate under continuous flow with a jet feeding liquid reactants to the tube's hemispherical base. It is a new 'green' approach to the organic synthesis with many industrial applications in cosmetics, protein folding and pharmaceutical production. The rate of reaction in the VFD is enhanced when the collision rate is increased. The aim of the project is to explain the fluid mechanics and optimize the performance of the device. One contribution to the increased yield is believed to be the high levels of shear stress. We attempt to enhance the shear stress by achieving high velocity gradients in the boundary layers. Another factor is the uncontrolled vibrations due to imperfections in the bearings and therefore it is important to assess their influence in the initial spreading. The surface area of the film should be maximized with respect to the rotation rate, geometry and orientation of the tube, flow rate, wettability and contact line dynamics. Experiments are presented for a flat disk and a curved bowl, establishing the optimum height of release, rotation rate and tube orientation. Vibrations were imposed to investigate the changes in the film formation. We discuss the implications of our results in the VFD.

  16. The Characteristics of natural convection heat transfer of Al2O3–water nano fluid flow in a vertical annulus pipe

    International Nuclear Information System (INIS)

    Reinaldy Nazar

    2016-01-01

    Results of several researches have shown that nano fluids have better thermal characteristics than conventional fluid (water). In this regard, ideas for using nano fluids as an alternative heat transfer fluid in the reactor coolant system have been well developed. Meanwhile the natural convection in a vertical annulus pipe is one of the important mechanisms of heat transfer and is found at the TRIGA research reactor, the new generation nuclear power plants and other energy conversion devices. On the other hand, the heat transfer characteristics of nano fluids in a vertical annulus pipe has not been known. Therefore, it is important to do research continuously to analyze the heat transfer nano fluids in a vertical annulus pipe. This study has carried out numerical analysis by using computer code of CFD (computational of fluids dynamic) on natural convection heat transfer characteristics of nano fluids flow of Al 2 O 3 -water 2 % volume in the vertical annulus pipe. The results showed an increase in heat transfer performance (Nusselt numbers - NU) by 20.5 % - 35 %. In natural convection mode with Rayleigh numbers 2.471 e +09 ≤ Ra ≤ 1.955 e +13 obtained empirical correlations for water is N U = 1.065 (R a (D H /x)) 0.179 and empirical correlations for Al 2 O 3 -water nano fluids is N U = 14.869 (R a (D H /x)) 0.115 .(author)

  17. The No-Slip Boundary Condition in Fluid Mechanics

    Indian Academy of Sciences (India)

    POiseuille flow, flow resistance. Before considering the case of fluids, i.e. gases and liquids,. ______ . ..... the cylinders. But it is very likely that he would have then guessed correctly that the drag would increase with the length. This historical note is added to emphasize how difficult it was to understand the motion of a fluid in ...

  18. Fluid mechanics a concise introduction to the theory

    CERN Document Server

    Yih, Chia-Shun

    1969-01-01

    Fundamentals ; the basic equations ; general theorems for the flow of an inviscid fluid ; irrotational flows of an inviscid fluid of constant density ; waves in an incompressible ; effects of viscosity ; heat transfer and boundary layers of a gas ; hydrodynamic stability ; turbulence ; basic thermodynamics ; curvilinear coordinates.

  19. The No-Slip Boundary Condition in Fluid Mechanics

    Indian Academy of Sciences (India)

    some basic ideas connected to this problem so that the historical notes added afterwards will be appreciated .... Stress in a Fluid. When the fluid is at rest. only the normal stresses are exerted, the tangential stresses being zero. The normal stress at a point does not depend on the direction and it is the hy- drostatic pressure.

  20. The Fluid Mechanics of the Bible: Miracles Explainable by Christian Science?

    Science.gov (United States)

    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.

  1. Teaching Fluid Mechanics to the Beginning Graduate Student--An Objective-Oriented Approach.

    Science.gov (United States)

    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…

  2. The early years of the Journal of Fluid Mechanics. Style and international impact

    Science.gov (United States)

    Moffatt, H. Keith

    2017-07-01

    The origins of the Journal of Fluid Mechanics, of which the first volume was published in 1956, are discussed, with reference to editorial correspondence during the early years of the Journal. This paper is based on a lecture given at the colloquium: A Century of Fluid Mechanics, 1870-1970, IMFT, Toulouse, France, 19-21 October 2016.

  3. Take-Home Experiments in Undergraduate Fluid Mechanics Education

    Science.gov (United States)

    Cimbala, John

    2007-11-01

    Hands-on take-home experiments, assigned as homework, are useful as supplements to traditional in-class demonstrations and laboratories. Students borrow the equipment from the department's equipment room, and perform the experiment either at home or in the student lounge or student shop work area. Advantages include: (1) easy implementation, especially for large classes, (2) low cost and easy duplication of multiple units, (3) no loss of lecture time since the take-home experiment is self-contained with all necessary instructions, and (4) negligible increase in student or teaching assistant work load since the experiment is assigned as a homework problem in place of a traditional pen and paper problem. As an example, a pump flow take-home experiment was developed, implemented, and assessed in our introductory junior-level fluid mechanics course at Penn State. The experimental apparatus consists of a bucket, tape measure, submersible aquarium pump, tubing, measuring cup, and extension cord. We put together twenty sets at a total cost of less than 20 dollars per set. Students connect the tube to the pump outlet, submerge the pump in water, and measure the volume flow rate produced at various outflow elevations. They record and plot volume flow rate as a function of outlet elevation, and compare with predictions based on the manufacturer's pump performance curve (head versus volume flow rate) and flow losses. The homework assignment includes an online pre-test and post-test to assess the change in students' understanding of the principles of pump performance. The results of the assessment support a significant learning gain following the completion of the take-home experiment.

  4. Mechanics of undulatory swimming in a frictional fluid.

    Science.gov (United States)

    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.

  5. Mechanics of undulatory swimming in a frictional fluid.

    Directory of Open Access Journals (Sweden)

    Yang Ding

    Full Text Available 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.

  6. Mechanisms and models of the dehydration self-organization in biological fluids

    International Nuclear Information System (INIS)

    Tarasevich, Yurii Yu

    2004-01-01

    The dehydration self-organization phenomenon in biological fluids attracted the attention of researchers slightly more than a decade ago. While seemingly simple (the structure formation is possible to observe even in domestic conditions), the effect turned out to be extremely complicated and to involve a number of interrelated processes of a different physical nature. The dehydration self-organization effect in biological fluids underlies a medical diagnostic technique patented in 40 countries of the world, while the mechanisms that underlie the technique still remain largely obscure. This review is an attempt to draw an integrated picture of the current state of the problem: to emphasize reliably established facts and the problems that remain to be solved, to put an end to speculation, and to characterize the available theories and models. An analysis of the literature sources allows us to draw the conclusion that the effects observed in the dehydration of biological fluids are typical for colloidal solutions in general and can be described in the framework of conventional physical approaches. (from the current literature)

  7. 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

  8. Natural occurrence and significance of fluids indicating high pressure and temperature

    Science.gov (United States)

    Roedder, E.

    1981-01-01

    Most natural minerals have formed from a fluid phase such as a silicate melt or a saline aqueous solution. Fluid inclusions are tiny volumes of such fluids that were trapped within the growing crystals. These inclusions can provide valuable but sometimes ambiguous data on the temperature, pressure, and composition of these fluids, many of which are not available from any other source. They also provide "visual autoclaves" in which it is possible to watch, through the microscope, the actual phase changes take place as the inclusions are heated. This paper reviews the methods of study and the results obtained, mainly on inclusions formed from highly concentrated solutions, at temperatures ???500??C. Many such fluids have formed as a result of immiscibility with silicate melt in igneous or high-temperature metamorphic rocks. These include fluids consisting of CO2, H2O, or hydrosaline melts that were <50% H2O. From the fluid inclusion evidence it is clear that a boiling, very hot, very saline fluid was present during the formation of most of the porphyry copper deposits in the world. Similarly, from the inclusion evidence it is clear that early (common) pegmatites formed from essentially silicate melts and that the late, rare-element-bearing and chamber-type pegmatites formed from a hydrosaline melt or a more dilute water solution. The evidence on whether this change in composition from early to late solutions was generally continuous or involved immiscibility is not as clear. ?? 1981.

  9. 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

  10. Power distribution transformers using natural ester fluids as dielectric and coolant

    Directory of Open Access Journals (Sweden)

    Jorge Iván Silva-Ortega

    2016-12-01

    Full Text Available Researches related to the use of Natural Ester Fluids as a refrigerant of power transformers have been developed in other countries with successful results. In Colombia there is no a procedure to control the use of these esters in electrical apparatus, so the current implementations are regulated by NTC 1465 standards for mineral esters. This new proposal involves the composition and the most relevant properties (the ignition resistance, impact on the lifetime of the insulating papers and the impact on the environment, which makes the application of natural esters fluids advantageous not only to preserve the environment but also to get a better performance of power transformers.

  11. Effects of fluids on rock deformation and fault slip: From nature to societal impact (Louis Néel Medal Lecture)

    Science.gov (United States)

    Spiers, Christopher J.

    2017-04-01

    Understanding the effects of fluid-rock interaction on rock and fault mechanical behaviour is central not only to understanding natural tectonic and seismogenic processes, and phenomena such as resource trapping, but also to evaluating the impact of industrial operations in the Earth's crust. These include activities ranging from extraction of geo-energy to geological storage of fuels, CO2 and wastes. For the assessment of both natural and induced geohazards, a physics-based approach to quantifying rock mechanical behaviour is unmissable. Microstructural studies of rocks deformed naturally in the mid and upper crust, or at seismogenic depths in subduction zones, show widespread evidence for brittle deformation (cataclasis), dissolution-precipitation transfer, fluid-related reactions producing weak minerals, and dilatation/cementation of fractures, cracks and pores. In addition, experimental work on rocks and simulated fault gouges has shown that the presence of water strongly influences their mechanical and transport properties. This implies the operation of fluid-assisted deformation mechanisms, such as stress corrosion cracking and diffusive mass transfer (pressure solution). More recently, other fluid-coupled deformation processes have been recognised, in rocks from peridotites and granites to sandstones, limestones and shales. In this lecture, I will give an overview of progress in this area. I will address the physics of pressure solution and stress corrosion cracking and how they contribute to the deformation and compaction of sandstone, carbonate and evaporite rocks in the mid and upper crust, under natural conditions and in the context of deformation caused by geo-resources production and geo-storage. New results on how these processes are affected by pore fluid salinity, gas content and CO2 activity will also be considered, as will data on the effects of mineral-fluid reactions and associated volume changes on rock deformation, fracturing and transport

  12. Fluid-to-fluid scaling for a gravity- and flashing-driven natural circulation loop

    International Nuclear Information System (INIS)

    Yadigaroglu, G.; Zeller, M.

    1994-01-01

    In certain natural-circulation reactor systems proposed recently, vapor generation takes place by flashing in an adiabatic riser above the core. A step-by-step facility design procedure was used to define suitable scaling criteria for a refrigerant-113 (R-113) experiment simulating the dynamics and stability of such a loop. The fact that vapor generation does not normally take place in the core allows additional flexibility in designing the model; almost perfect simulation can be achieved, mainly by reducing the height of the facility according to the liquid density ratio and scaling for similar void fraction distributions in the prototype and the model. ((orig.))

  13. The Influence of Fluid Overload on the Length of Mechanical Ventilation in Pediatric Congenital Heart Surgery.

    Science.gov (United States)

    Sampaio, Tatiana Z A L; O'Hearn, Katie; Reddy, Deepti; Menon, Kusum

    2015-12-01

    Fluid overload and prolonged mechanical ventilation lead to worse outcomes in critically ill children. However, the association between these variables in children following congenital heart surgery is unknown. The objectives of this study were to describe the association between fluid overload and duration of mechanical ventilation, oxygen requirement and radiologic findings of pulmonary and chest wall edema. This study is a retrospective chart review of patients who underwent congenital heart surgery between June 2010 and December 2013. Univariate and multivariate associations between maximum cumulative fluid balance and length of mechanical ventilation and OI were tested using the Spearman correlation test and multiple linear regression models, respectively. There were 85 eligible patients. Maximum cumulative fluid balance was associated with duration of mechanical ventilation (adjusted analysis beta coefficient = 0.53, CI 0.38-0.66, P mechanical ventilation (P = 0.012 and 0.014, respectively). Fluid overload is associated with prolonged duration of mechanical ventilation and PICU length of stay after congenital heart surgery. Fluid overload was also associated with physiological markers of respiratory restriction. A randomized controlled trial of a restrictive versus liberal fluid replacement strategy is necessary in this patient population, but in the meantime, accumulating observational evidence suggests that cautious use of fluid in the postoperative care may be warranted.

  14. 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

  15. The No-Slip Boundary Condition in Fluid Mechanics

    Indian Academy of Sciences (India)

    Ideas leading to the resolution of the problem of no-slip condition for fluid velocity at a solid surface are traced in this concluding part of the article. In the continuum limit velocity slip being zero is established beyond any doubt now. Even turbulent flows which have a large velocity gradient near a wall have to satisfy the ...

  16. 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

  17. The No-Slip Boundary Condition in Fluid Mechanics

    Indian Academy of Sciences (India)

    Historical Development. A brief and excellent review of this problem of velocity slip in fluid flow is given in the book by Goldstein [1]. We freely borrow from this book adding some explanations and supple- ments based on the earlier discussion in Part 1. We saw that Newton tacitly assumed the no-slip condition in the.

  18. Mechanism of thermoluminescence in Vietnam natural quartz

    International Nuclear Information System (INIS)

    Tran Ngoc; Nguyen Manh Son; Phan Tien Dung; Trinh The Cuong; Nguyen Trong Thanh; Vu Xuan Quang

    2006-01-01

    Thermoluminescence properties of the Vietnam's natural quartz showed a number of peaks in the glow curve at 100 o C and 325 o C. the TL emission spectrum mainly consisted of three broad emission bands located at around 380 nm (3.26 eV), 470 nm (2.64 eV) and 610 nm (2.03 eV). These peaks were attributed to the [H 3 O 4 ] 0 hole centres, [AlO 4 ] 0 centres and E ' centres (oxygen vacancy), respectively. The main effect of blue light (450 nm) exposure was the appearance of the distinctive 110 o C TL peak and a reduction of the 325 o C TL peak. The observed relationship between TL intensity and illumination wavelength was consistent with those reported in the work of Botter-Jensen et al. (1994b) who suggested a linear relationship between logarithm of intensity and the photon energy. (author)

  19. A computational fluid dynamics model for designing heat exchangers based on natural convection

    NARCIS (Netherlands)

    Dirkse, M.H.; Loon, van W.K.P.; Walle, van der T.; Speetjens, S.L.; Bot, G.P.A.

    2006-01-01

    A computational fluid dynamics model was created for the design of a natural convection shell-and-tube heat exchanger with baffles. The flow regime proved to be turbulent and this was modelled using the k¿¿ turbulence model. The features of the complex geometry were simplified considerably resulting

  20. Stability analysis of natural convection in superposed fluid and porous layers

    International Nuclear Information System (INIS)

    Hirata, S.C.; Goyeau, B.; Gobin, D.; Cotta, R.M.

    2005-01-01

    A linear stability analysis of the onset of thermal natural convection in superposed fluid and porous layers is called out. The resulting eigenvalue problem is solved using a integral transformation technique. The effect of the variation of the Darcy number on the stability of the system is analyzed. (authors)

  1. Stability analysis of natural convection in superposed fluid and porous layers

    Energy Technology Data Exchange (ETDEWEB)

    Hirata, S.C.; Goyeau, B.; Gobin, D. [Paris-11 Univ. - Paris-6, FAST - UMR CNRS 7608, 91 - Orsay (France); Cotta, R.M. [Rio de Janeiro Univ. (LTTC/PEM/EE/COPPE/UFRJ), RJ (Brazil)

    2005-07-01

    A linear stability analysis of the onset of thermal natural convection in superposed fluid and porous layers is called out. The resulting eigenvalue problem is solved using a integral transformation technique. The effect of the variation of the Darcy number on the stability of the system is analyzed. (authors)

  2. A direct method of natural frequency analysis on pipeline conveying fluid with both ends supported

    International Nuclear Information System (INIS)

    Huang Yimin; Ge Seng; Wu Wei; Jie He

    2012-01-01

    Highlights: ► A direct method which derived from Ferrari's method was used to solve quartic equations. ► Frequency equations of pipeline conveying fluid with both ends supported was studied. ► Each order natural frequencies can be obtained by using the direct method. ► The first five critical flow velocities were obtained by using numerical method. - Abstract: The natural frequency equations of fluid–structure interaction in pipeline conveying fluid with both ends supported is investigated by a direct method, and the direct method is derived from Ferrari's method which is used to solve quartic equations. The dynamic equation of pipeline conveying fluid with two variables is obtained by Hamilton's variation principle based on Euler–Bernoulli Beam theory. By using the separation of variables method and the derived method from Ferrari's method, the natural frequency equations and the critical flow velocity equations of pipeline conveying fluid with both ends supported are obtained in mathematical decoupling. Each order natural frequencies and critical flow velocities can be obtained by using numerical method. The first five order dimensionless critical flow velocities are obtained, and the results indicate that clamped–simply supported is less stable than clamped–clamped supported and more stable than simply–simply supported. All the conclusions can be applied to nuclear installations and other engineering fields of improving the vibration.

  3. Does amniotic fluid volume affect fetofetal transfusion in monochorionic twin pregnancies? Modelling two possible mechanisms

    Science.gov (United States)

    Umur, Asli; van Gemert, Martin J. C.; Ross, Michael G.

    2002-06-01

    Clinical evidence suggests that increased amniotic fluid volume due to polyhydramnios increases placental vascular resistance. We have sought to model the possible effects of an increased amniotic fluid volume on the net fetofetal transfusion in monochorionic twin pregnancies. We wanted to compare these effects with the results of previous simulations, which aimed to explain why the twin-twin transfusion syndrome (TTTS) placentas more often include bidirectional arteriovenous (AV) rather than AV plus arterioarterial (AA) anastomoses. We extended our mathematical model of TTTS by simulating two different mechanisms that increase the placental vascular resistance as a consequence of polyhydramnios. First, there is an increase in the placental capillary resistance and hence in deep AV and opposite AV (denoted as VA) resistances due to polyhydramnios. Second, there is an increase in the resistance of chorionic veins due to polyhydramnios, assuming that these veins act as Starling resistors. We then simulated the effects of polyhydramnios on different placental anastomotic patterns. The results were as follows. In the first mechanism (polyhydramnios affects AV-VA resistances), an increased amniotic fluid volume hardly affected bidirectional AV, but slightly decreased fetofetal transfusion in AV plus AA anastomoses. However, for these effects to change the natural development of the pregnancy, polyhydramnios needed to persist for approximately 4 weeks, and by comparing the effects of polyhydramnios with the effects of amnioreduction, amnioreduction was more beneficial for normalizing the donor amniotic fluid volume. Therefore, these beneficial effects due to polyhydramnios have no practical clinical significance. In the second mechanism (Starling resistor for chorionic veins), polyhydramnios slightly increased fetofetal transfusion and hence slightly increased TTTS severity in bidirectional AV and AV plus VV, but did not affect AV plus AA anastomoses. In conclusion, we

  4. Early Fluid Overload Prolongs Mechanical Ventilation in Children With Viral-Lower Respiratory Tract Disease.

    Science.gov (United States)

    Ingelse, Sarah A; Wiegers, Hanke M G; Calis, Job C; van Woensel, Job B; Bem, Reinout A

    2017-03-01

    Viral-lower respiratory tract disease is common in young children worldwide and is associated with high morbidity. Acute respiratory failure due to viral-lower respiratory tract disease necessitates PICU admission for mechanical ventilation. In critically ill patients in PICU settings, early fluid overload is common and associated with adverse outcomes such as prolonged mechanical ventilation and increased mortality. It is unclear, however, if this also applies to young children with viral-lower respiratory tract disease induced acute respiratory failure. In this study, we aimed to investigate the relation of early fluid overload with adverse outcomes in mechanically ventilated children with viral-lower respiratory tract disease in a retrospective dataset. Retrospective cohort study. Single, tertiary referral PICU. One hundred thirty-five children (mechanical ventilation admitted to the PICU of the Academic Medical Center, Amsterdam between 2008 and 2014. None. The cumulative fluid balance on day 3 of mechanical ventilation was compared against duration of mechanical ventilation (primary outcome) and daily mean oxygen saturation index (secondary outcome), using uni- and multivariable linear regression. In 132 children, the mean cumulative fluid balance on day 3 was + 97.9 (49.2) mL/kg. Higher cumulative fluid balance on day 3 was associated with a longer duration of mechanical ventilation in multivariable linear regression (β = 0.166; p = 0.048). No association was found between the fluid status and oxygen saturation index during the period of mechanical ventilation. Early fluid overload is an independent predictor of prolonged mechanical ventilation in young children with viral-lower respiratory tract disease. This study suggests that avoiding early fluid overload is a potential target to reduce duration of mechanical ventilation in these children. Prospective testing in a clinical trial is warranted to support this hypothesis.

  5. Fluid mechanics phenomena in microgravity; ASME Winter Annual Meeting, Anaheim, CA, Nov. 8-13, 1992

    Science.gov (United States)

    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.

  6. Mechanics of magnetic fluid column in strong magnetic fields

    International Nuclear Information System (INIS)

    Polunin, V.M.; Ryapolov, P.A.; Platonov, V.B.

    2017-01-01

    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.

  7. Formulation of the Chip Cleanability Mechanics from Fluid Transport

    OpenAIRE

    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...

  8. Fluid Mechanical Aspects of the Gas-Lift Technique

    Science.gov (United States)

    Guet, S.; Ooms, G.

    2006-01-01

    The gas-lift technique comprises the injection of gas bubbles in vertical oil wells to increase production. It is based on a reduction of the tubing gravitational pressure gradient. Several fluid-flow phenomena influencing such vertical gas-liquid flows are discussed. These effects include the radial distribution of void fraction and of gas and liquid velocity, flow regime changes, and system stability problems. Associated consequences for gas-lift performance and related optimization approaches are also discussed.

  9. Methodology for Developing Teaching Activities and Materials for Use in Fluid Mechanics Courses in Undergraduate Engineering Programs

    Science.gov (United States)

    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…

  10. Crystal Growth and Fluid Mechanics Problems in Directional Solidification

    Science.gov (United States)

    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.

  11. Rheological Properties with Temperature Response Characteristics and a Mechanism of Solid-Free Polymer Drilling Fluid at Low Temperatures

    Directory of Open Access Journals (Sweden)

    Sheng Wang

    2016-12-01

    Full Text Available The rheological properties of drilling fluid have important effects during drilling in natural gas hydrate at low temperatures. The present study was performed using theoretical analysis. Experiments and micro-analyses were carried out to determine the rheological properties with temperature response characteristics and the mechanism involved in solid-free polymer drilling fluid (SFPDF at low temperatures when drilling in permafrost with natural gas hydrates (NGH. The curves of shear stress with the shear rates of three kinds of polymer drilling fluids, Semen Lepidii natural vegetable gum, polyacrylamide, and xanthan gum, were drawn. Then, statistical and related analyses of test data were performed using Matlab ver. 8.0. Through regression analysis, the Herschel–Bulkley model was used to characterize the rheological characteristics of SFPDF. On this basis, the laws regarding the rheological properties of the three kinds of SFPDF under changing temperatures were analyzed and rheological properties with temperature response state equations were established. Next, the findings of previous studies on rheological properties with temperature response characteristics of the SFPDF were reviewed. Finally, the rheological properties with temperature response mechanisms were assessed using scanning electron microscopy and infrared spectrum analysis.

  12. A numerical investigation of the fluid mechanical sewing machine

    Science.gov (United States)

    Brun, P.-T.; Ribe, N. M.; Audoly, B.

    2012-04-01

    A thin thread of viscous fluid falling onto a moving belt generates a surprising variety of patterns depending on the belt speed, fall height, flow rate, and fluid properties. Here, we simulate this experiment numerically using the discrete viscous threads method that can predict the non-steady dynamics of thin viscous filaments, capturing the combined effects of inertia and of deformation by stretching, bending, and twisting. Our simulations successfully reproduce nine out of ten different patterns previously seen in the laboratory and agree closely with the experimental phase diagram of Morris et al. [Phys. Rev. E 77, 066218 (2008)], 10.1103/PhysRevE.77.066218. We propose a new classification of the patterns based on the Fourier spectra of the longitudinal and transverse motion of the point of contact of the thread with the belt. These frequencies appear to be locked in most cases to simple ratios of the frequency Ωc of steady coiling obtained in the limit of zero belt speed. In particular, the intriguing "alternating loops" pattern is produced by combining the first five multiples of Ωc/3.

  13. Experiments and Modeling of G-Jitter Fluid Mechanics

    Science.gov (United States)

    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.

  14. Mechanical properties of natural fibre reinforced polymer composites

    Indian Academy of Sciences (India)

    During the last few years, natural fibres have received much more attention than ever before from the research community all over the world. These natural fibres offer a number of advantages over traditional synthetic fibres. In the present communication, a study on the synthesis and mechanical properties of new series of ...

  15. Numerical Simulation of the ``Fluid Mechanical Sewing Machine''

    Science.gov (United States)

    Brun, Pierre-Thomas; Audoly, Basile; Ribe, Neil

    2011-11-01

    A thin thread of viscous fluid falling onto a moving conveyor belt generates a wealth of complex ``stitch'' patterns depending on the belt speed and the fall height. To understand the rich nonlinear dynamics of this system, we have developed a new numerical code for simulating unsteady viscous threads, based on a discrete description of the geometry and a variational formulation for the viscous stresses. The code successfully reproduces all major features of the experimental state diagram of Morris et al. (Phys. Rev. E 2008). Fourier analysis of the motion of the thread's contact point with the belt suggests a new classification of the observed patterns, and reveals that the system behaves as a nonlinear oscillator coupling the pendulum modes of the thread.

  16. The NASA Lewis Research Center Internal Fluid Mechanics Facility

    Science.gov (United States)

    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.

  17. Personal Computer (PC) based image processing applied to fluid mechanics

    Science.gov (United States)

    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.

  18. Schaum’s outline of fluid mechanics and hydraulics

    CERN Document Server

    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.

  19. Boundary Domain Integral Method for Double Diffusive Natural Convection in Porous Media Saturated with Compressible Fluid

    Science.gov (United States)

    Kramer, J.; Jecl, R.; Škerget, L.

    2008-09-01

    In the present work, a Boundary Domain Integral Method, which has been already established for the solution of viscous incompressible fluid flow through porous media, is extended to capture compressible fluid flow in porous media. The presented numerical scheme was used for solving the problem of double diffusive natural convection in a square porous cavity heated from a side, while the horizontal walls are maintained at different concentrations. The Brinkman extension of Darcy equation is used to model the flow through porous medium. The velocity-vorticity formulation is employed enabeling the computation scheme to be partitioned into kinematic and kinetic parts. The results of double diffusive natural convection in porous cavity are presented in terms of velocity, temperature and concentration redistributions.

  20. NMR detected metabolites in complex natural fluids. Quinic acid in apple juice

    Directory of Open Access Journals (Sweden)

    Ailiesei Gabriela Liliana

    2015-12-01

    Full Text Available Different types of 1D and 2D NMR experiments were used to completely characterize quinic acid and demonstrate its presence in complex mixtures. The identification of quinic acid in apple juice was done without any separation step. The NMR experiments presented in this study can be used to analyze other metabolites in different complex natural fluids, of vegetal or biological origin.

  1. On modifications of fluid inclusions in quartz : re-equilibration experiments and thermodynamical calculations on fluids in natural quartz

    NARCIS (Netherlands)

    Bakker, R.J.

    1992-01-01

    Fluids in rocks can be traced to great depths, and are found in crustal rocks as well as in mantle rocks. Information about the deep fluid which is obtained from fluid inclusions must be handled with care, for the way up after entrapment in a crystal is long and full of interferences at different

  2. Parametric numerical investigaion of natural convection in a heat-generating fluid with phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Aksenova, A.E.; Chudanov, V.V.; Strizhov, V.F.; Vabishchevich, P.N. [Institute of Nuclear Safety Russian Academy Science, Moscow (Russian Federation)

    1995-09-01

    Unsteady natural convection of a heat-generating fluid with phase transitions in the enclosures of a square section with isothermal rigid walls is investigated numerically for a wide range of dimensionless parameters. The quasisteady state solutions of conjugate heat and mass transfer problem are compared with available experimental results. Correlation relations for heat flux distributions at the domain boundaries depending on Rayleigh and Ostrogradskii numbers are obtained. It is shown that generally heat transfer is governed both by natural circulation and crust formation phenomena. Results of this paper may be used for analysis of experiments with prototypic core materials.

  3. Mechanics of fluid flow over compliant wrinkled polymeric surfaces

    Science.gov (United States)

    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.

  4. Combustion research in the Internal Fluid Mechanics Division

    Science.gov (United States)

    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.

  5. Use of Facebook in Teaching: A Case Study of a Fluid Mechanics Course

    Science.gov (United States)

    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…

  6. Mechanics of layered anisotropic poroelastic media with applications to effective stress for fluid permeability

    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

  7. Structural and mechanical characterisation of natural hydrofractures: example from the mines of Panasqueira, Portugal

    Science.gov (United States)

    Jaques, Luís; Pascal, Christophe; Yamaji, Atsushi; Vieira, Romeu

    2015-04-01

    Hydrofractures are mostly tensile fractures created by relatively high pore fluid pressures but under relatively low differential stresses and may originate barren joints and mineral veins. They can retain significant porosity at geological time-scales, providing preferential pathways for crustal fluids and often host mineral deposits. The mines of Panasqueira, central Portugal, represent the largest W-Sn deposit currently mined in western Europe and constitutes a fossil record of natural hydrofracturing at presumably high levels of pore pressure in the upper crust. The ore deposit comprises an extensive sub-horizontal quartz vein network hosted by a regional metasedimentary sequence of Palaeozoic age, which was previously folded, foliated and metamorphosed to greenschist facies during the Hercynian Orogeny. The vein system is connected to a greisenized cupola of the underlying granitic intrusion, evidenced by the pronounced contact metamorphism. The extensive network of underground excavations allows for exceptional exposure of the geological structures, and gives the possibility to use the mines of Panasqueira as a natural laboratory to understand the mechanisms pertaining to natural hydrofracture. Paleostress analyses using vein data, complemented by fluid inclusion and geothermometry studies were conducted. Preliminary results of vein attitudes indicate a cluster distribution of the poles with σ3 vertical, as expected. The other stress axes were oriented NW-SE (σ1) and NE-SW (σ2), respectively. Microthermometry of fluid inclusions in quartz related to the main opening stages of the vein structures indicates the occurrence of a low salinity fluid belonging to the system H2O-NaCl-CO2-(CH4)-(N2). Contemporaneous arsenopyrite indicates compositional average results of 33,5-34,0 atomic % As. The further achievement of new data will permit the calculation of the "full" stress state associated to the formation of the quartz veins.

  8. The fluid mechanics of scleral buckling surgery for the repair of retinal detachment.

    Science.gov (United States)

    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.

  9. Current research activities: Applied and numerical mathematics, fluid mechanics, experiments in transition and turbulence and aerodynamics, and computer science

    Science.gov (United States)

    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.

  10. Bio-mimetic mechanisms of natural hierarchical materials: a review.

    Science.gov (United States)

    Chen, Qiang; Pugno, Nicola M

    2013-03-01

    Natural selection and evolution develop a huge amount of biological materials in different environments (e.g. lotus in water and opuntia in desert). These biological materials possess many inspiring properties, which hint scientists and engineers to find some useful clues to create new materials or update the existing ones. In this review, we highlight some well-studied (e.g. nacre shell) and newly-studied (e.g. turtle shell) natural materials, and summarize their hierarchical structures and mechanisms behind their mechanical properties, from animals to plants. These fascinating mechanisms suggest to researchers to investigate natural materials deeply and broadly, and to design or fabricate new bio-inspired materials to serve our life. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. A parallel computing tool for large-scale simulation of massive fluid injection in thermo-poro-mechanical systems

    Science.gov (United States)

    Karrech, Ali; Schrank, Christoph; Regenauer-Lieb, Klaus

    2015-10-01

    Massive fluid injections into the earth's upper crust are commonly used to stimulate permeability in geothermal reservoirs, enhance recovery in oil reservoirs, store carbon dioxide and so forth. Currently used models for reservoir simulation are limited to small perturbations and/or hydraulic aspects that are insufficient to describe the complex thermal-hydraulic-mechanical behaviour of natural geomaterials. Comprehensive approaches, which take into account the non-linear mechanical deformations of rock masses, fluid flow in percolating pore spaces, and changes of temperature due to heat transfer, are necessary to predict the behaviour of deep geo-materials subjected to high pressure and temperature changes. In this paper, we introduce a thermodynamically consistent poromechanics formulation which includes coupled thermal, hydraulic and mechanical processes. Moreover, we propose a numerical integration strategy based on massively parallel computing. The proposed formulations and numerical integration are validated using analytical solutions of simple multi-physics problems. As a representative application, we investigate the massive injection of fluids within deep formation to mimic the conditions of reservoir stimulation. The model showed, for instance, the effects of initial pre-existing stress fields on the orientations of stimulation-induced failures.

  12. Fluid mechanics of directional solidification at reduced gravity

    Science.gov (United States)

    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.

  13. Fluid Mechanics of Heart Valves and Their Replacements

    Science.gov (United States)

    Sotiropoulos, Fotis; Le, Trung Bao; Gilmanov, Anvar

    2016-01-01

    As the pulsatile cardiac blood flow drives the heart valve leaflets to open and close, the flow in the vicinity of the valve resembles a pulsed jet through a nonaxisymmetric orifice with a dynamically changing area. As a result, three-dimensional vortex rings with intricate topology emerge that interact with the complex cardiac anatomy and give rise to shear layers, regions of recirculation, and flow instabilities that could ultimately lead to transition to turbulence. Such complex flow patterns, which are inherently valve- and patient-specific, lead to mechanical forces at scales that can cause blood cell damage and thrombosis, increasing the likelihood of stroke, and can trigger the pathogenesis of various life-threatening valvular heart diseases. We summarize the current understanding of flow phenomena induced by heart valves, discuss their linkage with disease pathways, and emphasize the research advances required to translate in-depth understanding of valvular hemodynamics into effective patient therapies.

  14. Fluid Mechanics of Capillary-Elastic Instabilities in Microgravity Environment

    Science.gov (United States)

    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.

  15. Research in progress in applied mathematics, numerical analysis, fluid mechanics, and computer science

    Science.gov (United States)

    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.

  16. Shape matters: Near-field fluid mechanics dominate the collective motions of ellipsoidal squirmers.

    Science.gov (United States)

    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.

  17. Mechanics of Undulatory Swimming in a Frictional Fluid

    Science.gov (United States)

    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. PMID:23300407

  18. Cure Characteristics and Physico-Mechanical Properties of Natural ...

    African Journals Online (AJOL)

    MICHAEL

    Department of Chemistry, Delta State University, Abraka, Nigeria. ABSTRACT: The cure characteristics and the physico-mechanical properties of natural rubber, standard. Nigerian rubber, SNR10 filled with cherry seed shell (CSS) and standard carbon black CB (N330) were determined. The results showed that the scorch, ...

  19. Biomarkers and mechanisms of natural disease resistance in dairy cows

    NARCIS (Netherlands)

    Altena, van S.E.C.

    2016-01-01

    The aim of this thesis was to define and test biomarkers for disease resistance in dairy cows and to determine the underlying mechanism in natural disease resistance. The health status of the cows is an important issue in dairy farming. Due to the mandatory reduction in the use of antibiotics,

  20. 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)

  1. Natural computing for mechanical systems research: A tutorial overview

    Science.gov (United States)

    Worden, Keith; Staszewski, Wieslaw J.; Hensman, James J.

    2011-01-01

    A great many computational algorithms developed over the past half-century have been motivated or suggested by biological systems or processes, the most well-known being the artificial neural networks. These algorithms are commonly grouped together under the terms soft or natural computing. A property shared by most natural computing algorithms is that they allow exploration of, or learning from, data. This property has proved extremely valuable in the solution of many diverse problems in science and engineering. The current paper is intended as a tutorial overview of the basic theory of some of the most common methods of natural computing as they are applied in the context of mechanical systems research. The application of some of the main algorithms is illustrated using case studies. The paper also attempts to give some indication as to which of the algorithms emerging now from the machine learning community are likely to be important for mechanical systems research in the future.

  2. Mechanics and natural philosophy before the scientific revolution

    CERN Document Server

    Gavroglu, Kostas; Roux, Sophie

    2008-01-01

    Modern mechanics was forged in the seventeenth century from materials inherited from Antiquity and transformed in the period from the Middle Ages through to the sixteenth century. These materials were transmitted through a number of textual traditions and within several disciplines and practices, including ancient and medieval natural philosophy, statics, the theory and design of machines, and mathematics. This volume deals with a variety of moments in the history of mechanics when conflicts arose within one textual tradition, between different traditions, or between textual traditions and the wider world of practice. Its purpose is to show how the accommodations sometimes made in the course of these conflicts ultimately contributed to the emergence of modern mechanics. The first part of the volume is concerned with ancient mechanics and its transformations in the Middle Ages; the second part with the reappropriation of ancient mechanics and especially with the reception of the Pseudo-Aristotelian Mechanica i...

  3. 10th International Symposium on Applications of Laser Techniques to Fluid Mechanics

    CERN Document Server

    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...

  4. 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.

  5. Early Fluid Overload Prolongs Mechanical Ventilation in Children With Viral-Lower Respiratory Tract Disease

    NARCIS (Netherlands)

    Ingelse, Sarah A.; Wiegers, Hanke M. G.; Calis, Job C.; van Woensel, Job B.; Bem, Reinout A.

    2017-01-01

    Viral-lower respiratory tract disease is common in young children worldwide and is associated with high morbidity. Acute respiratory failure due to viral-lower respiratory tract disease necessitates PICU admission for mechanical ventilation. In critically ill patients in PICU settings, early fluid

  6. Fluid Mechanics and Complex Variable Theory: Getting Past the 19th Century

    Science.gov (United States)

    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…

  7. Natural Rubber Nanocomposite with Human-Tissue-Like Mechanical Characteristic

    Science.gov (United States)

    Murniati, Riri; Novita, Nanda; Sutisna; Wibowo, Edy; Iskandar, Ferry; Abdullah, Mikrajuddin

    2017-07-01

    The blends of synthetic rubber and natural rubber with nanosilica were prepared using a blending technique in presence of different filler volume fraction. The effect of filler on morphological and mechanical characteristics was studied. Utilization of human cadaver in means of medical study has been commonly used primarily as tools of medical teaching and training such as surgery. Nonetheless, human cadaver brought inevitable problems. So it is necessary to find a substitute material that can be used to replace cadavers. In orthopaedics, the materials that resemble in mechanical properties to biological tissues are elastomers such as natural rubber (latex) and synthetic rubber (polyurethanes, silicones). This substitution material needs to consider the potential of Indonesia to help the development of the nation. Indonesia is the second largest country producer of natural rubber in the world. This paper aims to contribute to adjusting the mechanical properties of tissue-mimicking materials (TMMs) to the recommended range of biological tissue value and thus allow the development of phantoms with greater stability and similarity to human tissues. Repeatability for the phantom fabrication process was also explored. Characteristics were then compared to the control and mechanical characteristics of different human body part tissue. Nanosilica is the best filler to produce the best nanocomposite similarities with human tissue. We produced composites that approaching the properties of human internal tissues.

  8. Magnetic isolation of particles suspended in synovial fluid for diagnostics of natural joint chondropathies.

    Science.gov (United States)

    Mendel, Kalia; Eliaz, Noam; Benhar, Itai; Hendel, David; Halperin, Nahum

    2010-11-01

    Millions of people are stricken with the degenerative joint disease known as osteoarthritis. Osteoarthritis is associated with biochemical and mechanical processes, and is characterized by loss of articular cartilage and hypertrophy of bone. As cartilage and bone particles are released into the synovial fluid, a variety of biomarkers have been suggested for the analysis of this fluid. Here we have developed a method for isolating bone and cartilage wear particles suspended in the synovial fluid of the hip, knee and ankle joints of humans, based on specific magnetization of collagens I and II. Bio-ferrography is used to capture the particles on glass slides, allowing microscopic, chemical and statistical analyses. The relations between the level of the disease and the number, dimensions, shape and chemical composition of the particles were established. The method, which was found to be sensitive and reliable, can easily be extended to other applications, such as diagnosis of cancer and infectious diseases, determination of the efficacy of drugs or optimization of implants. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  9. Variational principles of fluid mechanics and electromagnetism: imposition and neglect of the Lin constraint

    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

  10. Mechanical membrane for the separation of a paramagnetic constituent from a fluid

    Science.gov (United States)

    Maurice, David

    2017-05-02

    The disclosure provides an apparatus and method for the separation of a paramagnetic component from a mixture using a mechanical membrane apparatus. The mechanical membrane comprises a supporting material having a plurality of pores where each pore is surrounded by a plurality of magnetic regions. The magnetic regions augment a magnetic field on one side of the supporting material while mitigating the field to near zero on the opposite side. In operation, a flow of fluid such as air comprising a paramagnetic component such as O.sub.2 is directed toward the mechanical membrane, and the paramagnetic component is typically attracted toward a magnetic field surrounding a pore while dimagnetic components such as N.sub.2 are generally repelled. As some portion of the fluid passes through the plurality of magnetic apertures to the opposite side of the mechanical membrane, the mechanical membrane generates a fluid enriched in the paramagnetic component. Alternately, the magnetic field may act to repel the paramagnetic component while diamagnetic components such as N.sub.2 are generally unaffected and pass to the opposite side of the mechanical membrane.

  11. New structural and mechanical insights on natural hydrofractures, Panasqueira Mines, Portugal.

    Science.gov (United States)

    Jaques Ribeiro, L. M.; Pascal, C.; Yamaji, A.; Pinto, F.

    2015-12-01

    Hydrofractures are mostly tensile fractures like barren joints or mineral veins created by relatively high pore fluid pressures but under relatively low differential stresses. They can retain significant porosity at geological time-scales, providing preferential pathways for crustal fluids and often host mineral deposits. The mines of Panasqueira, central Portugal, represent the largest W-Sn deposit currently mined in western Europe and constitutes a fossil record of natural hydrofracturing at presumably high levels of pore pressure in the upper crust. The ore deposit comprises an extensive sub-horizontal vein network hosted by a regional metasedimentary sequence of Palaeozoic age, which was folded, foliated and metamorphosed to greenschist facies during the Hercynian Orogeny. The vein system is connected to a greisenized cupola of the underlying granitic intrusion, evidenced by the pronounced contact metamorphism. The extensive network of underground excavations allows for exceptional exposure of the geological structures, and gives the possibility to use the mines of Panasqueira as a natural laboratory in order to understand the mechanisms driving its formation and propagation. Paleostress analyses using vein data, complemented with fluid inclusion and geothermometry/geobarometry studies were conducted. Preliminary results of vein attitudes indicate a cluster distribution of the poles with σ3 vertical. The other stress axes were oriented NW-SE (σ1) and NE-SW (σ2), respectively. Microthermometry of fluid inclusions in quartz related to the main opening stages of the veins evidence low salinity fluids belonging to the system H2O-NaCl-CO2-(CH4)-(N2). The respective homogenization temperatures fall in the range of 250-320˚C. Coeval arsenopyrite contains 33,5-34,0 atomic % As, corresponding to mineralisation temperatures of ~450 ˚C. Fluid isochores together with the formation temperatures derived from arsenopyrite compositions suggest fluid paleopressures of ~300

  12. Production of Natural Gas and Fluid Flow in Tight Sand Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Maria Cecilia Bravo

    2006-06-30

    This document reports progress of this research effort in identifying relationships and defining dependencies between macroscopic reservoir parameters strongly affected by microscopic flow dynamics and production well performance in tight gas sand reservoirs. These dependencies are investigated by identifying the main transport mechanisms at the pore scale that should affect fluids flow at the reservoir scale. A critical review of commercial reservoir simulators, used to predict tight sand gas reservoir, revealed that many are poor when used to model fluid flow through tight reservoirs. Conventional simulators ignore altogether or model incorrectly certain phenomena such as, Knudsen diffusion, electro-kinetic effects, ordinary diffusion mechanisms and water vaporization. We studied the effect of Knudsen's number in Klinkenberg's equation and evaluated the effect of different flow regimes on Klinkenberg's parameter b. We developed a model capable of explaining the pressure dependence of this parameter that has been experimentally observed, but not explained in the conventional formalisms. We demonstrated the relevance of this, so far ignored effect, in tight sands reservoir modeling. A 2-D numerical simulator based on equations that capture the above mentioned phenomena was developed. Dynamic implications of new equations are comprehensively discussed in our work and their relative contribution to the flow rate is evaluated. We performed several simulation sensitivity studies that evidenced that, in general terms, our formalism should be implemented in order to get more reliable tight sands gas reservoirs' predictions.

  13. Bilateral Patching in Retinal Detachment: Fluid Mechanics and Retinal “Settling”

    Science.gov (United States)

    2011-01-01

    Purpose. 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. Methods. 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. Results. 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. Conclusions. 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. PMID:21666245

  14. Mechanical property evaluation of natural fiber coir composite

    International Nuclear Information System (INIS)

    Harish, S.; Michael, D. Peter; Bensely, A.; Lal, D. Mohan; Rajadurai, A.

    2009-01-01

    The fiber which serves as a reinforcement in reinforced plastics may be synthetic or natural. Past studies show that only artificial fibers such as glass, carbon etc., have been used in fiber-reinforced plastics. Although glass and other synthetic fiber-reinforced plastics possess high specific strength, their fields of application are very limited because of their inherent higher cost of production. In this connection, an investigation has been carried out to make use of coir, a natural fiber abundantly available in India. Natural fibers are not only strong and lightweight but also relatively very cheap. In the present work, coir composites are developed and their mechanical properties are evaluated. Scanning electron micrographs obtained from fractured surfaces were used for a qualitative evaluation of the interfacial properties of coir/epoxy and compared with glass fiber/epoxy. These results indicate that coir can be used as a potential reinforcing material for making low load bearing thermoplastic composites

  15. NATURAL REGENERATION MECHANISMS IN A SEASONAL DECIDUOUS FOREST FRAGMENT

    Directory of Open Access Journals (Sweden)

    Marta Silvana Volpato Sccoti

    2011-09-01

    Full Text Available Due to the loss of biodiversity and natural habitat because of the forests fragmentation, it is the needed to find alternatives that allow the recovery of these environments. Thus, this study aimed to obtain information about the potential of natural regeneration mechanisms (seed rain, soil seed bank, seedling bank and established natural regeneration in a seasonal deciduous forest fragment in Santa Maria, RS state, in order to conserve and to recover these ecosystems. The study was conducted in a systematic way, having as a point of departure the demarcation of 14 sampling plots of 2000 sq m. From those plots, 70 subplots were randomly selected to evaluate the natural regeneration mechanisms. The seed rain was evaluated during one year based on the material that was monthly collected and analyzed from the collectors. To the study of the soil seed bank, soil samplings of 25cmx25cmx5cm were taken and the collected material was monitored during 7 months, observing the seed germination. The natural regeneration was evaluated in two classes: seedling bank and established The seed rain presented medium density of 1350 seeds m-², in which 73 species, predominantly arboreal, were observed. In the soil seed bank, 108 species were observed, in which 74 % were herbaceous. In the seedling bank, 48 species were found and they were heliophilous and sciaphilous species, while in the established natural regeneration, 37 species were found, prevailing sciaphilous. This study concluded that the species with the greatest potential to perpetuate in the studied area were Gymnanthes concolor, Soroceae bonplandii, Eugenia rostrifolia, Trichilia claussenii, Trichilia elegans and Dasyphylum spinescens, and they are highly indicated to the enrichment of the area. The species Myrocarpus frondosus, Cupania vernalis, Nectandra megapotamica and Syagrus rommanzoffiana showed certain restriction, depending on the silvicultural treatments in the forest to assure their

  16. Ultrasound Microbubble Treatment Enhances Clathrin-Mediated Endocytosis and Fluid-Phase Uptake through Distinct Mechanisms.

    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

  17. The Fast and Non-capillary Fluid Filling Mechanism in the Hummingbird's Tongue

    Science.gov (United States)

    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.

  18. Structural characterization and mechanical properties of polypropylene reinforced natural fibers

    Science.gov (United States)

    Karim, M. A. A.; Zaman, I.; Rozlan, S. A. M.; Berhanuddin, N. I. C.; Manshoor, B.; Mustapha, M. S.; Khalid, A.; Chan, S. W.

    2017-10-01

    Recently the development of natural fiber composite instead of synthetics fiber has lead to eco-friendly product manufacturing to meet various applications in the field of automotive, construction and manufacturing. The use of natural fibers offer an alternative to the reinforcing fibers because of their good mechanical properties, low density, renewability, and biodegradability. In this present research, the effects of maleic anhydride polypropylene (MAPP) on the mechanical properties and material characterization behaviour of kenaf fiber and coir fiber reinforced polypropylene were investigated. Different fractions of composites with 10wt%, 20wt% and 30wt% fiber content were prepared by using brabender mixer at 190°C. The 3wt% MAPP was added during the mixing. The composites were subsequently molded with injection molding to prepare the test specimens. The mechanical properties of the samples were investigated according to ISO 527 to determine the tensile strength and modulus. These results were also confirmed by the SEM machine observations of fracture surface of composites and FTIR analysis of the chemical structure. As the results, the presence of MAPP helps increasing the mechanical properties of both fibers and 30wt% kenaf fiber with 3wt% MAPP gives the best result compare to others.

  19. Fluid and electrolyte homeostasis during spaceflight: Elucidation of mechanisms in a primate

    Science.gov (United States)

    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).

  20. Coupling analysis of frictional heat of fluid film and thermal deformation of mechanical seal end faces

    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)

  1. Fluid Mechanical Interactions In The Active Creeping Chihshang Fault Zone In Eastern Taiwan

    Science.gov (United States)

    Dong, J.; Mu, C.; Lee, J.; Guglielmi, Y.; Angelier, J.; Lin, C.

    2007-12-01

    The Chihshang thrust fault is one of the most active segments of the Longitudinal Valley fault (LVF) situated along the plate suture between the Philippine Sea plate and the Eurasian plate in eastern Taiwan. During the past two decades, different surface monitoring efforts have been undertaken across the Chihshang fault at different spatial and temporal scales. Some interesting phenomena were observed, revealing a close interactions between fluids, creep in the shallow fault segment and seismogenic zone at depth : (1) seasonal variation clearly influence Chihshang fault creep rate; (2) coseismic slip propagation was attenuated at shallow depth during the 2003 Mw=6.5 Chengkung earthquake and followed by a dramatic postseismic creep; (3) a decreasing creep rate was observed before the 2003 earthquake and the total crust shortening after Chengkung earthquake compensated the deficit of surface creep about 3-4 years before the earthquake. To better understand the role of fluids in the creeping of Chihchang fault, subsurface geophysical investigation, in-situ hydro-mechanical tests and long-term pressure, deformation and seismic monitoring were initiated within the frame of an integrated project called Chihshang Fault Monitoring Observatory.. Eight boreholes were drilled at a depth of 30-100 m through the Chihshang fault fault zone at the Chinyuan site. Pore pressure variations in hydraulic observation wells induced by artificial pumping and injections and natural seasonal variation were monitored, together with surface electrical 4D tomography. Creeping was monitored with both creepmeters and tiltmeters set in surface and TDRs set in boreholes. First results show a complex fault zone affecting several hydrogeological sedimentary units with a high variability of hydraulic properties, 6 10-4 to 2 10-8 of storativity values and 10-4 to 4 10-6 m2/s transmissivity values respectively. Groundwater flow is parallel to the deformation zone direction that is characterized by

  2. Tensor Arithmetic, Geometric and Mathematic Principles of Fluid Mechanics in Implementation of Direct Computational Experiments

    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.

  3. Enhancing the Connection to Undergraduate Engineering Students: A Hands-On and Team-Based Approach to Fluid Mechanics

    Science.gov (United States)

    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…

  4. Fluid mechanics of human fetal right ventricles from image-based computational fluid dynamics using 4D clinical ultrasound scans.

    Science.gov (United States)

    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.

  5. Polymer films removed from solid surfaces by nanostructured fluids: microscopic mechanism and implications for the conservation of cultural heritage.

    Science.gov (United States)

    Raudino, Martina; Selvolini, Giulia; Montis, Costanza; Baglioni, Michele; Bonini, Massimo; Berti, Debora; Baglioni, Piero

    2015-03-25

    Complex fluids based on amphiphilic formulations are emerging, particularly in the field of conservation of works of art, as effective and safe liquid media for the removal of hydrophobic polymeric coatings. The comprehension of the cleaning mechanism is key to designing tailored fluids for this purpose. However, the interaction between nanostructured fluids and hydrophobic polymer films is still poorly understood. In this study, we show how the combination of confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM) provides interesting and complementary insight into this process. We focused on the interaction between an ethyl methacrylate/methyl acrylate 70:30 copolymer film deposited onto a glass surface and a water/nonionic surfactant/2-butanone (MEK) ternary system, with MEK being a good solvent and water being a nonsolvent for the polymer. Our results indicate a synergy between the organic solvent and the surfactant assemblies: MEK rapidly swells the outer layers of the polymer film allowing for the subsequent diffusion of solvent molecules, while the amphiphile decreases the interfacial energy between the polymeric coating and the liquid phase, favoring dewetting and dispersion of swollen polymer droplets in the aqueous phase. The chemical nature of the surfactant and the microstructure of the assemblies determine both the kinetics and the overall efficiency of polymer removal, as assessed by comparing the behavior of similar formulations containing an anionic surfactant (sodium dodecyl sulfate, SDS).

  6. Thermal fluid-solid interaction model and experimental validation for hydrostatic mechanical face seals

    Science.gov (United States)

    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.

  7. Formation Damage due to Drilling and Fracturing Fluids and Its Solution for Tight Naturally Fractured Sandstone Reservoirs

    Directory of Open Access Journals (Sweden)

    Tianbo Liang

    2017-01-01

    Full Text Available Drilling and fracturing fluids can interact with reservoir rock and cause formation damage that impedes hydrocarbon production. Tight sandstone reservoir with well-developed natural fractures has a complex pore structure where pores and pore throats have a wide range of diameters; formation damage in such type of reservoir can be complicated and severe. Reservoir rock samples with a wide range of fracture widths are tested through a multistep coreflood platform, where formation damage caused by the drilling and/or fracturing fluid is quantitatively evaluated and systematically studied. To further mitigate this damage, an acidic treating fluid is screened and evaluated using the same coreflood platform. Experimental results indicate that the drilling fluid causes the major damage, and the chosen treating fluid can enhance rock permeability both effectively and efficiently at least at the room temperature with the overburden pressure.

  8. A review of Green's function methods in computational fluid mechanics: Background, recent developments and future directions

    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

  9. Spotlight on the use of new natural surfactants in colloidal gas aphron (CGA) fluids: A mechanistic study

    Science.gov (United States)

    Ali Ahmadi, Mohammad; Galedarzadeh, Morteza; Reza Shadizadeh, Seyed

    2017-12-01

    Colloidal gas aphron-based (CGA) drilling fluids are defined as gas bubbles with diameters in ranges of 10 to 100 microns which are created by intensive stirring of an aphronizer surfactant solution at high speed. Furthermore, CGA-based drilling fluid properties like stability and aphron size distribution extremely depend on the inherent characteristics of the aphronizer surfactant. The selection of an appropriate surface active agent plays a vital role in the generation of micro-bubbles with the favorable characteristics. The primary motivation behind this paper is to evaluate the potential of new natural surfactants as aphronizer in CGA-based drilling fluids. Here, two new natural based surfactants derived from roots of Glycyrrhiza glabra and leaves of Matricaria recutita plant are implemented for the preparation of aphron-based fluids. The physico-chemical properties of the aphronized fluids prepared from these surfactants are studied by different fundamental tests comprising rheological characterizations, bubble size measurements, and stability tests. The effect of polymer and surfactant concentration was also evaluated. According to the experimental outcomes of this research, the two introduced natural surfactants are appropriate for generating CGA-based drilling fluids while they have no environmental impacts and have very low cost in comparison to commercial and industrial surfactants.

  10. Study of natural circulation for the design of a research reactor using computational fluid dynamics and evolutionary computation techniques

    International Nuclear Information System (INIS)

    Oliveira, Andre Felipe da Silva de

    2012-01-01

    Safety is one of the most important and desirable characteristics in a nuclear plant Natural circulation cooling systems are noted for providing passive safety. These systems can be used as mechanism for removing the residual heat from the reactor, or even as the main cooling system for heated sections, such as the core. In this work, a computational fluid dynamics (CFD) code called CFX is used to simulate the process of natural circulation in a research reactor pool after its shutdown. The physical model studied is similar to the Open Pool Australian Light water reactor (OPAL), and contains the core, cooling pool, reflecting tank, circulation pipes and chimney. For best computing performance, the core region was modeled as a porous medium, where the parameters were obtained from a separately detailed CFD analysis. This work also aims to study the viability of the implementation of Differential Evolution algorithm for optimization the physical and operational parameters that, obeying the laws of similarity, lead to a test section on a reduced scale of the reactor pool.

  11. ION EXCHANGE MECHANISM OF Cr+3 ON NATURALLY OCCURRING CLINOPTILOLITE

    Directory of Open Access Journals (Sweden)

    M.A.S.D. de Barros

    1997-09-01

    Full Text Available Ion exchange isotherms are very important tools to achieve a better comprehension of cation removal by means of zeolite treatment. In this work, three isotherms were obtained (at 298K, at 313K and at 333K from natural pretreated Na+ clinoptilolite. The ion exchange was carried out with Cr+3 ions. The isotherms’ shape is similar to the classical type "b" isotherm, according to the arrangement proposed by Breck (1984. Mathematical fitting was applied to the experimental points (Table Curve software to obtain a representative curve thereof. From such fittings, points were simulated and then used to construct the Kielland plots, whose shape was associated with an ion exchange mechanism. Straight lines were obtained as an indication that, although the zeolite used is of natural occurrence and presents impurities such as mordenite and clays, only one site is involved in the ion exchange process

  12. A Numerical Hydro-Chemo-Mechanical Model for Fault Activation under Reactive Fluid Flow

    Science.gov (United States)

    Pouya, A.; Tounsi, H.; Rohmer, J.

    2015-12-01

    The migration of CO2-rich fluid in fractured rock masses can cause processes such as mineral dissolution and precipitation, chemically induced weakening, which can affect the long-term mechanical and transport properties of the rock mass as well as the stability of fault systems. Some numerical approaches are already available in the literature for modelling the dissolution/precipitation phenomena in fractures (e.g. Yasuhara & Elsworth 2007) as well as subcritical crack propagation (e.g. Park et al. 2007). Generally, the dissolution is supposed to increase the rock porosity and, in this way, decrease the rock strength. Some experimental data are available for the variation of rock strength and stiffness parameters with the porosity and so as a consequence of dissolution process (Bemer et al. 2004). Also the effect of chemical processes on the mechanical stability has been studied and modelled numerically in the framework of continuum materials and the context, in particular, of weathering in underground galleries (Ghabezloo & Pouya 2006). In the context of fault systems, a complete numerical modelling of the stability evolution with the flow of a reactive fluid has not yet been done. In this paper we present a simplified, but complete, set of equations for a whole system of coupled hydro-chemo-mechanical process of reactive fluid flow inside a fault. These equations have been implemented in Porofis, a FEM numerical code specially conceived for HCM processes in porous fractured media. We show how this numerical method allows to model the coupled HCM processes in the fault and the evolution of the mechanical stability in presence of in situ stresses and reactive fluid flow.

  13. 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.

  14. Production of mullite from natural raw materials using mechanical activation

    International Nuclear Information System (INIS)

    Feitosa, G.; Pinheiro, D.G.; Chinelatto, A.L.; Chinelatto, A.S.A

    2009-01-01

    Mullite, ceramic structure consisting by alumina and silica, is present in different ceramic industry, as refractory, white ceramic, titles and advanced ceramics. This is because this material presents high resistance mechanical and high resistance in high temperatures, beyond low expansion coefficients and thermal conductivity. On the other hand, the mullite production needs high temperatures. This work had as objective the production of mullite from natural raw materials, using mechanical activation. Bauxite and quartz had been mixed in the stoichiometric composition and the mixture was submitted to high energy milling for different times. Then non milled powders and milled powders had been sintered in different temperatures. The characterization was made by X Ray diffraction and scanning electronic microscopy. The results demonstrated that the high energy milling affects the mullite formation, decreasing the temperature in that it is formed. (author)

  15. Effective Hydro-Mechanical Properties of Fluid-Saturated Fracture Networks

    Science.gov (United States)

    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.

  16. Experimental study of chemical-mechanical coupling during percolation of reactive fluid through rocks under stress, in the context of the CO2 geological sequestration

    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)

  17. A Computational Fluid Dynamics Study of Turbulence, Radiation, and Combustion Models for Natural Gas Combustion Burner

    Directory of Open Access Journals (Sweden)

    Yik Siang Pang

    2018-01-01

    Full Text Available This paper presents a Computational Fluid Dynamics (CFD study of a natural gas combustion burner focusing on the effect of combustion, thermal radiation and turbulence models on the temperature and chemical species concentration fields. The combustion was modelled using the finite rate/eddy dissipation (FR/EDM and partially premixed flame models. Detailed chemistry kinetics CHEMKIN GRI-MECH 3.0 consisting of 325 reactions was employed to model the methane combustion. Discrete ordinates (DO and spherical harmonics (P1 model were employed to predict the thermal radiation. The gas absorption coefficient dependence on the wavelength is resolved by the weighted-sum-of-gray-gases model (WSGGM. Turbulence flow was simulated using Reynolds-averaged Navier-Stokes (RANS based models. The findings showed that a combination of partially premixed flame, P1 and standard k-ε (SKE gave the most accurate prediction with an average deviation of around 7.8% of combustion temperature and 15.5% for reactant composition (methane and oxygen. The results show the multi-step chemistry in the partially premixed model is more accurate than the two-step FR/EDM. Meanwhile, inclusion of thermal radiation has a minor effect on the heat transfer and species concentration. SKE turbulence model yielded better prediction compared to the realizable k-ε (RKE and renormalized k-ε (RNG. The CFD simulation presented in this work may serve as a useful tool to evaluate a performance of a natural gas combustor. Copyright © 2018 BCREC Group. All rights reserved Received: 26th July 2017; Revised: 9th October 2017; Accepted: 30th October 2017; Available online: 22nd January 2018; Published regularly: 2nd April 2018 How to Cite: Pang, Y.S., Law, W.P., Pung, K.Q., Gimbun, J. (2018. A Computational Fluid Dynamics Study of Turbulence, Radiation, and Combustion Models for Natural Gas Combustion Burner. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (1: 155-169 (doi:10.9767/bcrec

  18. Mechanisms of children's exposure to nature: Predicting adulthood environmental citizenship and commitment to nature-based activities

    Science.gov (United States)

    Stanley T. Asah; David N. Bengston; Lynne M. Westphal; Catherine H. Gowan

    2017-01-01

    Childhood-nature experiences have lifelong effects on environmental citizenship and commitment to nature-based activities. But, it is unclear whether, and to what extent, the different mechanisms through which children and youth experience nature are associated with these outcomes. To test these associations, an online questionnaire assessing mechanisms of childhood...

  19. Statistical mechanics of fluids adsorbed in planar wedges: finite contact angle.

    Science.gov (United States)

    Henderson, J R

    2004-06-01

    I consider the statistical mechanics of inhomogeneous fluids applied to fluids adsorbed in planar wedges. Exact results are described that belong to an infinite subset of models defined as the intersection of any two identical semi-infinite planar wall-fluid potentials. This geometry is interesting as a generic example of adsorption onto structured interfaces and of interfacial phase transitions controlled by the substrate geometry. Previously described virial theorems are extended to the case of a general wall-fluid model. This enables the consideration of wedge filling when Young's contact angle far from the wedge apex is finite. The virial theorems generate two important relations: the wedge sum rules. The first sum rule links the interfacial free energy far from the wedge apex to the structure induced at the apex. The second sum rule links the free energy of the apex region to the structure induced by the apex. When Young's contact angle at the wedge walls is finite these relations further yield an exact result for the macroscopic contact angle in terms of the nanoscopic structure at the three-phase contact line (the intersection of the liquid-vapor surface with a wedge wall): the contact angle sum rule. These exact results are of direct relevance to computer simulation studies of adsorbed films. In addition, they take on special significance in the vicinity of continuous interfacial phase transitions: an approach to complete filling and the filling transition at bulk liquid-vapor coexistence.

  20. The mechanism of fluid secretion in the rabbit pancreas studied by means of various inhibitors.

    Science.gov (United States)

    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.

  1. Res, veluti per machinas, conficiatur: natural history and the 'mechanical' reform of natural philosophy.

    Science.gov (United States)

    Stewart, Ian G

    2012-01-01

    This paper revisits Bacon's persistent 'mechanical' imagery by which he described the 'aid' through which the human mind would be rendered adequate to framing axioms about nature's processes and properties that underlie all natural phenomena. It argues that the role Bacon ascribed to his own insights into the properties and motions of matter is crucial for grasping such instrumental imagery, because his own writings--both methodological and natural historical--need to be read as themselves comprising, at least in incipient form, the very instruments of which they speak. From that reflexive standpoint, this paper in particular focuses on the 'aid' to the senses that his natural histories were to have offered under the interpretative guidance offered by the Novum organum and other works. The 'hypothetical' status to which Bacon is often thought to have accorded his own natural philosophical insights does not adequately take into account the transformative power Bacon thought these insights should have through his own writings. The fact that Bacon was keenly sensitive to the psychological effects of textual authority in his intellectual milieu prompts new reflection concerning how he intended his own texts to be read, and how we should read them.

  2. Natural agents: cellular and molecular mechanisms of photoprotection.

    Science.gov (United States)

    Afaq, Farrukh

    2011-04-15

    The skin is the largest organ of the body that produces a flexible and self-repairing barrier and protects the body from most common potentially harmful physical, environmental, and biological insults. Solar ultraviolet (UV) radiation is one of the major environmental insults to the skin and causes multi-tiered cellular and molecular events eventually leading to skin cancer. The past decade has seen a surge in the incidence of skin cancer due to changes in life style patterns that have led to a significant increase in the amount of UV radiation that people receive. Reducing excessive exposure to UV radiation is desirable; nevertheless this approach is not easy to implement. Therefore, there is an urgent need to develop novel strategies to reduce the adverse biological effects of UV radiation on the skin. A wide variety of natural agents have been reported to possess substantial skin photoprotective effects. Numerous preclinical and clinical studies have elucidated that natural agents act by several cellular and molecular mechanisms to delay or prevent skin cancer. In this review article, we have summarized and discussed some of the selected natural agents for skin photoprotection. Copyright © 2010 Elsevier Inc. All rights reserved.

  3. Mechanical stratigraphic controls on natural fracture spacing and penetration

    Science.gov (United States)

    McGinnis, Ronald N.; Ferrill, David A.; Morris, Alan P.; Smart, Kevin J.; Lehrmann, Daniel

    2017-02-01

    Fine-grained low permeability sedimentary rocks, such as shale and mudrock, have drawn attention as unconventional hydrocarbon reservoirs. Fracturing - both natural and induced - is extremely important for increasing permeability in otherwise low-permeability rock. We analyze natural extension fracture networks within a complete measured outcrop section of the Ernst Member of the Boquillas Formation in Big Bend National Park, west Texas. Results of bed-center, dip-parallel scanline surveys demonstrate nearly identical fracture strikes and slight variation in dip between mudrock, chalk, and limestone beds. Fracture spacing tends to increase proportional to bed thickness in limestone and chalk beds; however, dramatic differences in fracture spacing are observed in mudrock. A direct relationship is observed between fracture spacing/thickness ratio and rock competence. Vertical fracture penetrations measured from the middle of chalk and limestone beds generally extend to and often beyond bed boundaries into the vertically adjacent mudrock beds. In contrast, fractures in the mudrock beds rarely penetrate beyond the bed boundaries into the adjacent carbonate beds. Consequently, natural bed-perpendicular fracture connectivity through the mechanically layered sequence generally is poor. Fracture connectivity strongly influences permeability architecture, and fracture prediction should consider thin bed-scale control on fracture heights and the strong lithologic control on fracture spacing.

  4. The interior working mechanism and temperature characteristics of a fluid based micro-vibration isolator

    Science.gov (United States)

    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.

  5. The anti-apoptotic effect of fluid mechanics preconditioning by cells membrane and mitochondria in rats brain microvascular endothelial cells.

    Science.gov (United States)

    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.

  6. Biofluid mechanics of special organs and the issue of system control. Sixth International Bio-Fluid Mechanics Symposium and Workshop, March 28-30, 2008 Pasadena, California.

    Science.gov (United States)

    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.

  7. Multidimensional proteomics analysis of amniotic fluid to provide insight into the mechanisms of idiopathic preterm birth.

    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

  8. Extrema principles of entrophy production and energy dissipation in fluid mechanics

    Science.gov (United States)

    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.

  9. Effect of fluid balance on alveolar-arterial oxygen gradient in mechanically ventilated patients.

    Science.gov (United States)

    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.

  10. Numerical analysis of the fluid dynamics in a natural circulation loop

    International Nuclear Information System (INIS)

    Angelo, Gabriel

    2013-01-01

    Natural circulation loops apply to many engineering applications such as: water heating solar energy system (thermo-siphons), thermal management of electrical components (voltage converter), geothermal energy, nuclear reactors, etc. In pressurized water nuclear reactors, known as PWR's, the natural circulation loops are employed to ensure passive safety. In critical situations, the heat transfer will occur only by natural convection, without any external control or mechanical devices. This feature is desired and has been considered in modern nuclear reactor projects. This work consists of a numerical study of the natural circulation loop, located at the Instituto de Pesquisas Energeticas e Nucleares / Comissao Nacional de Energia Nuclear in Sao Paulo, Brazil, in order to establish the flow pattern in single phase conditions. The comparison of numerical results to experiments in transient condition revealed significant deviations for the Zero Equation turbulence model. Intermediate deviations for the Eddy Viscosity Turbulence Equation (EVTE), k - ω, SST e SSG models. And the best results are obtained by the k - ε e DES models (with better results for the k - ε model). (author)

  11. Coupled hydro-mechanical simulations of discrete fluid-driven fracture propagation through fractured rock masses using a lattice modeling approach

    Science.gov (United States)

    Kim, K.; Rutqvist, J.; Birkholzer, J. T.

    2016-12-01

    Fluid-driven fractures are critically important in a number of geoengineering application, such as to increase the permeability of an oil/gas reservoir and stimulate the productivity. On the contrary, near the underground storage sites for radioactive wastes or carbon dioxide, the propagation of fractures induced by pressurized gas should be avoided to detain the pollutants. Numerous numerical models have been developed to reproduce the physical phenomena of the fluid-driven fractures and have better understanding of the fracturing mechanism. However, it is still challenging to explicitly model the fluid-driven fracture propagation because it involves tightly coupled hydro-mechanical behavior with a singularity at the crack tip and complex interactions with pre-existing discontinuities in heterogeneous rock masses. This study investigates hydraulic fracture propagation and formation of discrete fracture networks using a coupled hydro-mechanical simulation code, TOUGH-RBSN. The modeling tool combines a multiphase fluid flow and heat transport simulator, TOUGH2, with a geomechanical and fracture-damage model, called the rigid-body-spring network (RBSN). Fractures are modeled as discrete features, and hydrological properties (e.g., permeability, porosity) of fracture elements are evaluated by fracture opening and aperture changes calculated at time steps of the simulations. Modeling capabilities for hydraulic fracturing processes are presented through simulations of a virtual fractured reservoir consisting of multiple pre-existing natural fractures. Case studies are conducted by changing the reservoir configurations, such as confining stress condition (e.g., degree of stress anisotropy), the matrix permeability, and the viscosity of injected fluid. In the preliminary results, the stress field and the fluid pressure distribution are provided to demonstrate modeling of complex hydro-mechanical interactions between propagating fractures and pre-existing fractures. The

  12. Transient computational fluid dynamics analysis of emergency core cooling injection at natural circulation conditions

    International Nuclear Information System (INIS)

    Scheuerer, Martina; Weis, Johannes

    2012-01-01

    Highlights: ► Pressurized thermal shocks are important phenomena for plant life extension and aging. ► The thermal-hydraulics of PTS have been studied experimentally and numerically. ► In the Large Scale Test Facility a loss of coolant accident was investigated. ► CFD software is validated to simulate the buoyancy driven flow after ECC injection. - Abstract: Within the framework of the European Nuclear Reactor Integrated Simulation Project (NURISP), computational fluid dynamics (CFD) software is validated for the simulation of the thermo-hydraulics of pressurized thermal shocks. A proposed validation experiment is the test series performed within the OECD ROSA V project in the Large Scale Test Facility (LSTF). The LSTF is a 1:48 volume-scaled model of a four-loop Westinghouse pressurized water reactor (PWR). ROSA V Test 1-1 investigates temperature stratification under natural circulation conditions. This paper describes calculations which were performed with the ANSYS CFD software for emergency core cooling injection into one loop at single-phase flow conditions. Following the OECD/NEA CFD Best Practice Guidelines (Mahaffy, 2007) the influence of grid resolution, discretisation schemes, and turbulence models (shear stress transport and Reynolds stress model) on the mixing in the cold leg were investigated. A half-model was used for these simulations. The transient calculations were started from a steady-state solution at natural circulation conditions. The final calculations were obtained in a complete model of the downcomer. The results are in good agreement with data.

  13. On the mechanical interaction between a fluid-filled fracture and the earth's surface

    Science.gov (United States)

    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

  14. Echinococcus multilocularis vesicular fluid inhibits activation and proliferation of natural killer cells.

    Science.gov (United States)

    Bellanger, Anne-Pauline; Mougey, Valentine; Pallandre, Jean-Rene; Gbaguidi-Haore, Houssein; Godet, Yann; Millon, Laurence

    2017-08-25

    Alveolar echinococcosis is a severe chronic helminthic disease that mimics slow-growing liver cancer. The immune evasion strategy of Echinococcus multilocularis Leuckart, 1863 remains poorly understood. The aim of this study was to investigate in vitro the impact of E. multilocularis vesicular fluid (Em-VF) on peripheral blood mononuclear cells (PBMC) and on natural killer (NK) cells. PBMC and NK cells were exposed to Em-VF (1 µg/ml) during six days. The effect of Em-VF was assessed on CD69, viability and proliferation, and on and transforming growth factor β (TGF-β), interferon γ (IFN-γ), interleukin 17 (IL-17) and interleukin 10, using flow cytometry and ELISA, respectively. Exposure to Em-VF had no bearing on PBMC's viability, proliferation and expression of CD69. In contrast, higher levels of IL-17 at day three and of TGF-β at day six were observed in PBMC supernatant after exposure to Em-VF (p test). Exposure to Em-VF induced a significant decrease of CD69 expression of NK cells at day three and a significant decrease of proliferation of NK cells at day six (p test). In contrast, NK cells viability and levels of cytokines did not vary significantly over Em-VF stimulation. Exposure to Em-VF had a significant bearing on activation and proliferation of NK cells. NK cells may play an important role in the immune response of the host against E. multilocularis.

  15. Thermo-fluid analysis of water cooled research reactors in natural convection

    International Nuclear Information System (INIS)

    Veloso, Maria Auxiliadora Fortini

    2004-01-01

    The STHIRP-1 computer program, which fundamentals are described in this work, uses the principles of the subchannels analysis and has the capacity to simulate, under steady state and transient conditions, the thermal and hydraulic phenomena which occur inside the core of a water-refrigerated research reactor under a natural convection regime. The models and empirical correlations necessary to describe the flow phenomena which can not be described by theoretical relations were selected according to the characteristics of the reactor operation. Although the primary objective is the calculation of research reactors, the formulation used to describe the fluid flow and the thermal conduction in the heater elements is sufficiently generalized to extend the use of the program for applications in power reactors and other thermal systems with the same features represented by the program formulations. To demonstrate the analytical capacity of STHIRP-l, there were made comparisons between the results calculated and measured in the research reactor TRIGA IPR-R1 of CDTN/CNEN. The comparisons indicate that the program reproduces the experimental data with good precision. Nevertheless, in the future there must be used more consistent experimental data to corroborate the validation of the program. (author)

  16. Understanding fluid transport through the multiscale pore network of a natural shale

    Directory of Open Access Journals (Sweden)

    Davy Catherine A.

    2017-01-01

    Full Text Available The pore structure of a natural shale is obtained by three imaging means. Micro-tomography results are extended to provide the spatial arrangement of the minerals and pores present at a voxel size of 700 nm (the macroscopic scale. FIB/SEM provides a 3D representation of the porous clay matrix on the so-called mesoscopic scale (10-20 nm; a connected pore network, devoid of cracks, is obtained for two samples out of five, while the pore network is connected through cracks for two other samples out of five. Transmission Electron Microscopy (TEM is used to visualize the pore space with a typical pixel size of less than 1 nm and a porosity ranging from 0.12 to 0.25. On this scale, in the absence of 3D images, the pore structure is reconstructed by using a classical technique, which is based on truncated Gaussian fields. Permeability calculations are performed with the Lattice Boltzmann Method on the nanoscale, on the mesoscale, and on the combination of the two. Upscaling is finally done (by a finite volume approach on the bigger macroscopic scale. Calculations show that, in the absence of cracks, the contribution of the nanoscale pore structure on the overall permeability is similar to that of the mesoscale. Complementarily, the macroscopic permeability is measured on a centimetric sample with a neutral fluid (ethanol. The upscaled permeability on the macroscopic scale is in good agreement with the experimental results.

  17. Cerebrospinal Fluid Prion Disease Biomarkers in Pre-clinical and Clinical Naturally Occurring Scrapie.

    Science.gov (United States)

    Llorens, Franc; Barrio, Tomás; Correia, Ângela; Villar-Piqué, Anna; Thüne, Katrin; Lange, Peter; Badiola, Juan José; Schmitz, Matthias; Lachmann, Ingolf; Bolea, Rosa; Zerr, Inga

    2018-03-23

    The analysis of the cerebrospinal fluid (CSF) biomarkers in patients with suspected prion diseases became a useful tool in diagnostic routine. Prion diseases can only be identified at clinical stages when the disease already spread throughout the brain and massive neuronal damage occurs. Consequently, the accuracy of CSF tests detecting non-symptomatic patients is unknown. Here, we aimed to investigate the usefulness of CSF-based diagnostic tests in pre-clinical and clinical naturally occurring scrapie. While decreased total prion protein (PrP) levels and positive PrP seeding activity were already detectable at pre-symptomatic stages, the surrogate markers of neuronal damage total tau (tau) and 14-3-3 proteins were exclusively increased at clinical stages. The present findings confirm that alterations in PrP levels and conformation are primary events in the pathology of prion diseases preceding neuronal damage. Our work also supports the potential use of these tests in the screening of pre-symptomatic scrapie and human prion disease cases.

  18. Chemical nature of implant-derived titanium(IV) ions in synovial fluid

    International Nuclear Information System (INIS)

    Silwood, Christopher J.L.; Grootveld, Martin

    2005-01-01

    Previous investigations have indicated a deleterious leakage of Ti(III) and/or Ti(IV) species from Ti-Al-V alloy joint prostheses into adjacent tissue, synovium or synovial fluid (SF) in vivo. In view of the importance of the particular chemical nature of such complexes in determining their biological activity, we have employed high field proton ( 1 H) NMR spectroscopy to 'speciate' Ti(IV) in inflammatory SF. Treatment of osteoarthritic SF samples with increasing concentrations of Ti(IV) (0.10-1.03 mM [TiO(C 2 O 4 ) 2 ] 2- ) gave rise to a specific broadening of the citrate proton resonances, indicating that this bioavailable oxygen-donor ligand plays an important role in complexing implant-derived Ti(IV). 1 H NMR analysis of Ti(IV)-loaded SF samples subsequently treated with a large excess of ascorbate (0.05 M) showed that this added Ti(IV) chelator was only poorly effective in removing this metal ion from Ti(IV)-citrate/Ti(IV)-oxycitrate complexes. The results obtained here provide evidence for complexation of the low-molecular-mass (non-protein-bound) fraction of implant-derived Ti(IV) by citrate in vivo

  19. Activation mechanisms of natural killer cells during influenza virus infection.

    Directory of Open Access Journals (Sweden)

    Ilwoong Hwang

    Full Text Available During early viral infection, activation of natural killer (NK cells elicits the effector functions of target cell lysis and cytokine production. However, the cellular and molecular mechanisms leading to NK cell activation during viral infections are incompletely understood. In this study, using a model of acute viral infection, we investigated the mechanisms controlling cytotoxic activity and cytokine production in response to influenza (flu virus. Analysis of cytokine receptor deficient mice demonstrated that type I interferons (IFNs, but not IL-12 or IL-18, were critical for the NK cell expression of both IFN-γ and granzyme B in response to flu infection. Further, adoptive transfer experiments revealed that NK cell activation was mediated by type I IFNs acting directly on NK cells. Analysis of signal transduction molecules showed that during flu infection, STAT1 activation in NK cells was completely dependent on direct type I IFN signaling, whereas STAT4 activation was only partially dependent. In addition, granzyme B induction in NK cells was mediated by signaling primarily through STAT1, but not STAT4, while IFN-γ production was mediated by signaling through STAT4, but not STAT1. Therefore, our findings demonstrate the importance of direct action of type I IFNs on NK cells to mount effective NK cell responses in the context of flu infection and delineate NK cell signaling pathways responsible for controlling cytotoxic activity and cytokine production.

  20. Research on the porous flow of the mechanism of viscous-elastic fluids displacing residual oil droplets in micro pores

    Science.gov (United States)

    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.

  1. 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

  2. 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.

  3. Mass sensors with mechanical traps for weighing single cells in different fluids.

    Science.gov (United States)

    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.

  4. Elastic contact mechanics: percolation of the contact area and fluid squeeze-out.

    Science.gov (United States)

    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.

  5. A diffusion tensor imaging tractography algorithm based on Navier-Stokes fluid mechanics.

    Science.gov (United States)

    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.

  6. Ups and downs of using ``kitchen sink'' experiments in an introductory fluid mechanics class

    Science.gov (United States)

    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.

  7. On the intrinsic nature of jump coefficients at the interface between a porous medium and a free fluid region

    International Nuclear Information System (INIS)

    Jamet, D.; Chandesris, M.

    2009-01-01

    In this paper, we discuss the physical nature Of the jump parameters that generally appear in the expression for the jump conditions at a fluid/porous interface. These jump parameters are generally thought of as intrinsic interfacial properties, just like surface tension in the case of fluid/fluid interfaces. Based on a two-step up-scaling analysis, we show that jump parameters can be interpreted as surface-excess quantities. The value of a surface-excess quantity is shown to depend linearly on the position of the discontinuous interface and is therefore not an intrinsic property. We propose a theoretical approach that allows to introduce genuine intrinsic interfacial properties and to propose a best choice for the position of the discontinuous interface. We show that these properties are tightly related to the definition of the interfacial zone. This theoretical approach is successfully assessed on three important cases: a laminar flow parallel to a fluid/porous interface, a turbulent flow perpendicular to a porous/fluid interface and heat transfer perpendicular to a fluid/porous interface. It is believed that this approach is general enough to be applied to any interfacial transport phenomenon. (authors)

  8. Fluid mechanic phenomena relating to flow control in conduits and pumps

    Science.gov (United States)

    Bayazit, Yilmaz

    The attainment of controlled homogenized fluid flow is a major issue in the efficient utilization of internal flows for applications as diverse as heat exchange, electrostatic filtration, water purification, particle conveyance, swirl control, and waste disposal. Among the candidate methodologies for accomplishing the homogenization task, perforated plates provide exceptional versatility and adaptability. The principle that underlies perforated plate flow control is the tendency of a flowing fluid to seek the path of least resistance. This tendency is coupled with the capability of the fluid to "see" what lies ahead, enabling it to adjust its trajectory. That capability is due to streamwise diffusion, which transfers information both upstream and downstream. In contrast, advection is a one-way information transfer mechanism, the direction of transfer coinciding with the direction of fluid motion. The degree of homogenization afforded by perforated plates depends on several geometrical and operating parameters. The geometrical parameters include: (a) plate porosity, (b) plate thickness, (c) aperture diameter, (d) pattern of aperture deployment, and (e) distance between apertures. With respect to operating parameters, those investigated here encompass (f) fluid velocity, (g) flow regime, and (h) angle of attack. Nondimensionalization diminished the total number of parameters to five. Numerical simulation was employed to solve the three-dimensional flow covering a Reynolds number range from 0.01 to 25,000. Results extracted from the solutions included dimensionless pressure drop, downstream distance for disturbance decay, vector diagrams and streamlines, and flow regime boundaries. A paradox where the pressure drop for a thin plate exceeded that for a thick plate was rationalized. The pressure drop characteristics of a perforated plate are akin to those for a porous medium. The Darcy-Forchheimer pressure drop model was extended into the turbulent flow regime for the

  9. Arsenic in hydrothermal apatite: Oxidation state, mechanism of uptake, and comparison between experiments and nature

    Science.gov (United States)

    Liu, Weihua; Mei, Yuan; Etschmann, Barbara; Brugger, Joël; Pearce, Mark; Ryan, Chris G.; Borg, Stacey; Wykes, Jeremey; Kappen, Peter; Paterson, David; Boesenberg, Ulrike; Garrevoet, Jan; Moorhead, Gareth; Falkenberg, Gerald

    2017-01-01

    expected to be the dominant As form in hydrothermal fluids. These results show that incorporation of As in apatite is a complicated process, and sensitive to the local fluid composition during crystallization, and that some of the complexity in As zoning in partially reacted apatite may be due to local fluctuations of As(V)/As(III) ratios in the fluid and to kinetic effects during the mineral replacement reaction. Our study shows for the first time that As(III) can be incorporated into the apatite structure, although not as efficiently as As(V). Uptake of As(III) is probably highly dependent on the reaction mechanism. As(III)O33- moieties replace phosphate groups, but cause a high strain on the lattice; as a result, As(III) is easily exchanged (or oxidized) for As(V) during hydrothermal recrystallization, and the fully reacted grains only record the preferred oxidation state (i.e., As(V)) from mixed-oxidation state solutions. Overall this study shows that the observed oxidation state of As in apatite may not reflect the original As(III)/As(V) ratio of the parent fluid, due to the complex nature of As(III) uptake and possible in situ oxidation during recrystallization.

  10. A Mechanism for Cytoplasmic Streaming: Kinesin-Driven Alignment of Microtubules and Fast Fluid Flows.

    Science.gov (United States)

    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

  11. Numerical Modeling and Investigation of Fluid-Driven Fracture Propagation in Reservoirs Based on a Modified Fluid-Mechanically Coupled Model in Two-Dimensional Particle Flow Code

    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.

  12. ACTIVITY OF NATURAL KILLER CELLS IN BIOLOGICAL FLUIDS FROM PATIENTS WITH COLORECTAL AND OVARIAN CANCERS

    Directory of Open Access Journals (Sweden)

    N. V. Yunusova

    2017-01-01

    Full Text Available Objective. To compare the functional activity of natural killer cells in peripheral blood and ascites from patients with different stages of colorectal and ovarian cancers and benign ovarian tumors. Material and methods. The study included 10 patients with stage IIIC ovarian cancer (FIGO, 2009, 5 patients with benign ovarian tumors (BOTs, and 15 patients with colorectal cancer (T2–4N0–2M0 . The control group consisted of 5 healthy donors. To evaluate the number and functional activity of NK-cells in peripheral blood and ascites, the FACS Canto II Flow Cytometer was used. Results. In peripheral blood of patients with ovarian and colorectal cancers, the relative number of activated NK-cells capable of secreting granzyme B (GB (CD56 + CD107a + GB + PF- was significantly lower and the proportion of degranulated NK-cells (CD56 + CD107a + GB- PF- was higher than those of healthy donors. Low total NK-cell counts in peripheral blood were a distinctive feature of ovarian cancer patients (p<0.05. The proportion of activated peripheral blood NK-cells, containing granules of cytolytic enzymes GB and perforin (PF increased with tumor growth. However, lymph node metastasis in patients with colorectal cancer did not affect the level and activation of NK-cells. The comparative analysis of NK-populations in patients with benign and malignant ovarian tumors revealed that the level of CD56 + cells was significantly higher in tumor ascites compared to peripheral blood. In patients with BTs, the levels of CD56 + CD107a + and activated CD56 + CD107a + GB-PF-degranulated cells was higher in ascites than in blood. In patients with ovarian cancer, the level of degranulated cells was higher in peripheral blood than in malignant ascites. Conclusion. The tumor cells and tumor microenvironment were found to affect the number and the functional activity of NK-cells. The accumulation of free fluid within the peritoneal cavity in patients with both benign and malignant

  13. International Symposium on Boundary Element Methods : Advances in Solid and Fluid Mechanics

    CERN Document Server

    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 ...

  14. Benchmark Simulation of Natural Circulation Cooling System with Salt Working Fluid Using SAM

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, K. K.; Scarlat, R. O.; Hu, R.

    2017-09-03

    Liquid salt-cooled reactors, such as the Fluoride Salt-Cooled High-Temperature Reactor (FHR), offer passive decay heat removal through natural circulation using Direct Reactor Auxiliary Cooling System (DRACS) loops. The behavior of such systems should be well-understood through performance analysis. The advanced system thermal-hydraulics tool System Analysis Module (SAM) from Argonne National Laboratory has been selected for this purpose. The work presented here is part of a larger study in which SAM modeling capabilities are being enhanced for the system analyses of FHR or Molten Salt Reactors (MSR). Liquid salt thermophysical properties have been implemented in SAM, as well as properties of Dowtherm A, which is used as a simulant fluid for scaled experiments, for future code validation studies. Additional physics modules to represent phenomena specific to salt-cooled reactors, such as freezing of coolant, are being implemented in SAM. This study presents a useful first benchmark for the applicability of SAM to liquid salt-cooled reactors: it provides steady-state and transient comparisons for a salt reactor system. A RELAP5-3D model of the Mark-1 Pebble-Bed FHR (Mk1 PB-FHR), and in particular its DRACS loop for emergency heat removal, provides steady state and transient results for flow rates and temperatures in the system that are used here for code-to-code comparison with SAM. The transient studied is a loss of forced circulation with SCRAM event. To the knowledge of the authors, this is the first application of SAM to FHR or any other molten salt reactors. While building these models in SAM, any gaps in the code’s capability to simulate such systems are identified and addressed immediately, or listed as future improvements to the code.

  15. Finite Element Analysis of Mechanical Characteristics of Dropped Eggs Based on Fluid-Solid Coupling Theory

    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.

  16. Multidimensional Generalized Functions in Aeroacoustics and Fluid Mechanics. Part 1; Basic Concepts and Operations

    Science.gov (United States)

    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.

  17. Natural convection in nano-fluids: Are the thermophoresis and Brownian motion effects significant in nano-fluid heat transfer enhancement?

    International Nuclear Information System (INIS)

    Haddad, Zoubida; Abu-Nada, Eiyad; Oztop, Hakan F.; Mataoui, Amina

    2012-01-01

    Natural convection heat transfer and fluid flow of CuO-Water nano-fluids is studied using the Rayleigh-Benard problem. A two component non-homogenous equilibrium model is used for the nano-fluid that incorporates the effects of Brownian motion and thermophoresis. Variable thermal conductivity and variable viscosity are taken into account in this work. Finite volume method is used to solve governing equations. Results are presented by streamlines, isotherms, nano-particle distribution, local and mean Nusselt numbers and nano-particle profiles at top and bottom side. Comparison of two cases as absence of Brownian and thermophoresis effects and presence of Brownian and thermophoresis effects showed that higher heat transfer is formed with the presence of Brownian and thermophoresis effect. In general, by considering the role of thermophoresis and Brownian motion, an enhancement in heat transfer is observed at any volume fraction of nano-particles. However, the enhancement is more pronounced at low volume fraction of nano-particles and the heat transfer decreases by increasing nano-particle volume fraction. On the other hand, by neglecting the role of thermophoresis and Brownian motion, deterioration in heat transfer is observed and this deterioration elevates by increasing the volume fraction of nano-particles. (authors)

  18. The nature of hydrothermal fluids in the Kahang porphyry copper deposit (Northeast of Isfahan based on mineralography, fluid inclusion and stable isotopic data

    Directory of Open Access Journals (Sweden)

    Salimeh Sadat Komeili

    2017-02-01

    Full Text Available Introduction The Kahang Cu- Mo deposit is situated approximately 73 Km northeast of Isfahan. Asadi (2007 identified a geological reserve of 40 Mt (proven reserve grading at 0.53 Cu, 0.02 Mo and estimated reserve of 120 Mt. All the rock types in the region have been subjected to hydrothermal solutions which gave rise to three different alteration facies. The dacite and rhyodacite volcanic rocks and granitic- granodioritic stocks have experienced phyllic alteration. Disseminated and stockwork siliceous veins are the major styles of mineralization in this zone. Intermediate argillitic alteration developed on a part of dacitic and rhyodacitic rocks whereas andesite and basaltic-andesite plus related pyroclastic rocks have been subjected to propyllitic alteration. This paper presents the results of geological and mineralogical studies carried out in the Kahang area. This preliminary information is integrated with additional data on ore mineralogy, fluid inclusions and stable isotopes in view of understanding the genesis of the Cu- Mo deposit and the nature of the fluids involved in ore formation. Materials and Methods A total of 18 polished thin sections were prepared at the University of Isfahan for optical study. Fluid inclusions study was carried out on 8 double polished quartz thin sections (stockworks containing ore mineralization from phyllic zone. H – O stable isotope analysis was performed on 4 quartz samples from siliceous stockworks (from phyllic altered zone and one vein epidote sample (from propyllitic zone. All isotopic analyses were performed at the University of Oregan, Oregan, USA. Discussion In the investigated mineralization area, the hypogene zone is characterized by the presence of pyrite, chalcopyrite, bornite and magnetite. Hematite, goethite, jarosite, malachite and azurite are the predominant minerals of supergene zone. The major textures of the primary sulfides are disseminated, vein and veinlet. Pyrite is the most common

  19. Working regime identification for natural circulation loops by comparative thermalhydraulic analyses with three fluids under identical operating conditions

    International Nuclear Information System (INIS)

    Sarkar, Milan K.S.; Basu, Dipankar N.

    2015-01-01

    Highlights: • Thermalhydraulic analyses of NCL to justify the use of supercritical condition. • Mass flow rate of supercritical loop increases with heater power till a maxima. • Supercritical loop suffer from HTD beyond the maxima with jump in fluid temperature. • HTD is pronounced at higher sink temperatures and pressures just above critical. • Supercritical CO 2 is preferred fluid till the HTD and single-phase water afterwards. - Abstract: Computational investigation for comparative thermalhydraulic analyses of rectangular natural circulation loops is performed to propose a guideline for selecting the working fluid and nature of the loop, subcritical or supercritical, under identical levels of operating parameters like pressure, heating power and coolant temperature. A 3-d uniform-diameter loop geometry is developed with horizontal heating and cooling. Heating is provided in constant heat flux mode, whereas cooling is through a constant temperature sink. Due to favourable thermophysical properties and environmental conformity, water, CO 2 and R134a are selected as possible working fluids. Operational parameters are set so as to have sub- to supercritical condition for CO 2 , supercritical for R134a and single-phase liquid for water. Mass flow rate for supercritical fluid rapidly increases with heater power, when the fluid is allowed to cross the pseudocritical point during its passage through the heater, and exhibits a maxima. Drastic fall in mass flow rate can be observed beyond the maxima, accompanied by a jump in maximum fluid temperature and a rapid decline in sink-side heat transfer coefficient. That can be identified as heat transfer deterioration in supercritical natural circulation loops, a highly undesirable situation from loop safety point of view. Allowable working range of heater power can be enhanced by increasing system pressure and decreasing sink temperature. For any specified set of operating conditions, CO 2 -based supercritical loops

  20. Fluid-Thermal-Structural Coupled Analysis of a Radial Inflow Micro Gas Turbine Using Computational Fluid Dynamics and Computational Solid Mechanics

    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.

  1. Characterization of immiscible fluid displacement processes with various capillary numbers and viscosity ratios in 3D natural sandstone

    Science.gov (United States)

    Tsuji, Takeshi; Jiang, Fei; Christensen, Kenneth T.

    2016-09-01

    To characterize the influence of reservoir conditions upon multiphase flow, we calculated fluid displacements (drainage processes) in 3D pore spaces of Berea sandstone using two-phase lattice Boltzmann (LB) simulations. The results of simulations under various conditions were used to classify the resulting two-phase flow behavior into three typical fluid displacement patterns on the diagram of capillary number (Ca) and viscosity ratio of the two fluids (M). In addition, the saturation of the nonwetting phase was calculated and mapped on the Ca-M diagram. We then characterized dynamic pore-filling events (i.e., Haines jumps) from the pressure variation of the nonwetting phase, and linked this behavior to the occurrence of capillary fingering. The results revealed the onset of capillary fingering in 3D natural rock at a higher Ca than in 2D homogeneous granular models, with the crossover region between typical displacement patterns broader than in the homogeneous granular model. Furthermore, saturation of the nonwetting phase mapped on the Ca-M diagram significantly depends on the rock models. These important differences between two-phase flow in 3D natural rock and in 2D homogeneous models could be due to the heterogeneity of pore geometry in the natural rock and differences in pore connectivity. By quantifying two-phase fluid behavior in the target reservoir rock under various conditions (e.g., saturation mapping on the Ca-M diagram), our approach could provide useful information for investigating suitable reservoir conditions for geo-fluid management (e.g., high CO2 saturation in CO2 storage).

  2. The Fundamental Natural Frequency and Critical Flow Velocity Evaluation of a Simply Supported Stepped Pipe Conveying Fluid

    Directory of Open Access Journals (Sweden)

    Mustafa Baqir Hunain

    2017-08-01

    Full Text Available This work investigated the fundamental natural frame frequency and critical inlet flow velocity of the simply supported stepped pipe conveying fluid. The influence of some outline parameters, similar pipe diameter ratio with different cross-sectional areas (sudden enlargement or sudden contraction, length ratio, and thickness were studied. A theoretical model for the dynamic behavior of the pipe was investigated. The dynamic behavior of the stepped pipe carrying fluid was described by means of finite element technique. A computer program has been promoted utilizing Matlab language in order to predict the vibration characteristics and to embrace the theoretical work. It was found that the fundamental natural frequency of the stepped pipe decreased in different percentages with increasing inlet fluid flow velocity. The outer diameter ratio, length ratio, and thickness of the stepped pipe conveying fluid had a great effect on the dynamic behavior of stepped pipe. The fundamental natural frame frequency increased as the length ratios (L2/L1 and the outer diameter ratios (Od2/Od1 decreased. When the length ratio of the pipe being less than 1, the effect of the diameter ratio on the critical inlet flow velocity was obvious. As the outer diameter ratios (Od2/Od1 increased, the inlet critical flow velocity increased, until being reached to the maximum value, then it dropped smoothly. The fundamental frame frequency of the stepped pipe increased as the thickness of the stepped pipe increased until being reached to the maximum value ,then it dropped smoothly. For each inlet fluid flow velocity, length ratios, and diameter ratios there was an optimum pipe thickness that gave the best dynamic characteristics.

  3. On the stability of natural convection in a porous vertical slab saturated with an Oldroyd-B fluid

    Science.gov (United States)

    Shankar, B. M.; Shivakumara, I. S.

    2017-06-01

    The stability of the conduction regime of natural convection in a porous vertical slab saturated with an Oldroyd-B fluid has been studied. A modified Darcy's law is utilized to describe the flow in a porous medium. The eigenvalue problem is solved using Chebyshev collocation method and the critical Darcy-Rayleigh number with respect to the wave number is extracted for different values of physical parameters. Despite the basic state being the same for Newtonian and Oldroyd-B fluids, it is observed that the basic flow is unstable for viscoelastic fluids—a result of contrast compared to Newtonian as well as for power-law fluids. It is found that the viscoelasticity parameters exhibit both stabilizing and destabilizing influence on the system. Increase in the value of strain retardation parameter Λ _2 portrays stabilizing influence on the system while increasing stress relaxation parameter Λ _1 displays an opposite trend. Also, the effect of increasing ratio of heat capacities is to delay the onset of instability. The results for Maxwell fluid obtained as a particular case from the present study indicate that the system is more unstable compared to Oldroyd-B fluid.

  4. Inclination angle effect on natural convection in a square cavity partially filled with non-Newtonian fluids layer

    Science.gov (United States)

    Alsabery, Ammar I.; Hussain, Salam H.; Saleh, Habibis; Hashim, Ishak

    2015-09-01

    The problem of inclination angle effect on natural convection in a square cavity partially filled with non-Newtonian fluid layer is studied numerically using The Finite Volume Method. Governing equations are solved over wide range of Darcy number (10-5 ≤ Da ≤ 10-1), power-law index(0.6 ≤ n ≤ 1.4), the inclination angle of the cavity (0° ≤ ω ≤ 90°), Rayleigh number (Ra = 105) and porous layer thickness (S = 0.5). The results presented for values of the governing parameters in terms of streamlines in both porous/non-Newtonian fluid-layer, isotherms in both porous/non-Newtonian fluid-layer and average Nusselt number. It is shown that the heat transfer has maximum value when the power-law index is less than one (pseudoplastic fluid), and then decreases remarkably as the power-law index increases. The results have possible applications in heat-removal and heat-storage non-Newtonian fluid-saturated porous systems.

  5. The transition from natural convection to thermomagnetic convection of a magnetic fluid in a non-uniform magnetic field

    Science.gov (United States)

    Szabo, Peter S. B.; Früh, Wolf-Gerrit

    2018-02-01

    Magnetic fluid flow and heat transfer by natural and thermomagnetic convection was studied numerically in a square enclosure. The aim was to investigate the transition from natural convection to thermomagnetic convection by exploring situations where buoyancy and the Kelvin body force would be opposing each other such that the magnetic effects would in some cases be the dominant factor throughout the domain and in other cases only in a part of the fluid. The numerical model coupled the solution of the magnetostatic field equation with the heat and fluid flow equations to simulate the fluid flow under a realistic magnetic field generated by a permanent magnet. The results suggest that the domain of influence over the flow field is largely aligned with the domain of dominance of the respective driving force. The result is that the transition from a single buoyancy-driven convection cell to a single thermomagnetically driven cell is via a two-cell structure and that the local effect on the flow field leads to a global effect on the heat transfer with a minimum of the Nusselt number in the transition region.

  6. High-performance coupled poro-hydro-mechanical models to resolve fluid escape pipes

    Science.gov (United States)

    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.

  7. A detailed fluid mechanics study of tilting disk mechanical heart valve closure and the implications to blood damage.

    Science.gov (United States)

    Manning, Keefe B; Herbertson, Luke H; Fontaine, Arnold A; Deutsch, Steven

    2008-08-01

    Hemolysis and thrombosis are among the most detrimental effects associated with mechanical heart valves. The strength and structure of the flows generated by the closure of mechanical heart valves can be correlated with the extent of blood damage. In this in vitro study, a tilting disk mechanical heart valve has been modified to measure the flow created within the valve housing during the closing phase. This is the first study to focus on the region just upstream of the mitral valve occluder during this part of the cardiac cycle, where cavitation is known to occur and blood damage is most severe. Closure of the tilting disk valve was studied in a "single shot" chamber driven by a pneumatic pump. Laser Doppler velocimetry was used to measure all three velocity components over a 30 ms period encompassing the initial valve impact and rebound. An acrylic window placed in the housing enabled us to make flow measurements as close as 200 microm away from the closed occluder. Velocity profiles reveal the development of an atrial vortex on the major orifice side of the valve shed off the tip of the leaflet. The vortex strength makes this region susceptible to cavitation. Mean and maximum axial velocities as high as 7 ms and 20 ms were recorded, respectively. At closure, peak wall shear rates of 80,000 s(-1) were calculated close to the valve tip. The region of the flow examined here has been identified as a likely location of hemolysis and thrombosis in tilting disk valves. The results of this first comprehensive study measuring the flow within the housing of a tilting disk valve may be helpful in minimizing the extent of blood damage through the combined efforts of experimental and computational fluid dynamics to improve mechanical heart valve designs.

  8. Natural convection in a composite fluid-porous cavity by the boundary element method

    International Nuclear Information System (INIS)

    Jecl, R.; Skerget, L.

    2005-01-01

    The main purpose of this work is to present the use of the boundary element method (BEM) for analyzing the convective fluid flow and heat transfer in composite fluid-porous media domain when the fluid is compressible. In our case the flow is modeled by utilizing the Brinkman extended Darcy momentum equation (Brinkman model) which is commonly used when it is important to satisfy the no-slip boundary condition and when one wishes to compare flows in porous medium with those in pure fluids. The Brinkman equation reduce to the classical Navier Stokes equation for clear fluid when the permeability tends to infinity (porosity is equal to unity), i.e. when the solid matrix in the porous medium disappears and, when the permeability is finite the equation is valid for porous medium. Therefore it is possible to handle porous medium free fluid interface problems by changing the properties of the medium in the computational domain appropriately. Our goal is to widen the applicability of the computational model based on the boundary domain integral method (BDIM) which is an extension of the classical BEM. The governing equations are transformed by using the velocity-vorticity variables formulation and therefore the computation scheme is partitioned into kinematic and kinetic part. (authors)

  9. Influence of size, shape, type of nanoparticles, type and temperature of the base fluid on natural convection MHD of na

    Directory of Open Access Journals (Sweden)

    P. Sudarsana Reddy

    2016-03-01

    Full Text Available In this paper, we have presented MHD natural convection boundary layer flow, heat and mass transfer characteristics of nanofluid through porous media over a vertical cone influenced by different aspects of nanoparticles such as size, shape, type of nanoparticles and type of the base fluid and working temperature of base fluid. To increase the physical significance of the problem, we have taken dynamic viscosity and thermal conductivity as the functions of local volume fraction of nanoparticles. The drift-flux model of nanofluids, Brownian motion, thermophoresis, and enhancement ratio parameters are also considered in the present analysis. The influence of non-dimensional parameters such as magnetic field (M, buoyancy ratio parameter (Nr, conductivity parameter (Nc, viscosity parameter (Nv, Brownian motion parameter (Nb, thermophoresis parameter (Nt, Lewis number (Le on velocity, temperature and volume fraction of nanoparticles in the boundary layer region is examined in detail. Furthermore the impact of these parameters on local Nusselt number (Nux and enhancement ratio hnfhbf is also investigated. The results of present study reveal that significant natural convection heat transfer enhancement is noticed as the size of nanoparticles decreases. Moreover, type of the nanoparticles and type of the base fluid also influenced the natural convection heat transfer.

  10. Modeling Coupled Processes for Multiphase Fluid Flow in Mechanically Deforming Faults

    Science.gov (United States)

    McKenna, S. A.; Pike, D. Q.

    2011-12-01

    Modeling of coupled hydrological-mechanical processes in fault zones is critical for understanding the long-term behavior of fluids within the shallow crust. Here we utilize a previously developed cellular-automata (CA) model to define the evolution of permeability within a 2-D fault zone under compressive stress. At each time step, the CA model calculates the increase in fluid pressure within the fault at every grid cell. Pressure surpassing a critical threshold (e.g., lithostatic stress) causes a rupture in that cell, and pressure is then redistributed across the neighboring cells. The rupture can cascade through the spatial domain and continue across multiple time steps. Stress continues to increase and the size and location of rupture events are recorded until a percolating backbone of ruptured cells exists across the fault. Previous applications of this model consider uncorrelated random fields for the compressibility of the fault material. The prior focus on uncorrelated property fields is consistent with development of a number of statistical physics models including percolation processes and fracture propagation. However, geologic materials typically express spatial correlation and this can have a significant impact on the results of the pressure and permeability distributions. We model correlation of the fault material compressibility as a multiGaussian random field with a correlation length defined as the full-width at half maximum (FWHM) of the kernel used to create the field. The FWHM is varied from contract DE-AC04-94AL85000

  11. CFD investigation of turbulence models for mechanical agitation of non-Newtonian fluids in anaerobic digesters.

    Science.gov (United States)

    Wu, Binxin

    2011-02-01

    This study evaluates six turbulence models for mechanical agitation of non-Newtonian fluids in a lab-scale anaerobic digestion tank with a pitched blade turbine (PBT) impeller. The models studied are: (1) the standard k-ɛ model, (2) the RNG k-ɛ model, (3) the realizable k-ɛ model, (4) the standard k-ω model, (5) the SST k-ω model, and (6) the Reynolds stress model. Through comparing power and flow numbers for the PBT impeller obtained from computational fluid dynamics (CFD) with those from the lab specifications, the realizable k-ɛ and the standard k-ω models are found to be more appropriate than the other turbulence models. An alternative method to calculate the Reynolds number for the moving zone that characterizes the impeller rotation is proposed to judge the flow regime. To check the effect of the model setup on the predictive accuracy, both discretization scheme and numerical approach are investigated. The model validation is conducted by comparing the simulated velocities with experimental data in a lab-scale digester from literature. Moreover, CFD simulation of mixing in a full-scale digester with two side-entry impellers is performed to optimize the installation. Copyright © 2010 Elsevier Ltd. All rights reserved.

  12. A study of biological chemistry on the nature of jaw cysts. On the maintainance of homoeostasis in jaw cyst fluid.

    Science.gov (United States)

    Suzuki, M

    1975-06-01

    Jaw cyst lining cells have an active transporting mechanism for Na+ ion and K+ion, a secreting mechanism and a selecting mechanism, and they allow permeation of electrolytes, lipids and protein into cysts. The components within the cysts have a controlling metabolism, and keep the system stable. Tumour wall cells of cystic ameloblastoma have only a passive transporting mechanism for various substances. Their nature differs from that of jaw cyst lining cells.

  13. Methodology for developing teaching activities and materials for use in fluid mechanics courses in undergraduate engineering programs

    OpenAIRE

    Gámez Montero, Pedro Javier; Raush Alviach, Gustavo Adolfo; Domènech Rubio, Luis Miguel; Castilla López, Roberto; García Vilchez, Mercedes; Moreno Llagostera, Hipòlit; Carbo Bech, Alberto Antonio

    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 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....

  14. [Concepts of basic physics that every cardiovascular surgeon should know: part I - mechanics of fluids].

    Science.gov (United States)

    Oliveira, Marcos Aurélio Barboza de; Alves, Fernanda Tomé; Silva, Marcos Vinícius Pinto e; Croti, Ulisses Alexandre; Godoy, Moacir Fernandes de; Braile, Domingo Marcolino

    2010-01-01

    The professional activity that the cardiovascular surgeon performs is much more than a simple gesture to mechanically operate the patient's heart. There is in every act of intraoperative most notions of physiology and physics than we generally realize. This paper discusses, in the light of mathematics, on the dynamics of fluids, ie blood, focused on invasive measurements of blood pressure, the effect of vessel size on its internal resistance and the flow passing through it in conversion of various units of measurements of pressure and resistance, blood viscosity and its relationship to the vessel, hemodilution, differences in laminar and turbulent flow, velocity and blood pressure and wall tension after a stenosis and the origin of poststenotic aneurysm. This study is not to enable the reader to the knowledge of all physics, but to show it as a useful tool in explaining phenomena known in the routine of cardiovascular surgery.

  15. Proceedings of the fourteenth symposium on energy engineering sciences: Mechanical sciences; Solids and fluids

    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.

  16. Thermal and Fluid Mechanical Investigation of an Internally Cooled Piston Rod

    Science.gov (United States)

    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.

  17. Relaxation time diagram for identifying heat generation mechanisms in magnetic fluid hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Enio, E-mail: lima@cab.cnea.gov.ar; De Biasi, Emilio; Zysler, Roberto D.; Vasquez Mansilla, Marcelo; Mojica-Pisciotti, Mary L. [Centro Atómico Bariloche/CONICET (Argentina); Torres, Teobaldo E.; Calatayud, M. Pilar; Marquina, C.; Ricardo Ibarra, M.; Goya, Gerardo F. [Universidad de Zaragoza, Instituto de Nanociencia de Aragón INA (Spain)

    2014-12-15

    We present a versatile diagram to envisage the dominant relaxation mechanism of single-domain magnetic nanoparticles (MNPs) under alternating magnetic fields, as those used in magnetic fluid hyperthermia (MFH). The diagram allows estimating the heating efficiency, measured by the Specific Power Absorption (SPA), originated in the magnetic and viscous relaxation times of single-domain MNPs for a given frequency of the ac magnetic field (AFM). The diagram has been successfully applied to different colloids, covering a wide variety of MNPs with different magnetic anisotropy and particle size, and dispersed in different viscous liquid carriers. From the general diagram, we derived a specific chart based on the Linear Response Theory in order to easily estimate the experimental condition for the optimal SPA values of most colloids currently used in MFH.

  18. Analytical solutions for transport processes fluid mechanics, heat and mass transfer

    CERN Document Server

    Brenn, Günter

    2017-01-01

    This book provides analytical solutions to a number of classical problems in transport processes, i.e. in fluid mechanics, heat and mass transfer. Expanding computing power and more efficient numerical methods have increased the importance of computational tools. However, the interpretation of these results is often difficult and the computational results need to be tested against the analytical results, making analytical solutions a valuable commodity. Furthermore, analytical solutions for transport processes provide a much deeper understanding of the physical phenomena involved in a given process than do corresponding numerical solutions. Though this book primarily addresses the needs of researchers and practitioners, it may also be beneficial for graduate students just entering the field. .

  19. Stroke volume variation compared with pulse pressure variation and cardiac index changes for prediction of fluid responsiveness in mechanically ventilated patients

    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.

  20. Mechanical properties of natural fibre reinforced polymer composites

    Indian Academy of Sciences (India)

    Wintec

    green composites involving Hibiscus sabdariffa fibre as a reinforcing material in urea–formaldehyde (UF) resin based polymer ... mixed Hibiscus sabdariffa fibre reinforced polymer composites such as tensile, compressive and wear proper- ties were ... in natural fibres and its applications in various fields. Natural fibres are ...

  1. Microstructure and Mechanical Properties of Aligned Natural Fibre Composites

    DEFF Research Database (Denmark)

    Rask, Morten

    Recently, there has been a great interest in developing and maturing natural fibre composites for structural applications. Natural fibres derived from plants such as flax and hemp have the potential to compete with traditional glass fibres as reinforcements in polymer matrices, due to good specific...

  2. Mechanical stresses in carotid plaques using MRI-based fluid-structure interaction models

    DEFF Research Database (Denmark)

    Kock, Samuel A; Nygaard, Jens Vinge; Eldrup, Nikolaj

    2008-01-01

    fluid-structure interaction (FSI) simulations of carotid atherosclerotic plaques were performed facilitating in-vivo estimation of longitudinal internal fibrous cap stresses. The FSI simulation combined finite element analysis (FEA) with computational fluid dynamics (CFD) simulations of blood...

  3. Viscoelastic fluid-structure interactions between flexible circular cylinder and wormlike micelle solution: Role of structural natural frequency

    Science.gov (United States)

    Dey, Anita; Modarres-Sadeghi, Yahya; Rothstein, Jonathan

    2017-11-01

    It is well known that when a flexible or flexibly-mounted structure is placed perpendicular to a Newtonian fluid flow, it can oscillate due to the shedding of separated vortices at high Reynolds numbers. Unlike Newtonian fluids, the flow of viscoelastic fluids can become unstable even at infinitesimal Reynolds numbers due to a purely elastic flow instability. We have recently shown that these elastic flow instabilities can drive the motion of different flexible structures including sheets and cylinders. In this talk, we will present an investigation into the influence of a varying natural frequency of a flexible circular cylinder on the form, frequency and amplitude of the viscoelastic fluid-structure interactions with the goal of understanding lock-in behavior for these interactions. The static and dynamic responses of the cylinder will be presented for a range of flow velocities for wormlike micelle solutions with varying viscosity and relaxation time. The time variation and state of stress of the flow field will be shown using particle image velocimetry and flow-induced birefringence images. Finally, the non-linear dynamics of the structural motion will be investigated to understand an observed transition from a symmetric to an asymmetric flow field and oscillation behavior.

  4. Surface Roughness Effects on Fluid Transport Through a Natural Rock Fracture

    Energy Technology Data Exchange (ETDEWEB)

    Crandall, D.M.; Ahmadi, Goodarz; Smith, D.H.

    2008-04-01

    Fluid flow through rock fractures can be orders of magnitude faster than through the adjacent low-permeability rock. Understanding how fluid moves through these pathways is important for the prediction of sequestered CO2 transport in geologic reservoirs. Reservoir-scale, discrete-fracture simulators use simplified models of flow through fractures to determine transport properties in complex fracture networks. A high level of approximation is required in these reservoir-scale simulations due to the number of fractures within the domain of interest and because of the limited amount of information that can be obtained from geophysical well-logs (Long et al. (1996)). For this study, flow simulations through a CT-scanned fracture were performed to evaluate different fluid transport parameters that are important in geological flow analysis. The ‘roughness’ of the fracture was varied to determine the effect of the bumpy fracture walls on the fluid flow. The permeability and effective aperture were determined for flow under a constant pressure head. The fracture roughness is shown to dramatically reduce the flow through the fracture, and various relations are described.

  5. Steps of Supercritical Fluid Extraction of Natural Products and Their Characteristic Times

    Czech Academy of Sciences Publication Activity Database

    Sovová, Helena

    2012-01-01

    Roč. 66, SI (2012), s. 73-79 ISSN 0896-8446 R&D Projects: GA MŠk 2B06049 Institutional support: RVO:67985858 Keywords : supercritical fluid extraction * vegetable oils * essential oils Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.732, year: 2012

  6. Analysis of fluid lubrication mechanisms in metal forming at mesoscopic scale

    DEFF Research Database (Denmark)

    Dubar, L.; Hubert, C.; Christiansen, Peter

    2012-01-01

    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...

  7. Numerical simulation for flow and heat transfer to Carreau fluid with magnetic field effect: Dual nature study

    Science.gov (United States)

    Hashim; Khan, Masood; Alshomrani, Ali Saleh

    2017-12-01

    This article considers a realistic approach to examine the magnetohydrodynamics (MHD) flow of Carreau fluid induced by the shrinking sheet subject to the stagnation-point. This study also explores the impacts of non-linear thermal radiation on the heat transfer process. The governing equations of physical model are expressed as a system of partial differential equations and are transformed into non-linear ordinary differential equations by introducing local similarity variables. The economized equations of the problem are numerically integrated using the Runge-Kutta Fehlberg integration scheme. In this study, we explore the condition of existence, non-existence, uniqueness and dual nature for obtaining numerical solutions. It is found that the solutions may possess multiple natures, upper and lower branch, for a specific range of shrinking parameter. Results indicate that due to an increment in the magnetic parameter, range of shrinking parameter where a dual solution exists, increases. Further, strong magnetic field enhances the thickness of the momentum boundary layer in case of the second solution while for first solution it reduces. We further note that the fluid suction diminishes the fluid velocity and therefore the thickness of the hydrodynamic boundary layer decreases as well. A critical analysis with existing works is performed which shows that outcome are benchmarks with these works.

  8. 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

  9. Mechanical properties of natural fibre reinforced polymer composites

    Indian Academy of Sciences (India)

    In the present communication, a study on the synthesis and mechanical properties of new series of green composites involving Hibiscus sabdariffa fibre as a reinforcing material in urea–formaldehyde (UF) resin based polymer matrix has been reported. Static mechanical properties of randomly oriented intimately mixed ...

  10. Alterations in cancer cell mechanical properties after fluid shear stress exposure: a micropipette aspiration study

    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

  11. Mechanical behavior of a fluid-sensitive material during liquid diffusion

    Science.gov (United States)

    Widiastuti, Indah; Sbarski, Igor; Masood, S. H.

    2014-05-01

    This paper described the analytical study that we performed in an attempt to understand the combined effect of liquid diffusion and temperature on the mechanical response of viscoelastic liquid-sensitive material. A constitutive equation for linear viscoelasticity, which includes the effect of liquid diffusion, is used to model the mechanical response of a fluid-sensitive polymer such as PLA-based bioplastic. The viscoelastic characteristics which represent material degradation due to liquid diffusion were expressed using a creep-based formulation represented by Burger's model. Creep experiment data were fitted to the Burgers model to provide a liquid content-dependent set of input data for subsequent time-dependent analysis. Further, analytical solutions for stresses and deformations were obtained from the corresponding elastic solution by applying the Correspondence Principle, using previously defined material characteristics. Spatial and time variations of stress and deformation were evaluated to give a precise description of the material behavior under hygroscopic conditions. We propose a stress concentration factor to take into account the liquid diffusion-induced stress that may result in a failure of an application. The results emphasize the importance of considering liquid diffusion and viscoelastic properties in the design of components using liquid-absorbable material.

  12. Fluid mechanics of the human eye: aqueous humour flow in the anterior chamber.

    Science.gov (United States)

    Fitt, A D; Gonzalez, G

    2006-01-01

    We consider and compare the various different kinds of flow that may take place in the anterior chamber of a human eye. The physical mechanisms responsible for causing such flows may be classified as follows: (i) buoyancy-driven flow arising from the temperature difference between the anterior surface of the cornea and the iris, (ii) flow generated by the aqueous production of the ciliary body, (iii) flow generated by the interaction between buoyancy and gravity while sleeping while sleeping in a face-up position, (iv) flow generated by phakodenesis (lens tremor), (v) flow generated by Rapid Eye Movement (REM) during sleep. Each flow is studied using a traditional fluid mechanics/asymptotic analysis approach. We also assess the veracity of a hypothesis that was recently advanced [see Maurice, D.M., 1998. The Von Sallman Lecture 1996: An ophthalmological explanation of REM sleep. Exp. Eye. Res. 66, 139-145, for details] to suggest that, contrary to previous opinion, the purpose of REM during sleep is to ensure corneal respiration in the absence of the buoyant mixing that routinely takes place due to (i) above during waking conditions.

  13. Irreversible Aspects of Continuum Mechanics and Transfer of Physical Characteristics in Moving Fluids : Symposia

    CERN Document Server

    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...

  14. Mechanical study of the Chartreuse Fold-and-Thrust Belt: relationships between fluids overpressure and decollement within the Toarcian source-rock

    Science.gov (United States)

    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

  15. Influence of Reduced Mass Flow Rate and Chamber Backpressure on Swirl Injector Fluid Mechanics

    Science.gov (United States)

    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.

  16. On acoustics of cavitating flows and wave mechanics of two-phase fluids; Zur Akustik kavitierender Stroemungen und Wellenmechanik zweiphasiger Fluide

    Energy Technology Data Exchange (ETDEWEB)

    Ricoeur, A.

    2000-07-01

    The subject under consideration is the development and propagation of sound in two-phase flows. The investigations are focused on fluids, which are composed of liquid and gas. The gaseous phase may consist of both noncondensable gas and of vapour, originating from phase transitions of the liquid. Fields of application are, among others, flow noise, sonochemistry, the acoustical surveillance of industrial flow processes or ocean acoustics. A stochastic model, which describes spectral properties of noise sources, conditioned by imploding vapour bubbles, is connected to transfer functions. The latter are based on constitutive equations, accounting for the wave mechanics of the two-phase fluids. In combination with a numerical algorithm they permit for the calculation of noise spectra at any distance from the noise sources. The field problem is solved by implementing the constitutive equations into a hybrid boundary element method, which combines low discretization effort with fast evaluation of domain variables. The constitutive equations are based on models for the dynamics of gas- and vapour bubbles. Therefore, the nonlinear and linear bubble dynamics are extensively investigated. Furthermore, fundamental knowledge concerning wave dispersion in two-phase fluids is presented. The constitutive equation for pseudocavitation is experimentally verified by means of an acoustical wave guide. Additionally the experimental set-up serves for investigating fluid-structure-interaction. (orig.) [German] Die Arbeit befasst sich mit der Entstehung und Ausbreitung von Schall in Zweiphasenstroemungen. Betrachtet werden Fluide aus Fluessigkeit und Gas, deren Gasphase sowohl als nichtkondensierendes Gas, als auch in Gestalt des Dampfes der Fluessigkeit vorliegt. Anwendungen liegen beispielsweise in der Stroemungsakustik, der Sonochemie, der akustischen Ueberwachung verfahrenstechnischer Prozesse oder der Meeresakustik. Ein stochastisches Modell zur spektralen Beschreibung von

  17. Angiographic methods for the study of fluid mechanical factors in atherogenesis.

    Science.gov (United States)

    Smedby, O

    1992-01-01

    The purpose of this thesis is to investigate the feasibility of using angiographic methods to study, in vivo, fluid mechanical phenomena believed to influence the development and localization of atherosclerotic lesions, in particular, separated flow. This involved developing a method to recognize separated flow by digital analysis of cineangiography films, testing this method both with model measurements and in a clinical material, and a detailed analysis of certain methodological problems. In addition, methods have been developed to measure the tortuosity of arteries, a phenomenon which may, according to fluid mechanical theory, promote the occurrence of separated flow. In a glass model of an arterial bifurcation, a pump generated a pulsatile flow resembling that in large arteries. Using LDV (laser Doppler velocimetry) as a reference method, three velocity profiles in the symmetry plane of the model were recorded. During diastole, extensive separated flow was demonstrated in the larger branch of the bifurcation. The flow was then cineradiographed during injection of contrast medium, and the image sequence was transferred to an image analysis workstation. Treating the image sequence as a set of time-intensity curves, time parameters representing the arrival time of the contrast agent were computed. In the resulting parametric images, zones of delayed filling were identified and found to correspond to the separated flow. Viscosity was measured for seven radiographic contrast media and, as expected, the highest values were found for the largest molecules. For iohexol and ioxaglate, which were studied in detail, a linear relation to temperature and a quadratic relation to concentration were found. Whole-blood viscosity was measured for 5 healthy volunteers at high and low shear rates, before and after mixing with contrast agents in varying proportions. At low shear, viscosity decreased, while at high shear, it increased with increasing contrast concentration. The

  18. Embedding Hands-On Mini Laboratory Experiences in a Core Undergraduate Fluid Mechanics Course: A Pilot Study

    Science.gov (United States)

    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…

  19. Implementation of a Modular Hands-on Learning Pedagogy: Student Attitudes in a Fluid Mechanics and Heat Transfer Course

    Science.gov (United States)

    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…

  20. Structural Characteristics and Swelling Mechanism of Two Commercial Nitrile-Butadiene Elastomers in Various Fluids

    Science.gov (United States)

    2012-01-06

    reported here. The fluids used in these investigations included toluene, o- xylene , p- xylene , mesitylene, HISOL- 15, n-hexane, ethanol, tert-butyl...were monitored as a function of time. Structural characterization of the elastomer was done using x-ray diffraction and FTIR spectroscopy. Time...fluids are reported here. The fluids used in these investigations included toluene, o- xylene , p- xylene , mesitylene, HISOL-15, n-hexane, ethanol, tert

  1. Mechanics of granular-frictional-visco-plastic fluids in civil and mining engineering

    Science.gov (United States)

    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.

  2. Comparison of Venous Return Characteristics with Right Ventricular Mechanics During Cephalic Fluid Shift

    Science.gov (United States)

    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

  3. Numerical Study of Mechanical Stirring in Case of Yield Stress Fluid with Circular Anchor Impeller

    Directory of Open Access Journals (Sweden)

    Brahim MEBARKI

    2011-09-01

    Full Text Available In this work the characterization of hydrodynamic fields of incompressible yield stress fluid with regularization model of Bercovier and Engelman in a cylindrical vessel not chicaned equipped with circular anchor stirrer was undertaken by means of numerical simulation using computational fluid dynamics. Simulations flow of a Bingham fluid agitated by straights blades anchor was used to validate the rheological model implemented of the fluid treated. The flow structures, and especially the effect of inertia, the plasticity and the yield stress, are discussed. We have analyzed also the influence of rheological parameters on the hydrodynamic flow behaviours, such as the velocity components and the global characteristic like power consumption.

  4. Effects of natural increase in temperature on clay formations and determination of the course and the effects of geothermal fluids

    International Nuclear Information System (INIS)

    Polizzano, C.; Benvegnu, F.; Giannotti, G.; Brandimarte, U.

    1986-01-01

    The behaviour of clay cover towards the geothermal fluids rising up to the surface may represent an excellent natural analogue of the potential migration processes from deep waste repositories in clay formations. The ENEA is conducting research in an appropriate area near M. Amiata in southern Tuscany in order to contribute to solving the problem of the expected impermeability of clay formations. Geothermal fields may namely give an opportunity of studying a case of clay behaviour at a scale corresponding to size and time considered in waste disposal. In the considered area a relevant geothermal field is still active. A clay complex represents the impermeable cover of the local geothermal field. Several endogenous phenomena indicate the preferential ways of migrations of fluids from the basement throughout the cover. The data obtained by the present research prove that the upward flow of fluids, is possible only in the points of reduced thickness of the cover where very important faulting or granulometric discontinuity occur. This situation typically occurs at the border and not in the central part of the clay basins

  5. Modelling the fluid mechanics of cilia and flagella in reproduction and development.

    Science.gov (United States)

    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.

  6. Mechanisms of sampling interstitial fluid from skin using a microneedle patch.

    Science.gov (United States)

    Samant, Pradnya P; Prausnitz, Mark R

    2018-04-16

    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 < capillary action < osmosis < pressure-driven convection, under the conditions studied. These findings were in agreement with independent theoretical modeling that considered transport within skin, across the interface between skin and µpores, and within µpores to the skin surface. This analysis indicated that the rate-limiting step for ISF 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.

  7. 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.

  8. Lung Mucosa Lining Fluid Modification of Mycobacterium tuberculosis to Reprogram Human Neutrophil Killing Mechanisms.

    Science.gov (United States)

    Arcos, Jesús; Diangelo, Lauren E; Scordo, Julia M; Sasindran, Smitha J; Moliva, Juan I; Turner, Joanne; Torrelles, Jordi B

    2015-09-15

    We have shown that human alveolar lining fluid (ALF) contains homeostatic hydrolases capable of altering the Mycobacterium tuberculosis cell wall and subsequently its interaction with human macrophages. Neutrophils are also an integral part of the host immune response to M. tuberculosis infection. Here we show that the human lung mucosa influences M. tuberculosis interaction with neutrophils, enhancing the intracellular killing of ALF-exposed M. tuberculosis and up-regulating the expression of tumor necrosis factor and interleukin 8. In contrast, ALF-exposed M. tuberculosis does not induce neutrophil apoptosis or necrosis, degranulation, or release of extracellular traps, and it decreases the oxidative response. These results suggest an important role for the human alveolar mucosa: increasing the innate capacity of the neutrophil to recognize and kill M. tuberculosis by favoring the use of intracellular mechanisms, while at the same time limiting neutrophil extracellular inflammatory responses to minimize their associated tissue damage. © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  9. Numerical investigation of the deformation mechanism of a bubble or a drop rising or falling in another fluid

    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)

  10. Evaluation of absorbents for an absorption heat pump using natural organic working fluids (eco-energy city project)

    Energy Technology Data Exchange (ETDEWEB)

    Hisajima, Daisuke; Sakiyama, Ryoko; Nishiguchi, Akira [Hitachi Ltd., Tsuchiura (Japan). Mechanical Engineering Research Lab.

    1999-07-01

    The present situation of electric power supply and energy consumption in Japan has made it necessary to develop a new absorption air conditioning system which has low electric energy consumption, uses natural organic refrigerants, and can work as a heat pump in winter. Estimating vapor and liquid equilibrium of new pairs of working fluids is prerequisite to developing the new absorption heat pump system. In this phase of the work, methods for estimating vapor and liquid equilibrium that take into account intermolecular force were investigated. Experimental and calculated data on natural organic materials mixtures were considered to find optimum candidates, and then a procedure for evaluation was chosen. Several candidate absorbents were selected that used isobutane and dimethyl ether as refrigerants. (orig.)

  11. Does amniotic fluid volume affect fetofetal transfusion in monochorionic twin pregnancies? Modelling two possible mechanisms

    NARCIS (Netherlands)

    Umur, Asli; van Gemert, Martin J. C.; Ross, Michael G.

    2002-01-01

    Clinical evidence suggests that increased amniotic fluid volume due to polyhydrarnnios increases placental vascular resistance. We have sought to model the possible effects of an increased amniotic fluid volume oil the net fetofetal transfusion in monochorionic twin pregnancies. We wanted to compare

  12. Neural Mechanisms of Circadian Regulation of Natural and Drug Reward

    Directory of Open Access Journals (Sweden)

    Lauren M. DePoy

    2017-01-01

    Full Text Available Circadian rhythms are endogenously generated near 24-hour variations of physiological and behavioral functions. In humans, disruptions to the circadian system are associated with negative health outcomes, including metabolic, immune, and psychiatric diseases, such as addiction. Animal models suggest bidirectional relationships between the circadian system and drugs of abuse, whereby desynchrony, misalignment, or disruption may promote vulnerability to drug use and the transition to addiction, while exposure to drugs of abuse may entrain, disrupt, or perturb the circadian timing system. Recent evidence suggests natural (i.e., food and drug rewards may influence overlapping neural circuitry, and the circadian system may modulate the physiological and behavioral responses to these stimuli. Environmental disruptions, such as shifting schedules or shorter/longer days, influence food and drug intake, and certain mutations of circadian genes that control cellular rhythms are associated with altered behavioral reward. We highlight the more recent findings associating circadian rhythms to reward function, linking environmental and genetic evidence to natural and drug reward and related neural circuitry.

  13. Improving yield by exploiting mechanisms underlying natural variation of photosynthesis.

    Science.gov (United States)

    Lawson, Tracy; Kramer, David M; Raines, Christine A

    2012-04-01

    Increasing photosynthesis in C3 species has been identified as an approach to increase the yield of crop plants. Most of our knowledge of photosynthetic performance has come from studies in which plants were grown in controlled growth conditions but plants in natural environments have to cope with unpredictable and rapidly changing conditions. Plants adapt to the light environment in which they grow and this is demonstrated by the differences in anatomy and morphology of leaves in sun and shade leaves. Superimposed on this are the dynamic responses of plants to rapid changes in the light environment that occur throughout the day. Application of next generation sequencing (NGS), QTL analysis and innovative phenomic screening can provide information to underpin approaches for breeding of higher yielding crop plants. Copyright © 2012. Published by Elsevier Ltd.

  14. Understanding natural moisturizing mechanisms: implications for moisturizer technology.

    Science.gov (United States)

    Chandar, Prem; Nole, Greg; Johnson, Anthony W

    2009-07-01

    Dry skin and moisturization are important topics because they impact the lives of many individuals. For most individuals, dry skin is not a notable concern and can be adequately managed with current moisturizing products. However, dry skin can affect the quality of life of some individuals because of the challenges of either harsh environmental conditions or impaired stratum corneum (SC) dry skin protection processes resulting from various common skin diseases. Dry skin protection processes of the SC, such as the development of natural moisturizing factor (NMF), are complex, carefully balanced, and easily perturbed. We discuss the importance of the filaggrin-NMF system and the composition of NMF in both healthy and dry skin, and also reveal new insights that suggest the properties required for a new generation of moisturizing technologies.

  15. Natural electroweak symmetry breaking from scale invariant Higgs mechanism

    International Nuclear Information System (INIS)

    Farzinnia, Arsham; He, Hong-Jian; Ren, Jing

    2013-01-01

    We construct a minimal viable extension of the standard model (SM) with classical scale symmetry. Its scalar sector contains a complex singlet in addition to the SM Higgs doublet. The scale-invariant and CP-symmetric Higgs potential generates radiative electroweak symmetry breaking à la Coleman–Weinberg, and gives a natural solution to the hierarchy problem, free from fine-tuning. Besides the 125 GeV SM-like Higgs particle, it predicts a new CP-even Higgs (serving as the pseudo-Nambu–Goldstone boson of scale symmetry breaking) and a CP-odd scalar singlet (providing the dark matter candidate) at weak scale. We systematically analyze experimental constraints from direct LHC Higgs searches and electroweak precision tests, as well as theoretical bounds from unitarity, triviality and vacuum stability. We demonstrate the viable parameter space, and discuss implications for new Higgs searches at the upcoming LHC runs and the on-going direct detections of dark matter

  16. Structural controls and mechanisms of diffusion in natural silicate melts

    Science.gov (United States)

    Henderson, P.; Nolan, J.; Cunningham, G. C.; Lowry, R. K.

    1985-04-01

    trend. This and the other relationships are used to elucidate possible mechanisms of diffusion. Exchange mechanisms appear to be common, with the preservation of local charge balance. Li and Na diffuse by a distinct mechanism which involves exchange of similar or identical ions. The diffusion behaviour of the smaller alkali metal ions is sufficiently distinct from all other cations to indicate that diffusion could be an important factor in the geochemical fractionation of the alkali elements.s

  17. Puncture mechanics of cnidarian cnidocysts: a natural actuator

    Directory of Open Access Journals (Sweden)

    Eddington David T

    2009-09-01

    Full Text Available Abstract Background Cnidocysts isolated from cnidarian organisms are attractive as a drug-delivery platform due to their fast, efficient delivery of toxins. The cnidocyst could be utilized as the means to deliver therapeutics in a wearable drug-delivery patch. Cnidocysts have been previously shown to discharge upon stimulation via electrical, mechanical, and chemical pathways. Cnidocysts isolated from the Portuguese Man O' War jellyfish (Physalia physalis are attractive for this purpose because they possess relatively long threads, are capable of puncturing through hard fish scales, and are stable for years. Results As a first step in using cnidocysts as a functional component of a drug delivery system, the puncture mechanics of the thread were characterized. Tentacle-contained cnidocysts were used as a best-case scenario due to physical immobilization of the cnidocysts within the tentacle. Ex vivo tentacle-contained cnidocysts from Physalia possessed an elastic modulus puncture threshold of approximately 1-2 MPa, based on puncture tests of materials with a gamut of hardness. Also, a method for inducing discharge of isolated cnidocysts was found, utilizing water as the stimulant. Preliminary lectin-binding experiments were performed using fluorophore-conjugated lectins as a possible means to immobilize the isolated cnidocyst capsule, and prevent reorientation upon triggering. Lectins bound homogeneously to the surface of the capsule, suggesting the lectins could be used for cnidocyst immobilization but not orientation. Conclusion Cnidocysts were found to puncture materials up to 1 MPa in hardness, can be discharged in a dry state using water as a stimulant, and bind homogeneously to lectins, a potential means of immobilization. The information gained from this preliminary work will aid in determining the materials and design of the patch that could be used for drug delivery.

  18. Mathematical Model for Supercritical Fluid Extraction of Natural Products and Extraction Curve Evaluation

    Czech Academy of Sciences Publication Activity Database

    Sovová, Helena

    2005-01-01

    Roč. 33, č. 1 (2005), s. 35-52 ISSN 0896-8446 R&D Projects: GA AV ČR IAA4072102 Institutional research plan: CEZ:AV0Z4072921 Keywords : supercritical extraction * natural products * model Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.144, year: 2005

  19. Mechanism and physiologic significance of the suppression of cholesterol esterification in human interstitial fluid

    Directory of Open Access Journals (Sweden)

    Norman Eric Miller

    2016-07-01

    Full Text Available Cholesterol esterification in high density lipoproteins (HDLs by lecithin:cholesterol acyltransferase (LCAT promotes unesterified cholesterol (UC transfer from red cell membranes to plasma in vitro. However, it does not explain the transfer of UC from most peripheral cells to interstitial fluid in vivo, as HDLs in afferent peripheral lymph are enriched in UC. Having already reported that the endogenous cholesterol esterification rate (ECER in lymph is only five per cent of that in plasma, we have now explored the underlying mechanism. In peripheral lymph from 20 healthy men, LCAT concentration, LCAT activity (assayed using an optimized substrate, and LCAT specific activity averaged respectively 11.8, 10.3, and 84.9 per cent of plasma values. When recombinant human LCAT was added to lymph, the increments in enzyme activity were similar to those when LCAT was added to plasma. Addition of apolipoprotein AI (apo AI, fatty acid-free albumin, Intralipid, or the d<1.006 g/ml plasma fraction had no effect on ECER. During incubation of lymph plus plasma, the ECER was similar to that observed with buffer plus plasma. When lymph was added to heat-inactivated plasma, the ECER was 11-fold greater than with lymph plus buffer. Addition of discoidal proteoliposomes of apo AI and phosphatidycholine (PC to lymph increased ECER ten-fold, while addition of apo AI/PC/UC discs did so by only six-fold. We conclude that the low ECER in lymph is due to a property of the HDLs, seemingly substrate inhibition of LCAT by excess cell-derived UC. This is reversed when lymph enters plasma, consequent upon redistribution of UC from lymph HDLs to plasma lipoproteins.

  20. An experimental study of the fluid mechanics associated with porous walls

    Science.gov (United States)

    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.

  1. 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.

  2. Natural aggregate totally replacement by mechanically treated concrete waste

    Directory of Open Access Journals (Sweden)

    Junak Jozef

    2015-06-01

    Full Text Available This paper presents the results obtained from the research focused on the utilization of crushed concrete waste aggregates as a partial or full replacement of 4/8 and 8/16 mm natural aggregates fraction in concrete strength class C 16/20. Main concrete characteristics such as workability, density and compressive strength were studied. Compressive strength testing intervals for samples with recycled concrete aggregates were 2, 7, 14 and 28 days. The amount of water in the mixtures was indicative. For mixture resulting consistency required slump grade S3 was followed. Average density of all samples is in the range of 2250 kg/m3 to 2350 kg/m3. The highest compressive strength after 28 days of curing, 34.68 MPa, reached sample, which contained 100% of recycled material in 4/8 mm fraction and 60% of recycled aggregates in 8/16 mm fraction. This achieved value was only slightly different from the compressive strength 34.41 MPa of the reference sample.

  3. Positive Fluid Balance Is Associated with Higher Mortality and Prolonged Mechanical Ventilation in Pediatric Patients with Acute Lung Injury

    Directory of Open Access Journals (Sweden)

    Heidi R. Flori

    2011-01-01

    Full Text Available Introduction. We analyzed a database of 320 pediatric patients with acute lung injury (ALI, to test the hypothesis that positive fluid balance is associated with worse clinical outcomes in children with ALI. Methods. This is a post-hoc analysis of previously collected data. Cumulative fluid balance was analyzed in ml per kilogram per day for the first 72 hours after ALI while in the PICU. The primary outcome was mortality; the secondary outcome was ventilator-free days. Results. Positive fluid balance (in increments of 10 mL/kg/24 h was associated with a significant increase in both mortality and prolonged duration of mechanical ventilation, independent of the presence of multiple organ system failure and the extent of oxygenation defect. These relationships remained unchanged when the subgroup of patients with septic shock (n=39 were excluded. Conclusions. Persistently positive fluid balance may be deleterious to pediatric patients with ALI. A confirmatory, prospective randomized controlled trial of fluid management in pediatric patients with ALI is warranted.

  4. Flectofin: a hingeless flapping mechanism inspired by nature.

    Science.gov (United States)

    Lienhard, J; Schleicher, S; Poppinga, S; Masselter, T; Milwich, M; Speck, T; Knippers, J

    2011-12-01

    This paper presents a novel biomimetic approach to the kinematics of deployable systems for architectural purposes. Elastic deformation of the entire structure replaces the need for local hinges. This change becomes possible by using fibre-reinforced polymers (FRP) such as glass fibre reinforced polymer (GFRP) that can combine high tensile strength with low bending stiffness, thus offering a large range of calibrated elastic deformations. The employment of elasticity within a structure facilitates not only the generation of complex geometries, but also takes the design space a step further by creating elastic kinetic structures, here referred to as pliable structures. In this paper, the authors give an insight into the abstraction strategies used to derive elastic kinetics from plants, which show a clear interrelation of form, actuation and kinematics. Thereby, the focus will be on form-finding and simulation methods which have been adopted to generate a biomimetic principle which is patented under the name Flectofin®. This bio inspired hingeless flapping device is inspired by the valvular pollination mechanism that was derived and abstracted from the kinematics found in the Bird-Of-Paradise flower (Strelitzia reginae, Strelitziaceae).

  5. Flectofin: a hingeless flapping mechanism inspired by nature

    International Nuclear Information System (INIS)

    Lienhard, J; Schleicher, S; Knippers, J; Poppinga, S; Masselter, T; Milwich, M; Speck, T

    2011-01-01

    This paper presents a novel biomimetic approach to the kinematics of deployable systems for architectural purposes. Elastic deformation of the entire structure replaces the need for local hinges. This change becomes possible by using fibre-reinforced polymers (FRP) such as glass fibre reinforced polymer (GFRP) that can combine high tensile strength with low bending stiffness, thus offering a large range of calibrated elastic deformations. The employment of elasticity within a structure facilitates not only the generation of complex geometries, but also takes the design space a step further by creating elastic kinetic structures, here referred to as pliable structures. In this paper, the authors give an insight into the abstraction strategies used to derive elastic kinetics from plants, which show a clear interrelation of form, actuation and kinematics. Thereby, the focus will be on form-finding and simulation methods which have been adopted to generate a biomimetic principle which is patented under the name Flectofin®. This bio inspired hingeless flapping device is inspired by the valvular pollination mechanism that was derived and abstracted from the kinematics found in the Bird-Of-Paradise flower (Strelitzia reginae, Strelitziaceae).

  6. Semiclassical statistical mechanics of two-dimensional hard-body fluids.

    Science.gov (United States)

    Karki, Shanker S; Karki, Bimal P; Dey, Tarun K; Sinha, Suresh K

    2005-01-01

    The problem of calculating the thermodynamic properties of two-dimensional semiclassical hard-body fluids is studied. Explicit expressions are given for the first-order quantum corrections to the free energy, equation of state, and virial coefficients. The numerical results are calculated for the planar hard dumbbell fluid. Significant features are the increase in quantum corrections with increasing eta and increasing L*=L/sigma(0). (c) 2005 American Institute of Physics.

  7. The fluid control mechanism of bionic structural heterogeneous composite materials and its potential application in enhancing pump efficiency

    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.

  8. Computational Fluid Dynamics Modeling to Improve Natural Flow Rate and Sweet Pepper Productivity in Greenhouse

    OpenAIRE

    W. Limtrakarn; P. Boonmongkol; A. Chompupoung; K. Rungprateepthaworn; J. Kruenate; P. Dechaumphai

    2012-01-01

    Natural flow rate and sweet peppers productivity in tropical greenhouse are improved by CFD simulation is the main objective of this research work. Most of the greenhouse types today are in the arch shape. To develop an improved greenhouse structure for the region, the arch type was built and used as the control model. Mae Sar Mai agriculture research station under the royal project foundation was selected as the field test site. Temperature sensors with data logger were installed to monitor ...

  9. Magneto-Fluid Dynamics Fundamentals and Case Studies of Natural Phenomena

    CERN Document Server

    Lorrain, Paul; Houle, Stéphane

    2006-01-01

    This book concerns the generation of electric currents and of electric space charges inside conducting media that move in magnetic fields. The authors postulate nothing but the Maxwell equations. They discuss at length the disk dynamo, which serves as a model for the natural self-excited dynamos that generate magnetic fields such as that of sunspots. There are 36 Examples and 13 Case Studies. The Case Studies concern solar phenomena -- magnetic elements, sunspots, spicules, coronal loops -- and the Earth's magnetic field.

  10. Valuable natural products from marine and freshwater macroalgae obtained from supercritical fluid extracts.

    Science.gov (United States)

    Messyasz, Beata; Michalak, Izabela; Łęska, Bogusława; Schroeder, Grzegorz; Górka, Bogusława; Korzeniowska, Karolina; Lipok, Jacek; Wieczorek, Piotr; Rój, Edward; Wilk, Radosław; Dobrzyńska-Inger, Agnieszka; Górecki, Henryk; Chojnacka, Katarzyna

    2018-01-01

    The biologically active compounds (fatty acids, pigments, phenolics, and flavonoid content) were studied in supercritical fluid extracts from the biomass of marine ( Ulva clathrata , Cladophora glomerata , Polysiphonia fucoides , and their multi-species mixture) and freshwater ( C. glomerata ) macroalgae. Different extraction techniques were used in order to compare differences in the biologically active compound composition of the macroalgal extracts. The results indicated that the saturated and unsaturated fatty acids ranged from C9:0 to C22:0. The analysis of differences in the composition of unsaturated to saturated fatty acids in extracts showed that palmitic acid (C16:0) and oleic acid (C18:1, n-9) reached the highest value not only in marine monospecies and multi-species biomass but also in the freshwater macroalga C. glomerata . When comparing the similarity between the concentration of fatty acids and the ratio of the concentration of unsaturated fatty acids to saturated in macroalgal extracts, we found small but not statistically significant variations in values between years (up to 10%). This is acceptable for applications as a stable raw material for industrial purposes. Significantly higher values of fatty acids, carotenoids, and chlorophylls were obtained in the case of SC-CO 2 extraction. The active ingredients of polyphenols, possessing antioxidant activity ranged from approximately 2-4%. Moreover, flavonoids represented less than 10% of the total content of polyphenolic compounds. The extraction efficiency of polyphenols was higher from a mixture of marine algae for the ultrasound-assisted extraction compared to freshwater. All these findings show that marine and freshwater macroalgae, as a raw material, have the optimal biologically active compounds composition for cosmetics.

  11. Evaluation of some natural water-insoluble cellulosic material as lost circulation control additives in water-based drilling fluid

    Directory of Open Access Journals (Sweden)

    Ahmed Mohamed Alsabagh

    2015-12-01

    In this work, three natural water-insoluble cellulosic materials; peanut hulls, bagasse and sawdust were investigated as lost circulation control materials. One hundred and eight different LCM samples made of various materials were tested with mud. The experiments were conducted in a permeability plugging apparatus (PPA at a differential pressure of 100 psi and 300 psi, using 10, 60 and 90 ceramic discs. The performance of each LCM sample was determined based on the amount of spurt loss and total fluid loss of the mud according to the American Petroleum Institute (API standard. The obtained results showed that, the amount of the fluid loss depends on the LCM material, concentration and size distribution, testing results show that, the peanut gives the best results among the bagasse and sawdust, especially fine size which exhibited better results in the filtration characteristics due to the better filling properties of this size. Peanut hulls, bagasse and sawdust show a slight effect on the rheological properties of the mud. The results were discussed on light of particle size distribution.

  12. Evaluation of reduced chemical kinetic mechanisms used for modeling mild combustion for natural gas

    Directory of Open Access Journals (Sweden)

    Hamdi Mohamed

    2009-01-01

    Full Text Available A numerical and parametric study was performed to evaluate the potential of reduced chemistry mechanisms to model natural gas chemistry including NOx chemistry under mild combustion mode. Two reduced mechanisms, 5-step and 9-step, were tested against the GRI-Mech3.0 by comparing key species, such as NOx, CO2 and CO, and gas temperature predictions in idealized reactors codes under mild combustion conditions. It is thus concluded that the 9-step mechanism appears to be a promising reduced mechanism that can be used in multi-dimensional codes for modeling mild combustion of natural gas.

  13. Natural phenolic antioxidants in human fluids: analytical approaches and antioxidant capacity studies

    International Nuclear Information System (INIS)

    Zhang, K.; Zuo, Y.

    2006-01-01

    Phenolic compounds are the most abundant natural antioxidants in our diet. Epidemiological studies have shown the possible prevention effects of consumption of fruits and vegetables rich in phenolic compounds on degenerative diseases, such as cardiovascular diseases and cancers. However, there is a serious lack of fundamental knowledge on the uptake and metabolism of phenolic compounds in humans. It is clear that phenolic molecules, only absorbed by humans, can exert biological effects. This review presents a current knowledge on the analytical methods, antioxidant capacity measurements, as well as research strategies related to natural phenolic antioxidants on human health. Both GC-MS and LC-MS have proved to be very useful analytical techniques that can be employed to identify and quantitate targeted phenolic antioxidants and their metabolites in biofluids. Free radical quenching tests provide a direct measurement of antioxidant capacity but lack specificity and may oversimplify the in vivo human physiological environment. Research strategies are diverse and mainly focused on positive health effect of antioxidants. In the future studies, multiple potential bioactivities, both positive and negative, should be considered. (author)

  14. Flippin' Fluid Mechanics - Quasi-experimental Pre-test and Post-test Comparison Using Two Groups

    Science.gov (United States)

    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.

  15. An integrated mechanism of pediatric pseudotumor cerebri syndrome: evidence of bioenergetic and hormonal regulation of cerebrospinal fluid dynamics.

    Science.gov (United States)

    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.

  16. The influence of different inflow configurations on computational fluid dynamics in a novel three-leaflet mechanical heart valve prosthesis.

    Science.gov (United States)

    Sievers, Hans-Hinrich; Schubert, Kathrin; Jamali, Ashkan; Scharfschwerdt, Michael

    2018-03-30

    A novel mechanical heart valve was developed with a special focus on avoiding anticoagulation. Computational fluid dynamics were used for the research design. Here, the effect of different anatomical inflow geometries on flow characteristics is evaluated. Flow and pressure simulations were performed on a novel 3-leaflet mechanical heart valve in a fully open position at 2 flow rates related to the peak and end-systolic flow. The computational fluid dynamics model was designed according to 4 different (1 cylindrical, 3 conical with increasing diameter) anatomical configurations of the left ventricular outflow tract derived from an inverse heart model. With increasing inflow diameter, the flow velocity decreased for both flow rates, from 1543 mm/s in cylindrical configuration to 1475 mm/s in conical configuration for a flow rate of 18 l/min. However, there was no further decrease for the inflow diameters 38 and 48 mm. The velocity profile became broader with increasing inflow diameter and the maximal pressure decreased. At the leading edge, velocity almost stagnated, while the pressure increased and the reflection point moved downstream. No occurrence of dead space was observed with the different configurations and flow rates. An analysis of different anatomical inflow configurations by computational fluid dynamic simulations showed a more homogenous velocity profile and lower flow velocity values with increasing inflow diameter up to 38 mm in this novel 3-leaflet mechanical heart valve.

  17. Thermodynamic and fluid mechanic analysis of rapid pressurization in a dead-end tube

    Science.gov (United States)

    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

  18. The mechanism of propulsion of a model microswimmer in a viscoelastic fluid next to a solid boundary

    Science.gov (United States)

    Ives, Thomas R.; Morozov, Alexander

    2017-12-01

    In this paper, we study the swimming of a model organism, the so-called Taylor's swimming sheet, in a viscoelastic fluid close to a solid boundary. This situation comprises natural habitats of many swimming microorganisms, and while previous investigations have considered the effects of both swimming next to a boundary and swimming in a viscoelastic fluid, seldom have both effects been considered simultaneously. We re-visit the small wave amplitude result obtained by Elfring and Lauga ["Theory of locomotion through complex fluids," in Complex Fluids in Biological Systems, Biological and Medical Physics, Biomedical Engineering, edited by S. E. Spagnolie (Springer New York, New York, NY, 2015), pp. 283-317] and give a mechanistic explanation to the decoupling of the effects of viscoelasticity, which tend to slow the sheet, and the presence of the boundary, which tends to speed up the sheet. We also develop a numerical spectral method capable of finding the swimming speed of a waving sheet with an arbitrary amplitude and waveform. We use it to show that the decoupling mentioned earlier does not hold at finite wave amplitudes and that for some parameters the presence of a boundary can cause the viscoelastic effects to increase the swimming speed of microorganisms.

  19. Enhancement of mechanical properties and interfacial adhesion by chemical odification of natural fibre reinforced polypropylene composites

    CSIR Research Space (South Africa)

    Erasmus, E

    2008-11-01

    Full Text Available , to improve their mechanical properties. Various chemical treatments with acrylic acid, 4-pentanoic acid, 2,4-pentadienoic acid and 2-methyl-4-pentanoic acid were investigated. The natural fibre reinforced polypropylene composites were processed by compression...

  20. Mechanical properties of uniaxial natural fabric Grewia tilifolia reinforced epoxy based composites: Effects of chemical treatment

    CSIR Research Space (South Africa)

    Jayaramudu, J

    2014-07-01

    Full Text Available The effects of chemical treatment on the mechanical, morphological, and chemical resistance properties of uniaxial natural fabrics, Grewia tilifolia/epoxy composites, were studied. In order to enhance the interfacial bonding between the epoxy matrix...

  1. Experimental study of chemical-mechanical coupling during percolation of reactive fluid through rocks under stress, in the context of the CO{sub 2} geological sequestration; Etude experimentale du couplage chimie-mecanique lors de la percolation d'un fluide reactif dans des roches sous contrainte, dans le contexte de la sequestration geologique du CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Le Guen, Y

    2006-10-15

    CO{sub 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{sub 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{sup -12} s{sup -1} on the strain rate. Simultaneously, fluids were analysed in order to quantify fluid-rock interactions. For limestone samples, percolation of CO{sub 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{sub 2} which increases rock solubility and reaction kinetics. On the opposite, small effect of CO{sub 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)

  2. Pengembangan Tungku Gasifikasi Arang Biomassa Tipe Natural Draft Gasification Berdasarkan Analisis Computational Fluid Dynamics (CFD

    Directory of Open Access Journals (Sweden)

    Erlanda Augupta Pane

    2014-10-01

    Full Text Available A biomass stove based on natural draft gasification (NDG has been developed in a previous study (Nelwa, et al. 2013 by using simulation based on heat transfer and equilibrium modeling. In this study, a CFD simulation was performed in order to analyze the effect of chimney height, and inlet hole diameter of the stove to the performance of the stove. The results of simulation showed that power produced by stove was between 1863.9 J/s until 2585.7 J/s, and its gasification efficiency was 67.11%. The results of simulation also showed that charcoal gasification produces combustible gases (CO, CH4, and H2 at the bottom and the center of stove, and then they were oxidized by secondary air at the top of stove. This oxidation reaction produces sufficient heat energy which can be used for cooking process.

  3. Natural convection in a horizontal fluid layer periodically heated from above and below.

    Science.gov (United States)

    Hossain, M Z; Floryan, J M

    2015-08-01

    Natural convection in a horizontal slot heated from above and from below has been considered. Each heating has a certain spatial distribution. It has been demonstrated that a wide variety of convection patterns can be generated by changing the relative position of both heating patterns. A significant intensification of convection, compared to convection resulting from heating applied at one wall only, results if there is no phase shift between both patterns, while a significant reduction of convection results from the phase shift corresponding to half of the heating wavelength. The system generates a nonzero mean shear stress at each wall for all phase shifts except shifts corresponding to half of and one full heating wavelength. This effect, which is generated within one convection cell, gives rise to a global force which may lead to a thermally induced drift of the walls if such a drift was allowed.

  4. Darboux Transformation and Soliton Solutions for a Variable-Coefficient Modified Kortweg-de Vries Model from Fluid Mechanics, Ocean Dynamics, and Plasma Mechanics

    International Nuclear Information System (INIS)

    Gai Xiaoling; Gao Yitian; Meng Dexin; Wang Lei; Sun Zhiyuan; Feng Qian; Wang Mingzhen; Yu Xin; Zhu Shunhui; Lue Xing

    2010-01-01

    This paper is to investigate a variable-coefficient modified Kortweg-de Vries (vc-mKdV) model, which describes some situations from fluid mechanics, ocean dynamics, and plasma mechanics. By the Ablowitz-Kaup-Newell-Segur procedure and symbolic computation, the Lax pair of the vc-MKdV model is derived. Then, based on the aforementioned Lax pair, the Darboux transformation is constructed and a new one-soliton-like solution is obtained as well. Features of the one-soliton-like solution are analyzed and graphically discussed to illustrate the influence of the variable coefficients in the solitonlike propagation. (general)

  5. A computational analysis on homogeneous-heterogeneous mechanism in Carreau fluid flow

    Science.gov (United States)

    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.

  6. [Coupled Analysis of Fluid-Structure Interaction of a Micro-Mechanical Valve for Glaucoma Drainage Devices].

    Science.gov (United States)

    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

  7. High performance nature of biodegradable polymeric nanocomposites for oil-well drilling fluids

    Directory of Open Access Journals (Sweden)

    Tarek M. Madkour

    2016-06-01

    Full Text Available Multi-walled carbon nanotube (MWCNT and graphene nanoplatelet reinforced thermoplastic poly(lactic acid (PLA biodegradable nanocomposites were designed and prepared using solution casting techniques. The prepared biodegradable polymers are expected to provide an environmentally friendly alternative to petroleum-based polymers. Both nanocomposite systems exhibited better thermal stability and improved mechanical performance over the unreinforced polymer exhibiting excellent strength and degradability. The addition of graphene nanofiller in varied amounts was aimed to enhance the thermal and mechanical properties of the nanocomposites even further and incorporate the outstanding characteristics of graphene nanoplatelets into the nanocomposites. The polymeric nanocomposites showed also superior advantages for oil drilling relevances, automotive lubricating purposes, membrane technology and food packaging. Scanning electron microscopy images indicated a homogeneous dispersion of the nanofiller within the polymeric matrix at low filler loadings and a cluster formation at higher loadings that could be responsible for the polymeric matrix movement restrictions. The enthalpy of mixing (the polymer and the nanofiller measured could explain the cause of the repulsive interactions between the nanoparticles and the polymeric chains, which created an additional excluded volume that the polymeric segments were restricted to occupy, thus forcing the conformational characteristics of the polymeric chains to deviate away from those of the bulk chains. The prepared polymeric nano composites (poly lactic acid carbon nano tube and poly lactic acid graphene nanoplatelets were utilized in the formulation of oil-base mud as a viscosifier. The rheological, filtration properties and electrical stability of the oil based mud formulation with the new polymeric nanocomposite were studied and the result compared to the oil-based mud formulation with commercial viscosifier.

  8. Relationship of adsorption mechanism of antigens by aluminum-containing adjuvants to in vitro elution in interstitial fluid.

    Science.gov (United States)

    Jiang, Dongping; Morefield, Garry L; HogenEsch, Harm; Hem, Stanley L

    2006-03-06

    The objective of this research was to determine how the mechanism by which antigens adsorb to aluminum-containing adjuvants affects the elution upon exposure to interstitial fluid. Antigens (alpha lactalbumin, bovine serum albumin, lysozyme and myoglobin) that adsorb to aluminum-containing adjuvants principally by electrostatic attraction were found to elute readily in vitro when exposed to interstitial fluid. Phosphorylated antigens (alpha casein, hepatitis B surface antigen and phosphorylated bovine serum albumin) that adsorb to aluminum-containing adjuvants principally by ligand exchange exhibit little if any elution during 12-24 h in vitro exposure to interstitial fluid. Dephosphorylated alpha casein, which contains less than two phosphate groups, was less strongly adsorbed by ligand exchange in comparison to alpha casein, which contains eight phosphate groups. Dephosphorylated alpha casein was completely eluted when exposed to interstitial fluid. The results of this study lead to the generalization that antigens that adsorb to aluminum-containing adjuvants by electrostatic attraction are more likely to elute upon intramuscular or subcutaneous administration than antigens that adsorb by ligand exchange.

  9. Time-resolved PIV technique for high temporal resolution measurement of mechanical prosthetic aortic valve fluid dynamics.

    Science.gov (United States)

    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

  10. The application of computational fluid dynamics to natural river channels: Eddy resolving versus mean flow approaches

    Science.gov (United States)

    Keylock, C. J.; Constantinescu, G.; Hardy, R. J.

    2012-12-01

    In the last decade, as computing power has increased, there has been an explosion in the use of eddy-resolving numerical methods in the engineering, earth and environmental sciences. For complex geomorphic flows, where accurate field investigations are difficult to perform and where experiments may be difficult to scale, these numerical approaches are beginning to give key insights into the nature of these flows. Eddy-resolving methods such as Large and Detached Eddy Simulation (LES/DES) may be contrasted with the time-averaged, three-dimensional simulations that only really began to be applied seriously in geomorphology fifteen years ago. While the potential of LES for geomorphology has been examined previously, DES is a relatively recent method that deserves further consideration. In this paper, we explain the method and then utilise examples from meander and confluence flows, as well as flow near the bed of a gravel bed river, to highlight the improvements to both the representation of the mean flow, and to the representation of time-varying processes, that result from the use of LES/DES. Some suggestions are provided for the future use of such techniques in geomorphology.

  11. Computational Fluid Dynamics Modeling to Improve Natural Flow Rate and Sweet Pepper Productivity in Greenhouse

    Directory of Open Access Journals (Sweden)

    W. Limtrakarn

    2012-01-01

    Full Text Available Natural flow rate and sweet peppers productivity in tropical greenhouse are improved by CFD simulation is the main objective of this research work. Most of the greenhouse types today are in the arch shape. To develop an improved greenhouse structure for the region, the arch type was built and used as the control model. Mae Sar Mai agriculture research station under the royal project foundation was selected as the field test site. Temperature sensors with data logger were installed to monitor variation of temperature inside the greenhouse. The measured temperature data were used as the boundary conditions for the CFD analysis. A new greenhouse model with two-step roof shape was designed and the air flow behavior was simulated by using CFD. Regarding CFD results the air flow rate of the new model is about 39% higher than that of old model. The maximum temperature of the new model is lower than that of the old one. The sweet paper growths in both greenhouse models were measured and compared. Results show that the new model obtains 4°C lower maximum temperature in day time, 97% in number and 90% in weight higher the first grade pepper productivity than the old one.

  12. Grain-scale numerical modeling of granular mechanics and fluid dynamics and application in a glacial context

    DEFF Research Database (Denmark)

    Damsgaard, Anders; Egholm, David Lundbek; Beem, Lucas H.

    , 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-dynamics...... rheology, which limit our ability to predict ice sheet dynamics in a changing climate. In this talk I will present the soft-body Discrete Element Method which is a Lagrangian method I use in order to simulate the unique and diverse nature of granular dynamics in the subglacial environment. However...... solver in order to include grain-fluid feedbacks, which prove to be important for stick-slip behavior of glaciers. All code is open source and freely licensed....

  13. Andreas Acrivos Dissertation Award: Onset of Dynamic Wetting Failure - The Mechanics of High-Speed Fluid Displacement

    Science.gov (United States)

    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

  14. Assessing the Effect of Natural and Induced Fractures on Long-Term CO2 Storage in the Northern Appalachian Basin Using Thermo-Hydro-Mechanical Modeling

    Science.gov (United States)

    Raziperchikolaee, S.; Kelley, M. E.; Main, J.

    2017-12-01

    Natural and induced fractures in a caprock could allow CO2 to migrate out of the intended storage reservoirs in the CO2 sequestration process. We evaluate, through the use of coupled hydro-mechanical numerical modeling, the effectiveness of the Cambrian-Ordovician caprock system in the northern Appalachian Basin for providing long-term containment of CO2 in the presence of existing and induced fractures. Resistivity image and acoustic image logs from wells in the study area were used characterize natural fractures in the caprock zone. The logs showed no compelling evidence of pervasive natural fracturing of the caprock; however, limited natural fractures occur in small isolated patches. Therefore, we modeled natural fractures as isolated features of limited size using the dual-porosity method. The modeling results show that the caprock is effective at preventing CO2 breakthrough in the presence of a natural fracture that partially penetrates the caprock; however, the caprock would be ineffective for containing CO2 if the fracture fully penetrates caprock. To assess induced fractures, coupled fluid-flow, geomechanical, and fracture mechanics modeling was conducted to model the effect of an induced fracture on the sealing integrity of the caprock. First, a fracture mechanics model was used to generate the injection-induced hydraulic fracture and calculate its dimensions (height, length, width). Then, a fluid-flow model was used to evaluate the impacts of the fracture on caprock sealing effectiveness. A significant observation is that the hydraulic fracture was confined to the reservoir (Rose Run sandstone) and did not extend upward into the caprock because the reservoir has the lower minimum horizontal stress. Our study shows that both natural and induced fractures can affect long term CO2 storage depending on size of natural fracture zone, geological and geomechanical properties of reservoir and caprock formations as well as injection parameters.

  15. 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

  16. Mechanisms underlying rhythmic locomotion: body–fluid interaction in undulatory swimming

    Science.gov (United States)

    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

  17. Mechanisms underlying rhythmic locomotion: body-fluid interaction in undulatory swimming.

    Science.gov (United States)

    Chen, J; Friesen, W O; Iwasaki, T

    2011-02-15

    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.

  18. Home blood sodium monitoring, sliding-scale fluid prescription and subcutaneous DDAVP for infantile diabetes insipidus with impaired thirst mechanism

    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.

  19. Natural convection in Bingham plastic fluids from an isothermal spheroid: Effects of fluid yield stress, viscous dissipation and temperature-dependent viscosity

    Science.gov (United States)

    Gupta, Anoop Kumar; Gupta, Sanjay; Chhabra, Rajendra Prasad

    2017-08-01

    In this work, the buoyancy-induced convection from an isothermal spheroid is studied in a Bingham plastic fluid. Extensive results on the morphology of approximate yield surfaces, temperature profiles, and the local and average Nusselt numbers are reported to elucidate the effects of the pertinent dimensionless parameters: Rayleigh number, 102 ≤ Ra ≤ 106; Prandtl number, 20 ≤ Pr ≤ 100; Bingham number, 0 ≤ Bn ≤ 103, and aspect ratio, 0.2 ≤ e ≤ 5. Due to the fluid yield stress, fluid-like (yielded) and solid-like (unyielded) regions coexist in the flow domain depending upon the prevailing stress levels vis-a-vis the value of the fluid yield stress. The yielded parts progressively grow in size with the rising Rayleigh number while this tendency is countered by the increasing Bingham and Prandtl numbers. Due to these two competing effects, a limiting value of the Bingham number ( Bn max) is observed beyond which heat transfer occurs solely by conduction due to the solid-like behaviour of the fluid everywhere in the domain. Such limiting values bear a positive dependence on the Rayleigh number ( Ra) and aspect ratio ( e). In addition to this, oblate shapes ( e 1) impede it. Finally, simple predictive expressions for the maximum Bingham number and the average Nusselt number are developed which can be used to predict a priori the overall heat transfer coefficient in a new application. Also, a criterion is developed in terms of the composite parameter Bn• Gr-1/2 which predicts the onset of convection in such fluids. Similarly, another criterion is developed which delineates the conditions for the onset of settling due to buoyancy effects. The paper is concluded by presenting limited results to delineate the effects of viscous dissipation and the temperature-dependent viscosity on the Nusselt number. Both these effects are seen to be rather small in Bingham plastic fluids.

  20. Computational and experimental fluid mechanics. Draft version of annex to final report for period January 1st 1993 to December 31st 1997

    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)

  1. Heat Transfer and Fluid Mechanics Institute, Meeting, 25th, University of California, Davis, Calif., June 21-23, 1976, Proceedings

    Science.gov (United States)

    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.

  2. Mechanical behavior of glass fiber polyester hybrid composite filled with natural fillers

    Science.gov (United States)

    Gupta, G.; Gupta, A.; Dhanola, A.; Raturi, A.

    2016-09-01

    Now-a-days, the natural fibers and fillers from renewable natural resources offer the potential to act as a reinforcing material for polymer composite material alternative to the use of synthetic fiber like as; glass, carbon and other man-made fibers. Among various natural fibers and fillers like banana, wheat straw, rice husk, wood powder, sisal, jute, hemp etc. are the most widely used natural fibers and fillers due to its advantages like easy availability, low density, low production cost and reasonable physical and mechanical properties This research work presents the effect of natural fillers loading with 5%, 10% and 15% on mechanical behavior of polyester based hybrid composites. The result of test depicted that hybrid composite has far better properties than single fibre glass reinforced composite under impact and flexural loads. However it is found that the hybrid composite have better strength as compared to single glass fibre composites.

  3. Mechanisms of arsenic enrichment in geothermal and petroleum reservoirs fluids in Mexico.

    Science.gov (United States)

    Birkle, Peter; Bundschuh, Jochen; Sracek, Ondra

    2010-11-01

    The lack of chemical similarity between thermal fluids in geothermal and petroleum reservoirs in Mexico indicates a distinct origin for arsenic in both types of reservoirs. Deep fluids from geothermal reservoirs along the Transmexican Volcanic Belt (TMVB) are characterized by elevated arsenic concentrations, within a range between 1 and 100 mg L(-1) at a depth from 600 to 3000 m b.s.l. Based on hierarchical cluster analysis (HCA), arsenic is linked to typical geothermal species like lithium, silica, and boron. The lack of correlation between arsenic and salinity reflects the importance of secondary water-rock interaction processes. The predominance of arsenic compared to Fe- and Cu-concentrations, and the occurrence of secondary minerals (sulfides and clay minerals) in temperature-dependent hydrothermal zones, supports this hypothesis. Neither magmatic fluids input, nor As mineralization is a prerequisite for As enrichment in Mexican geothermal fluids. In contrast, petroleum reservoir waters from sedimentary basins in SE-Mexico show maximum As concentrations of 2 mg L(-1), at depths from 2900 to 6100 m b.s.l. The linear chloride-arsenic correlation indicates that evaporated seawater represents the major source for aqueous arsenic in oil reservoirs, and only minor arsenic proportions are derived from interaction with carbonate host rock. Speciation modeling suggests the lack of arsenic solubility control in both geothermal and petroleum reservoirs, but precipitation/co-precipitation of As with secondary sulfides could occur in petroleum reservoirs with high iron concentrations. Geothermal fluids from magmatic-type reservoirs (Los Azufres and Los Humeros at the TMVB and Las Tres Vírgenes with a granodioritic basement) show relative constant arsenic concentrations through varying temperature conditions, which indicates that temperatures above 230-250 °C provide optimal and stable conditions for arsenic mobility. In contrast, temperature conditions for sedimentary

  4. Mechanism and materialism British natural philosophy in the age of reason

    CERN Document Server

    Schofield, Robert E

    1970-01-01

    Robert Schofield explores the rational elements of British experimental natural philosophy in the 18th century by tracing the influence of two opposing concepts of the nature of matter and its action-mechanism and materialism. Both concepts rested on the Newtonian interpretation of their proponents, although each developed more or less independently. By integrating the developments in all the areas of experimental natural philosophy, describing their connections and the influences of Continental science, natural theology, and to a lesser degree social and institutional changes, the author dem

  5. Thermo-fluid analysis of water cooled research reactors in natural convection; Analise termofluidodinamica de reatores nucleares de pesquisa refrigerados a agua em regime de conveccao natural

    Energy Technology Data Exchange (ETDEWEB)

    Veloso, Maria Auxiliadora Fortini

    2004-07-01

    The STHIRP-1 computer program, which fundamentals are described in this work, uses the principles of the subchannels analysis and has the capacity to simulate, under steady state and transient conditions, the thermal and hydraulic phenomena which occur inside the core of a water-refrigerated research reactor under a natural convection regime. The models and empirical correlations necessary to describe the flow phenomena which can not be described by theoretical relations were selected according to the characteristics of the reactor operation. Although the primary objective is the calculation of research reactors, the formulation used to describe the fluid flow and the thermal conduction in the heater elements is sufficiently generalized to extend the use of the program for applications in power reactors and other thermal systems with the same features represented by the program formulations. To demonstrate the analytical capacity of STHIRP-l, there were made comparisons between the results calculated and measured in the research reactor TRIGA IPR-R1 of CDTN/CNEN. The comparisons indicate that the program reproduces the experimental data with good precision. Nevertheless, in the future there must be used more consistent experimental data to corroborate the validation of the program. (author)

  6. Hydrodynamic instabilities in miscible fluids

    Science.gov (United States)

    Truzzolillo, Domenico; Cipelletti, Luca

    2018-01-01

    Hydrodynamic instabilities in miscible fluids are ubiquitous, from natural phenomena up to geological scales, to industrial and technological applications, where they represent the only way to control and promote mixing at low Reynolds numbers, well below the transition from laminar to turbulent flow. As for immiscible fluids, the onset of hydrodynamic instabilities in miscible fluids is directly related to the physics of their interfaces. The focus of this review is therefore on the general mechanisms driving the growth of disturbances at the boundary between miscible fluids, under a variety of forcing conditions. In the absence of a regularizing mechanism, these disturbances would grow indefinitely. For immiscible fluids, interfacial tension provides such a regularizing mechanism, because of the energy cost associated to the creation of new interface by a growing disturbance. For miscible fluids, however, the very existence of interfacial stresses that mimic an effective surface tension is debated. Other mechanisms, however, may also be relevant, such as viscous dissipation. We shall review the stabilizing mechanisms that control the most common hydrodynamic instabilities, highlighting those cases for which the lack of an effective interfacial tension poses deep conceptual problems in the mathematical formulation of a linear stability analysis. Finally, we provide a short overview on the ongoing research on the effective, out of equilibrium interfacial tension between miscible fluids.

  7. Hydrodynamic instabilities in miscible fluids.

    Science.gov (United States)

    Truzzolillo, Domenico; Cipelletti, Luca

    2018-01-24

    Hydrodynamic instabilities in miscible fluids are ubiquitous, from natural phenomena up to geological scales, to industrial and technological applications, where they represent the only way to control and promote mixing at low Reynolds numbers, well below the transition from laminar to turbulent flow. As for immiscible fluids, the onset of hydrodynamic instabilities in miscible fluids is directly related to the physics of their interfaces. The focus of this review is therefore on the general mechanisms driving the growth of disturbances at the boundary between miscible fluids, under a variety of forcing conditions. In the absence of a regularizing mechanism, these disturbances would grow indefinitely. For immiscible fluids, interfacial tension provides such a regularizing mechanism, because of the energy cost associated to the creation of new interface by a growing disturbance. For miscible fluids, however, the very existence of interfacial stresses that mimic an effective surface tension is debated. Other mechanisms, however, may also be relevant, such as viscous dissipation. We shall review the stabilizing mechanisms that control the most common hydrodynamic instabilities, highlighting those cases for which the lack of an effective interfacial tension poses deep conceptual problems in the mathematical formulation of a linear stability analysis. Finally, we provide a short overview on the ongoing research on the effective, out of equilibrium interfacial tension between miscible fluids.

  8. Impact of melting heat transfer and nonlinear radiative heat flux mechanisms for the generalized Burgers fluids

    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

  9. 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

  10. Hydraulic and mechanical properties of natural fractures in low-permeability rock

    International Nuclear Information System (INIS)

    Pyrack-Nolte, L.J.; Myer, L.R.; Cook, N.G.W.; Witherspoon, P.A.

    1987-01-01

    The results of a comprehensive laboratory study of the mechanical displacement, permeability, and void geometry of single rock fractures in a quartz monzonite are summarized and analyzed. A metal-injection technique was developed that provided quantitative data on the precise geometry of the void spaces between the fracture surfaces and the areas of contact at different stresses. At effective stresses of less than 20 MPa fluid flow was proportional to the mean fracture aperture raised to a power greater than 3. As stress was increased, contact area was increased and void spaces become interconnected by small tortuous channels that constitute the principal impediment to fluid flow. At effective stresses higher than 20 MPa, the mean fracture aperture continued to diminish with increasing stress, but this had little effect on flow because the small tortuous flow channels deformed little with increasing stress

  11. Mechanical behavior of concrete and related porous materials under partial saturation: The effective stress and the viscous softening due to movement of nanometer-scale pore fluid

    Science.gov (United States)

    Vlahinic, Ivan

    It has been said that porous materials are like music: the gaps are as important as the filled-in bits. In other words, in addition to the solid structure, pore characteristics such as size and morphology play a crucial role in defining the overall physical properties of the porous materials. This work goes a step further and examines the behaviors of some porous media that arise when the pore network is occupied by two fluids, principally air and water, as a result of drying or wetting. Such a state gives rise to fluid capillarity which can generate significant negative fluid pressures. In the first part, a constitutive model for drying of an elastic porous medium is proposed and then extended to derive a novel expression for effective stress in partially saturated media. The model is motivated by the fact that in a system that is saturated by two different fluids, two different pressure inherently act on the surfaces of the pore network. This causes a non-uniform strain field in the solid structure, something that is not explicitly accounted for in the classic formulations of this problem. We use some standard micromechanical homogenization techniques to estimate the extent of the 'non-uniformity' and on this basis, evaluate the validity of the classic Bishop effective stress expression for partially saturated materials. In the second part, we examine a diverse class of porous materials which behave in an unexpected (and even counterintuitive) way under the internal moisture fluctuations. In particular, during wetting and drying alike, the solid viscosity of these materials appears to soften, sometimes by an order of magnitude or more. Under load, this can lead to significantly increased rates of deformations. On account of the recent experimental and theoretical findings on the nature of water flow in nanometer-size hydrophillic spaces, we provide a physical explanation for the viscous softening and propose a constitutive law on this basis. To this end, it also

  12. Improving students' meaningful learning on the predictive nature of quantum mechanics

    Directory of Open Access Journals (Sweden)

    Rodolfo Alves de Carvalho Neto

    2009-03-01

    Full Text Available This paper deals with research about teaching quantum mechanics to 3rd year high school students and their meaningful learning of its predictive aspect; it is based on the Master’s dissertation of one of the authors (CARVALHO NETO, 2006. While teaching quantum mechanics, we emphasized its predictive and essentially probabilistic nature, based on Niels Bohr’s complementarity interpretation (BOHR, 1958. In this context, we have discussed the possibility of predicting measurement results in well-defined experimental contexts, even for individual events. Interviews with students reveal that they have used quantum mechanical ideas, suggesting their meaningful learning of the essentially probabilistic predictions of quantum mechanics.

  13. A new technique in constructing closed-form solutions for nonlinear PDEs appearing in fluid mechanics and gas dynamics

    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.

  14. Benefits of using natural ester fluids in insulation systems; Beneficios do uso de fluidos de esteres naturais nos sistemas de isolamento

    Energy Technology Data Exchange (ETDEWEB)

    Bingenheimer, David; Fiacco, Eugene Del; Rapp, Kevin [Cooper Power Systems (United States); Mak, Jose [B e M Pesquisa e Desenvolvimento, Campinas, SP (Brazil); Franchini, Luiz [Itaipu Transformadores, Itapolis, SP (Brazil); Vasconcellos, Vagner [Companhia Paulista de Forca e Luz (CPFL), Campinas, SP (Brazil)

    2011-10-15

    For use as dielectric fluids, the natural esters have, compared with mineral oils, longer life and better thermal characteristics, which allows the fabrication of smaller transformers, more profitable and fire safety. Furthermore, are extracted from seeds, renewable raw materials, recyclable, biodegradable and nontoxic produced locally, which translates into environmental, economic and social benefits.

  15. Shale hydration inhibition characteristics and mechanism of a new amine-based additive in water-based drilling fluids

    Directory of Open Access Journals (Sweden)

    Pezhman Barati

    2017-12-01

    Full Text Available In this work, shale hydration Inhibition performance of tallow amine ethoxylate as a shale stabilizer in water based drilling fluid, was investigated through these tests: bentonite hydration inhibition test, bentonite sedimentation test, drill cutting recovery test, dynamic linear swelling test, wettability test, isothermal water adsorption test, and zeta potential test. The results showed that bentonite particles are not capable of being hydrated or dispersed in the mediums containing tallow amine ethoxylate; tallow amine ethoxylate had shown a comparable and competitive inhibition performance with potassium chloride as a common shale stabilizer in drilling industry. Some amine functional groups exist in tallow amine ethoxylate structure which are capable of forming hydrogen bonding with surfaces of bentonite particles. This phenomenon decreased the water adsorption on bentonite particles' surfaces which results in reduction of swelling. Tallow amine ethoxylate is also compatible with other common drilling fluid additives. Keywords: Drilling fluids, Dynamic linear swelling, Hydrogen bond, Mechanism, Shale stabilizer, Tallow amine ethoxylate, Wettability, Zeta potential, Amine-based additive

  16. Mechanical properties and mophology natural rubber blend with bentonit and carbon black

    Science.gov (United States)

    Ginting, E. M.; Bukit, N.; Muliani; Frida, E.

    2017-07-01

    Purpose of this study was to determine the mechanical properties and morphology of composite natural rubber and natural bentonite with addition of Na-bentonite filler and carbon black to natural rubber. The method is carried material mixed with filler composition variations (0,10,20,30) phr using open mill for 6 min. Results of the open mill is vulcanized at a temperature of 170°C. Further testing mechanical properties and morphology. Results showed that the addition of Na-bentonite filler and carbon black influence on the mechanical properties of tensile strength, elongation at break, modulus of elasticity, hardness, and strong tear. Morphological results showed cavities in the rubber compound and the occurrence agglomeration.

  17. Formation of conical fractures in sedimentary basins: Experiments involving pore fluids and implications for sandstone intrusion mechanisms

    Science.gov (United States)

    Mourgues, R.; Bureau, D.; Bodet, L.; Gay, A.; Gressier, J. B.

    2012-01-01

    a flat cone. We make use of a P.I.V. (Particle Imaging Velocimetry) technique to analyse plastic deformation, showing that these inclined fractures are opened in mixed modes. Close to the surface, they change into steep shear bands where fluids can infiltrate. The final morphology of the fracture network is very similar to the common tripartite architecture of various injection complexes, indicating that different mechanisms may be involved in the formation of dykes. Feeder dykes under the sill zones may open as tensile fractures, while overlying dykes may be guided by the deformation induced by the growth of sills. These deformation conditions may also favour the formation of fluid escape structures and pockmarks.

  18. 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

  19. Probing helium interfaces with light scattering: from fluid mechanics to statistical physics.

    Science.gov (United States)

    Wolf, P E; Bonnet, F; Guyon, L; Lambert, T; Perraud, S; Puech, L; Rousset, B; Thibault, P

    2009-02-01

    We have investigated the formation of helium droplets in two physical situations. In the first one, droplets are atomised from superfluid or normal liquid by a fast helium vapour flow. In the second, droplets of normal liquid are formed inside porous glasses during the process of helium condensation. The context, aims, and results of these experiments are reviewed, with focus on the specificity of light scattering by helium. In particular, we discuss how, for different reasons, the closeness to unity of the index of refraction of helium allows in both cases to minimise the problem of multiple scattering and obtain results which it would not be possible to get using other fluids.

  20. Characterization of site-specific biomechanical properties of human meniscus-Importance of collagen and fluid on mechanical nonlinearities.

    Science.gov (United States)

    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.

  1. Status, Antimicrobial Mechanism, and Regulation of Natural Preservatives in Livestock Food Systems

    OpenAIRE

    Lee, Na-Kyoung; Paik, Hyun-Dong

    2016-01-01

    This review discusses the status, antimicrobial mechanisms, application, and regulation of natural preservatives in livestock food systems. Conventional preservatives are synthetic chemical substances including nitrates/nitrites, sulfites, sodium benzoate, propyl gallate, and potassium sorbate. The use of artificial preservatives is being reconsidered because of concerns relating to headache, allergies, and cancer. As the demand for biopreservation in food systems has increased, new natural a...

  2. MFGA-IDT2 workshop: Astrophysical and geophysical fluid mechanics: the impact of data on turbulence theories

    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

  3. Observer differentiation of proximal enamel mechanical defects versus natural proximal dental caries with computed dental radiography.

    Science.gov (United States)

    Kang, B C; Farman, A G; Scarfe, W C; Goldsmith, L J

    1996-10-01

    Various models have been used to study the accuracy of imaging systems for detection of dental caries. This study compares the ability of dentists to detect mechanically created defects versus natural dental caries cavitations on the proximal surfaces of extracted teeth with Computed Dental Radiography (Schick Industries, Long Island City, N.Y.). Detection rates are investigated according to lesion depth to permit comparisons to be made between studies in the literature with other mechanical defects or natural caries models. Discrimination of natural caries versus artificial defects with Computed Dental Radiography is also compared with a previous report that used standard dental film. Fifty-two extracted molar and premolar teeth were mounted into representative sets of maxillary and mandibular posterior arches for bite-wing radiography. There were 16 proximal surfaces with natural caries and 28 proximal surfaces with mechanical defects. An optical bench was used to ensure constant beam geometry. A 1.8 cm acrylic soft tissue equivalent attenuator was placed in front of the receptor. Thirty dentists acted independently as observers to differentiate between sound proximal tooth surfaces, natural dental caries, and mechanical defects. Evaluation of intra- and interobserver variability was made with use of the kappa statistic. The Zelen test of odds ratios was used to test for homogeneity, and the Mantel-Haenszel analysis plus stratified logistic regression were used for inference about the common odds ratio. Significance was set at p detection was 74% for mechanical defects and 67% for natural caries. The odds of detecting a mechanical defect were 1.40 times the odds of finding natural dental caries cavitation of the same depth. Lesion depth did influence the probability of correctly identifying the presence of a lesion; the odds of identifying cavitation increased 1.41 times with every 0.1 mm increase in lesion depth. Correct designation of lesion type was 1.42 times

  4. BSim models for 2 case-studies of naturally and mechanically ventilated daycare institutions

    Energy Technology Data Exchange (ETDEWEB)

    Kalyanova, O.; Heiselberg, P.

    2009-06-15

    The report intends to provide complete information necessary for evaluation of assumptions made in the models and conclusions derived from the results of simulation of two different institutions in various operational modes. Thermal models are prepared for two day-care buildings, one which is mechanically ventilated and one which is naturally ventilated. All simulations were preformed in BSim, and all the models are simulated in the current version og BSim which is version 6,8,9,8. The results of the simulations showed that it is possible to reduce energy use for ventilation, both in mechanically and naturally ventilated child care center without compromising indoor air quality. (ln)

  5. Statistical mechanics of transport processes in active fluids: Equations of hydrodynamics.

    Science.gov (United States)

    Klymko, Katherine; Mandal, Dibyendu; Mandadapu, Kranthi K

    2017-11-21

    The equations of hydrodynamics including mass, linear momentum, angular momentum, and energy are derived by coarse-graining the microscopic equations of motion for systems consisting of rotary dumbbells driven by internal torques. In deriving the balance of linear momentum, we find that the symmetry of the stress tensor is broken due to the presence of non-zero torques on individual particles. The broken symmetry of the stress tensor induces internal spin in the fluid and leads us to consider the balance of internal angular momentum in addition to the usual moment of momentum. In the absence of spin, the moment of momentum is the same as the total angular momentum. In deriving the form of the balance of total angular momentum, we find the microscopic expressions for the couple stress tensor that drives the spin field. We show that the couple stress contains contributions from both intermolecular interactions and the active forces. The presence of spin leads to the idea of balance of moment of inertia due to the constant exchange of particles in a small neighborhood around a macroscopic point. We derive the associated balance of moment of inertia at the macroscale and identify the moment of inertia flux that induces its transport. Finally, we obtain the balances of total and internal energy of the active fluid and identify the sources of heat and heat fluxes in the system.

  6. Statistical mechanics of transport processes in active fluids: Equations of hydrodynamics

    Science.gov (United States)

    Klymko, Katherine; Mandal, Dibyendu; Mandadapu, Kranthi K.

    2017-11-01

    The equations of hydrodynamics including mass, linear momentum, angular momentum, and energy are derived by coarse-graining the microscopic equations of motion for systems consisting of rotary dumbbells driven by internal torques. In deriving the balance of linear momentum, we find that the symmetry of the stress tensor is broken due to the presence of non-zero torques on individual particles. The broken symmetry of the stress tensor induces internal spin in the fluid and leads us to consider the balance of internal angular momentum in addition to the usual moment of momentum. In the absence of spin, the moment of momentum is the same as the total angular momentum. In deriving the form of the balance of total angular momentum, we find the microscopic expressions for the couple stress tensor that drives the spin field. We show that the couple stress contains contributions from both intermolecular interactions and the active forces. The presence of spin leads to the idea of balance of moment of inertia due to the constant exchange of particles in a small neighborhood around a macroscopic point. We derive the associated balance of moment of inertia at the macroscale and identify the moment of inertia flux that induces its transport. Finally, we obtain the balances of total and internal energy of the active fluid and identify the sources of heat and heat fluxes in the system.

  7. Universal poroelastic mechanism for hydraulic signals in biomimetic and natural branches.

    Science.gov (United States)

    Louf, J-F; Guéna, G; Badel, E; Forterre, Y

    2017-10-17

    Plants constantly undergo external mechanical loads such as wind or touch and respond to these stimuli by acclimating their growth processes. A fascinating feature of this mechanical-induced growth response is that it can occur rapidly and at long distance from the initial site of stimulation, suggesting the existence of a fast signal that propagates across the whole plant. The nature and origin of the signal is still not understood, but it has been recently suggested that it could be purely mechanical and originate from the coupling between the local deformation of the tissues (bending) and the water pressure in the plant vascular system. Here, we address the physical origin of this hydromechanical coupling using a biomimetic strategy. We designed soft artificial branches perforated with longitudinal liquid-filled channels that mimic the basic features of natural stems and branches. In response to bending, a strong overpressure is generated in the channels that varies quadratically with the bending curvature. A model based on a mechanism analogous to the ovalization of hollow tubes enables us to predict quantitatively this nonlinear poroelastic response and identify the key physical parameters that control the generation of the pressure pulse. Further experiments conducted on natural tree branches reveal the same phenomenology. Once rescaled by the model prediction, both the biomimetic and natural branches fall on the same master curve, enlightening the universality of our poroelastic mechanism for the generation of hydraulic signals in plants.

  8. Development of innovative architecture of the organizational and economic mechanism for the nature protection management

    Science.gov (United States)

    Mikhailov, V. G.; Kiseleva, T. V.; Karasev, V. A.; Mikhailov, G. S.; Skukin, V. A.

    2017-05-01

    The problems of the efficient functioning of environmental and economic systems of various levels on the basis of the adequate organizational and economic management mechanism are considered in the article. The purpose of the study is the analysis and development of theoretical provisions for the formation of a modern, innovative organizational and economic mechanism of the nature protection management. The compliance matrix of the innovative elements presented in the structure of the organizational and economic mechanism of the nature protection management is developed. The main result of the study is the improvement of the existing management mechanism to minimize the negative impact on the environment, including through the incentive system, and to improve the financial performance of the economic entity. The practical component of the study conducted can be recommended to municipal, regional and federal authorities, as well as the industrial enterprises, to support the adoption of the effective, environmentally sound management decisions that are consistent with the global concept of sustainable development.

  9. McKenzie treatment versus mulligan sustained natural apophyseal glides for chronic mechanical low back pain

    OpenAIRE

    Waqqar, Saira; Shakil-ur-Rehman, Syed; Ahmad, Shakeel

    2016-01-01

    Background and Objective: Chronic mechanical low back pain is common among different age groups and genders. Different manual therapy techniques combined with exercise therapy and electrotherapy modalities play an important role in its management. Our objective was to compare the effects of McKenzie extension exercisesprogram (EEP) versus Mulligan Sustained Natural Apophyseal Glides (SNAGs) for chronic mechanical low back pain (CMLBP). Methods: This randomized control trial (RCT) was conducte...

  10. Estimation of the physiological mechanical conditioning in vascular tissue engineering by a predictive fluid-structure interaction approach.

    Science.gov (United States)

    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.

  11. Fluid flow and reactive mass transport modeling of reducing mechanisms in the formation of unconformity-related uranium deposits

    International Nuclear Information System (INIS)

    Yang, J.

    2014-01-01

    Unconformity-related uranium deposits in sedimentary basins represent the most important and profitable deposits among other types of uranium deposits, however their origin is still not fully understood. To better understand their formation, and in particular to address possible reducing mechanisms in the precipitation of uraninite, we develop a highly conceptualized 2-D model that fully couples fluid flow and heat transfer with reactive mass transport. We consider a series of numerical scenarios and examine the effect of graphite zone and Fe-rich silicates as the carbon-based and the inorganic-based reducing agents on the ore genesis. Our numerical results reveal that both the reducing mechanisms can lead to the precipitation of uraninite below the unconformity interface away from the faulted zone. Physiochemical parameters such as oxygen fugacity and temperature play a significant role in localization of the uraninite. Localization of these deposits is in relation to the decrease of oxygen fugacity, generally resulting from the interaction of oxidized uranium-bearing fluids with the reductants. Uraninites precipitate simultaneously with hematite in the areas experiencing reduction of oxygen fugacity and having a temperature of 180-200°C and a pH of 2.5- 4.5. Wide-spread alteration halos in the basement and around the uranium deposit include hematite, Mg-chlorite, and muscovite associated with minor amounts of pyrite and K-feldspar alteration. These results have important geological and exploration implications. (author)

  12. Fluid balance and length of mechanical ventilation in children admitted to a single Pediatric Intensive Care Unit.

    Science.gov (United States)

    Vidal, Solange; Pérez, Augusto; Eulmesekian, Pablo

    2016-08-01

    Associations between cumulative fluid balance and a prolonged duration of assisted mechanical ventilation have been described in adults. The aim of this study was to evaluate whether fluid balance in the first 48 hours of assisted mechanical ventilation initiation was associated with a prolonged duration of this process among children in the Pediatric Intensive Care Unit (PICU). Retrospective cohort of patients in the PICU o, Hospital Italiano de Buenos Aires, between 1/1/2010 and 6/30/2012. Balance was calculated in percentage of body weight; prolonged mechanical ventilation was defined as >7 days, and confounders were registered. Univariate and multivariate analyses were performed. Two hundred and forty-nine patients were mechanically ventilated for over 48 hours; 163 were included in the study. Balance during the first 48 hours of mechanical ventilation was 5.7% ± 5.86; 82 patients (50.3%) were on mechanical ventilation for more than 7 days. Age 〈 4 years old (OR 3.21, 95% CI 1.38-7.48, p 0.007), respiratory disease (OR 4.94, 95% CI 1.51-16.10, p 0.008), septic shock (OR 4.66, 95% CI 1.10-19.65, p 0.036), Pediatric Logistic Organ Dysfunction (PELOD) 〉 10 (OR 2.44, 95% CI 1.234.85, p 0.011), and positive balance 〉 13% (OR 4.02, 95% CI 1.08-15.02, p 0.038) were associated with prolonged mechanical ventilation. The multivariate model resulted in an OR 2.58, 95% CI: 1.17-5.58, p= 0.018 for PELOD 〉 10, and an OR 3.7, 95% CI: 0.91-14.94, p= 0.066 for positive balance 〉 13%. Regarding prolonged mechanical ventilation, the multivariate model showed an independent association with organ dysfunction (PELOD 〉 10) and a trend towards an association with positive balance 〉 13%. Sociedad Argentina de Pediatría.

  13. Personal computer (PC) based image processing applied to fluid mechanics research

    Science.gov (United States)

    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.

  14. Large Matched-Index-of-Refraction (MIR) Flow Systems for International Collaboration In Fluid Mechanics

    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.

  15. Impact of melting heat transfer and nonlinear radiative heat flux mechanisms for the generalized Burgers fluids

    Science.gov (United States)

    Khan, Waqar Azeem; Khan, Masood; Irfan, Muhammad; Alshomrani, A. S.

    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.

  16. Engineering Mathematics I : Electromagnetics, Fluid Mechanics, Material Physics and Financial Engineering

    CERN Document Server

    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 ...

  17. Experimental studies in fluid mechanics and materials science using acoustic levitation

    Science.gov (United States)

    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.

  18. Physics of continuous media problems and solutions in electromagnetism, fluid mechanics and MHD

    CERN Document Server

    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...

  19. 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.

  20. The Preliminary Stretching Effect on Mechanical Properties of Natural and Synthetic Polyamide fibres and Conformational Transitions

    Science.gov (United States)

    Aksakal, Baki; Phoshkina, Svetlana P.; Darvish, Diana M.; Tsobkallo, Ekaterina S.; Alekberov, Vilayet

    2007-04-01

    The preliminary stretching effect on mechanical properties of natural (wool, hair, and silk) and synthetic polyamide fibres (nylon, capron) and conformational transitions are investigated by using a tensile tester. It is shown that α-keratin fibres (wool and hair) show silk-like properties and properties of synthetic polyamide fibres for preliminary extension of 18-24% and 34-38%, respectively.

  1. Plant management in natural areas: balancing chemical, mechanical, and cultural control methods

    Science.gov (United States)

    Steven Manning; James. Miller

    2011-01-01

    After determining the best course of action for control of an invasive plant population, it is important to understand the variety of methods available to the integrated pest management professional. A variety of methods are now widely used in managing invasive plants in natural areas, including chemical, mechanical, and cultural control methods. Once the preferred...

  2. Bed Microenvironment in Hospital Patient Rooms with Natural or Mechanical Ventilation

    DEFF Research Database (Denmark)

    Melikov, Arsen Krikor; Li, Yuguo; Georgiev, Emanuil

    2012-01-01

    We studied how to provide patients in bed with thermally comfortable microenvironment in both naturally and mechanically ventilated hospital rooms for both winter and summer seasons. A climate chamber was used to resemble a hospital room and thermal manikin to simulate a patient lying in a bed...

  3. DNA DAMAGE REPAIR AND CELL CYCLE CONTROL: A NATURAL BIO-DEFENSE MECHANISM

    Science.gov (United States)

    DNA DAMAGE REPAIR AND CELL CYCLE CONTROL: A natural bio-defense mechanismAnuradha Mudipalli.Maintenance of genetic information, including the correct sequence of nucleotides in DNA, is essential for replication, gene expression, and protein synthesis. DNA lesions onto...

  4. Cure and mechanical properties of recycled NdFeB–natural rubber ...

    Indian Academy of Sciences (India)

    NdFeB) powder and natural rubber (NR) were prepared by the two-roll mill technique. Their mechanical and cure properties were studied as a function of NdFeB loading from 0–120 phr. With increasing magnetic loading, the cure time of the ...

  5. Numerical Modeling of Variable Fluid Injection-Rate Modes on Fracturing Network Evolution in Naturally Fractured Formations

    Directory of Open Access Journals (Sweden)

    Yu Wang

    2016-05-01

    Full Text Available In this study, variable injection-rate technology was numerically investigated in a pre-existing discrete fracture network (DFN formation, the Tarim Basin in China. A flow-stress-damage (FSD coupling model has been used in an initial attempt towards how reservoir response to variable injection-rates at different hydraulic fracturing stages. The established numerical model simultaneously considered the macroscopic and microscopic heterogeneity characteristics. Eight numerical cases were studied. Four cases were used to study the variable injection-rate technology, and the other four cases were applied for a constant injection-rate in order to compare with the variable injection-rate technology. The simulation results show that the variable injection-rate technology is a potentially good method to a form complex fracturing networks. The hydraulic fracturing effectiveness when increasing the injection-rate at each stage is the best, also, the total injected fluid is at a minimum. At the initial stage, many under-fracturing points appear around the wellbore with a relatively low injection-rate; the sudden increase of injection rate drives the dynamic propagation of hydraulic fractures along many branching fracturing points. However, the case with decreasing injection rate is the worst. By comparing with constant injection-rate cases, the hydraulic fracturing effectiveness with variable flow rate technology is generally better than those with constant injection-rate technology. This work strongly links the production technology and hydraulic fracturing effectiveness evaluation and aids in the understanding and optimization of hydraulic fracturing simulations in naturally fractured reservoirs.

  6. Simulations of Magnetic Reconnection - Kinetic Mechanisms Underlying the Fluid Description of Ions

    Science.gov (United States)

    Aunai, icolas; Belmont, Gerard; Smets, Roch

    2012-01-01

    Because of its ability to transfer the energy stored in magnetic field together with the breaking of the flux freezing constraint, magnetic reconnection is considered as one of the most important phenomena in plasma physics. When it happens in a collision less environment such as the terrestrial magnetosphere, it should a priori be modelled with in the framework of kinetic physics. The evidence of kinetic features has incidentally for a long time, been shown by researchers with the help of both numerical simulations and satellite observations. However, most of our understanding of the process comes from the more intuitive fluid interpretation with simple closure hypothesis which do not include kinetic effects. To what extent are these two separate descriptions of the same phenomenon related? What is the role of kinetic effects in the averaged/fluid dynamics of reconnection? This thesis addresses these questions for the proton population in the particular case of anti parallel merging with the help of 2D Hybrid simulations. We show that one can not assume, as is usually done, that the acceleration of the proton flow is only due to the Laplace force. Our results show, for symmetric and asymmetric connection, the importance of the pressure force, opposed to the electric one on the separatrices, in the decoupling region. In the symmetric case, we emphasize the kinetic origin of this force by analyzing the proton distribution functions and explain their structure by studying the underlying particle dynamics. Protons, as individual particles, are shown to bounce in the electric potential well created by the Hall effect. The spatial divergence of this well results in a mixing in phase space responsible for the observed structure of the pressure tensor. A detailed energy budget analysis confirms the role of the pressure force for the acceleration; but, contrary to what is sometimes assumed, it also reveals that the major part of the incoming Poynting flux is transferred to

  7. [Advances in the molecular mechanism of natural bacterial transformation--a review].

    Science.gov (United States)

    Sun, Dongchang; Zhang, Yanmei; Shi, Yuefeng

    2012-01-01

    Naturally transformable bacteria are able to take up DNA to acquire new genetic traits in the environment. To be naturally transformed, bacteria need to establish a physiological state, called natural competence, in which DNA uptake and processing genes are expressed. DNA uptake proteins assemble a complex to pull exogenous DNA into the cytoplasm where it can recombine with the genome DNA or establish as a plasmid. In general, DNA uptake of bacteria could be divided into two stages: DNA is transported from the milieu to the periplasm at the first stage (for Gram-negative bacteria) and is translocated across the inner membrane at the second stage. Our work and other studies revealed new plasmid DNA transformation modes in Escherichia coli. Here, we first reviewed recent advances in the molecular mechanism of natural transformation and then described the distinctive plasmid transformation mode in E. coli.

  8. Natural weathering effects on the mechanical and surface properties of polyphenylene sulphide (PPS) composites

    Energy Technology Data Exchange (ETDEWEB)

    Sinmazcelik, Tamer [Mechanical Engineering Department, Kocaeli University, Veziroglu Campus, izmit 41040 (Turkey): TUBITAK-MRC, MCTRI, P.O. Box 21, 41470 Gebze (Turkey)]. E-mail: tamersc@yahoo.com

    2006-07-01

    In this paper, Natural weathering effects on the mechanical and surface properties of polyphenylene sulphide (PPS) composites were studied. Injection moulded short glass fibre and short glass fibre/calcium carbonate particle filled (hybrid) PPS composites were investigated. These specimens were subjected to natural weathering in izmit, Turkey for 3216 h. Instrumented charpy impact tests were performed on a charpy pendulum type tester. The surfaces of the samples were examined by scanning electron microscopy (SEM). It is demonstrated that particle reinforcement (additional to the random oriented short glass fibre) reduces the impact performance of composite material but the material becomes more resistant to weathering. Percentage decrease in the impact strength after natural weathering of fibre/particle filled PPS composite is smaller compared to short fibre filled PPS composite. On the other hand, surface morphology of CaCO{sub 3} particle reinforced PPS composite is affected less from natural weathering and this material should be considered for outdoor applications.

  9. Fluid Mechanics Experiments as a Unifying Theme in the Physics Instrumentation Laboratory Course

    Science.gov (United States)

    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.

  10. 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...

  11. Status, Antimicrobial Mechanism, and Regulation of Natural Preservatives in Livestock Food Systems.

    Science.gov (United States)

    Lee, Na-Kyoung; Paik, Hyun-Dong

    2016-01-01

    This review discusses the status, antimicrobial mechanisms, application, and regulation of natural preservatives in livestock food systems. Conventional preservatives are synthetic chemical substances including nitrates/nitrites, sulfites, sodium benzoate, propyl gallate, and potassium sorbate. The use of artificial preservatives is being reconsidered because of concerns relating to headache, allergies, and cancer. As the demand for biopreservation in food systems has increased, new natural antimicrobial compounds of various origins are being developed, including plant-derived products (polyphenolics, essential oils, plant antimicrobial peptides (pAMPs)), animal-derived products (lysozymes, lactoperoxidase, lactoferrin, ovotransferrin, antimicrobial peptide (AMP), chitosan and others), and microbial metabolites (nisin, natamycin, pullulan, ε-polylysine, organic acid, and others). These natural preservatives act by inhibiting microbial cell walls/membranes, DNA/RNA replication and transcription, protein synthesis, and metabolism. Natural preservatives have been recognized for their safety; however, these substances can influence color, smell, and toxicity in large amounts while being effective as a food preservative. Therefore, to evaluate the safety and toxicity of natural preservatives, various trials including combinations of other substances or different food preservation systems, and capsulation have been performed. Natamycin and nisin are currently the only natural preservatives being regulated, and other natural preservatives will have to be legally regulated before their widespread use.

  12. Expanding the Enzyme Universe: Accessing Non-Natural Reactions by Mechanism-Guided Directed Evolution

    Science.gov (United States)

    Renata, Hans; Wang, Z. Jane

    2015-01-01

    High selectivities and exquisite control over reaction outcomes entice chemists to use biocatalysts in organic synthesis. However, many useful reactions are not accessible because they are not in nature’s known repertoire. We will use this review to outline an evolutionary approach to engineering enzymes to catalyze reactions not found in nature. We begin with examples of how nature has discovered new catalytic functions and how such evolutionary progressions have been recapitulated in the laboratory starting from extant enzymes. We then examine non-native enzyme activities that have been discovered and exploited for chemical synthesis, emphasizing reactions that do not have natural counterparts. The new functions have mechanistic parallels to the native reaction mechanisms that often manifest as catalytic promiscuity and the ability to convert from one function to the other with minimal mutation. We present examples of how non-natural activities have been improved by directed evolution, mimicking the process used by nature to create new catalysts. Examples of new enzyme functions include epoxide opening reactions with non-natural nucleophiles catalyzed by a laboratory-evolved halohydrin dehalogenase, cyclopropanation and other carbene transfer reactions catalyzed by cytochrome P450 variants, and non-natural modes of cyclization by a modified terpene synthase. Lastly, we describe discoveries of non-native catalytic functions that may provide future opportunities for expanding the enzyme universe. PMID:25649694

  13. Bioprocess scale-up/down as integrative enabling technology: from fluid mechanics to systems biology and beyond.

    Science.gov (United States)

    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.

  14. Final design, fluid dynamic and structural mechanical analysis of a liquid hydrogen Moderator for the European Spallation Source

    Science.gov (United States)

    Bessler, Y.; Henkes, C.; Hanusch, F.; Schumacher, P.; Natour, G.; Butzek, M.; Klaus, M.; Lyngh, D.; Kickulies, M.

    2017-02-01

    The European Spallation Source (ESS) is currently in the construction phase and should have first beam on Target in 2019. ESS, located in Sweden, will be the most powerful spallation neutron source worldwide, with the goal to produce neutrons for research. As an in-kind partner the Forschungszentrum Juelich will among others, design and manufacture the four liquid hydrogen Moderators, which are located above and below the Target. Those vessels are confining the cold hydrogen used to reduce the energy level of the fast neutrons, produced by spallation in the Target, in order to make the neutrons usable for neutron scattering instruments. Due to the requirements [1], a fluid dynamic analysis with pressure and temperature depended hydrogen data, taking into account the pseudo critical phenomena and the pulsed neutronic heating (pressure waves) is necessary. With the fluid dynamic results, a structure mechanical analysis including radiation damage investigation (RCC-MRx code [5]), low temperature properties as well as strength reduction by welding can be realized. Finally, the manufacturing and welding completes the design process.

  15. Development of instructional manual encouraging student active learning for high school teaching on fluid mechanics through Torricelli's tank experiment

    Science.gov (United States)

    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.

  16. Fundamental trends in fluid-structure interaction

    CERN Document Server

    Galdi, Giovanni P

    2010-01-01

    The interaction of a fluid with a solid body is a widespread phenomenon in nature, occurring at different scales and different applied disciplines. Interestingly enough, even though the mathematical theory of the motion of bodies in a liquid is one of the oldest and most classical problems in fluid mechanics, mathematicians have, only very recently, become interested in a systematic study of the basic problems related to fluid-structure interaction, from both analytical and numerical viewpoints. ""Fundamental Trends in Fluid-Structure Interaction"" is a unique collection of important papers wr

  17. Development of an Off-Axis Digital Holographic Microscope for Large Scale Measurement in Fluid Mechanics

    Science.gov (United States)

    Tamrin, K. F.; Rahmatullah, B.; Samuri, S. M.

    Holographic particle image velocimetry is a promising technique to probe and characterize complex flow dynamics since it is a truly three-dimensional (3D) three-component measurement technique. The technique simply records the coherent light scattered by small seeding particles that are assumed to faithfully follow the flow and uses it to reconstruct the event afterward. Reconstruction of the event is usually performed using a digital video microscope mounted on a 3D translation stage. The microscope records the intensity only which consequently results in loss of phase information. The objective of this paper is to develop and apply digital holographic microscopy with the aim to recover the phase information. Digital holographic microscopy has immense potentials in microscale solid and fluid measurements as it offers the possibility of digital wavefront processing by manipulating amplitude and phase of the recorded holograms. In this paper, we have developed an off-axis digital holographic microscope to capture both amplitude and phase of the reconstructed object simultaneously. This inherently solves twin image problem in the recorded digital holograms. The microscope was integrated into the reconstruction system and was successfully used to digitize holographic images of 10 μm polystyrene spheres and 1 μm olive oil droplets. The spatial resolution of the system is 0.63 μm, and the field of view is 1250 × 625 μm2. A 3D holographic reconstruction using a k-space analysis (wave-vector) of the optical field is applied to numerically refocus the images. Another potential application includes digital wavefront processing to compensate for aberration in the images.

  18. Ultrasonic, Molecular and Mechanical Testing Diagnostics in Natural Fibre Reinforced, Polymer-Stabilized Earth Blocks

    Directory of Open Access Journals (Sweden)

    C. Galán-Marín

    2013-01-01

    Full Text Available The aim of this research study was to evaluate the influence of utilising natural polymers as a form of soil stabilization, in order to assess their potential for use in building applications. Mixtures were stabilized with a natural polymer (alginate and reinforced with wool fibres in order to improve the overall compressive and flexural strength of a series of composite materials. Ultrasonic pulse velocity (UPV and mechanical strength testing techniques were then used to measure the porous properties of the manufactured natural polymer-soil composites, which were formed into earth blocks. Mechanical tests were carried out for three different clays which showed that the polymer increased the mechanical resistance of the samples to varying degrees, depending on the plasticity index of each soil. Variation in soil grain size distributions and Atterberg limits were assessed and chemical compositions were studied and compared. X-ray diffraction (XRD, X-ray fluorescence spectroscopy (XRF, and energy dispersive X-ray fluorescence (EDXRF techniques were all used in conjunction with qualitative identification of the aggregates. Ultrasonic wave propagation was found to be a useful technique for assisting in the determination of soil shrinkage characteristics and fibre-soil adherence capacity and UPV results correlated well with the measured mechanical properties.

  19. Molecular Mechanisms and Metabolomics of Natural Polyphenols Interfering with Breast Cancer Metastasis.

    Science.gov (United States)

    Ci, Yingqian; Qiao, Jinping; Han, Mei

    2016-12-17

    Metastatic cancers are the main cause of cancer-related death. In breast primary cancer, the five-year survival rate is close to 100%; however, for metastatic breast cancer, that rate drops to a mere 25%, due in part to the paucity of effective therapeutic options for treating metastases. Several in vitro and in vivo studies have indicated that consumption of natural polyphenols significantly reduces the risk of cancer metastasis. Therefore, this review summarizes the research findings involving the molecular mechanisms and metabolomics of natural polyphenols and how they may be blocking breast cancer metastasis. Most natural polyphenols are thought to impair breast cancer metastasis through downregulation of MMPs expression, interference with the VEGF signaling pathway, modulation of EMT regulator, inhibition of NF-κB and mTOR expression, and other related mechanisms. Intake of natural polyphenols has been shown to impact endogenous metabolites and complex biological metabolic pathways in vivo. Breast cancer metastasis is a complicated process in which each step is modulated by a complex network of signaling pathways. We hope that by detailing the reported interactions between breast cancer metastasis and natural polyphenols, more attention will be directed to these promising candidates as effective adjunct therapies against metastatic breast cancer in the clinic.

  20. The Role of Biologically Active Ingredients from Natural Drug Treatments for Arrhythmias in Different Mechanisms.

    Science.gov (United States)

    Li, Jie; Hu, Dan; Song, Xiaoli; Han, Tao; Gao, Yonghong; Xing, Yanwei

    2017-01-01

    Arrhythmia is a disease that is caused by abnormal electrical activity in the heart rate or rhythm. It is the major cause of cardiovascular morbidity and mortality. Although several antiarrhythmic drugs have been used in clinic for decades, their application is often limited by their adverse effects. As a result, natural drugs, which have fewer side effects, are now being used to treat arrhythmias. We searched for all articles on the role of biologically active ingredients from natural drug treatments for arrhythmias in different mechanisms in PubMed. This study reviews 19 natural drug therapies, with 18 active ingredient therapies, such as alkaloids, flavonoids, saponins, quinones, and terpenes, and two kinds of traditional Chinese medicine compound (Wenxin-Keli and Shensongyangxin), all of which have been studied and reported as having antiarrhythmic effects. The primary focus is the proposed antiarrhythmic mechanism of each natural drug agent. Conclusion . We stress persistent vigilance on the part of the provider in discussing the use of natural drug agents to provide a solid theoretical foundation for further research on antiarrhythmia drugs.

  1. Non-canonical programmed cell death mechanisms triggered by natural compounds.

    Science.gov (United States)

    Diederich, Marc; Cerella, Claudia

    2016-10-01

    Natural compounds are the fundament of pharmacological treatments and more than 50% of all anticancer drugs are of natural origins or at least derived from scaffolds present in Nature. Over the last 25 years, molecular mechanisms triggered by natural anticancer compounds were investigated. Emerging research showed that molecules of natural origins are useful for both preventive and therapeutic purposes by targeting essential hallmarks and enabling characteristics described by Hanahan and Weinberg. Moreover, natural compounds were able to change the differentiation status of selected cell types. One of the earliest response of cells treated by pharmacologically active compounds is the change of its morphology leading to ultra-structural perturbations: changes in membrane composition, cytoskeleton integrity, alterations of the endoplasmic reticulum, mitochondria and of the nucleus lead to formation of morphological alterations that are a characteristic of both compound and cancer type preceding cell death. Apoptosis and autophagy were traditionally considered as the most prominent cell death or cell death-related mechanisms. By now multiple other cell death modalities were described and most likely involved in response to chemotherapeutic treatment. It can be hypothesized that especially necrosis-related phenotypes triggered by various treatments or evolving from apoptotic or autophagic mechanisms, provide a more efficient therapeutic outcome depending on cancer type and genetic phenotype of the patient. In fact, the recent discovery of multiple regulated forms of necrosis and the initial elucidation of the corresponding cell signaling pathways appear nowadays as important tools to clarify the immunogenic potential of non-canonical forms of cell death induction. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. SPARC/osteonectin, an endogenous mechanism for targeting albumin to the blood-cerebrospinal fluid interface during brain development

    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 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...... that SPARC may be one of the molecules that govern the uptake and delivery of proteins from blood to the CSF. The results also confirm that protein transfer across the blood-CSF barrier is developmentally and physiologically regulated....

  3. Effects of suture position on left ventricular fluid mechanics under mitral valve edge-to-edge repair.

    Science.gov (United States)

    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.

  4. The physics of hearing: fluid mechanics and the active process of the inner ear.

    Science.gov (United States)

    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

  5. 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

  6. Structure, corrosion behavior and mechanical property of a novel poly(vinyl alcohol) composite in simulated body fluid.

    Science.gov (United States)

    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.

  7. Proceedings of a Symposium on Perspectives in Fluid Mechanics Held in Pasadena, California on 10-12 January 1985

    Science.gov (United States)

    1988-07-29

    perfect gas : hot, liquid water stands in the conduit between eruptions , and then boils and changes through a complex unloading process into a droplet...Faithful) and sufficient pressure to keep deeper water from massive boiling and eruption . And 170 FIG. 15. (a) A seismic record from Karkar volcano , Papua...has for decades been attributed to magma motion in volcanoes , but the quantitative nature of the mechanism causing it has been elusive. The geyser

  8. 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

  9. Effects of microstructure transformation on mechanical properties, corrosion behaviors of Mg-Zn-Mn-Ca alloys in simulated body fluid.

    Science.gov (United States)

    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.

  10. Mechanisms and Evidence of Genital Coevolution: The Roles of Natural Selection, Mate Choice, and Sexual Conflict.

    Science.gov (United States)

    Brennan, Patricia L R; Prum, Richard O

    2015-07-01

    Genital coevolution between the sexes is expected to be common because of the direct interaction between male and female genitalia during copulation. Here we review the diverse mechanisms of genital coevolution that include natural selection, female mate choice, male-male competition, and how their interactions generate sexual conflict that can lead to sexually antagonistic coevolution. Natural selection on genital morphology will result in size coevolution to allow for copulation to be mechanically possible, even as other features of genitalia may reflect the action of other mechanisms of selection. Genital coevolution is explicitly predicted by at least three mechanisms of genital evolution: lock and key to prevent hybridization, female choice, and sexual conflict. Although some good examples exist in support of each of these mechanisms, more data on quantitative female genital variation and studies of functional morphology during copulation are needed to understand more general patterns. A combination of different approaches is required to continue to advance our understanding of genital coevolution. Knowledge of the ecology and behavior of the studied species combined with functional morphology, quantitative morphological tools, experimental manipulation, and experimental evolution have been provided in the best-studied species, all of which are invertebrates. Therefore, attention to vertebrates in any of these areas is badly needed. Copyright © 2015 Cold Spring Harbor Laboratory Press; all rights reserved.

  11. Mechanical Properties of Injection Molded and Compression Molded Samples from Nature-Butadiene Rubber

    Directory of Open Access Journals (Sweden)

    Skrobak Adam

    2016-01-01

    Full Text Available The aim of this paper is to show what extent there is an impact on the mechanical properties (tensile strength and tear strength of a standardized testing sample made of rubber compound based on nature rubber and butadiene rubber produced by injection molding in comparison with a sample produced by classic preparation (cutting out a compression molded plate according to the standard ISO 23529. For realization of this study it was necessary to design and produce an injection mold for all types testing samples. Subsequently, mechanical properties such as the tensile stress-strain and tear strenght of compression molded samples and injection molded samples were studied, compared and discussed.

  12. Combined particle-image velocimetry and force analysis of the three-dimensional fluid-structure interaction of a natural owl wing.

    Science.gov (United States)

    Winzen, A; Roidl, B; Schröder, W

    2016-04-01

    Low-speed aerodynamics has gained increasing interest due to its relevance for the design process of small flying air vehicles. These small aircraft operate at similar aerodynamic conditions as, e.g. birds which therefore can serve as role models of how to overcome the well-known problems of low Reynolds number flight. The flight of the barn owl is characterized by a very low flight velocity in conjunction with a low noise emission and a high level of maneuverability at stable flight conditions. To investigate the complex three-dimensional flow field and the corresponding local structural deformation in combination with their influence on the resulting aerodynamic forces, time-resolved stereoscopic particle-image velocimetry and force and moment measurements are performed on a prepared natural barn owl wing. Several spanwise positions are measured via PIV in a range of angles of attack [Formula: see text] 6° and Reynolds numbers 40 000 [Formula: see text] 120 000 based on the chord length. Additionally, the resulting forces and moments are recorded for -10° ≤ α ≤ 15° at the same Reynolds numbers. Depending on the spanwise position, the angle of attack, and the Reynolds number, the flow field on the wing's pressure side is characterized by either a region of flow separation, causing large-scale vortical structures which lead to a time-dependent deflection of the flexible wing structure or wing regions showing no instantaneous deflection but a reduction of the time-averaged mean wing curvature. Based on the force measurements the three-dimensional fluid-structure interaction is assumed to considerably impact the aerodynamic forces acting on the wing leading to a strong mechanical loading of the interface between the wing and body. These time-depending loads which result from the flexibility of the wing should be taken into consideration for the design of future small flying air vehicles using flexible wing structures.

  13. Geo-mechanical consequences of large scale fluid storage in the Utsira formation in the North Sea

    Science.gov (United States)

    Wangen, Magnus; Gasda, Sarah; Bjørnarå, Tore

    2016-04-01

    The Utsira formation in the North Sea is a more than 400 km long formation of Pliocene sand with a thickness in the range from 50m to 350m. The porosity of the Utsira formation is estimated to 35% and the permeability is of the order Darcy (1e-12 m2). This formation is being considered as a possible site for large scale CO2 storage, because of its large storage capacity and good permeability. In this work we look at the geo-mechanical implications of injecting "large'' volumes of fluid in the Utsira formation. Our modelling is based on Biot's poro-elasticity in combination with one-phase and two phase flow. We compare the pressure build-up from injection of brine with the pressure build-up from from injection of supercritical CO2. Well placement and near well modelling is not a part of the modelling. We study four different injection scenarios over 25 years, which have injection rates: 1 Mt/year, 10 Mt/year, 100 Mt/year and 1000 Mt/year. We observe that the pressure plume scales with the injection rate, which is the same behaviour as with Theis solution for pressure build-up. A particular concern is the mechanical properties of the Utsira sand and the cap rock. The cap rock is a Quaternary shale with a Young's modulus measured to 0.25 GPa and a Poisson ratio 0.25. A Young's modulus for the Utsira sand, which can be used to model expansion of the formation, is not measured. It is reasonable to assume that the loose sand has a low Young's modulus. We have tested low values of the Young's modulus for the sand and we get considerable mechanical expansion of the Utsira formation, even in the case of low pressure build-up from the fluid injection. Almost all the surface (seabed) uplift is linked to mechanical expansion of the sand. The strain of the Utsira formation and related surface uplift can be estimated with simple 1D models. Vertical 1D models apply because of the large lateral extent of the pressure plume compared to the thickness of the formation. The limits of

  14. Mechanical Resistance to Compression Poured Earth, Mixed With Natural Latex Obtained From Tabernaemontanaalba Mill Apocynaceae.

    OpenAIRE

    Erick. Zarazua-Portes; Carlos Zuñiga-Leal; Rocio Rafaela Gallegos-Villela; Yolanda G. Aranda-Jiménez

    2016-01-01

    Pouredearthis presented as an environmentally friendly alternative for building. This technique uses hearth components and stabilizers, plus some natural additives or chemicals that can alter mechanical strength characteristics.Current studies show that concrete has higher value in terms of compressive strength and durability according to dosages of these components, but it is necessary to analyze other stabilizers that reduce building cost. In this study, samples of soil denominated Champayá...

  15. Testing mechanical properties of natural stone used as a building material

    Czech Academy of Sciences Publication Activity Database

    Hasníková, Hana

    2013-01-01

    Roč. 20, č. 5 (2013), s. 427-435 ISSN 1802-1484 R&D Projects: GA ČR(CZ) GBP105/12/G059 Grant - others:Evropská komise(XE) FP-2007-SSP-5A STONECORE Institutional support: RVO:68378297 Keywords : mechanical properties * non-destructive testing * natural stone * historical buildings * ultrasound Subject RIV: JN - Civil Engineering http://www.engineeringmechanics.cz/obsahy.html?R=20&C=5

  16. Investigation of the Mechanism That Powers DNA Translocation During Bacterial Natural Transformation

    OpenAIRE

    Foster, Hannah

    2016-01-01

    If deoxyribonucleic acids are the building blocks of life, perhaps the proteins that move, shape, and assemble nucleic acids should be called architects. These proteins come in every size and shape and have vastly different roles and mechanisms, but they share one thing in common: they help determine what life looks like by their interactions with DNA and RNA. Several of these protein architects play integral roles in the spread of genetic material among bacteria in natural transformation, th...

  17. Mechanism of the toxicity induced by natural humic acid on human vascular endothelial cells

    OpenAIRE

    Kihara, Yusuke; Yustiawati; Tanaka, Masato; Gumiri, Sulmin; Ardianor; Hosokawa, Toshiyuki; Tanaka, Shunitz; Saito, Takeshi; Kurasaki, Masaaki

    2012-01-01

    Humic acid (HA), a group of high-molecular weight organic compounds characterized by an ability to bind heavy metals, is normally found in natural water. Although the impairment of vascular endothelial cells in the presence of humic substances has been reported to be involved in some diseases, the mechanisms responsible for this involvement remain unclear. In this study, we examined the cytotoxicity of HA obtained from peatland in Central Kalimantan, Indonesia, to human vascular endothelial c...

  18. Coupled deformation and fluid-flow behavior of a natural fracture in the CSM in situ test block

    International Nuclear Information System (INIS)

    Gertsch, L.S.

    1989-01-01

    The primary goal was the evaluation of an in situ block test as a data source for modeling the coupled flow and mechanical behavior of natural rock fractures. The experiments were conducted with the Colorado School of Mines in situ test block, an 8 m 3 (280 ft 3 ) gneiss cube which has been the focus of several previous studies. A single continuous fracture within the block was surrounded with instruments to measure stresses, deformations, and gas conductivity. The setup was subjected to combinations of normal and shear stress by pressurizing the block sides differentially with hydraulic flatjacks. The induced fracture deformation, as measured by two separate sensor systems, did not correlate closely with the fracture conductivity changes or with each other. The test fracture is more complicated physically than two parallel rock faces. Many joints which were not detected by mapping intersect the test fracture and strongly influence its behavior. These invisible joints create sub-blocks which react complexly to changes in applied load. The flow tests reflected the aggregate sub-block dislocations in the flow path. The deformation readings, however, were the movements of discrete points sparsely located among the sub-blocks. High-confidence extrapolation of block test results to large volumes, such as required for nuclear waste repository design, is not feasible currently. Present instrumentation does not sample rock mass behavior in situ at the proper scales. More basically, however, a fundamental gap exists between the nature of jointed rock and our conception of it. Therefore, the near-field rock mass must be discounted as an easily controllable barrier to groundwater flow, until radically different approaches to rock mass testing and modeling are developed

  19. Comparison of bronchoalveolar lavage fluid examination and other diagnostic techniques with the Baermann technique for detection of naturally occurring Aelurostrongylus abstrusus infection in cats.

    Science.gov (United States)

    Lacorcia, Lauren; Gasser, Robin B; Anderson, Garry A; Beveridge, Ian

    2009-07-01

    To evaluate the diagnostic sensitivity and specificity of bronchoalveolar lavage (BAL) fluid examination and other diagnostic techniques, compared with the use of the Baermann technique performed on fecal samples as the reference standard, for detection of naturally occurring Aelurostrongylus abstrusus infection in a population of cats. Cross-sectional study. Cadavers of 80 semiferal domestic cats. BAL fluid collection and analysis, necropsy, examination of fecal samples and minced lung tissue via the Baermann technique, fecal sedimentation-flotation, and histologic examination of lung tissue were performed. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for detection of A abstrusus infection were calculated. On the basis of fecal Baermann test results, prevalence of infection was 13.8%. Sensitivity (NPV) of tests was as follows: Baermann technique on minced lung tissue, 81.8% (97.2%); fecal flotation-sedimentation, 63.6% (94.5%); stereomicroscopic examination of BAL fluid combined with cytologic examination of BAL fluid, 54.5% (93.2%); stereomicroscopic examination of BAL fluid alone, 45.4% (92.0%); cytologic examination of BAL fluid alone, 36.4% (90.8%); histologic examination of lung tissue, 45.4% (91.8%); and gross lung appearance, 36.4% (90.8%). Specificity and PPV of all tests were 100%, with the exception of histologic examination of lung tissue (specificity, 97.1%; PPV, 71.4%), which identified infected cats that had negative fecal Baermann test results. The Baermann technique was the most sensitive test for detection of A abstrusus infection. On the basis of the prevalence of 13.8% in this study, A abstrusus infection should be considered in pet cats.

  20. Fault-controlled permeability and fluid flow in low-porosity crystalline rocks: an example from naturally fractured geothermal systems in the Southern Andes

    Science.gov (United States)

    Arancibia, G.; Roquer, T.; Sepúlveda, J.; Veloso, E. A.; Morata, D.; Rowland, J. V.

    2017-12-01

    Fault zones can control the location, emplacement, and evolution of economic mineral deposits and geothermal systems by acting as barriers and/or conduits to crustal fluid flow (e.g. magma, gas, oil, hydro-geothermal and groundwater). The nature of the fault control permeability is critical in the case of fluid flow into low porosity/permeability crystalline rocks, since structural permeability provides the main hydraulic conductivity to generate a natural fractured system. However, several processes accompanying the failure of rocks (i.e. episodic permeability given by cycling ruptures, mineral precipitation from fluids in veins, dissolution of minerals in the vicinity of a fracture) promote a complex time-dependent and enhancing/reducing fault-controlled permeability. We propose the Southern Volcanic Zone (Southern Andes, Chile) as a case study to evaluate the role of the structural permeability in low porosity crystalline rocks belonging to the Miocene North Patagonian Batholith. Recently published studies propose a relatively well-constrained first-order role of two active fault systems, the arc-parallel (NS to NNE trending) Liquiñe Ofqui Fault System and the arc-oblique (NW trending) Andean Transverse Fault Zones, in fluid flow at crustal scales. We now propose to examine the Liquiñe ( 39°S) and Maihue ( 40°S) areas as sites of interaction between these fault systems, in order to evaluate a naturally fractured geothermal system. Preliminary results indicate upwelling of thermal water directly from fractured granite or from fluvial deposits overlying granitoids. Measured temperatures of thermal springs suggest a low- to medium-enthalpy system, which could potentially be harnessed for use in geothermal energy applications (e.g. heating, wood dryer and green house), which are much needed in Southern Chile. Future work will aim to examine the nature of structural permeability from the regional to the microscopic scale connecting the paleo- and current- fluid