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1

CalTech Chemical Engineering: Fluid Mechanics  

NSDL National Science Digital Library

This website describes a research project focused on fluid mechanics and transport processes, with an emphasis on "problems at the interface between continuum mechanics and statistical mechanics." The John F. Brady research group uses its own computational method known as Stokesian Dynamics to study complex fluids, and develop and solve macroscopic equations to describe transport in heterogeneous media. Most of the abstracts from the more recent publications are available online. Videos produced as part of the group's research include, Diffusion in Simple Shear Flow, Stokesian Dynamics: Pressure Driven Flow of Suspensions, Stokesian Dynamics Simulation of an Electroreological Fluid, Statistical Mechanics of Bubbly Liquids, Simulation of Colloidal, and Brownian Dynamics. There are also a few presentations that are available online in the pdf format.

2

Fluid Mechanics.  

ERIC Educational Resources Information Center

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)

Drazin, Philip

1987-01-01

3

Fluid Mechanics and Hydrology  

NASA Astrophysics Data System (ADS)

Present day Engineers need to understand water, its properties, its distribution as well as its movement. Certain engineering disciplines may require a course in Hydraulics and Hydrology. However, most other disciplines require courses in Fluid Mechanics and Thermodynamics. The author believes Hydrology is an essential knowledge that most engineers should possess, regardless of their discipline. Water is consumed or circulated in huge quantities in certain types of industries and location of water resources / supply may play a key role in the selection of a future factory site. Pulp and Paper Manufacturing Industries, Chemical Industries, Heat Treatment Facilities are just a few that one can mention. A typical Engineering Fluid Mechanics Course normally covers the broad discipline of Engineering Mechanics that is concerned with the behavior of Liquids and gases at rest or in motion. Water, of course is one of the liquids discussed. Regardless, Engineers are totally ignorant of the subject matter of Hydrology or the Hydrologic Cycle and their importance in the twenty-first century Engineering Environment. In this short paper, the author outlines the methods of successfully incorporating Hydrology into an Engineering Fluid Mechanics Course.

Osterkamp, W. R.; Gray, J. R.; Narayanan, M.

2002-12-01

4

Mechanical Engineering  

NSDL National Science Digital Library

This site contains a broad overview of the mechanical engineering program at the Massachusetts Institute of Technology. It is one of the broadest and most versatile of the engineering professions. The site features lecture notes, assignments, solutions, online textbooks, projects, study groups and exams. This is a nice broad overview of available courses within this program.

2011-01-18

5

An Introduction to Thermal-Fluid Engineering  

Microsoft Academic Search

This text is the first to provide an integrated introduction to basic engineering topics and the social implications of engineering practice. Aimed at beginning engineering students, the book presents the basic ideas of thermodynamics, fluid mechanics, heat transfer, and combustion through a real-world engineering situation. It relates the engine to the atmosphere in which it moves and exhausts its waste

Zellman Warhaft

1998-01-01

6

An Introduction to Thermal-Fluid Engineering  

NASA Astrophysics Data System (ADS)

This text is the first to provide an integrated introduction to basic engineering topics and the social implications of engineering practice. Aimed at beginning engineering students, the book presents the basic ideas of thermodynamics, fluid mechanics, heat transfer, and combustion through a real-world engineering situation. It relates the engine to the atmosphere in which it moves and exhausts its waste products. The book also discusses the greenhouse effect and atmospheric inversions, and the social implications of engineering in a crowded world with increasing energy demands. Students in mechanical, civil, agricultural, environmental, aerospace, and chemical engineering will welcome this engaging, well-illustrated introduction to thermal-fluid engineering.

Warhaft, Zellman

1998-01-01

7

Principles of fluid mechanics  

SciTech Connect

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.

Kreider, J.F.

1985-01-01

8

CVEN 489-501 Group Project: Environmental Fluid Mechanics Research and Comparison to Engineering Practice  

Microsoft Academic Search

For this project, teams of two students each will work together to research a topic in environmental fluid mechanics, write a report in a format con sistent with this project description, and prepare a short in-class presentation. Students are fre e to choose their own topics, or they may choose from a list of suggestions. The report may be in

Scott A. Socolofsky; Kuang-An Chang

9

A Fluid Mechanics Hypercourse  

NASA Astrophysics Data System (ADS)

This CD-ROM is designed to accompany James Fay's Introduction to Fluid Mechanics. An enhanced hypermedia version of the textbook, it offers a number of ways to explore the fluid mechanics domain. These include a complete hypertext version of the original book, physical-experiment video clips, excerpts from external references, audio annotations, colored graphics, review questions, and progressive hints for solving problems. Throughout, the authors provide expert guidance in navigating the typed links so that students do not get lost in the learning process. System requirements: Macintosh with 68030 or greater processor and with at least 16 Mb of RAM. Operating System 6.0.4 or later for 680x0 processor and System 7.1.2 or later for Power-PC. CD-ROM drive with 256- color capability. Preferred display 14 inches or above (SuperVGA with 1 megabyte of VRAM). Additional system font software: Computer Modern postscript fonts (CM/PS Screen Fonts, CMBSY10, and CMTT10) and Adobe Type Manager (ATM 3.0 or later). James A. Fay is Professor Emeritus and Senior Lecturer in the Department of Mechanical Engineering at MIT.

Fay, James A.; Sonwalkar, Nishikant

1996-05-01

10

Relativistic Fluid Mechanics  

Microsoft Academic Search

fluid mechanics may be characterized as a theory that describes the state of a fluid by means of five functions of at most four independent variables. The latter variables are of two kinds: three variables determining a point in a three­ dimensional Euclidean space and a fourth one labeling absolute time on some sta ndard universal clock. The five functions,

A. H. Taub

1978-01-01

11

Quantitative, single shot, two-dimensional spontaneous Raman measurements for fluid mechanics and engine applications  

Microsoft Academic Search

Spontaneous Raman Scattering was used for quantitative, two-dimensional, single-shot measurements of species concentration in optically accessible confinements and in an experimental single-cylinder internal combustion engine. The study comprised three parts. In the first part, the technique was used for methane concentration measurements in a laminar jet issuing into compressed nitrogen (10 bar, 293 K). The injection Reynolds number was 550.

Dimitrios Constantinou Kyritsis

1998-01-01

12

Quantitative, single shot, two-dimensional spontaneous Raman measurements for fluid mechanics and engine applications  

NASA Astrophysics Data System (ADS)

Spontaneous Raman Scattering was used for quantitative, two-dimensional, single-shot measurements of species concentration in optically accessible confinements and in an experimental single-cylinder internal combustion engine. The study comprised three parts. In the first part, the technique was used for methane concentration measurements in a laminar jet issuing into compressed nitrogen (10 bar, 293 K). The injection Reynolds number was 550. Initial results showed unexpected structures in the acquired concentration profiles. Thus, the steadiness of the laminar flow was confirmed with high speed shadowgraph movies and laser induced fluorescence measurements. Eventually, it was proven that the structures were due to characteristics of the camera system. A technique was then devised for the proper acquisition and processing of data and spatial resolution of 500 mum was achieved. Methane number density equal to 12% of the number density of pure methane (0.247E+26 molecules/msp3) was then measured with a signal-to-noise ratio of approximately 3. The measurements were compared with the results of direct numerical simulation of the flow field. In the second part, measurements in a laminar hydrogen jet were taken. Because of the reduced Raman signal of hydrogen, the incident laser power was increased by installing the pressurized chamber within the laser cavity. This yielded an increase in power by a factor of 2.5. For the measurement of the laser sheet intensity in the laser cavity, insertion of a fluorescent dye cell and Rayleigh scattering were used and evaluated comparatively. The precise location of the waist of the laser sheet was determined by trial and error. The spatial resolution of the measurements was 650 mum and a number density of 0.371E+26 hydrogen molecules/msp3 was measured with a signal-to-noise ratio of 3. The measurements were again compared with results of direct numerical simulation. In the third part, the feasibility of two-dimensional single-shot Spontaneous Raman measurements in an engine cylinder was established. Measurements of methane concentration after direct injection in the cylinder of an experimental single-cylinder engine were taken. The engine was not fired to avoid laser induced incandescence interference. The spatial resolution was limited to 800 mum by the thickness of the laser sheet. Fast mixing of the methane jet was documented but a precise evaluation of the equivalence ratio was beyond the resolution of this first attempt. Finally, existing hardware for data acquisition and algorithms for two dimensional data reduction were reviewed and recommendations were made for the extraction of quantitative information from two-dimensional, single-shot Spontaneous Raman signals which are weak and noisy.

Kyritsis, Dimitrios Constantinou

13

Lord Kelvin on fluid mechanics  

NASA Astrophysics Data System (ADS)

William Thomson, Baron Kelvin of Largs, was the best-known British scientist of his day, who made fundamental contributions to many areas of physics and engineering. Though his life and work have been much studied, his contributions to fluid mechanics have received far less attention that those in heat, electricity, magnetism, geophysics, "ether theory" and telegraphy. After a general introduction, Kelvin's writings on fluid mechanics are comprehensively surveyed. These reveal the interplay of his mathematical expertise and physical intuition, his deployment of physical analogies, and the origins of some of his work in later-abandoned speculations. Among lasting contributions are his circulation theorem and minimum energy theorem, the misnamed "Stokes' theorem", a generalization of Green's theorem, the method of stationary phase, and much on vortices, instabilities, tides and water waves.

Craik, Alex D. D.

2012-06-01

14

Start Up Research Effort in Fluid Mechanics. Advanced Methods for Acoustic and Thrust Benefits for Aircraft Engine Nozzle  

NASA Technical Reports Server (NTRS)

In accordance with the project plan for the report period in the proposal titled above, HU and FML teams investigated two sets of concepts for reduction of noise and improvement in efficiency for jet exhaust nozzles of aircraft engines and screws for mixers, fans, propellers and boats. The main achievements in the report period are: (a) Publication of the paper in the AIAA Journal, which described our concepts and some results. (b) The Award in the Civil Research and Development Foundation (CRDF) competition. This 2 year grant for Hampton University (HU) and Central AeroHydrodynamic Institute (TSAGI, Moscow, Russia) supports the research implementation under the current NASA FAR grant. (c) Selection for funding by NASA HQ review panel of the Partnership Awards Concept Paper. This two year grant also will support our current FAR grant. (d) Publication of a Mobius Strip concept in NASA Technical Briefs, June, 1996, and a great interest of many industrial companies in this invention. Successful experimental results with the Mobius shaped screw for mixers, which save more than 30% of the electric power by comparison with the standard screws. Creation of the scientific-popular video-film which can be used for commercial and educational purposes. (e) Organization work, joint meetings and discussions of the NASA LARC JNL Team and HU professors and administration for the solution of actual problems and effective work of the Fluid Mechanics Laboratory at Hampton University. In this report the main designs are enumerated. It also contains for both concept sets: (1) the statement of the problem for each design, some results, publications, inventions, patents, our vision for continuation of this research, and (2) present and expected problems in the future.

White, Samuel G.; Gilinsky, Mikhail M.

1997-01-01

15

Fluid mechanics revisited  

NASA Astrophysics Data System (ADS)

Öttinger's recent nontraditional incorporation of fluctuations into the formulation of the friction matrix appearing in the phenomenological GENERIC theory of nonequilibrium irreversible processes is shown to furnish transport equations for single-component gases and liquids undergoing heat transfer which support the view that revisions to the Navier-Stokes-Fourier (N-S-F) momentum/energy equation set are necessary, as empirically proposed by the author on the basis of an experimentally supported theory of diffuse volume transport. The hypothesis that the conventional N-S-F equations prevail without modification only in the case of “incompressible” fluids, where the density ? of the fluid is uniform throughout, serves to determine the new phenomenological parameter ?? appearing in the GENERIC friction matrix. In the case of ideal gases the consequences of this constitutive hypothesis are shown to yield results identical to those derived theoretically by Öttinger on the basis of a “proper” coarse-graining of Boltzmann's kinetic equation. A major consequence of the present work is that the fluid's specific momentum density v is equal to its volume velocity vv, rather than to its mass velocity vm, contrary to current views dating back 250 years to Euler. In the case of rarefied gases the proposed modifications are also observed to agree with those resulting from Klimontovich's molecularly based, albeit ad hoc, self-diffusion addendum to Boltzmann's collision integral. Despite the differences in their respective physical models-molecular vs. phenomenological-the role played by Klimontovich's collisional addition to Boltzmann's equation in modifying the N-S-F equations is noted to constitute a molecular counterpart of Öttinger's phenomenological fluctuation addition to the GENERIC friction matrix. Together, these two theories collectively recognize the need to address multiple- rather than single- encounter collisions between a test molecule and its neighbors when formulating physically satisfactory statistical-mechanical theories of irreversible transport processes in gases. Overall, the results of the present work implicitly support the unorthodox view, implicit in the GENERIC scheme, that the translation of Newton's discrete mass-point molecular mechanics into continuum mechanics, the latter as embodied in the Cauchy linear momentum equation of fluid mechanics, cannot be correctly effected independently of the laws of thermodynamics. While Öttinger's modification of GENERIC necessitates fundamental changes in the foundations of fluid mechanics in regard to momentum transport, no basic changes are required in the foundations of linear irreversible thermodynamics (LIT) beyond recognizing the need to add volume to the usual list of extensive physical properties undergoing transport in single-species fluid continua, namely mass, momentum and energy. An alternative, nonGENERICally based approach to LIT, derived from our findings, is outlined at the conclusion of the paper. Finally, our proposed modifications of both Cauchy's linear momentum equation and Newton's rheological constitutive law for fluid-phase continua are noted to be mirrored by counterparts in the literature for solid-phase continua dating back to the classical interdiffusion experiments of Kirkendall and their subsequent interpretation by Darken in terms of diffuse volume transport.

Brenner, Howard

2006-10-01

16

Applied Fluid Mechanics. Lecture Notes.  

ERIC Educational Resources Information Center

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

Gregg, Newton D.

17

Selected topics of fluid mechanics  

USGS Publications Warehouse

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 the Euler, Froude, Reynolds, Weber, and Cauchy numbers are defined as essential tools for interpreting and using experimental data. The derivations of the energy and momentum equations are treated in detail. One-dimensional equations for steady nonuniform flow are developed, and the restrictions applicable to the equations are emphasized. Conditions of uniform and gradually varied flow are discussed, and the origin of the Chezy equation is examined in relation to both the energy and the momentum equations. The inadequacy of all uniform-flow equations as a means of describing gradually varied flow is explained. Thus, one of the definitive problems of river hydraulics is analyzed in the light of present knowledge. This report is the outgrowth of a series of short schools conducted during the spring and summer of 1953 for engineers of the Surface Water Branch, Water Resources Division, U. S. Geological Survey. The topics considered are essentially the same as the topics selected for inclusion in the schools. However, in order that they might serve better as a guide and outline for informal study, the arrangement of the writer's original lecture notes has been considerably altered. The purpose of the report, like the purpose of the schools which inspired it, is to build a simple but strong framework of the fundamentals of fluid mechanics. It is believed that this framework is capable of supporting a detailed analysis of most of the practical problems met by the engineers of the Geological Survey. It is hoped that the least accomplishment of this work will be to inspire the reader with the confidence and desire to read more of the recent and current technical literature of modern fluid mechanics.

Kindsvater, Carl E.

1958-01-01

18

A Design-Oriented Approach to the Integration of Thermodynamics, Fluid Mechanics, and Heat Transfer in the Undergraduate Mechanical Engineering Curriculum.  

ERIC Educational Resources Information Center

This paper describes two parallel efforts that attempt to implement a new approach to the teaching of thermal fluids engineering. In one setting, at the Massachusetts Institute of Technology (MIT), the subject matter is integrated into a single year-long subject at the introductory level. In the second setting, at Victoria (British Columbia,…

Whale, MacMurray D.; Cravalho, Ernest G.

19

Microprocessors in fluid power engineering  

SciTech Connect

Microprocessors and digital electronics may well take over most control functions in engineering and will also open up many new possibilities. This IMechE conference provided a forum of engineers to discuss the state of the technology. Subjects covered include: analogue valves and hydraulic controls; transducers; use of microprocessors in off-line processing activities; and the use of microprocessors in closed loop processing. Papers include a review of the application of microprocessors to electrohydraulic control systems; test rig control; a low cost microprocessor to fluid power interface valve; micro-electronics in flowmeters and other transducers; on-line monitoring of mining hydraulic systems; and computer controlled pneumatic servo drives.

Not Available

1984-01-01

20

The Physics of Fluid Mechanics  

NSDL National Science Digital Library

From drinking fountains at playgrounds, water systems in homes, and working bathrooms at schools to hydraulic bridges and levee systems, fluid mechanics are an essential part of daily life. Fluid mechanics, the study of how forces are applied to fluids, is outlined in this unit as a sequence of two lessons and three corresponding activities. The first lesson provides a basic introduction to Pascal's law, Archimedes' principle and Bernoulli's principle and presents fundamental definitions, equations and problems to solve with students, as well as engineering applications. The second lesson provides a basic introduction to above-ground storage tanks, their pervasive use in the Houston Ship Channel, and different types of storage tank failure in major storms and hurricanes. The unit concludes with students applying what they have learned to determine the stability of individual above-ground storage tanks given specific storm conditions so they can analyze their stability in changing storm conditions, followed by a project to design their own storage tanks to address the issues of uplift, displacement and buckling in storm conditions.

National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs,

21

Respiratory fluid mechanics  

PubMed Central

This article covers several aspects of respiratory fluid mechanics that have been actively investigated by our group over the years. For the most part, the topics involve two-phase flows in the respiratory system with applications to normal and diseased lungs, as well as therapeutic interventions. Specifically, the topics include liquid plug flow in airways and at airway bifurcations as it relates to surfactant, drug, gene, or stem cell delivery into the lung; liquid plug rupture and its damaging effects on underlying airway epithelial cells as well as a source of crackling sounds in the lung; airway closure from “capillary-elastic instabilities,” as well as nonlinear stabilization from oscillatory core flow which we call the “oscillating butter knife;” liquid film, and surfactant dynamics in an oscillating alveolus and the steady streaming, and surfactant spreading on thin viscous films including our discovery of the Grotberg–Borgas–Gaver shock.

Grotberg, James B.

2011-01-01

22

Ann Wagner, Mechanical Engineer.  

ERIC Educational Resources Information Center

Presents a profile of Ann Wagner, a mechanical engineer at the Goddard Space Flight Center in Maryland, and her job responsibilities there. Also includes a brief history of mechanical engineering as well as a sample graph and data activity sheet with answers. (AIM)

Bennett, Betsy K.

1996-01-01

23

On the fluid mechanics of fires  

SciTech Connect

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.

TIESZEN,SHELDON R.

2000-02-29

24

On the Fluid Mechanics of Fires  

NASA Astrophysics Data System (ADS)

Fluid mechanics research related to fire is reviewed with a focus on canonical flows, multiphysics coupling aspects, and experimental and numerical techniques. Fire is a low-speed, chemically reacting flow in which buoyancy plays an important role. Fire research has focused on two canonical flows, the reacting boundary layer and the reacting free plume. There is rich, multilateral, bidirectional coupling among fluid mechanics and scalar transport, combustion, and radiation. There is only a limited experimental fluid mechanics database for fire owing to measurement difficulties in the harsh environment and to 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.

Tieszen, Sheldon R.

25

Some connections between fluid mechanics and the solving of industrial and environmental fluid-flow problems  

Microsoft Academic Search

The ways in which advances in fluid mechanics have led to improvements in engineering design are discussed, with attention to the stimulation of fluid mechanics research by industrial and environmental problems. The development of many practical uses of fluid flow without the benefit of scientific study is also emphasized. Among the topics discussed are vortices and coherent structures in turbulent

J. C. R. Hunt

1981-01-01

26

FLUID MECHANICS AND HOMELAND SECURITY  

Microsoft Academic Search

Homeland security involves many applications of fluid mechanics and offers many opportunities for research and development. This review explores a wide selection of fluids topics in counterterrorism and suggests future directions. Broad topics range from preparedness and deterrence of impending terrorist attacks to detection, re- sponse, and recovery. Specific topics include aircraft hardening, blast mitigation, sensors and sampling, explosive detection,

Gary S. Settles

2006-01-01

27

Engine & Vehicle Mechanics Curriculum.  

ERIC Educational Resources Information Center

This competency-based curriculum includes all competencies a student will acquire in an engine and vehicle mechanics educational program. It follows guidelines established for automobile technician training programs leading toward certification and addresses requirements of the National Institute for Automotive Service Excellence (ASE). The…

Alaska State Dept. of Education, Juneau. Div. of Adult and Vocational Education.

28

Respiratory Fluid Mechanics  

NASA Astrophysics Data System (ADS)

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.

Grotberg, James

2005-11-01

29

Research in Applied Mathematics, Fluid Mechanics and Computer Science  

NASA Technical Reports Server (NTRS)

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.

1999-01-01

30

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

NASA Technical Reports Server (NTRS)

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.

1995-01-01

31

Numerical methods for fluid transient analysis; Proceedings of the Applied Mechanics, Bioengineering, and Fluids Engineering Conference, Houston, TX, June 20-22, 1983  

NASA Astrophysics Data System (ADS)

Among the topics discussed are implicit methods for the solution of the one-dimensional wave equation, second-order explicit methods for transient flow analysis, a generalized implicit finite difference method for transient analysis of compressible and incompressible fluid flows, the modeling of transient two-component flow with a four-point implicit method, one-dimensional transient gas flow with internal heating, transient pressure wave radial and axial variations, and vaporous and gaseous cavitation simulation. Also discussed are variable celerity modeling by the method of characteristics, a numerical model for transients in petroleum product pipelines, solid-liquid-gas mixture one-dimensional transient flows, hydraulic transients in tunnels with concurrent open channel and pressurized flow, and waterhammer transient control with dynamic programming of valve stoking. For individual items see A84-13235 to A84-13238

Martin, C. S.; Chaudhry, M. H.

32

Engineering fluid flow using sequenced microstructures  

NASA Astrophysics Data System (ADS)

Controlling the shape of fluid streams is important across scales: from industrial processing to control of biomolecular interactions. Previous approaches to control fluid streams have focused mainly on creating chaotic flows to enhance mixing. Here we develop an approach to apply order using sequences of fluid transformations rather than enhancing chaos. We investigate the inertial flow deformations around a library of single cylindrical pillars within a microfluidic channel and assemble these net fluid transformations to engineer fluid streams. As these transformations provide a deterministic mapping of fluid elements from upstream to downstream of a pillar, we can sequentially arrange pillars to apply the associated nested maps and, therefore, create complex fluid structures without additional numerical simulation. To show the range of capabilities, we present sequences that sculpt the cross-sectional shape of a stream into complex geometries, move and split a fluid stream, perform solution exchange and achieve particle separation. A general strategy to engineer fluid streams into a broad class of defined configurations in which the complexity of the nonlinear equations of fluid motion are abstracted from the user is a first step to programming streams of any desired shape, which would be useful for biological, chemical and materials automation.

Amini, Hamed; Sollier, Elodie; Masaeli, Mahdokht; Xie, Yu; Ganapathysubramanian, Baskar; Stone, Howard A.; di Carlo, Dino

2013-05-01

33

The 1991 research program (of the Faculty of Mechanical Engineering)  

NASA Astrophysics Data System (ADS)

The main research activities and programs are overviewed. The following domains are covered: production techniques, production organization, transportation and storage, mechanical engineering automation, design and construction, ergonomics, design in plastics, thermal mechanics, heat transfer and fluid mechanics, biomedical mechanical engineering, materials science, and technical mechanics and tribology.

1991-05-01

34

Fluid Mechanics and Homeland Security  

NASA Astrophysics Data System (ADS)

Homeland security involves many applications of fluid mechanics and offers many opportunities for research and development. This review explores a wide selection of fluids topics in counterterrorism and suggests future directions. Broad topics range from preparedness and deterrence of impending terrorist attacks to detection, response, and recovery. Specific topics include aircraft hardening, blast mitigation, sensors and sampling, explosive detection, microfluidics and labs-on-a-chip, chemical plume dispersal in urban settings, and building ventilation. Also discussed are vapor plumes and standoff detection, nonlethal weapons, airborne disease spread, personal protective equipment, and decontamination. Involvement in these applications requires fluid dynamicists to think across the traditional boundaries of the field and to work with related disciplines, especially chemistry, biology, aerosol science, and atmospheric science.

Settles, Gary S.

2006-01-01

35

Engineering graphene mechanical systems.  

PubMed

We report a method to introduce direct bonding between graphene platelets that enables the transformation of a multilayer chemically modified graphene (CMG) film from a "paper mache-like" structure into a stiff, high strength material. On the basis of chemical/defect manipulation and recrystallization, this technique allows wide-range engineering of mechanical properties (stiffness, strength, density, and built-in stress) in ultrathin CMG films. A dramatic increase in the Young's modulus (up to 800 GPa) and enhanced strength (sustainable stress ?1 GPa) due to cross-linking, in combination with high tensile stress, produced high-performance (quality factor of 31,000 at room temperature) radio frequency nanomechanical resonators. The ability to fine-tune intraplatelet mechanical properties through chemical modification and to locally activate direct carbon-carbon bonding within carbon-based nanomaterials will transform these systems into true "materials-by-design" for nanomechanics. PMID:22764747

Zalalutdinov, Maxim K; Robinson, Jeremy T; Junkermeier, Chad E; Culbertson, James C; Reinecke, Thomas L; Stine, Rory; Sheehan, Paul E; Houston, Brian H; Snow, Eric S

2012-08-01

36

Structural engineering, mechanics and materials: Final report  

SciTech Connect

This report on structural engineering, mechanics and materials is divided into three parts: a discussion on using Lanczos vectors and Ritz vectors for computing dynamic responses: solution of viscously damped linear systems using a finite element displacement formulation; and vibration analysis of fluid-solid systems using a finite element displacement formulation. (JF)

Not Available

1988-01-01

37

Annual review of fluid mechanics, Volume 15  

NASA Astrophysics Data System (ADS)

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. (For individual items see A83-31077 to A83-31086)

van Dyke, M.; Wehausen, J. V.; Lumley, J. L.

38

Fluid Mechanics of Urban Environments  

NASA Astrophysics Data System (ADS)

The rapid urbanization of the Earth has led to highly populated cities that act as concentrated centers of anthropogenic stressors on the natural environment. The degradation of environmental quality due to such stressors, in turn, greatly impacts human behavior. Anthropogenic stressors largely originate as a result of coupling between man-made urban elements (i.e., networks of engineering and socio-economic infrastructures) and the environment, for which surrounding fluid motions play a key role. In recent years, research efforts have been directed at the understanding and modeling of fluid motions in urban areas, infrastructure dynamics and interactions thereof, with the hope of identifying environmental impacts of urbanization and complex outcomes (or ``emergent properties'') of nominally simple interactions between infrastructures and environment. Such consequences play an important role in determining the ``resilience'' of cities under anthropogenic stressors, defined as maintaining the structure and essential functions of an urbanity without regime shifts. Holistic integrated models that meld the dynamics of infrastructures and environment as well as ``quality of life'' attributes are becoming powerful decision-making tools with regard to sustainability of urban areas (continuance or even enhancement of socio-economic activities in harmony with the environment). The rudimentary forms of integrated models are beginning to take shape, augmented by comprehensive field studies and advanced measurement platforms to validate them. This presentation deals with the challenges of modeling urban atmosphere, subject to anthropogenic forcing. An important emergent property, the Urban Heat Island, and its role in determining resilience and sustainability of cities will be discussed based on the prediction of a coupled model.

Fernando, Harindra J.

2008-11-01

39

FLUID MECHANICS OF ARTIFICIAL HEART VALVES  

PubMed Central

SUMMARY 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 mechanical heart valves, these complications are believed to be associated with non-physiological blood flow patterns. 2. In the present review, we provide a bird’s-eye view of fluid mechanics for the major artificial heart valve types and highlight how the engineering approach has shaped this rapidly diversifying area of research. 3. Mechanical heart valve designs have evolved significantly, with the most recent designs providing relatively superior haemodynamics with very low aerodynamic resistance. However, high shearing of blood cells and platelets still pose significant design challenges and patients must undergo life-long anticoagulation therapy. Bioprosthetic or tissue valves do not require anticoagulants due to their distinct similarity to the native valve geometry and haemodynamics, but many of these valves fail structurally within the first 10–15 years of implantation. 4. These shortcomings have directed present and future research in three main directions in attempts to design superior artificial valves: (i) engineering living tissue heart valves; (ii) development of advanced computational tools; and (iii) blood experiments to establish the link between flow and blood damage.

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

2009-01-01

40

Diesel Engine Mechanics.  

ERIC Educational Resources Information Center

Written in student performance terms, this curriculum guide on diesel engine repair is divided into the following eight sections: an orientation to the occupational field and instructional program; instruction in operating principles; instruction in engine components; instruction in auxiliary systems; instruction in fuel systems; instruction in…

Foutes, William A.

41

Recent contributions to fluid mechanics  

NASA Astrophysics Data System (ADS)

The results of theoretical and experimental studies in various areas of fluid mechanics research are presented. Attention is given to half-model wing tests above and below stall, the vorticity field on wings, and vortex separation at the leading edge of slender wings. Turbulence modelling requirements of three-dimensional boundary layers are examined, as are the topology of viscous flowfields, instability and coherent structures in jet flows, and finite difference solutions for laminar boundary layer flows with separation. The isentropic MGD flow of a perfect plasma is investigated, together with transonic flow around an intake, the inclusion of curvature in models of turbine blade boundary layers, and turbulent heat transfer. Velocity fluctuation in a supersonic jet, a random walk and diffusion in two-dimensional Lagrangian systems, and the effects of mesh size of vortex shedding are studied. Consideration is given to similarity laws in dimensional analyses and to the Magnus effect on a boattailed shell at supersonic speeds. For individual items see A83-46455 to A83-46481

Haase, W.

42

NASA Ames Fluid Mechanics Laboratory research briefs  

NASA Technical Reports Server (NTRS)

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.

Davis, Sanford (editor)

1994-01-01

43

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

ERIC Educational Resources Information Center

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…

Cox, John S.

44

Multimedia Fluid Mechanics - Multilingual Version CD-ROM  

NASA Astrophysics Data System (ADS)

This CD-ROM offers an interactive tool for teaching undergraduate fluid mechanics. It features experiments that demonstrate fluid mechanical phenomena, animations of important principles and concepts, virtual laboratories in which students acquire data from the images, interactive computational exercises in which parameters can be varied, and other descriptive and illuminating material on applications. The material may be accessed randomly through a hyperlinked text, a search engine, a video library, and a glossary of terms. The new edition has been thoroughly updated and includes versions in English, Spanish and French.

Homsy, G. M.; Aref, H.; Breuer, K. S.; Hochgreb, S.; Koseff, J. R.; Munson, B. R.; Powell, K. G.; Robertson, C. R.; Thoroddsen, S. T.

2004-07-01

45

Application of Infrared Thermography in Fluid Mechanics.  

National Technical Information Service (NTIS)

The history of infrared thermography in fluid mechanics is outlined and special problems related to infrared thermography in wind tunnels are addressed: IR windows; distance between model and camera; model emissivity/conductivity problems; short duration ...

D. L. Balageas A. Bouchardy

1993-01-01

46

Shape Optimization in Fluid Mechanics  

Microsoft Academic Search

? Abstract This paper is a short and nonexhaustive,survey of some,recent devel- opments,in optimal shape design (OSD) for fluids. OSD is an interesting field both mathematically and for industrial applications. Existence, sensitivity, and compati- bility of discretizations are important theoretical issues. Efficient algorithmic,imple- mentations,with low complexity,are also critical. In this paper we discuss topological optimization, algorithmic differentiation, gradient smoothers, Computer

Bijan Mohammadi; Olivier Pironneau

2004-01-01

47

Topological fluid mechanics of stirring  

NASA Astrophysics Data System (ADS)

A new approach to regular and chaotic fluid advection is presented that utilizes the Thurston Nielsen classification theorem. The prototypical two-dimensional problem of stirring by a finite number of stirrers confined to a disk of fluid is considered. The theory shows that for particular ‘stirring protocols’ a significant increase in complexity of the stirred motion known as topological chaos occurs when three or more stirrers are present and are moved about in certain ways. In this sense prior studies of chaotic advection with at most two stirrers, that were, furthermore, usually fixed in place and simply rotated about their axes, have been ‘too simple’. We set out the basic theory without proofs and demonstrate the applicability of several topological concepts to fluid stirring. A key role is played by the representation of a given stirring protocol as a braid in a (2+1)-dimensional space time made up of the flow plane and a time axis perpendicular to it. A simple experiment in which a viscous liquid is stirred by three stirrers has been conducted and is used to illustrate the theory.

Boyland, Philip L.; Aref, Hassan; Stremler, Mark A.

2000-01-01

48

Some connections between fluid mechanics and the solving of industrial and environmental fluid-flow problems  

NASA Astrophysics Data System (ADS)

The ways in which advances in fluid mechanics have led to improvements in engineering design are discussed, with attention to the stimulation of fluid mechanics research by industrial and environmental problems. The development of many practical uses of fluid flow without the benefit of scientific study is also emphasized. Among the topics discussed are vortices and coherent structures in turbulent flows, lubrication, jet and multiphase flows, the control and exploitation of waves, the effect of unsteady forces on structures, and dispersion phenomena. Among the practical achievements covered are the use of bluff shields to control separated flow over truck bodies and reduce aerodynamic drag, ink-jet printing, hovercraft stability, fluidized-bed combustion, the fluid/solid instabilities caused by air flow around a computer memory floppy disc, and various wind turbines.

Hunt, J. C. R.

1981-05-01

49

Computational fluid mechanics and heat transfer  

Microsoft Academic Search

This book is intended to serve as a text for introductory courses in computational fluid mechanics and heat transfer for advanced undergraduates and\\/or first-year graduate students. The first part of the book presents basic concepts and provides an introduction to the fundamentals of finite-difference methods, while the second part is devoted to applications involving the equations of fluid mechanics and

D. A. Anderson; J. C. Tannehill; R. H. Pletcher

1984-01-01

50

Fluid mechanics of pulse detonation thrusters  

NASA Astrophysics Data System (ADS)

The advantages of constant volume combustion cycle as compared to constant pressure combustion in terms of thermodynamic efficiency have focused the researches of advanced propulsion on detonation engines. The paper gives coverage of efforts undertaken during past decades in adjusting detonations for propulsion applications, and highlights new challenges in studying fluid flow dynamics relevant to onset of detonation.

Phylippov, Yu. G.; Dushin, V. R.; Nikitin, V. F.; Nerchenko, V. A.; Korolkova, N. V.; Guendugov, V. M.

2012-07-01

51

Analogy between fluid cavitation and fracture mechanics  

NASA Technical Reports Server (NTRS)

When the stresses imposed on a fluid are sufficiently large, rupture or cavitation can occur. Such conditions can exist in many two-phase flow applications, such as the choked flows, which can occur in seals and bearings. Nonspherical bubbles with large aspect ratios have been observed in fluids under rapid acceleration and high shear fields. These bubbles are geometrically similar to fracture surface patterns (Griffith crack model) existing in solids. Analogies between crack growth in solid and fluid cavitation are proposed and supported by analysis and observation (photographs). Healing phenomena (void condensation), well accepted in fluid mechanics, have been observed in some polymers and hypothesized in solid mechanics. By drawing on the strengths of the theories of solid mechanics and cavitation, a more complete unified theory can be developed.

Hendricks, R. C.; Mullen, R. L.; Braun, M. J.

1983-01-01

52

Mechanical engineering department technical review  

SciTech Connect

The Mechanical Engineering Department Technical Review is published to: (1) inform the readers of various technical activities within the department, (2) promote exchange of ideas, and (3) give credit to the personnel who are achieving the results. The report is formatted into two parts: technical acievements and publication abstracts. The first is divided into eight sections, one for each division in the department providing the reader with the names of the personnel and the division accomplishing the work.

Carr, R.B. Denney, R.M. (eds.)

1981-01-01

53

Mechanical Engineering Department technical abstracts  

SciTech Connect

The Mechanical Engineering Department publishes listings of technical abstracts twice a year to inform readers of the broad range of technical activities in the Department, and to promote an exchange of ideas. Details of the work covered by an abstract may be obtained by contacting the author(s). Overall information about current activities of each of the Department's seven divisions precedes the technical abstracts.

Denney, R.M. (ed.)

1982-07-01

54

Standardized Curriculum for Diesel Engine Mechanics.  

ERIC Educational Resources Information Center

Standardized curricula are provided for two courses for the secondary vocational education program in Mississippi: diesel engine mechanics I and II. The eight units in diesel engine mechanics I are as follows: orientation; shop safety; basic shop tools; fasteners; measurement; engine operating principles; engine components; and basic auxiliary…

Mississippi State Dept. of Education, Jackson. Office of Vocational, Technical and Adult Education.

55

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

NASA Technical Reports Server (NTRS)

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.

1992-01-01

56

Computational fluid mechanics utilizing the variational principle of modeling damping seals  

NASA Technical Reports Server (NTRS)

An analysis for modeling damping seals for use in Space Shuttle main engine turbomachinery is being produced. Development of a computational fluid mechanics code for turbulent, incompressible flow is required.

Abernathy, J. M.; Farmer, R.

1985-01-01

57

Teaching Computational Fluid Dynamics (CFD) to Design Engineers  

NSDL National Science Digital Library

Computational Fluid Dynamics (CFD) can provide detailed thermal flow information, such as temperature field, pressure field and velocity field, in equipment and process in various industries. Due to the recent rapid growth of powerful computer resources and the development of commercial CFD software packages, CFD has been proven a useful tool for mechanical design engineers. CFD has also gained broad acceptance in the engineering education. It has been adopted in both undergraduate and graduate level courses in many universities. The teaching of CFD in current engineering education can be classified into two types, one is to focus on the numerical methods with little emphasis on using the software and the other is to introduce a CFD software as a virtual reality laboratory in Fluid Mechanics class without emphasis on teaching software. In the first type, students need strong mathematical background to succeed in the class and also need further training to effectively use modern commercial software for real industrial application. While in the second type, students only learned an abstract form of CFD processes, thus they will not be able to use CFD commercial software without further training in this area. This paper is about the use of CFD in teaching graduate students at this university who were in a two year design track program. Many of these students did not have a good background in mathematics, fluid dynamics, heat transfer, and programming, however, most of them were good at computer aided design in ProE and were very interested in learning CFD as a design tool in industries. STAR-CCM+ was chosen as the CFD software to teach students the entire CFD process in a single integrated software environment. After building a geometry model in ProE, students learned to import the CAD model, set up mesh model, physical model and solver, and postprocess the results in STAR-CCM+. Based on projects, CFD numerical methods and fundamentals of heat transfer and fluid flow were introduced to help students understand the CFD process, interpret, and validate simulation results.

Hu, Junling; Xiong, Xingguo; Zhang, Linfeng

2009-09-02

58

Geological fluid mechanics models at various scales  

Microsoft Academic Search

In this dissertation, I employ concepts from fluid mechanics to quantitatively investigate geological processes in hydrogeology and volcanology. These research topics are addressed by utilizing numerical and analytical models but also by conducting field and lab work. Percolation theory is of interest to a wide range of physical sciences and thus warrants research in itself. Therefore, I developed a computer

Martin Oliver Saar

2003-01-01

59

Application of infrared thermography in fluid mechanics  

Microsoft Academic Search

The history of infrared thermography in fluid mechanics is outlined and special problems related to infrared thermography in wind tunnels are addressed: IR windows; distance between model and camera; model emissivity\\/conductivity problems; short duration tests. The use of passive and active thermography to image the space distribution of the convective heat transfer at the wall of the model, in view

D. L. Balageas; A.-M. Bouchardy

1993-01-01

60

Application of laser techniques in fluid mechanics  

NASA Astrophysics Data System (ADS)

Optical methods are used to study the following problems in Fluid Mechanics: (1) propagation of solitary waves in water channels; (2) thermoconvective flow of petroleum-in-water emulsions; (3) flow distribution in combustion chambers; and (4) propagation of blood in human veins.

da Costa, German; Cote, Ramon; Guarnieri, Raniero; Mosqueda, Felix; Parra, Juan E.; Rengel, Miriam; Cataldo, Jose; Guarga, Rafael; Lezama, Arturo; Usera, Gabriel

1999-07-01

61

Fluid Mechanics, Drag Reduction and Advanced Configuration Aeronautics  

NASA Technical Reports Server (NTRS)

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.

Bushnell, Dennis M.

2000-01-01

62

Noise produced by fluid inhomogeneities. [in gas turbine engines  

NASA Technical Reports Server (NTRS)

In an actual engine system, one mechanism for production of hot spots is the burning of various fluid elements at various different mixture ratios. Variable mixture ratio means variable temperature, and this is the effect that has been studied insofar as a noise source is concerned. However, variable mixture ratio also implies variable molecular weight and heat capacity. The paper investigates whether either of these last two variations may be responsible for a significant noise source. The analysis is made within the context of one-dimensional unsteady flow as in the work of Candel (1972). A mixture of thermally perfect gases is assumed as the working fluid, and the fluid composition consists of species 1 and a small and variable mole fraction of species 2 which has different molecular weight and specific heats as compared with species 1. In the absence of changes in the ratio of specific heat (gamma), the entropy variations due to temperature and molecular weight variations are equivalent as a sound source. The portion of sound called 'gamma prime' noise is discussed.

Strahle, W. C.

1976-01-01

63

ADDRESSING ENVIRONMENTAL ENGINEERING CHALLENGES WITH COMPUTATIONAL FLUID DYNAMICS  

EPA Science Inventory

This paper discusses the status and application of Computational Fluid Dynamics )CFD) models to address environmental engineering challenges for more detailed understanding of air pollutant source emissions, atmospheric dispersion and resulting human exposure. CFD simulations ...

64

Fluidic multiplexer for fluid servomotors in a gas turbine engine  

SciTech Connect

This patent describes an improvement in a gas turbine engine. The improvement comprises: fluidic motors; fluid lines connecting the fluidic motors with a fluid multiplex r, the fluid multiplexer including; a drum; a housing having apertures and within which the drum is continuously unidirectionally rotatable; a conduit within the drum which sequentially connects each of the opening with a common fluid pressure source during rotation, the conduit comprising a bore and branches; and a servo valve means adapted to selectively connect the conduit to the common fluid pressure source.

Richards, J.C.; Smith, J.P. Jr.

1992-02-25

65

Neural Control Mechanisms and Body Fluid Homeostasis  

NASA Technical Reports Server (NTRS)

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.

Johnson, Alan Kim

1998-01-01

66

Annual review of fluid mechanics. Volume 22  

SciTech Connect

Topics presented include rapid granular flows, issues in viscoelastic fluid mechanics, wave loads on offshore structures, boundary layers in the general ocean circulation, parametrically forced surface waves, wave-mean flow interactions in the equatorial ocean, and local and global instabilities in spatially developing flows. Also presented are aerodynamics of human-powered flight, aerothermodynamics and transition in high-speed wind tunnels at NASA-Langley, wakes behind blunt bodies, and mixing, chaotic advection, and turbulence. Also addressed are the history of the Reynolds number, panel methods in computational fluid dynamics, numerical multipole and boundary integral equation techniques in Stokes flow, plasma turbulence, optical rheometry, and viscous-flow paradoxes.

Lumley, J.L.; Van Dyke, M.; Reed, H.L.

1990-01-01

67

Fluids  

NSDL National Science Digital Library

This Topic in Depth explores the Web's offerings on the physics of fluids. By an educational Web site called School for Champions, the first site is the Fluids lesson plan (1). Here, students or anyone interested can read about the basics of fluids and then take a short interactive quiz on the topic. The second site is maintained by Steve Lower of the Department of Chemistry at Simon Fraser University called Liquids and their Vapors (2). This Adobe Acrobat (.pdf) file contains an eighteen-page document that covers topics such as properties of liquids and changes of state. The next site contains an interactive multimedia activity presented by explorescience.com called Floating Log (3). The site allows users to explore how a fluid can affect buoyancy by letting them change the mass of the log and the fluid's density. The next site from Purdue University's Chemical Education Web site is called Liquids (4). This page describes the structure of liquids, what kinds of materials form liquids, vapor pressure, and more. The fifth site, offered by Professor M.S. Cramer at the College of Engineering at Virginia Tech, is entitled Gallery of Fluid Dynamics (5). It contains movies, animations, photographs, and descriptions of various fluid mechanics topics such as condensation, shock waves, and supersonic cars. Next comes the Innovative Technology Solutions Corporation's Fundamental Fluid Mechanics Movies Web site (6). Over thirty short films show how fluids move in various conditions including gravity waves, fire, material transport, and hydraulics. From the University of Waterloo's Department of Mechanical Engineering-Microelectronics Heat Transfer Laboratory comes the next site, called the Fluid Properties Calculator (7). This online tool allows users to select a fluid and enter a temperature to calculate various parameters such as density, viscosity, specific heat, and thermal diffusivity. The last site is the online journal Physics of Fluids (8), which is published monthly by the American Institute of Physics with the cooperation of The American Physical Society Division of Fluid Dynamics. The journal is "devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and complex or multiphase fluids" and provides free full-text articles for online viewing.

Brieske, Joel A.

2002-01-01

68

Technical abstracts: Mechanical engineering, 1990  

SciTech Connect

This document is a compilation of the published, unclassified abstracts produced by mechanical engineers at Lawrence Livermore National Laboratory (LLNL) during the calendar year 1990. Many abstracts summarize work completed and published in report form. These are UCRL-JC series documents, which include the full text of articles to be published in journals and of papers to be presented at meetings, and UCID reports, which are informal documents. Not all UCIDs contain abstracts: short summaries were generated when abstracts were not included. Technical Abstracts also provides descriptions of those documents assigned to the UCRL-MI (miscellaneous) category. These are generally viewgraphs or photographs presented at meetings. An author index is provided at the back of this volume for cross referencing.

Broesius, J.Y. (comp.)

1991-03-01

69

Unified system for holographic measurement in fluid and solid mechanics: application of the system to volumetric flow measurement in an internal combustion engine  

NASA Astrophysics Data System (ADS)

This paper reports holographic measurements of full-field 3D flows inside a production geometry 4-stoke internal combustion engine with extensive optical access through both the cylinder wall and the piston crown. The seeded flow is recorda at two instants as a reflection hologram of high numerical aperture. A purpose built holographic camera using a phase conjugate holographic optical element is used to compensate for the gross aberrations caused by imaging through a thick walled, glass cylinder. Fiber-optic, conjugate recognition and subsequent correlation of the complex amplitude recorded by the hologram facilitates sub- wavelength measurement of particle displacement without directional ambiguity. Preliminary measurements of the flow field within the cylinder at the bottom of the induction stroke are discussed. The results clearly show the potential of this technique to extract 3D velocity information in hostile environments.

Chan, Victor S.; Barnhart, Donald H.; Garner, Colin P.; Halliwell, Neil A.; Coupland, Jeremy M.

1999-10-01

70

Lattice gas automata for fluid mechanics  

NASA Astrophysics Data System (ADS)

A lattice gas is the representation of a gas by its restriction on the nodes of a regular lattice for discrete time steps. It was recently shown by Frisch, Hasslacher and Pomeau that such very simple models lead to the incompressible Navier-Stokes equation provided the lattice has enough symmetry and the local rules for collisions between particles obey the usual conservation laws of classical mechanics. We present here recent results of numerical simulations to illustrate the power of this new approach to fluid mechanics which may give new tools for numerical studies and build a bridge between cellular automata theory and complex physical problems.

D'humières, D.; Lallemand, P.

1986-12-01

71

Gasoline engine valve-train mechanism simulation  

Microsoft Academic Search

The paper describes the engine valve-train mechanism's dynamic analysis method, and introduces how to make dynamic simulation of it, and then makes the conclusions from the simulation results. In the process of simulation, first engine valve-train mechanism is modeled by CATIA software, and then models are imported into ADAMS software, so as to simulate the movement of engine valve-train mechanism.

Wang Xihui; Li Jing

2011-01-01

72

Comparing fluid mechanics models with experimental data.  

PubMed Central

The art of modelling the physical world lies in the appropriate simplification and abstraction of the complete problem. In fluid mechanics, the Navier-Stokes equations provide a model that is valid under most circumstances germane to animal locomotion, but the complexity of solutions provides strong incentive for the development of further, more simplified practical models. When the flow organizes itself so that all shearing motions are collected into localized patches, then various mathematical vortex models have been very successful in predicting and furthering the physical understanding of many flows, particularly in aerodynamics. Experimental models have the significant added convenience that the fluid mechanics can be generated by a real fluid, not a model, provided the appropriate dimensionless groups have similar values. Then, analogous problems can be encountered in making intelligible but independent descriptions of the experimental results. Finally, model predictions and experimental results may be compared if, and only if, numerical estimates of the likely variations in the tested quantities are provided. Examples from recent experimental measurements of wakes behind a fixed wing and behind a bird in free flight are used to illustrate these principles.

Spedding, G R

2003-01-01

73

Teaching Continuum Mechanics in a Mechanical Engineering Program  

ERIC Educational Resources Information Center

This paper introduces a graduate course, continuum mechanics, which is designed for and taught to graduate students in a Mechanical Engineering (ME) program. The significance of continuum mechanics in engineering education is demonstrated and the course structure is described. Methods used in teaching this course such as topics, class…

Liu, Yucheng

2011-01-01

74

Introduction of Manufacturing to Mechanical Engineering Students  

NSDL National Science Digital Library

In response to a need to include a course in the Mechanical Engineering curriculum that introduced the students to mechanical engineering practice, the University of South Carolina has recently modified a freshman level engineering graphics course to include engineering design, engineering analysis and manufacturing. The engineering graphics emphasis of the course was retained but now is applied to all areas of mechanical engineering practice rather than design communications.The students design parts by hand sketching and computer-aided design (CAD) three-dimensional modeling. Heat transfer and stress analyses are performed using a finite-element analysis (FEA) program. Parts are manufactured on a CNC 3-axis milling machine using NC codedeveloped on a computer-aided manufacturing (CAM) program. In addition, the course has been modified to include more project-based and hands-on learning.

Rhodes, Curtis A.

2009-10-29

75

Dictionary of mechanical engineering, third edition  

SciTech Connect

This dictionary provides coverage of terms currently used in mechanical and production engineering. Since the publication of the previous edition ten years ago many new terms have been added to the engineer's vocabulary, particularly in fields related to robotics, automation, and computer applications. This edition has been revised to cover a broader range of topics and contains many new illustrations and over 700 new entries. There are also appendices listing engineering symbols and abbreviations, and an extensive list of engineering organizations.

Nayler, G.H.F.

1985-01-01

76

Application of infrared thermography in fluid mechanics  

NASA Astrophysics Data System (ADS)

The history of infrared thermography in fluid mechanics is outlined and special problems related to infrared thermography in wind tunnels are addressed: IR windows; distance between model and camera; model emissivity/conductivity problems; short duration tests. The use of passive and active thermography to image the space distribution of the convective heat transfer at the wall of the model, in view of detecting the transition location, or of determining the convective fluxes (heat flux metrology) is discussed. The detection of transition is discussed and various other flow features detection (shock waves, separation, reattachment, vortices) are considered.

Balageas, D. L.; Bouchardy, A.-M.

77

Gasoline Engine Mechanics. Florida Vocational Program Guide.  

ERIC Educational Resources Information Center

This vocational program guide is intended to assist in the organization, operation, and evaluation of a program in gasoline engine mechanics in school districts, area vocational centers, and community colleges. The following topics are covered: job duties of small-engine mechanics; program content (curriculum framework and student performance…

University of South Florida, Tampa. Dept. of Adult and Vocational Education.

78

Small Engine Mechanics. Post Secondary Curriculum Guide.  

ERIC Educational Resources Information Center

This curriculum guide was designed for use in postsecondary small engine mechanics education programs in Georgia. Its purpose is to provide for the development of entry level skills in small engine mechanics in the areas of knowledge, theoretical structure, tool usage, diagnostic ability, related supportive skills, and occupational survival…

Watkins, James F.; And Others

79

Defining the Australian mechanical engineer  

Microsoft Academic Search

The attribute focus in engineering education now adopted by the engineering education accrediting bodies of the US, UK and Australia is based on meeting the assumed needs of professional practice. It is associated with an increasing expectation by employers of work-ready graduates rather than relying on subsequent work-based learning and experience to develop many of the essential professional practice attributes.

Clive Ferguson

2006-01-01

80

Mechanical Engineering Department engineering research: Annual report, FY 1986  

Microsoft Academic Search

This report provides information on the five areas of research interest in LLNL's Mechanical Engineering Department. In Computer Code Development, a solid geometric modeling program is described. In Dynamic Systems and Control, structure control and structure dynamics are discussed. Fabrication technology involves machine cutting, interferometry, and automated optical component manufacturing. Materials engineering reports on composite material research and measurement of

R. M. Denney; K. L. Essary; M. S. Genin; H. H. Highstone; J. D. Hymer; S. O. Taft

1986-01-01

81

The Fluid Mechanics of Carbon Dioxide Sequestration  

NASA Astrophysics Data System (ADS)

Humans are faced with a potentially disastrous global problem owing to the current emission of 32 gigatonnes of carbon dioxide (CO2) annually into the atmosphere. A possible way to mitigate the effects is to store CO2 in large porous reservoirs within the Earth. Fluid mechanics plays a key role in determining both the feasibility and risks involved in this geological sequestration. We review current research efforts looking at the propagation of CO2 within the subsurface, the possible rates of leakage, the mechanisms that act to stably trap CO2, and the geomechanical response of the crust to large-scale CO2 injection. We conclude with an outline for future research.

Huppert, Herbert E.; Neufeld, Jerome A.

2014-01-01

82

Geophysical Aspects of Non-Newtonian Fluid Mechanics  

Microsoft Academic Search

Non-Newtonian fluid mechanics is a vast subject that has several journals partly, or primarily, dedicated to its investigation\\u000a (Journal of Non-Newtonian Fluid Mechanics, Rheologica Acta, Journal of Fluid Mechanics, Journal of Rheology, amongst others).\\u000a It is an area of active research, both for industrial fluid problems and for applications elsewhere, notably geophysically\\u000a motivated issues such as the flow of lava

N. J. Balmforth; R. V. Craster

2001-01-01

83

A generating mechanism for apparent fluid slip in hydrophobic microchannels  

Microsoft Academic Search

Fluid slip has been observed experimentally in micro- and nanoscale flow devices by several investigators [e.g., Tretheway and Meinhart, Phys. Fluids 14, L9 (2002); Zhu and Granik, Phys. Rev. Lett. 87, 096105 (2001); Pit &etal;, Phys. Rev. Lett. 85, 980 (2000); and Choi &etal;, Phys. Fluids 15, 2897 (2003)]. This paper examines a possible mechanism for the measured fluid slip,

Derek C. Tretheway; Carl D. Meinhart

2004-01-01

84

Introductory Education for Mechanical Engineering by Exercise in Mechanical Disassembly  

NASA Astrophysics Data System (ADS)

An introductory program “Exercise for engineers in mechanical disassembly” is an exercise that ten students of every team disassemble a motor scooter to the components and then assemble again to the initial form in 15 weeks. The purpose of this program is to introduce mechanical engineering by touching the real machine and learning how it is composed from various mechanical parts to the students at the early period after the entrance into the university. Additional short lectures by young teachers and a special lecture by a top engineer in the industry encourage the students to combine the actual machine and the mechanical engineering subjects. Furthermore, various educations such as group leader system, hazard prediction training, parts filing are included in this program. As a result, students recognize the importance of the mechanical engineering study and the way of group working.

Matsui, Yoshio; Asakawa, Naoki; Iwamori, Satoru

85

Liquid rocket engine fluid-cooled combustion chambers  

NASA Technical Reports Server (NTRS)

A monograph on the design and development of fluid cooled combustion chambers for liquid propellant rocket engines is presented. The subjects discussed are (1) regenerative cooling, (2) transpiration cooling, (3) film cooling, (4) structural analysis, (5) chamber reinforcement, and (6) operational problems.

1972-01-01

86

Internal fluid mechanics research on supercomputers for aerospace propulsion systems  

Microsoft Academic Search

The Internal Fluid Mechanics Division of the NASA Lewis Research Center is combining the key elements of computational fluid dynamics, aerothermodynamic experiments, and advanced computational technology to bring internal computational fluid mechanics (ICFM) to a state of practical application for aerospace propulsion systems. The strategies used to achieve this goal are to: (1) pursue an understanding of flow physics, surface

Brent A. Miller; Bernhard H. Anderson; John R. Szuch

1988-01-01

87

Fluid mechanics of mathematics testing in Texas  

NASA Astrophysics Data System (ADS)

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.

Marder, Michael

2010-03-01

88

Fluid mechanics of spinner-flask bioreactors  

NASA Astrophysics Data System (ADS)

The dynamic environment within bioreactors used for in vitro tissue growth has been observed to affect the development of mammalian cells. Many studies have shown that moderate mechanical stress enhances growth of some tissues whereas high shear levels and turbulence seem to damage cells. In order to optimize the design and the operating conditions of bioreactors, it is important to understand the fluid-dynamic characteristics and to control the stress levels within these devices. The present research focuses on the characterization of the flow field within a spinner-flask bioreactor. The dynamic properties of the flow are investigated experimentally using particle-image velocimetry with a refractive-index-matched model. Phase-locked ensemble-averaging is employed to provide some information on the turbulence characteristics of the model culture medium in the vicinity of a model tissue construct.

Sucosky, Philippe; Neitzel, G. Paul

2000-11-01

89

Fluid mechanics experiments in oscillatory flow. Volume 1  

SciTech Connect

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{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 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).

Seume, J.; Friedman, G.; Simon, T.W. [Univ. of Minnesota, Minneapolis, MN (United States)

1992-03-01

90

Soil mechanics in engineering practice. Third edition  

Microsoft Academic Search

This Wiley classic presents both theoretical and practical knowledge of soil mechanics in engineering. Written by Karl Terzaghi, universally recognized as ``the father of geotechnical engineering,`` it has long been the standard in the field. It offers a fundamental understanding of how to determine and use soil properties needed for design and construction; points out appropriate nature and benefits of

K. Terzaghi; R. B. Peck; G. Mesri

1995-01-01

91

2.670 Mechanical Engineering Tools  

NSDL National Science Digital Library

This course, created by the Massachusetts Institute of Technology, introduces the fundamentals of machine tool and computer tool use. Students work with a variety of machine tools including the bandsaw, milling machine, and lathe. Instruction given on MATLABî, MAPLEî, XESSâ¢, and CAD. Assignments are project-oriented relating to mechanical engineering topics. It is recommended that students take this subject in the first IAP after declaring the major in Mechanical Engineering.

2011-01-19

92

The Status of Fluid Mechanics in Bioengineering Curricula.  

ERIC Educational Resources Information Center

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…

Miller, Gerald E.; Hyman, William A.

1981-01-01

93

Computational fluid dynamics; Giving a boost to engine design  

SciTech Connect

This paper reports that computational fluid dynamics (CFD) software is allowing automakers to compress development cycles and cut costs because the computer programs are allowing them to make fewer prototypes leading up to a finished engine design. Also with the help of the software, engines with better performance and reduced rates of fuel consumption and emissions are being designed. The CFD programs are being used mostly in parallel with test-bench analyses to judge the many prototypes that lead to the final design of an engine. The computer programs simulate processes such as combustion, cooling, and air intake by calculating parameters such as the temperatures, turbulence, and pressures associated with heat transfer and fluid flow in various engines. Without CFD, designers would have to first modify each new prototype and then evaluate it with instrumentation on a test-bench. According to engine designers, it is far easier and less expensive to first analyze the prototype by making changes to a CFD model. If the CFD simulation shows the new design is acceptable, then it is usually verified with physical tests. If it is unacceptable, however, the model can be easily manipulated until designers are satisfied that a new prototype should be built and verified with hardware tests.

O'Connor, L.

1992-05-01

94

Fluid Mechanics of Cricket and Tennis Balls  

NASA Astrophysics Data System (ADS)

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 mechanics of cricket and tennis balls will be discussed in detail with the help of latest test data, analyses and video clips.

Mehta, Rabindra D.

2009-11-01

95

A generating mechanism for apparent fluid slip in hydrophobic microchannels  

Microsoft Academic Search

Fluid slip has been observed experimentally in micro- and nanoscale flow devices by several investigators [e.g., Tretheway and Meinhart, Phys. Fluids 14, L9 (2002); Zhu and Granik, Phys. Rev. Lett. 87, 096105 (2001); Pit et al., Phys. Rev. Lett. 85, 980 (2000); and Choi et al., Phys. Fluids 15, 2897 (2003)]. This paper examines a possible mechanism for the measured

Derek C. Tretheway; Carl D. Meinhart

2004-01-01

96

Mechanical engineering aspects of TFTR  

SciTech Connect

This paper briefly presents the principles which characterize a tokamak and discusses the mechanical aspects of TFTR, particularly the toroidal field coils and the vacuum chamber, in the context of being key components common to all tokamaks. The mechanical loads on these items as well as other design requirements are considered and the solutions to these requirements as executed in TFTR are presented. Future technological developments beyond the scope of TFTR, which are necessary to bring the tokamak concept to a full fusion-power system, are also presented. Additional methods of plasma heating, current drive, and first wall designs are examples of items in this category.

Citrolo, J.C.

1983-04-01

97

Molecular Mechanisms of Cerebrospinal Fluid Production  

PubMed Central

The epithelial cells of the choroid plexuses secrete cerebrospinal fluid (CSF), by a process which involves the transport of Na+, Cl- and HCO3- from the blood to the ventricles of the brain. The unidirectional transport of ions is achieved due to the polarity of the epithelium, i.e. the ion transport proteins in the blood-facing (basolateral) membrane are different to those in the ventricular (apical) membrane. The movement of ions creates an osmotic gradient which drives the secretion of H2 O. A variety of methods (e.g. isotope flux studies, electrophysiological, RT-PCR, in situ hybridization and immunocytochemistry) have been used to determine the expression of ion transporters and channels in the choroid plexus epithelium. Most of these transporters have now been localized to specific membranes. For example, Na+-K+ ATPase, K+ channels and Na+-2Cl--K+ cotransporters are expressed in the apical membrane. By contrast the basolateral membrane contains Cl--HCO3 exchangers, a variety of Na+ coupled HCO3- transporters and K+-Cl- cotransporters. Aquaporin 1 mediates water transport at the apical membrane, but the route across the basolateral membrane is unknown. A model of CSF secretion by the mammalian choroid plexus is proposed which accommodates these proteins. The model also explains the mechanisms by which K+ is transported from the CSF to the blood.

BROWN, P. D.; DAVIES, S. L.; SPEAKE, T.; MILLAR, I. D.

2006-01-01

98

Computational structural mechanics for engine structures  

NASA Technical Reports Server (NTRS)

The computational structural mechanics (CSM) program at Lewis encompasses: (1) fundamental aspects for formulating and solving structural mechanics problems, and (2) development of integrated software systems to computationally simulate the performance/durability/life of engine structures. It is structured to mainly supplement, complement, and whenever possible replace, costly experimental efforts which are unavoidable during engineering research and development programs. Specific objectives include: investigate unique advantages of parallel and multiprocesses for: reformulating/solving structural mechanics and formulating/solving multidisciplinary mechanics and develop integrated structural system computational simulators for: predicting structural performances, evaluating newly developed methods, and for identifying and prioritizing improved/missing methods needed. Herein the CSM program is summarized with emphasis on the Engine Structures Computational Simulator (ESCS). Typical results obtained using ESCS are described to illustrate its versatility.

Chamis, C. C.

1989-01-01

99

The Cassini Main Engine Assembly Cover Mechanism  

NASA Technical Reports Server (NTRS)

This paper describes a micrometeroid protection system for the main engines of the Cassini spacecraft. The engine Cover Assembly is a deployable/restowable half sphere of multilayer insulation mounted to an articulatable frame over 2 meters (7 feet) in diameter. The Cover folds into a compact wedge only 25 cm (10 inches) at its maximum thickness. The micrometeroid environment and typical protection methods are described as well as the design details and development problems of the Cover Mechanism Assembly.

Sevilla, Donald R.

1997-01-01

100

The Quantum and Fluid Mechanics of Global Warming  

Microsoft Academic Search

Quantum physics and fluid mechanics are the foundation of any understanding of the Earth's climate. In this talk I invoke three well-known aspects of quantum mechanics to explore what will happen as the concentrations of greenhouse gases such as carbon dioxide continue to increase. Fluid dynamical models of the Earth's atmosphere, demonstrated here in live simulations, yield further insight into

Brad Marston

2008-01-01

101

Micro electromechanical systems (MEMS) for mechanical engineers  

SciTech Connect

The ongoing advances in Microelectromechanical Systems (MEMS) are providing man-kind the freedom to travel to dimensional spaces never before conceivable. Advances include new fabrication processes, new materials, tailored modeling tools, new fabrication machines, systems integration, and more detailed studies of physics and surface chemistry as applied to the micro scale. In the ten years since its inauguration, MEMS technology is penetrating industries of automobile, healthcare, biotechnology, sports/entertainment, measurement systems, data storage, photonics/optics, computer, aerospace, precision instruments/robotics, and environment monitoring. It is projected that by the turn of the century, MEMS will impact every individual in the industrial world, totaling sales up to $14 billion (source: System Planning Corp.). MEMS programs in major universities have spawned up all over the United States, preparing the brain-power and expertise for the next wave of MEMS breakthroughs. It should be pointed out that although MEMS has been initiated by electrical engineering researchers through the involvement of IC fabrication techniques, today it has evolved such that it requires a totally multi-disciplinary team to develop useful devices. Mechanical engineers are especially crucial to the success of MEMS development, since 90% of the physical realm involved is mechanical. Mechanical engineers are needed for the design of MEMS, the analysis of the mechanical system, the design of testing apparatus, the implementation of analytical tools, and the packaging process. Every single aspect of mechanical engineering is being utilized in the MEMS field today, however, the impact could be more substantial if more mechanical engineers are involved in the systems level designing. In this paper, an attempt is made to create the pathways for a mechanical engineer to enter in the MEMS field. Examples of application in optics and medical devices will be used to illustrate how mechanical engineers made impact. Through a basic understanding of the history of MEMS, the background physics and scaling in micromechanical systems, and an introduction to baseline MEMS processes, a mechanical engineer should be well on his way to Alice's wonderland in the ever-exciting playground of MEMS.

Lee, A. P., LLNL

1996-11-18

102

The Educational Needs of Graduate Mechanical Engineers in New Zealand.  

ERIC Educational Resources Information Center

Surveys graduate and undergraduate mechanical engineering students at the University of Auckland. Shows that the dominant work activities of New Zealand mechanical engineers include design and consultancy and that graduate engineers rapidly migrate into management. (Author/CCM)

Deans, J.

1999-01-01

103

Quantitative image processing in fluid mechanics  

NASA Technical Reports Server (NTRS)

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.

Hesselink, Lambertus; Helman, James; Ning, Paul

1992-01-01

104

Mechanobiology and the microcirculation: cellular, nuclear and fluid mechanics  

PubMed Central

Endothelial cells are stimulated by shear stress throughout the vasculature and respond with changes in gene expression and by morphological reorganization. Mechanical sensors of the cell are varied and include cell surface sensors that activate intracellular chemical signaling pathways. Here, possible mechanical sensors of the cell including reorganization of the cytoskeleton and the nucleus are discussed in relation to shear flow. A mutation in the nuclear structural protein lamin A, related to Hutchinson Gilford progeria syndrome, is reviewed specifically since the mutation results in altered nuclear structure and stiffer nuclei; animal models also suggest significantly altered vascular structure. Nuclear and cellular deformation of endothelial cells in response to shear stress provides partial understanding of possible mechanical regulation in the microcirculation. Increasing sophistication of fluid flow simulations inside the vessel is also an emerging area relevant to the microcirculation since visualization in situ is difficult. This integrated approach to study – including medicine, molecular and cell biology, biophysics and engineering – provides a unique understanding of multi-scale interactions in the microcirculation.

Dahl, Kris Noel; Kalinowski, Agnieszka; Pekkan, Kerem

2010-01-01

105

Application of the principle of similarity fluid mechanics  

NASA Technical Reports Server (NTRS)

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.

Hendricks, R. C.; Sengers, J. V.

1979-01-01

106

Conjugate heat transfer in oscillating fluid flow in Stirling engines  

NASA Astrophysics Data System (ADS)

The analysis of the wall thickness effects on the heat transfer (conjugate heat transfer) and of the abrupt cross-sectional area variation in oscillating fluid flows in view of applications to Stirling engine modeling is presented. The numerical analysis of the oscillating fluid flow has been carried out with a scheme that simulates a tube bundle heater. The effects of the viscosity and of thermal irreversibility are taken into account by the differential form of the entropy generation. The difference between the velocity and temperature profiles caused from pressure gradient oscillation or from piston motion, under the hypothesis of incompressible flow, are also shown. The formulation of the motion equations and energy equation for the solid walls are written in an axisymmetric reference frame. The computational analysis has been carried out by a multiple-purpose finite element program.

Devalba, M.; Rispoli, F.

107

Supercritical fluids in biomedical and tissue engineering applications: a review  

Microsoft Academic Search

Over the past several years, the definition of a scaffold for tissue\\u000d\\u000a engineering has changed dramatically, from a material that acts only as\\u000d\\u000a an inert structural support for cell attachment to serving as a more\\u000d\\u000a complex and dynamic environment for tissue development. This paper is a\\u000d\\u000a review on the existing and on the new emerging techniques based on\\u000d\\u000a supercritical fluid

A. R. C. Duarte; J. F. Mano; R. L. Reis

2009-01-01

108

Project - Centered Modules in Mechanical Systems Engineering  

Microsoft Academic Search

This paper presents a description of hardware and software modules used in dynamic systems an d controls and related courses in manufacturing systems, mechatronics, robotics, and automation in the Mechanical Engineering curriculum. The modules span across a common set of equipment and are designed for varying degrees of depth, depending on use in a given course. The objective is to

Daniel J. Cox

109

Mechanical control of tissue-engineered bone.  

PubMed

ABSTRACT: Bone is a load-bearing tissue and physical forces play key roles in the development and maintenance of its structure. Mechanical cues can stimulate the expression of an osteogenic phenotype, enhance matrix and mineral deposition, and influence tissue organization to improve the functional outcome of engineered bone grafts. In recent years, a number of studies have investigated the effects of biophysical forces on the bone formation properties of osteoprogenitor cells. The application of physiologically relevant stimuli to tissue-engineered bone may be determined through observation and understanding of forces to which osteoblasts, osteoclasts, and osteocytes are exposed in native bone. Subsequently, these cues may be parameterized and their effects studied in well-defined in vitro systems. The osteo-inductive effects of three specific mechanical cues - shear stress, substrate rigidity, and nanotopography - on cells cultured in monolayer or in three-dimensional biomaterial scaffolds in vitro are reviewed. Additionally, we address the time-dependent effects of mechanical cues on vascular infiltration and de novo bone formation in acellular scaffolds implanted into load-bearing sites in vivo. Recent studies employing cutting-edge advances in biomaterial fabrication and bioreactor design have provided key insights into the role of mechanical cues on cellular fate and tissue properties of engineered bone grafts. By providing mechanistic understanding, future studies may go beyond empirical approaches to rational design of engineering systems to control tissue development. PMID:23369796

Hung, Ben P; Hutton, Daphne L; Grayson, Warren L

2013-01-31

110

Performance characteristics of prototype MR engine mounts containing LORD glycol MR fluids  

Microsoft Academic Search

LORD Corporation has recently developed glycol-based MR fluids for use in applications such as engine mounts and bushing, in which the MR fluid will contact rubber and other oil-sensitive elastomers. To demonstrate the performance characteristics of these fluids, prototype MR engine mounts were designed and their dynamic stiffness and damping were tested. In one configuration, the MR mount contained a

Daniel E Barber; J David Carlson

2009-01-01

111

Performance Characteristics of Prototype MR Engine Mounts Containing Glycol MR Fluids  

Microsoft Academic Search

Lord Corporation has developed glycol-based magnetorheological (MR) fluids for use in applications such as engine mounts and bushings, in which the MR fluid will contact rubber or other oil-sensitive elastomers. Prototype MR fluid engine mounts were designed with either a simple MR valve or an MR valve in combination with an inertia track. The mounts were filled with glycol MR

Daniel E. Barber; J. David Carlson

2010-01-01

112

The Role of CFD in Undergraduate Fluid Mechanics Education  

NASA Astrophysics Data System (ADS)

Instruction of undergraduate fluid mechanics is greatly enhanced through integration of computational fluid dynamics (CFD) into fluid mechanics courses and labs. Specifically, students are able to visualize fluid flows with CFD and are better able to understand those flows by performing parametric studies. At Penn State, CFD has been carefully integrated into our introductory junior-level fluid mechanics course, yet displaces only about one class period. The key is to show demonstrations and assign homework that use CFD as a tool that helps students learn the basic concepts of fluid mechanics. The application of CFD (grid generation, boundary conditions, etc.), rather than numerical algorithms, is stressed. This is done through use of short, pre-defined templates for FlowLab, a student-friendly analysis and visualization package created by Fluent, Inc. The textbook by Cengel and Cimbala (McGraw-Hill 2006) contains 46 end-of-chapter homework problems that are used in conjunction with 42 FlowLab templates. Each exercise has been designed with two major learning objectives in mind: (1) enhance student understanding of a specific fluid mechanics concept, and (2) introduce the student to a specific capability and/or limitation of CFD through hands-on practice. More templates are being developed that emphasize the first objective. The flow of fluid between two concentric rotating cylinders is a good example of a problem that is solved approximately, analytically, and with CFD, and the results are compared to enhance learning.

Cimbala, John

2006-11-01

113

Diffuse-Interface Methods in Fluid Mechanics  

NASA Technical Reports Server (NTRS)

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.

Anderson, D. M.; McFadden, G. B.; Wheeler, A. A.

1997-01-01

114

Taking Fluid Mechanics to the General Public  

NASA Astrophysics Data System (ADS)

Fluid flow phenomena are omnipresent; they can be observed and described in many locations and circumstances. However, in most cases, their presence does not stimulate an interest in science. We consider successively domains of activities in which the presence of fluid flow phenomena can be used: natural sites, industrial ones, sporting events, artistic creations and presentations, the production of images and books, science museums, cultural centers, and also popular mass media. The last section is devoted to outreach activities that can be practiced within the educational system.

Guyon, Etienne; Guyon, Marie Yvonne

2014-01-01

115

Analysis of fluid/mechanical systems using EASY5  

NASA Technical Reports Server (NTRS)

This paper illustrates how the use of a general analysis package can simplify modeling and analyzing fluid/mechanical systems. One such package is EASY5, a Boeing Computer Services product. The basic transmission line equations for modeling piped fluid systems are presented, as well as methods of incorporating these equations into the EASY5 environment. The paper describes how this analysis tool has been used to model several fluid subsystems of the Space Shuttle Orbiter.

Clark, Robert W., Jr.; Arndt, Scott D.; Hurlbert, Eric A.

1992-01-01

116

Bernoulli and Newton in Fluid Mechanics  

ERIC Educational Resources Information Center

Bernoulli's theorem can be better understood with the aid of Newton's laws and the law of conservation of energy. Application of this theorem should involve only cases dealing with an interchange of velocity and pressure within a fluid under isentropic conditions. (DF)

Smith, Norman F.

1972-01-01

117

Fluid Mechanics in the Subtectorial Space  

NASA Astrophysics Data System (ADS)

In the subtectorial space, momentum is transported by the fluid to the stereocilia of the inner hair cell (IHC), resulting in bending of the hair bundle. The fluid must pass through the v-shaped arrangement of the outer hair cell (OHC) stereocilia and is "squeezed" between the tectorial membrane (TM) and the reticular lamina, especially due to the Hensen's stripe. Here, we analyze the flow field by means of numerical discretization. Since the geometry is complex, the finite-element-method is employed. An implementation is developed which allows computation in the frequency domain, based on a pressure stabilised velocity formulation. Matrix coupling with the structure is accomplished and a single solution step of the whole system matrix is sufficient to retrieve the displacement field of the fluid and structural parts. The proposed method allows a solution of the fluid-structure interaction in the subtectorial space within a reasonable time. For a two-dimensional mesh with 120,000 degrees of freedom of a complete cross-section of the organ of Corti, including stereocilia, the solution time is less than 20 seconds on a convential PC.

Baumgart, J.; Chiaradia, C.; Fleischer, M.; Yarin, Y.; Grundmann, R.; Gummer, A. W.

2009-02-01

118

Using Assessment in Fluid Mechanics Courses to Improve Student Learning and Motivation  

NASA Astrophysics Data System (ADS)

Building on the peer-instruction method of teaching documented by Eric Mazur, assessment-integrated instruction has affected student learning in basic fluid mechanics. This presentation will include description of the use in-class assessment systems for immediate assessment and feedback on student learning. The discussion will include description of assessment-integrated instruction in engineering, and the impact on study habits of the students, learning methods, and conceptual framework development. In addition, the presentation will include a description of the role of concept inventories, used to measure conceptual understanding, in teaching and learning in fluid mechanics.

Martin, Jay

2006-11-01

119

Lagrangian block hydrodynamics for environmental fluid mechanics simulations  

Microsoft Academic Search

The Lagrangian block hydrodynamics is formulated based on the block advection of fluid. By enforcing the mass and momentum conservations on the Lagrangian mesh, the numerical oscillation problem encountered in the classical Eulerian computational methods is circumvented. A large number of the previously computationally difficult problems in environmental fluid mechanics are successfully simulated using the method. Examples of these simulations

Lai-wai Tan; Vincent H. Chu

2010-01-01

120

Interaction mechanisms of natural ester dielectric fluid and Kraft paper  

Microsoft Academic Search

Sealed tube accelerated aging studies demonstrate a slower aging rate for cellulose insulation in natural (vegetable oil) ester dielectric fluid compared to the rate in conventional transformer oil. The interactions of natural ester fluid and cellulose insulation resulting in increased paper life are described by two interrelated chemical reaction mechanisms. Compared to the conventional transformer oil\\/Kraft paper system, the natural

K. J. Rapp; C. P. McShane; J. Luksich

2005-01-01

121

Analysis of Fluid/Mechanical Systems Using EASY5.  

National Technical Information Service (NTIS)

This paper illustrates how the use of a general analysis package can simplify modeling and analyzing fluid/mechanical systems. One such package is EASY5, a Boeing Computer Services product. The basic transmission line equations for modeling piped fluid sy...

R. W. Clark S. D. Arndt E. A. Hurlbert

1992-01-01

122

Application of the principle of similarity fluid mechanics  

NASA Technical Reports Server (NTRS)

The principle of similarity applied to fluid mechanics is described and illustrated. The concept of transforming the conservation equations by combining similarity principles for thermophysical properties with those for fluid flow is examined. The usefulness of the procedure is illustrated by applying such a transformation to calculate two phase critical mass flow through a nozzle.

Hendericks, R. C.; Sengers, J. V.

1979-01-01

123

Research Group Introduction : Mechanical Control Engineering Laboratory, Mechanical Engineering Department, Shibaura Institute of Technology  

NASA Astrophysics Data System (ADS)

Mechanical Control Engineering Laboratory focuses on the control theory and implementation for the robotic applications. The research themes include network based tele-operation, mobile robots control for network relay, autonomous outdoor mobile robot and biped robot.

??, ?

124

Neural mechanisms of general fluid intelligence  

Microsoft Academic Search

We used an individual-differences approach to test whether general fluid intelligence (gF) is mediated by brain regions that support attentional (executive) control, including subregions of the prefrontal cortex. Forty-eight participants first completed a standard measure of gF (Raven's Advanced Progressive Matrices). They then performed verbal and nonverbal versions of a challenging working-memory task (three-back) while their brain activity was measured

Jeremy R. Gray; Christopher F. Chabris; Todd S. Braver

2003-01-01

125

The contact angle in inviscid fluid mechanics  

Microsoft Academic Search

We show that in general, the specification of a contact angle condition at the contact line in inviscid fluid motions is incompatible\\u000a with the classical field equations and boundary conditions generally applicable to them. The limited conditions under which\\u000a such a specification is permissible are derived; however, these include cases where the static meniscus is not flat. In view\\u000a of

P. N. Shankar; R Kidambi

2005-01-01

126

Peritoneal fluid transport: mechanisms, pathways, methods of assessment.  

PubMed

Fluid removal during peritoneal dialysis is controlled by many mutually dependent factors and therefore its analysis is more complex than that of the removal of small solutes used as markers of dialysis adequacy. Many new tests have been proposed to assess quantitatively different components of fluid transport (transcapillary ultrafiltration, peritoneal absorption, free water, etc.) and to estimate the factors that influence the rate of fluid transport (osmotic conductance). These tests provide detailed information about indices and parameters that describe fluid transport, especially those concerning the problem of the permanent loss of ultrafiltration capacity (ultrafiltration failure). Different theories and respective mathematical models of mechanisms and pathways of fluid transport are presently discussed and applied, and some fluid transport issues are still debated. PMID:24215786

Waniewski, Jacek

2013-11-01

127

Zero-G fluid mechanics in animal and man  

NASA Technical Reports Server (NTRS)

Significant cardiovascular change occurs with spaceflight. Loss of normal hydrostatic pressure gradients (head-to-foot), present while upright on earth, results in significant headward fluid shift of vascular and interstitial fluids. The resultant fluid change also shifts the hydrostatic indifference point for the circulation. The persistent distention of neck veins and change in upper body tissue compliance initiates steps to adapt to and compensate for the sensed excess fluid. These result in a loss of intravascular volume through neuro-humoral mechanisms and the presence of a smaller heart size, leading to a state where the subject has a reduced adaptive capacity to stress, particularly to fluid shifts to the lower body as occurs when once again returning to earth. This article reviews what is known about the weightlessness-induced headward fluid shift and its effects on cardiovascular function.

Sandler, H.

1986-01-01

128

Electroresponsive aqueous silk protein as "smart" mechanical damping fluid.  

PubMed

Here we demonstrate the effectiveness of an electroresponsive aqueous silk protein polymer as a smart mechanical damping fluid. The aqueous polymer solution is liquid under ambient conditions, but is reversibly converted into a gel once subjected to an electric current, thereby increasing or decreasing in viscosity. This nontoxic, biodegradable, reversible, edible fluid also bonds to device surfaces and is demonstrated to reduce friction and provide striking wear protection. The friction and mechanical damping coefficients are shown to modulate with electric field exposure time and/or intensity. Damping coefficient can be modulated electrically, and then preserved without continued power for longer time scales than conventional "smart" fluid dampers. PMID:24750065

Jose, Rod R; Elia, Roberto; Tien, Lee W; Kaplan, David L

2014-05-14

129

Problems in forced unsteady fluid mechanics  

NASA Astrophysics Data System (ADS)

Forced unsteady fluid flows are examined from the point of view of positive implications of the time dependency. Particular problems examined in a forced unsteady mode are jets, wind tunnels, wings, ramps and diffusers, dump combustors and vortex structure. Two methods of forcing the flow are studied in detail: fluidic feedback and a cam-shaped rotor. The fluidic method produces an unsteady jet while the rotor acts as a time dependent vortex generator. Potential performance improvements with unsteady flow are evident in all of the flows examined.

Viets, H.; Platt, M.; Ball, M.; Bethke, R. J.; Bougine, D.

1981-11-01

130

High temperature mechanically pumped fluid loop for space applications : working fluid selection  

NASA Technical Reports Server (NTRS)

Mechanically pumped single-phase fluid loops are well suited for transporting and rejecting large amounts of waste heat from spacecraft electronics and power supplies. While past implementations of these loops on spacecraft have used moderate operating temperatures (less than 6OoC), higher operating temperatures would allow equivalent heat loads to be rejected by smaller and less massive radiators. A high temperature (100 to 15OOC) mechanically pumped fluid loop is currently being investigated at the Jet Propulsion Laboratory for use on future Mars missions. This paper details the trade study used to select the high temperature working fluid for the system and the initial development testing of loop components.

Paris, Anthony D.; Birur, Gajanana C.; Bhandari, Pradeep

2004-01-01

131

Problems in Microgravity Fluid Mechanics: G-Jitter Convection  

NASA Technical Reports Server (NTRS)

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.

Homsy, G. M.

2005-01-01

132

The quantum mechanics of perfect fluids  

NASA Astrophysics Data System (ADS)

We consider the canonical quantization of an ordinary fluid. The resulting long-distance effective field theory is derivatively coupled, and therefore strongly coupled in the UV. The system however exhibits a number of peculiarities, associated with the vortex degrees of freedom. On the one hand, these have formally a vanishing strong-coupling energy scale, thus suggesting that the effective theory's regime of validity is vanishingly narrow. On the other hand, we prove an analog of Coleman's theorem, whereby the semiclassical vacuum has no quantum counterpart, thus suggesting that the vortex premature strong-coupling phenomenon stems from a bad identification of the ground state and of the perturbative degrees of freedom. Finally, vortices break the usual connection between short distances and high energies, thus potentially impairing the unitarity of the effective theory.

Endlich, Solomon; Nicolis, Alberto; Rattazzi, Riccardo; Wang, Junpu

2011-04-01

133

Scalable, inquiry-based, multimodal modules for Engineering Mechanics curriculum  

Microsoft Academic Search

Students struggle to conceptualize Engineering Mechanics fundamentals because they cannot successfully visualize or intuitively comprehend the effects of external loads on mechanisms. Traditionally, Engineering Mechanics courses have been primarily lecture-based with little experimentation. The authors contend that through the use of scalable, inquiry-based, mutimodal modules, lower-division engineering students can more effectively interpret Engineering Mechanics concepts. An emphasis should be placed

Javier A. Kypuros; Constantine Tarawneh

2008-01-01

134

Analysis of the fluid mechanical sewing machine  

NASA Astrophysics Data System (ADS)

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 ?c 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 ?c/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.

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

2012-02-01

135

46 CFR 12.15-13 - Deck engine mechanic.  

Code of Federal Regulations, 2010 CFR

... 2009-10-01 false Deck engine mechanic. 12.15-13 Section 12.15-13...Department § 12.15-13 Deck engine mechanic. (a) An applicant for an endorsement as deck engine mechanic shall be a person holding an MMC...

2009-10-01

136

46 CFR 12.15-13 - Deck engine mechanic.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Deck engine mechanic. 12.15-13 Section 12.15-13...Department § 12.15-13 Deck engine mechanic. (a) An applicant for an endorsement as deck engine mechanic shall be a person holding an MMC...

2010-10-01

137

46 CFR 12.15-13 - Deck engine mechanic.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 false Deck engine mechanic. 12.15-13 Section 12.15-13...Department § 12.15-13 Deck engine mechanic. (a) An applicant for an endorsement as deck engine mechanic shall be a person holding an MMC...

2013-10-01

138

Maintainability Analysis in Concurrent Engineering of Mechanical Systems  

Microsoft Academic Search

Maintainability of the mechanical system should be considered from early stages of the design process to reduce its total life-cycle cost A computer-aided engineering environment that supports maintainability analysis of an evolving mechanical system design in a concurrent engineering environment is presented Its communication with the underlying concurrent engineering environment and capabilities to evaluate maintainability of the mechanical system are

Ranko Vujosevic

1995-01-01

139

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

ERIC Educational Resources Information Center

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…

Hrenya, Christine M.

2011-01-01

140

Annual review of fluid mechanics. Volume 21  

NASA Astrophysics Data System (ADS)

The present work discusses turbulence control in wall flows, mathematical analyses of viscoelastic flows, hypervelocity aerodynamics with chemical nonequilibrium, colloid transport by interfacial forces, the turbulent diffusion of flames, and boundary-layer receptivity to long-wave freestream disturbances. Also treated are biofluid mechanics, turbulent boundary-layer separation, the stability of three-dimensional boundary layers, coherent structures in transitional and turbulent shear flows, the atomic dispersion of dense gases, novel developments in CFD, rarefied gas dynamics, and ocean turbulence phenomena.

Lumley, John L.; van Dyke, Milton; Reed, Helen L.

141

The fluid mechanics of thrombus formation  

NASA Technical Reports Server (NTRS)

Experimental data are presented for the growth of thrombi (blood clots) in a stagnation point flow of fresh blood. Thrombus shape, size and structure are shown to depend on local flow conditions. The evolution of a thrombus is described in terms of a physical model that includes platelet diffusion, a platelet aggregation mechanism, and diffusion and convection of the chemical species responsible for aggregation. Diffusion-controlled and convection-controlled regimes are defined by flow parameters and thrombus location, and the characteristic growth pattern in each regime is explained. Quantitative comparisons with an approximate theoretical model are presented, and a more general model is formulated.

1972-01-01

142

Stirling engine control mechanism and method  

DOEpatents

A reciprocating-to-rotating motion conversion and power control device for a Stirling engine includes a hub mounted on an offset portion of the output shaft for rotation relative to the shaft and for sliding motion therealong which causes the hub to tilt relative to the axis of rotation of the shaft. This changes the angle of inclination of the hub relative to the shaft axis and changes the axial stroke of a set of arms connected to the hub and nutating therewith. A hydraulic actuating mechanism is connected to the hub for moving its axial position along the shaft. A balancing wheel is linked to the hub and changes its angle of inclination as the angle of inclination of the hub changes to maintain the mechanism in perfect balance throughout its range of motion.

Dineen, John J. (Durham, NH)

1983-01-01

143

A Mechanical Engine Simulator for Development of Aero Engine Failure Analysis Methods  

Microsoft Academic Search

\\u000a A mechanical engine simulator for method development is under construction at Berlin Institute of Technology. The new experimental\\u000a rig reflects nearly all mechanical characteristics of an aero engine. The mechanical engine simulator will enable the analysis\\u000a of diverse failure cases that need to be considered for an aero engine certification. Based on the experimental results using\\u000a the mechanical simulator, analytical

Robert Liebich

144

Notes on the KIVA-2 software and chemically reactive fluid mechanics  

NASA Astrophysics Data System (ADS)

Working notes regarding the mechanics of chemically reactive fluids with sprays, and their numerical simulation with the KIVA-2 software are presented. KIVA-2 is a large FORTRAN program developed at Los Alamos National Laboratory for internal combustion engine simulation. It is our hope that these notes summarize some of the necessary background material in fluid mechanics and combustion, explain the numerical methods currently used in KIVA-2 and similar combustion codes, and provide an outline of the overall structure of KIVA-2 as a representative combustion program, in order to aid the researcher in the task of implementing KIVA-2 or a similar combustion code on a massively parallel computer. The notes are organized into three parts as follows. In Part 1, a brief introduction to continuum mechanics, to fluid mechanics, and to the mechanics of chemically reactive fluids with sprays is presented. In Part 2, a close look at the governing equations of KIVA-2 is taken, and the methods employed in the numerical solution of these equations is discussed. Some conclusions are drawn and some observations are made in Part 3.

Holst, M. J.

1992-09-01

145

Computational fluid dynamic design of rocket engine pump components  

NASA Technical Reports Server (NTRS)

Integration of computational fluid dynamics (CFD) for design and analysis of turbomachinery components is needed as the requirements of pump performance and reliability become more stringent for the new generation of rocket engine. A fast grid generator, designed specially for centrifugal pump impeller, which allows a turbomachinery designer to use CFD to optimize the component design will be presented. The CFD grid is directly generated from the impeller blade G-H blade coordinates. The grid points are first generated on the meridional plane with the desired clustering near the end walls. This is followed by the marching of grid points from the pressure side of one blade to the suction side of a neighboring blade. This fast grid generator has been used to optimize the consortium pump impeller design. A grid dependency study has been conducted for the consortium pump impeller. Two different grid sizes, one with 10,000 grid points and one with 80,000 grid points were used for the grid dependency study. The effects of grid resolution on the turnaround time, including the grid generation and completion of the CFD analysis, is discussed. The impeller overall mass average performance is compared for different designs. Optimum design is achieved through systematic change of the design parameters. In conclusion, it is demonstrated that CFD can be effectively used not only for flow analysis but also for design and optimization of turbomachinery components.

Chen, Wei-Chung; Prueger, George H.; Chan, Daniel C.; Eastland, Anthony H.

1992-01-01

146

Internal fluid mechanics research on supercomputers for aerospace propulsion systems  

NASA Technical Reports Server (NTRS)

The Internal Fluid Mechanics Division of the NASA Lewis Research Center is combining the key elements of computational fluid dynamics, aerothermodynamic experiments, and advanced computational technology to bring internal computational fluid mechanics (ICFM) to a state of practical application for aerospace propulsion systems. The strategies used to achieve this goal are to: (1) pursue an understanding of flow physics, surface heat transfer, and combustion via analysis and fundamental experiments, (2) incorporate improved understanding of these phenomena into verified 3-D CFD codes, and (3) utilize state-of-the-art computational technology to enhance experimental and CFD research. Presented is an overview of the ICFM program in high-speed propulsion, including work in inlets, turbomachinery, and chemical reacting flows. Ongoing efforts to integrate new computer technologies, such as parallel computing and artificial intelligence, into high-speed aeropropulsion research are described.

Miller, Brent A.; Anderson, Bernhard H.; Szuch, John R.

1988-01-01

147

Engine retarder with reset auto-lash mechanism  

Microsoft Academic Search

This patent describes an engine retarding system of a gas compression release type including an internal combustion engine having exhaust valve means and pushtube means, hydraulic pressure supply means, hydraulically actuated first piston, and second piston means actuated by the pushtube means and hydraulically interconnected with the first piston means. The improvement comprises fluid passageway means formed through the first

Z. S. Meistrick; R. B. Price

1987-01-01

148

Modeling golf ball fluid mechanics - challenges and opportunities  

Microsoft Academic Search

Numerical simulation presents a powerful tool for understanding the fundamental fluid mechanics that influence golf ball aerodynamics, as well as providing an approach for ultimately analyzing and designing golf balls for manufacture. Robust and accurate simulation strategies are central to providing a means to screen designs prior to costly prototyping and field measurement. Results from a hierarchy of simulation strategies

Kyle Squires

2009-01-01

149

Fluid Mechanics of Wing Adaptation for Separation Control  

NASA Technical Reports Server (NTRS)

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.

Chandrasekhara, M. S.; Wilder, M. C.; Carr, L. W.; Davis, Sanford S. (Technical Monitor)

1997-01-01

150

Fluid flow in the osteocyte mechanical environment: a fluid-structure interaction approach.  

PubMed

Osteocytes are believed to be the primary sensor of mechanical stimuli in bone, which orchestrate osteoblasts and osteoclasts to adapt bone structure and composition to meet physiological loading demands. Experimental studies to quantify the mechanical environment surrounding bone cells are challenging, and as such, computational and theoretical approaches have modelled either the solid or fluid environment of osteocytes to predict how these cells are stimulated in vivo. Osteocytes are an elastic cellular structure that deforms in response to the external fluid flow imposed by mechanical loading. This represents a most challenging multi-physics problem in which fluid and solid domains interact, and as such, no previous study has accounted for this complex behaviour. The objective of this study is to employ fluid-structure interaction (FSI) modelling to investigate the complex mechanical environment of osteocytes in vivo. Fluorescent staining of osteocytes was performed in order to visualise their native environment and develop geometrically accurate models of the osteocyte in vivo. By simulating loading levels representative of vigorous physiological activity ([Formula: see text] compression and 300 Pa pressure gradient), we predict average interstitial fluid velocities [Formula: see text] and average maximum shear stresses [Formula: see text] surrounding osteocytes in vivo. Interestingly, these values occur in the canaliculi around the osteocyte cell processes and are within the range of stimuli known to stimulate osteogenic responses by osteoblastic cells in vitro. Significantly our results suggest that the greatest mechanical stimulation of the osteocyte occurs in the cell processes, which, cell culture studies have indicated, is the most mechanosensitive area of the cell. These are the first computational FSI models to simulate the complex multi-physics mechanical environment of osteocyte in vivo and provide a deeper understanding of bone mechanobiology. PMID:23567965

Verbruggen, Stefaan W; Vaughan, Ted J; McNamara, Laoise M

2014-01-01

151

FRONT DETAIL OF RIGHT ENGINE AND WING. MECHANICS CHECK METAL ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

FRONT DETAIL OF RIGHT ENGINE AND WING. MECHANICS CHECK METAL CHIP DETECTOR ON RIGHT ENGINE. THE LEADING EDGE FLAPS ON THE RIGHT WING ARE DOWN PRIOR TO LUBRICATION. - Greater Buffalo International Airport, Maintenance Hangar, Buffalo, Erie County, NY

152

A generating mechanism for apparent fluid slip in hydrophobic microchannels  

NASA Astrophysics Data System (ADS)

Fluid slip has been observed experimentally in micro- and nanoscale flow devices by several investigators [e.g., Tretheway and Meinhart, Phys. Fluids 14, L9 (2002); Zhu and Granik, Phys. Rev. Lett. 87, 096105 (2001); Pit et al., Phys. Rev. Lett. 85, 980 (2000); and Choi et al., Phys. Fluids 15, 2897 (2003)]. This paper examines a possible mechanism for the measured fluid slip, for water flowing over a hydrophobic surface. We extend the work of Lum et al. [J. Phys. Chem. B 103, 4570 (1999)], Zhu and Granick [Phys. Rev. Lett. 87, 096105 (2001)], Granick et al. [Nature Materials 2, 221 (2003)], and de Gennes [Langmuir 18, 3413 (2002)], who suggest slip develops from a depleted water region or vapor layer near a hydrophobic surface. By modeling the presence of either a depleted water layer or nanobubbles as an effective air gap at the wall, we calculate slip lengths for flow between two infinite parallel plates. The calculated slip lengths are consistent with experimental values when the gas layer is modeled as a continuum and significantly higher when rarefied gas conditions are assumed. The results suggest that the apparent fluid slip observed experimentally at hydrophobic surfaces may arise from either the presence of nanobubbles or a layer of low density fluid at the surface.

Tretheway, Derek C.; Meinhart, Carl D.

2004-05-01

153

Fluid mechanics mechanisms in the stall process of helicopters  

NASA Technical Reports Server (NTRS)

Recent experimental results from airfoils in the Mach number, Reynolds number, or reduced frequency ranges typical of helicopter rotor blades have identified the most influential flow mechanisms in the dynamic stall process. The importance of secondary shed vortices, downstream wake action, and the flow in the separated region is generally acknowledged but poorly understood. By means of surface pressure cross-correlations and flow field measurements in static stall, several new hypotheses have been generated. It is proposed that vortex shedding may be caused by acoustic disturbances propagating forward in the lower (pressure) surface boundary layer, that wake closure is a misnomer, and that the shed vortex leaves a trail of vorticity that forms a turbulent free shear layer. The known dynamic stall flow mechanisms are reviewed and the potential importance of recently proposed and hypothetical flow phenomena with respect to helicopter blade aeroelastic response are assessed.

Young, W. H., Jr.

1981-01-01

154

Mechanism and synergism in epithelial fluid and electrolyte secretion.  

PubMed

A central function of epithelia is the control of the volume and electrolyte composition of bodily fluids through vectorial transport of electrolytes and the obligatory H2O. In exocrine glands, fluid and electrolyte secretion is carried out by both acinar and duct cells, with the portion of fluid secreted by each cell type varying among glands. All acinar cells secrete isotonic, plasma-like fluid, while the duct determines the final electrolyte composition of the fluid by absorbing most of the Cl(-) and secreting HCO3 (-). The key transporters mediating acinar fluid and electrolyte secretion are the basolateral Na(+)/K(+) /2Cl(-) cotransporter, the luminal Ca(2+)-activated Cl(-) channel ANO1 and basolateral and luminal Ca(2+)-activated K(+) channels. Ductal fluid and HCO3 (-) secretion are mediated by the basolateral membrane Na(+)-HCO3 (-) cotransporter NBCe1-B and the luminal membrane Cl(-)/HCO3 (-) exchanger slc26a6 and the Cl(-) channel CFTR. The function of the transporters is regulated by multiple inputs, which in the duct include major regulation by the WNK/SPAK pathway that inhibit secretion and the IRBIT/PP1 pathway that antagonize the effects of the WNK/SPAK pathway to both stimulate and coordinate the secretion. The function of these regulatory pathways in secretory glands acinar cells is yet to be examined. An important concept in biology is synergism among signaling pathways to generate the final physiological response that ensures regulation with high fidelity and guards against cell toxicity. While synergism is observed in all epithelial functions, the molecular mechanism mediating the synergism is not known. Recent work reveals a central role for IRBIT as a third messenger that integrates and synergizes the function of the Ca(2+) and cAMP signaling pathways in activation of epithelial fluid and electrolyte secretion. These concepts are discussed in this review using secretion by the pancreatic and salivary gland ducts as model systems. PMID:24240699

Hong, Jeong Hee; Park, Seonghee; Shcheynikov, Nikolay; Muallem, Shmuel

2014-08-01

155

Testing of the Multi-Fluid Evaporator Engineering Development Unit  

NASA Technical Reports Server (NTRS)

Hamilton Sundstrand is under contract with the NASA Johnson Space Center to develop a scalable, evaporative heat rejection system called the Multi-Fluid Evaporator (MFE). It is being designed to support the Orion Crew Module and to support future Constellation missions. The MFE would be used from Earth sea level conditions to the vacuum of space. The current Shuttle configuration utilizes an ammonia boiler and flash evaporator system to achieve cooling at all altitudes. The MFE system combines both functions into a single compact package with significant weight reduction and improved freeze-up protection. The heat exchanger core is designed so that radial flow of the evaporant provides increasing surface area to keep the back pressure low. The multiple layer construction of the core allows for efficient scale up to the desired heat rejection rate. The full scale MFE prototype will be constructed with four core sections that, combined with a novel control scheme, manage the risk of freezing the heat exchanger cores. A sub-scale MFE engineering development unit (EDU) has been built, and is identical to one of the four sections of a full scale prototype. The EDU has completed testing at Hamilton Sundstrand. The overall test objective was to determine the thermal performance of the EDU. The first set of tests simulated how each of the four sections of the prototype would perform by varying the chamber pressure, evaporant flow rate, coolant flow rate and coolant temperature. A second set of tests was conducted with an outlet steam header in place to verify that the outlet steam orifices prevent freeze-up in the core while also allowing the desired thermal turn-down ratio. This paper discusses the EDU tests and results.

Quinn, Gregory; O'Connor, Ed; Riga, Ken; Anderson, Molly; Westheimer, David

2007-01-01

156

A fluid mechanical model for current-generating-feeding jellyfish  

NASA Astrophysics Data System (ADS)

Many jellyfish species, e.g. moon jellyfish Aurelia aurita, use body motion to generate fluid currents which carry their prey to the vicinity of their capture appendages. In this study, a model was developed to understand the fluid mechanics for this current-generating-feeding mode of jellyfish. The flow generated by free-swimming Aurelia aurita was measured using digital particle image velocimetry. The dynamics of prey (e.g., brine shrimp Artemia) in the flow field were described by a modified Maxey-Riley equation which takes into consideration the inertia of prey and the escape forces, which prey exert in the presence of predator. A Lagrangian analysis was used to identify the region of the flow in which prey can be captured by the jellyfish and the clearance rate was quantified. The study provides a new methodology to study biological current-generating-feeding and the transport and mixing of particles in fluid flow in general.

Peng, Jifeng; Dabiri, John

2008-11-01

157

Biology: An Important Agricultural Engineering Mechanism  

ERIC Educational Resources Information Center

Describes the field of bioengineering with particular emphasis on agricultural engineering, and presents the results of a survey of schools that combine biology and engineering in their curricula. (JR)

Henderson, S. M.

1974-01-01

158

Micro-CAE mechanical engineering software development  

Microsoft Academic Search

A concept in Microcomputer-Aided Engineering has been evolving and maturing at Lawrence Livermore National Laboratory during the past 4 years. In harmony with the goals of the project, several universities are participating in the development of software which will be useful both to engineering colleges and to practicing engineers. Among the universities who have had faculty participants in this project

W. Comfort; B. Davis

1985-01-01

159

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

NASA Astrophysics Data System (ADS)

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).

Vieira, Sheila Lopes; de Arruda, Antonio Celso Fonseca

160

A Sequential Fluid-mechanic Chemical-kinetic Model of Propane HCCI Combustion  

SciTech Connect

We have developed a methodology for predicting combustion and emissions in a Homogeneous Charge Compression Ignition (HCCI) Engine. This methodology combines a detailed fluid mechanics code with a detailed chemical kinetics code. Instead of directly linking the two codes, which would require an extremely long computational time, the methodology consists of first running the fluid mechanics code to obtain temperature profiles as a function of time. These temperature profiles are then used as input to a multi-zone chemical kinetics code. The advantage of this procedure is that a small number of zones (10) is enough to obtain accurate results. This procedure achieves the benefits of linking the fluid mechanics and the chemical kinetics codes with a great reduction in the computational effort, to a level that can be handled with current computers. The success of this procedure is in large part a consequence of the fact that for much of the compression stroke the chemistry is inactive and thus has little influence on fluid mechanics and heat transfer. Then, when chemistry is active, combustion is rather sudden, leaving little time for interaction between chemistry and fluid mixing and heat transfer. This sequential methodology has been capable of explaining the main characteristics of HCCI combustion that have been observed in experiments. In this paper, we use our model to explore an HCCI engine running on propane. The paper compares experimental and numerical pressure traces, heat release rates, and hydrocarbon and carbon monoxide emissions. The results show an excellent agreement, even in parameters that are difficult to predict, such as chemical heat release rates. Carbon monoxide emissions are reasonably well predicted, even though it is intrinsically difficult to make good predictions of CO emissions in HCCI engines. The paper includes a sensitivity study on the effect of the heat transfer correlation on the results of the analysis. Importantly, the paper also shows a numerical study on how parameters such as swirl rate, crevices and ceramic walls could help in reducing HC and CO emissions from HCCI engines.

Aceves, S M; Flowers, D L; Martinez-Frias, J; Smith, J R; Westbrook, C; Pitz, W; Dibble, R; Wright, J F; Akinyemi, W C; Hessel, R P

2000-11-29

161

Effect of Chamber Backpressure on Swirl Injector Fluid Mechanics  

NASA Technical Reports Server (NTRS)

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.

Kenny, R. Jeremy; Hulka, James R.; Moser, Marlow D.; Rhys, Noah O.

2008-01-01

162

Experimental Fluid Mechanics of Pulsatile Artificial Blood Pumps  

NASA Astrophysics Data System (ADS)

The fluid mechanics of artificial blood pumps has been studied since the early 1970s in an attempt to understand and mitigate hemolysis and thrombus formation by the device. Pulsatile pumps are characterized by inlet jets that set up a rotational "washing" pattern during filling. Strong regurgitant jets through the closed artificial heart valves have Reynolds stresses on the order of 10,000 dynes/cm2 and are the most likely cause of red blood cell damage and platelet activation. Although the flow in the pump chamber appears benign, low wall shear stresses throughout the pump cycle can lead to thrombus formation at the wall of the smaller pumps (10 50 cc). The local fluid mechanics is critical. There is a need to rapidly measure or calculate the wall shear stress throughout the device so that the results may be easily incorporated into the design process.

Deutsch, Steven; Tarbell, John M.; Manning, Keefe B.; Rosenberg, Gerson; Fontaine, Arnold A.

2006-01-01

163

Micro-Electro-Mechanical-Systems (MEMS) and Fluid Flows  

Microsoft Academic Search

The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators. These micro transducers are able to be integrated with signal conditioning and processing circuitry to form micro-electro-mechanical-systems (MEMS) that can perform real-time distributed control. This capability opens up a new territory for flow control research. On the other hand, surface effects dominate the fluid flowing

Chih-Ming Ho; Yu-Chong Tai

1998-01-01

164

Aeropropulsion 1987. Session 3: Internal Fluid Mechanics Research  

NASA Technical Reports Server (NTRS)

Internal fluid mechanics research at Lewis 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 presentations in this session summarize ongoing work and indicated future emphasis in three major research thrusts: namely, inlets, ducts, and nozzles; turbomachinery; and chemical reacting flows.

1987-01-01

165

Mechanical Engineering Research. Quarterly Progress Report, January-March 1982.  

National Technical Information Service (NTIS)

The Mechanical Engineering Research (MER) Program is supported by the Weapons Program. The mission of MER is to provide the key mechanical technologies required by the Weapons Program in anticipation of their actual needs. It emphasizes areas in which out...

W. W. Feng

1982-01-01

166

The fluid mechanics of the inner-ear disorder BPPV  

NASA Astrophysics Data System (ADS)

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.

Weidman, Michael; Squires, Todd; Stone, Howard

2001-11-01

167

Comparison of Differing Credit Hour Allotments for Thermodynamics and Fluid Mechanics Courses  

NSDL National Science Digital Library

Each institution determines how many credit hours will be allotted for each course. Thermodynamics and fluid mechanics in an undergraduate Bachelor of Science Mechanical Engineering curriculum in the United States typically are allotted three or four credit hours. For a semester system, this allows for 42-45 or 56-60 fifty-minute class sessions in three and four credit hour courses, respectively. Opinions vary whether thermodynamics and fluid mechanics should each be three credit hours, each be four credit hours, or one should be three and the other four. Two universities have conducted a study to determine the advantages, disadvantages, and consequences of three vs. four credit hours. One university has a four credit hour thermodynamics and a three credit hour fluid mechanics, while the other university has exactly the opposite. Through student surveys, course objectives/outcomes, course syllabi, instructors experiences, and average grades, conclusions are drawn on the effects of course length. Other issues are examined such as challenges facing instructors who have previously taught a four credit hour course that now must cover the same material within a three credit hour allotment. Finally recommendations are given for instructors that are allotted less than desirable credit hours.

Fletcher, Robert; Gerhart, Andrew; Gerhart, Philip

2011-05-06

168

Undergraduate Education of Mechanical and Manufacturing Engineering in China  

NSDL National Science Digital Library

This presentation gives an overview of Huazhong University of Science and Technology (HUST) undergraduate education and mechanical and manufacturing engineering programs, presents key issues facing the programs, and provides alternate solutions. Presented at the 2006 International Mechanical Engineering Education Conference, Beijing, China, March 31-April 4, 2007.

Peigen, Li

2009-11-23

169

An Innovative Improvement of Engineering Learning System Using Computational Fluid Dynamics Concept  

ERIC Educational Resources Information Center

An innovative concept of an electronic learning system has been established in an attempt to achieve a technology that provides engineering students with an instructive and affordable framework for learning engineering-related courses. This system utilizes an existing Computational Fluid Dynamics (CFD) package, Active Server Pages programming,…

Hung, T. C.; Wang, S. K.; Tai, S. W.; Hung, C. T.

2007-01-01

170

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines  

Microsoft Academic Search

Challenge Project C2N is dedicated to developing and applying high performance computing capabilities to accelerate the development of hypergolic and hybrid rocket engine concepts. Computational fluid dynamics is employed to model chemically reacting flows within engine combustion chambers and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments are presented and discussed.

Chiung-Chu Chen; Michael J. Nusca; Anthony J. Kotlar; Michael J. McQuaid

2009-01-01

171

Renal and Vascular Mechanisms of Thiazolidinedione-Induced Fluid Retention  

PubMed Central

Thiazolidinediones (TZDs) are peroxisome proliferator-activated receptor subtype ? (PPAR?) 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.

Yang, Tianxin; Soodvilai, Sunhapas

2008-01-01

172

Simulation of a traveling-wave thermoacoustic engine using computational fluid dynamics  

Microsoft Academic Search

A two-dimensional computational fluid dynamics (CFD) simulation study of a traveling-wave thermoacoustic engine is presented. The computations show an increase of the dynamic pressure when a linear temperature difference is applied across the regenerator. An amplification of the acoustic power through the engine is also illustrated. A satisfactory agreement between the calculated and expected gains of the traveling-wave thermoacoustic engine

J. A. Lycklama À Nijeholt; M. E. H. Tijani; S. Spoelstra

2005-01-01

173

Aerofoil flutter: fluid-mechanical analysis and wind tunnel testing  

NASA Astrophysics Data System (ADS)

This paper describes a three dimensional wing model, which has been developed for the purpose of studying flutter, both computationally and through wind tunnel testing. A three dimensional, laminar flow aerofoil wing, based on the NACA aerofoil has been designed. The natural frequencies for this aerofoil were obtained through modal analysis. A scale model wing, without taper was manufactured in the laboratory and tested in a wind tunnel. The pressure data was obtained from fluid flow analysis and the deformation results obtained through structural analysis. The analysis was performed in the ANSYS Workbench Environment, accessing FLUENT CFX for the computational fluid dynamics analysis and the ANSYS FEA package for the mechanical analysis. The computational results obtained are compared with the experimental data obtained in the wind tunnel. Comparison of the analysis and test results provides further understanding of the flutter characteristics.

Wensuslaus, A. L.; McMillan, A. J.

2012-08-01

174

Asymptotic investigations into the `fluid mechanical sewing machine'  

NASA Astrophysics Data System (ADS)

The fall of a slender viscous thread from a nozzle onto a moving horizontal belt exhibits a wide range of behaviour. Steady motion is observed above a critical belt speed. Below this speed the thread undergoes a buckling instability, and lays down on the belt a variety of stable, periodic patterns referred to as a `fluid mechanical sewing machine'. We expand on previous theoretical progress [1] by including the effects arising from the resistance of the thread to bending. While the bending resistance of a slender viscous thread is small, under certain circumstances it has a dominant effect. We work in the asymtotic limit of a slender thread, and investigate the full range of steady solutions. An asymptotic refinement to the estimate derived in [1] for the onset of buckling instability is presented, and the behaviour of the thread near onset is discussed. [1] S. Chiu-Webster & J.R. Lister, J. Fluid Mech. 569, 89-111.

Blount, Maurice; Lister, John

2008-11-01

175

Micro-CAE Mechanical Engineering Software Development.  

National Technical Information Service (NTIS)

A concept in Microcomputer-Aided Engineering has been evolving and maturing at Lawrence Livermore National Laboratory during the past 4 years. In harmony with the goals of the project, several universities are participating in the development of software ...

W. Comfort B. Davis

1985-01-01

176

Mechanical testing of selected engineering plastics.  

National Technical Information Service (NTIS)

Tensile stress-strain curves and tensile creep curves were generated for a number of candidate engineering plastics. Creep testing was performed with a sustained stress of 5000 psi. Both unfilled and filled (fiber-reinforced) plastics were investigated. N...

J. J. Scott R. L. Brady

1990-01-01

177

Solventless (Extruded) Power (N-5) - Mechanized Roll. Design Engineering for the Next Generation Mechanized Roll Facility.  

National Technical Information Service (NTIS)

Design engineering work on the next generation solventless propellant mechanized rolling facilities was conducted. Design criteria was developed and submitted to the Corps of Engineers so that the updated facility could be constructed. Results of plant-sc...

J. A. Montgomery J. S. Lampkin

1970-01-01

178

Future Directions for Mechanical, Manufacturing, and Industrial Engineering Technology Programs  

NSDL National Science Digital Library

Future Directions for Mechanical, Manufacturing, and Industrial Engineering Technology Programs presents viewpoints on the fields of Mechanical Engineering Technology (MET), Manufacturing Engineering Technology (MfgET), and Industrial Engineering Technology (IET). The authors are highly knowledgeable in their own right. In addition, each sought input from colleagues to gain a broad perspective. Each part begins with an overview of innovations in the field, covering both technical and educational issues. Then the future directions for the educational programs are explored, considering industry needs, curriculum design, laboratory experiences, pedagogy, accreditation, and interfaces with other fields.

Mott, Robert L.; Neff, Gregory; Stratton, Mark J.; Summers, Donna

2009-10-29

179

Digital color holography applied to fluid and structural mechanics  

NASA Astrophysics Data System (ADS)

In various domains such as acoustics, vibrations or fluid mechanics, non-invasive metrological tools, giving full-field measurements with very high spatial and temporal resolutions, need to be developed to validate the models and/or numerical simulations of the studied phenomena. In this way, ONERA and LAUM have developed optical real-time methods based on three-wavelength digital holographic interferometry to analyze either unsteady wake flows or vibrating kinematics or complex fields. These digital color holographic methods aim at avoiding panchromatic holographic plates and their related constraints. In the domain of fluids mechanics, an interferometric set-up is presented to generate micro fringes from the observed area. The data are processed thanks to direct and inverse Fourier transforms to obtain a gas density field and to study its evolution in time. In structural mechanics, a versatile interferometric imaging set-up, based on digital Fresnel holography, is presented. These new optical imaging methods result in full-field measurements with a high spatial resolution. This research ultimately aims at analyzing, in time, unsteady complex wake flows, vibrating kinematics and acoustic fields. A few examples are given and the possibilities and limits of these methods are discussed.

Desse, Jean-Michel; Picart, Pascal; Tankam, Patrice

2012-01-01

180

ADDRESSING ENVIRONMENTAL ENGINEERING CHALLENGES WITH COMPUTATIONAL FLUID DYNAMICS  

EPA Science Inventory

In the field of environmental engineering, modeling tools are playing an ever larger role in addressing air quality issues, including source pollutant emissions, atmospheric dispersion and human exposure risks. More detailed modeling of environmental flows requires tools for c...

181

Computational fluid dynamics: A virtual prototyping tool for materials engineering  

NASA Astrophysics Data System (ADS)

The use of computational fluid dynamics (CFD) software in many materials processing industries has grown tremendously in recent years. Computational fluid dynamics has been widely utilized for conducting virtual experiments, prototype testing, and parametric studies. Analysis using CFD complements and reduces physical testing, and it can result in a significant time and cost savings. In this article, the application of CFD to a variety of materials-processing problems is presented, with examples taken from the steel, aluminum, glass, semiconductor, and polymer processing fields.

Mukhopadhyay, A.; Devulapalli, B.; Dutta, A.; Grald, E. W.

2004-03-01

182

Review of coaxial flow gas core nuclear rocket fluid mechanics  

NASA Technical Reports Server (NTRS)

Almost all of the fluid mechanics research associated with the coaxial flow gas core reactor ended abruptly with the interruption of NASA's space nuclear program because of policy and budgetary considerations in 1973. An overview of program accomplishments is presented through a review of the experiments conducted and the analyses performed. Areas are indicated where additional research is required for a fuller understanding of cavity flow and of the factors which influence cold and hot flow containment. A bibliography is included with graphic material.

Weinstein, H.

1976-01-01

183

Communications: Mechanical Deformation of Dendrites by Fluid Flow  

NASA Technical Reports Server (NTRS)

It is generally accepted that liquid agitation during alloy solidification assists in crystal multiplication, as in dendrite fragmentation and the detachment of side arms in the mushy region of a casting. Even without deliberate stirring by electromagnetic or mechanical means, there is often vigorous interdendritic fluid flow promoted by natural thermosolutal convection. In this analysis, we shall estimate the stress at the root of a secondary dendrite arm of aluminum arising from the action of a flow of molten metal past the dendrite arm.

Pilling, J.; Hellawell, A.

1996-01-01

184

Application of Computational Fluid Dynamics in building services engineering  

Microsoft Academic Search

Application of Computational Fluid Dynamics to building services design is illustrated and reviewed. Principal areas of application are designs requiring an understanding of the air flow pattern, such as design of smoke control systems and air distribution in a heating, ventilation and air-conditioning system. In such an approach, the indoor air motion is described by a set of partial differential

W. K. Chow

1996-01-01

185

Common ground in engineering geology, soil mechanics and rock mechanics: past, present and future  

Microsoft Academic Search

Engineering geology, together with soil mechanics and rock mechanics, is commonly considered to be one of the three fundamental scientific disciplines in ground engineering. Historically, the interrelation between these three disciplines has never been free of ambiguity. This, for instance, is highlighted by the fact that both Karl von Terzaghi, the founder of soil mechanics, and Leopold Müller, the founder

Helmut Bock; Peter Blümling; Heinz Konietzky

2006-01-01

186

Modeling golf ball fluid mechanics - challenges and opportunities  

NASA Astrophysics Data System (ADS)

Numerical simulation presents a powerful tool for understanding the fundamental fluid mechanics that influence golf ball aerodynamics, as well as providing an approach for ultimately analyzing and designing golf balls for manufacture. Robust and accurate simulation strategies are central to providing a means to screen designs prior to costly prototyping and field measurement. Results from a hierarchy of simulation strategies applied to the flow around golf balls will be presented, ranging from Reynolds-averaged Navier-Stokes (RANS) computations to Direct Numerical Simulation (DNS). RANS methods, while leading to computationally efficient approaches, are challenged to represent using ad hoc turbulence models the subtle effects induced by surface dimpling. DNS on the other hand, offers a first-principles approach that enables detailed examination of mechanisms though carries a significant computational cost. Predictions from both techniques are contrasted; opportunities for advancing each technique are identified.

Squires, Kyle

2009-11-01

187

Magneto-fluid-mechanics free convection turbulent flow  

NASA Technical Reports Server (NTRS)

The present work is an experimental study of the influence of a uniform magnetic field on the structure of a free convection turbulent boundary layer in a conducting fluid. The boundary layer was formed along the heated vertical wall of a cell. The applied magnetic field was normal to the wall. The measured mean temperature profiles, temperature turbulent intensity distributions, and temperature spectra along the wall, indicated that transition from turbulent to laminar flow occurs at a constant value of the ratio (Rayleigh number)/(Hartmann number). The study of the recorded spectra indicated that the presence of the magnetic field enhances the mechanism of turbulent suppression due to the buoyancy forces. Finally, a possible mechanism by which turbulence is suppressed by the presence of a magnetic field is discussed.

Papailiou, D. D.; Lykoudis, P. S.

1974-01-01

188

Introducing CFD in Introductory Undergraduate Fluid Mechanics Courses  

NASA Astrophysics Data System (ADS)

Many instructors want to introduce CFD into their introductory junior-level fluid mechanics course, but cannot because it requires several hours of class time at the cost of displacement of other basic material. A simple but effective method is now available that has been used successfully at Penn State since Spring 2005. It requires minimal instructor preparation time and only about one class period. Namely, immediately after solving the Navier-Stokes equation analytically for simple flows such as Couette and Poiseuille flow, CFD is introduced as a modern tool for solving the same equations numerically. The application of CFD (grid generation, boundary conditions, etc.), rather than numerical algorithms, is stressed. Homework problems are then assigned using pre-defined templates for FlowLab, a student-friendly analysis and visualization package created by Fluent, Inc. The templates and exercises are designed to support and emphasize the theory and concepts taught in class and in the textbook. For example, the new textbook by Cengel and Cimbala (McGraw-Hill 2006) contains 46 end-of-chapter homework problems that are used in conjunction with 42 FlowLab templates. Each exercise has been designed with two major learning objectives in mind: (1) enhance student understanding of a specific fluid mechanics concept, and (2) introduce the student to a specific capability and/or limitation of CFD through hands-on practice.

Cimbala, John M.

2005-11-01

189

The Quantum and Fluid Mechanics of Global Warming  

NASA Astrophysics Data System (ADS)

Quantum physics and fluid mechanics are the foundation of any understanding of the Earth's climate. In this talk I invoke three well-known aspects of quantum mechanics to explore what will happen as the concentrations of greenhouse gases such as carbon dioxide continue to increase. Fluid dynamical models of the Earth's atmosphere, demonstrated here in live simulations, yield further insight into past, present, and future climates. Statistics of geophysical flows can, however, be ascertained directly without recourse to numerical simulation, using concepts borrowed from nonequilibrium statistical mechanicsootnotetextJ. B. Marston, E. Conover, and Tapio Schneider, ``Statistics of an Unstable Barotropic Jet from a Cumulant Expansion,'' arXiv:0705.0011, J. Atmos. Sci. (in press).. I discuss several other ways that theoretical physics may be able to contribute to a deeper understanding of climate changeootnotetextJ. Carlson, J. Harte, G. Falkovich, J. B. Marston, and R. Pierrehumbert, ``Physics of Climate Change'' 2008 Program of the Kavli Institute for Theoretical Physics..

Marston, Brad

2008-03-01

190

Fluid mechanics and spatial performance of face arrays  

SciTech Connect

This report describes the fluid mechanics and aerodynamic performance of the Free Air Carbon dioxide Enrichment (FACE) array tested at Yazoo City, MS, in September 1987. The report describes three fluid mechanical regimes: the near field, dominated by the injection jets; the array itself; and the flow downwind of the array. The distribution of gas inside the array is described by means of multiport CO{sub 2} sampling and perfluorocarbon tracers, at three different heights. For the plant canopy configuration existing at this time, the flow was nearly uniform with height. Although the centerline CO{sub 2} concentration was controlled to well within the design goal, {plus minus}20%, 80% of the time, the variability away from the center was somewhat greater. On average, {plus minus}20% variability was achieved within a 13 m diameter within the 22 m array. The CO{sub 2} concentration downwind of the array was generally down to ambient levels within a distance of 100 m. The dispersion efficiency of the array, as measured by the parameter XAu/Q, compared well with the Brookhaven National Laboratory (BNL) prototype which had been tested on SO{sub 2}. The dispersion was greater during the daytime than at night. Although theoretical calculations indicated that CO{sub 2} interference from the Mississippi Chemical Company (MCC) plant was possible, no definite instances of such interference were identified. 6 refs., 40 figs., 1 tab.

Lipfert, F.W.; Daum, M.L.; Hendrey, G.R.; Lewin, K.F.

1989-05-01

191

Failure-mechanism maps for engineering polymers  

Microsoft Academic Search

This paper reports on progress in assembling experimental data and simplified theoretical models for the deformation and fracture of engineering polymers into diagrams which summarize their inelastic response to stress. A number of regimes are identified: brittle fracture initiated by crazing or shear-banding; plasticity terminated by ductile fracture; cold-drawing; rubbery and viscous flow; a regime in which deformation is purely

Z. Bin Ahmad; M. F. Ashby

1988-01-01

192

Mathematical Building-Blocks in Engineering Mechanics  

ERIC Educational Resources Information Center

A gamut of mathematical subjects and concepts are taught within a handful of courses formally required of the typical engineering student who so often questions the relevancy of being bound to certain lower-division prerequisites. Basic classes at the undergraduate level, in this context, include: Integral and Differential Calculus, Differential…

Boyajian, David M.

2007-01-01

193

Shake, Rattle, and Roll: Nonlinear Dynamics in Mechanical Engineering  

Microsoft Academic Search

This presentation will focus on three mechanical engineering applications in which methods from nonlinear dynamics have been applied with success. Each topic will be briefly surveyed by outlining the development of a mathematical model, providing a description of the analysis tools employed, and showing the main results obtained. The applications are: vibration reduction in internal combustion engines, impact dynamics of

Steven Shaw

1997-01-01

194

Formula Student as Part of a Mechanical Engineering Curriculum  

ERIC Educational Resources Information Center

Formula Student (FS) is a multi-university student design competition managed by the UK Institution of Mechanical Engineers. Students are required to demonstrate and prove their creativity and engineering skills through the design, manufacture and financing of a small formula style race car. This paper seeks to explore the educational value that…

Davies, Huw Charles

2013-01-01

195

RECENT ADVANCES IN COMPUTATIONAL MECHANICS FOR CIVIL ENGINEERING  

NASA Astrophysics Data System (ADS)

In order to clarify mechanical phenomena in civil engineering, it is necessary to improve computational theory and technique in consideration of the particularity of objects to be analyzed and to update computational mechanics focusing on practical use. In addition to the analysis of infrastructure, for damage prediction of natural disasters such as earthquake, tsunami and flood, since it is essential to reflect broad ranges in space and time inherent to fields of civil engineering as well as material properties, it is important to newly develop computational method in view of the particularity of fields of civil engineering. In this context, research trend of methods of computational mechanics which is noteworthy for resolving the complex mechanics problems in civil engineering is reviewed in this paper.

Applied Mechanics Committee, Computational Mechanics Subcommittee,

196

Mechanical Engineering Design of the DREO Optical Recorder for SEASAT.  

National Technical Information Service (NTIS)

This paper contains a description of the mechanical engineering aspects of the DREO optical recorder for SEASAT. The concept, design and construction are discussed in detail. The device receives a signal from the satellite and converts it into an intensit...

D. J. Hidson V. H. Pede

1979-01-01

197

Complementarity Problems in Engineering Mechanics: Models and Solution.  

National Technical Information Service (NTIS)

A large class of problems in engineering mechanics involves a so- called 'complementarity' relationship representing the orthogonality of two sign-constrained vectors. Typical instances are plasticity laws and contact-like conditions. For state problems, ...

F. Tin-Loi, M. C. Ferris

1999-01-01

198

High Temperature mechanically pumped fluid loop for space applications - working fluid selection  

NASA Technical Reports Server (NTRS)

Mechanically pumped single-phase fluid loops are increasingly being used for heat rejection purposes in space applications. Examples of Earth orbiting missions using this technology include NSTS Shuttles (water and Freon-based loops) and the International Space Station (water and ammonia-based loops). For deep space missions, both the Mars Pathfinder (1996) and Mars Exploration Rover (2003) missions used mechanically pumped Freon-I 1 loops for their primary Heat Rejection Systems (HRS.) Mechanically pumped loops are particularly well suited for rejecting large amounts of waste heat from spacecraft and future missions incorporating components with extremely high thermal energy dissipation (e.g. radar instruments, Radioisotope-based power sources) are ideal candidates for their use. However, previous implementations of mechanically pumped loops were designed for moderate temperatures (below 6OOC) and, thus, would require relatively large radiators to reject high heat loads to space. Loops designed for a higher operating temperature would allow large amounts of heat to be rejected within the constraints of a mass efficient thermal control system.

Paris, Anthony D.; Birur, Gajanana C.

2004-01-01

199

Welcoming speech from Dean Faculty of Mechanical Engineering, UMP  

NASA Astrophysics Data System (ADS)

In the Name of Allah, the Most Beneficent, the Most Merciful. It is with great pleasure that I welcome the participants of the International Conference of Mechanical Engineering Research 2011. The Prophet Muhammad (peace be upon him) said 'Acquire knowledge and impart it to the people.' (Al Tirmidhi). The quest for knowledge has been from the beginning of time but knowledge only becomes valuable when it is disseminated and applied to benefit humankind. It is hoped that ICMER 2011 will be a platform to gather and disseminate the latest knowledge in mechanical engineering. Academicians, Scientist, Researchers and practitioners of mechanical engineering will be able to share and discuss new findings and applications of mechanical engineering. It is envisaged that the intellectual discourse will result in future collaborations between universities, research institutions and industry both locally and internationally. In particular it is expected that focus will be given to issues on environmental and energy sustainability. Researchers in the mechanical engineering faculty at UMP have a keen interest in technology to harness energy from the ocean. Lowering vehicle emissions has been a primary goal of researchers in the mechanical engineering faculty and the automotive engineering centre as well including developing vehicles using alternative fuels such as biodiesel and renewable sources such as solar driven electric vehicles. Finally I would like to congratulate the organizing committee for their tremendous efforts in organizing the conference. As I wrote this in the Holy Land of Makkah, I pray to Allah swt that the conference will be a success. Prof. Dr. Zahari Taha CEng, MIED, FASc Dean, Faculty of Mechanical Engineering Universiti Malaysia Pahang

Taha, Zahari

2012-09-01

200

Fast Prediction of HCCI Combustion with an Artificial Neural Network Linked to a Fluid Mechanics Code  

SciTech Connect

We have developed an artificial neural network (ANN) based combustion model and have integrated it into a fluid mechanics code (KIVA3V) to produce a new analysis tool (titled KIVA3V-ANN) that can yield accurate HCCI predictions at very low computational cost. The neural network predicts ignition delay as a function of operating parameters (temperature, pressure, equivalence ratio and residual gas fraction). KIVA3V-ANN keeps track of the time history of the ignition delay during the engine cycle to evaluate the ignition integral and predict ignition for each computational cell. After a cell ignites, chemistry becomes active, and a two-step chemical kinetic mechanism predicts composition and heat generation in the ignited cells. KIVA3V-ANN has been validated by comparison with isooctane HCCI experiments in two different engines. The neural network provides reasonable predictions for HCCI combustion and emissions that, although typically not as good as obtained with the more physically representative multi-zone model, are obtained at a much reduced computational cost. KIVA3V-ANN can perform reasonably accurate HCCI calculations while requiring only 10% more computational effort than a motored KIVA3V run. It is therefore considered a valuable tool for evaluation of engine maps or other performance analysis tasks requiring multiple individual runs.

Aceves, S M; Flowers, D L; Chen, J; Babaimopoulos, A

2006-08-29

201

Fluid Mechanics of Biological Surfaces and their Technological Application  

NASA Astrophysics Data System (ADS)

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.

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

202

Statistical mechanical description of supercritical fluid extraction and retrograde condensation  

NASA Astrophysics Data System (ADS)

The phenomena of supercritical fluid extraction (SFE) and its reverse effect, which is known as retrograde condensation (RC), have found new and important applications in industrial separation of chemical compounds and recovery and processing of natural products and fossil fuels. Full-scale industrial utilization of SFE/RC processes requires knowledge about thermodynamic and transport characteristics of the asymmetric mixtures involved and the development of predictive modeling and correlation techniques for performance of the SFE/RC system under consideration. In this report, through the application of statistical mechanical techniques, the reasons for the lack of accuracy of existing predictive approaches are described and they are improved. It is demonstrated that these techniques also allow us to study the effect of mixed supercritical solvents on the solubility of heavy solutes (solids) at different compositions of the solvents, pressures, and temperatures. Fluid phase equilibrium algorithms based on the conformal solution van der Waals mixing rules and different equations of state are presented for the prediction of solubilities of heavy liquid in supercritical gases. It is shown that the Peng-Robinson equation of state based on conformal solution theory can predict solubilites of heavy liquid in supercritical gases more accurately than the van der Waals and Redlich-Kwong equations of state.

Park, S. J.; Kwak, T. Y.; Mansoori, G. A.

1987-07-01

203

Enhancing Student Understanding of and Interest in Mechanical Engineering  

NSDL National Science Digital Library

The paper describes an effort to enhance student understanding of the mechanical engineering profession. A freshman course Introduction to Mechanical Engineering has been developed with the objective to address such topics as the necessity of good communication skills; professional ethics; the importance of innovation, critical thinking, team work, diversity, and life-long learning. The effectiveness of addressing these issues in a freshman course in comparison with the traditional approach to teaching an introductory mechanical engineering course has been assessed through a study involving student surveys administered in control and pilot class sections at the beginning and at the end of the course. The results of the study demonstrate that the pilot group of students exposed to novel course materials acquired enhanced understanding of the subjects identified by the Engineering Accreditation Commission (EAC) as professional skills.

Plumb, Carolyn; Vinogradov, Aleksandra

2011-04-06

204

Fluid mechanics relevant to flow through pretreatment of cellulosic biomass.  

PubMed

The present study investigates fluid mechanical properties of cellulosic feedstocks relevant to flow through (FT) pretreatment for biological conversion of cellulosic biomass. The results inform identifying conditions for which FT pretreatment can be implemented in a practical context. Measurements of pressure drop across packed beds, viscous compaction and water absorption are reported for milled and not milled sugarcane bagasse, switchgrass and poplar, and important factors impacting viscous flow are deduced. Using biomass knife-milled to pass through a 2mm sieve, the observed pressure drop was highest for bagasse, intermediate for switchgrass and lowest for poplar. The highest pressure drop was associated with the presence of more fine particles, greater viscous compaction and the degree of water absorption. Using bagasse without particle size reduction, the instability of the reactor during pretreatment above 140kg/m(3) sets an upper bound on the allowable concentration for continuous stable flow. PMID:24566286

Archambault-Léger, Véronique; Lynd, Lee R

2014-04-01

205

Fluid mechanical model of the acoustic impedance of small orifices  

NASA Technical Reports Server (NTRS)

A fluid mechanical model of the acoustic behavior of small orifices is presented which predicts orifice impedance as a function of incident sound pressure level, frequency, and orifice geometry. Agreement between predicted and measured values (in both water and air) of orifice impedance is excellent. The model shows that (1) the acoustic flow in the immediate neighborhood of the orifice can be modelled as a locally spherical flow, (2) within this near field, the flow is, to a first approximation, unsteady and incompressible, and (3) at very low sound pressure levels, the orifice viscous resistance is directly related to the effect of boundary-layer displacement along the walls containing the orifice, and the orifice reactance is directly related to the inertia of the oscillating flow in the orifice neighborhood.-

Hersh, A. S.; Rogers, T.

1975-01-01

206

Fluid mechanical model of the acoustic impedance of small orifices  

NASA Technical Reports Server (NTRS)

A fluid mechanical model of the acoustic behavior of small orifices is presented which predicts orifice resistance and reactance as a function of incident sound pressure level, frequency, and orifice geometry. Agreement between predicted and measured values is excellent. The model shows the following: (1) The acoustic flow in immediate neighborhood of the orifice can be modeled as a locally spherical flow. Within this near field, the flow is, to a first approximation, unsteady and incompressible. (2) At very low sound pressure levels, the orifice viscous resistance is directly related to the effect of boundary-layer displacement along the walls containing the orifice, and the orifice reactance is directly related to the inertia of the oscillating flow in the neighborhood of the orifice. (3) For large values of the incident acoustic pressure, the impedance is dominated by nonlinear jet-like effects. (4) For low values of the pressure, the resistance and reactance are roughly equal.

Hersh, A. S.; Rogers, T.

1976-01-01

207

Fluid mechanics constraints on LIPs origin and formation  

NASA Astrophysics Data System (ADS)

Large Igneous Provinces represent the most voluminous igneous events on our planets and have probably ponctuated the Earth history since at least 3 Gyr. Recent fluid mechanics experiments on thermal convection show that the existence and characteristics of LIPs put tight constraints on mantle dynamics, structure and evolution. In particular, a relatively quick emplacement, hot temperature and large volume of LIPs would require a origin of LIPs deep in the lower mantle, a mantle rheology which depends strongly on temperature, and the presence of chemical heterogeneities. In the latter case, the laboratory experiments further suggest that LIPs could be heterogeneous in composition, could be followed by a variety of volcanic activities, and could even trigger subduction.

Davaille, A.

2008-12-01

208

A cubic spline approximation for problems in fluid mechanics  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

209

Effect of fluid medium on mechanical behavior of carbon nanotube foam  

NASA Astrophysics Data System (ADS)

This study reports the constitutive response and energy absorption capabilities of fluid-impregnated carbon nanotube (CNT) foams under compressive loading as a function of fluid viscosity and loading rates. At all strain rates tested, we observe two characteristic regimes: below a critical value, increasing fluid viscosity increases the load bearing and energy absorption capacities; after a critical value of the fluid's viscosity, we observe a rapid decrease in the systems' mechanical performance. For a given fluid viscosity, the load bearing capacity of the structure slightly decreases with strain rate. A phenomenological model, accounting for fluid-CNT interaction, is developed to explain the observed mechanical behavior.

Misra, Abha; Kumar, Praveen; Raney, Jordan R.; Singhal, Anish; Lattanzi, Ludovica; Daraio, Chiara

2014-06-01

210

Fluid flow and fuel-air mixing in a motored two-dimensional Wankel rotary engine  

NASA Technical Reports Server (NTRS)

The implicit-factored method of Beam and Warming was employed to obtain numerical solutions to the conservation equations of mass, species, momentum, and energy to study the unsteady, multidimensional flow and mixing of fuel and air inside the combustion chambers of a two-dimensional Wankel rotary engine under motored conditions. The effects of the following engine design and operating parameters on fluid flow and fuel-air mixing during the intake and compression cycles were studied: engine speed, angle of gaseous fuel injection during compression cycle, and speed of the fuel leaving fuel injector.

Shih, T. I.-P.; Nguyen, H. L.; Stegeman, J.

1986-01-01

211

Prior Knowledge of Mechanics amongst First Year Engineering Students  

ERIC Educational Resources Information Center

In the last 25 years, A-level Mathematics syllabi have changed very considerably, introducing a broader range of application areas but reducing the previous emphasis on classical mechanics. This article describes a baseline survey undertaken to establish in detail the entry levels in mechanics for the cohort of students entering Engineering

Clements, Dick

2007-01-01

212

A SKELETAL KINETIC MECHANISM FOR PRF COMBUSTION IN HCCI ENGINES  

Microsoft Academic Search

A single zone thermodynamic model, coupled to a kinetic mechanism, is developed and is capable of predicting the ignition timing of Primary Reference Fuels (PRFs) in a Homogeneous Charge Compression Ignition (HCCI) engine. A new combination of kinetic mechanisms is used, which includes 120 reactions and 58 species for both ignition and high temperature reactions. The model is validated using

PATRICK KIRCHEN; MAHDI SHAHBAKHTI; CHARLES ROBERT KOCH

2007-01-01

213

The ARL/FEU (Fluids Engineering Unit) Semi-Anechoic Chamber.  

National Technical Information Service (NTIS)

This memorandum documents the design and acoustic characteristics of the ARL/Fluids Engineering Unit semi-anechoic chamber. It is located on the first floor of the Garfield Thomas Water Tunnel and has internal dimensions of 11 x 12 x 8 feet. The sound abs...

G. C. Lauchle E. Wong

1975-01-01

214

Modelling of a hydraulic engine mount with fluid–structure interaction finite element analysis  

Microsoft Academic Search

Hydraulic engine mount (HEM) is now widely used as a highly effective vibration isolator in automotive powertrain. A lumped parameter (LP) model is a traditional model for modelling the dynamic characteristics of HEM, in which the system parameters are usually obtained by experiments. In this paper, a fluid–structure interaction (FSI) finite element analysis (FEA) method and a non-linear FEA technology

Wen-Bin Shangguan; Zhen-Hua Lu

2004-01-01

215

Hydraulic Fluids and Jet Engine Oil: Pyrolysis and Aircraft Air Quality  

Microsoft Academic Search

Incidents of smoke in aircraft cabins often result from jet engine oil and\\/or hydraulic fluid that leaks into ventilation air, which can be subjected to temperatures that exceed 500 °C. Exposed flight-crew members have reported symptoms, including dizziness, nausea, disorientation, blurred vision, and tingling in the legs and arms. In this study, the authors investigated pyrolysis products of one jet

C. Van Netten; V. Leung

2001-01-01

216

High-Pressure Rocket Engine Turnaround Duct Computational Fluid Dynamics Analysis.  

National Technical Information Service (NTIS)

Current and projected high-pressure, staged-combustion rocket engine designs, such as the XLR129 and SSME, have introduced a type of turnaround duct flowpath wherein the turnaround is accompanied by an increase in mean radius and a decrease in fluid veloc...

G. B. Cox

1984-01-01

217

A systems approach to theoretical fluid mechanics: Fundamentals  

NASA Technical Reports Server (NTRS)

A preliminary application of the underlying principles of the investigator's general system theory to the description and analyses of the fluid flow system is presented. An attempt is made to establish practical models, or elements of the general fluid flow system from the point of view of the general system theory fundamental principles. Results obtained are applied to a simple experimental fluid flow system, as test case, with particular emphasis on the understanding of fluid flow instability, transition and turbulence.

Anyiwo, J. C.

1978-01-01

218

Education of Engineering Ethics for the First Grade Students of Mechanical System Engineering  

NASA Astrophysics Data System (ADS)

The class of engineering ethics carried out in the department of mechanical system engineering of Hiroshima University is introduced, and the effects of teaching engineering ethics are analyzed using the responses of students against questions by the instructor, their reports and the results of an examination. The analysis indicates the importance of case studies and good advice by an instructor to improve the skill of students to analyze and deal with problems concerned with engineering ethics. However, it is quite difficult to change ethical awareness of students to think of ethical problems of engineering at all times. The importance of teaching a fundamental knowledge of engineering ethics and the difficulty in evaluating an academic record of the class are also discussed.

Fukushima, Hiroshi

219

Thermomechanical analysis of freezing-induced cell-fluid-matrix interactions in engineered tissues  

PubMed Central

Successful cryopreservation of functional engineered tissues (ETs) is significant to tissue engineering and regenerative medicine, but it is extremely challenging to develop a successful protocol because the effects of cryopreservation parameters on the post-thaw functionality of ETs are not well understood. Particularly, the effects on the microstructure of their extracellular matrix (ECM) have not been well studied, which determines many functional properties of the ETs. In this study, we investigated the effects of two key cryopreservation parameters – i) freezing temperature and corresponding cooling rate; and ii) the concentration of cryoprotective agent (CPA) on the ECM microstructure as well as the cellular viability. Using dermal equivalent as a model ET and DMSO as a model CPA, freezing-induced spatiotemporal deformation and post-thaw ECM microstructure of ETs was characterized while varying the freezing temperature and DMSO concentrations. The spatial distribution of cellular viability and the cellular actin cytoskeleton was also examined. The results showed that the tissue dilatation increased significantly with reduced freezing temperature (i.e., rapid freezing). A maximum limit of tissue deformation was observed for preservation of ECM microstructure, cell viability and cell-matrix adhesion. The dilatation decreased with the use of DMSO, and a freezing temperature dependent threshold concentration of DMSO was observed. The threshold DMSO concentration increased with lowering freezing temperature. In addition, an analysis was performed to delineate thermodynamic and mechanical components of freezing-induced tissue deformation. The results are discussed to establish a mechanistic understanding of freezing-induced cell-fluid-matrix interaction and phase change behavior within ETs in order to improve cryopreservation of ETs.

Han, Bumsoo; Teo, Ka Yaw; Ghosh, Soham; Dutton, J. Craig; Grinnell, Frederick

2012-01-01

220

Harmony Search Applications in Mechanical, Chemical and Electrical Engineering  

Microsoft Academic Search

The primary aim of this chapter is to introduce the state of the art applications of the harmony search (HS) algorithm in\\u000a mechanical, chemical and electrical engineering fields. The HS algorithm has been broadly utilized in complex optimization\\u000a problems arising in most engineering applications. It has been reported to be a viable alternative to other conventional optimization\\u000a techniques in these

Mohammad Fesanghary

221

The mechanical integrity of in vivo engineered heterotopic bone  

Microsoft Academic Search

Recent advances in tissue engineering have aroused interest in growth of heterotopic bone for the repair of skeletal defects. This study demonstrates an in vivo method in minipigs of engineering individual human-sized mandible replacements of heterotopic bone with a mechanical integrity similar to natural bone.Ten individualized mandible replacement scaffolds were created using computer-aided design (CAD) techniques. Five had a resorbable

Patrick H. Warnke; Ingo N. G. Springer; Yahya Acil; Gerrit Julga; Jörg Wiltfang; Klaus Ludwig; Paul A. J. Russo; Eugene Sherry; Sureshan Sivananthan; Jürgen Hedderich; Hendrik Terheyden

2006-01-01

222

MECHANICAL DESIGN CRITERIA FOR INTERVERTEBRAL DISC TISSUE ENGINEERING  

PubMed Central

Due to the inability of current clinical practices to restore function to degenerated intervertebral discs, the arena of disc tissue engineering has received substantial attention in recent years. Despite tremendous growth and progress in this field, translation to clinical implementation has been hindered by a lack of well-defined functional benchmarks. Because successful replacement of the disc is contingent upon replication of some or all of its complex mechanical behaviour, it is critically important that disc mechanics be well characterized in order to establish discrete functional goals for tissue engineering. In this review, the key functional signatures of the intervertebral disc are discussed and used to propose a series of native tissue benchmarks to guide the development of engineered replacement tissues. These benchmarks include measures of mechanical function under tensile, compressive and shear deformations for the disc and its substructures. In some cases, important functional measures are identified that have yet to be measured in the native tissue. Ultimately, native tissue benchmark values are compared to measurements that have been made on engineered disc tissues, identifying measures where functional equivalence was achieved, and others where there remain opportunities for advancement. Several excellent reviews exist regarding disc composition and structure, as well as recent tissue engineering strategies; therefore this review will remain focused on the functional aspects of disc tissue engineering.

Nerurkar, Nandan L.; Elliott, Dawn M.; Mauck, Robert L.

2009-01-01

223

AN OVERVIEW OF THE SNS ACCELERATOR MECHANICAL ENGINEERING.  

SciTech Connect

The Spallation Neutron Source (SNS*) is an accelerator-based neutron source currently nearing completion at Oak Ridge National Laboratory. When completed in 2006, the SNS will provide a 1 GeV, 1.44 MW proton beam to a liquid mercury target for neutron production. SNS is a collaborative effort between six U.S. Department of Energy national laboratories and offered a unique opportunity for the mechanical engineers to work with their peers from across the country. This paper presents an overview of the overall success of the collaboration concentrating on the accelerator ring mechanical engineering along with some discussion regarding the relative merits of such a collaborative approach. Also presented are a status of the mechanical engineering installation and a review of the associated installation costs.

HSEUH, H.; LUDWIG, H.; MAHLER, G.; PAI, C.; PEARSON, C.; RANK, J.; TUOZZOLO, J.; WEI, J.

2006-06-23

224

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

NASA Technical Reports Server (NTRS)

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.

Farassat, Fereidoun; Myers, Michael K.

2011-01-01

225

Dynamics of fluid and light intensity in mechanically stirred photobioreactor.  

PubMed

Turbulent flows in a single-stage and a two-stage impeller-stirred photobioreactor with a simple geometric configuration were analyzed using computational fluid dynamics. The trajectories of the microorganisms entrained in the flow field were traced by the particle tracking method. By projecting these trajectories onto a radial-axial (r-z) plane with a given azimuth angle, we were able to observe four different dynamics zones: circulation, pure rotation, trap, and slow-motion. Within the pure rotation zone, turbulence can be observed near the edges of the impeller. The light intensity and the light/dark cycles subjected by the microorganisms differ significantly in these zones. These differences can be further changed by providing different incident light illuminations on the reactor surface. The dynamics zones can be altered by modifying the geometric configuration of the reactor and the impeller stirring mechanism. In combination with the utilization of different incident light illuminations, the light intensity dynamics and the light/dark cycles subjected by the microorganisms can be controlled such that an optimal photobioreactor design with a high efficiency of light utilization and a high formation rate of the biochemical products can be realized. PMID:23892110

Zhang, T

2013-10-10

226

Fluid mechanics of DNA double-strand filter elution.  

PubMed Central

Measurement of infrequent DNA double-strand breaks (DSB) in mammalian cells is essential for the understanding of cell damage by ionizing radiation and many DNA-reactive drugs. One of the most important assays for measuring DSB in cellular DNA is filter elution. This study is an attempt to determine whether standard concepts of fluid mechanics can yield a self-consistent model of this process. Major assumptions of the analysis are reptation through a channel formed by surrounding strands, with only strand ends captured by filter pores. Both viscosity and entanglement with surrounding strands are considered to determine the resistance to this motion. One important result is that the average elution time of a strand depends not only on its length, but also on the size distribution of the surrounding strands. This model is consistent with experimental observations, such as the dependence of elution kinetics upon radiation dose, but independence from the size of the DNA sample up to a critical filter loading, and possible overlap of elution times for strands of different length. It indicates how the dependence of elution time on the flow rate could reveal the relative importance of viscous and entanglement resistance, and also predicts the consequences of using different filters.

Rudinger, George; Blazek, Ed Robert

2002-01-01

227

The Fluid Dynamics of Solid Mechanical Shear Zones  

NASA Astrophysics Data System (ADS)

Shear zones in outcrops and core drillings on active faults commonly reveal two scales of localization, with centimeter to tens of meters thick deformation zones embedding much narrower zones of mm-scale to cm-scale. The narrow zones are often attributed to some form of fast instability such as earthquakes or slow slip events. Surprisingly, the double localisation phenomenon seem to be independent of the mode of failure, as it is observed in brittle cataclastic fault zones as well as ductile mylonitic shear zones. In both, a very thin layer of chemically altered, ultra fine grained ultracataclasite or ultramylonite is noted. We present an extension to the classical solid mechanical theory where both length scales emerge as part of the same evolutionary process of shearing the host rock. We highlight the important role of any type of solid-fluid phase transitions that govern the second degree localisation process in the core of the shear zone. In both brittle and ductile shear zones, chemistry stops the localisation process caused by a multiphysics feedback loop leading to an unstable slip. The microstructural evolutionary processes govern the time-scale of the transition between slow background shear and fast, intermittent instabilities in the fault zone core. The fast cataclastic fragmentation processes are limiting the rates of forming the ultracataclasites in the brittle domain, while the slow dynamic recrystallisation prolongs the transition to ultramylonites into a slow slip instability in the ductile realm.

Veveakis, E.; Regenauer-Lieb, K.

2014-05-01

228

A high throughput mechanical screening device for cartilage tissue engineering.  

PubMed

Articular cartilage enables efficient and near-frictionless load transmission, but suffers from poor inherent healing capacity. As such, cartilage tissue engineering strategies have focused on mimicking both compositional and mechanical properties of native tissue in order to provide effective repair materials for the treatment of damaged or degenerated joint surfaces. However, given the large number design parameters available (e.g. cell sources, scaffold designs, and growth factors), it is difficult to conduct combinatorial experiments of engineered cartilage. This is particularly exacerbated when mechanical properties are a primary outcome, given the long time required for testing of individual samples. High throughput screening is utilized widely in the pharmaceutical industry to rapidly and cost-effectively assess the effects of thousands of compounds for therapeutic discovery. Here we adapted this approach to develop a high throughput mechanical screening (HTMS) system capable of measuring the mechanical properties of up to 48 materials simultaneously. The HTMS device was validated by testing various biomaterials and engineered cartilage constructs and by comparing the HTMS results to those derived from conventional single sample compression tests. Further evaluation showed that the HTMS system was capable of distinguishing and identifying 'hits', or factors that influence the degree of tissue maturation. Future iterations of this device will focus on reducing data variability, increasing force sensitivity and range, as well as scaling-up to even larger (96-well) formats. This HTMS device provides a novel tool for cartilage tissue engineering, freeing experimental design from the limitations of mechanical testing throughput. PMID:24275442

Mohanraj, Bhavana; Hou, Chieh; Meloni, Gregory R; Cosgrove, Brian D; Dodge, George R; Mauck, Robert L

2014-06-27

229

Computational estimation of fluid mechanical benefits from a fluid deflector at the distal end of artificial vascular grafts.  

PubMed

Intimal hyperplasia at the distal anastomosis is considered to be an important determinant for arterial and arteriovenous graft failure. The connection between unhealthy hemodynamics and intimal hyperplasia motivates the use of computational fluid dynamics modeling to search for improved graft design. However, studies on the fluid mechanical impact on intimal hyperplasia at the suture line intrusion have previously been scanty. In the present work, we focus on intimal hyperplasia at the suture line and illustrate potential benefits from the introduction of a fluid deflector to shield the suture line from unhealthily high wall shear stress. PMID:23260571

Roos, M W; Wadbro, E; Berggren, M

2013-02-01

230

Mechanical engineers' handbook, energy and power. 3rd ed.  

SciTech Connect

In addition to chapters on thermophysical properties of fluids, fundamentals of fluid mechanics, thermodynamics, heat transfer, combustion, and furnaces, Book 4 of the Handbook features coverage of both conventional (gaseous and liquid fuels, coal, and nuclear) and alternative (solar, geothermal, and fuel cells) energy sources, plus chapters on power machinery, refrigeration and cryogenics, environmental issues, and thermal systems optimization. Much of the material in this book is new or extensively revised, including coverage of such topics as: Heat pipes; Wind turbines; Fuel cells; Thermal systems optimization; Combustion; Fans, blowers, compressors, and pumps; Indoor environmental control; and Fluid power. Chapters of particular interest are: Combustion by Eric Eddings; Furnaces by Carroll Cone; Gaseous fuels by Richard J. Reed; Coals, lignite, peat by James Keppeler; and Air pollution-control technologies by C.A. Miller.

Myer Kutz (ed.)

2005-12-15

231

Nanoscale engineering materials by supercritical fluid and atomic layer deposition  

NASA Astrophysics Data System (ADS)

With the development of material science and technology, modification of substrates, which have random geometry and high aspect ratio three dimensional (3D) complex structures, with desired functional, reactive and stable coatings becomes important and challenging. The ability to fabricate mono- or multi-layers of functional materials with precisely controlled dimensions, finely tuned composition and molecular structures, attracts significant interests in materials science and is the key to construct such devices and structures at nano- and micro-scale with desired properties. In this study, supercritical carbon dioxide (scCO2) has been studied as an alternative route for modifying substrates due to the unique gas-like (low viscosity, high diffusivity and zero surface tension) and liquid-like properties (high density). (1) The reaction kinetics of metal oxides thin film deposition from pyrolysis of metal organics in scCO2 was studied in detail. This method was demonstrated as a powerful technique to coat oxides, including Al2O3, Ga2O3 and others, into 3D high aspect ratio complex structure of carbon nanotubes (CNTs) forest. (2) The low temperature scCO 2 based hydrogenolysis process was developed as a useful way to functionalize aligned CNTs forest with dense Nickel nanoparticles. On the second part of this work, atomic layer deposition (ALD)/molecular layer deposition (MLD), as a vapor phase, stepwise and self-limiting vacuum based deposition process, was demonstrated as a powerful way to form highly conformal and uniform film onto substrates, even into highly complex 3D complex structures. In this study, (4) Metal oxide ALD is applied onto 3D electrospun polymer microfiber mats template to illustrate an effective and robust strategy to fabricate long and uniform metal oxide microtubes with precisely controllable wall thickness. Designer tubes of various sizes and different materials were demonstrated by using this method. (5) By further extending this technique, complex coaxial Al2O3/ZnO/Al2O3 multilayed microtubular structure is fabricated, which provides an unique platform to study the solid state reaction and diffusion process (Kirkendall Effect) between Al2 O3 shells and the confined middle ZnO layers by annealing the samples at 700°C. (6) The extension of ALD-MLD process of polyamides, zinc hybrid, aminosilane self assembly monolayers were studied by various techniques to illustrate the surface reaction mechanism.

Peng, Qing

232

Understanding fluid mechanics within electrokinetically pumped microfluidic chips  

Microsoft Academic Search

A model describing electroosmotic fluid pumping within glass microchannels is presented. Results of calculations of fluid flow within a manifold of intersecting channels are compared with experimental observations. The effect of channel length on leakage effects at electrokinetically controlled, valveless intersections is examined. The influence of changing the surface charge potential in one channel but not another is shown to

X. C. Qiu; Lianguang Hu; J. H. Masliyah; D. J. Harrison

1997-01-01

233

Control device for diesel engine intake air heater and priming fluid injection system  

SciTech Connect

This patent describes a diesel engine having an intake manifold provided with an electrical heater for heating incoming air through the intake manifold and a primer injector for injecting a priming fluid in the intake manifold. The engine has an oil pressure lubrication system and a coolant circulation system, control means comprising oil pressure sensor means and means inhibiting operation of the heater unless the oil pressure sensor means detects a predetermined oil pressure indicating circulation of lubricant in the oil pressure lubrication system.

Gluckman, D.

1987-05-26

234

An engineering model for adsorption of gases onto flat surfaces and clustering in supercritical fluids  

SciTech Connect

Physical adsorption is used in gas purification processes such as the removal of volatile organic compounds from stack gases, as a means of fractionating fluids that are difficult to separate by other methods, and in adsorbent regenerations using supercritical fluids. Physical adsorption is also of interest in transportation and storage of radioactive gases, in separation and purification of lower hydrocarbons, in supercritical extractions and chromatography, and in critical point drying. The authors present an engineering model to describe physical adsorption from sub- to supercritical conditions on flat walls and clustering in supercritical fluids using a single temperature-independent parameter for fluid-solid interactions. The fluid-solid potential is superimposed on the Peng-Robinson equation of state, and the configurational energy integral in the inhomogeneous fluid phase is simplified with a local density approximation. This model is capable of quantitative fits over wide pressure and temperature ranges. Model predictions for physical adsorption of pure gases on flat walls are compared with experimental surface excess data, and model predictions for describing the clustering phenomenon are compared with experimental fluorescence spectra.

Subramanian, R.; Pyada, H.; Lira, C.T. [Michigan State Univ., East Lansing, MI (United States). Dept. of Chemical Engineering

1995-11-01

235

Wentworth Institute Resource Guide for Mechanical Engineering Laboratory Manual.  

ERIC Educational Resources Information Center

This publication is a resource guide designed primarly as an aid to the instructor. All of the experiments contained in the Mechanical Engineering Laboratory Manual have been successfully completed under laboratory conditions by both staff and students. The results of these experiments have been computed and are presented in this publication. The…

Avakian, Harry; And Others

236

Basic Gasoline Engine Mechanics. Florida Vocational Program Guide.  

ERIC Educational Resources Information Center

This packet contains a program guide and Career Merit Achievement Plan (Career MAP) for the implementation of a basic gasoline engine mechanics program in Florida secondary and postsecondary schools. The program guide describes the program content and structure, provides a program description, lists job titles under the program, and includes a…

University of South Florida, Tampa. Dept. of Adult and Vocational Education.

237

Idea and practice for paperless education of Mechanical Engineering Drawing  

Microsoft Academic Search

The desirability and feasibility of paperless education in curriculum of Mechanical Engineering Drawing are discussed in this paper. Three measures are adapted in the whole education cycle and. A set of Web-based multimedia teaching material provides teacher to give his\\/her lecture in classroom vividly and a legible electrical reading book after school. An assignment system is an interactive toolkit for

Lianguan Shen; Mujun Li

2008-01-01

238

Production Engineering Measure for Mechanization of High Reliability Capacitors.  

National Technical Information Service (NTIS)

Work on the production design engineering and design of pilot line equipment continues. Of the 29 major subassemblies to be used in the mechanized high-reliability capacitor assembly operation, 14 are complete, and another 14 are in various stages of prod...

J. H. D. Folster P. M. Kennedy G. E. Walters

1965-01-01

239

Production Engineering Measure for Mechanization of High-Reliability Capacitors.  

National Technical Information Service (NTIS)

Work on the production design engineering and design of pilot line equipment continues. Of the 28 major subassemblies to be used in the mechanized high--reliability capacitor assembly operation, 10 are complete, and another 14 are in various stages of pro...

J. H. D. Folster P. M. Kennedy G. E. Walters

1964-01-01

240

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

ERIC Educational Resources Information Center

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…

Liu, Henry

241

Mechanical properties of magnetorheological fluids under squeeze-shear mode  

NASA Astrophysics Data System (ADS)

Magnetorheological (MR) fluids is very promising intelligent materials and it can rapidly by changed from a liquid state to a solid state in a magnetic field. Various industries are full of potential MR fluids applications, but current MR fluids have the limitation that their yield stresses are not strong enough to meet some industrial requirements. The crucial problem is how to enhance the yield stress of MR fluids. Electrorheological (ER) fluids, similar to MR fluids, can be achieved high strength under squeeze mode, which proposed a method to achieve high-efficiency MR fluids by study of shear after compression. The performance of MR fluids under squeeze-shear mode was inveatigated. Magnetic fields being generated by two coils carrying different magnitudes of DC electrical current were applied on the MR fluids when shearing after compression were carried out on a self-constructed test system. For each trail the current in the coil and the compressive force were kept constant and the instantaneous yield stress was recorded. The relations of compression stress versus compression strain, yield stress versus compression stress were studied under different applied currents. The ploting of compressive stress against compressive strain has been observed to have three regions: the first and third regions has a linear relationship and the second region has a zero increasing. The slope of the curve was found to be larger when the applied current was larger. The SG MRF2035 without compression process has a yield stress about 53kPa at most even if increasing the applied current. But after compression, the yield stress increase with the increasing compressive stress under the different applied currents. And some promising results are obtained, for example, when the applied current is 2.5A and the compressive stress is 2.0MPa, the yield stress exceeds 1100kPa. It showed that the yield stress of MR fluids after compression was much stronger than that of uncompressed MR fluids under the same applied current. The enhanced yield stress of MR fluids can be utilized to design the MR clutch and brake for new structure and will make MR fluids technology attractive for many applications.

Wang, Hong-yun; Zheng, Hui-qiang; Li, Yong-xian; Lu, Shuang

2008-12-01

242

Mechanics of Undulatory Swimming in a Frictional Fluid  

PubMed Central

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.

Ding, Yang; Sharpe, Sarah S.; Masse, Andrew; Goldman, Daniel I.

2012-01-01

243

Digital three-color holographic interferometry devoted to fluid mechanics  

NASA Astrophysics Data System (ADS)

This paper presents work and results performed with LAUM collaboration in digital three-color holographic interferometry applied to Fluid Mechanics. In this method, three different wavelengths are used as luminous light source of the interferometer and the optical setup generates three micro interferences fringes which constitute three spatial carrier frequencies. When these images are recorded with a color sensor, the resolution of reconstructed hologram depends on the pixel size and pixel number of the sensor used for recording and also, the shape and the overlapping of three filters of color sensor influence strongly the three reconstructed images. This problem can be directly visualized in 2D Fourier planes on red, green and blue channels. To better understand this problem and to avoid parasitic images generated at the reconstruction, three different sensors have been tested : a CCD sensor equipped with a Bayer filter, a Foveon sensor and a 3CCD sensor. The best results have been obtained with the last one. In the recording principle, interference micro fringes produced by the superimposition of three reference waves and three measurement waves can be simultaneously recorded on the three spectral bands (red, green, and blue). Phase and amplitude images are computed using 2D Fourier transform in delayed time. Spectral filtering is applied on each Fourier plane in order to eliminate the parasitic diffraction orders. Then, phase differences are obtained by subtracting the reference phase to the probe phase. Several optical setups were tested and the best configuration allows the visualization of field about 70mm and increases the sensitivity since the measurement wave crosses twice the test section. Interferences induced by the wake flow have been recorded and intensities have been computed from the phase differences. Finally, one shows that fringes obtained with this process are those found with real-time color holographic interferometry using classical holographic plates.

Desse, J. M.; Picart, P.; Tankam, P.

2010-09-01

244

Mechanical modulation of nascent stem cell lineage commitment in tissue engineering scaffolds.  

PubMed

Taking inspiration from tissue morphogenesis in utero, this study tests the concept of using tissue engineering scaffolds as delivery devices to modulate emergent structure-function relationships at early stages of tissue genesis. We report on the use of a combined computational fluid dynamics (CFD) modeling, advanced manufacturing methods, and experimental fluid mechanics (micro-piv and strain mapping) for the prospective design of tissue engineering scaffold geometries that deliver spatially resolved mechanical cues to stem cells seeded within. When subjected to a constant magnitude global flow regime, the local scaffold geometry dictates the magnitudes of mechanical stresses and strains experienced by a given cell, and in a spatially resolved fashion, similar to patterning during morphogenesis. In addition, early markers of mesenchymal stem cell lineage commitment relate significantly to the local mechanical environment of the cell. Finally, by plotting the range of stress-strain states for all data corresponding to nascent cell lineage commitment (95% CI), we begin to "map the mechanome", defining stress-strain states most conducive to targeted cell fates. In sum, we provide a library of reference mechanical cues that can be delivered to cells seeded on tissue engineering scaffolds to guide target tissue phenotypes in a temporally and spatially resolved manner. Knowledge of these effects allows for prospective scaffold design optimization using virtual models prior to prototyping and clinical implementation. Finally, this approach enables the development of next generation scaffolds cum delivery devices for genesis of complex tissues with heterogenous properties, e.g., organs, joints or interface tissues such as growth plates. PMID:23660249

Song, Min Jae; Dean, David; Knothe Tate, Melissa L

2013-07-01

245

Coupled fluid and solid mechanics study for improved permeability estimation of fines' invaded porous materials  

NASA Astrophysics Data System (ADS)

The problem of fine particle infiltration is seen in fields from subsurface transport, to drug delivery to industrial slurry flows. Sediment filtration and pathogen retention are well-known subsurface engineering problems that have been extensively studied through different macroscopic, microscopic and experimental modeling techniques Due to heterogeneity, standard constitutive relationships and models yield poor predictions for flow (e.g. permeability) and rock properties (e.g. elastic moduli) of the invaded (damaged) porous media. This severely reduces our ability to, for instance, predict retention, pressure build-up, newly formed flow pathways or porous medium mechanical behavior. We chose a coupled computational fluid dynamics (CFD) - discrete element modeling (DEM) approach to simulate the particulate flow through porous media represented by sphere packings. In order to minimize the uncertainty involved in estimating the flow properties of porous media on Darcy scale and address the dynamic nature of filtration process, this microscopic approach is adapted as a robust method that can incorporate particle interaction physics as well as the heterogeneity of the porous medium.. The coupled simulation was done in open-source packages which has both CFD (openFOAM) and DEM components (LIGGGHTS). We ran several sensitivity analyses over different parameters such as particle/grain size ratio, fluid viscosity, flow rate and sphere packing porosity in order to investigate their effects on the depth of invasion and damaged porous medium permeability. The response of the system to the variation of different parameters is reflected through different clogging mechanism; for instance, bridging is the dominant mechanism of pore-throat clogging when larger particles penetrate into the packing, whereas, in case of fine particles which are much smaller than porous medium grains (1/20 in diameter), this mechanism is not very effective due to the frequent formation and destruction of particle bridges. Finally, depending on the material and fluids that penetrate into the porous medium, the ionic forces might play a significant role in the filtration process. We thus also report on influence of particle attachment (and detachment) on the type of clogging mechanisms. Pore scale simulations allow for visualization and understanding of fundamental processes, and, further, the velocity fields are integrated into a distinctly non-monotonic permeability-porosity/(depth of penetration) relationship.

Mirabolghasemi, M.; Prodanovic, M.

2012-12-01

246

Fracture mechanics criteria for turbine engine hot section components  

NASA Technical Reports Server (NTRS)

The application of several fracture mechanics data correlation parameters to predicting the crack propagation life of turbine engine hot section components was evaluated. An engine survey was conducted to determine the locations where conventional fracture mechanics approaches may not be adequate to characterize cracking behavior. Both linear and nonlinear fracture mechanics analyses of a cracked annular combustor liner configuration were performed. Isothermal and variable temperature crack propagation tests were performed on Hastelloy X combustor liner material. The crack growth data was reduced using the stress intensity factor, the strain intensity factor, the J integral, crack opening displacement, and Tomkins' model. The parameter which showed the most effectiveness in correlation high temperature and variable temperature Hastelloy X crack growth data was crack opening displacement.

Meyers, G. J.

1982-01-01

247

Engine retarder with reset auto-lash mechanism  

SciTech Connect

This patent describes an engine retarding system of a gas compression release type including an internal combustion engine having exhaust valve means and pushtube means, hydraulic pressure supply means, hydraulically actuated first piston, and second piston means actuated by the pushtube means and hydraulically interconnected with the first piston means. The improvement comprises fluid passageway means formed through the first piston means between the high and the low pressure sides, reset valve means positioned substantially within the adjustable stop means for reciprocating motion. The reset valve means has a valve face formed on one end thereof and adapted to seat against the high pressure side of the first piston means thereby sealing the fluid passageway means, first biasing means adapted to bias the reset valve means toward the first piston means, second biasing means adapted to bias the reset valve means away from the first piston means when the first piston means approaches its second position, third piston means mounted within the reset valve means for reciprocating motion therewith and movable between first and second positions. The first biasing means are also adapted to bias the third piston means toward the second position of the third piston means. The third piston means have passageway means formed therethrough, and check valve means located in the passageway means of the third piston means and adapted to hydraulically lock the third piston means in the second position.

Meistrick, Z.S.; Price, R.B.

1987-11-17

248

Adaptive Local Grid Refinement in Computational Fluid Mechanics.  

National Technical Information Service (NTIS)

Several promising new techniques for efficient and accurate numerical solution of large-scale fluid flow problems have been developed. These methods include self-adaptive mesh modification techniques for applications requiring front-tracking and local gri...

R. E. Ewing M. B. Allen M. J. Djomehri J. H. George E. L. Isaacson

1987-01-01

249

Fluid pressure transients and mechanical coupling in decollement zones  

NASA Astrophysics Data System (ADS)

Accretionary wedges syn-sedimentary decollements are low friction fault zones and generally lie in the aseismic portion of the subduction plane updip of the seismogenic zone. Understanding the role of fluid migration and fluid pressure has been an important target of ODP, with legs 110 and 156 on Barbados accretionary wedge and legs 131, 190, 196 on Nankai accretionary wedge. In both settings, arguments based in great part on microstructural observations suggested pore pressure cycling. Logging while drilling data also indicate that decollements can keep a high water content in spite of the generally compactive nature of the deformation observed at the micro-scale. Theory and modeling show that high pore pressure fronts may propagate spontaneously along a decollement under certain conditions, which include a strong dependency of permeability on pore pressure. However, there are important differences between the Barbados case and the Nankai case. In Barbados, pore fluid chemistry indicates transient fluid migration along the decollement from a smectite diagenesis fluid source at depths. On the Nankai Muroto transect, smectite diagenesis occurs in the trench and there is no clear fluid migration signal at decollement level. This suggests that pressure cycling may occur without significant horizontal flow along the decollement. A conceptual model is proposed in which transient fluid pressure transfer from the underthrust sequence to the decollement and pore pressure in the decollement are controlled by the stress state in the underthrust sequence. Studies of anisotropic physical properties indicate strong decoupling at the decollement level and suggest an extensional state of stress is maintained in the underthrust sequence. Slip along the decollement increases the extensional stress in the underthrust sequence at the tip of the slipping zone and promotes fluid flow into the slipping zone.

Henry, P.; Bourlange, S.

2003-12-01

250

Fundamental studies of fluid mechanics and stability in porous media  

SciTech Connect

We have been active in four areas: Numerical and analytical studies of viscous fingering in miscible displacements, including non- monotonic mobility profiles; numerical and analytical studies of the effect of non-Newtonian fluid characteristics on instabilities; experimental studies of instabilities of moving contact lines for Newtonian and non-Newtonian fluids; and studies of natural convective energy transport due to time-dependent body forces.

Homsy, G.M.

1992-07-01

251

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

NASA Technical Reports Server (NTRS)

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.

Kenny, R Jeremy; Hulka, James R.

2008-01-01

252

Mechanism of wear control by the lubricant in diesel engines  

SciTech Connect

At today's low oil consumption rates, high speed diesel engines with chromium-faced rings have experienced corrosive wear problems. This report defines the alkalinity required to prevent these wear problems; and the appropriate oil drain interval. In addition, the mechanisms of chromium-faced ring wear are identified. The study is based on three different engine types - direct injection two-cycle (DDA 8V-71TA), direct injection four-cycle (Mack ETAZ 673), and precombustion chamber four-cycle (Caterpillar 1Y73).

McGeehan, J.A.; Kulkarni

1987-01-01

253

Investigation of the in vitro culture process for skeletal-tissue-engineered constructs using computational fluid dynamics and experimental methods.  

PubMed

The in vitro culture process via bioreactors is critical to create tissue-engineered constructs (TECs) to repair or replace the damaged tissues/organs in various engineered applications. In the past, the TEC culture process was typically treated as a black box and performed on the basis of trial and error. Recently, computational fluid dynamics (CFD) has demonstrated its potential to analyze the fluid flow inside and around the TECs, therefore, being able to provide insight into the culture process, such as information on the velocity field and shear stress distribution that can significantly affect such cellular activities as cell viability and proliferation during the culture process. This paper briefly reviews the CFD and experimental methods used to investigate the in vitro culture process of skeletal-type TECs in bioreactors, where mechanical deformation of the TEC can be ignored. Specifically, this paper presents CFD modeling approaches for the analysis of the velocity and shear stress fields, mass transfer, and cell growth during the culture process and also describes various particle image velocimetry (PIV) based experimental methods to measure the velocity and shear stress in the in vitro culture process. Some key issues and challenges are also identified and discussed along with recommendations for future research. PMID:23363205

Hossain, Md Shakhawath; Chen, X B; Bergstrom, D J

2012-12-01

254

Modelling of a hydraulic engine mount with fluid-structure interaction finite element analysis  

NASA Astrophysics Data System (ADS)

Hydraulic engine mount (HEM) is now widely used as a highly effective vibration isolator in automotive powertrain. A lumped parameter (LP) model is a traditional model for modelling the dynamic characteristics of HEM, in which the system parameters are usually obtained by experiments. In this paper, a fluid-structure interaction (FSI) finite element analysis (FEA) method and a non-linear FEA technology are used to determine the system parameters, and a fully coupled FSI model is developed for modelling the static and lower-frequency performance of an HEM. A FSI FEA technique is used to estimate the parameters of volumetric compliances, equivalent piston area, inertia and resistance of the fluid in the inertia track and the decoupler of an HEM. A non-linear FEA method is applied to determine the dynamic stiffness of rubber spring of the HEM. The system parameters predicated by FEA are compared favorably with experimental data and/or analytical solutions. A numerical simulation for an HEM with an inertia track and a free decoupler is performed based on the FSI model and the LP model along with the estimated system parameters, and again the simulation results are compared with experimental data. The calculated time histories of some variables in the model, such as the pressure in the upper chamber, the displacement of the free decoupler and the volume flow through the inertia track and the decoupler, under different excitations, elucidate the working mechanism of the HEM. The pressure distribution calculated with the FSI model in the chambers of the HEM validates the assumption that the pressure distribution in the upper and lower chamber is uniform in the LP model. The work conducted in the paper demonstrates that the methods for estimating the system parameters in the LP model and the FSI model for modelling HEM are effective, with which the dynamic characteristic analysis and design optimization of an HEM can be performed before its prototype development, and this can ensure its low cost and high quality for development.

Shangguan, Wen-Bin; Lu, Zhen-Hua

2004-08-01

255

Simulation of a traveling-wave thermoacoustic engine using computational fluid dynamics  

NASA Astrophysics Data System (ADS)

A two-dimensional computational fluid dynamics (CFD) simulation study of a traveling-wave thermoacoustic engine is presented. The computations show an increase of the dynamic pressure when a linear temperature difference is applied across the regenerator. An amplification of the acoustic power through the engine is also illustrated. A satisfactory agreement between the calculated and expected gains of the traveling-wave thermoacoustic engine is obtained. The expected gain is defined as the ratio of the absolute temperatures at the ends of the regenerator. Nonlinear phenomena that cannot be captured by existing linear theory, like streaming mass flows and vortices formation, are also visualized. It is concluded that CFD codes could be used in the future to predict and optimize thermoacoustic systems. This is an important step towards the development of nonlinear simulation tools for the high-amplitude thermoacoustic systems that are needed for practical use.

Lycklama À Nijeholt, J. A.; Tijani, M. E. H.; Spoelstra, S.

2005-10-01

256

Sensing fluid viscosity and density through mechanical impedance measurement using a whisker transducer  

NASA Astrophysics Data System (ADS)

This paper presents a new technique for fluid viscosity and density sensing through measuring the mechanical impedance of the fluid load applied on a sphere. A piezoelectric whisker transducer (WT) is proposed which acts simultaneously as both the actuator to excite the sphere tip to oscillate in the fluid and the sensor to measure the force, velocity and mechanical impedance. The relationship between mechanical impedance of the fluid load and electrical impedance of the WT is derived based on a transduction matrix model which characterizes the electro-mechanical transduction process of the WT in both directions. The mechanical impedance is further related to the fluid viscosity and density using a theoretical model. The establishment of this fluid-mechanical-electrical relationship allows the WT to extract the fluid viscosity and density conveniently and accurately just from its electrical impedance. Experimental studies are carried out to calibrate the WT and test its performance using glycerol-water mixtures. It is concluded that the WT is capable of providing results comparable to those of standard viscometers within a wide measurement range due to its low working frequency and large vibration amplitude. Its unique self-actuation-and-sensing feature makes it a suitable solution for online fluid sensing.

Ju, Feng; Ling, Shih-Fu

2013-05-01

257

Experiments in Creative Engineering at the Department of Mechanical Engineering in Kurume National College of Technology  

NASA Astrophysics Data System (ADS)

We present a program to learn ability to solve problems on engineering. This program is called “Experiments in creative engineering” in the department of mechanical engineering in Kurume National College of Technology advanced engineering school. In the program, students have to determine own theme and manufacture experimental devices or some machines by themselves. The students must also perform experiments to valid the function and performance of their devices by themselves. The restriction of the theme is to manufacture a device which function dose not basically exist in the world with limited cost (up to 20,000Yen) . As the results of questionnaire of students, the program would be very effective to the creative education for the students.

Tanaka, Hiroshi; Hashimura, Shinji; Hiroo, Yasuaki

258

National Aeronautics and Space Administration Subject Category - D - Engineering.  

National Technical Information Service (NTIS)

Reports in the category cover: engineering (general); communications; electronics and electrical engineering; fluid mechanics and heat transfer instrumentation and photography; lasers and masers; mechanical engineering; quality assurance and reliability; ...

1989-01-01

259

Thermal/Fluid Analysis of a Composite Heat Exchanger for Use on the RLV Rocket Engine  

NASA Technical Reports Server (NTRS)

As part of efforts to design a regeneratively cooled composite nozzle ramp for use on the reusable vehicle (RLV) rocket engine, an C-SiC composites heat exchanger concept was proposed for thermal performance evaluation. To test the feasibility of the concept, sample heat exchanger panels were made to fit the Glenn Research Center's cell 22 for testing. Operation of the heat exchanger was demonstrated in a combustion environment with high heat fluxes similar to the RLV Aerospike Ramp. Test measurements were reviewed and found to be valuable for the on going fluid and thermal analysis of the actual RLV composite ramp. Since the cooling fluid for the heat exchanger is water while the RLV Ramp cooling fluid is LH2, fluid and thermal models were constructed to correlate to the specific test set-up. The knowledge gained from this work will be helpful for analyzing the thermal response of the actual RLV Composite Ramp. The coolant thermal properties for the models are taken from test data. The heat exchanger's cooling performance was analyzed using the Generalized Fluid System Simulation Program (GFSSP). Temperatures of the heat exchanger's structure were predicted in finite element models using Patran and Sinda. Results from the analytical models and the tests show that RSC's heat exchanger satisfied the combustion environments in a series of 16 tests.

Nguyen, Dalton

2002-01-01

260

Thermal/Fluid Analysis of a Composite Heat Exchanger for Use on the RLV Rocket Engine  

NASA Technical Reports Server (NTRS)

As part of efforts to design a regeneratively cooled composite nozzle ramp for use on the reusable vehicle (RLV) rocket engine, a C-SiC composite heat exchanger concept was proposed for thermal performance evaluation. To test the feasibility of the concept, sample heat exchanger panels were made to fit the Glenn Research Center's cell 22 for testing. Operation of the heat exchanger was demonstrated in a combustion environment with high heat fluxes similar to the RLV Aerospike Ramp. Test measurements were reviewed and found to be valuable for the on-going fluid and thermal analysis of the actual RLV composite ramp. Since the cooling fluid for the heat exchanger is water while the RLV Ramp cooling fluid is LH2, fluid and therma models were constructed to correlate to the specific test set-up. The knowledge gained from this work will be helpful for analyzing the thermal response of the actual RLV Composite Ramp. The coolant thermal properties for the models are taken from test data. The heat exchanger's cooling performance was analyzed using the Generalized Fluid System Simulation Program (GFSSP). Temperatures of the heat exchanger's structure were predicted in finite element models using Patran and Sinda. Results from the analytical models and the tests show that RSC's heat exchanger satisfied the combustion environments in a series of 16 tests.

Nguyen, Dalton; Turner, Larry D. (Technical Monitor)

2001-01-01

261

PREFACE: 1st International Conference on Mechanical Engineering Research 2011 (ICMER2011)  

NASA Astrophysics Data System (ADS)

The year 2010 represented a significant milestone in the history of the Mechanical Engineering community with the organization of the first and second national level conferences (National Conference in Mechanical Engineering for Research, 1st and 2nd NCMER) at Universiti Malaysia Pahang on 26-27 May and 3-4 December 2010. The conferences attracted a large number of delegates from different premier academic and research institutions in the country to participate and share their research experiences at the conference. The International Conference on Mechanical Engineering Research (ICMER 2011) followed on from the first and second conferences due to good support from researchers. The ICMER 2011 is a good platform for researchers and postgraduate students to present their latest finding in research. The conference covers a wide range of topics including the internal combustion engine, machining processes, heat and mass transfer, fuel, biomechanical analysis, aerodynamic analysis, thermal comfort, computational techniques, design and simulation, automotive transmission, optimization techniques, hybrid electric vehicles, engine vibration, heat exchangers, finite element analysis, computational fluid dynamics, green energy, vehicle dynamics renewable energy, combustion, design, product development, advanced experimentation techniques, to name but a few. The international conference has helped to bridge the gap between researchers working at different institutions and in different countries to share their knowledge and has helped to motivate young scientists with their research. This has also given some clear direction for further research from the deliberations of the conference. Several people have contributed in different ways to the success of the conference. We thank the keynote speakers and all authors of the contributed papers, for the cooperation rendered to us in the publication of the CD conference proceedings. In particular, we would like to place on record our thanks to the expert reviewers who have spared their time reviewing the papers. We also highly appreciate the assistance offered by many volunteers in the preparation of the conference proceedings. All papers in ICMER 2011 have the opportunity to be published in IOP Conference Series: Materials Science and Engineering, (indexed by Scopus, Ei Compendex, Inspec), International Journal of Automotive and Mechanical Engineering (IJAME) and Journal of Mechanical Engineering and Sciences (JMES). Professor Dr Hj Rosli Abu Bakar Chairman ICMER 2011

Abu Bakar, Rosli

2012-09-01

262

Microfabrication of hierarchical structures for engineered mechanical materials  

NASA Astrophysics Data System (ADS)

Materials found in nature present, in some cases, unique properties from their constituents that are of great interest in engineered materials for applications ranging from structural materials for the construction of bridges, canals and buildings to the fabrication of new lightweight composites for airplane and automotive bodies, to protective thin film coatings, amongst other fields. Research in the growing field of biomimetic materials indicates that the micro-architectures present in natural materials are critical to their macroscopic mechanical properties. A better understanding of the effect that structure and hierarchy across scales have on the material properties will enable engineered materials with enhanced properties. At the moment, very few theoretical models predict mechanical properties of simple materials based on their microstructures. Moreover these models are based on observations from complex biological systems. One way to overcome this challenge is through the use of microfabrication techniques to design and fabricate simple materials, more appropriate for the study of hierarchical organizations and microstructured materials. Arrays of structures with controlled geometry and dimension can be designed and fabricated at different length scales, ranging from a few hundred nanometers to centimeters, in order to mimic similar systems found in nature. In this thesis, materials have been fabricated in order to gain fundamental insight into the complex hierarchical materials found in nature and to engineer novel materials with enhanced mechanical properties. The materials fabricated here were mechanically characterized and compared to simple mechanics models to describe their behavior with the goal of applying the knowledge acquired to the design and synthesis of future engineered materials with novel properties.

Vera Canudas, Marc

263

Maximum-power quantum-mechanical Carnot engine.  

PubMed

In their work [J. Phys. A 33, 4427 (2000)], Bender, Brody, and Meister have shown by employing a two-state model of a particle confined in the one-dimensional infinite potential well that it is possible to construct a quantum-mechanical analog of the Carnot engine through changes of both the width of the well and the quantum state in a specific manner. Here, a discussion is developed about realizing the maximum power of such an engine, where the width of the well moves at low but finite speed. The efficiency of the engine at the maximum power output is found to be universal independently of any of the parameters contained in the model. PMID:21599125

Abe, Sumiyoshi

2011-04-01

264

Teaching Computer-Aided Design of Fluid Flow and Heat Transfer Engineering Equipment.  

ERIC Educational Resources Information Center

Describes a teaching program for fluid mechanics and heat transfer which contains both computer aided learning (CAL) and computer aided design (CAD) components and argues that the understanding of the physical and numerical modeling taught in the CAL course is essential to the proper implementation of CAD. (Author/CMV)

Gosman, A. D.; And Others

1979-01-01

265

Computational Fluid Dynamics Analysis Method Developed for Rocket-Based Combined Cycle Engine Inlet  

NASA Technical Reports Server (NTRS)

Renewed interest in hypersonic propulsion systems has led to research programs investigating combined cycle engines that are designed to operate efficiently across the flight regime. The Rocket-Based Combined Cycle Engine is a propulsion system under development at the NASA Lewis Research Center. This engine integrates a high specific impulse, low thrust-to-weight, airbreathing engine with a low-impulse, high thrust-to-weight rocket. From takeoff to Mach 2.5, the engine operates as an air-augmented rocket. At Mach 2.5, the engine becomes a dual-mode ramjet; and beyond Mach 8, the rocket is turned back on. One Rocket-Based Combined Cycle Engine variation known as the "Strut-Jet" concept is being investigated jointly by NASA Lewis, the U.S. Air Force, Gencorp Aerojet, General Applied Science Labs (GASL), and Lockheed Martin Corporation. Work thus far has included wind tunnel experiments and computational fluid dynamics (CFD) investigations with the NPARC code. The CFD method was initiated by modeling the geometry of the Strut-Jet with the GRIDGEN structured grid generator. Grids representing a subscale inlet model and the full-scale demonstrator geometry were constructed. These grids modeled one-half of the symmetric inlet flow path, including the precompression plate, diverter, center duct, side duct, and combustor. After the grid generation, full Navier-Stokes flow simulations were conducted with the NPARC Navier-Stokes code. The Chien low-Reynolds-number k-e turbulence model was employed to simulate the high-speed turbulent flow. Finally, the CFD solutions were postprocessed with a Fortran code. This code provided wall static pressure distributions, pitot pressure distributions, mass flow rates, and internal drag. These results were compared with experimental data from a subscale inlet test for code validation; then they were used to help evaluate the demonstrator engine net thrust.

1997-01-01

266

Cowboy Fluid Mechanics: Lariat Modes of a Viscous Rope  

NASA Astrophysics Data System (ADS)

A thin filament of viscous fluid falling onto a surface winds itself into a helical coil whose angular frequency of rotation ? depends on the fall height H, the flow rate, and the fluid properties. We have studied a novel variant of this phenomenon in which the nozzle ejecting the fluid rotates about a vertical axis at a constant rate ?. In laboratory experiments using viscous corn syrup, we observe that the filament coils in the normal way when ??. However, when ? ? and H is sufficiently large, a new ``lariat'' mode appears in which the filament is thrown outward in the form of a spiral of large diameter (up to tens of cm) rotating at a rate 0.9?. The transition between the coiling and lariat modes is hysteretic with respect to variations in ?. In addition to the laboratory experiments, we will also present preliminary results of numerical calculations of the lariat mode based on a ``slender body'' model for a viscous filament with inertia.

Ribe, Neil; Badr, Sarah; Morris, Stephen

2009-11-01

267

Topics in the fluid mechanics of viscoelastic liquids  

NASA Astrophysics Data System (ADS)

The behavior of some viscoelastic fluids was studied mathematically. As in transonic flows with the potential function, some fluids can undergo a change of type in the vorticity equation, and this gives rise to shocks in the first derivatives of the velocity components. These properties were recently shown to explain some unusual phenomena. Special flows for which similarity solutions exist are studied, and it is found that basic solutions can undergo a change of type in the vorticity equation. This is something that has not been shown before, because only perturbed flows of viscoelastic fluids have been studied. Particular attention is paid to the nonlinear model of White-Metzner. This model is found to become even more hyperbolic than the usual Maxwell models. Also, well posedness, i.e., stability due to short waves, is analyzed. This notion is very important since this kind of instability can lead to catastrophic behavior of numerical solutions. Conditions for well posedness are obtained. Also, the K-BKZ model is studied for which similar results are obtained. It is shown that the structure of this model is comparable to the White-Metzner's model. Finally, experimental measurements of interfacial tension between polymer melts at high temperatures are carried out. The technique of the spinning drop tensiometer, which consists of spinning a small amount of one fluid inside another one, is adapted until a steady shape is obtained. When the rotational speed is high enough, the shape of the inner fluid is a long cylinder with rounded ends. Then one can simply determine interfacial tension from the shape of the fluid. Careful measurements are done here for standard polymers.

Verdier, Claude

1990-08-01

268

Solenoidal Lipschitz truncation and applications in fluid mechanics  

NASA Astrophysics Data System (ADS)

We extend the Lipschitz truncation method to the setting of solenoidal functions. In particular, we approximate a solenoidal Sobolev function by a solenoidal Lipschitz function which differs from the original function only on a small set. Our main application is the existence of weak solutions to the two-dimensional Prandtl-Eyring fluid model which has almost linear growth. In this situation a correction via Bogovski? operators does not work. Furthermore, we extend the concept of almost A-harmonicity to the fluid context in the pressure free formulation.

Breit, D.; Diening, L.; Fuchs, M.

269

Maximum-power quantum-mechanical Carnot engine  

Microsoft Academic Search

In their work [J. Phys. AJPHAC50305-447010.1088\\/0305-4470\\/33\\/24\\/302 33, 4427 (2000)], Bender, Brody, and Meister have shown by employing a two-state model of a particle confined in the one-dimensional infinite potential well that it is possible to construct a quantum-mechanical analog of the Carnot engine through changes of both the width of the well and the quantum state in a specific manner.

Sumiyoshi Abe

2011-01-01

270

Maximum-power quantum-mechanical Carnot engine  

Microsoft Academic Search

In their work [J. Phys. A: Math. Gen. 33, 4427 (2000)], Bender, Brody, and\\u000aMeister have shown by employing a two-state model of a particle confined in the\\u000aone-dimensional infinite potential well that it is possible to construct a\\u000aquantum-mechanical analog of the Carnot engine through the changes of both the\\u000awidth of the well and the quantum state in

Sumiyoshi Abe

2010-01-01

271

Fluid flow, structural, and fracture mechanics modeling associated with hydraulic stimulation operations  

SciTech Connect

A summary review of hydraulic fracture modeling is given. The equations governing pertinent fluid flow, structural, and fracture mechanics responses are presented along with salient assumptions. The finite element modeling approach is used to discretize the field equations and compute the fracture dimensions, fluid pressure profile, leak-off, and stress intensity factors. In addition, the effects of frac fluid properties, layered strata, in situ stresses, and bi-material interface characteristics are discussed and numerical examples are presented. 50 refs.

Advani, S.H.; Lee, J.K.; Hamid, M.S.; Gurdogan, O.; Khattab, H.

1982-01-01

272

Slip, Swim, Mix, Pack: Fluid Mechanics at the Micron Scale  

Microsoft Academic Search

This talk summarizes my thesis work which was advised by Michael P. Brenner and Howard A. Stone at Harvard University and is devoted to fluid behavior at the micrometer length scale. We consider four different problems. We first address the topic of the no-slip boundary condition in Newtonian liquids. After briefly reviewing the field, we (1) present models for apparent

Eric Lauga

2006-01-01

273

Fluid Mechanics, Mass Transfer, and Optimization Studies of Hemodialyzers II.  

National Technical Information Service (NTIS)

A knowledge of membrane permeabilities and the mass transfer resistances through the blood and dialysate fluid films is necessary for the proper design and operation of hemodialyzers. Because urea is not the only solute that must be removed from a uremic ...

A. L. Babb C. J. Maurer

1968-01-01

274

The research of the conductive mechanism and properties of magnetorheological fluids  

NASA Astrophysics Data System (ADS)

We investigated the resistance response induced by the magnetic field in magnetorheological fluids, the resulting magnetization process alters the distribution of the ferromagnetic particles from unordered distribution to catenulate distribution. Consequently the electrical conductive property of the whole sample changes. A four-stage model has been built to describe the distinct characteristics of the variation of the magnetorheological fluids resistance with a sectional formalism, which is found in excellent agreement with the experimental results. Also, the application of the electrical properties of the magnetorheological fluids in the engineering field is discussed.

Chen, Xi; Zhu, Xiaoqiang; Xu, Zeyu; Lin, Yuanchang; He, Guotian

2013-06-01

275

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

NASA Technical Reports Server (NTRS)

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.

Siginer, Dennis A. (editor); Weislogel, Mark M. (editor)

1992-01-01

276

Gravity effects on fluid vibration in piping systems when using the structural mechanics method  

Microsoft Academic Search

It is shown how the influence of gravity can be incorporated without difficulty in the previously developed ``structural mechanics method'' [1] for the analysis of uniaxial vibration of compressible fluids in piping systems. Two separate effects are treated: (a) a stiffening or weakening of each fluid column depending on its orientation in the gravity field; (b) a linear density variation

A. Frid

1992-01-01

277

14 CFR 25.1182 - Nacelle areas behind firewalls, and engine pod attaching structures containing flammable fluid...  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Nacelle areas behind firewalls, and engine pod...Powerplant Fire Protection § 25.1182 Nacelle areas behind firewalls, and engine pod...containing flammable fluid lines. (a) Each nacelle area immediately behind the...

2009-01-01

278

14 CFR 25.1182 - Nacelle areas behind firewalls, and engine pod attaching structures containing flammable fluid...  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Nacelle areas behind firewalls, and engine pod...Powerplant Fire Protection § 25.1182 Nacelle areas behind firewalls, and engine pod...containing flammable fluid lines. (a) Each nacelle area immediately behind the...

2010-01-01

279

Mechanized fluid connector and assembly tool system with ball detents  

NASA Technical Reports Server (NTRS)

A fluid connector system is disclosed which includes a modified plumbing union having a rotatable member for drawing said union into a fluid tight condition. A drive tool is electric motor actuated and includes a reduction gear train providing an output gear engaging an integral peripheral spur gear on the rotatable member. Coaxial alignment means are attached to both the connector assembly and the drive tool. A hand lever actuated latching system includes a plurality of circumferentially spaced latching balls selectively wedged against the alignment means attached to the connector assembly or to secure the drive tool with its output gear in mesh with the integral peripheral spur gear. The drive motor is torque, speed, and direction controllable.

Zentner, Ronald C. (inventor); Smith, Steven A. (inventor)

1991-01-01

280

Molecular Mechanism of Pancreatic and Salivary Glands Fluid and HCO3? Secretion  

PubMed Central

Fluid and HCO3? secretion is a vital function of all epithelia and is required for the survival of the tissue. Aberrant fluid and HCO3? secretion is associated with many epithelial diseases, such as cystic fibrosis, pancreatitis, Sjögren’s syndrome and other epithelial inflammatory and autoimmune diseases. Significant progress has been made over the last 20 years in our understanding of epithelial fluid and HCO3? secretion, in particular by secretory glands. Fluid and HCO3? secretion by secretory glands is a two step process. Acinar cells secrete isotonic fluid in which the major salt is NaCl. Subsequently, the duct modifies the volume and electrolyte composition of the fluid to absorb the Cl? and secrete HCO3?. The relative volume secreted by acinar and duct cells and modification of electrolyte composition of the secreted fluids varies among secretory glands to meet their physiological functions. In the pancreas, acinar cells secrete small amount of NaCl-rich fluid, while the duct absorbs the Cl? and secretes HCO3? and the bulk of the fluid in the pancreatic juice. Fluid secretion appears to be driven by active HCO3? secretion. In the salivary glands, acinar cells secrete the bulk of the fluid in the saliva that contains high concentrations of Na+ and Cl? and fluid secretion is mediated by active Cl? secretion. The salivary glands duct absorbs both the Na+ and Cl? and secretes K+ and HCO3?. In this review, we focus on the molecular mechanism of fluid and HCO3? secretion by the pancreas and salivary glands, to highlight the similarities of the fundamental mechanisms of acinar and duct cell functions, and point the differences to meet glands specific secretions.

Lee, Min Goo; Ohana, Ehud; Park, Hyun Woo; Yang, Dongki; Muallem, Shmuel

2013-01-01

281

MECHANISMS OF FLUID SHEAR-INDUCED INHIBITION OF POPULATION GROWTH IN A RED-TIDE DINOFLAGELLATE  

EPA Science Inventory

Net population growth of some dinoflagellates is inhibited by fluid shear at shear stresses comparable with those generated during oceanic turbulence. Decreased net growth may occur through lowered cell division, increased mortality, or both. The dominant mechanism under various ...

282

Dynamic response analysis of a solar powered heliotropic fluid-mechanical drive system  

Microsoft Academic Search

This paper provides a summary of work performed during the design, construction, and subsequent analysis of a solar powered tracking mechanism. The mechanism utilizes basic mechanical and thermodynamic principles in its construction and operation. Data taken during the course of the research and reported in this paper reveal that with a particular combination of system components and working fluid, a

N. A. Cope; H. A. Ingley; E. A. Farber; C. A. Morrison

1981-01-01

283

Slip, swim, mix, pack: Fluid mechanics at the micron scale  

Microsoft Academic Search

This thesis is devoted to fluid behavior at the micrometer length scale and considers four different problems. We first address the topic of the no-slip boundary condition in Newtonian liquids. After reviewing the field, we present models for apparent slip in three distinct experimental settings: Steady pressure-driven flow over heterogeneous surfaces, unsteady drainage flow over surface-attached bubbles, and flow of

Eric Lauga

2005-01-01

284

Research on internal fluid mechanism between turbine blades  

Microsoft Academic Search

Up to now many turbo engines have been designed and manufactured by the method of determining the most efficient blade shape and blade arrangement based on test data such as cascade loss. In this research, a low speed cascade wind tunnel was manufactured with the objective of a detailed investigation of flow between blades in an axial flow turbine. A

Takamasa Yamamoto

1987-01-01

285

Protein-Hydrogel Interactions in Tissue Engineering: Mechanisms and Applications  

PubMed Central

Recent advances in our understanding of the sophistication of the cellular microenvironment and the dynamics of tissue remodeling during development, disease, and regeneration have increased our appreciation of the current challenges facing tissue engineering. As this appreciation advances, we are better equipped to approach problems in the biology and therapeutics of even more complex fields, such as stem cells and cancer. To aid in these studies, as well as the established areas of tissue engineering, including cardiovascular, musculoskeletal, and neural applications, biomaterials scientists have developed an extensive array of materials with specifically designed chemical, mechanical, and biological properties. Herein, we highlight an important topic within this area of biomaterials research, protein–hydrogel interactions. Due to inherent advantages of hydrated scaffolds for soft tissue engineering as well as specialized bioactivity of proteins and peptides, this field is well-posed to tackle major needs within emerging areas of tissue engineering. We provide an overview of the major modes of interactions between hydrogels and proteins (e.g., weak forces, covalent binding, affinity binding), examples of applications within growth factor delivery and three-dimensional scaffolds, and finally future directions within the area of hydrogel–protein interactions that will advance our ability to control the cell–biomaterial interface.

Zustiak, Silviya P.; Wei, Yunqian

2013-01-01

286

Mechanism of laser ablation in an absorbing fluid field  

SciTech Connect

Selection of a laser source for intravascular applications has frequently been predicated upon assumptions involving transmissibility in blood of the wavelength of light emitted by a given laser. Standard absorption curves for ultraviolet radiation in blood and infrared radiation in water would suggest that transmission of ultraviolet radiation through a blood field and infrared radiation through any aqueous fluid field would be insufficient for tissue ablation. The present series of experiments was undertaken to determine whether these theoretical predictions would in fact obviate the use of these wavelengths in a blood field. Specimens of normal human myocardium and/or polyvinylchloride were submerged under blood and water and irradiated with ultraviolet radiation (351 nm) delivered as a focused beam and via an optical fiber and infrared radiation (10,600 nm) delivered as a focused beam. Ablation of myocardium was successfully accomplished with a focused beam of both ultraviolet and infrared radiation under as much as 5 mm of blood and with ultraviolet radiation via an optical fiber with the fiber tip up to 3 mm distant from the tissue specimen. High-speed cine recordings of ablation carried out using a focused beam of laser radiation demonstrated that formation of a dynamic optical cavity is the basis for successful pulsed ultraviolet and infrared laser transanguineous tissue ablation. These results thus demonstrate that prediction of wavelength transmission through fluid media based on optical properties of a static fluid does not predict ability to accomplish ablation under dynamic circumstances of laser irradiation.

Isner, J.M.; DeJesus, S.R.; Clarke, R.H.; Gal, D.; Rongione, A.J.; Donaldson, R.F.

1988-01-01

287

Fluid dynamics in a Rotating-Detonation-Engine with micro-injectors  

NASA Astrophysics Data System (ADS)

Rotating detonation engines (RDE's) represent a natural extension of the extensively studied pulse detonation engines (PDE's) for obtaining propulsion from the high efficiency detonation cycle. RDE's require fuel and oxidizer under high pressure to be injected through micro-nozzles from one or two plenums (for premixed and non-premixed). This injection process is critically important to the stability and performance of the RDE. This paper studies the effect of this injection process on the detonation wave within the combustion chamber, with an emphasis on how the fluid dynamics are affected. Both two-dimensional and three-dimensional simulations are done using well proven numerical methods for both the combustion chamber and mixture plenums of an idealized RDE.

Schwer, Douglas

2011-11-01

288

A Practice-Integrated Undergraduate Curriculum in Mechanical Engineering  

NSDL National Science Digital Library

Project-based and experiential learning is becoming increasingly important in engineering education. When recently surveyed, a majority of the students in a junior-year class at the University of Pennsylvania stated that they learned more from a particular course that had a strong lab component than from any other college class. This student belief may stem from the internal confirmation of understanding that hands-on work provides. Students seem to gain confidence when they are able to apply class material successfully to real-world systems, rather solving text book problems on paper. It is not yet clear where the critical learning takes place, whether in the lab or in the associated lecture, but it is obvious from our experience that laboratory work catalyzes student understanding and excitement about mechanical engineering. Based on student feedback and our belief in the value of project-based and experiential learning, we have developed a practice-integrated mechanical engineering curriculum that spans the full four-year undergraduate experience. Our goal is to ingrain theoretical concepts and develop independent student thinking by gradually incorporating design into laboratory activities; by exposing students to systems and applications before developing all of the relevant theoretical concepts; and by motivating students to appreciate the importance and relevance of the theory by directly applying it in projects.

2011-05-04

289

A Microstructurally Motivated Model of the Mechanical Behavior of Tissue Engineered Blood Vessels  

Microsoft Academic Search

Mechanical models have potential to guide the development and use of engineered blood vessels as well as other engineered\\u000a tissues. This paper presents a microstructurally motivated, pseudoelastic, mechanical model of the biaxial mechanics of engineered\\u000a vessels in the physiologic pressure range. The model incorporates experimentally measured densities and alignments of engineered\\u000a collagen. Specifically, these microstructural and associated mechanical inputs were

Shannon L. M. Dahl; Megann E. Vaughn; Jin-Jia Hu; Niels J. B. Driessen; Frank P. T. Baaijens; Jay D. Humphrey; Laura E. Niklason

2008-01-01

290

Mechanical Role of Fluids in Earthquakes and Faulting  

NASA Astrophysics Data System (ADS)

Following the contributions of Hubbert and Rubey, the level of ambient pore pressure is of accepted importance for understanding the static frictional strength of faults. There are also important dynamical interactions between pore fluids and faulting. Some of those are addressed here, with examples to be chosen from the following: (1) Pore fluid presence at full saturation promotes strong localization in rapidly shearing granular materials, even in cases for which the friction coefficient increases rapidly with shearing rate [see Rice, Rudnicki and Tsai, this meeting]. (2) Thermal pressurization of earthquake faults during seismic slip may provide the primary weakening process during earthquakes in mature crustal fault zones; it provides a plausible basic explanation, based on geological and laboratory data, of the magnitudes of the fracture energies of earthquakes as inferred independently from seismological data [see web link below]. The process also seems to be active in some large landslides. (3) Pore pressure alterations are induced by rapid mode II slip on fault planes when they have bordering gouge or damage zones which are of dissimilar permeability and/or poroelastic properties. This provides a fuller, new perspective on effects of material dissimilarity across a slip surface on altering the effective normal stress and thus interacting with dynamic rupture [see Rudnicki and Rice, this meeting]. (4) Gouge dilatancy associated with slip-rate increases induces suction in the pore fluid, so as to partially stabilize faults against earthquake nucleation, and also to slow rupture propagation into shallow fault regions. An open question is that of when and if shear heating acts to aid nucleation; the effect seems negligible for nucleation under slow tectonic loading but may be important for nucleation driven by sudden steps in stress. (5) Permeability determines pore pressure gradients for given flow rates, but increases in pore pressure cause increases in permeability. That allows slow solitary waves of pore pressure increase which propagate upwards against gravity in fault zones that are reasonably sealed from their surroundings, following initiation by, e.g., breaching of a pressurized seal at depth. (6) Aseismic slip transients in subduction zones occur in an environment of active compaction and metamorphic fluid release, and fluids seem responsible for associated tremor as well. Recent modeling [see Liu and Rice, this meeting] links elevation of fluid pressure to the speed of along-strike propagation of slip transients. (7) Poroelastic responses to stress transfer have been detected for some earthquakes, and associated transient stress changes may play a role in aftershock sequences, although probably secondary in general. (8) Another type of fluid saturated ``fault zone'', in granulated sediments between dissimilar materials, is the bed of a mobile ice sheet. Some of the concepts in topics 1 to 4 above may have application to surges, ice streams, and glacial earthquakes. These various cases 1 to 8 involve many contributors in the geophysical community, and include collaborative current or recent studies of the author with Massimo Cocco (2), Yajing Liu (4, 6), Alan Rempel (2), John Rudnicki (1,3), Paul Segall (4), and Victor Tsai (1,8).

Rice, J. R.

2005-12-01

291

Ongoing Analysis of Rocket Based Combined Cycle Engines by the Applied Fluid Dynamics Analysis Group at Marshall Space Flight Center  

NASA Technical Reports Server (NTRS)

This paper presents the status of analyses on three Rocket Based Combined Cycle configurations underway in the Applied Fluid Dynamics Analysis Group (TD64). TD64 is performing computational fluid dynamics analysis on a Penn State RBCC test rig, the proposed Draco axisymmetric RBCC engine and the Trailblazer engine. The intent of the analysis on the Penn State test rig is to benchmark the Finite Difference Navier Stokes code for ejector mode fluid dynamics. The Draco engine analysis is a trade study to determine the ejector mode performance as a function of three engine design variables. The Trailblazer analysis is to evaluate the nozzle performance in scramjet mode. Results to date of each analysis are presented.

Ruf, Joseph; Holt, James B.; Canabal, Francisco

1999-01-01

292

Mechanical-engineering aspects of mirror-fusion technology  

SciTech Connect

The mirror approach to magnetic fusion has evolved from the original simple mirror cell to today's mainline effort: the tandem-mirror machine with thermal barriers. Physics and engineering research is being conducted throughout the world, with major efforts in Japan, the USSR, and the US. At least one facility under construction (MFTF-B) will approach equivalent energy breakeven in physics performance. Significant mechanical engineering development is needed, however, before a demonstration reactor can be constructed. The principal areas crucial to mirror reactor development include large high-field superconducting magnets, high-speed continuous vacuum-pumping systems, long-pulse high-power neutral-beam and rf-plasma heating systems, and efficient high-voltage high-power direct converters. Other areas common to all fusion systems include tritium handling technology, first-wall materials development, and fusion blanket design.

Fisher, D.K.; Doggett, J.N.

1982-07-15

293

Investigation of thermal-fluid mechanical characteristics of the capillary pump and the pumped two-phase loop  

NASA Technical Reports Server (NTRS)

This first semi-annual report summarized progress made on NASA Goddard Space Flight Center (GSFC) Grant NAG 5-834 during the period September 1, 1986 to February 28, 1987. The goal of the project is to gain a better understanding of the transient behavior of the Capillary Pump Loop (CPL) developed and tested by the GSFC. The investigation is directed toward development of analytical models to represent the transient thermal-fluid mechanic processes occurring in different parts of the CPL engineering model. Evaluation of the available test data has been the starting point for the investigation. Based on results of this evaluation, supplementary tests will be conducted by using a CPL test system already operational in the Heat Transfer laboratory of the university. Of particular interest is the oscillatory behavior of the CPL engineering model exhibited during some of the earlier test runs conducted at NASA-GSFC and Johnson Space Center (JSC).

Kiper, Ali M.

1987-01-01

294

Error Estimation and Uncertainty Propagation in Computational Fluid Mechanics  

NASA Technical Reports Server (NTRS)

Numerical simulation has now become an integral part of engineering design process. Critical design decisions are routinely made based on the simulation results and conclusions. Verification and validation of the reliability of the numerical simulation is therefore vitally important in the engineering design processes. We propose to develop theories and methodologies that can automatically provide quantitative information about the reliability of the numerical simulation by estimating numerical approximation error, computational model induced errors and the uncertainties contained in the mathematical models so that the reliability of the numerical simulation can be verified and validated. We also propose to develop and implement methodologies and techniques that can control the error and uncertainty during the numerical simulation so that the reliability of the numerical simulation can be improved.

Zhu, J. Z.; He, Guowei; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

295

Mechanotransduction in bone: osteoblasts are more responsive to fluid forces than mechanical strain  

NASA Technical Reports Server (NTRS)

Mechanical force applied to bone produces two localized mechanical signals on the cell: deformation of the extracellular matrix (substrate strain) and extracellular fluid flow. To study the effects of these stimuli on osteoblasts, MC3T3-E1 cells were grown on type I collagen-coated plastic plates and subjected to four-point bending. This technique produces uniform levels of physiological strain and fluid forces on the cells. Each of these parameters can be varied independently. Osteopontin (OPN) mRNA expression was used to assess the anabolic response of MC3T3-E1 cells. When fluid forces were low, neither strain magnitude nor strain rate was correlated with OPN expression. However, higher-magnitude fluid forces significantly increased OPN message levels independently of the strain magnitude or rate. These data indicate that fluid forces, and not mechanical stretch, influence OPN expression in osteoblasts and suggest that fluid forces induced by extracellular fluid flow within the bone matrix may play an important role in bone formation in response to mechanical loading.

Owan, I.; Burr, D. B.; Turner, C. H.; Qiu, J.; Tu, Y.; Onyia, J. E.; Duncan, R. L.

1997-01-01

296

Mechanism of Headward Fluid Shift During Exposure To Microgravity  

NASA Technical Reports Server (NTRS)

A prominent feature of early cardiovascular adaptation to the microgravity of space flight is a shift of blood and tissue fluid from the lower body to the upper body. Symptoms of this fluid shift include facial edema, nasal congestion, and headache. Normally on Earth, the human body is exposed to hydrostatic (gravitational) blood pressure gradients during upright posture. In this posture, mean arterial pressures at head, heart, and foot levels are approximately 70, 100, and 200 mm Hg, respectively. Theoretically, all hydrostatic pressures within arteries and veins are lost during exposure to microgravity so that mean arterial pressure in all regions of the body is uniform and approximately equal to that at heart level (100 mm Hg). Acute studies of 60 head-down tilt (simulated microgravity on Earth) indicate that facial edema is caused by: 1) elevation of capillary blood pressure from 28 to 34 mm Hg, 2) reduction of blood colloid osmotic pressure 22 to 18 mm Hg, and 3) 50% increase of blood perfusion in tissues of the head. Furthermore, as compared to microvasculature in the feet, microvessels of the head have a low capacity to constrict and diminish local perfusion. Elevation of blood and tissue fluid pressures/flow in the head may also explain the higher headward bone density associated with long-term head-down tilt. These mechanistic studies of head-down tilt, along with a better understanding of the relative stresses involved with upright posture and lower body negative pressure, have facilitated development of physiologic countermeasures to maintain astronaut health during microgravity. Presently no exercise hardware is available to provide a blood pressure gradient from head to feet in space. However, recent studies in our laboratory suggest that treadmill exercise within lower body negative pressure provides equivalent or greater physiologic stress as compared to similar upright exercise on Earth.

Hargens, Alan R.; Parazynski, Scott E.; Watenpaugh, Donald E.; Aratow, Michael; Murthy, Gita; Kawai, Yasuaki

1994-01-01

297

Use of piezoelectric multicomponent force measuring devices in fluid mechanics  

NASA Technical Reports Server (NTRS)

The characterisitics of piezoelectric multicomponent transducers are discussed, giving attention to the advantages of quartz over other materials. The main advantage of piezoelectric devices in aerodynamic studies is their ability to indicate rapid changes in the values of physical parameters. Problems in the accuracy of measurments by piezoelectric devices can be overcome by suitable design approaches. A practical example is given of how such can be utilized to measure rapid fluctuations of fluid forces exerted on a circular cylinder mounted in a water channel.

Richter, A.; Stefan, K.

1979-01-01

298

Singular mechanics and Landau two-fluid model of superfluidity  

NASA Astrophysics Data System (ADS)

We present a theoretical treatment of the Landau two-fluid model of superfluidity in liquid helium by means of the Dirac formalism. We introduce hydrodynamic considerations in a natural way by means of Lagrange multipliers. All constraints in phase space, in Dirac's sense, are second class and, as a consequence, the Dirac bracket differs strongly from the Poisson bracket. We calculate the Dirac bracket of the canonical variables, putting special interest on the density and the momentum density of the system. Our results generalize the results given by Dzyaloshinskii and Volovik and correct other published results.

Rodríguez-Núñez, José Jesus; Tello-Llanos, Ricardo

1991-06-01

299

Crystal Growth and Fluid Mechanics Problems in Directional Solidification  

NASA Technical Reports Server (NTRS)

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.

Tanveer, Saleh A.; Baker, Gregory R.; Foster, Michael R.

2001-01-01

300

Interactive simulations as teaching tools for engineering mechanics courses  

NASA Astrophysics Data System (ADS)

This study aimed to gauge the effect of interactive simulations in class as an active teaching strategy for a mechanics course. Engineering analysis and design often use the properties of planar sections in calculations. In the stress analysis of a beam under bending and torsional loads, cross-sectional properties are used to determine stress and displacement distributions in the beam cross section. The centroid, moments and products of inertia of an area made up of several common shapes (rectangles usually) may thus be obtained by adding the moments of inertia of the component areas (U-shape, L-shape, C-shape, etc). This procedure is used to calculate the second moments of structural shapes in engineering practice because the determination of their moments of inertia is necessary for the design of structural components. This paper presents examples of interactive simulations developed for teaching the ‘Mechanics and mechanisms’ course at the Universidad Politecnica de Madrid, Spain. The simulations focus on fundamental topics such as centroids, the properties of the moment of inertia, second moments of inertia with respect to two axes, principal moments of inertia and Mohr's Circle for plane stress, and were composed using Geogebra software. These learning tools feature animations, graphics and interactivity and were designed to encourage student participation and engagement in active learning activities, to effectively explain and illustrate course topics, and to build student problem-solving skills.

Carbonell, Victoria; Romero, Carlos; Martínez, Elvira; Flórez, Mercedes

2013-07-01

301

A review of interaction mechanisms in fluid-solid flows  

SciTech Connect

Multiphase flows have become the subject of considerable attention because of their importance in many industrial applications, such as fluidized beds, pneumatic transport of solids, coal combustion, etc. Fundamental research into the nature of pneumatic transport has made significant progress in identifying key parameters controlling the characteristics of these processes. The emphasis of this study is on a mixture composed of spherical particles of uniform size and a linearly viscous fluid. Section 1 introduces our approach and the importance of this study. In Section 2, the dynamics of a single particle as studied in classical hydrodynamics and fluid dynamics is presented. This has been a subject of study for more than 200 years. In Section 3, we review the literature for the constitutive relations as given in multiphase studies, i.e., generalization of single particle and as given in literature concerning the continuum theories of mixtures or multicomponent systems. In Section 4, a comparison between these representations and the earlier approach, i.e., forces acting on a single particle will be made. The importance of flow regimes, particle concentration, particle size and shape, rotation of the particle, effect of solid walls, etc. are discussed. 141 refs.

Johnson, G.; Rajagopal, K.R. (Pittsburgh Univ., PA (USA). Dept. of Mechanical Engineering); Massoudi, M. (USDOE Pittsburgh Energy Technology Center, PA (USA))

1990-09-01

302

Fluid transfer as a mechanism leading to endotension.  

PubMed

Some abdominal aortic aneurysms bridged with a minimally invasively introduced stent graft prosthesis increase in size without any diagnosable evidence of endoleakage (endotension). There are three possible pathways proposed through which undetectable low rates of blood flow may cause an aneurysm sac to be refilled: through the thrombus at the prosthesis attachment sites, through the clotted collaterals and through the clotted stent graft wall. If the inflow is more rapid than any drainage through the wall of the aneurysm is re-pressurised. However, critical magnitudes for the permeability of the clotted graft and the geometry of the thrombus at the aneurysm, necessary to inhibit endotension, are not known. The aim of this study was to determine which boundary conditions prevent endotension. An analytical model based on Darcy's Law was used to estimate the pressure in the aneurysm sac due to fluid transfer. Experimentally determined time- and pressure-dependent permeability of red and intraluminal thrombus, and of clotted graft materials were input into the model. The computational analysis showed that endotension is unlikely to be caused by fluid transfer from the collaterals or via the prosthesis attachment sites, but rather due to flow through the stent graft wall. Based on this study it can be stated that grafts with a permeability below 2e-13 mm(2) should diminish the occurrence of endotension. PMID:20674454

de Uhlenbrock, A Gebert; Wintzer, C; Imig, H; Morlock, M M

2010-10-01

303

A numerical investigation of the fluid mechanical sewing machine  

NASA Astrophysics Data System (ADS)

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)]. 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 ?c 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 ?c/3.

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

2012-04-01

304

Experiments and Modeling of G-Jitter Fluid Mechanics  

NASA Technical Reports Server (NTRS)

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.

Leslie, F. W.; Ramachandran, N.; Whitaker, Ann F. (Technical Monitor)

2002-01-01

305

Towards the unification of acoustics and fluid mechanics  

SciTech Connect

A comprehensive study of a modern acoustic technique is presented. The conservation laws of mass, momentum, and surface boundary conditions are cast in the form of an inhomogeneous wave equation, known today as Ffowcs Williams and Hawkings' equation. The result is general, capable of addressing three-dimensional, nonlinear, and unsteady flow problems of compressible and viscous fluids. The Green's function solution is used to transform the differential equation into integral form. The formulation is then linearized and viscosity is neglected. The pressure distribution on the surface of the NACA 0012 airfoil in subsonic non-lifting motion is determined. Comparison with experimental results shows good agreement, provided flow perturbations remain small. It is considered that the technique may evolve into an alternative aerodynamic method to current computational approaches.

Brandao, M.P. (Instituto Technologico de Aeronautica, Sao Jose (Brazil))

1989-11-01

306

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

NASA Technical Reports Server (NTRS)

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.

Cho, Y.-C.; Mclachlan, B. G.

1987-01-01

307

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

NASA Astrophysics Data System (ADS)

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.

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

2011-11-01

308

New Developments of Computational Fluid Dynamics and Their Applications to Practical Engineering Problems  

NASA Astrophysics Data System (ADS)

There have been considerable advances in Lattice Boltzmann (LB) based methods in the last decade. By now, the fundamental concept of using the approach as an alternative tool for computational fluid dynamics (CFD) has been substantially appreciated and validated in mainstream scientific research and in industrial engineering communities. Lattice Boltzmann based methods possess several major advantages: a) less numerical dissipation due to the linear Lagrange type advection operator in the Boltzmann equation; b) local dynamic interactions suitable for highly parallel processing; c) physical handling of boundary conditions for complicated geometries and accurate control of fluxes; d) microscopically consistent modeling of thermodynamics and of interface properties in complex multiphase flows. It provides a great opportunity to apply the method to practical engineering problems encountered in a wide range of industries from automotive, aerospace to chemical, biomedical, petroleum, nuclear, and others. One of the key challenges is to extend the applicability of this alternative approach to regimes of highly turbulent flows commonly encountered in practical engineering situations involving high Reynolds numbers. Over the past ten years, significant efforts have been made on this front at Exa Corporation in developing a lattice Boltzmann based commercial CFD software, PowerFLOW. It has become a useful computational tool for the simulation of turbulent aerodynamics in practical engineering problems involving extremely complex geometries and flow situations, such as in new automotive vehicle designs world wide. In this talk, we present an overall LB based algorithm concept along with certain key extensions in order to accurately handle turbulent flows involving extremely complex geometries. To demonstrate the accuracy of turbulent flow simulations, we provide a set of validation results for some well known academic benchmarks. These include straight channels, backward-facing steps, flows over a curved hill and typical NACA airfoils at various angles of attack including prediction of stall angle. We further provide numerous engineering cases, ranging from external aerodynamics around various car bodies to internal flows involved in various industrial devices. We conclude with a discussion of certain future extensions for complex fluids.

Chen, Hudong

2001-06-01

309

Wear mechanisms in moderate temperature gasoline engine service  

SciTech Connect

The mechanism of overhead valve train wear in moderate to low temperature service was studied using a modified fired V-D test and a motored V-D cam and cam-follower rig. High wear and low wear used oils from the fired test gave the correct relative wear in the motored test, indicating the motored test in a valid tool for studying wear mechanisms. Key factors affecting valve train wear were isolated and selectively introduced in a series of motored engine tests. Results from this study showed the expected increase in wear with a decrease in viscosity of unformulated lubricants. Added zinc dialkyldithiophosphate (ZDDP) reduced wear in a low viscosity lubricant and a used oil as anticipated. A high detergent, high wear oil, in an unused state, did not produce significant wear in the motored test even if all of the ZDDP was removed. Significant wear resulted only after exhaust gases (simulated blowby) were fed into the motored engine sump containing the high wear oil. Laboratory simulation of blowby effects showed the importance of wear resulting from oil aging by chemical reactions between the lubricant and blowby gases. This effect is important even when the viscosity of the lubricant is otherwise sufficient to preclude wear. Active ZDDP depletion by thermal and oxidative routes contributes to wear. Viscosity losses in the Sequence V-D test and in the fired test were large due to fuel dilution and Viscosity Index Improver shear which can lead to further increases in wear.

West, C.T.; Passut, C.A.; Chamot, E.

1986-01-01

310

Thermal-mechanical fatigue crack growth in aircraft engine materials  

NASA Astrophysics Data System (ADS)

A thermal mechanical fatigue (TMF) testing rig was built which is capable of studying the fatigue behaviors of gas turbine engine materials under simultaneous changes of temperatures and strains or stress. An advance alternating current potential drop (ACPD) measurement system was also developed which is capable of performing on-line monitoring of fatigue crack initiation and growth in specimen testing under isothermal and TMF conditions. Fatigue crack initiation and short crack growth data were obtained for titanium alloy specimens designed with notch features associated with bolt holes of compressor discs. TMF data were also obtained for two titanium alloys used in aircraft engine components. Those data explained the material fatigue behavior encountered in full-scale component testing. A complete fractographic analysis was performed on the tested specimens enhancing the understanding of the fatigue crack growth mechanisms and helping to formulate an analytical crack growth model. The ACPD fatigue crack monitoring technique was applied to the low cycle fatigue testing of Pratt & Whitney 1480 monocrystalline nickel alloy. A completely automated, computer controlled test procedure was developed which could obtain crack initiation and growth data with greater speed, precision, and reliability than previous methods.

Dai, Yi

1993-05-01

311

Nonequilibrium in statistical and fluid mechanics. Ensembles and their equivalence. Entropy driven intermittency  

NASA Astrophysics Data System (ADS)

We present a review of the chaotic hypothesis and discuss its applications to intermittency in statistical mechanics and fluid mechanics proposing a quantitative definition. Entropy creation rate is interpreted in terms of certain intermittency phenomena. An attempt at a theory of the experiment of Ciliberto-Laroche on the fluctuation law is presented.

Gallavotti, Giovanni

2000-06-01

312

Finite element procedures for coupled linear analysis of heat transfer, fluid and solid mechanics  

NASA Technical Reports Server (NTRS)

Coupled finite element formulations for fluid mechanics, heat transfer, and solid mechanics are derived from the conservation laws for energy, mass, and momentum. To model the physics of interactions among the participating disciplines, the linearized equations are coupled by combining domain and boundary coupling procedures. Iterative numerical solution strategy is presented to solve the equations, with the partitioning of temporal discretization implemented.

Sutjahjo, Edhi; Chamis, Christos C.

1993-01-01

313

The role of mechanical load-induced fluid flow in osteocyte nutrition and its clinical implications  

Microsoft Academic Search

It has been shown that diffusion alone cannot account for sufficient molecular transport in the porous yet relatively impermeable tissue of bone. An alternate mechanism for such transport is intrinsic to the functional role of bone in transferring loads within the musculoskeletal system. Namely, mechanical loading causes minute deformations within the poroelastic tissue of bone, resulting in extravascular fluid displacements,

M. L. Knothe Tate

1999-01-01

314

Applied environmental fluid mechanics: what's the weather in your backyard?  

NASA Astrophysics Data System (ADS)

The microclimates of the San Francisco Bay Area can lead to 30-40F differences in temperature from the coast to just 30 miles inland. The reasons for this include local topography which affects development of the atmospheric boundary layer. A Bay Area resident's experience of fog, air pollution, and weather events therefore differs greatly depending on exactly where they live. Such local weather phenomena provide a natural topic for introduction to boundary layer processes and are the basis of a new course developed at the University of California, Berkeley. This course complements the PI's research focus on numerical methods applied to atmospheric boundary layer flow over complex terrain. This new outreach and research-based course was created to teach students about the boundary layer and teach them how to use a community weather prediction model, WRF, to simulate conditions in the local area, while at the same time being actively involved in public outreach. The course was offered in the Civil and Environmental Engineering department with the collaboration and support of the Lawrence Hall of Science, Berkeley's public science museum. The students chose topics such as air quality, wind energy, climate change, and plume dispersion, all applied to the local San Francisco Bay Area. The students conducted independent research on their team projects, involving literature reviews, numerical model setup, and analysis of model results through comparison with field observations. The outreach component of the course included website design and culminated in demonstrations at the Lawrence Hall of Science. The seven student teams presented hands-on demos to 300-400 visitors, mostly kids 4-9 years old and their parents. Involving students directly in outreach efforts is hoped to encourage continued integration of research and education in their own careers. Early exposure to numerical modeling also improves student technical skills for future career experiences . Given positive feedback from students, the course will now be offered regularly as a senior design class which will also fulfill engineering graduation requirements.

Chow, F. K.

2011-12-01

315

Ongoing Analyses of Rocket Based Combined Cycle Engines by the Applied Fluid Dynamics Analysis Group at Marshall Space Flight Center  

NASA Technical Reports Server (NTRS)

This paper presents the status of analyses on three Rocket Based Combined Cycle (RBCC) configurations underway in the Applied Fluid Dynamics Analysis Group (TD64). TD64 is performing computational fluid dynamics (CFD) analysis on a Penn State RBCC test rig, the proposed Draco axisymmetric RBCC engine and the Trailblazer engine. The intent of the analysis on the Penn State test rig is to benchmark the Finite Difference Navier Stokes (FDNS) code for ejector mode fluid dynamics. The Draco analysis was a trade study to determine the ejector mode performance as a function of three engine design variables. The Trailblazer analysis is to evaluate the nozzle performance in scramjet mode. Results to date of each analysis are presented.

Ruf, Joseph H.; Holt, James B.; Canabal, Francisco

2001-01-01

316

Fluid and Solid Mechanical Implications of Vascular Stenting  

Microsoft Academic Search

Vascular stents have emerged as an effective treatment for occlusive vascular disease. Despite their success and widespread use, outcomes for patients receiving stents are still hampered by thrombosis and restensosis. As arteries attempt to adapt to the mechanical changes created by stents, they may in fact create a new flow-limiting situation similar to that which they were intended to correct.

Joel L. Berry

2002-01-01

317

Dynamic analysis of a hypocycloid mechanism with planetary gears for internal combustion engine  

Microsoft Academic Search

In this study, a new type hypocycloid mechanism with a special crank and a pair of additional planetary gears, distinct from a conventional mechanism, are presented. This new mechanism is applied to a single cylinder diesel engine for initial study, and the dynamic model of the new engine with hypocycloid mechanism is built based on virtual prototype technology. For the

Yunfeng Xue; Qungui Du; Fanglong Zhao; Junpeng Zhu

2008-01-01

318

Crystal growth and fluid mechanics problems in directional solidification  

NASA Technical Reports Server (NTRS)

Broadly speaking, our efforts have been concentrated in two aspects of directional solidification: (A) a more complete theoretical understanding of convection effects in a Bridgman apparatus; and (B) a clear understanding of scalings of various features of dendritic crystal growth in the sensitive limit of small capillary effects. For studies that fall within class A, the principal objectives are as follows: (A1) Derive analytical formulas for segregation, interfacial shape and fluid velocities in mathematically amenable asymptotic limits. (A2) Numerically verify and extend asymptotic results to other ranges of parameter space with a view to a broader physical understanding of the general trends. With respect to studies that fall within class B, the principal objectives include answering the following questions about dendritic crystal growth: (B1) Are there unsteady dendrite solutions in 2-D to the completely nonlinear time evolving equations in the small surface tension limit with only a locally steady tip region with well defined tip radius and velocity? Is anisotropy in surface tension necessary for the existence of such solutions as it is for a true steady state needle crystal? How does the size of such a local region depend on capillary effects, anisotropy and undercooling? (B2) How do the different control parameters affect the nonlinear amplification of tip noise and dendritic side branch coarsening?

Tanveer, Saleh; Baker, Gregory R.; Foster, Michael R.

1994-01-01

319

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

SciTech Connect

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 in some detail, as are permeabilities of some of the simpler types of fractured materials.

Berryman, J.G.

2010-06-01

320

Coupling of hierarchical fluid models with electrostatic and mechanical models for the dynamic analysis of MEMS  

NASA Astrophysics Data System (ADS)

The dynamical behavior of MEMS (micro-electro-mechanical systems) is often strongly affected by viscous fluid/air damping effects from the surrounding. These fluid/air damping effects have to be carefully taken into account during the design and optimization process, in order to get a realistic and reliable description of the device operation. In this paper, two hierarchical fluid models (the 2D compressible Reynold's squeeze film equation and the 2D compressible Navier-Stokes equations) are coupled with a 2D electro-mechanical solver for the dynamic analysis of MEMS to simulate and understand the effect of fluid damping on microstructures. The different physical domains (electrical, mechanical and fluidic) are coupled together using a Newton method for faster convergence. A Lagrangian description of all the physical domains makes it possible to compute the inter-domain coupling terms in the Jacobian matrix of the Newton method exactly. Several MEMS devices (a micromirror, a piggyback actuator, a lateral comb drive and a cantilever beam in air) have been simulated using the coupled electro-mechanical-fluidic solver and numerical results on the resonant frequency and the quality factor are compared with experimental data. The two hierarchical fluid models can be used judiciously (based on speed and accuracy) along with the electro-mechanical solver, depending on the type of MEMS device under consideration, thereby making the dynamic analysis of MEMS devices more efficient.

De, Sudipto K.; Aluru, N. R.

2006-08-01

321

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

Microsoft Academic Search

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. For individual titles, see A95-95212 through

Dennis A. Siginer; Mark M. Weislogel

1992-01-01

322

In house industrial training for mechanical engineering students: A multidisciplinary approach  

Microsoft Academic Search

The integrated knowledge in the application of mechanical engineering, microprocessor and electronic sensor technologies is becoming the basic skill of a modern engineer in machinery based processes. To meet this objective, we have developed a cross-disciplinary industrial training to teach essential hard technical and soft project skills to the mechanical engineering students in mid-curriculum. Ten groups of students were selected

S. K. Li; KK Lau; Vincent Li

2011-01-01

323

Physiologic mechanisms effecting circulatory and body fluid losses in weightlessness as shown by mathematical modeling.  

PubMed

The mechanisms causing large body water losses in weightlessness are not clear. It has long been considered that a central volume expansion drives the physiologic adaptation to a reduced total blood volume, with normal blood composition eventually regained. However, inflight venous pressure measures suggest that central volume expansion in weightlessness may be very transient, or that considerable cardiovascular adaptation to fluid shifts occurs on the ground while astronauts wait in the semi-supine pre-launch position. If a central volume stimulus does not persist, other mechanisms must drive the adaptation of circulation to a reduced blood volume and account for body fluid losses. Recent results from the SLS-1 mission suggest that body fluid volumes do not simply decline to new equilibria but that they decrease to a low point, then undergo some recovery. Similar "under-shoots" of body fluid volumes have also been shown in computer simulations, providing confidence in the validity of the model. The purpose of this study was to examine the mechanisms which could explain the loss of body fluids in weightlessness and how a cardiovascular preadaptation countermeasure we previously tested ameliorated body fluid losses. It is assumed that the physiology of head down tilt (HDT) provides a reasonably accurate analog of weightless exposure. PMID:11537415

Simanonok, K E; Srinivasan, R S; Charles, J B

1993-01-01

324

The fluid mechanics of continuous flow electrophoresis in perspective  

NASA Technical Reports Server (NTRS)

Buoyancy alters the flow in continuous flow electrophoresis chambers through the mechanism of hydrodynamic instability and, when the instability is supressed by careful cooling of the chamber boundaries, by restructuring the axial flow. The expanded roles of buoyancy follow upon adapting the size of the chamber and the electric field so as to fractionate certain sorts of cell populations. Scale-up problems, hydrodynamic stability and the altered flow fields are discussed to show how phenomena overlooked in the design and operations of narrow-gap devices take on an overwhelming importance in wide-gap chambers

Saville, D. A.

1980-01-01

325

Mechanism of Protein Kinetic Stabilization by Engineered Disulfide Crosslinks  

PubMed Central

The impact of disulfide bonds on protein stability goes beyond simple equilibrium thermodynamics effects associated with the conformational entropy of the unfolded state. Indeed, disulfide crosslinks may play a role in the prevention of dysfunctional association and strongly affect the rates of irreversible enzyme inactivation, highly relevant in biotechnological applications. While these kinetic-stability effects remain poorly understood, by analogy with proposed mechanisms for processes of protein aggregation and fibrillogenesis, we propose that they may be determined by the properties of sparsely-populated, partially-unfolded intermediates. Here we report the successful design, on the basis of high temperature molecular-dynamics simulations, of six thermodynamically and kinetically stabilized variants of phytase from Citrobacter braakii (a biotechnologically important enzyme) with one, two or three engineered disulfides. Activity measurements and 3D crystal structure determination demonstrate that the engineered crosslinks do not cause dramatic alterations in the native structure. The inactivation kinetics for all the variants displays a strongly non-Arrhenius temperature dependence, with the time-scale for the irreversible denaturation process reaching a minimum at a given temperature within the range of the denaturation transition. We show this striking feature to be a signature of a key role played by a partially unfolded, intermediate state/ensemble. Energetic and mutational analyses confirm that the intermediate is highly unfolded (akin to a proposed critical intermediate in the misfolding of the prion protein), a result that explains the observed kinetic stabilization. Our results provide a rationale for the kinetic-stability consequences of disulfide-crosslink engineering and an experimental methodology to arrive at energetic/structural descriptions of the sparsely populated and elusive intermediates that play key roles in irreversible protein denaturation.

Sanchez-Romero, Inmaculada; Ariza, Antonio; Wilson, Keith S.; Skj?t, Michael; Vind, Jesper; De Maria, Leonardo; Skov, Lars K.; Sanchez-Ruiz, Jose M.

2013-01-01

326

The Effects of Fluid Absorption on the Mechanical Properties of Joint Prostheses Components  

NASA Astrophysics Data System (ADS)

Ultra-high-molecular-weight polyethylene (UHMWPE) is the material playing the role of cartilage in human prosthetic joints. Wear debris from UHMWPE is a common reason for joint arthroplasty failure, and the exact mechanism responsible for wear remains an area of investigation. In this study, the microstructure of UHMWPE was examined as a function of fluid absorption. Samples with varying exposure to e-beam radiation (as part of the manufacturing process) were soaked for forty days in saline or artificial synovial fluid, under zero or 100 lbs load. Samples were then tensile-tested according to ASTM D-3895. The post-stressed material was then examined by transmission electron microscopy to evaluate the molecular response to stress, which correlates with macroscopic mechanical properties. Three parameters of the crystalline lamellae were measured: thickness, stacking ratio, and alignment to stress direction. Results indicate that fluid absorption does affect the mechanical properties of UHMWPE at both the microscopic and microscopic levels. )

Yarbrough, David; Viano, Ann

2010-02-01

327

Constraints from fluid inclusions on sulfide precipitation mechanisms and ore fluid migration in the Viburnum Trend lead district, Missouri  

USGS Publications Warehouse

Homogenization temperatures and freezing point depressions were determined for fluid inclusions in Bonneterre Dolomite-hosted dolomite cements in mine samples, as well as drill core from up to 13 km outside of the district. A well-defined cathodoluminescent zonation distinguishes dolomite growth zones as older or younger than main-stage mineralization. Homogenization temperatures and salinities in samples from mines are not systematically different from those of samples outside of the district. The absence of a significant, recognizable decrease in temperature either vertically within the section or east-west across the district, coupled with the minor amount of silica in the district, argues against cooling as a primary cause of sulfide precipitation. In a reduced sulfur mineralization model with Pb carried as chloride complexes, dilution is also a possible sulfide precipitation mechanism. The difference in Pb solubility in the extremes of the chloride concentration range, 3.9 vs. 5.9 molal, reaches 1 ppm only for pH values below approximately 4.5. The distribution of warm inclusions beyond the Viburnum Trend district implies that fluid migration was regional in scale. Elevated temperatures observed in fluid inclusions at shallow stratigraphic depths are consistent with a gravity flow hydrologic system characterized by rapid flow rates and the capacity for advective heat transport. -from Authors

Rowan, E. L.; Leach, D. L.

1989-01-01

328

Flow-loss, efficiency, and change-of-state calculations for fluid-flow engines and heat exchangers  

Microsoft Academic Search

A theoretical analysis of the energy losses in devices transfused by fluids is presented, with a focus on the phase-change processes affecting the fluid medium inside the device. Flow losses are shown to be equivalent to the dissipative work due to friction stresses, using their relationship to heat transfer or mechanical work in order to derive equations of flow efficiency

W. Bitterlich; D. Kestner; M. D. Patil

1983-01-01

329

Fluid mechanics of directional solidification at reduced gravity  

NASA Technical Reports Server (NTRS)

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.

Chen, C. F.

1992-01-01

330

The fluid mechanics of fire whirls: An inviscid model  

NASA Astrophysics Data System (ADS)

Whirling fire plumes are known to increase the danger of naturally occurring or post-disaster fires. In order for a fire whirl to exist, there must be an organized source of angular momentum to produce the large swirl velocities as air is entrained into the fire plume. These vorticity-driven fires occur over a large range of length and velocity scales, and significantly alter the entrainment and combustion dynamics. A new model is derived for a buoyant plume that incorporates angular rotation and neglects dissipation; the result is a form of the steady state Euler equations. Included is a general solution for large density and temperature variations. Results are presented that identify the mechanisms and their effects toward creating a fire whirl.

Battaglia, Francine; Rehm, Ronald G.; Baum, Howard R.

2000-11-01

331

Fluid Mechanics of Capillary-Elastic Instabilities in Microgravity Environment  

NASA Technical Reports Server (NTRS)

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.

Grotberg, James B.

2002-01-01

332

Separating Fluid Shear Stress from Acceleration during Vibrations in Vitro: Identification of Mechanical Signals Modulating the Cellular Response  

PubMed Central

The identification of the physical mechanism(s) by which cells can sense vibrations requires the determination of the cellular mechanical environment. Here, we quantified vibration-induced fluid shear stresses in vitro and tested whether this system allows for the separation of two mechanical parameters previously proposed to drive the cellular response to vibration – fluid shear and peak accelerations. When peak accelerations of the oscillatory horizontal motions were set at 1g and 60Hz, peak fluid shear stresses acting on the cell layer reached 0.5Pa. A 3.5-fold increase in fluid viscosity increased peak fluid shear stresses 2.6-fold while doubling fluid volume in the well caused a 2-fold decrease in fluid shear. Fluid shear was positively related to peak acceleration magnitude and inversely related to vibration frequency. These data demonstrated that peak shear stress can be effectively separated from peak acceleration by controlling specific levels of vibration frequency, acceleration, and/or fluid viscosity. As an example for exploiting these relations, we tested the relevance of shear stress in promoting COX-2 expression in osteoblast like cells. Across different vibration frequencies and fluid viscosities, neither the level of generated fluid shear nor the frequency of the signal were able to consistently account for differences in the relative increase in COX-2 expression between groups, emphasizing that the eventual identification of the physical mechanism(s) requires a detailed quantification of the cellular mechanical environment.

Uzer, Gunes; Manske, Sarah L; Chan, M Ete; Chiang, Fu-Pen; Rubin, Clinton T; Frame, Mary D; Judex, Stefan

2012-01-01

333

Third symposium on energy engineering sciences: proceedings. Thermofluids and solid mechanics  

SciTech Connect

The symposium reported on offered sessions on turbulence, solid mechanics and structures, turbulent heat transfer, combustion, heterogeneous fluids and fluid mixtures, fracture mechanics and damage, transport phenomena in solids, tribology, jets and external flows. Separate abstracts were prepared for 32 papers in these symposium proceedings. (LEW)

Not Available

1985-01-01

334

A turnstile mechanism for fronts propagating in fluid flows  

NASA Astrophysics Data System (ADS)

We consider the propagation of fronts in a periodically driven flowing medium. It is shown that the progress of fronts in these systems may be mediated by a turnstile mechanism akin to that found in chaotic advection. We first define the modified (``active'') turnstile lobes according to the evolution of point sources across a transport boundary. We then show that the lobe boundaries may be constructed from stable and unstable burning invariant manifolds (BIMs)--one-way barriers to front propagation analogous to traditional invariant manifolds for passive advection. Because the BIMs are one-dimensional curves in a three-dimensional (xy?) phase space, their projection into xy-space exhibits several key differences from their advective counterparts: (lobe) areas are not preserved, BIMs may self-intersect, and an intersection between stable and unstable BIMs does not map to another such intersection. These differences must be accommodated in the correct construction of the new turnstile. As an application, we consider a lobe-based treatment protocol for protecting an ocean bay from an invading algae bloom.

Mahoney, John R.; Mitchell, Kevin A.

2013-12-01

335

Study of nonlinear processes of a large experimental thermoacoustic-Stirling heat engine by using computational fluid dynamics  

Microsoft Academic Search

This article focuses on using computational fluid dynamics (CFD) method to study several important nonlinear phenomenon and processes of a large experimental thermoacoustic-Stirling heat engine. First, the simulated physical model was introduced, and the suitable numerical scheme and algorithm for the time-dependent compressible thermoacoustic system was determined through extensive numerical tests. Then, the simulation results of the entire evolution process

G. Y. Yu; E. C. Luo; W. Dai; J. Y. Hu

2007-01-01

336

Review on patents for mechanical stimulation of articular cartilage tissue engineering  

Microsoft Academic Search

To repair articular cartilage defects in osteoarthritic patients with three-dimensional tissue engineered chondrocyte grafts, requires the formation of new cartilage with sufficient mechanical properties. The premise is that mechanical stimulation during the culturing process is necessary to reach this aim. Therefore, mechanical stimulation systems have been integrated in aseptic bioreactors for in vitro cultivation of tissue engineered cartilage. These vary

Corrinus C. van Donkelaar; Ronny M. Schulz

2008-01-01

337

On the mechanism of wetting failure during fluid displacement along a moving substrate  

NASA Astrophysics Data System (ADS)

This work investigates the onset of wetting failure for displacement of Newtonian fluids in parallel channels. A hydrodynamic model is developed for planar geometries where an advancing fluid displaces a receding fluid along a moving substrate. The model is evaluated with three distinct approaches: (i) the low-speed asymptotic theory of Cox [J. Fluid Mech. 168, 169-194 (1986)], (ii) a one-dimensional (1D) lubrication approach, and (iii) a two-dimensional (2D) flow model solved with the Galerkin finite element method (FEM). Approaches (ii) and (iii) predict the onset of wetting failure at a critical capillary number Cacrit, which coincides with a turning point in the steady-state solution family for a given set of system parameters. The 1D model fails to accurately describe interface shapes near the three-phase contact line when air is the receding fluid, producing large errors in estimates of Cacrit for these systems. Analysis of the 2D flow solution reveals that strong pressure gradients are needed to pump the receding fluid away from the contact line. A mechanism is proposed in which wetting failure results when capillary forces can no longer support the pressure gradients necessary to steadily displace the receding fluid. The effects of viscosity ratio, substrate wettability, and fluid inertia are then investigated through comparisons of Cacrit values and characteristics of the interface shape. Surprisingly, the low-speed asymptotic theory (i) matches trends computed from (iii) throughout the entire investigated parameter space. Furthermore, predictions of Cacrit from the 2D flow model compare favorably to values measured in experimental air-entrainment studies, supporting the proposed wetting-failure mechanism.

Vandre, E.; Carvalho, M. S.; Kumar, S.

2013-10-01

338

Coupled compaction driven fluid flow and mechanical deformation in sedimentary basins  

NASA Astrophysics Data System (ADS)

Model experiments will be presented where compaction driven fluid flow is coupled to the viscous-plastic deformation of the skeleton matrix. The Darcy fluid flow during compaction is described by an advection-diffusion equation for the excess pressure with two source/sink terms that depend on the mechanical compressibility and viscous compaction of the pore space, the latter representing the effect of pressure solution. The coupling between the compacting and plastically deforming parts of the system is through the Drucker-Prager frictional-plastic yield criterion, so that the yield strength depends on the effective dynamical pressure. The coupled system is solved using a two-dimensional (2-D) finite element method. Several problems are solved to demonstrate the coupling between compaction driven fluid flow and mechanical deformation.

Huismans, R. S.

2012-12-01

339

Computers in engineering, 1991  

SciTech Connect

This book is covered under the following topics: Robotics, Computers in Fluid Mechanics/Thermal Systems, CAD/CAM/CAE, Finite Element techniques, Computers in Education, Engineering Database Management, and Artificial Intelligence and Expert Systems.

Gupta, G.; Shoup, T.E.

1991-01-01

340

Multidimensional Proteomics Analysis of Amniotic Fluid to Provide Insight into the Mechanisms of Idiopathic Preterm Birth  

Microsoft Academic Search

Background: 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. Methodology\\/Principal Findings: A proteomic fingerprint

Irina A. Buhimschi; Guomao Zhao; Victor A. Rosenberg; Sonya Abdel-Razeq; Stephen Thung; Catalin S. Buhimschi

2008-01-01

341

Heat transfer enhancement in nano-fluids suspensions: Possible mechanisms and explanations  

Microsoft Academic Search

The spectacular heat transfer enhancement revealed experimentally in nano-fluids suspensions is being investigated theoretically at the macro-scale level aiming at explaining the possible mechanisms that lead to such impressive experimental results. In particular, the possibility that thermal wave effects via hyperbolic heat conduction could have been the source of the excessively improved effective thermal conductivity of the suspension is shown

Johnathan J. Vadasz; Saneshan Govender; Peter Vadasz

2005-01-01

342

Fluid dynamics mechanism of disk flutter by measuring the pressure between disks  

Microsoft Academic Search

The mechanism of disk flutter excitation in hard disk drives was experimentally examined in terms of the fluid dynamics. The sensors for measuring the pressure between the rotating disks were used. It was found that there was correlation between the pressure fluctuation amplitude and the flutter amplitude and that the pressure fluctuation was strongly influenced by the rotational speed and

Satomitsu Imai

2001-01-01

343

Analysis of the Transient Behavior of Rotary Lip Seals-Fluid Mechanics and Bulk Deformation  

Microsoft Academic Search

A numerical model of the transient behavior of rotary lip seals has been developed. It includes a fluid mechanics analysis of the lubricating film, an elastic deformation analysis of the lip, and predicts the lip seal state at every instant of time during a transient in shaft speed. The lip seal state includes such quantities as the lubricating film thickness

Richard F. Salant

1998-01-01

344

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

ERIC Educational Resources Information Center

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…

Gynnild, Vidar; Myrhaug, Dag; Pettersen, Bjornar

2007-01-01

345

Notes on the KIVA-II software and chemically reactive fluid mechanics.  

National Technical Information Service (NTIS)

This report represents a set of working notes regarding the mechanics of chemically reactive fluids with sprays, and their numerical simulation with the KIVA-II software. KIVA-II is a large FORTRAN program developed at Los Alamos National Laboratory for i...

M. J. Holst

1992-01-01

346

The variational iteration method: An efficient scheme for handling fractional partial differential equations in fluid mechanics  

Microsoft Academic Search

Variational iteration method has been used to handle linear and nonlinear differential equations. The main property of the method lies in its flexibility and ability to solve nonlinear equations accurately and conveniently. In this work, a general framework of the variational iteration method is presented for analytical treatment of fractional partial differential equations in fluid mechanics. The fractional derivatives are

Zaid Odibat; Shaher Momani

2009-01-01

347

The Integration of Cost into Mechanical Engineering Design Curricula  

Microsoft Academic Search

The integration of cost into design courses in engineering and engineering technology programs is necessary to provide graduating engineers the skills to become immediate contributors to the goals and profits of their chosen companies. There are many methods that can be used, including sophisticated decision science techniques. One example of a teaching and analysis technique developed for use in strength

Gary S. Drigel

2008-01-01

348

Effects of Initial Seeding Density and Fluid Perfusion Rate on Formation of Tissue-Engineered Bone  

PubMed Central

We describe a novel bioreactor system for tissue engineering of bone that enables cultivation of up to six tissue constructs simultaneously, with direct perfusion and imaging capability. The bioreactor was used to investigate the relative effects of initial seeding density and medium perfusion rate on the growth and osteogenic differentiation patterns of bone marrow–derived human mesenchymal stem cells (hMSCs) cultured on three-dimensional scaffolds. Fully decellularized bovine trabecular bone was used as a scaffold because it provided suitable “biomimetic” topography, biochemical composition, and mechanical properties for osteogenic differentiation of hMSCs. Trabecular bone plugs were completely denuded of cellular material using a serial treatment with hypotonic buffers and detergents, seeded with hMSCs, and cultured for 5 weeks. Increasing seeding density from 30×106 cells/mL to 60×106 cells/mL did not measurably influence the characteristics of tissue-engineered bone, in contrast to an increase in the perfusion rate from 100 ?ms?1 to 400 ?ms?1, which radically improved final cell numbers, cell distributions throughout the constructs, and the amounts of bone proteins and minerals. Taken together, these findings suggest that the rate of medium perfusion during cultivation has a significant effect on the characteristics of engineered bone.

GRAYSON, WARREN L.; BHUMIRATANA, SARINDR; CANNIZZARO, CHRISTOPHER; CHAO, P.-H. GRACE; LENNON, DONALD P.; CAPLAN, ARNOLD I.; VUNJAK-NOVAKOVIC, GORDANA

2009-01-01

349

Effects of initial seeding density and fluid perfusion rate on formation of tissue-engineered bone.  

PubMed

We describe a novel bioreactor system for tissue engineering of bone that enables cultivation of up to six tissue constructs simultaneously, with direct perfusion and imaging capability. The bioreactor was used to investigate the relative effects of initial seeding density and medium perfusion rate on the growth and osteogenic differentiation patterns of bone marrow-derived human mesenchymal stem cells (hMSCs) cultured on three-dimensional scaffolds. Fully decellularized bovine trabecular bone was used as a scaffold because it provided suitable "biomimetic" topography, biochemical composition, and mechanical properties for osteogenic differentiation of hMSCs. Trabecular bone plugs were completely denuded of cellular material using a serial treatment with hypotonic buffers and detergents, seeded with hMSCs, and cultured for 5 weeks. Increasing seeding density from 30 x 10(6) cells/mL to 60 x 10(6) cells/mL did not measurably influence the characteristics of tissue-engineered bone, in contrast to an increase in the perfusion rate from 100 microms(-1) to 400 microms(-1), which radically improved final cell numbers, cell distributions throughout the constructs, and the amounts of bone proteins and minerals. Taken together, these findings suggest that the rate of medium perfusion during cultivation has a significant effect on the characteristics of engineered bone. PMID:18620487

Grayson, Warren L; Bhumiratana, Sarindr; Cannizzaro, Christopher; Chao, P-H Grace; Lennon, Donald P; Caplan, Arnold I; Vunjak-Novakovic, Gordana

2008-11-01

350

Rigid Body Dynamics in the Mechanical Engineering Laboratory  

NSDL National Science Digital Library

This paper describes a relatively simple method in which planar rigid body motion can be measured and analyzed in the context of an upper division mechanical engineering laboratory course. The overall intention of this work is to help facilitate upper division level laboratory projects in dynamics. Such projects are intended to provide students with the opportunity to i) apply and reinforce their knowledge of dynamics, ii) learn and practice modern experimental methods used to make and assess motion measurements, and iii) if possible, compare theoretical and measured results. The instrumentation involves the use of two inexpensive sensors a dual axis accelerometer and a rate gyro and a data acquisition system (such as LABVIEW). The accelerometer and rate gyro are fixed to the rigid body object. The rate gyro measures the planar angular velocity, which can be integrated with respect to time to yield angular orientation of the rigid body. With the use of this measured angular orientation, the accelerations measured by the accelerometer (which are measured in two directions fixed to the rigid body) can be resolved into directions fixed in space, and consequently integrated to yield velocity and position coordinates of the point on the rigid body where the accelerometer is attached. These experiments also highlight the importance of error estimation. Errors in acceleration and angular velocity measurement lead to errors in angular orientation and translational velocity and position components that generally grow with time (due to the time integration). An estimation of acceleration and angular velocity measurement errors can be made by calibrating the accelerometer and rate gyro using simple homemade devices. After describing how these experiments can be set up and performed in general, this paper will describe a specific experiment done in the authors junior mechanical engineering laboratory course. The rigid body object under study is a remote controlled car. The technique described above is used to find the position, velocity, orientation, and angular velocity of the car as a function of time. Results of the measurements and data analysis are compared with observations of the cars motion viewed by a video camera. An examination of this laboratory experience, with a discussion of intended learning objectives, an assessment of whether they are being achieved (based on surveys), and suggestions for improvement, will be included. The paper will conclude with some suggestions for additional rigid body motion experiments using this general method of motion measurement.

Nordenholz, Thomas

2011-05-31

351

Respiratory variations in the arterial pressure during mechanical ventilation reflect volume status and fluid responsiveness.  

PubMed

Optimal fluid management is one of the main challenges in the care of the critically ill. However, the physiological parameters that are commonly monitored and used to guide fluid management are often inadequate and even misleading. From 1987 to 1989 we published four experimental studies which described a method for predicting the response of the cardiac output to fluid administration during mechanical ventilation. The method is based on the analysis of the variations in the arterial pressure in response to a mechanical breath, which serves as a repetitive hemodynamic challenge. Our studies showed that the systolic pressure variation and its components are able to reflect even small changes in the circulating blood volume. Moreover, these dynamic parameters provide information about the slope of the left ventricular function curve, and therefore predict the response to fluid administration better than static preload parameters.Many new dynamic parameters have been introduced since then, including the pulse pressure (PPV) and stroke volume (SVV) variations, and various echocardiographic and other parameters. Though seemingly different, all these parameters are based on measuring the response to a predefined preload-modifying maneuver. The clinical usefulness of these 'dynamic' parameters is limited by many confounding factors, the recognition of which is absolutely necessary for their proper use.With more than 20 years of hindsight we believe that our early studies helped pave the way for the recognition that fluid administration should ideally be preceded by the assessment of "fluid responsiveness". The introduction of dynamic parameters into clinical practice can therefore be viewed as a significant step towards a more rational approach to fluid management. PMID:24737260

Perel, Azriel; Pizov, Reuven; Cotev, Shamay

2014-06-01

352

Auto Mechanics I. Learning Activity Packets (LAPs). Section C--Engine.  

ERIC Educational Resources Information Center

This document contains five learning activity packets (LAPs) that outline the study activities for the "engine" instructional area for an Auto Mechanics I course. The five LAPs cover the following topics: basic engine principles, cooling system, engine lubrication system, exhaust system, and fuel system. Each LAP contains a cover sheet that…

Oklahoma State Board of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

353

Effects of mechanical dispersion on the morphological evolution of a chemical dissolution front in a fluid-saturated porous medium  

NASA Astrophysics Data System (ADS)

SummaryThe dissolution-induced finger or wormhole patterns in porous medium or fracture rock play a crucial role in a variety of scientific, industrial, and engineering practices. Although previous studies have extensively presented a number of numerical models which couples a system of nonlinear governing equations of porosity change due to mineral dissolution, the conservations of groundwater flow and transport of chemical species to investigate the morphological pattern of a chemical dissolution front within a fluid-saturated porous medium, whereas the mechanical dispersion effect has generally been neglected in the model development. This study addresses the effects of mechanical dispersion on the morphological evolution of a chemical dissolution front for a variety of cases. Mechanical dispersion processes is incorporated with the coupled nonlinear governing equation system so as to rebuild a newly numerical model. The results of numerical simulations demonstrate that mechanical dispersion has pronounced impacts on the morphological pattern of the chemical dissolution front. For single local non-uniformity case, mechanical dispersion reduces the finger length of an unstable single-fingering front or retains the shape of a stable planar front while speeding up the front advancement. In the case of two local non-uniformities, adding mechanical dispersion with different flow conditions can yield one of the following results: (1) the shape of the stable planar front is maintained but its advancement is accelerated; (2) the shape of the unstable single-fingering front is maintained but its length is reduced; (3) the unstable double-fingering front is merged into an unstable single-fingering front; and (4) the shape of the unstable double-fingering front is preserved but its fingering length is reduced. A comparison between the behavior diagrams of dissolution front morphology (with and without considering mechanical dispersion) shows that the double-fingering front occurs under condition where the upstream pressure gradient is higher and the non-uniformity spacing is larger while mechanical dispersion is taken into consideration.

Chen, Jui-Sheng; Liu, Chen-Wuing; Lai, Geng-Xin; Ni, Chuen-Fa

2009-06-01

354

Mechanical Engineering of the Linac for the Spallation Neutron Source  

SciTech Connect

The linac for the Spallation Neutron Source (SNS) Project will accelerate an average current of 1 mA of H{sup {minus}} ions from 20 MeV to 1GeV for injection into an accumulator ring. The linac will be an intense source of H{sup {minus}} ions and as such requires advanced design techniques to meet project technical goals as well as to minimize costs. The DTL, CCDTL and CCL are 466m long and operate at 805 MHz with a maximum H{sup {minus}} input current of 28 mA and 7% rf duty factor. The Drift Tube Linac is a copper-plated steel structure using permanent magnetic quadrupoles. The Coupled-Cavity portions are brazed copper structures and use electromagnetic quads. RF losses in the copper are 80 MW, with total rf power supplied by 52 klystrons. Additionally, the linac is to be upgraded to the 2- and 4-MW beam power levels with no increase in duty factor. The authors give an overview of the linac mechanical engineering effort and discuss the special challenges and status of the effort.

Bultman, N.K.; Chen, Z.; Collier, M.; Erickson, J.L.; Guthrie, A.; Hunter, W.T.; Ilg, T.; Meyer, R.K.; Snodgrass, N.L.

1999-03-29

355

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

NASA Astrophysics Data System (ADS)

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.

Hart, R. D.

1981-02-01

356

Evaluation of space shuttle main engine fluid dynamic frequency response characteristics  

NASA Technical Reports Server (NTRS)

In order to determine the POGO stability characteristics of the space shuttle main engine liquid oxygen (LOX) system, the fluid dynamic frequency response functions between elements in the SSME LOX system was evaluated, both analytically and experimentally. For the experimental data evaluation, a software package was written for the Hewlett-Packard 5451C Fourier analyzer. The POGO analysis software is documented and consists of five separate segments. Each segment is stored on the 5451C disc as an individual program and performs its own unique function. Two separate data reduction methods, a signal calibration, coherence or pulser signal based frequency response function blanking, and automatic plotting features are included in the program. The 5451C allows variable parameter transfer from program to program. This feature is used to advantage and requires only minimal user interface during the data reduction process. Experimental results are included and compared with the analytical predictions in order to adjust the general model and arrive at a realistic simulation of the POGO characteristics.

Gardner, T. G.

1980-01-01

357

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

NASA Technical Reports Server (NTRS)

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).

Churchill, Susanne

1990-01-01

358

Stability of a dragged viscous thread: Onset of ``stitching'' in a fluid-mechanical ``sewing machine''  

NASA Astrophysics Data System (ADS)

A thin thread of viscous fluid that falls on a moving belt acts like a fluid-mechanical ``sewing machine,'' exhibiting a rich variety of ``stitch'' patterns including meanders, translated coiling, slanted loops, braiding, figures-of-eight, W-patterns, side kicks, and period-doubled patterns. Using a numerical linear stability analysis, we determine the critical belt speed and oscillation frequency of the first bifurcation, at which a steady dragged viscous thread becomes unstable to transverse oscillations or ``meandering.'' The predictions of the stability analysis agree closely with the experimental measurements of Chiu-Webster and Lister [J. Fluid Mech. 569, 89 (2006)]. Moreover, the critical belt speed and onset frequency for meandering are nearly identical to the contact-point migration speed and angular frequency, respectively, of steady coiling of a viscous thread on a stationary surface, implying a remarkable degree of dynamical similarity between the two phenomena.

Ribe, Neil M.; Lister, John R.; Chiu-Webster, Sunny

2006-12-01

359

Mechatronics: the future of mechanical engineering; past, present, and a vision for the future  

Microsoft Academic Search

Mechatronics is the synergistic integration of precision mechanical engineering, electronics, computational hardware and software in the design of products and processes. Mechatronics, the term coined in Japan in the '70s, has evolved to symbolize what mechanical design engineers do today worldwide. The revolutionary introduction of the microprocessor (or microcontroller) in the early '80s and ever increasing performance-cost ratio has changed

M. K. Ramasubramanian

2001-01-01

360

Recent Research Advances and Expectation of Mechanical Engineering Science in China  

Microsoft Academic Search

In recent years, a series of outstanding progresses and original innovations have been achieved in the fields of mechanical engineering, which provide a large number of novel theories, technologies and methodologies for our nation's economic construction and mechanical engineering. Some of them play great significance at home and abroad. Particularly, a few advanced subjects have gained their top level position

LEI Yuanzhong

361

Fluid load support and contact mechanics of hemiarthroplasty in the natural hip joint.  

PubMed

The articular cartilage covering the ends of the bones of diarthrodial synovial joints is thought to have evolved so that the loads are transferred under different and complex conditions, with a very high degree of efficiency and without compromising the structural integrity of the tissue for the life of an individual. These loading conditions stem from different activities such as walking, and standing. The integrity of cartilage may however become compromised due to congenital disease, arthritis or trauma. Hemiarthroplasty is a potentially conservative treatment when only the femoral cartilage is affected as in case of femoral neck fractures. In hemiarthroplasty, a metallic femoral prosthesis is used to articulate against the natural acetabular cartilage. It has also been hypothesized that biphasic lubrication is the predominant mechanism protecting the cartilage through a very high fluid load support which lowers friction. This may be altered due to hemiarthroplasty and have a direct effect on the frictional shear stresses and potentially cartilage degradation and wear. This study modelled nine activities of daily living and investigated the contact mechanics of a hip joint with a hemiarthroplasty, focussing particularly on the role of the fluid phase. It was shown that in most of the activities studied the peak contact stresses and peak fluid pressures were in the superior dome or lateral roof of the acetabulum. Total fluid load support was very high (~90%) in most of the activities which would shield the solid phase from being subjected to very high contact stresses. This was dependent not only on the load magnitude but also the direction and hence on the location of the contact area with respect to the cartilage coverage. Lower fluid load support was found when the contact area was nearer the edges where the fluid drained easily. PMID:20951626

Pawaskar, Sainath Shrikant; Ingham, Eileen; Fisher, John; Jin, Zhongmin

2011-01-01

362

Actuation fluid adapter for hydraulically-actuated electronically-controlled fuel injector and engine using same  

DOEpatents

A fuel injector adapter consists of a block defining a pressure communication passage therethrough and an actuation fluid passage. The actuation fluid passage includes three separate branches that open through an outer surface of the block at three separate locations.

Keyster, Eric S. (Peoria, IL); Merchant, Jack A. (Peoria, IL)

2002-01-01

363

On the statistical mechanics of fluids adsorbed in chemically non-symmetric linear wedges  

NASA Astrophysics Data System (ADS)

Recent work has seen models of fluids adsorbed in a wedge, or at an edge, emerge as a useful addition to our knowledge of inhomogeneous fluid phenomena, directly relevant to current interest on adsorption at structured substrates (so-called intelligent surfaces). The statistical mechanics of wedge/edge models has led to the identification of wall-fluid virial theorems, linking the thermodynamic properties of adsorbed fluids (surface tensions, line tensions, solvation torques) to integrals over moments of an exact representation of Derjaguin's disjoining pressure. These sum rules have proved particularly interesting for the consideration of capillarity (two-phase coexistence) within wedge geometry. This paper considers, instead, the geometric detail needed to fully define and utilise a wedge/edge model. Subtle issues arise concerning the choice of coordinate system and the choice of boundary condition far from the apex. Surprisingly, a significant body of useful results follow from analytic evaluation of the sum rules in the limit of low density (an ideal gas in a wedge). The lessons learnt are particularly relevant to computer simulators wishing to make use of these one-body sum rules and related statistical mechanics. In particular, how to evaluate the sum rule integrals for specific classes of models and what consequences to expect for generalizations to models possessing atomic detail.

Henderson, J. R.

2005-11-01

364

A Mechanism for Fluid Slip in a Hydrophobic Microchannel and the Effects of Absolute Pressure  

NASA Astrophysics Data System (ADS)

Apparent fluid slip has been observed experimentally in micro- and nano-scale flow devices by several investigators (e.g. Tretheway and Meinhart (2002), Zhu and Granik (2001), Pit et.al (2000) and Bruer (2002)). A possible mechanism for the apparent fluid slip is proposed for water flowing over a hydrophobic surface. Lum et. al. (1999) suggest a depleted water region or vapor layer develops near a hydrophobic surface. In addition, nanobubbles have been observed experimentally by Tyrell and Attard (2001). By modeling the presence of either a depleted layer or nanobubbles as an effective air gap at the wall, we calculate slip lengths for flow between two infinite parallel plates. The calculated slip lengths are consistent with experimental values when the gas layer is modeled as a continuum and significantly higher when rarefied gas conditions are assumed. The results suggest that the relatively large apparent fluid slip observed experimentally at hydrophobic surfaces may arises from either the presence of nano-bubbles or a layer of low density fluid at the surface. In addition, we explore the proposed mechanism by measuring velocity profiles and calculating slip lengths at various absolute pressures. From the model, the slip length is highly dependent on depleted layer thickness. An increase in absolute pressure should modify the hydrophobic effect and decrease the layer thickness, thus reducing the measured slip.

Tretheway, Derek; Stone, Shannon; Meinhart, Carl

2003-11-01

365

PREFACE: 40th anniversary of the Japan Society of Fluid Mechanics 40th anniversary of the Japan Society of Fluid Mechanics  

NASA Astrophysics Data System (ADS)

The Japan Society of Fluid Mechanics (JSFM) turned 40 years old in 2008. To celebrate the 40th anniversary, JSFM organized a one-day conference on 5 September 2008 at Kobe University Centennial Hall. The conference was composed of seven invited lectures: three of them were given by distinguished foreign researchers and four were given by relatively young but internationally active Japanese researchers. At the same time, JSFM planned to dedicate an issue of Fluid Dynamics Research (FDR) to the conference. This special issue, which contains six articles based on the lectures at the conference, is the fruition of the plan. The promising program of the conference and the fact that the second day of the Annual Meeting of JSFM was dedicated to this conference attracted a large audience (215 participants). The conference was indeed very successful, thanks to the outstanding lectures and active participation of the audience. I am sure that the articles in this special section, which cover several important areas in modern fluid dynamics, will also interest the readers of FDR. In particular, it will be a great pleasure to me if young researchers are stimulated and motivated by the articles. As the chair of the one-day conference, I would like to express my thanks to Prof. N D Katopodes, Prof. G J F van Heijst, Prof. S Zaleski, Prof. G Kawahara, Prof. S Takagi and Prof. Y Tsuji for their contributions to this special section. Taking this opportunity, I would also like to thank Prof. S Kida (President of JSFM in 2008), Prof. M Funakoshi (Editor-in-Chief of FDR) and the members of the organizing committee of the conference for their continued support and cooperation.

Aoki, Kazuo

2009-12-01

366

Computational fluid dynamics simulation of the air\\/suppressant flow in an uncluttered F18 engine nacelle  

Microsoft Academic Search

For the purposes of designing improved Halon-alternative fire suppression strategies for aircraft applications, Computational Fluid Dynamics (CFD) simulations of the air flow, suppressant transport, and air-suppressant mixing within an uncluttered F18 engine nacelle were performed. The release of inert gases from a Solid Propellant Gas Generator (SPGG) was analyzed at two different injection locations in order to understand the effect

A. R. Lopez; L. A. Gritzo; B. Hassan

1997-01-01

367

Evaluation of a new computational fluid dynamics model for internal combustion engines using hydrogen under motoring conditions  

Microsoft Academic Search

The present work conducts a preliminary evaluation of a new CFD (computational fluid dynamics) model, which is under development at the authors' laboratory. Using this model, it is feasible to understand how the intake manifold and in-cylinder geometry affect the in-cylinder flow field and the mixing processes taking place in an Otto (spark-ignition) engine. The model is applied on a

C. D. Rakopoulos; G. M. Kosmadakis; E. G. Pariotis

2009-01-01

368

Multidimensional Proteomics Analysis of Amniotic Fluid to Provide Insight into the Mechanisms of Idiopathic Preterm Birth  

Microsoft Academic Search

BackgroundThough 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.Methodology\\/Principal FindingsA proteomic fingerprint was generated from

Irina A. Buhimschi; Guomao Zhao; Victor A. Rosenberg; Sonya Abdel-Razeq; Stephen Thung; Catalin S. Buhimschi; Pisake Lumbiganon

2008-01-01

369

Magnetic Resonance Poroelastography: An Algorithm for Estimating the Mechanical Properties of Fluid-Saturated Soft Tissues  

Microsoft Academic Search

Magnetic resonance poroelastography (MRPE) is introduced as an alternative to single-phase model-based elastographic reconstruction methods. A 3-D finite element poroelastic inversion algorithm was developed to recover the mechanical properties of fluid-saturated tissues. The performance of this algorithm was assessed through a variety of numerical experiments, using synthetic data to probe its stability and sensitivity to the relevant model parameters. Preliminary

Phillip R. Perriñez; Francis E. Kennedy; Elijah E. W. Van Houten; John B. Weaver; Keith D. Paulsen

2010-01-01

370

Fluid dynamics mechanism of disk flutter by measuring the pressure between disks  

Microsoft Academic Search

The mechanism of disk-flutter excitation in hard disk drives was experimentally examined in terms of the fluid dynamics. Small pressure sensors for measuring the pressure between the rotating disks were placed in the shroud in the disk-radius direction. It was found that there is the strong correlation between pressure-fluctuation amplitude and disk-flutter amplitude. Therefore, the main force of flutter excitation

Satomitsu Imai; Syozo Saegusa

2000-01-01

371

Introductory remarks. [fluid mechanics research for the National Transonic Facility: theoretical aerodynamics  

NASA Technical Reports Server (NTRS)

Suggested fluid mechanics research to be conducted in the National Transonic Facility include: wind tunnel calibration; flat plate skin friction, flow visualization and measurement techniques; leading edge separation; high angle of attack separation; shock-boundary layer interaction; submarine shapes; low speed studies of cylinder normal to flow; and wall interference effects. These theoretical aerodynamic investigations will provide empirical inputs or validation data for computational aerodynamics, and increase the usefulness of existing wind tunnels.

Gessow, A.

1977-01-01

372

Active Class Composed with Mechanical Engineering and Environment  

NASA Astrophysics Data System (ADS)

This paper reports that the learning experience for a group working disassembling and assembling an internal combustion engine is constructed for a group working. At the same time, the environment education combined with basic studies is introduced with the aid of a Diesel engine running with biofuel. It is found that (1) the leaning experience enhances the leaning motivation and problem solution ability for students, (2) a group working disassembling and assembling an internal combustion engine is effective for greediness for learning, and (3) the environmental study attracts student.

Torii, Shuichi; Imamura, Yasuhiro; Ohshima, Yasutaka; Ariyoshi, Kouji

373

A Microstructurally Motivated Model of the Mechanical Behavior of Tissue Engineered Blood Vessels  

PubMed Central

Mechanical models have potential to guide the development and use of engineered blood vessels as well as other engineered tissues. This paper presents a microstructurally motivated, pseudoelastic, mechanical model of the biaxial mechanics of engineered vessels in the physiologic pressure range. The model incorporates experimentally measured densities and alignments of engineered collagen. Specifically, these microstructural and associated mechanical inputs were measured directly from engineered blood vessels that were cultured over periods of 5–7.5 weeks. To the best of our knowledge, this is the first successful application of either a phenomenological or a microstructurally motivated mechanical model to engineered vascular tissues. Model development revealed the need to use novel theoretical configurations to describe the strain history of engineered vessels. The constitutive equations developed herein suggested that collagen remodeled between 5 and 7.5 weeks during a 7.5-week culture period. This remodeling led to strain energies for collagen that differed with alignment, which likely resulted from undulations that varied with alignment. Finally, biaxial data emphasized that axial extensions increase stresses in engineered vessels in the physiologic pressure range, thereby providing a guideline for surgical use: engineered vessels should be implanted at appropriate axial extension to minimize adverse stress responses.

Dahl, Shannon L. M.; Vaughn, Megann E.; Hu, Jin-Jia; Driessen, Niels J. B.; Baaijens, Frank P. T.; Humphrey, Jay D.; Niklason, Laura E.

2008-01-01

374

Testing of the Engineering Model Electrical Power Control Unit for the Fluids and Combustion Facility  

NASA Technical Reports Server (NTRS)

The John H. Glenn Research Center at Lewis Field (GRC) in Cleveland, OH and the Sundstrand Corporation in Rockford, IL have designed and developed an Engineering Model (EM) Electrical Power Control Unit (EPCU) for the Fluids Combustion Facility, (FCF) experiments to be flown on the International Space Station (ISS). The EPCU will be used as the power interface to the ISS power distribution system for the FCF's space experiments'test and telemetry hardware. Furthermore. it is proposed to be the common power interface for all experiments. The EPCU is a three kilowatt 12OVdc-to-28Vdc converter utilizing three independent Power Converter Units (PCUs), each rated at 1kWe (36Adc @ 28Vdc) which are paralleled and synchronized. Each converter may be fed from one of two ISS power channels. The 28Vdc loads are connected to the EPCU output via 48 solid-state and current-limiting switches, rated at 4Adc each. These switches may be paralleled to supply any given load up to the 108Adc normal operational limit of the paralleled converters. The EPCU was designed in this manner to maximize allocated-power utilization. to shed loads autonomously, to provide fault tolerance. and to provide a flexible power converter and control module to meet various ISS load demands. Tests of the EPCU in the Power Systems Facility testbed at GRC reveal that the overall converted-power efficiency, is approximately 89% with a nominal-input voltage of 12OVdc and a total load in the range of 4O% to 110% rated 28Vdc load. (The PCUs alone have an efficiency of approximately 94.5%). Furthermore, the EM unit passed all flight-qualification level (and beyond) vibration tests, passed ISS EMI (conducted, radiated. and susceptibility) requirements. successfully operated for extended periods in a thermal/vacuum chamber, was integrated with a proto-flight experiment and passed all stability and functional requirements.

Kimnach, Greg L.; Lebron, Ramon C.; Fox, David A.

1999-01-01

375

Statistical Physics of Complex Fluids  

Microsoft Academic Search

The field of complex fluids is a rapidly developing, highly interdisciplinary field that brings together people from a plethora of backgrounds such as mechanical engineering, chemical engineering, materials science, applied mathematics, physics, chemistry and biology. In this melting pot of science, the traditional boundaries of various scientific disciplines have been set aside. It is this very property of the field

R Golestanian; M R H Khajehpour; M R Kolahchi; S Rouhani

2005-01-01

376

Solitary waves: a possible mechanism for rapid fluid transport in low permeability porous media  

NASA Astrophysics Data System (ADS)

Elastic porous media in which the rate of fluid pressure generation is high relative to the rate of fluid pressure diffusion and whose permeabilities are a sensitive function of effective stress may generate solitary waves manifest as discrete pulses of elevated pore pressure and porosity that can travel at velocities that are orders of magnitude greater than the velocities of the pore fluids in the background Darcian flow regime. Solitary waves may thus be important vehicles for fluid transport through porous media whose permeabilities are otherwise too low to allow significant rates of flow. Solitary waves have been hypothesized for diverse geologic settings and processes, including magmatic hydrothermal ore formation, magma transport, fault slip in accretionary wedges and at transform plate boundaries, and primary hydrocarbon migration in sedimentary basins. The present study has focused on solitary waves as agents of oil and methane transport through numerical simulation of their origin and behavior. The results show solitary waves to have limited capacity for transporting oil for several reasons: (1) the rate of fluid pressure generation by typical mechanisms like compaction disequilibrium and hydrocarbon formation is too low to allow solitary waves to form unless permeability is exceptionally low (10-24 to 10-25 m2), (2) solitary waves are only able to ascend no more than 1-2 km before dissipating to ambient pressure and porosity values, (3) the waves are too small and the frequency of their formation is too low to account for the amount of oil observed in the reservoirs that they have been hypothesized to feed. Solitary waves have been found to be more effective at transporting methane because of its lower density and viscosity compared to oil, provided that a mechanism for rapid pressure generation exists and permeabilities are very low. If those conditions exist, then solitary waves can ascend over two kilometers at rates on the order of 100's of meters per year compared to millimeters per year for solitary waves transporting oil.

Appold, Martin; Joshi, Ajit

2014-05-01

377

Mechanically Pumped Fluid Loop (MPFL) Technologies for Thermal Control of Future Mars Rovers  

NASA Technical Reports Server (NTRS)

Mechanically pumped fluid loop has been the basis of thermal control architecture for the last two Mars lander and rover missions and is the key part of the MSL thermal architecture. Several MPFL technologies are being developed for the MSL rover include long-life pumps, thermal control valves, mechanical fittings for use with CFC-11 at elevated temperatures of approx.100 C. Over three years of life tests and chemical compatibility tests on these MPFL components show that MPFL technology is mature for use on MSL. The advances in MPFL technologies for MSL Rover will benefit any future MPFL applications on NASA s Moon, Mars and Beyond Program.

Birur, Gaj; Bhandari, Pradeep; Prina, Mauro; Bame, Dave; Yavrouian, Andre; Plett, Gary

2006-01-01

378

Chemo-mechanical effects of fluid invasion into low permeability rocks  

NASA Astrophysics Data System (ADS)

Exploitation of unconventional gas and oil reservoirs requires injection of large quantities of water-based fluids during hydraulic fracturing treatments. On average only 5 - 30 % of treatment fluids are recovered during flowback from these wells. The large quantity of residual treatment water remains either in the created fracture network, or imbibes into the rock matrix immediately surrounding the fracture network. As such this residual water is spatially located at the critical junction between the reservoir and the hydraulic fracture completion. Besides potentially causing the loss of relative permeability to hydrocarbons in the matrix rock surrounding the fracture, this residual water disrupts the chemical equilibrium of the rock, hydrocarbon and connate water system - leading to a physically and chemically altered zone of rock immediately adjacent to the fracture face. Loss of rock strength in the altered zone due to chemo-mechanical effects is a serious problem. Clearly it is important to understand the rate of fluid imbibition, the total quantity of fluid imbibed into the rock matrix, the depth of the altered rock zone adjacent to the fracture, and the loss of rock strength in this zone. A new laboratory method has been developed to quantitatively measure fluid leakoff and imbibition at the fracture face of ultra-low permeability unconventional reservoir rocks. Plugs taken from shale, mudstone, or ultra-low permeability carbonate reservoir cores are placed under confinement pressures and temperatures, simulating reservoir conditions. A low-flow rate imbibition/leakoff experiment is performed on the plug. The mechanisms of invasion are both pressure driven leak-off and imbibition. In the second stage of the experiment the core is dissected using a mechanical scratch tester. Leak-off into the pore structure of the matrix can be discriminated from artifacts such as leakoff into coring induced micro-fractures. The results show that fluid imbibition can be highly variable depending on the specific rock. Results are being correlated with the petrology of the rock. In addition to the quantitative determination of leak off and imbibition rates, the method measures the unconfined compressive strength (UCS) of the rock as a function of depth. Precise determination of the water content as a function of plug depth results in a water saturation profile throughout the plug and enables us to correlate rock strength, water saturation and exposure time. Experimental results show that imbibition and fluid loss into ultralow permeability shales, mudstones and carbonates can be substantial but are also highly variable depending on the texture and composition of the rock. The depth of water invasion in the experimental time frame of three days ranges from 0.5 to 3 cm in nanoDarcy permeability shales. The rock strength declines with exposure time to the fracturing fluid and correlates with the invading fluid saturation. Depending on the rock - softening due to fluid exposure can reduce the UCS by 25 - 50% over a 3 day exposure period. Loss of rock strength can lead to increased proppant embedment and a reduction in fracture conductivity. Increased embedment of proppant in turn can lead to fines generation due to displacement of rock matrix material with the risk of reducing proppant pack conductivity.

Pagels, M.; Willberg, D.; Edelman, E.

2011-12-01

379

Interstitial Fluid Flow: The Mechanical Environment of Cells and Foundation of Meridians  

PubMed Central

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.

Yao, Wei; Ding, Guanghong

2012-01-01

380

Interstitial fluid flow: the mechanical environment of cells and foundation of meridians.  

PubMed

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. PMID:23365601

Yao, Wei; Li, Yabei; Ding, Guanghong

2012-01-01

381

Performance of Army Arctic Engine Oils in Hydraulic and Power Transmission Fluid Systems.  

National Technical Information Service (NTIS)

Development of the Army's new Arctic Engine Oil (OEA) Specification MIL-L-46167 required numerous laboratory and field engine evaluations as well as large scale laboratory and field testing of these new lubricants in military hydraulic and power transmiss...

S. J. Lestz P. D. Hopler T. C. Bowen

1975-01-01

382

Fluid Structural Analysis of Human Cerebral Aneurysm Using Their Own Wall Mechanical Properties  

PubMed Central

Computational Structural Dynamics (CSD) simulations, Computational Fluid Dynamics (CFD) simulation, and Fluid Structure Interaction (FSI) simulations were carried out in an anatomically realistic model of a saccular cerebral aneurysm with the objective of quantifying the effects of type of simulation on principal fluid and solid mechanics results. Eight CSD simulations, one CFD simulation, and four FSI simulations were made. The results allowed the study of the influence of the type of material elements in the solid, the aneurism's wall thickness, and the type of simulation on the modeling of a human cerebral aneurysm. The simulations use their own wall mechanical properties of the aneurysm. The more complex simulation was the FSI simulation completely coupled with hyperelastic Mooney-Rivlin material, normal internal pressure, and normal variable thickness. The FSI simulation coupled in one direction using hyperelastic Mooney-Rivlin material, normal internal pressure, and normal variable thickness is the one that presents the most similar results with respect to the more complex FSI simulation, requiring one-fourth of the calculation time.

Valencia, Alvaro; Burdiles, Patricio; Ignat, Miguel; Mura, Jorge; Rivera, Rodrigo; Sordo, Juan

2013-01-01

383

Fluid structural analysis of human cerebral aneurysm using their own wall mechanical properties.  

PubMed

Computational Structural Dynamics (CSD) simulations, Computational Fluid Dynamics (CFD) simulation, and Fluid Structure Interaction (FSI) simulations were carried out in an anatomically realistic model of a saccular cerebral aneurysm with the objective of quantifying the effects of type of simulation on principal fluid and solid mechanics results. Eight CSD simulations, one CFD simulation, and four FSI simulations were made. The results allowed the study of the influence of the type of material elements in the solid, the aneurism's wall thickness, and the type of simulation on the modeling of a human cerebral aneurysm. The simulations use their own wall mechanical properties of the aneurysm. The more complex simulation was the FSI simulation completely coupled with hyperelastic Mooney-Rivlin material, normal internal pressure, and normal variable thickness. The FSI simulation coupled in one direction using hyperelastic Mooney-Rivlin material, normal internal pressure, and normal variable thickness is the one that presents the most similar results with respect to the more complex FSI simulation, requiring one-fourth of the calculation time. PMID:24151523

Valencia, Alvaro; Burdiles, Patricio; Ignat, Miguel; Mura, Jorge; Bravo, Eduardo; Rivera, Rodrigo; Sordo, Juan

2013-01-01

384

Thermo-adjustable mechanical properties of polymer, lipid-based complex fluids  

NASA Astrophysics Data System (ADS)

Combined rheology (oscillatory and steady shear) and SAXS studies reveal details on the temperature-dependent, reversible mechanical properties of nonionic polymer, lipid-based complex fluids. Compositions prepared by introduction of the polymer as either a lipid conjugate or a triblock copolymer form an elastic gel as the temperature is increased to 18 C. The network is produced from PEO chain entanglement and physical crosslinks confined within the intervening aqueous layers of a multilamellar structured lyotropic mesophase. Although the complex fluids are weak gels, tuning of the gel strength can be achieved by temperature adjustment. The sol state formed at reduced temperature arises as a consequence of the well-solvated PEO chains adopting a non-interacting, conformational state. Complex fluids prepared with the triblock copolymers exhibit greater tunability in viscoelasticity than those containing the PEGylated-lipid conjugate because of the temperature-dependent water solubility of the central PPO block. The water solubility of PPO at reduced temperatures results in the polymer being expelled from the self-assembled amphiphilic bilayer, causing collapse of the swollen lamellar structure and loss of the PEO network. At elevated temperatures, the triblock reinserts into the bilayer producing an elastic gel. These studies identify macromolecular architectures for the facile preparation of dynamic soft materials possessing a range of mechanical properties that can be tuned by modest temperature control.

Firestone, Millicent; Lee, Sungwon

2012-02-01

385

Thermal and Mechanical Design Aspects of the LIFE Engine  

SciTech Connect

The Laser Inertial confinement fusion - Fission Energy (LIFE) engine encompasses the components of a LIFE power plant responsible for converting the thermal energy of fusion and fission reactions into electricity. The design and integration of these components must satisfy a challenging set of requirements driven by nuclear, thermal, geometric, structural, and materials considerations. This paper details a self-consistent configuration for the LIFE engine along with the methods and technologies selected to meet these stringent requirements. Included is discussion of plant layout, coolant flow dynamics, fuel temperatures, expected structural stresses, power cycle efficiencies, and first wall survival threats. Further research and to understand and resolve outstanding issues is also outlined.

Abbott, R P; Gerhard, M A; Latkowski, J F; Kramer, K J; Morris, K R; Peterson, P F; Seifried, J E

2008-10-25

386

Extrema principles of entrophy production and energy dissipation in fluid mechanics  

NASA Technical Reports Server (NTRS)

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.

Horne, W. Clifton; Karamcheti, Krishnamurty

1988-01-01

387

Extrema principles of entropy production and energy dissipation in fluid mechanics  

NASA Technical Reports Server (NTRS)

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 appear 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.

Horne, W. Clifton; Karamcheti, Krishnamurty

1988-01-01

388

Quiet Clean Short-Haul Experimental Engine (QCSEE). Under-the-Wing (UTW) Engine Boilerplate Nacelle Test Report. Volume 3: Mechanical Performance.  

National Technical Information Service (NTIS)

Results of initial tests of the under the wing experimental engine and boilerplate nacelle are presented. The mechanical performance of the engine is reported with emphasis on the advanced technology components. Technology elements of the propulsion syste...

1977-01-01

389

Heat Transfer and Fluid Mechanics Institute, 32nd, California State University, Sacramento, June 6, 7, 1991, Proceedings  

Microsoft Academic Search

The present conference on heat transfer and fluid mechanics encompasses heat transfer measurement, fluid flow, aerospace propulsion systems, research in building energy use, wind turbines, and computer modeling of blood flow, turbulent boundary layers, and vortex-shedding flow meters. Specific issues addressed include liquid crystal techniques in experimental heat transfer, temperature measurements in a turbulent boundary layer, the effect of suction

Frederick H. Reardon; Ngo D. Thinh

1991-01-01

390

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

Microsoft Academic Search

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

D. Schertzer; E. Falgarone

1996-01-01

391

Hypoxia-induced collagen crosslinking as a mechanism for enhancing mechanical properties of engineered articular cartilage  

PubMed Central

Objective The focus of tissue engineering of neocartilage has traditionally been on enhancing extracellular matrix and thus biomechanical properties. Emphasis has been placed on the enhancement of collagen type and quantity, and, concomitantly, tensile properties. The objective of this study was to improve crosslinking of the collagen network by testing the hypothesis that hypoxia could promote pyridinoline (PYR) crosslinks and, thus, improve neocartilage’s tensile properties. Methods Chondrocyte expression of lysyl oxidase (LOX), an enzyme responsible for the formation of collagen PYR crosslinks, was first assessed pre- and post- hypoxia application. Then, the mechanical properties of self-assembled neocartilage constructs were measured, after 4 weeks of culture, for groups exposed to 4% O2 at different initiation times and durations, i.e., during the 1st and 3rd weeks, 3rd and 4th weeks, 4th week only, continuously after cell seeding, or never. Results Results showed that LOX gene expression was upregulated ~20-fold in chondrocytes in response to hypoxia. Hypoxia applied during the 3rd and 4th weeks significantly increased PYR crosslinks without affecting collagen content. Excitingly, neocartilage tensile properties were increased ~2-fold. It should be noted that these properties exhibited a distinct temporal dependence to hypoxia exposure, since upregulation of these properties was due to hypoxia applied only during the 3rd and 4th weeks. Conclusion These data elucidate the role of hypoxia-mediated upregulation of LOX and subsequent increases in PYR crosslinks in engineered cartilage. These results hold promise toward applying hypoxia at precise time points to promote tensile integrity and direct construct maturation.

Makris, E.A.; Hu, J.C.; Athanasiou, K.A.

2013-01-01

392

Thermal and Mechanical Design Aspects of the LIFE Engine  

Microsoft Academic Search

The Laser Inertial confinement fusion - Fission Energy (LIFE) engine encompasses the components of a LIFE power plant responsible for converting the thermal energy of fusion and fission reactions into electricity. The design and integration of these components must satisfy a challenging set of requirements driven by nuclear, thermal, geometric, structural, and materials considerations. This paper details a self-consistent configuration

R P Abbott; M A Gerhard; J F Latkowski; K J Kramer; K R Morris; P F Peterson; J E Seifried

2008-01-01

393

CASE STUDY RESEARCH INTO AUSTRALIAN MECHANICAL ENGINEER ATTRIBUTES  

Microsoft Academic Search

Five point Likert scales were used. For attribute significance the five points were 'no use', 'rare', 'occasional', 'significant' or 'essential'. For graduate ability they were 'none', 'poor', 'moderate', 'significant' and 'excellent'. Respondents were allowed to straddle the Likert points. For example they could assess an attribute as 'rare' to 'occasional'. Attribute weightings took into account the proportion of engineers in

C. Ferguson

394

Critical Performance of Turbopump Mechanical Elements for Rocket Engine  

Microsoft Academic Search

It is generally acknowledged that bearings and axial seals have a tendency to go wrong compared with other rocket engine elements. And when those components have malfunction, missions scarcely succeed. However, fundamental performance (maximum rotational speed, minimum flow rate, power loss, durability, etc.) of those components has not been grasped yet. Purpose of this study is to grasp a critical

Satoshi Takada; Masataka Kikuchi; Takayuki Sudou; Fumiya Iwasaki; Yoshiaki Watanabe; Makoto Yoshida

2009-01-01

395

Investigating the Formation Mechanisms and Inorganic Precursors of Formate and Acetate in Lost City Hydrothermal Fluids  

NASA Astrophysics Data System (ADS)

Fluids from the Lost City Hydrothermal Field are rich in hydrogen and methane, with high pHs (9 - 11), as a result of serpentinization reactions at moderate temperatures of approximately 120-200°C. It has been predicted that organic carbon compounds would form abiologically under these chemical and thermal conditions from inorganic precursors, in the form of hydrocarbons and organic acids. Previous work has demonstrated the presence of high concentrations of both formate and acetate in the Lost City fluids [Lang et al., 2010, GCA]. Formate is the second most prevalent carbon species in the fluids and may provide local microbial communities with a necessary carbon source in the face of low dissolved inorganic carbon concentrations. The goals of this study are to constrain the formation mechanisms of these organic acids (abiotic vs. biotic) and to identify their inorganic precursors. Formate and acetate were isolated from multiple fluid samples by preparative high-performance liquid chromatography for isotopic analysis. The ?13C of formate is similar to that of Lost City methane, and consistent with an abiological origin. The isotopic signature of acetate is significantly different from these values, and may be indicative of a biological source. Radiocarbon measurements of the isolated formate are in progress and should allow us to determine if the precursor carbon is derived from a mantle or deep-seawater source. Alkaline hydrothermal systems have been proposed as potential sites to the origin of life and formate has been proposed as a critical intermediate towards the kinds of reduced carbon species found in biochemistry. Evidence of an abiological formation mechanism of formate at Lost City may significantly further our understanding of prebiotic chemistry.

Lang, S. Q.; Bernasconi, S. M.; Früh-Green, G.

2010-12-01

396

Of green monkeys and failed affordances: A case study of a mechanical engineering design course  

Microsoft Academic Search

This article reports on an ethnographic study of a mechanical engineering design class. The findings are based on participant observation of one student design team of three students as they designed, tested and built an engineered solution to a problem over a period of ten weeks. The paper describes the curricular efforts to provide social and material affordances both for

Wendy C. Newstetter

1998-01-01

397

Numerical simulation study of diesel engine based on new type of crankshaft connecting rod mechanism  

Microsoft Academic Search

Diesel engine works under mix combustion (constant volume and constant pressure) with low combustion rate and speed, resulting in its thermal efficiency is lower than the constant volume combustion type at the same compression rate. A diesel engine model with new type of crankshaft connecting rod mechanism which can stay in the TDC for a long time is developed to

Zhang Yong; Li Wei-Shan; Liu Xuan

2011-01-01

398

Dynamic mechanical properties of the tissue-engineered matrix associated with individual chondrocytes  

Microsoft Academic Search

The success of cell-based tissue engineering approaches in restoring biological function will be facilitated by a comprehensive fundamental knowledge of the temporal evolution of the structure and properties of the newly synthesized matrix. Here, we quantify the dynamic oscillatory mechanical behavior of the engineered matrix associated with individual chondrocytes cultured in vitro for up to 28 days in alginate scaffolds.

BoBae Lee; Lin Han; Eliot H. Frank; Susan Chubinskaya; Christine Ortiz; Alan J. Grodzinsky

2010-01-01

399

Proceedings of the eighth international conference on offshore mechanics and Arctic engineering. 1989  

SciTech Connect

This book contains the proceedings of the Eighth International Conference on Offshore Mechanics and Arctic Engineering. Topics covered include: CAD application in offshore structure fabrication; A force control system for robotic manipulators; and intersections for trimmed surface patches.

Patrikalakis, N.M. (Massachusetts Inst. of Tech., Cambridge, MA (USA)); Chung, J.S. (Colorado School of Mines, Golden, CO (USA)); Morgan, M.J. (Industrial Systems, Woodinville, WA (US))

1989-01-01

400

Mechanisms of engine wear and engine oil degradation in vehicles using M85 or gasoline  

Microsoft Academic Search

The results of several investigations indicate the extent to which driving cycle, oil formulation, and fuel type (either regular unleaded gasoline or M85) influence the nature and severity of engine-oil degradation and engine damage. Driving cycle greatly influenced mass loss of piston rings and main and connecting rod bearings. For example, short-trip, cold start service with M85 caused 80 times

S. E. Schwartz; C. J. Mettrick

1994-01-01

401

Field Observations of Fluid Transport in a Complex Heterogeneous Vadose Zone at the Idaho National Engineering and Environmental Laboratory (INEEL)  

NASA Astrophysics Data System (ADS)

Predicting fluid and contaminant transport in the vadose zone near the Idaho Nuclear Technology and Engineering Center (INTEC) at the INEEL has been problematic due to the complex geology underlying the site. In an attempt to better understand the controlling mechanism of subsurface fluid transport, a system of monitoring instruments were installed in boreholes around the perimeter of newly constructed percolation ponds, consisting of 2 cells each approximately 160,000 ft2 in area. The instrumented region surrounding the ponds has been designated as the Vadose Zone Research Park (VZRP). Continuous discharge to the south cell began in October 2002 at an average flux rate of 1.5 million gallons per day and continued until July 2003 at which time the discharge was switched to the north cell. Hydraulic data were collected nearly continuously, monitoring hydraulic responses to discharge events to both cells. Discharge to the south cell resulted in rapid vertical percolation until reaching the surficial gravel/basalt interface (at about 60 ft below ground surface) at which time rapid lateral transport was observed in a southern direction. A near steady state of water levels was reached during this 10-month period. Switching discharge location only 100 feet to the north cell drastically altered hydrological conditions and flow paths within the subsurface. Recharge was observed in several new locations, while some locations ceased receiving water from the ponds entirely. Other locations temporarily drained, then received "new water" from alternate flow paths a few days later. Prior to switching discharge locations, 3 wells were installed in the north cell at depths of 7 ft, 12 ft, and 19 ft below ground surface. The wells were instrumented with electrical conductivity probes to monitor discharge from the INTEC facility, which receives a high conductivity spike every 12 hours from water softener regeneration. Field observations show that water reached the 7 ft well within a couple hours after the switch, while the other 2 wells remain dry even after one month. Based on these data, it appears that discharge to the north cell percolates vertically to a depth of approximately 10 ft before reaching a low permeability zone, which diverts flow laterally in a northern direction. Field observations of hydrological data indicate that initial water arrival times and locations appear to be controlled by low permeability zones and fast pathways. Arrival progression was neither vertically nor laterally sequential. Importantly, field observations indicate that minor transients in discharge flux and/or location resulted in extreme changes in fluid transport behavior. Based on these observations, it is apparent that our original steady-state conceptual model needs to be modified to incorporate not only lithologic complexities, but also temporal changes in discharge location and flux. Continued field monitoring combined with ongoing tracer testing at the VZRP is aimed at providing the information needed to improve predictive models designed specifically for complex heterogeneous subsurface environments.

Baker, K.; Hull, L.; Mattson, E.; McLing, T.

2003-12-01

402

Intrinsically irreversible heat engine  

DOEpatents

A class of heat engines based on an intrinsically irreversible heat transfer process is disclosed. In a typical embodiment the engine comprises a compressible fluid that is cyclically compressed and expanded while at the same time being driven in reciprocal motion by a positive displacement drive means. A second thermodynamic medium is maintained in imperfect thermal contact with the fluid and bears a broken thermodynamic symmetry with respect to the fluid. The second thermodynamic medium is a structure adapted to have a low fluid flow impedance with respect to the compressible fluid, and which is further adapted to be in only moderate thermal contact with the fluid. In operation, thermal energy is pumped along the second medium due to a phase lag between the cyclical heating and cooling of the fluid and the resulting heat conduction between the fluid and the medium. In a preferred embodiment the engine comprises an acoustical drive and a housing containing a gas which is driven at a resonant frequency so as to be maintained in a standing wave. Operation of the engine at acoustic frequencies improves the power density and coefficient of performance. The second thermodynamic medium can be coupled to suitable heat exchangers to utilize the engine as a simple refrigeration device having no mechanical moving parts. Alternatively, the engine is reversible in function so as to be utilizable as a prime mover by coupling it to suitable sources and sinks of heat.

Wheatley, J.C.; Swift, G.W.; Migliori, A.

1984-01-01

403

Freshman Education Program Made Up of Lecture, Experiment and Practice for Mechanical Engineering Students  

NASA Astrophysics Data System (ADS)

A new curriculum, which instills an appreciation in mechanical engineering and motivates freshman students to pursue this discipline in a college of technology, is presented. The curriculum is composed of lecture, experiment and practice to foster self-education ability. Numerous new and unique teaching processes were developed to meet our objectives and were evaluated through anonymous student evaluations. Nearly all students, who participated in this curriculum, showed increased interest in pursuing mechanical engineering.

Izawa, Satoru; Tanaka, Kohichi; Kawamura, Takashi

404

Mechanism of homeotropic alignment of ferroelectric liquid crystals doped with ferro-fluid and applications  

NASA Astrophysics Data System (ADS)

We report homeotropic (HT) alignment of ferroelectric liquid crystal (FLC) doped with various concentrations of ferro-fluid (FF) without using any type of alignment layer. The FF induced HT alignment of FLC was found to be dependent on the doping concentration as revealed by optical micrographs, contact angle, and dielectric spectroscopy studies. Higher water contact angle of FF doped FLC films with respect to pure FLC film suggests higher surface energy of FF doped FLC than the surface energy of substrate. The physico-chemical mechanism together with steric model successfully explains the HT alignment of the studied FLC on the ITO substrate.

Joshi, Tilak; Singh, Shri; Choudhary, Amit; Pant, R. P.; Biradar, A. M.

2013-07-01

405

Multi-Class MPLS Resilience Mechanism Supporting Traffic Engineering  

Microsoft Academic Search

In the classical MPLS resilience scenario, the fault recovery mechanism can only be deployed in two ways: either 100% protects traffic in protection switching case, or unprotect traffic in rerouting case. Consequently, the resource consumption is too high for network to afford if the fast recovery mechanism (protection switching) is deployed in the whole network. One of the objectives of

He Huang; Jin Wang; Bo Yang; Peng Li

2006-01-01

406

Mechanism of vibration-induced repulsion force on a particle in a viscous fluid cell.  

PubMed

Space platforms such as the Space Shuttle and International Space Station have been considered an ideal environment for production of protein and semiconductor crystals of superior quality due to the negligible gravity-induced convection. Although it was believed that under microgravity environment diffusive mass transport would dominate the growth of the crystals, some related experiments have not shown satisfactory results possibly due to the movement of the growing crystals in fluid cells caused by small vibrations present in the space platforms called g-jitter. In ground-based experiments, there have been clear observations of attraction and repulsion of a solid particle with respect to a nearby wall of the fluid cell due to small vibrations. The present work is a numerical investigation on the physical mechanisms responsible for the repulsion force, which has been predicted to increase with the cell vibration frequency and amplitude, as well as the fluid viscosity. Moreover, the simulations have revealed that the repulsion force occurs mostly due to the increased pressure in the narrow gap between the particle and the nearest wall. PMID:24032936

Saadatmand, Mehrrad; Kawaji, Masahiro

2013-08-01

407

Mechanism of vibration-induced repulsion force on a particle in a viscous fluid cell  

NASA Astrophysics Data System (ADS)

Space platforms such as the Space Shuttle and International Space Station have been considered an ideal environment for production of protein and semiconductor crystals of superior quality due to the negligible gravity-induced convection. Although it was believed that under microgravity environment diffusive mass transport would dominate the growth of the crystals, some related experiments have not shown satisfactory results possibly due to the movement of the growing crystals in fluid cells caused by small vibrations present in the space platforms called g-jitter. In ground-based experiments, there have been clear observations of attraction and repulsion of a solid particle with respect to a nearby wall of the fluid cell due to small vibrations. The present work is a numerical investigation on the physical mechanisms responsible for the repulsion force, which has been predicted to increase with the cell vibration frequency and amplitude, as well as the fluid viscosity. Moreover, the simulations have revealed that the repulsion force occurs mostly due to the increased pressure in the narrow gap between the particle and the nearest wall.

Saadatmand, Mehrrad; Kawaji, Masahiro

2013-08-01

408

The fluid mechanics of copepod feeding in a turbulent flow: A theoretical approach  

NASA Astrophysics Data System (ADS)

An important area of biodynamics research is the interaction between predator and prey in nature. Several scales are significant for interactions between predator and prey over the life cycle of each organism. A key factor is the encounter probability (group and individual). On the basis of physical considerations, the group encounter probability depends upon the respective patch sizes (on the order of 10s of km) and their relative dispersion (or aggregation) rates in turbulent systems. The encounter probability at the individual level is affected by the relative motion of the predator and the prey and is controlled by the velocity spectrum. In addition, at the individual level, the striking distance of a predator will depend on motility and perception of the prey. Here we address the mechanics of copepod predation on phytoplankton and the coupling with the physics of turbulent fluid motions. Our aim is to review pertinent fluid dynamics, on scales of less than a few metres, to provide a framework in which to consider the role of fluctuating fluid velocities on copepod feeding.

Granata, T. C.; Dickey, T. D.

409

Numerical Simulation of Reactive Flow in Internal Combustion Engines.  

National Technical Information Service (NTIS)

Multidimensional numerical simulations of the reactive fluid flow in an internal combustion engine cylinder are useful in helping engine designers obtain insight into the physical mechanisms governing efficiency and pollutant formation. A comprehensive nu...

L. D. Cloutman J. K. Dukowicz J. D. Ramshaw

1980-01-01

410

The International Congress of Mechanical Engineering and Agricultural Sciences – CIIMCA 2013  

NASA Astrophysics Data System (ADS)

The organizing committee of The International Congress of Mechanical Engineering and Agricultural Sciences – CIIMCA 2013 – are pleased to present CIIMCA-2013: the first international conference focused on subjects of materials science, mechanical engineering and renewable energy organized by Mechanical Engineering Faculty of the ''Universidad Pontificia Bolivariana'' in Bucaramanga, Colombia. This conference aims to be a place to produce discussions on whole topics of the congress, between the scientists of Colombia and the world. We strongly believe that knowledge is fundamental to the development of our countries. For that reason this multidisciplinary conference is looking forward to integrate engineering, agricultural science and nanoscience and nanotechnology to produce a synergy of this area of knowledge and to achieve scientific and technological developments. Agriculture is a very important topic for our conference; in Colombia, agricultural science needs more attention from the scientific community and the government. In the Faculty of Mechanical Engineering we are beginning to work on these issues to produce knowledge and improve the conditions in our country. The CIIMCA conference is a great opportunity to create interpersonal relationships and networks between scientists around the world. The interaction between scientists is very important in the process of the construction of knowledge. The general chairman encourages and invites you to make friends, relationships and participate strongly in the symposia and all program activities. PhD Aduljay Remolina-Millán Principal Chairman, International Mechanical Engineering and Agricultural Sciences Congress – CIIMCA Msc Emil Hernández-Arroyo Principal Chairman, International Mechanical Engineering and Agricultural Sciences Congress – CIIMCA Conference photograph Conference photograph 'Universidad Pontificia Bolivariana seccional Bucaramanga' host of the first International Mechanical Engineering and Agricultural Sciences Congress – CIIMCA 2013 – Floridablanaca, Colombia. Conference photograph Closure of CIIMCA 2013. Details of the editorial committee and acknowledgements are available in the PDF.

Remolina-Millán, Aduljay; Hernández-Arroyo, Emil

2014-06-01

411

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines.  

National Technical Information Service (NTIS)

This paper describes the application of high performance computing to accelerate the development of hypergolic propulsion systems for tactical missiles. Computational fluid dynamics is employed to model the chemically reacting flow within a system's combu...

C. Chen M. J. McQuaid M. J. Nusca

2007-01-01

412

Heat Transfer and Fluid Dynamics Measurements in the Expansion Space of a Stirling Cycle Engine  

NASA Technical Reports Server (NTRS)

The heater (or acceptor) of a Stirling engine, where most of the thermal energy is accepted into the engine by heat transfer, is the hottest part of the engine. Almost as hot is the adjacent expansion space of the engine. In the expansion space, the flow is oscillatory, impinging on a two-dimensional concavely-curved surface. Knowing the heat transfer on the inside surface of the engine head is critical to the engine design for efficiency and reliability. However, the flow in this region is not well understood and support is required to develop the CFD codes needed to design modern Stirling engines of high efficiency and power output. The present project is to experimentally investigate the flow and heat transfer in the heater head region. Flow fields and heat transfer coefficients are measured to characterize the oscillatory flow as well as to supply experimental validation for the CFD Stirling engine design codes. Presented also is a discussion of how these results might be used for heater head and acceptor region design calculations.

Jiang, Nan; Simon, Terrence W.

2006-01-01

413

Mechanical Engineering Curricula: A Follow-up Study for the Future Effects of ABET EC2000  

NSDL National Science Digital Library

The Accreditation Board for Engineering and Technology (ABET) is recognized by the U.S. Department of Education as the sole agency responsible for accreditation of educational programs leading to degrees in engineering, engineering technology, and related engineering areas. In the late 1990s, engineering programs began transitioning to a new Engineering Criteria 2000 (EC2000). By 2001, all engineering programs were required to be accredited under the new criteria. The philosophy of Engineering Criteria 2000 is to allow institutions and programs to define their mission and objectives to meet the needs of their constituents and enable program differentiation. Emphasis is placed on continuous improvement of programs based on the input of constituents and a process that links outcomes and assessment to program objectives. This current paper is a follow-up study to a preliminary study conducted by the author in 2000 that looked at the initial effects of ABET EC2000. The earlier study examined selected mechanical engineering programs to discern the impact of EC2000 on curriculum development during the initial implementation phase of the new criteria. Data on the layout and composition of mechanical engineering curricula for nine schools in the United States with Ph.D. programs and nine schools without Ph.D. programs was presented and is updated in this current work. Current results are also compared to a study by Robert E. Mates from the State University of New York at Buffalo entitled a Survey of Undergraduate ME Programs, conducted in 1987. The conclusions identify changes that have occurred in mechanical engineering curricula as the EC2000 assessment process has matured.

Whiteman, Wayne

2009-09-09

414

A novel mechanism of insect resistance engineered into tobacco  

NASA Astrophysics Data System (ADS)

A major goal of plant genetic engineering is the introduction of agronomically desirable phenotypic traits into crop plants in situations where conventional breeding methods have been unsuccessful. One such target is enhanced resistance to insect pests which, in view of the estimated production losses world-wide and the heavy costs of protective treatments, is very important. We report here that a gene encoding a cowpea trypsin inhibitor, which has been shown to give some measure of field resistance to insect pests1, confers, when transferred to tobacco, enhanced resistance to this species' own herbivorous insect pests.

Hilder, Vaughan A.; Gatehouse, Angharad M. R.; Sheerman, Suzanne E.; Barker, Richard F.; Boulter, Donald

1987-11-01

415

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

NASA Astrophysics Data System (ADS)

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 hypothesize that the simulated effects of polyhydramnios are not the primary cause of the fact that TTTS placentas more often include bidirectional AV than AV plus AA anastomoses. Rather, the more likely explanation is the previously identified larger range of AA than VA anastomotic diameters that adequately compensate for the effects of the AV.

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

2002-06-01

416

Evolution of fluid-fault interactions across the upper continental crust inferred from seismological, mechanical and geochemical analyses.  

NASA Astrophysics Data System (ADS)

This study aims at deciphering the interactions between fluid and fault mechanics across the upper continental crust. Here, the influence of fluid overpressures on fault reactivation and earthquake triggering are investigated at the crustal scale. In order to reach this goal, an analysis combining seismology, structural geology, geochemistry and mechanics has been carried out along an active dextral strike-slip fault system in the Ubaye-Argentera region (southern French-Italian Alps). The interests of this fault system are its relationship to the 2003-2004 Ubaye seismic swarm (Jentatton et al., 2007) having occurred in the crystalline basement and its exposure in the Argentera crystalline basement massif located further south. The presence of fluid overpressures in the fault zone has been evidenced during the analysis of the 2003-2004 seismic swarm (Daniel et al., 2011, Leclère et al., 2012) and by the presence of quartz-chlorite mineralized veins (i.e. hydraulic fracturing) along the faults outcropping in the Argentera massif. We investigate the interactions between fluid and fault across the upper continental crust from the analysis of the 2003-2004 Ubaye swarm and the quartz-chlorite veins associated with a fault located in the continuity of the fault of the 2003-2004 Ubaye swarm. The fluid-fault interactions during the 2003-2004 Ubaye seismic swarm were analyzed by using focal mechanisms of 74 events, mechanical model based on the Mohr-Coulomb theory and the hydrogeologic context. The results show that the seismogenic zone of the Ubaye region is characterized by the development of supra-hydrostatic fluid overpressures in fault zone and that the fluids have meteoric origins. Conversely, the mechanical (i.e. Mohr-Coulomb model) and geochemical analyses (i.e. chemical and isotopic compositions) of the quartz-chlorite veins show that these veins were formed at or near the base of the seismogenic zone and with a fluid of metamorphic origin and under a lithostatic fluid pressure. The conditions of initiation of earthquakes at or near the base of the seismogenic zone deduced from geochemical and mechanical analyses of quartz-chlorite veins are then compared with those deduced from the analysis of the Ubaye seismic swarm occurring in the seismogenic zone. These results allow to propose a conceptual model of the interactions between fluid, fault and earthquake across the upper continental crust. This conceptual model shows that the brittle-ductile transition appears as an important limit separating two domains with different seismic and hydro-mechanical behaviors. Lastly, this study emphasizes the importance of associating seismological, mechanical and geochemical analyses to understand the fluid-tectonic interactions at crustal-scale.

Leclère, Henri; Lacroix, Brice; Fabbri, Olivier; Daniel, Guillaume; Cappa, Frédéric

2013-04-01

417

Current Results and Proposed Activities in Microgravity Fluid Dynamics  

NASA Technical Reports Server (NTRS)

The Institute for Problems in Mechanics' Laboratory work in mathematical and physical modelling of fluid mechanics develops models, methods, and software for analysis of fluid flow, instability analysis, direct numerical modelling and semi-empirical models of turbulence, as well as experimental research and verification of these models and their applications in technological fluid dynamics, microgravity fluid mechanics, geophysics, and a number of engineering problems. This paper presents an overview of the results in microgravity fluid dynamics research during the last two years. Nonlinear problems of weakly compressible and compressible fluid flows are discussed.

Polezhaev, V. I.

1996-01-01

418

Review of the Mechanical Engineering Challenges associated with the SNS* Power Ramp Up  

Microsoft Academic Search

Since commissioning of the SNS in April 2006 the beam power has been steadily increasing towards the design intensity of 1.4 MW. Several areas of the accelerator have been shown to require modifications, upgrades or new designs of mechanical equipment to support the power ramp schedule. This paper presents mechanical engineering design work implemented since initial commissioning along with a

Graeme R Murdoch; Mike Holding; Peter Ladd; Kerry G Potter; Roseberry Jr. R Tom

2008-01-01

419

General Mechanical Repair. Minor Automotive Maintenance, Small Engine [Repair, and] Welding: Competency Test Package.  

ERIC Educational Resources Information Center

This document contains the competency test package for three sections of a general mechanical repair course: minor automotive maintenance, small engine mechanics, and welding. Following a list of the common essential elements for trade and industrial education, competency tests for the three sections are provided. Each test includes unit name,…

Hamlin, Larry

420

Review of the Mechanical Engineering Challenges associated with the SNS* Power Ramp Up  

SciTech Connect

Since commissioning of the SNS in April 2006 the beam power has been steadily increasing towards the design intensity of 1.4 MW. Several areas of the accelerator have been shown to require modifications, upgrades or new designs of mechanical equipment to support the power ramp schedule. This paper presents mechanical engineering design work implemented since initial commissioning along with a review of current projects and discussion of mechanical engineering issues being addressed that are a direct result of design decisions made early in the project.

Murdoch, Graeme R [ORNL; Holding, Mike [ORNL; Ladd, Peter [ORNL; Potter, Kerry G [ORNL; Roseberry, Jr., R Tom [ORNL

2008-01-01

421

Stirling engine power control and motion conversion mechanism  

DOEpatents

A motion conversion device for converting between the reciprocating motion of the pistons in a Stirling engine and the rotating motion of its output shaft, and for changing the stroke and phase of the pistons, includes a lever pivoted at one end and having a cam follower at the other end. The piston rod engages the lever intermediate its ends and the cam follower engages a cam keyed to the output shaft. The lever pivot can be moved to change the length of the moment arm defined between the cam follower and the piston rod the change the piston stroke and force exerted on the cam, and the levers can be moved in opposite directions to change the phase between pistons.

Marks, David T. (Birmingham, MI)

1983-01-01

422

Stable Small Animal Mechanical Ventilation for Dynamic Lung Imaging to Support Computational Fluid Dynamics Models  

SciTech Connect

Pulmonary computational fluid dynamics models require 3D images to be acquired over multiple points in the dynamic breathing cycle, with no breath holds or changes in ventilatory mechanics. With small animals, these requirements result in long imaging times ({approx}90 minutes), over which lung mechanics, such as compliance, can gradually change if not carefully monitored and controlled. These changes, caused by derecruitment of parenchymal tissue, are manifested as an upward drift in peak inspiratory pressure or by changes in the pressure waveform and/or lung volume over the course of the experiment. We demonstrate highly repeatable mechanical ventilation in anesthetized rats over a long duration for pulmonary CT imaging throughout the dynamic breathing cycle. We describe significant updates to a basic commercial ventilator that was acquired for these experiments. Key to achieving consistent results was the implementation of periodic deep breaths, or sighs, of extended duration to maintain lung recruitment. In addition, continuous monitoring of breath-to-breath pressure and volume waveforms and long-term trends in peak inspiratory pressure and flow provide diagnostics of changes in breathing mechanics.

Jacob, Rick E.; Lamm, W. J.

2011-11-08

423

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines  

Microsoft Academic Search

This paper describes the application of high performance computing to accelerate the development of hypergolic propulsion systems for tactical missiles. Computational fluid dynamics is employed to model the chemically reacting flow within a systempsilas combustion chamber, and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments from the past year are presented and discussed.

Michael J. Nusca; Chiung-Chu Chen; Michael J. McQuaid

2008-01-01

424

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines  

Microsoft Academic Search

This paper describes the application of high performance computing to accelerate the development of hypergolic propulsion systems for tactical missiles. Computational fluid dynamics is employed to model the chemically reacting flow within a system's combustion chamber, and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments from the past year are presented and discussed.

Michael J. Nusca; Chiung-Chu Chen; Michael J. McQuaid

2007-01-01

425

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines  

Microsoft Academic Search

This paper describes the development and application of high performance computing for the acceleration of tactical missile hypergolic propulsion system development. Computational fluid dynamics is employed to model the chemically reacting flow within a system's combustion chamber, and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments from the past year are presented and discussed

Michael J. Nusca; Michael J. McQuaid

2006-01-01

426

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines  

Microsoft Academic Search

This paper describes the development and application of high performance computing for the acceleration of tactical missile hypergolic propulsion system development. Computational fluid dynamics (CFD) is employed to model the chemically reacting flow within a system?s combustion chamber, and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments from the past year are presented and discussed.

Michael J. Nusca; Michael J. McQuaid

2005-01-01

427

Application of the continuous wavelet transform to science and engineering problems: Fluid dynamics case studies  

Microsoft Academic Search

The continuous wavelet transform is demonstrated to be a versatile tool for the analysis of fluctuation phenomena which exhibit transient or intermittent\\/random frequency content. In particular, the capabilities of the continuous wavelet transform for obtaining quantitative measures of fluctuation characteristics are demonstrated through its application to three fluid dynamics problems which are representative of general problems involving transient dynamic response,

Donald Alfred Jordan Jr.

1998-01-01

428

Relaxation Methods Applied to Engineering Problems. XII. Fluid Motions Characterized by 'Free' Stream-Lines  

Microsoft Academic Search

This paper deals with problems which are like the percolation problems of Part VII (Shaw & Southwell 1941) in that a double condition, imposed at a boundary initially unknown, replaces the more usual single condition at a specified boundary. They relate to 'free' stream-lines in the hydrodynamical theory of inviscid fluids. For plane two-dimensional (steady) motions, the device of conformal

R. V. Southwell; Gillian Vaisey

1946-01-01

429

Mechanism of fluid-induced micro-earthquakes near Landau, Upper Rhine Graben, Germany  

NASA Astrophysics Data System (ADS)

Since 2006 micro-earthquakes (ML < 2.8) occur in the area of Landau, a town in the Central Upper Rhine Graben, Germany. These events are related to the injection of fluids into 2,500-3,500 m deep boreholes. Within the MAGS project (www.mags-projekt.de) the seismicity was monitored with a dense network of recording stations and the seismic waveforms were analysed in details. The complex 3-D geological structure complicates the application of 1-D methods, and tests were done using 3-D seismic waveform modelling with the SOFI3D FD method. About 1,300 events were detected with cross-correlation analyses, although the signal amplitudes are quite low and the noise level in the study area is high. A part of the events was localised with an absolute (HYPOSAT) and relative (hypoDD) method. The determined hypocentres are aligned along discrete elongated structures which are interpreted as preferred rupture zones. Fault plane solutions with FOCMEC indicate normal and strike-slip shear mechanisms. The preferred strike of the faults is NNW-SSE to NNE-SSW which is similar to the regional maximum horizontal stress direction (NNW-SSE). The study of seismic shear wave anisotropy indicates a fast polarisation direction which is also in NNW-SSE direction. This azimuth-dependent anisotropy as well as the other seismological and tectonic models are consistent with fluid-filled faults oriented in NNW-SSE direction which are (re-)activated by fluid injection at depth.

Ritter, Joachim; Frietsch, Michael; Gassner, Laura; Groos, Joern; Grund, Michael; Zeiss, Jens

2014-05-01

430

Role of the superposition principle for enhancing the efficiency of the quantum-mechanical Carnot engine.  

PubMed

The role of the superposition principle is discussed for the quantum-mechanical Carnot engine introduced by Bender, Brody, and Meister [J. Phys. A 33, 4427 (2000)]. It is shown that the efficiency of the engine can be enhanced by the superposition of quantum states. A finite-time process is also discussed and the condition of the maximum power output is presented. Interestingly, the efficiency at the maximum power is lower than that without superposition. PMID:22400509

Abe, Sumiyoshi; Okuyama, Shinji

2012-01-01

431

Inlet protein aggregation: a new mechanism for lubricating film formation with model synovial fluids  

PubMed Central

This paper reports a fundamental study of lubricant film formation with model synovial fluid components (proteins) and bovine serum (BS). The objective was to investigate the role of proteins in the lubrication process. Film thickness was measured by optical interferometry in a ball-on-disc device (mean speed range of 2–60?mm/s). A commercial cobalt–chromium (CoCrMo) metal femoral head was used as the stationary component. The results for BS showed complex time-dependent behaviour, which was not representative of a simple fluid. After a few minutes sliding BS formed a thin adherent film of 10–20?nm, which was attributed to protein absorbance at the surface. This layer was augmented by a hydrodynamic film, which often increased at slow speeds. At the end of the test deposited surface layers of 20–50?nm were measured. Imaging of the contact showed that at slow speeds an apparent ‘phase boundary’ formed in the inlet just in front of the Hertzian zone. This was associated with the formation of a reservoir of high-viscosity material that periodically moved through the contact forming a much thicker film. The study shows that proteins play an important role in the film-forming process and current lubrication models do not capture these mechanisms.

Fan, J; Myant, C W; Underwood, R; Cann, P M; Hart, A

2011-01-01

432

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

PubMed

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-? model, (2) the RNG k-? model, (3) the realizable k-? model, (4) the standard k-? model, (5) the SST k-? 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-? and the standard k-? 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. PMID:21216428

Wu, Binxin

2011-02-01

433

Skylab fluid mechanics simulations: Oscillation, rotation, collision and coalescence of water droplets under low-gravity environment  

NASA Technical Reports Server (NTRS)

Skylab 4 crew members performed a series of demonstrations showing the oscillations, rotations, as well as collision coalescence of water droplets which simulate various physical models of fluids under low gravity environment. The results from Skylab demonstrations provide information and illustrate the potential of an orbiting space-oriented research laboratory for the study of more sophisticated fluid mechanic experiments. Experiments and results are discussed.

Vaughan, O. H., Jr.; Hung, R. J.

1975-01-01

434

Valve operating mechanism for internal combustion and like-valved engines  

SciTech Connect

A valve operating mechanism is described for an internal combustion engine comprising of a piezo-electric actuating device arranged to drive an engine valve opening directly into a combustion chamber by the expansion of the piezo-electric actuating device such that expansion of the piezo-electric actuating device provides the sole motive force for opening the valve and control means to control an electrical feed to the piezo-electric actuating device in accordance with parameters of engine operation fed to it.

Moloney, P.J.

1986-06-10

435

Computational fluid dynamics simulation of the air/suppressant flow in an uncluttered F18 engine nacelle  

SciTech Connect

For the purposes of designing improved Halon-alternative fire suppression strategies for aircraft applications, Computational Fluid Dynamics (CFD) simulations of the air flow, suppressant transport, and air-suppressant mixing within an uncluttered F18 engine nacelle were performed. The release of inert gases from a Solid Propellant Gas Generator (SPGG) was analyzed at two different injection locations in order to understand the effect of injection position on the flow patterns and the mixing of air and suppression agent. An uncluttered engine nacelle was simulated to provide insight into the global flow features as well as to promote comparisons with previous nacelle fire tests and recent water tunnel tests which included little or no clutter. Oxygen concentration levels, fuel/air residence times that would exist if a small fuel leak were present, velocity contours, and streamline patterns are presented inside the engine nacelle. The numerical results show the influence of the gent release location on regions of potential flame extinction due to oxygen inerting and high flame strain. The occurrence of inflow through the exhaust ducts on the aft end of the nacelle is also predicted. As expected, the predicted oxygen concentration levels were consistently higher than the measured levels since a fire was not modeled in this analysis. Despite differences in the conditions of these simulations and the experiments, good agreement was obtained between the CFD predictions and the experimental measurements.

Lopez, A.R.; Gritzo, L.A.; Hassan, B.

1997-06-01

436

Fluid mechanics principle about manufacture technology of micro lens generated on needing positions  

NASA Astrophysics Data System (ADS)

In this paper a new technology of optic micro lens generated on needing positions is proposed. It is formed directly on positions where the mocro-lens is mounted. The technique is easy, quick and cheap. It has application prospects in astronavigation, military affairs, biology, chemistry and civil affair. In this paper fluid mechanics principle about the optic micro lens generated on needing positions is researched. A surface equation set of optic glue drip, which spreads on horizontal plane under surface tention, is given. The equation set reflect relations between coordinates of the surface curve. A numerical calculation method of the equation set is proposed. Some shape curves and curvature radius curves for different character parameters of the glu drip are given. Influences on shape of the micro lens through mixing nanometer quartz powder in the glue drip and milling the glass are discussed.

Wu, Jian; Yang, Yang; Yu, Kuanxin; Chen, Tao; Li, Yinghui; Wang, Chunyan

2012-11-01

437

Computational fluid dynamics insights in the design of mechanical heart valves.  

PubMed

Computational fluid dynamics (CFD) analysis can provide detailed, three-dimensional predictions of blood flow through mechanical heart valves, which can help to optimize valve hemodynamics and reduce the potential for blood clotting. A number of CFD studies, considering both forward and retrograde flow through valves, have been published. In this paper, a geometrically accurate CFD model capable of predicting the three-dimensional, time-dependent flow through an open ATS bileaflet valve is presented. A detailed picture of the blood flow is obtained, including small-scale flow features in the pivot regions. Results from the model can also be used to investigate the opening position of the ATS valve leaflets. Future work will be aimed toward improved models that provide valuable design information while minimizing the development time and computational resources required. Such practical CFD models clearly have the potential to reduce the costs, time scales, and risks associated with development of new heart valve designs. PMID:12081519

Kelly, Stuart G D

2002-07-01

438

Fluid mechanics simulation of fog formation associated with polluted atmosphere produced by energy related fuel combustion  

NASA Technical Reports Server (NTRS)

It is noted that large quantities of atmospheric aerosols with composition SO4(-2), NO3(-1), and NH4(+1) have been detected in highly industrialized areas. Most aerosol products come from energy-related fuel combustion. Fluid mechanics simulation of both microphysical and macrophysical processes is considered in studying the time dependent evolution of the saturation spectra of condensation nuclei associated with polluted and clean atmospheres during the time periods of advection fog formation. The results demonstrate that the condensation nuclei associated with a polluted atmosphere provide more favorable conditions than condensation nuclei associated with a clean atmosphere to produce dense advection fog, and that attaining a certain degree of supersaturation is not necessarily required for the formation of advection fog having condensation nuclei associated with a polluted atmosphere.

Hung, R. J.; Liaw, G. S.

1980-01-01

439

Fluid dynamic mechanisms and interactions within separated flows and their effects on missile aerodynamics  

NASA Astrophysics Data System (ADS)

Significant data and detailed results of a joint research effort investigating the fluid dynamic mechanisms and interactions within separated flows are presented. The results were obtained through analytical, experimental, and computational investigations of base flow related configurations. The research objectives focus on understanding the component mechanisms and interactions which establish and maintain separated flow regions. Flow models and theoretical analyses were developed to describe the base flowfield. The research approach has been to conduct extensive small-scale experiments on base flow configurations and to analyze these flows by component models and finite-difference techniques. The modeling of base flows of missiles (both powered and unpowered) for transonic and supersonic freestreams has been successful by component models. Research on plume effects and plume modeling indicated the need to match initial plume slope and plume surface curvature for valid wind tunnel simulation of an actual rocket plume. The assembly and development of a state-of-the-art laser Doppler velocimeter (LDV) system for experiments with two-dimensional small-scale models has been completed and detailed velocity and turbulence measurements are underway. The LDV experiments include the entire range of base flowfield mechanisms - shear layer development, recompression/reattachment, shock-induced separation, and plume-induced separation.

Addy, A. L.; Chow, W. L.; Korst, H. H.; White, R. A.

1983-05-01

440

Interstitial fluid flow in canaliculi as a mechanical stimulus for cancellous bone remodeling: in silico validation.  

PubMed

Cancellous bone has a dynamic 3-dimensional architecture of trabeculae, the arrangement of which is continually reorganized via bone remodeling to adapt to the mechanical environment. Osteocytes are currently believed to be the major mechanosensory cells and to regulate osteoclastic bone resorption and osteoblastic bone formation in response to mechanical stimuli. We previously developed a mathematical model of trabecular bone remodeling incorporating the possible mechanisms of cellular mechanosensing and intercellular communication in which we assumed that interstitial fluid flow activates the osteocytes to regulate bone remodeling