Science.gov

Sample records for actuating fluid pressure

  1. Cellular Pressure-Actuated Joint

    NASA Technical Reports Server (NTRS)

    McGuire, John R.

    2003-01-01

    A modification of a pressure-actuated joint has been proposed to improve its pressure actuation in such a manner as to reduce the potential for leakage of the pressurizing fluid. The specific joint for which the modification is proposed is a field joint in a reusable solid-fuel rocket motor (RSRM), in which the pressurizing fluid is a mixture of hot combustion gases. The proposed modification could also be applicable to other pressure-actuated joints of similar configuration.

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

    DOEpatents

    Keyster, Eric S.; Merchant, Jack A.

    2002-01-01

    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.

  3. High-pressure microhydraulic actuator

    DOEpatents

    Mosier, Bruce P [San Francisco, CA; Crocker, Robert W [Fremont, CA; Patel, Kamlesh D [Dublin, CA

    2008-06-10

    Electrokinetic ("EK") pumps convert electric to mechanical work when an electric field exerts a body force on ions in the Debye layer of a fluid in a packed bed, which then viscously drags the fluid. Porous silica and polymer monoliths (2.5-mm O.D., and 6-mm to 10-mm length) having a narrow pore size distribution have been developed that are capable of large pressure gradients (250-500 psi/mm) when large electric fields (1000-1500 V/cm) are applied. Flowrates up to 200 .mu.L/min and delivery pressures up to 1200 psi have been demonstrated. Forces up to 5 lb-force at 0.5 mm/s (12 mW) have been demonstrated with a battery-powered DC-DC converter. Hydraulic power of 17 mW (900 psi@ 180 uL/min) has been demonstrated with wall-powered high voltage supplies. The force and stroke delivered by an actuator utilizing an EK pump are shown to exceed the output of solenoids, stepper motors, and DC motors of similar size, despite the low thermodynamic efficiency.

  4. Laser microfluidics: fluid actuation by light

    NASA Astrophysics Data System (ADS)

    Delville, Jean-Pierre; de Saint Vincent, Matthieu Robert; Schroll, Robert D.; Chraïbi, Hamza; Issenmann, Bruno; Wunenburger, Régis; Lasseux, Didier; Zhang, Wendy W.; Brasselet, Etienne

    2009-03-01

    The development of microfluidic devices is still hindered by the lack of robust fundamental building blocks that constitute any fluidic system. An attractive approach is optical actuation because light field interaction is contactless and dynamically reconfigurable, and solutions have been anticipated through the use of optical forces to manipulate microparticles in flows. Following the concept of an 'optical chip' advanced from the optical actuation of suspensions, we propose in this survey new routes to extend this concept to microfluidic two-phase flows. First, we investigate the destabilization of fluid interfaces by the optical radiation pressure and the formation of liquid jets. We analyze the droplet shedding from the jet tip and the continuous transport in laser-sustained liquid channels. In the second part, we investigate a dissipative light-flow interaction mechanism consisting in heating locally two immiscible fluids to produce thermocapillary stresses along their interface. This opto-capillary coupling is implemented in adequate microchannel geometries to manipulate two-phase flows and propose a contactless optical toolbox including valves, droplet sorters and switches, droplet dividers or droplet mergers. Finally, we discuss radiation pressure and opto-capillary effects in the context of the 'optical chip' where flows, channels and operating functions would all be performed optically on the same device.

  5. Pressure-actuated joint system

    NASA Technical Reports Server (NTRS)

    McGuire, John R. (Inventor)

    2004-01-01

    A pressure vessel is provided that includes first and second case segments mated with one another. First and second annular rubber layers are disposed inboard of the first and second case segments, respectively. The second annular rubber layer has a slot extending from the radial inner surface across a portion of its thickness to define a main body portion and a flexible portion. The flexible portion has an interfacing surface portion abutting against an interfacing surface portion of the first annular rubber layer to follow movement of the first annular rubber layer during operation of the pressure vessel. The slot receives pressurized gas and establishes a pressure-actuated joint between the interfacing surface portions. At least one of the interfacing surface portions has a plurality of enclosed and sealed recesses formed therein.

  6. A MEMS Electrochemical Bellows Actuator for Fluid Metering Applications

    PubMed Central

    Sheybani, Roya; Gensler, Heidi; Meng, Ellis

    2013-01-01

    We present a high efficiency wireless MEMS electrochemical bellows actuator capable of rapid and repeatable delivery of boluses for fluid metering and drug delivery applications. Nafion®-coated Pt electrodes were combined with Parylene bellows filled with DI water to form the electrolysis-based actuator. The performance of actuators with several bellows configurations was compared for a range of applied currents (1-10 mA). Up to 75 boluses were delivered with an average pumping flow rate of 114.40 ± 1.63 μL/min. Recombination of gases into water, an important factor in repeatable and reliable actuation, was studied for uncoated and Nafion®-coated actuators. Real-time pressure measurements were conducted and the effects of temperature, physiological back pressure, and drug viscosity on delivery performance were investigated. Lastly, we present wireless powering of the actuator using a class D inductive powering system that allowed for repeatable delivery with less than 2% variation in flow rate values. PMID:22833156

  7. A MEMS electrochemical bellows actuator for fluid metering applications.

    PubMed

    Sheybani, Roya; Gensler, Heidi; Meng, Ellis

    2013-02-01

    We present a high efficiency wireless MEMS electrochemical bellows actuator capable of rapid and repeatable delivery of boluses for fluid metering and drug delivery applications. Nafion®-coated Pt electrodes were combined with Parylene bellows filled with DI water to form the electrolysis-based actuator. The performance of actuators with several bellows configurations was compared for a range of applied currents (1-10 mA). Up to 75 boluses were delivered with an average pumping flow rate of 114.40 ± 1.63 μL/min. Recombination of gases into water, an important factor in repeatable and reliable actuation, was studied for uncoated and Nafion®-coated actuators. Real-time pressure measurements were conducted and the effects of temperature, physiological back pressure, and drug viscosity on delivery performance were investigated. Lastly, we present wireless powering of the actuator using a class D inductive powering system that allowed for repeatable delivery with less than 2 % variation in flow rate values. PMID:22833156

  8. Pressure-actuated cellular structures.

    PubMed

    Pagitz, M; Lamacchia, E; Hol, J M A M

    2012-03-01

    Shape changing structures will play an important role in future engineering designs since rigid structures are usually only optimal for a small range of service conditions. Hence, a concept for reliable and energy-efficient morphing structures that possess a large strength to self-weight ratio would be widely applicable. We propose a novel concept for morphing structures that is inspired by the nastic movement of plants. The idea is to connect prismatic cells with tailored pentagonal and/or hexagonal cross sections such that the resulting cellular structure morphs into given target shapes for certain cell pressures. An efficient algorithm for computing equilibrium shapes as well as cross-sectional geometries is presented. The potential of this novel concept is demonstrated by several examples that range from a flagellum like propulsion device to a morphing aircraft wing. PMID:22278936

  9. Extreme pressure fluid sample transfer pump

    DOEpatents

    Halverson, Justin E.; Bowman, Wilfred W.

    1990-01-01

    A transfer pump for samples of fluids at very low or very high pressures comprising a cylinder having a piston sealed with an O-ring, the piston defining forward and back chambers, an inlet and exit port and valve arrangement for the fluid to enter and leave the forward chamber, and a port and valve arrangement in the back chamber for adjusting the pressure across the piston so that the pressure differential across the piston is essentially zero and approximately equal to the pressure of the fluid so that the O-ring seals against leakage of the fluid and the piston can be easily moved, regardless of the pressure of the fluid. The piston may be actuated by a means external to the cylinder with a piston rod extending through a hole in the cylinder sealed with a bellows attached to the piston head and the interior of the back chamber.

  10. Electrochemically actuated mercury pump for fluid flow and delivery

    NASA Technical Reports Server (NTRS)

    Ni, J.; Zhong, C. J.; Coldiron, S. J.; Porter, M. D.

    2001-01-01

    This paper describes the development of a prototype pumping system with the potential for incorporation into miniaturized, fluid-based analytical instruments. The approach exploits the well-established electrocapillarity phenomena at a mercury/electrolyte interface as the mechanism for pump actuation. That is, electrochemically induced changes in the surface tension of mercury result in the pistonlike movement of a mercury column confined within a capillary. We present herein theoretical and experimental assessments of pump performance. The design and construction of the pump are detailed, and the potential attributes of this design, including the generated pumping pressure, flow rate, and power consumption, are discussed. The possible miniaturization of the pump for use as a field-deployable, fluid-delivery device is also briefly examined.

  11. Pneumatically-actuated artificial cilia array for biomimetic fluid propulsion.

    PubMed

    Gorissen, Benjamin; de Volder, Michaël; Reynaerts, Dominiek

    2015-11-21

    Arrays of beating cilia emerged in nature as one of the most efficient propulsion mechanisms at a small scale, and are omnipresent in microorganisms. Previous attempts at mimicking these systems have foundered against the complexity of fabricating small-scale cilia exhibiting complex beating motions. In this paper, we propose for the first time arrays of pneumatically-actuated artificial cilia that are able to address some of these issues. These artificial cilia arrays consist of six highly flexible silicone rubber actuators with a diameter of 1 mm and a length of 8 mm that can be actuated independently from each other. In an experimental setup, the effects of the driving frequency, phase difference and duty cycle on the net flow in a closed-loop channel have been studied. Net fluid speeds of up to 19 mm s(-1) have been measured. Further, it is possible to invert the flow direction by simply changing the driving frequency or by changing the duty cycle of the driving block pulse pressure wave without changing the bending direction of the cilia. Using PIV measurements, we corroborate for the first time existing mathematical models of cilia arrays to measurements on prototypes. PMID:26439855

  12. Fluid logic control circuit operates nutator actuator motor

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Fluid logic control circuit operates a pneumatic nutator actuator motor. It has no moving parts and consists of connected fluid interaction devices. The operation of this circuit demonstrates the ability of fluid interaction devices to operate in a complex combination of series and parallel logic sequence.

  13. Light-driven actuation of fluids at microscale

    NASA Astrophysics Data System (ADS)

    Deshpande, Mandar; Saggere, Laxman

    2004-07-01

    This paper discusses the prospects of light-driven actuation particularly for actuating fluids at micro-scale for potential use in a novel retinal prosthesis and other drug delivery applications. The prosthesis is conceived to be comprised of an array of light-driven microfluidic-dispenser units, devices that eject very small amounts of fluids on the order of 1 picoliter per second in response to incident light energy in the range of 0.1-1 mW/cm2. A light-driven actuator, whose size will ideally be smaller than about 100 micrometers in diameter, independently powers each dispenser unit. Towards this application, various approaches for transducing light energy for actuation of fluids are explored. These approaches encompass both direct transduction of light energy to mechanical actuation of fluid and indirect transduction through an intermediary form of energy, for instance, light energy to thermal or electrical energy followed by mechanical actuation of fluid. Various existing schemes for such transduction are reviewed comprehensively and discussed from the standpoint of the application requirements. Direct transduction schemes exploiting recent developments in optically sensitive materials that exhibit direct strain upon illumination, particularly the photostrictive PLZT (Lanthanum modified Lead Zirconate Titanate), are studied for the current application, and results of some preliminary experiments involving measurement of photovoltage, photocurrent, and photo-induced strain in the meso-scale samples of the PLZT material are presented.

  14. Pressurized honeycombs as soft-actuators: a theoretical study

    PubMed Central

    Guiducci, Lorenzo; Fratzl, Peter; Bréchet, Yves J. M.; Dunlop, John W. C.

    2014-01-01

    The seed capsule of Delosperma nakurense is a remarkable example of a natural hygromorph, which unfolds its protecting valves upon wetting to expose its seeds. The beautiful mechanism responsible for this motion is generated by a specialized organ based on an anisotropic cellular tissue filled with a highly swelling material. Inspired by this system, we study the mechanics of a diamond honeycomb internally pressurized by a fluid phase. Numerical homogenization by means of iterative finite-element (FE) simulations is adapted to the case of cellular materials filled with a variable pressure fluid phase. Like its biological counterpart, it is shown that the material architecture controls and guides the otherwise unspecific isotropic expansion of the fluid. Deformations up to twice the original dimensions can be achieved by simply setting the value of input pressure. In turn, these deformations cause a marked change of the honeycomb geometry and hence promote a stiffening of the material along the weak direction. To understand the mechanism further, we also developed a micromechanical model based on the Born model for crystal elasticity to find an explicit relation between honeycomb geometry, swelling eigenstrains and elastic properties. The micromechanical model is in good qualitative agreement with the FE simulations. Moreover, we also provide the force-stroke characteristics of a soft actuator based on the pressurized anisotropic honeycomb and show how the internal pressure has a nonlinear effect which can result in negative values of the in-plane Poisson's ratio. As nature shows in the case of the D. nakurense seed capsule, cellular materials can be used not only as low-weight structural materials, but also as simple but convenient actuating materials. PMID:24966238

  15. Design and development of magnetorheological fluid-based passive actuator.

    PubMed

    Shokrollahi, Elnaz; Price, Karl; Drake, James M; Goldenberg, Andrew A

    2015-08-01

    We present the design and experimental validation of a magnetorheological (MR) fluid-based passive actuator for tele-robotic bone biopsy procedures. With Finite Element Method Magnet (FEMM) software, the required uniform magnetic field circuit design was simulated. An 1100 turn 24 AWG copper wire coil wrapped around a magnetic core was used to create a magnetic field. The field strength was measured with a Hall effect sensor, and compared to the simulation. The maximum magnetic field flux produced by a constant current of 1.4 A was 0.2 T, similar to the simulation results. A series of quasi-static experiments were conducted to characterize the forces generated by the MR fluid-based actuator under various currents up to 12 N. An analytical model was developed to validate the measurements from the passive actuator. PMID:26737387

  16. Active control of static pressure drop caused by hydraulic servo-actuator engage

    SciTech Connect

    Janlovic, J.

    1994-12-31

    Pressure drop caused by propagation of expansion waves in the source pipeline of fast high cyclic hydraulic actuator produces possible anomalies in its function. To prevent pressure drop it is possible to minimize wave effects by active control of actuator servo-valve throttle leakage. In the paper is presented synthesis of possible discrete active control of hydraulic actuator and its servo-valve for prevention expansion wave pressure drop. Control synthesis is based on static pressure increasing with decreasing of fluid flow velocity, which can be realized by lower throttle leakage. Some of the effects of assumed control are shown on corresponding diagrams of control valve throttle motion, piston displacement and its corresponding linear velocity.

  17. Modeling fluid structure interaction with shape memory alloy actuated morphing aerostructures

    NASA Astrophysics Data System (ADS)

    Oehler, Stephen D.; Hartl, Darren J.; Turner, Travis L.; Lagoudas, Dimitris C.

    2012-04-01

    The development of efficient and accurate analysis techniques for morphing aerostructures incorporating shape memory alloys (SMAs) continues to garner attention. These active materials have a high actuation energy density, making them an ideal replacement for conventional actuation mechanisms in morphing structures. However, SMA components are often exposed to the same highly variable environments experienced by the aeroelastic assemblies into which they are incorporated. This is motivating design engineers to consider modeling fluidstructure interaction for prescribing dynamic, solution-dependent boundary conditions. This work presents a computational study of a particular morphing aerostructure with embedded, thermally actuating SMA ribbons and demonstrates the effective use of fluid-structure interaction modeling. A cosimulation analysis is utilized to determine the surface deflections and stress distributions of an example aerostructure with embedded SMA ribbons using the Abaqus Finite Element Analysis (FEA) software suite, combined with an Abaqus Computational Fluid Dynamics (CFD) processor. The global FEA solver utilizes a robust user-defined material subroutine which contains an accurate three-dimensional SMA constitutive model. Variations in the ambient fluid environment are computed using the CFD solver, and fluid pressure is mapped into surface distributed loads. Results from the analysis are qualitatively validated with independently obtained data from representative flow tests previously conducted on a physical prototype of the same aerostructure.

  18. Holistic design and implementation of pressure actuated cellular structures

    NASA Astrophysics Data System (ADS)

    Gramüller, B.; Köke, H.; Hühne, C.

    2015-12-01

    Providing the possibility to develop energy-efficient, lightweight adaptive components, pressure-actuated cellular structures (PACS) are primarily conceived for aeronautics applications. The realization of shape-variable flaps and even airfoils provides the potential to safe weight, increase aerodynamic efficiency and enhance agility. The herein presented holistic design process points out and describes the necessary steps for designing a real-life PACS structure, from the computation of truss geometry to the manufacturing and assembly. The already published methods for the form finding of PACS are adjusted and extended for the exemplary application of a variable-camber wing. The transfer of the form-finding truss model to a cross-sectional design is discussed. The end cap and sealing concept is described together with the implementation of the integral fluid flow. Conceptual limitations due to the manufacturing and assembly processes are discussed. The method’s efficiency is evaluated by finite element method. In order to verify the underlying methods and summarize the presented work a modular real-life demonstrator is experimentally characterized and validates the numerical investigations.

  19. Fluid pressure balanced seal

    NASA Technical Reports Server (NTRS)

    Marsh, H. W. (Inventor)

    1966-01-01

    A seal which increases in effectiveness with increasing pressure is presented. The seal's functional capability throughout both static and dynamic operation makes it particularly useful for sealing ball valve ports. Other features of the seal include the ability to seal two opposed surfaces simultaneously, tolerance of small misalignments, tolerance of wide temperature ranges, ability to maintain positive sealing contact under conditions of internal or external pressurization, and ability to conform to slight irregularities in seal or surface contours.

  20. Development of a magneto-rheological fluid based hybrid actuation system

    NASA Astrophysics Data System (ADS)

    John, Shaju

    A hybrid hydraulic actuation system is proposed as an active pitch link for rotorcraft applications. Such an active pitch link can be used to implement Individual Blade Control (IBC) techniques for vibration and noise reduction, in addition to providing primary control for the helicopter. Conventional technologies like electric motors and hydraulic actuators have major disadvantages when it come to applications on a rotating environment. Centralized hydraulic system require the use of mechanically complex hydraulic slip rings and electric motors have high precision mechanical moving parts that make them unattractive in application with high centrifugal load. The high energy density of smart materials can be used to design hydraulic actuators in a compact package. MagnetoRheological (MR) fluids can be used as the working fluid in such a hybrid hydraulic actuation system to implement a valving system with no moving parts. Thus, such an actuation system can be theoretically well-suited for application in a rotating environment. To develop an actuation system based on an active material stack and MR fluidic valves, a fundamental understanding of the hydraulic circuit is essential. In order to address this issue, a theoretical model was developed to understand the effect of pumping chamber geometry on the pressure losses in the pumping chamber. Three dimensional analytical models were developed for steady and unsteady flow and the results were correlated to results obtained from Computation Fluid Dynamic simulation of fluid flow inside the pumping chamber. Fundamental understanding regarding the pressure losses in a pumping chamber are obtained from the modeling process. Vortices that form in the pumping chamber (during intake) and the discharge tube (during discharge) are identified as a major cause of pressure loss in the chamber. The role of vortices during dynamic operation is also captured through a frequency domain model. Extensive experimental studies were

  1. Analysis on oscillating actuator frequency influence of the fluid flow characterization for 2D contractile water jet thruster

    NASA Astrophysics Data System (ADS)

    Shaari, M. F.; Abu Bakar, H.; Nordin, N.; Saw, S. K.; Samad, Z.

    2013-12-01

    Contractile body is an alternative mechanism instead of rotating blade propeller to generate water jet for locomotion. The oscillating motion of the actuator at different frequencies varies the pressure and volume of the pressure chamber in time to draw in and jet out the water at a certain mass flow rate. The aim of this research was to analyze the influence of the actuating frequency of the fluid flow in the pressure chamber of the thruster during this inflation-deflation process. A 70mm × 70mm × 18mm (L × W × T) 2D water jet thruster was fabricated for this purpose. The contractile function was driven using two lateral pneumatic actuators where the fluid flow analysis was focused on the X-Y plane vector. Observation was carried out using a video camera and Matlab image measurement technique to determine the volume of the flowing mass. The result demonstrated that the greater actuating frequency decreases the fluid flow rate and the Reynolds number. This observation shows that the higher frequency would give a higher mass flow rate during water jet generation.

  2. A description of model 3B of the multipurpose ventricular actuating system. [providing controlled driving pressures

    NASA Technical Reports Server (NTRS)

    Webb, J. A., Jr.

    1974-01-01

    The multipurpose ventricular actuating system is a pneumatic signal generating device that provides controlled driving pressures for actuating pulsatile blood pumps. Overall system capabilities, the timing circuitry, and calibration instruction are included.

  3. Fluid pressure waves trigger earthquakes

    NASA Astrophysics Data System (ADS)

    Mulargia, Francesco; Bizzarri, Andrea

    2015-03-01

    Fluids-essentially meteoric water-are present everywhere in the Earth's crust, occasionally also with pressures higher than hydrostatic due to the tectonic strain imposed on impermeable undrained layers, to the impoundment of artificial lakes or to the forced injections required by oil and gas exploration and production. Experimental evidence suggests that such fluids flow along preferred paths of high diffusivity, provided by rock joints and faults. Studying the coupled poroelastic problem, we find that such flow is ruled by a nonlinear partial differential equation amenable to a Barenblatt-type solution, implying that it takes place in form of solitary pressure waves propagating at a velocity which decreases with time as v ∝ t [1/(n - 1) - 1] with n ≳ 7. According to Tresca-Von Mises criterion, these waves appear to play a major role in earthquake triggering, being also capable to account for aftershock delay without any further assumption. The measure of stress and fluid pressure inside active faults may therefore provide direct information about fault potential instability.

  4. Pressurized-fluid-operated engine

    SciTech Connect

    Holleyman, J.E.

    1990-01-30

    This patent describes a pressurized-fluid-operated reciprocating engine for providing output power by use of a pressurized gas that expands within the engine without combustion. It comprises: an engine block having a plurality of cylinders within which respective pistons are reciprocatable to provide a rotary power output; gas inlet means connected with the engine block for introducing a pressurized gas into the respective cylinders in a predetermined, timed relationship to provide a smooth power output from the engine; gas outlet means connected with the engine block for conveying exhaust gas from the respective cylinders after the gas expanded to move the pistons within the cylinders; and recirculation means extending between the inlet means and the outlet means for recirculation a predetermined quantity of exhaust gas. The recirculation means including ejector means for drawing exhaust gas into the recirculation means.

  5. New Actuators Using ER Fluid and Their Applications to Force Display Devices in Virtual Reality and Medical Treatments

    NASA Astrophysics Data System (ADS)

    Furusho, Junji; Sakaguchi, Masamichi

    We developed ER actuators with low inertia. ER actuator is a torque-controllable clutch which uses an electrorheological fluid. It is shown that this actuator has good properties for force display device, physical therapy treatment, etc. We developed new force display devices for virtual reality which use ER actuators.

  6. Fluid Power Multi-actuator Circuit Board with Microcomputer Control Option.

    ERIC Educational Resources Information Center

    McKechnie, R. E.; Vickers, G. W.

    1981-01-01

    Describes a portable fluid power engineering laboratory and class demonstration apparatus designed to enable students to design, build, and test multi-actuator circuits. Features a variety of standard pneumatic values and actuators fitted with quick disconnect couplings. Discusses sequencing circuit boards, microcomputer control, cost, and…

  7. Apparatus for unloading pressurized fluid

    DOEpatents

    Rehberger, Kevin M.

    1994-01-01

    An apparatus for unloading fluid, preferably pressurized gas, from containers in a controlled manner that protects the immediate area from exposure to the container contents. The device consists of an unloading housing, which is enclosed within at least one protective structure, for receiving the dispensed contents of the steel container, and a laser light source, located external to the protective structure, for opening the steel container instantaneously. The neck or stem of the fluid container is placed within the sealed interior environment of the unloading housing. The laser light passes through both the protective structure and the unloading housing to instantaneously pierce a small hole within the stem of the container. Both the protective structure and the unloading housing are specially designed to allow laser light passage without compromising the light's energy level. Also, the unloading housing allows controlled flow of the gas once it has been dispensed from the container. The external light source permits remote operation of the unloading device.

  8. Line Fluid Actuated Valve Development Program. [for application on the space shuttle

    NASA Technical Reports Server (NTRS)

    Lynch, R. A.

    1975-01-01

    The feasibility of a line-fluid actuated valve design for potential application as a propellant-control valve on the space shuttle was examined. Design and analysis studies of two prototype valve units were conducted and demonstrated performance is reported. It was shown that the line-fluid actuated valve concept offers distinct weight and electrical advantages over alternate valve concepts. Summaries of projected performance and design goals are also included.

  9. Smart glove: hand master using magnetorheological fluid actuators

    NASA Astrophysics Data System (ADS)

    Nam, Y. J.; Park, M. K.; Yamane, R.

    2007-12-01

    In this study, a hand master using five miniature magneto-rheological (MR) actuators, which is called 'the smart glove', is introduced. This hand master is intended to display haptic feedback to the fingertip of the human user interacting with any virtual objects in virtual environment. For the smart glove, two effective approaches are proposed: (i) by using the MR actuator which can be considered as a passive actuator, the smart glove is made simple in structure, high in power, low in inertia, safe in interface and stable in haptic feedback, and (ii) with a novel flexible link mechanism designed for the position-force transmission between the fingertips and the actuators, the number of the actuator and the weight of the smart glove can be reduced. These features lead to the improvement in the manipulability and portability of the smart glove. The feasibility of the constructed smart glove is verified through basic performance evaluation.

  10. Competition between pressure effects and airflow influence for the performance of plasma actuators

    SciTech Connect

    Kriegseis, J.; Barckmann, K.; Grundmann, S.; Frey, J.; Tropea, C.

    2014-05-15

    The present work addresses the combined influence of pressure variations and different airflow velocities on the discharge intensity of plasma actuators. Power consumption, plasma length, and discharge capacitance were investigated systematically for varying pressure levels (p = 0.1–1 bar) and airflow velocities (U{sub ∞}=0−100 m/s) to characterize and quantify the favorable and adverse effects on the discharge intensity. In accordance with previous reports, an increasing plasma actuator discharge intensity is observed for decreasing pressure levels. At constant pressure levels, an adverse airflow influence on the electric actuator performance is demonstrated. Despite the improved discharge intensity at lower pressure levels, the seemingly improved performance of the plasma actuators is accompanied with a more pronounced drop of the relative performance. These findings demonstrate the dependency of the (kinematic and thermodynamic) environmental conditions on the electric performance of plasma actuators, which in turn affects the control authority of plasma actuators for flow control applications.

  11. Design of a Magnetostrictive-Hydraulic Actuator Considering Nonlinear System Dynamics and Fluid-Structure Coupling

    NASA Astrophysics Data System (ADS)

    Larson, John Philip

    Smart material electro-hydraulic actuators (EHAs) utilize fluid rectification via one-way check valves to amplify the small, high-frequency vibrations of certain smart materials into large motions of a hydraulic cylinder. Although the concept has been demonstrated in previously, the operating frequency of smart material EHA systems has been limited to a small fraction of the available bandwidth of the driver materials. The focus of this work is to characterize and model the mechanical performance of a magnetostrictive EHA considering key system components: rectification valves, smart material driver, and fluid-system components, leading to an improved actuator design relative to prior work. The one-way valves were modeled using 3-D finite element analysis, and their behavior was characterized experimentally by static and dynamic experimental measurement. Taking into account the effect of the fluid and mechanical conditions applied to the valves within the pump, the dynamic response of the valve was quantified and applied to determine rectification bandwidth of different valve configurations. A novel miniature reed valve, designed for a frequency response above 10~kHz, was fabricated and tested within a magnetostrictive EHA. The nonlinear response of the magnetostrictive driver, including saturation and hysteresis effects, was modeled using the Jiles-Atherton approach to calculate the magnetization and the resulting magnetostriction based on the applied field calculated within the rod from Maxwell's equations. The dynamic pressure response of the fluid system components (pumping chamber, hydraulic cylinder, and connecting passages) was measured over a range of input frequencies. For the magnetostrictive EHA tested, the peak performance frequency was found to be limited by the fluid resonances within the system. A lumped-parameter modeling approach was applied to model the overall behavior of a magnetostrictive EHA, incorporating models for the reed valve response

  12. Efficient pressure-transformer for fluids

    NASA Technical Reports Server (NTRS)

    Morando, J. A.

    1970-01-01

    Fluid transformer utilizes fluid under pressure at one level to drive series of free pistons in positive displacement pump. Pump in turn delivers hydraulic fluid at different pressure level to a load. Transformer is constructed of corrosion resistant materials and is extremely light and compact in relation to capacity.

  13. Apparatus for unloading pressurized fluid

    DOEpatents

    Rehberger, K.M.

    1994-01-04

    An apparatus is described for unloading fluid, preferably pressurized gas, from containers in a controlled manner that protects the immediate area from exposure to the container contents. The device consists of an unloading housing, which is enclosed within at least one protective structure, for receiving the dispensed contents of the steel container, and a laser light source, located external to the protective structure, for opening the steel container instantaneously. The neck or stem of the fluid container is placed within the sealed interior environment of the unloading housing. The laser light passes through both the protective structure and the unloading housing to instantaneously pierce a small hole within the stem of the container. Both the protective structure and the unloading housing are specially designed to allow laser light passage without compromising the light's energy level. Also, the unloading housing allows controlled flow of the gas once it has been dispensed from the container. The external light source permits remote operation of the unloading device. 2 figures.

  14. Shape-variable seals for pressure actuated cellular structures

    NASA Astrophysics Data System (ADS)

    Gramüller, B.; Tempel, A.; Hühne, C.

    2015-09-01

    Sealing concepts that allow a large change of cross-sectional area are investigated. Shape variable seals are indispensable for biologically inspired pressure actuated cellular structures (PACS), which can be utilized to develop energy efficient, lightweight and adaptive structures for diverse applications. The extensibility, stiffness and load capacity requirements exceed the characteristics of state of the art solutions. This work focuses on the design of seals suitable for extensional deformations of more than 25%. In a first step, a number of concepts are generated. Then the most suitable concept is chosen, based on numerical characterization and experimental examination. The deformation supportive end cap (DSEC) yields satisfying results as it displays a stress optimized shape under maximum load, an energetically inexpensive bending-based deformation mechanism and utilizes the applied forces to support distortion. In the first real-life implementation of a double row PACS demonstrator, which contains the DSEC, the proof of concept is demonstrated.

  15. Fiber bundle model under fluid pressure.

    PubMed

    Amitrano, David; Girard, Lucas

    2016-03-01

    Internal fluid pressure often plays an important role in the rupture of brittle materials. This is a major concern for many engineering applications and for natural hazards. More specifically, the mechanisms through which fluid pressure, applied at a microscale, can enhance the failure at a macroscale and accelerate damage dynamics leading to failure remains unclear. Here we revisit the fiber bundle model by accounting for the effect of fluid under pressure that contributes to the global load supported by the fiber bundle. Fluid pressure is applied on the broken fibers, following Biot's theory. The statistical properties of damage avalanches and their evolution toward macrofailure are analyzed for a wide range of fluid pressures. The macroscopic strength of the new model appears to be strongly controlled by the action of the fluid, particularly when the fluid pressure becomes comparable with the fiber strength. The behavior remains consistent with continuous transition, i.e., second order, including for large pressure. The main change concerns the damage acceleration toward the failure that is well modeled by the concept of sweeping of an instability. When pressure is increased, the exponent β characterizing the power-law distribution avalanche sizes significantly decreases and the exponent γ characterizing the cutoff divergence when failure is approached significantly increases. This proves that fluid pressure plays a key role in failure process acting as destabilization factor. This indicates that macrofailure occurs more readily under fluid pressure, with a behavior that becomes progressively unstable as fluid pressure increases. This may have considerable consequences on our ability to forecast failure when fluid pressure is acting. PMID:27078437

  16. Fiber bundle model under fluid pressure

    NASA Astrophysics Data System (ADS)

    Amitrano, David; Girard, Lucas

    2016-03-01

    Internal fluid pressure often plays an important role in the rupture of brittle materials. This is a major concern for many engineering applications and for natural hazards. More specifically, the mechanisms through which fluid pressure, applied at a microscale, can enhance the failure at a macroscale and accelerate damage dynamics leading to failure remains unclear. Here we revisit the fiber bundle model by accounting for the effect of fluid under pressure that contributes to the global load supported by the fiber bundle. Fluid pressure is applied on the broken fibers, following Biot's theory. The statistical properties of damage avalanches and their evolution toward macrofailure are analyzed for a wide range of fluid pressures. The macroscopic strength of the new model appears to be strongly controlled by the action of the fluid, particularly when the fluid pressure becomes comparable with the fiber strength. The behavior remains consistent with continuous transition, i.e., second order, including for large pressure. The main change concerns the damage acceleration toward the failure that is well modeled by the concept of sweeping of an instability. When pressure is increased, the exponent β characterizing the power-law distribution avalanche sizes significantly decreases and the exponent γ characterizing the cutoff divergence when failure is approached significantly increases. This proves that fluid pressure plays a key role in failure process acting as destabilization factor. This indicates that macrofailure occurs more readily under fluid pressure, with a behavior that becomes progressively unstable as fluid pressure increases. This may have considerable consequences on our ability to forecast failure when fluid pressure is acting.

  17. Fuzzy logic controls pressure in Fracturing Fluid Characterization Facility

    SciTech Connect

    Rivera, V.P.; Farabee, L.M.

    1994-12-31

    A fuzzy logic pressure control system has been designed and implemented to deal with the demanding requirements of the Fracturing Fluid Characterization Facility (FFCF), a test bed that simulates downhole conditions for investigating fluid behavior during fracturing stimulation. Pressure control in the fracture simulator was difficult because of the wide range of fluid types and pumping conditions used and by the compliant structure of the simulator, which uses servo-controlled actuators to maintain a constant gap width under varying pressure conditions. The FFCF pressure control system must handle fluids that vary from water to high-viscosity gel slurries at flow rates ranging from 1/2 to 3 bbl/min. Conventional control approaches were successful only under very limited conditions. To solve this problem, a fuzzy logic controller (FLC) was developed to be a user function in the FFCF supervisory control and data acquisition system. Using several fuzzy logic rules, the FLC generates a position set point for a slurry throttling valve. An electro-hydraulic directional control valve uses the set point supplied by the FLC to position the active control element of the slurry throttling valve.

  18. Feasibility study of polyurethane shape-memory polymer actuators for pressure bandage application

    NASA Astrophysics Data System (ADS)

    Ahmad, Manzoor; Luo, Jikui; Miraftab, Mohsen

    2012-02-01

    The feasibility of laboratory-synthesized polyurethane-based shape-memory polymer (SMPU) actuators has been investigated for possible application in medical pressure bandages where gradient pressure is required between the ankle and the knee for treatment of leg ulcers. In this study, using heat as the stimulant, SMPU strip actuators have been subjected to gradual and cyclic stresses; their recovery force, reproducibility and reusability have been monitored with respect to changes in temperature and circumference of a model leg, and the stress relaxation at various temperatures has been investigated. The findings suggest that SMPU actuators can be used for the development of the next generation of pressure bandages.

  19. Magnetically Actuated Propellant Orientation, Controlling Fluids in a Low-Gravity Environment

    NASA Technical Reports Server (NTRS)

    Martin, James J.; Holt, James B.

    2000-01-01

    Cryogenic fluid management (CFM) is a technology area common to virtually every space transportation propulsion concept envisioned. Storage, supply, transfer and handling of sub-critical cryogenic fluids are basic capabilities that have long been needed by multiple programs and the need is expected to continue in the future. The use of magnetic fields provides another method, which could replace or augment current/traditional approaches, potentially simplifying vehicle operational constraints. The magnetically actuated propellant orientation (MAPO) program effort focused on the use of magnetic fields to control fluid motion as it relates to positioning (i.e. orientation and acquisition) of a paramagnetic substance such as LO2. Current CFM state- of-the-art systems used to control and acquire propellant in low gravity environments rely on liquid surface tension devices which employ vanes, fine screen mesh channels and baskets. These devices trap and direct propellant to areas where it's needed and have been used routinely with storable (non-cryogenic) propellants. However, almost no data exists r,egarding their operation in cryogenics and the use of such devices confronts designers with a multitude of significant technology issues. Typical problems include a sensitivity to screen dry out (due to thermal loads and pressurant gas) and momentary adverse accelerations (generated from either internal or external sources). Any of these problems can potentially cause the acquisition systems to ingest or develop vapor and fail. The use of lightweight high field strength magnets may offer a valuable means of augmenting traditional systems potentially mitigating or at least easing operational requirements. Two potential uses of magnetic fields include: 1) strategically positioning magnets to keep vent ports clear of liquid (enabling low G vented fill operations), and 2) placing magnets in the center or around the walls of the tank to create an insulating vapor pocket (between

  20. Fluid Dynamics of a Pressure Reducing Inlet

    NASA Technical Reports Server (NTRS)

    Russell, John M.

    2001-01-01

    Instruments for the monitoring of hazardous gases in and near the space shuttle collect sample gas at pressures on the order of one atmosphere and analyze their properties in an ultra-high vacuum by means of a quadrupole-mass-spectrometer partial pressure transducer. Sampling systems for such devices normally produce the required pressure reduction through combinations of vacuum pumps, fluid Tees and flow restrictors (e.g. orifices, sintered metal frits or capillaries). The present work presents an analytical model of the fluid dynamics of such a pressure reduction system which enables the calculation of the pressure in the receiver vessal in terms of system parameters known from the specifications for a given system (e.g. rated pumping speeds of the pumping hardware and the diameters of two orifices situated in two branches of a fluid Tee). The resulting formulas will expedite the fine tuning of instruments now under development and the design of later generations of such devices.

  1. Valve for fluid control

    DOEpatents

    Oborny, Michael C.; Paul, Phillip H.; Hencken, Kenneth R.; Frye-Mason, Gregory C.; Manginell, Ronald P.

    2001-01-01

    A valve for controlling fluid flows. This valve, which includes both an actuation device and a valve body provides: the ability to incorporate both the actuation device and valve into a unitary structure that can be placed onto a microchip, the ability to generate higher actuation pressures and thus control higher fluid pressures than conventional microvalves, and a device that draws only microwatts of power. An electrokinetic pump that converts electric potential to hydraulic force is used to operate, or actuate, the valve.

  2. Development of Haptic Display Actuated with Magnetorheological Fluid and Artificial Muscle (HAMA Device)

    NASA Astrophysics Data System (ADS)

    Kikuchi, Satoru; Hamamoto, Kazuhiko

    To operate in Immersive Virtual Environment (IVE) with standard devices, beginners will feel difficulties to do it because they are not intuitive devices. Haptic sense is very important for intuitive operation. But existing haptic device is not suited to use in IVE for reasons of displayed sense and the size of the device itself. A device that is a portable one can only display Force-Feedback sense, and a device that can display tactile sense is impossible to be mounted on a hand. In this paper we proposed Haptic display Actuated with Magnetorheological fluid and Artificial muscle (HAMA device). It is a potable haptic device that can display Force-Feedback and tactile sense. The device is constructed of two small devices, a device for displaying Force-Feedback sense and a device for displaying tactile sence. They use Artificial Muscle and Magnetorheological fluid for an actuator. This time we developed index finger part for a trial and evaluate it.

  3. Developing pressures: fluid forces driving morphogenesis.

    PubMed

    Navis, Adam; Bagnat, Michel

    2015-06-01

    Over several decades genetic studies have unraveled many molecular mechanisms that underlie the signaling networks guiding morphogenesis, but the mechanical forces at work remain much less well understood. Accumulation of fluid within a luminal space can generate outward hydrostatic pressure capable of shaping morphogenesis at several scales, ranging from individual organs to the entire vertebrate body-plan. Here, we focus on recent work that uncovered mechanical roles for fluid secretion during morphogenesis. Identifying the roles and regulation of fluid secretion will be instrumental for understanding the mechanics of morphogenesis as well as many human diseases of complex genetic and environmental origin including secretory diarrheas and scoliosis. PMID:25698116

  4. Remotely actuated localized pressure and heat apparatus and method of use

    NASA Technical Reports Server (NTRS)

    Merret, John B. (Inventor); Taylor, DeVor R. (Inventor); Wheeler, Mark M. (Inventor); Gale, Dan R. (Inventor)

    2004-01-01

    Apparatus and method for the use of a remotely actuated localized pressure and heat apparatus for the consolidation and curing of fiber elements in, structures. The apparatus includes members for clamping the desired portion of the fiber elements to be joined, pressure members and/or heat members. The method is directed to the application and use of the apparatus.

  5. Feasibility of controlling speed-dependent low-frequency brake vibration amplification by modulating actuation pressure

    NASA Astrophysics Data System (ADS)

    Sen, Osman Taha; Dreyer, Jason T.; Singh, Rajendra

    2014-12-01

    In this article, a feasibility study of controlling the low frequency torque response of a disc brake system with modulated actuation pressure (in the open loop mode) is conducted. First, a quasi-linear model of the torsional system is introduced, and analytical solutions are proposed to incorporate the modulation effect. Tractable expressions for three different modulation schemes are obtained, and conditions that would lead to a reduction in the oscillatory amplitudes are identified. Second, these conditions are evaluated with a numerical model of the torsional system with clearance nonlinearity, and analytical solutions are verified in terms of the trends observed. Finally, a laboratory experiment with a solenoid valve is built to modulate actuation pressure with a constant duty cycle, and time-frequency domain data are acquired. Measurements are utilized to assess analytical observations, and all methods show that the speed-dependent brake torque amplitudes can be altered with an appropriate modulation of actuation pressure.

  6. Cerebrospinal fluid pressure and the eye.

    PubMed

    Morgan, William H; Balaratnasingam, Chandrakumar; Lind, Christopher R P; Colley, Steve; Kang, Min H; House, Philip H; Yu, Dao-Yi

    2016-01-01

    Cerebrospinal fluid pressure (CSFP) interacts with intraocular pressure (IOP) and blood pressure to exert a major influence upon the eye, particularly the optic nerve head region. There is increased interest regarding the influence of CSFP upon disorders affecting this region, in particular glaucoma and idiopathic intracranial hypertension. Additionally, a high proportion of astronauts develop features similar to idiopathic intracranial hypertension that persist for years after returning to Earth. The factors that affect the CSFP influence upon the optic nerve and globe are likely to influence the outcome of various ophthalmic disorders. PMID:25877896

  7. Topology optimization of adaptive fluid-actuated cellular structures with arbitrary polygonal motor cells

    NASA Astrophysics Data System (ADS)

    Lv, Jun; Tang, Liang; Li, Wenbo; Liu, Lei; Zhang, Hongwu

    2016-05-01

    This paper mainly focuses on the fast and efficient design method for plant bioinspired fluidic cellular materials and structures composed of polygonal motor cells. Here we developed a novel structural optimization method with arbitrary polygonal coarse-grid elements based on multiscale finite element frameworks. The fluidic cellular structures are meshed with irregular polygonal coarse-grid elements according to their natural size and the shape of the imbedded motor cells. The multiscale base functions of solid displacement and hydraulic pressure are then constructed to bring the small-scale information of the irregular motor cells to the large-scale simulations on the polygonal coarse-grid elements. On this basis, a new topology optimization method based on the resulting polygonal coarse-grid elements is proposed to determine the optimal distributions or number of motor cells in the smart cellular structures. Three types of optimization problems are solved according to the usages of the fluidic cellular structures. Firstly, the proposed optimization method is utilized to minimize the system compliance of the load-bearing fluidic cellular structures. Second, the method is further extended to design biomimetic compliant actuators of the fluidic cellular materials due to the fact that non-uniform volume expansions of fluid in the cells can induce elastic action. Third, the optimization problem focuses on the weight minimization of the cellular structure under the constraints for the compliance of the whole system. Several representative examples are investigated to validate the effectiveness of the proposed polygon-based topology optimization method of the smart materials.

  8. Fluid Dynamics of Pressurized, Entrained Coal Gasifiers

    SciTech Connect

    1997-12-31

    Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena like erosion, heat transfer and solid capture. In this context, we are conducting a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea is to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employ a unique entrained gas-solid flow facility with the flexibility to recycle -rather than discard- gases other than air. By matching five dimensionless parameters, suspensions in mixtures of helium, carbon dioxide and sulfur hexafluoride simulate the effects of pressure and scale-up on the fluid dynamics of PECGS. Because it operates under cold, atmospheric conditions, the laboratory facility is ideal for detailed measurements. These activities are conducted with Air Products & Chemicals, Inc., which is a member of a consortium that includes Foster Wheeler and Deutsche Babcock Energie- und Umwelttechnik AG.

  9. Potential pressurized payloads: Fluid and thermal experiments

    NASA Technical Reports Server (NTRS)

    Swanson, Theodore D.

    1992-01-01

    Space Station Freedom (SSF) presents the opportunity to perform long term fluid and thermal experiments in a microgravity environment. This presentation provides perspective on the need for fluids/thermal experimentation in a microgravity environment, addresses previous efforts, identifies possible experiments, and discusses the capabilities of a proposed fluid physics/dynamics test facility. Numerous spacecraft systems use fluids for their operation. Thermal control, propulsion, waste management, and various operational processes are examples of such systems. However, effective ground testing is very difficult. This is because the effect of gravity induced phenomena, such as hydrostatic pressure, buoyant convection, and stratification, overcome such forces as surface tension, diffusion, electric potential, etc., which normally dominate in a microgravity environment. Hence, space experimentation is necessary to develop and validate a new fluid based technology. Two broad types of experiments may be performed on SSF: basic research and applied research. Basic research might include experiments focusing on capillary phenomena (with or without thermal and/or solutal gradients), thermal/solutal convection, phase transitions, and multiphase flow. Representative examples of applied research might include two-phase pressure drop, two-phase flow instabilities, heat transfer coefficients, fluid tank fill/drain, tank slosh dynamics, condensate removal enhancement, and void formation within thermal energy storage materials. In order to better support such fluid/thermal experiments on board SSF, OSSA has developed a conceptual design for a proposed Fluid Physics/Dynamics Facility (FP/DF). The proposed facility consists of one facility rack permanently located on SSF and one experimenter rack which is changed out as needed to support specific experiments. This approach will minimize the on-board integration/deintegration required for specific experiments. The FP/DF will have

  10. Fluid hydrogen at high density - Pressure dissociation

    NASA Technical Reports Server (NTRS)

    Saumon, Didier; Chabrier, Gilles

    1991-01-01

    A model for the Helmholtz free energy of fluid hydrogen at high density and high temperature is developed. This model aims at describing both pressure and temperature dissociation and ionization and bears directly on equations of state of partially ionized plasmas, as encountered in astrophysical situations and high-pressure experiments. This paper focuses on a mixture of hydrogen atoms and molecules and is devoted to the study of the phenomenon of pressure dissociation at finite temperatures. In the present model, the strong interactions are described with realistic potentials and are computed with a modified Weeks-Chandler-Andersen fluid perturbation theory that reproduces Monte Carlo simulations to better than 3 percent. Theoretical Hugoniot curves derived from the model are in excellent agreement with experimental data.

  11. Sensing of fluid viscoelasticity from piezoelectric actuation of cantilever flexural vibration

    NASA Astrophysics Data System (ADS)

    Park, Jeongwon; Jeong, Seongbin; Kim, Seung Joon; Park, Junhong

    2015-01-01

    An experimental method is proposed to measure the rheological properties of fluids. The effects of fluids on the vibration actuated by piezoelectric patches were analyzed and used in measuring viscoelastic properties. Fluid-structure interactions induced changes in the beam vibration properties and frequency-dependent variations of the complex wavenumber of the beam structure were used in monitoring these changes. To account for the effects of fluid-structure interaction, fluids were modelled as a simple viscoelastic support at one end of the beam. The measured properties were the fluid's dynamic shear modulus and loss tangent. Using the proposed method, the rheological properties of various non-Newtonian fluids were measured. The frequency range for which reliable viscoelasticity results could be obtained was 10-400 Hz. Viscosity standard fluids were tested to verify the accuracy of the proposed method, and the results agreed well with the manufacturer's reported values. The simple proposed laboratory setup for measurements was flexible so that the frequency ranges of data acquisition were adjustable by changing the beam's mechanical properties.

  12. Sensing of fluid viscoelasticity from piezoelectric actuation of cantilever flexural vibration.

    PubMed

    Park, Jeongwon; Jeong, Seongbin; Kim, Seung Joon; Park, Junhong

    2015-01-01

    An experimental method is proposed to measure the rheological properties of fluids. The effects of fluids on the vibration actuated by piezoelectric patches were analyzed and used in measuring viscoelastic properties. Fluid-structure interactions induced changes in the beam vibration properties and frequency-dependent variations of the complex wavenumber of the beam structure were used in monitoring these changes. To account for the effects of fluid-structure interaction, fluids were modelled as a simple viscoelastic support at one end of the beam. The measured properties were the fluid's dynamic shear modulus and loss tangent. Using the proposed method, the rheological properties of various non-Newtonian fluids were measured. The frequency range for which reliable viscoelasticity results could be obtained was 10-400 Hz. Viscosity standard fluids were tested to verify the accuracy of the proposed method, and the results agreed well with the manufacturer's reported values. The simple proposed laboratory setup for measurements was flexible so that the frequency ranges of data acquisition were adjustable by changing the beam's mechanical properties. PMID:25638114

  13. Fluid hydrogen at high density - Pressure ionization

    NASA Technical Reports Server (NTRS)

    Saumon, Didier; Chabrier, Gilles

    1992-01-01

    The Helmholtz-free-energy model for nonideal mixtures of hydrogen atoms and molecules by Saumon and Chabrier (1991) is extended to describe dissociation and ionization in similar mixtures in chemical equilibrium. A free-energy model is given that describes partial ionization in the pressure and temperature ionization region. The plasma-phase transition predicted by the model is described for hydrogen mixtures including such components as H2, H, H(+), and e(-). The plasma-phase transition has a critical point at Tc = 15,300 K and Pc = 0.614 Mbar, and thermodynamic instability is noted in the pressure-ionization regime. The pressure dissociation and ionization of fluid hydrogen are described well with the model yielding information on the nature of the plasma-phase transition. The model is shown to be valuable for studying dissociation and ionization in astrophysical objects and in high-pressure studies where pressure and temperature effects are significant.

  14. Sensing of fluid viscoelasticity from piezoelectric actuation of cantilever flexural vibration

    SciTech Connect

    Park, Jeongwon; Jeong, Seongbin; Kim, Seung Joon; Park, Junhong

    2015-01-15

    An experimental method is proposed to measure the rheological properties of fluids. The effects of fluids on the vibration actuated by piezoelectric patches were analyzed and used in measuring viscoelastic properties. Fluid-structure interactions induced changes in the beam vibration properties and frequency-dependent variations of the complex wavenumber of the beam structure were used in monitoring these changes. To account for the effects of fluid-structure interaction, fluids were modelled as a simple viscoelastic support at one end of the beam. The measured properties were the fluid’s dynamic shear modulus and loss tangent. Using the proposed method, the rheological properties of various non-Newtonian fluids were measured. The frequency range for which reliable viscoelasticity results could be obtained was 10–400 Hz. Viscosity standard fluids were tested to verify the accuracy of the proposed method, and the results agreed well with the manufacturer’s reported values. The simple proposed laboratory setup for measurements was flexible so that the frequency ranges of data acquisition were adjustable by changing the beam’s mechanical properties.

  15. An Experimental Two-Axial Actuator for a Tactile Display Capable of Presenting Pressure and Slippage Sensations

    NASA Astrophysics Data System (ADS)

    Ohka, Masahiro; Sawamoto, Yasuhiro; Matsukawa, Shiho; Miyaoka, Tetsu; Mitsuya, Yasunaga

    According to the previous psychophysical experimental results, since human beings feel different sensations for pressure and shearing vibration applied to their finger surface, a new tactile display array consisting of multi-axial micro actuators is required to enhance degree of tactile virtual reality. In the present paper, we experimentally design serial and parallel typed two-axial micro actuators, which are utilized for the key part of the tactile display. The serial typed two-axial actuator comprises bimorph actuators connected in series. The parallel typed two-axial actuator is composed of two bimorph piezoelectric actuators and two small links connected by three joints. We formulate kinematics for the parallel typed two-axial actuator because the endpoint is controlled in the two-dimensional coordinate. We perform a series of experiments to evaluate these two-dimensional actuators. Although the serial typed actuator has different characteristics on x- and y-directional coordinates, it has an advantage on compactness. On the other hand, the parallel typed two-axial actuator has almost same characteristics on both x- and y- coordinates, and has wide strokes of about 1mm. Considering these characteristics depended upon actuator type, we will design the tactile display combined the serial and parallel typed two-axial actuator.

  16. A dynamic pressure view cell for acoustic stimulation of fluids--Micro-bubble generation and fluid movement in porous media.

    PubMed

    Stewart, Robert A; Shaw, J M

    2015-09-01

    The development and baseline operation of an acoustic view cell for observing fluids, and fluid-fluid and fluid-solid interfaces in porous media over the frequency range of 10-5000 Hz is described. This range includes the industrially relevant frequency range 500-5000 Hz that is not covered by existing devices. Pressure waveforms of arbitrary shape are generated in a 17.46 mm ID by 200 mm and 690.5 mm long glass tubes at flow rates up to 200 ml/min using a syringe pump. Peak-to-peak amplitudes exceeding 80 kPa are readily realized at frequencies from 10 to 5000 Hz in bubble free fluids when actuated with 20 Vpp as exemplified using castor oil. At resonant frequencies, peak-to-peak pressure amplitudes exceeding 500 kPa were obtained (castor oil at 2100 Hz when actuated with 20 Vpp). Impacts of vibration on macroscopic liquid-liquid and liquid-vapour interfaces and interface movement are illustrated. Pressure wave transmission and attenuation in a fluid saturated porous medium, randomly packed 250-330 μm spherical silica beads, is also demonstrated. Attenuation differences and frequency shifts in resonant peaks are used to detect the presence and generation of dispersed micro-bubbles (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern outcomes. This knowledge will inform laboratory and pilot scale process studies, where nuisance vibrations may affect the interpretation of process outcomes, and large scale or in situ processes in aquifers or hydrocarbon reservoirs where imposed vibration may be deployed to improve aspects of process performance. Future work will include miscible interface observation and quantitative measurements in the bulk and in porous media where the roles of micro-bubbles comprise subjects of special interest. PMID:26429474

  17. Directed Fluid Flow Produced by Arrays of Magnetically Actuated Core-Shell Biomimetic Cilia

    NASA Astrophysics Data System (ADS)

    Fiser, B. L.; Shields, A. R.; Evans, B. A.; Superfine, R.

    2010-03-01

    We have developed a novel core-shell microstructure that we use to fabricate arrays of flexible, magnetically actuated biomimetic cilia. Our biomimetic cilia mimic the size and beat shape of biological cilia in order to replicate the transport of fluid driven by cilia in many biological systems including the determination of left-right asymmetry in the vertebrate embryonic nodal plate and mucociliary clearance in the lung. Our core-shell structures consist of a flexible poly(dimethylsiloxane) (PDMS) core surrounded by a shell of nickel approximately forty nanometers thick; by using a core-shell structure, we can tune the mechanical and magnetic properties independently. We present the fabrication process and the long-range transport that occurs above the beating biomimetic cilia tips and will report on progress toward biomimetic cilia induced flow in viscoelastic fluids similar to mucus in the human airway. These flows may have applications in photonics and microfluidics, and our structures may be further useful as sensors or actuators in microelectromechanical systems.

  18. Fault slip controlled by stress path and fluid pressurization rate

    NASA Astrophysics Data System (ADS)

    French, Melodie E.; Zhu, Wenlu; Banker, Jeremy

    2016-05-01

    The practice of injecting fluids into the crust is linked to regional increases in seismicity. Increasing fluid pressure along preexisting faults is believed to enhance seismicity rates by reducing the shear stress required for slip, but the processes that cause faults to slip under conditions of fluid pressurization are poorly constrained. We use experimental rock deformation to investigate the controls of fluid pressurization and pressurization rates on fault slip style. We show that pore fluid pressurization is less effective that mechanical changes in fault normal stress at initiating accelerated slip events. Fluid pressurization enhances the total slip, slip velocity, and shear stress drop of events initiated by mechanical changes in normal stress, and these parameters are correlated with pressurization rate, but not the magnitude of fluid pressure. This result is consistent with field-scale observations and indicates that processes active at the pore network scale affect induced seismicity.

  19. Pressure Actuated Leaf Seals for Improved Turbine Shaft Sealing

    NASA Technical Reports Server (NTRS)

    Grondahl, Clayton

    2006-01-01

    This presentation introduces a shaft seal in which leaf seal elements are constructed from slotted shim material formed and layered into a frusto-conical assembly. Limited elastic deflection of seal leaves with increasing system pressure close large startup clearance to a small, non-contacting, steady state running clearance. At shutdown seal elements resiliently retract as differential seal pressure diminishes. Large seal clearance during startup and shutdown provides a mechanism for rub avoidance. Minimum operating clearance improves performance and non-contacting operation promises long seal life. Design features of this seal, sample calculations at differential pressures up to 2400 psid and benefit comparison with brush and labyrinth seals is documented in paper, AIAA 2005 3985, presented at the Advanced Seal Technology session of the Joint Propulsion Conference in Tucson this past July. In this presentation use of bimetallic leaf material will be discussed. Frictional heating of bimetallic leaf seals during a seal rub can relieve the rub condition to some extent with a change in seal shape. Improved leaf seal rub tolerance is expected with bimetallic material.

  20. Pressure Transfer Functions for Interfacial Fluids Problems

    NASA Astrophysics Data System (ADS)

    Chen, Robin Ming; Hur, Vera Mikyoung; Walsh, Samuel

    2016-06-01

    We make a consistent derivation, from the governing equations, of the pressure transfer function in the small-amplitude Stokes wave regime and the hydrostatic approximation in the small-amplitude solitary water wave regime, in the presence of a background shear flow. The results agree with the well-known formulae in the zero vorticity case, but they incorporate the effects of vorticity through solutions to the Rayleigh equation. We extend the results to permit continuous density stratification and to internal waves between two constant-density fluids. Several examples are discussed.

  1. Valve assembly for use with high temperature and high pressure fluids

    DOEpatents

    De Feo, Angelo

    1982-01-01

    The valve assembly for use with high temperature and high pressure fluids has inner and outer spaced shells and a valve actuator support of inner and outer spaced members which are connected at their end portions to the inner and outer shells, respectively, to extend substantially normal to the longitudinal axis of the inner shell. A layer of resilient heat insulating material covers the outer surfaces of the inner shell and the inner actuator support member and is of a thickness to only occupy part of the spaces between the inner and outer shells and inner and outer actuator support members. The remaining portion of the space between the inner and outer shells and the space between the inner and outer members is substantially filled with a body of castable, rigid refractory material. A movable valve member is disposed in the inner shell. A valve actuator assembly is supported in the valve actuator support to extend into the inner shell for connection with the movable valve member for movement of the movable valve member to positions from a fully open to a fully closed position to control flow of fluid through the inner shell. An anchor mneans is disposed adjacent opposite sides of the axis of the valve actuator support and attached to the inner shell so that relative radial movement between the inner and outer shell is permitted by the layer of resilient heat insulating material and relative longitudinal movement of the inner shell to the outer shell is permitted in opposite directions from the anchor means to thereby maintain the functional integrity of the movable valve member by providing an area of the inner shell surrounding the movable valve member longitdinally stationary, but at the same time allowing radial movement.

  2. Fluid Dynamic of Pressurized Coal Gasifiers.

    SciTech Connect

    Louge, M.T.

    1997-11-01

    Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena like erosion, heat transfer and solid capture. In this context, we have conducted a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea was to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employed a unique entrained gas-solid flow facility with the flexibility to recycle -rather than discard- gases other than air. By matching five dimensionless parameters, experiments employing plastic and glass powders fluidized with mixtures of sulfur hexafluoride, carbon dioxide, helium and air at ambient temperature and pressure achieved hydrodynamic similarity with generic high-temperature risers of variable scale operating at 1 and 8 atm. We interpreted our results in the upper riser using steady, fully developed momentum balances for the gas and solid phases. This analysis showed that, for a wide range of experiments, two parameters capture the dependence of the pressure gradients upon the ratio of the mean gas and solid mass flow rates. The first is the ratio of the mean particle slip and superficial gas velocities. The second represents spatial correlations between the radial profiles of interstitial gas velocity and voidage. Variations of the first with dimensionless parameters indicated that our `atmospheric` and `pressurized` experiments conformed to distinct viscous and inertial regimes. In this study, we established also that the descending velocity

  3. Characterization of hydrofoil damping due to fluid-structure interaction using piezocomposite actuators

    NASA Astrophysics Data System (ADS)

    Seeley, Charles; Coutu, André; Monette, Christine; Nennemann, Bernd; Marmont, Hugues

    2012-03-01

    Hydroelectric power generation is an important non-fossil fuel power source to help meet the world’s energy needs. Fluid-structure interaction (FSI), in the form of mass loading and damping, governs the dynamic response of water turbines, such as Francis turbines. Although the effects of fluid mass loading are well documented, fluid damping is also a critical quantity that may limit vibration amplitudes during service, and therefore help to avoid premature failure of the turbines. However, fluid damping has received less attention in the literature. This paper presents an experimental investigation of damping due to FSI. Three hydrofoils were designed and built to investigate damping due to FSI. Piezoelectric actuation using macrofiber composites (MFCs) provided excitation to the hydrofoil test structure, independent of the flow conditions, to overcome the noisy environment. Natural frequency and damping estimates were experimentally obtained from sine sweep frequency response functions measured with a laser vibrometer through a window in the test section. The results indicate that, although the natural frequencies were not substantially affected by the flow, the damping ratios were observed to increase in a linear manner with respect to flow velocity.

  4. Fluid dynamic factors in tracheal pressure measurement.

    PubMed

    Chang, H K; Mortola, J P

    1981-07-01

    Because tracheal pressure measurement generally involves the use of a cannula or an endotracheal tube, fluid dynamic factors may cause a considerable artifact. We present a theoretical explanation of the observed apparent paradox in which the resistance of a tracheal cannula or an endotracheal tube is isolation was found to exceed the resistance of the airways plus the cannula or the tube in situ. By estimating the viscous dissipation and the kinetic energy change in a conduit with sudden variation of cross-sectional area, a predictive model is derived. The predictions are verified by a series of in vitro experiments with both steady and oscillatory flows. The experiments showed that the pressure recorded from the sidearm of a tracheal cannula or endotracheal tube contains an error which, in general, increased with the mean Reynolds' number of the through flow and also depends on the diameter ratio between the trachea and the tube or cannula, the position of the pressure tap, and the frequency of ventilation. When feasible, direct measurement with a needle in the trachea is suggested as a way to avoid the possible artifacts arising from the use fo a side tap of the cannula. Theoretical considerations, as well as in vitro and animal experiments, indicate that adding a properly chosen expansion to the tracheal cannula makes it possible to alter inspiratory and expiratory pressures selectively. This device may prove useful in control of breathing studies. PMID:7263418

  5. Electro-Mechanical Actuators

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The electro-mechanical actuator, a new electronics technology, is an electronic system that provides the force needed to move valves that control the flow of propellant to the engine. It is proving to be advantageous for the main propulsion system plarned for a second generation reusable launch vehicle. Hydraulic actuators have been used successfully in rocket propulsion systems. However, they can leak when high pressure is exerted on such a fluid-filled hydraulic system. Also, hydraulic systems require significant maintenance and support equipment. The electro-mechanical actuator is proving to be low maintenance and the system weighs less than a hydraulic system. The electronic controller is a separate unit powering the actuator. Each actuator has its own control box. If a problem is detected, it can be replaced by simply removing one defective unit. The hydraulic systems must sustain significant hydraulic pressures in a rocket engine regardless of demand. The electro-mechanical actuator utilizes power only when needed. A goal of the Second Generation Reusable Launch Vehicle Program is to substantially improve safety and reliability while reducing the high cost of space travel. The electro-mechanical actuator was developed by the Propulsion Projects Office of the Second Generation Reusable Launch Vehicle Program at the Marshall Space Flight Center.

  6. Actuation of flexoelectric membranes in viscoelastic fluids with applications to outer hair cells.

    PubMed

    Herrera-Valencia, E E; Rey, Alejandro D

    2014-11-28

    Liquid crystal flexoelectric actuation uses an imposed electric field to create membrane bending, and it is used by the outer hair cells (OHCs) located in the inner ear, whose role is to amplify sound through generation of mechanical power. Oscillations in the OHC membranes create periodic viscoelastic flows in the contacting fluid media. A key objective of this work on flexoelectric actuation relevant to OHCs is to find the relations and impact of the electromechanical properties of the membrane, the rheological properties of the viscoelastic media, and the frequency response of the generated mechanical power output. The model developed and used in this work is based on the integration of: (i) the flexoelectric membrane shape equation applied to a circular membrane attached to the inner surface of a circular capillary and (ii) the coupled capillary flow of contacting viscoelastic phases, such that the membrane flexoelectric oscillations drive periodic viscoelastic capillary flows, as in OHCs. By applying the Fourier transform formalism to the governing equation, analytical expressions for the transfer function associated with the curvature and electrical field and for the power dissipation of elastic storage energy were found. PMID:25332388

  7. Laboratory investigation of a fluid-dynamic actuator designed for CubeSats

    NASA Astrophysics Data System (ADS)

    Noack, Daniel; Brieß, Klaus

    2014-03-01

    In general, the attitude control systems (ACS) for precise spacecraft operations rely on reaction wheel technology for angular momentum exchange. In this paper, an alternative ACS concept using fluid rings for this task is presented. This novel actuator—based on Lorentz body force—uses a direct-current conduction pump to accelerate liquid metal within a circular channel structure. As working fluid for the fluid-dynamic actuator (FDA) serves the eutectic alloy Galinstan. Along with a microcontroller that runs the FDA, a MEMS gyroscope is implemented on the device for closed loop operation. Several models of FDAs for small satellites were tested successfully for various attitude control maneuvers on an air bearing platform. Thus advantageous performance has been achieved in terms of torque and power consumption in comparison to similarly dimensioned reaction wheels. Further considerable advantages are wear-free operations and higher reliability as well as expected passive damping properties. A next generation FDA prototype for nano-satellites is currently in development for in-orbit testing.

  8. FLUID PRESSURE AND CAM OPERATED VACUUM VALVE

    DOEpatents

    Batzer, T.H.

    1963-11-26

    An ultra-high vacuum valve that is bakable, reusable, and capable of being quickly opened and closed is described. A translationally movable valve gate having an annular ridge is adapted to contact an annular soft metal gasket disposed at the valve seat such that the soft metal gasket extends beyond the annular ridge on all sides. The valve gate is closed, by first laterally aligning the valve gate with the valve seat and then bringing the valve gate and valve seat into seating contact by the translational movement of a ramp-like wedging means that engages similar ramp-like stractures at the base of the valve gate to force the valve gate into essentially pressureless contact with the annular soft metal gasket. This gasket is then pressurized from beneath by a fluid thereby effecting a vacuura tight seal between the gasket and the ridge. (AEC)

  9. Apparatus for controlling pressure-activated actuator, and apparatus for controlling exhaust-gas recirculation

    SciTech Connect

    Hashimoto, M.; Demizu, A.

    1988-09-27

    This patent describes an apparatus for controlling the exhaust-gas circulation of an engine having an exhaust passage and an intake passage. The apparatus consists of: an exhaust-gas recirculation passage connected at one end to the intake passage and at the other end to the exhaust passage, for guiding part of the exhaust gas flowing through the exhaust passage to the intake passage; an exhaust-gas recirculation valve having a pressure chamber and a valve body being moved in accordance with the pressure within the chamber, for opening and closing the exhaust-gas recirculation passage; first valve means for selectively applying a negative pressure and atmospheric pressure to the pressure chamber, thereby to control the opening of the exhaust-gas recirculation valve means; a first duct provided between the first valve means and the pressure chamber; a second duct provided in parallel to the first duct and having choke means; second valve means for selectively connecting the first and second ducts to the pressure chamber; and control means for actuating the second valve means such that the first duct is connected to the pressure chamber in order to change the pressure within the chamber at high speed, and the second duct is connected to the chamber in order to change the pressure within the pressure chamber at low speed.

  10. Controlled differential pressure system for an enhanced fluid blending apparatus

    DOEpatents

    Hallman, Jr., Russell Louis

    2009-02-24

    A system and method for producing a controlled blend of two or more fluids. Thermally-induced permeation through a permeable tube is used to mix a first fluid from outside the tube with a second fluid flowing through the tube. Mixture ratios may be controlled by adjusting the temperature of the first fluid or by adjusting the pressure drop through the permeable tube. The combination of a back pressure control valve and a differential regulator is used to control the output pressure of the blended fluid. The combination of the back pressure control valve and differential regulator provides superior flow control of the second dry gas. A valve manifold system may be used to mix multiple fluids, and to adjust the volume of blended fluid produced, and to further modify the mixture ratio.

  11. Dynamic Hydraulic Fluid Stimulation Regulated Intramedullary Pressure

    PubMed Central

    Hu, Minyi; Serra-Hsu, Frederick; Bethel, Neville; Lin, Liangjun; Ferreri, Suzanne; Cheng, Jiqi; Qin, Yi-Xian

    2013-01-01

    Physical signals within bone, i.e. generated from mechanical loading, have the potential to initiate skeletal adaptation. Strong evidence has pointed to bone fluid flow (BFF) as a media between an external load and the bone cells, in which altered velocity and pressure can ultimately initiate the mechanotransduction and the remodeling process within bone. Load-induced BFF can be altered by factors such as intramedullary pressure (ImP) and/or bone matrix strain, mediating bone adaptation. Previous studies have shown that BFF induced by ImP alone, with minimum bone strain, can initiate bone remodeling. However, identifying induced ImP dynamics and bone strain factor in vivo using a non-invasive method still remains challenging. To apply ImP as a means for alteration of BFF, it was hypothesized that non-invasive dynamic hydraulic stimulation (DHS) can induce local ImP with minimal bone strain to potentially elicit osteogenic adaptive responses via bone-muscle coupling. The goal of this study was to evaluate the immediate effects on local and distant ImP and strain in response to a range of loading frequencies using DHS. Simultaneous femoral and tibial ImP and bone strain values were measured in three 15-month-old female Sprague Dawley rats during DHS loading on the tibia with frequencies of 1Hz to 10Hz. DHS showed noticeable effects on ImP induction in the stimulated tibia in a nonlinear fashion in response to DHS over the range of loading frequencies, where peaked at 2Hz. DHS at various loading frequencies generated minimal bone strain in the tibiae. Maximal bone strain measured at all loading frequencies was less than 8με. No detectable induction of ImP or bone strain was observed in the femur. This study suggested that oscillatory DHS may regulate the local fluid dynamics with minimal mechanical strain in bone, which serves critically in bone adaptation. These results clearly implied DHS’s potential as an effective, non-invasive intervention for osteopenia and

  12. Active noise control - Piezoceramic actuators in fluid/structure interaction models

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Fang, W.; Smith, R. C.

    1991-01-01

    A model for a 2-D acoustic cavity with a flexible boundary (a beam) controlled via piezoceramic patches producing bending moments in the beam is considered. The associated control problem for this fluid/structure interaction system to reduce the acoustic pressure in the cavity involves unbounded control inputs. Approximation methods in the context of an LQR state space formulation are discussed, and numerical results are presented to demonstrate the effectiveness of this approach in computing feedback controls for noise reduction.

  13. A hybrid ultrasonic motor and electrorheological fluid clutch actuator for force-feedback in MRI/fMRI.

    PubMed

    Chapuis, Dominique; Gassert, Roger; Burdet, Etienne; Bleuler, Hannes

    2008-01-01

    This paper presents a safe, electrically powered MR-compatible actuator with a large range of output impedance, which can be used at the entry of the scanner bore. This actuator is composed of an ultrasonic motor (USM) and a torque-controlled electrorheological fluid clutch which modulates the output torque of the USM. This paper describes the developments on the electrorheological fluid (ERF) clutch and its high voltage driver. The performances of the ERF brake constituting the clutch are evaluated, and its torque range is adapted using an epicyclic differential. The transmissible torque of the ERF clutch, i.e., the maximum system output torque, is 94.4 mNm and its drag torque is 2.6 mNm. The MR compatibility of the complete hybrid actuator is shown in extensive tests including subtraction of images and comparison of signal-to-noise ratios in powered and unpowered conditions. This novel MR-compatible actuator may be used to study the neural control of the hand. PMID:19163448

  14. Study of flow fields induced by surface dielectric barrier discharge actuator in low-pressure air

    SciTech Connect

    Che, Xueke E-mail: st@mail.iee.ac.cn; Nie, Wansheng; Tian, Xihui; Hou, Zhiyong; He, Haobo; Zhou, Penghui; Zhou, Siyin; Yang, Chao; Shao, Tao E-mail: st@mail.iee.ac.cn

    2014-04-15

    Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7 kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude.

  15. System-Level Design of a Shape Memory Alloy Actuator for Active Clearance Control in the High-Pressure Turbine

    NASA Technical Reports Server (NTRS)

    DeCastro, Jonathan A.; Melcher, Kevin J.; Noebe, Ronald D.

    2005-01-01

    This paper describes results of a numerical analysis evaluating the feasibility of high-temperature shape memory alloys (HTSMA) for active clearance control actuation in the high-pressure turbine section of a modern turbofan engine. The prototype actuator concept considered here consists of parallel HTSMA wires attached to the shroud that is located on the exterior of the turbine case. A transient model of an HTSMA actuator was used to evaluate active clearance control at various operating points in a test bed aircraft engine simulation. For the engine under consideration, each actuator must be designed to counteract loads from 380 to 2000 lbf and displace at least 0.033 inches. Design results show that an actuator comprised of 10 wires 2 inches in length is adequate for control at critical engine operating points and still exhibits acceptable failsafe operability and cycle life. A proportional-integral-derivative (PID) controller with integrator windup protection was implemented to control clearance amidst engine transients during a normal mission. Simulation results show that the control system exhibits minimal variability in clearance control performance across the operating envelope. The final actuator design is sufficiently small to fit within the limited space outside the high-pressure turbine case and is shown to consume only small amounts of bleed air to adequately regulate temperature.

  16. On the modeling of a piezoellectrically actuated micro-sensor for measurement of microscale fluid physical properties

    NASA Astrophysics Data System (ADS)

    Ghanbari, Mina; Hossainpour, Siamak; Rezazadeh, Ghader

    2015-11-01

    This paper deals with the analysis of a novel micro-electromechanical sensor for measurement of microscale fluid physical properties. The proposed sensor is made up of a micro-beam with one end fixed and a micro-plate as a sensing element at its free end, which is immersed in a microscale fluid media. As fluids show different behavior in microscale than in macroscale, the microscale fluid media have been modeled based on micro-polar theory. So non-classical properties of fluid that are absent in macroscale flows need to be measured. In order to actuate the sensor longitudinally, an AC voltage is applied to the piezoelectric layers on the upper and lower surfaces of the micro-beam. Coupled governing partial differential equations of motion of the fluid field and longitudinal vibration of the micro-beam have been derived based on micro-polar theory. The obtained governing differential equations with time-varying boundary conditions have been simplified and transformed to an enhanced form with homogenous boundary conditions. Then, they have been discretized over the beam and fluid domain using Galerkin-based reduced-order model. The dynamic response of the sensing element for different piezoelectric actuation voltages and different exciting frequencies has been studied. It has been shown that by investigating damping and inertial effect fluid loading on response of the micro-beam, properties of a microscale fluid can be measured. At the end, effects of geometrical parameters of the sensor on the response of sensing element have been studied.

  17. Evaluation of high-pressure drilling fluid supply systems

    SciTech Connect

    McDonald, M.C.; Reichman, J.M.; Theimer, K.J.

    1981-10-01

    A study was undertaken to help determine the technical and economic feasibility of developing a high-pressure fluid-jet drilling system for the production of geothermal wells. Three system concepts were developed and analyzed in terms of costs, component availability, and required new-component development. These concepts included a single-conduit system that supplies the downhole cutting nozzles directly via surface-located high-pressure pumps; a single-conduit system utilizing low-pressure surface pumps to supply and operate a high-pressure downhole pump, which in turn supplies the cutting nozzles; and a dual-conduit system supplying surface-generated high-pressure fluid for cutting via one conduit and low-pressure scavenging fluid via the other. It is concluded that the single-conduit downhole pump system concept has the greatest potential for success in this application. 28 figures, 11 tables.

  18. Fluid pressure and flow as a cause of bone resorption

    PubMed Central

    Fahlgren, Anna

    2010-01-01

    Background Unstable implants in bone become surrounded by an osteolytic zone. This is seen around loose screws, for example, but may also contribute to prosthetic loosening. Previous animal studies have shown that such zones can be induced by fluctuations in fluid pressure or flow, caused by implant instability. Method To understand the roles of pressure and flow, we describe the 3-dimensional distribution of osteolytic lesions in response to fluid pressure and flow in a previously reported rat model of aseptic loosening. 50 rats had a piston inserted in the proximal tibia, designed to produce 20 local spikes in fluid pressure of a clinically relevant magnitude (700 mmHg) twice a day. The spikes lasted for about 0.3 seconds. After 2 weeks, the pressure was measured in vivo, and the osteolytic lesions induced were studied using micro-CT scans. Results Most bone resorption occurred at pre-existing cavities within the bone in the periphery around the pressurized region, and not under the piston. This region is likely to have a higher fluid flow and less pressure than the area just beneath the piston. The velocity of fluid flow was estimated to be very high (roughly 20 mm/s). Interpretation The localization of the resorptive lesions suggests that high-velocity fluid flow is important for bone resorption induced by instability. PMID:20718695

  19. Calculating Mass Diffusion in High-Pressure Binary Fluids

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth

    2004-01-01

    A comprehensive mathematical model of mass diffusion has been developed for binary fluids at high pressures, including critical and supercritical pressures. Heretofore, diverse expressions, valid for limited parameter ranges, have been used to correlate high-pressure binary mass-diffusion-coefficient data. This model will likely be especially useful in the computational simulation and analysis of combustion phenomena in diesel engines, gas turbines, and liquid rocket engines, wherein mass diffusion at high pressure plays a major role.

  20. Microseismicity Induced by Fluid Pressure Drop (Laboratory Study)

    NASA Astrophysics Data System (ADS)

    Turuntaev, Sergey; Zenchenko, Evgeny; Melchaeva, Olga

    2013-04-01

    Pore pressure change in saturated porous rocks may result in its fracturing (Maury et Fourmaintraux, 1993) and corresponding microseismic event occurrences. Microseismicity due to fluid injection is considered in numerous papers (Maxwell, 2010, Shapiro et al., 2005). Another type of the porous medium fracturing is related with rapid pore pressure drop at some boundary. The mechanism of such fracturing was considered by (Khristianovich, 1985) as a model of sudden coal blowing and by (Alidibirov, Panov, 1998) as a model of volcano eruptions. If the porous saturated medium has a boundary where it directly contacted with fluid under the high pressure (in a hydraulic fracture or in a borehole), and the pressure at that boundary is dropped, the conditions for tensile cracks can be achieved at some distance from the boundary. In the paper, the results of experimental study of saturated porous sample fracturing due to pore pressure rapid drop are discussed. The samples (82 mm high, ∅60 mm) were made of quartz sand, which was cemented by "liquid glass" glue with mass fraction 1%. The sample (porosity 35%, uniaxial unconfined compression strength 2.5 MPa) was placed in a mould and saturated by oil. The upper end of the sample contacted with the mould upper lid, the lower end contacted with fluid. The fluid pressure was increased to 10 MPa and then discharged through the bottom nipple. The pressure increases/drops were repeated 30-50 times. Pore pressure and acoustic emission (AE) were registered by transducers mounted into upper and bottom lids of the mould. It was found, that AE sources (corresponded to microfracturing) were spreading from the open end to the closed end of the sample, and that maximal number of AE events was registered at some distance from the opened end. The number of AE pulses increased with every next pressure drop, meanwhile the number of pulses with high amplitudes diminished. It was found that AE maximal rate corresponded to the fluid pressure

  1. Thermally Actuated Hydraulic Pumps

    NASA Technical Reports Server (NTRS)

    Jones, Jack; Ross, Ronald; Chao, Yi

    2008-01-01

    Thermally actuated hydraulic pumps have been proposed for diverse applications in which direct electrical or mechanical actuation is undesirable and the relative slowness of thermal actuation can be tolerated. The proposed pumps would not contain any sliding (wearing) parts in their compressors and, hence, could have long operational lifetimes. The basic principle of a pump according to the proposal is to utilize the thermal expansion and contraction of a wax or other phase-change material in contact with a hydraulic fluid in a rigid chamber. Heating the chamber and its contents from below to above the melting temperature of the phase-change material would cause the material to expand significantly, thus causing a substantial increase in hydraulic pressure and/or a substantial displacement of hydraulic fluid out of the chamber. Similarly, cooling the chamber and its contents from above to below the melting temperature of the phase-change material would cause the material to contract significantly, thus causing a substantial decrease in hydraulic pressure and/or a substantial displacement of hydraulic fluid into the chamber. The displacement of the hydraulic fluid could be used to drive a piston. The figure illustrates a simple example of a hydraulic jack driven by a thermally actuated hydraulic pump. The pump chamber would be a cylinder containing encapsulated wax pellets and containing radial fins to facilitate transfer of heat to and from the wax. The plastic encapsulation would serve as an oil/wax barrier and the remaining interior space could be filled with hydraulic oil. A filter would retain the encapsulated wax particles in the pump chamber while allowing the hydraulic oil to flow into and out of the chamber. In one important class of potential applications, thermally actuated hydraulic pumps, exploiting vertical ocean temperature gradients for heating and cooling as needed, would be used to vary hydraulic pressures to control buoyancy in undersea research

  2. Constant-Differential-Pressure Two-Fluid Accumulator

    NASA Technical Reports Server (NTRS)

    Piecuch, Benjamin; Dalton, Luke T.

    2010-01-01

    A two-fluid accumulator has been designed, built, and demonstrated to provide an acceptably close approximation to constant differential static pressure between two fluids over the full ranges of (1) accumulator stroke, (2) rates of flow of the fluids, and (3) common static pressure applied to the fluids. Prior differential- pressure two-fluid accumulators are generally not capable of maintaining acceptably close approximations to constant differential pressures. The inadequacies of a typical prior differential-pressure two-fluid accumulator can be summarized as follows: The static differential pressure is governed by the intrinsic spring rate (essentially, the stiffness) of an accumulator tank. The spring rate can be tailored through selection of the tank-wall thickness, selection of the number and/or shape of accumulator convolutions, and/or selection of accumulator material(s). Reliance on the intrinsic spring rate of the tank results in three severe limitations: (1) The spring rate and the expulsion efficiency tend to be inversely proportional to each other: that is to say, as the stiffness (and thus the differential pressure) is increased, the range of motion of the accumulator is reduced. (2) As the applied common static pressure increases, the differential pressure tends to decrease. An additional disadvantage, which may or may not be considered limiting, depending on the specific application, is that an increase in stiffness entails an increase in weight. (3) The additional weight required by a low expulsion efficiency accumulator eliminates the advantage given to such gas storage systems. The high expulsion efficiency provided by this two-fluid accumulator allows for a lightweight, tightly packaged system, which can be used in conjunction with a fuel cell-based system.

  3. Optimization of Sensing and Feedback Control for Vibration/Flutter of Rotating Disk by PZT Actuators via Air Coupled Pressure

    PubMed Central

    Yan, Tianhong; Xu, Xinsheng; Han, Jianqiang; Lin, Rongming; Ju, Bingfeng; Li, Qing

    2011-01-01

    In this paper, a feedback control mechanism and its optimization for rotating disk vibration/flutter via changes of air-coupled pressure generated using piezoelectric patch actuators are studied. A thin disk rotates in an enclosure, which is equipped with a feedback control loop consisting of a micro-sensor, a signal processor, a power amplifier, and several piezoelectric (PZT) actuator patches distributed on the cover of the enclosure. The actuator patches are mounted on the inner or the outer surfaces of the enclosure to produce necessary control force required through the airflow around the disk. The control mechanism for rotating disk flutter using enclosure surfaces bonded with sensors and piezoelectric actuators is thoroughly studied through analytical simulations. The sensor output is used to determine the amount of input to the actuator for controlling the response of the disk in a closed loop configuration. The dynamic stability of the disk-enclosure system, together with the feedback control loop, is analyzed as a complex eigenvalue problem, which is solved using Galerkin’s discretization procedure. The results show that the disk flutter can be reduced effectively with proper configurations of the control gain and the phase shift through the actuations of PZT patches. The effectiveness of different feedback control methods in altering system characteristics and system response has been investigated. The control capability, in terms of control gain, phase shift, and especially the physical configuration of actuator patches, are also evaluated by calculating the complex eigenvalues and the maximum displacement produced by the actuators. To achieve a optimal control performance, sizes, positions and shapes of PZT patches used need to be optimized and such optimization has been achieved through numerical simulations. PMID:22163788

  4. Osmotic generation of 'anomalous' fluid pressures in geological environments

    USGS Publications Warehouse

    Neuzii, C.E.

    2000-01-01

    Osmotic pressures are generated by differences in chemical potential of a solution across a membrane. But whether osmosis can have a significant effect on the pressure of fluids in geological environments has been controversial, because the membrane properties of geological media are poorly understood. 'Anomalous' pressures - large departures from hydrostatic pressure that are not explicable in terms of topographic or fluid-density effects are widely found in geological settings, and are commonly considered to result from processes that alter the pore or fluid volume, which in turn implies crustal changes happening at a rate too slow to observe directly. Yet if osmosis can explain some anomalies, there is no need to invoke such dynamic geological processes in those cases. Here I report results of a nine- year in situ measurement of fluid pressures and solute concentrations in shale that are consistent with the generation of large (up to 20 MPa) osmotic-pressure anomalies which could persist for tens of millions of years. Osmotic pressures of this magnitude and duration can explain many of the pressure anomalies observed in geological settings. The require, however, small shale porosity and large contrasts in the amount of dissolved solids in the pore waters - criteria that may help to distinguish between osmotic and crystal-dynamic origins of anomalous pressures.

  5. Influence of flow rate on aerosol particle size distributions from pressurized and breath-actuated inhalers.

    PubMed

    Smith, K J; Chan, H K; Brown, K F

    1998-01-01

    Particle size distribution of delivered aerosols and the total mass of drug delivered from the inhaler are important determinants of pulmonary deposition and response to inhalation therapy. Inhalation flow rate may vary between patients and from dose to dose. The Andersen Sampler (AS) cascade impactor operated at flow rates of 30 and 55 L/min and the Marple-Miller Impactor (MMI) operated at flow rates of 30, 55, and 80 L/min were used in this study to investigate the influence of airflow rate on the particle size distributions of inhalation products. Total mass of drug delivered from the inhaler, fine particle mass, fine particle fraction, percentage of nonrespirable particles, and amount of formulation retained within the inhaler were determined by ultraviolet spectrophotometry for several commercial bronchodilator products purchased in the marketplace, including a pressurized metered-dose inhaler (pMDI), breath-actuated pressurized inhaler (BAMDI), and three dry powder inhalers (DPIs), two containing salbutamol sulphate and the other containing terbutaline sulphate. Varying the flow rate through the cascade impactor produced no significant change in performance of the pressurized inhalers. Increasing the flow rate produced a greater mass of drug delivered and an increase in respirable particle mass and fraction from all DPIs tested. PMID:10346666

  6. Modeling actuation forces and strains in nastic structures

    NASA Astrophysics Data System (ADS)

    Matthews, Luke A.; Giurgiutiu, Victor

    2006-03-01

    Nastic structures are capable of three dimensional shape change using biological principles borrowed from plant motion. The plant motor cells increase or decrease in size through a change in osmotic pressure. When nonuniform cell swelling occurs, it causes the plant tissue to warp and change shape, resulting it net movement, known as nastic motion, which is the same phenomena that causes plants to angle their broad leaf and flower surfaces to face light sources. The nastic structures considered in this paper are composed of a bilayer of microactuator arrays with a fluid reservoir in between the two layers. The actuators are housed in a thin plate and expand when water from the fluid reservoir is pumped into the actuation chamber through a phospholipid bilayer with embedded active transport proteins, which move the water from the low pressure fluid reservoir into a high pressure actuation chamber. Increasing water pressure inside the actuator causes lateral expansion and axial bulging, and the non-uniform net volume change of actuators throughout the nastic structure results in twisting or bending shape change. Modifying the actuation displacement allows controlled volume change. This paper presents an analytical model of the driving and blocking forces involved in actuation, as well as stress and strain that occurs due to the pressure changes. Actuation is driven by increasing osmotic pressure, and blocking forces are taken into consideration to plan actuator response so that outside forces do not counteract the displacement of actuation. Nastic structures are designed with use in unmanned aerial vehicles in mind, so blocking forces are modeled to be similar to in-flight conditions. Stress in the system is modeled so that any residual strain or lasting deformation can be determined, as well as a lifespan before failure from repeated actuation. The long-term aim of our work is to determine the power and energy efficiency of nastic structures actuation mechanism.

  7. Engine with hydraulic fuel injection and ABS circuit using a single high pressure pump

    DOEpatents

    Bartley, Bradley E.; Blass, James R.; Gibson, Dennis H.

    2001-01-01

    An engine system comprises a hydraulically actuated fuel injection system and an ABS circuit connected via a fluid flow passage that provides hydraulic fluid to both the fuel injection system and to the ABS circuit. The hydraulically actuated system includes a high pressure pump. The fluid control passage is in fluid communication with an outlet from the high pressure pump.

  8. Device damps fluid pressure oscillations in vent valve

    NASA Technical Reports Server (NTRS)

    Nein, H. J.

    1968-01-01

    Device, containing a tuned series arrangement of two plenum chambers and two orifices, damps high pressure fluid oscillations in a vent valve. Used in conjunction with vent valves, it relieves gas pressure that develops in liquid hydrogen and liquid oxygen tanks used on a space vehicle.

  9. Tissue fluid pressures - From basic research tools to clinical applications

    NASA Technical Reports Server (NTRS)

    Hargens, Alan R.; Akeson, Wayne H.; Mubarak, Scott J.; Owen, Charles A.; Gershuni, David H.

    1989-01-01

    This paper describes clinical applications of two basic research tools developed and refined in the past 20 years: the wick catheter (for measuring tissue fluid pressure) and the colloid osmometer (for measuring osmotic pressure). Applications of the osmometer include estimations of the reduced osmotic pressure of sickle-cell hemoglobin with deoxygenation, and of reduced swelling pressure of human nucleus pulposus with hydration or upon action of certain enzymes. Clinical uses of the wick-catheter technique include an improvement of diagnosis and treatment of acute and chronic compartment syndromes, the elucidation of the tissue pressure thresholds for neuromuscular dysfunction, and the development of a better tourniquet for orthopedics.

  10. Development of micropump-actuated negative pressure pinched injection for parallel electrophoresis on array microfluidic chip.

    PubMed

    Li, Bowei; Jiang, Lei; Xie, Hua; Gao, Yan; Qin, Jianhua; Lin, Bingcheng

    2009-09-01

    A micropump-actuated negative pressure pinched injection method is developed for parallel electrophoresis on a multi-channel LIF detection system. The system has a home-made device that could individually control 16-port solenoid valves and a high-voltage power supply. The laser beam is excitated and distributes to the array separation channels for detection. The hybrid Glass-PDMS microfluidic chip comprises two common reservoirs, four separation channels coupled to their respective pneumatic micropumps and two reference channels. Due to use of pressure as a driving force, the proposed method has no sample bias effect for separation. There is only one high-voltage supply needed for separation without relying on the number of channels, which is significant for high-throughput analysis, and the time for sample loading is shortened to 1 s. In addition, the integrated micropumps can provide the versatile interface for coupling with other function units to satisfy the complicated demands. The performance is verified by separation of DNA marker and Hepatitis B virus DNA samples. And this method is also expected to show the potential throughput for the DNA analysis in the field of disease diagnosis. PMID:19681052

  11. Pressurized fluid torque driver control and method

    NASA Technical Reports Server (NTRS)

    Cook, Joseph S., Jr. (Inventor)

    1994-01-01

    Methods and apparatus are provided for a torque driver including a displaceable gear to limit torque transfer to a fastener at a precisely controlled torque limit. A biasing assembly biases a first gear into engagement with a second gear for torque transfer between the first and second gear. The biasing assembly includes a pressurized cylinder controlled at a constant pressure that corresponds to a torque limit. A calibrated gage and valve is used to set the desired torque limit. One or more coiled output linkages connect the first gear with the fastener adaptor which may be a socket for a nut. A gear tooth profile provides a separation force that overcomes the bias to limit torque at the desired torque limit. Multiple fasteners may be rotated simultaneously to a desired torque limit if additional output spur gears are provided. The torque limit is adjustable and may be different for fasteners within the same fastener configuration.

  12. An Approach to the Prototyping of an Optimized Limited Stroke Actuator to Drive a Low Pressure Exhaust Gas Recirculation Valve.

    PubMed

    Gutfrind, Christophe; Dufour, Laurent; Liebart, Vincent; Vannier, Jean-Claude; Vidal, Pierre

    2016-01-01

    The purpose of this article is to describe the design of a limited stroke actuator and the corresponding prototype to drive a Low Pressure (LP) Exhaust Gas Recirculation (EGR) valve for use in Internal Combustion Engines (ICEs). The direct drive actuator topology is an axial flux machine with two air gaps in order to minimize the rotor inertia and a bipolar surface-mounted permanent magnet in order to respect an 80° angular stroke. Firstly, the actuator will be described and optimized under constraints of a 150 ms time response, a 0.363 N·m minimal torque on an angular range from 0° to 80° and prototyping constraints. Secondly, the finite element method (FEM) using the FLUX-3D(®) software (CEDRAT, Meylan, France) will be used to check the actuator performances with consideration of the nonlinear effect of the iron material. Thirdly, a prototype will be made and characterized to compare its measurement results with the analytical model and the FEM model results. With these electromechanical behavior measurements, a numerical model is created with Simulink(®) in order to simulate an EGR system with this direct drive actuator under all operating conditions. Last but not least, the energy consumption of this machine will be estimated to evaluate the efficiency of the proposed EGR electromechanical system. PMID:27213398

  13. An Approach to the Prototyping of an Optimized Limited Stroke Actuator to Drive a Low Pressure Exhaust Gas Recirculation Valve

    PubMed Central

    Gutfrind, Christophe; Dufour, Laurent; Liebart, Vincent; Vannier, Jean-Claude; Vidal, Pierre

    2016-01-01

    The purpose of this article is to describe the design of a limited stroke actuator and the corresponding prototype to drive a Low Pressure (LP) Exhaust Gas Recirculation (EGR) valve for use in Internal Combustion Engines (ICEs). The direct drive actuator topology is an axial flux machine with two air gaps in order to minimize the rotor inertia and a bipolar surface-mounted permanent magnet in order to respect an 80° angular stroke. Firstly, the actuator will be described and optimized under constraints of a 150 ms time response, a 0.363 N·m minimal torque on an angular range from 0° to 80° and prototyping constraints. Secondly, the finite element method (FEM) using the FLUX-3D® software (CEDRAT, Meylan, France) will be used to check the actuator performances with consideration of the nonlinear effect of the iron material. Thirdly, a prototype will be made and characterized to compare its measurement results with the analytical model and the FEM model results. With these electromechanical behavior measurements, a numerical model is created with Simulink® in order to simulate an EGR system with this direct drive actuator under all operating conditions. Last but not least, the energy consumption of this machine will be estimated to evaluate the efficiency of the proposed EGR electromechanical system. PMID:27213398

  14. The Role of Interstitial Fluid Pressurization in Articular Cartilage Lubrication

    PubMed Central

    Ateshian, Gerard A.

    2009-01-01

    Over the last two decades, considerable progress has been reported in the field of cartilage mechanics that impacts our understanding of the role of interstitial fluid pressurization on cartilage lubrication. Theoretical and experimental studies have demonstrated that the interstitial fluid of cartilage pressurizes considerably under loading, potentially supporting most of the applied load under various transient or steady-state conditions. The fraction of the total load supported by fluid pressurization has been called the fluid load support. Experimental studies have demonstrated that the friction coefficient of cartilage correlates negatively with this variable, achieving remarkably low values when the fluid load support is greatest. A theoretical framework that embodies this relationship has been validated against experiments, predicting and explaining various outcomes, and demonstrating that a low friction coefficient can be maintained for prolonged loading durations under normal physiological function. This paper reviews salient aspects of this topic, as well as its implications for improving our understanding of boundary lubrication by molecular species in synovial fluid and the cartilage superficial zone. Effects of cartilage degeneration on its frictional response are also reviewed. PMID:19464689

  15. Modeling, fabrication and plasma actuator coupling of flexible pressure sensors for flow separation detection and control in aeronautical applications

    NASA Astrophysics Data System (ADS)

    Francioso, L.; De Pascali, C.; Pescini, E.; De Giorgi, M. G.; Siciliano, P.

    2016-06-01

    Preventing the flow separation could enhance the performance of propulsion systems and future civil aircraft. To this end, a fast detection of boundary layer separation is mandatory for a sustainable and successful application of active flow control devices, such as plasma actuators. The present work reports on the design, fabrication and functional tests of low-cost capacitive pressure sensors coupled with dielectric barrier discharge (DBD) plasma actuators to detect and then control flow separation. Finite element method (FEM) simulations were used to obtain information on the deflection and the stress distribution in different-shaped floating membranes. The sensor sensitivity as a function of the pressure load was also calculated by experimental tests. The results of the calibration of different capacitive pressure sensors are reported in this work, together with functional tests in a wind tunnel equipped with a curved wall plate on which a DBD plasma actuator was mounted to control the flow separation. The flow behavior was experimentally investigated by particle image velocimetry (PIV) measurements. Statistical and spectral analysis, applied to the output signals of the pressure sensor placed downstream of the profile leading edge, demonstrated that the sensor is able to discriminate different ionic wind velocity and turbulence conditions. The sensor sensitivity in the 0–100 Pa range was experimentally measured and it ranged between 0.0030 and 0.0046 pF Pa‑1 for the best devices.

  16. PACS—Realization of an adaptive concept using pressure actuated cellular structures

    NASA Astrophysics Data System (ADS)

    Gramüller, B.; Boblenz, J.; Hühne, C.

    2014-10-01

    A biologically inspired concept is investigated which can be utilized to develop energy efficient, lightweight and applicational flexible adaptive structures. Building a real life morphing unit is an ambitious task as the numerous works in the particular field show. Summarizing fundamental demands and barriers regarding shape changing structures, the basic challenges of designing morphing structures are listed. The concept of Pressure Actuated Cellular Structures (PACS) is arranged within the recent morphing activities and it is shown that it complies with the underlying demands. Systematically divided into energy-related and structural subcomponents the working principle is illuminated and relationships between basic design parameters are expressed. The analytical background describing the physical mechanisms of PACS is presented in concentrated manner. This work focuses on the procedure of dimensioning, realizing and experimental testing of a single cell and a single row cantilever made of PACS. The experimental outcomes as well as the results from the FEM computations are used for evaluating the analytical methods. The functionality of the basic principle is thus validated and open issues are determined pointing the way ahead.

  17. Tubular dielectric elastomer actuator for active fluidic control

    NASA Astrophysics Data System (ADS)

    McCoul, David; Pei, Qibing

    2015-10-01

    We report a novel low-profile, biomimetic dielectric elastomer tubular actuator capable of actively controlling hydraulic flow. The tubular actuator has been established as a reliable tunable valve, pinching a secondary silicone tube completely shut in the absence of a fluidic pressure bias or voltage, offering a high degree of resistance against fluidic flow, and able to open and completely remove this resistance to flow with an applied low power actuation voltage. The system demonstrates a rise in pressure of ∼3.0 kPa when the dielectric elastomer valve is in the passive, unactuated state, and there is a quadratic fall in this pressure with increasing actuation voltage, until ∼0 kPa is reached at 2.4 kV. The device is reliable for at least 2000 actuation cycles for voltages at or below 2.2 kV. Furthermore, modeling of the actuator and fluidic system yields results consistent with the observed experimental dependence of intrasystem pressure on input flow rate, actuator prestretch, and actuation voltage. To our knowledge, this is the first actuator of its type that can control fluid flow by directly actuating the walls of a tube. Potential applications may include an implantable artificial sphincter, part of a peristaltic pump, or a computerized valve for fluidic or pneumatic control.

  18. A dynamic pressure view cell for acoustic stimulation of fluids—Micro-bubble generation and fluid movement in porous media

    NASA Astrophysics Data System (ADS)

    Stewart, Robert A.; Shaw, J. M.

    2015-09-01

    The development and baseline operation of an acoustic view cell for observing fluids, and fluid-fluid and fluid-solid interfaces in porous media over the frequency range of 10-5000 Hz is described. This range includes the industrially relevant frequency range 500-5000 Hz that is not covered by existing devices. Pressure waveforms of arbitrary shape are generated in a 17.46 mm ID by 200 mm and 690.5 mm long glass tubes at flow rates up to 200 ml/min using a syringe pump. Peak-to-peak amplitudes exceeding 80 kPa are readily realized at frequencies from 10 to 5000 Hz in bubble free fluids when actuated with 20 Vpp as exemplified using castor oil. At resonant frequencies, peak-to-peak pressure amplitudes exceeding 500 kPa were obtained (castor oil at 2100 Hz when actuated with 20 Vpp). Impacts of vibration on macroscopic liquid-liquid and liquid-vapour interfaces and interface movement are illustrated. Pressure wave transmission and attenuation in a fluid saturated porous medium, randomly packed 250-330 μm spherical silica beads, is also demonstrated. Attenuation differences and frequency shifts in resonant peaks are used to detect the presence and generation of dispersed micro-bubbles (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern outcomes. This knowledge will inform laboratory and pilot scale process studies, where nuisance vibrations may affect the interpretation of process outcomes, and large scale or in situ processes in aquifers or hydrocarbon reservoirs where imposed vibration may be deployed to improve aspects of process performance. Future work will include miscible interface observation and quantitative measurements in the bulk and in porous media where the roles of micro-bubbles comprise subjects of special interest.

  19. Subminiature hydraulic actuator

    NASA Technical Reports Server (NTRS)

    Sevart, F. D.

    1978-01-01

    Subminiature, single-vane rotary actuator for wind-tunnel test-model control-surface actuation systems presents severe torque and system band-pass requirements with stringent space and weight limitations. Actuator has very low leakage of fluid from one side to other, permitting use in precision position servo-systems.

  20. Estimating pore fluid pressures during the Youngstown, Ohio earthquakes

    NASA Astrophysics Data System (ADS)

    Hsieh, P. A.

    2014-12-01

    Several months after fluid injection began in December 2010 at the Northstar 1 well in Youngstown, Ohio, low-magnitude earthquakes were detected in the Youngstown area, where no prior earthquakes had been detected. Concerns that the injection might have triggered the earthquakes lead to shutdown of the well in December 2011. Earthquake relocation analysis by Kim (2013, J. Geophy. Res., v 118, p. 3506-3518) showed that, from March 2011 to January 2012, 12 earthquakes with moment magnitudes of 1.8 to 3.9 occurred at depths of 3.5 to 4 km in the Precambrian basement along a previously unmapped vertical fault. The 2.8 km deep Northstar 1 well, which penetrated the top 60 m of the basement, appeared to have been drilled into the same fault. The earthquakes occurred at lateral distances of 0 to 1 km from the well. The present study aims to estimate the fluid pressure increase due to injection. The groundwater flow model MODFLOW is used to simulate fluid pressure propagation from the well injection interval into the basement fault and two permeable sandstone layers above the basement. The basement rock away from the fault is assumed impermeable. Reservoir properties (permeability and compressibility) of the fault and sandstone layers are estimated by calibrating the model to match injection history and wellhead pressure recorded daily during the operational period. Although the available data are not sufficient to uniquely determine reservoir properties, it is possible to determine reasonable ranges. Simulated fluid pressure increases at the locations and times of the earthquakes range from less than 0.01 MPa to about 1 MPa. Pressure measurements in the well after shut-in might enhance the estimation of reservoir properties. Such data could also improve the estimation of pore fluid pressure increase due to injection.

  1. Exact solutions: neutral and charged static perfect fluids with pressure

    NASA Astrophysics Data System (ADS)

    Bijalwan, Naveen

    2012-01-01

    We show in this article that charged fluid with pressure derived by Bijalwan (Astrophys. Space. Sci. doi:10.1007/s10509-011-0691-0, 011a) can be used to model classical electron, quark, neutron stars and pulsar with charge matter, quasi black hole, white dwarf, super-dense star etc. Recent analysis by Bijalwan (Astrophys. Space. Sci., 2011d) that all charged fluid solutions in terms of pressure mimic the classical electron model are partially correct because solutions by Bijalwan (Astrophys. Space. Sci. doi:10.1007/s10509-011-0691-0, 011a) may possess a neutral counterpart. In this paper we characterized solutions in terms of pressure for charged fluids that have and do not have a well behaved neutral counter part considering same spatial component of metric e λ for neutral and charged fluids. We discussed solution by Gupta and Maurya (Astrophys. Space Sci. 331(1):135-144, 2010a) and solutions by Bijalwan (Astrophys. Space Sci. doi:10.1007/s10509-011-0735-5, 2011b; Astrophys. Space Sci. doi:10.1007/s10509-011-0780-0, 2011c; Astrophys. Space Sci., 2011d) such that charged fluids possess and do not possess a neutral counterpart as special cases, respectively. For brevity, we only present some analytical results in this paper.

  2. Preliminary design of a simple passive toe exercise apparatus with a flexible metal hydride actuator for pressure ulcer prevention.

    PubMed

    Ino, Shuichi; Sato, Mitsuru; Hosono, Minako; Nakajima, Sawako; Yamashita, Kazuhiko; Izumi, Takashi

    2010-01-01

    In an aging society, social demands for home-based rehabilitation and assistive technologies by healthcare and welfare services are globally increasing. The progress of quality-of-life technologies and rehabilitation science is a very important and urgent issue for elderly and disabled individuals as well as for their caregivers. Thus, there is a substantial need to develop simple bedside apparatuses for both continuous exercise of joints and for power assistance for standing to prevent and manage disuse syndromes (e.g., pressure ulcers, joint contractures and muscular atrophy). Unfortunately, there are currently no commercially-available actuators compatible with the human requirements of flexibility, quietness, lightness and a high power-to-weight ratio. To fulfill the above demands, we have developed a novel actuation device using a metal hydride (MH) alloy and a laminate film, called the flexible MH actuator, as a human-friendly force generator for healthcare and welfare services. In this paper, we show the basic structure and characteristics of the flexible MH actuator used to create a passive exercise system for preventing disuse syndromes. To evaluate the efficiency of passive exercise for bedsore prevention, subcutaneous blood flow during passive exercise at common pressure-ulcer sites is measured by a laser blood flow meter. The force and range-of-motion angle required for a passive exercise apparatus is also examined with the help of a professional physical therapist. Based on these findings, a prototype of a passive exercise apparatus is fabricated using the flexible MH actuator technology, and its operation characteristics are preliminarily verified using a thermoelectric control system. PMID:21096304

  3. Earthquakes, fluid pressures and rapid subduction zone metamorphism

    NASA Astrophysics Data System (ADS)

    Viete, D. R.

    2013-12-01

    High-pressure/low-temperature (HP/LT) metamorphism is commonly incomplete, meaning that large tracts of rock can remain metastable at blueschist- and eclogite-facies conditions for timescales up to millions of years [1]. When HP/LT metamorphism does take place, it can occur over extremely short durations (<<1 Myr) [1-2]. HP/LT metamorphism must be associated with processes that allow large volumes of rock to remain unaffected over long periods of time, but then suddenly undergo localized metamorphism. Existing models for HP/LT metamorphism have focussed on the role of fluids in providing heat for metamorphism [2] or catalyzing metamorphic reactions [1]. Earthquakes in subduction zone settings can occur to depths of 100s of km. Metamorphic dehydration and the associated development of elevated pore pressures in HP/LT metamorphic rocks has been identified as a cause of earthquake activity at such great depths [3-4]. The process of fracturing/faulting significantly increases rock permeability, causing channelized fluid flow and dissipation of pore pressures [3-4]. Thus, deep subduction zone earthquakes are thought to reflect an evolution in fluid pressure, involving: (1) an initial increase in pore pressure by heating-related dehydration of subduction zone rocks, and (2) rapid relief of pore pressures by faulting and channelized flow. Models for earthquakes at depth in subduction zones have focussed on the in situ effects of dehydration and then sudden escape of fluids from the rock mass following fracturing [3-4]. On the other hand, existing models for rapid and incomplete metamorphism in subduction zones have focussed only on the effects of heating and/or hydration with the arrival of external fluids [1-2]. Significant changes in pressure over very short timescales should result in rapid mineral growth and/or disequilibrium texture development in response to overstepping of mineral reaction boundaries. The repeated process of dehydration-pore pressure development

  4. Hydrodynamics of Denver basin: explanation of subnormal fluid pressures

    USGS Publications Warehouse

    Belitz, K.; Bredehoeft, J.D.

    1988-01-01

    Shows that 1) subnormal fluid pressures can be explained as a consequence of steady-state regional ground-water flow, 2) shale is an important factor in the regional flow system, and 3) depth is an important control on the distribution of hydraulic conductivity. -from Authors

  5. Theoretical Insights for Practical Handling of Pressurized Fluids

    ERIC Educational Resources Information Center

    Aranda, Alfonso; Rodriguez, Maria del Prado

    2006-01-01

    The practical scenarios discussed in a chemistry or chemical engineering course that use solid or liquid reactants are presented. Important ideas to be considered when handling pressurized fluids are provided and three typical examples are described to enable students develop secondary skills such as the selective search of data, identification of…

  6. Properties of planetary fluids at high shock pressures and temperatures

    SciTech Connect

    Nellis, W.J.; Mitchell, A.C.; Holmes, N.C.; McCandless, P.C.

    1991-03-01

    Models of the interiors of Uranus and Neptune are discussed. Pressures and temperatures in the interiors can be achieved in representative constituent molecular fluids by shock compression. Experimental techniques are described and recent results for synthetic Uranus and hydrogen are discussed. 19 refs., 4 figs., 1 tab.

  7. Thermostatic Valves Containing Silicone-Oil Actuators

    NASA Technical Reports Server (NTRS)

    Bhandari, Pradeep; Birur, Gajanana C.; Bame, David P.; Karlmann, Paul B.; Prina, Mauro; Young, William; Fisher, Richard

    2009-01-01

    Flow-splitting and flow-mixing thermally actuated spool valves have been developed for controlling flows of a heat-transfer fluid in a temperature-regulation system aboard the Mars Science Laboratory (MSL) rover. Valves like these could also be useful in terrestrial temperature-regulation systems, including automobile air-conditioning systems and general refrigeration systems. These valves are required to provide smoother actuation over a wider temperature range than the flow-splitting, thermally actuated spool valves used in the Mars Explorer Rover (MER). Also, whereas the MER valves are unstable (tending to oscillate) in certain transition temperature ranges, these valves are required not to oscillate. The MER valves are actuated by thermal expansion of a wax against spring-loaded piston rods (as in common automotive thermostats). The MSL valves contain similar actuators that utilize thermal expansion of a silicone oil, because silicone-oil actuators were found to afford greater and more nearly linear displacements, needed for smoother actuation, over the required wider temperature range. The MSL valves also feature improved spool designs that reflect greater understanding of fluid dynamics, consideration of pressure drops in valves, and a requirement for balancing of pressures in different flow branches.

  8. Bonding changes in hot fluid hydrogen at megabar pressures

    PubMed Central

    Subramanian, Natarajan; Goncharov, Alexander F.; Struzhkin, Viktor V.; Somayazulu, Maddury; Hemley, Russell J.

    2011-01-01

    Raman spectroscopy in laser-heated diamond anvil cells has been employed to probe the bonding state and phase diagram of dense hydrogen up to 140 GPa and 1,500 K. The measurements were made possible as a result of the development of new techniques for containing and probing the hot, dense fluid, which is of fundamental importance in physics, planetary science, and astrophysics. A pronounced discontinuous softening of the molecular vibron was found at elevated temperatures along with a large broadening and decrease in intensity of the roton bands. These phenomena indicate the existence of a state of the fluid having significantly modified intramolecular bonding. The results are consistent with the existence of a pressure-induced transformation in the fluid related to the presence of a temperature maximum in the melting line as a function of pressure. PMID:21447715

  9. Simulation Tool for Dielectric Barrier Discharge Plasma Actuators at Atmospheric and Sub-Atmospheric Pressures: SBIR Phase I Final Report

    NASA Technical Reports Server (NTRS)

    Likhanskii, Alexandre

    2012-01-01

    This report is the final report of a SBIR Phase I project. It is identical to the final report submitted, after some proprietary information of administrative nature has been removed. The development of a numerical simulation tool for dielectric barrier discharge (DBD) plasma actuator is reported. The objectives of the project were to analyze and predict DBD operation at wide range of ambient gas pressures. It overcomes the limitations of traditional DBD codes which are limited to low-speed applications and have weak prediction capabilities. The software tool allows DBD actuator analysis and prediction for subsonic to hypersonic flow regime. The simulation tool is based on the VORPAL code developed by Tech-X Corporation. VORPAL's capability of modeling DBD plasma actuator at low pressures (0.1 to 10 torr) using kinetic plasma modeling approach, and at moderate to atmospheric pressures (1 to 10 atm) using hydrodynamic plasma modeling approach, were demonstrated. In addition, results of experiments with pulsed+bias DBD configuration that were performed for validation purposes are reported.

  10. Fluid pressure and reaction zone formation at a lithological interface

    NASA Astrophysics Data System (ADS)

    Malvoisin, Benjamin; Podladchikov, Yuri

    2014-05-01

    Chemical composition variations in reaction zones between two distinct lithologies are generally interpreted in terms of chemical potential gradients and diffusion process. Concentration profiles can then be used to quantify the species diffusion coefficients or the time scale of geological events. However, chemical potential gradients are also functions of temperature and pressure and local variations of these parameters can thus potentially modify the diffusion process. In northern Corsica, a centimeter scale reaction zone formed under blueschist conditions at a serpentinite - marble contact of sedimentary origin. Three sub-zones having chemical compositions evolving from one rock end-member to another divide the reaction zone along sharp interfaces. At the reaction zone - marble interface, marble decarbonation occurs to form wollastonite and carbonaceous matter. Thermodynamic calculations for this reaction and the respective increase in density of 25 % and 7 % in the bulk rock and in the garnet minerals are interpreted as records of a pressure gradient during reaction zone formation. Moreover, the formation of a volatile-free sub-zone in the reaction zone from reaction between the H2O-bearing serpentinite and the CO2-bearing marble released fluids at the contact. The impact of such a release on the fluid pressure was modelled by considering the effects of both the rock compaction and the transport of fluid by hydraulic diffusion. Modelling results indicates that > 0.5 GPa fluid overpressure can be generated at the contact if devolatilization rates are of the order of the one experimentally measured (> 10-5 kg of fluid/m3 of rock/s). The resulting pressure gradient is of the order of magnitude of the one necessary to counter-balance the effect on chemical potential of the chemical composition variations across the contact. Finally, after the reaction has run to completion, the model predicts that fluid rapidly diffuses away from the interface which thus stops

  11. Artificial cutting-fluid smoke generation: effect of pressure.

    PubMed

    McEntire, R H; Somers, W K

    1979-07-01

    Industrial smoke from cutting fluid poses a potential carcinogenic hazard to workers. For toxicity tests, an artificial smoke device needs to be designed. Such a device would be easy to construct if it were known that smoke is a function of heat during cutting processes and not the cutting pressures. Gas chromatograph response was the same for smoke generated with and without pressure. The implication is that smoke generated during a metal cutting process is due to high temperature and is not influenced by the cutting surface pressures. PMID:484479

  12. Interstitial Fluid Colloid Osmotic Pressure in Healthy Children

    PubMed Central

    Guthe, Hans Jørgen Timm; Indrebø, Marianne; Nedrebø, Torbjørn; Norgård, Gunnar; Wiig, Helge; Berg, Ansgar

    2015-01-01

    Objective The colloid osmotic pressure (COP) of plasma and interstitial fluid play important roles in transvascular fluid exchange. COP values for monitoring fluid balance in healthy and sick children have not been established. This study set out to determine reference values of COP in healthy children. Materials and Methods COP in plasma and interstitial fluid harvested from nylon wicks was measured in 99 healthy children from 2 to 10 years of age. Nylon wicks were implanted subcutaneously in arm and leg while patients were sedated and intubated during a minor surgical procedure. COP was analyzed in a colloid osmometer designed for small fluid samples. Results The mean plasma COP in all children was 25.6 ± 3.3 mmHg. Arbitrary division of children in four different age groups, showed no significant difference in plasma or interstitial fluid COP values for patients less than 8 years, whereas patients of 8-10 years had significant higher COP both in plasma and interstitial fluid. There were no gender difference or correlation between COP in interstitial fluid sampled from arm and leg and no significant effect on interstitial COP of gravity. Prolonged implantation time did not affect interstitial COP. Conclusion Plasma and interstitial COP in healthy children are comparable to adults and COP seems to increase with age in children. Knowledge of the interaction between colloid osmotic forces can be helpful in diseases associated with fluid imbalance and may be crucial in deciding different fluid treatment options. Trial Registration ClinicalTrials.gov NCT01044641 PMID:25853713

  13. Pressure of Newtonian fluid flow through curved pipes and elbows

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Zhang, Xinxin; Sun, Haosen; Chen, Mingjiu; Lu, Xiaoyang; Wang, Yuancheng; Liu, Xueting

    2013-08-01

    Under conditions of high temperature and high pressure, the non-uniformity of pressure loads has intensified the stress concentration which impacts the safety of curved pipes and elbows. This paper focuses on the pressure distribution and flow characteristic in a curved 90° bend pipe with circular cross-sections, which are widely used in industrial applications. These flow and pressure characteristics in curved bend pipes have been researched by employing numerical simulation and theoretical analysis. Based on the dimensionless analysis method a formula for the pressure of Newtonian fluid flow through the elbow pipes is deduced. Also the pressure distributions of several elbows with different curvature ratio R/D are obtained by numerical methods. The influence of these non-dimensional parameters such as non-dimensional curvature ratio, Reynolds number and non-dimensional axial angle α and circumferential angle β on the pressure distribution in elbow pipes is discussed in detail. A number of important results have been achieved. This paper provides theoretical and numerical methods to understand the mechanical property of fluid flow in elbow pipes, to analyze the stress and to design the wall thickness of elbow pipes.

  14. Interstitial fluid pressure in soft tissue as a result of an externally applied contact pressure.

    PubMed

    Darling, A L; Yalavarthy, P K; Doyley, M M; Dehghani, H; Pogue, B W

    2007-07-21

    Manipulation of interstitial fluid pressure (IFP) has a clinical potential when used in conjunction with near-infrared spectroscopy for the detection of breast cancer. In order to better interpret how the applied pressure alters the vascular space and interstitial water volumes in breast tissue, a study on tissue-mimicking, gelatin phantoms was carried out to mimic the translation of external force into internal pressures. A complete set of three-dimensional (3D) pressure maps were obtained for the interior volumes of phantoms as an external force of 10 mmHg was applied, using mixtures of elastic moduli 19 and 33 kPa to simulate adipose and fibroglandular values of breast tissue. Corresponding linear elastic finite element analysis (FEA) cases were formulated. Shear stress, nonlinear mechanical properties, gravity and tissue geometry were all observed to contribute to internal pressure distribution, with surface shear stresses increasing internal pressures near the surface to greater than twice the applied external pressure. Average pressures by depth were predicted by the linear elastic FEA models. FEA models were run for cases mimicking a 93 kPa tumor inclusion within regions of adipose, fibroglandular tissue, and a composite of the two tissue types to illustrate the localized high fluid pressures caused by a tumor when an external force is applied. The conclusion was that external contact forces can generate potentially clinically useful fluid pressure magnitudes in regions of sharp effective elastic modulus gradients, such as tumor boundaries. PMID:17664598

  15. Electrically actuatable doped polymer flakes and electrically addressable optical devices using suspensions of doped polymer flakes in a fluid host

    DOEpatents

    Trajkovska-Petkoska, Anka; Jacobs, Stephen D.; Marshall, Kenneth L.; Kosc, Tanya Z.

    2010-05-11

    Doped electrically actuatable (electrically addressable or switchable) polymer flakes have enhanced and controllable electric field induced motion by virtue of doping a polymer material that functions as the base flake matrix with either a distribution of insoluble dopant particles or a dopant material that is completely soluble in the base flake matrix. The base flake matrix may be a polymer liquid crystal material, and the dopants generally have higher dielectric permittivity and/or conductivity than the electrically actuatable polymer base flake matrix. The dopant distribution within the base flake matrix may be either homogeneous or non-homogeneous. In the latter case, the non-homogeneous distribution of dopant provides a dielectric permittivity and/or conductivity gradient within the body of the flakes. The dopant can also be a carbon-containing material (either soluble or insoluble in the base flake matrix) that absorbs light so as to reduce the unpolarized scattered light component reflected from the flakes, thereby enhancing the effective intensity of circularly polarized light reflected from the flakes when the flakes are oriented into a light reflecting state. Electro-optic devices contain these doped flakes suspended in a host fluid can be addressed with an applied electric field, thus controlling the orientation of the flakes between a bright reflecting state and a non-reflecting dark state.

  16. Fast step-response settling of micro electrostatic actuators operated at low air pressure using input shaping

    NASA Astrophysics Data System (ADS)

    Mol, L.; Rocha, L. A.; Cretu, E.; Wolffenbuttel, R. F.

    2009-07-01

    Squeeze-film damping is highly inadequate in low-pressure systems or in systems where air pressure and/or gap dimensions are poorly defined. Input shaping has been used to circumvent the oscillations typically associated with under-damped mass-spring-damper systems and drastically decrease the settling time. The proposed method does not rely on feedback but solely on the system dynamics. The required input signal is derived analytically from the differential equation describing the system. The resulting device response is simulated and experimentally verified on an electrostatically actuated microstructure. Settling occurs even faster than for an equivalent critically damped system.

  17. Fluid film force control in lubricated journal bearings by means of a travelling wave generated with a piezoelectric actuators' system

    NASA Astrophysics Data System (ADS)

    Iula, Antonio; Lamberti, Nicola; Savoia, Alessandro; Caliano, Giosue

    2012-05-01

    In this work an experimental evaluation of the possiblity to influence and control the fluid film forces in the gap of a lubricated journal bearing by means of a rotating travelling wave is carried out. The travellig wave is generated by two power actuators opportunely positioned on the outer surface of the bearing and electrically driven with a phase shift of 90°. Each transducer is designed to work at the natural frequency of the radial nonaxisymmetrical mode 0-5 (23.6 kHz). Experimental results show that the travelling wave is capable to control the motion of an oil drop on the inner surface of the bearing and that it is capable to put in rotation a rotor layed on the drop oil via the viscous forces in the oil drop itself.

  18. Dependency of hydromechanical properties of monzonitic granite on confining pressure and fluid pressure under compression

    NASA Astrophysics Data System (ADS)

    Wang, Huanling; Xu, Weiya; Lui, Zaobao; Chao, Zhiming; Meng, Qingxiang

    2016-05-01

    Monzonitic granite is a low-permeability rock. Monzonitic granite formations are ideal for underground storage of oil due to their low permeability and high mechanical strength. In this study, a series of coupled hydromechanical triaxial tests are carried out using monzonitic granite specimens. The influence of confining and fluid pressures on stress, strain, and permeability is investigated. Failure characteristics under different confining and fluid pressures are discussed based on the analysis of macro fracture planes and micro scanning electron microscopy (SEM). The test results show that the change of permeability with stress and strain reflects the deformation stages of compaction, compression, crack propagation, coalesce, and failure of cracks. Due to the low porosity, the change of permeability is small in the initial phases of compaction and compression, whereas there is a significant increase in permeability when new cracks start to develop and coalesce. Confining pressures have a significant impact on the strength and permeability, particularly the crack damage stress of the rock. Compared with confining pressure, the effect of fluid pressure on rock strength and crack damage stress is small. For the monzonitic granite specimens tested, changing the confining pressure results in different failure modes, whereas the fluid pressure has a relatively small effect on the failure modes.

  19. Superconducting linear actuator

    NASA Technical Reports Server (NTRS)

    Johnson, Bruce; Hockney, Richard

    1993-01-01

    Special actuators are needed to control the orientation of large structures in space-based precision pointing systems. Electromagnetic actuators that presently exist are too large in size and their bandwidth is too low. Hydraulic fluid actuation also presents problems for many space-based applications. Hydraulic oil can escape in space and contaminate the environment around the spacecraft. A research study was performed that selected an electrically-powered linear actuator that can be used to control the orientation of a large pointed structure. This research surveyed available products, analyzed the capabilities of conventional linear actuators, and designed a first-cut candidate superconducting linear actuator. The study first examined theoretical capabilities of electrical actuators and determined their problems with respect to the application and then determined if any presently available actuators or any modifications to available actuator designs would meet the required performance. The best actuator was then selected based on available design, modified design, or new design for this application. The last task was to proceed with a conceptual design. No commercially-available linear actuator or modification capable of meeting the specifications was found. A conventional moving-coil dc linear actuator would meet the specification, but the back-iron for this actuator would weigh approximately 12,000 lbs. A superconducting field coil, however, eliminates the need for back iron, resulting in an actuator weight of approximately 1000 lbs.

  20. Pressure is not a state function for generic active fluids

    NASA Astrophysics Data System (ADS)

    Solon, A. P.; Fily, Y.; Baskaran, A.; Cates, M. E.; Kafri, Y.; Kardar, M.; Tailleur, J.

    2015-08-01

    Pressure is the mechanical force per unit area that a confined system exerts on its container. In thermal equilibrium, it depends only on bulk properties--such as density and temperature--through an equation of state. Here we show that in a wide class of active systems the pressure depends on the precise interactions between the active particles and the confining walls. In general, therefore, active fluids have no equation of state. Their mechanical pressure exhibits anomalous properties that defy the familiar thermodynamic reasoning that holds in equilibrium. The pressure remains a function of state, however, in some specific and well-studied active models that tacitly restrict the character of the particle-wall and/or particle-particle interactions.

  1. Validation of an All-Pressure Fluid Drop Model: Heptane Fluid Drops in Nitrogen

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.; Bulzan, Daniel L. (Technical Monitor)

    2000-01-01

    Despite the fact that supercritical fluids occur both in nature and in industrial situations, the fundamentals of their behavior is poorly understood because supercritical fluids combine the characteristics of both liquids and gases, and therefore their behavior is not intuitive. There are several specific reasons for the lack of understanding: First, data from (mostly optical) measurements can be very misleading because regions of high density thus observed are frequently identified with liquids. A common misconception is that if in an experiment one can optically identify "drops" and "ligaments", the observed fluid must be in a liquid state. This inference is incorrect because in fact optical measurements detect any large change (i.e. gradients) in density. Thus, the density ratio may be well below Omicron(10(exp 3)) that characterizes its liquid/gas value, but the measurement will still identify a change in the index of refraction providing that the change is sudden (steep gradients). As shown by simulations of supercritical fluids, under certain conditions the density gradients may remain large during the supercritical binary fluids mixing, thus making them optically identifiable. Therefore, there is no inconsistency between the optical observation of high density regions and the fluids being in a supercritical state. A second misconception is that because a fluid has a liquid-like density, it is appropriate to model it as a liquid. However, such fluids may have liquid-like densities while their transport properties differ from those of a liquid. Considering that the critical pressure of most fuel hydrocarbons used in Diesel and gas turbine engines is in the range of 1.5 - 3 MPa, and the fact that the maximum pressure attained in these engines is about 6 Mps, it is clear that the fuel in the combustion chamber will experience both subcritical and supercritical conditions. Studies of drop behavior over a wide range of pressures were performed in the past

  2. MRI contrast agent concentration and tumor interstitial fluid pressure.

    PubMed

    Liu, L J; Schlesinger, M

    2016-10-01

    The present work describes the relationship between tumor interstitial fluid pressure (TIFP) and the concentration of contrast agent for dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). We predict the spatial distribution of TIFP based on that of contrast agent concentration. We also discuss the cases for estimating tumor interstitial volume fraction (void fraction or porosity of porous medium), ve, and contrast volume transfer constant, K(trans), by measuring the ratio of contrast agent concentration in tissue to that in plasma. A linear fluid velocity distribution may reflect a quadratic function of TIFP distribution and lead to a practical method for TIFP estimation. To calculate TIFP, the parameters or variables should preferably be measured along the direction of the linear fluid velocity (this is in the same direction as the gray value distribution of the image, which is also linear). This method may simplify the calculation for estimating TIFP. PMID:27343032

  3. Pore fluid pressure, apparent friction, and Coulomb failure

    USGS Publications Warehouse

    Beeler, N.M.; Simpson, R.W.; Hickman, S.H.; Lockner, D.A.

    2000-01-01

    Many recent studies of stress-triggered seismicity rely on a fault failure model with a single free parameter, the apparent coefficient of friction, presumed to be a material constant with possible values 0 ≤ μ′ ≤ 1. These studies may present a misleading view of fault strength and the role of pore fluid pressure in earthquake failure. The parameter μ′ is intended to incorporate the effects of both friction and pore pressure, but is a material constant only if changes in pore fluid pressure induced by changes in stress are proportional to the normal stress change across the potential failure plane. Although specific models of fault zones permit such a relation, neither is it known that fault zones within the Earth behave this way, nor is this behavior expected in all cases. In contrast, for an isotropic homogeneous poroelastic model the pore pressure changes are proportional to changes in mean stress, μ′ is not a material constant, and −∞ ≤ μ′ ≤ +∞. Analysis of the change in Coulomb failure stress for tectonically loaded reverse and strike-slip faults shows considerable differences between these two pore pressure models, suggesting that such models might be distinguished from one another using observations of triggered seismicity (e.g., aftershocks). We conclude that using the constant apparent friction model exclusively in studies of Coulomb failure stress is unwise and could lead to significant errors in estimated stress change and seismic hazard.

  4. Cerebrospinal fluid pressure in conscious head-down tilted rats

    NASA Technical Reports Server (NTRS)

    Severs, Walter B.; Morrow, Bret A.; Keil, Lanny C.

    1991-01-01

    The acute effects of a 1-h -45 deg head-down tilt on continouously recorded cerebrospinal fluid pressure (PCSF) of conscious rats are studied in order to investigate the shift of blood volume into the thoracic cavity in microgravity. PCSF, evaluated in 15-min time blocks over a 3-h experiment, increased slightly (less than 0.05) during the first 30 min of a control hour at 0 deg. There was a transient increase for about 5 min immediately after tilt (-45 deg) that may have been due to head movement after the position change. PCSF was statistically unchanged (above 0.05) during the second (-45 deg) hour and the third (0 deg) recovery hour. It is shown that the dynamics of intracranial pressure regulation can accommodate the acute cephalad fluid shift after tilting.

  5. Diffusion NMR of Fluids Confined to Mesopores under High Pressures

    NASA Astrophysics Data System (ADS)

    Zeigermann, Philipp; Dvoyashkin, Muslim; Gläser, Roger; Valiullin, Rustem

    2011-03-01

    Supercritical fluids are extensively used in various chemical applications including processes involving porous solids. The knowledge of their transport in bulk as well as under spatial confinements is critical for modeling and optimizing chemical reactions. In this contribution, we describe a high-pressure cell designed for pulsed field gradient NMR studies of diffusion of supercritical solvents in mesoporous materials. Some preliminary results on diffusion properties of ethane in bulk phase and confined to pores of mesoporous silicon obtained in a broad range of pressures below and above the critical temperature are reported.

  6. Documentation and Control of Flow Separation on a Low Pressure Turbine Linear Cascade of Pak-B Blades Using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Corke, Thomas c.; Thomas, FLint, O.; Huang, Junhui

    2007-01-01

    This work involved the documentation and control of flow separation that occurs over low pressure turbine (LPT) blades at low Reynolds numbers. A specially constructed linear cascade was utilized to study the flow field over a generic LPT cascade consisting of Pratt & Whitney "Pak-B" shaped blades. Flow visualization, surface pressure measurements, LDV measurements, and hot-wire anemometry were conducted to examine the flow fields with and without separation control. Experimental conditions were chosen to give a range of chord Reynolds numbers (based on axial chord and inlet velocity) from 10,000 to 100,000, and a range of freestream turbulence intensities from u'/U(infinity) = 0.08 to 2.85 percent. The blade pressure distributions were measured and used to identify the region of separation that depends on Reynolds number and the turbulence intensity. Separation control was performed using dielectric barrier discharge (DBD) plasma actuators. Both steady and unsteady actuation were implemented and found to work well. The comparison between the steady and unsteady actuators showed that the unsteady actuators worked better than the steady ones. For the steady actuators, it was found that the separated region is significantly reduced. For the unsteady actuators, where the signal was pulsed, the separation was eliminated. The total pressure losses (a low Reynolds number) was reduced by approximately a factor of two. It was also found that lowest plasma duty cycle (10 percent in this work) was as effective as the highest plasma duty cycle (50 percent in this work). The mechanisms of the steady and unsteady plasma actuators were studied. It was suggested by the experimental results that the mechanism for the steady actuators is turbulence tripping, while the mechanism for the unsteady actuators is to generate a train of spanwise structures that promote mixing.

  7. Adjustable steam producing flexible orifice independent of fluid pressure

    NASA Technical Reports Server (NTRS)

    Morrison, Andrew D. (Inventor)

    1992-01-01

    A self-adjusting choke for a fluids nozzle includes a membrane constructed of a single piece of flexible or elastic material. This flexible material is shaped to fit into the outlet of a nozzle. The body of the membrane has at least two flow channels, from one face to the other, which directs two streams of water to cross at the opening of the nozzle or at some point beyond. The elasticity and thickness of the membrane is selected to match the range of expected pressures and fluid velocities. The choke may have more than two flow channels, as long as they are aligned adjacent to one another and directed towards each other at the exit face. In a three orifice embodiment, one is directed upward, one is directed downward, and the one in the middle is directed forward. In this embodiment all three fluid streams intersect at some point past the nozzle opening. Under increased pressure the membrane will deform causing the orifices to realign in a more forward direction, causing the streams to intersect at a smaller angle. This reduces the force with which the separate streams impact each other, still allowing the separate streams to unify into a single stable spiralling stream in spite of the increased pressure.

  8. Fluid Pressure Anomalies in Shallow Intraplate Argillaceous Formations

    NASA Astrophysics Data System (ADS)

    Neuzil, C.

    2015-12-01

    Fluid transport in shales and other argillaceous formations is difficult to study because these materials often have extremely low permeability. However, recent investigations have revealed a number of instances of apparently isolated highs or lows in pore fluid potential in shallow (< ~ 1 km depth) argillaceous formations in intraplate settings. The presence (or absence) of such pressure anomalies may provide clues to fluid flow. Formations with the pressure anomalies are distinguished by (1) smaller ratios of hydraulic conductivity to formation thickness and (2) smaller hydraulic (or pressure) diffusivities than those without anomalies. This is consistent with water-saturated transient Darcian flow caused by strain at rates of ~ 10-17 to 10-16 s-1, by significant perturbing events in the past 104 to 106 years or by some combination of the two. Plausible causes include erosional downwasting, tectonic strain, and glaciation. In this conceptualization the anomalies constrain formation-scale flow properties, flow history, and local geological forcing in the last 106 years and in particular indicate zones of low permeability (10-19 - 10-22 m2) that could be useful for isolation of nuclear waste.

  9. One-shot valve may be remotely actuated

    NASA Technical Reports Server (NTRS)

    Kami, S.

    1965-01-01

    One-shot valve, with spring-loaded plunger and sealing diaphragm, incorporates an emergency release actuated by a remote sensor. The plunger is released by the electrical melting of a fuse link and pierces the valve seal. The valve lowers fluid pressure in a container without losing the contained fluid.

  10. Actuated atomizer

    NASA Technical Reports Server (NTRS)

    Tilton, Charles (Inventor); Weiler, Jeff (Inventor); Palmer, Randall (Inventor); Appel, Philip (Inventor)

    2008-01-01

    An actuated atomizer is adapted for spray cooling or other applications wherein a well-developed, homogeneous and generally conical spray mist is required. The actuated atomizer includes an outer shell formed by an inner ring; an outer ring; an actuator insert and a cap. A nozzle framework is positioned within the actuator insert. A base of the nozzle framework defines swirl inlets, a swirl chamber and a swirl chamber. A nozzle insert defines a center inlet and feed ports. A spool is positioned within the coil housing, and carries the coil windings having a number of turns calculated to result in a magnetic field of sufficient strength to overcome the bias of the spring. A plunger moves in response to the magnetic field of the windings. A stop prevents the pintle from being withdrawn excessively. A pintle, positioned by the plunger, moves between first and second positions. In the first position, the head of the pintle blocks the discharge passage of the nozzle framework, thereby preventing the atomizer from discharging fluid. In the second position, the pintle is withdrawn from the swirl chamber, allowing the atomizer to release atomized fluid. A spring biases the pintle to block the discharge passage. The strength of the spring is overcome, however, by the magnetic field created by the windings positioned on the spool, which withdraws the plunger into the spool and further compresses the spring.

  11. Frictional heating, fluid pressure, and the resistance to fault motion

    NASA Astrophysics Data System (ADS)

    Lachenbruch, Arthur H.

    1980-11-01

    Expansion of pore fluid caused by frictional heating might have an important effect on the factional resistance and temperature during an earthquake and a controlling influence on the physics of the earthquake process. When confined water is heated, the pressure increases rapidly (≳10 bars/°C). As Sibson (1973) has pointed out, this could cause a sharp reduction of effective normal stress and dynamic friction on the fault surface. Whether or not this transient stress reduction occurs depends upon the tandem operation of several processes, any of which can break the chain that links frictional heat to frictional stress: the friction must cause an appreciable temperature rise (imposing conditions on the width of the shear zone and rate of conductive transport); the temperature rise must cause an appreciable fluid pressure rise (imposing conditions on the rate of pore dilatation or hydrofracturing, and the rate of Darcian transport); the fluid pressure rise must cause an appreciable reduction of friction (requiring the presence of a continuous fluid phase). Each process depends upon event duration, particle velocity, and the initial value of dynamic friction. With the present uncertainty in the controlling parameters (principally permeability, width of the shear zone, initial stress, and factors controlling transient hydrofracture and pore dilatation) a wide variety of fault behavior is possible. Limits to fault behavior for various ranges of the controlling parameters can be estimated from the governing equations, however, and results can be summarized graphically. If the effective stress law applies and pore dilatation is unimportant, dynamic friction would drop from an initial value of 1 kbar to ˜100 bars when shear strain reached 10 for most earthquakes if the permeability were less than 0.1 μdarcy; the maximum temperature rise would be only ˜150°C irrespective of final strain. If the permeability were ≳100 mdarcies, however, friction would be unaffected

  12. 21 CFR 880.2460 - Electrically powered spinal fluid pressure monitor.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Electrically powered spinal fluid pressure monitor... Personal Use Monitoring Devices § 880.2460 Electrically powered spinal fluid pressure monitor. (a) Identification. An electrically powered spinal fluid pressure monitor is an electrically powered device used...

  13. 21 CFR 880.2460 - Electrically powered spinal fluid pressure monitor.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Electrically powered spinal fluid pressure monitor... Personal Use Monitoring Devices § 880.2460 Electrically powered spinal fluid pressure monitor. (a) Identification. An electrically powered spinal fluid pressure monitor is an electrically powered device used...

  14. 21 CFR 880.2460 - Electrically powered spinal fluid pressure monitor.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Electrically powered spinal fluid pressure monitor... Personal Use Monitoring Devices § 880.2460 Electrically powered spinal fluid pressure monitor. (a) Identification. An electrically powered spinal fluid pressure monitor is an electrically powered device used...

  15. 21 CFR 880.2460 - Electrically powered spinal fluid pressure monitor.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Electrically powered spinal fluid pressure monitor... Personal Use Monitoring Devices § 880.2460 Electrically powered spinal fluid pressure monitor. (a) Identification. An electrically powered spinal fluid pressure monitor is an electrically powered device used...

  16. 21 CFR 880.2460 - Electrically powered spinal fluid pressure monitor.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Electrically powered spinal fluid pressure monitor... Personal Use Monitoring Devices § 880.2460 Electrically powered spinal fluid pressure monitor. (a) Identification. An electrically powered spinal fluid pressure monitor is an electrically powered device used...

  17. Estimation of Tumor Interstitial Fluid Pressure (TIFP) Noninvasively.

    PubMed

    Liu, Long Jian; Brown, Stephen L; Ewing, James R; Ala, Brigitte D; Schneider, Kenneth M; Schlesinger, Mordechay

    2016-01-01

    Tumor interstitial fluid pressure (TIFP), is a physiological parameter with demonstrated predictive value for a tumor's aggressiveness, drug delivery, as well as response to treatments such as radiotherapy and chemotherapy. Despite its utility, measurement of TIFP has been limited by the need for invasive procedures. In this work, the theoretical basis for approaching the absolute value of TIFP and the experimental method for noninvasively measuring TIFP are presented. Given specific boundary and continuity conditions, we convert theoretical variables into measurable variables by applying MRI technology. The work shows that TIFP in the central region of the tumor can be estimated by an analysis of the variation of tissue fluid motion in the tumor rim and surrounding tissue. It is determined from three noninvasive measurable parameters: i) an estimate of the velocity of the tumor interstitial fluid at the tumor surface, which is maximal, ii) a measurement of the distance from the tumor surface to where the tumor exudates are absorbed (or normalized), and iii) an estimate of the hydraulic conductivity of the interstitium through which the tumor exudate travels. We experimentally show that the fluid flow within the tumor rim is not uniform, even for a round shaped tumor, and demonstrate the procedures for the noninvasive measurement of TIFP. PMID:27467886

  18. Estimation of Tumor Interstitial Fluid Pressure (TIFP) Noninvasively

    PubMed Central

    Liu, Long Jian; Brown, Stephen L.; Ewing, James R.; Ala, Brigitte D.; Schneider, Kenneth M.

    2016-01-01

    Tumor interstitial fluid pressure (TIFP), is a physiological parameter with demonstrated predictive value for a tumor’s aggressiveness, drug delivery, as well as response to treatments such as radiotherapy and chemotherapy. Despite its utility, measurement of TIFP has been limited by the need for invasive procedures. In this work, the theoretical basis for approaching the absolute value of TIFP and the experimental method for noninvasively measuring TIFP are presented. Given specific boundary and continuity conditions, we convert theoretical variables into measurable variables by applying MRI technology. The work shows that TIFP in the central region of the tumor can be estimated by an analysis of the variation of tissue fluid motion in the tumor rim and surrounding tissue. It is determined from three noninvasive measurable parameters: i) an estimate of the velocity of the tumor interstitial fluid at the tumor surface, which is maximal, ii) a measurement of the distance from the tumor surface to where the tumor exudates are absorbed (or normalized), and iii) an estimate of the hydraulic conductivity of the interstitium through which the tumor exudate travels. We experimentally show that the fluid flow within the tumor rim is not uniform, even for a round shaped tumor, and demonstrate the procedures for the noninvasive measurement of TIFP. PMID:27467886

  19. Rotational viscometer for high-pressure high-temperature fluids

    DOEpatents

    Carr, Kenneth R.

    1985-01-01

    The invention is a novel rotational viscometer which is well adapted for use with fluids at high temperatures and/or pressures. In one embodiment, the viscometer includes a substantially non-magnetic tube having a closed end and having an open end in communication with a fluid whose viscosity is to be determined. An annular drive magnet is mounted for rotation about the tube. The tube encompasses and supports a rotatable shaft assembly which carries a rotor, or bob, for insertion in the fluid. Affixed to the shaft are (a) a second magnet which is magnetically coupled to the drive magnet and (b) a third magnet. In a typical operation, the drive magnet is rotated to turn the shaft assembly while the shaft rotor is immersed in the fluid. The viscous drag on the rotor causes the shaft assembly to lag the rotation of the drive magnet by an amount which is a function of the amount of viscous drag. A first magnetic pickup generates a waveform whose phase is a function of the angular position of the drive magnet. A second magnetic pickup generates a waveform whose phase is a function of the angular position of the third magnet. An output is generated indicative of the phase difference between the two waveforms.

  20. Rotational viscometer for high-pressure, high-temperature fluids

    DOEpatents

    Carr, K.R.

    1983-06-06

    The invention is a novel rotational viscometer which is well adapted for use with fluids at high temperatures and/or pressures. In one embodiment, the viscometer include a substantially non-magnetic tube having a closed end and having an open end in communication with a fluid whose viscosity is to be determined. An annular drive magnet is mounted for rotation about the tube. The tube encompasses and supports a rotatable shaft assembly which carries a rotor, or bob, for insertion in the fluid. Affixed to the shaft are (a) a second magnet which is magnetically coupled to the drive magnet and (b) a third magnet. In a typical operation, the drive magnet is rotated to turn the shaft assembly while the shaft rotor is immersed in the fluid. The viscous drag on the rotor causes the shaft assembly to lag the rotation of the drive magnet by an amount which is a function of the amount of viscous drag. A first magnetic pickup generates a waveform whose phase is a function of the angular position of the drive magnet. A second magnetic pickup generates a waveform whose phase is a function of the angular position of the third magnet. Means are provided to generate an output indicative of the phase difference between the two waveforms. The viscometer is comparatively simple, inexpensive, rugged, and does not require shaft seals.

  1. Extended fluid models: Pressure tensor effects and equilibria

    SciTech Connect

    Cerri, S. S.; Henri, P.; Califano, F.; Pegoraro, F.; Del Sarto, D.; Faganello, M.

    2013-11-15

    We consider the use of “extended fluid models” as a viable alternative to computationally demanding kinetic simulations in order to manage the global large scale evolution of a collisionless plasma while accounting for the main effects that come into play when spatial micro-scales of the order of the ion inertial scale d{sub i} and of the thermal ion Larmor radius ρ{sub i} are formed. We present an extended two-fluid model that retains finite Larmor radius (FLR) corrections to the ion pressure tensor while electron inertia terms and heat fluxes are neglected. Within this model we calculate analytic FLR plasma equilibria in the presence of a shear flow and elucidate the role of the magnetic field asymmetry. Using a Hybrid Vlasov code, we show that these analytic equilibria offer a significant improvement with respect to conventional magnetohydrodynamic shear-flow equilibria when initializing kinetic simulations.

  2. Passively actuated valve

    SciTech Connect

    Modro, S. Michael; Ougouag, Abderrafi M.

    2005-09-20

    A passively actuated valve for isolating a high pressure zone from a low pressure zone and discontinuing the isolation when the pressure in the high pressure zone drops below a preset threshold. If the pressure in the high pressure zone drops below the preset threshold, the valve opens and allows flow from the high pressure zone to the low pressure zone. The valve remains open allowing pressure equalization and back-flow should a pressure inversion between the two pressure zone occur.

  3. Numerical Simulations of Flow Separation Control in Low-Pressure Turbines using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.; Ashpis, D. E.

    2007-01-01

    A recently introduced phenomenological model to simulate flow control applications using plasma actuators has been further developed and improved in order to expand its use to complicated actuator geometries. The new modeling approach eliminates the requirement of an empirical charge density distribution shape by using the embedded electrode as a source for the charge density. The resulting model is validated against a flat plate experiment with quiescent environment. The modeling approach incorporates the effect of the plasma actuators on the external flow into Navier Stokes computations as a body force vector which is obtained as a product of the net charge density and the electric field. The model solves the Maxwell equation to obtain the electric field due to the applied AC voltage at the electrodes and an additional equation for the charge density distribution representing the plasma density. The new modeling approach solves the charge density equation in the computational domain assuming the embedded electrode as a source therefore automatically generating a charge density distribution on the surface exposed to the flow similar to that observed in the experiments without explicitly specifying an empirical distribution. The model is validated against a flat plate experiment with quiescent environment.

  4. VPF and interstitial fluid pressure in brain oedema.

    PubMed

    Sirovskiy, E; Kornienko, V; Moshkin, A; Amcheslavskiy, V; Ingorokva, G; Glazman, L

    1990-01-01

    Monitoring of VFP and local brain interstitial fluid pressure was performed in 169 patients after removal of hemispheric gliomas, basal and subtentorial tumours. On the basis of CT-data 97% of the patients had postoperative oedema of various severity and spreading. The location of the tumour determined both the degree and severity of oedema as well as VFP and ISFP. Different mechanisms of oedema formation may be involved depending on localization of the tumour. Thus, we can propose a hypothesis of the mechanisms of oedema development in neurosurgical pathology. PMID:2089955

  5. Application of High-Pressure Cold Spray for an Internal Bore Repair of a Navy Valve Actuator

    NASA Astrophysics Data System (ADS)

    Widener, C. A.; Carter, M. J.; Ozdemir, O. C.; Hrabe, R. H.; Hoiland, B.; Stamey, T. E.; Champagne, V. K.; Eden, T. J.

    2016-01-01

    Cold spray is a reduced temperature, supersonic thermal spray process that is increasingly being used to perform repairs on high-value components. In this case, a valve actuator internal bore sealing surface was repaired on an aluminum 6061 hydraulic valve body using high-pressure cold spray. Corrosion damage to non-critical surfaces was also repaired, allowing the part to be returned to service. A high-pressure cold spray system was used to deposit gas-atomized 6061 aluminum powder using helium. The internal bore surfaces were approximately 100 mm in diameter with a depth of nearly 200 mm, and were sprayed using a 45° nozzle 65 mm in length. Modeling predictions validated the approach, and were used to identify a favorable nozzle geometry and process window combination. The minimum required adhesion strength on critical surfaces was 69 MPa. The average adhesion strength was 71.4 MPa, with glue failures on ASTM C633 bond test specimens. The actuator subsequently passed all bench top service related testing, was qualified as an approved repair, and is now in service. This was a first of its kind repair for cold spray, and demonstrates that it is a viable repair technology and is ready for broader implementation.

  6. Normal pressure hydrocephalus. Influences on cerebral hemodynamic and cerebrospinal fluid pressure--chemical autoregulation

    SciTech Connect

    Meyer, J.S.; Tachibana, H.; Hardenberg, J.P.; Dowell, R.E. Jr.; Kitagawa, Y.; Mortel, K.F.

    1984-02-01

    Blood flow in the cerebral gray matter was measured in normal pressure hydrocephalus and Alzheimer disease by 133Xe inhalation. Flow values in the frontal and temporal gray matter increased after lowering cerebrospinal fluid (CSF) pressure by lumbar puncture in normal pressure hydrocephalus (p less than 0.05) and also after shunting. One case with cerebral complications did not improve clinically. In Alzheimer disease the reverse (decreases in flow in the gray matter) occurred after removal of CSF. Normal pressure hydrocephalus was associated with impaired cerebral vasomotor responsiveness during 100% oxygen and 5% carbon dioxide inhalation. This complication was restored toward normal after CSF removal and/or shunting. Cerebral blood flow measurements appear to be useful for confirming the diagnosis of normal pressure hydrocephalus and predicting the clinical benefit from shunting.

  7. MEMS fluidic actuator

    DOEpatents

    Kholwadwala, Deepesh K.; Johnston, Gabriel A.; Rohrer, Brandon R.; Galambos, Paul C.; Okandan, Murat

    2007-07-24

    The present invention comprises a novel, lightweight, massively parallel device comprising microelectromechanical (MEMS) fluidic actuators, to reconfigure the profile, of a surface. Each microfluidic actuator comprises an independent bladder that can act as both a sensor and an actuator. A MEMS sensor, and a MEMS valve within each microfluidic actuator, operate cooperatively to monitor the fluid within each bladder, and regulate the flow of the fluid entering and exiting each bladder. When adjacently spaced in a array, microfluidic actuators can create arbitrary surface profiles in response to a change in the operating environment of the surface. In an embodiment of the invention, the profile of an airfoil is controlled by independent extension and contraction of a plurality of actuators, that operate to displace a compliant cover.

  8. Isentropic decompression of fluids from crustal and mantle pressures

    NASA Technical Reports Server (NTRS)

    Kieffer, S. W.; Delany, J. M.

    1979-01-01

    Criteria are derived according to which the flow of single-phase magmatic fluids and the rarefaction expansion of low-viscosity liquids and gases may be considered approximately isentropic. Graphs of entropy vs. density with contours of constant pressure and mass fraction are used to examine the possible thermodynamic histories of H2O and CO2 decompressing isentropically from crustal and upper mantle pressures; these graphs offer a simple visual representation of a number of thermodynamic variables involved in isentropic processes. It is shown how the graphs can be used to examine the behavior of volatiles that (1) ascend in volcanic systems originating at different depths within the earth, and (2) decompress from a shock Hugoniot state. Entropy-density graphs are presented separately for H2O and CO2.

  9. Quantitative Analysis of Cerebrospinal Fluid Pressure Gradients in Healthy Volunteers and Patients with Normal Pressure Hydrocephalus

    PubMed Central

    HAYASHI, Naokazu; MATSUMAE, Mitsunori; YATSUSHIRO, Satoshi; HIRAYAMA, Akihiro; ABDULLAH, Afnizanfaizal; KURODA, Kagayaki

    2015-01-01

    Magnetic resonance imaging (MRI) can depict not only anatomical information, but also physiological factors such as velocity and pressure gradient. Measurement of these physiological factors is necessary to understand the cerebrospinal fluid (CSF) environment. In this study we quantified CSF motion in various parts of the CSF space, determined changes in the CSF environment with aging, and compared CSF pressure gradient between patients with idiopathic normal pressure hydrocephalus (iNPH) and healthy elderly volunteers. Fifty-seven healthy volunteers and six iNPH patients underwent four-dimensional (4D) phase-contrast (PC) MRI. CSF motion was observed and the pressure gradient of CSF was quantified in the CSF space. In healthy volunteers, inhomogeneous CSF motion was observed whereby the pressure gradient markedly increased in the center of the skull and gradually decreased in the periphery of the skull. For example, the pressure gradient at the ventral surface of the brainstem was 6.6 times greater than that at the convexity of the cerebrum. The pressure gradient was statistically unchanged with aging. The pressure gradient of patients with iNPH was 3.2 times greater than that of healthy volunteers. The quantitative analysis of 4D-PC MRI data revealed that the pressure gradient of CSF can be used to understand the CSF environment, which is not sufficiently given by subjective impression of the anatomical image. PMID:26226976

  10. Improving plasma actuator performance at low pressure, and an analysis of the pointing capabilities of cubeSats using Plasmonic Force Propulsion (PFP) thrusters

    NASA Astrophysics Data System (ADS)

    Friz, Paul Daniel

    This thesis details the work done on two unrelated projects, plasma actuators, an aerodynamic flow control device, and Plasmonic Force Propulsion (PFP) thrusters, a space propulsion system for small satellites. The first half of the thesis is a paper published in the International Journal of Flow Control on plasma actuators. In this paper the thrust and power consumption of plasma actuators with varying geometries was studied at varying pressure. It was found that actuators with longer buried electrodes produce the most thrust over all and that they substantially improved thrust at low pressure. In particular actuators with 75 mm buried electrodes produced 26% more thrust overall and 34% more thrust at low pressure than the standard 15 mm design. The second half details work done modeling small satellite attitude and reaction control systems in order to compare the use of Plasmonic Force Propulsion thrusters with other state of the art reaction control systems. The model uses bang bang control algorithms and assumes the worst case scenario solar radiation pressure is the only disturbing force. It was found that the estimated 50-500 nN of thrust produced by PFP thrusters would allow the spacecraft which use them extremely high pointing and positioning accuracies (<10-9 degrees and 3 pm). PFP thrusters still face many developmental challenges such as increasing specific impulse which require more research, however, they have great potential to be an enabling technology for future NASA missions such as the Laser Interferometer Space Antenna, and The Stellar Imager.

  11. Melange rheology, fluid pressure distribution, and seismic style (Invited)

    NASA Astrophysics Data System (ADS)

    Fagereng, A.; Sibson, R. H.

    2010-12-01

    Subduction megathrusts accommodate shear displacements in a range of seismic styles, including standard earthquakes, non-volcanic tremor, and continuous and transitory aseismic slip. Subduction channel shear zones, containing highly sheared, fluid-saturated trench-fill sediments intermingled with fragments of oceanic crust, are commonly inferred to occur along active subduction thrust interfaces. If this interpretation is correct, these plate boundary faults are not discrete planes, but may resemble the mélange shear zones commonly found in exhumed subduction-related rock assemblages. In such shear zones, deformation is accommodated by a mixture of continuous matrix flow and localized slip on numerous shear discontinuities. The dominant deformation mode in a mélange appears to depend critically on the ratio of competent to incompetent material, with shear discontinuities localized along lithological contacts or within competent domains, while matrix flow accommodates shearing by distributed strain. If the style of strain/displacement accommodation in a mélange reflects the partitioning between aseismic and seismic slip, the proportion of competent material seems likely to be a significant factor affecting seismic style within subduction channel shear zones. Along the Hikurangi margin, New Zealand, interseismic coupling varies from strong in the south to weak in the north. Variations in accretionary prism geometry indicate that the megathrust is mechanically stronger in the weakly coupled segment, than in the strongly coupled region. Thus, along this megathrust, weak coupling appears to occur on a relatively strong fault segment, while strong coupling relates to weak segments of the plate boundary. This may be caused by a fluid pressure difference, where frictional sliding is preferred in the strongly coupled, mechanically weak segment, where the incoming plate is relatively smooth and the overlying plate inferred to be relatively impermeable. In the weakly

  12. Raman Scattering from Solid and Fluid Helium at High Pressure

    NASA Astrophysics Data System (ADS)

    Watson, George Henry, Jr.

    Raman spectra were measured in solid helium at two molar volumes: 7.74 cm('3) ("10 kbar") and 9.06 cm('3) ("5 kbar"). The Raman-active E(,2g) phonon has been observed in the hcp phase of each crystal. The volume dependence measured for this phonon frequency is well represented by the mode Gruneisen parameter (gamma) = 1.06 + 0.097 V. Conventional lattice dynamics, using modern helium potentials, predicts a frequency and volume dependence for the E(,2g) phonon in good agreement with the measurements over this range of volume. Temperature dependence of the E(,2g) phonon frequency and linewidth was measured under isochoric conditions. Over the limited range of temperature in which the hcp phase exists, the thermal shift of frequency was measured to be negative by an amount no more than 1 cm('-1). The phonon linewidth was observed to be non-zero at 0 K, increasing in width with increasing temperature. The temperature dependence is compatible with a strong interaction between the E(,2g) phonon and zone-edge phonons, where the optical phonon combines with a transverse acoustic phonon to create a longitudinal acoustic phonon. In addition, second-order Raman spectra were collected for both high-pressure solid phases, hcp and fcc. Structure has been observed in the two-phonon portion of the solid helium spectra and is remarkably similar in both phases. Significant intensity extends beyond the expected cut-off for two-phonon processes, though to a decreasing extent with increasing pressure. Thus multi-phonon processes remain important in helium even at high pressure. Raman scattering from dense fluid helium shows clear departure from the behavior of collision-induced scattering from the more classical fluids. Even at room temperature, a departure from the usual roughly-exponential behavior is observed at low frequency in helium at high pressure. The departure becomes even more pronounced near the freezing temperature, with a dramatic reduction in low-frequency intensity

  13. Characterization of piezoelectric macrofiber composite actuated winglets

    NASA Astrophysics Data System (ADS)

    Guha, T. K.; Oates, W. S.; Kumar, R.

    2015-06-01

    The present study primarily focuses on the design, development, and structural characterization of an oscillating winglet actuated using a piezoelectric macrofiber composite (MFC). The primary objective is to study the effect of controlled wingtip oscillations on the evolution of wingtip vortices, with a goal of weakening these potentially harmful tip vortices by introducing controlled instabilities through both spatial and temporal perturbations producible through winglet oscillations. MFC-actuated winglets have been characterized under different input excitation and pressure-loading conditions. The winglet oscillations show bimodal behavior for both structural and actuation modes of resonance. The oscillatory amplitude at these actuation modes increases linearly with the magnitude of excitation. During wind-tunnel tests, fluid-structure interactions led to structural vibrations of the wing. The effect of these vibrations on the overall winglet oscillations decreased when the strength of actuation increased. At high input excitation, the actuated winglet was capable of generating controlled oscillations. As a proof of concept, the current study has demonstrated that microfiber composite-actuated winglets produce sufficient displacements to alter the development of the wingtip vortex.

  14. Effects of magmatic and metamorphic volatiles on the evolution of fluid-rock interactions and fluid pressure during contact metamorphism

    SciTech Connect

    Hanson, R.B. )

    1992-01-01

    Finite difference models of hydrothermal flow around a cooling intrusion that include fluid production from the magma during crystallization and from wall rocks during heating are used to investigate the evolution of fluid pressure and fluid-rock interactions during the contact metamorphism. For a granodiorite intrusion with a width of 9 km and releasing just 1: H[sub 2]O linearly during crystallization, fluid production elevates fluid pressures to lithostatic values above and adjacent to the intrusion when permeabilities are less than 1 [mu]D (10[sup [minus]18] m[sup 2]). Alternatively, hydrofracturing resulting from fluid production would be sufficient to create and maintain a time-averaged permeability of 1 [mu]D for 50,000 years: permeability decreases gradually with time afterward until the magma crystallizes (350,000 years). In detail, the history depends strongly on how fluids are released from the crystallizing magma. The effect is comparable to that obtained for devolatilization of 5% H[sub 2]O by weight over heating of 400 C in adjacent wall rocks. Fluid production dominates other mechanisms for elevating fluid pressures such as thermal expansion of pore fluids or ductile strain. In models with both magmatic and metamorphic fluids, fluid flow is outward from the inner aureole for much of the cooling history at wall-rock permeabilities of [le]100 [mu]D. Extensive up-temperature flow is not predicted. The evolution of flow is such that magmatic fluids can initially dominate fluid-rock interactions in a plume above the intrusion, although the timing of interaction of magmatic and metamorphic waters is sensitive to the detailed devolatilization histories. Initial pore fluids rapidly become insignificant in the overall fluid budget. Surface or external fluids infiltrate only late in the cooling history, as rocks within a few kilometers of the intrusion are cooling.

  15. Pressurized fluids for extraction of cedarwood oil from Juniperus virginianna.

    PubMed

    Eller, Fred J; Taylor, Scott L

    2004-04-21

    The extraction of cedarwood oil (CWO) using liquid carbon dioxide (LC-CO(2)) was investigated and compared to supercritical fluid extraction, including the effects of extraction pressure and length of extraction. The chemical composition of the extracts was monitored over the course of the extraction as well. The cumulative yields of CWO from cedarwood chips using 80 L of carbon dioxide varied very little treatment to treatment, with all temperature/pressure combinations yielding between 3.55 and 3.88% CWO, and the cumulative yields were statistically equivalent. The rate of extraction was highest under the supercritical extraction conditions (i.e., 100 degrees C and 6000 psi). Under the liquid CO(2) conditions (i.e., 25 degrees C), the extraction rates did not vary significantly with extraction pressure. However, there were differences in the chemical composition of the collected CWO. Extractions at 100 degrees C gave a much lower ratio of cedrol/cedrene than extractions at 25 degrees C. The highest ratio of cedrol/cedrene was obtained using 25 degrees C and 1500 psi. The use of subcritical water was also investigated for the extraction of CWO as well. Although some CWO was extracted using this method, the temperature/pressure combinations that gave the highest weight percentage yields also gave oils with an off odor while those combinations that gave a higher quality oil had very low yields. It appears that the high temperatures and acidic conditions cause a dehydration of the tertiary alcohol, cedrol, to its hydrocarbon analogue, cedrene, during CO(2) or pressurized water extractions of cedarwood. PMID:15080642

  16. Computational fluid dynamics modeling of coal gasification in a pressurized spout-fluid bed

    SciTech Connect

    Zhongyi Deng; Rui Xiao; Baosheng Jin; He Huang; Laihong Shen; Qilei Song; Qianjun Li

    2008-05-15

    Computational fluid dynamics (CFD) modeling, which has recently proven to be an effective means of analysis and optimization of energy-conversion processes, has been extended to coal gasification in this paper. A 3D mathematical model has been developed to simulate the coal gasification process in a pressurized spout-fluid bed. This CFD model is composed of gas-solid hydrodynamics, coal pyrolysis, char gasification, and gas phase reaction submodels. The rates of heterogeneous reactions are determined by combining Arrhenius rate and diffusion rate. The homogeneous reactions of gas phase can be treated as secondary reactions. A comparison of the calculated and experimental data shows that most gasification performance parameters can be predicted accurately. This good agreement indicates that CFD modeling can be used for complex fluidized beds coal gasification processes. 37 refs., 7 figs., 5 tabs.

  17. Fluid budgets along the northern Hikurangi subduction margin, New Zealand: the effect of a subducting seamount on fluid pressure

    NASA Astrophysics Data System (ADS)

    Ellis, Susan; Fagereng, Åke; Barker, Dan; Henrys, Stuart; Saffer, Demian; Wallace, Laura; Williams, Charles; Harris, Rob

    2015-07-01

    We estimate fluid sources around a subducted seamount along the northern Hikurangi subduction margin of New Zealand, using thermomechanical numerical modelling informed by wedge structure and porosities from multichannel seismic data. Calculated fluid sources are input into an independent fluid-flow model to explore the key controls on overpressure generation to depths of 12 km. In the thermomechanical models, sediment transport through and beneath the wedge is calculated assuming a pressure-sensitive frictional rheology. The change in porosity, pressure and temperature with calculated rock advection is used to compute fluid release from compaction and dehydration. Our calculations yield more precise information about source locations in time and space than previous averaged estimates for the Hikurangi margin. The volume of fluid release in the wedge is smaller than previously estimated from margin-averaged calculations (˜14 m3 yr-1 m-1), and is exceeded by fluid release from underlying (subducting) sediment (˜16 m3 yr-1 m-1). Clay dehydration contributes only a small quantity of fluid by volume (˜2 m3 yr-1 m-1 from subducted sediment), but the integrated effect is still significant landward of the seamount. Fluid source terms are used to estimate fluid pressures around a subducting seamount in the fluid-flow models, using subducted sediment permeability derived from porosity, and testing two end-members for décollement permeability. Models in which the décollement acts as a fluid conduit predict only moderate fluid overpressure in the wedge and subducting sediment. However, if the subduction interface becomes impermeable with depth, significant fluid overpressure develops in subducting sediment landward of the seamount. The location of predicted fluid overpressure and associated dehydration reactions is consistent with the idea that short duration, shallow, slow slip events (SSEs) landward of the seamount are caused by anomalous fluid pressures; alternatively

  18. Strain localization driven by co-seismic pore fluid pressurization

    NASA Astrophysics Data System (ADS)

    Rice, James; Platt, John; Brantut, Nicolas; Rudnicki, John

    2015-04-01

    The absence of a thermal anomaly associated with the San Andreas fault, and low driving stress resolved on it, suggest that such mature faults weaken dramatically during seismic slip. Thermal pressurization (TP) and thermal decomposition (TD) are two mechanisms to explain this co-seismic weakening. Both rely on elevated pore pressures in a fluid-saturated gouge, with TP achieving this through thermal expansion of native pore fluid and TD by releasing additional pore fluid (e.g., H2O or CO2) during a reaction. We use a one-dimensional model for a fluid-saturated gouge layer sheared between two undeforming half-spaces to study how TP (Rice et al., Platt et al., JGR-B, 2014) and TD (Platt et al., submitted JGR-B) drive seismic strain localization. A linear stability analysis is first used to predict the localized zone thickness for each of the weakening mechanisms. Using representative parameters for fault gouge we predict localized zone thicknesses of a few tens of microns, in line with laboratory (Kitajima et al., 2010) and field (Chester and Chester, 1998) observations. Next we use numerical simulations to study how the localized zone develops once nonlinear effects become important. These show that the final localized zone thickness is very similar to the linear stability prediction. In the simulations, the onset of localization accelerates fault weakening, making co-seismic strain localization an important consideration, apparently neglected in all current earthquake simulations. Finally we show how a secondary instability can lead to migration of the deforming zone across the gouge layer. This instability is driven by hydrothermal diffusion for TP, and by reactant depletion for TD. Our results show that migration must be taken into account when inferring the width of the deforming zone from field observations. Even when the zone of localized straining is only a few tens of microns wide, migration can lead to a final strain profile with a zone of roughly uniform

  19. Strain localization driven by co-seismic pore fluid pressurization

    NASA Astrophysics Data System (ADS)

    Platt, J. D.; Brantut, N.; Rice, J. R.; Rudnicki, J. W.

    2014-12-01

    The absence of a thermal anomaly associated with the San Andreas fault, and low driving stress resolved on it, suggest that such mature faults weaken dramatically during seismic slip. Thermal pressurization (TP) and thermal decomposition (TD) are two mechanisms to explain this co-seismic weakening. Both rely on elevated pore pressures in a fluid-saturated gouge, with TP achieving this through thermal expansion of native pore fluid and TD by releasing additional pore fluid (e.g., H2O or CO2) during a reaction. We use a one-dimensional model for a fluid-saturated gouge layer sheared between two undeforming half-spaces to study how TP (Rice et al., Platt et al., JGR-B, 2014) and TD (Platt et al., submitted JGR-B) drive seismic strain localization. A linear stability analysis is first used to predict the localized zone thickness for each of the weakening mechanisms. Using representative parameters for fault gouge we predict localized zone thicknesses of a few tens of microns, in line with laboratory (Kitajima et al., 2010) and field (Chester and Chester, 1998) observations. Next we use numerical simulations to study how the localized zone develops once nonlinear effects become important. These show that the final localized zone thickness is very similar to the linear stability prediction. In the simulations, the onset of localization accelerates fault weakening, making co-seismic strain localization an important consideration, apparently neglected in all current earthquake simulations. Finally we show how a secondary instability can lead to migration of the deforming zone across the gouge layer. This instability is driven by hydrothermal diffusion for TP, and by reactant depletion for TD. Our results show that migration must be taken into account when inferring the width of the deforming zone from field observations. Even when the zone of localized straining is only a few tens of microns wide, migration can lead to a final strain profile with a zone of roughly uniform

  20. Coupling changes in densities and porosity to fluid pressure variations in reactive porous fluid flow: Local thermodynamic equilibrium

    NASA Astrophysics Data System (ADS)

    Malvoisin, Benjamin; Podladchikov, Yury Yu.; Vrijmoed, Johannes C.

    2015-12-01

    Mineralogical reactions which generate or consume fluids play a key role during fluid flow in porous media. Such reactions are linked to changes in density, porosity, permeability, and fluid pressure which influence fluid flow and rock deformation. To understand such a coupled system, equations were derived from mass conservation and local thermodynamic equilibrium. The presented mass conservative modeling approach describes the relationships among evolving fluid pressure, porosity, fluid and solid density, and devolatilization reactions in multicomponent systems with solid solutions. This first step serves as a framework for future models including aqueous speciation and transport. The complexity of univariant and multivariant reactions is treated by calculating lookup tables from thermodynamic equilibrium calculations. Simplified cases were also investigated to understand previously studied formulations. For nondeforming systems or systems divided into phases of constant density, the equations can be reduced to porosity wave equations with addition of a reactive term taking the volume change of reaction into account. For closed systems, an expression for the volume change of reaction and the associated pressure increase can be obtained. The key equations were solved numerically for the case of devolatilization of three different rock types that may enter a subduction zone. Reactions with positive Clapeyron slope lead to an increase in porosity and permeability with decreasing fluid pressure resulting in sharp fluid pressure gradients around a negative pressure anomaly. The opposite trend is obtained for reactions having a negative Clapeyron slope during which sharp fluid pressure gradients were only generated around a positive pressure anomaly. Coupling of reaction with elastic deformation induces a more efficient fluid flow for reactions with negative Clapeyron slope than for reactions with positive Clapeyron slope.

  1. Simply actuated closure for a pressure vessel - Design for use to trap deep-sea animals

    NASA Technical Reports Server (NTRS)

    Yayanos, A. A.

    1977-01-01

    A pressure vessel is described that can be closed by a single translational motion within 1 sec. The vessel is a key component of a trap for small marine animals and operates automatically on the sea floor. As the vessel descends to the sea floor, it is subjected both internally and externally to the high pressures of the deep sea. The mechanism for closing the pressure vessel on the sea floor is activated by the timed release of the ballast which was used to sink the trap. As it rises to the sea surface, the internal pressure of the vessel remains near the value present on the sea floor. The pressure vessel has been used in simulated ocean deployments and in the deep ocean (9500 m) with a 75%-85% retention of the deep-sea pressure. Nearly 100% retention of pressure can be achieved by using an accumulator filled with a gas.

  2. Fast electrochemical actuator

    NASA Astrophysics Data System (ADS)

    Uvarov, I. V.; Postnikov, A. V.; Svetovoy, V. B.

    2016-03-01

    Lack of fast and strong microactuators is a well-recognized problem in MEMS community. Electrochemical actuators can develop high pressure but they are notoriously slow. Water electrolysis produced by short voltage pulses of alternating polarity can overcome the problem of slow gas termination. Here we demonstrate an actuation regime, for which the gas pressure is relaxed just for 10 μs or so. The actuator consists of a microchamber filled with the electrolyte and covered with a flexible membrane. The membrane bends outward when the pressure in the chamber increases. Fast termination of gas and high pressure developed in the chamber are related to a high density of nanobubbles in the chamber. The physical processes happening in the chamber are discussed so as problems that have to be resolved for practical applications of this actuation regime. The actuator can be used as a driving engine for microfluidics.

  3. A Procedure for Measuring Microplastics using Pressurized Fluid Extraction.

    PubMed

    Fuller, Stephen; Gautam, Anil

    2016-06-01

    A method based on pressurized fluid extraction (PFE) was developed for measuring microplastics in environmental samples. This method can address some limitations of the current microplastic methods and provide laboratories with a simple analytical method for quantifying common microplastics in a range of environmental samples. The method was initially developed by recovering 101% to 111% of spiked plastics on glass beads and was then applied to a composted municipal waste sample with spike recoveries ranging from 85% to 94%. The results from municipal waste samples and soil samples collected from an industrial area demonstrated that the method is a promising alternative for determining the concentration and identity of microplastics in environmental samples. PMID:27172172

  4. Quintessence Field as a Perfect Cosmic Fluid of Constant Pressure

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Zhong; Ouyang, Jun; Yang, Huan-Xiong

    2015-03-01

    We study the cosmology of a quintessence scalar field which is equivalent to a non-barotropic perfect fluid of constant pressure. The coincidence problem is alleviated by such a quintessence equation-of-state that interpolates between plateau of zero at large redshifts and plateau of minus one as the redshift approaches to zero. The quintessence field is neither a unified dark matter nor a mixture of cosmological constant and cold dark matter, relying on the facts that the quintessence density contrasts of sub-horizon modes would undergo a period of late-time decline and the squared sound speeds of quintessence perturbations do not vanish. What a role does the quintessence play is dynamic dark energy, its clustering could remarkably reduce the growth rate of the density perturbations of non-relativistic matters. Supported in part by National Natural Science Foundation of China under Grant No. 11235010

  5. Pneumatic well casing pressure regulating system

    SciTech Connect

    Flohr, M.C.

    1987-10-20

    A pneumatic well casing pressure regulating system is described comprising: a hydraulically actuated choke for relieving well casing pressure; a continually running source of pneumatic pressure pulses; first means for applying pulses of hydraulic fluid corresponding to the pneumatic pressure pulses to the choke for opening the choke one step for each pulse of hydraulic fluid when actual casing pressure is higher than a desired casing pressure; and second means for applying pulses of hydraulic fluid corresponding to the pneumatic pressure pulses to the choke for closing the choke one step for each pulse of hydraulic fluid when actual casing pressure is less than a desired casing pressure.

  6. Larger-Stroke Piezoelectrically Actuated Microvalve

    NASA Technical Reports Server (NTRS)

    Yang, Eui-Hyeok

    2003-01-01

    A proposed normally-closed microvalve would contain a piezoelectric bending actuator instead of a piezoelectric linear actuator like that of the microvalve described in the preceding article. Whereas the stroke of the linear actuator of the preceding article would be limited to approximately equal to 6 micrometers, the stroke of the proposed bending actuator would lie in the approximate range of 10 to 15 micrometers-large enough to enable the microvalve to handle a variety of liquids containing suspended particles having sizes up to 10 m. Such particulate-laden liquids occur in a variety of microfluidic systems, one example being a system that sorts cells or large biomolecules for analysis. In comparison with the linear actuator of the preceding article, the bending actuator would be smaller and less massive. The combination of increased stroke, smaller mass, and smaller volume would be obtained at the cost of decreased actuation force: The proposed actuator would generate a force in the approximate range of 1 to 4 N, the exact amount depending on operating conditions and details of design. This level of actuation force would be too low to enable the valve to handle a fluid at the high pressure level mentioned in the preceding article. The proposal encompasses two alternative designs one featuring a miniature piezoelectric bimorph actuator and one featuring a thick-film unimorph piezoelectric actuator (see figure). In either version, the valve would consume a power of only 0.01 W when actuated at a frequency of 100 Hz. Also, in either version, it would be necessary to attach a soft elastomeric sealing ring to the valve seat so that any particles that settle on the seat would be pushed deep into the elastomeric material to prevent or reduce leakage. The overall dimensions of the bimorph version would be 7 by 7 by 1 mm. The actuator in this version would generate a force of 1 N and a stroke of 10 m at an applied potential of 150 V. The actuation force would be

  7. Improved Electrohydraulic Linear Actuators

    NASA Technical Reports Server (NTRS)

    Hamtil, James

    2004-01-01

    A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to many industrial uses, such as steam turbines, process control valves, dampers, motion control, etc. The advantageous features of the improved electrohydraulic linear actuators are best described with respect to shortcomings of prior electrohydraulic linear actuators that the improved ones are intended to supplant. The flow of hydraulic fluid to the two ports of the actuator cylinder is controlled by a servo valve that is controlled by a signal from a servo amplifier that, in turn, receives an analog position-command signal (a current having a value between 4 and 20 mA) from a supervisory control system of the facility. As the position command changes, the servo valve shifts, causing a greater flow of hydraulic fluid to one side of the cylinder and thereby causing the actuator piston to move to extend or retract a piston rod from the actuator body. A linear variable differential transformer (LVDT) directly linked to the piston provides a position-feedback signal, which is compared with the position-command signal in the servo amplifier. When the position-feedback and position-command signals match, the servo valve moves to its null position, in which it holds the actuator piston at a steady position.

  8. Pressure updating methods for the steady-state fluid equations

    NASA Technical Reports Server (NTRS)

    Fiterman, A.; Turkel, E.; Vatsa, V.

    1995-01-01

    We consider the steady state equations for a compressible fluid. Since we wish to solve for a range of speeds we must consider the equations in conservation form. For transonic speeds these equations are of mixed type. Hence, the usual approach is to add time derivatives to the steady state equations and then march these equations in time. One then adds a time derivative of the density to the continuity equation, a derivative of the momentum to the momentum equation and a derivative of the total energy to the energy equation. This choice is dictated by the time consistent equations. However, since we are only interested in the steady state this is not necessary. Thus we shall consider the possibility of adding a time derivative of the pressure to the continuity equation and similar modifications for the energy equation. This can then be generalized to adding combinations of time derivatives to each equation since these vanish in the steady state. When using acceleration techniques such as residual smoothing, multigrid, etc. these are applied to the pressure rather than the density. Hence, the code duplicates the behavior of the incompressible equations for low speeds.

  9. Sound-driven fluid dynamics in pressurized carbon dioxide.

    PubMed

    van Iersel, Maikel M; Mettin, Robert; Benes, Nieck E; Schwarzer, Dirk; Keurentjes, Jos T F

    2010-07-28

    Using high-speed visualization we demonstrate that ultrasound irradiation of pressurized carbon dioxide (CO(2)) induces phenomena that do not occur in ordinary liquids at ambient conditions. For a near-critical mixture of CO(2) and argon, sonication leads to extremely fast local phase separation, in which the system enters and leaves the two-phase region with the frequency of the imposed sound field. This phase transition can propagate with the speed of sound, but can also be located at fixed positions in the case of a standing sound wave. Sonication of a vapor-liquid interface creates a fine dispersion of liquid and vapor, irrespective whether the ultrasound horn is placed in the liquid or the vapor phase. In the absence of an interface, sonication of the liquid leads to ejection of a macroscopic vapor phase from the ultrasound horn with a velocity of several meters per second in the direction of wave propagation. The findings reported here potentially provide a tunable and noninvasive means for enhancing mass and heat transfer in high-pressure fluids. PMID:20687647

  10. Phantom model of physiologic intracranial pressure and cerebrospinal fluid dynamics.

    PubMed

    Bottan, Simone; Poulikakos, Dimos; Kurtcuoglu, Vartan

    2012-06-01

    We describe herein a novel life-size phantom model of the intracranial cavity and its validation. The cerebrospinal fluid (CSF) domains including ventricular, cysternal, and subarachnoid spaces were derived via magnetic resonance imaging. Brain mechanical properties and cranio-spinal compliance were set based on published data. Both bulk and pulsatile physiologic CSF flow were modeled. Model validation was carried out by comparisons of flow and pressure measurements in the phantom with published in vivo data of healthy subjects. Physiologic intracranial pressure with 10 mmHg mean and 0.4 mmHg peak pulse amplitude was recorded in the ventricles. Peak CSF flow rates of 0.2 and 2 ml/s were measured in the cerebral aqueduct and subarachnoid space, respectively. The phantom constitutes a first-of-its-kind approach to modeling physiologic intracranial dynamics in vitro. Herein, we describe the phantom design and manufacturing, definition and implementation of its operating parameters, as well as the validation of the modeled dynamics. PMID:22333981

  11. Electropneumatic actuator, phase 1

    NASA Astrophysics Data System (ADS)

    Bloomfield, D. P.

    1989-10-01

    The program demonstrated the feasibility of an electropneumatic actuator which can be used in manufacturing applications. The electropneumatic actuator, an alternative to the electric, hydraulic, and pneumatic actuators used in industry, consists of an electrochemical compressor, a power supply, and an actuator. The electrochemical compressor working fluid is hydrogen and a solvent such as water or ammonia. The compressor has no moving parts and runs on low voltage DC. The actuator is a conventional, commercially available unit. Researchers designed, constructed, and tested the electrochemical compressor in conjunction with the actuator, power supply, and computerized control. The one inch actuator can lift a fifty pound weight a distance of ten inches in about 1.5 minutes. The electrochemically powered system is capable of driving its loaded actuator to a prescribed location at a controlled rate. A defined set of design changes will combine the compressor and actuator in the same housing, and will develop two orders of magnitude increased actuator speed at the same or higher force levels.

  12. Interstitial Pressure in Pancreatic Ductal Adenocarcinoma Is Dominated by a Gel-Fluid Phase.

    PubMed

    DuFort, Christopher C; DelGiorno, Kathleen E; Carlson, Markus A; Osgood, Ryan J; Zhao, Chunmei; Huang, Zhongdong; Thompson, Curtis B; Connor, Robert J; Thanos, Christopher D; Scott Brockenbrough, J; Provenzano, Paolo P; Frost, Gregory I; Michael Shepard, H; Hingorani, Sunil R

    2016-05-10

    Elevated interstitial fluid pressure can present a substantial barrier to drug delivery in solid tumors. This is particularly true of pancreatic ductal adenocarcinoma, a highly lethal disease characterized by a robust fibroinflammatory response, widespread vascular collapse, and hypoperfusion that together serve as primary mechanisms of treatment resistance. Free-fluid pressures, however, are relatively low in pancreatic ductal adenocarcinoma and cannot account for the vascular collapse. Indeed, we have shown that the overexpression and deposition in the interstitium of high-molecular-weight hyaluronan (HA) is principally responsible for generating pressures that can reach 100 mmHg through the creation of a large gel-fluid phase. By interrogating a variety of tissues, tumor types, and experimental model systems, we show that an HA-dependent fluid phase contributes substantially to pressures in many solid tumors and has been largely unappreciated heretofore. We investigated the relative contributions of both freely mobile fluid and gel fluid to interstitial fluid pressure by performing simultaneous, real-time fluid-pressure measurements with both the classical wick-in-needle method (to estimate free-fluid pressure) and a piezoelectric pressure catheter transducer (which is capable of capturing pressures associated with either phase). We demonstrate further that systemic treatment with pegylated recombinant hyaluronidase (PEGPH20) depletes interstitial HA and eliminates the gel-fluid phase. This significantly reduces interstitial pressures and leaves primarily free fluid behind, relieving the barrier to drug delivery. These findings argue that quantifying the contributions of free- and gel-fluid phases to hydraulically transmitted pressures in a given cancer will be essential to designing the most appropriate and effective strategies to overcome this important and frequently underestimated resistance mechanism. PMID:27166818

  13. Pressure and Thrust Measurements of a High-Frequency Pulsed-Detonation Actuator

    NASA Technical Reports Server (NTRS)

    Nguyen, Namtran C.; Cutler, Andrew D.

    2008-01-01

    This paper describes the development of a small-scale, high-frequency pulsed detonation actuator. The device utilized a fuel mixture of H2 and air, which was injected into the device at frequencies of up to 1200 Hz. Pulsed detonations were demonstrated in an 8-inch long combustion volume, at approx.600 Hz, for the lambda/4 mode. The primary objective of this experiment was to measure the generated thrust. A mean value of thrust was measured up to 6.0 lb, corresponding to specific impulse of 2611 s. This value is comparable to other H2-fueled pulsed detonation engines (PDEs) experiments. The injection and detonation frequency for this new experimental case was approx.600 Hz, and was much higher than typical PDEs, where frequencies are usually less than 100 Hz. The compact size of the model and high frequency of detonation yields a thrust-per-unit-volume of approximately 2.0 lb/cu in, and compares favorably with other experiments, which typically have thrust-per-unit-volume values of approximately 0.01 lb/cu in.

  14. Self-actuated device

    DOEpatents

    Hecht, Samuel L.

    1984-01-01

    A self-actuated device, of particular use as a valve or an orifice for nuclear reactor fuel and blanket assemblies, in which a gas produced by a neutron induced nuclear reaction gradually accumulates as a function of neutron fluence. The gas pressure increase occasioned by such accumulation of gas is used to actuate the device.

  15. Intracranial pressure, its components and cerebrospinal fluid pressure-volume compensation.

    PubMed

    Kasprowicz, M; Lalou, D A; Czosnyka, M; Garnett, M; Czosnyka, Z

    2016-09-01

    Clinical measurement of intracranial pressure (ICP) is often performed to aid diagnosis of hydrocephalus. This review discusses analysis of ICP and its components' for the investigation of cerebrospinal fluid (CSF) dynamics. The role of pulse, slow and respiratory waveforms of ICP in diagnosis, prognostication and management of hydrocephalus is presented. Two methods related to ICP measurement are listed: an overnight monitoring of ICP and a constant-rate infusion study. Due to the dynamic nature of ICP, a 'snapshot' manometric measurement of ICP is of limited use as it might lead to unreliable results. Therefore, monitoring of ICP over longer time combined with analysis of its waveforms provides more detailed information on the state of pressure-volume compensation. The infusion study implements ICP signal processing and CSF circulation model analysis in order to assess the cerebrospinal dynamics variables, such as CSF outflow resistance, compliance of CSF space, pressure amplitude, reference pressure, and CSF formation. These parameters act as an aid tool in diagnosis and prognostication of hydrocephalus and can be helpful in the assessment of a shunt malfunction. PMID:26666840

  16. Role of interstitial fluid pressurization in TMJ lubrication.

    PubMed

    Zimmerman, B K; Bonnevie, E D; Park, M; Zhou, Y; Wang, L; Burris, D L; Lu, X L

    2015-01-01

    In temporomandibular joints (TMJs), the disc and condylar cartilage function as load-bearing, shock-absorbing, and friction-reducing materials. The ultrastructure of the TMJ disc and cartilage is different from that of hyaline cartilage in other diarthrodial joints, and little is known about their lubrication mechanisms. In this study, we performed micro-tribometry testing on the TMJ disc and condylar cartilage to obtain their region- and direction-dependent friction properties. Frictional tests with a migrating contact area were performed on 8 adult porcine TMJs at 5 different regions (anterior, posterior, central, medial, and lateral) in 2 orthogonal directions (anterior-posterior and medial-lateral). Some significant regional differences were detected, and the lateral-medial direction showed higher friction than the anterior-posterior direction on both tissues. The mean friction coefficient of condylar cartilage against steel was 0.027, but the disc, at 0.074, displayed a significantly higher friction coefficient. The 2 tissues also exhibited different frictional dependencies on sliding speed and normal loading force. Whereas the friction of condylar cartilage decreased with increased sliding speed and was independent of the magnitude of normal force, friction of the disc showed no dependence on sliding speed but decreased as normal force increased. Further analysis of the Péclet number and frictional coefficients suggested that condylar cartilage relies on interstitial fluid pressurization to a greater extent than the corresponding contact area of the TMJ disc. PMID:25297115

  17. Role of Interstitial Fluid Pressurization in TMJ Lubrication

    PubMed Central

    Zimmerman, B.K.; Bonnevie, E.D.; Park, M.; Zhou, Y.; Wang, L.; Burris, D.L.

    2015-01-01

    In temporomandibular joints (TMJs), the disc and condylar cartilage function as load-bearing, shock-absorbing, and friction-reducing materials. The ultrastructure of the TMJ disc and cartilage is different from that of hyaline cartilage in other diarthrodial joints, and little is known about their lubrication mechanisms. In this study, we performed micro-tribometry testing on the TMJ disc and condylar cartilage to obtain their region- and direction-dependent friction properties. Frictional tests with a migrating contact area were performed on 8 adult porcine TMJs at 5 different regions (anterior, posterior, central, medial, and lateral) in 2 orthogonal directions (anterior-posterior and medial-lateral). Some significant regional differences were detected, and the lateral-medial direction showed higher friction than the anterior-posterior direction on both tissues. The mean friction coefficient of condylar cartilage against steel was 0.027, but the disc, at 0.074, displayed a significantly higher friction coefficient. The 2 tissues also exhibited different frictional dependencies on sliding speed and normal loading force. Whereas the friction of condylar cartilage decreased with increased sliding speed and was independent of the magnitude of normal force, friction of the disc showed no dependence on sliding speed but decreased as normal force increased. Further analysis of the Péclet number and frictional coefficients suggested that condylar cartilage relies on interstitial fluid pressurization to a greater extent than the corresponding contact area of the TMJ disc. PMID:25297115

  18. Pore fluid pressure and shear behavior in debris flows of different compositions

    NASA Astrophysics Data System (ADS)

    Kaitna, Roland; Palucis, Marisa; Yohannes, Bereket; Hill, Kimberly; Dietrich, William

    2016-04-01

    Debris flows are mixtures of sediment and water that can have a wide range of different grain size distributions and water contents. The composition of the material is expected to have a strong effect on the development of pore fluid pressures in excess to hydrostatic, which in turn might affect the internal deformation behavior. We present a set of large scale experiments with debris flow mixtures of different compositions in a 4-m diameter rotating drum. Longitudinal profiles of basal fluid pressure and normal stress were measured and a probe to determine fluid pressure at different depths within the flow was developed and tested. Additionally we determined vertical profiles of mean particle velocities in the flow interior by measuring small variations of conductivity of the passing material and calculating the time lag between signals from two independent measurements at a small, known distance apart. Mean values of basal pore fluid pressure range from hydrostatic pressure for gravel-water flows to nearly complete liquefaction for muddy mixtures having a wide grain size distribution. The data indicate that the presence of fines dampens fluctuations of normalized fluid pressure and normal stress and concentrates shear at the base. The mobility of grain-fluid flows is strongly enhanced by a combination of fines in suspension as part of the interstitial fluid and a wide grain size distribution. Excess fluid pressure may arise from fluid displacement by converging grains at the front of the flow and the slow settling of grains through a highly viscous non-Newtonian fluid. Our findings support the need for pore pressure evolution and diffusion equations in debris flow models as they depend on particle size distributions. This study contributes to the understanding of the production of excess fluid pressure in grain fluid mixtures and may guide the development of constitutive models that describe natural events.

  19. Electrostatic actuators for portable microfluidic systems

    NASA Astrophysics Data System (ADS)

    Tice, Joshua

    minimize actuation potentials while eliminating stiction. Two strategies were developed to overcome challenges with electrode screening in the presence of aqueous fluids. First, instead of using the electrostatic actuators to interact directly with aqueous solutions, the actuators were used to regulate pressurized control lines for pneumatic microvalves. Secondly, by adopting a normally-closed architecture, the actuators were converted into microvalves capable of directly interacting with aqueous solutions. The two strategies are complementary, and together should enable sophisticated microfluidic systems for applications ranging from point-of-care diagnostics to portable chemical detection. To conclude the dissertation, I demonstrate a proof-of-principle microfluidic system that contained sixteen independently-operated electrostatic valves, operated with battery-operated electrical ancillaries in a hand-held format.

  20. Bernoulli's Principle Applied to Brain Fluids: Intracranial Pressure Does Not Drive Cerebral Perfusion or CSF Flow.

    PubMed

    Schmidt, Eric; Ros, Maxime; Moyse, Emmanuel; Lorthois, Sylvie; Swider, Pascal

    2016-01-01

    In line with the first law of thermodynamics, Bernoulli's principle states that the total energy in a fluid is the same at all points. We applied Bernoulli's principle to understand the relationship between intracranial pressure (ICP) and intracranial fluids. We analyzed simple fluid physics along a tube to describe the interplay between pressure and velocity. Bernoulli's equation demonstrates that a fluid does not flow along a gradient of pressure or velocity; a fluid flows along a gradient of energy from a high-energy region to a low-energy region. A fluid can even flow against a pressure gradient or a velocity gradient. Pressure and velocity represent part of the total energy. Cerebral blood perfusion is not driven by pressure but by energy: the blood flows from high-energy to lower-energy regions. Hydrocephalus is related to increased cerebrospinal fluid (CSF) resistance (i.e., energy transfer) at various points. Identification of the energy transfer within the CSF circuit is important in understanding and treating CSF-related disorders. Bernoulli's principle is not an abstract concept far from clinical practice. We should be aware that pressure is easy to measure, but it does not induce resumption of fluid flow. Even at the bedside, energy is the key to understanding ICP and fluid dynamics. PMID:27165887

  1. Rayleigh-Taylor modes in constant-density incompressible fluids accelerated by radiation pressure. [astrophysical models

    NASA Technical Reports Server (NTRS)

    Krolik, J. H.

    1977-01-01

    The paper examines the behavior of linear perturbations in an incompressible fluid undergoing acceleration by radiation pressure, with reference to processes occurring in quasars, supernovae, and planetary nebulae. It is shown that, contrary to prior expectation, fluids accelerated by radiation pressure, are not always unstable to Rayleigh-Taylor modes. Some are, in fact, unstable, but the nature of the instability is qualitatively different.

  2. Ductile creep and compaction: A mechanism for transiently increasing fluid pressure in mostly sealed fault zones

    USGS Publications Warehouse

    Sleep, N.H.; Blanpied, M.L.

    1994-01-01

    A simple cyclic process is proposed to explain why major strike-slip fault zones, including the San Andreas, are weak. Field and laboratory studies suggest that the fluid within fault zones is often mostly sealed from that in the surrounding country rock. Ductile creep driven by the difference between fluid pressure and lithostatic pressure within a fault zone leads to compaction that increases fluid pressure. The increased fluid pressure allows frictional failure in earthquakes at shear tractions far below those required when fluid pressure is hydrostatic. The frictional slip associated with earthquakes creates porosity in the fault zone. The cycle adjusts so that no net porosity is created (if the fault zone remains constant width). The fluid pressure within the fault zone reaches long-term dynamic equilibrium with the (hydrostatic) pressure in the country rock. One-dimensional models of this process lead to repeatable and predictable earthquake cycles. However, even modest complexity, such as two parallel fault splays with different pressure histories, will lead to complicated earthquake cycles. Two-dimensional calculations allowed computation of stress and fluid pressure as a function of depth but had complicated behavior with the unacceptable feature that numerical nodes failed one at a time rather than in large earthquakes. A possible way to remove this unphysical feature from the models would be to include a failure law in which the coefficient of friction increases at first with frictional slip, stabilizing the fault, and then decreases with further slip, destabilizing it. ?? 1994 Birkha??user Verlag.

  3. Evolution of pore fluid pressures in a stimulated geothermal reservoir inferred from earthquake focal mechanisms

    NASA Astrophysics Data System (ADS)

    Terakawa, T.; Deichmann, N.

    2014-12-01

    We developed an inversion method to estimate the evolution of pore fluid pressure fields from earthquake focal mechanism solutions based on the Bayesian statistical inference and Akaike's Bayesian information criterion (ABIC). This method's application to induced seismicity in the Basel enhanced geothermal system in Switzerland shows the evolution of pore fluid pressures in response to fluid injection experiments. For a few days following the initiation of the fluid injection, overpressurized fluids are concentrated around the borehole and then anisotropically propagate within the reservoir until the bleed-off time. Then, the pore fluid pressure in the vicinity of the borehole drastically decreases, and overpressurized fluids become isolated in a few major fluid pockets. The pore fluid pressure in these pockets gradually decreases with time. The pore fluid pressure in the reservoir is less than the minimum principal stress at each depth, indicating that the hydraulic fracturing did not occur during stimulation. This suggests that seismic events may play an important role to promote the development of permeable channels, particularly southeast of the borehole where the largest seismic event (ML 3.4) occurred. This is not directly related to a drastic decrease in fault strength at the hypocenter, but rather the positive feedback between permeability enhancement and poro-elastic and stress transfer loading from slipping interfaces. These processes likely contribute to this event's nucleation.

  4. Non-invasive method of measuring cerebral spinal fluid pressure

    NASA Technical Reports Server (NTRS)

    Borchert, Mark S. (Inventor); Lambert, James L. (Inventor)

    2000-01-01

    The invention provides a method of non-invasively determining intracranial pressure from measurements of an eye. A parameter of an optic nerve of the eye is determined, along with an intraocular pressure of the eye. The intracranial pressure may be determined from the intraocular pressure and the parameter.

  5. The pressures of suction feeding: the relation between buccal pressure and induced fluid speed in centrarchid fishes.

    PubMed

    Higham, Timothy E; Day, Steven W; Wainwright, Peter C

    2006-09-01

    Suction feeding fish rapidly expand their oral cavity, resulting in a flow of water directed towards the mouth that is accompanied by a drop in pressure inside the buccal cavity. Pressure inside the mouth and fluid speed external to the mouth are understood to be mechanically linked but the relationship between them has never been empirically determined in any suction feeder. We present the first simultaneous measurements of fluid speed and buccal pressure during suction feeding in fishes. Digital particle image velocimetry (DPIV) and high-speed video were used to measure the maximum fluid speed in front of the mouth of four largemouth bass and three bluegill sunfish by positioning a vertical laser sheet on the mid-sagittal plane of the fish. Peak magnitude of pressure inside the buccal cavity was quantified using a transducer positioned within a catheter that opened into the dorsal wall of the buccal cavity. In both species the time of peak pressure preceded the time of peak fluid speed by as much as 42 ms, indicating a role for unsteady flow effects in shaping this relation. We parameterized an existing model of suction feeding to determine whether the relationship between peak pressures and fluid speeds that we observed could be predicted using just a few kinematic variables. The model predicted much higher fluid speeds than we measured at all values of peak pressure and gave a scaling exponent between them (0.51) that was higher than observed (0.36 for largemouth bass, 0.38 for bluegill). The scaling between peak buccal pressure and peak fluid speed at the mouth aperture differed in the two species, supporting the recent conclusion that species morphology affects this relation such that a general pattern may not hold. PMID:16916963

  6. Development of abnormal fluid pressures beneath a ramping thrust sheet: Where's the evidence

    SciTech Connect

    Wiltschko, D.V.; Smith, R.E. . Dept. of Geology and Center for Tectonophysics)

    1992-01-01

    Many models for the mechanics of fold and thrust belts hold that fluid pressure is locally, or even everywhere, abnormal, thus aiding both internal deformation and motion along the base. Recent support comes from studies of accretionary prisms where drill-stem measurements of both fluid flow in fault zones and formation pressure are pointed to as evidence for a hydrodynamic system characterized by wide-spread excess fluid pressure. However, despite the general acceptance of high fluid pressure (Pf) as a potentially important controlling mechanism for thrust motion, and despite nearly 30 years of looking, direct evidence for abnormal fluid pressure in ancient continental thrust belts is either rare or ambiguous. The authors have developed a two-dimensional model for the evolution of fluid pressure within and beneath a ramping thrust sheet. In the model, the fluid and heat flow equations are solved and applied at each time step. The model accounts for porosity compaction, thermal pressuring, and fluid flow. Results of this model show, first, that high fluid pressure can be developed during deposition, before thrust motion. The authors used typical rates of deposition, duration of deposition, and a simplified three-layer stratigraphy for North American thrust belts. Second, the models show that high Pf can be maintained and/or further enhanced during thrusting depending upon the permeabilities assigned to the model hydrostratigraphic section. Of the rock properties studied in detail, modes are most sensitive to permeability. Nevertheless, the models show that for best guesses of the relevant rock properties it should be possible to find evidence for high fluid pressure in, (1) the crests of ramp anticlines and, (2) the toe region, especially in the lower plate.

  7. Comprehensive piezoceramic actuator review

    NASA Astrophysics Data System (ADS)

    Taylor, Chris J.; Washington, Gregory N.

    2002-07-01

    Piezoceramic actuation has become an area of increased interest in the past ten years. Having been used for many years as sensors in such applications as pressure transducers and smoke detectors, piezoceramics are now being used as prime movers in fuel injectors and valve lifters. In an effort to aid the engineering community, this paper will conduct a comprehensive review of several piezoceramic actuators. Classical design parameters will be derived for each actuator such as blocked force and free stroke. In addition, more esoteric entities such as mechanical efficiency and energy density will also be derived. The result will be design metrics of popular piezoceramic actuators containing vital design equations, validated with empirical data. Of the many different configurations of piezoceramic actuators, this paper will investigate the bimorph and unimorph bender. These actuator types are finding increased use in semi-active structural damping, energy harvesting and vibration control. The work in this paper will show experimental verification of various actuator types as well as theoretical derivations. In addition to unimorphs, bimorphs and stack actuators a novel type of unimorph bender, the THUNDER actuator (developed and licensed by NASA) will be included in the review.

  8. Pressure multiplying dispenser

    DOEpatents

    DeFord, Henry S.; Moss, Owen R.

    1986-01-01

    A pressure multiplying dispenser for delivering fluid, preferably as a spray to the atmosphere, from a source of fluid, preferably a spray bottle, is described. The dispenser includes in combination a hollow cylindrical member, a nozzle delivery tube within the cylindrical member and a hollow actuator piston slideable within the cylindrical member which acts to multiply the pressure of a squeeze applied to the spray bottle.

  9. Engine having a high pressure hydraulic system and low pressure lubricating system

    DOEpatents

    Bartley, Bradley E.; Blass, James R.; Gibson, Dennis H.

    2000-01-01

    An engine includes a high pressure hydraulic system having a high pressure pump and at least one hydraulically-actuated device attached to an engine housing. A low pressure engine lubricating system is attached to the engine housing and includes a circulation conduit fluidly connected to an outlet from the high pressure pump.

  10. Effects of actuator limits in bifurcation control with applications to active control of fluid instabilities in turbomachinery

    NASA Astrophysics Data System (ADS)

    Wang, Yong

    Bifurcations are ubiquitous in engineering applications. Subcritical bifurcations are typically associated with hysteresis and catastrophic instability inception, while supercritical bifurcations are usually associated with gradual and more benign instability inception. With the assumption that the bifurcating modes are linearly unstabilizable, we give a constructive procedure of designing feedback laws to change the criticality of bifurcations from subcritical to supercritical. Algebraic necessary and sufficient conditions are obtained under which the criticality of a simple steady-state or Hopf bifurcation can be changed to supercritical by a smooth feedback. The effects of magnitude saturation, bandwidth, and rate limits are important issues in control engineering. We give qualitative estimates of the region of attraction to the stabilized bifurcating equilibrium/periodic orbits under these constraints. We apply the above theoretical results to the Moore-Greitzer model in active control of rotating stall and surge in gas turbine engines. Though linear stabilizability can be achieved using distributed actuation, it limits the practical usefulness due to considerations of affordability and reliability. On the other hand, simple but practically promising actuation schemes such as outlet bleed valves, a couple of air injectors, and magnetic bearings will make the system loss of linear stabilizability, thus the control design becomes a challenging task. The above mentioned theory in bifurcation stabilization can be applied to these cases. We analyze the effects of magnitude and rate saturations in active control of rotating stall using bleed valves. Analytic formulas are obtained for the operability enhancement as a function of system parameters, noise level, and actuator magnitude and rate limits. The formulas give good qualitative predictions when compared with experiments. Our conclusion is that actuator magnitude and rate limits are serious limiting factors in

  11. Simulation Tool for Dielectric Barrier Discharge Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Likhanskii, Alexander

    2014-01-01

    Traditional approaches for active flow separation control using dielectric barrier discharge (DBD) plasma actuators are limited to relatively low speed flows and atmospheric conditions. This results in low feasibility of the DBDs for aerospace applications. For active flow control at turbine blades, fixed wings, and rotary wings and on hypersonic vehicles, DBD plasma actuators must perform at a wide range of conditions, including rarified flows and combustion mixtures. An efficient, comprehensive, physically based DBD simulation tool can optimize DBD plasma actuators for different operation conditions. Researchers are developing a DBD plasma actuator simulation tool for a wide range of ambient gas pressures. The tool will treat DBD using either kinetic, fluid, or hybrid models, depending on the DBD operational condition.

  12. Laplace-Pressure Actuation of Liquid Metal Devices For Reconfigurable Electromagnetics

    NASA Astrophysics Data System (ADS)

    Cumby, Brad Lee

    it is resilient and shapeable to allow for reconfigurability. In this dissertation, first background information is given on the existing technology for reconfigurable microwave devices and the basic principles that these mechanisms are based upon. Then a new reconfigurable method is introduced that utilizes Laplace pressure. Materials that are associated with using liquid metals are discussed and an overall systematic view is given to provide a set of proof of concepts that are more applied and understandable by electronic designers and engineers. Finally a novel approach to making essential measurements of liquid metal microwave devices is devised and discussed. This dissertation encompasses a complete device design from materials used for fabrication, fabrication methods and measurement processes to provide a knowledge base for designing liquid metal microwave devices.

  13. A fault constitutive relation accounting for thermal pressurization of pore fluid

    USGS Publications Warehouse

    Andrews, D.J.

    2002-01-01

    The heat generated in a slip zone during an earthquake can raise fluid pressure and thereby reduce frictional resistance to slip. The amount of fluid pressure rise depends on the associated fluid flow. The heat generated at a given time produces fluid pressure that decreases inversely with the square root of hydraulic diffusivity times the elapsed time. If the slip velocity function is crack-like, there is a prompt fluid pressure rise at the onset of slip, followed by a slower increase. The stress drop associated with the prompt fluid pressure rise increases with rupture propagation distance. The threshold propagation distance at which thermally induced stress drop starts to dominate over frictionally induced stress drop is proportional to hydraulic diffusivity. If hydraulic diffusivity is 0.02 m2/s, estimated from borehole samples of fault zone material, the threshold propagation distance is 300 m. The stress wave in an earthquake will induce an unknown amount of dilatancy and will increase hydraulic diffusivity, both of which will lessen the fluid pressure effect. Nevertheless, if hydraulic diffusivity is no more than two orders of magnitude larger than the laboratory value, then stress drop is complete in large earthquakes.

  14. Effect of increase in intraperitoneal pressure on fluid distribution in tissue using finite difference method

    NASA Astrophysics Data System (ADS)

    Putri, Selmi; Arif, Idam; Khotimah, Siti Nurul

    2015-04-01

    In this study, peritoneal dialysis transport system was numerically simulated using finite difference method. The increase in the intraperitoneal pressure due to coughing has a high value outside the working area of the void volume fraction of the hydrostatic pressure θ(P). Therefore to illustrate the effects of the pressure increment, the pressure of working area is chosen between 1 and 3 mmHg. The effects of increased pressure in peritoneal tissue cause more fluid to flow into the blood vessels and lymph. Furthermore, the increased pressure in peritoneal tissue makes the volumetric flux jv and solute flux js across the tissue also increase. The more fluid flow into the blood vessels and lymph causes the fluid to flow into tissue qv and the glucose flow qs to have more negative value and also decreases the glucose concentration CG in the tissue.

  15. High pressure stopped-flow apparatus for the rapid mixing and subsequent study of two fluids under high hydrostatic pressures

    NASA Astrophysics Data System (ADS)

    Karan, Daniel M.; Macey, Robert I.

    1980-08-01

    A stopped-flow apparatus is described for the rapid mixing and subsequent study of two dissimilar fluids under pressures up to 1200 bar. The device consists of two identical pressure chambers which contain the two fluids, a third pressure chamber which contains gas to maintain the pressure in the system, an optical port for photometric observation, and various connections. The device has been used to measure reaction times on the order of a hundred milliseconds to tens of seconds, using a maximum of 2 ml of each reagent per experimental determination. The dead time is found to be 5-25 ms with minium average flow velocities of 2.0 m/s. The construction and operation of the device are described and examples of water transport data in red blood cells and the bromophenolblue indicated chemical reaction of NaHCO3 and HCl under pressure are presented.

  16. A fluid pressure and deformation analysis for geological sequestration of carbon dioxide

    SciTech Connect

    Xu, Zhijie; Fang, Yilin; Scheibe, Timothy D.; Bonneville, Alain

    2012-06-07

    We present a hydro-mechanical model and deformation analysis for geological sequestration of carbon dioxide. The model considers the poroelastic effects by taking into account the two-way coupling between the geomechanical response and the fluid flow process in greater detail. In order for analytical solutions, the simplified hydro-mechanical model includes the geomechanical part that relies on the theory of linear elasticity, while the fluid flow is based on the Darcy’s law. The model was derived through coupling the two parts using the standard linear poroelasticity theory. Analytical solutions for fluid pressure field were obtained for a typical geological sequestration scenario and the solutions for ground deformation were obtained using the method of Green’s function. Solutions predict the temporal and spatial variation of fluid pressure, the effect of permeability and elastic modulus on the fluid pressure, the ground surface uplift, and the radial deformation during the entire injection period.

  17. Scalability of Localized Arc Filament Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2008-01-01

    Temporal flow control of a jet has been widely studied in the past to enhance jet mixing or reduce jet noise. Most of this research, however, has been done using small diameter low Reynolds number jets that often have little resemblance to the much larger jets common in real world applications because the flow actuators available lacked either the power or bandwidth to sufficiently impact these larger higher energy jets. The Localized Arc Filament Plasma Actuators (LAFPA), developed at the Ohio State University (OSU), have demonstrated the ability to impact a small high speed jet in experiments conducted at OSU and the power to perturb a larger high Reynolds number jet in experiments conducted at the NASA Glenn Research Center. However, the response measured in the large-scale experiments was significantly reduced for the same number of actuators compared to the jet response found in the small-scale experiments. A computational study has been initiated to simulate the LAFPA system with additional actuators on a large-scale jet to determine the number of actuators required to achieve the same desired response for a given jet diameter. Central to this computational study is a model for the LAFPA that both accurately represents the physics of the actuator and can be implemented into a computational fluid dynamics solver. One possible model, based on pressure waves created by the rapid localized heating that occurs at the actuator, is investigated using simplified axisymmetric simulations. The results of these simulations will be used to determine the validity of the model before more realistic and time consuming three-dimensional simulations are conducted to ultimately determine the scalability of the LAFPA system.

  18. Intraarticular pressures in a gravity-fed arthroscopy fluid delivery system.

    PubMed

    Arangio, G; Kostelnik, K E

    1992-01-01

    Seven consecutive patients undergoing arthroscopic surgery in a gravity-fed fluid delivery system were studied. The average minimum adequate intraarticular pressure (MAIP) was 55 mm Hg. The height of a saline bag above the knee necessary to achieve this average MAIP was 75 cm. There was a positive correlation between diastolic blood pressure and the minimum adequate intraarticular pressure in this study. There was no positive correlation between systolic blood pressure and the MAIP. PMID:1418206

  19. High accuracy differential pressure measurements using fluid-filled catheters - A feasibility study in compliant tubes.

    PubMed

    Rotman, Oren Moshe; Weiss, Dar; Zaretsky, Uri; Shitzer, Avraham; Einav, Shmuel

    2015-09-18

    High accuracy differential pressure measurements are required in various biomedical and medical applications, such as in fluid-dynamic test systems, or in the cath-lab. Differential pressure measurements using fluid-filled catheters are relatively inexpensive, yet may be subjected to common mode pressure errors (CMP), which can significantly reduce the measurement accuracy. Recently, a novel correction method for high accuracy differential pressure measurements was presented, and was shown to effectively remove CMP distortions from measurements acquired in rigid tubes. The purpose of the present study was to test the feasibility of this correction method inside compliant tubes, which effectively simulate arteries. Two tubes with varying compliance were tested under dynamic flow and pressure conditions to cover the physiological range of radial distensibility in coronary arteries. A third, compliant model, with a 70% stenosis severity was additionally tested. Differential pressure measurements were acquired over a 3 cm tube length using a fluid-filled double-lumen catheter, and were corrected using the proposed CMP correction method. Validation of the corrected differential pressure signals was performed by comparison to differential pressure recordings taken via a direct connection to the compliant tubes, and by comparison to predicted differential pressure readings of matching fluid-structure interaction (FSI) computational simulations. The results show excellent agreement between the experimentally acquired and computationally determined differential pressure signals. This validates the application of the CMP correction method in compliant tubes of the physiological range for up to intermediate size stenosis severity of 70%. PMID:26087881

  20. Debris-flow deposition: Effects of pore-fluid pressure and friction concentrated at flow margins

    USGS Publications Warehouse

    Major, J.J.; Iverson, R.M.

    1999-01-01

    Measurements of pore-fluid pressure and total bed-normal stress at the base of several ???10 m3 experimental debris flows provide new insight into the process of debris-flow deposition. Pore-fluid pressures nearly sufficient to cause liquefaction were developed and maintained during flow mobilization and acceleration, persisted in debris-flow interiors during flow deceleration and deposition, and dissipated significantly only during postdepositional sediment consolidation. In contrast, leading edges of debris flows exhibited little or no positive pore-fluid pressure. Deposition therefore resulted from grain-contact friction and bed friction concentrated at flow margins. This finding contradicts models that invoke widespread decay of excess pore-fluid pressure, uniform viscoplastic yield strength, or pervasive grain-collision stresses to explain debris-flow deposition. Furthermore, the finding demonstrates that deposit thickness cannot be used to infer the strength of flowing debris.

  1. Method and apparatus for actuating vehicle transmission

    SciTech Connect

    Ishida, H.; Ishihara, M.; Uriuhara, M.

    1988-11-15

    This patent describes a method of actuating a vehicle parallel-gear transmission having gears and an internal lever for moving shift blocks connected with shift rods and shift forks for changing gear ratios of the transmission, a hydraulically controlled select actuator operatively connected to the internal lever for moving the internal lever in a select direction, a hydraulically controlled shift actuator operatively connected to the internal lever for moving the internal lever in a shift direction substantially normal to the select direction, a hydraulically controlled clutch actuator for connecting and disconnecting a clutch of the transmission, and a common fluid discharge passage connected to fluid discharge ports of the select and shift actuators and a fluid discharge port of the clutch actuator, the select and shift actuators being alternately actuatable to effect a gear changing operation.

  2. The change in orientation of subsidiary shears near faults containing pore fluid under high pressure

    USGS Publications Warehouse

    Byerlee, J.

    1992-01-01

    Byerlee, J., 1992. The change in orientation of subsidiary shears near faults containing pore fluid under high pressure. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors. Tectonophysics, 211: 295-303. The mechanical effects of a fault containing near-lithostatic fluid pressure in which fluid pressure decreases monotonically from the core of the fault zone to the adjacent country rock is considered. This fluid pressure distribution has mechanical implications for the orientation of subsidiary shears around a fault. Analysis shows that the maximum principal stress is oriented at a high angle to the fault in the country rock where the pore pressure is hydrostatic, and rotates to 45?? to the fault within the fault zone where the pore pressure is much higher. This analysis suggests that on the San Andreas fault, where heat flow constraints require that the coefficient of friction for slip on the fault be less than 0.1, the pore fluid pressure on the main fault is 85% of the lithostatic pressure. The observed geometry of the subsidiary shears in the creeping section of the San Andreas are broadly consistent with this model, with differences that may be due to the heterogeneous nature of the fault. ?? 1992.

  3. Micromachined lead zirconium titanate thin-film-cantilever-based acoustic emission sensor with poly(N-isopropylacrylamide) actuator for increasing contact pressure

    NASA Astrophysics Data System (ADS)

    Feng, Guo-Hua; Chen, Wei-Ming

    2016-05-01

    This paper presents an innovative acousticemission (AE) sensor with a cantilever sensing structure. A hydrothermal lead zirconium titanate (PZT) film was deposited on the cantilever for AE sensing, and an SU8 micropillar at the free end of the cantilever served as an AE wave coupler; in addition, a poly(N-isopropylacrylamide)-based thermoresponsive actuator was integrated with the cantilever to increase the contact pressure exerted on the target. The AE sensor showed higher performance compared with an existing commercial AE sensor. Micromachining technology was used to fabricate AE sensors, and an array of four sensors was fabricated on a 50 μm thick titanium substrate of dimensions 15 mm × 15 mm. The piezoelectric properties of the hydrothermal PZT film were verified by electrically driving the cantilever and measuring the displacement; the piezoelectric constant d 31 of the cantilever was 2.43 pC N‑1. The output force of the sensing cantilever generated by activating the thermoresponsive actuator was determined. For an electrical power input of 2.5 W, the maximum force output at the SU8 micropillar was 1 N. This force corresponded to the application of a pressure of 1.4 MPa on the target. Pencil lead break tests were conducted to determine and compare the performance of the proposed AE sensor with commercial sensors. Here, experimental and theoretical discussions on the effect of the activation of the thermoresponsive actuator of the proposed AE sensor on AE detection are presented.

  4. Prediction of pressure drop in fluid tuned mounts using analytical and computational techniques

    NASA Technical Reports Server (NTRS)

    Lasher, William C.; Khalilollahi, Amir; Mischler, John; Uhric, Tom

    1993-01-01

    A simplified model for predicting pressure drop in fluid tuned isolator mounts was developed. The model is based on an exact solution to the Navier-Stokes equations and was made more general through the use of empirical coefficients. The values of these coefficients were determined by numerical simulation of the flow using the commercial computational fluid dynamics (CFD) package FIDAP.

  5. Combustion powered linear actuator

    DOEpatents

    Fischer, Gary J.

    2007-09-04

    The present invention provides robotic vehicles having wheeled and hopping mobilities that are capable of traversing (e.g. by hopping over) obstacles that are large in size relative to the robot and, are capable of operation in unpredictable terrain over long range. The present invention further provides combustion powered linear actuators, which can include latching mechanisms to facilitate pressurized fueling of the actuators, as can be used to provide wheeled vehicles with a hopping mobility.

  6. Magnetically Actuated Propellant Orientation Experiment, Controlling Fluid Motion With Magnetic Fields in a Low-Gravity Environment

    NASA Technical Reports Server (NTRS)

    Martin, J. J.; Holt, J. B.

    2000-01-01

    This report details the results of a series of fluid motion experiments to investigate the use of magnets to orient fluids in a low-gravity environment. The fluid of interest for this project was liquid oxygen (LO2) since it exhibits a paramagnetic behavior (is attracted to magnetic fields). However, due to safety and handling concerns, a water-based ferromagnetic mixture (produced by Ferrofluidics Corporation) was selected to simplify procedures. Three ferromagnetic fluid mixture strengths and a nonmagnetic water baseline were tested using three different initial fluid positions with respect to the magnet. Experiment accelerometer data were used with a modified computational fluid dynamics code termed CFX-4 (by AEA Technologies) to predict fluid motion. These predictions compared favorably with experiment video data, verifying the code's ability to predict fluid motion with and without magnetic influences. Additional predictions were generated for LO2 with the same test conditions and geometries used in the testing. Test hardware consisted of a cylindrical Plexiglas tank (6-in. bore with 10-in. length), a 6,000-G rare Earth magnet (10-in. ring), three-axis accelerometer package, and a video recorder system. All tests were conducted aboard the NASA Reduced-Gravity Workshop, a KC-135A aircraft.

  7. Stress, fluid pressure and structural permeability in seismogenic crust, North Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Sibson, Richard H.; Rowland, Julie V.

    2003-08-01

    Stress and fluid-pressure conditions within seismogenic crust are compared for two subparallel belts of active deformation and fluid redistribution associated with the obliquely convergent Pacific-Australia plate boundary in the North Island of New Zealand. Whereas seismic activity on extensional normal faults in the arc-backarc Taupo volcanic zone is restricted to <8 km depth in a high heat-flow, near-hydrostatic fluid-pressure regime undergoing vigorous hydrothermal convection, rupturing along the thrust interface of the contractional Hikurangi subduction margin and in its hangingwall extends to ~25 km depth in crust with fluids overpressured towards lithostatic values. The contrast in fluid-pressure levels stems partly from the abundance of low-permeability mudrocks in the forearc and partly from superior containment of overpressures by a compressional thrust-fault regime. Maximum supportable levels of differential stress and fluid pressure are critically interdependent in the overpressured regime of the Hikurangi subduction margin. Frictional instability leading to fault rupture in such settings may be triggered by increasing fluid pressure as well as by accumulating shear stress, so that nucleation and recurrence of earthquake ruptures are likely to be affected by cycling of fluid pressure through fault-valve action as well as by stress accumulation. Coupling across the subduction interface is also likely to be highly sensitive to the degree of overpressuring. Different factors are responsible for the localization of active deformation within the two crustal seismic belts. Within the magmatically active Taupo volcanic zone, thermal weakening is clearly responsible for concentrating seismicity and deformation with respect to the surrounding crust. However, in the hangingwall of the Hikurangi subduction margin, where heat flow has been reduced by subduction refrigeration and frictional interaction extends to ~25 km depth, relative weakening arises principally

  8. Quick-response servo amplifies small hydraulic pressure differences

    NASA Technical Reports Server (NTRS)

    Wiegard, D. E.

    1966-01-01

    Hydraulic servo, which quickly diverts fluid to either of two actuators, controls the flow rates and pressures within a hydraulic system so that the output force of the servo system is independent of the velocity of the mechanism which the system actuates. This servo is a dynamic feedback control device.

  9. One-dimensional pore pressure diffusion of different grain-fluid mixtures

    NASA Astrophysics Data System (ADS)

    von der Thannen, Magdalena; Kaitna, Roland

    2015-04-01

    During the release and the flow of fully saturated debris, non-hydrostatic fluid pressure can build up and probably dissipate during the event. This excess fluid pressure has a strong influence on the flow and deposition behaviour of debris flows. Therefore, we investigate the influence of mixture composition on the dissipation of non-hydrostatic fluid pressures. For this we use a cylindrical pipe of acrylic glass with installed pore water pressure sensors in different heights and measure the evolution of the pore water pressure over time. Several mixtures with variable content of fine sediment (silt and clay) and variable content of coarse sediment (with fixed relative fractions of grains between 2 and 32 mm) are tested. For the fines two types of clay (smectite and kaolinite) and loam (Stoober Lehm) are used. The analysis is based on the one-dimensional consolidation theory which uses a diffusion coefficient D to model the decay of excess fluid pressure over time. Starting from artificially induced super-hydrostatic fluid pressures, we find dissipation coefficients ranging from 10-5 m²/s for liquid mixtures to 10-8 m²/s for viscous mixtures. The results for kaolinite and smectite are quite similar. For our limited number of mixtures the effect of fines content is more pronounced than the effect of different amounts of coarse particles.

  10. Fluid flow in subduction zones: The role of solid rheology and compaction pressure

    NASA Astrophysics Data System (ADS)

    Wilson, Cian R.; Spiegelman, Marc; van Keken, Peter E.; Hacker, Bradley R.

    2014-09-01

    Arc volcanoes tend to occur at locations where the slab is at approximately 100 km depth but most models of fluid production from the downgoing slab suggest fluids are released over a wide range of depths. Reconciling the models with the observations suggests that focusing of slab-produced fluids is necessary if flux-melting is a primary mechanism for the production of arc magmas. This paper investigates one possible mechanism for inducing focusing of fluid flow toward the sub-arc mantle. Through a series of simplified models we explore the role of compaction pressure gradients in modifying fluid flow. These gradients are produced by variations in fluid flux interacting with the permeability and viscosity structure of the solid mantle. When these gradients are neglected, high-permeability systems are dominated by buoyancy and fluid flow is primarily vertical. However, when included, compaction pressure terms have three principal effects: (i) enhancement of upslope flow within high-permeability layers in the slab produced by local dehydration reactions, (ii) deflection of fluids along the sloping rheologically strengthening region in the upper thermal boundary layer, and (iii) production of non-linear porosity waves that locally modulate the flow of fluids and can allow significant transient accumulation of fluids. We demonstrate significant localization of fluid flux toward the sub-arc region due to the permeability and solid viscosity structure. We also estimate the amount of melting expected among the different models and show that models with compaction pressure could produce ∼10% flux melting, whereas distributed fluid flow produces ≲1% in most cases.

  11. Active Faulting and Pore-Fluid Pressure in the Taiwan Thrust Belt

    NASA Astrophysics Data System (ADS)

    Yue, L.; Suppe, J.

    2004-12-01

    Pore-fluid pressures significantly in excess of hydrostatic are thought to play an important role in the mechanics of overthrust faulting (Hubbert and Rubey, 1959). However in western Taiwan we argue, based upon a regional analysis of fluid pressures in 76 deep wells, that fluid pressures on the Pliocene Chinshui Shale detachment and ramp of the Chelungpu thrust system that ruptured the surface during 1999 Chi-Chi earthquake (Mw = 7.6) are within the hydrostatic regime and not overpressured. The fluid pressure data are obtained from in-situ borehole pressure measurements (formation tests), from densities of drilling muds, and from analysis of sonic logs using standard petroleum methods show fluid pressures in western Taiwan are stratigraphically controlled, as is typical of clastic sedimentary basins. The analysis provides constraints not only on present-day fluid pressure, but also pressures before uplift and erosion of growing structures which causes a large drop in overpressures. The top of the present overpressured zone is located at Miocene Nankang-Tsouho Formation in the north of Miao-Li, rises to the south to the Nanchuang and Kueichulin Formations in central Taiwan and only reaches the level of the Pliocene Chinshui Shale near Chia-Li (north of Tainan). Therefore the Chelungpu thrust sheet is everywhere in hydrostatic since this thrust runs along the Chinshui shale. This leads us to the conclusion that the static (ambient) pore-fluid overpressure plays no role in controlling fault friction of the Chelungpu thrust. The shallow detachment must be sliding under other mechanisms. Other shallow thrusts penetrated by drilling such as the Hsincheng thrust between Chingtsaohu and Paoshan anticlines and the Luchukeng thrust west of Yunghoshan anticline are also within hydrostatic regime. None of these thrust were ever overpressured as shown by the fossil top of overpressures which is based upon the deviation of porosity controlled shale velocities from the normal

  12. Size-dependent characteristics of electrostatically actuated fluid-conveying carbon nanotubes based on modified couple stress theory

    PubMed Central

    Rastgoo, Abbas; Ahmadian, Mohammad Taghi

    2013-01-01

    Summary The paper presents the effects of fluid flow on the static and dynamic properties of carbon nanotubes that convey a viscous fluid. The mathematical model is based on the modified couple stress theory. The effects of various fluid parameters and boundary conditions on the pull-in voltages are investigated in detail. The applicability of the proposed system as nanovalves or nanosensors in nanoscale fluidic systems is elaborated. The results confirm that the nanoscale system studied in this paper can be properly applied for these purposes. PMID:24367746

  13. Electrical conductivity measurements of aqueous fluids under pressure with a hydrothermal diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Ni, Huaiwei; Chen, Qi; Keppler, Hans

    2014-11-01

    Electrical conductivity data of aqueous fluids under pressure can be used to derive the dissociation constants of electrolytes, to assess the effect of ionic dissociation on mineral solubility, and to interpret magnetotelluric data of earth's interior where a free fluid phase is present. Due to limitation on the tensile strength of the alloy material of hydrothermal autoclaves, previous measurements of fluid conductivity were mostly restricted to less than 0.4 GPa and 800 °C. By adapting a Bassett-type hydrothermal diamond anvil cell, we have developed a new method for acquiring electrical conductivity of aqueous fluids under pressure. Our preliminary results for KCl solutions using the new method are consistent with literature data acquired with the conventional method, but the new method has great potential for working in a much broader pressure range.

  14. Porphyry-copper ore shells form at stable pressure-temperature fronts within dynamic fluid plumes.

    PubMed

    Weis, P; Driesner, T; Heinrich, C A

    2012-12-21

    Porphyry-type ore deposits are major resources of copper and gold, precipitated from fluids expelled by crustal magma chambers. The metals are typically concentrated in confined ore shells within vertically extensive vein networks, formed through hydraulic fracturing of rock by ascending fluids. Numerical modeling shows that dynamic permeability responses to magmatic fluid expulsion can stabilize a front of metal precipitation at the boundary between lithostatically pressured up-flow of hot magmatic fluids and hydrostatically pressured convection of cooler meteoric fluids. The balance between focused heat advection and lateral cooling controls the most important economic characteristics, including size, shape, and ore grade. This self-sustaining process may extend to epithermal gold deposits, venting at active volcanoes, and regions with the potential for geothermal energy production. PMID:23160957

  15. High pressure induced phase transition and superdiffusion in anomalous fluid confined in flexible nanopores

    SciTech Connect

    Bordin, José Rafael; Krott, Leandro B. Barbosa, Marcia C.

    2014-10-14

    The behavior of a confined spherical symmetric anomalous fluid under high external pressure was studied with Molecular Dynamics simulations. The fluid is modeled by a core-softened potential with two characteristic length scales, which in bulk reproduces the dynamical, thermodynamical, and structural anomalous behavior observed for water and other anomalous fluids. Our findings show that this system has a superdiffusion regime for sufficient high pressure and low temperature. As well, our results indicate that this superdiffusive regime is strongly related with the fluid structural properties and the superdiffusion to diffusion transition is a first order phase transition. We show how the simulation time and statistics are important to obtain the correct dynamical behavior of the confined fluid. Our results are discussed on the basis of the two length scales.

  16. Viscosity of fluid nitrogen to pressures of 10 GPa.

    PubMed

    Abramson, Evan H

    2014-10-01

    Shear viscosities of supercritical nitrogen have been measured in the high-pressure diamond-anvil cell, to 673 K and pressures in excess of 10 GPa, using a rolling-sphere technique. The entire set of data, along with lower pressure data from the literature, can be fit to a two-parameter expression in reduced viscosity and reduced residual entropy. The fit spans densities from the dilute gas to 5x the critical density, and two orders magnitude in temperature and in viscosity, with a maximum deviation of 20%. Reduced viscosities scale as ρ(4)/T and comport with the theory of state "isomorphs" for "Roskilde-simple" systems. The new data allow direct comparison with results of molecular dynamic simulations at high densities. PMID:25215593

  17. Surface Deformation Caused by Pressure Changes in the Fluid Core

    NASA Technical Reports Server (NTRS)

    Fang, Ming; Hager, Bradford H.; Herring, Thomas A.

    1995-01-01

    Pressure load Love numbers are presented for the mantle deformation induced by the variation of the pressure field at the core mantle boundary (CNB). We find that the CMB geostrophic pressure fields, derived from 'frozen-flux' core surface flow estimates at epochs 1965 and 1975, produce a relative radial velocity (RRV) field in the range of 3mm/decade with uplift near the equator and subsidence near the poles. The contribution of this mechanism to the change in the length of day (l.o.d) is small --- about 2.3 x 10(exp -2) ms/decade. The contribution to the time variation of the ellipticity coefficient is more important --- -1.3 x 10(exp -11)/yr.

  18. Optimally oriented ``fault-valve'' thrusts: Evidence for aftershock-related fluid pressure pulses?

    NASA Astrophysics Data System (ADS)

    Micklethwaite, S.

    2008-04-01

    A thrust-vein network from the Triumph gold deposit, Western Australia, is explained in terms of an extremely high rate of fluid-pressure increase, prior to failure, relative to the rate of stress increase. The thrust fault is a small-displacement fault characterized by a thick, fault-parallel shear vein, plus multiple low-angle extension veins, with orientations that demonstrate the thrust was optimally oriented relative to the locally imposed crustal stresses. Large extension veins have irregular margins, are dominantly composed of coarse milky quartz with no obvious laminations or solid inclusion trails, and are regularly spaced along the thrust (1-2 m). The fault-vein geometries indicate the Triumph thrust is a rare candidate for "fault-valve" failure of an optimally oriented thrust, and it is possible the structure formed in a small number of failure events, during load weakening of the thrust. An analysis using the Coulomb criterion shows that load weakening of a thrust occurs when fluid pressure increases relative to tectonic stress by a factor dependent on the orientation of the thrust. Thrust and reverse faults in dry crust load strengthen prior to failure, but the poroelastic behavior of sealed, fluid-saturated crust is enough to induce load weakening in compressive environments; thus poroelastic load weakening is expected to be an important failure mechanism in hydrothermal environments. However, in the case of the Triumph thrust, dilatant shear failure necessitates a fluid pressure increase which is an order of magnitude larger still. The observations and results are consistent with a pulse of high fluid pressure migrating up through fault or fracture networks that have elevated permeability relative to the wall rock, under conditions of transiently low differential stress. Fluid pressure differences resulted between the fault and wall rock, leading to extension fracture and fault failure. Such conditions may occur when adjacent large earthquakes induce

  19. Characteristics of silicone fluid as a pressure transmitting medium in diamond anvil cells

    NASA Astrophysics Data System (ADS)

    Shen, Yongrong; Kumar, Ravhi S.; Pravica, Michael; Nicol, Malcolm F.

    2004-11-01

    The properties of a silicone fluid with initial viscosity of 1 cst as a pressure transmitting medium for diamond anvil cells have been determined by ruby R1 line broadening and R1-R2 separation measurements to 64 GPa at ambient temperature. By these criteria, the silicone fluid is as good a pressure medium as a 4:1 methanol:ethanol mixture at low pressures to about 20 GPa, and is better than the mixture at higher pressures. Although argon media are better than the silicone at pressures to 30 GPa, this silicone behaves as well as argon at higher pressures. Furthermore, the silicone is easier to load than argon and is almost chemically inert.

  20. Linear actuator for a bleed valve

    SciTech Connect

    Moore, R.G. Jr.

    1993-06-08

    In a control system for a turbine engine having a variable geometry air compressor, the improvement is described in the actuator assembly comprising: a housing having a bore therein with an inlet port connected to receive the first fluid pressure and an outlet port connected to the surrounding environment; a piston located in the housing for separating the bore into a first chamber and a second chamber, the first chamber being connected to the inlet port and the second chamber being connected to the outlet port; a restriction located in the outlet port to control the communication of any fluid pressure in the second chamber to the environment; a sleeve located in the housing, the sleeve having a radial slot therein; a shaft having a first end journaled in the sleeve and a second end that extends through the housing, the shaft having a blind bore therein connected to receive compressor discharge fluid pressure, the shaft having an opening therein from the blind bore aligned in a plane with the radial slot in the sleeve, the shaft being connected to the piston and rotated thereby as a function of linear movement of the piston by the second pressure differential to position the opening with respect to the radial slot and correspondingly create a variable opening from the blind bore to the second chamber, the second end being connected by the linkage to the variable geometry air compressor; and resilient means for urging the piston toward the first chamber in opposition to the second pressure differential, the second fluid pressure being developed by compressor discharge fluid pressure flowing from the blind bore through the variable opening into the second chamber and fluid pressure in the second chamber flowing through the restriction in the outlet port to the surrounding environment, the second pressure differential moving the piston and shaft and correspondingly the linkage to linearly change the geometry of the air compressor.

  1. Field Observations of Basal Forces and Fluid Pore Pressure in a Debris Flow

    NASA Astrophysics Data System (ADS)

    McArdell, B. W.; Bartelt, P.; Kowalski, J.

    2006-12-01

    The interaction of the soil material and interstitial fluid is central to understanding the dynamics of debris flows, however it has been rarely investigated for natural debris flows. Using results from a large force plate (4 m wide, 2 m long) installed on the bed of the Illgraben torrent channel, Switzerland, we describe measurements of normal, shear, and fluid pore pressure for a naturally-released debris flow with a front speed of 1.4 ms-1 that traveled more than 2 km along a gently-sloping (8 to 10%) channel. Peak values of all parameters were observed near the relatively dry granular flow front (flow depth= 1.05 m, normal stress= 23 kPa, shear stress= 2.8 kPa, basal fluid pore pressure= 15 kPa) and decreased approximately in-phase with the flow depth over the remainder of the flow. Assuming that the depths of the fluid and solid phases are identical after 20 s, as indicated by video recordings, and that a static description of the pressure distribution within the fluid phase is approximately valid, the ratio of effective stress to shear stress yields plausible estimates of the Coulomb basal friction angle near the front of the flow. Large non-lithostatic pressures are not apparent in our data; calculated bulk densities of the flow remaining at about 2200 kgm-3 over the most of the flow. The bulk density of the fluid phase calculated from the measured fluid pore pressure and flow height, assuming a hydrostatic pore pressure distribution, is 1200---1300 kgm-3. An alternative explanation is that the fluid pressure contains both hydrostatic and dynamics components. To explore this idea, we assume that a dynamic pore pressure component is proportional to the strength of the shearing of the solid phase or to the strength of the collisions of the particles comprising the solid phase, which we approximate using data from a geophone installed on the force plate. We find only a weak correlation between the geophone signal and a dynamic pore pressure component for this

  2. Comparison of extraction techniques, including supercritical fluid, high-pressure solvent, and soxhlet, for organophosphorus hydraulic fluids from soil.

    PubMed

    David, M D; Seiber, J N

    1996-09-01

    The efficiencies of three extraction techniques for removal of nonpesticidal organophosphates from soil were determined. Traditional Soxhlet extraction was compared to supercritical fluid extraction (SFE) and a low solvent volume flow through technique referred to here as high-pressure solvent extraction (HPSE). SFE, optimized by varying parameters of temperature, pressure, and methanol polarity modifier, showed at least 90% efficiency in the extraction of OPs from both spiked and native soils. HPSE experiments showed efficient and consistent recoveries over a range of temperatures up to 200 °C and pressures up to 170 atm. Recovery of TCP from spiked soils with HPSE depends on the system variables of temperature and pressure, which dictate density and flow rate. HPSE provided extraction efficiencies comparable to those obtained with Soxhlet extraction and SFE but with substantial savings of time and cost. PMID:21619371

  3. PRESSURIZED FLUIDS FOR EXTRACTION OF ESSENTIAL OILS FROM JUNIPERUS VIRGINIANNA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The extraction of cedarwood oil (CWO) using liquid carbon dioxide (LC-CO2) was investigated, including the effects of extraction pressure and length of extraction. The chemical composition of the extracts were monitored over the course of the extraction as well. When 80 liters of carbon dioxide we...

  4. Labyrinth and cerebral-spinal fluid pressure changes in guinea pigs and monkeys during simulated zero G

    NASA Technical Reports Server (NTRS)

    Parker, D. E.

    1977-01-01

    This study was undertaken to explore the hypothesis that shifts of body fluids from the legs and torso toward the head contribute to the motion sickness experienced by astronauts and cosmonauts. The shifts in body fluids observed during zero-G exposure were simulated by elevating guinea pigs' and monkeys' torsos and hindquarters. Cerebral-spinal fluid pressure was recorded from a transducer located in a brain ventricle; labyrinth fluid pressure was recorded from a pipette cemented in a hole in a semicircular canal. An anticipated divergence in cerebral-spinal fluid pressure and labyrinth fluid pressure during torso elevation was not observed. The results of this study do not support a fluid shift mechanism of zero-G-induced motion sickness. However, a more complete test of the fluid shift mechanism would be obtained if endolymph and perilymph pressure changes were determined separately; we have been unable to perform this test to date.

  5. High Pressure, Transport Properties of Fluids: Theory and Data from Levitated Fluid-Drops at Combustion-Relevant Temperatures

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Ohaska, K.

    2001-01-01

    The objective of this investigation is to derive a set of consistent mixing rules for calculating diffusivities and thermal diffusion factors over a thermodynamic regime encompassing the subcritical and supercritical ranges. These should serve for modeling purposes, and therefore for accurate simulations of high pressure phenomena such as fluid disintegration, turbulent flows and sprays. A particular consequence of this work will be the determination of effective Lewis numbers for supercritical conditions, thus enabling the examination of the relative importance of heat and mass transfer at supercritical pressures.

  6. A thermopneumatically actuated bistable microvalve

    NASA Astrophysics Data System (ADS)

    Yang, Bocong; Wang, Boxiong; Schomburg, Werner Karl

    2010-09-01

    A bistable polymer microvalve with a thermopneumatic actuator has been developed. The microvalve was fabricated by micro milling of a polymer combined with sputtering and photolithography. The valve comprises two 2/2-way valves which are alternately switched such that they can be connected to serve as a 3/2-way valve. Two permanent magnets work with a movable soft magnet to keep the valve in its current state, resulting in bistable switching with a minimum energy of 320 mJ. An air flow rate of 1.36 L min-1 is achieved at 20 °C with a pressure difference of 200 kPa. No leakage is observed up to a differential pressure of 350 kPa. Flowing and switching performances were also tested at different temperatures. Sealing the flow channels from the actuator chamber makes the valve less sensitive to the temperature and other properties of the fluid to be switched. An initial gap between the valve seat and the silicone sealing membrane at least reduces the sticking problem. Switching time is found to be significantly influenced by the thickness of the heating membrane. With an 8 µm thick heating membrane, a response time of 10 ms can be achieved.

  7. Dynamic response of intraocular pressure and biomechanical effects of the eye considering fluid-structure interaction.

    PubMed

    Salimi, S; Park, S Simon; Freiheit, T

    2011-09-01

    The vibration characteristics of shell structures such as eyes have been shown to vary with intraocular pressure (IOP). Therefore, vibration characteristics of the eye have the potential to provide improved correlation to IOP over traditional IOP measurements. As background to examine an improved IOP correlation, this paper develops a finite element model of an eye subject to vibration. The eye is modeled as a shell structure filled with inviscid pressurized fluid in which there is no mean flow. This model solves a problem of a fluid with coupled structural interactions of a generally spherically shaped shell system. The model is verified by comparing its vibrational characteristics with an experimental modal analysis of an elastic spherical shell filled with water. The structural dynamic effects due to change in pressure of the fluid are examined. It is shown that the frequency response of this fluid-solid coupled system has a clear increase in natural frequency as the fluid pressure rises. The fluid and structure interaction is important for accurate prediction of system dynamics. This model is then extended to improve its accuracy in modeling the eye by including the effect of the lens to study corneal vibration. The effect of biomechanical parameters such as the thicknesses of different parts of the eye and eye dimensions in altering measured natural frequencies is investigated and compared to the influence of biomechanical parameters in Goldmann applanation tonometry models. The dynamic response of the eye is found to be less sensitive to biomechanical parameters than the applanation tonometry model. PMID:22010744

  8. Stable electroosmotically driven actuators

    NASA Astrophysics Data System (ADS)

    Sritharan, Deepa; Motsebo, Mylene; Tumbic, Julia; Smela, Elisabeth

    2013-04-01

    We have previously presented "nastic" actuators based on electroosmotic (EO) pumping of fluid in microchannels using high electric fields for potential application in soft robotics. In this work we address two challenges facing this technology: applying EO to meso-scale devices and the stability of the pumping fluid. The hydraulic pressure achieved by EO increases with as 1/d2, where d is the depth of the microchannel, but the flow rate (which determines the stroke and the speed) is proportional to nd, where n is the number of channels. Therefore to get high force and high stroke the device requires a large number of narrow channels, which is not readily achievable using standard microfabrication techniques. Furthermore, for soft robotics the structure must be soft. In this work we present a method of fabricating a three-dimensional porous elastomer to serve as the array of channels based on a sacrificial sugar scaffold. We demonstrate the concept by fabricating small pumps. The flexible devices were made from polydimethylsiloxane (PDMS) and comprise the 3D porous elastomer flanked on either side by reservoirs containing electrodes. The second issue addressed here involves the pumping fluid. Typically, water is used for EO, but water undergoes electrolysis even at low voltages. Since EO takes place at kV, these systems must be open to release the gases. We have recently reported that propylene carbonate (PC) is pumped at a comparable rate as water and is also stable for over 30 min at 8 kV. Here we show that PC is, however, degraded by moisture, so future EO systems must prevent water from reaching the PC.

  9. The role of fluid pressure in fault creep vs. frictional instability: insights from rock deformation experiments on carbonates

    NASA Astrophysics Data System (ADS)

    Scuderi, Marco M.; Collettini, Cristiano

    2016-04-01

    Fluid overpressure is one of the primary mechanisms for tectonic fault slip. This mechanism is appealing as fluids lubricate the fault and fluid pressure, Pf, reduces the effective normal stress that holds the fault in place. However, current models of earthquake nucleation imply that stable sliding is favored by the increase of pore fluid pressure. Despite this opposite effects, currently, there are only a few studies on the role of fluid pressure under controlled, laboratory conditions. Here, we use laboratory experiments, conducted on a biaxial apparatus within a pressure vessel on limestone fault gouge, to: 1) evaluate the rate- and state- friction parameters as the pore fluid pressure is increased from hydrostatic to near lithostatic values and 2) fault creep evolution as a function of a step increase in fluid pressure. In this second suite of experiments we reached 85% of the maximum shear strength and than in load control we induced fault slip by increasing fluid pressure. Our data show that the friction rate parameter (a-b) evolves from slightly velocity strengthening to velocity neutral behaviour and the critical slip distance, Dc, decreases from about 100 to 20 μm as the pore fluid pressure is increased. Fault creep is slow (i.e 0.001μm/s) away from the maximum shear strength and for small increases in fluid pressure and it accelerates near the maximum shear strength and for larger fluid pressure build-ups, where we observe episodic accelerations/decelerations that in some cases evolve to small dynamic events. Our data suggest that fluid overpressure can increase aseismic creep with the development of frictional instability. Since fault rheology and fault stability parameters change with fluid pressure, we suggest that a comprehensive characterization of these parameters is fundamental for better assessing the role of fluid pressure in natural and human induced earthquakes.

  10. Burial diagenesis and geochemical alterations and their relationship to high fluid pressures, Frio and Vicksburg shales

    SciTech Connect

    Bott, W.F. Jr.; Tieh, T.T.

    1987-09-01

    Depth-related mineralogic changes in Frio and Vicksburg shales from Ann-Mag field, Brooks County, Texas, were studied to assess the nature and extent of burial diagenesis and geochemical alterations, and to determine their relationship to development of high fluid pressures. Mixed-layer illite-smectite and illite dominate the mineralogy of the shales. Burial diagenesis has transformed randomly interstratified illite/smectite to regularly interstratified illite/smectite and to illite, over a depth range of 6000-10,400 ft (1828-3170 m). The quantity of expandable smectite layers in the fine clay fraction decreases from 70% in the shallowest sample to 22% in the deepest sample, whereas illite increases from 27 to 61%. Alteration of feldspar in the fine silt fraction probably provided the potassium required in this reaction. An abrupt increase of smectite to illite alteration occurs at a depth of approximately 8900 ft (2713 m), corresponding to a temperature of 224/sup 0/F (107/sup 0/C). Fluid pressures estimated from conductivity data and measured pressures show that, at this depth, a significant increase in fluid pressure takes place. Associated with this increase is a decrease in shale density. These relationships suggest that high fluid pressures in this field are caused by clay transformation reactions that expel interlayer water into the pore spaces. Upward movement of pore fluids in thick shales is also suggested by extractable cation determinations.

  11. The Balance of Fluid and Osmotic Pressures across Active Biological Membranes with Application to the Corneal Endothelium.

    PubMed

    Cheng, Xi; Pinsky, Peter M

    2015-01-01

    The movement of fluid and solutes across biological membranes facilitates the transport of nutrients for living organisms and maintains the fluid and osmotic pressures in biological systems. Understanding the pressure balances across membranes is crucial for studying fluid and electrolyte homeostasis in living systems, and is an area of active research. In this study, a set of enhanced Kedem-Katchalsky (KK) equations is proposed to describe fluxes of water and solutes across biological membranes, and is applied to analyze the relationship between fluid and osmotic pressures, accounting for active transport mechanisms that propel substances against their concentration gradients and for fixed charges that alter ionic distributions in separated environments. The equilibrium analysis demonstrates that the proposed theory recovers the Donnan osmotic pressure and can predict the correct fluid pressure difference across membranes, a result which cannot be achieved by existing KK theories due to the neglect of fixed charges. The steady-state analysis on active membranes suggests a new pressure mechanism which balances the fluid pressure together with the osmotic pressure. The source of this pressure arises from active ionic fluxes and from interactions between solvent and solutes in membrane transport. We apply the proposed theory to study the transendothelial fluid pressure in the in vivo cornea, which is a crucial factor maintaining the hydration and transparency of the tissue. The results show the importance of the proposed pressure mechanism in mediating stromal fluid pressure and provide a new interpretation of the pressure modulation mechanism in the in vivo cornea. PMID:26719894

  12. The Balance of Fluid and Osmotic Pressures across Active Biological Membranes with Application to the Corneal Endothelium

    PubMed Central

    Cheng, Xi; Pinsky, Peter M.

    2015-01-01

    The movement of fluid and solutes across biological membranes facilitates the transport of nutrients for living organisms and maintains the fluid and osmotic pressures in biological systems. Understanding the pressure balances across membranes is crucial for studying fluid and electrolyte homeostasis in living systems, and is an area of active research. In this study, a set of enhanced Kedem-Katchalsky (KK) equations is proposed to describe fluxes of water and solutes across biological membranes, and is applied to analyze the relationship between fluid and osmotic pressures, accounting for active transport mechanisms that propel substances against their concentration gradients and for fixed charges that alter ionic distributions in separated environments. The equilibrium analysis demonstrates that the proposed theory recovers the Donnan osmotic pressure and can predict the correct fluid pressure difference across membranes, a result which cannot be achieved by existing KK theories due to the neglect of fixed charges. The steady-state analysis on active membranes suggests a new pressure mechanism which balances the fluid pressure together with the osmotic pressure. The source of this pressure arises from active ionic fluxes and from interactions between solvent and solutes in membrane transport. We apply the proposed theory to study the transendothelial fluid pressure in the in vivo cornea, which is a crucial factor maintaining the hydration and transparency of the tissue. The results show the importance of the proposed pressure mechanism in mediating stromal fluid pressure and provide a new interpretation of the pressure modulation mechanism in the in vivo cornea. PMID:26719894

  13. Nucleation of frictional instability caused by fluid pressurization in subducted blueschist

    NASA Astrophysics Data System (ADS)

    Sawai, Michiyo; Niemeijer, André R.; Plümper, Oliver; Hirose, Takehiro; Spiers, Christopher J.

    2016-03-01

    Pore pressure is an important factor in controlling the slip instability of faults and thus the generation of earthquakes. Particularly slow earthquakes are widespread in subduction zones and usually linked to the occurrence of high pore pressure. Yet the influence of fluid pressure and effective stress on the mechanics of earthquakes is poorly understood. Therefore, we performed shear experiments on blueschist fault rocks, which likely exist at depth in cold and old subduction zones, to investigate the influence of effective stress on frictional behavior. Our results show potentially unstable behavior at temperatures characterizing the seismogenic zone, as well as a transition from stable to unstable behavior with decreasing effective normal stress, which is mechanically equivalent to increasing fluid pressure. This transition is a prerequisite for generating slow earthquakes. Our results imply that high pore pressures are a key factor for nucleating slip leading to both megathrust and slow earthquakes.

  14. Effect of initial fluid-system pressures on the behavior of a rupture-disc pressure-relief device

    SciTech Connect

    Hsieh, B.J.; Shin, Y.W.; Kot, C.A.

    1983-01-01

    Rupture disc assemblies are used in piping network systems as a pressure-relief device to protect the system from being exposed to excess pressures. Among the various disc assemblies, the reverse-buckling type is chosen for application in the Clinch River Breeder Reactor. This rupture-disc assembly consists of a portion of a thin spherical shell with its convex side subjected to the fluid system. The reverse-buckling type rupture disc assemblies have been used successfully in environments where the fluid is gas, i.e. highly compressible, and their performances have been judged as adequate in the liquid environment. To analyze the piping system, an analysis method is needed taking into consideration of the fluid/disc interaction, the nonlinear dynamic buckling phenomenon of the disc, and the possible cavitation of the fluid. A computer code SWAAM-I had been written at the Components Technology Division, Argonne National Laboratory. Among its many functions, one is to compute the response of 1-dimensional pressure pulse propagation including the effects of many different types of boundary conditions and possible pipe plasticity.

  15. Catalytic gasification studies in a pressurized fluid-bed unit

    SciTech Connect

    Mudge, L.K.; Baker, E.G.; Mitchell, D.H.; Robertus, R.J.; Brown, M.D.

    1983-07-01

    The purpose of the project is to evaluate the technical and economic feasibility of producing specific gas products via the catalytic gasification of biomass. This report presents the results of research conducted from October 1980 to November 1982. In the laboratory scale studis, active catalysts were developed for generation of synthesis gases from wood by steam gasification. A trimetallic catalyst, Ni-Co-Mo on silica-alumina doped with 2 wt % Na, was found to retain activity indefinitely for generation of a methanol synthesis gas from wood at 1380/sup 0/F (750/sup 0/C) and 1 atm (100 kPa) absolute pressure. Catalysts for generation of a methane-rich gas were deactivated rapidly and could not be regenerated as required for economic application. Sodium carbonate and potassium carbonate were effective as catalysts for conversion of wood to synthesis gases and methane-rich gas and should be economically viable. Catalytic gasification conditions were found to be suitable for processing of alternative feedstocks: bagasse, alfalfa, rice hulls, and almond hulls. The PDU was operated successfully at absolute pressures of up to 10 atm (1000 kPa) and temperatures of up to 1380/sup 0/F (750/sup 0/C). Yields of synthesis gases at elevated pressure were greater than those used for previous economic evaluations. A trimetallic catalyst, Ni-Cu-Mo on silica-alumina, did not display a long life as did the doped trimetallic catalyst used in laboratory studies. A computer program for a Radio Shack TRS-80 Model I microcomputer was developed to evaluate rapidly the economics of producing either methane or methanol from wood. The program is based on economic evaluations reported in previous studies. Improved yields from the PDU studies were found to result in a reduction of about 9 cents/gal in methanol cost.

  16. Osmoregulation and interstitial fluid pressure changes in humans during water immersion

    SciTech Connect

    Khosla, S.S.; Dubois, A.B.

    1981-09-01

    The mechanisms of the observed fluid shifts and intracellular osmoregulatory changes accompanying diuresis upon water immersion in man are investigated. Urinary and plasma electrolyte concentrations, plasma amino acid concentrations and interstitial fluid pressures were measured in subjects before, during and after immersion in 34 C water up to their necks for 1 hour. In experiments where vasopressin was administered prior to immersion, urinary sodium, potassium and osmolal clearances are found to increase significantly during immersion, accompanied by decreases in hematocrit, plasma sodium, chloride and potassium concentrations, osmolality and proteins and increases in total plasma CO2 content, threonine, proline, methionine and alanine, plasma volume and red blood cell volume. In experiments without vasopressin injection, interstitial fluid pressure is observed to decrease on the average by up to 2.10 cm H2O during immersion. It is concluded that hyposmotic fluid is mobilized into the blood from interstitial and other extravascular spaces, probably including intracellular volumes, during immersion.

  17. The role of cerebrospinal fluid pressure in glaucoma pathophysiology: the dark side of the optic disc.

    PubMed

    Morgan, William H; Yu, Dao Yi; Balaratnasingam, Chandrakumar

    2008-08-01

    It is generally accepted that glaucoma occurs when intraocular pressure (IOP) is raised above atmospheric pressure beyond tolerable limits for the optic disc. However, the other, unseen side of the optic disc is not air but a set of pressure compartments dominated by the cerebrospinal fluid (CSF) within the subarachnoid space. This invisibility has made investigation difficult; however, in recent decades there has been increased interest in this corollary to IOP. We briefly review the anatomy of the optic nerve subarachnoid space and its pressure relationships to intracranial, retrolaminar, and orbital tissue pressures. The CSF pressure is equivalent to IOP in its influence on translaminar pressure gradient and optic disk surface movement. At low CSF pressure, its influence on retrolaminar tissue pressure is reduced tending to minimize an increase in translaminar pressure gradient. The available evidence suggests that orbital tissue pressure provides this moderating influence. CSF pressure affects axonal transport, which is known to be important in glaucoma etiology and retinal venous outflow and pressures. Recent attempts to develop noninvasive measurement of CSF pressure have increased our knowledge of retinal venous changes in glaucoma. Further work in this area is likely to greatly increase our understanding of glaucoma. PMID:18703953

  18. Force interaction of high pressure glow discharge with fluid flow for active separation control

    SciTech Connect

    Roy, Subrata; Gaitonde, Datta V.

    2006-02-15

    Radio frequency based discharges at atmospheric pressures are the focus of increased interest in aerodynamics because of the wide range of potential applications including, specifically, actuation in flows at moderate speeds. Recent literature describing promising experimental observations, especially on separation control, has spurred efforts in the development of parallel theoretical modeling to lift limitations in the current understanding of the actuation mechanism. The present effort demonstrates higher fidelity first-principle models in a multidimensional finite-element framework to predict surface discharge-induced momentum exchange. The complete problem of a dielectric barrier discharge at high pressure with axially displaced electrodes is simulated in a self-consistent manner. Model predictions for charge densities, the electric field, and gas velocity distributions are shown to mimic trends reported in the experimental literature. Results show that a residual of electrons remains deposited on the dielectric surface downstream of the exposed powered electrode for the entire duration of the cycle and causes a net electric force in the direction from the electrode to the downstream surface. For the first time, results document the mitigation process of a separation bubble formed due to flow past a flat plate inclined at 12 degree sign angle of attack. This effort sets the basis for extending the formulation further to include polyphase power input in multidimensional settings, and to apply the simulation method to flows past common aerodynamic configurations.

  19. Dual reservoir tank for propellant hydraulic fluid for internal combustion engine hydraulically driven cooling fan and for power steering actuating fluid

    SciTech Connect

    Fukami, K.; Inagaki, M.; Oomura, S.; Hamamoto, T.

    1989-01-03

    This patent describes an internal combustion engine reservoir tank comprising a dividing wall between: (a) a first reservoir tank portion for storing a reserve of the first propellant hydraulic fluid, the first flow being taken from the first reservoir tank portion and being returned to the first reservoir tank portion; and (b) a second reservoir tank portion directly adjacent the first reservoir tank portion for storing a reserve of the second propellant hydraulic fluid, the second flow being taken from the second reservoir tank portion and being returned to the second reservoir tank portion.

  20. Effluent characterization from a conical pressurized fluid bed

    NASA Technical Reports Server (NTRS)

    Priem, R. J.; Rollbuhler, R. J.; Patch, R. W.

    1977-01-01

    To obtain useable corrosion and erosion results it was necessary to have data with several levels of particulate matter in the hot gases. One level of particulate loading was as low as possible so that ideally no erosion and only corrosion occurred. A conical fluidized bed was used to obtain some degree of filtration through the top of the bed which would not be highly fluidized. This would minimize the filtration required for the hot gases or conversely the amount of particulate matter in the hot gases after a given level of filtration by cyclones and/or filters. The data obtained during testing characterized the effluent from the bed at different test conditions. A range of bed heights, coal flows, air flows, limestone flows, and pressure are represented. These tests were made to determine the best operating conditions prior to using the bed to determine erosion and corrosion rates of typical turbine blade materials.

  1. A multigrid fluid pressure solver handling separating solid boundary conditions.

    PubMed

    Chentanez, Nuttapong; Müller-Fischer, Matthias

    2012-08-01

    We present a multigrid method for solving the linear complementarity problem (LCP) resulting from discretizing the Poisson equation subject to separating solid boundary conditions in an Eulerian liquid simulation’s pressure projection step. The method requires only a few small changes to a multigrid solver for linear systems. Our generalized solver is fast enough to handle 3D liquid simulations with separating boundary conditions in practical domain sizes. Previous methods could only handle relatively small 2D domains in reasonable time, because they used expensive quadratic programming (QP) solvers. We demonstrate our technique in several practical scenarios, including nonaxis-aligned containers and moving solids in which the omission of separating boundary conditions results in disturbing artifacts of liquid sticking to solids. Our measurements show, that the convergence rate of our LCP solver is close to that of a standard multigrid solver. PMID:22411885

  2. METAL FILTERS FOR PRESSURIZED FLUID BED COMBUSTION (PFBC) APPLICATIONS

    SciTech Connect

    M.A. Alvin

    2004-01-02

    Advanced coal and biomass-based gas turbine power generation technologies (IGCC, PFBC, PCFBC, and Hipps) are currently under development and demonstration. Efforts at the Siemens Westinghouse Power Corporation (SWPC) have been focused on the development and demonstration of hot gas filter systems as an enabling technology for power generation. As part of the demonstration effort, SWPC has been actively involved in the development of advanced filter materials and component configuration, has participated in numerous surveillance programs characterizing the material properties and microstructure of field-tested filter elements, and has undertaken extended, accelerated filter life testing programs. This report reviews SWPC's material and component assessment efforts, identifying the performance, stability, and life of porous commercial metal, advanced alloy, and intermetallic filters under simulated, pressurized fluidized-bed combustion (PFBC) conditions.

  3. Molecular simulation of pressure-driven fluid flow in nanoporous membranes

    NASA Astrophysics Data System (ADS)

    Takaba, Hiromitsu; Onumata, Yasushi; Nakao, Shin-ichi

    2007-08-01

    An extended nonequilibrium molecular dynamics technique has been developed to investigate the transport properties of pressure-driven fluid flow in thin nanoporous membranes. Our simulation technique allows the simulation of the pressure-driven permeation of liquids through membranes while keeping a constant driving pressure using fluctuating walls. The flow of argon in the liquid state was simulated on applying an external pressure difference of 2.4×106Pa through the slitlike and cylindrical pores. The volume flux and velocity distribution in the membrane pores were examined as a function of pore size, along with the interaction with the pore walls, and these were compared with values estimated using the Hagen-Poiseuille flow. The calculated velocity strongly depends on the strength of the interaction between the fluid and the atoms in the wall when the pore size is approximately <20σ. The calculated volume flux also shows a dependence on the interaction between the fluid and the atoms in the wall. The Hagen-Poiseuille law overestimates or underestimates the flux depending on the interaction. From the analysis of calculated results, a good linear correlation between the density of the fluid in the membrane pores and the deviation of the flux estimated from the Hagen-Poiseuille flow was found. This suggests that the flux deviation in nanopore from the Hagen-Poiseuille flow can be predicted based on the fluid density in the pores.

  4. Fail-safe electric actuator

    SciTech Connect

    Wright, J.J.

    1988-07-19

    In combination with a control mechanism characterized by the ability to be moved from inoperative to operative position and back, a fail-safe actuator device for automatically returning the control mechanism to inoperative position when interruption of electric power occurs is described which comprises: a fluid-driven vaned torque actuator: electric-motor-driven fluid power means for operating the torque actuator; electrically operated valve means for controlling the power fluid flow between the torque actuator and the fluid power generating means; at least one shaft projecting from the torque actuator; coupling means for operatively connecting the shaft to the control mechanism to be operated by the failsafe actuator device; reversible means for storing energy, the reversible means being operatively connected to the shaft; a limit-switch operating cam mounted on and rotable with the shaft; a limit switch positioned for activation by the limit-switch operating cam; and electric circuitry means for interconnecting the motordriven fluid power generating means, the valve means, and the limit switch.

  5. Undrained heating and anomalous pore-fluid pressurization of a hardened cement paste

    NASA Astrophysics Data System (ADS)

    Ghabezloo, S.; Sulem, J.; Saint-Marc, J.

    2009-04-01

    Temperature increase in a fluid-saturated porous material in undrained condition leads to volume change and pore pressure increase due to the discrepancy between the thermal expansion coefficients of the pore fluid and of the pore volume. This increase of the pore fluid pressure induces a reduction of the effective mean stress, and can lead to shear failure or hydraulic fracturing. This phenomenon is important is important in environmental engineering for radioactive (exothermal) waste disposal in deep clay geological formations as well as in geophysics in the studies of rapid fault slip events when shear heating tends to increase the pore pressure and to decrease the effective compressive stress and the shearing resistance of the fault material (Sulem et al. 2007). This is also important in petroleum engineering where the reservoir rock and the well cement lining undergo sudden temperature changes for example when extracting heavy oils by steam injection methods. This rapid increase of temperature could damage cement sheath integrity of wells and lead to loss of zonal isolation. The values of the thermal pressurization coefficient, defined as the pore pressure increase due to a unit temperature increase in undrained condition, is largely dependent upon the nature of the material, the state of stress, the range of temperature change, the induced damage. The large variability of the thermal pressurization coefficient reported in the literature for different porous materials with values from 0.01MPa/°C to 1.5MPa/°C highlights the necessity of laboratory studies. This phenomenon of thermal pressurization is studied experimentally for a fluid-saturated hardened cement paste in an undrained heating test. Careful analysis of the effect of the dead volume of the drainage system of the triaxial cell has been performed based on a simple correction method proposed by Ghabezloo and Sulem (2008, 2009). The drained and undrained thermal expansion coefficients of the hardened

  6. Near-infrared spectroscopic determination of salinity and internal pressure of fluid inclusions in minerals.

    PubMed

    Kagi, Hiroyuki; Kiyasu, Akiko; Akagi, Tasuku; Nara, Masayuki; Sawaki, Takayuki

    2006-04-01

    A near-infrared (NIR) spectroscopic method is proposed to achieve the simultaneous determination of salinity and internal pressure of fluid inclusions in natural minerals. A combination band between the anti-symmetric stretching and bending vibrations of molecular water at approximately 5180 cm-1 was observed for standard salt solutions and natural minerals containing fluid inclusions with known salinities. A curve-fitting procedure was used to analyze the change in the band shape of the combination. Justification of the calibration was confirmed by observation of fluid inclusions in natural minerals whose salinities had already been determined using microthermometry. The detection limit of the present method is 1 NaCl-eq wt. %. The minimum size of fluid inclusions that produced well-resolved spectra was approximately 30 microm. This method was applied to assess micro fluid inclusions in a natural diamond with cubic growth habit (cuboid). The salinity and residual pressure of those fluid inclusions were estimated respectively as 4.4 wt. % NaCl-eq and 0.6-0.8 GPa. The present method is complementary to Raman microscopy and microthermometry for the determination of salinity in fluid inclusions of geological samples. PMID:16613640

  7. Pore geometry of Berea sandstone and numerical simulation of fluid flow by LBM under pressurization

    NASA Astrophysics Data System (ADS)

    Takahashi, M.; Sato, M.

    2012-12-01

    The Berea sandstone has a clear bedding plane and not clear cross lamina in cm size specimen, which is mainly caused by grain orientation and void space in microscopic scale. During the confined triaxial compression test, we measured permeability of Berea sandstone by constant head test for three mutually perpendicular directions under effective confining pressure and increasing differential axial stress. In general, the permeability of Berea sandstones decreased slightly with increasing the effective confining pressure and axial differential stress. Permeability anisotropy was also observed in the normal and two parallel directions to the bedding planes. We introduced the three-dimensional medial axis (3DMA) method of Lindquist et al. (2000) to quantify the flow-relevant geometric properties of the voids structure in Berea sandstone. Using these data, we also evaluated the number of connecting path between two faces, tortuosity and the shortest path distribution within an arbitrary region of Berea sandstone specimen. Geometrical information on the number of connecting path in an arbitrary volume CT data shows reasonable correlation between permeability anisotropy and mutually perpendicular directions normal and parallel to bedding planes. In addition, we introduced numerical simulation of fluid flow of pressurized Berea sandstone by LBM, to discuss the permeability reduction caused by pressurization. We obtained the detail distributions of fluid pressure, fluid velocity and its vector distribution in rather narrow voids space more than 10 μm. It is confirmed that pressurization caused decrease of the connecting path and the shortest path between arbitrary faces, and then caused a complex condition of on fluid pressure and fluid velocity.

  8. Mounting Pressure in the Microenvironment: Fluids, Solids, and Cells in Pancreatic Ductal Adenocarcinoma.

    PubMed

    DuFort, Christopher C; DelGiorno, Kathleen E; Hingorani, Sunil R

    2016-06-01

    The microenvironment influences the pathogenesis of solid tumors and plays an outsized role in some. Our understanding of the stromal response to cancers, particularly pancreatic ductal adenocarcinoma, has evolved from that of host defense to tumor offense. We know that most, although not all, of the factors and processes in the microenvironment support tumor epithelial cells. This reappraisal of the roles of stromal elements has also revealed potential vulnerabilities and therapeutic opportunities to exploit. The high concentration in the stroma of the glycosaminoglycan hyaluronan, together with the large gel-fluid phase and pressures it generates, were recently identified as primary sources of treatment resistance in pancreas cancer. Whereas the relatively minor role of free interstitial fluid in the fluid mechanics and perfusion of tumors has been long appreciated, the less mobile, gel-fluid phase has been largely ignored for historical and technical reasons. The inability of classic methods of fluid pressure measurement to capture the gel-fluid phase, together with a dependence on xenograft and allograft systems that inaccurately model tumor vascular biology, has led to an undue emphasis on the role of free fluid in impeding perfusion and drug delivery and an almost complete oversight of the predominant role of the gel-fluid phase. We propose that a hyaluronan-rich, relatively immobile gel-fluid phase induces vascular collapse and hypoperfusion as a primary mechanism of treatment resistance in pancreas cancers. Similar properties may be operant in other solid tumors as well, so revisiting and characterizing fluid mechanics with modern techniques in other autochthonous cancers may be warranted. PMID:27072672

  9. How ubiquitous are aftershock sequences driven by high pressure fluids at depth?

    NASA Astrophysics Data System (ADS)

    Miller, S. A.

    2008-12-01

    Strong evidence suggests that two earthquake-aftershock episodes, the 2004 Niigata (Japan) sequence and the 1997 Umbria-Marche (Italy) sequence, were driven by high pressure fluids at depth. Since Niigata was in a compressional environment and Umbria-Marche in extension, a question arises about whether such a mechanism is more general than just these two cases. Although it is not clear by what mechanism fluids of sufficient volume can be trapped in the lower crust, if such pockets of high pressure fluids exist, then they must necessarily be expelled when a large earthquake provides the hydraulic connection to the hydrostatically pressured free surface. In this talk, aftershock data is analyzed for a number of different earthquakes in a variety of tectonic settings, including 1992 Landers, 1994 Northridge, and the 2001 Bhuj earthquakes. Comparisons are made between model results of the evolved fluid pressure state from a high pressure source at depth, and the spatio-temporal distributions of aftershocks. The data is further analyzed and compared with model results for differences in the rate of aftershocks (p-value in Omori's Law) and their dependence on the orientation of the mainshock relative to the prevailing regional stress field.

  10. Measurement of the Density of Base Fluids at Pressures 0.422 to 2.20 Gpa

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.; Jacobson, B. O.; Bergstroem, S. I.

    1985-01-01

    The influence of pressure on the density of six base fluids is experimentally studied for a range of pressures from 0.422 to 2.20 GPa. An important parameter used to describe the results is the change in relative volume with change in pressure dv sub r/dp. For pressures less than the solidification pressure (p ps) a small change in pressure results in a large change in dv sub r/ps. For pressures greater than the solidification pressure (p ps) there is no change in dv sub r/dp with changing pressure. The solidification pressures of the base fluids varies considerably, as do the slopes that the experimental data assumes for p ps. A new formula is developed that describes the effect of pressure on density in terms of four constants. These constants vary for the different base fluids tested.

  11. Micromechanism linear actuator with capillary force sealing

    DOEpatents

    Sniegowski, Jeffry J.

    1997-01-01

    A class of micromachine linear actuators whose function is based on gas driven pistons in which capillary forces are used to seal the gas behind the piston. The capillary forces also increase the amount of force transmitted from the gas pressure to the piston. In a major subclass of such devices, the gas bubble is produced by thermal vaporization of a working fluid. Because of their dependence on capillary forces for sealing, such devices are only practical on the sub-mm size scale, but in that regime they produce very large force times distance (total work) values.

  12. A method for suppression of pressure pulses in fluid-filled piping: Theoretical analysis

    SciTech Connect

    Shin, Y.W.; Wiedermann, A.H.

    1988-06-01

    A simple, nondestructive method to suppress pressure pulses in a fluid-filled piping is theoretically analyzed, and the result provides the basis needed for design and evaluation of a pressure-pulse suppression device based on the proposed theory. The method is based on forming of fluid jets in the event of a pressure surge such that the pulse height as well as the energy of the pulse are reduced. The result for pressure pulses in the range of practical interest shows that a substantial reduction can be attained in the pulse height with accompanied reduction of pulse energy remaining in the system. The analysis also reveals that a certain amount of trade-off exists in the design of the suppression device; a certain level of pulse energy remaining in the system must be accepted in order to limit the pulse height below a certain level and vice versa. 7 refs., 5 figs.

  13. Biocatalytic Synthesis of Acrylates in Supercritical Fluids: Tuning Enzyme Activity by Changing Pressure

    NASA Astrophysics Data System (ADS)

    Kamat, Sanjay V.; Iwaskewycz, Brian; Beckman, Eric J.; Russell, Alan J.

    1993-04-01

    Supercritical fluids are a unique class of non-aqueous media in which biocatalytic reactions can occur. The physical properties of supercritical fluids, which include gas-like diffusivities and liquid-like densities, can be predictably controlled with changing pressure. This paper describes how adjustment of pressure, with the subsequent predictable changes of the dielectric constant and Hildebrand solubility parameter for fluoroform, ethane, sulfur hexafluoride, and propane, can be used to manipulate the activity of lipase in the transesterification of methylmethacrylate with 2-ethyl-1-hexanol. Of particular interest is that the dielectric constant of supercritical fluoroform can be tuned from approximately 1 to 8, merely by increasing pressure from 850 to 4000 psi (from 5.9 to 28 MPa). The possibility now exists to predictably alter both the selectivity and the activity of a biocatalyst merely by changing pressure.

  14. The dissociation and equation of state of dense fluid oxygen at high pressures and high temperatures.

    PubMed

    Chen, Q F; Cai, L C; Zhang, Y; Gu, Y J

    2008-03-14

    The dissociation, pressure, and internal energy of dense fluid oxygen at high temperatures and densities have been calculated from the free-energy functions using the self-consistent fluid variational theory. In this paper, we focused on a mixture of oxygen atoms and molecules, and investigated the phenomenon of pressure dissociation at finite temperature. The single-shock Hugoniot derived from this equation of state agrees well with gas-gun experiments for pressure versus density. The equation of state and dissociation degree are predicted in the ranges of temperature of 5000-16,000 K and density of 0.1-4.5 g/cm(3). These data are formulated in the analytical forms of dissociation degree-density-temperature and pressure-density-temperature equation of state. PMID:18345911

  15. A Pressure Based Multi-Fluid Algorithm for Multiphase Flow

    NASA Astrophysics Data System (ADS)

    Ming, P. J.; Zhang, W. P.; Lei, G. D.; Zhu, M. G.

    A new finite volume-based numerical algorithm for predicting multiphase flow phenomena is presented. The method is formulated on an orthogonal coordinate system in collocated primitive variables. The SIMPLE-like algorithms are based on the prediction and correction procedure, and they are extended for all speed range. The object of the present work is to extent single phase SIMPLE algorithm to multiphase flow. The overview of the algorithm is described and relevant numerical issues are discussed extensively, including implicit process of the moment interaction with “partial elimination” (of the drag term), introduction of under-relaxation factor, formulation of momentum interpolation, and pressure correction equation. This model is based on the k-ɛ model assumed that the turbulence is dictated by the continuous phase. Thus only the transport equation for the continuous phase turbulence energy kc needed to be solved while a algebraic turbulence model is used for dispersed phase. The present author also designed a general program with FORTRAN90 program language for the new algorithm based on the household code General Transport Equation Analyzer (GTEA). The performance of the new method is assessed by solving a 3D bubbly two-phase flow in a vertical pipe. A good agreement is achieved between the numerical result and experimental data in the literature.

  16. Properties of planetary fluids at high pressures and temperatures

    NASA Technical Reports Server (NTRS)

    Nellis, W. J.; Holmes, N. C.; Mitchell, A. C.

    1991-01-01

    Observational data obtained by the Voyager space probes to the giant planets Jupiter, Saturn, Uranus, and Neptune have provided valuable information, which is used to refine the picture of the nature of the interiors of these planets. Major results from the Voyager missions include observations of substantial magnetic fields and improved models of internal density distributions. The goal is to obtain equations of state and electrical conductivity data for planetary gases (H2 and He) and the ices (H2O, CH4, and NH3, and their mixtures), which are considered to be the major constituents of the giant planets. These data are needed to test theoretical data bases used to construct models of the chemical composition of planetary interiors, models which are consistent with observables such as mass, diameter, gravitational moments, rotation rate, and magnetic field. The 100 GPa (1 Mbar) pressures and several 1000 K temperatures in the giant planets can be achieved in the lab by the shock compression of liquid specimens. Results are briefly examined.

  17. The role of fluid pressure in frictional stability and earthquake triggering: insights from laboratory experiments

    NASA Astrophysics Data System (ADS)

    Collettini, Cristiano; Scuderi, Marco

    2015-04-01

    Fluid overpressure has been proposed as one of the primary mechanisms that facilitate earthquake slip along faults. However, elastic dislocation theory combined with friction laws suggests that fluid overpressure may inhibit the dynamic instabilities that result in earthquakes, by controlling the critical fault stiffness (kc). This controversy poses a serious problem in our understanding of earthquake physics, with severe implications for both natural and human-induced seismic hazard. Nevertheless, currently, there are no systematic studies on the role of fluid pressure under controlled, laboratory conditions for which the evolution of friction parameters and slip stability can be measured. We have used a state-of-the-art biaxial rock deformation apparatus within a pressure vessel, in order to allow a true triaxial stress field, in a double direct shear configuration. We tested carbonate fault gouge, Carrara marble, sieved to a grain size of 125 μm. Normal stresses and confining pressure were held constant throughout the experiment at values of 5 to 40 MPa, and the pore fluid pressure was varied from hydrostatic up to near lithostatic values. Shear stress was induced by a constant displacement rate and sliding velocities varied from 0.1-1000 μm/s, in order to evaluate slip stability via rate- and state- dependent frictional parameters, such as (a-b), Dc and kc. Our data show that sliding velocity controls the values of friction parameters. In addition we observe a general increase of (a-b) and a decrease of Dc with increasing fluid pressure. Our observations suggest that fluid overpressure does not only facilitate fault reactivation but it also influences frictional parameters with important implications for fault stability and earthquake triggering.

  18. Pneumatic actuator with hydraulic control

    NASA Astrophysics Data System (ADS)

    Everett, Hobart R., Jr.

    1992-11-01

    The present invention provides a pneumatically powered actuator having hydraulic control for both locking and controlling the velocity of an output rod without any sponginess. The invention includes a double-acting pneumatic actuator having a bore, a piston slidably engaged within the bore, and a control rod connected to the piston. The double-acting pneumatic actuator is mounted to a frame. A first double-acting hydraulic actuator having a bore, a piston slidably engaged within the bore, and a follower rod mounted to the piston is mounted to the frame such that the follower rod is fixedly connected to the control rod. The maximum translation of the piston within the bore of the first double-acting hydraulic actuator provides a volumetric displacement V1. The present invention also includes a second double-acting hydraulic actuator having a bore, a piston slidably engaged within the bore, and an output rod mounted to the piston. The maximum translation of the piston within the bore of the second double-acting hydraulic actuator provides a volumetric displacement V2, where V2=V1. A pair of fluid ports in each of the first and second double-acting hydraulic cylinders are operably connected by fluid conduits, one of which includes a valve circuit which may be used to control the velocity of the output rod or to lock the output rod in a static position by regulating the flow of hydraulic fluid between the double-acting cylinders.

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

    USGS Publications Warehouse

    Roedder, E.

    1981-01-01

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

  20. Fluid dynamic modelling of renal pelvic pressure during endoscopic stone removal

    NASA Astrophysics Data System (ADS)

    Oratis, Alexandros; Subasic, John; Bird, James; Eisner, Brian

    2015-11-01

    Endoscopic kidney stone removal procedures are known to increase internal pressure in the renal pelvis, the kidney's urinary collecting system. High renal pelvic pressure incites systemic absorption of irrigation fluid, which can increase the risk of postoperative fever and sepsis or the unwanted absorption of electrolytes. Urologists choose the appropriate surgical procedure based on patient history and kidney stone size. However, no study has been conducted to compare the pressure profiles of each procedure, nor is there a precise sense of how the renal pelvic pressure scales with various operational parameters. Here we develop physical models for the flow rates and renal pelvic pressure for various procedures. We show that the results of our models are consistent with existing urological data on each procedure and that the models can predict pressure profiles where data is unavailable.

  1. The role of fluid pressure in induced vs. triggered seismicity: insights from rock deformation experiments on carbonates.

    PubMed

    Scuderi, Marco M; Collettini, Cristiano

    2016-01-01

    Fluid overpressure is one of the primary mechanisms for tectonic fault slip, because fluids lubricate the fault and fluid pressure reduces the effective normal stress that holds the fault in place. However, current models of earthquake nucleation, based on rate- and state- friction laws, imply that stable sliding is favoured by the increase of pore fluid pressure. Despite this controversy, currently, there are only a few studies on the role of fluid pressure under controlled, laboratory conditions. Here, we use laboratory experiments, to show that the rate- and state- friction parameters do change with increasing fluid pressure. We tested carbonate gouges from sub hydrostatic to near lithostatic fluid pressure conditions, and show that the friction rate parameter (a - b) evolves from velocity strengthening to velocity neutral behaviour. Furthermore, the critical slip distance, Dc, decreases from about 90 to 10 μm. Our data suggest that fluid overpressure plays an important role in controlling the mode of fault slip. Since fault rheology and fault stability parameters change with fluid pressure, we suggest that a comprehensive characterization of these parameters is fundamental for better assessing the role of fluid pressure in natural and human induced earthquakes. PMID:27112408

  2. The role of fluid pressure in induced vs. triggered seismicity: insights from rock deformation experiments on carbonates

    PubMed Central

    Scuderi, Marco M.; Collettini, Cristiano

    2016-01-01

    Fluid overpressure is one of the primary mechanisms for tectonic fault slip, because fluids lubricate the fault and fluid pressure reduces the effective normal stress that holds the fault in place. However, current models of earthquake nucleation, based on rate- and state- friction laws, imply that stable sliding is favoured by the increase of pore fluid pressure. Despite this controversy, currently, there are only a few studies on the role of fluid pressure under controlled, laboratory conditions. Here, we use laboratory experiments, to show that the rate- and state- friction parameters do change with increasing fluid pressure. We tested carbonate gouges from sub hydrostatic to near lithostatic fluid pressure conditions, and show that the friction rate parameter (a − b) evolves from velocity strengthening to velocity neutral behaviour. Furthermore, the critical slip distance, Dc, decreases from about 90 to 10 μm. Our data suggest that fluid overpressure plays an important role in controlling the mode of fault slip. Since fault rheology and fault stability parameters change with fluid pressure, we suggest that a comprehensive characterization of these parameters is fundamental for better assessing the role of fluid pressure in natural and human induced earthquakes. PMID:27112408

  3. The role of fluid pressure in induced vs. triggered seismicity: insights from rock deformation experiments on carbonates

    NASA Astrophysics Data System (ADS)

    Scuderi, Marco M.; Collettini, Cristiano

    2016-04-01

    Fluid overpressure is one of the primary mechanisms for tectonic fault slip, because fluids lubricate the fault and fluid pressure reduces the effective normal stress that holds the fault in place. However, current models of earthquake nucleation, based on rate- and state- friction laws, imply that stable sliding is favoured by the increase of pore fluid pressure. Despite this controversy, currently, there are only a few studies on the role of fluid pressure under controlled, laboratory conditions. Here, we use laboratory experiments, to show that the rate- and state- friction parameters do change with increasing fluid pressure. We tested carbonate gouges from sub hydrostatic to near lithostatic fluid pressure conditions, and show that the friction rate parameter (a ‑ b) evolves from velocity strengthening to velocity neutral behaviour. Furthermore, the critical slip distance, Dc, decreases from about 90 to 10 μm. Our data suggest that fluid overpressure plays an important role in controlling the mode of fault slip. Since fault rheology and fault stability parameters change with fluid pressure, we suggest that a comprehensive characterization of these parameters is fundamental for better assessing the role of fluid pressure in natural and human induced earthquakes.

  4. [Alterations of cerebrospinal fluid pressure in experimental communicating hydrocephalus. Response of CSF-pressure to increased CO2-tension (author's transl)].

    PubMed

    Strecker, E P; Schmidt-Hieber, M; Kauffmann, G; Berg, G; Mathias, K

    1977-07-15

    The response of cerebrospinal fluid pressure to increased arterial carbon dioxide tension was examined in 5 control dogs and 7 dogs with experimental communicating hydrocephalus. The cerebrospinal fluid pressure in control animals only rose to 35 mm Hg after elevation of the arterial CO2 tension. In dogs with experimental communicating hydrocephalus, however, a significant rise of intracranial pressure to 60 mm Hg can be demonstrated. This is accompained by a marked simultaneous decrease of cerebral perfusion pressure in hydrocephalic animals. Progression of communicating hydrocephalus can be explained as damage to the cerebral tissue by increased intracranial pressure waves and by ischemia due to low cerebral perfusion pressure. PMID:20069

  5. Fluid pressure responses for a Devil's Slide-like system: problem formulation and simulation

    USGS Publications Warehouse

    Thomas, Matthew A.; Loague, Keith; Voss, Clifford I.

    2015-01-01

    This study employs a hydrogeologic simulation approach to investigate subsurface fluid pressures for a landslide-prone section of the central California, USA, coast known as Devil's Slide. Understanding the relative changes in subsurface fluid pressures is important for systems, such as Devil's Slide, where slope creep can be interrupted by episodic slip events. Surface mapping, exploratory core, tunnel excavation records, and dip meter data were leveraged to conceptualize the parameter space for three-dimensional (3D) Devil's Slide-like simulations. Field observations (i.e. seepage meter, water retention, and infiltration experiments; well records; and piezometric data) and groundwater flow simulation (i.e. one-dimensional vertical, transient, and variably saturated) were used to design the boundary conditions for 3D Devil's Slide-like problems. Twenty-four simulations of steady-state saturated subsurface flow were conducted in a concept-development mode. Recharge, heterogeneity, and anisotropy are shown to increase fluid pressures for failure-prone locations by up to 18.1, 4.5, and 1.8% respectively. Previous estimates of slope stability, driven by simple water balances, are significantly improved upon with the fluid pressures reported here. The results, for a Devil's Slide-like system, provide a foundation for future investigations

  6. Pressure drop and pumping power for fluid flow through round tubes

    NASA Technical Reports Server (NTRS)

    Jelinek, D.

    1973-01-01

    Program, written for Hewlett-Packard 9100A electronic desk computer provides convenient and immediate solution to problem of calculating pressure drop and fluid pumping power for flow through round tubes. Program was designed specifically for steady-state analysis and assumes laminar flow.

  7. X-ray Compton scattering experiments for fluid alkali metals at high temperatures and pressures

    SciTech Connect

    Matsuda, K. Fukumaru, T.; Kimura, K.; Yao, M.; Tamura, K.; Katoh, M.; Kajihara, Y.; Inui, M.; Itou, M.; Sakurai, Y.

    2015-08-17

    We have developed a high-pressure vessel and a cell for x-ray Compton scattering measurements of fluid alkali metals. Measurements have been successfully carried out for alkali metal rubidium at elevated temperatures and pressures using synchrotron radiation at SPring-8. The width of Compton profiles (CPs) of fluid rubidium becomes narrow with decreasing fluid density, which indicates that the CPs sensitively detect the effect of reduction in the valence electron density. At the request of all authors of the paper, and with the agreement of the Proceedings Editor, an updated version of this article was published on 10 September 2015. The original article supplied to AIP Publishing was not the final version and contained PDF conversion errors in Formulas (1) and (2). The errors have been corrected in the updated and re-published article.

  8. Piezoelectric Actuators On A Cold Finger

    NASA Technical Reports Server (NTRS)

    Kuo, Chin-Po; Garba, John A.; Glaser, Robert J.

    1995-01-01

    Developmental system for active suppression of vibrations of cold finger includes three piezoelectric actuators bonded to outer surface. Actuators used to suppress longitudinal and lateral vibrations of upper end of cold finger by applying opposing vibrations. Cold finger in question is part of a cryogenic system associated with an infrared imaging detector. When fully developed, system would be feedback sensor/control/actuator system automatically adapting to changing vibrational environment and suppresses pressure-induced vibrations by imposing compensatory vibrations via actuators.

  9. Miniature linear-to-rotary motion actuator

    NASA Technical Reports Server (NTRS)

    Sorokach, Michael R., Jr.

    1993-01-01

    A miniature hydraulic actuation system capable of converting linear actuator motion to control surface rotary motion has been designed for application to active controls on dynamic wind tunnel models. Due to space constraints and the torque requirements of an oscillating control surface at frequencies up to 50 Hertz, a new actuation system was developed to meet research objectives. This new actuation system was designed and developed to overcome the output torque limitations and fluid loss/sealing difficulties associated with an existing vane type actuator. Static control surface deflections and dynamic control surface oscillations through a given angle are provided by the actuation system. The actuator design has been incorporated into a transonic flutter model with an active trailing edge flap and two active spoilers. The model is scheduled for testing in the LaRC 16 Foot Transonic Dynamics Tunnel during Summer 1993. This paper will discuss the actuation system, its design, development difficulties, test results, and application to aerospace vehicles.

  10. Shear-flow excitation mechanisms of recessed localized arc-filament plasma actuators

    NASA Astrophysics Data System (ADS)

    Kleinman, R. R.; Bodony, D. J.; Freund, J. B.

    2010-11-01

    Localized arc-filament plasma actuators, placed near the nozzle lip of a laboratory jet, have recently been demonstrated to have sufficient control authority to significantly excite the jet downstream [M. Samimy et al., J. Fluid Mech. 578, 305 (2007)]. This class of plasma actuator, which in this application is recessed in a small cavity near the nozzle lip, causes intense local heating. This heating is thought to be the root mechanism of its influence on the flow, but how this principally entropic thermal source couples with the vortical jet shear layer turbulence downstream is unclear. We investigate this using direct numerical simulations, which match the flow conditions of the corresponding experiment, including Reynolds number, but are two-dimensional to ease computational expense. Despite this obvious modeling approximation, the simulations include the key features of the laboratory system: a thin boundary layer, a plasma-like thermal source in a small recessed cavity, a nozzle lip, and a downstream free shear layer. Results are shown to match the temperature and near-field pressure measured in the laboratory actuators. It is found that the cavity, which was initially included to shield the actuator plasma from the flow, is essential for its action. Thermal expansion within the cavity leads to an ejection of fluid from it, which perturbs the boundary layer and the downstream mixing layer. There is a finite baroclinic torque, but its effects are relatively minor. An alternate actuator designed to mimic the pressure effects of the full actuator, without its concomitant thermal heating, is nearly as effective at exciting the shear layer. An actuator model without the cavity recess does not provide effective actuation. These results suggest that there is significant potential to optimize the actuation authority through design of cavity recesses that augment its effect.

  11. Nonlinear fluid/structure interaction relating a rupture-disc pressure-relief device. [LMFBR

    SciTech Connect

    Hsieh, B.J.; Kot, C.A.; Shin, Y.W.; Youngdahl, C.K.

    1983-01-01

    Rupture disc assemblies are used in piping network systems as a pressure-relief device. The reverse-buckling type is chosen for application in a liquid metal fast breeder reactor. This assembly is used successfully in systems in which the fluid is highly compressible, such as air; the opening up of the disc by the knife setup is complete. However, this is not true for a liquid system; it had been observed experimentally that the disc may open up only partially or not at all. Therefore, to realistically understand and represent a rupture disc assembly in a liquid environment, the fluid-structure interactions between the liquid medium and the disc assembly must be considered. The methods for analyzing the fluid and the disc and the mechanism interconnecting them are presented. The fluid is allowed to cavitate through a column-cavitation model and the disc is allowed to become plastically deformed through the classic Von Mises' yield criteria, when necessary.

  12. Fluid pressure driven fibril reinforcement in creep and relaxation tests of articular cartilage.

    PubMed

    Li, L P; Korhonen, R K; Iivarinen, J; Jurvelin, J S; Herzog, W

    2008-03-01

    Biological tissues exhibit diverse mechanical behaviors because of complex material properties. As has been shown for ligaments and intervertebral discs, mathematical models often appear to well predict load responses individually by adjusting model parameters, but likely fail to describe several different load responses simultaneously using the same model parameters. In the present study, we attempted to describe and explain both creep and relaxation responses of articular cartilage using a fibril-reinforced model, which has been successfully used to account for the load response of the relaxation tests of articular cartilage. Experiments were performed on bovine articular cartilage disks (n=8) using multi-step loading protocols, involving both creep and relaxation in each protocol. The experimental results indicated that mechanical changes, such as fiber recruitment in collagen network during stretch, recovered fully upon unloading. Creep loading did not affect relaxation properties, and vice versa. Relaxation proceeded much faster than creep, because of different fluid pressure profiles. The load sharing among the proteoglycan matrix, collagen network and fluid pressurization was predicted to differ for the creep and relaxation testing. The experimentally observed strong creep and relaxation responses in unconfined compression could not be predicted if either fibril reinforcement or fluid pressurization were neglected. It was essential to consider the interplay between nonlinear fibril reinforcement and fluid pressurization for the transient response (this interplay may be best termed as fluid pressure driven fibril reinforcement). Fibril reinforcement played a relatively insignificant role in the compressive load response at equilibrium, in agreement with previous findings for cartilage stress relaxation testing. PMID:17524700

  13. High-angle reverse faults, fluid-pressure cycling, and mesothermal gold-quartz deposits

    NASA Astrophysics Data System (ADS)

    Sibson, Richard H.; Robert, Francois; Poulsen, K. Howard

    1988-06-01

    Many mesothermal gold-quartz deposits are localized along high-angle reverse or reverse-oblique shear zones within greenstone belt terrains. Characteristically, these fault-hosted vein deposits exhibit a mixed "brittle-ductile" style of deformation (discrete shears and vein fractures as well as a schistose shear-zone fabric) developed under greenschist facies metamorphic conditions. Many of the vein systems are of considerable vertical extent (>2 km); they include steeply dipping fault veins (lenticular veins subparallel to the shear-zone schistosity) and, in some cases, associated flats (subhorizontal extensional veins). Textures of both vein sets record histories of incremental deposition. We infer that the vein sets developed near the roofs of active metamorphic/magmatic systems and represent the roots of brittle, high-angle reverse fault systems extending upward through the seismogenic regime. Friction theory and field relations suggest that the high-angle reverse faults acted as valves, promoting cyclic fluctuations in fluid pressure from supralithostatic to hydrostatic values. Because of their unfavorable orientation in the prevailing stress field, reactivation of the faults could only occur when fluid pressure exceeded the lithostatic load. Seismogenic fault failure then created fracture permeability within the rupture zone, allowing sudden draining of the geopressured reservoir at depth. Incremental opening of flats is attributed to the prefailure stage of supralithostatic fluid pressures; deposition within fault veins is attributed to the immediate postfailure discharge phase. Hydrothermal self-sealing leads to reaccumulation of fluid pressure and a repetition of the cycle. Mutual crosscutting relations between the two vein sets are a natural consequence of the cyclicity of the process. Abrupt fluid-pressure fluctuations from this fault-valve behavior of reverse faults seem likely to be integral to the mineralizing process at this

  14. Towards a non-linear theory for fluid pressure and osmosis in shales

    NASA Astrophysics Data System (ADS)

    Droghei, Riccardo; Salusti, Ettore

    2015-04-01

    In exploiting deep hydrocarbon reservoirs, often injections of fluid and/or solute are used. To control and avoid troubles as fluid and gas unexpected diffusions, a reservoir characterization can be obtained also from observations of space and time evolution of micro-earthquake clouds resulting from such injections. This is important since several among the processes caused by fluid injections can modify the deep matrix. Information about the evolution of such micro-seismicity clouds therefore plays a realistic role in the reservoir analyses. To reach a better insight about such processes, and obtain a better system control, we here analyze the initial stress necessary to originate strong non linear transients of combined fluid pressure and solute density (osmosis) in a porous matrix. All this can indeed perturb in a mild (i.e. a linear diffusion) or dramatic non linear way the rock structure, till inducing rock deformations, micro-earthquakes or fractures. I more detail we here assume first a linear Hooke law relating strain, stress, solute density and fluid pressure, and analyze their effect in the porous rock dynamics. Then we analyze its generalization, i.e. the further non linear effect of a stronger external pressure, also in presence of a trend of pressure or solute in the whole region. We moreover characterize the zones where a sudden arrival of such a front can cause micro-earthquakes or fractures. All this allows to reach a novel, more realistic insight about the control of rock evolution in presence of strong pressure fronts. We thus obtain a more efficient reservoir control to avoid large geological perturbations. It is of interest that our results are very similar to those found by Shapiro et al.(2013) with a different approach.

  15. A fast pressure-correction method for incompressible two-fluid flows

    NASA Astrophysics Data System (ADS)

    Dodd, Michael S.; Ferrante, Antonino

    2014-09-01

    We have developed a new pressure-correction method for simulating incompressible two-fluid flows with large density and viscosity ratios. The method's main advantage is that the variable coefficient Poisson equation that arises in solving the incompressible Navier-Stokes equations for two-fluid flows is reduced to a constant coefficient equation, which can be solved with an FFT-based, fast Poisson solver. This reduction is achieved by splitting the variable density pressure gradient term in the governing equations. The validity of this splitting is demonstrated from our numerical tests, and it is explained from a physical viewpoint. In this paper, the new pressure-correction method is coupled with a mass-conserving volume-of-fluid method to capture the motion of the interface between the two fluids but, in general, it could be coupled with other interface advection methods such as level-set, phase-field, or front-tracking. First, we verified the new pressure-correction method using the capillary wave test-case up to density and viscosity ratios of 10,000. Then, we validated the method by simulating the motion of a falling water droplet in air and comparing the droplet terminal velocity with an experimental value. Next, the method is shown to be second-order accurate in space and time independent of the VoF method, and it conserves mass, momentum, and kinetic energy in the inviscid limit. Also, we show that for solving the two-fluid Navier-Stokes equations, the method is 10-40 times faster than the standard pressure-correction method, which uses multigrid to solve the variable coefficient Poisson equation. Finally, we show that the method is capable of performing fully-resolved direct numerical simulation (DNS) of droplet-laden isotropic turbulence with thousands of droplets using a computational mesh of 10243 points.

  16. Cochlear and cerebrospinal fluid pressure: their inter-relationship and control mechanisms.

    PubMed

    Marchbanks, R J; Reid, A

    1990-06-01

    The patency of the cochlear aqueduct is a key factor in intra-cochlear hydromechanics. If patent, the cerebrospinal fluid (CSF) provides the reference pressure for the perilymph and also to a large extent the endolymph, since Reissner's membrane can only withstand a relatively small pressure differential. The aqueduct often becomes sealed as a natural process of ageing. In this instance the reference pressure is from a source, its position unknown, within the boundaries of the cochlea itself. Relatively large and rapid changes in the cerebrospinal fluid pressure may result from everyday events such as coughing (ca. 175 mm saline) and sneezing (ca. 250 mm saline). The resistive nature of the cochlear aqueduct and the mechanical compliance of the cochlear windows are probably important factors in limiting the amount of stress, and therefore possible damage, which may occur to the cochlea and cochlear windows for a given pressure change within the CSF system. A narrow aqueduct and compliant cochlear windows reduce the risk of structural damage. In practice, this should mean that the risk of structural damage will be increased by any process which reduces the compliance of one or both of the cochlear windows, for example, extremes of middle ear pressure perhaps brought about by Eustachian tube dysfunction or rapid barometric pressure changes. Techniques are now available which provide non-invasive indirect measures of perilymphatic pressure and CSF-perilymphatic pressure transfer. The tympanic membrane displacement measurement technique has been used to provide reliable measures of perilymphatic pressure and CSF-perilymphatic pressure transfer on an individual subject basis.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2194603

  17. Low-g fluid mixing - Further results from the Tank Pressure Control Experiment

    NASA Technical Reports Server (NTRS)

    Bentz, M. D.; Knoll, R. H.; Hasan, M. M.; Lin, C. S.

    1993-01-01

    The Tank Pressure Control Experiment (TPCE) made its first space flight on STS-43 in 1991. Its objective was to test the effectiveness of low-energy axial jet mixing at controlling pressures in low gravity. The experiment used refrigerant 113 at near-saturation conditions, at an 83 percent fill level, to simulate the fluid dynamics and thermodynamics of cryogenic fluids in future space applications. Results from this flight were reported previously. TPCE was again flown in space on STS-52 in 1992, this time primarily to study boiling and related thermal phenomena which will be reported elsewhere. However additional mixing and pressure control data were obtained from the reflight that supplement the data from the first flight.

  18. Numerical Modeling of Pressurization of Cryogenic Propellant Tank for Integrated Vehicle Fluid System

    NASA Technical Reports Server (NTRS)

    Majumdar, Alok K.; LeClair, Andre C.; Hedayat, Ali

    2016-01-01

    This paper presents a numerical model of pressurization of a cryogenic propellant tank for the Integrated Vehicle Fluid (IVF) system using the Generalized Fluid System Simulation Program (GFSSP). The IVF propulsion system, being developed by United Launch Alliance, uses boiloff propellants to drive thrusters for the reaction control system as well as to run internal combustion engines to develop power and drive compressors to pressurize propellant tanks. NASA Marshall Space Flight Center (MSFC) has been running tests to verify the functioning of the IVF system using a flight tank. GFSSP, a finite volume based flow network analysis software developed at MSFC, has been used to develop an integrated model of the tank and the pressurization system. This paper presents an iterative algorithm for converging the interface boundary conditions between different component models of a large system model. The model results have been compared with test data.

  19. Identification of an average temperature and a dynamical pressure in a multitemperature mixture of fluids.

    PubMed

    Gouin, Henri; Ruggeri, Tommaso

    2008-07-01

    We present a classical approach to a mixture of compressible fluids when each constituent has its own temperature. The introduction of an average temperature together with the entropy principle dictates the classical Fick law for diffusion and also novel constitutive equations associated with the difference of temperatures between the components. The constitutive equations fit with results recently obtained through a Maxwellian iteration procedure in extended thermodynamics theory of multitemperature mixtures. The differences of temperatures between the constituents imply the existence of a dynamical pressure even if the fluids have a zero bulk viscosity. The nonequilibrium dynamical pressure can be measured and may be convenient in several physical situations, such as, for example, in cosmological circumstances where--as many authors assert--a dynamical pressure played a major role in the evolution of the early universe. PMID:18764046

  20. Earthquake dynamics. Mapping pressurized volcanic fluids from induced crustal seismic velocity drops.

    PubMed

    Brenguier, F; Campillo, M; Takeda, T; Aoki, Y; Shapiro, N M; Briand, X; Emoto, K; Miyake, H

    2014-07-01

    Volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth. Here, we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations. We used records of seismic noise from the Japanese Hi-net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves. We suggest, therefore, that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems. PMID:24994652

  1. Hydraulically actuated well shifting tool

    SciTech Connect

    Roth, B.A.

    1992-10-20

    This patent describes a hydraulically actuated shifting tool for actuating a sliding member in a well tool. It comprises: a housing having a hydraulic fluid bore therein; shifting dog means positioned on the housing for movement away and toward the housing; locking dog means positioned on the housing for movement away and toward the body; shifting dog hydraulic actuating means in fluid communication with the bore for causing engagement of the shifting dogs with the sliding member; locking dog hydraulic actuating means in communication with the bore for causing engagement of the locking dogs with the locking means; and hydraulic shifting means in communication with the bore for causing relative movement between the shifting dog means and the locking dog means for shifting the sliding sleeve.

  2. Nonlinear fluid/structure interaction relating a rupture-disc pressure-relief device

    SciTech Connect

    Hsieh, B.J.; Kot, C.A.; Shin, Y.W.; Youngdahi, C.K.

    1983-01-01

    Rupture disc assemblies are used in piping network systems as pressure-relief devices. The reverse-buckling type discs are chosen for application in heat transport systems of liquid metal fast breeder reactors. When the pressure on the disc is of sufficient magnitude and duration, the disc develops large displacement, is consequently torn open by a cutting-knife setup and thus relieves the excess pressure. Such disc assemblies are used very successfully in systems in which the fluid is highly compressible, e.g., air; the opening of the disc by the knife setup is complete. However, this is not true for a liquid system; in this case it has been observed experimentally that the disc may open up only partially or not at all. Therefore, to understand and realistically represent a rupture disc assembly in a liquid environment, the fluid-structure interactions between the liquid medium and the disc assembly must be considered. In this paper, methods for analyzing the fluid and the disc and the mechanism interconnecting them are presented. When necessary the fluid is allowed to cavitate through a column separation model and the disc can become plastically deformed using the classic Von Mises' yield criteria.

  3. Method and tool for controlling fluid flow from a tubing string into a low pressure earth formation

    SciTech Connect

    Gurley, D.G.; Nelson, W.F.

    1981-04-07

    A tool is disclosed for controlling flow of treating fluid from a tubing string into an earth formation, in which the bottom hole pressure is less than the hydrostatic pressure of the fluid in the string. In another application, the tool is used in conjunction with a wash tool to wash sediment out of casing perforations and slotted liners. Before the downhole operation is commenced, a slidable piston in this tool closes off fluid outlet ports, to prevent the fluid from ''gravity flowing'' out of the tubing string. The piston is held in the closed position by the co-action of an adjusting bolt and a compression spring. The fluid is released from the tubing string by applying sufficient fluid pressure against the piston to overcome the spring load and thus move the piston downwardly past the fluid outlet port.

  4. Water solubility measurements in supercritical fluids and high-pressure liquids using near-infrared spectroscopy

    SciTech Connect

    Jackson, K.; Bowman, L.E.; Fulton, J.L.

    1995-07-15

    A small amount of water added to a supercritical fluid can greatly increase the solubility of polar species in nonpolar fluids. These modified supercritical solutions significantly expand the use of the fluids in separations and reactions. In order to successfully utilize these systems, information on the miscibility or solubility of water in the fluid is required. Often solubility data are not available for water in a supercritical fluid under a given set of temperature and pressure conditions, and a costly set of equipment must be assembled in order to make these measurements. A relatively fast and inexpensive technique to measure water solubilities using a simple long path length optical cell in an FT-IR spectrometer is described. This technique is also applicable to common and newly developed refrigerants where water solubilities are often unknown at temperatures much above ambient. In this paper, water solubility data in carbon dioxide and two types of refrigerants (chlorodifluoromethane, R22; 1,1,1,2-tetrafluoroethane, R134a) are presented for temperatures from approximately 40 to 110{degree}C and pressures from approximately 10 to 344.8 bar. 26 refs., 6 figs., 4 tabs.

  5. Contact and pressure balance structures in two-fluid cosmic-ray hydrodynamics

    NASA Technical Reports Server (NTRS)

    Webb, G. M.; Brio, M.; Zank, G. P.; Story, T.

    1995-01-01

    The role of cosmic-ray-modified contact discontinuities and pressure balance structures in two-fluid cosmic-ray hydrodynamics in one Cartesian space dimension are investigated by means of analytic and numerical solution examples, as well as by weakly nonlinear asymptotics. The fundamental wave modes of the two-fluid cosmic-ray hydrodynamic equations in the long-wavelength limit consist of the backward and forward propagating cosmic-ray-modified sound waves, with sound speed dependent on both the cosmic-ray and thermal gas pressures; the contact discontinuity; and a pressure balance mode in which the sum ofthe cosmic ray and thermal gas pressure perturbations is zero. The pressure balance mode, like the contact discontinuity is advected with the background flow. The interaction of the pressure balance mode with the contact discontinuity is investigated by means of the method of multiple scales. The thermal gas and cosmic-ray pressure perturbations satisfy a linear diffusion equation, and entropy perturbations arising from nonisentropic initial conditions for the thermal gas are frozen into the fluid. The contact discontinuity and pressure balance eigenmodes both admit nonzero perturbations in the thermal gas, whereas the cosmic-ray-modified sound waves are isentropic. The total entropy perturbation is shared between the contact discontinuity and pressure balance eigenmodes, and examples are given in which there is a transfer of entropy between the two modes. In particular, N-wave type density disturbances are obtained which arise as a result of the entropy transfer between the two modes. A weakly nonlinear geometric optics perturbation expansion is used to study the long timescale evolution of the short-wavelength entropy wave and the thermal gas sound waves in a slowly varying, large-scale background flow. The weakly nonlinear geometric optics expansion is also used to generalize previous studies of squeezing instability for short-wavelength sound waves in the two

  6. Modeling strain and pore pressure associated with fluid extraction: The Pathfinder Ranch experiment

    NASA Astrophysics Data System (ADS)

    Barbour, Andrew J.; Wyatt, Frank K.

    2014-06-01

    Strainmeters can be subject to hydrologic effects from pumping of nearby water wells, depending on the state of the local rock. Strain signals associated with hydrology are generally not used and regarded as troublesome because they are much larger than most tectonic signals (e.g., tides or slow slip episodes in Cascadia), but here we show that fluid extraction leads to detectable strain and pore pressure signals, which we use to constrain valuable material properties of the rock, namely the hydraulic diffusivity and elastic shear modulus. We collected multiple years of pump activity at two active water wells near a pair of Plate Boundary Observatory borehole strainmeters in southern California. These data demonstrate clearly the connection between fluid extraction and deformation: the onset of transient strains and pore pressures is strongly correlated with both the onset of fluid extraction, and the sizes of the transient signals are strongly correlated with cumulative extraction volumes. These data also suggest that the instruments are a possible tool for remote monitoring of fluid injection and withdrawal. Based on poroelastic modeling, we find estimates of hydraulic diffusivity (0.061 m2s-1 to 0.126 m2s-1) which are consistent with data for fractured igneous rock, and estimates of shear modulus (39.7 MPa to 101 MPa) which are comparable to data for shallow granodiorite—expected to be weak from weathering, and other sources of damage (e.g., faulting). We infer that crustal rock in this region is drained at shallow depths by pervasive, hydraulically conductive fractures: as a result of changes in applied stress, fluid flow will occur rather than a sustained change in pore fluid pressure.

  7. Pulse pressure variation and stroke volume variation to predict fluid responsiveness in patients undergoing carotid endarterectomy

    PubMed Central

    Kim, Kyung Mi; Choi, Soo Joo; Kim, Myung Hee; Park, Mi Hye; Heo, Burn Young

    2013-01-01

    Background During carotid endarterectomy (CEA), hemodynamic stability and adequate fluid management are crucial to prevent perioperative cerebral stroke, myocardial infarction and hyperperfusion syndrome. Both pulse pressure variation (PPV) and stroke volume variation (SVV), dynamic preload indices derived from the arterial waveform, are increasingly advocated as predictors of fluid responsiveness in mechanically ventilated patients. The aim of this study was to evaluate the accuracy of PPV and SVV for predicting fluid responsiveness in patients undergoing CEA. Methods Twenty seven patients undergoing CEA were enrolled in this study. PPV, SVV and cardiac output (CO) were measured before and after fluid loading of 500 ml of hydroxyethyl starch solution. Fluid responsiveness was defined as an increase in CO ≥ 15%. The ability of PPV and SVV to predict fluid responsiveness was assessed using receiver operating characteristic (ROC) analysis. Results Both PPV and SVV measured before fluid loading are associated with changes in CO caused by fluid expansion. The ROC analysis showed that PPV and SVV predicted response to volume loading (area under the ROC curve = 0.854 and 0.841, respectively, P < 0.05). A PPV ≥ 9.5% identified responders (Rs) with a sensitivity of 71.4% and a specificity of 90.9%, and a SVV ≥ 7.5% identified Rs with a sensitivity of 92.9% and a specificity of 63.6%. Conclusions Both PPV and SVV values before volume loading are associated with increased CO in response to volume expansion. Therefore, PPV and SVV are useful predictors of fluid responsiveness in patients undergoing CEA. PMID:24101958

  8. An earthquake instability model based on faults containing high fluid-pressure compartments

    USGS Publications Warehouse

    Lockner, D.A.; Byerlee, J.D.

    1995-01-01

    It has been proposed that large strike-slip faults such as the San Andreas contain water in seal-bounded compartments. Arguments based on heat flow and stress orientation suggest that in most of the compartments, the water pressure is so high that the average shear strength of the fault is less than 20 MPa. We propose a variation of this basic model in which most of the shear stress on the fault is supported by a small number of compartments where the pore pressure is relatively low. As a result, the fault gouge in these compartments is compacted and lithified and has a high undisturbed strength. When one of these locked regions fails, the system made up of the neighboring high and low pressure compartments can become unstable. Material in the high fluid pressure compartments is initially underconsolidated since the low effective confining pressure has retarded compaction. As these compartments are deformed, fluid pressure remains nearly unchanged so that they offer little resistance to shear. The low pore pressure compartments, however, are overconsolidated and dilate as they are sheared. Decompression of the pore fluid in these compartments lowers fluid pressure, increasing effective normal stress and shear strength. While this effect tends to stabilize the fault, it can be shown that this dilatancy hardening can be more than offset by displacement weakening of the fault (i.e., the drop from peak to residual strength). If the surrounding rock mass is sufficiently compliant to produce an instability, slip will propagate along the fault until the shear fracture runs into a low-stress region. Frictional heating and the accompanying increase in fluid pressure that are suggested to occur during shearing of the fault zone will act as additional destabilizers. However, significant heating occurs only after a finite amount of slip and therefore is more likely to contribute to the energetics of rupture propagation than to the initiation of the instability. We present

  9. Subsurface fluid pressures from drill-stem tests, Uinta Basin, Utah

    USGS Publications Warehouse

    Nelson, P.H.

    2002-01-01

    High fluid pressures are known to be associated with oil and gas fields in the Uinta Basin, Utah. Shut-in pressure measurements from drill-stem tests show how pressure varies with depth and by area within the basin. The data base used in this report incorporates over 2,000 pressure measurements from drill-stem tests in wells completed prior to 1985. However, the number of useful pressure measurements is considerably less, because many drill-stem tests fail to stabilize at the actual formation pressure if the permeability is low. By extracting the maximum pressure measurements recorded in a collection of wells within an area, the trend of formation pressure within that area can be approximated. Areal compilations of pressures from drill-stem tests show that overpressured rock formations occur throughout much of the northern and eastern areas of the Uinta Basin. In particular, significant overpressuring (0.5 < pressure gradient < 0.8 psi/ft) is found throughout much of the Altamont-Bluebell field at depths ranging from 10,000 to 13,000 ft, equivalent to 5,000 to 8,000 ft below sea level. Limited data indicate that the pressure gradient declines at depths greater than 13,000 ft. An underpressured zone appears to exist in the Altamont-Bluebell field at depths shallower than 5,000 ft. Throughout the eastern Uinta Basin, moderately overpressured zones (0.46 < pressure gradient < 0.5 psi/ft) are common, with local evidence of significantly overpressured zones, but pressure gradients greater than 0.6 psi/ft are rare.

  10. Simultaneous extraction and derivatization of 2-chlorovinylarsonous acid from soils using supercritical and pressurized fluids.

    PubMed

    Chaudot, X; Tambuté, A; Caude, M

    2000-08-01

    Supercritical carbon dioxide and pressurized fluids are compared for the extraction with in situ derivatization of 2-chlorovinylarsonous acid (CVAA) from a series of seven spiked soils. Samples are allowed to age (up to 42 days) and periodically extracted. Sample ageing leads to a recovery decrease due to the development of strong interactions between CVAA and matrix active sites, as time elapses. A similar behavior is observed when usual ultrasonic extraction is performed. Supercritical fluid extraction (SFE) with in situ derivatization leads to the highest recovery. Moreover, SFE allows a solvent consumption reduction. A limit of detection of 0.2 microg/g is reached with the SFE method. PMID:10949499

  11. Effect of lower-body positive pressure on postural fluid shifts in men

    NASA Technical Reports Server (NTRS)

    Hinghofer-Szalkay, H.; Kravik, S. E.; Greenleaf, J. E.

    1988-01-01

    The effect of the lower-body positive pressure (LBPP) on the orthostatic fluid and protein shifts were investigated in five men during combined tilt-table/antigravity suit inflation and deflation experiments. Changes in the mass densities of venous blood and plasma were measured and the values were used to calculate the densities of erythrocytes, whole-body blood, and shifted fluid. It was found that the application of 60 mm Hg LBPP during 60-deg head-up tilt prevented about half of the postural hemoconcentration occurring during passive head-up tilt.

  12. Solubility of Aragonite in Aqueous Fluids at High Pressure and High Temperature

    NASA Astrophysics Data System (ADS)

    Facq, Sébastien; Daniel, Isabelle; Petitgirard, Sylvain; Cardon, Hervé; Sverjensky, Dimitri

    2014-05-01

    Deep crustal and mantle aqueous fluids play a crucial role in geologic processes occurring in the Earth's interior, especially at high PT conditions. Dissolved carbon appears to be a major element constituting these aqueous fluids, occurring under the form of molecular species (CO2, CO, CH4), ionic species such as carbonate or bicarbonate ions or some more complex organic compounds [1]. However, the nature and the content of the chemical species constituting these C-bearing aqueous fluids may strongly be affected by the environmental geologic conditions such as the pressure and the temperature range. If fluid speciation and solubility of carbonate minerals are well characterized at HT and relatively low pressure, less is evident at pressure above 2 GPa where experimental challenges make trickier speciation and solubility measurements. Thanks to recent advances in theoretical aqueous geochemistry [1-3], combined experimental and theoretical efforts allow now the investigation of speciation and solubility of carbonate minerals with pure water at higher PT conditions than previously feasible [4]. However, direct measurements of solubility of carbonate minerals at HP-HT conditions are still needed to help to the development of quantitative models of carbon transport by aqueous fluids in subduction zones and validate existing aqueous speciation model. In this study, we present recent X-ray fluorescence measurements and thermodynamic model of solubility of carbonate in aqueous fluids at pressure up to 5 GPa. The amount of dissolved aragonite in the fluid has been measured from the intensity of the Ca K-lines at the ESRF-ID27 using an externally-heated membrane-type diamond anvil cell and an incident monochromatic focused X-Ray beam at 20 keV. The combination of the XRF data on dissolution of CaCO3mineral combined to previous speciation results permits now to calculate the solubility KS of aragonite a pressure in excess of 2 GPa. [1] Manning, C. E. et al., Review in

  13. Analysis of transient flow and starting pressure gradient of power-law fluid in fractal porous media

    NASA Astrophysics Data System (ADS)

    Tan, Xiao-Hua; Li, Xiao-Ping; Zhang, Lie-Hui; Liu, Jian-Yi; Cai, Jianchao

    2015-09-01

    A transient flow model for power-law fluid in fractal porous media is derived by combining transient flow theory with the fractal properties of tortuous capillaries. Pressure changes of transient flow for power-law fluid in fractal porous media are related to pore fractal dimension, tortuosity fractal dimension and the power-law index. Additionally, the starting pressure gradient model of power-law fluid in fractal porous media is established. Good agreement between the predictions of the present model and that of the traditional empirical model is obtained, the sensitive parameters that influence the starting pressure gradient are specified and their effects on the starting pressure gradient are discussed.

  14. Self-contained hybrid electro-hydraulic actuators using magnetostrictive and electrostrictive materials

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Anirban

    Hybrid electro-hydraulic actuators using smart materials along with flow rectification have been widely reported in recent years. The basic operation of these actuators involves high frequency bidirectional operation of an active material that is converted into unidirectional fluid motion by a set of valves. While theoretically attractive, practical constraints limit the efficacy of the solid-fluid hybrid actuation approach. In particular, inertial loads, fluid viscosity and compressibility combine with loss mechanisms inherent in the active material to limit the effective bandwidth of the driving actuator and the total output power. A hybrid actuator was developed by using magnetostrictive TerFeNOL-D as the active driving element and hydraulic oil as the working fluid. Tests, both with and without an external load, were carried out to measure the unidirectional performance of the actuator at different pumping frequencies and operating conditions. The maximum no-load output velocity was 84 mm/s with a 51 mm long rod and 88 mm/s with a 102 mm long rod, both noted around 325 Hz pumping frequency, while the blocked force was close to 89 N. Dynamic tests were performed to analyze the axial vibration characteristics of the Terfenol-D rods and frequency responses of the magnetic circuits. A second prototype actuator employing the same actuation principle was then designed by using the electrostrictive material PMN-32%PT as the driving element. Tests were conducted to measure the actuator performance for varying electrical input conditions and fluid bias pressures. The peak output velocity obtained was 330 mm/s while the blocked force was 63 N. The maximum volume flow rate obtained with the PMN-based actuator was more than double that obtained from the Terfenol-D--based actuator. Theoretical modeling of the dynamics of the coupled structural-hydraulic system is extremely complex and several models have been proposed earlier. At high pumping frequencies, the fluid inertia

  15. Fluid dynamics of a pressure measuring system for underground explosive tests

    SciTech Connect

    Dykhuizen, R.C.

    1987-01-01

    Numerical and analytical models are used to optimize a pressure measuring system for underground nuclear tests. This system uses a long pipe filled with gas to communicate the pressure level to a transducer in a pressure chamber remote from the explosion cavity. The pressure chamber and pipe are pressurized above the final pressure expected from the explosion. During the explosion, the high pressure gas blows down, preventing debris from entering and clogging the system. The models were first checked against the Junior Jade test series, which used an undergound non-nuclear explosion to simulate a nuclear test. It was found that the measured pressure oscillated for some time before settling down to a steady value. This is shown to be a result of an organ pipe oscillation that can develop in the short pipes used for this test series. The analytical model provided a simple means to optimize the system design parameters and showed that changing the working fluid from nitrogen to helium would improve the time response of the system significantly. The numerical model is then used to obtain more accurate predictions of the sytem response. 2 refs., 5 figs., 1 tab.

  16. Dynamic Arterial Elastance in Predicting Arterial Pressure Increase After Fluid Challenge During Robot-Assisted Laparoscopic Prostatectomy

    PubMed Central

    Seo, Hyungseok; Kong, Yu-Gyeong; Jin, Seok-Joon; Chin, Ji-Hyun; Kim, Hee-Yeong; Lee, Yoon-Kyung; Hwang, Jai-Hyun; Kim, Young-Kug

    2015-01-01

    Abstract During robot-assisted laparoscopic prostatectomy, specific physiological conditions such as carbon dioxide insufflation and the steep Trendelenburg position can alter the cardiac workload and cerebral hemodynamics. Inadequate arterial blood pressure is associated with hypoperfusion, organ damage, and poor outcomes. Dynamic arterial elastance (Ea) has been proposed to be a useful index of fluid management in hypotensive patients. We therefore evaluated whether dynamic Ea can predict a mean arterial pressure (MAP) increase ≥ 15% after fluid challenge during pneumoperitoneum and the steep Trendelenburg position. We enrolled 39 patients receiving robot-assisted laparoscopic prostatectomy. Fluid challenge was performed with 500 mL colloids in the presence of preload-dependent conditions and arterial hypotension. Patients were classified as arterial pressure responders or arterial pressure nonresponders according to whether they showed an MAP increase ≥15% after fluid challenge. Dynamic Ea was defined as the ratio between the pulse pressure variation and stroke volume variation. Receiver operating characteristic curve analysis was performed to assess the arterial pressure responsiveness after fluid challenge during robot-assisted laparoscopic prostatectomy. Of the 39 patients, 17 were arterial pressure responders and 22 were arterial pressure nonresponders. The mean dynamic Ea before fluid challenge was significantly higher in arterial pressure responders than in arterial pressure nonresponders (0.79 vs 0.61, P < 0.001). In receiver operating characteristic curve analysis, dynamic Ea showed an area under the curve of 0.810. The optimal cut-off value of dynamic Ea for predicting an MAP increase of ≥ 15% after fluid challenge was 0.74. Dynamic Ea can predict an MAP increase ≥ 15% after fluid challenge during robot-assisted laparoscopic prostatectomy. This result suggests that evaluation of arterial pressure responsiveness using dynamic Ea helps to

  17. Actuator-valve interface optimization

    SciTech Connect

    Burchett, O.L.; Jones, R.L.

    1986-01-01

    A computer code, Actuator Valve Response (AVR), has been developed to optimize the explosive actuator-valve interface parameters so that the valve plunger velocity is at a maximum when the plunger reaches the valve tubes. The code considers three forces to act on the valve plunger before the plunger reaches the valve tubes. These are the pressure force produced by the actuator, the shear force necessary to shear the seal disks on the actuator and the valve plunger, and the friction force caused by friction between the plunger and the plunger bore. The three forces are modeled by expressions that are explicitly functions of the plunger displacement. A particular actuator-valve combination was analyzed with the computer code AVR with four different combinations of valve plunger seal disk shear strength and initial friction force. (LEW)

  18. Field experiment gathers friction-pressure data for CO{sub 2}-energized fluids

    SciTech Connect

    Tan, H.C.; Sandy, J.M.; McGowen, J.M.; Ridens, J.C.

    1995-11-01

    A field experiment was conducted on a well with 10,000 ft of 3{1/2}-in., 12.9-lbm/ft tubing to gather friction-pressure data for CO{sub 2}-energized fluids. Seventy-three stages were pumped at various rates, gel concentrations, proppant concentrations, and CO{sub 2} qualities to gather sufficient data for modeling and for correlation development. Four side-pocket bundle carriers, with two electronic memory gauges per carrier, were installed at 2,500-ft intervals to monitor pressure and temperature. Four computer data-acquisition systems were used to confirm the integrity of the data collected. The actual friction data that were collected demonstrate the effects of treatment rate, gel concentration, CO{sub 2} quality, proppant concentration, and wellbore depth. This information will help researchers better understand the friction-pressure behavior of CO{sub 2}-energized fluids and should enhance treatment diagnostics, the design of friction-pressure correlations, and existing friction-pressure correlations.

  19. Effect of pressure on an enzymatic reaction in a supercritical fluid

    SciTech Connect

    Erickson, J.C.; Schyns, P.; Cooney, C.L. . Dept. of Chemical Engineering)

    1990-02-01

    Three different authors have reported on the use of four different enzymes in supercritical fluids. Lipase carries out transesterification reactions in the presence of supercritical carbon dioxide. Polyphenyl oxidase is active in supercritical CO{sub 2} and fluoroform. It has been shown that alkaline phosphatase and cholesterol oxidase are active in supercritical CO{sub 2}. More recently, an examination of the effect of aggregation of cholesterol on cholesterol oxidase activity in CO{sub 2} using electron paramagnetic resonance (EPR) was done. They found that when cosolvents which promoted aggregation were added, the reaction rate increased in proportion to the amount of aggregation. To date, no data on the effect of pressure on reaction rate have been presented. The objective of this work is to determine whether pressure-induced changes in the physical properties of a supercritical fluid solvent affect the rate of an enzymatic reaction and if so, which properties are responsible for the change.

  20. A method for pressure-pulse suppression in fluid-filled piping

    SciTech Connect

    Shin, Y.W.; Bielick, E.F. ); Wiedermann, A.H. ); Ockert, C.E. )

    1989-01-01

    A simple, nondestructive method to suppress pressure pulses in fluid-filled piping was proposed and theoretically analyzed earlier. In this paper, the proposed method is verified experimentally. The results of experiments performed for the range of parameters of practical importance indicated that the attenuation of pressure pulses was in accordance with the theoretical predictions. This paper describes the experimental setup and the test models of the proposed pulse suppression devices and discusses the experimental results. In particular, the measured attenuation factors are presented and compared with the theoretical predictions. 8 ref., 17 fig., 2 tab.

  1. Draft tube pressure pulsation predictions in Francis turbines with transient Computational Fluid Dynamics methodology

    NASA Astrophysics Data System (ADS)

    Melot, M.; Nennemann, B.; Désy, N.

    2014-03-01

    An automatic Computational Fluid Dynamics (CFD) procedure that aims at predicting Draft Tube Pressure Pulsations (DTPP) at part load is presented. After a brief review of the physics involved, a description of the transient numerical setup is given. Next, the paper describes a post processing technique, namely the separation of pressure signals into synchronous, asynchronous and random pulsations. Combining the CFD calculation with the post-processing technique allows the quantification of the potential excitation of the mechanical system during the design phase. Consequently it provides the hydraulic designer with a tool to specifically target DTPP and thus helps in the development of more robust designs for part load operation of turbines.

  2. Physics based simulation of seismicity induced in the vicinity of a high-pressure fluid injection

    NASA Astrophysics Data System (ADS)

    McCloskey, J.; NicBhloscaidh, M.; Murphy, S.; O'Brien, G. S.; Bean, C. J.

    2013-12-01

    High-pressure fluid injection into subsurface is known, in some cases, to induce earthquakes in the surrounding volume. The increasing importance of ';fracking' as a potential source of hydrocarbons has made the seismic hazard from this effect an important issue the adjudication of planning applications and it is likely that poor understanding of the process will be used as justification of refusal of planning in Ireland and the UK. Here we attempt to understand some of the physical controls on the size and frequency of induced earthquakes using a physics-based simulation of the process and examine resulting earthquake catalogues The driver for seismicity in our simulations is identical to that used in the paper by Murphy et al. in this session. Fluid injection is simulated using pore fluid movement throughout a permeable layer from a high-pressure point source using a lattice Boltzmann scheme. Diffusivities and frictional parameters can be defined independently at individual nodes/cells allowing us to reproduce 3-D geological structures. Active faults in the model follow a fractal size distribution and exhibit characteristic event size, resulting in a power-law frequency-size distribution. The fluid injection is not hydraulically connected to the fault (i.e. fluid does not come into physical contact with the fault); however stress perturbations from the injection drive the seismicity model. The duration and pressure-time function of the fluid injection can be adjusted to model any given injection scenario and the rate of induced seismicity is controlled by the local structures and ambient stress field as well as by the stress perturbations resulting from the fluid injection. Results from the rate and state fault models of Murphy et al. are incorporated to include the effect of fault strengthening in seismically quite areas. Initial results show similarities with observed induced seismic catalogues. Seismicity is only induced where the active faults have not been

  3. Experimental Studies of Dynamic Fault Weakening Due to Thermal Pore-Fluid Pressurization

    NASA Astrophysics Data System (ADS)

    Goldsby, D. L.; Tullis, T. E.; Okazaka, K.; Platt, J. D.; Mitchell, T. M.

    2014-12-01

    Thermal pressurization is a co-seismic weakening mechanism driven by the thermal expansion of native pore fluids, which leads to elevated pore pressures and significant co-seismic weakening. While thermal pressurization has been studied theoretically for many decades, and has been invoked in recent earthquake simulations, its activation in laboratory experiments has remained elusive. Several high-speed friction experiments yield indirect evidence for thermal pressurization, yet none have directly linked with existing theoretical models or the relevant physical parameters -- such as permeability, slip, and slip rate - that control the weakening rate. We are conducting thermal pressurization experiments on fluid-saturated, low-permeability rocks (primarily Fredrick diabase; also SAFOD gouge) at slip rates up to ~5 mm/s, with constant confining pressures in the range 21-149 MPa and initial pore pressures in the range 10-25 MPa. The impractically low permeability of the diabase, ~10-23 m2, is increased prior to the friction test by thermally cracking the samples, yielding measured permeabilities in the range 1.3*10-18 to 6.1*10-19 m2. These permeabilites are high enough to allow sample saturation over one to several days, but also low enough to confine pore pressure rises during rapid sliding and allow thermal pressurization to occur. In recent experiments we also embed a thermocouple ~1-2 mm from the sliding surface, and use the resulting data to calibrate a finite element model that calculates the sliding surface temperature. One experiment revealed a rapid decay of shear stress by ~25% following a step-change in velocity from 10 μm/s to 4.8 mm/s. For the first 28 mm of slip the experimentally measured shear stress agrees closely with the theoretical solution for slip on a plane (Rice [2006]) with an inferred slip weakening distance of ~500 mm, which is in the range predicted by inserting laboratory determined rock and fluid properties into the formula for L* from

  4. Subharmonic aided pressure estimation for monitoring interstitial fluid pressure in tumours -in vitro and in vivo proof of concept

    PubMed Central

    Halldorsdottir, V G; Dave, J K; Eisenbrey, J R; Machado, P; Zhao, H; Liu, J B; Merton, D A; Forsberg, F

    2014-01-01

    The feasibility of using subharmonic aided pressure estimation (SHAPE) to noninvasively estimate interstitial fluid pressure (IFP) was studied. In vitro, radiofrequency signals, from 0.2 ml/l of Definity (Lantheus Medical Imaging, N Billerica, MA) were acquired within a water-tank with a Sonix RP ultrasound scanner (Ultrasonix, Richmond, BC, Canada; fT/R=6.7/3.35 MHz and fT/R =10/5 MHz) and the subharmonic amplitudes of the signals were compared over 0–50 mmHg. In vivo, five swine with naturally occurring melanomas were studied. Subharmonic signals were acquired from tumours and surrounding tissue during infusion of Definity and compared to needle-based pressure measurements. Both in vitro and in vivo, an inverse linear relationship between hydrostatic pressure and subharmonic amplitude was observed with r2=0.63–0.95; p<0.05, maximum amplitude drop 11.36 dB at 10 MHz and −8 dB, and r2 as high as 0.97; p<0.02 (10 MHz and −4/−8 dB most promising), respectively, indicating that SHAPE may be useful in monitoring IFP. PMID:24856899

  5. Subharmonic aided pressure estimation for monitoring interstitial fluid pressure in tumours--in vitro and in vivo proof of concept.

    PubMed

    Halldorsdottir, V G; Dave, J K; Eisenbrey, J R; Machado, P; Zhao, H; Liu, J B; Merton, D A; Forsberg, F

    2014-09-01

    The feasibility of using subharmonic aided pressure estimation (SHAPE) to noninvasively estimate interstitial fluid pressure (IFP) was studied. In vitro, radiofrequency signals, from 0.2 ml/l of Definity (Lantheus Medical Imaging, N Billerica, MA) were acquired within a water-tank with a Sonix RP ultrasound scanner (Analogic Ultrasound, Richmond, BC, Canada; fT/R=6.7/3.35 MHz and fT/R=10/5 MHz) and the subharmonic amplitudes of the signals were compared over 0-50 mmHg. In vivo, five swine with naturally occurring melanomas were studied. Subharmonic signals were acquired from tumours and surrounding tissue during infusion of Definity and compared to needle-based pressure measurements. Both in vitro and in vivo, an inverse linear relationship between hydrostatic pressure and subharmonic amplitude was observed with r(2)=0.63-0.95; p<0.05, maximum amplitude drop 11.36 dB at 10 MHz and -8 dB, and r(2) as high as 0.97; p<0.02 (10 MHz and -4/-8 dB most promising), respectively, indicating that SHAPE may be useful in monitoring IFP. PMID:24856899

  6. Process-Based Characterizations of Subsurface Fluid Pressures for a Devil's Slide-like System

    NASA Astrophysics Data System (ADS)

    Thomas, M.; Loague, K.

    2014-12-01

    Coastal margins commonly host slope stability hazards that are influenced by hydrologic, geologic, and / or anthropogenic perturbations. A firm foundation for rigorously understanding the component contributions and process-based linkages among hydrologic and geomorphic response is comprehensive physics-based simulation. This study is motivated by the hydrologically-driven, creeping and episodic deep-seated bedrock slides that intersect a former section of the Pacific Coast Highway in the active landslide zone at Devil's Slide near Pacifica, California. For this study, deterministic-conceptual hydrogeologic simulation was employed to estimate fluid pressures for saturated three-dimensional (3D) subsurface systems. One-dimensional (1D) vertical, transient, variably-saturated simulations were conducted to establish the position of the water table (i.e., the upper boundary condition) for the 3D steady-state saturated problems which encode the geologic information for heterogeneous and anisotropic systems. The concept-development effort undertaken here demonstrates that, for a Devil's Slide-like system: (i) specific climatic conditions facilitate variable lag times associated with water-table dynamics, (ii) recharge is the most sensitive parameter to establish risk-averse estimates of fluid pressure, (iii) nuances in the 3D flow field related to fault zone characteristics markedly influence fluid pressures, and (iv) it is unlikely that seasonal fluctuations in the regional water table account for severe failure modes. The simulated fluid pressures encourage new interdisciplinary data discovery to investigate the spatial and temporal persistence of perched water in the study area. To capture event-driven failures for the Devil's Slide site, future efforts should develop characterizations of the unsaturated near surface with a rigor similar to the treatment of the saturated zone demonstrated by this study.

  7. Probe systems for measuring static pressure and turbulence intensity in fluid streams

    NASA Technical Reports Server (NTRS)

    Rossow, Vernon J. (Inventor)

    1993-01-01

    A method and an apparatus for measuring time-averaged static or ambient pressure and turbulence intensity in a turbulent stream are discussed. The procedure involves placing a plurality of probes in the stream. Each probe responds in a different manner to characteristics of the fluid stream, preferably as a result of having varying cross sections. The responses from the probes are used to eliminate unwanted components in the measured quantities for accurate determination of selected characteristics.

  8. [Fluid and sodium balance and blood pressure control in APD/CAPD].

    PubMed

    Freida, P

    2007-10-01

    Cardiovascular disease remains the leading cause of death in ESRD patients related to long-standing hypertension. Early studies had recognized the favourable effect of PD in controlling hypertension but it was soon realized that such benefit was not sustained. A U shaped trend of hypertension in patients on PD has been recently demonstrated as a result of a steadily increased blood pressure partly attributed to fluid retention resulting from lower sodium removal with time. Effort in selecting the best strategy of ultrafiltration for a single patient along with a careful and frequent monitoring of combined 24 hours sodium elimination coupled with dietician counseling can improve significantly fluid an sodium balance which in turn will result in much better blood pressure control. The contribution of progress in biocompatibility of PD fluid that better preserve renal function and the implementation of the first glucose polymer Icodextrin were key interventions in that aim. Further studies should be conducted to assess the power of innovative PD solutions--Low Sodium PDF and/or Bimodal Ultrafiltration--in enhancing fluid and sodium removal during CAPD/APD programmes. PMID:18340683

  9. Apparatus and method for fatigue testing of a material specimen in a high-pressure fluid environment

    DOEpatents

    Wang, Jy-An; Feng, Zhili; Anovitz, Lawrence M; Liu, Kenneth C

    2013-06-04

    The invention provides fatigue testing of a material specimen while the specimen is disposed in a high pressure fluid environment. A specimen is placed between receivers in an end cap of a vessel and a piston that is moveable within the vessel. Pressurized fluid is provided to compression and tension chambers defined between the piston and the vessel. When the pressure in the compression chamber is greater than the pressure in the tension chamber, the specimen is subjected to a compression force. When the pressure in the tension chamber is greater than the pressure in the compression chamber, the specimen is subjected to a tension force. While the specimen is subjected to either force, it is also surrounded by the pressurized fluid in the tension chamber. In some examples, the specimen is surrounded by hydrogen.

  10. Hydraulic Pressure during Fluid Flow Regulates Purinergic Signaling and Cytoskeleton Organization of Osteoblasts

    PubMed Central

    Gardinier, Joseph D.; Gangadharan, Vimal; Wang, Liyun; Duncan, Randall L.

    2014-01-01

    During physiological activities, osteoblasts experience a variety of mechanical forces that stimulate anabolic responses at the cellular level necessary for the formation of new bone. Previous studies have primarily investigated the osteoblastic response to individual forms of mechanical stimuli. However in this study, we evaluated the response of osteoblasts to two simultaneous, but independently controlled stimuli; fluid flow-induced shear stress (FSS) and static or cyclic hydrostatic pressure (SHP or CHP, respectively). MC3T3-E1 osteoblasts-like cells were subjected to 12dyn/cm2 FSS along with SHP or CHP of varying magnitudes to determine if pressure enhances the anabolic response of osteoblasts during FSS. For both SHP and CHP, the magnitude of hydraulic pressure that induced the greatest release of ATP during FSS was 15 mmHg. Increasing the hydraulic pressure to 50 mmHg or 100 mmHg during FSS attenuated the ATP release compared to 15 mmHg during FSS. Decreasing the magnitude of pressure during FSS to atmospheric pressure reduced ATP release to that of basal ATP release from static cells and inhibited actin reorganization into stress fibers that normally occurred during FSS with 15 mmHg of pressure. In contrast, translocation of nuclear factor kappa B (NFκB) to the nucleus was independent of the magnitude of hydraulic pressure and was found to be mediated through the activation of phospholipase-C (PLC), but not src kinase. In conclusion, hydraulic pressure during FSS was found to regulate purinergic signaling and actin cytoskeleton reorganization in the osteoblasts in a biphasic manner, while FSS alone appeared to stimulate NFκB translocation. Understanding the effects of hydraulic pressure on the anabolic responses of osteoblasts during FSS may provide much needed insights into the physiologic effects of coupled mechanical stimuli on osteogenesis. PMID:24910719

  11. Modeling and Simulation of Aerodynamic Single Dielectric Barrier Discharge Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Orlov, Dmitri; Font, Gabriel

    2008-11-01

    This work presents different approaches to modeling of the plasma actuator, an electrical flow control device, which is now widely used in aerodynamics for separation control, lift enhancement, drag reduction and flight control without moving surfaces. Study of the physics of the discharge in air at atmospheric pressure was performed using particle (PIC-DSMC) and fluid plasma simulations. Based on the experimentally obtained data electro-static and lumped-element circuit models were developed for engineering purposes. Numerical flow simulations were performed to study the effect of the plasma body force on the neutral fluid. The results agreed well with the experiments. An application of the plasma actuators to the leading-edge separation control on the NACA 0021 airfoil was studied numerically. The results were obtained for a range of angles of attack. Improvement in the airfoil characteristics was observed in numerical simulations at high angles of attack in cases with plasma actuation.

  12. High fluid pressures and high fluid flow rates in the Megasplay Fault Zone, NanTroSEIZE Kumano Transect, SW Japan

    NASA Astrophysics Data System (ADS)

    Moore, J. Casey; Barrett, Myles; Thu, Moe Kyaw

    2012-08-01

    Annular pressure while drilling data shows high fluid overpressures at Site C0001 in part of the megasplay fault zone of the NanTroSEIZE transect across the subduction zone of SW Japan. Mostly standard annular pressures while drilling occur at three other sites, including two penetrating major faults. The two holes at Site C0001 show a step up to lithostatic annular pressure at about 500 mbsf, following initial indicators of overpressure at about 375 mbsf (meters below seafloor). The annular pressure remains high and increasing to total depth of 1000 mbsf. Seismic lines through the site show bright reflectors in the zone of initial annular pressure increase. Borehole images, sonic velocities, and resistivity all suggest a zone of fractures, from about 490 to 630 mbsf. A hydraulic model of the fluid system explains the observed pressures by influx of formation fluid at about 500 mbsf. The combination of a natural influx of 3300 l/m plus 2200 l/m from the drilling system can explain the observed annular pressures. The highly fractured zone that bleeds fluids to the borehole may be sealed by a localized zone of compressive stress or by overlying gas hydrates.

  13. Detection of potential leakage pathways from geological carbon storage by fluid pressure data assimilation

    NASA Astrophysics Data System (ADS)

    González-Nicolás, Ana; Baù, Domenico; Alzraiee, Ayman

    2015-12-01

    One of the main concerns of geological carbon storage (GCS) systems is the risk of leakage through "weak" permeable areas of the sealing formation or caprock. Since the fluid pressure pulse travels faster than the carbon dioxide (CO2) plume across the storage reservoir, the fluid overpressure transmitted into overlying permeable formations through caprock discontinuities is potentially detectable sooner than actual CO2 leakage occurs. In this work, an inverse modeling method based on fluid pressure measurements collected in strata above the target CO2 storage formation is proposed, which aims at identifying the presence, the location, and the extent of possible leakage pathways through the caprock. We combine a three-dimensional subsurface multiphase flow model with ensemble-based data assimilation algorithms to recognize potential caprock discontinuities that could undermine the long-term safety of GCS. The goal of this work is to examine and compare the capabilities of data assimilation algorithms such as the ensemble smoother (ES) and the restart ensemble Kalman filter (REnKF) to detect the presence of brine and/or CO2 leakage pathways, potentially in real-time during GCS operations. For the purpose of this study, changes in fluid pressure in the brine aquifer overlying to CO2 storage formation aquifer are hypothetically observed in monitoring boreholes, or provided by time-lapse seismic surveys. Caprock discontinuities are typically characterized locally by higher values of permeability, so that the permeability distribution tends to fit to a non-Gaussian bimodal process, which hardly complies with the requirements of the ES and REnKF algorithms. Here, issues related to the non-Gaussianity of the caprock permeability field are investigated by developing and applying a normal score transform procedure. Results suggest that the REnKF is more effective than the ES in characterizing caprock discontinuities.

  14. Flow Separation Control Over a Ramp Using Sweeping Jet Actuators

    NASA Technical Reports Server (NTRS)

    Koklu, Mehti; Owens, Lewis R.

    2014-01-01

    Flow separation control on an adverse-pressure-gradient ramp model was investigated using various flow-control methods in the NASA Langley 15-Inch Wind Tunnel. The primary flow-control method studied used a sweeping jet actuator system to compare with more classic flow-control techniques such as micro-vortex generators, steady blowing, and steady- and unsteady-vortex generating jets. Surface pressure measurements and a new oilflow visualization technique were used to characterize the effects of these flow-control actuators. The sweeping jet actuators were run in three different modes to produce steady-straight, steady-angled, and unsteady-oscillating jets. It was observed that all of these flow-control methods are effective in controlling the separated flows on the ramp model. The steady-straight jet energizes the boundary layer by momentum addition and was found to be the least effective method for a fixed momentum coefficient. The steady-angled jets achieved better performance than the steady-straight jets because they generate streamwise vortices that energize the boundary layer by mixing high-momentum fluid with near wall low-momentum fluid. The unsteady-oscillating jets achieved the best performance by increasing the pressure recovery and reducing the downstream flow separation. Surface flow visualizations indicated that two out-of-phase counter-rotating vortices are generated per sweeping jet actuator, while one vortex is generated per vortex-generating jets. The extra vortex resulted in increased coverage, more pressure recovery, and reduced flow separation.

  15. Facts and myths of cerebrospinal fluid pressure for the physiology of the eye.

    PubMed

    Jonas, Jost B; Wang, Ningli; Yang, Diya; Ritch, Robert; Panda-Jonas, Songhomitra

    2015-05-01

    The orbital cerebrospinal fluid pressure (CSFP) represents the true counter-pressure against the intraocular pressure (IOP) across the lamina cribrosa and is, therefore, one of the two determinants of the trans-lamina cribrosa pressure difference (TLPD). From this anatomic point of view, an elevated TLPD could be due to elevated IOP or abnormally low orbital CSFP. Both experimental and clinical studies have suggested that a low CSFP could be associated with glaucomatous optic neuropathy in normal-pressure glaucoma. These included monkey studies with an experimental long-term reduction in CSFP, and clinical retrospective and prospective studies on patients with normal-pressure glaucoma. Since the choroidal blood drains via the vortex veins through the superior ophthalmic vein into the intracranial cavernous sinus, anatomy suggests that the CSFP could influence choroidal thickness. A population-based study revealed that thicker subfoveal choroidal thickness was associated with higher CSFP. Since the central retinal vein passes through the orbital CSF space, anatomy suggests that the retinal venous pressure should be at least as high as the orbital CSFP. Other experimental, clinical or population-based studies suggested an association between higher CSFP and higher retinal venous pressure and wider retinal veins. Consequently, a higher estimated CSFP was associated with arterial hypertensive retinopathy (with respect to the dilated retinal vein diameter and higher arterial-to-venous diameter) and with the prevalence, severity and incidence of diabetic retinopathy. Physiologically, CSFP was related with higher IOP. The influence of the CSFP on the episcleral venous pressure and/or a regulation of both CSFP and IOP by a center in the dorsomedial/perifornical hypothalamus may be responsible for this. In summary, the CSFP may be an overlooked parameter in ocular physiology and pathology. Abnormal changes in the CSFP, in particular in relationship to the IOP, may have

  16. Scale-dependent coupling of hysteretic capillary pressure, trapping, and fluid mobilities

    NASA Astrophysics Data System (ADS)

    Doster, F.; Celia, M. A.; Nordbotten, J. M.

    2012-12-01

    Many applications of multiphase flow in porous media, including CO2-storage and enhanced oil recovery, require mathematical models that span a large range of length scales. In the context of numerical simulations, practical grid sizes are often on the order of tens of meters, thereby de facto defining a coarse model scale. Under particular conditions, it is possible to approximate the sub-grid-scale distribution of the fluid saturation within a grid cell; that reconstructed saturation can then be used to compute effective properties at the coarse scale. If both the density difference between the fluids and the vertical extend of the grid cell are large, and buoyant segregation within the cell on a sufficiently shorte time scale, then the phase pressure distributions are essentially hydrostatic and the saturation profile can be reconstructed from the inferred capillary pressures. However, the saturation reconstruction may not be unique because the parameters and parameter functions of classical formulations of two-phase flow in porous media - the relative permeability functions, the capillary pressure -saturation relationship, and the residual saturations - show path dependence, i.e. their values depend not only on the state variables but also on their drainage and imbibition histories. In this study we focus on capillary pressure hysteresis and trapping and show that the contribution of hysteresis to effective quantities is dependent on the vertical length scale. By studying the transition from the two extreme cases - the homogeneous saturation distribution for small vertical extents and the completely segregated distribution for large extents - we identify how hysteretic capillary pressure at the local scale induces hysteresis in all coarse-scale quantities for medium vertical extents and finally vanishes for large vertical extents. Our results allow for more accurate vertically integrated modeling while improving our understanding of the coupling of capillary

  17. Clinical comparison of the Spiegelberg parenchymal transducer and ventricular fluid pressure

    PubMed Central

    Chambers, I; Siddique, M; Banister, K; Mendelow, A

    2001-01-01

    The Spiegelberg brain pressure catheter is a low cost implantable intracranial pressure measuring system which has the unique ability to perform regular automatic zeroing. A new version of the catheter has become available with a subdural bolt fixation to allow insertion of the device into the brain parenchyma. The accuracy of this system has been evaluated in comparison with a ventricular fluid pressure method in a series of patients to determine its accuracy and utility in the clinical environment.
 Hourly readings from the Spiegelberg system have been compared with those obtained using a standard pressure transducer connected to an external ventricular drain. Measurements continued while there was a clinical need for CSF drainage.
 Eleven patients were recruited to the study and data were recorded for periods ranging from 40 to 111 hours. A good agreement between the two systems was obtained. In 10 cases the mean difference was less than ±1.5 mm Hg and the dynamic changes in value were contemporaneous. In one case an intracerebral haemorrhage developed around the tips of the Spiegelberg catheter and significant differences occurred between the two methods of measurement.
 In conclusion, the Spiegelberg parenchymal transducer provides an accurate measurement of intracranial pressure when compared with ventricular pressure. The transducer was found to be robust in the clinical environment and very popular with the nursing staff. Further studies may determine whether the complication rate of this system is comparable with other available devices.

 PMID:11511715

  18. Syrinx fluid transport: modeling pressure-wave-induced flux across the spinal pial membrane.

    PubMed

    Elliott, N S J

    2012-03-01

    Syrinxes are fluid-filled cavities of the spinal cord that characterize syringomyelia, a disease involving neurological damage. Their formation and expansion is poorly understood, which has hindered successful treatment. Syrinx cavities are hydraulically connected with the spinal subarachnoid space (SSS) enveloping the spinal cord via the cord interstitium and the network of perivascular spaces (PVSs), which surround blood vessels penetrating the pial membrane that is adherent to the cord surface. Since the spinal canal supports pressure wave propagation, it has been hypothesized that wave-induced fluid exchange across the pial membrane may play a role in syrinx filling. To investigate this conjecture a pair of one-dimensional (1-d) analytical models were developed from classical elastic tube theory coupled with Darcy's law for either perivascular or interstitial flow. The results show that transpial flux serves as a mechanism for damping pressure waves by alleviating hoop stress in the pial membrane. The timescale ratio over which viscous and inertial forces compete was explicitly determined, which predicts that dilated PVS, SSS flow obstructions, and a stiffer and thicker pial membrane-all associated with syringomyelia-will increase transpial flux and retard wave travel. It was also revealed that the propagation of a pressure wave is aided by a less-permeable pial membrane and, in contrast, by a more-permeable spinal cord. This is the first modeling of the spinal canal to include both pressure-wave propagation along the spinal axis and a pathway for fluid to enter and leave the cord, which provides an analytical foundation from which to approach the full poroelastic problem. PMID:22482686

  19. Cr(III) solubility in aqueous fluids at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Watenphul, Anke; Schmidt, Christian; Jahn, Sandro

    2014-02-01

    Trivalent chromium is generally considered relatively insoluble in aqueous fluids and melts. However, numerous counterexamples in nature indicate Cr(III) mobilization by aqueous fluids during metamorphism or hydrothermal alteration of chromite-bearing rocks, or by pegmatite melts. So far, very little is known about the chromium concentrations and speciation in such fluids. In this study, the solubility of eskolaite (Cr2O3) in 1.6-4.2 m aqueous HCl solutions was determined in situ at elevated pressures up to 1 GPa and temperatures ranging between 400 and 700 °C using synchrotron micro-X-ray fluorescence spectroscopy (μ-XRF). Determined concentrations of dissolved Cr ranged between about 900-18,000 ppm, with the highest concentrations found at 500 °C and 861 MPa. The Cr(III) solubility in aqueous HCl fluids is retrograde in the studied temperature range and increases with pressure. In addition, Cr(III) complexation in these fluids was explored by Raman spectroscopy on a 12.3 mass% HCl fluid in equilibrium with eskolaite at 400 and 600 °C, 0.3-1.6 GPa. All spectra show two prominent Cr-Cl stretching bands at about 275 and 325 cm-1, which display some fine structure, and in some spectra weak bands in the region between 380 and 500 cm-1. The sum of the integrated intensities of the two dominant bands reveals qualitatively the same changes with temperature along an isochore, with pressure at constant temperature, and with the time required for equilibration as the Cr(III) concentrations in the fluid determined by μ-XRF. Complementary ab initio molecular dynamics simulations of a 4 m HCl solution at two different densities (0.8 and 0.97 g/cm3) and temperatures (427 and 727 °C) were performed to investigate the vibrational properties of various(O)y3-x and (O)y(OH)z3-x-z complexes with 3⩽x+z⩽4 and 0⩽y⩽2. Quasi-normal mode analysis reveals that both the tetrahedral symmetric and antisymmetric Cr-Cl stretching vibrations of CrCl4(H2O)0-2- have characteristic

  20. Cavitation in hydraulic fluids. I - Inception in shear flow. II - Delay time for stepwise reduction in pressure

    NASA Astrophysics Data System (ADS)

    Yamaguchi, A.

    1980-09-01

    A novel concentric-cylinder test apparatus was used to study the onset of cavitation in hydraulic fluids with allowance for the effects of shear. The fluids tested were base oils and include four types of paraffinic mineral oils and two types of naphthenic oils. In addition, the delay time of gaseous cavitation in seven types of hydraulic fluids and tap water was measured for a stepwise reduction in pressure from atmospheric pressure to given pressure. The longest delay time for the incipient cavitation is obtained for water-glycol fluids, and the second longest for tap water. Petroleum-based hydraulic fluids and the phosphate ester have almost the same delay times, which are slightly longer than for the base oil.

  1. Atrial natriuretic factor increases splenic microvascular pressure and fluid extravasation in the rat

    PubMed Central

    Sultanian, Richard; Deng, Yiming; Kaufman, Susan

    2001-01-01

    The spleen is an important site of atrial natriuretic factor (ANF)-induced fluid extravasation into the systemic lymphatic system. The mechanism underlying this process was studied in a blood-perfused (1 ml min−1) rat spleen using the double occlusion technique. To ensure that our observations were spleen specific, a similar protocol was repeated in the hindquarters. Rat ANF(1-28), infused into the splenic artery of anaesthetized male rats, caused a dose-dependent (0.3-59 pmol min−1) increase in microvascular pressure from 11.3 ± 0.7 to 14.9 ± 0.5 mmHg and in post-capillary resistance from 7.2 ± 0.6 to 10.1 ± 1.1 mmHg ml−1. ANF elicited no change in splenic pre-capillary resistance or in hindquarter haemodynamics. Intrasplenic ANF (6.5 pmol min−1) caused a sustained increase in intrasplenic fluid efflux from 0.1 ± 0.1 to 0.3 ± 0.1 ml min−1, and in capillary filtration coefficient (Kf) from 1.2 ± 0.5 to 2.4 ± 0.6 ml mmHg−1 min−1 (100 g tissue)−1. Mechanical elevation of splenic intravascular pressure (from 11.3 ± 0.7 to 22.4 ± 0.2 mmHg) significantly increased intrasplenic fluid extravasation (from 0.4 ± 0.3 to 1.4 ± 0.3 ml min−1). The natriuretic peptide receptor-C (NPRC)-specific agonist C-ANF(4-23) (12.5 and 125 pmol min−1) did not alter splenic intravascular pressure or pre-/post-capillary resistance. The ANF antagonist A71915 (8.3 and 83 pmol min−1), which blocks ANF-stimulated cGMP production via natriuretic peptide receptor-A (NPRA), inhibited the ANF-induced changes in splenic microvascular pressure and post-capillary resistance. It is concluded that ANF enhances the extravasation of isoncotic fluid from the splenic vasculature both by raising intrasplenic microvascular pressure (increased post-capillary resistance) and by increasing filtration area. The constrictive activity of ANF on the splenic vasculature is mediated through NPRA. PMID:11351034

  2. Pulmonary responses to lower body negative pressure and fluid loading during head-down tilt bedrest.

    PubMed

    Hillebrecht, A; Schulz, H; Meyer, M; Baisch, F; Beck, L; Blomqvist, C G

    1992-01-01

    Exposure to microgravity redistributes body fluids with important secondary effects on cardiovascular function. We tested the hypothesis that the fluid shifts also affect pulmonary gas exchange. Microgravity was simulated in six male volunteers by a 10-day period of bedrest at 6 degrees head-down tilt (HDT). Lower body negative pressure (LBNP) and intravenous saline loading superimposed acute changes in fluid distribution on the prolonged effects of HDT. HDT produced relative dehydration and hypovolemia with decreased pulmonary blood flow and diffusing capacity. Before bedrest, pulmonary blood flow decreased by 24% during LBNP and diffusing capacity by 7%, while functional residual capacity increased by 14% (p less than 0.05). Intravenous saline loading caused a 24% increase in pulmonary blood-flow (p less than 0.05). Functional residual capacity decreased by 10% and diffusing capacity by 6% (p less than 0.05). Lung tissue volume did not change significantly. Head-down tilt had only minor effects on the responses to LBNP and saline loading. We conclude that LBNP and intravenous saline loading produce major changes in pulmonary blood-flow and minor effects on pulmonary gas exchange, and that the response to acute changes in fluid distribution is not significantly altered during simulated microgravity. PMID:1509892

  3. The effect of large property fluctuations on turbulent heat transfer to supercritical pressure fluids in pipes

    NASA Astrophysics Data System (ADS)

    Pecnik, Rene; Nemati, Hassan; Patel, Ashish; Boersma, Bendiks Jan

    2014-11-01

    When a fluid slightly above the thermodynamic critical pressure is heated, such that the fluid's state crosses the pseudo-critical line, no distinct liquid to gas phase transition occur. However, the fluid properties change abruptly. If these property variations occur in a turbulent flow the conventional behavior of turbulence is strongly altered. We study the influence of these large property fluctuations in forced convection heat transfer to supercritical carbon dioxide in a pipe, with DNS at a Karman number of Re = 180 (based on the pipe inlet conditions). At the inlet the temperature is slightly below the pseudo-critical point, such that during the heating process the developing thermal boundary layer crosses the pseudo-critical line. We show that the occurring property fluctuations have a strong effect on the averaged wall enthalpy if a constant wall heat flux boundary condition (infinite thermal effusivity ratio of fluid to solid) is used. By changing the boundary conditions to constant wall temperature (vanishing thermal effusivity ratio) these fluctuations are eliminated at the wall and the heat transfer coefficient is decreased.

  4. Nonlinear wave evolution in pressure-driven stratified flow of Newtonian and Herschel-Bulkley fluids

    NASA Astrophysics Data System (ADS)

    Valluri, Prashant; Sahu, Kirti; Ding, Hang; Spelt, Peter; Matar, Omar; Lawrence, Chris

    2007-11-01

    Pressure-driven stratified channel flow of a Newtonian fluid flowing over a Herschel-Bulkley (HB) fluid is considered. The effects of yield stress and shear-thinning rheology on the nonlinear wave evolution are studied using numerical simulations; the HB rheology is regularized at low shear rates using a bi-viscosity formulation. Two different numerical methods were used to carry out the computations: a level-set method (based on that by Spelt, J. Comput. Phys. 2005) and a diffuse-interface method (based on that by Ding et al., J. Comput. Phys., in press). The simulations, which account for fluid inertia, surface tension and gravity are validated against linear theory predictions at early times. The results at later times show the spatio-temporal evolution into the nonlinear regime wherein waves are strongly deformed, leading to the onset of drop entrainment. It is shown that the apparent viscosity in the region of the HB fluid directly involved in the onset of entrainment is almost constant; unyielded regions are confined to wave troughs at late stages of the nonlinear evolution.

  5. Flow and Drag Formulas for Simple Quadrics. [pressure drag and flow equations for an ellipsoid in incompressible fluids

    NASA Technical Reports Server (NTRS)

    Zahm, A. F.

    1979-01-01

    The pressure distribution and resistance found by theory and experiment for simple quadrics fixed in an infinite uniform stream of practically incompressible fluid are calculated. The experimental values pertain to air and some liquids, especially water; the theoretical refer sometimes to perfect, again to viscid fluids. Formulas for the velocity at all points of the flow field are given. Pressure and pressure drag are discussed for a sphere, a round cylinder, the elliptic cylinder, the prolate and oblate spheroid, and the circular disk. The velocity and pressure in an oblique flow are examined.

  6. Simulation of a Supercritical Fluid Flow with Large Temperature Difference under the Assumption of Constant Pressure

    NASA Astrophysics Data System (ADS)

    Komurasaki, Satoko

    2015-11-01

    Eruption of geothermally heated water from the hydrothermal vent in deep oceans of depth over 2,000 meters is numerically simulated. The hydrostatic pressure of water is assumed to be over 200 atmospheres, and the temperature of heated water is occasionally more than 300°C. Under these conditions, a part of heated water can be in the supercritical state, and the physical properties can change significantly by the temperature. Particularly, thermal diffusivity at the critical temperature becomes so small, which prevents heat diffusion, and the temperature gradients can become high. Simulation of this kind of fluid flow can be carried out only by using a highly robust scheme. In this paper, a scheme for a highly-unsteady-flow computation is introduced, and a supercritical fluid flow with a large temperature difference is simulated at a constant pressure. In the computation, the compressible Navier-Stokes equations are solved using a method for the incompressible equations under constant pressure. The equations are approximated by the multidirectional finite difference method and KK scheme is used to stabilize the high-accuracy computation. This work was partially supported by Grant-in-Aid for Scientific Research from MEXT/JSPS (26610119).

  7. Pressure dependence of fluid transport properties of shallow fault systems in the Nankai subduction zone

    NASA Astrophysics Data System (ADS)

    Tanikawa, Wataru; Mukoyoshi, Hideki; Lin, Weiren; Hirose, Takehiro; Tsutsumi, Akito

    2014-12-01

    We measured fluid transport properties at an effective pressure of 40 MPa in core samples of sediments and fault rocks collected by the Integrated Ocean Drilling Program (IODP) NanTroSEIZE drilling project Expedition 316 from the megasplay fault system (site C0004) and the frontal thrust (site C0007) in the Nankai subduction zone. Permeability decreased with effective pressure as a power law function. Permeability values in the fault zones were 8 × 10-18 m2 at site C0004 and 9 × 10-18 m2 at site C0007. Stratigraphic variation in transport properties suggests that the megasplay fault zone may act as a barrier to fluid flow, but the frontal thrust fault zone might not. Depth variation in permeability at site C0007 is probably controlled by the mechanical compaction of sediment. Hydraulic diffusivity at shallow depths was approximately 1 × 10-6 m2 s-1 in both fault zones, which is small enough to lead to pore pressure generation that can cause dynamic fault weakening. However, absence of a very low permeable zone, which may have formed in the Japan Trench subduction zone, might prevent facilitation of huge shallow slips during Nankai subduction zone earthquakes. Porosity tests under dry conditions might have overestimated the porosity.

  8. Development of a fluid friction control valve for pressure letdown in hot dirty gas streams

    SciTech Connect

    Novack, M.

    1990-09-01

    Control valves required for pressure letdown service in future commercial coal conversion plants will be subjected to severe service at a temperature and pressure as high as 1800{degree}F and 800 psig, respectively, in a gaseous environment leading to valve erosion and corrosion. This report describes the design and development of a fluid friction control valve (FFCV) for these severe pressure reduction applications. The FFCV is designed to dissipate friction-induced energy losses uniformly over an extended surface flow path, and thus eliminate pressure reduction taking place in a single-step process. This important feature of the FFCV, by which the fluid mixture velocity is significantly reduced, has the potential of minimizing or even eliminating the problems associated with conventional-type control valves. The component parts of the FFCV exposed to the hot gas flow stream were fabricated from Inconel Alloy 625, a high strength nickel-chromium-molybdenum alloy used in high temperature corrosive environments. The FFCV underwent combined parametric and endurance tests at temperatures and pressures of up to 1500 F and 1000 psig, respectively, at gas stream flowrates of up to 100 lb/hr. To simulate abrasive ash/char particulate as found in conversion plant gas streams, three forms of silica powders were used. Over the course of 53 test runs, the FFCV was subjected to a cumulative endurance test duration of 164 hours, of which 55 hours were with silica particulate in the gas stream. During these tests the FFCV maintained its structural integrity and operated without clogging or jamming. Upon completion of testing, examination of the internal valve surfaces exposed to the gas stream showed no discernable erosion. 1 ref., 23 figs., 3 tabs.

  9. Actuator-valve interface optimization. [Explosive actuators

    SciTech Connect

    Burchett, O.L.; Jones, R.L.

    1987-02-01

    The interface of explosive actuator driven valves can be optimized to maximize the velocity of the valve plunger by using the computer code Actuator-Valve Response. Details of the AVR model of the actuator driven valve plunger and the results of optimizing an actuator-valve interface with AVR are presented. 5 refs., 5 figs., 3 tabs.

  10. Sensing the characteristic acoustic impedance of a fluid utilizing acoustic pressure waves

    PubMed Central

    Antlinger, Hannes; Clara, Stefan; Beigelbeck, Roman; Cerimovic, Samir; Keplinger, Franz; Jakoby, Bernhard

    2012-01-01

    Ultrasonic sensors can be used to determine physical fluid parameters like viscosity, density, and speed of sound. In this contribution, we present the concept for an integrated sensor utilizing pressure waves to sense the characteristic acoustic impedance of a fluid. We note that the basic setup generally allows to determine the longitudinal viscosity and the speed of sound if it is operated in a resonant mode as will be discussed elsewhere. In this contribution, we particularly focus on a modified setup where interferences are suppressed by introducing a wedge reflector. This enables sensing of the liquid's characteristic acoustic impedance, which can serve as parameter in condition monitoring applications. We present a device model, experimental results and their evaluation. PMID:23565036

  11. Fluid pressure and fault strength: insights from load-controlled experiments on carbonate-bearing rocks

    NASA Astrophysics Data System (ADS)

    Spagnuolo, E.; Violay, M.; Nielsen, S. B.; Di Toro, G.

    2013-12-01

    Fluid pressure Pf has been indicated as a major factor controlling natural (e.g., L'Aquila, Italy, 2009 Mw 6.3) and induced seismicity (e.g., Wilzetta, Oklahoma, 2011 Mw 5.7). The Terzaghi's principle states that the effective normal stress σeff= σn (1- α Pf ), with α the Biot coefficient and σn the normal stress, is reduced in proportion to Pf. A value of α=1 is often used by default; however, within a complex fault core of inhomogeneous permeability, α may vary in a yet poorly understood way. To shed light on this problem, we conducted experiments on carbonate-bearing rock samples (Carrara marble) in room humidity conditions and in the presence of pore fluids (drained conditions), where a pre-cut fault is loaded by shear stress τ in a rotary apparatus (SHIVA) under constant σn=15 MPa. Two types of tests were performed with fluids: (1) the fluid pressure was kept constant at Pf=5 MPa (close to hydrostatic conditions at a depth of 0.5 km) and the fault was driven to failure instability by gradually increasing τ; (2) the fluid pressure was kept at Pf=5 MPa and τ was increased until close to instability (τ = 7 MPa): at this point Pf was raised of 0.5 MPa every 10 s up to Pf =10 MPa to induce a main (failure) instability. Assuming α=1 and an effective peak strength (τp)eff=μp σeff at failure, the experiments reveal that: 1) (τp)eff is sensitive to the shear loading rate: fast loading rates (0.5 MPa every 20 s) induce higher peak shear-stress values than slow loading rates (0.5 MPa every 40 s). Such effect is not observed (minor or inexistent) in the absence of pore fluids. 2) Under fast loading rates the (τp)eff may surpass that measured in the absence of pore fluids under identical effective normal stress σeff. 3) An increase of Pf does not necessarily induce the main instability (within the time intervals studied here, i.e. up to ~10 s) even if the effective strength threshold is largely surpassed (e.g., (τp)eff=1.3 μp σeff). We interpret these

  12. Determination of the internal pressure of fluid inclusions by using Raman spectroscopy.

    PubMed

    Yang, Yuping; Zheng, Haifei; Sun, Qiang; Li, Jiankang; Chen, Zhenghui

    2013-07-01

    In situ Raman spectroscopic measurements of H2O-NaCl systems with three different salinities (0, 5.0, and 10.0 wt% NaCl) in the region of O-H stretching vibration were obtained at pressures up to 1800 MPa and temperatures from 298 to 453 K, with a hydrothermal diamond-anvil cell. The peak position was determined by fitting the obtained O-H stretching band with one Gaussian component. At a given temperature, the shift of the band decreased systematically with increasing pressure, and the data show a good linear relationship. For systems of different salinity, the slopes of the isotherms seem to be independent of temperature under the conditions investigated. With increasing salinity, the slope of the isotherm gradually increases. The relationships measured for the shift of the O-H stretching band with temperature, salinity, and pressure can be used to determine the internal pressure and isochore of fluid inclusions as well as the formation temperature and pressure of host minerals. PMID:23816134

  13. Coherent Raman scattering in high-pressure/high-temperature fluids: An overview

    SciTech Connect

    Schmidt, S.C.; Moore, D.S.

    1990-01-01

    The present understanding of high-pressure/high-temperature dense-fluid behavior is derived almost exclusively from hydrodynamic and thermodynamic measurements. Such results average over the microscopic aspects of the materials and are, therefore, insufficient for a complete understanding of fluid behavior. At the present, dense-fluid models can be verified only to the extend that they agree with the macroscopic measurements. Recently, using stimulated Raman scattering, Raman induced Kerr effect scattering, and coherent anti-Stokes Raman scattering, we have been able to probe some of the microscopic phenomenology of these dense fluids. In this paper, we discuss primarily the use of CARS in conjunction with a two-stage light-gas gun to obtain vibrational spectra of shock-compressed liquid N{sub 2}, O{sub 2}, CO, their mixtures, CH{sub 3}NO{sub 2}, and N{sub 2}O. These experimental spectra are compared to synthetic spectra calculated using a semiclassical model for CARS intensities and best fit vibrational frequencies, peak Raman susceptibilities, and Raman linewidths. For O{sub 2}, the possibility of resonance enhancement from collision-induced absorption is addressed. Shifts in the vibrational frequencies reflect the influence of increased density and temperature on the intramolecular motion. The derived parameters suggest thermal equilibrium of the vibrational levels is established less than a few nanoseconds after shock passage. Vibrational temperatures are obtained that agree with those derived from equation-of-state calculations. Measured linewidths suggest that vibrational dephasing times have decreased to subpicosecond values at the highest shock pressures.

  14. Varifocal liquid-filled microlens operated by an electroactive polymer actuator.

    PubMed

    Choi, Seung Tae; Lee, Jeong Yub; Kwon, Jong Oh; Lee, Seungwan; Kim, Woonbae

    2011-05-15

    We designed, fabricated, and characterized varifocal microlenses, whose focal length varies along with the deformation of a transparent elastomer membrane under hydraulic pressure tailored by electroactive polymer actuators. The microfluidic channel of the microlens was designed to be embedded between silicon and glass so that transient fluctuation of the optical fluid and elastomer membrane is effectively suppressed, and thus the microlens is optically stabilized in a reduced time. Multilayered poly(vinylidene fluoride-trifluoroethylene-clorotrifluoroethylene) actuators were also developed and integrated onto the microfluidic chambers. We demonstrated that the developed microlenses are suitable for use in microimaging systems to make their foci tunable. PMID:21593935

  15. Cerebrospinal Fluid Hypernatremia Elevates Sympathetic Nerve Activity and Blood Pressure via the Rostral Ventrolateral Medulla.

    PubMed

    Stocker, Sean D; Lang, Susan M; Simmonds, Sarah S; Wenner, Megan M; Farquhar, William B

    2015-12-01

    Elevated NaCl concentrations of the cerebrospinal fluid increase sympathetic nerve activity (SNA) in salt-sensitive hypertension. Neurons of the rostral ventrolateral medulla (RVLM) play a pivotal role in the regulation of SNA and receive mono- or polysynaptic inputs from several hypothalamic structures responsive to hypernatremia. Therefore, the present study investigated the contribution of RVLM neurons to the SNA and pressor response to cerebrospinal fluid hypernatremia. Lateral ventricle infusion of 0.15 mol/L, 0.6 mol/L, and 1.0 mol/L NaCl (5 µL/10 minutes) produced concentration-dependent increases in lumbar SNA, adrenal SNA, and arterial blood pressure, despite no change in splanchnic SNA and a decrease in renal SNA. Ganglionic blockade with chlorisondamine or acute lesion of the lamina terminalis blocked or significantly attenuated these responses, respectively. RVLM microinjection of the gamma-aminobutyric acid (GABAA) agonist muscimol abolished the sympathoexcitatory response to intracerebroventricular infusion of 1 mol/L NaCl. Furthermore, blockade of ionotropic glutamate, but not angiotensin II type 1, receptors significantly attenuated the increase in lumbar SNA, adrenal SNA, and arterial blood pressure. Finally, single-unit recordings of spinally projecting RVLM neurons revealed 3 distinct populations based on discharge responses to intracerebroventricular infusion of 1 mol/L NaCl: type I excited (46%; 11/24), type II inhibited (37%; 9/24), and type III no change (17%; 4/24). All neurons with slow conduction velocities were type I cells. Collectively, these findings suggest that acute increases in cerebrospinal fluid NaCl concentrations selectively activate a discrete population of RVLM neurons through glutamate receptor activation to increase SNA and arterial blood pressure. PMID:26416846

  16. Dynamics of transcapillary fluid transfer and plasma volume during lower body negative pressure.

    PubMed

    Lundvall, J; Bjerkhoel, P; Edfeldt, H; Ivarsson, C; Länne, T

    1993-02-01

    Lower body negative pressure (LBNP) is a stimulus frequently used to study reflex circulatory responses in humans. Studies have provided data on LBNP-induced blood pooling; however, the possibility that LBNP also might be associated with an important loss of plasma fluid has attracted little attention. Therefore this problem was analysed in male volunteers exposed to prolonged (10 min) high (70-75 mmHg) LBNP. Data on LBNP-induced blood pooling that were more reliable than in previous literature were also provided. LBNP caused early pooling of more than 870 ml of blood. Rapid filtration of plasma into the exposed tissues occurred throughout LBNP. The cumulative oedema in the legs and buttocks averaged as much as 460 ml, and additional quite large volumes of plasma apparently accumulated in other parts of the lower body. Concomitantly, there was compensatory absorption of extravascular fluid in the upper body. The net decrease in plasma volume (PV) was still large and averaged 491 +/- 29(SE) ml. Two aspects of the demonstrated process of transcapillary fluid fluxes and PV decline may be emphasized. Firstly, in conjunction with the primary large redistribution of intravascular volume, it certainly implies that LBNP is a potent stimulus as also indicated by a progressive increase in heart rate (HR) and a progressive decline in systolic pressure throughout experimental intervention. In fact, LBNP-induced circulatory stress clearly has bearings on the extreme hypovolaemic situation provided by the pressure-bottle haemorrhage technique used in animals. Secondly, it not only offers an interesting example of the dynamics of PV but appears to have more general validity with regard to states characterized by gravitational shifts of blood (hydrostatic load), like upright exercise and quiet standing. PMID:8475742

  17. A rocking multianvil: elimination of chemical segregation in fluid-saturated high-pressure experiments

    NASA Astrophysics Data System (ADS)

    Schmidt, Max W.; Ulmer, Peter

    2004-04-01

    Fluid saturated high-pressure experiments often result in strongly zoned experimental charges, this hinders experimentation in chemically homogeneous systems which in turn has serious consequences on equilibration, reaction progress, and (apparent) phase stabilities. In order to overcome these problems, a 600-ton press accommodating either a multianvil or end-loaded piston cylinder module has been mounted in such a way that it can be turned by 180°, thus inverting its position in the gravity field. During turning, hydraulic pressure, heating power, and cooling water remain connected allowing fully controlled pressures and temperatures during experiments. A series of experiments at 13 GPa, 950°C, on a serpentine bulk composition in the MgO-SiO 2-H 2O system demonstrates that continuous turning at a rate of 2 turns/min results in a nearly homogeneous charge composed of phase E + enstatite. The same experiment at static conditions resulted in four mineral zones: quench phase E, enstatite, enstatite + phase E, and phase E + phase A. Phase A disappears in experiments at a turning rate ≥1 turn/min. A static 15-min experiment shows that zonation already forms within this short time span. Placing two short capsules within a single static experiment reveals that the fluid migrates to the hot spot in each capsule and is not gravitationally driven toward the top. The zonation pattern follows isotherms within the capsule, and the degree of zonation increases with temperature gradient (measured as 10 °C within a capsule) and run time. Our preferred interpretation is that Soret diffusion causes a density-stratified fluid within the capsule that does not convect in a static experiment and results in temperature dependant chemical zonation. The aggravation of zonation and appearance of additional phases with run time can be explained with a dissolution-reprecipitation process where the cold spot of the capsule is relatively MgO enriched and the hot spot relatively SiO 2 and H

  18. Hydraulic actuator for an electric circuit breaker

    DOEpatents

    Imam, Imdad [Colonie, NY

    1983-01-01

    This actuator comprises a fluid motor having a piston, a breaker-opening space at one side of the piston, and a breaker-closing space at its opposite side. An accumulator freely communicates with the breaker-opening space for supplying pressurized fluid thereto during a circuit breaker opening operation. The breaker-opening space and the breaker-closing space are connected by an impeded flow passage. A pilot valve opens to allow the pressurized liquid in the breaker-closing space to flow to a back chamber of a normally closed main valve to cause the main valve to be opened during a circuit breaker opening operation to release the pressurized liquid from the breaker-closing space. An impeded passage affords communication between the back chamber and a sump located on the opposite side of the main valve from the back chamber. The pilot valve and impeded passage allow rapid opening of the main valve with pressurized liquid from the breaker closing side of the piston.

  19. Hydraulic actuator for an electric circuit breaker

    DOEpatents

    Imam, I.

    1983-05-17

    This actuator comprises a fluid motor having a piston, a breaker-opening space at one side of the piston, and a breaker-closing space at its opposite side. An accumulator freely communicates with the breaker-opening space for supplying pressurized fluid thereto during a circuit breaker opening operation. The breaker-opening space and the breaker-closing space are connected by an impeded flow passage. A pilot valve opens to allow the pressurized liquid in the breaker-closing space to flow to a back chamber of a normally closed main valve to cause the main valve to be opened during a circuit breaker opening operation to release the pressurized liquid from the breaker-closing space. An impeded passage affords communication between the back chamber and a sump located on the opposite side of the main valve from the back chamber. The pilot valve and impeded passage allow rapid opening of the main valve with pressurized liquid from the breaker closing side of the piston. 3 figs.

  20. Internally supported flexible duct joint. [device for conducting fluids in high pressure systems

    NASA Technical Reports Server (NTRS)

    Kuhn, R. F., Jr. (Inventor)

    1975-01-01

    An internally supported, flexible duct joint for use in conducting fluids under relatively high pressures in systems where relatively large deflection angles must be accommodated is presented. The joint includes a flexible tubular bellows and an elongated base disposed within the bellows. The base is connected through radiating struts to the bellows near mid-portion and to each of the opposite end portions of the bellows through a pivotal connecting body. A motion-controlling linkage is provided for linking the connecting bodies, whereby angular displacement of the joint is controlled and uniformity in the instantaneous bend radius of the duct is achieved as deflection is imposed.

  1. Rotary actuator

    NASA Technical Reports Server (NTRS)

    Brudnicki, Myron (Inventor)

    1995-01-01

    Rotary actuators and other mechanical devices incorporating shape memory alloys are provided herein. Shape memory alloys are a group of metals which when deformed at temperatures below their martensite temperatures, resume the shapes which they had prior to the deformation if they are heated to temperatures above their austensite temperatures. Actuators in which shape memory alloys are employed include bias spring types, in which springs deform the shape memory alloy (SMA), and differential actuators, which use two SMA members mechanically connected in series. Another type uses concentric cylindrical members. One member is in the form of a sleeve surrounding a cylinder, both being constructed of shape memory alloys. Herein two capstans are mounted on a shaft which is supported in a framework. Each capstan is capable of rotating the shaft. Shape memory wire, as two separate lengths of wire, is wrapped around each capstan to form a winding around that capstan. The winding on one capstan is so wrapped that the wire is in a prestretched state. The winding on the other capstan is so wrapped that the wire is in a taut, but not a prestretched, state. Heating one performs work in one direction, thus deforming the other one. When the other SMA is heated the action is reversed.

  2. Influence of pressure, temperature, and pore fluid on the frequency-dependent attenuation of elastic waves in Berea sandstone

    NASA Astrophysics Data System (ADS)

    O'hara, Stephen G.

    1985-07-01

    The effects of pore fluid, effective stress, pore fluid pressure, and temperature on the frequency dependence of elastic wave attenuation in Berea sandstone are interrelated in a series of systematic experiments. The attenuation of both the extensional and torsional modes of cylindrical samples of the sandstone is measured on the frequency range 3-30 kHz. To simulate conditions within the earth, the sandstone is subjected to confining stress to 70.0 MPa and temperature from 24.0 °C to 120.0 °C. Confining pressure and pore fluid pressure are varied independently. Data for two different pore fluids, brine and n-heptane, suggest that a scaling law exists for the pressure and temperature dependence of the attenuation in terms of the pore fluid. The logarithmic decrement of the sandstone is almost frequency independent in a vacuum evacuated sample, but shows a linear frequency dependence, once the sample is saturated. Extrapolation of this linear trend to low frequencies suggests that the decrement in fluid-filled sandstone is effectively frequency independent at seismic frequencies (<100 Hz). The frequency dependence becomes more pronounced as either the effective stress or the temperature is decreased. When the difference between the external stress on the sandstone and the pore fluid pressure is large, the attenuation depends only on the effective stress and is relatively temperature independent. But at low effective stress, the attenuation increases linearly with increasing pore fluid pressure and decreases linearly with increasing temperature. While a specific model is lacking, the attenuation process is apparently influenced most strongly by chemical processes at the pore fluid-matrix interface accompanied by subtle changes in the sandstone matrix dimensions.

  3. Multilayer out-of-plane overlap electrostatic energy harvesting structure actuated by blood pressure for powering intra-cardiac implants

    NASA Astrophysics Data System (ADS)

    Deterre, M.; Risquez, S.; Bouthaud, B.; Dal Molin, R.; Woytasik, M.; Lefeuvre, E.

    2013-12-01

    We present an innovative multilayer out-of-plane electrostatic energy harvesting device conceived in view of scavenging energy from regular blood pressure in the heart. This concept involves the use of a deformable packaging for the implant in order to transmit the blood pressure to the electrostatic transducer. As shown in previous work, this is possible by using thin metal micro-bellows structure, providing long term hermeticity and high flexibility. The design of the electrostatic device has overcome several challenges such as the very low frequency of the mechanical excitation (1 to 2 Hz) and the small available room in the medical implant. Analytical and numerical models have been used to maximize the capacitance variation, and hence to optimize the energy conversion. We have theoretically shown that a 25-layer transducer with 6-mm diameter and 1-mm thickness could harvest at least 20 mJ per heart beat in the left ventricle under a maximum voltage of 75 V. These results show that the proposed concept is promising and could power the next generation of leadless pacemakers.

  4. Implantable device for in-vivo intracranial and cerebrospinal fluid pressure monitoring

    DOEpatents

    Ericson, Milton N.; McKnight, Timothy E.; Smith, Stephen F.; Hylton, James O.

    2003-01-01

    The present invention relates to a completely implantable intracranial pressure monitor, which can couple to existing fluid shunting systems as well as other internal monitoring probes. The implant sensor produces an analog data signal which is then converted electronically to a digital pulse by generation of a spreading code signal and then transmitted to a location outside the patient by a radio-frequency transmitter to an external receiver. The implanted device can receive power from an internal source as well as an inductive external source. Remote control of the implant is also provided by a control receiver which passes commands from an external source to the implant system logic. Alarm parameters can be programmed into the device which are capable of producing an audible or visual alarm signal. The utility of the monitor can be greatly expanded by using multiple pressure sensors simultaneously or by combining sensors of various physiological types.

  5. Development of Design Tools for Flow-Control Actuators

    NASA Technical Reports Server (NTRS)

    Mathew, Jose; Gallas, Quentin; Cattafesta, Louis N., III

    2003-01-01

    This report discusses the: 1. Development coupled electro/fluid/structural lumped-element model (LEM) of a prototypical flow-control actuator. 2. Validation the coupled electro/fluid/structural dynamics lumped-element models. 3. Development simple, yet effective, design tools for actuators. 4. Development structural dynamic models that accurately characterize the dynamic response of piezoelectric flap actuators using the Finite Element Method (FEW as well as analytical methods. 5. Perform a parametric study of a piezo-composite flap actuator. 6.Develop an optimization scheme for maximizing the actuator performance.

  6. Compact valve actuation mechanism

    NASA Technical Reports Server (NTRS)

    Brogdon, James William (Inventor); Gill, David Keith (Inventor)

    2000-01-01

    A valve actuation device. The device may include a free floating valve bridge movably supported within a cavity in the engine housing. The bridge may be provided with a cavity and an orifice arrangement for pumping gases entrained with lubricating fluid toward the piston stems as the bridge reciprocates back and forth. The device may also include a rocker arm that has a U-shaped cross-sectional shape for receiving at least a portion of the valve bridge, valve stem valve spring and spring retainer therein. The rocker arm may be provided with lubrication passages for directing lubrication to the point wherein it is pivotally affixed to the engine housing.

  7. Modular droplet actuator drive

    NASA Technical Reports Server (NTRS)

    Pollack, Michael G. (Inventor); Paik, Philip (Inventor)

    2011-01-01

    A droplet actuator drive including a detection apparatus for sensing a property of a droplet on a droplet actuator; circuitry for controlling the detection apparatus electronically coupled to the detection apparatus; a droplet actuator cartridge connector arranged so that when a droplet actuator cartridge electronically is coupled thereto: the droplet actuator cartridge is aligned with the detection apparatus; and the detection apparatus can sense the property of the droplet on a droplet actuator; circuitry for controlling a droplet actuator coupled to the droplet actuator connector; and the droplet actuator circuitry may be coupled to a processor.

  8. Effect of endoscopic third ventriculostomy on cerebrospinal fluid pressure in the cerebral ventricles.

    PubMed

    Farnoush, Azadeh; Tan, Kristy; Juge, Lauriane; Bilston, Lynne E; Cheng, Shaokoon

    2016-01-01

    We aimed to show how endoscopic third ventriculostomy (ETV) treatment may affect cerebrospinal fluid (CSF) flow dynamics in hydrocephalus, with and without aqueductal stenosis. Hydrocephalus is a neurological disorder which is characterized by enlarged brain ventricles. The periodic motion of CSF flow as a function of the cardiac cycle was prescribed as the inlet boundary condition at the foramen of Monro, and ETV was modeled as a 5mm diameter hole in the anterior wall of the third ventricle. The results show that ETV reduces the pressure in the ventricles by nine-fold in the model with aqueductal stenosis, and three-fold in the model without aqueductal stenosis. More importantly, ETV changes the temporal characteristics of the CSF pressure waveform in the model without aqueductal stenosis, such that there is higher pressure in the ventricle during diastole. This study suggests that changes in the temporal characteristics of the CSF pressure waveform in the ventricles may be the reason why ETV treatment is not effective for hydrocephalus without aqueductal stenosis. PMID:26277641

  9. Radial-directed fluid-pressure-loaded all-metal-sealed gate valve

    DOEpatents

    Batzer, Thomas H.

    1992-01-01

    A large diameter gate valve uses a radially directed fluid pressure loaded all metal seal formed by engaging and disengaging a fixed and a moveable seal element. The fixed element is formed of a circular flange which contains a pressure chamber with a deformable wall, and is mounted to the valve body. The moving seal element contains an annular recess which mates with the circular flange, and is carried on a moveable sub-frame which moves on a frame fixed in the valve body. The valve opening defines an axis in a first direction, and the sub-frame moves through the valve body in a second direction which is substantially perpendicular to the first direction. The sub-frame and moveable seal element move in the second direction until the moveable element reaches a stop mounted in the valve body at which position the moveable element is aligned with but spaced apart from the fixed element. As the sub-frame continues to move in the second direction, the moveable element is forced to move toward and engage the fixed element. The pressure chamber in the flange is then pressurized to complete the seal.

  10. Reconstruction of fluid (over-)pressure evolution from sub-seismic fractures in folds and foreland basins

    NASA Astrophysics Data System (ADS)

    Beaudoin, Nicolas; Lacombe, Olivier; Bellahsen, Nicolas; Emmanuel, Laurent

    2013-04-01

    Deciphering the evolution of pressure, temperature and chemistry of fluids during fold history is a challenging problem. While temperature and chemistry of paleo-fluids can be determined using vein mineralizations in fault zones and/or in diffuse sub-seismic fracture sets, few methods exist to constrain the evolution through time of fluid pressure, especially when no hydrocarbons are encountered. This contribution aims at presenting and discussing a new approach to reconstruct the evolution of fluid pressure based on paleostress analyses. The combination of stress inversion of fault slip data and calcite twin data with rock mechanics data allows determining both the orientations and the magnitudes of principal stresses during basin evolution. Assuming no burial change through time, the comparison of the computed magnitudes of the effective vertical stress with its theoretical value (calculated with respect to the paleo-overburden and hydrostatic fluid pressure) may be used to quantitatively estimate fluid overpressure in limestones at different steps of the tectonic history. Alternatively, if hydrostatic fluid pressure is assumed to prevail in the system from step to step, results likely reflect overburden variations. The application focuses on the diffuse fracture populations observed in limestones of the famous Mississippian-Permian Madison and Phosphoria formations in Laramide basement-cored folds of the Rocky Mountains: the Sheep Mountain and the Rattlesnake Mountain anticlines (Bighorn Basin, Wyoming, USA). The location of these basement-folds on each edge of the Bighorn Basin ensures that depositional and erosional events can be neglected before folding, and thus grants the opportunity to constrain and to discuss the level of fluid overpressure during both the Sevier (thin-skinned) and Laramide (thick-skinned) related Layer-Parallel Shortening (LPS) phases at both fold scale and basin scale. Results highlight an initial fluid overpressure in limestones buried

  11. Experimental Studies of Dynamic Fault Weakening Due to Thermal Pressurization of Pore Fluids

    NASA Astrophysics Data System (ADS)

    Goldsby, David; Tullis, Terry; Platt, John; Okazaki, Keishi

    2016-04-01

    High-velocity friction experiments and geophysical observations suggest that mature faults weaken dramatically during seismic slip. However, while many coseismic weakening mechanisms have been proposed, it is still unclear which mechanisms are most important or how the efficiency of weakening varies within the seismogenic zone. Thermal pressurization is one possible coseismic weakening mechanism driven by the thermal expansion of native pore fluids, which leads to elevated pore pressures and significant coseismic weakening. While thermal pressurization has been studied theoretically for many decades, and invoked in recent earthquake simulations, its activation in laboratory experiments has remained elusive. Several high-speed friction studies have yielded indirect evidence for thermal pressurization, yet none has directly linked with existing theoretical models or the relevant physical parameters, such as permeability, slip, and slip rate, that control the weakening rate. To fill this gap, we are conducting thermal pressurization experiments on fluid-saturated, low-permeability rocks (Frederick diabase) at slip rates up to ~5 mm/s, at constant confining pressures in the range 21-149 MPa and initial imposed pore pressures in the range 10-25 MPa. The impractically low permeability of the as-is diabase, ~10-23 m2, is increased prior to the test by thermal cracking, yielding measured permeabilities in the range 1.3*10-18 to 6.1*10-19 m2. These values of permeability are high enough to allow sample saturation over one to several days, but low enough to confine the elevated pore pressures generated by frictional heating during rapid sliding. Our experiments reveal a rapid decay of shear stress following a step-change in velocity from 10 μm/s to 4.8 mm/s. In one test, the decrease in shear stress of ~25% over the first 28 mm of slip at 4.8 mm/s agrees closely with the theoretical solution for slip on a plane (Rice [2006]), with an inferred slip-weakening distance of ~500

  12. Remarks on the Pressure Distribution over the Surface of an Ellipsoid, Moving Translationally Through a Perfect Fluid

    NASA Technical Reports Server (NTRS)

    Munk, Max M.

    1979-01-01

    The pressure distribution over ellipsoids when in translatory motion through a perfect fluid is calculated. A method to determine the magnitude of the velocity and of the pressure at each point of the surface of an ellipsoid of rotation is described.

  13. Modeling of interstitial fluid movement in soft tissue under negative pressure - relevance to treatment of tissue swelling.

    PubMed

    Iivarinen, Jarkko T; Korhonen, Rami K; Jurvelin, Jukka S

    2016-08-01

    Exact physiological mechanisms behind the potential positive treatment effects of pathological tissue swelling (edema), such as increased interstitial fluid flow, are poorly understood. Finite-element model was created and the model response was matched with the deformation data from the negative pressure (suction) measurements in human (N = 11) forearm. Two experimental suction protocols were simulated to evaluate their impact on interstitial fluid flow in soft tissues. Simulated continuous suction was up to 27 times more efficient in fluid transportation compared to the cyclic suction. The continuous suction that transports the interstitial fluid effectively may help to decrease soft tissue edema. PMID:26499361

  14. Hybrid (Kinetic Ion/Fluid Electron) Simulations of Reconnection Including Electron Pressure Anisotropy

    NASA Astrophysics Data System (ADS)

    Le, A.; Daughton, W. S.

    2015-12-01

    Fully kinetic simulations have shown that the structure of the thin current sheets that form during collisionless reconnection can fall into a variety of regimes depending on the electron pressure anisotropy [1]. Furthermore, recent two-fluid simulations with anisotropic electron equations of state appropriate for reconnection confirm that the electron pressure anisotropy may drive highly elongated current sheets in the reconnection exhaust [2]. While fully kinetic simulations are useful to model small regions of the Earth's magnetosphere, they are still far too expensive for global modeling. Thus, we have implemented the electron equations of state in the hybrid (kinetic ions and fluid electrons) code H3D [3], and initial 2D hybrid simulations of reconnection agree well with fully kinetic simulations. The updated hybrid code is a first step towards including electron anisotropy and full ion kinetics in global simulations of Earth's magnetosphere and laboratory experiments. [1] Le et al., Phys. Rev. Lett. 110, 135004 (2013)[2] Ohia et al., Phys. Rev. Lett. 109, 115004 (2012) [3] Karimabadi et al., Phys. Plasmas 21, 062308 (2014)

  15. A Validated All-Pressure Fluid Drop Model and Lewis Number Effects for a Binary Mixture

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.

    1999-01-01

    The differences between subcritical liquid drop and supercritical fluid drop behavior are discussed. Under subcritical, evaporative high emission rate conditions, a film layer is present in the inner part of the drop surface which contributes to the unique determination of the boundary conditions; it is this film layer which contributes to the solution's convective-diffusive character. In contrast, under supercritical condition as the boundary conditions contain a degree of arbitrariness due to the absence of a surface, and the solution has then a purely diffusive character. Results from simulations of a free fluid drop under no-gravity conditions are compared to microgravity experimental data from suspended, large drop experiments at high, low and intermediary temperatures and in a range of pressures encompassing the sub-and supercritical regime. Despite the difference between the conditions of the simulations and experiments (suspension vs. free floating), the time rate of variation of the drop diameter square is remarkably well predicted in the linear curve regime. The drop diameter is determined in the simulations from the location of the maximum density gradient, and agrees well with the data. It is also shown that the classical calculation of the Lewis number gives qualitatively erroneous results at supercritical conditions, but that an effective Lewis number previously defined gives qualitatively correct estimates of the length scales for heat and mass transfer at all pressures.

  16. Fast-acting valve actuator

    DOEpatents

    Cho, Nakwon

    1980-01-01

    A fast-acting valve actuator utilizes a spring driven pneumatically loaded piston to drive a valve gate. Rapid exhaust of pressurized gas from the pneumatically loaded side of the piston facilitates an extremely rapid piston stroke. A flexible selector diaphragm opens and closes an exhaust port in response to pressure differentials created by energizing and de-energizing a solenoid which controls the pneumatic input to the actuator as well as selectively providing a venting action to one side of the selector diaphragm.

  17. Exploring the speed-resolution limits of supercritical fluid chromatography at ultra-high pressures.

    PubMed

    Pauw, Ruben De; Shoykhet Choikhet, Konstantin; Desmet, Gert; Broeckhoven, Ken

    2014-12-29

    The limits of supercritical fluid chromatography have been experimentally explored using inlet pressures at the limits of the current commercial instrumentation (400-600 bar), as well as pressures significantly surpassing this (up to 1050 bar). It was found that efficiencies in the range of 200,000 theoretical plates can be achieved for a void time t0 of roughly 6min using superficially porous particles (2.7 and 4.6μm) while remaining within the pressure limits of current commercial instrumentation and columns. If lower efficiencies are sufficient (<100, 000 plates), smaller particles (e.g. 1.8μm) provide the best trade-off between analysis time and efficiency. Apparent efficiencies of 83,000 (k'=2.2) to 76,000 (k'=6.6) plates could be achieved for void times around 1min by pushing the pressure limits up to 1050 bar on a column length of 500mm. As the optimal mobile phase velocity for these small particle columns is even higher, it is required to use narrow-bore columns (2.1mm ID) to remain within the instrument limits of flow rate. The smaller column volume however puts a strain on the separation efficiency due to extra-column band broadening, resulting in losses up to 50% for weakly retained compounds for column lengths below 250mm. It is also illustrated that when using sub-2μm particles, especially for separations where a significant amount of organic modifier is required, the current pressure limits of state-of-the-art instrumentation can sometimes be insufficient. For a gradient running from 4 to 40 v% methanol on a 300mm column at the optimal flow rate the pressure increases from 420 to 810 bar. Operating SFC-columns with a large pressure gradient induces several (undesired) side effects which have been investigated as well. It has been found that, since the viscosity increases strongly with pressure in SFC, the optimal flow rate and the minimal plate height can significantly change when the column length is changed. Whereas e.g. a 3×150mm column (2.7

  18. On the Fluid Leakage Rate and Pressure Evaluation of Abandoned Non-Penetrating Wells.

    NASA Astrophysics Data System (ADS)

    Islam, J.; Zhan, H.

    2014-12-01

    Understanding flow leakage through abandoned wells that are potential pathways of contamination due to injecting unwanted fluids in geologically deep storage aquifers have become an intensively investigated subject in the subsurface hydrology and petroleum engineering. This study represents a semi-analytical transient solution for estimating leakage rate by pressure change evaluation through an abandoned non-penetrating well (ANW) coupled with an injection well. The leakage rate can be estimated using the Darcy's law by evaluating pressure change between the upper and the lower aquifers through ANW. The analysis was conducted by solving the diffusivity equations of fluid flow in the aquifer coupled with the pipe flow through ANW. The single-phase flow is considered in this study that is capable of explaining both fluid and CO2 plume flow in an aquifer system by neglecting the variable density effect. The result is compared with that of Avci's (1994) which dealt with an abandoned fully penetrating well. The result indicates the similar type of curve trend, which is observed by applying a range of aquifer properties as well as distance between the injection and leakage pathway. The important finding is that the leakage rate through ANW is about 50% compared to the fully penetrating well of Avci's (1994). The sensitivity analyses indicate that parameter leakage coefficient (A), transmissivity ratio (TD) and radial distance (R) between injection and ANW are the most sensitive to the leakage rate and the rest of the parameters are less sensitive. Because of availability of limited analytical and complex numerical solution, this simple new approach is going to provide a simple means to estimate leakage flow for realistic field condition.

  19. Measurements of seismic attenuation and transient fluid pressure in partially saturated Berea sandstone: evidence of fluid flow on the mesoscopic scale

    NASA Astrophysics Data System (ADS)

    Tisato, Nicola; Quintal, Beatriz

    2013-10-01

    A novel laboratory technique is proposed to investigate wave-induced fluid flow on the mesoscopic scale as a mechanism for seismic attenuation in partially saturated rocks. This technique combines measurements of seismic attenuation in the frequency range from 1 to 100 Hz with measurements of transient fluid pressure as a response of a step stress applied on top of the sample. We used a Berea sandstone sample partially saturated with water. The laboratory results suggest that wave-induced fluid flow on the mesoscopic scale is dominant in partially saturated samples. A 3-D numerical model representing the sample was used to verify the experimental results. Biot's equations of consolidation were solved with the finite-element method. Wave-induced fluid flow on the mesoscopic scale was the only attenuation mechanism accounted for in the numerical solution. The numerically calculated transient fluid pressure reproduced the laboratory data. Moreover, the numerically calculated attenuation, superposed to the frequency-independent matrix anelasticity, reproduced the attenuation measured in the laboratory in the partially saturated sample. This experimental-numerical fit demonstrates that wave-induced fluid flow on the mesoscopic scale and matrix anelasticity are the dominant mechanisms for seismic attenuation in partially saturated Berea sandstone.

  20. Estimating maximum sustainable injection pressure duringgeological sequestration of CO2 using coupled fluid flow andgeomechanical fault-slip analysis

    SciTech Connect

    Rutqvist, J.; Birkholzer, J.; Cappa, F.; Tsang, C.-F.

    2006-10-17

    This paper demonstrates the use of coupled fluid flow andgeomechanical fault slip (fault reactivation) analysis to estimate themaximum sustainable injection pressure during geological sequestration ofCO2. Two numerical modeling approaches for analyzing faultslip areapplied, one using continuum stress-strain analysis and the other usingdiscrete fault analysis. The results of these two approaches to numericalfault-slip analyses are compared to the results of a more conventionalanalytical fault-slip analysis that assumes simplified reservoirgeometry. It is shown that the simplified analytical fault-slip analysismay lead to either overestimation or underestimation of the maximumsustainable injection pressure because it cannot resolve importantgeometrical factors associated with the injection induced spatialevolution of fluid pressure and stress. We conclude that a fully couplednumerical analysis can more accurately account for the spatial evolutionof both insitu stresses and fluid pressure, and therefore results in amore accurate estimation of the maximum sustainable CO2 injectionpressure.

  1. Modulation of the interstitial fluid pressure by high intensity focused ultrasound as a way to alter local fluid and solute movement: insights from a mathematical model.

    PubMed

    Sassaroli, E; O'Neill, B E

    2014-11-21

    High intensity focused ultrasound (HIFU) operated in thermal mode has been reported to reduce interstitial fluid pressure and improve the penetration of large macromolecules and nanoparticles in tumor and normal tissue. Little is understood about how the interstitial fluid pressure and velocity as well as the interstitial macromolecule transport are affected by HIFU exposure. A mathematical model is presented here which sheds light on the initial biophysical changes brought about HIFU. Our continuum model treats tissue as an effective poro-elastic material that reacts to elevated temperatures with a rapid drop in interstitial elastic modulus. Using parameters from the literature, the model is extrapolated to derive information on the effect in tumors, and to predict its impact on the convective and diffusive transport of macromolecular drugs. The model is first solved using an analytical approximation with step-wise changes at each boundary, and then solved numerically starting from a Gaussian beam approximation of the ultrasound treatment. Our results indicate that HIFU causes a rapid drop in interstitial fluid pressure that may be exploited to facilitate convection of macromolecules from vasculature to the exposed region. However, following a short recovery period in which the interstitial fluid pressure is normalized, transport returns to normal and the advantages disappear over time. The results indicate that this effect is strongest for the delivery of large molecules and nanoparticles that are in the circulation at the time of treatment. The model may be easily applied to more complex situations involving effects on vascular permeability and diffusion. PMID:25327766

  2. Modulation of the interstitial fluid pressure by high intensity focused ultrasound as a way to alter local fluid and solute movement: insights from a mathematical model

    NASA Astrophysics Data System (ADS)

    Sassaroli, E.; O'Neill, B. E.

    2014-11-01

    High intensity focused ultrasound (HIFU) operated in thermal mode has been reported to reduce interstitial fluid pressure and improve the penetration of large macromolecules and nanoparticles in tumor and normal tissue. Little is understood about how the interstitial fluid pressure and velocity as well as the interstitial macromolecule transport are affected by HIFU exposure. A mathematical model is presented here which sheds light on the initial biophysical changes brought about HIFU. Our continuum model treats tissue as an effective poro-elastic material that reacts to elevated temperatures with a rapid drop in interstitial elastic modulus. Using parameters from the literature, the model is extrapolated to derive information on the effect in tumors, and to predict its impact on the convective and diffusive transport of macromolecular drugs. The model is first solved using an analytical approximation with step-wise changes at each boundary, and then solved numerically starting from a Gaussian beam approximation of the ultrasound treatment. Our results indicate that HIFU causes a rapid drop in interstitial fluid pressure that may be exploited to facilitate convection of macromolecules from vasculature to the exposed region. However, following a short recovery period in which the interstitial fluid pressure is normalized, transport returns to normal and the advantages disappear over time. The results indicate that this effect is strongest for the delivery of large molecules and nanoparticles that are in the circulation at the time of treatment. The model may be easily applied to more complex situations involving effects on vascular permeability and diffusion.

  3. Modulation of the interstitial fluid pressure by high intensity focused ultrasound as a way to alter local fluid and solute movement: insights from a mathematical model

    PubMed Central

    Sassaroli, E; O’Neill, B E

    2014-01-01

    High intensity focused ultrasound (HIFU) operated in thermal mode has been reported to reduce interstitial fluid pressure and improve the penetration of large macromolecules and nanoparticles in tumor and normal tissue. Little is understood about how the interstitial fluid pressure and velocity as well as the interstitial macromolecule transport are affected by HIFU exposure. A mathematical model is presented here which sheds light on the initial biophysical changes brought about HIFU. Our continuum model treats tissue as an effective poro-elastic material that reacts to elevated temperatures with a rapid drop in interstitial elastic modulus. Using parameters from the literature, the model is extrapolated to derive information on the effect in tumors, and to predict its impact on the convective and diffusive transport of macromolecular drugs. The model is first solved using an analytical approximation with step-wise changes at each boundary, and then solved numerically starting from a Gaussian beam approximation of the ultrasound treatment. Our results indicate that HIFU causes rapid drop in interstitial fluid pressure that may be exploited to facilitate convection of macromolecules from vasculature to the exposed region. However, following a short recovery period in which the interstitial fluid pressure is normalized, transport returns to normal and the advantages disappear over time. The results indicate that this effect is strongest for the delivery of large molecules and nanoparticles that are in the circulation at the time of treatment. The model may be easily applied to more complex situations involving effects on vascular permeability and diffusion. PMID:25327766

  4. Vehicle having hydraulic and power steering systems using a single high pressure pump

    DOEpatents

    Bartley, Bradley E.; Blass, James R.; Gibson, Dennis H.

    2001-06-22

    A vehicle comprises a plurality of wheels attached to a vehicle housing. Also attached to the vehicle housing is a power steering system, including a fluid flow circuit, which is operably coupled to a number of the wheels. An internal combustion engine attached to the vehicle housing is connected to a hydraulically actuated system that includes a high pressure pump. An outlet of the high pressure pump is in fluid communication with the fluid flow circuit.

  5. Partial melting, fluid supercriticality and element mobility in ultrahigh-pressure metamorphic rocks during continental collision

    NASA Astrophysics Data System (ADS)

    Zheng, Yong-Fei; Xia, Qiong-Xia; Chen, Ren-Xu; Gao, Xiao-Ying

    2011-08-01

    Partial melting at continental lithosphere depths plays an important role in generating geochemical variations in igneous rocks. In particular, dehydration melting of ultrahigh-pressure (UHP) metamorphic rocks during continental collision provides a petrological link to intracrustal differentiation with respect to the compositional evolution of continental crust. While island arc magmatism represents one end-member of fluid-induced large-scale melting in the mantle wedge during subduction of the oceanic crust, the partial melting of UHP rocks can be viewed as the other end-member of fluid-induced small-scale anatexis during exhumation of the deeply subducted continental crust. This latter type of melting is also triggered by metamorphic dehydration in response to P-T changes during the continental collision. It results in local occurrences of hydrous melts (even supercritical fluids) as felsic veinlets between boundaries of and multiphase solid inclusions in UHP metamorphic minerals as well as local accumulation of veinlet-like felsic leucosomes in foliated UHP metamorphic rocks and metamorphically grown zircons in orogenic peridotites. Thus, very low-degree melts of UHP rocks provide a window into magmatic processes that operated in continental subduction zones. This article presents a review on available results from experimental petrology concerning the possibility of partial melting under conditions of continental subduction-zone metamorphism, and petrological evidence for the occurrence of dehydration-driven in-situ partial melting in natural UHP rocks during the continental collision. Although the deeply subducted continental crust is characterized by a relative lack of aqueous fluids, the partial melting in UHP rocks commonly takes place during decompression exhumation to result in local in-situ occurrences of felsic melts at small scales. This is caused by the local accumulation of aqueous fluids due to the breakdown of hydrous minerals and the exsolution

  6. Remarks on the Pressure Distribution over the Surface of an Ellipsoid, Moving Translationally Through a Perfect Fluid

    NASA Technical Reports Server (NTRS)

    Munk, Max M

    1924-01-01

    This note, prepared for the National Advisory Committee for Aeronautics, contains a discussion of the pressure distribution over ellipsoids when in translatory motion through a perfect fluid. An easy and convenient way to determine the magnitude of the velocity and of the pressure at each point of the surface of an ellipsoid of rotation is described. The knowledge of such pressure distribution is of great practical value for the airship designer. The pressure distribution over the nose of an airship hull is known to be in such good agreement with the theoretical distribution as to permit basing the computation of the nose stiffening structure on the theoretical distribution of pressure.

  7. Multi-objective control of nonlinear boiler-turbine dynamics with actuator magnitude and rate constraints.

    PubMed

    Chen, Pang-Chia

    2013-01-01

    This paper investigates multi-objective controller design approaches for nonlinear boiler-turbine dynamics subject to actuator magnitude and rate constraints. System nonlinearity is handled by a suitable linear parameter varying system representation with drum pressure as the system varying parameter. Variation of the drum pressure is represented by suitable norm-bounded uncertainty and affine dependence on system matrices. Based on linear matrix inequality algorithms, the magnitude and rate constraints on the actuator and the deviations of fluid density and water level are formulated while the tracking abilities on the drum pressure and power output are optimized. Variation ranges of drum pressure and magnitude tracking commands are used as controller design parameters, determined according to the boiler-turbine's operation range. PMID:22959740

  8. Effect of Head Position on Cerebrospinal Fluid Pressure in Cats: Comparison with Artificial Model

    PubMed Central

    Klarica, Marijan; Radoš, Milan; Draganić, Pero; Erceg, Gorislav; Orešković, Darko; Maraković, Jurica; Bulat, Marin

    2006-01-01

    Aim To demonstrate that changes in the cerebrospinal fluid (CSF) pressure in the cranial cavity and spinal canal after head elevation from the horizontal level occur primarily due to the biophysical characteristics of the CSF system, ie, distensibility of the spinal dura. Methods Experiments in vivo were performed on cats and a new artificial model of the CSF system with dimensions similar to the CSF system in cats, consisting of non-distensible cranial and distensible spinal part. Measurements of the CSF pressure in the cranial and spinal spaces were performed in chloralose-anesthetized cats (n = 10) in the horizontal position on the base of a stereotaxic apparatus (reference zero point) and in the position in which the head was elevated to 5 cm and 10 cm above that horizontal position. Changes in the CSF pressure in the cranial and spinal part of the model were measured in the cranial part positioned in the same way as the head in cats (n = 5). Results When the cat was in the horizontal position, the values of the CSF pressure in the cranial (11.9 ± 1.1 cm H2O) and spinal (11.8 ± 0.6 cm H2O) space were not significantly different. When the head was elevated 5 cm or 10 cm above the reference zero point, the CSF pressure in the cranium significantly decreased to 7.7 ± 0.6 cm H2O and 4.7 ± 0.7 cm H2O, respectively, while the CSF pressure in the spinal space significantly increased to 13.8 ± 0.7 cm H2O and 18.5 ± 1.6 cm H2O, respectively (P<0.001 for both). When the artificial CSF model was positioned in the horizontal level and its cranial part elevated by 5 cm and 10 cm, the changes in the pressure were the same as those in the cats when in the same hydrostatic position. Conclusions The new model of the CSF system used in our study faithfully mimicked the changes in the CSF pressure in cats during head elevation in relation to the body. Changes in the pressure in the model were not accompanied by the changes in fluid volume in

  9. Light-Driven Polymeric Bimorph Actuators

    NASA Technical Reports Server (NTRS)

    Adamovsky, Gregory; Sarkisov, Sergey S.; Curley, Michael J.

    2009-01-01

    Light-driven polymeric bimorph actuators are being developed as alternatives to prior electrically and optically driven actuators in advanced, highly miniaturized devices and systems exemplified by microelectromechanical systems (MEMS), micro-electro-optical-mechanical systems (MEOMS), and sensor and actuator arrays in smart structures. These light-driven polymeric bimorph actuators are intended to satisfy a need for actuators that (1) in comparison with the prior actuators, are simpler and less power-hungry; (2) can be driven by low-power visible or mid-infrared light delivered through conventional optic fibers; and (3) are suitable for integration with optical sensors and multiple actuators of the same or different type. The immediate predecessors of the present light-driven polymeric bimorph actuators are bimorph actuators that exploit a photorestrictive effect in lead lanthanum zirconate titanate (PLZT) ceramics. The disadvantages of the PLZT-based actuators are that (1) it is difficult to shape the PLZT ceramics, which are hard and brittle; (2) for actuation, it is necessary to use ultraviolet light (wavelengths < 380 nm), which must be generated by use of high-power, high-pressure arc lamps or lasers; (3) it is difficult to deliver sufficient ultraviolet light through conventional optical fibers because of significant losses in the fibers; (4) the response times of the PLZT actuators are of the order of several seconds unacceptably long for typical applications; and (5) the maximum mechanical displacements of the PLZT-based actuators are limited to those characterized by low strains beyond which PLZT ceramics disintegrate because of their brittleness. The basic element of a light-driven bimorph actuator of the present developmental type is a cantilever beam comprising two layers, at least one of which is a polymer that exhibits a photomechanical effect (see figure). The dominant mechanism of the photomechanical effect is a photothermal one: absorption of

  10. An investigation into the relationship between small intestinal fluid secretion and systemic arterial blood pressure in the anesthetized rat.

    PubMed

    Lucas, Michael L; Morrison, James D

    2015-05-01

    The effects of changes in the steady level of diastolic blood pressure on fluid flux across the jejunum has been investigated in the anesthetized rat during perfusion with a nutrient-free and Na(+)-free solution. Diastolic blood pressure was manipulated by intravenous infusions, during the jejunal perfusions, of vasodilators (vasoactive intestinal polypeptide, acetyl-β-methylcholine, and phentolamine) and a vasoconstrictor (arginine vasopressin), each of which acts through a different cellular mechanism. The outcome was that fluid flux was related by a parabolic relationship with diastolic blood pressure in which net secretion occurred over the range 40-100 mmHg, whereas net absorption was recorded at diastolic pressures exceeding 100 mmHg and below 40 mmHg. Against a background of normal absorption promoted by perfusion with 145 mmol L(-1) Na(+)/5 mmol L(-1) glucose solution, reductions in diastolic blood pressure markedly reduced the mean rate of fluid absorption by 58% overall, whereas the rate of glucose absorption remained unchanged. Our results were explained on the basis that vasodilatation led to increased capillary pressure and then to net filtration of fluid from the mesenteric capillary bed. Experiments in which Escherichia coli heat-stable toxin was added to the jejunal perfusate confirmed the absence of a secretory response, which was consistent with the absence of effect of the toxin on diastolic blood pressure. PMID:26019291

  11. An investigation into the relationship between small intestinal fluid secretion and systemic arterial blood pressure in the anesthetized rat

    PubMed Central

    Lucas, Michael L; Morrison, James D

    2015-01-01

    The effects of changes in the steady level of diastolic blood pressure on fluid flux across the jejunum has been investigated in the anesthetized rat during perfusion with a nutrient-free and Na+-free solution. Diastolic blood pressure was manipulated by intravenous infusions, during the jejunal perfusions, of vasodilators (vasoactive intestinal polypeptide, acetyl-β-methylcholine, and phentolamine) and a vasoconstrictor (arginine vasopressin), each of which acts through a different cellular mechanism. The outcome was that fluid flux was related by a parabolic relationship with diastolic blood pressure in which net secretion occurred over the range 40–100 mmHg, whereas net absorption was recorded at diastolic pressures exceeding 100 mmHg and below 40 mmHg. Against a background of normal absorption promoted by perfusion with 145 mmol L−1 Na+/5 mmol L−1 glucose solution, reductions in diastolic blood pressure markedly reduced the mean rate of fluid absorption by 58% overall, whereas the rate of glucose absorption remained unchanged. Our results were explained on the basis that vasodilatation led to increased capillary pressure and then to net filtration of fluid from the mesenteric capillary bed. Experiments in which Escherichia coli heat-stable toxin was added to the jejunal perfusate confirmed the absence of a secretory response, which was consistent with the absence of effect of the toxin on diastolic blood pressure. PMID:26019291

  12. Effect of Nasal Obstruction on Continuous Positive Airway Pressure Treatment: Computational Fluid Dynamics Analyses

    PubMed Central

    Wakayama, Tadashi; Suzuki, Masaaki; Tanuma, Tadashi

    2016-01-01

    Objective Nasal obstruction is a common problem in continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea and limits treatment compliance. The purpose of this study is to model the effects of nasal obstruction on airflow parameters under CPAP using computational fluid dynamics (CFD), and to clarify quantitatively the relation between airflow velocity and pressure loss coefficient in subjects with and without nasal obstruction. Methods We conducted an observational cross-sectional study of 16 Japanese adult subjects, of whom 9 had nasal obstruction and 7 did not (control group). Three-dimensional reconstructed models of the nasal cavity and nasopharynx with a CPAP mask fitted to the nostrils were created from each subject’s CT scans. The digital models were meshed with tetrahedral cells and stereolithography formats were created. CPAP airflow simulations were conducted using CFD software. Airflow streamlines and velocity contours in the nasal cavities and nasopharynx were compared between groups. Simulation models were confirmed to agree with actual measurements of nasal flow rate and with pressure and flow rate in the CPAP machine. Results Under 10 cmH2O CPAP, average maximum airflow velocity during inspiration was 17.6 ± 5.6 m/s in the nasal obstruction group but only 11.8 ± 1.4 m/s in the control group. The average pressure drop in the nasopharynx relative to inlet static pressure was 2.44 ± 1.41 cmH2O in the nasal obstruction group but only 1.17 ± 0.29 cmH2O in the control group. The nasal obstruction and control groups were clearly separated by a velocity threshold of 13.5 m/s, and pressure loss coefficient threshold of approximately 10.0. In contrast, there was no significant difference in expiratory pressure in the nasopharynx between the groups. Conclusion This is the first CFD analysis of the effect of nasal obstruction on CPAP treatment. A strong correlation between the inspiratory pressure loss coefficient and maximum airflow

  13. Misfire tolerant combustion-powered actuation

    DOEpatents

    Spletzer, Barry L.; Fischer, Gary J.; Marron, Lisa C.; Kuehl, Michael A.

    2001-01-01

    The present invention provides a combustion-powered actuator that is suitable for intermittent actuation, that is suitable for use with atmospheric pressure carburetion, and that requires little electrical energy input. The present invention uses energy from expansion of pressurized fuel to effectively purge a combustion chamber, and to achieve atmospheric pressure carburetion. Each purge-fill-power cycle can be independent, allowing the actuator to readily tolerate misfires. The present invention is suitable for use with linear and rotary operation combustion chambers, and is suitable for use in a wide variety of applications.

  14. Magnetostrictive Pressure Regulating System

    NASA Technical Reports Server (NTRS)

    Richard, James A. (Inventor); Pickens, Herman L. (Inventor)

    2013-01-01

    A magnetostrictive pressure regulating system includes a magnetostrictive valve that incorporates a magnetostrictive actuator with at least one current-carrying coil disposed thereabout. A pressure force sensor, in fluid communication with the fluid exiting the valve, includes (i) a magnetostrictive material, (ii) a magnetic field generator in proximity to the magnetostrictive material for inducing a magnetic field in and surrounding the magnetostrictive material wherein lines of magnetic flux passing through the magnetostrictive material are defined, and (iii) a sensor positioned adjacent to the magnetostrictive material and in the magnetic field for measuring changes in at least one of flux angle and flux density when the magnetostrictive material experiences an applied force that is aligned with the lines of magnetic flux. The pressure of the fluid exiting the valve causes the applied force. A controller coupled to the sensor and to the current-carrying coil adjusts a current supplied to the current-carrying coil based on the changes so-measured.

  15. PFLOW: A 3-D Numerical Modeling Tool for Calculating Fluid-Pressure Diffusion from Coulomb Strain

    NASA Astrophysics Data System (ADS)

    Wolf, L. W.; Lee, M.; Meir, A.; Dyer, G.; Ma, K.; Chan, C.

    2009-12-01

    A new 3D time-dependent pore-pressure diffusion model PFLOW is developed to investigate the response of pore fluids to the crustal deformation generated by strong earthquakes in heterogeneous geologic media. Given crustal strain generated by changes in Coulomb stress, this MATLAB-based code uses Skempton's coefficient to calculate resulting changes fluid pressure. Pore-pressure diffusion can be tracked over time in a user-defined model space with user-prescribed Neumann or Dirchilet boundary conditions and with spatially variable values of permeability. PFLOW employs linear or quadratic finite elements for spatial discretization and first order or second order, explicit or implicit finite difference discretization in time. PFLOW is easily interfaced with output from deformation modeling programs such as Coulomb (Toda et al., 2007) or 3D-DEF (Gomberg and Ellis, 1994). The code is useful for investigating to first-order the evolution of pore pressure changes induced by changes in Coulomb stress and their possible relation to water-level changes in wells or changes in stream discharge. It can also be used for student research and classroom instruction. As an example application, we calculate the coseismic pore pressure changes and diffusion induced by volumetric strain associated with the 1999 Chi-Chi earthquake (Mw = 7.6) in Taiwan. The Chi-Chi earthquake provides an unique opportunity to investigate the spatial and time-dependent poroelastic response of near-field rocks and sediments because there exist extensive observational data of water-level changes and crustal deformation. The integrated model allows us to explore whether changes in Coulomb stress can adequately explain hydrologic anomalies observed in areas such as Taiwan’s western foothills and the Choshui River alluvial plain. To calculate coseismic strain, we use the carefully calibrated finite fault-rupture model of Ma et al. (2005) and the deformation modeling code Coulomb 3.1 (Toda et al., 2007

  16. Proteomic Assessment of Fluid Shifts and Association with Visual Impairment and Intracranial Pressure in Twin Astronauts

    NASA Technical Reports Server (NTRS)

    Rana, Brinda K.; Stenger, Michael B.; Lee, Stuart M. C.; Macias, Brandon R.; Siamwala, Jamila; Piening, Brian Donald; Hook, Vivian; Ebert, Doug; Patel, Hemal; Smith, Scott; Snyder, Mike; Hargens, Alan R.

    2016-01-01

    BACKGROUND: Astronauts participating in long duration space missions are at an increased risk of physiological disruptions. The development of visual impairment and intracranial pressure (VIIP) syndrome is one of the leading health concerns for crew members on long-duration space missions; microgravity-induced fluid shifts and chronic elevated cabin CO2 may be contributing factors. By studying physiological and molecular changes in one identical twin during his 1-year ISS mission and his ground-based co-twin, this work extends a current NASA-funded investigation to assess space flight induced "Fluid Shifts" in association with the development of VIIP. This twin study uniquely integrates physiological and -omic signatures to further our understanding of the molecular mechanisms underlying space flight-induced VIIP. We are: (i) conducting longitudinal proteomic assessments of plasma to identify fluid regulation-related molecular pathways altered by long-term space flight; and (ii) integrating physiological and proteomic data with genomic data to understand the genomic mechanism by which these proteomic signatures are regulated. PURPOSE: We are exploring proteomic signatures and genomic mechanisms underlying space flight-induced VIIP symptoms with the future goal of developing early biomarkers to detect and monitor the progression of VIIP. This study is first to employ a male monozygous twin pair to systematically determine the impact of fluid distribution in microgravity, integrating a comprehensive set of structural and functional measures with proteomic, metabolomic and genomic data. This project has a broader impact on Earth-based clinical areas, such as traumatic brain injury-induced elevations of intracranial pressure, hydrocephalus, and glaucoma. HYPOTHESIS: We predict that the space-flown twin will experience a space flight-induced alteration in proteins and peptides related to fluid balance, fluid control and brain injury as compared to his pre-flight protein

  17. Memory metal actuator

    NASA Technical Reports Server (NTRS)

    Ruoff, C. F. (Inventor)

    1985-01-01

    A mechanical actuator can be constructed by employing a plurality of memory metal actuator elements in parallel to control the amount of actuating force. In order to facilitate direct control by digital control signals provided by a computer or the like, the actuating elements may vary in stiffness according to a binary relationship. The cooling or reset time of the actuator elements can be reduced by employing Peltier junction cooling assemblies in the actuator.

  18. Fluid transients in pipes. Estimation of maximum pressures and forces in steam lines

    NASA Astrophysics Data System (ADS)

    1986-09-01

    Available as part of the ESDU Sub-series on Fluid Mechanics (Internal Flow), this document gives a graphical method for estimating the time-dependent pressure changes and piping forces that follow from a rapid value closure in a one-pipe system of constant cross-section carrying superheated steam. The method also assumes a frictionless flow and ignores wave steepening effects. A computer program listing in FORTRAN is also included that applies to any gas that obeys the perfect gas law, and takes into account the effects of both wall friction and wave steepening. In that case sections of the pipeline can have different cross-sectional areas and that can be used to treat a pipeline with branched ends. Worked examples are included for both methods and in the case of the computer program show specimen print-out of the input data, and of the output which includes the time variation of pressure, velocity and density at three points in the pipeline chosen by the user together with values of maximum and minimum pressure at 25 points (a value that is also open to choice by the user). The example is run for a valve with a linear variation of area with time, and for one with a nonlinear characteristic.

  19. Pressurized fluid extraction for quantitative recovery of chloroacetanilide and nitrogen heterocyclic herbicides in soil.

    PubMed

    Zhu, Y; Yanagihara, K; Guo, F; Li, Q X

    2000-09-01

    Pressurized fluid extraction (PFE) is a new sample extraction method operated at elevated temperatures and pressures with liquid solvents. The use of PFE was investigated for the extraction of four Hawaiian clayey soils fortified with the selected chloroacetanilide and nitrogen heterocyclic herbicides Alachlor, Bromacil, Hexazinone, Metribuzin, and Tebuthiuron. The effects of operation temperature, pressure, flush volume, and static cycles on PFE performance were studied. Water was the most effective modifier of PFE for quantitative recoveries of the five herbicides in soils. The simple extraction method required pretreatment of the soil with 37.6% water and subsequent two-static-cycle extraction with a total of 32 mL of acetone at 1500 psi and 100 degrees C. Average recoveries of Alachlor, Bromacil, Hexazinone, Metribuzin, and Tebuthiuron ranged from 93 to 103% by the water-assisted PFE, compared with only 68-83% recoveries of the corresponding chemicals when no water was used. The extraction time and total organic solvent consumption were reduced from 18 h and 300 mL by Soxhlet to 22 min or less and 80 mL or less of organic solvent by PFE. PMID:10995321

  20. An evaluation of pore pressure diffusion into a shale overburden and sideburden induced by production-related changes in reservoir fluid pressure

    NASA Astrophysics Data System (ADS)

    Ricard, Ludovic P.; MacBeth, Colin; HajNasser, Yesser; Schutjens, Peter

    2012-06-01

    It is commonplace in the simulation of reservoir fluid flow induced by hydrocarbon production to regard shales as barriers to flow. Whilst this appears correct for fluid exchange, this is not the case for the fluid pressure component of this process. Indeed, the authors observe that pore pressure reduction due to reservoir depletion can propagate significant distances into the shale overburden or sideburden over the production time scale. Shales may deplete their pore pressures by more than 10% of that experienced in the reservoir sand for distances of tens of metres to kilometres into the shale, depending on the production history, duration and the specific shale properties. An important factor controlling these results is heterogeneity of the shale sediments, and the pressure diffusion process can be considerably enhanced by the presence of silt laminations and streaks. These results suggest a possible risk to drillers when advancing towards the top of a depleting reservoir or when drilling a well alongside an already depleted reservoir. Our analyses conclude that pore pressure diffusion should be considered as a factor in geomechanical and fluid flow reservoir modelling, and in mud weight determination during infill drilling.

  1. Actuator operated microvalves

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S. (Inventor)

    2008-01-01

    An actuator operated microvalve and the method of making same is disclosed and claimed. The microvalve comprises a SiC housing which includes a first lower portion and a second upper portion. The lower portion of the SiC housing includes a passageway therethrough, a microvalve seat, and a moveable SiC diaphragm. The SiC diaphragm includes a centrally located boss and radially extending corrugations which may be sinusoidally shaped. The boss of the SiC diaphragm moves and modulates in a range of positions between a closed position wherein the boss interengages said microvalve seat prohibiting communication of fluid through the passageway and a fully open position when the boss is spaced apart from the seat at its maximum permitting communication of fluid through said passageway. The actuator includes a SiC top plate affixed to the boss of the diaphragm and a first electrode and the second upper portion of the SiC housing further includes a second electrode.

  2. Closed form Vaidya-Tikekar type charged fluid spheres with pressure

    NASA Astrophysics Data System (ADS)

    Bijalwan, Naveen; Gupta, Y. K.

    2011-08-01

    Recently, Bijalwan (Astrophys. Space Sci. doi: 10.1007/s10509-011-0691-0 , 2011) discussed all important solutions of charged fluid spheres with pressure and Gupta et al. (Astrophys. Space Sci. doi: 10.1007/s10509-010-0561-1 , 2010) found first closed form solutions of charged Vaidya-Tikekar (V-T) type super-dense star. We extend here the approach evolved by Bijalwan (Astrophys. Space Sci. doi: 10.1007/s10509-011-0691-0 , 2011) to find all possible closed form solutions of V-T type super-dense stars. The existing solutions of Vaidya-Tikekar type charged fluid spheres considering particular form of electric field intensity are being used to model massive stars. Infact at present maximum masses of the star models are found to be 8.223931 M Θ and 8.460857 M Θ subject to ultra-relativistic and non-relativistic conditions respectively. But these stars with such are large masses are not well behaved due to decreasing velocity of sound in the interior of star. We present new results concerning the existence of static, electrically charged perfect fluid spheres that have a regular interior. It is observed that electric intensity used in this article can be used to model superdense stars with ultrahigh surface density of the order 2×1014 gm/cm3 which may have maximum mass 7.26368240 M Θ for ultra-relativistic condition and velocity of sound found to be decreasing towards pressure free interface. We solve the Einstein-Maxwell equations considering a general barotropic equation of state with pressure. For brevity we don't present a detailed analysis of the derived solutions in this paper.

  3. Active structural growth in central Taiwan in relationship to large earthquakes and pore-fluid pressures

    NASA Astrophysics Data System (ADS)

    Yue, Li-Fan

    Central Taiwan is subject to a substantial long-term earthquake risk with a population of five million and two disastrous earthquakes in the last century, the 1935 ML=7.1 Tuntzuchiao and 1999 Mw=7.6 Chi-Chi earthquakes. Rich data from these earthquakes combined with substantial surface and subsurface data accumulated from petroleum exploration form the basis for these studies of the growth of structures in successive large earthquakes and their relationships to pore-fluid pressures. Chapter 1 documents the structural context of the bedding-parallel Chelungpu thrust that slipped in the Chi-Chi earthquake by showing for this richly instrumented earthquake the close geometric relationships between the complex 3D fault shape and the heterogeneous coseismic displacements constrained by geodesy and seismology. Chapter 2 studies the accumulation of deformation by successive large earthquakes by studying the deformation of flights of fluvial terraces deposited over the Chelungpu and adjacent Changhua thrusts, showing the deformation on a timescale of tens of thousands of years. Furthermore these two structures, involving the same stratigraphic sequence, show fundamentally different kinematics of deformation with associated contrasting hanging-wall structural geometries. The heights and shapes of deformed terraces allowed testing of existing theories of fault-related folding. Furthermore terrace dating constrains a combined shortening rate of 37 mm/yr, which is 45% of the total Taiwan plate-tectonic rate, and indicates a substantial earthquake risk for the Changhua thrust. Chapter 3 addresses the long-standing problem of the mechanics of long-thing thrust sheets, such as the Chelungpu and Changhua thrusts in western Taiwan, by presenting a natural test for the classic Hubbert-Rubey hypothesis, which argues that ambient excess pore-fluid pressure substantially reduces the effective fault friction allowing the thrusts to move. Pore-fluid pressure data obtained from 76 wells

  4. Thermally actuated piston micromirror arrays

    NASA Astrophysics Data System (ADS)

    Cowan, William D.; Bright, Victor M.

    1997-07-01

    This paper reports design and characterization testing of thermally actuated piston micromirror arrays. The micromirrors were fabricated in the DARPA-sponsored MUMPs polysilicon surface micromachining process. The power averaging characteristic of thermal actuation is exploited in a novel line addressing scheme which reduces wiring for an n2 array to 2n wires. Mirror deflections were measured with a microscope laser interferometer system equipped with a vacuum chamber. Data presented includes device uniformity, frequency response, and deflection versus drive power for varied ambient pressure. Initial test results confirm that thermally actuated piston micromirrors offer several advantages over more common electrostatic designs. Thermally actuated micromirrors offer greater deflections at drive voltages compatible with CMOS circuitry. Measured thermal piston micromirror deflection versus drive voltage is nonlinear, but does not exhibit the 'snap through instability' characteristic of electrostatic devices. Operation of thermally actuated devices in rarefied ambient significantly decreases power dissipation. For a given deflection range, the power reduction facilitated by vacuum operation makes large arrays feasible. Frequency response of thermally actuated devices is limited by the ability of the device to dissipate heat, but operation at 1 kHz rates is feasible.

  5. On axial temperature gradients due to large pressure drops in dense fluid chromatography.

    PubMed

    Colgate, Sam O; Berger, Terry A

    2015-03-13

    The effect of energy degradation (Degradation is the creation of net entropy resulting from irreversibility.) accompanying pressure drops across chromatographic columns is examined with regard to explaining axial temperature gradients in both high performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). The observed effects of warming and cooling can be explained equally well in the language of thermodynamics or fluid dynamics. The necessary equivalence of these treatments is reviewed here to show the legitimacy of using whichever one supports the simpler determination of features of interest. The determination of temperature profiles in columns by direct application of the laws of thermodynamics is somewhat simpler than applying them indirectly by solving the Navier-Stokes (NS) equations. Both disciplines show that the preferred strategy for minimizing the reduction in peak quality caused by temperature gradients is to operate columns as nearly adiabatically as possible (i.e. as Joule-Thomson expansions). This useful fact, however, is not widely familiar or appreciated in the chromatography community due to some misunderstanding of the meaning of certain terms and expressions used in these disciplines. In fluid dynamics, the terms "resistive heating" or "frictional heating" have been widely used as synonyms for the dissipation function, Φ, in the NS energy equation. These terms have been widely used by chromatographers as well, but often misinterpreted as due to friction between the mobile phase and the column packing, when in fact Φ describes the increase in entropy of the system (dissipation, ∫TdSuniv>0) due to the irreversible decompression of the mobile phase. Two distinctly different contributions to the irreversibility are identified; (1) ΔSext, viscous dissipation of work done by the external surroundings driving the flow (the pump) contributing to its warming, and (2) ΔSint, entropy change accompanying decompression of

  6. Fluid Shifts: Otoacoustical Emission Changes in Response to Posture and Lower Body Negative Pressure

    NASA Technical Reports Server (NTRS)

    Melgoza, R.; Kemp, D.; Ebert, D.; Danielson, R.; Stenger, M.; Hargens, A.; Dulchavsky, S.

    2016-01-01

    INTRODUCTION: The purpose of the NASA Fluid Shifts Study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to correlate these findings with vision changes and other elements of the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. Due to the invasive nature of direct measures of ICP, a noninvasive technique of monitoring ICP is desired for use during spaceflight. The phase angle and amplitude of otoacoustic emissions (OAEs) have been shown to be sensitive to posture change and ICP (1, 2), therefore use of OAEs is an attractive option. OAEs are low-level sounds produced by the sensory cells of the cochlea in response to auditory stimulation. These sounds travel peripherally from the cochlea, through the oval window, to the ear canal where they can be recorded. OAE transmission is sensitive to changes in the stiffness of the oval window, occurring as a result of changes in cochlear pressure. Increased stiffness of the oval window largely affects the transmission of sound from the cochlea at frequencies between 800 Hz and 1600 Hz. OAEs can be self-recorded in the laboratory or on the ISS using a handheld device. Our primary objectives regarding OAE measures in this experiment were to 1) validate this method during preflight testing of each crewmember (while sitting, supine and in head-down tilt position), and 2) determine if OAE measures (and presumably ICP) are responsive to lower body negative pressure and to spaceflight. METHODS: Distortion-product otoacoustic emissions (DPOAEs) and transient evoked otoacoustic emissions (TEOAEs) were recorded preflight using the Otoport Advance OAE system (Otodynamics Ltd., Hatfield, UK). Data were collected in four conditions (seated

  7. Drive piston assembly for a valve actuator assembly

    DOEpatents

    Sun, Zongxuan

    2010-02-23

    A drive piston assembly is provided that is operable to selectively open a poppet valve. The drive piston assembly includes a cartridge defining a generally stepped bore. A drive piston is movable within the generally stepped bore and a boost sleeve is coaxially disposed with respect to the drive piston. A main fluid chamber is at least partially defined by the generally stepped bore, drive piston, and boost sleeve. First and second feedback chambers are at least partially defined by the drive piston and each are disposed at opposite ends of the drive piston. At least one of the drive piston and the boost sleeve is sufficiently configured to move within the generally stepped bore in response to fluid pressure within the main fluid chamber to selectively open the poppet valve. A valve actuator assembly and engine are also provided incorporating the disclosed drive piston assembly.

  8. Self-actuating and locking control for nuclear reactor

    DOEpatents

    Chung, Dong K.

    1982-01-01

    A self-actuating, self-locking flow cutoff valve particularly suited for use in a nuclear reactor of the type which utilizes a plurality of fluid support neutron absorber elements to provide for the safe shutdown of the reactor. The valve comprises a substantially vertical elongated housing and an aperture plate located in the housing for the flow of fluid therethrough, a substantially vertical elongated nozzle member located in the housing and affixed to the housing with an opening in the bottom for receiving fluid and apertures adjacent a top end for discharging fluid. The nozzle further includes two sealing means, one located above and the other below the apertures. Also located in the housing and having walls surrounding the nozzle is a flow cutoff sleeve having a fluid opening adjacent an upper end of the sleeve, the sleeve being moveable between an upper open position wherein the nozzle apertures are substantially unobstructed and a closed position wherein the sleeve and nozzle sealing surfaces are mated such that the flow of fluid through the apertures is obstructed. It is a particular feature of the present invention that the valve further includes a means for utilizing any increase in fluid pressure to maintain the cutoff sleeve in a closed position. It is another feature of the invention that there is provided a means for automatically closing the valve whenever the flow of fluid drops below a predetermined level.

  9. A Parylene Bellows Electrochemical Actuator

    PubMed Central

    Li, Po-Ying; Sheybani, Roya; Gutierrez, Christian A.; Kuo, Jonathan T. W.; Meng, Ellis

    2011-01-01

    We present the first electrochemical actuator with Parylene bellows for large-deflection operation. The bellows diaphragm was fabricated using a polyethylene-glycol-based sacrificial molding technique followed by coating in Parylene C. Bellows were mechanically characterized and integrated with a pair of interdigitated electrodes to form an electrochemical actuator that is suitable for low-power pumping of fluids. Pump performance (gas generation rate and pump efficiency) was optimized through a careful examination of geometrical factors. Overall, a maximum pump efficiency of 90% was achieved in the case of electroplated electrodes, and a deflection of over 1.5 mm was demonstrated. Real-time wireless operation was achieved. The complete fabrication process and the materials used in this actuator are bio-compatible, which makes it suitable for biological and medical applications. PMID:21318081

  10. Fluid shifts, vasodilatation and ambulatory blood pressure reduction during long duration spaceflight

    PubMed Central

    Norsk, Peter; Asmar, Ali; Damgaard, Morten; Christensen, Niels Juel

    2015-01-01

    Acute weightlessness in space induces a fluid shift leading to central volume expansion. Simultaneously, blood pressure is either unchanged or decreased slightly. Whether these effects persist for months in space is unclear. Twenty-four hour ambulatory brachial arterial pressures were automatically recorded at 1–2 h intervals with portable equipment in eight male astronauts: once before launch, once between 85 and 192 days in space on the International Space Station and, finally, once at least 2 months after flight. During the same 24 h, cardiac output (rebreathing method) was measured two to five times (on the ground seated), and venous blood was sampled once (also seated on the ground) for determination of plasma catecholamine concentrations. The 24 h average systolic, diastolic and mean arterial pressures (mean ± se) in space were reduced by 8 ± 2 mmHg (P = 0.01; ANOVA), 9 ± 2 mmHg (P < 0.001) and 10 ± 3 mmHg (P = 0.006), respectively. The nightly blood pressure dip of 8 ± 3 mmHg (P = 0.015) was maintained. Cardiac stroke volume and output increased by 35 ± 10% and 41 ± 9% (P < 0.001); heart rate and catecholamine concentrations were unchanged; and systemic vascular resistance was reduced by 39 ± 4% (P < 0.001). The increase in cardiac stroke volume and output is more than previously observed during short duration flights and might be a precipitator for some of the vision problems encountered by the astronauts. The spaceflight vasodilatation mechanism needs to be explored further. PMID:25774397

  11. Pressure and fluid saturation prediction in a multicomponent reservoir, using combined seismic and electromagnetic imaging

    SciTech Connect

    Hoversten, G.M.; Gritto, Roland; Washbourne, John; Daley, Tom

    2002-06-10

    This paper presents a method for combining seismic and electromagnetic measurements to predict changes in water saturation, pressure, and CO{sub 2} gas/oil ratio in a reservoir undergoing CO{sub 2} flood. Crosswell seismic and electromagnetic data sets taken before and during CO{sub 2} flooding of an oil reservoir are inverted to produce crosswell images of the change in compressional velocity, shear velocity, and electrical conductivity during a CO{sub 2} injection pilot study. A rock properties model is developed using measured log porosity, fluid saturations, pressure, temperature, bulk density, sonic velocity, and electrical conductivity. The parameters of the rock properties model are found by an L1-norm simplex minimization of predicted and observed differences in compressional velocity and density. A separate minimization, using Archie's law, provides parameters for modeling the relations between water saturation, porosity, and the electrical conductivity. The rock-properties model is used to generate relationships between changes in geophysical parameters and changes in reservoir parameters. Electrical conductivity changes are directly mapped to changes in water saturation; estimated changes in water saturation are used along with the observed changes in shear wave velocity to predict changes in reservoir pressure. The estimation of the spatial extent and amount of CO{sub 2} relies on first removing the effects of the water saturation and pressure changes from the observed compressional velocity changes, producing a residual compressional velocity change. This velocity change is then interpreted in terms of increases in the CO{sub 2}/oil ratio. Resulting images of the CO{sub 2}/oil ratio show CO{sub 2}-rich zones that are well correlated to the location of injection perforations, with the size of these zones also correlating to the amount of injected CO{sub 2}. The images produced by this process are better correlated to the location and amount of injected

  12. Ultrasonic Quantification of Tumor Interstitial Fluid Pressure Through Scanning Acoustic Microscopy

    NASA Astrophysics Data System (ADS)

    Pflanzer, Ralph; Shelke, Amit; Bereiter-Hahn, Jürgen; Hofmann, Matthias

    High tumor interstitial fluid pressure (TIFP) is characteristic of solid tumors. Elevated TIFP inhibits the assimilation of macromolecular therapeutics in tumor tissue as well as it induces mechanical strain triggering cell proliferation in solid tumors. Common solid epithelial tumors of A431 carcinoma cells exhibit a TIFP of about 10-15 mmHg measured conventionally through wick-in-needle technique. A new scheme to determine topography and acoustic impedance in solid tumor is proposed through scanning acoustic microscopy. The change in amplitude and time of flight at 30 MHz acoustic signal is used to quantify the growth pattern and to calibrate elevation of TIFP. The wide variability of amplitude and frequency in topographic sections indicate discrete envelopes of individual tumors with localized TIFP. Further investigations in applying this non-invasive method as a means of measuring TIFP in subcutaneous mice xenograft tumors in situ could also enhance understanding of tumor microenvironment and vessel architecture in living tissue.

  13. Small-Scale Metal Tanks for High Pressure Storage of Fluids

    NASA Technical Reports Server (NTRS)

    London, Adam (Inventor)

    2016-01-01

    Small scale metal tanks for high-pressure storage of fluids having tank factors of more than 5000 meters and volumes of ten cubic inches or less featuring arrays of interconnected internal chambers having at least inner walls thinner than gage limitations allow. The chambers may be arranged as multiple internal independent vessels. Walls of chambers that are also portions of external tank walls may be arcuate on the internal and/or external surfaces, including domed. The tanks may be shaped adaptively and/or conformally to an application, including, for example, having one or more flat outer walls and/or having an annular shape. The tanks may have dual-purpose inlet/outlet conduits of may have separate inlet and outlet conduits. The tanks are made by fusion bonding etched metal foil layers patterned from slices of a CAD model of the tank. The fusion bonded foil stack may be further machined.

  14. Research program: The investigation of heat transfer and fluid flow at low pressure

    NASA Astrophysics Data System (ADS)

    El-Genk, M. S.; Philbin, J. S.; Foushee, F. C.

    1986-04-01

    This paper gives an overview of a multiyear joint research program being conducted at the University of New Mexico (UNM) with support from Sandia National Laboratories and GA Technologies. This research focuses on heat removal and fluid dynamics in flow regimes characterized by low pressure and low Reynolds number. The program was motivated by a desire to characterize and analyze cooling in a broad class of TRIGA-type reactors under: (1) typical operating conditions, (2) anticipated, new operating regimes, and (3) postulated accident conditions. It has also provided experimental verification of analytical tools used in design analysis. The paper includes descriptions of the UNM thermal-hydraulics test facility and the experimental test sections. During the first two years experiments were conducted using single, electrically heated rod in water and air annuli. This configuration provides an observable and serviceable simulation of a fuel rod and its coolant channel.

  15. Laboratory experiments and continuous fluid monitoring at Campi Flegrei to understand pressure transients in hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Woith, Heiko; Mangiacapra, Annarita; Chiodini, Giovanni; Pilz, Marco; Walter, Thomas

    2015-04-01

    The hydrothermal system beneath Campi Flegrei is strongly affected by sub-surface processes as manifested by the existence of a geothermal "plume" below Solfatara (Bruno et al. 2007), associated with formation of new fumaroles and the spatial pattern of exhalation vents. Within the frame of MED-SUV (The MED-SUV project has received funding from the European Union Seventh Framework Programme (FP7) under Grant agreement no 308665), pressure tansients in the hydrothermal system of Campi Flegrei shall be studied using a combination of laboratory experiments and continuous pressure/temperature monitoring at fumaroles, mudpools, hot springs, and geothermal wells. Four groundwater monitoring sites were installed in September 2013: one in the Fangaia mud pool inside Solfatara and three within the geothermal area of Agnano, which is located roughly 3 km to the East of the Solfatara crater. In 2014 additional sensors were installed in Pisciarelli. Autonomous devices are being used to record the water level and water temperature at 10 minute intervals. Records reveal significant changes of the hydrothermal system in September 2013 at the Agnano main spring during the night from 23 to 24 September. Both, the water level and the water temperature dropped significantly, confirmed by visual inspection of the spa operators. The pool of the main spring almost emptied and the flow rate was significantly reduced, implying a profound change in the system. Similar water level drops occurred in the following months. Gas bubbles are likely to play a major role with respect to spatio-temporal variations in shallow fluid systems below Solfatara. Thus, additional to the field measurements we investigate potential bubble-related mechanisms capable to increase fluid pressure. The BubbleLab at GFZ has been setup. We are able to simulate earthquake ground motions with a shaking table, track the size and velocity of rising bubbles via a camera system, and quantify transients with a set of

  16. Characteristics of time-varying intracranial pressure on blood flow through cerebral artery: A fluid-structure interaction approach.

    PubMed

    Syed, Hasson; Unnikrishnan, Vinu U; Olcmen, Semih

    2016-02-01

    Elevated intracranial pressure is a major contributor to morbidity and mortality in severe head injuries. Wall shear stresses in the artery can be affected by increased intracranial pressures and may lead to the formation of cerebral aneurysms. Earlier research on cerebral arteries and aneurysms involves using constant mean intracranial pressure values. Recent advancements in intracranial pressure monitoring techniques have led to measurement of the intracranial pressure waveform. By incorporating a time-varying intracranial pressure waveform in place of constant intracranial pressures in the analysis of cerebral arteries helps in understanding their effects on arterial deformation and wall shear stress. To date, such a robust computational study on the effect of increasing intracranial pressures on the cerebral arterial wall has not been attempted to the best of our knowledge. In this work, fully coupled fluid-structure interaction simulations are carried out to investigate the effect of the variation in intracranial pressure waveforms on the cerebral arterial wall. Three different time-varying intracranial pressure waveforms and three constant intracranial pressure profiles acting on the cerebral arterial wall are analyzed and compared with specified inlet velocity and outlet pressure conditions. It has been found that the arterial wall experiences deformation depending on the time-varying intracranial pressure waveforms, while the wall shear stress changes at peak systole for all the intracranial pressure profiles. PMID:26701867

  17. Intra-Operative Fluid Management in Adult Neurosurgical Patients Undergoing Intracranial Tumour Surgery: Randomised Control Trial Comparing Pulse Pressure Variance (PPV) and Central Venous Pressure (CVP)

    PubMed Central

    Salins, Serina Ruth; Kumar, Amar Nandha; Korula, Grace

    2016-01-01

    Introduction Fluid management in neurosurgery presents specific challenges to the anaesthesiologist. Dynamic para-meters like Pulse Pressure Variation (PPV) have been used successfully to guide fluid management. Aim To compare PPV against Central Venous Pressure (CVP) in neurosurgical patients to assess hemodynamic stability and perfusion status. Materials and Methods This was a single centre prospective randomised control trial at a tertiary care centre. A total of 60 patients undergoing intracranial tumour excision in supine and lateral positions were randomised to two groups (Group 1, CVP n=30), (Group 2, PPV n=30). Intra-operative fluid management was titrated to maintain baseline CVP in Group 1(5-10cm of water) and in Group 2 fluids were given to maintain PPV less than 13%. Acid base status, vital signs and blood loss were monitored. Results Although intra-operative hypotension and acid base changes were comparable between the groups, the patients in the CVP group had more episodes of hypotension requiring fluid boluses in the first 24 hours post surgery. {CVP group median (25, 75) 2400ml (1850, 3110) versus PPV group 2100ml (1350, 2200) p=0.03} The patients in the PPV group received more fluids than the CVP group which was clinically significant. {2250 ml (1500, 3000) versus 1500ml (1200, 2000) median (25, 75) (p=0.002)}. The blood loss was not significantly different between the groups The median blood loss in the CVP group was 600ml and in the PPV group was 850 ml; p value 0.09. Conclusion PPV can be used as a reliable index to guide fluid management in neurosurgical patients undergoing tumour excision surgery in supine and lateral positions and can effectively augment CVP as a guide to fluid management. Patients in PPV group had better hemodynamic stability and less post operative fluid requirement. PMID:27437329

  18. Effects of the taxanes paclitaxel and docetaxel on edema formation and interstitial fluid pressure.

    PubMed

    Brønstad, Aurora; Berg, Ansgar; Reed, Rolf K

    2004-08-01

    Interstitial fluid pressure (P(if)) is important for maintaining constant interstitial fluid volume. In several acute inflammatory reactions, a dramatic lowering of P(if) has been observed, increasing transcapillary filtration pressure and favoring initial and rapid edema formation. This lowering of P(if) seems to involve dynamic beta(1)-integrin-mediated interactions between connective tissue cells and extracellular matrix (ECM) fibers. beta(1)-Integrins are adhesion receptors responsible for the attachment of connective tissue cells to the ECM providing a force-transmitting physical link between the ECM and cytoskeleton. Disruption of actin filaments leads to lowering of P(if) and edema formation, suggesting a role for actin filaments. The aim of this study was to further investigate the role of the cytoskeleton in the control of P(if) by studying the effect of microtubuli fixation using paclitaxel and docetaxel. P(if) was measured with the micropuncture technique. Albumin extravasation (E(alb)) was measured using (125)I-labeled albumin. Paclitaxel and docetaxel were tested locally on foot skin in female Wistar rats. Paclitaxel (6 mg/ml) reduced P(if) from -1.5 +/- 1.0 mmHg in controls to -4.9 +/- 2.6 mmHg after 30 min (P < 0.05) in a dose-dependent manner (P < 0.05). Docetaxel caused a similar lowering of P(if). Both paclitaxel and docetaxel increased E(alb) compared with Cremophor EL and saline control (P < 0.05). Pretreatment with phalloidin before paclitaxel, causing fixation of actin filaments, abolished the lowering of P(if) caused by paclitaxel. This study confirms several previous studies demonstrating that connective tissue cells influence P(if) and edema formation. PMID:15059777

  19. Predictive models for pressure-driven fluid infusions into brain parenchyma.

    PubMed

    Raghavan, Raghu; Brady, Martin

    2011-10-01

    Direct infusions into brain parenchyma of biological therapeutics for serious brain diseases have been, and are being, considered. However, individual brains, as well as distinct cytoarchitectural regions within brains, vary in their response to fluid flow and pressure. Further, the tissue responds dynamically to these stimuli, requiring a nonlinear treatment of equations that would describe fluid flow and drug transport in brain. We here report in detail on an individual-specific model and a comparison of its prediction with simulations for living porcine brains. Two critical features we introduced into our model-absent from previous ones, but requirements for any useful simulation-are the infusion-induced interstitial expansion and the backflow. These are significant determinants of the flow. Another feature of our treatment is the use of cross-property relations to obtain individual-specific parameters that are coefficients in the equations. The quantitative results are at least encouraging, showing a high fraction of overlap between the computed and measured volumes of distribution of a tracer molecule and are potentially clinically useful. Several improvements are called for; principally a treatment of the interstitial expansion more fundamentally based on poroelasticity and a better delineation of the diffusion tensor of a particle confined to the interstitial spaces. PMID:21891847

  20. Airborne Shaped Sonic Boom Demonstration Pressure Measurements with Computational Fluid Dynamics Comparisons

    NASA Technical Reports Server (NTRS)

    Haering, Edward A., Jr.; Murray, James E.; Purifoy, Dana D.; Graham, David H.; Meredith, Keith B.; Ashburn, Christopher E.; Stucky, Mark

    2005-01-01

    The Shaped Sonic Boom Demonstration project showed for the first time that by careful design of aircraft contour the resultant sonic boom can maintain a tailored shape, propagating through a real atmosphere down to ground level. In order to assess the propagation characteristics of the shaped sonic boom and to validate computational fluid dynamics codes, airborne measurements were taken of the pressure signatures in the near field by probing with an instrumented F-15B aircraft, and in the far field by overflying an instrumented L-23 sailplane. This paper describes each aircraft and their instrumentation systems, the airdata calibration, analysis of the near- and far-field airborne data, and shows the good to excellent agreement between computational fluid dynamics solutions and flight data. The flights of the Shaped Sonic Boom Demonstration aircraft occurred in two phases. Instrumentation problems were encountered during the first phase, and corrections and improvements were made to the instrumentation system for the second phase, which are documented in the paper. Piloting technique and observations are also given. These airborne measurements of the Shaped Sonic Boom Demonstration aircraft are a unique and important database that will be used to validate design tools for a new generation of quiet supersonic aircraft.

  1. Biomimetic actuator

    NASA Astrophysics Data System (ADS)

    Bouda, Vaclav; Boudova, Lea; Haluzikova, Denisa

    2005-05-01

    The aim of the presentation is to propose an alternative model of mammalian skeletal muscle function, which reflects the simplicity of nature and can be applied in engineering. Van der Waals attractive and repulsive electrostatic forces are assumed to control the design of internal structures and functions of contractile units of the muscles - sarcomere. The role of myosin heads is crucial for the higher order formation. The model of the myosin head lattice is the working model for the sarcomere contraction interpretation. The contraction is interpreted as a calcium induced phase transition of the lattice, which results in relative actin-myosin sliding and/or force generation. The model should provide the engineering science with a simple analogy to technical actuators of high performance.

  2. Overall heat transfer coefficient and pressure drop in a typical tubular exchanger employing alumina nano-fluid as the tube side hot fluid

    NASA Astrophysics Data System (ADS)

    Kabeel, A. E.; Abdelgaied, Mohamed

    2015-08-01

    Nano-fluids are used to improve the heat transfer rates in heat exchangers, especially; the shell-and-tube heat exchanger that is considered one of the most important types of heat exchangers. In the present study, an experimental loop is constructed to study the thermal characteristics of the shell-and-tube heat exchanger; at different concentrations of Al2O3 nonmetallic particles (0.0, 2, 4, and 6 %). This material concentrations is by volume concentrations in pure water as a base fluid. The effects of nano-fluid concentrations on the performance of shell and tube heat exchanger have been conducted based on the overall heat transfer coefficient, the friction factor, the pressure drop in tube side, and the entropy generation rate. The experimental results show that; the highest heat transfer coefficient is obtained at a nano-fluid concentration of 4 % of the shell side. In shell side the maximum percentage increase in the overall heat transfer coefficient has reached 29.8 % for a nano-fluid concentration of 4 %, relative to the case of the base fluid (water) at the same tube side Reynolds number. However; in the tube side the maximum relative increase in pressure drop has recorded the values of 12, 28 and 48 % for a nano-material concentration of 2, 4 and 6 %, respectively, relative to the case without nano-fluid, at an approximate value of 56,000 for Reynolds number. The entropy generation reduces with increasing the nonmetallic particle volume fraction of the same flow rates. For increase the nonmetallic particle volume fraction from 0.0 to 6 % the rate of entropy generation decrease by 10 %.

  3. Overall heat transfer coefficient and pressure drop in a typical tubular exchanger employing alumina nano-fluid as the tube side hot fluid

    NASA Astrophysics Data System (ADS)

    Kabeel, A. E.; Abdelgaied, Mohamed

    2016-08-01

    Nano-fluids are used to improve the heat transfer rates in heat exchangers, especially; the shell-and-tube heat exchanger that is considered one of the most important types of heat exchangers. In the present study, an experimental loop is constructed to study the thermal characteristics of the shell-and-tube heat exchanger; at different concentrations of Al2O3 nonmetallic particles (0.0, 2, 4, and 6 %). This material concentrations is by volume concentrations in pure water as a base fluid. The effects of nano-fluid concentrations on the performance of shell and tube heat exchanger have been conducted based on the overall heat transfer coefficient, the friction factor, the pressure drop in tube side, and the entropy generation rate. The experimental results show that; the highest heat transfer coefficient is obtained at a nano-fluid concentration of 4 % of the shell side. In shell side the maximum percentage increase in the overall heat transfer coefficient has reached 29.8 % for a nano-fluid concentration of 4 %, relative to the case of the base fluid (water) at the same tube side Reynolds number. However; in the tube side the maximum relative increase in pressure drop has recorded the values of 12, 28 and 48 % for a nano-material concentration of 2, 4 and 6 %, respectively, relative to the case without nano-fluid, at an approximate value of 56,000 for Reynolds number. The entropy generation reduces with increasing the nonmetallic particle volume fraction of the same flow rates. For increase the nonmetallic particle volume fraction from 0.0 to 6 % the rate of entropy generation decrease by 10 %.

  4. Engine control system having pressure-based timing

    DOEpatents

    Willi, Martin L.; Fiveland, Scott B.; Montgomery, David T.; Gong, Weidong

    2011-10-04

    A control system for an engine having a first cylinder and a second cylinder is disclosed having a first engine valve movable to regulate a fluid flow of the first cylinder and a first actuator associated with the first engine valve. The control system also has a second engine valve movable to regulate a fluid flow of the second cylinder and a sensor configured to generate a signal indicative of a pressure within the first cylinder. The control system also has a controller that is in communication with the first actuator and the sensor. The controller is configured to compare the pressure within the first cylinder with a desired pressure and selectively regulate the first actuator to adjust a timing of the first engine valve independently of the timing of the second engine valve based on the comparison.

  5. Slow slip pulses driven by thermal pressurization of pore fluid: theory and observational constraints

    NASA Astrophysics Data System (ADS)

    Garagash, D.

    2012-12-01

    We discuss recently developed solutions for steadily propagating self-healing slip pulses driven by thermal pressurization (TP) of pore fluid [Garagash, 2012] on a fault with a constant sliding friction. These pulses are characterized by initial stage of undrained weakening of the fault (when fluid/heat can not yet escape the frictionally heated shear zone), which gives way to partial restrengthening due to increasing hydrothermal diffusion under conditions of diminished rate of heating, leading to eventual locking of the slip. The rupture speed of these pulses is decreasing function of the thickness (h) of the principal shear zone. We find that "thick" shear zones, h >> hdyna, where hdyna = (μ/τ0) (ρc/fΛ)(4α/cs), can support aseismic TP pulses propagating at a fraction hdyna/h of the shear wave speed cs, while "thin" shear zones, h˜hdyna or thinner, can only harbor seismic slip. (Here μ - shear modulus, τ0 - the nominal fault strength, f - sliding friction, ρc - the heat capacity of the fault gouge, Λ - the fluid thermal pressurization factor, α - hydrothermal diffusivity parameter of the gouge). For plausible range of fault parameters, hdyna is between 10s to 100s of micrometers, suggesting that slow slip transients propagating at 1 to 10 km/day may occur in the form of a TP slip pulse accommodated by a meter-thick shear zone. We verify that this is, indeed, a possibility by contrasting the predictions for aseismic, small-slip TP pulses operating at seismologically-constrained, near-lithostatic pore pressure (effective normal stress ≈ 3 to 10 MPa) with the observations (slip duration at a given fault location ≈ week, propagation speed ≈ 15 km/day, and the inferred total slip ≈ 2 to 3 cm) for along-strike propagation of the North Cascadia slow slip events of '98-99 [Dragert et al., 2001, 2004]. Furthermore, we show that the effect of thermal pressurization on the strength of the subduction interface is comparable to or exceeds that of the rate

  6. Numerical Simulation of a High-Lift Configuration with Embedded Fluidic Actuators

    NASA Technical Reports Server (NTRS)

    Vatsa, Veer N.; Casalino, Damiano; Lin, John C.; Appelbaum, Jason

    2014-01-01

    Numerical simulations have been performed for a vertical tail configuration with deflected rudder. The suction surface of the main element of this configuration is embedded with an array of 32 fluidic actuators that produce oscillating sweeping jets. Such oscillating jets have been found to be very effective for flow control applications in the past. In the current paper, a high-fidelity computational fluid dynamics (CFD) code known as the PowerFLOW(Registered TradeMark) code is used to simulate the entire flow field associated with this configuration, including the flow inside the actuators. The computed results for the surface pressure and integrated forces compare favorably with measured data. In addition, numerical solutions predict the correct trends in forces with active flow control compared to the no control case. Effect of varying yaw and rudder deflection angles are also presented. In addition, computations have been performed at a higher Reynolds number to assess the performance of fluidic actuators at flight conditions.

  7. The Role of Fluid Pressure in Earthquake Triggering: Insights from an Experimental Study of Frictional Stability of Carbonates

    NASA Astrophysics Data System (ADS)

    Collettini, C.; Scuderi, M.

    2015-12-01

    Fluid overpressure has been often proposed as one of the primary mechanisms that facilitate earthquake slip along faults. However, elastic dislocation theory combined with rate- and state- friction laws suggests that fluid overpressure may inhibit the dynamic instabilities that result in earthquakes, by reducing the critical rheological fault stiffness, kc. This controversy poses a serious problem in our understanding of earthquake physics, with severe implications for seismic hazard and human-induced seismicity. Nevertheless, currently, there are only a few systematic studies on the role of fluid pressure under controlled, laboratory conditions for which the evolution of friction parameters and slip stability can be measured. We have used a biaxial rock deformation apparatus within a pressure vessel, in order to allow a true triaxial stress field, in a double direct shear configuration. We tested carbonate fault gouge, Carrara marble, sieved to a grain size of 125 microns. Normal stresses and confining pressure were held constant throughout the experiment at values of 5 to 40 MPa, and the pore fluid pressure was varied from hydrostatic up to near lithostatic values. Shear stress was induced by a constant displacement rate and sliding velocities varied from 0.1-100 microns/s, in order to evaluate slip stability via rate- and state- dependent frictional parameters, such as (a-b), Dc. With increasing fluid pressure we observe an evolution of (a-b) from slightly velocity strengthening to velocity neutral and a reduction in Dc from about 100 to 20 microns. Our analysis on carbonate fault gouges indicates that the increase in fluid pressure not only favour fault reactivation but it also makes the fault more prone to generate earthquake instabilities.

  8. Non-equilibrium pressure control of the height of a large-scale, ground-coupled, rotating fluid column

    NASA Astrophysics Data System (ADS)

    Ash, R. L.; Zardadkhan, I. R.

    2013-05-01

    When a ground-coupled, rotating fluid column is modeled incorporating non-equilibrium pressure forces in the Navier-Stokes equations, a new exact solution results. The solution has been obtained in a similar manner to the classical equilibrium solution. Unlike the infinite-height, classical solution, the non-equilibrium pressure solution yields a ground-coupled rotating fluid column of finite height. A viscous, non-equilibrium Rankine vortex velocity distribution, developed previously, was used to demonstrate how the viscous and non-equilibrium pressure gradient forces, arising in the vicinity of the velocity gradient discontinuity that is present in the classical Rankine vortex model, effectively isolate the rotating central fluid column from the outer potential vortex region. Thus, the non-equilibrium region acts to confine and shield the central, rigid-body-like, rotating fluid core, justifying this examination of how such a rotating fluid column can interact with the ground. The resulting non-equilibrium ground-coupled, rotating fluid column solution was employed to estimate the central column heights of three well-documented dust devils, and the central column height predictions were consistent with published dust devil height statistics.

  9. Plasma actuators for bluff body flow control

    NASA Astrophysics Data System (ADS)

    Kozlov, Alexey V.

    The aerodynamic plasma actuators have shown to be efficient flow control devices in various applications. In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. This work is motivated by the need to reduce landing gear noise for commercial transport aircraft via an effective streamlining created by the actuators. The experiments are performed at Re D = 20,000...164,000. Circular cylinders in cross-flow are chosen for study since they represent a generic flow geometry that is similar in all essential aspects to a landing gear oleo or strut. The minimization of the unsteady flow separation from the models and associated large-scale wake vorticity by using actuators reduces the radiated aerodynamic noise. Using either steady or unsteady actuation at ReD = 25,000, Karman shedding is totally eliminated, turbulence levels in the wake decrease significantly and near-field sound pressure levels are reduced by 13.3 dB. Unsteady actuation at an excitation frequency of St D = 1 is found to be most effective. The unsteady actuation also has the advantage that total suppression of shedding is achieved for a duty cycle of only 25%. However, since unsteady actuation is associated with an unsteady body force and produces a tone at the actuation frequency, steady actuation is more suitable for noise control applications. Two actuation strategies are used at ReD = 82,000: spanwise and streamwise oriented actuators. Near field microphone measurements in an anechoic wind tunnel and detailed study of the near wake using LDA are presented in the study. Both spanwise and streamwise actuators give nearly the same noise reduction level of 11.2 dB and 14.2 dB, respectively, and similar changes in the wake velocity profiles. The contribution of the actuator induced noise is found to be small compared to the natural shedding

  10. Dual simulations of fluid flow and seismic wave propagation in a fractured network: effects of pore pressure on seismic signature

    NASA Astrophysics Data System (ADS)

    Vlastos, S.; Liu, E.; Main, I. G.; Schoenberg, M.; Narteau, C.; Li, X. Y.; Maillot, B.

    2006-08-01

    Fluid flow in the Earth's crust plays an important role in a number of geological processes. In relatively tight rock formations such flow is usually controlled by open macrofractures, with significant implications for ground water flow and hydrocarbon reservoir management. The movement of fluids in the fractured media will result in changes in the pore pressure and consequently will cause changes to the effective stress, traction and elastic properties. The main purpose of this study is to numerically examine the effect of pore pressure changes on seismic wave propagation (i.e. the effects of pore pressures on amplitude, arrival time, frequency content). This is achieved by using dual simulations of fluid flow and seismic propagation in a common 2-D fracture network. Note that the dual simulations are performed separately as the coupled simulations of fluid flow and seismic wave propagations in such fracture network is not possible because the timescales of fluid flow and wave propagation are considerably different (typically, fluid flows in hours, whereas wave propagation in seconds). The flow simulation updates the pore pressure at consecutive time steps, and thus the elastic properties of the rock, for the seismic modelling. In other words, during each time step of the flow simulations, we compute the elastic response corresponding to the pore pressure distribution. The relationship between pore pressure and fractures is linked via an empirical relationship given by Schoenberg and the elastic response of fractures is computed using the equivalent medium theory described by Hudson and Liu. Therefore, we can evaluate the possibility of inferring the changes of fluid properties directly from seismic data. Our results indicate that P waves are not as sensitive to pore pressure changes as S and coda (or scattered) waves. The increase in pore pressure causes a shift of the energy towards lower frequencies, as shown from the spectrum (as a result of scattering

  11. Investigation of SSME alternate high pressure fuel turbopump lift-off seal fluid and structural dynamic interaction

    NASA Technical Reports Server (NTRS)

    Elrod, David A.

    1989-01-01

    The Space Shuttle main engine (SSME) alternate turbopump development program (ATD) high pressure fuel turbopump (HPFTP) design utilizes an innovative lift-off seal (LOS) design that is located in close proximity to the turbine end bearing. Cooling flow exiting the bearing passes through the lift-off seal during steady state operation. The potential for fluid excitation of lift-off seal structural resonances is investigated. No fluid excitation of LOS resonances is predicted. However, if predicted LOS natural frequencies are significantly lowered by the presence of the coolant, pressure oscillations caused by synchronous whirl of the HPFTP rotor may excite a resonance.

  12. Numerical Model of Hydraulic Fracturing Fluid Transport in the Subsurface with Pressure Transient, Density Effects, and Imbibition

    NASA Astrophysics Data System (ADS)

    Birdsell, D.; Rajaram, H.; Dempsey, D.; Viswanathan, H.

    2014-12-01

    Understanding the transport of hydraulic fracturing (HF) fluid that is injected into the deep subsurface for shale gas extraction is important to ensure that shallow drinking water aquifers are not contaminated from an environmental and public health perspective and to understand formation damage from an oil and gas production perspective. Upward pressure gradients, permeable pathways such as faults or improperly abandoned wellbores, and the density contrast of the HF fluid to the surrounding brine encourages upward HF fluid migration. In contrast, the very low shale permeability and the imbibition of water into partially-saturated shale may sequester much of the HF fluid. Using the Finite Element Heat and Mass Transfer Code (FEHM), single-phase flow and transport simulations are performed to quantify how much HF fluid is removed via the wellbore as flowback and produced water and how much reaches overlying aquifers; imbibition is calculated with a semi-analytical one-dimensional solution and treated as a sink term. The travel time for HF fluid to reach the shallow aquifers is highly dependent on the amount of water imbibed and the suction applied to the well. If imbibition rates and suction are small, the pressure transient due to injection and the density contrast allows rapid upward plume migration at early times. The density contrast diminishes considerably within tens to hundreds of years as mixing occurs. We present estimates of HF fluid migration to shallow aquifers during the first 1,000 years after hydraulic fracturing begins for ranges of subsurface properties.

  13. Inductively coupled microfluidic pressure meter for in vivo monitoring of cerebrospinal fluid shunt function.

    PubMed

    Song, S-H; Gillies, G T; Begley, M R; Utz, M; Broaddus, W C

    2012-04-01

    A microfluidic pressure sensor with inductively coupled, wireless readout capability has been developed for integration into cerebrospinal fluid shunt valve implants. The sensor consists of a deformable PDMS film that is bonded over a microfluidic reservoir, forming a fluidic capacitor. Deflection of the capacitor membrane is detected remotely through a shift in the resonance frequency of a micro-fabricated LC circuit. Sensors were fabricated by a combination of conventional MEMS technologies and rapid soft lithography. A direct pattern transfer technique was used to pattern the deformable PDMS film with a metal coating for the capacitive readout. The mechanical response of the fluidic capacitor was characterized by measuring the deflection of the PDMS film using an extrinsic Fabry-Perot interferometer (EFPI), and wireless sensing was demonstrated by the shift in resonance frequency of the sensor via an inductively coupled antenna. The sensor transduces pressure into a change in resonant frequency with sensitivity > 3.4 ppm Pa⁻¹ and responsivity 4.6 kHz Pa⁻¹, over a dynamic range of 0~3 kPa. PMID:22316101

  14. Fluid flow analysis of the SSME high pressure fuel and oxidizer turbine coolant systems

    NASA Technical Reports Server (NTRS)

    Teal, G. A.

    1989-01-01

    The objective is to provide improved analysis capability for the Space Shuttle Main Engine (SSME) high pressure fuel and oxidizer turbine coolant systems. Each of the systems was analyzed to determine fluid flow rate and thermodynamic and transport properties at all key points in the systems. Existing computer codes were used as a baseline for these analyses. These codes were modified to provide improved analysis capability. The major areas of improvement are listed. A review of the drawings was performed, and pertinent geometry changes were included in the models. Improvements were made in the calculation of thermodynamic and transport properties for a mixture of hydrogen and steam. A one-dimensional turbine model for each system is included as a subroutine to each code. This provides a closed loop analysis with a minimum of required boundary conditions as input. An improved labyrinth seal model is included in the high pressure fuel turbine coolant model. The modifications and the analysis results are presented in detail.

  15. Flow rate dictates permeability enhancement during fluid pressure oscillations in laboratory experiments

    NASA Astrophysics Data System (ADS)

    Candela, Thibault; Brodsky, Emily E.; Marone, Chris; Elsworth, Derek

    2015-04-01

    Seismic waves have been observed to increase the permeability in fractured aquifers. A detailed, predictive understanding of the process has been hampered by a lack of constraint on the primary physical controls. What aspect of the oscillatory forcing is most important in determining the magnitude of the permeability enhancement? Here we present laboratory results showing that flow rate is the primary control on permeability increases in the laboratory. We fractured Berea sandstone samples under triaxial stresses of tens of megapascals and applied dynamic fluid stresses via pore pressure oscillations. In each experiment, we varied either the amplitude or the frequency of the pressure changes. Amplitude and frequency each separately correlated with the resultant permeability increase. More importantly, the permeability changes correlate with the flow rate in each configuration, regardless of whether flow rate variations were driven by varying amplitude or frequency. We also track the permeability evolution during a single set of oscillations by measuring the phase lags (time delays) of successive oscillations. Interpreting the responses with a poroelastic model shows that 80% of the permeability enhancement is reached during the first oscillation and the final permeability enhancement scales exponentially with the imposed change in flow rate integrated over the rock volume. The establishment of flow rate as the primary control on permeability enhancement from seismic waves opens the door to quantitative studies of earthquake-hydrogeological coupling. The result also suggests that reservoir permeability could be engineered by imposing dynamic stresses and changes in flow rate.

  16. Flow rate dictates permeability enhancement during fluid pressure oscillations in laboratory experiments

    NASA Astrophysics Data System (ADS)

    Brodsky, E. E.; Candela, T.; Elsworth, D.; Marone, C.

    2014-12-01

    Seismic waves have been observed to increase the permeability in fractured aquifers. A detailed, predictive understanding of the process has been hampered by a lack of constraint on the primary physical controls. What aspect of the oscillatory forcing is most important in determining the magnitude of the permeability enhancement? Here we present laboratory results showing that flow rate is the primary control on permeability increases in the laboratory. We fractured Berea sandstone samples under triaxial stresses of tens of megapascals, and applied dynamic fluid-stresses via pore pressure oscillations. In each experiment, we varied either the amplitude or the frequency of the pressure changes. Amplitude and frequency each separately correlated with the resultant permeability increase. More importantly, the permeability changes correlate with the flow rate in each configuration, regardless of whether flow rate variations were driven by varying amplitude or frequency. We also track the permeability evolution during a single set of oscillations by measuring the phase lags (time delays) of successive oscillations. Interpreting the responses with a poroelastic model shows that 80% of the permeability enhancement is reached during the first oscillation and the final permeability enhancement scales exponentially with the imposed change in flow rate integrated over the rock volume. The establishment of flow rate as the primary control on permeability enhancement from seismic waves opens the door to quantitative studies of earthquake-hydrogeological coupling. The result also suggests that reservoir permeability could be engineered by imposing dynamic stresses and changes in flow rate.

  17. Variation in Lithium Isotopes During Fluid-Shale Interactions at Elevated Pressure and Temperature

    NASA Astrophysics Data System (ADS)

    Phan, T. T.; Paukert, A. N.; Hakala, A.

    2015-12-01

    Naturally-occurring isotopes are useful tracers of fluid mixing in complex natural systems, and have been applied towards evaluating the sources of elevated total dissolved solids in water produced from unconventional oil and gas operations. Prior investigations showed that elevated Li in saline waters co-produced with natural gas during Marcellus Shale development resulted from mixing of hydraulic fracturing fluid (HFF) and Li-rich formation water. However, specific contributions to the Li isotope signature from reactions between the HFF and shale remained unclear. This study focused on HFF-shale reactions that could affect the Li budget and isotope composition in Marcellus Shale produced water in a series of flow through experiments conducted at fixed temperature and pressure (66oC, 20MPa) comparable to formation conditions. Synthetic HFF was prepared by mixing either freshwater or a lab-derived saline water with chemical additives commonly used in hydraulic fracturing. Outcrop cores of Marcellus Shale were artificially fractured either parallel to or perpendicular to bedding prior to loading into the flow-through apparatus, and each experiment was performed with a unique HFF composition continuously pumped through a fresh core (15 cm in length, 3.8 cm in diameter). Initial fluid and cumulative effluents collected after 2 days and 7 days from the start of the experiment were measured for concentrations of cations and anions. Multi-collector ICP-MS was used to measure lithium isotope ratios (δ7Li). Preliminary results show that dissolution of carbonate minerals occurred in both replicate experiments with freshwater-based HFF (pH 2) as shown by a large decrease in Li/Ca from 0.8 (initial fluid) to 0.003 (effluents on day 2 and day 7) with no significant change in Li concentration. This is consistent with low Li in carbonate cement (<2%) and water soluble (<8%) and exchangeable (<2%) fractions of Marcellus Shale. Variation in δ7Li values is within analytical

  18. Modeling the fluid-dynamics and oxygen consumption in a porous scaffold stimulated by cyclic squeeze pressure.

    PubMed

    Ferroni, Marco; Giusti, Serena; Nascimento, Diana; Silva, Ana; Boschetti, Federica; Ahluwalia, Arti

    2016-08-01

    The architecture and dynamic physical environment of tissues can be recreated in-vitro by combining 3D porous scaffolds and bioreactors able to apply controlled mechanical stimuli on cells. In such systems, the entity of the stimuli and the distribution of nutrients within the engineered construct depend on the micro-structure of the scaffolds. In this work, we present a new approach for optimizing computational fluid-dynamics (CFD) models for the investigation of fluid-induced forces generated by cyclic squeeze pressure within a porous construct, coupled with oxygen consumption of cardiomyocytes. A 2D axial symmetric macro-scaled model of a squeeze pressure bioreactor chamber was used as starting point for generating time dependent pressure profiles. Subsequently the fluid movement generated by the pressure fields was coupled with a complete 3D micro-scaled model of a porous protein cryogel. Oxygen transport and consumption inside the scaffold was evaluated considering a homogeneous distribution of cardiomyocytes throughout the structure, as confirmed by preliminary cell culture experiments. The results show that a 3D description of the system, coupling a porous geometry and time dependent pressure driven flow with fluid-structure-interaction provides an accurate and meaningful description of the microenvironment in terms of shear stress and oxygen distribution than simple stationary 2D models. PMID:27189671

  19. An Irrigation Suction System Using a Pressurized Fluid High-Flow Pump System in Comparison with a Standard Cuff Pressure System: Technical Note.

    PubMed

    Murai, Yasuo; Matano, Fumihiro; Toda, Shigeki; Kobayashi, Shiro; Morita, Akio

    2016-05-01

    Objective In neurosurgical operations, such as clipping of ruptured cerebral aneurysms, irrigation of the operative field is a basic and extremely important surgical technique. Various irrigation-suction (IS) systems have been marketed for irrigation of operative fields in neurosurgery. However, with these devices, we often must increase the cuff pressure to maintain fluid power and change the fluid bag relatively frequently. We report the usefulness of pressurized irrigation fluid with the Niagara high-flow irrigation system (NI). Method Using both the NI system and an IS, we altered pressure and duration to investigate differences in flow rate. Results There was no change in flow rate 80 minutes after pressurization of the NI system, and flow rates decreased slightly. Additionally, flow rates using NI were sensitive to changes in pressure. Conclusion This system has reduced the workload of assisting nurses and surgeons during surgery. Thus we consider the technique to be very useful for neurosurgical operations that require delicate procedures. PMID:25915502

  20. Powerful Electromechanical Linear Actuator

    NASA Technical Reports Server (NTRS)

    Cowan, John R.; Myers, William N.

    1994-01-01

    Powerful electromechanical linear actuator designed to replace hydraulic actuator that provides incremental linear movements to large object and holds its position against heavy loads. Electromechanical actuator cleaner and simpler, and needs less maintenance. Two principal innovative features that distinguish new actuator are use of shaft-angle resolver as source of position feedback to electronic control subsystem and antibacklash gearing arrangement.

  1. Faulting processes at high fluid pressures: An example of fault valve behavior from the Wattle Gully Fault, Victoria, Australia

    NASA Astrophysics Data System (ADS)

    Cox, Stephen F.

    1995-07-01

    The internal structures of the Wattle Gully Fault provide insights about the mechanics and dynamics of fault systems exhibiting fault valve behavior in high fluid pressure regimes. This small, high-angle reverse fault zone developed at temperatures near 300°C in the upper crust, late during mid-Devonian regional crustal shortening in central Victoria, Australia. The Wattle Gully Fault forms part of a network of faults that focused upward migration of fluids generated by metamorphism and devolatilisation at deeper crustal levels. The fault has a length of around 800 m and a maximum displacement of 50 m and was oriented at 60° to 80° to the maximum principal stress during faulting. The structure was therefore severely misoriented for frictional reactivation. This factor, together with the widespread development of steeply dipping fault fill quartz veins and associated subhorizontal extension veins within the fault zone, indicates that faulting occurred at low shear stresses and in a near-lithostatic fluid pressure regime. The internal structures of these veins, and overprinting relationships between veins and faults, indicate that vein development was intimately associated with faulting and involved numerous episodes of fault dilatation and hydrothermal sealing and slip, together with repeated hydraulic extension fracturing adjacent to slip surfaces. The geometries, distribution and internal structures of veins in the Wattle Gully Fault Zone are related to variations in shear stress, fluid pressure, and near-field principal stress orientations during faulting. Vein opening is interpreted to have been controlled by repeated fluid pressure fluctuations associated with cyclic, deformation-induced changes in fault permeability during fault valve behavior. Rates of recovery of shear stress and fluid pressure after rupture events are interpreted to be important factors controlling time dependence of fault shear strength and slip recurrence. Fluctuations in shear stress

  2. Flight control actuation system

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Gaines, Louie T. (Inventor); Evans, Paul S. (Inventor); Kern, James I. (Inventor)

    2004-01-01

    A flight control actuation system comprises a controller, electromechanical actuator and a pneumatic actuator. During normal operation, only the electromechanical actuator is needed to operate a flight control surface. When the electromechanical actuator load level exceeds 40 amps positive, the controller activates the pneumatic actuator to offset electromechanical actuator loads to assist the manipulation of flight control surfaces. The assistance from the pneumatic load assist actuator enables the use of an electromechanical actuator that is smaller in size and mass, requires less power, needs less cooling processes, achieves high output forces and adapts to electrical current variations. The flight control actuation system is adapted for aircraft, spacecraft, missiles, and other flight vehicles, especially flight vehicles that are large in size and travel at high velocities.

  3. Commonwealth Edison Company pressure locking test report

    SciTech Connect

    Bunte, B.D.; Kelly, J.F.

    1996-12-01

    Pressure Locking is a phenomena which can cause the unseating thrust for a gate valve to increase dramatically from its typical static unseating thrust. This can result in the valve actuator having insufficient capability to open the valve. In addition, this can result in valve damage in cases where the actuator capability exceeds the valve structural limits. For these reasons, a proper understanding of the conditions which may cause pressure locking and thermal binding, as well as a methodology for predicting the unseating thrust for a pressure locked or thermally bound valve, are necessary. This report discusses the primary mechanisms which cause pressure locking. These include sudden depressurization of piping adjacent to the valve and pressurization of fluid trapped in the valve bonnet due to heat transfer. This report provides a methodology for calculating the unseating thrust for a valve which is pressure locked. This report provides test data which demonstrates the accuracy of the calculation methodology.

  4. Influence of Pore-Fluid Pressure on Elastic Wave Velocity and Electrical Conductivity in Water-Saturated Rocks

    NASA Astrophysics Data System (ADS)

    Higuchi, A.; Watanabe, T.

    2013-12-01

    Pore-fluid pressure in seismogenic zones can play a key role in the occurrence of earthquakes (e.g., Sibson, 2009). Its evaluation via geophysical observations can lead to a good understanding of seismic activities. The evaluation requires a thorough understanding of the influence of the pore-fluid pressure on geophysical observables like seismic velocity and electrical conductivity. We have studied the influence of pore-fluid pressure on elastic wave velocity and electrical conductivity in water-saturated rocks. Fine grained (100-500μm) biotite granite (Aji, Kagawa pref., Japan) was used as rock samples. The density is 2.658-2.668 g/cm3, and the porosity 0.68-0.87%. The sample is composed of 52.8% plagioclase, 36.0% Quartz, 3.0% K-feldspar, 8.2% biotite. SEM images show that a lot of grain boundaries are open. Few intracrystalline cracks were observed. Following the method proposed by David and Zimmerman (2012), the distribution function of crack aspect ratio was evaluated from the pressure dependence of compressional and shear wave velocities in a dry sample. Cylindrical sample has dimensions of 25 mm in diameter and 30 mm in length, and saturated with 0.01 mol/l KCl aqueous solution. Compressional and shear wave velocities were measured with the pulse transmission technique (PZT transducers, f=2 MHz), and electrical conductivity the two-electrode method (Ag-AgCl electrodes, f=1 Hz-100 kHz). Simultaneous measurements of velocities and conductivity were made using a 200 MPa hydrostatic pressure vessel, in which confining and pore-fluid pressures can be separately controlled. The pore-fluid is electrically insulated from the metal work of the pressure vessel by using a newly designed plastic device (Watanabe and Higuchi, 2013). The confining pressure was progressively increased up to 25 MPa, while the pore-fluid pressure was kept at 0.1 MPa. It took five days or longer for the electrical conductivity to become stationary after increasing the confining pressure

  5. The Influence of Body Position on Cerebrospinal Fluid Pressure Gradient and Movement in Cats with Normal and Impaired Craniospinal Communication

    PubMed Central

    Radoš, Milan; Erceg, Gorislav; Petošić, Antonio; Jurjević, Ivana

    2014-01-01

    Intracranial hypertension is a severe therapeutic problem, as there is insufficient knowledge about the physiology of cerebrospinal fluid (CSF) pressure. In this paper a new CSF pressure regulation hypothesis is proposed. According to this hypothesis, the CSF pressure depends on the laws of fluid mechanics and on the anatomical characteristics inside the cranial and spinal space, and not, as is today generally believed, on CSF secretion, circulation and absorption. The volume and pressure changes in the newly developed CSF model, which by its anatomical dimensions and basic biophysical features imitates the craniospinal system in cats, are compared to those obtained on cats with and without the blockade of craniospinal communication in different body positions. During verticalization, a long-lasting occurrence of negative CSF pressure inside the cranium in animals with normal cranio-spinal communication was observed. CSF pressure gradients change depending on the body position, but those gradients do not enable unidirectional CSF circulation from the hypothetical site of secretion to the site of absorption in any of them. Thus, our results indicate the existence of new physiological/pathophysiological correlations between intracranial fluids, which opens up the possibility of new therapeutic approaches to intracranial hypertension. PMID:24748150

  6. Earthquake Fracture Energies and Weakening of Faults by Thermal Pressurization of Pore Fluid

    NASA Astrophysics Data System (ADS)

    Rice, J. R.

    2003-12-01

    Seismic inferences of fracture energy G constrain how fault strength degrades during slip and allow testing of candidate physical mechanisms. Recently G has been estimated by interpreting parameters from seismic slip inversions within a self-healing rupture model (Rice, Sammis and Parsons, 2003), and by studying the scaling of radiated energy and stress drop with earthquake size (Abercrombie and Rice, 2003). Those and earlier studies suggest that for larger events (slip > 0.1 m), G ranges from 0.1 to 10 MJ/m2 with average of 2-4 MJ/m2. There is a clear trend for G to increase with slip over the broad range from mm to m slip. Sibson-Lachenbruch thermal pressurization of pore water is examined as a possible general fault weakening mechanism for large crustal events. For adiabatic and undrained conditions, with strength given by the effective stress law with a constant friction coefficient f, the thermal properties of water in this context (Lachenbruch, 1980; Mase and Smith, 1988) lead to G = 1.7 (σ n - po) (1 + r) h. Here h is shearing zone thickness, σ n is normal stress, assumed constant during slip, po is ambient pore pressure, and r is the ratio fractional volume change of pore space per unit pore pressure increase divided by the compressibility of the pore fluid. Dilatancy is neglected; if confined to only the early phases of slip, it decreases po from ambient and so increases G, but the effect may be modest. The model predicts exponential decay of strength with slip, with e-folding slip distance 1.7 (1 + r) h / f. The total temperature rise in K is ≈ 0.6 (1 + r) (σ n - po) where the latter factor is in MPa. Estimating r = 1-2 and evaluating σ n - po as overburden minus hydrostatic pore pressure at 7 km as a representative centroidal depth for large crustal events, we obtain G ≈ 1-6 MJ/m2 for h = 2 to 10 mm. Shear zone thicknesses towards the lower end of such a range are suggested by recent field studies (Chester and Chester, 1998), which identify a

  7. A magnetorheological actuation system: test and model

    NASA Astrophysics Data System (ADS)

    John, Shaju; Chaudhuri, Anirban; Wereley, Norman M.

    2008-04-01

    Self-contained actuation systems, based on frequency rectification of the high frequency motion of an active material, can produce high force and stroke output. Magnetorheological (MR) fluids are active fluids whose rheological properties can be altered by the application of a magnetic field. By using MR fluids as the energy transmission medium in such hybrid devices, a valving system with no moving parts can be implemented and used to control the motion of an output cylinder shaft. The MR fluid based valves are configured in the form of an H-bridge to produce bi-directional motion in an output cylinder by alternately applying magnetic fields in the two opposite arms of the bridge. The rheological properties of the MR fluid are modeled using both Bingham plastic and bi-viscous models. In this study, the primary actuation is performed using a compact terfenol-D rod driven pump and frequency rectification of the rod motion is done using passive reed valves. The pump and reed valve configuration along with MR fluidic valves form a compact hydraulic actuation system. Actuator design, analysis and experimental results are presented in this paper. A time domain model of the actuator is developed and validated using experimental data.

  8. Evolution of initially contracting Bianchi class A models in the presence of an ultra-stiff anisotropic pressure fluid

    NASA Astrophysics Data System (ADS)

    Barrow, John D.; Ganguly, Chandrima

    2016-06-01

    We study the behaviour of Bianchi class A universes containing an ultra-stiff isotropic ghost field and a fluid with anisotropic pressures which is also ultra-stiff on the average. This allows us to investigate whether cyclic universe scenarios, like the ekpyrotic model, do indeed lead to isotropization on approach to a singularity (or bounce) in the presence of dominant ultra-stiff pressure anisotropies. We specialize to consider the closed Bianchi type IX universe, and show that when the anisotropic pressures are stiffer on average than any isotropic ultra-stiff fluid then, if they dominate on approach to the singularity, it will be anisotropic. We include an isotropic ultra-stiff ghost fluid with negative energy density in order to create a cosmological bounce at finite volume in the absence of the anisotropic fluid. When the dominant anisotropic fluid is present it leads to an anisotropic cosmological singularity rather than an isotropic bounce. The inclusion of anisotropic stresses generated by collisionless particles in an anisotropically expanding universe is therefore essential for a full analysis of the consequences of a cosmological bounce or singularity in cyclic universes.

  9. Quantitative evaluation of changes in gait after extended cerebrospinal fluid drainage for normal pressure hydrocephalus.

    PubMed

    Yang, Felix; Hickman, Thu-Trang; Tinl, Megan; Iracheta, Christine; Chen, Grace; Flynn, Patricia; Shuman, Matthew E; Johnson, Tatyana A; Rice, Rebecca R; Rice, Isaac M; Wiemann, Robert; Johnson, Mark D

    2016-06-01

    Idiopathic normal pressure hydrocephalus (iNPH) is characterized by gait instability, urinary incontinence and cognitive dysfunction. These symptoms can be relieved by cerebrospinal fluid (CSF) drainage, but the time course and nature of the improvements are poorly characterized. Attempts to prospectively identify iNPH patients responsive to CSF drainage by evaluating presenting gait quality or via extended lumbar cerebrospinal fluid drainage (eLCD) trials are common, but the reliability of such approaches is unclear. Here we combine eLCD trials with computerized quantitative gait measurements to predict shunt responsiveness in patients undergoing evaluation for possible iNPH. In this prospective cohort study, 50 patients presenting with enlarged cerebral ventricles and gait, urinary, and/or cognitive difficulties were evaluated for iNPH using a computerized gait analysis system during a 3day trial of eLCD. Gait speed, stride length, cadence, and the Timed Up and Go test were quantified before and during eLCD. Qualitative assessments of incontinence and cognition were obtained throughout the eLCD trial. Patients who improved after eLCD underwent ventriculoperitoneal shunt placement, and symptoms were reassessed serially over the next 3 to 15months. There was no significant difference in presenting gait characteristics between patients who improved after drainage and those who did not. Gait improvement was not observed until 2 or more days of continuous drainage in most cases. Symptoms improved after eLCD in 60% of patients, and all patients who improved after eLCD also improved after shunt placement. The degree of improvement after eLCD correlated closely with that observed after shunt placement. PMID:26775149

  10. Dielectric elastomer actuators with hydrostatic coupling

    NASA Astrophysics Data System (ADS)

    Carpi, Federico; Frediani, Gabriele; De Rossi, Danilo

    2009-03-01

    The rapidly growing adoption of dielectric elastomer (DE) actuators as a high performance EAP technology for many kinds of new applications continuously opens new technical challenges, in order to take always the most from each adopted device and actuating configuration. This paper presents a new type of DE actuators, which show attractive potentialities for specific application needs. The concept here proposed adopts an incompressible fluid to mechanically couple active and passive parts. The active parts work according to the DE actuation principle, while the passive parts represent the end effector, in contact with the load. The fluid is used to transfer actuation hydrostatically from an active to a passive part and, then, to the load. This can provide specific advantages, including improved safety and less stringent design constraints for the architecture of the actuator, especially for soft end effectors. Such a simple concept can be readily implemented according to different shapes and intended functionalities of the resulting actuators. The paper describes the structure and the performance of the first prototype devices developed so far.

  11. Pressure-temperature-fluid constraints for the Emmaville-Torrington emerald deposit, New South Wales, Australia: Fluid inclusion and stable isotope studies

    NASA Astrophysics Data System (ADS)

    Loughrey, Lara; Marshall, Dan; Jones, Peter; Millsteed, Paul; Main, Arthur

    2012-06-01

    The Emmaville-Torrington emeralds were first discovered in 1890 in quartz veins hosted within a Permian metasedimentary sequence, consisting of meta-siltstones, slates and quartzites intruded by pegmatite and aplite veins from the Moule Granite. The emerald deposit genesis is consistent with a typical granite-related emerald vein system. Emeralds from these veins display colour zonation alternating between emerald and clear beryl. Two fluid inclusion types are identified: three-phase (brine+vapour+halite) and two-phase (vapour+liquid) fluid inclusions. Fluid inclusion studies indicate the emeralds were precipitated from saline fluids ranging from approximately 33 mass percent NaCl equivalent. Formational pressures and temperatures of 350 to 400 °C and approximately 150 to 250 bars were derived from fluid inclusion and petrographic studies that also indicate emerald and beryl precipitation respectively from the liquid and vapour portions of a two-phase (boiling) system. The distinct colour zonations observed in the emerald from these deposits is the first recorded emerald locality which shows evidence of colour variation as a function of boiling. The primary three-phase and primary two-phase FITs are consistent with alternating chromium-rich `striped' colour banding. Alternating emerald zones with colourless beryl are due to chromium and vanadium partitioning in the liquid portion of the boiling system. The chemical variations observed at Emmaville-Torrington are similar to other colour zoned emeralds from other localities worldwide likely precipitated from a boiling system as well.

  12. Actuator device for artificial leg

    NASA Technical Reports Server (NTRS)

    Burch, J. L. (Inventor)

    1976-01-01

    An actuator device is described for moving an artificial leg of a person having a prosthesis replacing an entire leg and hip joint. The device includes a first articulated hip joint assembly carried by the natural leg and a second articulated hip joint assembly carried by the prosthesis whereby energy from the movement of the natural leg is transferred by a compressible fluid from the first hip joint assembly to the second hip joint assembly for moving the artificial leg.

  13. Peristaltic pump made of dielectric elastomer actuators

    NASA Astrophysics Data System (ADS)

    Lotz, Peter; Matysek, Marc; Schlaak, Helmut F.

    2009-03-01

    The functional principle of peristaltic motion is inspired by the pattern in which hollow organs move. The technology of dielectric elastomer actuators provides the possibility to design a very compact peristaltic pump. The geometries of the whole pump and the actuator elements have been determined by numerical simulations of the mechanical behaviour and the fluid dynamics. With eight independent actuators the pumping channel is self-sealing and there is no need for any valves. The first generation of this pump is able to generate flow rates up to 0.36 μl/min.

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

    NASA Technical Reports Server (NTRS)

    Leslie, Ian H.

    1989-01-01

    Three models have been applied to very rapid compression of oxygen in a dead-ended tube. Pressures as high as 41 MPa (6000 psi) leading to peak temperatures of 1400 K are predicted. These temperatures are well in excess of the autoignition temperature (750 K) of teflon, a frequently used material for lining hoses employed in oxygen service. These findings are in accord with experiments that have resulted in ignition and combustion of the teflon, leading to the combustion of the stainless steel braiding and catastrophic failure. The system analyzed was representative of a capped off-high-pressure oxygen line, which could be part of a larger system. Pressurization of the larger system would lead to compression in the dead-end line, and possible ignition of the teflon liner. The model consists of a large plenum containing oxygen at the desired pressure (500 to 6000 psi). The plenum is connected via a fast acting valve to a stainless steel tube 2 cm inside diameter. Opening times are on the order of 15 ms. Downstream of the valve is an orifice sized to increase filling times to around 100 ms. The total length from the valve to the dead-end is 150 cm. The distance from the valve to the orifice is 95 cm. The models describe the fluid mechanics and thermodynamics of the flow, and do not include any combustion phenomena. A purely thermodynamic model assumes filling to be complete upstream of the orifice before any gas passes through the orifice. This simplification is reasonable based on experiment and computer modeling. Results show that peak temperatures as high as 4800 K can result from recompression of the gas after expanding through the orifice. An approximate transient model without an orifice was developed assuming an isentropic compression process. An analytical solution was obtained. Results indicated that fill times can be considerably shorter than valve opening times. The third model was a finite difference, 1-D transient compressible flow model. Results from

  15. Carbonation by fluid-rock interactions at high-pressure conditions: Implications for carbon cycling in subduction zones

    NASA Astrophysics Data System (ADS)

    Piccoli, Francesca; Vitale Brovarone, Alberto; Beyssac, Olivier; Martinez, Isabelle; Ague, Jay J.; Chaduteau, Carine

    2016-07-01

    Carbonate-bearing lithologies are the main carbon carrier into subduction zones. Their evolution during metamorphism largely controls the fate of carbon, regulating its fluxes between shallow and deep reservoirs. Recent estimates predict that almost all subducted carbon is transferred into the crust and lithospheric mantle during subduction metamorphism via decarbonation and dissolution reactions at high-pressure conditions. Here we report the occurrence of eclogite-facies marbles associated with metasomatic systems in Alpine Corsica (France). The occurrence of these marbles along major fluid-conduits as well as textural, geochemical and isotopic data indicating fluid-mineral reactions are compelling evidence for the precipitation of these carbonate-rich assemblages from carbonic fluids during metamorphism. The discovery of metasomatic marbles brings new insights into the fate of carbonic fluids formed in subducting slabs. We infer that rock carbonation can occur at high-pressure conditions by either vein-injection or chemical replacement mechanisms. This indicates that carbonic fluids produced by decarbonation reactions and carbonate dissolution may not be directly transferred to the mantle wedge, but can interact with slab and mantle-forming rocks. Rock-carbonation by fluid-rock interactions may have an important impact on the residence time of carbon and oxygen in subduction zones and lithospheric mantle reservoirs as well as carbonate isotopic signatures in subduction zones. Furthermore, carbonation may modulate the emission of CO2 at volcanic arcs over geological time scales.

  16. A fluid inclusion study of fluid pressure and salinity variations in the footwall of the rector branch thrust, North Carolina, U.S.A.

    NASA Astrophysics Data System (ADS)

    O'Hara, Kieran; Haak, Amy

    1992-05-01

    Last melting and homogenization temperatures of fluid inclusions from plastically deformed bedding-parallel quartz veins in the footwall of the Rector Branch thrust, North Carolina, were studied as a function of distance from the thrust. Fluid inclusions and microstructures in mylonitic rocks within the thrust zone were also examined. Fluid inclusions in quartz veins which display evidence for intracrystalline plasticity (e.g. subgrain polygonization) occur along subgrain boundaries and have higher homogenization temperatures ( Tn) and a wider range (120-320°C) compared to less deformed samples. Maximum Th values, which approach the temperature of deformation (300 ± 20° C), apparently reflect leakage of inclusions along subgrain boundaries. Minimum Th values (120-160°C), on the other hand, record near lithostatic conditions (2.6 kb) at 300°C. Maximum last melting temperatures ( Tm) increase from -20 to -4°C with decreasing distance to the thrust, corresponding to a decrease in salinity of the fluid from 23 to 3 wt% (NaCl equivalent). The decrease in salinity towards the fault is interpreted as due to infiltration of the fault at depth (to approximately 10 km) by surface derived waters during periods of fault zone dilatancy. Inclusions along healed microcracks in quartz from the fault zone display higher salinity (17-26 wt% NaCl equiv.) and are interpreted to reflect enhanced fluid-rock interaction in the fault zone due to hydration reactions. The fluid pressure and salinity variations are consistent with a combined dilatancy-hydraulic fracturing model for the Rector Branch thrust. Previously documented bulk rock volume losses for this fault zone are inferred to have been produced by the fluxing of the fault zone with undersaturated surface derived fluids.

  17. Fluid Shifts Before, During and After Prolonged Space Flight and Their Association with Intracranial Pressure and Visual Impairment

    NASA Technical Reports Server (NTRS)

    Stenger, Michael; Hargens, Alan; Dulchavsky, Scott

    2014-01-01

    Future human space travel will primarily consist of long duration missions onboard the International Space Station or exploration class missions to Mars, its moons, or nearby asteroids. Current evidence suggests that long duration missions might increase risk of permanent ocular structural and functional changes, possibly due to increased intracranial pressure resulting from a spaceflight-induced cephalad (headward) fluid shift.

  18. Fast circulation of cerebrospinal fluid: an alternative perspective on the protective role of high intracranial pressure in ocular hypertension.

    PubMed

    Wostyn, Peter; De Groot, Veva; Van Dam, Debby; Audenaert, Kurt; Killer, Hanspeter Esriel; De Deyn, Peter Paul

    2016-05-01

    As ocular hypertension refers to a condition in which the intraocular pressure is consistently elevated but without development of glaucoma, study of it may provide important clues to factors that may play a protective role in glaucoma. β-amyloid, one of the key histopathological findings in Alzheimer's disease, has been reported to increase by chronic elevation of intraocular pressure in animals with experimentally induced ocular hypertension and to cause retinal ganglion cell death, pointing to similarities in molecular cell death mechanisms between glaucoma and Alzheimer's disease. On the other hand, recent studies have reported that intracranial pressure is higher in patients with ocular hypertension compared with controls, giving rise to the idea that elevated intracranial pressure may provide a protective effect for the optic nerve by decreasing the trans-lamina cribrosa pressure difference. The speculation that the higher intracranial pressure reported in ocular hypertension patients may protect against glaucoma mainly through a lower trans-lamina cribrosa pressure difference remains at least questionable. Here, we present an alternative viewpoint, according to which the protective effect of higher intracranial pressure could be due, at least in part, to a pressure-independent mechanism, namely faster cerebrospinal fluid production leading to increased cerebrospinal fluid turnover with enhanced removal of potentially neurotoxic waste products that accumulate in the optic nerve. This suggests a new hypothesis for glaucoma, which, just like Alzheimer's disease, may be considered then as an imbalance between production and clearance of neurotoxins, including β-amyloid. If confirmed, then strategies to improve cerebrospinal fluid flow are reasonable and could provide a new therapeutic approach for stopping the neurotoxic β-amyloid pathway in glaucoma. PMID:26691953

  19. The influence of coughing on cerebrospinal fluid pressure in an in vitro syringomyelia model with spinal subarachnoid space stenosis

    PubMed Central

    2009-01-01

    Background The influence of coughing, on the biomechanical environment in the spinal subarachnoid space (SAS) in the presence of a cerebrospinal fluid flow stenosis, is thought to be an important etiological factor in craniospinal disorders, including syringomyelia (SM), Chiari I malformation, and hydrocephalus. The aim of this study was to investigate SAS and syrinx pressures during simulated coughing using in vitro models and to provide information for the understanding of the craniospinal fluid system dynamics to help develop better computational models. Methods Four in vitro models were constructed to be simplified representations of: 1) non-communicating SM with spinal SAS stenosis; 2) non-communicating SM due to spinal SAS stenosis with a distensible spinal column; 3) non-communicating SM post surgical removal of a spinal SAS stenosis; and 4) a spinal SAS stenosis due to spinal trauma. All of the models had a flexible spinal cord. To simulate coughing conditions, an abrupt CSF pressure pulse (~ 5 ms) was imposed at the caudal end of the spinal SAS by a computer-controlled pump. Pressure measurements were obtained at 4 cm intervals along the spinal SAS and syrinx using catheter tip transducers. Results Pressure measurements during a simulated cough, showed that removal of the stenosis was a key factor in reducing pressure gradients in the spinal SAS. The presence of a stenosis resulted in a caudocranial pressure drop in the SAS, whereas pressure within the syrinx cavity varied little caudocranially. A stenosis in the SAS caused the syrinx to balloon outward at the rostral end and be compressed at the caudal end. A >90% SAS stenosis did not result in a significant Venturi effect. Increasing compliance of the spinal column reduced forces acting on the spinal cord. The presence of a syrinx in the cord when there was a stenosis in the SAS, reduced pressure forces in the SAS. Longitudinal pressure dissociation acted to suck fluid and tissue caudocranially in the

  20. Mechanisms of proximal tubule sodium transport regulation that link extracellular fluid volume and blood pressure.

    PubMed

    McDonough, Alicia A

    2010-04-01

    One-hundred years ago, Starling articulated the interdependence of renal control of circulating blood volume and effective cardiac performance. During the past 25 years, the molecular mechanisms responsible for the interdependence of blood pressure (BP), extracellular fluid volume (ECFV), the renin-angiotensin system (RAS), and sympathetic nervous system (SNS) have begun to be revealed. These variables all converge on regulation of renal proximal tubule (PT) sodium transport. The PT reabsorbs two-thirds of the filtered Na(+) and volume at baseline. This fraction is decreased when BP or perfusion pressure is increased, during a high-salt diet (elevated ECFV), and during inhibition of the production of ANG II; conversely, this fraction is increased by ANG II, SNS activation, and a low-salt diet. These variables all regulate the distribution of the Na(+)/H(+) exchanger isoform 3 (NHE3) and the Na(+)-phosphate cotransporter (NaPi2), along the apical microvilli of the PT. Natriuretic stimuli provoke the dynamic redistribution of these transporters along with associated regulators, molecular motors, and cytoskeleton-associated proteins to the base of the microvilli. The lipid raft-associated NHE3 remains at the base, and the nonraft-associated NaPi2 is endocytosed, culminating in decreased Na(+) transport and increased PT flow rate. Antinatriuretic stimuli return the same transporters and regulators to the body of the microvilli associated with an increase in transport activity and decrease in PT flow rate. In summary, ECFV and BP homeostasis are, at least in part, maintained by continuous and acute redistribution of transporter complexes up and down the PT microvilli, which affect regulation of PT sodium reabsorption in response to fluctuations in ECFV, BP, SNS, and RAS. PMID:20106993

  1. The validity of the one-dimensional fluid model of electrical breakdown in synthetic air at low pressure

    NASA Astrophysics Data System (ADS)

    Jovanović, A. P.; Stankov, M. N.; Marković, V. Lj.; Stamenković, S. N.

    2013-12-01

    In this letter the validity of the fluid model used to simulate the electrical breakdown in air at low pressure is discussed. The new method for the determination of the ionization source term for the mixed gases is proposed. Paschen's curve obtained by the fluid model is compared to the available experimental data. The electron and ions density profiles calculated by the fluid model are presented. Based on Ohm's law, the current and voltage waveforms are calculated and compared to the ones measured by the oscilloscope in the synthetic-air filled tube with stainless-steel electrodes. It is shown that the one-dimensional fluid model can be used for modeling the electrical breakdown at pd values higher than Paschen's minimum and to determine stationary values of electron and ions densities.

  2. Fluid dynamics of pressurized, entrained coal gasifiers. Tenth quarterly technical progress report, April 1, 1996--June 30, 1996

    SciTech Connect

    Louge, M.Y.

    1996-10-01

    Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena Re erosion, heat transfer and solid capture. In this context, we are conducting a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea is to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employ a unique entrained gas-solid flow facility with the flexibility to recycle -rather than discard- gases other than air. By matching five dimensionless parameters, suspensions in mixtures of helium, carbon dioxide and sulfur hexafluoride simulate the effects of pressure and scale-up on the fluid dynamics of PECGs. Because it operates under cold, atmospheric conditions, the laboratory facility is ideal for detailed measurements.

  3. The influence of hydrostatic pressure on trans-synovial fluid movement and on capsular expansion in the rabbit knee.

    PubMed

    Levick, J R

    1979-04-01

    1. The flow of Ringer solution or paraffin oil from an infusion reservoir into the cavity of the knee (stifle) joint was measured in anesthetized rabbits, as intraarticular pressure was progressively elevated from its intrinsic slightly subatmospheric value to +25 cm H2O. 2. Paraffin oil did not penetrate the tissues lining the joint cavity, yet a continuous flow of oil occurred into the joint at pressures over +2 cm H2O. It was concluded that the joint investment behaved as a visco-elastic tissue. 3. Trans-synovial flow of Ringer solution was calculated by correcting the observed inflow for visco-elastic expansion of the joint capsule. At intra-articular pressures +2 to +9 cm H2O, trans-synovial flow increased at an average rate of 0.49 microliter min-1.cm H2O-1. The hydraulic conductivity of the synovium was therefore similar to that of subcutaneous connective tissue. At around +9 cm H2O, the 'breaking pressure', the slope of the pressure-flow relationship increased by almost sixfold to 2.81 microliter min-1.cm H2O-1. 4. Changes in joint visco-elasticity, synovial surface area, blood pressure, colloid osmotic pressure of plasma and of joint fluid, and inflammation were excluded as explanations of the marked increase in rate of fluid absorption, which is tentatively attributed to increases in synovial hydraulic conductivity. Some physiological and clinical implications of the data are discussed. PMID:458708

  4. Hybrid simulations of magnetic reconnection with kinetic ions and fluid electron pressure anisotropy

    DOE PAGESBeta

    Le, A.; Daughton, W.; Karimabadi, H.; Egedal, J.

    2016-03-16

    We present the first hybrid simulations with kinetic ions and recently developed equations of state for the electron fluid appropriate for reconnection with a guide field. The equations of state account for the main anisotropy of the electron pressure tensor.Magnetic reconnection is studied in two systems, an initially force-free current sheet and a Harris sheet. The hybrid model with the equations of state is compared to two other models, hybrid simulations with isothermal electrons and fully kinetic simulations. Including the anisotropicequations of state in the hybrid model provides a better match to the fully kinetic model. In agreement with fullymore » kinetic results, the main feature captured is the formation of an electron current sheet that extends several ion inertial lengths. This electron current sheet modifies the Hall magnetic field structure near the X-line, and it is not observed in the standard hybrid model with isotropic electrons. The saturated reconnection rate in this regime nevertheless remains similar in all three models. Here, implications for global modeling are discussed.« less

  5. Vibration-based damage detection for filament wound pressure vessel filled with fluid

    NASA Astrophysics Data System (ADS)

    Zhou, W.; Wu, Z.; Li, H.

    2008-03-01

    Filament wound pressure vessels have been extensively used in industry and engineering. The existing damage detection and health monitoring methods for these vessels, such as X-ray and ultrasonic scan, can not meet the requirement of online damage detection; moreover optical grating fibre can only sense the local damage, but not the damage far away from the location of sensors. Vibration-based damage detection methods have the potential to meet such requirements. There methods are based on the fact that damages in a structure results in a change in structural dynamic characteristics. A damage detection method based on a residual associated with output-only subspace-based modal identification and global or focused chi^2-tests built on that residual has been proposed and successfully experimented on a variety of test cases. The purpose of this work is to describe the damage detection method and apply this method to assess the composite structure filled with fluid. The results of identification and damage detection will be presented.

  6. Tumor interstitial fluid pressure as an early-response marker for anticancer therapeutics.

    PubMed

    Ferretti, Stephane; Allegrini, Peter R; Becquet, Mike M; McSheehy, Paul Mj

    2009-09-01

    Solid tumors have a raised interstitial fluid pressure (IFP) due to high vessel permeability, low lymphatic drainage, poor perfusion, and high cell density around the blood vessels. To investigate tumor IFP as an early-response biomarker, we have tested the effect of seven anticancer chemotherapeutics including cytotoxics and targeted cytostatics in 13 experimental tumor models. IFP was recorded with the wick-in-needle method. Models were either ectopic or orthotopic and included mouse and rat syngeneic as well as human xenografts in nude mice. The mean basal IFP was between 4.4 and 15.2mm Hg; IFP was lowest in human tumor xenografts and highest in rat syngeneic models. Where measured, basal IFP correlated positively with relative tumor blood volume (rTBV) determined by dynamic contrast-enhanced magnetic resonance imaging. Most chemotherapeutics sooner (2 or 3 days) or later (6 or 7 days) lowered tumor IFP significantly, and the cytotoxic patupilone caused the greatest decrease in IFP. In rat mammary orthotopic BN472 tumors, significant drug-induced decreases in IFP and rTBV correlated positively with each other for both patupilone and the cytostatic vatalanib. In the two orthotopic models studied, early decreases in IFP were significantly (P < or = .005) correlated with late changes in tumor volume. Thus, drug-induced decreases in tumor IFP are an early marker of response to therapy, which could aid clinical development. PMID:19724681

  7. Electrical conductivity of lawsonite and dehydrating fluids at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Manthilake, Geeth; Mookherjee, Mainak; Bolfan-Casanova, Nathalie; Andrault, Denis

    2015-09-01

    Lawsonite is a calcium-aluminum bearing hydrous silicate mineral with CaAl2Si2O7(OH)2.H2O stoichiometry. It is thermodynamically stable in the hydrated oceanic crust. Low-velocity anomalies observed in the cold subducted slabs have been related to the unusual shear wave velocities of lawsonite eclogite. However, electrical conductivity of lawsonite at high pressure and temperature remains unknown. In this study, we measured the electrical conductivity of lawsonite at 7 GPa, and temperatures ranging from 298 K-1320 K. At 1173 K, the electrical conductivity of lawsonite is around 10-1 S/m. A sharp increase of electrical conductivity is observed at temperatures exceeding the dehydration ~1258 K. The high electrical conductivity up to 101 S/m observed in our experiments is due to the presence of highly conductive fluid and could explain the low resistivity observed at 150-250 km depths in subduction zone settings such as NE Japan, northern, and central Chile.

  8. Diffusion tensor imaging of idiopathic normal-pressure hydrocephalus and the cerebrospinal fluid tap test.

    PubMed

    Kang, Kyunghun; Yoon, Uicheul; Choi, Woohyuk; Lee, Ho-Won

    2016-05-15

    We evaluated relationships between diffusion tensor imaging (DTI) findings and clinical profiles in idiopathic normal-pressure hydrocephalus (INPH) patients, along with differences in DTI parameters between cerebrospinal fluid tap test (CSFTT) responders and non-responders. Fifty-four INPH patients constituted the final group for analysis. Fractional anisotropy (FA), axial diffusivity, radial diffusivity, and mean diffusivity were assessed using atlas-based tract-mapping methods on 20 different fiber tracts. Uncorrected results revealed that CSFTT non-responders, when compared to responders, exhibited lower FA in the left anterior thalamic radiation (ATR), left cingulum-hippocampus (CgH), and left inferior fronto-occipital fasciculus (IFO) and higher axial diffusivity, radial diffusivity, and mean diffusivity in the left CgH and left inferior longitudinal fasciculus (ILF). FA values in the ATR (bilateral), corticospinal tract (right), IFO (bilateral), and ILF (bilateral) were negatively correlated with Unified Parkinson's Disease Rating Scale motor scores. In the right CgH, FA values showed significant positive correlations with Korean-Mini Mental State Examination scores and negative correlations with Clinical Dementia Rating Scale scores. Our findings may suggest a possibility for considering microstructural changes of white matter in patients with ventriculomegaly as potential imaging markers for the prediction of CSFTT responders. Unique patterns of white matter microstructural changes, as measured using DTI, might underlie impairments in distinct symptom domains in patients with INPH. PMID:27084223

  9. Fluid model of a single striated filament in an RF plasma jet at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Sigeneger, F.; Loffhagen, D.

    2016-06-01

    The filaments occurring in an RF argon atmospheric-pressure plasma jet are investigated by means of numerical modelling. The special setup of the jet leads to the establishment of filaments in very regular modes under certain conditions. Such a single filament generated in the active volume between the powered and grounded electrode is described by a time-dependent, spatially two-dimensional fluid model. This self-consistent model includes those mechanisms which can lead to constriction and stratification such as the heat balance equation and the dependence of electron collision rate coefficients on the ionization degree. A curved filament with a contracted radial profile of particle densities and very pronounced striations along its trace has been obtained by the model calculation for a typical discharge parameter condition of the plasma jet. The resulting calculated electron density and mean energy in the filament as well as the period length of the striations agree qualitatively with recent experimental observations. The analysis of the ionization budget makes clear that the constriction and stratification is mainly caused by the different nonlinear dependences of ionization and recombination rates on the electron density.

  10. Interstitial Fluid Pressure and Vascularity of Intradermal and Intramuscular Human Tumor Xenografts

    SciTech Connect

    Gulliksrud, Kristine; Galappathi, Kanthi; Rofstad, Einar K.

    2011-05-01

    Purpose: High interstitial fluid pressure (IFP) in tumors has been shown to be associated with poor prognosis. Mechanisms underlying the intertumor heterogeneity in IFP were investigated in this study. Methods and Materials: A-07 melanoma xenografts were transplanted intradermally or intramuscularly in BALB/c nu/nu mice. IFP was measured in the center of the tumors with a Millar catheter. Tumor blood perfusion and extracellular volume fraction were assessed by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). The necrotic fraction, vascular density, and vessel diameters of the tumors were determined by image analysis of histological preparations. Results: Significant intertumor heterogeneity in IFP, blood perfusion, and microvascular morphology was observed whether the tumors were transplanted intradermally or intramuscularly. High IFP was mainly a consequence of high resistance to blood flow caused by low vessel diameters in either transplantation site. IFP decreased with increasing blood perfusion in intradermal tumors and increased with increasing blood perfusion in intramuscular tumors, mainly because the morphology of the tumor microvasculature differed systematically between the two tumor models. Conclusion: The potential of DCE-MRI as a noninvasive method for assessing the IFP of tumors may be limited because any relationship between IFP and blood perfusion may differ with the tumor growth site.

  11. High-Pressure Transport Properties Of Fluids: Theory And Data From Levitated Drops At Combustion-Relevant Temperatures

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth; Ohsaka, Kenichi

    2003-01-01

    Although the high pressure multicomponent fluid conservation equations have already been derived and approximately validated for binary mixtures by this PI, the validation of the multicomponent theory is hampered by the lack of existing mixing rules for property calculations. Classical gas dynamics theory can provide property mixing-rules at low pressures exclusively. While thermal conductivity and viscosity high-pressure mixing rules have been documented in the literature, there is no such equivalent for the diffusion coefficients and the thermal diffusion factors. The primary goal of this investigation is to extend the low pressure mixing rule theory to high pressures and validate the new theory with experimental data from levitated single drops. The two properties that will be addressed are the diffusion coefficients and the thermal diffusion factors. To validate/determine the property calculations, ground-based experiments from levitated drops are being conducted.

  12. Fluid source and pressure temperature conditions of high-salinity fluids in syn-tectonic veins from the Northeastern Apuan Alps (Northern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Montomoli, Chiara; Ruggieri, Giovanni; Carosi, Rodolfo; Dini, Andrea; Genovesi, Marianna

    Structural studies on syn-tectonic veins cropping out in the northeastern sector of the Apuan Alps metamorphic complex (Northern Apennines, Italy) revealed two sets of veins: (1) type A fibrous veins within the “Scisti sericitici Formation”, related to a late-D1 tectonic phase; (2) B-veins, within the “Diaspri Formation” that developed between late-D1 and D2 tectonic phases. The mineralogy of the A (quartz, chlorite, hematite with minor amounts of apatite, allanite-(Ce), thorite and synchysite) and B-veins (quartz only) reflects the mineralogical composition of the host-rocks: quartz, chlorite, white mica and accessory minerals (apatite, zircon, titanite) occur in the “Scisti sericitici Formation”, while quartz is the main phase in the “Diaspri Formation”. The study of fluid inclusions trapped in quartz crystals of the syn-tectonic veins shows that the inclusions are always oversaturated in NaCl at room temperature and their salinities range from 29.5 to 37 wt.% NaCl equiv. The isochore of the earliest trapped fluid inclusions (type IA; primary inclusions in fiber quartz of A veins), coupled with mineralogical geothermometric data, constrains the pressure-temperature conditions to around 325-300 MPa and 370-380 °C during the late-D1 phase. Subsequent trapping of inclusion types IIA, IIB, IIIA, IIIB and VB in the two vein sets probably occurred during a pressure-temperature decrease (down to 220-245 MPa and 260-270 °C) at a lithostatic thermal gradient of 30 °C/km. Type IVB inclusions, on the other hand, were probably trapped at lower pressure (between lithostatic and hydrostatic conditions) during a transient pressure drop resulting from fault-valve action. SEM/EDS analyses on salts precipitated within opened inclusions confirmed the NaCl-rich compositions of the trapped fluids and also revealed the presence of minor amounts of Ca, K and Mn in the salts. A fluid circulation model, based on mineralogical and fluid inclusion data, was proposed for

  13. Hydrostatically coupled dielectric elastomer actuators for tactile displays and cutaneous stimulators

    NASA Astrophysics Data System (ADS)

    Carpi, Federico; Frediani, Gabriele; De Rossi, Danilo

    2010-04-01

    Hydrostatic coupling has been recently reported as a means to improve versatility and safety of dielectric elastomer (DE) actuators. Hydrostatically coupled DE actuators rely on an incompressible fluid that mechanically couples a DE-based active part to a passive part interfaced to the load. In this paper, we present ongoing development of bubble-like versions of such transducers, made of silicone and oil. In particular, the paper describes millimeter-scale actuators, currently being developed as soft, light, acoustically silent and cheap devices for two types of applications: tactile displays and cutaneous stimulators. In both cases, the most significant advantages of the proposed technology are represented by high versatility for design (due to the fluid based transmission mechanism), tailorable stiffness perceived by the user (obtained by adjusting the internal fluid pressure), and suitable electrical safety (enabled by both a passive interface with the user and the insulating internal fluid). Millimeter-scale prototypes showed a resonance frequency of about 250 Hz, which represents the value at which Pacinian cutaneous mechanoreceptors exhibit maximum sensitivity; this provides an optimum condition to eventually code tactile information dynamically, either in combination or as an alternative to static driving.

  14. Engine having a variable valve actuation system

    DOEpatents

    Hefler, Gregory W.

    2005-10-12

    An engine has a cylinder head having a first surface and a second surface spaced from the first surface. A valve is moveably connected to the cylinder head. A rocker arm is connected to the valve, and a rocker shaft having a first location spaced a maximum distance from the cylinder head is connected to the rocker arm. A support member has and an actuator fluid passage network. The actuator fluid passage network defines a volume. The support member is connected to the cylinder head and is positioned such that a majority of the volume of the actuator fluid passage network is between the first location of the rocker shaft and the second surface of the cylinder head.

  15. Engine having a variable valve actuation system

    DOEpatents

    Hefler, Gregory W.

    2004-10-12

    An engine has a cylinder head having a first surface and a second surface spaced from the first surface. A valve is moveably connected to the cylinder head. A rocker arm is connected to the valve, and a rocker shaft having a first location spaced a maximum distance from the cylinder head is connected to the rocker arm. A support member has and an actuator fluid passage network. The actuator fluid passage network defines a volume. The support member is connected to the cylinder head and is positioned such that a majority of the volume of the actuator fluid passage network is between the first location of the rocker shaft and the second surface of the cylinder head.

  16. Performance study of a hydrogen powered metal hydride actuator

    NASA Astrophysics Data System (ADS)

    Mainul Hossain Bhuiya, Md; Kim, Kwang J.

    2016-04-01

    A thermally driven hydrogen powered actuator integrating metal hydride hydrogen storage reactor, which is compact, noiseless, and able to generate smooth actuation, is presented in this article. To test the plausibility of a thermally driven actuator, a conventional piston type actuator was integrated with LaNi5 based hydrogen storage system. Copper encapsulation followed by compaction of particles into pellets, were adopted to improve overall thermal conductivity of the reactor. The operation of the actuator was thoroughly investigated for an array of operating temperature ranges. Temperature swing of the hydride reactor triggering smooth and noiseless actuation over several operating temperature ranges were monitored for quantification of actuator efficiency. Overall, the actuator generated smooth and consistent strokes during repeated cycles of operation. The efficiency of the actuator was found to be as high as 13.36% for operating a temperature range of 20 °C-50 °C. Stress-strain characteristics, actuation hysteresis etc were studied experimentally. Comparison of stress-strain characteristics of the proposed actuator with traditional actuators, artificial muscles and so on was made. The study suggests that design modification and use of high pressure hydride may enhance the performance and broaden the application horizon of the proposed actuator in future.

  17. Ferroelectric Fluid Flow Control Valve

    NASA Technical Reports Server (NTRS)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    1999-01-01

    An active valve is controlled and driven by external electrical actuation of a ferroelectric actuator to provide for improved passage of the fluid during certain time periods and to provide positive closure of the valve during other time periods. The valve provides improved passage in the direction of flow and positive closure in the direction against the flow. The actuator is a dome shaped internally prestressed ferroelectric actuator having a curvature, said dome shaped actuator having a rim and an apex. and a dome height measured from a plane through said rim said apex that varies with an electric voltage applied between an inside and an outside surface of said dome shaped actuator.

  18. High-angle reverse faulting in northern New Brunswick, Canada, and its implications for fluid pressure levels

    NASA Astrophysics Data System (ADS)

    Sibson, Richard H.

    The 1982 Miramichi earthquake sequence in northern New Brunswick included four shocks in the magnitude range, 5.7 > m, > 5.0, and extensive aftershock activity. Rupturing occurred within granitic terrain on a pair of NNE—SSW-striking, opposite-facing, high-angle reverse faults which converge at the mainshock focal depth of ≈7 km. It seems probable that the earthquake sequence involved the reactivation under horizontal compression of an existing set of steep normal faults, perhaps derived from Mesozoic rifting of the Atlantic continental margin. The symmetry of the V-shaped profile of faults in WNW—ESE section suggests that the maximum principal compressive stress (σ 1) during reactivation was subhorizontal and the least principal stress (σ 3) was subvertical, so that the reactivation angle between σ 1 and the faults corresponded to the 50-65° dip of the faults. Stress analysis of the conditions for frictional reactivation of existing cohesionless faults shows that pore-fluid pressures approaching or exceeding lithostatic values are required for reshear at such high reactivation angles, with the implication that the earthquake sequence was triggered by locally elevated fluid pressure. While the source and composition of the inferred high pressure fluids are uncertain, a mixed H 2O—CO 2 fluid of mantle origin seems most likely.

  19. Microbial Diversity in Ultra-High-Pressure Rocks and Fluids from the Chinese Continental Scientific Drilling Project in China

    PubMed Central

    Zhang, Gengxin; Dong, Hailiang; Xu, Zhiqin; Zhao, Donggao; Zhang, Chuanlun

    2005-01-01

    Microbial communities in ultra-high-pressure (UHP) rocks and drilling fluids from the Chinese Continental Scientific Drilling Project were characterized. The rocks had a porosity of 1 to 3.5% and a permeability of ∼0.5 mDarcy. Abundant fluid and gas inclusions were present in the minerals. The rocks contained significant amounts of Fe2O3, FeO, P2O5, and nitrate (3 to 16 ppm). Acridine orange direct counting and phospholipid fatty acid analysis indicated that the total counts in the rocks and the fluids were 5.2 × 103 to 2.4 × 104 cells/g and 3.5 × 108 to 4.2 × 109 cells/g, respectively. Enrichment assays resulted in successful growth of thermophilic and alkaliphilic bacteria from the fluids, and some of these bacteria reduced Fe(III) to magnetite. 16S rRNA gene analyses indicated that the rocks were dominated by sequences similar to sequences of Proteobacteria and that most organisms were related to nitrate reducers from a saline, alkaline, cold habitat; however, some phylotypes were either members of a novel lineage or closely related to uncultured clones. The bacterial communities in the fluids were more diverse and included Proteobacteria, Bacteroidetes, gram-positive bacteria, Planctomycetes, and Candidatus taxa. The archaeal diversity was lower, and most sequences were not related to any known cultivated species. Some archaeal sequences were 90 to 95% similar to sequences recovered from ocean sediments or other subsurface environments. Some archaeal sequences from the drilling fluids were >93% similar to sequences of Sulfolobus solfataricus, and the thermophilic nature was consistent with the in situ temperature. We inferred that the microbes in the UHP rocks reside in fluid and gas inclusions, whereas those in the drilling fluids may be derived from subsurface fluids. PMID:15933024

  20. Thermally actuated valve

    NASA Technical Reports Server (NTRS)

    Silver, R. H.

    1973-01-01

    Effective seal in one-shot valve is made by shrink-fitting ball within cylinder; thermal expansion of cylinder, caused by contiguous source of heat, will release ball and open valve. Valve can also be adapted for repeated operation and made capable of being opened without pressurized fluid.

  1. The solubility of rocks in metamorphic fluids: A model for rock-dominated conditions to upper mantle pressure and temperature

    NASA Astrophysics Data System (ADS)

    Galvez, Matthieu E.; Manning, Craig E.; Connolly, James A. D.; Rumble, Douglas

    2015-11-01

    Fluids exert a key control on the mobility of elements at high pressure and temperature in the crust and mantle. However, the prediction of fluid composition and speciation in compositionally complex fluid-rock systems, typically present in subduction zones, has been hampered by multiple challenges. We develop a computational framework to study the role of phase equilibria and complex solid-solutions on aqueous fluid speciation in equilibrium with rocks to 900 °C and 3 GPa. This is accomplished by merging conventional phase-equilibrium modeling involving electrolyte-free molecular fluids, with an electrostatic approach to model solute-solute and solute-solvent interactions in the fluid phase. This framework is applied to constrain the activity ratios, composition of aqueous solutes, and pH of a fluid in equilibrium with a pelite lithology. Two solvent compositions are considered: pure H2O, and a COH fluid generated by equilibration of H2O and graphite. In both cases, we find that the pH is alkaline. Disparities between the predicted peralkalinity of our fluid ([Na ] + [K ]) / [Al ] ∼ 6 to 12 and results from independent mineral solubility experiments (∼2) point to the presence of Na-K-Al-Si polymers representing ca. 60 to 85% of the total K and Al content of the fluid at 600 °C and 2.2 GPa, and to an important fraction of dissolved Ca and Mg not accounted for in present speciation models. The addition of graphite to the system reduces the relative permittivity by ca. 40% at elevated T and low P, triggers the formation of C-bearing anions, and brings the pH closer to neutrality by up to 0.6 units at low T. This ionic C pool represents up to 45 mol% of the fluid ligands at elevated P, and is dominant at low P despite the low ionic strength of the fluid (<0.05). The present study offers new possibilities for exploring redox- pH dependent processes that govern volatile, major and trace element partitioning between rocks and fluids in experimental or natural

  2. Calibration and assessment of a fluid-filled catheter-transducer system for the measurement of ventricular diastolic pressures.

    PubMed

    Brennan, E G; O'Hare, N J

    1998-08-01

    A concise set of experiments is described which detail the calibration of a fluid-filled catheter-transducer system and the assessment of a widely used industrial algorithm for determining end-diastolic pressures using that system. First, the static response of the catheter-transducer system was evaluated in vitro by inserting the catheter into a graduated cylinder of saline. Twelve observations revealed a systematic undervaluation of pressure by the system of 1.78 mmHg with 95% limits of agreement ranging from -6.22 to 2.66 mmHg. Next, the dynamic response was evaluated in vivo by performing a transient step-response test. The system had an adequate dynamic response (fn = 11.12 Hz) for intraventricular pressure waveform replication but was considerably underdamped (beta = 0.16). Finally, the ability of the analysis software to detect the point of end-diastole and evaluate end-diastolic pressure was assessed by comparing system output with manual measurements of end-diastolic pressure in 12 patients. The mean difference between manually determined end-diastolic pressure and system output was 0.83 +/- 1.68 mm Hg. This difference is clinically insignificant and shows that the more noteworthy source of error is in the manometer-transducer emphasizing the importance of calibration and quality assurance of fluid-filled catheter-transducer systems for use in clinical cardiology or research. PMID:9735891

  3. Interstitial fluid pressure, vascularity and metastasis in ectopic, orthotopic and spontaneous tumours

    PubMed Central

    Lunt, Sarah Jane; Kalliomaki, Tuula MK; Brown, Allison; Yang, Victor X; Milosevic, Michael; Hill, Richard P

    2008-01-01

    Background High tumour interstitial fluid pressure (IFP) has been adversely linked to poor drug uptake in patients, and to treatment response following radiotherapy in cervix cancer patients. In this study we measured IFP values in a selection of murine and xenograft models, spontaneously arising or transplanted either intramuscularly (i/m) or orthotopically and analysed their relationship to tumour vascularity and metastatic spread. Methods KHT-C murine fibrosarcoma, ME180 and SiHa human cervix carcinoma were grown either intramuscularly (i/m), sub-cutaneously (s/c) or orthotopically. Polyoma middle-T (MMTV-PyMT) transgenic spontaneous mammary tumours were studied either as spontaneous tumours or following orthotopic or i/m transplantation. IFP was measured in all tumours using the wick-in-needle method. Spontaneous metastasis formation in the lungs or lymph nodes was assessed in all models. An immunohistochemical analysis of tumour hypoxia, vascular density, lymphatic vascular density and proliferation was carried out in ME180 tumours grown both i/m and orthotopically. Blood flow was also assessed in the ME180 model using high-frequency micro-ultrasound functional imaging. Results Tumour IFP was heterogeneous in all the models irrespective of growth site: KHT-C i/m: 2–42 mmHg, s/c: 1–14 mmHg, ME180: i/m 5–68 mmHg, cervix 4–21 mmHg, SiHa: i/m 20–56 mmHg, cervix 2–26 mmHg, MMTV-PyMT: i/m: 13–45 mmHg, spontaneous 2–20 mmHg and transplanted 2–22 mmHg. Additionally, there was significant variation between individual tumours growing in the same mouse, and there was no correlation between donor and recipient tumour IFP values. Metastatic dissemination to the lungs or lymph nodes demonstrated no correlation with tumour IFP. Tumour hypoxia, proliferation, and lymphatic or blood vessel density also showed no relationship with tumour IFP. Speckle variance analysis of ultrasound images showed no differences in vascular perfusion between ME180 tumours grown

  4. Active Control of F/A-18 Vertical Tail Buffeting using Piezoelectric Actuators

    NASA Technical Reports Server (NTRS)

    Sheta, Essam F.; Moses, Robert W.; Huttsell, Lawerence J.; Harrand, Vincent J.

    2003-01-01

    Vertical tail buffeting is a serious multidisciplinary problem that limits the performance of twin-tail fighter aircraft. The buffet problem occurs at high angles of attack when the vortical flow breaks down ahead of the vertical tails resulting in unsteady and unbalanced pressure loads on the vertical tails. This paper describes a multidisciplinary computational investigation for buffet load alleviation of full F/A-18 aircraft using distributed piezoelectric actuators. The inboard and outboard surfaces of the vertical tail are equipped with piezoelectric actuators to control the buffet responses in the first bending and torsion modes. The electrodynamics of the smart structure are expressed with a three-dimensional finite element model. A single-input-single-output controller is designed to drive the active piezoelectric actuators. High-fidelity multidisciplinary analysis modules for the fluid dynamics, structure dynamics, electrodynamics of the piezoelectric actuators, fluid-structure interfacing, and grid motion are integrated into a multidisciplinary computing environment that controls the temporal synchronization of the analysis modules. Peak values of the power spectral density of tail tip acceleration are reduced by as much as 22% in the first bending mode and by as much as 82% in the first torsion mode. RMS values of tip acceleration are reduced by as much as 12%.

  5. Nonlinear dynamic modeling for smart material electro-hydraulic actuator development

    NASA Astrophysics Data System (ADS)

    Larson, John P.; Dapino, Marcelo J.

    2013-03-01

    Smart material electro-hydraulic actuators use hydraulic rectification by one-way check valves to amplify the motion of smart materials, such as magnetostrictives and piezoelectrics, in order to create compact, lightweight actuators. A piston pump driven by a smart material is combined with a hydraulic cylinder to form a self-contained, power-by-wire actuator that can be used in place of a conventional hydraulic system without the need for hydraulic lines and a centralized pump. The performance of an experimental actuator driven by a 12.7 mm diameter, 114 mm length Terfenol-D rod is evaluated over a range of applied input frequencies, loads, and currents. The peak performance achieved is 37 W, moving a 220 N load at a rate of 17 cm/s and producing a blocked pressure of 12.5 MPa. Additional tests are conducted to quantify the dynamic behavior of the one-way reed valves using a scanning laser vibrometer to identify the frequency response of the reeds and the effect of the valve seat and fluid mass loading. A lumped-parameter model is developed for the system that includes valve inertia and fluid response nonlinearities, and the model results are compared with the experimental data.

  6. In situ multipurpose time-resolved spectrometer for monitoring nanoparticle generation in a high-pressure fluid

    SciTech Connect

    Wei, Shaoyu; Saitow, Ken-ichi

    2012-07-15

    We developed a multipurpose time-resolved spectrometer for studying the dynamics of nanoparticles generated by pulsed-laser ablation (PLA) in a high-pressure fluid. The apparatus consists of a high-pressure optical cell and three spectrometers for in situ measurements. The optical cell was designed for experiments at temperatures up to 400 K and pressures up to 30 MPa with fluctuations within {+-}0.1% h{sup -1}. The three spectrometers were used for the following in situ measurements at high pressures: (i) transient absorption spectrum measurements from 350 to 850 nm to investigate the dynamics of nanoparticle generation from nanoseconds to milliseconds after laser irradiation, (ii) absorption spectrum measurements from 220 to 900 nm to observe the time evolution of nanoparticles from seconds to hours after laser ablation, and (iii) dynamic light scattering measurements to track nanoparticles with sizes from 10 nm to 10 {mu}m in the time range from seconds to hours after laser ablation. By combining these three spectrometers, we demonstrate in situ measurements of gold nanoparticles generated by PLA in supercritical fluids. This is the first report of in situ time-resolved measurements of the dynamics of nanoparticles generated in a supercritical fluid.

  7. Investigation of the Pressure Distribution in a Flow of a Viscous Fluid in a Pipeline Under Hydraulic-Shock Conditions with Account for the Relaxation Properties of the Fluid

    NASA Astrophysics Data System (ADS)

    Kudinov, I. V.; Kudinov, V. A.

    2014-03-01

    An exact analytical solution of the hyperbolic equation defining the pressure distribution in a viscous fluid flowing in a pipeline under the conditions of a hydraulic shock with account for the relaxation properties of the fluid has been obtained. It was established, based on a comparison of calculation and experimental data, that the relaxation properties of such a fluid determine the degree of nonstationarity of its fl ow and, hence, the wall friction of the fluid or its shear stress. It is shown that, in the case of nonstationary movement of a viscous fluid in a pipeline under hydraulic-shock conditions, the pressure jump caused by the hydraulic shock differs markedly in form (it is longer in time) from that in the case of quasi-stationary movement of this fluid under the identical conditions. The same effect (although weaker) was detected for decrease in the indicated pressure jump.

  8. Fluid resuscitation guided by sublingual partial pressure of carbon dioxide during hemorrhagic shock in a porcine model.

    PubMed

    Xu, Jiefeng; Ma, Linhao; Sun, Shijie; Lu, Xiaoye; Wu, Xiaobo; Li, Zilong; Tang, Wanchun

    2013-04-01

    To avoid aggressive fluid resuscitation during hemorrhagic shock, fluid resuscitation is best guided by a specific measurement of tissue perfusion. We investigated whether fluid resuscitation guided by sublingual PCO2 would reduce the amount of resuscitation fluid without compromising the outcomes of hemorrhagic shock. Ten male domestic pigs weighing between 34 and 37 kg were used. Forty-five percent of estimated blood volume was removed during an interval of 1 h. The animals were then randomized to receive fluid resuscitation based on either sublingual PCO2 or blood pressure (BP). In the sublingual PCO2-guided group, resuscitation was initiated when sublingual PCO2 exceeded 70 Torr and stopped when it decreased to 50 Torr. In the BP-guided group, resuscitation was initiated when mean aortic pressure decreased to 60 mmHg and stopped when it increased to 90 mmHg. First, Ringer's lactate solution (RLS) of 30 mL kg was administered; subsequently, the shed blood was transfused if sublingual PCO2 remained greater than 50 Torr in the sublingual PCO2-guided group or mean aortic pressure was less than 90 mmHg in the BP-guided group. All the animals were monitored for 4 h and observed for an additional 68 h. In the sublingual PCO2-guided group, fluid resuscitation was required in only 40% of the animals. In addition, a significantly lower volume of RLS (170 ± 239 mL, P = 0.005 vs. BP-guided group) was administered without the need for blood infusion in this group. However, in the BP-guided group, all the animals required a significantly larger volume of fluid (955 ± 381 mL), including both RLS and blood. There were no differences in postresuscitation tissue microcirculation, myocardial and neurologic function, and 72-h survival between groups. During hemorrhagic shock, fluid resuscitation guided by sublingual PCO2 significantly reduced the amount of resuscitation fluid without compromising the outcomes of hemorrhagic shock. PMID:23364438

  9. High-pressure migmatites as source of fluids during subduction and crustal thickening: the case of the Ulten Zone

    NASA Astrophysics Data System (ADS)

    Braga, Roberto; Massonne, Hans-Joachim; Mazza, Sarah; Bondi, Mirella

    2010-05-01

    In subduction and continent collision zones, submersed continental crust will dehydrate and eventually melt at peak pressure-temperature (PT) conditions or during subsequent exhumation, thus forming migmatitic units like those exposed in denuded orogens. If we consider a sialic continental crust containing hydrous phases (micas ± amphibole ± epidote), the melt fraction generated at pressure generally below 4 GPa will be a hydrous granitic magma. Experimental petrology [1] and geochemistry [2] indicate that high-pressure and relatively cool granitic magmas could incorporate as much as 10 or more wt% H2O, depending on PT path, partial melting degree and initial hydrous fluid content (as intergranular free fluid and H2O stored in hydrous minerals) of the source rock. As a consequence, high-pressure migmatites produced during the submersion of continental crust in a subduction or continental collision zone may act as a sink of hydrous fluids as long as the crust is partially molten. Upon cooling and decompression towards subsolidus conditions, the fluid stored in the migmatitic leucosome will be released. These fluids have the potential to remove incompatible elements (e.g., large ion lithophile elements; light rare earth elements) from the crustal reservoir and, eventually in subduction zones, enhance the crystallization of hydrous and carbonated metasomatic phases such as amphibole, phlogopite and carbonates into the adjacent mantle [3]. However, what we direct observe and measure in high-pressure migmatites occurring in orogenic belts is the fluid linked to the actual hydrated phases, the amount and composition of which might have changed due to subsolidus evolution and late fluid influx, unrelated with the precedent geodynamic evolution. In order to estimate the fluid contribution of a crustal unit involved in an orogenic collisional setting, we have modelled the fluid content of the Ulten Zone crust, which records high PT metamorphism accompanied by white mica

  10. Effects of coarse grain size distribution and fine particle content on pore fluid pressure and shear behavior in experimental debris flows

    NASA Astrophysics Data System (ADS)

    Kaitna, Roland; Palucis, Marisa C.; Yohannes, Bereket; Hill, Kimberly M.; Dietrich, William E.

    2016-02-01

    Debris flows are typically a saturated mixture of poorly sorted particles and interstitial fluid, whose density and flow properties depend strongly on the presence of suspended fine sediment. Recent research suggests that grain size distribution (GSD) influences excess pore pressures (i.e., pressure in excess of predicted hydrostatic pressure), which in turn plays a governing role in debris flow behaviors. We report a series of controlled laboratory experiments in a 4 m diameter vertically rotating drum where the coarse particle size distribution and the content of fine particles were varied independently. We measured basal pore fluid pressures, pore fluid pressure profiles (using novel sensor probes), velocity profiles, and longitudinal profiles of the flow height. Excess pore fluid pressure was significant for mixtures with high fines fraction. Such flows exhibited lower values for their bulk flow resistance (as measured by surface slope of the flow), had damped fluctuations of normalized fluid pressure and normal stress, and had velocity profiles where the shear was concentrated at the base of the flow. These effects were most pronounced in flows with a wide coarse GSD distribution. Sustained excess fluid pressure occurred during flow and after cessation of motion. Various mechanisms may cause dilation and contraction of the flows, and we propose that the sustained excess fluid pressures during flow and once the flow has stopped may arise from hindered particle settling and yield strength of the fluid, resulting in transfer of particle weight to the fluid. Thus, debris flow behavior may be strongly influenced by sustained excess fluid pressures controlled by particle settling rates.

  11. Micromachined electrostatic vertical actuator

    DOEpatents

    Lee, Abraham P.; Sommargren, Gary E.; McConaghy, Charles F.; Krulevitch, Peter A.

    1999-10-19

    A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

  12. Preferential dissolution of SiO2 from enstatite to H2 fluid under high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Shinozaki, Ayako; Kagi, Hiroyuki; Hirai, Hisako; Ohfuji, Hiroaki; Okada, Taku; Nakano, Satoshi; Yagi, Takehiko

    2016-04-01

    Stability and phase relations of coexisting enstatite and H2 fluid were investigated in the pressure and temperature regions of 3.1-13.9 GPa and 1500-2000 K using laser-heated diamond-anvil cells. XRD measurements showed decomposition of enstatite upon heating to form forsterite, periclase, and coesite/stishovite. In the recovered samples, SiO2 grains were found at the margin of the heating hot spot, suggesting that the SiO2 component dissolved in the H2 fluid during heating, then precipitated when its solubility decreased with decreasing temperature. Raman and infrared spectra of the coexisting fluid phase revealed that SiH4 and H2O molecules formed through the reaction between dissolved SiO2 and H2. In contrast, forsterite and periclase crystals were found within the hot spot, which were assumed to have replaced the initial orthoenstatite crystals without dissolution. Preferential dissolution of SiO2 components of enstatite in H2 fluid, as well as that observed in the forsterite H2 system and the quartz H2 system, implies that H2-rich fluid enhances Mg/Si fractionation between the fluid and solid phases of mantle minerals.

  13. Ultra high efficiency/low pressure supercritical fluid chromatography with superficially porous particles for triglyceride separation.

    PubMed

    Lesellier, E; Latos, A; de Oliveira, A Lopes

    2014-01-31

    This paper reports the development of the separation of vegetable oil triglycerides (TG) in supercritical chromatography (SFC), using superficially porous particles (SPPs). The SPP, having a small diameter (2-3μm), provide a higher theoretical plate number (N), which allows to improve separation of critical pairs of compounds. However, compared to fully porous particles of larger diameter (5μm), the pressure drop is also increased. Fortunately, supercritical fluids have a low viscosity, which allows coupling several columns to achieve high N values, while maintaining flow rate above 1ml/min, ensuring a ultra high efficiency (UHE) at low pressure (LP) (below 40MPa), with regards to the one reached with liquid and sub-two micron particles (around 100MPa). The use of two detector systems (UV and ELSD) connected in series to the UHE-LP-SFC system provides complementary responses, due to their specific detection principles. Working in a first part with three coupled Kinetex C18 columns (45cm total length), the effect of modifier nature and percentage were studied with two reference oils, argan and rapeseed, chosen for their different and well-known TG composition. The analytical method was developed from previous studies performed with fully porous particles (FPP). Optimized conditions with three Kinetex were as follows: 17°C, 12% of ACN/MeOH (90/10; v/v). With these conditions, and by using an increased length of Kinetex C18 column (60cm), another additional column was selected from ten different commercial SPP C18 bonded phases, by applying a Derringer function on varied parameters: theoretical plate number (TPN), separation index (SI) for critical pairs of peaks (the peaks of compounds difficult to separate due to subtle structural differences), the analysis duration, and the total peak number. This function normalizes the values of any parameters, between 0 and 1, from the worst value to the better, allowing to take account of various parameters in the final

  14. Spectral element modelling of fault-plane reflections arising from fluid pressure distributions

    NASA Astrophysics Data System (ADS)

    Haney, Matthew; Snieder, Roel; Ampuero, Jean-Paul; Hofmann, Ronny

    2007-08-01

    The presence of fault-plane reflections in seismic images, besides indicating the locations of faults, offers a possible source of information on the properties of these poorly understood zones. To better understand the physical mechanism giving rise to fault-plane reflections in compacting sedimentary basins, we numerically model the full elastic wavefield via the spectral element method (SEM) for several different fault models. Using well log data from the South Eugene Island field, offshore Louisiana, we derive empirical relationships between the elastic parameters (e.g. P-wave velocity and density) and the effective-stress along both normal compaction and unloading paths. These empirical relationships guide the numerical modelling and allow the investigation of how differences in fluid pressure modify the elastic wavefield. We choose to simulate the elastic wave equation via SEM since irregular model geometries can be accommodated and slip boundary conditions at an interface, such as a fault or fracture, are implemented naturally. The method we employ for including a slip interface retains the desirable qualities of SEM in that it is explicit in time and, therefore, does not require the inversion of a large matrix. We perform a complete numerical study by forward modelling seismic shot gathers over a faulted earth model using SEM followed by seismic processing of the simulated data. With this procedure, we construct post-stack time-migrated images of the kind that are routinely interpreted in the seismic exploration industry. We dip filter the seismic images to highlight the fault-plane reflections prior to making amplitude maps along the fault plane. With these amplitude maps, we compare the reflectivity from the different fault models to diagnose which physical mechanism contributes most to observed fault reflectivity. To lend physical meaning to the properties of a locally weak fault zone characterized as a slip interface, we propose an equivalent

  15. Electromagnetic rotational actuation.

    SciTech Connect

    Hogan, Alexander Lee

    2010-08-01

    There are many applications that need a meso-scale rotational actuator. These applications have been left by the wayside because of the lack of actuation at this scale. Sandia National Laboratories has many unique fabrication technologies that could be used to create an electromagnetic actuator at this scale. There are also many designs to be explored. In this internship exploration of the designs and fabrications technologies to find an inexpensive design that can be used for prototyping the electromagnetic rotational actuator.

  16. Therapeutic implications of tumor interstitial fluid pressure in subcutaneous RG-2 tumors1

    PubMed Central

    Navalitloha, Yot; Schwartz, Erica S.; Groothuis, Elizabeth N.; Allen, Cathleen V.; Levy, Robert M.; Groothuis, Dennis R.

    2006-01-01

    Increased interstitial fluid pressure (IFP) in brain tumors results in rapid removal of drugs from tumor extracellular space. We studied the effects of dexamethasone and hypothermia on IFP in s.c. RG-2 rat gliomas, because they could potentially be useful as means of maintaining drug concentrations in human brain tumors. We used dexamethasone, external hypothermia, combined dexamethasone and hypothermia, and infusions of room temperature saline versus chilled saline. We measured tumor IFP and efflux half-time of 14C-sucrose from tumors. In untreated s.c. tumors, IFP was 9.1 ± 2.1 mmHg, tumor temperature was 33.7°C ± 0.7°C, and efflux half-time was 7.3 ± 0.7 min. Externally induced hypothermia decreased tumor temperature to 8.9°C ± 2.9°C, tumor IFP decreased to 3.2 ± 1.1 mmHg, and efflux half-time increased to 13.5 min. Dexamethasone decreased IFP to 2.4 ± 1.0 mmHg and increased efflux half-time to 15.4 min. Combined hypothermia and dexamethasone further increased the efflux half-time to 17.6 min. We tried to lower the tumor temperature by chilling the infusion solution, but at an infusion rate of 48 μl/min, the efflux rate was the same for room temperature saline and 15°C saline. The efflux rate was increased in both infusion groups, which suggests that efflux due to tumor IFP and that of the infusate were additive. Since lowering tumor IFP decreases efflux from brain tumors, it provides a means to increase drug residence time, which in turn increases the time-concentration exposure product of therapeutic drug available to tumor. PMID:16775223

  17. Measurement of cardiac left ventricular pressure in conscious rats using a fluid-filled catheter.

    PubMed

    Schenk, J; Hebden, A; McNeill, J H

    1992-05-01

    A fluid-filled catheter consisting of 100 cm of PE50 polyethylene tubing welded to 7 cm of PE10 polyethylene tubing (PE50/PE10) was constructed for the purpose of measuring the rate of left ventricular pressure development (+dP/dt) in conscious, freely moving rats. Prior to in vivo experiments, four PE50/PE10 catheters were randomly selected, and their natural frequencies and damping ratios were determined using a square wave impact. The mean (n = 4), natural frequency of these catheters was shown to be 35.0 +/- 5.5 Hz, and the mean damping ratio was 0.83 +/- 0.10. Natural frequency plotted against increasing PE50 tubing length was shown to have a slope of -0.44 Hz/cm with a correlation coefficient of 0.99. The effect of the 7-cm PE10 tubing segment on the catheter damping ratio was also demonstrated. One of the four PE50/PE10 type catheters exhibited a damping ratio of 0.74 +/- 0.09. When the 7-cm PE10 tube was removed, the damping ratio was reduced to 0.31 +/- 0.04. Left ventricular +dP/dt obtained in conscious rats with a PE50/PE10 catheter (n = 7; 6300 +/- 300 mmHg/sec) was significantly less than the +dP/dt obtained using a 100-cm PE50 catheter (n = 6; 9400 +/- 400 mmHg/sec). The results of this study make it clear that the PE50/PE10 catheter is suitable for the measurement of left ventricular +dP/dt in the conscious rat, and that catheter design has a profound influence on both the catheter natural frequency and damping ratio. PMID:1498344

  18. [Investigation of high pore fluid pressure in the Uinta Basin, Utah]. Final report

    SciTech Connect

    1998-11-01

    High pore fluid pressures, approaching lithostatic, are observed in the deepest sections of the Uinta basin, Utah. The authors analyzed the cause of the anomalous overpressures with a 3-dimensional, numerical model of the evolution of the basin, including compaction disequilibrium and hydrocarbon generation as possible mechanisms. The numerical model builds the basin through time, coupling the structural, thermal and hydrodynamic evolution, and includes in situ hydrocarbon generation and migration. They used the evolution model to evaluate overpressure mechanisms and oil migration patterns for different possible conceptual models of the geologic history. Model results suggest that observed overpressures in the Uinta basin are probably caused by ongoing oil generation in strata with specific conditions of permeability, relative permeability, TOC content, and oil viscosity. They conducted a sensitivity analysis that suggests for oil generation to cause overpressures, the necessary conditions are: oil viscosity is {approximately}0.05 cP or higher, intrinsic permeability is {approximately}5 {times} 10{sup {minus}18} m{sup 2} or lower, and source rock TOC values are {approximately}0.5% or higher. The authors also analyzed hydrocarbon migration patterns in the basin and how they are affected by the basin`s structural history. Oil migration patterns produced by the model are consistent with published oil production maps: oil moves from the deep Altamont source rocks toward Redwash, the eastern Douglas Creek Arch area, and southward towards the Sunnyside tar-sands and Book Cliffs. Peak oil generation occurs from the time of maximum burial in the mid-Tertiary ({approximately}35 to {approximately}30 Ma). Most differential uplift of the basin`s flanks probably occurs well after this time, and most oil migration to the basin`s southern and eastern flanks occurs prior to uplift of these flanks. Model results show that if the basin`s flanks are uplifted too soon, reduced

  19. Pressure locking test results

    SciTech Connect

    DeWall, K.G.; Watkins, J.C.; McKellar, M.G.; Bramwell, D.

    1996-12-01

    The U.S. Nuclear Regulatory Commission (NRC), Office of Nuclear Regulatory Research, is funding the Idaho National Engineering Laboratory (INEL) in performing research to provide technical input for their use in evaluating responses to Generic Letter 95-07, {open_quotes}Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves.{close_quotes} Pressure locking and thermal binding are phenomena that make a closed gate valve difficult to open. This paper discusses only the pressure locking phenomenon in a flexible-wedge gate valve; the authors will publish the results of their thermal binding research at a later date. Pressure locking can occur when operating sequences or temperature changes cause the pressure of the fluid in the bonnet (and, in most valves, between the discs) to be higher than the pressure on the upstream and downstream sides of the disc assembly. This high fluid pressure presses the discs against both seats, making the disc assembly harder to unseat than anticipated by the typical design calculations, which generally consider friction at only one of the two disc/seat interfaces. The high pressure of the bonnet fluid also changes the pressure distribution around the disc in a way that can further contribute to the unseating load. If the combined loads associated with pressure locking are very high, the actuator might not have the capacity to open the valve. The results of the NRC/INEL research discussed in this paper show that the relationship between bonnet pressure and pressure locking stem loads appears linear. The results also show that for this valve, seat leakage affects the bonnet pressurization rate when the valve is subjected to thermally induced pressure locking conditions.

  20. Self-actuating reactor shutdown system

    DOEpatents

    Barrus, Donald M.; Brummond, Willian A; Peterson, Leslie F.

    1988-01-01

    A control system for the automatic or self-actuated shutdown or "scram" of a nuclear reactor. The system is capable of initiating scram insertion by a signal from the plant protection system or by independent action directly sensing reactor conditions of low-flow or over-power. Self-actuation due to a loss of reactor coolant flow results from a decrease of pressure differential between the upper and lower ends of an absorber element. When the force due to this differential falls below the weight of the element, the element will fall by gravitational force to scram the reactor. Self-actuation due to high neutron flux is accomplished via a valve controlled by an electromagnet and a thermionic diode. In a reactor over-power, the diode will be heated to a change of state causing the electromagnet to be shorted thereby actuating the valve which provides the changed flow and pressure conditions required for scramming the absorber element.

  1. Practical expressions for the internal energy and pressure of Yukawa fluids.

    PubMed

    Khrapak, Sergey A; Thomas, Hubertus M

    2015-02-01

    Simple practical expressions that allow estimation of thermodynamic properties of Yukawa fluids in a wide range of coupling, up to the fluid-solid phase transition, are presented. These expressions demonstrate excellent agreement with the available results from numerical simulations. The approach provides simple and accurate tools to estimate thermodynamic properties of Yukawa fluids and related systems in a broad range of parameters. PMID:25768619

  2. AMSD Cryo Actuator Testing

    NASA Technical Reports Server (NTRS)

    Mullette, Mark; Matthews, Gary; Russell, Kevin (Technical Monitor)

    2002-01-01

    The actuator technology required for AMSD and subsequently NGST are critical in the successful development for future cryogenic systems. Kodak has undertaken an extensive test plan to determine the performance of the force actuators developed under the AMSD program. These actuators are currently in testing at MSFC and are expected to finish this test cycle in early June 2002.

  3. Dual drive actuators

    NASA Technical Reports Server (NTRS)

    Packard, D. T.

    1982-01-01

    A new class of electromechanical actuators is described. These dual drive actuators were developed for the NASA-JPL Galileo Spacecraft. The dual drive actuators are fully redundant and therefore have high inherent reliability. They can be used for a variety of tasks, and they can be fabricated quickly and economically.

  4. Squeeze Film Problems of Long Partial Journal Bearings for Non-Newtonian Couple Stress Fluids with Pressure-Dependent Viscosity

    NASA Astrophysics Data System (ADS)

    Lin, Jaw-Ren; Chu, Li-Ming; Hung, Chi-Ren; Lu, Rong-Fang

    2011-09-01

    According to the experimental work of C. Barus in Am. J. Sci. 45, 87 (1893) [1], the dependency of liquid viscosity on pressure is exponential. Therefore, we extend the study of squeeze film problems of long partial journal bearings for Stokes non-Newtonian couple stress fluids by considering the pressure-dependent viscosity in the present paper. Through a small perturbation technique, we derive a first-order closed-form solution for the film pressure, the load capacity, and the response time of partial-bearing squeeze films. It is also found that the non-Newtonian couple-stress partial bearings with pressure-dependent viscosity provide better squeeze-film characteristics than those of the bearing with constant-viscosity situation.

  5. Static spherically-symmetric perfect fluids with pressure equal to energy density

    NASA Astrophysics Data System (ADS)

    Yadav, R. B. S.; Saini, S. L.

    1991-12-01

    An exact, static, and spherically-symmetric solution is presented of Einstein's field equations for a homogeneous perfect fluid core surrounded by a field of Zel'dovich's fluid which is asymptotically homaloidal. The equation of state for the fluid is taken as p = p, which describes several important cases, e.g., radiation, relativistic degenerate Fermi gas, and probably very dense baryon matter. If the fluid satisfies p = p and if in addition its motion is irrotational, then such a source has the same stress energy tensor as that of a massless scalar field.

  6. Fluid Pressure Increases in Hydrothermal Systems Induced by Seismic Waves: Possible Triggers of Earthquakes and Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Roeloffs, E.

    2002-12-01

    That seismic waves trigger microseismicity in hydrothermal settings hundreds of km from the epicenter is plausibly linked to seismic-wave-induced fluid pressure changes at these distances. Although fluid pressure decreases have been observed in diverse settings, in the hydrothermal system at Long Valley, California, that seismic waves from earthquakes increase fluid pressure or discharge. Other published data, from thermal springs in Japan, Yellowstone, and Klamath Falls, Oregon, support the idea that seismic waves have induced pressure and discharge changes and that, in hydrothermal systems, these changes are usually increases. Temperature increases in seafloor hydrothermal vents within days after earthquakes as distant as 220 km imply, moreover, that seismic waves enhance conductance of vertical fluid flow pathways. The influence of seismic waves (wavelengths of km), on hot, fluid-filled subsurface fractures (apertures of mm to cm) could proceed by several mechanisms. Local fluid flow induced at crack walls could remove mineral seals. Spatially uniform acceleration can move gas bubbles relative to denser liquid and solid phases. Thermal expansion can elevate pressure around hot fluid that has penetrated upward. By lowering effective stress and directly weakening faults that are themselves flow paths, seismic waves could initiate processes leading to volcanic eruptions or other earthquakes where sufficient subsurface magma or elastic strain energy have previously accumulated. This type of earthquake-volcano linkage could explain why volcanos statistically erupt more frequently up to 5 years after M>7 earthquakes hundreds of km distant. For example, 11 months elapsed after the Ms 7.8 Luzon (Phillipines) earthquake before Mount Pinatubo erupted on June 15, 1991, 100 km away. Steam emission and 3 M4+ earthquakes in the Pinatubo area followed within days of the Luzon event, however, and a hydrothermal explosion on April 2 started the continuous unrest that built to

  7. Numerical simulation of blood flow and interstitial fluid pressure in solid tumor microcirculation based on tumor-induced angiogenesis

    NASA Astrophysics Data System (ADS)

    Zhao, Gaiping; Wu, Jie; Xu, Shixiong; Collins, M. W.; Long, Quan; König, Carola S.; Jiang, Yuping; Wang, Jian; Padhani, A. R.

    2007-10-01

    A coupled intravascular transvascular interstitial fluid flow model is developed to study the distributions of blood flow and interstitial fluid pressure in solid tumor microcirculation based on a tumor-induced microvascular network. This is generated from a 2D nine-point discrete mathematical model of tumor angiogenesis and contains two parent vessels. Blood flow through the microvascular network and interstitial fluid flow in tumor tissues are performed by the extended Poiseuille’s law and Darcy’s law, respectively, transvascular flow is described by Starling’s law; effects of the vascular permeability and the interstitial hydraulic conductivity are also considered. The simulation results predict the heterogeneous blood supply, interstitial hypertension and low convection on the inside of the tumor, which are consistent with physiological observed facts. These results may provide beneficial information for anti-angiogenesis treatment of tumor and further clinical research.

  8. Linear instability of pressure-driven channel flow of a Newtonian and a Herschel-Bulkley fluid

    NASA Astrophysics Data System (ADS)

    Sahu, K. C.; Valluri, P.; Spelt, P. D. M.; Matar, O. K.

    2007-12-01

    The linear stability characteristics of pressure-driven two-layer channel flow are considered, wherein a Newtonian fluid layer overlies a layer of a Herschel-Bulkley fluid. A pair of coupled Orr-Sommerfeld eigenvalue equations are derived and solved using an efficient spectral collocation method for cases in which unyielded regions are absent. An asymptotic analysis is also carried out in the long-wave limit, the results of which are in excellent agreement with the numerical predictions. Our analytical and numerical results indicate that increasing the dimensionless yield stress, prior to the formation of unyielded plugs below the interface, is destabilizing. Increasing the shear-thinning tendency of the lower fluid is stabilizing.

  9. [Pressure-dependent outflow resistance in cerebrospinal fluid dynamics: evaluation a calculation model for diagnosis of normal pressure hydrocephalus in an animal experiment with H-Tx rats].

    PubMed

    Meier, U; Kiefer, M

    2001-04-01

    The internationally accepted methods of calculating cerebrospinal fluid dynamics proceed from the assumption of a pressure-independent resistance to CSF outflow. Our new model focusses on the pressure-dependency of this resistance. In it, we monitor the entire pressure course over time, p(t) during and after infusion. A comparison of the pressure rise, On(p), during infusion, and the decrease, Off(p), to the same pressure level, permits the creation of all the formulas for C(p) and R(p). The simultaneous measurement of resistance and compliance during a single intervention allows us to minimize patient exertion. In contrast to the classical methods, it is not necessary for the ICP to reach a plateau. Our mathematical model differs from the static examination model by describing a pressure-dependent slope of the function for the resistance. This has been demonstrated in a study using H-Tx rats. In this way, we are able to take the non-linearity of the CSF resorption into consideration. PMID:11388039

  10. Fluid Pressure, Uplift Erosion and In-situ Stress in the Tiechanshan Anticline of Western Taiwan Fold-thrust Belt

    NASA Astrophysics Data System (ADS)

    Hung, J.; Wu, J.

    2011-12-01

    We define regional fossil and present tops of overpressure by in-situ repeated fluid pressure measurements from over 40 wells and sonic log data from 10 wells in the Tiechanshan Anticline of western Taiwan Fold-thrust Belt. Those boundaries define current fluid hydrostatic and overpressured zones as well as fossil zones before uplift and erosion. The amounts of regional erosion are comparable to those estimated independently from structural cross sections. Results indicate that the uplift and erosion strongly affects the stratigraphic level of overpressured zones, which drop downward in response to the removal of overburden. By adding the drilling mud density along with repeated formation tests, fluid pressures (Pf) were estimated to 5 km depth. Excess fluid pressure values at depths greater than 5 km are derived from extrapolating the linear overpressure gradients from fluid retention depth of ~2 km. Extremely high pore pressures (λ=0.8) are observed at depths below 3.8 km. Lower than hydrostatic pressures (~ 9.47 MPa/km) are observed in the gas-bearing reservoir sandstone. The magnitudes of in-situ stress of vertical stress (Sv) and minimum horizontal stress (Shmin) were measured from density logs and hydrofrac data of leak-off tests and fluid injection, respectively. The gradient of Shmin is ~ 17.46 MPa/km or equivalent to 0.74 of Sv (~23.60 MPa/km). A detailed structure contour map of the top of the reservoir sand, combined with the measured Shmin and Sv, show that the stress state in the Tiechanshan field is predominantly strike-slip (SHmax>SV>Shmin). An upper-bound value of the maximum horizontal stress (SHmax) constrained by frictional limits and the coefficient of friction (μ=0.6) is about 27.36 MPa/km. Caliper logs from two wells show that the mean azimuth of preferred orientation of borehole breakouts are in ~028o N. Consequently, the maximum horizontal stress axis tends 118oN, which is sub-parallel to the far-field plate-convergence direction.

  11. The Effect of Pressure Ratio on Unsteady Fluid-Structure Interaction Characteristics of Ball Type Control Valve

    NASA Astrophysics Data System (ADS)

    Du, Yang; Tu, Shan; Wang, Hongjuan

    Two-way sequential fluid-structure interaction method was used to analyze and discuss the characteristics of unsteady fluid-structure interaction of the complex flow channel of a steam turbine ball type control valve. Research indicates that when the pressure ratio changes as a sine wave, its flow rate occurs a sine wave change, and the maximum flow rate value of 57.46kg•s-1 occurs in the minimum pressure ratio condition. The longitudinal force of the structure domain decreases with the reduction of the pressure ratio, and points to the opposite direction of the flow. The la