Bonneau, Dominique; Souchet, Dominique
2014-01-01
This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.
Load responsive hydrodynamic bearing
Kalsi, Manmohan S.; Somogyi, Dezso; Dietle, Lannie L.
2002-01-01
A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.
Thermo-hydrodynamic lubrication in hydrodynamic bearings
Bonneau, Dominique; Souchet, Dominique
2014-01-01
This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the thermo-hydrodynamic and the thermo-elasto-hydrodynamic lubrication. The algorithms are methodically detailed and each section is thoroughly illustrated.
Hydrodynamic bearing lubricated with magnetic fluids
International Nuclear Information System (INIS)
Urreta, H; Leicht, Z; Sanchez, A; Agirre, A; Kuzhir, P; Magnac, G
2009-01-01
This paper summarizes the work carried out in the development of hydrodynamic lubricated journal bearings with magnetic fluids. Two different fluids have been analyzed, one ferrofluid from FERROTEC APG s10n and one magnetorheological fluid from LORD Corp., MRF122-2ED. Theoretical analysis has been carried out with numerical solutions of Reynolds equation, based on apparent viscosity modulation for ferrofluid and Bingham model for MR fluid. To validate this model, one test bench has been designed, manufactured and set up, where preliminary results shown in this paper demonstrate that magnetic fluids can be used to develop active journal bearings.
Inducer Hydrodynamic Load Measurement Devices
Skelley, Stephen E.; Zoladz, Thomas F.
2002-01-01
Marshall Space Flight Center (MSFC) has demonstrated two measurement devices for sensing and resolving the hydrodynamic loads on fluid machinery. The first - a derivative of the six component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This "rotating balance" was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining both the amplitude and frequency content associated with operating in various cavitation modes. The second device - a high frequency response pressure transducer surface mounted on a rotating component - was merely an extension of existing technology for application in water. MSFC has recently completed experimental evaluations of both the rotating balance and surface-mount transducers in a water test loop. The measurement bandwidth of the rotating balance was severely limited by the relative flexibility of the device itself, resulting in an unexpectedly low structural bending mode and invalidating the higher frequency response data. Despite these limitations, measurements confirmed that the integrated loads on the four-bladed inducer respond to both cavitation intensity and cavitation phenomena. Likewise, the surface-mount pressure transducers were subjected to a range of temperatures and flow conditions in a non-rotating environment to record bias shifts and transfer functions between the transducers and a reference device. The pressure transducer static performance was within manufacturer's specifications and dynamic response accurately followed that of the reference.
Modeling of dynamically loaded hydrodynamic bearings at low Sommerfeld numbers
DEFF Research Database (Denmark)
Thomsen, Kim
Current state of the art within the wind industry dictates the use of conventional rolling element bearings for main bearings. As wind turbine generators increase in size and output, so does the size of the main bearings and accordingly also the cost and potential risk of failure modes. The cost...... and failure risk of rolling element bearings do, however, grow exponentially with the size. Therefore hydrodynamic bearings can prove to be a competitive alternative to the current practice of rolling element bearings and ultimately help reducing the cost and carbon footprint of renewable energy generation....... The challenging main bearing operation conditions in a wind turbine pose a demanding development task for the design of a hydrodynamic bearing. In general these conditions include operation at low Reynolds numbers with frequent start and stop at high loads as well as difficult operating conditions dictated...
On the computation of electrical resistance of hydrodynamic journal bearing
Directory of Open Access Journals (Sweden)
Eleonora Pop
2014-12-01
Full Text Available The paper approaches the mathematical model of electrical resistance of hydrodynamic journal bearing under different parameters of operation so as to predict bearing performance and safe load carrying capacity. The currents circulating in the journal bearing of electrical machine causes reducing of lifespan by appearance of pitting on their surface and the degradation of the lubricant. In a hydrodynamic journal bearing, the zone of minimum film thickness, load-carrying oil film varies along the circumference of a bearing through its length. This has been found to form a capacitor of varying capacitance between the journal and the bearings dependent on permittivity of the lubricant used, the bearing length, the eccentricity ratio and the clearance ratio. Besides this, load-carrying on oil film offers resistance that depends on operating parameters and resistivity of the lubricant.
Numerical analysis of hydrodynamic journal bearings lubricated with ferrofluid
Montazeri, H.
2008-01-01
The current work focuses on studying the hydrodynamic characteristics of flow in journal bearings lubricated with ferrofluid. The bearing has an infinite length and operates under incompressible laminar flow and steady conditions. Assuming linear behaviour for the magnetic material of the
Measured displacement coefficients of an adjustable hydrodynamic journal rotor bearing
Martin, J. K.
2013-01-01
In simulating a proposed machine tool grinding wheel design, a bearing system comprised a stationary spindle or shaft with fluid film bearings supporting a belt driven rotor. Two hydrodynamic bearings acted in parallel, and built into the shaft were the means to effect continuous pro-active adjustments to their performance characteristics during operation, irrespective of load, speed and other running conditions. The design is outlined, as is a specially constructed test rig for evaluating it...
Active Vibration Control of Hydrodynamic Journal Bearings
Tůma, J.; Šimek, J.; Škuta, J.; Los, J.; Zavadil, J.
Rotor instability is one of the most serious problems of high-speed rotors supported by sliding bearings. With constantly increasing parameters, new machines problems with rotor instability are encountered more and more often. Even though there are many solutions based on passive improvement of the bearing geometry to enlarge the operational speed range of the journal bearing, the paper deals with a working prototype of a system for the active vibration control of journal bearings with the use of piezoactuators. The actively controlled journal bearing consists of a movable bushing, which is actuated by two piezoactuators. It is assumed that the journal vibration is measured by a pair of proximity probes. Force produced by piezoactuators and acting at the bushing is controlled according to error signals derived from the proximity probe output signals. The active vibration control was tested with the use of a test rig, which consists of a rotor supported by two controllable journal bearings and driven by an inductive motor up to 23,000 rpm. As it was proved by experiments the active vibration control extends considerably the range of the rotor operational speed.
Steady State Thermo-Hydrodynamic Analysis of Two-Axial groove and Multilobe Hydrodynamic Bearings
Directory of Open Access Journals (Sweden)
C. Bhagat
2014-12-01
Full Text Available Steady state thermo-hydrodynamic analysis of two axial groove and multi lobe oil journal bearings is performed in this paper. To study the steady state thermo-hydrodynamic characteristics Reynolds equation is solved simultaneously along with the energy equation and heat conduction equation in bush and shaft. The effect of groove geometry, cavitation in the fluid film, the recirculation of lubricant, shaft speed has also been taken into account. Film temperature in case of three-lobe bearing is found to be high as compared to other studied bearing configurations. The data obtained from this analysis can be used conveniently in the design of such bearings, which are presented in dimensionless form.
Konstantinos Katsaros; Dimitrios A. Bompos; Pantelis G. Nikolakopoulos; Stephanos Theodossiades
2018-01-01
The hydrodynamic lubrication and thermal analysis of tilting pad thrust bearings has been a major subject for many studies in the field of tribology. There is only a limited number of studies regarding thrust bearings with coated surfaces. The purpose of this study is to build a parametric, iterative algorithm in order to perform a complete thermal and hydrodynamic lubrication analysis for pivoted pad thrust bearings with coatings. The analytical model is mainly based on the energy, continuit...
A study on compliant layers and its influence on dynamic response of a hydrodynamic journal bearing
DEFF Research Database (Denmark)
Thomsen, Kim; Klit, Peder
2011-01-01
For some hydrodynamic bearing applications polymer-lined bearings are chosen over traditional metal alloy bearings due to their better wear and friction properties when operating at very thin films, e.g. in the mixed lubrication region. The introduction of a compliant layer also affects the dynamic...... used to evaluate hydrodynamic bearing designs: dynamic response, maximum pressure, minimum film thickness, wear, power loss and temperature response. The primary findings are that the maximum pressures are reduced significantly and this comes at the expense of slightly higher eccentricity ratios during...
Directory of Open Access Journals (Sweden)
Lukas Bernhauser
2017-03-01
Full Text Available Increasing quality demands of combustion engines require, amongst others, improvements of the engine’s acoustics and all (subcomponents mounted to the latter. A significant impact to the audible tonal noise spectrum results from the vibratory motions of fast-rotating turbocharger rotor systems in multiple hydrodynamic bearings such as floating bearing rings. Particularly, the study of self-excited non-linear vibrations of the rotor-bearing systems is crucial for the understanding, prevention or reduction of the noise and, consequently, for a sustainable engine acoustics development. This work presents an efficient modeling approach for the investigation, optimization, and design improvement of complex turbocharger rotors in hydrodynamic journal bearings, including floating bearing rings with circular and non-circular bearing geometries. The capability of tonal non-synchronous vibration prevention using non-circular bearing shapes is demonstrated with dynamic run-up simulations of the presented model. These findings and the performance of our model are compared and validated with results of a classical Laval/Jeffcott rotor-bearing model and a specific turbocharger model found in the literature. It is shown that the presented simulation method yields fast and accurate results and furthermore, that non-circular bearing shapes are an effective measure to reduce or even prevent self-excited tonal noise.
A study on synchronously whirling motion of hydrodynamic journal bearings
International Nuclear Information System (INIS)
Rho, Byoung Hoo; Kim, Kyung Woong
2001-01-01
In this paper, a control algorithm which is synchronously excitation the bearing with whirl speed of rotor is employed to suppress the whirl instability and unbalance response of the rotor-bearing system. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than a conventional analysis with the Renolds condition. The stabilities and unbalance responses of the rotor-bearing system are investigated for various control gains and phase differences between the bearing and journal motion. It is shown that the unbalance response of the system can be greatly improved by synchronous control of the bearing, and there is an optimum phase difference, which gives the minimum unbalance response of the system, for given operating condition. It is also found that the onset speed of the instability can be greatly increased by synchronous control of the bearing
A study on synchronously whirling motion of hydrodynamic journal bearings
Energy Technology Data Exchange (ETDEWEB)
Rho, Byoung Hoo; Kim, Kyung Woong [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)
2001-09-01
In this paper, a control algorithm which is synchronously excitation the bearing with whirl speed of rotor is employed to suppress the whirl instability and unbalance response of the rotor-bearing system. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than a conventional analysis with the Renolds condition. The stabilities and unbalance responses of the rotor-bearing system are investigated for various control gains and phase differences between the bearing and journal motion. It is shown that the unbalance response of the system can be greatly improved by synchronous control of the bearing, and there is an optimum phase difference, which gives the minimum unbalance response of the system, for given operating condition. It is also found that the onset speed of the instability can be greatly increased by synchronous control of the bearing.
Energy Technology Data Exchange (ETDEWEB)
Hagenhoff, M.; Sauer, M. [Main-Metall-Giesserei Fritz Schorr GmbH und Co. KG, Altenglan (Germany)
2004-10-01
Hydrodynamic sliding bearings are considered only in cases when roller bearings reach their speed limits and there is no other solution. However, this view neglects the fact that there are modern, optimised sliding bearings which have more advantages over roller bearings than should be expected. Many producers of sliding bearings also have computer programs enabling them to offer customised solutions, i.e. optimal adaptation of the bearings to their specific operating conditions. (orig.) [German] Hydrodynamische Gleitlager werden oft erst dann in Betracht gezogen, wenn man an die Drehzahlgrenzen von Waelzlagern stoesst und keine andere sinnvolle Alternative mehr in Frage kommt. Dabei uebersieht man leicht, dass es moderne, optimierte Gleitlagerkonstruktionen gibt, die weitaus haeufiger ihre Staerken im Vergleich zu Waelzlagern ausspielen koennen als zunaechst vermutet. Viele Gleitlagerhersteller haben zudem heute Berechnungsprogramme zur Verfuegung, die eine optimale Anpassung der Lager an die speziellen Betriebsbedingungen erlauben. (orig.)
Biomedical device prototype based on small scale hydrodynamic cavitation
Directory of Open Access Journals (Sweden)
Morteza Ghorbani
2018-03-01
Full Text Available This study presents a biomedical device prototype based on small scale hydrodynamic cavitation. The application of small scale hydrodynamic cavitation and its integration to a biomedical device prototype is offered as an important alternative to other techniques, such as ultrasound therapy, and thus constitutes a local, cheap, and energy-efficient solution, for urinary stone therapy and abnormal tissue ablation (e.g., benign prostate hyperplasia (BPH. The destructive nature of bubbly, cavitating, flows was exploited, and the potential of the prototype was assessed and characterized. Bubbles generated in a small flow restrictive element (micro-orifice based on hydrodynamic cavitation were utilized for this purpose. The small bubbly, cavitating, flow generator (micro-orifice was fitted to a small flexible probe, which was actuated with a micromanipulator using fine control. This probe also houses an imaging device for visualization so that the emerging cavitating flow could be locally targeted to the desired spot. In this study, the feasibility of this alternative treatment method and its integration to a device prototype were successfully accomplished.
Biomedical device prototype based on small scale hydrodynamic cavitation
Ghorbani, Morteza; Sozer, Canberk; Alcan, Gokhan; Unel, Mustafa; Ekici, Sinan; Uvet, Huseyin; Koşar, Ali
2018-03-01
This study presents a biomedical device prototype based on small scale hydrodynamic cavitation. The application of small scale hydrodynamic cavitation and its integration to a biomedical device prototype is offered as an important alternative to other techniques, such as ultrasound therapy, and thus constitutes a local, cheap, and energy-efficient solution, for urinary stone therapy and abnormal tissue ablation (e.g., benign prostate hyperplasia (BPH)). The destructive nature of bubbly, cavitating, flows was exploited, and the potential of the prototype was assessed and characterized. Bubbles generated in a small flow restrictive element (micro-orifice) based on hydrodynamic cavitation were utilized for this purpose. The small bubbly, cavitating, flow generator (micro-orifice) was fitted to a small flexible probe, which was actuated with a micromanipulator using fine control. This probe also houses an imaging device for visualization so that the emerging cavitating flow could be locally targeted to the desired spot. In this study, the feasibility of this alternative treatment method and its integration to a device prototype were successfully accomplished.
Study of hydrodynamic behaviour of large bearings depending on the viscosity of the lubricant
Directory of Open Access Journals (Sweden)
Barabas Sorin
2017-01-01
Full Text Available The research refers to study of hydrodynamic behavior of large bearings equipped with automatic lubrication system, where the liquid used may have a viscosity with variable values depending on the temperature or depending on the additive used. The introduction of additives with nanoparticles causes modification of viscosity and a significant reduction of friction coefficient. This study establishes a direct link between the friction, viscosity and tensions that occur in the contact area. Experimental studies confirm improving tribological properties of the contact area between the bearing rollers and raceways, through attracting nanoparticles on surfaces in contact and reducing friction coefficient. Accomplished finite element analysis showed decrease of the contact stresses, therefore decrease of the wear and increase the life of the bearing. Research has concluded that influencing viscosity and friction coefficient of lubricant can result in reducing wear of the bearing components, as well as increase the lifetime of bearing.
Dynamic Parameter Identification of Hydrodynamic Bearing-Rotor System
Directory of Open Access Journals (Sweden)
Zhiqiang Song
2015-01-01
Full Text Available A new method called modal parameter genetic time domain identification was employed to study the characteristics of the bearing-rotor system. A multifrequency signal decomposition technology to identify the main components of the measured signal and reject the image mode produced by noise has been used. The first- and second-order natural frequency and damping ratios of the shaft system are identified. Furthermore, because of the deficiency of the traditional least square method, a new genetic identification method to identify the bearing dynamic characteristic parameters has been proposed. The method has been effective albeit with few testing points and operation cases. The derivation of oil-film dynamic coefficients could also provide a basis for shaft system natural vibration characteristic and vibration response analysis. Using the identified dynamic coefficients as the supporting condition, the shaft system modal characteristics were studied. The calculated first- and second-order natural frequencies match quite well those obtained from the modal parameter identification. It was proved that the modal parameter and physical parameter identification methods utilized in this paper are reasonable.
Vibration of a rotating shaft on hydrodynamic bearings: multi-scales surface effects
International Nuclear Information System (INIS)
Rebufa, Jocelyn
2016-01-01
The hydrodynamic bearing provides good damping properties in rotating machineries. However, the performances of rotor-bearings systems are highly impacted by nonlinear effects that are difficult to analyze. The rotor dynamics prediction requires advanced models for the flow in the bearings. The surface of the bearings seems to have a strong impact on the lubricant flow, acting on the static and dynamic properties of the rotating parts. This study aims to enhance the simulation of the bearings' surface state effect on the motion of the rotating shaft. The flexible shaft interacts with textured hydrodynamic bearings. Multi-scales homogenization is used in a multi-physics algorithm in order to describe the fluid-structure interaction. Different models are used to account for the cavitation phenomenon in the bearings. Nonlinear harmonic methods allow efficient parametric studies of periodic solutions as well as their stability. Moreover, a test rig has been designed to compare predictions to real measurements. Several textured shaft samples modified with femto-seconds LASER surface texturing are tested. In most cases the experimental study showed similar results than the simulation. Enhancements of the vibration behaviors of the rotor-bearing system have been revealed for certain texturing patterns. The self-excited vibration, also known as 'oil whirl' phenomenon, is stabilized on a wide rotating frequency range. However, the simulation tool does not predict well the enhancements that are observed. Vortices in surface texturing patterns have been revealed numerically with Navier-Stokes equation resolution. These results are opposed to the classical lubrication hypothesis. It is also a possible explanation of the enhancements that are experimentally measured with textured bearings. (author) [fr
Directory of Open Access Journals (Sweden)
Konstantinos Katsaros
2018-05-01
Full Text Available The hydrodynamic lubrication and thermal analysis of tilting pad thrust bearings has been a major subject for many studies in the field of tribology. There is only a limited number of studies regarding thrust bearings with coated surfaces. The purpose of this study is to build a parametric, iterative algorithm in order to perform a complete thermal and hydrodynamic lubrication analysis for pivoted pad thrust bearings with coatings. The analytical model is mainly based on the energy, continuity and Navier–Stokes equations, which are solved numerically with the Semi-Implicit Method for Pressure Linked Equations Consistent (SIMPLEC method. The analysis focuses on a single pivoted pad of the thrust bearing. The thermal properties of the coating material are taken into account and the resulting thermal and flow fields are solved. The basic hydrodynamic and tribological characteristics are calculated for an uncoated, a Babbitt coated, a PTFE coated and a diamond like carbon (DLC coated pivoted pad thrust bearing. The pressure and the film thickness distribution, as well as the load capacity and the frictional forces, are determined for several pad positions and velocities of the rotor. A mineral oil lubricant is used to estimate the shear thinning or thickening effects on the pad tribological performance. The results indicate that pads coated with PTFE and DLC show lower friction forces compared to the common steel and Babbitt applications. At the same time, the DLC coating seems to affect the bearing’s flow and thermal fields less than the PTFE, making it more suitable for thrust bearings applications.
International Nuclear Information System (INIS)
Hattori, Hitoshi; Fukushima, Harunobu; Yoshii, Yasuo; Nakamuta, Hironori; Iwase, Mitsuo; Kitade, Koichi
2009-01-01
In this paper, a high rigidity and high speed rotating mechanism using a new concept hydrodynamic bearing in X-ray tube for high speed computed tomography is proposed. In order to obtain both the stability and the high load carrying capacity, the hydrodynamic bearing lubricated by liquid metal (Gallium alloy), named as the hybrid hydrodynamic bearing generates the lubricating film by wedge effect on the plane region between the spiral grooves under high loading condition. The parallelism between the bearing and the rotating body can be secured by optimizing the rigidity distribution of stationary shaft in the proposed rotating mechanism. By carrying out the fundamental design by numerical analyses, it has been made clear that the hybrid hydrodynamic bearing and the rotating mechanism are suitable for the X-ray tube used in the CT with ever-increasingly scanning speed. (author)
Hydrodynamic Fluid Film Bearings and Their Effect on the Stability of Rotating Machinery
National Research Council Canada - National Science Library
Andres, Luis S
2006-01-01
.... This design parameter shows the static performance of the bearing as rotor speed increases. Rotordynamic force coefficients are introduced and their effect on the stability of a rotor-bearing system thoroughly discussed...
Non fuel bearing component(NFBC) inspection device
International Nuclear Information System (INIS)
Kurokawa, Hideyuki; Kosaka, Tatsuya.
1994-01-01
The device of the present invention continuously inspects the length and abrasion/corrosion states for a plurality of non-fuel bearing components (NFBC) under water in a pit. That is, the device comprises the following components. Two sets of frames are planted vertically on a pit wall. A support stand capable of opening and closing is disposed at the upper portion of the frame to sustain each control rods of the NFBC. An abrasion/corrosion measuring tool is disposed vertically movably on the frame at the lower portion of the support stand for detecting abrasion/corrosion states on the surface of each of the fuel rods. A lifting device is disposed outside of the pit for lifting the abrasion/corrosion measuring tools. The measuring tool is disposed vertically movably at a lower portion of the frame for measuring the length of each of the control rods. Then NFBCs are inserted and positioned reliably underwater in the pit, the length of the NFBCs and the abrasion/corrosion states on the surface of the control rod can be observed, the inspecting tools can be exchanged easily since the support stand is capable of opening and closing, and the inspection can be made continuously because of the dual structure according to the present invention. (I.S.)
Directory of Open Access Journals (Sweden)
Breńkacz Łukasz
2017-12-01
Full Text Available Hydrodynamic bearings are commonly used in ship propulsion systems. Typically, they are calculated using numerical or experimental methods. This paper presents an experimental study through which it has been possible to estimate 24 dynamic coefficients of two hydrodynamic slide bearings operating under nonlinear conditions. During the investigation, bearing mass coefficients are identified by means of a newly developed algorithm. An impact hammer was used to excite vibration of the shaft. The approximation by means of the least squares method was applied to determine bearing dynamic coefficients. Based on the performed research, the four (i.e. two main and two crosscoupled coefficients of stiffness, damping and mass for each bearing were obtained. The mass coefficients add up to the complex shaft weight. These values are not required for modeling dynamics of the machine because the rotor mass is usually known, however, they may serve as a good indicator to validate the correctness of the stiffness and damping coefficients determined. Additionally, the experimental research procedure was described. The signals of displacements in the bearings and the excitation forces used for determination of the bearing dynamic coefficients were shown. The study discussed in this article is about a rotor supported by two hydrodynamic bearings operating in a nonlinear manner. On the basis of computations, the results of bearing dynamic coefficients were presented for a selected speed.
Tunable Microfluidic Devices for Hydrodynamic Fractionation of Cells and Beads: A Review
Directory of Open Access Journals (Sweden)
Jafar Alvankarian
2015-11-01
Full Text Available The adjustable microfluidic devices that have been developed for hydrodynamic-based fractionation of beads and cells are important for fast performance tunability through interaction of mechanical properties of particles in fluid flow and mechanically flexible microstructures. In this review, the research works reported on fabrication and testing of the tunable elastomeric microfluidic devices for applications such as separation, filtration, isolation, and trapping of single or bulk of microbeads or cells are discussed. Such microfluidic systems for rapid performance alteration are classified in two groups of bulk deformation of microdevices using external mechanical forces, and local deformation of microstructures using flexible membrane by pneumatic pressure. The main advantage of membrane-based tunable systems has been addressed to be the high capability of integration with other microdevice components. The stretchable devices based on bulk deformation of microstructures have in common advantage of simplicity in design and fabrication process.
Energy Technology Data Exchange (ETDEWEB)
Melin, Alexander M [ORNL; Kisner, Roger A [ORNL; Fugate, David L [ORNL; Holcomb, David Eugene [ORNL
2015-01-01
Embedding instrumentation and control Embedding instrumentation and control (I\\&C) at the component level in nuclear power plants can improve component performance, lifetime, and resilience by optimizing operation, reducing the constraints on physical design, and providing on-board prognostics and diagnostics. However, the extreme environments that many nuclear power plant components operate in makes embedding instrumentation and control at the component level difficult. Successfully utilizing embedded I\\&C requires developing a deep understanding of the system's dynamics and using that knowledge to overcome material and physical limitations imposed by the environment. In this paper, we will develop a coupled dynamic model of a high temperature (700 $^\\circ$C) canned rotor pump that incorporates rotordynamics, hydrodynamics, and active magnetic bearing dynamics. Then we will compare two control design methods, one that uses a simplified decoupled model of the system and another that utilizes the full coupled system model. It will be seen that utilizing all the available knowledge of the system dynamics in the controller design yield an order of magnitude improvement in the magnitude of the magnetic bearing response to disturbances at the same level of control effort, a large reduction in the settling time of the system, and a smoother control action.
ISS Ammonia Pump Failure, Recovery, and Lesson Learned A Hydrodynamic Bearing Perspective
Bruckner, Robert J.; Manco, Richard A., II
2014-01-01
The design, development, and operation of long duration spaceflight hardware has become an evolutionary process in which meticulous attention to details and lessons learned from previous experiences play a critical role. Invaluable to this process is the ability to retrieve and examine spaceflight hardware that has experienced a premature failure. While these situations are rare and unfortunate, the failure investigation and recovery from the event serve a valuable purpose in advancing future space mechanism development. Such a scenario began on July 31, 2010 with the premature failure of an ammonia pump on the external active thermal control system of the International Space Station. The ground-based inspections of the returned pump and ensuing failure investigation revealed five potential bearing forces that were un-accounted for in the design phase and qualification testing of the pump. These forces could combine in a number of random orientations to overload the pump bearings leading to solid-surface contact, wear, and premature failure. The recovery plan identified one of these five forces as being related to the square of the operating speed of the pump and this fact was used to recover design life through a change in flight rules for the operation of the pump module. Through the course of the failure investigation, recovery, and follow-on assessment of pump wear life, design guidance has been developed to improve the life of future mechanically pumped thermal control systems for both human and robotic exploration missions.
Bhushan, B.; Ruscitto, D.; Gray, S.
1978-01-01
Material coatings for an air-lubricated, compliant journal bearing for an automotive gas turbine engine were exposed to service test temperatures of 540 C or 650 C for 300 hours, and to 10 temperature cycles from room temperatures to the service test temperatures. Selected coatings were then put on journal and partial-arc foils and tested in start-stop cycle tests at 14 kPa (2 psi) loading for 2000 cycles. Half of the test cycles were performed at a test chamber service temperature of 540 C (1000 F) or 650 C (1200 F); the other half were performed at room temperature. Based on test results, the following combinations and their service temperature limitations are recommended: HL-800 TM (CdO and graphite) on foil versus chrome carbide on journal up to 370 C (700 F); NASA PS 120 (Tribaloy 400, silver and CaF2 on journal versus uncoated foil up to 540 C (1000 F); and Kaman DES on journal and foil up to 640 C (1200 F). Kaman DES coating system was further tested successfully at 35 kPa (5 psi) loading for 2000 start-stop cycles.
Hydrodynamics of Safety Injection Tank with Fluidic Device in Recent Regulation
Energy Technology Data Exchange (ETDEWEB)
Bang, Young Seok; Yoo, Seung Hun [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)
2016-10-15
Safety Injection Tank (SIT) with Fluidic Device (FD) has been used in several APR1400 nuclear power plants. It was designed to provide a longer passive safety injection than the existing accumulator to improve the safety for Large Break Loss-of-Coolant Accident (LBLOCA) by changing the injected flow through the FD and the standpipe of the SIT. As a result, high flow injection phase and the subsequent low flow one can be achieved as longer than the existing accumulator. The present paper discusses the major concerns related to SIT hydrodynamics and the directions to resolution recently concerned. Modeling of SIT/FD by total hydraulic resistances, potential of nitrogen intrusion, and effect of initial pressure of SIT testing are included. Based on the discussion, a table of the important phenomena of the SIT/FD was proposed with the relevancy of the calculation models applied. The present paper discussed the SIT hydrodynamics including the modeling of SIT/FD by total hydraulic resistances, potential of nitrogen intrusion, and effect of initial pressure of SIT testing. Also a table of the important phenomena of the SIT/FD was proposed with the relevancy of the calculation models applied. The following conclusions are obtained uncertainty due to the assumption of the total Kfactor as constant for high flow, transition phase, and low flow phase should be considered and nitrogen intrusion phenomena during the transition phase should be considered with a conservatism, especially considering the current situation of nonmeasuring the standpipe level.
Hydrodynamics of Safety Injection Tank with Fluidic Device in Recent Regulation
International Nuclear Information System (INIS)
Bang, Young Seok; Yoo, Seung Hun
2016-01-01
Safety Injection Tank (SIT) with Fluidic Device (FD) has been used in several APR1400 nuclear power plants. It was designed to provide a longer passive safety injection than the existing accumulator to improve the safety for Large Break Loss-of-Coolant Accident (LBLOCA) by changing the injected flow through the FD and the standpipe of the SIT. As a result, high flow injection phase and the subsequent low flow one can be achieved as longer than the existing accumulator. The present paper discusses the major concerns related to SIT hydrodynamics and the directions to resolution recently concerned. Modeling of SIT/FD by total hydraulic resistances, potential of nitrogen intrusion, and effect of initial pressure of SIT testing are included. Based on the discussion, a table of the important phenomena of the SIT/FD was proposed with the relevancy of the calculation models applied. The present paper discussed the SIT hydrodynamics including the modeling of SIT/FD by total hydraulic resistances, potential of nitrogen intrusion, and effect of initial pressure of SIT testing. Also a table of the important phenomena of the SIT/FD was proposed with the relevancy of the calculation models applied. The following conclusions are obtained uncertainty due to the assumption of the total Kfactor as constant for high flow, transition phase, and low flow phase should be considered and nitrogen intrusion phenomena during the transition phase should be considered with a conservatism, especially considering the current situation of nonmeasuring the standpipe level
Hydrodynamic gene delivery in human skin using a hollow microneedle device.
Dul, M; Stefanidou, M; Porta, P; Serve, J; O'Mahony, C; Malissen, B; Henri, S; Levin, Y; Kochba, E; Wong, F S; Dayan, C; Coulman, S A; Birchall, J C
2017-11-10
Microneedle devices have been proposed as a minimally invasive delivery system for the intradermal administration of nucleic acids, both plasmid DNA (pDNA) and siRNA, to treat localised disease or provide vaccination. Different microneedle types and application methods have been investigated in the laboratory, but limited and irreproducible levels of gene expression have proven to be significant challenges to pre-clinical to clinical progression. This study is the first to explore the potential of a hollow microneedle device for the delivery and subsequent expression of pDNA in human skin. The regulatory approved MicronJet600® (MicronJet hereafter) device was used to deliver reporter plasmids (pCMVβ and pEGFP-N1) into viable excised human skin. Exogenous gene expression was subsequently detected at multiple locations that were distant from the injection site but within the confines of the bleb created by the intradermal bolus. The observed levels of gene expression in the tissue are at least comparable to that achieved by the most invasive microneedle application methods e.g. lateral application of a microneedle. Gene expression was predominantly located in the epidermis, although also evident in the papillary dermis. Optical coherence tomography permitted real time visualisation of the sub-surface skin architecture and, unlike a conventional intradermal injection, MicronJet administration of a 50μL bolus appears to create multiple superficial microdisruptions in the papillary dermis and epidermis. These were co-localised with expression of the pCMVβ reporter plasmid. We have therefore shown, for the first time, that a hollow microneedle device can facilitate efficient and reproducible gene expression of exogenous naked pDNA in human skin using volumes that are considered to be standard for intradermal administration, and postulate a hydrodynamic effect as the mechanism of gene delivery. Copyright © 2017 Elsevier B.V. All rights reserved.
Eling, R.P.T.; te Wierik, M.; van Ostayen, R.A.J.; Rixen, D.J.
2016-01-01
Journal bearings are used to support rotors in a wide range of applications. In order to ensure reliable operation, accurate analyses of these rotor-bearing systems are crucial. Coupled analysis of the rotor and the journal bearing is essential in the case that the rotor is flexible. The accuracy of
A Novel Bearing Lubricating Device Based on the Piezoelectric Micro-Jet
Directory of Open Access Journals (Sweden)
Kai Li
2016-02-01
Full Text Available A novel bearing lubricating device, which is embedded in gyroscope’s bearing system and based on the theory of the piezoelectric micro-jet, was designed for this study. The embedded structure of a bearing lubricating system can make effective use of the limited space of bearing systems without increasing the whole mass of the system. The drop-on-demand (DOD lubrication can be realized by the piezoelectric micro-jet system to implement the long acting lubrication of the bearing system. A mathematical model of inlet boundary conditions was established to carry on the numerical simulation based on CFD. The motion states of the droplets with different voltage excitations were analyzed via numerical simulations, and the injection performances of the piezoelectric micro-jet lubricating device were tested in accordance with past experiments. The influences of different parameters of voltage excitation on injection performance were obtained, and the methods of adjusting the injection performance to meet different requirements are given according to the analyses of the results. The mathematical model and numerical simulation method were confirmed by comparing the results of past simulations and experiments.
Chen, Runlin; Wei, Yangyang; Shi, Zhaoyang; Yuan, Xiaoyang
2016-01-01
The identification accuracy of dynamic characteristics coefficients is difficult to guarantee because of the errors of the measurement system itself. A novel dynamic calibration method of measurement system for dynamic characteristics coefficients is proposed in this paper to eliminate the errors of the measurement system itself. Compared with the calibration method of suspension quality, this novel calibration method is different because the verification device is a spring-mass system, which can simulate the dynamic characteristics of sliding bearing. The verification device is built, and the calibration experiment is implemented in a wide frequency range, in which the bearing stiffness is simulated by the disc springs. The experimental results show that the amplitude errors of this measurement system are small in the frequency range of 10 Hz–100 Hz, and the phase errors increase along with the increasing of frequency. It is preliminarily verified by the simulated experiment of dynamic characteristics coefficients identification in the frequency range of 10 Hz–30 Hz that the calibration data in this frequency range can support the dynamic characteristics test of sliding bearing in this frequency range well. The bearing experiments in greater frequency ranges need higher manufacturing and installation precision of calibration device. Besides, the processes of calibration experiments should be improved. PMID:27483283
2010-05-01
Type of Lubrication for a Tilting Pad Thrust Bearing ,” ASME Journal of Lubrication Technology, 96 Ser F (1), pp. 22-27. [9] Gregory, R.S., 1974...1986, “Measurements of Maximum Temperature in Tilting - Pad Thrust Bearings ,” Technical Preprints - Presented at the ASLE 41st Annual Meeting. (ASLE...Safar [7] provides a modified Reynolds number analysis on hydrostatic thrust bearing performance parameters including the effects of tilt . Finally, San
Directory of Open Access Journals (Sweden)
Rob Eling
2016-09-01
Full Text Available Journal bearings are used to support rotors in a wide range of applications. In order to ensure reliable operation, accurate analyses of these rotor-bearing systems are crucial. Coupled analysis of the rotor and the journal bearing is essential in the case that the rotor is flexible. The accuracy of prediction of the model at hand depends on its comprehensiveness. In this study, we construct three bearing models of increasing modeling comprehensiveness and use these to predict the response of two different rotor-bearing systems. The main goal is to evaluate the correlation with measurement data as a function of modeling comprehensiveness: 1D versus 2D pressure prediction, distributed versus lumped thermal model, Newtonian versus non-Newtonian fluid description and non-mass-conservative versus mass-conservative cavitation description. We conclude that all three models predict the existence of critical speeds and whirl for both rotor-bearing systems. However, the two more comprehensive models in general show better correlation with measurement data in terms of frequency and amplitude. Furthermore, we conclude that a thermal network model comprising temperature predictions of the bearing surroundings is essential to obtain accurate predictions. The results of this study aid in developing accurate and computationally-efficient models of flexible rotors supported by plain journal bearings.
Field Tests on Hydrodynamic and Hybrid Operation of a Bidirectional Thrust Bearing of a Pump-Turbine
Directory of Open Access Journals (Sweden)
Michał Wasilczuk
2017-12-01
Full Text Available In vertical shaft pump turbines operating in pumped storage power plants an important role is played by a thrust bearing. Due to the bidirectional character of operation, thrust bearing tilting pads have to be supported symmetrically, which is known to be unfavourable from the point of view of their performance. Large thrust bearings have to be carefully designed so as to minimise excessive thermo-elastic pad deformations. The research into fluid film thrust bearings has been quite extensive over the years, comprising theoretical studies of bearing properties with the use of more and more sophisticated calculation codes. On the other hand, the availability of experimental field data on bearing operation is limited, for obvious reasons. In this paper the authors present part of the results of extensive field tests of a large bearing of a pump-turbine they have conducted in a pumped storage power plant. Hopefully this data will be of interest to other researchers to compare theoretical predictions to measurement data.
2008-12-03
STB stainless steel housing. Drive End Thrust Collar Free End Splash Guard Slave Thrust Bearing Face STB Flange Figure 12: Exploded view of slave...Bulk Flow Analysis of Hybrid Thrust Bearing for Process Fluid Applications.” ASME Trans., Journal of Tribology , January, Vol. 122 (1), pp. 170-180...ASME Journal of Tribology , Vol. 123, pp. 768-776 [5] San Andrés, L., (2006), “MEEN 626 Notes 2 Derivation of the Classical Reynolds Equation for
Energy Technology Data Exchange (ETDEWEB)
Ruiz, Rafael O.; Di Liscia, Marcelo H.; Diaz, Sergio E. [Universidad Simon Bolivar, Sartendejas, Baruta (Venezuela)
2007-11-15
The identification of the dynamic coefficients in air bearings is fundamental for a suitable roto-dynamic analysis. The present paper shows the development of an algorithm that allows the direct obtaining of the dynamic coefficients in hydrodynamic air bearings as much of numerical form as experimental. The testing bench used consists of two magnetic bearings, which support the rotor in their ends and work as well as actuators allowing inducing controlled orbits in the rotor. The test bearing is located between the magnetic bearings. The dynamic forces generated in the air bearing are registered from three load cells. The algorithm was developed in a commercial code of graphical programming, through which the signals can be collected, controlled and processed. The nonlinear behavior of this type of bearings makes difficult the calculation of the dynamic coefficients, therefore the processing of the signals in frequencial space facilitates, in a certain way, its handling. On the other hand, the numerical model was compared with the experimental results obtaining acceptable approaches in magnitude as well as in behavior. The numerical dynamic coefficients calculation was realized solving the Reynolds differential equation for a compressible fluid in the thickness of the gas film, taking into consideration the fluid mass flow that is introduced, as well as the pressure loss suffered by the same in passing through the feeding orifices. The numerical methods utilized include the solution of the differential equation of Reynolds for finite differences, the calculation of the profile realizing successive iterations and the calculation of the hydrodynamics forces through the Simpson numerical integration. The numerical dynamic coefficients were found applying a minimum squared technique to the hydrodynamic stresses generated in simulating an orbit of the rotor at a determined frequency and velocity, allowing in this way the calculation of the synchronous and asynchronous
Directory of Open Access Journals (Sweden)
Horacio Toniolo
2014-07-01
Full Text Available Floating objects designed to divert woody debris—known as debris diversion devices—can protect hydrokinetic turbines deployed in rivers; they also change the hydrodynamic conditions of a river, at least locally. Modifications associated with velocity adjustments in both magnitude and direction would be expected. Thus, one could assume that extra macro-turbulent levels would be found immediately behind a device and downstream of that location. This article presents a set of cross-sectional and longitudinal velocity measurements carried out to quantify these effects. Results show important changes in the velocity components. In addition, significant changes in the vorticity field, calculated along cross-sectional profiles, demonstrate the role of a submerged chain used to maintain the debris diversion device in place. More importantly, findings suggest that hydrokinetic turbines should not be installed in a river’s central area behind a debris diversion device, due to the additional turbulence created by the submerged chain.
Nisar, Ubaid Ahmed; Ashraf, Waqas; Qamar, Shamsul
In this article, one and two-dimensional hydrodynamical models of semiconductor devices are numerically investigated. The models treat the propagation of electrons in a semiconductor device as the flow of a charged compressible fluid. It plays an important role in predicting the behavior of electron flow in semiconductor devices. Mathematically, the governing equations form a convection-diffusion type system with a right hand side describing the relaxation effects and interaction with a self consistent electric field. The proposed numerical scheme is a splitting scheme based on the kinetic flux-vector splitting (KFVS) method for the hyperbolic step, and a semi-implicit Runge-Kutta method for the relaxation step. The KFVS method is based on the direct splitting of macroscopic flux functions of the system on the cell interfaces. The second order accuracy of the scheme is achieved by using MUSCL-type initial reconstruction and Runge-Kutta time stepping method. Several case studies are considered. For validation, the results of current scheme are compared with those obtained from the splitting scheme based on the NT central scheme. The effects of various parameters such as low field mobility, device length, lattice temperature and voltage are analyzed. The accuracy, efficiency and simplicity of the proposed KFVS scheme validates its generic applicability to the given model equations. A two dimensional simulation is also performed by KFVS method for a MESFET device, producing results in good agreement with those obtained by NT-central scheme.
Huang, Feimin; Li, Tianhong; Yu, Huimin; Yuan, Difan
2018-06-01
We are concerned with the global existence and large time behavior of entropy solutions to the one-dimensional unipolar hydrodynamic model for semiconductors in the form of Euler-Poisson equations in a bounded interval. In this paper, we first prove the global existence of entropy solution by vanishing viscosity and compensated compactness framework. In particular, the solutions are uniformly bounded with respect to space and time variables by introducing modified Riemann invariants and the theory of invariant region. Based on the uniform estimates of density, we further show that the entropy solution converges to the corresponding unique stationary solution exponentially in time. No any smallness condition is assumed on the initial data and doping profile. Moreover, the novelty in this paper is about the unform bound with respect to time for the weak solutions of the isentropic Euler-Poisson system.
International Nuclear Information System (INIS)
Wong Unhong; Wong Honcheng; Tang Zesheng
2010-01-01
The smoothed particle hydrodynamics (SPH), which is a class of meshfree particle methods (MPMs), has a wide range of applications from micro-scale to macro-scale as well as from discrete systems to continuum systems. Graphics hardware, originally designed for computer graphics, now provide unprecedented computational power for scientific computation. Particle system needs a huge amount of computations in physical simulation. In this paper, an efficient parallel implementation of a SPH method on graphics hardware using the Compute Unified Device Architecture is developed for fluid simulation. Comparing to the corresponding CPU implementation, our experimental results show that the new approach allows significant speedups of fluid simulation through handling huge amount of computations in parallel on graphics hardware.
Directory of Open Access Journals (Sweden)
Zhelyazov Todor
2018-01-01
Full Text Available The contribution is focused on the numerical modelling, simulation and analysis of a lead-core bearing device for passive seismic isolation. An accurate finite element model of a lead-core bearing device is presented. The model is designed to analyse both mechanical and thermo-mechanical responses of the seismic isolator to different loading conditions. Specifically, the mechanical behaviour in a typical identification test is simulated. The response of the lead-core bearing device to circular sinusoidal paths is analysed. The obtained shear displacement – shear force relationship is compared to experimental data found in literature sources. The hypothesis that heating of the lead-core during cyclic loading affects the degrading phenomena in the bearing device is taken into account. Constitutive laws are defined for each material: lead, rubber and steel. Both predefined constitutive laws (in the used general–purpose finite element code and semi-analytical procedures aimed at a more accurate modelling of the constitutive relations are tested. The results obtained by finite element analysis are to be further used to calibrate a macroscopic model of the lead-core bearing device seen as a single-degree-of-freedom mechanical system.
Hydrodynamic gene delivery in human skin using a hollow microneedle device
Dul, M.; Stefanidou, M.; Porta, P.; Serve, J.; O'Mahony, Conor; Malissen, B.; Henri, S.; Levin, Y.; Kochba, E.; Wong, F. S.; Dayan, C.; Coulman, S. A.; Birchall, J. C.
2017-01-01
Microneedle devices have been proposed as a minimally invasive delivery system for the intradermal administration of nucleic acids, both plasmid DNA (pDNA) and siRNA, to treat localised disease or provide vaccination. Different microneedle types and application methods have been investigated in the laboratory, but limited and irreproducible levels of gene expression have proven to be significant challenges to pre-clinical to clinical progression. This study is the first to explore the potenti...
Additively manufactured custom load-bearing implantable devices: grounds for caution
Directory of Open Access Journals (Sweden)
Elisabetta M Zanetti
2017-08-01
Full Text Available Background Additive manufacturing technologies are being enthusiastically adopted by the orthopaedic community since they are providing new perspectives and new possibilities. First applications were finalised for educational purposes, pre-operative planning, and design of surgical guides; recent applications also encompass the production of implantable devices where 3D printing can bring substantial benefits such as customization, optimization, and manufacturing of very complex geometries. The conceptual smoothness of the whole process may lead to the idea that any medical practitioner can use a 3D printer and her/his imagination to design and produce novel products for personal or commercial use. Aims Outlining how the whole process presents more than one critical aspects, still demanding further research in order to allow a safe application of this technology for fully-custom design, in particular confining attention to orthopaedic/orthodontic prostheses defined as components responding mainly to a structural function. Methods Current knowledge of mechanical properties of additively manufactured components has been examined along with reasons why the behaviour of these components might differ from traditionally manufactured components. The structural information still missing for mechanical design is outlined. Results Mechanical properties of additively manufactured components are not completely known, and especially fatigue limit needs to be examined further. Conclusion At the present stage, with reference to load-bearing implants subjected to many loading cycles, the indication of custom-made additively manufactured medical devices should be restricted to the cases with no viable alternative.
Horwatich, Judy A.; Bannerman, Roger T.
2012-01-01
A hydrodynamic-settling device was installed in 2004 to treat stormwater runoff from a roof and parking lot located at the Water Utility Administration Building in Madison, Wis. The U.S. Geological Survey, in cooperation with the Wisconsin Department of Natural Resources, the City of Madison, cities in the Waukesha Permit Group, Hydro International, Earth Tech, Inc., National Sanitation Foundation International, and the U.S. Environmental Protection Agency, monitored the device from November 2005 through September 2006 to evaluate it as part of the U.S. Environmental Protection Agency's Environmental Technology Verification Program. Twenty-three runoff events monitored for flow volume and water quality at the device's inlet and outlet were used to calculate the percentage of pollutant reduction for the device. The geometric mean concentrations of suspended sediment (SS), "adjusted" total suspended solids (TSS), total phosphorus (TP), dissolved phosphorus (DP), total recoverable zinc (TZn), and total recoverable copper (TCu) measured at the inlet were 107 mg/L (milligrams per liter), 92 mg/L, 0.17 mg/L, 0.05 mg/L, 38 μg/L (micrograms per liter), and 12 μg/L, respectively, and these concentrations are in the range of values observed in stormwater runoff from other parking lots in Wisconsin and Michigan. Efficiency of the settling device was calculated using the efficiency ratio and summation of loads (SOL) methods. Using the efficiency ratio method, the device reduced concentrations of SS, and DP, by 19, and 15, percent, respectively. Using the efficiency ratio method, the device increased "adjusted" TSS and TZn concentrations by 5 and 19, respectively. Bypass occurred for 3 of the 23 runoff events used in this assessment, and the bypass flow and water-quality concentrations were used to determine the efficiency of the bypass system. Concentrations of SS, "adjusted" TSS, and DP were reduced for the system by 18, 5, and 18, respectively; however, TZn increased by 5
Saeed, Diyar; Shalli, Shanaz; Fumoto, Hideyuki; Ootaki, Yoshio; Horai, Tetsuya; Anzai, Tomohiro; Zahr, Roula; Horvath, David J; Massiello, Alex L; Chen, Ji-Feng; Dessoffy, Raymond; Catanese, Jacquelyn; Benefit, Stephen; Golding, Leonard A R; Fukamachi, Kiyotaka
2010-06-01
Zirconia is a ceramic with material properties ideal for journal bearing applications. The purpose of this study was to evaluate the use of zirconium oxide (zirconia) as a blood journal bearing material in the DexAide right ventricular assist device. Zirconia ceramic was used instead of titanium to manufacture the DexAide stator housing without changing the stator geometry or the remaining pump hardware components. Pump hydraulic performance, journal bearing reliability, biocompatibility, and motor efficiency data of the zirconia stator were evaluated in six chronic bovine experiments for 14-91 days and compared with data from chronic experiments using the titanium stator. Pump performance data including average in vivo pump flows and speeds using a zirconia stator showed no statistically significant difference to the average values for 16 prior titanium stator in vivo studies, with the exception of a 19% reduction in power consumption. Indices of hemolysis were comparable for both stator types. Results of coagulation assays and platelet aggregation tests for the zirconia stator implants showed no device-induced increase in platelet activation. Postexplant evaluation of the zirconia journal bearing surfaces showed no biologic deposition in any of the implants. In conclusion, zirconia ceramic can be used as a hemocompatible material to improve motor efficiency while maintaining hydraulic performance in a blood journal bearing application.
Horwatich, Judy A.; Bannerman, Roger T.; Pearson, Robert
2011-01-01
The treatment efficiencies of two prefabricated stormwater-treatment devices were tested at a freeway site in a high-density urban part of Milwaukee, Wisconsin. One treatment device is categorized as a hydrodynamic-settling device (HSD), which removes pollutants by sedimentation and flotation. The other treatment device is categorized as a stormwater-filtration device (SFD), which removes pollutants by filtration and sedimentation. During runoff events, flow measurements were recorded and water-quality samples were collected at the inlet and outlet of each device. Efficiency-ratio and summation-of-load (SOL) calculations were used to estimate the treatment efficiency of each device. Event-mean concentrations and loads that were decreased by passing through the HSD include total suspended solids (TSS), suspended sediment (SS), total phosphorus (TP), total copper (TCu), and total zinc (TZn). The efficiency ratios for these constituents were 42, 57, 17, 33, and 23 percent, respectively. The SOL removal rates for these constituents were 25, 49, 10, 27, and 16 percent, respectively. Event-mean concentrations and loads that increased by passing through the HSD include chloride (Cl), total dissolved solids (TDS), and dissolved zinc (DZn). The efficiency ratios for these constituents were -347, -177, and 20 percent, respectively. Four constituents—dissolved phosphorus (DP), chemical oxygen demand (COD), total polycyclic aromatic hydrocarbon (PAH), and dissolved copper (DCu)—are not included in the list of computed efficiency ratio and SOL because the variability between sampled inlet and outlet pairs were not significantly different. Event-mean concentrations and loads that decreased by passing through the SFD include TSS, SS, TP, DCu, TCu, DZn, TZn, and COD. The efficiency ratios for these constituents were 59, 90, 40, 21, 66, 23, 66, and 18, respectively. The SOLs for these constituents were 50, 89, 37, 19, 60, 20, 65, and 21, respectively. Two constituents—DP and
van Lieshout, Remko; Pisters, Martijn F; Vanwanseele, Benedicte; de Bie, Rob A; Wouters, Eveline J; Stukstette, Mirelle J
2016-01-01
Partial weight bearing is frequently instructed by physical therapists in patients after lower-limb trauma or surgery. The use of biofeedback devices seems promising to improve the patient's compliance with weight-bearing instructions. SmartStep and OpenGo-Science are biofeedback devices that provide real-time feedback. For a successful implementation, usability of the devices is a critical aspect and should be tested from a user's perspective. To describe the usability from the physical therapists' and a patients' perspective of Smartstep and OpenGo-Science to provide feedback on partial weight bearing during supervised rehabilitation of patients after lower-limb trauma or surgery. In a convergent mixed-methods design, qualitative and quantitative data were collected. Usability was subdivided into user performance, satisfaction and acceptability. Patients prescribed with partial weight bearing and their physical therapists were asked to use SmartStep and OpenGo-Science during supervised rehabilitation. Usability was qualitatively tested by a think-aloud method and a semi-structured interview and quantitatively tested by the System-Usability-Scale (SUS) and closed questions. For the qualitative data thematic content analyses were used. Nine pairs of physical therapists and their patients participated. The mean SUS scores for patients and physical therapists were for SmartStep 70 and 53, and for OpenGo-Science 79 and 81, respectively. Scores were interpreted with the Curved Grading Scale. The qualitative data showed that there were mixed views and perceptions from patients and physical therapists on satisfaction and acceptability. This study gives insight in the usability of two biofeedback devices from the patient's and physical therapist's perspective. The overall usability from both perspectives seemed to be acceptable for OpenGo-Science. For SmartStep, overall usability seemed only acceptable from the patient's perspective. The study findings could help
International Nuclear Information System (INIS)
Kim, Min Kyu; Kim, Jung Han; Choi, In Kil
2012-01-01
Seismic safety of NPP is one of the most important issues in a nuclear field after great east Japan earthquake in 2011. For the improvement of seismic safety of nuclear power plant, seismic isolation is the easiest solution for increasing the seismic safety. Otherwise, the application of seismic isolation devices for nuclear power plants doesn't make the seismic risk of NPP increases always. The rubber bearing have many uncertainties of material properties and large displacement should absorb according to the application of isolation devices. In this study, for the evaluation of uncertainty of the material properties of rubber bearing, material tests for rubber and mechanical properties test for natural rubber bearing were performed. For the evaluation of effect of hardness of rubber, 4 kinds of rubber hardness for material property tests and 2 kinds of rubber hardness for mechanical property test were considered. As a result, the variation of material properties is higher than that of mechanical properties of natural rubber bearings
Ma, W.
2013-04-01
Microfiltration is an important microfluidic technique suitable for enrichment and isolation of cells. However, cell lysing could occur due to hydrodynamic damage that may be detrimental for medical diagnostics. Therefore, we conducted a systematic study of hydrodynamic cell lysing in a high-throughput Circular Multi-Channel Microfiltration (CMCM) device integrated with a polycarbonate membrane. HeLa cells (cervical cancer cells) were driven into the CMCM at different flow rates. The viability of the cells in the CMCM was examined by fluorescence microscopy using Acridine Orange (AO)/Ethidium Bromide (EB) as a marker for viable/dead cells. A simple analytical cell viability model was derived and a 3D numerical model was constructed to examine the correlation of between cell lysing and applied shear stress under varying flow rate and Reynolds number. The measured cell viability as a function of the shear stress was consistent with theoretical and numerical predictions when accounting for cell size distribution. © 2013 IEEE.
Ma, W.; Liu, D.; Shagoshtasbi, H.; Shukla, A.; Nugroho, E. S.; Zohar, Y.; Lee, Y.-K.
2013-01-01
Microfiltration is an important microfluidic technique suitable for enrichment and isolation of cells. However, cell lysing could occur due to hydrodynamic damage that may be detrimental for medical diagnostics. Therefore, we conducted a systematic study of hydrodynamic cell lysing in a high-throughput Circular Multi-Channel Microfiltration (CMCM) device integrated with a polycarbonate membrane. HeLa cells (cervical cancer cells) were driven into the CMCM at different flow rates. The viability of the cells in the CMCM was examined by fluorescence microscopy using Acridine Orange (AO)/Ethidium Bromide (EB) as a marker for viable/dead cells. A simple analytical cell viability model was derived and a 3D numerical model was constructed to examine the correlation of between cell lysing and applied shear stress under varying flow rate and Reynolds number. The measured cell viability as a function of the shear stress was consistent with theoretical and numerical predictions when accounting for cell size distribution. © 2013 IEEE.
Nisar, Ubaid Ahmed; Ashraf, Waqas; Qamar, Shamsul
2016-08-01
Numerical solutions of the hydrodynamical model of semiconductor devices are presented in one and two-space dimension. The model describes the charge transport in semiconductor devices. Mathematically, the models can be written as a convection-diffusion type system with a right hand side describing the relaxation effects and interaction with a self consistent electric field. The proposed numerical scheme is a splitting scheme based on the conservation element and solution element (CE/SE) method for hyperbolic step, and a semi-implicit scheme for the relaxation step. The numerical results of the suggested scheme are compared with the splitting scheme based on Nessyahu-Tadmor (NT) central scheme for convection step and the same semi-implicit scheme for the relaxation step. The effects of various parameters such as low field mobility, device length, lattice temperature and voltages for one-space dimensional hydrodynamic model are explored to further validate the generic applicability of the CE/SE method for the current model equations. A two dimensional simulation is also performed by CE/SE method for a MESFET device, producing results in good agreement with those obtained by NT-central scheme.
The R and D D's bearing test benches
International Nuclear Information System (INIS)
Vialettes, J.M.
1997-01-01
In power generation plants, rotating machines are involved in energy transformation processes and safety systems. The bearings supporting the rotors and the thrust bearings play a crucial role in the reliability of these machines. The phenomena encountered straddle several disciplines: hydrodynamics, tribology, thermomechanics, materials and vibrations in a specific environment, namely: thin fluid film, solid mechanical components and shaft rotation. Means of analysing the behaviour of these components (bearings and thrust bearings) have been developed and implemented. These consists of the EDYOS (Etude Dynamique des Organes de Supportage) code for dynamically studying bearing devices and several related bench tests. In reality, in order to understand the complex physical phenomena encountered in these components, it is vital to carry out analyses and experimental validations. Since these investigations cannot be carried out on actual machines, test benches have been built which can subject the sample bearings to the equivalent stresses. (author)
DEFF Research Database (Denmark)
Thomsen, Kim; Klit, Peder
2012-01-01
A flexure journal bearing design is proposed that will improve operational behaviour of a journal bearing at pronounced misalignment. Using a thermoelastohydrodynamic model, it is shown that the proposed flexure journal bearing has vastly increased the hydrodynamic performance compared to the stiff...... bearing when misaligned. The hydrodynamic performance is evaluated on lubricant film thickness, pressure and temperature. Furthermore, the influence of a compliant bearing liner is investigated and it is found that it increases the hydrodynamic performance when applied to a stiff bearing, whereas...... the liner has practically no influence on the flexure journal bearing's performance....
FUNDAMENTALS OF STRUCTURAL TYPOLOGY DEVICE DESIGN WITH A GAS BEARING LAYER
Directory of Open Access Journals (Sweden)
I. A. Аvtsinоv
2015-01-01
Full Text Available We describe the typical stages of a structural typology of devices allowing them to design quality in the automatic mode on the known parameters of products (parts and the required processing operations with them. In the first stage classification it was organized as a piece of specific products and devices for the manipulation of the latter. Specifics items described their physical – mechanical properties, geometry and their application. The most frequently described specific products are used in pharmaceutical, perfume, food, microelectronics, electrical engineering, electronics. The main elements of the proposed device is a carrier working surface over which a thin layer of gas is created. Depending on the position (horizontal or vertical of the form of its movement (rotation, rotational – translational or is stationary, and the configuration of the carrier operating the surface implement various manufacturing operations (targeting, positioning, shaping, classification, transport, heat treatment, weight control, assembly, culling, and others. The second stage was to mathematically describe the relationship of the specificity of piece goods, with design features of devices supporting the work surface and sold them operations. For this purpose, the device has been used in discrete mathematics, with which you can produce a description of all types of devices, and then make a conclusion such as the work surface meets the specified requirements. The apparent advantage of using predicate logic to this problem is fairly simple implementation of the algorithm of structural typology, which can be expressed using a declarative programming language. In the third phase, work is underway to create the necessary algorithmic language program "Prolog" and presented the structure of the imperative and declarative implementation of the algorithm.
da Silva, Isaias; Horikawa, Oswaldo; Cardoso, Jose R; Camargo, Fernando A; Andrade, Aron J P; Bock, Eduardo G P
2011-05-01
In previous studies, we presented main strategies for suspending the rotor of a mixed-flow type (centrifugal and axial) ventricular assist device (VAD), originally presented by the Institute Dante Pazzanese of Cardiology (IDPC), Brazil. Magnetic suspension is achieved by the use of a magnetic bearing architecture in which the active control is executed in only one degree of freedom, in the axial direction of the rotor. Remaining degrees of freedom, excepting the rotation, are restricted only by the attraction force between pairs of permanent magnets. This study is part of a joint project in development by IDPC and Escola Politecnica of São Paulo University, Brazil. This article shows advances in that project, presenting two promising solutions for magnetic bearings. One solution uses hybrid cores as electromagnetic actuators, that is, cores that combine iron and permanent magnets. The other solution uses actuators, also of hybrid type, but with the magnetic circuit closed by an iron core. After preliminary analysis, a pump prototype has been developed for each solution and has been tested. For each prototype, a brushless DC motor has been developed as the rotor driver. Each solution was evaluated by in vitro experiments and guidelines are extracted for future improvements. Tests have shown good results and demonstrated that one solution is not isolated from the other. One complements the other for the development of a single-axis-controlled, hybrid-type magnetic bearing for a mixed-flow type VAD. © 2011, Copyright the Authors. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.
Luciano, Rezzolla
2013-01-01
Relativistic hydrodynamics is a very successful theoretical framework to describe the dynamics of matter from scales as small as those of colliding elementary particles, up to the largest scales in the universe. This book provides an up-to-date, lively, and approachable introduction to the mathematical formalism, numerical techniques, and applications of relativistic hydrodynamics. The topic is typically covered either by very formal or by very phenomenological books, but is instead presented here in a form that will be appreciated both by students and researchers in the field. The topics covered in the book are the results of work carried out over the last 40 years, which can be found in rather technical research articles with dissimilar notations and styles. The book is not just a collection of scattered information, but a well-organized description of relativistic hydrodynamics, from the basic principles of statistical kinetic theory, down to the technical aspects of numerical methods devised for the solut...
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 1; Issue 9. Hydrodynamic Lubrication Experiment with 'Floating' Drops. Jaywant H Arakeri K R Sreenivas. General Article Volume 1 Issue 9 September 1996 pp 51-58. Fulltext. Click here to view fulltext PDF. Permanent link:
Milne-Thomson, L M
2011-01-01
This classic exposition of the mathematical theory of fluid motion is applicable to both hydrodynamics and aerodynamics. Based on vector methods and notation with their natural consequence in two dimensions - the complex variable - it offers more than 600 exercises and nearly 400 diagrams. Prerequisites include a knowledge of elementary calculus. 1968 edition.
Energy Technology Data Exchange (ETDEWEB)
Bulatov, A.I.; Chernov, V.S.; Prokopov, L.I.; Proselkov, Yu.M.; Tikhonov, Yu.P.
1980-01-15
A hydrodynamic disperser is suggested which contains a housing, slit nozzles installed on a circular base arranged opposite from each other, resonators secured opposite the nozzle and outlet sleeve. In order to improve the effectiveness of dispersion by throttling the flow, each resonator is made in the form of a crimped plate with crimpings that decrease in height in a direction towards the nozzle.
Zhou, Jie; Tan, Xiaodong; Song, Xiangjing; Zhang, Kaining; Fang, Jing; Peng, Lin; Qi, Wencai; Nie, Zonghui; Li, Ming; Deng, Rui; Yan, Chaofang
2015-03-01
Copper-bearing intrauterine device (IUD) insertion for long-term contraceptive use is high in China, but there has been evidence that first-year discontinuation rate of copper-bearing IUD has also increased rapidly in recent years especially among rural married women. To investigate long-term use of copper-bearing IUD, the authors examined the 7-year temporal trends of copper-bearing IUD discontinuation in a population-based birth-cohort study among 720 rural married women in China, from 2004 to 2012. Women requesting contraception were followed-up twice per year after the insertion of IUD. The gross cumulative life table discontinuation rates were calculated for each of the main reasons for discontinuation as well as for all reasons combined. By the end of 7 years, 384 discontinuations were observed. With a stepped-up trend, the gross cumulative life table rate for discontinuation increased from 10.06 (95% confidence interval = 7.86-12.27) per 100 women by the first year to 52.69 (95% confidence interval = 48.94-56.44) per 100 women by the end of 7 years, which increased rapidly in the first 2 years after copper-bearing IUD insertion, flattened out gradually in the following 2 years, then increased again in the last 3 years. Among reported method failure, expulsion and side effects were the main reasons for discontinuation of the copper-bearing IUD but not pregnancy. Personal reasons, such as renewal by personal will had influenced copper-bearing IUD use since the second year and should not be neglected. Based on this study, the temporal trends of copper-bearing IUD discontinuation was in a stepped-up trend in 7 years after insertion. Both reported method failure (expulsion and side effect) and personal reason had effect on the discontinuation of copper-bearing IUD, but pregnancy was no more the most important reason affecting the use of copper-bearing IUD. © 2014 APJPH.
van Lieshout, Remko; Pisters, Martijn F.; Vanwanseele, Benedicte; de Bie, Rob A.; Wouters, Eveline J.; Stukstette, Mirelle J.
2016-01-01
Background Partial weight bearing is frequently instructed by physical therapists in patients after lower-limb trauma or surgery. The use of biofeedback devices seems promising to improve the patient’s compliance with weight-bearing instructions. SmartStep and OpenGo-Science are biofeedback devices that provide real-time feedback. For a successful implementation, usability of the devices is a critical aspect and should be tested from a user’s perspective. Aim To describe the usability from the physical therapists’ and a patients’ perspective of Smartstep and OpenGo-Science to provide feedback on partial weight bearing during supervised rehabilitation of patients after lower-limb trauma or surgery. Methods In a convergent mixed-methods design, qualitative and quantitative data were collected. Usability was subdivided into user performance, satisfaction and acceptability. Patients prescribed with partial weight bearing and their physical therapists were asked to use SmartStep and OpenGo-Science during supervised rehabilitation. Usability was qualitatively tested by a think-aloud method and a semi-structured interview and quantitatively tested by the System-Usability-Scale (SUS) and closed questions. For the qualitative data thematic content analyses were used. Results Nine pairs of physical therapists and their patients participated. The mean SUS scores for patients and physical therapists were for SmartStep 70 and 53, and for OpenGo-Science 79 and 81, respectively. Scores were interpreted with the Curved Grading Scale. The qualitative data showed that there were mixed views and perceptions from patients and physical therapists on satisfaction and acceptability. Conclusion This study gives insight in the usability of two biofeedback devices from the patient’s and physical therapist’s perspective. The overall usability from both perspectives seemed to be acceptable for OpenGo-Science. For SmartStep, overall usability seemed only acceptable from the
On the validity of the classical hydrodynamic lubrication theory applied to squeeze film dampers
International Nuclear Information System (INIS)
Danaila, S; Moraru, L
2010-01-01
Squeeze film dampers (SFD) are devices utilized to control vibrations of the shafts of high-speed rotating machinery. The SFD - squirrel cage combination is probably the most used system for tuning the stiffness and damping of the supports for rotors installed on ball bearings. Squeeze film dampers are essentially hydrodynamic bearings which contain the ball bearings housings of ball-bearings supported shafts. Consequently, the oil film within the SFD are influenced only by the precession and nutation of the shaft, that is the flow of the oil within the damper is not directly influenced by the spin of the rotor. However, in the classical theory, the flow in the thin film is also governed by the Reynolds equation. In this paper, some of the limits of the classical theory of the SFD are discussed and theoretical and experimental studies, which illustrate the ideas presented herein, are presented as well. The orbits of an unbalanced rotor that is supported by a ball-bearings-SFD-squirrel-cage assembly at one end and by rigidly mounted ball bearings at the other end are computed using the bearing forces provided by the classical short bearing theory. The numerical model also includes the properties of the squirrel cage. The parameters of the squirrel cage were measured, together with the effect of the friction within the assembly. Experimental unbalance responses were also collected for various rotation speeds and unbalances to validate the numerical simulations.
The R and D D`s bearing test benches; Les bancs d`essais de paliers de la DER
Energy Technology Data Exchange (ETDEWEB)
Vialettes, J.M. [Service Ensembles de Production, Departement Machines, Direction des Etudes et Recherches, Electricite de France (EDF), 92 - Clamart (France)
1997-01-01
In power generation plants, rotating machines are involved in energy transformation processes and safety systems. The bearings supporting the rotors and the thrust bearings play a crucial role in the reliability of these machines. The phenomena encountered straddle several disciplines: hydrodynamics, tribology, thermomechanics, materials and vibrations in a specific environment, namely: thin fluid film, solid mechanical components and shaft rotation. Means of analysing the behaviour of these components (bearings and thrust bearings) have been developed and implemented. These consists of the EDYOS (Etude Dynamique des Organes de Supportage) code for dynamically studying bearing devices and several related bench tests. In reality, in order to understand the complex physical phenomena encountered in these components, it is vital to carry out analyses and experimental validations. Since these investigations cannot be carried out on actual machines, test benches have been built which can subject the sample bearings to the equivalent stresses. (author) 14 figs.
International Nuclear Information System (INIS)
Colgate, S.A.
1981-01-01
The explosion of a star supernova occurs at the end of its evolution when the nuclear fuel in its core is almost, or completely, consumed. The star may explode due to a small residual thermonuclear detonation, type I SN or it may collapse, type I and type II SN leaving a neutron star remnant. The type I progenitor should be thought to be an old accreting white dwarf, 1.4 M/sub theta/, with a close companion star. A type II SN is thought to be a massive young star 6 to 10 M/sub theta/. The mechanism of explosion is still a challenge to our ability to model the most extreme conditions of matter and hydrodynamics that occur presently and excessively in the universe. 39 references
Renilson, Martin
2015-01-01
This book adopts a practical approach and presents recent research together with applications in real submarine design and operation. Topics covered include hydrostatics, manoeuvring, resistance and propulsion of submarines. The author briefly reviews basic concepts in ship hydrodynamics and goes on to show how they are applied to submarines, including a look at the use of physical model experiments. The issues associated with manoeuvring in both the horizontal and vertical planes are explained, and readers will discover suggested criteria for stability, along with rudder and hydroplane effectiveness. The book includes a section on appendage design which includes information on sail design, different arrangements of bow planes and alternative stern configurations. Other themes explored in this book include hydro-acoustic performance, the components of resistance and the effect of hull shape. Readers will value the author’s applied experience as well as the empirical expressions that are presented for use a...
Guyon, Etienne; Petit, Luc; Mitescu, Catalin D
2015-01-01
This new edition is an enriched version of the textbook of fluid dynamics published more than 10 years ago. It retains the same physically oriented pedagogical perspective. This book emphasizes, as in the first edition, experimental inductive approaches and relies on the study of the mechanisms at play and on dimensional analysis rather than more formal approaches found in many classical textbooks in the field. The need for a completely new version also originated from the increase, over the last few decades, of the cross-overs between the mechanical and physical approaches, as is visible in international meetings and joint projects. Hydrodynamics is more widely linked today to other fields of experimental sciences: materials, environment, life sciences and earth sciences, as well as engineering sciences.
International Nuclear Information System (INIS)
Wilkins, M.L.
1979-01-01
Various aspects of hydrodynamics and elastic--plastic flow are introduced for the purpose of defining hydrodynamic terms and explaining what some of the important hydrodynamic concepts are. The first part covers hydrodynamic theory; and discussed fundamental hydrodynamic equations, discontinuities, and shock, detonation, and elastic--plastic waves. The second part deals with applications of hydrodynamic theory to material equations of state, spall, Taylor instabilities, and detonation pressure measurements
International Nuclear Information System (INIS)
Okada, Yasuo; Suhara, Junji; Tamura, Tadashi; Ohta, Kazuya; Moro, Satoshi
2003-01-01
Three dimensional (3D) seismic isolation device has been developed to use for the base isolation system of the heavy building like a nuclear reactor building. The developed device is the 3D seismic isolation device that consists of the laminated rubber baring as a horizontal isolation device and the rolling seal type air spring as the vertical isolation device in series. In this research, the 3D seismic isolation device reduction model whose scale is 1/10 is made and the workability of the device by the horizontal and vertical dynamic load is examined. Two experiment parameters are considered. One is the case that the structure of the part that the horizontal load and the vertical load contact is pin condition and the other is the case of the roller condition. As a result of the examination, the workability of the vertical direction is confirmed when the horizontal load acts. The pressure resistant ability test for the air spring is performed by the monotonic pressurization. As the result, it is confirmed that pressure resistant ability improved by restricting the side deformation of the air spring and that the material of the existing air spring can withstand high pressure use sufficiently. As the result, it is confirmed that the developed 3D seismic isolation device is applicable to the actual plant. This study was performed under the sponsorship of the Ministry of Economy, Trade and Industry of Japan. (author)
International Nuclear Information System (INIS)
Pryce, M.H.L.
1985-01-01
A dominant mechanism contributing to hydrodynamic dispersion in fluid flow through rocks is variation of travel speeds within the channels carrying the fluid, whether these be interstices between grains, in granular rocks, or cracks in fractured crystalline rocks. The complex interconnections of the channels ensure a mixing of those parts of the fluid which travel more slowly and those which travel faster. On a macroscopic scale this can be treated statistically in terms of the distribution of times taken by a particle of fluid to move from one surface of constant hydraulic potential to another, lower, potential. The distributions in the individual channels are such that very long travel times make a very important contribution. Indeed, while the mean travel time is related to distance by a well-defined transport speed, the mean square is effectively infinite. This results in an asymmetrical plume which differs markedly from a gaussian shape. The distribution of microscopic travel times is related to the distribution of apertures in the interstices, or in the microcracks, which in turn are affected in a complex way by the stresses acting on the rock matrix
Bruinsma, Robijn; Grosberg, Alexander Y.; Rabin, Yitzhak; Zidovska, Alexandra
2014-01-01
Following recent observations of large scale correlated motion of chromatin inside the nuclei of live differentiated cells, we present a hydrodynamic theory—the two-fluid model—in which the content of a nucleus is described as a chromatin solution with the nucleoplasm playing the role of the solvent and the chromatin fiber that of a solute. This system is subject to both passive thermal fluctuations and active scalar and vector events that are associated with free energy consumption, such as ATP hydrolysis. Scalar events drive the longitudinal viscoelastic modes (where the chromatin fiber moves relative to the solvent) while vector events generate the transverse modes (where the chromatin fiber moves together with the solvent). Using linear response methods, we derive explicit expressions for the response functions that connect the chromatin density and velocity correlation functions to the corresponding correlation functions of the active sources and the complex viscoelastic moduli of the chromatin solution. We then derive general expressions for the flow spectral density of the chromatin velocity field. We use the theory to analyze experimental results recently obtained by one of the present authors and her co-workers. We find that the time dependence of the experimental data for both native and ATP-depleted chromatin can be well-fitted using a simple model—the Maxwell fluid—for the complex modulus, although there is some discrepancy in terms of the wavevector dependence. Thermal fluctuations of ATP-depleted cells are predominantly longitudinal. ATP-active cells exhibit intense transverse long wavelength velocity fluctuations driven by force dipoles. Fluctuations with wavenumbers larger than a few inverse microns are dominated by concentration fluctuations with the same spectrum as thermal fluctuations but with increased intensity. PMID:24806919
Kapich, Davorin D.
1987-01-01
A bearing system includes backup bearings for supporting a rotating shaft upon failure of primary bearings. In the preferred embodiment, the backup bearings are rolling element bearings having their rolling elements disposed out of contact with their associated respective inner races during normal functioning of the primary bearings. Displacement detection sensors are provided for detecting displacement of the shaft upon failure of the primary bearings. Upon detection of the failure of the primary bearings, the rolling elements and inner races of the backup bearings are brought into mutual contact by axial displacement of the shaft.
Numerical investigation of cavitation flow in journal bearing geometry
Stücke P.; Schmidt M.; Riedel M.
2013-01-01
The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal...
Bearing assemblies, apparatuses, and motor assemblies using the same
Sexton, Timothy N.; Cooley, Craig H.; Knuteson, Cody W.
2015-12-29
Various embodiments of the invention relate to bearing assemblies, apparatuses and motor assemblies that include geometric features configured to impart a selected amount of heat transfer and/or hydrodynamic film formation. In an embodiment, a bearing assembly may include a plurality of superhard bearing pads distributed circumferentially about an axis. At least some of the plurality of superhard bearing pads may include a plurality of sub-superhard bearing elements defining a bearing surface. At least some of the plurality of sub-superhard bearing elements may be spaced from one another by one or more voids to impart a selected amount of heat transfer and hydrodynamic film formation thereon during operation. The bearing assembly may also include a support ring that carries the plurality of superhard bearing pads. In addition, at least a portion of the sub-superhard bearing elements may extend beyond the support ring.
Directory of Open Access Journals (Sweden)
Jong Wan Hu
2014-12-01
Full Text Available Base isolation has been used as one of the most wildly accepted seismic protection systems that should substantially dissociate a superstructure from its substructure resting on a shaking ground, thereby sustainably preserving entire structures against earthquake forces as well as inside non-structural integrities. Base isolation devices can operate very effectively against near-fault (NF ground motions with large velocity pulses and permanent ground displacements. In this study, comparative advantages for using lead-rubber bearing (LRB isolation systems are mainly investigated by performing nonlinear dynamic time-history analyses with NF ground motions. The seismic responses with respects to base shears and inter-story drifts are compared according to the installation of LRB isolation systems in the frame building. The main function of the base LRB isolator is to extend the period of structural vibration by increasing lateral flexibility in the frame structure, and thus ground accelerations transferred into the superstructure can dramatically decrease. Therefore, these base isolation systems are able to achieve notable mitigation in the base shear. In addition, they make a significant contribution to reducing inter-story drifts distributed over the upper floors. Finally, the fact that seismic performance can be improved by installing isolation devices in the frame structure is emphasized herein through the results of nonlinear dynamic analyses.
Method to Increase Performance of Foil Bearings Through Passive Thermal Management
Bruckner, Robert
2013-01-01
This invention is a new approach to designing foil bearings to increase their load capacity and improve their reliability through passive thermal management. In the present case, the bearing is designed in such a way as to prevent the carryover of lubricant from the exit of one sector to the inlet of the ensuing sector of the foil bearing. When such passive thermal management techniques are used, bearing load capacity is improved by multiples, and reliability is enhanced when compared to current foil bearings. This concept has recently been tested and validated, and shows that load capacity performance of foil bearings can be improved by a factor of two at relatively low speeds with potentially greater relative improvements at higher speeds. Such improvements in performance with respect to speed are typical of foil bearings. Additionally, operation of these newly conceived bearings shows much more reliability and repeatable performance. This trait can be exploited in machine design to enhance safety, reliability, and overall performance. Finally, lower frictional torque has been demonstrated when operating at lower (non-load capacity) loads, thus providing another improvement above the current state of the art. The objective of the invention is to incorporate features into a foil bearing that both enhance passive thermal management and temperature control, while at the same time improve the hydrodynamic (load capacity) performance of the foil bearing. Foil bearings are unique antifriction devices that can utilize the working fluid of a machine as a lubricant (typically air for turbines and motors, liquids for pumps), and as a coolant to remove excess energy due to frictional heating. The current state of the art of foil bearings utilizes forced cooling of the bearing and shaft, which represents poor efficiency and poor reliability. This invention embodies features that utilize the bearing geometry in such a manner as to both support load and provide an inherent and
International Nuclear Information System (INIS)
Bai Jingping
2001-01-01
Infiltrating type hydrodynamic way controls the formation of interbedding oxidation zone type uranium deposit. The author analyzes hydrodynamic condition of Songliao basin and concludes that during evolution and development of Songliao basin, Water-bearing petrofabric of Mingshui Formation and above inherit completely infiltrating hydrodynamic way as they were deposited and that Sifangtai Formation inherit the way to some extent, that below Sifangtai Formation water bearing petrofabric were completely reformed in northern part of Songliao watershed. The contact line between infiltrating and out filtrating type hydrodynamic way, e.g. underground water dividing lines formed in different geological period, restricts development of interbedding oxidation zone in this period and controls uranium mineralization
Menke, John R.; Boeker, Gilbert F.
1976-05-11
1. An improved journal bearing comprising in combination a non-rotatable cylindrical bearing member having a first bearing surface, a rotatable cylindrical bearing member having a confronting second bearing surface having a plurality of bearing elements, a source of lubricant adjacent said bearing elements for supplying lubricant thereto, each bearing element consisting of a pair of elongated relatively shallowly depressed surfaces lying in a cylindrical surface co-axial with the non-depressed surface and diverging from one another in the direction of rotation and obliquely arranged with respect to the axis of rotation of said rotatable member to cause a flow of lubricant longitudinally along said depressed surfaces from their distal ends toward their proximal ends as said bearing members are rotated relative to one another, each depressed surface subtending a radial angle of less than 360.degree., and means for rotating said rotatable bearing member to cause the lubricant to flow across and along said depressed surfaces, the flow of lubricant being impeded by the non-depressed portions of said second bearing surface to cause an increase in the lubricant pressure.
Elasto-hydrodynamic lubrication
Dowson, D; Hopkins, D W
1977-01-01
Elasto-Hydrodynamic Lubrication deals with the mechanism of elasto-hydrodynamic lubrication, that is, the lubrication regime in operation over the small areas where machine components are in nominal point or line contact. The lubrication of rigid contacts is discussed, along with the effects of high pressure on the lubricant and bounding solids. The governing equations for the solution of elasto-hydrodynamic problems are presented.Comprised of 13 chapters, this volume begins with an overview of elasto-hydrodynamic lubrication and representation of contacts by cylinders, followed by a discussio
Elementary classical hydrodynamics
Chirgwin, B H; Langford, W J; Maxwell, E A; Plumpton, C
1967-01-01
Elementary Classical Hydrodynamics deals with the fundamental principles of elementary classical hydrodynamics, with emphasis on the mechanics of inviscid fluids. Topics covered by this book include direct use of the equations of hydrodynamics, potential flows, two-dimensional fluid motion, waves in liquids, and compressible flows. Some general theorems such as Bernoulli's equation are also considered. This book is comprised of six chapters and begins by introducing the reader to the fundamental principles of fluid hydrodynamics, with emphasis on ways of studying the motion of a fluid. Basic c
Directory of Open Access Journals (Sweden)
E. Petrella
2018-01-01
Full Text Available Messinian evaporates are widely distributed in the Mediterranean Sea as outcropping sediments in small marginal basins and in marine cores. Progressive filling of subbasins led to the formation of complex aquifer systems in different regions where hypersaline and fresh water coexist and interact in different manner. It also generates a significant diversification of groundwater hydrochemical signature and different microbial communities. In the case study, the hydrogeology and hydrochemistry of the whole system are influenced by good hydraulic connection between the shallower pyroclastic horizon and the underlying evaporate-bearing fine-grained Messinian succession. This is demonstrated by the merge of hydrogeological, chemical, isotopic, and microbiological data. No mixing with deep ascending waters has been observed. As shown by geophysical, hydraulic, and microbiological investigations, the hydraulic heterogeneity of the Messinian bedrock, mainly due to karstified evaporitic interstrata/lenses, causes the hydraulic head to significantly vary with depth. Somewhere, the head increases with the depth’s increase and artesian flow conditions are locally observed. Moreover, the metagenomic investigations demonstrated the existence of a poor hydraulic connection within the evaporate-bearing fine-grained succession at metric and decametric scales, therefore leading to a patchwork of geochemical (and microbiological subenvironments.
Servo Reduces Friction In Flexure Bearing
Clingman, W. Dean
1991-01-01
Proposed servocontrol device reduces such resistive torques as stiction, friction, ripple, and cogging in flexure bearing described in LAR-14348, "Flexure Bearing Reduces Startup Friction". Reduces frictional "bump" torque encountered when bearing ball runs into buildup of grease on bearing race. Also used as cable follower to reduce torque caused by cable and hoses when they bend because of motion of bearing. New device includes torquer across ball race. Torquer controlled by servo striving to keep flexure at null, removing torque to outer ring. In effect, device is inner control loop reducing friction, but does not control platforms or any outer-control-loop functions.
Skarstrom, C.W.
1960-09-01
A gas lubricated bearing for a rotating shaft is described. The assembly comprises a stationary collar having an annular member resiliently supported thereon. The collar and annular member are provided with cooperating gas passages arranged for admission of pressurized gas which supports and lubricates a bearing block fixed to the rotatable shaft. The resilient means for the annular member support the latter against movement away from the bearing block when the assembly is in operation.
Schwartz, C.C.; Miller, S.D.; Haroldson, M.A.; Feldhamer, G.; Thompson, B.; Chapman, J.
2003-01-01
The grizzly bear inspires fear, awe, and respect in humans to a degree unmatched by any other North American wild mammal. Like other bear species, it can inflict serious injury and death on humans and sometimes does. Unlike the polar bear (Ursus maritimus) of the sparsely inhabited northern arctic, however, grizzly bears still live in areas visited by crowds of people, where presence of the grizzly remains physically real and emotionally dominant. A hike in the wilderness that includes grizzly bears is different from a stroll in a forest from which grizzly bears have been purged; nighttime conversations around the campfire and dreams in the tent reflect the presence of the great bear. Contributing to the aura of the grizzly bear is the mixture of myth and reality about its ferocity. unpredictable disposition, large size, strength, huge canines, long claws, keen senses, swiftness, and playfulness. They share characteristics with humans such as generalist life history strategies. extended periods of maternal care, and omnivorous diets. These factors capture the human imagination in ways distinct from other North American mammals. Precontact Native American legends reflected the same fascination with the grizzly bear as modern stories and legends (Rockwell 1991).
Determining the hydrodynamic indices of contractions
International Nuclear Information System (INIS)
Blagov, Eh.E.
2002-01-01
The new dependences, making it possible only by measuring the flow rate and pressure drop on the contraction device (CD) with the known geometry, including the regulatory organ, in the non-crisis mode of the turbulent flow to calculate all the hydrodynamic indices of this device, including the pressure reduction in the jet contraction, are obtained. This simplifies and accelerates the CD hydraulic tests of all types. The new methodology for determining the cavitation factual start on the CD is proposed [ru
Hydrostatic and hybrid bearing design
Rowe, W B
1983-01-01
Hydrostatic and Hybrid Bearing Design is a 15-chapter book that focuses on the bearing design and testing. This book first describes the application of hydrostatic bearings, as well as the device pressure, flow, force, power, and temperature. Subsequent chapters discuss the load and flow rate of thrust pads; circuit design, flow control, load, and stiffness; and the basis of the design procedures and selection of tolerances. The specific types of bearings, their design, dynamics, and experimental methods and testing are also shown. This book will be very valuable to students of engineering des
Ream, L. W.
1974-01-01
A test program was conducted to determine the performance characteristics of gas-lubricated cruciform-mounted tilting-pad journal bearings and a damped spiral-groove thrust bearing designed for the Brayton cycle rotating unit (BRU). Hydrostatic, hybrid (simultaneously hydrostatic and hydrodynamic), and hydrodynamic tests were conducted in argon gas at ambient pressure and temperature ranges representative of operation to the 10.5 kWe BRU power-generating level. Performance of the gas lubricated bearings is presented including hydrostatic gas flow rates, bearing clearances, bearing temperatures, and transient performance.
Changes in plain bearing technology
Koring, Rolf
2012-01-01
A unique fusion of theoretical and practical knowledge, Changes in Plain Bearing Technology, by Rolf Koring, covers a meaningful range of expertise in this field.Drawing from years of experience in design development, materials selection, and their correlation to real-life part failure, this title, co-published by SAE International and expert Verlag (Germany), concentrates on hydrodynamic bearings lined with white metals, also known as Babbits.Written under the assumption that even the most mature body of knowledge can be revisited and improved, Changes in Plain Bearing Technology is a courageous and focused approach to questioning accepted test results and looking at alternative material compounds, and their application suitability.The process, which leads to innovative answers on how the technology is transforming itself to respond to new market requirements, shows how interdisciplinary thinking can recognize new potential in long-established industrial modus operandi.Tackling the highly complex issue of co...
Granular Gases: Probing the Boundaries of Hydrodynamics
International Nuclear Information System (INIS)
Goldhirsch, I.
1999-01-01
The dissipative nature of the particle interactions in granular systems renders granular gases mesoscopic and bearing some similarities to regular gases in the ''continuum transition regime'' where shear rates and/or thermal gradients are very large). The following properties of granular gases support the above claim: (i). Mean free times are of the same order as macroscopic time scales (inverse shear rates); (ii). Mean free paths can be macroscopic and comparable to the system's dimensions; (iii). Typical flows are supersonic; (iv). Shear rates are typically ''large''; (v). Stress fields are scale (resolution) dependent; (vi). Burnett and super-Burnett corrections to both the constitutive relations and the boundary conditions are of importance; (vii). Single particle distribution functions can be far from Gaussian. It is concluded that while hydrodynamic descriptions of granular gases are relevant, they are probing the boundaries of applicability of hydrodynamics and perhaps slightly beyond
Hydrodynamic optical soliton tunneling
Sprenger, P.; Hoefer, M. A.; El, G. A.
2018-03-01
A notion of hydrodynamic optical soliton tunneling is introduced in which a dark soliton is incident upon an evolving, broad potential barrier that arises from an appropriate variation of the input signal. The barriers considered include smooth rarefaction waves and highly oscillatory dispersive shock waves. Both the soliton and the barrier satisfy the same one-dimensional defocusing nonlinear Schrödinger (NLS) equation, which admits a convenient dispersive hydrodynamic interpretation. Under the scale separation assumption of nonlinear wave (Whitham) modulation theory, the highly nontrivial nonlinear interaction between the soliton and the evolving hydrodynamic barrier is described in terms of self-similar, simple wave solutions to an asymptotic reduction of the Whitham-NLS partial differential equations. One of the Riemann invariants of the reduced modulation system determines the characteristics of a soliton interacting with a mean flow that results in soliton tunneling or trapping. Another Riemann invariant yields the tunneled soliton's phase shift due to hydrodynamic interaction. Soliton interaction with hydrodynamic barriers gives rise to effects that include reversal of the soliton propagation direction and spontaneous soliton cavitation, which further suggest possible methods of dark soliton control in optical fibers.
Energy Technology Data Exchange (ETDEWEB)
Bożek, Piotr, E-mail: piotr.bozek@fis.agh.edu.pl
2016-12-15
The scenario assuming a collective expansion stage in collisions of small systems, p-A, d-Au, and {sup 3}He-Au is discussed. A review of the observables predicted in relativistic hydrodynamic models in comparison with experimental data is presented, with arguments indicating the presence of collective expansion. The limits of applicability of the hydrodynamic model are addressed. We briefly indicate possible applications of the collective flow in small systems to study the space-time dynamics at very small scales in relativistic collisions.
Hemolytic potential of hydrodynamic cavitation.
Chambers, S D; Bartlett, R H; Ceccio, S L
2000-08-01
The purpose of this study was to determine the hemolytic potentials of discrete bubble cavitation and attached cavitation. To generate controlled cavitation events, a venturigeometry hydrodynamic device, called a Cavitation Susceptibility Meter (CSM), was constructed. A comparison between the hemolytic potential of discrete bubble cavitation and attached cavitation was investigated with a single-pass flow apparatus and a recirculating flow apparatus, both utilizing the CSM. An analytical model, based on spherical bubble dynamics, was developed for predicting the hemolysis caused by discrete bubble cavitation. Experimentally, discrete bubble cavitation did not correlate with a measurable increase in plasma-free hemoglobin (PFHb), as predicted by the analytical model. However, attached cavitation did result in significant PFHb generation. The rate of PFHb generation scaled inversely with the Cavitation number at a constant flow rate, suggesting that the size of the attached cavity was the dominant hemolytic factor.
Hydrodynamical description of collective flow
Huovinen, Pasi
2003-01-01
I review how hydrodynamical flow is related to the observed flow in ultrarelativistic heavy ion collisions and how initial conditions, equation of state and freeze-out temperature affect flow in hydrodynamical models.
Dissipative relativistic hydrodynamics
International Nuclear Information System (INIS)
Imshennik, V.S.; Morozov, Yu.I.
1989-01-01
Using the comoving reference frame in the general non-inertial case, the relativistic hydrodynamics equations are derived with an account for dissipative effects in the matter. From the entropy production equation, the exact from for the dissipative tensor components is obtained. As a result, the closed system of equations of dissipative relativistic hydrodynamics is obtained in the comoving reference frame as a relativistic generalization of the known Navier-Stokes equations for Lagrange coordinates. Equations of relativistic hydrodynamics with account for dissipative effects in the matter are derived using the assocoated reference system in general non-inertial case. True form of the dissipative tensor components is obtained from entropy production equation. Closed system of equations for dissipative relativistic hydrodynamics is obtained as a result in the assocoated reference system (ARS) - relativistic generalization of well-known Navier-Stokes equations for Lagrange coordinates. Equation system, obtained in this paper for ARS, may be effectively used in numerical models of explosive processes with 10 51 erg energy releases which are characteristic for flashes of supernovae, if white dwarf type compact target suggested as presupernova
International Nuclear Information System (INIS)
Lee, A.S.; Preece, G.E.
1988-01-01
A hydrostatic bearing for the lower end of the vertical shaft of a sodium pump comprises a support shell encircling the shaft and a bush located between the shell and shaft. Liquid sodium is fed from the pump outlet to the bush/shaft and bush/shell interfaces to provide hydrostatic support. The bush outer surface and the shell inner surface are of complementary part-spherical shape and the bush floats relative to the shaft so that the bush can align itself with the shaft axis. Monitoring of the relative rotational speed of the bush with respect to the shaft (such rotation being induced by the viscous drag forces present) is also performed for the purposes of detecting abnormal operation of the bearing or partial seizure, at least one magnet is rotatable with the bush, and a magnetic sensor provides an output having a frequency related to the speed of the bush. (author)
Microflow Cytometers with Integrated Hydrodynamic Focusing
Directory of Open Access Journals (Sweden)
Martin Schmidt
2013-04-01
Full Text Available This study demonstrates the suitability of microfluidic structures for high throughput blood cell analysis. The microfluidic chips exploit fully integrated hydrodynamic focusing based on two different concepts: Two-stage cascade focusing and spin focusing (vortex principle. The sample—A suspension of micro particles or blood cells—is injected into a sheath fluid streaming at a substantially higher flow rate, which assures positioning of the particles in the center of the flow channel. Particle velocities of a few m/s are achieved as required for high throughput blood cell analysis. The stability of hydrodynamic particle positioning was evaluated by measuring the pulse heights distributions of fluorescence signals from calibration beads. Quantitative assessment based on coefficient of variation for the fluorescence intensity distributions resulted in a value of about 3% determined for the micro-device exploiting cascade hydrodynamic focusing. For the spin focusing approach similar values were achieved for sample flow rates being 1.5 times lower. Our results indicate that the performances of both variants of hydrodynamic focusing suit for blood cell differentiation and counting. The potential of the micro flow cytometer is demonstrated by detecting immunologically labeled CD3 positive and CD4 positive T-lymphocytes in blood.
Hydrodynamic dispersion of microswimmers in suspension
Martin, Matthieu; Rafaï, Salima; Peyla, Philippe
2014-11-01
In our laboratory, we study hydrodynamics of suspensions of micro-swimmers. These micro-organisms are unicellular algae Chlamydomonas Rheinhardii which are able to swim by using their flagella. The swimming dynamics of these micro-swimmers can be seen as a random walk, in absence of any kind of interaction. In addition, these algae have the property of being phototactic, i.e. they swim towards the light. Combining this property with a hydrodynamic flow, we were able to reversibly separate algae from the rest of the fluid. But for sufficiently high volume fraction, these active particles interact with each other. We are now interested in how the coupling of hydrodynamic interactions between swimmers and phototaxis can modify the swimming dynamics at the scale of the suspension. To this aim, we conduct experiments in microfluidic devices to study the dispersion of the micro-organisms in a the liquid phase as a function of the volume fraction. We show that the dispersion of an assembly of puller type microswimmers is quantitatively affected by hydrodynamics interactions. Phd student.
Directory of Open Access Journals (Sweden)
Renato Brancati
1999-01-01
determined after acquiring and analysing the orbits described by the journal axis for assigned unbalance values in different operating conditions. Analysis of the results shows some particular operating features that were not entirely predicted by the theoretical model and which may give rise to malfunctions in the rotor-tilting pad bearings system. The tests were carried out in the rotor dynamics laboratory of the Dipartimento di Ingegneria Meccanica per l'Energetica at the University of Naples.
Energy Technology Data Exchange (ETDEWEB)
Aoi, K.; Ozawa, T.
1986-06-10
A bearing arrangement is described for the camshaft of an internal combustion engine or the like which camshaft is formed along its length in axial order with a first bearing surface, a first cam lobe, a second bearing surface, a second cam lobe, a third bearing surface, a third cam lobe and a fourth bearing surface, the improvement comprising first bearing means extending around substantially the full circumference of the first bearing surface and journaling the first bearing surface, second bearing means extending around substantially less than the circumference of the second bearing surface and journaling the second bearing surface, third bearing means extending around substantially less than the circumference of the third bearing surface and journaling the third bearing surface, and fourth bearing means extending around substantially the full circumference of the fourth bearing surface and journaling the first bearing surface.
Numerical Investigation of Pressure Profile in Hydrodynamic Lubrication Thrust Bearing.
Najar, Farooq Ahmad; Harmain, G A
2014-01-01
Reynolds equation is solved using finite difference method (FDM) on the surface of the tilting pad to find the pressure distribution in the lubricant oil film. Different pressure profiles with grid independence are described. The present work evaluates pressure at various locations after performing a thorough grid refinement. In recent similar works, this aspect has not been addressed. However, present study shows that it can have significant effect on the pressure profile. Results of a sector shaped pad are presented and it is shown that the maximum average value of pressure is 12% (approximately) greater than the previous results. Grid independence occurs after 24 × 24 grids. A parameter "ψ" has been proposed to provide convenient indicator of obtaining grid independent results. ψ = |(P refinedgrid - P Refrence-grid)/P refinedgrid|, ψ ≤ ε, where "ε" can be fixed to a convenient value and a constant minimum film thickness value of 75 μm is used in present study. This important parameter is highlighted in the present work; the location of the peak pressure zone in terms of (r, θ) coordinates is getting shifted by changing the grid size which will help the designer and experimentalist to conveniently determine the position of pressure measurement probe.
Numerical Investigation of Pressure Profile in Hydrodynamic Lubrication Thrust Bearing
Najar, Farooq Ahmad; Harmain, G. A.
2014-01-01
Reynolds equation is solved using finite difference method (FDM) on the surface of the tilting pad to find the pressure distribution in the lubricant oil film. Different pressure profiles with grid independence are described. The present work evaluates pressure at various locations after performing a thorough grid refinement. In recent similar works, this aspect has not been addressed. However, present study shows that it can have significant effect on the pressure profile. Results of a sector shaped pad are presented and it is shown that the maximum average value of pressure is 12% (approximately) greater than the previous results. Grid independence occurs after 24 × 24 grids. A parameter “ψ” has been proposed to provide convenient indicator of obtaining grid independent results. ψ = |(P refinedgrid − P Refrence-grid)/P refinedgrid|, ψ ≤ ε, where “ε” can be fixed to a convenient value and a constant minimum film thickness value of 75 μm is used in present study. This important parameter is highlighted in the present work; the location of the peak pressure zone in terms of (r, θ) coordinates is getting shifted by changing the grid size which will help the designer and experimentalist to conveniently determine the position of pressure measurement probe. PMID:27350977
Hydrodynamics of Turning Flocks
Yang, Xingbo; Marchetti, M. Cristina
2014-01-01
We present a hydrodynamic model of flocking that generalizes the familiar Toner-Tu equations to incorporate turning inertia of well-polarized flocks. The continuum equations controlled by only two dimensionless parameters, orientational inertia and alignment strength, are derived by coarse graining the inertial spin model recently proposed by Cavagna et al. The interplay between orientational inertia and bend elasticity of the flock yields anisotropic spin waves that mediate the propagation o...
Self-Bearing Motor-Generator for Flywheels, Phase I
National Aeronautics and Space Administration — Self-bearing or ?bearingless? motors perform both motor and bearing support functions but such devices have not yet achieved speeds above 15,000 rpm. The innovation...
Hydrodynamics of insect spermatozoa
Pak, On Shun; Lauga, Eric
2010-11-01
Microorganism motility plays important roles in many biological processes including reproduction. Many microorganisms propel themselves by propagating traveling waves along their flagella. Depending on the species, propagation of planar waves (e.g. Ceratium) and helical waves (e.g. Trichomonas) were observed in eukaryotic flagellar motion, and hydrodynamic models for both were proposed in the past. However, the motility of insect spermatozoa remains largely unexplored. An interesting morphological feature of such cells, first observed in Tenebrio molitor and Bacillus rossius, is the double helical deformation pattern along the flagella, which is characterized by the presence of two superimposed helical flagellar waves (one with a large amplitude and low frequency, and the other with a small amplitude and high frequency). Here we present the first hydrodynamic investigation of the locomotion of insect spermatozoa. The swimming kinematics, trajectories and hydrodynamic efficiency of the swimmer are computed based on the prescribed double helical deformation pattern. We then compare our theoretical predictions with experimental measurements, and explore the dependence of the swimming performance on the geometric and dynamical parameters.
A Three-Dimensional Foil Bearing Performance Map Applied to Oil-Free Turbomachinery
2009-04-01
stress brought on by excessive viscous power loss; therefore a map that graphically relates component and system-level parameters (bearing size, applied...Introduction Foil bearings are self-acting, hydrodynamic gas bearings that use air as their working fluid . Their use in rotating systems eliminates the...weight, maintenance requirements, speed, and temperature limitations associated with conventional oil-lubricated rotor supports (i.e., bearings, dampers
Application of Hydrodynamic Cavitation for Food and Bioprocessing
Gogate, Parag R.
Hydrodynamic cavitation can be simply generated by the alterations in the flow field in high speed/high pressure devices and also by passage of the liquid through a constriction such as orifice plate, venturi, or throttling valve. Hydrodynamic cavitation results in the formation of local hot spots, release of highly reactive free radicals, and enhanced mass transfer rates due to turbulence generated as a result of liquid circulation currents. These conditions can be suitably applied for intensification of different bioprocessing applications in an energy-efficient manner as compared to conventionally used ultrasound-based reactors. The current chapter aims at highlighting different aspects related to hydrodynamic cavitation, including the theoretical aspects for optimization of operating parameters, reactor designs, and overview of applications relevant to food and bioprocessing. Some case studies highlighting the comparison of hydrodynamic cavitation and acoustic cavitation reactors will also be discussed.
Titan's hydrodynamically escaping atmosphere
Strobel, Darrell F.
2008-02-01
The upper atmosphere of Titan is currently losing mass at a rate ˜(4-5)×10 amus, by hydrodynamic escape as a high density, slow outward expansion driven principally by solar UV heating by CH 4 absorption. The hydrodynamic mass loss is essentially CH 4 and H 2 escape. Their combined escape rates are restricted by power limitations from attaining their limiting rates (and limiting fluxes). Hence they must exhibit gravitational diffusive separation in the upper atmosphere with increasing mixing ratios to eventually become major constituents in the exosphere. A theoretical model with solar EUV heating by N 2 absorption balanced by HCN rotational line cooling in the upper thermosphere yields densities and temperatures consistent with the Huygens Atmospheric Science Investigation (HASI) data [Fulchignoni, M., and 42 colleagues, 2005. Nature 438, 785-791], with a peak temperature of ˜185-190 K between 3500-3550 km. This model implies hydrodynamic escape rates of ˜2×10 CHs and 5×10 Hs, or some other combination with a higher H 2 escape flux, much closer to its limiting value, at the expense of a slightly lower CH 4 escape rate. Nonthermal escape processes are not required to account for the loss rates of CH 4 and H 2, inferred by the Cassini Ion Neutral Mass Spectrometer (INMS) measurements [Yelle, R.V., Borggren, N., de la Haye, V., Kasprzak, W.T., Niemann, H.B., Müller-Wodarg, I., Waite Jr., J.H., 2006. Icarus 182, 567-576].
How to fake hydrodynamic signals
Energy Technology Data Exchange (ETDEWEB)
Romatschke, Paul [Department of Physics, 390 UCB, University of Colorado at Boulder, Boulder, CO (United States); Center for Theory of Quantum Matter, University of Colorado, Boulder, CO 80309 (United States)
2016-12-15
Flow signatures in experimental data from relativistic ion collisions, are usually interpreted as a fingerprint of the presence of a hydrodynamic phase during the evolution of these systems. I review some theoretical ideas to ‘fake’ this hydrodynamic behavior in p+A and A+A collisions. I find that transverse flow and femtoscopic measurements can easily be forged through non-hydrodynamic evolution, while large elliptic flow requires some non-vanishing interactions in the hot phase.
Hydrodynamic Investigation of a Concentric Cylindrical OWC Wave Energy Converter
Directory of Open Access Journals (Sweden)
Yu Zhou
2018-04-01
Full Text Available A fixed, concentric, cylindrical oscillating water column (OWC wave energy converter (WEC is proposed for shallow offshore sites. Compared with the existing shoreline OWC device, this wave energy device is not restricted by the wave directions and coastline geography conditions. Analytical solutions are derived based on the linear potential-flow theory and eigen-function expansion technique to investigate hydrodynamic properties of the device. Three typical free-surface oscillation modes in the chamber are discussed, of which the piston-type mode makes the main contribution to the energy conversion. The effects of the geometrical parameters on the hydrodynamic properties are further investigated. The resonance frequency of the chamber, the power extraction efficiency, and the effective frequency bandwidth of the device is discussed, amongst other topics. It is found that the proposed OWC-WEC device with a lower draft and wider chamber breadth has better power extraction ability.
Modeling hydrodynamic cavitation
Energy Technology Data Exchange (ETDEWEB)
Kumar, P.S.; Pandit, A.B. [Mumbai Univ. (India). Chemical Engineering Div.
1999-12-01
Cavitation as a source and method of energy input for chemical processing is increasingly studied due to its ability to generate localized high temperatures and pressures under nearly ambient conditions. Compared to cavitation generated by ultrasound, hydrodynamic cavitation has been proved to be a very energy-efficient alternative. A simple and unified model has been developed to study the cavitation phenomena in hydraulic systems with emphasis on the venturi tube and high-speed homogenizer. The model has been found to be satisfactory in explaining the effect of operating variables and equipment geometry on two different modes of cavitation generation qualitatively and in some cases quantitatively. (orig.)
Hydrodynamics of Ship Propellers
DEFF Research Database (Denmark)
Breslin, John P.; Andersen, Poul
This book deals with flows over propellers operating behind ships, and the hydrodynamic forces and moments which the propeller generates on the shaft and on the ship hull.The first part of the text is devoted to fundamentals of the flow about hydrofoil sections (with and without cavitation...... of an intermittently cavitating propeller in a wake and the pressures and forces it exerts on the shaft and on the ship hull is examined. A final chapter discusses the optimization of efficiency of compound propulsors. The authors have taken care to clearly describe physical concepts and mathematical steps. Appendices...
Foundations of radiation hydrodynamics
Mihalas, Dimitri
1999-01-01
Radiation hydrodynamics is a broad subject that cuts across many disciplines in physics and astronomy: fluid dynamics, thermodynamics, statistical mechanics, kinetic theory, and radiative transfer, among others. The theory developed in this book by two specialists in the field can be applied to the study of such diverse astrophysical phenomena as stellar winds, supernova explosions, and the initial phases of cosmic expansion, as well as the physics of laser fusion and reentry vehicles. As such, it provides students with the basic tools for research on radiating flows.Largely self-contained,
Numerical investigation of cavitation flow in journal bearing geometry
Riedel, M.; Schmidt, M.; Stücke, P.
2013-04-01
The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD) are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.
Numerical investigation of cavitation flow in journal bearing geometry
Directory of Open Access Journals (Sweden)
Stücke P.
2013-04-01
Full Text Available The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.
Nanoscale hydrodynamics near solids
Camargo, Diego; de la Torre, J. A.; Duque-Zumajo, D.; Español, Pep; Delgado-Buscalioni, Rafael; Chejne, Farid
2018-02-01
Density Functional Theory (DFT) is a successful and well-established theory for the study of the structure of simple and complex fluids at equilibrium. The theory has been generalized to dynamical situations when the underlying dynamics is diffusive as in, for example, colloidal systems. However, there is no such a clear foundation for Dynamic DFT (DDFT) for the case of simple fluids in contact with solid walls. In this work, we derive DDFT for simple fluids by including not only the mass density field but also the momentum density field of the fluid. The standard projection operator method based on the Kawasaki-Gunton operator is used for deriving the equations for the average value of these fields. The solid is described as featureless under the assumption that all the internal degrees of freedom of the solid relax much faster than those of the fluid (solid elasticity is irrelevant). The fluid moves according to a set of non-local hydrodynamic equations that include explicitly the forces due to the solid. These forces are of two types, reversible forces emerging from the free energy density functional, and accounting for impenetrability of the solid, and irreversible forces that involve the velocity of both the fluid and the solid. These forces are localized in the vicinity of the solid surface. The resulting hydrodynamic equations should allow one to study dynamical regimes of simple fluids in contact with solid objects in isothermal situations.
Anisotropic nonequilibrium hydrodynamic attractor
Strickland, Michael; Noronha, Jorge; Denicol, Gabriel S.
2018-02-01
We determine the dynamical attractors associated with anisotropic hydrodynamics (aHydro) and the DNMR equations for a 0 +1 d conformal system using kinetic theory in the relaxation time approximation. We compare our results to the nonequilibrium attractor obtained from the exact solution of the 0 +1 d conformal Boltzmann equation, the Navier-Stokes theory, and the second-order Mueller-Israel-Stewart theory. We demonstrate that the aHydro attractor equation resums an infinite number of terms in the inverse Reynolds number. The resulting resummed aHydro attractor possesses a positive longitudinal-to-transverse pressure ratio and is virtually indistinguishable from the exact attractor. This suggests that an optimized hydrodynamic treatment of kinetic theory involves a resummation not only in gradients (Knudsen number) but also in the inverse Reynolds number. We also demonstrate that the DNMR result provides a better approximation of the exact kinetic theory attractor than the Mueller-Israel-Stewart theory. Finally, we introduce a new method for obtaining approximate aHydro equations which relies solely on an expansion in the inverse Reynolds number. We then carry this expansion out to the third order, and compare these third-order results to the exact kinetic theory solution.
Lubrication analysis of the thrust bearing in the main coolant pump of SMART
International Nuclear Information System (INIS)
Lee, J. S.; Park, J. S.; Kim, J. H.; Hur, H.; Kim, J. I.
2001-01-01
Thrust bearing and journal bearings are installed in the main coolant pump for SMART to support the rotating shaft with proper lubrication. The canned motor type main coolant pumps are arranged vertically on the reactor vessel and especially the MCP bearings are lubricated with water without external lubricating oil supply. Because axial load capacity of the thrust bearing can hardly meet requirement to acquire hydrodynamic or fluid film lubrication state, self-lubrication characteristics of silicon graphite meterials would be needed. Lubricational analysis method for thrust bearing for the main coolant pump of SMART is proposed, and lubricational characteristics of the bearing generated by solving the Reynolds equation are examined in this paper
Mechanical design problems associated with turbopump fluid film bearings
Evces, Charles R.
1990-01-01
Most high speed cryogenic turbopumps for liquid propulsion rocket engines currently use ball or roller contact bearings for rotor support. The operating speeds, loads, clearances, and environments of these pumps combine to make bearing wear a limiting factor on turbopump life. An example is the high pressure oxygen turbopump (HPOTP) used in the Space Shuttle Main Engine (SSME). Although the HPOTP design life is 27,000 seconds at 30,000 rpms, or approximately 50 missions, bearings must currently be replaced after 2 missions. One solution to the bearing wear problem in the HPOTP, as well as in future turbopump designs, is the utilization of fluid film bearings in lieu of continuous contact bearings. Hydrostatic, hydrodynamic, and damping seal bearings are all replacement candidates for contact bearings in rocket engine high speed turbomachinery. These three types of fluid film bearings have different operating characteristics, but they share a common set of mechanical design opportunities and difficulties. Results of research to define some of the mechanical design issues are given. Problems considered include transient strat/stop rub, non-operational rotor support, bearing wear inspection and measurement, and bearing fluid supply route. Emphasis is given to the HPOTP preburner pump (PBP) bearing, but the results are pertinent to high-speed cryogenic turbomachinery in general.
Towards the concept of hydrodynamic cavitation control
Chatterjee, Dhiman; Arakeri, Vijay H.
1997-02-01
A careful study of the existing literature available in the field of cavitation reveals the potential of ultrasonics as a tool for controlling and, if possible, eliminating certain types of hydrodynamic cavitation through the manipulation of nuclei size present in a flow. A glass venturi is taken to be an ideal device to study the cavitation phenomenon at its throat and its potential control. A piezoelectric transducer, driven at the crystal resonant frequency, is used to generate an acoustic pressure field and is termed an ‘ultrasonic nuclei manipulator (UNM)’. Electrolysis bubbles serve as artificial nuclei to produce travelling bubble cavitation at the venturi throat in the absence of a UNM but this cavitation is completely eliminated when a UNM is operative. This is made possible because the nuclei, which pass through the acoustic field first, cavitate, collapse violently and perhaps fragment and go into dissolution before reaching the venturi throat. Thus, the potential nuclei for travelling bubble cavitation at the venturi throat seem to be systematically destroyed through acoustic cavitation near the UNM. From the solution to the bubble dynamics equation, it has been shown that the potential energy of a bubble at its maximum radius due to an acoustic field is negligible compared to that for the hydrodynamic field. Hence, even though the control of hydrodynamic macro cavitation achieved in this way is at the expense of acoustic micro cavitation, it can still be considered to be a significant gain. These are some of the first results in this direction.
Hydrodynamic Forces on Composite Structures
2014-06-01
NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited HYDRODYNAMIC ...Thesis 4. TITLE AND SUBTITLE HYDRODYNAMIC FORCES ON COMPOSITE STRUCTURES 5. FUNDING NUMBERS 6. AUTHOR(S) Scott C. Millhouse 7. PERFORMING...angles yields different free surface effects including vortices and the onset of cavitation . 14. SUBJECT TERMS Fluid structure interaction, FSI, finite
Black brane entropy and hydrodynamics
Booth, I.; Heller, M.P.; Spaliński, M.
2010-01-01
A generalization of entropy to near-equilibrium phenomena is provided by the notion of a hydrodynamic entropy current. Recent advances in holography have lead to the formulation of fluid-gravity duality, a remarkable connection between the hydrodynamics of certain strongly coupled media and dynamics
Black brane entropy and hydrodynamics
Booth, I.; Heller, M.P.; Spaliński, M.
2011-01-01
A generalization of entropy to near-equilibrium phenomena is provided by the notion of a hydrodynamic entropy current. Recent advances in holography have lead to the formulation of fluid-gravity duality, a remarkable connection between the hydrodynamics of certain strongly coupled media and dynamics
A hydrodynamic formalism for Brownian systems
International Nuclear Information System (INIS)
Pina, E.; Rosales, M.A.
1981-01-01
A formal hydrodynamic approach to Brownian motion is presented and the corresponding equations are derived. Hydrodynamic quantities are expressed in terms of the physical variables characterizing the Brownian systems. Contact is made with the hydrodynamic model of Quantum Mechanics. (author)
Foundations of radiation hydrodynamics
Mihalas, D.; Mihalas, B. W.
This book is the result of an attempt, over the past few years, to gather the basic tools required to do research on radiating flows in astrophysics. The microphysics of gases is discussed, taking into account the equation of state of a perfect gas, the first and second law of thermodynamics, the thermal properties of a perfect gas, the distribution function and Boltzmann's equation, the collision integral, the Maxwellian velocity distribution, Boltzmann's H-theorem, the time of relaxation, and aspects of classical statistical mechanics. Other subjects explored are related to the dynamics of ideal fluids, the dynamics of viscous and heat-conducting fluids, relativistic fluid flow, waves, shocks, winds, radiation and radiative transfer, the equations of radiation hydrodynamics, and radiating flows. Attention is given to small-amplitude disturbances, nonlinear flows, the interaction of radiation and matter, the solution of the transfer equation, acoustic waves, acoustic-gravity waves, basic concepts of special relativity, and equations of motion and energy.
International Nuclear Information System (INIS)
Koehler, H.S.
1983-01-01
The Time-Dependent Hartree-Fock theory provides a microscopic approach to the scattering of heavy ions. Fundamental in this theory is a mean-(one-body) field. The calculation of this field from a two-body effective interaction makes the theory microscopic. Many-body effects are included by the Brueckner definition of this interaction; the reaction-matrix. In excited media it is in general complex allowing for decays. The imaginary part relates directly to the collision-term in a transport equation. We treat this term by the time-relaxation-method. This implies an extension of the TDHF-equation to include two-body collisions. Hydrodynamic equations are derived from this new equation. The solution of the two equations agree quantitatively for short-relaxation-times. Relaxation-times are calculated as a function of temperature. (orig.)
Hydrodynamics of Peristaltic Propulsion
Athanassiadis, Athanasios; Hart, Douglas
2014-11-01
A curious class of animals called salps live in marine environments and self-propel by ejecting vortex rings much like jellyfish and squid. However, unlike other jetting creatures that siphon and eject water from one side of their body, salps produce vortex rings by pumping water through siphons on opposite ends of their hollow cylindrical bodies. In the simplest cases, it seems like some species of salp can successfully move by contracting just two siphons connected by an elastic body. When thought of as a chain of timed contractions, salp propulsion is reminiscent of peristaltic pumping applied to marine locomotion. Inspired by salps, we investigate the hydrodynamics of peristaltic propulsion, focusing on the scaling relationships that determine flow rate, thrust production, and energy usage in a model system. We discuss possible actuation methods for a model peristaltic vehicle, considering both the material and geometrical requirements for such a system.
Hydrodynamic effects on coalescence.
Energy Technology Data Exchange (ETDEWEB)
Dimiduk, Thomas G.; Bourdon, Christopher Jay; Grillet, Anne Mary; Baer, Thomas A.; de Boer, Maarten Pieter; Loewenberg, Michael (Yale University, New Haven, CT); Gorby, Allen D.; Brooks, Carlton, F.
2006-10-01
The goal of this project was to design, build and test novel diagnostics to probe the effect of hydrodynamic forces on coalescence dynamics. Our investigation focused on how a drop coalesces onto a flat surface which is analogous to two drops coalescing, but more amenable to precise experimental measurements. We designed and built a flow cell to create an axisymmetric compression flow which brings a drop onto a flat surface. A computer-controlled system manipulates the flow to steer the drop and maintain a symmetric flow. Particle image velocimetry was performed to confirm that the control system was delivering a well conditioned flow. To examine the dynamics of the coalescence, we implemented an interferometry capability to measure the drainage of the thin film between the drop and the surface during the coalescence process. A semi-automated analysis routine was developed which converts the dynamic interferogram series into drop shape evolution data.
Degradation of chlorocarbons driven by hydrodynamic cavitation
Energy Technology Data Exchange (ETDEWEB)
Wu, Z.L.; Ondruschka, B.; Braeutigam, P. [Institut fuer Technische Chemie und Umweltchemie, Friedrich-Schiller-Universitaet Jena, Jena (Germany)
2007-05-15
To provide an efficient lab-scale device for the investigation of the degradation of organic pollutants driven by hydrodynamic cavitation, the degradation kinetics of chloroform and carbon tetrachloride and the increase of conductivity in aqueous solutions were measured. These are values which were not previously available. Under hydrodynamic cavitation conditions, the degradation kinetics for chlorocarbons was found to be pseudo first-order. Meanwhile, C-H and C-Cl bonds are broken, and Cl{sub 2}, Cl{sup .}, Cl{sup -} and other ions released can increase the conductivity and enhance the oxidation of KI in aqueous solutions. The upstream pressures of the orifice plate, the cavitation number, and the solution temperature have substantial effects on the degradation kinetics. A decreased cavitation number can result in more cavitation events and enhances the degradation of chlorocarbons and/or the oxidation of KI. A decrease in temperature is generally favorable to the cavitation chemistry. Organic products from the degradation of carbon tetrachloride and chloroform have demonstrated the formation and recombination of free radicals, e.g., CCl{sub 4}, C{sub 2}Cl{sub 4}, and C{sub 2}Cl{sub 6} are produced from the degradation of CHCl{sub 3}. CHCl{sub 3} and C{sub 2}Cl{sub 6} are produced from the degradation of CCl{sub 4}. Both the chemical mechanism and the reaction kinetics of the degradation of chlorocarbons induced by hydrodynamic cavitation are consistent with those obtained from the acoustic cavitation. Therefore, the technology of hydrodynamic cavitation should be a good candidate for the removal of organic pollutants from water. (Abstract Copyright [2007], Wiley Periodicals, Inc.)
VibroCav : Hydrodynamic Vibration and Cavitation Technology
Bakker, T.W.
2012-01-01
Vibration and cavitation can be generated in many ways and serve many useful purposes. This study describes physical aspects of useful vibration and cavitation for a broad spectrum of applications at atmospheric or elevated pressures. After a review of available devices, hydrodynamic
Failure of GIMBAL bearing in directional GYRO
International Nuclear Information System (INIS)
Pervaiz, R.; Baig, N.A.; Shahid, M.; Ahmad, A.; Chohan, G.Y.
2003-01-01
This paper relates to the directional gyro of a sensing device used in indigenously developed surface-to-surface missile. The assembling of more than one thousand components in the form of several sub assemblies including hundreds of silver solders of this device was done in the hundred-thousands-class clean room according to assembly procedure. Whereas more than twenty bearings including gimbals bearings were assembled in the ten-thousands-class clean room after inspection/ testing them on beating testing system as per routine. The device was entered in testing and adjustment phase after successful completion of assembly work. The directional gyro qualified all the tests except the most critical one, the drift-rate. The drift-rate of outer gimbal was 60% more than permissible limit whereas drift-rate of inner gimbal was found O.K. It was diagnosed that at least one inner gimbal bearing out of two had some problem. The results were same after rebalancing of gimbals three times. The directional gyro was disassembled in clean room and the radial-thrust-bearing was recovered and flange bearing which are inner gimbal bearings. They were checked on bearing testing system and it was found that flange-bearing had more friction than permissible limit and hence rejected but radial thrust bearing were declared O.K. The gyro was reassembled with new O.K. flange bearing and the assembly work was completed in all respects. The sensing device qualified all the tests including the drift-rate. This case study is being presented to emphasize the importance of careful assembly of gyro in clean environment. (author)
Survey of Damage Investigation of Babbitted Industrial Bearings
Directory of Open Access Journals (Sweden)
Lyle A. Branagan
2015-04-01
Full Text Available This survey collects the efforts to understand the sources and consequences of damage to babbitted industrial bearings, which operate by means of a hydrodynamic, or hydrostatic, film. Major individual damage types are discussed in the context of major damage categories.
Hydrodynamic cavitation for sonochemical effects.
Moholkar, V S; Kumar, P S; Pandit, A B
1999-03-01
A comparative study of hydrodynamic and acoustic cavitation has been made on the basis of numerical solutions of the Rayleigh-Plesset equation. The bubble/cavity behaviour has been studied under both acoustic and hydrodynamic cavitation conditions. The effect of varying pressure fields on the collapse of the cavity (sinusoidal for acoustic and linear for hydrodynamic) and also on the latter's dynamic behaviour has been studied. The variations of parameters such as initial cavity size, intensity of the acoustic field and irradiation frequency in the case of acoustic cavitation, and initial cavity size, final recovery pressure and time for pressure recovery in the case of hydrodynamic cavitation, have been found to have significant effects on cavity/bubble dynamics. The simulations reveal that the bubble/cavity collapsing behaviour in the case of hydrodynamic cavitation is accompanied by a large number of pressure pulses of relatively smaller magnitude, compared with just one or two pulses under acoustic cavitation. It has been shown that hydrodynamic cavitation offers greater control over operating parameters and the resultant cavitation intensity. Finally, a brief summary of the experimental results on the oxidation of aqueous KI solution with a hydrodynamic cavitation set-up is given which supports the conclusion of this numerical study. The methodology presented allows one to manipulate and optimise of specific process, either physical or chemical.
Recent development of hydrodynamic modeling
Hirano, Tetsufumi
2014-09-01
In this talk, I give an overview of recent development in hydrodynamic modeling of high-energy nuclear collisions. First, I briefly discuss about current situation of hydrodynamic modeling by showing results from the integrated dynamical approach in which Monte-Carlo calculation of initial conditions, quark-gluon fluid dynamics and hadronic cascading are combined. In particular, I focus on rescattering effects of strange hadrons on final observables. Next I highlight three topics in recent development in hydrodynamic modeling. These include (1) medium response to jet propagation in di-jet asymmetric events, (2) causal hydrodynamic fluctuation and its application to Bjorken expansion and (3) chiral magnetic wave from anomalous hydrodynamic simulations. (1) Recent CMS data suggest the existence of QGP response to propagation of jets. To investigate this phenomenon, we solve hydrodynamic equations with source term which exhibits deposition of energy and momentum from jets. We find a large number of low momentum particles are emitted at large angle from jet axis. This gives a novel interpretation of the CMS data. (2) It has been claimed that a matter created even in p-p/p-A collisions may behave like a fluid. However, fluctuation effects would be important in such a small system. We formulate relativistic fluctuating hydrodynamics and apply it to Bjorken expansion. We found the final multiplicity fluctuates around the mean value even if initial condition is fixed. This effect is relatively important in peripheral A-A collisions and p-p/p-A collisions. (3) Anomalous transport of the quark-gluon fluid is predicted when extremely high magnetic field is applied. We investigate this possibility by solving anomalous hydrodynamic equations. We found the difference of the elliptic flow parameter between positive and negative particles appears due to the chiral magnetic wave. Finally, I provide some personal perspective of hydrodynamic modeling of high energy nuclear collisions
SPECIAL RELATIVISTIC HYDRODYNAMICS WITH GRAVITATION
Energy Technology Data Exchange (ETDEWEB)
Hwang, Jai-chan [Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu (Korea, Republic of); Noh, Hyerim [Korea Astronomy and Space Science Institute, Daejon (Korea, Republic of)
2016-12-20
Special relativistic hydrodynamics with weak gravity has hitherto been unknown in the literature. Whether such an asymmetric combination is possible has been unclear. Here, the hydrodynamic equations with Poisson-type gravity, considering fully relativistic velocity and pressure under the weak gravity and the action-at-a-distance limit, are consistently derived from Einstein’s theory of general relativity. An analysis is made in the maximal slicing, where the Poisson’s equation becomes much simpler than our previous study in the zero-shear gauge. Also presented is the hydrodynamic equations in the first post-Newtonian approximation, now under the general hypersurface condition. Our formulation includes the anisotropic stress.
Similarity flows in relativistic hydrodynamics
International Nuclear Information System (INIS)
Blaizot, J.P.; Ollitrault, J.Y.
1986-01-01
In ultra-relativistic heavy ion collisions, one expects in particular to observe a deconfinement transition leading to a formation of quark gluon plasma. In the framework of the hydrodynamic model, experimental signatures of such a plasma may be looked for as observable consequences of a first order transition on the evolution of the system. In most of the possible scenario, the phase transition is accompanied with discontinuities in the hydrodynamic flow, such as shock waves. The method presented in this paper has been developed to treat without too much numerical effort such discontinuous flow. It relies heavily on the use of similarity solutions of the hydrodynamic equations
Lotic Water Hydrodynamic Model
Energy Technology Data Exchange (ETDEWEB)
Judi, David Ryan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tasseff, Byron Alexander [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-01-23
Water-related natural disasters, for example, floods and droughts, are among the most frequent and costly natural hazards, both socially and economically. Many of these floods are a result of excess rainfall collecting in streams and rivers, and subsequently overtopping banks and flowing overland into urban environments. Floods can cause physical damage to critical infrastructure and present health risks through the spread of waterborne diseases. Los Alamos National Laboratory (LANL) has developed Lotic, a state-of-the-art surface water hydrodynamic model, to simulate propagation of flood waves originating from a variety of events. Lotic is a two-dimensional (2D) flood model that has been used primarily for simulations in which overland water flows are characterized by movement in two dimensions, such as flood waves expected from rainfall-runoff events, storm surge, and tsunamis. In 2013, LANL developers enhanced Lotic through several development efforts. These developments included enhancements to the 2D simulation engine, including numerical formulation, computational efficiency developments, and visualization. Stakeholders can use simulation results to estimate infrastructure damage and cascading consequences within other sets of infrastructure, as well as to inform the development of flood mitigation strategies.
Hydrodynamics of rotating superfluids
International Nuclear Information System (INIS)
Chandler, E.A.
1981-01-01
In this thesis, a coarse grained hydrodynamics is developed from the exact description of Tkachenko. To account for the dynamics of the vortex lattice, the macroscopic vortex displacement field is treated as an independent degree of freedom. The conserved energy is written in terms of the coarse-grained normal fluid, superfluid, and vortex velocities and includes an elastic energy associated with deformations of the vortex lattice. Equations of motion consistent with the conservation of energy, entropy and vorticity and containing mutual friction terms arising from microscopic interactions between normal fluid excitations and the vortex lines are derived. When the vortex velocity is eliminated from the damping terms, this system of equations becomes essentially that of BK with added elastic terms in the momentum stress tensor and energy current. The dispersion relation and damping of the first and second sound modes and the two transverse modes sustained by the system are investigated. It is shown that mutual friction mixes the transverse modes of the normal and superfluid components and damps the transverse mode associated with the relative velocity of these components, making this wave evanescent in the plane perpendicular to the rotation axis. The wave associated with transverse motion of the total mass current is a generalized Tkachenko mode, whose dispersion relation reduces to that derived by Tkachenko wave when the wavevector lies in this plane
Advanced in Macrostatistical Hydrodynamics
International Nuclear Information System (INIS)
Graham, A.L.; Tetlow, N.; Abbott, J.R.; Mondy, L.S.; Brenner, H.
1993-01-01
An overview is presented of research that focuses on slow flows of suspensions in which colloidal and inertial effects are negligibly small (Macrostatistical Hydrodynamics). First, we describe nuclear magnetic resonance imaging experiments to quantitatively measure particle migration occurring in concentrated suspensions undergoing a flow with a nonuniform shear rate. These experiments address the issue of how the flow field affects the microstructure of suspensions. In order to understand the local viscosity in a suspension with such a flow-induced, spatially varying concentration, one must know how the viscosity of a homogeneous suspension depends on such variables as solids concentration and particle orientation. We suggest the technique of falling ball viscometry, using small balls, as a method to determine the effective viscosity of a suspension without affecting the original microstructure significantly. We also describe data from experiments in which the detailed fluctuations of a falling ball's velocity indicate the noncontinuum nature of the suspension and may lead to more insights into the effects of suspension microstructure on macroscopic properties. Finally, we briefly describe other experiments that can be performed in quiescent suspensions (in contrast to the use of conventional shear rotational viscometers) in order to learn more about the microstructure and boundary effects in concentrated suspensions
Engineering Hydrodynamic AUV Hulls
Allen, J.
2016-12-01
AUV stands for autonomous underwater vehicle. AUVs are used in oceanography and are similar to gliders. MBARIs AUVs as well as other AUVs map the ocean floor which is very important. They also measure physical characteristics of the water, such as temperature and salinity. My science fair project for 4th grade was a STEM activity in which I built and tested 3 different AUV bodies. I wanted to find out which design was the most hydrodynamic. I tested three different lengths of AUV hulls to see which AUV would glide the farthest. The first was 6 inches. The second was 12 inches and the third was 18 inches. I used clay for the nosecone and cut a ruler into two and made it the fin. Each AUV used the same nosecone and fin. I tested all three designs in a pool. I used biomimicry to create my hypothesis. When I was researching I found that long slim animals swim fastest. So, my hypothesis is the longer AUV will glide farthest. In the end I was right. The longer AUV did glide the farthest.
Passive magnetic bearing configurations
Post, Richard F [Walnut Creek, CA
2011-01-25
A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.
Superconductor bearings, flywheels and transportation
International Nuclear Information System (INIS)
Werfel, F N; Floegel-Delor, U; Rothfeld, R; Riedel, T; Goebel, B; Wippich, D; Schirrmeister, P
2012-01-01
This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS–FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN 2 . More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.
Hydrodynamics of electrons in graphene
Lucas, Andrew; Chung Fong, Kin
2018-02-01
Generic interacting many-body quantum systems are believed to behave as classical fluids on long time and length scales. Due to rapid progress in growing exceptionally pure crystals, we are now able to experimentally observe this collective motion of electrons in solid-state systems, including graphene. We present a review of recent progress in understanding the hydrodynamic limit of electronic motion in graphene, written for physicists from diverse communities. We begin by discussing the ‘phase diagram’ of graphene, and the inevitable presence of impurities and phonons in experimental systems. We derive hydrodynamics, both from a phenomenological perspective and using kinetic theory. We then describe how hydrodynamic electron flow is visible in electronic transport measurements. Although we focus on graphene in this review, the broader framework naturally generalizes to other materials. We assume only basic knowledge of condensed matter physics, and no prior knowledge of hydrodynamics.
Analytic approaches to relativistic hydrodynamics
Energy Technology Data Exchange (ETDEWEB)
Hatta, Yoshitaka
2016-12-15
I summarize our recent work towards finding and utilizing analytic solutions of relativistic hydrodynamic. In the first part I discuss various exact solutions of the second-order conformal hydrodynamics. In the second part I compute flow harmonics v{sub n} analytically using the anisotropically deformed Gubser flow and discuss its dependence on n, p{sub T}, viscosity, the chemical potential and the charge.
Hydrodynamic aspects of flotation separation
Directory of Open Access Journals (Sweden)
Peleka Efrosyni N.
2016-01-01
Full Text Available Flotation separation is mainly used for removing particulates from aqueous dispersions. It is widely used for ore beneficiation and recovering valuable materials. This paper reviews the hydrodynamics of flotation separations and comments on selected recent publications. Units are distinguished as cells of ideal and non-ideal flow. A brief introduction to hydrodynamics is included to explain an original study of the hybrid flotation-microfiltration cell, effective for heavy metal ion removal.
An introduction to astrophysical hydrodynamics
Shore, Steven N
1992-01-01
This book is an introduction to astrophysical hydrodynamics for both astronomy and physics students. It provides a comprehensive and unified view of the general problems associated with fluids in a cosmic context, with a discussion of fluid dynamics and plasma physics. It is the only book on hydrodynamics that addresses the astrophysical context. Researchers and students will find this work to be an exceptional reference. Contents include chapters on irrotational and rotational flows, turbulence, magnetohydrodynamics, and instabilities.
Feasibility of Applying Active Lubrication to Dynamically Loaded Fluid Film Bearings
DEFF Research Database (Denmark)
Estupinan, Edgar Alberto; Santos, Ilmar
2009-01-01
The feasibility of modifying the dynamics of the thin fluid films of dynamically loaded journal bearings, using different strategies of active lubrication is studied in this work. A significant reduction in the vibration levels, wear and power friction losses, is expected. Particularly, the focus...... of this study is on the analysis of main crankshaft bearings, where the conventional hydrodynamic lubrication is modified by injecting oil at actively controllable pressures, through orifices circumferentially located along the bearing surface....
Analysis of a Thrust Bearing with Flexible Pads and Flexible Supports
DEFF Research Database (Denmark)
Klit, Peder; Thomsen, Kim
2007-01-01
A theoretical analysis of a hydrodynamic thrust bearing is presented. The bearing investigated is used in an ndustrial product. The lubricant is water, but the results are valid also for other lubricants.At first the results from a 1-dimensional model for the fluid film forces and the associated...... deformation of the bearing geometry is presented. This model enlightens the influence of pad flexibility and support location and flexibility. Subsequently results from a 2-dimensional model of the bearing is presented. The model is used to carry out an optimization of the bearing design, and the obtained...
Estimation of Alignment and Transverse Load in Multi-Bearing Rotor System
Tom J. Chalko; Dong-Xu Li
1997-01-01
The paper presents a method for estimation of a multi-bearing machine alignment on the basis of measured eccentricities of the shaft in machine bearings. The method uses a linear FEM model of the rotor and the non-linear models of machine bearings. In the presented example, the non-linear models of hydrodynamic bearings are used, but it is shown, that the method could be easily applied to other types of bearings. In addition to the alignment estimation, the method allows to estimate the unkno...
Directory of Open Access Journals (Sweden)
Sezar Gülbaz
2015-01-01
Full Text Available The land development and increase in urbanization in a watershed affect water quantityand water quality. On one hand, urbanization provokes the adjustment of geomorphicstructure of the streams, ultimately raises peak flow rate which causes flood; on theother hand, it diminishes water quality which results in an increase in Total SuspendedSolid (TSS. Consequently, sediment accumulation in downstream of urban areas isobserved which is not preferred for longer life of dams. In order to overcome thesediment accumulation problem in dams, the amount of TSS in streams and inwatersheds should be taken under control. Low Impact Development (LID is a BestManagement Practice (BMP which may be used for this purpose. It is a land planningand engineering design method which is applied in managing storm water runoff inorder to reduce flooding as well as simultaneously improve water quality. LID includestechniques to predict suspended solid loads in surface runoff generated over imperviousurban surfaces. In this study, the impact of LID-BMPs on surface runoff and TSS isinvestigated by employing a calibrated hydrodynamic model for Sazlidere Watershedwhich is located in Istanbul, Turkey. For this purpose, a calibrated hydrodynamicmodel was developed by using Environmental Protection Agency Storm WaterManagement Model (EPA SWMM. For model calibration and validation, we set up arain gauge and a flow meter into the field and obtain rainfall and flow rate data. Andthen, we select several LID types such as retention basins, vegetative swales andpermeable pavement and we obtain their influence on peak flow rate and pollutantbuildup and washoff for TSS. Consequently, we observe the possible effects ofLID on surface runoff and TSS in Sazlidere Watershed.
Directory of Open Access Journals (Sweden)
Kustosz R.
2015-09-01
Full Text Available Constructions of the mechanical-bearingless centrifugal blood pumps utilize different types of non-contact physical bearings, which allows to balance the forces that have an impact on the pump impeller, stabilizing its position in the pump house without wall contact. The paper presents investigations of the hybrid (passive magnetic bearings and hydrodynamic bearings suspension system for the centrifugal blood pump. Numerical simulations were used to evaluate the hydrodynamic bearing lifting force and magnetic bearing forces interaction. An important aspect of rotor suspension system design was the nominal gap in hydrodynamic bearing area in order to reduce the blood damage risk in this region. The analyses results confirmed that for a small diameter centrifugal pump, the nominal operating hydrodynamic bearing gap could be established within the range from 0.033 to 0.072 mm.
Plain bearing stresses due to forming and oil film pressure
Energy Technology Data Exchange (ETDEWEB)
Burke-Veliz, A; Reed, P A S; Syngellakis, S [University of Southampton, School of Engineering Sciences, Southampton SO17 1BJ (United Kingdom); Wang, D; Wahdy, N; Merritt, D, E-mail: allan.burke@itesm.m [MAHLE Engine Systems UK Ltd, 2 Central park Drive, Rugby CV23 0WE (United Kingdom)
2009-08-01
This paper describes a methodology for assessing critical stress ranges arising in automotive plain bearings during engine operations. An industry-produced and run simulation program provides information on oil film pressure and overall bearing deformation during accelerated performance tests. This code performs an elasto-hydrodynamic lubrication analysis accounting for the compliance of the housing and journal. Finite element analyses of a multilayer bearing are performed to assess the conditions responsible for possible fatigue damage over the bearing lining. The residual stresses arising from the forming and fitting process are first assessed. The stress analyses over the engine cycle show the intensity and distribution of cyclic tensile and compressive stresses in the bearing. The location of maximum stress range is found to be consistent with the damage observed in accelerated fatigue tests. Critical zones are identified in the lining for possible fatigue crack initiation and growth studies.
Plain bearing stresses due to forming and oil film pressure
International Nuclear Information System (INIS)
Burke-Veliz, A; Reed, P A S; Syngellakis, S; Wang, D; Wahdy, N; Merritt, D
2009-01-01
This paper describes a methodology for assessing critical stress ranges arising in automotive plain bearings during engine operations. An industry-produced and run simulation program provides information on oil film pressure and overall bearing deformation during accelerated performance tests. This code performs an elasto-hydrodynamic lubrication analysis accounting for the compliance of the housing and journal. Finite element analyses of a multilayer bearing are performed to assess the conditions responsible for possible fatigue damage over the bearing lining. The residual stresses arising from the forming and fitting process are first assessed. The stress analyses over the engine cycle show the intensity and distribution of cyclic tensile and compressive stresses in the bearing. The location of maximum stress range is found to be consistent with the damage observed in accelerated fatigue tests. Critical zones are identified in the lining for possible fatigue crack initiation and growth studies.
Hydrodynamic escape from planetary atmospheres
Tian, Feng
Hydrodynamic escape is an important process in the formation and evolution of planetary atmospheres. Due to the existence of a singularity point near the transonic point, it is difficult to find transonic steady state solutions by solving the time-independent hydrodynamic equations. In addition to that, most previous works assume that all energy driving the escape flow is deposited in one narrow layer. This assumption not only results in less accurate solutions to the hydrodynamic escape problem, but also makes it difficult to include other chemical and physical processes in the hydrodynamic escape models. In this work, a numerical model describing the transonic hydrodynamic escape from planetary atmospheres is developed. A robust solution technique is used to solve the time dependent hydrodynamic equations. The method has been validated in an isothermal atmosphere where an analytical solution is available. The hydrodynamic model is applied to 3 cases: hydrogen escape from small orbit extrasolar planets, hydrogen escape from a hydrogen rich early Earth's atmosphere, and nitrogen/methane escape from Pluto's atmosphere. Results of simulations on extrasolar planets are in good agreement with the observations of the transiting extrasolar planet HD209458b. Hydrodynamic escape of hydrogen from other hypothetical close-in extrasolar planets are simulated and the influence of hydrogen escape on the long-term evolution of these extrasolar planets are discussed. Simulations on early Earth suggest that hydrodynamic escape of hydrogen from a hydrogen rich early Earth's atmosphere is about two orders magnitude slower than the diffusion limited escape rate. A hydrogen rich early Earth's atmosphere could have been maintained by the balance between the hydrogen escape and the supply of hydrogen into the atmosphere by volcanic outgassing. Origin of life may have occurred in the organic soup ocean created by the efficient formation of prebiotic molecules in the hydrogen rich early
Piezoelectric actuators in the active vibration control system of journal bearings
Tůma, J.; Šimek, J.; Mahdal, M.; Pawlenka, M.; Wagnerova, R.
2017-07-01
The advantage of journal hydrodynamic bearings is high radial load capacity and operation at high speeds. The disadvantage is the excitation of vibrations, called an oil whirl, after crossing a certain threshold of the rotational speed. The mentioned vibrations can be suppressed using the system of the active vibration control with piezoactuators which move the bearing bushing. The motion of the bearing bushing is controlled by a feedback controller, which responds to the change in position of the bearing journal which is sensed by a pair of capacitive sensors. Two stacked linear piezoactuators are used to actuate the position of the bearing journal. This new bearing enables not only to damp vibrations but also serves to maintain the desired bearing journal position with an accuracy of micrometers. The paper will focus on the effect of active vibration control on the performance characteristics of the journal bearing.
The Thermohydrodynamic Analysis of Sliding Bearing High-Speed Motorized Spindle by Rotor Dynamic
Directory of Open Access Journals (Sweden)
Li Songsheng
2017-01-01
Full Text Available This is paper presents thermohydrodynamic characteristics of high speed motorized spindle sliding bearing rotor system. The dynamic characteristic of the oil film bearing is affected by temperature increment, thereby affecting the high-speed spindle rotor system dynamics. This study applied the hydrodynamic lubrication theory, the influence of temperature on the viscosity of lubricating oil, associated with the bearing stiffness, oil film damping and other performance parameters, is considered in generalized Reynolds equation of oil film bearing. The theoretical model of the sliding bearing rotor system is established by using the transfer matrix method to analyze the dynamic characteristic and verified by experiments. The results show the high temperature environment in the motorized spindle and the friction of the bearing lead to oil temperature rise and viscosity reduction, which influences the bearing capacity, stiffness and damping, hence impact on the critical speeds and modal shapes of the sliding bearing rotor system.
Soliton Gases and Generalized Hydrodynamics
Doyon, Benjamin; Yoshimura, Takato; Caux, Jean-Sébastien
2018-01-01
We show that the equations of generalized hydrodynamics (GHD), a hydrodynamic theory for integrable quantum systems at the Euler scale, emerge in full generality in a family of classical gases, which generalize the gas of hard rods. In this family, the particles, upon colliding, jump forward or backward by a distance that depends on their velocities, reminiscent of classical soliton scattering. This provides a "molecular dynamics" for GHD: a numerical solver which is efficient, flexible, and which applies to the presence of external force fields. GHD also describes the hydrodynamics of classical soliton gases. We identify the GHD of any quantum model with that of the gas of its solitonlike wave packets, thus providing a remarkable quantum-classical equivalence. The theory is directly applicable, for instance, to integrable quantum chains and to the Lieb-Liniger model realized in cold-atom experiments.
Anomalous hydrodynamics of Weyl materials
Monteiro, Gustavo; Abanov, Alexander
Kinetic theory is a useful tool to study transport in Weyl materials when the band-touching points are hidden inside a Fermi surface. It accounts, for example, for the negative magnetoresistance caused by the chiral magnetic effect and quantum oscillations (SdH effect) in the magnetoresistance together within the same framework. As an alternative approach to kinetic theory we also consider the regime of strong interactions where hydrodynamics can be applicable. A variational principle of these hydrodynamic equations can be found in and provide a natural framework to study hydrodynamic surface modes which correspond to the strongly-interacting physics signature of Fermi arcs. G.M. acknowledges the financial support from FAPESP.
Brownian dynamics with hydrodynamic interactions
International Nuclear Information System (INIS)
Ermak, D.L.; McCammon, J.A.
1978-01-01
A method for simulating the Brownian dynamics of N particles with the inclusion of hydrodynamic interactions is described. The particles may also be subject to the usual interparticle or external forces (e.g., electrostatic) which have been included in previous methods for simulating Brownian dynamics of particles in the absence of hydrodynamic interactions. The present method is derived from the Langevin equations for the N particle assembly, and the results are shown to be consistent with the corresponding Fokker--Planck results. Sample calculations on small systems illustrate the importance of including hydrodynamic interactions in Brownian dynamics simulations. The method should be useful for simulation studies of diffusion limited reactions, polymer dynamics, protein folding, particle coagulation, and other phenomena in solution
DEFF Research Database (Denmark)
van Leeuwen, Theo; Caldas-Coulthardt, Carmen
2014-01-01
This paper presents a semiotic analysis of a key cultural artefact, the teddy bear. After introducing the iconography of the teddy bear, it analyses different kinds of stories to show how teddy bears are endowed with meaning in everyday life: stories from children's books, reminiscenses by adults...... bears have traditionally centred on interpersonal relations within the nuclear family, but have recently been institutionalized and commercialized....
Abnormal pressures as hydrodynamic phenomena
Neuzil, C.E.
1995-01-01
So-called abnormal pressures, subsurface fluid pressures significantly higher or lower than hydrostatic, have excited speculation about their origin since subsurface exploration first encountered them. Two distinct conceptual models for abnormal pressures have gained currency among earth scientists. The static model sees abnormal pressures generally as relict features preserved by a virtual absence of fluid flow over geologic time. The hydrodynamic model instead envisions abnormal pressures as phenomena in which flow usually plays an important role. This paper develops the theoretical framework for abnormal pressures as hydrodynamic phenomena, shows that it explains the manifold occurrences of abnormal pressures, and examines the implications of this approach. -from Author
Anisotropic hydrodynamics: Motivation and methodology
Energy Technology Data Exchange (ETDEWEB)
Strickland, Michael
2014-06-15
In this proceedings contribution I review recent progress in our understanding of the bulk dynamics of relativistic systems that possess potentially large local rest frame momentum-space anisotropies. In order to deal with these momentum-space anisotropies, a reorganization of relativistic viscous hydrodynamics can be made around an anisotropic background, and the resulting dynamical framework has been dubbed “anisotropic hydrodynamics”. I also discuss expectations for the degree of momentum-space anisotropy of the quark–gluon plasma generated in relativistic heavy ion collisions at RHIC and LHC from second-order viscous hydrodynamics, strong-coupling approaches, and weak-coupling approaches.
Hydrodynamics of oceans and atmospheres
Eckart, Carl
1960-01-01
Hydrodynamics of Oceans and Atmospheres is a systematic account of the hydrodynamics of oceans and atmospheres. Topics covered range from the thermodynamic functions of an ideal gas and the thermodynamic coefficients for water to steady motions, the isothermal atmosphere, the thermocline, and the thermosphere. Perturbation equations, field equations, residual equations, and a general theory of rays are also presented. This book is comprised of 17 chapters and begins with an introduction to the basic equations and their solutions, with the aim of illustrating the laws of dynamics. The nonlinear
Hydrodynamic constants from cosmic censorship
International Nuclear Information System (INIS)
Nakamura, Shin
2008-01-01
We study a gravity dual of Bjorken flow of N=4 SYM-theory plasma. We point out that the cosmic censorship hypothesis may explain why the regularity of the dual geometry constrains the hydrodynamic constants. We also investigate the apparent horizon of the dual geometry. We find that the dual geometry constructed on Fefferman-Graham (FG) coordinates is not appropriate for examination of the apparent horizon since the coordinates do not cover the trapped region. However, the preliminary analysis on FG coordinates suggests that the location of the apparent horizon is very sensitive to the hydrodynamic parameters. (author)
Hydrodynamic simulation of elliptic flow
Kolb, P F; Ruuskanen, P V; Heinz, Ulrich W
1999-01-01
We use a hydrodynamic model to study the space-time evolution transverse to the beam direction in ultrarelativistic heavy-ion collisions with nonzero impact parameters. We focus on the influence of early pressure on the development of radial and elliptic flow. We show that at high energies elliptic flow is generated only during the initial stages of the expansion while radial flow continues to grow until freeze-out. Quantitative comparisons with SPS data from semiperipheral Pb+Pb collisions suggest the applicability of hydrodynamical concepts already $\\approx$ 1 fm/c after impact.
Anomalous hydrodynamics in two dimensions
Indian Academy of Sciences (India)
Abstract. A new approach is presented to discuss two-dimensional hydrodynamics with gauge and gravitational anomalies. Exact constitutive relations for the stress tensor and charge current are obtained. Also, a connection between response parameters and anomaly coefficients is discussed. These are new results which, ...
Topics in fluctuating nonlinear hydrodynamics
International Nuclear Information System (INIS)
Milner, S.T.
1986-01-01
Models of fluctuating nonlinear hydrodynamics have enjoyed much success in explaining the effect of long-wavelength fluctuations in diverse hydrodynamic systems. This thesis explores two such problems; in both, the body of hydrodynamic assumptions powerfully constrains the predictions of a well-posed theory. The effects of layer fluctuations in smectic-A liquid crystals are first examined. The static theory (introduced by Grinstein and Pelcovits) is reviewed. Ward identities, resulting from the arbitrariness of the layering direction, are derived and exploited. The static results motivate an examination of dynamic fluctuation effects. A new sound-damping experiment is proposed that would probe singular dependence of viscosities on applied stress. A theory of Procaccia and Gitterman that reaction rates of chemically reacting binary mixtures are drastically reduced near their thermodynamic critical points is analyzed. Hydrodynamic arguments and Van Hove theory are applied, concluding that the PG idea is drastically slowed, and spatially varying composition fluctuations are at best slowed down over a narrow range of wavenumbers
Radiation hydrodynamics in the laboratory
International Nuclear Information System (INIS)
1985-12-01
This report contains a collection of five preprints devoted to the subject of laser induced phenomena of radiation hydrodynamics. These preprints cover approximately the contents of the presentations made by the MPQ experimental laser-plasma group at the 17th European Conference on Laser Interaction with Matter (ECLIM), Rome, November 18-22, 1985. (orig.)
Numerical Hydrodynamics in General Relativity
Directory of Open Access Journals (Sweden)
Font José A.
2003-01-01
Full Text Available The current status of numerical solutions for the equations of ideal general relativistic hydrodynamics is reviewed. With respect to an earlier version of the article, the present update provides additional information on numerical schemes, and extends the discussion of astrophysical simulations in general relativistic hydrodynamics. Different formulations of the equations are presented, with special mention of conservative and hyperbolic formulations well-adapted to advanced numerical methods. A large sample of available numerical schemes is discussed, paying particular attention to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. A comprehensive summary of astrophysical simulations in strong gravitational fields is presented. These include gravitational collapse, accretion onto black holes, and hydrodynamical evolutions of neutron stars. The material contained in these sections highlights the numerical challenges of various representative simulations. It also follows, to some extent, the chronological development of the field, concerning advances on the formulation of the gravitational field and hydrodynamic equations and the numerical methodology designed to solve them.
Hydrodynamics of a quark droplet
DEFF Research Database (Denmark)
Bjerrum-Bohr, Johan J.; Mishustin, Igor N.; Døssing, Thomas
2012-01-01
We present a simple model of a multi-quark droplet evolution based on the hydrodynamical description. This model includes collective expansion of the droplet, effects of the vacuum pressure and surface tension. The hadron emission from the droplet is described following Weisskopf's statistical...
Hydrodynamic instabilities in inertial fusion
International Nuclear Information System (INIS)
Hoffman, N.M.
1994-01-01
This report discusses topics on hydrodynamics instabilities in inertial confinement: linear analysis of Rayleigh-Taylor instability; ablation-surface instability; bubble rise in late-stage Rayleigh-Taylor instability; and saturation and multimode interactions in intermediate-stage Rayleigh-Taylor instability
Dynamic Characteristics of Rotors on Passive and Active Thrust Fluid-film Bearings with Fixed Pads
Directory of Open Access Journals (Sweden)
Babin Alexander
2018-01-01
Full Text Available Application of fluid-film bearings in rotor machines in many cases could have no alternative due to obvious advantages when compared to roller element bearings. Integration of information technology in mechanical engineering resulting in emergence of a new field of research – mechatronic bearings which allowed tracking condition of the most important parts of a machine and adjusting operational parameters of the system. Application of servo valves to control the flow rate through a fluid-film bearing is the most universal and simple way of rotor’s position control due to relative simplicity of modelling and absence of need to radically change the design of conventional hydrodynamic bearings. In the present paper numerical simulations of passive (conventional as opposed to mechatronic and active hybrid thrust fluid-film bearings with a central feeding chamber are presented, that are parts of a mechatronic rotor-bearing node. Numerical model of an active thrust bearing is based on solution of equations of hydrodynamics, rotor dynamics and an additional model of a servo valve. Various types of control have been investigated: P, PI and PID control, and the dynamic behaviour of a system has been estimated under various loads, namely static, periodic and impulse. A design of a test rig has been proposed to study passive and active thrust fluid-film bearings aimed at, among other, validation of numerical results of active bearings simulation.
International Nuclear Information System (INIS)
R Paul Drake
2004-01-01
OAK-B135 This is the final report from the project Hydrodynamics by High-Energy-Density Plasma Flow and Hydrodynamics and Radiation Hydrodynamics with Astrophysical Applications. This project supported a group at the University of Michigan in the invention, design, performance, and analysis of experiments using high-energy-density research facilities. The experiments explored compressible nonlinear hydrodynamics, in particular at decelerating interfaces, and the radiation hydrodynamics of strong shock waves. It has application to supernovae, astrophysical jets, shock-cloud interactions, and radiative shock waves
Simulation of seismic signals from asymmetric LANL hydrodynamic calculations
International Nuclear Information System (INIS)
Stevens, J.L.; Rimer, N.; Halda, E.J.; Barker, T.G.; Davis, C.G.; Johnson, W.E.
1993-01-01
Hydrodynamic calculations of an asymmetric nuclear explosion source were propagated to teleseismic distances to investigate the effects of the asymmetric source on seismic signals. The source is an explosion in a 12 meter long canister with the device at one end of the canister and a metal plate adjacent to the explosion. This produces a strongly asymmetric two-lobed source in the hydrodynamic region. The hydrodynamic source is propagated to the far field using a three-step process. The Eulerian hydrodynamic code SOIL was used by LANL to calculate the material velocity, density, and internal energy up to a time of 8.9 milliseconds after the explosion. These quantities were then transferred to an initial grid for the Lagrangian elastic/plastic finite difference code CRAM, which was used by S-CUBED to propagate the signal through the region of nonlinear deformation into the external elastic region. The cavity size and shape at the time of the overlay were determined by searching for a rapid density change in the SOIL grid, and this interior region was then rezoned into a single zone. The CRAM calculation includes material strength and gravity, and includes the effect of the free surface above the explosion. Finally, far field body waves were calculated by integrating over a closed surface in the elastic region and using the representation theorem. A second calculation was performed using an initially spherical source for comparison with the asymmetric calculation
Rode, Karyn D.; Stirling, Ian
2017-01-01
Polar bears are the largest of the eight species of bears found worldwide and are covered in a pigment-free fur giving them the appearance of being white. They are the most carnivorous of bear species consuming a high-fat diet, primarily of ice-associated seals and other marine mammals. They range throughout the circumpolar Arctic to the southernmost extent of seasonal pack ice.
Analytic solutions of hydrodynamics equations
International Nuclear Information System (INIS)
Coggeshall, S.V.
1991-01-01
Many similarity solutions have been found for the equations of one-dimensional (1-D) hydrodynamics. These special combinations of variables allow the partial differential equations to be reduced to ordinary differential equations, which must then be solved to determine the physical solutions. Usually, these reduced ordinary differential equations are solved numerically. In some cases it is possible to solve these reduced equations analytically to obtain explicit solutions. In this work a collection of analytic solutions of the 1-D hydrodynamics equations is presented. These can be used for a variety of purposes, including (i) numerical benchmark problems, (ii) as a basis for analytic models, and (iii) to provide insight into more complicated solutions
DEFF Research Database (Denmark)
Nielsen, Nick; Pedersen, Sandra Bleuenn; Sørensen, Jens Ager
2015-01-01
In this paper, we introduce the EcoBears concept that aims to augment household appliances with functional and aesthetic features to promote their "use'' and "longevity of use'' to prevent their disposal. The EcoBears also aim to support the communication of environmental issues in the home setting....... We present our initial design and implementation of the EcoBears that consist of two bear modules (a mother and her cub). We also present our preliminary concept validations and lessons learned to be considered for future directions....
Bearing restoration by grinding
Hanau, H.; Parker, R. J.; Zaretsky, E. V.; Chen, S. M.; Bull, H. L.
1976-01-01
A joint program was undertaken by the NASA Lewis Research Center and the Army Aviation Systems Command to restore by grinding those rolling-element bearings which are currently being discarded at aircraft engine and transmission overhaul. Three bearing types were selected from the UH-1 helicopter engine (T-53) and transmission for the pilot program. No bearing failures occurred related to the restoration by grinding process. The risk and cost of a bearing restoration by grinding programs was analyzed. A microeconomic impact analysis was performed.
Energy Technology Data Exchange (ETDEWEB)
Norris, S.; Rosentrater, L.; Eid, P.M. [WWF International Arctic Programme, Oslo (Norway)
2002-05-01
Polar bears, the world's largest terrestrial carnivore, spend much of their lives on the arctic sea ice. This is where they hunt and move between feeding, denning, and resting areas. The world population, estimated at 22,000 bears, is made up of 20 relatively distinct populations varying in size from a few hundred to a few thousand animals. About 60 per cent of all polar bears are found in Canada. In general, the status of this species is stable, although there are pronounced differences between populations. Reductions in the extent and thickness of sea ice has lead the IUCN Polar Bear Specialist Group to describe climate change as one of the major threats facing polar bears today. Though the long-term effects of climate change will vary in different areas of the Arctic, impacts on the condition and reproductive success of polar bears and their prey are likely to be negative. Longer ice-free periods resulting from earlier break-up of sea ice in the spring and later formation in the fall is already impacting polar bears in the southern portions of their range. In Canada's Hudson Bay, for example, bears hunt on the ice through the winter and into early summer, after which the ice melts completely, forcing bears ashore to fast on stored fat until freeze-up in the fall. The time bears have on the ice to hunt and build up their body condition is cut short when the ice melts early. Studies from Hudson Bay show that for every week earlier that ice break-up occurs, bears will come ashore 10 kg lighter and in poorer condition. It is likely that populations of polar bears dividing their time between land and sea will be severely reduced and local extinctions may occur as greenhouse gas emissions continue to rise and sea ice melts. Expected changes in regional weather patterns will also impact polar bears. Rain in the late winter can cause maternity dens to collapse before females and cubs have departed, thus exposing occupants to the elements and to predators. Such
Laser driven hydrodynamic instability experiments
International Nuclear Information System (INIS)
Remington, B.A.; Weber, S.V.; Haan, S.W.; Kilkenny, J.D.; Glendinning, S.G.; Wallace, R.J.; Goldstein, W.H.; Wilson, B.G.; Nash, J.K.
1993-01-01
An extensive series of experiments has been conducted on the Nova laser to measure hydrodynamic instabilities in planar foils accelerated by x-ray ablation. Single mode experiments allow a measurement of the fundamental growth rates from the linear well into the nonlinear regime. Two-mode foils allow a first direct observation of mode coupling. Surface-finish experiments allow a measurement of the evolution of a broad spectrum of random initial modes
Rapidity correlations test stochastic hydrodynamics
International Nuclear Information System (INIS)
Zin, C; Gavin, S; Moschelli, G
2017-01-01
We show that measurements of the rapidity dependence of transverse momentum correlations can be used to determine the characteristic time τ π that dictates the rate of isotropization of the stress energy tensor, as well as the shear viscosity ν = η/sT . We formulate methods for computing these correlations using second order dissipative hydrodynamics with noise. Current data are consistent with τ π /ν ∼ 10 but targeted measurements can improve this precision. (paper)
Hydrodynamic simulations of expanding shells
Czech Academy of Sciences Publication Activity Database
Wünsch, Richard; Palouš, Jan; Ehlerová, Soňa
2004-01-01
Roč. 289, 3-4 (2004), s. 35-36 ISSN 0004-640X. [From observation to self-consistent modelling of the ISM in galaxies. Porto, 03.09.2002-05.09.2002] R&D Projects: GA AV ČR KSK1048102 Keywords : hydrodynamic simulations * ISM * star formation Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.597, year: 2004
Hydrodynamic Limit of Multiple SLE
Hotta, Ikkei; Katori, Makoto
2018-04-01
Recently del Monaco and Schleißinger addressed an interesting problem whether one can take the limit of multiple Schramm-Loewner evolution (SLE) as the number of slits N goes to infinity. When the N slits grow from points on the real line R in a simultaneous way and go to infinity within the upper half plane H, an ordinary differential equation describing time evolution of the conformal map g_t(z) was derived in the N → ∞ limit, which is coupled with a complex Burgers equation in the inviscid limit. It is well known that the complex Burgers equation governs the hydrodynamic limit of the Dyson model defined on R studied in random matrix theory, and when all particles start from the origin, the solution of this Burgers equation is given by the Stieltjes transformation of the measure which follows a time-dependent version of Wigner's semicircle law. In the present paper, first we study the hydrodynamic limit of the multiple SLE in the case that all slits start from the origin. We show that the time-dependent version of Wigner's semicircle law determines the time evolution of the SLE hull, K_t \\subset H\\cup R, in this hydrodynamic limit. Next we consider the situation such that a half number of the slits start from a>0 and another half of slits start from -a exact solutions, we will discuss the universal long-term behavior of the multiple SLE and its hull K_t in the hydrodynamic limit.
Hydrodynamical model with massless constituents
International Nuclear Information System (INIS)
Chiu, C.B.; Wang, K.H.
1974-01-01
Within the constituent hydrodynamical model, it is shown that the total number of constituents is conserved, if these constituents are massless and satisfy the Fermi-Dirac distribution. A simple scheme for the transition from the constituent-phase to the hadron-phase is suggested, and the hadron inclusive momentum spectra are presented for this case. This phase transition scheme predicts the average transverse momentum of meson resonances which is compatible with the data. (U.S.)
External Coulomb-Friction Damping For Hydrostatic Bearings
Buckmann, Paul S.
1992-01-01
External friction device damps vibrations of shaft and hydrostatic ring bearing in which it turns. Does not rely on wear-prone facing surfaces. Hydrostatic bearing ring clamped in radially flexing support by side plates clamped against radial surfaces by spring-loaded bolts. Plates provide friction against radial motions of shaft.
Black Hole Scrambling from Hydrodynamics.
Grozdanov, Sašo; Schalm, Koenraad; Scopelliti, Vincenzo
2018-06-08
We argue that the gravitational shock wave computation used to extract the scrambling rate in strongly coupled quantum theories with a holographic dual is directly related to probing the system's hydrodynamic sound modes. The information recovered from the shock wave can be reconstructed in terms of purely diffusionlike, linearized gravitational waves at the horizon of a single-sided black hole with specific regularity-enforced imaginary values of frequency and momentum. In two-derivative bulk theories, this horizon "diffusion" can be related to late-time momentum diffusion via a simple relation, which ceases to hold in higher-derivative theories. We then show that the same values of imaginary frequency and momentum follow from a dispersion relation of a hydrodynamic sound mode. The frequency, momentum, and group velocity give the holographic Lyapunov exponent and the butterfly velocity. Moreover, at this special point along the sound dispersion relation curve, the residue of the retarded longitudinal stress-energy tensor two-point function vanishes. This establishes a direct link between a hydrodynamic sound mode at an analytically continued, imaginary momentum and the holographic butterfly effect. Furthermore, our results imply that infinitely strongly coupled, large-N_{c} holographic theories exhibit properties similar to classical dilute gases; there, late-time equilibration and early-time scrambling are also controlled by the same dynamics.
Numerical Hydrodynamics in Special Relativity.
Martí, José Maria; Müller, Ewald
2003-01-01
This review is concerned with a discussion of numerical methods for the solution of the equations of special relativistic hydrodynamics (SRHD). Particular emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods in SRHD. Results of a set of demanding test bench simulations obtained with different numerical SRHD methods are compared. Three applications (astrophysical jets, gamma-ray bursts and heavy ion collisions) of relativistic flows are discussed. An evaluation of various SRHD methods is presented, and future developments in SRHD are analyzed involving extension to general relativistic hydrodynamics and relativistic magneto-hydrodynamics. The review further provides FORTRAN programs to compute the exact solution of a 1D relativistic Riemann problem with zero and nonzero tangential velocities, and to simulate 1D relativistic flows in Cartesian Eulerian coordinates using the exact SRHD Riemann solver and PPM reconstruction. Supplementary material is available for this article at 10.12942/lrr-2003-7 and is accessible for authorized users.
Characterization and measurement of hybrid gas journal bearings
Lawrence, Tom Marquis
This thesis concentrates on the study of hybrid gas journal bearings (bearings with externally pressurized mass addition). It differs from most work in that it goes back to "basics" to explore the hydrodynamic phenomena in the bearing gap. The thesis compares geometrically identical bearings with 2 configurations of external pressurization, porous liners where mass-addition compensation is varied by varying the liner's permeability, and bushings with 2 rows of 6 feedholes where the mass-addition compensation is varied by the feedhole diameter. Experimentally, prototype bearings with mass-addition compensation that spans 2 orders of magnitude with differing clearances are built and their aerostatic properties and mass addition characteristics are thoroughly tested. The fundamental equations for compressible, laminar, Poiseuille flow are used to suggest how the mass flow "compensation" should be mathematically modeled. This is back-checked against the experimental mass flow measurements and is used to determine a mass-addition compensation parameter (called Kmeas) for each prototype bushing. In so doing, the methodology of modeling and measuring the mass addition in a hybrid gas bearing is re-examined and an innovative, practical, and simple method is found that makes it possible to make an "apples-to-apples" comparison between different configurations of external pressurization. This mass addition model is used in conjunction with the Reynolds equation to perform theory-based numerical analysis of virtual hybrid gas journal bearings (CFD experiments). The first CFD experiments performed use virtual bearings modeled to be identical to the experimental prototypes and replicate the experimental work. The results are compared and the CFD model is validated. The ontological significance of appropriate dimensionless similitude parameters is re-examined and a, previously lacking, complete set of similitude factors is found for hybrid bearings. A new practical method is
Several particular aspects of hydrostatic shaft guide bearings in mechanical liquid sodium pumps
International Nuclear Information System (INIS)
Elie, X.
A number of problems arise with immersed hydrostatic shaft guide bearings in sodium pumps, mainly at high-temperature operation. Experience has shown that a substantial bearing clearance is required which, in present designs, takes a considerable amount of fluid from the pumps. A new design is suggested, resulting in a very appreciable reduction in the additional flow requirement, while maintaining a comparable load capacity by a hydrodynamic effect
An experimental investigation of hydrodynamic cavitation in micro-Venturis
Mishra, Chandan; Peles, Yoav
2006-10-01
The existence of hydrodynamic cavitation in the flow of de-ionized water through micro-Venturis has been witnessed in the form of traveling bubble cavitation and fully developed streamer bubble/supercavitation, and their mechanisms have been discussed. High-speed photography and flow visualization disclose inchoate cavitation bubbles emerging downstream from the micro-Venturi throat and the presence of a single streamer bubble/supercavity, which is equidistant from the micro device walls. The supercavity initiates inside the diffuser section and extends until the microchannel exit and proceeds to bifurcate the incoming flow. This article strives to provide numerical data and experimental details of hydrodynamic cavitation taking place within micro-Venturis.
Entropy-limited hydrodynamics: a novel approach to relativistic hydrodynamics
Guercilena, Federico; Radice, David; Rezzolla, Luciano
2017-07-01
We present entropy-limited hydrodynamics (ELH): a new approach for the computation of numerical fluxes arising in the discretization of hyperbolic equations in conservation form. ELH is based on the hybridisation of an unfiltered high-order scheme with the first-order Lax-Friedrichs method. The activation of the low-order part of the scheme is driven by a measure of the locally generated entropy inspired by the artificial-viscosity method proposed by Guermond et al. (J. Comput. Phys. 230(11):4248-4267, 2011, doi: 10.1016/j.jcp.2010.11.043). Here, we present ELH in the context of high-order finite-differencing methods and of the equations of general-relativistic hydrodynamics. We study the performance of ELH in a series of classical astrophysical tests in general relativity involving isolated, rotating and nonrotating neutron stars, and including a case of gravitational collapse to black hole. We present a detailed comparison of ELH with the fifth-order monotonicity preserving method MP5 (Suresh and Huynh in J. Comput. Phys. 136(1):83-99, 1997, doi: 10.1006/jcph.1997.5745), one of the most common high-order schemes currently employed in numerical-relativity simulations. We find that ELH achieves comparable and, in many of the cases studied here, better accuracy than more traditional methods at a fraction of the computational cost (up to {˜}50% speedup). Given its accuracy and its simplicity of implementation, ELH is a promising framework for the development of new special- and general-relativistic hydrodynamics codes well adapted for massively parallel supercomputers.
Thermohydrodynamic analysis of cryogenic liquid turbulent flow fluid film bearings, phase 2
Sanandres, Luis
1994-01-01
The Phase 2 (1994) Annual Progress Report presents two major report sections describing the thermal analysis of tilting- and flexure-pad hybrid bearings, and the unsteady flow and transient response of a point mass rotor supported on fluid film bearings. A literature review on the subject of two-phase flow in fluid film bearings and part of the proposed work for 1995 are also included. The programs delivered at the end of 1994 are named hydroflext and hydrotran. Both codes are fully compatible with the hydrosealt (1993) program. The new programs retain the same calculating options of hydrosealt plus the added bearing geometries, and unsteady flow and transient forced response. Refer to the hydroflext & hydrotran User's Manual and Tutorial for basic information on the analysis and instructions to run the programs. The Examples Handbook contains the test bearing cases along with comparisons with experimental data or published analytical values. The following major tasks were completed in 1994 (Phase 2): (1) extension of the thermohydrodynamic analysis and development of computer program hydroflext to model various bearing geometries, namely, tilting-pad hydrodynamic journal bearings, flexure-pad cylindrical bearings (hydrostatic and hydrodynamic), and cylindrical pad bearings with a simple elastic matrix (ideal foil bearings); (2) improved thermal model including radial heat transfer through the bearing stator; (3) calculation of the unsteady bulk-flow field in fluid film bearings and the transient response of a point mass rotor supported on bearings; and (4) a literature review on the subject of two-phase flows and homogeneous-mixture flows in thin-film geometries.
DEFF Research Database (Denmark)
Estupinan, Edgar Alberto; Santos, Ilmar
2009-01-01
elements are supported by fluid film bearings, where the hydrodynamic interaction forces are described by the Reynolds equation. The system of nonlinear equations is numerically solved for three different restrictive conditions of the motion of the crank, where the third case takes into account lateral...... and tilting oscillations of the extremity of the crankshaft. The numerical results of the behaviour of the journal bearings for each case are presented giving some insights into design parameters such as, maximum oil film pressure, minimum oil film thickness, maximum vibration levels and dynamic reaction...
CHF Enhancement by Surface Patterning based on Hydrodynamic Instability Model
Energy Technology Data Exchange (ETDEWEB)
Seo, Han; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of)
2015-05-15
If the power density of a device exceeds the CHF point, bubbles and vapor films will be covered on the whole heater surface. Because vapor films have much lower heat transfer capabilities compared to the liquid layer, the temperature of the heater surface will increase rapidly, and the device could be damaged due to the heater burnout. Therefore, the prediction and the enhancement of the CHF are essential to maximizing the efficient heat removal region. Numerous studies have been conducted to describe the CHF phenomenon, such as hydrodynamic instability theory, macrolayer dryout theory, hot/dry spot theory, and bubble interaction theory. The hydrodynamic instability model, proposed by Zuber, is the predominant CHF model that Helmholtz instability attributed to the CHF. Zuber assumed that the Rayleigh-Taylor (RT) instability wavelength is related to the Helmholtz wavelength. Lienhard and Dhir proposed a CHF model that Helmholtz instability wavelength is equal to the most dangerous RT wavelength. In addition, they showed the heater size effect using various heater surfaces. Lu et al. proposed a modified hydrodynamic theory that the Helmholtz instability was assumed to be the heater size and the area of the vapor column was used as a fitting factor. The modified hydrodynamic theories were based on the change of Helmholtz wavelength related to the RT instability wavelength. In the present study, the change of the RT instability wavelength, based on the heater surface modification, was conducted to show the CHF enhancement based on the heater surface patterning in a plate pool boiling. Sapphire glass was used as a base heater substrate, and the Pt film was used as a heating source. The patterning surface was based on the change of RT instability wavelength. In the present work the study of the CHF was conducted using bare Pt and patterned heating surfaces.
CFD Analysis of A Starved Four-Pad Tilting-Pad Journal Bearing with An Elastic Support of Pads
Parovay, E. F.; Falaleev, S. V.
2018-01-01
Tilting-pad journal bearings are widely used in technics. Oil starvation operation regime is not common for hydrodynamic bearings. However, correctly designed low-flow journal bearing have to operate efficiently and consistently on high rotor speeds. An elastic support of bearing pads is a set of elastic pins made of steel. Elastic support allows pads to self-align and achieve an optimal operational mode. The article presents the thermohydrodynamic performance of an axial journal bearing. The study deals with 60 mm diameter four-pad tilting-pad journal bearing, submitted to a static load varying from 1000 to 30000 N with a rotating speed varying from 1000 to 10000 rpm. The investigation focuses on numerical studying the characteristics of low-flow tilting-pad journal bearings under oil starvation conditions. Dependencies of the bearing performance on the load, rotational speed of the shaft, and the size of the radial clearance are presented.
Droplet motion in microfluidic networks: Hydrodynamic interactions and pressure-drop measurements
Sessoms, D. A.; Belloul, M.; Engl, W.; Roche, M.; Courbin, L.; Panizza, P.
2009-07-01
We present experimental, numerical, and theoretical studies of droplet flows in hydrodynamic networks. Using both millifluidic and microfluidic devices, we study the partitioning of monodisperse droplets in an asymmetric loop. In both cases, we show that droplet traffic results from the hydrodynamic feedback due to the presence of droplets in the outlet channels. We develop a recently-introduced phenomenological model [W. Engl , Phys. Rev. Lett. 95, 208304 (2005)] and successfully confront its predictions to our experimental results. This approach offers a simple way to measure the excess hydrodynamic resistance of a channel filled with droplets. We discuss the traffic behavior and the variations in the corresponding hydrodynamic resistance length Ld and of the droplet mobility β , as a function of droplet interdistance and confinement for channels having circular or rectangular cross sections.
A Systems Approach to the Solid Lubrication of Foil Air Bearings for Oil-Free Turbomachinery
DellaCorte, Christopher; Zaldana, Antonio R.; Radil, Kevin C.
2002-01-01
Foil air bearings are self-acting hydrodynamic bearings which rely upon solid lubricants to reduce friction and minimize wear during sliding which occurs at start-up and shut-down when surface speeds are too low to allow the formation of a hydrodynamic air film. This solid lubrication is typically accomplished by coating the non-moving foil surface with a thin, soft polymeric film. The following paper introduces a systems approach in which the solid lubrication is provided by a combination of self lubricating shaft coatings coupled with various wear resistant and lubricating foil coatings. The use of multiple materials, each providing different functions is modeled after oil-lubricated hydrodynamic sleeve bearing technology which utilizes various coatings and surface treatments in conjunction with oil lubricants to achieve optimum performance. In this study, room temperature load capacity tests are performed on journal foil air bearings operating at 14,000 rpm. Different shaft and foil coating technologies such as plasma sprayed composites, ceramic, polymer and inorganic lubricant coatings are evaluated as foil bearing lubricants. The results indicate that bearing performance is improved through the individual use of the lubricants and treatments tested. Further, combining several solid lubricants together yielded synergistically better results than any material alone.
Adaptive Spindle Balancing Using Magnetically Levitated Bearings
International Nuclear Information System (INIS)
BARNEY, PATRICK S.; LAUFFER, JAMES P.; PETTEYS, REBECCA; REDMOND, JAMES M.; SULLIVAN, WILLIAM N.
1999-01-01
A technological break through for supporting rotating shafts is the active magnetic bearing (AMB). Active magnetic bearings offer some important advantages over conventional ball, roller or journal bearings such as reduced frictional drag, no physical contact in the bearing, no need for lubricants, compatibility with high vacuum and ultra-clean environments, and ability to control shaft position within the bearing. The disadvantages of the AMB system are the increased cost and complexity, reduced bearing stiffness and the need for a controller. Still, there are certain applications, such as high speed machining, biomedical devices, and gyroscopes, where the additional cost of an AMB system can be justified. The inherent actuator capabilities of the AMB offer the potential for active balancing of spindles and micro-shaping capabilities for machine tools, The work presented in this paper concentrates on an AMB test program that utilizes the actuator capability to dynamically balance a spindle. In this study, an unbalanced AMB spindle system was enhanced with an LMS (Least Mean Squares) algorithm combined with an existing PID (proportional, integral, differential) control. This enhanced controller significantly improved the concentricity of an intentionally unbalanced shaft. The study included dynamic system analysis, test validation, control design and simulation, as well as experimental implementation using a digital LMS controller
Solitonic Dispersive Hydrodynamics: Theory and Observation
Maiden, Michelle D.; Anderson, Dalton V.; Franco, Nevil A.; El, Gennady A.; Hoefer, Mark A.
2018-04-01
Ubiquitous nonlinear waves in dispersive media include localized solitons and extended hydrodynamic states such as dispersive shock waves. Despite their physical prominence and the development of thorough theoretical and experimental investigations of each separately, experiments and a unified theory of solitons and dispersive hydrodynamics are lacking. Here, a general soliton-mean field theory is introduced and used to describe the propagation of solitons in macroscopic hydrodynamic flows. Two universal adiabatic invariants of motion are identified that predict trapping or transmission of solitons by hydrodynamic states. The result of solitons incident upon smooth expansion waves or compressive, rapidly oscillating dispersive shock waves is the same, an effect termed hydrodynamic reciprocity. Experiments on viscous fluid conduits quantitatively confirm the soliton-mean field theory with broader implications for nonlinear optics, superfluids, geophysical fluids, and other dispersive hydrodynamic media.
Annual Report: Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications
Energy Technology Data Exchange (ETDEWEB)
R. Paul Drake
2005-12-01
We report the ongoing work of our group in hydrodynamics and radiative hydrodynamics with astrophysical applications. During the period of the existing grant, we have carried out two types of experiments at the Omega laser. One set of experiments has studied radiatively collapsing shocks, obtaining high-quality scaling data using a backlit pinhole and obtaining the first (ever, anywhere) Thomson-scattering data from a radiative shock. Other experiments have studied the deeply nonlinear development of the Rayleigh-Taylor (RT) instability from complex initial conditions, obtaining the first (ever, anywhere) dual-axis radiographic data using backlit pinholes and ungated detectors. All these experiments have applications to astrophysics, discussed in the corresponding papers either in print or in preparation. We also have obtained preliminary radiographs of experimental targets using our x-ray source. The targets for the experiments have been assembled at Michigan, where we also prepare many of the simple components. The above activities, in addition to a variety of data analysis and design projects, provide good experience for graduate and undergraduates students. In the process of doing this research we have built a research group that uses such work to train junior scientists.
Hydrodynamic interactions in active colloidal crystal microrheology
Weeber, R; Harting, JDR Jens
2012-01-01
In dense colloids it is commonly assumed that hydrodynamic interactions do not play a role. However, a found theoretical quantification is often missing. We present computer simulations that are motivated by experiments where a large colloidal particle is dragged through a colloidal crystal. To qualify the influence of long-ranged hydrodynamics, we model the setup by conventional Langevin dynamics simulations and by an improved scheme with limited hydrodynamic interactions. This scheme signif...
Performance of an active electric bearing for rotary micromotors
International Nuclear Information System (INIS)
Han, F T; Wang, L; Wu, Q P; Liu, Y F
2011-01-01
An electric bearing used to support a micromachined rotor of variable-capacitance motors was designed and tested in order to study the characteristics of this frictionless bearing. Electrostatic suspension of a ring-shaped rotor in five degrees of freedom is required to eliminate the mechanical bearing and thus the friction and wear between the rotor and the substrate. Bulk microfabrication-based glass/silicon/glass bonding is chosen for this device, allowing the fabrication of large area sense capacitors and rotor, which make the device potentially suitable for the development of an electrostatically suspended micromachined gyroscope. The device and its basic operating principle are described, as well as the dynamics of the rotor and basic design considerations of the electric bearing system. A theoretical relationship to relate the characteristics of a classical lag–lead compensator to the stiffness properties of the electric bearing is developed to explain the experimental bearing measurements. The experimental results of closed-loop frequency response, suspension stiffness and drive voltage effects are presented and discussed for the bearing operated initially in the atmospheric environment. The performance of a tri-axial electrostatic accelerometer has also been experimentally investigated on the prototype of the electric bearing system
Disruptive Innovation in Numerical Hydrodynamics
Energy Technology Data Exchange (ETDEWEB)
Waltz, Jacob I. [Los Alamos National Laboratory
2012-09-06
We propose the research and development of a high-fidelity hydrodynamic algorithm for tetrahedral meshes that will lead to a disruptive innovation in the numerical modeling of Laboratory problems. Our proposed innovation has the potential to reduce turnaround time by orders of magnitude relative to Advanced Simulation and Computing (ASC) codes; reduce simulation setup costs by millions of dollars per year; and effectively leverage Graphics Processing Unit (GPU) and future Exascale computing hardware. If successful, this work will lead to a dramatic leap forward in the Laboratory's quest for a predictive simulation capability.
Laser driven hydrodynamic instability experiments
International Nuclear Information System (INIS)
Remington, B.A.; Weber, S.V.; Haan, S.W.; Kilkenny, J.D.; Glendinning, S.G.; Wallace, R.J.; Goldstein, W.H.; Wilson, B.G.; Nash, J.K.
1992-01-01
We have conducted an extensive series of experiments on the Nova laser to measure hydrodynamic instabilities in planar foils accelerated by x-ray ablation. Single mode experiments allow a measurement of the fundamental growth rates from the linear well into the nonlinear regime; multimode foils allow an assessment of the degree of mode coupling; and surface-finish experiments allow a measurement of the evolution of a broad spectrum of random initial modes. Experimental results and comparisons with theory and simulations are presented
Hydrodynamics of post CHF region
International Nuclear Information System (INIS)
Ishii, M.; De Jarlais, G.
1984-04-01
Among various two-phase flow regimes, the inverted flow in the post-dryout region is relatively less well understood due to its special heat transfer conditions. The review of existing data indicates further research is needed in the areas of basic hydrodynamics related to liquid core disintegration mechanisms, slug and droplet formations, entrainment, and droplet size distributions. In view of this, the inverted flow is studied in detail both analytically and experimentally. Criteria for initial flow regimes in the post-dryout region are given. Preliminary models for subsequent flow regime transition criteria are derived together with correlations for a mean droplet diameter based on the adiabatic simulation data
Problems in astrophysical radiation hydrodynamics
International Nuclear Information System (INIS)
Castor, J.I.
1983-01-01
The basic equations of radiation hydrodynamics are discussed in the regime that the radiation is dynamically as well as thermally important. Particular attention is paid to the question of what constitutes an acceptable approximate non-relativistic system of dynamical equations for matter and radiation in this regime. Further discussion is devoted to two classes of application of these ideas. The first class consists of problems dominated by line radiation, which is sensitive to the velocity field through the Doppler effect. The second class is of problems in which the advection of radiation by moving matter dominates radiation diffusion
Hydrodynamics and stellar winds an introduction
Maciel, Walter J
2014-01-01
Stellar winds are a common phenomenon in the life of stars, from the dwarfs like the Sun to the red giants and hot supergiants, constituting one of the basic aspects of modern astrophysics. Stellar winds are a hydrodynamic phenomenon in which circumstellar gases expand towards the interstellar medium. This book presents an elementary introduction to the fundamentals of hydrodynamics with an application to the study of stellar winds. The principles of hydrodynamics have many other applications, so that the book can be used as an introduction to hydrodynamics for students of physics, astrophysics and other related areas.
Hydrodynamic interactions in active colloidal crystal microrheology.
Weeber, R; Harting, J
2012-11-01
In dense colloids it is commonly assumed that hydrodynamic interactions do not play a role. However, a found theoretical quantification is often missing. We present computer simulations that are motivated by experiments where a large colloidal particle is dragged through a colloidal crystal. To qualify the influence of long-ranged hydrodynamics, we model the setup by conventional Langevin dynamics simulations and by an improved scheme with limited hydrodynamic interactions. This scheme significantly improves our results and allows to show that hydrodynamics strongly impacts the development of defects, the crystal regeneration, as well as the jamming behavior.
Wardle, F
2015-01-01
Ultra-precision bearings can achieve extreme accuracy of rotation, making them ideal for use in numerous applications across a variety of fields, including hard disk drives, roundness measuring machines and optical scanners. Ultraprecision Bearings provides a detailed review of the different types of bearing and their properties, as well as an analysis of the factors that influence motion error, stiffness and damping. Following an introduction to basic principles of motion error, each chapter of the book is then devoted to the basic principles and properties of a specific type of bearin
A Novel Disintegration Tester for Solid Dosage Forms Enabling Adjustable Hydrodynamics.
Kindgen, Sarah; Rach, Regine; Nawroth, Thomas; Abrahamsson, Bertil; Langguth, Peter
2016-08-01
A modified in vitro disintegration test device was designed that enables the investigation of the influence of hydrodynamic conditions on disintegration of solid oral dosage forms. The device represents an improved derivative of the compendial PhEur/USP disintegration test device. By the application of a computerized numerical control, a variety of physiologically relevant moving velocities and profiles can be applied. With the help of computational fluid dynamics, the hydrodynamic and mechanical forces present in the probe chamber were characterized for a variety of device moving speeds. Furthermore, a proof of concept study aimed at the investigation of the influence of hydrodynamic conditions on disintegration times of immediate release tablets. The experiments demonstrated the relevance of hydrodynamics for tablet disintegration, especially in media simulating the fasted state. Disintegration times increased with decreasing moving velocity. A correlation between experimentally determined disintegration times and computational fluid dynamics predicted shear stress on tablet surface was established. In conclusion, the modified disintegration test device is a valuable tool for biorelevant in vitro disintegration testing of solid oral dosage forms. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.
Hydrodynamic analysis of oscillating water column wave energy devices
DEFF Research Database (Denmark)
Bingham, Harry B.; Ducasse, Damien; Nielsen, Kim
2015-01-01
in the experiments and compared to calculations. The model is considered in both fixed and freely floating, slack-moored conditions. Comparisons are also made to experimental measurements on a single fixed chamber. The capture width ratio in each case is predicted based on the pressures in the chambers. Good...
International Nuclear Information System (INIS)
Ferapontov, E.V.
2002-01-01
Hydrodynamic surfaces are solutions of hydrodynamic-type systems viewed as non-parametrized submanifolds of the hodograph space. We propose an invariant differential-geometric characterization of hydrodynamic surfaces by expressing the curvature form of the characteristic web in terms of the reciprocal invariants. (author)
Optimal design of Tilting-Pad Thrust Bearings with High Pressure Injection Pockets
DEFF Research Database (Denmark)
Heinrichson, Niels; Santos, Ilmar
2006-01-01
A thermo-elasto-hydrodynamic(TEHD) model based on the Reynolds equation has been used to study the effect of oil injection pockets on the performance of tilting pad thrust bearings. The optimal position of the pivot both with respect to load carrying capacity and minimal power consumption is seen...
Investigation of journal orbit and flow pattern in a dynamically loaded journal bearing
DEFF Research Database (Denmark)
Christiansen, Christian Kim; Walther, Jens Honore; Klit, Peder
2017-01-01
A hydrodynamic journal bearing has been investigated using both the traditional two-dimensional (2D) Reynolds equation, and the full solution being the three-dimensional (3D) Navier-Stokes equations. The two approaches are compared by performing an investigation of two inlet groove designs: the a...
An introduction to relativistic hydrodynamics
Energy Technology Data Exchange (ETDEWEB)
Font, Jose A [Departamento de AstronomIa y AstrofIsica, Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot (Valencia) (Spain)
2007-11-15
We review formulations of the equations of (inviscid) general relativistic hydrodynamics and (ideal) magnetohydrodynamics, along with methods for their numerical solution. Both systems can be cast as first-order, hyperbolic systems of conservation laws, following the explicit choice of an Eulerian observer and suitable fluid and magnetic field variables. During the last fifteen years, the so-called (upwind) high-resolution shock-capturing schemes based on Riemann solvers have been successfully extended from classical to relativistic fluid dynamics, both special and general. Nowadays, general relativistic hydrodynamical simulations in relativistic astrophysics are routinely performed, particularly within the test-fluid approximation but also for dynamical spacetimes. While such advances also hold true in the case of the MHD equations, the astrophysical applications investigated so far are still limited, yet the field is bound to witness major developments in the near future. The article also presents a brief overview of numerical techniques, providing state-of-the-art examples of their applicability to general relativistic fluids and magneto-fluids in characteristic scenarios of relativistic astrophysics.
CHASM Challenge Problem: Lagrangian Hydrodynamics
Energy Technology Data Exchange (ETDEWEB)
Hornung, R [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Keasler, J [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Gokhale, M [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2010-09-10
Computer simulations of many science and engineering problems require modeling the equations of hydrodynamics which describe the motion of materials relative to each other induced by various forces. Many important DoD simulation problems involve complex multi-material systems that undergo large deformations. Examples include the analysis of armor defense, penetration mechanics, blast effects, structural integrity, and conventional munitions such as shaped charges and explosively formed projectiles. Indeed, the original motivation for developing codes that solve the equations of hydrodynamics, herein referred to as “hydrocodes”, was to solve problems with defense applications. The FY2010 Requirements Analysis Report issued by the DoD High Performance Computing Modernization Program (HPCMP) Office shows that a major portion of DoD HPC activities involves hydrocodes [HPCMP2010]. The report surveyed 496 projects across the Services and various Agencies, representing 4,050 HPCMP users at more than 125 locations, including government, contractors, and academia, and grouped each project into one of ten categories.
Fluctuating hydrodynamics for ionic liquids
Energy Technology Data Exchange (ETDEWEB)
Lazaridis, Konstantinos [Department of Mathematics and Statistics, Washington State University, Pullman, 99163 (United States); Wickham, Logan [Department of Computer Science, Washington State University, Richland, 99354 (United States); Voulgarakis, Nikolaos, E-mail: n.voulgarakis@wsu.edu [Department of Mathematics and Statistics, Washington State University, Pullman, 99163 (United States)
2017-04-25
We present a mean-field fluctuating hydrodynamics (FHD) method for studying the structural and transport properties of ionic liquids in bulk and near electrified surfaces. The free energy of the system consists of two competing terms: (1) a Landau–Lifshitz functional that models the spontaneous separation of the ionic groups, and (2) the standard mean-field electrostatic interaction between the ions in the liquid. The numerical approach used to solve the resulting FHD-Poisson equations is very efficient and models thermal fluctuations with remarkable accuracy. Such density fluctuations are sufficiently strong to excite the experimentally observed spontaneous formation of liquid nano-domains. Statistical analysis of our simulations provides quantitative information about the properties of ionic liquids, such as the mixing quality, stability, and the size of the nano-domains. Our model, thus, can be adequately parameterized by directly comparing our prediction with experimental measurements and all-atom simulations. Conclusively, this work can serve as a practical mathematical tool for testing various theories and designing more efficient mixtures of ionic liquids. - Highlights: • A new fluctuating hydrodynamics method for ionic liquids. • Description of ionic liquid morphology in bulk and near electrified surfaces. • Direct comparison with experimental measurements.
Roller bearing geometry design
Savage, M.; Pinkston, B. H. W.
1976-01-01
A theory of kinematic stabilization of rolling cylinders is extended and applied to the design of cylindrical roller bearings. The kinematic stabilization mechanism puts a reverse skew into the rolling elements by changing the roller taper. Twelve basic bearing modification designs are identified amd modeled. Four have single transverse convex curvature in their rollers while eight have rollers which have compound transverse curvature made up of a central cylindrical band surrounded by symmetric bands with slope and transverse curvature. The bearing designs are modeled for restoring torque per unit axial displacement, contact stress capacity, and contact area including dynamic loading, misalignment sensitivity and roller proportion. Design programs are available which size the single transverse curvature roller designs for a series of roller slopes and load separations and which design the compound roller bearings for a series of slopes and transverse radii of curvature. The compound rollers are proportioned to have equal contact stresses and minimum size. Design examples are also given.
Department of Homeland Security — Subset of BEAR (Bi-Weekly Examination Analysis and Reporting) data used for financial audit remediation reporting within the Coast Guard Business Intelligence (CGBI)...
Hydrodynamic characteristics of sailfish and swordfish
Sagong, Woong; Jeon, Woo-Pyung; Choi, Haecheon
2009-11-01
The sailfish and swordfish are known as fastest sea animals, reaching their maximum speeds of more than 100km/h. Recently, Sagong et al. (2008, Phys. Fluids) investigated the role of V- shaped protrusions existing on the sailfish skin in the skin-friction reduction but those protrusions did not make a direct role in reducing drag. On the other hand, the long bill has been regarded as a device of reducing drag by separation delay through turbulence generation. In the present study, we investigate the hydrodynamic characteristics of sailfish and swordfish by installing the stuffed ones in a wind tunnel and measuring the drag on their bodies and boundary-layer velocities above the body surfaces. The drag coefficients of sailfish and swordfish are 0.0075 and 0.009 based on the free-stream velocity and wetted area, respectively. They are comparable to or smaller than those of other kinds of fish such as the dogfish, tuna and trout. Next, the role of bill on the drag is studied. The drag without bill or with an artificial short bill is lower than that with the original long bill, indicating that the bill does not reduce the drag at all. From the velocity measurement near the body surfaces, we found that flow separation does not occur even without bill, and thus the conjecture that the flow separation is delayed through turbulence generation by the bill is not valid.
Harris, Tedric A
2001-01-01
One of the most well-known experts in the field brings cutting-edge research to practitioners in the new edition of this important reference. Covers the improved mathematical calculations for rolling bearing endurance developed by the American Society of Mechanical Engineers and the Society of Lubrication and Tribology Engineers. Updated with new material on Condition-Based Maintenance, new testing methods, and new bearing materials.
Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor); Weinberg, Brian (Inventor)
2011-01-01
A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.
Experimental investigation of hydrodynamic cavitation through orifices of different geometries
Rudolf, Pavel; Kubina, Dávid; Hudec, Martin; Kozák, Jiří; Maršálek, Blahoslav; Maršálková, Eliška; Pochylý, František
Hydrodynamic cavitation in single and multihole orifices was experimentally investigated to assess their hydraulic characteristics: loss coefficients, inception cavitation number, cavitation number for transition to supercavitation. Significant difference for singlehole and multihole orifices was observed in terms of the measured loss coefficient. It is significantly more effective to use multihole orifices, where energy dissipation is much lower.It was found that using scaling factor given by ratio of orifice thickness suggests linear behaviour of both loss coefficient and inception cavitation number. Orifices seem to be convenient choice as flow constriction devices inducing cavitation due to their simplicity.
Degradation of BTEX in aqueous solution by hydrodynamic cavitation
Energy Technology Data Exchange (ETDEWEB)
Braeutigam, P.; Wu, Z.-L.; Stark, A.; Ondruschka, B. [Institute for Technical Chemistry and Environmental Chemistry, Friedrich Schiller University, Jena (Germany)
2009-05-15
A self-made low-pressure device (up to 100 psi) for hydrodynamic cavitation was tested with the reaction of BTEX (benzene, toluene, ethylbenzene, and xylenes) in water. Experimental parameters, such as inlet pressure, solution temperature, and concentration of the chosen substrates, as well as the effect of different restrictions were investigated. The energy efficiency of the process was measured in comparison to two acoustic cavitation systems (24 and 850 kHz). The products of the BTEX degradation were identified and a pyrolytic degradation pathway is concluded. (Abstract Copyright [2009], Wiley Periodicals, Inc.)
Experimental investigation of hydrodynamic cavitation through orifices of different geometries
Directory of Open Access Journals (Sweden)
Rudolf Pavel
2017-01-01
Full Text Available Hydrodynamic cavitation in single and multihole orifices was experimentally investigated to assess their hydraulic characteristics: loss coefficients, inception cavitation number, cavitation number for transition to supercavitation. Significant difference for singlehole and multihole orifices was observed in terms of the measured loss coefficient. It is significantly more effective to use multihole orifices, where energy dissipation is much lower.It was found that using scaling factor given by ratio of orifice thickness suggests linear behaviour of both loss coefficient and inception cavitation number. Orifices seem to be convenient choice as flow constriction devices inducing cavitation due to their simplicity.
Hydrodynamic Overview at Hot Quarks 2016
International Nuclear Information System (INIS)
Noronha-Hostler, Jacquelyn
2017-01-01
Event-by-event relativistic hydrodynamics has been extremely successful in describing flow observables in heavy-ion collisions. However, the initial state and viscosity simultaneously affect comparisons to data so a discussion of experimental observables that help to distinguish the two follows. Specific problems that arise in the hydrodynamical modeling at the Beam Energy Scan are also addressed. (paper)
Two-fluid hydrodynamic model for semiconductors
DEFF Research Database (Denmark)
Maack, Johan Rosenkrantz; Mortensen, N. Asger; Wubs, Martijn
2018-01-01
The hydrodynamic Drude model (HDM) has been successful in describing the optical properties of metallic nanostructures, but for semiconductors where several different kinds of charge carriers are present an extended theory is required. We present a two-fluid hydrodynamic model for semiconductors...
Energy Technology Data Exchange (ETDEWEB)
Ederer, U.G. [Miba Gleitlager GmbH, Laakrichen (Austria)
2005-07-01
Bearing failures are consequences of system deficiencies which cause an inadequate function of the hydrodynamic action and, thereby, too high a friction, at least locally. The bearing overheats, what ultimately leads to its destruction and that of adjacent components. These 'consequential damages' are frequently severe. We identify, therefore, early stages of malfunction, already as 'bearing damage'. In this condition, a diagnosis and remedial measures to avoid total destruction are possible. Typical bearing conditions, possible causes and remedies are described herein. (orig.)
Directory of Open Access Journals (Sweden)
Dalei Jing
2017-07-01
Full Text Available In the present study, a modified Reynolds equation including the electrical double layer (EDL-induced electroviscous effect of lubricant is established to investigate the effect of the EDL on the hydrodynamic lubrication of a 1D slider bearing. The theoretical model is based on the nonlinear Poisson–Boltzmann equation without the use of the Debye–Hückel approximation. Furthermore, the variation in the bulk electrical conductivity of the lubricant under the influence of the EDL is also considered during the theoretical analysis of hydrodynamic lubrication. The results show that the EDL can increase the hydrodynamic load capacity of the lubricant in a 1D slider bearing. More importantly, the hydrodynamic load capacity of the lubricant under the influence of the EDL shows a non-monotonic trend, changing from enhancement to attenuation with a gradual increase in the absolute value of the zeta potential. This non-monotonic hydrodynamic lubrication is dependent on the non-monotonic electroviscous effect of the lubricant generated by the EDL, which is dominated by the non-monotonic electrical field strength and non-monotonic electrical body force on the lubricant. The subject of the paper is the theoretical modeling and the corresponding analysis.
Deterministic hydrodynamics: Taking blood apart
Davis, John A.; Inglis, David W.; Morton, Keith J.; Lawrence, David A.; Huang, Lotien R.; Chou, Stephen Y.; Sturm, James C.; Austin, Robert H.
2006-10-01
We show the fractionation of whole blood components and isolation of blood plasma with no dilution by using a continuous-flow deterministic array that separates blood components by their hydrodynamic size, independent of their mass. We use the technology we developed of deterministic arrays which separate white blood cells, red blood cells, and platelets from blood plasma at flow velocities of 1,000 μm/sec and volume rates up to 1 μl/min. We verified by flow cytometry that an array using focused injection removed 100% of the lymphocytes and monocytes from the main red blood cell and platelet stream. Using a second design, we demonstrated the separation of blood plasma from the blood cells (white, red, and platelets) with virtually no dilution of the plasma and no cellular contamination of the plasma. cells | plasma | separation | microfabrication
The hydrodynamic theory of detonation
Langweiler, Heinz
1939-01-01
This report derives equations containing only directly measurable constants for the quantities involved in the hydrodynamic theory of detonation. The stable detonation speed, D, is revealed as having the lowest possible value in the case of positive material velocity, by finding the minimum of the Du curve (u denotes the speed of the gases of combustion). A study of the conditions of energy and impulse in freely suspended detonating systems leads to the disclosure of a rarefaction front traveling at a lower speed behind the detonation front; its velocity is computed. The latent energy of the explosive passes into the steadily growing detonation zone - the region between the detonation front and the rarefaction front. The conclusions lead to a new definition of the concept of shattering power. The calculations are based on the behavior of trinitrotoluene.
Fluctuating nonlinear hydrodynamics of flocking
Yadav, Sunil Kumar; Das, Shankar P.
2018-03-01
Starting from a microscopic model, the continuum field theoretic description of the dynamics of a system of active ingredients or "particles" is presented. The equations of motion for the respective collective densities of mass and momentum follow exactly from that of a single element in the flock. The single-particle dynamics has noise and anomalous momentum dependence in its frictional terms. The equations for the collective densities are averaged over a local equilibrium distribution to obtain the corresponding coarse grained equations of fluctuating nonlinear hydrodynamics (FNH). The latter are the equations used frequently for describing active systems on the basis of intuitive arguments. The transport coefficients which appear in the macroscopic FNH equations are determined in terms of the parameters of the microscopic dynamics.
Hydrodynamics and phases of flocks
International Nuclear Information System (INIS)
Toner, John; Tu Yuhai; Ramaswamy, Sriram
2005-01-01
We review the past decade's theoretical and experimental studies of flocking: the collective, coherent motion of large numbers of self-propelled 'particles' (usually, but not always, living organisms). Like equilibrium condensed matter systems, flocks exhibit distinct 'phases' which can be classified by their symmetries. Indeed, the phases that have been theoretically studied to date each have exactly the same symmetry as some equilibrium phase (e.g., ferromagnets, liquid crystals). This analogy with equilibrium phases of matter continues in that all flocks in the same phase, regardless of their constituents, have the same 'hydrodynamic'-that is, long-length scale and long-time behavior, just as, e.g., all equilibrium fluids are described by the Navier-Stokes equations. Flocks are nonetheless very different from equilibrium systems, due to the intrinsically nonequilibrium self-propulsion of the constituent 'organisms'. This difference between flocks and equilibrium systems is most dramatically manifested in the ability of the simplest phase of a flock, in which all the organisms are, on average moving in the same direction (we call this a 'ferromagnetic' flock; we also use the terms 'vector-ordered' and 'polar-ordered' for this situation) to exist even in two dimensions (i.e., creatures moving on a plane), in defiance of the well-known Mermin-Wagner theorem of equilibrium statistical mechanics, which states that a continuous symmetry (in this case, rotation invariance, or the ability of the flock to fly in any direction) can not be spontaneously broken in a two-dimensional system with only short-ranged interactions. The 'nematic' phase of flocks, in which all the creatures move preferentially, or are simply oriented preferentially, along the same axis, but with equal probability of moving in either direction, also differs dramatically from its equilibrium counterpart (in this case, nematic liquid crystals). Specifically, it shows enormous number fluctuations, which
Anomalous hydrodynamics kicks neutron stars
Energy Technology Data Exchange (ETDEWEB)
Kaminski, Matthias, E-mail: mski@ua.edu [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States); Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 5C2 (Canada); Uhlemann, Christoph F. [Department of Physics, University of Washington, Seattle, WA 98195 (United States); Bleicher, Marcus [Frankfurt Institute for Advanced Studies, Goethe-Universität Frankfurt (Germany); Institut für Theoretische Physik, Goethe Universität Frankfurt (Germany); Schaffner-Bielich, Jürgen [Institut für Theoretische Physik, Goethe Universität Frankfurt (Germany)
2016-09-10
Observations show that, at the beginning of their existence, neutron stars are accelerated briskly to velocities of up to a thousand kilometers per second. We argue that this remarkable effect can be explained as a manifestation of quantum anomalies on astrophysical scales. To theoretically describe the early stage in the life of neutron stars we use hydrodynamics as a systematic effective-field-theory framework. Within this framework, anomalies of the Standard Model of particle physics as underlying microscopic theory imply the presence of a particular set of transport terms, whose form is completely fixed by theoretical consistency. The resulting chiral transport effects in proto-neutron stars enhance neutrino emission along the internal magnetic field, and the recoil can explain the order of magnitude of the observed kick velocities.
Study on mechanical properties of laminated rubber bearing with small shape factor
International Nuclear Information System (INIS)
Mazda, T.; Ootori, Y.; Yabana, S.; Hirata, K.; Ishida, K.
1995-01-01
Laminated rubber bearings with a small shape factor are regarded as one of the most promising isolation devices to reduce the vertical seismic load of a nuclear power plant. In this study, three types of natural rubber bearings with different aspect ratios (diameter/total thickness of rubber) and one high-damping rubber bearing are tested under varied loading conditions. Basic characteristics and ultimate characteristics of the bearings are made clear, and applicability of estimation formula and analysis method are verified
Biomimetic shark skin: design, fabrication and hydrodynamic function.
Wen, Li; Weaver, James C; Lauder, George V
2014-05-15
Although the functional properties of shark skin have been of considerable interest to both biologists and engineers because of the complex hydrodynamic effects of surface roughness, no study to date has successfully fabricated a flexible biomimetic shark skin that allows detailed study of hydrodynamic function. We present the first study of the design, fabrication and hydrodynamic testing of a synthetic, flexible, shark skin membrane. A three-dimensional (3D) model of shark skin denticles was constructed using micro-CT imaging of the skin of the shortfin mako (Isurus oxyrinchus). Using 3D printing, thousands of rigid synthetic shark denticles were placed on flexible membranes in a controlled, linear-arrayed pattern. This flexible 3D printed shark skin model was then tested in water using a robotic flapping device that allowed us to either hold the models in a stationary position or move them dynamically at their self-propelled swimming speed. Compared with a smooth control model without denticles, the 3D printed shark skin showed increased swimming speed with reduced energy consumption under certain motion programs. For example, at a heave frequency of 1.5 Hz and an amplitude of ± 1 cm, swimming speed increased by 6.6% and the energy cost-of-transport was reduced by 5.9%. In addition, a leading-edge vortex with greater vorticity than the smooth control was generated by the 3D printed shark skin, which may explain the increased swimming speeds. The ability to fabricate synthetic biomimetic shark skin opens up a wide array of possible manipulations of surface roughness parameters, and the ability to examine the hydrodynamic consequences of diverse skin denticle shapes present in different shark species. © 2014. Published by The Company of Biologists Ltd.
Climate Drives Polar Bear Origins
In their provocative analysis of northern bears (“Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage,” Reports, 20 April, p. 344), F. Hailer et al. use independent nuclear loci to show that polar bears originated during the middle Pleistocene, rather than during t...
Watchable Wildlife: The Black Bear
Lynn L. Rogers
1992-01-01
Black bears are the bears people most often encounter. Black bears live in forests over much of North America, unlike grizzlies that live only in Alaska, northern and western Canada, and the northern Rocky Mountains. This brochure presents the latest information on black bear life and how this species responds to an ever-increasing number of campers, hikers, and...
Hydrodynamic dispersion within porous biofilms
Davit, Y.
2013-01-23
Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher\\'s equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels\\' network; (2) the solute\\'s diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport. © 2013 American Physical Society.
Morison, K R; Hutchinson, C A
2009-01-01
The Weissler reaction in which iodide is oxidised to a tri-iodide complex (I(3)(-)) has been widely used for measurement of the intensity of ultrasonic and hydrodynamic cavitation. It was used in this work to compare ultrasonic cavitation at 24 kHz with hydrodynamic cavitation using two different devices, one a venturi and the other a sudden expansion, operated up to 8.7 bar. Hydrodynamic cavitation had a maximum efficiency of about 5 x 10(-11) moles of I(3)(-) per joule of energy compared with the maximum of almost 8 x 10(-11) mol J(-1) for ultrasonic cavitation. Hydrodynamic cavitation was found to be most effective at 10 degrees C compared with 20 degrees C and 30 degrees C and at higher upstream pressures. However, it was found that in hydrodynamic conditions, even without cavitation, I(3)(-) was consumed at a rapid rate leading to an equilibrium concentration. It was concluded that the Weissler reaction was not a good model reaction for the assessment of the effectiveness of hydrodynamic cavitation.
Tribology of alternative bearings.
Fisher, John; Jin, Zhongmin; Tipper, Joanne; Stone, Martin; Ingham, Eileen
2006-12-01
The tribological performance and biological activity of the wear debris produced has been compared for highly cross-linked polyethylene, ceramic-on-ceramic, metal-on-metal, and modified metal bearings in a series of in vitro studies from a single laboratory. The functional lifetime demand of young and active patients is 10-fold greater than the estimated functional lifetime of traditional polyethylene. There is considerable interest in using larger diameter heads in these high demand patients. Highly cross-linked polyethylene show a four-fold reduction in functional biological activity. Ceramic-on-ceramic bearings have the lowest wear rates and least reactive wear debris. The functional biological activity is 20-fold lower than with highly cross-linked polyethylene. Hence, ceramic-on-ceramic bearings address the tribological lifetime demand of highly active patients. Metal-on-metal bearings have substantially lower wear rates than highly cross-linked polyethylene and wear decreases with head diameter. Bedding in wear is also lower with reduced radial clearance. Differential hardness ceramic-on-metal bearings and the application of ceramic-like coatings reduce metal wear and ion levels.
Vranish, John M. (Inventor)
2010-01-01
A partial gear bearing including an upper half, comprising peak partial teeth, and a lower, or bottom, half, comprising valley partial teeth. The upper half also has an integrated roller section between each of the peak partial teeth with a radius equal to the gear pitch radius of the radially outwardly extending peak partial teeth. Conversely, the lower half has an integrated roller section between each of the valley half teeth with a radius also equal to the gear pitch radius of the peak partial teeth. The valley partial teeth extend radially inwardly from its roller section. The peak and valley partial teeth are exactly out of phase with each other, as are the roller sections of the upper and lower halves. Essentially, the end roller bearing of the typical gear bearing has been integrated into the normal gear tooth pattern.
Optimal design of a hydrodynamic separator for treating runoff from roadways.
Tran, Duyen; Kang, Joo-Hyon
2013-02-15
This study investigated the removal efficiency of target pollutants from an underground stormwater treatment device (a hydrodynamic separator), focusing on the overall performance of the devices of a catchment. An approach for sizing an underground stormwater treatment device was developed, in order to obtain the required reduction percentage of the total suspended solids (TSS) generated from a given impervious catchment. The United States Environmental Protection Agency's stormwater management model (SWMM) was used for developing contours to help determine the size of the device, with respect to the maximum inflow to the device (or bypass rate), and the catchment area served by the device. Additionally, three different configurations of underground stormwater treatment devices were examined. It was found that, for a given catchment area, a single large device provides slightly better performance than multiple small devices. The approach we propose here can be useful to determine the sizes, as well as to clarify the efficiencies, of different installation configurations of underground stormwater treatment device (e.g. a hydrodynamic separator) in relation to their bypass rates and site specific conditions, such as rainfall characteristics and the catchment area to be served. Copyright © 2012 Elsevier Ltd. All rights reserved.
Radial oil injection applied to main engine bearings: evaluation of injection control rules
DEFF Research Database (Denmark)
Estupiñan, EA; Santos, Ilmar
2012-01-01
, the dynamic behaviour of the main bearing of a medium-size engine is theoretically analysed when the engine operates with controllable radial oil injection and four different injection control rules. The theoretical investigation is based on a single-cylinder combustion engine model. The performance......The performance of main bearings in a combustion engine affects key functions such as durability, noise and vibration. Thus, with the aim of reducing friction losses and vibrations between the crankshaft and the bearings, the work reported here evaluates different strategies for applying...... controllable radial oil injection to main crankshaft journal bearings. In an actively lubricated bearing, conventional hydrodynamic lubrication is combined with controllable hydrostatic lubrication, where the oil injection pressures can be modified depending on the operational conditions. In this study...
Relativistic conformal magneto-hydrodynamics from holography
International Nuclear Information System (INIS)
Buchbinder, Evgeny I.; Buchel, Alex
2009-01-01
We use the AdS/CFT correspondence to study first-order relativistic viscous magneto-hydrodynamics of (2+1)-dimensional conformal magnetic fluids. It is shown that the first order magneto-hydrodynamics constructed following Landau and Lifshitz from the positivity of the entropy production is inconsistent. We propose additional contributions to the entropy motivated dissipative current and, correspondingly, new dissipative transport coefficients. We use the strongly coupled M2-brane plasma in external magnetic field to show that the new magneto-hydrodynamics leads to self-consistent results in the shear and sound wave channels.
Dileptons from transport and hydrodynamical models
International Nuclear Information System (INIS)
Huovinen, P.; Koch, V.
2000-01-01
Transport and hydrodynamical models used to describe the expansion stage of a heavy-ion collision at the CERN SPS give different dilepton spectrum even if they are tuned to reproduce the observed hadron spectra. To understand the origin of this difference we compare the dilepton emission from transport and hydrodynamical models using similar initial states in both models. We find that the requirement of pion number conservation in a hydrodynamical model does not change the dilepton emission. Also the mass distribution from the transport model indicates faster cooling and longer lifetime of the fireball
Tuning bacterial hydrodynamics with magnetic fields
Pierce, C. J.; Mumper, E.; Brown, E. E.; Brangham, J. T.; Lower, B. H.; Lower, S. K.; Yang, F. Y.; Sooryakumar, R.
2017-06-01
Magnetotactic bacteria are a group of motile prokaryotes that synthesize chains of lipid-bound, magnetic nanoparticles called magnetosomes. This study exploits their innate magnetism to investigate previously unexplored facets of bacterial hydrodynamics at surfaces. Through use of weak, uniform, external magnetic fields and local, micromagnetic surface patterns, the relative strength of hydrodynamic, magnetic, and flagellar force components is tuned through magnetic control of the bacteria's orientation. The resulting swimming behaviors provide a means to experimentally determine hydrodynamic parameters and offer a high degree of control over large numbers of living microscopic entities. The implications of this controlled motion for studies of bacterial motility near surfaces and for micro- and nanotechnology are discussed.
CHOLLA: A NEW MASSIVELY PARALLEL HYDRODYNAMICS CODE FOR ASTROPHYSICAL SIMULATION
Energy Technology Data Exchange (ETDEWEB)
Schneider, Evan E.; Robertson, Brant E. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
2015-04-15
We present Computational Hydrodynamics On ParaLLel Architectures (Cholla ), a new three-dimensional hydrodynamics code that harnesses the power of graphics processing units (GPUs) to accelerate astrophysical simulations. Cholla models the Euler equations on a static mesh using state-of-the-art techniques, including the unsplit Corner Transport Upwind algorithm, a variety of exact and approximate Riemann solvers, and multiple spatial reconstruction techniques including the piecewise parabolic method (PPM). Using GPUs, Cholla evolves the fluid properties of thousands of cells simultaneously and can update over 10 million cells per GPU-second while using an exact Riemann solver and PPM reconstruction. Owing to the massively parallel architecture of GPUs and the design of the Cholla code, astrophysical simulations with physically interesting grid resolutions (≳256{sup 3}) can easily be computed on a single device. We use the Message Passing Interface library to extend calculations onto multiple devices and demonstrate nearly ideal scaling beyond 64 GPUs. A suite of test problems highlights the physical accuracy of our modeling and provides a useful comparison to other codes. We then use Cholla to simulate the interaction of a shock wave with a gas cloud in the interstellar medium, showing that the evolution of the cloud is highly dependent on its density structure. We reconcile the computed mixing time of a turbulent cloud with a realistic density distribution destroyed by a strong shock with the existing analytic theory for spherical cloud destruction by describing the system in terms of its median gas density.
CHOLLA: A NEW MASSIVELY PARALLEL HYDRODYNAMICS CODE FOR ASTROPHYSICAL SIMULATION
International Nuclear Information System (INIS)
Schneider, Evan E.; Robertson, Brant E.
2015-01-01
We present Computational Hydrodynamics On ParaLLel Architectures (Cholla ), a new three-dimensional hydrodynamics code that harnesses the power of graphics processing units (GPUs) to accelerate astrophysical simulations. Cholla models the Euler equations on a static mesh using state-of-the-art techniques, including the unsplit Corner Transport Upwind algorithm, a variety of exact and approximate Riemann solvers, and multiple spatial reconstruction techniques including the piecewise parabolic method (PPM). Using GPUs, Cholla evolves the fluid properties of thousands of cells simultaneously and can update over 10 million cells per GPU-second while using an exact Riemann solver and PPM reconstruction. Owing to the massively parallel architecture of GPUs and the design of the Cholla code, astrophysical simulations with physically interesting grid resolutions (≳256 3 ) can easily be computed on a single device. We use the Message Passing Interface library to extend calculations onto multiple devices and demonstrate nearly ideal scaling beyond 64 GPUs. A suite of test problems highlights the physical accuracy of our modeling and provides a useful comparison to other codes. We then use Cholla to simulate the interaction of a shock wave with a gas cloud in the interstellar medium, showing that the evolution of the cloud is highly dependent on its density structure. We reconcile the computed mixing time of a turbulent cloud with a realistic density distribution destroyed by a strong shock with the existing analytic theory for spherical cloud destruction by describing the system in terms of its median gas density
Polar bears: the fate of an icon.
Fitzgerald, Kevin T
2013-11-01
Polar bears are one of the most iconic animals on our planet. Worldwide, even people who would never see one are drawn to these charismatic arctic ice hunters. They are the world's largest terrestrial carnivore, and despite being born on land, they spend most of their lives out on the sea ice and are considered a marine mammal. Current global studies estimate there are around 20,000 animals in some 19 discrete circumpolar populations. Aside from pregnant females denning in the winter months to give birth, the white bears do not hibernate. They spend their winters on the sea ice hunting seals, an activity they are spectacularly adapted for. Research on these animals is incredibly difficult because of the inhospitable surroundings they inhabit and how inaccessible they make the bears. For many years, the sum of our understanding of the natural history of polar bears came from tracks, scats, the remains of their kills, abandoned dens, and anecdotal observations of native hunters, explorers, and early biologists. Nonetheless, the last 40 years have seen a much better picture of their biology emerge thanks to, first, dedicated Canadian researchers and, later, truly international efforts of workers from many countries. Veterinarians have contributed to our knowledge of the bears by delivering and monitoring anesthesia, obtaining blood samples, performing necropsies, investigating their reproduction, conducting radiotelemetry studies, and examining their behavior. Recently, new technologies have been developed that revolutionize the study of the lives and natural history of undisturbed polar bears. These advances include better satellite radiotelemetry equipment and the development of remote-controlled miniature devices equipped with high-definition cameras. Such new modalities provide dramatic new insights into the life of polar bears. The remarkable degree of specialized adaptation to life on the sea ice that allowed the bears to be successful is the very reason that
Magnetically leviated superconducting bearing
Weinberger, Bernard R.; Lynds, Jr., Lahmer
1993-01-01
A magnetically levitated superconducting bearing includes a magnet (2) mounted on a shaft (12) that is rotatable around an axis of rotation and a Type II superconductor (6) supported on a stator (14) in proximity to the magnet (2). The superconductor (6) is positioned so that when it is cooled to its superconducting state in the presence of a magnetic field, it interacts with the magnet (2) to produce an attractive force that levitates the magnet (2) and supports a load on the shaft (12). The interaction between the superconductor (6) and magnet(2) also produces surface screening currents (8) that generate a repulsive force perpendicular to the load. The bearing also has means for maintaining the superconductor at a temperature below its critical temperature (16, 18). The bearing could also be constructed so the magnet (2) is supported on the stator (14) and the superconductor (6) is mounted on the shaft (12). The bearing can be operated by cooling the superconductor (6) to its superconducting state in the presence of a magnetic field.
Conformal invariance in hydrodynamic turbulence
International Nuclear Information System (INIS)
Falkovich, Gregory
2007-01-01
This short survey is written by a physicist. It contains neither theorems nor precise definitions. Its main content is a description of the results of numerical solution of the equations of fluid mechanics in the regime of developed turbulence. Due to limitations of computers, the results are not very precise. Despite being neither exact nor rigorous, the findings may nevertheless be of interest for mathematicians. The main result is that the isolines of some scalar fields (vorticity, temperature) in two-dimensional turbulence belong to the class of conformally invariant curves called SLE (Scramm-Loewner evolution) curves. First, this enables one to predict and find a plethora of quantitative relations going far beyond what was known previously about turbulence. Second, it suggests relations between phenomena that seemed unrelated, like the Euler equation and critical percolation. Third, it shows that one is able to get exact analytic results in statistical hydrodynamics. In short, physicists have found something unexpected and hope that mathematicians can help to explain it.
The hydrodynamics of swimming microorganisms
International Nuclear Information System (INIS)
Lauga, Eric; Powers, Thomas R
2009-01-01
Cell motility in viscous fluids is ubiquitous and affects many biological processes, including reproduction, infection and the marine life ecosystem. Here we review the biophysical and mechanical principles of locomotion at the small scales relevant to cell swimming, tens of micrometers and below. At this scale, inertia is unimportant and the Reynolds number is small. Our emphasis is on the simple physical picture and fundamental flow physics phenomena in this regime. We first give a brief overview of the mechanisms for swimming motility, and of the basic properties of flows at low Reynolds number, paying special attention to aspects most relevant for swimming such as resistance matrices for solid bodies, flow singularities and kinematic requirements for net translation. Then we review classical theoretical work on cell motility, in particular early calculations of swimming kinematics with prescribed stroke and the application of resistive force theory and slender-body theory to flagellar locomotion. After examining the physical means by which flagella are actuated, we outline areas of active research, including hydrodynamic interactions, biological locomotion in complex fluids, the design of small-scale artificial swimmers and the optimization of locomotion strategies.
Superconducting levitation applications to bearings and magnetic transportation
Moon, Francis C
1994-01-01
Presents the fundamental principles governing levitation of material bodies by magnetic fields without too much formal theory. Defines the technology of magnetic bearings, especially those based on superconductivity, and demonstrates the key roles that magnetics, mechanics and dynamics play in the complete understanding of magnetic levitation and its bearings. Features extensive figures and photos of Mag-Lev devices and summarizes recent U.S. research studies in an effort to regain the lead in Mag-Lev technologies
Framing Camera Improvements and hydrodynamic Experiments
National Research Council Canada - National Science Library
Drake, R. P
2007-01-01
.... We also propose to participate in hydrodynamic experiments at NRL whenever they occur, to prepare for an experiment for NIKE to study the onset of turbulence via the Kelvin Helmholtz instability...
Hydrodynamic limit of interacting particle systems
International Nuclear Information System (INIS)
Landim, C.
2004-01-01
We present in these notes two methods to derive the hydrodynamic equation of conservative interacting particle systems. The intention is to present the main ideas in the simplest possible context and refer for details and references. (author)
Hydrodynamic approach to electronic transport in graphene
Energy Technology Data Exchange (ETDEWEB)
Narozhny, Boris N. [Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, Karlsruhe (Germany); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Gornyi, Igor V. [Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe (Germany); Ioffe Physical Technical Institute, St. Petersburg (Russian Federation); Mirlin, Alexander D. [Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe (Germany); Petersburg Nuclear Physics Institute, St. Petersburg (Russian Federation); Schmalian, Joerg [Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Institute for Solid State Physics, Karlsruhe Institute of Technology, Karlsruhe (Germany)
2017-11-15
The last few years have seen an explosion of interest in hydrodynamic effects in interacting electron systems in ultra-pure materials. In this paper we briefly review the recent advances, both theoretical and experimental, in the hydrodynamic approach to electronic transport in graphene, focusing on viscous phenomena, Coulomb drag, non-local transport measurements, and possibilities for observing nonlinear effects. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Improvements to SOIL: An Eulerian hydrodynamics code
International Nuclear Information System (INIS)
Davis, C.G.
1988-04-01
Possible improvements to SOIL, an Eulerian hydrodynamics code that can do coupled radiation diffusion and strength of materials, are presented in this report. Our research is based on the inspection of other Eulerian codes and theoretical reports on hydrodynamics. Several conclusions from the present study suggest that some improvements are in order, such as second-order advection, adaptive meshes, and speedup of the code by vectorization and/or multitasking. 29 refs., 2 figs
Relabeling symmetries in hydrodynamics and magnetohydrodynamics
International Nuclear Information System (INIS)
Padhye, N.; Morrison, P.J.
1996-04-01
Lagrangian symmetries and concomitant generalized Bianchi identities associated with the relabeling of fluid elements are found for hydrodynamics and magnetohydrodynamics (MHD). In hydrodynamics relabeling results in Ertel's theorem of conservation of potential vorticity, while in MHD it yields the conservation of cross helicity. The symmetries of the reduction from Lagrangian (material) to Eulerian variables are used to construct the Casimir invariants of the Hamiltonian formalism
Actuators for Active Magnetic Bearings
Directory of Open Access Journals (Sweden)
Eric H. Maslen
2017-10-01
Full Text Available The literature of active magnetic bearing (AMB technology dates back to at least 1937 when the earliest work that clearly describes an active magnetic bearing system was published by Jesse Beams [...
Chaotic hydrodynamics of fluidized beds
Energy Technology Data Exchange (ETDEWEB)
Van der Stappen, M.L.M. [Unit Process and Systems Engineering, Advanced Manufacturing Technology Group, Unilever Research Laboratorium, Vlaardingen (Netherlands)
1996-12-31
The major goals of this thesis are: (1) to develop and evaluate an analysis method based on techniques from non-linear chaos theory to characterize the nonlinear hydrodynamics of gas-solids fluidized beds quantitatively; and (2) to determine the dependence of the chaotic invariants on the operating conditions and investigate how the chaos analysis method can be profitably applied to improve scale-up and design of gas-solids fluidized bed reactors. Chaos theory is introduced in chapter 2 with emphasis on analysis techniques for (experimental) time series, known from literature at the start of this work (1990-1991). In chapter 3, the testing of existing and newly developed techniques on both model and fluidized bed data is described. This leads to the development of the chaos analysis method to analyze measured pressure fluctuations time series of a fluidized bed. Following, in chapter 4, this method is tested and all choices for the parameters are evaluated. The influence of the experimental parameters and external disturbances on the measurements and analysis results is discussed and quantified. The result is a chaos measurement and analysis protocol, which is further used in this work. In chapter 5, the applications to fluidized beds are discussed. It is shown that the entropy is a good measure for the characterization of the dynamical behavior of gas-solids bubbling/slugging fluidized beds. Entropy is applied to characterize the influence of the operating conditions, to assess regime transitions and to analyze dimensionless similar beds of different scale. Quantitative design correlations that relate entropy to the operating parameters (including the bed diameter) are described. Finally, it is discussed how the results of this work might be used in scaling up the chaotic dynamics of fluidized beds. The overall conclusions and outlook from this work are presented in chapter 6. 182 refs.
Hydrodynamics of soft active matter
Marchetti, M. C.; Joanny, J. F.; Ramaswamy, S.; Liverpool, T. B.; Prost, J.; Rao, Madan; Simha, R. Aditi
2013-07-01
This review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical properties of living matter: biofilaments and molecular motors in vitro or in vivo, collections of motile microorganisms, animal flocks, and chemical or mechanical imitations. A major goal of this review is to integrate several approaches proposed in the literature, from semimicroscopic to phenomenological. In particular, first considered are “dry” systems, defined as those where momentum is not conserved due to friction with a substrate or an embedding porous medium. The differences and similarities between two types of orientationally ordered states, the nematic and the polar, are clarified. Next, the active hydrodynamics of suspensions or “wet” systems is discussed and the relation with and difference from the dry case, as well as various large-scale instabilities of these nonequilibrium states of matter, are highlighted. Further highlighted are various large-scale instabilities of these nonequilibrium states of matter. Various semimicroscopic derivations of the continuum theory are discussed and connected, highlighting the unifying and generic nature of the continuum model. Throughout the review, the experimental relevance of these theories for describing bacterial swarms and suspensions, the cytoskeleton of living cells, and vibrated granular material is discussed. Promising extensions toward greater realism in specific contexts from cell biology to animal behavior are suggested, and remarks are given on some exotic active-matter analogs. Last, the outlook for a quantitative understanding of active matter, through the interplay of detailed theory with controlled experiments on simplified systems, with living or artificial constituents, is summarized.
Telemetry experiments with a hibernating black bear
Craighead, J. J.; Varney, J. R.; Sumner, J. S.; Craighead, F. C., Jr.
1972-01-01
The objectives of this research were to develop and test telemetry equipment suitable for monitoring physiological parameters and activity of a hibernating bear in its den, to monitor this data and other environmental information with the Nimbus 3 IRLS data collection system, and to refine immobilizing, handling, and other techniques required in future work with wild bears under natural conditions. A temperature-telemetering transmitter was implanted in the abdominal cavity of a captive black bear and body temperature data was recorded continuously during a 3 month hibernation period. Body temperatures ranging between 37.5 and 31.8 C were observed. Body temperature and overall activity were influenced by disturbances and ambient den temperature. Nychthemeral temperature changes were not noticable. A load cell weight recording device was tested for determining weight loss during hibernation. Monitoring of data by satellite was not attempted. The implanted transmitter was removed and the bear was released with a radiolocation collar at the conclusion of the experiment.
DEFF Research Database (Denmark)
Heinrichson, Niels; Santos, Ilmar
2006-01-01
This is Part I of a two-part series of papers describing the effects of high pressure injection pockets on the operating conditions of tilting-pad thrust bearings. A numerical model based on the Reynolds equation is developed extending the three dimensional thermo-elasto-hydrodynamic (TEHD......) analysis of tilting-pad thrust bearings to include the effects of high pressure injection and recesses in the bearing pad. The model is applied to the analysis of an existing bearing of large dimensions and the influence of the pocket is analyzed. It is shown that a shallow pocket positively influences...... the performance of the bearing as it has characteristics similar to those of a parallel step bearing....
Johnson, Jo-Ann; Tough, Suzanne
2012-01-01
To provide an overview of delayed child-bearing and to describe the implications for women and health care providers. Delayed child-bearing, which has increased greatly in recent decades, is associated with an increased risk of infertility, pregnancy complications, and adverse pregnancy outcome. This guideline provides information that will optimize the counselling and care of Canadian women with respect to their reproductive choices. Maternal age is the most important determinant of fertility, and obstetric and perinatal risks increase with maternal age. Many women are unaware of the success rates or limitations of assisted reproductive technology and of the increased medical risks of delayed child-bearing, including multiple births, preterm delivery, stillbirth, and Caesarean section. This guideline provides a framework to address these issues. Studies published between 2000 and August 2010 were retrieved through searches of PubMed and the Cochrane Library using appropriate key words (delayed child-bearing, deferred pregnancy, maternal age, assisted reproductive technology, infertility, and multiple births) and MeSH terms (maternal age, reproductive behaviour, fertility). The Internet was also searched using similar key words, and national and international medical specialty societies were searched for clinical practice guidelines and position statements. Data were extracted based on the aims, sample, authors, year, and results. The quality of evidence was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1). The Society of Obstetricians and Gynaecologists of Canada. RECOMMENDATIONS 1. Women who delay child-bearing are at increased risk of infertility. Prospective parents, especially women, should know that their fecundity and fertility begin to decline significantly after 32 years of age. Prospective parents should know that assisted reproductive technologies cannot guarantee a live birth or completely
1993-01-01
The u.s. government bulks large in the nation's financial markets. The huge volume of government-issued and -sponsored debt affects the pricing and volume ofprivate debt and, consequently, resource allocation between competing alternatives. What is often not fully appreciated is the substantial influence the federal government wields overresource allocation through its provisionofcreditandrisk-bearing services to the private economy. Because peopleand firms generally seekto avoid risk, atsomeprice they are willing to pay another party to assume the risk they would otherwise face. Insurance companies are a class of private-sector firms one commonly thinks of as providing these services. As the federal government has expanded its presence in the U.S. economy during this century, it has increasingly developed programs aimed at bearing risks that the private sector either would not take on at any price, or would take on but atapricethoughtto besogreatthatmostpotentialbeneficiarieswouldnotpurchase the coverage. To...
Passive magnetic bearing system
Post, Richard F.
2014-09-02
An axial stabilizer for the rotor of a magnetic bearing provides external control of stiffness through switching in external inductances. External control also allows the stabilizer to become a part of a passive/active magnetic bearing system that requires no external source of power and no position sensor. Stabilizers for displacements transverse to the axis of rotation are provided that require only a single cylindrical Halbach array in its operation, and thus are especially suited for use in high rotation speed applications, such as flywheel energy storage systems. The elimination of the need of an inner cylindrical array solves the difficult mechanical problem of supplying support against centrifugal forces for the magnets of that array. Compensation is provided for the temperature variation of the strength of the magnetic fields of the permanent magnets in the levitating magnet arrays.
Stacked magnet superconducting bearing
International Nuclear Information System (INIS)
Rigney, T.K. II; Saville, M.P.
1993-01-01
A superconducting bearing is described, comprising: a plurality of permanent magnets magnetized end-to-end and stacked side-by-side in alternating polarity, such that flux lines flow between ends of adjacent magnets; isolating means, disposed between said adjacent magnets, for reducing flux leakage between opposing sides of said adjacent magnets; and a member made of superconducting material having at least one surface in communication with said flux lines
International Nuclear Information System (INIS)
Tope, W.G.; Nixon, D.A.; Smith, M.L.; Stone, T.J.; Vogel, R.A.; Schofield, W.D.
1995-01-01
Fernald radium bearing ore residue waste, stored within Silos 1 and 2 (K-65) and Silo 3, will be vitrified for disposal at the Nevada Test Site (NTS). A comprehensive, parametric evaluation of waste form, packaging, and transportation alternatives was completed to identify the most cost-effective approach. The impacts of waste loading, waste form, regulatory requirements, NTS waste acceptance criteria, as-low-as-reasonably-achievable principles, and material handling costs were factored into the recommended approach
Hanoca, P.; Ramakrishna, H. V.
2018-03-01
This work is related to develop a methodology to model and simulate the TEHD using the sequential application of CFD and CSD. The FSI analyses are carried out using ANSYS Workbench. In this analysis steady state, 3D Navier-Stoke equations along with energy equation are solved. Liquid properties are introduced where the viscosity and density are the function of pressure and temperature. The cavitation phenomenon is adopted in the analysis. Numerical analysis has been carried at different speeds and surfaces temperatures. During the analysis, it was found that as speed increases, hydrodynamic pressures will also increases. The pressure profile obtained from the Roelands equation is more sensitive to the temperature as compared to the Barus equation. The stress distributions specify the significant positions in the bearing structure. The developed method is capable of giving latest approaching into the physics of elasto hydrodynamic lubrication.
Hockney, Richard L. (Inventor); Downer, James R. (Inventor); Eisenhaure, David B. (Inventor); Hawkey, Timothy J. (Inventor); Johnson, Bruce G. (Inventor)
1990-01-01
A magnetic bearing system for enabling translational motion includes a carriage and a shaft for movably supporting the carriage; a first magnetic bearing fixed to one of the carriage and shaft and slidably received in a first channel of the other of the carriage and shaft. The first channel is generally U shaped with two side walls and a back wall. The magnetic bearing includes a pair of spaced magnetic pole pieces, each pole piece having a pair of electromagnetic coils mounted on poles on opposite ends of the pole piece proximate the side walls, and a third electromagnetic coil mounted on a pole of the pole piece proximate the backwall; a motion sensor for sensing translational motion along two axes and rotationally about three axes of the carriage and shaft relative to each other; and a correction circuit responsive to the sensor for generating a correction signal to drive the coils to compensate for any misalignment sensed between the carriage and the shaft.
Bagal, Manisha V; Gogate, Parag R
2014-05-01
Diclofenac sodium, a widely detected pharmaceutical drug in wastewater samples, has been selected as a model pollutant for degradation using novel combined approach of hydrodynamic cavitation and heterogeneous photocatalysis. A slit venturi has been used as cavitating device in the hydrodynamic cavitation reactor. The effect of various operating parameters such as inlet fluid pressure (2-4 bar) and initial pH of the solution (4-7.5) on the extent of degradation have been studied. The maximum extent of degradation of diclofenac sodium was obtained at inlet fluid pressure of 3 bar and initial pH as 4 using hydrodynamic cavitation alone. The loadings of TiO2 and H2O2 have been optimised to maximise the extent of degradation of diclofenac sodium. Kinetic study revealed that the degradation of diclofenac sodium fitted first order kinetics over the selected range of operating protocols. It has been observed that combination of hydrodynamic cavitation with UV, UV/TiO2 and UV/TiO2/H2O2 results in enhanced extents of degradation as compared to the individual schemes. The maximum extent of degradation as 95% with 76% reduction in TOC has been observed using hydrodynamic cavitation in conjunction with UV/TiO2/H2O2 under the optimised operating conditions. The diclofenac sodium degradation byproducts have been identified using LC/MS analysis. Copyright © 2013 Elsevier B.V. All rights reserved.
Dey, Ranabir; Raj M, Kiran; Bhandaru, Nandini; Mukherjee, Rabibrata; Chakraborty, Suman
2014-05-21
The present work comprehensively addresses the hydrodynamic characteristics through microchannels with lotus leaf replica (exhibiting low adhesion and superhydrophobic properties) walls. The lotus leaf replica is fabricated following an efficient, two-step, soft-molding process and is then integrated with rectangular microchannels. The inherent biomimetic, superhydrophobic surface-liquid interfacial hydrodynamics, and the consequential bulk flow characteristics, are critically analyzed by the micro-particle image velocimetry technique. It is observed that the lotus leaf replica mediated microscale hydrodynamics comprise of two distinct flow regimes even within the low Reynolds number paradigm, unlike the commonly perceived solely apparent slip-stick dominated flows over superhydrophobic surfaces. While the first flow regime is characterized by an apparent slip-stick flow culminating in an enhanced bulk throughput rate, the second flow regime exhibits a complete breakdown of the aforementioned laminar and uni-axial flow model, leading to a predominantly no-slip flow. Interestingly, the critical flow condition dictating the transition between the two hydrodynamic regimes is intrinsically dependent on the micro-confinement effect. In this regard, an energetically consistent theoretical model is also proposed to predict the alterations in the critical flow condition with varying microchannel configurations, by addressing the underlying biomimetic surface-liquid interfacial conditions. Hence, the present research endeavour provides a new design-guiding paradigm for developing multi-functional microfluidic devices involving biomimetic, superhydrophobic surfaces, by judicious exploitation of the tunable hydrodynamic characteristics in the two regimes.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint femoral (hemi-hip) trunnion-bearing... Devices § 888.3380 Hip joint femoral (hemi-hip) trunnion-bearing metal/polyacetal cemented prosthesis. (a) Identification. A hip joint femoral (hemi-hip) trunnion-bearing metal/polyacetal cemented prosthesis is a two...
International Nuclear Information System (INIS)
Dickinson, R.J.; Pennell, W.E.; Wasko, J.
1984-01-01
A liquid metal pump bearing support comprises a series of tangentially oriented spokes that connect the bearing cylinder to the pump internals structure. The spokes may be arranged in a plurality of planes extending from the bearing cylinder to the pump internals with the spokes in one plane being arranged alternately with those in the next plane. The bearing support structure provides the pump with sufficient lateral support for the bearing structure together with the capability of accommodating differential thermal expansion without adversely affecting pump performance
Bearing construction for refrigeration compresssor
Middleton, Marc G.; Nelson, Richard T.
1988-01-01
A hermetic refrigeration compressor has a cylinder block and a crankshaft rotatable about a vertical axis to reciprocate a piston in a cylinder on the cylinder block. A separate bearing housing is secured to the central portion of the cylinder block and extends vertically along the crankshaft, where it carries a pair of roller bearings to journal the crankshaft. The crankshaft has a radially extending flange which is journaled by a thrust-type roller bearing above the bearing housing to absorb the vertical forces on the crankshaft so that all three of the roller bearings are between the crankshaft and the bearing housing to maintain and control the close tolerances required by such bearings.
2012-11-26
... Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC; Notice of..., 2012, Black Bear Hydro Partners, LLC, sole licensee (transferor) and Black Bear Development Holdings, LLC and Black Bear SO, LLC (transferees) filed an application for the partial the transfer of licenses...
Anisotropic hydrodynamics for conformal Gubser flow
Energy Technology Data Exchange (ETDEWEB)
Strickland, Michael; Nopoush, Mohammad [Kent State University, Kent OH 44242 (United States); Ryblewski, Radoslaw [The H. Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków (Poland)
2016-12-15
In this proceedings contribution, we review the exact solution of the anisotropic hydrodynamics equations for a system subject to Gubser flow. For this purpose, we use the leading-order anisotropic hydrodynamics equations which assume that the distribution function is ellipsoidally symmetric in local-rest-frame momentum. We then prove that the SO(3){sub q} symmetry in de Sitter space constrains the anisotropy tensor to be of spheroidal form with only one independent anisotropy parameter remaining. As a consequence, the exact solution reduces to the problem of solving two coupled non-linear differential equations. We show that, in the limit that the relaxation time goes to zero, one obtains Gubser's ideal hydrodynamic solution and, in the limit that the relaxation time goes to infinity, one obtains the exact free streaming solution obtained originally by Denicol et al. For finite relaxation time, we solve the equations numerically and compare to the exact solution of the relaxation-time-approximation Boltzmann equation subject to Gubser flow. Using this as our standard, we find that anisotropic hydrodynamics describes the spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches.
Hydrodynamic Modeling and Its Application in AUC.
Rocco, Mattia; Byron, Olwyn
2015-01-01
The hydrodynamic parameters measured in an AUC experiment, s(20,w) and D(t)(20,w)(0), can be used to gain information on the solution structure of (bio)macromolecules and their assemblies. This entails comparing the measured parameters with those that can be computed from usually "dry" structures by "hydrodynamic modeling." In this chapter, we will first briefly put hydrodynamic modeling in perspective and present the basic physics behind it as implemented in the most commonly used methods. The important "hydration" issue is also touched upon, and the distinction between rigid bodies versus those for which flexibility must be considered in the modeling process is then made. The available hydrodynamic modeling/computation programs, HYDROPRO, BEST, SoMo, AtoB, and Zeno, the latter four all implemented within the US-SOMO suite, are described and their performance evaluated. Finally, some literature examples are presented to illustrate the potential applications of hydrodynamics in the expanding field of multiresolution modeling. © 2015 Elsevier Inc. All rights reserved.
Anisotropic hydrodynamics for conformal Gubser flow
International Nuclear Information System (INIS)
Strickland, Michael; Nopoush, Mohammad; Ryblewski, Radoslaw
2016-01-01
In this proceedings contribution, we review the exact solution of the anisotropic hydrodynamics equations for a system subject to Gubser flow. For this purpose, we use the leading-order anisotropic hydrodynamics equations which assume that the distribution function is ellipsoidally symmetric in local-rest-frame momentum. We then prove that the SO(3)_q symmetry in de Sitter space constrains the anisotropy tensor to be of spheroidal form with only one independent anisotropy parameter remaining. As a consequence, the exact solution reduces to the problem of solving two coupled non-linear differential equations. We show that, in the limit that the relaxation time goes to zero, one obtains Gubser's ideal hydrodynamic solution and, in the limit that the relaxation time goes to infinity, one obtains the exact free streaming solution obtained originally by Denicol et al. For finite relaxation time, we solve the equations numerically and compare to the exact solution of the relaxation-time-approximation Boltzmann equation subject to Gubser flow. Using this as our standard, we find that anisotropic hydrodynamics describes the spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches.
Introgressive hybridization: brown bears as vectors for polar bear alleles.
Hailer, Frank
2015-03-01
The dynamics and consequences of introgression can inform about numerous evolutionary processes. Biologists have therefore long been interested in hybridization. One challenge, however, lies in the identification of nonadmixed genotypes that can serve as a baseline for accurate quantification of admixture. In this issue of Molecular Ecology, Cahill et al. (2015) analyse a genomic data set of 28 polar bears, eight brown bears and one American black bear. Polar bear alleles are found to be introgressed into brown bears not only near a previously identified admixture zone on the Alaskan Admiralty, Baranof and Chichagof (ABC) Islands, but also far into the North American mainland. Elegantly contrasting admixture levels at autosomal and X chromosomal markers, Cahill and colleagues infer that male-biased dispersal has spread these introgressed alleles away from the Late Pleistocene contact zone. Compared to a previous study on the ABC Island population in which an Alaskan brown bear served as a putatively admixture-free reference, Cahill et al. (2015) utilize a newly sequenced Swedish brown bear as admixture baseline. This approach reveals that brown bears have been impacted by introgression from polar bears to a larger extent (up to 8.8% of their genome), than previously known, including the bear that had previously served as admixture baseline. No evidence for introgression of brown bear into polar bear is found, which the authors argue could be a consequence of selection. Besides adding new exciting pieces to the puzzle of polar/brown bear evolutionary history, the study by Cahill and colleagues highlights that wildlife genomics is moving from analysing single genomes towards a landscape genomics approach. © 2015 John Wiley & Sons Ltd.
Evaluation of the Thermal Effects in Tilting Pad Bearing
Directory of Open Access Journals (Sweden)
G. B. Daniel
2013-01-01
Full Text Available The analysis of thermal effects is of expressive importance in the context of rotordynamics to evaluate the behavior of hydrodynamic bearings because these effects can influence their dynamic characteristics under specific operational conditions. For this reason, a thermohydrodynamic model is developed in this work, in which the pressure distribution in the oil film and the temperature distribution are calculated together. From the pressure distribution, the velocity distribution field is determined, as well as the viscous dissipation, and consequently, the temperature distribution. The finite volume method is applied to solve the Reynolds equation and the energy equation in the thermohydrodynamic model (THD. The results show that the temperature is higher as the rotational speed increases due to the shear rate of the oil film. The maximum temperature in the bearing occurs in the overloaded pad, near the outlet boundary. The experimental tests were performed in a tilting pad journal bearing operating in a steam turbine to validate the model. The comparison between the experimental and numerical results provides a good correlation. The thermohydrodynamic lubrication developed in this assignment is promising to consistently evaluate the behavior of the tilting pad journal bearing operating in relatively high rotational speeds.
Calculation of hydrostatic radial bearing for main circulating pump of 500 BIKS type
International Nuclear Information System (INIS)
Hnatek, T.; Sojka, P.
1978-01-01
Computer calculations of the radial hydrostatic bearing were performed for the main circulating pump of the 500 BIKS type designed for WWER reactors. The calculations were based on the Reynolds equation of thin layer hydrodynamic pressure in turbulent flow. Relations were derived for orifice reducer flow. In contrast to previous calculations conducted for laminar flow, the results are more accurate because the nature of bearing lubrication evidently is turbulent. The required loading of 21,700 N in normal pump operation is fully compensated at a full eccentricity of 0.77. Operating tests of the pump also confirmed that the actual radial forces on the rotor did not attain the desired loading. On the other hand, thanks to the bearing brass design, the bearing is capable of short-time operation with limit eccentricity, ie., at start, in deceleration and in emergency conditions. (Z.M.)
Oladeinde, Mobolaji Humphrey; Akpobi, John Ajokpaoghene
2011-10-01
The hydrodynamic and magnetohydrodynamic (MHD) lubrication problem of infinitely wide inclined and parabolic slider bearings is solved numerically using the finite element method. The bearing configurations are discretized into three-node isoparametric quadratic elements. Stiffness integrals obtained from the weak form of the governing equations are solved using Gauss quadrature to obtain a finite number of stiffness matrices. The global system of equations obtained from enforcing nodal continuity of pressure for the bearings are solved using the Gauss-Seidel iterative scheme with a convergence criterion of 10-10. Numerical computations reveal that, when compared for similar profile and couple stress parameters, greater pressure builds up in a parabolic slider compared to an inclined slider, indicating a greater wedge effect in the parabolic slider. The parabolic slider bearing is also shown to develop a greater load capacity when lubricated with magnetic fluids. The superior performance of parabolic slider bearing is more pronounced at greater Hartmann numbers for identical bearing structural parameters. It is also shown that when load carrying capacity is the yardstick for comparison, the parabolic slider bearings are superior to the inclined bearings when lubricated with couple stress or magnetic lubricants.
Novel maglev pump with a combined magnetic bearing.
Onuma, Hiroyuki; Murakami, Michiko; Masuzawa, Toru
2005-01-01
The newly developed pump is a magnetically levitated centrifugal blood pump in which active and passive magnetic bearings are integrated to construct a durable ventricular assist device. The developed maglev centrifugal pump consists of an active magnetic bearing, a passive magnetic bearing, a levitated impeller, and a motor stator. The impeller is set between the active magnetic bearing and the motor stator. The active magnetic bearing uses four electromagnets to control the tilt and the axial position of the impeller. The radial movement of the levitated impeller is restricted with the passive stability dependent upon the top stator and the passive permanent magnetic bearing to reduce the energy consumption and the control system complexity. The top stator was designed based upon a magnetic field analysis to develop the maglev pump with sufficient passive stability in the radial direction. By implementing this analysis design, the oscillating amplitude of the impeller in the radial direction was cut in half when compared with the simple shape stator. This study concluded that the newly developed maglev centrifugal pump displayed excellent levitation performance and sufficient pump performance as a ventricular assist device.
Self lubricating fluid bearings
International Nuclear Information System (INIS)
Kapich, D.D.
1980-01-01
The invention concerns self lubricating fluid bearings, which are used in a shaft sealed system extending two regions. These regions contain fluids, which have to be isolated. A first seal is fluid tight for the first region between the carter shaft and the shaft. The second seal is fluid tight between the carter and the shaft, it communicates with the second region. The first fluid region is the environment surrounding the shaft carter. The second fluid region is a part of a nuclear reactor which contains the cooling fluid. The shaft is conceived to drive a reactor circulating and cooling fluid [fr
A theoretical study of hydrodynamic cavitation.
Arrojo, S; Benito, Y
2008-03-01
The optimization of hydrodynamic cavitation as an AOP requires identifying the key parameters and studying their effects on the process. Specific simulations of hydrodynamic bubbles reveal that time scales play a major role on the process. Rarefaction/compression periods generate a number of opposing effects which have demonstrated to be quantitatively different from those found in ultrasonic cavitation. Hydrodynamic cavitation can be upscaled and offers an energy efficient way of generating cavitation. On the other hand, the large characteristic time scales hinder bubble collapse and generate a low number of cavitation cycles per unit time. By controlling the pressure pulse through a flexible cavitation chamber design these limitations can be partially compensated. The chemical processes promoted by this technique are also different from those found in ultrasonic cavitation. Properties such as volatility or hydrophobicity determine the potential applicability of HC and therefore have to be taken into account.
Shear viscosity, cavitation and hydrodynamics at LHC
International Nuclear Information System (INIS)
Bhatt, Jitesh R.; Mishra, Hiranmaya; Sreekanth, V.
2011-01-01
We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid becomes invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early stage. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal terms used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.
The RAGE radiation-hydrodynamic code
Energy Technology Data Exchange (ETDEWEB)
Gittings, Michael; Clover, Michael; Betlach, Thomas; Byrne, Nelson; Ranta, Dale [Science Applications International Corp. MS A-1, 10260 Campus Point Drive, San Diego, CA 92121 (United States); Weaver, Robert; Coker, Robert; Dendy, Edward; Hueckstaedt, Robert; New, Kim; Oakes, W Rob [Los Alamos National Laboratory, MS T087, PO Box 1663, Los Alamos, NM 87545 (United States); Stefan, Ryan [TaylorMade-adidas Golf, 5545 Fermi Court, Carlsbad, CA 92008-7324 (United States)], E-mail: michael.r.clover@saic.com
2008-10-01
We describe RAGE, the 'radiation adaptive grid Eulerian' radiation-hydrodynamics code, including its data structures, its parallelization strategy and performance, its hydrodynamic algorithm(s), its (gray) radiation diffusion algorithm, and some of the considerable amount of verification and validation efforts. The hydrodynamics is a basic Godunov solver, to which we have made significant improvements to increase the advection algorithm's robustness and to converge stiffnesses in the equation of state. Similarly, the radiation transport is a basic gray diffusion, but our treatment of the radiation-material coupling, wherein we converge nonlinearities in a novel manner to allow larger timesteps and more robust behavior, can be applied to any multi-group transport algorithm.
The RAGE radiation-hydrodynamic code
International Nuclear Information System (INIS)
Gittings, Michael; Clover, Michael; Betlach, Thomas; Byrne, Nelson; Ranta, Dale; Weaver, Robert; Coker, Robert; Dendy, Edward; Hueckstaedt, Robert; New, Kim; Oakes, W Rob; Stefan, Ryan
2008-01-01
We describe RAGE, the 'radiation adaptive grid Eulerian' radiation-hydrodynamics code, including its data structures, its parallelization strategy and performance, its hydrodynamic algorithm(s), its (gray) radiation diffusion algorithm, and some of the considerable amount of verification and validation efforts. The hydrodynamics is a basic Godunov solver, to which we have made significant improvements to increase the advection algorithm's robustness and to converge stiffnesses in the equation of state. Similarly, the radiation transport is a basic gray diffusion, but our treatment of the radiation-material coupling, wherein we converge nonlinearities in a novel manner to allow larger timesteps and more robust behavior, can be applied to any multi-group transport algorithm
Three Types of Active Lubrication Systems for the Main Bearings of Reciprocating Machines
DEFF Research Database (Denmark)
Santos, Ilmar; Pulido, E. E.
2010-01-01
method (flexible components). The main equations that govern the dynamics of the injection for a hydraulic-actuated, a piezoelectric-actuated and a mechanical-actuated oil injector are presented in this study. The global system is numerically solved using as a case of study a single-cylinder combustion......In the paper the authors investigate three different schemes for the realization of the controllable oil injection system to be couple to the main engine bearings. The use of active lubrication in fluid film bearings helps to enhance the hydrodynamic fluid film by increasing the fluid film...
Chaotic Dynamics of Cage Behavior in a High-Speed Cylindrical Roller Bearing
Directory of Open Access Journals (Sweden)
Long Chen
2016-01-01
Full Text Available This paper presents a mathematical model to investigate the nonlinear dynamic behavior of cage in high-speed cylindrical bearing. Variations of cage behavior due to varying cage eccentricity and cage guidance gap are observed. Hydrodynamic behavior in cage contacts is taken into consideration for a more realistic calculation of acting forces owing to high working speed. Analysis of real-time cage dynamic behavior on radial plane is carried out using chaos theory based on the theoretical and mathematical model established in the paper. The analytical results of this paper provide a solid foundation for designing and manufacturing of high-speed cylindrical roller bearing.
Optimization of residual heat removal pump axial thrust and axial bearing
International Nuclear Information System (INIS)
Schubert, F.
1996-01-01
The residual heat removal (RHR) pumps of German 1300 megawatt pressurized-water reactor (PWR) power plants are of the single stage end suction type with volute casing or with diffuser and forged circular casing. Due to the service conditions the pumps have to cover the full capacity range as well as a big variation in suction static pressure. This results in a big difference in the axial thrust that has to be borne by the axial bearing. Because these pumps are designed to operate without auxiliary systems (things that do not exist can not fail), they are equipped with antifriction bearings and sump oil lubrication. To minimize the heat production within the bearing casing, a number of PWR plants have pumps with combined axial/radial bearings of the ball type. Due to the fact that the maximum axial thrust caused by static pressure and hydrodynamic forces on the impeller is too big to be borne by that type of axial bearing, the impellers were designed to produce a hydrodynamic axial force that counteracts the static axial force. Thus, the resulting axial thrust may change direction when the static pressure varies
Optimization of residual heat removal pump axial thrust and axial bearing
Energy Technology Data Exchange (ETDEWEB)
Schubert, F.
1996-12-01
The residual heat removal (RHR) pumps of German 1300 megawatt pressurized-water reactor (PWR) power plants are of the single stage end suction type with volute casing or with diffuser and forged circular casing. Due to the service conditions the pumps have to cover the full capacity range as well as a big variation in suction static pressure. This results in a big difference in the axial thrust that has to be borne by the axial bearing. Because these pumps are designed to operate without auxiliary systems (things that do not exist can not fail), they are equipped with antifriction bearings and sump oil lubrication. To minimize the heat production within the bearing casing, a number of PWR plants have pumps with combined axial/radial bearings of the ball type. Due to the fact that the maximum axial thrust caused by static pressure and hydrodynamic forces on the impeller is too big to be borne by that type of axial bearing, the impellers were designed to produce a hydrodynamic axial force that counteracts the static axial force. Thus, the resulting axial thrust may change direction when the static pressure varies.
Linear and Non-Linear Control Techniques Applied to Actively Lubricated Journal Bearings
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2003-01-01
The main objectives of actively lubricated bearings are the simultaneous reduction of wear and vibration between rotating and stationary machinery parts. For reducing wear and dissipating vibration energy until certain limits, one can count with the conventional hydrodynamic lubrication. For furt......The main objectives of actively lubricated bearings are the simultaneous reduction of wear and vibration between rotating and stationary machinery parts. For reducing wear and dissipating vibration energy until certain limits, one can count with the conventional hydrodynamic lubrication....... For further reduction of shaft vibrations one can count with the active lubrication action, which is based on injecting pressurised oil into the bearing gap through orifices machined in the bearing sliding surface. The design and efficiency of some linear (PD, PI and PID) and non-linear controllers, applied...... vibration reduction of unbalance response of a rigid rotor, where the PD and the non-linear P controllers show better performance for the frequency range of study (0 to 80 Hz). The feasibility of eliminating rotor-bearing instabilities (phenomena of whirl) by using active lubrication is also investigated...
Impact of hydrodynamic stresses on bacterial flagella
Das, Debasish; Riley, Emily; Lauga, Eric
2017-11-01
The locomotion of bacteria powered by helical filaments, such as Escherichia coli, critically involves the generation of flows and hydrodynamic stresses which lead to forces and moments balanced by the moment applied by the bacterial rotary motor (which is embedded in the cell wall) and the deformation of the short flexible hook. In this talk we use numerical computations to accurately compute these hydrodynamic stresses, to show how they critically lead to fluid-structure instabilities at the whole-cell level, and enquire if they can be used to rationalise experimental measurements of bacterial motor torques. ERC Consolidator Grant.
Hydrodynamics of quark-gluon plasmas
International Nuclear Information System (INIS)
Blaizot, J.P.
1986-06-01
This paper reviews some aspects of the hydrodynamics of quark-gluon plasmas. Various stages of ultra-relativistic heavy ion collisions are described. Several estimates of the maximum energy density expected to be achieved in these collisions are compared. Discontinuities which may be induced in the hydrodynamic flow by a phase transition are described and a convenient numerical method designed to deal with such discontinuous flows is briefly presented. Finally, the correlations between particle transverse momenta and multiplicities are analyzed and one discusses to which extent these correlations could signal the occurrence of a phase transition in heavy ion collisions
FDTD for Hydrodynamic Electron Fluid Maxwell Equations
Directory of Open Access Journals (Sweden)
Yingxue Zhao
2015-05-01
Full Text Available In this work, we develop a numerical method for solving the three dimensional hydrodynamic electron fluid Maxwell equations that describe the electron gas dynamics driven by an external electromagnetic wave excitation. Our numerical approach is based on the Finite-Difference Time-Domain (FDTD method for solving the Maxwell’s equations and an explicit central finite difference method for solving the hydrodynamic electron fluid equations containing both electron density and current equations. Numerical results show good agreement with the experiment of studying the second-harmonic generation (SHG from metallic split-ring resonator (SRR.
Modeling of laser-driven hydrodynamics experiments
di Stefano, Carlos; Doss, Forrest; Rasmus, Alex; Flippo, Kirk; Desjardins, Tiffany; Merritt, Elizabeth; Kline, John; Hager, Jon; Bradley, Paul
2017-10-01
Correct interpretation of hydrodynamics experiments driven by a laser-produced shock depends strongly on an understanding of the time-dependent effect of the irradiation conditions on the flow. In this talk, we discuss the modeling of such experiments using the RAGE radiation-hydrodynamics code. The focus is an instability experiment consisting of a period of relatively-steady shock conditions in which the Richtmyer-Meshkov process dominates, followed by a period of decaying flow conditions, in which the dominant growth process changes to Rayleigh-Taylor instability. The use of a laser model is essential for capturing the transition. also University of Michigan.
Fish stocking density impacts tank hydrodynamics
DEFF Research Database (Denmark)
Rasmussen, Michael R.; Lunger, Angela; Laursen, Jesper
2006-01-01
The effect of stocking density upon the hydrodynamics of a circular tank, configured in a recirculation system, was investigated. Red drums Sciaenops ocellatus of approximately 140 g wet weight, were stocked at five rates varying from 0 to 12 kg m-3. The impact of the presence of fish upon tank...... hydrodynamics was established using in-tank-based Rhodamine WT fluorometry at a flow rate of 0.23 l s-1 (tank exchange rate of 1.9 h-1). With increasing numbers of animals, curvilinear relationships were observed for dispersion coefficients and tank mixing times. Stocking densities of 3, 6, 9 and 12 kg m-3...
Introduction to physics mechanics, hydrodynamics thermodynamics
Frauenfelder, P
2013-01-01
Introduction of Physics: Mechanics , Hydrodynamics, Thermodynamics covers the principles of matter and its motion through space and time, as well as the related concepts of energy and force. This book is composed of eleven chapters, and begins with an introduction to the basic principles of mechanics, hydrodynamics, and thermodynamics. The subsequent chapters deal with the statics of rigid bodies and the dynamics of particles and rigid bodies. These topics are followed by discussions on elasticity, mechanics of fluids, the basic concept of thermodynamic, kinetic theory, and crystal structure o
Shadowfax: Moving mesh hydrodynamical integration code
Vandenbroucke, Bert
2016-05-01
Shadowfax simulates galaxy evolution. Written in object-oriented modular C++, it evolves a mixture of gas, subject to the laws of hydrodynamics and gravity, and any collisionless fluid only subject to gravity, such as cold dark matter or stars. For the hydrodynamical integration, it makes use of a (co-) moving Lagrangian mesh. The code has a 2D and 3D version, contains utility programs to generate initial conditions and visualize simulation snapshots, and its input/output is compatible with a number of other simulation codes, e.g. Gadget2 (ascl:0003.001) and GIZMO (ascl:1410.003).
Active control of magneto-hydrodynamic instabilities in hot plasmas
2015-01-01
During the past century, world-wide energy consumption has risen dramatically, which leads to a quest for new energy sources. Fusion of hydrogen atoms in hot plasmas is an attractive approach to solve the energy problem, with abundant fuel, inherent safety and no long-lived radioactivity. However, one of the limits on plasma performance is due to the various classes of magneto-hydrodynamic instabilities that may occur. The physics and control of these instabilities in modern magnetic confinement fusion devices is the subject of this book. Written by foremost experts, the contributions will provide valuable reference and up-to-date research reviews for "old hands" and newcomers alike.
Thermal rectification based on phonon hydrodynamics and thermomass theory
Directory of Open Access Journals (Sweden)
Dong Yuan
2016-06-01
Full Text Available The thermal diode is the fundamental device for phononics. There are various mechanisms for thermal rectification, e.g. different temperature dependent thermal conductivity of two ends, asymmetric interfacial resistance, and nonlocal behavior of phonon transport in asymmetric structures. The phonon hydrodynamics and thermomass theory treat the heat conduction in a fluidic viewpoint. The phonon gas flowing through the media is characterized by the balance equation of momentum, like the Navier-Stokes equation for fluid mechanics. Generalized heat conduction law thereby contains the spatial acceleration (convection term and the viscous (Laplacian term. The viscous term predicts the size dependent thermal conductivity. Rectification appears due to the MFP supersession of phonons. The convection term also predicts rectification because of the inertia effect, like a gas passing through a nozzle or diffuser.
Nanoprecipitation in bearing steels
International Nuclear Information System (INIS)
Barrow, A.T.W.; Rivera-Diaz-del-Castillo, P.E.J.
2011-01-01
θ-phase is the main hardening species in bearing steels and appears in both martensitically and bainitically hardened microstructures. This work presents a survey of the microstrucural features accompanying nanoprecipitation in bearing steels. Nanoprecipitate structures formed in 1C-1.5Cr wt.% with additions of Cr, Mn, Mo, Si and Ni are studied. The work is combined with thermodynamic calculations and neural networks to predict the expected matrix composition, and whether this will transform martensitically or bainitically. Martensite tetragonality, composition and the amount of retained austenite are related to hardness and the type of nanoprecipitate structures in martensitic grades. The θ-phase volume fraction, the duration of the bainite to austenite transformation and the amount of retained austenite are related to hardness and a detailed quantitative description of the precipitate nanostructures. Such description includes compositional studies using energy-dispersive spectroscopy, which shows that nanoprecipitate formation takes place under paraequilibrium. Special attention is devoted to a novel two-step bainite tempering process which shows maximum hardness; we prove that this is the most effective process for incorporating solute into the precipitates, which are finer than those resulting from one-step banitic transformation processes.
Superconducting bearings in flywheels
Energy Technology Data Exchange (ETDEWEB)
Coombs, T.A.; Campbell, A.M.; Ganney, I.; Lo, W. [Cambridge Univ. (United Kingdom). Interdisciplinary Research Centre in Superconductivity (IRC); Twardowski, T. [International Energy Systems, Chester High Road, Neston, South Wirral (United Kingdom); Dawson, B. [British Nuclear Fuels, Capenhurst, South Wirral (United Kingdom)
1998-05-01
Investigations are being carried out into the use of superconducting magnetic bearings to levitate energy storage flywheels. In a planned program of work, Cambridge University are aiming to produce a practical bearing system for Pirouette(TM). The Pirouette(TM) system is designed to provide 5 kWh of recoverable energy which is currently recoverable at a rate of 5 kW (future revisions will provide up to 50 kW). IES (a British Nuclear Fuels subsidiary) the owners of the Pirouette(TM) machine have supplied Cambridge with a flywheel. This flywheel weighs >40 kg and is being levitated using an Evershed-type arrangement in which the superconductor is being used to stabilize the interaction between two magnets. To date we have demonstrated stable levitation in static and low speed tests in a rig designed for low speeds of rotation in air. A second rig which is currently under construction at BNFL will run in vacuum at speeds of up to 50 (orig.) 5 refs.
Directory of Open Access Journals (Sweden)
R. Fargère
2012-01-01
Full Text Available Some interactions between the dynamic and tribological behaviour of geared transmissions are examined, and a number of experimental and simulation results are compared. A model is introduced which incorporates most of the possible interactions between gears, shafts and hydrodynamic journal bearings. It combines (i a specific element for wide-faced gears that includes the normal contact conditions between actual mating teeth, that is, with tooth shape deviations and mounting errors, (ii shaft finite elements, and (iii the external forces generated by journal bearings determined by directly solving Reynolds' equation. The simulation results are compared with the measurement obtained on a high-precision test rig with single-stage spur and helical gears supported by hydrodynamic journal bearings. The experimental and simulation results compare well thus validating the simulation strategy both at the global and local scales.
Influence of surface texturing on the performance of tilting pad thrust bearings
Gropper, Daniel; Wang, Ling; Harvey, Terry J.; Meck, Klaus-Dieter; Gviniashvili, Vladimir
2016-01-01
Surface textures have been shown to have the potential of enhancing the performance of hydrodynamic bearings and many other applications. However, a comprehensive literature review by the authors has revealed that the application of surface texturing is still limited due to major challenges, such as the complexity of computational models and the large variety of operating conditions encountered in conventional industrial applications. In the present work, the potential of surface texturing fo...
SHABERTH - ANALYSIS OF A SHAFT BEARING SYSTEM (CRAY VERSION)
Coe, H. H.
1994-01-01
The SHABERTH computer program was developed to predict operating characteristics of bearings in a multibearing load support system. Lubricated and non-lubricated bearings can be modeled. SHABERTH calculates the loads, torques, temperatures, and fatigue life for ball and/or roller bearings on a single shaft. The program also allows for an analysis of the system reaction to the termination of lubricant supply to the bearings and other lubricated mechanical elements. SHABERTH has proven to be a valuable tool in the design and analysis of shaft bearing systems. The SHABERTH program is structured with four nested calculation schemes. The thermal scheme performs steady state and transient temperature calculations which predict system temperatures for a given operating state. The bearing dimensional equilibrium scheme uses the bearing temperatures, predicted by the temperature mapping subprograms, and the rolling element raceway load distribution, predicted by the bearing subprogram, to calculate bearing diametral clearance for a given operating state. The shaft-bearing system load equilibrium scheme calculates bearing inner ring positions relative to the respective outer rings such that the external loading applied to the shaft is brought into equilibrium by the rolling element loads which develop at each bearing inner ring for a given operating state. The bearing rolling element and cage load equilibrium scheme calculates the rolling element and cage equilibrium positions and rotational speeds based on the relative inner-outer ring positions, inertia effects, and friction conditions. The ball bearing subprograms in the current SHABERTH program have several model enhancements over similar programs. These enhancements include an elastohydrodynamic (EHD) film thickness model that accounts for thermal heating in the contact area and lubricant film starvation; a new model for traction combined with an asperity load sharing model; a model for the hydrodynamic rolling and
Computational design of rolling bearings
Nguyen-Schäfer, Hung
2016-01-01
This book comprehensively presents the computational design of rolling bearings dealing with many interdisciplinary difficult working fields. They encompass elastohydrodynamics (EHD), Hertzian contact theory, oil-film thickness in elastohydrodynamic lubrication (EHL), bearing dynamics, tribology of surface textures, fatigue failure mechanisms, fatigue lifetimes of rolling bearings and lubricating greases, Weibull distribution, rotor balancing, and airborne noises (NVH) in the rolling bearings. Furthermore, the readers are provided with hands-on essential formulas based on the up-to-date DIN ISO norms and helpful examples for computational design of rolling bearings. The topics are intended for undergraduate and graduate students in mechanical and material engineering, research scientists, and practicing engineers who want to understand the interactions between these working fields and to know how to design the rolling bearings for automotive industry and many other industries.
Grease lubrication in rolling bearings
Lugt, Piet M
2012-01-01
The definitive book on the science of grease lubrication for roller and needle bearings in industrial and vehicle engineering. Grease Lubrication in Rolling Bearings provides an overview of the existing knowledge on the various aspects of grease lubrication (including lubrication systems) and the state of the art models that exist today. The book reviews the physical and chemical aspects of grease lubrication, primarily directed towards lubrication of rolling bearings. The first part of the book covers grease composition, properties and rheology, including thermal
Impact of Hydrodynamics on Oral Biofilm Strength
Paramonova, E.; Kalmykowa, O. J.; van der Mei, H. C.; Busscher, H. J.; Sharma, P. K.
2009-01-01
Mechanical removal of oral biofilms is ubiquitously accepted as the best way to prevent caries and periodontal diseases. Removal effectiveness strongly depends on biofilm strength. To investigate the influence of hydrodynamics on oral biofilm strength, we grew single- and multi-species biofilms of
Hydrodynamic states of phonons in insulators
Directory of Open Access Journals (Sweden)
S.A. Sokolovsky
2012-12-01
Full Text Available The Chapman-Enskog method is generalized for accounting the effect of kinetic modes on hydrodynamic evolution. Hydrodynamic states of phonon system of insulators have been studied in a small drift velocity approximation. For simplicity, the investigation was carried out for crystals of the cubic class symmetry. It has been found that in phonon hydrodynamics, local equilibrium is violated even in the approximation linear in velocity. This is due to the absence of phonon momentum conservation law that leads to a drift velocity relaxation. Phonon hydrodynamic equations which take dissipative processes into account have been obtained. The results were compared with the standard theory based on the local equilibrium validity. Integral equations have been obtained for calculating the objects of the theory (including viscosity and heat conductivity. It has been shown that in low temperature limit, these equations are solvable by iterations. Steady states of the system have been considered and an expression for steady state heat conductivity has been obtained. It coincides with the famous result by Akhiezer in the leading low temperature approximation. It has been established that temperature distribution in the steady state of insulator satisfies a condition of heat source absence.
Magneto-hydrodynamical model for plasma
Liu, Ruikuan; Yang, Jiayan
2017-10-01
Based on the Newton's second law and the Maxwell equations for the electromagnetic field, we establish a new 3-D incompressible magneto-hydrodynamics model for the motion of plasma under the standard Coulomb gauge. By using the Galerkin method, we prove the existence of a global weak solution for this new 3-D model.
Statistical analysis of hydrodynamic cavitation events
Gimenez, G.; Sommer, R.
1980-10-01
The frequency (number of events per unit time) of pressure pulses produced by hydrodynamic cavitation bubble collapses is investigated using statistical methods. The results indicate that this frequency is distributed according to a normal law, its parameters not being time-evolving.
Filter-Feeding Zoobenthos and Hydrodynamics
DEFF Research Database (Denmark)
Riisgård, Hans Ulrik; Larsen, Poul Scheel
2017-01-01
interplay between benthic filter feeders and hydrodynamics. Starting from the general concept of grazing potential and typical data on benthic population densities its realization is considered, first at the level of the individual organism through the processes of pumping and trapping of food particles...
does earthworms density really modify soil's hydrodynamic ...
African Journals Online (AJOL)
N. Ababsa,, M. Kribaa, D. Addad, L. Tamrabet and M. Baha
1 mai 2016 ... Journal of Fundamental and Applied Sciences is licensed under a Creative Commons Attribution-NonCommercial 4.0. International License. Libraries Resource Directory. We are listed under Research Associations category. DOES EARTHWORMS DENSITY REALLY MODIFY SOIL'S HYDRODYNAMIC.
PHANTOM: Smoothed particle hydrodynamics and magnetohydrodynamics code
Price, Daniel J.; Wurster, James; Nixon, Chris; Tricco, Terrence S.; Toupin, Stéven; Pettitt, Alex; Chan, Conrad; Laibe, Guillaume; Glover, Simon; Dobbs, Clare; Nealon, Rebecca; Liptai, David; Worpel, Hauke; Bonnerot, Clément; Dipierro, Giovanni; Ragusa, Enrico; Federrath, Christoph; Iaconi, Roberto; Reichardt, Thomas; Forgan, Duncan; Hutchison, Mark; Constantino, Thomas; Ayliffe, Ben; Mentiplay, Daniel; Hirsh, Kieran; Lodato, Giuseppe
2017-09-01
Phantom is a smoothed particle hydrodynamics and magnetohydrodynamics code focused on stellar, galactic, planetary, and high energy astrophysics. It is modular, and handles sink particles, self-gravity, two fluid and one fluid dust, ISM chemistry and cooling, physical viscosity, non-ideal MHD, and more. Its modular structure makes it easy to add new physics to the code.
Numerical methods for hydrodynamic stability problems
International Nuclear Information System (INIS)
Fujimura, Kaoru
1985-11-01
Numerical methods for solving the Orr-Sommerfeld equation, which is the fundamental equation of the hydrodynamic stability theory for various shear flows, are reviewed and typical numerical results are presented. The methods of asymptotic solution, finite difference methods, initial value methods and expansions in orthogonal functions are compared. (author)
Hydrodynamic relaxations in dissipative particle dynamics
Hansen, J. S.; Greenfield, Michael L.; Dyre, Jeppe C.
2018-01-01
This paper studies the dynamics of relaxation phenomena in the standard dissipative particle dynamics (DPD) model [R. D. Groot and P. B. Warren, J. Chem. Phys. 107, 4423 (1997)]. Using fluctuating hydrodynamics as the framework of the investigation, we focus on the collective transverse and longitudinal dynamics. It is shown that classical hydrodynamic theory predicts the transverse dynamics at relatively low temperatures very well when compared to simulation data; however, the theory predictions are, on the same length scale, less accurate for higher temperatures. The agreement with hydrodynamics depends on the definition of the viscosity, and here we find that the transverse dynamics are independent of the dissipative and random shear force contributions to the stress. For high temperatures, the spectrum for the longitudinal dynamics is dominated by the Brillouin peak for large length scales and the relaxation is therefore governed by sound wave propagation and is athermal. This contrasts the results at lower temperatures and small length scale, where the thermal process is clearly present in the spectra. The DPD model, at least qualitatively, re-captures the underlying hydrodynamical mechanisms, and quantitative agreement is excellent at intermediate temperatures for the transverse dynamics.
Hydrodynamic modelling of hydrostatic magnesium extrusion
Moodij, Ellen; de Rooij, Matthias B.; Schipper, Dirk J.
2006-01-01
Wilson’s hydrodynamic model of the hydrostatic extrusion process is extended to meet the geometry found on residual billets. The transition from inlet to work zone of the process is not considered sharp as in the model of Wilson but as a rounded edge, modelled by a parabolic function. It is shown
Dilepton production in schematic causal viscous hydrodynamics
International Nuclear Information System (INIS)
Song, Taesoo; Han, Kyong Chol; Ko, Che Ming
2011-01-01
Assuming that in the hot dense matter produced in relativistic heavy-ion collisions, the energy density, entropy density, and pressure as well as the azimuthal and space-time rapidity components of the shear tensor are uniform in the direction transversal to the reaction plane, we derive a set of schematic equations from the Isreal-Stewart causal viscous hydrodynamics. These equations are then used to describe the evolution dynamics of relativistic heavy-ion collisions by taking the shear viscosity to entropy density ratio of 1/4π for the initial quark-gluon plasma (QGP) phase and of 10 times this value for the later hadron-gas (HG) phase. Using the production rate evaluated with particle distributions that take into account the viscous effect, we study dilepton production in central heavy-ion collisions. Compared with results from the ideal hydrodynamics, we find that although the dilepton invariant mass spectra from the two approaches are similar, the transverse momentum spectra are significantly enhanced at high transverse momenta by the viscous effect. We also study the transverse momentum dependence of dileptons produced from QGP for a fixed transverse mass, which is essentially absent in the ideal hydrodynamics, and find that this so-called transverse mass scaling is violated in the viscous hydrodynamics, particularly at high transverse momenta.
Hydrodynamic forces on inundated bridge decks
2009-05-01
The hydrodynamic forces experienced by an inundated bridge deck have great importance in the design of bridges. Specifically, the drag force, lift force, and the moment acting on the bridge deck under various levels of inundation and a range of flow ...
The quantum hydrodynamics of the Sutherland model
International Nuclear Information System (INIS)
Stone, Michael; Gutman, Dmitry
2008-01-01
We show that the form of the chiral condition found by Abanov et al in the quantum hydrodynamics of the Sutherland model arises because there are two distinct inner products with respect to which the chiral Hamiltonian is Hermitian, but only one with respect to which the full, non-chiral, Hamiltonian is Hermitian
Hydrodynamic impact response, a flexible view
Vredeveldt, A.W.; Hoogeland, M.; Janssen, G.Th.M.
2001-01-01
The popularity of high-speed craft is steadily increasing. Until now, much attention has been focussed on the hydrodynamic aspects of these craft. The structural design of these vessels is usually considered in a quasi static sense. However, due to the requirement of light ship structures, fast ship
Universal hydrodynamics of non-conformal branes
International Nuclear Information System (INIS)
Kanitscheider, Ingmar; Skenderis, Kostas
2009-01-01
We examine the hydrodynamic limit of non-conformal branes using the recently developed precise holographic dictionary. We first streamline the discussion of holography for backgrounds that asymptote locally to non-conformal brane solutions by showing that all such solutions can be obtained from higher dimensional asymptotically locally AdS solutions by suitable dimensional reduction and continuation in the dimension. As a consequence, many holographic results for such backgrounds follow from the corresponding results of the Asymptotically AdS case. In particular, the hydrodynamics of non-conformal branes is fully determined in terms of conformal hydrodynamics. Using previous results on the latter we predict the form of the non-conformal hydrodynamic stress tensor to second order in derivatives. Furthermore we show that the ratio between bulk and shear viscosity is fixed by the generalized conformal structure to be ζ/η = 2(1/(d-1)-c s 2 ), where c s is the speed of sound in the fluid.
Detailed simulation of morphodynamics : 1. Hydrodynamic model
Nabi, M.; De Vriend, H.J.; Mosselman, E.; Sloff, C.J.; Shimizu, Y.
2012-01-01
We present a three-dimensional high-resolution hydrodynamic model for unsteady incompressible flow over an evolving bed topography. This is achieved by using a multilevel Cartesian grid technique that allows the grid to be refined in high-gradient regions and in the vicinity of the river bed. The
Progress of magnetic-suspension systems and magnetic bearings in the USSR
International Nuclear Information System (INIS)
Kuzin, A.V.
1992-01-01
This paper traces the development and progress of magnetic suspension systems and magnetic bearings in the USSR. The paper describes magnetic bearings for turbomachines, magnetic suspension systems for vibration isolation, some special measuring devices, wind tunnels, and other applications. The design, principles of operation, and dynamic characteristics of the system are presented
Study on the prevention of spragging in a tilting pad journal bearing using the variation of preload
International Nuclear Information System (INIS)
Yang, Seong Heon; Park, Chul Hyun; Ha, Hyun Cheon; Kim, Chae Sil
2001-01-01
Tilting pad journal bearings have been widely used in a high speed rotating machinery, such as steam turbines and gas turbines, owing to their inherent stability characteristics. However, some peculiar fatigue failure in the babbitt metal due to spragging has been continuously occurred at the leading edge of the upper pads. The spragging is defined as the pad vibration initiated on the upper unloaded pads in tilting pad journal bearing. This paper describes both several kinds of bearing failure related with spragging and the theoretical investigation on the prevention of the spragging phenomenon using the variation of preload. Results show that positive preload(m>0.5) assures all pads remain statically loaded under all operating conditions. For the change of design parameter to prevent spragging, thermo-hydrodynamic lubrication and rotor dynamic analysis were performed to verify temperature limitation on bearing and vibration problems on rotor bearing system
New Star-Like Surfacetexture for Enhanced Hydrodynamic Lubrication Performance
Directory of Open Access Journals (Sweden)
Uddin M.S.
2017-09-01
Full Text Available This paper presents a numerical modelling and optimization of a new ‘star-like’ geometric texture shape with an aim to improve tribological performance. Initial studies showed that the triangle effect is the most dominant in reducing the friction. Motivated with this, a ‘star-like’ texture shape consisting of a series of triangular spikes around the centre of the texture is proposed. It is hypothesised that by increasing the triangular effect on a texture shape, the converging micro-wedge effect is expected to increase, hence increasing the film pressure and reducing the friction. Using the well-known Reynolds boundary conditions, numerical modelling of surface texturing is implemented via finite difference method. Simulation results showed that the number of apex points of the new ‘star-like’ texture has a significant effect on the film pressure and the friction coefficient. A 6-pointed texture at a texture density of 0.4 is shown to be the optimum shape. The new optimum star-like texture reduces the friction coefficient by 80%, 64.39%, 19.32% and 16.14%, as compared to ellipse, chevron, triangle and circle, respectively. This indicates the potential benefit of the proposed new shape in further enhancing the hydrodynamic lubrication performance of slider bearing contacts.
Prevention of Roller Bearing-Initiated Burnoffs in Railroad Freight Car Journals
1979-01-01
The objective of this program was to determine the technical feasibility and cost effectiveness of constructing three separate devices for the prevention of catastrophic roller bearing-initiated, railroad journal failure. 1. Construction of a low cos...
Rotor Rolling over a Water-Lubricated Bearing
Shatokhin, V. F.
2018-02-01
gyroscopic damping components facilitate the developing rolling of the rotor over the bearing. If measures taken to decrease these components in the damping devices and bearings are met with success, the onset of asynchronous rolling-over with the growing amplitudes occurs after a longer period of time.
RELATIONSHIP BETWEEN ROLLING AND SLIP RESISTANCE IN ROLLING BEARINGS
Directory of Open Access Journals (Sweden)
L. M. Bondarenko
2016-06-01
Full Text Available Purpose. About one of the causes of slip rolling is known from the second half of the 19th century, it was believed that the slip resistance appears at the place of contact due to different speeds on the arc of contact. Only in the mid-20th century it was proved that this resistance is negligible in rolling resistance. However (for some unknown reason it is ignored the fact that in practice in rolling bearings may rotate both the inner ring with a stationary outer one, and vice versa almost in equal relations. It is not taken into account the fact that the ball or roller in the rolling bearings runs the different distance along the roller path of the outer and inner bearing cages in one revolution. This fact is not taken into account in determining the calculated values for the friction coefficient of a rolling bearing reduced to the shaft. Therefore, the aim of this work is to determine the influence of path length on the track riding the outer and inner race of the bearing on the determination of the calculated value of the coefficient of friction of rolling bearings is given to the shaft. Methodology. The solution technique is based on the theory of plane motion of a rigid body, the theory of Hertzian contact deformation and the analytical dependencies for determination of coefficient of rolling friction. Findings. The obtained dependences on determination of rolling resistance of the balls or rollers along the bearing tracks of inner and outer bearing cages as well as path difference metering of the rolling on them allows to analytically obtain the rolling resistance and slipping for any size of bearings and different devices of bearing units. It is also possible at the design stage of rolling nodes to handle not only the design but also the content of the node. Originality. Using the analytical dependences for determination of the rolling resistance of bodies at point and line contacts, and also account for the difference in the path of the
Doyon, Benjamin; Dubail, Jérôme; Konik, Robert; Yoshimura, Takato
2017-11-01
The theory of generalized hydrodynamics (GHD) was recently developed as a new tool for the study of inhomogeneous time evolution in many-body interacting systems with infinitely many conserved charges. In this Letter, we show that it supersedes the widely used conventional hydrodynamics (CHD) of one-dimensional Bose gases. We illustrate this by studying "nonlinear sound waves" emanating from initial density accumulations in the Lieb-Liniger model. We show that, at zero temperature and in the absence of shocks, GHD reduces to CHD, thus for the first time justifying its use from purely hydrodynamic principles. We show that sharp profiles, which appear in finite times in CHD, immediately dissolve into a higher hierarchy of reductions of GHD, with no sustained shock. CHD thereon fails to capture the correct hydrodynamics. We establish the correct hydrodynamic equations, which are finite-dimensional reductions of GHD characterized by multiple, disjoint Fermi seas. We further verify that at nonzero temperature, CHD fails at all nonzero times. Finally, we numerically confirm the emergence of hydrodynamics at zero temperature by comparing its predictions with a full quantum simulation performed using the NRG-TSA-abacus algorithm. The analysis is performed in the full interaction range, and is not restricted to either weak- or strong-repulsion regimes.
Assurance Cases for Medical Devices
2011-04-28
the patient, and the hospital setting. Some pumps allow the patient to control part of the injection process (e.g. to inject more painkiller ...overdose, incorrect therapy, etc. Design and development decisions that bear on safety and effectiveness http://www.fda.gov/MedicalDevices
Superconducting bearings for flywheel applications
Energy Technology Data Exchange (ETDEWEB)
Abrahamsen, Asger Bech
2001-05-01
A literature study on the application of superconducting bearings in energy storage flywheel systems. The physics of magnetic levitation and superconductors are presented in the first part of the report, followed by a discussion of the literature found on the applications of superconducting bearings in flywheels. (au)
Superconducting bearings for flywheel applications
DEFF Research Database (Denmark)
Abrahamsen, A.B.
2001-01-01
A literature study on the application of superconducting bearings in energy storage flywheel systems. The physics of magnetic levitation and superconductors are presented in the first part of the report, followed by a discussion of the literature found onthe applications of superconducting bearings...
Hydrodynamic lift for single cell manipulation in a femtosecond laser fabricated optofluidic chip
Directory of Open Access Journals (Sweden)
Bragheri Francesca
2017-08-01
Full Text Available Single cell sorting based either on fluorescence or on mechanical properties has been exploited in the last years in microfluidic devices. Hydrodynamic focusing allows increasing the efficiency of theses devices by improving the matching between the region of optical analysis and that of cell flow. Here we present a very simple solution fabricated by femtosecond laser micromachining that exploits flow laminarity in microfluidic channels to easily lift the sample flowing position to the channel portion illuminated by the optical waveguides used for single cell trapping and analysis.
Space Station alpha joint bearing
Everman, Michael R.; Jones, P. Alan; Spencer, Porter A.
1987-01-01
Perhaps the most critical structural system aboard the Space Station is the Solar Alpha Rotary Joint which helps align the power generation system with the sun. The joint must provide structural support and controlled rotation to the outboard transverse booms as well as power and data transfer across the joint. The Solar Alpha Rotary Joint is composed of two transition sections and an integral, large diameter bearing. Alpha joint bearing design presents a particularly interesting problem because of its large size and need for high reliability, stiffness, and on orbit maintability. The discrete roller bearing developed is a novel refinement to cam follower technology. It offers thermal compensation and ease of on-orbit maintenance that are not found in conventional rolling element bearings. How the bearing design evolved is summarized. Driving requirements are reviewed, alternative concepts assessed, and the selected design is described.
Flywheel Challenge: HTS Magnetic Bearing
International Nuclear Information System (INIS)
Werfel, F N; Floegel-Delor, U; Riedel, T; Rothfeld, R; Wippich, D; Goebel, B
2006-01-01
A 200 mm cylindrical engineering prototype high temperature superconducting (HTS) was designed and fabricated. Measurements show that the 17 kg PM rotor can suspend safely 1000 kg in axial direction and 470 kg radially. The rationale for the bearing performance is to stabilize a 400 kg rotor of a new compact 5 kWh/280 kW flywheel energy storage system (COM - FESS). Measurements of the magnetic bearing force, stiffness and drag-torque are presented indicated the successful targeting a milestone in the HTS bearing technology. The influence of the PM configuration and the YBCO temperature on the bearing performance was experimentally studied, providing high-force or high-stiffness behaviour. The axial stiffness 5 kN/mm at 0.5 mm displacement is the highest value of a HTS bearing we know
Efficient inactivation of MS-2 virus in water by hydrodynamic cavitation.
Kosel, Janez; Gutiérrez-Aguirre, Ion; Rački, Nejc; Dreo, Tanja; Ravnikar, Maja; Dular, Matevž
2017-11-01
The aim of this study was to accurately quantify the impact of hydrodynamic cavitation on the infectivity of bacteriophage MS2, a norovirus surrogate, and to develop a small scale reactor for testing the effect of hydrodynamic cavitation on human enteric viruses, which cannot be easily prepared in large quantities. For this purpose, 3 mL scale and 1 L scale reactors were constructed and tested. Both devices were efficient in generating hydrodynamic cavitation and in reducing the infectivity of MS2 virus. Furthermore, they reached more than 4 logs reductions of viral infectivity, thus confirming the scalability of hydrodynamic cavitation for this particular application. As for the mechanism of page inactivation, we suspect that cavitation generated OH - radicals formed an advanced oxidation process, which could have damaged the host's recognition receptors located on the surface of the bacteriophage. Additional damage could arise from the high shear forces inside the cavity. Moreover, the effectiveness of the cavitation was higher for suspensions containing low initial viral titers that are in similar concentration to the ones found in real water samples. According to this, cavitation generators could prove to be a useful tool for treating virus-contaminated wastewaters in the future. Copyright © 2017 Elsevier Ltd. All rights reserved.
Kidney stone erosion by micro scale hydrodynamic cavitation and consequent kidney stone treatment.
Perk, Osman Yavuz; Şeşen, Muhsincan; Gozuacik, Devrim; Koşar, Ali
2012-09-01
The objective of this study is to reveal the potential of micro scale hydrodynamic bubbly cavitation for the use of kidney stone treatment. Hydrodynamically generated cavitating bubbles were targeted to the surfaces of 18 kidney stone samples made of calcium oxalate, and their destructive effects were exploited in order to remove kidney stones in in vitro experiments. Phosphate buffered saline (PBS) solution was used as the working fluid under bubbly cavitating conditions in a 0.75 cm long micro probe of 147 μm inner diameter at 9790 kPa pressure. The surface of calcium oxalate type kidney stones were exposed to bubbly cavitation at room temperature for 5 to 30 min. The eroded kidney stones were visually analyzed with a high speed CCD camera and using SEM (scanning electron microscopy) techniques. The experiments showed that at a cavitation number of 0.017, hydrodynamic bubbly cavitation device could successfully erode stones with an erosion rate of 0.31 mg/min. It was also observed that the targeted application of the erosion with micro scale hydrodynamic cavitation may even cause the fracture of the kidney stones within a short time of 30 min. The proposed treatment method has proven to be an efficient instrument for destroying kidney stones.
EVALUATION OF A LOW FRICTION - HIGH EFFICIENCY ROLLER BEARING ENGINE
Energy Technology Data Exchange (ETDEWEB)
Kolarik, Robert V. II; Shattuck, Charles W.; Copper, Anthony P.
2009-06-30
This Low Friction (High Efficiency Roller Bearing) Engine (LFE) report presents the work done by The Timken Company to conduct a technology demonstration of the benefits of replacing hydrodynamic bearings with roller bearings in the crankshaft and camshaft assemblies of an internal combustion engine for the purpose of collecting data sufficient to prove merit. The engines in the present study have been more extensively converted to roller bearings than any previous studies (40 needle roller bearings per engine) to gain understanding of the full potential of application of bearing technology. The project plan called for comparative testing of a production vehicle which was already respected for having demonstrated low engine friction levels with a rollerized version of that engine. Testing was to include industry standard tests for friction, emissions and fuel efficiency conducted on instrumented dynamometers. Additional tests for fuel efficiency, cold start resistance and other measures of performance were to be made in the actual vehicle. Comparative measurements of noise, vibration and harshness (NVH), were planned, although any work to mitigate the suspected higher NVH level in the rollerized engine was beyond the scope of this project. Timken selected the Toyota Avalon with a 3.5L V-6 engine as the test vehicle. In an attempt to minimize cost and fabrication time, a ‘made-from’ approach was proposed in which as many parts as possible would be used or modified from production parts to create the rollerized engine. Timken commissioned its test partner, FEV Engine Technology, to do a feasibility study in which they confirmed that using such an approach was possible to meet the required dimensional restrictions and tolerances. In designing the roller bearing systems for the crank and cam trains, Timken utilized as many production engine parts as possible. The crankshafts were produced from production line forgings, which use Timken steel, modified with special
Journal bearing impedance descriptions for rotordynamic applications
Childs, D.W.; Moes, H.; Leeuwen, van H.J.
1977-01-01
Bearing impedance vectors are introduced for plain journal bearings which define the bearing reaction force components as a function of the bearing motion. Impedance descriptions are developed directly for the approximate Ocvirk (short) and Sommerfeld (long) bearing solutions. The impedance vector
Modelling hydrodynamic parameters to predict flow assisted corrosion
International Nuclear Information System (INIS)
Poulson, B.; Greenwell, B.; Chexal, B.; Horowitz, J.
1992-01-01
During the past 15 years, flow assisted corrosion has been a worldwide problem in the power generating industry. The phenomena is complex and depends on environment, material composition, and hydrodynamic factors. Recently, modeling of flow assisted corrosion has become a subject of great importance. A key part of this effort is modeling the hydrodynamic aspects of this issue. This paper examines which hydrodynamic parameter should be used to correlate the occurrence and rate of flow assisted corrosion with physically meaningful parameters, discusses ways of measuring the relevant hydrodynamic parameter, and describes how the hydrodynamic data is incorporated into the predictive model
Tapered Microfluidic for Continuous Micro-Object Separation Based on Hydrodynamic Principle.
Ahmad, Ida Laila; Ahmad, Mohd Ridzuan; Takeuchi, Masaru; Nakajima, Masahiro; Hasegawa, Yasuhisa
2017-12-01
Recent advances in microfluidic technologies have created a demand for a simple and efficient separation intended for various applications such as food industries, biological preparation, and medical diagnostic. In this paper, we report a tapered microfluidic device for passive continuous separation of microparticles by using hydrodynamic separation. By exploiting the hydrodynamic properties of the fluid flow and physical characteristics of micro particles, effective size based separation is demonstrated. The tapered microfluidic device has widening geometries with respect to specific taper angle which amplify the sedimentation effect experienced by particles of different sizes. A mixture of 3-μm and 10-μm polystyrene microbeads are successfully separated using 20° and 25° taper angles. The results obtained are in agreement with three-dimensional finite element simulation conducted using Abaqus 6.12. Moreover, the feasibility of this mechanism for biological separation is demonstrated by using polydisperse samples consists of 3-μm polystyrene microbeads and human epithelial cervical carcinoma (HeLa) cells. 98% of samples purity is recovered at outlet 1 and outlet 3 with flow rate of 0.5-3.0 μl/min. Our device is interesting despite adopting passive separation approach. This method enables straightforward, label-free, and continuous separation of multiparticles in a stand-alone device without the need for bulky apparatus. Therefore, this device may become an enabling technology for point of care diagnosis tools and may hold potential for micrototal analysis system applications.
Optimization of rock-bit life based on bearing failure criteria
International Nuclear Information System (INIS)
Feav, M.J.; Thorogood, J.L.; Whelehan, O.P.; Williamson, H.S.
1992-01-01
This paper reports that recent advances in rock-bit seal technology have allowed greater predictability of bearing life. Cone loss following bearing failure incurs costs related to remedial activities. A risk analysis approach, incorporating bearing-life relationships and the inter-dependence of drilling events, is used to formulate a bit-run cost-optimization method. The procedure enables a choice to be made between elastomeric and metal seals on a lowest-replacement-cost basis. The technique also provides a formal method for assessing the opportunity cost for using a device to detect bit-bearing failures downhole
Hydrodynamic Cavitation-Assisted Synthesis of Nanocalcite
Directory of Open Access Journals (Sweden)
Shirish H. Sonawane
2010-01-01
Full Text Available A systematic study was made on the synthesis of nanocalcite using a hydrodynamic cavitation reactor. The effects of various parameters such as diameter and geometry of orifice, CO2 flow rate, and Ca(OH2 concentration were investigated. It was observed that the orifice diameter and its geometry had significant effect on the carbonation process. The reaction rate was significantly faster than that observed in a conventional carbonation process. The particle size was significantly affected by the reactor geometry. The results showed that an orifice with 5 holes of 1 mm size resulted in the particle size reduction to 37 nm. The experimental investigation reveals that hydrodynamic cavitation may be more energy efficient.
Application of hydrodynamics to heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Felsberger, Lukas
2014-12-02
The Bjorken model is a simple tool for making rough predictions of the hydrodynamic evolution of the thermalized matter created in a heavy ion collision. The advantage of the model clearly lies in its simplicity, rather than accuracy. As it is still used for making rough estimations 'by hand', in this thesis, I investigate in which cases the Bjorken model gives useful results and in which it is not recommended. For central collisions, I show which critical size the nuclei should have so that the Bjorken model can be applied. For non-central collisions, I demonstrate that using Glauber initial conditions combined with the Bjorken evolution, leads to reasonable results up to large impact parameters. Finally, I study the case of a non-ideal (viscous) description of the thermalized matter which leads to strongly differing results if first- or second-order hydrodynamics is applied.
Hyperbolic metamaterial lens with hydrodynamic nonlocal response
DEFF Research Database (Denmark)
Yan, Wei; Mortensen, N. Asger; Wubs, Martijn
2013-01-01
We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves...... of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion curves numerically. As an application, we find that the focusing characteristics of a HMM lens...... in the local-response approximation and in the hydrodynamic Drude model can differ considerably. In particular, the optimal frequency for imaging in the nonlocal theory is blueshifted with respect to that in the local theory. Thus, to detect whether nonlocal response is at work in a hyperbolic metamaterial, we...
Application of hydrodynamics to heavy ion collisions
International Nuclear Information System (INIS)
Felsberger, Lukas
2014-01-01
The Bjorken model is a simple tool for making rough predictions of the hydrodynamic evolution of the thermalized matter created in a heavy ion collision. The advantage of the model clearly lies in its simplicity, rather than accuracy. As it is still used for making rough estimations 'by hand', in this thesis, I investigate in which cases the Bjorken model gives useful results and in which it is not recommended. For central collisions, I show which critical size the nuclei should have so that the Bjorken model can be applied. For non-central collisions, I demonstrate that using Glauber initial conditions combined with the Bjorken evolution, leads to reasonable results up to large impact parameters. Finally, I study the case of a non-ideal (viscous) description of the thermalized matter which leads to strongly differing results if first- or second-order hydrodynamics is applied.
Hydrodynamic interaction between bacteria and passive sphere
Zhang, Bokai; Ding, Yang; Xu, Xinliang
2017-11-01
Understanding hydrodynamic interaction between bacteria and passive sphere is important for identifying rheological properties of bacterial and colloidal suspension. Over the past few years, scientists mainly focused on bacterial influences on tracer particle diffusion or hydrodynamic capture of a bacteria around stationary boundary. Here, we use superposition of singularities and regularized method to study changes in bacterial swimming velocity and passive sphere diffusion, simultaneously. On this basis, we present a simple two-bead model that gives a unified interpretation of passive sphere diffusion and bacterial swimming. The model attributes both variation of passive sphere diffusion and changes of speed of bacteria to an effective mobility. Using the effective mobility of bacterial head and tail as an input function, the calculations are consistent with simulation results at a broad range of tracer diameters, incident angles and bacterial shapes.
The role of Weyl symmetry in hydrodynamics
Diles, Saulo
2018-04-01
This article is dedicated to the analysis of Weyl symmetry in the context of relativistic hydrodynamics. Here is discussed how this symmetry is properly implemented using the prescription of minimal coupling: ∂ → ∂ + ωA. It is shown that this prescription has no problem to deal with curvature since it gives the correct expressions for the commutator of covariant derivatives. In hydrodynamics, Weyl gauge connection emerges from the degrees of freedom of the fluid: it is a combination of the expansion and entropy gradient. The remaining degrees of freedom, shear, vorticity and the metric tensor, are see in this context as charged fields under the Weyl gauge connection. The gauge nature of the connection provides natural dynamics to it via equations of motion analogous to the Maxwell equations for electromagnetism. As a consequence, a charge for the Weyl connection is defined and the notion of local charge is analyzed generating the conservation law for the Weyl charge.
Heat capacity of liquids: A hydrodynamic approach
Directory of Open Access Journals (Sweden)
T. Bryk
2015-03-01
Full Text Available We study autocorrelation functions of energy, heat and entropy densities obtained by molecular dynamics simulations of supercritical Ar and compare them with the predictions of the hydrodynamic theory. It is shown that the predicted by the hydrodynamic theory single-exponential shape of the entropy density autocorrelation functions is perfectly reproduced for small wave numbers by the molecular dynamics simulations and permits the calculation of the wavenumber-dependent specific heat at constant pressure. The estimated wavenumber-dependent specific heats at constant volume and pressure, Cv(k and Cp(k, are shown to be in the long-wavelength limit in good agreement with the macroscopic experimental values of Cv and Cp for the studied thermodynamic points of supercritical Ar.
Hydrodynamics of ultra-relativistic bubble walls
Directory of Open Access Journals (Sweden)
Leonardo Leitao
2016-04-01
Full Text Available In cosmological first-order phase transitions, gravitational waves are generated by the collisions of bubble walls and by the bulk motions caused in the fluid. A sizeable signal may result from fast-moving walls. In this work we study the hydrodynamics associated to the fastest propagation modes, namely, ultra-relativistic detonations and runaway solutions. We compute the energy injected by the phase transition into the fluid and the energy which accumulates in the bubble walls. We provide analytic approximations and fits as functions of the net force acting on the wall, which can be readily evaluated for specific models. We also study the back-reaction of hydrodynamics on the wall motion, and we discuss the extrapolation of the friction force away from the ultra-relativistic limit. We use these results to estimate the gravitational wave signal from detonations and runaway walls.
Hydrodynamics of ultra-relativistic bubble walls
Energy Technology Data Exchange (ETDEWEB)
Leitao, Leonardo, E-mail: lleitao@mdp.edu.ar; Mégevand, Ariel, E-mail: megevand@mdp.edu.ar
2016-04-15
In cosmological first-order phase transitions, gravitational waves are generated by the collisions of bubble walls and by the bulk motions caused in the fluid. A sizeable signal may result from fast-moving walls. In this work we study the hydrodynamics associated to the fastest propagation modes, namely, ultra-relativistic detonations and runaway solutions. We compute the energy injected by the phase transition into the fluid and the energy which accumulates in the bubble walls. We provide analytic approximations and fits as functions of the net force acting on the wall, which can be readily evaluated for specific models. We also study the back-reaction of hydrodynamics on the wall motion, and we discuss the extrapolation of the friction force away from the ultra-relativistic limit. We use these results to estimate the gravitational wave signal from detonations and runaway walls.
Hyperbolic metamaterial lens with hydrodynamic nonlocal response.
Yan, Wei; Mortensen, N Asger; Wubs, Martijn
2013-06-17
We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion curves numerically. As an application, we find that the focusing characteristics of a HMM lens in the local-response approximation and in the hydrodynamic Drude model can differ considerably. In particular, the optimal frequency for imaging in the nonlocal theory is blueshifted with respect to that in the local theory. Thus, to detect whether nonlocal response is at work in a hyperbolic metamaterial, we propose to measure the near-field distribution of a hyperbolic metamaterial lens.
Smoothed Particle Hydrodynamics Coupled with Radiation Transfer
Susa, Hajime
2006-04-01
We have constructed a brand-new radiation hydrodynamics solver based upon Smoothed Particle Hydrodynamics, which works on a parallel computer system. The code is designed to investigate the formation and evolution of first-generation objects at z ≳ 10, where the radiative feedback from various sources plays important roles. The code can compute the fraction of chemical species e, H+, H, H-, H2, and H+2 by by fully implicit time integration. It also can deal with multiple sources of ionizing radiation, as well as radiation at Lyman-Werner band. We compare the results for a few test calculations with the results of one-dimensional simulations, in which we find good agreements with each other. We also evaluate the speedup by parallelization, which is found to be almost ideal, as long as the number of sources is comparable to the number of processors.
Transversal expansion study in the Landau hydrodynamic
International Nuclear Information System (INIS)
Pottag, F.W.
1984-01-01
The system of equations in the frame of Landau's hydrodynamical model for multiparticle production at high energies is studied. Taking as a first approximation the one-dimensional exact due to Khalatnikov, and a special set of curvilinear coordinates, the radial part is separated from the longitudinal one in the equations of motion, and a system of partial differential equations (non-linear, hyperbolic) is obtained for the radial part. These equations are solved numerically by the method of caracteristics. The hydrodynamical variables are obtained over all the three-dimensional-flow region as well as its variation with the mass of the initially expanding system. Both, the transverse rapidity distribution of the fluid and the inclusive particle distribution at 90 0 in the center of mass system, are calculated. The last one is compared with recent experimental data. (author) [pt
Numerical Hydrodynamics and Magnetohydrodynamics in General Relativity
Directory of Open Access Journals (Sweden)
Font José A.
2008-09-01
Full Text Available This article presents a comprehensive overview of numerical hydrodynamics and magnetohydrodynamics (MHD in general relativity. Some significant additions have been incorporated with respect to the previous two versions of this review (2000, 2003, most notably the coverage of general-relativistic MHD, a field in which remarkable activity and progress has occurred in the last few years. Correspondingly, the discussion of astrophysical simulations in general-relativistic hydrodynamics is enlarged to account for recent relevant advances, while those dealing with general-relativistic MHD are amply covered in this review for the first time. The basic outline of this article is nevertheless similar to its earlier versions, save for the addition of MHD-related issues throughout. Hence, different formulations of both the hydrodynamics and MHD equations are presented, with special mention of conservative and hyperbolic formulations well adapted to advanced numerical methods. A large sample of numerical approaches for solving such hyperbolic systems of equations is discussed, paying particular attention to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. As previously stated, a comprehensive summary of astrophysical simulations in strong gravitational fields is also presented. These are detailed in three basic sections, namely gravitational collapse, black-hole accretion, and neutron-star evolutions; despite the boundaries, these sections may (and in fact do overlap throughout the discussion. The material contained in these sections highlights the numerical challenges of various representative simulations. It also follows, to some extent, the chronological development of the field, concerning advances in the formulation of the gravitational field, hydrodynamics and MHD equations and the numerical methodology designed to solve them. To keep the length of this article reasonable
On an incompressible model in radiation hydrodynamics
Czech Academy of Sciences Publication Activity Database
Ducomet, B.; Nečasová, Šárka
2015-01-01
Roč. 38, č. 4 (2015), s. 765-774 ISSN 0170-4214 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : radiation hydrodynamics * incompressible Navier-Stokes-Fourier system * weak solution Subject RIV: BA - General Mathematics Impact factor: 1.002, year: 2015 http://onlinelibrary.wiley.com/doi/10.1002/mma.3107/abstract
Relativistic charged fluids: hydrodynamic and kinetic approaches
International Nuclear Information System (INIS)
Debbasch, F.; Bonnaud, G.
1991-10-01
This report gives a rigorous and consistent hydrodynamic and kinetic description of a charged fluid and the basis equations, in a relativistic context. This study should lead to a reliable model, as much analytical as numerical, of relativistic plasmas which will appear in the interaction of a strong laser field with a plasma. For simplicity, we limited our study to a perfect fluid or, in other words, we disregarded the energy dissipation processes inside the fluid [fr
Resolution of hydrodynamical equations for transverse expansions
International Nuclear Information System (INIS)
Hama, Y.; Pottag, F.W.
1984-01-01
The three-dimensional hydrodynamical expansion is treated with a method similar to that of Milekhin, but more explicit. Although in the final stage one have to appeal to numerical calculation, the partial differential equations governing the transverse expansions are treated without transforming them into ordinary equations with an introduction of averaged quantities. It is only concerned with the formalism and the numerical results will be given in the next paper. (Author) [pt
Viscosity effect in Landau's hydrodynamical model
International Nuclear Information System (INIS)
Hoang, T.F.; Phua, K.K.; Nanyang Univ., Singapore
1979-01-01
The Bose-Einstein distribution is used to investigate Landau's hydrodynamical model with viscosity. In case the viscosity dependence on the temperature is T 3 , the correction to the multiplicity behaves like I/E and is found to be negligible for the pp data. A discussion is presented on a possibility of reconciling E 1 / 2 and logE dependence of the multiplicity law. (orig.)
On the convexity of relativistic hydrodynamics
International Nuclear Information System (INIS)
Ibáñez, José M; Martí, José M; Cordero-Carrión, Isabel; Miralles, Juan A
2013-01-01
The relativistic hydrodynamic system of equations for a perfect fluid obeying a causal equation of state is hyperbolic (Anile 1989 Relativistic Fluids and Magneto-Fluids (Cambridge: Cambridge University Press)). In this report, we derive the conditions for this system to be convex in terms of the fundamental derivative of the equation of state (Menikoff and Plohr1989 Rev. Mod. Phys. 61 75). The classical limit is recovered. Communicated by L Rezzolla (note)
Towards granular hydrodynamics in two dimensions
International Nuclear Information System (INIS)
Grossman, E.L.; Zhou, T.; Ben-Naim, E.; Ben-Naim, E.
1997-01-01
We study steady-state properties of inelastic gases in two dimensions in the presence of an energy source. We generalize previous hydrodynamic treatments to situations where high and low density regions coexist. The theoretical predictions compare well with numerical simulations in the nearly elastic limit. It is also seen that the system can achieve a nonequilibrium steady state with asymmetric velocity distributions, and we discuss the conditions under which such situations occur. copyright 1997 The American Physical Society
Stochastic Hydrodynamic Synchronization in Rotating Energy Landscapes
Koumakis, N.; Di Leonardo, R.
2013-01-01
Hydrodynamic synchronization provides a general mechanism for the spontaneous emergence of coherent beating states in independently driven mesoscopic oscillators. A complete physical picture of those phenomena is of definite importance to the understanding of biological cooperative motions of cilia and flagella. Moreover, it can potentially suggest novel routes to exploit synchronization in technological applications of soft matter. We demonstrate that driving colloidal particles in rotating ...
Hyperbolic metamaterial lens with hydrodynamic nonlocal response
Yan, Wei; Mortensen, N. Asger; Wubs, Martijn
2013-01-01
We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion cu...
Hydrodynamic attraction of swimming microorganisms by surfaces
Berke, Allison P.; Turner, Linda; Berg, Howard C.; Lauga, Eric
2008-01-01
Cells swimming in confined environments are attracted by surfaces. We measure the steady-state distribution of smooth-swimming bacteria (Escherichia coli) between two glass plates. In agreement with earlier studies, we find a strong increase of the cell concentration at the boundaries. We demonstrate theoretically that hydrodynamic interactions of the swimming cells with solid surfaces lead to their re-orientation in the direction parallel to the surfaces, as well as their attraction by the c...
Resolution of hydrodynamical equations for transverse expansions
International Nuclear Information System (INIS)
Hama, Y.; Pottag, F.W.
1985-01-01
The three-dimensional hydrodynamical expansion is treated with a method similar to that of Milekhin, but more explicit. Although in the final stage we have to appeal to numerical calculation, the partial differential equations governing the transverse expansions are treated without transforming them into ordinary equations with an introduction of averaged quantities. The present paper is concerned with the formalism and the numerical results will be reported in another paper. (Author) [pt
Eastern slopes grizzly bear project
Energy Technology Data Exchange (ETDEWEB)
NONE
2001-01-01
The cumulative effects of human activities on the grizzly bears in the central Canadian Rockies are not well known. As a result, a project was initiated in 1994 to address the urgent requirement for accurate scientific information on the habitat and populations of grizzly bears in the area of the Banff National Park and Kananaskis Country. This area is probably the most heavily used and developed area where the grizzly still survives. The information gathered throughout the course of this study will be used to better protect and manage the bears and other sensitive carnivores in the region. Using telemetry, researchers are monitoring 25 grizzly bears which were radio-collared in a 22,000 square-kilometer area in the upper Bow Valley drainage of the eastern Alberta slopes. The researchers involved in the project are working with representatives from Husky Oil and Talisman Energy on the sound development of the Moose Mountain oil and gas field without adversely affecting the grizzly bear population. Information collected over seven years indicated that the grizzly bears have few and infrequent offspring. Using the information gathered so far, the location of the Moose Mountain to Jumping Pound pipeline was carefully selected, since the bears recover very slowly from high mortality, and also considering that the food and cover had already been compromised by the high number of roads, trails and other human activities in the area. The status of the population and habitat of the grizzly bear will be assessed upon the conclusion of the field research phase in 2001. Models will be updated using the data obtained during eight years and will assist in the understanding of complex variables that affect grizzly bears.
EFFECT OF BEARING MACROGEOMETRY ON BEARING PERFORMANCE IN ELASTOHYDRODYNAMIC LUBRICATION
Directory of Open Access Journals (Sweden)
Emin GÜLLÜ
2000-01-01
Full Text Available During manufacturing, ideal dimension and mutual positioning of machine elements proposed in project desing can be achieved only within certain range of tolerances. These tolerances, being classified in two groups, related to micro and macro geometry of machine elements, don't have to effect the functioning of these elements. So, as for all machine elements, investigation of the effects of macro and micro tolerances for journal bearings is important. In this study, we have investigated the effect of macro geometric irregularities of journal bearings on performance characteristics. In this regard, we have studied the change of bearing performance in respect to deviation from ideal circle for an elliptic shaft with small ovality rolling in circular journal bearing.
Hydrodynamic Modeling of Santa Marta's Big Marsh
International Nuclear Information System (INIS)
Saldarriaga, Juan
1991-01-01
The ecological degradation of Santa Marta's Big Marsh and their next areas it has motivated the realization of diagnosis studies and design by several state and private entities. One of the recommended efforts for international advisory it was to develop an ecological model that allowed the handling of the water body and the economic test of alternative of solution to those ecological problems. The first part of a model of this type is in turn a model that simulates the movement of the water inside the marsh, that is to say, a hydrodynamic model. The realization of this was taken charge to the civil engineering department, on the part of Colciencias. This article contains a general explanation of the hydrodynamic pattern that this being developed by a professors group. The ecological causes are described and antecedent, the parts that conform the complex of the Santa Marta big Marsh The marsh modeling is made and it is explained in qualitative form the model type Hydrodynamic used
Hydrodynamic model research in Waseda group
International Nuclear Information System (INIS)
Muroya, Shin
2010-01-01
Constructing 'High Energy Material Science' had been proposed by Namiki as the guiding principle for the scientists of the high energy physics group lead by himself in Waseda University when the author started to study multiple particle production in 1980s toward the semi-phenomenological model for the quark gluon plasma (QGP). Their strategy was based on three stages to build an intermediate one between the fundamental theory of QCD and the phenomenological model. The quantum theoretical Langevin equation was taken up as the semi-phenomenological model at the intermediate stage and the Landau hydrodynamic model was chosen as the phenomenological model to focus on the 'phase transition' of QGP. A review is given here over the quantum theoretical Langevin equation formalism developed there and followed by the further progress with the 1+1 dimensional viscous fluid model as well as the hydrodynamic model with cylindrical symmetry. The developments of the baryon fluid model and Hanbury-Brown Twiss effect are also reviewed. After 1995 younger generation physicists came to the group to develop those models further. Activities by Hirano, Nonaka and Morita beyond the past generation's hydrodynamic model are picked up briefly. (S. Funahashi)
The hydrodynamic size of polymer stabilized nanocrystals
Energy Technology Data Exchange (ETDEWEB)
Krueger, Karl M; Al-Somali, Ali M; Mejia, Michelle; Colvin, Vicki L [Department of Chemistry, Rice University, MS-60 6100 Main Street, Houston, TX 77005 (United States)
2007-11-28
For many emerging applications, nanocrystals are surface functionalized with polymers to control self-assembly, prevent aggregation, and promote incorporation into polymer matrices and biological systems. The hydrodynamic diameter of these nanoparticle-polymer complexes is a critical factor for many applications, and predicting this size is complicated by the fact that the structure of the grafted polymer at a nanocrystalline interface is not generally established. In this work we evaluate using size-exclusion chromatography the overall hydrodynamic diameter of nanocrystals (Au, CdSe, d<5 nm) surface coated with polystyrene of varying molecular weight. The polymer is tethered to the nanoparticles via a terminal thiol to provide strong attachment. Our data show that at full coverage the polymer assumes a brush conformation and is 44% longer than the unbound polymer in solution. The brush conformation is confirmed by comparison with models used to describe polymer brushes at flat interfaces. From this work, we suggest an empirical formula which predicts the hydrodynamic diameter of polymer coated nanoparticles based on the size of the nanoparticle core and the size of the randomly coiled unbound polymer in solution.
Hydrodynamic slip length as a surface property
Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.
2016-02-01
Equilibrium and nonequilibrium molecular dynamics simulations were conducted in order to evaluate the hypothesis that the hydrodynamic slip length is a surface property. The system under investigation was water confined between two graphite layers to form nanochannels of different sizes (3-8 nm). The water-carbon interaction potential was calibrated by matching wettability experiments of graphitic-carbon surfaces free of airborne hydrocarbon contamination. Three equilibrium theories were used to calculate the hydrodynamic slip length. It was found that one of the recently reported equilibrium theories for the calculation of the slip length featured confinement effects, while the others resulted in calculations significantly hindered by the large margin of error observed between independent simulations. The hydrodynamic slip length was found to be channel-size independent using equilibrium calculations, i.e., suggesting a consistency with the definition of a surface property, for 5-nm channels and larger. The analysis of the individual trajectories of liquid particles revealed that the reason for observing confinement effects in 3-nm nanochannels is the high mobility of the bulk particles. Nonequilibrium calculations were not consistently affected by size but by noisiness in the smallest systems.
Hydrodynamic instabilities in astrophysics and ICF
International Nuclear Information System (INIS)
Paul Drake, R.
2005-01-01
Inertial fusion systems and astrophysical systems both involve hydrodynamic effects, including sources of pressure, shock waves, rarefactions, and plasma flows. In the evolution of such systems, hydrodynamic instabilities naturally evolve. As a result, a fundamental understanding of hydrodynamic instabilities is necessary to understand their behavior. In addition, high-energy-density facilities designed for ICF purposes can be used to provide and experimental basis for understanding astrophysical processes. In this talk. I will discuss the instabilities that appear in astrophysics and ICF from the common perspective of the basic mechanisms at work. Examples will be taken from experiments aimed at ICF, from astrophysical systems, and from experiments using ICF systems to address issues in astrophysics. The high-energy-density research facilities of today can accelerate small but macroscopic amounts of material to velocities above 100 km/s, can heat such material to temperature above 100 eV, can produce pressures far above a million atmospheres (10''12 dybes/cm''2 or 0.1 TPascal), and can do experiments under these conditions that address basic physics issues. This enables on to devise experiments aimed directly at important process such as the Rayleigh Taylor instability at an ablating surface or at an embedded interface that is accelerating, the Richtmeyer Meshkov evolution of shocked interfaces, and the Kelvin-Helmholtz instability of shear flows. The talk will include examples of such phenomena from the laboratory and from astrophysics, and will discuss experiments to study them. (Author)
Non-contacting "snubber bearing" for passive magnetic bearing systems
Post, Richard F
2017-08-22
A new non-contacting magnetic "snubber" bearing is provided for application to rotating systems such as vehicular electromechanical battery systems subject to frequent accelerations. The design is such that in the equilibrium position the drag force of the snubber is very small (milliwatts). However in a typical case, if the rotor is displaced by as little as 2 millimeters a large restoring force is generated without any physical contact between the stationary and rotating parts of the snubber bearing.
Bears, Big and Little. Young Discovery Library Series.
Pfeffer, Pierre
This book is written for children 5 through 10. Part of a series designed to develop their curiosity, fascinate them and educate them, this volume describes: (1) the eight species of bears, including black bear, brown bear, grizzly bear, spectacled bear, sun bear, sloth bear, polar bear, and giant panda; (2) geographical habitats of bears; (3)…
DEFF Research Database (Denmark)
Santos, Ilmar; Cerda Varela, Alejandro Javier
2013-01-01
The servo valve input signal and the radial injection pressure are the two main parameters responsible for dynamically modifying the journal oil film pressure and generating active fluid film forces in controllable fluid film bearings. Such fluid film forces, resulting from a strong coupling...... domain and the application of such a controllable bearing as a calibrated shaker aiming at determining the frequency response function (FRF) of rotordynamic systems; b) experimental quantification of the influence of the supply pressure and servo valve input signal on the FRF of rotor-journal bearing...... between hydrodynamic, hydrostatic and controllable lubrication regimes, can be used either to control or to excite rotor lateral vibrations. An accurate characterization of the active oil film forces is of fundamental importance to elucidate the feasibility of applying the active lubrication as non...
On the nonlinear dynamics of two types of backup bearings - Theoretical and experimental aspects
DEFF Research Database (Denmark)
Lahriri, Said; Santos, Ilmar F.; Weber, Hans I.
2012-01-01
mass unbalance, instabilities generated by aerodynamic and hydrodynamic forces in seals and bearings among others. The contact event gives rise to normal and friction forces exerted on the rotor at impact events. The friction force plays a significant role by transferring some rotational energy...... bearing (annular guide) and for the new disk-pin backup bearing. For the conventional annular guide setup, it is reasonable to superpose an impact condition to the rub, where the rotor spin energy can be fully transformed into rotor lateral movements. Using a nonideal drive, i.e., an electric motor...... without any kind of velocity feedback control, it is even possible to almost stop the rotor spin under rubbing conditions. All the rotational energy will be transformed in a kind of self-excited rotor lateral vibration with repeated impacts against the housing. The vibration of the housing is coupled...
On the nonlinear dynamics of two types of backup bearings - Theoretical and experimental aspects
DEFF Research Database (Denmark)
Lahriri, Said; Santos, Ilmar; Hartmann, Henning
2012-01-01
sudden mass unbalance, instabilities generated by aerodynamic and hydrodynamic forces in seals and bearings among others. The contact event gives rise to normal and friction forces exerted on the rotor at impact events. The friction force plays a significant role by transferring some rotational energy...... bearing (annular guide) as well for the new disk-pin backup bearing. For the conventional annular guide setup, it is reasonable to superpose an impact condition to the rub, where the rotor spin energy can be fully transformed into rotor lateral movements. Using a non ideal drive, i.e. an electric motor...... without any kind of velocity feedback control, it is even possible to almost stop the rotor spin under rubbing conditions. All the rotational energy will be transformed in a kind of "self-excited" rotor lateral vibration with repeated impacts against the housing. The vibration of the housing is coupled...
International Nuclear Information System (INIS)
Fauvel, E.
2002-01-01
This report deals with a transpiring wall reactor for supercritical water oxidation of organic effluents. The singularity of the reactor lies on the inner porous tube made of alumina to minimise both limiting problems, corrosion and salt precipitation. The presence of the inner tube implies a rather complex hydrodynamics. Thus, an hydrodynamic study was performed, in an original way, in a supercritical fluid using the method of the residence time distribution. It enabled to determine the hydrodynamic model of the reactor. Moreover, an inspecting device of the resistance of the inner tube to thermal gradients was developed. Lastly, the performances of the transpiring wall reactor were tested on model compounds such as sodium sulphate and the mixture of dodecane/tributylphosphate. (author) [fr
Water-bearing explosive compositions
Energy Technology Data Exchange (ETDEWEB)
Gay, G M
1970-12-21
An explosive water-bearing composition, with high detonation velocity, comprises a mixture of (1) an inorganic oxidizer salt; (2) nitroglycerine; (3) nitrocellulose; (4) water; and (5) a water thickening agent. (11 claims)
Ball Bearings Equipped for In Situ Lubrication on Demand
Marchetti, Mario; Jones, William R., Jr.; Pepper, Stephen V.; Jansen, Mark; Predmore, Roamer
2005-01-01
In situ systems that provide fresh lubricants to ball/race contacts on demand have been developed to prolong the operational lives of ball bearings. These systems were originally intended to be incorporated into ball bearings in mechanisms that are required to operate in outer space for years, in conditions in which lubricants tend to deteriorate and/or evaporate. These systems may also be useful for similarly prolonging bearing lifetimes on Earth. Reservoirs have been among the means used previously to resupply lubricants. Lubricant- resupply reservoirs are bulky and add complexity to bearing assemblies. In addition, such a reservoir cannot be turned on or off as needed: it supplies lubricant continuously, often leading to an excess of lubricant in the bearing. A lubricator of the present type includes a porous ring cartridge attached to the inner or the outer ring of a ball bearing (see Figure 1). Oil is stored in the porous cartridge and is released by heating the cartridge: Because the thermal expansion of the oil exceeds that of the cartridge, heating causes the ejection of some oil. A metal film can be deposited on a face of the cartridge to serve as an electrical-resistance heater. The heater can be activated in response to a measured increase in torque that signals depletion of oil from the bearing/race contacts. Because the oil has low surface tension and readily wets the bearing-ring material, it spreads over the bearing ring and eventually reaches the ball/race contacts. The Marangoni effect (a surface-tension gradient associated with a temperature gradient) is utilized to enhance the desired transfer of lubricant to the ball/race contacts during heating. For a test, a ball bearing designed for use at low speed was assembled without lubricant and equipped with a porous-ring lubricator, the resistance heater of which consumed a power of less than 1 W when triggered on by a torque-measuring device. In the test, a load of 20 lb (.89 N) was applied and the
Failure analysis of superconducting bearings
Energy Technology Data Exchange (ETDEWEB)
Rastogi, Amit; Campbell, A M; Coombs, T A [Department of Engineering, University of Cambridge, Cambridge CB2 1PZ (United Kingdom)
2006-06-01
The dynamics of superconductor bearings in a cryogenic failure scenario have been analyzed. As the superconductor warms up, the rotor goes through multiple resonance frequencies, begins to slow down and finally touches down when the superconductor goes through its transition temperature. The bearing can be modelled as a system of springs with axial, radial and cross stiffness. These springs go through various resonant modes as the temperature of the superconductor begins to rise. We have presented possible explanations for such behavio0008.
Superconducting composite for magnetic bearings
International Nuclear Information System (INIS)
Rigney, T.K. II.
1995-01-01
A composite includes granules of Type II superconducting material and granules of rare-earth permanent magnets that are distributed in a binder. The composite is a two-phase structure that combines the properties of the superconductor and magnets with the flexibility and toughness of a polymeric material. A bearing made from this composite has the load capacity and stiffness of a permanent magnet bearing with added stability from a Type II superconducting material. 7 figs
Laminar motion of the incompressible fluids in self-acting thrust bearings with spiral grooves.
Velescu, Cornel; Popa, Nicolae Calin
2014-01-01
We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the "pumping" direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances) and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc.), for the laminar and permanent motion regime.
Laminar Motion of the Incompressible Fluids in Self-Acting Thrust Bearings with Spiral Grooves
Directory of Open Access Journals (Sweden)
Cornel Velescu
2014-01-01
Full Text Available We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the “pumping” direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc., for the laminar and permanent motion regime.
Fish biorobotics: kinematics and hydrodynamics of self-propulsion.
Lauder, George V; Anderson, Erik J; Tangorra, James; Madden, Peter G A
2007-08-01
As a result of years of research on the comparative biomechanics and physiology of moving through water, biologists and engineers have made considerable progress in understanding how animals moving underwater use their muscles to power movement, in describing body and appendage motion during propulsion, and in conducting experimental and computational analyses of fluid movement and attendant forces. But it is clear that substantial future progress in understanding aquatic propulsion will require new lines of attack. Recent years have seen the advent of one such new avenue that promises to greatly broaden the scope of intellectual opportunity available to researchers: the use of biorobotic models. In this paper we discuss, using aquatic propulsion in fishes as our focal example, how using robotic models can lead to new insights in the study of aquatic propulsion. We use two examples: (1) pectoral fin function, and (2) hydrodynamic interactions between dorsal and caudal fins. Pectoral fin function is characterized by considerable deformation of individual fin rays, as well as spanwise (along the length) and chordwise (across the fin) deformation and area change. The pectoral fin can generate thrust on both the outstroke and instroke. A robotic model of the pectoral fin replicates this result, and demonstrates the effect of altering stroke kinematics on the pattern of force production. The soft dorsal fin of fishes sheds a distinct vortex wake that dramatically alters incoming flow to the tail: the dorsal fin and caudal fin act as dual flapping foils in series. This design can be replicated with a dual-foil flapping robotic device that demonstrates this phenomenon and allows examination of regions of the flapping performance space not available to fishes. We show how the robotic flapping foil device can also be used to better understand the significance of flexible propulsive surfaces for locomotor performance. Finally we emphasize the utility of self
Ryu, Brian; Dhong, Charles; Frechette, Joelle
While it is well known that surface asperities and roughness alter the hydrodynamic drag of a non-colloidal sphere down an inclined plane, less is known about how the hydrodynamic drag is modified if the asperities and roughness are connected through a network of drainage channels, which allows the movement of fluid between asperities. We investigate the rotational and translation motion of spheres on several pairs of surfaces that have the same porosity and asperity size, but one surface has interconnected drainage channels whereas the other does not. These can have direct relevance to lubricated surfaces such as ball bearings in industrial settings, or biological relevance of leucocyte movement across rough surfaces. Provost's Undergraduate Research Awards, Office of Naval Research, National Science Foundation.
Energy Technology Data Exchange (ETDEWEB)
Takiguchi, M; Suhara, T; Ato, S; Someya, T [Musashi Institute of Technology, Tokyo (Japan)
1997-10-01
Piston pin bearings are engine parts placed under severe lubricating condition because of the high unit load and temperature and the low sliding speeds. Therefore, they are vulnerable to many lubrication problems such as abnormal wear, scuffs and seizures. In our recent study, the bearing friction were measured using a original measuring device and it was found out that the lubricating conditions of piston pin boss bearings are non-fluid lubrication due to the oil starvation. In this study, we have also measured the lubricating oil behavior around the pin boss bearing using a special cylinder with glass window, and analyzed the relationship between the friction force and the oil behavior at the pin boss bearings in a actual operating gasoline engine. 2 refs., 9 figs., 1 tab.
Biofeedback device for patients on axillary crutches.
Ang, E J; Goh, J C; Bose, K; Toh, S L; Choo, A
1989-08-01
The axillary crutch is commonly prescribed as an ambulatory aid to patients with temporal or permanent disability in the lower extremity. When fitting the axillary crutch, it is important that the user be instructed not to bear excessive weight on the axillary bar. Excessive weight bearing on the axillary bar can result in a sevenfold increase in the reaction force under the armpit. This force may be a contributory factor to crutch paralysis or thrombosis of the axillobrachial artery. In order to prevent this occurrence an electronic biofeedback device was designed and developed for use in the training of 3-point swing-through axillary crutch ambulation. It detects excessive weight bearing on the axillary bar during crutch ambulation and produces an audible signal which prompts the patient to make necessary adjustment to relieve load bearing on the axillary bar. The design and development of the biofeedback device is discussed in this paper.
Effect of hydrodynamic action in peristaltic pump of blood gases analyzer ABL 555
Directory of Open Access Journals (Sweden)
Ali K. Mohammed
2018-01-01
Full Text Available In this research, we studied the effect of hydrodynamic action in peristaltic pump of blood gases analyzer ABL 555 which made by (Radiometer-Copenhagen, by using theories of tribology and Reynolds equation on performance of blood film convergence area, we analyzing the influence of theoretical model for peristaltic pump (consist of steeper motor and 4 cylindrical bearings distributed on circular disc rotating around capillary tube, by using (MATLAB R 2012b programing with numerical solution of finite difference method in 5 nodes element , we fined the blood film thickness and the pressure on contact area grid ( consist from annual and axial lines , then influence of viscosity of blood on pressure generated in limited temperature of ambient and velocity of motor , and flow rate of blood in tube. The important conclusions appear that the rotating sliding movement of motor cause low pressure (positive while the rolling cylindrical rollers of bearings cause high pressure (negative which lead to push the blood in tube, that mean the direction of rotating blood opposite the direction of rotating motor of peristaltic pump, also the viscosity of blood effect on velocity of flow and the speed of motor with bearings, and the effect of blood film thickness effect on pressure generated in tube. DOI: http://dx.doi.org/10.25130/tjes.24.2017.18
Assessment for hydrodynamic masses of HANARO flow tubes
Energy Technology Data Exchange (ETDEWEB)
Ryu, Jeong Soo; Cho, Yeong Garp; Kim, Doo Kie; Woo, Jong Sug; Park, Jin Ho
2000-06-01
The effect of hydrodynamic masses is investigated in dynamic characteristics and seismic response analyses of the submerged HANARO hexagonal flow tubes. Consistent hydrodynamic masses of the surrounding water are evaluated by the prepared program using the finite element method, in which arbitrary cross-sections of submerged structures and boundary conditions of the surrounding fluid can be considered. Also lumped hydrodynamic masses are calculated using simple formula applied to hexagonal flow tubes in the infinite fluid. Modal analyses and seismic response spectrum analyses were performed using hydrodynamic masses obtained by the finite element method and the simple formula. The results of modal analysis were verified by comparing the results measured from modal tests. And the displacement results of the seismic response spectrum analysis were assessed by comparing the consistent and the lumped hydrodynamic masses obtained by various methods. Finally practical criteria based on parametric studies are proposed as the lumped hydrodynamic masses for HANARO flow tubes.
Assessment for hydrodynamic masses of HANARO flow tubes
International Nuclear Information System (INIS)
Ryu, Jeong Soo; Cho, Yeong Garp; Kim, Doo Kie; Woo, Jong Sug; Park, Jin Ho
2000-06-01
The effect of hydrodynamic masses is investigated in dynamic characteristics and seismic response analyses of the submerged HANARO hexagonal flow tubes. Consistent hydrodynamic masses of the surrounding water are evaluated by the prepared program using the finite element method, in which arbitrary cross-sections of submerged structures and boundary conditions of the surrounding fluid can be considered. Also lumped hydrodynamic masses are calculated using simple formula applied to hexagonal flow tubes in the infinite fluid. Modal analyses and seismic response spectrum analyses were performed using hydrodynamic masses obtained by the finite element method and the simple formula. The results of modal analysis were verified by comparing the results measured from modal tests. And the displacement results of the seismic response spectrum analysis were assessed by comparing the consistent and the lumped hydrodynamic masses obtained by various methods. Finally practical criteria based on parametric studies are proposed as the lumped hydrodynamic masses for HANARO flow tubes
Development of an aerostatic bearing system for roll-to-roll printed electronics
Chen, Shasha; Chen, Weihai; Liu, Jingmeng; Chen, Wenjie; Jin, Yan
2018-06-01
Roll-to-roll printed electronics is proved to be an effective way to fabricate electrical devices on various substrates. High precision overlay alignment plays a key role to create multi-layer electrical devices. Multiple rollers are adopted to support and transport the substrate web. In order to eliminate the negative effect of the machining error and assembling error of the roller, a whole roll-to-roll system including two aerostatic bearing devices with arrayed restrictors is proposed in this paper. Different to the conventional roller, the aerostatic bearing device can create a layer of air film between the web and the device to realize non-contact support and transport. Based on simplified Navier–Stokes equations, the theoretical model of the air film is established. Moreover, the pressure distribution of the whole flow field and single restrictor in different positions are modeled by conducting numerical simulation with computational fluid dynamics (CFD) software FLUENT. The load capacity curves and stiffness curves are generated to provide guidance for optimizing the structure of the device. A prototype of the aerostatic bearing system is set up and the experiment tests are carried out. For the proposed aerostatic bearing roller with a diameter of 100 mm and length of 200 mm, the experimental results show the aerostatic bearing method can achieve the position accuracy in a range of 1 μm in the vertical direction of the web, which is much better than that using existing methods.
Triboluminescent tamper-indicating device
Johnston, Roger G.; Garcia, Anthony R. E.
2002-01-01
A tamper-indicating device is described. The device has a transparent or translucent cylindrical body that includes triboluminescent material, and an outer opaque layer that prevents ambient light from entering. A chamber in the body holds an undeveloped piece of photographic film bearing an image. The device is assembled from two body members. One of the body members includes a recess for storing film and an optical assembly that can be adjusted to prevent light from passing through the assembly and exposing the film. To use the device with a hasp, the body members are positioned on opposite sides of a hasp, inserted through the hasp, and attached. The optical assembly is then manipulated to allow any light generated from the triboluminescent materials during a tampering activity that damages the device to reach the film and destroy the image on the film.
Pressurized waterproof case electronic device
Berumen, Michael L.
2013-01-31
A pressurized waterproof case for an electronic device is particularly adapted for fluid-tight containment and operation of a touch-screen electronic device or the like therein at some appreciable water depth. In one example, the case may be formed as an enclosure having an open top panel or face covered by a flexible, transparent membrane or the like for the operation of the touchscreen device within the case. A pressurizing system is provided for the case to pressurize the case and the electronic device therein to slightly greater than ambient in order to prevent the external water pressure from bearing against the transparent membrane and pressing it against the touch screen, thereby precluding operation of the touch screen device within the case. The pressurizing system may include a small gas cartridge or may be provided from an external source.
An overview of hydrodynamic studies of mineralization
Directory of Open Access Journals (Sweden)
Guoxiang Chi
2011-07-01
Full Text Available Fluid flow is an integral part of hydrothermal mineralization, and its analysis and characterization constitute an important part of a mineralization model. The hydrodynamic study of mineralization deals with analyzing the driving forces, fluid pressure regimes, fluid flow rate and direction, and their relationships with localization of mineralization. This paper reviews the principles and methods of hydrodynamic studies of mineralization, and discusses their significance and limitations for ore deposit studies and mineral exploration. The driving forces of fluid flow may be related to fluid overpressure, topographic relief, tectonic deformation, and fluid density change due to heating or salinity variation, depending on specific geologic environments and mineralization processes. The study methods may be classified into three types, megascopic (field observations, microscopic analyses, and numerical modeling. Megascopic features indicative of significantly overpressured (especially lithostatic or supralithostatic fluid systems include horizontal veins, sand injection dikes, and hydraulic breccias. Microscopic studies, especially microthermometry of fluid inclusions and combined stress analysis and microthermometry of fluid inclusion planes (FIPs can provide important information about fluid temperature, pressure, and fluid-structural relationships, thus constraining fluid flow models. Numerical modeling can be carried out to solve partial differential equations governing fluid flow, heat transfer, rock deformation and chemical reactions, in order to simulate the distribution of fluid pressure, temperature, fluid flow rate and direction, and mineral precipitation or dissolution in 2D or 3D space and through time. The results of hydrodynamic studies of mineralization can enhance our understanding of the formation processes of hydrothermal deposits, and can be used directly or indirectly in mineral exploration.
Hydrodynamic evolution of neutron star merger remnants
Liu, Men-Quan; Zhang, Jie
2017-11-01
Based on the special relativistic hydrodynamic equations and updated cooling function, we investigate the long-term evolution of neutron stars merger (NSM) remnants by a one-dimensional hydrodynamic code. Three NSM models from one soft equation of state, SFHo, and two stiff equations of state, DD2 and TM1, are used to compare their influences on the hydrodynamic evolution of remnants. We present the luminosity, mass and radius of remnants, as well as the velocity, temperature and density of shocks. For a typical interstellar medium (ISM) density with solar metallicity, we find that the NSM remnant from the SFHo model makes much more changes to ISM in terms of velocity, density and temperature distributions, compared with the case of DD2 and TM1 models. The maximal luminosity of the NSM remnant from the SFHo model is 3.4 × 1038 erg s-1, which is several times larger than that from DD2 and TM1 models. The NSM remnant from the SFHo model can maintain high luminosity (>1038 erg s-1) for 2.29 × 104 yr. Furthermore, the density and temperature of remnants at the maximal luminosity are not sensitive to the power of the original remnant. For the ISM with the solar metallicity and nH = 1 cm- 3, the density of the first shock ∼10-23 g cm-3 and the temperature ∼3 × 105 K in the maximal luminosity phase; The temperature of the first shock decreases and there is a thin 'dense' shell with density ∼10-21 g cm-3 after the maximal luminosity. These characteristics may be helpful for future observations of NSM remnants.
Computer simulation of the fire-tube boiler hydrodynamics
Directory of Open Access Journals (Sweden)
Khaustov Sergei A.
2015-01-01
Full Text Available Finite element method was used for simulating the hydrodynamics of fire-tube boiler with the ANSYS Fluent 12.1.4 engineering simulation software. Hydrodynamic structure and volumetric temperature distribution were calculated. The results are presented in graphical form. Complete geometric model of the fire-tube boiler based on boiler drawings was considered. Obtained results are suitable for qualitative analysis of hydrodynamics and singularities identification in fire-tube boiler water shell.
Measurement of beam driven hydrodynamic turbulence
International Nuclear Information System (INIS)
Norem, J.; Black, E.; Bandura, L.; Errede, D.; Cummings, M. A. C.
2003-01-01
Cooling intense muon beams in liquid hydrogen absorbers introduces kW of heating to the cold fluid, which will drive turbulent flow. The amount of turbulence may be sufficient to help cool the liquid, but calculations are difficult. We have used a 20 MeV electron beam in a water tank to look at the scale of the beam driven convection and turbulence. The density and flow measurements are made with schlieren and Ronchi systems. We describe the optical systems and the turbulence measured. These data are being used to calibrate hydrodynamic calculations of convection driven and forced flow cooling in muon cooling absorbers
The frontal method in hydrodynamics simulations
Walters, R.A.
1980-01-01
The frontal solution method has proven to be an effective means of solving the matrix equations resulting from the application of the finite element method to a variety of problems. In this study, several versions of the frontal method were compared in efficiency for several hydrodynamics problems. Three basic modifications were shown to be of value: 1. Elimination of equations with boundary conditions beforehand, 2. Modification of the pivoting procedures to allow dynamic management of the equation size, and 3. Storage of the eliminated equations in a vector. These modifications are sufficiently general to be applied to other classes of problems. ?? 1980.
Hydrodynamic instabilities in inertial confinement fusion
International Nuclear Information System (INIS)
Hoffman, N.M.
1995-01-01
The focus of these (two) lectures is on buoyancy-driven instabilities of the Rayleigh-Taylor type, which are commonly regarded as the most important kind of hydrodynamic instability in inertial-confinement-fusion implosions. The paper is intended to be pedagogical rather than research-oriented, and so is by no means a comprehensive review of work in this field. Rather, it is hoped that the student will find here a foundation on which to build an understanding of current research, and the experienced researcher will find a compilation of useful results. (author)
Hydrodynamic Study Of Column Bioleaching Processes
Directory of Open Access Journals (Sweden)
Sadowski Zygmunt
2015-06-01
Full Text Available The modelling of flow leaching solution through the porous media has been considered. The heap bioleaching process can be tested using the column experimental equipment. This equipment was employed to the hydrodynamic studies of copper ore bioleaching. The copper ore (black shale ore with the support, inertial materials (glass small balls and polyethylene beads was used to the bioleaching tests. The packed beds were various composition, the ore/support ratio was changed. The correlation between the bed porosity and bioleaching kinetics, and copper recovery was investigated.
Hydrodynamic instabilities in an ablation front
International Nuclear Information System (INIS)
Piriz, A R; Portugues, R F
2004-01-01
The hydrodynamic stability of an ablation front is studied for situations in which the wavelength of the perturbations is larger than the distance to the critical surface where the driving radiation is absorbed. An analytical model is presented, and it shows that under conditions in which the thermal flux is limited within the supercritical region of the ablative corona, the front may behave like a flame or like an ablation front, depending on the perturbation wavelength. For relatively long wavelengths the critical and ablation surfaces practically lump together into a unique surface and the front behaves like a flame, whereas for the shortest wavelengths the ablation front substructure is resolved
Hydrodynamic instabilities in an ablation front
Energy Technology Data Exchange (ETDEWEB)
Piriz, A R; Portugues, R F [E.T.S.I. Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain)
2004-06-01
The hydrodynamic stability of an ablation front is studied for situations in which the wavelength of the perturbations is larger than the distance to the critical surface where the driving radiation is absorbed. An analytical model is presented, and it shows that under conditions in which the thermal flux is limited within the supercritical region of the ablative corona, the front may behave like a flame or like an ablation front, depending on the perturbation wavelength. For relatively long wavelengths the critical and ablation surfaces practically lump together into a unique surface and the front behaves like a flame, whereas for the shortest wavelengths the ablation front substructure is resolved.
Self-acting and hydrodynamic shaft seals
Ludwig, L. P.
1973-01-01
Self-acting and hydrodynamic seals are described. The analytical procedures are outlined for obtaining a seal force balance and the operating film thickness. Particular attention is given to primary ring response (seal vibration) to rotating seat face runout. This response analysis revealed three different vibration modes. Proposed applications of self-acting seals in gas turbine engines and in rocket vehicle turbopumps are described. Also experimental data on self-acting face seals operating under simulated gas turbine conditions are given; these data show the feasibility of operating the seal at conditions of 345 newtons per square centimeter (500 psi) and 152 meters per second (500 ft/sec) sliding speed.
Hydrodynamics and Elasticity of Charged Black Branes
DEFF Research Database (Denmark)
Gath, Jakob
We consider long-wavelength perturbations of charged black branes to first order in a uidelastic derivative expansion. At first order the perturbations decouple and we treat the hydrodynamic and elastic perturbations separately. To put the results in a broader perspective, we present the rst...... as a seed solution, we obtain a class of charged black brane geometries carrying smeared Maxwell charge in Einstein-Maxwell-dilaton theory. In the specific case of ten-dimensional space-time we furthermore use T-duality to generate bent black branes with higher-form charge, including smeared D...
Control of hydrodynamic cavitation using ultrasonic
Chatterjee, Dhiman; Arakeri, Vijay H.
2003-11-01
Hydrodynamic cavitation is known to have many harmful effects like surface damage and generation of noise. We investigated the use of ultrasonics to control traveling bubble cavitation. Ultrasonic pressure field, produced by a piezoelectric crystal, was applied to modify the nuclei size distribution. Effects of continuous-wave (CW) and pulsed excitations were studied. At low dissolved gas content the CW-mode performed better than the pulsed one, whereas for high gas content the pulsed one was more effective. The dominant mechanisms were Bjerknes force and rectified diffusion in these two cases. Simultaneous excitation by two crystals in CW and pulsed modes was seen to control cavitation better.
Hydrodynamics in a swarm of rising bubbles
International Nuclear Information System (INIS)
Riboux, G.
2007-04-01
In many applications, bubbles are used to agitate a liquid in order to enhance mixing and transfer. This work is devoted to the study of the hydrodynamics in a stable bubble column. Experimentally, we have determined the properties of the velocity fluctuations inside and behind a homogeneous swarm of rising bubbles for different bubble sizes and gas volume fractions α: self-similarity in α 0,4 , spectrum in k -3 and integral length scale controlled by buoyancy. Numerically, we have reproduced these properties by means of large-scale simulations, the bubbles being modeled by volume-forces. This confirms that the dynamics is controlled by wake interactions. (author)
Experimental hydrodynamics of swimming in fishes
Tytell, Eric Daniel
2005-11-01
The great diversity of fish body shapes suggests that they have adapted to different selective pressures. For many fishes, the pressures include hydrodynamic demands: swimming efficiently or accelerating rapidly, for instance. However, the hydrodynamic advantages or disadvantages to specific morphologies are poorly understood. In particular, eels have been considered inefficient swimmers, but they migrate long distances without feeding, a task that requires efficient swimming. This dissertation, therefore, begins with an examination of the swimming hydrodynamics of American eels, Anguilla rostrata, at steady swimming speeds from 0.5 to 2 body lengths (L) per second and during accelerations from -1.4 to 1.3 L s -2. The final chapter examines the hydrodynamic effects of body shape directly by describing three-dimensional flow around swimming bluegill sunfish, Lepomis macrochirus. In all chapters, flow is quantified using digital particle image velocimetry, and simultaneous kinematics are measured from high-resolution digital video. The wake behind a swimming eel in the horizontal midline plane is described first. Rather than producing a wake with fluid jets angled backwards, like in fishes such as sunfish, eels have a wake with exclusively lateral jets. The lack of downstream momentum indicates that eels balance the axial forces of thrust and drag evenly over time and over their bodies, and therefore do not change axial fluid momentum. This even balance, present at all steady swimming speeds, is probably due to the relatively uniform body shape of eels. As eels accelerate, thrust exceeds drag, axial momentum increases, and the wake approaches that of other fishes. During steady swimming, though, the lack of axial momentum prevents direct efficiency estimation. The effect of body shape was examined directly by measuring flow in multiple transverse planes along the body of bluegill sunfish swimming at 1.2 L s-1. The dorsal and anal fin, neglected in many previous
49 CFR 229.69 - Side bearings.
2010-10-01
... 49 Transportation 4 2010-10-01 2010-10-01 false Side bearings. 229.69 Section 229.69....69 Side bearings. (a) Friction side bearings with springs designed to carry weight may not have more than 25 percent of the springs in any one nest broken. (b) Friction side bearings may not be run in...
Hydrodynamization and transient modes of expanding plasma in kinetic theory
Heller, Michal P.; Spalinski, Michal
2016-01-01
We study the transition to hydrodynamics in a weakly-coupled model of quark-gluon plasma given by kinetic theory in the relaxation time approximation. Our studies uncover qualitative similarities to the results on hydrodynamization in strongly coupled gauge theories. In particular, we demonstrate that the gradient expansion in this model has vanishing radius of convergence. The asymptotic character of the hydrodynamic gradient expansion is crucial for the recently discovered applicability of hydrodynamics at large gradients. Furthermore, the analysis of the resurgent properties of the series provides, quite remarkably, indication for the existence of a novel transient, damped oscillatory mode of expanding plasmas in kinetic theory.
Hydrodynamics in a Degenerate, Strongly Attractive Fermi Gas
Thomas, John E.; Kinast, Joseph; Hemmer, Staci; Turlapov, Andrey; O'Hara, Ken; Gehm, Mike; Granade, Stephen
2004-01-01
In summary, we use all-optical methods with evaporative cooling near a Feshbach resonance to produce a strongly interacting degenerate Fermi gas. We observe hydrodynamic behavior in the expansion dynamics. At low temperatures, collisions may not explain the expansion dynamics. We observe hydrodynamics in the trapped gas. Our observations include collisionally-damped excitation spectra at high temperature which were not discussed above. In addition, we observe weakly damped breathing modes at low temperature. The observed temperature dependence of the damping time and hydrodynamic frequency are not consistent with collisional dynamics nor with collisionless mean field interactions. These observations constitute the first evidence for superfluid hydrodynamics in a Fermi gas.
21 CFR 812.5 - Labeling of investigational devices.
2010-04-01
... investigational device shipped solely for research on or with laboratory animals shall bear on its label the following statement: “CAUTION—Device for investigational use in laboratory animals or other tests that do...—Investigational device. Limited by Federal (or United States) law to investigational use.” The label or other...
Experimental contribution to the study of gas bearings
International Nuclear Information System (INIS)
Gobert, G.
1962-01-01
Developments for gas-lubricated bearings are discussed. The study of how the fluid film behaves compared to what one can expect is discussed. Various devices are described which have allowed us to go up to peripheral velocity greater than 400 m/s, leading to rotational speed of several thousand revolutions per second. This is obtained by using an automatic setting for the distance between fixed and rotating walls. (author) [fr
Noise estimation of oil lubricated journal bearings
International Nuclear Information System (INIS)
Rho, Byoung Hoo; Kim, Kyung Woong
2003-01-01
Noise estimating procedures of oil lubricated journal bearings are presented. Nonlinear analysis of rotor-bearing system including unbalance mass of the rotor is performed in order to obtain acoustical properties of the bearing. Acoustical properties of the bearing are investigated through frequency analysis of the pressure fluctuation of the fluid film calculated from the nonlinear analysis. Noise estimating procedures presented in this paper could aid in the evaluation and understanding of acoustical properties of oil lubricated journal bearings
Improved Swimming Performance in Hydrodynamically- coupled Airfoils
Heydari, Sina; Shelley, Michael J.; Kanso, Eva
2017-11-01
Collective motion is a widespread phenomenon in the animal kingdom from fish schools to bird flocks. Half of the known fish species are thought to exhibit schooling behavior during some phase of their life cycle. Schooling likely occurs to serve multiple purposes, including foraging for resources and protection from predators. Growing experimental and theoretical evidence supports the hypothesis that fish can benefit from the hydrodynamic interactions with their neighbors, but it is unclear whether this requires particular configurations or regulations. Here, we propose a physics-based approach that account for hydrodynamic interactions among swimmers based on the vortex sheet model. The benefit of this model is that it is scalable to a large number of swimmers. We start by examining the case of two swimmers, heaving plates, moving in parallel and in tandem. We find that for the same heaving amplitude and frequency, the coupled-swimmers move faster and more efficiently. This increase in velocity depends strongly on the configuration and separation distance between the swimmers. Our results are consistent with recent experimental findings on heaving airfoils and underline the role of fluid dynamic interactions in the collective behavior of swimmers.
Hydrodynamic optical-field-ionized plasma channels
Shalloo, R. J.; Arran, C.; Corner, L.; Holloway, J.; Jonnerby, J.; Walczak, R.; Milchberg, H. M.; Hooker, S. M.
2018-05-01
We present experiments and numerical simulations which demonstrate that fully ionized, low-density plasma channels could be formed by hydrodynamic expansion of plasma columns produced by optical field ionization. Simulations of the hydrodynamic expansion of plasma columns formed in hydrogen by an axicon lens show the generation of 200 mm long plasma channels with axial densities of order ne(0 ) =1 ×1017cm-3 and lowest-order modes of spot size WM≈40 μ m . These simulations show that the laser energy required to generate the channels is modest: of order 1 mJ per centimeter of channel. The simulations are confirmed by experiments with a spherical lens which show the formation of short plasma channels with 1.5 ×1017cm-3≲ne(0 ) ≲1 ×1018cm-3 and 61 μ m ≳WM≳33 μ m . Low-density plasma channels of this type would appear to be well suited as multi-GeV laser-plasma accelerator stages capable of long-term operation at high pulse repetition rates.
Mix and hydrodynamic instabilities on NIF
Smalyuk, V. A.; Robey, H. F.; Casey, D. T.; Clark, D. S.; Döppner, T.; Haan, S. W.; Hammel, B. A.; MacPhee, A. G.; Martinez, D.; Milovich, J. L.; Peterson, J. L.; Pickworth, L.; Pino, J. E.; Raman, K.; Tipton, R.; Weber, C. R.; Baker, K. L.; Bachmann, B.; Berzak Hopkins, L. F.; Bond, E.; Caggiano, J. A.; Callahan, D. A.; Celliers, P. M.; Cerjan, C.; Dixit, S. N.; Edwards, M. J.; Felker, S.; Field, J. E.; Fittinghoff, D. N.; Gharibyan, N.; Grim, G. P.; Hamza, A. V.; Hatarik, R.; Hohenberger, M.; Hsing, W. W.; Hurricane, O. A.; Jancaitis, K. S.; Jones, O. S.; Khan, S.; Kroll, J. J.; Lafortune, K. N.; Landen, O. L.; Ma, T.; MacGowan, B. J.; Masse, L.; Moore, A. S.; Nagel, S. R.; Nikroo, A.; Pak, A.; Patel, P. K.; Remington, B. A.; Sayre, D. B.; Spears, B. K.; Stadermann, M.; Tommasini, R.; Widmayer, C. C.; Yeamans, C. B.; Crippen, J.; Farrell, M.; Giraldez, E.; Rice, N.; Wilde, C. H.; Volegov, P. L.; Gatu Johnson, M.
2017-06-01
Several new platforms have been developed to experimentally measure hydrodynamic instabilities in all phases of indirect-drive, inertial confinement fusion implosions on National Ignition Facility. At the ablation front, instability growth of pre-imposed modulations was measured with a face-on, x-ray radiography platform in the linear regime using the Hydrodynamic Growth Radiography (HGR) platform. Modulation growth of "native roughness" modulations and engineering features (fill tubes and capsule support membranes) were measured in conditions relevant to layered DT implosions. A new experimental platform was developed to measure instability growth at the ablator-ice interface. In the deceleration phase of implosions, several experimental platforms were developed to measure both low-mode asymmetries and high-mode perturbations near peak compression with x-ray and nuclear techniques. In one innovative technique, the self-emission from the hot spot was enhanced with argon dopant to "self-backlight" the shell in-flight. To stabilize instability growth, new "adiabat-shaping" techniques were developed using the HGR platform and applied in layered DT implosions.
A web portal for hydrodynamical, cosmological simulations
Ragagnin, A.; Dolag, K.; Biffi, V.; Cadolle Bel, M.; Hammer, N. J.; Krukau, A.; Petkova, M.; Steinborn, D.
2017-07-01
This article describes a data centre hosting a web portal for accessing and sharing the output of large, cosmological, hydro-dynamical simulations with a broad scientific community. It also allows users to receive related scientific data products by directly processing the raw simulation data on a remote computing cluster. The data centre has a multi-layer structure: a web portal, a job control layer, a computing cluster and a HPC storage system. The outer layer enables users to choose an object from the simulations. Objects can be selected by visually inspecting 2D maps of the simulation data, by performing highly compounded and elaborated queries or graphically by plotting arbitrary combinations of properties. The user can run analysis tools on a chosen object. These services allow users to run analysis tools on the raw simulation data. The job control layer is responsible for handling and performing the analysis jobs, which are executed on a computing cluster. The innermost layer is formed by a HPC storage system which hosts the large, raw simulation data. The following services are available for the users: (I) CLUSTERINSPECT visualizes properties of member galaxies of a selected galaxy cluster; (II) SIMCUT returns the raw data of a sub-volume around a selected object from a simulation, containing all the original, hydro-dynamical quantities; (III) SMAC creates idealized 2D maps of various, physical quantities and observables of a selected object; (IV) PHOX generates virtual X-ray observations with specifications of various current and upcoming instruments.
Hydrodynamic instability experiments on the Nova laser
International Nuclear Information System (INIS)
Remington, B.A.; Glendinning, S.G.; Kalantar, D.H.
1996-08-01
Hydrodynamic instabilities in compressible plasmas play a critical role in the fields of inertial confinement fusion (ICF), astrophysics, and high energy-density physics. We are, investigating hydrodynamic instabilities such as the Rayleigh-Taylor (RT) instability, at high compression at the Nova laser in a series of experiments, both in planar and in spherical geometry. In the indirect drive approach, a thermal x-ray drive is generated by focusing the Nova laser beams into a Au cylindrical radiation cavity (hohlraum). Issues in the instability evolution that we are examining are shock propagation and foil compression, RT growth of 2D versus 3D single-mode perturbations, drive pulse shape, perturbation location at the ablation front versus at an embedded interface, and multimode perturbation growth and nonlinear saturation. The effects of convergence on RT growth are being investigated both with hemispherical implosions of packages mounted on the hohlraum wall and with spherical implosions of capsules at the center of the hohlraum. Single-mode perturbations are pre-imposed at the ablation front of these capsules as a seed for the RT growth. In our direct drive experiments, we are investigating the effect of laser imprinting and subsequent RT growth on planar foils, both at λ Laser = 1/3 μm and 1/2 μm. An overview is given describing recent progress in each of these areas
Mesoscale simulations of hydrodynamic squirmer interactions.
Götze, Ingo O; Gompper, Gerhard
2010-10-01
The swimming behavior of self-propelled microorganisms is studied by particle-based mesoscale simulations. The simulation technique includes both hydrodynamics and thermal fluctuations that are both essential for the dynamics of microswimmers. The swimmers are modeled as squirmers, i.e., spherical objects with a prescribed tangential surface velocity, where the focus of thrust generation can be tuned from pushers to pullers. For passive squirmers (colloids), we show that the velocity autocorrelation function agrees quantitatively with the Boussinesq approximation. Single active squirmers show a persistent random-walk behavior, determined by forward motion, lateral diffusion, and orientational fluctuations, in agreement with theoretical predictions. For pairs of squirmers, which are initially swimming in parallel, we find an attraction for pushers and a repulsion for pullers, as expected. The hydrodynamic force between squirmer pairs is calculated as a function of the center-to-center distances d(cm) and is found to be consistent with a logarithmic distance dependence for d(cm) less than about two sphere diameters; here, the force is considerably stronger than expected from the far-field expansion. The dependence of the force strength on the asymmetry of the polar surface velocity is obtained. During the collision process, thermal fluctuations turn out to be very important and to strongly affect the postcollision velocity directions of both squirmers.
The Coupling of Radiation and Hydrodynamics
International Nuclear Information System (INIS)
Lowrie, R.B.; Morel, J.E.; Hittinger, J.A.
1999-01-01
The coupling of radiation transport and hydrodynamics is discussed for the Eulerian frame. The discussion is aimed at developing a suitable set of equations for nonrelativistic radiation hydrodynamics (RHD) that can be numerically integrated using high-resolution methods for conservation laws. We outline how numerical methods based on a wave decomposition may be developed, along with the importance of conservation, particularly in the equilibrium regime. The properties of the RHD equations are examined through asymptotic and dispersion analyses. The conditions required to obtain the classical equilibrium limit are rigorously studied. The results show that a simple coupling term developed recently by Morel, which retains a minimum of relativistic corrections, may be sufficient for nonrelativistic flows. We also give two constraints on the relativistic corrections that result in retaining terms on the order of the truncation. In addition, the dispersion results for the P 1 approximation are studied in detail and are compared with both the exact-transport results and a full relativistic treatment. We also examine some nonintuitive behavior in the dispersion results. copyright copyright 1999. The American Astronomical Society
Hydrodynamic Forces from Steep Waves in Rivers
Energy Technology Data Exchange (ETDEWEB)
Loevoll, A.
1996-12-31
The reservoir behind a hydroelectric power production dam has an enormous potential for destruction in case of a dam break. The present doctoral thesis evaluates the hydrodynamic forces from steep waves in rivers. In the laboratory, forces on a structure shaped as a vertical cylinder of rectangular cross section were measured, and the threshold condition for the bed sediment was investigated. A wave parameter {alpha} is introduced to describe the gradient of a wave front. The flow condition in the flume was reproduced by a 3-D numerical model. For various values of the wave parameter the forces were measured and compared to the drag force calculated from measured depth and velocity. From these comparisons the hydrodynamic force can be calculated as drag only, even in the case of a breaking wave front. The contribution from inertia relative to drag depends on the size of the structure. For larger structures the contributions may be important in steep waves. To study the initiation of motion (of sediments) under unsteady flow, waves of various parameter values were passed over a gravel covered bed. The initiation of motion starts before the peak of the wave, and is given by Shield`s relation if the friction slope is applied. No dependence upon the wave gradient was found. A relation was established which gives the critical shear stress if the friction slope is estimated by the bottom slope. 65 refs., 41 figs., 10 tabs.
Hydrodynamic Forces from Steep Waves in Rivers
International Nuclear Information System (INIS)
Loevoll, A.
1996-01-01
The reservoir behind a hydroelectric power production dam has an enormous potential for destruction in case of a dam break. The present doctoral thesis evaluates the hydrodynamic forces from steep waves in rivers. In the laboratory, forces on a structure shaped as a vertical cylinder of rectangular cross section were measured, and the threshold condition for the bed sediment was investigated. A wave parameter α is introduced to describe the gradient of a wave front. The flow condition in the flume was reproduced by a 3-D numerical model. For various values of the wave parameter the forces were measured and compared to the drag force calculated from measured depth and velocity. From these comparisons the hydrodynamic force can be calculated as drag only, even in the case of a breaking wave front. The contribution from inertia relative to drag depends on the size of the structure. For larger structures the contributions may be important in steep waves. To study the initiation of motion (of sediments) under unsteady flow, waves of various parameter values were passed over a gravel covered bed. The initiation of motion starts before the peak of the wave, and is given by Shield's relation if the friction slope is applied. No dependence upon the wave gradient was found. A relation was established which gives the critical shear stress if the friction slope is estimated by the bottom slope. 65 refs., 41 figs., 10 tabs
Hydrodynamic modeling and explosive compaction of ceramics
International Nuclear Information System (INIS)
Hoenig, C.; Holt, A.; Finger, M.; Kuhl, W.
1977-01-01
High-density ceramics with high-strength microstructure were achieved by explosive compaction. Well-characterized Al 2 O 3 , AlN, and boron powders were explosively compacted in both cylindrical and flat plate geometries. In cylindrical geometries compacted densities between 91 and 98 percent of theoretical were achieved. Microhardness measurements indicated that the strength and integrity of the microstructure were comparable to conventionally fabricated ceramics, even though all samples with densities greater than 90 percent theoretical contained macrocracks. Fractured surfaces evaluated by SEM showed evidence of boundary melting. Equation of state data for porous Al 2 O 3 were used to calculate the irreversible work done on the sample as a function of pressure. This was expressed as a percentage of the total sample which could be melted. Calculations show that very little melting can be expected in samples shocked to less than 3 GPa. Significant melting and grain boundary fusion can be expected in samples shocked to pressures greater than 8 GPa. Hydrodynamic modeling of right cylinder compaction with detonation at one end was attempted by using a two-dimensional computer code. The complications of this analysis led to experiments using plane shock waves. Flat-plate compaction assemblies were designed and analyzed by 2-D hydrodynamic codes. The use of porous shock attenuators was evaluated. Experiments were performed on aluminum oxide powders in plane wave geometry. Microstructure evaluations were made as a function of location in the flat plate samples. 11 figures, 1 table
'Dodo' and 'Baby Bear' Trenches
2008-01-01
NASA's Phoenix Mars Lander's Surface Stereo Imager took this image on Sol 11 (June 5, 2008), the eleventh day after landing. It shows the trenches dug by Phoenix's Robotic Arm. The trench on the left is informally called 'Dodo' and was dug as a test. The trench on the right is informally called 'Baby Bear.' The sample dug from Baby Bear will be delivered to the Phoenix's Thermal and Evolved-Gas Analyzer, or TEGA. The Baby Bear trench is 9 centimeters (3.1 inches) wide and 4 centimeters (1.6 inches) deep. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.
Removal of Microcystis aeruginosa using hydrodynamic cavitation: performance and mechanisms.
Li, Pan; Song, Yuan; Yu, Shuili
2014-10-01
Algal blooms are a seasonal problem in eutrophic water bodies, and novel approaches to algal removal are required. The effect of hydrodynamic cavitation (HC) on the removal of Microcystis aeruginosa was investigated using a laboratory scale device. Samples treated by HC were subsequently grown under illuminated culture conditions. The results demonstrated that a short treatment with HC could effectively settle naturally growing M. aeruginosa without breaking cells. Algal cell density and chlorophyll-a of a sample treated for 10 min were significantly decreased by 88% andv 94%, respectively, after 3 days culture. Various HC operating parameters were investigated, showing that inhibition of M. aeruginosa growth mainly depended on treatment time and pump pressure. Electron microscopy confirmed that sedimentation of algae was attributable to the disruption of intracellular gas vesicles. Damage to the photosynthetic apparatus also contributed to the inhibition of algal growth. Free radicals produced by the cavitation process could be as an indirect indicator of the intensity of HC treatment, although they inflicted minimal damage on the algae. In conclusion, we suggest that HC represents a potentially highly effective and sustainable approach to the removal of algae from water systems. Copyright © 2014 Elsevier Ltd. All rights reserved.
Investigation of hydrodynamic behaviour of membranes using radiotracer techniques
Directory of Open Access Journals (Sweden)
Zakrzewska-Trznadel G.
2013-05-01
Full Text Available The aim of the work was to study membrane devices using short-lived radioisotopes like Ba-137m and Ga-68 as tracers. These radioisotopes were obtained from radionuclide generators: Cs-137/Ba-137m and Ge-68/Ga-68. The first radionuclide, namely Ba-137m with a half-life of 2.55 minutes was applied as a liquid phase tracer for studying hydrodynamic conditions inside the membrane apparatus. The membrane module with ceramic membranes was tested by using Ba-137m. The experiments showed that this radionuclide with a short half-life is a perfect tracer for liquid phase, whereas Ga-68 with longer half-life equal to 68 minutes was considered as a solid phase (bentonite tracer. Ga-68 was used to gain more knowledge about the phenomena occurring in the membrane boundary layer. After kinetic studies of isotope adsorption into the carrier material, the growth rate of the deposit layer as well as deposit's thickness on the flat-sheet membrane were studied. The influence of such process parameters like pressure, linear velocity of liquid and feed concentration on formation of the bentonite layer on the membrane surface was studied.
Energy Technology Data Exchange (ETDEWEB)
Reese, Jason A; Keenihan, James R; Gaston, Ryan S; Kauffmann, Keith L; Langmaid, Joseph A; Lopez, Leonardo; Maak, Kevin D; Mills, Michael E; Ramesh, Narayan; Teli, Samar R
2017-03-21
The present invention is premised upon an improved photovoltaic device ("PV device"), more particularly to an improved photovoltaic device with a multilayered photovoltaic cell assembly and a body portion joined at an interface region and including an intermediate layer, at least one interconnecting structural member, relieving feature, unique component geometry, or any combination thereof.
Reese, Jason A.; Keenihan, James R.; Gaston, Ryan S.; Kauffmann, Keith L.; Langmaid, Joseph A.; Lopez, Leonardo C.; Maak, Kevin D.; Mills, Michael E.; Ramesh, Narayan; Teli, Samar R.
2015-06-02
The present invention is premised upon an improved photovoltaic device ("PV device"), more particularly to an improved photovoltaic device with a multilayered photovoltaic cell assembly and a body portion joined at an interface region and including an intermediate layer, at least one interconnecting structural member, relieving feature, unique component geometry, or any combination thereof.
Reese, Jason A.; Keenihan, James R.; Gaston, Ryan S.; Kauffmann, Keith L.; Langmaid, Joseph A.; Lopez, Leonardo C.; Maak, Kevin D.; Mills, Michael E.; Ramesh, Narayan; Teli, Samar R.
2015-09-01
The present invention is premised upon an improved photovoltaic device ("PV device"), more particularly to an improved photovoltaic device (10) with a multilayered photovoltaic cell assembly (100) and a body portion (200) joined at an interface region (410) and including an intermediate layer (500), at least one interconnecting structural member (1500), relieving feature (2500), unique component geometry, or any combination thereof.
Maintenance free gas bearing helium blower for nuclear plant
Molyneaux, A., Dr; Harris, M., Prof; Sharkh, S., Prof; Hill, S.; de Graaff, T.
2017-08-01
This paper describes the design, testing and operation of novel helium blowers used to recirculate the helium blanketing gas in the nuclear reactor used as a neutron source at the Institut Laue Langevan, Grenoble, France. The laser sintered shrouded centrifugal wheel operates at speeds up to 45000 rpm supported on helium lubricated hydrodynamic spiral groove bearings, and is driven by a sensorless permanent magnet motor. The entire machine is designed to keep the helium gas (polluted by a small amount of D2O) out of contact with any iron or copper materials which would contribute to the corrosion of parts of the circuit. It is designed to have zero maintenance during a lifetime of 40,000 hours of continuous operation. This paper will describe the spiral groove journal and thrust bearings. Design and manufacture of the 1 kW motor and centrifugal wheel will be explained including their CFD and FEA analyses. Measurements of rotor displacement will be presented showing the behaviour under factory testing as well as details of the measured centrifugal wheel and motor performances. Two machines are incorporated into the circuit to provide redundancy and the first blower has been in continuous operation since Jan 2015. The blower was designed, manufactured, assembled and tested in the UK using predominantly UK suppliers.
Journal Bearing Analysis Suite Released for Planetary Gear System Evaluation
Brewe, David E.; Clark, David A.
2005-01-01
Planetary gear systems are an efficient means of achieving high reduction ratios with minimum space and weight. They are used in helicopter, aerospace, automobile, and many industrial applications. High-speed planetary gear systems will have significant dynamic loading and high heat generation. Hence, they need jet lubrication and associated cooling systems. For units operating in critical applications that necessitate high reliability and long life, that have very large torque loading, and that have downtime costs that are significantly greater than the initial cost, hydrodynamic journal bearings are a must. Computational and analytical tools are needed for sufficiently accurate modeling to facilitate optimal design of these systems. Sufficient physics is needed in the model to facilitate parametric studies of design conditions that enable optimal designs. The first transient journal bearing code to implement the Jacobsson-Floberg-Olsson boundary conditions, using a mass-conserving algorithm devised by Professor Emeritus Harold Elrod of Columbia University, was written by David E. Brewe of the U.S. Army at the NASA Lewis Research Center1 in 1983. Since then, new features and improved modifications have been built into the code by several contributors supported through Army and NASA funding via cooperative agreements with the University of Toledo (Professor Ted Keith, Jr., and Dr. Desikakary Vijayaraghavan) and National Research Council Programs (Dr. Vijayaraghavan). All this was conducted with the close consultation of Professor Elrod and the project management of David Brewe.
Removal of blue-green algae using the hybrid method of hydrodynamic cavitation and ozonation.
Wu, Zhilin; Shen, Haifeng; Ondruschka, Bernd; Zhang, Yongchun; Wang, Weimin; Bremner, David H
2012-10-15
A suspension of Microcystis aeruginosa (30 μg L(-1)chlorophyll a) was circulated in a hydrodynamic cavitation device and ozone was introduced at the suction side of the pump. The removal of algae over 10 min using hydrodynamic cavitation alone and ozone alone is less than 15% and 35%, respectively. The destruction of algae rises significantly from 24% in the absence of the orifice to 91% with the optimized orifice on 5 min of processing using hydrodynamic cavitation along with ozone (HC/O(3)) and the utilization of ozone increases from 32% to 61%. Interestingly, the suction process is more effective than the extrusion method (positive pressure) and the optimal bulk temperature for algal elimination was found to be 20 °C. Increasing the input concentration of ozone is favorable for the removal of algae but leads to a greater loss of ozone and a decrease in the utilization of ozone. Under the optimal conditions, the algal cells and chlorophyll a are completely destroyed in 10 min by use of the hybrid method. Copyright © 2012 Elsevier B.V. All rights reserved.
Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry.
Xiao, Feng; Li, Xiaoyan; Lam, Kitming; Wang, Dongsheng
2012-01-01
The hydrodynamic behavior of diatom aggregates has a significant influence on the interactions and flocculation kinetics of algae. However, characterization of the hydrodynamics of diatoms and diatom aggregates in water is rather difficult. In this laboratory study, an advanced visualization technique in particle image velocimetry (PIV) was employed to investigate the hydrodynamic properties of settling diatom aggregates. The experiments were conducted in a settling column filled with a suspension of fluorescent polymeric beads as seed tracers. A laser light sheet was generated by the PIV setup to illuminate a thin vertical planar region in the settling column, while the motions of particles were recorded by a high speed charge-coupled device (CCD) camera. This technique was able to capture the trajectories of the tracers when a diatom aggregate settled through the tracer suspension. The PIV results indicated directly the curvilinear feature of the streamlines around diatom aggregates. The rectilinear collision model largely overestimated the collision areas of the settling particles. Algae aggregates appeared to be highly porous and fractal, which allowed streamlines to penetrate into the aggregate interior. The diatom aggregates have a fluid collection efficiency of 10%-40%. The permeable feature of aggregates can significantly enhance the collisions and flocculation between the aggregates and other small particles including algal cells in water.
Shao, Meng; Xiao, Chengsi; Sun, Jinwei; Shao, Zhuxiao; Zheng, Qiuhong
2017-12-01
The paper analyzes hydrodynamic characteristics and the strength of a novel dot-matrix oscillating wave energy converter, which is in accordance with nowadays’ research tendency: high power, high efficiency, high reliability and low cost. Based on three-dimensional potential flow theory, the paper establishes motion control equations of the wave energy converter unit and calculates wave loads and motions. On this basis, a three-dimensional finite element model of the device is built to check its strength. Through the analysis, it can be confirmed that the WEC is feasible and the research results could be a reference for wave energy’s exploration and utilization.
Hydrodynamic simulations of light ion beam-matter interactions: ablative acceleration of thin foils
International Nuclear Information System (INIS)
Devore, C.R.; Gardner, J.H.; Boris, J.P.; Mosher, D.
1984-01-01
A one-dimensional model is used to study the hydrodynamic response of thin foils to bombardment by an intense proton beam. The beam targets are single- and multilayer planar foils of gold and polystyrene. The main conclusion is that the efficiency of conversion of incident beam energy to directed kinetic energy of the target is maximized by using a multilayer design. For beam parameters associated with the Gamble II device at the Naval Research Laboratory, the simulations yield payload velocities of over 5 cm/μs and energy conversion efficiencies of over 30%. The implications of these results for inertial confinement fusion research are discussed. (author)
Sassa, S.
2017-12-01
This presentation shows some recent research advances on tsunami-seabed-structure interaction following the 2011 Tohoku Earthquake Tsunami, Japan. It presents a concise summary and discussion of utilizing a geotechnical centrifuge and a large-scale hydro flume for the modelling of tsunami-seabed-structure interaction. I highlight here the role of tsunami-induced seepage in piping/boiling, erosion and bearing capacity decrease and failure of the rubble/seabed foundation. A comparison and discussion are made on the stability assessment for the design of tsunami-resistant structures on the basis of the results from both geo-centrifuge and large-scale hydrodynamic experiments. The concurrent processes of the instability involving the scour of the mound/sandy seabed, bearing capacity failure and flow of the foundation and the failure of caisson breakwaters under tsunami overflow and seepage coupling are made clear in this presentation. Three series of experiments were conducted under fifty gravities. The first series of experiments targeted the instability of the mounds themselves, and the second series of experiments clarified how the mound scour would affect the overall stability of the caissons. The third series of experiments examined the effect of a countermeasure on the basis of the results from the two series of experiments. The experimental results first demonstrated that the coupled overflow-seepage actions promoted the development of the mound scour significantly, and caused bearing capacity failure of the mound, resulting in the total failure of the caisson breakwater, which otherwise remained stable without the coupling effect. The velocity vectors obtained from the high-resolution image analysis illustrated the series of such concurrent scour/bearing-capacity-failure/flow processes leading to the instability of the breakwater. The stability of the breakwaters was significantly improved with decreasing hydraulic gradient underneath the caissons due to an
Hydrodynamic cavitation: a bottom-up approach to liquid aeration
Raut, J.S.; Stoyanov, S.D.; Duggal, C.; Pelan, E.G.; Arnaudov, L.N.; Naik, V.M.
2012-01-01
We report the use of hydrodynamic cavitation as a novel, bottom-up method for continuous creation of foams comprising of air microbubbles in aqueous systems containing surface active ingredients, like proteins or particles. The hydrodynamic cavitation was created using a converging-diverging nozzle.
Hydrodynamics of ponderomotive interactions in a collisionless plasma
International Nuclear Information System (INIS)
Kono, M.; Skoric, M.M.; ter Haar, D.
1987-01-01
A hydrodynamic treatment of ponderomotive interactions in a collisionless plasma is presented and it is shown that consistent hydrodynamics leads to the correct expression for the solenoidal ponderomotive electron current density, a result previously thought to be derivable only in the framework of the warm-plasma kinetic theory
Three aspects of critical phenomenons: fundamental, hydrodynamic, conceptual
International Nuclear Information System (INIS)
Beysens, D.
1993-01-01
After a recall of the leading results relative to the universality class of fluids, examples of how well known universal prevision are held in check by fluids specificities, especially hydrodynamics. Applications of critical phenomenons tool to damping, hydrodynamic instabilities, turbulence are described. (A.B.). 11 refs., 7 figs., 1 tab
Hydrodynamics of a Multistage Wet Scrubber Incineration Conditions
Said, M. M.; Manyele, S. V.; Raphael, M. L.
2012-01-01
The objective of the study was to determine the hydrodynamics of the two stage counter-current cascade wet scrubbers used during incineration of medical waste. The dependence of the hydrodynamics on two main variables was studied: Inlet air flow rate and inlet liquid flow rate. This study introduces a new wet scrubber operating features, which are…
Behavior of passive admixture in a vortical hydrodynamic field
Bobrov, R.O.; Kyrylyuk, A.V; Zatovsky, A.V.
2006-01-01
The motion of passive admixture of spherical particles in the stationary hydrodynamic field of a swirling flow is studied. A spherical particle of a given mass in the hydrodynamic field of a swirling flow is located on a certain circular orbit, where the centrifugal force is compensated by the
International Nuclear Information System (INIS)
Yabana, Shuichi; Matsuda, Akihiro
2003-01-01
In this study, design procedure on three-dimensional base isolation system is developed. Base isolation system proposed by CRIEPI uses thick rubber bearing and damper as isolation device. As for thick rubber bearings, design formula for evaluating vertical stiffness is proposed, and design conditions regarding size and vertical pressure are investigated. Figure-U type lead damper is proposed as three-dimensional damper and by loading tests its mechanical characteristics is evaluated. The concept of multi-layered interconnected rubber bearing, which is advantageous over large scale bearing in manufacturability, is proposed and its good performance is confirmed by the loading test. Through the response analyses, it is shown the rocking response of the proposed three-dimensional base isolation system is very small and not influential to the system, and the reduction of the vertical response is attained using the proposed isolation device. (author)
Tauviqirrahman, M.; Bayuseno, A. P.; Muchammad, Jamari, J.
2016-04-01
Surfaces with high superoleophobicity have attracted important attention because of their potential applications in scientific and industrial field. Especially classical metal bearing are faced with lubrication problem, because metal surface shows typically oleophilicity. The development of superolephobic metal surfaces which repel oil liquid droplet have significant applications in preventing the stiction. In addition, for classical bearing with texturing, the cavitation occurence is often considered as the main cause of the deterioration of the lubrication performance and thus shorten the lifetime of the bearing. In the present study, the exploration of the influence of adding the superoleophobic layer on the improvement of the performance of partially textured bearing in preventing the cavitation was performed. Navier slip model was used to model the behavior of the superoleophobic layer. A formulation of the modified Reynolds equation with mass-conserving boundary conditions was derived and the pressure distribution was of particular interest. The equations of lubrication were discretized using a finite volume method and solved using a tri-diagonal-matrix-algortihm. In this calculation, it was shown that after introducing the superoleophobic layer at the leading edge of the contact, the cavitation occurence can be prevented and thus the increased hydrodynamic pressure is found. However, the results showed that for deeper texture, the deterioration of the load support is noted. This findings may have useful implications to extend the life time of textured bearing.
Biological implications of the hydrodynamics of swimming at or near the surface and in shallow water
International Nuclear Information System (INIS)
Blake, R W
2009-01-01
The origins and effects of wave drag at and near the surface and in shallow water are discussed in terms of the dispersive waves generated by streamlined technical bodies of revolution and by semi-aquatic and aquatic animals with a view to bearing on issues regarding the design and function of autonomous surface and underwater vehicles. A simple two-dimensional model based on energy flux, allowing assessment of drag and its associated wave amplitude, is applied to surface swimming in Lesser Scaup ducks and is in good agreement with measured values. It is argued that hydrodynamic limitations to swimming at speeds associated with the critical Froude number (∼0.5) and hull speed do not necessarily set biological limitations as most behaviours occur well below the hull speed. From a comparative standpoint, the need for studies on the hull displacement of different forms is emphasized. For forms in surface proximity, drag is a function of both Froude and Reynolds numbers. Whilst the depth dependence of wave drag is not particularly sensitive to Reynolds number, its magnitude is, with smaller and slower forms subject to relatively less drag augmentation than larger, faster forms that generate additional resistance due to ventilation and spray. A quasi-steady approach to the hydrodynamics of swimming in shallow water identifies substantial drag increases relative to the deeply submerged case at Froude numbers of about 0.9 that could limit the performance of semi-aquatic and aquatic animals and autonomous vehicles. A comparative assessment of fast-starting trout and upside down catfish shows that the energy losses of fast-starting fish are likely to be less for fish in surface proximity in deep water than for those in shallow water. Further work on unsteady swimming in both circumstances is encouraged. Finally, perspectives are offered as to how autonomous surface and underwater vehicles in surface proximity and shallow water could function to avoid prohibitive
Biological implications of the hydrodynamics of swimming at or near the surface and in shallow water
Energy Technology Data Exchange (ETDEWEB)
Blake, R W [Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada)], E-mail: blake@zoology.ubc.ca
2009-03-01
The origins and effects of wave drag at and near the surface and in shallow water are discussed in terms of the dispersive waves generated by streamlined technical bodies of revolution and by semi-aquatic and aquatic animals with a view to bearing on issues regarding the design and function of autonomous surface and underwater vehicles. A simple two-dimensional model based on energy flux, allowing assessment of drag and its associated wave amplitude, is applied to surface swimming in Lesser Scaup ducks and is in good agreement with measured values. It is argued that hydrodynamic limitations to swimming at speeds associated with the critical Froude number ({approx}0.5) and hull speed do not necessarily set biological limitations as most behaviours occur well below the hull speed. From a comparative standpoint, the need for studies on the hull displacement of different forms is emphasized. For forms in surface proximity, drag is a function of both Froude and Reynolds numbers. Whilst the depth dependence of wave drag is not particularly sensitive to Reynolds number, its magnitude is, with smaller and slower forms subject to relatively less drag augmentation than larger, faster forms that generate additional resistance due to ventilation and spray. A quasi-steady approach to the hydrodynamics of swimming in shallow water identifies substantial drag increases relative to the deeply submerged case at Froude numbers of about 0.9 that could limit the performance of semi-aquatic and aquatic animals and autonomous vehicles. A comparative assessment of fast-starting trout and upside down catfish shows that the energy losses of fast-starting fish are likely to be less for fish in surface proximity in deep water than for those in shallow water. Further work on unsteady swimming in both circumstances is encouraged. Finally, perspectives are offered as to how autonomous surface and underwater vehicles in surface proximity and shallow water could function to avoid prohibitive
Electromagnetic device of linear displacement
International Nuclear Information System (INIS)
Savary, F.; Le Saulnier, G.
1986-01-01
The device moves a rod integral with a nuclear reactor control element. It has a grab for the rod operated by a mobil pole drive by a coil carried by a surrounding sealed casing, a second grab with fixed and mobile poles with facing surfaces shaped to limit the variation of magnetic force with distance between them, and a plunger driven by a coil to bear against another mobile pole moved by a coil. The invention proposes a device ensuring a displacement while the impact forces at the different level of the mechanism are reduced [fr
Aguayo-Ortiz, A; Mendoza, S; Olvera, D
2018-01-01
In this article we develop a Primitive Variable Recovery Scheme (PVRS) to solve any system of coupled differential conservative equations. This method obtains directly the primitive variables applying the chain rule to the time term of the conservative equations. With this, a traditional finite volume method for the flux is applied in order avoid violation of both, the entropy and "Rankine-Hugoniot" jump conditions. The time evolution is then computed using a forward finite difference scheme. This numerical technique evades the recovery of the primitive vector by solving an algebraic system of equations as it is often used and so, it generalises standard techniques to solve these kind of coupled systems. The article is presented bearing in mind special relativistic hydrodynamic numerical schemes with an added pedagogical view in the appendix section in order to easily comprehend the PVRS. We present the convergence of the method for standard shock-tube problems of special relativistic hydrodynamics and a graphical visualisation of the errors using the fluctuations of the numerical values with respect to exact analytic solutions. The PVRS circumvents the sometimes arduous computation that arises from standard numerical methods techniques, which obtain the desired primitive vector solution through an algebraic polynomial of the charges.
Shrestha, Bishwash; Ahsan, Syed N.; Aureli, Matteo
2018-01-01
In this paper, we present a comprehensive experimental study on harmonic oscillations of a submerged rigid plate in a quiescent, incompressible, Newtonian, viscous fluid. The fluid-structure interaction problem is analyzed from both qualitative and quantitative perspectives via a detailed particle image velocimetry (PIV) experimental campaign conducted over a broad range of oscillation frequency and amplitude parameters. Our primary goal is to identify the effect of the oscillation characteristics on the mechanisms of fluid-structure interaction and on the dynamics of vortex shedding and convection and to elucidate the behavior of hydrodynamic forces on the oscillating structure. Towards this goal, we study the flow in terms of qualitative aspects of its pathlines, vortex shedding, and symmetry breaking phenomena and identify distinct hydrodynamic regimes in the vicinity of the oscillating structure. Based on these experimental observations, we produce a novel phase diagram detailing the occurrence of distinct hydrodynamic regimes as a function of relevant governing nondimensional parameters. We further study the hydrodynamic forces associated with each regime using both PIV and direct force measurement via a load cell. Our quantitative results on experimental estimation of hydrodynamic forces show good agreement against predictions from the literature, where numerical and semi-analytical models are available. The findings and observations in this work shed light on the relationship between flow physics, vortex shedding, and convection mechanisms and the hydrodynamic forces acting on a rigid oscillating plate and, as such, have relevance to various engineering applications, including energy harvesting devices, biomimetic robotic system, and micro-mechanical sensors and actuators.
Hydrodynamic Coefficients Identification and Experimental Investigation for an Underwater Vehicle
Directory of Open Access Journals (Sweden)
Shaorong XIE
2014-02-01
Full Text Available Hydrodynamic coefficients are the foundation of unmanned underwater vehicles modeling and controller design. In order to reduce identification complexity and acquire necessary hydrodynamic coefficients for controllers design, the motion of the unmanned underwater vehicle was separated into vertical motion and horizontal motion models. Hydrodynamic coefficients were regarded as mapping parameters from input forces and moments to output velocities and acceleration of the unmanned underwater vehicle. The motion models of the unmanned underwater vehicle were nonlinear and Genetic Algorithm was adopted to identify those hydrodynamic coefficients. To verify the identification quality, velocities and acceleration of the unmanned underwater vehicle was measured using inertial sensor under the same conditions as Genetic Algorithm identification. Curves similarity between measured velocities and acceleration and those identified by Genetic Algorithm were used as optimizing standard. It is found that the curves similarity were high and identified hydrodynamic coefficients of the unmanned underwater vehicle satisfied the measured motion states well.
Advanced Active-Magnetic-Bearing Thrust-Measurement System
Imlach, Joseph; Kasarda, Mary; Blumber, Eric
2008-01-01
An advanced thrust-measurement system utilizes active magnetic bearings to both (1) levitate a floating frame in all six degrees of freedom and (2) measure the levitation forces between the floating frame and a grounded frame. This system was developed for original use in measuring the thrust exerted by a rocket engine mounted on the floating frame, but can just as well be used in other force-measurement applications. This system offers several advantages over prior thrust-measurement systems based on mechanical support by flexures and/or load cells: The system includes multiple active magnetic bearings for each degree of freedom, so that by selective use of one, some, or all of these bearings, it is possible to test a given article over a wide force range in the same fixture, eliminating the need to transfer the article to different test fixtures to obtain the benefit of full-scale accuracy of different force-measurement devices for different force ranges. Like other active magnetic bearings, the active magnetic bearings of this system include closed-loop control subsystems, through which the stiffness and damping characteristics of the magnetic bearings can be modified electronically. The design of the system minimizes or eliminates cross-axis force-measurement errors. The active magnetic bearings are configured to provide support against movement along all three orthogonal Cartesian axes, and such that the support along a given axis does not produce force along any other axis. Moreover, by eliminating the need for such mechanical connections as flexures used in prior thrust-measurement systems, magnetic levitation of the floating frame eliminates what would otherwise be major sources of cross-axis forces and the associated measurement errors. Overall, relative to prior mechanical-support thrust-measurement systems, this system offers greater versatility for adaptation to a variety of test conditions and requirements. The basic idea of most prior active-magnetic-bearing
The correct "ball bearings" data.
Caroni, C
2002-12-01
The famous data on fatigue failure times of ball bearings have been quoted incorrectly from Lieblein and Zelen's original paper. The correct data include censored values, as well as non-fatigue failures that must be handled appropriately. They could be described by a mixture of Weibull distributions, corresponding to different modes of failure.
Little Bear Fire Summary Report
Sarah McCaffrey; Melanie Stidham; Hannah. Brenkert-Smith
2013-01-01
In June 2012, immediately after the Little Bear Fire burned outside Ruidoso, New Mexico, a team of researchers interviewed fire managers, local personnel, and residents to understand perceptions of the event itself, communication, evacuation, and pre-fire preparedness. The intensity of fire behavior and resulting loss of 242 homes made this a complex fire with a...
Satellite monitoring of black bear.
Craighead, J. J.; Craighead, F. C., Jr.; Varney, J. R.; Cote, C. E.
1971-01-01
Description of a feasibility experiment recently performed to test the use of a satellite system for telemetering environmental and physiological data from the winter den of a 'hibernating' black bear, Ursus americanus. The instrumentation procedure and evaluations of the equipment performance and sensory data obtained are discussed in detail.
Genomic evidence of geographically widespread effect of gene flow from polar bears into brown bears
Cahill, James A; Stirling, Ian; Kistler, Logan; Salamzade, Rauf; Ersmark, Erik; Fulton, Tara L; Stiller, Mathias; Green, Richard E; Shapiro, Beth
2015-01-01
© 2014 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd. Polar bears are an arctic, marine adapted species that is closely related to brown bears. Genome analyses have shown that polar bears are distinct and genetically homogeneous in comparison to brown bears. However, these analyses have also revealed a remarkable episode of polar bear gene flow into the population of brown bears that colonized the Admiralty, Baranof and Chichagof islands (ABC islands) of Alaska. Here, we...
Technical specifications for the successful fabrication of laminated seismic isolation bearings
Energy Technology Data Exchange (ETDEWEB)
Kulak, R F [Argonne National Laboratory, Argonne, IL (United States)
1992-07-01
High damping steel-laminated elastomeric seismic isolation bearings are becoming a preferred device for isolating large buildings and structures. In the United States, the current reference design for the Advanced Liquid Metal Reactor uses laminated bearings for seismic isolation. These bearings are constructed from alternating layers of rubber and steel plates. They are typically designed for shear strains between 50 to 100 percent and expected to sustain two to three times these levels for beyond design basis loading considerations. The technical specifications used to procure these bearings are an important factor in assuring thatthe bearings meet the performance requirements of the design. The key aspects of the current version of the Technical Specifications are discussed in this paper. (author)
Technical specifications for the successful fabrication of laminated seismic isolation bearings
International Nuclear Information System (INIS)
Kulak, R.F.
1992-01-01
High damping laminated elastomeric bearings are becoming one of the preferred devices for isolating large buildings and structures. IN the United States, the current reference design for the Advanced Liquid Metal Reactor uses laminated bearings for seismic isolation. These bearing are constructed from alternating layers of rubber and steel plates. They are typically designed for shear strains between 50 to 100 percent and expected to sustain two to three times these levels for beyond design basis loading considerations. The technical specifications used to procure these bearings are an important factor in assuring that the bearings that are installed under nuclear structures meet the performance requirements of the design. The key aspects of the current version of the Technical Specifications are discussed in this paper
International Nuclear Information System (INIS)
Kim, Min Kyu; Kim, Jung-Han; Choi, In-Kil
2014-01-01
Dynamic characteristic tests of full scale lead rubber bearing were performed for the evaluation of performance criteria of isolation system for nuclear power plants. For the dynamic test for a full scale rubber bearing, two 1500mm diameter lead rubber bearings were manufactured. The viewpoints of this dynamic test are determination of an ultimate shear strain level of lead rubber bearing, behavior of rubber bearing according to static and dynamic input motion, sinusoidal and random (earthquake) motion, and 1-dimentional and 2-dimensional input motion. In this study, seismic isolation device tests were performed for the evaluation of performance criteria of isolation system. Through this test, it can be recognized that in the case of considering a mechanical property test, dynamic and multi degree of loading conditions should be determined. But these differences should be examined how much affect to the global structural behavior
Technical specifications for the successful fabrication of laminated seismic isolation bearings
International Nuclear Information System (INIS)
Kulak, R.F.
1992-01-01
High damping steel-laminated elastomeric seismic isolation bearings are becoming a preferred device for isolating large buildings and structures. In the United States, the current reference design for the Advanced Liquid Metal Reactor uses laminated bearings for seismic isolation. These bearings are constructed from alternating layers of rubber and steel plates. They are typically designed for shear strains between 50 to 100 percent and expected to sustain two to three times these levels for beyond design basis loading considerations. The technical specifications used to procure these bearings are an important factor in assuring that the bearings meet the performance requirements of the design. The key aspects of the current version of the Technical Specifications are discussed in this paper. (author)
Microscopic hydrodynamics study with nuclear track membrane
International Nuclear Information System (INIS)
Shilun Guo; Yuhua Zhao; Yulan Wang; Hiuhong Hao; Brandt, R.; Vater, P.
1988-01-01
Microscopic hydrodynamics has been studied using different liquids and nuclear track membranes with pores perpendicularly piercing through them. The flow rate of water and alcohol has been studied with polycarbonate track membranes with pore diameters 1.48 micrometres and 1.08 micrometres. It has been shown that the flow rate both for water and alcohol on a microscopic scale can be determined by the Poiseuille law which characterizes macroscopic laminar flow. The Reynolds number used in macroscopic fluid flow has been calculated from the flow rate and parameters of the liquids and the geometry of the pores. It has been shown that this Reynolds number can also be used to characterize microscopic flow. Based on the above results, the filtration capacity (or limit) of polycarbonate track microfilters for water had been calculated. Some possible limits on the application of the calculation are pointed out and discussed. (author)
Generalized hydrodynamic correlations and fractional memory functions
Rodríguez, Rosalio F.; Fujioka, Jorge
2015-12-01
A fractional generalized hydrodynamic (GH) model of the longitudinal velocity fluctuations correlation, and its associated memory function, for a complex fluid is analyzed. The adiabatic elimination of fast variables introduces memory effects in the transport equations, and the dynamic of the fluctuations is described by a generalized Langevin equation with long-range noise correlations. These features motivate the introduction of Caputo time fractional derivatives and allows us to calculate analytic expressions for the fractional longitudinal velocity correlation function and its associated memory function. Our analysis eliminates a spurious constant term in the non-fractional memory function found in the non-fractional description. It also produces a significantly slower power-law decay of the memory function in the GH regime that reduces to the well-known exponential decay in the non-fractional Navier-Stokes limit.
Hydrodynamic advantages of swimming by salp chains.
Sutherland, Kelly R; Weihs, Daniel
2017-08-01
Salps are marine invertebrates comprising multiple jet-propelled swimming units during a colonial life-cycle stage. Using theory, we show that asynchronous swimming with multiple pulsed jets yields substantial hydrodynamic benefit due to the production of steady swimming velocities, which limit drag. Laboratory comparisons of swimming kinematics of aggregate salps ( Salpa fusiformis and Weelia cylindrica ) using high-speed video supported that asynchronous swimming by aggregates results in a smoother velocity profile and showed that this smoother velocity profile is the result of uncoordinated, asynchronous swimming by individual zooids. In situ flow visualizations of W. cylindrica swimming wakes revealed that another consequence of asynchronous swimming is that fluid interactions between jet wakes are minimized. Although the advantages of multi-jet propulsion have been mentioned elsewhere, this is the first time that the theory has been quantified and the role of asynchronous swimming verified using experimental data from the laboratory and the field. © 2017 The Author(s).
Tears of Venom: Hydrodynamics of Reptilian Envenomation
Young, Bruce A.; Herzog, Florian; Friedel, Paul; Rammensee, Sebastian; Bausch, Andreas; van Hemmen, J. Leo
2011-05-01
In the majority of venomous snakes, and in many other reptiles, venom is conveyed from the animal’s gland to the prey’s tissue through an open groove on the surface of the teeth and not through a tubular fang. Here we focus on two key aspects of the grooved delivery system: the hydrodynamics of venom as it interacts with the groove geometry, and the efficiency of the tooth-groove-venom complex as the tooth penetrates the prey’s tissue. We show that the surface tension of the venom is the driving force underlying the envenomation dynamics. In so doing, we explain not only the efficacy of the open groove, but also the prevalence of this mechanism among reptiles.
Modeling the hydrodynamics of Phloem sieve plates
DEFF Research Database (Denmark)
Jensen, Kaare Hartvig; Mullendore, Daniel Leroy; Holbrook, Noel Michele
2012-01-01
Sieve plates have an enormous impact on the efficiency of the phloem vascular system of plants, responsible for the distribution of photosynthetic products. These thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play...... understood. We propose a theoretical model for quantifying the effect of sieve plates on the phloem in the plant, thus unifying and improving previous work in the field. Numerical simulations of the flow in real and idealized phloem channels verify our model, and anatomical data from 19 plant species...... a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged. The resistance to the flow of viscous sap in the phloem vascular system is strongly affected by the presence of the sieve plates, but the hydrodynamics of the flow through them remains poorly...
An analytical model of flagellate hydrodynamics
DEFF Research Database (Denmark)
Dölger, Julia; Bohr, Tomas; Andersen, Anders Peter
2017-01-01
solution by Oseen for the low Reynolds number flow due to a point force outside a no-slip sphere. The no-slip sphere represents the cell and the point force a single flagellum. By superposition we are able to model a freely swimming flagellate with several flagella. For biflagellates with left......–right symmetric flagellar arrangements we determine the swimming velocity, and we show that transversal forces due to the periodic movements of the flagella can promote swimming. For a model flagellate with both a longitudinal and a transversal flagellum we determine radius and pitch of the helical swimming......Flagellates are unicellular microswimmers that propel themselves using one or several beating flagella. We consider a hydrodynamic model of flagellates and explore the effect of flagellar arrangement and beat pattern on swimming kinematics and near-cell flow. The model is based on the analytical...
Flow stabilization with active hydrodynamic cloaks.
Urzhumov, Yaroslav A; Smith, David R
2012-11-01
We demonstrate that fluid flow cloaking solutions, based on active hydrodynamic metamaterials, exist for two-dimensional flows past a cylinder in a wide range of Reynolds numbers (Re's), up to approximately 200. Within the framework of the classical Brinkman equation for homogenized porous flow, we demonstrate using two different methods that such cloaked flows can be dynamically stable for Re's in the range of 5-119. The first highly efficient method is based on a linearization of the Brinkman-Navier-Stokes equation and finding the eigenfrequencies of the least stable eigenperturbations; the second method is a direct numerical integration in the time domain. We show that, by suppressing the von Kármán vortex street in the weakly turbulent wake, porous flow cloaks can raise the critical Reynolds number up to about 120 or five times greater than for a bare uncloaked cylinder.
Hydrodynamic Interactions in Active and Passive Matter
Krafnick, Ryan C.
Active matter is present at all biological length scales, from molecular apparatuses interior to cells, to swimming microscopic organisms, to birds, fish, and people. Its properties are varied and its applications diverse, but our understanding of the fundamental driving forces of systems with these constituents remains incomplete. This thesis examines active matter suspensions, exploring the role of hydrodynamic interactions on the unique and emergent properties therein. Both qualitative and quantitative impacts are considered, and care is taken in determining the physical origin of the results in question. It is found that fluid dynamical interactions are fundamentally, qualitatively important, and much of the properties of a system can be explained with an effective energy density defined via the fluid fields arising from the embedded self-propelling entities themselves.
Using river locks to teach hydrodynamic concepts
Carvalho-Santos, Vagson L.; Mendes, Thales C.; Silva, Enisvaldo C.; Rios, Márcio L.; Silva, Anderson A. P.
2013-11-01
In this work, the use of a river lock as a non-formal setting for teaching hydrodynamical concepts is proposed. In particular, we describe the operation of a river lock situated at the Sobradinho dam, on the São Francisco River (Brazil). A model to represent and to analyse the dynamics of river lock operation is presented and we derive the dynamical equations for the rising of the water column as an example to understand the Euler equation. Furthermore, with this activity, we enable the integration of content initially introduced in the classroom with practical applications, thereby allowing the association of physical themes to content relevant in disciplines such as history and geography. In addition, experiences of this kind enable teachers to talk about the environmental and social impacts caused by the construction of a dam and, consequently, a crossover of concepts has been made possible, leading to more meaningful learning for the students.
Hydrodynamics of compressible superfluids in confined geometries
International Nuclear Information System (INIS)
Malmi-Kakkada, Abdul N; Valls, Oriol T; Dasgupta, Chandan
2014-01-01
We present a study of the hydrodynamics of compressible superfluids in confined geometries. We use a perturbative procedure in terms of the dimensionless expansion parameter (v/v s ) 2 where v is the typical speed of the flow and v s is the speed of sound. A zero value of this parameter corresponds to the incompressible limit. We apply the procedure to two specific problems: the case of a trapped superfluid with a Gaussian profile of the local density, and that of a superfluid confined in a rotating obstructed cylinder. We find that the corrections due to finite compressibility which are, as expected, negligible for liquid He, are important but amenable to the perturbative treatment for typical ultracold atomic systems. (paper)
Using river locks to teach hydrodynamic concepts
International Nuclear Information System (INIS)
Carvalho-Santos, Vagson L; Mendes, Thales C; Silva, Enisvaldo C; Rios, Márcio L; Silva, Anderson A P
2013-01-01
In this work, the use of a river lock as a non-formal setting for teaching hydrodynamical concepts is proposed. In particular, we describe the operation of a river lock situated at the Sobradinho dam, on the São Francisco River (Brazil). A model to represent and to analyse the dynamics of river lock operation is presented and we derive the dynamical equations for the rising of the water column as an example to understand the Euler equation. Furthermore, with this activity, we enable the integration of content initially introduced in the classroom with practical applications, thereby allowing the association of physical themes to content relevant in disciplines such as history and geography. In addition, experiences of this kind enable teachers to talk about the environmental and social impacts caused by the construction of a dam and, consequently, a crossover of concepts has been made possible, leading to more meaningful learning for the students. (paper)
Hydrodynamical winds from a geometrically thin disk
International Nuclear Information System (INIS)
Fukue, Jun
1989-01-01
Hydrodynamical winds emanating from the surface of a geometrically thin disk under the gravitational field of the central object are examined. The attention is focused on the transonic nature of the flow. For a given configuration of streamlines, the flow fields are divided into three regions: the inner region where the gas near the disk plane is gravitationally bound to form a corona; the intermediate wind region where multiple critical points appear and the gas flows out from the disk passing through critical points; and the outer region where the gas is unbound to escape to infinity without passing through critical points. This behavior of disk winds is due to the shape of the gravitational potential of the central object along the streamline and due to the energy source distribution at the flow base on the disk plane where the potential in finite. (author)
Hydrodynamics, fields and constants in gravitational theory
International Nuclear Information System (INIS)
Stanyukovich, K.P.; Mel'nikov, V.N.
1983-01-01
Results of original inveatigations into problems of standard gravitation theory and its generalizations are presented. The main attention is paid to the application of methods of continuous media techniques in the gravitation theory; to the specification of the gravitation role in phenomena of macro- and microworld, accurate solutions in the case, when the medium is the matter, assigned by hydrodynamic energy-momentum tensor; and to accurate solutions for the case when the medium is the field. GRT generalizations are analyzed, such as the new cosmologic hypothesis which is based on the gravitation vacuum theory. Investigations are performed into the quantization of cosmological models, effects of spontaneous symmetry violation and particle production in cosmology. Graeity theory with fundamental Higgs field is suggested in the framework of which in the atomic unit number one can explain possible variations of the effective gravitational bonds, and in the gravitation bond, variations of masses of all particles
Hydrodynamic models for slurry bubble column reactors
Energy Technology Data Exchange (ETDEWEB)
Gidaspow, D. [IIT Center, Chicago, IL (United States)
1995-12-31
The objective of this investigation is to convert a {open_quotes}learning gas-solid-liquid{close_quotes} fluidization model into a predictive design model. This model is capable of predicting local gas, liquid and solids hold-ups and the basic flow regimes: the uniform bubbling, the industrially practical churn-turbulent (bubble coalescence) and the slugging regimes. Current reactor models incorrectly assume that the gas and the particle hold-ups (volume fractions) are uniform in the reactor. They must be given in terms of empirical correlations determined under conditions that radically differ from reactor operation. In the proposed hydrodynamic approach these hold-ups are computed from separate phase momentum balances. Furthermore, the kinetic theory approach computes the high slurry viscosities from collisions of the catalyst particles. Thus particle rheology is not an input into the model.
Formulating viscous hydrodynamics for large velocity gradients
International Nuclear Information System (INIS)
Pratt, Scott
2008-01-01
Viscous corrections to relativistic hydrodynamics, which are usually formulated for small velocity gradients, have recently been extended from Navier-Stokes formulations to a class of treatments based on Israel-Stewart equations. Israel-Stewart treatments, which treat the spatial components of the stress-energy tensor τ ij as dynamical objects, introduce new parameters, such as the relaxation times describing nonequilibrium behavior of the elements τ ij . By considering linear response theory and entropy constraints, we show how the additional parameters are related to fluctuations of τ ij . Furthermore, the Israel-Stewart parameters are analyzed for their ability to provide stable and physical solutions for sound waves. Finally, it is shown how these parameters, which are naturally described by correlation functions in real time, might be constrained by lattice calculations, which are based on path-integral formulations in imaginary time
Fish locomotion: kinematics and hydrodynamics of flexible foil-like fins
Lauder, George V.; Madden, Peter G. A.
2007-11-01
The fins of fishes are remarkable propulsive devices that appear at the origin of fishes about 500 million years ago and have been a key feature of fish evolutionary diversification. Most fish species possess both median (midline) dorsal, anal, and caudal fins as well as paired pectoral and pelvic fins. Fish fins are supported by jointed skeletal elements, fin rays, that in turn support a thin collagenous membrane. Muscles at the base of the fin attach to and actuate each fin ray, and fish fins thus generate their own hydrodynamic wake during locomotion, in addition to fluid motion induced by undulation of the body. In bony fishes, the jointed fin rays can be actively deformed and the fin surface can thus actively resist hydrodynamic loading. Fish fins are highly flexible, exhibit considerable deformation during locomotion, and can interact hydrodynamically during both propulsion and maneuvering. For example, the dorsal and anal fins shed a vortex wake that greatly modifies the flow environment experienced by the tail fin. New experimental kinematic and hydrodynamic data are presented for pectoral fin function in bluegill sunfish. The highly flexible sunfish pectoral fin moves in a complex manner with two leading edges, a spanwise wave of bending, and substantial changes in area through the fin beat cycle. Data from scanning particle image velocimetry (PIV) and time-resolved stereo PIV show that the pectoral fin generates thrust throughout the fin beat cycle, and that there is no time of net drag. Continuous thrust production is due to fin flexibility which enables some part of the fin to generate thrust at all times and to smooth out oscillations that might arise at the transition from outstroke to instroke during the movement cycle. Computational fluid dynamic analyses of sunfish pectoral fin function corroborate this conclusion. Future research on fish fin function will benefit considerably from close integration with studies of robotic model fins.
TOOL ASSEMBLY WITH BI-DIRECTIONAL BEARING
Longhurst, G.E.
1961-07-11
A two-direction motion bearing which is incorporated in a refueling nuclear fuel element trsnsfer tool assembly is described. A plurality of bi- directional bearing assembliesare fixed equi-distantly about the circumference of the transfer tool assembly to provide the tool assembly with a bearing surface- for both axial and rotational motion. Each bi-directional bearing assembly contains a plurality of circumferentially bulged rollers mounted in a unique arrangement which will provide a bearing surface for rotational movement of the tool assembly within a bore. The bi-direc tional bearing assembly itself is capable of rational motion and thus provides for longitudinal movement of the tool assembly.
Estimating Wear Of Installed Ball Bearings
Keba, John E.; Mcvey, Scott E.
1993-01-01
Simple inspection and measurement technique makes possible to estimate wear of balls in ball bearing, without removing bearing from shaft on which installed. To perform measurement, one observes bearing cage while turning shaft by hand to obtain integral number of cage rotations and to measure, to nearest 2 degrees, number of shaft rotations producing cage rotations. Ratio between numbers of cages and shaft rotations depends only on internal geometry of bearing and applied load. Changes in turns ratio reflect changes in internal geometry of bearing provided measurements made with similar bearing loads. By assuming all wear occurs on balls, one computes effective value for this wear from change in turns ratio.
Hydrodynamical fluctuations in smooth shear flows
International Nuclear Information System (INIS)
Chagelishvili, G.D.; Khujadze, G.R.; Lominadze, J.G.
1999-11-01
Background of hydrodynamical fluctuations in a intrinsically/stochastically forced, laminar, uniform shear flow is studied. The employment of so-called nonmodal mathematical analysis makes it possible to represent the background of fluctuations in a new light and to get more insight into the physics of its formation. The basic physical processes responsible for the formation of vortex and acoustic wave fluctuation backgrounds are analyzed. Interplay of the processes at low and moderate shear rates is described. Three-dimensional vortex fluctuations around a given macroscopic state are numerically calculated. The correlation functions of the fluctuations of physical quantities are analyzed. It is shown that there exists subspace D k in the wave-number space (k-space) that is limited externally by spherical surface with radius k ν ≡ A/ν (where A is the velocity shear parameter, ν - the kinematic viscosity) in the nonequilibrium open system under study. The spatial Fourier harmonics of vortex as well as acoustic wave fluctuations are strongly subjected by flow shear (by the open character of the system) at wave-numbers satisfying the condition k ν . Specifically it is shown that in D k : The fluctuations are non-Markovian; the spatial spectral density of energy of the vortex fluctuations by far exceeds the white-noise; the term of a new type associated to the hydrodynamical fluctuation of velocity appears in the correlation function of pressure; the fluctuation background of the acoustic waves is completely different at low and moderate shear rates (at low shear rates it is reduced in D k in comparison to the uniform (non-shear) flow; at moderate shear rates it it comparable to the background of the vortex fluctuations). The fluctuation background of both the vortex and the acoustic wave modes is anisotropic. The possible significance of the fluctuation background of vortices for the subcritical transition to turbulence and Brownian motion of small macroscopic
On the Hydrodynamics of Anomalocaris Tail Fins.
Sheppard, K A; Rival, D E; Caron, J-B
2018-04-25
Anomalocaris canadensis, a soft-bodied stem-group arthropod from the Burgess Shale, is considered the largest predator of the Cambrian period. Thanks to a series of lateral flexible lobes along its dorso-ventrally compressed body, it is generally regarded as an efficient swimmer, well-adapted to its predatory lifestyle. Previous theoretical hydrodynamic simulations have suggested a possible optimum in swimming performance when the lateral lobes performed as a single undulatory lateral fin, comparable to the pectoral fins in skates and rays. However, the role of the unusual fan-like tail of Anomalocaris has not been previously explored. Swimming efficiency and maneuverability deduced from direct hydrodynamic analysis are here studied in a towing tank facility using a three-vane physical model designed as an abstraction of the tail fin. Through direct force measurements, it was found that the model exhibited a region of steady-state lift and drag enhancement at angles of attack greater than 25° when compared to a triangular-shaped reference model. This would suggest that the resultant normal force on the tail fin of Anomalocaris made it well-suited for turning maneuvers, giving it the ability to turn quickly and through small radii of curvature. These results are consistent with an active predatory lifestyle, although detailed kinematic studies integrating the full organism, including the lateral lobes, would be required to test the effect of the tail fin on overall swimming performance. This study also highlights a possible example of evolutionary convergence between the tails of Anomalocaris and birds, which, in both cases, are well-adapted to efficient turning maneuvers.
Hydrodynamics of circulating and bubbling fluidized beds
International Nuclear Information System (INIS)
Gidaspow, D.P.; Tsuo, Y.P.; Ding, J.
1991-01-01
This paper reports that a review of modeling of the hydrodynamics of fluidization of bubbling beds showed that inviscid two-fluid models were able to predict a great deal of the behavior of bubbling beds because the dominant mechanism of energy dissipation is the drag between the particles and the fluid. The formation, the growth and the bursting of bubbles were predicted. Predicted wall-to-bed heat transfer coefficients and velocity profiles of jets agreed with measurements. Time average porosity distributions agreed with measurements done using gamma-ray densitometers without the use of any adjustable parameters. However, inviscid models could not correctly predict rates of erosion around tubes immersed into fluidized beds. To correctly model such behavior, granular stresses involving solids viscosity were added into the computer model. This viscosity arises due to random collision of particles. Several models fro this viscosity were investigated and the results compared to measurements of solids distributions in two-dimensional beds and to particle velocities reported in the literature. While in the case of bubbling beds the solids viscosity plays the role of a correction, modeling of a circulating fluidized bed (CFB) without a viscosity is not possible. Recent experimental data obtained at IIT and at IGT show that in CFB the solids viscous dissipation is responsible for as much as half of the pressure drop. From such measurement, solids viscosities were computed. These were used in the two fluid hydrodynamic model, to predict radial solids distributions and solids velocities which matched the experimental distributions. Most important, the model predicted cluster formation and transient internal circulation which is responsible for the favorable characteristics of CFBs, such as good wall-to-bed heat transfer. Video tape movies of computations compared favorably with high speed movies of the experiments
Full sphere hydrodynamic and dynamo benchmarks
Marti, P.
2014-01-26
Convection in planetary cores can generate fluid flow and magnetic fields, and a number of sophisticated codes exist to simulate the dynamic behaviour of such systems. We report on the first community activity to compare numerical results of computer codes designed to calculate fluid flow within a whole sphere. The flows are incompressible and rapidly rotating and the forcing of the flow is either due to thermal convection or due to moving boundaries. All problems defined have solutions that alloweasy comparison, since they are either steady, slowly drifting or perfectly periodic. The first two benchmarks are defined based on uniform internal heating within the sphere under the Boussinesq approximation with boundary conditions that are uniform in temperature and stress-free for the flow. Benchmark 1 is purely hydrodynamic, and has a drifting solution. Benchmark 2 is a magnetohydrodynamic benchmark that can generate oscillatory, purely periodic, flows and magnetic fields. In contrast, Benchmark 3 is a hydrodynamic rotating bubble benchmark using no slip boundary conditions that has a stationary solution. Results from a variety of types of code are reported, including codes that are fully spectral (based on spherical harmonic expansions in angular coordinates and polynomial expansions in radius), mixed spectral and finite difference, finite volume, finite element and also a mixed Fourier-finite element code. There is good agreement between codes. It is found that in Benchmarks 1 and 2, the approximation of a whole sphere problem by a domain that is a spherical shell (a sphere possessing an inner core) does not represent an adequate approximation to the system, since the results differ from whole sphere results. © The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society.
Variational description of multifluid hydrodynamics: Uncharged fluids
Prix, Reinhard
2004-02-01
We present a formalism for Newtonian multifluid hydrodynamics derived from an unconstrained variational principle. This approach provides a natural way of obtaining the general equations of motion for a wide range of hydrodynamic systems containing an arbitrary number of interacting fluids and superfluids. In addition to spatial variations we use “time shifts” in the variational principle, which allows us to describe dissipative processes with entropy creation, such as chemical reactions, friction or the effects of external non-conservative forces. The resulting framework incorporates the generalization of the entrainment effect originally discussed in the case of the mixture of two superfluids by Andreev and Bashkin. In addition to the conservation of energy and momentum, we derive the generalized conservation laws of vorticity and helicity, and the special case of Ertel’s theorem for the single perfect fluid. We explicitly discuss the application of this framework to thermally conducting fluids, superfluids, and superfluid neutron star matter. The equations governing thermally conducting fluids are found to be more general than the standard description, as the effect of entrainment usually seems to be overlooked in this context. In the case of superfluid 4He we recover the Landau-Khalatnikov equations of the two-fluid model via a translation to the “orthodox” framework of superfluidity, which is based on a rather awkward choice of variables. Our two-fluid model for superfluid neutron star matter allows for dissipation via mutual friction and also “transfusion” via β reactions between the neutron fluid and the proton-electron fluid.
EFFECT OF CLEARANCE THE BALL BEARINGS ON INCORRECT WORK OF THREE-SUPORT BEARING SHAFT
Directory of Open Access Journals (Sweden)
Jarosław KACZOR
2014-06-01
Full Text Available Durability deep groove ball bearings depends on factors (called attributes design, technological and operational. Among the design features one of the most important is play in the bearings. Polish Norm shows five groups of looseness in the bearings, in which the play range from 0 to 105 microns. Manufacturers of rolling bearings they only play group, which has a bearing data, without giving the exact value of the slack. Aim of this study is to determine how it affects the play in the bearings to work three-bearing shafts, including elasticity and resilience three-bearing shafts.
Effective modelling of acoustofluidic devices
DEFF Research Database (Denmark)
Ley, Mikkel Wennemoes Hvitfeld
, and 3) acoustic streaming patterns in the devices considered in model 2). 1) We derive an effective model for numerical studies of hydrodynamic particle-particle interactions in microfluidic high-concentration suspensions. A suspension of microparticles placed in a microfluidic channel and influenced......, and of the momentum transfer between the particles and the suspension. 2) We derive a full 3D numerical model for the coupled acoustic fields in mm-sized water-filled glass capillaries, calculating pressure field in the liquid coupled to the displacement field of the glass channel, taking into account mixed standing...... for the acoustic field in glass capillary devices derived in 2), we make an effective model for calculating the acoustic streaming velocity in 3D. To do this, we use recent analytical results that allows calculation of the acoustic streaming field resulting from channel-wall oscillations in any direction...
Isotopic study of the wear of sliding bearings with plastic friction surface
International Nuclear Information System (INIS)
Pandur, J.; Varkonyi, A.
1978-01-01
A new complex device has been elaborated for the investigation of the duration of bearings in the Institute of Isotopes of the Hungarian Academy of Sciences. The simultaneous determination of wear by an isotopic method the coefficient of friction by means of a Wheatstone bridge and the bearing temperature by means of a thermoresistor is described. Dynamic loading and variable revolution per minute are applied to produce a forced wear of the bearings. The isotopically labelled wear products are removed by oil and the collected sample is measured by a scintillation detector. Wear of a steel axle in plastic housing and plastic coated axle in cast iron housing was determined. (V.N.)
Journal and Wave Bearing Impedance Calculation Software
Hanford, Amanda; Campbell, Robert
2012-01-01
The wave bearing software suite is a MALTA application that computes bearing properties for user-specified wave bearing conditions, as well as plain journal bearings. Wave bearings are fluid film journal bearings with multi-lobed wave patterns around the circumference of the bearing surface. In this software suite, the dynamic coefficients are outputted in a way for easy implementation in a finite element model used in rotor dynamics analysis. The software has a graphical user interface (GUI) for inputting bearing geometry parameters, and uses MATLAB s structure interface for ease of interpreting data. This innovation was developed to provide the stiffness and damping components of wave bearing impedances. The computational method for computing bearing coefficients was originally designed for plain journal bearings and tilting pad bearings. Modifications to include a wave bearing profile consisted of changing the film thickness profile given by an equation, and writing an algorithm to locate the integration limits for each fluid region. Careful consideration was needed to implement the correct integration limits while computing the dynamic coefficients, depending on the form of the input/output variables specified in the algorithm.
Kindgen, Sarah; Wachtel, Herbert; Abrahamsson, Bertil; Langguth, Peter
2015-09-01
Disintegration of oral solid dosage forms is a prerequisite for drug dissolution and absorption and is to a large extent dependent on the pressures and hydrodynamic conditions in the solution that the dosage form is exposed to. In this work, the hydrodynamics in the PhEur/USP disintegration tester were investigated using computational fluid dynamics (CFD). Particle image velocimetry was used to validate the CFD predictions. The CFD simulations were performed with different Newtonian and non-Newtonian fluids, representing fasted and fed states. The results indicate that the current design and operating conditions of the disintegration test device, given by the pharmacopoeias, are not reproducing the in vivo situation. This holds true for the hydrodynamics in the disintegration tester that generates Reynolds numbers dissimilar to the reported in vivo situation. Also, when using homogenized US FDA meal, representing the fed state, too high viscosities and relative pressures are generated. The forces acting on the dosage form are too small for all fluids compared to the in vivo situation. The lack of peristaltic contractions, which generate hydrodynamics and shear stress in vivo, might be the major drawback of the compendial device resulting in the observed differences between predicted and in vivo measured hydrodynamics. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.
Garcia-Crespo, Andres Jose
2013-12-10
A sealing device for sealing a gap between a dovetail of a bucket assembly and a rotor wheel is disclosed. The sealing device includes a cover plate configured to cover the gap and a retention member protruding from the cover plate and configured to engage the dovetail. The sealing device provides a seal against the gap when the bucket assemply is subjected to a centrifugal force.
Tai, Yu-Chong (Inventor); Zheng, Siyang (Inventor); Lin, Jeffrey Chun-Hui (Inventor); Kasdan, Harvey L. (Inventor)
2017-01-01
Described herein are particular embodiments relating to a microfluidic device that may be utilized for cell sensing, counting, and/or sorting. Particular aspects relate to a microfabricated device that is capable of differentiating single cell types from dense cell populations. One particular embodiment relates a device and methods of using the same for sensing, counting, and/or sorting leukocytes from whole, undiluted blood samples.
International Nuclear Information System (INIS)
Qurnell, F.D.; Patterson, C.B.
1979-01-01
A gauge supporting device for measuring say a square tube comprises a pair of rods or guides in tension between a pair of end members, the end members being spaced apart by a compression member or members. The tensioned guides provide planes of reference for measuring devices moved therealong on a carriage. The device is especially useful for making on site dimensional measurements of components, such as irradiated and therefore radioactive components, that cannot readily be transported to an inspection laboratory. (UK)
Stable isotopes to detect food-conditioned bears and to evaluate human-bear management
Hopkins, John B.; Koch, Paul L.; Schwartz, Charles C.; Ferguson, Jake M.; Greenleaf, Schuyler S.; Kalinowski, Steven T.
2012-01-01
We used genetic and stable isotope analysis of hair from free-ranging black bears (Ursus americanus) in Yosemite National Park, California, USA to: 1) identify bears that consume human food, 2) estimate the diets of these bears, and 3) evaluate the Yosemite human–bear management program. Specifically, we analyzed the isotopic composition of hair from bears known a priori to be food-conditioned or non-food-conditioned and used these data to predict whether bears with an unknown management status were food-conditioned (FC) or non-food-conditioned (NFC). We used a stable isotope mixing model to estimate the proportional contribution of natural foods (plants and animals) versus human food in the diets of FC bears. We then used results from both analyses to evaluate proactive (population-level) and reactive (individual-level) human–bear management, and discussed new metrics to evaluate the overall human–bear management program in Yosemite. Our results indicated that 19 out of 145 (13%) unknown bears sampled from 2005 to 2007 were food-conditioned. The proportion of human food in the diets of known FC bears likely declined from 2001–2003 to 2005–2007, suggesting proactive management was successful in reducing the amount of human food available to bears. In contrast, reactive management was not successful in changing the management status of known FC bears to NFC bears, or in reducing the contribution of human food to the diets of FC bears. Nine known FC bears were recaptured on 14 occasions from 2001 to 2007; all bears were classified as FC during subsequent recaptures, and human–bear management did not reduce the amount of human food in the diets of FC bears. Based on our results, we suggest Yosemite continue implementing proactive human–bear management, reevaluate reactive management, and consider removing problem bears (those involved in repeated bear incidents) from the population.