Science.gov (United States)

This paper presents a numerical investigation of laminar flows and heat transfer in a horizontal rectangular channel whose top and bottom plates have been punched out in the form of a delta wing. The flow structure with respect to the generation, transport, and stability of vortices in laminar horizontal channel flows with combined forced and free convection are reported. To include free convection, Boussinesq approximation of the buoyancy is used and the flow medium is treated as incompressible.

KoreaScience (Korea)

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Energy Technology Data Exchange (ETDEWEB)

As in all vehicles of this type, low weight and aerodynamic drag must be achieved without compromising safety, and in an extremely rugged structure. This has been done by using a chrome-molybdenum steel space-frame, surrounded by a Kevlar/foam sandwich body shell. The solar panel wing, which uses a laminar flow section to obtain low drag, does not tilt except when the vehicle is stationary. A high degree of redundancy is built into the vehicle; for example there are two motors and transmissions, the solar array is divided into seven parallel sub-arrays, and the power electronics is multiply redundant. Built entirely in the garage of a suburban house, the Australian Geographic Team Marsupial car cost less than US$50,000 to construct.

Science.gov (United States)

impflrtant to the understanding of complex vortical flows. ... tions like the slender wing, flow separations are controlled in the s,. ...... 10, AGARD LS-121, Dec. ...

Science.gov (United States)

Detailed three dimensional wing kinematics and aerodynamic characteristics are experimentally presented for the free flight of a beetle, Allomyrina dichotoma, which has a pair of elytra (fore wings) and hind wings. The kinematic parameters of the wing motion, such as the wing tip trajectory, angle of attack, torsion angle, and camber deformation, are obtained from a 3D reconstruction technique that involves the use of two or three synchronized high-speed cameras to digitize various points marked on the wings. Our data show outstanding characteristics of wing deformation and flexibility in the free flight of the beetle. To find out the mechanism of aerodynamic force, the leading edge vortex (LEV) and trailing edge vortex (TEV) on both elytron and hind wing were observed by using smoke wire visualization and digital ...

British Library Electronic Table of Contents (United Kingdom)

Flow visualization experiments are conducted in water tunnel for low aspect ratio cropped wings at low Reynolds number. The experimental results show that the model sweep angle ? influences the formation and development of the leading-edge vortex. For wings with ? =0?, the dominant flow structure is transverse vortex. When ??26?, the dual vortex structure can be observed at some angles of attack, and it is confirmed that the dual vortex is a special structure for flow over low aspect ratio wing at low Reynolds number. For ??56? wings, the dual vortex structure can be observed in a large range of attack angles. Moreover, in comparison with the outer vortex, the breakdown position of the primary vortex is delayed, and the larger the ?, the later the breakdown location at the same angle of at...

Science.gov (United States)

Engine flow simulation was provided by four separately mounted air ejectors connected to a high-pressure air supply. The engine nacelle center lines were ...

Science.gov (United States)

include modeling geometric complexities, coupling between the flow and the .... noted that the AGARD 445.6 wing data set, which has been widely used for .... higher-level computational aeroelastic code validations at transonic flow separation ...

Science.gov (United States)

Numerical solutions for fully developed laminar flow in internally finned tubes with trapezoidal and triangular fin profiles were given with Finite Element Method (FEM): The heat transfer characteristics were obtained and compared under the boundary conditions of uniform heat flux, uniform wall temperature, and the third boundary condition with finite wall thermal conductivity considered. The numerical results show that boundary conditions have pronounced effects on the temperature field. Furthermore, a new mechanism on the heat transfer augmentation of internally finned tubes is proposed.

International Nuclear Information System (INIS)

Several aspects of heat transfer at the annular two phase flow regime are considered. Nucleate boiling is supposed to be absent. Theoretical solutions for cases of laminar and turbulent flow in the liquid film, respectively, are considered, when steam presence does not effect the heat transfer. Heat transfer in annular flows is also considered, where steam phase consists totally or partially of the so-called incondensable gas. In this case steam phase can be a considerable resistance to heat transfer.

Energy Technology Data Exchange (ETDEWEB)

This book presents the papers given at a conference on two-phase flow. Topics considered at the conference included the thermal hydraulics of a feedwater pipe breakage, pressure losses, measurement of void fraction in a rod bundle, laminar filmwise condensation, natural circulation, flow models, bubble dynamics, cavitation, water hammer, and heat transfer augmentation.

Science.gov (United States)

The flow and heat transfers associated with a plane laminar flow past a forward-facing step were analyzed using a power-law numerical scheme combined with a false vorticity-stream function approach. To improve the traditional wall-vorticity boundary condition, a novel method, based on an accurate description of the nonslip wall condition, was developed and utilized. The convergence for a 56 x 49 grid system was obtained in about 350 iterations. The computed reattachment distances in the upper separated region agree with the available experimental data for a blunt plate. The heat transfer augmentation is significant across the step; however, it is counterbalanced by the deterioration of heat transfer immediately upstream of the step.

International Nuclear Information System (INIS)

The development of new electro-optical instrumentation for studying the annular dispersed two-phase flow regime is described. The system measures the thickness of the water film and droplet size and velocity distributions which would be encountered in such a flow regime. The water film thickness is measured by an improved capacitance method with a short time constant using newly developed sensor electrodes. The electrodes are made flush with the inner wall of a cylindrical tube and do not disturb the flow. In the test equipment, steady, laminar flow of water along the inner wall of the tube is controlled by appropriate valves and a porous jacket while droplets are introduced by means of a special spray nozzle.

Energy Technology Data Exchange (ETDEWEB)

Heat transfer augmentation techniques (passive, active or a combination of passive and active methods) are commonly used in areas such as process industries, heating and cooling in evaporators, thermal power plants, air- conditioning equipment, refrigerators, radiators for space vehicles, automobiles, etc. Passive techniques, where inserts are used in the flow passage to augment the heat transfer rate, are advantageous compared with active techniques, because the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger. In design of compact heat exchangers, passive techniques of heat transfer augmentation can play an important role if a proper passive insert configuration can be selected according to the heat exchanger working condition (both flow and heat transfer conditions). In the past decade, several studies on the passive techniques of heat transfer augmentation have been reported. ...

International Nuclear Information System (INIS)

MR images of steady and pulsatile disturbed flow, obtained with use of flow-compensated spin-echo (SE) and cine pulse sequences, revealed excellent flow visualization in three dimensions. Phantoms, built from molds of actual blood vessels, reproduced laminar, disturbed, or turbulent flow. Video recording (VR), performed under conditions equivalent to those of the MR experiments, showed separation zones identical to those seen on SE images. Pulsatile flow studies showed complex patterns of vortical flow on cine images and VR. Varying pulse sequence details changed contrast but not flow patterns. The validation of MR observations by VR has implications for clinical cine imaging and low abnormal signals observed on MR angiograms.

Energy Technology Data Exchange (ETDEWEB)

The current work focuses on the pressure drop, heat transfer and stability in two phase flow in microchannels with hydraulic diameter of less than one hundred microns. Experiments were conducted in smooth microchannels of hydraulic diameter of 45, 65 {mu}m, and a rough microchannel of hydraulic diameter of 70 {mu}m, with deionised water as the working fluid. The local saturation pressure and temperature vary substantially over the length of the channel. In order to correctly predict the local saturation temperature and subsequently the heat transfer characteristics, numerical techniques have been used in conjunction with the conventional two phase pressure drop models. The Lockhart-Martinelli (liquid-laminar, vapour-laminar) model is found to predict the two phase pressure drop data within 20%. The instability in two phase flow is quantified; it is found that microchannels of smaller hydraulic diameter ...

Science.gov (United States)

Natural laminar-flow (NLF) airfoils are those which can achieve significant extents of laminar flow (greater than or equal to 30% chord) solely through favorable pressure gradients. Studies have shown that vertical-axis wind turbines (VAWTs) using NLF sections as blade elements have the potential of producing energy at a significantly lower cost (approx. =20%) than turbines of current design. Sandia National Laboratories (SNL) is now in the process of procuring a blade set for its 17-m-diameter research turbine which will use NLF sections as blade elements. This paper describes the design of this blade set. The blade set design began with the definition of a family of three approximately 50% chord NLF sections (15, 18, and 21% t/c). These definitions involved numerically establishing airfoil contours giving section characteristics anticipated to be favorable in the VAWT context and then screening these using a VAWT ...

British Library Electronic Table of Contents (United Kingdom)

Purpose - This study seeks to explore the aerodynamic performance of wings with different shapes at low Reynolds numbers. Design/methodology/approach - The airfoils of these wings are made from aluminum plates, and the maximum cord length and wingspan are 15?cm. Wings A to D are plates with 6 percent Gottingen camber but different wing planforms. The forward-half sections of wings E and F are dragonfly-like, whereas the rear-half sections of wings E and F are flat and positively cambered, respectively. The aspect ratios of these wings are close to one, and the ratios of plate thickness to the maximum cord length are 1.3 percent. Experimental results indicate that the wings with Gottingen camber have a superior lift and lift-to-drag ratio, whereas the wings with dragonfly-like airfoils perf...

International Nuclear Information System (INIS)

Mass transfer to a wall of a horizontal rectangular channel reactor was investigated by the limiting current technique for Reynolds numbers ranging from 200 to 32000. Overall mass transfer coefficients at various mass transfer surface angles were obtained while the reactor was operated under isothermal and non-isothermal conditions. Dimensionless correlations were developed for isothermal flows from 25 to 55"oC and for non-isothermal flows with applied temperature differences up to 30"oC. In the laminar flow range natural convection dominated, but under turbulent conditions combined natural and forced convection prevailed. Mass transfer was approximately doubled under optimum selection of channel surface rotation, temperature gradient and flow rate. (author)

Energy Technology Data Exchange (ETDEWEB)

The laminar incompressible hydrodynamically fully developed and thermally developing flow is studied in a curved square duct with four longitudinal fins. The duct is successively subjected to constant wall temperature, to circumferentially uniform temperature and axially linearly or exponentially varying temperature. The local and fully developed Nusselt numbers are examined for various values of the Dean number and it is found that the heat transfer rate increases for high fins. The parameters that affect the entry length are studied and the fluctuations of the local Nu that appear in the entrance region are investigated. Temperature contour plots are presented for the visualization of the temperature field and functional relations for the Nusselt number are proposed in terms of the Dean and Prandtl numbers. (orig.)

British Library Electronic Table of Contents (United Kingdom)

The present contribution deals with the thermophoresis particle deposition and thermal radiation effects on the flow, heat and mass transfer characteristics in a viscous fluid over a semi-infinite vertical porous plate. The governing boundary layer equations are written into a dimensionless form by similarity transformations. The transformed coupled nonlinear ordinary differential equations are solved numerically by means of the fourth-order Runge?Kutta method with a shooting technique. The effects of different parameters on the dimensionless velocity, temperature, and concentration profiles are shown graphically. In addition, results for the local skin-friction coefficient, the local Nusselt number, and the local Sherwood number are tabulated and discussed.

International Nuclear Information System (INIS)

A liquid column was used for the experiments reported in Part 1. However, it only gives the observation of the effect of fast reaction because the liquid flow was controlled to uniform laminar flow and the contact is limited to short time of around 10 ms. In practical absorbing operation, turbulence is involved in liquid flow, and the residence time for contact is long. Hence, the absorption of trace iodine in the purified air has been experimented by using a constant interface area type stirred absorption tank. Prior to the experiment, the characteristics of the absorption tank was investigated by conducting pure carbon dioxide absorption test with purified water. It gave the conclusion that the tank was sufficiently usable for fundamental researches. In short contact time absorption, the iodine dissolved and absorbed in liquid phase is affected by reaction of hypoiodous acid and poly-iodide ion ...

CERN Document Server

If high-redshift QSOs are ejected from the nuclei of low-redshift galaxies, as some have claimed, a large portion of their redshift must be intrinsic (non-Doppler). If these intrinsic components have preferred values, redshifts will tend to cluster around these preferred values and produce peaks in the redshift distribution. Doppler ejection and Hubble flow components will broaden each peak. Because ejection velocities are randomly directed and Hubble flow components are always positive, in this model all peaks are expected to show an asymmetry, extending further out in the red wing. If peaks are present showing this predicted asymmetry, it can lead directly to an estimate of quasar distances. Using two quasar samples, one with high redshifts and one with low, it is shown here that not only do all peaks in these two redshift distributions occur at previously predicted preferred values, they also all show the predicted extra ...

Energy Technology Data Exchange (ETDEWEB)

Film boiling is the mode if boiling during which the hot surface is separated from the vaporizing liquid by a nearly continuous film vapor. Film boiling is usually considered a very undesirable boiling regime since it is a relatively quiet and inefficient mode of heat transfer, particularly as compared to nucleate boiling. It is customary to analyze the two-phase flow regime of laminar flow film boiling by assuming the two-phase flow regime of laminar flow film boiling by assuming an idealized vapor film flow characterized by a smooth liquid-vapor interface. However, during stable flow film boiling, the wavy nature of the liquid-vapor interface and its role in local heat and mass transport have been largely ignored. The vapor interface is rarely stationary. Interfacial waves may substantially augment the heat transfer ...

Energy Technology Data Exchange (ETDEWEB)

Experimental investigation of heat transfer and friction factor characteristics of circular tube fitted with full-length helical screw element of different twist ratio, and helical screw inserts with spacer length 100, 200, 300 and 400mm have been studied with uniform heat flux under laminar flow condition. The experimental data obtained are verified with those obtained from plain tube published data. The effect of spacer length on heat transfer augmentation and friction factor, and the effect of twist ratio on heat transfer augmentation and friction factor have been presented separately. The decrease in Nusselt number for the helical twist with spacer length is within 10% for each subsequent 100mm increase in spacer length. The decrease in friction factor is nearly two times lower than the full length helical twist at low Reynolds number, and four times lower than the full length helical twist at high Reynolds number for all twist ratio. The ...

Energy Technology Data Exchange (ETDEWEB)

The unsteady two-dimensional laminar flow of a viscous incompressible electrically conducting micro polar fluid via a porous medium past a semi-infinite vertical porous moving plate in the presence of a transverse magnetic field is studied. A uniform magnetic field acts perpendicularly to the porous surface in which absorbs the micro polar fluid with a suction velocity varying with time. The effects of material parameters on the velocity and temperature fields across the boundary layer are investigated. The method of solution can be applied for small perturbation approximation. Numerical results of velocity and temperature distributions of micro polar fluids are compared with the corresponding flow problems for a Newtonian fluid. (author)

Energy Technology Data Exchange (ETDEWEB)

The authors study, in forced convection, the evaporation of an Ostwaldian film flowing over an isothermal inclined plane surface to determine the influence of the behaviour index of the liquid on the dynamic and thermal characteristics of liquid-air system. The liquid flow is considered partially two-dimensional whereas for the air it is two-dimensional. The coupled equations with the interfacial conditions are solved using a fully implicit finite differences method. From the study, it appears that the behaviour index influences considerably the transfers which are more important for pseudo-plastic liquids than for dilatant ones. (authors)

International Nuclear Information System (INIS)

To encourage the application of robotics technology for routine radiobench applications, a laboratory dedicated to the research and development of contained robotic systems is being constructed. The facility will have several robots located in laminar flow hoods, and the hoods are being designed to allow the possibility for multiple robots to work together. This paper presents both the design features of the hoods and the general layout of the laboratory, and also discusses an application of a robotic system for the routine nuclear counting of gamma tube samples. The gamma tube system is presently operating in one of the routine analysis laboratories. 5 figs.

Science.gov (United States)

... Competition ... 4. TITLE AND SUBTITLE Competition and Innovation in the US Fixed-Wing Military Aircraft Industry 5a. CONTRACT NUMBER 5b. ...

Energy Technology Data Exchange (ETDEWEB)

Heat and momentum transport in self-sustained oscillatory viscous flows is investigated by direct numerical simulation using the spectral element method. Above a critical Reynolds number, these flows bifurcate to a time-periodic, self-sustained oscillatory state. Traveling waves are observed, even at moderately low Reynolds numbers, inducing self-sustained oscillations that result in very well-mixed flows, which, in turn, lead to convective heat transfer augmentation. These oscillatory states are investigated and correlations between the time- and space-averaged Nusselt and Reynolds numbers are obtained. The transport phenomena of heat and momentum due to the oscillatory components of the flow are analyzed by looking at the phase portraits of velocity and temperature, investigating the behavior of the terms involving their fluctuations, as well as considering the correlation coefficients between the ...

Energy Technology Data Exchange (ETDEWEB)

The catalytically stabilised thermal combustion (CST) of lean hydrogen-air mixtures was investigated numerically in a turbulent channel flow configuration using a two-dimensional elliptic model with detailed heterogeneous and homogeneous chemical reactions. Comparison between turbulent and laminar cases having the same incoming mean properties shows that turbulence inhibits homogeneous ignition due to increased heat transport away from the near-wall layer. The peak root-mean-square temperature and species fluctuations are always located outside the extent of the homogeneous reaction zone indicating that thermochemical fluctuations have no significant influence on gaseous combustion. (author) 4 figs., 6 refs.

British Library Electronic Table of Contents (United Kingdom)

The present investigation focuses on the study of design parameters for a generic fan-in-wing configuration. The objective is to evaluate the performance of a fan-in-wing concept in a Short-Take-Off and Landing situation. The results presented are also of interest for transition between hover and a wing-sustained flight for a Vertical Take Off and Landing concept. Steady Reynolds Averaged Navier-Stokes computations using an actuator disk technique are performed. The results show a good agreement with experimental data and simulation results obtained in previous investigations for a generic wind tunnel model. A parametric study is conducted for a more realistic wing planform. For a single fan installed in the wing, the streamwise and spanwise influence on the wing aerodynamics is studied. I...

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Abstract not provided

British Library Electronic Table of Contents (United Kingdom)

A numerical model is developed to study electrolyte dependent kinetics in fuel cells. The model is based on the Poisson-Nernst-Planck (PNP) and generalized-Frumkin-Butler-Volmer (gFBV) equations, and is used to understand how the diffuse layer and ionic transport play a role in the performance difference between acidic and alkaline systems. The laminar flow fuel cell (LFFC) is used as the model fuel cell architecture to allow for the appropriate comparison of equivalent acidic and alkaline systems. We study the overall cell performance and individual electrode polarizations of acidic and alkaline fuel cells for both balanced and unbalanced electrode kinetics as well as in the presence of transport limitations. The results predict cell behavior based on electrolyte composition that strongly...

British Library Electronic Table of Contents (United Kingdom)

The heat transfer a characteristics and friction factor in the horizontal double pipes of flat tubes with full length helical screw element of different twist ratio and helical screw inserts with different spacer length are investigated. Cold and hot water are used as working fluid in tube side and shell side respectively. The experiments covered a range of Reynolds numbers 5.7x102Re1.31x103. The effect of spacer length on the heat transfer augmentation and friction factor and the effect of twist ratio on heat transfer augmentation and friction factor have been presented separately. The study shows that, the Nusslet number (Nu) and friction factor (f) decrease with the increase of S or Y for flat tube. The comparison between the data of present plain circular with that of previous plain ci...

UK PubMed Central (United Kingdom)

The structure of the skin in the epauletted fruit bat (Epomophorus wahlbergi) wing and body trunk was studied with a view to understanding possible adaptations for gas metabolism and...Full Text Available

Science.gov (United States)

No Abstract Available

Energy Technology Data Exchange (ETDEWEB)

This disclosure provides a solar rechargeable aircraft that is inexpensive to produce, is steerable, and can remain airborne almost indefinitely. The preferred aircraft is a span-loaded flying wing, having no fuselage or rudder. Travelling at relatively slow speeds, and having a two-hundred foot wingspan that mounts photovoltaic cells on most all of the wing`s top surface, the aircraft uses only differential thrust of its eight propellers to turn. Each of five sections of the wing has one or more engines and photovoltaic arrays, and produces its own lift independent of the other sections, to avoid loading them. Five two-sided photovoltaic arrays, in all, are mounted on the wing, and receive photovoltaic energy both incident on top of the wing, and which is incident also from below, through a bottom, transparent surface. The aircraft is capable of a top speed of about ninety miles ...

Energy Technology Data Exchange (ETDEWEB)

The unsteady state heat transfer behaviour of a vertical wall subject to the effects of uniform radiation is investigated and the dimensional analysis of combined heat transfers by conduction, convection and radiation is presented. The convective heat transfer coefficients used in the numerical model are determined experimentally by means of an assembly resembling the conditions encountered in the dwelling (variable temperatures and heat flows in time and space, wall associated with a floor, radiative flux outside the wall). In routine conditions (homogeneous wall dimensions, temperature differentials less than 40/sup 0/C), it is shown that the problem depends in practice on three parameters (instead of five) and that nomographs can give the energy accumulated in the wall as a function of its geometric and thermal charactersitics and the external conditions (type and thickness of material, changes in incident flux, convection over the height of the wall in ...

Energy Technology Data Exchange (ETDEWEB)

We intend to solve equations governing turbulent plane-vertical isotherm and non isotherm jets by taking into account inflow conditions at the exit of the nozzle. The analysis is focused on the influence of these conditions on this type of flow. Two cases are considered (uniform and parabolic velocity and temperature profiles). A finite difference scheme is developed to solve the governing equations. This numeric model allows us to show that the region of fully developed regime begins much nearer the nozzle for the turbulent case than for the laminar flow case. Indeed, the turbulence increases the mixing between the incoming gas from the nozzle and the ambient fluid, and consequently the size of the potential core zone decreases. The results are compared to other works introducing mathematical variables based on the energy conservation for the case of the mixed convection and the momentum conservation for the forced ...

Energy Technology Data Exchange (ETDEWEB)

A multi-faceted research program has been performed to investigate in detail several aspects of free and forced convective cooling of underground electric cable systems. There were two main areas of investigation. The first one reported in this volume dealt with the fluid dynamic and thermal aspects of various components of the cable system. In particular, friction factors for laminar flow in the cable pipes with various configurations were determined using a finite element technique; the temperature distributions and heat transfer in splices were examined using a combined analytical numerical technique; the pressure drop and heat transfer characteristics of cable pipes in the transitional and turbulent flow regime were determined experimentally in a model study; and full-scale model experimental work was carried out to determine the fluid dynamic and thermal characteristics of entrance and exit chambers for the cooling ...

International Nuclear Information System (INIS)

Plasma surface interactions in tokamaks are known to create significant quantities of dust, which settles onto surfaces and accumulates in the vacuum vessel. In ITER, a loss of vacuum accident may result in the release of dust which will be radioactive and/or toxic, and provides increased surface area for chemical reactions or dust explosion. A new method of analysis has been developed for modeling dust resuspension and transport in loss of vacuum accidents. The aerosol dynamic equation is solved via the user defined scalar (UDS) capability in the commercial CFD code Fluent. Fluent solves up to 50 generic transport equations for user defined scalars, and allows customization of terms in these equations through user defined functions (UDF). This allows calculation of diffusion coefficients based on local flow properties, inclusion of body forces such as gravity and thermophoresis in the convection term, and user defined source terms. The code accurately reproduces ...

International Nuclear Information System (INIS)

This paper presents direct measurements of the aerodynamic forces on the wing of a free-flying, insect-like ornithopter that was modeled on a hawk moth (Manduca sexta). A micro differential pressure sensor was fabricated with micro electro mechanical systems (MEMS) technology and attached to the wing of the ornithopter. The sensor chip was less than 0.1% of the wing area. The mass of the sensor chip was 2.0 mg, which was less than 1% of the wing mass. Thus, the sensor was both small and light in comparison with the wing, resulting in a measurement system that had a minimal impact on the aerodynamics of the wing. With this sensor, the 'pressure coefficient' of the ornithopter wing was measured during both steady airflow and actual free flight. The maximum pressure coefficient observed for steady airflow conditions was 1.4 at an angle of ...

Energy Technology Data Exchange (ETDEWEB)

In cooling systems, an improved control of scale deposit and corrosion processes is a major challenge and an realistic evaluation tool for water treatments is of the utmost economic importance. In this study, a channel flow cell was used to allow in-situ electrochemical measurements in well defined electrolyte tube flowing conditions. An expression of the mass transfer towards the electrode was established where the diffusion-limited current is a function of Re{sup 1/3} in the laminar regime and was verified experimentally using the redox couples Fe[CN]{sub 6}{sup 4-}/ Fe[CN]{sub 6}{sup 3-} and O{sub 2}/OH{sup -}. This hydrodynamically controlled experimental device was developed to investigate scale deposit processes and to evaluate scale inhibitor efficiency using a electrochemical quartz crystal microbalance. Experiments were performed on three different waters, at various flow rates and ...

Energy Technology Data Exchange (ETDEWEB)

Numerical solutions given by a vorticity-velocity method are presented for combined free and forced laminar convection in the thermal entrance region of a horizontal rectangular channel without the assumptions of large Prandtl number and small Grashof number. The channel wall is heated with a uniform wall heat flux. Typical developments of temperature profile, secondary flow, and axial velocity at various axial positions in the entrance region are presented. Local friction factor and Nusselt number variations are shown for Rayleigh numbers Ra = 10{sup 4}, 3 {times} 10{sup 4}, 6 {times} 10{sup 4}, and 10{sup 5} with the Prandtl number as a parameter. The solution for the limiting case of large Prandtl number and small Grashof number obtained from the present study confirms the data of existing literature. It is observed that the large Prandtl number assumption is valid for Pr = 10 when Ra {le} 3 {times} 10{sup 4} but for a larger Prandtl number ...

Energy Technology Data Exchange (ETDEWEB)

Flame lengths inside circular tubes, using an (in-shot) atmospheric burner design commonly found in gas-fired residential furnaces were visually observed for natural gas and air under various operating conditions. The flame length data were reduced into dimensionless flame lengths, which were shown to be linearly proportional to the Peclet number of the fuel and air mixture. The dimensionless flame length dependence reported does not scale according to the classical flame models: pre-mixed (laminar) flame or diffusion flame. Instead, the flame length dependence was found to scale with the fuel burn speed, gas/mixture properties (evaluated at the adiabatic flame temperature), and flow parameters. Currently, this is the only flame length study available for the standard atmospheric burner designs commonly used in residential heating products. The results and data reduction provide an easy method to compute flame length penetrations inside ...

Energy Technology Data Exchange (ETDEWEB)

The heat transfer a characteristics and friction factor in the horizontal double pipes of flat tubes with full length helical screw element of different twist ratio and helical screw inserts with different spacer length are investigated. Cold and hot water are used as working fluid in tube side and shell side respectively. The experiments covered a range of Reynolds numbers 5.7 x 10{sup 2} {<=} Re {<=} 1.31 x 10{sup 3}. The effect of spacer length on the heat transfer augmentation and friction factor and the effect of twist ratio on heat transfer augmentation and friction factor have been presented separately. The study shows that, the Nusslet number (Nu) and friction factor (f) decrease with the increase of S or Y for flat tube. The comparison between the data of present plain circular with that of previous plain circular tube showed a good agreement between them but the data of present plain flat tube showed a higher in heat transfer and pressure drop than that of plain ...

Energy Technology Data Exchange (ETDEWEB)

Fully coupled, Newton-Krylov algorithms are investigated for solving strongly coupled, nonlinear systems of partial differential equations arising in the field of computational fluid dynamics. Primitive variable forms of the steady incompressible and compressible Navier-Stokes and energy equations that describe the flow of a laminar Newtonian fluid in two-dimensions are specifically considered. Numerical solutions are obtained by first integrating over discrete finite volumes that compose the computational mesh. The resulting system of nonlinear algebraic equations are linearized using Newton`s method. Preconditioned Krylov subspace based iterative algorithms then solve these linear systems on each Newton iteration. Selected Krylov algorithms include the Arnoldi-based Generalized Minimal RESidual (GMRES) algorithm, and the Lanczos-based Conjugate Gradients Squared (CGS), Bi-CGSTAB, and Transpose-Free Quasi-Minimal Residual (TFQMR) algorithms. ...

Science.gov (United States)

... results show that, despite the extensive clam and oyster aquaculture in Baynes Sound, natural environmental attributes were the ... ...

Science.gov (United States)

of Aspect Ratio 2 With NACA 0005-63 Thickness Distribution,. Cambered and Twisted for a Trapezoidal Span Load Distribution. NACA RM A50K27a,, ...

Energy Technology Data Exchange (ETDEWEB)

A detailed experimental investigation of the application of fractal geometry concepts in determining the turbulent burning velocity in the wrinkled flame regime of turbulent premixed combustion was conducted. The fractal dimension and cutoff scales were determined for six different turbulent flames in the wrinkled flame regime, where the turbulence intensity, turbulent length scale, and equivalence ratio were varied. Unlike previous reports, it has proved possible to obtain the fractal dimension and inner and outer cutoffs from individual flame images. From this individual data, the pdf distributions of all three fractal parameters, along with the distribution of the predicted increase in surface area, may be determined. The analysis of over 300 flame images for each flame condition provided a sufficient sample size to accurately define the pdf distributions and their means. However, the predicted S{sub T}/S{sub L}, calculated using fractal parameters, was significantly below the ...

International Nuclear Information System (INIS)

Primary Ewing's sarcoma of the skull is a very rare entity. We report MRI findings in a case of Ewing's sarcoma of the greater wing of sphenoid in a 4-year-old patient. Magnetic resonance imaging showed markedly heterogenous signal intensity with areas of haemorrhage and necrosis. It also demonstrated the exact extent of tumour due to its multiplanar capabilities and was, therefore, helpful in planning surgery. Copyright (2002) Blackwell Science Pty Ltd

UK PubMed Central (United Kingdom)

Previous studies of insect flight control have been statistical in approach, simply correlating wing kinematics with body kinematics or force production. Kinematics and forces are linked by Newtonian...Full Text Available

UK PubMed Central (United Kingdom)

A 37 year old male was referred to our centre for management of episcleritis with peripheral keratitis in the right eye. He had a history of ocular discomfort in the right eye of 1 week duration. Slitlamp...Full Text Available

Science.gov (United States)

... M. Taylor, T. Kurt Kyser. (2009) Feather isotope analysis discriminates age-classes of Western, Least, and Semipalmated sandpipers when plumage ... ...

International Nuclear Information System (INIS)

The current--density profile of a focused ion beam (FIB) has a central peak accompanied by broader ''wings'' that, while unimportant in lithographic applications, can lead to unwanted effects during an implantation operation. The origin of the wings, and hence the best way to minimize them, is not clear and needs further study. We have measured the line profiles of several of the ions available in our FIB machine as a function of a number of variables, under ultrahigh vacuum (UHV) conditions. No effects are observed from changes in emission current or deliberate defocusing of the objective lens. There are some changes with beam aperture and/or current, but the biggest differences seem to be associated with a change of source type and hence, possibly, with a change in the source/extractor configuration or in the alloy and the emission process. The wing amplitudes are appreciably lower than many previously observed, and their ...

UK PubMed Central (United Kingdom)

We tested the hypothesis that long-term familiarity with neighbors is advantageous by determining whether male red-winged blackbirds (Agelaius phoeniceus) breeding adjacent to familiar neighbors have...Full Text Available

Science.gov (United States)

... 45 SW Staff and NASA on movement, intensity, weather conditions, ...... a) All surfaces of the vehicle susceptible to precipitation particle impact have been ... hydrometeors falling through the 0 deg C level and beginning to melt. ...

UK PubMed Central (United Kingdom)

Normal brain development requires a series of highly complex and interrelated steps. This process presents many opportunities for errors to occur, which could result in developmental defects...Full Text Available

Science.gov (United States)

The unsteady aerodynamic forces of a model fruit fly wing in flapping motion were investigated by numerically solving the Navier-Stokes equations. The flapping motion consisted of translation and rotation [the translation velocity (u(t)) varied according to the simple harmonic function (SHF), and the rotation was confined to a short period around stroke reversal]. First, it was shown that for a wing of given geometry with u(t) varying as the SHF, the aerodynamic force coefficients depended only on five non-dimensional parameters, i.e. Reynolds number (Re), stroke amplitude (Phi), mid-stroke angle of attack (alpha(m)), non-dimensional duration of wing rotation (Delta tau(r)) and rotation timing [the mean translation velocity at radius of the second moment of wing area (U), the mean chord length (c) and c/U were used as reference velocity, length and time, respectively]. Next, the force coefficients were ...

British Library Electronic Table of Contents (United Kingdom)

A novel continuous laminar shear structuring crystallizer with a suitable cooling system was designed and built. This is a new method to continuously crystallize edible fat in the desirable polymorphic form from the melt while being uniformly sheared.The machine consists of four main sections: Feed unit, shearing mechanism, cooling system and power unit. In each of these sections specific design considerations are taken into account which makes the process controllable and continuous. The shearing unit is made of two concentric cylinders. The internal cylinder is stationary and has a cooling system inside for temperature control. The outer cylinder rotates to produce a uniform shear in the sample fluid placed in the 1.5mm gap between the cylinders. The sample's feed rate is controlled whil...

Science.gov (United States)

The solar array wings were deployed by swinging two half-blanket boxes open from a folded hinge launch position .... pure-water by-product of the shuttle's fuel cell power generators because ..... outgassing limits, flammability limits, ... Foale fills a water microbiology bag for in-flight analysis. ...

Energy Technology Data Exchange (ETDEWEB)

A correlation was developed for laminar film condensation on vertical fluted surfaces. The theoretical analysis of Panchal and Bell was used for defining important physical property groups. The experimental data of Combs et al. were used to validate the proposed correlation. The experimental database used in the present study included four flute geometries that could be approximated to cosine-type flutes and seven fluids. The resulting correlation can predict the average condensate heat transfer coefficient within {+-}20%.

CERN Document Server

We present a large set of merger simulations of early-type disc galaxies with mass ratios of 1:1 and 3:1 and 10% of the total disc mass in gas. In contrast to the collisionless case equal-mass mergers with gas do not result in very boxy remnants which is caused by the suppression of box orbits and the change of the projected shape of minor-axis tube orbits in the more axisymmetric remnants. The isophotal shape of 3:1 remnants and the global kinematic properties of 1:1 and 3:1 remnants are only weakly affected by the presence of gas. 1:1 remnants are slowly rotating whereas 3:1 remnants are fast rotating and discy. The shape of the stellar LOSVD is strongly influenced by gas. The LOSVDs of collisionless remnants have broad leading wings while their gaseous counterparts show steep leading wings, more consistent with observations of elliptical galaxies. We show that this change is also caused by the suppressed populating of box orbits and it is ...

Science.gov (United States)

In the current wind turbine generation system, there are substantial problems such as the maximum power of the wind turbine cannot be obtained under the fluctuating wind speed, high in cost and low in annual net electricity production (due to mismatch between a generator and a wind turbine). A new wind turbine generator optimized for the wind turbine output is presented in order to solve such problems. This wind turbine generator consists of a permanent magnet generator, a reactor and a rectifier, and uses neither a control circuit which requires standby electricity nor a PWM converter having a switching element. By selecting most appropriate combination of the permanent magnet generator having multiple windings and the reactor connected in series with each winding, the maximum output of the wind turbine can be obtained without using a control circuit. The new wind turbine generator was directly coupled with the straight wing non-articulated vertical axis wind ...

Energy Technology Data Exchange (ETDEWEB)

The Asejire dam at Ibadan, Nigeria was constructed in the late sixties for the purpose of providing water for the city of Ibadan (presently about 4,5 million inhabitants). It is located on the Oshun river approximately fifteen miles from the city. In 1982 cracks were observed on the wing walls and although these continued to develop, no attempt was made at that time to investigate their causes and no repair was carried out. In 1989 the SGI ENGINEERING Group of Geneva, Switzerland was appointed as the consultant for the complete refurbishment of the Asejire water scheme. The consortium Degremont-Poat-Clemessy was awarded the contract for the project. The African Development Bank and the Nigerian Government have provided the loan to finance the project.

Science.gov (United States)

... of drag measurements with the AGARD Nozzle Afterbody ... are discussed separately from flows with a ... bubbles introduce typical flow phenomena that ...

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

International Nuclear Information System (INIS)

Presented are the results of the investigation of the kinetics and micromechanism of the failure in impact bending of oriented-crystallized specimens having the eutectic composition Ni_3Al-Ni_3Nb and of the bimetal composed of 45 steel + M3 copper. The failure kinetics was studied by high-speed filming, whereas the fractures were studied by electron fractography. The particularities of the failure of the laminar-type composite materials were found. Analyzed was the effect of the kinetic factors and the mechanism of failure upon its energy consumption.

Science.gov (United States)

PMID:747753

Energy Technology Data Exchange (ETDEWEB)

A flow pattern or flow regime is the characteristics spatial distribution of the phases of fluid in a duct. Since heat transfer and pressure drop are dependent on the characteristic distribution of the phases, it is necessary to describe flow patterns in an appropriate manner so that a hydrodynamic or heat transfer theory applicable to that pattern can be chosen. The objective of the present analysis is to create a flow regime map based on physical modeling of vapor/liquid interaction phenomena in a microgravity environment. In the present work, four basic flow patterns are defined: dispersed flow, stratified flow, slug flow, and annular flow. Fluid properties, liquid and vapor flow rates, and pipe size were chosen as the principal parameters. It is assumed that a transition from ...

Energy Technology Data Exchange (ETDEWEB)

Questions are examined of prospecting for nonanticlinical traps within North Sakhalin, their spatial distribution and evaluation of the outlook for oil and gas content. Traps of tapering and facial substitution on wings and periclines of local elevations, accumulative bar and erosion-accumulative channel are isolated. THe hypothesis is made that it is possible to form stratigraphic traps above the discrepancy and below it. It is noted that formation of zones of lithological tapering and facial substitution are associated with areas of the exchange of the sedimentation situation. The primary role of the shore and coastal zones in the formation of the examined types of nonanticlinal traps is established. The Okhino-Ekhabinskiy region in North Sakhalin is isolated as the primary object for prospecting for nonanticlinal traps.

Science.gov (United States)

Three in vivo assays were used to measure the immunocompetence of chickens in two generations of a selection experiment. The obtained data were used to estimate the variance components for sire and dam for antibody production to Pasteurella multocida and Mycoplasma gallisepticum vaccines, for T-cell-mediated immunity evaluated by a phytohemagglutinin wing web assay, and for clearance of foreign particles from the circulatory system. Heritabilities of and genetic correlations among these immunological traits were calculated from the sire variance components. Heritability estimates of the immunological traits based on the sire component of variance ranged from .06 to .53, and genetic correlations among immunological traits were generally negative. PMID:1956847

Energy Technology Data Exchange (ETDEWEB)

By applying the mass, momentum, and angular momentum conservation laws and the maximum flow rate principle to swirling, effectively inviscid, incompressible flows in a circular tube with a sudden expansion and the direct-flow and reversed-flow Borda mouthpieces the dependence of the flow rate coefficient and mechanical energy losses on the radius ratio and nondimensional circulation is obtained. Several calculating approaches with potential and helical motion are introduced and investigated. In the case of helical motion, as the swirl decreases the axial core of the flow is found to close with a sudden change of the flow parameters.

Science.gov (United States)

... percent by interbasin ground-water flow into the Hueco Bolson, and 2 percent by flow into creeks and ... ...

Science.gov (United States)

A method for calculating flow through an airfoil cascade drawn on a surface of revolution is discussed. The three-dimensional flow was assumed to be represented by part-channels of varying width. The basic equations are the equation of continuity and the ...

Science.gov (United States)

... been demonstrated in steady compressible flows. ... steady Compressible Flow on an Oscillating Airfoil ... of Oscillating Airfoils", AGARD-CP-552, Aug. ...

Science.gov (United States)

... Calculations of asymmetric separated flow past circular ... in Missile Aerodynamics, AGARD CP 336 ... three-dimensional vortex flows in aerodynamics. ...

Science.gov (United States)

... Calculations of asymmetric separated flow past circular ... in Missile Aerodynamics, AGARD-CP-336 ... Marconi Asymmetric separated flows about sharp ...

British Library Electronic Table of Contents (United Kingdom)

Morphologies of modified starches prepared using different methods were examined by scanning electron microscopy (SEM). These SEM micrographs provide the following results. To begin with, starch granules underwent a series of changes which resulted in the morphology of modified starch quite different from the native starch with different the methods during the process of modification. For example, hollows emerge on the granules of maltodextrin with low value of dextrose equivalent (DE) prepared by means of spray-drying, but they fell to pieces with the increasing value of DE. The granules of pregelatinized starches manufactured with extrusion technology also showed irregular stone shapes and holes within them while those produced by means of drum-drying presented irregular laminar structur...

Energy Technology Data Exchange (ETDEWEB)

The absorption of carbonyl sulfide in aqueous methyldiethanolamine (MDEA) was studied over a range of temperatures and MDEA concentrations. MDEA is commonly used for selective absorption of hydrogen sulfide in the presence of carbon dioxide. However, sulfur in the form of COS may also be present and it is necessary that estimates of absorption rates of this compound be made. The objective of this study is to determine the physiochemical properties needed to predict COS absorption rates in aqueous MDEA. Free gas solubility and the diffusivity of COS in MDEA solutions were measured over the temperature range 15 to 40{sup 0}C for MDEA concentrations up to 30 weight per cent using the nitrous oxide analogy method. Solubilities were measured volumetrically in an equilibrium cell and diffusivities were measured using a laminar liquid jet absorber. The kinetics of the reaction between COS and MDEA were studied by measuring absorption rates in a single wetted-sphere ...

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Not Available

KoreaScience (Korea)

Full Text Available

Science.gov (United States)

PMID:476294

Science.gov (United States)

... CHANNELS, TWO PHASE FLOW, WAVES, IGNITERS, GAS FLOW, HOWITZERS, CARTRIDGE CASES, COMBUSTIBLE CARTRIDGE CASES. ...

Science.gov (United States)

PMID:534760

Energy Technology Data Exchange (ETDEWEB)

Visualizations by real-time neutron radiography are demonstrated of various flow patterns of nitrogen gas-water two-phase flow in a stainless-steel tube, water inverted annular flow in a stainless-steel tube, flashing flow in an aluminium nozzle and fluidized bed in aluminium tube and vessels. Photographs every 1/60 s are presented by an image processing method to show the dynamic behaviours of the various flow patterns. It is shown that this visualization method can be applied efficiently to multiphase flow researches and will be applicable to multiphase flows in industrial machines. (author).

Energy Technology Data Exchange (ETDEWEB)

Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

Energy Technology Data Exchange (ETDEWEB)

A real-time neutron radiography (RTNR) system is used to determine two-phase flow parameters for a horizontal co-current two-phase flow channel with a cylindrical 37 rod bundle. Image processing techniques are applied to visualize the two-phase flow, and to determine flow regime, cross-sectional averaged void fraction, time averaged void fraction, and void distribution. The experimentally determined flow regime map disagrees with existing flow regime models developed for the cylindrical rod bundles. A new flow regime is observed and designated large amplitude stratified wavy (LASW) flow. The results show that the LASW flow regime may be due to a combination of undeveloped flow phenomena, boundary conditions, and circumferential cross flow occuring in the ...

Energy Technology Data Exchange (ETDEWEB)

Between 25 and 30 percent of total known petroleum reserves are contained within oil-laden fractured reservoirs where the dominant flow path is through the fractures. Economic oil recoveries from fractured reservoirs depend on a better understanding of the flow in fractures and networks of fractures. However, the flow of heavy oil and water, and particularly the flow regime map for two-phase immiscible flow has received less attention in contrast with gas-liquid flow in fractures. This paper discussed the use of flow pattern observations in a Hele-Shaw cell to generate two-phase flow regime maps. The paper investigated the effect of fracture gap and fluid viscosities on flow regimes. A correlation based on different flow and fracture properties was developed to define ...

Energy Technology Data Exchange (ETDEWEB)

A two-phase flow regime map is developed experimentally and theoretically for a vertical hexagonal flow channel with and without a 36-finned rod hexagonal bundle. This type of flow channel is of interest to MAPLE-type nuclear research reactors. The flow regime maps are determined by visual observations and observation of waveforms shown by a capacitance-type void fraction meter. The experimental results show that the inclusion of the finned hexagonal bundle shifts the flow regime transition boundaries toward higher water flow rates. Existing flow regime maps based on pipe flow require slight modifications when applied to the hexagonal flow channel with and without a MAPLE-type finned hexagonal bundle. The proposed theoretical model agrees well with experimental results.

Energy Technology Data Exchange (ETDEWEB)

This report documents the results of a project funded by DoD's Strategic Environmental Research and Development Program (SERDP) on the science behind development of predictive models for soot emission from gas turbine engines. Measurements of soot formation were performed in laminar flat premixed flames and turbulent non-premixed jet flames at 1 atm pressure and in turbulent liquid spray flames under representative conditions for takeoff in a gas turbine engine. The laminar flames and open jet flames used both ethylene and a prevaporized JP-8 surrogate fuel composed of n-dodecane and m-xylene. The pressurized turbulent jet flame measurements used the JP-8 surrogate fuel and compared its combustion and sooting characteristics to a world-average JP-8 fuel sample. The pressurized jet flame measurements demonstrated that the surrogate was representative of JP-8, with a somewhat higher tendency to soot formation. The premixed flame ...

International Nuclear Information System (INIS)

Many pump reliability problems in the Nuclear Power Plants (NPPs) are being attributed to the operation of the pump at flow rates well below its best efficiency point(BEP). Generally, the manufacturer and the user try to avert such problems by specifying a minimum flow, below which the pump should not be operated. Pump minimum flow usually involves two considerations. The first consideration is normally termed the 'thermal minimum flow', which is that flow required to prevent the fluid inside the pump from reaching saturation conditions. The other consideration is often referred to as 'mechanical minimum flow', which is that flow required to prevent mechanical damage. However, the criteria for specifying such a minimum flow are not clearly understood by all parties concerned. Also various factor and information for ...

International Nuclear Information System (INIS)

This paper describes the study of particles' dispersion in an isotropic turbulent flow. The particle's motion and the turbulent flow characteristics are calculated independently. While the particles' displacement is computed by the author's code, the flow is simulated with a commercial code : PowerFLOW. The particles and the flow are coupled through the relative velocity component of the aerodynamic force. When the simulated flow is turbulent, a turbulence regeneration model is used in order to get the flow instantaneous velocity. Validation of the method is done by comparing the particles' dispersion obtained with experimental results from literature and with the results calculated by FLUENT. Good accordance is found between numerical studies and experimental results. However, comparison between results of PowerFLOW ...

International Nuclear Information System (INIS)

In order to understand the detail transient two-phase flow structure, more advanced two-phase flow instrumentation is required. One advanced technique for flow visualization is real-time neutron radiography. Reconstruction method of visualized radiographic image of liquid metal two-phase flow generated by the real-time neutron radiography system is proposed in this paper. Image processing techniques for noise reduction and image enhancement are discussed in detail. (author).

Energy Technology Data Exchange (ETDEWEB)

This report outlines on the corrosive damage which is inherent to a high temperature environment and introduces on thermal spraying system taking an example of a gas turbine. The recent coatings by thermal spraying for high temperature environment are positively used in such applications as a hearth roll for continuous annealing, a roll for hot dipped steelplate, a solid electrolyte for fuel cell, boilers and rockets. The coating formed will be positively used because of a convenient thermal spraying and availability of various sprayable materials. This report describes the following items. Corrosive damage under the high temperature environment. Types of high temperature corrosive coating by a thermal spraying and utilization thereof. Outline of MCrAlX alloy, and merits thereof. Coating to a turbine wing by rduced pressure plasma thermal spraying. In general, it is urgently needed to establish the methods of characteristics measurement and the evaluation method ...

CERN Document Server

We search for an infrared signature of the transiting extrasolar planet HD 209458b during secondary eclipse. Our method, which we call `occultation spectroscopy,' searches for the disappearance and reappearance of weak spectral features due to the exoplanet as it passes behind the star and later reappears. We argue that at the longest infrared wavelengths, this technique becomes preferable to conventional `transit spectroscopy'. We observed the system in the wing of the strong nu-3 band of methane near 3.6 microns during two secondary eclipses, using the VLT/ISAAC spectrometer at a spectral resolution of 3300. Our analysis, which utilizes a model template spectrum, achieves sufficient precision to expect detection of the spectral structure predicted by an irradiated, low-opacity (cloudless), low-albedo, thermochemical equilibrium model for the exoplanet atmosphere. However, our observations show no evidence for the presence of this spectrum from the exoplanet, with ...

Energy Technology Data Exchange (ETDEWEB)

The use of a non-dedicated GPS receiver system for attitude determination was assessed in airborne mode through a test conducted at Sandia National Laboratories. Four independent NovAtel GPSCard{trademark} receivers were installed in Sandia`s Twin Engine Otter with two antennas mounted on the fuselage and two on the wing tips at separations of 6 to 18 m. A strapdown INS was also on board the aircraft in order to provide an independent attitude reference at rates between 4 and 10 Hz. During the multi-day test, GPS measurements were recorded between 1 and 10 Hz. Carrier phase measurements were post-processed using a double difference approach developed at The University of Calgary in which integer ambiguities were resolved in seconds using the known antenna separations as constraints. The tracking capability of the system is demonstrated under dynamics consisting of roll and pitch angles up to 45 and 12 degrees, respectively. Comparisons between the GPS and INS ...

CERN Document Server

Over the last decade {\\it ab initio} modeling of material properties has become widespread in diverse fields of research. It has proved to be a powerful tool for predicting various properties of matter under extreme conditions. We apply modern computational chemistry and materials science methods, including density functional theory (DFT), to solve lingering problems in the modeling of the dense atmospheres of cool white dwarfs ($T_{\\rm eff}\\rm <7000 \\, K$). Our work on the revision and improvements of the absorption mechanisms in the hydrogen and helium dominated atmospheres resulted in a new set of atmosphere models. By inclusion of the Ly-$\\rm \\alpha$ red wing opacity we successfully fitted the entire spectral energy distributions of known cool DA stars. In the subsequent work we fitted the majority of the coolest stars with hydrogen-rich models. This finding challenges our understanding of the spectral evolution of cool white dwarfs. We discuss a few ...

Energy Technology Data Exchange (ETDEWEB)

The following subjects are dealt with: physics of indoor air flow, flow in individual rooms, exchange of air and pollution between individual building zones and with the outside world, thermal coupling with the building shell, thermal comfort and air quality, evaluation of the ventilation. figs., tabs., refs.

Energy Technology Data Exchange (ETDEWEB)

The multidimensional countercurrent two-phase flow regimes that occur in a pressurized-water reactor (PWR) vessel downcomer during the refill phase of a large-break loss-of-coolant accident are studied using a transparent 1/10 scale model of a PWR vessel. The various flow regimes and their distribution in the downcomer have been identified and mapped for a range of air-water flooding experiments. The two-phase flow patterns that are identified in the downcomer included various types of film flows, droplet flows, countercurrent churn flows and cocurrent flows depending on the flooding condition. Through observation of the two-phase flow dynamics it was deduced that the physical mechanisms associated with the flooding processes could be separated into a liquid entrainment process and a film flow ...

Energy Technology Data Exchange (ETDEWEB)

Traditional two-phase flow-regime criteria based on the gas and liquid superficial velocities may not be suitable to the analyses of rapid transient or entrance flows by the two-fluid model. Under these conditions, it is postulated that direct geometrical parameters such as the void fraction are conceptually simpler and therefore more reliable parameters to be used in flow-regime criteria than the traditional parameters. From this point of view, new flow-regime criteria for upward gas-liquid flow in vertical tubes have been developed considering the mechanisms of flow-regime transitions. These new criteria can be compared to existing criteria and experimental data under steady-state and fully developed flow conditions by using relative velocity correlations. The criteria showed reasonable agreements with the existing data for atmospheric ...

UK PubMed Central (United Kingdom)

Instantaneous cross sectional flow velocity profiles from early mitral flow in 10 healthy men were constructed by time interpolation of the velocity data from each point in sequentially delayed two...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

The Tevatron accelerator at Fermilab incorporates long two-phase helium passages. During magnet design, the generalized flow map of Baker was used to predict homogeneous flow. Longer than expected magnet time constants led to this investigation. The importance of predicting the flow regime has been amplified with the advent of non-horizontal accelerator designs. A test setup was constructed at Fermilab to investigate two-phase helium flow regimes for conditions practical in accelerator designs. The setup consisted of a standard Tevatron satellite refrigerator, subcooling dewar, heater, 35 m long transfer line, and a specialized end box. A knife blade on the midplane of the transfer line diverted the flow from the upper and lower halves of the pipe to separate vessels in the end box. The amount of liquid above and below the plane was measured at various total mass ...

British Library Electronic Table of Contents (United Kingdom)

The details of pulsating stochastic flows accompanying the interaction of a microwave filament (regarded as a heated rarefied channel) and an aerodynamic body in supersonic flow are examined numerically using the Euler equations. Symmetrical and asymmetrical filament locations relative to the aerodynamic body are considered. The flowfields are characterized by large scale pulsations and small scale stochastic fluctuations. The mechanisms of the formation of these flow structures are discussed. Two qualitatively different kinds of flowfields are observed depending on the magnitude of the filament radius, with domination of the pulsations of flow parameters or stochastic phenomena. Flow instabilities inherent to the problems under interest are described. The problems are considered in both p...

International Nuclear Information System (INIS)

In FY 1984 three specific tasks which are all related to not-well-understood two-phase phenomena of importance to LWR accidents have been identified under the program. These three tasks are: (1) inverted annular flow experiments and modeling; (2) hot leg U-bend two-phase flow simulation study; and (3) development and evaluation of two-phase flow scaling criteria. Some of the important results obtained under Tasks (1) and (2) are reported in this paper.

Science.gov (United States)

This paper deals with a mixed convection water flow in a horizontal rectangular duct, uniformly heated from one lateral vertical wall and thermally insulated elsewhere. The supplied heat flux induces a secondary flow, which structure is constituted of one longitudinal roll in the considered aspect ratio (? = 1.9), embedded into a return flow of possibly large stream wise extension (up to twenty channel heights). Such situation induces helicoidal trajectories for the fluid flow particles, which contributes to a heat transfer enhancement compared to purely forced convection flow.

International Nuclear Information System (INIS)

A visual study of film boiling is carried out to determine the flow regime transition in the post-CHF region. An idealized inverted annular flow is obtained by introducing a liquid jet of Freon 113 through a nozzle, precisely centered with respect to the internal diameter of the test section, with an annular gas flow. The respective ranges for liquid and gas velocities are 0.05-0.5 and 0.03-8.2 m s"-"1. Nitrogen and helium are used in the study. For the present configuration, there are four flow regimes; namely, the smooth inverted annular flow-section, the rough wavy, agitated and dispersed flow regimes. (author).

International Nuclear Information System (INIS)

This paper describes a series of tests investigating two-phase flow regimes in a transparent model of a PWR hot leg. Test conditions were selected to cover a wide range of gas and liquid superficial velocities (.01 m/s 2 m/s) were also performed for comparison with semi-analytical predictions. Results include average void fractions, flow rates, and visual characterizations of the two-phase flow phenomena. Results show generally good agreement with Taitel and Duckler flow regime map and Zuber-Findlay correlation for average void fraction in vertical pipes. Results also indicate that flow regimes and collapsed liquid level (void fraction) are more strongly dependent on air flow rate (air superficial velocity) than water flow rate (water superficial velocity).

UK PubMed Central (United Kingdom)

Absolute measurements of cerebral blood flow (CBF) are an important endpoint in studies of cerebral pathophysiology. Currently no accepted method exists for in vivo longitudinal...Full Text Available

Science.gov (United States)

... lated Reynolds number for separation is too small. Now ... lol (1959). 6.) F.Schultz-Grunow On stability of Couette flow, AGARD- ...

Science.gov (United States)

Jan 31, 2002 ... Sequential Flow of EDA Functionality for Flow with Separation ...... for Automated Air Traffic Management," AGARD Lecture Series No. ...

International Nuclear Information System (INIS)

... 5. Formation of the annular two-phase flow regime, with a wavy film on the

Science.gov (United States)

... of the cycle shows that the separation area ea. ... with suitable flow solvers based on the Reynolds ... AGARD 75th Fluid Dynamics Panel Meeting and ...

UK PubMed Central (United Kingdom)

Flow cytometry (FCM) is widely used in health research and in treatment for a variety of tasks, such as in the diagnosis and monitoring of leukemia and lymphoma patients, providing the counts of helper-T...Full Text Available

CERN Document Server

Protoplanetary disks start their lives with a dust free inner region where the temperatures are higher than the sublimation temperature of solids. As the star illuminates the innermost particles, which are immersed in gas at the sublimation edge, these particles are subject to a photophoretic force. We examine the motion of dust particles at the inner edge of protoplanetary disks due to photophoretic drag. We find that, in a laminar disk, photophoretic drag increases the size of the inner hole after accretion onto the central body has become subdued. This region within the hole becomes an optically transparent zone containing gas and large dusty particles (>>10 cm), but devoid of, or strongly depleted in, smaller dust aggregates. Photophoresis can clear the inner disk of dust out to 10 AU in less than 1 Myr. At late times, the edge reaches a stable equilibrium between inward drift and photophoretic outward drift, at a distance of some tens of AU. Eventually, ...

International Nuclear Information System (INIS)

There are three main types of radiation-processed composite material derived from plastics and fibrous natural polymers. The first are the monomer-impregnated, radiation-treated wood-plastic composites (WPC). They became a commercial success in the early 1970s. More recently, work has focused on improving the WPCs by creating in them interpenetrating network (IPN) systems by the use of appropriate multifunctional oligomers and monomers. The main kinetic features of radiation-initiated chain polymerization remain applicable even in impregnated wood. The second type are the plastics filled or reinforced with dispersed wood fiber or other cellulosics (WFRP). In their case, radiation processing offers a new opportunity to apply radiation-reactive adhesion promoters between wood or cellulosic fibers and the thermoplastic matrices. The third type are the laminar composites made by electron beam coating of wood-based agglomerate sheets and boards. This chapter reviews the ...

Energy Technology Data Exchange (ETDEWEB)

Asymmetric plasma divided by the magnetic filter (MF) is numerically simulated by the one-dimensional particle-in-cell code VSIM1D. Depending on the asymmetry, the system behaves static or dynamic. In the static state, the potentials of the main plasma and the sub-plasma are given by the sheath potentials, {phi}{sub M} - 3T{sub Me}/e and {phi}{sub S} - 3T{sub Se}/e, respectively, with e being an electron charge and T{sub Me} and T{sub Se} being electron temperatures (T{sub Me} > T{sub Se}). In the dynamics state, while {phi}{sub M} - 3T{sub Me}/e, {phi}{sub S} oscillates periodically between {phi}{sub S,min} - 3T{sub Se}/e and {phi}{sub S,max} - 3T{sub Me}/e. The ions accelerated by the time varying potential gap get into the sub-plasma and excite the laminar shock waves. This periodic phenomenon can be understood as a limit cycle due to transitions between two bifurcated states of {phi}{sub S,min} and {phi}{sub S,max}. (author)

Energy Technology Data Exchange (ETDEWEB)

In this study, the effects of hydrogen peroxide on laminar, premixed, methane-air flames at atmospheric pressure and temperature were investigated using CHEMKIN III and GRI 3.5 mechanism. The range of fuel/air equivalence ratio {phi} was varied from 0.6 to 1.2, and the amount of hydrogen peroxide was altered from 0% to 20% volumetric fraction of the methane-hydrogen peroxide (air excluded) mixture. The burning velocity was found to increase with increasing hydrogen peroxide addition, with a relatively larger increase for the fuel-richer mixtures ({delta}S{sub u} up to 15 cm/s for {phi} {approx}=1.2). The adiabatic flame temperature rose with hydrogen peroxide addition, and the temperature rise per unit hydrogen peroxide addition was more significant ({delta}T up to 100 K) for the leaner mixtures. For the same mixture stoichiometry, adding hydrogen peroxide also increased CO concentration and NO{sub x} emissions somewhat. Accordingly, the benefits of adding hydrogen ...

International Nuclear Information System (INIS)

A visual study of film boiling using photographic and high speed motion-picture methods was carried out to determine the flow regime transition criteria in the post-CHF region. An idealized inverted annular flow was obtained by introducing a liquid jet of Freon 113 through a nozzle, precisely centered with respect to the internal diameter of the test section, with an annular gas flow. The respective ranges for liquid and gas exit velocities were 0.05 to 0.5 and 0.03 to 7.9 m/s. Nitrogen and helium were used in the study. For the present configuration, there are four basic flow regimes. Beginning from the nozzle exit, there is a smooth, inverted annular flow section with liquid in the core and gas in the annulus; followed by the rough wavy section with an intact liquid core, the agitated and the dispersed flow regimes. For a given liquid jet velocity, the axial ...

International Nuclear Information System (INIS)

In this paper, we report on the analysis of reverse flow in inverted U-tubes of a steam generator under natural circulation condition. The mechanism of reverse flow in inverted U-tubes of the steam generator with natural circulation is graphically analyzed by using the full-range characteristic curve of parallel U-tubes. The mathematical model and numerical calculation method for analyzing the reverse flow in inverted U-tubes of the steam generator with natural circulation have been developed. The reverse flow in an inverted U-tube steam generator of a simulated pressurized water reactor with natural circulation in analyzed. Through the calculation, the mass flow rates of normal and reverse flows in individual U-tubes are obtained. The predicted sharp drop of the fluid temperature in the inlet plenum of the steam generator due to reverse ...

Energy Technology Data Exchange (ETDEWEB)

Multi-dimensional modelling of two-phase flow requires accurate constitutive relationships for interfacial parameters such as interfacial heat transfer, void fraction distribution, interfacial area, etc. However, existing diagnostic systems for measurement of two-phase flow parameters have difficulty measuring two or three-dimensional void distributions required for determination of interfacial parameters. In this work, a Real-Time Neutron Radiography (RTNR) system is developed for non-intrusive measurement of two-phase flow parameters in nuclear fuel channels at low thermal neutron fluxes (on the order of 10{sup 6}n/cm{sup 2}-s). This advanced radiation technique has the advantage of measuring two-phase flow in 3 1/2 dimensions (x,{integral}dy,t) where the 1/2 dimension refers to an integrated or averaged space dimension. Pipe flow channels, annulus flow ...

International Nuclear Information System (INIS)

A theoretical analysis of two-dimensional unsteady flow in a porous medium bounded by a horizontal wall is presented as a perturbation on a basic flow. It is assumed that the perturbation is occasioned by a sudden suction at the wall. Even for a highly permeable medium the characteristic Reynolds number in porous media flow is usually small and asymptotic solutions are developed by the Laplace transform technique. It is observed that the perturbed shear stress at the wall decays exponentially with time. (author). 5 refs.

KoreaScience (Korea)

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Science.gov (United States)

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KoreaScience (Korea)

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International Nuclear Information System (INIS)

The presentation deals with the flows on the primary side of a horizontal steam generator under conditions typical to natural circulation cooling of the reactor. The main goal is to analyse the effect of primary flow patterns on the heat transfer capability of the steam generator. Conclusions pertinent to steam generator modelling with system codes are also drawn. (10 refs., 9 figs., 4 tabs.).

International Nuclear Information System (INIS)

The seawater in the intake structure flows into the large pump to with draw excess heat from the turbine steam condenser. In the intake structure of a nuclear power plant, undesirable pump operating characteristics such as vortices, impeller damages and non-uniform pump-approach flow around the pump bells take place frequently due to poorly-arranged intake geometry. In this study, physical modeling test was performed to predict the hydraulic phenomenon, and proposed flow control devices.

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A numerical calculation procedure applicable to cavity-type receiver configurations and flow conditions was developed. Flow visualization experiments were performed, and experimental measurements of quantities valuable for the development of the numerical calculation procedure were made. The investigation is focussed on a configuration which is strongly two-dimensional in the mean flow structure (but turbulent in a truly three-dimensional sense). (LEW)

International Nuclear Information System (INIS)

Heat transfer augmentation by straight grid spacers in rod bundles is studied for single phase flow and for post critical heat flux dispersed flow. The heat transfer effect of swirling grid spacers in single phase flow is also examined. Governing heat transfer mechanisms are analyzed, and predictive formulations are established. For single phase flow, the local heat transfer at a straight spacer and at its upstream or downstream locations are treated separately. 18 refs.

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KoreaScience (Korea)

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... such as renal flow scan or a formal kidney X-ray, called an intravenous pyelogram ( IVP ), may help ...

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The purpose of the work described in this dissertation is to increase the understanding of injection-pultrusion process. Three major substudies related to injection-pultrusion have been completed: measurement of the compressibility of fiber reinforcements, measurement of in-plane and transverse resin flow through fiber reinforcements, and development of a resin flow model. This dissertation also presents results of an experimental and analytical investigation of in-plane and transverse resin flow through fiber reinforcements.

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British Library Electronic Table of Contents (United Kingdom)

In this study, the effects of channel surface wettability, cross-sectional geometry and orientation on the two-phase flow in parallel gas channels of proton exchange membrane fuel cells (PEMFCs) are investigated. Ex situ experiments were conducted in flow channels with three different surface wettability (hydrophilically coated, uncoated, and hydrophobically coated), three cross-sectional geometries (rectangular, sinusoidal and trapezoidal), and two orientations (vertical and horizontal). Flow pattern map, individual channel flow variation due to maldistribution, pressure drop and flow visualization images were used to analyze the two-phase flow characteristics. It is found that hydrophilically coated gas channels are advantageous over uncoated or slightly hydrophobic channels regarding un...

International Nuclear Information System (INIS)

Object: To permit a valve operation test to be periodically made during plant operation without causing variations in plant power by detecting flow control valve defect on the basis of a valve aperture alteration instruction. Structure: Step signals which are equal in absolute value and opposite in sign are coupled to the input side of flow controllers provided on the recycling loops of two or more recycling flow control systems. With these inputs the aperture of the flow control valve on one side is increased (or reduced) while the aperture of the valve on the other side is reduced (or increased). As a result, the recycling flow rate in the loop on one side is increased (or reduced) while that on the other side is reduced (or increased). Whether the valve is normally operating or not is confirmed by checking the recycling flow rate and valve aperture. ...

British Library Electronic Table of Contents (United Kingdom)

There are two difficulties encountered in modeling valveless micropumps using lumped-element methods. The pressure loss coefficient for fluidic diodes used in valveless pumps to rectify flow depends on the flow direction. A problem arises in choosing the proper loss correlation because the flow direction is not known a priori. Another problem is the quadratic form of the equation for the flow through the fluidic diodes, which brings about multiple solutions. The above problems become even more serious in multi-chamber cases. They are overcome in this study by suitably formulating the flow resistance. In addition, the flow inertia is accounted for in the unsteady model. The steady and unsteady models are evaluated by comparing with CFD simulations, which also serve to illustrate the flow fi...

British Library Electronic Table of Contents (United Kingdom)

Hydrological classification constitutes the first step of a new holistic framework for developing regional environmental flow criteria: the ?Ecological Limits of Hydrologic Alteration (ELOHA)?. The aim of this study was to develop a classification for 390 stream sections of the Segura River Basin based on 73 hydrological indices that characterize their natural flow regimes. The hydrological indices were calculated with 25?years of natural monthly flows (1980/81?2005/06) derived from a rainfall-runoff model developed by the Spanish Ministry of Environment and Public Works. These indices included, at a monthly or annual basis, measures of duration of droughts and central tendency and dispersion of flow magnitude (average, low and high flow conditions). Principal Component Analysis (PCA) indi...

International Nuclear Information System (INIS)

The present paper deals with the experimental determination of pressure drop across a four-cusped vertical channel. This geometry represents, ideally, the blockage condition in a typical pressurized water reactor with core degraded by accident. Experiments were performed for both single and two-phase flow. Water was utilized for the single-phase measurements whilst simultaneous flow of air and water simulated the steam-water flow. Observation of the prevailing two-phase flow regime was carried out, so that its mechanism could be fully understood. The averaged void fraction was also measured, by the gamma-ray attenuation technique. A wide range of water and air mass flow rates was covered, so that all flow conditions, possible to exist in a reactor with LOCA, could be investigated. New correlations for pressure drop are proposed. (Author).

International Nuclear Information System (INIS)

A Real-Time Neutron Radiography (RTNR) system and a high speed X-ray Computed tomography (X-CT) system are compared for measurement of two-phase flow. Each system is used to determine the flow regime, and the void fraction distribution in a vertical annulus flow channel. A standard optical video system is also used to observe the flow regime. The annulus flow channel is operated as a bubble column and measurements obtained for gas flow rates from 0.0 to 30.01/min. The flow regimes observed by all three measurement systems through image analysis shows that the two-dimensional void fraction distribution can be obtained. The X-CT system is shown to have a superior temporal resolution capable of resolving the void fraction distribution in an (r,#theta#) plane in 33.0 ms. Void fraction distribution for bubbly flow and slug ...

Energy Technology Data Exchange (ETDEWEB)

A safety analysis code to design a pressurized water reactor and to obtain the licenses including entire proprietary rights is under development in domestic R and D project. The tasks of KAERI is to develop the constitutive relations including models for defining flow regimes and flow regime related models for inter-phase friction, wall frictions, wall heat transfer, and interphase heat and mass transfer in the two-phase three-field equations. In this paper, the process will be presented for choosing the best flow regime maps which occur in gas-liquid two-phase flow in horizontal and vertical tubes.

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We have developed EOS7M, a ferrofluid flow and transport module for TOUGH2. EOS7M calculates the magnetic forces on ferrofluid caused by an external magnetic field and allows simulation of flow and advective transport of ferrofluid-water mixtures through porous media. Such flow problems are strongly coupled and well suited to the TOUGH2 framework. Preliminary applications of EOS7M to some simple pressure and flow problems for which experiments were carried out in the lab show good qualitative agreement with the laboratory results.

International Nuclear Information System (INIS)

A diagnosis of the refrigerant flows in a refrigerator was carried out by real-time neutron radiography. The thermal neutron radiography system of JRR-3M in Japan Atomic Energy Research Institute and the real-time image processing system developed by Musashi Institute of Technology were used. Freon evaporating flows in the evaporator, condensing flows in the condenser, flashing flows in the capillary tube and flows in the accumulator were visualized and the dynamic behaviors under practical conditions were clarified. In the case of the capillary tube of 0.8 mm i.d., a cooled-CCD camera was utilized. (orig.).

Energy Technology Data Exchange (ETDEWEB)

A proton exchange membrane fuel cell (PEMFC) must maintain a balance between the hydration level required for efficient proton transfer and excess liquid water that can impede the flow of gases to the electrodes where the reactions take place. Therefore, it is critically important to understand the two-phase flow of liquid water combined with either the hydrogen (anode) or air (cathode) streams. In this paper, we describe the design of an in situ test apparatus that enables investigation of two-phase channel flow within PEMFCs, including the flow of water from the porous gas diffusion layer (GDL) into the channel gas flows; the flow of water within the bipolar plate channels themselves; and the dynamics of flow through multiple channels connected to common manifolds which maintain a uniform pressure differential across all possible ...

International Nuclear Information System (INIS)

The two-phase flow regime transition in a large diameter (I.D.=200mm) vertical pipe was experimentally investigated using a dual-sensor optical probe. The flow transitions from bubbly to chum without an intermediate slug flow regime as the air flow rate is increased. The transition boundaries developed for bubbly to slug flow in small diameter pipes are compared to the bubbly to chum flow transition of the present experiment. The bubbly to chum transition occurs at a void fraction of about 0.15 compared to 0.25 for bubbly to slug transition in small diameter pipes. The radial distribution of bubble diameter, bubble frequency, bubble velocity and local void fraction were obtained using a dual-sensor optical probe at different flow conditions. The Probability Density Function (PDF) and Cumulative Distribution Function (CDF) of the bubble ...

International Nuclear Information System (INIS)

Liquid metal cooling for the first wall and blanket of a magnetic confinement fusion reactor has various advantages. However, it has the disadvantages of large magnetohydrodynamic pressure drops and heat transfer deterioration under a strong magnetic field. Thus, the present authors have proposed cooling with a helium-lithium annular mist flow as well as the cooling with a liquid metal boiling flow, and as fundamental studies, investigated the effect of a magnetic field on the flow characteristics and heat transfer of liquid metal two-phase systems since the 1970s. In the present paper we summarize the important findings obtained from our experimental studies for (i) an air-mercury stratified flow in a horizontal rectangular channel, (ii) a helium-lithium annular mist flow in a horizontal rectangular channel, (iii) the mercury pool boiling on a horizontal surface, and (iv) ...

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Sudden changes in the temperature of flowing liquids can result in transient buoyancy forces which strongly impact the flow hydrodynamics via flow stratification. These effects have been studied for the case of potential flow of stratified liquids to line sinks, but not for moderator flow in SRS reactors. Standard codes, such as TRAC and COMMIX, do not have the capability to capture the stratification effect, due to strong numerical diffusion which smears away the hot/cold fluid interface. A related problem with standard codes is the inability to track plumes injected into the liquid flow, again due to numerical diffusion. The combined effects of buoyant stratification and plume dispersion have been identified as being important in operation the Supplementary Safety System which injects neutron-poison ink into SRS reactors to provide safe shutdown in the event ...

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The purpose of the study is to investigate the heat transfer augmentation method for a wavy channel type heat exchanger. Experimental studies were carried out, by installation of flow guide-plates with simple structure, to clarify the effects on the augmentation whether the effects are brought by the flow acceleration or by the increase of intensity of turbulence due to the flow seperation, and to determine optimum shape of flow guide-plates. The shape and dimensions of the experimental apparatus are as follows; channel width H of 30 mm, rectangular section with breadth of 300 mm, wavy duct with a bend angle of 60/sup 0/ and straight pipe of 2H length. Air stream was flowed through the duct with Reynolds number of 1.7 x 10/sup 4/ only. As the results, following conclusions were obtained. (1) Wavy duct with large bend angle and without inserting flow guide-plates ...

International Nuclear Information System (INIS)

In a positive polarity induction adder each of the induction cavities is a cathode, which emits electrons at a unique potential. These broad spectrum electrons strongly affect Magnetically Insulated Transmission Line (MITL) behavior. Electron flow decreases the cavity-to-MITL coupling efficiency, and reduces the power transport efficiency along the system. Also, the operating impedance of the MITL is lowered, reducing the diode impedance required for good coupling and good total system power efficiency. It is therefore imperative to understand the details of MITL electron flow. In previous work, measurement of MITL electron flow for a twenty-stage linear induction adder (Hermes III), operated in positive polarity, was compared with simulations. There was qualitative agreement, but some differences were noted. For example, measured electron flow in the first cavities was greater than in the simulations. ...

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The Computational Fluid Dynamics(CFD) study was conducted to assess the new design concept introduced to solve the issues on the flow deviation between SG cassettes and the supporting structure design of the flow distributing plate subjected to the flow induced vibration. Flow field from MCP to the bottom of SG was modeled for 2-dimensional(2D) CFD analysis and then sensitivity analysis on major design parameters was conducted using commercial CFD code, Fluent. The cases for detailed 3D analysis were selected based on the result of 2D analysis and the detailed 3-dimensional(3D) analysis was conducted for these selected cases using Fluent code. Flow field was modeled by RNG model and wall function, 2nd upwind scheme, porous model, structured or hybrid grid. The analysis result shows that the maximum deviation of flow distribution between SG cassettes was reduced ...

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A descriptive model and design procedure for the DC electromagnetic flow coupler is developed based on a quasi-one-dimensional analysis previously developed for the DC electromagnetic pump. It is shown that for a particular flow coupler geometry, the total efficiency and the pressure gradients through the pump and generator depend on two parameters - the Hartmann number and the ratio of the pump flow rate to generator flow rate. Thus, for a fixed Hartmann number the efficiency depends only on the flow ratio. However, for a fixed pressure rise through the pump it is shown that the efficiency depends only on the Hartmann number. Nomographs showing the operating characteristics and critical design points are presented. Example calculations for a full-size unit, suitable for use in a liquid-metal cooled fast breeder reactor, are also discussed using the design nomographs.

International Nuclear Information System (INIS)

Decay heat removal capability under boiling condition was studied using an LMFBR fuel subassembly mockup loop. The sodium flow was driven by natural convection through the loop in which was installed a 37-pin bundle heated electrically over a length of 45 cm. The heat flux furnished by the pins was increased stepwise, upon which the two-phase flow regime changed from bubble to slug flow and then to annular or annular mist flow. Dryout occurred even in slug flow regime, but only momentarily, and permanent dryout was not observed before establichment of annular flow. A suitable criterion for permanent dryout is considered to be 0.5 average exit sodium vapor quality. The results indicated that upon occurrence of sodium boiling, the coolability of fuel subassembly would be maintained by natural convection after reactor shutdown. (author).

International Nuclear Information System (INIS)

Thermal hydraulics of a liquid metal is important to design the blanket of a magnetic confined fusion reactor. Since a liquid metal has high thermal and electrical conductivity, the flow characteristics are often different from those of an ordinary liquid like water especially in thermal convection and under a magnetic field. It is difficult to simulate such flows in a liquid metal cooled blanket by water. Flow visualization is a popular method to study thermal hydraulics. Since most of metals are visible by neutron rays, neutron radiography is available to the flow visualization of a liquid metal. The purpose of this study is to develop a visualization technique of the flow in a liquid metal by real-time neutron radiography using the tracer and the dye injection methods. A real-time thermal neutron radiography system of JRR-3M in Japan Atomic Energy Research Institute was used for ...

British Library Electronic Table of Contents (United Kingdom)

The investigation of steam, water, and air flow characteristics in horizontal channel is a part of major investigations program at the Lithuanian Energy Institute. The objective of this program is to identify condensation effects on two-phase flow stability and to predict conditions when rapid condensation could be induced in two-phase condensable flow. This article presents investigation of steam-water and air multiphase flow in nearly horizontal rectangular channel. The experimental data for pressure drop and interfacial and wall shear stresses in the channel with uniform distribution of void fraction are presented in this paper. Overall channel dimensions are length = 1.2 m, width = 0.02 m, height = 0.1 m; however, the test section was about 0.84 m in length. Three different flow types ...

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A hypothesis on the transition of a fully water-saturated coal bed methane reservoir from single-phase flow through unsaturated flow to the two-phase flow regime was developed and substantiated using field data. The concept of parameter measurement windows was introduced to obtain the required reservoir parameters from flow testing. A new empirical relationship for capillary pressure vs. saturation, referred to as the Fermi distribution, was developed and shown to fit the capillary pressure-saturation data for coal, sandstone, and other consolidated and unconsolidated materials. New approximate analytic solutions for flow to a sink from an infinite coal bed reservoir with desorbing methane have been developed and verified using numerical models for the following cases: (1) single-phase gas flow with desorption; (2) single-phase water flow in ...

Energy Technology Data Exchange (ETDEWEB)

Characteristics of pressure drop and heat transfer have been investigated for a lithium single-phase flow and a helium-lithium two-phase flow in a horizontal conducting circular channel in the presence of a uniform transverse magnetic field up to 1.4 T as related to the lithium cooling for magnetic-confinement fusion reactors. By the application of the magnetic field to the lithium single-phase flow, remarkable heat transfer enhancement has been observed at the top wall due to the suppression of the mixed convection occurring in the low Peclet number range, while appreciable heat transfer deterioration appeared in the high Peclet number range. It has been confirmed that the helium-lithium two-phase flow can reduce the high magnetohydrodynamic (MHD) pressure drop in a lithium single-phase flow, and it can provide much better heat transfer performance than that in a helium ...

UK PubMed Central (United Kingdom)

BackgroundWhile the gene flow in some organisms is strongly affected by physical barriers and geographical distance, other highly mobile species are able to overcome such constraints....Full Text Available

Science.gov (United States)

Experimental results are presented for a new and unique heat transfer augmentation technique in tubes. The technique consists of inserting a porous mesh structure into the flow passage of the tube. Due to the increased degree of turbulence, both the singl...

Science.gov (United States)

Dippold, V., S. Mohler , Validation of the Wind-US Unstructured Flow Solver .... Hamed, A. and A. Mohamed, Assessment of Shock Induced Flow Separation and ...... Nozzles for Hypersonic Propulsion, NASA CR 185197, AGARD Symposium ...

UK PubMed Central (United Kingdom)

1. Previous studies have shown that electrical stimulation (ES) of the guinea-pig cochlea causes a neurally mediated increase in cochlear blood flow (CBF). It is known that the centrifugal neuronal...Full Text Available

UK PubMed Central (United Kingdom)

An optical flow gradient algorithm was applied to spontaneously forming networks of neurons and glia in culture imaged by fluorescence optical microscopy in order to map functional calcium signaling...Full Text Available

Science.gov (United States)

Analytical method of theoretical simulation of collective hydrodynamic instabilities of intensive flows of discrete radiators, interacting with each other only through the coherent fields of their spontaneous radiation in corresponding media was suggested...

Energy Technology Data Exchange (ETDEWEB)

The oil production is largely transported in pipelines operating in two-phase flow regime. The predominant flow pattern is the slug flow, which is characterized by intermittent succession of liquid slugs followed by long gas bubbles. This paper addresses specifically to the capture of the intermittently feature of slug flows using a compressible slug tracking model. The intermittency rules the bubble to bubble interactions, defines the bubble coalescence rate, changes the size of the bubbles, alters the pressure drop among other flow properties. The inlet sizes and velocities of the bubbles and slugs are estimated based on experimentally determined distributions characterized by its mean value and standard deviation. The inlet intermittency, transmitted through the inlet boundary condition, results in a better match of the fluctuating flow properties along the ...

International Nuclear Information System (INIS)

In the region of annular liquid film-mist flow, the behavior of the droplets formed from the liquid film and the rate of formation are the subjects to be clarified in connection with the forecast of dry-out point, which becomes a problem in the region of high dryness such as reactor cooling system and steam generators. Many researches have been performed on such problem in vertical tubes, but the characteristics in horizontal flow have not yet been sufficiently clarified. This series of research is to clarify various characteristics, such as the velocity of vapor phase, the flow rate distribution of droplets, the formation and adhesion of droplets and the structure of liquid film, in the region of liquid film-mist flow, where liquid film exists on the bottom of a horizontal rectangular channel, and vapor flow is accompanied by droplets. In this study, by the measurement of the ...

International Nuclear Information System (INIS)

To increase further the accuracy of flow regime and considering the non-stationary characteristics of differential pressure fluctuation signals of gas-liquid two-phase flow, the flow regime identification method based on recurrence quantification analysis (RQA) and multi-sensor data fusion techniques is put forward. First of all, the recurrence quantification analysis method is used to extract the nonlinear feature parameters of the differential pressure fluctuation signals of gas-liquid two-phase flow, and data fusion of feature layer is conducted by QRA feature parameters of differential pressure signals of three pressure measure intervals, and composes the fusion feature vectors. The fused characteristic vector are input into the support vector machine for identify flow regime. The identification results for four typical flow regimes of air-water two-phase ...

International Nuclear Information System (INIS)

A technique was developed that permits fluid flow to be visualized even where the flow is completely shrouded by metal. The technique employs real-time neutron radiography, which is similar to x-ray radiography except a collimated beam of neutrons is used. Various combinations of neutron-opaque tracer materials were tested with neutron-transparent fluid. Neutron opaque tracers, such as solid particles, fluid droplets, and streaklines were imaged through metal walls as they convected in neutron-transparent ambient fluid. Visualization of bubbles/voids were evaluated for possible future applications. Surface-flow patterns were also imaged by using neutron-opaque tufts. These techniques were evaluated for image contrast, resolution, and the ability to accurately track fluid flow fields. The techniques were also modeled to optimize contrast in various flow configurations. Imaging ...

CERN Document Server

We present faster approximation algorithms for generalized network flow problems. A generalized flow is one in which the flow out of an edge differs from the flow into the edge by a constant factor. We limit ourselves to the lossy case, when these factors are at most 1. Our algorithm uses a standard interior-point algorithm to solve a linear program formulation of the network flow problem. The system of linear equations that arises at each step of the interior-point algorithm takes the form of a symmetric M-matrix. We present an algorithm for solving such systems in nearly linear time. The algorithm relies on the Spielman-Teng nearly linear time algorithm for solving linear systems in diagonally-dominant matrices. For a graph with m edges, our algorithm obtains an additive epsilon approximation of the maximum generalized flow and minimum cost generalized ...

UK PubMed Central (United Kingdom)

IntroductionFlow diversion is a new approach to the endovascular treatment of intracranial aneurysms which uses a high density mesh stent to induce sac thrombosis. These devices...Full Text Available

Science.gov (United States)

... LC Cgraphic AncIy.;:i3 of Plasmia Flows;" Dept. of Aero-Astro, Enga., The Ohio S~ate Uni vevsity; ASI) TIch. DocutuutaL.'y lRepL. ...

International Nuclear Information System (INIS)

The endovascular treatment of atherosclerotic intracranial arterial stenoses has previously been based on balloon dilatation or the deployment of a balloon expandable stent. Both methods have advantages (balloon: flexibility; balloon expandable stent: high radial force) and drawbacks (balloon: risk of elastic recoil and dissection; balloon expandable stent: limited flexibility, risk of injury to the vessel due to excessive straightening, overexpansion at ends of stent). A new combination of balloon dilatation, followed by the deployment of a self-expanding microstent has been applied in 15 patients with atherosclerotic arterial stenoses, symptomatic despite medical treatment. An anatomically and clinically adequate result was achieved in all patients. The initial degree of stenosis was 72% (mean). Balloon dilatation resulted in an average residual stenosis of 54% (mean), reduced further to a mean of 38% after stent deployment. Arterial dissection, occlusion of the target artery or ...

International Nuclear Information System (INIS)

Suspension direct current plasma spraying allows achieving finely structured coatings whose thickness is between few tens and few hundreds of micrometres. Drops (200-300 ?m in diameter) or liquid jets are mechanically injected in the plasma jet. With radial injection they are rapidly (a few ?s) fragmented into droplets (a few ?m in diameter). The latter are vaporized (in a few ?s) and the solid particles contained in suspension droplets are accelerated and melted by the plasma jet. As in conventional plasma spraying (CPS), much smaller splats (with diameters between 0.2 and 3 ?m and thicknesses between 30 and 200 nm) are arranged in layers up to form the coating. The low inertia of particles requires spray distances between 40 and 60 mm which induces plasma heat fluxes up to 22 MW m-2 participating in coating densification. Even more than in CPS, the plasma jet fluctuations, particularly for plasmas containing di-atomic gases, perturb drops penetration and fragmentation. It has been ...

International Nuclear Information System (INIS)