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Sample records for annular two-phase jet

  1. Two-phase viscoelastic jetting

    SciTech Connect

    Yu, J-D; Sakai, S.; Sethian, J.A.

    2008-12-10

    A coupled finite difference algorithm on rectangular grids is developed for viscoelastic ink ejection simulations. The ink is modeled by the Oldroyd-B viscoelastic fluid model. The coupled algorithm seamlessly incorporates several things: (1) a coupled level set-projection method for incompressible immiscible two-phase fluid flows; (2) a higher-order Godunov type algorithm for the convection terms in the momentum and level set equations; (3) a simple first-order upwind algorithm for the convection term in the viscoelastic stress equations; (4) central difference approximations for viscosity, surface tension, and upper-convected derivative terms; and (5) an equivalent circuit model to calculate the inflow pressure (or flow rate) from dynamic voltage.

  2. Interfacial shear modeling in two-phase annular flow

    SciTech Connect

    Kumar, R.; Edwards, D.P.

    1996-07-01

    A new interfacial shear stress model called the law of the interface model, based on the law of the wall approach in turbulent flows, has been developed and locally applied in a fully developed, adiabatic, two-phase annular flow in a duct. Numerical results have been obtained using this model in conjunction with other models available in the literature that are required for the closure of the continuity and momentum equations. These results have been compared with droplet velocity data (using laser Doppler velocimetry and hot film anemometry), void fraction data (using gamma densitometry) and pressure drop data obtained in a R-134A refrigerant test facility. Droplet velocity results match the experimental data well, however, the prediction of the void fraction is less accurate. The poor prediction of void fraction, especially for the low void fraction cases, appears to be due to the lack of a good mechanistic model for entrainment.

  3. Two-phase flow instabilities in a vertical annular channel

    SciTech Connect

    Babelli, I.; Nair, S.; Ishii, M.

    1995-09-01

    An experimental test facility was built to study two-phase flow instabilities in vertical annular channel with emphasis on downward flow under low pressure and low flow conditions. The specific geometry of the test section is similar to the fuel-target sub-channel of the Savannah River Site (SRS) Mark 22 fuel assembly. Critical Heat Flux (CHF) was observed following flow excursion and flow reversal in the test section. Density wave instability was not recorded in this series of experimental runs. The results of this experimental study show that flow excursion is the dominant instability mode under low flow, low pressure, and down flow conditions. The onset of instability data are plotted on the subcooling-Zuber (phase change) numbers stability plane.

  4. Bistability and hysteresis of annular impinging jets

    NASA Astrophysics Data System (ADS)

    Tisovsky, Tomas

    2016-06-01

    In present study, the bistability and hysteresis of annular impinging jets is investigated. Annular impinging jets are simulated using open source CFD code - OpenFOAM. Both flow field patterns of interest are obtained and hysteresis is found by means of dynamic mesh simulation. Effect of nozzle exit velocity on resulting hysteresis loop is also illustrated.

  5. Characterization of annular two-phase gas-liquid flows in microgravity

    NASA Technical Reports Server (NTRS)

    Bousman, W. Scott; Mcquillen, John B.

    1994-01-01

    A series of two-phase gas-liquid flow experiments were developed to study annular flows in microgravity using the NASA Lewis Learjet. A test section was built to measure the liquid film thickness around the perimeter of the tube permitting the three dimensional nature of the gas-liquid interface to be observed. A second test section was used to measure the film thickness, pressure drop and wall shear stress in annular microgravity two-phase flows. Three liquids were studied to determine the effects of liquid viscosity and surface tension. The result of this study provide insight into the wave characteristics, pressure drop and droplet entrainment in microgravity annular flows.

  6. Two-Phase Annular Flow in Helical Coil Flow Channels in a Reduced Gravity Environment

    NASA Technical Reports Server (NTRS)

    Keshock, Edward G.; Lin, Chin S.

    1996-01-01

    A brief review of both single- and two-phase flow studies in curved and coiled flow geometries is first presented. Some of the complexities of two-phase liquid-vapor flow in curved and coiled geometries are discussed, and serve as an introduction to the advantages of observing such flows under a low-gravity environment. The studies proposed -- annular two-phase air-water flow in helical coil flow channels are described. Objectives of the studies are summarized.

  7. Vapor core turbulence in annular two-phase flow

    SciTech Connect

    Trabold, T.A.; Kumar, R.

    1998-06-01

    This paper reports a new technique to measure vapor turbulence in two-phase flows using hot-film anemometry. Continuous vapor turbulence measurements along with local void fraction, droplet frequency, droplet velocity and droplet diameter were measured in a thin, vertical duct. By first eliminating the portion of the output voltage signal resulting from the interaction of dispersed liquid droplets with the HFA sensor, the discrete voltage samples associated with the vapor phase were separately analyzed. The data revealed that, over the range of liquid droplet sizes and concentrations encountered, the presence of the droplet field acts to enhance vapor turbulence. In addition, there is evidence that vapor turbulence is significantly influenced by the wall-bounded liquid film. The present results are qualitatively consistent with the limited data available in the open literature.

  8. Liquid jet pumps for two-phase flows

    SciTech Connect

    Cunningham, R.G.

    1995-06-01

    Isothermal compression of a bubbly secondary fluid in a mixing-throat and diffuser is described by a one-dimensional flow model of a liquid-jet pump. Friction-loss coefficients used in the four equations may be determined experimentally, or taken from the literature. The model reduces to the liquid-jet gas compressor case if the secondary liquid is zero. Conversely, a zero secondary-gas flow reduces the liquid-jet gas and liquid (LJGL) model to that of the familiar liquid-jet liquid pump. A ``jet loss`` occurs in liquid-jet pumps if the nozzle tip is withdrawn from the entrance plane of the throat, and jet loss is included in the efficiency equations. Comparisons are made with published test data for liquid-jet liquid pumps and for liquid-jet gas compressors. The LJGL model is used to explore jet pump responses to two-phase secondary flows, nozzle-to-throat area ratio, and primary-jet velocity. The results are shown in terms of performance curves versus flow ratios. Predicted peak efficiencies are approximately 50 percent. Under sever operating conditions, LJGL pump performance curves exhibit maximum-flow ratios or cut-offs. Cut-offs occurs when two-phase secondary-flow steams attain sonic values at the entry of the mixing throat. A dimensionless number correlates flow-ratio cut-offs with pump geometry and operating conditions. Throat-entry choking of the secondary flow can be predicted, hence avoided, in designing jet pumps to hand two-phase fluids.

  9. A jet polishing technique for thinning two phase materials

    SciTech Connect

    Witcomb, M.J. ); Dahmen, U. )

    1990-11-01

    A common problem in the preparation of thin foils for transmission electron microscopy is the different thinning rate in two-phase materials. Often this leads to foils in which the majority, or matrix, phase is evenly polished while the minority, or precipitate, phase is either etched out or stands proud of the surrounding material. In the present report we describe a two-stage jet polishing technique that has been used successfully on different relatively coarse two-phase structures. 3 figs.

  10. Modelling Air and Water Two-Phase Annular Flow in a Small Horizontal Pipe

    NASA Astrophysics Data System (ADS)

    Yao, Jun; Yao, Yufeng; Arini, Antonino; McIiwain, Stuart; Gordon, Timothy

    2016-06-01

    Numerical simulation using computational fluid dynamics (CFD) has been carried out to study air and water two-phase flow in a small horizontal pipe of an inner diameter of 8.8mm, in order to investigate unsteady flow pattern transition behaviours and underlying physical mechanisms. The surface liquid film thickness distributions, determined by either wavy or full annular flow regime, are shown in reasonable good agreement with available experimental data. It was demonstrated that CFD simulation was able to predict wavy flow structures accurately using two-phase flow sub-models embedded in ANSYS-Fluent solver of Eulerian-Eulerian framework, together with a user defined function subroutine ANWAVER-UDF. The flow transient behaviours from bubbly to annular flow patterns and the liquid film distributions revealed the presence of gas/liquid interferences between air and water film interface. An increase of upper wall liquid film thickness along the pipe was observed for both wavy annular and full annular scenarios. It was found that the liquid wavy front can be further broken down to form the water moisture with liquid droplets penetrating upwards. There are discrepancies between CFD predictions and experimental data on the liquid film thickness determined at the bottom and the upper wall surfaces, and the obtained modelling information can be used to assist further 3D user defined function subroutine development, especially when CFD simulation becomes much more expense to model full 3D two-phase flow transient performance from a wavy annular to a fully developed annular type.

  11. Experimental study of a two-phase surface jet

    NASA Astrophysics Data System (ADS)

    Perret, Matias; Esmaeilpour, Mehdi; Politano, Marcela S.; Carrica, Pablo M.

    2013-04-01

    Results of an experimental study of a two-phase jet are presented, with the jet issued near and below a free surface, parallel to it. The jet under study is isothermal and in fresh water, with air injectors that allow variation of the inlet air volume fraction between 0 and 13 %. Measurements of water velocity have been performed using LDV, and the jet exit conditions measured with PIV. Air volume fraction, bubble velocity and chord length distributions were measured with sapphire optical local phase detection probes. The mean free surface elevation and RMS fluctuations were obtained using local phase detection probes as well. Visualization was performed with laser-induced fluorescence. Measurements reveal that the mean free surface elevation and turbulent fluctuations significantly increase with the injection of air. The water normal Reynolds stresses are damped by the presence of bubbles in the bulk of the liquid, but very close to the free surface the effect is reversed and the normal Reynolds stresses increase slightly for the bubbly flow. The Reynolds shear stresses < {u^' } w^' } } rangle decrease when bubbles are injected, indicating turbulence attenuation, and are negative at deeper locations, as turbulent eddies shed downward carry high axial momentum deeper into the flow. Flow visualization reveals that the two-phase jet is lifted with the presence of bubbles and reaches the free surface sooner. Significant bubble coalescence is observed, leading to an increase in mean bubble size as the jet develops. The coalescence near the free surface is particularly strong, due to the time it takes the bubbles to pierce the free surface, resulting in a considerable increase in the local air volume fraction. In addition to first explore a bubbly surface jet, the comprehensive dataset reported herein can be used to validate two-phase flow models and computational tools.

  12. Dynamics of face and annular seals with two-phase flow

    NASA Technical Reports Server (NTRS)

    Hughes, William F.; Basu, Prithwish; Beatty, Paul A.; Beeler, Richard M.; Lau, Stephen

    1989-01-01

    A detailed study was made of face and annular seals under conditions where boiling, i.e., phase change of the leaking fluid, occurs within the seal. Many seals operate in this mode because of flashing due to pressure drop and/or heat input from frictional heating. High pressure, water pumps, industrial chemical pumps, and cryogenic pumps are mentioned as a few of many applications. The initial motivation was the LOX-GOX seals for the space shuttle main engine, but the study was expanded to include any face or annular seal where boiling occurs. Some of the distinctive behavior characteristics of two-phase seals were discussed, particularly their axial stability. While two-phase seals probably exhibit instability to disturbances of other degrees of freedom such as wobble, etc., under certain conditions, such analyses are too complex to be treated at present. Since an all liquid seal (with parallel faces) has a neutral axial stiffness curve, and is stabilized axially by convergent coning, other degrees of freedom stability analyses are necessary. However, the axial stability behavior of the two-phase seal is always a consideration no matter how well the seal is aligned and regardless of the speed. Hence, axial stability is thought of as the primary design consideration for two-phase seals and indeed the stability behavior under sub-cooling variations probably overshadows other concerns. The main thrust was the dynamic analysis of axial motion of two-phase face seals, principally the determination of axial stiffness, and the steady behavior of two-phase annular seals. The main conclusions are that seals with two-phase flow may be unstable if improperly balanced. Detailed theoretical analyses of low (laminar) and high (turbulent) leakage seals are presented along with computer codes, parametric studies, and in particular a simplified PC based code that allows for rapid performance prediction. A simplified combined computer code for the performance prediction over the

  13. Dynamics of face and annular seals with two-phase flow

    NASA Technical Reports Server (NTRS)

    Hughes, William F.; Basu, Prithwish; Beatty, Paul A.; Beeler, Richard M.; Lau, Stephen

    1988-01-01

    A detailed study was made of face and annular seals under conditions where boiling, i.e., phase change of the leaking fluid, occurs within the seal. Many seals operate in this mode because of flashing due to pressure drop and/or heat input from frictional heating. Some of the distinctive behavior characteristics of two phase seals are discussed, particularly their axial stability. The main conclusions are that seals with two phase flow may be unstable if improperly balanced. Detailed theoretical analyses of low (laminar) and high (turbulent) leakage seals are presented along with computer codes, parametric studies, and in particular a simplified PC based code that allows for rapid performance prediction: calculations of stiffness coefficients, temperature and pressure distributions, and leakage rates for parallel and coned face seals. A simplified combined computer code for the performance prediction over the laminar and turbulent ranges of a two phase flow is described and documented. The analyses, results, and computer codes are summarized.

  14. Flow field simulation of gas-water two phase flow in annular channel

    NASA Astrophysics Data System (ADS)

    Ji, Pengcheng; Dong, Feng

    2014-04-01

    The gas-water two-phase flow is very common in the industrial processes. the deep understanding of the two-phase flow state is to achieve the production equipment design and safe operation. In the measurement of gas-water two-phase flow, the differential pressure sensor is widely used, and some measurement model of multiphase flow have been concluded. The differential pressure is generated when fluid flowing through the throttling components to calculate flow rate. This paper mainly focuses on two points: 1. The change rule of the parameters include velocity, pressure, phase fraction as the change of time, when the phase inlet velocity is given. 2. Analysis the distribution of the parameters above-mentioned at a certain moment under the condition of different water inlet velocity. Three-dimensional computational fluid dynamics (CFD) approach was used to simulate gas-water two-phase flow fluid in the annular channel, which is composed of horizontal pipe and long- waist cone sensor. The simulation results were obtained from FLUENT software.

  15. Numerical calculation of two-phase turbulent jets

    SciTech Connect

    Saif, A.A.

    1995-05-01

    Two-phase turbulent round jets were numerically simulated using a multidimensional two-phase CFD code based on the two-fluid model. The turbulence phenomena were treated with the standard k-{epsilon} model. It was modified to take into account the additional dissipation of turbulent kinetic energy by the dispersed phase. Within the context of the two-fluid model it is more appropriate and physically justified to treat the diffusion by an interfacial force in the momentum equation. In this work, the diffusion force and the additional dissipation effect by the dispersed phase were modeled starting from the classical turbulent energy spectrum analysis. A cut-off frequency was proposed to decrease the dissipation effect by the dispersed phase when large size particles are introduced in the flow. The cut-off frequency combined with the bubble-induced turbulence effect allows for an increase in turbulence for large particles. Additional care was taken in choosing the right kind of experimental data from the literature so that a good separate effect test was possible for their models. The models predicted the experimental data very closely and they were general enough to predict extreme limit cases: water-bubble and air-droplet jets.

  16. A Local Condensation Analysis Representing Two-phase Annular Flow in Condenser/radiator Capillary Tubes

    NASA Technical Reports Server (NTRS)

    Karimi, Amir

    1991-01-01

    NASA's effort for the thermal environmental control of the Space Station Freedom is directed towards the design, analysis, and development of an Active Thermal Control System (ATCS). A two phase, flow through condenser/radiator concept was baselined, as a part of the ATCS, for the radiation of space station thermal load into space. The proposed condenser rejects heat through direct condensation of ATCS working fluid (ammonia) in the small diameter radiator tubes. Analysis of the condensation process and design of condenser tubes are based on the available two phase flow models for the prediction of flow regimes, heat transfer, and pressure drops. The prediction formulas use the existing empirical relationships of friction factor at gas-liquid interface. An attempt is made to study the stability of interfacial waves in two phase annular flow. The formulation is presented of a stability problem in cylindrical coordinates. The contribution of fluid viscosity, surface tension, and transverse radius of curvature to the interfacial surface is included. A solution is obtained for Kelvin-Helmholtz instability problem which can be used to determine the critical and most dangerous wavelengths for interfacial waves.

  17. CORRELATION FOR LIQUID ENTRAINMENT IN ANNULAR TWO-PHASE FLOW OF LOW VISCOUS FLUID

    SciTech Connect

    Ishii, Mamoru; Mishima, Kaichiro

    1981-03-01

    The droplet entrainment from a liquid film by gas flow is important to mass, momentum, and energy transfer in annular two-phase flow. The amount of entrainment can significantly affect occurrences of the dryout and post-dryout heat flux as well as the rewetting phenomena of a hot dry surface. In view of these, a correlation for the amount of entrained liquid in annular flow has been developed from a simple model and experimental data. There are basically two different regions of entrainment, namely, the entrance and quasiequilibrium regions. The correlation for the equilibrium region is expressed in terms of the dimensionless gas flux, diameter, and total liquid Reynolds number. The entrance effect is taken into account by an exponential relaxation function. It has been shown that this new model can satisfactorily correlate wide ranges of experimental data for water. Furthermore, the necessary distance for the development of entrainment is identified. These correlations, therefore, can supply accurate information on entrainment which have not been available previously. (author)

  18. The Annular Two-phase Flow on Rod Bundle: The Effects of Spacers

    NASA Astrophysics Data System (ADS)

    Kunugi, Tomoaki; Pham, Son; Kawara, Zensaku; Yokomine, Takehiko

    2013-11-01

    The annular two-phase flow on rod bundle keeps an important role in many heat exchange systems but our knowledge about it, especially the interaction between the liquid film flowing on the rods' surfaces and the spacers is very limited. This study is aimed to the investigation of how the spacer affects the disturbance waves of the flow in a 3 × 3 simulating BWR fuel rod bundle test section. Firstly, the characteristics of the disturbance waves at both upstream and downstream locations of the spacer were obtained by using reflected light arrangement with a high speed camera Phantom V7.1 (Vision Research Inc.) and a Nikon macro lens 105mm f/2.8. The data showed that the parameters such as frequency and circumferential coherence of the disturbance waves are strongly modified when they go through the spacer. Then, the observations at the locations right before and after the spacer were performed by using the back light arrangement with the same high speed camera and a Cassegrain optical system (Seika Cooperation). The obtained images at micro-scale of time and space provided the descriptions of the wavy interface behaviors right before and after the spacer as well as different droplets creation processes caused by the presence of this spacer.

  19. Effect of Pressure with Wall Heating in Annular Two-Phase Flow

    SciTech Connect

    R. Kumar; T.A. Trabold

    2000-10-31

    The local distributions of void fraction, interfacial frequency and velocity have been measured in annular flow of R-134a through a wall-heated, high aspect ratio duct. High aspect ratio ducts provide superior optical access to tubes or irregular geometries. This work expands upon earlier experiments conducted with adiabatic flows in the same test section. Use of thin, transparent heater films on quartz windows provided sufficient electrical power capacity to produce the full range of two-phase conditions of interest. With wall vapor generation, the system pressure was varied from 0.9 to 2.4 MPa, thus allowing the investigation of flows with liquid-to-vapor density ratios covering the range of about 7 to 27, far less than studied in air-water and similar systems. There is evidence that for a given cross-sectional average void fraction, the local phase distributions can be different depending on whether the vapor phase is generated at the wall, or upstream of the test section inlet. In wall-heated flows, local void fraction profiles measured across both the wide and narrow test section dimensions illustrate the profound effect that pressure has on the local flow structure; notably, increasing pressure appears to thin the wall-bounded liquid films and redistribute liquid toward the edges of the test section. This general trend is also manifested in the distributions of mean droplet diameter and interfacial area density, which are inferred from local measurements of void fraction, droplet frequency and velocity. At high pressure, the interfacial area density is increased due to the significant enhancement in droplet concentration.

  20. An experimental investigation of straight and curved annular wall jets

    NASA Technical Reports Server (NTRS)

    Rodman, L. C.; Wood, N. J.; Roberts, L.

    1987-01-01

    Accurate turbulence measurements taken in wall jet flows are difficult to obtain, due to high intensity turbulence and problems in achieving two-dimensionality. The problem is compounded when streamwise curvature of the flow is introduced, since the jet entrainment and turbulence levels are greatly increased over the equivalent planar values. In this experiment, two-dimensional straight and curved incompressible wall jet flows are simulated by having a jet blow axially over a cylinder. Hot wire measurements and some Laser Doppler Velocimetry measurements are presented for straight and curved wall jet flows. The results for the straight wall showed good agreement between the annular flow data and the rectangular data taken by previous researchers. For the jets with streamwise curvature, there was agreement between the annular and corresponding rectangular jets for the flow region closest to the slot exit. An integral analysis was used as a simple technique to interpret the experimental results. Integral momentum calculations were performed for both straight and curved annular and two dimensional wall jets. The results of the calculation were used to identify transverse curvature parameters and to predict the values of those parameters which would delineate the region where the annular flow can satisfactorily simulate two dimensional flow.

  1. Droplet entrainment correlation for high pressure annular two-phase flow

    SciTech Connect

    Lopez de Betodano, M.A.; Jan, Cheng-Shiun; Beus, S.G.

    1996-01-01

    The amount of entrainment in annular flow is essential to predict the point of dryout. Most of the entrainment correlations available in the literature are obtained from air-water low pressure data. However many important industrial applications involve high pressure annular flows. There are very few correlations applicable in this range and they are solely based on empirical data fits. Comparing the low pressure entrainment data of Cousins and Hewitt (1968) and the high pressure data of Keeys et. al. (1970) and Wurtz (1978) with existing correlations, the agreement at high pressure is generally poor, except for the empirical correlation of Nigmatulin and Krushenok (1989) which depends on a Weber number that includes the droplet concentration. We propose a new semi-mechanistic entrainment correlation for fully developed annular flow conditions: E = (0.9642)/(1 + (3836/We{sub C})). It is developed based on the droplet continuity equation and the entrainment rate model of Dallman et. al. (1979). This model is then modified to introduce a Weber number that includes the droplet concentration, We{sub C}. This Weber number is shown to scale the available high and low pressure air-water and steam-water data better than the other definitions. Because the new correlation is based on a model of entrainment rate it may be used as a starting point in the development of a correlation for this process applicable to high pressure water-steam annular flows. A correlation is suggested pending validation with high pressure entrainment rate data. 12 refs., 11 figs.

  2. Theoretical and pragmatic modeling of governing equations for two-phase flow in bubbly and annular flow regimes

    SciTech Connect

    Bottoni, M.; Ajuha, S.; Sengpiel, W.

    1994-12-31

    Starting from the rigorous formulation of the conservation equations for mass, momentum and enthalpy derived for a two-phase flow by volume-averaging microscopic balance equations over Eulerian control cells, the article discusses the formulation of the terms describing exchanges between the phases. Two flow regimes are taken into consideration; bubbly flow, applicable for small or medium void fractions, and annular flow, for large void fractions. When lack of knowledge of volume-averaged physical quantities makes the rigorously formulated terms useless for computational purposes, modeling of these terms is discussed.

  3. Theoretical and pragmatic modelling of governing equations for a two-phase flow in bubbly and annular flow regimes

    SciTech Connect

    Bottoni, M.; Sengpiel, W.

    1992-12-01

    Starting from the rigorous formulation of the conservation equations for mass, momentum and enthalpy, derived for a two-phase flow by volume averaging microscopic balance equations over Eulerian control cells, the article discusses the formulation of the terms describing exchanges between the phases. Two flow regimes are taken into consideration, bubbly flow, applicable for small or medium void fractions, and annular flow, for large void fractions. When lack of knowledge of volume-averaged physical quantities make the rigorously formulated terms useless for computational purposes, modelling of these terms is discussed. 3 figs., 15 refs.

  4. Theoretical and pragmatic modelling of governing equations for a two-phase flow in bubbly and annular flow regimes

    SciTech Connect

    Bottoni, M. . Materials and Components Technology Div.); Sengpiel, W. . Inst. fuer Reaktorsicherheit)

    1992-01-01

    Starting from the rigorous formulation of the conservation equations for mass, momentum and enthalpy, derived for a two-phase flow by volume averaging microscopic balance equations over Eulerian control cells, the article discusses the formulation of the terms describing exchanges between the phases. Two flow regimes are taken into consideration, bubbly flow, applicable for small or medium void fractions, and annular flow, for large void fractions. When lack of knowledge of volume-averaged physical quantities make the rigorously formulated terms useless for computational purposes, modelling of these terms is discussed. 3 figs., 15 refs.

  5. Film Thickness Prediction in an Annular Two-Phase Flow Through Bends

    NASA Astrophysics Data System (ADS)

    Tkaczyk, P. M.; Morvan, H. P.

    2010-09-01

    A finite volume method-based CFD model has been developed in the commercial code Star CD to simulate the annular gas-liquid flow through the 30°, 60° and 90° bends. The liquid film is solved explicitly by means of a modified Volume of Fluid (VOF) method. The droplets are traced using a Lagrangian technique. The film to droplets (entrainment) and droplets to film (stick, bounce, spread and splash) interactions are taken into account using sub-models to complement the VOF model. A good agreement is found between the computed film thickness value and those cited in the literature.

  6. Simulation of two phase flow of liquid - solid in the annular space in drilling operation

    NASA Astrophysics Data System (ADS)

    Kootiani, Reza Cheraghi; Samsuri, Ariffin Bin

    2014-10-01

    Drilling cutting transfer is an important factor in oil and gas wells drilling. So that success drilling operation is directly dependent on the quality of clean the wellbore drilling operation. In this paper, modeled upward flow of liquid - solid in the annular concentric and non-concentric in the well drilling by Euler two - fluid model and then analysis using numerical method. Numerical simulation of liquid - solid flow evaluated initially with a Newtonian fluid (water) and then a non-Newtonian fluid (CMC solution 0.4%). After that, investigated the effect of parameters such as flow rate, rotating drill pipe and out of centered on drilling operations. The results show that drilling cutting transfer is improve due to the rotation of drill pipe particularly in drilling operations.

  7. Jet mixing and emission characteristics of transverse jets in annular and cylindrical confined crossflow

    NASA Technical Reports Server (NTRS)

    Bain, D. B.; Smith, C. E.; Holdeman, J. D.

    1995-01-01

    Three dimensional turbulent reacting CFD analyses were performed on transverse jets injected into annular and cylindrical (can) confined crossflows. The goal was to identify and assess mixing differences between annular and can geometries. The approach taken was to optimize both annular and can configurations by systematically varying orifice spacing until lowest emissions were achieved, and then compare the results. Numerical test conditions consisted of a jet-to-mainstream mass-flow ratio of 3.2 and a jet-to-mainstream momentum-flux ratio (J) of 30. The computational results showed that the optimized geometries had similar emission levels at the exit of the mixing section although the annular configuration did mix-out faster. For lowest emissions, the density correlation parameter (C = (S/H) square root of J) was 2.35 for the annular geometry and 3.5 for the can geometry. For the annular geometry, the constant was about twice the value seen for jet mixing at low mass-flow ratios (i.e., MR less than 0.5). For the can geometry, the constant was about 1 1/2 times the value seen for low mass-flow ratios.

  8. Effects of Gravity on Bubble Formation in an Annular Jet

    NASA Technical Reports Server (NTRS)

    Koepp, R. A.; Parthasarathy, R. N.; Gollahalli, S. R.

    2004-01-01

    The effects of gravity on the bubble formation in an annular jet were studied. The experiments were conducted in the 2.2-second drop tower at the NASA Glenn Research Center. Terrestrial gravity experiments were conducted at the Fluid Dynamics Research Laboratory at the University of Oklahoma. Stainless steel tubing with inner diameters of 1/8" (gas inner annulus) and 5/16" (liquid outer annulus) served as the injector. A rectangular test section, 6" x 6" x 14" tall, made out of half-inch thick Lexan was used. Images of the annular jet were acquired using a high-speed camera. The effects of gravity and varying liquid and gas flow rates on bubble size, wavelength, and breakup length were documented. In general, the bubble diameter was found to be larger in terrestrial gravity than in microgravity for varying Weber numbers (0.05 - 0.16 and 5 - 11) and liquid flow rates (1.5 ft/s - 3.0 ft/s). The wavelength was found to be larger in terrestrial gravity than in microgravity, but remained constant for varying Weber numbers. For low Weber numbers (0.05 - 0.16), the breakup length in microgravity was significantly higher than in terrestrial gravity. Comparison with linear stability analysis showed estimated bubble sizes within 9% of experimental bubble sizes. Bubble size compared to other terrestrial gravity experiments with same flow conditions showed distinct differences in bubble size, which displayed the importance of injector geometry on bubble formation.

  9. On the motion of an annular viscous jet

    NASA Astrophysics Data System (ADS)

    Smolka, Linda; North, Justin; Guerra, Bree

    2006-11-01

    We experimentally examine the motion of an annular jet of viscous fluid flowing down the outside of a thin, vertical fiber. As other authors have observed, perturbations develop along the free surface of the jet; our focus is on the instability that leads to the formation of these perturbations. We observe a striking transition in the perturbation dynamics at a critical flow rate, Qc. Above Qc, the distance from the orifice that perturbations form oscillates in time, and the spacing between perturbations varies, typically leading to the coalescence of neighboring perturbations. For fixed Q below Qc, the distance from the orifice that perturbations form is constant, and the spacing between consecutive perturbations remains fixed as they travel down the length of the fiber (2 meters). We find the growth of the perturbations is initially rapid followed by a slower phase as they saturate in size. We compare the nascent perturbation growth to theoretical predictions developed from a long-wave model (Craster & Matar, J. Fluid Mech. 553, 85-105 (2006)).

  10. A two-phase model for subcooled and superheated liquid jets

    SciTech Connect

    Muralidhar, R.; Jersey, G.R.; Krambeck, F.J.; Sundaresan, S.

    1995-12-31

    This paper describes a two-phase jet model for predicting the liquid rainout (capture) and composition of subcooled and superheated HF/additive pressurized liquid releases. The parent droplets of the release mixture constitute the fist phase. The second phase can in general be a vapor-liquid fog. The drops are not in equilibrium with the fog phase with which they exchange mass and energy. The fog at any location is assumed to be in local equilibrium. Correlations are developed for predicting the initial drop size for hydrodynamic breakup of jets. Applications are discussed in this paper for HF/additive mixtures. The fog phase calculations account for HF oligomerization and HF-water complex formation in the vapor phase and equilibrium between the liquid and vapor in the fog. The model incorporates jet trajectory calculations and hence can predict the amount of liquid rained out (liquid capture) and the capture distance. The HF captures predicted by the model for various release conditions are in agreement with small and large scale release experiments.

  11. Two-phase liquid-liquid flows generated by impinging liquid jets

    NASA Astrophysics Data System (ADS)

    Tsaoulidis, Dimitrios; Li, Qi; Angeli, Panagiota

    2015-11-01

    Two-phase flows in intensified small-scale systems find increasing applications in (bio)chemical analysis and synthesis, fuel cells, polymerisation, and separation processes (solvent extraction). Current nuclear spent fuel reprocessing separation technologies have been developed many decades ago and have not taken account recent advances on process intensification which can drive down plant size and economics. In this work, intensified impinging jets will be developed to create dispersions by bringing the two liquid phases into contact through opposing small channels. A systematic set of experiments has been undertaken, to investigate the hydrodynamic characteristics, to develop predictive models, and enable comparisons with other contactors. Drop size distribution and mixing intensity will be investigated for liquid-liquid mixtures as a function of various parameters using high speed imaging and conductivity probes.

  12. High pressure annular two-phase flow in a narrow duct. Part 1: Local measurements in the droplet field, and Part 2: Three-field modeling

    SciTech Connect

    Trabold, T.A.; Kumar, R.

    1999-07-01

    In Part 1, detailed measurements were made in a high pressure, adiabatic (boiled at the inlet) annular flow in a narrow, high aspect ratio duct using a gamma densitometer, hot-film anemometer and high-speed video photography. Measurements of void fraction, droplet frequency, velocity, drop size, and interfacial area concentration have been made to support the three field computational capability. An important aspect of this testing is the use of a modeling fluid (R-134a) in a vertical duct which permits visual access in annular flow. This modeling fluid accurately simulates the low liquid-to-vapor density ratio of steam-water flows at high pressures. These measurements have been taken in a narrow duct of hydraulic diameter 4.85 mm, and a cross-section aspect ratio of 22.5. However, the flow displays profiles of various shapes not only in the narrow dimension, but also in the width dimension. In particular, the shape of the droplet profiles depends on the entrained droplet flux from the edges in the vapor core. The average diameter from these profiles compare well with the models developed in the literature. Interfacial area concentration for these low density ratio flows is higher than the highest concentration reported for air-water flows. Video records show that along with the bow-shaped waves, three-dimensional {lambda}-shaped waves appear in annular flows for high flow rates. Part 2 outlines the development of a three-field modeling approach in annular flow and the predictive capability of an analysis code. Models have been developed here or adapted from the literature for the thin film near the wall as well as the droplets in the vapor core, and have been locally applied in a fully developed, two-phase adiabatic boiling annular flow in a duct heated at the inlet at high pressure. Numerical results have been obtained using these models that are required for the closure of the continuity and momentum equations. The two-dimensional predictions are compared with

  13. A Non-Heating Experimental Study on the Two-Phase Natural Circulation through the Annular Gap between Reactor Vessel and Insulation under External Vessel Cooling

    SciTech Connect

    Ha, K.S.; Park, R.J.; Cho, Y.R.; Kim, S.B.; Kim, H.D.; Kim, H.M.; Kim, K.Y.

    2004-07-01

    To improve the margin for IVR in high-power reactors, some design improvements of the vessel/insulation configuration to increase the heat removal rate by two-phase natural circulation have been proposed. To observe and evaluate the two-phase natural circulation phenomena through the gap between the reactor vessel and the insulation in the APR1400 under external reactor vessel cooling, the T-HERMES program has been performed, that is, the THERMES- SCALE, T-HERMES-SMALL, HERMES-HALF, and T-HERMES-CFD studies. In this paper, the HERMES-HALF study, which is one of the T-HERMES programs, is introduced. The HERMES-HALF is a non-heating experimental study on the two-phase natural circulation through the annular gap between the reactor vessel and the insulation. The objectives of this HERMES-HALF study are to observe and evaluate the two-phase natural circulation phenomena through the gap between the reactor vessel and the insulation in the APR1400. For these purposes, a half-scaled experimental facility is prepared utilizing the results of a scaling analysis to simulate the APR1400 reactor and insulation system. The behaviors of the boiling-induced two-phase natural circulation flow in the insulation gap are observed, and the liquid mass flow rates driven by the natural circulation loop and void fraction distribution are measured. And numerical analyses of the HERMES-HALF experiments using CFX-5.6 code have also been performed by solving unsteady, three-dimensional Reynolds-averaged Navier-Stokes equations for multiphase flows with the zero equation turbulence model. By the experimental flow observation and numerical predictions, weak recirculation flows in the near region of the shear key are observed. The void fraction monotonically increases from the water inlet to the shear key region. There exists a short decrease of the void fraction after passing through the shear key due to geometrical expansion and the recirculation flow caused by the shear key. The variation of

  14. Modeling of a Two-Phase Jet Pump with Phase Change, Shocks and Temperature-Dependent Properties

    NASA Technical Reports Server (NTRS)

    Sherif, S. A.

    1998-01-01

    One of the primary motivations behind this work is the attempt to understand the physics of a two-phase jet pump which constitutes part of a flow boiling test facility at NASA-Marshall. The flow boiling apparatus is intended to provide data necessary to design highly efficient two-phase thermal control systems for aerospace applications. The facility will also be capable of testing alternative refrigerants and evaluate their performance using various heat exchangers with enhanced surfaces. The test facility is also intended for use in evaluating single-phase performance of systems currently using CFC refrigerants. Literature dealing with jet pumps is abundant and covers a very wide array of application areas. Example application areas include vacuum pumps which are used in the food industry, power station work, and the chemical industry; ejector systems which have applications in the aircraft industry as cabin ventilators and for purposes of jet thrust augmentation; jet pumps which are used in the oil industry for oil well pumping; and steam-jet ejector refrigeration, to just name a few. Examples of work relevant to this investigation includes those of Fairuzov and Bredikhin (1995). While past researchers have been able to model the two-phase flow jet pump using the one-dimensional assumption with no shock waves and no phase change, there is no research known to the author apart from that of Anand (1992) who was able to account for condensation shocks. Thus, one of the objectives of this work is to model the dynamics of fluid interaction between a two-phase primary fluid and a subcooled liquid secondary fluid which is being injected employing atomizing spray injectors. The model developed accounts for phase transformations due to expansion, compression, and mixing. It also accounts for shock waves developing in the different parts of the jet pump as well as temperature and pressure dependencies of the fluid properties for both the primary two-phase mixture and the

  15. A new linearized theory of laminar film condensation of two phase annular flow in a capillary pumped loop

    NASA Technical Reports Server (NTRS)

    Hsu, Y. K.; Swanson, T.; Mcintosh, R.

    1988-01-01

    Future large space based facilities, such as Space Station, will require energy management systems capable of transporting tens of kilowatts of heat over a hundred meters or more. This represents better than an order of magnitude improvement over current technology. Two-phase thermal systems are currently being developed to meet this challenge. Condensation heat transfer plays a very important role in this system. The present study attempts an analytic solution to the set of linearized partial differential equations. The axial velocity and temperature functions were found to be Bessel functions which have oscillatory behavior. This result agrees qualitatively with the experimental evidence from tests at both NASA Goddard Space Flight Center and elsewhere.

  16. Analysis and Modeling of a Two-Phase Jet Pump of a Thermal Management System for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Sherif, S.A.; Hunt, P. L.; Holladay, J. B.; Lear, W. E.; Steadham, J. M.

    1998-01-01

    Jet pumps are devices capable of pumping fluids to a higher pressure by inducing the motion of a secondary fluid employing a high speed primary fluid. The main components of a jet pump are a primary nozzle, secondary fluid injectors, a mixing chamber, a throat, and a diffuser. The work described in this paper models the flow of a two-phase primary fluid inducing a secondary liquid (saturated or subcooled) injected into the jet pump mixing chamber. The model is capable of accounting for phase transformations due to compression, expansion, and mixing. The model is also capable of incorporating the effects of the temperature and pressure dependency in the analysis. The approach adopted utilizes an isentropic constant pressure mixing in the mixing chamber and at times employs iterative techniques to determine the flow conditions in the different parts of the jet pump.

  17. Analysis and Modeling of a Two-Phase Jet Pump of a Flow Boiling Test Facility for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Sherif, S. A.; Steadham, Justin M.

    1996-01-01

    Jet pumps are devices capable of pumping fluids to a higher pressure employing a nozzle/diffuser/mixing chamber combination. A primary fluid is usually allowed to pass through a converging-diverging nozzle where it can accelerate to supersonic speeds at the nozzle exit. The relatively high kinetic energy that the primary fluid possesses at the nozzle exit is accompanied by a low pressure region in order to satisfy Bernoulli's equation. The low pressure region downstream of the nozzle exit permits a secondary fluid to be entrained into and mixed with the primary fluid in a mixing chamber located downstream of the nozzle. Several combinations may exist in terms of the nature of the primary and secondary fluids in so far as whether they are single or two-phase fluids. Depending on this, the jet pump may be classified as gas/gas, gas/liquid, liquid/liquid, two-phase/liquid, or similar combinations. The mixing chamber serves to create a homogeneous single-phase or two-phase mixture which enters a diffuser where the high kinetic energy of the fluid is converted into pressure energy. If the fluid mixture entering the diffuser is in the supersonic flow regime, a normal shock wave usually develops inside the diffuser. If the fluid mixture is one that can easily change phase, a condensation shock would normally develop. Because of the overall rise in pressure in the diffuser as well as the additional rise in pressure across the shock layer, condensation becomes more likely. Associated with the pressure rise across the shock is a velocity reduction from the supersonic to the subsonic range. If the two-phase flow entering the diffuser is predominantly gaseous with liquid droplets suspended in it, it will transform into a predominantly liquid flow containing gaseous bubbles (bubbly flow) somewhere in the diffuser. While past researchers have been able to model the two-phase flow jet pump using the one-dimensional assumption with no shock waves and no phase change, there is no

  18. Two-phase PIV measurements of particle suspension in a forced impinging jet

    NASA Astrophysics Data System (ADS)

    Mulinti, Rahul; Kiger, Ken

    2010-11-01

    The condition of rotorcraft brownout is characterized by intense dust suspension that is uplifted during landing and takeoff operations in regions covered with loose sediment. To predict particle suspension and sedimentation within coupled particle-laden flows, detailed characterization of the micro-scale mechanics is needed within a prototypical flow that captures the essence of the rotorcraft/ground wake interactions. Two-phase PIV has been used to study the interaction of a sediment bed made of glass spheres with characteristic flow structures reminiscent from flow within a rotor wake. In order to make reliable simultaneous two-phase PIV measurements, a phase discrimination algorithm from a single two-phase image has been implemented. The validity of the separation is checked by processing images that consisted only of the very small tracer particles, or only the dispersed phase particles, and examining how much "cross-talk" was present between the phases. The mobilization and wall-normal flux of particulates by the vortex-wall interaction will be reported for several different operational conditions, and correlated to the local vortex conditions.

  19. The clinical application of “jetting suture” technique in annular repair under microendoscopic discectomy

    PubMed Central

    Qi, Lei; Li, Mu; Si, Haipeng; Wang, Liang; Jiang, Yunpeng; Zhang, Shuai; Li, Le

    2016-01-01

    Abstract To introduce a new designed suture technique in annular repair under the microendoscopic discectomy (MED) surgery and to evaluate the clinical application of the technique in annular repair under MED with at least 2-year follow-up period. A new method of annular repair was designed and named “jetting suture” technique. Thirty consecutive patients with lumbar disc herniation were enrolled in the prospective single-cohort observational study. Patients were followed up at intervals of preoperative, postoperative 1 week, 3 months, 6 months, 1 year, and last follow-up. The clinical outcomes were evaluated by using Japanese Orthopaedic Association (JOA) score, Oswestry Disability Index, and modified Mcnab criteria. The procedure was successfully performed in all cases. No case required conversion to an open procedure. The mean age of patients was 36.6 years. Average blood loss was 45.8 ± 10.2 mL. The preoperative symptoms were alleviated significantly after surgery. All the standardized measures improved significantly at the last follow-up, including JOA score (10.1 to 26.6; P < 0.05) and Oswestry Disability Index (75.3 to 9.6; P < 0.05). Improvement rate of JOA score was 86.4%. Approximately 83.4% of patients reported good or excellent outcomes based on modified Mcnab criteria. No postoperative complication and recurrence of disc herniation was reported. The designed “jetting suture” technique in annular repair under MED can be performed safely and effectively. It could be a viable alternative to annular repair under lumbar discectomy. PMID:27495101

  20. Measurements in the annular shear layer of high subsonic and under-expanded round jets

    NASA Astrophysics Data System (ADS)

    Feng, Tong; McGuirk, James J.

    2016-01-01

    An experimental study has been undertaken to document compressibility effects in the annular shear layers of axisymmetric jets. Comparison is made of the measured flow development with the well-documented influence of compressibility in planar mixing layers. High Reynolds number (~106) and high Mach number jets issuing from a convergent nozzle at nozzle pressure ratios (NPRs) from 1.28 to 3.0 were measured using laser Doppler anemometry instrumentation. Detailed radial profile data are reported, particularly within the potential core region, for mean velocity, turbulence rms, and turbulence shear stress. For supercritical NPRs the presence of the pressure waves in the inviscid shock cell region as the jet expanded back to ambient pressure was found to exert a noticeable effect on shear layer location, causing this to shift radially outwards at high supercritical NPR conditions. After a boundary layer to free shear layer transition zone, the turbulence development displayed a short region of similarity before adjustment to near-field merged jet behaviour. Peak turbulence rms reduction due to compressibility was similar to that observed in planar layers with radial rms suppression much stronger than axial. Comparison of the compressibility-modified annular shear layer growth rate with planar shear layer data on the basis of the convective Mach number ( M C) showed notable differences; in the annular shear layer, compressibility effects began at lower M C and displayed a stronger reduction in growth. For high Mach number aerospace propulsion applications involving round jets, the current measurements represent a new data set for the calibration/validation of compressibility-affected turbulence models.

  1. PTV implementation on two-phase flow in a forced impinging jet

    NASA Astrophysics Data System (ADS)

    Mulinti, Rahul; Kiger, Kenneth

    2011-11-01

    Two-phase flow experiments have been conducted to predict particle suspension and sedimentation within coupled particle-laden flows relevant to rotorcraft brownout conditions. A hybrid PIV/PTV technique has been implemented to improve the performance in high concentration regions, while still retaining the flexibility inherent to PTV to resolve multi-valued velocity displacements within a given interrogation region. These processing tools have been optimized and their reliability has been validated using synthetic particle images in a prescribed Taylor-Green vortex flow model. The parametric space of investigation included particle image density, Stokes number and image delay times. Experiments have been conducted to study the interaction of a mobile sediment bed with characteristic flow structures similar to those within a rotor wake. The mobilization conditions and wall-normal flux of particulates by the vortex-wall interaction will be reported for different particle size classes, and are correlated to the local vortex conditions such as vortex decay and its subsequent three dimensionalization. The effect of turbulent coupling between the particle and fluid momentum, as based on a point-particle drag law valid for dilute concentrations of particles has been examined. Work supported by AFOSR under grant FA9550-08-1-0406.

  2. Physical and Mathematical Modeling of Two-Phase Flows in a HOLLOW JET NOZZLE

    NASA Astrophysics Data System (ADS)

    Chatterjee, Debasish; Mazumdar, Dipak; Patil, Sujay Pandit

    2007-10-01

    The HOLLOW JET NOZZLE (HJN) is a heat exchanger used for the removal of superheat from molten steel between tundish and mold. It is a relatively new technology, developed by CRM, Belgium, through engineering the design of the conventional submerged entry nozzle (SEN) in continuous casting. In the present study, fluid-flow phenomena in a HJN system were investigated experimentally via a 0.23-scale water model, designed and operated on the basis of a Froude scaling criterion. Parallel to such, numerical simulation was carried out via FLUENT 6.1 embodying a turbulent, VOF-based, multiphase flow calculation procedure. These, in general, indicated that the incoming liquid, following its impingement on the solid baffle, spreads radially and flows down as a thin liquid film along the wall of the HJN. A large number of experiments were carried out to determine the radial spread of the impinging water jet and its point of attachment on the wall of the HJN as a function of volumetric flow rate, baffle geometry and dimensions, diameter of HJN, etc. These indicated that baffle geometry and dimensions together with the diameter of the HJN influence the point of attachment (or the corresponding “attachment distance”) most. It was demonstrated that attachment distance and the associated contact area between the flowing liquid and HJN wall can be considerably improved by appropriately modifying the currently employed baffle design. Such experimental findings were corroborated well by the FLUENT-based numerical procedure, which was in general able to capture the intricacies of film flow in the HJN system reasonably accurately. In addition to these, simplified models for attachment distance and film thickness have been developed and proposed for axisymmetrical HJN operation. Based on such, a relatively simple differential heat flow model has been developed for prediction of melt temperature in an industrial HJN system. It is demonstrated that in the absence of any elaborate

  3. Mixing and NOx Emission Calculations of Confined Reacting Jet Flows in Cylindrical and Annular Ducts

    NASA Technical Reports Server (NTRS)

    Oechsle, Victor L.; Connor, Christopher H.; Holdeman, James D. (Technical Monitor)

    2000-01-01

    Rapid mixing of cold lateral jets with hot cross-stream flows in confined configurations is of practical interest in gas turbine combustors as it strongly affects combustor exit temperature quality, and gaseous emissions in for example rich-lean combustion. It is therefore important to further improve our fundamental understanding of the important processes of dilution jet mixing especially when the injected jet mass flow rate exceeds that of the cross-stream. The results reported in this report describe some of the main flow characteristics which develop in the mixing process in a cylindrical duct. A three-dimensional computational fluid dynamics (CFD) code has been used to predict the mixing flow field characteristics and NOx emission in a quench section of a rich-burn/quick-mix/lean-burn (RQL) combustor. Sixty configurations have been analyzed in both circular and annular geometries in a fully reacting environment simulating the operating condition of an actual RQL gas turbine combustion liner. The evaluation matrix was constructed by varying the number of orifices per row and orifice shape. Other parameters such as J (momentum-flux ratio), MR (mass flowrate ratio), DR (density ratio), and mixer sector orifice ACd (effective orifice area) were maintained constant throughout the entire study. The results indicate that the mixing flow field can be correlated with the NOx production if they are referenced with the stoichiometric equivalence ratio value and not the equilibrium value. The mixing flowfields in both circular and annular mixers are different. The penetration of equal jets in both annular and circular geometries is vastly different which significantly affects the performance of the mixing section. In the computational results with the circular mixer, most of the NOx formation occurred behind the orifice starting at the orifice wake region. General trends have been observed in the NOx production as the number of orifices is changed and this appears to be

  4. Influence of swirl on the initial merging zone of a turbulent annular jet

    NASA Astrophysics Data System (ADS)

    Vanierschot, M.; Van den Bulck, E.

    2008-10-01

    This paper presents an extensive study of the influence of swirl on the initial region of an annular jet. A total of five different swirl numbers S are investigated: one at zero swirl, one at low swirl (S=0.18), two at intermediate swirl (S =0.37 and 0.57), and one at high swirl (S=0.74). The flow fields are measured using the stereoscopic particle image velocimetry (PIV) technique. A detailed study on the accuracy of the PIV measurements is presented, including a validation with laser Doppler anemometry data. In this way a detailed set of accurate data is presented of the three components of velocity and the root-mean square value of their fluctuations in a plane through the central axis of the geometry. Despite its simple geometry, the immediate flow field of an annular jet is very complex. The concentric central tube of the nozzle acts as a bluff body to the flow, thus creating a central recirculation zone (CRZ) behind it. At low swirl numbers the swirl induced pressure gradients alter the structure of the CRZ significantly, increasing its complexity. The CRZ becomes toroidal and the jet fluid is entrained near the apex. At intermediate swirl numbers a vortex breakdown bubble appears downstream which moves upstream with increasing swirl. At high swirl, the CRZ and breakdown bubble merge which creates a complex and highly anisotropic flow field.

  5. Break-up and atomization of a round water jet by a high-speed annular air jet

    NASA Astrophysics Data System (ADS)

    Lasheras, J. C.; Villermaux, E.; Hopfinger, E. J.

    1998-02-01

    The near- and far-field break-up and atomization of a water jet by a high-speed annular air jet are examined by means of high-speed flow visualizations and phase Doppler particle sizing techniques. Visualization of the jet's near field and measurements of the frequencies associated with the gas liquid interfacial instabilities are used to study the underlying physical mechanisms involved in the primary break-up of the water jet. This process is shown to consist of the stripping of water sheets, or ligaments, which subsequently break into smaller lumps or drops. An entrainment model of the near-field stripping of the liquid is proposed, and shown to describe the measured liquid shedding frequencies. This simplified model explains qualitatively the dependence of the shedding frequency on the air/water momentum ratio in both initially laminar and turbulent water jets. The role of the secondary liquid break-up in the far-field atomization of the water jet is also investigated, and an attempt is made to apply the classical concepts of local isotropy to explain qualitatively the measurement of the far-field droplet size distribution and its dependence on the water to air mass and momentum ratios. Models accounting for the effect of the local turbulent dissipation rate in the gas on both the break-up and coalescence of the droplets are developed and compared with the measurements of the variation of the droplet size along the jet's centreline. The total flux of kinetic energy supplied by the gas per unit total mass of the spray jet was found to be the primary parameter determining the secondary break-up and coalescence of the droplets in the far field.

  6. Flashing liquid jets and two-phase droplet dispersion I. Experiments for derivation of droplet atomisation correlations.

    PubMed

    Cleary, Vincent; Bowen, Phil; Witlox, Henk

    2007-04-11

    The large-scale release of a liquid contained at upstream conditions above its local atmospheric boiling point is a scenario often given consideration in process industry risk analysis. Current-hazard quantification software often employs simplistic equilibrium two-phase approaches. Scaled water experiments have been carried out measuring droplet velocity and droplet size distributions for a range of exit orifice aspect ratios (L/d) and conditions representing low to high superheat. 2D Phase-Doppler Anemometry has been utilised to characterise droplet kinematics and spray quality. Droplet size correlations have been developed for non-flashing, the transition between non-flashing and flashing, and fully flashing jets. Using high-speed shadowography, transition between regimes is defined in terms of criteria identified in the external flow structure. An overview companion paper provides a wider overview of the problem and reports implementation of these correlations into consequence models and subsequent validation. The fluid utilised throughout is water, hence droplet correlations are developed in non-dimensional form to allow extrapolation to other fluids through similarity scaling, although verification of model performance for other fluids is required in future studies. Data is reduced via non-dimensionalisation in terms of the Weber number and Jakob number, essentially representing the fluid mechanics and thermodynamics of the system, respectively. A droplet-size distribution correlation has also been developed, conveniently presented as a volume undersize distribution based on the Rosin-Rammler distribution. Separate correlations are provided for sub-cooled mechanical break-up and fully flashing jets. This form of correlation facilitates rapid estimates of likely mass rainout quantities, as well as full distribution information for more rigorous two-phase thermodynamic modelling in the future. PMID:16956721

  7. Comparison of Y-jet and OIL effervescent atomizers based on internal and external two-phase flow characteristics

    NASA Astrophysics Data System (ADS)

    Mlkvik, Marek; Zaremba, Matous; Jedelsky, Jan; Jicha, Miroslav

    2016-03-01

    Presented paper focuses on spraying of two viscous liquids (μ = 60 and 143 mPa·s) by two types of twinfluid atomizers with internal mixing. We compared the well-known Y-jet atomizer with the less known, "outside in liquid" (OIL), configuration of the effervescent atomizer. The required liquid viscosity was achieved by using the water-maltodextrin solutions of different concentrations. Both the liquids were sprayed at two gas inlet pressures (Δp = 0.14 and 0.28 MPa) and various gas-to-liquid ratios (GLR = 2.5%, 5%, 10% and 20%). The comparison was focused on four characteristics: liquid flow-rate (for the same working regimes, defined by Δp and GLR), internal flow regimes, Weber numbers of a liquid breakup (We) and droplet sizes. A high-speed camera and Malvern Spraytec laser diffraction system were used to obtain necessary experimental data. Comparing the results of our experiments, we can state that for both the liquids the OIL atomizer reached higher liquid flow-rates at corresponding working regimes, it was typical by annular internal flow and higher We in the near-nozzle region at all the working regimes. As a result, it produced considerably smaller droplets than the second tested atomizing device, especially for GLR < 10%.

  8. The Penetration Behavior of an Annular Gas-Solid Jet Impinging on a Liquid Bath: Comparison with a Conventional Circular Jet

    NASA Astrophysics Data System (ADS)

    Park, Sung Sil; Dyussekenov, Nurzhan; Sohn, H. Y.

    2010-02-01

    The top-blow injection technique of a gas-solid mixture through a circular lance is used in the Mitsubishi Continuous Smelting Process. One of the inherent problems associated with this injection is the severe erosion of the hearth refractory below the lances. A new configuration of the lance to form an annular gas-solid jet rather than a circular jet was designed in the laboratory scale. With this new configuration, solid particles leave the lance at a much lower velocity than the gas, and the penetration behavior of the jet is significantly different than with the circular lance in which the solid particles leave the lance at the same high velocity as the gas. The results of cold model tests using an air-sand jet issuing from a circular lance and an annular lance into a water bath showed that the penetration of the annular jet is much less sensitive to the variations in particle feed rate as well as gas velocity than that of the circular jet. Correlation equations for the penetration depth for both circular and annular jets show agreement among the experimentally obtained values.

  9. Structure optimization of an annular jet pump using design of experiment method and CFD

    NASA Astrophysics Data System (ADS)

    Long, X. P.; Zeng, Q. L.; Yang, X. L.; Xiao, L.

    2012-11-01

    This paper adopts DOE (the design of experiment method) to find out the optimum structure combination of an annular jet pump for maximum efficiency. The annular jet pump (AJP) model used by previous researcher, which area ratio is 1.75, was chosen as the simulation prototype. The performance data from the experiment were used to validate the simulation results. Then four important factors namely the flow ratio, the relative throat length and the included angles of the diffuser and the suction chamber were selected for the structure optimization by DOE. The most desirable combination is obtained, namely suction angle of 15 degree, throat length of 2.45 times of throat diameter, diffuser angle of 4 degree. The flow ratio corresponding to the most desirable combination is 0.6. The maximum efficiency predicted by the design method is 36.3% close to that of the CFD results 35.8%. The flow ratio has prevailing influence on the AJP efficiency. In the three construction parameters, the relative throat length has greater influence on the AJP performance than the diffuser angle and the suction angle. With proper experimental design method, effort to experiment could be greatly saved and analysis of experiment results could be more logical.

  10. A numerical study of an axisymmetric two-phase jet with allowance for the after-combustion of particles in the slipstream

    NASA Astrophysics Data System (ADS)

    Gilinskii, M. M.; Stasenko, A. L.; Tolstov, V. N.

    A model is proposed which describes the gas thermodynamics of a nonuniform ideal gas mixture containing an oxidizer and finely dispersed particles, with allowance made for heat transfer between the phases. The results of a numerical study are presented for a supersonic two-phase jet where initially uniform particles are first accelerated, then enter the slipstream, and disappear as a result of oxidation.

  11. Flight velocity influence on jet noise of conical ejector, annular plug and segmented suppressor nozzles

    NASA Technical Reports Server (NTRS)

    Brausch, J. F.

    1972-01-01

    An F106 aircraft with a J85-13 engine was used for static and flight acoustic and aerodynamic tests of a conical ejector, an unsuppressed annular plug, and three segmented suppressor nozzles. Static 100 ft. arc data, corrected for influences other than jet noise, were extrapolated to a 300 ft. sideline for comparison to 300 ft. altitude flyover data at M = 0.4. Data at engine speeds of 80 to 100% (max dry) static and 88 to 100% flight are presented. Flight velocity influence on noise is shown on peak OASPL and PNL, PNL directivity, EPNL and chosen spectra. Peak OASPL and PNL plus EPNL suppression levels are included showing slightly lower flight than static peak PNL suppression but greater EPNL than peak PNL suppression. Aerodynamic performance was as anticipated and closely matched model work for the 32-spoke nozzle.

  12. Analytical and experimental investigation of flow fields of annular jets with and without swirling flow

    NASA Technical Reports Server (NTRS)

    Simonson, M. R.; Smith, E. G.; Uhl, W. R.

    1974-01-01

    Analytical and experimental studies were performed to define the flowfield of annular jets, with and, without swirling flow. The analytical model treated configurations with variations of flow angularities, radius ratio, and swirl distributions. Swirl distributions characteristic of stator vanes and rotor blade rows, where the total pressure and swirl distributions are related were incorporated in the mathematical model. The experimental studies included tests of eleven nozzle models, both with and, without swirling exhaust flow. Flowfield surveys were obtained and used for comparison with the analytical model. This comparison of experimental and analytical studies served as the basis for evaluation of several empirical constants as required for application of the analysis to the general flow configuration. The analytical model developed during these studies is applicable to the evaluation of the flowfield and overall performance of the exhaust of statorless lift fan systems that contain various levels of exhaust swirl.

  13. The clinical application of "jetting suture" technique in annular repair under microendoscopic discectomy: A prospective single-cohort observational study.

    PubMed

    Qi, Lei; Li, Mu; Si, Haipeng; Wang, Liang; Jiang, Yunpeng; Zhang, Shuai; Li, Le

    2016-08-01

    To introduce a new designed suture technique in annular repair under the microendoscopic discectomy (MED) surgery and to evaluate the clinical application of the technique in annular repair under MED with at least 2-year follow-up period.A new method of annular repair was designed and named "jetting suture" technique. Thirty consecutive patients with lumbar disc herniation were enrolled in the prospective single-cohort observational study. Patients were followed up at intervals of preoperative, postoperative 1 week, 3 months, 6 months, 1 year, and last follow-up. The clinical outcomes were evaluated by using Japanese Orthopaedic Association (JOA) score, Oswestry Disability Index, and modified Mcnab criteria.The procedure was successfully performed in all cases. No case required conversion to an open procedure. The mean age of patients was 36.6 years. Average blood loss was 45.8 ± 10.2 mL. The preoperative symptoms were alleviated significantly after surgery. All the standardized measures improved significantly at the last follow-up, including JOA score (10.1 to 26.6; P < 0.05) and Oswestry Disability Index (75.3 to 9.6; P < 0.05). Improvement rate of JOA score was 86.4%. Approximately 83.4% of patients reported good or excellent outcomes based on modified Mcnab criteria. No postoperative complication and recurrence of disc herniation was reported.The designed "jetting suture" technique in annular repair under MED can be performed safely and effectively. It could be a viable alternative to annular repair under lumbar discectomy. PMID:27495101

  14. The Penetration Behavior of an Annular Gas-Solid Jet Impinging on a Liquid Bath: The Effects of the Density and Size of Solid Particles

    NASA Astrophysics Data System (ADS)

    Chang, J. S.; Sohn, H. Y.

    2012-08-01

    Top-blow injection of a gas-solid jet through a circular lance is used in the Mitsubishi Continuous Smelting Process. One problem associated with this injection is the severe erosion of the hearth refractory below the lances. A new configuration of the lance to form an annular gas-solid jet rather than the circular jet was designed in this laboratory. With this new configuration, the solid particles fed through the center tube leave the lance at a much lower velocity than the gas, and the penetration behavior of the jet is significantly different from that with a circular lance where the solid particles leave the lance at the same high velocity as the gas. In previous cold-model investigations in this laboratory, the effects of the gas velocity, particle feed rate, lance height of the annular lance, and the cross-sectional area of the gas jet were studied and compared with the circular lance. This study examined the effect of the density and size of the solid particles on the penetration behavior of the annular gas-solid jet, which yielded some unexpected results. The variation in the penetration depth with the density of the solid particles at the same mass feed rate was opposite for the circular lance and the annular lance. In the case of the circular lance, the penetration depth became shallower as the density of the solid particles increased; on the contrary, for the annular lance, the penetration depth became deeper with the increasing density of particles. However, at the same volumetric feed rate of the particles, the density effect was small for the circular lance, but for the annular lance, the jets with higher density particles penetrated more deeply. The variation in the penetration depth with the particle diameter was also different for the circular and the annular lances. With the circular lance, the penetration depth became deeper as the particle size decreased for all the feed rates, but with the annular lance, the effect of the particle size was

  15. Planar Pressure Field Determination in the Initial Merging Zone of an Annular Swirling Jet Based on Stereo-PIV Measurements

    PubMed Central

    Vanierschot, Maarten; Van den Bulck, Eric

    2008-01-01

    In this paper the static pressure field of an annular swirling jet is measured indirectly using stereo-PIV measurements. The pressure field is obtained from numerically solving the Poisson equation, taken into account the axisymmetry of the flow At the boundaries no assumptions are made and the exact boundary conditions are applied. Since all source terms can be measured using stereo-PIV and the boundary conditions are exact, no assumptions other than axisymmetry had to be made in the calculation of the pressure field. The advantage of this method of indirect pressure measurement is its high spatial resolution compared to the traditional pitot probes. Moreover this method is non-intrusive while the insertion of a pitot tube disturbs the flow It is shown that the annular swirling flow can be divided into three regimes: a low, an intermediate and a high swirling regime. The pressure field of the low swirling regime is the superposition of the pressure field of the non-swirling jet and a swirl induced pressure field due to the centrifugal forces of the rotating jet. As the swirl increases, the swirl induced pressure field becomes dominant and for the intermediate and high swirling regimes, the simple radial equilibrium equation holds.

  16. Inverted velocity profile semi-annular nozzle jet exhaust noise experiments

    NASA Technical Reports Server (NTRS)

    Goodykoontz, J. H.

    1983-01-01

    Experimental noise data are shown for a conical nozzle with a semi-annular secondary flow passage having secondary to primary velocity ratios ranging from 1.0 to 1.4. Spectral data are presented at different directivity angles in the flyover plane with the semi-annular flow passage located either on the same side or opposite side relative to an observer. A 10.0 cm diameter primary conical nozzle was used with a 2.59 cm and 5.07 cm wide annular gap secondary nozzle. Similar trends were observed for both nozzle configurations. In general, near the peak noise location and at velocity ratios greater than 1.0, noise levels were larger on the side where the secondary passage was closest to an observer. At velocity ratios near 1.0 the opposite was true. When compared to predicted noise levels for a conical nozzle alone operating at the same ideal thrust, the semi-annular configuration showed no benefit in terms of noise attenuation.

  17. Combustion of liquid fuel in the counter-swirled jets of a gas turbine plant annular combustion chamber

    NASA Astrophysics Data System (ADS)

    Tumanovskii, A. G.; Semichastnyi, N. N.; Sokolov, K. Iu.

    1986-03-01

    Tests were carried out on an annular combustion chamber rig with a stabilizer of the type used in the GTN-25 gas turbine plant to determine the feasibility of burning a liquid fuel (diesel fuel, GOST 4749-73) in a combustion chamber of this type. Very high performance was obtained for a number of important characteristics of the microflame combustion process in counterswirled jets where all the air was supplied through the front unit of the chamber. However, the tests did not make it possible to solve some of the problems which arise when operating under full-scale conditions, such as the required high combustion efficiency under variable operating conditions of a gas turbine plant; elimination of soot formation at the walls of the stabilizer and the internal surfaces of the pipes supplying fuel to the atomizers; and a decrease in smoking under conditions of excess air factor.

  18. Performance comparisons of Navy jet mix and MIL-F-5624A (JP-3) fuels in tubular and annular combustors / Richard J. McCafferty

    NASA Technical Reports Server (NTRS)

    Mccafferty, Richard J

    1954-01-01

    The performances of Navy Jet Mix and MIL-F-5624A (JP-3) fuels were compared in J33, J47, and NACA experimental annular combustion chambers. Combustion efficiencies, altitude operational limits, and carbon-forming tendencies wer determined and discussed. The results indicate that Jet Mix fuel can be utilized satisfactorily in a number of current turbojet engines over the normal operating range. Small differences in combustion efficiences and altitude operational limits existed between the two fuels but these differences depended on the particular combustor and simulated altitude and rotor speed condition. Excessive carbon deposition is not predicted for Jet Mix fuel, although this property may be marginal.

  19. The ground vortex flow field associated with a jet in a cross flow impinging on a ground plane for uniform and annular turbulent axisymmetric jets. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Cavage, William M.; Kuhlman, John M.

    1993-01-01

    An experimental study was conducted of the impingement of a single circular jet on a ground plane in a cross flow. This geometry is a simplified model of the interaction of propulsive jet exhaust from a V/STOL aircraft with the ground in forward flight. Jets were oriented normal to the cross flow and ground plane. Jet size, cross flow-to-jet velocity ratio, ground plane-to-jet board spacing, and jet exit turbulence level and mean velocity profile shape were all varied to determine their effects on the size of the ground vortex interaction region which forms on the ground plane, using smoke injection into the jet. Three component laser Doppler velocimeter measurements were made with a commercial three color system for the case of a uniform jet with exit spacing equal to 5.5 diameters and cross flow-to-jet velocity ratio equal to 0.11. The flow visualization data compared well for equivalent runs of the same nondimensional jet exit spacing and the same velocity ratio for different diameter nozzles, except at very low velocity ratios and for the larger nozzle, where tunnel blockage became significant. Variation of observed ground vortex size with cross flow-to-jet velocity ratio was consistent with previous studies. Observed effects of jet size and ground plane-to-jet board spacing were relatively small. Jet exit turbulence level effects were also small. However, an annular jet with a low velocity central core was found to have a significantly smaller ground vortex than an equivalent uniform jet at the same values of cross flow-to-jet velocity ratio and jet exit-to-ground plane spacing. This may suggest a means of altering ground vortex behavior somewhat, and points out the importance of proper simulation of jet exit velocity conditions. LV data indicated unsteady turbulence levels in the ground vortex in excess of 70 percent.

  20. Effect of Inner-tube Position on Heat Transfer of Laminar Annular Impinging Jet with Confined Wall

    NASA Astrophysics Data System (ADS)

    Ichimiya, Koichi; Fukumoto, Hiromichi; Miyazawa, Toshiyoshi

    Present paper describes on the heat transfer and flow characteristics of a laminar annular impinging jet for various positions of inner-tube. In the first case, inner-tube is protruded to the flow passage. In the second case, inner-tube is retracted and relatively, outer-tube with confined insulated wall is protruded. Numerical values were obtained for the dimensionless distance between nozzle and impingement surface, H =0.5,1.0, the diameter ratio, d/D=0.2~0.6, the protrusion or retraction dimensionless length, L/H=0.0~0.8 at the Reynolds number, Re=1,000,the Prandtl number, Pr =0.72 and Grashof number, Gr = 1,000, In the first case, the flow is divided into the stagnant regionand the recirculated region in the minor flow and the major flow region. The local heat transfer for minor flow is depressed with increase of L/H. In the second case, the heat transfer increases locally with increase of L/H. Consequently, local heat transfer is controlled by combining protrusion and retraction.

  1. Study of an underexpanded annular wall jet past an axisymmetric backward-facing step

    NASA Astrophysics Data System (ADS)

    Espina, Pedro Ivan

    1997-12-01

    Gas-metal atomization is a process by which liquid metal is transformed into a metal powder. The metal powders produced through gas-metal atomization exhibit chemical homogeneity and refined microstructures that cannot be obtained by conventional casting techniques. Given their enhanced properties, the products made from these powders find applications ranging from jet-engine parts to medical implants. The heart of a gas-metal atomizer is a device known as the 'atomization nozzle assembly', which forces the interaction between a high-speed gas jet and a liquid stream of molten metal. Because the control of a molten stream of metal can be difficult, atomization control strategies have historically been focused on the gas- delivery-system of the atomizers. Thus, in this investigation, the gas-only flow in a close-coupled, gas- metal atomizer is studied to determine the influence of operational parameters on the structure of the flow field. Both experimental and numerical results are presented. First, the numerical method used is evaluated by modeling flat-plate boundary layers at various free stream velocities; further validation is conducted by modeling an axisymmetric base flow for which experimental and numerical data are available for comparison. Comparisons between the Schlieren images produced experimentally and numerical results are carried out, focusing on the evaluation of turbulence model parameters. The same methodology was then used to model the gas-only atomization flow produced at conventional operational conditions. A parametric study was conducted to determine the effects of jet exit pressure ratio, jet temperature ratio, and base mass injection (to model, at least approximately, some of the effects of the liquid phase). Based on the results obtained in the validation stage, it is concluded that the Chien k-ɛ turbulence model yields excessively high production of turbulence kinetic energy dissipation rate in this type of flow. It is shown that a 10

  2. Annular pancreas

    MedlinePlus

    ... page: //medlineplus.gov/ency/article/001142.htm Annular pancreas To use the sharing features on this page, please enable JavaScript. An annular pancreas is a ring of pancreatic tissue that encircles ...

  3. Counter-gradient transport in the combustion of a premixed CH{sub 4}/air annular jet by combined PIV/OH-LIF

    SciTech Connect

    Troiani, G.; Marrocco, M.; Giammartini, S.; Casciola, C.M.

    2009-03-15

    A combination of PIV/OH laser induced fluorescence technique is used to measure the conditional - burned and unburned - gas velocity in a turbulent premixed CH{sub 4}/air annular bluff-body stabilized burner. By changing the equivalence ratio from lean to almost stoichiometric, the energy budget of the recirculating region anchoring the flame is altered in such a way to increasingly lift the flame away from the jet exit. The overall turbulence intensity interacting with each flame is thus systematically varied in a significant range, allowing for a parametric study of its effect on turbulent scalar transport under well controlled conditions, always well within the flamelet regime. The component of the flux normal to the average front is found to reverse its direction, confirming the Bray number as a good indicator of gradient/counter-gradient behavior, once the actual incoming turbulence level felt locally by the flame is assumed as the proper control parameter. (author)

  4. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume II. Chapters 6-10)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    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.

  5. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume III. Chapters 11-14)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    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.

  6. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume IV. Chapters 15-19)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    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.

  7. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume I. Chapters 1-5)

    SciTech Connect

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    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.

  8. Two-phase flow

    NASA Technical Reports Server (NTRS)

    Tacina, Robert R.

    1986-01-01

    An experimental program to characterize the spray from candidate nozzles for icing-cloud simulation is discussed. One canidate nozzle, which is currently used for icing research, has been characterized for flow and drop size. The median-volume diameter (MVD) from this air-assist nozzle is compared with correlations in the literature. The new experimental spray facility is discussed, and the drop-size instruments are discussed in detail. Since there is no absolute standard for drop-size measurements and there are other limitations, such as drop -size range and velocity range, several instruments are used and results are compared. A two-phase model was developed at Pennsylvania State University. The model uses the k-epsilon model of turbulence in the continous phase. Three methods for treating the discrete phase are used: (1) a locally homogeneous flow (LHF) model, (2) a deterministic separated flow (DSF) model, and (3) a stochastic separated flow (SSF) model. In the LHF model both phases have the same velocity and temperature at each point. The DSF model provides interphase transport but ignores the effects of turbulent fluctuations. In the SSF model the drops interact with turbulent eddies whose properties are determined by the k-epsilon turbulence model. The two-phase flow model has been extended to include the effects of evaporation and combustion.

  9. Planar Rayleigh scattering and laser-induced fluorescence for visualization of a hot, Mach 2 annular air jet

    NASA Astrophysics Data System (ADS)

    Balla, R. Jeffrey

    1994-10-01

    Planar Rayleigh scattering (PRS) and planar laser-induced fluorescence (PLIF) were used to investigate the vitiated air component of a coaxial hydrogen/vitiated air nonpremixed turbulent jet flame that is ejected at a Mach number of 2. All experiments were performed with a xenon chloride tunable excimer laser. Planar information for both techniques was obtained using laser sheets 6 cm high, 5 cm wide, and 300 micron thick. In this flow field, the effective Rayleigh cross section of the components in the vitiated air was assumed to be independent of composition. Therefore, the PRS technique produced signals which were proportional to total density. When the flow field was assumed to be at a known and uniform pressure, the PRS signal data for the vitiated air could be converted to temperature information. Also, PLIF images were generated by probing the OH molecule. These images contain striation patterns attributed to small localized instantaneous temperature nonuniformities. The results from the PLIF and PRS techniques were used to show that this flow field contains a nongaseous component, most likely liquid water that can be reduced by increasing the settling chamber wall temperature.

  10. Planar Rayleigh scattering and laser-induced fluorescence for visualization of a hot, Mach 2 annular air jet

    NASA Technical Reports Server (NTRS)

    Balla, R. Jeffrey

    1994-01-01

    Planar Rayleigh scattering (PRS) and planar laser-induced fluorescence (PLIF) were used to investigate the vitiated air component of a coaxial hydrogen/vitiated air nonpremixed turbulent jet flame that is ejected at a Mach number of 2. All experiments were performed with a xenon chloride tunable excimer laser. Planar information for both techniques was obtained using laser sheets 6 cm high, 5 cm wide, and 300 micron thick. In this flow field, the effective Rayleigh cross section of the components in the vitiated air was assumed to be independent of composition. Therefore, the PRS technique produced signals which were proportional to total density. When the flow field was assumed to be at a known and uniform pressure, the PRS signal data for the vitiated air could be converted to temperature information. Also, PLIF images were generated by probing the OH molecule. These images contain striation patterns attributed to small localized instantaneous temperature nonuniformities. The results from the PLIF and PRS techniques were used to show that this flow field contains a nongaseous component, most likely liquid water that can be reduced by increasing the settling chamber wall temperature.

  11. Granuloma annulare.

    PubMed

    Gupta, Diptesh; Hess, Brian; Bachegowda, Lohith

    2010-01-01

    We present a case of a 77-year-old, diabetic male with a 20-year history of a migratory erythematous, asymptomatic, generalized, nonscaly, and nonitchy rash that started over the dorsum of his left hand. On examination, there were multiple annular erythematous plaques, distributed symmetrically and diffusely over his torso and arms, with central clearing and no scales. A punch biopsy of the skin helped us to arrive at the diagnosis of a generalized granuloma annulare (GA). GA is a benign, self-limiting skin condition of unknown etiology that is often asymptomatic. The cause of this condition is unknown, but it has been associated with diabetes mellitus, infections such as HIV, and malignancies such as lymphoma. These lesions typically start as a ring of flesh-colored papules that slowly progress with central clearing. Lack of symptoms, scaling, or associated vesicles helps to differentiate GA from other skin conditions such as tinea corporis, pityriasis rosea, psoriasis, or erythema annulare centrifugum. Treatment is often not needed as the majority of these lesions are self-resolving within 2 years. Treatment may be pursued for cosmetic reasons. Available options include high-dose steroid creams, PUVA, cryotherapy, or drugs such as niacinamide, infliximab, Dapsone, and topical calcineurin inhibitors. PMID:20209383

  12. Axisymmetric annular curtain stability

    NASA Astrophysics Data System (ADS)

    Ahmed, Zahir U.; Khayat, Roger E.; Maissa, Philippe; Mathis, Christian

    2012-06-01

    A temporal stability analysis was carried out to investigate the stability of an axially moving viscous annular liquid jet subject to axisymmetric disturbances in surrounding co-flowing viscous gas media. We investigated in this study the effects of inertia, surface tension, the gas-to-liquid density ratio, the inner-to-outer radius ratio and the gas-to-liquid viscosity ratio on the stability of the jet. With an increase in inertia, the growth rate of the unstable disturbances is found to increase. The dominant (or most unstable) wavenumber decreases with increasing Reynolds number for larger values of the gas-to-liquid viscosity ratio. However, an opposite tendency for the most unstable wavenumber is predicted for small viscosity ratio in the same inertia range. The surrounding gas density, in the presence of viscosity, always reduces the growth rate, hence stabilizing the flow. There exists a critical value of the density ratio above which the flow becomes stable for very small viscosity ratio, whereas for large viscosity ratio, no stable flow appears in the same range of the density ratio. The curvature has a significant destabilizing effect on the thin annular jet, whereas for a relatively thick jet, the maximum growth rate decreases as the inner radius increases, irrespective of the surrounding gas viscosity. The degree of instability increases with Weber number for a relatively large viscosity ratio. In contrast, for small viscosity ratio, the growth rate exhibits a dramatic dependence on the surface tension. There is a small Weber number range, which depends on the viscosity ratio, where the flow is stable. The viscosity ratio always stabilizes the flow. However, the dominant wavenumber increases with increasing viscosity ratio. The range of unstable wavenumbers is affected only by the curvature effect.

  13. Granuloma Annulare.

    PubMed

    Keimig, Emily Louise

    2015-07-01

    Granuloma annulare (GA) is a noninfectious granulomatous skin condition that can present with a variety of cutaneous morphologies. It is characterized by collagen degeneration, mucin deposition, and palisaded or interstitial histiocytes. Although the mechanism underlying development of GA is unknown, studies point to a cell-mediated hypersensitivity reaction to an as-yet undetermined antigen. Systemic associations with diabetes, thyroid disorders, lipid abnormalities, malignancy, and infection are described in atypical GA. Treatment is divided into localized skin-directed therapies and systemic immunomodulatory or immunosuppressive therapies. The selected treatment modality should be based on disease severity, comorbid conditions, consideration of potential side effects, and patient preference. PMID:26143416

  14. Two-phase/two-phase heat exchanger analysis

    NASA Technical Reports Server (NTRS)

    Kim, Rhyn H.

    1992-01-01

    A capillary pumped loop (CPL) system with a condenser linked to a double two-phase heat exchanger is analyzed numerically to simulate the performance of the system from different starting conditions to a steady state condition based on a simplified model. Results of the investigation are compared with those of similar apparatus available in the Space Station applications of the CPL system with a double two-phase heat exchanger.

  15. [Granuloma annulare].

    PubMed

    Butsch, F; Weidenthaler-Barth, B; von Stebut, E

    2015-11-01

    Granuloma annulare is a benign, chronic inflammatory skin disease. Its pathogenesis is still unclear, but reports on infections as a trigger can be found. In addition, some authors reported an association with other systemic disease, e.g., cancer, trauma, and diabetes mellitus; however, these have not been verified. The clinical picture of granuloma annulare ranges from the localized form predominantly at the extremities to disseminated, subcutaneous, or perforating forms. Diagnosis is based on the typical clinical presentation which may be confirmed by a biopsy. Histologically, necrobiotic areas within granulomatous inflammation are typical. The prognosis of the disease is good with spontaneous resolution being frequently observed, especially in localized forms. Disseminated manifestations tend to persist longer, and recurrences are reported. When choosing between different therapeutic options, the benign disease character versus the individual degree of suffering and the potential therapy side effects must be considered. For local treatment, topical application of corticosteroids is most common. Disseminated forms can be treated systemically with corticosteroids for several weeks; alternatively, dapsone, hydroxychloroquine, retinoids, fumaric acid, cyclosporine, and anti-TNFα appear to be effective. PMID:26487494

  16. Behavior interrelationships in annular flow

    NASA Astrophysics Data System (ADS)

    Schubring, Duwayne

    Two-phase gas-liquid flow occurs in many types of industrial boiling and condensing heat transfer equipment, including the reactor cores of boiling water nuclear reactors (BWRs) and the steam generators of pressurized water reactors (PWRs). In annular flow, the liquid phase often travels as both a thin film around the wall (containing disturbance waves and base film) and as entrained droplets in the central gas core. Gas bubbles are also often entrained into this film. Annular flow displays several quantifiable flow behaviors, including pressure loss, disturbance waves, and film thickness, along with micro-scale velocity profiles and fluctuations in the liquid film. The conventional approach to annular flow closely links film thickness and pressure loss, but relies on an assumed film velocity profile and does not consider disturbance waves explicitly. The present work seeks to explore a more complete range of behaviors in both horizontal and vertical flow to explore the relationships among them and thereby improve modeling of annular flow. Several of these investigations employ quantitative visualization. Modern optics and computing (in the form of non-trivial data reduction codes) are applied to the study of two-phase flow to process images of a physical experiment to quantify behavior information. Quantitative visualization allows for rapid acquisition of a large volume of flow behavior data, which allows for analysis of the flow behaviors themselves and how they relate to one another and to global modeling. By integrating behavior data from these quantitative visualizations and other conventional experimental investigations, a new two-region (base film and disturbance wave) model is proposed that can be implemented given only flow rates, external geometry, and fluid properties.

  17. Definition of two-phase flow behaviors for spacecraft design

    NASA Technical Reports Server (NTRS)

    Reinarts, Thomas R.; Best, Frederick R.; Miller, Katherine M.; Hill, Wayne S.

    1991-01-01

    Data for complete models of two-phase flow in microgravity are taken from in-flight experiments and applied to an adiabatic flow-regime analysis to study the feasibility of two-phase systems for spacecraft. The data are taken from five in-flight experiments by Hill et al. (1990) in which a two-phase pump circulates a freon mixture and vapor and liquid flow streams are measured. Adiabatic flow regimes are analyzed based on the experimental superficial velocities of liquid and vapor, and comparisons are made with the results of two-phase flow regimes at 1 g. A motion analyzer records the flow characteristics at a rate of 1000 frames/sec, and stratified flow regimes are reported at 1 g. The flow regimes observed under microgravitational conditions are primarily annular and include slug and bubbly-slug regimes. The present data are of interest to the design and analysis of two-phase thermal-management systems for use in space missions.

  18. Studies of two phase flow

    NASA Technical Reports Server (NTRS)

    Witte, Larry C.

    1994-01-01

    The development of instrumentation for the support of research in two-phase flow in simulated microgravity conditions was performed. The funds were expended in the development of a technique for characterizing the motion and size distribution of small liquid droplets dispersed in a flowing gas. Phenomena like this occur in both microgravity and normal earth gravity situations inside of conduits that are carrying liquid-vapor mixtures at high flow rates. Some effort to develop a conductance probe for the measurement of liquid film thickness was also expended.

  19. Spacecraft heat transfer by two-phase flow method

    NASA Technical Reports Server (NTRS)

    Hye, A.

    1985-01-01

    A refrigerator/freezer has been designed with an oil-free compressor to provide an economical two-phase flow system for heat transfer. A computer simulation has been done for the condenser and evaporator to determine the design parameters, such as length, diameter, and flow regimes, for different refrigerants and load requirements. A large Reynolds number was considered to ensure annular flow (in order to maximize heat transfer coefficients) and large Froude number. The simulation was correlated with the test data of a vapor compression refrigerator/freezer flown on STS-4 (which provided information on vapor compression in a zero-gravity environment). The two-phase system will be used for the Spacelab mission SLS-1 and can be used in future spacecraft and high-speed aircraft, where weight, volume, and power requirements are critical.

  20. Subcutaneous granuloma annulare.

    PubMed

    Requena, Luis; Fernández-Figueras, María Teresa

    2007-06-01

    Subcutaneous granuloma annulare is a rare clinicopathologic variant of granuloma annulare, characterized by subcutaneous nodules that may appear alone or in association with intradermal lesions. The pathogenesis of this deep variant of granuloma annulare remains uncertain. Subcutaneous granuloma annulare appears more frequently in children and young adults, and the lesions consist of subcutaneous nodules with no inflammatory appearance at the skin surface, most commonly located on the anterior aspects of the lower legs, hands, head, and buttocks. Usually, subcutaneous granuloma annulare is an authentic and exclusive panniculitic process with no dermal participation, although in 25% of the patients lesions of subcutaneous granuloma annulare coexist with the classic findings of granuloma annulare in the dermis. Histopathologically, subcutaneous granuloma annulare consist of areas of basophilic degeneration of collagen bundles with peripheral palisading granulomas involving the connective tissue septa of the subcutis. Usually, the area of necrobiosis in subcutaneous granuloma annulare is larger than in the dermal counterpart. The central necrobiotic areas contain increased amounts of connective tissue mucin and nuclear dust from neutrophils between the degenerated collagen bundles. Eosinophils are more common in subcutaneous granuloma annulare than in the dermal counterpart. There are not descriptions of subcutaneous granuloma annulare showing a histopathologic pattern of the so-called incomplete or interstitial variant. Histopathologic differential diagnosis of subcutaneous granuloma annulare includes rheumatoid nodule, necrobiosis lipoidica and epithelioid sarcoma. PMID:17544961

  1. Separation of gas from liquid in a two-phase flow system

    NASA Technical Reports Server (NTRS)

    Hayes, L. G.; Elliott, D. G.

    1973-01-01

    Separation system causes jets which leave two-phase nozzles to impinge on each other, so that liquid from jets tends to coalesce in center of combined jet streams while gas phase is forced to outer periphery. Thus, because liquid coalescence is achieved without resort to separation with solid surfaces, cycle efficiency is improved.

  2. Two phase titanium aluminide alloy

    DOEpatents

    Deevi, Seetharama C.; Liu, C. T.

    2001-01-01

    A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.

  3. Two-phase nickel aluminides

    NASA Technical Reports Server (NTRS)

    Khadkikar, P. S.; Vedula, K.; Shabel, B. S.

    1987-01-01

    The as-extruded microstructures of two alloys in the two phase field consisting of Ni3Al and NiAl in the Ni-Al phase diagram exhibit fibrous morphology and consist of Ll(2) Ni3Al and B2 NiAl. These as-extruded microstructures can be modified dramatically by suitable heat treatments. Martensite plus NiAl or martensite plus Ni3Al microstructures are obtained upon quenching from 1523 K. Aging of martensite at 873 K results in the recently identified phase Ni5Al, whereas aging at 1123 K reverts the microstructures to Ni3Al plus NiAl. The microstructures with predominantly martensite of Ni5Al3 phases are brittle in tension at room temperature. The latter microstructure does not deform plastically even in compression at room temperature. However, some promise of room temperature tensile ductility is indicated by the Ni3Al plus NiAl phase mixtures.

  4. Two-phase potential flow

    NASA Technical Reports Server (NTRS)

    Wallis, Graham B.

    1989-01-01

    Some features of two recent approaches of two-phase potential flow are presented. The first approach is based on a set of progressive examples that can be analyzed using common techniques, such as conservation laws, and taken together appear to lead in the direction of a general theory. The second approach is based on variational methods, a classical approach to conservative mechanical systems that has a respectable history of application to single phase flows. This latter approach, exemplified by several recent papers by Geurst, appears generally to be consistent with the former approach, at least in those cases for which it is possible to obtain comparable results. Each approach has a justifiable theoretical base and is self-consistent. Moreover, both approaches appear to give the right prediction for several well-defined situations.

  5. Influence of two-phase flow characteristic on critical heat flux in low pressure

    SciTech Connect

    Inoue, Akira; Lee, Sangryoul

    1996-08-01

    Estimation of the critical heat flux (CHF) in a boiling two-phase flow is one of the important subjects for the safety of water-cooled reactors and other energy systems. In the case of a boiling two-phase flow at low pressure, flow pattern and void fraction are easy to change by the power input and the flow becomes more complex due to low density of gas phase. The CHF is affected by the flow pattern. In this study, the CHFs were measured over wide quality range from the subcooled boiling to the annular-mist flow. By using Pyrex glass tube as a test channel, the two-phase flow situation was observed. Graphite rod or stainless steel tube was used as a heater rod and installed at the center of the glass tube. Two-phase flow was formed by steam injection to circulating water at an upstream region of the test section. The flow pattern was kept nearly constant over the length of test section due to the low input power density into the fluid. Then, the characteristics of CHF could be investigated at each flow patterns of bubbly, slug, annular and annular-mist flow. In the subcooled boiling region of bubbly flow, the CHF decreased with increase of quality and was less sensitive to flow rate. In the slug flow region, the CHF showed a minimum value. With more increase of quality in the annular flow, the CHF increased and reached a peak value at a certain quality depending on a flow rate. The peak of CHF occurred almost at a constant vapor mass velocity. In the annular-mist flow region, the CHF decreased with increase of quality. In the region, the effect of heated length on the CHF was systematically measured and validity of an analytical model considering dryout of liquid film based on formation of a dry patch was investigated.

  6. Annular pancreas (image)

    MedlinePlus

    Annular pancreas is an abnormal ring or collar of pancreatic tissue that encircles the duodenum (the part of the ... intestine that connects to stomach). This portion of pancreas can constrict the duodenum and block or impair ...

  7. Mechanically expandable annular seal

    DOEpatents

    Gilmore, Richard F.

    1983-01-01

    A mechanically expandable annular reusable seal assembly to form an annular hermetic barrier between two stationary, parallel, and planar containment surfaces. A rotatable ring, attached to the first surface, has ring wedges resembling the saw-tooth array of a hole saw. Matching seal wedges are slidably attached to the ring wedges and have their motion restricted to be perpendicular to the second surface. Each seal wedge has a face parallel to the second surface. An annular elastomer seal has a central annular region attached to the seal wedges' parallel faces and has its inner and outer circumferences attached to the first surface. A rotation of the ring extends the elastomer seal's central region perpendicularly towards the second surface to create the fluidtight barrier. A counterrotation removes the barrier.

  8. Mechanically expandable annular seal

    DOEpatents

    Gilmore, R.F.

    1983-07-19

    A mechanically expandable annular reusable seal assembly to form an annular hermetic barrier between two stationary, parallel, and planar containment surfaces is described. A rotatable ring, attached to the first surface, has ring wedges resembling the saw-tooth array of a hole saw. Matching seal wedges are slidably attached to the ring wedges and have their motion restricted to be perpendicular to the second surface. Each seal wedge has a face parallel to the second surface. An annular elastomer seal has a central annular region attached to the seal wedges' parallel faces and has its inner and outer circumferences attached to the first surface. A rotation of the ring extends the elastomer seal's central region perpendicularly towards the second surface to create the fluid tight barrier. A counter rotation removes the barrier. 6 figs.

  9. Measurement of thickness of thin water film in two-phase flow by capacitance method

    SciTech Connect

    Sun, R.K.; Kolbe, W.F.; Leskovar, B.; Turko, B.

    1981-09-01

    A technique has been developed for measuring water film thickness in a two-phase annular flow system by the capacitance method. An experimental model of the flow system with two types of electrodes mounted on the inner wall of a cylindrical tube has been constructed and evaluated. The apparatus and its ability to observe fluctuations and wave motions of the water film passing over the electrodes is described in some detail.

  10. The numerical calculation of heat transfer performance for annular flow of liquid nitrogen in a vertical annular channel

    NASA Astrophysics Data System (ADS)

    Sun, Shufeng; Wu, Yuyuan; Zhao, Rongyi

    2001-04-01

    According to a separated phase flow model for vertical annular two-phase flow in an annular channel, the liquid film thickness, distributions of velocities and temperatures in the liquid layer are predicted in the range of heat fluxes: 6000-12000 W/m 2, mass flux: 500-1100 kg/m2 s. The pressure drop along the flow channel and heat transfer coefficient are also calculated. The liquid film thickness is in the order of micrometers and heat transfer coefficient is 2800-7800 W/m2 K of liquid nitrogen boiling in narrow annular channels. The measured heat transfer coefficient is 29% higher than the calculated values. With the mass flux increasing and the gap of the annular channel decreasing, pressure drop and heat transfer coefficient increase.

  11. Modeling of density loaded two-phase flows

    SciTech Connect

    Mostafa, A.A. )

    1991-01-01

    In this paper a mathematical model for densely loaded particle-laden flows is proposed to account for particle collisions and particle-turbulence interaction. The coupled conservation equations are based on a Eulerian scheme for the gas and a stochastic Lagrangian technique for the particles. The model was validated against the experimental data of densely loaded particle-laden jet flows. The comparison between the computational results and measurements suggested that both turbulence modulation and particle collisions are important and should be considered in an accurate analysis of dense two-phase flows.

  12. Two-phase flow research. Phase I. Two-phase nozzle research. Final report

    SciTech Connect

    Toner, S.J.

    1981-07-01

    An investigation of energy transfer in two-phase nozzles was conducted. Experimental performance of converging-diverging nozzles operating on air-water mixtures is presented for a wide range of parameters. Thrust measurements characterized the performance and photographic documentation was used to visually observe the off-design regimes. Thirty-six nozzle configurations were tested to determine the effects of convergence angle, area ratio, and nozzle length. In addition, the pressure ratio and mass flowrate ratio were varied to experimentally map off-design performance. The test results indicate the effects of wall friction and infer temperature and velocity differences between phases and the effect on nozzle performance. The major conclusions reached were: the slip ratio between the phases, gas velocity to liquid velocity, is shown to be below about 4 or 5, and, in most of the test cases run, was estimated to between about 1-1/2 to 2-1/2; in all cases except the free-jet the mass )

  13. Calculation of two-phase flow in gas turbine combustors

    SciTech Connect

    Tolpadi, A.K.

    1995-10-01

    A method is presented for computing steady two-phase turbulent combusting flow in a gas turbine combustor. The gas phase equations are solved in an Eulerian frame of reference. The two-phase calculations are performed by using a liquid droplet spray combustion a model and treating the motion of the evaporating fuel droplets in a Lagrangian frame of reference. The numerical algorithm employs nonorthogonal curvilinear coordinates, a multigrid iterative solution procedure, the standard k-{epsilon} turbulence model, and a combustion model comprising an assumed shape probability density function and the conserved scalar formulation. The trajectory computation of the fuel provides the source terms for all the gas phase equations. This two-phase model was applied to a real piece of combustion hardware in the form of a modern GE/SNECMA single annular CFM56 turbofan engine combustor. For the purposes of comparison, calculations were also performed by treating the fuel as a single gaseous phase. The effect on the solution of two extreme situations of the fuel as a gas and initially as a liquid was examined. The distribution of the velocity field and the conserved scalar within the combustor, as well as the distribution of the temperature field in the reaction zone and in the exhaust, were all predicted with the combustor operating both at high-power and low-power (ground idle) conditions. The calculated exit gas temperature was compared with test rig measurements. Under both low and high-power conditions, the temperature appeared to show an improved agreement with the measured data when the calculations were performed with the spray model as compared to a single-phase calculation.

  14. One- and two-phase nozzle flows

    SciTech Connect

    Chang, I.S.

    1980-01-01

    A time-dependent technique, in conjunction with the boundary-fitted coordinates system, is applied to solve a gas-only one-phase flow and a fully-coupled, gas-particle two-phase flow inside nozzles with small throat radii of curvature, steep wall gradients, and submerged configurations. The emphasis of the study has been placed on one- and two-phase flow in the transonic region. Various particle sizes and particle mass fractions have been investigated in the two-phase flow. The salient features associated with the two-phase nozzle flow compared with those of the one-phase flow are illustrated through the calculations of the JPL nozzle, the Titan III solid rocket motor, and the submerged nozzle configuration found in the Inertial Upper Stage (IUS) solid rocket motor.

  15. Two-Phase Flow Separator Investigation

    NASA Video Gallery

    The goal of the Two-Phase Flow Separator investigation is to help increase understanding of how to separate gases and liquids in microgravity. Many systems on the space station contain both liquids...

  16. Two-phase flow studies. Final report

    SciTech Connect

    Kestin, J.; Maeder, P.F.

    1980-08-01

    Progress on the following is reported: literature survey, design of two-phase flow testing facility, design of nozzle loop, thermophysical properties, design manual, and advanced energy conversion systems. (MHR)

  17. Estimation of shear stress in counter-current gas-liquid annular two-phase flow

    NASA Astrophysics Data System (ADS)

    Abe, Yutaka; Akimoto, Hajime; Murao, Yoshio

    1991-01-01

    The accuracy of the correlations of the friction factor is important for the counter-current flow (CCF) analysis with two-fluid model. However, existing two fluid model codes use the correlations of friction factors for co-current flow or correlation developed based on the assumption of no wall shear stress. The assessment calculation for two fluid model code with those existing correlations of friction factors shows the falling water flow rate is overestimated. Analytical model is developed to calculate the shear stress distribution in water film at CCF in order to get the information on the shear stress at the interface and the wall. The analytical results with the analysis model and Bharathan's CCF data shows that the wall shear stress acting on the falling water film is almost the same order as the interfacial shear stress and the correlations for co-current flow cannot be applied to the counter-current flow. Tentative correlations of the interfacial and the wall friction factors are developed based on the results of the present study.

  18. SILVA: EDF two-phase 1D annular model of a CFB boiler furnace

    SciTech Connect

    Montat, D.; Fauquet, P.; Lafanechere, L.; Bursi, J.M.

    1997-12-31

    Aiming to improve its knowledge of CFB boilers, EDF has initiated a R and D program including: laboratory work on mock-ups, numerical modelling and on-site tests in CFB power plants. One of the objectives of this program is the development of a comprehensive steady-state 1D model of the solid circulation loop, named SILVA, for plant operation and design evaluation purposes. This paper describes its mathematical and physical modelling. Promising validation of the model on cold mock-up and industrial CFB is presented.

  19. Two-Phase Potential Flow. Final report

    SciTech Connect

    Wallis, G.B.

    1999-06-11

    The objective of this work was to devise essentially exact solutions to a set of well-defined basic problems of inviscid fluid flow with particulate inclusions. This would help to establish a sound basis for fundamental theoretical developments in the field of two-phase flow. The results of this effort have ranged from basic theorems and the formulation of conservation laws for two-phase mixtures, to detailed predictions for specific geometrical patterns and experimental confirmation of these results.

  20. Two Phase Flow Mapping and Transition Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Parang, Masood; Chao, David F.

    1998-01-01

    In this paper, recent microgravity two-phase flow data for air-water, air-water-glycerin, and air- water-Zonyl FSP mixtures are analyzed for transition from bubbly to slug and from slug to annular flow. It is found that Weber number-based maps are inadequate to predict flow-pattern transition, especially over a wide range of liquid flow rates. It is further shown that slug to annular flow transition is dependent on liquid phase Reynolds number at high liquid flow rate. This effect may be attributed to growing importance of liquid phase inertia in the dynamics of the phase flow and distribution. As a result a new form of scaling is introduced to present data using liquid Weber number based on vapor and liquid superficial velocities and Reynolds number based on liquid superficial velocity. This new combination of the dimensionless parameters seem to be more appropriate for the presentation of the microgravity data and provides a better flow pattern prediction and should be considered for evaluation with data obtained in the future. Similarly, the analysis of bubble to slug flow transition indicates a strong dependence on both liquid inertia and turbulence fluctuations which seem to play a significant role on this transition at high values of liquid velocity. A revised mapping of data using a new group of dimensionless parameters show a better and more consistent description of flow transition over a wide range of liquid flow rates. Further evaluation of the proposed flow transition mapping will have to be made after a wider range of microgravity data become available.

  1. Erythematous Granuloma Annulare

    PubMed Central

    Jang, Eun Joo; Lee, Ji Yeoun; Kim, Mi Kyeong

    2011-01-01

    Granuloma annulare (GA) is a common, benign, chronic inflammatory disorder, which is characterized by grouped papules in an enlarging annular shape. It has been described in several clinical subtypes, including localized, generalized, subcutaneous, perforating, and erythematous types. Even though generalized, subcutaneous, and perforating types of GA are unusual, there are several reports of those types. However, erythematous or patch GA, has not been reported yet in the Korean literature. Herein, we report a 42-year-old woman with pruritic erythematous patches, which occurred on the extremities without preceding event, and showed typical clinical and histopatologic findings of erythematous GA. PMID:21909221

  2. A numerical study of two-phase flow in gas turbine combustors

    NASA Astrophysics Data System (ADS)

    Tolpadi, A. K.

    1992-07-01

    A method is presented for computing steady two-phase turbulent combusting flow in a gas turbine combustor. The gas phase equations are solved in an Eulerian frame of reference. The two-phase calculations are performed by using a liquid droplet spray combustion model and treating the motion of the evaporating fuel droplets in a Lagrangian frame of reference. The numerical algorithm employs nonorthogonal curvilinear coordinates, a multigrid iterative solution procedure, the standard k-epsilon turbulence model, and a combustion model made up of an assumed shape probability density function and the conserved scalar formulation. The trajectory computation of the fuel provides the source terms for all the gas phase equations. Results of the application of the two-phase model to a modern GE/SNECMA single annular CFM56 turbofan engine combustor are reported.

  3. Performance tests of a two phase ejector

    SciTech Connect

    Harrell, G.S.; Kornhauser, A.A.

    1995-12-31

    The ejector expansion refrigeration cycle is a modified vapor compression cycle in which a two phase ejector is used to recover a portion of the work otherwise lost in the expansion valve. The ejector improves cycle performance by increasing compressor inlet pressure and by lowering the quality of liquid entering the evaporator. Theoretically, a cooling COP improvement of approximately 23% is achievable for a typical refrigerating cycle and an ideal ejector. If the ejector performed as well as typical single phase ejectors an improvement of 12% could be achieved. Previous tests have demonstrated a smaller 3.7% improvement; the difference is in the poor performance of the two phase ejector. The purpose of this research is to understand the operating characteristics of the two phase ejector and to devise design improvements. A two phase ejector test rig has been constructed and tested. Preliminary data show performance superior to previously tested two phase ejectors, but still inferior to single phase ejectors. Ejector performance corresponds to refrigeration cycle COP improvements ranging from 3.9% to 7.6%.

  4. Laser Doppler velocimeter measurements and laser sheet imaging in an annular combustor model. M.S. Thesis, Final Report

    NASA Technical Reports Server (NTRS)

    Dwenger, Richard Dale

    1995-01-01

    An experimental study was conducted in annular combustor model to provide a better understanding of the flowfield. Combustor model configurations consisting of primary jets only, annular jets only, and a combination of annular and primary jets were investigated. The purpose of this research was to provide a better understanding of combustor flows and to provide a data base for comparison with computational models. The first part of this research used a laser Doppler velocimeter to measure mean velocity and statistically calculate root-mean-square velocity in two coordinate directions. From this data, one Reynolds shear stress component and a two-dimensional turbulent kinetic energy term was determined. Major features of the flowfield included recirculating flow, primary and annular jet interaction, and high turbulence. The most pronounced result from this data was the effect the primary jets had on the flowfield. The primary jets were seen to reduce flow asymmetries, create larger recirculation zones, and higher turbulence levels. The second part of this research used a technique called marker nephelometry to provide mean concentration values in the combustor. Results showed the flow to be very turbulent and unsteady. All configurations investigated were highly sensitive to alignment of the primary and annular jets in the model and inlet conditions. Any imbalance between primary jets or misalignment of the annular jets caused severe flow asymmetries.

  5. Dynamic characteristics of two-phase media

    SciTech Connect

    Fedotovskiy, V.S.; Sinyavskiy, V.F.; Terenik, L.V.; Spirov, V.S.

    1990-01-01

    This paper presents the results of investigations into the effective dynamic properties of heterogeneous media formed by a liquid and rigid spherical or cylindrical inclusions contained in it. Oscillations of a pipeline with a two-phase mixture in the general case having a non-uniform distribution of phases over the cross section are considered. Relations are obtained for the effective mass and hydrodynamic damping that determine the frequencies and dynamic-response factors. Oscillations of the bundles of elastic rods in a liquid are considered as in a two-phase mixture formed by a liquid and cylindrical inclusions and which has equivalent inertia and viscous properties.

  6. Two phase detonation studies conducted in 1971

    NASA Technical Reports Server (NTRS)

    Nicholls, J. A.

    1972-01-01

    A report is presented describing the research conducted on five phases: (1) ignition of fuel drops by a shock wave and passage of a shock wave over a burning drop, (2) the energy release pattern of a two-phase detonation with controlled drop sizes, (3) the attenuation of shock and detonation waves passing over an acoustic liner, (4) experimental and theoretical studies of film detonations, and (5) a simplified analytical model of a rotating two-phase detonation wave in a rocket motor.

  7. Two-phase computational fluid dynamics

    SciTech Connect

    Rothe, P.H.

    1991-07-26

    The results of the project illustrate the feasibility of multiphase computerized fluid dynamics (CFD) software. Existing CFD software is capable of simulating particle fields, certain droplet fields, and certain free surface flows, and does so routinely in engineering applications. Stratified flows can be addressed by a multiphase CFD code, once one is developed with suitable capabilities. The groundwork for such a code has been laid. Calculations performed for stratified flows demonstrate the accuracy achievable and the convergence of the methodology. Extension of the stratified flow methodology to other segregated flows such as slug or annular faces no inherent limits. The research has commercial application in the development of multiphase CFD computer programs.

  8. Annular flow film characteristics in variable gravity.

    PubMed

    MacGillivray, Ryan M; Gabriel, Kamiel S

    2002-10-01

    Annular flow is a frequently occurring flow regime in many industrial applications. The need for a better understanding of this flow regime is driven by the desire to improve the design of many terrestrial and space systems. Annular two-phase flow occurs in the mining and transportation of oil and natural gas, petrochemical processes, and boilers and condensers in heating and refrigeration systems. The flow regime is also anticipated during the refueling of space vehicles, and thermal management systems for space use. Annular flow is mainly inertia driven with little effect of buoyancy. However, the study of this flow regime is still desirable in a microgravity environment. The influence of gravity can create an unstable, chaotic film. The absence of gravity, therefore, allows for a more stable and axisymmetric film. Such conditions allow for the film characteristics to be easily studied at low gas flow rates. Previous studies conducted by the Microgravity Research Group dealt with varying the gas or liquid mass fluxes at a reduced gravitational acceleration.(1,2) The study described here continues this work by examining the effect of changing the gravitational acceleration (hypergravity) on the film characteristics. In particular, the film thickness and the associated pressure drops are examined. The film thickness was measured using a pair of two-wire conductance probes. Experimental data was collected over a range of annular flow set points by changing the liquid and gas mass flow rates, the liquid-to-gas density ratio and the gravitational acceleration. The liquid-to-gas density ratio was varied by collecting data with helium-water and air-water at the same flow rates. The gravitational effect was examined by collecting data during the microgravity and pull-up (hypergravity) portions of the parabolic flights. PMID:12446332

  9. Improved Two-Phase Switching Regulator

    NASA Technical Reports Server (NTRS)

    Rippel, W. E.

    1984-01-01

    Coupled-inductor polyphase regulator has better efficiency and lower inductor losses. Improved two-phase switching regulator employs negative coupling between inductors to achieve better power-to-weight ratio while reducing peak switching currents and inductor losses. Improvement of about 35 percent using new technique.

  10. Two-phase flow in fractured rock

    SciTech Connect

    Davies, P.; Long, J.; Zuidema, P.

    1993-11-01

    This report gives the results of a three-day workshop on two-phase flow in fractured rock. The workshop focused on two-phase flow processes that are important in geologic disposal of nuclear waste as experienced in a variety of repository settings. The goals and objectives of the workshop were threefold: exchange information; describe the current state of understanding; and identify research needs. The participants were divided into four subgroups. Each group was asked to address a series of two-phase flow processes. The following groups were defined to address these processes: basic flow processes; fracture/matrix interactions; complex flow processes; and coupled processes. For each process, the groups were asked to address these four issues: (1) describe the two-phase flow processes that are important with respect to repository performance; (2) describe how this process relates to the specific driving programmatic issues given above for nuclear waste storage; (3) evaluate the state of understanding for these processes; and (4) suggest additional research to address poorly understood processes relevant to repository performance. The reports from each of the four working groups are given here.

  11. Condensing, Two-Phase, Contact Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Cox, R. L.; Oren, J. A.; Sauer, L. W.

    1988-01-01

    Two-phase heat exchanger continuously separates liquid and vapor phases of working fluid and positions liquid phase for efficient heat transfer. Designed for zero gravity. Principle is adapted to other phase-separation applications; for example, in thermodynamic cycles for solar-energy conversion.

  12. Segmented annular combustor

    DOEpatents

    Reider, Samuel B.

    1979-01-01

    An industrial gas turbine engine includes an inclined annular combustor made up of a plurality of support segments each including inner and outer walls of trapezoidally configured planar configuration extents and including side flanges thereon interconnected by means of air cooled connector bolt assemblies to form a continuous annular combustion chamber therebetween and wherein an air fuel mixing chamber is formed at one end of the support segments including means for directing and mixing fuel within a plenum and a perforated header plate for directing streams of air and fuel mixture into the combustion chamber; each of the outer and inner walls of each of the support segments having a ribbed lattice with tracks slidably supporting porous laminated replaceable panels and including pores therein for distributing combustion air into the combustion chamber while cooling the inner surface of each of the panels by transpiration cooling thereof.

  13. Granuloma annulare, patch type.

    PubMed

    Victor, Frank C; Mengden, Stephanie

    2008-01-01

    A 64-year-old man was referred to the Bellevue Hospital Center Dermatology Clinic for evaluation of an asymptomatic eruption on his left inner arm, which had been present for 4 months and was unresponsive to topical anti-fungal therapy. One month after the initial eruption, 2 similar, asymptomatic lesions appeared on the right inner arm. The lesions were slowly expanding. A biopsy specimen from the left medial arm was consistent with interstitial granuloma annulare. The patient's clinical presentation was consistent with patch-type granuloma annulare. He was treated with a mid-potency topical glucocorticoid twice daily for 4 weeks without benefit. Since the eruption was asymptomatic, treatment was discontinued. PMID:18627757

  14. Theory and tests of two-phase turbines

    NASA Technical Reports Server (NTRS)

    Elliott, D. G.

    1982-01-01

    A theoretical model for two-phase turbines was developed. Apparatus was constructed for testing one- and two-stage turbines (using speed decrease from stage to stage). Turbines were tested with water and nitrogen mixtures and refrigerant 22. Nozzle efficiencies were 0.78 (measured) and 0.72 (theoretical) for water and nitrogen mixtures at a water/nitrogen mixture ratio of 68, by mass; and 0.89 (measured) and 0.84 (theoretical) for refrigerant 22 expanding from 0.02 quality to 0.28 quality. Blade efficiencies (shaft power before windage and bearing loss divided by nozzle jet power) were 0.63 (measured) and 0.71 (theoretical) for water and nitrogen mixtures and 0.62 (measured) and 0.63 (theoretical) for refrigerant 22 with a single stage turbine, and 0,70 (measured) and 0.85 (theoretical) for water and nitrogen mixtures with a two-stage turbine.

  15. Apparatus for monitoring two-phase flow

    DOEpatents

    Sheppard, John D.; Tong, Long S.

    1977-03-01

    A method and apparatus for monitoring two-phase flow is provided that is particularly related to the monitoring of transient two-phase (liquid-vapor) flow rates such as may occur during a pressurized water reactor core blow-down. The present invention essentially comprises the use of flanged wire screens or similar devices, such as perforated plates, to produce certain desirable effects in the flow regime for monitoring purposes. One desirable effect is a measurable and reproducible pressure drop across the screen. The pressure drop can be characterized for various known flow rates and then used to monitor nonhomogeneous flow regimes. Another useful effect of the use of screens or plates in nonhomogeneous flow is that such apparatus tends to create a uniformly dispersed flow regime in the immediate downstream vicinity. This is a desirable effect because it usually increases the accuracy of flow rate measurements determined by conventional methods.

  16. Dynamic failure in two-phase materials

    SciTech Connect

    Fensin, S. J.; Walker, E. K.; Cerreta, E. K.; Trujillo, C. P.; Martinez, D. T.; Gray, G. T.

    2015-12-21

    Previous experimental research has shown that microstructural features such as interfaces, inclusions, vacancies, and heterogeneities can all act as voidnucleation sites. However, it is not well understood how important these interfaces are to damage evolution and failure as a function of the surrounding parentmaterials. In this work, we present results on three different polycrystallinematerials: (1) Cu, (2) Cu-24 wt. %Ag, and (3) Cu-15 wt. %Nb which were studied to probe the influence of bi-metal interfaces onvoidnucleation and growth. These materials were chosen due to the range of difference in structure and bulk properties between the two phases. The initial results suggest that when there are significant differences between the bulk properties (for example: stacking fault energy, melting temperature, etc.) the type of interface between the two parent materials does not principally control the damage nucleation and growth process. Rather, it is the “weaker” material that dictates the dynamic spall strength of the overall two-phase material.

  17. Pumped two-phase heat transfer loop

    NASA Technical Reports Server (NTRS)

    Edelstein, Fred

    1988-01-01

    A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes several independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.

  18. Pumped two-phase heat transfer loop

    NASA Technical Reports Server (NTRS)

    Edelstein, Fred (Inventor)

    1987-01-01

    A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes a plurality of independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.

  19. Zero-G two phase flow regime modeling in adiabatic flow

    NASA Astrophysics Data System (ADS)

    Reinarts, Thomas R.; Best, Frederick R.; Wheeler, Montgomery; Miller, Katheryn M.

    1993-01-01

    Two-phase flow, thermal management systems are currently being considered as an alternative to conventional, single phase systems for future space missions because of their potential to reduce overall system mass, size, and pumping power requirements. Knowledge of flow regime transitions, heat transfer characteristics, and pressure drop correlations is necessary to design and develop two-phase systems. This work is concerned with microgravity, two-phase flow regime analysis. The data come from a recent sets of experiments. The experiments were funded by NASA Johnson Space Center (JSC) and conducted by NASA JSC with Texas A&M University. The experiment was on loan to NASA JSC from Foster-Miller, Inc., who constructed it with funding from the Air Force Phillips Laboratory. The experiment used R12 as the working fluid. A Foster-Miller two phase pump was used to circulate the two phase mixture and allow separate measurements of the vapor and liquid flow streams. The experimental package was flown 19 times for 577 parabolas aboard the NASA KC-135 aircraft which simulates zero-G conditions by its parabolic flight trajectory. Test conditions included bubbly, slug and annular flow regimes in 0-G. The superficial velocities of liquid and vapor have been obtained from the measured flow rates and are presented along with the observed flow regimes and several flow regime transition predictions. None of the predictions completely describe the transitions as indicated by the data.

  20. Theory and tests of two-phase turbines

    SciTech Connect

    Elliot, D.G.

    1982-03-15

    Two-phase turbines open the possibility of new types of power cycles operating with extremely wet mixtures of steam and water, organic fluids, or immiscible liquids and gases. Possible applications are geothermal power, waste-heat recovery, refrigerant expansion, solar conversion, transportation turbine engines, and engine bottoming cycles. A theoretical model for two-phase impulse turbines was developed. Apparatus was constructed for testing one- and two-stage turbines (using speed decrease from stage to stage). Turbines were tested with water-and-nitrogen mixtures and Refrigerant 22. Nozzle efficiencies were 0.78 (measured) and 0.72 (theoretical) for water-and-nitrogen mixtures at a water/nitrogen mixture ratio of 68, by mass; and 0.89 (measured) and 0.84 (theoretical) for Refrigerant 22 expanding from 0.02 quality to 0.28 quality. Blade efficiencies (shaft power before windage and bearing loss divided by nozzle jet power) were 0.63 (measured) and 0.71 (theoretical) for water-and-nitrogen mixtures and 0.62 (measured) and 0.63 (theoretical) for Refrigerant 22 with a single-stage turbine, and 0.70 (measured) and 0.85 (theoretical) for water-and-nitrogen mixtures with a two-stage turbine.

  1. Two-phase charge-coupled device

    NASA Technical Reports Server (NTRS)

    Kosonocky, W. F.; Carnes, J. E.

    1973-01-01

    A charge-transfer efficiency of 99.99% per stage was achieved in the fat-zero mode of operation of 64- and 128-stage two-phase charge-coupled shift registers at 1.0-MHz clock frequency. The experimental two-phase charge-coupled shift registers were constructed in the form of polysilicon gates overlapped by aluminum gates. The unidirectional signal flow was accomplished by using n-type substrates with 0.5 to 1.0 ohm-cm resistivity in conjunction with a channel oxide thickness of 1000 A for the polysilicon gates and 3000 A for the aluminum gates. The operation of the tested shift registers with fat zero is in good agreement with the free-charge transfer characteristics expected for the tested structures. The charge-transfer losses observed when operating the experimental shift registers without the fat zero are attributed to fast interface state trapping. The analytical part of the report contains a review backed up by an extensive appendix of the free-charge transfer characteristics of CCD's in terms of thermal diffusion, self-induced drift, and fringing field drift. Also, a model was developed for the charge-transfer losses resulting from charge trapping by fast interface states. The proposed model was verified by the operation of the experimental two-phase charge-coupled shift registers.

  2. Two-phase flow centrifugal pump performance

    NASA Astrophysics Data System (ADS)

    Chisely, Eugene Andras

    The performance of centrifugal pumps subjected to a liquid-gas-mixture flow is a significant concern to manufacturers and to some users such as Chemical, Nuclear Power Plants, and Gas-Oil Industries. Particularly in the nuclear power industry, the prediction of performance degradation under the two-phase flow conditions occurring in a Loss of Coolant Accident (LOCA) is a significant part of the overall analysis of that accident. In this experimental work, the pressure distribution was measured in a rotating, partially shrouded, open, radial impeller and volute under a wide range of air-water two-phase flow conditions. To obtain these pressure measurements, small-diameter pressure-tap holes were drilled through the casing of the radial pump. High speed photography was used to determine the flow regime of the air-water mixture through the vane and in the volute. An analytical model was developed to predict the radial pump single- and two-phase flow pressure distribution. This distribution was compared with the test data for different suction void fractions. The physical mechanism responsible for pump performance degradation was also investigated.

  3. The rheology of two-phase magmas

    NASA Astrophysics Data System (ADS)

    Llewellin, E. W.; Mader, H. M.; Mueller, S.

    2012-12-01

    Great advances in our understanding of the rheology of two-phase magmatic suspensions (magma with either bubbles or crystals in it) have been made in recent years. These advances are based on laboratory experiments with both magma and analogue materials, and on analytical and numerical modelling. The current state-of-the-art is the culmination of scores of studies undertaken by scores of research groups and presented in scores of publications. Consequently, whilst it is possible to construct a sophisticated rheological description of a two-phase magma based on a few easily-measured properties (melt composition, crystal/vesicle volume fraction, CSD/VSD, etc.) the task of determining how best to do this is daunting to the non-specialist. We present a straightforward, practical, algorithmic approach to determining the rheology of two-phase magma to the degree of sophistication appropriate to most modelling applications. The approach is based on a broad synthesis of the literature, on new experimental data, and on new theoretical analysis.

  4. Research on Plasma Synthetic Jet Actuator

    NASA Astrophysics Data System (ADS)

    Che, X. K.; Nie, W. S.; Hou, Z. Y.

    2011-09-01

    Circular dielectric barrier surface discharge (DBDs) actuator is a new concept of zero mass synthetic jet actuator. The characteristic of discharge and flow control effect of annular-circular plasma synthetic jet actuator has been studied by means of of numerical simulation and experiment. The discharge current density, electron density, electrostatic body force density and flowfield have been obtained. The results show annular-circular actuator can produce normal jet whose velocity will be greater than 2.0 m/s. The jet will excite circumfluence. In order to insure the discharge is generated in the exposed electrode annular and produce centripetal and normal electrostatic body force, the width and annular diameter of exposed electrode must be big enough, or an opposite phase drove voltage potential should be applied between the two electrodes.

  5. Annular recuperator design

    DOEpatents

    Kang, Yungmo

    2005-10-04

    An annular heat recuperator is formed with alternating hot and cold cells to separate counter-flowing hot and cold fluid streams. Each cold cell has a fluid inlet formed in the inner diameter of the recuperator near one axial end, and a fluid outlet formed in the outer diameter of the recuperator near the other axial end to evenly distribute fluid mass flow throughout the cell. Cold cells may be joined with the outlet of one cell fluidly connected to the inlet of an adjacent downstream cell to form multi-stage cells.

  6. Numerical Simulation of Two Phase Flows

    NASA Technical Reports Server (NTRS)

    Liou, Meng-Sing

    2001-01-01

    Two phase flows can be found in broad situations in nature, biology, and industry devices and can involve diverse and complex mechanisms. While the physical models may be specific for certain situations, the mathematical formulation and numerical treatment for solving the governing equations can be general. Hence, we will require information concerning each individual phase as needed in a single phase. but also the interactions between them. These interaction terms, however, pose additional numerical challenges because they are beyond the basis that we use to construct modern numerical schemes, namely the hyperbolicity of equations. Moreover, due to disparate differences in time scales, fluid compressibility and nonlinearity become acute, further complicating the numerical procedures. In this paper, we will show the ideas and procedure how the AUSM-family schemes are extended for solving two phase flows problems. Specifically, both phases are assumed in thermodynamic equilibrium, namely, the time scales involved in phase interactions are extremely short in comparison with those in fluid speeds and pressure fluctuations. Details of the numerical formulation and issues involved are discussed and the effectiveness of the method are demonstrated for several industrial examples.

  7. Dynamic failure in two-phase materials

    NASA Astrophysics Data System (ADS)

    Fensin, S. J.; Walker, E. K.; Cerreta, E. K.; Trujillo, C. P.; Martinez, D. T.; Gray, G. T.

    2015-12-01

    Previous experimental research has shown that microstructural features such as interfaces, inclusions, vacancies, and heterogeneities can all act as void nucleation sites. However, it is not well understood how important these interfaces are to damage evolution and failure as a function of the surrounding parent materials. In this work, we present results on three different polycrystalline materials: (1) Cu, (2) Cu-24 wt. %Ag, and (3) Cu-15 wt. %Nb which were studied to probe the influence of bi-metal interfaces on void nucleation and growth. These materials were chosen due to the range of difference in structure and bulk properties between the two phases. The initial results suggest that when there are significant differences between the bulk properties (for example: stacking fault energy, melting temperature, etc.) the type of interface between the two parent materials does not principally control the damage nucleation and growth process. Rather, it is the "weaker" material that dictates the dynamic spall strength of the overall two-phase material.

  8. Dynamic failure in two-phase materials

    DOE PAGESBeta

    Fensin, S. J.; Walker, E. K.; Cerreta, E. K.; Trujillo, C. P.; Martinez, D. T.; Gray, G. T.

    2015-12-21

    Previous experimental research has shown that microstructural features such as interfaces, inclusions, vacancies, and heterogeneities can all act as voidnucleation sites. However, it is not well understood how important these interfaces are to damage evolution and failure as a function of the surrounding parentmaterials. In this work, we present results on three different polycrystallinematerials: (1) Cu, (2) Cu-24 wt. %Ag, and (3) Cu-15 wt. %Nb which were studied to probe the influence of bi-metal interfaces onvoidnucleation and growth. These materials were chosen due to the range of difference in structure and bulk properties between the two phases. The initial resultsmore » suggest that when there are significant differences between the bulk properties (for example: stacking fault energy, melting temperature, etc.) the type of interface between the two parent materials does not principally control the damage nucleation and growth process. Rather, it is the “weaker” material that dictates the dynamic spall strength of the overall two-phase material.« less

  9. Portal Annular Pancreas

    PubMed Central

    Harnoss, Jonathan M.; Harnoss, Julian C.; Diener, Markus K.; Contin, Pietro; Ulrich, Alexis B.; Büchler, Markus W.; Schmitz-Winnenthal, Friedrich H.

    2014-01-01

    Abstract Portal annular pancreas (PAP) is an asymptomatic congenital pancreas anomaly, in which portal and/or mesenteric veins are encased by pancreas tissue. The aim of the study was to determine the role of PAP in pancreatic surgery as well as its management and potential complication, specifically, postoperative pancreatic fistula (POPF). On the basis of a case report, the MEDLINE and ISI Web of Science databases were systematically reviewed up to September 2012. All articles describing a case of PAP were considered. In summary, 21 studies with 59 cases were included. The overall prevalence of PAP was 2.4% and the patients' mean (SD) age was 55.9 (16.2) years. The POPF rate in patients with PAP (12 pancreaticoduodenectomies and 3 distal pancreatectomies) was 46.7% (in accordance with the definition of the International Study Group of Pancreatic Surgery). Portal annular pancreas is a quite unattended pancreatic variant with high prevalence and therefore still remains a clinical challenge to avoid postoperative complications. To decrease the risk for POPF, attentive preoperative diagnostics should also focus on PAP. In pancreaticoduodenectomy, a shift of the resection plane to the pancreas tail should be considered; in extensive pancreatectomy, coverage of the pancreatic remnant by the falciform ligament could be a treatment option. PMID:25207658

  10. Condensation of Forced Convection Two-Phase Flow in a Miniature Tube

    NASA Technical Reports Server (NTRS)

    Begg, E.; Faghri, A.; Krustalev, D.

    1999-01-01

    A physical/mathematical model of annular film condensation at the inlet of a miniature tube has been developed. In the model, the liquid flow is coupled with the vapor flow along the liquid-vapor interface through the interfacial temperature, heat flux, shear stress, and pressure jump conditions due to surface tension effects. The model predicts the shape of the liquid-vapor interface along the condenser and leads to the conclusion that there is complete condensation at a certain distance from the condenser inlet. The numerical results show that complete condensation of the incoming vapor is possible at comparatively low heat loads and that this is a special case of a more general condensation regime with two-phase bubbly flow downstream of the initial annular film condensation region. Observations from the flow visualization experiment confirm the existence and qualitative features of annular film condensation leading to the complete condensation phenomenon in a small diameter (3.25 mm) circular tube condenser.

  11. Nodal analysis of two-phase instabilities

    SciTech Connect

    Lahey, R.T. Jr.; Garea, V.P.

    1995-10-01

    Nodal models having moving nodal boundaries have been developed for the analysis of two-phase flow instabilities in a boiling channel. The first model, which was based on a Galerkin method for the discretization, has been found to be accurate in the prediction of the onset of instabilities as well as the frequency of oscillations. This model however, had some problems with the prediction of chaotic phenomena and did not allow for flow reversal in the channel. A second nodal model, based on a finite difference approach, has been found to perform better for the prediction of non-linear response and it also allows for flow reversal. Both models are numerically more efficient than the existing fixed grid models for instabilities analysis.

  12. Stability of oscillatory two phase Couette flow

    NASA Technical Reports Server (NTRS)

    Coward, Adrian V.; Papageorgiou, Demetrios T.

    1993-01-01

    We investigate the stability of two phase Couette flow of different liquids bounded between plane parallel plates. One of the plates has a time dependent velocity in its own plane, which is composed of a constant steady part and a time harmonic component. In the absence of time harmonic modulations, the flow can be unstable to an interfacial instability if the viscosities are different and the more viscous fluid occupies the thinner of the two layers. Using Floquet theory, we show analytically in the limit of long waves, that time periodic modulations in the basic flow can have a significant influence on flow stability. In particular, flows which are otherwise unstable for extensive ranges of viscosity ratios, can be stabilized completely by the inclusion of background modulations, a finding that can have useful consequences in many practical applications.

  13. Vertical two-phase flow regimes and pressure gradients: Effect of viscosity

    SciTech Connect

    Da Hlaing, Nan; Sirivat, Anuvat; Siemanond, Kitipat; Wilkes, James O.

    2007-05-15

    The effect of liquid viscosity on the flow regimes and the corresponding pressure gradients along the vertical two-phase flow was investigated. Experiment was carried out in a vertical transparent tube of 0.019 m in diameter and 3 m in length and the pressure gradients were measured by a U-tube manometer. Water and a 50 vol.% glycerol solution were used as the working fluids whose kinematic viscosities were 0.85 x 10{sup -6} and 4.0 x 10{sup -6} m{sup 2}/s, respectively. In our air-liquid annular two-phase flow, the liquid film of various thicknesses flowed adjacent to the wall and the gas phase flowed at the center of the tube. The superficial air velocity, j{sub air}, was varied between 0.0021 and 58.7 m/s and the superficial liquid velocity, j{sub liquid}, was varied between 0 and 0.1053 m/s. In the bubble, the slug and the slug-churn flow regimes, the pressure gradients decreased with increasing Reynolds number. But in the annular and the mist flow regimes, pressure gradients increased with increasing Reynolds number. Finally, the experimentally measured pressure gradient values were compared and are in good agreement with the theoretical values. (author)

  14. Reconfigurable mosaic annular arrays.

    PubMed

    Thomenius, Kai E; Wodnicki, Robert; Cogan, Scott D; Fisher, Rayette A; Burdick, Bill; Smith, L Scott; Khuri-Yakub, Pierre; Lin, Der-Song; Zhuang, Xuefeng; Bonitz, Barry; Davies, Todd; Thomas, Glen; Woychik, Charles

    2014-07-01

    Mosaic annular arrays (MAA) based on reconfigurable array (RA) transducer electronics assemblies are presented as a potential solution for future highly integrated ultrasonic transducer subsystems. Advantages of MAAs include excellent beam quality and depth of field resulting from superior elevational focus compared with 1-D electronically scanned arrays, as well as potentially reduced cost, size, and power consumption resulting from the use of a limited number of beamforming channels for processing a large number of subelements. Specific design tradeoffs for these highly integrated arrays are discussed in terms of array specifications for center frequency, element pitch, and electronic switch-on resistance. Large-area RAs essentially function as RC delay lines. Efficient architectures which take into account RC delay effects are presented. Architectures for integration of the transducer and electronics layers of large-area array implementations are reviewed. PMID:24960699

  15. KC-135 zero-gravity two phase flow pressure drop: Experiments and modeling

    NASA Astrophysics Data System (ADS)

    Lambert, Anne; Reinarts, Thomas R.; Best, Frederick R.; Hill, Wayne S.

    1991-01-01

    Two-phase flow, thermal management systems are currently being considered as an alternative to conventional, single phase systems for future space missions because of their potential to reduce overall system mass, size, and pumping power requirements. Knowledge of flow regime transitions, heat transfer characteristics, and pressure drop correlations is necessary to design and develop two-phase systems. This work is concerned with microgravity, two-phase flow pressure drop experiments. The data are those of a recent experiment (Hill and Best 1990) funded by the U.S. Air Force and conducted by Foster-Miller in conjunction with Texas A&M University. A boiling and condensing experiment was built in which R-12 was used as the working fluid. A Foster-Miller two phase pump was used to circulate a freon mixture and allow separate measurements of the vapor and liquid flow streams. The experimental package was flown five times aboard the NASA KC-135 aircraft which simulates 0-``g'' conditions by its parabolic flight trajectory. Test conditions included stratified and annual flow regimes in 1-``g'' which became bubbly, slug or annular flow regimes in 0-``g''. A portion of the current work outlines a methodology to analyze data for two-phase, 0-g experimental studies. A technique for correcting the raw pressure drop data collected from the test package is given. The Corrected pressure drop measurements are compared with predictive model. The corrected pressure drop measurements show no statistically significant difference between the 1-``g'' and 0-``g'' tests for mass flow rates between 0.00653 and 0.0544 kg/s in an 8 mm ID tube. An annular flow model gave the best overall predictions of pressure drop. The homogeneous, and Beattle and Whalley (1982) models showed good agreement with the pressure drops measured for the slug and bubbly/slug flow conditions. The two-phase multiplier deduced from the data appeared to follow the Martinelli-Nelson trend but at lower values than for

  16. PASSIVE CONTROL OF PARTICLE DISPERSION IN A PARTICLE-LADEN CIRCULAR JET USING ELLIPTIC CO-ANNULAR FLOW: A MEANS FOR IMPROVING UTILIZATION AND EMISSION REDUCTIONS IN PULVERIZED COAL BURNER

    SciTech Connect

    Ahsan R. Choudhuri

    2003-06-01

    A passive control technology utilizing elliptic co-flow to control the particle flinging and particle dispersion in a particle (coal)-laden flow was investigated using experimental and numerical techniques. Preferential concentration of particles occurs in particle-laden jets used in pulverized coal burner and causes uncontrollable NO{sub x} formation due to inhomogeneous local stoichiometry. This particular project was aimed at characterizing the near-field flow behavior of elliptic coaxial jets. The knowledge gained from the project will serve as the basis of further investigation on fluid-particle interactions in an asymmetric coaxial jet flow-field and thus is important to improve the design of pulverized coal burners where non-homogeneity of particle concentration causes increased NO{sub x} formation.

  17. Tracer Partitioning in Two-Phase Flow

    NASA Astrophysics Data System (ADS)

    Sathaye, K.; Hesse, M. A.

    2012-12-01

    The concentration distributions of geochemical tracers in a subsurface reservoir can be used as an indication of the reservoir flow paths and constituent fluid origin. In this case, we are motivated by the origin of marked geochemical gradients in the Bravo Dome natural CO2 reservoir in northeastern New Mexico. This reservoir contains 99% CO2 with various trace noble gas components and overlies the formation brine in a sloping aquifer. It is thought that magmatic CO2 entered the reservoir, and displaced the brine. This displacement created gradients in the concentrations of the noble gases. Two models to explain noble gas partitioning in two-phase flow are presented here. The first model assumes that the noble gases act as tracers and uses a first order non-linear partial differential equation to compute the volume fraction of each phase along the displament path. A one-way coupled partial differential equation determines the tracer concentration, which has no effect on the overall flow or phase saturations. The second model treats each noble gas as a regular component resulting in a three-component, two-phase system. As the noble gas injection concentration goes to zero, we see the three-component system behave like the one-way coupled system of the first model. Both the analytical and numerical solutions are presented for these models. For the process of a gas displacing a liquid, we see that a noble gas tracer with greater preference for the gas phase, such as Helium, will move more quickly along the flowpath than a heavier tracer that will more easily enter the liquid phase, such as Argon. When we include partial miscibility of both the major and trace components, these differences in speed are shown in a bank of the tracer at the saturation front. In the three component model, the noble gas bank has finite width and concentration. In the limit where the noble gas is treated as a tracer, the width of the bank is zero and the concentration increases linearly

  18. Concomitant occurrence of patch granuloma annulare and classical granuloma annulare.

    PubMed

    Tsuruta, Daisuke; Sowa, Junko; Hiroyasu, Sho; Ishii, Masamitsu; Kobayashi, Hiromi

    2011-05-01

    Granuloma annulare (GA) is characterized clinically as annularly-distributed, erythematous papules on the extremities in children and adolescents. GA is recognized histologically as palisading granulomas with central degenerated collagen and mucin deposits. Here, we present a case of concomitant occurrence of patch GA (PGA), the most rare type of GA, and classical GA in a patient. A 60-year-old man was referred to our hospital for asymptomatic eruptions on the upper arms, forearms, right flank and right lateral chest. Clinical examination revealed annular erythematous plaques composed of numerous small papules on bilateral upper arms and forearms. Moreover, an indurative, exudative erythematous to violaceous plaque was present on the right lateral chest and right flank. Histopathology of the former was compatible with palisade-type GA, and the latter interstitial-type GA. This is the first report of PGA concomitant with "classical" annular papular lesions. PMID:21352310

  19. Two-phase flow pressure drop and heat transfer during condensation in microchannels with uniform and converging cross-sections

    NASA Astrophysics Data System (ADS)

    Kuo, Ching Yi; Pan, Chin

    2010-09-01

    This study experimentally investigates steam condensation in rectangular microchannels with uniform and converging cross-sections and a mean hydraulic diameter of 135 µm. The steam flow in the microchannels was cooled by water cross-flowing along its bottom surface, which is different from other methods reported in the literature. The flow patterns, two-phase flow pressure drop and condensation heat transfer coefficient are determined. The microchannels with the uniform cross-section design have a higher heat transfer coefficient than those with the converging cross-section under condensation in the mist/annular flow regimes, although the latter work best for draining two-phase fluids composed of uncondensed steam and liquid water, which is consistent with the result of our previous study. From the experimental results, dimensionless correlations of condensation heat transfer for the mist and annular flow regions and a two-phase frictional multiplier are developed for the microchannels with both types of cross-section designs. The experimental data agree well with the obtained correlations, with the maximum mean absolute errors of 6.4% for the two-phase frictional multiplier and 6.0% for the condensation heat transfer.

  20. Condensation in a two-phase pool

    SciTech Connect

    Duffey, R.B.; Hughes, E.D.

    1991-12-31

    We consider the case of vapor condensation in a liquid pool, when the heat transfer is controlled by heat losses through the walls. The analysis is based on drift flux theory for phase separation in the pool, and determines the two-phase mixture height for the pool. To our knowledge this is the first analytical treatment of this classic problem that gives an explicit result, previous work having established the result for the evaporative case. From conservation of mass and energy in a one-dimensional steady flow, together with a void relation between the liquid and vapor fluxes, we determine the increase in the mixture level from the base level of the pool. It can be seen that the thermal and hydrodynamic influences are separable. Thus, the thermal influence of the wall heat transfer appears through its effect on the condensing length L*, so that at high condensation rates the pool is all liquid, and at low rates overflows (the level swell or foaming effect). Similarly, the phase separation effect hydrodynamically determines the height via the relative velocity of the mixture to the entering flux. We examine some practical applications of this result to level swell in condensing flows, and also examine some limits in ideal cases.

  1. Condensation in a two-phase pool

    SciTech Connect

    Duffey, R.B. ); Hughes, E.D. )

    1991-01-01

    We consider the case of vapor condensation in a liquid pool, when the heat transfer is controlled by heat losses through the walls. The analysis is based on drift flux theory for phase separation in the pool, and determines the two-phase mixture height for the pool. To our knowledge this is the first analytical treatment of this classic problem that gives an explicit result, previous work having established the result for the evaporative case. From conservation of mass and energy in a one-dimensional steady flow, together with a void relation between the liquid and vapor fluxes, we determine the increase in the mixture level from the base level of the pool. It can be seen that the thermal and hydrodynamic influences are separable. Thus, the thermal influence of the wall heat transfer appears through its effect on the condensing length L*, so that at high condensation rates the pool is all liquid, and at low rates overflows (the level swell or foaming effect). Similarly, the phase separation effect hydrodynamically determines the height via the relative velocity of the mixture to the entering flux. We examine some practical applications of this result to level swell in condensing flows, and also examine some limits in ideal cases.

  2. Keratocytes generate traction forces in two phases.

    PubMed

    Burton, K; Park, J H; Taylor, D L

    1999-11-01

    Forces generated by goldfish keratocytes and Swiss 3T3 fibroblasts have been measured with nanonewton precision and submicrometer spatial resolution. Differential interference contrast microscopy was used to visualize deformations produced by traction forces in elastic substrata, and interference reflection microscopy revealed sites of cell-substratum adhesions. Force ranged from a few nanonewtons at submicrometer spots under the lamellipodium to several hundred nanonewtons under the cell body. As cells moved forward, centripetal forces were applied by lamellipodia at sites that remained stationary on the substratum. Force increased and abruptly became lateral at the boundary of the lamellipodium and the cell body. When the cell retracted at its posterior margin, cell-substratum contact area decreased more rapidly than force, so that stress (force divided by area) increased as the cell pulled away. An increase in lateral force was associated with widening of the cell body. These mechanical data suggest an integrated, two-phase mechanism of cell motility: (1) low forces in the lamellipodium are applied in the direction of cortical flow and cause the cell body to be pulled forward; and (2) a component of force at the flanks pulls the rear margins forward toward the advancing cell body, whereas a large lateral component contributes to detachment of adhesions without greatly perturbing forward movement. PMID:10564269

  3. Two-Phase Quality/Flow Meter

    NASA Technical Reports Server (NTRS)

    Moerk, J. Steven (Inventor); Youngquist, Robert C. (Inventor); Werlink, Rudy J. (Inventor)

    1999-01-01

    A quality and/or flow meter employs a capacitance probe assembly for measuring the dielectric constant of flow stream, particularly a two-phase flow stream including liquid and gas components.ne dielectric constant of the flow stream varies depending upon the volume ratios of its liquid and gas components, and capacitance measurements can therefore be employed to calculate the quality of the flow, which is defined as the volume ratio of liquid in the flow to the total volume ratio of gas and liquid in the flow. By using two spaced capacitance sensors, and cross-correlating the time varying capacitance values of each, the velocity of the flow stream can also be determined. A microcontroller-based processing circuit is employed to measure the capacitance of the probe sensors.The circuit employs high speed timer and counter circuits to provide a high resolution measurement of the time interval required to charge each capacitor in the probe assembly. In this manner, a high resolution, noise resistant, digital representation of each of capacitance value is obtained without the need for a high resolution A/D converter, or a high frequency oscillator circuit. One embodiment of the probe assembly employs a capacitor with two ground plates which provide symmetry to insure that accurate measurements are made thereby.

  4. Phase discrimination method for simultaneous two-phase separation in time-resolved stereo PIV measurements

    NASA Astrophysics Data System (ADS)

    Cheng, Y.; Pothos, S.; Diez, F. J.

    2010-12-01

    A phase discrimination method for two-phase PIV is presented that is capable of simultaneously separating the two phases from time-resolved stereoscopic PIV images taken in a particle-laden jet. The technique developed expands on previous work done by Khalitov and Longmire (Exp Fluids 32:252-268, 2002), where by means of image processing techniques, a raw two-phase PIV image can be separated into two single-phase images according to particle size and intensity distributions. The technique is expanded through the use of three new image processing algorithms to separate particles of similar size (up to an order of magnitude better than published work) for fields of view much larger than previously considered. It also addresses the known problem of noisy background images produced by high-speed CMOS cameras, which makes the particle detection and separation from the noisy background difficult, through the use of a novel fast Fourier transform background filter.

  5. Manufacture of annular cermet articles

    DOEpatents

    Forsberg, Charles W.; Sikka, Vinod K.

    2004-11-02

    A method to produce annular-shaped, metal-clad cermet components directly produces the form and avoids multiple fabrication steps such as rolling and welding. The method includes the steps of: providing an annular hollow form with inner and outer side walls; filling the form with a particulate mixture of ceramic and metal; closing, evacuating, and hermetically sealing the form; heating the form to an appropriate temperature; and applying force to consolidate the particulate mixture into solid cermet.

  6. Emerging Two-Phase Cooling Technologies for Power Electronic Inverters

    SciTech Connect

    Hsu, J.S.

    2005-08-17

    In order to meet the Department of Energy's (DOE's) FreedomCAR and Vehicle Technologies (FVCT) goals for volume, weight, efficiency, reliability, and cost, the cooling of the power electronic devices, traction motors, and generators is critical. Currently the power electronic devices, traction motors, and generators in a hybrid electric vehicle (HEV) are primarily cooled by water-ethylene glycol (WEG) mixture. The cooling fluid operates as a single-phase coolant as the liquid phase of the WEG does not change to its vapor phase during the cooling process. In these single-phase systems, two cooling loops of WEG produce a low temperature (around 70 C) cooling loop for the power electronics and motor/generator, and higher temperature loop (around 105 C) for the internal combustion engine. There is another coolant option currently available in automobiles. It is possible to use the transmission oil as a coolant. The oil temperature exists at approximately 85 C which can be utilized to cool the power electronic and electrical devices. Because heat flux is proportional to the temperature difference between the device's hot surface and the coolant, a device that can tolerate higher temperatures enables the device to be smaller while dissipating the same amount of heat. Presently, new silicon carbide (SiC) devices and high temperature direct current (dc)-link capacitors, such as Teflon capacitors, are available but at significantly higher costs. Higher junction temperature (175 C) silicon (Si) dies are gradually emerging in the market, which will eventually help to lower hardware costs for cooling. The development of high-temperature devices is not the only way to reduce device size. Two-phase cooling that utilizes the vaporization of the liquid to dissipate heat is expected to be a very effective cooling method. Among two-phase cooling methods, different technologies such as spray, jet impingement, pool boiling and submersion, etc. are being developed. The Oak Ridge

  7. THE TWO PHASES OF GALAXY FORMATION

    SciTech Connect

    Oser, Ludwig; Naab, Thorsten; Johansson, Peter H.; Burkert, Andreas; Ostriker, Jeremiah P.

    2010-12-20

    Cosmological simulations of galaxy formation appear to show a 'two-phase' character with a rapid early phase at z {approx}> 2 during which 'in situ' stars are formed within the galaxy from infalling cold gas followed by an extended phase since z {approx}< 3 during which 'ex situ' stars are primarily accreted. In the latter phase, massive systems grow considerably in mass and radius by accretion of smaller satellite stellar systems formed at quite early times (z>3) outside of the virial radius of the forming central galaxy. These tentative conclusions are obtained from high-resolution re-simulations of 39 individual galaxies in a full cosmological context with present-day virial halo masses ranging from 7 x 10{sup 11} M{sub sun} h {sup -1} {approx} 1.7 x 10{sup 11} M{sub sun} h {sup -1}) assembly is dominated by accretion and merging with about 80% of the stars added by the present day. In general the simulated galaxies approximately double their mass since z = 1. For massive systems this mass growth is not accompanied by significant star formation. The majority of the in situ created stars are formed at z>2, primarily out of cold gas flows. We recover the observational result of 'archaeological downsizing', where the most massive galaxies harbor the oldest stars. We find that this is not in contradiction with hierarchical structure

  8. STUDIES OF TWO-PHASE PLUMES IN STRATIFIED ENVIRONMENTS

    SciTech Connect

    Scott A. Socolofsky; Brian C. Crounse; E. Eric Adams

    1998-11-18

    Two-phase plumes play an important role in the more practical scenarios for ocean sequestration of CO{sub 2}--i.e. dispersing CO{sub 2} as a buoyant liquid from either a bottom-mounted or ship-towed pipeline. Despite much research on related applications, such as for reservoir destratification using bubble plumes, our understanding of these flows is incomplete, especially concerning the phenomenon of plume peeling in a stratified ambient. To address this deficiency, we have built a laboratory facility in which we can make fundamental measurements of plume behavior. Although we are using air, oil and sediments as our sources of buoyancy (rather than CO{sub 2}), by using models, our results can be directly applied to field scale CO{sub 2} releases to help us design better CO{sub 2} injection systems, as well as plan and interpret the results of our up-coming international field experiment. The experimental facility designed to study two-phase plume behavior similar to that of an ocean CO{sub 2} release includes the following components: 1.22 x 1.22 x 2.44 m tall glass walled tank; Tanks and piping for the two-tank stratification method for producing step- and linearly-stratified ambient conditions; Density profiling system using a conductivity and temperature probe mounted to an automated depth profiler; Lighting systems, including a virtual point source light for shadowgraphs and a 6 W argon-ion laser for laser induced fluorescence (LIF) imaging; Imaging system, including a digital, progressive scanning CCD camera, computerized framegrabber, and image acquisition and analysis software; Buoyancy source diffusers having four different air diffusers, two oil diffusers, and a planned sediment diffuser; Dye injection method using a Mariotte bottle and a collar diffuser; and Systems integration software using the Labview graphical programming language and Windows NT. In comparison with previously reported experiments, this system allows us to extend the parameter range of

  9. Flow pattern and heat transfer behavior of boiling two-phase flow in inclined pipes

    NASA Astrophysics Data System (ADS)

    Liu, Dezhang; Ning, Ouyang

    1992-09-01

    Movable Electrical Conducting Probe (MECP), a kind of simple and reliable measuring transducer, used for predicting full-flow-path flow pattern in a boiling vapor/liquid two-phase flow is introduced in this paper. When the test pipe is set at different inclination angles, several kinds of flow patterns, such as bubble, slug, churn, intermittent, and annular flows, may be observed in accordance with the locations of MECP. By means of flow pattern analysis, flow field numerical calculations have been carried out, and heat transfer coefficient correlations along full-flow-path derived. The results show that heat transfer performance of boiling two-phase flow could be significantly augmented as expected in some flow pattern zones. The results of the investigation, measuring techniques and conclusions contained in this paper would be a useful reference in foundational research for prediction of flow pattern and heat transfer behavior in boiling two-phase flow, as well as for turbine vane liquid-cooling design.

  10. Two-phase gas-liquid flow characteristics inside a plate heat exchanger

    SciTech Connect

    Nilpueng, Kitti; Wongwises, Somchai

    2010-11-15

    In the present study, the air-water two-phase flow characteristics including flow pattern and pressure drop inside a plate heat exchanger are experimentally investigated. A plate heat exchanger with single pass under the condition of counter flow is operated for the experiment. Three stainless steel commercial plates with a corrugated sinusoidal shape of unsymmetrical chevron angles of 55 and 10 are utilized for the pressure drop measurement. A transparent plate having the same configuration as the stainless steel plates is cast and used as a cover plate in order to observe the flow pattern inside the plate heat exchanger. The air-water mixture flow which is used as a cold stream is tested in vertical downward and upward flow. The results from the present experiment show that the annular-liquid bridge flow pattern appeared in both upward and downward flows. However, the bubbly flow pattern and the slug flow pattern are only found in upward flow and downward flow, respectively. The variation of the water and air velocity has a significant effect on the two-phase pressure drop. Based on the present data, a two-phase multiplier correlation is proposed for practical application. (author)

  11. Two-phase phenomena, minority games, and herding models

    NASA Astrophysics Data System (ADS)

    Zheng, B.; Qiu, T.; Ren, F.

    2004-04-01

    The recently discovered two-phase phenomenon in financial markets [Nature 421, 130 (2003)] is examined with the German financial index DAX, minority games, and dynamic herding models. It is observed that the two-phase phenomenon is an important characteristic of financial dynamics, independent of volatility clustering. An interacting herding model correctly produces the two-phase phenomenon.

  12. Dynamics of coupled and uncoupled two-phase flows in a slab mold

    NASA Astrophysics Data System (ADS)

    Sánchez-Pérez, R.; García-Demedices, L.; Ramos, J. Palafox; Díaz-Cruz, M.; Morales, R. D.

    2004-02-01

    Two-phase flows in a mold of a slab caster are studied using water modeling, particle-image velocimetry (PIV), and computational fluid-dynamics techniques. Two-way coupled flows are observed in liquidgas systems, because both phases influence each other’s momentum transfer. In addition to this concept, PIV measurements indicate the existence of structurally coupled flows, where the velocity vectors of both phases observe similar orientations. When the drag forces of the liquid, exerted on the bubbles, exceed a certain value of the inertial forces of the liquid phase, at high mass loads of gas (ratio of mass flow rates of the gas phase and the liquid phase), the flow becomes structurally coupled. These types of flows promote large oscillations of the meniscus level. Two jets, liquid and bubble, were identified; the latter always reported larger angles than the first, independent of the gas load. Thus, a gas-rich jet is located closer to the lower edge of the submerged entry nozzle (SEN) port, and the liquid-rich jet is found above this position. The liquid-jet angle approaches that of the SEN port when the flow becomes structurally coupled. Structurally uncoupled flows report gas jets that follow torrent-type patterns which are well explained using a multiphase fluid-dynamics model. Structurally coupled flows yield gas jets with a continuous pattern.

  13. Stability of Wavy Films in Gas-Liquid Two-Phase Flows at Normal and Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Balakotaiah, V.; Jayawardena, S. S.

    1996-01-01

    For flow rates of technological interest, most gas-liquid flows in pipes are in the annular flow regime, in which, the liquid moves along the pipe wall in a thin, wavy film and the gas flows in the core region. The waves appearing on the liquid film have a profound influence on the transfer rates, and hence on the design of these systems. We have recently proposed and analyzed two boundary layer models that describe the characteristics of laminar wavy films at high Reynolds numbers (300-1200). Comparison of model predictions to 1-g experimental data showed good agreement. The goal of our present work is to understand through a combined program of experimental and modeling studies the characteristics of wavy films in annular two-phase gas-liquid flows under normal as well as microgravity conditions in the developed and entry regions.

  14. An Experimental Study of Swirling Flows as Applied to Annular Combustors

    NASA Technical Reports Server (NTRS)

    Seal, Michael Damian, II

    1997-01-01

    This thesis presents an experimental study of swirling flows with direct applications to gas turbine combustors. Two separate flowfields were investigated: a round, swirling jet and a non-combusting annular combustor model. These studies were intended to allow both a further understanding of the behavior of general swirling flow characteristics, such as the recirculation zone, as well as to provide a base for the development of computational models. In order to determine the characteristics of swirling flows the concentration fields of a round, swirling jet were analyzed for varying amount of swirl. The experimental method used was a light scattering concentration measurement technique known as marker nephelometry. Results indicated the formation of a zone of recirculating fluid for swirl ratios (rotational speed x jet radius over mass average axial velocity) above a certain critical value. The size of this recirculation zone, as well as the spread angle of the jet, was found to increase with increase in the amount of applied swirl. The annular combustor model flowfield simulated the cold-flow characteristics of typical current annular combustors: swirl, recirculation, primary air cross jets and high levels of turbulence. The measurements in the combustor model made by the Laser Doppler Velocimetry technique, allowed the evaluation of the mean and rms velocities in the three coordinate directions, one Reynold's shear stress component and the turbulence kinetic energy: The primary cross jets were found to have a very strong effect on both the mean and turbulence flowfields. These cross jets, along with a large step change in area and wall jet inlet flow pattern, reduced the overall swirl in the test section to negligible levels. The formation of the strong recirculation zone is due mainly to the cross jets and the large step change in area. The cross jets were also found to drive a four-celled vortex-type motion (parallel to the combustor longitudinal axis) near the

  15. Hydrodynamic Dryout in Two-Phase Flows: Observations of Low Bond Number Systems

    NASA Technical Reports Server (NTRS)

    Weislogel, Mark M.; McQuillen, John B.

    1998-01-01

    Dryout occurs readily in certain slug and annular two-phase flows for systems that exhibit partial wetting. The mechanism for the ultimate rupture of the film is attributed to van der Waals forces, but the pace towards rupture is quickened by the surface tension instability (Rayleigh-type) of the annular film left by the advancing slug and by the many perturbations of the free surface present in the Re(sub g) approximately 0(10(exp 3)), Re(sub l) approximately 0(10(exp 4)), and Ca approximately 0(10(exp -1) flows. Results from low-gravity experiments using three different test fluids are presented and discussed. For the range of tests conducted, the effect of increasing viscosity is shown to eliminate the film rupture while the decrease of surface tension via a surfactant additive is shown to dramatically enhance it. Laboratory measurements using capillary tubes are presented which reveal the sensitivity of the dryout phenomena to particulate and surfactant contamination. Rom such observations, dryout due to the hydrodynamic-van der Waals instability can be expected in a certain range of flow parameters in the absence of heat transfer. The addition of heat transfer may only exacerbate the problem by producing thermal transport lines replete with "hot spots." A caution to this effect is issued to future space systems designers concerning the use of partially wetting working fluids.

  16. Annular Eclipse as Seen by Hinode

    NASA Video Gallery

    This timelapse shows an annular eclipse as seen by JAXA's Hinode satellite on Jan. 4, 2011. An annular eclipse occurs when the moon, slightly more distant from Earth than on average, moves directly...

  17. A bi-directional two-phase/two-phase heat exchanger

    NASA Technical Reports Server (NTRS)

    Ku, Jentung; Ottenstein, Laura

    1993-01-01

    This paper describes the design and test of a heat exchanger that transfers heat from one two-phase thermal loop to another with very small drops in temperature and pressure. The heat exchanger condenses the vapor in one loop while evaporating the liquid in the other without mixing of the condensing and evaporating fluids. The heat exchanger is bidirectional in that it can transfer heat in reverse, condensing on the normally evaporating side and vice versa. It is fully compatible with capillary pumped loops and mechanically pumped loops. Test results verified that performance of the heat exchanger met the design requirements. It demonstrated a heat transfer rate of 6800 watts in the normal mode of operation and 1000 watts in the reverse mode with temperature drops of less than 5 C between two thermal loops.

  18. Two-phase flow measurements with advanced instrumented spool pieces

    SciTech Connect

    Turnage, K.C.

    1980-09-01

    A series of two-phase, air-water and steam-water tests performed with instrumented piping spool pieces is described. The behavior of the three-beam densitometer, turbine meter, and drag flowmeter is discussed in terms of two-phase models. Results from application of some two-phase mass flow models to the recorded spool piece data are shown. Results of the study are used to make recommendations regarding spool piece design, instrument selection, and data reduction methods to obtain more accurate measurements of two-phase flow parameters. 13 refs., 23 figs., 1 tab.

  19. Eosinophilic annular erythema in childhood - Case report.

    PubMed

    Abarzúa, Alvaro; Giesen, Laura; Silva, Sergio; González, Sergio

    2016-01-01

    Eosinophilic annular erythema is a rare, benign, recurrent disease, clinically characterized by persistent, annular, erythematous lesions, revealing histopathologically perivascular infiltrates with abundant eosinophils. This report describes an unusual case of eosinophilic annular erythema in a 3-year-old female, requiring sustained doses of hydroxychloroquine to be adequately controlled. PMID:27579748

  20. Eosinophilic annular erythema in childhood - Case report*

    PubMed Central

    Abarzúa, Alvaro; Giesen, Laura; Silva, Sergio; González, Sergio

    2016-01-01

    Eosinophilic annular erythema is a rare, benign, recurrent disease, clinically characterized by persistent, annular, erythematous lesions, revealing histopathologically perivascular infiltrates with abundant eosinophils. This report describes an unusual case of eosinophilic annular erythema in a 3-year-old female, requiring sustained doses of hydroxychloroquine to be adequately controlled. PMID:27579748

  1. Two-Phase PIV: Fuel-Spray Interaction with Surrounding Air

    NASA Astrophysics Data System (ADS)

    Dankers, Stefan; Gotthardt, Mark; Stengler, Thomas; Ohmstede, Gerhard; Hentschel, Werner

    The demand for improvement of combustion-engine processes leads to a great need for detailed experimental information about the complicated processes of injection, breakup and propagation of the fuel jet and the vaporization of the fuel. Thus, in the presented work it was the aim to visualize the air flow that is induced by the injected fuel jet and also to explore the air entrainment into the fuel spray. This was done using two-phase PIV (particle image velocimetry). The fuel jet was illuminated with a Nd:YAG PIV-laser and PIV analysis was done by simply measuring the elastically scattered light of the fuel droplets. For the investigation of the surrounding air propylene-carbonate doped with DCM-dye was dispersed and the droplets were added to the continuous gas flow upstream of the chamber. Scattered and fluorescence signals, respectively, were detected perpendicular to the laser sheet with a CCD camera. To detect the gas flow, the scattered light from the liquid fuel was suppressed by an OG 590 longpass filter glass that transmits the fluorescence signal of the DCM-dye. It was possible to measure both the fuel jet and the gas flow in the presence of the fuel spray and a clear separation of the two phases could be achieved. In both (fuel and air) vector pictures corresponding vortices could be identified near the air/fuel boundary layer. Maximum velocities in the jet are depending on the operation conditions up to 150ms-1 and the gas flow has typically a velocity of 1 to 10ms-1. In the region next to the injector the air was pressed away during the injection. After the end of the injection a strong fast air entrainment flow into this region can be observed that compensates the pressure difference.

  2. Exhaust emissions of a double annular combustor: Parametric study

    NASA Technical Reports Server (NTRS)

    Schultz, D. F.

    1974-01-01

    A full scale double-annular ram-induction combustor designed for Mach 3.0 cruise operation was tested. Emissions of oxides of nitrogen, carbon monoxide, unburned hydrocarbons, and smoke were measured over a range of combustor operating variables including reference velocity, inlet air temperature and pressure, and exit average temperature. ASTM Jet-A fuel was used for these tests. An equation is provided relating oxides of nitrogen emissions as a function of the combustor, operating variables. A small effect of radial fuel staging on reducing exhaust emissions (which were originally quite low) is demonstrated.

  3. Numerical analysis of the flows in annular slinger combustors

    NASA Astrophysics Data System (ADS)

    Huebner, S.; Exley, T.

    1990-07-01

    Improved gas-turbine combustor design techniques are developed through the application of CFD flow predictions. The conservation equations of mass, momentum, and energy are solved using the finite-volume approach of Spalding. The geometry is a three-dimensional region of cyclic symmetry for a selected annular slinger combustor of reasonable performance. The flow is assumed nonreacting, isothermal, and turbulent. Mixing of the dilution jet stream with the bulk combustor flow is simulated by assuming different inlet temperatures for the two mass sources and noting the temperature profile at the combustor exit plane. A flow visualization experiment is performed on cold flow conditions and reasonably corroborates the CFD predictions.

  4. Flow regime classification in air magnetic fluid two-phase flow

    NASA Astrophysics Data System (ADS)

    Kuwahara, T.; DeVuyst, F.; Yamaguchi, H.

    2008-05-01

    A new experimental/numerical technique of classification of flow regimes (flow patterns) in air-magnetic fluid two-phase flow is proposed in the present paper. The proposed technique utilizes the electromagnetic induction to obtain time-series signals of the electromotive force, allowing us to make a non-contact measurement. Firstly, an experiment is carried out to obtain the time-series signals in a vertical upward air-magnetic fluid two-phase flow. The signals obtained are first treated using two kinds of wavelet transforms. The data sets treated are then used as input vectors for an artificial neural network (ANN) with supervised training. In the present study, flow regimes are classified into bubbly, slug, churn and annular flows, which are generally the main flow regimes. To validate the flow regimes, a visualization experiment is also performed with a glycerin solution that has roughly the same physical properties, i.e., kinetic viscosity and surface tension, as a magnetic fluid used in the present study. The flow regimes from the visualization are used as targets in an ANN and also used in the estimation of the accuracy of the present method. As a result, ANNs using radial basis functions are shown to be the most appropriate for the present classification of flow regimes, leading to small classification errors.

  5. Flow regime classification in air-magnetic fluid two-phase flow.

    PubMed

    Kuwahara, T; De Vuyst, F; Yamaguchi, H

    2008-05-21

    A new experimental/numerical technique of classification of flow regimes (flow patterns) in air-magnetic fluid two-phase flow is proposed in the present paper. The proposed technique utilizes the electromagnetic induction to obtain time-series signals of the electromotive force, allowing us to make a non-contact measurement. Firstly, an experiment is carried out to obtain the time-series signals in a vertical upward air-magnetic fluid two-phase flow. The signals obtained are first treated using two kinds of wavelet transforms. The data sets treated are then used as input vectors for an artificial neural network (ANN) with supervised training. In the present study, flow regimes are classified into bubbly, slug, churn and annular flows, which are generally the main flow regimes. To validate the flow regimes, a visualization experiment is also performed with a glycerin solution that has roughly the same physical properties, i.e., kinetic viscosity and surface tension, as a magnetic fluid used in the present study. The flow regimes from the visualization are used as targets in an ANN and also used in the estimation of the accuracy of the present method. As a result, ANNs using radial basis functions are shown to be the most appropriate for the present classification of flow regimes, leading to small classification errors. PMID:21694270

  6. Effective property models for homogeneous two-phase flows

    SciTech Connect

    Awad, M.M.; Muzychka, Y.S.

    2008-10-15

    Using an analogy between thermal conductivity of porous media and viscosity in two-phase flow, new definitions for two-phase viscosity are proposed. These new definitions satisfy the following two conditions: namely (i) the two-phase viscosity is equal to the liquid viscosity at the mass quality = 0% and (ii) the two-phase viscosity is equal to the gas viscosity at the mass quality = 100%. These new definitions can be used to compute the two-phase frictional pressure gradient using the homogeneous modeling approach. These new models are assessed using published experimental data of two-phase frictional pressure gradient in circular pipes, minichannels and microchannels in the form of Fanning friction factor (f{sub m}) versus Reynolds number (Re{sub m}). The published data include different working fluids such as R-12, R-22, argon (R740), R717, R134a, R410A and propane (R290) at different diameters and different saturation temperatures. Models are assessed on the basis minimizing the root mean square error (e{sub RMS}). It is shown that these new definitions of two-phase viscosity can be used to analyze the experimental data of two-phase frictional pressure gradient in circular pipes, minichannels and microchannels using simple friction models. (author)

  7. Magnetohydrodynamic generators using two-phase liquid-metal flows

    NASA Technical Reports Server (NTRS)

    Petrick, M.

    1969-01-01

    Two-phase flow generator cycle of a magnetohydrodynamic /MHD/ generator uses a working fluid which is compressible and treated as an expanding gas. The two-phase mixture passes from the heat source through the MHD generator, where the expansion process takes place and the electrical energy is extracted.

  8. Response of two-phase droplets to intense electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Spann, James F.; Maloney, Daniel J.; Lawson, William F.; Casleton, Kent H.

    1993-01-01

    The behavior of two-phase droplets subjected to high intensity radiation pulses is studied. Droplets are highly absorbing solids in weakly absorbing liquid medium. The objective of the study was to define heating thresholds required for causing explosive boiling and secondary atomization of the fuel droplet. The results point to mechanisms for energy storage and transport in two-phase systems.

  9. Two-phase flows within systems with ambient pressure

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    In systems where the design inlet and outlet pressures are maintained above the thermodynamic critical pressure, it is often assumed that two phase flows within the system cannot occur. Designers rely on this simple rule of thumb to circumvent problems associated with a highly compressible two phase flow occurring within the supercritical pressure system along with the uncertainties in rotordynamics, load capacity, heat transfer, fluid mechanics, and thermophysical property variations. The simple rule of thumb is adequate in many low power designs but is inadequate for high performance turbomachines and linear systems, where two phase regions can exist even though outlet pressure is greater than critical pressure. Rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two phase zone can differ significantly from those for a single-phase zone. Using the Reynolds equation the angular velocity, eccentricity, geometry, and ambient conditions are varied to determine the point of two phase flow incipience.

  10. Theoretical and experimental study of inverted annular film boiling and regime transition during reflood transients

    NASA Astrophysics Data System (ADS)

    Mohanta, Lokanath

    from single tube experiments. The root mean square error in predicting the FLECHT-SEASET data is 20% whereas for single tube data it is 12%. In previous studies, the transition criterion from the IAFB to the ISFB regime is purely empirical. In this work, a theoretical stability analysis of a liquid jet co-flowing with its vapor in a tube is carried out to seek a better understanding of the underlying physics of the regime transition. The effect of heat and mass transfer at the interface is included in the stability analysis. Also, the effect of viscous force is included in the stability analysis, by employing the viscous potential flow method. The wavelength that is responsible for breakup of the liquid core in IAFB is predicted in the present analysis and is compared with the adiabatic experiments of IAFB from the literature. The effects of various controlling parameters including the relative Weber number, vapor Reynolds number, velocity ratio, density ratio and viscosity ratio of vapor and liquid are studied to understand the physics of transition. Finally a physics-based heat transfer model is proposed for heat transfer in the ISFB regime using the wavelength obtained from the stability analysis. Keywords: Inverted annular film boiling, Two-phase heat transfer, Subcooled flow film boiling, Inverted slug film boiling, Regime transition, Void fraction in post CHF regime, Rod bundle, Spacer grid, Stability, Two-phase flow, Kelvin-Helmholtz instability, Capillary instability, Co-axial jets, Viscous potential flow, Interfacial heat and mass transfer.

  11. Concentration Measurements in a Cold Flow Model Annular Combustor Using Laser Induced Fluorescence

    NASA Technical Reports Server (NTRS)

    Morgan, Douglas C.

    1996-01-01

    A nonintrusive concentration measurement method is developed for determining the concentration distribution in a complex flow field. The measurement method consists of marking a liquid flow with a water soluble fluorescent dye. The dye is excited by a two dimensional sheet of laser light. The fluorescent intensity is shown to be proportional to the relative concentration level. The fluorescent field is recorded on a video cassette recorder through a video camera. The recorded images are analyzed with image processing hardware and software to obtain intensity levels. Mean and root mean square (rms) values are calculated from these intensity levels. The method is tested on a single round turbulent jet because previous concentration measurements have been made on this configuration by other investigators. The previous results were used to comparison to qualify the current method. These comparisons showed that this method provides satisfactory results. 'Me concentration measurement system was used to measure the concentrations in the complex flow field of a model gas turbine annular combustor. The model annular combustor consists of opposing primary jets and an annular jet which discharges perpendicular to the primary jets. The mixing between the different jet flows can be visualized from the calculated mean and rms profiles. Concentration field visualization images obtained from the processing provide further qualitative information about the flow field.

  12. Effect of swirl on mixing of co-axial jets

    NASA Astrophysics Data System (ADS)

    Singh, S. N.; Agrawal, D. P.; Malhotra, R. C.; Raghava, A. K.

    1991-03-01

    The imposition of swirl on coaxial jets exhausting into confined space, akin to a combustor model, has far reaching effects on their mixing and flow development. In the present paper, the influence of swirl on both the jets has been determined in terms of velocity and pressure distributions in the confined space. It has been shown that swirl in the central jet leads to faster mixing whereas higher swirl in the annular jet improves both mixing and development.

  13. Annular arc accelerator shock tube

    NASA Technical Reports Server (NTRS)

    Leibowitz, L. P. (Inventor)

    1976-01-01

    An annular arc accelerator shock tube employs a cold gas driver to flow a stream of gas from an expansion section through a high voltage electrode section to a test section, thus driving a shock wave in front of it. A glow discharge detects the shock wave and actuates a trigger generator which in turn fires spark-gap switches to discharge a bank of capacitors across a centered cathode and an annular anode in tandem electrode sections. The initial shock wave passes through the anode section from the cathode section thereby depositing energy into the flow gas without the necessity of any diaphragm opening in the gas flow from the expansion section through the electrode sections.

  14. Optic imaging of single and two-phase pressure-driven flows in nano-scale channels.

    PubMed

    Wu, Qihua; Ok, Jeong Tae; Sun, Yongpeng; Retterer, S T; Neeves, Keith B; Yin, Xiaolong; Bai, Baojun; Ma, Yinfa

    2013-03-21

    Microfluidic and nanofluidic devices have undergone rapid development in recent years. Functions integrated onto such devices provide lab-on-a-chip solutions for many biomedical, chemical, and engineering applications. In this paper, a lab-on-a-chip technique for direct visualization of the single- and two-phase pressure-driven flows in nano-scale channels was developed. The nanofluidic chip was designed and fabricated; concentration dependent fluorescence signal correlation was developed for the determination of flow rate. Experiments of single and two-phase flow in nano-scale channels with 100 nm depth were conducted. The linearity correlation between flow rate and pressure drop in nanochannels was obtained and fit closely into Poiseuille's Law. Meanwhile, three different flow patterns, single, annular, and stratified, were observed from the two-phase flow in the nanochannel experiments and their special features were described. A two-phase flow regime map for nanochannels is presented. Results are of critical importance to both fundamental study and many applications. PMID:23370894

  15. Energy Focusability of Annular Beams

    NASA Astrophysics Data System (ADS)

    Astadjov, Dimo N.

    2010-01-01

    A simulation of coherent annular flat two-level beams by two-dimensional Fast Fourier Transform is presented. After parameterization of the source beam (the `input') we examined the influence of its parameters on the shape and proportions of the output beam profile. The output pattern has a prominent central peak and faint rings concentrically surrounding it. The fraction of the central peak energy to the whole energy of beam, PF0 gives a notion of energy spread within the focal spot: PF0 is a function of beam annularity, k (i.e. `inside diameter/outside diameter' ratio) and the intensity dip, Idip of annulus central area (i.e. ring intensity minus central-bottom intensity, normalized). Up to k = 0.8 and Idip = 0.75, PF0 does not change too much—it is ⩾0.7 which is ⩾90% of PF0 maximum (0.778 at k = 0 and Idip = 0). Simulations revealed that even great changes in the shape of input beam annulus lead to small variations in the energy spread of output beam profile in the range of practical use of coherent annular beams.

  16. Void fraction correlations in two-phase horizontal flow

    SciTech Connect

    Papathanassiou, G.; Maeder, P.F.; DiPippo, R.; Dickinson, D.A.

    1983-05-01

    This study examines some physical mechanisms which impose limits on the possible existence of two-phase flow in a horizontal pipe. With the aid of this analysis and the use of the Martinelli variable, X, a method is developed which determines the range of possible void fractions for a given two-phase flow. This method affords a means of direct comparison among void fraction correlations, as well as between correlation predictions and experimental results. In this respect, four well-known void fraction correlations are compared against each other and with experimental results obtained in the Brown University Two-Phase Flow Research Facility.

  17. What types of investors generate the two-phase phenomenon?

    NASA Astrophysics Data System (ADS)

    Ryu, Doojin

    2013-12-01

    We examine the two-phase phenomenon described by Plerou, Gopikrishnan, and Stanley (2003) [1] in the KOSPI 200 options market, one of the most liquid options markets in the world. By analysing a unique intraday dataset that contains information about investor type for each trade and quote, we find that the two-phase phenomenon is generated primarily by domestic individual investors, who are generally considered to be uninformed and noisy traders. In contrast, our empirical results indicate that trades by foreign institutions, who are generally considered informed and sophisticated investors, do not exhibit two-phase behaviour.

  18. Computation of the flow field in an annular gas turbine combustor

    NASA Technical Reports Server (NTRS)

    Cline, Michael C.; Deur, John M.; Micklow, Gerald J.; Harper, Michael R.; Kundu, Krishna P.

    1993-01-01

    The KIVA-II code was modified to calculate the 3D flow field in a typical annular gas turbine combustor. The airblast fuel nozzle, cooling baffle, cooling slots, primary and dilution jets, and effusion cooling (bleed) pads were accounted for in this calculation. The turbulence and combustion were modeled using the k-epsilon model and laminar Arrhenius kinetics, respectively. The fuel was modeled as an evaporating liquid spray. The results illustrate the complicated flow fields present in such combustors. From the results obtained to date it appears that the modified KIVA-II code can be used to study the effects of different annular combustor designs and operating conditions.

  19. Characterization and modeling of two-phase heat transfer in chip-scale non-uniformly heated microgap channels

    NASA Astrophysics Data System (ADS)

    Ali, Ihab A.

    Chen correlation and the 24 data points classified as being in Annular flow, using a recently proposed Intermittent/Annular transition criterion. A semi-numerical first-order technique, using the Chen correlation, was found to yield acceptable prediction accuracy (17%) for the wall temperature distribution and hot spots in non-uniformly heated "real world" microgap channels cooled by two-phase flow. Heat transfer coefficients in the 100-micron channel were found to reach an Annular flow peak of ˜8 kW/m2K at G=1500 kg/m 2s and vapor quality of x=10%. In a 500-micron channel, the Annular heat transfer coefficient was found to reach 9 kW/m2K at 270 kg/m2s mass flux and 14% vapor quality level. The peak two-phase HFE-7100 heat transfer coefficient values were nearly 2.5-4 times higher (at similar mass fluxes) than the single-phase HFE-7100 values and sometimes exceeded the cooling capability associated with water under forced convection. An alternative classification of heat transfer coefficients, based on the variable slope of the observed heat transfer coefficient curve), was found to yield good agreement with the Chen correlation predictions in the pseudo-annular flow regime (22%) but to fall to 38% when compared to the Shah correlation for data in the pseudo-intermittent flow regime.

  20. Transient two-phase performance of LOFT reactor coolant pumps

    SciTech Connect

    Chen, T.H.; Modro, S.M.

    1983-01-01

    Performance characteristics of Loss-of-Fluid Test (LOFT) reactor coolant pumps under transient two-phase flow conditions were obtained based on the analysis of two large and small break loss-of-coolant experiments conducted at the LOFT facility. Emphasis is placed on the evaluation of the transient two-phase flow effects on the LOFT reactor coolant pump performance during the first quadrant operation. The measured pump characteristics are presented as functions of pump void fraction which was determined based on the measured density. The calculated pump characteristics such as pump head, torque (or hydraulic torque), and efficiency are also determined as functions of pump void fractions. The importance of accurate modeling of the reactor coolant pump performance under two-phase conditions is addressed. The analytical pump model, currently used in most reactor analysis codes to predict transient two-phase pump behavior, is assessed.

  1. Dynamical mechanism of two-phase phenomena in financial markets

    NASA Astrophysics Data System (ADS)

    Lim, Gyuchang; Yong Kim, Soo; Kim, Kyungsik; Lee, Dong-In; Park, Sang-Bum

    2007-12-01

    Two-phase behavior of the Korean treasury bond (KTB) futures in the Korean exchange market is investigated in this study. To show that the two-phase phenomena are due to heavy-tailed behavior of distribution of price returns, actual data from the KTB futures market with shuffled data and a generated time series are examined according to the Brownian process. In addition, we study the correlation inherent in the KTB futures and its Brownian walk, describing the extent to which the volatility clustering plays a crucial role in equilibrium and nonequilibrium states of financial markets. It is shown that the two-phase behavior essentially results from heavy-tailed behavior of the distribution of price returns. This two-phase behavior does not appear to be relevant to volatility clustering.

  2. Momentum flux in two phase two component low quality flow

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Graham, R. W.; Henry, R. E.

    1972-01-01

    In two phase flow systems line losses comprise frictional and momentum pressure drops. For design purposes, it would be desirable to estimate the line losses employing a one-dimensional calculation. Two methods for computing one-dimensional momentum flux at a test section discharge station are compared to the experimental value for a range of two-phase flow conditions. The one-dimensional homogeneous model appears to be more accurate generally in predicting the momentum than the variable slip model.

  3. Magnetohydrodynamics stability of a streaming annular cylindrical liquid surface

    NASA Astrophysics Data System (ADS)

    Radwan, Ahmed E.; Elazab, Samia S.; Hydia, Wafaa M.

    1997-08-01

    The instability of a streaming annular magnetized fluid jet surrounding a solid mantle subject to capillary, inertia, fluid kinetic pressure gradient and Lorentz forces has been developed for all kind of perturbations. Several recent works are recovered as limiting cases from the present result. The analytical discussion results are confirmed along with numerical and asymptotic analysis methods. The streaming has a strong destabilizing influence in hydrodynamic, magnetodynamic and hydromagnetics versions. That influence is found to be independent of the kind of perturbation and idem the stabilizing effect of the magnetic field pervaded the interior of the annular fluid jet model. An external longitudinal magnetic field is strongly stabilizing in both axisymmetric and non-axisymmetric perturbation modes. An external transverse varying magnetic field is destabilizing or stabilizing according to restrictions. Large values for the parameter of the transverse field is needed so that stability due to this transverse field may arise and thence the model stability states are modified. The streaming destabilizing influence may be overcome if the intensity of the axials fields interior and exterior the model is so strong that the Alfvén magnetic velocity is much larger than the basic streaming velocity of the fluid in the unperturbed initial state.

  4. Investigating an annular nozzle on combustion products of hydrocarbon fuels

    NASA Astrophysics Data System (ADS)

    Levin, V. A.; Afonina, N. E.; Gromov, V. G.; Smekhov, G. D.; Khmelevsky, A. N.; Markov, V. V.

    2013-09-01

    Full-scale and computational experiments were used to investigate the flows in the jet thrust unit with annular nozzle and deflector in the form of a spherical segment. The used working gas was the combustion products of air mixtures with acetylene, gas-phase aviation kerosene, and natural gas. Experimental studies were carried out in a hot-shot wind tunnel in the range of stagnation pressure from 0.48 to 2.05 MPa. The calculations for the cases of combustion products outflow in terrestrial and high altitude conditions were performed with the original computer program that used the Euler and Navier-Stokes systems supplemented by equations of chemical kinetics. It was found that the thrust of the jet module with an annular nozzle at high altitude almost twice exceeds the sound nozzle thrust, but is lesser (about 25 %) than the thrust of the ideal calculated Laval nozzle; the difference therewith decreases markedly with the decrease of flight altitude and stagnation pressure.

  5. The measurement of gas-liquid two-phase flows in a small diameter pipe using a dual-sensor multi-electrode conductance probe

    NASA Astrophysics Data System (ADS)

    Zhai, Lu-Sheng; Bian, Peng; Han, Yun-Feng; Gao, Zhong-Ke; Jin, Ning-De

    2016-04-01

    We design a dual-sensor multi-electrode conductance probe to measure the flow parameters of gas-liquid two-phase flows in a vertical pipe with an inner diameter of 20 mm. The designed conductance probe consists of a phase volume fraction sensor (PVFS) and a cross-correlation velocity sensor (CCVS). Through inserting an insulated flow deflector in the central part of the pipe, the gas-liquid two-phase flows are forced to pass through an annual space. The multiple electrodes of the PVFS and the CCVS are flush-mounted on the inside of the pipe wall and the outside of the flow deflector, respectively. The geometry dimension of the PVFS is optimized based on the distribution characteristics of the sensor sensitivity field. In the flow loop test of vertical upward gas-liquid two-phase flows, the output signals from the dual-sensor multi-electrode conductance probe are collected by a data acquisition device from the National Instruments (NI) Corporation. The information transferring characteristics of local flow structures in the annular space are investigated using the transfer entropy theory. Additionally, the kinematic wave velocity is measured based on the drift velocity model to investigate the propagation behavior of the stable kinematic wave in the annular space. Finally, according to the motion characteristics of the gas-liquid two-phase flows, the drift velocity model based on the flow patterns is constructed to measure the individual phase flow rate with higher accuracy.

  6. Granuloma annulare in herpes zoster scars.

    PubMed

    Ohata, C; Shirabe, H; Takagi, K; Kawatsu, T

    2000-03-01

    A 54-year-old Japanese female developed granuloma annulare twice in herpes zoster scars. Soon after the second event, she developed ulcerative colitis, which was well controlled by sulfonamides and corticosteroid suppository. She had no history of diabetes mellitus. There was no recurrence of granuloma annulare by June of 1999. Granuloma annulare might have contributed to the complications of ulcerative colitis, although this had not been noticed before. PMID:10774142

  7. Annular Solar Eclipse of 10 May 1994

    NASA Technical Reports Server (NTRS)

    Espenak, Fred; Anderson, Jay

    1993-01-01

    An annular eclipse of the Sun will be widely visible from the Western Hemisphere on 10 May 1994. The path of the Moon's shadow passes through Mexico, the United States of America, maritime Canada, the North Atlantic, the Azores and Morocco. Detailed predictions for this event are presented and include tables of geographic coordinates of the annular path, local circumstances for hundreds of cities, maps of the path of annular and partial eclipse, weather prospects, and the lunar limb profile.

  8. Studies of Two-Phase Flow Dynamics and Heat Transfer at Reduced Gravity Conditions

    NASA Technical Reports Server (NTRS)

    Witte, Larry C.; Bousman, W. Scott; Fore, Larry B.

    1996-01-01

    The ability to predict gas-liquid flow patterns is crucial to the design and operation of two-phase flow systems in the microgravity environment. Flow pattern maps have been developed in this study which show the occurrence of flow patterns as a function of gas and liquid superficial velocities as well as tube diameter, liquid viscosity and surface tension. The results have demonstrated that the location of the bubble-slug transition is affected by the tube diameter for air-water systems and by surface tension, suggesting that turbulence-induced bubble fluctuations and coalescence mechanisms play a role in this transition. The location of the slug-annular transition on the flow pattern maps is largely unaffected by tube diameter, liquid viscosity or surface tension in the ranges tested. Void fraction-based transition criteria were developed which separate the flow patterns on the flow pattern maps with reasonable accuracy. Weber number transition criteria also show promise but further work is needed to improve these models. For annular gas-liquid flows of air-water and air- 50 percent glycerine under reduced gravity conditions, the pressure gradient agrees fairly well with a version of the Lockhart-Martinelli correlation but the measured film thickness deviates from published correlations at lower Reynolds numbers. Nusselt numbers, based on a film thickness obtained from standard normal-gravity correlations, follow the relation, Nu = A Re(sup n) Pr(exp l/3), but more experimental data in a reduced gravity environment are needed to increase the confidence in the estimated constants, A and n. In the slug flow regime, experimental pressure gradient does not correlate well with either the Lockhart-Martinelli or a homogeneous formulation, but does correlate nicely with a formulation based on a two-phase Reynolds number. Comparison with ground-based correlations implies that the heat transfer coefficients are lower at reduced gravity than at normal gravity under the same

  9. Modeling Primary Breakup: A Three-Dimensional Eulerian Level Set/Vortex Sheet Method for Two-Phase Interface Dynamics

    NASA Technical Reports Server (NTRS)

    Herrmann, M.

    2003-01-01

    This paper is divided into four parts. First, the level set/vortex sheet method for three-dimensional two-phase interface dynamics is presented. Second, the LSS model for the primary breakup of turbulent liquid jets and sheets is outlined and all terms requiring subgrid modeling are identified. Then, preliminary three-dimensional results of the level set/vortex sheet method are presented and discussed. Finally, conclusions are drawn and an outlook to future work is given.

  10. Study of two-phase flows in reduced gravity

    NASA Astrophysics Data System (ADS)

    Roy, Tirthankar

    Study of gas-liquid two-phase flows under reduced gravity conditions is extremely important. One of the major applications of gas-liquid two-phase flows under reduced gravity conditions is in the design of active thermal control systems for future space applications. Previous space crafts were characterized by low heat generation within the spacecraft which needed to be redistributed within the craft or rejected to space. This task could easily have been accomplished by pumped single-phase loops or passive systems such as heat pipes and so on. However with increase in heat generation within the space craft as predicted for future missions, pumped boiling two-phase flows are being considered. This is because of higher heat transfer co-efficients associated with boiling heat transfer among other advantages. Two-phase flows under reduced gravity conditions also find important applications in space propulsion as in space nuclear power reactors as well as in many other life support systems of space crafts. Two-fluid model along with Interfacial Area Transport Equation (IATE) is a useful tool available to predict the behavior of gas-liquid two-phase flows under reduced gravity conditions. It should be noted that considerable differences exist between two-phase flows under reduced and normal gravity conditions especially for low inertia flows. This is because due to suppression of the gravity field the gas-liquid two-phase flows take a considerable time to develop under reduced gravity conditions as compared to normal gravity conditions. Hence other common methods of analysis applicable for fully developed gas-liquid two-phase flows under normal gravity conditions, like flow regimes and flow regime transition criteria, will not be applicable to gas-liquid two-phase flows under reduced gravity conditions. However the two-fluid model and the IATE need to be evaluated first against detailed experimental data obtained under reduced gravity conditions. Although lot of studies

  11. Annular Flow Liquid Film Dynamics in Pipes and Bod Bundle

    NASA Astrophysics Data System (ADS)

    Ju, Peng

    Average liquid film thickness is important for detailed mechanistic modeling of annular two-phase flow in engineering applications. The existing models and correlations either have large relative errors or narrow application range. Because of this, a new liquid film thickness model has been developed for vertical annular flow in pipes based on three databases. The model includes the pressure, liquid and gas velocities, diameter, and viscosity effects on liquid film thickness. Analysis indicates the film thickness to be a function of Weber numbers for both liquid and gas, and the viscosity number. The model is compared with film thickness data which considers a wide range of liquid and gas superficial velocities, system pressure, fluid properties, as well as several pipe diameters. The trend in the current and available film thickness models at various system conditions are analyzed, highlighting the improvement and widening applicability of the new model. The newly proposed film thickness model results in an average relative error of 14% considering the complete database. Interfacial friction factor in annular two-phase flow is essential both for detailed modeling of two-fluid model and the calculation of pressure gradient. Most of the existing correlations on interfacial friction factor are based on Wallis 1969's correlation, which considers the interfacial friction factor as a function of film thickness. In this research, a new correlation of interfacial friction factor that is based on the wave characteristics has been proposed. The wave characteristics is considered to be a function of a group of non-dimensional numbers. Since the effects of wave characteristics for ripples waves and disturbance waves on interfacial friction factors are different, the correlation is divided into two sub-correlations based on these two wave regimes. The new correlation has been compared with a wide range of data. From the data comparison, the new correlation shows significant

  12. Microgravity fluid management in two-phase thermal systems

    NASA Technical Reports Server (NTRS)

    Parish, Richard C.

    1987-01-01

    Initial studies have indicated that in comparison to an all liquid single phase system, a two-phase liquid/vapor thermal control system requires significantly lower pumping power, demonstrates more isothermal control characteristics, and allows greater operational flexibility in heat load placement. As a function of JSC's Work Package responsibility for thermal management of space station equipment external to the pressurized modules, prototype development programs were initiated on the Two-Phase Thermal Bus System (TBS) and the Space Erectable Radiator System (SERS). JSC currently has several programs underway to enhance the understanding of two-phase fluid flow characteristics. The objective of one of these programs (sponsored by the Microgravity Science and Applications Division at NASA-Headquarters) is to design, fabricate, and fly a two-phase flow regime mapping experiment in the Shuttle vehicle mid-deck. Another program, sponsored by OAST, involves the testing of a two-phase thermal transport loop aboard the KC-135 reduced gravity aircraft to identify system implications of pressure drop variation as a function of the flow quality and flow regime present in a representative thermal system.

  13. Transient well testing in two-phase geothermal reservoirs

    SciTech Connect

    Aydelotte, S.R.

    1980-03-01

    A study of well test analysis techniques in two-phase geothermal reservoirs has been conducted using a three-dimensional, two-phase, wellbore and reservoir simulation model. Well tests from Cerro Prieto and the Hawaiian Geothermal project have been history matched. Using these well tests as a base, the influence of reservoir permeability, porosity, thickness, and heat capacity, along with flow rate and fracturing were studied. Single and two-phase transient well test equations were used to analyze these tests with poor results due to rapidly changing fluid properties and inability to calculate the flowing steam saturation in the reservoir. The injection of cold water into the reservoir does give good data from which formation properties can be calculated.

  14. Thermal Vibrational Convection in a Two-phase Stratified Liquid

    NASA Technical Reports Server (NTRS)

    Chang, Qingming; Alexander, J. Iwan D.

    2007-01-01

    The response of a two-phase stratified liquid system subject to a vibration parallel to an imposed temperature gradient is analyzed using a hybrid thermal lattice Boltzmann method (HTLB). The vibrations considered correspond to sinusoidal translations of a rigid cavity at a fixed frequency. The layers are thermally and mechanically coupled. Interaction between gravity-induced and vibration-induced thermal convection is studied. The ability of applied vibration to enhance the flow, heat transfer and interface distortion is investigated. For the range of conditions investigated, the results reveal that the effect of vibrational Rayleigh number and vibrational frequency on a two-phase stratified fluid system is much different than that for a single-phase fluid system. Comparisons of the response of a two-phase stratified fluid system with a single-phase fluid system are discussed.

  15. Two-Phase flow instrumentation for nuclear accidents simulation

    NASA Astrophysics Data System (ADS)

    Monni, G.; De Salve, M.; Panella, B.

    2014-11-01

    The paper presents the research work performed at the Energy Department of the Politecnico di Torino, concerning the development of two-phase flow instrumentation and of models, based on the analysis of experimental data, that are able to interpret the measurement signals. The study has been performed with particular reference to the design of power plants, such as nuclear water reactors, where the two-phase flow thermal fluid dynamics must be accurately modeled and predicted. In two-phase flow typically a set of different measurement instruments (Spool Piece - SP) must be installed in order to evaluate the mass flow rate of the phases in a large range of flow conditions (flow patterns, pressures and temperatures); moreover, an interpretative model of the SP need to be developed and experimentally verified. The investigated meters are: Turbine, Venturi, Impedance Probes, Concave sensors, Wire mesh sensor, Electrical Capacitance Probe. Different instrument combinations have been tested, and the performance of each one has been analyzed.

  16. Confocal Annular Josephson Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Monaco, Roberto

    2016-04-01

    The physics of Josephson tunnel junctions drastically depends on their geometrical configurations and here we show that also tiny geometrical details play a determinant role. More specifically, we develop the theory of short and long annular Josephson tunnel junctions delimited by two confocal ellipses. The behavior of a circular annular Josephson tunnel junction is then seen to be simply a special case of the above result. For junctions having a normalized perimeter less than one, the threshold curves in the presence of an in-plane magnetic field of arbitrary orientations are derived and computed even in the case with trapped Josephson vortices. For longer junctions, a numerical analysis is carried out after the derivation of the appropriate motion equation for the Josephson phase. We found that the system is modeled by a modified and perturbed sine-Gordon equation with a space-dependent effective Josephson penetration length inversely proportional to the local junction width. Both the fluxon statics and dynamics are deeply affected by the non-uniform annulus width. Static zero-field multiple-fluxon solutions exist even in the presence of a large bias current. The tangential velocity of a traveling fluxon is not determined by the balance between the driving and drag forces due to the dissipative losses. Furthermore, the fluxon motion is characterized by a strong radial inward acceleration which causes electromagnetic radiation concentrated at the ellipse equatorial points.

  17. Confocal Annular Josephson Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Monaco, Roberto

    2016-09-01

    The physics of Josephson tunnel junctions drastically depends on their geometrical configurations and here we show that also tiny geometrical details play a determinant role. More specifically, we develop the theory of short and long annular Josephson tunnel junctions delimited by two confocal ellipses. The behavior of a circular annular Josephson tunnel junction is then seen to be simply a special case of the above result. For junctions having a normalized perimeter less than one, the threshold curves in the presence of an in-plane magnetic field of arbitrary orientations are derived and computed even in the case with trapped Josephson vortices. For longer junctions, a numerical analysis is carried out after the derivation of the appropriate motion equation for the Josephson phase. We found that the system is modeled by a modified and perturbed sine-Gordon equation with a space-dependent effective Josephson penetration length inversely proportional to the local junction width. Both the fluxon statics and dynamics are deeply affected by the non-uniform annulus width. Static zero-field multiple-fluxon solutions exist even in the presence of a large bias current. The tangential velocity of a traveling fluxon is not determined by the balance between the driving and drag forces due to the dissipative losses. Furthermore, the fluxon motion is characterized by a strong radial inward acceleration which causes electromagnetic radiation concentrated at the ellipse equatorial points.

  18. Studies of Two-Phase Gas-Liquid Flow in Microgravity. Ph.D. Thesis, Dec. 1994

    NASA Technical Reports Server (NTRS)

    Bousman, William Scott

    1995-01-01

    Two-phase gas-liquid flows are expected to occur in many future space operations. Due to a lack of buoyancy in the microgravity environment, two-phase flows are known to behave differently than those in earth gravity. Despite these concerns, little research has been conducted on microgravity two-phase flow and the current understanding is poor. This dissertation describes an experimental and modeling study of the characteristics of two-phase flows in microgravity. An experiment was operated onboard NASA aircraft capable of producing short periods of microgravity. In addition to high speed photographs of the flows, electronic measurements of void fraction, liquid film thickness, bubble and wave velocity, pressure drop and wall shear stress were made for a wide range of liquid and gas flow rates. The effects of liquid viscosity, surface tension and tube diameter on the behavior of these flows were also assessed. From the data collected, maps showing the occurrence of various flow patterns as a function of gas and liquid flow rates were constructed. Earth gravity two-phase flow models were compared to the results of the microgravity experiments and in some cases modified. Models were developed to predict the transitions on the flow pattern maps. Three flow patterns, bubble, slug and annular flow, were observed in microgravity. These patterns were found to occur in distinct regions of the gas-liquid flow rate parameter space. The effect of liquid viscosity, surface tension and tube diameter on the location of the boundaries of these regions was small. Void fraction and Weber number transition criteria both produced reasonable transition models. Void fraction and bubble velocity for bubble and slug flows were found to be well described by the Drift-Flux model used to describe such flows in earth gravity. Pressure drop modeling by the homogeneous flow model was inconclusive for bubble and slug flows. Annular flows were found to be complex systems of ring-like waves and a

  19. Two Phase Flow and Space-Based Applications

    NASA Technical Reports Server (NTRS)

    McQuillen, John

    1999-01-01

    A reduced gravity environment offers the ability to remove the effect of buoyancy on two phase flows whereby density differences that normally would promote relative velocities between the phases and also alter the shape of the interface are removed. However, besides being a potent research tool, there are also many space-based technologies that will either utilize or encounter two-phase flow behavior, and as a consequence, several questions must be addressed. This paper presents some of these technologies missions. Finally, this paper gives a description of web-sites for some funding.

  20. Two-Phase Model of Combustion in Explosions

    SciTech Connect

    Kuhl, A L; Khasainov, B; Bell, J

    2006-06-19

    A two-phase model for Aluminum particle combustion in explosions is proposed. It combines the gas-dynamic conservation laws for the gas phase with the continuum mechanics laws of multi-phase media, as formulated by Nigmatulin. Inter-phase mass, momentum and energy exchange are prescribed by the Khasainov model. Combustion is specified as material transformations in the Le Chatelier diagram which depicts the locus of thermodynamic states in the internal energy-temperature plane according to Kuhl. Numerical simulations are used to show the evolution of two-phase combustion fields generated by the explosive dissemination of a powdered Al fuel.

  1. Microgravity experiments with a simple two-phase thermal system

    SciTech Connect

    Crowley, C.J.; Sam, R.G. )

    1991-01-10

    Microgravity experiments with a simple two-phase thermal system are described. Microgravity experiments aboard the NASA KC-135 aircraft provide variable acceleration 0.01g to 2g, with low gravity for 20 to 25 seconds. The two-phase loop allows the vapor and liquid phases to flow together between the evaporator and the condenser. It incorporates and evaporator where heat transfer is controlled by forced convection, an adiabatic transport section where transparent piping provides visualization of the flow regime, and a condenser where heat transfer is controlled by the shear between the gas and liquid phases. Stable operation of the system is observed during the variable accleration.

  2. Momentum flux in two phase two component low quality flow.

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Graham, R. W.; Henry, R. E.

    1972-01-01

    Values of a one-dimensional momentum flux at a test section discharge station of a two-phase two-component low quality flow computed by two methods, one based on a one-dimensional homogeneous model and the other on a variable slip model, are compared to experimental values for a range of two-phase flow conditions. The comparison seems to indicate the superior accuracy in momentum flux predictions to be on the side of the one-dimensional homogeneous model.

  3. Experimental investigation of the two-phase flow regimes and pressure drop in horizontal mini-size rectangular test section

    NASA Astrophysics Data System (ADS)

    Elazhary, Amr Mohamed; Soliman, Hassan M.

    2012-10-01

    An experimental study was conducted in order to investigate two-phase flow regimes and fully developed pressure drop in a mini-size, horizontal rectangular channel. The test section was machined in the form of an impacting tee junction in an acrylic block (in order to facilitate visualization) with a rectangular cross-section of 1.87-mm height on 20-mm width on the inlet and outlet sides. Pressure drop measurement and flow regime identification were performed on all three sides of the junction. Air-water mixtures at 200 kPa (abs) and room temperature were used as the test fluids. Four flow regimes were identified visually: bubbly, plug, churn, and annular over the ranges of gas and liquid superficial velocities of 0.04 ≤ JG ≤ 10 m/s and 0.02 ≤ JL ≤ 0.7 m/s, respectively, and a flow regime map was developed. Accuracy of the pressure-measurement technique was validated with single-phase, laminar and turbulent, fully developed data. Two-phase experiments were conducted for eight different inlet conditions and various mass splits at the junction. Comparisons were conducted between the present data and former correlations for the fully developed two-phase pressure drop in rectangular channels with similar sizes. Wide deviations were found among these correlations, and the correlations that agreed best with the present data were identified.

  4. Granuloma annulare with prominent lymphoid infiltrates ("pseudolymphomatous" granuloma annulare).

    PubMed

    Cota, Carlo; Ferrara, Gerardo; Cerroni, Lorenzo

    2012-05-01

    Granuloma annulare (GA) is characterized histopathologically by 3 patterns: necrobiotic granuloma, interstitial incomplete form and, rarely, sarcoidal or tuberculoid granuloma. The amount of lymphoid infiltrate in GA is usually limited. We describe 10 cases of GA with prominent "pseudolymphomatous" lymphoid infiltrates mimicking cutaneous lymphoid hyperplasia. Patients were 6 males and 4 females (mean age 49.9 years, median age 47 years, age range 25-70). Lesions were localized to a limited area of the body (n = 6), or involved the entire trunk (n = 3), or were generalized (n = 1). The correct clinical diagnosis of GA was provided only in 30% of the cases. In all cases, histopathologic features were characterized by dense, nodular, superficial, and deep infiltrates of lymphocytes. Immunohistology revealed predominance of T lymphocytes in 7 of 7 tested cases. This "pseudolymphomatous" variant of GA represents a pitfall in the histopathologic diagnosis of the disease and may be misinterpreted as other types of cutaneous lymphoproliferative disorders. PMID:22207445

  5. Non-axisymmetric annular curtain stability

    NASA Astrophysics Data System (ADS)

    Ahmed, Zahir U.; Khayat, Roger E.; Maissa, Philippe; Mathis, Christian

    2013-08-01

    A stability analysis of non-axisymmetric annular curtain is carried out for an axially moving viscous jet subject in surrounding viscous gas media. The effect of inertia, surface tension, gas-to-liquid density ratio, inner-to-outer radius ratio, and gas-to-liquid viscosity ratio on the stability of the jet is studied. In general, the axisymmetric disturbance is found to be the dominant mode. However, for small wavenumber, the non-axisymmetric mode is the most unstable mode and the one likely observed in reality. Inertia and the viscosity ratio for non-axisymmetric disturbances show a similar stability influence as observed for axisymmetric disturbances. The maximum growth rate in non-axisymmetric flow, interestingly, appears at very small wavenumber for all inertia levels. The dominant wavenumber increases (decreases) with inertia for non-axisymmetric (axisymmetric) flow. Gas-to-liquid density ratio, curvature effect, and surface tension, however, exhibit an opposite influence on growth rate compared to axisymmetric disturbances. Surface tension tends to stabilize the flow with reductions of the unstable wavenumber range and the maximum growth rate as well as the dominant wavenumber. The dominant wavenumber remains independent of viscosity ratio indicating the viscosity ratio increases the breakup length of the sheet with very little influence on the size of the drops. The range of unstable wavenumbers is affected only by curvature in axisymmetric flow, whereas all the stability parameters control the range of unstable wavenumbers in non-axisymmetric flow. Inertia and gas density increase the unstable wavenumber range, whereas the radius ratio, surface tension, and the viscosity ratio decrease the unstable wavenumber range. Neutral curves are plotted to separate the stable and unstable domains. Critical radius ratio decreases linearly and nonlinearly with the wavenumber for axisymmetric and non-axisymmetric disturbances, respectively. At smaller Weber numbers, a

  6. Diffusion-controlled grain growth in two-phase solids

    SciTech Connect

    Fan, D.; Chen, L.Q.

    1997-08-01

    Microstructural evolution and the kinetics of grain growth in volume-conserved two-phase solids were investigated using two-dimensional (2-D) computer simulations based on a diffuse-interface field model. In this model, a two-phase microstructure is described by non-conserved field variables which represent crystallographic orientations of grains in each phase and by a conserved composition field variable which distinguishes the compositional difference between the two phases. The temporal and spatial evolution of these field variables were obtained through a numerical solution to the time-dependent Ginzburg-Landau (TDGL) equations. The effect of the ratios of grain boundary energies to interfacial energy on the microstructure features was systematically studied. It was found that grain growth in a volume-conserved two-phase solid is controlled by long-range diffusion and follows the power growth law, R{sup m} {minus} R{sup m}{sub o} = kt with m = 3 in the scaling regime for all cases studied, including the microstructures containing only quadrijunctions. The effects of volume fractions and initial microstructures are discussed.

  7. Low gravity two-phase flow with heat transfer

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    1991-01-01

    A realistic model for the transfer line chilldown operation under low-gravity conditions is developed to provide a comprehensive predictive capability on the behavior of liquid vapor, two-phase diabatic flows in pipes. The tasks described involve the development of numerical code and the establishment of the necessary experimental data base for low-gravity simulation.

  8. Coal-Face Fracture With A Two-Phase Liquid

    NASA Technical Reports Server (NTRS)

    Collins, E. R., Jr.

    1985-01-01

    In new method for mining coal without explosive, two-phase liquid such as CO2 and water, injected at high pressure into deeper ends of holes drilled in coal face. Liquid permeates coal seam through existing microfractures; as liquid seeps back toward face, pressure eventually drops below critical value at which dissolved gas flashvaporizes, breaking up coal.

  9. Two-phase flow in helical and spiral coils

    NASA Technical Reports Server (NTRS)

    Keshock, Edward G.; Bush, Mia L.; Omrani, Adel; Yan, An

    1995-01-01

    Coiled tube heat exchangers involving two-phase flows are used in a variety of application areas, extending from the aerospace industry to petrochemical, refrigeration land power generation industries. The optimal design in each situation requires a fundamental understanding of the heat, mass and momentum transfer characteristic of the flowing two-phase mixture. However, two-phase flows in lengths of horizontal or vertical straight channels with heat transfer are often quite difficult in themselves to understand sufficiently well to permit accurate system designs. The present study has the following general objectives: (1) Observe two-phase flow patterns of air-water and R-113 working fluids over a range of flow conditions, for helical and spiral coil geometries, of circular and rectangular cross-section; (2) Compare observed flow patterns with predictions of existing flow maps; (3) Study criteria for flow regime transitions for possible modifications of existing flow pattern maps; and (4) Measure associated pressure drops across the coiled test sections over the rage of flow conditions specified.

  10. Numerical studies of gravity effects in two-phase reservoirs

    SciTech Connect

    Bodvarsson, G.S.; Cox, B.L.

    1986-06-01

    Numerical studies are performed to investigate the effects of localized feed zones on the pressure transients in two-phase reservoirs. It is shown that gravity effects can significantly affect the pressure transients, because of the large difference in the density of liquid water and vapor. Pressure transients for shallow and deep feed zones and the resulting fluid flow patterns are discussed.

  11. Power production with two-phase expansion through vapor dome

    SciTech Connect

    Amend, W.E.; Toner, S.J.

    1984-08-07

    In a system wherein a fluid exhibits a regressive vapor dome in a T-S diagram, the following are provided: a two-phase nozzle receiving the fluid in pressurized and heated liquid state and expanding the received liquid into saturated or superheated vapor state, and apparatus receiving the saturated or superheated vapor to convert the kinetic energy thereof into power.

  12. Two-phase alkali-metal experiments in reduced gravity

    SciTech Connect

    Antoniak, Z.I.

    1986-06-01

    Future space missions envision the use of large nuclear reactors utilizing either a single or a two-phase alkali-metal working fluid. The design and analysis of such reactors require state-of-the-art computer codes that can properly treat alkali-metal flow and heat transfer in a reduced-gravity environment. A literature search of relevant experiments in reduced gravity is reported on here, and reveals a paucity of data for such correlations. The few ongoing experiments in reduced gravity are noted. General plans are put forth for the reduced-gravity experiments which will have to be performed, at NASA facilities, with benign fluids. A similar situation exists regarding two-phase alkali-metal flow and heat transfer, even in normal gravity. Existing data are conflicting and indequate for the task of modeling a space reactor using a two-phase alkali-metal coolant. The major features of past experiments are described here. Data from the reduced-gravity experiments with innocuous fluids are to be combined with normal gravity data from the two-phase alkali-metal experiments. Analyses undertaken here give every expectation that the correlations developed from this data base will provide a valid representation of alkali-metal heat transfer and pressure drop in reduced gravity.

  13. Flow Pattern Phenomena in Two-Phase Flow in Microchannels

    NASA Astrophysics Data System (ADS)

    Keska, Jerry K.; Simon, William E.

    2004-02-01

    Space transportation systems require high-performance thermal protection and fluid management techniques for systems ranging from cryogenic fluid management devices to primary structures and propulsion systems exposed to extremely high temperatures, as well as for other space systems such as cooling or environment control for advanced space suits and integrated circuits. Although considerable developmental effort is being expended to bring potentially applicable technologies to a readiness level for practical use, new and innovative methods are still needed. One such method is the concept of Advanced Micro Cooling Modules (AMCMs), which are essentially compact two-phase heat exchangers constructed of microchannels and designed to remove large amounts of heat rapidly from critical systems by incorporating phase transition. The development of AMCMs requires fundamental technological advancement in many areas, including: (1) development of measurement methods/systems for flow-pattern measurement/identification for two-phase mixtures in microchannels; (2) development of a phenomenological model for two-phase flow which includes the quantitative measure of flow patterns; and (3) database development for multiphase heat transfer/fluid dynamics flows in microchannels. This paper focuses on the results of experimental research in the phenomena of two-phase flow in microchannels. The work encompasses both an experimental and an analytical approach to incorporating flow patterns for air-water mixtures flowing in a microchannel, which are necessary tools for the optimal design of AMCMs. Specifically, the following topics are addressed: (1) design and construction of a sensitive test system for two-phase flow in microchannels, one which measures ac and dc components of in-situ physical mixture parameters including spatial concentration using concomitant methods; (2) data acquisition and analysis in the amplitude, time, and frequency domains; and (3) analysis of results

  14. Two-phase convective CO2 dissolution in saline aquifers

    DOE PAGESBeta

    Martinez, M. J.; Hesse, M. A.

    2016-01-30

    Geologic carbon storage in deep saline aquifers is a promising technology for reducing anthropogenic emissions into the atmosphere. Dissolution of injected CO2 into resident brines is one of the primary trapping mechanisms generally considered necessary to provide long-term storage security. Given that diffusion of CO2 in brine is woefully slow, convective dissolution, driven by a small increase in brine density with CO2 saturation, is considered to be the primary mechanism of dissolution trapping. Previous studies of convective dissolution have typically only considered the convective process in the single-phase region below the capillary transition zone and have either ignored the overlyingmore » two-phase region where dissolution actually takes place or replaced it with a virtual region with reduced or enhanced constant permeability. Our objective is to improve estimates of the long-term dissolution flux of CO2 into brine by including the capillary transition zone in two-phase model simulations. In the fully two-phase model, there is a capillary transition zone above the brine-saturated region over which the brine saturation decreases with increasing elevation. Our two-phase simulations show that the dissolution flux obtained by assuming a brine-saturated, single-phase porous region with a closed upper boundary is recovered in the limit of vanishing entry pressure and capillary transition zone. For typical finite entry pressures and capillary transition zone, however, convection currents penetrate into the two-phase region. As a result, this removes the mass transfer limitation of the diffusive boundary layer and enhances the convective dissolution flux of CO2 more than 3 times above the rate assuming single-phase conditions.« less

  15. Two-phase convective CO2 dissolution in saline aquifers

    DOE PAGESBeta

    Martinez, Mario J.; Hesse, Marc A.

    2016-01-01

    Geologic carbon storage in deep saline aquifers is a promising technology for reducing anthropogenic emissions into the atmosphere. Dissolution of injected CO2 into resident brines is one of the primary trapping mechanisms generally considered necessary to provide long-term storage security. Given that diffusion of CO2 in brine is woefully slow, convective dissolution, driven by a small increase in brine density with CO2 saturation, is considered to be the primary mechanism of dissolution trapping. Previous studies of convective dissolution have typically only considered the convective process in the single-phase region below the capillary transition zone and have either ignored the overlyingmore » two-phase region where dissolution actually takes place or replaced it with a virtual region with reduced or enhanced constant permeability. Our objective is to improve estimates of the long-term dissolution flux of CO2 into brine by including the capillary transition zone in two-phase model simulations. In the fully two-phase model, there is a capillary transition zone above the brine-saturated region over which the brine saturation decreases with increasing elevation. Our two-phase simulations show that the dissolution flux obtained by assuming a brine-saturated, single-phase porous region with a closed upper boundary is recovered in the limit of vanishing entry pressure and capillary transition zone. For typical finite entry pressures and capillary transition zone, however, convection currents penetrate into the two-phase region. As a result, this removes the mass transfer limitation of the diffusive boundary layer and enhances the convective dissolution flux of CO2 more than 3 times above the rate assuming single-phase conditions.« less

  16. Two-phase convective CO2 dissolution in saline aquifers

    NASA Astrophysics Data System (ADS)

    Martinez, M. J.; Hesse, M. A.

    2016-01-01

    Geologic carbon storage in deep saline aquifers is a promising technology for reducing anthropogenic emissions into the atmosphere. Dissolution of injected CO2 into resident brines is one of the primary trapping mechanisms generally considered necessary to provide long-term storage security. Given that diffusion of CO2 in brine is woefully slow, convective dissolution, driven by a small increase in brine density with CO2 saturation, is considered to be the primary mechanism of dissolution trapping. Previous studies of convective dissolution have typically only considered the convective process in the single-phase region below the capillary transition zone and have either ignored the overlying two-phase region where dissolution actually takes place or replaced it with a virtual region with reduced or enhanced constant permeability. Our objective is to improve estimates of the long-term dissolution flux of CO2 into brine by including the capillary transition zone in two-phase model simulations. In the fully two-phase model, there is a capillary transition zone above the brine-saturated region over which the brine saturation decreases with increasing elevation. Our two-phase simulations show that the dissolution flux obtained by assuming a brine-saturated, single-phase porous region with a closed upper boundary is recovered in the limit of vanishing entry pressure and capillary transition zone. For typical finite entry pressures and capillary transition zone, however, convection currents penetrate into the two-phase region. This removes the mass transfer limitation of the diffusive boundary layer and enhances the convective dissolution flux of CO2 more than 3 times above the rate assuming single-phase conditions.

  17. By-pass pigs for two-phase flow pipelines

    SciTech Connect

    Wu, H.L.; Spronsen, G. van; Klaus, E.H.; Stewart, D.M.

    1996-12-31

    Pigging two-phase pipelines normally leads to the generation of large liquid slug volumes in front of the pig requiring excessively large separators or slug catchers. The concept of using a high by-pass pig to disperse the liquid and reduce the maximum liquid production rate prior to pig arrival is under investigation by Shell Exploration and Production companies. A simulation model of the dynamics of the pig and related two-phase flow behavior in the pipeline was used to predict the performance of by-pass pigs. Field trials in a dry gas pipeline were carried out to provide friction data and to validate the model. It was then used to explore operating possibilities in a two-phase lie which led to the follow-up trial in a 15.6 km, 20 inch OD two-phase offshore interfield pipeline with risers. Whereas the volume of liquid swept in front of the pig would be 179 m{sup 3} if the by-pass fraction were zero, a reduction of 70% to 53m{sup 3} was achieved in the field with a by-pass fraction of 10%. The predicted mobility of the high by-pass pig in the pipeline and risers was verified and the beneficial effects due to the by-pass concept exceeded the prediction of the simplified model. The significant gains of using a by-pass pig in modifying gas and liquid production rates during pigging operation have been demonstrated. The method can widen the possibility of applying two-phase flow pipeline transportation to cases where separator or slug catcher capacity are limited for reasons of practicality or cost.

  18. Means of manufacturing annular arrays

    DOEpatents

    Day, R.A.

    1985-10-10

    A method is described for manufacturing an annular acoustic transducer array from a plate of transducer material, which enables production of precision aligned arrays at low cost. The circular plate is sawed along at least two lines that are radial to the axis of the plate. At steps along each radial cut, the plate is rotated first in one direction and then in an opposite direction by a predetermined angle such as slightly less than 90/sup 0/. The cuts result in the forming of several largely ring-shaped lands, each largely ring-shaped land being joined to the other rings of different radii by thin portions of the plate, and each ring being cut into segments. The bridges that join different rings hold the transducer together until it can be mounted on a lens.

  19. Investigations of two-phase flame propagation under microgravity conditions

    NASA Astrophysics Data System (ADS)

    Gokalp, Iskender

    2016-07-01

    Investigations of two-phase flame propagation under microgravity conditions R. Thimothée, C. Chauveau, F. Halter, I Gökalp Institut de Combustion, Aérothermique, Réactivité et Environnement (ICARE), CNRS, 1C Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France This paper presents and discusses recent results on two-phase flame propagation experiments we carried out with mono-sized ethanol droplet aerosols under microgravity conditions. Fundamental studies on the flame propagation in fuel droplet clouds or sprays are essential for a better understanding of the combustion processes in many practical applications including internal combustion engines for cars, modern aircraft and liquid rocket engines. Compared to homogeneous gas phase combustion, the presence of a liquid phase considerably complicates the physico-chemical processes that make up combustion phenomena by coupling liquid atomization, droplet vaporization, mixing and heterogeneous combustion processes giving rise to various combustion regimes where ignition problems and flame instabilities become crucial to understand and control. Almost all applications of spray combustion occur under high pressure conditions. When a high pressure two-phase flame propagation is investigated under normal gravity conditions, sedimentation effects and strong buoyancy flows complicate the picture by inducing additional phenomena and obscuring the proper effect of the presence of the liquid droplets on flame propagation compared to gas phase flame propagation. Conducting such experiments under reduced gravity conditions is therefore helpful for the fundamental understanding of two-phase combustion. We are considering spherically propagating two-phase flames where the fuel aerosol is generated from a gaseous air-fuel mixture using the condensation technique of expansion cooling, based on the Wilson cloud chamber principle. This technique is widely recognized to create well-defined mono-size droplets

  20. Two Phase Flow Modeling: Summary of Flow Regimes and Pressure Drop Correlations in Reduced and Partial Gravity

    NASA Technical Reports Server (NTRS)

    Balasubramaniam, R.; Rame, E.; Kizito, J.; Kassemi, M.

    2006-01-01

    The purpose of this report is to provide a summary of state-of-the-art predictions for two-phase flows relevant to Advanced Life Support. We strive to pick out the most used and accepted models for pressure drop and flow regime predictions. The main focus is to identify gaps in predictive capabilities in partial gravity for Lunar and Martian applications. Following a summary of flow regimes and pressure drop correlations for terrestrial and zero gravity, we analyze the fully developed annular gas-liquid flow in a straight cylindrical tube. This flow is amenable to analytical closed form solutions for the flow field and heat transfer. These solutions, valid for partial gravity as well, may be used as baselines and guides to compare experimental measurements. The flow regimes likely to be encountered in the water recovery equipment currently under consideration for space applications are provided in an appendix.

  1. A monotonicity preserving conservative sharp interface flow solver for high density ratio two-phase flows

    NASA Astrophysics Data System (ADS)

    Le Chenadec, Vincent; Pitsch, Heinz

    2013-09-01

    This paper presents a novel approach for solving the conservative form of the incompressible two-phase Navier-Stokes equations. In order to overcome the numerical instability induced by the potentially large density ratio encountered across the interface, the proposed method includes a Volume-of-Fluid type integration of the convective momentum transport, a monotonicity preserving momentum rescaling, and a consistent and conservative Ghost Fluid projection that includes surface tension effects. The numerical dissipation inherent in the Volume-of-Fluid treatment of the convective transport is localized in the interface vicinity, enabling the use of a kinetic energy conserving discretization away from the singularity. Two- and three-dimensional tests are presented, and the solutions shown to remain accurate at arbitrary density ratios. The proposed method is then successfully used to perform the detailed simulation of a round water jet emerging in quiescent air, therefore suggesting the applicability of the proposed algorithm to the computation of realistic turbulent atomization.

  2. A monotonicity preserving conservative sharp interface flow solver for high density ratio two-phase flows

    SciTech Connect

    Le Chenadec, Vincent; Pitsch, Heinz

    2013-09-15

    This paper presents a novel approach for solving the conservative form of the incompressible two-phase Navier–Stokes equations. In order to overcome the numerical instability induced by the potentially large density ratio encountered across the interface, the proposed method includes a Volume-of-Fluid type integration of the convective momentum transport, a monotonicity preserving momentum rescaling, and a consistent and conservative Ghost Fluid projection that includes surface tension effects. The numerical dissipation inherent in the Volume-of-Fluid treatment of the convective transport is localized in the interface vicinity, enabling the use of a kinetic energy conserving discretization away from the singularity. Two- and three-dimensional tests are presented, and the solutions shown to remain accurate at arbitrary density ratios. The proposed method is then successfully used to perform the detailed simulation of a round water jet emerging in quiescent air, therefore suggesting the applicability of the proposed algorithm to the computation of realistic turbulent atomization.

  3. Sealing arrangement with annular flexible disc

    DOEpatents

    Pennell, William E.; Honigsberg, Charles A.

    1983-01-01

    Fluid sealing arrangements including an annular shaped flexible disc having enlarged edges disposed within channel-shaped annular receptacles which are spaced from one another. The receptacles form an annular region for contacting and containing the enlarged edges of the disc, and the disc is preloaded to a conical configuration. The disc is flexibly and movably supported within the receptacles so that unevenly distributed relative motion between the components containing the receptacles is accommodated without loss of sealing contact between the edges of the disc and the walls of the receptacles.

  4. Etizolam-induced superficial erythema annulare centrifugum.

    PubMed

    Kuroda, K; Yabunami, H; Hisanaga, Y

    2002-01-01

    Erythema annulare centrifugum (EAC) is characterized by slowly enlarging annular erythematous lesions. Although the origin is not clear in most cases, EAC has been associated with infections, medications, and in rare cases, underlying malignancy. We describe a patient who developed annular erythematous lesions after etizolam administration. The eruptions were typical of the superficial form of EAC, both clinically and histopathologically. The lesions disappeared shortly after discontinuation of the medication. Patch testing with etizolam gave positive results. To our knowledge this is the first reported case of etizolam-induced superficial EAC. PMID:11952667

  5. A New Void Fraction Measurement Method for Gas-Liquid Two-Phase Flow in Small Channels

    PubMed Central

    Li, Huajun; Ji, Haifeng; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing; Wu, Guohua

    2016-01-01

    Based on a laser diode, a 12 × 6 photodiode array sensor, and machine learning techniques, a new void fraction measurement method for gas-liquid two-phase flow in small channels is proposed. To overcome the influence of flow pattern on the void fraction measurement, the flow pattern of the two-phase flow is firstly identified by Fisher Discriminant Analysis (FDA). Then, according to the identification result, a relevant void fraction measurement model which is developed by Support Vector Machine (SVM) is selected to implement the void fraction measurement. A void fraction measurement system for the two-phase flow is developed and experiments are carried out in four different small channels. Four typical flow patterns (including bubble flow, slug flow, stratified flow and annular flow) are investigated. The experimental results show that the development of the measurement system is successful. The proposed void fraction measurement method is effective and the void fraction measurement accuracy is satisfactory. Compared with the conventional laser measurement systems using standard laser sources, the developed measurement system has the advantages of low cost and simple structure. Compared with the conventional void fraction measurement methods, the proposed method overcomes the influence of flow pattern on the void fraction measurement. This work also provides a good example of using low-cost laser diode as a competent replacement of the expensive standard laser source and hence implementing the parameter measurement of gas-liquid two-phase flow. The research results can be a useful reference for other researchers’ works. PMID:26828488

  6. A New Void Fraction Measurement Method for Gas-Liquid Two-Phase Flow in Small Channels.

    PubMed

    Li, Huajun; Ji, Haifeng; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing; Wu, Guohua

    2016-01-01

    Based on a laser diode, a 12 × 6 photodiode array sensor, and machine learning techniques, a new void fraction measurement method for gas-liquid two-phase flow in small channels is proposed. To overcome the influence of flow pattern on the void fraction measurement, the flow pattern of the two-phase flow is firstly identified by Fisher Discriminant Analysis (FDA). Then, according to the identification result, a relevant void fraction measurement model which is developed by Support Vector Machine (SVM) is selected to implement the void fraction measurement. A void fraction measurement system for the two-phase flow is developed and experiments are carried out in four different small channels. Four typical flow patterns (including bubble flow, slug flow, stratified flow and annular flow) are investigated. The experimental results show that the development of the measurement system is successful. The proposed void fraction measurement method is effective and the void fraction measurement accuracy is satisfactory. Compared with the conventional laser measurement systems using standard laser sources, the developed measurement system has the advantages of low cost and simple structure. Compared with the conventional void fraction measurement methods, the proposed method overcomes the influence of flow pattern on the void fraction measurement. This work also provides a good example of using low-cost laser diode as a competent replacement of the expensive standard laser source and hence implementing the parameter measurement of gas-liquid two-phase flow. The research results can be a useful reference for other researchers' works. PMID:26828488

  7. Twin Jet

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda; Bozak, Rick

    2010-01-01

    Many subsonic and supersonic vehicles in the current fleet have multiple engines mounted near one another. Some future vehicle concepts may use innovative propulsion systems such as distributed propulsion which will result in multiple jets mounted in close proximity. Engine configurations with multiple jets have the ability to exploit jet-by-jet shielding which may significantly reduce noise. Jet-by-jet shielding is the ability of one jet to shield noise that is emitted by another jet. The sensitivity of jet-by-jet shielding to jet spacing and simulated flight stream Mach number are not well understood. The current experiment investigates the impact of jet spacing, jet operating condition, and flight stream Mach number on the noise radiated from subsonic and supersonic twin jets.

  8. A Two-Phase Metaheuristic for Farm Workscheduling

    NASA Astrophysics Data System (ADS)

    Guan, Senlin; Nakamura, Morikazu; Shikanai, Takeshi; Okazaki, Takeo

    This paper proposes a two-phase metaheuristic approach to planning daily farm work for agriculture production corporations. The two-phase metaheuristic contains the optimization of resources assignment and searching schedule based on Genetic Algorithm and hybrid Petri nets model. In the experiment, the effect on optimizing the resource assignment and priority list, initializing population of GA with sorted chromosomes by waiting time, inheriting priority list from tasks in the previous resources assignment enhanced the evolutionary speed and solution quality. The computational experiment revealed high effectiveness for constructing farm work schedule with high ratio of resource utilization. The proposed approach also contributes a referential scheme for combining metaheuristic to solve scheduling problem under constraints.

  9. Gelfand-type problem for two-phase porous media

    PubMed Central

    Gordon, Peter V.; Moroz, Vitaly

    2014-01-01

    We consider a generalization of the Gelfand problem arising in Frank-Kamenetskii theory of thermal explosion. This generalization is a natural extension of the Gelfand problem to two-phase materials, where, in contrast to the classical Gelfand problem which uses a single temperature approach, the state of the system is described by two different temperatures. We show that similar to the classical Gelfand problem the thermal explosion occurs exclusively owing to the absence of stationary temperature distribution. We also show that the presence of interphase heat exchange delays a thermal explosion. Moreover, we prove that in the limit of infinite heat exchange between phases the problem of thermal explosion in two-phase porous media reduces to the classical Gelfand problem with renormalized constants. PMID:24611025

  10. Method and apparatus for monitoring two-phase flow. [PWR

    DOEpatents

    Sheppard, J.D.; Tong, L.S.

    1975-12-19

    A method and apparatus for monitoring two-phase flow is provided that is particularly related to the monitoring of transient two-phase (liquid-vapor) flow rates such as may occur during a pressurized water reactor core blow-down. The present invention essentially comprises the use of flanged wire screens or similar devices, such as perforated plates, to produce certain desirable effects in the flow regime for monitoring purposes. One desirable effect is a measurable and reproducible pressure drop across the screen. The pressure drop can be characterized for various known flow rates and then used to monitor nonhomogeneous flow regimes. Another useful effect of the use of screens or plates in nonhomogeneous flow is that such apparatus tends to create a uniformly dispersed flow regime in the immediate downstream vicinity. This is a desirable effect because it usually increases the accuracy of flow rate measurements determined by conventional methods.

  11. Melt-band instabilities with two-phase damage

    NASA Astrophysics Data System (ADS)

    Rudge, John F.; Bercovici, David

    2015-05-01

    Deformation experiments on partially molten rocks in simple shear form melt bands at 20° to the shear plane instead of at the expected 45° principal compressive stress direction. These melt bands may play an important role in melt focusing in mid-ocean ridges. Such shallow bands are known to form for two-phase media under shear if strongly non-Newtonian power-law creep is employed for the solid phase, or anisotropy imposed. However laboratory experiments show that shallow bands occur regardless of creep mechanism, even in diffusion creep, which is nominally Newtonian. Here we propose that a couple of forms of two-phase damage allow for shallow melt bands even in diffusion creep.

  12. A study of two phase flow in fracture networks

    SciTech Connect

    Karasaki, K.; Pruess, K.; Vomvoris, S.; Segan, S.

    1994-12-31

    Accurate characterization of the two-phase flow behavior of the fractured rock mass is vital to the safety of a potential high level nuclear waste repository in the unsaturated, fractured welded tuff at Yucca Mountain, NV. A tool for studying the two-phase flow properties of a fracture networks was developed. It is based on a simple mechanistic model in which the capillary pressure of a fracture is a unique function of the aperture. Whether a particular fracture element is occupied by wetting fluid or non-wetting fluid is determined by allowability and accessibility criteria. Relative permeability characteristics of a simulated fracture network were investigated using the model. Different assumptions are examined regarding the interactions between phases. In all cases, strong phase interference was observed. Hysteresis effects and irreducible saturation were also explained based on the model.

  13. A pumped two-phase cooling system for spacecraft

    NASA Technical Reports Server (NTRS)

    Ollendorf, S.; Costello, F. A.

    1983-01-01

    A pumped, two-phase heat-transport system is being developed for possible use for temperature control of scientific instruments on future NASA missions. As compared to a single-phase system, this two-phase system can maintain tighter temperature control with less pumping power. A laboratory model of the system has been built and tested. The measured heat transfer coefficients were approximately the same as in heat pipes, 220 Btu/hr-sq ft-F, as compared to 25 Btu/hr-sq ft-F for single-phase liquid flow. Heat shearing between experiments has been demonstrated wherein vapor generated in the cold plate of an active experiment was condensed in a cold, unheated experiment. System stability has been observed. However, additional development is needed. The use of non-azeotropic mixtures of coolants appears especially promising as a simple way to determine exit quality and thus control the flow rates to prevent dryout.

  14. Computer simulation of two-phase flow in nuclear reactors

    SciTech Connect

    Wulff, W.

    1992-09-01

    Two-phase flow models dominate the economic resource requirements for development and use of computer codes for analyzing thermohydraulic transients in nuclear power plants. Six principles are presented on mathematical modeling and selection of numerical methods, along with suggestions on programming and machine selection, all aimed at reducing the cost of analysis. Computer simulation is contrasted with traditional computer calculation. The advantages of run-time interactive access operation in a simulation environment are demonstrated. It is explained that the drift-flux model is better suited for two-phase flow analysis in nuclear reactors than the two-fluid model, because of the latter`s closure problem. The advantage of analytical over numerical integration is demonstrated. Modeling and programming techniques are presented which minimize the number of needed arithmetical and logical operations and thereby increase the simulation speed, while decreasing the cost.

  15. A review of two-phase flow-induced vibration

    NASA Astrophysics Data System (ADS)

    Chen, S. S.

    1987-08-01

    Two-phase flow exists in many shell-and-tube heat exchangers and power generation components. The flowing fluid is a source of energy that can induce small-amplitude subcritical oscillations and large-amplitude dynamic instabilities. In fact, many practical system components have experienced excessive flow-induced vibrations. To prevent unacceptable flow-induced vibration, we must understand excitation mechanisms, develop analytical and experimental techniques, and provide reliable design guidelines. Thus, we are conducting a comprehensive program to study structural vibration in components subjected to two-phase flow. This report reviews the current understanding of vibration of circular cylinders in quiescent fluid, crossflow, and axial flow, with emphasis on excitation mechanisms, mathematical models, and available experimental data. A unified theory is presented for cylinders oscillating under different flow conditions. Based on the theory, future research needs are outlined.

  16. Cascade modeling of single and two-phase turbulence

    NASA Astrophysics Data System (ADS)

    Bolotnov, Igor A.

    The analysis of turbulent two-phase flows requires closure models in order to perform reliable computational multiphase fluid dynamics (CFMD) analyses. A turbulence cascade model, which tracks the evolution of the turbulent kinetic energy between the various eddy sizes, has been developed for the analysis of the single and bubbly two-phase turbulence. Various flows are considered including the decay of isotropic grid-induced turbulence, uniform shear flow and turbulent channel flow. The model has been developed using a "building block" approach by moving from modeling of simpler turbulent flows (i.e., homogeneous, isotropic decay) to more involved turbulent flows (i.e., non-homogeneous channel flow). The spectral cascade-transport model's performance has been assessed against a number of experimental and direct numerical simulation (DNS) results.

  17. Tests on Thrust Augmenters for Jet Propulsion

    NASA Technical Reports Server (NTRS)

    Jacobs, Eastman N; Shoemaker, James M

    1932-01-01

    This series of tests was undertaken to determine how much the reaction thrust of a jet could be increased by the use of thrust augmenters and thus to give some indication as to the feasibility of jet propulsion for airplanes. The tests were made during the first part of 1927 at the Langley Memorial Aeronautical Laboratory. A compressed air jet was used in connection with a series of annular guides surrounding the jet to act as thrust augmenters. The results show that, although it is possible to increase the thrust of a jet, the increase is not large enough to affect greatly the status of the problem of the application of jet propulsion to airplanes.

  18. Theory and Tests of Two-Phase Turbines

    NASA Technical Reports Server (NTRS)

    Elliott, D. G.

    1986-01-01

    New turbines open possibility of new types of power cycles. Report describes theoretical analysis and experimental testing of two-phase impulse turbines. Such turbines open possibility of new types of power cycles operating with extremely wet mixtures of steam and water, organic fluids, or immiscible liquids and gases. Possible applications are geothermal power, waste-heat recovery, refrigerant expansion, solar conversion, transportation, and engine-bottoming cycles.

  19. Two-fluid model for two-phase flow

    NASA Astrophysics Data System (ADS)

    Ishii, M.

    1987-06-01

    The two-fluid model formulation is discussed in detail. The emphasis of the paper is on the three-dimensional formulation and the closure issues. The origin of the interfacial and turbulent transfer terms in the averaged formulation is explained and their original mathematical forms are examined. The interfacial transfer of mass, momentum, and energy is proportional to the interfacial area and driving force. This is not a postulate but a result of the careful examination of the mathematical form of the exact interfacial terms. These two effects are considered separately. Since all the interfacial transfer terms involve the interfacial area concentration, the accurate modeling of the local interfacial area concentration is the first step to be taken for a development of a reliable two-fluid model closure relations. The interfacial momentum interaction has been studied in terms of the standard-drag, lift, virtual mass, and Basset forces. Available analytical and semi-empirical correlations and closure relations are reviewed and existing shortcomings are pointed out. The other major area of importance is the modeling of turbulent transfer in two-phase flow. The two-phase flow turbulence problem is coupled with the phase separation problem even in a steady-state fully developed flow. Thus the two-phase turbulence cannot be understood without understanding the interfacial drag and lift forces accurately. There are some indications that the mixing length type model may not be sufficient to describe the three-dimensional turbulent and flow structures. Although it is a very difficult challenge, the two-phase flow turbulence should be investigated both experimentally and analytically with long time-scale research.

  20. Recent advances in two-phase flow numerics

    SciTech Connect

    Mahaffy, J.H.; Macian, R.

    1997-07-01

    The authors review three topics in the broad field of numerical methods that may be of interest to individuals modeling two-phase flow in nuclear power plants. The first topic is iterative solution of linear equations created during the solution of finite volume equations. The second is numerical tracking of macroscopic liquid interfaces. The final area surveyed is the use of higher spatial difference techniques.

  1. Two-phase, gas-liquid flows in static mixers

    SciTech Connect

    Shah, N.F.; Kale, D.D. )

    1992-02-01

    This paper reports that static mixers are used for many gas-liquid two-phase operations. some of the typical applications are processing of natural gas to remove hydrogen sulfide or carbon dioxide, waste water treatment, dissolution of gases, hydrogenation, chlorination, and so on. They have experimentally studied the pressure drop for oxygen-water system in a bubble column packed with Sulzer-Koch-type mixing elements. They observed that the ratio of pressure drop through the packed bubble column to that through the unpacked one was slightly greater than one. The suitability of static mixers to mix fluids of very widely different viscosities has been demonstrated. Two-phase operations in polymer industry involve very viscous fluids. Due to the high viscosity of these fluids, the flow will be predominantly in laminar region for both fluids. There are no data on gas-liquid two-phase systems incorporating viscous Newtonian and non-Newtonian fluids where flows are predominantly in laminar region.

  2. An experimental investigation of two-phase liquid oxygen pumping

    NASA Technical Reports Server (NTRS)

    Gross, L. A.

    1973-01-01

    The results of an experimental program to explore the feasibility of pumping two-phase oxygen (liquid and gas) at the pump inlet are reported. Twenty-one cavitation tests were run on a standard J-2 oxygen pump at the MSFC Components Test Laboratory. All tests were run with liquid oxygen 5 to 10 K above the normal boiling point temperature. During ten tests run at approximately at the pump inlet were noted before complete pump performance 50 percent of the nominal operating speed, two phase conditions were achieved. Vapor volumes of 40 to 50 percent at the pump inlet were noted before complete pump performance loss. The experimental results compared to predictions. Nine cavitation tests run at the nominal pump speed over a 5 K temperature range showed progressively lower net positive suction head (NPSH) requirements as temperature was increased. Two-phase operation was not achieved. The temperature varying NPSH data were used to calculate thermodynamic effects on NPSH, and the results were compared to existing data.

  3. Method and apparatus for continuous annular electrochromatography

    DOEpatents

    Scott, Charles D.

    1987-01-01

    Separation of complex mixtures and solutions can be carried out using a method and apparatus for continuous annular electrochromatography. Solutes are diverted radially by an imposed electrical field as they move downward in a rotating chromatographic column.

  4. Granuloma Annulare Treated with Excimer Laser

    PubMed Central

    Ragi, Jennifer; Milgraum, Sandy

    2012-01-01

    Objective: To review the current therapy for granuloma annulare and report a case of refractory generalized granuloma annulare successfully treated with excimer laser. A discussion about the characteristics of excimer laser and the mechanism of its effectiveness is presented. Design: Patient case report and literature review. Setting: Outpatient dermatology practice. Participants: A 73-year-old woman suffering from generalized granuloma annulare for more than 40 years. Measurements: Change in clinical appearance of lesions. Results: Use of excimer laser therapy resulted in prompt and complete resolution in treated areas with no residual skin changes or side effects. Conclusion: Excimer laser therapy is a powerful treatment modality with minimal side effects for patients with granuloma annulare. Further study is necessary to elucidate optimal dosing, long-term efficacy, and safety profile. PMID:23198013

  5. Two-phase gravity currents in geological CO2 storage

    NASA Astrophysics Data System (ADS)

    Neufeld, J. A.; Golding, M.; Hesse, M. A.; Huppert, H. E.

    2010-12-01

    Geological carbon capture and storage, in which compressed CO2 is injected into deep saline aquifers for permanent storage, forms an integral part of CO2 mitigation strategies. At representative reservoir conditions CO2 is buoyant and may therefore leak into surface waters or the atmosphere. The leakage of CO2 back into the atmosphere may be prevented by the formation of disconnected immobile residual CO2 in the wake of the migrating plume. Here we constrain the magnitude of residual trapping by considering a two-phase model of the buoyancy driven propagation of a plume of injected CO2 within a saline aquifer. The buoyant rise of CO2 within saline aquifers is the principal mechanism through which CO2 contacts the host reservoir. Most simplified models of CO2 migration have assumed that the capillary transition zone is negligible relative to the current thickness and that the fluids are separated by a sharp interface. The results anticipate that such currents quickly become highly localized at the top boundary of reservoirs resulting in a concomitant reduction in residual trapping. However, such single-phase models neglect both the interfacial tension and large viscosity difference between the injected CO2 and the ambient pore fluid. The key challenge in two-phase gravity currents is the modeling of the variation in CO2 saturation with depth within the current. Here we use a standard model that considers the functional dependence of the relative permeability and capillary pressure on saturation to describe the two-phase flow. We anticipate that, after an initial transient, the extent of the current is much greater than its depth and that the capillary pressures within the current are balanced by gravity in this limit. This balance, called gravity-capillary equilibrium, and the fact that flow is predominantly horizontal within the current determine the saturation profile. Realizing that flow is driven primarily by gradients in the hydrostatic pressure, as in single

  6. Two-phase gravity currents in CO2 sequestration

    NASA Astrophysics Data System (ADS)

    Neufeld, Jerome; Golding, Madeleine; Hesse, Marc

    2010-05-01

    Geological carbon capture and storage (CCS), in which compressed CO2 is injected into deep saline aquifers for permanent storage, forms an integral part of CO2 mitigation strategies. At representative reservoir conditions CO2 is buoyant and may therefore leak into surface waters or the atmosphere. The leakage of CO2 back into the atmosphere may be prevented by the formation of disconnected immobile residual CO2 in the wake of the migrating plume. Here we constrain the magnitude of residual trapping by considering a two-phase model of the buoyancy driven propagation of a plume of injected CO2 within a saline aquifer. The buoyant rise of CO2 within saline aquifers is the principal mechanism through which CO2 contacts the host reservoir. Most simplified models of CO2 migration have assumed that the capillary transition zone is negligible relative to the current thickness and that the fluids are separated by a sharp interface. The results anticipate that such currents quickly become highly localized at the top boundary of reservoirs resulting in a concomitant reduction in residual trapping. However, such single-phase models neglect both the interfacial tension and large viscosity difference between the injected CO2 and the ambient pore fluid. The key challenge in two-phase gravity currents is the modeling of the variation in CO2 saturation with depth within the current. Here we use a standard model that considers the functional dependence of the relative permeability and capillary pressure on saturation to describe the two-phase flow. We anticipate that, after an initial transient, the extent of the current is much greater than its depth and that the capillary pressures within the current are balanced by gravity in this limit. This balance, called gravity-capillary equilibrium, and the fact that flow is predominantly horizontal within the current determine the saturation profile. Realizing that flow is driven primarily by gradients in the hydrostatic pressure, as in

  7. Annular-Cross-Section CFE Chamber

    NASA Technical Reports Server (NTRS)

    Sharnez, Rizwan; Sammons, David W.

    1994-01-01

    Proposed continuous-flow-electrophoresis (CFE) chamber of annular cross section offers advantages over conventional CFE chamber, and wedge-cross-section chamber described in "Increasing Sensitivity in Continuous-Flow Electrophoresis" (MFS-26176). In comparison with wedge-shaped chamber, chamber of annular cross section virtually eliminates such wall effects as electro-osmosis and transverse gradients of velocity. Sensitivity enhanced by incorporating gradient maker and radial (collateral) flow.

  8. [Treatment of disseminated granuloma annulare with anthralin].

    PubMed

    Jantke, M E; Bertsch, H-P; Schön, M P; Fuchs, T

    2011-12-01

    Granuloma annulare is a benign, often asymptomatic and self-limiting granulomatous skin disease. In cases of disseminated granuloma annulare, spontaneous regression is considerably less frequent than in localized forms so that therapy is often desired. Systemic treatments should always be assessed critically and reserved for patients who are severely affected and in whom treatment approaches with few side effects such as local application of anthralin do not suffice to achieve a satisfactory effect. PMID:21656108

  9. Annular gel reactor for chemical pattern formation

    DOEpatents

    Nosticzius, Zoltan; Horsthemke, Werner; McCormick, William D.; Swinney, Harry L.; Tam, Wing Y.

    1990-01-01

    The present invention is directed to an annular gel reactor suitable for the production and observation of spatiotemporal patterns created during a chemical reaction. The apparatus comprises a vessel having at least a first and second chamber separated one from the other by an annular polymer gel layer (or other fine porous medium) which is inert to the materials to be reacted but capable of allowing diffusion of the chemicals into it.

  10. Adaptive optics scanning ophthalmoscopy with annular pupils

    PubMed Central

    Sulai, Yusufu N.; Dubra, Alfredo

    2012-01-01

    Annular apodization of the illumination and/or imaging pupils of an adaptive optics scanning light ophthalmoscope (AOSLO) for improving transverse resolution was evaluated using three different normalized inner radii (0.26, 0.39 and 0.52). In vivo imaging of the human photoreceptor mosaic at 0.5 and 10° from fixation indicates that the use of an annular illumination pupil and a circular imaging pupil provides the most benefit of all configurations when using a one Airy disk diameter pinhole, in agreement with the paraxial confocal microscopy theory. Annular illumination pupils with 0.26 and 0.39 normalized inner radii performed best in terms of the narrowing of the autocorrelation central lobe (between 7 and 12%), and the increase in manual and automated photoreceptor counts (8 to 20% more cones and 11 to 29% more rods). It was observed that the use of annular pupils with large inner radii can result in multi-modal cone photoreceptor intensity profiles. The effect of the annular masks on the average photoreceptor intensity is consistent with the Stiles-Crawford effect (SCE). This indicates that combinations of images of the same photoreceptors with different apodization configurations and/or annular masks can be used to distinguish cones from rods, even when the former have complex multi-modal intensity profiles. In addition to narrowing the point spread function transversally, the use of annular apodizing masks also elongates it axially, a fact that can be used for extending the depth of focus of techniques such as adaptive optics optical coherence tomography (AOOCT). Finally, the positive results from this work suggest that annular pupil apodization could be used in refractive or catadioptric adaptive optics ophthalmoscopes to mitigate undesired back-reflections. PMID:22808435