Bubble shape in horizontal and near horizontal intermittent flow

International Nuclear Information System (INIS)

Gu, Hanyang; Guo, Liejin

2015-01-01

Highlights: • The bubble shapes in intermittent flows are presented experimentally. • The nose-tail inversion phenomenon appears at a low Froude number in downward pipe. • Transition from plug to slug flow occurs when the bubble tail changes from staircase pattern to hydraulic jump. - Abstract: This paper presents an experimental study of the shape of isolated bubbles in horizontal and near horizontal intermittent flows. It is found that the shapes of the nose and body of bubble depend on the Froude number defined by gas/liquid mixture velocity in a pipe, whereas the shape of the back of bubble region depends on both the Froude number and bubble length. The photographic studies show that the transition from plug to slug flow occurs when the back of the bubble changes from staircase pattern to hydraulic jump with the increase of the Froude number and bubble length. The effect of pipe inclination on characteristics of bubble is significant: The bubble is inversely located in a downwardly inclined pipe when the Froude number is low, and the transition from plug flow to slug flow in an upward inclined pipe is more ready to occur compared with that in a downwardly inclined pipe

Wire-mesh sensor, ultrasound and high-speed videometry applied for the characterization of horizontal gas-liquid slug flow

Science.gov (United States)

Ofuchi, C. Y.; Morales, R. E. M.; Arruda, L. V. R.; Neves, F., Jr.; Dorini, L.; do Amaral, C. E. F.; da Silva, M. J.

2012-03-01

Gas-liquid flows occur in a broad range of industrial applications, for instance in chemical, petrochemical and nuclear industries. Correct understating of flow behavior is crucial for safe and optimized operation of equipments and processes. Thus, measurement of gas-liquid flow plays an important role. Many techniques have been proposed and applied to analyze two-phase flows so far. In this experimental research, data from a wire-mesh sensor, an ultrasound technique and high-speed camera are used to study two-phase slug flows in horizontal pipes. The experiments were performed in an experimental two-phase flow loop which comprises a horizontal acrylic pipe of 26 mm internal diameter and 9 m length. Water and air were used to produce the two-phase flow and their flow rates are separately controlled to produce different flow conditions. As a parameter of choice, translational velocity of air bubbles was determined by each of the techniques and comparatively evaluated along with a mechanistic flow model. Results obtained show good agreement among all techniques. The visualization of flow obtained by the different techniques is also presented.

Cellular properties of slug flow in vertical co-current gas-liquid flow: slug-churn transition

International Nuclear Information System (INIS)

Lusseyran, Francois

1990-01-01

This research thesis reports the study and description of the structure of a slug flow regime in a co-current vertical cylindrical duct, and the characterization and prediction of its transition towards a slug-churn (de-structured) regime. Flow physical mechanisms highlighted by the measurement of two important dynamics variables (wall friction and thickness of liquid films) are related to hypotheses of cellular models. The author first proposes an overview of slug flow regimes: theoretical steady and one-dimensional analysis, mass assessment equations of cellular models, application to the assessment of the flow rate and of the thickness of the film surrounding the gas slug. In the second part, the author addresses the slug flow regime transition towards the slug-churn regime: assessment of the evolution of flow dynamic properties, use of average wall friction analysis to obtain a relevant transition criterion. The third part presents experimental conditions, and measurement methods: conductometry for thickness measurement, polarography for wall friction measurement, and gas phase detection by using an optic barrier or optic fibres [fr

Direct contact condensation induced transition from stratified to slug flow

International Nuclear Information System (INIS)

Strubelj, Luka; Ezsoel, Gyoergy; Tiselj, Iztok

2010-01-01

Selected condensation-induced water hammer experiments performed on PMK-2 device were numerically modelled with three-dimensional two-fluid models of computer codes NEPTUNE C FD and CFX. Experimental setup consists of the horizontal pipe filled with the hot steam that is being slowly flooded with cold water. In most of the experimental cases, slow flooding of the pipe was abruptly interrupted by a strong slugging and water hammer, while in the selected experimental runs performed at higher initial pressures and temperatures that are analysed in the present work, the transition from the stratified into the slug flow was not accompanied by the water hammer pressure peak. That makes these cases more suitable tests for evaluation of the various condensation models in the horizontally stratified flows and puts them in the range of the available CFD (Computational Fluid Dynamics) codes. The key models for successful simulation appear to be the condensation model of the hot vapour on the cold liquid and the interfacial momentum transfer model. The surface renewal types of condensation correlations, developed for condensation in the stratified flows, were used in the simulations and were applied also in the regions of the slug flow. The 'large interface' model for inter-phase momentum transfer model was compared to the bubble drag model. The CFD simulations quantitatively captured the main phenomena of the experiments, while the stochastic nature of the particular condensation-induced water hammer experiments did not allow detailed prediction of the time and position of the slug formation in the pipe. We have clearly shown that even the selected experiments without water hammer present a tough test for the applied CFD codes, while modelling of the water hammer pressure peaks in two-phase flow, being a strongly compressible flow phenomena, is beyond the capability of the current CFD codes.

Experimental characterization of solid particle transport by slug flow using Particle Image Velocimetry

International Nuclear Information System (INIS)

Goharzadeh, A; Rodgers, P

2009-01-01

This paper presents an experimental study of gas-liquid slug flow on solid particle transport inside a horizontal pipe with two types of experiments conducted. The influence of slug length on solid particle transportation is characterized using high speed photography. Using combined Particle Image Velocimetry (PIV) with Refractive Index Matching (RIM) and fluorescent tracers (two-phase oil-air loop) the velocity distribution inside the slug body is measured. Combining these experimental analyses, an insight is provided into the physical mechanism of solid particle transportation due to slug flow. It was observed that the slug body significantly influences solid particle mobility. The physical mechanism of solid particle transportation was found to be discontinuous. The inactive region (in terms of solid particle transport) upstream of the slug nose was quantified as a function of gas-liquid composition and solid particle size. Measured velocity distributions showed a significant drop in velocity magnitude immediately upstream of the slug nose and therefore the critical velocity for solid particle lifting is reached further upstream.

Characterization of horizontal air–water two-phase flow

Energy Technology Data Exchange (ETDEWEB)

Kong, Ran; Kim, Seungjin, E-mail: skim@psu.edu

2017-02-15

Highlights: • A visualization study is performed to develop flow regime map in horizontal flow. • Database in horizontal bubbly flow is extended using a local conductivity probe. • Frictional pressure drop analysis is performed in horizontal bubbly flow. • Drift flux analysis is performed in horizontal bubbly flow. - Abstract: This paper presents experimental studies performed to characterize horizontal air–water two-phase flow in a round pipe with an inner diameter of 3.81 cm. A detailed flow visualization study is performed using a high-speed video camera in a wide range of two-phase flow conditions to verify previous flow regime maps. Two-phase flows are classified into bubbly, plug, slug, stratified, stratified-wavy, and annular flow regimes. While the transition boundaries identified in the present study compare well with the existing ones (Mandhane et al., 1974) in general, some discrepancies are observed for bubbly-to-plug/slug, and plug-to-slug transition boundaries. Based on the new transition boundaries, three additional test conditions are determined in horizontal bubbly flow to extend the database by Talley et al. (2015a). Various local two-phase flow parameters including void fraction, interfacial area concentration, bubble velocity, and bubble Sauter mean diameter are obtained. The effects of increasing gas flow rate on void fraction, bubble Sauter mean diameter, and bubble velocity are discussed. Bubbles begin to coalesce near the gas–liquid layer instead of in the highly packed region when gas flow rate increases. Using all the current experimental data, two-phase frictional pressure loss analysis is performed using the Lockhart–Martinelli method. It is found that the coefficient C = 24 yields the best agreement with the data with the minimum average difference. Moreover, drift flux analysis is performed to predict void-weighted area-averaged bubble velocity and area-averaged void fraction. Based on the current database, functional

Influence of the initial conditions for the numerical simulation of two-phase slug flow

Energy Technology Data Exchange (ETDEWEB)

Pachas Napa, Alex A.; Morales, Rigoberto E.M.; Medina, Cesar D. Perea

2010-07-01

Multiphase flows in pipelines commonly show several patterns depending on the flow rate, geometry and physical properties of the phases. In oil production, the slug flow pattern is the most common among the others. This flow pattern is characterized by an intermittent succession in space and time of an aerated liquid slug and an elongated gas bubble with a liquid film. Slug flow is studied through the slug tracking model described as one-dimensional and Lagrangian frame referenced. In the model, the mass and the momentum balance equations are applied in control volumes constituted by the gas bubble and the liquid slug. Initial conditions must be determined, which need to reproduce the intermittence of the flow pattern. These initial conditions are given by a sequence of flow properties for each unit cell. Properties of the unit cell in initial conditions should reflect the intermittence, for which they can be analyzed in statistical terms. Therefore, statistical distributions should be obtained for the slug flow variables. Distributions are complemented with the mass balance and the bubble design model. The objective of the present work is to obtain initial conditions for the slug tracking model that reproduce a better adjustment of the fluctuating properties for different pipe inclinations (horizontal, vertical or inclined). The numerical results are compared with experimental data obtained by PFG/FEM/UNICAMP for air-water flow at 0 deg, 45 deg and 90 deg and good agreement is observed. (author)

Investigation of vertical slug flow with advanced two-phase flow instrumentation

International Nuclear Information System (INIS)

Mi, Y.; Ishii, M.; Tsoukalas, L.H.

2001-01-01

Extensive experiments of vertical slug flow were carried out with an electromagnetic flowmeter and an impedance void-meter in an air-water two-phase experimental loop. The basic principles of these instruments in vertical slug flow measurements are discussed. Time series of the liquid velocity and the impedance were separated into two parts corresponding to the Taylor bubble and the liquid slug. Characteristics of slug flow, such as the void fractions, probabilities and lengths of the Taylor bubble and liquid slug, slug unit velocity, area-averaged liquid velocity, and liquid film velocity of the Taylor bubble tail, etc., were obtained. For the first time, the area-averaged liquid velocity of slug flow was revealed by the electromagnetic flowmeter. It is realized that the void fraction of the liquid slug is determined by the turbulent intensity due to the relative liquid motion between the Taylor bubble tail region and its wake region. A correlation of the void fraction of the liquid slug is developed based on experimental results obtained from a test section with 50.8 mm i.d. The results of this study suggest a promising improvement in understanding of vertical slug flow

Modeling of two-phase slug flow

International Nuclear Information System (INIS)

Fabre, J.; Line, A.

1992-01-01

When gas and liquid flow in a pipe, over a range of flow rates, a flow pattern results in which sequences of long bubbles, almost filling the pipe cross section, are successively followed by liquid slugs that may contain small bubbles. This flow pattern, usually called slug flow, is encountered in numerous practical situations, such as in the production of hydrocarbons in wells and their transportation in pipelines; the production of steam and water in geothermal power plants; the boiling and condensation in liquid-vapor systems of thermal power plants; emergency core cooling of nuclear reactors; heat and mass transfer between gas and liquid in chemical reactors. This paper provides a review of two phase slug flow modeling

Slug flooding in air-water countercurrent vertical flow

International Nuclear Information System (INIS)

Lee, Jae Young; Raman, Roger; Chang, Jen-Shih

2000-01-01

This paper is to study slug flooding in the vertical air-water countercurrent flow loop with a porous liquid injector in the upper plenum. More water penetration into the bottom plenum in slug flooding is observed than the annular flooding because the flow regime changes from the slug flow regime or periodic slug/annular flow regime to annular flow regime due to the hysteresis between the onset of flooding and the bridging film. Experiments were made tubes of 0.995 cm, 2.07 cm, and 5.08 cm in diameter. A mechanistic model for the slug flooding with the solitary wave whose height is four time of the mean film thickness is developed to produce relations of the critical liquid flow rate and the mean film thickness. After fitting the critical liquid flow rate with the experimental data as a function of the Bond number, the gas flow rate for the slug flooding is obtained by substituting the critical liquid flow rate to the annular flooding criteria. The present experimental data evaluate the slug flooding condition developed here by substituting the correlations for mean film thickness models in the literature. The best prediction was made by the correlation for the mean film thickness of the present study which is same as Feind's correlation multiplied by 1.35. (author)

Wire-mesh and ultrasound techniques applied for the characterization of gas-liquid slug flow

Energy Technology Data Exchange (ETDEWEB)

Ofuchi, Cesar Y.; Sieczkowski, Wytila Chagas; Neves Junior, Flavio; Arruda, Lucia V.R.; Morales, Rigoberto E.M.; Amaral, Carlos E.F.; Silva, Marco J. da [Federal University of Technology of Parana, Curitiba, PR (Brazil)], e-mails: ofuchi@utfpr.edu.br, wytila@utfpr.edu.br, neves@utfpr.edu.br, lvrarruda@utfpr.edu.br, rmorales@utfpr.edu.br, camaral@utfpr.edu.br, mdasilva@utfpr.edu.br

2010-07-01

Gas-liquid two-phase flows are found in a broad range of industrial applications, such as chemical, petrochemical and nuclear industries and quite often determine the efficiency and safety of process and plants. Several experimental techniques have been proposed and applied to measure and quantify two-phase flows so far. In this experimental study the wire-mesh sensor and an ultrasound technique are used and comparatively evaluated to study two-phase slug flows in horizontal pipes. The wire-mesh is an imaging technique and thus appropriated for scientific studies while ultrasound-based technique is robust and non-intrusive and hence well suited for industrial applications. Based on the measured raw data it is possible to extract some specific slug flow parameters of interest such as mean void fraction and characteristic frequency. The experiments were performed in the Thermal Sciences Laboratory (LACIT) at UTFPR, Brazil, in which an experimental two-phase flow loop is available. The experimental flow loop comprises a horizontal acrylic pipe of 26 mm diameter and 9 m length. Water and air were used to produce the two phase flow under controlled conditions. The results show good agreement between the techniques. (author)

Online recognition of the multiphase flow regime and study of slug flow in pipeline

International Nuclear Information System (INIS)

Guo Liejin; Bai Bofeng; Zhao Liang; Wang Xin; Gu Hanyang

2009-01-01

sensor performance. Among various flow patterns of gas-liquid flow, slug flow occurs frequently in the petroleum, chemical, civil and nuclear industries. In the offshore oil and gas field, the maximum slug length and its statistical distribution are very important for the design of separator and downstream processing facility at steady state operations. However transient conditions may be encountered in the production, such as operational upsets, start-up, shut-down, pigging and blowdown, which are key operational and safety issues related to oil field development. So it is necessary to have an understanding the flow parameters under transient conditions. In this paper, the evolution of slug length along a horizontal pipe in gas-liquid flow is also studied in details and then an experimental study of flowrate transients in slug flow is provided. Also, the special gas-liquid flow phenomena easily encountered in the life span of offshore oil fields, called severe slugging, is studied experimentally and some results are presented.

Influence of vapor phase turbulent stress to the onset of slugging in a horizontal pipe

International Nuclear Information System (INIS)

Park, Jee Won

1995-01-01

An influence of the vapor phase turbulent stress(i, e., the two-phase Reynolds stress)to the characteristics of two-phase system in a horizontal pipe has been theoretically investigated. The average two-fluid model has been constituted with closure relations for stratified flow in a horizontal pipe. A vapor phase turbulent stress model for the regular interface geometry has been included. It is found that the second order waves propagate in opposite direction with almost the same speed in the moving frame of reference of the liquid phase velocity. Using the well-posedness limit of the two-phase system, the dispersed-stratified flow regime boundary has been modeled. Two-phase Froude number has been found to be a convenient parameter in quantifying the onset of slugging as a function of the global void fraction. The influence of the vapor phase turbulent stress was found to stabilize the flow stratification. 4 figs., 12 refs. (Author)

Multiphase flow measurement in the slug regime using ultrasonic measurement techniques and slug closure model

OpenAIRE

Al-lababidi , Salem

2006-01-01

Multiphase flow in the oil and gas industry covers a wide range of flows. Thus, over the last decade, the investigation, development and use of multiphase flow metering system have been a major focus for the industry worldwide. However, these meters do not perform well in slug flow conditions. The present work involves experimental investigations of multiphase flow measurement under slug flow conditions. A two-phase gas/liquid facility was designed and constructed at Cranfie...

Modeling the scooping phenomenon for the heat transfer in liquid–gas horizontal slug flows

International Nuclear Information System (INIS)

Bassani, Carlos L.; Pereira, Fernando H.G.; Barbuto, Fausto A.A.; Morales, Rigoberto E.M.

2016-01-01

Highlights: • A low computational tool for heat transfer prediction on slug flows is presented. • The scooping phenomenon is modeled on a stationary approach. • The scooping phenomenon improved in 8% the heat transfer results. - Abstract: The heat transfer between the deep sea waters and the oil and gas mixtures flowing through production lines is a common situation in the petroleum industry. The optimum prediction of the liquid–gas flow parameters along those lines, when the intermittent flow pattern known as slug flow is dominant, has extreme importance in facilities' design. The mixture temperature drop caused by the colder sea waters, which can be regarded as an infinite medium with constant temperature, directly affects physical properties of the fluids such as the viscosity and specific mass. Gas expansion may also occur due to pressure and temperature gradients, thus changing the flow hydrodynamics. Finally, the temperature gradient affects the thermodynamic equilibrium between the phases, favoring wax deposition and thus increasing pressure drops or even blocking the production line. With those issues in mind, the present work proposes a stationary model to predict the mixture temperature distribution and the two-phase flow heat transfer coefficient based on the mass, momentum and energy conservation equations applied to different unit cell regions. The main contribution of the present work is the modeling of the thermal scooping phenomenon, i.e., the heat transfer between two adjacent unit cells due to the mass flux known as scooping. The model was implemented as a structured Fortran95 code with an upwind difference scheme. The results were compared to experimental data and presented good agreement. The analysis showed that the inclusion of the scooping phenomenon into the model resulted in an averaged 8% improvement in the temperature gradient calculation and heat transfer coefficient prediction for the flowing mixture.

Theoretical investigation of flow regime for boiling water two-phase flow in horizontal rectangular narrow channels

International Nuclear Information System (INIS)

Zhang Chunwei; Qiu Suizheng; Yan Mingyu; Wang Bulei; Nie Changhua

2005-01-01

The flow regime transition criteria for the boiling water two-phase flow in horizontal rectangular narrow channels (1 x 20 mm, 2 x 20 mm) were theoretically explored. The discernible flow patterns were bubble, intermittent slug, churn, annular and steam-water separation flow. By using two-fluid model, equations of conservation of momentum were established for the two-phase flow. New flow-regime criteria were obtained and agreed well with the experiment data. (authors)

Slug Flow Analysis in Vertical Large Diameter Pipes

Science.gov (United States)

Roullier, David

The existence of slug flow in vertical co-current two-phase flow is studied experimentally and theoretically. The existence of slug flow in vertical direction implies the presence of Taylor bubbles separated by hydraulically sealed liquid slugs. Previous experimental studies such as Ombere-Ayari and Azzopardi (2007) showed the evidence of the non-existence of Taylor bubbles for extensive experimental conditions. Models developed to predict experimental behavior [Kocamustafaogullari et al. (1984), Jayanti and Hewitt. (1990) and Kjoolas et al. (2017)] suggest that Taylor bubbles may disappear at large diameters and high velocities. A 73-ft tall and 101.6-mm internal diameter test facility was used to conduct the experiments allowing holdup and pressure drop measurements at large L/D. Superficial liquid and gas velocities varied from 0.05-m/s to 0.2 m/s and 0.07 m/s to 7.5 m/s, respectively. Test section pressure varied from 38 psia to 84 psia. Gas compressibility effect was greatly reduced at 84 psia. The experimental program allowed to observe the flow patterns for flowing conditions near critical conditions predicted by previous models (air-water, 1016 mm ID, low mixture velocities). Flow patterns were observed in detail using wire-mesh sensor measurements. Slug-flow was observed for a narrow range of experimental conditions at low velocities. Churn-slug and churn-annular flows were observed for most of the experimental data-points. Cap-bubble flow was observed instead of bubbly flow at low vSg. Wire-mesh measurements showed that the liquid has a tendency to remain near to the walls. The standard deviation of radial holdup profile correlates to the flow pattern observed. For churn-slug flow, the profile is convex with a single maximum near the pipe center while it exhibits a concave shape with two symmetric maxima close to the wall for churn-annular flow. The translational velocity was measured by two consecutive wire-mesh sensor crosscorrelation. The results show

Hydrodynamics of slug flow in a vertical narrow rectangular channel under laminar flow condition

International Nuclear Information System (INIS)

Wang, Yang; Yan, Changqi; Cao, Xiaxin; Sun, Licheng; Yan, Chaoxing; Tian, Qiwei

2014-01-01

Highlights: • Slug flow hydrodynamics in a vertical narrow rectangular duct were investigated. • The velocity of trailing Taylor bubble undisturbed by the leading one was measured. • Correlation of Taylor bubble velocity with liquid slug length ahead it was proposed. • Evolution of length distributions of Taylor bubble and liquid slug was measured. • The model of predicted length distributions was applied to the rectangular channel. - Abstract: The hydrodynamics of gas–liquid two-phase slug flow in a vertical narrow rectangular channel with the cross section of 2.2 mm × 43 mm is investigated using a high speed video camera system. Simultaneous measurements of velocity and duration of Taylor bubble and liquid slug made it possible to determine the length distributions of the liquid slug and Taylor bubble. Taylor bubble velocity is dependent on the length of the liquid slug ahead, and an empirical correlation is proposed based on the experimental data. The length distributions of Taylor bubbles and liquid slugs are positively skewed (log-normal distribution) at all measuring positions for all flow conditions. A modified model based on that for circular tubes is adapted to predict the length distributions in the present narrow rectangular channel. In general, the experimental data is well predicted by the modified model

Stratified flow instability and slug formation leading to condensation-induced water hammer in a horizontal refrigerant pipe

International Nuclear Information System (INIS)

Samuel Martin, C.

2005-01-01

Full text of publication follows: An experimental apparatus was designed for the purpose of investigating the phenomenon of condensation-induced water hammer in an ammonia refrigeration system. Water hammer was initiated by introducing warm ammonia gas over static subcooled ammonia liquid placed in a horizontal 146.3 mm diameter carbon steel pipe 6.0 m in length. By means of fast response piezoelectric pressure transducers and a high speed data acquisition system rapid dynamic pressures were recorded whenever a shock event occurred. Moreover, by means of top-mounted diaphragm pressure transducers the speed of liquid slugs propagating along the pipe was determined. The occurrence of condensation induced water hammer depended upon three major variables; namely, (1) initial liquid depth, (2) liquid temperature, and (3) mass flow rate of warm gas. For given liquid depth and temperature, once the warm gas threshold conditions were exceeded shocks occurred with greater magnitude as the mass flow rate of gas input was increased. With adequate subcooling condensation-induced water hammer occurred for initial liquid depths ranging from 25% to 95% of internal pipe diameter. The threshold mass flow rate of warm gas necessary to initiate water hammer was greater as the initial liquid depth was lowered. Based upon experimental results obtained from four pressure transducers located on the top of the test pipe conditions corresponding to bridging were ascertained. For various initial liquid depths the onset of instability from stratified flow to bridging was correlated with the Taitel-Dukler instability criterion. (author)

A study on the instability criterion for the stratified flow in horizontal pipe at cocurrent flow conditions

Energy Technology Data Exchange (ETDEWEB)

Sung, Chang Kyung [Korea Electric Power Research Institute, Taejon (Korea, Republic of)

1998-12-31

This paper presents a theoretical approach of the instability criterion from stratified to nonstratified flow in horizontal pipe at cocurrent flow conditions. The new theoretical instability criterion for the stratified and nonstratified flow transition in horizontal pipe has been developed by hyperbolic equations in two-phase flow. Critical flow condition criterion and onset of slugging at cocurrent flow condition correspond to zero and imaginary characteristics which occur when the hyperbolicity of a stratified two-phase flow is broken, respectively. Through comparison between results predicted by the present flow is broken, respectively. Through comparison between results predicted by the present theory and the Kukita et al. [1] experimental data of pipes, it is shown that they are in good agreement with data. 4 refs., 2 figs. (Author)

A study on the instability criterion for the stratified flow in horizontal pipe at cocurrent flow conditions

Energy Technology Data Exchange (ETDEWEB)

Sung, Chang Kyung [Korea Electric Power Research Institute, Taejon (Korea, Republic of)

1997-12-31

This paper presents a theoretical approach of the instability criterion from stratified to nonstratified flow in horizontal pipe at cocurrent flow conditions. The new theoretical instability criterion for the stratified and nonstratified flow transition in horizontal pipe has been developed by hyperbolic equations in two-phase flow. Critical flow condition criterion and onset of slugging at cocurrent flow condition correspond to zero and imaginary characteristics which occur when the hyperbolicity of a stratified two-phase flow is broken, respectively. Through comparison between results predicted by the present flow is broken, respectively. Through comparison between results predicted by the present theory and the Kukita et al. [1] experimental data of pipes, it is shown that they are in good agreement with data. 4 refs., 2 figs. (Author)

Quasi-3D Modelling of Two-Phase Slug Flow in Pipes

Directory of Open Access Journals (Sweden)

S. Mo

2014-03-01

Full Text Available In this paper, we present progress obtained by the Quasi 3-Dimensional (Q3D model for pipe flows. This model is based on a multi-fluid multi-field formulation with construction and tracking of the large-scale interfaces (LSIs. The computational time is significantly reduced compared to full 3D by using a specially adopted slice-averaging technique. However, the slice-averaging generates new terms in the model equations. These terms are related to important mechanisms such as wall shear stress and turbulence production at side walls. We present some basic performance tests of the Q3D model, including single phase wall friction and the velocities of single Taylor bubbles at inclinations ranging from horizontal to vertical. Finally we report the performance of the model for slug flow in horizontal and 10° inclined pipes. The model reproduces the experimental data satisfactorily for both cases in a very short simulation time compared to full 3D.

Experimental investigation and CFD simulation of horizontal stratified two-phase flow phenomena

International Nuclear Information System (INIS)

Vallee, Christophe; Hoehne, Thomas; Prasser, Horst-Michael; Suehnel, Tobias

2008-01-01

For the investigation of stratified two-phase flow, two horizontal channels with rectangular cross-section were built at Forschungszentrum Dresden-Rossendorf (FZD). The channels allow the investigation of air/water co-current flows, especially the slug behaviour, at atmospheric pressure and room temperature. The test-sections are made of acrylic glass, so that optical techniques, like high-speed video observation or particle image velocimetry (PIV), can be applied for measurements. The rectangular cross-section was chosen to provide better observation possibilities. Moreover, dynamic pressure measurements were performed and synchronised with the high-speed camera system. CFD post-test simulations of stratified flows were performed using the code ANSYS CFX. The Euler-Euler two fluid model with the free surface option was applied on grids of minimum 4 x 10 5 control volumes. The turbulence was modelled separately for each phase using the k-ω-based shear stress transport (SST) turbulence model. The results compare very well in terms of slug formation, velocity, and breaking. The qualitative agreement between calculation and experiment is encouraging and shows that CFD can be a useful tool in studying horizontal two-phase flow

Experimental investigation and CFD simulation of horizontal stratified two-phase flow phenomena

International Nuclear Information System (INIS)

Vallee, Christophe; Hohne, Thomas; Prasser, Horst-Michael; Suhnel, Tobias

2007-01-01

For the investigation of stratified two-phase flow, two horizontal channels with rectangular cross-section were built at Forschungszentrum Rossendorf. The channels allow the investigation of air/water co-current flows, especially the slug behaviour, at atmospheric pressure and room temperature. The test-sections are made of acrylic glass, so that optical techniques, like high-speed video observation or particle image velocimetry (PIV), can be applied for measurements. The rectangular cross-section was chosen to provide better observation possibilities. Moreover, dynamic pressure measurements were performed and synchronized with the high-speed camera system. CFD post test simulations of stratified flows were performed using the code ANSYS CFX. The Euler- Euler two fluid model with the free surface option was applied on grids of minimum 4.10 5 control volumes. The turbulence was modelled separately for each phase using the k-ω based shear stress transport (SST) turbulence model. The results compare very well in terms of slug formation, velocity, and breaking. The qualitative agreement between calculation and experiment is encouraging and shows that CFD can be a useful tool in studying horizontal two-phase flow. (authors)

Experimental investigation and CFD simulation of horizontal stratified two-phase flow phenomena

Energy Technology Data Exchange (ETDEWEB)

Vallee, Christophe [Forschungszentrum Dresden-Rossendorf e.V., Dresden (Germany)], E-mail: c.vallee@fzd.de; Hoehne, Thomas; Prasser, Horst-Michael; Suehnel, Tobias [Forschungszentrum Dresden-Rossendorf e.V., Dresden (Germany)

2008-03-15

For the investigation of stratified two-phase flow, two horizontal channels with rectangular cross-section were built at Forschungszentrum Dresden-Rossendorf (FZD). The channels allow the investigation of air/water co-current flows, especially the slug behaviour, at atmospheric pressure and room temperature. The test-sections are made of acrylic glass, so that optical techniques, like high-speed video observation or particle image velocimetry (PIV), can be applied for measurements. The rectangular cross-section was chosen to provide better observation possibilities. Moreover, dynamic pressure measurements were performed and synchronised with the high-speed camera system. CFD post-test simulations of stratified flows were performed using the code ANSYS CFX. The Euler-Euler two fluid model with the free surface option was applied on grids of minimum 4 x 10{sup 5} control volumes. The turbulence was modelled separately for each phase using the k-{omega}-based shear stress transport (SST) turbulence model. The results compare very well in terms of slug formation, velocity, and breaking. The qualitative agreement between calculation and experiment is encouraging and shows that CFD can be a useful tool in studying horizontal two-phase flow.

Two-phase flow and pressure drop in T-junctions with horizontal run and vertical branch

International Nuclear Information System (INIS)

Katsaounis, A.

1987-01-01

Visual observations of single- and two-phase dividing flow and pressure drop measurements were performed in T-junctions with horizontal run and vertical branch. Both tees used were geometrically similar, in a scale of 1:4. The measurements were performed for plug/slug and stratified flow pattern regime in horizontal tube. Based on the single-phase form-resistance pressure drop correlation of Gardel a corresponded calculation model was developed for the two-phase flow verified by the own measurements. (orig.) [de

Numerical simulation of two-phase slug flow with liquid carryover in different diameter ratio T-junction

Science.gov (United States)

Pao, W.; Hon, L.; Saieed, A.; Ban, S.

2017-10-01

A smaller diameter conduit pointing at 12 o’clock position is typically hot-tapped to a horizontal laying production header in offshore platform to tap produced gas for downstream process train. This geometric feature is commonly known as T-junction. The nature of multiphase fluid splitting at the T-junction is a major operational challenge due to unpredictable production environment. Often, excessive liquid carryover occurs in the T-junction, leading to complete platform trip and halt production. This is because the downstream process train is not designed to handle excessive liquid. The objective of this research is to quantify the effect of different diameter ratio on phase separation efficiency in T-junction. The liquid carryover is modelled as two-phase air-water flow using Eulerian Mixture Model coupled with Volume of Fluid Method to mimic the slug flow in the main pipe. The focus in this paper is 0.0254 m (1 inch) diameter horizontal main arm and vertical branch arm with diameter ratio of 1.0, 0.5 and 0.3. The present research narrowed the investigation to only slug flow regime using Baker’s map as reference. The investigation found that, contrary to common believe, smaller diameter ratio T-junction perform worse than larger diameter ratio T-junction.

Flow measurement in bubbly and slug flow regimes using the electromagnetic flowmeter developed

International Nuclear Information System (INIS)

Cha, Jae Eun; Ahn, Yeh Chan; Seo, Kyung Woo; Kim, Moo Hwan

2002-01-01

In order to investigate the characteristics of electromagnetic flowmeter in two-phase flow, an AC electromagnetic flowmeter was designed and manufactured. In various flow conditions, the signals and noises from the flowmeter were obtained and analyzed by comparison with the observed flow patterns with a high speed CCD camera. The experiment with the void simulators in which rod shaped non-conducting material was used was carried out to investigate the effect of the bubble position and the void fraction on the flowmeter. Based on the results from the void simulator, two-phase flow experiments encompassed from bubbly to slug flow regime were conducted. The simple relation ΔU TP = ΔU SP /(1-α) was verified with measurements of the potential difference and the void fraction. Due to the lack of homogeneity in a real two-phase flow, the discrepancy between the relation and the present measurement was slightly increased with void fraction and also liquid volumetric flux j f . Whereas there is no difference in the shape of the raw signal between single-phase flow and bubbly flow, the signal amplitude for bubbly flow is higher than that for single-phase flow at the same water flow rate, since the passage area of the water flow is reduced. In the case of slug flow, the phase and the amplitude of the flowmeter output show dramatically the flow characteristics around each slug bubble and the position of a slug bubble itself. Therefore, the electromagnetic flowmeter shows a good possibility of being useful for identifying the flow regimes

A test section design to simulate horizontal two-phase air-water flow

International Nuclear Information System (INIS)

Faccini, Jose Luiz H.; Cesar, Silvia B.G.; Coutinho, Jorge A.; Freitas, Sergio Carlos; Addor, Pedro N.

2002-01-01

In this work an air-water two-phase flow horizontal test section assembling at Nuclear Engineering Institute (IEN) is presented. The test section was designed to allow four-phase flow patterns to be simulated: bubble flow, stratified flow, wave flow and slug flow. These flow patterns will be identified by non-conventional ultrasonic techniques which have been developed to meet this particular application. Based on the separated flow and drift-flux models the test section design steps are shown. A description of the test section and its instrumentation and data acquisition system is also provided. (author)

Kinetics of gravity-driven slug flow in partially wettable capillaries of varying cross section

Science.gov (United States)

Nissan, Alon; Wang, Qiuling; Wallach, Rony

2016-11-01

A mathematical model for slug (finite liquid volume) motion in not-fully-wettable capillary tubes with sinusoidally varying cross-sectional areas was developed. The model, based on the Navier-Stokes equation, accounts for the full viscous terms due to nonuniform geometry, the inertial term, the slug's front and rear meniscus hysteresis effect, and dependence of contact angle on flow velocity (dynamic contact angle). The model includes a velocity-dependent film that is left behind the advancing slug, reducing its mass. The model was successfully verified experimentally by recording slug movement in uniform and sinusoidal capillary tubes with a gray-scale high-speed camera. Simulation showed that tube nonuniformity has a substantial effect on slug flow pattern: in a uniform tube it is monotonic and depends mainly on the slug's momentary mass/length; an undulating tube radius results in nonmonotonic flow characteristics. The static nonzero contact angle varies locally in nonuniform tubes owing to the additional effect of wall slope. Moreover, the nonuniform cross-sectional area induces slug acceleration, deceleration, blockage, and metastable-equilibrium locations. Increasing contact angle further amplifies the geometry effect on slug propagation. The developed model provides a modified means of emulating slug flow in differently wettable porous media for intermittent inlet water supply (e.g., raindrops on the soil surface).

Heat transfer to air-water two-phase flow in slug/churn region

International Nuclear Information System (INIS)

Wadekar, V.V.; Tuzla, K.; Chen, J.C.

1996-01-01

Measured heat transfer data for air-water two-phase flow in the slug/churn flow region are reported. The measurements were obtained from a 1.3 m tall, 15.7 mm diameter vertical tube test-section. It is observed that the data exhibit different heat transfer characteristics to those predicted by the standard correlations for the convective component of flow boiling heat transfer. Comparison with the predictions of a slug flow model for evaporation shows a significant overprediction of the data. The reason for the overprediction is attributed to the sensible heating requirement of the gas phase. The slug flow model is therefore suitably modified for non-evaporating two-phase flow. This specially adapted model is found to give reasonably good predictions of the measured data

A conservative fully implicit algorithm for predicting slug flows

Science.gov (United States)

Krasnopolsky, Boris I.; Lukyanov, Alexander A.

2018-02-01

An accurate and predictive modelling of slug flows is required by many industries (e.g., oil and gas, nuclear engineering, chemical engineering) to prevent undesired events potentially leading to serious environmental accidents. For example, the hydrodynamic and terrain-induced slugging leads to unwanted unsteady flow conditions. This demands the development of fast and robust numerical techniques for predicting slug flows. The presented in this paper study proposes a multi-fluid model and its implementation method accounting for phase appearance and disappearance. The numerical modelling of phase appearance and disappearance presents a complex numerical challenge for all multi-component and multi-fluid models. Numerical challenges arise from the singular systems of equations when some phases are absent and from the solution discontinuity when some phases appear or disappear. This paper provides a flexible and robust solution to these issues. A fully implicit formulation described in this work enables to efficiently solve governing fluid flow equations. The proposed numerical method provides a modelling capability of phase appearance and disappearance processes, which is based on switching procedure between various sets of governing equations. These sets of equations are constructed using information about the number of phases present in the computational domain. The proposed scheme does not require an explicit truncation of solutions leading to a conservative scheme for mass and linear momentum. A transient two-fluid model is used to verify and validate the proposed algorithm for conditions of hydrodynamic and terrain-induced slug flow regimes. The developed modelling capabilities allow to predict all the major features of the experimental data, and are in a good quantitative agreement with them.

Statistical criterion for Bubbly-slug flow transition

Energy Technology Data Exchange (ETDEWEB)

Zigler, J; Elias, E [Technion-Israel Inst. of Tech., Haifa (Israel). Dept. of Mechanical Engineering

1996-12-01

The investigation of flow pattern transitions is still an interesting problem in the research of multiphase Row. It has been studied theoretically, and experimental confirmation of the models has been found by many investigators. The present paper deals with a statistical approach to bubbly-slug transitions in a vertical upward two phase flow and a new transition criterion is deduced from experimental data (authors).

Dynamics of a two-phase flow through a minichannel: Transition from churn to slug flow

Science.gov (United States)

Górski, Grzegorz; Litak, Grzegorz; Mosdorf, Romuald; Rysak, Andrzej

2016-04-01

The churn-to-slug flow bifurcations of two-phase (air-water) flow patterns in a 2mm diameter minichannel were investigated. With increasing a water flow rate, we observed the transition of slugs to bubbles of different sizes. The process was recorded by a digital camera. The sequences of light transmission time series were recorded by a laser-phototransistor sensor, and then analyzed using the recurrence plots and recurrence quantification analysis (RQA). Due to volume dependence of bubbles velocities, we observed the formation of periodic modulations in the laser signal.

Flow near the meniscus of a pressure-driven water slug in microchannels

International Nuclear Information System (INIS)

Kim, Sung Wook; Jin, Song Wan; Yoo, Jung Yul

2006-01-01

Micro-PIV system with a high speed CCD camera is used to measure the flow field near the advancing meniscus of a water slug in microchannels. Image shifting technique combined with meniscus detecting technique is proposed to measure the relative velocity of the liquid near the meniscus in a moving reference frame. The proposed method is applied to an advancing front of a slug in microchannels with rectangular cross section. In the case of hydrophilic channel, strong flow from the center to the side wall along the meniscus occurs, while in the case of the hydrophobic channel, the fluid flows in the opposite direction. Further, the velocity near the side wall is higher than the center region velocity, exhibiting the characteristics of a strong shear-driven flow. This phenomenon is explained to be due to the existence of small gaps between the slug and the channel wall at each capillary corner so that the gas flows through the gaps inducing high shear on the slug surface. Simulation of the shape of a static droplet inside a cubic cell obtained by using the Surface Evolver program is supportive of the existence of the gap at the rectangular capillary corners. The flow fields in the circular capillary, in which no such gap exists, are also measured. The results show that a similar flow pattern to that of the hydrophilic rectangular capillary (i.e., center-to-wall flow) is always exhibited regardless of the wettability of the channel wall, which is also indicative of the validity of the above-mentioned assertion

Recreating Riser Slugging Flow Based on an Economic Lab-sized Setup

DEFF Research Database (Denmark)

Hansen, Lasse; Pedersen, Simon; Yang, Zhenyu

2013-01-01

As a kind of periodic phenomenon, the slugging flow in the offshore oil & gas production addresses a lot of attentions, due to its limitation of production rate, periodic overload processing facilities, and even direct cause of emergent shutdown. This work studies the emulation of the riser...... slugging flow in the offshore oil & gas production, by constructing an economical lab-sized setup in the university campus. Firstly, the construction and used components for the lab setup are illustrated; then, the constructed setup is validated by checking the consistency with some existing typical riser...

Numerical analysis of water hammer induced by injection of subcooled water into steam flow in a horizontal pipe

International Nuclear Information System (INIS)

Minato, Akihiko; Nagoyoshi, Takuji; Nakamura, Akira; Fujii, Yuzo; Aya, Izuo; Yamane, Kenji

2004-01-01

Subcooled water injection into steam flow in piping systems may generate a water column containing a large steam slug. The steam slug collapses due to rapid condensation and interfaces on both sides collides with each other. Water hammer takes place and sharp pressure pulse propagates through the pipe. The purpose of this study is to show capability of the present numerical simulation method for predictions of pressure transient and loads on a piping system following steam slug collapse. A three-dimensional computer code for transient gas-liquid two-phase flow was applied to simulate an experiment of steam-condensation-induced water hammer with a horizontal polycarbonate pipe. The code was based on the extended two-fluid model, which treated interface motion using the VOF (Volume of Fluid) technique. The Godunov scheme of highly compressible single-phase flow was modified for application to the Riemann problem solution of gas-liquid mixture. Analysis of local steam slug collapse resulted in comparable peak pressure and pulse width of pressure transients with the observation. The calculation of pressure pulse propagation and impact load on piping system showed the quasi-steady pressure load was imposed especially on elbow at 1/10 of water hammer peak pressure. (author)

Aldolase catalyzed L-phenylserine synthesis in a slug-flow microfluidic system - Performance and diastereoselectivity studies

NARCIS (Netherlands)

Čech, J.; Hessel, V.; Přibyl, M.

2017-01-01

We study synthesis of . L-phenylserine catalyzed by the enzyme . L-threonine aldolase in a slug-flow microfluidic system. Slug-flow arrangement allows for the continuous refilling of sparingly soluble substrate (benzaldehyde) into an aqueous reaction mixture. We identified suitable composition of an

Two-fluid model for transient analysis of slug flow in oil wells

International Nuclear Information System (INIS)

Cazarez-Candia, O.; Benitez-Centeno, O.C.; Espinosa-Paredes, G.

2011-01-01

In this work it is presented a transient, one-dimensional, adiabatic model for slug flow simulation, which appears when liquid (mixture of oil and water) and gas flow simultaneously through pipes. The model is formed by space and time averaged conservation equations for mass, momentum and energy for each phase, the numerical solution is based on the finite difference technique in the implicit scheme. Velocity, pressure, volumetric fraction and temperature profiles for both phases were predicted for inclination angles from the horizontal to the vertical position (unified model) and ascendant flow. Predictions from the model were validated using field data and ten correlations commonly used in the oil industry. The effects of gas heating or cooling, due to compression and expansion processes, on the predictions and numerical stability, were studied. It was found that when these effects are taken into account, a good behavior of temperature predictions and numerical stability are obtained. The model presents deviations lower than 14% regarding field data and it presents better predictions than most of the correlations.

Two-fluid model for transient analysis of slug flow in oil wells

Energy Technology Data Exchange (ETDEWEB)

Cazarez-Candia, O., E-mail: ocazarez@imp.mx [Instituto Mexicano del Petroleo, Eje central Lazaro Cardenas No. 152, Col. San Bartolo Atepehuacan, Mexico D.F. 07730 (Mexico); Instituto Tecnologico de Zacatepec, Depto. de Metal-Mecanica, Calzada Tecnologico, No. 27, Zacatepec, Morelos 62780 (Mexico); Benitez-Centeno, O.C. [Centro Nacional de Investigacion y Desarrollo Tecnologico, Depto. de Mecanica, Interior Internado Palmira s/n, Col. Palmira, Cuernavaca, Morelos 62490 (Mexico); Espinosa-Paredes, G. [Area de Ingenieria en Recursos Energeticos, Universidad Autonoma Metropolitana-Iztapalapa, Av San Rafael Atlixco No 186, Col. Vicentina 55-534, Mexico D.F. 09340 (Mexico)

2011-06-15

In this work it is presented a transient, one-dimensional, adiabatic model for slug flow simulation, which appears when liquid (mixture of oil and water) and gas flow simultaneously through pipes. The model is formed by space and time averaged conservation equations for mass, momentum and energy for each phase, the numerical solution is based on the finite difference technique in the implicit scheme. Velocity, pressure, volumetric fraction and temperature profiles for both phases were predicted for inclination angles from the horizontal to the vertical position (unified model) and ascendant flow. Predictions from the model were validated using field data and ten correlations commonly used in the oil industry. The effects of gas heating or cooling, due to compression and expansion processes, on the predictions and numerical stability, were studied. It was found that when these effects are taken into account, a good behavior of temperature predictions and numerical stability are obtained. The model presents deviations lower than 14% regarding field data and it presents better predictions than most of the correlations.

Development of converter to change gas-liquid two-phase slug flow to bubbly flow in a vertical tube

International Nuclear Information System (INIS)

Sakaguchi, T.; Minagawa, H.; Hamaguchi, H.; Shakutusi, H.; Ono, M.; Mizuta, H.

1989-01-01

The mechanical and/or the thermal fatigue fracture of pipelines due to the pulsating characteristics of slug flow will be prevented if slug flow is changed to bubbly flow. Then kinds of flow pattern converters were developed and tested in a vertical tube of 30.3 mm I.D. This paper reports that the converter composed of five stages of porous plates is useful. The sintered porous plates of spherical particles made acrylonitrile-butadiene-styrene resin and bronze are selected from 76 kinds of porous plates

A PLIC-VOF-Based Simulation of Water-Organic Slug Flow Characteristics in a T-Shaped Microchannel

Directory of Open Access Journals (Sweden)

Xian Wang

2013-01-01

Full Text Available A water-organic slug flow in a T-shaped microchannel was numerically studied due to its importance in the microreactor system. Various factors affecting the flow mode were studied, for example, channel width, fluid viscosity, interfacial tension, and inlet velocity. The volume of fluid (VOF method was used to track the liquid-liquid interface, and the piecewise-liner interface construction (PLIC technique was adopted to get a sharp interface. The interfacial tension was simulated with continuum surface force (CSF, model and the wall adhesion boundary condition was taken into consideration. The results show that strong vortexes appear in both phases at the meeting sites of main and lateral channels where an organic slug is producing. Inlet velocity influences the slug length and flow mode greatly. The ratio between the slug lengths of two phases in the main channel is almost equal to the ratio between their inlet velocities. If the slug is produced, the interfacial tension and organic viscosity have less effect on the slug length for 200 μm microchannel. The slug producing rate is much higher in a narrow channel than that in a wide channel.

Evaluation analysis of correlations for predicting the void fraction and slug velocity of slug flow in an inclined narrow rectangular duct

Energy Technology Data Exchange (ETDEWEB)

Yan, Chaoxing, E-mail: yanchaoxing0808@163.com [Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin 150001 (China); Yan, Changqi, E-mail: Changqi_yan@163.com [Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin 150001 (China); Shen, Yunhai [Science and Technology on Reactor System Design Technology Laboratory, Nuclear Power Institute of China, Chengdu 610041 (China); Sun, Licheng; Wang, Yang [Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin 150001 (China)

2014-07-01

Highlights: • 46 void fraction correlations are evaluated on void fraction. • Evaluation of void fraction correlations on slug velocity is studied. • Effect of void fraction correlations on separated frictional pressure drop is studied. • Drift-flux type correlation shows best agreement with experimental data. • Evaluation is investigated in different flow regions. - Abstract: A visualized investigation was conducted on inclined upward air–water slug flow in a narrow rectangular duct with the cross section of 43 mm × 3.25 mm. The slug velocity and void fraction were obtained through image processing. 46 correlations for predicting void fraction, covering the types of slip ratio, Kβ, Lockhart and Martinelli, drift-flux and general were evaluated against the experimental data. In the experiment, four inclined conditions including 0°, 10°, 20° and 30° were investigated and the ranges of gas and liquid superficial velocity were 0.16–2.63 m/s and 0.12–3.59 m/s, respectively. The results indicate that the inclination has no significant influence on prediction error for a given correlation and the drift-flux type correlations are more competitive than the others in the prediction of slug velocity and void fraction. In addition, most of drift-flux type correlations are quite accurate in turbulent flow region, while they provide relative poor predictions in laminar flow region. As for the frictional pressure drop separated from the measured total pressure drop, the deviation arising from the calculation of the void fraction by different correlations is significant in laminar flow region, whereas is negligible in turbulent flow region.

An experimental study of gravity-driven countercurrent two-phase flow in horizontal and inclined channels

International Nuclear Information System (INIS)

Lillibridge, K.H.; Ghiaasiaan, S.M.; Abdel-Khalik, S.I.

1994-01-01

Countercurrent two-phase flow in horizontal and inclined channels, connecting a sealed liquid-filled reservoir to the atmosphere, is experimentally studied. This type of gravity-driven countercurrent two-phase flow can occur during the operation of passive safety coolant injection systems of advanced reactors. It can also occur in the pressurizer surge line of pressurized water reactors during severe accidents when the hot leg becomes voided. Four distinct flow regimes are identified: (a) stratified countercurrent, which mainly occurs when the channel is horizontal; (b) intermittent stratified-slug; (c) oscillating, which occurs when the angle of inclination is ≥30 deg; and (d) annular countercurrent. The characteristics of each regime and their sensitivity to important geometric parameters are examined. The superficial velocities in the stratified countercurrent and oscillating regimes are empirically correlated

A semi-analytical solution for slug tests in an unconfined aquifer considering unsaturated flow

Science.gov (United States)

Sun, Hongbing

2016-01-01

A semi-analytical solution considering the vertical unsaturated flow is developed for groundwater flow in response to a slug test in an unconfined aquifer in Laplace space. The new solution incorporates the effects of partial penetrating, anisotropy, vertical unsaturated flow, and a moving water table boundary. Compared to the Kansas Geological Survey (KGS) model, the new solution can significantly improve the fittings of the modeled to the measured hydraulic heads at the late stage of slug tests in an unconfined aquifer, particularly when the slug well has a partially submerged screen and moisture drainage above the water table is significant. The radial hydraulic conductivities estimated with the new solution are comparable to those from the KGS, Bouwer and Rice, and Hvorslev methods. In addition, the new solution also can be used to examine the vertical conductivity, specific storage, specific yield, and the moisture retention parameters in an unconfined aquifer based on slug test data.

The dynamics of slug trains in volcanic conduits: Evidence for expansion driven slug coalescence

Science.gov (United States)

Pering, T. D.; McGonigle, A. J. S.; James, M. R.; Capponi, A.; Lane, S. J.; Tamburello, G.; Aiuppa, A.

2017-12-01

Strombolian volcanism is a ubiquitous form of activity, driven by the ascent and bursting of bubbles of slug morphology. Whilst considerable attention has been devoted to understanding the behaviour of individual slugs in this regime, relatively little is known about how inter-slug interactions modify flow conditions. Recently, we reported on high temporal frequency strombolian activity on Etna, in which the larger erupted slug masses were followed by longer intervals before the following explosion than the smaller bursts (Pering et al., 2015). We hypothesised that this behaviour arose from the coalescence of ascending slugs causing a prolonged lag before arrival of the next distinct bubble. Here we consider the potential importance of inter-slug interactions for the dynamics of strombolian volcanism, by reporting on the first study into the behaviour of trains of ascending gas slugs, scaled to the expansion rates in volcanic conduits. This laboratory analogue study illustrates that slugs in trains rise faster than individual slugs, and can be associated with aspects of co-current flow. The work also highlights that coalescence and inter-slug interactions play an important role in modulating slug train behaviour. We also report, for the first time, on slug coalescence driven by vertical expansion of the trailing slug, a process which can occur, even where the leading slug base ascent velocity is greater than that of the trailing slug.

Interfacial area, velocity and void fraction in two-phase slug flow

International Nuclear Information System (INIS)

Kojasoy, G.; Riznic, J.R.

1997-01-01

The internal flow structure of air-water plug/slug flow in a 50.3 mm dia transparent pipeline has been experimentally investigated by using a four-sensor resistivity probe. Liquid and gas volumetric superficial velocities ranged from 0.55 to 2.20 m/s and 0.27 to 2.20 m/s, respectively, and area-averaged void fractions ranged from about 10 to 70%. The local distributions of void fractions, interfacial area concentration and interface velocity were measured. Contributions from small spherical bubbles and large elongated slug bubbles toward the total void fraction and interfacial area concentration were differentiated. It was observed that the small bubble void contribution to the overall void fraction was small indicating that the large slug bubble void fraction was a dominant factor in determining the total void fraction. However, the small bubble interfacial area contribution was significant in the lower and upper portions of the pipe cross sections

Transformation of a Water Slug in Free Fall Under the Conditions of Exposure to an Air Flow Orthogonal to the Direction of the Slug Motion

Science.gov (United States)

Volkov, R. S.; Zabelin, M. V.; Kuznetsov, G. V.; Strizhak, P. A.

2016-07-01

An experimental study has been made of the influence of an orthogonal (side) air flow propagating with a velocity to 5 m/s on the phases of transformation of a water slug with an initial volume of 0.05-0.5 liter in free fall from a height of 3 m. Use was made of Phantom V411 and Phantom Miro M310 high-speed video cameras and a Tema Automotive software system with the function of continuous tracking. The laws of retardation of the phases of transformation of the water slug from the instant of formation to that of formation of a droplet cloud under the action of the air flow orthogonal to the direction of the slug motion, and also of the deceleration, removal, and destruction of the droplets and fragments of water separating from the slug surface, have been established.

PageRank versatility analysis of multilayer modality-based network for exploring the evolution of oil-water slug flow.

Science.gov (United States)

Gao, Zhong-Ke; Dang, Wei-Dong; Li, Shan; Yang, Yu-Xuan; Wang, Hong-Tao; Sheng, Jing-Ran; Wang, Xiao-Fan

2017-07-14

Numerous irregular flow structures exist in the complicated multiphase flow and result in lots of disparate spatial dynamical flow behaviors. The vertical oil-water slug flow continually attracts plenty of research interests on account of its significant importance. Based on the spatial transient flow information acquired through our designed double-layer distributed-sector conductance sensor, we construct multilayer modality-based network to encode the intricate spatial flow behavior. Particularly, we calculate the PageRank versatility and multilayer weighted clustering coefficient to quantitatively explore the inferred multilayer modality-based networks. Our analysis allows characterizing the complicated evolution of oil-water slug flow, from the opening formation of oil slugs, to the succedent inter-collision and coalescence among oil slugs, and then to the dispersed oil bubbles. These properties render our developed method particularly powerful for mining the essential flow features from the multilayer sensor measurements.

Horizontal Air-Water Flow Analysis with Wire Mesh Sensor

International Nuclear Information System (INIS)

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

2012-01-01

A Wire Mesh Sensor, based on the measurement of the local instantaneous conductivity of the two-phase mixture, has been used to characterize the fluid dynamics of the gas–liquid interface in a horizontal pipe flow. Experiments with a pipe of a nominal diameter of 19.5 mm and total length of 6 m, have been performed with air/water mixtures, at ambient conditions. The flow quality ranges from 0.00016 to 0.22 and the superficial velocities range from 0.1 to 10.5 m/s for air and from 0.02 to 1.7 m/s for water; the flow pattern is stratified, slug/plug and annular. A sensor (WMS200) with an inner diameter of 19.5 mm and a measuring matrix of 16×16 points equally distributed over the cross-section has been chosen for the measurements. From the analysis of the Wire Mesh Sensor digital signals the average and the local void fraction are evaluated and the flow patterns are identified with reference to space, time and flow rate boundary conditions.

Lava Fountaining Discharge Regime driven by Slug-to-Churn Flow Transition. (Invited)

Science.gov (United States)

Ripepe, M.; Pioli, L.; Marchetti, E.; Ulivieri, G.

2013-12-01

Lava fountaining episodes at Etna volcano appear characterized by the transition between Strombolian and Hawaiian end-member eruptive styles. There is no evidence for this transition in the seismic (i.e. seismic tremor) signal. However, infrasonic records provide unprecedented evidence on this flow transition. Each eruptive episode is characterized by distinctive common trend in the amplitude, waveform and frequency content of the infrasonic wavefield, which evidences the shift from discrete, and transient, strombolian to sustained, and oscillatory, lava fountain dynamics. Large scale experiments on the dynamics of two-phase flow of basaltic magmas show how the transition between different regimes mainly depends on gas volume flow, which in turn controls pressure distribution within the conduit and also magma vesicularity. In particular, while regular large bubble bursting is associated with slug flow regime, large amplitude and low frequency column oscillations are associated with churn flow. In large pipes, transition from slug to churn flow regime is independent on conduit diameter and it is reached at high superficial gas velocity. Lava fountaining episodes at Etna can be thus interpreted as induced by the transition from the slug (discrete strombolian) to churn flow (sustained lava fountain) regimes that is reflecting an increase in the gas discharge rate. Based on laboratory experiments, we calculate that transition between these two end-member explosive regimes at Etna occurs when gas superficial velocity is 76 m/s for near-the-vent stagnant magma conditions.

The Slug and Churn Turbulence Characteristics of Oil-Gas-Water Flows in a Vertical Small Pipe

Science.gov (United States)

Liu, Weixin; Han, Yunfeng; Wang, Dayang; Zhao, An; Jin, Ningde

2017-08-01

The intention of the present study was to investigate the slug and churn turbulence characteristics of a vertical upward oil-gas-water three-phase flow. We firstly carried out a vertical upward oil-gas-water three-phase flow experiment in a 20-mm inner diameter (ID) pipe to measure the fluctuating signals of a rotating electric field conductance sensor under different flow patterns. Afterwards, typical flow patterns were identified with the aid of the texture structures in a cross recurrence plot. Recurrence quantitative analysis and multi-scale cross entropy (MSCE) algorithms were applied to investigate the turbulence characteristics of slug and churn flows with the varying flow parameters. The results suggest that with cross nonlinear analysis, the underlying dynamic characteristics in the evolution from slug to churn flow can be well understood. The present study provides a novel perspective for the analysis of the spatial-temporal evolution instability and complexity in oil-gas-water three-phase flow.

Hydrodynamics of gas-liquid slug flow along vertical pipes in turbulent regime-An experimental study

Energy Technology Data Exchange (ETDEWEB)

Mayor, T.S.; Ferreira, V.; Pinto, A.M.F.R. [Centro de Estudos de Fenomenos de Transporte, Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias 4200-465 Porto (Portugal); Campos, J.B.L.M. [Centro de Estudos de Fenomenos de Transporte, Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias 4200-465 Porto (Portugal)], E-mail: jmc@fe.up.pt

2008-08-15

An experimental study on free-bubbling gas-liquid (air-water) vertical slug flow was developed using a non-intrusive image analysis technique. The flow pattern in the near-wake of the bubbles and in the main liquid between bubbles was turbulent. A single correlation for the bubble-to-bubble interaction is proposed, relating the trailing bubble velocity to the length of the liquid slug ahead of the bubble. The proposed correlation is shown to be independent of column diameter, column vertical coordinate, superficial liquid and gas velocities and the velocity and length of the leading bubble. Frequency distribution curves, averages, modes and standard deviations are reported, for distributions of bubble velocity, bubble length and liquid slug length, for each experimental condition studied. Good agreement was found between theoretical predictions and experimental results regarding the upward velocity of undisturbed bubbles, in a 0.032 m internal diameter column. A considerable discrepancy was found, though, for a 0.052 m internal diameter column. The acquired experimental data are crucial for the development and validation of a robust slug flow simulator.

Hydrodynamics of gas-liquid slug flow along vertical pipes in turbulent regime-An experimental study

International Nuclear Information System (INIS)

Mayor, T.S.; Ferreira, V.; Pinto, A.M.F.R.; Campos, J.B.L.M.

2008-01-01

An experimental study on free-bubbling gas-liquid (air-water) vertical slug flow was developed using a non-intrusive image analysis technique. The flow pattern in the near-wake of the bubbles and in the main liquid between bubbles was turbulent. A single correlation for the bubble-to-bubble interaction is proposed, relating the trailing bubble velocity to the length of the liquid slug ahead of the bubble. The proposed correlation is shown to be independent of column diameter, column vertical coordinate, superficial liquid and gas velocities and the velocity and length of the leading bubble. Frequency distribution curves, averages, modes and standard deviations are reported, for distributions of bubble velocity, bubble length and liquid slug length, for each experimental condition studied. Good agreement was found between theoretical predictions and experimental results regarding the upward velocity of undisturbed bubbles, in a 0.032 m internal diameter column. A considerable discrepancy was found, though, for a 0.052 m internal diameter column. The acquired experimental data are crucial for the development and validation of a robust slug flow simulator

Transition from annular flow to plug/slug flow in condensation of steam in microchannels

Energy Technology Data Exchange (ETDEWEB)

Quan, Xiaojun; Cheng, Ping; Wu, Huiying [School of Mechanical and Power Engineering, Shanghai Jiaotong University, 800 Dong Chuan Road, Shanghai 200240 (China)

2008-02-15

A visualization study has been conducted to investigate the transition from annular flow to plug/slug flow in the condensation of steam in two different sets of parallel microchannels, having hydraulic diameters of 90 {mu}m and 136 {mu}m, respectively. The steam in the parallel microchannels was cooled on the bottom by forced convection of water and by natural convection of air from the top. It is found that the location, where the transition from annular flow to plug/slug flow takes place, depends on mass flux and cooling rate of steam. The effects of mass flux and cooling rate on the occurrence frequency of the injection flow in a single microchannel, having a hydraulic diameter of 120 {mu}m and 128 {mu}m, respectively, are investigated. It is found that two different shapes of injection flow occur in the smooth annular flow in microchannels: injection flow with unsteady vapor ligament occurring at low mass flux (or high cooling rate) and injection flow with steady vapor ligament occurring at high mass flux (or low cooling rate). It is also found that increase of steam mass flux, decrease of cooling rate, or decrease of the microchannel diameter tends to enhance instability of the condensate film on the wall, resulting in occurrence of the injection flow further toward the outlet with an increase in occurrence frequency. (author)

Mass transfer coefficient of slug flow for organic solvent-aqueous system in a microreactor

Energy Technology Data Exchange (ETDEWEB)

Tuek, Ana Jurinjak; Anic, Iva; Kurtanjek, Zelimir; Zelic, Bruno [University of Zagreb, Zagreb (Croatia)

2015-06-15

Application of microreactor systems could be the next break-through in the intensification of chemical and biochemical processes. The common flow regime for organic solvent-aqueous phase two-phase systems is a segmented flow. Internal circulations in segments cause high mass transfer and conversion. We analyzed slug flow in seven systems of organic solvents and aqueous phase. To analyze how slug lengths in tested systems depend on linear velocity and physical and chemical properties of used organic solvents, regression models were proposed. It was shown that models based on linearization of approximation by potentials give low correlation for slug length prediction; however, application of an essential nonlinear model of multiple layer perception (MLP) neural network gives high correlation with R{sup 2}=0.9. General sensitivity analysis was applied for the MLP neural network model, which showed that 80% of variance in slug length for the both phases is accounted for the viscosity and density of the organic phases; 10% is accounted by surface tension of the organic phase, while molecular masses and flow rates each account for 5%. For defined geometry of microreactor, mass transfer has been determined by carrying out the neutralization experiment with NaOH where acetic acid diffuses from organic phase (hexane) into aqueous phase. Estimated mass transfer coefficients were in the range k{sub L}a=4,652-1,9807 h{sup -1}.

Mass transfer coefficient of slug flow for organic solvent-aqueous system in a microreactor

International Nuclear Information System (INIS)

Tuek, Ana Jurinjak; Anic, Iva; Kurtanjek, Zelimir; Zelic, Bruno

2015-01-01

Application of microreactor systems could be the next break-through in the intensification of chemical and biochemical processes. The common flow regime for organic solvent-aqueous phase two-phase systems is a segmented flow. Internal circulations in segments cause high mass transfer and conversion. We analyzed slug flow in seven systems of organic solvents and aqueous phase. To analyze how slug lengths in tested systems depend on linear velocity and physical and chemical properties of used organic solvents, regression models were proposed. It was shown that models based on linearization of approximation by potentials give low correlation for slug length prediction; however, application of an essential nonlinear model of multiple layer perception (MLP) neural network gives high correlation with R 2 =0.9. General sensitivity analysis was applied for the MLP neural network model, which showed that 80% of variance in slug length for the both phases is accounted for the viscosity and density of the organic phases; 10% is accounted by surface tension of the organic phase, while molecular masses and flow rates each account for 5%. For defined geometry of microreactor, mass transfer has been determined by carrying out the neutralization experiment with NaOH where acetic acid diffuses from organic phase (hexane) into aqueous phase. Estimated mass transfer coefficients were in the range k L a=4,652-1,9807 h -1

Drift flux model as approximation of two fluid model for two phase dispersed and slug flow in tube

International Nuclear Information System (INIS)

Nigmatulin, R.I.

1995-01-01

The analysis of one-dimensional schematizing for non-steady two-phase dispersed and slug flow in tube is presented. Quasi-static approximation, when inertia forces because of the accelerations of the phases may be neglected, is considered. Gas-liquid bubbly and slug vertical upward flows are analyzed. Non-trivial theoretical equations for slip velocity for these flows are derived. Juxtaposition of the derived equations for slip velocity with the famous Zuber-Findlay correlation as cross correlation coefficients is criticized. The generalization of non-steady drift flux Wallis theory taking into account influence of wall friction on the bubbly or slug flows for kinematical waves is considered

Drift flux model as approximation of two fluid model for two phase dispersed and slug flow in tube

Energy Technology Data Exchange (ETDEWEB)

Nigmatulin, R.I.

1995-09-01

The analysis of one-dimensional schematizing for non-steady two-phase dispersed and slug flow in tube is presented. Quasi-static approximation, when inertia forces because of the accelerations of the phases may be neglected, is considered. Gas-liquid bubbly and slug vertical upward flows are analyzed. Non-trivial theoretical equations for slip velocity for these flows are derived. Juxtaposition of the derived equations for slip velocity with the famous Zuber-Findlay correlation as cross correlation coefficients is criticized. The generalization of non-steady drift flux Wallis theory taking into account influence of wall friction on the bubbly or slug flows for kinematical waves is considered.

Cellular properties of slug flow in vertical co-current gas-liquid flow: slug-churn transition; Caracteristiques cellulaires du regime a poches en ecoulement gaz-liquide co-courant vertical. Transition vers le regime destructure

Energy Technology Data Exchange (ETDEWEB)

Lusseyran, Francois

1990-12-13

This research thesis reports the study and description of the structure of a slug flow regime in a co-current vertical cylindrical duct, and the characterization and prediction of its transition towards a slug-churn (de-structured) regime. Flow physical mechanisms highlighted by the measurement of two important dynamics variables (wall friction and thickness of liquid films) are related to hypotheses of cellular models. The author first proposes an overview of slug flow regimes: theoretical steady and one-dimensional analysis, mass assessment equations of cellular models, application to the assessment of the flow rate and of the thickness of the film surrounding the gas slug. In the second part, the author addresses the slug flow regime transition towards the slug-churn regime: assessment of the evolution of flow dynamic properties, use of average wall friction analysis to obtain a relevant transition criterion. The third part presents experimental conditions, and measurement methods: conductometry for thickness measurement, polarography for wall friction measurement, and gas phase detection by using an optic barrier or optic fibres [French] Les ecoulements gaz-liquide en conduite verticale presentent quatre configurations ou regimes d'ecoulement. Ce travail porte sur le regime a poches et sur la transition vers la configuration qui lui succede: le regime destructure (churn flow). Les mesures sont effectuees a 200D du point d'injection du gaz, dans une conduite de 12.2 mm de diametre et pour le couple de fluides eau-azote. Les deux principales grandeurs mesurees en fonction des flux d'entree sont: le frottement parietal instantane (methode electrochimique) et l'epaisseur de film instantanee (methode conductimetrique). Une detection optique simultanee de la presence des phases permet un traitement conditionnel de la base de donnees. Les caracteristiques de la cellule moyenne representative de chaque point de fonctionnement en sont deduites: longueur de la cellule

Lactic Acid Extraction and Mass Transfer Characteristics in Slug Flow Capillary Microreactors

NARCIS (Netherlands)

Susanti, S.; Winkelman, J.G.N.; Schuur, Boelo; heeres, h.j.; Yue, J.

2016-01-01

Capillary microreactors operated under the slug flow regime were investigated for the separation of lactic acid from the aqueous phase using liquid–liquid reactive extraction. The experiments were performed at a 1:1 flow ratio of the aqueous to organic phases in a setup consisting of an inlet Y-type

Real-time measurement of gas and liquid flow rates in two-phase slug flow by an advanced electromagnetic flowmeter and conductance probes

International Nuclear Information System (INIS)

Kim Jongrok; Ahn Yeh-Chan; Oh Byung Do; Kang Deok-Hong; Kim Moo Hwan

2005-01-01

Full text of publication follows: In order to measure the liquid mean velocity (cross-sectional average) in two-phase flow with an electromagnetic flowmeter, each flow pattern must be considered separately because of their different flow characteristics. Since bubbly flow can be approximated as a homogeneous mixture of gas and liquid at the same velocity, there are no additional measurement difficulties compared to single-phase flow. Cha et al. (2002) and Knoll (1991) reported that this approximation gives rise to no more than a 5% error in the liquid flow rate when the void fraction is less than 0.25. Annular flow measurements are also similar to those of single-phase flow if the film is assumed to be uniform and smooth, and the gas core is located at the center of the flow tube. Slug flow, however, is the most complicated, since the liquid axial velocity over a slug unit experiences considerable acceleration or deceleration. Therefore an electromagnetic flowmeter with high temporal resolution is needed. In slug flow, film velocity measurements are also difficult to perform because the liquid film is very thin and can be easily disturbed, thus altering the flow field. Only two experimental results for liquid film velocity measurement could be found. They were performed using photo-chromic dye method (DeJesus, 1997) and PIV technique (Polonsky et al., 1999). In this study, an advanced electromagnetic flow-metry was developed to measure liquid mean velocity with high transients. In addition, two ring-type conductance meters were manufactured to measure void fraction and its propagation speed in slug flow. The signal of conductance meter with two rings depends on liquid temperature. Therefore a conductance meter with three rings designed by Coney (1973), which is independent of liquid temperature, was used and experimentally proved. The manufactured conductance meters showed a good repeatability and agreement with the analytical solution by Coney (1973). From the

Prematurely terminated slug tests

International Nuclear Information System (INIS)

Karasaki, K.

1990-07-01

A solution of the well response to a prematurely terminated slug test (PTST) is presented. The advantages of a PTST over conventional slug tests are discussed. A systematized procedure of a PTST is proposed, where a slug test is terminated in the midpoint of the flow point, and the subsequent shut-in data is recorded and analyzed. This method requires a downhole shut-in device and a pressure transducer, which is no more than the conventional deep-well slug testing. As opposed to slug tests, which are ineffective when a skin is present, more accurate estimate of formation permeability can be made using a PTST. Premature termination also shortens the test duration considerably. Because in most cases no more information is gained by completing a slug test to the end, the author recommends that conventional slug tests be replaced by the premature termination technique. This study is part of an investigation of the feasibility of geologic isolation of nuclear wastes being carried out by the US Department of Energy and the National Cooperative for the Storage of Radioactive Waste of Switzerland

The use of a low-cost gas-liquid flow meter to monitor severe slugging

DEFF Research Database (Denmark)

Andreussi, Paolo; Bonizzi, Marco; Ciandri, Paolo

2017-01-01

A very simple, low-cost gas-liquid flow meter that only employs conventional field instrumentation has been used to monitor severe slugging occurring at the exit of a vertical pipe. This meter was originally developed for conventional oil field applications [1] and is based on the readings...... method to monitor severe slugging by means of low cost instrumentation, in particular, by replacing a cumbersome instrument such as a gamma-densitometer with a differential pressure transmitter. In field operation, the multiphase orifice used in these experiments can be replaced by a calibrated control...... of a multiphase orifice and the pressure drops of the gas-liquid mixture flowing in a vertical section of the pipe. Liquid and gas flow rates have been determined by means of semi-empirical equations developed for the specific set of flow parameters (geometry, flow rates, physical properties) adopted in a series...

Characterization of Flow Dynamics and Reduced-Order Description of Experimental Two-Phase Pipe Flow

Science.gov (United States)

Viggiano, Bianca; SkjæRaasen, Olaf; Tutkun, Murat; Cal, Raul Bayoan

2017-11-01

Multiphase pipe flow is investigated using proper orthogonal decomposition for tomographic X-ray data, where holdup, cross sectional phase distributions and phase interface characteristics are obtained. Instantaneous phase fractions of dispersed flow and slug flow are analyzed and a reduced order dynamical description is generated. The dispersed flow displays coherent structures in the first few modes near the horizontal center of the pipe, representing the liquid-liquid interface location while the slug flow case shows coherent structures that correspond to the cyclical formation and breakup of the slug in the first 10 modes. The reconstruction of the fields indicate that main features are observed in the low order dynamical descriptions utilizing less than 1 % of the full order model. POD temporal coefficients a1, a2 and a3 show interdependence for the slug flow case. The coefficients also describe the phase fraction holdup as a function of time for both dispersed and slug flow. These flows are highly applicable to petroleum transport pipelines, hydroelectric power and heat exchanger tubes to name a few. The mathematical representations obtained via proper orthogonal decomposition will deepen the understanding of fundamental multiphase flow characteristics.

Water hammer phenomena occurring in nuclear power installations while filling horizontal pipe containing saturated steam with liquid

Energy Technology Data Exchange (ETDEWEB)

Selivanov, Y.F.; Kirillov, P.L.; Yefanov, A.D. [Institute of Physics and Power Engineering, Obninsk (Russian Federation)

1995-09-01

The potentiality of the water hammer occurrence in nuclear reactor loop components has been considered under the conditions of filling a steam-containing pipeline leg involving horizontal and vertical sections with liquid subcooled to the saturation temperature. As a result of free discharging from the tank, the liquid enters the horizontal pipeline. When the liquid slug formation in the pipeline is fulfilled. The pressure drop being occurred in steam flowing along the pipelines causes the liquid slug to move to the pipeline inlet. When the liquid slug decelerates, a water hammer occurs. This mechanism of water hammer occurrence is tested by experiments. The regimes of the occurrence of multiple considerable water hammers were identified.

Water hammer phenomena occurring in nuclear power installations while filling horizontal pipe containing saturated steam with liquid

International Nuclear Information System (INIS)

Selivanov, Y.F.; Kirillov, P.L.; Yefanov, A.D.

1995-01-01

The potentiality of the water hammer occurrence in nuclear reactor loop components has been considered under the conditions of filling a steam-containing pipeline leg involving horizontal and vertical sections with liquid subcooled to the saturation temperature. As a result of free discharging from the tank, the liquid enters the horizontal pipeline. When the liquid slug formation in the pipeline is fulfilled. The pressure drop being occurred in steam flowing along the pipelines causes the liquid slug to move to the pipeline inlet. When the liquid slug decelerates, a water hammer occurs. This mechanism of water hammer occurrence is tested by experiments. The regimes of the occurrence of multiple considerable water hammers were identified

Severe Slugging in Air-Water Hybrid Riser System

Directory of Open Access Journals (Sweden)

Jing Gong

2014-11-01

Full Text Available In the subsea pipeline gathering system, severe slugging flow is prone to occur. Severe slugging flow brings major threat to production and flow assurance in oil and gas industry due to periodical pressure oscillation and large liquid volume. Currently many researchers pay much more attention on L-shaped riser, catenaries, and S-shaped riser; little research has been made on hybrid riser, which is applied in the Africa West and Gulf of Mexico oil fields. Flow characteristics simulation for hybrid riser is made in this paper, using the one-dimensional and quasi-equilibrium model to simulate not only the riser-base pressure, severe slugging period, and the liquid slug length of the whole system but also base-pressure in the flexible pipe section. The calculated results match well with the experiment data. Besides, the influence of flexible pipe to the severe slugging characteristics of hybrid riser system is analyzed, which are significant for the determination of riser structure.

Investigation of air-water flow in a horizontal pipe with 90 degree bends using wire mesh sensors

Energy Technology Data Exchange (ETDEWEB)

Bowden, R.C.; Yang, S.K., E-mail: robert.bowden@cnl.ca, E-mail: sun-kyu.yang@cnl.ca [Canadian Nuclear Laboratories, Chalk River, ON (Canada)

2015-07-01

Wire mesh sensors were used to investigate the void fraction distribution along a 9 meter long, 50.8 mm diameter, horizontal test section that contained two 90 degree bends. Deionised water and compressed air were used as the working fluids, with the bubbly flow regime achieved at a superficial liquid velocity of 3.5 m/s and superficial gas velocities that varied between 0.1 and 1.2 m/s. The effects of superficial gas velocity and axial location on the void fraction distribution were investigated. Bubble and slug flow patterns were identified using a probability density function analysis based on a Gaussian mixture model. (author)

A droplet entrainment model for horizontal segregated flows

Energy Technology Data Exchange (ETDEWEB)

Höhne, Thomas, E-mail: T.Hoehne@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf (HZDR) – Institute of Fluid Dynamics, P.O. Box 510119, D-01314 Dresden (Germany); Hänsch, Susann [Imperial College, Department of Mechanical Engineering, South Kensington Campus, London SW7 2AZ (United Kingdom)

2015-05-15

Highlights: • We further developed the flow morphology detection model AIAD. • An advanced droplet entrainment model was introduced. • The new approach is applied against HAWAC experiments. - Abstract: One limitation in simulating horizontal segregated flows is that there is no treatment of droplet formation mechanisms at wavy surfaces. For self-generating waves and slugs, the interfacial momentum exchange and the turbulence parameters have to be modeled correctly. Furthermore, understanding the mechanism of droplet entrainment for heat and mass transfer processes is of great importance in the chemical and nuclear industry. The development of general computational fluid dynamics models is an essential precondition for the application of CFD codes to the modeling of flow related phenomena. The new formulation for the interfacial drag at the free surface and turbulence parameters within the algebraic interfacial area density model (AIAD) represents one step toward a more physical description of free surface flows including less empiricism. The AIAD approach allows the use of different physical models depending on the local fluid morphology inside a macro-scale multi-fluid framework. A further step of improving the modeling of free interfaces lies within the consideration of droplet entrainment mechanisms. In this paper a new sub-grid entrainment model is proposed, which assumes that due to liquid turbulence the interface gets rough and wavy leading to the formation of droplets. Therefore, the droplet entrainment model requires the consideration of an additional droplet phase, which is described with an own set of balance equations in the spirit of the particle model. Two local key factors determine the rate of droplet entrainment: the liquid turbulent kinetic energy as well as the outward velocity gradient of the liquid relative to the interface motion. The new droplet entrainment approach is included into CFD simulations for attempting to reproduce existing

Automatic discrimination of bubbles and slugs in two-phase gas-liquid flow and measurement of the respective velocities

International Nuclear Information System (INIS)

Fitremann, J.M.; Guilpin, C.; Postaire, J.

1976-01-01

The measurement of the interface velocity in a two-phase gas-liquid flow is a difficult problem, owing to the dispersion of the velocity components of individual bubbles, gas-slugs, droplets, waves, etc. An entirely automatic method is presented, it gives the velocity of slugs and bubbles independently, by discrimination of local phase probe signals into a 'slug' signal and a 'bubble' signal feeding a shape-recognition program. Both discriminated void fractions are also calculated by the apparatus [fr

An investigation on near wall transport characteristics in an adiabatic upward gas-liquid two-phase slug flow

Science.gov (United States)

Zheng, Donghong; Che, Defu

2007-08-01

The near-wall transport characteristics, inclusive of mass transfer coefficient and wall shear stress, which have a great effect on gas-liquid two-phase flow induced internal corrosion of low alloy pipelines in vertical upward oil and gas mixing transport, have been both mechanistically and experimentally investigated in this paper. Based on the analyses on the hydrodynamic characteristics of an upward slug unit, the mass transfer in the near wall can be divided into four zones, Taylor bubble nose zone, falling liquid film zone, Taylor bubble wake zone and the remaining liquid slug zone; the wall shear stress can be divided into two zones, the positive wall shear stress zone associated with the falling liquid film and the negative wall shear stress zone associated with the liquid slug. Based on the conventional mass transfer and wall shear stress characteristics formulas of single phase liquid full-pipe turbulent flow, corrected normalized mass transfer coefficient formula and wall shear stress formula are proposed. The calculated results are in good agreement with the experimental data. The shear stress and the mass transfer coefficient in the near wall zone are increased with the increase of superficial gas velocity and decreased with the increase of superficial liquid velocity. The mass transfer coefficients in the falling liquid film zone and the wake zone of leading Taylor bubble are lager than those in the Taylor bubble nose zone and the remaining liquid slug zone, and the wall shear stress associated falling liquid film is larger than that associated the liquid slug. The mass transfer coefficient is within 10-3 m/s, and the wall shear stress below 103 Pa. It can be concluded that the alternate wall shear stress due to upward gas-liquid slug flow is considered to be the major cause of the corrosion production film fatigue cracking.

Numerical Study on Bubble Dynamics and Two-Phase Frictional Pressure Drop of Slug Flow Regime in Adiabatic T-junction Square Microchannel

Directory of Open Access Journals (Sweden)

K. Kishor

2017-10-01

Full Text Available In this study, bubble dynamics and frictional pressure drop associated with gas liquid two-phase slug flow regime in adiabatic T-junction square microchannel has been investigated using CFD. A comprehensive study on the mechanism of bubble formation via squeezing and shearing regime is performed. The randomness and recirculation profiles observed in the squeezing regime are significantly higher as compared to the shearing regime during formation of the slug. Further, effects of increasing gas velocity on bubble length are obtained at fixed liquid velocities and simulated data displayed good agreement with available correlations in literature. The frictional pressure drop for slug flow regime from simulations are also obtained and evaluated against existing separated flow models. A regression correlation has also been developed by modifying C-parameter using separated flow model, which improves the prediction of two-phase frictional pressure drop data within slug flow region, with mean absolute error of 10 %. The influences of fluid properties such as liquid viscosity and surface tension on the two-phase frictional pressure drop are also investigated and compared with developed correlation. The higher liquid viscosity and lower surface tension value resulted in bubble formation via shearing regime.

Experimental Study of Stable Surfaces for Anti-Slug Control in Multi-phase Flow

DEFF Research Database (Denmark)

Pedersen, Simon; Løhndorf, Petar Durdevic; Yang, Zhenyu

2014-01-01

-phase flow dynamics, the slug can be avoided or eliminated by proper facility design and control of operational conditions. Based on a testing facility which can emulate a pipeline-riser or a gas-lifted production well in a scaled-down manner, this paper experimentally studies the correlations of key...

Two-phase countercurrent flow in a model of a pressurized water reactor hot leg

International Nuclear Information System (INIS)

Wongwises, S.

1996-01-01

The onset of flooding or countercurrent flow limitation (CCFL) determines the maximum rate at which one phase can flow countercurrently to another phase. In the present study, the experimental data of the CCFL for gas and liquid in a horizontal pipe with a bend are investigated. The different mechanisms that lead to flooding and that are dependent on the liquid flow rate are observed. For low and intermediate liquid flow rates, the onset of flooding appears simultaneously with the slugging of unstable waves that are formed at the crest of the hydraulic jump. At low liquid flow rates, slugging appears close to the bend; at higher liquid flow rates, it appears far away from the bend, in the horizontal section. For high liquid flow rates, no hydraulic jump is observed, and flooding occurs as a result of slug formation at the end of the horizontal pipe. The effects of the inclination angle of the bends, the liquid inlet conditions and the length of the horizontal pipes are of significance for the onset of flooding. A mathematical model of Ardron and Banerjee is modified to predict the onset of flooding. Flooding curves calculated by this model are compared with present experimental data and those of other researchers. The predictions of the onset of flooding as a function of the length-to-diameter ratio are in reasonable agreement with the experimental data. (orig.)

Experimental investigations and modelling on the transition from bubble to slug flow in vertical pipes

International Nuclear Information System (INIS)

Lucas, D.; Krepper, E.; Prasser, H.M.

2003-01-01

To qualify CFD codes for two-phase flows, they have to be equipped with constitutive laws describing the interaction between the gaseous and the liquid phases. In the case of bubble flow this particularly concerns the forces acting on the bubbles and bubble coalescence and break-up. To obtain detailed experimental data, an electrode wire-mesh sensor was used, which enables the measurement of the phase distribution with a very high resolution in space and in time. Air-water flow at ambient conditions in a vertical pipe (51.2 mm inner diameter) is investigated to have well defined boundary conditions. Local bubble size distributions are calculated from the data. The measurements were done in different distances from the gas injection device. As a result the development of bubble size distributions as well as the development of the radial gas fraction profiles can be studied. It was found, that the bubble size distribution as well as local effects determine the transition from bubble flow to slug flow. The data are used for the development of a model, which predicts the development of the bubble size distribution and the transition from bubble flow to slug flow in case of stationary flow in a vertical pipe. (orig.)

Challenges in Slug Modeling and Control for Offshore Oil and Gas Productions

DEFF Research Database (Denmark)

Pedersen, Simon; Løhndorf, Petar Durdevic; Yang, Zhenyu

2017-01-01

The upstream offshore multi-phase well-pipeline-riser installations are facing huge challenges related to slugging flow: An unstable flow regime where the flow rates, pressures and temperatures oscillate in the multi-phase pipelines. One typical severe slug is induced by vertical wells or risers...... most models require specific facility and operating data which, unfortunately, often is not available from most offshore installations. Anti-slug control have been investigated for several decades in oil & gas industry, but many of these existing methods suffer the consequent risk of simultaneously...... reducing the oil & gas production. This paper concludes that slug is a well defined phenomenon, but even though it has been investigated for several decades the current anti-slug control methods still have problems related to robustness. It is predicted that slug-induced challenges will be even more severe...

Stability Analysis of Reactive Multiphase Slug Flows in Microchannels

Directory of Open Access Journals (Sweden)

Alejandro A. Munera Parra

2014-05-01

Full Text Available Conducting multiphase reactions in micro-reactors is a promising strategy for intensifying chemical and biochemical processes. A major unresolved challenge is to exploit the considerable benefits offered by micro-scale operation for industrial scale throughputs by numbering-up whilst retaining the underlying advantageous flow characteristics of the single channel system in multiple parallel channels. Fabrication and installation tolerances in the individual micro-channels result in different pressure losses and, thus, a fluid maldistribution. In this work, an additional source of maldistribution, namely the flow multiplicities, which can arise in a multiphase reactive or extractive flow in otherwise identical micro-channels, was investigated. A detailed experimental and theoretical analysis of the flow stability with and without reaction for both gas-liquid and liquid-liquid slug flow has been developed. The model has been validated using the extraction of acetic acid from n-heptane with the ionic liquid 1-Ethyl-3-methylimidazolium ethyl sulfate. The results clearly demonstrate that the coupling between flow structure, the extent of reaction/extraction and pressure drop can result in multiple operating states, thus, necessitating an active measurement and control concept to ensure uniform behavior and optimal performance.

Slug control system; Sistema de controle de golfadas

Energy Technology Data Exchange (ETDEWEB)

Borges Filho, Alvaro de Miranda; Meira, Marco Antonio Alves de; Vaz, Celio Eduardo Martins [PETROBRAS, Macae, RJ (Brazil). Unidade de Negocios da Bacia de Campos

2004-07-01

Due to the characteristics of flow, gas can separate from oil in the pipelines and risers that link subsea manifolds to production offshore platforms, forming liquid and gas slugs in the production separator. Liquid slugs can cause overflow in the separators. Gas slugs can cause burning in the flare due to the limitation in the turbo-compressors acceleration. In both cases the consequences are loss of production or shut-downs. This paper presents a Slug Control System designed to attenuate severe gas and liquid flow variations. The system consist of a control valve installed in the separator inlet, transmitters, a controller, control algorithm and a monitoring station. This system is operating since October 2003 in a production offshore platform, in Campus Basin, Brazil, with excellent results, reducing the gas burning in 45% without oil production loss. (author)

On the interaction of Taylor bubbles rising in two-phase co-current slug flow in vertical columns: turbulent wakes

Energy Technology Data Exchange (ETDEWEB)

Pinto, A.M.F.R.; Campos, J.B.L. [Centro de Estudos de Fenomenos de Transporte, Universidade do Porto Rua (Portugal); Coelho Pinheiro, M.N. [Dept. de Engenharia Quimica, Politecnico de Coimbra (Portugal)

2001-12-01

An experimental study on the interaction between Taylor bubbles rising through a co-current flowing liquid in a vertical tube with 32 mm of internal diameter is reported. The flow pattern in the bubble's wake was turbulent and the flow regime in the liquid slug was either turbulent or laminar. When the flow regime in the liquid slug is turbulent (i) the minimum distance between bubbles above which there is no interaction is 5D-6D; (ii) the bubble's rising velocity is in excellent agreement with the Nicklin relation; (iii) the experimental values of the bubble length compare well with theoretical predictions (Barnea 1990); (iv) the distance between consecutive bubbles varied from 13D to 16D and is insensitive to the liquid Reynolds number. When the flow regime in the liquid slug is laminar (i) the wake length is about 5D-6D; (ii) the minimum distance between bubbles above which there is no interaction is higher than 25D; (iii) the bubble's rising velocity is significantly smaller than theoretical predictions. These results were explained in the light of the findings of Pinto et al. (1998) on coalescence of two Taylor bubbles rising through a co-current liquid. (orig.)

Analytic solutions to linear, time-dependent fission product deposition models for isothermal laminar, slug, or multiregion flow conditions

International Nuclear Information System (INIS)

Durkee, J.W. Jr.

1983-01-01

The time-dependent convective-diffusion equation with radioactive decay is solved analytically in axisymmetric cylindrical geometry for laminar and slug velocity profiles under isothermal conditions. Concentration dependent diffusion is neglected. The laminar flow solution is derived using the method of separation of variables and Frobenius' technique for constructing a series expansion about a regular singular point. The slug flow multiregion solution is obtained using the method of separation of variables. The Davidon Variable Metric Minimization algorithm is used to compute the coupling coefficients. These solutions, which describe the transport of fission products in a flowing stream, are then used to determine the concentration of radioactive material deposited on a conduit wall using a standard mass transfer model. Fission product deposition measurements for five diffusion tubes in a Fort St. Vrain High-Temperature Gas-Cooled reactor plateout probe are analyzed. Using single region slug and laminar models, the wall mass transfer coefficients, diffusion coefficients, and inlet concentrations are determined using least squares analysis. The diffusion coefficients and inlet concentrations are consistent between tubes. The derived diffusion coefficients and wall mass transfer coefficients are in relative agreement with known literature values

Pressure suppression pool hydrodynamic studies for horizontal vent exit of Indian PHWR containment

International Nuclear Information System (INIS)

Mohan, N.; Bajaj, S.S.; Saha, P.

1994-01-01

The standard Indian PHWR incorporates a pressure suppression type of containment system with a suppression pool.The design of KAPS (Kakrapar Atomic Power Station) suppression pool system adopts a modified system of downcomers having horizontal vents as compared to vertical vents of NAPS (Narora Atomic Power Station). Hydrodynamic studies for vertical vents have been reported earlier. This paper presents hydrodynamic studies for horizontal type vent system during LOCA. These studies include the phenomenon of vent clearing (where the water slug standing in downcomer initially is injected to wetwell due to rapid pressurization of drywell) followed by pool swell (elevation of pool water due to formation of bubbles due to air mass entering pool at the exit of horizontal vents from drywell). The analysis performed for vent clearing and pool swell is based on rigorous thermal hydraulic calculation consisting of conservation of air-steam mixture mass, momentum and thermal energy and mass of air. Horizontal vent of downcomer is modelled in such a way that during steam-air flow, variation of flow area due to oscillating water surface in downcomer could be considered. Calculation predicts that the vent gets cleared in about 1.0 second and the corresponding downward slug velocity in the downcomer is 4.61 m/sec. The maximum pool swell for a conservative lateral expansion is calculated to be 0.56 m. (author). 3 refs., 12 figs

Slug to churn transition analysis using wire-mesh sensor

Science.gov (United States)

H. F. Velasco, P.; Ortiz-Vidal, L. E.; Rocha, D. M.; Rodriguez, O. M. H.

2016-06-01

A comparison between some theoretical slug to churn flow-pattern transition models and experimental data is performed. The flow-pattern database considers vertical upward air-water flow at standard temperature and pressure for 50 mm and 32 mm ID pipes. A briefly description of the models and its phenomenology is presented. In general, the performance of the transition models is poor. We found that new experimental studies describing objectively both stable and unstable slug flow-pattern are required. In this sense, the Wire Mesh Sensor (WMS) can assist to that aim. The potential of the WMS is outlined.

Plant-Wide Anti-Slug Control for Offshore Oil and Gas Processes

DEFF Research Database (Denmark)

Pedersen, Simon

In offshore Oil & Gas production processes the undesired severe slug flow regime can be present. The negative impact of severe slug is crucial to the production rate and process safety. In this work, the severe slugs which occur in the well-pipeline-riser system are experimentally and theoretically...... better than the ones developed for Pt . Furthermore, an alternative transmitter is experimentally investigated for online slug detection and monitoring. The transmitter is an Electrical Resistance Tomography (ERT) sensor measuring the electrical resistance over the cross-area section...

Characteristic behavior of bubbles and slugs in transient two-phase flow using image-processing method

International Nuclear Information System (INIS)

Goto, Shoji; Ishizaki, Yasuo; Ohashi, Hirotada; Akiyama, Mamoru

1995-01-01

Simulation of transient two-phase flow has been performed by solving transient hydrodynamic equations. However, constitution relations used in this simulation are primarily based on steady-state experimental results. Thus it is important to understand the transient behavior of bubbles and slugs, in particular, transient behavior of the void fraction, the interfacial area and the flow pattern, to confirm the applicability of the present simulation method and to advance two-phase flow simulation further. The present study deals with measurement of transient two-phase flow. We have measured local and instantaneous void fractions using imaging techniques, and compared the experimental data with simulation results. (author)

Review of Slug Detection, Modeling and Control Techniques for Offshore Oil & Gas Production Processes

DEFF Research Database (Denmark)

Pedersen, Simon; Løhndorf, Petar Durdevic; Yang, Zhenyu

2015-01-01

The current offshore oil & gas multi-phase production and transportation installations have big challenges related with the slugging flow: An unstable multi-phase flow regime where the flow rates, pressures and temperatures oscillate in the considered processes. Slug can be caused by different...... operating conditions and installation structures. The most severe slugs are often induced in long vertical risers or production wells, where liquid blocks gas at the riser/well base and correspondingly it causes the pressure to accumulate and hence originates the oscillating performance. There are many...... of these methods can simultaneously reduce the oil & gas production, which is a very big concern as the production rate is the key evaluation parameter for offshore production. We conclude that the slugging flow is a well-defined phenomenon, even though this subject has been extensively investigated in the past...

Program determines two-phase flow

International Nuclear Information System (INIS)

Yamashiro, C.E.; Espiell, L.G.S.; Farina, I.H.

1986-01-01

When a mixture of a gas and a liquid flows along a horizontal pipe, it is possible to have up to seven different flow patterns. These flow patterns are: 1. Dispersed. When nearly all the liquid is entrained as spray by the gas; 2. Annular. The liquid forms a film around the inside wall of the pipe, and the gas flows at a high velocity as a central core; 3. Bubble. Bubbles of gas move along at about the same velocity as the liquid; 4. Stratified. The liquid flows along the bottom of the pipe and the gas flows above over a smooth gas-liquid interface; 5. Wave. Is similar to stratified except the interface is disturbed by waves moving in the direction of flow; 6. Slug. Waves are picked up periodically in the form of frothy slugs that move at a much greater velocity than the average liquid velocity; 7. Plug. Alternate plugs of liquid and gas move along the pipe

Emulation and Control of Slugging Flows in a Gas-Lifted Offshore Oil Production Well Through a Lab-sized Facility

DEFF Research Database (Denmark)

Jepsen, Kasper Lund; Hansen, Leif; Mai, Christian

2013-01-01

flow and pressures in the production well system, which is referred to as the slugging flow problem. This instability is mainly due to the casing-heading mechanism. This work investigates the possibility to use a feedback control for stabilizing the production operation without sacrificing...... the production capability. A labsized production well system is constructed in an economic manner. Afterwards, a simple nonlinear model is derived according to physical principles and then verified with the experimental facility. A observer-based state feedback control is designed to handle the potential...... slugging problem. The developed controller manipulates the openness degree of the production choke based on feedback a number of pressure measurements. The current simulation results showed satisfactory control performances by stabilizing the system operation at some relatively large production rate which...

The model coupling fluid flow in reservoir with flow in horizontal wellbore

Energy Technology Data Exchange (ETDEWEB)

Liu, Xiangping; Jiang, Zhixiang [RIPED-TEXACO Horizontal Well Technology Laboratory (United States)

1998-12-31

Three-dimensional pressure distributions of oil flow in a reservoir with horizontal well were derived, and a new formula to calculate pressure drop along the horizontal wellbore was developed based on the principle of conservation of matter and momentum. The formula considers the effect of influx into the horizontal wellbore from the reservoir on pressure drop in the wellbore. A mathematical model to couple fluid flow in the reservoir with flow in the horizontal wellbore is presented. Model results and experimental data showed good correspondence. Results showed the influence of pressure drop on well performance. 13 refs., 2 tabs., 7 figs.

Investigations on flow reversal in stratified horizontal flow

International Nuclear Information System (INIS)

Staebler, T.; Meyer, L.; Schulenberg, T.; Laurien, E.

2005-01-01

The phenomena of flow reversal in stratified flows are investigated in a horizontal channel with application to the Emergency Core Cooling System (ECCS) in Pressurized Water Reactors (PWR). In case of a Loss-of-Coolant-Accident (LOCA), coolant can be injected through a secondary pipe within the feeding line of the primary circuit, the so called hot leg, counter-currently to the steam flow. It is essential that the coolant reaches the reactor core to prevent overheating. Due to high temperatures in such accident scenarios, steam is generated in the core, which escapes from the reactor vessel through the hot leg. In case of sufficiently high steam flow rates, only a reduced amount of coolant or even no coolant will be delivered to the reactor core. The WENKA test facility at the Institute for Nuclear and Energy Technologies (IKET) at Forschungszentrum Karlsruhe is capable to investigate the fluid dynamics of two-phase flows in such scenarios. Water and air flow counter-currently in a horizontal channel made of clear acrylic glass to allow full optical access. Flow rates of water and air can be varied independently within a wide range. Once flow reversal sets in, a strong hysteresis effect must be taken into account. This was quantified during the present investigations. Local experimental data are needed to expand appropriate models on flow reversal in horizontal two-phase flow and to include them into numerical codes. Investigations are carried out by means of Particle Image Velocimetry (PIV) to obtain local flow velocities without disturbing the flow. Due to the wavy character of the flow, strong reflections at the interfacial area must be taken into account. Using fluorescent particles and an optical filter allows eliminating the reflections and recording only the signals of the particles. The challenges in conducting local investigations in stratified wavy flows by applying optical measurement techniques are discussed. Results are presented and discussed allowing

Transition from condensation-induced counter-current flow to dispersed flow

International Nuclear Information System (INIS)

Gale, J.; Tiselj, I.

2004-01-01

Model of transition from the horizontally stratified condensation-induced counter-current flow to slug flow has been analyzed with computer code WAHA and compared to the experimental data obtained in the steamline of the PMK2 test facility of Hungarian Atomic Energy Institute. The experiment was performed in the steamline initially filled with hot vapor that was gradually flooded with cold liquid. Successful simulation of the condensation-induced water hammer that follows the transition, requires accurate description of the horizontally stratified and slug flow regimes and criteria for transition between both flow regimes. Current version of the WAHA code, not verified for the condensation induced type of the water hammer, predicts the water-hammer pressure peak that exceeds 600 bar, while the measured pressure is p m = 170 ± 50 bar. Sensitivity analysis of the inter-phase exchange terms and transition conditions, pointed to the most important closure relations for heat, mass and momentum transfer. The main conclusion of the analysis is large uncertainty of the simulations: minor modification of the crucial correlations can lead to a severe water-hammer in one case, or to the 'calm' transient without pressure peaks in the other case. Large uncertainty is observed in experiments. The same simulation was performed also with RELAP5 code. However, no water hammer was predicted. (author)

Neuronal responses to water flow in the marine slug tritonia diomedea

Directory of Open Access Journals (Sweden)

Jeffrey Blackwell

2005-07-01

Full Text Available The marine slug Tritonia diomedea must rely on its ability to touch and smell in order to navigate because it is blind. The primary factor that influences its crawling direction is the direction of water flow (caused by tides in nature. The sensory cells that detect flow and determine flow direction have not been identified. The lateral branch of Cerebral Nerve 2 (latCeN2 has been identified as the nerve that carries sensory axons to the brain from the flow receptors inthe oral tentacles. Backfilling this nerve to the brain resulted in the labeling of a number of cells located throughout the brain. Most of the labeled cells are concentrated in the cerebral ganglion where the nerve enters the brain. The medial and lateral branches of CeN2 were backfilled for comparison of the pattern of cells from each nerve. A map of the cells innervated by latCeN2 reveals the location of the stained cells. Extracellular recording from latCeN2 revealed its involvement in the detection of water flow and orientation. The nerve becomes active in response to water flow stimulation. Intracellular recordings of the electrical activity of these cells in a live animal will be the next step to determine if these cells are the flow receptors.

Flow regimes

International Nuclear Information System (INIS)

Kh'yuitt, G.

1980-01-01

An introduction into the problem of two-phase flows is presented. Flow regimes arizing in two-phase flows are described, and classification of these regimes is given. Structures of vertical and horizontal two-phase flows and a method of their identification using regime maps are considered. The limits of this method application are discussed. The flooding phenomena and phenomena of direction change (flow reversal) of the flow and interrelation of these phenomena as well as transitions from slug regime to churn one and from churn one to annular one in vertical flows are described. Problems of phase transitions and equilibrium are discussed. Flow regimes in tubes where evaporating liquid is running, are described [ru

Experimental studies of flooding in nearly horizontal pipes

International Nuclear Information System (INIS)

Choi, Ki Yong

1993-02-01

To investigate the flooding phenomenon in nearly horizontal pipes the experimental studies are performed in the facility with the length of 2160mm, with three different inner diameters of 40mm, 60mm, and 70mm, and with the various inclination angles. Air and water approximately at room temperature and at atmospheric pressure are used as test fluids. The local void factions are measured by the three conductance probes located at the inlet, middle, and exit of water flow, respectively. Two mechanisms governing the transition to flooding are proposed. The effects of pipe end geometry, pipe diameter, and inclination angle are investigated and the comparisons with the slug formation models are conducted. It is found in this study that the transition to flooding is originated from two mechanisms i.e. 'wave instability' and 'high head flooding', and two regions (sub-critical and super-critical) coexist if the air flow increases up to a criticalvalue. It is observed that large roll waves are grown to the critical amplitude in the sub-critical region, does not show any dustive growth phenomenon. When the void fraction in the sub-critical region is used as the parameter for the flooding criterion, Ishii's slug formation model predicts the data without systematid errors. On the other hand, when the voide fraction in the super-critical region is selected as the parameter, Taitel's slug formation model best fitsthe data. Data obtained in the condition of high head flooding are not in good agreement with the results predicted by the slug formation models. Also, the transition criterion to the onset of flooding is very sensitive to the inclination angle, and the effect of pipe end geometry on the onset of flooding is negligible

Flow mapping for ESS horizontal target

Energy Technology Data Exchange (ETDEWEB)

Takeda, Y.; Kikura, H.; Taishi, T. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-09-01

Flow behaviour for ESS horizontal target is studied experimentally using two dimensional water model. A velocity field of stationary flow in reaction zone has been obtained. Three dimensional effect was also studied as a spanwise flow structure. (author) 3 figs., 3 refs.

Fluid Mechanics of Taylor Bubbles and Slug Flows in Vertical Channels

International Nuclear Information System (INIS)

Anglart, Henryk; Podowski, Michael Z.

2002-01-01

Fluid mechanics of Taylor bubbles and slug flows is investigated in vertical, circular channels using detailed, three-dimensional computational fluid dynamics simulations. The Volume of Fluid model with the interface-sharpening algorithm, implemented in the commercial CFX4 code, is used to predict the shape and velocity of Taylor bubbles moving along a vertical channel. Several cases are investigated, including both a single Taylor bubble and a train of bubbles rising in water. It is shown that the potential flow solution underpredicts the water film thickness around Taylor bubbles. Furthermore, the computer simulations that are performed reveal the importance of properly modeling the three-dimensional nature of phenomena governing the motion of Taylor bubbles. Based on the present results, a new formula for the evaluation of bubble shape is derived. Both the shape of Taylor bubbles and the bubble rise velocity predicted by the proposed model agree well with experimental observations. Furthermore, the present model shows good promise in predicting the coalescence of Taylor bubbles

Computational investigations of the mixing performance inside liquid slugs generated by a microfluidic T-junction.

Science.gov (United States)

Li, Yuehao; Reddy, Rupesh K; Kumar, Challa S S R; Nandakumar, Krishnaswamy

2014-09-01

Droplet-based microfluidics has gained extensive research interest as it overcomes several challenges confronted by conventional single-phase microfluidics. The mixing performance inside droplets/slugs is critical in many applications such as advanced material syntheses and in situ kinetic measurements. In order to understand the effects of operating conditions on the mixing performance inside liquid slugs generated by a microfluidic T-junction, we have adopted the volume of fluid method coupled with the species transport model to study and quantify the mixing efficiencies inside slugs. Our simulation results demonstrate that an efficient mixing process is achieved by the intimate collaboration of the twirling effect and the recirculating flow. Only if the reagents are distributed transversely by the twirling effect, the recirculating flow can bring in convection mechanism thus facilitating mixing. By comparing the mixing performance inside slugs at various operating conditions, we find that slug size plays the key role in influencing the mixing performance as it determines the amount of fluid to be distributed by the twirling effect. For the cases where short slugs are generated, the mixing process is governed by the fast convection mechanism because the twirling effect can distribute the fluid to the flow path of the recirculating flow effectively. For cases with long slugs, the mixing process is dominated by the slow diffusion mechanism since the twirling effect is insufficient to distribute the large amount of fluid. In addition, our results show that increasing the operating velocity has limited effects on improving the mixing performance. This study provides the insight of the mixing process and may benefit the design and operations of droplet-based microfluidics.

Slug flow model for infiltration into fractured porous media

International Nuclear Information System (INIS)

Martinez, M.J.

1999-01-01

A model for transient infiltration into a periodically fractured porous layer is presented. The fracture is treated as a permeable-walled slot and the moisture distribution is in the form of a slug being an advancing meniscus. The wicking of moisture from the fracture to the unsaturated porous matrix is a nonlinear diffusion process and is approximately by self-similar solutions. The resulting model is a nonlinear Volterra integral equation with a weakly singular kernel. Numerical analysis provides solutions over a wide range of the parameter space and reveals the asymptotic forms of the penetration of this slug in terms of dimensionless variables arising in the model. The numerical solutions corroborate asymptotic results given earlier by Nitao and Buscheck (1991), and by Martinez (1988). Some implications for the transport of liquid in fractured rock are discussed

Two-phase flow patterns in horizontal rectangular minichannel

Directory of Open Access Journals (Sweden)

Ron’shin Fedor

2016-01-01

Full Text Available The two-phase flow in a short horizontal channel of rectangular cross-section of 1 × 19 mm2 has been studied experimentally. Five conventional two-phase flow patterns have been detected (bubble, churn, stratified, annular and jet and transitions between them have been determined. It is shown that a change in the width of the horizontal channels has a substantial effect on the boundaries between the flow regimes.

A development of multiphase flow facility

International Nuclear Information System (INIS)

Ismail Mustapha; Jaafar Abdullah

2004-01-01

Multiphase liquid flow facility shall be enabling to transport of oil/gas/water in pipelines. In horizontal pipelines, the different flow patterns that could be observed. The flow pattern will depend mainly on the gas and liquid velocities, and gas liquid ratio. For very high liquid velocities and low gas liquid ratios, the dispersed bubble flow is observed. For low flow rates of liquid and gas, a smooth or wavy stratified flow is expected. For intermediate liquid velocities, rolling waves of liquids are formed. The rolling waves increase to the point of forming a plug flow and a slug flow. For very high gas velocities, the annular flow is observed Also include a tillable test section allowing for testing at any angle between 0 0 degree from horizontal, lowering the measurement uncertainties and increased capabilities with respect to flow rates and gas fractions. (Author)

On intermittent flow characteristics of gas–liquid two-phase flow

Energy Technology Data Exchange (ETDEWEB)

Thaker, Jignesh; Banerjee, Jyotirmay, E-mail: jbaner@gmail.com

2016-12-15

Highlights: • Unified correlations for intermittent flow characteristics are developed. • Influence of inflow conditions on intermittent flow characteristics is analysed. • Developed correlations can be used for effective design of piping components. - Abstract: Flow visualisation experiments are reported for intermittent regime of gas–liquid two-phase flow. Intermittent flow characteristics, which include plug/slug frequency, liquid plug/slug velocity, liquid plug/slug length, and plug/slug bubble length are determined by image processing of flow patterns captured at a rate of 1600 frames per second (FPS). Flow characteristics are established as a function of inlet superficial velocity of both the phases (in terms of Re{sub SL} and Re{sub SG}). The experimental results are first validated with the existing correlations for slug flow available in literature. It is observed that the correlations proposed in literature for slug flow do not accurately predict the flow characteristics in the plug flow regime. The differences are clearly highlighted in this paper. Based on the measured database for both plug and slug flow regime, modified correlations for the intermittent flow regime are proposed. The correlations reported in the present paper, which also include plug flow characteristics will aid immensely to the effective design and optimization of operating conditions for safer operation of two-phase flow piping systems.

MULTIPHASE DROPLET/SLUG BREAK-UP MECHANISM IN MICROFLUIDIC T-JUNCTIONS AT VARIOUS WEBER NUMBERS

Directory of Open Access Journals (Sweden)

Wan Leng (Dawn Leow

2011-10-01

Full Text Available Normal 0 false false false EN-MY X-NONE X-NONE The formation of immiscible liquid droplets, or slugs, in microchannels features the advantages of volume control and mixing enhancement over single-phase microflows. Although the applications of droplet-based microfluidics have been widely demonstrated, the fundamental physics governing droplet break-up remains an area of active research. This study defines an effective Weber (Weeff number that characterizes the interplay of interfacial tension, shear stress and channel pressure drop in driving slug formation in T-junction microchannel for a relative range of low, intermediate and high flow rates. The immiscible fluid system in this study consists of Tetradecane slug formation in Acetonitrile. The progressive deformation of slug interfaces during break-up events is observed. Experimental results indicate that, at a relatively low Weeff, clean slug break-up occurs at the intersection of the side and main channels. At intermediate Weeff, the connecting neck of the dispersed phase is stretched to a short and thin trail of laminar flow prior to breaking up a short distance downstream of the T-junction. At a relatively high Weeff, the connecting neck develops into a longer and thicker trail of laminar flow that breaks up further downstream of the main channel.

Severe slugging in gas-liquid two-phase pipe flow

NARCIS (Netherlands)

Malekzadeh, R.

2012-01-01

transportation facilities. In an offshore oil and gas production facility, pipeline-riser systems are required to transport two-phase hydrocarbons from subsurface oil and gas wells to a central production platform. Severe slugs reaching several thousands pipe diameters may occur when transporting

SlugIn 1.0: A Free Tool for Automated Slug Test Analysis.

Science.gov (United States)

Martos-Rosillo, Sergio; Guardiola-Albert, Carolina; Padilla Benítez, Alberto; Delgado Pastor, Joaquín; Azcón González, Antonio; Durán Valsero, Juan José

2018-05-01

The correct characterization of aquifer parameters is essential for water-supply and water-quality investigations. Slug tests are widely used for these purposes. While free software is available to interpret slug tests, some codes are not user-friendly, or do not include a wide range of methods to interpret the results, or do not include automatic, inverse solutions to the test data. The private sector has also generated several good programs to interpret slug test data, but they are not free of charge. The computer program SlugIn 1.0 is available online for free download, and is demonstrated to aid in the analysis of slug tests to estimate hydraulic parameters. The program provides an easy-to-use Graphical User Interface. SlugIn 1.0 incorporates automated parameter estimation and facilitates the visualization of several interpretations of the same test. It incorporates solutions for confined and unconfined aquifers, partially penetrating wells, skin effects, shape factor, anisotropy, high hydraulic conductivity formations and the Mace test for large-diameter wells. It is available in English and Spanish and can be downloaded from the web site of the Geological Survey of Spain. Two field examples are presented to illustrate how the software operates. © 2018, National Ground Water Association.

Research for rolling effects on flow pattern of gas-water flow in horizontal tubes

International Nuclear Information System (INIS)

Luan Feng; Yan Changqi

2007-01-01

The flow pattern transition of two-phase flow is caused by the inertial force resulted from rolling and incline of horizontal tubes under rolling state. an experimental study on the flow patterns of gas-water flow was carried out in horizontal tubes under rolling state, which rolling period is 15 second and rolling angle is 10 degrees, and a pattern flow picture is shown. It was found that there are two flow patterns in one rolling period under some gas flux and water flux. (authors)

Intelligent sensors for evaluating reservoir and well profiles in horizontal wells : Saudi Arabia case histories

Energy Technology Data Exchange (ETDEWEB)

Al-Buali, M.H.; Dashash, A.A. [Saudi Aramco, Dhahran (Saudi Arabia); El Gammal, T.; Arevalo, F.; Torne, J. [Halliburton Energy Services, Calgary, AB (Canada)

2010-07-01

Horizontal wells are commonly used in Saudi Arabia because they have proven advantages in optimizing production and cost. However, in order to ensure proper production, these wells occasionally require downhole measurements of the flow profile; wellbore parameters such as water entry points; and productivity index for remedial action, such as water shut off or well stimulation. Evaluating the performance of a well also contributes to a better understanding of sweep, water production and cross flow, particularly in long reach wells. The most common flow regime at downhole conditions is a stratified flow regime in which lighter oil flows on top and heavier water flows on bottom. Slugging and bubbling flow regimes are typical of low oil flow rate and are considered unstable flow regimes. This paper described a new generation of production logging tools (PLTs) that have been used on some horizontal wet producers located in Saudi Arabia. The new PLTs consists of arrays of spinners and sensors to log the entire cross section to describe the horizontal flow regime and measure the downhole production and phases. In an effort to find the best logging procedure, the PLT was tested using two methods, notably coiled tubing (CT) and wireline tractor. It was concluded that PLTs are reliable and accurate. Case studies involving planning, deployment, data acquisition, and detailed analysis of PLTs were presented. 35 refs., 1 tab., 20 figs.

Flow visualization study of post critical heat flux region for inverted bubbly, slug and annular flow regimes

International Nuclear Information System (INIS)

Denten, J.G.; Ishii, M.

1988-11-01

A visual study of film boiling using still photographic and high- speed motion picture methods was carried out in order to analyze the post-CHF hydrodynamics for steady-state inlet pre-CHF two-phase flow regimes. Pre-CHF two-phase flow regimes were established by introducing Freon 113 liquid and nitrogen gas into a jet core injection nozzle. An idealized, post-CHF two-phase core initial flow geometry (cylindrical multiphase jet core surrounded by a coaxial annulus of gas) was established at the nozzle exit by introducing nitrogen gas into the annular gap between the jet nozzle two-phase effluent and the heated test section inlet. For the present study three basic post-CHF flow regimes have been observed: the rough wavy regime (inverted annular flow preliminary break down), the agitated regime (transition between inverted annular and dispersed droplet flow), and the dispersed ligament/droplet regime. For pre-CHF bubbly flow in the jet nozzle, the post-CHF flow (beginning from jet nozzle exit/heated test section inlet) consists of the rough wavy regime, followed by the agitated and then the dispersed ligament/droplet regime. In the same way, for pre-CHF slug flow in the jet core, the post-CHF flow is comprised of the agitated regime at the nozzle exit, followed by the dispersed regime. Pre-CHF annular jet core flow results in a small, depleted post-CHF agitated flow regime at the nozzle exit, immediately followed by the dispersed ligament/droplet regime. Observed post dryout hydrodynamic behavior is reported, with particular attention given to the transition flow pattern between inverted annular and dispersed droplet flow. 43 refs., 20 figs., 5 tabs

Analyses and estimates of hydraulic conductivity from slug tests in alluvial aquifer underlying Air Force Plant 4 and Naval Air Station-Joint Reserve Base Carswell Field, Fort Worth, Texas

Science.gov (United States)

Houston, Natalie A.; Braun, Christopher L.

2004-01-01

This report describes the collection, analyses, and distribution of hydraulic-conductivity data obtained from slug tests completed in the alluvial aquifer underlying Air Force Plant 4 and Naval Air Station-Joint Reserve Base Carswell Field, Fort Worth, Texas, during October 2002 and August 2003 and summarizes previously available hydraulic-conductivity data. The U.S. Geological Survey, in cooperation with the U.S. Air Force, completed 30 slug tests in October 2002 and August 2003 to obtain estimates of horizontal hydraulic conductivity to use as initial values in a ground-water-flow model for the site. The tests were done by placing a polyvinyl-chloride slug of known volume beneath the water level in selected wells, removing the slug, and measuring the resulting water-level recovery over time. The water levels were measured with a pressure transducer and recorded with a data logger. Hydraulic-conductivity values were estimated from an analytical relation between the instantaneous displacement of water in a well bore and the resulting rate of head change. Although nearly two-thirds of the tested wells recovered 90 percent of their slug-induced head change in less than 2 minutes, 90-percent recovery times ranged from 3 seconds to 35 minutes. The estimates of hydraulic conductivity range from 0.2 to 200 feet per day. Eighty-three percent of the estimates are between 1 and 100 feet per day.

Multivariate recurrence network analysis for characterizing horizontal oil-water two-phase flow.

Science.gov (United States)

Gao, Zhong-Ke; Zhang, Xin-Wang; Jin, Ning-De; Marwan, Norbert; Kurths, Jürgen

2013-09-01

Characterizing complex patterns arising from horizontal oil-water two-phase flows is a contemporary and challenging problem of paramount importance. We design a new multisector conductance sensor and systematically carry out horizontal oil-water two-phase flow experiments for measuring multivariate signals of different flow patterns. We then infer multivariate recurrence networks from these experimental data and investigate local cross-network properties for each constructed network. Our results demonstrate that a cross-clustering coefficient from a multivariate recurrence network is very sensitive to transitions among different flow patterns and recovers quantitative insights into the flow behavior underlying horizontal oil-water flows. These properties render multivariate recurrence networks particularly powerful for investigating a horizontal oil-water two-phase flow system and its complex interacting components from a network perspective.

Influence of riser-induced slugs on the downstream separation processes

DEFF Research Database (Denmark)

Pedersen, Simon; Løhndorf, Petar Durdevic; Yang, Zhenyu

2017-01-01

In Oil & Gas installations the severe slug is an undesired flow regime due to the negative impact on the production rate and facility safety. This study will evaluate the severe riser-induced slugs’ influence to a typical separation process, consisting of a 3-phase gravity separator physically...... linked to a de-oiling hydrocyclone, based on experimental tests performed on a laboratory testing facility. Several scenarios are compared, while three PID controllers’ coefficients are kept constant for all the tests: The separator pressure, water level, and hydrocyclone pressure-drop-ratio (PDR......) controllers. Each respective scenario makes a comparison between uncontrolled, open-, and closed-loop anti-slug control configurations. It is concluded that both open- and closed-loop anti-slug control strategies improve the water level and PDR setpoint tracking equally well, but that the closed-loop strategy...

Two-phase flow characteristic of inverted bubbly, slug and annular flow in post-critical heat flux region

International Nuclear Information System (INIS)

Ishii, M.; Denten, J.P.

1988-01-01

Inverted annular flow can be visualized as a liquid jet-like core surrounded by a vapor annulus. While many analytical and experimental studies of heat transfer in this regime have been performed, there is very little understanding of the basic hydrodynamics of the post-CHF flow field. However, a recent experimental study was done that was able to successfully investigate the effects of various steady-state inlet flow parameters on the post-CHF hydrodynamics of the film boiling of a single phase liquid jet. This study was carried out by means of a visual photographic analysis of an idealized single phase core inverted annular flow initial geometry (single phase liquid jet core surrounded by a coaxial annulus of gas). In order to extend this study, a subsequent flow visualization of an idealized two-phase core inverted annular flow geometry (two-phase central jet core, surrounded by a coaxial annulus of gas) was carried out. The objective of this second experimental study was to investigate the effect of steady-state inlet, pre-CHF two-phase jet core parameters on the hydrodynamics of the post-CHF flow field. In actual film boiling situations, two-phase flows with net positive qualities at the CHF point are encountered. Thus, the focus of the present experimental study was on the inverted bubbly, slug, and annular flow fields in the post dryout film boiling region. Observed post dryout hydrodynamic behavior is reported. A correlation for the axial extent of the transition flow pattern between inverted annular and dispersed droplet flow (the agitated regime) is developed. It is shown to depend strongly on inlet jet core parameters and jet void fraction at the dryout point. 45 refs., 9 figs., 4 tabs

Two-phase flow characteristic of inverted bubbly, slug, and annular flow in post-critical heat flux region

International Nuclear Information System (INIS)

Ishii, M.; Denten, J.P.

1989-01-01

Inverted annular flow can be visualized as a liquid jet-like core surrounded by a vapor annulus. While many analytical and experimental studies of heat transfer in this regime have been performed, there is very little understanding of the basic hydrodynamics of the post-critical heat flux (CHF) flow field. However, a recent experimental study was done that was able to successfully investigate the effects of various steady-state inlet flow parameters on the post-CHF hydrodynamics of the film boiling of a single phase liquid jet. This study was carried out by means of a visual photographic analysis of an idealized single phase core inverted annular flow initial geometry (single phase liquid jet core surrounded by a coaxial annulus of gas). In order to extend this study, a subsequent flow visualization of an idealized two-phase core inverted annular flow geometry (two-phase central jet core, surrounded by a coaxial annulus of gas) was carried out. The objective of this second experimental study was to investigate the effect of steady-state inlet, pre-CHF two-phase jet core parameters on the hydrodynamics of the post-CHF flow field. In actual film boiling situations, two-phase flows with net positive qualities at the CHF point are encountered. Thus, the focus of the present experimental study was on the inverted bubbly, slug, and annular flow fields in the post dryout film boiling region. Observed post dryout hydrodynamic behavior is reported. A correlation for the axial extent of the transition flow pattern between inverted annular and dispersed droplet flow (the agitated regime) is developed. It is shown to depend strongly on inlet jet core parameters and jet void fraction at the dryout point

Development of Next Generation Multiphase Pipe Flow Prediction Tools

Energy Technology Data Exchange (ETDEWEB)

Tulsa Fluid Flow

2008-08-31

closure relation development for different flow conditions. Modeling studies were performed in two parts, Technology Assessment and Model Development and Enhancement. The results of the Technology assessment study indicated that the performance of the current state of the art two-phase flow models was poor especially for three-phase pipeline flow when compared with the existing data. As part of the model development and enhancement study, a new unified model for gas-oil-water three-phase pipe flow was developed. The new model is based on the dynamics of slug flow, which shares transition boundaries with all the other flow patterns. The equations of slug flow are used not only to calculate the slug characteristics, but also to predict transitions from slug flow to other flow patterns. An experimental program including three-phase gas-oil-water horizontal flow and two-phase horizontal and inclined oil-water flow testing was conducted utilizing a Tulsa University Fluid Flow Projects Three-phase Flow Facility. The experimental results were incorporated into the unified model as they became available, and model results were used to better focus and tailor the experimental study. Finally, during the Period 2, a new three-phase databank has been developed using the data generated during this project and additional data available in the literature. The unified model to predict the gas-oil-water three phase flow characteristics was tested by comparing the prediction results with the data. The results showed good agreements.

Simultaneous PIV and pulsed shadow technique in slug flow: a solution for optical problems

Energy Technology Data Exchange (ETDEWEB)

Nogueira, S. [Karman Institute for Fluid Dynamics, Chaussee de Waterloo 72, B-1640, Rhode Saint Genese (Belgium); Centro de Estudos de Fenomenos de Transporte, Departamento de Eng. Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto (Portugal); Sousa, R.G.; Pinto, A.M.F.R.; Campos, J.B.L.M. [Centro de Estudos de Fenomenos de Transporte, Departamento de Eng. Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto (Portugal); Riethmuller, M.L. [Karman Institute for Fluid Dynamics, Chaussee de Waterloo 72, B-1640, Rhode Saint Genese (Belgium)

2003-12-01

A recent technique of simultaneous particle image velocimetry (PIV) and pulsed shadow technique (PST) measurements, using only one black and white CCD camera, is successfully applied to the study of slug flow. The experimental facility and the operating principle are described. The technique is applied to study the liquid flow pattern around individual Taylor bubbles rising in an aqueous solution of glycerol with a dynamic viscosity of 113 x 10{sup -3} Pa s. With this technique the optical perturbations found in PIV measurements at the bubble interface are completely solved in the nose and in annular liquid film regions as well as in the rear of the bubble for cases in which the bottom is flat. However, for Taylor bubbles with concave oblate bottoms, some optical distortions appear and are discussed. The measurements achieved a spatial resolution of 0.0022 tube diameters. The results reported show high precision and are in agreement with theoretical and experimental published data. (orig.)

Analytical solution of velocity for ammonia-water horizontal falling-film flow

International Nuclear Information System (INIS)

Zhang, Qiang; Gao, Yide

2016-01-01

Highlights: • We built a new falling-film flow model that analyzed the film flow characteristics. • We have obtained a new formula of film thickness over the horizontal tube. • We derived analysis solution to analyze the effect of inertial force to velocity in the entrance region of liquid film. • It described the characters of the ammonia-waterfalling-film film over the horizontal tube. • It is good for falling-film absorption, generation and evaporation to optimizing the design parameters and further improving the capabilities. - Abstract: A new horizontal tube falling film velocity model was built and calculated to analyze the problem of film flow conditions. This model also analyzed the film thickness distribution in horizontal tube falling film flow and considered the effect of the inertial force on velocity. The film thickness and velocity profile can be obtained based on the principle of linear superposition, a method of separation of variables that introduces the effect of variable inertial force on the velocity profile in the process of falling-film absorption. The film flow condition and the film thickness distribution at different fluid Reynolds numbers (Re) and tube diameters were calculated and compared with the results of the Crank–Nicolson numerical solution under the same conditions. The results show that the film flow condition out of a horizontal tube and that the film thickness increases with the fluid Re. At a specific Re and suitable tube diameter, the horizontal tube reaches a more uniform film. Finally, the analysis results have similar trend with the experimental and numerical predicted data in literature.

Experimental Study on Flow Boiling of Carbon Dioxide in a Horizontal Microfin Tube

Science.gov (United States)

Kuwahara, Ken; Ikeda, Soshi; Koyama, Shigeru

This paper deals with the experimental study on flow boiling heat transfer of carbon dioxide in a micro-fin tube. The geometrical parameters of micro-fin tube used in this study are 6.07 mm in outer diameter, 5.24 mm in average inner diameter, 0.256 mm in fin height, 20.4 in helix angle, 52 in number of grooves and 2.35 in area expansion ratio. Flow patterns and heat transfer coefficients were measured at 3-5 MPa in pressure, 300-540 kg/(m2s) in mass velocity and -5 to 15 °C in CO2 temperature. Flow patterns of wavy flow, slug flow and annular flow were observed. The measured heat transfer coefficients of micro-fin tube were 10-40 kW/(m2K). Heat transfer coefficients were strongly influenced by pressure.

Determination of C0-60 in Cobalt Slugs and Slabs and Radionuclides in Curium Sampler Slugs L-Reactor Disassembly Basin

International Nuclear Information System (INIS)

Casella, V.R.

2004-01-01

Co-60 was historically produced in the SRS reactors. Cobalt slugs were irradiated in the early 1970s. Post-production, remaining cobalt slugs (including slab form) were consolidated for storage. There are approximately nine hundred cobalt slugs currently stored awaiting final disposition. These slugs had historically incomplete documentation for activity rates; therefore, assaying was required in order to determine their activity levels. Since the gamma dose rate from these slugs is extremely high, the most cost effective way to shield a source of this magnitude from personnel and the radiation detector was to use the basin water in which the slugs are stored as the shield. A sodium iodide gamma detector was placed above a specially designed air collimator assembly, so that slug was at least eight feet from the detector and was shielded by the basin water. Using a sodium iodide detector and multichannel analyzer system and an underwater collimator assembly, Co-60 concentrations we re determined for Disassembly Basin cobalt slugs and slabs and 18 curium sampler slugs. The total activity of all of the assayed slugs summed to 31,783 curies. From the Co-60 concentrations of the curium sampler slugs, the irradiation flux was determined for the known irradiation time. The amounts of Pu-238, 239, 240, 241, 242; Am-241, 243; and Cm-242, 244 produced were then obtained based on the original amount of Pu-239 irradiated

DIVERGENT HORIZONTAL SUB-SURFACE FLOWS WITHIN ACTIVE REGION 11158

Energy Technology Data Exchange (ETDEWEB)

Jain, Kiran; Tripathy, S. C.; Hill, F., E-mail: kjain@nso.edu, E-mail: stripathy@nso.edu, E-mail: fhill@nso.edu [National Solar Observatory, 950 N Cherry Avenue, Tucson, AZ 85719 (United States)

2015-07-20

We measure the horizontal subsurface flow in a fast emerging active region (AR; NOAA 11158) using the ring-diagram technique and the Helioseismic and Magnetic Imager high spatial resolution Dopplergrams. This AR had a complex magnetic structure and displayed significant changes in morphology during its disk passage. Over a period of six days from 2011 February 11 to 16, the temporal variation in the magnitude of the total velocity is found to follow the trend of magnetic field strength. We further analyze regions of individual magnetic polarity within AR 11158 and find that the horizontal velocity components in these sub-regions have significant variation with time and depth. The leading and trailing polarity regions move faster than the mixed-polarity region. Furthermore, both zonal and meridional components have opposite signs for trailing and leading polarity regions at all depths showing divergent flows within the AR. We also find a sharp decrease in the magnitude of total horizontal velocity in deeper layers around major flares. It is suggested that the re-organization of magnetic fields during flares, combined with the sunspot rotation, decreases the magnitude of horizontal flows or that the flow kinetic energy has been converted into the energy released by flares. After the decline in flare activity and sunspot rotation, the flows tend to follow the pattern of magnetic activity. We also observe less variation in the velocity components near the surface but these tend to increase with depth, further demonstrating that the deeper layers are more affected by the topology of ARs.

FLOW DISTRIBUTION IN A SOLAR COLLECTOR PANEL WITH HORIZONTAL FINS

DEFF Research Database (Denmark)

Fan, Jianhua; Shah, Louise Jivan; Furbo, Simon

2005-01-01

The objective of this work is to theoretically and experimentally investigate the flow and temperature distribution in a solar collector panel with an absorber consisting of horizontal fins. Fluid flow and heat transfer in the collector panel are studied by means of computational fluid dynamics...... (CFD) calculations. Further, experimental investigations of a 12.5 m² solar collector panel with 16 parallel connected horizontal fins are carried out. The flow distribution through the absorber is evaluated by means of temperature measurements on the backside of the absorber tubes. The measured...

Gas-liquid-liquid three-phase flow pattern and pressure drop in a microfluidic chip : similarities with gas-liquid/liquid-liquid flows

NARCIS (Netherlands)

Yue, J.; Rebrov, E.; Schouten, J.C.

2014-01-01

We report a three-phase slug flow and parallel-slug flow as two major flow patterns found under the nitrogen-decane-water flow through a glass microfluidic chip which features a long microchannel with a hydraulic diameter of 98 µm connected to a cross-flow mixer. The three-phase slug flow pattern is

Feasibility of oil recovery by chemical flooding through horizontal wells

Energy Technology Data Exchange (ETDEWEB)

El-Abbas, A.M.; El-Sallaly, M. E.; Sayyouh, M. H.; El-Batanony, M. H.; Darwich, T. M.; Desouky, S. M. [Cairo Univ (Egypt)

1998-12-31

Crude oil production in the Gulf of Suez by polymer, surfactant, and surfactant/polymer flooding from a horizontal well in a scaled five-spot sandpacked model was studied. The suitability of the enhanced oil recovery predictive models, developed by the U.S. Department of Energy, was investigated for their ability to predict the experimental data and to assess the feasibility of oil recovery by chemical flooding. Good agreement was found between the predicted and experimental values. Experimental results showed that oil recovery was significantly affected by the physical properties of the crude oil and chemical solutions; that oil recovery was higher for a polymer flooding than for a surfactant flooding operation; and that oil recovery was improved by increasing the perforated length ratio up to a value of 0.81. A tendency for oil recovery to decrease was observed when the horizontal well was positioned below or above the central axis path of the formation at the advanced injection stages; and oil recovery by surfactant or polymer flooding was significantly affected by the onset timing of the surfactant or polymer slug injection. The oil-water bank stability in surfactant and polymer flooding processes was found to be dependent on slug size and slug injection time. 23 refs., 1 tab., 17 figs.

A mechanistic determination of horizontal flow regime bound using void wave celerity

Energy Technology Data Exchange (ETDEWEB)

Park, J.W. [Ajou Univ., Suwon (Korea, Republic of)

1995-09-01

The two-phase flow regime boundaries in a horizontal channel has been investigated by using the behavior of the second order void wave celerities. The average two-fluid model has been constituted with closure relations for horizontally stratified and bubbly flows. A vapor phase turbulent stress model for a smooth interface geometry has been included. It is found that the second order waves (i.e., eigenvalues) propagate in opposite direction with almost the same speed when the liquid phase is stationary. Using the well-posedness limit of the two-phase system, the dispersed-stratified flow regime boundary has been modeled. Two-phase Froude number has been theoretically found to be a convenient parameter in quantifying the flow regime boundary as a function of the void fraction. It is found that interaction between void wave celerities become stronger as the two-phase Froude number is reduced. This result should be interpreted as that gravity and the relative velocity are key parameters in determining flow regime boundaries in a horizontal flow. The influence of the vapor phase turbulent stress found to stabilize the flow stratification. This study clearly shows that the average two-fluid model is very effective for a mechanistic determination of horizontal flow regimes if appropriate closure relations are developed.

A mechanistic determination of horizontal flow regime bound using void wave celerity

International Nuclear Information System (INIS)

Park, J.W.

1995-01-01

The two-phase flow regime boundaries in a horizontal channel has been investigated by using the behavior of the second order void wave celerities. The average two-fluid model has been constituted with closure relations for horizontally stratified and bubbly flows. A vapor phase turbulent stress model for a smooth interface geometry has been included. It is found that the second order waves (i.e., eigenvalues) propagate in opposite direction with almost the same speed when the liquid phase is stationary. Using the well-posedness limit of the two-phase system, the dispersed-stratified flow regime boundary has been modeled. Two-phase Froude number has been theoretically found to be a convenient parameter in quantifying the flow regime boundary as a function of the void fraction. It is found that interaction between void wave celerities become stronger as the two-phase Froude number is reduced. This result should be interpreted as that gravity and the relative velocity are key parameters in determining flow regime boundaries in a horizontal flow. The influence of the vapor phase turbulent stress found to stabilize the flow stratification. This study clearly shows that the average two-fluid model is very effective for a mechanistic determination of horizontal flow regimes if appropriate closure relations are developed

Numerical simulation of two-phase flow in horizontal interconnected subchannels

International Nuclear Information System (INIS)

Shourki, M.; Carver, M.B.; Tahir, A.

1985-01-01

Different subchannel computer codes have been successfully used for the thermal-hydraulic analysis of coolant flow in vertical fuel channels. None of these methods, however, is suitable for two-phase flow in horizontal fuel channels, such as those of the CANDU nuclear reactors, due to the lack of appropriate constitutive relationships that can correctly account for the gravity separation effects. A transverse vapor drift model that accounts for the combined effect of gravity separation and turbulent diffusion has been incorporated into the existing subchannel computer code SAGA. Although the basic structure of the code remains similar to SAGA III, some modifications in both the mathematical formulation and numerical solution have been incorporated. These modifications resulted in significant improvements in the code's ability to model horizontal two-phase subchannel flow. The new version of the code was tested and found to be capable of simulating the complex exchange phenomenon between adjacent horizontal subchannels caused by the interaction of turbulent diffusion, pressure gradient, and gravity-induced cross flows. The code predictions were compared with experimental data obtained from two different sources and showed good agreement

Falling film flow, heat transfer and breakdown on horizontal tubes

International Nuclear Information System (INIS)

Rogers, J.T.

1980-11-01

Knowledge of falling film flow and heat transfer characteristics on horizontal tubes is required in the assessment of certain CANDU reactor accident sequences for those CANDU reactors which use moderator dump as one of the shut-down mechanisms. In these reactors, subsequent cooling of the calandria tubes is provided by falling films produced by sprays. This report describes studies of falling film flow and heat transfer characteristics on horizontal tubes. Analyses using integral methods are given for laminar and turbulent flow, ignoring and accounting for momentum effects in the film. Preliminary experiments on film flow stability on horizontal tubes are described and various mechanisms of film breakdown are examined. The work described in this report shows that in LOCA with indefinitely delayed ECI in the NPD or Douglas Point (at 70 percent power) reactors, the falling films on the calandria tubes will not be disrupted by any of the mechanisms considered, provided that the pressure tubes do not sag onto the calandria tubes. However, should the pressure tubes sag onto the calandria tubes, film disruption will probably occur

Complex networks from experimental horizontal oil–water flows: Community structure detection versus flow pattern discrimination

International Nuclear Information System (INIS)

Gao, Zhong-Ke; Fang, Peng-Cheng; Ding, Mei-Shuang; Yang, Dan; Jin, Ning-De

2015-01-01

We propose a complex network-based method to distinguish complex patterns arising from experimental horizontal oil–water two-phase flow. We first use the adaptive optimal kernel time–frequency representation (AOK TFR) to characterize flow pattern behaviors from the energy and frequency point of view. Then, we infer two-phase flow complex networks from experimental measurements and detect the community structures associated with flow patterns. The results suggest that the community detection in two-phase flow complex network allows objectively discriminating complex horizontal oil–water flow patterns, especially for the segregated and dispersed flow patterns, a task that existing method based on AOK TFR fails to work. - Highlights: • We combine time–frequency analysis and complex network to identify flow patterns. • We explore the transitional flow behaviors in terms of betweenness centrality. • Our analysis provides a novel way for recognizing complex flow patterns. • Broader applicability of our method is demonstrated and articulated

Two-phase flow through small branches in a horizontal pipe with stratified flow

International Nuclear Information System (INIS)

Smoglie, C.

1985-02-01

In the field of reactor safety the occurrence of a small break in a horizontal primary coolant pipe is of great importance. This report presents the description and results of experiments designed to determine the mass flow rate and quality through a small break at the bottom, the top or the side of a main pipe with stratified gas-liquid flow. If the interface level is far below (above) the branch, only single-phase gas (liquid) flow enters the branch. For smaller distances the interface is locally deformed because of the pressure decrease due to the fluid acceleration near the branch inlet (Bernoulli effect) and liquid (gas) can be entrained. This report contains photographs illustrating the flow phenomena as well as a general correlation to determine the beginning of entrainment. Results are presented on the branch mass flow rate and quality as a function of a normalized distance between the interface and the branch inlet. A model was developed which enables to predict the branch quality and mass flux. Results from air-water flow through horizontal branches, were extrapolated for steam water flow at high pressure with critical branch mass flux. (orig./HS) [de

Magnitude and sign correlations in conductance fluctuations of horizontal oil water two-phase flow

International Nuclear Information System (INIS)

Zhu, L; Jin, N D; Gao, Z K; Zong, Y B; Zhai, L S; Wang, Z Y

2012-01-01

In experiment we firstly define five typical horizontal oil-water flow patterns. Then we introduce an approach for analyzing signals by decomposing the original signals increment into magnitude and sign series and exploring their scaling properties. We characterize the nonlinear and linear properties of horizontal oil-water two-phase flow, which relate to magnitude and sign series respectively. We find that the joint distribution of different scaling exponents can effectively identify flow patterns, and the detrended fluctuation analysis (DFA) on magnitude and sign series can represent typical horizontal oil-water two-phase flow dynamics characteristics. The results indicate that the magnitude and sign decomposition method can be a helpful tool for characterizing complex dynamics of horizontal oil-water two-phase flow.

Split core experiments; Part I. Axial neutron flux distribution measurements in the reactor core with a central horizontal reflector

Energy Technology Data Exchange (ETDEWEB)

Strugar, P; Raisic, N; Obradovic, D; Jovanovic, S [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

1965-05-01

A series of critical experiments were performed on the RB reactor in order to determine the thermal neutron flux increase in the central horizontal reflector formed by a split reactor core. The objectives of these experiments were to study the possibilities of improving the thermal neutron flux characteristics of the neutron beam in the horizontal beam tube of the RA research reactor. The construction of RA reactor enables to split the core in two, to form a central horizontal reflector in front of the beam tube. This is achieved by replacing 2% enriched uranium slugs in the fuel channel by dummy aluminium slugs. The purpose of the first series of experiments was to study the gain in thermal neutron component inside the horizontal reflector and the loss of reactivity as a function of the lattice pitch and central reflector thickness.

A status report on artificial lift systems and challenges in North Dakota horizontal completions

Energy Technology Data Exchange (ETDEWEB)

Fangmeier, K. [Amerada Hess Corp., ND (United States)

2005-07-01

Partially pressure depleted reservoirs and unfavorable horizontal flow geometries can impact artificial lift designs and diagnostics. In addition, terrain slugging, drilling fines, high gas volume fractions, H{sub 2}S gas and high bottom hole temperatures also pose challenges. This paper provides an overview of various systems utilized by Amerada Hess, a company which examines methods of reducing gas lift gas volumes to achieve maximum flow. A description of naturally fractured reservoirs and limited natural fractures was provided. A comparison was presented between the original conditions at Beaver Lodge Madison and existing conditions with horizontal development. Various artificial lift challenges were examined. It was suggested that high volume lift utilizing gas lift was the preferred artificial lift system for high volume wells. It was noted that downhole sensors can be used as an indicator of potential run life. However, reliability is limited by downhole operating temperatures and electrical ground faults. A comparison of friendly and unfriendly flow systems was presented, as well as a gas lift pressure chart. A summary of average gas volume systems was provided as well as an example of a response to increase drawdown. Examples of downhole Electric Submersible Pump (ESP) sensors were provided, as well as possible flowing pressure profiles in horizontal completion because of the constraints of lift capacity. It was concluded that a single point injection and proven gas lift system is the next step in high volume lift strategy. 2 tabs, 16 figs.

Counter-current flow in a vertical to horizontal tube with obstructions

Energy Technology Data Exchange (ETDEWEB)

Tye, P.; Matuszkiewicz, A.; Teyssedou, A. [Institut de Genie Nucleaire, Quebec (Canada)] [and others

1995-09-01

This paper presents experimental results on counter-current flow and flooding in an elbow between a vertical and a horizontal run. The experimental technique used allowed not only the flooding limit to be determined, but also the entire partial delivery region to be studied as well. The influence that various size orifices placed in the horizontal run have on both the delivered liquid flow rates and on the flooding limits is also examined. It is observed that both the flooding limits and the delivered liquid flow rates decrease with decreasing orifice size. Further, it is also observed that the mechanisms that govern the partial delivery of the liquid are significantly different when an orifice is present in the horizontal leg as compared to the case when no orifice is present.

Study of gas-water flow in horizontal rectangular channels

Science.gov (United States)

Chinnov, E. A.; Ron'shin, F. V.; Kabov, O. A.

2015-09-01

The two-phase flow in the narrow short horizontal rectangular channels 1 millimeter in height was studied experimentally. The features of formation of the two-phase flow were studied in detail. It is shown that with an increase in the channel width, the region of the churn and bubble regimes increases, compressing the area of the jet flow. The areas of the annular and stratified flow patterns vary insignificantly.

3-dimensional Simulation of an Air-lift Pump from Bubbly to Slug Flow

Energy Technology Data Exchange (ETDEWEB)

Jo, Hongrae; Jo, Daeseong [Kyungpook National Univ, Daegu (Korea, Republic of)

2015-10-15

The air-lift pump has been used in various applications with its merit that it can pump up without any moving parts. E.g. coffee percolator, petroleum industry, suction dredge, OTEC i.e. ocean thermal energy conversion and so on. By the merit, it has high durability for high temperature water or vapor, and fluid-solid mixture like waste water, muddy water and crude, which cause problems when it's pumped up with general pumps. In this regard, the air-lift pump has been one of the most desirable technology. A typical air-lift pump configuration is illustrated in Figure 01. The principle of this pump is very simple. When air is injected from the injector at bottom of a submerged tube, i.e., air bubbles are suspended in the liquid, the average density of the mixture in the tube is less than that of the surrounding fluid in the reservoir. Then hydrostatic pressure over the length of the tube is decreased. This buoyancy force causes a pumping action. The comparison of the simulated results, experimental result, and theoretical result is been able by data shown as Figure 04. They have similar trends but they also have a little differences because there are some limits of simulating the flow regimes. At the different flow condition, different coefficients for friction factor or pressure drop should be used, but this simulation uses a laminar condition and the theoretical equations are valid only for slug regime where the air flow rate is lower than the other regimes. From these causes, the differences has arisen, and difference comes bigger as the air flow rate increases, i.e., becoming annular flow regime or churn flow regime.

Mechanistic multidimensional analysis of horizontal two-phase flows

International Nuclear Information System (INIS)

Tselishcheva, Elena A.; Antal, Steven P.; Podowski, Michael Z.

2010-01-01

The purpose of this paper is to discuss the results of analysis of two-phase flow in horizontal tubes. Two flow situations have been considered: gas/liquid flow in a long straight pipe, and similar flow conditions in a pipe with 90 deg. elbow. The theoretical approach utilizes a multifield modeling concept. A complete three-dimensional two-phase flow model has been implemented in a state-of-the-art computational multiphase fluid dynamics (CMFD) computer code, NPHASE. The overall model has been tested parametrically. Also, the results of NPHASE simulations have been compared against experimental data for a pipe with 90 deg. elbow.

Slug-annular transition with particular reference to narrow rectangular ducts

International Nuclear Information System (INIS)

Jones, O.C. Jr.; Zuber, N.

1978-01-01

The transition from slug-flow to annular-flow in two-phase, gas-liquid mixtures is analyzed. A transition equation is derived which agrees well when compared with objective data determined from the disappearance of the low-void peak in the void fluctuation probability density in a rectangular duct. Application to other geometries is suggested and tabular recommendations given for determination of the drift flux coefficient, K, based on results in the literature

Numerical simulation of two-phase flow in horizontal interconnected subchannels

International Nuclear Information System (INIS)

Shoukri, M.; Tahir, A.; Carver, M.B.

1983-01-01

Different subchannel computer codes have been successfully used for the thermal-hydraulic analysis of coolant flow in vertical fuel channels. However, none of these methods is suitable for two-phase flow in horizontal fuel channels, such as those of the CANDU nuclear reactors, due to the lack of appropriate constitutive relationships that can correctly account for the gravity separation effects. This paper describes the incorporation of a transverse vapour drift model which accounts for the combined effect of gravity separation and turbulent diffusion into the existing subchannel computer code SAGA. Although the basic structure of the code remains similar to SAGA III some modifications in both the mathematical formulation and numerical solution have been incorporated. These modifications resulted in significant improvements in the code's ability in modelling horizontal two-phase subchannel flow. The new version of the code was tested and found to be capable of simulating the complex exchange phenomenon between adjacent horizontal subchannels caused by the interaction of turbulent diffusion, pressure gradient as well as gravity induced cross flows. The code predictions were compared with experimental data obtained from two different sources and showed good agreement

Modelling Nitrogen Transformation in Horizontal Subsurface Flow ...

African Journals Online (AJOL)

A mathematical model was developed to permit dynamic simulation of nitrogen interaction in a pilot horizontal subsurface flow constructed wetland receiving effluents from primary facultative pond. The system was planted with Phragmites mauritianus, which was provided with root zone depth of 75 cm. The root zone was ...

The application of neural networks to flow regime identification

International Nuclear Information System (INIS)

Embrechts, M.; Yapo, T.C.; Lahey, R.T. Jr.

1993-01-01

This paper deals with the application of a Kohonen map for the identification of two-phase flow regimes where a mixture of gas and fluid flows through a horizontal tube. Depending on the relative flow velocities of the gas and the liquid phase, four distinct flow regimes can be identified: Wavy flow, plug flow, slug flow and annular flow. A schematic of these flow regimes is presented. The objective identification of two-phase flow regimes constitutes an important and challenging problem for the design of safe and reliable nuclear power plants. Previous attempts to classify these flow regimes are reviewed by Franca and Lahey. The authors describe how a Kohonen map can be applied to distinguish between flow regimes based on the Fourier power spectra and wavelet transforms of pressure drop fluctuations. The Fourier power spectra allowed the Kohonen map to identify the flow regimes successfully. In contrast, the Kohonen maps based on a wavelet transform could only distinguish between wavy and annular flows. An analysis of typical two-phase pressure drop data for an air/water mixture in a horizontal pipe is presented. Use of the wavelet transform and the Kohonen feature map are discussed

Transition of Gas-Liquid Stratified Flow in Oil Transport Pipes

Directory of Open Access Journals (Sweden)

D. Lakehal

2011-12-01

Full Text Available Large-Scale Simulation results of the transition of a gas-liquid stratified flow to slug flow regime in circular 3D oil transport pipes under turbulent flow conditions expressed. Free surface flow in the pipe is treated using the Level Set method. Turbulence is approached via the LES and VLES methodologies extended to interfacial two-phase flows. It is shown that only with the Level Set method the flow transition can be accurately predicted, better than with the two-fluid phase-average model. The transition from stratified to slug flow is found to be subsequent to the merging of the secondary wave modes created by the action of gas shear (short waves with the first wave mode (high amplitude long wave. The model is capable of predicting global flow features like the onset of slugging and slug speed. In the second test case, the model predicts different kinds of slugs, the so-called operating slugs formed upstream that fill entirely the pipe with water slugs of length scales of the order of 2-4 D, and lower size (1-1.5 D disturbance slugs, featuring lower hold-up (0.8-0.9. The model predicts well the frequency of slugs. The simulations revealed important parameter effects on the results, such as two-dimensionality, pipe length, and water holdup.

Void fraction in horizontal bulk flow boiling at high flow qualities

International Nuclear Information System (INIS)

Collado, Fancisco J.; Monne, Carlos; Pascau, Antonio

2008-01-01

In this work, a new thermodynamic prediction of the vapor void fraction in bulk flow boiling, which is the core process of many energy conversion systems, is analyzed. The current heat balance is based on the flow quality, which is closely related to the measured void fraction, although some correlation for the vapor-liquid velocity ratio is needed. So here, it is suggested to work with the 'static' or thermodynamic quality, which is directly connected to the void fraction through the densities of the phases. Thus, the relation between heat and the mixture enthalpy (here based on the thermodynamic quality instead of the flow one) should be analyzed in depth. The careful void fraction data taken by Thom during the 'Cambridge project' for horizontal saturated flow boiling with high flow qualities (≤0.8) have been used for this analysis. As main results, first, we have found that the applied heat and the increment of the proposed thermodynamic enthalpy mixture throughout the heated duct do not agree, and for closure, a parameter is needed. Second, it has been checked that this parameter is practically equal to the classic velocity ratio or 'slip' ratio, suggesting that it should be included in a true thermodynamic heat balance. Furthermore, it has been clearly possible to improve the 'Cambridge project' correlations for the 'slip' ratio, here based on inlet pressure and water velocity, and heat flux. The calculated void fractions compare quite well with the measured ones. Finally, the equivalence of the suggested new heat balance with the current one through the 'slip' ratio is addressed. Highlighted is the same new energetic relation for saturated flow boiling that has been recently confirmed by the authors for Knights data, also taken during the 'Cambridge project', which include not only horizontal but also vertical upwards flows with moderate outlet flow quality (≤0.2)

Two-phase flow patterns and their relationship to two-phase heat transfer

International Nuclear Information System (INIS)

Hewitt, G.F.

1977-01-01

The objective of this lecture was to discuss the general nature of two phase flows, to define the various regimes of flow and to discuss the influence of these regimes on the heat transfer processes taking place. The methods of regime delineation are briefly described and regime descriptions introduced for both vertical and horizontal flows in tubes. ''Flow regime maps'' have been widely used as an aid to determination of the regime which occurs in a given situation. Some of the more widely used maps are described and the limitations of this approach discussed. There have been many attempts to obtain a better phenomenological description of two phase flow patterns. In this lecture, these attempts will be reviewed in the context of the bubble/plug, plug/churn and churn/annular flow transitions in vertical flow. The latter two transitions are related to the flooding/flow reversal phenomena. For horizontal flows, recent work on the onset of slugging will be reviewed. In flows with evaporation or condensation, the situation is influenced by departures from thermodynamic equilibrium and the types of departure observed are discuss briefly. Flow patterns and their relationships with heat transfer regimes are then reviewed for the case of condensation in horizontal tubes and evaporation in vertical tubes

FLOW DISTRIBUTION IN A SOLAR COLLECTOR PANEL WITH HORIZONTAL ABSORBER STRIPS

DEFF Research Database (Denmark)

Fan, Jianhua; Shah, Louise Jivan; Furbo, Simon

2007-01-01

The objective of this work is to theoretically and experimentally investigate the flow and temperature distribution in a solar collector panel with an absorber consisting of horizontal strips. Fluid flow and heat transfer in the collector panel are studied by means of computational fluid dynamics...... (CFD) calculations. Further, experimental investigations of a 12.5 m² solar collector panel with 16 parallel connected horizontal fins are carried out. The flow distribution through the absorber is evaluated by means of temperature measurements on the backside of the absorber tubes. The measured...... collector fluid, and by increased collector tilt and inlet temperature, the flow distribution gets worse resulting in a decreased collector efficiency and an increased risk of boiling in the upper part of the collector panel. Keywords: Solar collector; Flow distribution; Computational Fluid Dynamics (CFD...

Pressure loss in two-phase flow through a microchannel rod bundle

International Nuclear Information System (INIS)

Smith, A.C.; Hamm, L.L.; Qureshi, Z.; Steeper, T.J.

1998-01-01

The purpose of the microchannel rod bundle two-phase flow test described here was to provide data for benchmarking safety analyses for the accelerator production of tritium (APT). The objective was to obtain pressure loss data for a typical accelerator target rod bundle over a wide range of two-phase flow conditions. The test rod bundle assembly was fabricated for single-phase pressure drop tests conducted at Los Alamos National Laboratory (LANL) and subsequently used for the two-phase flow testing described here. The results for a typical case are given. These results fall generally in the slug flow regime for the horizontal flow results of Fukano and Kariyasaki for a 1.0-mm circular channel. Fukano and Kariyasaki found that surface tension effects were dominant in the 1-mm channel and report no churn regime. The results were also compared with the flow regime maps given by Triplett et al. for flow in discrete microchannels. Triplett employed both circular and trapezoidal channels, the latter to approximate the rod bundle interstitial flow channel shape. It was found that the rod bundle flow fell across the slug-to-churn flow regime transition reported by Triplett. This is consistent with the expectation that cross flow among channels would result in turbulent mixing and would suppress the formation of large discrete bubbles

Numerical and experimental study of the slug-flow regime in a mixture of castor and paraffin oils in a T-type microchannel

Science.gov (United States)

Minakov, A. V.; Shebeleva, A. A.; Yagodnitsyna, A. A.; Kovalev, A. V.; Bilsky, A. V.

2017-09-01

The slow-flug regime in a mixture of castor and paraffin oils in a T-type microchannel with crosssectional dimensions of 200 × 400 μm has been studied by numerical and experimental methods. The domain of existence of the slow-flug regime in this system has been determined. Dependence of the paraffin-oil slug length on the ratio of flow rates of the mixture components is established. Comparison of the calculated and experimental data shows their good agreement.

Evolution of long wave disturbances in horizontal gas-liquid flows

International Nuclear Information System (INIS)

Kuru, W.C.; Montalbano, E.D.; Brennecke, J.F.; McCready, M.J.

1993-01-01

Coherent nonlinear interactions between linearly stable, long wavelength modes and modes that are near the peak of the growth rate are observed in experiments. These open-quotes side-bandclose quotes interactions are suggested as the mechanism for initiation of long wavelength modes that are otherwise predicted to be stable from linear stability theory. Quadratic interaction theory is used to provide insight into when long wavelength modes will appear and how their frequency will be selected. The present work differs from previous side band analyses in that a low frequency mode is retained as a dominant mode (consistent with observations). Because of its relevance to continued growth of long wavelength disturbances and possibly slug formation and owing to its importance in modeling flow regime transitions, a discussion of the validity of the one-dimensional macroscopic equations and the boundary-layer equations as models of long wavelength disturbances for the two-layer stability problem is given in the context of laminar flow of a fluid over a solid wavy surface

Analysis of two-phase flow and boiling heat transfer in inclined channel of core-catcher

International Nuclear Information System (INIS)

Tahara, M.; Suzuki, Y.; Abe, N.; Kurita, T.; Hamazaki, R.; Kojima, Y.

2008-01-01

Passive Corium Cooling System (CCS) provides a function of ex-vessel debris cooling and molten core stabilization during a severe accident. CCS features inclined cooling channels arranged axi-symmetrically below the core-catcher basin. In order to estimate the coolability of the inclined cooling channel, it is indispensable to identify the flow pattern of the two-phase flow in the cooling channel. Several former studies for the two-phase flow pattern in the inclined channel are referred. Taitel and Dukler (1976) developed a prediction method of the flow pattern transition in horizontal and near horizontal tubes. Barnea et al. (1980) showed the flow pattern map of upward flow with 10 degrees inclination. Sakaguti et al. (1996) observed the two-phase flow patterns in the horizontal pipe connected with slightly upward pipe, in which the flow pattern in the pipe with a bending part was expressed by the combination of a basic flow pattern and some auxiliary flow patterns. Then we investigated these studies In order to identify the flow patterns observed in the inclined cooling channel of CCS. Furthermore we experimentally observed the flow patterns in the inclined cooling channel with various inlet conditions. As a result of the investigation and observation, typical flow patterns in the inclined cooling channel were identified. Two typical flow patterns were observed depending on the steam flow rate, one of which is 'elongated bubble 'flow, and the other is 'churn with collapsing backward and upward slug 'flow The flow and heat transfer in the inclined channel of CCS is analyzed by using a two-phase analysis code employing two-fluid model in which the constitutive equations for the two-phase flow in inclined channels are incorporated. That is, drift flux parameter for each of the elongated bubble flow, and the churn with collapsing backward and upward slug flow are incorporated to the two-phase analysis code, which are based on the rising velocity of the long bubble in

Nitrogen Transformation and Removal in Horizontal Surface Flow ...

African Journals Online (AJOL)

The potential use of Constructed Mangrove Wetlands (CMWs) as a cheaper, effective and appropriate method for Nitrogen removal from domestic sewage of coastal zone in peri-urban cities was investigated from August 2007 to. September, 2008. Field investigations were made on horizontal surface flow constructed ...

Survey of nematodes associated with terrestrial slugs in Norway.

Science.gov (United States)

Ross, J L; Ivanova, E S; Hatteland, B A; Brurberg, M B; Haukeland, S

2016-09-01

A survey of nematodes associated with terrestrial slugs was conducted for the first time in Norway. A total of 611 terrestrial slugs were collected from 32 sample sites. Slugs were identified by means of morphological examination, dissection of genitalia and molecular analysis using mitochondrial DNA. Twelve slug species were identified, representing four different slug families. Internal nematodes were identified by means of morphological analysis and the sequencing of the 18S rRNA gene. Of the sample sites studied, 62.5% were found to be positive for nematode parasites, with 18.7% of all slugs discovered being infected. Five nematode species were identified in this study: Alloionema appendiculatum, Agfa flexilis, Angiostoma limacis, Angiostoma sp. and Phasmarhabditis hermaphrodita. Of these species, only one nematode was previously undescribed (Angiostoma sp.). This is the first record of the presence of A. appendiculatum, A. flexilis and A. limacis in Norway.

Void fraction in horizontal bulk flow boiling at high flow qualities

Energy Technology Data Exchange (ETDEWEB)

Collado, Fancisco J.; Monne, Carlos [Dpto. de Ingenieria Mecanica, Universidad de Zaragoza-CPS, Maria de Luna 3, 50018-Zaragoza (Spain); Pascau, Antonio [Dpto. de Ciencia de los Materiales y Fluidos, Universidad de Zaragoza-CPS, Maria de Luna 3, 50018-Zaragoza (Spain)

2008-04-15

In this work, a new thermodynamic prediction of the vapor void fraction in bulk flow boiling, which is the core process of many energy conversion systems, is analyzed. The current heat balance is based on the flow quality, which is closely related to the measured void fraction, although some correlation for the vapor-liquid velocity ratio is needed. So here, it is suggested to work with the 'static' or thermodynamic quality, which is directly connected to the void fraction through the densities of the phases. Thus, the relation between heat and the mixture enthalpy (here based on the thermodynamic quality instead of the flow one) should be analyzed in depth. The careful void fraction data taken by Thom during the 'Cambridge project' for horizontal saturated flow boiling with high flow qualities ({<=}0.8) have been used for this analysis. As main results, first, we have found that the applied heat and the increment of the proposed thermodynamic enthalpy mixture throughout the heated duct do not agree, and for closure, a parameter is needed. Second, it has been checked that this parameter is practically equal to the classic velocity ratio or 'slip' ratio, suggesting that it should be included in a true thermodynamic heat balance. Furthermore, it has been clearly possible to improve the 'Cambridge project' correlations for the 'slip' ratio, here based on inlet pressure and water velocity, and heat flux. The calculated void fractions compare quite well with the measured ones. Finally, the equivalence of the suggested new heat balance with the current one through the 'slip' ratio is addressed. Highlighted is the same new energetic relation for saturated flow boiling that has been recently confirmed by the authors for Knights data, also taken during the 'Cambridge project', which include not only horizontal but also vertical upwards flows with moderate outlet flow quality ({<=}0.2). (author)

Mixed convection flow past a horizontal plate

Directory of Open Access Journals (Sweden)

Savić Lj.

2005-01-01

Full Text Available The mixed convection flow past a horizontal plate being aligned through a small angle of attack to a uniform free stream will be considered in the limit of large Reynolds number and small Richardson number. Even a small angle of inclination of the wake is sufficient for the buoyancy force to accelerate the flow in the wake which causes a velocity overshoot in the wake. Moreover a hydrostatic pressure difference across the wake induces a correction to the potential flow which influences the inclination of the wake. Thus the wake and the correction of the potential flow have to be determined simultaneously. However, it turns out that solutions exist only if the angle of attack is sufficiently large. Solutions are computed numerically and the influence of the buoyancy on the lift coefficient is determined.

Horizontal stratified flow model for the 1-D module of WCOBRA/TRAC-TF2: modeling and validation

Energy Technology Data Exchange (ETDEWEB)

Liao, J.; Frepoli, C.; Ohkawa, K., E-mail: liaoj@westinghouse.com [Westinghouse Electric Company LLC, LOCA Integrated Services I, Cranberry Twp, Pennsylvania (United States)

2011-07-01

For a two-phase flow in a horizontal pipe, the individual phases may separate by gravity. This horizontal stratification significantly impacts the interfacial drag, interfacial heat transfer and wall drag of the two phase flow. For a PWR small break LOCA, the horizontal stratification in cold legs is a highly important phenomenon during loop seal clearance, boiloff and recovery periods. The low interfacial drag in the stratified flow directly controls the time period for the loop clearance and the level of residual water in the loop seal. Horizontal stratification in hot legs also impacts the natural circulation stage of a small break LOCA. In addition, the offtake phenomenon and cold leg condensation phenomenon are also affected by the occurrence of horizontal stratification in the cold legs. In the 1-D module of the WCOBRA/TRAC-TF2 computer code, a horizontal stratification criterion was developed by combining the Taitel-Dukler model and the Wallis-Dobson model, which approximates the viscous Kelvin-Helmholtz neutral stability boundary. The objective of this paper is to present the horizontal stratification model implemented in the code and its assessment against relevant data. The adequacy of the horizontal stratification transition criterion is confirmed by examining the code-predicted flow regime in a horizontal pipe with the measured data in the flow regime map. The void fractions (or liquid level) for the horizontal stratified flow in cold leg or hot leg are predicted with a reasonable accuracy. (author)

Experimental Study of Stable Surfaces for Anti-Slug Control in Multi-phase Flow

DEFF Research Database (Denmark)

Pedersen, Simon; Løhndorf, Petar Durdevic; Stampe, Kasper

2016-01-01

, the slug can be avoided or eliminated by proper facility design or control of operational conditions. Based on a testing facility which can emulate a pipeline-riser or a gas-lifted production well in a scaled-down manner, this paper experimentally studies the correlations of key operational parameters...

Estimation of gas wall shear stress in horizontal stratified gas-liquid pipe flow

International Nuclear Information System (INIS)

Newton, C.H.; Behnia, M.

1996-01-01

Two-phase pipe flows occur in many industrial applications, such as condensers and evaporators, chemical processing equipment, nuclear reactors, and oil pipelines. A variety of basic mechanistic flow models for predicting the pressure gradient and liquid loading characteristics of these types of flows to assist in design calculations has emerged over the past two decades, especially for the stratified and slug flow regimes. These models generally rely on a number of basic assumptions and empirical closure equations. Possibly the most notable of these relates to the evaluation of interfacial shear stresses. However, one of the most important yet least discussed assumptions used in most of these models is that the phase wall shear stresses can be accurately estimated from correlations developed for single-phase pipe flows. The object of this article is to present measurements of gas wall shear up to locations in close proximity to the gas-liquid interface for a variety of interface conditions in developed flow, and to determine the effects of the interface on average gas wall friction factors. In this context the interface may be smooth, rippled or wavy

Flow distribution in a solar collector panel with horizontally inclined absorber strips

DEFF Research Database (Denmark)

Fan, Jianhua; Shah, Louise Jivan; Furbo, Simon

2007-01-01

The objective of this work is to theoretically and experimentally investigate the flow and temperature distribution in a solar collector panel with an absorber consisting of horizontally inclined strips. Fluid flow and heat transfer in the collector panel are studied by means of computational fluid...... dynamics (CFD) calculations. Further, experimental investigations of a 12.5 m(2) solar collector panel with 16 parallel connected horizontal fins are carried out. The flow distribution through the absorber is evaluated by means of temperature measurements on the backside of the absorber tubes. The measured...... rate, properties of solar collector fluid, solar collector fluid inlet temperature and collector tilt angle are shown. The flow distribution through the absorber fins is uniform if high flow rates are used. By decreased flow rate and decreased content of glycol in the glycol/water mixture used as solar...

Design and numerical simulation on an auto-cumulative flowmeter in horizontal oil-water two-phase flow.

Science.gov (United States)

Xie, Beibei; Kong, Lingfu; Kong, Deming; Kong, Weihang; Li, Lei; Liu, Xingbin; Chen, Jiliang

2017-11-01

In order to accurately measure the flow rate under the low yield horizontal well conditions, an auto-cumulative flowmeter (ACF) was proposed. Using the proposed flowmeter, the oil flow rate in horizontal oil-water two-phase segregated flow can be finely extracted. The computational fluid dynamics software Fluent was used to simulate the fluid of the ACF in oil-water two-phase flow. In order to calibrate the simulation measurement of the ACF, a novel oil flow rate measurement method was further proposed. The models of the ACF were simulated to obtain and calibrate the oil flow rate under different total flow rates and oil cuts. Using the finite-element method, the structure of the seven conductance probes in the ACF was simulated. The response values for the probes of the ACF under the conditions of oil-water segregated flow were obtained. The experiments for oil-water segregated flow under different heights of the oil accumulation in horizontal oil-water two-phase flow were carried out to calibrate the ACF. The validity of the oil flow rate measurement in horizontal oil-water two-phase flow was verified by simulation and experimental results.

Method for confirming flow pattern of gas-water flow in horizontal tubes under rolling state

International Nuclear Information System (INIS)

Luan Feng; Yan Changqi

2008-01-01

An experimental study on the flow patterns of gas-water flow was carried out in horizontal tubes under rolling state. It was found that the pressure drop of two phase flow was with an obvious periodical characteristic. The flow pattern of the gas-water flow was distinguished according to the characteristics of the pressure drop in this paper. It was proved that the characteristics of the pressure drop can distinguish the flow pattern of gas-water flow correctly through comparing with the result of careful observation and high speed digital camera. (authors)

A nematode that can manipulate the behaviour of slugs.

Science.gov (United States)

Morris, Alex; Green, Michael; Martin, Hayley; Crossland, Katie; Swaney, William T; Williamson, Sally M; Rae, Robbie

2018-06-01

The ability of parasites to manipulate the behaviour of their hosts has evolved multiple times, and has a clear fitness benefit to the parasite in terms of facilitating growth, reproduction and transfer to suitable hosts. The mechanisms by which these behavioural changes are induced are poorly understood, but in many cases parasite manipulation of serotonergic signalling in the host brain is implicated. Here we report that Phasmarhabditis hermaphrodita, a parasite of terrestrial gastropod molluscs, can alter the behaviour of slugs. Uninfected slugs (Deroceras panormitanum, Arion subfuscus and Arion hortensis) avoid areas where P. hermaphrodita is present, but slugs infected with P. hermaphrodita are more likely to be found where the nematodes are present. This ability is specific to P. hermaphrodita and other nematodes (Steinernema carpocapsae and Heterorhabditis bacteriophora) do not induce this behavioural change. To investigate how P. hermaphrodita changes slug behaviour we exposed slugs to fluoxetine (a selective serotonin reuptake inhibitor) and cyproheptadine (a serotonin receptor antagonist). Uninfected slugs fed fluoxetine no longer avoided areas where P. hermaphrodita was present; and conversely, infected slugs fed cyproheptadine showed no increased attraction to areas with nematodes. These findings suggest that a possible mechanism by which P. hermaphrodita is able to manipulate parasite avoidance behaviour in host slugs is by manipulating serotonergic signalling in the brain, and that increased serotonin levels are potentially associated with a reduction in parasite avoidance. Copyright © 2018 Elsevier B.V. All rights reserved.

Convection flow study within a horizontal fluid layer under the action of gas flow

Directory of Open Access Journals (Sweden)

Kreta Aleksei

2016-01-01

Full Text Available Experimental investigation of convective processes within horizontal evaporating liquid layer under shear–stress of gas flow is presented. It is found the structures of the convection, which move in opposite direction relative to each other. First convective structure moves in reverse direction with the flow of gas, and the second convective structure moves towards the gas flow. Convection flow within the liquid layer is registered with help of PIV technique. Average evaporation flow rate of Ethanol liquid layer under Air gas flow is measured. Influence of the gas velocity, at a constant temperature of 20 °C, on the evaporation flow rate has been studied.

Role of the Slug Transcription Factor in Chemically-Induced Skin Cancer

Directory of Open Access Journals (Sweden)

Kristine von Maltzan

2016-02-01

Full Text Available The Slug transcription factor plays an important role in ultraviolet radiation (UVR-induced skin carcinogenesis, particularly in the epithelial-mesenchymal transition (EMT occurring during tumor progression. In the present studies, we investigated the role of Slug in two-stage chemical skin carcinogenesis. Slug and the related transcription factor Snail were expressed at high levels in skin tumors induced by 7,12-dimethylbenz[α]anthracene application followed by 12-O-tetradecanoylphorbol-13-acetate (TPA treatment. TPA-induced transient elevation of Slug and Snail proteins in normal mouse epidermis and studies in Slug transgenic mice indicated that Slug modulates TPA-induced epidermal hyperplasia and cutaneous inflammation. Although Snail family factors have been linked to inflammation via interactions with the cyclooxygenase-2 (COX-2 pathway, a pathway that also plays an important role in skin carcinogenesis, transient TPA induction of Slug and Snail appeared unrelated to COX-2 expression. In cultured human keratinocytes, TPA induced Snail mRNA expression while suppressing Slug expression, and this differential regulation was due specifically to activation of the TPA receptor. These studies show that Slug and Snail exhibit similar patterns of expression during both UVR and chemical skin carcinogenesis, that Slug and Snail can be differentially regulated under some conditions and that in vitro findings may not recapitulate in vivo results.

The effects of viscosity, surface tension, and flow rate on gasoil-water flow pattern in microchannels

Energy Technology Data Exchange (ETDEWEB)

Boogar, Rahman Sadeghi; Gheshlaghi, Reza; Mahdavi, Mahmood Akhavan [Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

2013-01-15

A microchannel was fabricated with glass tubes to investigate the effect of viscosity, surface tension, and flow rate on the liquid-liquid two-phase flow regime. Water and gasoil were selected as aqueous and organic working fluids, respectively. The two fluids were injected into the microchannel and created either slug or parallel profile depending on the applied conditions. The range of Reynolds and capillary numbers was chosen in such a way that neither inertia nor interfacial tension forces were negligible. Xanthan gum was used to increase viscosity and Triton X-100 (TX-100) and Sodium Dodecyl Sulfate (SDS) were used to reduce the interfacial tension. The results demonstrated that higher value of viscosity and flow rate increased interfacial area, but slug flow regime remained unchanged. The two surfactants showed different effects on the flow regime and interfacial area. Addition of TX-100 did not change the slug flow but decreased the interfacial area. In contrast, addition of SDS increased interfacial area by decreasing the slug’s length in the low concentrations and by switching from slug to parallel regime at high concentrations.

Visualization of Two Phase Flow in a Horizontal Flow with Electrical Resistance Tomography based on Extended Kalman Filter

International Nuclear Information System (INIS)

Lee, Jeong Seong; Malik, Nauman Muhammad; Khambampati, Anil Kumar; Rashid, Ahmar; Kim, Sin; Kim, Kyung Youn

2008-01-01

For the visualization of the phase distribution in two phase flows, the electrical resistance tomography (ERT) technique is introduced. In ERT, the internal resistivity distribution is reconstructed based on the known sets of the injected currents and measured voltages on the surface of the object. The physical relationship between the internal resistivity and the surface voltages is governed by a partial differential equation with appropriate boundary conditions. This paper considers the estimation of the phase distribution with ERT in two phase flow in a horizontal flow using extended Kalman filter. To evaluate the reconstruction performance of the proposed algorithm, the experiments simulated two phase flows in a horizontal flow were carried out. The experiments with two phase flow phantom were done to suggest a practical implication of this research in detecting gas bubble in a feed water pipe of heat transfer systems

The E-cadherin repressor slug and progression of human extrahepatic hilar cholangiocarcinoma

Directory of Open Access Journals (Sweden)

Wang Xin-sheng

2010-07-01

Full Text Available Abstract Objectives This study explored the expression and function of Slug in human extrahepatic hilar cholangiocarcinoma (EHC to identify its role in tumor progression. Methods The expression of Snail and Slug mRNA in 52 human tissue samples of EHC was investigated. The mRNA of Snail and Slug were quantified using reverse transcriptase-PCR, and correlations with E-cadherin expression and clinicopathological factors were investigated. We then investigated transfection of Slug cDNA in endogenous E-cadherin-positive human EHC FRH0201 cells, selectively induced the loss of E-cadherin protein expression, and then small interfering RNA (siRNA for inhibition of Slug expression in endogenous Slug-positive human EHC QBC939 cells, selectively induced the loss of Slug protein expression. A Boyden chamber transwell assay was used for invasion. Results Slug mRNA was overexpressed in 18 cases (34.6% of EHC compared with adjacent noncancerous tissue. E-Cadherin protein expression determined in the same 52 cases by immunohistochemistry was significantly down-regulated in those cases with Slug mRNA overexpression (P = 0.0001. The tumor and nontumor ratio of Slug mRNA was correlated with nodal metastasis(p = 0.0102, distant metastasis (p = 0.0001and Survival time(p = 0.0443. However, Snail mRNA correlated with neither E-cadherin expression nor tumor invasiveness. By inhibiting Slug expression by RNA interference, we found that reduced Slug levels upregulated E-cadherin and decreased invasion in QBC939 cell. When the QBC939 cells was infected with Slug cDNA,, significant E-cadherin was downregulated and increased invasion in QBC939 cell. Conclusions The results suggested that Slug expression plays an important role in both the regulation of E-cadherin expression and in the acquisition of invasive potential in human EHC. Slug is possibly a potential target for an antitumor therapy blocking the functions of invasion and metastasis in human EHCs.

Periodic flow patterns of the magnetic fluid in microchannel

International Nuclear Information System (INIS)

Chang, C.-W.; Cheng, Y.-T.; Tsai, C.-Y.; Chien, J.-H.; Wang, P.-Y.; Chen, P.-H.

2007-01-01

In this study, of interests are the periodic flow patterns of the oil-based magnetic fluid in microchannels. A microfluidic chip is made of poly-dimethylsiloxane (PDMS) and contains cross-shape microchannels. The microchannels are 1000 μm in width and 200 μm in depth. A syringe pump was used to drive the fluids. Periodic flow patterns were seen and the slugs of magnetic fluid and DI water were generated. The operating factors discussed in the present work are the flow rates and the magnetic field. The frequency of generation of the slugs increases with increase in the flow rates. Besides, by settling the permanent magnet around the microchannel, the periods of the slug generation are changed. Different positions of the magnet lead to different periods for generating the slugs. By adjusting operating conditions, to control the frequency and the volume of the slugs is practical

Temporal and spatial evolution characteristics of gas-liquid two-phase flow pattern based on image texture spectrum descriptor

Science.gov (United States)

Zhou, Xi-Guo; Jin, Ning-De; Wang, Zhen-Ya; Zhang, Wen-Yin

2009-11-01

The dynamic image information of typical gas-liquid two-phase flow patterns in vertical upward pipe is captured by a highspeed dynamic camera. The texture spectrum descriptor is used to describe the texture characteristics of the processed images whose content is represented in the form of texture spectrum histogram, and four time-varying characteristic parameter indexes which represent image texture structure of different flow patterns are extracted. The study results show that the amplitude fluctuation of texture characteristic parameter indexes of bubble flow is lowest and shows very random complex dynamic behavior; the amplitude fluctuation of slug flow is higher and shows intermittent motion behavior between gas slug and liquid slug, and the amplitude fluctuation of churn flow is the highest and shows better periodicity; the amplitude fluctuation of bubble-slug flow is from low to high and oscillating frequence is higher than that of slug flow, and includes the features of both slug flow and bubble flow; the slug-churn flow loses the periodicity of slug flow and churn flow, and the amplitude fluctuation is high. The results indicate that the image texture characteristic parameter indexes of different flow pattern can reflect the flow characteristics of gas-liquid two-phase flow, which provides a new approach to understand the temporal and spatial evolution of flow pattern dynamics.

Boolean logic analysis for flow regime recognition of gas–liquid horizontal flow

International Nuclear Information System (INIS)

Ramskill, Nicholas P; Wang, Mi

2011-01-01

In order to develop a flowmeter for the accurate measurement of multiphase flows, it is of the utmost importance to correctly identify the flow regime present to enable the selection of the optimal method for metering. In this study, the horizontal flow of air and water in a pipeline was studied under a multitude of conditions using electrical resistance tomography but the flow regimes that are presented in this paper have been limited to plug and bubble air–water flows. This study proposes a novel method for recognition of the prevalent flow regime using only a fraction of the data, thus rendering the analysis more efficient. By considering the average conductivity of five zones along the central axis of the tomogram, key features can be identified, thus enabling the recognition of the prevalent flow regime. Boolean logic and frequency spectrum analysis has been applied for flow regime recognition. Visualization of the flow using the reconstructed images provides a qualitative comparison between different flow regimes. Application of the Boolean logic scheme enables a quantitative comparison of the flow patterns, thus reducing the subjectivity in the identification of the prevalent flow regime

Investigation of Two-Phase Flow in Short Horizontal Mini Channel Height of 1 MM

Directory of Open Access Journals (Sweden)

Ron’shin Fedor

2016-01-01

Full Text Available The experiments with two-phase flow in the short horizontal rectangular minichannel with the height of 1 mm and width of 29 mm have been carried out using water and gas nitrogen. The five two-phase flow patterns have been recognized in the minichannel: churn, stratified, annular, bubble, and jet. These regimes are plotted on a graph and the boundaries between them determine precisely. The height of a horizontal minichannels has a significant role on boundaries between the flow regimes.

Non-invasive classification of gas–liquid two-phase horizontal flow regimes using an ultrasonic Doppler sensor and a neural network

International Nuclear Information System (INIS)

Abbagoni, Baba Musa; Yeung, Hoi

2016-01-01

The identification of flow pattern is a key issue in multiphase flow which is encountered in the petrochemical industry. It is difficult to identify the gas–liquid flow regimes objectively with the gas–liquid two-phase flow. This paper presents the feasibility of a clamp-on instrument for an objective flow regime classification of two-phase flow using an ultrasonic Doppler sensor and an artificial neural network, which records and processes the ultrasonic signals reflected from the two-phase flow. Experimental data is obtained on a horizontal test rig with a total pipe length of 21 m and 5.08 cm internal diameter carrying air-water two-phase flow under slug, elongated bubble, stratified-wavy and, stratified flow regimes. Multilayer perceptron neural networks (MLPNNs) are used to develop the classification model. The classifier requires features as an input which is representative of the signals. Ultrasound signal features are extracted by applying both power spectral density (PSD) and discrete wavelet transform (DWT) methods to the flow signals. A classification scheme of ‘1-of-C coding method for classification’ was adopted to classify features extracted into one of four flow regime categories. To improve the performance of the flow regime classifier network, a second level neural network was incorporated by using the output of a first level networks feature as an input feature. The addition of the two network models provided a combined neural network model which has achieved a higher accuracy than single neural network models. Classification accuracies are evaluated in the form of both the PSD and DWT features. The success rates of the two models are: (1) using PSD features, the classifier missed 3 datasets out of 24 test datasets of the classification and scored 87.5% accuracy; (2) with the DWT features, the network misclassified only one data point and it was able to classify the flow patterns up to 95.8% accuracy. This approach has demonstrated the

Non-invasive classification of gas-liquid two-phase horizontal flow regimes using an ultrasonic Doppler sensor and a neural network

Science.gov (United States)

Musa Abbagoni, Baba; Yeung, Hoi

2016-08-01

The identification of flow pattern is a key issue in multiphase flow which is encountered in the petrochemical industry. It is difficult to identify the gas-liquid flow regimes objectively with the gas-liquid two-phase flow. This paper presents the feasibility of a clamp-on instrument for an objective flow regime classification of two-phase flow using an ultrasonic Doppler sensor and an artificial neural network, which records and processes the ultrasonic signals reflected from the two-phase flow. Experimental data is obtained on a horizontal test rig with a total pipe length of 21 m and 5.08 cm internal diameter carrying air-water two-phase flow under slug, elongated bubble, stratified-wavy and, stratified flow regimes. Multilayer perceptron neural networks (MLPNNs) are used to develop the classification model. The classifier requires features as an input which is representative of the signals. Ultrasound signal features are extracted by applying both power spectral density (PSD) and discrete wavelet transform (DWT) methods to the flow signals. A classification scheme of ‘1-of-C coding method for classification’ was adopted to classify features extracted into one of four flow regime categories. To improve the performance of the flow regime classifier network, a second level neural network was incorporated by using the output of a first level networks feature as an input feature. The addition of the two network models provided a combined neural network model which has achieved a higher accuracy than single neural network models. Classification accuracies are evaluated in the form of both the PSD and DWT features. The success rates of the two models are: (1) using PSD features, the classifier missed 3 datasets out of 24 test datasets of the classification and scored 87.5% accuracy; (2) with the DWT features, the network misclassified only one data point and it was able to classify the flow patterns up to 95.8% accuracy. This approach has demonstrated the

Slug-flow dynamics with phase change heat transfer in compact heat exchangers with oblique wavy walls

Science.gov (United States)

Morimoto, Kenichi; Kinoshita, Hidenori; Matsushita, Ryo; Suzuki, Yuji

2017-11-01

With abundance of low-temperature geothermal energy source, small-scale binary-cycle power generation system has gained renewed attention. Although heat exchangers play a dominant role in thermal efficiency and the system size, the optimum design strategy has not been established due to complex flow phenomena and the lack of versatile heat transfer models. In the present study, the concept of oblique wavy walls, with which high j/f factor is achieved by strong secondary flows in single-phase system, is extended to two-phase exchangers. The present analyses are based on evaporation model coupled to a VOF technique, and a train of isolated bubbles is generated under the controlled inlet quality. R245fa is adopted as a low boiling-point working media, and two types of channels are considered with a hydraulic diameter of 4 mm: (i) a straight circular pipe and (ii) a duct with oblique wavy walls. The focus is on slug-flow dynamics with evaporation under small capillary but moderate Weber numbers, where the inertial effect as well as the surface tension is of significance. A possible direction of the change in thermo-physical properties is explored by assuming varied thermal conductivity. Effects of the vortical motions on evaporative heat transfer are highlighted. This work has been supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan.

Measurement of the single and two phase flow using newly developed average bidirectional flow tube

International Nuclear Information System (INIS)

Yun, Byong Jo; Euh, Dong Jin; Kang, Kyung Ho; Song, Chul Hwa; Baek, Won Pil

2005-01-01

A new instrument, an average BDFT (Birectional Flow Tube), was proposed to measure the flow rate in single and two phase flows. Its working principle is similar to that of the pitot tube, wherein the dynamic pressure is measured. In an average BDFT, the pressure measured at the front of the flow tube is equal to the total pressure, while that measured at the rear tube is slightly less than the static pressure of the flow field due to the suction effect downstream. The proposed instrument was tested in air/water vertical and horizontal test sections with an inner diameter of 0.08m. The tests were performed primarily in single phase water and air flow conditions to obtain the amplification factor(k) of the flow tube in the vertical and horizontal test sections. Tests were also performed in air/water vertical two phase flow conditions in which the flow regimes were bubbly, slug, and churn turbulent flows. In order to calculate the phasic mass flow rates from the measured differential pressure, the Chexal dirft-flux correlation and a momentum exchange factor between the two phases were introduced. The test results show that the proposed instrument with a combination of the measured void fraction, Chexal drift-flux correlation, and Bosio and Malnes' momentum exchange model could predict the phasic mass flow rates within a 15% error. A new momentum exchange model was also proposed from the present data and its implementation provides a 5% improvement to the measured mass flow rate when compared to that with the Bosio and Malnes' model

Context-Dependent Passive Avoidance Learning in the Terrestrial Slug Limax.

Science.gov (United States)

Fujisaki, Yuko; Matsuo, Ryota

2017-12-01

The terrestrial slug Limax has been used as a model animal for studying the neural mechanisms underlying associative olfactory learning. The slug also innately exhibits negative phototactic behavior using its eyes. In the present study, we developed an experimental paradigm for quantification of slug's negative phototaxis behavior, and investigated whether the nature of the negative phototaxis can be modified by learning experience. The experimental set-up consists of light and dark compartments, between which the slug can move freely. During conditioning, the slug was placed in the light compartment, and an aversive stimulus (quinidine sulfate solution) was applied when it reached the dark compartment. After a single conditioning session, the time to reach the dark compartment significantly increased when it was tested following 24 hr or one week. Protein synthesis inhibition immediately following the conditioning impaired the memory retention at one week but not at 24 hr. The retrieval of the memory was context-dependent, as the time to reach the dark compartment did not significantly increase if the slug was placed on a floor with a different texture in the memory retention test. If the aversive stimulus was applied when the slug was in the light compartment, the time to reach the dark compartment did not increase after 24 hr. This is the first report demonstrating the capability of the slug to form context-dependent passive avoidance memory that can be established in a single conditioning session.

Wavelet analysis of interfacial waves in cocurrent two-phase flow in horizontal duct

International Nuclear Information System (INIS)

Kondo, Masaya; Kukita, Yutaka

1996-07-01

Wavelet analysis was applied to spatially-growing interfacial waves in a cocurrent gas/liquid two-phase flow. The wave growth plays a key role in the transition from stratified-wavy to slug flow, which is an important phenomena in many engineering applications. Of particular interest to the present study was the quick growth or decay of particular waves which were observed in experiments together with the general growth of waves with distance in the flow direction. Among the several wavelet functions tested in the present study, the Morlet wavelet and the Gabor function were found to have spectral and spatial resolutions suitable to the analysis of interfacial wave data taken by the authors. The analysis revealed that 1) the spectral components composing the interfacial waves are propagating at different phase velocities which agree to the theoretical velocities of deep-water waves, 2) the group velocity of the waves also agrees to the deep-water theory, and 3) the quick growth and decay of particular waves occur as a result of the superposition of spectral components with different phase velocities. (author)

Mass transfer in horizontal flow channels with thermal gradients

International Nuclear Information System (INIS)

Bendrich, G.; Shemilt, L.W.

1997-01-01

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

SLUG (SNAI2) deletions in patients with Waardenburg disease.

Science.gov (United States)

Sánchez-Martín, Manuel; Rodríguez-García, Arancha; Pérez-Losada, Jesús; Sagrera, Ana; Read, Andrew P; Sánchez-García, Isidro

2002-12-01

Waardenburg syndrome (WS; deafness with pigmentary abnormalities) is a congenital disorder caused by defective function of the embryonic neural crest. Depending on additional symptoms, WS is classified into four types: WS1, WS2, WS3 and WS4. WS1 and WS3 are caused by mutations in PAX3, whereas WS2 is heterogenous, being caused by mutations in the microphthalmia (MITF) gene in some but not all affected families. The identification of Slugh, a zinc-finger transcription factor expressed in migratory neural crest cells, as the gene responsible for pigmentary disturbances in mice prompted us to analyse the role of its human homologue SLUG in neural crest defects. Here we show that two unrelated patients with WS2 have homozygous deletions in SLUG which result in absence of the SLUG product. We further show that Mitf is present in Slug-deficient cells and transactivates the SLUG promoter, and that Slugh and Kit genetically interact in vivo. Our findings further define the locus heterogeneity of WS2 and point to an essential role of SLUG in the development of neural crest-derived human cell lineages: its absence causes the auditory-pigmentary symptoms in at least some individuals with WS2.

Effect of completion geometry and phasing on single-phase liquid flow behaviour in horizontal wells

Energy Technology Data Exchange (ETDEWEB)

Yuan, H.; Sarica, C.; Brill, P. [Tulsa Unov., OK (United States)

1998-12-31

The effects of completion geometries and the phasing and density of injection openings in horizontal wells was studied. A total of 1,257 tests were conducted for no fluid injections, no main flow at the test section inlet, and with fluid injection for Reynolds numbers ranging from 4,000 to 60,000 and for influx to main flow rate ratios ranging from 1/5 to 1/2000. Results demonstrated the dramatic effects of completion geometry, phasing density, Reynolds number and main flow rate on the pressure behaviour and therefore on the production behaviour of the well. A general friction factor expression for horizontal wells with multiple injection openings was developed based on the conservation of mass and momentum and using a commercial Computational Fluid Dynamics (CFD) computer program to determine the length of the flow developing region in a horizontal well. A field example is presented to show the importance of using the proper friction factor correlation to calculate the pressure drop in a horizontal well. 32 refs., 4 tabs., 20 figs.

Is a combination of different natural substances suitable for slug (Arion spp.) control?

Energy Technology Data Exchange (ETDEWEB)

Laznik, Ž.; Trdan, S.

2016-11-01

In a laboratory study we investigated the contact and barrier efficacy of different natural substances (wood ash, sawdust, hydrated lime, and diatomaceous earth) against slugs of the genus Arion, an important agricultural pest. Natural substances were tested individually and in combination with each other. The experiment was carried out in plastic petri dishes and in glass insectaria. Moistened tampons and fresh leaves of lettuce were placed into both experimental arenas. The slugs were starved for 48 hours prior to the experiment. Six categories of behaviour were identified for slugs in the presence of the natural substances: (1) slug survived the experiment, (2) slug died during the experiment, (3) slug crossed the barrier, (4) slug did not cross the barrier, (5) slug fed on the lettuce, and (6) slug did not feed on the lettuce. The effect of different treatments (natural substances) was significant. The results of our study have shown that hydrated lime had the best contact efficacy on slugs (the mortality of slugs was 100%), both individually and in combination with other substances. The treatments with hydrated lime also proved to be the most efficient barrier preventing slugs from feeding on lettuce. Hydrated lime shows great potential in Arion control in our investigation; however, further research is needed to investigate the practical value (how to avoid the problem when the substance becomes wet), safety and economics of hydrated lime used in this way. (Author)

Flow Through A Horizontal Porous Channel With A Harmonic ...

African Journals Online (AJOL)

In this research work we provide a finite element solution to the problem of the flow through a horizontal channel with a harmonic pressure gradient. Results obtained shows that the velocity and temperature increases with time and that a turning point occurs in the temperature profile due to the viscous dissipation effect.

Empirical Correlations and CFD Simulations of Vertical Two-Phase Gas-Liquid (Newtonian and Non-Newtonian) Slug Flow Compared Against Experimental Data of Void Fraction

DEFF Research Database (Denmark)

Ratkovich, Nicolas Rios; Majumder, S.K.; Bentzen, Thomas Ruby

2013-01-01

Gas-Newtonian liquid two-phase flows (TPFs) are presented in several industrial processes (e.g. oil-gas industry). In spite of the common occurrence of these TPFs, the understanding of them is limited compared to single-phase flows. Various studies on TPF focus on developing empirical correlations...... based on large sets of experimental data for void fraction, which have proven accurate for specific conditions for which they were developed limiting their applicability. On the other hand, few studies focus on gas-non-Newtonian liquids TPFs, which are very common in chemical processes. The main reason...... is due to the characterization of the viscosity, which determines the hydraulic regime and flow behaviours of the system. The focus of this study is the analysis of the TPF (slug flow) for Newtonian and non-Newtonian liquids in a vertical pipe in terms of void fraction using computational fluid dynamics...

Design and Analysis of Horizontal Axial Flow Motor Shroud

Science.gov (United States)

Wang, Shiming; Shen, Yu

2018-01-01

The wind turbine diffuser can increase the wind energy utilization coefficient of the wind turbine, and the addition of the shroud to the horizontal axis wind turbine also plays a role of accelerating the flow of the condensate. First, the structure of the shroud was designed and then modeled in gambit. The fluent software was used to establish the mathematical model for simulation. The length of the shroud and the opening angle of the shroud are analyzed to determine the best shape of the shroud. Then compared the efficiency with or without the shroud, through the simulation and the experiment of the water tank, it is confirmed that the horizontal axis of the shroud can improve the hydrodynamic performance.

SLUG promotes prostate cancer cell migration and invasion via CXCR4/CXCL12 axis.

Science.gov (United States)

Uygur, Berna; Wu, Wen-Shu

2011-11-10

SLUG is a zinc-finger transcription factor of the Snail/Slug zinc-finger family that plays a role in migration and invasion of tumor cells. Mechanisms by which SLUG promotes migration and invasion in prostate cancers remain elusive. Expression level of CXCR4 and CXCL12 was examined by Western blot, RT-PCR, and qPCR analyses. Forced expression of SLUG was mediated by retroviruses, and SLUG and CXCL12 was downregulated by shRNAs-expressing lentiviruses. Migration and invasion of prostate cancer were measured by scratch-wound assay and invasion assay, respectively. We demonstrated that forced expression of SLUG elevated CXCR4 and CXCL12 expression in human prostate cancer cell lines PC3, DU145, 22RV1, and LNCaP; conversely, reduced expression of SLUG by shRNA downregulated CXCR4 and CXCL12 expression at RNA and protein levels in prostate cancer cells. Furthermore, ectopic expression of SLUG increased MMP9 expression and activity in PC3, 22RV1, and DU-145 cells, and SLUG knockdown by shRNA downregulated MMP9 expression. We showed that CXCL12 is required for SLUG-mediated MMP9 expression in prostate cancer cells. Moreover, we found that migration and invasion of prostate cancer cells was increased by ectopic expression of SLUG and decreased by SLUG knockdown. Notably, knockdown of CXCL12 by shRNA impaired SLUG-mediated migration and invasion in prostate cancer cells. Lastly, our data suggest that CXCL12 and SLUG regulate migration and invasion of prostate cancer cells independent of cell growth. We provide the first compelling evidence that upregulation of autocrine CXCL12 is a major mechanism underlying SLUG-mediated migration and invasion of prostate cancer cells. Our findings suggest that CXCL12 is a therapeutic target for prostate cancer metastasis.

Numerical simulation of 2D fluidized bed and slug-flow pnuematic conveying using the discrete element method

International Nuclear Information System (INIS)

Zhang, Z.; Li, M.; Xie, Z.; Barron, R.M.

2002-01-01

In recent years, the two-fluids model in an Eulerian-Eulerian coordinate system has been the main tool for solving two-phase flow problems because of its convenient mathematical representation and its feasibility for large-scale computations. However, the assumptions of local equilibrium and continuity for the solid phase in the two-fluids model essentially mask the nonuniform and discontinuous features of the solid phase flow. This paper discusses a further study of the particle flow dynamics in two kinds of fluidized beds and a horizontal plug-flow pneumatic conveying pipe

Pattern recognition techniques for horizontal and vertically upward multiphase flow measurement

Science.gov (United States)

Arubi, Tesi I. M.; Yeung, Hoi

2012-03-01

The oil and gas industry need for high performing and low cost multiphase meters is ever more justified given the rapid depletion of conventional oil reserves that has led oil companies to develop smaller and marginal fields and reservoirs in remote locations and deep offshore, thereby placing great demands for compact and more cost effective solutions of on-line continuous multiphase flow measurement for well testing, production monitoring, production optimisation, process control and automation. The pattern recognition approach for clamp-on multiphase measurement employed in this study provides one means for meeting this need. High speed caesium-137 radioisotope-based densitometers were installed vertically at the top of a 50.8mm and 101.6mm riser as well as horizontally at the riser base in the Cranfield University multiphase flow test facility. A comprehensive experimental campaign comprising flow conditions typical of operating conditions found in the Petroleum Industry was conducted. The application of a single gamma densitometer unit, in conjunction with pattern recognition techniques to determine both the phase volume fractions and velocities to yield the individual phase flow rates of horizontal and vertically upward multiphase flows was investigated. The pattern recognition systems were trained to map the temporal fluctuations in the multiphase mixture density with the individual phase flow rates using statistical features extracted from the gamma counts signals as their inputs. Initial results yielded individual phase flow rate predictions to within ±5% relative error for the two phase airwater flows and ±10% for three phase air-oil-water flows data.

Two-phase flow through small branches in a horizontal pipe with stratified flow

International Nuclear Information System (INIS)

Smoglie, C.

1984-12-01

This report presents the description and results of experiments designed to determine the mass flow rate and quality through a small break at the bottom, the top or the side of a main pipe with stratified gas-liquid flow. If the interface level is far below (above) the branch, only single-phase gas (liquid) flow enters the branch. For smaller distances the interface is locally deformed because of the pressure decrease due to the fluid acceleration near the branch inlet (Bernoulli effect) and liquid (gas) can be entrained. This report contains photographs illustrating the flow phenomena as well as a general correlation to determine the beginning of entrainment. Results are presented on the branch mass flow rate and quality as a function of a normalized distance between the interface and the branch inlet. A model was developed which enables to predict the branch quality and mass flux. Results from air-water flow through horizontal branches, were extrapolated for steam water flow at high pressure with critical branch mass flux. (orig./HP) [de

An Experimental Study of Oil / Water Flow in Horizontal Pipes

Energy Technology Data Exchange (ETDEWEB)

Elseth, Geir

2001-07-01

The purpose of this thesis is to study the behaviour of the simultaneous flow of oil and water in horizontal pipes. In this connection, two test facilities are used. Both facilities have horizontal test sections with inner pipe diameters equal to 2 inches. The largest facility, called the model oil facility, has reservoirs of 1 m{sub 3} of each medium enabling flow rates as high as 30 m{sub 3}/h, which corresponds to mixture velocities as high as 3.35 m/s. The flow rates of oil and water can be varied individually producing different flow patterns according to variations in mixture velocity and input water cut. Two main classes of flows are seen, stratified and dispersed. In this facility, the main focus has been on stratified flows. Pressure drops and local phase fractions are measured for a large number of flow conditions. Among the instruments used are differential pressure transmitters and a traversing gamma densitometer, respectively. The flow patterns that appear are classified in flow pattern maps as functions of either mixture velocity and water cut or superficial velocities. From these experiments a smaller number of stratified flows are selected for studies of velocity and turbulence. A laser Doppler anemometer (LDA) is applied for these measurements in a transparent part of the test section. To be able to produce accurate measurements a partial refractive index matching procedure is used. The other facility, called the matched refractive index facility, has a 0.2 m{sub 3} reservoir enabling mainly dispersed flows. Mixture velocities range from 0.75 m/s to 3 m/s. The fluids in this facility are carefully selected to match the refractive index of the transparent part of the test section. A full refractive index matching procedure is carried out producing excellent optical conditions for velocity and turbulence studies by LDA. In addition, pressure drops and local phase fractions are measured. (author)

Two-phase flow regimes for counter-current air-water flows in narrow rectangular channels

International Nuclear Information System (INIS)

Kim, Byong Joo; Sohn, Byung Hu; Jeong, Si Young

2001-01-01

A study of counter-current two-phase flow in narrow rectangular channels has been performed. Two-phase flow regimes were experimentally investigated in a 760 mm long and 100 mm wide test section with 2.0 and 5.0 mm gap widths. The resulting flow regime maps were compared with the existing transition criteria. The experimental data and the transition criteria of the models showed relatively good agreement. However, the discrepancies between the experimental data and the model predictions of the flow regime transition became pronounced as the gap width increased. As the gap width increased the transition gas superficial velocities increased. The critical void fraction for the bubbly-to-slug transition was observed to be about 0.25. The two-phase distribution parameter for the slug flow was larger for the narrower channel. The uncertainties in the distribution parameter could lead to a disagreement in slug-to-churn transition between the experimental findings and the transition criteria. For the transition from churn to annular flow the effect of liquid superficial velocity was found to be insignificant

Ferrofluid-in-oil two-phase flow patterns in a flow-focusing microchannel

Science.gov (United States)

Sheu, T. S.; Chen, Y. T.; Lih, F. L.; Miao, J. M.

This study investigates the two-phase flow formation process of water-based Fe3O4 ferrofluid (dispersed phase) in a silicon oil (continuous phase) flow in the microfluidic flow-focusing microchannel under various operational conditions. With transparent PDMS chip and optical microscope, four main two-phase flow patterns as droplet flow, slug flow, ring flow and churn flow are observed. The droplet shape, size, and formation mechanism were also investigated under different Ca numbers and intended to find out the empirical relations. The paper marks an original flow pattern map of the ferrofluid-in-oil flows in the microfluidic flow-focusing microchannels. The flow pattern transiting from droplet flow to slug flow appears for an operational conditions of QR < 1 and Lf / W < 1. The power law index that related Lf / W to QR was 0.36 in present device.

Stratification of bubbly horizontal flows: modeling and experimental validation

International Nuclear Information System (INIS)

Bottin, M.

2010-01-01

Hot films and optical probes enabled the acquisition of measurements in bubbly flows at 5, 20 and 40 diameters from the inlet of the vein on the METERO facility which test section is a horizontal circular pipe of 100 mm inner diameter. The distribution of the different phases, the existence of coalescence and sedimentation mechanisms, the influence of the liquid and gas flow rates, the radial and axial evolutions are analyzed thanks to fast camera videos and numerous and varied experimental results (void fraction, bubbles sizes, interfacial area, mean and fluctuating velocities and turbulent kinetic energy of the liquid phase). Some models, based on the idea that the flow reaches an equilibrium state sufficiently far from the inlet of the pipe, were developed to simulate mean interfacial area and turbulent kinetic energy transports in bubbly flows. (author)

Production of a high-velocity water slug using an impacting technique

Science.gov (United States)

Dehkhoda, S.; Bourne, N. K.

2014-02-01

A pulsed water jet consists of a series of discrete water slugs travelling at high velocity. Immediately after striking a target, these slugs apply high-intensity, short-duration transient stress pulses reaching an amplitude known as the water hammer pressure, followed by low-intensity, long-duration stationary stress at a lower stagnation pressure. The magnitude and duration of the water hammer and stagnation pressures are controlled by the size and quality of the water slugs. The use of water jets for rock cutting in mining operations is a centuries-old technology; however, practical methods for producing high-energy water slugs repeatedly have proven difficult. This can be partly due to the fact that the geometrical properties of a jet and so its effectiveness in creating damage is controlled and influenced by the method that is employed to generate the water slugs. This paper investigates the quality of a single water slug produced using an impacting technique where a hammer strikes a piston, resting on top of a water-filled chamber. The coherence and integrity of the jet core was of concern in this study. The impact impulse of the formed water jet was measured in a Kel-F target material using an embedded PVDF (Polyvinylidene fluoride) shock gauge. The recorded stress waveform was then used to determine the unity and endurance of the water slug stream once travelled through air.

Horizontal two phase flow pattern identification by neural networks

International Nuclear Information System (INIS)

Crivelaro, Kelen Cristina Oliveira; Seleghim Junior, Paulo; Hervieu, Eric

1999-01-01

A multiphase fluid can flow according to several flow regimes. The problem associated with multiphase systems are basically related to the behavior of macroscopic parameters, such as pressure drop, thermal exchanges and so on, and their strong correlation to the flow regime. From the industrial applications point of view, the safety and longevity of equipment and systems can only be assured when they work according to the flow regimes for which they were designed to. This implies in the need to diagnose flow regimes in real time. The automatic diagnosis of flow regimes represents an objective of extreme importance, mainly for applications on nuclear and petrochemical industries. In this work, a neural network is used in association to a probe of direct visualization for the identification of a gas-liquid flow horizontal regimes, developed in an experimental circuit. More specifically, the signals produced by the probe are used to compose a qualitative image of the flow, which is promptly sent to the network for the recognition of the regimes. Results are presented for different transitions among the flow regimes, which demonstrate the extremely satisfactory performance of the diagnosis system. (author)

Flow regime visualization and pressure drops of HFO-1234yf, R-134a and R-410A during downward two-phase flow in vertical return bends

International Nuclear Information System (INIS)

Padilla, Miguel; Revellin, Rémi; Wallet, Jérémy; Bonjour, Jocelyn

2013-01-01

Highlights: ► Visual observation of two-phase flow regimes during downward flow in a return bend. ► Bubble and vapor slug dynamical behaviors in downward slug flow are reported. ► Perturbation lengths up- and downstream of the return bend have been investigated. ► Measurement of 285 pressure drop data points for HFO-1234yf, R-134a and R-410A. -- Abstract: This paper provides a qualitative visual observation of the two-phase flow patterns for HFO-1234yf and R-134a during downward flow in a vertical 6.7 mm inner diameter glass return bend. The different flow regimes observed are: slug, intermittent and annular flows. Bubble and vapor slug dynamical behaviors in downward slug flow are reported for HFO-1234yf. In addition, to determine the perturbation lengths up- and downstream of the return bend, the total pressure drop has been measured at different pressure tap location up- and downstream of the singularity. Furthermore, 285 pressure drop data points measured for two-phase flow of HFO-1234yf, R-134a and R-410A in vertical downward flow return bends are presented. The flow behavior in the return bend, which is subjected to the complex combined actions of gravity and centrifugal force was expressed in terms of the vapor Froude number. This experimental pressure drop database, which is included in the appendix, is compared to four well-known prediction methods available in the literature

A study of Two-Phase Flow Regime Maps in Vertical and Horizontal Pipes

International Nuclear Information System (INIS)

Kim, Kyung Doo; Kang, Doo Hyuk

2007-10-01

A safety analysis code to design a pressurized water reactor and to obtain the licences including entire proprietary rights is under development in domestic research and development project. The purpose and scope of this report is to develop the flow regimes related models for inter-phase friction, wall frictions, wall heat transfer, and inter-phase heat and mass transfer in two-phase three-field equations. In order to choose choose the flow regime criteria, we have investigated various exiting best-estimate T/H codes in this chapter 2. They are the RELAP5-3D, TRAC-M, CATHARE, MARS codes. Around 500 references used in these codes have been collected and reviewed. Also we have investigated eleven papers in detail. In chapter 3, based on the selected flow regimes, the flow regime maps for a gas-liquid flow in horizontal and vertical tubes have decided including the mechanisms of flow regime transition regions. Conclusively, the process will be presented for choosing the best flow regime maps which occur in gas-liquid two-phase flow in horizontal and vertical pipes. We will look forward to decide the constitutive relations based upon the flow regime maps that are determined in this works. The constitutive relations will be used for the code under development

Steady particulate flows in a horizontal rotating cylinder

Science.gov (United States)

Yamane, K.; Nakagawa, M.; Altobelli, S. A.; Tanaka, T.; Tsuji, Y.

1998-06-01

Results of discrete element method (DEM) simulation and magnetic resonance imaging (MRI) experiments are compared for monodisperse granular materials flowing in a half-filled horizontal rotating cylinder. Because opacity is not a problem for MRI, a long cylinder with an aspect ratio ˜7 was used and the flow in a thin transverse slice near the center was studied. The particles were mustard seeds and the ratio of cylinder diameter to particle diameter was approximately 50. The parameters compared were dynamic angle of repose, velocity field in a plane perpendicular to the cylinder axis, and velocity fluctuations at rotation rates up to 30 rpm. The agreement between DEM and MRI was good when the friction coefficient and nonsphericity were adjusted in the simulation for the best fit.

Axisymmetric, Ventilated Supercavitation in Unsteady, Horizontal Flow

Science.gov (United States)

Kawakami, Ellison; Lee, Seung-Jae; Arndt, Roger

2012-11-01

Drag reduction and/or speed augmentation of marine vehicles by means of supercavitation is a topic of great interest. During the initial launch of a supercavitating vehicle, an artificial supercavity is required until the vehicle can reach conditions at which a natural supercavity can be sustained. Previous studies at Saint Anthony Falls Laboratory (SAFL) focused on the behavior of ventilated supercavities in steady horizontal flows. In open waters, vehicles can encounter unsteady flows, especially when traveling under waves. A study has been carried out at SAFL to investigate the effects of unsteady flow on axisymmetric supercavities. An attempt is made to duplicate sea states seen in open waters. In an effort to track cavity dimensions throughout a wave cycle, an automated cavity tracking script has been developed. Using a high speed camera and the proper software, it is possible to synchronize cavity dimensions with pressure measurements taken inside the cavity. Results regarding supercavity shape, ventilation demand, cavitation parameters and closure methods are presented. It was found that flow unsteadiness caused a decrease in the overall length of the supercavity while having only a minimal effect on the maximum diameter. The supercavity volume varied with cavitation number and a possible relationship between the two is being explored. (Supported by ONR)

Three-dimensional one-way bubble tracking method for the prediction of developing bubble-slug flows in a vertical pipe. 1st report, models and demonstration

International Nuclear Information System (INIS)

Tamai, Hidesada; Tomiyama, Akio

2004-01-01

A three-dimensional one-way bubble tracking method is one of the most promising numerical methods for the prediction of a developing bubble flow in a vertical pipe, provided that several constitutive models are prepared. In this study, a bubble shape, an equation of bubble motion, a liquid velocity profile, a pressure field, turbulent fluctuation and bubble coalescence are modeled based on available knowledge on bubble dynamics. Bubble shapes are classified into four types in terms of bubble equivalent diameter. A wake velocity model is introduced to simulate approaching process among bubbles due to wake entrainment. Bubble coalescence is treated as a stochastic phenomenon with the aid of coalescence probabilities that depend on the sizes of two interacting bubbles. The proposed method can predict time-spatial evolution of flow pattern in a developing bubble-slug flow. (author)

Horizontal liquid film-mist two phase flow, (1)

International Nuclear Information System (INIS)

Akagawa, Koji; Sakaguchi, Tadashi; Fujii, Terushige; Nakatani, Yoji; Nakaseko, Kosaburo.

1979-01-01

The characteristics of liquid film in annular spray flow, the generation of droplets from liquid film and the transport of droplets to a wall are the important matters in the planning and design of nuclear reactor cooling system and the channels of steam generators. The study on the liquid film spray flow is scarce, and its characteristics are not yet elucidated. The purpose of this series of studies is to clarify the characteristics of liquid film, the generation, diffusion and distribution of droplets and pressure loss in the liquid film spray flow composed of the liquid film on the lower wall and spraying gas flow in a rectangular, horizontal channel. In this paper, the concentration distribution and the diffusion coefficient of droplets on a cross section in the region of flow completion are reported. The experimental apparatuses and the experimental method, the flow rate of droplets and the velocity distribution of gas phase, the concentration distribution and the diffusion coefficient of droplets, and the diameter of generated droplets are explained. The equation for the concentration distribution of droplets using dimensionless characteristic value was derived. The mean diffusion coefficient of droplets was constant on a cross section, and the effects of gravity and turbulent diffusion can be evaluated. (Kako, I.)

Assessment of horizontal in-tube condensation models using MARS code. Part I: Stratified flow condensation

Energy Technology Data Exchange (ETDEWEB)

Jeon, Seong-Su [Department of Engineering Project, FNC Technology Co., Ltd., Bldg. 135-308, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Department of Nuclear Engineering, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Hong, Soon-Joon, E-mail: sjhong90@fnctech.com [Department of Engineering Project, FNC Technology Co., Ltd., Bldg. 135-308, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Park, Ju-Yeop; Seul, Kwang-Won [Korea Institute of Nuclear Safety, 19 Kuseong-dong, Yuseong-gu, Daejon (Korea, Republic of); Park, Goon-Cherl [Department of Nuclear Engineering, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of)

2013-01-15

Highlights: Black-Right-Pointing-Pointer This study collected 11 horizontal in-tube condensation models for stratified flow. Black-Right-Pointing-Pointer This study assessed the predictive capability of the models for steam condensation. Black-Right-Pointing-Pointer Purdue-PCCS experiments were simulated using MARS code incorporated with models. Black-Right-Pointing-Pointer Cavallini et al. (2006) model predicts well the data for stratified flow condition. Black-Right-Pointing-Pointer Results of this study can be used to improve condensation model in RELAP5 or MARS. - Abstract: The accurate prediction of the horizontal in-tube condensation heat transfer is a primary concern in the optimum design and safety analysis of horizontal heat exchangers of passive safety systems such as the passive containment cooling system (PCCS), the emergency condenser system (ECS) and the passive auxiliary feed-water system (PAFS). It is essential to analyze and assess the predictive capability of the previous horizontal in-tube condensation models for each flow regime using various experimental data. This study assessed totally 11 condensation models for the stratified flow, one of the main flow regime encountered in the horizontal condenser, with the heat transfer data from the Purdue-PCCS experiment using the multi-dimensional analysis of reactor safety (MARS) code. From the assessments, it was found that the models by Akers and Rosson, Chato, Tandon et al., Sweeney and Chato, and Cavallini et al. (2002) under-predicted the data in the main condensation heat transfer region, on the contrary to this, the models by Rosson and Meyers, Jaster and Kosky, Fujii, Dobson and Chato, and Thome et al. similarly- or over-predicted the data, and especially, Cavallini et al. (2006) model shows good predictive capability for all test conditions. The results of this study can be used importantly to improve the condensation models in thermal hydraulic code, such as RELAP5 or MARS code.

The evaluation of validity of the RELAP5/Mod3 flow regime map for horizontal small diameter tubes at low pressure

Energy Technology Data Exchange (ETDEWEB)

Agafonova, N. [St. Petersburg State Technical Univ. (Russian Federation); Banati, J. [Lappeenranta Univ. of Technology (Finland)

1997-12-31

RELAP5/MOD3 code was developed for Western type power water reactors with vertical steam generators. Thus, this code should be validated also for WWER design with horizontal steam generators. In application for horizontal steam generators the situation with two-phase flow inside small diameter tubes is possible when the first circuit pressure drops in accident below the pressure level in the boiling water. It is known that computer codes have not always modelled correctly the two-phase flow inside horizontal tubes at low pressures (less than 4-6 MPa). It may be the result of erroneous prediction of the flow regime. Correct prediction of the flow regime is especially important for the fully or partly stratified flow in horizontal tubes. The aim of this study is the attempt of verification of the flow regime map, which is used in the RELAP5/MOD3 computer code for two-phase flow in horizontal small diameter tubes. `Small diameter tube` means according RELAP5/MOD3 that the inner diameter of the tube is less (or equal) than 0.018 m. The inner tube diameter in horizontal steam generators is equal 0.013 m. (orig.). 19 refs.

The evaluation of validity of the RELAP5/Mod3 flow regime map for horizontal small diameter tubes at low pressure

Energy Technology Data Exchange (ETDEWEB)

Agafonova, N [St. Petersburg State Technical Univ. (Russian Federation); Banati, J [Lappeenranta Univ. of Technology (Finland)

1998-12-31

RELAP5/MOD3 code was developed for Western type power water reactors with vertical steam generators. Thus, this code should be validated also for WWER design with horizontal steam generators. In application for horizontal steam generators the situation with two-phase flow inside small diameter tubes is possible when the first circuit pressure drops in accident below the pressure level in the boiling water. It is known that computer codes have not always modelled correctly the two-phase flow inside horizontal tubes at low pressures (less than 4-6 MPa). It may be the result of erroneous prediction of the flow regime. Correct prediction of the flow regime is especially important for the fully or partly stratified flow in horizontal tubes. The aim of this study is the attempt of verification of the flow regime map, which is used in the RELAP5/MOD3 computer code for two-phase flow in horizontal small diameter tubes. `Small diameter tube` means according RELAP5/MOD3 that the inner diameter of the tube is less (or equal) than 0.018 m. The inner tube diameter in horizontal steam generators is equal 0.013 m. (orig.). 19 refs.

Unsteady Flow in a Horizontal Double-Sided Symmetric Thin Liquid Films

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Joseph G. ABDULAHAD

2017-06-01

Full Text Available In this paper a mathematical model is constructed to describe a two dimensional incompressible flow in a symmetric horizontal thin liquid film for unsteadies flow. We apply the Navier-Stokes equations with specified boundary conditions and we obtain the equation of the film thickness by using the similarity method in which we can isolate the explicit time dependence and then the shape of the film will depend on one variable only.

Slug controls stem/progenitor cell growth dynamics during mammary gland morphogenesis.

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Mayssa Nassour

Full Text Available Morphogenesis results from the coordination of distinct cell signaling pathways controlling migration, differentiation, apoptosis, and proliferation, along stem/progenitor cell dynamics. To decipher this puzzle, we focused on epithelial-mesenchymal transition (EMT "master genes". EMT has emerged as a unifying concept, involving cell-cell adhesion, migration and apoptotic pathways. EMT also appears to mingle with stemness. However, very little is known on the physiological role and relevance of EMT master-genes. We addressed this question during mammary morphogenesis. Recently, a link between Slug/Snai2 and stemness has been described in mammary epithelial cells, but EMT master genes actual localization, role and targets during mammary gland morphogenesis are not known and we focused on this basic question.Using a Slug-lacZ transgenic model and immunolocalization, we located Slug in a distinct subpopulation covering about 10-20% basal cap and duct cells, mostly cycling cells, coexpressed with basal markers P-cadherin, CK5 and CD49f. During puberty, Slug-deficient mammary epithelium exhibited a delayed development after transplantation, contained less cycling cells, and overexpressed CK8/18, ER, GATA3 and BMI1 genes, linked to luminal lineage. Other EMT master genes were overexpressed, suggesting compensation mechanisms. Gain/loss-of-function in vitro experiments confirmed Slug control of mammary epithelial cell luminal differentiation and proliferation. In addition, they showed that Slug enhances specifically clonal mammosphere emergence and growth, cell motility, and represses apoptosis. Strikingly, Slug-deprived mammary epithelial cells lost their potential to generate secondary clonal mammospheres.We conclude that Slug pathway controls the growth dynamics of a subpopulation of cycling progenitor basal cells during mammary morphogenesis. Overall, our data better define a key mechanism coordinating cell lineage dynamics and morphogenesis, and

An invasive slug exploits an ant-seed dispersal mutualism.

Science.gov (United States)

Meadley Dunphy, Shannon A; Prior, Kirsten M; Frederickson, Megan E

2016-05-01

Plant-animal mutualisms, such as seed dispersal, are often vulnerable to disruption by invasive species. Here, we show for the first time how a non-ant invasive species negatively affects seed dispersal by ants. We examined the effects of several animal species that co-occur in a temperate deciduous forest-including native and invasive seed-dispersing ants (Aphaenogaster rudis and Myrmica rubra, respectively), an invasive slug (Arion subfuscus), and native rodents-on a native myrmecochorous plant, Asarum canadense. We experimentally manipulated ant, slug, and rodent access to seed depots and measured seed removal. We also video-recorded depots to determine which other taxa interact with seeds. We found that A. rudis was the main disperser of seeds and that A. subfuscus consumed elaiosomes without dispersing seeds. Rodent visitation was rare, and rodent exclusion had no significant effect on seed or elaiosome removal. We then used data obtained from laboratory and field mesocosm experiments to determine how elaiosome robbing by A. subfuscus affects seed dispersal by A. rudis and M. rubra. We found that elaiosome robbing by slugs reduced seed dispersal by ants, especially in mesocosms with A. rudis, which picks up seeds more slowly than M. rubra. Taken together, our results show that elaiosome robbing by an invasive slug reduces seed dispersal by ants, suggesting that invasive slugs can have profound negative effects on seed dispersal mutualisms.

SLUG-STOCHASTICALLY LIGHTING UP GALAXIES. I. METHODS AND VALIDATING TESTS

Energy Technology Data Exchange (ETDEWEB)

Da Silva, Robert L.; Fumagalli, Michele; Krumholz, Mark [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

2012-02-01

The effects of stochasticity on the luminosities of stellar populations are an often neglected but crucial element for understanding populations in the low-mass or the low star formation rate regime. To address this issue, we present SLUG, a new code to 'Stochastically Light Up Galaxies'. SLUG synthesizes stellar populations using a Monte Carlo technique that properly treats stochastic sampling including the effects of clustering, the stellar initial mass function, star formation history, stellar evolution, and cluster disruption. This code produces many useful outputs, including (1) catalogs of star clusters and their properties such as their stellar initial mass distributions and their photometric properties in a variety of filters, (2) two dimensional histograms of color-magnitude diagrams of every star in the simulation, and (3) the photometric properties of field stars and the integrated photometry of the entire simulated galaxy. After presenting the SLUG algorithm in detail, we validate the code through comparisons with STARBURST99 in the well-sampled regime, and with observed photometry of Milky Way clusters. Finally, we demonstrate SLUG's capabilities by presenting outputs in the stochastic regime. SLUG is publicly distributed through the Web site http://sites.google.com/site/runslug/.

Bed diameter effects and incipient slugging in gas fluidized beds

International Nuclear Information System (INIS)

Agarwal, P.K.

1986-01-01

The coalescence and growth of bubble swarms formed at the distributor of a fluidized bed gives rise to lateral as well as vertical distributions of bubble properties. However, existing models employ average bubble properties obtained largely from semi-empirical considerations. In a recent Paper, the author developed a bubble growth model based on a population balance approach. Analytical expressions were derived for the bubble characteristic distributions and averages. However, the model, developed for unconstrained growth, did not take into account the effect of the bed diameter and the possibility of slugging. In this Paper, the model is extended to take these aspects into account. A slugging criterion is also developed which is expected to be valid for the regime where incipient slugging depends on the bed height as well as the region where bed height does not significantly affect minimum slugging conditions

An analysis direct-contact condensation in horizontal cocurrent stratified flow of steam and cold water

International Nuclear Information System (INIS)

Lee, Suk Ho; Kim, Hho Jung

1992-01-01

The physical benchmark problem on the direct-contact condensation under the horizontal cocurrent stratified flow was analyzed using the RELAP5/MOD2 and /MOD3 one-dimensional model. Analysis was performed for the Northwestern experiments, which involved condensing steam/water flow in a rectangular channel. The study showed that the RELAP5 interfacial heat transfer model, under the horizontal stratified flow regime, predicted the condensation rate well though the interfacial heat transfer area was underpredicted. However, some discrepancies in water layer thickness and local heat transfer coefficient with experimental results were found especially when there is a wavy interface, and those were satisfied only within the range. (Author)

Ecoulements diphasiques gaz-liquide à poches et à bouchons en conduites Two-Phase Gas-Liquid Slug Flow in Pipes

Directory of Open Access Journals (Sweden)

Ferschneider G.

2006-11-01

Full Text Available Les écoulements diphasiques gaz-liquide ont été étudiés afin de contribuer à développer des modèles de calculs prédictifs des pertes de charge dans les conduites de production des bruts pétroliers. Les expériences nécessaires ont été réalisées sur la boucle diphasique de Boussens dans les conditions suivantes représentatives des conditions industrielles : diamètre 6 , longueur 120 m, disposition de la conduite horizontale ou faiblement ascendante, couple de fluide gaz naturel-huile légère. Le gradient de pression, le contenu global, et la distribution locale des phases ont été mesurés. Le traitement des équations de conservation phasique intégrées sur la section par différents types de moyennes a permis de développer un modèle cellulaire qui inclue un nombre limité d'équations constitutives nécessaires à sa fermeture. Ce modèle prédétermine convenablement le gradient de pression, le contenu gaz global et la longueur des poches et des bouchons. Two-phase gas-liquid flows were analyzed so as to develop models for prediction of pressure drops in crude-oil production lines. The experiments were performed on the two-phase loop at Boussens under the following representative industrial conditions: 6 diameter, 120 m length, horizontal or slightly rising pipe, couple of fluids natural gas and light oil. The pressure gradient, average content and local phase distribution were measured. Conservation phase equations integrated along the cross-section were processed by different time-averaged operators so as to develop a cellular model including a limited number of constitutive equations required for its closure. This model suitably predetermines the pressure gradient, the average gas content and the length of gas and liquid slug.

Production polyphasique. Modélisation des écoulements à bouchons Multiphase Production Slug-Flow Modeling

Directory of Open Access Journals (Sweden)

Drouffe J. M.

2006-11-01

Full Text Available L'exploitation des hydrocarbures en mer reste une activité coûteuse et qui peut, même, se révéler, éventuellement dangereuse. Les concepts de production polyphasique tels que Poséidon permettent à la fois : - une réduction importante des coûts de production; - la suppression des risques humains liés à la présence permanente en mer d'équipes importantes. Les programmes de simulation des écoulements diphasiques actuellement disponibles pour la mise en oeuvre de ces concepts, sont tous basés sur une approche déterministeclassique. Cet article présente une nouvelle approche statistiquenon conventionnelle qui devrait nous permettre de mieux préciser les caractéristiques des écoulements à bouchons et donc de pouvoir mieux dimensionner et exploiter nos futures installations de production et transport polyphasique longue distance. Offshore hydrocarbon production remains a costly venture, and even one that might possibly be dangerous. Multiphase production concepts such as Poseidon make for both a considerable reduction in production costs and the elimination of human risks linked to the constant offshore presence of large crews. The two-phase flow simulation programs now available for implementing such concepts are all based on a standard deterministicapproach. This article describes a new and unconventional statisticalapproach that we feel more accurately describes the characteristics of slug flows and hence is more effecting for the sizing and operating of future production and long-distance pipelining installations.

The Finite Element Analysis for a Mini-Conductance Probe in Horizontal Oil-Water Two-Phase Flow

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Weihang Kong

2016-08-01

Full Text Available Oil-water two-phase flow is widespread in petroleum industry processes. The study of oil-water two-phase flow in horizontal pipes and the liquid holdup measurement of oil-water two-phase flow are of great importance for the optimization of the oil production process. This paper presents a novel sensor, i.e., a mini-conductance probe (MCP for measuring pure-water phase conductivity of oil-water segregated flow in horizontal pipes. The MCP solves the difficult problem of obtaining the pure-water correction for water holdup measurements by using a ring-shaped conductivity water-cut meter (RSCWCM. Firstly, using the finite element method (FEM, the spatial sensitivity field of the MCP is investigated and the optimized MCP geometry structure is determined in terms of the characteristic parameters. Then, the responses of the MCP for the oil-water segregated flow are calculated, and it is found that the MCP has better stability and sensitivity to the variation of water-layer thickness in the condition of high water holdup and low flow velocity. Finally, the static experiments for the oil-water segregated flow were carried out and a novel calibration method for pure-water phase conductivity measurements was presented. The validity of the pure-water phase conductivity measurement with segregated flow in horizontal pipes was verified by experimental results.

The Finite Element Analysis for a Mini-Conductance Probe in Horizontal Oil-Water Two-Phase Flow.

Science.gov (United States)

Kong, Weihang; Kong, Lingfu; Li, Lei; Liu, Xingbin; Xie, Ronghua; Li, Jun; Tang, Haitao

2016-08-24

Oil-water two-phase flow is widespread in petroleum industry processes. The study of oil-water two-phase flow in horizontal pipes and the liquid holdup measurement of oil-water two-phase flow are of great importance for the optimization of the oil production process. This paper presents a novel sensor, i.e., a mini-conductance probe (MCP) for measuring pure-water phase conductivity of oil-water segregated flow in horizontal pipes. The MCP solves the difficult problem of obtaining the pure-water correction for water holdup measurements by using a ring-shaped conductivity water-cut meter (RSCWCM). Firstly, using the finite element method (FEM), the spatial sensitivity field of the MCP is investigated and the optimized MCP geometry structure is determined in terms of the characteristic parameters. Then, the responses of the MCP for the oil-water segregated flow are calculated, and it is found that the MCP has better stability and sensitivity to the variation of water-layer thickness in the condition of high water holdup and low flow velocity. Finally, the static experiments for the oil-water segregated flow were carried out and a novel calibration method for pure-water phase conductivity measurements was presented. The validity of the pure-water phase conductivity measurement with segregated flow in horizontal pipes was verified by experimental results.

Experiment and numerical simulation of bubbly two-phase flow across horizontal and inclined rod bundles

International Nuclear Information System (INIS)

Serizawa, A.; Huda, K.; Yamada, Y.; Kataoka, I.

1997-01-01

Experimental and numerical analyses were carried out on vertically upward air-water bubbly two-phase flow behavior in both horizontal and inclined rod bundles with either in-line or staggered array. The inclination angle of the rod bundle varied from 0 to 60 with respect to the horizontal. The measured phase distribution indicated non-uniform characteristics, particularly in the direction of the rod axis when the rods were inclined. The mechanisms for this non-uniform phase distribution is supposed to be due to: (1) Bubble segregation phenomenon which depends on the bubble size and shape: (2) bubble entrainment by the large scale secondary flow induced by the pressure gradient in the horizontal direction which crosses the rod bundle; (3) effects of bubble entrapment by vortices generated in the wake behind the rods which travel upward along the rod axis; and (4) effect of bubble entrainment by local flows sliding up along the front surface of the rods. The liquid velocity and turbulence distributions were also measured and discussed. In these speculations, the mechanisms for bubble bouncing at the curved rod surface and turbulence production induced by a bubble were discussed, based on visual observations. Finally, the bubble behaviors in vertically upward bubbly two-phase flow across horizontal rod bundle were analyzed based on a particle tracking method (one-way coupling). The predicted bubble trajectories clearly indicated the bubble entrapment by vortices in the wake region. (orig.)

Mixed convection between horizontal plates and consequences for chemical vapor deposition flows

International Nuclear Information System (INIS)

Chiu, K.C.

1986-01-01

To simulate the fluid dynamics of VD systems, mixed convection between horizontal plates (AR = width/height = 10) heated from below was studied by laser Doppler anemometry in a range 1368 < Ra < 8300 and 15 < R3 < 170. The entrance effects were characterized by two lengths: one for the onset of bouyancy-driven instability, and one for the full development of longitudinal convection rolls. Explicit expressions for both entrance lengths are given in terms of Ra and Re. In addition, unsteady longitudinal convection rolls were observed. These are discussed in terms of the admixture of transverse convection rolls and/or contributions from upstream turbulence. For the fully developed region it is shown analytically that the transverse velocities of the longitudinal convection rolls, v and w, are independent of the forced flow and are identical to those of the two-dimensional Rayleigh-Benard convection rolls. These fundamental results serve as a base for the discussion of horizontal CVD flows. The entrance and sidewall effects are found to have pronounced influences on the flow patterns observed in CVD (AR = 2) reactors

Visualization of two-phase gas-liquid flow regimes in horizontal and slightly-inclined circular tubes

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Livia Alves [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Nuclear Engineering Institute (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)], E-mail: livia@lasme.coppe.ufrj.br; Cunha Filho, Jurandyr; Su, Jian [Coordenacao dos Programas de Pos-Graduacao de Engenharia (COPPE/UFRJ), RJ (Brazil). Nuclear Engineering Program], Emails: cunhafilho@lasme.coppe.ufrj.br, sujian@lasme.coppe.ufrj.br; Faccini, Jose Luiz Horacio [Nuclear Engineering Institute (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)], E-mail: faccini@ien.gov.br

2010-07-01

In this paper a flow visualization study was performed for two-phase gas-liquid flow in horizontal and slightly inclined tubes. The test section consists of a 2.54 cm inner diameter stainless steel circular tube, followed by a transparent acrylic tube with the same inner diameter. The working fluids were air and water, with liquid superficial velocities ranging from 0:11 to 3:28 m/s and gas superficial velocities ranging from 0:27 to 5:48 m/s. Flow visualization was executed for upward flow at 5 deg and 10 deg and downward flow at 2:5 deg, 5 deg and 10 deg, as well as for horizontal flow. The visualization technique consists of a high-speed digital camera that records images at rates of 125 and 250 frames per second of a concurrent air-water mixture through a transparent part of the tube. From the obtained images, the flow regimes were identified (except for annular flow), observing the effect of inclination angles on flow regime transition boundaries. Finally, the experimental results were compared with empirical and theoretical flow pattern maps available in literature. (author)

Development of two-phase Flow Model, 'SOBOIL', for Sodium

International Nuclear Information System (INIS)

Hahn, Do Hee; Chang, Won Pyo; Kim, In Chul; Kwon, Young Min; Lee, Yong Bum

2000-03-01

The objective of this research is to develop a sodium two-phase flow analysis model, 'SOBOIL', for the assessment of the initial stage of the KALIMER HCDA (Hypotherical Core Disruptive Accident). The 'SOBOIL' is basically similar to the multi-bubble slug ejection model used in SAS2A[1]. When a bubble is formed within the liquid slug, the bubble fills the whole cross section of the coolant channel except for a film left on the cladding or on the structure. Up to nine bubbles, separated by the liquid slugs, are allowed in the channel at any time. Each liquid slug flow rate in the model is performed in 2 steps. In the first step, the preliminary flow rate in the liquid slug is calculated neglecting the effect of changes in the vapor bubble pressures over the time step. The temperature and pressure distributions, and interface velocity at the interface between the liquid slug and vapor bubble are also calculated during this process. The new vapor temperature and pressure are then determined from the balance between the net energy transferred into the vapor and the change of the vapor energy. The liquid flow is finally calculated considering the change of the vapor pressure over a time step and the calculation is repeated until specified elapsed time is met. Continuous effort, therefore, must be made on the examination and improvement for the model to become reliable. To this end, much interest must be concentrated in the relevant international collaborations for access to a reference model or test data for the verification

Integrity of high-velocity water slug generated by an impacting technique

Science.gov (United States)

Dehkhoda, Sevda; Bourne, Neil

2013-06-01

A pulsed water jet is a series of discrete water slugs travelling at high velocity. Immediately after striking a target, these slugs apply high-intensity, short-duration transient stress known as the water hammer pressure, followed by low-intensity, long-duration stationary stress at the stagnation pressure. The magnitude and duration of the water hammer and stagnation pressures are controlled by the size and quality of the water slugs. The use of water jets for rock cutting in mining operations is a centuries-old technology; however, practical methods for producing high-energy water slugs repeatedly have proven difficult. This can be partly due to the fact that the geometrical properties of a jet and so its effectiveness in creating damage is controlled and influenced by the method that is employed to generate the water slugs. This paper investigates the integrity of a single water slug produced using an impacting technique where a hammer strikes a piston, resting on top of a water-filled chamber. The coherence of the generated water pulse was of concern in this study. If repeated shock reflections within the chamber were transmitted or were carried into the internal geometry of nozzle, the emerging jet could pulsate. The impact impulse of the formed water jet was measured in a Kel-F target material using an embedded PVDF (Polyvinylidene fluoride) shock gauge. The recorded stress waveform was then used to study the quality and endurance of the water pulse stream as it travelled through air.

A model for cell type localization in the migrating slug of ...

Indian Academy of Sciences (India)

PRAKASH

. Localization of the three major cell types within the migrating slug stage is a dynamic process (Sternfeld 1992;. A model for cell type localization in the migrating slug of Dictyostelium discoideum based on differential chemotactic sensitivity to ...

The root flow of horizontal axis wind turbine blades : Experimental analysis and numerical validation

NARCIS (Netherlands)

Akay, B.

2016-01-01

Despite a long research history in the field of wind turbine aerodynamics, horizontal axis wind turbine (HAWT) blade's root flow aerodynamics is among the least understood topics. In this thesis work, a detailed investigation of the root flow is performed to gain a better insight into the features

Flow visualization of two-phase flows using photochromic dye activation method

International Nuclear Information System (INIS)

Kawaji, M.; Ahmad, W.; DeJesus, J.M.; Sutharshan, B.; Lorencez, C.; Ojha, M.

1993-01-01

A non-intrusive flow visualization technique based on light activation of photochromic dye material has been used to obtain velocity profiles in gas-liquid flows including annular, slug and stratified flows. The preliminary results revealed several important two-phase flow mechanisms that have not been clearly seen previously. (orig.)

Experimental measurements of the cavitating flow after horizontal water entry

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Thang Tat; Thai, Nguyen Quang; Phuong, Truong Thi [Institute of Mechanics (IMECH), Vietnam Academy of Science and Technology (VAST), 264—Doi Can, Ba Dinh, Hanoi (Viet Nam); Hai, Duong Ngoc, E-mail: ntthang@imech.vast.vn, E-mail: dnhai@vast.vn, E-mail: nqthai@imech.vast.vn, E-mail: ttphuong@imech.vast.vn [Graduate University of Science and Technology (GUST), VAST, 18—Hoang Quoc Viet, Cau Giay, Hanoi (Viet Nam)

2017-10-15

Water-entry cavitating flow is of considerable importance in underwater high-speed applications. That is because of the drag-reduction effect that concerns the presence of a cavity around moving objects. Though the study of the flow has long been carried out, little data are documented in literature so far. Besides, currently, in the case of unsteady flow, experimental measurements of some flow parameters such as the cavity pressure still encounter difficulties. Hence continuing research efforts are of important significance. The objective of this study is to investigate experimentally the unsteady cavitating flow after the horizontal water entry of projectiles. An experimental apparatus has been developed. Qualitative and quantitative optical visualizations of the flow have been carried out by using high-speed videography. Digital image processing has been applied to analyzing the recorded flow images. Based on the known correlations between the ellipsoidal super-cavity’s size and the corresponding cavitation number, the cavity pressure has been measured by utilizing the data of image processing. A comparison between the partial- and super-cavitating flow regimes is reported. The received results can be useful for the design of high-speed underwater projectiles. (paper)

Method and device for characterization of two-phase flow in pipes

International Nuclear Information System (INIS)

Skarsvaag, K.; Sunde, A.J.

1993-01-01

Gamma radiation transmission measurements are made with one-shot-collimation to determine the distribution of voids within a gas-liquid mixture flowing in a pipe. The distribution of voids in selected portions of the pipe, taken together with statistical and logical tests applied thereto, provides information from which are determined: type of flow pattern or flow regime, the profile of a large gas bubble in slug flow, and the gas and the liquid volume flow rates in slug flow. 4 refs

An advanced ultrasonic technique for slow and void fraction measurements of two-phase flow

International Nuclear Information System (INIS)

Faccini, J.L.H.; Su, J.; Harvel, G.D.; Chang, J.S.

2004-01-01

In this paper, we present a hybrid type counterpropagating transmission ultrasonic technique (CPTU) for flow and time averaging ultrasonic transmission intensity void fraction measurements (TATIU) of air-water two-phase flow, which is tested in the new two-phase flow test section mounted recently onto an existing single phase flow rig. The circular pipe test section is made of 51.2 mm stainless steel, followed by a transparent extruded acrylic pipe aimed at flow visualization. The two-phase flow rig operates in several flow regimes: bubbly, smooth stratified, wavy stratified and slug flow. The observed flow patterns are compared with previous experimental and numerical flow regime map for horizontal two phase flows. These flow patterns will be identified by time averaging transmission intensity ultrasonic techniques which have been developed to meet this particular application. A counterpropagating transmission ultrasonic flowmeter is used to measure the flow rate of liquid phase. A pulse-echo TATIU ultrasonic technique used to measure the void fraction of the horizontal test section is presented. We can draw the following conclusions: 1) the ultrasonic system was able to characterize the 2 flow patterns simulated (stratified and plug flow); 2) the results obtained for water volumetric fraction require more experimental work to determine exactly the technique uncertainties but, a priori, they are consistent with earlier work; and 3) the experimental uncertainties can be reduced by improving the data acquisition system, changing the acquisition time interval from seconds to milliseconds

Convection Study by PIV Method Within Horizontal Liquid Layer Evaporating Into Inert Gas Flow

Directory of Open Access Journals (Sweden)

Kreta Aleksei

2016-01-01

Full Text Available The paper is devoted to the experimental study of convection in a horizontal evaporating liquid layer (ethanol of limited size under the action of gas flow (air. The two-dimensional velocity field in the liquid layer is obtained using the PIV method. The existence of a vortex convective flow within a liquid layer directed towards the gas flow has been revealed.

Core-annular flow through a horizontal pipe : Hydrodynamic counterbalancing of buoyancy force on core

NARCIS (Netherlands)

Ooms, G.; Vuik, C.; Poesio, P.

2007-01-01

A theoretical investigation has been made of core-annular flow: the flow of a high-viscosity liquid core surrounded by a low-viscosity liquid annular layer through a horizontal pipe. Special attention is paid to the question of how the buoyancy force on the core, caused by a density difference

SNAI2/Slug promotes growth and invasion in human gliomas

International Nuclear Information System (INIS)

Yang, Hong Wei; Menon, Lata G; Black, Peter M; Carroll, Rona S; Johnson, Mark D

2010-01-01

Numerous factors that contribute to malignant glioma invasion have been identified, but the upstream genes coordinating this process are poorly known. To identify genes controlling glioma invasion, we used genome-wide mRNA expression profiles of primary human glioblastomas to develop an expression-based rank ordering of 30 transcription factors that have previously been implicated in the regulation of invasion and metastasis in cancer. Using this approach, we identified the oncogenic transcriptional repressor, SNAI2/Slug, among the upper tenth percentile of invasion-related transcription factors overexpressed in glioblastomas. SNAI2 mRNA expression correlated with histologic grade and invasive phenotype in primary human glioma specimens, and was induced by EGF receptor activation in human glioblastoma cells. Overexpression of SNAI2/Slug increased glioblastoma cell proliferation and invasion in vitro and promoted angiogenesis and glioblastoma growth in vivo. Importantly, knockdown of endogenous SNAI2/Slug in glioblastoma cells decreased invasion and increased survival in a mouse intracranial human glioblastoma transplantation model. This genome-scale approach has thus identified SNAI2/Slug as a regulator of growth and invasion in human gliomas

A Comprehensive Prediction Model of Hydraulic Extended-Reach Limit Considering the Allowable Range of Drilling Fluid Flow Rate in Horizontal Drilling.

Science.gov (United States)

Li, Xin; Gao, Deli; Chen, Xuyue

2017-06-08

Hydraulic extended-reach limit (HERL) model of horizontal extended-reach well (ERW) can predict the maximum measured depth (MMD) of the horizontal ERW. The HERL refers to the well's MMD when drilling fluid cannot be normally circulated by drilling pump. Previous model analyzed the following two constraint conditions, drilling pump rated pressure and rated power. However, effects of the allowable range of drilling fluid flow rate (Q min  ≤ Q ≤ Q max ) were not considered. In this study, three cases of HERL model are proposed according to the relationship between allowable range of drilling fluid flow rate and rated flow rate of drilling pump (Q r ). A horizontal ERW is analyzed to predict its HERL, especially its horizontal-section limit (L h ). Results show that when Q min  ≤ Q r  ≤ Q max (Case I), L h depends both on horizontal-section limit based on rated pump pressure (L h1 ) and horizontal-section limit based on rated pump power (L h2 ); when Q min  drilling fluid flow rate, while L h2 keeps decreasing as the drilling fluid flow rate increases. The comprehensive model provides a more accurate prediction on HERL.

Influence of Catalysis and Oxidation on Slug Calorimeter Measurements in Arc Jets

Science.gov (United States)

Nawaz, Anuscheh; Driver, Dave; TerrazasSalinas, Imelda

2012-01-01

Arc jet tests play a critical role in the characterization and certification of thermal protection materials and systems (TPS). The results from these arc jet tests feed directly into computational models of material response and aerothermodynamics to predict the performance of the TPS in flight. Thus the precise knowledge of the plasma environment to which the test material is subjected, is invaluable. As one of the environmental parameters, the heat flux is commonly measured. The measured heat flux is used to determine the plasma enthalpy through analytical or computational models. At NASA Ames Research Center (ARC), slug calorimeters of a geometrically similar body to the test article are routinely used to determine the heat flux. A slug calorimeter is a thermal capacitance-type calorimeter that uses the temperature rise in a thermally insulated slug to determine the heat transfer rate, see Figure 1(left). Current best practices for measuring the heat flux with a slug calorimeter are described in ASTM E457 - 96. Both the calorimeter body and slug are made of Oxygen Free High Conductivity Copper, and are cleaned before each run.

Applicability of slug interference testing of hydraulic characterization of contaminated aquifer sites

International Nuclear Information System (INIS)

Spane, F.A.; Swanson, L.C.

1993-10-01

Aquifer test methods available for characterizing hazardous waste sites are sometimes restricted because of problems with disposal of contaminated groundwater. These problems, in part, have made slug tests a more desirable method of determining hydraulic properties at such sites. However, in higher permeability formations (i.e., transmissivities ≥ 1 x 10 -3 m 2 /s), slug test results often cannot be analyzed and give, at best, only a lower limit for transmissivity. A need clearly exists to develop test methods that can be used to characterize higher permeability aquifers without removing large amounts of contaminated groundwater. One hydrologic test method that appears to hold promise for characterizing such sites is the slug interference test. To assess the applicability of this test method for use in shallow alluvial aquifer systems, slug interference tests have been conducted, along with more traditional aquifer testing methods, at several Hanford multiple-well sites. Transmissivity values estimated from the slug interference tests were comparable (within a factor of 2 to 3) to values calculated using traditional testing methods, and made it possible to calculate the storativity or specific yield for the intervening test formation. The corroboration of test results indicates that slug interference testing is a viable hydraulic characterization method in transmissive alluvial aquifers, and may represent one of the few test methods that can be used in sensitive areas where groundwater is contaminated

Prediction of gas and liquid turbulent mixing rates between rod bundle subchannels in a two-phase slug-churn flow

International Nuclear Information System (INIS)

Kawahara, Akimaro; Sadatomi, Michio; Tomino, Takayoshi

2000-01-01

This paper presents a slug-churn flow model for predicting turbulent mixing rates of both gas and liquid phases between adjacent subchannels in a BWR fuel rod bundle. In the model, the mixing rate of the liquid phase is calculated as the sum of the three components, i.e., turbulent diffusion, convective transfer and pressure difference fluctuations between the subchannels. The components of turbulent diffusion and convective transfer are calculated from Sadatomi et al.'s (1996) method, applicable to single-phase turbulent mixing, by considering the effect of the increment of liquid velocity due to the presence of gas phase. The component of the pressure difference fluctuations is evaluated from a newly developed correlation. The mixing rate of the gas phase, on the other side, is calculated from a simple relation of mixing rate between gas and liquid phases. The validity of the proposed model has been confirmed with the turbulent mixing rates data of Rudzinski et al. as well as the present authors. (author)

Interfacial condensation heat transfer for countercurrent steam-water wavy flow in a horizontal circular pipe

Energy Technology Data Exchange (ETDEWEB)

Lee, Kyung Won; Chun, Moon Hyun [Korea Advanced Institute of Science and Technolgy, Taejon (Korea, Republic of); Chu, In Cheol [KAERI, Taejon (Korea, Republic of)

2000-10-01

An experimental study of interfacial condensation heat transfer has been performed for countercurrent steam-water wavy flow in a horizontal circular pipe. A total of 105 local interfacial condensation heat transfer coefficients have been obtained for various combinations of test parameters. Two empirical Nusselt number correlations were developed and parametric effects of steam and water flow rates and the degree of water subcooling on the condensation heat transfer were examined. For the wavy interface condition, the local Nusselt number is more strongly sensitive to the steam Reynolds number than water Reynolds number as opposed to the case of smooth interface condition. Comparisons of the present circular pipe data with existing correlations showed that existing correlations developed for rectangular channels are not directly applicable to a horizontal circular pipe flow.

Lateral Mixing Mechanisms in Vertical and Horizontal Interconnected Subchannel Two-Phase Flows

International Nuclear Information System (INIS)

Gencay, Sarman; Teyssedou, Alberto; Tye, Peter

2002-01-01

A lateral mixing model based on equal volume exchange between two laterally interconnected subchannels is presented. The following mixing mechanisms are taken into account in this model: (a) diversion cross flow, caused by the lateral pressure difference between adjacent subchannels; (b) turbulent void diffusion, which is governed by the lateral void fraction difference between the subchannels; (c) void drift, responsible for the tendency of the vapor phase to drift toward unobstructed regions; and (d) buoyancy drift, which takes into account the effect of gravity in horizontal flows. Experimental two-phase air-water data obtained using two test sections having different geometries and orientations are used to determine the diffusion coefficients required by the mixing model. Under the absence of diversion crossflow, i.e., negligible lateral pressure difference between the subchannels, it is observed that the diffusion coefficient increases with increasing average void fraction in the subchannels. Moreover, for vertical flows turbulent void diffusion seems to be considerably affected by the geometry of the subchannels. For horizontal flows under nonsymmetric inlet void fraction conditions, even though the interconnected subchannels have the same geometry, different turbulent void diffusion and void drift coefficients are required to satisfy the conditions of hydrodynamic equilibrium. In the present study this condition is achieved by introducing a new void drift coefficient expressed as a correction term applied to the turbulent void drift term

Online slug detection in multi-phase transportation pipelines using electrical tomography

DEFF Research Database (Denmark)

Pedersen, Simon; Mai, Christian; Hansen, Leif

2015-01-01

in the pipelines is a highly investigated topic. To eliminate the slug in an online manner real-time slug detection methods are often required. Traditionally topside pressure transmitters upstream a 3-phase separator have been used as the controlled variable. In this paper Electrical Resistivity Tomography (ERT...

Online Slug Detection in Multi-phase Transportation Pipelines Using Electrical Tomography

DEFF Research Database (Denmark)

Pedersen, Simon; Mai, Christian; Hansen, Leif

2015-01-01

in the pipelines is a highly investigated topic. To eliminate the slug in an online manner real-time slug detection methods are often required. Traditionally topside pressure transmitters upstream a 3-phase separator have been used as the controlled variable. In this paper Electrical Resistivity Tomography (ERT...

UNDERWATER ANALYSIS OF IRRADIATED REACTOR SLUGS FOR Co-60 AND OTHER RADIONUCLIDES AT THE SAVANNAH RIVER SITE

International Nuclear Information System (INIS)

CASELLA, VITO

2004-01-01

Co-60 was produced in the Savannah River Site (SRS) reactors in the 1970s, and the irradiated cobalt reactor slugs were stored in a reactor basin at SRS. Since the activity rates of these slugs were not accurately known, assaying was required. A sodium iodide gamma detector was placed above a specially designed air collimator assembly, so that the slug was eight to nine feet from the detector and was shielded by the basin water. Also, 18 curium sampler slugs, used to produce Cm-244 from Pu-239, were to be disposed of with the cobalt slugs. The curium slugs were also analyzed with a High Purity Germanium (HPGE) detector in an attempt to identify any additional radionuclides produced from the irradiation. Co-60 concentrations were determined for reactor disassembly basin cobalt slugs and the 18 curium sampler slugs. The total Co-60 activity of all of the assayed slugs in this work summed to 31,783 curies on 9/15/03. From the Co-60 concentrations of the curium sampler slugs, the irradiation flux was determined for the known irradiation time. The amounts of Pu-238,-239,-240,-241,-242; Am-241,-243; and Cm-242,-244 produced were then obtained based on the original amount of Pu-239 irradiated

Effect of Gas- and Liquid-injection Methods on Formation of Bubble and Liquid Slug at Merging Micro T-junction

Energy Technology Data Exchange (ETDEWEB)

Lee, Jun Kyoung [Kyungnam Univ., Changwon (Korea, Republic of); Lee, Chi Young [Pukyong Nat’l Univ., Busan (Korea, Republic of)

2016-04-15

In the present experimental study, the effect of gas- and liquid-injected methods on the formation of bubble and liquid slug at the merging micro T-junction of a square microchannel with dimensions 600 μm × 600 μm was investigated. Nitrogen and water were used as test fluids. The superficial velocities of the liquid and gas were in the range of 0.05 - 1 m/s, and 0.1 - 1 m/s, respectively, where the Taylor flow was observed. The bubble length, liquid slug length, bubble velocity, and bubble generation frequency were measured by analyzing the images captured using a high-speed camera. Under similar inlet superficial velocity conditions, in the case of gas injection to the main channel at the merging T-junction (T{sub g}as-liquid), the lengths of the bubble and liquid slug were longer, and the bubble generation frequency was lower than in the case of liquid injection to the main channel at the merging T-junction (T{sub l}iquid-gas). On the other hand, in both cases, the bubble velocity was almost the same. The previous correlation proposed using experimental data for T{sub l}iquid-gas had predicted the present experimental data of bubble length, bubble velocity, liquid slug length, and bubble generation frequency for T{sub g}as-liquid to be ~24%, ~9%, ~39%, ~55%, respectively.

Flooding characteristics of gas-liquid two-phase flow in a horizontal U bend pipe

International Nuclear Information System (INIS)

Sakaguchi, T.; Hosokawa, S.; Fujii, Y.

1995-01-01

For next-generation nuclear reactors, hybrid safety systems which consist of active and passive safety systems have been planned. Steam generators with horizontal U bend pipelines will be used as one of the passive safety systems. It is required to clarify flow characteristics, especially the onset of flooding, in the horizontal U bend pipelines in order to examine their safety. Flooding in vertical pipes has been studied extensively. However, there is little study on flooding in the horizontal U bend pipelines. It is supposed that the onset of flooding in the horizontal U bend pipelines is different from that in vertical pipes. On the other hand, liquid is generated due to condensation of steam in pipes of the horizontal steam generators at the loss of coolant accident because the steam generators will be used as a condenser of a cooling system of steam from the reactor. It is necessary to simulate this situation by the supply of water at the middle of horizontal pipe. In the present paper, experiments were carried out using a horizontal U bend pipeline with a liquid supply section in the midway of pipeline. The onset of flooding in the horizontal U bend pipeline was measured. Effects of the length of horizontal pipe and the radius of U bend on the onset of flooding were discussed

Flooding characteristics of gas-liquid two-phase flow in a horizontal U bend pipe

Energy Technology Data Exchange (ETDEWEB)

Sakaguchi, T.; Hosokawa, S.; Fujii, Y. [Kobe Univ. (Japan)] [and others

1995-09-01

For next-generation nuclear reactors, hybrid safety systems which consist of active and passive safety systems have been planned. Steam generators with horizontal U bend pipelines will be used as one of the passive safety systems. It is required to clarify flow characteristics, especially the onset of flooding, in the horizontal U bend pipelines in order to examine their safety. Flooding in vertical pipes has been studied extensively. However, there is little study on flooding in the horizontal U bend pipelines. It is supposed that the onset of flooding in the horizontal U bend pipelines is different from that in vertical pipes. On the other hand, liquid is generated due to condensation of steam in pipes of the horizontal steam generators at the loss of coolant accident because the steam generators will be used as a condenser of a cooling system of steam from the reactor. It is necessary to simulate this situation by the supply of water at the middle of horizontal pipe. In the present paper, experiments were carried out using a horizontal U bend pipeline with a liquid supply section in the midway of pipeline. The onset of flooding in the horizontal U bend pipeline was measured. Effects of the length of horizontal pipe and the radius of U bend on the onset of flooding were discussed.

An evaluation of slug interference tests for aquifer characterization at the Hanford Site

International Nuclear Information System (INIS)

Spane, F.A. Jr.; Thorne, P.D.

1992-01-01

Slug interference tests are conducted by instantaneously changing the water level in a well and monitoring the aquifer response at one or more observation wells. The applicability of this method for hydraulic characterization of a high permeability unconfined aquifer at the Hanford Site was evaluated. Analytical techniques were used to predict slug interference responses over a range of aquifer hydraulic conditions and observation well distances. This was followed by a field test of the proposed technique. The results showed that slug interference testing can be used to characterize aquifers having transmissivities up to 10 -1 m 2 /s compared to a maximum transmissivity of about 10 -3 m 2 /s for single-well slug tests. The amplitude of the pressure response measured at the observation well is primarily determined by aquifer storativity, while the time-lag of the pressure peak is mainly controlled by the transmissivity. Several recommendations are made optimizing the results of slug interference tests in higher permeability, unconfined to semiconfined aquifers

Experimental on two sensors combination used in horizontal pipe gas-water two-phase flow

International Nuclear Information System (INIS)

Wu, Hao; Dong, Feng

2014-01-01

Gas-water two phase flow phenomenon widely exists in production and living and the measurement of it is meaningful. A new type of long-waist cone flow sensor has been designed to measure two-phase mass flow rate. Six rings structure of conductance probe is used to measure volume fraction and axial velocity. The calibration of them have been made. Two sensors have been combined in horizontal pipeline experiment to measure two-phase flow mass flow rate. Several model of gas-water two-phase flow has been discussed. The calculation errors of total mass flow rate measurement is less than 5% based on the revised homogeneous flow model

Unsteady flow of an incompressible fluid in a horizontal porous medium with suction

International Nuclear Information System (INIS)

Bestman, A.R.

1988-04-01

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

Suggestion of an average bidirectional flow tube for the measurement of single and two phase flow rate

International Nuclear Information System (INIS)

Yun, B.J.; Kang, K.H.; Euh, D.J.; Song, C.H.; Baek, W.P.

2005-01-01

Full text of publication follows: A new type instrumentation, average bidirectional flow tube, was suggested to apply to the single and two phase flow condition. Its working principle is similar to that of the Pitot tube. The pressure measured at the front of the flow tube is equal to the total pressure, while that measured at the rear tube is slightly less than static pressure of flow field due to the suction effect at the downstream. It gives an amplification effect of measured pressure difference at the flow tube. The proposed instrumentation has the characteristics that it could be applicable to low flow condition and measure bidirectional flow. It was tested in the air-water vertical and horizontal test sections which have 0.08 m inner diameter. The pressure difference across the average bidirectional flow tube, system pressure, average void fraction and injection phasic mass flow rates were measured on the measuring plane. Test was performed primarily in the single phase water and air flow condition to get the amplification factor k of the flow tube. The test was also performed in the air-water two phase flow condition and the covered flow regimes were bubbly, slug, churn turbulent flow in the vertical pipe and stratified flow in the horizontal pipe. In order to calculate the phasic and total mass flow rates from the measured differential pressure, Chexal drift-flux correlation and momentum exchange factor between the two phases were introduced. The test result shows that the suggested instrumentation with the measured void fraction, Chexal drift-flux correlation and Bosio and Malnes' momentum exchange model can predict the phasic mass flow rates within 15% error compared to the true values. A new momentum exchange model was also suggested and it gives up to 5% improvement of the measured mass flow rate compared to combination of Bosio and Malnes' momentum exchange model. (authors)

Post-Dryout Heat Transfer to a Refrigerant Flowing in Horizontal Evaporator Tubes

Science.gov (United States)

Mori, Hideo; Yoshida, Suguru; Kakimoto, Yasushi; Ohishi, Katsumi; Fukuda, Kenichi

Studies of the post-dryout heat transfer were made based on the experimental data for HFC-134a flowing in horizontal smooth and spiral1y grooved (micro-fin) tubes and the characteristics of the post-dryout heat transfer were c1arified. The heat transfer coefficient at medium and high mass flow rates in the smooth tube was lower than the single-phase heat transfer coefficient of the superheated vapor flow, of which mass flow rate was given on the assumption that the flow was in a thermodynamic equilibrium. A prediction method of post-dryout heat transfer coefficient was developed to reproduce the measurement satisfactorily for the smooth tube. The post dryout heat transfer in the micro-fin tube can be regarded approximately as a superheated vapor single-phase heat transfer.

Vibration response of a pipe subjected to two-phase flow: Analytical formulations and experiments

Energy Technology Data Exchange (ETDEWEB)

Ortiz-Vidal, L. Enrique, E-mail: leortiz@sc.usp.br [Department of Mechanical Engineering, Sao Carlos School of Engineering, University of Sao Paulo (USP), Av., Trabalhador São-carlense, 400, 13566-970 São Carlos, SP (Brazil); Mureithi, Njuki W., E-mail: njuki.mureithi@polymtl.ca [Department of Mechanical Engineering, Polytechnique Montreal, Département de Géniemécanique 2900, H3T 1J7 Montreal, QC (Canada); Rodriguez, Oscar M.H., E-mail: oscarmhr@sc.usp.br [Department of Mechanical Engineering, Sao Carlos School of Engineering, University of Sao Paulo (USP), Av., Trabalhador São-carlense, 400, 13566-970 São Carlos, SP (Brazil)

2017-03-15

Highlights: • Analytical formulations for two-phase flow-induced vibration (2-FIV) are presented. • Standard deviation of acceleration pipe response is a function of the square of shear velocity. • Peak frequency is correlated to hydrodynamic mass and consequently to void fraction. • Dynamic pipe response increases with increasing mixture velocity and void fraction. • Hydrodynamic mass in 2-FIV in horizontal pipe is proportional to mixture density. - Abstract: This paper treats the two-phase flow-induced vibration in pipes. A broad range of two-phase flow conditions, including bubbly, dispersed and slug flow, were tested in a clamped-clamped straight horizontal pipe. The vibration response of both transversal directions for two span lengths was measured. From experimental results, an in-depth discussion on the nature of the flow excitation and flow-parameters influence is presented. The hydrodynamic mass parameter is also studied. Experimental results suggest that it is proportional to mixture density. On the other hand, two analytical formulations were developed and tested against experimental results. One formulation predicts the quadratic trend between standard deviation of acceleration and shear velocity found in experiments. The other formulation indicates that the peak-frequency of vibration response depends strongly on void fraction. It provides accurate predictions of peak-frequency, predicting 97.6% of the data within ±10% error bands.

Regional Quasi-Three-Dimensional Unsaturated-Saturated Water Flow Model Based on a Vertical-Horizontal Splitting Concept

Directory of Open Access Journals (Sweden)

Yan Zhu

2016-05-01

Full Text Available Due to the high nonlinearity of the three-dimensional (3-D unsaturated-saturated water flow equation, using a fully 3-D numerical model is computationally expensive for large scale applications. A new unsaturated-saturated water flow model is developed in this paper based on the vertical/horizontal splitting (VHS concept to split the 3-D unsaturated-saturated Richards’ equation into a two-dimensional (2-D horizontal equation and a one-dimensional (1-D vertical equation. The horizontal plane of average head gradient in the triangular prism element is derived to split the 3-D equation into the 2-D equation. The lateral flow in the horizontal plane of average head gradient represented by the 2-D equation is then calculated by the water balance method. The 1-D vertical equation is discretized by the finite difference method. The two equations are solved simultaneously by coupling them into a unified nonlinear system with a single matrix. Three synthetic cases are used to evaluate the developed model code by comparing the modeling results with those of Hydrus1D, SWMS2D and FEFLOW. We further apply the model to regional-scale modeling to simulate groundwater table fluctuations for assessing the model applicability in complex conditions. The proposed modeling method is found to be accurate with respect to measurements.

A method for the estimation of dual transmissivities from slug tests

Science.gov (United States)

Wolny, Filip; Marciniak, Marek; Kaczmarek, Mariusz

2018-03-01

Aquifer homogeneity is usually assumed when interpreting the results of pumping and slug tests, although aquifers are essentially heterogeneous. The aim of this study is to present a method of determining the transmissivities of dual-permeability water-bearing formations based on slug tests such as the pressure-induced permeability test. A bi-exponential rate-of-rise curve is typically observed during many of these tests conducted in heterogeneous formations. The work involved analyzing curves deviating from the exponential rise recorded at the Belchatow Lignite Mine in central Poland, where a significant number of permeability tests have been conducted. In most cases, bi-exponential movement was observed in piezometers with a screen installed in layered sediments, each with a different hydraulic conductivity, or in fissured rock. The possibility to identify the flow properties of these geological formations was analyzed. For each piezometer installed in such formations, a set of two transmissivity values was calculated piecewise based on the interpretation algorithm of the pressure-induced permeability test—one value for the first (steeper) part of the obtained rate-of-rise curve, and a second value for the latter part of the curve. The results of transmissivity estimation for each piezometer are shown. The discussion presents the limitations of the interpretational method and suggests future modeling plans.

Two-phase flow in short horizontal rectangular microchannels with a height of 300 μm

Science.gov (United States)

Chinnov, E. A.; Ron'shin, F. V.; Kabov, O. A.

2015-09-01

The two-phase flow in a narrow short horizontal channel with a rectangular cross section is studied experimentally. The channel has a width of 10, 20, or 30 mm and a height of 300 μm. The specifics of formation of such two-phase flows are investigated. It is demonstrated that the regions of bubble and churn flow regimes grow and constrain the region of jet flow as the channel gets wider. The boundaries of the regions of annular and stratified flow regimes remain almost unaltered.

OIL SLUGS FOR PRODUCTION OF PISTON RING

Directory of Open Access Journals (Sweden)

V. F. Bevza

2008-01-01

Full Text Available The developed technological process of continuously cyclic casting by frosting allows to receive high-quality hollow cylindrical slugs of cast iron for production of critical parts. 

Experimental Study of Flow Boiling Heat Transfer in a Horizontal Microfin Tube

OpenAIRE

Yu, Jian; Koyama, Shigeru; Momoki, Satoru

1995-01-01

An experimental study on flow boiling heat transfer in a horizontal microfin tube is conducted with pure refrigerants HFC134a, HCFC123 and HCFC22 using a water-heated double-tube type test section. The test microfin tube is a copper tube having the following dimensions: 8.37mm mean inside diameter, 0.168mm fin height, 60fin number and 18 degree of helix angle. The local heat transfer coefficients for both counter and parallel flows are measured in a range of heat flux of 1 to 93W/m^2, mass ve...

Development of a mesh-type computer tomography for the two-phase flow

International Nuclear Information System (INIS)

Lee, Jae Young; Lee, In Wook

1998-01-01

This paper is to describe the development of a mesh-type computer tomography for the two-phase flow. The sensor is made of many parallel wires in the orthogonal orientation. A demultiplexer circuits is developed for electrodes to supply driving voltage and for data acquisition system to get the output voltage form the electrode unit. For the reconstruction of image a direct inversion algorithm is adopted. Full automation is provided from the data sensing to the image construction. Through the careful calibariation and field tests in the horizontal and vertical two-phase loop, the present sensor detect images for the solitary wave and the slug realistically. This sensor could be a useful tool in the laboratory experiments

Cell-State Transitions Regulated by SLUG Are Critical for Tissue Regeneration and Tumor Initiation

Directory of Open Access Journals (Sweden)

Sarah Phillips

2014-05-01

Full Text Available Perturbations in stem cell activity and differentiation can lead to developmental defects and cancer. We use an approach involving a quantitative model of cell-state transitions in vitro to gain insights into how SLUG/SNAI2, a key developmental transcription factor, modulates mammary epithelial stem cell activity and differentiation in vivo. In the absence of SLUG, stem cells fail to transition into basal progenitor cells, while existing basal progenitor cells undergo luminal differentiation; together, these changes result in abnormal mammary architecture and defects in tissue function. Furthermore, we show that in the absence of SLUG, mammary stem cell activity necessary for tissue regeneration and cancer initiation is lost. Mechanistically, SLUG regulates differentiation and cellular plasticity by recruiting the chromatin modifier lysine-specific demethylase 1 (LSD1 to promoters of lineage-specific genes to repress transcription. Together, these results demonstrate that SLUG plays a dual role in repressing luminal epithelial differentiation while unlocking stem cell transitions necessary for tumorigenesis.

Development of two-phase Flow Model, 'SOBOIL', for Sodium

Energy Technology Data Exchange (ETDEWEB)

Hahn, Do Hee; Chang, Won Pyo; Kim, In Chul; Kwon, Young Min; Lee, Yong Bum

2000-03-01

The objective of this research is to develop a sodium two-phase flow analysis model, 'SOBOIL', for the assessment of the initial stage of the KALIMER HCDA (Hypotherical Core Disruptive Accident). The 'SOBOIL' is basically similar to the multi-bubble slug ejection model used in SAS2A[1]. When a bubble is formed within the liquid slug, the bubble fills the whole cross section of the coolant channel except for a film left on the cladding or on the structure. Up to nine bubbles, separated by the liquid slugs, are allowed in the channel at any time. Each liquid slug flow rate in the model is performed in 2 steps. In the first step, the preliminary flow rate in the liquid slug is calculated neglecting the effect of changes in the vapor bubble pressures over the time step. The temperature and pressure distributions, and interface velocity at the interface between the liquid slug and vapor bubble are also calculated during this process. The new vapor temperature and pressure are then determined from the balance between the net energy transferred into the vapor and the change of the vapor energy. The liquid flow is finally calculated considering the change of the vapor pressure over a time step and the calculation is repeated until specified elapsed time is met. Continuous effort, therefore, must be made on the examination and improvement for the model to become reliable. To this end, much interest must be concentrated in the relevant international collaborations for access to a reference model or test data for the verification.

Resolution of thermal striping issue downstream of a horizontal pipe elbow in stratified pipe flow

International Nuclear Information System (INIS)

Kuzay, T.M.; Kasza, K.E.

1985-01-01

A thermally stratified pipe flow produced by a thermal transient when passing through a horizontal elbow as a result of secondary flow gives rise to large thermal fluctuations on the inner curvature wall of the downstream piping. These fluctuations were measured in a specially instrumented horizontal pipe and elbow system on a test set-up using water in the Mixing Components Technology Facility (MCTF) at Argonne National Laboratory (ANL). This study is part of a larger program which is studying the influence of thermal buoyancy on general reactor component performance. This paper discusses the influence of pipe flow generated thermal oscillations on the thermal stresses induced in the pipe walls. The instrumentation was concentrated around the exit plane of the 90 0 sweep elbow, since prior tests had indicated that the largest thermal fluctuations would occur within about one hydraulic diameter downstream of the elbow exit. The thermocouples were located along the inner curvature of the piping and measured the near surface fluid temperature. The test matrix involved thermal downramps under turbulent flow conditions

Effect of surface wettability on flow patterns in vertical gas-liquid two-phase flow

International Nuclear Information System (INIS)

Nakamura, D.

2005-01-01

To examine the effect of the surface characteristics on the flow regime in two-phase flow, visualization study was performed using three test pipes, namely a no-coating pipe, a water-attracting coating pipe, a water-shedding coating pipe. Three flow regime maps were obtained based on the visual observation in the three pipes. In the water-attracting coating pipe, the slug flow-to-churn flow transition boundary was shifted to higher gas velocity at a given liquid velocity, whereas the churn flow-to-annular flow transition boundary was shifted to lower gas velocity at a given liquid velocity. In the water shedding coating pipe, the inverted-churn flow regime was observed in the region where the churn flow regime was to be observed in a no-coating pipe, whereas the droplet flow regime was observed in the region where the annular flow regime was to be observed in a no-coating pipe. The criteria for the slug flow-to-inverted-churn flow transition and the inverted-churn flow-to-droplet flow transition were modeled by force balance approaches. The modeled transition criteria could predict the observed flow transition boundaries reasonably well. (authors)

Investigation of straitified and countercurrent flows in horizontal piping during a loss-of-coolant accident

International Nuclear Information System (INIS)

Bourteele, J.P.

1980-06-01

The ECTHOR program consists in a loop having as objective to study the flow regimes in horizontal pipings (stratification, countercurrent flows) in conditions representative of small break transients within commercial PWR. The ECTHOR tests are in process. Experimental results are already available and are presented in this paper: scaling problem, U tube experiments, hot leg experiments, high pressure tests

Pattern transitions of oil-water two-phase flow with low water content in rectangular horizontal pipes probed by terahertz spectrum.

Science.gov (United States)

Feng, Xin; Wu, Shi-Xiang; Zhao, Kun; Wang, Wei; Zhan, Hong-Lei; Jiang, Chen; Xiao, Li-Zhi; Chen, Shao-Hua

2015-11-30

The flow-pattern transition has been a challenging problem in two-phase flow system. We propose the terahertz time-domain spectroscopy (THz-TDS) to investigate the behavior underlying oil-water flow in rectangular horizontal pipes. The low water content (0.03-2.3%) in oil-water flow can be measured accurately and reliably from the relationship between THz peak amplitude and water volume fraction. In addition, we obtain the flow pattern transition boundaries in terms of flow rates. The critical flow rate Qc of the flow pattern transitions decreases from 0.32 m3 h to 0.18 m3 h when the corresponding water content increases from 0.03% to 2.3%. These properties render THz-TDS particularly powerful technology for investigating a horizontal oil-water two-phase flow system.

An analytic solution to the time-dependent first-daughter fission-product plateout problem for multi-region isothermal slug flow

International Nuclear Information System (INIS)

Durkee, J.W. Jr.; Lee, C.E.

1985-01-01

The time-dependent, axisymmetric, isothermal slug flow convective-diffusion equation with radioactive decay is solved analytically to predict the behavior of a first-daughter fission-product undergoing gaseous transport through multiple materials in a cylindrical pipe. The integration coefficients are determined using the Davidon variable metric minimization method. The behavior of fission-product material deposited on the conduit wall is described by a standard mass-transfer model. The time-dependent plateout rate behavior, determined previously for parent fission-product deposition, is again evident for daughter product plateout. Dominance of the daughter plateout by parent deposition characteristics is apparent. The determination of the daughter wall mass-transfer and diffusion coefficient using a least-squares analysis of measured data depends upon a reasonably low ratio of parent/daughter half-lives. This is illustrated with 137 Cs/ 137 Ba(=2x10 5 ) and 140 Ba/ 140 La(=7.6), where for 137 Cs/ 137 Ba the solution sensitivity to the 137 Ba deposition parameters is small and for 140 Ba/ 140 La a reasonable solution is readily obtained. (author)

Features of two-phase flow patterns in horizontal rectangular microchannels of height 50 μm

Directory of Open Access Journals (Sweden)

Ron’shin Fedor

2016-01-01

Full Text Available The horizontal microchannel with the height of 50 micrometres and width of 40 mm of a rectangular cross-section has been used to study two-phase flow. The classical patterns of two-phase flow in the channel (bubble, stratified, churn, jet, and annular have been detected. Experimental information allows us to define the characteristics of the regimes and to determine precisely the boundaries between the patterns of the two-phase flows.

On the coupled unsaturated–saturated flow process induced by vertical, horizontal, and slant wells in unconfined aquifers

Directory of Open Access Journals (Sweden)

X. Liang

2017-03-01

established with special consideration of the coupled unsaturated–saturated flow process and the well orientation. Groundwater flow in the saturated zone is described by a three-dimensional governing equation and a linearized three-dimensional Richards' equation in the unsaturated zone. A solution in the Laplace domain is derived by the Laplace–finite-Fourier-transform and the method of separation of variables, and the semi-analytical solutions are obtained using a numerical inverse Laplace method. The solution is verified by a finite-element numerical model. It is found that the effects of the unsaturated zone on the drawdown of a pumping test exist at any angle of inclination of the pumping well, and this impact is more significant in the case of a horizontal well. The effects of the unsaturated zone on the drawdown are independent of the length of the horizontal well screen. The vertical well leads to the largest water volume drained from the unsaturated zone (W during the early pumping time, and the effects of the well orientation on W values become insignificant at the later time. The screen length of the horizontal well does not affect W for the whole pumping period. The proposed solutions are useful for the parameter identification of pumping tests with a general well orientation (vertical, horizontal, and slant in unconfined aquifers affected from above by the unsaturated flow process.

Local Nusselt number enhancement during gas-liquid Taylor bubble flow in a square mini-channel: An experimental study

International Nuclear Information System (INIS)

Majumder, Abhik; Mehta, Balkrishna; Khandekar, Sameer

2013-01-01

Taylor bubble flow takes place when two immiscible fluids (liquid-liquid or gas-liquid) flow inside a tube of capillary dimensions within specific range of volume flow ratios. In the slug flows where gas and liquid are two different phases, liquid slugs are separated by elongated Taylor bubbles. This singular flow pattern is observed in many engineering mini-/micro-scale devices like pulsating heat pipes, gas-liquid-solid monolithic reactors, micro-two-phase heat exchangers, digital micro-fluidics, micro-scale mass transfer process, fuel cells, etc. The unique and complex flow characteristics require understanding on local, as well as global, spatio-temporal scales. In the present work, the axial stream-wise profile of the fluid and wall temperature for air-water (i) isolated single Taylor bubble and, (ii) a train of Taylor bubbles, in a horizontal square channel of size 3.3 mm x 3.3 mm x 350 mm, heated from the bottom (heated length = 175 mm), with the other three sides kept insulated, are reported at different gas volume flow ratios. The primary aim is to study the enhancement of heat transfer due to the Taylor bubble train flow, in comparison with thermally developing single-phase flows. Intrusion of a bubble in the liquid flow drastically changes the local temperature profiles. The axial distribution of time-averaged local Nusselt number (Nu z ) shows that Taylor bubble train regime increases the transport of heat up to 1.2-1.6 times more as compared with laminar single-phase liquid flow. In addition, for a given liquid flow Reynolds number, the heat transfer enhancement is a function of the geometrical parameters of the unit cell, i.e., the length of adjacent gas bubble and water plug. (authors)

Application of two-phase flow for cooling of hybrid microchannel PV cells: A comparative study

International Nuclear Information System (INIS)

Valeh-e-Sheyda, Peyvand; Rahimi, Masoud; Karimi, Ebrahim; Asadi, Masomeh

2013-01-01

Highlights: ► Showing cooling potential of gas–liquid two-phase flow in microchannels for PV cell. ► Introducing the concept of using slug flow in microchannels for cooling of PV cells. ► In single-phase flow, increasing the liquid flow rate enhances the PV power. ► Showing that in two-phase flow the output power related the fluid flow regime. ► By coupling PV and microchannel an increase up to 38% in output power was observed. - Abstract: This paper reports the experimental data from performance of two-phase flows in a small hybrid microchannel solar cell. Using air and water as two-phase fluid, the experiments were conducted at indoor condition in an array of rectangular microchannels with a hydraulic diameter of 0.667 mm. The gas superficial velocity ranges were between 0 and 3.27 m s −1 while liquid flow rate was 0.04 m s −1 . The performance analysis of the PV cell at slug and transitional slug/annular flow regimes are the focus of this study. The influence of two-phase working fluid on PV cell cooling was compared with single-phase. In addition, the great potential of slug flow for heat removal enhancement in PV/T panel was investigated. The obtained data showed the proposed hybrid system could substantially increases the output power of PV solar cells

Interfacial shear stress in stratified flow in a horizontal rectangular duct

International Nuclear Information System (INIS)

Lorencez, C.; Kawaji, M.; Murao, Y.

1995-01-01

Interfacial shear stress has been experimentally examined for both cocurrent and countercurrent stratified wavy flows in a horizontal interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress values at high gas flow rates which could be attributed to the assumptions and procedures involved in each method. The interfacial waves and secondary motions were also found to have significant effects on the accuracy of Reynolds stress and turbulence kinetic energy extrapolation methods

Interfacial shear stress in stratified flow in a horizontal rectangular duct

Energy Technology Data Exchange (ETDEWEB)

Lorencez, C.; Kawaji, M. [Univ. of Toronto (Canada); Murao, Y. [Tokushima Univ. (Japan)] [and others

1995-09-01

Interfacial shear stress has been experimentally examined for both cocurrent and countercurrent stratified wavy flows in a horizontal interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress values at high gas flow rates which could be attributed to the assumptions and procedures involved in each method. The interfacial waves and secondary motions were also found to have significant effects on the accuracy of Reynolds stress and turbulence kinetic energy extrapolation methods.

Understanding the formation process of the liquid slug in a hilly-terrain wet natural gas pipeline

DEFF Research Database (Denmark)

Yang, Yan; Li, Jingbo; Wang, Shuli

2017-01-01

condition on the liquid slug formation is discussed including pipe diameter, inclination angle, gas superficial velocity and liquid holdup. The results show that the pipe is blocked by the liquid slug at the moment of slug formed. The pipe pressure suddenly increases, and then decreases gradually...... in the process of liquid slug formation and motion. The pipe pressure drop and liquid holdup decrease along with the increasing inclination angle of ascending pipe. On the contrary, they rise with the increase of the inclination angle of descending pipe. Higher gas superficial velocity and liquid holdup result...

Flow structure from a horizontal cylinder coincident with a free surface in shallow water flow

Directory of Open Access Journals (Sweden)

Kahraman Ali

2012-01-01

Full Text Available Vortex formation from a horizontal cylinder coincident with a free surface of a shallow water flow having a depth of 25.4 [mm] was experimentally investigated using the PIV technique. Instantaneous and time-averaged flow patterns in the wake region of the cylinder were examined for three different cylinder diameter values under the fully developed turbulent boundary layer condition. Reynolds numbers were in the range of 1124£ Re£ 3374 and Froude numbers were in the range of 0.41 £ Fr £ 0.71 based on the cylinder diameter. It was found that a jet-like flow giving rise to increasing the flow entrainment between the core and wake regions depending on the cylinder diameter was formed between the lower surface of the cylinder and bottom surface of the channel. Vorticity intensity, Reynolds stress correlations and the primary recirculating bubble lengths were grown to higher values with increasing the cylinder diameter. On the other hand, in the case of the lowest level of the jet-like flow emanating from the beneath of the smallest cylinder, the variation of flow characteristics were attenuated significantly in a shorter distance. The variation of the reattachment location of the separated flow to the free-surface is a strong function of the cylinder diameter and the Froude number.

Critical investigations and model development on countercurrent flow of gas and liquid in horizontal and vertical channels

International Nuclear Information System (INIS)

Mewes, D.; Beckmann, H.

1989-01-01

Countercurrent flow of steam and water occurs in the horizontal and vertical lines of a PWR in case of a LOCA. In order to predict the emergency core cooling behaviour in case of a large or small break LOCA it is important to calculate the volumetric flow rate of water which will get to the reactor core. Theoretical and experimental results of countercurrent flow in horizontal and vertical channels given by publication and reports are critically reviewed for the purpose of a more physical understanding of the flow phenomena. The influence of geometry, pressure and other boundary conditions are emphasized. The existing models which are developed to calculate the onset of flooding are based on experimental results of small test facilities. The applicability of these models to large geometries and high pressures as well as the consideration of condensation and entrainment are investigated. (orig./HP) [de

Prediction of turbulent mixing rates of both gas and liquid phases between adjacent subchannels in a two-phase slug-churn flow

International Nuclear Information System (INIS)

Kawahara, A.; Sadatomi, M.; Tomino, T.; Sato, Y.

1998-01-01

This paper presents a slug-churn flow model for predicting turbulent mixing rates of both gas and liquid phase between adjacent subchannels in a BWR fuel rod bundle. In the model, the mixing rate of the liquid phase is calculated as the sum of the three components, i.e., turbulent diffusion, convective transfer and pressure difference fluctuations between the subchannels. The compenents of turbulent diffusion and convective transfer are calculated from Sadatomi et al.'s (1996) method, applicable to single-phase turbulent mixing by considering the effect of the increment of liquid velocity due to the presence of gas phase. The component of the pressure difference fluctuations is evaluated from a newly developed correlations. The mixing rate of the gas phase, on the other side, is calculated from a simple relation of mixing rate between gas and liquid phases. The validity of the proposed model has been confirmed with the turbulent mixing rates data of Rudzinski et al. as well as the present authors

Thevetia peruviana (Family: Apocynaceae in the control of slug and snail pests

Directory of Open Access Journals (Sweden)

A. Panigrahi

1994-06-01

Full Text Available An aqueous extract prepared from Kernels of the fruit of Thevetia peruviana (Pers. Schumann (Family : Apocynaceae was found under experimental conditions, to be toxic ti the slug Laevicaulis alte (Férussac and the snail Achatina fulica Bowdich, the important agrihorticultural pests of Indo-Pacific countries. Concentrations as low as 1% (w/v killed all the slugs exposed in less than 981.00 (± SD 22.76 min, and 2% of the extract killed 100% of the slugs L. alte and 50%, 50% and 30% of the snail A. fulica in between 92.34 (± SD 6.63 - 321.33 (± SD 4.14 and 271.20 (± SD 17.54 - 298.26 (± SD 16.69 min respectively. The most effective concentration of the extract was 20%; it killed 100% of exposed slugs and snails within a short time (40-50 and 90-1440 min respectively when the extract was exposed on the soil in experimental trays or when it was applied to potato slices offered as food to the gastropods.

Reconstruction of a constructed wetland with horizontal subsurface flow after 18 years of operation.

Science.gov (United States)

Hudcová, Tereza; Vymazal, Jan; Dunajský, Michal Kriška

2013-01-01

The constructed wetland (CW) for 326 PE with horizontal subsurface flow at Kotenčice, Central Bohemia, Czech Republic, was built in 1994. Despite the relatively high efficiency of the CW, the filtration beds suffered from clogging, and therefore it was decided in 2011 to rebuild the whole system. The new treatment system was built as an experimental system consisting of four different combinations of horizontal and vertical beds. The major aim of the design was to determine the best hybrid combination which then could be used in the future for refurbishment of older horizontal flow CWs or for the new systems. The mechanical pretreatment consists of mechanical bar screens, a new Imhoff tank, and the original settling tank which has been converted into the accumulation tank from where the wastewater is pumped into the wetlands. The filters are planted with Phragmites australis, Phalaris arundinacea, Iris pseudacorus, Iris sibirica, Glyceria maxima and Lythrum salicaria in order to evaluate and compare various plant species' effect on the treatment process. The new technology includes a tertiary treatment which consists of a greenhouse with a photo-reactor for the cultivation of algae and hydroponic systems (residual nutrients removal), sludge reed-beds and a composting field.

An analytical study on groundwater flow in drainage basins with horizontal wells

Science.gov (United States)

Wang, Jun-Zhi; Jiang, Xiao-Wei; Wan, Li; Wang, Xu-Sheng; Li, Hailong

2014-06-01

Analytical studies on release/capture zones are often limited to a uniform background groundwater flow. In fact, for basin-scale problems, the undulating water table would lead to the development of hierarchically nested flow systems, which are more complex than a uniform flow. Under the premise that the water table is a replica of undulating topography and hardly influenced by wells, an analytical solution of hydraulic head is derived for a two-dimensional cross section of a drainage basin with horizontal injection/pumping wells. Based on the analytical solution, distributions of hydraulic head, stagnation points and flow systems (including release/capture zones) are explored. The superposition of injection/pumping wells onto the background flow field leads to the development of new internal stagnation points and new flow systems (including release/capture zones). Generally speaking, the existence of n injection/pumping wells would result in up to n new internal stagnation points and up to 2n new flow systems (including release/capture zones). The analytical study presented, which integrates traditional well hydraulics with the theory of regional groundwater flow, is useful in understanding basin-scale groundwater flow influenced by human activities.

miR-34 increases in vitro PANC-1 cell sensitivity to gemcitabine via targeting Slug/PUMA.

Science.gov (United States)

Zhang, Qing-An; Yang, Xu-Hai; Chen, Dong; Yan, Xiang; Jing, Fu-Chun; Liu, Hong-Qian; Zhang, Ronghua

2018-01-01

miR-34 was deregulated in tumor tissues compared with corresponding noncancerous tissue samples. Furthermore, miR-34 may contribute to cancer-stromal interaction associated with cancer progression. However, whether miR-34 could decrease chemoresistance of cancer cells to chemotherapeutic agent remains unclear. In our study, we examined whether overexpression of miR-34 could sensitize gemcitabine -mediated apoptosis in human pancreatic cancer PANC-1 cells. We found that miR-34 markedly induced gemcitabine -mediated apoptosis in PANC-1 cells. miR-34 induced down-regulation of Slug expression and upregulation of p53 up-regulated modulator of apoptosis (PUMA) expression. The over-expression of Slug or downregulation of PUMA by Slug cDNA or PUMA siRNA transfection markedly blocked miR-34-induced gemcitabine sensitization. Furthermore, miR-34 induced PUMA expression by downregulation of Slug. Taken together, our study demonstrates that miR-34 enhances sensitization against gemcitabine-mediated apoptosis through the down-regulation of Slug expression, and up-regulation of Slug-dependent PUMA expression.

Characterization of interfacial waves in horizontal core-annular flow

Science.gov (United States)

Tripathi, Sumit; Bhattacharya, Amitabh; Singh, Ramesh; Tabor, Rico F.

2016-11-01

In this work, we characterize interfacial waves in horizontal core annular flow (CAF) of fuel-oil and water. Experimental studies on CAF were performed in an acrylic pipe of 15.5mm internal diameter, and the time evolution of the oil-water interface shape was recorded with a high speed camera for a range of different flow-rates of oil (Qo) and water (Qw). The power spectrum of the interface shape shows a range of notable features. First, there is negligible energy in wavenumbers larger than 2 π / a , where a is the thickness of the annulus. Second, for high Qo /Qw , there is no single dominant wavelength, as the flow in the confined annulus does not allow formation of a preferred mode. Third, for lower Qo /Qw , a dominant mode arises at a wavenumber of 2 π / a . We also observe that the power spectrum of the interface shape depends weakly on Qw, and strongly on Qo, perhaps because the net shear rate in the annulus appears to depend weakly on Qw as well. We also attempt to build a general empirical model for CAF by relating the interfacial stress (calculated via the mean pressure gradient) to the flow rate in the annulus, the annular thickness and the core velocity. Authors are thankful to Orica Mining Services (Australia) for the financial support.

A state of the art on the flooding phenomena and countercurrent flow limiting modeling

Energy Technology Data Exchange (ETDEWEB)

Jeong, Young Jong; Chang, Won Pyo [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1996-07-01

Countercurrent flow limiting phenomenon and its modeling for vertical and nearly horizontal pipes has been reviewed in two phase flow. A number of analytical and empirical model have been developed for flooding in the vertical pipes and annulars. These may be classified as stability theory, envelope theory, static equilibrium theory, slug formation theory, Wallis correlation, and Kutateladze correlation. The theories and empirical correlations are reviewed and comparison with the various experimental data. The scatter of the experimental data is large because of the different flooding condition and because of the influence of the experimental conditions. Application of flooding for PWR best estimate system codes is reviewed. The codes provide the user options to implement CCFL correlation for the specific geometry. The codes can accommodate generally Wallis, Kutateladze, or Bankoff correlation. 4 tabs., 36 figs., 52 refs. (Author).

A state of the art on the flooding phenomena and countercurrent flow limiting modeling

International Nuclear Information System (INIS)

Jeong, Young Jong; Chang, Won Pyo

1996-07-01

Countercurrent flow limiting phenomenon and its modeling for vertical and nearly horizontal pipes has been reviewed in two phase flow. A number of analytical and empirical model have been developed for flooding in the vertical pipes and annulars. These may be classified as stability theory, envelope theory, static equilibrium theory, slug formation theory, Wallis correlation, and Kutateladze correlation. The theories and empirical correlations are reviewed and comparison with the various experimental data. The scatter of the experimental data is large because of the different flooding condition and because of the influence of the experimental conditions. Application of flooding for PWR best estimate system codes is reviewed. The codes provide the user options to implement CCFL correlation for the specific geometry. The codes can accommodate generally Wallis, Kutateladze, or Bankoff correlation. 4 tabs., 36 figs., 52 refs. (Author)

Internal Representation and Memory Formation of Odor Preference Based on Oscillatory Activities in a Terrestrial Slug

Science.gov (United States)

Sekiguchi, Tatsuhiko; Furudate, Hiroyuki; Kimura, Tetsuya

2010-01-01

The terrestrial slug "Limax" exhibits a highly developed ability to learn odors with a small nervous system. When a fluorescent dye, Lucifer Yellow (LY), is injected into the slug's body cavity after odor-taste associative conditioning, a group of neurons in the procerebral (PC) lobe, an olfactory center of the slug, is labeled by LY. We examined…

The current status of theoretically based approaches to the prediction of the critical heat flux in flow boiling

International Nuclear Information System (INIS)

Weisman, J.

1991-01-01

This paper reports on the phenomena governing the critical heat flux in flow boiling. Inducts which vary with the flow pattern. Separate models are needed for dryout in annular flow, wall overheating in plug or slug flow and formation of a vapor blanket in dispersed flow. The major theories and their current status are described for the annular and dispersed regions. The need for development of the theoretical approach in the plug and slug flow region is indicated

Numerical Investigation of Ice Slurry Flow in a Horizontal Pipe

Science.gov (United States)

Rawat, K. S.; Pratihar, A. K.

2018-02-01

In the last decade, phase changing material slurry (PCMS) gained much attention as a cooling medium due to its high energy storage capacity and transportability. However the flow of PCM slurry is a complex phenomenon as it affected by various parameters, i.e. fluid properties, velocity, particle size and concentration etc.. In the present work ice is used as a PCM and numerical investigation of heterogeneous slurry flow has been carried out using Eulerian KTGF model in a horizontal pipe. Firstly the present model is validated with existing experiment results available in the literature, and then model is applied to the present problem. Results show that, flow is almost homogeneous for ethanol based ice slurry with particle diameter of 0.1 mm at the velocity of 1 m/s. It is also found that ice particle distribution is more uniform at higher velocity, concentration of ice and ethanol in slurry. Results also show that ice concentration increases on the top of the pipe, and the effect of particle wall collision is more significant at higher particle diameter.

The horizontally homogeneous model equations of incompressible atmospheric flow in general orthogonal coordinates

DEFF Research Database (Denmark)

Jørgensen, Bo Hoffmann

2003-01-01

The goal of this brief report is to express the model equations for an incompressible flow which is horizontally homogeneous. It is intended as a computationally inexpensive starting point of a more complete solution for neutral atmospheric flow overcomplex terrain. This idea was set forth...... by Ayotte and Taylor (1995) and in the work of Beljaars et al. (1987). Unlike the previous models, the present work uses general orthogonal coordinates. Strong conservation form of the model equations is employedto allow a robust and consistent numerical procedure. An invariant tensor form of the model...

Gas6 induces cancer cell migration and epithelial–mesenchymal transition through upregulation of MAPK and Slug

Energy Technology Data Exchange (ETDEWEB)

Lee, Yunhee [Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Immunotherapy Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon (Korea, Republic of); Lee, Mira [Immunotherapy Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon (Korea, Republic of); Kim, Semi, E-mail: semikim@kribb.re.kr [Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Immunotherapy Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon (Korea, Republic of)

2013-04-26

Highlights: •We investigated the molecular mechanisms underlying Gas6-mediated cancer cell migration. •Gas6 treatment and subsequent Axl activation induce cell migration and EMT via upregulation of Slug. •Slug expression mediated by Gas6 is mainly through c-Jun and ATF-2 in an ERK1/2 and JNK-dependent manner. •The Gas6/Axl-Slug axis may be exploited as a target for anti-cancer metastasis therapy. -- Abstract: Binding of Gas6 to Axl (Gas6/Axl axis) alters cellular functions, including migration, invasion, proliferation, and survival. However, the molecular mechanisms underlying Gas6-mediated cell migration remain poorly understood. In this study, we found that Gas6 induced the activation of JNK and ERK1/2 signaling in cancer cells expressing Axl, resulting in the phosphorylation of activator protein-1 (AP-1) transcription factors c-Jun and ATF-2, and induction of Slug. Depletion of c-Jun or ATF-2 by siRNA attenuated the Gas6-induced expression of Slug. Slug expression was required for cell migration and E-cadherin reduction/vimentin induction induced by Gas6. These results suggest that Gas6 induced cell migration via Slug upregulation in JNK- and ERK1/2-dependent mechanisms. These data provide an important insight into the molecular mechanisms mediating Gas6-induced cell migration.

Resolution of thermal striping issue downstream of a horizontal pipe elbow in stratified pipe flow. [LMFBR

Energy Technology Data Exchange (ETDEWEB)

Kuzay, T.M.; Kasza, K.E.

1985-01-01

A thermally stratified pipe flow produced by a thermal transient when passing through a horizontal elbow as a result of secondary flow gives rise to large thermal fluctuations on the inner curvature wall of the downstream piping. These fluctuations were measured in a specially instrumented horizontal pipe and elbow system on a test set-up using water in the Mixing Components Technology Facility (MCTF) at Argonne National Laboratory (ANL). This study is part of a larger program which is studying the influence of thermal buoyancy on general reactor component performance. This paper discusses the influence of pipe flow generated thermal oscillations on the thermal stresses induced in the pipe walls. The instrumentation was concentrated around the exit plane of the 90/sup 0/ sweep elbow, since prior tests had indicated that the largest thermal fluctuations would occur within about one hydraulic diameter downstream of the elbow exit. The thermocouples were located along the inner curvature of the piping and measured the near surface fluid temperature. The test matrix involved thermal downramps under turbulent flow conditions.

Simulation of buoyancy-induced turbulent flow from a hot horizontal jet

KAUST Repository

El-Amin, Mohamed

2014-02-01

Experimental visualizations and numerical simulations of a horizontal hot water jet entering cold water into a rectangular storage tank are described. Three different temperature differences and their corresponding Reynolds numbers are considered. Both experimental visualization and numerical computations are carried out for the same flow and thermal conditions. The realizable k - ε model is used for modeling the turbulent flow while the buoyancy is modeled using the Boussinesq approximation. Polynomial approximations of the water properties are used to compare with the Boussinesq approximation. Numerical solutions are obtained for unsteady flow while pressure, velocity, temperature and turbulence distributions inside the water tank as well as the Froude number are analyzed. The experimental visualizations are performed at intervals of five seconds for all different cases. The simulated results are compared with the visualized results, and both of them show the stratification phenomena and buoyancy force effects due to temperature difference and density variation. After certain times, depending on the case condition, the flow tends to reach a steady state. © 2014 Publishing House for Journal of Hydrodynamics.

Information content of slug tests for estimating hydraulic properties in realistic, high-conductivity aquifer scenarios

Science.gov (United States)

Cardiff, Michael; Barrash, Warren; Thoma, Michael; Malama, Bwalya

2011-06-01

SummaryA recently developed unified model for partially-penetrating slug tests in unconfined aquifers ( Malama et al., in press) provides a semi-analytical solution for aquifer response at the wellbore in the presence of inertial effects and wellbore skin, and is able to model the full range of responses from overdamped/monotonic to underdamped/oscillatory. While the model provides a unifying framework for realistically analyzing slug tests in aquifers (with the ultimate goal of determining aquifer properties such as hydraulic conductivity K and specific storage Ss), it is currently unclear whether parameters of this model can be well-identified without significant prior information and, thus, what degree of information content can be expected from such slug tests. In this paper, we examine the information content of slug tests in realistic field scenarios with respect to estimating aquifer properties, through analysis of both numerical experiments and field datasets. First, through numerical experiments using Markov Chain Monte Carlo methods for gauging parameter uncertainty and identifiability, we find that: (1) as noted by previous researchers, estimation of aquifer storage parameters using slug test data is highly unreliable and subject to significant uncertainty; (2) joint estimation of aquifer and skin parameters contributes to significant uncertainty in both unless prior knowledge is available; and (3) similarly, without prior information joint estimation of both aquifer radial and vertical conductivity may be unreliable. These results have significant implications for the types of information that must be collected prior to slug test analysis in order to obtain reliable aquifer parameter estimates. For example, plausible estimates of aquifer anisotropy ratios and bounds on wellbore skin K should be obtained, if possible, a priori. Secondly, through analysis of field data - consisting of over 2500 records from partially-penetrating slug tests in a

Two-phase flow induced parametric vibrations in structural systems

International Nuclear Information System (INIS)

Hara, Fumio

1980-01-01

This paper is divided into two parts concerning piping systems and a nuclear fuel pin system. The significant experimental results concerning the random vibration induced in an L-shaped pipe by air-water two-phase flow and the theoretical analysis of the vibration are described in the first part. It was clarified for the first time that the parametric excitation due to the periodic changes of system mass, centrifugal force and Coriolis force was the mechanism of exciting the vibration. Moreover, the experimental and theoretical analyses of the mechanism of exciting vibration by air-water two-phase flow in a straight, horizontal pipe were carried out, and the first natural frequency of the piping system was strongly related to the dominant frequency of void signals. The experimental results on the vibration of a nuclear fuel pin model in parallel air-water two-phase flow are reported in the latter part. The relations between vibrational strain variance and two-phase flow velocity or pressure fluctuation, and the frequency characteristics of vibrational strain variance were obtained. The theoretical analysis of the dynamic interaction between air-water two-phase flow and a fuel pin structure, and the vibrational instability of fuel pins in alternate air and water slugs or in large bubble flow are also reported. (Kako, I.)

Slug silencing inhibited perineural invasion through regulation of EMMPRIN expression in human salivary adenoid cystic carcinoma.

Science.gov (United States)

Wu, Baolei; Wei, Jianhua; Hu, Zhiqiang; Shan, Chun; Wang, Lei; Zhang, Chenping; Yang, Xi; Yang, Xinjie; Lei, Delin

2016-02-01

Salivary adenoid cystic carcinoma (SACC) is the most frequent salivary gland malignancy with a unique characteristic that has been named perineural invasion (PNI). EMMPRIN is a transmembrane glycoprotein that has been demonstrated to promote PNI in SACC. Slug, one of the most effective promoters of the epithelial-to-mesenchymal transition (EMT), has been found to be associated with PNI in SACC. The aim of the present study was to investigate the roles and relationships of Slug, EMMPRIN, and E-cadherin in the PNI process of SACC. The expression levels of Slug, EMMPRIN, and E-cadherin in 115 primary SACC cases were statistically analyzed by immunohistochemistry. Simultaneously, the SACC cell line SACC-83 was transfected with recombinant plasmids of silencing Slug (si-Slug) and/or silencing EMMPRIN (si-EMMPRIN). The functions of Slug and EMMPRIN in the EMT and PNI process were assessed by reverse transcription PCR (RT-PCR), western blotting, morphological observation, scratch test, migration assay, and in vitro perineural invasion assay. The immunohistochemical statistics revealed that the high expression of Slug and EMMPRIN and the low expression of E-cadherin were significantly associated with the PNI of SACC (P EMMPRIN expression (P EMMPRIN expression were both significantly negatively associated with E-cadherin expression (P EMMPRIN silencing both significantly inhibited EMMPRIN expression but promoted E-cadherin expression in SACC-83 cells (P EMMPRIN, or both induced cell morphology changes and inhibited tumor cell motility and PNI ability in SACC-83 cells (P EMMPRIN and then upregulating E-cadherin in the PNI process of SACC. The present study indicated that Slug and EMMPRIN are potential biomarkers and therapeutic targets for the diagnosis and treatment of PNI in human SACC.

Method of measuring horizontal fluid flow in cased off subsurface formations

International Nuclear Information System (INIS)

Paap, H.J.; Arnold, D.M.; Scott, H.D.

1980-01-01

An improved method is described for determining the flow rate of earth formation liquids moving horizontally past a steel casing in a well borehole, by neutron irradiation and subsequent decay measurements of the 24 Na produced by thermal neutron capture. The system described compensates for spurious gamma radiation such as that from 56 Mn, produced by neutron irradiation of 55 Mn in the steel casing, by taking measurements for at least three separate measured time intervals in an iterative procedure. (U.K.)

Analysis of the formation mechanism of the slug and jet center hole of axisymmetric shaped charges

Science.gov (United States)

Baoxiang, Ren; Gang, Tao; Peng, Wen; Changxing, Du; Chunqiao, Pang; Hongbo, Meng

2018-06-01

In the jet formation process of axisymmetric shaped charges, the slug is also formed. There is always a central hole in the symmetry axis of the jet and slug. The phenomenon was rarely mentioned and analyzed by the classical theory of shaped charges. For this problem, this paper attempts to explain the existence of the central hole in the jet and slug. Based on the analysis of recovery slug, we know that the jet and slug are in solid state in the process of formation. Through the analysis of X-flash radiographs of the stretching jet and particulation fracture, it is confirmed that the center holes in the jet are also present. Meanwhile, through the analysis of the microstructure of the recovered slug, it is found that there is a wave disturbance near the surface of the central hole. It can be speculated that the wave disturbance also exist in the jet. This effect may be one of the reasons for jet breakup. Due to the presence of the central hole in the jet, the density deficit of the jet obtained by other tests is very reasonable.

Spatial variability of hydraulic conductivity of an unconfined sandy aquifer determined by a mini slug test

DEFF Research Database (Denmark)

Bjerg, Poul Løgstrup; Hinsby, Klaus; Christensen, Thomas Højlund

1992-01-01

The spatial variability of the hydraulic conductivity in a sandy aquifer has been determined by a mini slug test method. The hydraulic conductivity (K) of the aquifer has a geometric mean of 5.05 × 10−4 m s−1, and an overall variance of 1n K equal to 0.37 which corresponds quite well to the results...... obtained by two large scale tracer experiments performed in the aquifer. A geological model of the aquifer based on 31 sediment cores, proposed three hydrogeological layers in the aquifer concurrent with the vertical variations observed with respect to hydraulic conductivity. The horizontal correlation......, to be in the range of 0.3–0.5 m compared with a value of 0.42 m obtained in one of the tracer tests performed....

Effects of roll waves on annular flow heat transfer at horizontal condenser tube

International Nuclear Information System (INIS)

Kondo, Masaya; Nakamura, Hideo; Anoda, Yoshinari; Sakashita, Akihiro

2002-01-01

Heat removal characteristic of a horizontal in-tube condensation heat exchanger is under investigation to be used for a passive containment cooling system (PCCS) of a next generation-type BWR. Flow regime observed at the inlet of the condenser tube was annular flow, and the local heat transfer rate was ∼20% larger than the prediction by the Dobson-Chato correlation. Roll waves were found to appear on the liquid film in the annular flow. The measured local condensation heat transfer rate was being closely related to the roll waves frequency. Based on these observations, a model is proposed which predicts the condensation heat transfer coefficient for annular flows around the tube inlet. The proposed model predicts well the influences of pressure, local gas-phase velocity and film thickness. (author)

The effect of diameter on vertical and horizontal flow boiling crisis in a tube cooled by Freon-12

International Nuclear Information System (INIS)

Merilo, M.; Ahmad, S.Y.

1979-03-01

The influence of test section orientation and diameter on flow boiling crisis occurring in tubes has been studied experimentally using Freon-12 as a coolant. At low mass flux the critical heat flux (CHF) was lower in horizontal flow than in vertical. As either the liquid or vapour velocity, or both, were increased the vertical and horizontal CHF results converged. Above a mass flux of 4 Mg.m -2 .s -1 the results were essentially identical. The effect of tube diameter on boiling crisis in general depends crucially on the parameters which are maintained constant when the comparison is made. (author)

Productivity and injectivity of horizontal wells

Energy Technology Data Exchange (ETDEWEB)

Aziz, Khalid

2000-03-06

One of the key issues addressed was pressure drop in long horizontal wells and its influence on well performance. Very little information is available in the literature on flow in pipes with influx through pipe walls. Virtually all of this work has been in small diameter pipes and with single-phase flow. In order to address this problem new experimental data on flow in horizontal and near horizontal wells have been obtained. Experiments were conducted at an industrial facility on typical 6 1/8 ID, 100 feet long horizontal well model. The new data along with available information in the literature have been used to develop new correlations and mechanistic models. Thus it is now possible to predict, within reasonable accuracy, the effect of influx through the well on pressure drop in the well.

The Gastropod Menace: Slugs on Brassica Plants Affect Caterpillar Survival through Consumption and Interference with Parasitoid Attraction.

Science.gov (United States)

Desurmont, Gaylord A; Zemanova, Miriam A; Turlings, Ted C J

2016-03-01

Terrestrial molluscs and insect herbivores play a major role as plant consumers in a number of ecosystems, but their direct and indirect interactions have hardly been explored. The omnivorous nature of slugs makes them potential disrupters of predator-prey relationships, as a direct threat to small insects and through indirect, plant-mediated effects. Here, we examined the effects of the presence of two species of slugs, Arion rufus (native) and A. vulgaris (invasive) on the survivorship of young Pieris brassicae caterpillars when feeding on Brassica rapa plants, and on plant attractiveness to the main natural enemy of P. brassicae, the parasitoid Cotesia glomerata. In two separate predation experiments, caterpillar mortality was significantly higher on plants co-infested with A. rufus or A. vulgaris. Moreover, caterpillar mortality correlated positively with slug mass and leaf consumption by A. vulgaris. At the third trophic level, plants infested with slugs and plants co-infested with slugs and caterpillars were far less attractive to parasitoids than plants damaged by caterpillars only, independently of slug species. Chemical analyses confirmed that volatile emissions, which provide foraging cues for parasitoids, were strongly reduced in co-infested plants. Our study shows that the presence of slugs has the potential to affect insect populations, directly via consumptive effects, and indirectly via changes in plant volatiles that result in a reduced attraction of natural enemies. The fitness cost for P. brassicae imposed by increased mortality in presence of slugs may be counterbalanced by the benefit of escaping its parasitoids.

Transient two-phase flow

International Nuclear Information System (INIS)

Hsu, Y.Y.

1974-01-01

The following papers related to two-phase flow are summarized: current assumptions made in two-phase flow modeling; two-phase unsteady blowdown from pipes, flow pattern in Laval nozzle and two-phase flow dynamics; dependence of radial heat and momentum diffusion; transient behavior of the liquid film around the expanding gas slug in a vertical tube; flooding phenomena in BWR fuel bundles; and transient effects in bubble two-phase flow. (U.S.)

Fully developed laminar flow of two immiscible liquids through horizontal pipes: a variational approach

Energy Technology Data Exchange (ETDEWEB)

Kurban, Adib Paulo Abdalla [PETROBRAS, Rio de Janeiro (Brazil). Centro de Pesquisas; Bannwart, Antonio Carlos [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica

1990-12-31

The fully developed laminar flow of two immiscible liquids with both different viscosities and densities through a horizontal round pipe is studied. The interface between the fluids as well as their flow fields are determined by the use of a variational principle: the so called viscous dissipation principle: The results foreseen by this paper are in agreement with the physical observation (e.g. Southern and Ballman) that the more viscous fluid is total or partially encapsulated by the less viscous one. (author) 8 refs., 4 figs.

Fully developed laminar flow of two immiscible liquids through horizontal pipes: a variational approach

Energy Technology Data Exchange (ETDEWEB)

Kurban, Adib Paulo Abdalla [PETROBRAS, Rio de Janeiro (Brazil). Centro de Pesquisas; Bannwart, Antonio Carlos [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica

1991-12-31

The fully developed laminar flow of two immiscible liquids with both different viscosities and densities through a horizontal round pipe is studied. The interface between the fluids as well as their flow fields are determined by the use of a variational principle: the so called viscous dissipation principle: The results foreseen by this paper are in agreement with the physical observation (e.g. Southern and Ballman) that the more viscous fluid is total or partially encapsulated by the less viscous one. (author) 8 refs., 4 figs.

Visualization of cross-sectional flow structure during condensation of steam in a slightly inclined horizontal tube

Energy Technology Data Exchange (ETDEWEB)

Puseya, Andree; Kim, H. [Kyung Hee University, Yongin (Korea, Republic of); Kwon, T. S. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

These flow characteristics called flow patterns still depend on a proper visualization technique in order to identify such local distribution. These proper distributions will have a dependence on the inclination of the tube as well, as it was demonstrated by Lips and Mayer. This work is focused on presenting an experimental investigation to visualize the cross sectional two-phase flow structure for condensation of steam in a horizontal tube and identify the liquid-gas interface using the axial-viewing technique. This innovative technique developed by Hewitt and more recently used in visualization works by Badie, permits the achievement to identify those systems in the area of interest by looking directly into the two-phase flow system during condensation of steam inside a pipe with technology such a high speed camera. An experimental work to visualize and locate the liquid-gas interface for steam condensation in horizontal tubes with slightly inclination was developed on this research The experimental results shows that the axial viewing technique works well with condensation phenomena and can be used for further developments in the field such as determination of liquid film geometry and calculation of void fraction.

Structure of two-phase air-water flows. Study of average void fraction and flow patterns

International Nuclear Information System (INIS)

Roumy, R.

1969-01-01

This report deals with experimental work on a two phase air-water mixture in vertical tubes of different diameters. The average void fraction was measured in a 2 metre long test section by means of quick-closing valves. Using resistive probes and photographic techniques, we have determined the flow patterns and developed diagrams to indicate the boundaries between the various patterns: independent bubbles, agglomerated bubbles, slugs, semi-annular, annular. In the case of bubble flow and slug flow, it is shown that the relationship between the average void fraction and the superficial velocities of the phases is given by: V sg = f( ) * g(V sl ). The function g(V sl ) for the case of independent bubbles has been found to be: g(V sl ) = V sl + 20. For semi-annular and annular flow conditions; it appears that the average void fraction depends, to a first approximation only on the ratio V sg /V sl . (author) [fr

A Review of the Multilevel Slug Test for Characterizing Aquifer Heterogeneity

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Chia-Shyun Chen

2012-01-01

Full Text Available All aquifers are heterogeneous to a certain degree. The spatial distribution of hydraulic conductivity K(x, y, z, or aquifer heterogeneity, significantly influences the groundwater flow movement and associated solute transport. Of particular importance in designing an in-situ remediation plan is a knowledge of low-K layers because they are less accessible to remedial agents and form a bottleneck in remediation. The characterization of aquifer heterogeneity is essential to the solution of many practical and scientific groundwater problems. This article reviews the field technique using the multilevel slug test (MLST, which determines a series of K estimates at depths of interest in a well by making use of a double-packer system. The K(z obtained manifests the vertical variation of hydraulic conductivity in the vicinity of the test well, and the combination of K(z from different wells gives rise to a three-dimensional description of K(x, y, z. The MLST response is rather sensitive to hydraulic conductivity variation; e.g., it is oscillatory for highly permeable conditions (K > 5 × 10-4 m s-1 and a nonoscillatory for K < 5 × 10-4 m s-1. In this article we discuss the instrumentation of the double-packer system, the implementation of the depth-specific slug test, the data analysis methods for a spectrum of response characteristics usually observed in the field, and field applications of the MLST.

New transient-flow modelling of a multiple-fractured horizontal well

International Nuclear Information System (INIS)

Jia, Yong-Lu; Wang, Ben-Cheng; Nie, Ren-Shi; Wang, Dan-Ling

2014-01-01

A new transient-flow modelling of a multiple-fractured horizontal well is presented. Compared to conventional modelling, the new modelling considered more practical physical conditions, such as various inclined angles for different fractures, different fracture intervals, different fracture lengths and partially penetrating fractures to formation. A kind of new mathematical method, including a three-dimensional eigenvalue and orthogonal transform, was created to deduce the exact analytical solutions of pressure transients for constant-rate production in real space. In order to consider a wellbore storage coefficient and skin factor, we used a Laplace-transform approach to convert the exact analytical solutions to the solutions in Laplace space. Then the numerical solutions of pressure transients in real space were gained using a Stehfest numerical inversion. Standard type curves were plotted to describe the transient-flow characteristics. Flow regimes were clearly identified from type curves. Furthermore, the differences between the new modelling and the conventional modelling in pressure transients were especially compared and discussed. Finally, an example application to show the accordance of the new modelling with real conditions was implemented. Our new modelling is different from, but more practical than, conventional modelling. (paper)

Herbivory of an invasive slug is affected by earthworms and the composition of plant communities.

Science.gov (United States)

Zaller, Johann G; Parth, Myriam; Szunyogh, Ilona; Semmelrock, Ines; Sochurek, Susanne; Pinheiro, Marcia; Frank, Thomas; Drapela, Thomas

2013-05-13

Biodiversity loss and species invasions are among the most important human-induced global changes. Moreover, these two processes are interlinked as ecosystem invasibility is considered to increase with decreasing biodiversity. In temperate grasslands, earthworms serve as important ecosystem engineers making up the majority of soil faunal biomass. Herbivore behaviour has been shown to be affected by earthworms, however it is unclear whether these effects differ with the composition of plant communities. To test this we conducted a mesocosm experiment where we added earthworms (Annelida: Lumbricidae) to planted grassland communities with different plant species composition (3 vs. 12 plant spp.). Plant communities had equal plant densities and ratios of the functional groups grasses, non-leguminous forbs and legumes. Later, Arion vulgaris slugs (formerly known as A. lusitanicus; Gastropoda: Arionidae) were added and allowed to freely choose among the available plant species. This slug species is listed among the 100 worst alien species in Europe. We hypothesized that (i) the food choice of slugs would be altered by earthworms' specific effects on the growth and nutrient content of plant species, (ii) slug herbivory will be less affected by earthworms in plant communities containing more plant species than in those with fewer plant species because of a more readily utilization of plant resources making the impacts of earthworms less pronounced. Slug herbivory was significantly affected by both earthworms and plant species composition. Slugs damaged 60% less leaves when earthworms were present, regardless of the species composition of the plant communities. Percent leaf area consumed by slugs was 40% lower in communities containing 12 plant species; in communities containing only three species earthworms increased slug leaf area consumption. Grasses were generally avoided by slugs. Leaf length and number of tillers was increased in mesocosms containing more plant

The formation of sporadic E layers by a vortical perturbation excited in a horizontal wind shear flow

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G. G. Didebulidze

2008-06-01

Full Text Available The formation of the mid-latitude sporadic E layers (E_s layers by an atmospheric vortical perturbation excited in a horizontal shear flow (horizontal wind with a horizontal linear shear is investigated. A three-dimensional atmospheric vortical perturbation (atmospheric shear waves, whose velocity vector is in the horizontal plane and has a vertical wavenumber k_z≠0, can provide a vertical shear of the horizontal wind. The shear waves influence the vertical transport of heavy metallic ions and their convergence into thin and dense horizontal layers. The proposed mechanism takes into account the dynamical influence of the shear wave velocity in the horizontal wind on the vertical drift velocity of the ions. It also can explain the multi-layer structure of E_s layers. The pattern of the multi-layer structure depends on the value of the shear-wave vertical wavelength, the ion-neutral collision frequency and the direction of the background horizontal wind. The modelling of formation of sporadic E layers with a single and a double peak is presented. Also, the importance of shear wave coupling with short-period atmospheric gravity waves (AGWs on the variations of sporadic E layer ion density is examined and discussed.

Random signal tomographical analysis of two-phase flow

International Nuclear Information System (INIS)

Han, P.; Wesser, U.

1990-01-01

This paper reports on radiation tomography which is a useful tool for studying the internal structures of two-phase flow. However, general tomography analysis gives only time-averaged results, hence much information is lost. As a result, it is sometimes difficult to identify the flow regime; for example, the time-averaged picture does not significantly change as an annual flow develops from a slug flow. A two-phase flow diagnostic technique based on random signal tomographical analysis is developed. It extracts more information by studying the statistical variation of the measured signal with time. Local statistical parameters, including mean value, variance, skewness and flatness etc., are reconstructed from the information obtained by a general tomography technique. More important information are provided by the results. Not only the void fraction can be easily calculated, but also the flow pattern can be identified more objectively and more accurately. The experimental setup is introduced. It consisted of a two-phase flow loop, an X-ray system, a fan-like five-beam detector system and a signal acquisition and processing system. In the experiment, for both horizontal and vertical test sections (aluminum and steel tube with Di/Do = 40/45 mm), different flow situations are realized by independently adjusting air and water mass flow. Through a glass tube connected with the test section, some typical flow patterns are visualized and used for comparing with the reconstruction results

An Evaluation of the Bouwer and Rice Method of Slug Test Analysis

Science.gov (United States)

Brown, David L.; Narasimhan, T. N.; Demir, Z.

1995-05-01

The method of Bouwer and Rice (1976) for analyzing slug test data is widely used to estimate hydraulic conductivity (K). Based on steady state flow assumptions, this method is specifically intended to be applicable to unconfined aquifers. Therefore it is of practical value to investigate the limits of accuracy of the K estimates obtained with this method. Accordingly, using a numerical model for transient flow, we evaluate the method from two perspectives. First, we apply the method to synthetic slug test data and study the error in estimated values of K. Second, we analyze the logical basis of the method. Parametric studies helped assess the role of the effective radius parameter, specific storage, screen length, and well radius on the estimated values of K. The difference between unconfined and confined systems was studied via conditions on the upper boundary of the flow domain. For the cases studied, the Bouwer and Rice analysis was found to give good estimates of K, with errors ranging from 10% to 100%. We found that the estimates of K were consistently superior to those obtained with Hvorslev's (1951) basic time lag method. In general, the Bouwer and Rice method tends to underestimate K, the greatest errors occurring in the presence of a damaged zone around the well or when the top of the screen is close to the water table. When the top of the screen is far removed from the upper boundary of the system, no difference is manifest between confined and unconfined conditions. It is reasonable to infer from the simulated results that when the screen is close to the upper boundary, the results of the Bouwer and Rice method agree more closely with a "confined" idealization than an "unconfined" idealization. In effect, this method treats the aquifer system as an equivalent radial flow permeameter with an effective radius, Re, which is a function of the flow geometry. Our transient simulations suggest that Re varies with time and specific storage. Thus the effective

Combination of rapamycin, CI-1040, and 17-AAG inhibits metastatic capacity of prostate cancer via Slug inhibition.

Directory of Open Access Journals (Sweden)

Guanxiong Ding

Full Text Available Though prostate cancer (PCa has slow progression, the hormone refractory (HRCP and metastatic entities are substantially lethal and lack effective treatments. Transcription factor Slug is critical in regulating metastases of various tumors including PCa. Here we studied targeted therapy against Slug using combination of 3 drugs targeting 3 pathways respectively converging via Slug and further regulating PCa metastasis. Using in vitro assays we confirmed that Slug up-regulation incurred inhibition of E-cadherin that was anti-metastatic, and inhibited Bim-regulated cell apoptosis in PCa. Upstream PTEN/Akt, mTOR, Erk, and AR/Hsp90 pathways were responsible for Slug up-regulation and each of these could be targeted by rapamycin, CI-1040, and 17-AAG respectively. In 4 PCa cell lines with different traits in terms of PTEN loss and androgen sensitivity we tested the efficacy of mono- and combined therapy with the drugs. We found that metastatic capacity of the cells was maximally inhibited only when all 3 drugs were combined, due to the crosstalk between the pathways. 17-AAG decreases Slug expression via blockade of HSP90-dependent AR stability. Combination of rapamycin and CI-1040 diminishes invasiveness more potently in PCa cells that are androgen insensitive and with PTEN loss. Slug inhibited Bim-mediated apoptosis that could be rescued by mTOR/Erk/HSP90 inhibitors. Using mouse models for circulating PCa DNA quantification, we found that combination of mTOR/Erk/HSP90 inhibitors reduced circulating PCa cells in vivo significantly more potently than combination of 2 or monotherapy. Conclusively, combination of mTOR/Erk/Hsp90 inhibits metastatic capacity of prostate cancer via Slug inhibition.

Analysis of pumping tests of partially penetrating wells in an unconfined aquifer using inverse numerical optimization

Science.gov (United States)

Hvilshøj, S.; Jensen, K. H.; Barlebo, H. C.; Madsen, B.

1999-08-01

Inverse numerical modeling was applied to analyze pumping tests of partially penetrating wells carried out in three wells established in an unconfined aquifer in Vejen, Denmark, where extensive field investigations had previously been carried out, including tracer tests, mini-slug tests, and other hydraulic tests. Drawdown data from multiple piezometers located at various horizontal and vertical distances from the pumping well were included in the optimization. Horizontal and vertical hydraulic conductivities, specific storage, and specific yield were estimated, assuming that the aquifer was either a homogeneous system with vertical anisotropy or composed of two or three layers of different hydraulic properties. In two out of three cases, a more accurate interpretation was obtained for a multi-layer model defined on the basis of lithostratigraphic information obtained from geological descriptions of sediment samples, gammalogs, and flow-meter tests. Analysis of the pumping tests resulted in values for horizontal hydraulic conductivities that are in good accordance with those obtained from slug tests and mini-slug tests. Besides the horizontal hydraulic conductivity, it is possible to determine the vertical hydraulic conductivity, specific yield, and specific storage based on a pumping test of a partially penetrating well. The study demonstrates that pumping tests of partially penetrating wells can be analyzed using inverse numerical models. The model used in the study was a finite-element flow model combined with a non-linear regression model. Such a model can accommodate more geological information and complex boundary conditions, and the parameter-estimation procedure can be formalized to obtain optimum estimates of hydraulic parameters and their standard deviations.

Characterization of two-phase flow regimes in horizontal tubes using 81mKr tracer experiments.

Science.gov (United States)

Oriol, Jean; Leclerc, Jean Pierre; Berne, Philippe; Gousseau, Georges; Jallut, Christian; Tochon, Patrice; Clement, Patrice

2008-10-01

The diagnosis of heat exchangers on duty with respect to flow mal-distributions needs the development of non-intrusive inlet-outlet experimental techniques in order to perform an online fault diagnosis. Tracer experiments are an example of such techniques. They can be applied to mono-phase heat exchangers but also to multi-phase ones. In this case, the tracer experiments are more difficult to perform. In order to check for the capabilities of tracer experiments to be used for the flow mal-distribution diagnosis in the case of multi-phase heat exchangers, we present here a preliminary study on the simplest possible system: two-phase flows in a horizontal tube. (81m)Kr is used as gas tracer and properly collimated NaI (TI) crystal scintillators as detectors. The specific shape of the tracer response allows two-phase flow regimes to be characterized. Signal analysis allows the estimation of the gas phase real average velocity and consequently of the liquid phase real average velocity as well as of the volumetric void fraction. These results are compared successfully to those obtained with liquid phase tracer experiments previously presented by Oriol et al. 2007. Characterization of the two-phase flow regimes and liquid dispersion in horizontal and vertical tubes using coloured tracer and no intrusive optical detector. Chem. Eng. Sci. 63(1), 24-34, as well as to those given by correlations from literature.

Characterization of two-phase flow regimes in horizontal tubes using 81mKr tracer experiments

International Nuclear Information System (INIS)

Oriol, Jean; Leclerc, Jean Pierre; Berne, Philippe; Gousseau, Georges; Jallut, Christian; Tochon, Patrice; Clement, Patrice

2008-01-01

The diagnosis of heat exchangers on duty with respect to flow mal-distributions needs the development of non-intrusive inlet-outlet experimental techniques in order to perform an online fault diagnosis. Tracer experiments are an example of such techniques. They can be applied to mono-phase heat exchangers but also to multi-phase ones. In this case, the tracer experiments are more difficult to perform. In order to check for the capabilities of tracer experiments to be used for the flow mal-distribution diagnosis in the case of multi-phase heat exchangers, we present here a preliminary study on the simplest possible system: two-phase flows in a horizontal tube. 81m Kr is used as gas tracer and properly collimated NaI (TI) crystal scintillators as detectors. The specific shape of the tracer response allows two-phase flow regimes to be characterized. Signal analysis allows the estimation of the gas phase real average velocity and consequently of the liquid phase real average velocity as well as of the volumetric void fraction. These results are compared successfully to those obtained with liquid phase tracer experiments previously presented by Oriol et al. 2007. Characterization of the two-phase flow regimes and liquid dispersion in horizontal and vertical tubes using coloured tracer and no intrusive optical detector. Chem. Eng. Sci. 63(1), 24-34, as well as to those given by correlations from literature

Measurement and study of amplitudes and velocities of void fraction waves in two-phase gas-liquid flow ranging from bubbly flow to slug flow

International Nuclear Information System (INIS)

Tournaire, Agnes

1987-01-01

The objective of this research thesis is to study the behaviour of waves at the vicinity of the bubble-slug transition, and to compare it with the one predicted by models. The author also addresses the bubbly regime, and particularly the evolution of wave amplitude whereas studies had been until then limited to the study of wave speed. The first part of the thesis reports the development of a system of vacuum rate measurements in cylindrical duct. The second part proposes the description of the experimental installation, and the third part reports experimental results and discusses them. Finally, the author compares these results with those predicted by using a kinematic modelling [fr

Air-lift pumps characteristics under two-phase flow conditions

International Nuclear Information System (INIS)

Kassab, Sadek Z.; Kandil, Hamdy A.; Warda, Hassan A.; Ahmed, Wael H.

2009-01-01

Air-lift pumps are finding increasing use where pump reliability and low maintenance are required, where corrosive, abrasive, or radioactive fluids in nuclear applications must be handled and when a compressed air is readily available as a source of a renewable energy for water pumping applications. The objective of the present study is to evaluate the performance of a pump under predetermined operating conditions and to optimize the related parameters. For this purpose, an air-lift pump was designed and tested. Experiments were performed for nine submergence ratios, and three risers of different lengths with different air injection pressures. Moreover, the pump was tested under different two-phase flow patterns. A theoretical model is proposed in this study taking into account the flow patterns at the best efficiency range where the pump is operated. The present results showed that the pump capacity and efficiency are functions of the air mass flow rate, submergence ratio, and riser pipe length. The best efficiency range of the air-lift pumps operation was found to be in the slug and slug-churn flow regimes. The proposed model has been compared with experimental data and the most cited models available. The proposed model is in good agreement with experimental results and found to predict the liquid volumetric flux for different flow patterns including bubbly, slug and churn flow patterns

Development of an electrical sensor for measurement of void fraction and identification of flow regime in a horizontal pipe

International Nuclear Information System (INIS)

Won, Woo Yeon; Lee, Yeon Gun; Lee, Bo An; Ko, Min Seok; Kim, Sin

2015-01-01

The electrical signals of the electrical impedance sensor depend on the flow structure as well as the void fraction. For this reason, the electrical responses to a given void fraction differ according to the flow pattern. For reliable void fraction measurement, hence, information on the flow pattern should be given. Based on this idea, a new improved conductance sensor is proposed in this study to measure the void fraction and simultaneously determine the flow pattern of the air-water two-phase mixture in a horizontal pipe. The proposed sensor is composed of a 3-electrode set of adjacent and opposite electrodes. The opposite electrodes measures the void fraction, the adjacent electrode serves to determine the flow patterns. Prior to the real applications of the proposed approach, several numerical calculations based on the FEM are performed to optimize the electrode and insulator sizes in terms of the sensor linearity. The numerical results are assessed in comparison with the data from static experiments. The sensor system is applied for a horizontal flow loop with 40 mm in inner diameter and 5 m in length and its measurement performance for the void fraction is compared with that of a wire-mesh sensor system. In this study, an electrical sensor for measuring the void fraction and identifying flow pattern in horizontal pipes has been designed. For optimization of the sensor, numerical analysis have been performed in order to determine the geometry and verified it through static experiments. Also, the loop experiments were conducted for several flow rate conditions covering stratified and intermittent flow regimes and the experimental results for the void fractions measured by the proposed sensor were compared with those of a wire-mesh sensor. The comparison results are in overall good agreements

Investigation of Steam Flow Behavior During Horizontal Injection into Vertical Annulus

International Nuclear Information System (INIS)

Yoon, Sang H.; Kim, Won J.; Ku, Ja H.; Suh, Kune Y.; Song, Chul H.

2004-01-01

Qualification of uncertainty margins for accidents, which are classified as the design basis accidents, requires thermal hydraulic codes and related code models with an enhanced level of sophistication. In a cold leg break accident, the flow in downcomer is multidimensional and the velocity distribution of the steam flow in downcomer serves as a good example. For observation of the flow behavior near the break, experiments are performed to measure the velocity of the steam flow in a vessel scaled down from the APR1400 (Advanced Power Reactor 1400 MWe). In this case, the steam has a quality approaching unity and thus is dealt with as a single-phase gas. The velocity of the steam flow is measured by micro-Pitot tubes arranged horizontally and vertically around the outer shell of the 1/20 scaled-down test vessel OMEGA (Optimized Multidimensional Experiment Geometric Apparatus). A commercial computational fluid dynamics code yields analytic results of multidimensional flow motion in the complex annular passage with flow obstacles. CFX is run with well-defined boundary conditions to obtain velocity profiles of the steam flow in the annular downcomer. Results of CFX shed light on the experimental setup as to fixing the location and angle of the micro-Pitot tubes, and correcting the sensitivity of the micro- Pitot tubes, for instance. This study aims to improve the multidimensional capability of the MARS code, which is based on RELAP5 and COBRA-IV, in predicting the multiphase flow behavior in the reactor downcomer. MARS is currently based on one- and two-dimensional flow analyses, which tends to distort total flow due to misrepresentation of the local phenomena. It is thus necessary to scrutinize the steam flow path and mechanistically model the momentum variation. These experimental and analytical results can locally be applied to developing the models of specific forms and essential phenomena treated in MARS. (authors)

Optimization of Operation Parameters for Helical Flow Cleanout with Supercritical CO2 in Horizontal Wells Using Back-Propagation Artificial Neural Network.

Science.gov (United States)

Song, Xianzhi; Peng, Chi; Li, Gensheng; He, Zhenguo; Wang, Haizhu

2016-01-01

Sand production and blockage are common during the drilling and production of horizontal oil and gas wells as a result of formation breakdown. The use of high-pressure rotating jets and annular helical flow is an effective way to enhance horizontal wellbore cleanout. In this paper, we propose the idea of using supercritical CO2 (SC-CO2) as washing fluid in water-sensitive formation. SC-CO2 is manifested to be effective in preventing formation damage and enhancing production rate as drilling fluid, which justifies tis potential in wellbore cleanout. In order to investigate the effectiveness of SC-CO2 helical flow cleanout, we perform the numerical study on the annular flow field, which significantly affects sand cleanout efficiency, of SC-CO2 jets in horizontal wellbore. Based on the field data, the geometry model and mathematical models were built. Then a numerical simulation of the annular helical flow field by SC-CO2 jets was accomplished. The influences of several key parameters were investigated, and SC-CO2 jets were compared to conventional water jets. The results show that flow rate, ambient temperature, jet temperature, and nozzle assemblies play the most important roles on wellbore flow field. Once the difference between ambient temperatures and jet temperatures is kept constant, the wellbore velocity distributions will not change. With increasing lateral nozzle size or decreasing rear/forward nozzle size, suspending ability of SC-CO2 flow improves obviously. A back-propagation artificial neural network (BP-ANN) was successfully employed to match the operation parameters and SC-CO2 flow velocities. A comprehensive model was achieved to optimize the operation parameters according to two strategies: cost-saving strategy and local optimal strategy. This paper can help to understand the distinct characteristics of SC-CO2 flow. And it is the first time that the BP-ANN is introduced to analyze the flow field during wellbore cleanout in horizontal wells.

Optimization of Operation Parameters for Helical Flow Cleanout with Supercritical CO2 in Horizontal Wells Using Back-Propagation Artificial Neural Network.

Directory of Open Access Journals (Sweden)

Xianzhi Song

Full Text Available Sand production and blockage are common during the drilling and production of horizontal oil and gas wells as a result of formation breakdown. The use of high-pressure rotating jets and annular helical flow is an effective way to enhance horizontal wellbore cleanout. In this paper, we propose the idea of using supercritical CO2 (SC-CO2 as washing fluid in water-sensitive formation. SC-CO2 is manifested to be effective in preventing formation damage and enhancing production rate as drilling fluid, which justifies tis potential in wellbore cleanout. In order to investigate the effectiveness of SC-CO2 helical flow cleanout, we perform the numerical study on the annular flow field, which significantly affects sand cleanout efficiency, of SC-CO2 jets in horizontal wellbore. Based on the field data, the geometry model and mathematical models were built. Then a numerical simulation of the annular helical flow field by SC-CO2 jets was accomplished. The influences of several key parameters were investigated, and SC-CO2 jets were compared to conventional water jets. The results show that flow rate, ambient temperature, jet temperature, and nozzle assemblies play the most important roles on wellbore flow field. Once the difference between ambient temperatures and jet temperatures is kept constant, the wellbore velocity distributions will not change. With increasing lateral nozzle size or decreasing rear/forward nozzle size, suspending ability of SC-CO2 flow improves obviously. A back-propagation artificial neural network (BP-ANN was successfully employed to match the operation parameters and SC-CO2 flow velocities. A comprehensive model was achieved to optimize the operation parameters according to two strategies: cost-saving strategy and local optimal strategy. This paper can help to understand the distinct characteristics of SC-CO2 flow. And it is the first time that the BP-ANN is introduced to analyze the flow field during wellbore cleanout in

Model for melt blockage (slug) relocation and physico-chemical interactions during core degradation under severe accident conditions

International Nuclear Information System (INIS)

Veshchunov, M.S.; Shestak, V.E.

2008-01-01

The model describing massive melt blockage (slug) relocation and physico-chemical interactions with steam and surrounding fuel rods of a bundle is developed on the base of the observations in the CORA tests. Mass exchange owing to slug oxidation and fuel rods dissolution is described by the previously developed 2D model for the molten pool oxidation. Heat fluxes in oxidising melt along with the oxidation heat effect at the melt relocation front are counterbalanced by the heat losses in the surrounding media and the fusion heat effect of the Zr claddings attacked by the melt. As a result, the slug relocation velocity is calculated from the heat flux matches at the melt propagation front (Stefan problem). A numerical module simulating the slug behaviour is developed by tight coupling of the heat and mass exchange modules. The new model demonstrates a reasonable capability to simulate the main features of the massive slug behaviour observed in the CORA-W1 test

A Simple Approach to Characterize Gas-Aqueous Liquid Two-phase Flow Configuration Based on Discrete Solid-Liquid Contact Electrification.

Science.gov (United States)

Choi, Dongwhi; Lee, Donghyeon; Kim, Dong Sung

2015-10-14

In this study, we first suggest a simple approach to characterize configuration of gas-aqueous liquid two-phase flow based on discrete solid-liquid contact electrification, which is a newly defined concept as a sequential process of solid-liquid contact and successive detachment of the contact liquid from the solid surface. This approach exhibits several advantages such as simple operation, precise measurement, and cost-effectiveness. By using electric potential that is spontaneously generated by discrete solid-liquid contact electrification, the configurations of the gas-aqueous liquid two-phase flow such as size of a gas slug and flow rate are precisely characterized. According to the experimental and numerical analyses on parameters that affect electric potential, gas slugs have been verified to behave similarly to point electric charges when the measuring point of the electric potential is far enough from the gas slug. In addition, the configuration of the gas-aqueous liquid two-phase microfluidic system with multiple gas slugs is also characterized by using the presented approach. For a proof-of-concept demonstration of using the proposed approach in a self-triggered sensor, a gas slug detector with a counter system is developed to show its practicality and applicability.

Flow Boiling on a Downward-Facing Inclined Plane Wall of Core Catcher

International Nuclear Information System (INIS)

Kim, Hyoung Tak; Bang, Kwang Hyun; Suh, Jung Soo

2013-01-01

In order to investigate boiling behavior on downward-facing inclined heated wall prior to the CHF condition, an experiment was carried out with 1.2 m long rectangular channel, inclined by 10 .deg. from the horizontal plane. High speed video images showed that the bubbles were sliding along the heated wall, continuing to grow and combining with the bubbles growing at their nucleation sites in the downstream. These large bubbles continued to slide along the heated wall and formed elongated slug bubbles. Under this slug bubble thin liquid film layer on the heated wall was observed and this liquid film prevents the wall from dryout. The length, velocity and frequency of slug bubbles sliding on the heated wall were measured as a function of wall heat flux and these parameters were used to develop wall boiling model for inclined, downward-facing heated wall. One approach to achieve coolable state of molten core in a PWR-like reactor cavity during a severe accident is to retain the core melt on a so-called core catcher residing on the reactor cavity floor after its relocation from the reactor pressure vessel. The core melt retained in the core catcher is cooled by water coolant flowing in an inclined cooling channel underneath as well as the water pool overlaid on the melt layer. Two-phase flow boiling with downward-facing heated wall such as this core catcher cooling channel has drawn a special attention because this orientation of heated wall may reach boiling crisis at lower heat flux than that of a vertical or upward-facing heated wall. Nishikawa and Fujita, Howard and Mudawar, Qiu and Dhir have conducted experiments to study the effect of heater orientation on boiling heat transfer and CHF. SULTAN experiment was conducted to study inclined large-scale structure coolability by water in boiling natural convection. In this paper, high-speed visualization of boiling behavior on downward-facing heated wall inclined by 10 .deg. is presented and wall boiling model for the

Analytical Solution for Time-drawdown Response to Constant Pumping from a Homogeneous, Confined Horizontal Aquifer with Unidirectional Flow

Science.gov (United States)

Parrish, K. E.; Zhang, J.; Teasdale, E.

2007-12-01

An exact analytical solution to the ordinary one-dimensional partial differential equation is derived for transient groundwater flow in a homogeneous, confined, horizontal aquifer using Laplace transformation. The theoretical analysis is based on the assumption that the aquifer is homogeneous and one-dimensional (horizontal); confined between impermeable formations on top and bottom; and of infinite horizontal extent and constant thickness. It is also assumed that there is only a single pumping well penetrating the entire aquifer; flow is everywhere horizontal within the aquifer to the well; the well is pumping with a constant discharge rate; the well diameter is infinitesimally small; and the hydraulic head is uniform throughout the aquifer before pumping. Similar to the Theis solution, this solution is suited to determine transmissivity and storativity for a two- dimensional, vertically confined aquifer, such as a long vertically fractured zone of high permeability within low permeable rocks or a long, high-permeability trench inside a low-permeability porous media. In addition, it can be used to analyze time-drawdown responses to pumping and injection in similar settings. The solution can also be used to approximate the groundwater flow for unconfined conditions if (1) the variation of transmissivity is negligible (groundwater table variation is small in comparison to the saturated thickness); and (2) the unsaturated flow is negligible. The errors associated with the use of the solution to unconfined conditions depend on the accuracies of the above two assumptions. The solution can also be used to assess the impacts of recharge from a seasonal river or irrigation canal on the groundwater system by assuming uniform, time- constant recharge along the river or canal. This paper presents the details for derivation of the analytical solution. The analytical solution is compared to numerical simulation results with example cases. Its accuracy is also assessed and

An analytic data analysis method for oscillatory slug tests.

Science.gov (United States)

Chen, Chia-Shyun

2006-01-01

An analytical data analysis method is developed for slug tests in partially penetrating wells in confined or unconfined aquifers of high hydraulic conductivity. As adapted from the van der Kamp method, the determination of the hydraulic conductivity is based on the occurrence times and the displacements of the extreme points measured from the oscillatory data and their theoretical counterparts available in the literature. This method is applied to two sets of slug test response data presented by Butler et al.: one set shows slow damping with seven discernable extremities, and the other shows rapid damping with three extreme points. The estimates of the hydraulic conductivity obtained by the analytic method are in good agreement with those determined by an available curve-matching technique.

Identification of two-phase flow regimes under variable gravity conditions

International Nuclear Information System (INIS)

Kamiel S Gabriel; Huawei Han

2005-01-01

Full text of publication follows: Two-phase flow is becoming increasingly important as we move into new and more aggressive technologies in the twenty-first century. Some of its many applications include the design of efficient heat transport systems, the transfer and storage of cryogenic fluids, and condensation and flow boiling processes in heat exchangers and energy transport systems. Two-phase flow has many applications in reduced gravity environments experienced in orbiting spacecraft and earth observation satellites. Examples are heat transport systems, the transfer and storage of cryogenic fluids, and condensation and flow boiling processes in heat exchangers. A concave parallel plate capacitance sensor has been developed to measure void fraction for the purpose of objectively identifying flow regimes. The sensor has been used to collect void-fraction data at microgravity conditions aboard the NASA and ESA zero-gravity aircraft. It is shown that the flow regimes can be objectively determined from the probability density functions of the void fraction signals. It was shown that under microgravity conditions four flow regimes exist: bubbly flow, characterized by discrete gas bubbles flowing in the liquid; slug flow, consisting of Taylor bubbles separated by liquid slugs which may or may not contain several small gas bubbles; transitional flow, characterized by the liquid flowing as a film at the tube wall, and the gas phase flowing in the center with the frequent appearance of chaotic, unstable slugs; and annular flow in which the liquid flows as a film along the tube wall and the gas flows uninterrupted through the center. Since many two-phase flow models are flow regime dependent, a method that can accurately and objectively determine flow regimes is required. (authors)

Identification of two-phase flow regimes under variable gravity conditions

Energy Technology Data Exchange (ETDEWEB)

Kamiel S Gabriel [University of Ontario Institute of Technology 2000 Simcoe Street North, Oshawa, ON L1H 7K4 (Canada); Huawei Han [Mechanical Engineering Department, University of Saskatchewan 57 Campus Dr., Saskatoon, Saskatchewan, S7N 5A9 (Canada)

2005-07-01

Full text of publication follows: Two-phase flow is becoming increasingly important as we move into new and more aggressive technologies in the twenty-first century. Some of its many applications include the design of efficient heat transport systems, the transfer and storage of cryogenic fluids, and condensation and flow boiling processes in heat exchangers and energy transport systems. Two-phase flow has many applications in reduced gravity environments experienced in orbiting spacecraft and earth observation satellites. Examples are heat transport systems, the transfer and storage of cryogenic fluids, and condensation and flow boiling processes in heat exchangers. A concave parallel plate capacitance sensor has been developed to measure void fraction for the purpose of objectively identifying flow regimes. The sensor has been used to collect void-fraction data at microgravity conditions aboard the NASA and ESA zero-gravity aircraft. It is shown that the flow regimes can be objectively determined from the probability density functions of the void fraction signals. It was shown that under microgravity conditions four flow regimes exist: bubbly flow, characterized by discrete gas bubbles flowing in the liquid; slug flow, consisting of Taylor bubbles separated by liquid slugs which may or may not contain several small gas bubbles; transitional flow, characterized by the liquid flowing as a film at the tube wall, and the gas phase flowing in the center with the frequent appearance of chaotic, unstable slugs; and annular flow in which the liquid flows as a film along the tube wall and the gas flows uninterrupted through the center. Since many two-phase flow models are flow regime dependent, a method that can accurately and objectively determine flow regimes is required. (authors)

Evaluation of the effects of the radial constant-head boundary in slug tests

Science.gov (United States)

Dai, Yunfeng; Zhou, Zhifang; Zhao, Yanrong; Cui, Ziteng

2015-03-01

A semianalytical model of slug tests, conducted in a completely penetrating well within a radial constant-head boundary, was derived. The model, based on the Cooper et al. (1967) model, estimates the hydraulic conductivity and storage coefficient through the matching of type curves. Type curves of the semianalytical solution were plotted, and the effect of the distance of the radial constant-head boundary is discussed. For different storage coefficients, the critical distances of the effect of the constant-head boundary were determined. The effect of the storage coefficient on the response of the water head in slug tests with a radial constant-head boundary of a certain distance is also shown. To verify the model, laboratory slug-test experiments were carried out using a cylindrical test platform, in which an artificial confined coarse-sand aquifer was built. Pumping tests were also executed using the test platform. The Cooper et al. (1967) model and new semianalytical model were used to analyze measurements; the hydraulic conductivity and storage coefficient determined using the two methods were compared to demonstrate the importance of the radial constant-head boundary. A model considering the inertial effect was also used to analyze the slug-test measurements, and although the water head response did not oscillate greatly, the inertial effect affected the slug-test calculation result. The laboratory experiments indicate that the proposed semianalytical model is reasonable and reliable. Cooper HH, Bredehoeft JD, Papadopulos IS (1967) Response of a finite-diameter well to an instantaneous charge of water, Water Resour Res 3(1):263-269.

Experimental investigation on the droplet entrainment from interfacial waves in air-water horizontal stratified flow

International Nuclear Information System (INIS)

Bae, Byeong Geon; Yun, Byong Jo; Kim, Kyoung Du

2014-01-01

It was mainly due to the fact that droplet entrainment affects the Peak Cladding Temperature (PCT) of the nuclear fuel rod in the Postulated accident conditions of NPP. Recently, droplet entrainment in the horizontally arranged primary piping system for the NPP is of interest because it affects directly the steam binding phenomena in the steam generators. Pan and Hanratty correlation is the only applicable one for the droplet entrainment rate model for horizontal flow. Moreover, there are no efforts for the model development on the basis of the droplet entrainment principal and physics phenomena. More recently, Korea Atomic Energy Research Institute (KAERI) proposed a new mechanistic droplet generation model applicable in the horizontal pipe for the SPACE code. However, constitutive relations in this new model require three model coefficients which have not yet been decided. The purpose of present work is determining three model coefficients by visualization experiment. For these model coefficients, the major physical parameters regarding the interfacial disturbance wave should be measured in this experiments. There are the wave slope, liquid fraction, wave hypotenuse length, wave velocity, wave frequency, and wavelength in the major physical parameters. The experiment was conducted at an air water horizontal rectangular channel with the PIV system. In this study, the experimental conditions were stratified-way flow during the droplet generation. Three coefficients were determined based on several data related to the interfacial wave. Additionally, we manufactured the parallel wire conductance probe to measure the fluctuating water level over time, and compared the wave height measured by the parallel wire conductance probe and image processing from images taken by high speed camera. Experimental investigation was performed for droplet entrainment from phase interface wave in an air-water stratified flow. In the experiments, we measured major physical parameters

An investigation of particle behavior in gas-solid horizontal pipe flow by an extended LDA technique

Energy Technology Data Exchange (ETDEWEB)

Yong Lu; Donald H. Glass; William J. Easson [University of Edinburgh, Edinburgh (United Kingdom). Institute for Materials and Processes

2009-12-15

An extended Laser Doppler Anemometry (LDA) technique has been developed to measure the distributions of particle velocities and particle number rates over a whole pipe cross-section in a dilute pneumatic conveying system. The first extension concentrates on the transform matrix for predicting the laser beams' cross point in a pipe according to the shift coordinate of the 3D computer-controlled traverse system on which the probes of the LDA system were mounted. The second focuses on the proper LDA sample rate for the measurement of gas-solid pipe flow with polydisperse particles. A suitable LDA sample rate should ensure that enough data is recorded in the measurement interval to precisely calculate the particle mean velocity or other statistical values at every sample point. The present study explores the methodology as well as the fundamentals of measurements, using a laser facility, of the cross-sectional distributions of solid phase. In the horizontal gas-solid pipe flow (glass beads less than 110 {mu}m), the experimental data show that the cross-sectional flow patterns of the solid phase can be classified by annulus-like flow describing the axial particle velocity contours and stratified flow characterising particle number rate distribution over a cross-section. Thus, the cross-sectional flow pattern of the solid phase in a horizontal pipe may be annular or stratified dependent on whether the axial particle velocity or particle number rate is the phenomenon studied. 13 refs., 16 figs., 1 tab.

Effectiveness of horizontal air flow fans supporting natural ventilation in a Mediterranean multi-span greenhouse

OpenAIRE

López, Alejandro; Valera, Diego Luis; Molina-Aiz, Francisco Domingo; Peña, Araceli

2013-01-01

Natural ventilation is the most important method of climate control in Mediterranean greenhouses. In this study, the microclimate and air flow inside a Mediterranean greenhouse were evaluated by means of sonic anemometry. Experiments were carried out in conditions of moderate wind (≈ 4.0 m s-1), and at low wind speed (≈ 1.8 m s-1) the natural ventilation of the greenhouse was supplemented by two horizontal air flow fans. The greenhouse is equipped with a single roof vent opening t...

Parameter studies to determine sensitivity of slug impact loads to properties of core surrounding structures

International Nuclear Information System (INIS)

Gvildys, J.

1985-01-01

A sensitivity study of the HCDA slug impact response of fast reactor primary containment to properties of core surrounding structures was performed. Parameters such as the strength of the radial shield material, mass, void, and compressibility properties of the gas plenum material, mass of core material, and mass and compressibility properties of the coolant were used as variables to determine the magnitude of the slug impact loads. The response of the reactor primary containment and the partition of energy were also given. A study was also performed using water as coolant to study the difference in slug impact loads

THERMOSS: a thermohydraulic model of flow stagnation in a horizontal fuel channel

International Nuclear Information System (INIS)

Gulshani, P.; Caplan, M.Z.; Spinks, N.J.

1984-01-01

Following a postulated inlet-side small break in the CANDU reactor, emergency coolant is injected to refull the horizontal fuel channels and remove the decay heat. As part of the accident analysis, the effects of loss of forced circulation during the accident are predicted. A break size exists for which, at the end of pump rundown, the break force balances the natural circulation force and the channel flow is reduced to near zero. The subcooled, stagnant channel condition is referred to as the standing-start condition. Subsequently, the channel coolant boils and stratifies. Eventually the steam flow from the channel heats up the endfitting to the saturation temperature and reaches the vertical feeder. The resulting buoyancy-induced flow then refills the channel. One dimensional, two-fluid conservation equations are solved in closed form to predict the duration of stagnation. In this calculation the channel water level is an important intermediate variable because it determines the amount of steam production

Characteristics of Buoyancy Driven Natural Ventilation through Horizontal Openings

DEFF Research Database (Denmark)

Li, Zhigang

through horizontal openings. Two cases of full-scale measurements of buoyancy driven natural ventilation through horizontal openings are performed: one horizontal opening and one horizontal opening combined with one vertical opening. For the case of one horizontal opening, the measurements are made....... Computational fluid dynamics (CFD) are used to study these two air flow cases. The air flow rate and air flow pattern are predicted and compared with the full-scale measurements. The measurement data are used to compare two CFD models: standard k- ε model and large eddy simulation (LES) model. The cases...... transient, unstable and complex, and the air flow rates oscillate with time. Correlations between the Froude number Fr and the opening ratio L/D are obtained, which is reasonable agreement with Epstein's formula derived from brine-water measurements, but the obtained Fr values show considerable deviations...

Characteristic Value Method of Well Test Analysis for Horizontal Gas Well

Directory of Open Access Journals (Sweden)

Xiao-Ping Li

2014-01-01

Full Text Available This paper presents a study of characteristic value method of well test analysis for horizontal gas well. Owing to the complicated seepage flow mechanism in horizontal gas well and the difficulty in the analysis of transient pressure test data, this paper establishes the mathematical models of well test analysis for horizontal gas well with different inner and outer boundary conditions. On the basis of obtaining the solutions of the mathematical models, several type curves are plotted with Stehfest inversion algorithm. For gas reservoir with closed outer boundary in vertical direction and infinite outer boundary in horizontal direction, while considering the effect of wellbore storage and skin effect, the pseudopressure behavior of the horizontal gas well can manifest four characteristic periods: pure wellbore storage period, early vertical radial flow period, early linear flow period, and late horizontal pseudoradial flow period. For gas reservoir with closed outer boundary both in vertical and horizontal directions, the pseudopressure behavior of the horizontal gas well adds the pseudosteady state flow period which appears after the boundary response. For gas reservoir with closed outer boundary in vertical direction and constant pressure outer boundary in horizontal direction, the pseudopressure behavior of the horizontal gas well adds the steady state flow period which appears after the boundary response. According to the characteristic lines which are manifested by pseudopressure derivative curve of each flow period, formulas are developed to obtain horizontal permeability, vertical permeability, skin factor, reservoir pressure, and pore volume of the gas reservoir, and thus the characteristic value method of well test analysis for horizontal gas well is established. Finally, the example study verifies that the new method is reliable. Characteristic value method of well test analysis for horizontal gas well makes the well test analysis

ΔNp63α induces the expression of FAT2 and Slug to promote tumor invasion

Science.gov (United States)

Dang, Tuyen T.; Westcott, Jill M.; Maine, Erin A.; Kanchwala, Mohammed; Xing, Chao; Pearson, Gray W.

2016-01-01

Tumor invasion can be induced by changes in gene expression that alter cell phenotype. The transcription factor ΔNp63α promotes basal-like breast cancer (BLBC) migration by inducing the expression of the mesenchymal genes Slug and Axl, which confers cells with a hybrid epithelial/mesenchymal state. However, the extent of the ΔNp63α regulated genes that support invasive behavior is not known. Here, using gene expression analysis, ChIP-seq, and functional testing, we find that ΔNp63α promotes BLBC motility by inducing the expression of the atypical cadherin FAT2, the vesicular binding protein SNCA, the carbonic anhydrase CA12, the lipid binding protein CPNE8 and the kinase NEK1, along with Slug and Axl. Notably, lung squamous cell carcinoma migration also required ΔNp63α dependent FAT2 and Slug expression, demonstrating that ΔNp63α promotes migration in multiple tumor types by inducing mesenchymal and non-mesenchymal genes. ΔNp63α activation of FAT2 and Slug influenced E-cadherin localization to cell-cell contacts, which can restrict spontaneous cell movement. Moreover, live-imaging of spheroids in organotypic culture demonstrated that ΔNp63α, FAT2 and Slug were essential for the extension of cellular protrusions that initiate collective invasion. Importantly, ΔNp63α is co-expressed with FAT2 and Slug in patient tumors and the elevated expression of ΔNp63α, FAT2 and Slug correlated with poor patient outcome. Together, these results reveal how ΔNp63α promotes cell migration by directly inducing the expression of a cohort of genes with distinct cellular functions and suggest that FAT2 is a new regulator of collective invasion that may influence patient outcome. PMID:27081041

ESTIMATION OF THE DECREASING OF 137 CS SEDIMENT IN THE SOIL DUE TO HORIZONTAL FLOWING

Directory of Open Access Journals (Sweden)

O. N. Prokof'ev

2008-01-01

Full Text Available The purpose of work is to estimate the possible decreasing of the density of  137 Cs sediment in the soil influenced by the horizontal flowing basing on the analysis of on location observations on the density of  137 Cs sediment in the soil after the Chernobyl accident.

Assessment of RELAP5-3D copyright using data from two-dimensional RPI flow tests

International Nuclear Information System (INIS)

Davis, C.B.

1998-01-01

The capability of the RELAP5-3D copyright computer code to perform multi-dimensional thermal-hydraulic analysis was assessed using data from steady-state flow tests conducted at Rensselaer Polytechnic Institute (RPI). The RPI data were taken in a two-dimensional test section in a low-pressure air/water loop. The test section consisted of a thin vertical channel that simulated a two-dimensional slice through the core of a pressurized water reactor. Single-phase and two-phase flows were supplied to the test section in an asymmetric manner to generate a two-dimensional flow field. A traversing gamma densitometer was used to measure void fraction at many locations in the test section. High speed photographs provided information on the flow patterns and flow regimes. The RPI test section was modeled using the multi-dimensional component in RELAP5-3D Version BF06. Calculations of three RPI experiments were performed. The flow regimes predicted by the base code were in poor agreement with those observed in the tests. The two-phase regions were observed to be in the bubbly and slug flow regimes in the test. However, nearly all of the junctions in the horizontal direction were calculated to be in the stratified flow regime because of the relatively low velocities in that direction. As a result, the void fraction predictions were also in poor agreement with the measured values. Significantly improved results were obtained in sensitivity calculations with a modified version of the code that prevented the horizontal junctions from entering the stratified flow regime. These results indicate that the code's logic in the determination of flow regimes in a multi-dimensional component must be improved. The results of the sensitivity calculations also indicate that RELAP5-3D will provide a significant multi-dimensional hydraulic analysis capability once the flow regime prediction is improved

Characterization of two-phase flow regimes in horizontal tubes using {sup 81m}Kr tracer experiments

Energy Technology Data Exchange (ETDEWEB)

Oriol, Jean [LPAC, CEA Grenoble, 17, rue des Martyrs, 38054 Grenoble Cedex 9 (France); Leclerc, Jean Pierre [Laboratoire des Sciences du Genie Chimique (LSGC), Nancy-Universite, CNRS, BP 20451, F-54001 Nancy (France)], E-mail: leclerc@ensic.inpl-nancy.fr; Berne, Philippe; Gousseau, Georges [L2T, CEA Grenoble, 17, rue des Martyrs, 38054 Grenoble Cedex 9 (France); Jallut, Christian [Universite de Lyon, Universite Lyon 1, LAGEP, UMR CNRS 5007, ESCPE, 43 Bd du 11 novembre 1918, 69622 Villeurbanne Cedex (France); Tochon, Patrice; Clement, Patrice [GRETh, CEA Grenoble, 17, rue des Martyrs, 38054 Grenoble Cedex 9 (France)

2008-10-15

The diagnosis of heat exchangers on duty with respect to flow mal-distributions needs the development of non-intrusive inlet-outlet experimental techniques in order to perform an online fault diagnosis. Tracer experiments are an example of such techniques. They can be applied to mono-phase heat exchangers but also to multi-phase ones. In this case, the tracer experiments are more difficult to perform. In order to check for the capabilities of tracer experiments to be used for the flow mal-distribution diagnosis in the case of multi-phase heat exchangers, we present here a preliminary study on the simplest possible system: two-phase flows in a horizontal tube. {sup 81m}Kr is used as gas tracer and properly collimated NaI (TI) crystal scintillators as detectors. The specific shape of the tracer response allows two-phase flow regimes to be characterized. Signal analysis allows the estimation of the gas phase real average velocity and consequently of the liquid phase real average velocity as well as of the volumetric void fraction. These results are compared successfully to those obtained with liquid phase tracer experiments previously presented by Oriol et al. 2007. Characterization of the two-phase flow regimes and liquid dispersion in horizontal and vertical tubes using coloured tracer and no intrusive optical detector. Chem. Eng. Sci. 63(1), 24-34, as well as to those given by correlations from literature.

Numerical analysis of the flow field in a sloshing tank with a horizontal perforated plate

Science.gov (United States)

Jin, Heng; Liu, Yong; Li, Huajun; Fu, Qiang

2017-08-01

Liquid sloshing is a type of free surface flow inside a partially filled water tank. Sloshing exerts a significant effect on the safety of liquid transport systems; in particular, it may cause large hydrodynamic loads when the frequency of the tank motion is close to the natural frequency of the tank. Perforated plates have recently been used to suppress the violent movement of liquids in a sloshing tank at resonant conditions. In this study, a numerical model based on OpenFOAM (Open Source Field Operation and Manipulation), an open source computed fluid dynamic code, is used to investigate resonant sloshing in a swaying tank with a submerged horizontal perforated plate. The numerical results of the free surface elevations are first verified using experimental data, and then the flow characteristics around the perforated plate and the fluid velocity distribution in the entire tank are examined using numerical examples. The results clearly show differences in sloshing motions under first-order and third-order resonant frequencies. This study provides a better understanding of the energy dissipation mechanism of a horizontal perforated plate in a swaying tank.

Condensation Analysis of Steam/Air Mixtures in Horizontal Tubes

International Nuclear Information System (INIS)

Lee, Kwon Yeong; Bae, Sung Won; Kim, Moo Hwan

2008-01-01

Perhaps the most common flow configuration in which a convective condensation occurs is a flow in a horizontal circular tube. This configuration is encountered in air-conditioning and refrigeration condensers as well as condensers in Rankine power cycles. Although a convective condensation is also sometimes contrived to occur in a co-current vertical downward flow, a horizontal flow is often preferred because the flow can be repeatedly passed through the heat exchanger core in a serpentine fashion without trapping liquid or vapor in the return bends. Many researchers have investigated a in-tube condensation for horizontal heat exchangers. However, almost all of them obtained tube section-averaged data without a noncondensable gas. Recently, Wu and Vierow have experimentally studied the condensation of steam in a horizontal heat exchanger with air present. In order to measure the condenser tube inner surface temperatures and to calculate the local heat fluxes, they developed an innovative thermocouple design that allowed for nonintrusive measurements. Here we developed a theoretical model using the heat and mass analogy to analyze a steam condensation with a noncondensable gas in horizontal tubes

Statistical Analysis of Nitrogen in the Soil of Constructed Wetland with Horizontal Sub-Surface Flow

Directory of Open Access Journals (Sweden)

Jakubaszek Anita

2014-06-01

Full Text Available The removal of nitrogen compounds in constructed wetlands depends on various physical, chemical and biomechanical factors as well as on conditions of the environment. The paper presents the results of a statistical analysis of the depositing of nitrogen at HSSF (horizontal subsurface flow construcred wetland. The results of the substrate showed that the highest contents of nitrogen existed in the surface soil layer up to 20 cm of the depth. Nitrogen accumulation decreased in the deposit with depth, and in the direction of the wastewater flow.

Theoretical study of evaporation heat transfer in horizontal microfin tubes: stratified flow model

Energy Technology Data Exchange (ETDEWEB)

Honda, H; Wang, Y S [Kyushu Univ., Inst. for Materials Chemistry and Engineering, Kasuga, Fukuoka (Japan)

2004-08-01

The stratified flow model of evaporation heat transfer in helically grooved, horizontal microfin tubes has been developed. The profile of stratified liquid was determined by a theoretical model previously developed for condensation in horizontal microfin tubes. For the region above the stratified liquid, the meniscus profile in the groove between adjacent fins was determined by a force balance between the gravity and surface tension forces. The thin film evaporation model was applied to predict heat transfer in the thin film region of the meniscus. Heat transfer through the stratified liquid was estimated by using an empirical correlation proposed by Mori et al. The theoretical predictions of the circumferential average heat transfer coefficient were compared with available experimental data for four tubes and three refrigerants. A good agreement was obtained for the region of Fr{sub 0}<2.5 as long as partial dry out of tube surface did not occur. (Author)

INTERRELATION OF RHOMBICITY AND OCCURRENCE OF INTERNAL CRACKS AT CONTINUOUS CASTING OF SORTED SLUG

Directory of Open Access Journals (Sweden)

Ju. A. Samojlovich

2008-01-01

Full Text Available Analysis of deformations and stresses in cross section of sorted uninterruptedly-casted slugs at their solidification and cooling within limits of crystallizer with the aim of determination of possibilities for occurrence of internal cracks of diagonal type is carried out on basis of mathematical modeling, the peculiarities of the slug skin cooling at its shrinkage and separation from crystallizer wall are revealed.

Ultraviolet Radiation and the Slug Transcription Factor Induce Proinflammatory and Immunomodulatory Mediator Expression in Melanocytes

Directory of Open Access Journals (Sweden)

Stephanie H. Shirley

2012-01-01

Full Text Available Despite extensive investigation, the precise contribution of the ultraviolet radiation (UVR component of sunlight to melanoma etiology remains unclear. UVR induces keratinocytes to secrete proinflammatory and immunomodulatory mediators that promote inflammation and skin tumor development; expression of the slug transcription factor in keratinocytes is required for maximal production of these mediators. In the present studies we examined the possibility that UVR-exposed melanocytes also produce proinflammatory mediators and that Slug is important in this process. Microarray studies revealed that both UVR exposure and Slug overexpression altered transcription of a variety of proinflammatory mediators by normal human melanocytes; some of these mediators are also known to stimulate melanocyte growth and migration. There was little overlap in the spectra of cytokines produced by the two stimuli. However IL-20 was similarly induced by both stimuli and the NFκB pathway appeared to be important in both circumstances. Further exploration of UVR-induced and Slug-dependent pathways of cytokine induction in melanocytes may reveal novel targets for melanoma therapy.

The mucosal toxicity of different benzalkonium chloride analogues evaluated with an alternative test using slugs.

Science.gov (United States)

Adriaens, E; Dierckens, K; Bauters, T G; Nelis, H J; van Goethem, F; Vanparys, P; Remon, J P

2001-07-01

The objective of this study was to evaluate the mucosal toxicity of different benzalkonium chloride (BAC) analogues using slugs as the alternative test organism. The effect of different BAC analogues on the mucosal tissue of slugs was determined from the protein, lactate dehydrogenase, and alkaline phosphatase released from the foot mucosa after treatment. Additionally, mucus production and reduction in body weight of the slugs were measured. The eye irritation potency of the molecules was evaluated with the Bovine Corneal Opacity and Permeability (BCOP) assay. The antimicrobial activity of the different BAC analogues was also assessed. All BAC analogues induced severe damage to the mucosal epithelium of the slugs, and the irritation increased with decreasing alkyl chain length: BAC-C16 or = BAC-C16 > BAC-C12. The BAC-C14 exhibited higher activity than the BAC-mix. The toxicity and activity of BAC analogues depend on the alkyl chain length. The use of BAC-C14 as a conservative agent in pharmaceutical preparations instead of the BAC-mix should be considered.

Microgravity Two-Phase Flow Transition

Science.gov (United States)

Parang, M.; Chao, D.

1999-01-01

Two-phase flows under microgravity condition find a large number of important applications in fluid handling and storage, and spacecraft thermal management. Specifically, under microgravity condition heat transfer between heat exchanger surfaces and fluids depend critically on the distribution and interaction between different fluid phases which are often qualitatively different from the gravity-based systems. Heat transfer and flow analysis in two-phase flows under these conditions require a clear understanding of the flow pattern transition and development of appropriate dimensionless scales for its modeling and prediction. The physics of this flow is however very complex and remains poorly understood. This has led to various inadequacies in flow and heat transfer modeling and has made prediction of flow transition difficult in engineering design of efficient thermal and flow systems. In the present study the available published data for flow transition under microgravity condition are considered for mapping. The transition from slug to annular flow and from bubbly to slug flow are mapped using dimensionless variable combination developed in a previous study by the authors. The result indicate that the new maps describe the flow transitions reasonably well over the range of the data available. The transition maps are examined and the results are discussed in relation to the presumed balance of forces and flow dynamics. It is suggested that further evaluation of the proposed flow and transition mapping will require a wider range of microgravity data expected to be made available in future studies.

Boron dilution transients during natural circulation flow in PWR-Experiments and CFD simulations

Energy Technology Data Exchange (ETDEWEB)

Hoehne, Thomas [Forschungszentrum Dresden-Rossendorf (FZD)-Institute of Safety Research, P.O. Box 510119, D-01314 Dresden (Germany)], E-mail: T.Hoehne@fzd.de; Kliem, Soeren; Rohde, Ulrich; Weiss, Frank-Peter [Forschungszentrum Dresden-Rossendorf (FZD)-Institute of Safety Research, P.O. Box 510119, D-01314 Dresden (Germany)

2008-08-15

Coolant mixing in the cold leg, downcomer and the lower plenum of pressurized water reactors is an important phenomenon mitigating the reactivity insertion into the core. Therefore, mixing of the de-borated slugs with the ambient coolant in the reactor pressure vessel was investigated at the four loops 1:5 scaled Rossendorf coolant mixing model (ROCOM) mixing test facility. In particular thermal hydraulics analyses have shown, that weakly borated condensate can accumulate in the pump loop seal of those loops, which do not receive a safety injection. After refilling of the primary circuit, natural circulation in the stagnant loops can re-establish simultaneously and the de-borated slugs are shifted towards the reactor pressure vessel (RPV). In the ROCOM experiments, the length of the flow ramp and the initial density difference between the slugs and the ambient coolant was varied. From the test matrix experiments with 0 resp. 2% density difference between the de-borated slugs and the ambient coolant were used to validate the CFD software ANSYS CFX. To model the effects of turbulence on the mean flow a higher order Reynolds stress turbulence model was employed and a mesh consisting of 6.4 million hybrid elements was utilized. Only the experiments and CFD calculations with modeled density differences show stratification in the downcomer. Depending on the degree of density differences the less dense slugs flow around the core barrel at the top of the downcomer. At the opposite side, the lower borated coolant is entrained by the colder safety injection water and transported to the core. The validation proves that ANSYS CFX is able to simulate appropriately the flow field and mixing effects of coolant with different densities.

Experimental investigation and physical description of stratified flow in horizontal channels

International Nuclear Information System (INIS)

Staebler, T.

2007-05-01

data which are needed to develop and validate models of horizontal counter-current stratified flows. (orig.)

Application of Ceramic Bond Coating for Reusable Melting Crucible of Metallic Fuel Slugs

Energy Technology Data Exchange (ETDEWEB)

Kim, Ki-Hwan; Song, Hoon; Ko, Young-Mo; Park, Jeong-Yong; Lee, Chan-Bock [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Hong, Ki-Won [Chungnam National University, Daejeon (Korea, Republic of)

2016-10-15

Metal fuel slugs of the driver fuel assembly have been fabricated by injection casting of the fuel alloys under a vacuum state or an inert atmosphere. Traditionally, metal fuel such as a U-Zr alloy system for SFR has been melted in slurry-coated graphite crucibles and cast in slurry-coated quartz tube molds to prevent melt/material interactions. Reactive coatings and porous coatings can be a source of melt contaminations, and fuel losses, respectively. Ceramic Y{sub 2}O{sub 3}, TiC, and TaC coating materials showed no penetration in the protective layer after a melt dipping test. However, the ceramic coating materials showed separations in the coating interface between the substrate and coating layer, or between the coating layer and fuel melt after the dipping test. All plasma-spray coated methods maintained a sound coating state after a dipping test with U-10wt.%Zr melt. A single coating Y{sub 2}O{sub 3}(150) layer and double coating layer of TaC(50)-Y{sub 2}O{sub 3}(100), showed a sound state or little penetration in the protective layer after a dipping test with U-10wt.%Zr-5wt.%RE melt. Injection casting experiments of U-10wt.%Zr and U-10wt.%Zr-5wt.%RE fuel slugs have been performed to investigate the feasibility of a reusable crucible of the metal fuel slugs. U–10wt.%Zr and U–10wt.%Zr–5wt.%RE fuel slugs have been soundly fabricated without significant interactions of the graphite crucibles. Thus, the ceramic plasma-spray coatings are thought to be promising candidate coating methods for a reusable graphite crucible to fabricate metal fuel slugs.

Simulation of the distribution of flow and phases in vertical and horizontal bundles using the ASSERT-4 subchannel code

International Nuclear Information System (INIS)

Carver, M.B.; Tahir, A.; Kiteley, J.C.; Banas, A.O.; Rowe, D.S.; Midvidy, W.I.

1990-01-01

ASSERT-4 is a subchannel code based on the non-equilibrium equations of two-fluid flow. The paper briefly describes the equations and constitutive models used in the code, and reviews a number of validation exercises in which code results were compared to measurements in vertical and horizontal two-phase flows. (orig.)

Statistic characteristics of the gas-liquid flow in a vertical minichannel

Science.gov (United States)

Kozulin, I. A.; Kuznetsov, V. V.

2010-03-01

The gas-liquid upward flow was studied in a rectangular minichannel of 1.75×3.8 mm and length of 0.7 m. The experiments were carried out within the range of the gas superficial velocity from 0.1 to 10 m/s and the liquid superficial velocity from 0.07 to 0.7 m/s for the co-current H2O/CO2 flow under the conditions of saturation. The method for the two-beam laser scanning of structure and determination of statistic characteristics of the two-phase flow was worked through. The slug-bubble, slug, transitional, churn, and annular flows were distinguished. The statistics characteristics of liquid and gas phases motion in a minichannel were obtained for the first time including the velocities of phase motion.

Prediction of evaporation heat transfer coefficient based on gas-liquid two-phase annular flow regime in horizontal microfin tubes

International Nuclear Information System (INIS)

Wang Yueshe; Wang Yanling; Wang, G.-X.; Honda, Hiroshi

2009-01-01

A physical model of gas-liquid two-phase annular flow regime is presented for predicting the enhanced evaporation heat transfer characteristics in horizontal microfin tubes. The model is based on the equivalence of a periodical distortion of the disturbance wave in the substrate layer. Corresponding to the stratified flow model proposed previously by authors, the dimensionless quantity Fr 0 = G/[gd e ρ v (ρ l - ρ v )] 0.5 may be used as a measure for determining the applicability of the present theoretical model, which was used to restrict the transition boundary between the stratified-wavy flow and the annular/intermittent flows. Comparison of the prediction of the circumferential average heat transfer coefficient with available experimental data for four tubes and three refrigerants reveals that a good agreement is obtained or the trend is better than that of the previously developed stratified flow model for Fr 0 > 4.0 as long as the partial dry out of tube does not occur. Obviously, the developed annular model is applicable and reliable for evaporation in horizontal microfin tubes under the case of high heat flux and high mass flux.

Prediction of evaporation heat transfer coefficient based on gas-liquid two-phase annular flow regime in horizontal microfin tubes

Energy Technology Data Exchange (ETDEWEB)

Wang Yueshe, E-mail: wangys@mail.xjtu.edu.cn [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Yanling, Wang [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Wang, G -X [Mechanical Engineering Department, The University of Akron, Akron, OH 44325-3903 (United States); Honda, Hiroshi [Kyushu University, 337 Kasuya-machi, Kasuya-gun, Kukuoka 811-2307 (Japan)

2009-10-15

A physical model of gas-liquid two-phase annular flow regime is presented for predicting the enhanced evaporation heat transfer characteristics in horizontal microfin tubes. The model is based on the equivalence of a periodical distortion of the disturbance wave in the substrate layer. Corresponding to the stratified flow model proposed previously by authors, the dimensionless quantity Fr{sub 0} = G/[gd{sub e}{rho}{sub v}({rho}{sub l} - {rho}{sub v})]{sup 0.5} may be used as a measure for determining the applicability of the present theoretical model, which was used to restrict the transition boundary between the stratified-wavy flow and the annular/intermittent flows. Comparison of the prediction of the circumferential average heat transfer coefficient with available experimental data for four tubes and three refrigerants reveals that a good agreement is obtained or the trend is better than that of the previously developed stratified flow model for Fr{sub 0} > 4.0 as long as the partial dry out of tube does not occur. Obviously, the developed annular model is applicable and reliable for evaporation in horizontal microfin tubes under the case of high heat flux and high mass flux.

Mixed convection boundary-layer flow from a horizontal circular cylinder with a constant surface heat flux

Energy Technology Data Exchange (ETDEWEB)

Nazar, R.; Amin, N. [Department of Mathematics, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Pop, I. [Faculty of Mathematics, University of Cluj, R-3400 Cluj, CP 253 (Romania)

2004-02-01

The laminar mixed convection boundary-layer flow of a viscous and incompressible fluid past a horizontal circular cylinder, which is maintained at a constant heat flux and is placed in a stream flowing vertically upward has been theoretically studied in this paper. The solutions for the flow and heat transfer characteristics are evaluated numerically for different values of the mixed convection parameter {lambda} with the Prandtl number Pr = 1 and 7, respectively. It is found, as for the case of a heated or cooled cylinder, considered by Merkin [5], that assisting flow delays separation of the boundary-layer and can, if the assisting flow is strong enough, suppress it completely. The opposing flow, on the other side, brings the separation point nearer to the lower stagnation point and for sufficiently strong opposing flows there will not be a boundary-layer on the cylinder. (orig.)

Entropy Generation on Nanofluid Flow through a Horizontal Riga Plate

Directory of Open Access Journals (Sweden)

Tehseen Abbas

2016-06-01

Full Text Available In this article, entropy generation on viscous nanofluid through a horizontal Riga plate has been examined. The present flow problem consists of continuity, linear momentum, thermal energy, and nanoparticle concentration equation which are simplified with the help of Oberbeck-Boussinesq approximation. The resulting highly nonlinear coupled partial differential equations are solved numerically by means of the shooting method (SM. The expression of local Nusselt number and local Sherwood number are also taken into account and discussed with the help of table. The physical influence of all the emerging parameters such as Brownian motion parameter, thermophoresis parameter, Brinkmann number, Richardson number, nanoparticle flux parameter, Lewis number and suction parameter are demonstrated graphically. In particular, we conferred their influence on velocity profile, temperature profile, nanoparticle concentration profile and Entropy profile.

Study of dynamics of two-phase flow through a minichannel by means of recurrences

Science.gov (United States)

Litak, Grzegorz; Górski, Grzegorz; Mosdorf, Romuald; Rysak, Andrzej

2017-05-01

By changing air and water flow rates in the two-phase (air-water) flow through a minichannel, we observed the evolution of air bubbles and slugs patterns. This spatiotemporal behaviour was identified qualitatively by using a digital camera. Simultaneously, we provided a detailed analysis of these phenomena by using the corresponding sequences of light transmission time series recorded with a laser-phototransistor sensor. To distinguish particular patterns, we used recurrence plots and recurrence quantification analysis. Finally, we showed that the maxima of various recurrence quantificators obtained from the laser time series could follow the bubble and slugs patterns in studied ranges of air and water flows.

Expression of transcription factors Slug in the lens epithelial cells undergoing epithelial-mesenchymal transition induced by connective tissue growth factor

Directory of Open Access Journals (Sweden)

Ying-Na Wang

2015-10-01

Full Text Available AIM:To investigate the expression of transcription factors Slug in human lens epithelial cells (HLECs undergoing epithelial-mesenchymal transition (EMT induced by connective tissue growth factor (CTGF.METHODS: HLECs were treated with CTGF of different concentrations (20, 50 and 100 ng/mL or without CTGF (control for 24h. The morphological changes of HLECs were analysed by microscopy. The expression and cellular localization of Slug was evaluated by immumo-fluorescence. Expressions of Slug, E-cadherin and alpha smooth muscle actin (α-SMA were further determined by Western blot analysis. RESULTS: HLECs showed spidle fibrolasts-like characteristics and loosely connected each other after CTGF treatment. The immuno-fluorescence staining indicated that Slug was localized in the nuclei and its expression was induced by CTGF. The relative expressions of Slug protein were 1.64±0.11, 1.96 ±0.03, 3.12 ±0.10, and 4.08±0.14, respectively, in response to control group and treatment with CTGF of 20, 50 and 100 ng/mL (F=443.86, PCONCLUSION: Transcription factor Slug may be involved in EMT of HLECs induced by CTGF in vitro.

Analysis of slug tests in formations of high hydraulic conductivity.

Science.gov (United States)

Butler, James J; Garnett, Elizabeth J; Healey, John M

2003-01-01

A new procedure is presented for the analysis of slug tests performed in partially penetrating wells in formations of high hydraulic conductivity. This approach is a simple, spreadsheet-based implementation of existing models that can be used for analysis of tests from confined or unconfined aquifers. Field examples of tests exhibiting oscillatory and nonoscillatory behavior are used to illustrate the procedure and to compare results with estimates obtained using alternative approaches. The procedure is considerably simpler than recently proposed methods for this hydrogeologic setting. Although the simplifications required by the approach can introduce error into hydraulic-conductivity estimates, this additional error becomes negligible when appropriate measures are taken in the field. These measures are summarized in a set of practical field guidelines for slug tests in highly permeable aquifers.

Simulation of Turbulent Wake at Mixing of Two Confined Horizontal Flows

Directory of Open Access Journals (Sweden)

Rok Krpan

2018-01-01

Full Text Available The development of a turbulent mixing layer at mixing of two horizontal water streams with slightly different densities is studied by the means of numerical simulation. The mixing of such flows can be modelled as the flow of two components, where the concentration of one component in the mixing region is described as a passive scalar. The velocity field remains common over the entire computational domain, where the density and viscosity difference due to the concentration mainly affects the turbulent fluctuations in the mixing region. The numerical simulations are performed with the open source code OpenFOAM using two different approaches for turbulence modelling, Reynolds Averaged Navier Stokes equations (RANS and Large Eddy Simulation (LES. The simulation results are discussed and compared with the benchmark experiment obtained within the frame of OECD/NEA benchmark test. A good agreement with experimental results is obtained in the case of the single liquid experiment. A high discrepancy between the simulated and the experimental velocity fluctuations in the case of mixing of the flows with the slightly different densities and viscosities triggered a systematic investigation of the modelling approaches that helped us to find out and interpret the main reasons for the disagreement.

Stereoscopic particle image velocimetry investigations of the mixed convection exchange flow through a horizontal vent

Science.gov (United States)

Varrall, Kevin; Pretrel, Hugues; Vaux, Samuel; Vauquelin, Olivier

2017-10-01

The exchange flow through a horizontal vent linking two compartments (one above the other) is studied experimentally. This exchange is here governed by both the buoyant natural effect due to the temperature difference of the fluids in both compartments, and the effect of a (forced) mechanical ventilation applied in the lower compartment. Such a configuration leads to uni- or bi-directional flows through the vent. In the experiments, buoyancy is induced in the lower compartment thanks to an electrical resistor. The forced ventilation is applied in exhaust or supply modes and three different values of the vent area. To estimate both velocity fields and flow rates at the vent, measurements are realized at thermal steady state, flush the vent in the upper compartment using stereoscopic particle image velocimetry (SPIV), which is original for this kind of flow. The SPIV measurements allows the area occupied by both upward and downward flows to be determined.

Developmental assessment of RELAP5/MOD3 code against ROSA-IV/TPTF horizontal two-phase flow experiments

International Nuclear Information System (INIS)

Kukita, Yutaka; Asaka, Hideaki; Anoda, Yoshinari; Ishiguro, Misako; Tasaka, Kanji; Mimura, Yuichi; Nemoto, Toshiyuki.

1990-03-01

A developmental version of the RELAP5/Mod3 code (as of June 1989) was assessed for accuracy using experimental data taken for high-pressure (7MPa) steam-water two-phase flow in a large-diameter (0.18 m) horizontal-pipe test section of the ROSA-IV Two-Phase Flow Test Facility (TPTF). The agreement between the measured and calculated test section void fractions was much better than that for the previous generation of RELAP5 (MOD2). The improvement was achieved primarily due to the code changes with respect to the flow stratification criterion and interfacial-drag calculation scheme. (author)

Heat transfer characteristics of liquid-gas Taylor flows incorporating microencapsulated phase change materials

International Nuclear Information System (INIS)

Howard, J A; Walsh, P A

2014-01-01

This paper presents an investigation on the heat transfer characteristics associated with liquid-gas Taylor flows in mini channels incorporating microencapsulated phase change materials (MPCM). Taylor flows have been shown to result in heat transfer enhancements due to the fluid recirculation experienced within liquid slugs which is attributable to the alternating liquid slug and gas bubble flow structure. Microencapsulated phase change materials (MPCM) also offer significant potential with increased thermal capacity due to the latent heat required to cause phase change. The primary aim of this work was to examine the overall heat transfer potential associated with combining these two novel liquid cooling technologies. By investigating the local heat transfer characteristics, the augmentation/degradation over single phase liquid cooling was quantified while examining the effects of dimensionless variables, including Reynolds number, liquid slug length and gas void fraction. An experimental test facility was developed which had a heated test section and allowed MPCM-air Taylor flows to be subjected to a constant heat flux boundary condition. Infrared thermography was used to record high resolution experimental wall temperature measurements and determine local heat transfer coefficients from the thermal entrance point. 30.2% mass particle concentration of the MPCM suspension fluid was examined as it provided the maximum latent heat for absorption. Results demonstrate a significant reduction in experimental wall temperatures associated with MPCM-air Taylor flows when compared with the Graetz solution for conventional single phase coolants. Total enhancement in the thermally developed region is observed to be a combination of the individual contributions due to recirculation within the liquid slugs and also absorption of latent heat. Overall, the study highlights the potential heat transfer enhancements that are attainable within heat exchange devices employing MPCM

Ultraviolet Radiation and the Slug Transcription Factor Induce Pro inflammatory and Immunomodulatory Mediator Expression in Melanocytes

International Nuclear Information System (INIS)

Shirley, S. H.; Kusewitt, D. F.; Grimm, E. A.

2012-01-01

Despite extensive investigation, the precise contribution of the ultraviolet radiation (UVR) component of sunlight to melanoma etiology remains unclear. UVR induces keratinocytes to secrete pro inflammatory and immunomodulatory mediators that promote inflammation and skin tumor development; expression of the slug transcription factor in keratinocytes is required for maximal production of these mediators. In the present studies we examined the possibility that UVR-exposed melanocytes also produce pro inflammatory mediators and that Slug is important in this process. Micro array studies revealed that both UVR exposure and Slug overexpression altered transcription of a variety of pro inflammatory mediators by normal human melanocytes; some of these mediators are also known to stimulate melanocyte growth and migration. There was little overlap in the spectra of cytokines produced by the two stimuli. However IL-20 was similarly induced by both stimuli and the NFκB pathway appeared to be important in both circumstances. Further exploration of UVR-induced and Slug-dependent pathways of cytokine induction in melanocytes may reveal novel targets for melanoma therapy.

Velocity and turbulence measurements of oil-water flow in horizontal and slightly inclined pipes using PIV

OpenAIRE

Kumara, W.A.S.; Halvorsen, Britt; Melaaen, Morten Christian

2009-01-01

Oil-water flows in horizontal and slightly inclined pipes are investigated using Particle Image Velocimetry (PIV). PIV offers a powerful non-invasive tool to study such flow fields. The experiments are conducted in a 15 m long, 56 mm diameter, inclinable steel pipe using Exxsol D60 oil (viscosity 1.64 mPa s, density 790 kg/m3) and water (viscosity 1.0 mPa s, density 996 kg/m3) as test fluids. The test pipe inclination is changed in the range from 5° upward to 5° downward. The experiments are ...

Experimental study for flow regime of downward air-water two-phase flow in a vertical narrow rectangular channel

Energy Technology Data Exchange (ETDEWEB)

Kim, T. H.; Yun, B. J.; Jeong, J. H. [Pusan National University, Geunjeong-gu, Busan (Korea, Republic of)

2015-05-15

Studies were mostly about flow in upward flow in medium size circular tube. Although there are great differences between upward and downward flow, studies on vertical upward flow are much more active than those on vertical downward flow in a channel. In addition, due to the increase of surface forces and friction pressure drop, the pattern of gas-liquid two-phase flow bounded to the gap of inside the rectangular channel is different from that in a tube. The downward flow in a rectangular channel is universally applicable to cool the plate type nuclear fuel in research reactor. The sub-channel of the plate type nuclear fuel is designed with a few millimeters. Downward air-water two-phase flow in vertical rectangular channel was experimentally observed. The depth, width, and length of the rectangular channel is 2.35 mm, 66.7 mm, and 780 mm, respectively. The test section consists of transparent acrylic plates confined within a stainless steel frame. The flow patterns of the downward flow in high liquid velocity appeared to be similar to those observed in previous studies with upward flow. In downward flow, the transition lines for bubbly-slug and slug-churn flow shift to left in the flow regime map constructed with abscissa of the superficial gas velocity and ordinate of the superficial liquid velocity. The flow patterns observed with downward flow at low liquid velocity are different from those with upward flow.

Experimental study of inverted-annular-flow hydrodynamics utilizing an adiabatic simulation

International Nuclear Information System (INIS)

De Jarlais, G.

1983-03-01

In experiments, inverted annular flow was simulated adiabatically with turbulent water jets, issuing downward from long aspect nozzles, enclosed in gas annuli. Velocities, diameters, and gas species were varied, and core jet length, shape, break-up mode, and dispersed-core droplet sizes were recorded at approximately 750 data points. Inverted annular flow was observed to develop into inverted slug flow at low relative velocities, and into dispersed droplet flow at high relative velocities. For both of the above transitions from inverted annular flow, correlations for core jet length were developed by extending work done on free liquid jets to include this new, coaxial, jet disintegration phenomenon. Jet break-up length is correlated as a function of jet diameter, jet Reynolds number, jet Weber number, void fraction, and gas Weber number. Correlations for core shape, break-up mechanisms and dispersed core droplet size for the case of transition to inverted slug flow were developed

Characteristics of two-phase flow pattern transitions and pressure drop of five refrigerants in horizontal circular small tubes

Energy Technology Data Exchange (ETDEWEB)

Pamitran, A.S. [Department of Mechanical Engineering, University of Indonesia, Kampus Baru UI, Depok 16424 (Indonesia); Choi, Kwang-Il [Graduate School, Chonnam National University, San 96-1, Dunduk-Dong, Yeosu, Chonnam 550-749 (Korea); Oh, Jong-Taek [Department of Refrigeration and Air Conditioning Engineering, Chonnam National University, San 96-1, Dunduk-Dong, Yeosu, Chonnam 550-749 (Korea); Hrnjak, Pega [Department of Mechanical Science and Engineering, ACRC, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, IL 61801 (United States)

2010-05-15

An experimental investigation on the characteristics of two-phase flow pattern transitions and pressure drop of R-22, R-134a, R-410A, R-290 and R-744 in horizontal small stainless steel tubes of 0.5, 1.5 and 3.0 mm inner diameters is presented. Experimental data were obtained over a heat flux range of 5-40 kW/m{sup 2}, mass flux range of 50-600 kg/(m{sup 2} s), saturation temperature range of 0-15 C, and quality up to 1.0. Experimental data were evaluated with Wang et al. and Wojtan et al. [Wang, C.C., Chiang, C.S., Lu, D.C., 1997. Visual observation of two-phase flow pattern of R-22, R-134a, and R-407C in a 6.5-mm smooth tube. Exp. Therm. Fluid Sci. 15, 395-405; Wojtan, L., Ursenbacher, T., Thome, J.R., 2005. Investigation of flow boiling in horizontal tubes: part I - a new diabatic two-phase flow pattern map. Int. J. Heat Mass Transfer 48, 2955-2969.] flow pattern maps. The effects of mass flux, heat flux, saturation temperature and inner tube diameter on the pressure drop of the working refrigerants are reported. The experimental pressure drop was compared with the predictions from some existing correlations. A new two-phase pressure drop model that is based on a superposition model for two-phase flow boiling of refrigerants in small tubes is presented. (author)

Flow map and measurement of void fraction and heat transfer coefficient using an image analysis technique for flow boiling of water in a silicon microchannel

International Nuclear Information System (INIS)

Singh, S G; Duttagupta, S P; Jain, A; Sridharan, A; Agrawal, Amit

2009-01-01

The present work focuses on the generation of the flow regime map for two-phase water flow in microchannels of a hydraulic diameter of 140 µm. An image analysis algorithm has been developed and utilized to obtain the local void fraction. The image processing technique is also employed to identify and estimate the percentage of different flow regimes and heat transfer coefficient, as a function of position, heat flux and mass flow rate. Both void fraction and heat transfer coefficient are found to increase monotonically along the length of the microchannel. At low heat flux and low flow rates, bubbly, slug and annular flow regimes are apparent. However, the flow is predominately annular at high heat flux and high flow rate. A breakup of the flow frequency suggests that the flow is bistable in the annular regime, in that at a fixed location, the flow periodically switches from single-phase liquid to annular and vice versa. Otherwise, the occurrence of three regimes—single-phase liquid, bubbly and slug are observed. These results provide several useful insights about two-phase flow in microchannels besides being of fundamental interest

A mini slug test method for determination of a local hydraulic conductivity of an unconfined sandy aquifer

DEFF Research Database (Denmark)

Hinsby, Klaus; Bjerg, Poul Løgstrup; Andersen, Lars J.

1992-01-01

distributed measurements of a local hydraulic conductivity at a tracer test site at Vejen, Denmark. The mini slug test results calculated by a modified Dax slug test analysing method, applying the elastic storativity in the Dax equations instead of the specific yield, are in good accordance with the results...

The displacement of oil polymer slug considering of adsorption effects; Deslocamento de oleo por banco de polimero considerando os efeitos de adsorcao

Energy Technology Data Exchange (ETDEWEB)

Ribeiro, Priscila M. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Pires, Adolfo P. [Universidade Estadual do Norte Fluminense (UENF), Campos dos Goytacazes, RJ (Brazil)

2008-07-01

Among different Enhanced Oil Recovery methods, the injection of chemical solutions plays an important role in mature fields additional recovery. The continuous injection of this kind of fluid would be very expensive, so, the injection of chemical slugs is an attractive alternative to improve the recovery of mature oil fields. Analytical models for 1-D displacement of oil by water with chemical compounds have been developed since the 1960's. This paper presents the 1-D analytical solution of the injection of a chemical slug followed by water drive into an oil reservoir. A flow potential associated with the conservation of water phase is introduced and used as a new independent variable instead of time. This technique permits splitting the system of equations into a thermodynamic system and one transport equation. Another important application of these solutions is the prediction of chemical flooding regardless of the transport properties (relative permeabilities and viscosities). (author)

Experimental study on two-phase flow in horizontal duct using a visualization technique

International Nuclear Information System (INIS)

Oliveira, Livia A.; Tomas, Bruno T.; Cunha Filho, Jurandyr S.; Su, Jian

2009-01-01

In this paper an experimental study is performed for visualization of water-air two phase flow, stratified and intermittent, in a 51 mm internal diameter circular section horizontal tube. The study consists in filming a water-air mixture passin by a transparent interval of the tube, using a high speed camera. After that, the obtained images are analysed frame after frame and then, data are extracted of weight of gas-liquid interfaces, length and gas bubbles speeds. Then, these data are verified with experimental and theoretical correlations available in the literature

Correlation of Slug gene expression with lymph node metastasis and invasion molecule expression in oral squamous cell carcinoma tissue

Directory of Open Access Journals (Sweden)

Shan-Ming Lu

2017-10-01

Full Text Available Objective: To study the correlation of Slug gene expression with lymph node metastasis and invasion molecule expression in oral squamous cell carcinoma tissue. Methods: Oral squamous cell carcinoma tissue surgical removed in Affiliated Stomatological Hospital of Nanjing Medical University between March 2015 and April 2017 was selected and divided into the oral squamous cell carcinoma tissue with neck lymph node metastasis and the oral squamous cell carcinoma tissues without lymph node metastasis according to the condition of lymph node metastasis. The expression of Slug, epithelial-mesenchymal transition molecules and invasion molecules in the oral squamous cell carcinoma tissue were detected. Results: Slug, N-cadherin, Vimentin, CD147, OPN, GRP78, SDF-1 and CXCR4 protein expression in oral squamous cell carcinoma tissue with neck lymph node metastasis were significantly higher than those in oral squamous cell carcinoma tissue without lymph node metastasis while E-cadherin, P120ctn and ZO-1 protein expression were significantly lower than those in oral squamous cell carcinoma tissue without lymph node metastasis; N-cadherin, Vimentin, CD147, OPN, GRP78, SDF-1 and CXCR4 protein expression in oral squamous cell carcinoma tissue with high Slug expression were significantly higher than those in oral squamous cell carcinoma tissue with low Slug expression while E-cadherin, P120ctn and ZO-1 protein expression were significantly lower than those in oral squamous cell carcinoma tissue with low Slug expression. Conclusion: The highly expressed Slug in oral squamous cell carcinoma tissue can promote the epithelial-mesenchymal transition and invasion of the cells to participate in the lymph node metastasis of tumor cells.

Flow regime mapping of vertical two-phase downflow in a ribbed annulus

International Nuclear Information System (INIS)

Kielpinski, A.L.

1992-01-01

Two-phase flow regimes have been mapped for vertical, cocurrent downflow in a narrow annulus which is partially segmented by the presence of longitudinal ribs. This geometry and flow condition has application to the analysis of a Large-Break Loss of Coolant Accident (LB-LOCA) in the production K-Reactor at the Savannah River Site (SRS). The ribbed annular geometry, particularly the presence of non-sealing ribs, gives rise to some unique phenomenological features. The flow behavior is influenced by the partial segmentation of the annulus into four quadrants or subchannels. A random element is induced by the natural bowing of the slender tubes; the width of the azimuthal flow path between two subchannels at a given axial location is indeterminate, and can take on any value between zero and the maximum clearance of 7.6 x l0 -4 m. When the rib gap is zero at a given location, it is at a maximum 180P away at the same axial location. The range of rib gaps is spanned in a single test section, as it would be also in a reactor assembly. As a result of these effects, flow regime maps obtained by other researchers for downflow in annuli are not accurate for defining flow regimes in a ribbed annulus. Flow regime transitions similar to those noted by, e.g., Bamea, were observed; the locations of these transitions were displaced with respect to the transition equations derived by Bamea. Experimental bubble rise velocity measurements were also obtained in the same test section. The bubble rise velocities were much higher than expected from the theory developed for slug bubbles in tubes, unribbed annuli, and rectangular channels. An elliptical-cap bubble rises faster than a slug bubble of the same area. Large, slug-shaped bubbles injected into the test section were observed to reduce in size as they rose, due to interaction with a longitudinal rib. They thereby adopted a shape more like an elliptical-cap bubble, hence rising faster than the original slug bubble

Visualized investigation on flow regimes for vertical upward steam–water flow in a heated narrow rectangular channel

International Nuclear Information System (INIS)