Interferometric phase velocity measurements in the auroral electrojet

International Nuclear Information System (INIS)

Labelle, J.; Kinter, P.M.; Kelley, M.C.

1986-01-01

A double-probe electric field detector and two spatially separated fixed-bias Langmuir probes were flown on a Taurus-Tomahawk sounding rocket launched from Poker Flat Research Range in March 1982. Interesting wave data have been obtained from about 10 s of the downleg portion of the flight during which the rocket passed through the auroral electrojet. Here the electric field receiver and both density fluctuation (deltan/n) receivers responded to a broad band of turbulence centered at 105 km altitude and at frequencies generally below 4 kHz. Closer examination of the two deltan/n turbulent waveforms reveals that they are correlated, and from the phase difference between the two signals, the phase velocity of the waves in the rocket reference frame is inferred. The magnitude and direction of the observed phase velocity are consistent either with waves which travel at the ion sound speed (Csub(s)) or with waves which travel at the electron drift velocity. The observed phase velocity varies by about 50% over a 5 km altitude range - an effect which probably results from shear in the zonal neutral wind, although unfortunately no simultaneous neutral wind measurements exist to confirm this. (author)

Measurement of transient two-phase flow velocity using statistical signal analysis of impedance probe signals

International Nuclear Information System (INIS)

Leavell, W.H.; Mullens, J.A.

1981-01-01

A computational algorithm has been developed to measure transient, phase-interface velocity in two-phase, steam-water systems. The algorithm will be used to measure the transient velocity of steam-water mixture during simulated PWR reflood experiments. By utilizing signals produced by two, spatially separated impedance probes immersed in a two-phase mixture, the algorithm computes the average transit time of mixture fluctuations moving between the two probes. This transit time is computed by first, measuring the phase shift between the two probe signals after transformation to the frequency domain and then computing the phase shift slope by a weighted least-squares fitting technique. Our algorithm, which has been tested with both simulated and real data, is able to accurately track velocity transients as fast as 4 m/s/s

Modelling of two-phase flow based on separation of the flow according to velocity

International Nuclear Information System (INIS)

Narumo, T.

1997-01-01

The thesis concentrates on the development work of a physical one-dimensional two-fluid model that is based on Separation of the Flow According to Velocity (SFAV). The conventional way to model one-dimensional two-phase flow is to derive conservation equations for mass, momentum and energy over the regions occupied by the phases. In the SFAV approach, the two-phase mixture is divided into two subflows, with as distinct average velocities as possible, and momentum conservation equations are derived over their domains. Mass and energy conservation are treated equally with the conventional model because they are distributed very accurately according to the phases, but momentum fluctuations follow better the flow velocity. Submodels for non-uniform transverse profile of velocity and density, slip between the phases within each subflow and turbulence between the subflows have been derived. The model system is hyperbolic in any sensible flow conditions over the whole range of void fraction. Thus, it can be solved with accurate numerical methods utilizing the characteristics. The characteristics agree well with the used experimental data on two-phase flow wave phenomena Furthermore, the characteristics of the SFAV model are as well in accordance with their physical counterparts as of the best virtual-mass models that are typically optimized for special flow regimes like bubbly flow. The SFAV model has proved to be applicable in describing two-phase flow physically correctly because both the dynamics and steady-state behaviour of the model has been considered and found to agree well with experimental data This makes the SFAV model especially suitable for the calculation of fast transients, taking place in versatile form e.g. in nuclear reactors

On the use of nuclear magnetic resonance to measure velocity and its fluctuations in single-phase and two-phase flows

International Nuclear Information System (INIS)

Jullien, Pierre

2013-01-01

This work deals with the use of NMR to measure velocity and its fluctuations in single-phase and two-phase flows. PGSE and imaging sequences have been used to determine the velocity distributions in upward turbulent pipe flows. NMR signals have been analysed in detail and the main artifacts have been characterized and suppressed. The measuring technique has been validated by comparison with a reference published data. A first comparison to 'homemade' hot-wire results in single-phase flow of water is presented and is very promising. Preliminary NMR results in two-phase flows emphasize the interest of NMR to benchmark velocity measurements in two-phase flows. Prospects of research have been identified, which will pave the way for the sequel of this research. (author) [fr

Automated measurement and classification of pulmonary blood-flow velocity patterns using phase-contrast MRI and correlation analysis.

Science.gov (United States)

van Amerom, Joshua F P; Kellenberger, Christian J; Yoo, Shi-Joon; Macgowan, Christopher K

2009-01-01

An automated method was evaluated to detect blood flow in small pulmonary arteries and classify each as artery or vein, based on a temporal correlation analysis of their blood-flow velocity patterns. The method was evaluated using velocity-sensitive phase-contrast magnetic resonance data collected in vitro with a pulsatile flow phantom and in vivo in 11 human volunteers. The accuracy of the method was validated in vitro, which showed relative velocity errors of 12% at low spatial resolution (four voxels per diameter), but was reduced to 5% at increased spatial resolution (16 voxels per diameter). The performance of the method was evaluated in vivo according to its reproducibility and agreement with manual velocity measurements by an experienced radiologist. In all volunteers, the correlation analysis was able to detect and segment peripheral pulmonary vessels and distinguish arterial from venous velocity patterns. The intrasubject variability of repeated measurements was approximately 10% of peak velocity, or 2.8 cm/s root-mean-variance, demonstrating the high reproducibility of the method. Excellent agreement was obtained between the correlation analysis and radiologist measurements of pulmonary velocities, with a correlation of R2=0.98 (P<.001) and a slope of 0.99+/-0.01.

Modelling of two-phase flow based on separation of the flow according to velocity

Energy Technology Data Exchange (ETDEWEB)

Narumo, T. [VTT Energy, Espoo (Finland). Nuclear Energy

1997-12-31

The thesis concentrates on the development work of a physical one-dimensional two-fluid model that is based on Separation of the Flow According to Velocity (SFAV). The conventional way to model one-dimensional two-phase flow is to derive conservation equations for mass, momentum and energy over the regions occupied by the phases. In the SFAV approach, the two-phase mixture is divided into two subflows, with as distinct average velocities as possible, and momentum conservation equations are derived over their domains. Mass and energy conservation are treated equally with the conventional model because they are distributed very accurately according to the phases, but momentum fluctuations follow better the flow velocity. Submodels for non-uniform transverse profile of velocity and density, slip between the phases within each subflow and turbulence between the subflows have been derived. The model system is hyperbolic in any sensible flow conditions over the whole range of void fraction. Thus, it can be solved with accurate numerical methods utilizing the characteristics. The characteristics agree well with the used experimental data on two-phase flow wave phenomena Furthermore, the characteristics of the SFAV model are as well in accordance with their physical counterparts as of the best virtual-mass models that are typically optimized for special flow regimes like bubbly flow. The SFAV model has proved to be applicable in describing two-phase flow physically correctly because both the dynamics and steady-state behaviour of the model has been considered and found to agree well with experimental data This makes the SFAV model especially suitable for the calculation of fast transients, taking place in versatile form e.g. in nuclear reactors. 45 refs. The thesis includes also five previous publications by author.

A two-phase pressure drop calculation code based on a new method with a correlation factor obtained from an assessment of existing correlations

International Nuclear Information System (INIS)

Chun, Moon Hyun; Oh, Jae Guen

1989-01-01

Ten methods of the total two-phase pressure drop prediction based on five existing models and correlations have been examined for their accuracy and applicability to pressurized water reactor conditions. These methods were tested against 209 experimental data of local and bulk boiling conditions: Each correlations were evaluated for different ranges of pressure, mass velocity and quality, and best performing models were identified for each data subsets. A computer code entitled 'K-TWOPD' has been developed to calculate the total two phase pressure drop using the best performing existing correlations for a specific property range and a correction factor to compensate for the predicted error of the selected correlations. Assessment of this code shows that the present method fits all the available data within ±11% at a 95% confidence level compared with ± 25% for the existing correlations. (Author)

Propagation of the Semidiurnal Internal Tide: Phase Velocity Versus Group Velocity

Science.gov (United States)

Zhao, Zhongxiang

2017-12-01

The superposition of two waves of slightly different wavelengths has long been used to illustrate the distinction between phase velocity and group velocity. The first-mode M2 and S2 internal tides exemplify such a two-wave model in the natural ocean. The M2 and S2 tidal frequencies are 1.932 and 2 cycles per day, respectively, and their superposition forms a spring-neap cycle in the semidiurnal band. The spring-neap cycle acts like a wave, with its frequency, wave number, and phase being the differences of the M2 and S2 internal tides. The spring-neap cycle and energy of the semidiurnal internal tide propagate at the group velocity. Long-range propagation of M2 and S2 internal tides in the North Pacific is observed by satellite altimetry. Along a 3,400 km beam spanning 24°-54°N, the M2 and S2 travel times are 10.9 and 11.2 days, respectively. For comparison, it takes the spring-neap cycle 21.1 days to travel over this distance. Spatial maps of the M2 phase velocity, the S2 phase velocity, and the group velocity are determined from phase gradients of the corresponding satellite observed internal tide fields. The observed phase and group velocities agree with theoretical values estimated using the World Ocean Atlas 2013 annual-mean ocean stratification.

Determination of drift-flux velocity as a function of two-phase flow patterns

International Nuclear Information System (INIS)

Austregesilo Filho, H.

1986-01-01

A method is suggested for the calculation of drift-flux velocity as a function of two-phase flow patterns determined analytically. This model can be introduced in computer codes for thermal hydraulic analyses based mainly on homogeneous assumptions, in order to achieve a more realis tic description of two-phase flow phenomena, which is needed for the simulation of accidents in nuclear power plants for which phase separation effects are dominant, e.g., small break accidents. (Author) [pt

Effects of Particles Collision on Separating Gas–Particle Two-Phase Turbulent Flows

KAUST Repository

Sihao, L. V.

2013-10-10

A second-order moment two-phase turbulence model incorporating a particle temperature model based on the kinetic theory of granular flow is applied to investigate the effects of particles collision on separating gas–particle two-phase turbulent flows. In this model, the anisotropy of gas and solid phase two-phase Reynolds stresses and their correlation of velocity fluctuation are fully considered using a presented Reynolds stress model and the transport equation of two-phase stress correlation. Experimental measurements (Xu and Zhou in ASME-FED Summer Meeting, San Francisco, Paper FEDSM99-7909, 1999) are used to validate this model, source codes and prediction results. It showed that the particles collision leads to decrease in the intensity of gas and particle vortices and takes a larger effect on particle turbulent fluctuations. The time-averaged velocity, the fluctuation velocity of gas and particle phase considering particles colli-sion are in good agreement with experimental measurements. Particle kinetic energy is always smaller than gas phase due to energy dissipation from particle collision. Moreover, axial– axial and radial–radial fluctuation velocity correlations have stronger anisotropic behaviors. © King Fahd University of Petroleum and Minerals 2013

On measuring surface wave phase velocity from station–station cross-correlation of ambient signal

DEFF Research Database (Denmark)

Boschi, Lapo; Weemstra, Cornelis; Verbeke, Julie

2012-01-01

We apply two different algorithms to measure surface wave phase velocity, as a function of frequency, from seismic ambient noise recorded at pairs of stations from a large European network. The two methods are based on consistent theoretical formulations, but differ in the implementation: one met...

A void fraction model for annular two-phase flow

Energy Technology Data Exchange (ETDEWEB)

Tandon, T.N.; Gupta, C.P.; Varma, H.K.

1985-01-01

An analytical model has been developed for predicting void fraction in two-phase annular flow. In the analysis, the Lockhart-Martinelli method has been used to calculate two-phase frictional pressure drop and von Karman's universal velocity profile is used to represent the velocity distribution in the annular liquid film. Void fractions predicted by the proposed model are generally in good agreement with a available experimental data. This model appears to be as good as Smith's correlation and better than the Wallis and Zivi correlations for computing void fraction.

Experimental observation of both negative and positive phase velocities in a two-dimensional sonic crystal

International Nuclear Information System (INIS)

Lu, Ming-Hui; Feng, Liang; Liu, Xiao-Ping; Liu, Xiao-Kang; Chen, Yan-Feng; Zhu, Yong-Yuan; Mao, Yi-Wei; Zi, Jian

2007-01-01

Both negative and positive phase velocities for acoustic waves have been experimentally established in a two-dimensional triangular sonic crystal (SC) consisting of steel cylinders embedded in air at first. With the increase of the SCs thickness layer by layer in the experiments, phase shifts decrease in the second band but increase in the first band, showing the negative and the positive phase velocities, respectively. Moreover, the dispersion relation of the SC is constructed by the phase information, which is consistent well with the theoretical results. These abundant characteristics of acoustic wave propagation in the SC might be useful for the device applications

Development of two-dimensional velocity field measurement using particle tracking velocimetry on neutron radiography

International Nuclear Information System (INIS)

Saito, Y.; Mishima, K.; Suzuki, T.; Matsubayashi, M.

2003-01-01

The structures of liquid metal two-phase flow are investigated for analyzing the core meltdown accident of fast reactor. The experiments of high-density ratio two-phase flow for lead-bismuth molten metal and nitrogen gases are conducted to understand in detail. The liquid phase velocity distributions of lead-bismuth molten metal are measured by neutron radiography using Au-Cd tracer particles. The liquid phase velocity distributions are obtained usually by using particle image velocimetry (PIV) on the neutron radiography. The PIV, however is difficult to get the velocity vector distribution quantitatively. An image of neutron radiography is divided into two images of the bubbles and the tracer particles each in particle tracking velocimetry (PTV), which distinguishes tracer contents in the bubble from them in the liquid phase. The locations of tracer particles in the liquid phase are possible to determine by particle mask correlation method, in which the bubble images are separated from the tracer images by Σ-scaling method. The particle tracking velocimetry give a full detail of the velocity vector distributions of the liquid phase in two-phase flow, in comparison with the PIV method. (M. Suetake)

Analysis of water hammer in two-component two-phase flows

International Nuclear Information System (INIS)

Warde, H.; Marzouk, E.; Ibrahim, S.

1989-01-01

The water hammer phenomena caused by a sudden valve closure in air-water two-phase flows must be clarified for the safety analysis of LOCA in reactors and further for the safety of boilers, chemical plants, pipe transport of fluids such as petroleum and natural gas. In the present work water hammer phenomena caused by sudden valve closure in two-component two-phase flows are investigated theoretically and experimentally. The phenomena are more complicated than in single phase-flows due to the fact of the presence of compressible component. Basic partial differential equations based on a one-dimensional homogeneous flow model are solved by the method of characteristic. The analysis is extended to include friction in a two-phase mixture depending on the local flow pattern. The profiles of the pressure transients, the propagation velocity of pressure waves and the effect of valve closure on the transient pressure are found. Different two-phase flow pattern and frictional pressure drop correlations were used including Baker, Chesholm and Beggs and Bril correlations. The effect of the flow pattern on the characteristic of wave propagation is discussed primarily to indicate the effect of void fraction on the velocity of wave propagation and on the attenuation of pressure waves. Transient pressure in the mixture were recorded at different air void fractions, rates of uniform valve closure and liquid flow velocities with the aid of pressure transducers, transient wave form recorders interfaced with an on-line pc computer. The results are compared with computation, and good agreement was obtained within experimental accuracy

A model for the two-point velocity correlation function in turbulent channel flow

International Nuclear Information System (INIS)

Sahay, A.; Sreenivasan, K.R.

1996-01-01

A relatively simple analytical expression is presented to approximate the equal-time, two-point, double-velocity correlation function in turbulent channel flow. To assess the accuracy of the model, we perform the spectral decomposition of the integral operator having the model correlation function as its kernel. Comparisons of the empirical eigenvalues and eigenfunctions with those constructed from direct numerical simulations data show good agreement. copyright 1996 American Institute of Physics

Multi-dimensional modeling of two-phase flow in rod bundles and interpretation of velocities measured in BWRs by the cross-correlation technique

International Nuclear Information System (INIS)

Analytis, G.Th.; Luebbesmeyer, D.

1984-04-01

The authors present an as precise as possible interpretation of velocity measurements in BWRs by the cross-correlation technique, which is based on the radially non-uniform quality and velocity distribution in BWR type bundles, as well as on our knowledge about the spatial 'field of view' of the in-core neutron detectors. After formulating the three-dimensional two-fluid model volume/time averaged equations and pointing out some problems associated with averaging, they expound a little on the turbulence mixing and void drift effects, as well as on the way they are modelled in advanced subchannel analysis codes like THERMIT or COBRA-TF. Subsequently, some comparisons are made between axial velocities measured in a commercial BWR by neutron noise analysis, and the steam velocities of the four subchannels nearest to the instrument tube of one of the four bundles as predicted by COBRA-III and by THERMIT. Although as expected, for well-known reasons, COBRA-III predicts subchannel steam velocities which are close to each other, THERMIT correctly predicts in the upper half of the core three largely different steam velocities in the three different types of BW0 subchannels (corner, edge and interior). (Auth.)

Development of New Correlation and Assessment of Correlations for Two-Phase Pressure Drop in Rectangular Microchannels

International Nuclear Information System (INIS)

Choi, Chi Woong; Yu, Dong In; Kim, Moo Hwan

2010-01-01

There are two kinds of models in two-phase pressured drop; homogeneous flow model and separated flow model. Many previous researchers have developed correlations for two-phase pressure drop in a microchannel. Most correlations were modified Lockhart and Martinelli's correlation, which was based on the separated flow model. In this study, experiments for adiabatic liquid water and nitrogen gas flow in rectangular microchannels were conducted to investigate two-phase pressure drop in the rectangular microchannels. Two-phase frictional pressure drop in the rectangular microchannels is highly related with flow regime. Homogeneous model with six two-phase viscosity models: Owen(21)'s, MacAdams(22)'s, Cicchitti et al.(23)'s, Dukler et al.(24)'s, Beattie and Whalley(25)'s, Lin et al.(26)'s models and six separated flow models: Lockhart and Martinelli(27)'s, Chisholm(31)'s, Zhang et al.(15)'s, Lee and Lee(5)'s, Moriyama and Inue(4)'s, Qu and Mudawar(8)'s models were assessed with our experimental data. The best two-phase viscosity model is Beattie and Whalley's model. The best separated flow model is Qu and Mudawar's correlation. Flow regime dependency in both homogeneous and separated flow models was observed. Therefore, new flow pattern based correlations for both homogeneous and separated flow models were individually proposed

Pressure Drop Correlations of Single-Phase and Two-Phase Flow in Rolling Tubes

International Nuclear Information System (INIS)

Xia-xin Cao; Chang-qi Yan; Pu-zhen Gao; Zhong-ning Sun

2006-01-01

A series of experimental studies of frictional pressure drop for single phase and two-phase bubble flow in smooth rolling tubes were carried out. The tube inside diameters were 15 mm, 25 mm and 34.5 mm respectively, the rolling angles of tubes could be set as 10 deg. and 20 deg., and the rolling periods could be set as 5 s, 10 s and 15 s. Combining with the analysis of single-phase water motion, it was found that the traditional correlations for calculating single-phase frictional coefficient were not suitable for the rolling condition. Based on the experimental data, a new correlation for calculating single-phase frictional coefficient under rolling condition was presented, and the calculations not only agreed well with the experimental data, but also could display the periodically dynamic characteristics of frictional coefficients. Applying the new correlation to homogeneous flow model, two-phase frictional pressure drop of bubble flow in rolling tubes could be calculated, the results showed that the relative error between calculation and experimental data was less than ± 25%. (authors)

A new correlation for two-phase critical discharge coefficient

International Nuclear Information System (INIS)

Park, Jong Woon; Chun, Moon Hyun

1989-01-01

A new simple correlation for subcooled and two-phase critical flow discharge coefficient has been developed by stepwise regression technique. The new discharge coefficient has three independent variables and they are length to hydraulic diameter ratio, degree of subcooling, and stagnation temperature. The new discharge coefficient is applied as a multiplier to homogeneous equilibrium model and Abauf's single phase critical mass flux calculation equation. This method has been tested for its accuracy by comparing with experimental data. Results of the comparison show that the agreement between the predictions with new correlation and the experimental data is good for pipes and nozzles with vertical upward flow for subcooled upstream condition and nozzles with horizontal configuration for two-phase upstream condition

Magnetic resonance velocity imaging of liquid and gas two-phase flow in packed beds.

Science.gov (United States)

Sankey, M H; Holland, D J; Sederman, A J; Gladden, L F

2009-02-01

Single-phase liquid flow in porous media such as bead packs and model fixed bed reactors has been well studied by MRI. To some extent this early work represents the necessary preliminary research to address the more challenging problem of two-phase flow of gas and liquid within these systems. In this paper, we present images of both the gas and liquid velocities during stable liquid-gas flow of water and SF(6) within a packing of 5mm spheres contained within columns of diameter 40 and 27 mm; images being acquired using (1)H and (19)F observation for the water and SF(6), respectively. Liquid and gas flow rates calculated from the velocity images are in agreement with macroscopic flow rate measurements to within 7% and 5%, respectively. In addition to the information obtained directly from these images, the ability to measure liquid and gas flow fields within the same sample environment will enable us to explore the validity of assumptions used in numerical modelling of two-phase flows.

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

Two-phase air-water stratified flow measurement using ultrasonic techniques

International Nuclear Information System (INIS)

Fan, Shiwei; Yan, Tinghu; Yeung, Hoi

2014-01-01

In this paper, a time resolved ultrasound system was developed for investigating two-phase air-water stratified flow. The hardware of the system includes a pulsed wave transducer, a pulser/receiver, and a digital oscilloscope. The time domain cross correlation method is used to calculate the velocity profile along ultrasonic beam. The system is able to provide velocities with spatial resolution of around 1mm and the temporal resolution of 200μs. Experiments were carried out on single phase water flow and two-phase air-water stratified flow. For single phase water flow, the flow rates from ultrasound system were compared with those from electromagnetic flow (EM) meter, which showed good agreement. Then, the experiments were conducted on two-phase air-water stratified flow and the results were given. Compared with liquid height measurement from conductance probe, it indicated that the measured velocities were explainable

Dividing phases in two-phase flow and modeling of interfacial drag

Energy Technology Data Exchange (ETDEWEB)

Narumo, T.; Rajamaeki, M. [VTT Energy (Finland)

1997-07-01

Different models intended to describe one-dimensional two-phase flow are considered in this paper. The following models are introduced: conventional six-equation model, conventional model equipped with terms taking into account nonuniform transverse velocity distribution of the phases, several virtual mass models and a model in which the momentum equations have been derived by using the principles of Separation of the Flow According to Velocity (SFAV). The dynamics of the models have been tested by comparing their characteristic velocities to each other and against experimental data. The results show that the SFAV-model makes a hyperbolic system and predicts the propagation velocities of disturbances with the same order of accuracy as the best tested virtual mass models. Furthermore, the momentum interaction terms for the SFAV-model are considered. These consist of the wall friction terms and the interfacial friction term. The authors model wall friction with two independent terms describing the effect of each fluid on the wall separately. In the steady state, a relationship between the slip velocity and friction coefficients can be derived. Hence, the friction coefficients for the SFAV-model can be calculated from existing correlations, viz. from a drift-flux correlation and a wall friction correlation. The friction model was tested by searching steady-state distributions in a partial BWR fuel channel and comparing the relaxed values with the drift-flux correlation, which agreed very well with each other. In addition, response of the flow to a sine-wave disturbance in the water inlet flux was calculated as function of frequency. The results of the models differed from each other already with frequency of order 5 Hz, while the time constant for the relaxation, obtained from steady-state distribution calculation, would have implied significant differences appear not until with frequency of order 50 Hz.

Dividing phases in two-phase flow and modeling of interfacial drag

International Nuclear Information System (INIS)

Narumo, T.; Rajamaeki, M.

1997-01-01

Different models intended to describe one-dimensional two-phase flow are considered in this paper. The following models are introduced: conventional six-equation model, conventional model equipped with terms taking into account nonuniform transverse velocity distribution of the phases, several virtual mass models and a model in which the momentum equations have been derived by using the principles of Separation of the Flow According to Velocity (SFAV). The dynamics of the models have been tested by comparing their characteristic velocities to each other and against experimental data. The results show that the SFAV-model makes a hyperbolic system and predicts the propagation velocities of disturbances with the same order of accuracy as the best tested virtual mass models. Furthermore, the momentum interaction terms for the SFAV-model are considered. These consist of the wall friction terms and the interfacial friction term. The authors model wall friction with two independent terms describing the effect of each fluid on the wall separately. In the steady state, a relationship between the slip velocity and friction coefficients can be derived. Hence, the friction coefficients for the SFAV-model can be calculated from existing correlations, viz. from a drift-flux correlation and a wall friction correlation. The friction model was tested by searching steady-state distributions in a partial BWR fuel channel and comparing the relaxed values with the drift-flux correlation, which agreed very well with each other. In addition, response of the flow to a sine-wave disturbance in the water inlet flux was calculated as function of frequency. The results of the models differed from each other already with frequency of order 5 Hz, while the time constant for the relaxation, obtained from steady-state distribution calculation, would have implied significant differences appear not until with frequency of order 50 Hz

A two-phase model of aquifer heterogeneity

International Nuclear Information System (INIS)

Moltyaner, G.L.

1994-11-01

A two-phase model of a fluid-saturated geologic medium is developed with groundwater velocity (rather than the hydraulic conductivity) as the primary model parameter. The model describes the groundwater flow, contaminant transport processes, and geologic medium structure at the local-scale of a continuum representation and relates structure to processes quantitatively. In this model, the heterogeneity of a geologic medium is characterized either in terms of the spatial variability in the bulk (local-scale) fluid density and sediment density, or in terms of variability in the local-scale porosity and effective grain diameter. The local-scale continuity equations resulting from these properties are derived for both phases. The effective grain diameter is employed to quantify the geologic structure. Velocity is employed to quantify the transport process. Since structure controls process, a high correlation is observed between the effective grain diameter and velocity. The observed correlation leads to a new formulation of Darcy's law without invoking the concept of a fictitious (Darcy's) velocity. The local-scale groundwater flow equation is developed on the basis of the new formulation. (author). 16 refs., 4 figs

Functional analysis of third ventriculostomy patency with phase-contrast MRI velocity measurements

International Nuclear Information System (INIS)

Lev, S.; Bhadelia, R.A.; Estin, D.; Heilman, C.B.; Wolpert, S.M.

1997-01-01

Our purpose was to explore the utility of cine phase-contrast MRI velocity measurements in determining the functional status of third ventriculostomies, and to correlate the quantitative velocity data with clinical follow-up. We examined six patients with third ventriculostomies and 12 normal subjects by phase-contrast MRI. The maximum craniocaudal to maximum caudocranial velocity range was measured at regions of interest near the third ventricular floor, and in cerebrospinal fluid anterior to the upper pons and spinal cord on midline sagittal images. Ratios of the velocities of both the third ventricle and prepontine space to the space anterior to the spinal cord were obtained. The velocities near the third ventricular floor and in the pontine cistern were significantly higher in patients than in normal subjects, but the velocity anterior to the spinal cord was similar between the groups. The velocity ratios, used to normalize individual differences, were also higher in patients than in controls. Two patients had lower velocity ratios than their fellows at the third ventricular floor and in the pontine cistern; one required a shunt 11 months later, while in the other, who had a third ventricular/thalamic tumor, the lower values probably reflect distortion of the third ventricular floor. We conclude that phase-contrast MR velocity measurements, specifically the velocity ratio between the high pontine cistern and the space anterior to the spinal cord, can help determine the functional status of third ventriculostomies. (orig.)

Two-phase modeling of DDT: Structure of the velocity-relaxation zone

International Nuclear Information System (INIS)

Kapila, A.K.; Son, S.F.; Bdzil, J.B.; Menikoff, R.; Stewart, D.S.

1997-01-01

The structure of the velocity relaxation zone in a hyperbolic, nonconservative, two-phase model is examined in the limit of large drag, and in the context of the problem of deflagration-to-detonation transition in a granular explosive. The primary motivation for the study is the desire to relate the end states across the relaxation zone, which can then be treated as a discontinuity in a reduced, equivelocity model, that is computationally more efficient than its parent. In contrast to a conservative system, where end states across thin zones of rapid variation are determined principally by algebraic statements of conservation, the nonconservative character of the present system requires an explicit consideration of the structure. Starting with the minimum admissible wave speed, the structure is mapped out as the wave speed increases. Several critical wave speeds corresponding to changes in the structure are identified. The archetypal structure is partly dispersed, monotonic, and involves conventional hydrodynamic shocks in one or both phases. The picture is reminiscent of, but more complex than, what is observed in such (simpler) two-phase media as a dusty gas. copyright 1997 American Institute of Physics

Phased-array vector velocity estimation using transverse oscillations

DEFF Research Database (Denmark)

Pihl, Michael Johannes; Marcher, Jønne; Jensen, Jørgen Arendt

2012-01-01

.79 to 0.92, indicating a correlation between the performance metrics of the TO spectrum and the velocity estimates. Because these performance metrics are much more readily computed, the TO fields can be optimized faster for improved velocity estimation of both simulations and measurements. For simulations......, but with a poorer performance compared with a 128-element transducer. The simulation and experimental results demonstrate that the TO method is suitable for use in conjunction with a phased-array transducer, and that 2-D vector velocity estimation is possible down to a depth of 15 cm....

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

Science.gov (United States)

Cleary, Vincent; Bowen, Phil; Witlox, Henk

2007-04-11

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

Design and construction of two phases flow meter

International Nuclear Information System (INIS)

Nor Paiza Mohamad Hasan

2002-01-01

This paper deals with design of the gamma ray correlometer and flow loop system for measuring the velocity between two parallel cross-sections of a pipeline. In the laboratory, the radioisotope source and detector were collimated by brass with small beam slit respectively. The flow loop system consists of transparent pipeline, adjustable frequency pump and water container. As a result, when the construction of the flow loop and correlometer is completed, the velocity of two phases flow can be measured by the cross-correlation techniques. (Author)

Geometric phases and quantum correlations of superconducting two-qubit system with dissipative effect

International Nuclear Information System (INIS)

Xue, Liyuan; Yu, Yanxia; Cai, Xiaoya; Pan, Hui; Wang, Zisheng

2016-01-01

Highlights: • We find that the Pancharatnam phases include the information of quantum correlations. • We show that the sudden died and alive phenomena of quantum entanglement is original in the transition of Pancharatnam phase. • We find that the faster the Pancharatnam phases change, the slower the quantum correlations decay. • We find that a subspace of quantum entanglement can exist in the Y-state. • Our results provide a useful approach experimentally to implement the time-dependent geometric quantum computation. - Abstract: We investigate time-dependent Pancharatnam phases and the relations between such geometric phases and quantum correlations, i.e., quantum discord and concurrence, of superconducting two-qubit coupling system in dissipative environment with the mixture effects of four different eigenstates of density matrix. We find that the time-dependent Pancharatnam phases not only keep the motion memory of such a two-qubit system, but also include the information of quantum correlations. We show that the sudden died and alive phenomena of quantum entanglement are intrinsic in the transition of Pancharatnam phase in the X-state and the complex oscillations of Pancharatnam phase in the Y-state. The faster the Pancharatnam phases change, the slower the quantum correlations decay. In particular, we find that a subspace of quantum entanglement can exist in the Y-state by choosing suitable coupling parameters between two-qubit system and its environment, or initial conditions.

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.

Governing equations for a seriated continuum: an unequal velocity model for two-phase flow

International Nuclear Information System (INIS)

Solbrig, C.W.; Hughes, E.D.

1975-05-01

The description of the flow of two-phase fluids is important in many engineering devices. Unexpected transient conditions which occur in these devices cannot, in general, be treated with single-component momentum equations. Instead, the use of momentum equations for each phase is necessary in order to describe the varied transient situations which can occur. These transient conditions can include phases moving in the opposite directions, such as steam moving upward and liquid moving downward, as well as phases moving in the same direction. The derivation of continuity and momentum equations for each phase and an overall energy equation for the mixture are presented. Terms describing interphase forces are described. A seriated (series of) continuum is distinguished from an interpenetrating medium by the representation of interphase friction with velocity differences in the former and velocity gradients in the latter. The seriated continuum also considers imbedded stationary solid surfaces such as occur in nuclear reactor cores. These stationary surfaces are taken into account with source terms. Sufficient constitutive equations are presented to form a complete set of equations. Methods are presented to show that all these coefficients are determinable from microscopic models and well known experimental results. Comparison of the present deviation with previous work is also given. The equations derived here may also be employed in certain multiphase, multicomponent flow applications. (U.S.)

Turbulence in two-phase flows

International Nuclear Information System (INIS)

Sullivan, J.P.; Houze, R.N.; Buenger, D.E.; Theofanous, T.G.

1981-01-01

Hot film Anemometry and Laser Doppler Velocimetry have been employed in this work to study the turbulence characteristics of Bubbly and Stratified two-phase flows, respectively. Extensive consistency checks were made to establish the reliability and hence the utility of these experimental techniques for the measurement of turbulence in two-phase flows. Buoyancy-driven turbulence in vertical bubbly flows has been identified experimentally and correlated in terms of a shear velocity superposition approach. This approach provides a criterion for the demarcation of the buoyancy-driven turbulence region from the wall shear-generated turbulence region. Our data confirm the roughly isotropic behavior expected for buoyancy-driven turbulence. Upgrading of our experimental system will permit investigations of the wall-shear dominated regime (i.e., isotropy, superposition approach, etc.). The stratified flow data demonstrate clearly that the maximum in the mean velocity profile does not coincide with the zero shear plane, indicating the existence of a negative eddy viscosity region. Previous studies do not take into account this difference and thus they yield incorrect friction factor data in addition to certain puzzling behavior in the upper wall region. The conditioned turbulence data in the wavy region indicate interesting trends and that an appropriate normalization of intensities must take into account the shear velocity at the interfacial (wavy) region

A Two-Radius Circular Array Method: Extracting Independent Information on Phase Velocities of Love Waves From Microtremor Records From a Simple Seismic Array

Science.gov (United States)

Tada, T.; Cho, I.; Shinozaki, Y.

2005-12-01

We have invented a Two-Radius (TR) circular array method of microtremor exploration, an algorithm that enables to estimate phase velocities of Love waves by analyzing horizontal-component records of microtremors that are obtained with an array of seismic sensors placed around circumferences of two different radii. The data recording may be done either simultaneously around the two circles or in two separate sessions with sensors distributed around each circle. Both Rayleigh and Love waves are present in the horizontal components of microtremors, but in the data processing of our TR method, all information on the Rayleigh waves ends up cancelled out, and information on the Love waves alone are left to be analyzed. Also, unlike the popularly used frequency-wavenumber spectral (F-K) method, our TR method does not resolve individual plane-wave components arriving from different directions and analyze their "vector" phase velocities, but instead directly evaluates their "scalar" phase velocities --- phase velocities that contain no information on the arrival direction of waves --- through a mathematical procedure which involves azimuthal averaging. The latter feature leads us to expect that, with our TR method, it is possible to conduct phase velocity analysis with smaller numbers of sensors, with higher stability, and up to longer-wavelength ranges than with the F-K method. With a view to investigating the capabilities and limitations of our TR method in practical implementation to real data, we have deployed circular seismic arrays of different sizes at a test site in Japan where the underground structure is well documented through geophysical exploration. Ten seismic sensors were placed equidistantly around two circumferences, five around each circle, with varying combinations of radii ranging from several meters to several tens of meters, and simultaneous records of microtremors around circles of two different radii were analyzed with our TR method to produce

One-dimensional transient unequal velocity two-phase flow by the method of characteristics

International Nuclear Information System (INIS)

Rasouli, F.

1981-01-01

An understanding of two-phase flow is important when one is analyzing the accidental loss of coolant or when analyzing industrial processes. If a pipe in the steam generator of a nuclear reactor breaks, the flow will remain critical (or choked) for almost the entire blowdown. For this reason the knowledge of the two-phase maximum (critical) flow rate is important. A six-equation model--consisting of two continuity equations, two energy equations, a mixture momentum equation, and a constitutive relative velocity equation--is solved numerically by the method of characteristics for one-dimensional, transient, two-phase flow systems. The analysis is also extended to the special case of transient critical flow. The six-equation model is used to study the flow of a nonequilibrium sodium-argon system in a horizontal tube in which the nonequilibrium sodium-argon system in a horizontal tube in which the critical flow condition is at the entrance. A four-equation model is used to study the pressure-pulse propagation rate in an isothermal air-water system, and the results that are found are compared with the experimental data. Proper initial and boundary conditions are obtained for the blowdown problem. The energy and mass exchange relations are evaluated by comparing the model predictions with results of void-fraction and heat-transfer experiments. A simplified two-equation model is obtained for the special case of two incompressible phases. This model is used in the preliminary analysis of batch sedimentation. It is also used to predict the shock formation in the gas-solid fluidized bed

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.

Relationships of the phase velocity with the microarchitectural parameters in bovine trabecular bone in vitro: Application of a stratified model

Science.gov (United States)

Lee, Kang Il

2012-08-01

The present study aims to provide insight into the relationships of the phase velocity with the microarchitectural parameters in bovine trabecular bone in vitro. The frequency-dependent phase velocity was measured in 22 bovine femoral trabecular bone samples by using a pair of transducers with a diameter of 25.4 mm and a center frequency of 0.5 MHz. The phase velocity exhibited positive correlation coefficients of 0.48 and 0.32 with the ratio of bone volume to total volume and the trabecular thickness, respectively, but a negative correlation coefficient of -0.62 with the trabecular separation. The best univariate predictor of the phase velocity was the trabecular separation, yielding an adjusted squared correlation coefficient of 0.36. The multivariate regression models yielded adjusted squared correlation coefficients of 0.21-0.36. The theoretical phase velocity predicted by using a stratified model for wave propagation in periodically stratified media consisting of alternating parallel solid-fluid layers showed reasonable agreements with the experimental measurements.

Void fraction and interfacial velocity in gas-liquid upward two-phase flow across tube bundles

International Nuclear Information System (INIS)

Ueno, T.; Tomomatsu, K.; Takamatsu, H.; Nishikawa, H.

1997-01-01

Tube failures due to flow-induced vibration are a major problem in heat exchangers and many studies on the problem of such vibration have been carried out so far. Most studies however, have not focused on two-phase flow behavior in tube bundles, but have concentrated mainly on tube vibration behavior like fluid damping, fluid elastic instability and so on. Such studies are not satisfactory for understanding the design of heat exchangers. Tube vibration behavior is very complicated, especially in the case of gas-liquid two-phase flow, so it is necessary to investigate two-phase flow behavior as well as vibration behavior before designing heat exchangers. This paper outlines the main parameters that characterize two-phase behavior, such as void fraction and interfacial velocity. The two-phase flow analyzed here is gas-liquid upward flow across a horizontal tube bundle. The fluids tested were HCFC-123 and steam-water. HCFC-123 stands for Hydrochlorofluorocarbon. Its chemical formula is CHCl 2 CF 3 , which has liquid and gas densities of 1335 and 23.9 kg/m 3 at a pressure of 0.40 MPa and 1252 and 45.7 kg/m 3 at a pressure of 0.76 MPa. The same model tube bundle was used in the two tests covered in this paper, to examine the similarity law of two-phase flow behavior in tube bundles using HCFC-123 and steam-water two-phase flow. We also show numerical simulation results for the two fluid models in this paper. We do not deal with vibration behavior and the relationship between vibration behavior and two-phase flow behavior. (author)

Constitutive equations for two-phase flows

International Nuclear Information System (INIS)

Boure, J.A.

1974-12-01

The mathematical model of a system of fluids consists of several kinds of equations complemented by boundary and initial conditions. The first kind equations result from the application to the system, of the fundamental conservation laws (mass, momentum, energy). The second kind equations characterize the fluid itself, i.e. its intrinsic properties and in particular its mechanical and thermodynamical behavior. They are the mathematical model of the particular fluid under consideration, the laws they expressed are so called the constitutive equations of the fluid. In practice the constitutive equations cannot be fully stated without reference to the conservation laws. Two classes of model have been distinguished: mixture model and two-fluid models. In mixture models, the mixture is considered as a single fluid. Besides the usual friction factor and heat transfer correlations, a single constitutive law is necessary. In diffusion models, the mixture equation of state is replaced by the phasic equations of state and by three consitutive laws, for phase change mass transfer, drift velocity and thermal non-equilibrium respectively. In the two-fluid models, the two phases are considered separately; two phasic equations of state, two friction factor correlations, two heat transfer correlations and four constitutive laws are included [fr

Hydrodynamics of single- and two-phase flow in inclined rod arrays

International Nuclear Information System (INIS)

Ebeling-Koning, D.B.; Todreas, N.E.

1983-09-01

Required inputs for thermal-hydraulic codes are constitutive relations for fluid-solid flow resistance, in single-phase flow, and interfacial momentum exchange (relative phase motion), in two-phase flow. An inclined rod array air-water experiment was constructed to study the hydrodynamics of multidimensional porous medium flow in rod arrays. Velocities, pressures, and bubble distributions were measured in square rod arrays of P/d = 1.5, at 0, 30, 45, and 90 degree inclinations to the vertical flow direction. Constitutive models for single-phase flow resistance are reviewed, new comprehensive models developed, and an assessment with previously published and new data made. The principle of superimposing one-dimensional correlations proves successful for turbulent single-phase inclined flow. For bubbly two-phase incline flow a new flow separation phenomena was observed and modeled. A two-region liquid velocity model is developed to explain the experimentally observed phenomena. Fundamental data for bubbles rising in rod arrays were also taken

Influence and applicability of wire-mesh sensor to acquire two phase flow dynamics

International Nuclear Information System (INIS)

Kanai, Taizo; Furuya, Masahiro; Arai, Takahiro; Shirakawa, Kenetsu

2011-01-01

Wire-mesh sensors (WMS) are able to measure void distributions and velocity profile at high speed. Immersing the wire-mesh affects the structure of two-phase flow. Experiments were performed for single rising air bubble in a vertical pipe of i.d. 50 mm and 224 mm at water velocities ranging from 0.05 to 0.52 m/s and 0.42 to 0.83 m/s. Distortion of a relatively large bubble with the wire-mesh was small in the water velocity over 0.25 m/s and confirmed by cross-correlation analysis as well. Bubble rising velocity acquired by WMS is in good agreement with that estimated high-speed camera in the experimental range. WMS has applicability to acquire two phase flow dynamics in the water velocity over 0.25 m/s. (author)

High speed ultrasonic system to measure bubbles velocities in a horizontal two-phase flow

International Nuclear Information System (INIS)

Cunha Filho, Jurandyr S.; Jian Su; Farias, Marcos S.; Faccini, Jose L.H.; Lamy, Carlos A.

2009-01-01

In this work, a non invasive technique consisting of a high speed ultrasonic multitransducer pulse-echo system was developed to characterize gas-liquid two-phase flow parameters that are important in the study of the primary refrigeration circuit of nuclear reactors. The high speed ultrasonic system consists of two transducers (10 MHz/φ 6.35 mm), a generator/multiplexer board, and software that selects and has a data acquisition system of the ultrasonic signals. The resolutions of the system and the pulse time generated from each transducer are, respectively, 10 ns and 1.06 ms. The system initially was used in the local instantaneous measurement of gas-liquid interface in a circular horizontal pipe test section made of a 5 m long stainless steel pipe of 51.2 mm inner diameter, where the elongated bubbles velocity was measured (Taylor bubbles). The results show that the high speed ultrasonic pulse-echo system provides good results for the determination of elongated bubbles velocities. (author)

A model relating Eulerian spatial and temporal velocity correlations

Science.gov (United States)

Cholemari, Murali R.; Arakeri, Jaywant H.

2006-03-01

In this paper we propose a model to relate Eulerian spatial and temporal velocity autocorrelations in homogeneous, isotropic and stationary turbulence. We model the decorrelation as the eddies of various scales becoming decorrelated. This enables us to connect the spatial and temporal separations required for a certain decorrelation through the ‘eddy scale’. Given either the spatial or the temporal velocity correlation, we obtain the ‘eddy scale’ and the rate at which the decorrelation proceeds. This leads to a spatial separation from the temporal correlation and a temporal separation from the spatial correlation, at any given value of the correlation relating the two correlations. We test the model using experimental data from a stationary axisymmetric turbulent flow with homogeneity along the axis.

Visualization and measurement of liquid velocity field of gas-liquid metal two-phase flow using neutron radiography

International Nuclear Information System (INIS)

Saito, Yasushi; Suzuki, Tohru; Matsubayashi, Masahito

2000-01-01

In a core melt accident of a fast breeder reactor, a possibility of re-criticality is anticipated in the molten fuel-steel mixture pool. One of the mechanisms to suppress the re-criticality is the boiling of steel in the molten fuel-steel mixture pool because of the negative void reactivity effect. To evaluate the reactivity change due to boiling, it is necessary to know the characteristics of gas-liquid two-phase flow in the molten fuel-steel mixture pool. For this purpose, boiling bubbles in a molten fuel-steel mixture pool were simulated by adiabatic gas bubbles in a liquid metal pool to study the basic characteristics of gas-liquid metal two-phase mixture. Visualization of the two-phase mixture and measurements of liquid phase velocity and void fraction were conducted by using neutron radiography and image processing techniques. From these measurements, the basic characteristics of gas-liquid metal two-phase mixture were clarified. (author)

Exploring Capabilities of Electrical Capacitance Tomography Sensor and Velocity Analysis of Two-Phase R-134A Flow Through a Sudden Expansion

Science.gov (United States)

2017-05-01

area ratio φ angle of rod density of liquid phase (kg/m3) density of vapor phase (kg/m3) ...heat transfer in order to manage the ever-increasing airframe and engine heat loads. Two-phase liquid -vapor refrigerant systems are one solution for...the heat removal from these systems. However, they require more study before implementation. This study examines the velocities of two-phase liquid

Relationships of the phase velocity with the micro architectural parameters in bovine trabecular bone in vitro: application of a stratified model

Energy Technology Data Exchange (ETDEWEB)

Lee, Kang Il [Kangwon National University, Chuncheon (Korea, Republic of)

2012-08-15

The present study aims to provide insight into the relationships of the phase velocity with the micro architectural parameters in bovine trabecular bone in vitro. The frequency-dependent phase velocity was measured in 22 bovine femoral trabecular bone samples by using a pair of transducers with a diameter of 25.4 mm and a center frequency of 0.5 MHz. The phase velocity exhibited positive correlation coefficients of 0.48 and 0.32 with the ratio of bone volume to total volume and the trabecular thickness, respectively, but a negative correlation coefficient of -0.62 with the trabecular separation. The best univariate predictor of the phase velocity was the trabecular separation, yielding an adjusted squared correlation coefficient of 0.36. The multivariate regression models yielded adjusted squared correlation coefficients of 0.21 - 0.36. The theoretical phase velocity predicted by using a stratified model for wave propagation in periodically stratified media consisting of alternating parallel solid-fluid layers showed reasonable agreements with the experimental measurements.

Relationships of the phase velocity with the micro architectural parameters in bovine trabecular bone in vitro: application of a stratified model

International Nuclear Information System (INIS)

Lee, Kang Il

2012-01-01

The present study aims to provide insight into the relationships of the phase velocity with the micro architectural parameters in bovine trabecular bone in vitro. The frequency-dependent phase velocity was measured in 22 bovine femoral trabecular bone samples by using a pair of transducers with a diameter of 25.4 mm and a center frequency of 0.5 MHz. The phase velocity exhibited positive correlation coefficients of 0.48 and 0.32 with the ratio of bone volume to total volume and the trabecular thickness, respectively, but a negative correlation coefficient of -0.62 with the trabecular separation. The best univariate predictor of the phase velocity was the trabecular separation, yielding an adjusted squared correlation coefficient of 0.36. The multivariate regression models yielded adjusted squared correlation coefficients of 0.21 - 0.36. The theoretical phase velocity predicted by using a stratified model for wave propagation in periodically stratified media consisting of alternating parallel solid-fluid layers showed reasonable agreements with the experimental measurements.

Control of group velocity by phase-changing collisions

International Nuclear Information System (INIS)

Goren, C.; Rosenbluh, M.; Wilson-Gordon, A.D.; Friedmann, H.

2005-01-01

We discuss the influence of phase-changing collisions on the group velocities in Doppler-broadened, cycling, degenerate two-level systems where F e =F g +1 and F g >0, interacting with pump and probe lasers, that exhibit electromagnetically induced absorption (EIA). Two model systems are considered: the N system where the pump and probe are polarized perpendicularly, and EIA is due to transfer of coherence (TOC), and the double two-level system (TLS) where both lasers have the same polarization, and EIA is due to transfer of population (TOP). For the case of Doppler-broadened EIA TOC, which occurs at low pump intensity, there is a switch from positive to negative dispersion and group velocity, as the rate of phase-changing collisions is increased. For the case of EIA TOP at low pump intensity, the dispersion and group velocity remain negative even when the collision rate is increased. Pressure-induced narrowing, accompanied by an increase in the magnitude of the negative dispersion and a decrease in the magnitude of the negative group velocity, occurs in both EIA TOC and EIA TOP, at low pump intensity. When the pump intensity is increased, a switch from negative to positive dispersion and group velocity, with increasing collision rate, also occurs in the double TLS system. However, the effect is far smaller than in the case of the N system at low pump intensity

Two-phase wall friction model for the trace computer code

International Nuclear Information System (INIS)

Wang Weidong

2005-01-01

The wall drag model in the TRAC/RELAP5 Advanced Computational Engine computer code (TRACE) has certain known deficiencies. For example, in an annular flow regime, the code predicts an unphysical high liquid velocity compared to the experimental data. To address those deficiencies, a new wall frictional drag package has been developed and implemented in the TRACE code to model the wall drag for two-phase flow system code. The modeled flow regimes are (1) annular/mist, (2) bubbly/slug, and (3) bubbly/slug with wall nucleation. The new models use void fraction (instead of flow quality) as the correlating variable to minimize the calculation oscillation. In addition, the models allow for transitions between the three regimes. The annular/mist regime is subdivided into three separate regimes for pure annular flow, annular flow with entrainment, and film breakdown. For adiabatic two-phase bubbly/slug flows, the vapor phase primarily exists outside of the boundary layer, and the wall shear uses single-phase liquid velocity for friction calculation. The vapor phase wall friction drag is set to zero for bubbly/slug flows. For bubbly/slug flows with wall nucleation, the bubbles are presented within the hydrodynamic boundary layer, and the two-phase wall friction drag is significantly higher with a pronounced mass flux effect. An empirical correlation has been studied and applied to account for nucleate boiling. Verification and validation tests have been performed, and the test results showed a significant code improvement. (authors)

Measurement of phase interaction in dispersed gas-particle two-phase flow by phase-doppler anemometry

Directory of Open Access Journals (Sweden)

Mergheni Ali Mohamed

2008-01-01

Full Text Available For simultaneous measurement of size and velocity distributions of continuous and dispersed phases in a two-phase flow a technique phase-Doppler anemometry was used. Spherical glass particles with a particle diameter range from 102 up to 212 µm were used. In this two-phase flow an experimental results are presented which indicate a significant influence of the solid particles on the flow characteristics. The height of influence of these effects depends on the local position in the jet. Near the nozzle exit high gas velocity gradients exist and therefore high turbulence production in the shear layer of the jet is observed. Here the turbulence intensity in the two-phase jet is decreased compared to the single-phase jet. In the developed zone the velocity gradient in the shear layer is lower and the turbulence intensity reduction is higher. .

Heat transfer to a dispersed two-phase flow and detailed quench front velocity research

International Nuclear Information System (INIS)

Boer, T.C. de; Molen, S.B. van der

1985-01-01

A programme to obtain a data base for 'Boildown and Reflood' computer code development and to obtain information on the influence of non-uniform temperature and/or power profile on the quench front velocity and prequench heat transfer, including unheated wall and grid effects, has been undertaken. It is in two parts. In the first (for the tube, annulus and a 4-rod bundle) an early wetting of the unheated shroud is shown. This leads to an increase in quench front velocity and in liquid transport downstream from the quench front. For the inverted annular flow regime the extended Bromley correlation gives good agreement with the experimental data. In the second part (36-rod bundle reflood test programme) the wall-temperature differences in the radial direction gives rise to heat transfer processes which are described and explained. (U.K.)

Seafloor age dependence of Rayleigh wave phase velocities in the Indian Ocean

Science.gov (United States)

Godfrey, Karen E.; Dalton, Colleen A.; Ritsema, Jeroen

2017-05-01

Variations in the phase velocity of fundamental-mode Rayleigh waves across the Indian Ocean are determined using two inversion approaches. First, variations in phase velocity as a function of seafloor age are estimated using a pure-path age-dependent inversion method. Second, a two-dimensional parameterization is used to solve for phase velocity within 1.25° × 1.25° grid cells. Rayleigh wave travel time delays have been measured between periods of 38 and 200 s. The number of measurements in the study area ranges between 4139 paths at a period of 200 s and 22,272 paths at a period of 40 s. At periods Rodriguez Triple Junction and the Australian-Antarctic Discordance and anomalously low velocities immediately to the west of the Central Indian Ridge.

Two-phase flow instrumentation research at RPI

International Nuclear Information System (INIS)

Lahey, R.T. Jr.; Krycuk, G.

1979-01-01

Novel instrumentation for the measurement of void fraction and phase velocity was developed. An optical digital interferometer and a dual beam x-ray equipment were designed for detection of voids. Pitot tube measurements were made to understand two-phase flow phenomena in liquid phase velocity

Prediction of shear wave velocity using empirical correlations and artificial intelligence methods

Science.gov (United States)

Maleki, Shahoo; Moradzadeh, Ali; Riabi, Reza Ghavami; Gholami, Raoof; Sadeghzadeh, Farhad

2014-06-01

Good understanding of mechanical properties of rock formations is essential during the development and production phases of a hydrocarbon reservoir. Conventionally, these properties are estimated from the petrophysical logs with compression and shear sonic data being the main input to the correlations. This is while in many cases the shear sonic data are not acquired during well logging, which may be for cost saving purposes. In this case, shear wave velocity is estimated using available empirical correlations or artificial intelligent methods proposed during the last few decades. In this paper, petrophysical logs corresponding to a well drilled in southern part of Iran were used to estimate the shear wave velocity using empirical correlations as well as two robust artificial intelligence methods knows as Support Vector Regression (SVR) and Back-Propagation Neural Network (BPNN). Although the results obtained by SVR seem to be reliable, the estimated values are not very precise and considering the importance of shear sonic data as the input into different models, this study suggests acquiring shear sonic data during well logging. It is important to note that the benefits of having reliable shear sonic data for estimation of rock formation mechanical properties will compensate the possible additional costs for acquiring a shear log.

Prediction of shear wave velocity using empirical correlations and artificial intelligence methods

Directory of Open Access Journals (Sweden)

Shahoo Maleki

2014-06-01

Full Text Available Good understanding of mechanical properties of rock formations is essential during the development and production phases of a hydrocarbon reservoir. Conventionally, these properties are estimated from the petrophysical logs with compression and shear sonic data being the main input to the correlations. This is while in many cases the shear sonic data are not acquired during well logging, which may be for cost saving purposes. In this case, shear wave velocity is estimated using available empirical correlations or artificial intelligent methods proposed during the last few decades. In this paper, petrophysical logs corresponding to a well drilled in southern part of Iran were used to estimate the shear wave velocity using empirical correlations as well as two robust artificial intelligence methods knows as Support Vector Regression (SVR and Back-Propagation Neural Network (BPNN. Although the results obtained by SVR seem to be reliable, the estimated values are not very precise and considering the importance of shear sonic data as the input into different models, this study suggests acquiring shear sonic data during well logging. It is important to note that the benefits of having reliable shear sonic data for estimation of rock formation mechanical properties will compensate the possible additional costs for acquiring a shear log.

New sensor for measurement of low air flow velocity. Phase I final report

International Nuclear Information System (INIS)

Hashemian, H.M.; Hashemian, M.; Riggsbee, E.T.

1995-08-01

The project described here is the Phase I feasibility study of a two-phase program to integrate existing technologies to provide a system for determining air flow velocity and direction in radiation work areas. Basically, a low air flow sensor referred to as a thermocouple flow sensor has been developed. The sensor uses a thermocouple as its sensing element. The response time of the thermocouple is measured using an existing in-situ method called the Loop Current Step Response (LCSR) test. The response time results are then converted to a flow signal using a response time-versus-flow correlation. The Phase I effort has shown that a strong correlation exists between the response time of small diameter thermocouples and the ambient flow rate. As such, it has been demonstrated that thermocouple flow sensors can be used successfully to measure low air flow rates that can not be measured with conventional flow sensors. While the thermocouple flow sensor developed in this project was very successful in determining air flow velocity, determining air flow direction was beyond the scope of the Phase I project. Nevertheless, work was performed during Phase I to determine how the new flow sensor can be used to determine the direction, as well as the velocity, of ambient air movements. Basically, it is necessary to use either multiple flow sensors or move a single sensor in the monitoring area and make flow measurements at various locations sweeping the area from top to bottom and from left to right. The results can then be used with empirical or physical models, or in terms of directional vectors to estimate air flow patterns. The measurements can be made continuously or periodically to update the flow patterns as they change when people and objects are moved in the monitoring area. The potential for using multiple thermocouple flow sensors for determining air flow patterns will be examined in Phase II

Internal structure and interfacial velocity development for bubbly two-phase flow

International Nuclear Information System (INIS)

Kocamustafaogullari, G.; Huang, W.D.

1994-01-01

This paper describes an experimental study of the internal structure of air-water flowing horizontally. The double-sensor resistivity probe technique was applied for measurements of local interfacial parameters, including void fraction, interfacial area concentration, bubble size distributions, bubble passing frequency and bubble interface velocity. Bubbly flow patterns at several flow conditions were examined at three axial locations, L/D=25, 148 and 253, in which the first measurement represents the entrance region where the flow develops, and the second and third may represent near fully developed bubbly flow patterns. The experimental results are presented in three-dimensional perspective plots of the interfacial parameters over the cross-section. These multi-dimensional presentations showed that the local values of the void fraction, interfacial area concentration and bubble passing frequency were nearly constant over the cross-section at L/D=25, with slight local peaking close to the channel wall. Although similar local peakings were observed at the second and third locations, the internal flow structure segregation due to buoyancy appeared to be very strong in the axial direction. A simple comparison of profiles of the interfacial parameters at the three locations indicated that the flow pattern development was a continuous process. Finally, it was shown that the so-called ''fully developed'' bubbly two-phase flow pattern cannot be established in a horizontal pipe and that there was no strong correspondence between void fraction and interface velocity profiles. ((orig.))

Effect of particle velocity fluctuations on the inertia coupling in two-phase flow

International Nuclear Information System (INIS)

Drew, D.A.

1989-01-01

Consistent forms for the interfacial force, the interfacial pressure, the Reynolds stresses and the particle stress have been derived for the inviscid, irrotational incompressible flow of fluid in a dilute suspension of spheres. The particles are assumed to have a velocity distribution, giving rise to an effective pressure and stress in the particle phase. The velocity fluctuations also contribute in the fluid Reynolds stress and in the (elastic) stress field inside the spheres. The relation of these constitutive equations to the force on an individual sphere is discussed

A First Layered Crustal Velocity Model for the Western Solomon Islands: Inversion of Measured Group Velocity of Surface Waves using Ambient Noise Cross-Correlation

Science.gov (United States)

Ku, C. S.; Kuo, Y. T.; Chao, W. A.; You, S. H.; Huang, B. S.; Chen, Y. G.; Taylor, F. W.; Yih-Min, W.

2017-12-01

Two earthquakes, MW 8.1 in 2007 and MW 7.1 in 2010, hit the Western Province of Solomon Islands and caused extensive damage, but motivated us to set up the first seismic network in this area. During the first phase, eight broadband seismic stations (BBS) were installed around the rupture zone of 2007 earthquake. With one-year seismic records, we cross-correlated the vertical component of ambient noise recorded in our BBS and calculated Rayleigh-wave group velocity dispersion curves on inter-station paths. The genetic algorithm to invert one-dimensional crustal velocity model is applied by fitting the averaged dispersion curves. The one-dimensional crustal velocity model is constituted by two layers and one half-space, representing the upper crust, lower crust, and uppermost mantle respectively. The resulted thickness values of the upper and lower crust are 6.4 and 14.2 km, respectively. Shear-wave velocities (VS) of the upper crust, lower crust, and uppermost mantle are 2.53, 3.57 and 4.23 km/s with the VP/VS ratios of 1.737, 1.742 and 1.759, respectively. This first layered crustal velocity model can be used as a preliminary reference to further study seismic sources such as earthquake activity and tectonic tremor.

Local measurement of interfacial area, interfacial velocity and liquid turbulence in two-phase flow

International Nuclear Information System (INIS)

Hibiki, T.; Hogsett, S.; Ishii, M.

1998-01-01

Double sensor probe and hotfilm anemometry methods were developed for measuring local flow characteristics in bubbly flow. The formulation for the interfacial area concentration measurement was obtained by improving the formulation derived by Kataoka and Ishii. The assumptions used in the derivation of the equation were verified experimentally. The interfacial area concentration measured by the double sensor probe agreed well with one by the photographic method. The filter to validate the hotfilm anemometry for measuring the liquid velocity and turbulent intensity in bubbly flow was developed based on removing the signal due to the passing bubbles. The local void fraction, interfacial area concentration, interfacial velocity, Sauter mean diameter, liquid velocity, and turbulent intensity of vertical upward air-water flow in a round tube with inner diameter of 50.8 mm were measured by using these methods. A total of 54 data sets were acquired consisting of three superficial gas flow rates, 0.039, 0.067, and 0.147 m/s, and three superficial liquid flow rates, 0.60, 1.00, and 1.30 m/s. The measurements were performed at the three locations: L/D=2, 32, and 62. This data is expected to be used for the development of reliable constitutive relations which reflect the true transfer mechanisms in two-phase flow. (author)

Effect of void fraction correlations on two-phase pressure drop during flow boiling in narrow rectangular channel

International Nuclear Information System (INIS)

Huang, Dong; Gao, Puzhen; Chen, Chong; Lan, Shu

2013-01-01

Highlights: • Most of the slip ratio models and the Lockhart–Martinelli parameter based models give similar results. • The drift flux void fraction models give relatively small values. • The effect of void fraction correlations on two-phase friction pressure drop is inconspicuous. • The effect of void fraction correlations on two-phase acceleration pressure drop is significant. - Abstract: The void fraction of water during flow boiling in vertical narrow rectangular channel is experimentally investigated. The void fraction is indirectly determined using the present experimental data with various void fraction correlations or models published in the open literature. The effects of mass flux, mass quality, system pressure and inlet subcooling on the void fraction and pressure drop are discussed in detail. In addition, comparison and discussion among the numerous void fraction correlations are carried out. The effect of void fraction correlations on two-phase pressure drop is presented as well. The results reveal that most of the slip ratio correlations and the Lockhart–Martinelli parameter based void fraction correlations have results close to each other at mass quality higher than 0.2. The drift flux void fraction correlations give small values which are incompatible with other models making it inapplicable for narrow rectangular channel. The alteration of void fraction correlations has an inconspicuous effect on two-phase frictional pressure drop, while an obvious effect on two-phase accelerational pressure drop during flow boiling in narrow rectangular channel

On-line velocity measurements using phase probes at the SuperHILAC

International Nuclear Information System (INIS)

Feinberg, B.; Meaney, D.; Thatcher, R.; Timossi, C.

1987-12-01

Phase probes have been placed in several external beam lines at the LBL heavy ion linear accelerator (SuperHILAC) to provide non- destructive velocity measurements independent of the ion being accelerated. The system uses three probes in each line to obtain accurate velocity measurements at all beam energies. Automatic gain control and signal analysis are performed so that the energy/nucleon along with up to three probe signals are displayed on a vector graphics display with a refresh rate better than twice per second. The system uses a sensitive pseudo-correlation technique to pick out the signal from the noise, features simultaneous measurements of up to four ion velocities when more than one beam is being accelerated, and is controlled by a touch-screen operator interface. It is accurate to within /+-/0.25% and has provisions for on-line calibration tests. The phase probes thus provide a velocity measurement independent of the mass defect associated with the use of crystal detectors, which can become significant for heavy elements. They are now used as a routine tuning aid to ensure proper bunch structure, and as a beam velocity monitor. 3 refs., 5 figs

Phase velocity enhancement of linear explosive shock tubes

Science.gov (United States)

Loiseau, Jason; Serge, Matthew; Szirti, Daniel; Higgins, Andrew; Tanguay, Vincent

2011-06-01

Strong, high density shocks can be generated by sequentially detonating a hollow cylinder of explosives surrounding a thin-walled, pressurized tube. Implosion of the tube results in a pinch that travels at the detonation velocity of the explosive and acts like a piston to drive a shock into the gas ahead of it. In order to increase the maximum shock velocities that can be obtained, a phase velocity generator can be used to drag an oblique detonation wave along the gas tube at a velocity much higher than the base detonation velocity of the explosive. Since yielding and failure of the gas tube is the primary limitation of these devices, it is desirable to retain the dynamic confinement effects of a heavy-walled tamper without interfering with operation of the phase velocity generator. This was accomplished by cutting a slit into the tamper and introducing a phased detonation wave such that it asymmetrically wraps around the gas tube. This type of configuration has been previously experimentally verified to produce very strong shocks but the post-shock pressure and shock velocity limits have not been investigated. This study measured the shock trajectory for various fill pressures and phase velocities to ascertain the limiting effects of tube yield, detonation obliquity and pinch aspect ratio.

Measurement of two-dimensional bubble velocity by Using tri-fiber-optical Probe

International Nuclear Information System (INIS)

Yang Ruichang; Zheng Rongchuan; Zhou Fanling; Liu Ruolei

2009-01-01

In this study, an advanced measuring system with a tri-single-fiber-optical-probe has been developed to measure two-dimensional vapor/gas bubble velocity. The use of beam splitting devices instead of beam splitting lens simplifies the optical system, so the system becomes more compact and economic, and more easy to adjust. Corresponding to using triple-optical probe for measuring two-dimensional bubble velocity, a data processing method has been developed, including processing of bubble signals, cancelling of unrelated signals, determining of bubble velocity with cross correlation technique and so on. Using the developed two-dimensional bubble velocity measuring method, the rising velocity of air bubbles in gravitational field was measured. The measured bubble velocities were compared with the empirical correlation available. Deviation was in the range of ±30%. The bubble diameter obtained by data processing is in good accordance with that observed with a synchro-scope and a camera. This shows that the method developed here is reliable.

Fast X-ray imaging of two-phase flows: Application to cavitating flows

International Nuclear Information System (INIS)

Khlifa, Ilyass

2014-01-01

A promising method based on fast X-ray imaging has been developed to investigate the dynamics and the structure of complex two-phase flows. It has been applied in this work on cavitating flows created inside a Venturi-type test section and helped therefore to better understand flows inside cavitation pockets. Seeding particles were injected into the flow to trace the liquid phase. Thanks to the characteristics of the beam provided by the APS synchrotron (Advance Photon Source, USA), high definition X-ray images of the flow containing simultaneously information for both liquid and vapour were obtained. Velocity fields of both phases were thus calculated using image cross-correlation algorithms. Local volume fractions of vapour have also been obtained using local intensities of the images. Beforehand however, image processing is required to separate phases for velocity measurements. Validation methods of all applied treatments were developed, they allowed to characterise the measurement accuracy. This experimental technique helped us to have more insight into the dynamic of cavitating flows and especially demonstrates the presence of significant slip velocities between phases. (author)

Effect of Phase Transformations on Seismic Velocities

Science.gov (United States)

Weidner, D. J.; Li, L.; Whitaker, M.; Triplett, R.

2017-12-01

The radial velocity structure of the Earth consists of smooth variations of velocities with depth punctuated by abrupt changes of velocity, which are typically due to multivariant phase transformations, where high - low pressure phases can coexist. In this mixed phase region, both the effective shear and bulk moduli will be significantly reduced by the dynamic interaction of the propagating wave and the phase transition if the period of the wave is long enough relative to the kinetic time so that some of the transition can take place. In this presentation, we will give examples from both laboratory studies of phases transitions of Earth minerals and the calculated velocity profile based on our models. We focus on understanding the time limiting factor of the phase transformation in order to extrapolate laboratory results to Earth observations. Both the olivine to ringwoodite transition and KLB-1 partial melting are explored. We find that when the transformation requires diffusion, the kinetics are often slowed down considerably and as a result the diffusivity of atoms become the limiting factor of characteristic time. Specifically Fe-Mg exchange rate in the olivine-ringwoodite phase transition becomes the limiting factor that seismic waves are likely to sample. On the other hand, partial melting is an extremely fast phase transformation at seismic wave periods. We present evidence that ultrasonic waves, with a period of a few tens of nanoseconds, are slowed by the reduction of the effective elastic moduli in this case.

Multiparticle imaging velocimetry measurements in two-phase flow

International Nuclear Information System (INIS)

Hassan, Y.A.

1998-01-01

The experimental flow visualization tool, Particle Image Velocimetry (PIV), is being extended to determine the velocity fields in two and three-dimensional, two-phase fluid flows. In the past few years, the technique has attracted quite a lot of interest. PIV enables fluid velocities across a region of a flow to be measured at a single instant in time in global domain. This instantaneous velocity profile of a given flow field is determined by digitally recording particle (microspheres or bubbles) images within the flow over multiple successive video frames and then conducting flow pattern identification and analysis of the data. This paper presents instantaneous velocity measurements in various two and three- dimensional, two-phase flow situations. (author)

Correlations for the partition behavior of proteins in aqueous two-phase systems

DEFF Research Database (Denmark)

Schmidt, A.S.; Andrews, B.A.; Asenjo, J.A.

1996-01-01

to its high hydrophilicity. In the case of subtilisin and trypsin inhibitor, their high concentrations in the top phase were due to their hydrophobic nature (hydrophobic interaction with PEG) and small size (negligible steric exclusion). The maximum concentration in the bottom phase for trypsin inhibitor...... of the overall protein concentration, by the ratio between the ''saturation'' equations of the two individual phases. Better correlations were obtained when an empirical sigmoidal Boltzmann equation was fitted to the data, since in virtually all cases the partition coefficient is constant at low protein...

Development of multidimensional two-phase flow measurement sensor in rod bundle

International Nuclear Information System (INIS)

Arai, Takahiro; Furuya, Masahiro; Shirakawa, Kenetsu; Kanai, Taizo

2011-01-01

In order to acquire multidimensional two-phase flow in 10x10 bundle, SubChannel Void Sensor (SCVC) consisting of 11-wire by 11-wire and 10-rod by 10-rod electrodes is developed. A conductance value in a proximity region of one wire and another gives void fraction in the center of subchannel region. A phasic velocity can be estimated by using two layers of wire meshes, like as so-called wire mesh sensor. 121 points (=11x11) of void fraction as well as those of phasic velocity are acquired. It is peculiarity of the devised sensor that void fraction near rod surface can be estimated by a conductance value in a proximity region of one wire and one rod. 400 additional points of void fraction in 10x10 bundle can be, therefore, acquired. The time resolution of measurement is up to 1250 frames (cross sections) per second. We capability in a 10x10 bundle with o.d. 10 mm and 3110 mm long is demonstrated. The devised sensor is installed in 8 height levels to acquire the two-phase flow dynamics along axial direction. A pair of sensor layers is mounted in each level and is placed by 30 mm apart with each other to estimate a phasic velocity distribution on the basis of cross-correlation function of the two layers. Air bubbles are injected through sintered metal nozzles from the bottom end of 10x10 rods. Air flow rate distribution can vary with a controlled valves connected to each nozzle. The devised sensor exhibited the quasi three-dimensional flow structures, i.e. void fraction, phasic velocity and bubble chord length distributions. These quasi three-dimensional structures explorer complexity of two-phase flow dynamics such as coalescence and breakup of bubbles in the transient phasic velocity distributions. (author)

Rayleigh-wave phase-velocity maps and three-dimensional shear velocity structure of the western US from local non-plane surface wave tomography

Science.gov (United States)

Pollitz, F.F.; Snoke, J. Arthur

2010-01-01

We utilize two-and-three-quarter years of vertical-component recordings made by the Transportable Array (TA) component of Earthscope to constrain three-dimensional (3-D) seismic shear wave velocity structure in the upper 200 km of the western United States. Single-taper spectral estimation is used to compile measurements of complex spectral amplitudes from 44 317 seismograms generated by 123 teleseismic events. In the first step employed to determine the Rayleigh-wave phase-velocity structure, we implement a new tomographic method, which is simpler and more robust than scattering-based methods (e.g. multi-plane surface wave tomography). The TA is effectively implemented as a large number of local arrays by defining a horizontal Gaussian smoothing distance that weights observations near a given target point. The complex spectral-amplitude measurements are interpreted with the spherical Helmholtz equation using local observations about a succession of target points, resulting in Rayleigh-wave phase-velocity maps at periods over the range of 18–125 s. The derived maps depend on the form of local fits to the Helmholtz equation, which generally involve the nonplane-wave solutions of Friederich et al. In a second step, the phase-velocity maps are used to derive 3-D shear velocity structure. The 3-D velocity images confirm details witnessed in prior body-wave and surface-wave studies and reveal new structures, including a deep (>100 km deep) high-velocity lineament, of width ∼200 km, stretching from the southern Great Valley to northern Utah that may be a relic of plate subduction or, alternatively, either a remnant of the Mojave Precambrian Province or a mantle downwelling. Mantle seismic velocity is highly correlated with heat flow, Holocene volcanism, elastic plate thickness and seismicity. This suggests that shallow mantle structure provides the heat source for associated magmatism, as well as thinning of the thermal lithosphere, leading to relatively high

Precollisional velocity correlations in a hard-disk fluid with dissipative collisions.

Science.gov (United States)

Soto, R; Piasecki, J; Mareschal, M

2001-09-01

Velocity correlations are studied in granular fluids, modeled by the inelastic hard sphere gas. Making a density expansion of the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy for the evolution of the reduced distributions, we predict the presence of precollisional velocity correlations. They are created by the propagation through correlated sequences of collisions (ring events) of the velocity correlations generated after dissipative collisions. The correlations have their origin in the dissipative character of collisions, being always present in granular fluids. The correlations, that manifest microscopically as an alignment of the velocities of a colliding pair produce modifications of collisional averages, in particular, the virial pressure. The pressure shows a reduction with respect to the elastic case as a consequence of the velocity alignment. Good qualitative agreement is obtained for the comparison of the numerical evaluations of the obtained analytical expressions and molecular dynamics results that showed evidence of precollisional velocity correlations [R. Soto and M. Mareschal, Phys. Rev. E 63, 041303 (2001)].

Coupling two-phase fluid flow with two-phase darcy flow in anisotropic porous media

KAUST Repository

Chen, J.

2014-06-03

This paper reports a numerical study of coupling two-phase fluid flow in a free fluid region with two-phase Darcy flow in a homogeneous and anisotropic porous medium region. The model consists of coupled Cahn-Hilliard and Navier-Stokes equations in the free fluid region and the two-phase Darcy law in the anisotropic porous medium region. A Robin-Robin domain decomposition method is used for the coupled Navier-Stokes and Darcy system with the generalized Beavers-Joseph-Saffman condition on the interface between the free flow and the porous media regions. Obtained results have shown the anisotropic properties effect on the velocity and pressure of the two-phase flow. 2014 Jie Chen et al.

Coupling Two-Phase Fluid Flow with Two-Phase Darcy Flow in Anisotropic Porous Media

Directory of Open Access Journals (Sweden)

Jie Chen

2014-06-01

Full Text Available This paper reports a numerical study of coupling two-phase fluid flow in a free fluid region with two-phase Darcy flow in a homogeneous and anisotropic porous medium region. The model consists of coupled Cahn-Hilliard and Navier-Stokes equations in the free fluid region and the two-phase Darcy law in the anisotropic porous medium region. A Robin-Robin domain decomposition method is used for the coupled Navier-Stokes and Darcy system with the generalized Beavers-Joseph-Saffman condition on the interface between the free flow and the porous media regions. Obtained results have shown the anisotropic properties effect on the velocity and pressure of the two-phase flow.

Two-phase flow characteristics of HFC and HCFC fluid

International Nuclear Information System (INIS)

Ueno, T.; Matsuda, K.; Kusakabe, T.

1998-01-01

Some two-phase flow characteristics of HFC and HCFC fluid have been investigated experimentally. Fluids used in this experiment are HCFC22 (hereinafter called 'R22'), HCFC123 (hereinafter called 'R123') and Mixture of HFC fluid (hereinafter called 'R407C'). The fluid R407C are mixture of HFC32, HFC134a and HFC125, and their concentrations are 23wt%, 52wt% and 25wt%, respectively. This paper presents main flow parameters such as void fraction, interfacial velocities, bubble diameter distribution and pressure drop multiplier, which can characterize flow behavior. The void fractions and interfacial velocities were measured at some local positions in the single pipe using the bi-optical probe(hereinafter called 'BOP'). The procedure to calculate the void fraction from the void signals obtained by BOP were adopted the so-called slice method. The effects of slice levels on the void fraction were discussed taking into account bubble diameter. The new correlation of slice level as the function of void fraction has been proposed. The area-averaged void fractions obtained from BOP's void signals using new correlation were compared with void fractions obtained from pressure drops. The area-averaged interfacial velocities were also compared with the superficial gas velocities. It was concluded that the accuracy of BOP measurements are 5% for void fraction and less than 8.5% for interfacial velocity

On Bell correlations for the phase space of two entangled light modes

International Nuclear Information System (INIS)

Leonhardt, U.

1993-01-01

Bell's sign anticorrelations were studied for the phase space of two entangled light modes (or harmonic oscillators). States with the same symmetry as in Bell's example approach the anticorrelation function of the original Einstein-Podolsky-Rosen state as a universal limit for strong correlations. A Bell inequality is not violated. (orig.)

Velocity-pressure correlation measurements in complex free shear flows

International Nuclear Information System (INIS)

Naka, Yoshitsugu; Obi, Shinnosuke

2009-01-01

Simultaneous measurements of fluctuating velocity and pressure were performed in various turbulent free shear flows including a turbulent mixing layer and the wing-tip vortex trailing from a NACA0012 half-wing. Two different methods for fluctuating static pressure measurement were considered: a direct method using a miniature Pitot tube and an indirect method where static pressure was calculated from total pressure. The pressure obtained by either of these methods was correlated with the velocity measured by an X-type hot-wire probe. The results from these two techniques agreed with each other in the turbulent mixing layer. In the wing-tip vortex case, however, some discrepancies were found, although overall characteristics of the pressure-related statistics were adequately captured by both methods.

Generalized drift-flux correlation

International Nuclear Information System (INIS)

Takeuchi, K.; Young, M.Y.; Hochreiter, L.E.

1991-01-01

A one-dimensional drift-flux model with five conservation equations is frequently employed in major computer codes, such as TRAC-PD2, and in simulator codes. In this method, the relative velocity between liquid and vapor phases, or slip ratio, is given by correlations, rather than by direct solution of the phasic momentum equations, as in the case of the two-fluid model used in TRAC-PF1. The correlations for churn-turbulent bubbly flow and slug flow regimes were given in terms of drift velocities by Zuber and Findlay. For the annular flow regime, the drift velocity correlations were developed by Ishii et al., using interphasic force balances. Another approach is to define the drift velocity so that flooding and liquid hold-up conditions are properly simulated, as reported here. The generalized correlation is used to reanalyze the MB-2 test data for two-phase flow in a large-diameter pipe. The results are applied to the generalized drift flux velocity, whose relationship to the other correlations is discussed. Finally, the generalized drift flux correlation is implemented in TRAC-PD2. Flow reversal from countercurrent to cocurrent flow is computed in small-diameter U-shaped tubes and is compared with the flooding curve

Experimental study on local resistance of two-phase flow through spacer grid with rod bundle

International Nuclear Information System (INIS)

Yan Chaoxing; Yan Changqi; Sun Licheng; Tian Qiwei

2015-01-01

The experimental study on local resistance of single-phase and two-phase flows through a spacer grid in a vertical channel with 3 × 3 rod bundle was carried out under the normal temperature and pressure. For the case of single-phase flow, the liquid Reynolds number covered the range of 290-18 007. For the case of two-phase flow, the ranges of gas and liquid superficial velocities were 0.013-3.763 m/s and 0.076-1.792 m/s, respectively. A correlation for predicting local resistance of single-phase flow was given based on experimental results. Eight classical two-phase viscosity formulae for homogeneous model were evaluated against the experimental data of two-phase flow. The results show that Dukler model predicts the experimental data well in the range of Re 1 < 9000 while McAdams correlation is the best one for Re 1 ≥ 9000. For all experimental data, Dukler model provides the best prediction with the mean relative error of 29.03%. A new correlation is fitted for the range of Re 1 < 9000 by considering mass quality, two- phase Reynolds number and liquid and gas densities, resulting in a good agreement with the experimental data. (authors)

Reconfigurable Wave Velocity Transmission Lines for Phased Arrays

Science.gov (United States)

Host, Nick; Chen, Chi-Chih; Volakis, John L.; Miranda, Felix

2013-01-01

Phased array antennas showcase many advantages over mechanically steered systems. However, they are also more complex, heavy and most importantly costly. This presentation paper presents a concept which overcomes these detrimental attributes by eliminating all of the phase array backend (including phase shifters). Instead, a wave velocity reconfigurable transmission line is used in a series fed array arrangement to allow phase shifting with one small (100mil) mechanical motion. Different configurations of the reconfigurable wave velocity transmission line are discussed and simulated and experimental results are presented.

Heat transfer in two-phase flow of helium

International Nuclear Information System (INIS)

Subbotin, V.I.; Deev, V.I.; Solodovnikov, V.V.; Arkhipov, V.V.

1986-01-01

The results of experimental study of heat transfer in two-phase helium flow are presented. The effect of operating parameters (pressure, mass velocity, heat flux and quality) on boiling heat transfer intensity was investigated. A significant influence of boiling process prehistory on heat transfer coefficients was demonstrated. On the basis of experimental data obtained three typical regimes of flow boiling heat transfer were found. Analogy of heat transfer in flow boiling and pool boiling of helium and noncryogenic liquids was established. Correlations were developed which are in close agreement with available heat transfer data

Wave Tank Studies of Phase Velocities of Short Wind Waves

Science.gov (United States)

Ermakov, S.; Sergievskaya, I.; Shchegolkov, Yu.

Wave tank studies of phase velocities of short wind waves have been carried out using Ka-band radar and an Optical Spectrum Analyser. The phase velocities were retrieved from measured radar and optical Doppler shifts, taking into account measurements of surface drift velocities. The dispersion relationship was studied in centimetre (cm)- and millimetre(mm)-scale wavelength ranges at different fetches and wind speeds, both for a clean water surface and for water covered with surfactant films. It is ob- tained that the phase velocities do not follow the dispersion relation of linear capillary- gravity waves, increasing with fetch and, therefore, depending on phase velocities of dominant decimetre (dm)-centimetre-scale wind waves. One thus can conclude that nonlinear cm-mm-scale harmonics bound to the dominant wind waves and propagat- ing with the phase velocities of the decimetric waves are present in the wind wave spectrum. The resulting phase velocities of short wind waves are determined by re- lation between free and bound waves. The relative intensity of the bound waves in the spectrum of short wind waves is estimated. It is shown that this relation depends strongly on the surfactant concentration, because the damping effect due to films is different for free and bound waves; this results to changes of phase velocities of wind waves in the presence of surfactant films. This work was supported by MOD, UK via DERA Winfrith (Project ISTC 1774P) and by RFBR (Project 02-05-65102).

Lagrangian velocity correlations in homogeneous isotropic turbulence

International Nuclear Information System (INIS)

Gotoh, T.; Rogallo, R.S.; Herring, J.R.; Kraichnan, R.H.

1993-01-01

The Lagrangian velocity autocorrelation and the time correlations for individual wave-number bands are computed by direct numerical simulation (DNS) using the passive vector method (PVM), and the accuracy of the method is studied. It is found that the PVM is accurate when K max /k d ≥2 where K max is the maximum wave number carried in the simulation and k d is the Kolmogorov wave number. The Eulerian and Lagrangian time correlations for various wave-number bands are compared. At moderate to high wave number the Eulerian time correlation decays faster than the Lagrangian, and the effect of sweep on the former is observed. The time scale of the Eulerian correlation is found to be (kU 0 ) -1 while that of the Lagrangian is [∫ 0 k p 2 E(p)dp] -1/2 . The Lagrangian velocity autocorrelation in a frozen turbulent field is computed using the DIA, ALHDIA, and LRA theories and is compared with DNS measurements. The Markovianized Lagrangian renormalized approximation (MLRA) is compared with the DNS, and good agreement is found for one-time quantities in decaying turbulence at low Reynolds numbers and for the Lagrangian velocity autocorrelation in stationary turbulence at moderate Reynolds number. The effect of non-Gaussianity on the Lagrangian correlation predicted by the theories is also discussed

Fundamental research of two-phase flows with high liquid/gas density ratios

International Nuclear Information System (INIS)

Mishima, Kaichiro; Hibiki, Takashi; Saito, Yasushi; Tobita, Yoshiharu; Konishi, Kensuke; Suzuki, Tohru

2000-07-01

In order to analyze the boiling of a fuel-steel mixture pool formed during the core disruptive accident in a fast breeder reactor, it is important to understand the flow characteristics of gas-liquid two-phase pools containing molten reactor materials. Since the liquid/gas density ratio is high, the characteristics of such two-phase flows may differ from those of ordinary flows such as water/air flow. In this study, as a fundamental research of two-phase flows with a high liquid/gas density ratio, the experiments were performed to visualize and measure molten metal (lead-bismuth)/nitrogen gas two-phase flows using a neutron radiography technique. From these experiments, fundamental data such as bubble shapes, void fractions and liquid velocity fields were obtained. In addition, the momentum exchange model of SIMMER-III, which has been developed by JNC, was assessed and improved using the experimental data. In the visualization by neutron radiography, it was found that deformed ellipsoidal bubbles could be seen with smaller gas flux or lower void fractions, and spherical cap bubbles could be seen with larger gas flux or higher void fractions. In addition, a correlation applicable to SIMMER-III was proposed through a comparison between the experimental data and traditional empirical correlations. Furthermore, a visualization experiment using gold-cadmium tracer particles showed that the image processing technique used in the quantification of void fractions is applicable to the measurement of the liquid velocity fields. On the other hand, in the analysis by SIMMER-III, it was confirmed that the original momentum exchange model was appropriate for ellipsoidal bobby flows and that the accuracy of SIMMER-III for cap bubbly flows was much improved with the proposed correlation. Moreover, a new procedure, in which the appropriate drag coefficient could be automatically selected according to bubble shape, was developed. The SIMMER-III code improved through this study can

Flashing liquid jets and two-phase droplet dispersion

International Nuclear Information System (INIS)

Cleary, Vincent; Bowen, Phil; Witlox, Henk

2007-01-01

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

Phase velocity of nonlinear plasma waves in the laser beat-wave accelerator

International Nuclear Information System (INIS)

Spence, W.L.

1985-01-01

The suggested plasma-laser accelerator is an attempt to achieve a very high energy gradient by resonantly exciting a longitudinal wave traveling at close to the speed of light in cold plasma by means of the beat-wave generated by the transverse fields in two laser beams. Previous calculations to all orders in v/sub z/ have been done essentially from the laboratory frame point of view and have treated the plasma wave as having sharply defined phase velocity equal to the speed of light. However a high energy particle beam undergoing acceleration sees the plasma wave from a nearly light-like frame of reference and hence is very sensitive to small deviations in its phase velocity. Here the authors introduce a calculational scheme that includes all orders in v/sub z/ and in the plasma density, and additionally takes into account the influence of plasma nonlinearities on the wave's phase velocity. The main assumption is that the laser frequencies are very large compared to the plasma frequency - under which they are able to in essence formally sum up all orders of forward Raman scattering. They find that the nonlinear plasma wave does not have simply a single phase velocity - it is really a superposition of many - but that the beat-wave which drives it is usefully described by a non-local effective phase velocity function

Characterizing the correlations between local phase fractions of gas–liquid two-phase flow with wire-mesh sensor

Science.gov (United States)

Liu, W. L.; Dong, F.

2016-01-01

Understanding of flow patterns and their transitions is significant to uncover the flow mechanics of two-phase flow. The local phase distribution and its fluctuations contain rich information regarding the flow structures. A wire-mesh sensor (WMS) was used to study the local phase fluctuations of horizontal gas–liquid two-phase flow, which was verified through comparing the reconstructed three-dimensional flow structure with photographs taken during the experiments. Each crossing point of the WMS is treated as a node, so the measurement on each node is the phase fraction in this local area. An undirected and unweighted flow pattern network was established based on connections that are formed by cross-correlating the time series of each node under different flow patterns. The structure of the flow pattern network reveals the relationship of the phase fluctuations at each node during flow pattern transition, which is then quantified by introducing the topological index of the complex network. The proposed analysis method using the WMS not only provides three-dimensional visualizations of the gas–liquid two-phase flow, but is also a thorough analysis for the structure of flow patterns and the characteristics of flow pattern transition. This article is part of the themed issue ‘Supersensing through industrial process tomography’. PMID:27185959

Characterizing the correlations between local phase fractions of gas-liquid two-phase flow with wire-mesh sensor.

Science.gov (United States)

Tan, C; Liu, W L; Dong, F

2016-06-28

Understanding of flow patterns and their transitions is significant to uncover the flow mechanics of two-phase flow. The local phase distribution and its fluctuations contain rich information regarding the flow structures. A wire-mesh sensor (WMS) was used to study the local phase fluctuations of horizontal gas-liquid two-phase flow, which was verified through comparing the reconstructed three-dimensional flow structure with photographs taken during the experiments. Each crossing point of the WMS is treated as a node, so the measurement on each node is the phase fraction in this local area. An undirected and unweighted flow pattern network was established based on connections that are formed by cross-correlating the time series of each node under different flow patterns. The structure of the flow pattern network reveals the relationship of the phase fluctuations at each node during flow pattern transition, which is then quantified by introducing the topological index of the complex network. The proposed analysis method using the WMS not only provides three-dimensional visualizations of the gas-liquid two-phase flow, but is also a thorough analysis for the structure of flow patterns and the characteristics of flow pattern transition. This article is part of the themed issue 'Supersensing through industrial process tomography'. © 2016 The Author(s).

Non-Darcy interfacial dynamics of air-water two-phase flow in rough fractures under drainage conditions.

Science.gov (United States)

Chang, Chun; Ju, Yang; Xie, Heping; Zhou, Quanlin; Gao, Feng

2017-07-04

Two-phase flow interfacial dynamics in rough fractures is fundamental to understanding fluid transport in fractured media. The Haines jump of non-Darcy flow in porous media has been investigated at pore scales, but its fundamental processes in rough fractures remain unclear. In this study, the micron-scale Haines jump of the air-water interface in rough fractures was investigated under drainage conditions, with the air-water interface tracked using dyed water and an imaging system. The results indicate that the interfacial velocities represent significant Haines jumps when the meniscus passes from a narrow "throat" to a wide "body", with jump velocities as high as five times the bulk drainage velocity. Locally, each velocity jump corresponds to a fracture aperture variation; statistically, the velocity variations follow an exponential function of the aperture variations at a length scale of ~100 µm to ~100 mm. This spatial-scale-invariant correlation may indicate that the high-speed local velocities during the Haines jump would not average out spatially for a bulk system. The results may help in understanding the origin of interface instabilities and the resulting non-uniform phase distribution, as well as the micron-scale essence of the spatial and temporal instability of two-phase flow in fractured media at the macroscopic scale.

Pulsar velocity observations: Correlations, interpretations, and discussion

International Nuclear Information System (INIS)

Helfand, D.J.; Tademaru, E.

1977-01-01

From an examination of the current sample of 12 pulsars with measured proper motions and the z-distribution of the much larger group of over 80 sources with measured period derivatives, we develop a self-consistent picture of pulsar evolution. The apparent tendency of pulsars to move parallel to the galactic plane is explained as the result of various selection effects. A method for calculating the unmeasurable radial velocity of a pulsar is presented; it is shown that the total space velocities thus obtained are consistent with the assumption of an extreme Population I origin for pulsars which subsequently move away from the plane with a large range of velocities. The time scale for pulsar magnetic field decay is derived from dynamical considerations. A strong correlation of the original pulsar field strength with the magnitude of pulsar velocity is discussed. This results in the division of pulsars into two classes: Class A sources characterized by low space velocities, a small scale height, and low values of P 0 P 0 ; and Class B sources with a large range of velocities (up to 1000 km s -1 ), a much greater scale height, and larger values of initial field strength. It is postulated that Class A sources originate in tight binaries where their impulse acceleration at birth is insufficient to remove them from the system, while the Class B sources arise from single stars or loosely bound binaries and are accelerated to high velocities by their asymmetric radiation force. The evolutionary picture which is developed is shown to be consistent with a number of constraints imposed by supernova rates, the relative frequency of massive binaries and Class A sources, theoretical field-decay times, and the overall pulsar galactic distribution

Basic equations of interfacial area transport in gas-liquid two-phase flow

International Nuclear Information System (INIS)

Kataoka, I.; Yoshida, K.; Naitoh, M.; Okada, H.; Morii, T.

2011-01-01

The rigorous and consistent formulations of basic equations of interfacial area transport were derived using correlation functions of characteristic function of each phase and velocities of each phase. Turbulent transport term of interfacial area concentration was consistently derived and related to the difference between interfacial velocity and averaged velocity of each phase. Constitutive equations of turbulent transport terms of interfacial area concentration were proposed for bubbly flow. New transport model and constitutive equations were developed for churn flow. These models and constitutive equations are validated by experimental data of radial distributions of interfacial area concentration in bubbly and churn flow. (author)

Studies in boiling heat transfer in two phase flow through tube arrays: nucleate boiling heat transfer coefficient and maximum heat flux as a function of velocity and quality of Freon-113

International Nuclear Information System (INIS)

Rahmani, R.

1983-01-01

The nucleate boiling heat-transfer coefficient and the maximum heat flux were studied experimentally as functions of velocity, quality and heater diameter for single-phase flow, and two-phase flow of Freon-113 (trichlorotrifluorethane). Results show: (1) peak heat flux: over 300 measured peak heat flux data from two 0.875-in. and four 0.625-in.-diameter heaters indicated that: (a) for pool boiling, single-phase and two-phase forced convection boiling the only parameter (among hysteresis, rate of power increase, aging, presence and proximity of unheated rods) that has a statistically significant effect on the peak heat flux is the velocity. (b) In the velocity range (0 0 position or the point of impact of the incident fluid) and the top (180 0 position) of the test element, respectively

Melting along the Hugoniot and solid phase transition for Sn via sound velocity measurements

Science.gov (United States)

Song, Ping; Cai, Ling-cang; Tao, Tian-jiong; Yuan, Shuai; Chen, Hong; Huang, Jin; Zhao, Xin-wen; Wang, Xue-jun

2016-11-01

It is very important to determine the phase boundaries for materials with complex crystalline phase structures to construct their corresponding multi-phase equation of state. By measuring the sound velocity of Sn with different porosities, different shock-induced melting pressures along the solid-liquid phase boundary could be obtained. The incipient shock-induced melting of porous Sn samples with two different porosities occurred at a pressure of about 49.1 GPa for a porosity of 1.01 and 45.6 GPa for a porosity of 1.02, based on measurements of the sound velocity. The incipient shock-induced melting pressure of solid Sn was revised to 58.1 GPa using supplemental measurements of the sound velocity. Trivially, pores in Sn decreased the shock-induced melting pressure. Based on the measured longitudinal sound velocity data, a refined solid phase transition and the Hugoniot temperature-pressure curve's trend are discussed. No bcc phase transition occurs along the Hugoniot for porous Sn; further investigation is required to understand the implications of this finding.

Non-Darcy behavior of two-phase channel flow.

Science.gov (United States)

Xu, Xianmin; Wang, Xiaoping

2014-08-01

We study the macroscopic behavior of two-phase flow in porous media from a phase-field model. A dissipation law is first derived from the phase-field model by homogenization. For simple channel geometry in pore scale, the scaling relation of the averaged dissipation rate with the velocity of the two-phase flow can be explicitly obtained from the model which then gives the force-velocity relation. It is shown that, for the homogeneous channel surface, Dacry's law is still valid with a significantly modified permeability including the contribution from the contact line slip. For the chemically patterned surfaces, the dissipation rate has a non-Darcy linear scaling with the velocity, which is related to a depinning force for the patterned surface. Our result offers a theoretical understanding on the prior observation of non-Darcy behavior for the multiphase flow in either simulations or experiments.

Staging of gastric adenocarcinoma using two-phase spiral CT: correlation with pathologic staging

International Nuclear Information System (INIS)

Seo, Tae Seok; Lee, Dong Ho; Ko, Young Tae; Lim, Joo Won

1998-01-01

To correlate the preoperative staging of gastric adenocarcinoma using two-phase spiral CT with pathologic staging. One hundred and eighty patients with gastric cancers confirmed during surgery underwent two-phase spiral CT, and were evaluated retrospectively. CT scans were obtained in the prone position after ingestion of water. Scans were performed 35 and 80 seconds after the start of infusion of 120mL of non-ionic contrast material with the speed of 3mL/sec. Five mm collimation, 7mm/sec table feed and 5mm reconstruction interval were used. T-and N-stage were determined using spiral CT images, without knowledge of the pathologic results. Pathologic staging was later compared with CT staging. Pathologic T-stage was T1 in 70 cases(38.9%), T2 in 33(18.3%), T3 in 73(40.6%), and T4 in 4(2.2%). Type-I or IIa elevated lesions accouted for 10 of 70 T1 cases(14.3%) and flat or depressed lesions(type IIb, IIc, or III) for 60(85.7%). Pathologic N-stage was NO in 85 cases(47.2%), N1 in 42(23.3%), N2 in 31(17.2%), and N3 in 22(12,2%). The detection rate of early gastric cancer using two-phase spiral CT was 100.0%(10 of 10 cases) among elevated lesions and 78.3%(47 of 60 cases) among flat or depressed lesions. With regard to T-stage, there was good correlation between CT image and pathology in 86 of 180 cases(47.8%). Overstaging occurred in 23.3%(42 of 180 cases) and understaging in 28.9%(52 of 180 cases). With regard to N-stage, good correlation between CT image and pathology was noted in 94 of 180 cases(52.2%). The rate of understaging(31.7%, 57 of 180 cases) was higher than that of overstaging(16.1%, 29 of 180 cases)(p<0.001). The detection rate of early gastric cancer using two-phase spiral CT was 81.4%, and there was no significant difference in detectability between elevated and depressed lesions. Two-phase spiral CT for determing the T-and N-stage of gastric cancer was not effective;it was accurate in abont 50% of cases understaging tended to occur.=20

CORRELATION BETWEEN UTERINE ARTERY FLOW VELOCITY ...

African Journals Online (AJOL)

CORRELATION BETWEEN UTERINE ARTERY FLOW VELOCITY WAVEFORMS AND ENDOMETRIAL HISTOPATHOLOGY IN WOMEN WITH PERIMENOPAUSAL AND POSTMENOPAUSAL BLEEDING. Dr. Ebtesam Saied, Dr. Ismail El Garhy(MD), Dr. Farid I. Hassan(MD), Dr. Adel-Gamil Abd-Allah, Abd El Shafy Ibrahim ...

Correlation of right atrial appendage velocity with left atrial appendage velocity and brain natriuretic Peptide.

Science.gov (United States)

Kim, Bu-Kyung; Heo, Jung-Ho; Lee, Jae-Woo; Kim, Hyun-Soo; Choi, Byung-Joo; Cha, Tae-Joon

2012-03-01

Left atrial appendage (LAA) anatomy and function have been well characterized both in healthy and diseased people, whereas relatively little attention has been focused on the right atrial appendage (RAA). We sought to evaluate RAA flow velocity and to compare these parameters with LAA indices and with a study of biomarkers, such as brain natriuretic peptide, among patients with sinus rhythm (SR) and atrial fibrillation (AF). In a series of 79 consecutive patients referred for transesophageal echocardiography, 43 patients (23 with AF and 20 controls) were evaluated. AF was associated with a decrease in flow velocity for both LAA and RAA [LAA velocity-SR vs. AF: 61 ± 22 vs. 29 ± 18 m/sec (p vs. AF: 46 ± 20 vs. 19 ± 8 m/sec (p brain natriuretic peptide (BNP). AF was associated with decreased RAA and LAA flow velocities. RAA velocity was found to be positively correlated with LAA velocity and negatively correlated with BNP. The plasma BNP concentration may serve as a determinant of LAA and RAA functions.

Nonlinear correlations in phase-space resolved fluctuations at drift wave frequencies

Energy Technology Data Exchange (ETDEWEB)

Skiff, F [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States); Uzun, I [Institute for Plasma Research, University of Maryland, College Park, Maryland 20742 (United States); Diallo, A [Centre de Recherches en Physique des Plasams EPF, Lausanne (Switzerland)

2007-12-15

In an effort to better understand plasma transport, we measure fluctuations associated with drift instabilities resolved in the ion phase-space. Primary attention is given to fluctuations near the electron drift frequency where there are two general components to the observed fluctuations. From two (spatial) point measurements of the ion distribution function with a variable separation along the magnetic field, a number of statistical measures of the fluctuations are calculated including cross-correlation and cross-bicoherence. Both fluid ({omega}/k >> v{sub ti}) and kinetic ({omega}/k {approx} v{sub ti}) components are observed in the fluctuations. The nonlinear interactions are found to depend strongly on the ion particle velocity.

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

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.

Wavelet phase analysis of two velocity components to infer the structure of interscale transfers in a turbulent boundary-layer

Energy Technology Data Exchange (ETDEWEB)

Keylock, Christopher J [Sheffield Fluid Mechanics Group and Department of Civil and Structural Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom); Nishimura, Kouichi, E-mail: c.keylock@sheffield.ac.uk [Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan)

2016-04-15

Scale-dependent phase analysis of velocity time series measured in a zero pressure gradient boundary layer shows that phase coupling between longitudinal and vertical velocity components is strong at both large and small scales, but minimal in the middle of the inertial regime. The same general pattern is observed at all vertical positions studied, but there is stronger phase coherence as the vertical coordinate, y, increases. The phase difference histograms evolve from a unimodal shape at small scales to the development of significant bimodality at the integral scale and above. The asymmetry in the off-diagonal couplings changes sign at the midpoint of the inertial regime, with the small scale relation consistent with intense ejections followed by a more prolonged sweep motion. These results may be interpreted in a manner that is consistent with the action of low speed streaks and hairpin vortices near the wall, with large scale motions further from the wall, the effect of which penetrates to smaller scales. Hence, a measure of phase coupling, when combined with a scale-by-scale decomposition of perpendicular velocity components, is a useful tool for investigating boundary-layer structure and inferring process from single-point measurements. (paper)

Wavelet phase analysis of two velocity components to infer the structure of interscale transfers in a turbulent boundary-layer

International Nuclear Information System (INIS)

Keylock, Christopher J; Nishimura, Kouichi

2016-01-01

Scale-dependent phase analysis of velocity time series measured in a zero pressure gradient boundary layer shows that phase coupling between longitudinal and vertical velocity components is strong at both large and small scales, but minimal in the middle of the inertial regime. The same general pattern is observed at all vertical positions studied, but there is stronger phase coherence as the vertical coordinate, y, increases. The phase difference histograms evolve from a unimodal shape at small scales to the development of significant bimodality at the integral scale and above. The asymmetry in the off-diagonal couplings changes sign at the midpoint of the inertial regime, with the small scale relation consistent with intense ejections followed by a more prolonged sweep motion. These results may be interpreted in a manner that is consistent with the action of low speed streaks and hairpin vortices near the wall, with large scale motions further from the wall, the effect of which penetrates to smaller scales. Hence, a measure of phase coupling, when combined with a scale-by-scale decomposition of perpendicular velocity components, is a useful tool for investigating boundary-layer structure and inferring process from single-point measurements. (paper)

Velocity-dependent quantum phase slips in 1D atomic superfluids.

Science.gov (United States)

Tanzi, Luca; Scaffidi Abbate, Simona; Cataldini, Federica; Gori, Lorenzo; Lucioni, Eleonora; Inguscio, Massimo; Modugno, Giovanni; D'Errico, Chiara

2016-05-18

Quantum phase slips are the primary excitations in one-dimensional superfluids and superconductors at low temperatures but their existence in ultracold quantum gases has not been demonstrated yet. We now study experimentally the nucleation rate of phase slips in one-dimensional superfluids realized with ultracold quantum gases, flowing along a periodic potential. We observe a crossover between a regime of temperature-dependent dissipation at small velocity and interaction and a second regime of velocity-dependent dissipation at larger velocity and interaction. This behavior is consistent with the predicted crossover from thermally-assisted quantum phase slips to purely quantum phase slips.

Correlated motion of two atoms trapped in a single-mode cavity field

International Nuclear Information System (INIS)

Asboth, Janos K.; Domokos, Peter; Ritsch, Helmut

2004-01-01

We study the motion of two atoms trapped at distant positions in the field of a driven standing-wave high-Q optical resonator. Even without any direct atom-atom interaction the atoms are coupled through their position dependent influence on the intracavity field. For sufficiently good trapping and low cavity losses the atomic motion becomes significantly correlated and the two particles oscillate in their wells preferentially with a 90 deg. relative phase shift. The onset of correlations seriously limits cavity cooling efficiency, raising the achievable temperature to the Doppler limit. The physical origin of the correlation can be traced back to a cavity mediated crossfriction, i.e., a friction force on one particle depending on the velocity of the second particle. Choosing appropriate operating conditions allows for engineering these long range correlations. In addition this cross-friction effect can provide a basis for sympathetic cooling of distant trapped clouds

Laser Doppler measurements in two-phase flows

International Nuclear Information System (INIS)

Durst, F.; Zare, M.

1976-01-01

Basic theory for laser-Doppler velocity measurements of large reflecting or refracting surfaces is provided. It is shown that the Doppler-signals contain information of the velocity and size of the large bodies, and relationships for transforming velocity and radius of curvature of moving spheres are presented. Preliminary experiments verified the analytical findings and demonstrated the applicability of the method to some two-phase flows

Film boiling from spheres in single- and two-phase flow

International Nuclear Information System (INIS)

Liu, C.; Theofanous, T.G.; Yuen, W.W.

1992-01-01

Experimental data on film boiling heat transfer from single, inductively heated, spheres in single- and two-phase flow (saturated water and steam, respectively) are presented. In the single-phase-flow experiments water velocities ranged from 0.1 to 2.0 m/s; in the two-phase-flow experiments superficial water and steam velocities covered 0.1 to 0.6 m/s and 4 to 10 m/s, respectively. All experiments were run at atmospheric pressure and with sphere temperatures from 900C down to quenching. Limited interpretations of the single-phase- flow data are possible, but the two-phase-flow data are new and unique

Measurement of phase interaction in dispersed gas-particle two-phase flow by phase-doppler anemometry

OpenAIRE

Mergheni Ali Mohamed; Ben Ticha Hmaied; Sautet Jen-Charles; Godard Gille; Ben Nasrallah Sassi

2008-01-01

For simultaneous measurement of size and velocity distributions of continuous and dispersed phases in a two-phase flow a technique phase-Doppler anemometry was used. Spherical glass particles with a particle diameter range from 102 up to 212 µm were used. In this two-phase flow an experimental results are presented which indicate a significant influence of the solid particles on the flow characteristics. The height of influence of these effects depends on the local position in the jet. Near t...

Quantum phase space theory for the calculation of v·j vector correlations

International Nuclear Information System (INIS)

Hall, G.E.

1995-01-01

The quantum state-counting phase space theory commonly used to describe barrierless dissociation is recast in a helicity basis to calculate photofragment v·j correlations. Counting pairs of fragment states with specific angular momentum projection numbers on the relative velocity provides a simple connection between angular momentum conservation and the v·j correlation, which is not so evident in the conventional basis for phase space state counts. The upper bound on the orbital angular momentum, l, imposed by the centrifugal barrier cannot be included simply in the helicity basis, where l is not a good quantum number. Two approaches for a quantum calculation of the v·j correlation are described to address this point. An application to the photodissociation of NCCN is consistent with recent classical phase space calculations of Cline and Klippenstein. The observed vector correlation exceeds the phase space theory prediction. The authors take this as evidence of incomplete mixing of the K states of the linear parent molecule at the transition state, corresponding to an evolution of the body-fixed projection number K into the total helicity of the fragment pair state. The average over a thermal distribution of parent angular momentum in the special case of a linear molecule does not significantly reduce the v·j correlation below that computed for total J = 0

Steady state flow analysis of two-phase natural circulation in multiple parallel channel loop

International Nuclear Information System (INIS)

Bhusare, V.H.; Bagul, R.K.; Joshi, J.B.; Nayak, A.K.; Kannan, Umasankari; Pilkhwal, D.S.; Vijayan, P.K.

2016-01-01

Highlights: • Liquid circulation velocity increases with increasing superficial gas velocity. • Total two-phase pressure drop decreases with increasing superficial gas velocity. • Channels with larger driving force have maximum circulation velocities. • Good agreement between experimental and model predictions. - Abstract: In this work, steady state flow analysis has been carried out experimentally in order to estimate the liquid circulation velocities and two-phase pressure drop in air–water multichannel circulating loop. Experiments were performed in 15 channel circulating loop. Single phase and two-phase pressure drops in the channels have been measured experimentally and have been compared with theoretical model of Joshi et al. (1990). Experimental measurements show good agreement with model.

Experiments in polydisperse two-phase turbulent flows

International Nuclear Information System (INIS)

Bachalo, W.D.; Houser, M.J.

1985-01-01

Aspects of turbulent two-phase flow measurements obtained with a laser Doppler velocimeter that was modified to also obtain particle size were investigated. Simultaneous measurements of the particle size and velocity allowed the determination of the lag characteristics of particles over a range of sizes. Relatively large particles were found to respond well to the turbulent fluctuations in low speed flows. Measurements of sprays were obtained at various points throughout the spray plume. Velocity measurements for each drop size class were obtained and revealed the relative velocity relaxation with downstream distance. The evolution of the rms velocities for each size class was also examined. Difficulties associated with seeding polydispersions to obtain gas phase turbulence data were discussed. Several approaches for mitigating the errors due to seed particle concentration bias were reviewed

Propagation of small disturbances in two phases, one component flow (1963)

International Nuclear Information System (INIS)

Boure, J.

1963-01-01

A small disturbance is, shown to give rise to two waves: a pressure (sonic) wave and a continuity wave. Their propagation velocities are calculated. These velocities are independent of the disturbance amplitude. The sonic velocity is primarily a function of that one corresponding to the same medium with no flow and of the liquid phase velocity. It is also a function of the physical properties of the phases on the saturation line, of the slip laws and of the void fraction. The continuity wave velocity is only a function of the slip laws, of the void fraction and of the velocity of either phase. It appears two kinds of critical flow rates which are calculated. The void fraction and the liquid and gas velocities variations are calculated. These results are extended to the case of a real loop and an approximative method is given for the treatment of this case. (author) [fr

Parallel two-phase-flow-induced vibrations in fuel pin model

International Nuclear Information System (INIS)

Hara, Fumio; Yamashita, Tadashi

1978-01-01

This paper reports the experimental results of vibrations of a fuel pin model -herein meaning the essential form of a fuel pin from the standpoint of vibration- in a parallel air-and-water two-phase flow. The essential part of the experimental apparatus consisted of a flat elastic strip made of stainless steel, both ends of which were firmly supported in a circular channel conveying the two-phase fluid. Vibrational strain of the fuel pin model, pressure fluctuation of the two-phase flow and two-phase-flow void signals were measured. Statistical measures such as power spectral density, variance and correlation function were calculated. The authors obtained (1) the relation between variance of vibrational strain and two-phase-flow velocity, (2) the relation between variance of vibrational strain and two-phase-flow pressure fluctuation, (3) frequency characteristics of variance of vibrational strain against the dominant frequency of the two-phase-flow pressure fluctuation, and (4) frequency characteristics of variance of vibrational strain against the dominant frequency of two-phase-flow void signals. The authors conclude that there exist two kinds of excitation mechanisms in vibrations of a fuel pin model inserted in a parallel air-and-water two-phase flow; namely, (1) parametric excitation, which occurs when the fundamental natural frequency of the fuel pin model is related to the dominant travelling frequency of water slugs in the two-phase flow by the ratio 1/2, 1/1, 3/2 and so on; and (2) vibrational resonance, which occurs when the fundamental frequency coincides with the dominant frequency of the two-phase-flow pressure fluctuation. (auth.)

On the use of nuclear magnetic resonance to characterize vertical two-phase bubbly flows

International Nuclear Information System (INIS)

Lemonnier, H.; Jullien, P.

2011-01-01

Research highlights: → We provide a complete theory of the PGSE measurement in single and two-phase flow. → Friction velocity can be directly determinated from measured velocity distributions. → Fast determination of moments shorten PGSE process with small loss of accuracy. → Turbulent diffusion measurements agree well with known trends and existing models. → We think NMR can be a tool to benchmark thermal anemometry in two-phase flow. - Abstract: Since the pioneering work of who showed that NMR can be used to measure accurately the mean liquid velocity and void fraction in two-phase pipe flow, it has been shown that NMR signal can also characterize the turbulent eddy diffusivity and velocity fluctuations. In this paper we provide an in depth validation of these statements together with a clarification of the nature of the mean velocity that is actually measured by NMR PFGSE sequence. The analysis shows that the velocity gradient at the wall is finely space-resolved and allows the determination of the friction velocity in single-phase flows. Next turbulent diffusion measurements in two-phase flows are presented, analyzed and compared to existing data and models. It is believed that NMR velocity measurement is sufficiently understood that it can be utilized to benchmark thermal anemometry in two-phase flows. Theoretical results presented in this paper also show how this can be undertaken.

Studying Suspended Sediment Mechanism with Two-Phase PIV

Science.gov (United States)

Matinpour, H.; Atkinson, J. F.; Bennett, S. J.; Guala, M.

2017-12-01

Suspended sediment transport affects soil erosion, agriculture and water resources quality. Turbulent diffusion is the most primary force to maintain sediments in suspension. Although extensive previous literature have been studying the interactions between turbulent motion and suspended sediment, mechanism of sediments in suspension is still poorly understood. In this study, we investigate suspension of sediments as two distinct phases: one phase of sediments and another phase of fluid with turbulent motions. We designed and deployed a state-of-the-art two-phase PIV measurement technique to discriminate these two phases and acquire velocities of each phase separately and simultaneously. The technique that we have developed is employing a computer-vision based method, which enables us to discriminate sediment particles from fluid tracer particles based on two thresholds, dissimilar particle sizes and different particle intensities. Results indicate that fluid turbulence decreases in the presence of suspended sediments. Obtaining only sediment phase consecutive images enable us to compute fluctuation sediment concentration. This result enlightens understanding of complex interaction between the fluctuation velocities and the fluctuation of associated mass and compares turbulent viscosity with turbulent eddy diffusivity experimentally.

New Models for Velocity/Pressure-Gradient Correlations in Turbulent Boundary Layers

Science.gov (United States)

Poroseva, Svetlana; Murman, Scott

2014-11-01

To improve the performance of Reynolds-Averaged Navier-Stokes (RANS) turbulence models, one has to improve the accuracy of models for three physical processes: turbulent diffusion, interaction of turbulent pressure and velocity fluctuation fields, and dissipative processes. The accuracy of modeling the turbulent diffusion depends on the order of a statistical closure chosen as a basis for a RANS model. When the Gram-Charlier series expansions for the velocity correlations are used to close the set of RANS equations, no assumption on Gaussian turbulence is invoked and no unknown model coefficients are introduced into the modeled equations. In such a way, this closure procedure reduces the modeling uncertainty of fourth-order RANS (FORANS) closures. Experimental and direct numerical simulation data confirmed the validity of using the Gram-Charlier series expansions in various flows including boundary layers. We will address modeling the velocity/pressure-gradient correlations. New linear models will be introduced for the second- and higher-order correlations applicable to two-dimensional incompressible wall-bounded flows. Results of models' validation with DNS data in a channel flow and in a zero-pressure gradient boundary layer over a flat plate will be demonstrated. A part of the material is based upon work supported by NASA under award NNX12AJ61A.

Measurements of liquid-phase turbulence in gas–liquid two-phase flows using particle image velocimetry

International Nuclear Information System (INIS)

Zhou, Xinquan; Doup, Benjamin; Sun, Xiaodong

2013-01-01

Liquid-phase turbulence measurements were performed in an air–water two-phase flow loop with a circular test section of 50 mm inner diameter using a particle image velocimetry (PIV) system. An optical phase separation method-–planar laser-induced fluorescence (PLIF) technique—which uses fluorescent particles and an optical filtration technique, was employed to separate the signals of the fluorescent seeding particles from those due to bubbles and other noises. An image pre-processing scheme was applied to the raw PIV images to remove the noise residuals that are not removed by the PLIF technique. In addition, four-sensor conductivity probes were adopted to measure the radial distribution of the void fraction. Two benchmark tests were performed: the first was a comparison of the PIV measurement results with those of similar flow conditions using thermal anemometry from previous studies; the second quantitatively compared the superficial liquid velocities calculated from the local liquid velocity and void fraction measurements with the global liquid flow rate measurements. The differences of the superficial liquid velocity obtained from the two measurements were bounded within ±7% for single-phase flows and two-phase bubbly flows with the area-average void fraction up to 18%. Furthermore, a preliminary uncertainty analysis was conducted to investigate the accuracy of the two-phase PIV measurements. The systematic uncertainties due to the circular pipe curvature effects, bubble surface reflection effects and other potential uncertainty sources of the PIV measurements were discussed. The purpose of this work is to facilitate the development of a measurement technique (PIV-PLIF) combined with image pre-processing for the liquid-phase turbulence in gas–liquid two-phase flows of relatively high void fractions. The high-resolution data set can be used to more thoroughly understand two-phase flow behavior, develop liquid-phase turbulence models, and assess high

MR flow velocity measurement using 2D phase contrast, assessment of imaging parameters

International Nuclear Information System (INIS)

Akata, Soichi; Fukushima, Akihiro; Abe, Kimihiko; Darkanzanli, A.; Gmitro, A.F.; Unger, E.C.; Capp, M.P.

1999-01-01

The two-dimensional (2D) phase contrast technique using balanced gradient pulses is utilized to measure flow velocities of cerebrospinal fluid and blood. Various imaging parameters affect the accuracy of flow velocity measurements to varying degrees. Assessment of the errors introduced by changing the imaging parameters are presented and discussed in this paper. A constant flow phantom consisting of a pump, a polyethylene tube and a flow meter was assembled. A clinical 1.5 Tesla MR imager was used to perform flow velocity measurements. The phase contrast technique was used to estimate the flow velocity of saline through the phantom. The effects of changes in matrix size, flip angle, flow compensation, and velocity encoding (VENC) value were tested in the pulse sequence. Gd-DTPA doped saline was used to study the effect of changing T1 on the accuracy of flow velocity measurement. Matrix size (within practical values), flip angle, and flow compensation had minimum impact on flow velocity measurements. T1 of the solution also had no effect on the accuracy of measuring the flow velocity. On the other hand, it was concluded that errors as high as 20% can be expected in the flow velocity measurements if the VENC value is not properly chosen. (author)

MR flow velocity measurement using 2D phase contrast, assessment of imaging parameters

Energy Technology Data Exchange (ETDEWEB)

Akata, Soichi; Fukushima, Akihiro; Abe, Kimihiko [Tokyo Medical Coll. (Japan); Darkanzanli, A.; Gmitro, A.F.; Unger, E.C.; Capp, M.P.

1999-11-01

The two-dimensional (2D) phase contrast technique using balanced gradient pulses is utilized to measure flow velocities of cerebrospinal fluid and blood. Various imaging parameters affect the accuracy of flow velocity measurements to varying degrees. Assessment of the errors introduced by changing the imaging parameters are presented and discussed in this paper. A constant flow phantom consisting of a pump, a polyethylene tube and a flow meter was assembled. A clinical 1.5 Tesla MR imager was used to perform flow velocity measurements. The phase contrast technique was used to estimate the flow velocity of saline through the phantom. The effects of changes in matrix size, flip angle, flow compensation, and velocity encoding (VENC) value were tested in the pulse sequence. Gd-DTPA doped saline was used to study the effect of changing T1 on the accuracy of flow velocity measurement. Matrix size (within practical values), flip angle, and flow compensation had minimum impact on flow velocity measurements. T1 of the solution also had no effect on the accuracy of measuring the flow velocity. On the other hand, it was concluded that errors as high as 20% can be expected in the flow velocity measurements if the VENC value is not properly chosen. (author)

Determination of velocity vector angles using the directional cross-correlation method

DEFF Research Database (Denmark)

Kortbek, Jacob; Jensen, Jørgen Arendt

2005-01-01

and then select the angle with the highest normalized correlation between directional signals. The approach is investigated using Field II simulations and data from the experimental ultrasound scanner RASMUS and with a parabolic flow having a peak velocity of 0.3 m/s. A 7 MHz linear array transducer is used......A method for determining both velocity magnitude and angle in any direction is suggested. The method uses focusing along the velocity direction and cross-correlation for finding the correct velocity magnitude. The angle is found from beamforming directional signals in a number of directions......-time ) between signals to correlate, and a proper choice varies with flow angle and flow velocity. One performance example is given with a fixed value of k tprf for all flow angles. The angle estimation on measured data for flow at 60 ◦ to 90 ◦ , yields a probability of valid estimates between 68% and 98...

A technique for plasma velocity-space cross-correlation

Science.gov (United States)

Mattingly, Sean; Skiff, Fred

2018-05-01

An advance in experimental plasma diagnostics is presented and used to make the first measurement of a plasma velocity-space cross-correlation matrix. The velocity space correlation function can detect collective fluctuations of plasmas through a localized measurement. An empirical decomposition, singular value decomposition, is applied to this Hermitian matrix in order to obtain the plasma fluctuation eigenmode structure on the ion distribution function. A basic theory is introduced and compared to the modes obtained by the experiment. A full characterization of these modes is left for future work, but an outline of this endeavor is provided. Finally, the requirements for this experimental technique in other plasma regimes are discussed.

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.

Power spectral density of velocity fluctuations estimated from phase Doppler data

Science.gov (United States)

Jedelsky, Jan; Lizal, Frantisek; Jicha, Miroslav

2012-04-01

Laser Doppler Anemometry (LDA) and its modifications such as PhaseDoppler Particle Anemometry (P/DPA) is point-wise method for optical nonintrusive measurement of particle velocity with high data rate. Conversion of the LDA velocity data from temporal to frequency domain - calculation of power spectral density (PSD) of velocity fluctuations, is a non trivial task due to nonequidistant data sampling in time. We briefly discuss possibilities for the PSD estimation and specify limitations caused by seeding density and other factors of the flow and LDA setup. Arbitrary results of LDA measurements are compared with corresponding Hot Wire Anemometry (HWA) data in the frequency domain. Slot correlation (SC) method implemented in software program Kern by Nobach (2006) is used for the PSD estimation. Influence of several input parameters on resulting PSDs is described. Optimum setup of the software for our data of particle-laden air flow in realistic human airway model is documented. Typical character of the flow is described using PSD plots of velocity fluctuations with comments on specific properties of the flow. Some recommendations for improvements of future experiments to acquire better PSD results are given.

Power spectral density of velocity fluctuations estimated from phase Doppler data

Directory of Open Access Journals (Sweden)

Jicha Miroslav

2012-04-01

Full Text Available Laser Doppler Anemometry (LDA and its modifications such as PhaseDoppler Particle Anemometry (P/DPA is point-wise method for optical nonintrusive measurement of particle velocity with high data rate. Conversion of the LDA velocity data from temporal to frequency domain – calculation of power spectral density (PSD of velocity fluctuations, is a non trivial task due to nonequidistant data sampling in time. We briefly discuss possibilities for the PSD estimation and specify limitations caused by seeding density and other factors of the flow and LDA setup. Arbitrary results of LDA measurements are compared with corresponding Hot Wire Anemometry (HWA data in the frequency domain. Slot correlation (SC method implemented in software program Kern by Nobach (2006 is used for the PSD estimation. Influence of several input parameters on resulting PSDs is described. Optimum setup of the software for our data of particle-laden air flow in realistic human airway model is documented. Typical character of the flow is described using PSD plots of velocity fluctuations with comments on specific properties of the flow. Some recommendations for improvements of future experiments to acquire better PSD results are given.

Spatiotemporal Signal Analysis via the Phase Velocity Transform

International Nuclear Information System (INIS)

Mattor, Nathan

2000-01-01

The phase velocity transform (PVT) is an integral transform that divides a function of space and time into components that propagate at uniform phase velocities without distortion. This paper examines the PVT as a method to analyze spatiotemporal fluctuation data. The transform is extended to systems with discretely sampled data on a periodic domain, and applied to data from eight azimuthally distributed probes on the Sustained Spheromak Physics Experiment (SSPX). This reveals features not shown by Fourier analysis, particularly regarding nonsinusoidal mode structure. (c) 2000 The American Physical Society

Numerical method for two-phase flow discontinuity propagation calculation

International Nuclear Information System (INIS)

Toumi, I.; Raymond, P.

1989-01-01

In this paper, we present a class of numerical shock-capturing schemes for hyperbolic systems of conservation laws modelling two-phase flow. First, we solve the Riemann problem for a two-phase flow with unequal velocities. Then, we construct two approximate Riemann solvers: an one intermediate-state Riemann solver and a generalized Roe's approximate Riemann solver. We give some numerical results for one-dimensional shock-tube problems and for a standard two-phase flow heat addition problem involving two-phase flow instabilities

Phase correlation of foreign exchange time series

Science.gov (United States)

Wu, Ming-Chya

2007-03-01

Correlation of foreign exchange rates in currency markets is investigated based on the empirical data of USD/DEM and USD/JPY exchange rates for a period from February 1 1986 to December 31 1996. The return of exchange time series is first decomposed into a number of intrinsic mode functions (IMFs) by the empirical mode decomposition method. The instantaneous phases of the resultant IMFs calculated by the Hilbert transform are then used to characterize the behaviors of pricing transmissions, and the correlation is probed by measuring the phase differences between two IMFs in the same order. From the distribution of phase differences, our results show explicitly that the correlations are stronger in daily time scale than in longer time scales. The demonstration for the correlations in periods of 1986-1989 and 1990-1993 indicates two exchange rates in the former period were more correlated than in the latter period. The result is consistent with the observations from the cross-correlation calculation.

Improvement of Estimation method for two-phase flow in a large-diameter pipe. Pt. 4. Effect of the inlet boundary condition of the upward flow section on flow characteristics

International Nuclear Information System (INIS)

Yoneda, Kimitoshi; Okawa, Tomio; Zhou, Shirong

1999-01-01

In nuclear power plants, many large-diameter pipes are subject to gas-liquid two-phase flow. For rational design and performance estimation, the flow in the pipes should be predicted accurately. With the correlation used at present, however, the flow analysis can not reach desirable precision. This is partly due to the lack of understanding of the two-phase flow characteristics in large-diameter pipes. Therefore, steam-water two-phase flow in a vertical pipe (155 mm i.d.) was investigated empirically. Lateral distribution data of phase volume fraction, gas velocity and bubble diameter were obtained. The effects of the inlet boundary condition were also observed. The drift velocity in the developing region was considerably affected by the inlet boundary condition. By deriving the correlation of mean bubble diameter as a function of void fraction and pressure, the empirical data was predicted with high accuracy compared with the existing correlation used in best-estimate codes of nuclear reactor safety analysis. (author)

Numerical simulation of gas-liquid two-phase flow and convective heat transfer in a micro tube

International Nuclear Information System (INIS)

Fukagata, Koji; Kasagi, Nobuhide; Ua-arayaporn, Poychat; Himeno, Takehiro

2007-01-01

Numerical simulation of an air and water two-phase flow in a 20 μm ID tube is carried out. A focus is laid upon the flow and heat transfer characteristics in bubble-train flows. An axisymmetric two-dimensional flow is assumed. The finite difference method is used to solve the governing equations, while the level set method is adopted for capturing the interface of gas and liquid. In each simulation, the mean pressure gradient and the wall heat flux are kept constant. The simulation is repeated under different conditions of pressure gradient and void fraction. The superficial Reynolds numbers of gas and liquid phases studied are 0.34-13 and 16-490, respectively, and the capillary number is 0.0087-0.27. Regardless of the flow conditions, the gas-phase velocity is found approximately 1.2 times higher than the liquid-phase velocity. This is in accordance with the Armand correlation valid for two-phase flows in macro-sized tubes. The two-phase friction coefficient is found to be scaled with the Reynolds number based on the effective viscosity of the Einstein type. The computed wall temperature distribution is qualitatively similar to that observed experimentally in a mini channel. The local Nusselt number beneath the bubble is found notably higher than that of single-phase flow

Solid phase stability of molybdenum under compression: Sound velocity measurements and first-principles calculations

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiulu [Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, P.O. Box 919-102, 621900 Mianyang, Sichuan (China); Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, 621010 Mianyang, Sichuan (China); Liu, Zhongli [Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, P.O. Box 919-102, 621900 Mianyang, Sichuan (China); College of Physics and Electric Information, Luoyang Normal University, 471022 Luoyang, Henan (China); Jin, Ke; Xi, Feng; Yu, Yuying; Tan, Ye; Dai, Chengda; Cai, Lingcang [Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, P.O. Box 919-102, 621900 Mianyang, Sichuan (China)

2015-02-07

The high-pressure solid phase stability of molybdenum (Mo) has been the center of a long-standing controversy on its high-pressure melting. In this work, experimental and theoretical researches have been conducted to check its solid phase stability under compression. First, we performed sound velocity measurements from 38 to 160 GPa using the two-stage light gas gun and explosive loading in backward- and forward-impact geometries, along with the high-precision velocity interferometry. From the sound velocities, we found no solid-solid phase transition in Mo before shock melting, which does not support the previous solid-solid phase transition conclusion inferred from the sharp drops of the longitudinal sound velocity [Hixson et al., Phys. Rev. Lett. 62, 637 (1989)]. Then, we searched its structures globally using the multi-algorithm collaborative crystal structure prediction technique combined with the density functional theory. By comparing the enthalpies of body centered cubic structure with those of the metastable structures, we found that bcc is the most stable structure in the range of 0–300 GPa. The present theoretical results together with previous ones greatly support our experimental conclusions.

Study on two phase flow characteristics in annular pulsed extraction column with different ratio of annular width to column diameter

International Nuclear Information System (INIS)

Qin Wei; Dai Youyuan; Wang Jiading

1994-01-01

Annular pulsed extraction column can successfully provide large throughput and can be made critically safe for fuel reprocessing. This investigation is to study the two phase flow characteristics in annular pulsed extraction column with four different annular width. 30% TBP (in kerosene)-water is used (water as continuous phase). Results show that modified Pratt correlation is valid under the experimental operation conditions for the annular pulsed extraction column. The characteristic velocity U K decreased with the increase of energy input and increased with the increase of the ratio of annular width to column diameter. Flooding velocity correlation is suggested. The deviation of the calculated values from the experimental data is within +20% for four annular width in a pulsed extraction column

Measurement of gas-liquid two-phase flow in micro-pipes by a capacitance sensor.

Science.gov (United States)

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

2014-11-26

A capacitance measurement system is developed for the measurement of gas-liquid two-phase flow in glass micro-pipes with inner diameters of 3.96, 2.65 and 1.56 mm, respectively. As a typical flow regime in a micro-pipe two-phase flow system, slug flow is chosen for this investigation. A capacitance sensor is designed and a high-resolution and high-speed capacitance measurement circuit is used to measure the small capacitance signals based on the differential sampling method. The performance and feasibility of the capacitance method are investigated and discussed. The capacitance signal is analyzed, which can reflect the voidage variation of two-phase flow. The gas slug velocity is determined through a cross-correlation technique using two identical capacitance sensors. The simulation and experimental results show that the presented capacitance measurement system is successful. Research work also verifies that the capacitance sensor is an effective method for the measurement of gas liquid two-phase flow parameters in micro-pipes.

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Analysis of two-phase flow instability in vertical boiling channels I: development of a linear model for the inlet velocity perturbation

International Nuclear Information System (INIS)

Hwang, D.H.; Yoo, Y.J.; Kim, K.K.

1998-08-01

A linear model, named ALFS, is developed for the analysis of two-phase flow instabilities caused by density wave oscillation and flow excursion in a vertical boiling channel with constant pressure drop conditions. The ALFS code can take into account the effect of the phase velocity difference and the thermally non-equilibrium phenomena, and the neutral boundary of the two-phase flow instability was analyzed by D-partition method. Three representative two-phase flow models ( i.e. HEM, DEM, and DNEM) were examined to investigate the effects on the stability analysis. As the results, it reveals that HEM shows the most conservative prediction of heat flux at the onset of flow instability. three linear models, Ishiis DEM, Sahas DNEM, and ALFS model, were applied to Sahas experimental data of density wave oscillation, and as the result, the mean and standard deviation of the predicted-to-measured heat flux at the onset of instability were calculated as 0.93/0.162, 0.79/0.112, and 0.95/0.143, respectively. For the long test section, however, ALFS model tends to predict the heat fluxes about 30 % lower than the measured values. (author). 14 refs

Circumferential-wave phase velocities for empty, fluid-immersed spherical metal shells

DEFF Research Database (Denmark)

Überall, Herbert; Claude Ahyi, A.; Raju, P. K.

2001-01-01

Our earlier studies regarding acoustic scattering resonances and the dispersive phase velocities of the surface waves that generate them, have demonstrated the effectiveness of obtaining phase velocity dispersion curves from the known acoustic resonance frequencies, and their accuracy. This possi...

Energy Demodulation Algorithm for Flow Velocity Measurement of Oil-Gas-Water Three-Phase Flow

Directory of Open Access Journals (Sweden)

Yingwei Li

2014-01-01

Full Text Available Flow velocity measurement was an important research of oil-gas-water three-phase flow parameter measurements. In order to satisfy the increasing demands for flow detection technology, the paper presented a gas-liquid phase flow velocity measurement method which was based on energy demodulation algorithm combing with time delay estimation technology. First, a gas-liquid phase separation method of oil-gas-water three-phase flow based on energy demodulation algorithm and blind signal separation technology was proposed. The separation of oil-gas-water three-phase signals which were sampled by conductance sensor performed well, so the gas-phase signal and the liquid-phase signal were obtained. Second, we used the time delay estimation technology to get the delay time of gas-phase signals and liquid-phase signals, respectively, and the gas-phase velocity and the liquid-phase velocity were derived. At last, the experiment was performed at oil-gas-water three-phase flow loop, and the results indicated that the measurement errors met the need of velocity measurement. So it provided a feasible method for gas-liquid phase velocity measurement of the oil-gas-water three-phase flow.

Local gas- and liquid-phase measurements for air-water two-phase flows in a rectangular channel

International Nuclear Information System (INIS)

Zhou, X.; Sun, X.; Williams, M.; Fu, Y.; Liu, Y.

2014-01-01

Local gas- and liquid-phase measurements of various gas-liquid two-phase flows, including bubbly, cap-bubbly, slug, and churn-turbulent flows, were performed in an acrylic vertical channel with a rectangular cross section of 30 mm x 10 mm and height of 3.0 m. All the measurements were carried out at three measurement elevations along the flow channel, with z/D h = 9, 72, and 136, respectively, to study the flow development. The gas-phase velocity, void fraction, and bubble number frequency were measured using a double-sensor conductivity probe. A high-speed imaging system was utilized to perform the flow regime visualization and to provide additional quantitative information of the two-phase flow structure. An image processing scheme was developed to obtain the gas-phase velocity, void fraction, Sauter mean diameter, bubble number density, and interfacial area concentration. The liquid-phase velocity and turbulence measurements were conducted using a particle image velocimetry-planar laser-induced fluorescence (PIV-PLIF) system, which enables whole-field and high-resolution data acquisition. An optical phase separation method, which uses fluorescent particles and optical filtration technique, is adopted to extract the velocity information of the liquid phase. An image pre-processing scheme is imposed on the raw PIV images acquired to remove noises due to the presence of bubble residuals and optically distorted particles in the images captured by the PIV-PLIF system. Due to the better light access and less bubble distortion in the narrow rectangular channel, the PIV-PLIF system were able to perform reasonably well in flows of even higher void fractions as compared to the situations with circular pipe test sections. The flow conditions being studied covered various flow regime transitions, void fractions, and liquid-phase flow Reynolds numbers. The obtained experimental data can also be used to validate two-phase CFD results. (author)

Strongly coupled dispersed two-phase flows; Ecoulements diphasiques disperses fortement couples

Energy Technology Data Exchange (ETDEWEB)

Zun, I.; Lance, M.; Ekiel-Jezewska, M.L.; Petrosyan, A.; Lecoq, N.; Anthore, R.; Bostel, F.; Feuillebois, F.; Nott, P.; Zenit, R.; Hunt, M.L.; Brennen, C.E.; Campbell, C.S.; Tong, P.; Lei, X.; Ackerson, B.J.; Asmolov, E.S.; Abade, G.; da Cunha, F.R.; Lhuillier, D.; Cartellier, A.; Ruzicka, M.C.; Drahos, J.; Thomas, N.H.; Talini, L.; Leblond, J.; Leshansky, A.M.; Lavrenteva, O.M.; Nir, A.; Teshukov, V.; Risso, F.; Ellinsen, K.; Crispel, S.; Dahlkild, A.; Vynnycky, M.; Davila, J.; Matas, J.P.; Guazelli, L.; Morris, J.; Ooms, G.; Poelma, C.; van Wijngaarden, L.; de Vries, A.; Elghobashi, S.; Huilier, D.; Peirano, E.; Minier, J.P.; Gavrilyuk, S.; Saurel, R.; Kashinsky, O.; Randin, V.; Colin, C.; Larue de Tournemine, A.; Roig, V.; Suzanne, C.; Bounhoure, C.; Brunet, Y.; Tanaka, A.T.; Noma, K.; Tsuji, Y.; Pascal-Ribot, S.; Le Gall, F.; Aliseda, A.; Hainaux, F.; Lasheras, J.; Didwania, A.; Costa, A.; Vallerin, W.; Mudde, R.F.; Van Den Akker, H.E.A.; Jaumouillie, P.; Larrarte, F.; Burgisser, A.; Bergantz, G.; Necker, F.; Hartel, C.; Kleiser, L.; Meiburg, E.; Michallet, H.; Mory, M.; Hutter, M.; Markov, A.A.; Dumoulin, F.X.; Suard, S.; Borghi, R.; Hong, M.; Hopfinger, E.; Laforgia, A.; Lawrence, C.J.; Hewitt, G.F.; Osiptsov, A.N.; Tsirkunov, Yu. M.; Volkov, A.N.

2003-07-01

flow, current distribution and mass transfer along a vertical gas evolving electrode; a two-way coupled model for dilute multiphase flows. Topic 3: turbulence modulation by particles, droplets or bubbles in dense systems: influence of particles on the transition to turbulence in pipe flow; comparison between a point particle model and a finite-diameter-model for the particle turbulence interaction in a suspension; the effect on turbulence by bubbles rising through it under buoyancy; the physical mechanisms of modifying the structure of turbulent homogeneous shear flows by dispersed particles; influence of hydrodynamic interactions between particles on the turbulent flow in a suspension; review of relationships between Lagrangian and Eulerian scales; a two-point PDF for modelling turbulent dispersed two-phase flows and derivation of a two field model; mathematical and numerical modeling of two-phase compressible flows with micro-inertia. Topic 4: collective effects in dispersed two-phase flows clustering and phase distribution: hydrodynamic structure of downward bubbly flow; influence of gravity on the dynamics of a turbulent bubbly pipe flow; experimental study of two-phase flows; particle clusters formed in dispersed gas-solid flows: simulations and experiments; experimental study of the turbulence in bubbly flows at high void fraction; first step in the study of the correlation between air/water flow fluctuations and random buffering forces; clustering and settling velocity of micro-droplets in a grid turbulence. Topic 5: large scale instabilities and gravity driven dispersed flows: new 'non-isothermal' linear instability modes in fluidized beds and bubbly flows; large scale instability in a confined buoyant shear layer; convective instability in uniform dispersed layers; structures in gravity driven bubbly flows; effects of concentration profiles on velocity profiles in sewer; pyroclastic density currents viewed as mammoth scale two-phase flows; mixing and

A new maximum likelihood blood velocity estimator incorporating spatial and temporal correlation

DEFF Research Database (Denmark)

Schlaikjer, Malene; Jensen, Jørgen Arendt

2001-01-01

and space. This paper presents a new estimator (STC-MLE), which incorporates the correlation property. It is an expansion of the maximum likelihood estimator (MLE) developed by Ferrara et al. With the MLE a cross-correlation analysis between consecutive RF-lines on complex form is carried out for a range...... of possible velocities. In the new estimator an additional similarity investigation for each evaluated velocity and the available velocity estimates in a temporal (between frames) and spatial (within frames) neighborhood is performed. An a priori probability density term in the distribution...... of the observations gives a probability measure of the correlation between the velocities. Both the MLE and the STC-MLE have been evaluated on simulated and in-vivo RF-data obtained from the carotid artery. Using the MLE 4.1% of the estimates deviate significantly from the true velocities, when the performance...

Zero-G two phase flow regime modeling in adiabatic flow

International Nuclear Information System (INIS)

Reinarts, T.R.; Best, F.R.; Wheeler, M.; Miller, K.M.

1993-01-01

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

Relative Seismic Velocity Variations Correlate with Deformation at Kīlauea Volcano.

Science.gov (United States)

Donaldson, C.; Caudron, C.; Green, R. G.; White, R. S.

2016-12-01

Passive interferometry using ambient seismic noise is an appealing monitoring tool at volcanoes. The continuous nature of seismic noise provides better temporal resolution than earthquake interferometry and ambient noise may be sensitive to changes at depths that do not deform the volcano surface. Despite this, to our knowledge, no studies have yet comprehensively compared deformation and velocity at a volcano over a significant length of time. We use a volcanic tremor source (approximately 0.3 - 1.0 Hz) at Kīlauea volcano as a source for interferometry to measure relative velocity changes with time. The tremor source that dominates the cross correlations is located under the Halema'uma'u caldera at Kīlauea summit. By cross-correlating the vertical component of day-long seismic records between 200 pairs of stations, we extract coherent and temporally consistent coda wave signals with time lags of up to 70 seconds. Our resulting time series of relative velocity shows a remarkable correlation with the tilt record measured at Kīlauea summit. Kīlauea summit is continually inflating and deflating as the level of the lava lake rises and falls. During these deflation-inflation (DI) events the tilt increases (inflation), as the velocity increases, on the scale of days to weeks. In contrast, we also detect a longer-term velocity decrease between 2011-2015 as the volcano slowly inflates. We suggest that variations in velocity result from opening and closing cracks and pores due to changes in magma pressurization. Early modeling results indicate that pressurizing magma reservoirs at different depths can result in opposite changes in compression/extension at the surface. The consistent correlation of relative velocity and deformation in this study provides an opportunity to better understand the mechanism causing velocity changes, which currently limits the scope of passive interferometry as a monitoring tool.

Velocity correlations in laboratory insect swarms

Science.gov (United States)

Ni, R.; Ouellette, N. T.

2015-12-01

In contrast to animal groups such as bird flocks or migratory herds that display net, directed motion, insect swarms do not possess global order. Without such order, it is difficult to define and characterize the transition to collective behavior in swarms; nevertheless, visual observation of swarms strongly suggests that swarming insects do behave collectively. It has recently been suggested that correlation rather than order is the hallmark of emergent collective behavior. Here, we report measurements of spatial velocity correlation functions in laboratory mating swarms of the non-biting midge Chironomus riparius. Although we find some correlation at short distances, our swarms are in general only weakly correlated, in contrast to what has been observed in field studies. Our results hint at the potentially important role of environmental conditions on collective behavior, and suggest that general indicators of the collective nature of swarming are still needed.

Numerical analysis of critical two-phase flow in a convergent-divergent nozzle

International Nuclear Information System (INIS)

Romstedt, P.; Werner, W.

1985-01-01

The numerical calculation of critical two-phase flow in a convergent-divergent nozzle is complicated by a singularity of the fluid flow equations at the unknown critical point. This paper describes a method which is able to calculate critical state and its location without any additional assumptions. The critical state is identified by its mathematical properties: characteristics and solvability of linear systems with singular matrix. Because the numerically evaluable mathematical properties are only necessary conditions for the existence of critical flow, some physical ''compatibility-criteria'' (flow velocity equals two-phase sonic velocity, critical flow is independent of downstream flow state variations) are used as a substitute for mathematically sufficient conditions. Numerical results are shown for the critical flow in a LOBI nozzle; the two-phase flow is described by a model with equal phase velocities and thermodynamic non-equilibrium

Pressure-Velocity Correlations in the Cove of a Leading Edge Slat

Science.gov (United States)

Wilkins, Stephen; Richard, Patrick; Hall, Joseph

2015-11-01

One of the major sources of aircraft airframe noise is related to the deployment of high-lift devices, such as leading-edge slats, particularly when the aircraft is preparing to land. As the engines are throttled back, the noise produced by the airframe itself is of great concern, as the aircraft is low enough for the noise to impact civilian populations. In order to reduce the aeroacoustic noise sources associated with these high lift devices for the next generation of aircraft an experimental investigation of the correlation between multi-point surface-mounted fluctuating pressures measured via flush-mounted microphones and the simultaneously measured two-component velocity field measured via Particle Image Velocimetry (PIV) is studied. The development of the resulting shear-layer within the slat cove is studied for Re =80,000, based on the wing chord. For low Mach number flows in air, the major acoustic source is a dipole acoustic source tied to fluctuating surface pressures on solid boundaries, such as the underside of the slat itself. Regions of high correlations between the pressure and velocity field near the surface will likely indicate a strong acoustic dipole source. In order to study the underlying physical mechanisms and understand their role in the development of aeroacoustic noise, Proper Orthogonal Decomposition (POD) by the method of snapshots is employed on the velocity field. The correlation between low-order reconstructions and the surface-pressure measurements are also studied.

Model for definition of heat transfer coefficient in an annular two-phase flow

International Nuclear Information System (INIS)

Khun, J.

1976-01-01

Near-wall heat exchange in a vertical tube at high vapor velocity in a two-phase vapor and liquid flow is investigated. The flow divides inside the tube into a near-wall liquid film and a vapor nucleus containing liquid droplets, with the boundaries being uniform. The liquid film thickness determines the main resistance during heat transfer between the wall and vapor nucleus. The theoretical model presented is verified in water vaporization experiments, the R12 cooling agent and certain hydrocarbons. The loss of friction pressure is determined by the Lockart-Martinelli method. The approximately universal Carman velocity profile is used to evaluate the velocity in film, and basing on this, film thickness is determined. The parameter ranges were: Resub(vap)=10 4 -3x10 6 , Resub(liq.)=0.9-10. The theoretical model ensures good correlation with the experiment

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.

Two phase transitions in Nuclear Physics

International Nuclear Information System (INIS)

Bes, D.R.

1985-01-01

The status of the art of the problem associated with two phase transitions in the nuclear matter, viz.: the disappearance of the nuclear superfluiditiy with the raising of the rotation velocity and the appearance of an octupolar deformation in the actinide zone, is presented. (L.C.) [pt

Phase coherence induced by correlated disorder.

Science.gov (United States)

Hong, Hyunsuk; O'Keeffe, Kevin P; Strogatz, Steven H

2016-02-01

We consider a mean-field model of coupled phase oscillators with quenched disorder in the coupling strengths and natural frequencies. When these two kinds of disorder are uncorrelated (and when the positive and negative couplings are equal in number and strength), it is known that phase coherence cannot occur and synchronization is absent. Here we explore the effects of correlating the disorder. Specifically, we assume that any given oscillator either attracts or repels all the others, and that the sign of the interaction is deterministically correlated with the given oscillator's natural frequency. For symmetrically correlated disorder with zero mean, we find that the system spontaneously synchronizes, once the width of the frequency distribution falls below a critical value. For asymmetrically correlated disorder, the model displays coherent traveling waves: the complex order parameter becomes nonzero and rotates with constant frequency different from the system's mean natural frequency. Thus, in both cases, correlated disorder can trigger phase coherence.

Background velocity inversion by phase along reflection wave paths

KAUST Repository

Yu, Han; Guo, Bowen; Schuster, Gerard T.

2014-01-01

A background velocity model containing the correct lowwavenumber information is desired for both the quality of the migration image and the success of waveform inversion. We propose to invert for the low-wavenumber part of the velocity model by minimizing the phase difference between predicted and observed reflections. The velocity update is exclusively along the reflection wavepaths and, unlike conventional FWI, not along the reflection ellipses. This allows for reconstructing the smoothly varying parts of the background velocity model. Tests with synthetic data show both the benefits and limitations of this method.

Background velocity inversion by phase along reflection wave paths

KAUST Repository

Yu, Han

2014-08-05

A background velocity model containing the correct lowwavenumber information is desired for both the quality of the migration image and the success of waveform inversion. We propose to invert for the low-wavenumber part of the velocity model by minimizing the phase difference between predicted and observed reflections. The velocity update is exclusively along the reflection wavepaths and, unlike conventional FWI, not along the reflection ellipses. This allows for reconstructing the smoothly varying parts of the background velocity model. Tests with synthetic data show both the benefits and limitations of this method.

Non-local correlations via Wigner-Yanase skew information in two SC-qubit having mutual interaction under phase decoherence

Science.gov (United States)

Mohamed, Abdel-Baset A.

2017-10-01

An analytical solution of the master equation that describes a superconducting cavity containing two coupled superconducting charge qubits is obtained. Quantum-mechanical correlations based on Wigner-Yanase skew information, as local quantum uncertainty and uncertainty-induced quantum non-locality, are compared to the concurrence under the effects of the phase decoherence. Local quantum uncertainty exhibits sudden changes during its time evolution and revival process. Sudden death and sudden birth occur only for entanglement, depending on the initial state of the two coupled charge qubits, while the correlations of skew information does not vanish. The quantum correlations of skew information are found to be sensitive to the dephasing rate, the photons number in the cavity, the interaction strength between the two qubits, and the qubit distribution angle of the initial state. With a proper initial state, the stationary correlation of the skew information has a non-zero stationary value for a long time interval under the phase decoherence, that it may be useful in quantum information and computation processes.

Validation of two-phase flow code THYC on VATICAN experiment

International Nuclear Information System (INIS)

Maurel, F.; Portesse, A.; Rimbert, P.; Thomas, B.

1997-01-01

As part of a comprehensive program for THYC validation (THYC is a 3-dimensional two-phase flow computer code for PWR core configuration), an experimental project > has been initiated by the Direction des Etudes et Recherches of Electricite de France. Two mock-ups tested in Refrigerant-114, VATICAN-1 (with simple space grids) and VATICAN-2 (with mixing grids) were set up to investigate void fraction distributions using a single beam gamma densitometer. First, experiments were conducted with the VATICAN-1 mock-up. A set of constitutive laws to be used in rod bundles was determined but some doubts still remain for friction losses closure laws for oblique flow over tubes. From VATICAN-2 tests, calculations were performed using the standard set of correlations. Comparison with the experimental data shows an underprediction of void fraction by THYC in disturbed regions. Analyses highlight the poor treatment of axial relative velocity in these regions. A fitting of the radial and axial relative velocity values in the disturbed region improves the prediction of void fraction by the code but without any physical explanation. More analytical experiments should be carried out to validate friction losses closure laws for oblique flows and relative velocity downstream of a mixing grid. (author)

Validation of two-phase flow code THYC on VATICAN experiment

Energy Technology Data Exchange (ETDEWEB)

Maurel, F.; Portesse, A.; Rimbert, P.; Thomas, B. [EDF/DER, Dept. TTA, 78 - Chatou (France)

1997-12-31

As part of a comprehensive program for THYC validation (THYC is a 3-dimensional two-phase flow computer code for PWR core configuration), an experimental project <> has been initiated by the Direction des Etudes et Recherches of Electricite de France. Two mock-ups tested in Refrigerant-114, VATICAN-1 (with simple space grids) and VATICAN-2 (with mixing grids) were set up to investigate void fraction distributions using a single beam gamma densitometer. First, experiments were conducted with the VATICAN-1 mock-up. A set of constitutive laws to be used in rod bundles was determined but some doubts still remain for friction losses closure laws for oblique flow over tubes. From VATICAN-2 tests, calculations were performed using the standard set of correlations. Comparison with the experimental data shows an underprediction of void fraction by THYC in disturbed regions. Analyses highlight the poor treatment of axial relative velocity in these regions. A fitting of the radial and axial relative velocity values in the disturbed region improves the prediction of void fraction by the code but without any physical explanation. More analytical experiments should be carried out to validate friction losses closure laws for oblique flows and relative velocity downstream of a mixing grid. (author)

Cross-correlation of instantaneous phase increments in pressure-flow fluctuations: Applications to cerebral autoregulation

Science.gov (United States)

Chen, Zhi; Hu, Kun; Stanley, H. Eugene; Novak, Vera; Ivanov, Plamen Ch.

2006-03-01

We investigate the relationship between the blood flow velocities (BFV) in the middle cerebral arteries and beat-to-beat blood pressure (BP) recorded from a finger in healthy and post-stroke subjects during the quasisteady state after perturbation for four different physiologic conditions: supine rest, head-up tilt, hyperventilation, and CO2 rebreathing in upright position. To evaluate whether instantaneous BP changes in the steady state are coupled with instantaneous changes in the BFV, we compare dynamical patterns in the instantaneous phases of these signals, obtained from the Hilbert transform, as a function of time. We find that in post-stroke subjects the instantaneous phase increments of BP and BFV exhibit well-pronounced patterns that remain stable in time for all four physiologic conditions, while in healthy subjects these patterns are different, less pronounced, and more variable. We propose an approach based on the cross-correlation of the instantaneous phase increments to quantify the coupling between BP and BFV signals. We find that the maximum correlation strength is different for the two groups and for the different conditions. For healthy subjects the amplitude of the cross-correlation between the instantaneous phase increments of BP and BFV is small and attenuates within 3-5 heartbeats. In contrast, for post-stroke subjects, this amplitude is significantly larger and cross-correlations persist up to 20 heartbeats. Further, we show that the instantaneous phase increments of BP and BFV are cross-correlated even within a single heartbeat cycle. We compare the results of our approach with three complementary methods: direct BP-BFV cross-correlation, transfer function analysis, and phase synchronization analysis. Our findings provide insight into the mechanism of cerebral vascular control in healthy subjects, suggesting that this control mechanism may involve rapid adjustments (within a heartbeat) of the cerebral vessels, so that BFV remains steady in

A review of damping of two-phase flows

International Nuclear Information System (INIS)

Hara, Fumio

1993-01-01

Damping of two-phase flows has been recognized as one of the most unknown parameters in analyzing vibrational characteristics of structures subjected to two-phase flows since it seems to be influenced by many physical parameters involved in the physics of dynamic energy dissipation of a vibrating structure, for example, liquid viscosity, surface tension, flow velocity, mass ratio, frequency, void fraction, flow regime and so forth. This paper deals with a review of scientific works done to date on the damping of two phase flows and discussions about what has been clarified and what has not been known to us, or what kinds of research are needed about two-phase flow damping. The emphasis is put on the definition of two-phase fluid damping, damping measurement techniques, damping characteristics in relation to two phase flow configurations, and damping generation mechanisms

Estimation of velocity vector angles using the directional cross-correlation method

DEFF Research Database (Denmark)

Kortbek, Jacob; Jensen, Jørgen Arendt

2006-01-01

and then select the angle with the highest normalized correlation between directional signals. The approach is investigated using Field II simulations and data from the experimental ultrasound scanner RASMUS and a circulating flow rig with a parabolic flow having a peak velocity of 0.3 m/s. A 7 MHz linear array......A method for determining both velocity magnitude and angle in any direction is suggested. The method uses focusing along the velocity direction and cross-correlation for finding the correct velocity magnitude. The angle is found from beamforming directional signals in a number of directions...... transducer is used with a normal transmission of a focused ultrasound field. In the simulations the relative standard deviation of the velocity magnitude is between 0.7% and 7.7% for flow angles between 45 deg and 90 deg. The study showed that angle estimation by directional beamforming can be estimated...

Correlation Water Velocity and TSS with Natural Radionuclides Activity

International Nuclear Information System (INIS)

Tri Harningsih; Muzakky; Agus Taftazani

2007-01-01

Correlation water velocity and TSS with natural radionuclides activity has been studied. For that purpose, the study is to correlation water velocity and TSS with radionuclides on water and sediment samples in alongside river Code Yogyakarta. This research selected radionuclides, for examples Ra-226, Pb-212, Ac- 228, and K-40. Election of this radionuclides to spread over gamma gross composition alongside river of Code. Gamma gross influenced by water velocity and TSS, so that require to correct between water velocity and TSS to radionuclides. Sampling water and sediment conducted when dry season of August, 2006 at 11 locations, start from Boyong Bridge until Pacar Bridge. Result of analysis showed that water velocity range from 8-1070 L/dt and TSS range from 2.81 E-06 - 8.02 E-04 mg/L. The accumulation of radionuclides in water samples non correction water velocity for Ra-226: 0.302-2.861 Bq/L, Pb-212: 0.400-3.390 Bq/L, Ac- 228: 0.0029-0.0047 Bq/L and K-40: 0.780-9.178 Bq/L. The accumulation of radionuclide in water samples correction water velocity for Ra-226: 1.112-70.454 Bq/L, Pb-212: 0.850-77.113 Bq/L, Ac-228: 0.7187- 60.859 Bq/L and K-40: 2.420-208.8 Bq/L. While distribution of radionuclide in sediment for the Ra-226: 0.0012-0.0211 Bq/kg, Pb-212: 0.0017-0.0371 Bq/kg, Ac-228: 0.0021-0.0073 Bq/kg and K-40: 0.0006-0.0084 Bq/kg. (author)

Two-Phase Quality/Flow Meter

Science.gov (United States)

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

1999-01-01

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

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

Mechanical disequilibria in two-phase flow models: approaches by relaxation and by a reduced model

International Nuclear Information System (INIS)

Labois, M.

2008-10-01

This thesis deals with hyperbolic models for the simulation of compressible two-phase flows, to find alternatives to the classical bi-fluid model. We first establish a hierarchy of two-phase flow models, obtained according to equilibrium hypothesis between the physical variables of each phase. The use of Chapman-Enskog expansions enables us to link the different existing models to each other. Moreover, models that take into account small physical unbalances are obtained by means of expansion to the order one. The second part of this thesis focuses on the simulation of flows featuring velocity unbalances and pressure balances, in two different ways. First, a two-velocity two-pressure model is used, where non-instantaneous velocity and pressure relaxations are applied so that a balancing of these variables is obtained. A new one-velocity one-pressure dissipative model is then proposed, where the arising of second-order terms enables us to take into account unbalances between the phase velocities. We develop a numerical method based on a fractional step approach for this model. (author)

Fluid-elastic force measurements acting on a tube bundle in two-phase cross flow

International Nuclear Information System (INIS)

Inada, Fumio; Kawamura, Koji; Yasuo, Akira

1996-01-01

Fluid-elastic force acting on a square tube bundle of P/D = 1.47 in air-water two-phase cross flow was measured to investigate the characteristics and to clarify whether the fluid elastic vibration characteristics could be expressed using two-phase mixture characteristics. Measured fluid elastic forces were separated into fluid-elastic force coefficients such as added mass, added stiffness, and added damping coefficient. The added damping coefficient was separated into a two-phase damping and a flow-dependent component as in previous research (Carlucci, 1981 and 1983; Pettigrew, 1994). These coefficients were nondimensionalized with two-phase mixture characteristics such as void fraction, mixture density and mixture velocity, which were obtained using the drift-flux model with consideration given to the model. The result was compared with the result obtained with the homogeneous model. It was found that fluid-elastic force coefficients could be expressed with two-phase flow mixture characteristics very well in the experimental result, and that better result can be derived using the slip model as compared to the homogeneous model. Added two-phase flow, which could be expressed as a function of void fraction, where two-phase damping was nondimensionalized with the relative velocity between the gas and liquid phases used as a reference velocity. Using these, the added stiffness coefficient and flow-dependent component of damping could be expressed very well as a function of nondimensional mixture velocity

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

Coherent effects on two-photon correlation and directional emission of two two-level atoms

International Nuclear Information System (INIS)

Ooi, C. H. Raymond; Kim, Byung-Gyu; Lee, Hai-Woong

2007-01-01

Sub- and superradiant dynamics of spontaneously decaying atoms are manifestations of collective many-body systems. We study the internal dynamics and the radiation properties of two atoms in free space. Interesting results are obtained when the atoms are separated by less than half a wavelength of the atomic transition, where the dipole-dipole interaction gives rise to new coherent effects, such as (a) coherence between two intermediate collective states, (b) oscillations in the two-photon correlation G (2) , (c) emission of two photons by one atom, and (d) the loss of directional correlation. We compare the population dynamics during the two-photon emission process with the dynamics of single-photon emission in the cases of a Λ and a V scheme. We compute the temporal correlation and angular correlation of two successively emitted photons using the G (2) for different values of atomic separation. We find antibunching when the atomic separation is a quarter wavelength λ/4. Oscillations in the temporal correlation provide a useful feature for measuring subwavelength atomic separation. Strong directional correlation between two emitted photons is found for atomic separation larger than a wavelength. We also compare the directionality of a photon spontaneously emitted by the two atoms prepared in phased-symmetric and phased-antisymmetric entangled states vertical bar ±> k 0 =e ik 0 ·r 1 vertical bar a 1 ,b 2 >±e ik 0 ·r 2 vertical bar b 1 ,a 2 > by a laser pulse with wave vector k 0 . Photon emission is directionally suppressed along k 0 for the phased-antisymmetric state. The directionality ceases for interatomic distances less than λ/2

Liquid-phase turbulence measurements in air-water two-phase flows over a wide range of void fractions

Energy Technology Data Exchange (ETDEWEB)

Zhou, Xinquan [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, 201 W. 19th Ave., Columbus, OH 43210 (United States); Sun, Xiaodong, E-mail: sun.200@osu.edu [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, 201 W. 19th Ave., Columbus, OH 43210 (United States); Liu, Yang [Nuclear Engineering Program, Department of Mechanical Engineering, Virginia Tech, 635 Prices Fork Road, Blacksburg, VA 24061 (United States)

2016-12-15

This paper focuses on liquid-phase turbulence measurements in air-water two-phase flows over a wide range of void fractions and flow regimes, spanning from bubbly, cap-bubbly, slug, to churn-turbulent flows. The measurements have been conducted in two test facilities, the first one with a circular test section and the second one with a rectangular test section. A particle image velocimetry-planar laser-induced fluorescence (PIV-PLIF) system was used to acquire local liquid-phase turbulence information, including the time-averaged velocity and velocity fluctuations in the streamwise and spanwise directions, and Reynolds stress. An optical phase separation method using fluorescent particles and optical filtration technique was adopted to extract the liquid-phase velocity information. An image pre-processing scheme was imposed on the raw PIV images acquired to remove noise due to the presence of bubble residuals and optically distorted particles in the raw PIV images. Four-sensor conductivity probes and high-speed images were also used to acquire the gas-phase information, which was aimed to understand the flow interfacial structure. The highest area-averaged void fraction covered in the measurements for the circular and rectangular test sections was about 40%.

Liquid-phase turbulence measurements in air-water two-phase flows over a wide range of void fractions

International Nuclear Information System (INIS)

Zhou, Xinquan; Sun, Xiaodong; Liu, Yang

2016-01-01

This paper focuses on liquid-phase turbulence measurements in air-water two-phase flows over a wide range of void fractions and flow regimes, spanning from bubbly, cap-bubbly, slug, to churn-turbulent flows. The measurements have been conducted in two test facilities, the first one with a circular test section and the second one with a rectangular test section. A particle image velocimetry-planar laser-induced fluorescence (PIV-PLIF) system was used to acquire local liquid-phase turbulence information, including the time-averaged velocity and velocity fluctuations in the streamwise and spanwise directions, and Reynolds stress. An optical phase separation method using fluorescent particles and optical filtration technique was adopted to extract the liquid-phase velocity information. An image pre-processing scheme was imposed on the raw PIV images acquired to remove noise due to the presence of bubble residuals and optically distorted particles in the raw PIV images. Four-sensor conductivity probes and high-speed images were also used to acquire the gas-phase information, which was aimed to understand the flow interfacial structure. The highest area-averaged void fraction covered in the measurements for the circular and rectangular test sections was about 40%.

Lossy effects on the lateral shifts in negative-phase-velocity medium

International Nuclear Information System (INIS)

You Yuan

2009-01-01

Theoretical investigations of the lateral shifts of the reflected and transmitted beams were performed, using the stationary-phase approach, for the planar interface of a conventional medium and a lossy negative-phase-velocity medium. The lateral shifts exhibit different behaviors beyond and below a certain angle, for both incident p-polarized and incident s-polarized plane waves. Loss in the negative-phase-velocity medium affects lateral shifts greatly, and may cause changes from negative to positive values for p-polarized incidence

Two-phase flow measurements with advanced instrumented spool pieces and local conductivity probes

International Nuclear Information System (INIS)

Turnage, K.G.; Davis, C.E.

1979-01-01

A series of two-phase, air-water and steam-water tests performed with instrumented spool pieces and with conductivity probes obtained from Atomic Energy of Canada, Ltd. is described. The behavior of the three-beam densitometer, turbine meter, and drag flowmeter is discussed in terms of two-phase models. Application of some two-phase mass flow models to the recorded spool piece data is made and preliminary results are shown. Velocity and void fraction information derived from the conductivity probes is presented and compared to velocities and void fractions obtained using the spool piece instrumentation

Multi-dimensional two-phase flow measurements in a large-diameter pipe using wire-mesh sensor

International Nuclear Information System (INIS)

Kanai, Taizo; Furuya, Masahiro; Arai, Takahiro; Shirakawa, Kenetsu; Nishi, Yoshihisa; Ueda, Nobuyuki

2011-01-01

The authors developed a method of measurement to determine the multi-dimensionality of two phase flow. A wire-mesh sensor (WMS) can acquire a void fraction distribution at a high temporal and spatial resolution and also estimate the velocity of a vertical rising flow by investigating the signal time-delay of the upstream WMS relative to downstream. Previously, one-dimensional velocity was estimated by using the same point of each WMS at a temporal resolution of 1.0 - 5.0 s. The authors propose to extend this time series analysis to estimate the multi-dimensional velocity profile via cross-correlation analysis between a point of upstream WMS and multiple points downstream. Bubbles behave in various ways according to size, which is used to classify them into certain groups via wavelet analysis before cross-correlation analysis. This method was verified by air-water straight and swirl flows within a large-diameter vertical pipe. A high-speed camera is used to set the parameter of cross-correlation analysis. The results revealed that for the rising straight and swirl flows, large scale bubbles tend to move to the center, while the small bubble is pushed to the outside or sucked into the space where the large bubbles existed. Moreover, it is found that this method can estimate the rotational component of velocity of the swirl flow as well as measuring the multi-dimensional velocity vector at high temporal resolutions of 0.2 s. (author)

Two-fluid model of two-phase flow in a pin bundle of a nuclear reactor

International Nuclear Information System (INIS)

Chawla, T.C.; Ishii, M.

1980-01-01

By considering two-phase flow as a field which is subdivided into two turbulent single-phase regions with moving boundaries separating the two constituent phases, such that the differential balances for three-dimensional turbulent flow hold for each subregion and for the interface, we perform the Eulerian area averaging over the cross-sectional area of each phase in a given channel and segment averaging of transverse momentum equation along the phase intercepts at the interchannel boundaries. To simplify the governing equations obtained as a result of these operations, we invoke the assumption that the motion of the fluid in each phase is dominantly in axial direction, that is the transverse components of velocity are small compared to axial components. We further assume that the variation of axial component of velocity within a channel is much stronger than the variation along the axial direction. We also assume that similar arguments can also be applied to the variation of enthalpy in a channel. As a result of these considerations, we obtain two sets of continuity, momentum, and energy equations describing motion of each phase in the axial direction. The phasic interaction terms which appear in these equations are governed by interfacial transfer conditions obtained from interface balances. The segment-averaged transverse-momentum equation for each phase provides the governing equation for cross flow. (author)

Ultrasonic sound speed of hydrating calcium sulphate hemihydrate; part 2, the correlation of sound velocity to hydration degree

NARCIS (Netherlands)

de Korte, A.C.J.; Brouwers, Jos; Fischer, H.B; Matthes, C.; Beuthan, C.

2011-01-01

In this article the sound velocity through a mix is correlated to the hydration degree of the mix. Models are presented predicting the sound velocity through fresh slurries and hardened products. These two states correspond to the starting and finishing point of the hydration process. The present

Ultrasonic sound speed of hydrating calcium sulphate hemihydrate; Part 2, The correlation of sound velocity to hydration degree

NARCIS (Netherlands)

Korte, de A.C.J.; Brouwers, H.J.H.; Fischer, H.B.; Mattes, Chr.; Beutha, C.

2011-01-01

In this article the sound velocity through a mix is correlated to the hydration degree of the mix. Models are presented predicting the sound velocity through fresh slurries and hardened products. These two states correspond to the starting and finishing point of the hydration process. The present

The velocity correlation function in cosmic-ray diffusion theory

International Nuclear Information System (INIS)

Forman, M.A.

1977-01-01

The concept of velocity correlation functions is introduced and applied to the calculation of cosmic ray spatial diffusion coefficients. It is assumed that the pitch angle scattering coefficient is already known from some other theory, and is reasonably well-behaved. Previous results for the coefficient for diffusion parallel to the mean field are recovered when the velocity-changing mechanism is artificially restricted to pitch angle scattering. The velocity correlation method is then applied to the more general case where there are fluctuations in the local mean field. It is found that the parallel diffusion coefficient is reduced in proportion to the amplitude of the field fluctuations, and that the ratio of the perpendicular to parallel diffusion coefficients cannot be greater than 2 >/B 0 2 . It is shown in the appendix that the Liouville form of the scattering equation implies that the Fokker-Planck coefficients (Δμ 2 )/Δt=2Dsub(μμ) and (Δμ)/Δt=deltaDsub(μμ)/deltaμ, and that all higher-order coefficients are identically zero. (Auth.)

Two-phase flow measurement by pulsed neutron activation techniques

International Nuclear Information System (INIS)

Kehler, P.

1978-01-01

The Pulsed Neutron Activation (PNA) technique for measuring the mass flow velocity and the average density of two-phase mixtures is described. PNA equipment can be easily installed at different loops, and PNA techniques are non-intrusive and independent of flow regimes. These features of the PNA technique make it suitable for in-situ measurement of two-phase flows, and for calibration of more conventional two-phase flow measurement devices. Analytic relations governing the various PNA methods are derived. The equipment and procedures used in the first air-water flow measurement by PNA techniques are discussed, and recommendations are made for improvement of future tests. In the present test, the mass flow velocity was determined with an accuracy of 2 percent, and average densities were measured down to 0.08 g/cm 3 with an accuracy of 0.04 g/cm 3 . Both the accuracy of the mass flow velocity measurement and the lower limit of the density measurement are functions of the injected activity and of the total number of counts. By using a stronger neutron source and a larger number of detectors, the measurable density can be decreased by a factor of 12 to .007 g/cm 3 for 12.5 cm pipes, and to even lower ranges for larger pipes

Modeling and numerical study of two phase flow

International Nuclear Information System (INIS)

Champmartin, A.

2011-01-01

This thesis describes the modelization and the simulation of two-phase systems composed of droplets moving in a gas. The two phases interact with each other and the type of model to consider directly depends on the type of simulations targeted. In the first part, the two phases are considered as fluid and are described using a mixture model with a drift relation (to be able to follow the relative velocity between the two phases and take into account two velocities), the two-phase flows are assumed at the equilibrium in temperature and pressure. This part of the manuscript consists of the derivation of the equations, writing a numerical scheme associated with this set of equations, a study of this scheme and simulations. A mathematical study of this model (hyperbolicity in a simplified framework, linear stability analysis of the system around a steady state) was conducted in a frame where the gas is assumed baro-tropic. The second part is devoted to the modelization of the effect of inelastic collisions on the particles when the time of the simulation is shorter and the droplets can no longer be seen as a fluid. We introduce a model of inelastic collisions for droplets in a spray, leading to a specific Boltzmann kernel. Then, we build caricatures of this kernel of BGK type, in which the behavior of the first moments of the solution of the Boltzmann equation (that is mass, momentum, directional temperatures, variance of the internal energy) are mimicked. The quality of these caricatures is tested numerically at the end. (author) [fr

Investigation of the propagation characteristics in turbulent dispersed two-phase flow

International Nuclear Information System (INIS)

Sami, S.M.

1980-01-01

The propagation characteristics of turbulent dispersed two-phase flows have been studied experimentally using the Pitot tube associated with a conical hot-film anemometer. It is found that the mixture velocity increases with decreasing volumetric mixing ratio of the air and water. The void fraction distribution shows homogeneity across the test section in the special case of fully developed boundary layer two-phase flow. An expression is obtained which relates the local mixture velocity to the local void fraction, gas and liquid densities, and volumetric gas-liquid ratio

How decays and final-state interactions affect velocity correlations in heavy-ion collisions

International Nuclear Information System (INIS)

Wieand, K.L.; Pratt, S.E.; Balantekin, A.B.

1992-01-01

We study rapidity correlations by calculating two-particle correlation functions and fractorial moments for a simple thermal model of ultrarelativistic-heavy-ion collisions. In this model correlations arise from decays of unstable hadrons and the final-state interactions of the measured particles. These correlations are shown to be similar but smaller than correlations due to phase separation. (orig.)

Hydrodynamics of single- and two-phase flow in inclined rod arrays

International Nuclear Information System (INIS)

Todreas, N.E.

1984-01-01

Required inputs for thermal-hydraulic codes are constitutive relations for fluid-solid flow resistance, in single-phase flow, and interfacial momentum exchange (relative phase motion), in two-phase flow. An inclined rod array air-water experiment was constructed to study the hydrodynamics of multidimensional porous medium flow in rod arrays. Velocities, pressures, bubble distributions, and void fractions were measured in inline and rotational square rod arrays of P/d = 1.5, at 0, 30, 45, and 90 degree inclinations to the vertical flow direction. Constitutive models for single-phase flow resistance are reviewed, new comprehensive models developed, and an assessment with previously published and new data made. The principle of superimposing one-dimensional correlations proves successful for turbulent single-phase inclined flow. For bubbly two-phase yawed flow through incline rod arrays a new flow separation phenomena was observed and modeled. Bubbles of diameters significantly smaller than the rod diameter travel along the rod axis, while larger diameter bubbles move through the rod array gaps. The outcome is a flow separation not predictable with current interfacial momentum exchange models. This phenomenon was not observed in rotated square rod arrays. Current interfacial momentum exchange models were confirmed for this rod arrangement. Models for the two phase flow resistance multiplier for cross flow were reviewed and compared with data from cross and yawed flow rod arrays. Both drag and lift components of the multiplier were well predicted by the homogenous model. Other models reviewed overpredicted the data by a factor of two

Uncertainty in RELAP5/MOD3.2 calculations for interfacial drag in downward two-phase flow

International Nuclear Information System (INIS)

Clark, Collin; Schlegel, Joshua P.; Hibiki, Takashi; Ishii, Mamoru; Kinoshita, Ikuo

2016-01-01

Highlights: • Uncertainty propagation is key for best estimate code reliability. • Uncertainty in drift flux correlations used to evaluate uncertainty in interfacial drag. • Bias and error have been compared for various models. - Abstract: RELAP5/MOD3.2 is a thermal-hydraulic system analysis code used to predict the response of nuclear reactor coolant systems in the event of certain accident scenarios. It is important that RELAP and other system analysis codes are able to accurately predict various two-phase flow phenomena, particularly the interfacial transfers between the liquid and gas phases. It is also important to understand how much uncertainty exists in these predictions due to uncertainties in the constitutive relations used to close the two-fluid model. In this paper, the uncertainty in the interfacial drag calculated by RELAP5/MOD3.2 due to errors in the drift-flux models used to close the model is evaluated and compared to the correlation developed by Goda et al. (2003). The case of downward flow is considered due to the importance of co-current and counter-current downward flow for predicting behavior in the downcomer of reactor systems during small-break Loss of Coolant Accidents (LOCAs) in nuclear reactor systems. The overall uncertainty in the interfacial force calculations due to error in the distribution parameter models were found to have a bias of +8.1% and error of 20.1% for the models used in RELAP5, and a bias of −30.8% and error of 23.1% for the correlation of Goda et al. (2003). However this analysis neglects the effects of compensating errors in the drift-flux parameters, as the drift velocity is assumed to be perfectly accurate. More physically meaningful results could be obtained if the distribution parameter and drift velocity were calculated directly from local phase concentration and velocity measurements, however no studies were available which included all of this information.

Secure optical verification using dual phase-only correlation

International Nuclear Information System (INIS)

Liu, Wei; Liu, Shutian; Zhang, Yan; Xie, Zhenwei; Liu, Zhengjun

2015-01-01

We introduce a security-enhanced optical verification system using dual phase-only correlation based on a novel correlation algorithm. By employing a nonlinear encoding, the inherent locks of the verification system are obtained in real-valued random distributions, and the identity keys assigned to authorized users are designed as pure phases. The verification process is implemented in two-step correlation, so only authorized identity keys can output the discriminate auto-correlation and cross-correlation signals that satisfy the reset threshold values. Compared with the traditional phase-only-correlation-based verification systems, a higher security level against counterfeiting and collisions are obtained, which is demonstrated by cryptanalysis using known attacks, such as the known-plaintext attack and the chosen-plaintext attack. Optical experiments as well as necessary numerical simulations are carried out to support the proposed verification method. (paper)

Mass and heat transfer at the outer surface of helical coils under single and two phase flow

International Nuclear Information System (INIS)

Abdel-Aziz, M.H.; Nirdosh, I.; Sedahmed, G.H.

2016-01-01

Highlights: • The work aims to develop reactors which need rapid temperature control. • Mass and heat transfer at the outer surface of helical coils was studied experimentally. • The experiments were conducted under gas sparing, single and two phase flow. • Variables were helical tube diameter, physical properties, and gas and liquid velocity. • Results verification in terms of natural convection and surface renewal mechanism was explained. - Abstract: The mass transfer behavior of the outer surface of vertical helical coil was studied by the electrochemical technique under single phase flow, gas sparging and two phase flow. Variables studied were helical tube diameter, physical properties of the solution, solution velocity and superficial gas velocity. The mass transfer data were correlated by dimensionless equations. Mass transfer enhancement ratio in case of two phase flow ranged from 1.1 to 4.9 compared to single phase flow. Implication of the results for the design and operation of helical coil reactors used to conduct L–S exothermic diffusion controlled reactions which need rapid temperature control were outlined. In this case the inner coil surface will act as a cooler while the outer surface will act a reaction surface. Immobilized enzyme catalyzed biochemical reactions where heat sensitive materials may be involved represent an example for the reactions which can employ the helical coil reactor. Also the importance of the results in the design of and operation of diffusion controlled membrane processes which employ helical coil membrane was noted. In view of the analogy between heat and mass transfer the possibility of using the results in the design and operation of helical coil heat exchangers was highlighted.

The Effect of Velocity Correlation on the Spatial Evolution of Breakthrough Curves in Heterogeneous Media

Science.gov (United States)

Massoudieh, A.; Dentz, M.; Le Borgne, T.

2017-12-01

In heterogeneous media, the velocity distribution and the spatial correlation structure of velocity for solute particles determine the breakthrough curves and how they evolve as one moves away from the solute source. The ability to predict such evolution can help relating the spatio-statistical hydraulic properties of the media to the transport behavior and travel time distributions. While commonly used non-local transport models such as anomalous dispersion and classical continuous time random walk (CTRW) can reproduce breakthrough curve successfully by adjusting the model parameter values, they lack the ability to relate model parameters to the spatio-statistical properties of the media. This in turns limits the transferability of these models. In the research to be presented, we express concentration or flux of solutes as a distribution over their velocity. We then derive an integrodifferential equation that governs the evolution of the particle distribution over velocity at given times and locations for a particle ensemble, based on a presumed velocity correlation structure and an ergodic cross-sectional velocity distribution. This way, the spatial evolution of breakthrough curves away from the source is predicted based on cross-sectional velocity distribution and the connectivity, which is expressed by the velocity transition probability density. The transition probability is specified via a copula function that can help construct a joint distribution with a given correlation and given marginal velocities. Using this approach, we analyze the breakthrough curves depending on the velocity distribution and correlation properties. The model shows how the solute transport behavior evolves from ballistic transport at small spatial scales to Fickian dispersion at large length scales relative to the velocity correlation length.

A Comprehensive Review on Measurement and Correlation Development of Capillary Pressure for Two-Phase Modeling of Proton Exchange Membrane Fuel Cells

Directory of Open Access Journals (Sweden)

Chao Si

2015-01-01

Full Text Available Water transport and the corresponding water management strategy in proton exchange membrane (PEM fuel cells are quite critical for the improvement of the cell performance. Accuracy modeling of water transport in porous electrodes strongly depends on the appropriate constitutive relationship for capillary pressure which is referred to as pc-s correlation, where pc is the capillary pressure and s is the fraction of saturation in the pores. In the present PEM fuel cell two-phase models, the Leverett-Udell pc-s correlation is widely utilized which is proposed based on fitting the experimental data for packed sands. However, the size and structure of pores for the commercial porous electrodes used in PEM fuel cells differ from those for the packed sands significantly. As a result, the Leverett-Udell correlation should be improper to characterize the two-phase transport in the porous electrodes. In the recent decade, many efforts were devoted to measuring the capillary pressure data and developing new pc-s correlations. The objective of this review is to review the most significant developments in recent years concerning the capillary pressure measurements and the developed pc-s correlations. It is expected that this review will be beneficial to develop the improved PEM fuel cell two-phase model.

Two-phase flow in a diverging nozzle

International Nuclear Information System (INIS)

Wadle, M.

1986-05-01

Stationary two-phase flow experiments were performed with steam-water and air-water mixtures in a well-instrumented horizontal diverging nozzle. The test section consisted of a constant diameter tube, the friction-section, followed by an expansion, the diffusor, which has a tanh-contour and finally another constant diameter tube. The diameter ratio sigma=D1/D2 is 16/80. For the steam-water experiments the flow parameters were: 0 2 and for air-water mixtures (0 2 ). The initial conditions were varied to achieve subcritical and critical mass flow rates. A new model for the pressure recovery in an abrupt expansion is presented. It is based on the superficial velocity concept and agrees well with the steam-water and the water-air experimental data as well as with the experiments of other authors. The experiments were also calculated with the two-phase code DUESE. The Drift-Flux models in this code as well as the constitutive correlations and their empirical constants could be tested. It is shown, that a 1D Drift-Flux code can handle the highly transient flow in the diffusor if the proper drift model is used. In a 1D simulation it is only necessary that the computational flow area is expanded to its full width within an axial length which is equivalent to the real contour. (orig./GL) [de

Rayleigh Wave Phase Velocities Beneath the Central and Southern East African Rift System

Science.gov (United States)

Adams, A. N.; Miller, J. C.

2017-12-01

This study uses the Automated Generalized Seismological Data Function (AGSDF) method to develop a model of Rayleigh wave phase velocities in the central and southern portions of the East African Rift System (EARS). These phase velocity models at periods of 20-100s lend insight into the lithospheric structures associated with surficial rifting and volcanism, as well as basement structures that pre-date and affect the course of rifting. A large dataset of >700 earthquakes is used, comprised of Mw=6.0+ events that occurred between the years 1995 and 2016. These events were recorded by a composite array of 176 stations from twelve non-contemporaneous seismic networks, each with a distinctive array geometry and station spacing. Several first-order features are resolved in this phase velocity model, confirming findings from previous studies. (1) Low velocities are observed in isolated regions along the Western Rift Branch and across the Eastern Rift Branch, corresponding to areas of active volcanism. (2) Two linear low velocity zones are imaged trending southeast and southwest from the Eastern Rift Branch in Tanzania, corresponding with areas of seismic activity and indicating possible incipient rifting. (3) High velocity regions are observed beneath both the Tanzania Craton and the Bangweulu Block. Furthermore, this model indicates several new findings. (1) High velocities beneath the Bangweulu Block extend to longer periods than those found beneath the Tanzania Craton, perhaps indicating that rifting processes have not altered the Bangweulu Block as extensively as the Tanzania Craton. (2) At long periods, the fast velocities beneath the Bangweulu Block extend eastwards beyond the surficial boundaries, to and possibly across the Malawi Rift. This may suggest the presence of older, thick blocks of lithosphere in regions where they are not exposed at the surface. (3) Finally, while the findings of this study correspond well with previous studies in regions of overlapping

Relationship between lower limbs kinematic variables and effectiveness of sprint during maximum velocity phase.

Science.gov (United States)

Struzik, Artur; Konieczny, Grzegorz; Grzesik, Kamila; Stawarz, Mateusz; Winiarski, Sławomir; Rokita, Andrzej

2015-01-01

The aim of the study was to determine the relationships between time of running over a 15-25 m section of a 30-meter run along a straight line and changes in the angle and angular velocity observed in ankle, knee and hip joints. Therefore, the authors attempted to answer the question of whether a technique of lower limbs movement during the phase of sprint maximum velocity significantly correlates with the time of running over this section. A group of 14 young people from the Lower Silesia Voivodeship Team participated in the experiment. A Fusion Smart Speed System was employed for running time measurements. The kinematic data were recorded using Noraxon MyoMotion system. There were observed statistically significant relationships between sprint time over a section from 15 to 25 m and left hip rotation (positive) and between this time and left and right ankle joint dorsi-plantar flexion (negative). During the maximum velocity phase of a 30 m sprint, the effect of dorsi-plantar flexion performed in the whole range of motion was found to be beneficial. This can be attributed to the use of elastic energy released in the stride cycle. Further, hip rotation should be minimized, which makes the stride aligned more along a line of running (a straight line) instead of from side to side.

An On-Chip RBC Deformability Checker Significantly Improves Velocity-Deformation Correlation

Directory of Open Access Journals (Sweden)

Chia-Hung Dylan Tsai

2016-10-01

Full Text Available An on-chip deformability checker is proposed to improve the velocity–deformation correlation for red blood cell (RBC evaluation. RBC deformability has been found related to human diseases, and can be evaluated based on RBC velocity through a microfluidic constriction as in conventional approaches. The correlation between transit velocity and amount of deformation provides statistical information of RBC deformability. However, such correlations are usually only moderate, or even weak, in practical evaluations due to limited range of RBC deformation. To solve this issue, we implemented three constrictions of different width in the proposed checker, so that three different deformation regions can be applied to RBCs. By considering cell responses from the three regions as a whole, we practically extend the range of cell deformation in the evaluation, and could resolve the issue about the limited range of RBC deformation. RBCs from five volunteer subjects were tested using the proposed checker. The results show that the correlation between cell deformation and transit velocity is significantly improved by the proposed deformability checker. The absolute values of the correlation coefficients are increased from an average of 0.54 to 0.92. The effects of cell size, shape and orientation to the evaluation are discussed according to the experimental results. The proposed checker is expected to be useful for RBC evaluation in medical practices.

Flow velocity measurement by using zero-crossing polarity cross correlation method

International Nuclear Information System (INIS)

Xu Chengji; Lu Jinming; Xia Hong

1993-01-01

Using the designed correlation metering system and a high accurate hot-wire anemometer as a calibration device, the experimental study of correlation method in a tunnel was carried out. The velocity measurement of gas flow by using zero-crossing polarity cross correlation method was realized and the experimental results has been analysed

Research on one-dimensional two-phase flow

International Nuclear Information System (INIS)

Adachi, Hiromichi

1988-10-01

In Part I the fundamental form of the hydrodynamic basic equations for a one-dimensional two-phase flow (two-fluid model) is described. Discussions are concentrated on the treatment of phase change inertial force terms in the equations of motion and the author's equations of motion which have a remarkable uniqueness on the following three points. (1) To express force balance of unit mass two-phase fluid instead of that of unit volume two-phase fluid. (2) To pick up the unit existing mass and the unit flowing mass as the unit mass of two-phase fluid. (3) To apply the kinetic energy principle instead of the momentum low in the evaluation of steady inertial force term. In these three, the item (1) is for excluding a part of momentum change or kinetic energy change due to mass change of the examined part of fluid, which is independent of force. The item (2) is not to introduce a phenomenological physical model into the evaluation of phase change inertial force term. And the item (3) is for correctly applying the momentum law taking into account the difference of representative velocities between the main flow fluid (vapor phase or liquid phase) and the phase change part of fluid. In Part II, characteristics of various kinds of high speed two-phase flow are clarified theoretically by the basic equations derived. It is demonstrated that the steam-water two-phase critical flow with violent flashing and the airwater two-phase critical flow without phase change can be described with fundamentally the same basic equations. Furthermore, by comparing the experimental data from the two-phase critical discharge test and the theoretical prediction, the two-phase discharge coefficient, C D , for large sharp-edged orifice is determined as the value which is not affected by the experimental facility characteristics, etc. (author)

Assessment of Two-Phase Flow Heat Transfer Correlations for Molten Core-Concrete Interaction Study

International Nuclear Information System (INIS)

Tourniaire, B.; Varo, O.

2006-01-01

The prediction of heat transfer between corium pool and concrete basemat is of particular significance in the framework of the study of PWR's severe accident. Heat transfer directly governs the ablation velocity of concrete in case of molten core-concrete interaction (MCCI) and, consequently, the time delay when the reactor cavity may fail. From a restricted hydrodynamic point of view, this issue is related to heat transfer between a heated bubbling pool and a porous wall with gas injection. Several experimental studies have been performed with simulant materials and many correlations have been provided to address this issue. The main purpose of this paper is to assess these correlations from comparisons against the available experimental data. After a review of these data, the different correlations are presented. Attention focuses here on the correlations generally used in MCCI study: Kutateladze-Malenkov, Konsetov and BALI correlations. The Deckwer's correlation is also included in this review. The comparisons between the results of these correlations and the experimental data are then discussed. (authors)

Study on two-phase flow in a coolant channel of a plate-type fuel with use of neutron radiography technique

International Nuclear Information System (INIS)

Mishima, K.; Hibiki, T.; Nishihara, H.

1992-01-01

Two-phase flow in a narrow rectangular duct is important related to abnormal cooling conditions of a MTR type research reactor. In view of this, flow regime, void fraction, slug bubble velocity and pressure loss were measured for rectangular ducts with a narrow gap. The neutron radiography technique was used to visualize the flow and the void fraction was obtained by image processing. The void fraction was correlated well by the drift flux model with existing correlation for the distribution parameter which was about 1.35. Similar results were obtained for slug bubble velocity, however the distribution parameter was in the range from 1.0 to 1.2. The frictional pressure loss was correlated well by the Chisholm-Laird correlation. In collaboration with previously obtained data, it was found that the Chisholm's parameter C, however, changed from 21 to zero as the gap decreased. (author)

Analysis of forced convective transient boiling by homogeneous model of two-phase flow

International Nuclear Information System (INIS)

Kataoka, Isao

1985-01-01

Transient forced convective boiling is of practical importance in relation to the accident analysis of nuclear reactor etc. For large length-to-diameter ratio, the transient boiling characteristics are predicted by transient two-phase flow calculations. Based on homogeneous model of two-phase flow, the transient forced convective boiling for power and flow transients are analysed. Analytical expressions of various parameters of transient two-phase flow have been obtained for several simple cases of power and flow transients. Based on these results, heat flux, velocity and time at transient CHF condition are predicted analytically for step and exponential power increases, and step, exponential and linear velocity decreases. The effects of various parameters on heat flux, velocity and time at transient CHF condition have been clarified. Numerical approach combined with analytical method is proposed for more complicated cases. Solution method for pressure transient are also described. (author)

Nuclear techniques and cross-correlation methods for spectral analysis in two-phase flow measurements in mineral pipelines

Energy Technology Data Exchange (ETDEWEB)

Brandao, Luis E.B.; Salgado, Cesar M., E-mail: brandaos@ien.gov.br, E-mail: otero@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Divisao de Radiofarmacos; Sicilliano, Umberto C.C.S., E-mail: umberto.cassara@poli.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Dept. de Metalurgia

2013-07-01

In mineral industry is common to use water to transport pellets inside pipes. In these units, the correct measurement of flow (both solid and liquid phase) is important to guarantee a safe operation. Cross correlation flow meters are devices specially suited to be used in dual-phase flow and they are based on measure the transit time due the disturbances registered between two points, in our case gamma attenuation from radioactive sources. The emphasis of this work is the application of gamma transmission and scattering technique associated with spectral analysis methods to measure the flow of solid phase in a liquid fluid in side the pipe. The detectors and the sources are out side of the tube and are positioned 10.0 cm distant one from the other. The photons of transmission/scattering gamma radiation were registered, and across-correlation method was applied to measure the flow and spectral analysis was used to study the flow profile inside the pipe. (author)

Some investigations on the mean and fluctuating velocities of an oscillating Taylor bubble

International Nuclear Information System (INIS)

Madani, Sara; Caballina, Ophelie; Souhar, Mohamed

2012-01-01

Highlights: ► The unsteady motion of an oscillating Taylor bubble has been studied. ► A non-dimensionalized velocity differential equation is numerically solved. ► The role of dimensionless numbers on the dynamics of the bubble is highlighted. ► Mean and fluctuating velocities and the phase shift are experimentally investigated. ► Correlations allowing the prediction of these latter parameters are proposed. - Abstract: The slug flow characterized by large elongated bubbles also called Taylor bubbles is widely encountered in nuclear reactor steam generators, cooling plants, reboilers, etc. The analysis of slug flow is very important as the instability caused by such flows can affect the safety features of nuclear reactors and other two-phase flow equipments. In this paper, we study the motion of a Taylor bubble rising in stagnant fluids in a vertical oscillating pipe. The investigation is restricted to high Reynolds numbers and to an intermediate range of Bond numbers where the effects of surface tension can be considered. The Froude number ranged between 0.22 and 0.33. Firstly, detailed analysis of models proposed in the literature for the motion of a Taylor bubble in an unsteady acceleration field is realized. The velocity differential equation obtained in the case of potential and axisymmetric flow without surface tension given in the literature is first non-dimensionalized to highlight dimensionless numbers. Then, the instantaneous velocity of the bubble is numerically determined. Mean and fluctuating velocities as well as the phase shift (U ¯ b , U f and φ) are estimated by using a technique based on the nonlinear least squares method. Results enable a discussion on the role played by dimensionless numbers on the dynamics of the bubble. It is found that the two parameters, the relative acceleration and the Bond number (a and Bo) have a governing role on the evolution of mean and fluctuating velocities while the ratio of the oscillation amplitude to

Determination of bubble parameters in two-phase flow

International Nuclear Information System (INIS)

Oliveira Lira, C.A.B. de.

1980-01-01

A development of a probe-detector system for measurement of bubble parameters like size, rise velocity and void fraction in two-phase flow is presented. The method uses an electro resistivity probe and a compact electronic circuit has been developed for obtain this purpose. (author)

Stationary echo canceling in velocity estimation by time-domain cross-correlation

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt

1993-01-01

The application of stationary echo canceling to ultrasonic estimation of blood velocities using time-domain cross-correlation is investigated. Expressions are derived that show the influence from the echo canceler on the signals that enter the cross-correlation estimator. It is demonstrated...

Characterization of the two-phase Taylor Couette flow

International Nuclear Information System (INIS)

Mehel A; Gabillet B; Djeridi H

2005-01-01

The focus of the present study concerns the effects of a dispersed phase on the structure of a quasi periodic Couette Taylor flow. The two phase flow patterns are investigated experimentally for the Taylor number Ta=780. Small bubbles (0.035 times as small as the gap) are generated by agitation of the upper free surface. Larger bubbles (0.15 times as small as the gap) are produced by injection at the bottom of the apparatus associated with a pressure drop. Void fraction, bubble size and velocity are measured, as well as the azimuthal and axial velocity components of the liquid. A premature transition to turbulence is pointed out and discussed according to the bubble size and their localization in the gap. (authors)

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

Nonlinear Analysis of Two-phase Circumferential Motion in the Ablation Circumstance

Science.gov (United States)

Xiao-liang, Xu; Hai-ming, Huang; Zi-mao, Zhang

2010-05-01

In aerospace craft reentry and solid rocket propellant nozzle, thermal chemistry ablation is a complex process coupling with convection, heat transfer, mass transfer and chemical reaction. Based on discrete vortex method (DVM), thermal chemical ablation model and particle kinetic model, a computational module dealing with the two-phase circumferential motion in ablation circumstance is designed, the ablation velocity and circumferential field can be thus calculated. The calculated nonlinear time series are analyzed in chaotic identification method: relative chaotic characters such as correlation dimension and the maximum Lyapunov exponent are calculated, fractal dimension of vortex bulbs and particles distributions are also obtained, thus the nonlinear ablation process can be judged as a spatiotemporal chaotic process.

A compact x-ray system for two-phase flow measurement

Science.gov (United States)

Song, Kyle; Liu, Yang

2018-02-01

In this paper, a compact x-ray densitometry system consisting of a 50 kV, 1 mA x-ray tube and several linear detector arrays is developed for two-phase flow measurement. The system is capable of measuring void fraction and velocity distributions with a spatial resolution of 0.4 mm per pixel and a frequency of 1000 Hz. A novel measurement model has been established for the system which takes account of the energy spectrum of x-ray photons and the beam hardening effect. An improved measurement accuracy has been achieved with this model compared with the conventional log model that has been widely used in the literature. Using this system, void fraction and velocity distributions are measured for a bubbly and a slug flow in a 25.4 mm I.D. air-water two-phase flow test loop. The measured superficial gas velocities show an error within  ±4% when compared with the gas flowmeter for both conditions.

Nonlinear dynamics of two-phase flow

International Nuclear Information System (INIS)

Rizwan-uddin

1986-01-01

Unstable flow conditions can occur in a wide variety of laboratory and industry equipment that involve two-phase flow. Instabilities in industrial equipment, which include boiling water reactor (BWR) cores, steam generators, heated channels, cryogenic fluid heaters, heat exchangers, etc., are related to their nonlinear dynamics. These instabilities can be of static (Ledinegg instability) or dynamic (density wave oscillations) type. Determination of regions in parameters space where these instabilities can occur and knowledge of system dynamics in or near these regions is essential for the safe operation of such equipment. Many two-phase flow engineering components can be modeled as heated channels. The set of partial differential equations that describes the dynamics of single- and two-phase flow, for the special case of uniform heat flux along the length of the channel, can be reduced to a set of two coupled ordinary differential equations [in inlet velocity v/sub i/(t) and two-phase residence time tau(t)] involving history integrals: a nonlinear ordinary functional differential equation and an integral equation. Hence, to solve these equations, the dependent variables must be specified for -(nu + tau) ≤ t ≤ 0, where nu is the single-phase residence time. This system of nonlinear equations has been solved analytically using asymptotic expansion series for finite but small perturbations and numerically using finite difference techniques

Three dimensional turbulence structure measurements in air/water two phase flow

International Nuclear Information System (INIS)

Wang, S.K.L.

1986-01-01

The phenomena of turbulent air/water two phase upward and downward flows in a circular test section were investigated. Important flow quantities such as void fraction, liquid velocity, and Reynolds stresses were measured by using both single sensor and three sensor hot film probes. A digital data processing technique based on combined derivative and level thresholding was developed to determine the local void fraction from hot-film anemometer signals. The measured local void fraction was integrated and the result was compared with the chordal averaged void fraction measured by a gamma ray densitometer. It was found that the local measurement underestimated local void fraction due to surface tension effects and bubble deflection by the probe. A correlation based on local parameters characterizing probe/bubble interaction was developed, and it corrected the measured void fraction successfully. The measured void fraction profiles in upward flow and downward flow showed two distinct patterns. In upward flow, bubbles tend to migrate toward the wall and the void fraction profile shows a sharp peak near the wall. In downward flow, as the liquid velocity increases, the wall peaking phenomenon fades out and bubbles tend to migrate toward the center of the pipe

Two pion correlation from SPACER

International Nuclear Information System (INIS)

Csoergoe, T.; Zimanyi, J.; Pratt, S.

1989-12-01

The correlation function for neutral and negative pions produced in ultrarelativistic heavy ion collisions was calculated without free parameters based on a space-time version of the LUND model, called SPACER: Simulation of Phase space distribution of Atomic nuclear Collisions in Energetic Reactions. This method includes the effect of Bose correlations for the emitted pion pair. Effects arising from correlations between space-time and momentum space distributions are investigated. The results are compared to the data of two different experiments. The role and interpretation of the chaocity parameter are discussed. (D.G.) 14 refs.; 4 figs

Power spectral density of velocity fluctuations estimated from phase Doppler data

OpenAIRE

Jicha Miroslav; Lizal Frantisek; Jedelsky Jan

2012-01-01

Laser Doppler Anemometry (LDA) and its modifications such as PhaseDoppler Particle Anemometry (P/DPA) is point-wise method for optical nonintrusive measurement of particle velocity with high data rate. Conversion of the LDA velocity data from temporal to frequency domain – calculation of power spectral density (PSD) of velocity fluctuations, is a non trivial task due to nonequidistant data sampling in time. We briefly discuss possibilities for the PSD estimation and specify limitations caused...

A Dual Conductance Sensor for Simultaneous Measurement of Void Fraction and Structure Velocity of Downward Two-Phase Flow in a Slightly Inclined Pipe.

Science.gov (United States)

Lee, Yeon-Gun; Won, Woo-Youn; Lee, Bo-An; Kim, Sin

2017-05-08

In this study, a new and improved electrical conductance sensor is proposed for application not only to a horizontal pipe, but also an inclined one. The conductance sensor was designed to have a dual layer, each consisting of a three-electrode set to obtain two instantaneous conductance signals in turns, so that the area-averaged void fraction and structure velocity could be measured simultaneously. The optimum configuration of the electrodes was determined through numerical analysis, and the calibration curves for stratified and annular flow were obtained through a series of static experiments. The fabricated conductance sensor was applied to a 45 mm inner diameter U-shaped downward inclined pipe with an inclination angle of 3° under adiabatic air-water flow conditions. In the tests, the superficial velocities ranged from 0.1 to 3.0 m/s for water and from 0.1 to 18 m/s for air. The obtained mean void fraction and the structure velocity from the conductance sensor were validated against the measurement by the wire-mesh sensor and the cross-correlation technique for the visualized images, respectively. The results of the flow regime classification and the corresponding time series of the void fraction at a variety of flow velocities were also discussed.

Frictional resistance of adiabatic two-phase flow in narrow rectangular duct under rolling conditions

International Nuclear Information System (INIS)

Xing, Dianchuan; Yan, Changqi; Sun, Licheng; Jin, Guangyuan; Tan, Sichao

2013-01-01

Highlights: ► Two-phase flow frictional resistance in narrow duct in rolling is studied. ► Frictional resistance behaviors in rolling are divided into three regions. ► Transient frictional pressure drop fluctuates synchronously with rolling motion. ► Conventional correlations are evaluated against experimental data in rolling motion. ► New correlation for transient frictional resistance in rolling motion is developed. - Abstract: Frictional resistance of air-water two-phase flow in a narrow rectangular duct subjected to rolling motion was investigated experimentally. Time-averaged and transient frictional pressure drop under rolling condition were compared with conventional correlation in laminar flow region (Re l l ⩽ 1400) and turbulent flow region (Re l > 1400) respectively. The result shows that, despite no influence on time-averaged frictional resistance, rolling motion does induce periodical fluctuation of the pressure drop in laminar and transition flow regions. Transient frictional pressure drop fluctuates synchronously with the rolling motion both in laminar and in transition flow region, while it is nearly invariable in turbulent flow region. The fluctuation amplitude of the Relative frictional pressure gradient decreases with the increasing of the superficial velocities. Lee and Lee (2002) correlation and Chisholm (1967) correlation could satisfactorily predict time-averaged frictional pressure drop under rolling conditions, whereas poorly predict the transient frictional pressure drop when it fluctuates periodically. A new correlation with better accuracy for predicting the transient frictional pressure drop in rolling motion is achieved by modifying the Chisholm (1967) correlation on the basis of analyzing the present experimental results with a great number of data points

Hydrodynamic prediction of multidimensional single- and two-phase flow in rod arrays. Progress report, January 1-December 31, 1983

International Nuclear Information System (INIS)

Ebeling-Koning, D.B.; Robinson, J.T.; Todreas, N.E.

1984-01-01

The objective of this research is to develop comprehensive constitutive models for multidimensional two-phase flow in rod arrays. The constitutive parameters are the solid-fluid flow resistance and the gas-liquid interfacial momentum exchange force. This report covers work in four areas: (1) a correlation for flow resistance across banks of tubes which is independent of rod arrangement has been developed. The correlation was developed from data from three rod arrangements covering a Reynolds number range (based on superficial velocity) of 1 to 40,000; (2) complete pressure drop data for water flows in the laminar region in crossflow and 45 0 inclined rod arrays were taken; (3) the development of a model for the interfacial momentum exchange force in bubbly flows has been completed. This model has been validated against single bubble velocity data in inclined rod arrays. The model has been cast in a form suitable for implementation to two-fluid computer codes; and (4) rise velocities of bubbles in 0 0 , 45 0 , and 90 0 inclined rod arrays have been measured. This data should prove useful for the development of a bubble drag coefficient model for rod arrays

A semi-empirical two phase model for rocks

International Nuclear Information System (INIS)

Fogel, M.B.

1993-01-01

This article presents data from an experiment simulating a spherically symmetric tamped nuclear explosion. A semi-empirical two-phase model of the measured response in tuff is presented. A comparison is made of the computed peak stress and velocity versus scaled range and that measured on several recent tuff events

Numerical simulation and experimental verification of a flat two-phase thermosyphon

International Nuclear Information System (INIS)

Zhang Ming; Liu Zhongliang; Ma Guoyuan; Cheng Shuiyuan

2009-01-01

The flat two-phase thermosyphon is placed between the heat source and the heat sink, which can achieve the uniform heat flux distribution and improve the performance of heat sink. In this paper, a two-dimensional heat and mass transfer model for a disk-shaped flat two-phase thermosyphon is developed. By solving the equations of continuity, momentum and energy numerically, the vapor velocity and temperature distributions of the flat two-phase thermosyphon are obtained. An analysis is also carried out on the ability of flat two-phase thermosyphon to spread heat and remove hot spots. In order to observe boiling and condensation phenomena, a transparent flat two-phase thermosyphon is manufactured and studied experimentally. The experimental results are compared with numerical results, which verify the physical and mathematical model of the flat two-phase thermosyphon. In order to study the main factors affecting the axial thermal resistance of two-phase thermosyphon, the temperatures inside the flat two-phase thermosyphon are measured and analyzed

Stationary two-phase flow evaluation by the dynamic slip model

International Nuclear Information System (INIS)

Stevanovic, D.

1986-01-01

The equations which describe a dynamic slip model for stationary conditions are given in the paper. The basic solving procedure by the code DVOF4 is briefly described. The results are verified on the experiment FRIGG 313014. besides the void fraction and the vapor and liquid phase temperatures, the following parameters are plotted and explained: vapor phase generation rate, vapor and liquid phase velocities, slip between the phases, interfacial surface, friction drag between each phase and the wall, two-phase flow friction multiplier and pressure drop along the channel. (author)

Analysis of one-dimensional nonequilibrium two-phase flow using control volume method

International Nuclear Information System (INIS)

Minato, Akihiko; Naitoh, Masanori

1987-01-01

A one-dimensional numerical analysis model was developed for prediction of rapid flow transient behavior involving boiling. This model was based on six conservation equations of time averaged parameters of gas and liquid behavior. These equations were solved by using a control volume method with an explicit time integration. This model did not use staggered mesh scheme, which had been commonly used in two-phase flow analysis. Because void fraction and velocity of each phase were defined at the same location in the present model, effects of void fraction on phase velocity calculation were treated directly without interpolation. Though non-staggered mesh scheme was liable to cause numerical instability with zigzag pressure field, stability was achieved by employing the Godunov method. In order to verify the present analytical model, Edwards' pipe blow down and Zaloudek's initially subcooled critical two-phase flow experiments were analyzed. Stable solutions were obtained for rarefaction wave propagation with boiling and transient two-phase flow behavior in a broken pipe by using this model. (author)

Comparison of shear wave velocity measurements assessed with two different ultrasound systems in an ex-vivo tendon strain phantom.

Science.gov (United States)

Rosskopf, Andrea B; Bachmann, Elias; Snedeker, Jess G; Pfirrmann, Christian W A; Buck, Florian M

2016-11-01

The purpose of this study is to compare the reliability of SW velocity measurements of two different ultrasound systems and their correlation with the tangent traction modulus in a non-static tendon strain model. A bovine tendon was fixed in a custom-made stretching device. Force was applied increasing from 0 up to 18 Newton. During each strain state the tangent traction modulus was determined by the stretcher device, and SW velocity (m/s) measurements using a Siemens S3000 and a Supersonic Aixplorer US machine were done for shear modulus (kPa) calculation. A strong significant positive correlation was found between SW velocity assessed by the two ultrasound systems and the tangent traction modulus (r = 0.827-0.954, p Aixplorer 0.25 ± 0.3 m/s (p = 0.034). Mean difference of SW velocity between the two US-systems was 0.37 ± 0.3 m/s (p = 0.012). In conclusion, SW velocities are highly dependent on mechanical forces in the tendon tissue, but for controlled mechanical loads appear to yield reproducible and comparable measurements using different US systems.

CFD-DEM Simulation of Minimum Fluidisation Velocity in Two Phase Medium

Directory of Open Access Journals (Sweden)

H Khawaja

2016-09-01

Full Text Available In this work, CFD-DEM (computational fluid dynamics - discrete element method has been used to model the 2 phase flow composed of solid particle and gas in the fluidised bed. This technique uses the Eulerian and the Langrangian methods to solve fluid and particles respectively. Each particle is treated as a discrete entity whose motion is governed by Newton's laws of motion. The particle-particle and particle-wall interaction is modelled using the classical contact mechanics. The particles motion is coupled with the volume averaged equations of the fluid dynamics using drag law. In fluidised bed, particles start experiencing drag once the fluid is passing through. The solid particles response to it once drag experienced is just equal to the weight of the particles. At this moment pressure drop across the bed is just equal to the weight of particles divide by the cross-section area. This is the first regime of fluidization, also referred as ‘the regime of minimum fluidization’. In this study, phenomenon of minimum fluidization is studied using CFD-DEM simulation with 4 different sizes of particles 0.15 mm, 0.3 mm, 0.6 mm, and 1.2 mm diameters. The results are presented in the form of pressure drop across the bed with the fluid superficial velocity. The achieved results are found in good agreement with the experimental and theoretical data available in literature.

Three-dimensional numerical modeling of turbulent single-phase and two-phase flow in curved pipes

International Nuclear Information System (INIS)

Xin, R.C.; Dong, Z.F.; Ebadian, M.A.

1996-01-01

In this study, three-dimensional single-phase and two-phase flows in curved pipes have been investigated numerically. Two different pipe configurations were computed. When the results of the single-phase flow simulation were compared with the experimental data, a fairly good agreement was achieved. A flow-developing process has been suggested in single-phase flow, in which the turbulence is stronger near the outer tube wall than near the inner tube wall. For two-phase flow, the Eulerian multiphase model was used to simulate the phase distribution of a three-dimensional gas-liquid bubble flow in curved pipe. The RNG/κ-ε turbulence model was used to determine the turbulence field. An inlet gas void fraction of 5 percent was simulated. The gas phase effects on the liquid phase flow velocity have been examined by comparing the results of single-phase flow and two-phase flow. The findings show that for the downward flow in the U bend, the gas concentrates at the inner portion of the cross section at φ = π/18 - π/6 in most cases. The results of the phase distribution simulation are compared to experimental observations qualitatively and topologically

Effects of resistance training using known vs unknown loads on eccentric-phase adaptations and concentric velocity.

Science.gov (United States)

Hernández-Davó, J L; Sabido, R; Behm, D G; Blazevich, A J

2018-02-01

The aims of this study were to compare both eccentric- and concentric-phase adaptations in highly trained handball players to 4 weeks of twice-weekly rebound bench press throw training with varying loads (30%, 50% and 70% of one-repetition maximum [1-RM]) using either known (KL) or unknown (UL) loads and to examine the relationship between changes in eccentric- and concentric-phase performance. Twenty-eight junior team handball players were divided into two experimental groups (KL or UL) and a control group. KL subjects were told the load prior each repetition, while UL were blinded. For each repetition, the load was dropped and then a rebound bench press at maximum velocity was immediately performed. Both concentric and eccentric velocity as well as eccentric kinetic energy and musculo-articular stiffness prior to the eccentric-concentric transition were measured. Results showed similar increases in both eccentric velocity and kinetic energy under the 30% 1-RM but greater improvements under 50% and 70% 1-RM loads for UL than KL. UL increased stiffness under all loads (with greater magnitude of changes). KL improved concentric velocity only under the 30% 1-RM load while UL also improved under 50% and 70% 1-RM loads. Improvements in concentric movement velocity were moderately explained by changes in eccentric velocity (R 2 =.23-.62). Thus, UL led to greater improvements in concentric velocity, and the improvement is potentially explained by increases in the speed (as well as stiffness and kinetic energy) of the eccentric phase. Unknown load training appears to have significant practical use for the improvement of multijoint stretch-shortening cycle movements. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Frictional pressure drop of steam-water two-phase flow in helical coils with small helix diameter of HTR-10

International Nuclear Information System (INIS)

Bi Qincheng; Chen Tingkuan; Luo Yushan; Zheng Jianxue

1996-01-01

Experiments of steam-water two-phase flow frictional pressure drop through five vertically and horizontally positioned helical coils were carried out in the high pressure steam water test loop of Xi'an Jiaotong University. Two kinds of tube with inner diameters of 10 mm and 12 mm were used to form the coils. The helix diameter was 115 mm with coil pitch 22.5 mm. The experimental conditions were: pressure p = 4-14 MPa, mass velocity G = 400-2000 kg/(m 2 ·s), and inner wall heat flux q = 0-750 kW/m 2 . Theoretical analysis with a semi-empirical correlation was made to predict the two-phase flow fictional pressure drop through these kinds of helical coils

Rayleigh and Love Wave Phase Velocities in the Northern Gulf Coast of the United States

Science.gov (United States)

Li, A.; Yao, Y.

2017-12-01

The last major tectonic event in the northern Gulf Coast of the United States is Mesozoic continental rifting that formed the Gulf of Mexico. This area also experienced igneous activity and local uplifts during Cretaceous. To investigate lithosphere evolution associated with the rifting and igneous activity, we construct Rayleigh and Love wave phase velocity models at the periods of 6 s to 125 s in the northern Gulf Coast from Louisiana to Alabama including the eastern Ouachita and southern Appalachian orogeny. The phase velocities are derived from ambient noise and earthquake data recorded at the 120 USArray Transportable Array stations. At periods below 20 s, phase velocity maps are characterized by significant low velocities in the Interior Salt Basin and Gulf Coast Basin, reflecting the effects of thick sediments. The northern Louisiana and southern Arkansas are imaged as a low velocity anomaly in Rayleigh wave models but a high velocity anomaly of Love wave at the periods of 14 s to 30 s, indicating strong lower crust extension to the Ouachita front. High velocity is present in the Mississippi Valley Graben from period 20 s to 35 s, probably reflecting a thin crust or high-velocity lower crust. At longer periods, low velocities are along the Mississippi River to the Gulf Coast Basin, and high velocity anomaly mainly locates in the Black Warrior Basin between the Ouachita Belt and Appalachian Orogeny. The magnitude of anomalies in Love wave images is much smaller than that in Rayleigh wave models, which is probably due to radial anisotropy in the upper mantle. A 3-D anisotropic shear velocity model will be developed from the phase velocities and will provide more details for the crust and upper mantle structure beneath the northern Gulf of Mexico continental margin.

Development of three-dimensional individual bubble-velocity measurement method by bubble tracking

International Nuclear Information System (INIS)

Kanai, Taizo; Furuya, Masahiro; Arai, Takahiro; Shirakawa, Kenetsu; Nishi, Yoshihisa

2012-01-01

A gas-liquid two-phase flow in a large diameter pipe exhibits a three-dimensional flow structure. Wire-Mesh Sensor (WMS) consists of a pair of parallel wire layers located at the cross section of a pipe. Both the parallel wires cross at 90o with a small gap and each intersection acts as an electrode. The WMS allows the measurement of the instantaneous two-dimensional void-fraction distribution over the cross-section of a pipe, based on the difference between the local instantaneous conductivity of the two-phase flow. Furthermore, the WMS can acquire a phasic-velocity on the basis of the time lag of void signals between two sets of WMS. Previously, the acquired phasic velocity was one-dimensional with time-averaged distributions. The authors propose a method to estimate the three-dimensional bubble-velocity individually WMS data. The bubble velocity is determined by the tracing method. In this tracing method, each bubble is separated from WMS signal, volume and center coordinates of the bubble is acquired. Two bubbles with near volume at two WMS are considered as the same bubble and bubble velocity is estimated from the displacement of the center coordinates of the two bubbles. The validity of this method is verified by a swirl flow. The proposed method can successfully visualize a swirl flow structure and the results of this method agree with the results of cross-correlation analysis. (author)

Measurement system of bubbly flow using ultrasonic velocity profile monitor and video data processing unit. 2. Flow characteristics of bubbly countercurrent flow

International Nuclear Information System (INIS)

Aritomi, Masanori; Zhou, Shirong; Nakajima, Makoto; Takeda, Yasushi; Mori, Michitsugu.

1997-01-01

The authors have developed a measurement system which is composed of an ultrasonic velocity profile monitor and a video data processing unit in order to clarify its multi-dimensional flow characteristics in bubbly flows and to offer a data base to validate numerical codes for multi-dimensional two-phase flow. In this paper, the measurement system was applied for bubbly countercurrent flows in a vertical rectangular channel. At first, both bubble and water velocity profiles and void fraction profiles in the channel were investigated statistically. Next, turbulence intensity in a continuous liquid phase was defined as a standard deviation of velocity fluctuation, and the two-phase multiplier profile of turbulence intensity in the channel was clarified as a ratio of the standard deviation of flow fluctuation in a bubbly countercurrent flow to that in a water single phase flow. Finally, the distribution parameter and drift velocity used in the drift flux model for bubbly countercurrent flows were calculated from the obtained velocity profiles of both phases and void fraction profile, and were compared with the correlation proposed for bubbly countercurrent flows. (author)

Surface wave phase velocities between Bulgaria and the Czech Republic

Czech Academy of Sciences Publication Activity Database

Gaždová, Renata; Kolínský, Petr; Popova, I.; Dimitrova, L.

2011-01-01

Roč. 18, č. 2 (2011), s. 16-23 ISSN 1803-1447. [OVA´11 – New Knowledge and Measurements in Seismology, Engineering Geophysics and Geotechnics. Ostrava, 12.04.2011-14.04.2011] R&D Projects: GA ČR GA205/09/1244 Institutional research plan: CEZ:AV0Z30460519 Keywords : surface waves * phase velocity * shear wave velocity Subject RIV: DC - Siesmology, Volcanology, Earth Structure http://www.caag.cz/egrse/2011-2/03%20gazdova_ova.pdf

Phase and group velocities for Lamb waves in DOP-26 iridium alloy sheet

International Nuclear Information System (INIS)

Simpson, W.A.; McGuire, D.J.

1994-07-01

The relatively coarse grain structure of iridium weldments limits the ultrasonic inspection of these structures to frequencies in the low megahertz range. As the material thickness is nominally 0.635 mm for clad vent set capsules, the low frequencies involved necessarily entail the generation of Lamb waves m the specimen. These waves are, of course, dispersive and detailed knowledge of both the phase and group velocities is required in order to determine accurately the location of flaws detected using Lamb waves. Purpose of this study is to elucidate the behavior of Lamb waves propagating in the capsule alloy and to quantify the velocities so that accurate flaw location is ensured. We describe a numerical technique for computing the phase velocities of Lamb waves (or of any other type of guided wave) and derive the group velocities from this information. A frequency-domain method is described for measuring group velocity when multiple Lamb modes are present and mutually interfering in the time domain, and experimental confirmation of the group velocity is presented for the capsule material

Circumferential-wave phase velocities for empty, fluid-immersed spherical metal shells

DEFF Research Database (Denmark)

Überall, Herbert; Ahyi, A. C.; Raju, P. K.

2002-01-01

In earlier studies of acoustic scattering resonances and of the dispersive phase velocities of surface waves that generate them [see, e.g., Talmant et al., J. Acoust. Soc. Am. 86, 278–289 (1989) for spherical aluminum shells] we have demonstrated the effectiveness and accuracy of obtaining phase ...

Two-phase flux simulations by robots

International Nuclear Information System (INIS)

Barrera, F.D.

1997-01-01

Two-Phase flow systems are studied following the statistical formulation, which takes into account the bubble population balances. This is done by means of automata simulation. Geometrical automata are associated to the dispersed phase, and are represented by discs on the plane, resembling bubbles moving in a fluid environment. Following pre-determined rules, the automata evolve, and useful statistical information about their interaction is obtained. This information is applied in the present work to study the mechanisms that induce bubble coalescence. Models for one and two sized automata are presented. It was found that in the case of the model for one size, the probability of interaction among bubbles and the pair correlation function depends not only on the void fraction, but also on the number of elements of the dispersed phase. A correlation for the collision probability between two bubbles is obtained, and this result was extended to the pair correlation function. For the case of systems with two characteristic sizes, a model was formulated for analyzing the interaction among bubbles of the two groups. The interaction of bubbles for one and two sized systems were related by a symmetry factor, which shows the dependence of the interaction among bubbles with the size distribution. By means of the automata simulation, the phenomena of bubble confinement and screening were characterized. It was found that the first phenomenon is stronger in systems with greater distance among bubbles, and that the second effect increases with void fraction and bubble number. (author)

Liquid velocity in upward and downward air-water flows

International Nuclear Information System (INIS)

Sun Xiaodong; Paranjape, Sidharth; Kim, Seungjin; Ozar, Basar; Ishii, Mamoru

2004-01-01

Local characteristics of the liquid phase in upward and downward air-water two-phase flows were experimentally investigated in a 50.8-mm inner-diameter round pipe. An integral laser Doppler anemometry (LDA) system was used to measure the axial liquid velocity and its fluctuations. No effect of the flow direction on the liquid velocity radial profile was observed in single-phase liquid benchmark experiments. Local multi-sensor conductivity probes were used to measure the radial profiles of the bubble velocity and the void fraction. The measurement results in the upward and downward two-phase flows are compared and discussed. The results in the downward flow demonstrated that the presence of the bubbles tended to flatten the liquid velocity radial profile, and the maximum liquid velocity could occur off the pipe centerline, in particular at relatively low flow rates. However, the maximum liquid velocity always occurred at the pipe center in the upward flow. Also, noticeable turbulence enhancement due to the bubbles in the two-phase flows was observed in the current experimental flow conditions. Furthermore, the distribution parameter and the void-weighted area-averaged drift velocity were obtained based on the definitions

NMR studies of granular media and two-phase flow in porous media

Science.gov (United States)

Yang, Xiaoyu

This dissertation describes two experimental studies of a vibrofluidized granular medium and a preliminary study of two-phase fluid flow in a porous medium using Nuclear Magnetic Resonance (NMR). The first study of granular medium is to test a scaling law of the rise in center of mass in a three-dimensional vibrofluidized granular system. Our granular system consisted of mustard seeds vibrated vertically at 40 Hz from 0g to 14g. We used Magnetic Resonance Imaging (MRI) to measure density profile in vibrated direction. We observed that the rise in center of mass scaled as nu 0alpha/Nlbeta with alpha = 1.0 +/- 0.2 and beta = 0.5 +/- 0.1, where nu 0 is the vibration velocity and Nl is the number of layers of grains in the container. A simple theory was proposed to explain the scaling exponents. In the second study we measured both density and velocity information in the same setup of the first study. Pulsed Field Gradient (PFG)-NMR combined with MRI was used to do this measurement. The granular system was fully fluidized at 14.85g 50 Hz with Nl ≤ 4. The velocity distributions at horizontal and vertical direction at different height were measured. The distributions were nearly-Gaussian far from sample bottom and non-Gaussian near sample bottom. Granular temperature profiles were calculated from the velocity distributions. The density and temperature profile were fit to a hydrodynamic theory. The theory agreed with experiments very well. A temperature inversion near top was also observed and explained by additional transport coefficient from granular hydrodynamics. The third study was the preliminary density measurement of invading phase profile in a two-phase flow in porous media. The purpose of this study was to test an invasion percolation with gradient (IPG) theory in two-phase flow of porous media. Two phases are dodecane and water doped with CuSO4. The porous medium was packed glass beads. The front tail width sigma and front width of invading phase were

The influence of gas phase velocity fluctuations on primary atomization and droplet deformation

Science.gov (United States)

Kourmatzis, A.; Masri, A. R.

2014-02-01

The effects of grid-generated velocity fluctuations on the primary atomization and subsequent droplet deformation of a range of laminar liquid jets are examined using microscopic high-speed backlit imaging of the break-up zone and laser Doppler anemometry of the gas phase separately. This is done for fixed gas mean flow conditions in a miniature wind tunnel experiment utilizing a selection of fuels, turbulence-generating grids and two syringe sizes. The constant mean flow allows for an isolated study of velocity fluctuation effects on primary atomization in a close approximation to homogeneous decaying turbulence. The qualitative morphology of the primary break-up region is examined over a range of turbulence intensities, and spectral analysis is performed in order to ascertain the break-up frequency which, for a case of no grid, compares well with the existing literature. The addition of velocity fluctuations tends to randomize the break-up process. Slightly downstream of the break-up region, image processing is conducted in order to extract a number of metrics, which do not depend on droplet sphericity, and these include droplet aspect ratio and orientation, the latter quantity being somewhat unconventional in spray characterization. A turbulent Weber number which takes into account gas phase fluctuations is utilized to characterize the resulting droplet shapes, in addition to a mean Weber number . Above a a clear positive relationship exists between the mean aspect ratio of droplets and the turbulent Weber number where is varied by altering all relevant variables including the velocity root mean square, the initial droplet diameter, the surface tension and the density.

Sound velocities of the 23 Å phase at high pressure and implications for seismic velocities in subducted slabs

Science.gov (United States)

Cai, N.; Chen, T.; Qi, X.; Inoue, T.; Li, B.

2017-12-01

Dense hydrous phases are believed to play an important role in transporting water back into the deep interior of the Earth. Recently, a new Al-bearing hydrous Mg-silicate, named the 23 Å phase (ideal composition Mg12Al2Si4O16(OH)14), was reported (Cai et al., 2015), which could be a very important hydrous phase in subducting slabs. Here for the first time we report the measurements of the compressional and shear wave velocities of the 23 Å phase under applied pressures up to 14 GPa and room temperature, using a bulk sample with a grain size of less than 20 μm and density of 2.947 g/cm3. The acoustic measurements were conducted in a 1000-ton uniaxial split-cylinder multi-anvil apparatus using ultrasonic interferometry techniques (Li et al., 1996). The pressures were determined in situ by using an alumina buffer rod as the pressure marker (Wang et al., 2015). A dual-mode piezoelectric transducer enabled us to measure P and S wave travel times simultaneously, which in turn allowed a precise determination of the sound velocities and elastic bulk and shear moduli at high pressures. A fit to the acoustic data using finite strain analysis combined with a Hashin-Shtrikman (HS) bounds calculation yields: Ks0 = 113.3 GPa, G0 = 42.8 GPa, and K' = 3.8, G' = 1.9 for the bulk and shear moduli and their pressure derivatives. The velocities (especially for S wave) of this 23 Å phase (ambient Vp = 7.53 km/s, Vs = 3.72 km/s) are lower than those of phase A, olivine, pyrope, etc., while the Vp/Vs ratio (from 2.02 to 1.94, decreasing with increasing pressure) is quite high. These results suggest that a hydrous assemblage containing 23 Å phase should be distinguishable from a dry one at high pressure and temperature conditions relevant to Al-bearing subducted slabs.

DISTRIBUTION OF TWO-PHASE FLOW IN A DISTRIBUTOR

Directory of Open Access Journals (Sweden)

AZRIDJAL AZIZ

2012-02-01

Full Text Available The flow configuration and distribution behavior of two-phase flow in a distributor made of acrylic resin have been investigated experimentally. In this study, air and water were used as two-phase flow working fluids. The distributor consists of one inlet and two outlets, which are set as upper and lower, respectively. The flow visualization at the distributor was made by using a high–speed camera. The flow rates of air and water flowing out from the upper and lower outlet branches were measured. Effects of inclination angle of the distributor were investigated. By changing the inclination angle from vertical to horizontal, uneven distributions were also observed. The distribution of two-phase flow through distributor tends even flow distribution on the vertical position and tends uneven distribution on inclined and horizontal positions. It is shown that even distribution could be achieved at high superficial velocities of both air and water.

Superhilac real-time velocity measurements

International Nuclear Information System (INIS)

Feinberg, B.; Meaney, D.; Thatcher, R.; Timossi, C.

1987-03-01

Phase probes have been placed in several external beam lines at the LBL heavy ion linear accelerator (SuperHILAC) to provide non-destructive velocity measurements independent of the ion being accelerated. The existing system has been improved to provide the following features: a display refresh rate better than twice per second, a sensitive pseudo-correlation technique to pick out the signal from the noise, simultaneous measurements of up to four ion velocities when more than one beam is being accelerated, and a touch-screen operator interface. These improvements allow the system to be used as a routine tuning aid and beam velocity monitor

Correlating P-wave Velocity with the Physico-Mechanical Properties of Different Rocks

Science.gov (United States)

Khandelwal, Manoj

2013-04-01

In mining and civil engineering projects, physico-mechanical properties of the rock affect both the project design and the construction operation. Determination of various physico-mechanical properties of rocks is expensive and time consuming, and sometimes it is very difficult to get cores to perform direct tests to evaluate the rock mass. The purpose of this work is to investigate the relationships between the different physico-mechanical properties of the various rock types with the P-wave velocity. Measurement of P-wave velocity is relatively cheap, non-destructive and easy to carry out. In this study, representative rock mass samples of igneous, sedimentary, and metamorphic rocks were collected from the different locations of India to obtain an empirical relation between P-wave velocity and uniaxial compressive strength, tensile strength, punch shear, density, slake durability index, Young's modulus, Poisson's ratio, impact strength index and Schmidt hammer rebound number. A very strong correlation was found between the P-wave velocity and different physico-mechanical properties of various rock types with very high coefficients of determination. To check the sensitivity of the empirical equations, Students t test was also performed, which confirmed the validity of the proposed correlations.

An investigation of subchannel analysis models for single-phase and two-phase flow

Energy Technology Data Exchange (ETDEWEB)

Hwang, Dae Hyun

1996-01-01

The governing equations and lateral transport modelings of subchannel analysis code, which is the most widely used tool for the analysis of thermal hydraulics fields in reactor cores, have been thoroughly investigated in this study. The procedure for the derivation of subchannel integral balance equations from the local instantaneous phase equations was investigated by stages. The characteristics of governing equations according to the treatment of phase velocity were studies, and the equations based on the drift-flux equilibrium formulation have been derived. Turbulent mixing and void drift modeling, which affect considerably to the accuracy of subchannel analysis code, have been reviewed. In addition, some representative modelings of single-phase and two-phase turbulent mixing models have been introduced. (author). 5 tabs., 4 figs., 16 refs.

Bayesian analysis of radial velocity data of GJ667C with correlated noise: evidence for only two planets

Science.gov (United States)

Feroz, F.; Hobson, M. P.

2014-02-01

GJ667C is the least massive component of a triple star system which lies at a distance of about 6.8 pc (22.1 light-year) from the Earth. GJ667C has received much attention recently due to the claims that it hosts up to seven planets including three super-Earths inside the habitable zone. We present a Bayesian technique for the analysis of radial velocity (RV) data sets in the presence of correlated noise component (`red noise'), with unknown parameters. We also introduce hyper-parameters in our model in order to deal statistically with under- or overestimated error bars on measured RVs as well as inconsistencies between different data sets. By applying this method to the RV data set of GJ667C, we show that this data set contains a significant correlated (red) noise component with correlation time-scale for HARPS data of the order of 9 d. Our analysis shows that the data only provide strong evidence for the presence of two planets: GJ667Cb and c with periods 7.19 and 28.13 d, respectively, with some hints towards the presence of a third signal with period 91 d. The planetary nature of this third signal is not clear and additional RV observations are required for its confirmation. Previous claims of the detection of additional planets in this system are due the erroneous assumption of white noise. Using the standard white noise assumption, our method leads to the detection of up to five signals in this system. We also find that with the red noise model, the measurement uncertainties from HARPS for this system are underestimated at the level of ˜50 per cent.

Probing the 'nutcracker' by two-pion correlation

International Nuclear Information System (INIS)

Hirano, Tetsufumi; Morita, Kenji

2001-01-01

We investigate the 'nutcracker' phenomenon by studying two-pion correlation functions of non-central relativistic heavy-ion collisions. We apply the full (3+1)-dimensional hydro-dynamic model with first order phase transition. Based on numerical results which shows the 'nutcracked' freeze-out hypersurface, we calculate the two-pion correlation functions. In the case of snapshot hypersurfaces which clearly show the nut-shell structure, we find a interesting behavior at high relative momenta. We discuss the possibility of observing the phenomenon in heavy ion experiments. (author)

Upper mantle compositional variations and discontinuity topography imaged beneath Australia from Bayesian inversion of surface-wave phase velocities and thermochemical modeling

DEFF Research Database (Denmark)

Khan, A.; Zunino, Andrea; Deschamps, F.

2013-01-01

Here we discuss the nature of velocity heterogeneities seen in seismic tomography images of Earth's mantle whose origins and relation to thermochemical variations are yet to be understood. We illustrate this by inverting fundamental-mode and higher-order surface-wave phase velocities for radial....../Fe and Mg/Si values relative to surrounding mantle. Correlated herewith are thermal variations that closely follow surface tectonics. We also observe a strong contribution to lateral variations in structure and topography across the “410 km” seismic discontinuity from thermochemically induced phase......-wave tomography models with other regional models is encouraging. Radial anisotropy is strongest at 150/200 km depth beneath oceanic/continental areas, respectively, and appears weak and homogeneous below. Finally, geoid anomalies are computed for a subset of sampled model and compared to observations....

Two-phased flow component loss data

International Nuclear Information System (INIS)

Fairhurst, C.P.

1983-01-01

Pressure loss measurements were made for valves and orifice plates under horizontal and vertical two-phase, air/water flow. The results displayed similar trends and were successfully correlated using a semi-empirical approach. (author)

Measurement and simulation of the turbulent dispersion of a radioactive tracer in a two-phase flow system

Energy Technology Data Exchange (ETDEWEB)

Hensel, F; Rohde, U

1998-10-01

The turbulent dispersion of a radiotracer in an experimental setup with a natural convection liquid-gaseous flow was investigated. A liquid-gaseous bubbly flow was generated in a narrow tank by injection of pressurized air into water or by catalytic disintegration of H{sub 2}O{sub 2}. Turbulent Prandtl numbers for gas and tracer dispersion were varied. In the case of higher gas superficial velocities (J{sub gas}{approx}5-15 mm/s), a reasonable agreement was achieved between calculated and measured tracer transport velocity and dispersion coefficient values. A nearly linear correlation between j{sub gas} and D was found in agreement with other authors. The calculation results contribute to a better understanding of the phenomena and interpretation of the measurement results as well as to the validation of the CFD code for turbulent two-phase flow applications. Further investigations are necessary to improve the agreement in the cases of H{sub 2}O{sub 2} disintegration and low gas superficial velocities. (orig.)

Measurement and simulation of the turbulent dispersion of a radioactive tracer in a two-phase flow system

International Nuclear Information System (INIS)

Hensel, F.; Rohde, U.

1998-01-01

The turbulent dispersion of a radiotracer in an experimental setup with a natural convection liquid-gaseous flow was investigated. A liquid-gaseous bubbly flow was generated in a narrow tank by injection of pressurized air into water or by catalytic disintegration of H 2 O 2 . Turbulent Prandtl numbers for gas and tracer dispersion were varied. In the case of higher gas superficial velocities (J gas ∼5-15 mm/s), a reasonable agreement was achieved between calculated and measured tracer transport velocity and dispersion coefficient values. A nearly linear correlation between j gas and D was found in agreement with other authors. The calculation results contribute to a better understanding of the phenomena and interpretation of the measurement results as well as to the validation of the CFD code for turbulent two-phase flow applications. Further investigations are necessary to improve the agreement in the cases of H 2 O 2 disintegration and low gas superficial velocities. (orig.)

Refrigeration. Two-Phase Flow. Flow Regimes and Pressure Drop

DEFF Research Database (Denmark)

Knudsen, Hans-Jørgen Høgaard

2002-01-01

The note gives the basic definitions used in two-phase flow. Flow regimes and flow regimes map are introduced. The different contributions to the pressure drop are stated together with an imperical correlation from the litterature.......The note gives the basic definitions used in two-phase flow. Flow regimes and flow regimes map are introduced. The different contributions to the pressure drop are stated together with an imperical correlation from the litterature....

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

An evaluation of state-of-the-art two-velocity two-phase flow models and their applicability to nuclear reactor transient analysis. Volume 2. Theoretical bases. Final report

International Nuclear Information System (INIS)

Hughes, E.D.; Lyczkowski, R.W.; McFadden, J.H.

1976-02-01

A state-of-the-art review was conducted in order to provide the nuclear industry with a publicly available assessment of two velocity thermal-hydraulic models and their applicability to nuclear reactor technology. The two major objectives of this state-of-the-art evaluation were: (1) document the basic theory in a consistent self-contained report; and (2) apply a prototype 'two-velocity' code (UVUT) to a limited number of separate effect tests. The theoretical basis of the two-velocity models given in Volume 2 is divided into three parts; Part I is the derivation of the basic differential equations; Part II describes in detail, the constitutive models required for closure of the system of equations; and Part III presents the numerical solution schemes

Experimental study of single- and two-phase flow fields around PWR steam generator tube support plates

International Nuclear Information System (INIS)

Bates, J.M.; Stewart, C.W.

1979-08-01

Laser-Doppler anemometry (LDA) was used to measure local mean axial velocities and turbulence intnsities at selected locations within a study model dimensionally protypic of an existing PWR steam generator design. The model tube bundle with support plate was installed in a special flow housing that formed part of an isothermal recirculating water flow loop. Flow conditions for this experiment were intended to simulate only typical single-phase flow velocities and were not an attempt to completely model actual steam generator, boiling, two-phase flow conditions. The measurements were performed in water at approximately 85 0 F with test section average velocities of approximately 0.55 and 1.1 fps. These conditions corresponded to Reynolds numbers of approximately 7,000 and approximately 14,000, respectively. Normalized velocity and turbulence intensity ratios are graphically reported. Additional qualitative, photographic investigations of air-water two-phase flows in a PWR steam generator study model were also performed

To the elementary theory of critical (maximum) flow rate of two-phase mixture in channels with various sections

International Nuclear Information System (INIS)

Nigmatulin, B.I.; Soplenkov, K.I.

1978-01-01

On the basis of the concepts of two-phase dispersive flow with various structures (bubble, vapour-drop etc) in the framework of the two-speed and two-temperature one-dimension stationary model of the current with provision for phase transitions the conditions, under which a critical (maximum) flow rate of two-phase mixture is achieved during its outflowing from a channel with the pre-set geometry, have been determined. It is shown, that for the choosen set of two-phase flow equations with the known parameters of deceleration and structure one of the critical conditions is satisfied: either solution of the set of equations corresponding a critical flow rate is a special one, i.e. passes through a special point locating between minimum and outlet channel sections where the carrying phase velocity approaches the value of decelerated sound speed in the mixture or the determinator of the initial set of equations equals zero for the outlet channel sections, i.e. gradients of the main flow parameters tend to +-infinity in this section, and carrying phase velocity also approaches the value of the decelerated sound velocity in the mixture

A fifth equation to model the relative velocity the 3-D thermal-hydraulic code THYC

International Nuclear Information System (INIS)

Jouhanique, T.; Rascle, P.

1995-11-01

E.D.F. has developed, since 1986, a general purpose code named THYC (Thermal HYdraulic Code) designed to study three-dimensional single and two-phase flows in rod tube bundles (pressurised water reactor cores, steam generators, condensers, heat exchangers). In these studies, the relative velocity was calculated by a drift-flux correlation. However, the relative velocity between vapor and liquid is an important parameter for the accuracy of a two-phase flow modelling in a three-dimensional code. The range of application of drift-flux correlations is mainly limited by the characteristic of the flow pattern (counter current flow ...) and by large 3-D effects. The purpose of this paper is to describe a numerical scheme which allows the relative velocity to be computed in a general case. Only the methodology is investigated in this paper which is not a validation work. The interfacial drag force is an important factor of stability and accuracy of the results. This force, closely dependent on the flow pattern, is not entirely established yet, so a range of multiplicator of its expression is used to compare the numerical results with the VATICAN test section measurements. (authors). 13 refs., 6 figs

Simultaneous two-phase flow measurement of spray mixing process by means of high-speed two-color PIV

International Nuclear Information System (INIS)

Zhang, Ming; Xu, Min; Hung, David L S

2014-01-01

In this article, a novel high-speed two-color PIV optical diagnostic technique has been developed and applied to simultaneously measure the velocity flow-fields of a multi-hole spark-ignition direct injection (SIDI) fuel injector spray and its ambient gas in a high-pressure constant volume chamber. To allow for the phase discrimination between the fuel droplets and ambient gas, a special tracer-filter system was designed. Fluorescent seeding particles with Sauter mean diameter (SMD) of 4.8 µm were used to trace the gas inside the chamber. With a single high-speed Nd:YLF laser sheet (527 nm) as the incident light source, the Mie-scattering signal marked the phase of the fuel spray, while the fluorescent signal generated from the seeding particles tracked the phase of ambient gas. A high-speed camera, with an image-doubler (mounted in front of the camera lens) that divided the camera pixels into two parts focusing on the same field of view, was used to collect the Mie-scattering signal and LIF (laser induced fluorescence) signal simultaneously with two carefully selected optical filters. To accommodate the large dynamic range of velocities in the two phases (1–2 orders of magnitude difference), two separation times (dt) were introduced. This technique was successfully applied to the liquid spray and ambient gas two-phase flow measurement. The measurement accuracy was compared with those from LDV (laser Doppler velocimetry) measurement and good agreement was obtained. Ambient gas motion surrounding the fuel spray was investigated and characterized into three zones. The momentum transfer process between the fuel spray and ambient gas in each zone was analyzed. The two-phase flow interaction under various superheated conditions was investigated. A strengthened momentum transfer from the liquid spray to the ambient was observed with increased superheat degree. (paper)

Molten corium concrete interaction: investigation of heat transfer in two-phase flow

International Nuclear Information System (INIS)

Amizic, Milan

2014-01-01

In the context of severe accident research for the second and the third generation of nuclear power plants, there are still open issues concerning some aspects of the concrete cavity ablation during the molten corium - concrete interaction (MCCI). The determination of heat transfer along the interfacial region between the molten corium pool and the ablating basemat concrete is crucial for the assessment of concrete ablation progression and eventually the basemat melt through. For the purpose of experimental investigation of thermal hydraulics inside a liquid pool agitated by gas bubbles, the CLARA project has been launched. The CLARA experiments are performed using simulant materials and they reveal the influence of superficial gas velocity, liquid viscosity and pool geometry on the heat transfer coefficient between the internally heated liquid pool and vertical and horizontal pool walls maintained at uniform temperature. The first test campaign has been conducted with the small pool configuration (50 cm * 25 cm * 25 cm). The tests have been performed with liquids covering a wide range of dynamic viscosity from approximately 1 mPa s to 10000 mPa s and the superficial gas velocity is varied up to 8 cm/s. This thesis comprises a brief description of MCCI phenomenology, literature reviews on the existing heat transfer correlations for two phase flow and the void fraction, a description of CLARA setup, experimental results and their interpretation. The experimental results are compared with existing models and some new models for the assessment of heat transfer coefficient in two-phase flow. (author) [fr

Interaction between local parameters of two-phase flow and random forces on a cylinder

International Nuclear Information System (INIS)

Sylviane Pascal-Ribot; Yves Blanchet; Franck Baj; Phillippe Piteau

2005-01-01

Full text of publication follows: In the frame of assessments of steam generator tube bundle vibrations, a study was conducted in order to investigate the effects of an air/water flow on turbulent buffeting forces induced on a cylinder. The main purpose is to relate the physical parameters characterizing an air/water two-phase crossflow with the structural loading of a fixed cylindrical tube. In this first approach, the experiments are carried out in a rectangular acrylic test section supplied with a vertical upward bubbly flow. This flow is transversally impeded by a fixed rigid 12,15 mm diameter cylinder. Different turbulence grids are used in order to modify two-phase characteristics such as bubble diameter, void fraction profile, fluctuation parameters. Preliminarily, a dimensional analysis of fluid-structure interaction under two-phase turbulent solicitations has enabled to identify a list of physically relevant variables which must be measured to evaluate the random forces. The meaning of these relevant parameters as well as the effect of flow patterns are discussed. Direct measurements of two-phase flow parameters are performed simultaneously with measurements of forces exerted on the cylinder. The main descriptive parameters of a two-phase flow are measured using a bi-optical probe, in particular void fraction profiles, interfacial velocities, bubble diameters, void fraction fluctuations. In the same time, the magnitude of random forces caused by two-phase flow is measured with a force transducer. A thorough analysis of the experimental data is then undertaken in order to correlate physical two-phase mechanisms with the random forces exerted on the cylinder. The hypotheses made while applying the dimensional analysis are verified and their pertinence is discussed. Finally, physical parameters involved in random buffeting forces applied on a transverse tube are proposed to scale the spectral magnitude of these forces and comparisons with other authors

Experimental study of flow monitoring instruments in air-water, two-phase downflow

International Nuclear Information System (INIS)

Sheppard, J.D.; Hayes, P.H.; Wynn, M.C.

1976-01-01

The performance of a turbine meter, target flow meter (drag disk), and a gamma densitometer was studied in air-water, two-phase vertical downflow. Air and water were metered into an 0.0889-m-ID (3.5-in.) piping system; air flows ranged from 0.007 to 0.3 m 3 /sec (16 to 500 scfm) and water flows ranged from 0.0006 to 0.03 m 3 /sec (10 to 500 gpm). The study included effects of flow rate, quality, flow regime, and flow dispersion on the mean and fluctuating components of the instrument signals. Wire screen flow dispersers located at the inlet to the test section had a significant effect on the readings of the drag disk and gamma densitometer, but had little effect on the turbine. Further, when flow dispersers were used, mass flow rates determined from the three instrument readings and a two-velocity, slip flow model showed good agreement with actual mass flow rate over a three-fold range in quality; mass flows determined with the drag disk and densitometer readings assuming homogeneous flow were nearly as accurate. However, when mass flows were calculated using the turbine and densitometer or turbine and drag disk readings assuming homogeneous flow, results were scattered and relatively inaccurate compared to the actual mass flows. Turbine meter data were used with a two-velocity turbine model and continuity relationships for each phase to determine the void fraction and mean phase velocities in the test section. The void fraction was compared with single beam gamma densitometer results and fluid momentum calculated from a two-velocity model was compared with drag disk readings

Eulerian-Eulerian two-phase numerical simulation of nanofluid laminar forced convection in a microchannel

International Nuclear Information System (INIS)

Kalteh, Mohammad; Abbassi, Abbas; Saffar-Avval, Majid; Harting, Jens

2011-01-01

In this paper, laminar forced convection heat transfer of a copper-water nanofluid inside an isothermally heated microchannel is studied numerically. An Eulerian two-fluid model is considered to simulate the nanofluid flow inside the microchannel and the governing mass, momentum and energy equations for both phases are solved using the finite volume method. For the first time, the detailed study of the relative velocity and temperature of the phases are presented and it has been observed that the relative velocity and temperature between the phases is very small and negligible and the nanoparticle concentration distribution is uniform. However, the two-phase modeling results show higher heat transfer enhancement in comparison to the homogeneous single-phase model. Also, the heat transfer enhancement increases with increase in Reynolds number and nanoparticle volume concentration as well as with decrease in the nanoparticle diameter, while the pressure drop increases only slightly.

Structure of the gas-liquid annular two-phase flow in a nozzle section

International Nuclear Information System (INIS)

Yoshida, Kenji; Kataoka, Isao; Ohmori, Syuichi; Mori, Michitsugu

2006-01-01

Experimental studies on the flow behavior of gas-liquid annular two-phase flow passing through a nozzle section were carried out. This study is concerned with the central steam jet injector for a next generation nuclear reactor. In the central steam jet injector, steam/water annular two-phase flow is formed at the mixing nozzle. To make an appropriate design and to establish the high-performance steam injector system, it is very important to accumulate the fundamental data of the thermo-hydro dynamic characteristics of annular flow passing through a nozzle section. On the other hand, the transient behavior of multiphase flow, in which the interactions between two-phases occur, is one of the most interesting scientific issues and has attracted research attention. In this study, the transient gas-phase turbulence modification in annular flow due to the gas-liquid phase interaction is experimentally investigated. The annular flow passing through a throat section is under the transient state due to the changing cross sectional area of the channel and resultantly the superficial velocities of both phases are changed compared with a fully developed flow in a straight pipe. The measurements for the gas-phase turbulence were precisely performed by using a constant temperature hot-wire anemometer, and made clear the turbulence structure such as velocity profiles, fluctuation velocity profiles. The behavior of the interfacial waves in the liquid film flow such as the ripple or disturbance waves was also observed. The measurements for the liquid film thickness by the electrode needle method were also performed to measure the base film thickness, mean film thickness, maximum film thickness and wave height of the ripple or the disturbance waves. (author)

Numerical study for two phase flow in the near nozzle region of turbine combustors

International Nuclear Information System (INIS)

Pervez, K.; Mushtaq, S.

1999-01-01

In the present study flow conditions in the near nozzle region of the combustion chamber have been investigated. There exists two-phase flow in this region. The overall performance and pollutant formation in the combustion chamber have been investigated. There exists two-phase flow in this region. The overall performance and pollutant formation in the combustion zone largely depends on the spray field in the near nozzle region the studies are conducted to determined the effects of multi jets on the flow pattern in the near nozzle region The phase doppler particle analyzer (PDPA) has been used to measure the velocities and sizes of the droplets. The flow field of two-phase liquid drop-air jets is formed from three injectors arranged in t line. Furthermore the two-phase flow field has been analyzed numerically also. The numerical analysis consists of two computational models, namely (i) 3 non-evaporating two-phase jets, (II) 3 evaporating two phase jets. The Eulerian-Eulerian approach in incorporated in both the numerical models. Since the flow is turbulent, a two-equation model (k-Epsilon) is implemented in the numerical analysis. Numerical solution of the conservation equation is obtained using PHOENICS computer code. Boundary conditions are provided from the experimental measurements. Numerical domain for the two models of the analysis starts at some distance (about 10 diameters of the injector orifice) where the atomization process is complete and droplet size and velocity could be measured experimentally. (author)

Heat transfer and friction correlations required to describe steam--water behavior in nuclear safety studies

International Nuclear Information System (INIS)

Solbrig, C.W.; McFadden, J.H.; Lyczkowski, R.W.; Hughes, E.D.

1975-01-01

The description of two-phase flow is important in nuclear safety studies. Recent two-phase flow descriptions are based upon unequal phase velocities and unequal phase temperatures (UVUT) theories with interphase interaction terms. These theories are more mechanistic than homogeneous theories and require more and different types of correlations than homogeneous theories. The UVUT theories require correlations (or models) which describe wall and interphase mass transfer, friction, momentum transfer, and heat transfer for all flow regimes and heat transfer regimes. A set of correlations is presented in this paper which can be used with UVUT theories. These correlations cover the complete range of parameters needed and in all cases are expected to yield reasonable numbers. (U.S.)

Void fraction fluctuations in two-phase gas-liquid flow

International Nuclear Information System (INIS)

Ulbrich, R.

1987-01-01

Designs of the apparatus in which two-phase gas-liquid flow occurs are usually based on the mean value of parameters such as pressure drop and void fraction. The flow of two-phase mixtures generally presents a very complicated flow structure, both in terms of the unsteady formation on the interfacial area and in terms of the fluctuations of the velocity, pressure and other variables within the flow. When the gas void fraction is near 0 or 1 / bubble or dispersed flow regimes / then oscillations of void fraction are very small. The intermittent flow such as plug and slug/ froth is characterized by alternately flow portions of liquid and gas. It influences the change of void fractions in time. The results of experimental research of gas void fraction fluctuations in two-phase adiabatic gas-liquid flow in a vertical pipe are presented

Two-phase flow phenomena in broken recirculation line of BWR

International Nuclear Information System (INIS)

Kato, Masami; Arai, Kenji; Narabayashi, Tadashi; Amano, Osamu.

1986-01-01

When a primary recirculation line of BWR is ruptured, a primary recirculation pump may be subjected to very high velocity two-phase flow and its speed may be accelerated by this flow. It is important for safety evaluation to estimate the pump behavior during blowdown. There are two problems involved in analyzing this behavior. One problem concerns the pump characteristics under two-phase flow. The other involves the two-phase conditions at the pump inlet. If the rupture occurs at a suction side of the pump, choking is considered to occur at a broken jet pump nozzle. Then, a void fraction becomes larger downstream from the jet pump nozzle and volumetric flow through the pump will be very high. However, there is little experimental data available on two-phase flow downstream from a choking plane. Blowdown tests were performed using a simulated broken recirculation line and measured data were analyzed by TRAC-PlA. Analytical results agreed with measured data. (author)

3D Vector Velocity Estimation using a 2D Phased Array

DEFF Research Database (Denmark)

Pihl, Michael Johannes; Jensen, Jørgen Arendt

2011-01-01

of using the TO method for estimation 3D velocity vectors, and the proposed decoupling is demonstrated. A 64x64 and a 32x32 elements transducer are emulated using Field II. Plug flow with a speed of 1 m/s in a small region is rotated in the XY -plane. A binary flow example with [vx,vy]=[1,0] and [0,1] m......A method to estimate the three dimensional (3D) velocity vector is presented is this paper. 3D velocity vector techniques are needed to measure the full velocity and characterize the complicated flow patterns in the human body. The Transverse Oscillation (TO) method introduces oscillations...... matrix transducer. For the 32x32 transducer, the mean and standard deviation for the speed are 0.94 0.11 m/s and for the angle bias -0.487.7. The simulation study clearly demonstrates, that the new method can be used to estimate the 3D velocity vector using a 2D phased matrix array, and that the velocity...

The role of ECoG magnitude and phase in decoding position, velocity and acceleration during continuous motor behavior

Directory of Open Access Journals (Sweden)

Jiri eHammer

2013-11-01

Full Text Available In neuronal population signals, including the electroencephalogram (EEG and electrocorticogram (ECoG, the low-frequency component (LFC is particularly informative about motor behavior and can be used for decoding movement parameters for brain-machine interface (BMI applications. An idea previously expressed, but as of yet not quantitatively tested, is that it is the LFC phase that is the main source of decodable information. To test this issue, we analyzed human ECoG recorded during a game-like, one-dimensional, continuous motor task with a novel decoding method suitable for unfolding magnitude and phase explicitly into a complex-valued, time-frequency signal representation, enabling quantification of the decodable information within the temporal, spatial and frequency domains and allowing disambiguation of the phase contribution from that of the spectral magnitude. The decoding accuracy based only on phase information was substantially (at least 2 fold and significantly higher than that based only on magnitudes for position, velocity and acceleration. The frequency profile of movement-related information in the ECoG data matched well with the frequency profile expected when assuming a close time-domain correlate of movement velocity in the ECoG, e.g., a (noisy copy of hand velocity. No such match was observed with the frequency profiles expected when assuming a copy of either hand position or acceleration. There was also no indication of additional magnitude-based mechanisms encoding movement information in the LFC range. Thus, our study contributes to elucidating the nature of the informative low-frequency component of motor cortical population activity and may hence contribute to improve decoding strategies and BMI performance.

Pulmonary branch arterial flow can be measured with cine MR velocity mapping

International Nuclear Information System (INIS)

Caputo, G.R.; Kondo, C.; Masui, T.; Foster, E.; Geraci, S.J.; O'Sullivan, M.; Higgins, C.B.

1990-01-01

This paper assesses the capability of cine MR phase velocity mapping (CVM) to measure main, right-sided, and left-sided pulmonary arterial (PA) blood flow. The authors examined a constant-flow phantom and nine healthy volunteers with use of 1.5-T MR imaging system (GE Signa) with phase velocity cine sequences. CVM correctly measured constant-flow phantom velocities (range, 20-190 cm/sec; r = .998, SEE = 4.2 cm/sec), and velocity with use of angulated planes to section the phantom tube perpendicularly. CVM peak systolic main PA velocity (79 cm/sec ± 10) correlated well with Doppler US measurements (80 cm/sec ± 7). CVM main PA flow correlated well with conventional cine MR LV stroke volume measurements (r = .98, SEE = 4.8 mL). Left and right PA flow on the angulated planes were 29 mL ± 7 and 34 mL ± 10, respectively

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)

Spectral calculations for pressure-velocity and pressure-strain correlations in homogeneous shear turbulence

Science.gov (United States)

Dutta, Kishore

2018-02-01

Theoretical analyses of pressure related turbulent statistics are vital for a reliable and accurate modeling of turbulence. In the inertial subrange of turbulent shear flow, pressure-velocity and pressure-strain correlations are affected by anisotropy imposed at large scales. Recently, Tsuji and Kaneda (2012 J. Fluid Mech. 694 50) performed a set of experiments on homogeneous shear flow, and estimated various one-dimensional pressure related spectra and the associated non-dimensional universal numbers. Here, starting from the governing Navier-Stokes dynamics for the fluctuating velocity field and assuming the anisotropy at inertial scales as a weak perturbation of an otherwise isotropic dynamics, we analytically derive the form of the pressure-velocity and pressure-strain correlations. The associated universal numbers are calculated using the well-known renormalization-group results, and are compared with the experimental estimates of Tsuji and Kaneda. Approximations involved in the perturbative calculations are discussed.

Two-level image authentication by two-step phase-shifting interferometry and compressive sensing

Science.gov (United States)

Zhang, Xue; Meng, Xiangfeng; Yin, Yongkai; Yang, Xiulun; Wang, Yurong; Li, Xianye; Peng, Xiang; He, Wenqi; Dong, Guoyan; Chen, Hongyi

2018-01-01

A two-level image authentication method is proposed; the method is based on two-step phase-shifting interferometry, double random phase encoding, and compressive sensing (CS) theory, by which the certification image can be encoded into two interferograms. Through discrete wavelet transform (DWT), sparseness processing, Arnold transform, and data compression, two compressed signals can be generated and delivered to two different participants of the authentication system. Only the participant who possesses the first compressed signal attempts to pass the low-level authentication. The application of Orthogonal Match Pursuit CS algorithm reconstruction, inverse Arnold transform, inverse DWT, two-step phase-shifting wavefront reconstruction, and inverse Fresnel transform can result in the output of a remarkable peak in the central location of the nonlinear correlation coefficient distributions of the recovered image and the standard certification image. Then, the other participant, who possesses the second compressed signal, is authorized to carry out the high-level authentication. Therefore, both compressed signals are collected to reconstruct the original meaningful certification image with a high correlation coefficient. Theoretical analysis and numerical simulations verify the feasibility of the proposed method.

Structure of two-phase adiabatic flow in air sparging regime in vertical cylindrical channel with water

Directory of Open Access Journals (Sweden)

V. I. Solonin

2014-01-01

Full Text Available The article presents a research of two-phase adiabatic flow in air sparging regime in vertical cylindrical channel filled with water. A purpose of the work is to obtain experimental data for further analysis of a character of the moving phases. Research activities used the optic methods PIV (Particle Image Visualization because of their noninvasiveness to obtain data without disturbing effect on the flow. A laser sheet illuminated the fluorescence particles, which were admixed in water along the channel length. A digital camera recorded their motion for a certain time interval that allowed building the velocity vector fields. As a result, gas phase velocity components typical for a steady area of the channel and their relations for various intensity of volume air rate were obtained. A character of motion both for an air bubble and for its surrounding liquid has been conducted. The most probable direction of phases moving in the channel under sparging regime is obtained by building the statistic scalar fields. The use of image processing enabled an analysis of the initial area of the air inlet into liquid. A characteristic curve of the bubbles offset from the axis for various intensity of volume gas rate and channel diameter is defined. A character of moving phases is obtained by building the statistic scalar fields. The values of vertical components of liquid velocity in the inlet part of channel are calculated. Using the obtained data of the gas phase velocities a true void fraction was calculated. It was compared with the values of void fraction, calculated according to the liquid level change in the channel. Obtained velocities were compared with those of the other researchers, and a small difference in their values was explained by experimental conditions. The article is one of the works to research the two-phase flows with no disturbing effect on them. Obtained data allow us to understand a character of moving the two-phase flows in

Research on boiling and two-phase flow

International Nuclear Information System (INIS)

Marinsek, Z.; Gaspersic, B.; Pavselj, D.; Tomsic, M.

1977-01-01

Report consists of three contributions. Experimental apparatus with pressure chamber (up to 25 bar and 250 deg C) was constructed including optical bubble detection device, and test measurements of mutual influence of boiling bubbles from two adjacent nucleation sites were performed; for analyses, a computer programme package for coincidence analyses of events was made, including data acquisition hardware. Two-phase pressure drop in subcooled Vertical annular water flow was measured, for pressures up to 10 bar, mass velocity 500 to 760 kg/m 2 s and vapour quality 0 to .01. Results agree fairly well with Martinelli-Nelson model

Propagation of small disturbances in two phases, one component flow (1963); Propagation de petites perturbations dans un ecoulement double phase a un seul constituant (1963)

Energy Technology Data Exchange (ETDEWEB)

Boure, J [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1963-07-01

A small disturbance is, shown to give rise to two waves: a pressure (sonic) wave and a continuity wave. Their propagation velocities are calculated. These velocities are independent of the disturbance amplitude. The sonic velocity is primarily a function of that one corresponding to the same medium with no flow and of the liquid phase velocity. It is also a function of the physical properties of the phases on the saturation line, of the slip laws and of the void fraction. The continuity wave velocity is only a function of the slip laws, of the void fraction and of the velocity of either phase. It appears two kinds of critical flow rates which are calculated. The void fraction and the liquid and gas velocities variations are calculated. These results are extended to the case of a real loop and an approximative method is given for the treatment of this case. (author) [French] On montre qu'une petite perturbation donne naissance a deux ondes: une onde de pression (onde sonique) et une onde de continuite. On calcule leurs vitesses de propagation qui sont independantes de l'amplitude de la perturbation. La vitesse du son depend des proprietes physiques des phases le long de la courbe de saturation, des lois du glissement, de la fraction volumique de vapeur. Elle depend surtout de la vitesse qu'il aurait dans le milieu immobile de meme fraction volumique de vapeur, et de la vitesse de la phase liquide. La vitesse de l'onde de continuite depend des lois du glissement, de la fraction volumique de vapeur et de la vitesse d'une des phases. Il apparait deux types de debits critiques que l'on calcule. On calcule egalement les variations de la fraction volumique de vapeur et des vitesses des phases dans la perturbation. On generalise des resultats precedents dans le cas d'un circuit reel et on propose une methode approchee pour traiter le probleme dans ce cas. (auteur)

Low-pressure dynamics of a natural-circulation two-phase flow loop

International Nuclear Information System (INIS)

Manera, A.; Kruijf, W.J.M. de; Hartmann, H.; Mudde, R.F.; Hagen, T.H.J.J. van der

2001-01-01

Flashing induced oscillations in a natural circulation loop are studied as function of heating power and inlet subcooling in symmetrical and asymmetrical power conditions. To unveil the effects of power/velocity asymmetries on the two-phase flow stability at low power and low pressure conditions different signals at several locations in the loop are recorded. In particular a Laser Doppler Anemometry set-up is used to measure the velocity simultaneously in two parallel channels and a wire-mesh sensor is used to measure the 2D void fraction distribution in a section of the ascendant part of the loop. (orig.)

Coherent control of the group velocity in a dielectric slab doped with duplicated two-level atoms

Science.gov (United States)

Ziauddin; Chuang, You-Lin; Lee, Ray-Kuang; Qamar, Sajid

2016-01-01

Coherent control of reflected and transmitted pulses is investigated theoretically through a slab doped with atoms in a duplicated two-level configuration. When a strong control field and a relatively weak probe field are employed, coherent control of the group velocity is achieved via changing the phase shift ϕ between control and probe fields. Furthermore, the peak values in the delay time of the reflected and transmitted pulses are also studied by varying the phase shift ϕ.

Analytical solution of laminar-laminar stratified two-phase flows with curved interfaces

International Nuclear Information System (INIS)

Brauner, N.; Rovinsky, J.; Maron, D.M.

1995-01-01

The present study represents a complete analytical solution for laminar two-phase flows with curved interfaces. The solution of the Navier-Stokes equations for the two-phases in bipolar coordinates provides the 'flow monograms' describe the relation between the interface curvature and the insitu flow geometry when given the phases flow rates and viscosity ratios. Energy considerations are employed to construct the 'interface monograms', whereby the characteristic interfacial curvature is determined in terms of the phases insitu holdup, pipe diameter, surface tension, fluids/wall adhesion and gravitation. The two monograms are then combined to construct the system 'operational monogram'. The 'operational monogram' enables the determination of the interface configuration, the local flow characteristics, such as velocity profiles, wall and interfacial shear stresses distribution as well as the integral characteristics of the two-phase flow: phases insitu holdup and pressure drop

Analytical solution of laminar-laminar stratified two-phase flows with curved interfaces

Energy Technology Data Exchange (ETDEWEB)

Brauner, N.; Rovinsky, J.; Maron, D.M. [Tel-Aviv Univ. (Israel)

1995-09-01

The present study represents a complete analytical solution for laminar two-phase flows with curved interfaces. The solution of the Navier-Stokes equations for the two-phases in bipolar coordinates provides the `flow monograms` describe the relation between the interface curvature and the insitu flow geometry when given the phases flow rates and viscosity ratios. Energy considerations are employed to construct the `interface monograms`, whereby the characteristic interfacial curvature is determined in terms of the phases insitu holdup, pipe diameter, surface tension, fluids/wall adhesion and gravitation. The two monograms are then combined to construct the system `operational monogram`. The `operational monogram` enables the determination of the interface configuration, the local flow characteristics, such as velocity profiles, wall and interfacial shear stresses distribution as well as the integral characteristics of the two-phase flow: phases insitu holdup and pressure drop.

Measurements and correlations of turbulent burning velocities over wide ranges of fuels and elevated pressures

KAUST Repository

Bradley, Derek; Lawes, Malcolm; Liu, Kexin; Mansour, Morkous S.

2013-01-01

The implosion technique has been used to extend measurements of turbulent burning velocities over greater ranges of fuels and pressures. Measurements have been made up to 3.5 MPa and at strain rate Markstein numbers as low as 23. The implosion technique, with spark ignition at two opposite wall positions within a fan-stirred spherical bomb is capable of measuring turbulent burning velocities, at higher pressures than is possible with central ignition. Pressure records and schlieren high speed photography define the rate of burning and the smoothed area of the flame front. The first aim of the study was to extend the previous measurements with ethanol and propane-air, with further measurements over wider ranges of fuels and equivalence ratios with mixtures of hydrogen, methane, 10% hydrogen-90% methane, toluene, and i-octane, with air. The second aim was to study further the low turbulence regime in which turbulent burning co-exists with laminar flame instabilities. Correlations are presented of turbulent burning velocity normalised by the effective rms turbulent velocity acting on the flame front, ut=u0k , with the Karlovitz stretch factor, K, for different strain rate Markstein numbers, a decrease in which increases ut=u0k . Experimental correlations are presented for the present measurements, combined with previous ones. Different burning regimes are also identified, extending from that of mixed turbulence/laminar instability at low values of K to that at high values of K, in which ut=u0k is gradually reduced due to increasing localised flame extinctions. © 2012 The Combustion Institute.

Experimental Study about Two-phase Damping Ratio on a Tube Bundle Subjected to Homogeneous Two-phase Flow

Energy Technology Data Exchange (ETDEWEB)

Sim, Woo Gun; Dagdan, Banzragch [Hannam Univ., Daejeon (Korea, Republic of)

2017-03-15

Two-phase cross flow exists in many shell-and-tube heat exchangers such as condensers, evaporators, and nuclear steam generators. The drag force acting on a tube bundle subjected to air/water flow is evaluated experimentally. The cylinders subjected to two-phase flow are arranged in a normal square array. The ratio of pitch to diameter is 1.35, and the diameter of the cylinder is 18 mm. The drag force along the flow direction on the tube bundles is measured to calculate the drag coefficient and the two-phase damping ratio. The two-phase damping ratios, given by the analytical model for a homogeneous two-phase flow, are compared with experimental results. The correlation factor between the frictional pressure drop and the hydraulic drag coefficient is determined from the experimental results. The factor is used to calculate the drag force analytically. It is found that with an increase in the mass flux, the drag force, and the drag coefficients are close to the results given by the homogeneous model. The result shows that the damping ratio can be calculated using the homogeneous model for bubbly flow of sufficiently large mass flux.

Vector velocity estimation using directional beam forming and cross-correlation

DEFF Research Database (Denmark)

2000-01-01

The two-dimensional velocity vector using a pulsed ultrasound field can be determined with the invention. The method uses a focused ultrasound field along the velocity direction for probing the moving medium under investigation. Several pulses are emitted and the focused received fields along...

Characterization of topological phases of dimerized Kitaev chain via edge correlation functions

Science.gov (United States)

Wang, Yucheng; Miao, Jian-Jian; Jin, Hui-Ke; Chen, Shu

2017-11-01

We study analytically topological properties of a noninteracting modified dimerized Kitaev chain and an exactly solvable interacting dimerized Kitaev chain under open boundary conditions by analyzing two introduced edge correlation functions. The interacting dimerized Kitaev chain at the symmetry point Δ =t and the chemical potential μ =0 can be exactly solved by applying two Jordan-Wigner transformations and a spin rotation, which permits us to calculate the edge correlation functions analytically. We demonstrate that the two edge correlation functions can be used to characterize the trivial, Su-Schrieffer-Heeger-like topological and topological superconductor phases of both the noninteracting and interacting systems and give their phase diagrams.

Well-posed Euler model of shock-induced two-phase flow in bubbly liquid

Science.gov (United States)

Tukhvatullina, R. R.; Frolov, S. M.

2018-03-01

A well-posed mathematical model of non-isothermal two-phase two-velocity flow of bubbly liquid is proposed. The model is based on the two-phase Euler equations with the introduction of an additional pressure at the gas bubble surface, which ensures the well-posedness of the Cauchy problem for a system of governing equations with homogeneous initial conditions, and the Rayleigh-Plesset equation for radial pulsations of gas bubbles. The applicability conditions of the model are formulated. The model is validated by comparing one-dimensional calculations of shock wave propagation in liquids with gas bubbles with a gas volume fraction of 0.005-0.3 with experimental data. The model is shown to provide satisfactory results for the shock propagation velocity, pressure profiles, and the shock-induced motion of the bubbly liquid column.

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.)

An evaluation of state-of-the-art two-velocity two-phase flow models and their applicability to nuclear reactor transient analysis. Volume 3. Data comparisons. Final report

International Nuclear Information System (INIS)

McFadden, J.H.; Lyczkowski, R.W.; Niederauer, G.F.

1976-02-01

A state-of-the-art review is conducted in order to provide the nuclear industry with a publicly available assessment of two-velocity thermal-hydraulic models and their applicability to nuclear reactor technology. The two major objectives of this state-of-the-art evaluation were: (1) document the basic theory in a consistent self-contained report; and (2) apply a prototype 'two-velocity' code (UVUT) to a limited number of separate effect tests. Volume 3 presents the data comparisons

Experimental study of natural two-phase flow circulation using a visualization technique

International Nuclear Information System (INIS)

Vinhas, Pedro A.M.; Su, Jian

2013-01-01

This paper presents an experimental study of natural two-phase flow in a circuit that simulates, on a smaller scale, a typical residual heat removal system of passive reactors APWR (Advanced Pressurized Water Reactor). The circuit was formed by a heater, a heat exchanger and piping. The experimental study was the application of a visualization technique, using a high speed camera, for measuring the size and speed of vapor bubbles generated in the heater with different power heating. The camera was positioned in the central region of the pipe connecting the heater to the heat exchanger, where there is a clear passage. The flow of images were processed and analyzed using commercial software that allowed the determination of the length and velocity of the bubbles. The results were then compared with correlations available in literature

Axial dispersion, holdup and slip velocity of dispersed phase in a pulsed sieve plate extraction column by radiotracer residence time distribution analysis.

Science.gov (United States)

Din, Ghiyas Ud; Chughtai, Imran Rafiq; Inayat, Mansoor Hameed; Khan, Iqbal Hussain

2008-12-01

Axial dispersion, holdup and slip velocity of dispersed phase have been investigated for a range of dispersed and continuous phase superficial velocities in a pulsed sieve plate extraction column using radiotracer residence time distribution (RTD) analysis. Axial dispersion model (ADM) was used to simulate the hydrodynamics of the system. It has been observed that increase in dispersed phase superficial velocity results in a decrease in its axial dispersion and increase in its slip velocity while its holdup increases till a maximum asymptotic value is achieved. An increase in superficial velocity of continuous phase increases the axial dispersion and holdup of dispersed phase until a maximum value is obtained, while slip velocity of dispersed phase is found to decrease in the beginning and then it increases with increase in superficial velocity of continuous phase.

The Condensation effect on the two-phase flow stability

International Nuclear Information System (INIS)

Abdou Mohamed, Hesham Nagah

2005-01-01

A one-dimensional analytical model has been developed to be used for the linear analysis of density-wave oscillations in a parallel heated channel and a natural circulation loop.The heater and the riser sections are divided into a single-phase and a two-phase region.The two-phase region is represented by the drift-flux model. The model accounts for aphasic slip and subcooled boiling.The localized friction at the heater and the riser exit is treated considering the two-phase mixture.Also the effects of the condensation in the riser and the change in the system pressure have been studied.The exact equation for the heated channel and the total loop pressure drop is perturbed around the steady state.he stability characteristics of the heated channel and the loop are investigated using the Root finding method criterion.The results are summarized on instability maps in the plane of subcooled boiling number vs. phase change number (i.e., inlet subcooling vs. heater heat flux).The predictions of the model are compared with experimental results published in open literature. The results show that, the treatment effect of localized friction in two-phase mixtures stabilizes the system and improves the agreement of the calculations with the experimental results.For a parallel heated channel, the results indicate a more stable system with high inlet restriction, low outlet restriction, and high inlet velocity. And for a natural circulation loop, an increase in the inlet restriction broadened the range of the continuous circulation mode and stabilized the system, a decrease in the exit restriction or the liquid charging level shifted to the right the range of the continuous circulation mode and stabilized the system and an increase in the riser condensation shifted to the right the range of the continuous circulation mode and stabilized the system.The results show that the model agrees well with the available experimental data. In particular, the results show the significance of

PIV in the two phases of hydrodynamic cavitation in a venturi type section

Science.gov (United States)

Fuzier, Sylvie; Coudert, Sébastien; Coutier Delgosha, Olivier

2012-11-01

The presence of cavitation can affect the performance of turbomachinery. Attached sheet cavities on the blades induce modifications of flow dynamics and turbulence properties. This phenomenon is studied here in a configuration of 2D flow in a venturi type section. Images of the bubbles as well as of the light emitted by fluorescent particles placed in the liquid are recorded simultaneously. Velocities of the bubbles and of the liquid phase are obtained by PIV. The slip velocity is analyzed function of the number of cavitation and other physical parameters. Different levels of turbulence are correlated with different bubble structures in the dipahasic cavity.

Spreading of correlations in the Falicov-Kimball model

Science.gov (United States)

Herrmann, Andreas J.; Antipov, Andrey E.; Werner, Philipp

2018-04-01

We study dynamical properties of the one- and two-dimensional Falicov-Kimball model using lattice Monte Carlo simulations. In particular, we calculate the spreading of charge correlations in the equilibrium model and after an interaction quench. The results show a reduction of the light-cone velocity with interaction strength at low temperature, while the phase velocity increases. At higher temperature, the initial spreading is determined by the Fermi velocity of the noninteracting system and the maximum range of the correlations decreases with increasing interaction strength. Charge order correlations in the disorder potential enhance the range of the correlations. We also use the numerically exact lattice Monte Carlo results to benchmark the accuracy of equilibrium and nonequilibrium dynamical cluster approximation calculations. It is shown that the bias introduced by the mapping to a periodized cluster is substantial, and that from a numerical point of view, it is more efficient to simulate the lattice model directly.

Unsteady flow of two-phase fluid in circular pipes under applied external magnetic and electrical fields

International Nuclear Information System (INIS)

Gedik, Engin; Recebli, Ziyaddin; Kurt, Hueseyin; Kecebas, Ali

2012-01-01

The unsteady viscous incompressible and electrically conducting of two-phase fluid flow in circular pipes with external magnetic and electrical field is considered in this present study. Effects of both uniform transverse external magnetic and electrical fields applied perpendicular to the fluid and each other on the two-phase (solid/liquid) unsteady flow is investigated numerically. While iron powders are being used as the first phase of two-phase fluid, pure water was used as the second phase. The system of the derived governing equations, which are based on the Navier-Stokes equations including Maxwell equations, are solved numerically by using Pdex4 function on the Matlab for both phases. The originality of this study is that, in addition to magnetic field, the effect of electrical field on two-phase unsteady fluids is being examined. The magnetic field which is applied on flow decreases the velocity of both phases, whereas the electrical field applied along with magnetic field acted to increase and decrease the velocity values depending on the direction of electrical field. Electrical field alone did not display any impact on two-phase flow. On the other hand, analytical and numerical results are compared and favorable agreements have been obtained. (authors)

Numerical predictions of bubbly two-phase flows with OpenFOAM

International Nuclear Information System (INIS)

Michta, E.; Fu, K.; Anglart, H.; Angele, K.

2011-01-01

A new model for simulation of bubbly two-phase flows has been developed and implemented into an open-source Computational Fluid Dynamics (CFD) code OpenFOAM. The model employs the two-fluid framework with closure relationships for the interfacial momentum transfer. The bubble size is calculated based on the solution of the interfacial area concentration equations. The predictions are validated against a wide range of experimental data containing measured void fraction, the phasic velocity and the interfacial area concentration. The new model demonstrates the ability to capture the wall peaking of void fraction for small bubbles. The predicted levels of void fraction and phasic velocities are in good agreement with measured data. (author)

Detection of various phases in liquids from the hypersound velocity and damping near closed phase-separation regions of solutions

International Nuclear Information System (INIS)

Kovalenko, K. V.; Krivokhizha, S. V.; Chaban, I. A.; Chaikov, L. L.

2008-01-01

Theoretical analysis revealed that experimental results obtained in our studies on hypersound propagation in a guaiacol-glycerol solution in the vicinity of the closed phase-separation region, double critical point, and special point, as well as the origin of these regions, can be explained by the presence of two different phases (I and II) of the solution with phase-transition temperature T 0 . Temperature T 0 coincides with the temperature at the center of closed phase-separation regions, as well as with the double critical point and with the special point. In (Frenkel) phase I, molecules are in potential wells whose depth exceeds the thermal energy of a molecule, while thermal energy in (gaslike) phase II is higher than the potential well depth. At the lower critical point, the thermodynamic potential of phase I is equal to the thermodynamic potential of the phase-separated solution. At the upper critical point, the thermodynamic potential of phase II is equal to the thermodynamic potential of the phase-separated solution. The observed broad dome of the hypersound absorption coefficient near T 0 can be explained by the contribution associated with fluctuations of the order parameter corresponding to the transition from phase I to phase II. The difference in the temperature coefficients of hypersound velocity on different sides of T 0 and some other effects are also explained

Synchronized Anti-Phase and In-Phase Oscillations of Intracellular Calcium Ions in Two Coupled Hepatocytes System

International Nuclear Information System (INIS)

Chuan-Sheng, Shen; Han-Shuang, Chen; Ji-Qian, Zhang

2008-01-01

We study the dynamic behaviour of two intracellular calcium oscillators that are coupled through gap junctions both to Ca 2+ and inositol(1,4,5)-trisphosphate (IP 3 ). It is found that synchronized anti-phase and in-phase oscillations of cytoplasmic calcium coexist in parameters space. Especially, synchronized anti-phase oscillations only occur near the onset of a Hopf bifurcation point when the velocity of IP 3 synthesis is increased. In addition, two kinds of coupling effects, i.e., the diffusions of Ca 2+ and IP 3 among cells on synchronous behaviour, are considered. We find that small coupling of Ca 2+ and large coupling of IP 3 facilitate the emergence of synchronized anti-phase oscillations. However, the result is contrary for the synchronized in-phase case. Our findings may provide a qualitative understanding about the mechanism of synchronous behaviour of intercellular calcium signalling

Generation of net sediment transport by velocity skewness in oscillatory sheet flow

Science.gov (United States)

Chen, Xin; Li, Yong; Chen, Genfa; Wang, Fujun; Tang, Xuelin

2018-01-01

This study utilizes a qualitative approach and a two-phase numerical model to investigate net sediment transport caused by velocity skewness beneath oscillatory sheet flow and current. The qualitative approach is derived based on the pseudo-laminar approximation of boundary layer velocity and exponential approximation of concentration. The two-phase model can obtain well the instantaneous erosion depth, sediment flux, boundary layer thickness, and sediment transport rate. It can especially illustrate the difference between positive and negative flow stages caused by velocity skewness, which is considerably important in determining the net boundary layer flow and sediment transport direction. The two-phase model also explains the effect of sediment diameter and phase-lag to sediment transport by comparing the instantaneous-type formulas to better illustrate velocity skewness effect. In previous studies about sheet flow transport in pure velocity-skewed flows, net sediment transport is only attributed to the phase-lag effect. In the present study with the qualitative approach and two-phase model, phase-lag effect is shown important but not sufficient for the net sediment transport beneath pure velocity-skewed flow and current, while the asymmetric wave boundary layer development between positive and negative flow stages also contributes to the sediment transport.

Slug flow transitions in horizontal gas/liquid two-phase flows. Dependence on channel height and system pressure for air/water and steam/water two-phase flows

International Nuclear Information System (INIS)

Nakamura, Hideo

1996-05-01

The slug flow transitions and related phenomena for horizontal two-phase flows were studied for a better prediction of two-phase flows that typically appear during the reactor loss-of-coolant accidents (LOCAs). For better representation of the flow conditions experimentally, two large-scaled facility: TPTF for high-pressure steam/water two-phase flows and large duct test facility for air/water two-phase flows, were used. The visual observation of the flow using a video-probe was performed in the TPTF experiments for good understanding of the phenomena. The currently-used models and correlations based mostly on the small-scale low-pressure experiments were reviewed and improved based on these experimental results. The modified Taitel-Dukler model for prediction of transition into slug flow from wavy flow and the modified Steen-Wallis correlation for prediction of onset of liquid entrainment from the interfacial waves were obtained. An empirical correlation for the gas-liquid interfacial friction factor was obtained further for prediction of liquid levels at wavy flow. The region of slug flow regime that is generally under influences of the channel height and system pressure was predicted well when these models and correlations were applied together. (author). 90 refs

Transient analysis of air-water two-phase flow in channels and bends

International Nuclear Information System (INIS)

Khan, H.J.; Ye, W.; Pertmer, G.A.

1992-01-01

The algorithm used in this paper is the Newton Block Gauss Seidel method, which has been applied to both simple and complex flow conditions in two-phase flow. This paper contains a description of difference techniques and an iterative solution algorithm that is used to solve the field and constitutive equations of the two-fluid model. In practice, this solution procedure has been proven to be stable and capable of generating solutions in problems where other schemes have failed. The method converges rapidly for reasonable error tolerances and is easily extended to three-dimensional geometries. Using air-water as the two-phase medium, transient flow behavior in several geometries of interest are shown. Flow through a vertical channel with flow obstruction, large U bends, and 90-deg bends are being demonstrated with variation of inlet void fraction and slip ratio. Significant changes in the velocity and void distribution profiles have been observed. Various regions of flow recirculation are obtained in the flow domain for each phase. The phasic velocity and void distributions are dominated by gravity-induced phase separation causing air to accumulate in the upper region. The influence of inlet slip ratio and interfacial momentum transfer on the transient flow profile has been demonstrated in detail

Experimental study on two-phase flow parameters of subcooled boiling in inclined annulus

International Nuclear Information System (INIS)

Lee, Tae Ho; Kim, Moon Oh; Park, Goon Cherl

1999-01-01

Local two-phase flow parameters of subcooled flow boiling in inclined annulus were measured to investigate the effect of inclination on the internal flow structure. Two-conductivity probe technique was applied to measured local gas phasic parameters, including void by fraction, vapor bubble frequency, chord length, vapor bubble velocity and interfacial area concentration. Local liquid velocity was measured by Pitot tube. Experiments were conducted for three angles of inclination: 0 o (vertical), 30 o , 60 o . The system pressure was maintained at atmospheric pressure. The range of average void fraction was up to 10 percent and the average liquid superficial velocities were less than 1.3 m/sec. The results of experiments showed that the distributions of two-phase flow parameters were influenced by the angle of channel inclination. Especially, the void fraction and chord length distributions were strongly affected by the increase of inclination angle, and flow pattern transition to slug flow was observed depending on the flow conditions. The profiles of vapor velocity, liquid velocity and interfacial area concentration were found to be affected by the non-symmetric bubble size distribution in inclined channel. Using the measured distributions of local phasic parameters, an analysis for predicting average void fraction was performed based on the drift flux model and flowing volumetric concentration. And it was demonstrated that the average void fraction can be more appropriately presented in terms of flowing volumetric concentration. (Author). 18 refs., 2 tabs., 18 figs

Study of pressure drop, void fraction and relative permeabilities of two phase flow through porous media

International Nuclear Information System (INIS)

Chu, W.; Dhir, V.K.; Marshall, J.

1983-01-01

An experimental investigation of two phase flow through porous layers formed of non-heated glass particles (nominal diameter 1 to 6 mm) has been made. Particulate bed depths of 30 cm and 70 cm were used. The effect of particle size, particle size distribution and bed porosity on void fraction and pressure drop through a particulate bed formed in a cylindrical test section has been investigated. The superficial velocity of liquid (water) is varied from 1.83 to 18.3 mm/s while the superficial velocity of gas (air) is varied from 0 to 68.4 mm/s. These superficial velocities were chosen so that pressure drop and void fraction measurement could be made for the porous layer in fixed and fluidized states. A model based on drift flux approach has been developed for the void fraction. Using the two phase friction pressure drop data, the relative permeabilities of the two phases have been concluded with void fraction. The void fraction and two phase friction pressure gradient in beds composed of mixtures of spherical particles as well as sharps of different nominal sizes have also been examined. It is found that the models for single size particles are also applicable to mixtures of particles if a mean particle diameter for the mixture is defined

Numerical simulation of transient, adiabatic, two-dimensional two-phase flow using the two-fluid model

International Nuclear Information System (INIS)

Neves Conti, T. das.

1983-01-01

A numerical method is developed to simulate adiabatic, transient, two-dimensional two-phase flow. The two-fluid model is used to obtain the mass and momentum conservation equations. These are solved by an iterative algorithm emphoying a time-marching scheme. Based on the corrective procedure of Hirt and Harlow a poisson equation is derived for the pressure field. This equation is finite-differenced and solved by a suitable matrix inversion technique. In the absence of experiment results several numerical tests were made in order to chec accuracy, convergence and stability of the proposed method. Several tests were also performed to check whether the behavior of void fraction and phasic velocities conforms with previous observations. (Author) [pt

Analysis of two-phase flow inter-subchannel mass and momentum exchanges by the two-fluid model approach

Energy Technology Data Exchange (ETDEWEB)

Ninokata, H. [Tokyo Institute of Technology (Japan); Deguchi, A. [ENO Mathematical Analysis, Tokyo (Japan); Kawahara, A. [Kumamoto Univ., Kumamoto (Japan)

1995-09-01

A new void drift model for the subchannel analysis method is presented for the thermohydraulics calculation of two-phase flows in rod bundles where the flow model uses a two-fluid formulation for the conservation of mass, momentum and energy. A void drift model is constructed based on the experimental data obtained in a geometrically simple inter-connected two circular channel test sections using air-water as working fluids. The void drift force is assumed to be an origin of void drift velocity components of the two-phase cross-flow in a gap area between two adjacent rods and to overcome the momentum exchanges at the phase interface and wall-fluid interface. This void drift force is implemented in the cross flow momentum equations. Computational results have been successfully compared to experimental data available including 3x3 rod bundle data.

Study on flow instabilities in two-phase mixtures

International Nuclear Information System (INIS)

Ishii, M.

1976-03-01

Various mechanisms that can induce flow instabilities in two-phase flow systems are reviewed and their relative importance discussed. In view of their practical importance, the density-wave instabilities have been analyzed in detail based on the one-dimensional two-phase flow formulation. The dynamic response of the system to the inlet flow perturbations has been derived from the model; thus the characteristic equation that predicts the onset of instabilities has been obtained. The effects of various system parameters, such as the heat flux, subcooling, pressure, inlet velocity, inlet orificing, and exit orificing on the stability boundary have been analyzed. In addition to numerical solutions, some simple stability criteria under particular conditions have been obtained. Both results have been compared with various experimental data, and a satisfactory agreement has been demonstrated

Review of two-phase instabilities

Energy Technology Data Exchange (ETDEWEB)

Kang, Han Ok; Seo, Han Ok; Kang, Hyung Suk; Cho, Bong Hyun; Lee, Doo Jeong

1997-06-01

KAERI is carrying out a development of the design for a new type of integral reactors. The once-through helical steam generator is important design features. The study on designs and operating conditions which prevent flow instability should precede the introduction of one-through steam generator. Experiments are currently scheduled to understand two-phase instability, evaluate the effect of each design parameter on the critical point, and determine proper inlet throttling for the prevention of instability. This report covers general two-phase instability with review of existing studies on this topics. The general classification of two phase flow instability and the characteristics of each type of instability are first described. Special attention is paid to BWR core flow instability and once-through steam generator instability. The reactivity feedback and the effect of system parameters are treated mainly for BWR. With relation to once-through steam generators, the characteristics of convective heating and dryout point oscillation are first investigated and then the existing experimental studies are summarized. Finally chapter summarized the proposed correlations for instability boundary conditions. (author). 231 refs., 5 tabs., 47 figs

An investigation of time-frequency domain phase-weighted stacking and its application to phase-velocity extraction from ambient noise's empirical Green's functions

Science.gov (United States)

Li, Guoliang; Niu, Fenglin; Yang, Yingjie; Xie, Jun

2018-02-01

The time-frequency domain phase-weighted stacking (tf-PWS) technique based on the S transform has been employed in stacking empirical Green's functions (EGFs) derived from ambient noise data, mainly due to its superior power in enhancing weak signals. Questions such as the induced waveform distortion and the feasibility of phase-velocity extraction are yet to be thoroughly explored. In this study, we investigate these issues by conducting extensive numerical tests with both synthetic data and USArray transportable array (TA) ambient noise data. We find that the errors in the measured phase velocities associated with waveform distortion caused by the tf-PWS depend largely on the way of how the inverse S transform (IST) is implemented. If frequency IST is employed in tf-PWS, the corresponding errors are generally less than 0.1 per cent, sufficiently small that the measured phase velocities can be safely used in regular surface wave tomography. On the other hand, if a time IST is used in tf-PWS, then the extracted phase velocities are systematically larger than those measured from linearly stacked ones, and the discrepancy can reach as much as ˜0.4 per cent at some periods. Therefore, if tf-PWS is used in stacking EGFs, then frequency IST is preferred to transform the stacked S spectra back to the time domain for the stacked EGFs.

Correlation between centre offsets and gas velocity dispersion of galaxy clusters in cosmological simulations

Science.gov (United States)

Li, Ming-Hua; Zhu, Weishan; Zhao, Dong

2018-05-01

The gas is the dominant component of baryonic matter in most galaxy groups and clusters. The spatial offsets of gas centre from the halo centre could be an indicator of the dynamical state of cluster. Knowledge of such offsets is important for estimate the uncertainties when using clusters as cosmological probes. In this paper, we study the centre offsets roff between the gas and that of all the matter within halo systems in ΛCDM cosmological hydrodynamic simulations. We focus on two kinds of centre offsets: one is the three-dimensional PB offsets between the gravitational potential minimum of the entire halo and the barycentre of the ICM, and the other is the two-dimensional PX offsets between the potential minimum of the halo and the iterative centroid of the projected synthetic X-ray emission of the halo. Haloes at higher redshifts tend to have larger values of rescaled offsets roff/r200 and larger gas velocity dispersion σ v^gas/σ _{200}. For both types of offsets, we find that the correlation between the rescaled centre offsets roff/r200 and the rescaled 3D gas velocity dispersion, σ _v^gas/σ _{200} can be approximately described by a quadratic function as r_{off}/r_{200} ∝ (σ v^gas/σ _{200} - k_2)2. A Bayesian analysis with MCMC method is employed to estimate the model parameters. Dependence of the correlation relation on redshifts and the gas mass fraction are also investigated.

Development of subchannel void measurement sensor and multidimensional two-phase flow dynamics in rod bundle

International Nuclear Information System (INIS)

Arai, T.; Furuya, M.; Kanai, T.; Shirakawa, K.

2011-01-01

An accurate subchannel database is crucial for modeling the multidimensional two-phase flow in a rod bundle and for validating subchannel analysis codes. Based on available reference, it can be said that a point-measurement sensor for acquiring void fractions and bubble velocity distributions do not infer interactions of the subchannel flow dynamics, such as a cross flow and flow distribution, etc. In order to acquire multidimensional two-phase flow in a 10×10 rod bundle with an o.d. of 10 mm and 3110 mm length, a new sensor consisting of 11-wire by 11-wire and 10-rod by 10-rod electrodes was developed. Electric potential in the proximity region between two wires creates a void fraction in the center subchannel region, like a so-called wire mesh sensor. A unique aspect of the devised sensor is that the void fraction near the rod surface can be estimated from the electric potential in the proximity region between one wire and one rod. The additional 400 points of void fraction and phasic velocity in 10×10 bundle can therefore be acquired. The devised sensor exhibits the quasi three-dimensional flow structures, i.e. void fraction, phasic velocity and bubble chord length distributions. These quasi three-dimensional structures exhibit the complexity of two-phase flow dynamics, such as coalescence and the breakup of bubbles in transient phasic velocity distributions. (author)

Analysis of Two-Phase Flow in Damper Seals for Cryogenic Turbopumps

Science.gov (United States)

Arauz, Grigory L.; SanAndres, Luis

1996-01-01

Cryogenic damper seals operating close to the liquid-vapor region (near the critical point or slightly su-cooled) are likely to present two-phase flow conditions. Under single phase flow conditions the mechanical energy conveyed to the fluid increases its temperature and causes a phase change when the fluid temperature reaches the saturation value. A bulk-flow analysis for the prediction of the dynamic force response of damper seals operating under two-phase conditions is presented as: all-liquid, liquid-vapor, and all-vapor, i.e. a 'continuous vaporization' model. The two phase region is considered as a homogeneous saturated mixture in thermodynamic equilibrium. Th flow in each region is described by continuity, momentum and energy transport equations. The interdependency of fluid temperatures and pressure in the two-phase region (saturated mixture) does not allow the use of an energy equation in terms of fluid temperature. Instead, the energy transport is expressed in terms of fluid enthalpy. Temperature in the single phase regions, or mixture composition in the two phase region are determined based on the fluid enthalpy. The flow is also regarded as adiabatic since the large axial velocities typical of the seal application determine small levels of heat conduction to the walls as compared to the heat carried by fluid advection. Static and dynamic force characteristics for the seal are obtained from a perturbation analysis of the governing equations. The solution expressed in terms of zeroth and first order fields provide the static (leakage, torque, velocity, pressure, temperature, and mixture composition fields) and dynamic (rotordynamic force coefficients) seal parameters. Theoretical predictions show good agreement with experimental leakage pressure profiles, available from a Nitrogen at cryogenic temperatures. Force coefficient predictions for two phase flow conditions show significant fluid compressibility effects, particularly for mixtures with low mass

Numerical analysis of interfacial growth and deformation in horizontal stratified two-phase flow by lattice Boltzmann method

International Nuclear Information System (INIS)

Ebihara, Ken-ichi

2005-03-01

paper, first, the validity and the usefulness of the lattice-gas model and the lattice Boltzmann method for the numerical analysis of two-phase flow are examined by applying the two-phase fluid model of these methods to the phenomena of the falling droplet and the rising bubble. Next, on the basis of the examination of its numerical results, the horizontal stratified two-phase flow, which is the fundamental and important flow and often observed in a practical situation, is simulated by use of the HCZ model that is the two-phase fluid model of the lattice Boltzmann method proposed by He, Chen, and Zhang. The HCZ model can simulate Rayleigh-Taylor instability which shows complex interfacial phenomena. It is verified that the simulated interfacial growth is subject to the Kelvin-Helmholtz instability theory and can reproduce the curve concerning the interfacial growth of the theoretical flow regime map proposed by Taitel and Dukler (T-D map). Furthermore, it is found that the interfacial growth in the channel with the narrow width needs more superficial flow velocity than that given by the T-D map. In the simulation of the droplet generation in the horizontal stratified two-phase flow, it is verified that the HCZ model can also reproduce the experimental correlation proposed by Ishii and Grolmes within the range of the distribution of experimental data. According to the results of this report, it is found that the HCZ model of the lattice Boltzmann method can simulate complex interfacial phenomena in the horizontal stratified two-phase flow and reproduce the theoretical flow regime map and the experimental correlation. Considering the application of this model to more practical two-phase flow, it is also seen that this model has some problems which have to be solved, such as practical density difference, thermal influence and so on. (author)

Film boiling heat transfer from a hot sphere falling in two-phase pool

International Nuclear Information System (INIS)

Bang, K. H.; Kim, K. Y.

1998-01-01

The purpose of the present study is to experimentally investigate film boiling heat trasfer from a hot sphere falling in steam-water two-phase pool, which is the key heat transfer mode in molten fuel and coolant mixing. To measure film boiling heat transfer coefficients on a spere falling in two-phase pool, a heated sphere with a thermocouple embedded at the center is dropped in a vertical tube filled with steam-water mixture. The present experiment is unique in making the heated sphere fall through the two-phase pool while the previous experiments were performed with stationary spheres in flowing fluid. The falling speed of the sphere is measured using a set of magnet pickup coils distributed along the tube. The ranges of the experimental conditions are: spere fall speed 0-0.5 m/s, average void fraction 0-25,% steam superficial velocity 0-0.25 m/s. The results show that the forced convection film boiling heat transfer coefficient decrease slightly as the steam superficial velocity (void fraction) is increased

MODELLING THE INTERACTION IN GAME SPORTS - RELATIVE PHASE AND MOVING CORRELATIONS

Directory of Open Access Journals (Sweden)

Martin Lames

2006-12-01

Full Text Available Model building in game sports should maintain the constitutive feature of this group of sports, the dynamic interaction process between the two parties. For single net/wall games relative phase is suggested to describe the positional interaction between the two players. 30 baseline rallies in tennis were examined and relative phase was calculated by Hilbert transform from the two time-series of lateral displacement and trajectory in the court respectively. Results showed that relative phase indicates some aspects of the tactical interaction in tennis. At a more abstract level the interaction between two teams in handball was studied by examining the relationship of the two scoring processes. Each process can be conceived as a random walk. Moving averages of the scoring probabilities indicate something like a momentary strength. A moving correlation (length = 20 ball possessions describes the momentary relationship between the teams' strength. Evidence was found that this correlation is heavily time-dependent, in almost every single game among the 40 examined ones we found phases with a significant positive as well as significant negative relationship. This underlines the importance of a dynamic view on the interaction in these games.

Numerical Predictions of Bubbly Two-Phase Flows with OpenFOAM

Directory of Open Access Journals (Sweden)

Edouard Michta

2012-12-01

Full Text Available A new model for simulation of bubbly two-phase flows has been developed and implemented into an open-source Computational Fluid Dynamics (CFD code OpenFOAM. The model employs the two-fluid framework with closure relationships for the interfacial momentum transfer. The bubble size is calculated based on the solution of the transport equation of the interfacial area concentration. The predictions are validated against selected data obtained in the DEDALE experiment and containing the measured void fraction, the phasic velocities and the interfacial area concentration. In general, good agreement between calculated and measured data is demonstrated; however, the relative phasic velocity is systematically over-predicted. The levels of void fraction and the observed wall void peaking are well captured in the calculations.

Two-phase alkali-metal experiments in reduced gravity

International Nuclear Information System (INIS)

Antoniak, Z.I.

1986-06-01

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

Damping and fluidelastic instability in two-phase cross-flow heat exchanger tube arrays

Science.gov (United States)

Moran, Joaquin E.

An experimental study was conducted to investigate damping and fluidelastic instability in tube arrays subjected to two-phase cross-flow. The purpose of this research was to improve our understanding of these phenomena and how they are affected by void fraction and flow regime. The model tube bundle had 10 cantilevered tubes in a parallel-triangular configuration, with a pitch ratio of 1.49. The two-phase flow loop used in this research utilized Refrigerant 11 as the working fluid, which better models steam-water than air-water mixtures in terms of vapour-liquid mass ratio as well as permitting phase changes due to pressure fluctuations. The void fraction was measured using a gamma densitometer, introducing an improvement over the Homogeneous Equilibrium Model (HEM) in terms of void fraction, density and velocity predictions. Three different damping measurement methodologies were implemented and compared in order to obtain a more reliable damping estimate. The methods were the traditionally used half-power bandwidth, the logarithmic decrement and an exponential fitting to the tube decay response. The decay trace was obtained by "plucking" the monitored tube from outside the test section using a novel technique, in which a pair of electromagnets changed their polarity at the natural frequency of the tube to produce resonance. The experiments showed that the half-power bandwidth produces higher damping values than the other two methods. The primary difference between the methods is caused by tube frequency shifting, triggered by fluctuations in the added mass and coupling between the tubes, which depend on void fraction and flow regime. The exponential fitting proved to be the more consistent and reliable approach to estimating damping. In order to examine the relationship between the damping ratio and mass flux, the former was plotted as a function of void fraction and pitch mass flux in an iso-contour plot. The results showed that damping is not independent of mass

Measurement of gas-liquid two-phase flow in bubble columns using ensemble correlation PIV

NARCIS (Netherlands)

Delnoij, E.; Kuipers, J.A.M.; van Swaaij, Willibrordus Petrus Maria; Westerweel, J.

2000-01-01

This paper highlights the development of a new ensemble correlation, multiphase flow PIV technique. The particular approach discussed in this paper is a straightforward extension of single-phase PIV and one of the major advantages of the technique is that it employs a single CCD camera. This

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.)

Weak-anisotropy approximations of P-wave phase and ray velocities for anisotropy of arbitrary symmetry

Czech Academy of Sciences Publication Activity Database

Farra, V.; Pšenčík, Ivan

2016-01-01

Roč. 60, č. 3 (2016), s. 403-418 ISSN 0039-3169 Institutional support: RVO:67985530 Keywords : weak anisotropy * P-wave * phase velocity * ray velocity Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.764, year: 2016

Analysis of gas-liquid metal two-phase flows using a reactor safety analysis code SIMMER-III

International Nuclear Information System (INIS)

Suzuki, Tohru; Tobita, Yoshiharu; Kondo, Satoru; Saito, Yasushi; Mishima, Kaichiro

2003-01-01

SIMMER-III, a safety analysis code for liquid-metal fast reactors (LMFRs), includes a momentum exchange model based on conventional correlations for ordinary gas-liquid flows, such as an air-water system. From the viewpoint of safety evaluation of core disruptive accidents (CDAs) in LMFRs, we need to confirm that the code can predict the two-phase flow behaviors with high liquid-to-gas density ratios formed during a CDA. In the present study, the momentum exchange model of SIMMER-III was assessed and improved using experimental data of two-phase flows containing liquid metal, on which fundamental information, such as bubble shapes, void fractions and velocity fields, has been lacking. It was found that the original SIMMER-III can suitably represent high liquid-to-gas density ratio flows including ellipsoidal bubbles as seen in lower gas fluxes. In addition, the employment of Kataoka-Ishii's correlation has improved the accuracy of SIMMER-III for gas-liquid metal flows with cap-shape bubbles as identified in higher gas fluxes. Moreover, a new procedure, in which an appropriate drag coefficient can be automatically selected according to bubble shape, was developed. Through this work, the reliability and the precision of SIMMER-III have been much raised with regard to bubbly flows for various liquid-to-gas density ratios

Does the application of gadolinium-DTPA have an impact on magnetic resonance phase contrast velocity measurements? Results from an in vitro study

Energy Technology Data Exchange (ETDEWEB)

Heverhagen, J.T. E-mail: heverhag@post.med.uni-marburg.de; Hoppe, M.; Klose, K.-J.; Wagner, H.-J

2002-10-01

Introduction/objective: To evaluate the potential influence of various concentrations of gadolinium (Gd)-DTPA on magnetic resonance phase contrast (MR PC) velocimetry. Material and methods: Imaging was done with a 1.0 T scanner using a standard Flash 2D sequence and a circular polarized extremity coil. In a validated flow phantom with a defined 75% area stenosis different concentrations of Gd-DTPA, diluted in a 10:1 water-yogurt mixture, MR PC measurements were correlated with a Doppler guide wire as gold standard. Results: MR PC measurements correlated well with the Doppler derived data (r=0.99; P<0.01; maximum pre-stenotic velocity: 21.6{+-}0.5 cm/s; maximum intra-stenotic velocity: 81.7{+-}0.6 cm/s). Following Gd-DTPA administration no significant (P>0.05; Student's t-test) flow measurement changes were noted (maximum pre-stenotic velocity: 21.3{+-}1.3 cm/s; maximum intra-stenotic velocity: 84.0{+-}3.6 cm/s). However, delineation of the perfused lumen was enhanced after the application of Gd-DTPA. Discussions and conclusion: The application of Gd-DTPA does not affect MR PC velocimetry. However, the application of contrast media allowed a more accurate vessel segmentation. MR PC measurements can be reliably carried out after application of Gd-DTPA.

Characterizing the correlations between local phase fractions of gas���liquid two-phase flow with wire-mesh sensor

OpenAIRE

Tan, C.; Liu, W. L.; Dong, F.

2016-01-01

Understanding of flow patterns and their transitions is significant to uncover the flow mechanics of two-phase flow. The local phase distribution and its fluctuations contain rich information regarding the flow structures. A wire-mesh sensor (WMS) was used to study the local phase fluctuations of horizontal gas���liquid two-phase flow, which was verified through comparing the reconstructed three-dimensional flow structure with photographs taken during the experiments. Each crossing point of t...

An Eulerian-Eulerian Approach to CFD Simulation of Two-Phase Bubble Column using ANSYS CFX Code

International Nuclear Information System (INIS)

Mohd Amirul Syafiq Mohd Yunos; Nur Khairunnisa Abd Halim; Siti Aslina Hussain

2016-01-01

Bubble columns are widely used as gas-liquid contactors and reactors in chemical, biochemical and petrochemical industries. Effective mixing, high interfacial area between phases, cheap to install and lack of moving parts are the main factors bubble column is chosen for the described processes. Understanding the complexity of the fluid dynamics of gas-liquid flow in bubble column is important due to its unsteady complex processes as well as application in the chemical and bioprocess industries. The gas-liquid of two-phase fluid flow system has been carried out to investigate the hydrodynamics parameters. An Eulerian-Eulerian approach was used to model air as the dispersed phase within a continuous phase of water using the commercial software ANSYSTM CFD software (CFX 14.0). The turbulence in the gas-liquid simulation is described by using the k-e model. This process occurs under the atmospheric pressure. The configuration of model consists of 0.2 m width, 0.2 m depth and 0.5 m height of rectangular bubble column equipped with a sparger at the bottom. Two different sparger designs, Sparger A with 4 holes and 2.6 mm diameter each and Sparger B with 81 holes and 0.5 mm diameter each are tested for three different value of superficial gas velocity of 0.0125 m/s, 0.0501 m/s and 0.0627 m/s. The volume fraction of model is described the behavior of bubble which is represented by the parameters of gas holdup, contact surface area and gas superficial velocity. The simulation was verified by comparing the two different model results. Comparison of simulation results with the experimental work data has provided a successful validation of the model. Results shows the contact surface area increasing with behavior of bubble and gas holdup increases with increasing superficial gas velocity but independent of the sparger design at high superficial velocity (>0.05 m/s). The highest value obtained which is represented of water superficial velocity, gas holdup and superficial gas

Numerical simulation of two-phase flow with front-capturing

International Nuclear Information System (INIS)

Tzanos, C.P.; Weber, D.P.

2000-01-01

Because of the complexity of two-phase flow phenomena, two-phase flow codes rely heavily on empirical correlations. This approach has a number of serious shortcomings. Advances in parallel computing and continuing improvements in computer speed and memory have stimulated the development of numerical simulation tools that rely less on empirical correlations and more on fundamental physics. The objective of this work is to take advantage of developments in massively parallel computing, single-phase computational fluid dynamics of complex systems, and numerical methods for front capturing in two-phase flows to develop a computer code for direct numerical simulation of two-phase flow. This includes bubble/droplet transport, interface deformation and topology change, bubble-droplet interactions, interface mass, momentum, and energy transfer. In this work, the Navier-Stokes and energy equations are solved by treating both phases as a single fluid with interfaces between the two phases, and a discontinuity in material properties across the moving interfaces. The evolution of the interfaces is simulated by using the front capturing technique of the level-set methods. In these methods, the boundary of a two-fluid interface is modeled as the zero level set of a smooth function φ. The level-set function φ is defined as the signed distance from the interface (φ is negative inside a droplet/bubble and positive outside). Compared to other front-capturing or front-tracking methods, the level-set approach is relatively easy to implement even in three-dimensional flows, and it has been shown to simulate well the coalescence and breakup of droplets/bubbles

Two-phase flow characteristics analysis code: MINCS

International Nuclear Information System (INIS)

Watanabe, Tadashi; Hirano, Masashi; Akimoto, Masayuki; Tanabe, Fumiya; Kohsaka, Atsuo.

1992-03-01

Two-phase flow characteristics analysis code: MINCS (Modularized and INtegrated Code System) has been developed to provide a computational tool for analyzing two-phase flow phenomena in one-dimensional ducts. In MINCS, nine types of two-phase flow models-from a basic two-fluid nonequilibrium (2V2T) model to a simple homogeneous equilibrium (1V1T) model-can be used under the same numerical solution method. The numerical technique is based on the implicit finite difference method to enhance the numerical stability. The code structure is highly modularized, so that new constitutive relations and correlations can be easily implemented into the code and hence evaluated. A flow pattern can be fixed regardless of flow conditions, and state equations or steam tables can be selected. It is, therefore, easy to calculate physical or numerical benchmark problems. (author)

Exploring the hole cleaning parameters of horizontal wellbore using two-phase Eulerian CFD approach

Directory of Open Access Journals (Sweden)

Satish K Dewangan

2016-03-01

Full Text Available The present investigation deals with the flow through concentric annulus with the inner cylinder in rotation. This work has got its importance in the petroleum industries in relation to the wellbore drilling. In wellbore drilling, the issue of the hole-cleaning is very serious problem especially in case of the horizontal drilling process. The effect of the various parameters like slurry flow velocity, inner cylinder rotational speed, inlet solid concentration which affect hole cleaning was discussed. Their effect on the pressure drop, wall shear stress, mixture turbulence kinetic energy, and solid-phase velocity and slip velocity were analyzed, which are responsible for solid-phase distribution. Flow was considered to be steady, incompressible and two-phase slurry flow with water as carrier fluid and silica sand as the secondary phase. Eulerian approach was used for modeling the slurry flow. Silica sand was considered of spherical shape with particle size of 180 µm. ANSYS FLUENT software was used for modeling and solution. Plotting was done using Tecplot software and Microsoft Office.

Phase reconstruction from velocity-encoded MRI measurements – A survey of sparsity-promoting variational approaches

KAUST Repository

Benning, Martin; Gladden, Lynn; Holland, Daniel; Schö nlieb, Carola-Bibiane; Valkonen, Tuomo

2014-01-01

for the reconstruction of phase-encoded magnetic resonance velocity images from sub-sampled k-space data. We are particularly interested in regularisers that correctly treat both smooth and geometric features of the image. These features are common to velocity imaging

Influence of the pore fluid on the phase velocity in bovine trabecular bone In Vitro: Prediction of the biot model

Science.gov (United States)

Lee, Kang Il

2013-01-01

The present study aims to investigate the influence of the pore fluid on the phase velocity in bovine trabecular bone in vitro. The frequency-dependent phase velocity was measured in 20 marrow-filled and water-filled bovine femoral trabecular bone samples. The mean phase velocities at frequencies between 0.6 and 1.2 MHz exhibited significant negative dispersions for both the marrow-filled and the water-filled samples. The magnitudes of the dispersions showed no significant differences between the marrow-filled and the water-filled samples. In contrast, replacement of marrow by water led to a mean increase in the phase velocity of 27 m/s at frequencies from 0.6 to 1.2 MHz. The theoretical phase velocities of the fast wave predicted by using the Biot model for elastic wave propagation in fluid-saturated porous media showed good agreements with the measurements.

Constraining the optical depth of galaxies and velocity bias with cross-correlation between the kinetic Sunyaev-Zeldovich effect and the peculiar velocity field

Science.gov (United States)

Ma, Yin-Zhe; Gong, Guo-Dong; Sui, Ning; He, Ping

2018-03-01

We calculate the cross-correlation function between the kinetic Sunyaev-Zeldovich (kSZ) effect and the reconstructed peculiar velocity field using linear perturbation theory, with the aim of constraining the optical depth τ and peculiar velocity bias of central galaxies with Planck data. We vary the optical depth τ and the velocity bias function bv(k) = 1 + b(k/k0)n, and fit the model to the data, with and without varying the calibration parameter y0 that controls the vertical shift of the correlation function. By constructing a likelihood function and constraining the τ, b and n parameters, we find that the quadratic power-law model of velocity bias, bv(k) = 1 + b(k/k0)2, provides the best fit to the data. The best-fit values are τ = (1.18 ± 0.24) × 10-4, b=-0.84^{+0.16}_{-0.20} and y0=(12.39^{+3.65}_{-3.66})× 10^{-9} (68 per cent confidence level). The probability of b > 0 is only 3.12 × 10-8 for the parameter b, which clearly suggests a detection of scale-dependent velocity bias. The fitting results indicate that the large-scale (k ≤ 0.1 h Mpc-1) velocity bias is unity, while on small scales the bias tends to become negative. The value of τ is consistent with the stellar mass-halo mass and optical depth relationship proposed in the literature, and the negative velocity bias on small scales is consistent with the peak background split theory. Our method provides a direct tool for studying the gaseous and kinematic properties of galaxies.

On the effect of velocity gradients on the depth of correlation in μPIV

International Nuclear Information System (INIS)

Mustin, B; Stoeber, B

2016-01-01

The present work revisits the effect of velocity gradients on the depth of the measurement volume (depth of correlation) in microscopic particle image velocimetry (μPIV). General relations between the μPIV weighting functions and the local correlation function are derived from the original definition of the weighting functions. These relations are used to investigate under which circumstances the weighting functions are related to the curvature of the local correlation function. Furthermore, this work proposes a modified definition of the depth of correlation that leads to more realistic results than previous definitions for the case when flow gradients are taken into account. Dimensionless parameters suitable to describe the effect of velocity gradients on μPIV cross correlation are derived and visual interpretations of these parameters are proposed. We then investigate the effect of the dimensionless parameters on the weighting functions and the depth of correlation for different flow fields with spatially constant flow gradients and with spatially varying gradients. Finally this work demonstrates that the results and dimensionless parameters are not strictly bound to a certain model for particle image intensity distributions but are also meaningful when other models for particle images are used. (paper)

On the effect of velocity gradients on the depth of correlation in μPIV

Science.gov (United States)

Mustin, B.; Stoeber, B.

2016-03-01

The present work revisits the effect of velocity gradients on the depth of the measurement volume (depth of correlation) in microscopic particle image velocimetry (μPIV). General relations between the μPIV weighting functions and the local correlation function are derived from the original definition of the weighting functions. These relations are used to investigate under which circumstances the weighting functions are related to the curvature of the local correlation function. Furthermore, this work proposes a modified definition of the depth of correlation that leads to more realistic results than previous definitions for the case when flow gradients are taken into account. Dimensionless parameters suitable to describe the effect of velocity gradients on μPIV cross correlation are derived and visual interpretations of these parameters are proposed. We then investigate the effect of the dimensionless parameters on the weighting functions and the depth of correlation for different flow fields with spatially constant flow gradients and with spatially varying gradients. Finally this work demonstrates that the results and dimensionless parameters are not strictly bound to a certain model for particle image intensity distributions but are also meaningful when other models for particle images are used.

Evolution of the structure of a gas-liquid two-phase flow in a large vertical pipe

International Nuclear Information System (INIS)

Horst-Michael Prasser; Matthias Beyer; Helmar Carl; Sabine Gregor; Dirk Lucas; Peter Schuetz; Frank-Peter Weiss

2005-01-01

Full text of publication follows: Experimental results on the evolution of the radial gas fraction profiles, gas velocity profiles and bubble size distributions in a gas-liquid two-phase flow along a large vertical pipe of 194 mm inner diameter are presented. The tests were performed at the TOPFLOW facility in Rossendorf, where two wire-mesh sensors were used to measure sequences of two-dimensional distributions of local instantaneous gas fraction within the complete pipe cross-section with a lateral resolution of 3 mm and a sampling frequency of 2500 Hz. This data is the basis for a fast flow visualization and for the calculation of the mentioned profiles. The gas fraction profiles were obtained by averaging the sequences over time, velocities were measured by cross-correlation of the signals of the two sensors, which were located on a short (63 mm) distance behind each other. The high resolution of the mesh sensors allows to identify regions of connected measuring points in the data array, which are filled with the gas phase. This method was used to obtain the bubble size distributions. In the experiments, the superficial velocities ranged from 0.04 to 8 m/s for the gas phase and from 0.04 to 1.6 m/s for the liquid. In this way, the experiments cover the range from bubbly to churn turbulent flow regimes. The evolution of the flow structure was studied by varying the distance between the gas injection and the sensor position. This distance was changed by the help of a so-called variable gas injection set-up. It consists of 6 gas injection units, each of them equipped with three rings of orifices in the pipe wall for the gas injection. These rings are fed with the gas phase from ring chambers, which can be individually controlled by valves. The middle ring has orifices of 4 mm diameter, while the upper and the lower rings have nozzles of 1 mm diameter. In this way, 18 different inlet lengths and two different gas injection geometries can be chosen. The latter

Non-equilibrium effects on the two-phase flow critical phenomenon

International Nuclear Information System (INIS)

Sami, S.M.

1988-01-01

In the present study, the choking criterion for nonhomogeneous nonequilibrium two phase flow is obtained by solving the two-fluid model conservation equations. The method of characteristics is employed to predict the critical flow conditions. Critical flow is established after the magnitude of the characteristic slopes (velocities). Critical flow conditions are reached when the smallest characteristic slope becomes equal to zero. Several expression are developed to determine the nonequilibrium mass and heat exchanges in terms of the system dependent parameters derivatives. In addition, comprehensive transition flow regime maps are employed in the calculation of interfacial heat and momentum transfer rates. Numerical results reveal that the proposed model reliably predicts the critical two-phase flow phenomenon under different inlet conditions and compares well with other existing models

Noncommutative nature of the addition of noncollinear velocities in special relativity and the geometric phase method (commemorating the publication centennial of A Sommerfeld's work)

International Nuclear Information System (INIS)

Malykin, Grigorii B

2010-01-01

In 1909, Arnold Sommerfeld used geometric calculations to show that the relativistic addition of two noncollinear velocities on an imaginary-radius sphere is a noncommutative operation. Sommerfeld was the first to use the geometric phase method to calculate the angle between the resulting velocities depending on the order in which they are added. For this, he related the value of this angle to the excess of the spherical triangle formed by the two original velocities and their sum. In 1931, Sommerfeld applied his method to analyze the Thomas precession. (from the history of physics)

Scaling Regimes in the Model of Passive Scalar Advected by the Turbulent Velocity Field with Finite Correlation Time. Influence of Helicity in Two-Loop Approximation

CERN Document Server

Chkhetiani, O G; Jurcisinova, E; Jurcisin, M; Mazzino, A; Repasan, M

2005-01-01

The advection of a passive scalar quantity by incompressible helical turbulent flow has been investigated in the framework of an extended Kraichnan model. Statistical fluctuations of the velocity field are assumed to have the Gaussian distribution with zero mean and defined noise with finite-time correlation. Actual calculations have been done up to two-loop approximation in the framework of the field-theoretic renormalization group approach. It turned out that the space parity violation (helicity) of a stochastic environment does not affect anomalous scaling which is the peculiar attribute of a corresponding model without helicity. However, stability of asymptotic regimes, where anomalous scaling takes place, and the effective diffusivity strongly depend on the amount of helicity.

The ATF two-frequency correlation reflectometer

International Nuclear Information System (INIS)

Hanson, G.R.; Wilgen, J.B.; Anabitarte, E.; Bell, J.D.; Harris, J.H.; Dunlap, J.L.; Thomas, C.E.

1990-01-01

The Advanced Toroidal Facility (ATF) density fluctuation reflectometer system consists of two individual reflectometers operating in the 30- to 40-GHz band. Each reflectometer consists of a tunable microwave source and a quadrature phase detector connected to the same antenna system. This arrangement allows two-frequency operation along the same radial chord for radial coherence measurements. The technique used in making radial coherence measurements is discussed and the results of such experiments are given. Initial experiments have shown high coherence when the frequencies of the two reflectometers are tuned close together and a clear loss of coherence as the radial separation of the cutoff layers is increased by increasing the frequency separation of the two reflectometers. Recent results have shown that local measurements of density fluctuations in plasmas with electron cyclotron heating (ECH) are possible and that detailed structure can be seen in the fluctuation spectra. In addition, radial correlation lengths have been found to be from 0.5 to 1.0 cm in ECH plasmas, with some frequency structures having correlation lengths up to 3 cm. In plasmas with neutral beam injection (NBI), the radial correlation lengths in the edge region have been found to be approximately 0.1--0.2 cm. 4 figs

Velocity measurements and identification of the flow pattern of vertical air-water flows with light-beam detectors

International Nuclear Information System (INIS)

Luebbesmeyer, D.; Leoni, B.

1980-07-01

A new detector for measuring fluid velocities in two-phase flows by means of Noise-Analysis (especially Transient-Cross-Correlation-technique) has been developed. The detector utilizes a light-beam which is modulated by changes in the transparency of the two-phase flow. The results of nine measurements for different flow-regimes of vertical air/water-flows are shown. A main topic of these investigations was to answer the question if it is possible to identify the flow-pattern by looking at the shape of different 'Noise-Analytical-functions' (like APSD, CPSD, CCF etc.). The results prove that light-beam sensors are good detectors for fluid-velocity measurements in different flow regimes and in a wide range of fluid velocities starting with values of about 0.08 m/s up to values of 40 m/s. With respect to flow-pattern identification only the time-signals and the shape of the cross-power-density-function (CPSD) seem to be useful. (Auth.)

Two-Phase Gas-Liquid Flow Structure Characteristics under Periodic Cross Forces Action

Directory of Open Access Journals (Sweden)

V. V. Perevezentsev

2015-01-01

Full Text Available The article presents a study of two-phase gas-liquid flow under the action of periodic cross forces. The work objective is to obtain experimental data for further analysis and have structure characteristics of the two-phase flow movement. For research, to obtain data without disturbing effect on the flow were used optic PIV (Particle Image Visualization methods because of their noninvasiveness. The cross forces influence was provided by an experimental stand design to change the angular amplitudes and the periods of channel movement cycle with two-phase flow. In the range of volume gas rates was shown a water flow rate versus the inclination angle of immovable riser section and the characteristic angular amplitudes and periods of riser section inclination cycle under periodic cross forces. Data on distribution of average water velocity in twophase flow in abovementioned cases were also obtained. These data allowed us to draw a conclusion that a velocity distribution depends on the angular amplitude and on the period of the riser section roll cycle. This article belongs to publications, which study two-phase flows with no disturbing effect on them. Obtained data give an insight into understanding a pattern of twophase gas-liquid flow under the action of periodic cross forces and can be used to verify the mathematical models of the CFD thermo-hydraulic codes. In the future, the work development expects taking measurements with more frequent interval in the ranges of angular amplitudes and periods of the channel movement cycle and create a mathematical model to show the action of periodic cross forces on two-phase gas-liquid flow.

Shear wave crustal velocity model of the Western Bohemian Massif from Love wave phase velocity dispersion

Czech Academy of Sciences Publication Activity Database

Kolínský, Petr; Málek, Jiří; Brokešová, J.

2011-01-01

Roč. 15, č. 1 (2011), s. 81-104 ISSN 1383-4649 R&D Projects: GA AV ČR IAA300460602; GA AV ČR IAA300460705; GA ČR(CZ) GA205/06/1780 Institutional research plan: CEZ:AV0Z30460519 Keywords : love waves * phase velocity dispersion * frequency-time analysis Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.326, year: 2011 www.springerlink.com/content/w3149233l60111t1/

Three-dimensional investigation of the two-phase flow structure in a bubbly pipe flow

International Nuclear Information System (INIS)

Schmidl, W.; Hassan, Y.A.; Ortiz-Villafuerte, J.

1996-01-01

Particle image velocimetry (PIV) is a nonintrusive measurement technique that can be used to study the structure of various fluid flows. PIV is used to measure the time-varying, full-field velocity data of a particle-seeded flow field within either a two-dimensional plane or three-dimensional volume. PIV is a very efficient measurement technique since it can obtain both qualitative and quantitative spatial information about the flow field being studied. The quantitative spatial velocity information can be further processed into information of flow parameters such as vorticity and turbulence over extended areas. The objective of this study was to apply recent advances and improvements in the PIV flow measurement technique to the full-field, nonintrusive analysis of a three-dimensional, two-phase fluid flow system in such a manner that both components of the two-phase system could be experimentally quantified

A numerical and experimental study of two-phase flow and heat transfer in a porous formation with localized heating from below

International Nuclear Information System (INIS)

Easterday, O.T.; Wang, C.Y.; Cheng, P.

1995-01-01

Understanding and predicting two-phase flow and heat transfer in porous media is of fundamental interest for a number of engineering applications. Examples include thermal technologies for remediation of contaminated subsurfaces, the extraction of geothermal energy from vapor-dominated reservoirs, and the assessment of high-level nuclear waste repositories. A numerical and experimental study is reported for two-phase flow and heat transfer in a horizontal porous formation with water through flow and partial heating from below. Based on a newly developed two-phase mixture model, numerical results of the temperature distribution, liquid saturation, liquid and vapor phase velocity fields are presented for three representative cases with varying inlet velocities. It is found that the resulting two-phase structure and flow patterns are strongly dependent upon the water inlet velocity and the bottom heat flux. The former parameter measures the flow along the horizontal direction, while the latter creates a relative motion between the phases in the vertical direction. Experiments are also performed to measure temperature distributions and to visualize the two-phase flow patterns. Qualitative agreement between experiments and numerical predictions is achieved. Overall, this combined experimental and numerical study has provided new insight into conjugate single- and two-phase flow and heat transfer in porous media, although future research is required if accurate modeling of these complex problems is to be accomplished

A Rotational Pressure-Correction Scheme for Incompressible Two-Phase Flows with Open Boundaries

Science.gov (United States)

Dong, S.; Wang, X.

2016-01-01

Two-phase outflows refer to situations where the interface formed between two immiscible incompressible fluids passes through open portions of the domain boundary. We present several new forms of open boundary conditions for two-phase outflow simulations within the phase field framework, as well as a rotational pressure correction based algorithm for numerically treating these open boundary conditions. Our algorithm gives rise to linear algebraic systems for the velocity and the pressure that involve only constant and time-independent coefficient matrices after discretization, despite the variable density and variable viscosity of the two-phase mixture. By comparing simulation results with theory and the experimental data, we show that the method produces physically accurate results. We also present numerical experiments to demonstrate the long-term stability of the method in situations where large density contrast, large viscosity contrast, and backflows occur at the two-phase open boundaries. PMID:27163909

New theoretical model for two-phase flow discharged from stratified two-phase region through small break

International Nuclear Information System (INIS)

Yonomoto, Taisuke; Tasaka, Kanji

1988-01-01

A theoretical and experimental study was conducted to understand two-phase flow discharged from a stratified two-phase region through a small break. This problem is important for an analysis of a small break loss-of-coolant accident (LOCA) in a light water reactor (LWR). The present theoretical results show that a break quality is a function of h/h b , where h is the elevation difference between a bulk water level in the upstream region and break and b the suffix for entrainment initiation. This result is consistent with existing eperimental results in literature. An air-water experiment was also conducted changing a break orientation as an experimental parameter to develop and assess the model. Comparisons between the model and the experimental results show that the present model can satisfactorily predict the flow rate and the quality at the break without using any adjusting constant when liquid entrainment occurs in a stratified two-phase region. When gas entrainment occurs, the experimental data are correlated well by using a single empirical constant. (author)

Visualization for gas-liquid two-phase flow using wire mesh tomography

International Nuclear Information System (INIS)

Motegi, Yuichi; Wanjiraniran, Weerin; Kikura, Hiroshige; Aritomi, Masanori; Yamauchi, Toyoaki

2003-01-01

Wire Mesh Tomography (WMT), which is system to measure two-phase flow, has been developed in our laboratory. Measurement principle of WMT is detecting conductivity difference between gas and liquid. WMT measures void fraction as raw date, and calculates gas velocity and bubble volume etc. In this paper, this measurement technique was applied to vertical circular pipe of 50 mm diameter and about 7 m heights. New Wire Mesh Sensor (WMS), which is measurement part of WMT, for circular pipe, have been made. When experiment was performed, superficial gas and water velocity. The effect of each flow parameter was found for void fraction, true gas velocity and bubble volume and the results was in good agreement with the past research, qualitatively. (author)

Investigation for vertical, two-phase steam-water flow of three turbine models

International Nuclear Information System (INIS)

Silverman, S.; Goodrich, L.D.

1977-01-01

One of the basic quantities of interest during a loss-of-coolant experiment (LOCE) is the primary system mass flow rate. Presently, there are no transducers commercially available which continuously measure this parameter. Therefore, a transducer was designed at EG and G Idaho, Inc. which combines a drag-disc and turbine into a single unit. The basis for the design was that the drag-disc would measure momentum flux (rhoV 2 ), the turbine would measure velocity and the mass flow rate could then be calculated from the two quantities by assuming a flow profile. For two-phase flow, the outputs are approximately proportional to the desired parameter, but rather large errors can be expected under those assumptions. Preliminary evaluation of the experimental two- and single-phase calibration data has resulted in uncertainty estimates of +-8% of range for the turbine and +-20% of range for the drag-disc. In an effort to reduce the errors, further investigations were made to determine what the drag-disc and turbine really measure. In the present paper, three turbine models for vertical, two-phase, steam/water flow are investigated; the Aya Model, the Rouhani Model, and a volumetric flow model. Theoretical predictions are compared with experimental data for vertical, two-phase steam/water flow. For the purposes of the mass flow calculation, velocity profiles were assumed to be flat for the free-field condition. It is appreciated that this may not be true for all cases investigated, but for an initial inspection, flat profiles were assumed

Effect of Coulomb friction on orientational correlation and velocity distribution functions in a sheared dilute granular gas.

Science.gov (United States)

Gayen, Bishakhdatta; Alam, Meheboob

2011-08-01

From particle simulations of a sheared frictional granular gas, we show that the Coulomb friction can have dramatic effects on orientational correlation as well as on both the translational and angular velocity distribution functions even in the Boltzmann (dilute) limit. The dependence of orientational correlation on friction coefficient (μ) is found to be nonmonotonic, and the Coulomb friction plays a dual role of enhancing or diminishing the orientational correlation, depending on the value of the tangential restitution coefficient (which characterizes the roughness of particles). From the sticking limit (i.e., with no sliding contact) of rough particles, decreasing the Coulomb friction is found to reduce the density and spatial velocity correlations which, together with diminished orientational correlation for small enough μ, are responsible for the transition from non-gaussian to gaussian distribution functions in the double limit of small friction (μ→0) and nearly elastic particles (e→1). This double limit in fact corresponds to perfectly smooth particles, and hence the maxwellian (gaussian) is indeed a solution of the Boltzmann equation for a frictional granular gas in the limit of elastic collisions and zero Coulomb friction at any roughness. The high-velocity tails of both distribution functions seem to follow stretched exponentials even in the presence of Coulomb friction, and the related velocity exponents deviate strongly from a gaussian with increasing friction.

Dual-mode nonlinear instability analysis of a confined planar liquid sheet sandwiched between two gas streams of unequal velocities and prediction of droplet size and velocity distribution using maximum entropy formulation

Science.gov (United States)

Dasgupta, Debayan; Nath, Sujit; Bhanja, Dipankar

2018-04-01

Twin fluid atomizers utilize the kinetic energy of high speed gases to disintegrate a liquid sheet into fine uniform droplets. Quite often, the gas streams are injected at unequal velocities to enhance the aerodynamic interaction between the liquid sheet and surrounding atmosphere. In order to improve the mixing characteristics, practical atomizers confine the gas flows within ducts. Though the liquid sheet coming out of an injector is usually annular in shape, it can be considered to be planar as the mean radius of curvature is much larger than the sheet thickness. There are numerous studies on breakup of the planar liquid sheet, but none of them considered the simultaneous effects of confinement and unequal gas velocities on the spray characteristics. The present study performs a nonlinear temporal analysis of instabilities in the planar liquid sheet, produced by two co-flowing gas streams moving with unequal velocities within two solid walls. The results show that the para-sinuous mode dominates the breakup process at all flow conditions over the para-varicose mode of breakup. The sheet pattern is strongly influenced by gas velocities, particularly for the para-varicose mode. Spray characteristics are influenced by both gas velocity and proximity to the confining wall, but the former has a much more pronounced effect on droplet size. An increase in the difference between gas velocities at two interfaces drastically shifts the droplet size distribution toward finer droplets. Moreover, asymmetry in gas phase velocities affects the droplet velocity distribution more, only at low liquid Weber numbers for the input conditions chosen in the present study.

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

Phase and group velocity tracing analysis of projected wave packet motion along oblique radar beams – qualitative analysis of QP echoes

Directory of Open Access Journals (Sweden)

F. S. Kuo

2007-02-01

Full Text Available The wave packets of atmospheric gravity waves were numerically generated, with a given characteristic wave period, horizontal wave length and projection mean wind along the horizontal wave vector. Their projection phase and group velocities along the oblique radar beam (vpr and vgr, with different zenith angle θ and azimuth angle φ, were analyzed by the method of phase- and group-velocity tracing. The results were consistent with the theoretical calculations derived by the dispersion relation, reconfirming the accuracy of the method of analysis. The RTI plot of the numerical wave packets were similar to the striation patterns of the QP echoes from the FAI irregularity region. We propose that the striation range rate of the QP echo is equal to the radial phase velocity vpr, and the slope of the energy line across the neighboring striations is equal to the radial group velocity vgr of the wave packet; the horizontal distance between two neighboring striations is equal to the characteristic wave period τ. Then, one can inversely calculate all the properties of the gravity wave responsible for the appearance of the QP echoes. We found that the possibility of some QP echoes being generated by the gravity waves originated from lower altitudes cannot be ruled out.

Instrumentation for localized measurements in two-phase flow conditions

International Nuclear Information System (INIS)

Neff, G.G.; Averill, R.H.; Shurts, S.W.

1979-01-01

Three types of instrumentation that have been developed by EG and G Idaho, Inc., and its predecessor, Aerojet Nuclear company, at the Idaho National Engineering Laboratory to investigate two-phase flow phenomenon in a nuclear reactor at the Loss-of-Fluid Test (LOFT) facility are discussed: (a) a combination drag disc-turbine transducer (DTT), (b) a multibeam nuclear hardened gamma densitometer system, and (c) a conductivity sensitive liquid level transducer (LLT). The DTT obtains data on the complex problem of two-phase flow conditions in the LOFT primary coolant system during a loss-os-coolant experiment (LOCE). The discussion of the DTT describes how a turbine, measuring coolant velocity, and a drag disc, measuring coolant momentum flux, can provide valuable mass flow data. The nuclear hardened gamma densitometer is used to obtain density and flow regime information for two-phase flow in the LOFT primary coolant system during a LOCE. The LLT is used to measure water and steam conditions within the LOFT reactor core during a LOCE. The LLT design and the type of data obtained are described

Strongly coupled fluid-particle flows in vertical channels. I. Reynolds-averaged two-phase turbulence statistics

International Nuclear Information System (INIS)

Capecelatro, Jesse; Desjardins, Olivier; Fox, Rodney O.

2016-01-01

Simulations of strongly coupled (i.e., high-mass-loading) fluid-particle flows in vertical channels are performed with the purpose of understanding the fundamental physics of wall-bounded multiphase turbulence. The exact Reynolds-averaged (RA) equations for high-mass-loading suspensions are presented, and the unclosed terms that are retained in the context of fully developed channel flow are evaluated in an Eulerian–Lagrangian (EL) framework for the first time. A key distinction between the RA formulation presented in the current work and previous derivations of multiphase turbulence models is the partitioning of the particle velocity fluctuations into spatially correlated and uncorrelated components, used to define the components of the particle-phase turbulent kinetic energy (TKE) and granular temperature, respectively. The adaptive spatial filtering technique developed in our previous work for homogeneous flows [J. Capecelatro, O. Desjardins, and R. O. Fox, “Numerical study of collisional particle dynamics in cluster-induced turbulence,” J. Fluid Mech. 747, R2 (2014)] is shown to accurately partition the particle velocity fluctuations at all distances from the wall. Strong segregation in the components of granular energy is observed, with the largest values of particle-phase TKE associated with clusters falling near the channel wall, while maximum granular temperature is observed at the center of the channel. The anisotropy of the Reynolds stresses both near the wall and far away is found to be a crucial component for understanding the distribution of the particle-phase volume fraction. In Part II of this paper, results from the EL simulations are used to validate a multiphase Reynolds-stress turbulence model that correctly predicts the wall-normal distribution of the two-phase turbulence statistics.

Strongly coupled fluid-particle flows in vertical channels. I. Reynolds-averaged two-phase turbulence statistics

Science.gov (United States)

Capecelatro, Jesse; Desjardins, Olivier; Fox, Rodney O.

2016-03-01

Simulations of strongly coupled (i.e., high-mass-loading) fluid-particle flows in vertical channels are performed with the purpose of understanding the fundamental physics of wall-bounded multiphase turbulence. The exact Reynolds-averaged (RA) equations for high-mass-loading suspensions are presented, and the unclosed terms that are retained in the context of fully developed channel flow are evaluated in an Eulerian-Lagrangian (EL) framework for the first time. A key distinction between the RA formulation presented in the current work and previous derivations of multiphase turbulence models is the partitioning of the particle velocity fluctuations into spatially correlated and uncorrelated components, used to define the components of the particle-phase turbulent kinetic energy (TKE) and granular temperature, respectively. The adaptive spatial filtering technique developed in our previous work for homogeneous flows [J. Capecelatro, O. Desjardins, and R. O. Fox, "Numerical study of collisional particle dynamics in cluster-induced turbulence," J. Fluid Mech. 747, R2 (2014)] is shown to accurately partition the particle velocity fluctuations at all distances from the wall. Strong segregation in the components of granular energy is observed, with the largest values of particle-phase TKE associated with clusters falling near the channel wall, while maximum granular temperature is observed at the center of the channel. The anisotropy of the Reynolds stresses both near the wall and far away is found to be a crucial component for understanding the distribution of the particle-phase volume fraction. In Part II of this paper, results from the EL simulations are used to validate a multiphase Reynolds-stress turbulence model that correctly predicts the wall-normal distribution of the two-phase turbulence statistics.

An experimental study on two-phase pressure drop in small diameter horizontal, downward inclined and vertical tubes

Directory of Open Access Journals (Sweden)

Autee Arun

2015-01-01

Full Text Available An experimental study of two-phase pressure drop in small diameter tubes orientated horizontally, vertically and at two other downward inclinations of θ= 300 and θ = 600 is described in this paper. Acrylic transparent tubes of internal diameters 4.0, 6.0, and 8.0 mm with lengths of 400 mm were used as the test section. Air-water mixture was used as the working fluid. Two-phase pressure drop was measured and compared with the existing correlations. These correlations are commonly used for calculation of pressure drop in macro and mini-microchannels. It is observed that the existing correlations are inadequate in predicting the two-phase pressure drop in small diameter tubes. Based on the experimental data, a new correlation has been proposed for predicting the two-phase pressure drop. This correlation is developed by modification of Chisholm parameter C by incorporating different parameters. It was found that the proposed correlation predicted two-phase pressure drop at satisfactory level.

Development of nuclear thermal hydraulic verification tests and evaluation technology - Development of the ultrasonic method for two-phase mixture level measurement in nuclear reactor

Energy Technology Data Exchange (ETDEWEB)

No, Hee Cheon; Kim, Sang Jae; Kim, Hyung Tae; Moon, Young Min [Korea Advanced Institute of Science and Technology, Taejon (Korea)

2000-04-01

An ultrasonic method is developed for the measurement of the two-phase mixture level in the reactor vessel or steam generator. The ultrasonic method is selected among the several non-nuclear two-phase mixture level measurement methods through two steps of selection procedure. A commercial ultrasonic level measurement method is modified for application into the high temperature, pressure, and other conditions. The calculation method of the ultrasonic velocity is modified to consider the medium as the homogeneous mixture of air and steam, and to be applied into the high temperature and pressure conditions. The cross-correlation technique is adopted as a detection method to reduced the effects of the attenuation and the diffused reflection caused by surface fluctuation. The waveguides are developed to reduce the loss of echo and to remove the effects of obstructs. The present experimental study shows that the developed ultrasonic method measures the two-phase mixture level more accurately than the conventional methods do. 21 refs., 60 figs., 13 tabs. (Author)

Velocity landscape correlation resolves multiple flowing protein populations from fluorescence image time series.

Science.gov (United States)

Pandžić, Elvis; Abu-Arish, Asmahan; Whan, Renee M; Hanrahan, John W; Wiseman, Paul W

2018-02-16

Molecular, vesicular and organellar flows are of fundamental importance for the delivery of nutrients and essential components used in cellular functions such as motility and division. With recent advances in fluorescence/super-resolution microscopy modalities we can resolve the movements of these objects at higher spatio-temporal resolutions and with better sensitivity. Previously, spatio-temporal image correlation spectroscopy has been applied to map molecular flows by correlation analysis of fluorescence fluctuations in image series. However, an underlying assumption of this approach is that the sampled time windows contain one dominant flowing component. Although this was true for most of the cases analyzed earlier, in some situations two or more different flowing populations can be present in the same spatio-temporal window. We introduce an approach, termed velocity landscape correlation (VLC), which detects and extracts multiple flow components present in a sampled image region via an extension of the correlation analysis of fluorescence intensity fluctuations. First we demonstrate theoretically how this approach works, test the performance of the method with a range of computer simulated image series with varying flow dynamics. Finally we apply VLC to study variable fluxing of STIM1 proteins on microtubules connected to the plasma membrane of Cystic Fibrosis Bronchial Epithelial (CFBE) cells. Copyright © 2018 Elsevier Inc. All rights reserved.

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

Numerical approximation of a binary fluid-surfactant phase field model of two-phase incompressible flow

KAUST Repository

Zhu, Guangpu

2018-04-17

In this paper, we consider the numerical approximation of a binary fluid-surfactant phase field model of two-phase incompressible flow. The nonlinearly coupled model consists of two Cahn-Hilliard type equations and incompressible Navier-Stokes equations. Using the Invariant Energy Quadratization (IEQ) approach, the governing system is transformed into an equivalent form, which allows the nonlinear potentials to be treated efficiently and semi-explicitly. we construct a first and a second-order time marching schemes, which are extremely efficient and easy-to-implement, for the transformed governing system. At each time step, the schemes involve solving a sequence of linear elliptic equations, and computations of phase variables, velocity and pressure are totally decoupled. We further establish a rigorous proof of unconditional energy stability for the semi-implicit schemes. Numerical results in both two and three dimensions are obtained, which demonstrate that the proposed schemes are accurate, efficient and unconditionally energy stable. Using our schemes, we investigate the effect of surfactants on droplet deformation and collision under a shear flow. The increase of surfactant concentration can enhance droplet deformation and inhibit droplet coalescence.

Numerical approximation of a binary fluid-surfactant phase field model of two-phase incompressible flow

KAUST Repository

Zhu, Guangpu; Kou, Jisheng; Sun, Shuyu; Yao, Jun; Li, Aifen

2018-01-01

In this paper, we consider the numerical approximation of a binary fluid-surfactant phase field model of two-phase incompressible flow. The nonlinearly coupled model consists of two Cahn-Hilliard type equations and incompressible Navier-Stokes equations. Using the Invariant Energy Quadratization (IEQ) approach, the governing system is transformed into an equivalent form, which allows the nonlinear potentials to be treated efficiently and semi-explicitly. we construct a first and a second-order time marching schemes, which are extremely efficient and easy-to-implement, for the transformed governing system. At each time step, the schemes involve solving a sequence of linear elliptic equations, and computations of phase variables, velocity and pressure are totally decoupled. We further establish a rigorous proof of unconditional energy stability for the semi-implicit schemes. Numerical results in both two and three dimensions are obtained, which demonstrate that the proposed schemes are accurate, efficient and unconditionally energy stable. Using our schemes, we investigate the effect of surfactants on droplet deformation and collision under a shear flow. The increase of surfactant concentration can enhance droplet deformation and inhibit droplet coalescence.

Measurement of void fraction and bubble size distribution in two-phase flow system

International Nuclear Information System (INIS)

Huahun, G.

1987-01-01

The importance of study two phase flow parameter and microstructure has appeared increasingly, with the development of two-phase flow discipline. In the paper, the measurement methods of several important microstructure parameter in a two phase flow vertical channel have been studied. Using conductance probe the two phase flow pattern and the average void fraction have been measured previously by the authors. This paper concerns microstructure of the bubble size distribution and local void fraction. The authors studied the methods of measuring bubble velocity, size distribution and local void fraction using double conductance probes and a set of apparatus. Based on our experiments and Yoshihiro work, a formula of calculated local void fraction has been deduced by using the statistical characteristics of bubbles in two phase flow and the relation between calculated bubble size and voltage has been determined. Finally the authors checked by using photograph and fast valve, which is classical but reliable. The results are the same with what has been studied before

Complex network analysis of phase dynamics underlying oil-water two-phase flows

Science.gov (United States)

Gao, Zhong-Ke; Zhang, Shan-Shan; Cai, Qing; Yang, Yu-Xuan; Jin, Ning-De

2016-01-01

Characterizing the complicated flow behaviors arising from high water cut and low velocity oil-water flows is an important problem of significant challenge. We design a high-speed cycle motivation conductance sensor and carry out experiments for measuring the local flow information from different oil-in-water flow patterns. We first use multivariate time-frequency analysis to probe the typical features of three flow patterns from the perspective of energy and frequency. Then we infer complex networks from multi-channel measurements in terms of phase lag index, aiming to uncovering the phase dynamics governing the transition and evolution of different oil-in-water flow patterns. In particular, we employ spectral radius and weighted clustering coefficient entropy to characterize the derived unweighted and weighted networks and the results indicate that our approach yields quantitative insights into the phase dynamics underlying the high water cut and low velocity oil-water flows. PMID:27306101

Numerical analysis of gas-liquid two-phase flow in secondary side of steam generator

Energy Technology Data Exchange (ETDEWEB)

Murase, Michio; Nakamura, Akira; Yagi, Yoshinori [Inst. of Nuclear Safety System Inc., Mihama, Fukui (Japan)

2002-09-01

The steam generator (SG) in a pressurized water reactor (PWR) is an important two-phase flow component as the boundary between the primary loop and the secondary loop. In this study, we performed gas-liquid two-phase flow analyses for SG reliability tests conduced by Nuclear Power Engineering Corporation (NUPEC) using the two-fluid model of a thermal-hydraulic computer code PHOENICS. In order to calculate the location of the boiling initiation accurately, detailed inputs were required for the friction coefficients affecting the velocity distribution and the heat transfer distribution. However, the velocity and heat transfer distributions did not greatly affect the void fractions in the upper region of the heat transfer tubes. The calculated void fractions agreed with the measured values within 4% as the local average and within 2% as an average in a cross-section, except the region of low void fractions. (author)

A general correlation of MPPS penetration as a function of face velocity with the model 8140 using the certitest 8160

Energy Technology Data Exchange (ETDEWEB)

Lifshutz, N.; Pierce, M. [Hollingsworth & Vose Company, West Groton, MA (United States)

1997-08-01

The CertiTest 8160 is a Condensation Nucleus Counter (CNC) based filtration test stand which permits measurement of penetration as a function of particle size. The Model 8140 is also a CNC based filtration test stand which provides a single penetration measurement for a fixed particle distribution aerosol challenge. A study was carried out measuring DOP penetration on a broad range of flat filtration media at various face velocities to compare these two instruments. The tests done on the CertiTest 8160 incorporated a range of particle sizes which encompassed the most penetrating particle size (MPPS). In this paper we present a correlation between the MPPS penetration as measured by the CertiTest 8160 and the penetration values obtained on the Model 8140. We observed that at the lowest air face velocities of the study the Model 8140 tended to overpredict the MPPS penetration as measured by the CertiTest 8160. We also present a correlation of MPPS penetration with face velocity which may be of use for extrapolation purposes. 5 refs., 8 figs.

Selective two-photon excitation of a vibronic state by correlated photons.

Science.gov (United States)

Oka, Hisaki

2011-03-28

We theoretically investigate the two-photon excitation of a molecular vibronic state by correlated photons with energy anticorrelation. A Morse oscillator having three sets of vibronic states is used, as an example, to evaluate the selectivity and efficiency of two-photon excitation. We show that a vibrational mode can be selectively excited with high efficiency by the correlated photons, without phase manipulation or pulse-shaping techniques. This can be achieved by controlling the quantum correlation so that the photon pair concurrently has two pulse widths, namely, a temporally narrow width and a spectrally narrow width. Though this concurrence is seemingly contradictory, we can create such a photon pair by tailoring the quantum correlation between two photons.

Hydrodynamic characteristics of a two-phase gas-liquid flow upward through a fixed bed of spherical particles

Directory of Open Access Journals (Sweden)

VELIZAR D. STANKOVIC

2001-01-01

Full Text Available The influence of an electrochemically generated gas phase on the hydrodynamic characteristics of a three-phase system has been examined. The two-phase fluid, (gas-liquid, in which the liquid phase is the continuous one, flows through a packed bed with glass spheres. The influence of the liquid velocity was examined, as well as the gas velocity and particle diameter on the pressure drop through the fixed bed. It was found that with increasing liquid velocity (wl = 0.0162–0.03 m/s, the relative pressure drop decreases through the fixed bed. With increasing current density, the pressure drop increases, since greater gas quantities stay behind in the fixed bed. Besides, it was found that with decreasing diameter of the glass particles, the relative pressure drop also decreases. The relationship betweeen the experimentally obtained friction factor and the Reynolds number was established.

Seismic Velocity/Temperature Correlations and a Possible New Geothermometer: Insights from Exploration of a High-Temperature Geothermal System on Montserrat, West Indies

Directory of Open Access Journals (Sweden)

Graham Alexander Ryan

2014-10-01

Full Text Available In 2013, two production wells were drilled into a geothermal reservoir on Montserrat, W.I. (West Indies Drilling results confirmed the main features of a previously developed conceptual model. The results confirm that below ~220 °C there is a negative correlation between reservoir temperature and seismic velocity anomaly. However, above ~220 °C there is a positive correlation. We hypothesise that anomalous variations in seismic velocity within the reservoir are controlled to first order by the hydrothermal mineral assemblage. This study suggests a new geophysical thermometer which can be used to estimate temperatures in three dimensions with unprecedented resolution and to indicate the subsurface fluid pathways which are the target of geothermal exploitation.

Extended random-phase approximation with three-body ground-state correlations

International Nuclear Information System (INIS)

Tohyama, M.; Schuck, P.

2008-01-01

An extended random-phase approximation (ERPA) which contains the effects of ground-state correlations up to a three-body level is applied to an extended Lipkin model which contains an additional particle-scattering term. Three-body correlations in the ground state are necessary to preserve the hermiticity of the Hamiltonian matrix of ERPA. Two approximate forms of ERPA which neglect the three-body correlations are also applied to investigate the importance of three-body correlations. It is found that the ground-state energy is little affected by the inclusion of the three-body correlations. On the contrary, three-body correlations for the excited states can become quite important. (orig.)

Fluid dynamics of airlift reactors; Two-phase friction factors

Energy Technology Data Exchange (ETDEWEB)

Garcia-Calvo, E. (Ingenieria Quimica, Facultad de Ciencias, Univ. de Alcala, 28871 Alcala de Henares (Spain))

1992-10-01

Airlift loop reactors (ALR) are useful equipment in biotechnology in a wide range of uses, however their design is not a simple task since prediction of fluid dynamics in these reactors is difficult. Most of the different strategies found in the literature in order to predict two main parameters, namely, gas holdup and liquid velocity, are based on energy or momentum balances. The balances include frictional effects, and it is not yet clear how to predict these effects. The objective of this article is to show how criteria corresponding to one-phase flow may be used in order to predict the frictional effects in ALRs. Based on a model proposed by Garcia-Calvo (1989, 1991), we simulated experimental data of liquid velocity profiles and gas holdup obtained by Young et al. in an ALR with two different configurations. Experimental data obtained in other three external ALRs with different shapes and sizes are also simulated.

Two-point density correlations of quasicondensates in free expansion

DEFF Research Database (Denmark)

Manz, S.; Bücker, R.; Betz, T.

2010-01-01

We measure the two-point density correlation function of freely expanding quasicondensates in the weakly interacting quasi-one-dimensional (1D) regime. While initially suppressed in the trap, density fluctuations emerge gradually during expansion as a result of initial phase fluctuations present...... in the trapped quasicondensate. Asymptotically, they are governed by the thermal coherence length of the system. Our measurements take place in an intermediate regime where density correlations are related to near-field diffraction effects and anomalous correlations play an important role. Comparison...

Evaluation of correlation between physical properties and ultrasonic pulse velocity of fired clay samples.

Science.gov (United States)

Özkan, İlker; Yayla, Zeliha

2016-03-01

The aim of this study is to establish a correlation between physical properties and ultrasonic pulse velocity of clay samples fired at elevated temperatures. Brick-making clay and pottery clay were studied for this purpose. The physical properties of clay samples were assessed after firing pressed clay samples separately at temperatures of 850, 900, 950, 1000, 1050 and 1100 °C. A commercial ultrasonic testing instrument (Proceq Pundit Lab) was used to evaluate the ultrasonic pulse velocity measurements for each fired clay sample as a function of temperature. It was observed that there became a relationship between physical properties and ultrasonic pulse velocities of the samples. The results showed that in consequence of increasing densification of the samples, the differences between the ultrasonic pulse velocities were higher with increasing temperature. These findings may facilitate the use of ultrasonic pulse velocity for the estimation of physical properties of fired clay samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of a Laser Dopper Anemometer technique for the measurement of two phase dispersed flow

International Nuclear Information System (INIS)

Srinivasan, J.

1978-05-01

A new optical technique using Laser-Doppler Anemometry is presented for the measurement of the local number densities and two-dimensional velocity probability densities of a turbulent dilute two-phase dispersion which has a distribution of particle size and a predominant direction of flow. This technique establishes that by a suitable scheme of discrimination on the signal amplitude, residence time and frequency of the Doppler signals caused by the scattered light from individual particles in the probing volume, the size distribution of moderately large particles in a dilute dispersed flow can be determined. The newly developed Laser-Doppler Anemometer (LDA) technique was applied to a solid particle-water two-phase flow and a water droplet-air two-phase flow. Particular emphasis was placed on turbulent two-phase water droplet-air flow inside a vertical rectangular channel. At each of nine different measuring locations along the transverse axis (starting at 250μ from the channel wall), over 20,000 Doppler signals were individually examined. The particle size and number density distributions, and the axial and lateral velocity distributions of both phases are reported. The analysis reveals some interesting features of two-phase dispersed flow. A film of water on the channel wall was formed due to the deposition of droplets from the flow. The water droplet entrainment from the wall film and the subsequent breakup of some of these into the flow are discussed. A discussion of the relationship between the particle distributions and turbulent flow characteristics is presented

Picosecond phase-velocity dispersion of hypersonic phonons imaged with ultrafast electron microscopy

International Nuclear Information System (INIS)

Cremons, Daniel R.; Du, Daniel X.; Flannigan, David J.

2017-01-01

We describe the direct imaging—with four-dimensional ultrafast electron microscopy—of the emergence, evolution, dispersion, and decay of photoexcited, hypersonic coherent acoustic phonons in nanoscale germanium wedges. Coherent strain waves generated via ultrafast in situ photoexcitation were imaged propagating with initial phase velocities of up to 35 km/s across discrete micrometer-scale crystal regions. We then observe that, while each wave front travels at a constant velocity, the entire wave train evolves with a time-varying phase-velocity dispersion, displaying a single-exponential decay to the longitudinal speed of sound (5 km/s) and with a mean lifetime of 280 ps. We also find that the wave trains propagate along a single in-plane direction oriented parallel to striations introduced during specimen preparation, independent of crystallographic direction. Elastic-plate modeling indicates the dynamics arise from excitation of a single, symmetric (dilatational) guided acoustic mode. Further, by precisely determining the experiment time-zero position with a plasma-lensing method, we find that wave-front emergence occurs approximately 100 ps after femtosecond photoexcitation, which matches well with Auger recombination times in germanium. We conclude by discussing the similarities between the imaged hypersonic strain-wave dynamics and electron/hole plasma-wave dynamics in strongly photoexcited semiconductors.

Picosecond phase-velocity dispersion of hypersonic phonons imaged with ultrafast electron microscopy

Science.gov (United States)

Cremons, Daniel R.; Du, Daniel X.; Flannigan, David J.

2017-12-01

Here, we describe the direct imaging—with four-dimensional ultrafast electron microscopy—of the emergence, evolution, dispersion, and decay of photoexcited, hypersonic coherent acoustic phonons in nanoscale germanium wedges. Coherent strain waves generated via ultrafast in situ photoexcitation were imaged propagating with initial phase velocities of up to 35 km/s across discrete micrometer-scale crystal regions. We observe that, while each wave front travels at a constant velocity, the entire wave train evolves with a time-varying phase-velocity dispersion, displaying a single-exponential decay to the longitudinal speed of sound (5 km/s) and with a mean lifetime of 280 ps. We also find that the wave trains propagate along a single in-plane direction oriented parallel to striations introduced during specimen preparation, independent of crystallographic direction. Elastic-plate modeling indicates the dynamics arise from excitation of a single, symmetric (dilatational) guided acoustic mode. Further, by precisely determining the experiment time-zero position with a plasma-lensing method, we find that wave-front emergence occurs approximately 100 ps after femtosecond photoexcitation, which matches well with Auger recombination times in germanium. We conclude by discussing the similarities between the imaged hypersonic strain-wave dynamics and electron/hole plasma-wave dynamics in strongly photoexcited semiconductors.

Cardiac magnetic resonance: is phonocardiogram gating reliable in velocity-encoded phase contrast imaging?

International Nuclear Information System (INIS)

Nassenstein, Kai; Schlosser, Thomas; Orzada, Stephan; Ladd, Mark E.; Maderwald, Stefan; Haering, Lars; Czylwik, Andreas; Jensen, Christoph; Bruder, Oliver

2012-01-01

To assess the diagnostic accuracy of phonocardiogram (PCG) gated velocity-encoded phase contrast magnetic resonance imaging (MRI). Flow quantification above the aortic valve was performed in 68 patients by acquiring a retrospectively PCG- and a retrospectively ECG-gated velocity-encoded GE-sequence at 1.5 T. Peak velocity (PV), average velocity (AV), forward volume (FV), reverse volume (RV), net forward volume (NFV), as well as the regurgitant fraction (RF) were assessed for both datasets, as well as for the PCG-gated datasets after compensation for the PCG trigger delay. PCG-gated image acquisition was feasible in 64 patients, ECG-gated in all patients. PCG-gated flow quantification overestimated PV (Δ 3.8 ± 14.1 cm/s; P = 0.037) and underestimated FV (Δ -4.9 ± 15.7 ml; P = 0.015) and NFV (Δ -4.5 ± 16.5 ml; P = 0.033) compared with ECG-gated imaging. After compensation for the PCG trigger delay, differences were only observed for PV (Δ 3.8 ± 14.1 cm/s; P = 0.037). Wide limits of agreement between PCG- and ECG-gated flow quantification were observed for all variables (PV: -23.9 to 31.4 cm/s; AV: -4.5 to 3.9 cm/s; FV: -35.6 to 25.9 ml; RV: -8.0 to 7.2 ml; NFV: -36.8 to 27.8 ml; RF: -10.4 to 10.2 %). The present study demonstrates that PCG gating in its current form is not reliable enough for flow quantification based on velocity-encoded phase contrast gradient echo (GE) sequences. (orig.)

Flow regime, void fraction and interfacial area transport and characteristics of co-current downward two-phase flow

Energy Technology Data Exchange (ETDEWEB)

Lokanathan, Manojkumar [School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907-2088 (United States); Hibiki, Takashi [School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, IN 47907-2017 (United States)

2016-10-15

are studied. Moreover, the interfacial area concentration and the bubble coalescence and breakup mechanisms are shown to vary in the axial direction as well as with flow rate, flow area and pressure drop. The liquid velocity field, bubble shape and shear stress are studied for a stationary slug bubble with downward liquid flow. Furthermore, the relationship between the plug and foam flow shape profiles, relative velocity, void fraction and gas slug velocity at an elevated pressure of 0.2 MPa studied by Sekoguchi et al. (1996) are also analyzed, together with the five plug flow sub-regime groups located in the low slip and high slip velocity regions. For the annular flow, the relationship between liquid film thickness, entrainment mechanisms, film velocity and shear stress are studied as well. Alike to plug flow, five sub-regimes in the annular flow are also examined along with the bubble and droplet entrainment mechanisms. The paper also discusses the pressure drop for bubbly, slug, foam, falling film and annular flow regimes, with a particular focus on the most accurate interfacial friction factor correlation for annular flow and its applicability for a wide range of pipe diameters. The flow instability of a system such as static and dynamic instability in the presence of a downcomer, for both single and parallel heated channels are examined too. Finally, the most accurate and versatile drift-flux correlation applicable to all downward flow regimes is highlighted and compared to drift-flux type correlations as it will be a stepping stone to attain a more accurate co-current downward flow transition model. Further experimental effort is essential to achieve a strong foothold in the understanding of co-current downward two-phase flow, as it is vital for nuclear engineering applications.

CSF flow: Correlation between signal void and CSF velocity measured by gated velocity phase-encoded MR imaging

International Nuclear Information System (INIS)

Mark, A.S.; Feinberg, D.A.

1986-01-01

The direction of the cerebrospinal fluid (CSF) flow in the foramen of Monro (FOM) and aqueduct was determined in 15 normal volunteers (5 of whom had also been studied with gated spin-echo sequences) using a cardiac-gated Fourier transform velocity imaging technique (VMR). The VMR showed that the periodic pattern of flow void seen in the aqueduct and FOM on the gated spin-echo images was due to antegrade CSF flow from the lateral ventricles into the third ventricle and aqueduct during systole and retrograde flow from the aqueduct into the third ventricle and lateral ventricles during late diastole. These findings could not be explained if the CSF pulsations originated in the third ventricle, as had been previously proposed, and suggest the lateral ventricles play an important role in the pulsatile motion of CSF

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.

Velocity correlations and spatial dependencies between neighbors in a unidirectional flow of pedestrians

Science.gov (United States)

Porzycki, Jakub; WÄ s, Jarosław; Hedayatifar, Leila; Hassanibesheli, Forough; Kułakowski, Krzysztof

2017-08-01

The aim of the paper is an analysis of self-organization patterns observed in the unidirectional flow of pedestrians. On the basis of experimental data from Zhang et al. [J. Zhang et al., J. Stat. Mech. (2011) P06004, 10.1088/1742-5468/2011/06/P06004], we analyze the mutual positions and velocity correlations between pedestrians when walking along a corridor. The angular and spatial dependencies of the mutual positions reveal a spatial structure that remains stable during the crowd motion. This structure differs depending on the value of n , for the consecutive n th -nearest-neighbor position set. The preferred position for the first-nearest neighbor is on the side of the pedestrian, while for further neighbors, this preference shifts to the axis of movement. The velocity correlations vary with the angle formed by the pair of neighboring pedestrians and the direction of motion and with the time delay between pedestrians' movements. The delay dependence of the correlations shows characteristic oscillations, produced by the velocity oscillations when striding; however, a filtering of the main frequency of individual striding out reduces the oscillations only partially. We conclude that pedestrians select their path directions so as to evade the necessity of continuously adjusting their speed to their neighbors'. They try to keep a given distance, but follow the person in front of them, as well as accepting and observing pedestrians on their sides. Additionally, we show an empirical example that illustrates the shape of a pedestrian's personal space during movement.

Two-dimensional, average velocity field across the Asal Rift, Djibouti from 1997-2008 RADARSAT data

Science.gov (United States)

Tomic, J.; Doubre, C.; Peltzer, G.

2009-12-01

Located at the western end of the Aden ridge, the Asal Rift is the first emerged section of the ridge propagating into Afar, a region of intense volcanic and tectonic activity. We construct a two-dimensional surface velocity map of the 200x400 km2 region covering the rift using the 1997-2008 archive of InSAR data acquired from ascending and descending passes of the RADARSAT satellite. The large phase signal due to turbulent troposphere conditions over the Afar region is mostly removed from the 11-year average line of sight (LOS) velocity maps, revealing a clear deformation signal across the rift. We combine the ascending and descending pass LOS velocity fields with the Arabia-Somalia pole of rotation adjusted to regional GPS velocities (Vigny et al., 2007) to compute the fields of the vertical and horizontal, GPS-parallel components of the velocity over the rift. The vertical velocity field shows a ~40 km wide zone of doming centered over the Fieale caldera associated with shoulder uplift and subsidence of the rift inner floor. Differential movement between shoulders and floor is accommodated by creep at 6 mm/yr on Fault γ and 2.7 mm/yr on Fault E. The horizontal field shows that the two shoulders open at a rate of ~15 mm/yr, while the horizontal velocity decreases away from the rift to the plate motion rate of ~11 mm/yr. Part of the opening is concentrated on faults γ (5 mm/yr) and E (4 mm/yr) and about 4 mm/yr is distributed between Fault E and Fault H in the southern part of the rift. The observed velocity field along a 60 km-long profile across the eastern part of the rift can be explained with a 2D mechanical model involving a 5-9 km-deep, vertical dyke expanding horizontally at a rate of 5 cm/yr, a 2 km-wide, 7 km-deep sill expanding vertically at 1cm/yr, and down-dip and opening of faults γ and E. Results from 3D rift models describing along-strike velocity decrease away from the Goubbet Gulf and the effects of a pressurized magma chamber will be

Two-phase air-solid stationary turbulent flow in a cylindrical tube, with a high massive concentration

International Nuclear Information System (INIS)

Fortier, Andre; Chen, Che Pen

1976-01-01

The momentum theorem, applied separately to the two phases (fluid and solid particles), together with the equations of continuity, gives two differential equations by which the pressure and the concentration along the longitudinal profile x can be computed. These equations can be obtained by introduction of several averaging procedures of physical significance. These quantities are defined in a simple manner for the general case. Using experimental measurements of solid particle velocities in a horizontal tube by radio-tracers, it is shown how to determine the three average coefficients: Λsub(g) friction coefficient of gas, Λsub(s) momentum loss coefficient of solid particles by impacts, against the wall, and Csub(D) drag coefficient due to the velocity difference between the two phases. This determination is based on the numerical solution of the two differential equations conveniently simplified [fr

Settling velocities in batch sedimentation