Measurement of gas flow velocities by laser-induced gratings

Energy Technology Data Exchange (ETDEWEB)

Hemmerling, B; Stampanoni-Panariello, A [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Kozlov, A D.N. [General Physics Institute, Moscow (Russian Federation)

1999-08-01

Time resolved light scattering from laser-induced electrostrictive gratings was used for the determination of flow velocities in air at room temperature. By measuring the velocity profile across the width of a slit nozzle we demonstrated the high spatial resolution (about 200 mm) of this novel technique. (author) 3 figs., 1 ref.

Gas transfer in a bubbly wake flow

Science.gov (United States)

Karn, A.; Gulliver, J. S.; Monson, G. M.; Ellis, C.; Arndt, R. E. A.; Hong, J.

2016-05-01

The present work reports simultaneous bubble size and gas transfer measurements in a bubbly wake flow of a hydrofoil, designed to be similar to a hydroturbine blade. Bubble size was measured by a shadow imaging technique and found to have a Sauter mean diameter of 0.9 mm for a reference case. A lower gas flow rate, greater liquid velocities, and a larger angle of attack all resulted in an increased number of small size bubbles and a reduced weighted mean bubble size. Bubble-water gas transfer is measured by the disturbed equilibrium technique. The gas transfer model of Azbel (1981) is utilized to characterize the liquid film coefficient for gas transfer, with one scaling coefficient to reflect the fact that characteristic turbulent velocity is replaced by cross-sectional mean velocity. The coefficient was found to stay constant at a particular hydrofoil configuration while it varied within a narrow range of 0.52-0.60 for different gas/water flow conditions.

Effects space velocity and gas velocity on DeNOx catalyst with HC reductant; HC tenka NOx kangen shokubai no kukan sokudo oyobi gas ryusoku no eikyo

Energy Technology Data Exchange (ETDEWEB)

Niimura, K.; Tsujimura, K.

1995-04-20

Discussions were given on the hydrocarbon added reduction catalyst method to reduce NOx in diesel engine exhaust gas. An experiment was carried out with actual exhaust gas from a diesel engine by using a copper ion exchanged zeolite catalyst that has been coated on a honeycomb type substrate, and using propylene as a reductant. When the catalyst volume was changed with the exhaust gas space velocity kept constant, the NOx conversion ratio decreased as the catalyst length is decreased, and the activity shifted to the lower temperature side. The NOx reduction efficiency increased if the faster the gas flow velocity. On the other hand, if the gas flow velocity is slow, the NOx reduction can be carried out with relatively small amount of the reductant. When the catalyst volume was changed with the passing gas amount kept constant, the NOx conversion ratio decreased largely if the catalyst length is decreased. Further, the NOx reduction characteristics shift to the higher temperature side. In the catalyst length direction, the NOx reduction activity shows a relatively uniform action. However, a detailed observation reveals that the reaction heat in the catalyst is transmitted to the wake improving the activity, hence the further down the flow, the NOx conversion ratio gets higher in efficiency. 5 refs., 5 figs., 3 tabs.

A New Approach for Accurate Prediction of Liquid Loading of Directional Gas Wells in Transition Flow or Turbulent Flow

Directory of Open Access Journals (Sweden)

Ruiqing Ming

2017-01-01

Full Text Available Current common models for calculating continuous liquid-carrying critical gas velocity are established based on vertical wells and laminar flow without considering the influence of deviation angle and Reynolds number on liquid-carrying. With the increase of the directional well in transition flow or turbulent flow, the current common models cannot accurately predict the critical gas velocity of these wells. So we built a new model to predict continuous liquid-carrying critical gas velocity for directional well in transition flow or turbulent flow. It is shown from sensitivity analysis that the correction coefficient is mainly influenced by Reynolds number and deviation angle. With the increase of Reynolds number, the critical liquid-carrying gas velocity increases first and then decreases. And with the increase of deviation angle, the critical liquid-carrying gas velocity gradually decreases. It is indicated from the case calculation analysis that the calculation error of this new model is less than 10%, where accuracy is much higher than those of current common models. It is demonstrated that the continuous liquid-carrying critical gas velocity of directional well in transition flow or turbulent flow can be predicted accurately by using this new model.

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)

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

International Nuclear Information System (INIS)

Nakamura, D.

2005-01-01

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

Velocity slip and translational nonequilibrium of ternary gas mixtures in free jet expansions

International Nuclear Information System (INIS)

Cattolica, R.J.; Gallagher, R.J.; Anderson, J.B.; Talbot, L.

1977-05-01

An aerodynamic isotope separation technique based on the velocity slip between gases in a rarefied flow has been proposed. To evaluate the efficiency of this separation technique, the velocity and translational temperature of the individual species in binary and ternary gas mixtures of argon and neon in helium have been studied in a low density hypersonic free jet. The velocity and temperature of the gas were determined from the Doppler shift and broadening of the fluorescence excited by an electron beam. Velocity slip and translational nonequilibrium were observed over a range of source pressures. A separation factor based on the velocity slip and temperatures was also determined. A comparison of the velocity slip, temperatures, and separation factor with the results of a Monte Carlo simulation of the flow field is presented

Correlations of drift velocity for gas-liquid two-phase flow in rod bundle

International Nuclear Information System (INIS)

Kataoka, Isao; Matsuura, Keizo; Serizawa, Akimi

2004-01-01

A new correlation was developed for the drift velocity for low inlet liquid flux in rod bundle. Based on authors' previous analysis of drift velocity for large diameter pipe, an analysis was made on the drift velocity in rod bundle. It is assumed that the large bubble of which size is several subchannel diameter behaves as slug bubble. Under this assumption, it becomes very important how to define equivalent diameter for rod bundle. In view of physical consideration of slug bubble behavior and previous analysis, an equivalent diameter based on the wetted perimeter was found to be most appropriate. Using this equivalent diameter, experimental data of drift velocity in rod bundle were correlated with dimensional analysis. It was found out that for small diameter (dimensionless diameter less than 48) drift velocity increased with square root of diameter which is same dependency of ordinary slug flow correlation. For larger diameter (dimensionless diameter is more than 48), drift velocity is almost constant and same as that of dimensionless diameter of 48. The physical meaning of this result was considered to be the instability of interface of large slug bubble. The density ratio between gas and liquid and viscosity of liquid phase were found to be the main parameters which affect the drift velocity. This is physically reasonable because density ratio is related to the buoyancy force and liquid viscosity is related to shear force near solid wall. The experimental data were correlated by density ratio and dimensionless liquid viscosity. The obtained dimensionless correlation for the drift velocity in rod bundle successfully correlated experimental data for various rod bundles (equivalent diameters), pressures, liquid fluxes etc. It is also consistent with the drift flux correlation for round tube. (author)

Video imaging measurement of interfacial wave velocity in air-water flow through a horizontal elbow

Science.gov (United States)

Al-Wazzan, Amir; Than, Cheok F.; Moghavvemi, Mahmoud; Yew, Chia W.

2001-10-01

Two-phase flow in pipelines containing elbows represents a common situation in the oil and gas industries. This study deals with the stratified flow regime between the gas and liquid phase through an elbow. It is of interest to study the change in wave characteristics by measuring the wave velocity and wavelength at the inlet and outlet of the elbow. The experiments were performed under concurrent air-water stratified flow in a horizontal transparent polycarbonate pipe of 0.05m diameter and superficial air and water velocities up to 8.97 and 0.0778 m/s respectively. A non-intrusive video imaging technique was applied to capture the waves. For image analysis, a frame by frame direct overlapping method was used to detect for pulsating flow and a pixel shifting method based on the detection of minimum values in the overlap function was used to determine wave velocity and wavelength. Under superficial gas velocity of less than 4.44 m/s, the results suggest a regular pulsating outflow produced by the elbow. At higher gas velocities, more random pulsation was found and the emergence of localized interfacial waves was detected. Wave velocities measured by this technique were found to produce satisfactory agreement with direct measurements.

Development of acoustic flow instruments for solid/gas pipe flows

International Nuclear Information System (INIS)

Sheen, S.H.; Raptis, A.C.

1986-05-01

Two nonintrusive acoustic flow sensing techniques are reported. One technique, passive in nature, simply measures the bandpassed acoustic noise level produced by particle/particle and particle/wall collisions. The noise levels, given in true RMS voltages or in autocorrelations, show a linear relationship to particle velocity but increase with solid concentration. Therefore, the passive technique requires calibration and a separate measure of solid concentration before it can be used to monitor the particle velocity. The second technique is based on the active cross-correlation principle. It measures particle velocity directly by correlating flow-related signatures at two sensing stations. The velocity data obtained by this technique are compared with measurements by a radioactive-particle time-of-flight (TOF) method. A multiplier of 1.53 is required to bring the acoustic data into agreement with the radioactive TOF result. The difference may originate from the difference in flow fields where particles are detected. The radioactive method senses particles mainly in the turbulent region and essentially measures average particle velocity across the pipe, while the acoustic technique detects particles near the pipe wall, and so measures the particle velocity in the viscous sublayer. Both techniques were tested in flows of limestone and air and 1-mm glass beads and air at the Argonne National Laboratory Solid/Gas Test Facility (SGFTF). The test matrix covered solid velocities of 20 to 30 m/s in a 2-in. pipe and solid-to-gas loading ratios of 6 to 22. 37 refs., 19 figs., 4 tabs

Investigation of the Flow Rate Effect Upstream of the Constant-Geometry Throttle on the Gas Mass Flow

Directory of Open Access Journals (Sweden)

Yu. M. Timofeev

2016-01-01

Full Text Available The turbulent-flow throttles are used in pneumatic systems and gas-supply ones to restrict or measure gas mass flow. It is customary to install the throttles in joints of pipelines (in teejoints and cross tees or in joints of pipelines with pneumatic automation devices Presently, in designing the pneumatic systems and gas-supply ones a gas mass flow through a throttle is calculated by a known equation derived from the Saint-Venant-Vantсel formula for the adiabatic flow of ideal gas through a nozzle from an unrestrictedly high capacity tank. Neglect of gas velocity at the throttle inlet is one of the assumptions taken in the development of the above equation. As may be seen in practice, in actual systems the diameters of the throttle and the pipe wherein it is mounted can be commensurable. Neglect of the inlet velocity therewith can result in an error when determining the required throttle diameter in design calculation and a flow rate in checking calculation, as well as when measuring a flow rate in the course of the test. The theoretical study has revealed that the flow velocity at the throttle inlet is responsible for two parameter values: the outlet flow velocity and the critical pressure ratio, which in turn determine the gas mass flow value. To calculate the gas mass flow, the dependencies are given in the paper, which allow taking into account the flow rate at the throttle inlet. The analysis of obtained dependencies has revealed that the degree of influence of inlet flow rate upon the mass flow is defined by two parameters: pressure ratio at the throttle and open area ratio of the throttle and the pipe wherein it is mounted. An analytical investigation has been pursued to evaluate the extent to which the gas mass flow through the throttle is affected by the inlet flow rate. The findings of the investigation and the indications for using the present dependencies are given in this paper. By and large the investigation allowed the

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

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Kreta Aleksei

2016-01-01

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

Method and system for gas flow mitigation of molecular contamination of optics

Science.gov (United States)

Delgado, Gildardo; Johnson, Terry; Arienti, Marco; Harb, Salam; Klebanoff, Lennie; Garcia, Rudy; Tahmassebpur, Mohammed; Scott, Sarah

2018-01-23

A computer-implemented method for determining an optimized purge gas flow in a semi-conductor inspection metrology or lithography apparatus, comprising receiving a permissible contaminant mole fraction, a contaminant outgassing flow rate associated with a contaminant, a contaminant mass diffusivity, an outgassing surface length, a pressure, a temperature, a channel height, and a molecular weight of a purge gas, calculating a flow factor based on the permissible contaminant mole fraction, the contaminant outgassing flow rate, the channel height, and the outgassing surface length, comparing the flow factor to a predefined maximum flow factor value, calculating a minimum purge gas velocity and a purge gas mass flow rate from the flow factor, the contaminant mass diffusivity, the pressure, the temperature, and the molecular weight of the purge gas, and introducing the purge gas into the semi-conductor inspection metrology or lithography apparatus with the minimum purge gas velocity and the purge gas flow rate.

Rarefied gas flow simulations using high-order gas-kinetic unified algorithms for Boltzmann model equations

Science.gov (United States)

Li, Zhi-Hui; Peng, Ao-Ping; Zhang, Han-Xin; Yang, Jaw-Yen

2015-04-01

This article reviews rarefied gas flow computations based on nonlinear model Boltzmann equations using deterministic high-order gas-kinetic unified algorithms (GKUA) in phase space. The nonlinear Boltzmann model equations considered include the BGK model, the Shakhov model, the Ellipsoidal Statistical model and the Morse model. Several high-order gas-kinetic unified algorithms, which combine the discrete velocity ordinate method in velocity space and the compact high-order finite-difference schemes in physical space, are developed. The parallel strategies implemented with the accompanying algorithms are of equal importance. Accurate computations of rarefied gas flow problems using various kinetic models over wide ranges of Mach numbers 1.2-20 and Knudsen numbers 0.0001-5 are reported. The effects of different high resolution schemes on the flow resolution under the same discrete velocity ordinate method are studied. A conservative discrete velocity ordinate method to ensure the kinetic compatibility condition is also implemented. The present algorithms are tested for the one-dimensional unsteady shock-tube problems with various Knudsen numbers, the steady normal shock wave structures for different Mach numbers, the two-dimensional flows past a circular cylinder and a NACA 0012 airfoil to verify the present methodology and to simulate gas transport phenomena covering various flow regimes. Illustrations of large scale parallel computations of three-dimensional hypersonic rarefied flows over the reusable sphere-cone satellite and the re-entry spacecraft using almost the largest computer systems available in China are also reported. The present computed results are compared with the theoretical prediction from gas dynamics, related DSMC results, slip N-S solutions and experimental data, and good agreement can be found. The numerical experience indicates that although the direct model Boltzmann equation solver in phase space can be computationally expensive

Velocity slip of gas mixtures in free jet expansions

International Nuclear Information System (INIS)

Cattolica, R.J.; Talbot, L.; Coe, D.

1976-11-01

Velocity slip in gas mixtures of argon and helium in axisymmetric free jet expansions has been measured using a grating monochromator together with a computer-controlled Fabry-Perot interferometer to observe the fluorescence excited by an electron beam. The Doppler shift between the fluorescence observed parallel and perpendicular to the centerline of the free jet was used to measure the mean velocity of a particular species along the jet centerline, employing the 4880 A line for argon and the 5016 A line for helium. By alternately tracking the parallel and perpendicular fluorescence, the Doppler shift due to the mean velocity was measured directly with an accuracy of 1 percent. Flow field surveys have been made in the initial acceleration region where the flow becomes hypersonic and in the far field region. The differences between argon and helium mean velocities (velocity slip) are in good agreement with molecular beam data and show a correlation with an inverse Knudsen number

Drift-flux parameters for upward gas flow in stagnant liquid

International Nuclear Information System (INIS)

Kataoka, Yoshiyuki; Suzuki, Hiroaki; Murase, Michio

1987-01-01

The drift-flux model is widely used for gas-liquid two phase flow analysis, because it is applicable to various flow patterns and a wide range of void fractions. The drift-flux parameters for upward gas flow in stagnant liquid, however, have not been well examined. In this study, the distribution parameter C o and the drift velocity V gj for stagnant liquid were derived from the void fraction correlation and boundary conditions of drift-flux parameters, and then compared with C o and V gj for high liquid velocities. Also using the two region model where a circular flow area was divided into an inner region of cocurrent up-flow and an outer annulus region of liquid down flow, C o and V gj for stagnant liquid and for high liquid velocity were compared. The results showed that C o values for stagnant liquid were larger than values for high liquid velocity, while V gj values were almost the same for both cases. (author)

Dryout characteristics and flow behavior of gas-water two-phase flow through U-shaped and inverted U-shaped bends

International Nuclear Information System (INIS)

Takemura, T.; Roko, K.; Shiraha, M.; Midoriyama, S.

1986-01-01

Experimental results are presented on the flow behavior, pressure drop characteristics, and dryout characteristics by joule heating for the gas-water flow through U-shaped and inverted U-shaped tubes invertical plane. The height of the vertical straight section of the test tube is 4100 mm, and two bend radii, 116 mm and 435 mm, are chosen for the experiments. The test tubes used are of transparent acrylic resin for the flow behavior test, and of stainless steel for the other tests, inside diameter being 18 mm for the former and 18.5 mm for the latter. Flow patterns in the vertical upflow and downflow sections are shown on the diagram of the superficial gas velocity versus liquid velocity. Further, the flow behavior in the bend section is made clear in relation to flow rates of gas and liquid. The pressure drop between inlet and outlet of the test tube for the made clear in relation to flow rates of gas and liquid. The pressure drop between inlet and outlet of the test tube for the two-phase flow is shown in comparison with that for the single-phase flow of water. The threshold conditions of dryout in the bend section by joule heatig are shown on the diagram of the superficial gas velocity versus liquid velocity. The location of the dryout in the bend section is also clarified. (orig.)

Experimental Study of gas-liquid two-phase flow affected by wall surface wettability

International Nuclear Information System (INIS)

Takamasa, T.; Hazuku, T.; Hibiki, T.

2008-01-01

To evaluate the effect of wall surface wettability on the characteristics of upward gas-liquid two-phase flow in a vertical pipe, an experimental study was performed using three test pipes: an acrylic pipe, a hydrophilic pipe and a hydrophobic pipe. Basic flow characteristics such as flow patterns, pressure drop and void fraction were measured in these three pipes. In the hydrophilic pipe, a slug to churn flow transition boundary was shifted to a higher gas velocity at a given liquid velocity, whereas a churn to annular flow transition boundary was shifted to a lower gas velocity at a given liquid velocity. In the hydrophobic pipe, an inverted-churn flow regime was observed in the region where the churn flow regime was observed in the acrylic pipe, while a droplet flow regime was observed in the region where an annular flow regime was observed in the acrylic pipe. At a high gas flow rate, the mean void fraction in the hydrophobic pipe was higher than in the acrylic pipe. The effect of surface wettability on frictional pressure loss was confirmed to be insignificant under the present experimental conditions

Imaging water velocity and volume fraction distributions in water continuous multiphase flows using inductive flow tomography and electrical resistance tomography

Science.gov (United States)

Meng, Yiqing; Lucas, Gary P.

2017-05-01

This paper presents the design and implementation of an inductive flow tomography (IFT) system, employing a multi-electrode electromagnetic flow meter (EMFM) and novel reconstruction techniques, for measuring the local water velocity distribution in water continuous single and multiphase flows. A series of experiments were carried out in vertical-upward and upward-inclined single phase water flows and ‘water continuous’ gas-water and oil-gas-water flows in which the velocity profiles ranged from axisymmetric (single phase and vertical-upward multiphase flows) to highly asymmetric (upward-inclined multiphase flows). Using potential difference measurements obtained from the electrode array of the EMFM, local axial velocity distributions of the continuous water phase were reconstructed using two different IFT reconstruction algorithms denoted RT#1, which assumes that the overall water velocity profile comprises the sum of a series of polynomial velocity components, and RT#2, which is similar to RT#1 but which assumes that the zero’th order velocity component may be replaced by an axisymmetric ‘power law’ velocity distribution. During each experiment, measurement of the local water volume fraction distribution was also made using the well-established technique of electrical resistance tomography (ERT). By integrating the product of the local axial water velocity and the local water volume fraction in the cross section an estimate of the water volumetric flow rate was made which was compared with a reference measurement of the water volumetric flow rate. In vertical upward flows RT#2 was found to give rise to water velocity profiles which are consistent with the previous literature although the profiles obtained in the multiphase flows had relatively higher central velocity peaks than was observed for the single phase profiles. This observation was almost certainly a result of the transfer of axial momentum from the less dense dispersed phases to the water

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

Science.gov (United States)

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

2010-03-01

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

Characteristics of low-mass-velocity vertical gas-liquid two-phase flow

International Nuclear Information System (INIS)

Adachi, Hiromichi; Abe, Yutaka; Kimura, Ko-ji

1995-01-01

In the present paper, characteristics of low mass velocity two-phase flow was analyzed based on a concept that pressure energy of two-phase flow is converted into acceleration work, gravitational work and frictional work, and the pressure energy consumption rate should be minimum at the stable two-phase flow condition. Experimental data for vertical upward air-water two-phase flow at atmospheric pressure was used to verify this concept and the turbulent model used in this method is optimized with the data. (author)

Prediction of critical transport velocity for preventing sand deposition in gas-oil multiphase production and well systems

Energy Technology Data Exchange (ETDEWEB)

Bello, O.O.; Reinicke, K.M. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). Inst. of Petroleum Engineering; Teodoriu, C. [Texas A and M Univ., College Station, TX (United States). Dept. of Petroleum Engineering

2008-10-23

The critical transport velocity is one of the key parameters for gas-oil-sand multiphase production and well system design and safe operation. Existing American Petroleum Institute Recommended Practice 14E (API RP 14E) for the sizing of multiphase flow systems suggests an equation to calculate threshold transport velocity. This equation only considers mixture density and does not account for factors such as fluid properties, gas-liquid flow patterns, sand loading, sand particle size, size distributions, shape factor and density. This work presents an improved computational methodology, which can be applied to estimate the critical transport velocity required to ensure efficient performance of gas-oil-sand multiphase production and well systems. The improved method is based on the modelling of three-phase gas-oil-sand pipe flow physics from first principle. Computations of the critical transport velocities show reasonable agreement with values calculated from mechanistic model (Danielson, 2007) for a relatively wide range of design and operating conditions. Compared with the mechanistic model (Danielson, 2007), the present method has no imposed limitations to the range of applicability. It is also takes into adequate account the effects of operating pressure, flow geometry, sand particle size, size distribution and shape factor, which have considerable influence on the critical transport velocity in gas-oil-sand multiphase production and well systems. (orig.)

Development of Hydroxyl Tagging Velocimetry for Low Velocity Flows

Science.gov (United States)

Andre, Matthieu A.; Bardet, Philippe M.; Burns, Ross A.; Danehy, Paul M.

2016-01-01

Hydroxyl tagging velocimetry (HTV) is a molecular tagging technique that relies on the photo-dissociation of water vapor into OH radicals and their subsequent tracking using laser induced fluorescence. Velocities are then obtained from time-of-flight calculations. At ambient temperature in air, the OH species lifetime is relatively short (<50 µs), making it suited for high speed flows. Lifetime and radicals formation increases with temperature, which allows HTV to also probe low-velocity, high-temperature flows or reacting flows such as flames. The present work aims at extending the domain of applicability of HTV, particularly towards low-speed (<10 m/s) and moderate (<500 K) temperature flows. Results are compared to particle image velocimetry (PIV) measurements recorded in identical conditions. Single shot and averaged velocity profiles are obtained in an air jet at room temperature. By modestly raising the temperature (100-200 degC) the OH production increases, resulting in an improvement of the signal-to-noise ratio (SNR). Use of nitrogen - a non-reactive gas with minimal collisional quenching - extends the OH species lifetime (to over 500 µs), which allows probing of slower flows or, alternately, increases the measurement precision at the expense of spatial resolution. Instantaneous velocity profiles are resolved in a 100degC nitrogen jet (maximum jet-center velocity of 6.5 m/s) with an uncertainty down to 0.10 m/s (1.5%) at 68% confidence level. MTV measurements are compared with particle image velocimetry and show agreement within 2%.

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)

MHD free convection flow of a visco-elastic (Kuvshiniski type dusty gas through a semi infinite plate moving with velocity decreasing exponentially with time and radiative heat transfer

Directory of Open Access Journals (Sweden)

Om Prakash

2011-06-01

Full Text Available The present paper is concerned with the study of MHD free convective flow of a visco-elastic (Kuvshinski type dusty gas through a porous medium induced by the motion of a semi-infinite flat plate under the influence of radiative heat transfer moving with velocity decreasing exponentially with time. The expressions for velocity distribution of a dusty gas and dust particles, concentration profile and temperature field are obtained. The effect of Schmidt number (Sc, Magnetic field parameter (M and Radiation parameter (N on velocity distribution of dusty gas and dust particles, concentration and temperature distribution are discussed graphically.

An analysis of numerical convergence in discrete velocity gas dynamics for internal flows

Science.gov (United States)

Sekaran, Aarthi; Varghese, Philip; Goldstein, David

2018-07-01

The Discrete Velocity Method (DVM) for solving the Boltzmann equation has significant advantages in the modeling of non-equilibrium and near equilibrium flows as compared to other methods in terms of reduced statistical noise, faster solutions and the ability to handle transient flows. Yet the DVM performance for rarefied flow in complex, small-scale geometries, in microelectromechanical (MEMS) devices for instance, is yet to be studied in detail. The present study focuses on the performance of the DVM for locally large Knudsen number flows of argon around sharp corners and other sources for discontinuities in the distribution function. Our analysis details the nature of the solution for some benchmark cases and introduces the concept of solution convergence for the transport terms in the discrete velocity Boltzmann equation. The limiting effects of the velocity space discretization are also investigated and the constraints on obtaining a robust, consistent solution are derived. We propose techniques to maintain solution convergence and demonstrate the implementation of a specific strategy and its effect on the fidelity of the solution for some benchmark cases.

Stress and Damage Induced Gas Flow Pattern and Permeability Variation of Coal from Songzao Coalfield in Southwest China

Directory of Open Access Journals (Sweden)

Minghui Li

2016-05-01

Full Text Available The permeability of coal is a critical parameter in estimating the performance of coal reservoirs. Darcy’s law describes the flow pattern that the permeability has a linear relationship with the flow velocity. However, the stress induced deformation and damage can significantly influence the gas flow pattern and permeability of coal. Coals from Songzao coalfield in Chongqing, southwest China were collected for the study. The gas flow velocities under different injection gas pressures and effective stresses in the intact coal and damaged coal were tested using helium, incorporating the role of gas flow pattern on the permeability of coal. The relationships between the flow velocity and square of gas pressure gradient were discussed, which can help us to investigate the transformation conditions of gas linear flow and gas nonlinear flow in the coal. The results showed that the gas flow in the intact coal existed pseudo-initial flow rate under low effective stress. The low-velocity non-Darcy gas flow gradually occurred and the start-up pressure gradient increased in the coal as the effective stress increased. The gas flow rate in the damaged coal increased nonlinearly as the square of pressure gradient increased under low effective stress. The instability of gas flow caused by high ratio of injection gas pressure over effective stress in the damaged coal contributed to the increase of the gas flow rate. As the effective stress increased, the increase of gas flow rate in coal turned to be linear. The mechanisms of the phenomena were explored according to the experimental results. The permeability of coal was corrected based on the relationships between the flow velocity and square of gas pressure gradient, which showed advantages in accurately estimating the performance of coal reservoirs.

Growth of a Massive Young Stellar Object Fed by a Gas Flow from a Companion Gas Clump

Energy Technology Data Exchange (ETDEWEB)

Chen, Xi; Shen, Zhiqiang [Shanghai Astronomical Observatories, Chinese Academy of Science, Nandan Rd. 80, Shanghai (China); Ren, Zhiyuan [National Astronomical Observatories, Chinese Academy of Science, Chaoyang District Datun Rd. A20, Beijing (China); Zhang, Qizhou [Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States); Qiu, Keping [School of Astronomy and Space Science, Nanjing University, 22 Hankou Rd., Nanjing, Jiangsu 210093 (China)

2017-02-01

We present a Submillimeter Array (SMA) observation toward the young massive double-core system G350.69-0.49. This system consists of a northeast (NE) diffuse gas bubble and a southwest (SW) massive young stellar object (MYSO), both clearly seen in the Spitzer images. The SMA observations reveal a gas flow between the NE bubble and the SW MYSO in a broad velocity range from 5 to 30 km s{sup −1} with respect to the system velocity. The gas flow is well confined within the interval between the two objects and traces a significant mass transfer from the NE gas bubble to the SW massive core. The transfer flow can supply the material accreted onto the SW MYSO at a rate of 4.2×10{sup −4} M{sub ⊙} yr{sup −1}. The whole system therefore suggests a mode for the mass growth in the MYSO from a gas transfer flow launched from its companion gas clump, despite the driving mechanism of the transfer flow not being fully determined from the current data.

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)

Hydromagnetic Rayleigh endash Taylor instability in high-velocity gas-puff implosions

International Nuclear Information System (INIS)

Roderick, N.F.; Peterkin, R.E. Jr.; Hussey, T.W.; Spielman, R.B.; Douglas, M.R.; Deeney, C.

1998-01-01

Experiments using the Saturn pulsed power generator have produced high-velocity z-pinch plasma implosions with velocities over 100 cm/μs using both annular and uniform-fill gas injection initial conditions. Both types of implosion show evidence of the hydromagnetic Rayleigh endash Taylor instability with the uniform-fill plasmas producing a more spatially uniform pinch. Two-dimensional magnetohydrodynamic simulations including unsteady flow of gas from a nozzle into the diode region have been used to investigate these implosions. The instability develops from the nonuniform gas flow field that forms as the gas expands from the injection nozzle. Instability growth is limited to the narrow unstable region of the current sheath. For the annular puff the unstable region breaks through the inner edge of the annulus increasing nonlinear growth as mass ejected from the bubble regions is not replenished by accretion. This higher growth leads to bubble thinning and disruption producing greater nonuniformity at pinch for the annular puff. The uniform puff provides gas to replenish bubble mass loss until just before pinch resulting in less bubble thinning and a more uniform pinch. copyright 1998 American Institute of Physics

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.

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

Air-water flow in a vertical pipe with sudden changes of superficial water velocity

International Nuclear Information System (INIS)

Horst-Michael Prasser; Eckhard Krepper; Thomas Frank

2005-01-01

Full text of publication follows: For further model development and the validation of CFD codes for two-phase flow applications experiments were carried out with a sudden change of the superficial velocity of water. The tests were performed in a vertical pipe of 51.2 mm diameter. The gas was injected through 19 capillaries of 0.8 mm inner diameter equally distributed over the cross section of the pipe. Measurements were taken by two wire-mesh sensors (24 x 24 points, 2500 Hz) mounted in a short distance (16 mm) behind each other. This sensor assembly was placed 3030 mm downstream of the gas injection. The change of the superficial water velocity was produced by a butterfly valve, the flap of which was perforated. In this way, a rapid closure of the valve caused a jump-like reduction of the liquid flow rate. The valve was located upstream of the gas injection. In a second series of tests a jump-like increase of the water flow rate was studied. Time sequences of the gas fraction profile were calculated from the wire-mesh sensor data over sampling periods of 0.2 s per profile. To increase the statistical reliability of the data, the transient was repeated several times and the data superposed (ensemble averaging). Gas velocity distributions were determined by correlation of the signals with the measurements of the second sensor. The tests enable the observation of the restructuring process of bubbly flow between two steady state conditions. The process is subdivided into three main stages: (1) the undisturbed flow before the velocity jump, (2) the passage of the bubbly flow formed under initial conditions, but travelling with the new velocity and (3) the bubbly flow generated under the new boundary conditions. Transient behaviour between these stages is reflected by the measured data. Special attention was paid to stage 2, where the radial gas fraction profiles change shape due to the excitation of the force balance acting on the bubbles. The experimental results for

Numerical calculation of velocity distribution near a vertical flat plate immersed in bubble flow

International Nuclear Information System (INIS)

Matsuura, Akihiro; Nakamura, Hajime; Horihata, Hideyuki; Hiraoka, Setsuro; Aragaki, Tsutomu; Yamada, Ikuho; Isoda, Shinji.

1992-01-01

Liquid and gas velocity distributions for bubble flow near a vertical flat plate were calculated numerically by using the SIMPLER method, where the flow was assumed to be laminar, two-dimensional, and at steady state. The two-fluid flow model was used in the numerical analysis. To calculate the drag force on a small bubble, Stokes' law for a rigid sphere is applicable. The dimensionless velocity distributions which were arranged with characteristic boundary layer thickness and maximum liquid velocity were adjusted with a single line and their forms were similar to that for single-phase wall-jet flow. The average wall shear stress derived from the velocity gradient at the plate wall was strongly affected by bubble diameter but not by inlet liquid velocity. The present dimensionless velocity distributions obtained numerically agreed well with previous experimental results, and the proposed numerical algorithm was validated. (author)

A study on the effect of gas flow rate on the wave characteristics in two-phase gas-liquid annular flow

Energy Technology Data Exchange (ETDEWEB)

Han Huawei [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, Oshawa, Ont., L1H 7K4 (Canada)]. E-mail: colin.han@uoit.ca; Zhu Zhenfeng [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, Sask., S7N 5A9 (Canada)]. E-mail: zhz752@mail.usask.ca; Gabriel, Kamiel [University of Ontario Institute of Technology, Oshawa, Ont., L1H 7K4 (Canada)]. E-mail: kamiel.gabriel@uoit.ca

2006-12-15

Interfacial waves play a very important role in the mass, momentum and energy transport phenomena in annular flow. In this paper, film thickness time-trace measurements for air-water annular flow were collected in a small vertical tube using a parallel wire probe. Using the data, a typical disturbance wave shape was obtained and wave properties (e.g., width, height, speed and roughness) were presented. The liquid mass flux ranged from 100 to 200 kg/m{sup 2} s and the gas mass flux ranged from 18 to 47 kg/m{sup 2} s. Disturbance wave characteristics were defined and the effects of changing the gas flow rate on the wave spacing, wave width, wave peak height and wave base height were studied. An average velocity model for the wave and base regions has been developed to determine the wave velocity. The investigation method could be further extended to annular-mist flow which frequently occurs in boiling water reactors.

A study on the effect of gas flow rate on the wave characteristics in two-phase gas-liquid annular flow

International Nuclear Information System (INIS)

Han Huawei; Zhu Zhenfeng; Gabriel, Kamiel

2006-01-01

Interfacial waves play a very important role in the mass, momentum and energy transport phenomena in annular flow. In this paper, film thickness time-trace measurements for air-water annular flow were collected in a small vertical tube using a parallel wire probe. Using the data, a typical disturbance wave shape was obtained and wave properties (e.g., width, height, speed and roughness) were presented. The liquid mass flux ranged from 100 to 200 kg/m 2 s and the gas mass flux ranged from 18 to 47 kg/m 2 s. Disturbance wave characteristics were defined and the effects of changing the gas flow rate on the wave spacing, wave width, wave peak height and wave base height were studied. An average velocity model for the wave and base regions has been developed to determine the wave velocity. The investigation method could be further extended to annular-mist flow which frequently occurs in boiling water reactors

Velocity measurements in a rigid ceramic filter in a parallel-flow arrangement

International Nuclear Information System (INIS)

Al-Hajeri, M.H.; Aroussi, A.; Witry, A.

2002-01-01

Rigid ceramic filters have been developed for cleaning the hot combustion gas streams upstream of the turbine in a combined cycle power plant. To obtain continues operation a periodic cleaning is necessary and the cleaning efficiency depends on the distribution of the filtration cake. Consequently uniform particle deposition on the filter element surface is desired. The flow around three filter elements in cross flow is investigated computationally using the commercial code FLUENT. Three filter elements are placed in a two-dimensional rectangle duct with fixed face velocity and varying the velocity ratio between the approach and face velocity. Particle trajectories are obtained for a number of particle diameters and different inlet (approach) velocity to face filtration velocity ratios to investigate the behavior of particles around the filter element. (author)

Numerical Investigation of PLIF Gas Seeding for Hypersonic Boundary Layer Flows

Science.gov (United States)

Johanson, Craig T.; Danehy, Paul M.

2012-01-01

Numerical simulations of gas-seeding strategies required for planar laser-induced fluorescence (PLIF) in a Mach 10 air flow were performed. The work was performed to understand and quantify adverse effects associated with gas seeding and to compare different flow rates and different types of seed gas. The gas was injected through a slot near the leading edge of a flat plate wedge model used in NASA Langley Research Center's 31- Inch Mach 10 Air Tunnel facility. Nitric oxide, krypton, and iodine gases were simulated at various injection rates. Simulation results showing the deflection of the velocity field for each of the cases are presented. Streamwise distributions of velocity and concentration boundary layer thicknesses as well as vertical distributions of velocity, temperature, and mass distributions are presented for each of the cases. Relative merits of the different seeding strategies are discussed.

Heat transfer to accelerating gas flows

International Nuclear Information System (INIS)

Kennedy, T.D.A.

1978-01-01

The development of fuels for gas-cooled reactors has resulted in a number of 'gas loop' experiments in materials-testing research reactors. In these experiments, efforts are made to reproduce the conditions expected in gas-cooled power reactors. Constant surface temperatures are sought over a short (300 mm) fuelled length, and because of entrance effects, an accelerating flow is required to increase the heat transfer down-stream from the entrance. Strong acceleration of a gas stream will laminarise the flow even at Reynolds Numbers up to 50000, far above values normally associated with laminar flow. A method of predicting heat transfer in this situation is presented here. An integral method is used to find the velocity profile; this profile is then used in an explicit finite-difference solution of the energy equation to give a temperature profile and resultant heat-transfer coefficient values. The Kline criterion, which compares viscous and disruptive forces, is used to predict whether the flow will be laminar. Experimental results are compared with predictions, and good agreement is found to exist. (author)

Velocity Dispersion of Ionized Gas and Multiple Supernova Explosions

Directory of Open Access Journals (Sweden)

Vasiliev E. O.

2015-06-01

Full Text Available We use 3D numerical simulations to study the evolution of the Hα intensity and velocity dispersion for single and multiple supernova (SN explosions. We find that the IHα– σ diagram obtained for simulated gas flows is similar in shape to that observed in dwarf galaxies. We conclude that colliding SN shells with significant difference in age are responsible for high velocity dispersion that reaches up to ≳ 100 km s−1. Such a high velocity dispersion could be hardly obtained for a single SN remnant. Peaks of velocity dispersion in the IHα– σ diagram may correspond to several isolated or merged SN remnants with moderately different ages. Degrading the spatial resolution in the Hα intensity and velocity dispersion maps makes the simulated IHα– σ diagrams close to those observed in dwarf galaxies not only in shape, but also quantitatively.

Prediction of strongly-heated internal gas flows

International Nuclear Information System (INIS)

McEligot, D.M.; Shehata, A.M.; Kunugi, Tomoaki

1997-01-01

The purposes of the present article are to remind practitioners why the usual textbook approaches may not be appropriate for treating gas flows heated from the surface with large heat fluxes and to review the successes of some recent applications of turbulence models to this case. Simulations from various turbulence models have been assessed by comparison to the measurements of internal mean velocity and temperature distributions by Shehata for turbulent, laminarizing and intermediate flows with significant gas property variation. Of about fifteen models considered, five were judged to provide adequate predictions

Gas-kinetic unified algorithm for hypersonic flows covering various flow regimes solving Boltzmann model equation in nonequilibrium effect

International Nuclear Information System (INIS)

Li, Zhihui; Ma, Qiang; Wu, Junlin; Jiang, Xinyu; Zhang, Hanxin

2014-01-01

Based on the Gas-Kinetic Unified Algorithm (GKUA) directly solving the Boltzmann model equation, the effect of rotational non-equilibrium is investigated recurring to the kinetic Rykov model with relaxation property of rotational degrees of freedom. The spin movement of diatomic molecule is described by moment of inertia, and the conservation of total angle momentum is taken as a new Boltzmann collision invariant. The molecular velocity distribution function is integrated by the weight factor on the internal energy, and the closed system of two kinetic controlling equations is obtained with inelastic and elastic collisions. The optimization selection technique of discrete velocity ordinate points and numerical quadrature rules for macroscopic flow variables with dynamic updating evolvement are developed to simulate hypersonic flows, and the gas-kinetic numerical scheme is constructed to capture the time evolution of the discretized velocity distribution functions. The gas-kinetic boundary conditions in thermodynamic non-equilibrium and numerical procedures are studied and implemented by directly acting on the velocity distribution function, and then the unified algorithm of Boltzmann model equation involving non-equilibrium effect is presented for the whole range of flow regimes. The hypersonic flows involving non-equilibrium effect are numerically simulated including the inner flows of shock wave structures in nitrogen with different Mach numbers of 1.5-Ma-25, the planar ramp flow with the whole range of Knudsen numbers of 0.0009-Kn-10 and the three-dimensional re-entering flows around tine double-cone body

Local studies in horizontal gas-liquid slug flow

International Nuclear Information System (INIS)

Sharma, S.; Lewis, S.; Kojasoy, G.

1998-01-01

The local axial velocity profile development in a horizontal air-water slug flow-pattern was experimentally investigated by simultaneously using two hot-film anemometers. One of the probes was exclusively used as phase identifier while the other probe was traversed for local velocity measurements. It was shown that the velocity rapidly develops into asymmetric but nearly fully-developed profiles within the liquid slugs whereas the velocity never develops into quasi-fully-developed profiles within the liquid layer underneath passing gas slugs. Transient nature of velocity at a given location was demonstrated. (author)

Studying the instantaneous velocity field in gas-sheared liquid films in a horizontal duct

Science.gov (United States)

Vasques, Joao; Tokarev, Mikhail; Cherdantsev, Andrey; Hann, David; Hewakandamby, Buddhika; Azzopardi, Barry

2016-11-01

In annular flow, the experimental validation of the basic assumptions on the liquid velocity profile is vital for developing theoretical models of the flow. However, the study of local velocity of liquid in gas-sheared films has proven to be a challenging task due to the highly curved and disturbed moving interface of the phases, small scale of the area of interrogation, high velocity gradients and irregular character of the flow. This study reports on different optical configurations and interface-tracking methods employed in a horizontal duct in order to obtain high-resolution particle image velocimetry (PIV) data in such types of complex flows. The experimental envelope includes successful measurements in 2D and 3D waves regimes, up to the disturbance wave regime. Preliminary data show the presence of complex structures in the liquid phase, which includes re-circulation areas below the liquid interface due to the gas-shearing action, together with non-uniform transverse movements of the liquid phase close to the wall due to the presence of 3D waves at the interface. With the aid of the moving interface-tracking, PIV, time-resolved particle-tracking velocimetry and vorticity measurements were performed.

Digital image processing based mass flow rate measurement of gas/solid two-phase flow

Energy Technology Data Exchange (ETDEWEB)

Song Ding; Peng Lihui; Lu Geng; Yang Shiyuan [Tsinghua National Laboratory for Information Science and Technology, Department of Automation, Tsinghua University, Beijing, 100084 (China); Yan Yong, E-mail: lihuipeng@tsinghua.edu.c [University of Kent, Canterbury, Kent CT2 7NT (United Kingdom)

2009-02-01

With the rapid growth of the process industry, pneumatic conveying as a tool for the transportation of a wide variety of pulverized and granular materials has become widespread. In order to improve plant control and operational efficiency, it is essential to know the parameters of the particle flow. This paper presents a digital imaging based method which is capable of measuring multiple flow parameters, including volumetric concentration, velocity and mass flow rate of particles in the gas/solid two phase flow. The measurement system consists of a solid state laser for illumination, a low-cost CCD camera for particle image acquisition and a microcomputer with bespoke software for particle image processing. The measurements of particle velocity and volumetric concentration share the same sensing hardware but use different exposure time and different image processing methods. By controlling the exposure time of the camera a clear image and a motion blurred image are obtained respectively. The clear image is thresholded by OTSU method to identify the particles from the dark background so that the volumetric concentration is determined by calculating the ratio between the particle area and the total area. Particle velocity is derived from the motion blur length, which is estimated from the motion blurred images by using the travelling wave equation method. The mass flow rate of particles is calculated by combining the particle velocity and volumetric concentration. Simulation and experiment results indicate that the proposed method is promising for the measurement of multiple parameters of gas/solid two-phase flow.

Digital image processing based mass flow rate measurement of gas/solid two-phase flow

International Nuclear Information System (INIS)

Song Ding; Peng Lihui; Lu Geng; Yang Shiyuan; Yan Yong

2009-01-01

With the rapid growth of the process industry, pneumatic conveying as a tool for the transportation of a wide variety of pulverized and granular materials has become widespread. In order to improve plant control and operational efficiency, it is essential to know the parameters of the particle flow. This paper presents a digital imaging based method which is capable of measuring multiple flow parameters, including volumetric concentration, velocity and mass flow rate of particles in the gas/solid two phase flow. The measurement system consists of a solid state laser for illumination, a low-cost CCD camera for particle image acquisition and a microcomputer with bespoke software for particle image processing. The measurements of particle velocity and volumetric concentration share the same sensing hardware but use different exposure time and different image processing methods. By controlling the exposure time of the camera a clear image and a motion blurred image are obtained respectively. The clear image is thresholded by OTSU method to identify the particles from the dark background so that the volumetric concentration is determined by calculating the ratio between the particle area and the total area. Particle velocity is derived from the motion blur length, which is estimated from the motion blurred images by using the travelling wave equation method. The mass flow rate of particles is calculated by combining the particle velocity and volumetric concentration. Simulation and experiment results indicate that the proposed method is promising for the measurement of multiple parameters of gas/solid two-phase flow.

DEM-CFD simulation of purge gas flow in a solid breeder pebble bed

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hao [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230027 (China); Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Li, Zhenghong [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); University of Science and Technology of China, Hefei 230027 (China); Guo, Haibing [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Ye, Minyou [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230027 (China); Huang, Hongwen, E-mail: inpclane@sina.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

2016-12-15

Solid tritium breeding blanket applying pebble bed concept is promising for fusion reactors. Tritium bred in the pebble bed is purged out by inert gas. The flow characteristics of the purge gas are important for the tritium transport from the solid breeder materials. In this study, a randomly packed pebble bed was generated by Discrete Element Method (DEM) and verified by radial porosity distribution. The flow parameters of the purge gas in channels were solved by Computational Fluid Dynamics (CFD) method. The results show that the normalized velocity magnitudes have the same damped oscillating patterns with radial porosity distribution. Besides, the bypass flow near the wall cannot be ignored in this model, and it has a slight increase with inlet velocity. Furthermore, higher purging efficiency becomes with higher inlet velocity and especially higher in near wall region.

Dependence of energy characteristics of ascending swirling air flow on velocity of vertical blowing

Science.gov (United States)

Volkov, R. E.; Obukhov, A. G.; Kutrunov, V. N.

2018-05-01

In the model of a compressible continuous medium, for the complete Navier-Stokes system of equations, an initial boundary problem is proposed that corresponds to the conducted and planned experiments and describes complex three-dimensional flows of a viscous compressible heat-conducting gas in ascending swirling flows that are initiated by a vertical cold blowing. Using parallelization methods, three-dimensional nonstationary flows of a polytropic viscous compressible heat-conducting gas are constructed numerically in different scaled ascending swirling flows under the condition when gravity and Coriolis forces act. With the help of explicit difference schemes and the proposed initial boundary conditions, approximate solutions of the complete system of Navier-Stokes equations are constructed as well as the velocity and energy characteristics of three-dimensional nonstationary gas flows in ascending swirling flows are determined.

Characterising gas behaviour during gas-liquid co-current up-flow in packed beds using magnetic resonance imaging

OpenAIRE

Collins, James HP; Sederman, Andrew John; Gladden, Lynn Faith; Afeworki, Mobae; Kushnerick, J Douglas; Thomann, Hans

2016-01-01

Magnetic resonance (MR) imaging techniques have been used to study gas phase dynamics during co-current up-flow in a column of inner diameter 43 mm, packed with spherical non-porous elements of diameters of 1.8, 3 and 5 mm. MR measurements of gas hold-up, bubble-size distribution, and bubble-rise velocities were made as a function of flow rate and packing size. Gas and liquid flow rates were studied in the range of 20–250 cm3 s−1 and 0–200 cm3 min−1, respectively. The gas hold-up within the b...

Surface Effects on Nanoscale Gas Flows

Science.gov (United States)

Beskok, Ali; Barisik, Murat

2010-11-01

3D MD simulations of linear Couette flow of argon gas confined within nano-scale channels are performed in the slip, transition and free molecular flow regimes. The velocity and density profiles show deviations from the kinetic theory based predictions in the near wall region that typically extends three molecular diameters (s) from each surface. Utilizing the Irwin-Kirkwood theorem, stress tensor components for argon gas confined in nano-channels are investigated. Outside the 3s region, three normal stress components are identical, and equal to pressure predicted using the ideal gas law, while the shear stress is a constant. Within the 3s region, the normal stresses become anisotropic and the shear stress shows deviations from its bulk value due to the surface virial effects. Utilizing the kinetic theory and MD predicted shear stress values, the tangential momentum accommodation coefficient for argon gas interacting with FCC structured walls (100) plane facing the fluid is calculated to be 0.75; this value is independent of the Knudsen number. Results show emergence of the 3s region as an additional characteristic length scale in nano-confined gas flows.

Gas flow characteristics of a time modulated APPJ: the effect of gas heating on flow dynamics

International Nuclear Information System (INIS)

Zhang, S; Sobota, A; Van Veldhuizen, E M; Bruggeman, P J

2015-01-01

This work investigates the flow dynamics of a radio-frequency (RF) non-equilibrium argon atmospheric pressure plasma jet. The RF power is at a frequency of 50 Hz or 20 kHz. Combined flow pattern visualizations (obtained by shadowgraphy) and gas temperature distributions (obtained by Rayleigh scattering) are used to study the formation of transient vortex structures in initial flow field shortly after the plasma is switched on and off in the case of 50 Hz modulation. The transient vortex structures correlate well with observed temperature differences. Experimental results of the fast modulated (20 kHz) plasma jet that does not induce changes of the gas temperature are also presented. The latter result suggests that momentum transfer by ions does not have dominant effect on the flow pattern close to the tube. It is argued that the increased gas temperature and corresponding gas velocity increase at the tube exit due to the plasma heating increases the admixing of surrounding air and reduces the effective potential core length. With increasing plasma power a reduction of the effective potential core length is observed with a minimum length for 5.6 W after which the length extends again. Possible mechanisms related to viscosity effects and ionic momentum transfer are discussed. (paper)

Foam flow in a model porous medium: II. The effect of trapped gas.

Science.gov (United States)

Jones, S A; Getrouw, N; Vincent-Bonnieu, S

2018-05-09

Gas trapping is an important mechanism in both Water or Surfactant Alternating Gas (WAG/SAG) and foam injection processes in porous media. Foams for enhanced oil recovery (EOR) can increase sweep efficiency as they decrease the gas relative permeability, and this is mainly due to gas trapping. However, gas trapping mechanisms are poorly understood. Some studies have been performed during corefloods, but little work has been carried out to describe the bubble trapping behaviour at the pore scale. We have carried out foam flow tests in a micromodel etched with an irregular hexagonal pattern. Image analysis of the foam flow allowed the bubble centres to be tracked and local velocities to be obtained. It was found that the flow in the micromodel is dominated by intermittency and localized zones of trapped gas. The quantity of trapped gas was measured both by considering the fraction of bubbles that were trapped (via velocity thresholding) and by measuring the area fraction containing immobile gas (via image analysis). A decrease in the quantity of trapped gas was observed for both increasing total velocity and increasing foam quality. Calculations of the gas relative permeability were made with the Brooks Corey equation, using the measured trapped gas saturations. The results showed a decrease in gas relative permeabilities, and gas mobility, for increasing fractions of trapped gas. It is suggested that the shear thinning behaviour of foam could be coupled to the saturation of trapped gas.

The influence of the tangential velocity of inner rotating wall on axial velocity profile of flow through vertical annular pipe with rotating inner surface

Directory of Open Access Journals (Sweden)

Sharf Abdusalam M.

2014-03-01

Full Text Available In the oil and gas industries, understanding the behaviour of a flow through an annulus gap in a vertical position, whose outer wall is stationary whilst the inner wall rotates, is a significantly important issue in drilling wells. The main emphasis is placed on experimental (using an available rig and computational (employing CFD software investigations into the effects of the rotation speed of the inner pipe on the axial velocity profiles. The measured axial velocity profiles, in the cases of low axial flow, show that the axial velocity is influenced by the rotation speed of the inner pipe in the region of almost 33% of the annulus near the inner pipe, and influenced inversely in the rest of the annulus. The position of the maximum axial velocity is shifted from the centre to be nearer the inner pipe, by increasing the rotation speed. However, in the case of higher flow, as the rotation speed increases, the axial velocity is reduced and the position of the maximum axial velocity is skewed towards the centre of the annulus. There is a reduction of the swirl velocity corresponding to the rise of the volumetric flow rate.

Velocities of gas and plasmas from real time holographic interferograms

International Nuclear Information System (INIS)

Deason, V.A.; Reynolds, L.D.; McIlwain, M.E.

1985-01-01

A truly noninvasive measurement technique for plasma velocity has not been demonstrated. Plasma velocities have been inferred using laser Doppler anemometry or photographic analysis of the position of smoke or small particles. This paper describes an alternate method based on the refractive index change created in a plasma by a gaseous probe material injected into the plasma. This disturbance of the refractive index can be monitored using interferometry. A multipass real time holographic interferometry system was used to follow the changes of the interferometric pattern, and the data was recorded using high speed cinematography. A transparent model of an industrial plasma torch was employed in these studies, and a number of different types of trace gas materials were used to track the plasma flow. Using a combination of multipass interferometry and a laser line absorbing gas, sufficient interferometric sensitivity was obtained to determine plasma velocities in the 100 m/s range. Based on these results, a working plasma torch was constructed. Further studies are planned using this torch and actual plasmas

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

Measurement system of bubbly flow using ultrasonic velocity profile monitor and video data processing unit

International Nuclear Information System (INIS)

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

1996-01-01

The authors have been developing a measurement system for bubbly flow in order to clarify its multi-dimensional flow characteristics and to offer a data base to validate numerical codes for multi-dimensional two-phase flow. In this paper, the measurement system combining an ultrasonic velocity profile monitor with a video data processing unit is proposed, which can measure simultaneously velocity profiles in both gas and liquid phases, a void fraction profile for bubbly flow in a channel, and an average bubble diameter and void fraction. Furthermore, the proposed measurement system is applied to measure flow characteristics of a bubbly countercurrent flow in a vertical rectangular channel to verify its capability. (author)

Transient heat transfer for helium gas flowing over a horizontal cylinder with exponentially increasing heat input

International Nuclear Information System (INIS)

Liu, Qiusheng; Fukuda, Katsuya

2003-01-01

The transient heat transfer coefficients for forced convection flow of helium gas over a horizontal cylinder were measured under wide experimental conditions. The platinum cylinder with a diameter of 1.0 mm was used as test heater and heated by electric current with an exponentially increasing heat input of Q 0 exp(t/τ). The gas flow velocities ranged from 5 to 35 m/s, the gas temperatures ranged from 25 to 80degC, and the periods of heat generation rate, τ, ranged from 40 ms to 20 s. The surface superheat and heat flux increase exponentially as the heat generation rate increases with the exponential function. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period τ longer than about 1 s, and it becomes higher for the period shorter than around 1 s. The transient heat transfer shows less dependence on the gas flowing velocity when the period becomes very shorter. The gas temperature in this study shows little influence on the heat transfer coefficient. Semi-empirical correlation for quasi-steady-state heat transfer was obtained based on the experimental data. The ratios of transient Nusselt number Nu tr to quasi-steady-state Nusselt number Nu st at various periods, flow velocities, and gas temperatures were obtained. The heat transfer shifts to the quasi-steady-state heat transfer for longer periods and shifts to the transient heat transfer for shorter periods at the same flow velocity. It also approaches the quasi-steady-state one for higher flow velocity at the same period. Empirical correlation for transient heat transfer was also obtained based on the experimental data. (author)

Investigation and visualization of liquid-liquid flow in a vertically mounted Hele-Shaw cell: flow regimes, velocity and shape of droplets

Science.gov (United States)

Shad, S.; Gates, I. D.; Maini, B. B.

2009-11-01

The motion and shape of a liquid drop flowing within a continuous, conveying liquid phase in a vertical Hele-Shaw cell were investigated experimentally. The continuous phase was more viscous and wetted the bounding walls of the Hele-Shaw cell. The gap between the Hele-Shaw plates was set equal to 0.0226 cm. Four different flow regimes were observed: (a) small-droplet flow, (b) elongated-droplet flow, (c) churn flow and (d) channel flow. At low capillary number, that is, when capillary forces are larger than viscous forces, the droplet shape was irregular and changed with time and distance, and it moved with lower velocity than that of the conveying phase. At higher capillary number, several different shapes of stabilized elongated and flattened drops were observed. In contrast to gas-liquid systems, the velocities of droplets are higher than that of conveying liquid. New correlations derived from dimensionless analysis and fitted to the experimental data were generated to predict the elongated-drop velocity and aspect ratio.

DSMC simulation of feed jet flow in gas centrifuge

International Nuclear Information System (INIS)

Jiang Dongjun; Zeng Shi

2011-01-01

Feed jet flow acts an important role for the counter-current in gas centrifuge. Direct simulation Monte-Carlo (DSMC) method was adopted to simulate the structure of the radial feed jet model. By setting the proper boundary conditions and the collision model of molecules, the flow distributions of the 2D radial feed jet were acquired under different feed conditions, including the wave structure of feed jet and the profile of the flow parameters. The analyses of the calculation results note the following flow phenomena: Near the radial outflow boundary, the obvious peaks of the flow parameters exist; higher speed of feed gas brings stronger influence on the flow field of the centrifuge; including the density, pressure and velocity of the gas, the distribution of the temperature is affected by the feed jet, at the outflow boundary, temperature to double times of the average value. (authors)

Evaporation-induced gas-phase flows at selective laser melting

Science.gov (United States)

Zhirnov, I.; Kotoban, D. V.; Gusarov, A. V.

2018-02-01

Selective laser melting is the method for 3D printing from metals. A solid part is built from powder layer-by-layer. A continuum-wave laser beam scans every powder layer to fuse powder. The process is studied with a high-speed CCD camera at the frame rate of 104 fps and the resolution up to 5 µm per pixel. Heat transfer and evaporation in the laser-interaction zone are numerically modeled. Droplets are ejected from the melt pool in the direction around the normal to the melt surface and the powder particles move in the horizontal plane toward the melt pool. A vapor jet is observed in the direction of the normal to the melt surface. The velocities of the droplets, the powder particles, and the jet flow and the mass loss due to evaporation are measured. The gas flow around the vapor jet is calculated by Landau's model of submerged jet. The measured velocities of vapor, droplets, and powder particles correlate with the calculated flow field. The obtained results show the importance of evaporation and the flow of the vapor and the ambient gas. These gas-dynamic phenomena can explain the formation of the denudated zones and the instability at high-energy input.

Measurement of gas-liquid two-phase flow around horizontal tube bundle using SF6-water. Simulating high-pressure high-temperature gas-liquid two-phase flow of PWR/SG secondary coolant side at normal pressure

International Nuclear Information System (INIS)

Ishikawa, Atsushi; Imai, Ryoj; Tanaka, Takahiro

2014-01-01

In order to improve prediction accuracy of analysis code used for design and development of industrial products, technology had been developed to create and evaluate constitutive equation incorporated in analysis code. The experimental facility for PWR/SG U tubes part was manufactured to measure local void fraction and gas-liquid interfacial velocity with forming gas-liquid upward two-phase flow simulating high-pressure high-temperature secondary coolant (water-steam) rising vertically around horizontal tube bundle. The experimental facility could reproduce flow field having gas-liquid density ratio equivalent to real system with no heating using SF6 (Sulfur Hexafluoride) gas at normal temperature and pressure less than 1 MPa, because gas-liquid density ratio, surface tension and gas-liquid viscosity ratio were important parameters to determine state of gas-liquid two-phase flow and gas-liquid density ratio was most influential. Void fraction was measured by two different methods of bi-optical probe and conductivity type probe. Test results of gas-liquid interfacial velocity vs. apparent velocity were in good agreement with existing empirical equation within 10% error, which could confirm integrity of experimental facility and appropriateness of measuring method so as to set up original constitutive equation in the future. (T. Tanaka)

Bulk velocity extraction for nano-scale Newtonian flows

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wenfei, E-mail: zwenfei@gmail.com [Key Laboratory of Mechanical Reliability for Heavy Equipments and Large Structures of Hebei Province, Yanshan University, Qinhuangdao 066004 (China); Sun, Hongyu [Key Laboratory of Mechanical Reliability for Heavy Equipments and Large Structures of Hebei Province, Yanshan University, Qinhuangdao 066004 (China)

2012-04-16

The conventional velocity extraction algorithm in MDS method has difficulty to determine the small flow velocity. This study proposes a new method to calculate the bulk velocity in nano-flows. Based on the Newton's law of viscosity, according to the calculated viscosities and shear stresses, the flow velocity can be obtained by numerical integration. This new method can overcome the difficulty existed in the conventional MDS method and improve the stability of the computational process. Numerical results show that this method is effective for the extraction of bulk velocity, no matter the bulk velocity is large or small. -- Highlights: ► Proposed a new method to calculate the bulk velocity in nano-flows. ► It is effective for the extraction of small bulk velocity. ► The accuracy, convergence and stability of the new method is good.

Bulk velocity extraction for nano-scale Newtonian flows

International Nuclear Information System (INIS)

Zhang, Wenfei; Sun, Hongyu

2012-01-01

The conventional velocity extraction algorithm in MDS method has difficulty to determine the small flow velocity. This study proposes a new method to calculate the bulk velocity in nano-flows. Based on the Newton's law of viscosity, according to the calculated viscosities and shear stresses, the flow velocity can be obtained by numerical integration. This new method can overcome the difficulty existed in the conventional MDS method and improve the stability of the computational process. Numerical results show that this method is effective for the extraction of bulk velocity, no matter the bulk velocity is large or small. -- Highlights: ► Proposed a new method to calculate the bulk velocity in nano-flows. ► It is effective for the extraction of small bulk velocity. ► The accuracy, convergence and stability of the new method is good.

Experimental investigation on flow patterns of gas-liquid two-phase upward flow through packed channel with spheres

International Nuclear Information System (INIS)

Zhang Nan; Sun Zhongning; Zhao Zhongnan

2011-01-01

Experiments of visualized two-phase upward flow were conducted in the packed channel, which filled with 3, 5, 8 mm in diameter of glass sphere respectively. The gas superficial velocity ranges from 0.005 to 1.172 m/s. The liquid superficial velocity ranges from 0.004 to 0.093 m/s. Four representative flow patterns were observed as bubbly flow, cluster flow, liquid-pulse flow and churn-pulse flow, and corresponding flow pattern maps were also presented. It is found that the pulse flow region is dominant. The comparisons of flow pattern map between packed channel and non-packed channel show that the bubbly flow region in packed channel is narrower than that of non-packed channel due to the packing. The comparisons of flow pattern maps for three different packing sizes show that the cluster flow region expands with the increase of the packing diameter. In the low liquid superficial velocity, the cluster flow directly changes to churn-pulse flow in the packed channel with 8 mm packing. (authors)

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.

Detonation velocity in poorly mixed gas mixtures

Science.gov (United States)

Prokhorov, E. S.

2017-10-01

The technique for computation of the average velocity of plane detonation wave front in poorly mixed mixture of gaseous hydrocarbon fuel and oxygen is proposed. Here it is assumed that along the direction of detonation propagation the chemical composition of the mixture has periodic fluctuations caused, for example, by layered stratification of gas charge. The technique is based on the analysis of functional dependence of ideal (Chapman-Jouget) detonation velocity on mole fraction (with respect to molar concentration) of the fuel. It is shown that the average velocity of detonation can be significantly (by more than 10%) less than the velocity of ideal detonation. The dependence that permits to estimate the degree of mixing of gas mixture basing on the measurements of average detonation velocity is established.

The measurement of low air flow velocities

NARCIS (Netherlands)

Aghaei, A.; Mao, X.G.; Zanden, van der A.J.J.; Schaik, W.H.J.; Hendriks, N.A.

2005-01-01

Air flow velocity is measured with an acoustic sensor, which can be used especially for measuring low air flow velocities as well as the temperature of the air simultaneously. Two opposite transducers send a sound pulse towards each other. From the difference of the transit times, the air flow

High Velocity Gas Gun

Science.gov (United States)

1988-01-01

A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

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)

Evolution of velocity dispersion along cold collisionless flows

International Nuclear Information System (INIS)

Banik, Nilanjan; Sikivie, Pierre

2016-01-01

We found that the infall of cold dark matter onto a galaxy produces cold collisionless flows and caustics in its halo. If a signal is found in the cavity detector of dark matter axions, the flows will be readily apparent as peaks in the energy spectrum of photons from axion conversion, allowing the densities, velocity vectors and velocity dispersions of the flows to be determined. We also discuss the evolution of velocity dispersion along cold collisionless flows in one and two dimensions. A technique is presented for obtaining the leading behaviour of the velocity dispersion near caustics. The results are used to derive an upper limit on the energy dispersion of the Big Flow from the sharpness of its nearby caustic, and a prediction for the dispersions in its velocity components

Gas flow and dust acceleration in a cometary Knudsen layer

CERN Document Server

Skorov, Yu V

1999-01-01

An analytical model of the innermost gas-dust coma region is proposed. The kinetic Knudsen layer adjacent to the surface of the cometary nucleus, where the initially non-equilibrium velocity distribution function of gas molecules $9 relaxes to Maxwell equilibrium distribution function and, as a result, the macro-characteristics of gas and dust flows vary several-fold, is considered. The gas phase model is based on the equations for mass, momentum and energy flux $9 conservation, and is a natural development of the Anisimov (1968) and Cercignani (1981) approaches. The analytical relations between the characteristics of the gas flow on the boundaries of the non- equilibrium layer and the $9 characteristics of the returning gas flow adsorbed by the surface are determined. These values form a consistent basis both for hydrodynamic models of the inner coma and for jet force models. Three particular models are presented: $9 (1) sublimation of a polyatomic one-component gas; (2) sublimation of a two-component polyat...

Visualisation of air–water bubbly column flow using array Ultrasonic Velocity Profiler

Directory of Open Access Journals (Sweden)

Munkhbat Batsaikhan

2017-11-01

Full Text Available In the present work, an experimental study of bubbly two-phase flow in a rectangular bubble column was performed using two ultrasonic array sensors, which can measure the instantaneous velocity of gas bubbles on multiple measurement lines. After the sound pressure distribution of sensors had been evaluated with a needle hydrophone technique, the array sensors were applied to two-phase bubble column. To assess the accuracy of the measurement system with array sensors for one and two-dimensional velocity, a simultaneous measurement was performed with an optical measurement technique called particle image velocimetry (PIV. Experimental results showed that accuracy of the measurement system with array sensors is under 10% for one-dimensional velocity profile measurement compared with PIV technique. The accuracy of the system was estimated to be under 20% along the mean flow direction in the case of two-dimensional vector mapping.

Heat transfer to a particle exposed to a rarefield ionized-gas flow

International Nuclear Information System (INIS)

Chen, X.; He, P.

1986-01-01

Analytical results are presented concerning the heat transfer to a spherical particle exposed to a high temperature, ionized- gas flow for the extreme case of free-molecule flow regime. It has been shown that the presence of relative velocity between the particle and the ionized gas reduces the floating potential on the particle, enhances the heat flux and causes appreciably non-uniform distribution of the local heat flux. Pronounced difference is found between metallic and non-metallic particles in the floating potential and the local heat flux distributions, in particular for the case with high gas-flow temperature. Relative contribution of atoms to the total heat flux is dominant for the case of low gas-flow temperature, while the heat flux is mainly caused by ions and electrons for the case of high gas-flow temperature

Measurement of LBE flow velocity profile by UDVP

International Nuclear Information System (INIS)

Kikuchi, Kenji; Takeda, Yasushi; Obayashi, Hiroo; Tezuka, Masao; Sato, Hiroshi

2006-01-01

Measurements of liquid metal lead-bismuth eutectic (LBE), flow velocity profile were realized in the spallation neutron source target model by the ultrasonic Doppler velocity profiler (UVDP) technique. So far, it has not been done well, because both of poor wetting property of LBE with stainless steels and poor performance of supersonic probes at high temperatures. The measurement was made for a return flow in the target model, which has coaxially arranged annular and tube channels, in the JAEA Lead Bismuth Loop-2 (JLBL-2). The surface treatment of LBE container was examined. It was found that the solder coating was effective to enhance an intensity of reflected ultrasonic wave. This treatment has been applied to the LBE loop, which was operated up to 150 deg. C. The electro magnetic pump generates LBE flow and the flow rate was measured by the electro magnetic flow meter. By changing the flow rate of LBE, velocity profiles in the target were measured. It was confirmed that the maximum velocity in the time-averaged velocity distribution on the target axis was proportional to the flow rate measured by the electro magnetic flow meter

An evaluation of gas transfer velocity parameterizations during natural convection using DNS

Science.gov (United States)

Fredriksson, Sam T.; Arneborg, Lars; Nilsson, Hâkan; Zhang, Qi; Handler, Robert A.

2016-02-01

Direct numerical simulations (DNS) of free surface flows driven by natural convection are used to evaluate different methods of estimating air-water gas exchange at no-wind conditions. These methods estimate the transfer velocity as a function of either the horizontal flow divergence at the surface, the turbulent kinetic energy dissipation beneath the surface, the heat flux through the surface, or the wind speed above the surface. The gas transfer is modeled via a passive scalar. The Schmidt number dependence is studied for Schmidt numbers of 7, 150 and 600. The methods using divergence, dissipation and heat flux estimate the transfer velocity well for a range of varying surface heat flux values, and domain depths. The two evaluated empirical methods using wind (in the limit of no wind) give reasonable estimates of the transfer velocity, depending however on the surface heat flux and surfactant saturation. The transfer velocity is shown to be well represented by the expression, ks=A |Bν|1/4 Sc-n, where A is a constant, B is the buoyancy flux, ν is the kinematic viscosity, Sc is the Schmidt number, and the exponent n depends on the water surface characteristics. The results suggest that A=0.39 and n≈1/2 and n≈2/3 for slip and no-slip boundary conditions at the surface, respectively. It is further shown that slip and no-slip boundary conditions predict the heat transfer velocity corresponding to the limits of clean and highly surfactant contaminated surfaces, respectively. This article was corrected on 22 MAR 2016. See the end of the full text for details.

Flow characteristics analysis of purge gas in unitary pebble beds by CFD simulation coupled with DEM geometry model for fusion blanket

Energy Technology Data Exchange (ETDEWEB)

Chen, Youhua [University of Science and Technology of China, Hefei, Anhui, 230027 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); Chen, Lei [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); Liu, Songlin, E-mail: slliu@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); Luo, Guangnan [University of Science and Technology of China, Hefei, Anhui, 230027 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China)

2017-01-15

Highlights: • A unitary pebble bed was built to analyze the flow characteristics of purge gas based on DEM-CFD method. • Flow characteristics between particles were clearly displayed. • Porosity distribution, velocity field distribution, pressure field distribution, pressure drop and the wall effects on velocity distribution were studied. - Abstract: Helium is used as the purge gas to sweep tritium out when it flows through the lithium ceramic and beryllium pebble beds in solid breeder blanket for fusion reactor. The flow characteristics of the purge gas will dominate the tritium sweep capability and tritium recovery system design. In this paper, a computational model for the unitary pebble bed was conducted using DEM-CFD method to study the purge gas flow characteristics in the bed, which include porosity distribution between pebbles, velocity field distribution, pressure field distribution, pressure drop as well as the wall effects on velocity distribution. Pebble bed porosity and velocity distribution with great fluctuations were found in the near-wall region and detailed flow characteristics between pebbles were displayed clearly. The results show that the numerical simulation model has an error with about 11% for estimating pressure drop when compared with the Ergun equation.

Surface shear stress dependence of gas transfer velocity parameterizations using DNS

Science.gov (United States)

Fredriksson, S. T.; Arneborg, L.; Nilsson, H.; Handler, R. A.

2016-10-01

Air-water gas-exchange is studied in direct numerical simulations (DNS) of free-surface flows driven by natural convection and weak winds. The wind is modeled as a constant surface-shear-stress and the gas-transfer is modeled via a passive scalar. The simulations are characterized via a Richardson number Ri=Bν/u*4 where B, ν, and u* are the buoyancy flux, kinematic viscosity, and friction velocity respectively. The simulations comprise 0Ric or kg=AShearu*Sc-n, Ri

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

Implementation of an ultrasonic instrument for simultaneous mixture and flow analysis of binary gas systems

Energy Technology Data Exchange (ETDEWEB)

Alhroob, M.; Boyd, G.; Hasib, A.; Pearson, B.; Srauss, M.; Young, J. [Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019, (United States); Bates, R.; Bitadze, A. [School of Physics and Astronomy, University of Glasgow, G12 8QQ, (United Kingdom); Battistin, M.; Berry, S.; Bonneau, P.; Botelho-Direito, J.; Bozza, G.; Crespo-Lopez, O.; DiGirolamo, B.; Favre, G.; Godlewski, J.; Lombard, D.; Zwalinski, L. [CERN, 1211 Geneva 23, (Switzerland); Bousson, N.; Hallewell, G.; Mathieu, M.; Rozanov, A. [Centre de Physique des Particules de Marseille, 163 Avenue de Luminy, 13288 Marseille Cedex 09, (France); Deterre, C.; O' Rourke, A. [Deutsches Elektronen-Synchrotron, Notkestrasse 85, D-22607 Hamburg, (Germany); Doubek, M.; Vacek, V. [Czech Technical University, Technick 4, 166 07 Prague 6, (Czech Republic); Degeorge, C. [Physics Department, Indiana University, Bloomington, IN 47405, (United States); Katunin, S. [B.P. Konstantinov Petersburg Nuclear Physics Institute (PNPI), 188300 St. Petersburg, (Russian Federation); Langevin, N. [Institut Universitaire de Technologie of Marseille, University of Aix-Marseille, 142 Traverse Charles Susini, 13013 Marseille, (France); McMahon, S. [Rutherford Appleton Laboratory - Science and Technology Facilities Council, Harwell Science and Innovation Campus, Didcot OX11 OQX, (United Kingdom); Nagai, K. [Department of Physics, Oxford University, Oxford OX1 3RH, (United Kingdom); Robinson, D. [Department of Physics and Astronomy, University of Cambridge, (United Kingdom); Rossi, C. [INFN - Genova, Via Dodecaneso 33, 16146 Genova, (Italy)

2015-07-01

Precision ultrasonic measurements in binary gas systems provide continuous real-time monitoring of mixture composition and flow. Using custom micro-controller-based electronics, we have developed an ultrasonic instrument, with numerous potential applications, capable of making continuous high-precision sound velocity measurements. The instrument measures sound transit times along two opposite directions aligned parallel to - or obliquely crossing - the gas flow. The difference between the two measured times yields the gas flow rate while their average gives the sound velocity, which can be compared with a sound velocity vs. molar composition look-up table for the binary mixture at a given temperature and pressure. The look-up table may be generated from prior measurements in known mixtures of the two components, from theoretical calculations, or from a combination of the two. We describe the instrument and its performance within numerous applications in the ATLAS experiment at the CERN Large Hadron Collider (LHC). The instrument can be of interest in other areas where continuous in-situ binary gas analysis and flowmetry are required. (authors)

Simulations of Micro Gas Flows by the DS-BGK Method

KAUST Repository

Li, Jun

2011-01-01

For gas flows in micro devices, the molecular mean free path is of the same order as the characteristic scale making the Navier-Stokes equation invalid. Recently, some micro gas flows are simulated by the DS-BGK method, which is convergent to the BGK equation and very efficient for low-velocity cases. As the molecular reflection on the boundary is the dominant effect compared to the intermolecular collisions in micro gas flows, the more realistic boundary condition, namely the CLL reflection model, is employed in the DS-BGK simulation and the influence of the accommodation coefficients used in the molecular reflection model on the results are discussed. The simulation results are verified by comparison with those of the DSMC method as criteria. Copyright © 2011 by ASME.

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

Directory of Open Access Journals (Sweden)

Kreta Aleksei

2016-01-01

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

SIZE REDUCTION OF ELECTROSTATIC PRECIPITATOR CHAMBER BY MODIFICATION OF GAS FLOW DISTRIBUTION

Directory of Open Access Journals (Sweden)

Beata Sładkowska-Rybka

2014-10-01

Full Text Available Electrostatic precipitators (ESP are one of the most effective devices for particulate emission control, removing from the exhaust gases even 99,9 % of dust particles. The collection efficiency of the ESP depends on a number of factors: mechanical design and electrical operating parameters, physical and chemical properties of cleaned gas, characteristic of dust particles suspended in the gas. Among the most important factors affecting the ESP effectiveness, the velocity and the distribution of gas flow in the ESP chamber should be also indicated. Significant increase in ESP efficiency is possible thanks to the application of Skewed Gas Flow Technology (SGFT. In this paper the computer simulations results are shown. Authors investigated the possibility of ESP chamber size reduction by modification of gas flow distribution.

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

Application of Fermat's Principle to Calculation of the Errors of Acoustic Flow-Rate Measurements for a Three-Dimensional Fluid Flow or Gas

Science.gov (United States)

Petrov, A. G.; Shkundin, S. Z.

2018-01-01

Fermat's variational principle is used for derivation of the formula for the time of propagation of a sonic signal between two set points A and B in a steady three-dimensional flow of a fluid or gas. It is shown that the fluid flow changes the time of signal reception by a value proportional to the flow rate independently of the velocity profile. The time difference in the reception of the signals from point B to point A and vice versa is proportional with a high accuracy to the flow rate. It is shown that the relative error of the formula does not exceed the square of the largest Mach number. This makes it possible to measure the flow rate of a fluid or gas with an arbitrary steady subsonic velocity field.

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)

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)

Transition of unsteady velocity profiles with reverse flow

Science.gov (United States)

Das, Debopam; Arakeri, Jaywant H.

1998-11-01

This paper deals with the stability and transition to turbulence of wall-bounded unsteady velocity profiles with reverse flow. Such flows occur, for example, during unsteady boundary layer separation and in oscillating pipe flow. The main focus is on results from experiments in time-developing flow in a long pipe, which is decelerated rapidly. The flow is generated by the controlled motion of a piston. We obtain analytical solutions for laminar flow in the pipe and in a two-dimensional channel for arbitrary piston motions. By changing the piston speed and the length of piston travel we cover a range of values of Reynolds number and boundary layer thickness. The velocity profiles during the decay of the flow are unsteady with reverse flow near the wall, and are highly unstable due to their inflectional nature. In the pipe, we observe from flow visualization that the flow becomes unstable with the formation of what appears to be a helical vortex. The wavelength of the instability [simeq R: similar, equals]3[delta] where [delta] is the average boundary layer thickness, the average being taken over the time the flow is unstable. The time of formation of the vortices scales with the average convective time scale and is [simeq R: similar, equals]39/([Delta]u/[delta]), where [Delta]u=(umax[minus sign]umin) and umax, umin and [delta] are the maximum velocity, minimum velocity and boundary layer thickness respectively at each instant of time. The time to transition to turbulence is [simeq R: similar, equals]33/([Delta]u/[delta]). Quasi-steady linear stability analysis of the velocity profiles brings out two important results. First that the stability characteristics of velocity profiles with reverse flow near the wall collapse when scaled with the above variables. Second that the wavenumber corresponding to maximum growth does not change much during the instability even though the velocity profile does change substantially. Using the results from the experiments and the

Simulation of neutral gas flow in a tokamak divertor using the Direct Simulation Monte Carlo method

International Nuclear Information System (INIS)

Gleason-González, Cristian; Varoutis, Stylianos; Hauer, Volker; Day, Christian

2014-01-01

Highlights: • Subdivertor gas flows calculations in tokamaks by coupling the B2-EIRENE and DSMC method. • The results include pressure, temperature, bulk velocity and particle fluxes in the subdivertor. • Gas recirculation effect towards the plasma chamber through the vertical targets is found. • Comparison between DSMC and the ITERVAC code reveals a very good agreement. - Abstract: This paper presents a new innovative scientific and engineering approach for describing sub-divertor gas flows of fusion devices by coupling the B2-EIRENE (SOLPS) code and the Direct Simulation Monte Carlo (DSMC) method. The present study exemplifies this with a computational investigation of neutral gas flow in the ITER's sub-divertor region. The numerical results include the flow fields and contours of the overall quantities of practical interest such as the pressure, the temperature and the bulk velocity assuming helium as model gas. Moreover, the study unravels the gas recirculation effect located behind the vertical targets, viz. neutral particles flowing towards the plasma chamber. Comparison between calculations performed by the DSMC method and the ITERVAC code reveals a very good agreement along the main sub-divertor ducts

Dynamic Gas Flow Effects on the ESD of Aerospace Vehicle Surfaces

Science.gov (United States)

Hogue, Michael D.; Kapat, Jayanta; Ahmed, Kareem; Cox, Rachel E.; Wilson, Jennifer G.; Calle, Luz M.; Mulligan, Jaysen

2016-01-01

The purpose of this work is to develop a dynamic version of Paschen's Law that takes into account the flow of ambient gas past aerospace vehicle surfaces. However, the classic Paschen's Law does not take into account the flow of gas of an aerospace vehicle, whose surfaces may be triboelectrically charged by dust or ice crystal impingement, traversing the atmosphere. The basic hypothesis of this work is that the number of electron-ion pairs created per unit distance by the electric field between the electrodes is mitigated by the electron-ion pairs removed per unit distance by the flow of gas. The revised Paschen equation must be a function of the mean velocity, v(sub xm), of the ambient gas and reduces to the classical version of Paschen's law when the gas mean velocity, v(sub xm) = 0. New formulations of Paschen's Law, taking into account Mach number and dynamic pressure, derived by the authors, will be discussed. These equations will be evaluated by wind tunnel experimentation later this year. Based on the results of this work, it is hoped that the safety of aerospace vehicles will be enhanced with a redefinition of electrostatic launch commit criteria. It is also possible that new products, such as new anti-static coatings, may be formulated from this data.

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

Energy Technology Data Exchange (ETDEWEB)

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

2008-08-15

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

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

International Nuclear Information System (INIS)

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

2008-01-01

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

Blood flow velocity in migraine attacks - a transcranial Doppler study

International Nuclear Information System (INIS)

Zwetsloot, C.P.; Caekebeke, J.F.V.; Jansen, J.C.; Odink, J.; Ferrari, M.D.

1991-01-01

A pulsed Doppler device was used to measure blood flow velocities in the common carotid artery, the extracranial part of the internal carotid artery, the external carotid artery, the middle cerebral artery, and the anterior cerebral artery in 31 migraneurs without aura (n=27) and with aura (n=4), both during and ouside an attack. The aims were to compare blood flow velocity during and between migraine attacks and to study asymmetries of the blood flow velocity. Compared with blood flow velocity values obtained in the attack-free interval, blood flow velocity was lower during attacks without aura in both common carotid arteries, but not in the other extra- and intracranial vessels which were examined. However, during attacks of migraine with aura, blood flow velocity tended to be lower in all examined vessels. There were no asymmetries of the blood flow velocity. It is suggested that during migraine attacks without aura there is a dissociation in blood flow regulation in the common carotid and middle cerebral arteries. 20 refs., 2 tabs

Blood flow velocity in migraine attacks - a transcranial Doppler study

Energy Technology Data Exchange (ETDEWEB)

Zwetsloot, C.P.; Caekebeke, J.F.V.; Jansen, J.C.; Odink, J.; Ferrari, M.D. (Rijksuniversiteit Leiden (Netherlands))

1991-05-01

A pulsed Doppler device was used to measure blood flow velocities in the common carotid artery, the extracranial part of the internal carotid artery, the external carotid artery, the middle cerebral artery, and the anterior cerebral artery in 31 migraneurs without aura (n=27) and with aura (n=4), both during and ouside an attack. The aims were to compare blood flow velocity during and between migraine attacks and to study asymmetries of the blood flow velocity. Compared with blood flow velocity values obtained in the attack-free interval, blood flow velocity was lower during attacks without aura in both common carotid arteries, but not in the other extra- and intracranial vessels which were examined. However, during attacks of migraine with aura, blood flow velocity tended to be lower in all examined vessels. There were no asymmetries of the blood flow velocity. It is suggested that during migraine attacks without aura there is a dissociation in blood flow regulation in the common carotid and middle cerebral arteries. 20 refs., 2 tabs.

Investigation of gas flow characteristics in proton exchange membrane fuel cell

International Nuclear Information System (INIS)

Kwac, Lee Ku; Kim, Hong Gun

2008-01-01

An investigation of electrochemical behavior of PEMFC (proton exchange membrane fuel cell) is performed by using a single-phase two-dimensional finite element analysis. Equations of current balance, mass balance, and momentum balance are implemented to simulate the behavior of PEMFC. The analysis results for the co-flow and counterflow mode of gas flow direction are examined in detail in order to compare how the gas flow direction affects quantitatively. The characteristics of internal properties, such as gas velocity distribution, mass fraction of the reactants, fraction of water and current density distribution in PEMFC are illustrated in the electrode and GDL (gas diffusion layer). It is found that the dry reactant gases can be well internally humidified and maintain high performance in the case of the counter-flow mode without external humidification while it is not advantageous for highly humidified or saturated reactant gases. It is also found that the co-flow mode improves the current density distribution with humidified normal condition compared to the counter-flow mode

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.

An Approach to Predict Debris Flow Average Velocity

Directory of Open Access Journals (Sweden)

Chen Cao

2017-03-01

Full Text Available Debris flow is one of the major threats for the sustainability of environmental and social development. The velocity directly determines the impact on the vulnerability. This study focuses on an approach using radial basis function (RBF neural network and gravitational search algorithm (GSA for predicting debris flow velocity. A total of 50 debris flow events were investigated in the Jiangjia gully. These data were used for building the GSA-based RBF approach (GSA-RBF. Eighty percent (40 groups of the measured data were selected randomly as the training database. The other 20% (10 groups of data were used as testing data. Finally, the approach was applied to predict six debris flow gullies velocities in the Wudongde Dam site area, where environmental conditions were similar to the Jiangjia gully. The modified Dongchuan empirical equation and the pulled particle analysis of debris flow (PPA approach were used for comparison and validation. The results showed that: (i the GSA-RBF predicted debris flow velocity values are very close to the measured values, which performs better than those using RBF neural network alone; (ii the GSA-RBF results and the MDEE results are similar in the Jiangjia gully debris flow velocities prediction, and GSA-RBF performs better; (iii in the study area, the GSA-RBF results are validated reliable; and (iv we could consider more variables in predicting the debris flow velocity by using GSA-RBF on the basis of measured data in other areas, which is more applicable. Because the GSA-RBF approach was more accurate, both the numerical simulation and the empirical equation can be taken into consideration for constructing debris flow mitigation works. They could be complementary and verified for each other.

Determination of flow rates of oil, water and gas in pipelines

Energy Technology Data Exchange (ETDEWEB)

Roach, G J; Watt, J S; Zastawny, H W [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Lucas Heights, NSW (Australia). Div. of Mineral Physics

1994-12-31

This paper describes a multiphase flow meter developed by CSIRO for determining of the flow rates of oil, water and gas in high pressure pipelines, and the results of a trial of this flow meter on an offshore oil platform. Two gamma-ray transmission gauges are mounted about a pipeline carrying the full flow of oil, water and gas. The flow rates are determined by combining single energy gamma-ray transmission measurements which determine the mass per unit area of fluids in the gamma-ray beam as a function of time, dual energy gamma-ray transmission (DUET) which determine the approximate mass fraction of oil in the liquids, cross-correlation of gamma-ray transmission measurements, with one gauge upstream of the other, which determines flow velocity, pressure and temperature measurements, and knowledge of the specific gravities of oil and (salt) water, and solubility of the gas in the liquids, all as a function of pressure and temperature. 3 figs.

Determination of flow rates of oil, water and gas in pipelines

Energy Technology Data Exchange (ETDEWEB)

Roach, G.J.; Watt, J.S.; Zastawny, H.W. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Lucas Heights, NSW (Australia). Div. of Mineral Physics

1993-12-31

This paper describes a multiphase flow meter developed by CSIRO for determining of the flow rates of oil, water and gas in high pressure pipelines, and the results of a trial of this flow meter on an offshore oil platform. Two gamma-ray transmission gauges are mounted about a pipeline carrying the full flow of oil, water and gas. The flow rates are determined by combining single energy gamma-ray transmission measurements which determine the mass per unit area of fluids in the gamma-ray beam as a function of time, dual energy gamma-ray transmission (DUET) which determine the approximate mass fraction of oil in the liquids, cross-correlation of gamma-ray transmission measurements, with one gauge upstream of the other, which determines flow velocity, pressure and temperature measurements, and knowledge of the specific gravities of oil and (salt) water, and solubility of the gas in the liquids, all as a function of pressure and temperature. 3 figs.

Determination of flow rates of oil, water and gas in pipelines

International Nuclear Information System (INIS)

Roach, G.J.; Watt, J.S.; Zastawny, H.W.

1993-01-01

This paper describes a multiphase flow meter developed by CSIRO for determining of the flow rates of oil, water and gas in high pressure pipelines, and the results of a trial of this flow meter on an offshore oil platform. Two gamma-ray transmission gauges are mounted about a pipeline carrying the full flow of oil, water and gas. The flow rates are determined by combining single energy gamma-ray transmission measurements which determine the mass per unit area of fluids in the gamma-ray beam as a function of time, dual energy gamma-ray transmission (DUET) which determine the approximate mass fraction of oil in the liquids, cross-correlation of gamma-ray transmission measurements, with one gauge upstream of the other, which determines flow velocity, pressure and temperature measurements, and knowledge of the specific gravities of oil and (salt) water, and solubility of the gas in the liquids, all as a function of pressure and temperature. 3 figs

The influence of liquid-gas velocity ratio on the noise of the cooling tower

Science.gov (United States)

Yang, Bin; Liu, Xuanzuo; Chen, Chi; Zhao, Zhouli; Song, Jinchun

2018-05-01

The noise from the cooling tower has a great influence on psychological performance of human beings. The cooling tower noise mainly consists of fan noise, falling water noise and mechanical noise. This thesis used DES turbulence model with FH-W model to simulate the flow and sound pressure field in cooling tower based on CFD software FLUENT and analyzed the influence of different kinds noise, which affected by diverse factors, on the cooling tower noise. It can be concluded that the addition of cooling water can reduce the turbulence and vortex noise of the rotor fluid field in the cooling tower at some extent, but increase the impact noise of the liquid-gas two phase. In general, the cooling tower noise decreases with the velocity ratio of liquid to gas increasing, and reaches the lowest when the velocity ratio of liquid to gas is close to l.

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

Grouping and trapping of evaporating droplets in an oscillating gas flow

International Nuclear Information System (INIS)

Katoshevski, David; Shakked, Tal; Sazhin, Sergei S.; Crua, Cyril; Heikal, Morgan R.

2008-01-01

A new approach to the analysis of droplet grouping in an oscillating gas flow is suggested. This is based on the investigation of droplet trajectories in the frame of reference moving with the phase velocity of the wave. Although the equations involved are relatively simple, the analysis shows distinctive characteristics of grouping and non-grouping cases. In the case of grouping, droplet trajectories converge to the points for which the ratio of flow velocity in this frame of reference and the amplitude of flow oscillations is less than 1, and the cosine of the arc sine of this ratio is positive. In the case of non-grouping, droplet trajectories in this frame of reference oscillate around the translational velocity close to the velocity of flow in the same frame of reference. The effect of droplet size on the grouping pattern is investigated. It has been pointed out that for the smaller droplets much more stable grouping is observed. The effect of droplet evaporation is studied in the limiting case when the contribution of the heat-up period can be ignored. It is shown that evaporation can lead to droplet grouping even in the case when the non-evaporating droplets are not grouped. This is related to the reduction in droplet diameter during the evaporation process. Coupling between gas and droplets is shown to decrease the grouping tendency. A qualitative agreement between predictions of the model and in-house experimental observations referring to Diesel engine sprays has been demonstrated

Propagation of atmospheric pressure helium plasma jet into ambient air at laminar gas flow

Science.gov (United States)

Pinchuk, M.; Stepanova, O.; Kurakina, N.; Spodobin, V.

2017-05-01

The formation of an atmospheric pressure plasma jet (APPJ) in a gas flow passing through the discharge gap depends on both gas-dynamic properties and electrophysical parameters of the plasma jet generator. The paper presents the results of experimental and numerical study of the propagation of the APPJ in a laminar flow of helium. A dielectric-barrier discharge (DBD) generated inside a quartz tube equipped with a coaxial electrode system, which provided gas passing through it, served as a plasma source. The transition of the laminar regime of gas flow into turbulent one was controlled by the photography of a formed plasma jet. The corresponding gas outlet velocity and Reynolds numbers were revealed experimentally and were used to simulate gas dynamics with OpenFOAM software. The data of the numerical simulation suggest that the length of plasma jet at the unvarying electrophysical parameters of DBD strongly depends on the mole fraction of ambient air in a helium flow, which is established along the direction of gas flow.

A development of multiphase flow facility

International Nuclear Information System (INIS)

Ismail Mustapha; Jaafar Abdullah

2004-01-01

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

Exploiting LSPIV to assess debris-flow velocities in the field

Science.gov (United States)

Theule, Joshua I.; Crema, Stefano; Marchi, Lorenzo; Cavalli, Marco; Comiti, Francesco

2018-01-01

The assessment of flow velocity has a central role in quantitative analysis of debris flows, both for the characterization of the phenomenology of these processes and for the assessment of related hazards. Large-scale particle image velocimetry (LSPIV) can contribute to the assessment of surface velocity of debris flows, provided that the specific features of these processes (e.g. fast stage variations and particles up to boulder size on the flow surface) are taken into account. Three debris-flow events, each of them consisting of several surges featuring different sediment concentrations, flow stages, and velocities, have been analysed at the inlet of a sediment trap in a stream in the eastern Italian Alps (Gadria Creek). Free software has been employed for preliminary treatment (orthorectification and format conversion) of video-recorded images as well as for LSPIV application. Results show that LSPIV velocities are consistent with manual measurements of the orthorectified imagery and with front velocity measured from the hydrographs in a channel recorded approximately 70 m upstream of the sediment trap. Horizontal turbulence, computed as the standard deviation of the flow directions at a given cross section for a given surge, proved to be correlated with surface velocity and with visually estimated sediment concentration. The study demonstrates the effectiveness of LSPIV in the assessment of surface velocity of debris flows and permit the most crucial aspects to be identified in order to improve the accuracy of debris-flow velocity measurements.

Preliminary evaluation of vector flow and spectral velocity estimation

DEFF Research Database (Denmark)

Pedersen, Mads Møller; Pihl, Michael Johannes; Haugaard, Per

Spectral estimation is considered as the golden standard in ultrasound velocity estimation. For spectral velocity estimation the blood flow angle is set by the ultrasound operator. Vector flow provides temporal and spatial estimates of the blood flow angle and velocity. A comparison of vector flow...... line covering the vessel diameter. A commercial ultrasound scanner (ProFocus 2202, BK Medical, Denmark) and a 7.6 MHz linear transducer was used (8670, BK Medical). The mean vector blood flow angle estimations were calculated {52(18);55(23);60(16)}°. For comparison the fixed angles for spectral...... estimation were obtained {52;56;52}°. The mean vector velocity estimates at PS {76(15);95(17);77(16)}cm/s and at end diastole (ED) {17(6);18(6);24(6)}cm/s were calculated. For comparison spectral velocity estimates at PS {77;110;76}cm/s and ED {18;18;20}cm/s were obtained. The mean vector angle estimates...

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

International Nuclear Information System (INIS)

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

2005-01-01

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

The in situ permeable flow sensor: A device for measuring groundwater flow velocity

International Nuclear Information System (INIS)

Ballard, S.; Barker, G.T.; Nichols, R.L.

1994-03-01

A new technology called the In Situ Permeable Flow Sensor has been developed at Sandia National Laboratories. These sensors use a thermal perturbation technique to directly measure the direction and magnitude of the full three dimensional groundwater flow velocity vector in unconsolidated, saturated, porous media. The velocity measured is an average value characteristic of an approximately 1 cubic meter volume of the subsurface. During a test at the Savannah River Site in South Carolina, two flow sensors were deployed in a confined aquifer in close proximity to a well which was screened over the entire vertical extent of the aquifer and the well was pumped at four different pumping rates. In this situation horizontal flow which is radially directed toward the pumping well is expected. The flow sensors measured horizontal flow which was directed toward the pumping well, within the uncertainty in the measurements. The observed magnitude of the horizontal component of the flow velocity increased linearly with pumping rate, as predicted by theoretical considerations. The measured horizontal component of the flow velocity differed from the predicted flow velocity, which was calculated with the assumptions that the hydraulic properties of the aquifer were radially homogeneous and isotropic, by less than a factor of two. Drawdown data obtained from other wells near the pumping well during the pump test indicate that the hydraulic properties of the aquifer are probably not radially homogeneous but the effect of the inhomogeneity on the flow velocity field around the pumping well was not modeled because the degree and distribution of the inhomogeneity are unknown. Grain size analysis of core samples from wells in the area were used to estimate the vertical distribution of hydraulic conductivity

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

A new method for ultrasound detection of interfacial position in gas-liquid two-phase flow.

Science.gov (United States)

Coutinho, Fábio Rizental; Ofuchi, César Yutaka; de Arruda, Lúcia Valéria Ramos; Neves, Flávio; Morales, Rigoberto E M

2014-05-22

Ultrasonic measurement techniques for velocity estimation are currently widely used in fluid flow studies and applications. An accurate determination of interfacial position in gas-liquid two-phase flows is still an open problem. The quality of this information directly reflects on the accuracy of void fraction measurement, and it provides a means of discriminating velocity information of both phases. The algorithm known as Velocity Matched Spectrum (VM Spectrum) is a velocity estimator that stands out from other methods by returning a spectrum of velocities for each interrogated volume sample. Interface detection of free-rising bubbles in quiescent liquid presents some difficulties for interface detection due to abrupt changes in interface inclination. In this work a method based on velocity spectrum curve shape is used to generate a spatial-temporal mapping, which, after spatial filtering, yields an accurate contour of the air-water interface. It is shown that the proposed technique yields a RMS error between 1.71 and 3.39 and a probability of detection failure and false detection between 0.89% and 11.9% in determining the spatial-temporal gas-liquid interface position in the flow of free rising bubbles in stagnant liquid. This result is valid for both free path and with transducer emitting through a metallic plate or a Plexiglas pipe.

Gas and particle motions in a rapidly decompressed flow

Science.gov (United States)

Johnson, Blair; Zunino, Heather; Adrian, Ronald; Clarke, Amanda

2017-11-01

To understand the behavior of a rapidly decompressed particle bed in response to a shock, an experimental study is performed in a cylindrical (D = 4.1 cm) glass vertical shock tube of a densely packed (ρ = 61%) particle bed. The bed is comprised of spherical glass particles, ranging from D50 = 44-297 μm between experiments. High-speed pressure sensors are incorporated to capture shock speeds and strengths. High-speed video and particle image velocimetry (PIV) measurements are collected to examine vertical and radial velocities of both the particles and gas to elucidate features of the shock wave and resultant expansion wave in the lateral center of the tube, away from boundaries. In addition to optically analyzing the front velocity of the rising particle bed, interaction between the particle and gas phases are investigated as the flow accelerates and the particle front becomes more dilute. Particle and gas interactions are also considered in exploring mechanisms through which turbulence develops in the flow. This work is supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science and Academic Alliance Program, under Contract No. DE-NA0002378.

Gaseous slip flow analysis of a micromachined flow sensor for ultra small flow applications

OpenAIRE

Jang, Jaesung; Wereley, Steven

2007-01-01

The velocity slip of a fluid at a wall is one of the most typical phenomena in microscale gas flows. This paper presents a flow analysis considering the velocity slip in a capacitive micro gas flow sensor based on pressure difference measurements along a microchannel. The tangential momentum accommodation coefficient (TMAC) measurements of a particular channel wall in planar microchannels will be presented while the previous micro gas flow studies have been based on the same TMACs on both wal...

Program determines two-phase flow

International Nuclear Information System (INIS)

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

1986-01-01

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

Gas flow parameter determination by molecular beam method

International Nuclear Information System (INIS)

Zarvin, A.E.; Sharafutdinov, R.G.

1977-01-01

This paper describes a molecular-beam system intended for studying nonequilibrium processes in supersonic rarefied gas flows. The system represented is a small molecular beam source placed inside the low intensity wind tunnel of the Institute of Thermophysics, Siberian Branch of the USSR Academy of Sciences. The time-of-flight method is used for measuring molecular velocity distribution functions on molecular beam axis. (Auth.)

Using Modelica to investigate the dynamic behaviour of the German national standard for high pressure natural gas flow metering

International Nuclear Information System (INIS)

Von der Heyde, M; Schmitz, G; Mickan, B

2016-01-01

This paper presents a computational model written in Modelica for the high pressure piston prover (HPPP) used as the national primary standard for high pressure natural gas flow metering in Germany. With a piston prover the gas flow rate is determined by measuring the time a piston needs to displace a certain volume of gas in a cylinder. Fluctuating piston velocity during measurement can be a significant source of uncertainty if not considered in an appropriate way. The model was built to investigate measures for the reduction of this uncertainty. Validation shows a good compliance of the piston velocity in the model with measured data for certain volume flow rates. Reduction of the piston weight, variation of the start valve switching time and integration of a flow straightener were found to reduce the piston velocity fluctuations in the model significantly. The fast and cost effective generation of those results shows the strength of the used modelling approach. (paper)

Numerical modeling of carrier gas flow in atomic layer deposition vacuum reactor: A comparative study of lattice Boltzmann models

International Nuclear Information System (INIS)

Pan, Dongqing; Chien Jen, Tien; Li, Tao; Yuan, Chris

2014-01-01

This paper characterizes the carrier gas flow in the atomic layer deposition (ALD) vacuum reactor by introducing Lattice Boltzmann Method (LBM) to the ALD simulation through a comparative study of two LBM models. Numerical models of gas flow are constructed and implemented in two-dimensional geometry based on lattice Bhatnagar–Gross–Krook (LBGK)-D2Q9 model and two-relaxation-time (TRT) model. Both incompressible and compressible scenarios are simulated and the two models are compared in the aspects of flow features, stability, and efficiency. Our simulation outcome reveals that, for our specific ALD vacuum reactor, TRT model generates better steady laminar flow features all over the domain with better stability and reliability than LBGK-D2Q9 model especially when considering the compressible effects of the gas flow. The LBM-TRT is verified indirectly by comparing the numerical result with conventional continuum-based computational fluid dynamics solvers, and it shows very good agreement with these conventional methods. The velocity field of carrier gas flow through ALD vacuum reactor was characterized by LBM-TRT model finally. The flow in ALD is in a laminar steady state with velocity concentrated at the corners and around the wafer. The effects of flow fields on precursor distributions, surface absorptions, and surface reactions are discussed in detail. Steady and evenly distributed velocity field contribute to higher precursor concentration near the wafer and relatively lower particle velocities help to achieve better surface adsorption and deposition. The ALD reactor geometry needs to be considered carefully if a steady and laminar flow field around the wafer and better surface deposition are desired

Numerical modeling of carrier gas flow in atomic layer deposition vacuum reactor: A comparative study of lattice Boltzmann models

Energy Technology Data Exchange (ETDEWEB)

Pan, Dongqing; Chien Jen, Tien [Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201 (United States); Li, Tao [School of Mechanical Engineering, Dalian University of Technology, Dalian 116024 (China); Yuan, Chris, E-mail: cyuan@uwm.edu [Department of Mechanical Engineering, University of Wisconsin-Milwaukee, 3200 North Cramer Street, Milwaukee, Wisconsin 53211 (United States)

2014-01-15

This paper characterizes the carrier gas flow in the atomic layer deposition (ALD) vacuum reactor by introducing Lattice Boltzmann Method (LBM) to the ALD simulation through a comparative study of two LBM models. Numerical models of gas flow are constructed and implemented in two-dimensional geometry based on lattice Bhatnagar–Gross–Krook (LBGK)-D2Q9 model and two-relaxation-time (TRT) model. Both incompressible and compressible scenarios are simulated and the two models are compared in the aspects of flow features, stability, and efficiency. Our simulation outcome reveals that, for our specific ALD vacuum reactor, TRT model generates better steady laminar flow features all over the domain with better stability and reliability than LBGK-D2Q9 model especially when considering the compressible effects of the gas flow. The LBM-TRT is verified indirectly by comparing the numerical result with conventional continuum-based computational fluid dynamics solvers, and it shows very good agreement with these conventional methods. The velocity field of carrier gas flow through ALD vacuum reactor was characterized by LBM-TRT model finally. The flow in ALD is in a laminar steady state with velocity concentrated at the corners and around the wafer. The effects of flow fields on precursor distributions, surface absorptions, and surface reactions are discussed in detail. Steady and evenly distributed velocity field contribute to higher precursor concentration near the wafer and relatively lower particle velocities help to achieve better surface adsorption and deposition. The ALD reactor geometry needs to be considered carefully if a steady and laminar flow field around the wafer and better surface deposition are desired.

Flow characteristics of centrifugal gas-liquid separator. Investigation with air-water two-phase flow experiment

International Nuclear Information System (INIS)

Yoneda, Kimitoshi; Inada, Fumio

2004-01-01

Air-water two-phase flow experiment was conducted to examine the basic flow characteristics of a centrifugal gas-liquid separator. Vertical transparent test section, which is 4 m in height, was used to imitate the scale of a BWR separator. Flow rate conditions of gas and liquid were fixed at 0.1 m 3 /s and 0.033 m 3 /s, respectively. Radial distributions of two-phase flow characteristics, such as void fraction, gas velocity and bubble chord length, were measured by traversing dual optical void probes in the test section, horizontally. The flow in the standpipe reached to quasi-developed state within the height-to-diameter aspect ratio H/D=10, which in turn can mean the maximum value for an ideal height design of a standpipe. The liquid film in the barrel showed a maximum thickness at 0.5 to 1 m in height from the swirler exit, which was a common result for three different standpipe length conditions, qualitatively and quantitatively. The empirical database obtained in this study would contribute practically to the validation of numerical analyses for an actual separator in a plant, and would also be academically useful for further investigations of two-phase flow in large-diameter pipes. (author)

Propagation of atmospheric pressure helium plasma jet into ambient air at laminar gas flow

International Nuclear Information System (INIS)

Pinchuk, M; Kurakina, N; Spodobin, V; Stepanova, O

2017-01-01

The formation of an atmospheric pressure plasma jet (APPJ) in a gas flow passing through the discharge gap depends on both gas-dynamic properties and electrophysical parameters of the plasma jet generator. The paper presents the results of experimental and numerical study of the propagation of the APPJ in a laminar flow of helium. A dielectric-barrier discharge (DBD) generated inside a quartz tube equipped with a coaxial electrode system, which provided gas passing through it, served as a plasma source. The transition of the laminar regime of gas flow into turbulent one was controlled by the photography of a formed plasma jet. The corresponding gas outlet velocity and Reynolds numbers were revealed experimentally and were used to simulate gas dynamics with OpenFOAM software. The data of the numerical simulation suggest that the length of plasma jet at the unvarying electrophysical parameters of DBD strongly depends on the mole fraction of ambient air in a helium flow, which is established along the direction of gas flow. (paper)

Verification procedures of ultrasonic flow meters for natural gas applications; Procedimento de verificacao de medidores ultra-sonicos para gas natural

Energy Technology Data Exchange (ETDEWEB)

Lourenco, Tulio C. [TRANSPETRO, Rio de Janeiro, RJ (Brazil)

2009-12-19

In recent years, the use of ultrasonic flow meters for natural gas applications has grown significantly, especially after the issuance of AGA Report 9 and AGA Report 10. The reasons this technology has stood out from the others, such as orifice-plates or turbines, are: accuracy, wide range ability, it is bi-directional, robustness, low maintenance and, mainly, integrated diagnostic parameters, such as sound velocity, signal quality and profile velocity analysis. TRANSPETRO currently operates 56 ultrasonic natural gas flow-meter systems. For operational control applications, 90% of the meters are ultrasonic, of which 85% are provided with internal diagnostic tools through the manufacturer's software. Within this perspective, it is essential and unquestionable that there are procedures and routines for ultrasonic flow-meter verification and analysis, in order to monitor their performance and integrity, in addition to the early identification of potential problems. This paper discusses the practical application of several tools and diagnostic parameters inherent in ultrasonic flow meters in periodical verifications using TRANSPETRO's procedure. (author)

Analysis of high-speed rotating flow inside gas centrifuge casing

Science.gov (United States)

Pradhan, Sahadev

2017-11-01

The generalized analytical model for the radial boundary layer inside the gas centrifuge casing in which the inner cylinder is rotating at a constant angular velocity Ωi while the outer one is stationary, is formulated for studying the secondary gas flow field due to wall thermal forcing, inflow/outflow of light gas along the boundaries, as well as due to the combination of the above two external forcing. The analytical model includes the sixth order differential equation for the radial boundary layer at the cylindrical curved surface in terms of master potential (χ) , which is derived from the equations of motion in an axisymmetric (r - z) plane. The linearization approximation is used, where the equations of motion are truncated at linear order in the velocity and pressure disturbances to the base flow, which is a solid-body rotation. Additional approximations in the analytical model include constant temperature in the base state (isothermal compressible Couette flow), high aspect ratio (length is large compared to the annular gap), high Reynolds number, but there is no limitation on the Mach number. The discrete eigenvalues and eigenfunctions of the linear operators (sixth-order in the radial direction for the generalized analytical equation) are obtained. The solutions for the secondary flow is determined in terms of these eigenvalues and eigenfunctions. These solutions are compared with direct simulation Monte Carlo (DSMC) simulations and found excellent agreement (with a difference of less than 15%) between the predictions of the analytical model and the DSMC simulations, provided the boundary conditions in the analytical model are accurately specified.

Plasma flow velocity measurements using a modulated Michelson interferometer

International Nuclear Information System (INIS)

Howard, J.

1997-01-01

This paper discusses the possibility of flow velocity reconstruction using passive spectroscopic techniques. We report some preliminary measurements of the toroidal flow velocity of hydrogen atoms in the RTP tokamak using a phase modulated Michelson interferometer. (orig.)

Steady Secondary Flows Generated by Periodic Compression and Expansion of an Ideal Gas in a Pulse Tube

Science.gov (United States)

Lee, Jeffrey M.

1999-01-01

This study establishes a consistent set of differential equations for use in describing the steady secondary flows generated by periodic compression and expansion of an ideal gas in pulse tubes. Also considered is heat transfer between the gas and the tube wall of finite thickness. A small-amplitude series expansion solution in the inverse Strouhal number is proposed for the two-dimensional axisymmetric mass, momentum and energy equations. The anelastic approach applies when shock and acoustic energies are small compared with the energy needed to compress and expand the gas. An analytic solution to the ordered series is obtained in the strong temperature limit where the zeroth-order temperature is constant. The solution shows steady velocities increase linearly for small Valensi number and can be of order I for large Valensi number. A conversion of steady work flow to heat flow occurs whenever temperature, velocity or phase angle gradients are present. Steady enthalpy flow is reduced by heat transfer and is scaled by the Prandtl times Valensi numbers. Particle velocities from a smoke-wire experiment were compared with predictions for the basic and orifice pulse tube configurations. The theory accurately predicted the observed steady streaming.

Local velocity measurements in lead-bismuth and sodium flows using the ultrasound doppler velocimetry

International Nuclear Information System (INIS)

Eckert, S.; Gerbeth, G.

2003-01-01

We will present measurements of the velocity profiles in liquid sodium and eutectic lead-bismuth by means of the Ultrasonic Doppler Velocimetry (UDV). A sodium flow in a rectangular duct exposed to an external, transverse magnetic field has been examined. To demonstrate the capability of UDV the transformation of the well-known turbulent, piston-like profile to an M-shaped velocity profile for growing magnetic field strength was observed. The significance of artifacts such as caused by the existence of reflecting interfaces in the measuring domain will be discussed. In the sodium case, the measurements were performed through the channel wall. An integrated ultrasonic sensor with acoustic wave-guide has been developed to overcome the limitation of ultrasonic transducers to temperatures lower than 200 .deg. C. This sensor can presently be applied at maximum temperatures up to 800 .deg. C. Stable and robust measurements have been performed in various PbBi flows in our laboratory at FZR as well as at the THESYS loop of the KALLA laboratory of the ForschungsZentrum Karlsruhe (FZK). We will also present experimental results obtained in a PbBi bubbly flow at 250...300 .deg. C. Argon bubbles were injected through a single orifice in a cylindrical container filled with stagnant PbBi. Velocity profiles were measured in the bubble plume. Mean values of the liquid as well as the bubble velocity were extracted from the data and will be presented as function of the gas flow rate

Gas-liquid flow around an obstacle in a vertical pipe

International Nuclear Information System (INIS)

Prasser, Horst-Michael; Beyer, Matthias; Frank, Thomas; Al Issa, Suleiman; Carl, Helmar; Pietruske, Heiko; Schuetz, Peter

2008-01-01

This paper presents a novel technique to study the two-phase flow field around an asymmetric obstruction in a vertical pipe with a nominal diameter of DN200. Main feature of the experiments is the shifting of a half-moon shaped diaphragm causing the obstruction along the axis of the pipe. In this way, the 3D void field is scanned with a stationary wire-mesh sensor that supplies data with a spatial resolution of 3 mm over the cross-section and a measuring frequency of 2.5 kHz. Besides the measurement of time-averaged void fraction fields and bubble-size distributions, novel data evaluation methods were developed to extract estimated liquid velocity profiles as well as lateral components of bubble velocities from the wire-mesh sensor data. The combination of void fraction fields and velocity profiles offer the opportunity to analyse a two-phase flow in a geometry that owns a series of features characteristic for complex components of power and chemical plant equipment. Such characteristics are sharp edges with flow separation, recirculation areas, jet formation, stagnation points and curved stream-lines. The tests were performed with an air-water flow at nearly ambient conditions and with a saturated steam-water mixture at 6.5 MPa. The superficial velocities of liquid and gas or, respectively, vapour were varied in a wide range. The flow structure upstream and downstream of the obstacle is characterized in detail. Bubble size dependent effects of bubble accumulation and migration are discussed on basis of void-fraction profiles decomposed into bubble-size classes. A pronounced influence of the fluid parameters was found in the behaviour of bubbles at the boundary of the jet coming from the non-obstructed part of the cross-section. In case of an air-water flow, bubbles are restrained from entering the jet, a phenomenon which was not observed in high-pressure steam-water flow. A detailed uncertainty analyse of the velocity assessments finishes the presented paper. A

Instrument for measuring flow velocities

International Nuclear Information System (INIS)

Griffo, J.

1977-01-01

The design described here means to produce a 'more satisfying instrument with less cost' than comparable instruments known up to now. Instead of one single turbine rotor, two similar ones but with opposite blade inclination and sense of rotation are to be used. A cylindrical measuring body is carrying in its axis two bearing blocks whose shape is offering little flow resistance. On the shaft, supported by them, the two rotors run in opposite direction a relatively small axial distance apart. The speed of each rotor is picked up as pulse recurrence frequency by a transmitter and fed to an electronic measuring unit. Measuring errors as they are caused for single rotors by turbulent flow, profile distortion of the velocity, or viscous flow are to be eliminated by means of the contrarotating turbines and the subsequently added electronic unit, because in these cases the adulterating increase of the angular velocity of one rotor is compensated by a corresponding deceleration of the other rotor. The mean value then indicated by the electronic unit has high accurancy of measurement. (RW) [de

The critical ionization velocity mechnism for the case of gas mixture

International Nuclear Information System (INIS)

Raadu, M.A.

1982-08-01

The theory of the critical ionization velocity mechnisms is discussed. In the case of gas mixture the critical velocity is expected to depend on the ionization cross sections. An analytic approximation is introduced which can be used to set limits on a generalized expression for the critical velocity of gas mixtures. (Author)

The universal sound velocity formula for the strongly interacting unitary Fermi gas

International Nuclear Information System (INIS)

Liu Ke; Chen Ji-Sheng

2011-01-01

Due to the scale invariance, the thermodynamic laws of strongly interacting limit unitary Fermi gas can be similar to those of non-interacting ideal gas. For example, the virial theorem between pressure and energy density of the ideal gas P = 2E/3V is still satisfied by the unitary Fermi gas. This paper analyses the sound velocity of unitary Fermi gases with the quasi-linear approximation. For comparison, the sound velocities for the ideal Boltzmann, Bose and Fermi gas are also given. Quite interestingly, the sound velocity formula for the ideal non-interacting gas is found to be satisfied by the unitary Fermi gas in different temperature regions. (general)

Numerical Simulation of Gas-Solid Two-Phase Flow for Four-Channels Pulverized Swirling Burner

Directory of Open Access Journals (Sweden)

Defu LI

2013-05-01

Full Text Available This article presents a mathematical model of cold gas-solid two-phase flow which is based on the cement rotary kiln in service. By altering the parameters of air supply system of four- channels pulverized burner, investigations are taken of that motion trajectory and particle distributions in the very turbulent field. The results show that motion trail of most particles in rotary kiln is a combination process of gradual diffusion and slow sedimentation; increasing internal flow velocity would aggravate coal particles to diffuse; external flow velocity should be controlled in a reasonable range.

Transient heat transfer for forced convection flow of helium gas

International Nuclear Information System (INIS)

Liu, Qiusheng; Fukuda, Katsuya; Sasaki, Kenji; Yamamoto, Manabu

1999-01-01

Transient heat transfer coefficients for forced convection flow of helium gas over a horizontal cylinder were measured using a forced convection test loop. The platinum heater with a diameter of 1.0 mm was heated by electric current with an exponential increase of Q 0 exp(t/τ). It was clarified that the heat transfer coefficient approaches the steady-state one for the period τ over 1 s, and it becomes higher for the period of τ shorter than 1 s. The transient heat transfer shows less dependent on the gas flowing velocity when the period becomes very shorter. Semi-empirical correlations for steady-state and transient heat transfer were developed based on the experimental data. (author)

Numerical simulation of gas flow through unsaturated fractured rock at Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Cooper, C.A.

1990-01-01

Numerical analysis is used to identify the physical phenomena associated with barometrically driven gas (air and water vapor) flow through unsaturated fractured rock at Yucca Mountain, Nevada. Results from simple finite difference simulations indicate that for a fractured rock scenario, the maximum velocity of air out of an uncased 10 cm borehole is 0.002 m s -1 . An equivalent porous medium (EPM) model was incorporated into a multiphase, multicomponent simulator to test more complex conceptual models. Results indicate that for a typical June day, a diurnal pressure wave propagates about 160 m into the surrounding Tiva Canyon hydrogeologic unit. Dry air that enters the formation evaporates water around the borehole which reduces capillary pressure. Multiphase countercurrent flow develops in the vicinity of the hole; the gas phase flows into the formation while the liquid phase flows toward the borehole. The effect occurs within 0.5 m of the borehole. The amount of water vapor leaving the formation during 1 day is 900 cm 3 . This is less than 0.1% of the total recharge into the formation, suggesting that the barometric effect may be insignificant in drying the unsaturated zone. However, gas phase velocities out of the borehole (3 m s -1 ), indicating that observed flow rates from wells along the east flank of Yucca Mountain were able to be simulated with a barometric model

Droplet size and velocity at the exit of a nozzle with two-component near critical and critical flow

International Nuclear Information System (INIS)

Lemonnier, H.; Camelo-Cavalcanti, E.S.

1993-01-01

Two-component critical flow modelling is an important issue for safety studies of various hazardous industrial activities. When the flow quality is high, the critical flow rate prediction is sensitive to the modelling of gas droplet mixture interfacial area. In order to improve the description of these flows, experiments were conducted with air-water flows in converging nozzles. The pressure was 2 and 4 bar and the gas mass quality ranged between 100% and 20%. The droplets size and velocity have been measured close to the outlet section of a nozzle with a 10 mm diameter throat. Subcritical and critical conditions were observed. These data are compared with the predictions of a critical flow model which includes an interfacial area model based on the classical ideas of Hinze and Kolmogorov. (authors). 9 figs., 12 refs

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

Energy Technology Data Exchange (ETDEWEB)

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

2010-07-01

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

Dynamic exercise enhances regional cerebral artery mean flow velocity

DEFF Research Database (Denmark)

Linkis, P; Jørgensen, L G; Olesen, H L

1995-01-01

Dynamic exercise enhances regional cerebral artery mean flow velocity. J. Appl. Physiol. 78(1): 12-16, 1995.--Anterior (ACA) and middle (MCA) cerebral artery mean flow velocities (Vmean) and pulsatility indexes were determined using transcranial Doppler in 14 subjects during dynamic exercise afte...

Plasma flow velocity measurements using a modulated Michelson interferometer

NARCIS (Netherlands)

Howard, J.; Meijer, F. G.

1997-01-01

This paper discusses the possibility of flow velocity reconstruction using passive spectroscopic techniques. We report some preliminary measurements of the toroidal flow velocity of hydrogen atoms in the RTP tokamak using a phase modulated Michelson interferometer. (C) 1997 Elsevier Science S.A.

A Novel Method for Determining the Gas Transfer Velocity of Carbon Dioxide in Streams

Science.gov (United States)

McDowell, M. J.; Johnson, M. S.

2016-12-01

Characterization of the global carbon cycle relies on the accurate quantification of carbon fluxes into and out of natural and human-dominated ecosystems. Among these fluxes, carbon dioxide (CO2) evasion from surface water has received increasing attention in recent years. However, limitations of current methods, including determination of the gas transfer velocity (k), compromise our ability to evaluate the significance of CO2 fluxes between freshwater systems and the atmosphere. We developed an automated method to determine gas transfer velocities of CO2 (kCO2), and tested it under a range of flow conditions for a first-order stream of a headwater catchment in southwestern British Columbia, Canada. Our method uses continuous in situ measurements of CO2 concentrations using two non-dispersive infrared (NDIR) sensors enclosed in water impermeable, gas permeable membranes (Johnson et al., 2010) downstream from a gas diffuser. CO2 was injected into the stream at regular intervals via a compressed gas tank connected to the diffuser. CO2 injections were controlled by a datalogger at fixed time intervals and in response to storm-induced changes in streamflow. Following the injection, differences in CO2 concentrations at known distances downstream from the diffuser relative to pre-injection baseline levels allowed us to calculate kCO2. Here we present relationships between kCO2 and hydro-geomorphologic (flow velocity, streambed slope, stream width, stream depth), atmospheric (wind speed and direction), and water quality (stream temperature, pH, electrical conductivity) variables. This method has advantages of being automatable and field-deployable, and it does not require supplemental gas chromatography, as is the case for propane injections typically used to determine k. The dataset presented suggests the potential role of this method to further elucidate the role that CO2 fluxes from headwater streams play in the global carbon cycle. Johnson, M. S., Billett, M. F

Influence of Flow Velocity on Tsunami Loss Estimation

Directory of Open Access Journals (Sweden)

Jie Song

2017-11-01

Full Text Available Inundation depth is commonly used as an intensity measure in tsunami fragility analysis. However, inundation depth cannot be taken as the sole representation of tsunami impact on structures, especially when structural damage is caused by hydrodynamic and debris impact forces that are mainly determined by flow velocity. To reflect the influence of flow velocity in addition to inundation depth in tsunami risk assessment, a tsunami loss estimation method that adopts both inundation depth and flow velocity (i.e., bivariate intensity measures in evaluating tsunami damage is developed. To consider a wide range of possible tsunami inundation scenarios, Monte Carlo-based tsunami simulations are performed using stochastic earthquake slip distributions derived from a spectral synthesis method and probabilistic scaling relationships of earthquake source parameters. By focusing on Sendai (plain coast and Onagawa (ria coast in the Miyagi Prefecture of Japan in a case study, the stochastic tsunami loss is evaluated by total economic loss and its spatial distribution at different scales. The results indicate that tsunami loss prediction is highly sensitive to modelling resolution and inclusion of flow velocity for buildings located less than 1 km from the sea for Sendai and Onagawa of Miyagi Prefecture.

CFD Validation of Gas Injection in Flowing Mercury over Vertical Smooth and Grooved Wall

International Nuclear Information System (INIS)

Abdou, Ashraf A.; Wendel, Mark W.; Felde, David K.; Riemer, Bernie

2009-01-01

The Spallation Neutron Source (SNS) is an accelerator-based neutron source at Oak Ridge National Laboratory (ORNL). The nuclear spallation reaction occurs when a proton beam hits liquid mercury. This interaction causes thermal expansion of the liquid mercury which produces high pressure waves. When these pressure waves hit the target vessel wall, cavitation can occur and erode the wall. Research and development efforts at SNS include creation of a vertical protective gas layer between the flowing liquid mercury and target vessel wall to mitigate the cavitation damage erosion and extend the life time of the target. Since mercury is opaque, computational fluid dynamics (CFD) can be used as a diagnostic tool to see inside the liquid mercury and guide the experimental efforts. In this study, CFD simulations of three dimensional, unsteady, turbulent, two-phase flow of helium gas injection in flowing liquid mercury over smooth, vertically grooved and horizontally grooved walls are carried out with the commercially available CFD code Fluent-12 from ANSYS. The Volume of Fluid (VOF) model is used to track the helium-mercury interface. V-shaped vertical and horizontal grooves with 0.5 mm pitch and about 0.7 mm depth were machined in the transparent wall of acrylic test sections. Flow visualization data of helium gas coverage through transparent test sections is obtained with a high-speed camera at the ORNL target test facility (TTF). The helium gas mass flow rate is 8 mg/min and introduced through a 0.5 mm diameter port. The local mercury velocity is 0.9 m/s. In this paper, the helium gas flow rate and the local mercury velocity are kept constant for the three cases. Time integration of predicted helium gas volume fraction over time is done to evaluate the gas coverage and calculate the average thickness of the helium gas layer. The predicted time-integrated gas coverage over vertically grooved and horizontally grooved test sections is better than over a smooth wall. The

Numerical simulation of the gas-solid flow in a square circulating fluidized bed with secondary air injection

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhengyang [Harbin Institute of Technology, Harbin (China). Post-doctor Station of Civil Engineering; Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.; Sun, Shaozeng; Zhao, Ningbo; Wu, Shaohua [Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.; Tan, Yufei [Harbin Institute of Technology, Harbin (China). School of Municipal and Environmental Engineering

2013-07-01

The dynamic behavior of gas-solid flow in an experimental square circulating fluidized bed setup (0.25 m x 0.25 m x 6.07 m) is predicted with numerical simulation based on the theory of Euler-Euler gas-solid two-phase flow and the kinetic theory of granular flows. The simulation includes the operation cases with secondary injection and without air-staging. The pressure drop profile, local solids concentration and particle velocity was compared with experimental results. Both simulation and experimental results show that solids concentration increases significantly below the secondary air injection ports when air-staging is adopted. Furthermore, the flow asymmetry in the solid entrance region of the bed was investigated based on the particle concentration/velocity profile. The simulation results are in agreement with the experimental results qualitatively.

The sound velocity in an equilibrium hadron gas

OpenAIRE

Prorok, Dariusz; Turko, Ludwik

2001-01-01

We calculate the velocity of sound in an ideal gas of massive hadrons with non-vanishing baryon number. The gas is in thermal and chemical equilibrium. Also we show that the temperature dependence $T(\\tau) \\cong T_{0} \\cdot ({\\tau_{0} \\over \\tau})^{c_{s}^{2}}$ is approximately valid, when the gas expands longitudinally according to the Bjorken law.

Hydrodynamic characteristics of the two-phase flow field at gas-evolving electrodes: numerical and experimental studies

Science.gov (United States)

Liu, Cheng-Lin; Sun, Ze; Lu, Gui-Min; Yu, Jian-Guo

2018-05-01

Gas-evolving vertical electrode system is a typical electrochemical industrial reactor. Gas bubbles are released from the surfaces of the anode and affect the electrolyte flow pattern and even the cell performance. In the current work, the hydrodynamics induced by the air bubbles in a cold model was experimentally and numerically investigated. Particle image velocimetry and volumetric three-component velocimetry techniques were applied to experimentally visualize the hydrodynamics characteristics and flow fields in a two-dimensional (2D) plane and a three-dimensional (3D) space, respectively. Measurements were performed at different gas rates. Furthermore, the corresponding mathematical model was developed under identical conditions for the qualitative and quantitative analyses. The experimental measurements were compared with the numerical results based on the mathematical model. The study of the time-averaged flow field, three velocity components, instantaneous velocity and turbulent intensity indicate that the numerical model qualitatively reproduces liquid motion. The 3D model predictions capture the flow behaviour more accurately than the 2D model in this study.

Development of an optical fiber flow velocity sensor.

Science.gov (United States)

Harada, Toshio; Kamoto, Kenji; Abe, Kyutaro; Izumo, Masaki

2009-01-01

A new optical fiber flow velocity sensor was developed by using an optical fiber information network system in sewer drainage pipes. The optical fiber flow velocity sensor operates without electric power, and the signals from the sensor can be transmitted over a long distance through the telecommunication system in the optical fiber network. Field tests were conducted to check the performance of the sensor in conduits in the pumping station and sewage pond managed by the Tokyo Metropolitan Government. Test results confirmed that the velocity sensor can be used for more than six months without any trouble even in sewer drainage pipes.

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)

A method for measuring the velocity flow field in the vicinity of a moving cascade

International Nuclear Information System (INIS)

Bammert, K.; Mobarak, A.

1977-01-01

Centrifugal compressors and blowers are often used for recycling the coolant gas in gas-cooled reactors. To achieve the required pressure ratios, highly loaded centrifugal compressors are built. The paper deals with a method of measuring the flow field in the vicinity of a moving impeller or cascade with hot wires. The relative flow pattern induced ahead of a cascade or impeller or the rotating wakes behind a moving cascade (which is important for loss evaluation) could be now measured with the help of a single hot wire. The wire should be rotated about the axis of the probe for 3 different inclinations with respect to the approaching flow. The method has been used for measuring the flow field in the vicinity of the inducer of a highly loaded centrifugal compressor. The results and the accuracy of the method are discussed and the mean values have been compared with the theoretically estimated velocities. (orig.) [de

Predicting the Agglomeration of Cohesive Particles in a Gas-Solid Flow and its Effect on the Solids Flow

Science.gov (United States)

Kellogg, Kevin; Liu, Peiyuan; Lamarche, Casey; Hrenya, Christine

2017-11-01

In flows of cohesive particles, agglomerates will readily form and break. These agglomerates are expected to complicate how particles interact with the surrounding fluid in multiphase flows, and consequently how the solids flow. In this work, a dilute flow of particles driven by gas against gravity is studied. A continuum framework, composed of a population balance to predict the formation of agglomerates, and kinetic-theory-based balances, is used to predict the flow of particles. The closures utilized for the birth and death rates due to aggregation and breakage in the population balance take into account how the impact velocity (the granular temperature) affects the outcome of a collision as aggregation, rebound, or breakage. The agglomerate size distribution and solids velocity predicted by the continuum framework are compared to discrete element method (DEM) simulations, as well to experimental results of particles being entrained from the riser of a fluidized bed. Dow Corning Corporation.

Flow Rates in Liquid Chromatography, Gas Chromatography and Supercritical Fluid Chromatography: A Tool for Optimization

Directory of Open Access Journals (Sweden)

Joris Meurs

2016-08-01

Full Text Available This paper aimed to develop a standalone application for optimizing flow rates in liquid chromatography (LC, gas chromatography (GC and supercritical fluid chromatography (SFC. To do so, Van Deemter’s equation, Knox’ equation and Golay’s equation were implemented in a MATLAB script and subsequently a graphical user interface (GUI was created. The application will show the optimal flow rate or linear velocity and the corresponding plate height for the set input parameters. Furthermore, a plot will be shown in which the plate height is plotted against the linear flow velocity. Hence, this application will give optimized flow rates for any set conditions with minimal effort.

Effects of superficial gas velocity and fluid property on the ...

African Journals Online (AJOL)

In the present study, the influence of superficial gas velocity and fluid properties on gas holdup and liquid circulation velocity in a three-phase external loop airlift column using polystyrene (0.0036 m diameter and 1025.55 kg/m3 density) and nylon-6 (0.0035 m diameter and 1084.24 kg/m3 density) particles with aqueous ...

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

Energy Technology Data Exchange (ETDEWEB)

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

2009-12-15

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

Effect of flow velocity on erosion-corrosion behaviour of QSn6 alloy

Science.gov (United States)

Huang, Weijiu; Zhou, Yongtao; Wang, Zhenguo; Li, Zhijun; Zheng, Ziqing

2018-05-01

The erosion-corrosion behaviour of QSn6 alloy used as propellers in marine environment was evaluated by erosion-corrosion experiments with/without cathodic protection, electrochemical tests and scanning electron microscope (SEM) observations. The analysis was focused on the effect of flow velocity. The dynamic polarization curves showed that the corrosion rate of the QSn6 alloy increased as the flow velocity increased, due to the protective surface film removal at higher velocities. The lowest corrosion current densities of 1.26 × 10‑4 A cm‑2 was obtained at the flow velocity of 7 m s‑1. Because of the higher particle kinetic energies at higher flow velocity, the mass loss rate of the QSn6 alloy increased as the flow velocity increased. The mass loss rate with cathodic protection was lower than that without cathodic protection under the same conditions. Also, the lowest mass loss rate of 0.7 g m‑2 · h‑1 was acquired at the flow velocity of 7 m s‑1 with cathodic protection. However, the increase rate of corrosion rate and mass loss were decreased with increasing the flow velocity. Through observation the SEM morphologies of the worn surfaces, the main wear mechanism was ploughing with/without cathodic protection. The removal rates of the QSn6 alloy increased as the flow velocity increased in both pure erosion and erosion-corrosion, whereas the erosion and corrosion intensified each other. At the flow velocity of 7 m s‑1, the synergy rate (ΔW) exceeded by 5 times the erosion rate (Wwear). Through establishment and observation the erosion-corrosion mechanism map, the erosion-corrosion was the dominant regime in the study due to the contribution of erosion on the mass loss rate exceeded the corrosion contribution. The QSn6 alloy with cathodic protection is feasible as propellers, there are higher security at lower flow velocity, such as the flow velocity of 7 m s‑1 in the paper.

Experimental study on liquid velocity in upward and downward two-phase flows

International Nuclear Information System (INIS)

Sun, X.; Paranjape, S.; Kim, S.; Ozar, B.; Ishii, M.

2003-01-01

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

Numerical Simulation and Analysis of Gas-Liquid Flow in a T-Junction Microchannel

Directory of Open Access Journals (Sweden)

Hongtruong Pham

2012-01-01

Full Text Available Gas-liquid flow in microchannels is widely used in biomedicine, nanotech, sewage treatment, and so forth. Particularly, owing to the high qualities of the microbubbles and spheres produced in microchannels, it has a great potential to be used in ultrasound imaging and controlled drug release areas; therefore, gas-liquid flow in microchannels has been the focus in recent years. In this paper, numerical simulation of gas-liquid flows in a T-junction microchannel was carried out with computational fluid dynamics (CFD software FLUENT and the Volume-of-Fluid (VOF model. The distribution of velocity, pressure, and phase of fluid in the microchannel was obtained, the pressure distribution along the channel walls was analyzed in order to give a better understanding on the formation of microbubbles in the T-junction microchannel.

Diastolic coronary artery pressure-flow velocity relationships in conscious man.

Science.gov (United States)

Dole, W P; Richards, K L; Hartley, C J; Alexander, G M; Campbell, A B; Bishop, V S

1984-09-01

We characterised the diastolic pressure-flow velocity relationship in the normal left coronary artery of conscious man before and after vasodilatation with angiographic contrast medium. Phasic coronary artery pressure and flow velocity were measured in ten patients during individual diastoles (0.5 to 1.0 s) using a 20 MHz catheter-tipped, pulsed Doppler transducer. All pressure-flow velocity curves were linear over the diastolic pressure range of 110 +/- 15 (SD) mmHg to 71 +/- 7 mmHg (r = 0.97 +/- 0.01). In the basal state, values for slope and extrapolated zero flow pressure intercept averaged 0.35 +/- 0.12 cm X s-1 X mmHg-1 and 51.7 +/- 8.6 mmHg, respectively. Vasodilatation resulted in a 2.5 +/- 0.5 fold increase in mean flow velocity. The diastolic pressure-flow velocity relationship obtained during peak vasodilatation compared to that during basal conditions was characterised by a steeper slope (0.80 +/- 0.48 cm X s-1 X mmHg-1, p less than 0.001) and lower extrapolated zero flow pressure intercept (37.9 +/- 9.8 mmHg, p less than 0.05). Mean right atrial pressure for the group averaged 4.4 +/- 1.7 mmHg, while left ventricular end-diastolic pressure averaged 8.7 +/- 2.8 mmHg. These observations in man are similar to data reported in the canine coronary circulation which are consistent with a vascular waterfall model of diastolic flow regulation. In this model, coronary blood flow may be regulated by changes in diastolic zero flow pressure as well as in coronary resistance.

An experimental and computational investigation of gas/particle flow in a vertical lifter

Energy Technology Data Exchange (ETDEWEB)

Mathisen, Anette

2010-07-01

Experimental and computational investigations of dilute gas/particle flow in a vertical lifter are performed. The effect of superficial gas velocity, particle density, particle size distribution and particle loading on particle velocities, particle fluctuations and particle cross-moment have been studied experimentally using laser Doppler anemometry (LDA) and particle image velocimetry (PIV). The results from the experimental investigation is compared with the computational investigation using FluentR. The experimental measurements are performed on a lab-scale vertical lifter, consisting of a fluidizing silo and a receiving tank with a glass pipe in which the solids phase is transported. The particles are placed in the fluidization tank and transport air enters at the bottom of the silo. The transport pipe is suspended above the inlet and as the transport air passes the opening, the particles are dragged into the air flow and transported upwards to the receiving tank. Fluidizing air is used to control the particle loading in the system and supplied through a distribution plate. The test section of the transport pipe is made of glass to enable the use of the optical laser based investigation techniques, LDA and PIV. Two types of powders are used, ZrO{sub 2} and glass, each with two different particle size distributions, average diameter of 260 and 530 micron and 120 and 518 micron, respectively. The experimental techniques LDA and PIV are used to investigate a dilute gas/particle vertical flow. The two techniques are also evaluated for use on this type of flow. LDA is a single point measurement technique, which means that one point is measured at a time. The acquisition stops when a pre-set criteria is reached, this can either be based on sample number or time. A measurement spanning over the whole cross-section of the pipe consists of several points. These points makes up a cross-sectional profile. PIV on the other hand is a whole field technique and consequently

A flow meter for ultrasonically measuring the flow velocity of fluids

DEFF Research Database (Denmark)

2015-01-01

The invention regards a flow meter for ultrasonically measuring the flow velocity of fluids comprising a duct having a flow channel with an internal cross section comprising variation configured to generate at least one acoustic resonance within the flow channel for a specific ultrasonic frequency......, and at least two transducers for generating and sensing ultrasonic pulses, configured to transmit ultrasonic pulses at least at said specific ultrasonic frequency into the flow channel such that the ultrasonic pulses propagate through a fluid flowing in the flow channel, wherein the flow meter is configured...

Reduced-order modellin for high-pressure transient flow of hydrogen-natural gas mixture

Science.gov (United States)

Agaie, Baba G.; Khan, Ilyas; Alshomrani, Ali Saleh; Alqahtani, Aisha M.

2017-05-01

In this paper the transient flow of hydrogen compressed-natural gas (HCNG) mixture which is also referred to as hydrogen-natural gas mixture in a pipeline is numerically computed using the reduced-order modelling technique. The study on transient conditions is important because the pipeline flows are normally in the unsteady state due to the sudden opening and closure of control valves, but most of the existing studies only analyse the flow in the steady-state conditions. The mathematical model consists in a set of non-linear conservation forms of partial differential equations. The objective of this paper is to improve the accuracy in the prediction of the HCNG transient flow parameters using the Reduced-Order Modelling (ROM). The ROM technique has been successfully used in single-gas and aerodynamic flow problems, the gas mixture has not been done using the ROM. The study is based on the velocity change created by the operation of the valves upstream and downstream the pipeline. Results on the flow characteristics, namely the pressure, density, celerity and mass flux are based on variations of the mixing ratio and valve reaction and actuation time; the ROM computational time cost advantage are also presented.

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.

Intermittent Lagrangian velocities and accelerations in three-dimensional porous medium flow.

Science.gov (United States)

Holzner, M; Morales, V L; Willmann, M; Dentz, M

2015-07-01

Intermittency of Lagrangian velocity and acceleration is a key to understanding transport in complex systems ranging from fluid turbulence to flow in porous media. High-resolution optical particle tracking in a three-dimensional (3D) porous medium provides detailed 3D information on Lagrangian velocities and accelerations. We find sharp transitions close to pore throats, and low flow variability in the pore bodies, which gives rise to stretched exponential Lagrangian velocity and acceleration distributions characterized by a sharp peak at low velocity, superlinear evolution of particle dispersion, and double-peak behavior in the propagators. The velocity distribution is quantified in terms of pore geometry and flow connectivity, which forms the basis for a continuous-time random-walk model that sheds light on the observed Lagrangian flow and transport behaviors.

Large eddy simulations of isothermal confined swirling flow in an industrial gas-turbine

International Nuclear Information System (INIS)

Bulat, G.; Jones, W.P.; Navarro-Martinez, S.

2015-01-01

Highlights: • We conduct a large eddy simulation of an industrial gas turbine. • The results are compared with measurements obtained under isothermal conditions. • The method reproduces the observed precessing vortex and central vortex cores. • The profiles of mean and rms velocities are found to be captured to a good accuracy. - Abstract: The paper describes the results of a computational study of the strongly swirling isothermal flow in the combustion chamber of an industrial gas turbine. The flow field characteristics are computed using large eddy simulation in conjunction with a dynamic version of the Smagorinsky model for the sub-grid-scale stresses. Grid refinement studies demonstrate that the results are essentially grid independent. The LES results are compared with an extensive set of measurements and the agreement with these is overall good. The method is shown to be capable of reproducing the observed precessing vortex and central vortex cores and the profiles of mean and rms velocities are found to be captured to a good accuracy. The overall flow structure is shown to be virtually independent of Reynolds number

Thermal particle image velocity estimation of fire plume flow

Science.gov (United States)

Xiangyang Zhou; Lulu Sun; Shankar Mahalingam; David R. Weise

2003-01-01

For the purpose of studying wildfire spread in living vegetation such as chaparral in California, a thermal particle image velocity (TPIV) algorithm for nonintrusively measuring flame gas velocities through thermal infrared (IR) imagery was developed. By tracing thermal particles in successive digital IR images, the TPIV algorithm can estimate the velocity field in a...

Self-determined shapes and velocities of giant near-zero drag gas cavities

KAUST Repository

Vakarelski, Ivan Uriev

2017-09-09

Minimizing the retarding force on a solid moving in liquid is the canonical problem in the quest for energy saving by friction and drag reduction. For an ideal object that cannot sustain any shear stress on its surface, theory predicts that drag force will fall to zero as its speed becomes large. However, experimental verification of this prediction has been challenging. We report the construction of a class of self-determined streamlined structures with this free-slip surface, made up of a teardrop-shaped giant gas cavity that completely encloses a metal sphere. This stable gas cavity is formed around the sphere as it plunges at a sufficiently high speed into the liquid in a deep tank, provided that the sphere is either heated initially to above the Leidenfrost temperature of the liquid or rendered superhydrophobic in water at room temperature. These sphere-in-cavity structures have residual drag coefficients that are typically less than Embedded Image those of solid objects of the same dimensions, which indicates that they experienced very small drag forces. The self-determined shapes of the gas cavities are shown to be consistent with the Bernoulli equation of potential flow applied on the cavity surface. The cavity fall velocity is not arbitrary but is uniquely predicted by the sphere density and cavity volume, so larger cavities have higher characteristic velocities.

Forming of film surface of very viscous liquid flowing with gas in pipes

Directory of Open Access Journals (Sweden)

Czernek Krystian

2017-01-01

Full Text Available The study presents the possible use of optoelectronic system for the measurement of the values, which are specific for hydrodynamics of two-phase gas liquid flow in vertical pipes, where a very-high-viscosity liquid forms a falling film in a pipe. The experimental method was provided, and the findings were presented and analysed for selected values, which characterize the two-phase flow. Attempt was also made to evaluate the effects of flow parameters and properties of the liquid on the gas-liquid interface value, which is decisive for the conditions of heat exchange and mass transfer in falling film equipment. The nature and form of created waves at various velocities were also described.

Advances in gas-liquid flows 1990

International Nuclear Information System (INIS)

Kim, J.M.; Hashemi, A.

1990-01-01

Gas-liquid two-phase flows commonly occur in nature and industrial applications. Rain, clouds, geysers, and waterfalls are examples of natural gas-liquid flow phenomena, whereas industrial applications can be found in nuclear reactors, steam generators, boilers, condensers, evaporators, fuel atomization, heat pipes, electronic equipment cooling, petroleum engineering, chemical process engineering, and many others. The household-variety phenomena such as garden sprinklers, shower, whirlpool bath, dripping faucet, boiling tea pot, and bubbling beer provide daily experience of gas-liquid flows. The papers presented in this volume reflect the variety and richness of gas-liquid two-phase flow and the increasing role it plays in modern technology. This volume contains papers dealing with some recent development in gas-liquid flow science and technology, covering basic gas-liquid flows, measurements and instrumentation, cavitation and flashing flows, countercurrent flow and flooding, flow in various components and geometries liquid metals and thermocapillary effects, heat transfer, nonlinear phenomena, instability, and other special and general topics related to gas-liquid flows

Pulsatile pressure driven rarefied gas flow in long rectangular ducts

Science.gov (United States)

Tsimpoukis, Alexandros; Valougeorgis, Dimitris

2018-04-01

The pulsatile pressure driven fully developed flow of a rarefied gas through an orthogonal duct is investigated, based on the time-dependent linear Bhatnagar, Gross, and Krook equation, by decomposing the flow into its steady and oscillatory parts. The investigation is focused on the oscillatory part, which is characterized by the gas rarefaction and oscillation parameters, the duct aspect ratio, and the accommodation coefficient. As the oscillation frequency is increased, the amplitude of all macroscopic quantities is decreased, while their phase angle lag is increased reaching the limiting value of π/2. As the gas becomes more rarefied, higher frequencies are needed to trigger this behavior. At small and moderate frequencies, there is a critical degree of gas rarefaction, where a maximum flow rate is obtained. As the duct aspect ratio is decreased and tends to zero, the flow rate and mean wall shear stress amplitudes are increased, while their phase angle lags are slightly affected. The accommodation coefficient has a significant effect on the amplitude and a very weak one on the phase angle of the macroscopic quantities. The computation of the inertia and viscous forces clarifies when the flow consists of only one oscillating viscous region or of two regions, namely, the inviscid piston flow in the core and the oscillating Stokes layer at the wall with the velocity overshooting. Finally, the time average oscillatory pumping power is increased as the oscillation frequency is reduced and its maximum value is one half of the corresponding steady one.

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

Science.gov (United States)

Bousman, William Scott

1995-01-01

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

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

Velocity bias induced by flow patterns around ADCPs and associated deployment platforms

Science.gov (United States)

Mueller, David S.

2015-01-01

Velocity measurements near the Acoustic Doppler Current Profiler (ADCP) are important for mapping surface currents, measuring velocity and discharge in shallow streams, and providing accurate estimates of discharge in the top unmeasured portion of the water column. Improvements to ADCP performance permit measurement of velocities much closer (5 cm) to the transducer than has been possible in the past (25 cm). Velocity profiles collected by the U.S. Geological Survey (USGS) with a 1200 kHz Rio Grande Zedhead ADCP in 2002 showed a negative bias in measured velocities near the transducers. On the basis of these results, the USGS initiated a study combining field, laboratory, and numerical modeling data to assess the effect of flow patterns caused by flow around the ADCP and deployment platforms on velocities measured near the transducers. This ongoing study has shown that the negative bias observed in the field is due to the flow pattern around the ADCP. The flow pattern around an ADCP violates the basic assumption of flow homogeneity required for an accurate three-dimensional velocity solution. Results, to date (2014), have indicated velocity biases within the measurable profile, due to flow disturbance, for the TRDI 1200 kHz Rio Grande Zedhead and the SonTek RiverSurveyor M9 ADCPs. The flow speed past the ADCP, the mount and the deployment platform have also been shown to play an important role in the magnitude and extent of the velocity bias.

Development of gas-solid direct contact heat exchanger by use of axial flow cyclone

Energy Technology Data Exchange (ETDEWEB)

Shimizu, Akihiko; Yokomine, Takehiko [Kyushu University (Japan). Interdisciplinary Graduate School of Engineering Sciences; Nagafuchi, Tatsuro [Miura Co. Ltd., Matsuyamashi (Japan)

2004-10-01

A heat exchanger between particulate or granular materials and gas is developed. It makes use of a swirling gas flow similar to the usual cyclone separators but the difference from them is that the swirl making gas is issued into the cyclone chamber with downward axial velocity component. After it turns the flow direction near the bottom of the chamber, the low temperature gas receives heat from high temperature particles supplied from above at the chamber's center. Through this configuration, a direct contact and quasi counter-flow heat exchange pattern is realized so that the effective recovery of heat carried by particles is achieved. A model heat exchanger was manufactured via several numerical experiments and its performances of heat exchange as well as particle recovery were examined. Attaching a small particle diffuser below the particle-feeding nozzle brought about a drastic improvement of the heat exchange performance without deteriorating the particle recovery efficiency. The outlet gas temperature much higher than the particle outlet temperature was finally obtained, which is never realized in the parallel flow heat exchanger. (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)

Hydrodynamic flow regimes, gas holdup, and liquid circulation in airlift reactors

Energy Technology Data Exchange (ETDEWEB)

Abashar, M.E.; Narsingh, U.; Rouillard, A.E.; Judd, R. [Univ. of Durban (South Africa)

1998-04-01

This study reports an experimental investigation into the hydrodynamic behavior of an external-loop airlift reactor (ALR) for the air-water system. Three distinct flow regimes are identified--namely homogeneous, transition, and heterogeneous regimes. The transition between homogeneous and heterogeneous flow is observed to occur over a wide range rather than being merely a single point as has been previously reported in the literature. A gas holdup correlation is developed for each flow regime. The correlations fit the experimental gas holdup data with very good accuracy (within {+-}5%). It would appear, therefore, that a deterministic equation to describe each flow regime is likely to exist in ALRs. This equation is a function of the reactor geometry and the system`s physical properties. New data concerning the axial variation of gas holdup is reported in which a minimum value is observed. This phenomenon is discussed and an explanation offered. Discrimination between two sound theoretical models--namely model 1 (Chisti et al., 1988) and model 2 (Garcia Calvo, 1989)--shows that model 1 predicts satisfactorily the liquid circulation velocity with an error of less than {+-} 10%. The good predictive features of model 1 may be due to the fact that it allows for a significant energy dissipation by wakes behind bubbles. Model 1 is now further improved by the new gas holdup correlations which are derived for the three different flow regimes.

Numerical modeling of turbulent evaporating gas-droplet two-phase flows in an afterburner diffusor of turbo-fan jet engines

Energy Technology Data Exchange (ETDEWEB)

Zhou, Lixing; Zhang, Jian [Qinghua Univ., Beijing (China)

1990-11-01

Two-dimensional turbulent evaporating gas-droplet two-phase flows in an afterburner diffusor of turbofan jet engines are simulated here by a k-epsilon turbulence model and a particle trajectory model. Comparison of predicted gas velocity and temperature distributions with experimental results for the cases without liquid spray shows good agreement. Gas-droplet two-phase flow predictions give plausible droplet trajectories, fuel-vapor concentration distribution, gas-phase velocity and temperature field in the presence of liquid droplets. One run of computation with this method is made for a particular afterburner. The results indicate that the location of the atomizers is not favorable to flame stabilization and combustion efficiency. The proposed numerical modeling can also be adopted for optimization design and performance evaluation of afterburner combustors of turbofan jet engines. 7 refs.

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)

Axial and radial velocities in the creeping flow in a pipe

Directory of Open Access Journals (Sweden)

Zuykov Andrey L'vovich

2014-05-01

Full Text Available The article is devoted to analytical study of transformation fields of axial and radial velocities in uneven steady creeping flow of a Newtonian fluid in the initial portion of the cylindrical channel. It is shown that the velocity field of the flow is two-dimensional and determined by the stream function. The article is a continuation of a series of papers, where normalized analytic functions of radial axial distributions in uneven steady creeping flow in a cylindrical tube with azimuthal vorticity and stream function were obtained. There is Poiseuille profile for the axial velocity in the uniform motion of a fluid at an infinite distance from the entrance of the pipe (at x = ∞, here taken equal to zero radial velocity. There is uniform distribution of the axial velocity in the cross section at the tube inlet at x = 0, at which the axial velocity is constant along the current radius. Due to the axial symmetry of the flow on the axis of the pipe (at r = 0, the radial velocities and the partial derivative of the axial velocity along the radius, corresponding to the condition of the soft function extremum, are equal to zero. The authors stated vanishing of the velocity of the fluid on the walls of the pipe (at r = R , where R - radius of the tube due to its viscous sticking and tightness of the walls. The condition of conservation of volume flow along the tube was also accepted. All the solutions are obtained in the form of the Fourier - Bessel. It is shown that the hydraulic losses at uniform creeping flow of a Newtonian fluid correspond to Poiseuille - Hagen formula.

Numerical simulation of gas-solid flow in an interconnected fluidized bed

Directory of Open Access Journals (Sweden)

Canneto Giuseppe

2015-01-01

Full Text Available The gas-particles flow in an interconnected bubbling fluidized cold model is simulated using a commercial CFD package by Ansys. Conservation equations of mass and momentum are solved using the Eulerian granular multiphase model. Bubbles formation and their paths are analyzed to investigate the behaviour of the bed at different gas velocities. Experimental tests, carried out by the cold model, are compared with simulation runs to study the fluidization quality and to estimate the circulation of solid particles in the bed.

Influence of type of aortic valve prosthesis on coronary blood flow velocity.

Science.gov (United States)

Jelenc, Matija; Juvan, Katja Ažman; Medvešček, Nadja Tatjana Ružič; Geršak, Borut

2013-02-01

Severe aortic valve stenosis is associated with high resting and reduced hyperemic coronary blood flow. Coronary blood flow increases after aortic valve replacement (AVR); however, the increase depends on the type of prosthesis used. The present study investigates the influence of type of aortic valve prosthesis on coronary blood flow velocity. The blood flow velocity in the left anterior descending coronary artery (LAD) and the right coronary artery (RCA) was measured intraoperatively before and after AVR with a stentless bioprosthesis (Sorin Freedom Solo; n = 11) or a bileaflet mechanical prosthesis (St. Jude Medical Regent; n = 11). Measurements were made with an X-Plore epicardial Doppler probe (Medistim, Oslo, Norway) following induction of hyperemia with an adenosine infusion. Preoperative and postoperative echocardiography evaluations were used to assess valvular and ventricular function. Velocity time integrals (VTI) were measured from the Doppler signals and used to calculate the proportion of systolic VTI (SF), diastolic VTI (DF), and normalized systolic coronary blood flow velocities (NSF) and normalized diastolic coronary blood flow velocities (NDF). The systolic proportion of the LAD VTI increased after AVR with the St. Jude Medical Regent prosthesis, which produced higher LAD SF and NSF values than the Sorin Freedom Solo prosthesis (SF, 0.41 ± 0.09 versus 0.29 ± 0.13 [P = .04]; NSF, 0.88 ± 0.24 versus 0.55 ± 0.17 [P = .01]). No significant changes in the LAD velocity profile were noted after valve replacement with the Sorin Freedom Solo, despite a significant reduction in transvalvular gradient and an increase in the effective orifice area. AVR had no effect on the RCA flow velocity profile. The coronary flow velocity profile in the LAD was significantly influenced by the type of aortic valve prosthesis used. The differences in the LAD velocity profile probably reflect differences in valve design and the systolic transvalvular flow pattern.

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

Intelligent gas-mixture flow sensor

NARCIS (Netherlands)

Lammerink, Theodorus S.J.; Dijkstra, Fred; Houkes, Z.; van Kuijk, J.C.C.; van Kuijk, Joost

A simple way to realize a gas-mixture flow sensor is presented. The sensor is capable of measuring two parameters from a gas flow. Both the flow rate and the helium content of a helium-nitrogen gas mixture are measured. The sensor exploits two measurement principles in combination with (local)

Fundamentals of gas particle flow

CERN Document Server

Rudinger, G

1980-01-01

Fundamentals of Gas-Particle Flow is an edited, updated, and expanded version of a number of lectures presented on the "Gas-Solid Suspensions” course organized by the von Karman Institute for Fluid Dynamics. Materials presented in this book are mostly analytical in nature, but some experimental techniques are included. The book focuses on relaxation processes, including the viscous drag of single particles, drag in gas-particles flow, gas-particle heat transfer, equilibrium, and frozen flow. It also discusses the dynamics of single particles, such as particles in an arbitrary flow, in a r

Thermocapillary and shear driven flows in gas/liquid system in annular duct

International Nuclear Information System (INIS)

Gaponenko, Yu; Shevtsova, V; Nepomnyashchy, A

2011-01-01

We report the results of numerical study of two-phase flows in annulus for different aspect ratios obtained in the frame of the JEREMI experiment preparation. The geometry of the physical problem is a cylindrical and non-deformable liquid bridge concentrically surrounded by an annular gas channel under conditions of zero gravity. Thermocapillary (Marangoni) convection in liquid bridge of Pr = 68 is analyzed in the case when the interface is subjected to an axial gas stream. The gas flow is counter-directed with respect to the Marangoni flow. The inlet gas velocity U 0 g , temperature difference ΔT between end rods of the liquid bridge and aspect ratio are the control parameters of the system. In the case when the gas stream comes from the cold side, it cools down the interface to a temperature lower than that of the liquid beneath, and in a certain region of the parameter space that cooling causes instability due to a temperature difference in the direction, perpendicular to the interface. The present study is focused on the influence of the aspect ratio on the existence and characteristic features of the oscillatory regime.

Thermistor based, low velocity isothermal, air flow sensor

International Nuclear Information System (INIS)

Cabrita, Admésio A C M; Mendes, Ricardo; Quintela, Divo A

2016-01-01

The semiconductor thermistor technology is applied as a flow sensor to measure low isothermal air velocities (<2 ms −1 ). The sensor is subjected to heating and cooling cycles controlled by a multifunctional timer. In the heating stage, the alternating current of a main AC power supply source guarantees a uniform thermistor temperature distribution. The conditioning circuit assures an adequate increase of the sensors temperature and avoids the thermal disturbance of the flow. The power supply interruption reduces the consumption from the source and extends the sensors life time. In the cooling stage, the resistance variation of the flow sensor is recorded by the measuring chain. The resistive sensor parameters proposed vary significantly and feature a high sensitivity to the flow velocity. With the aid of a computer, the data transfer, storage and analysis provides a great advantage over the traditional local anemometer readings. The data acquisition chain has a good repeatability and low standard uncertainties. The proposed method measures isothermal air mean velocities from 0.1 ms −1 to 2 ms −1 with a standard uncertainty error less than 4%. (paper)

Ultrasonic velocity profiling rheometry based on a widened circular Couette flow

International Nuclear Information System (INIS)

Shiratori, Takahisa; Tasaka, Yuji; Oishi, Yoshihiko; Murai, Yuichi

2015-01-01

We propose a new rheometry for characterizing the rheological properties of fluids. The technique produces flow curves, which represent the relationship between the fluid shear rate and shear stress. Flow curves are obtained by measuring the circumferential velocity distribution of tested fluids in a circular Couette system, using an ultrasonic velocity profiling technique. By adopting a widened gap of concentric cylinders, a designed range of the shear rate is obtained so that velocity profile measurement along a single line directly acquires flow curves. To reduce the effect of ultrasonic noise on resultant flow curves, several fitting functions and variable transforms are examined to best approximate the velocity profile without introducing a priori rheological models. Silicone oil, polyacrylamide solution, and yogurt were used to evaluate the applicability of this technique. These substances are purposely targeted as examples of Newtonian fluids, shear thinning fluids, and opaque fluids with unknown rheological properties, respectively. We find that fourth-order Chebyshev polynomials provide the most accurate representation of flow curves in the context of model-free rheometry enabled by ultrasonic velocity profiling. (paper)

Instability of shallow open channel flow with lateral velocity gradients

Energy Technology Data Exchange (ETDEWEB)

Lima, A C; Izumi, N, E-mail: adriano@eng.hokudai.ac.jp, E-mail: nizumi@eng.hokudai.ac.jp [River and Watershed Engineering Laboratory, Hokkaido University, Sapporo, 060-8628 (Japan)

2011-12-22

The turbulent flow in a wide rectangular open channel partially covered with vegetation is studied using linear stability analysis. In the base state normal flow condition, the water depth is constant and the transverse velocity vanishes, while there is a lateral gradient in the streamwise velocity with an inflexion point at the boundary between the vegetated zone and the main channel. The Reynolds stress is expressed by introducing the eddy viscosity, which is obtained from assuming a logarithmic distribution of the velocity near the bed. Perturbation expansions are introduced to the streamwise and transverse velocities, as well as to the water depth. The system of governing equations was solved in order to determine the maximum growth rate of the perturbations as a function of parameters which describe physical characteristics of the channel and the flow.

Extended Macroscopic Study of Dilute Gas Flow within a Microcavity

Directory of Open Access Journals (Sweden)

Mohamed Hssikou

2016-01-01

Full Text Available The behaviour of monatomic and dilute gas is studied in the slip and early transition regimes using the extended macroscopic theory. The gas is confined within a two-dimensional microcavity where the longitudinal sides are in the opposite motion with constant velocity ±Uw. The microcavity walls are kept at the uniform and reference temperature T0. Thus, the gas flow is transported only by the shear stress induced by the motion of upper and lower walls. From the macroscopic point of view, the regularized 13-moment equations of Grad, R13, are solved numerically. The macroscopic gas proprieties are studied for different values of the so-called Knudsen number (Kn, which gives the gas-rarefaction degree. The results are compared with those obtained using the classical continuum theory of Navier-Stokes and Fourier (NSF.

Two-phase gas bubble-liquid boundary layer flow along vertical and inclined surfaces

International Nuclear Information System (INIS)

Cheung, F.B.; Epstein, M.

1985-01-01

The behavior of a two-phase gas bubble-liquid boundary layer along vertical and inclined porous surfaces with uniform gas injection is investigated experimentally and analytically. Using argon gas and water as the working fluids, a photographical study of the two-phase boundary layer flow has been performed for various angles of inclination ranging from 45 0 to 135 0 and gas injection rates ranging from 0.01 to 0.1 m/s. An integral method has been employed to solve the system of equations governing the two-phase motion. The effects of the gas injection rate and the angle of inclination on the growth of the boundary layer have been determined. The predicted boundary layer thickness is found to be in good agreement with the experimental results. The calculated axial liquid velocity and the void fraction in the two-phase region are also presented along with the observed flow behavior

A gas kinetic scheme for hybrid simulation of partially rarefied flows

Science.gov (United States)

Colonia, S.; Steijl, R.; Barakos, G.

2017-06-01

Approaches to predict flow fields that display rarefaction effects incur a cost in computational time and memory considerably higher than methods commonly employed for continuum flows. For this reason, to simulate flow fields where continuum and rarefied regimes coexist, hybrid techniques have been introduced. In the present work, analytically defined gas-kinetic schemes based on the Shakhov and Rykov models for monoatomic and diatomic gas flows, respectively, are proposed and evaluated with the aim to be used in the context of hybrid simulations. This should reduce the region where more expensive methods are needed by extending the validity of the continuum formulation. Moreover, since for high-speed rare¦ed gas flows it is necessary to take into account the nonequilibrium among the internal degrees of freedom, the extension of the approach to employ diatomic gas models including rotational relaxation process is a mandatory first step towards realistic simulations. Compared to previous works of Xu and coworkers, the presented scheme is de¦ned directly on the basis of kinetic models which involve a Prandtl number correction. Moreover, the methods are defined fully analytically instead of making use of Taylor expansion for the evaluation of the required derivatives. The scheme has been tested for various test cases and Mach numbers proving to produce reliable predictions in agreement with other approaches for near-continuum flows. Finally, the performance of the scheme, in terms of memory and computational time, compared to discrete velocity methods makes it a compelling alternative in place of more complex methods for hybrid simulations of weakly rarefied flows.

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 ...

Channel flow analysis. [velocity distribution throughout blade flow field

Science.gov (United States)

Katsanis, T.

1973-01-01

The design of a proper blade profile requires calculation of the blade row flow field in order to determine the velocities on the blade surfaces. An analysis theory is presented for several methods used for this calculation and associated computer programs that were developed are discussed.

Measurement uncertainty budget of an interferometric flow velocity sensor

Science.gov (United States)

Bermuske, Mike; Büttner, Lars; Czarske, Jürgen

2017-06-01

Flow rate measurements are a common topic for process monitoring in chemical engineering and food industry. To achieve the requested low uncertainties of 0:1% for flow rate measurements, a precise measurement of the shear layers of such flows is necessary. The Laser Doppler Velocimeter (LDV) is an established method for measuring local flow velocities. For exact estimation of the flow rate, the flow profile in the shear layer is of importance. For standard LDV the axial resolution and therefore the number of measurement points in the shear layer is defined by the length of the measurement volume. A decrease of this length is accompanied by a larger fringe distance variation along the measurement axis which results in a rise of the measurement uncertainty for the flow velocity (uncertainty relation between spatial resolution and velocity uncertainty). As a unique advantage, the laser Doppler profile sensor (LDV-PS) overcomes this problem by using two fan-like fringe systems to obtain the position of the measured particles along the measurement axis and therefore achieve a high spatial resolution while it still offers a low velocity uncertainty. With this technique, the flow rate can be estimated with one order of magnitude lower uncertainty, down to 0:05% statistical uncertainty.1 And flow profiles especially in film flows can be measured more accurately. The problem for this technique is, in contrast to laboratory setups where the system is quite stable, that for industrial applications the sensor needs a reliable and robust traceability to the SI units, meter and second. Small deviations in the calibration can, because of the highly position depending calibration function, cause large systematic errors in the measurement result. Therefore, a simple, stable and accurate tool is needed, that can easily be used in industrial surroundings to check or recalibrate the sensor. In this work, different calibration methods are presented and their influences to the

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. .

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.

Effects of gas flow on oxidation reaction in liquid induced by He/O{sub 2} plasma-jet irradiation

Energy Technology Data Exchange (ETDEWEB)

Nakajima, Atsushi; Uchida, Giichiro, E-mail: uchida@jwri.osaka-u.ac.jp; Takenaka, Kosuke; Setsuhara, Yuichi [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Kawasaki, Toshiyuki [Department of Mechanical and Electrical Engineering, Nippon Bunri University, Oita, Oita 870-0397 (Japan); Koga, Kazunori; Sarinont, Thapanut; Amano, Takaaki; Shiratani, Masaharu [Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka, Fukuoka 819-0395 (Japan)

2015-07-28

We present here analysis of oxidation reaction in liquid by a plasma-jet irradiation under various gas flow patterns such as laminar and turbulence flows. To estimate the total amount of oxidation reaction induced by reactive oxygen species (ROS) in liquid, we employ a KI-starch solution system, where the absorbance of the KI-starch solution near 600 nm behaves linear to the total amount of oxidation reaction in liquid. The laminar flow with higher gas velocity induces an increase in the ROS distribution area on the liquid surface, which results in a large amount of oxidation reaction in liquid. However, a much faster gas flow conversely results in a reduction in the total amount of oxidation reaction in liquid under the following two conditions: first condition is that the turbulence flow is triggered in a gas flow channel at a high Reynolds number of gas flow, which leads to a marked change of the spatial distribution of the ROS concentration in gas phase. Second condition is that the dimpled liquid surface is formed by strong gas flow, which prevents the ROS from being transported in radial direction along the liquid surface.

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

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

Gas-liquid two-phase flow behavior in terrain-inclined pipelines for gathering transport system of wet natural gas

DEFF Research Database (Denmark)

Yang, Yan; Li, Jingbo; Wang, Shuli

2018-01-01

The Volume of Fluid method and Re-Normalisation Group (RNG) k-ε turbulence model were employed to predict the gas-liquid two-phase flow in a terrain-inclined pipeline with deposited liquids. The simulation was carried out in a 22.5 m terrain-inclined pipeline with a 150 mm internal diameter...... on the liquid level under the suction force which caused by the negative pressure around the elbow, and then it touched to the top of the pipe. When the liquid blocked the pipe, the pressure drop between the upstream and downstream of the elbow increased with the increase of the gas velocity. At larger gas...

Flow velocity calculation to avoid instability in a typical research reactor core

International Nuclear Information System (INIS)

Oliveira, Carlos Alberto de; Mattar Neto, Miguel

2011-01-01

Flow velocity through a research reactor core composed by MTR-type fuel elements is investigated. Core cooling capacity must be available at the same time that fuel-plate collapse must be avoided. Fuel plates do not rupture during plate collapse, but their lateral deflections can close flow channels and lead to plate over-heating. The critical flow velocity is a speed at which the plates collapse by static instability type failure. In this paper, critical velocity and coolant velocity are evaluated for a typical MTR-type flat plate fuel element. Miller's method is used for prediction of critical velocity. The coolant velocity is limited to 2/3 of the critical velocity, that is a currently used criterion. Fuel plate characteristics are based on the open pool Australian light water reactor. (author)

A special device used for measuring waste gas flow rate in the vent channel of Qinshan Nuclear Power Plant

International Nuclear Information System (INIS)

Zhang Yingjun; Zong Guifang; Shi Huaming; Yang Huimin; Jiang Yuana.

1988-01-01

A special Venturi-Pitot complex device is discribed which is used for measuring waste gas flow rate in the vent channel of Qinshan nuclear power plant. The device is located at the center of the channel. It can produce enlarged differential pressure signal under the condition of low gas velocity. And the flow resistance of this device is negligible. Experiments to determine the ratio of the velocity at the center of the channel to the average velocity were performed on a 1:12 test model. The special device was calibrated in a closed wind tunnel and its discharge coefficient was obtained. The uncertainty is ±3.5% and the nonlinearity is ±1.3%. The enlargement ratio and the discharge coefficient of the device are also deduced analytically on the basis of hydrodynamics theory

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

Transition of unsteady velocity profiles with reverse flow

OpenAIRE

Das, Debopam; Arakeri, Jaywant H

1998-01-01

This paper deals with the stability and transition to turbulence of wall-bounded unsteady velocity profiles with reverse flow. Such flows occur, for example, during unsteady boundary layer separation and in oscillating pipe flow. The main focus is on results from experiments in time-developing flow in a long pipe, which is decelerated rapidly. The flow is generated by the controlled motion of a piston. We obtain analytical solutions for laminar flow in the pipe and in a two-dimensional channe...

Imaging water velocity and volume fraction distributions in water continuous multiphase flows using inductive flow tomography and electrical resistance tomography

International Nuclear Information System (INIS)

Meng, Yiqing; Lucas, Gary P

2017-01-01

This paper presents the design and implementation of an inductive flow tomography (IFT) system, employing a multi-electrode electromagnetic flow meter (EMFM) and novel reconstruction techniques, for measuring the local water velocity distribution in water continuous single and multiphase flows. A series of experiments were carried out in vertical-upward and upward-inclined single phase water flows and ‘water continuous’ gas–water and oil–gas–water flows in which the velocity profiles ranged from axisymmetric (single phase and vertical-upward multiphase flows) to highly asymmetric (upward-inclined multiphase flows). Using potential difference measurements obtained from the electrode array of the EMFM, local axial velocity distributions of the continuous water phase were reconstructed using two different IFT reconstruction algorithms denoted RT#1, which assumes that the overall water velocity profile comprises the sum of a series of polynomial velocity components, and RT#2, which is similar to RT#1 but which assumes that the zero’th order velocity component may be replaced by an axisymmetric ‘power law’ velocity distribution. During each experiment, measurement of the local water volume fraction distribution was also made using the well-established technique of electrical resistance tomography (ERT). By integrating the product of the local axial water velocity and the local water volume fraction in the cross section an estimate of the water volumetric flow rate was made which was compared with a reference measurement of the water volumetric flow rate. In vertical upward flows RT#2 was found to give rise to water velocity profiles which are consistent with the previous literature although the profiles obtained in the multiphase flows had relatively higher central velocity peaks than was observed for the single phase profiles. This observation was almost certainly a result of the transfer of axial momentum from the less dense dispersed phases to the

MAGNETIZED GAS IN THE SMITH HIGH VELOCITY CLOUD

International Nuclear Information System (INIS)

Hill, Alex S.; McClure-Griffiths, Naomi M.; Mao, S. A.; Benjamin, Robert A.; Lockman, Felix J.

2013-01-01

We report the first detection of magnetic fields associated with the Smith High Velocity Cloud. We use a catalog of Faraday rotation measures toward extragalactic radio sources behind the Smith Cloud, new H I observations from the Robert C. Byrd Green Bank Telescope, and a spectroscopic map of Hα from the Wisconsin H-Alpha Mapper Northern Sky Survey. There are enhancements in rotation measure (RM) of ≈100 rad m –2 which are generally well correlated with decelerated Hα emission. We estimate a lower limit on the line-of-sight component of the field of ≈8 μG along a decelerated filament; this is a lower limit due to our assumptions about the geometry. No RM excess is evident in sightlines dominated by H I or Hα at the velocity of the Smith Cloud. The smooth Hα morphology of the emission at the Smith Cloud velocity suggests photoionization by the Galactic ionizing radiation field as the dominant ionization mechanism, while the filamentary morphology and high (≈1 Rayleigh) Hα intensity of the lower-velocity magnetized ionized gas suggests an ionization process associated with shocks due to interaction with the Galactic interstellar medium. The presence of the magnetic field may contribute to the survival of high velocity clouds like the Smith Cloud as they move from the Galactic halo to the disk. We expect these data to provide a test for magnetohydrodynamic simulations of infalling gas

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.

A Radiative Transfer Modeling Methodology in Gas-Liquid Multiphase Flow Simulations

Directory of Open Access Journals (Sweden)

Gautham Krishnamoorthy

2014-01-01

Full Text Available A methodology for performing radiative transfer calculations in computational fluid dynamic simulations of gas-liquid multiphase flows is presented. By considering an externally irradiated bubble column photoreactor as our model system, the bubble scattering coefficients were determined through add-on functions by employing as inputs the bubble volume fractions, number densities, and the fractional contribution of each bubble size to the bubble volume from four different multiphase modeling options. The scattering coefficient profiles resulting from the models were significantly different from one another and aligned closely with their predicted gas-phase volume fraction distributions. The impacts of the multiphase modeling option, initial bubble diameter, and gas flow rates on the radiation distribution patterns within the reactor were also examined. An increase in air inlet velocities resulted in an increase in the fraction of larger sized bubbles and their contribution to the scattering coefficient. However, the initial bubble sizes were found to have the strongest impact on the radiation field.

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.

Gas and particle velocity measurements in an induction plasma

International Nuclear Information System (INIS)

Lesinski, J.; Gagne, R.; Boulos, M.I.

1981-08-01

Laser doppler anemometry was used for the measurements of the plasma and particle velocity profiles in the coil region of an inductively coupled plasma. Results are reported for a 50 mm ID induction torch operated at atmospheric pressure with argon as the plasma gas. The oscillator frequency was 3 MHz and the power in the coil was varied between 4.6 and 10.5 kW. The gas velocity measurements were made using a fine carbon powder as a tracer (dp approx. = 1 μm). Measurements were also made with larger silicon particles (dp = 33 μm and sigma = 13 μm) centrally injected in the plasma under different operating conditions

Practical computation of multidimensional thermal flows in a gas centrifuge

International Nuclear Information System (INIS)

Berger, M.H.

1982-12-01

A finite-element theory is derived for Onsager's two-dimensional equation approximating the steady, viscous, gas motion in a high-speed centrifuge. A new high-order tensor product element is proposed to make the computations easy. The method of weighted residuals is used to construct the stiffness matrix, associated boundary integrals, and load vectors. Ekman suction conditions along horizontal surfaces are shown to be natural boundary conditions of the weak approximation. A class of pure bounary-value problems are solved for the field variables of interest. We evaluate the effect of Ekman suction on the flow by computing with and without suction. Also, we compute the case of pure two-dimensional flow where the azimuthal velocity perturbation is presumed to vanish. The effect of this simplifying assumption on the end-to-end temperature difference necessary for a given circulation is discussed. Numerical results are presented graphically and we show that the so-called streamfunction must be graphed in physical coordinates for the isolines to be streamlines. Only in this form do the velocity vectors lie tangent to the contours. Also, the radial velocity is redefined for graphical purposes

Pore-scale mechanisms of gas flow in tight sand reservoirs

Energy Technology Data Exchange (ETDEWEB)

Silin, D.; Kneafsey, T.J.; Ajo-Franklin, J.B.; Nico, P.

2010-11-30

Tight gas sands are unconventional hydrocarbon energy resource storing large volume of natural gas. Microscopy and 3D imaging of reservoir samples at different scales and resolutions provide insights into the coaredo not significantly smaller in size than conventional sandstones, the extremely dense grain packing makes the pore space tortuous, and the porosity is small. In some cases the inter-granular void space is presented by micron-scale slits, whose geometry requires imaging at submicron resolutions. Maximal Inscribed Spheres computations simulate different scenarios of capillary-equilibrium two-phase fluid displacement. For tight sands, the simulations predict an unusually low wetting fluid saturation threshold, at which the non-wetting phase becomes disconnected. Flow simulations in combination with Maximal Inscribed Spheres computations evaluate relative permeability curves. The computations show that at the threshold saturation, when the nonwetting fluid becomes disconnected, the flow of both fluids is practically blocked. The nonwetting phase is immobile due to the disconnectedness, while the permeability to the wetting phase remains essentially equal to zero due to the pore space geometry. This observation explains the Permeability Jail, which was defined earlier by others. The gas is trapped by capillarity, and the brine is immobile due to the dynamic effects. At the same time, in drainage, simulations predict that the mobility of at least one of the fluids is greater than zero at all saturations. A pore-scale model of gas condensate dropout predicts the rate to be proportional to the scalar product of the fluid velocity and pressure gradient. The narrowest constriction in the flow path is subject to the highest rate of condensation. The pore-scale model naturally upscales to the Panfilov's Darcy-scale model, which implies that the condensate dropout rate is proportional to the pressure gradient squared. Pressure gradient is the greatest near the

Theoretical and experimental studies on transient heat transfer for forced convection flow of helium gas over a horizontal cylinder

International Nuclear Information System (INIS)

Liu Qiusheng; Katsuya Fukuda; Zhang Zheng

2005-01-01

Forced convection transient heat transfer for helium gas at various periods of exponential increase of heat input to a horizontal cylinder (heater) was theoretically and experimentally studied. In the theoretical study, transient heat transfer was numerically solved based on a turbulent flow model. It was clarified that the surface superheat and heat flux increase exponentially as the heat generation rate increases with the exponential function. The temperature distribution near the cylinder becomes larger as the surface temperature increases. The values of numerical solution for surface temperature and heat flux agree well with the experimental data for the cylinder diameter of 1 mm. However, the heat flux shows difference from the experimental values for the cylinder diameters of 0.7 mm and 2.0 mm. In the experimental studies, the authors measured heat flux, surface temperature, and transient heat transfer coefficients for forced convection flow of helium gas over horizontal cylinders under wide experimental conditions. The platinum cylinders with diameters of 1.0 mm, 0.7 mm, and 2.0 mm were used as test heaters and heated by electric current with an exponential increase of Q 0exp (t/τ) . The gas flow velocities ranged from 2 to 10 m/s, the gas temperatures ranged from 303 to 353 K, and the periods ranged from 50 ms to 20 s. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period τ longer than about 1 s, and it becomes higher for the period shorter than around 1 s. The transient heat transfer shows less dependence on the gas flowing velocity when the period becomes very shorter. The heat transfer shifts to the quasi-steady-state heat transfer for longer periods and shifts to the transient heat transfer for shorter periods at the same flow velocity. It also approaches the quasi-steady-state one for higher flow velocity at the same period. The transient heat transfer coefficients show significant dependence on

Hydrodynamic boundary conditions for one-component liquid-gas flows on non-isothermal solid substrates

KAUST Repository

Xu, Xinpeng

2012-01-01

Recently, liquid-gas flows related to droplets, bubbles, and thin films on solid surfaces with thermal and wettability gradients have attracted widespread attention because of the many physical processes involved and their promising potential applications in biology, chemistry, and industry. Various new physical effects have been discovered at fluid-solid interfaces by experiments and molecular dynamics simulations, e.g., fluid velocity slip, temperature slip (Kapitza resistance), mechanical-thermal cross coupling, etc. There have been various models and theories proposed to explain these experimental and numerical observations. However, to the best of our knowledge,a continuum hydrodynamic model capable of predicting the temperature and velocity profiles of liquid-gas flows on non-isothermal, heterogeneous solid substrates is still absent. The purpose of this work is to construct a continuum model for simulating the liquid-gas flows on solid surfaces that are flat and rigid, and may involve wettability gradients and thermal gradients. This model is able to describe fluid velocity slip, temperature slip, and mechanical-thermal coupling that may occur at fluid-solid interfaces. For this purpose, we first employ the diffuse interface modeling to formulate the hydrodynamic equations for one-component liquid-gas flows in the bulk region. This reproduces the dynamic van der Waals theory of Onuki [Phys. Rev. Lett., 94: 054501, 2005]. We then extendWaldmann\\'s method [Z. Naturforsch. A, 22: 1269-1280, 1967] to formulate the boundary conditions at the fluid-solid interface that match the hydrodynamic equations in the bulk. The effects of the solid surface curvature are also briefly discussed in the appendix. The guiding principles of our model derivation are the conservation laws and the positive definiteness of entropy production together with the Onsager reciprocal relation. The derived model is self-consistent in the sense that the boundary conditions are

The structure of a jet in cross flow at low velocity ratios

International Nuclear Information System (INIS)

Gopalan, Shridhar; Abraham, Bruce M.; Katz, Joseph

2004-01-01

This paper examines in detail the flow structure and associated wall pressure fluctuations caused by the injection of a round, turbulent jet into a turbulent boundary layer. The velocity ratio, r, ratio of mean jet velocity to the mean cross flow, varies from 0.5 to 2.5 and the Reynolds number based on the cross flow speed and jet diameter is 1.9x10 4 . Particle image velocimetry is used to measure the flow and flush mounted pressure sensors installed at several locations used to determine the wall pressure. The results consist of sample instantaneous flow structures, distributions of mean velocity, vorticity and turbulence intensity, as well as wall pressure spectra. The flow structure depends strongly on the velocity ratio and there are two distinctly different regions. At low velocity ratios, namely r 2, the near-wall flow behind the jet resembles a Karman vortex street and the wall-normal vortical structures contain cross flow boundary layer vorticity. Autospectra of the pressure signals show that the effect of the jet is mainly in the 15-100 Hz range. At r 2, the wall pressure levels reach a plateau demonstrating the diminishing effect of the jet on the near-wall flow. Consistent with the flow structure, the highest wall pressure fluctuations occur off the jet centerline for r 2. Also, the advection speed of near-wall vortical structures increase with r at r 2 it is a constant

Relationship of 133Xe cerebral blood flow to middle cerebral arterial flow velocity in men at rest

Science.gov (United States)

Clark, J. M.; Skolnick, B. E.; Gelfand, R.; Farber, R. E.; Stierheim, M.; Stevens, W. C.; Beck, G. Jr; Lambertsen, C. J.

1996-01-01

Cerebral blood flow (CBF) was measured by 133Xe clearance simultaneously with the velocity of blood flow through the left middle cerebral artery (MCA) over a wide range of arterial PCO2 in eight normal men. Average arterial PCO2, which was varied by giving 4% and 6% CO2 in O2 and by controlled hyperventilation on O2, ranged from 25.3 to 49.9 mm Hg. Corresponding average values of global CBF15 were 27.2 and 65.0 ml 100 g min-1, respectively, whereas MCA blood-flow velocity ranged from 42.8 to 94.2 cm/s. The relationship of CBF to MCA blood-flow velocity over the imposed range of arterial PCO2 was described analytically by a parabola with the equation: CBF = 22.8 - 0.17 x velocity + 0.006 x velocity2 The observed data indicate that MCA blood-flow velocity is a useful index of CBF response to change in arterial PCO2 during O2 breathing at rest. With respect to baseline values measured while breathing 100% O2 spontaneously, percent changes in velocity were significantly smaller than corresponding percent changes in CBF at increased levels of arterial PCO2 and larger than CBF changes at the lower arterial PCO2. These observed relative changes are consistent with MCA vasodilation at the site of measurement during exposure to progressive hypercapnia and also during extreme hyperventilation hypocapnia.

Study of plasma-chemical NO-containing gas flow for treatment of wounds and inflammatory processes.

Science.gov (United States)

Pekshev, Alexander V; Shekhter, Anatoly B; Vagapov, Andrey B; Sharapov, Nikolay A; Vanin, Anatoly F

2018-02-28

This work is aimed at exhaustive and detailed study of chemical, physical and physico-chemical characteristics of NO-containing gas flow (NO-CGF) generated by a plasma-chemical generator of Plason device, which has been used in medical practice for more than 15 years for effectively healing wound and inflammatory conditions with exogenous nitric oxide (NO-therapy). Data was obtained on spatial structure of the gas flow, and values of its local parameters in axial and radial directions, such as nitric oxide content, velocity, temperature and mass flow density of nitric oxide, providing altogether the effectiveness of treatment by the exogenous NO-therapy method, were determined experimentally and by computations. It was demonstrated that plasma-chemical synthesis of NO from atmospheric air in a low direct current (DC) arc provides a high mass flow of nitric oxide at the level of 1.6-1.8 mg/s, while in the area of impact of NO-CGF on the biological tissue, on its axis, NO content is 400-600 ppm, flow velocity about 5 m/s, nitric oxide mass flow density 0.25-0.40 mg/(s·cm 2 ), temperature 40-60 °C. Tendencies were determined for designing new devices for further experimental biological and medical research in the field of NO-therapy: lowering the temperature of NO-CGF to ambient temperature will enable variation, in experiments, of the affecting flow parameters in a wide range up to their maximum values: NO content up to 2000 ppm, velocity up to 20 m/s, nitric oxide mass flow density up to 2.5 mg/(s·cm 2 ). Copyright © 2017. Published by Elsevier Inc.

Close entrainment of massive molecular gas flows by radio bubbles in the central galaxy of Abell 1795

Science.gov (United States)

Russell, H. R.; McNamara, B. R.; Fabian, A. C.; Nulsen, P. E. J.; Combes, F.; Edge, A. C.; Hogan, M. T.; McDonald, M.; Salomé, P.; Tremblay, G.; Vantyghem, A. N.

2017-12-01

We present new ALMA observations tracing the morphology and velocity structure of the molecular gas in the central galaxy of the cluster Abell 1795. The molecular gas lies in two filaments that extend 5-7 kpc to the N and S from the nucleus and project exclusively around the outer edges of two inner radio bubbles. Radio jets launched by the central active galactic nucleus have inflated bubbles filled with relativistic plasma into the hot atmosphere surrounding the central galaxy. The N filament has a smoothly increasing velocity gradient along its length from the central galaxy's systemic velocity at the nucleus to -370 km s^{-1}, the average velocity of the surrounding galaxies, at the furthest extent. The S filament has a similarly smooth but shallower velocity gradient and appears to have partially collapsed in a burst of star formation. The close spatial association with the radio lobes, together with the ordered velocity gradients and narrow velocity dispersions, shows that the molecular filaments are gas flows entrained by the expanding radio bubbles. Assuming a Galactic XCO factor, the total molecular gas mass is 3.2 ± 0.2 × 109 M⊙. More than half lies above the N radio bubble. Lifting the molecular clouds appears to require an infeasibly efficient coupling between the molecular gas and the radio bubble. The energy required also exceeds the mechanical power of the N radio bubble by a factor of 2. Stimulated feedback, where the radio bubbles lift low-entropy X-ray gas that becomes thermally unstable and rapidly cools in situ, provides a plausible model. Multiple generations of radio bubbles are required to lift this substantial gas mass. The close morphological association then indicates that the cold gas either moulds the newly expanding bubbles or is itself pushed aside and shaped as they inflate.

Viscosity estimation utilizing flow velocity field measurements in a rotating magnetized plasma

International Nuclear Information System (INIS)

Yoshimura, Shinji; Tanaka, Masayoshi Y.

2008-01-01

The importance of viscosity in determining plasma flow structures has been widely recognized. In laboratory plasmas, however, viscosity measurements have been seldom performed so far. In this paper we present and discuss an estimation method of effective plasma kinematic viscosity utilizing flow velocity field measurements. Imposing steady and axisymmetric conditions, we derive the expression for radial flow velocity from the azimuthal component of the ion fluid equation. The expression contains kinematic viscosity, vorticity of azimuthal rotation and its derivative, collision frequency, azimuthal flow velocity and ion cyclotron frequency. Therefore all quantities except the viscosity are given provided that the flow field can be measured. We applied this method to a rotating magnetized argon plasma produced by the Hyper-I device. The flow velocity field measurements were carried out using a directional Langmuir probe installed in a tilting motor drive unit. The inward ion flow in radial direction, which is not driven in collisionless inviscid plasmas, was clearly observed. As a result, we found the anomalous viscosity, the value of which is two orders of magnitude larger than the classical one. (author)

Heat transfer and velocity characteristics of single- and two-phase flows in a subsonic model gun

International Nuclear Information System (INIS)

Bicen, A.F.; Khezzar, L.; Schmidt, M.; Whitelaw, J.H.

1989-01-01

Heat transfer and velocity measurements are reported for single- and two-phase flows in the wake of an in-bore projectile propelled by an inert gas at an initial gauge pressure of 8 bars to an exit velocity over 40 m/s in ∼ 33 ms. The results show that with the single phase the turbulent velocity boundary layers occupy over 20% of the barrel radius and that the wall heat transfer increases with distance from the breech and decreases with time during the shot. In the initial chamber, and later in the shot, the heat transfer results are close to those obtained from a convection correlation for a steady turbulent boundary layer, contrary to those at locations swept by the projectile, which are higher by up to 50% throughout the shot. The two-phase flow results show that 55-μm particles with loadings of 1.3% and 4% by volume initially lag the fluid and this lag increases with distance from the breech. Later in the shot the particles catch up and lead the decelerating fluid by an amount that is greater, with the higher particle loading and with a tendency for the particle velocity to increase around the edge of the boundary layer

Proposed method for reconstructing velocity profiles using a multi-electrode electromagnetic flow meter

International Nuclear Information System (INIS)

Kollár, László E; Lucas, Gary P; Zhang, Zhichao

2014-01-01

An analytical method is developed for the reconstruction of velocity profiles using measured potential distributions obtained around the boundary of a multi-electrode electromagnetic flow meter (EMFM). The method is based on the discrete Fourier transform (DFT), and is implemented in Matlab. The method assumes the velocity profile in a section of a pipe as a superposition of polynomials up to sixth order. Each polynomial component is defined along a specific direction in the plane of the pipe section. For a potential distribution obtained in a uniform magnetic field, this direction is not unique for quadratic and higher-order components; thus, multiple possible solutions exist for the reconstructed velocity profile. A procedure for choosing the optimum velocity profile is proposed. It is applicable for single-phase or two-phase flows, and requires measurement of the potential distribution in a non-uniform magnetic field. The potential distribution in this non-uniform magnetic field is also calculated for the possible solutions using weight values. Then, the velocity profile with the calculated potential distribution which is closest to the measured one provides the optimum solution. The reliability of the method is first demonstrated by reconstructing an artificial velocity profile defined by polynomial functions. Next, velocity profiles in different two-phase flows, based on results from the literature, are used to define the input velocity fields. In all cases, COMSOL Multiphysics is used to model the physical specifications of the EMFM and to simulate the measurements; thus, COMSOL simulations produce the potential distributions on the internal circumference of the flow pipe. These potential distributions serve as inputs for the analytical method. The reconstructed velocity profiles show satisfactory agreement with the input velocity profiles. The method described in this paper is most suitable for stratified flows and is not applicable to axisymmetric flows in

Pressure and velocity dependence of flow-type cavitation erosion

CSIR Research Space (South Africa)

Auret, JG

1993-12-01

Full Text Available Previous results on the influence of water pressure and velocity on flow-type cavitations erosion, i.e. an increase in erosion rate with increasing velocity and peaking of erosion rate as a function of pressure, were confirmed by measurements with a...

Rarefaction effects in gas flows over curved surfaces

Science.gov (United States)

Dongari, Nishanth; White, Craig; Scanlon, Thomas J.; Zhang, Yonghao; Reese, Jason M.

2012-11-01

The fundamental test case of gas flow between two concentric rotating cylinders is considered in order to investigate rarefaction effects associated with the Knudsen layers over curved surfaces. We carry out direct simulation Monte Carlo simulations covering a wide range of Knudsen numbers and accommodation coefficients, and for various outer-to-inner cylinder radius ratios. Numerical data is compared with classical slip flow theory and a new power-law (PL) wall scaling model. The PL model incorporates Knudsen layer effects in near-wall regions by taking into account the boundary limiting effects on the molecular free paths. The limitations of both theoretical models are explored with respect to rarefaction and curvature effects. Torque and velocity profile comparisons also convey that mere prediction of integral flow parameters does not guarantee the accuracy of a theoretical model, and that it is important to ensure that prediction of the local flowfield is in agreement with simulation data.

Analysis of spatial and temporal spectra of liquid film surface in annular gas-liquid flow

Science.gov (United States)

Alekseenko, Sergey; Cherdantsev, Andrey; Heinz, Oksana; Kharlamov, Sergey; Markovich, Dmitriy

2013-09-01

Wavy structure of liquid film in annular gas-liquid flow without liquid entrainment consists of fast long-living primary waves and slow short-living secondary waves. In present paper, results of spectral analysis of this wavy structure are presented. Application of high-speed LIF technique allowed us to perform such analysis in both spatial and temporal domains. Power spectra in both domains are characterized by one-humped shape with long exponential tail. Influence of gas velocity, liquid Reynolds number, liquid viscosity and pipe diameter on frequency of the waves is investigated. When gravity effect is much lesser than the shear stress, similarity of power spectra at different gas velocities is observed. Using combination of spectral analysis and identification of characteristic lines of primary waves, frequency of generation of secondary waves by primary waves is measured.

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.)

Gas density fluctuations in the Perseus Cluster: clumping factor and velocity power spectrum

Energy Technology Data Exchange (ETDEWEB)

Zhuravleva, I.; Churazov, E.; Arevalo, P.; Schekochihin, A. A.; Allen, S. W.; Fabian, A. C.; Forman, W. R.; Sanders, J. S.; Simionescu, A.; Sunyaev, R.; Vikhlinin, A.; Werner, N.

2015-05-20

X-ray surface brightness fluctuations in the core of the Perseus Cluster are analysed, using deep observations with the Chandra observatory. The amplitude of gas density fluctuations on different scales is measured in a set of radial annuli. It varies from 7 to 12 per cent on scales of ~10–30 kpc within radii of 30–220 kpc from the cluster centre. Using a statistical linear relation between the observed amplitude of density fluctuations and predicted velocity, the characteristic velocity of gas motions on each scale is calculated. The typical amplitudes of the velocity outside the central 30 kpc region are 90–140 km s^-1 on ~20–30 kpc scales and 70–100 km s^-1 on smaller scales ~7–10 kpc. The velocity power spectrum (PS) is consistent with cascade of turbulence and its slope is in a broad agreement with the slope for canonical Kolmogorov turbulence. The gas clumping factor estimated from the PS of the density fluctuations is lower than 7–8 per cent for radii ~30–220 kpc from the centre, leading to a density bias of less than 3–4 per cent in the cluster core. Uncertainties of the analysis are examined and discussed. Future measurements of the gas velocities with the Astro-H, Athena and Smart-X observatories will directly measure the gas density–velocity perturbation relation and further reduce systematic uncertainties in this analysis.

Source modulation-correlation measurement for fissile mass flow in gas or liquid fissile streams

International Nuclear Information System (INIS)

Mihalczo, J.T.; March-Leuba, J.A.; Valentine, T.E.; Abston, R.A.; Mattingly, J.K.; Mullens, J.A.

1996-01-01

The method of monitoring fissile mass flow on all three legs of a blending point, where the input is high-enriched uranium (HEU) and low-enriched uranium (LEU) and the product is PEU, can yield the fissile stream velocity and, with calibration, the [sup235]U content. The product of velocity and content integrated over the pipe gives the fissile mass flow in each leg. Also, the ratio of fissile contents in each pipe: HEU/LEU, HEU/PEU, and PEU/LEU, are obtained. By modulating the source on the input HEU pipe differently from that on the output pipe, the HEU gas can be tracked through the blend point. This method can be useful for monitoring flow velocity, fissile content, and fissile mass flow in HEU blenddown of UF[sub 6] if the pressures are high enough to contain some of the induced fission products. This method can also be used to monitor transfer of fissile liquids and other gases and liquids that emit radiation delayed from particle capture. These preliminary experiments with the Oak Ridge apparatus show that the method will work and the modeling is adequate

Recognition and measurement gas-liquid two-phase flow in a vertical concentric annulus at high pressures

Science.gov (United States)

Li, Hao; Sun, Baojiang; Guo, Yanli; Gao, Yonghai; Zhao, Xinxin

2018-02-01

The air-water flow characteristics under pressure in the range of 1-6 MPa in a vertical annulus were evaluated in this report. Time-resolved bubble rising velocity and void fraction were also measured using an electrical void fraction meter. The results showed that the pressure has remarkable effect on the density, bubble size and rise velocity of the gas. Four flow patterns (bubble, cap-bubble, cap-slug, and churn) were also observed instead of Taylor bubble at high pressure. Additionally, the transition process from bubble to cap-bubble was investigated at atmospheric and high pressures, respectively. The results revealed that the flow regime transition criteria for atmospheric pressure do not work at high pressure, hence a new flow regime transition model for annular flow channel geometry was developed to predict the flow regime transition, which thereafter exhibited high accuracy at high pressure condition.

Magnetohydrodynamic flow of a rarefied gas near a time-varying accelerated plate

International Nuclear Information System (INIS)

Mishra, S.P.; Mohapatra, Priti

1975-01-01

The flow of an electrically conducting rarefied gas due to the time-varying motion of an infinite flat plate has been studied in the presence of a uniform magnetic field. The magnetic lines of force are taken to be fixed relative to the fluid. General expressions of the velocity and the skin friction have been compared by means of some qraphs and tables. (author)

Phase Resolved Angular Velocity Control of Cross Flow Turbines

Science.gov (United States)

Strom, Benjamin; Brunton, Steven; Polagye, Brian

2015-11-01

Cross flow turbines have a number of operational advantages for the conversion of kinetic energy in marine or fluvial currents, but they are often less efficient than axial flow devices. Here a control scheme is presented in which the angular velocity of a cross flow turbine with two straight blades is prescribed as a function of azimuthal blade position, altering the time-varying effective angle of attack. Flume experiments conducted with a scale model turbine show approximately an 80% increase in turbine efficiency versus optimal constant angular velocity and constant resistive torque control schemes. Torque, drag, and lateral forces on one- and two-bladed turbines are analyzed and interpreted with bubble flow visualization to develop a simple model that describes the hydrodynamics responsible for the observed increase in mean efficiency. Challenges associated with implementing this control scheme on commercial-scale devices are discussed. If solutions are found, the performance increase presented here may impact the future development of cross flow turbines.

Calculation of afterbody flows with a composite velocity formulation

Science.gov (United States)

Swanson, R. C.; Rubin, S. G.; Khosla, P. K.

1983-01-01

A recently developed technique for numerical solution of the Navier-Stokes equations for subsonic, laminar flows is investigated. It is extended here to allow for the computation of transonic and turbulent flows. The basic approach involves a multiplicative composite of the appropriate velocity representations for the inviscid and viscous flow regions. The resulting equations are structured so that far from the surface of the body the momentum equations lead to the Bernoulli equation for the pressure, while the continuity equation reduces to the familiar potential equation. Close to the body surface, the governing equations and solution techniques are characteristic of those describing interacting boundary layers. The velocity components are computed with a coupled strongly implicity procedure. For transonic flows the artificial compressibility method is used to treat supersonic regions. Calculations are made for both laminar and turbulent flows over axisymmetric afterbody configurations. Present results compare favorably with other numerical solutions and/or experimental data.

Influence of Gas Flow Rate on the Deposition Rate on Stainless Steel 202 Substrates

Directory of Open Access Journals (Sweden)

M.A. Chowdhury

2012-12-01

Full Text Available Solid thin films have been deposited on stainless steel 202 (SS 202 substrates at different flow rates of natural gas using a hot filament thermal chemical vapor deposition (CVD reactor. In the experiments, the variations of thin film deposition rate with the variation of gas flow rate have been investigated. The effects of gap between activation heater and substrate on the deposition rate have also been observed. Results show that deposition rate on SS 202 increases with the increase in gas flow rate within the observed range. It is also found that deposition rate increases with the decrease in gap between activation heater and substrate. In addition, friction coefficient and wear rate of SS 202 sliding against SS 304 under different sliding velocities are also investigated before and after deposition. The experimental results reveal that improved friction coefficient and wear rate is obtained after deposition than that of before deposition.

The Influences of Time and Velocity of Inert Gas on the Quality of theProcessing Product of Graphite Matrix on the Baking Step

International Nuclear Information System (INIS)

Imam-Dahroni; Dwi-Herwidhi; NS, Kasilani

2000-01-01

The research of the synthesis of matrix graphite on the step of bakingprocess was conducted, by focusing on the influence of time and velocityvariables of the inert gas. The investigation on baking times ranging from 5minutes to 55 minutes and by varying the velocity of inert gas from 0.30l/minute to 3.60 l/minute, resulted the product of different matrix.Optimizing at the time of operation and the flow rate of argon gas indicatedthat the baking time for 30 minutes and by the flow rate of argon gas of 2.60l/minute resulted best matrix graphite that has a hardness value of 11kg/mm 2 of hardness and the ductility of 1800 Newton. (author)

Cross-tail velocity component in the plasma sheet fast flows

Directory of Open Access Journals (Sweden)

N. P. Dmitrieva

2008-06-01

Full Text Available The flux transfer in the magnetotail plasma sheet is mainly provided by the tail-aligned fast plasma flows (Bursty Bulk Flows – BBFs. In this paper we study the events with a large cross-tail velocity component, including their occurrence and relationship to the standard BBFs. We found out that a significant part of large Vy events are a subgroup connected with the BBFs propagation. The maximal deviation of the velocity vector from the X direction (about 40–50 degrees, on average is observed near the BBFs' leading front in the sheath, where the fast flow interacts with surrounding plasma. The average variation of the velocity direction in the vicinity of the BBF resembles a plasma vortex. Our results support the model, in which the BBF represents a polarized, bubble-like flux tube, propagating through the plasma sheet.

Differential increases in blood flow velocity in the middle cerebral artery after tourniquet deflation during sevoflurane, isoflurane or propofol anaesthesia.

Science.gov (United States)

Kadoi, Y; Kawauchi, C H; Ide, M; Saito, S; Mizutani, A

2009-07-01

The purpose of this study was to examine the comparative effects of sevoflurane, isoflurane or propofol on cerebral blood flow velocity after tourniquet deflation during orthopaedic surgery. Thirty patients undergoing elective orthopaedic surgery were randomly divided into sevoflurane, isoflurane and propofol groups. Anaesthesia was maintained with sevoflurane, isoflurane or propofol infusion in 33% oxygen and 67% nitrous oxide, in whatever concentrations were necessary to keep bispectral index values between 45 and 50. Ventilatory rate or tidal volume was adjusted to target PaCO2 of 35 mmHg. A 2.0 MHz transcranial Doppler probe was attached to the patient's head at the temporal window and mean blood flow velocity in the middle cerebral artery was continuously measured. The extremity was exsanguinated with an Esmarch bandage and the pneumatic tourniquet was inflated to a pressure of 450 mmHg. Arterial blood pressure, heart rate, velocity in the middle cerebral artery and arterial blood gas analysis were measured every minute for 10 minutes after release of the tourniquet in all three groups. Velocity in the middle cerebral artery in the three groups increased for five minutes after tourniquet deflation. Because of the different cerebrovascular effects of the three agents, the degree of increase in flow velocity in the isoflurane group was greater than in the other two groups, the change in flow velocity in the propofol group being the lowest (at three minutes after deflation 40 +/- 7%, 32 +/- 6% and 28 +/- 10% in the isoflurane, sevoflurane and propofol groups respectively, P < 0.05).

Three-dimensional imaging of absolute blood flow velocity and blood vessel position under low blood flow velocity based on Doppler signal information included in scattered light from red blood cells

Science.gov (United States)

Kyoden, Tomoaki; Akiguchi, Shunsuke; Tajiri, Tomoki; Andoh, Tsugunobu; Hachiga, Tadashi

2017-11-01

The development of a system for in vivo visualization of occluded distal blood vessels for diabetic patients is the main target of our research. We herein describe two-beam multipoint laser Doppler velocimetry (MLDV), which measures the instantaneous multipoint flow velocity and can be used to observe the blood flow velocity in peripheral blood vessels. By including a motorized stage to shift the measurement points horizontally and in the depth direction while measuring the velocity, the path of the blood vessel in the skin could be observed using blood flow velocity in three-dimensional space. The relationship of the signal power density between the blood vessel and the surrounding tissues was shown and helped us identify the position of the blood vessel. Two-beam MLDV can be used to simultaneously determine the absolute blood flow velocity distribution and identify the blood vessel position in skin.

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

International Nuclear Information System (INIS)

Zhang, Qiang; Gao, Yide

2016-01-01

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

STARE velocities: 2. Evening westward electron flow

Directory of Open Access Journals (Sweden)

M. Uspensky

2004-04-01

Full Text Available Four evening events and one morning event of joint EISCAT/STARE observations during ~22h are considered and the differences between observed STARE line-of-sight (l-o-s velocities and EISCAT electron drift velocities projected onto the STARE beams are studied. We demonstrate that the double-pulse technique, which is currently in use in the STARE routine data handling, typically underestimates the true phase velocity as inferred from the multi-pulse STARE data. We show that the STARE velocities are persistently smaller (1.5–2 times than the EISCAT velocities, even for the multi-pulse data. The effect seems to be more pronounced in the evening sector when the Finland radar observes at large flow angles. We evaluate the performance of the ion-acoustic approach (IAA, Nielsen and Schlegel, 1985 and the off-orthogonal fluid approach (OOFA, Uspensky et al., 2003 techniques to predict the true electron drift velocity for the base event of 12 February 1999. The IAA technique predicts the convection reasonably well for enhanced flows of >~1000m/s, but not so well for slower ones. By considering the EISCAT N(h profiles, we derive the effective aspect angle and effective altitude of backscatter, and use this information for application of the OOFA technique. We demonstrate that the OOFA predictions for the base event are superior over the IAA predictions and thus, we confirm that OOFA predicts the electron velocities reasonably well in the evening sector, in addition to the morning sector, as concluded by Uspensky et al. (2003. To check how "robust" the OOFA model is and how successful it is for convection estimates without the EISCAT support, we analysed three additional evening events and one additional morning event for which information on N(h profiles was intentionally ignored. By accepting the mean STARE/EISCAT velocity ratio of 0.55 and the mean azimuth rotation of 9° (derived for the basic event, we show that the OOFA performs

Magnetic particle imaging for in vivo blood flow velocity measurements in mice

Science.gov (United States)

Kaul, Michael G.; Salamon, Johannes; Knopp, Tobias; Ittrich, Harald; Adam, Gerhard; Weller, Horst; Jung, Caroline

2018-03-01

Magnetic particle imaging (MPI) is a new imaging technology. It is a potential candidate to be used for angiographic purposes, to study perfusion and cell migration. The aim of this work was to measure velocities of the flowing blood in the inferior vena cava of mice, using MPI, and to evaluate it in comparison with magnetic resonance imaging (MRI). A phantom mimicking the flow within the inferior vena cava with velocities of up to 21 cm s‑1 was used for the evaluation of the applied analysis techniques. Time–density and distance–density analyses for bolus tracking were performed to calculate flow velocities. These findings were compared with the calibrated velocities set by a flow pump, and it can be concluded that velocities of up to 21 cm s‑1 can be measured by MPI. A time–density analysis using an arrival time estimation algorithm showed the best agreement with the preset velocities. In vivo measurements were performed in healthy FVB mice (n  =  10). MRI experiments were performed using phase contrast (PC) for velocity mapping. For MPI measurements, a standardized injection of a superparamagnetic iron oxide tracer was applied. In vivo MPI data were evaluated by a time–density analysis and compared to PC MRI. A Bland–Altman analysis revealed good agreement between the in vivo velocities acquired by MRI of 4.0  ±  1.5 cm s‑1 and those measured by MPI of 4.8  ±  1.1 cm s‑1. Magnetic particle imaging is a new tool with which to measure and quantify flow velocities. It is fast, radiation-free, and produces 3D images. It therefore offers the potential for vascular imaging.

Molecular Rayleigh Scattering Diagnostic for Dynamic Temperature, Velocity, and Density Measurements

Science.gov (United States)

Mielke, Amy R.; Elam, Kristie A.; Sung, Chi-Jen

2006-01-01

A molecular Rayleigh scattering technique is developed to measure dynamic gas temperature, velocity, and density in unseeded turbulent flows at sampling rates up to 16 kHz. A high power CW laser beam is focused at a point in an air jet plume and Rayleigh scattered light is collected and spectrally resolved. The spectrum of the light, which contains information about the temperature and velocity of the flow, is analyzed using a Fabry-Perot interferometer. The circular interference fringe pattern is divided into four concentric regions and sampled at 1 and 16 kHz using photon counting electronics. Monitoring the relative change in intensity within each region allows for measurement of gas temperature and velocity. Independently monitoring the total scattered light intensity provides a measure of gas density. A low speed heated jet is used to validate the measurement of temperature fluctuations and an acoustically excited nozzle flow is studied to validate velocity fluctuation measurements. Power spectral density calculations of the property fluctuations, as well as mean and fluctuating quantities are presented. Temperature fluctuation results are compared with constant current anemometry measurements and velocity fluctuation results are compared with constant temperature anemometry measurements at the same locations.

Radial flow gas dynamic laser

International Nuclear Information System (INIS)

Damm, F.C.

1975-01-01

The unique gas dynamic laser provides outward radial supersonic flow from a toroidal shaped stacked array of a plurality of nozzles, through a diffuser having ring shaped and/or linear shaped vanes, and through a cavity which is cylindrical and concentric with the stacked array, with the resultant laser beam passing through the housing parallel to the central axis of the diffuser which is coincident with the axis of the gas dynamic laser. Therefore, greater beam extraction flexibility is attainable, because of fewer flow shock disturbances, as compared to the conventional unidirectional flow gas dynamic laser in which unidirectional supersonic flow sweeps through a rectangular cavity and is exhausted through a two-dimensional diffuser. (auth)

Measurement of laminar burning velocities and Markstein lengths of diluted hydrogen-enriched natural gas

Energy Technology Data Exchange (ETDEWEB)

Miao, Haiyan; Jiao, Qi; Huang, Zuohua; Jiang, Deming [State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Eng., Xi' an Jiaotong University (China)

2009-01-15

The laminar flame characteristics of natural gas-hydrogen-air-diluent gas (nitrogen/CO{sub 2}) mixtures were studied in a constant volume combustion bomb at various diluent ratios, hydrogen fractions and equivalence ratios. Both unstretched laminar burning velocity and Markstein length were obtained. The results showed that hydrogen fraction, diluent ratio and equivalence ratio have combined influence on laminar burning velocity and flame instability. The unstretched laminar burning velocity is reduced at a rate that is increased with the increase of the diluent ratio. The reduction effect of CO{sub 2} diluent gas is stronger than that of nitrogen diluent gas. Hydrogen-enriched natural gas with high hydrogen fraction can tolerate more diluent gas than that with low hydrogen fraction. Markstein length can either increase or decrease with the increase of the diluent ratio, depending on the hydrogen fraction of the fuel. (author)

1st European Conference on Gas Micro Flows (GasMems 2012)

NARCIS (Netherlands)

Frijns, A.J.H.; Valougeorgis, D.; Colin, S.; Baldas, L.

2012-01-01

PREFACE The aim of the 1st European Conference on Gas Micro Flows is to advance research in Europe and worldwide in the field of gas micro flows as well as to improve global fundamental knowledge and to enable technological applications. Gas flows in microsystems are of great importance and touch

The boundary condition for vertical velocity and its interdependence with surface gas exchange

Science.gov (United States)

Kowalski, Andrew S.

2017-07-01

The law of conservation of linear momentum is applied to surface gas exchanges, employing scale analysis to diagnose the vertical velocity (w) in the boundary layer. Net upward momentum in the surface layer is forced by evaporation (E) and defines non-zero vertical motion, with a magnitude defined by the ratio of E to the air density, as w = E/ρ. This is true even right down at the surface where the boundary condition is w|0 = E/ρ|0 (where w|0 and ρ|0 represent the vertical velocity and density of air at the surface). This Stefan flow velocity implies upward transport of a non-diffusive nature that is a general feature of the troposphere but is of particular importance at the surface, where it assists molecular diffusion with upward gas migration (of H2O, for example) but opposes that of downward-diffusing species like CO2 during daytime. The definition of flux-gradient relationships (eddy diffusivities) requires rectification to exclude non-diffusive transport, which does not depend on scalar gradients. At the microscopic scale, the role of non-diffusive transport in the process of evaporation from inside a narrow tube - with vapour transport into an overlying, horizontal airstream - was described long ago in classical mechanics and is routinely accounted for by chemical engineers, but has been neglected by scientists studying stomatal conductance. Correctly accounting for non-diffusive transport through stomata, which can appreciably reduce net CO2 transport and marginally boost that of water vapour, should improve characterisations of ecosystem and plant functioning.

Measurement system of bubbly flow using Ultrasonic Velocity Profile Monitor and Video Data Processing Unit. 3. Comparison of flow characteristics between bubbly cocurrent and countercurrent flows

International Nuclear Information System (INIS)

Zhou, Shirong; Suzuki, Yumiko; Aritomi, Masanori; Matsuzaki, Mitsuo; Takeda, Yasushi; Mori, Michitsugu

1998-01-01

The authors have developed a new measurement system which consisted of an Ultrasonic Velocity Profile Monitor (UVP) and a Video Data Processing Unit (VDP) in order to clarify the two-dimensional flow characteristics in bubbly flows and to offer a data base to validate numerical codes for two-dimensional two-phase flow. In the present paper, the proposed measurement system is applied to fully developed bubbly cocurrent flows in a vertical rectangular channel. At first, both bubble and water velocity profiles and void fraction profiles in the channel were investigated statistically. In addition, the two-phase multiplier profile of turbulence intensity, which was defined as a ratio of the standard deviation of velocity fluctuation in a bubbly flow to that in a water single phase flow, were examined. Next, these flow characteristics were compared with those in bubbly countercurrent flows reported in our previous paper. Finally, concerning the drift flux model, the distribution parameter and drift velocity were obtained directly from both bubble and water velocity profiles and void fraction profiles, and their results were compared with those in bubbly countercurrent flows. (author)

An Efficient Hybrid DSMC/MD Algorithm for Accurate Modeling of Micro Gas Flows

KAUST Repository

Liang, Tengfei

2013-01-01

Aiming at simulating micro gas flows with accurate boundary conditions, an efficient hybrid algorithmis developed by combining themolecular dynamics (MD) method with the direct simulationMonte Carlo (DSMC)method. The efficiency comes from the fact that theMD method is applied only within the gas-wall interaction layer, characterized by the cut-off distance of the gas-solid interaction potential, to resolve accurately the gas-wall interaction process, while the DSMC method is employed in the remaining portion of the flow field to efficiently simulate rarefied gas transport outside the gas-wall interaction layer. A unique feature about the present scheme is that the coupling between the two methods is realized by matching the molecular velocity distribution function at the DSMC/MD interface, hence there is no need for one-toone mapping between a MD gas molecule and a DSMC simulation particle. Further improvement in efficiency is achieved by taking advantage of gas rarefaction inside the gas-wall interaction layer and by employing the "smart-wall model" proposed by Barisik et al. The developed hybrid algorithm is validated on two classical benchmarks namely 1-D Fourier thermal problem and Couette shear flow problem. Both the accuracy and efficiency of the hybrid algorithm are discussed. As an application, the hybrid algorithm is employed to simulate thermal transpiration coefficient in the free-molecule regime for a system with atomically smooth surface. Result is utilized to validate the coefficients calculated from the pure DSMC simulation with Maxwell and Cercignani-Lampis gas-wall interaction models. ©c 2014 Global-Science Press.

Lattice gas automaton scheme with stochastic particle movement for a rotated fluid flow

International Nuclear Information System (INIS)

Ishiguro, Misako

2002-01-01

Lattice gas automaton (LGA) models developed so far are just for Cartesian geometries, and no direct approach to rotated fluid flows is found. In this paper, LGA method is applied to model a two-dimensional rotated flow. Several problems specific to the rotated flow are to be solved: hexagonal lattice geometry to effectively identify the neighbors, boundary condition for irregular walls, multi-speed scheme to represent angular-oriented fluid velocity υ θ ≅γω, shape of macroscopic domain for statistics, formula to obtain macroscopic quantities such as density and mean fluid velocities, application method of Fermi-Dirac function to the initial particle arrangement. For this purpose, FHP-I type hexagonal lattice model is revised and a new LGA model with stochastic particle movement is proposed. The results of the trial calculation are shown. It is also investigated whether or not the underlying microscopic Boolean equations newly introduced leads to Navier-Stokes equation. (author)

Coupling compositional liquid gas Darcy and free gas flows at porous and free-flow domains interface

Energy Technology Data Exchange (ETDEWEB)

Masson, R., E-mail: roland.masson@unice.fr [LJAD, University Nice Sophia Antipolis, CNRS UMR 7351 (France); Team COFFEE INRIA Sophia Antipolis Méditerranée (France); Trenty, L., E-mail: laurent.trenty@andra.fr [Andra, Chatenay Malabry (France); Zhang, Y., E-mail: yumeng.zhang@unice.fr [LJAD, University Nice Sophia Antipolis, CNRS UMR 7351 (France); Team COFFEE INRIA Sophia Antipolis Méditerranée (France)

2016-09-15

This paper proposes an efficient splitting algorithm to solve coupled liquid gas Darcy and free gas flows at the interface between a porous medium and a free-flow domain. This model is compared to the reduced model introduced in [6] using a 1D approximation of the gas free flow. For that purpose, the gas molar fraction diffusive flux at the interface in the free-flow domain is approximated by a two point flux approximation based on a low-frequency diagonal approximation of a Steklov–Poincaré type operator. The splitting algorithm and the reduced model are applied in particular to the modelling of the mass exchanges at the interface between the storage and the ventilation galleries in radioactive waste deposits.

An efficient particle Fokker–Planck algorithm for rarefied gas flows

Energy Technology Data Exchange (ETDEWEB)

Gorji, M. Hossein; Jenny, Patrick

2014-04-01

This paper is devoted to the algorithmic improvement and careful analysis of the Fokker–Planck kinetic model derived by Jenny et al. [1] and Gorji et al. [2]. The motivation behind the Fokker–Planck based particle methods is to gain efficiency in low Knudsen rarefied gas flow simulations, where conventional direct simulation Monte Carlo (DSMC) becomes expensive. This can be achieved due to the fact that the resulting model equations are continuous stochastic differential equations in velocity space. Accordingly, the computational particles evolve along independent stochastic paths and thus no collision needs to be calculated. Therefore the computational cost of the solution algorithm becomes independent of the Knudsen number. In the present study, different computational improvements were persuaded in order to augment the method, including an accurate time integration scheme, local time stepping and noise reduction. For assessment of the performance, gas flow around a cylinder and lid driven cavity flow were studied. Convergence rates, accuracy and computational costs were compared with respect to DSMC for a range of Knudsen numbers (from hydrodynamic regime up to above one). In all the considered cases, the model together with the proposed scheme give rise to very efficient yet accurate solution algorithms.

Reduction of gas flow nonuniformity in gas turbine engines by means of gas-dynamic methods

Science.gov (United States)

Matveev, V.; Baturin, O.; Kolmakova, D.; Popov, G.

2017-08-01

Gas flow nonuniformity is one of the main sources of rotor blade vibrations in the gas turbine engines. Usually, the flow circumferential nonuniformity occurs near the annular frames, located in the flow channel of the engine. This leads to the increased dynamic stresses in blades and as a consequence to the blade damage. The goal of the research was to find an acceptable method of reducing the level of gas flow nonuniformity as the source of dynamic stresses in the rotor blades. Two different methods were investigated during this research. Thus, this study gives the ideas about methods of improving the flow structure in gas turbine engine. On the basis of existing conditions (under development or existing engine) it allows the selection of the most suitable method for reducing gas flow nonuniformity.

Nonintrusive performance measurement of a gas turbine engine in real time

Science.gov (United States)

DeSilva, Upul P.; Claussen, Heiko

2017-08-29

Performance of a gas turbine engine is monitored by computing a mass flow rate through the engine. Acoustic time-of-flight measurements are taken between acoustic transmitters and receivers in the flow path of the engine. The measurements are processed to determine average speeds of sound and gas flow velocities along those lines-of-sound. A volumetric flow rate in the flow path is computed using the gas flow velocities together with a representation of the flow path geometry. A gas density in the flow path is computed using the speeds of sound and a measured static pressure. The mass flow rate is calculated from the gas density and the volumetric flow rate.

Velocity field measurements of flow inside snout of zinc plating process using a single-frame PIV technique

Energy Technology Data Exchange (ETDEWEB)

Lee, S.J.

2000-05-01

In the continuous hot-dip galvanizing process of steel strips, the snout has been installed at the entering region of feeding strip into the molten zinc (Zn) pot. However, evaporated Zn particles in the snout cause ash imperfection on the galvanized steel strip surface. In order to resolve this problem, the flow field inside the snout, both on the deoxidisation gas flow above the free surface and the molten Zn flow in the Zn pot, has been investigated experientially. For a 1/10 scale water model, flow visualization and PIV (Particle Image Velocimetry) velocity field measurements were carried out at the strip speed V{sub s}= 1.5 m/s. Aluminum flakes (1{mu}m) and atomized olive oil (3{mu}m) were used as seeding particles to simulate the molten Zn flow and the deoxidisation gas flow, respectively. As a result, the liquid flow in the Zn pot is dominantly influenced by the up-rising flow in diagonal direction caused by the rotating sink roll. For gas flow in from of the strip inside the snout, the large-scale vortex formed by the downward moving strip is dominant. In the rear side of the strip, a counterclockwise vortex is formed and some of the flow following by the moving strip impinges on the free surface of molten Zn. The liquid flow in front of the strip is governed by the up-rising flow entering the snout, caused by the rotating sink roll. The moving strip affects dominantly the liquid flow behind the strip inside the snout, and large amounts of liquid are entrained and followed the moving strip toward the sink roll. A thin boundary layer is formed on the front side due to the up-rising flow, however, a relatively thick boundary layer is formed in the rear side of the strip. Inside the snout, the deoxidisation gas flow above the free surface is much faster than the liquid flow in the Zn pot. More ash imperfections are anticipated on the rear surface of the strip where larger influx flow moves toward the strip in the region near the free surface. (author)

[A capillary blood flow velocity detection system based on linear array charge-coupled devices].

Science.gov (United States)

Zhou, Houming; Wang, Ruofeng; Dang, Qi; Yang, Li; Wang, Xiang

2017-12-01

In order to detect the flow characteristics of blood samples in the capillary, this paper introduces a blood flow velocity measurement system based on field-programmable gate array (FPGA), linear charge-coupled devices (CCD) and personal computer (PC) software structure. Based on the analysis of the TCD1703C and AD9826 device data sheets, Verilog HDL hardware description language was used to design and simulate the driver. Image signal acquisition and the extraction of the real-time edge information of the blood sample were carried out synchronously in the FPGA. Then a series of discrete displacement were performed in a differential operation to scan each of the blood samples displacement, so that the sample flow rate could be obtained. Finally, the feasibility of the blood flow velocity detection system was verified by simulation and debugging. After drawing the flow velocity curve and analyzing the velocity characteristics, the significance of measuring blood flow velocity is analyzed. The results show that the measurement of the system is less time-consuming and less complex than other flow rate monitoring schemes.

Fourier analysis of cerebrospinal fluid flow velocities: MR imaging study. The Scandinavian Flow Group

DEFF Research Database (Denmark)

Thomsen, C; Ståhlberg, F; Stubgaard, M

1990-01-01

images. The phase information in the resultant image was converted to flow velocity with a calibration curve with the slope 26.5 radian.m-1.sec. The velocity versus time function was Fourier transformed and a continuous curve was fitted to the measured data with use of the first three harmonics...

Gage for gas flow measurement especially in gas-suction pipes

International Nuclear Information System (INIS)

Renner, K.; Stegmanns, W.

1978-01-01

The gage utilizes the differential pressure given by a differential pressure producer to generate, in a bypass, a partial gas flow measured by means of a direct-reading anemometer of windmill type. The partial gas flow is generated between pressure pick-up openings in the gas-suction pipe in front of a venturi insert and pressure pick-up openings at the bottleneck of the venturi insert. The reading of the anemometer is proportional to the main gas flow and independent of the variables of state and the properties of the gases to be measured. (RW) [de

Fuel bundle impact velocities due to reverse flow

International Nuclear Information System (INIS)

Wahba, N.N.; Locke, K.E.

1996-01-01

If a break should occur in the inlet feeder or inlet header of a CANDU reactor, the rapid depressurization will cause the channel flow(s) to reverse. Depending on the gap between the upstream bundle and shield plug, the string of bundles will accelerate in the reverse direction and impact with the upstream shield plug. The reverse flow impact velocities have been calculated for various operating states for the Bruce NGS A reactors. The sensitivity to several analysis assumptions has been determined. (author)

Comparison of thermal, salt and dye tracing to estimate shallow flow velocities: Novel triple-tracer approach

Science.gov (United States)

Abrantes, João R. C. B.; Moruzzi, Rodrigo B.; Silveira, Alexandre; de Lima, João L. M. P.

2018-02-01

The accurate measurement of shallow flow velocities is crucial to understand and model the dynamics of sediment and pollutant transport by overland flow. In this study, a novel triple-tracer approach was used to re-evaluate and compare the traditional and well established dye and salt tracer techniques with the more recent thermal tracer technique in estimating shallow flow velocities. For this purpose a triple tracer (i.e. dyed-salted-heated water) was used. Optical and infrared video cameras and an electrical conductivity sensor were used to detect the tracers in the flow. Leading edge and centroid velocities of the tracers were measured and the correction factors used to determine the actual mean flow velocities from tracer measured velocities were compared and investigated. Experiments were carried out for different flow discharges (32-1813 ml s-1) on smooth acrylic, sand, stones and synthetic grass bed surfaces with 0.8, 4.4 and 13.2% slopes. The results showed that thermal tracers can be used to estimate shallow flow velocities, since the three techniques yielded very similar results without significant differences between them. The main advantages of the thermal tracer were that the movement of the tracer along the measuring section was more easily visible than it was in the real image videos and that it was possible to measure space-averaged flow velocities instead of only one velocity value, with the salt tracer. The correction factors used to determine the actual mean velocity of overland flow varied directly with Reynolds and Froude numbers, flow velocity and slope and inversely with flow depth and bed roughness. In shallow flows, velocity estimation using tracers entails considerable uncertainty and caution must be taken with these measurements, especially in field studies where these variables vary appreciably in space and time.

Propagation of a cylindrical shock wave in a rotational axisymmetric isothermal flow of a non-ideal gas in magnetogasdynamics

Directory of Open Access Journals (Sweden)

G. Nath

2012-12-01

Full Text Available Self-similar solutions are obtained for unsteady, one-dimensional isothermal flow behind a shock wave in a rotational axisymmetric non-ideal gas in the presence of an azimuthal magnetic field. The shock wave is driven out by a piston moving with time according to power law. The fluid velocities and the azimuthal magnetic field in the ambient medium are assumed to be varying and obeying a power law. The density of the ambient medium is assumed to be constant. The gas is assumed to be non-ideal having infinite electrical conductivity and the angular velocity of the ambient medium is assumed to be decreasing as the distance from the axis increases. It is expected that such an angular velocity may occur in the atmospheres of rotating planets and stars. The effects of the non-idealness of the gas and the Alfven-Mach number on the flow-field are obtained. It is shown that the presence of azimuthal magnetic field and the rotation of the medium has decaying effect on the shock wave. Also, a comparison is made between rotating and non-rotating cases.

Gas-Dynamic Methods to Reduce Gas Flow Nonuniformity from the Annular Frames of Gas Turbine Engines

Science.gov (United States)

Kolmakova, D.; Popov, G.

2018-01-01

Gas flow nonuniformity is one of the main sources of rotor blade vibrations in the gas turbine engines. Usually, the flow circumferential nonuniformity occurs near the annular frames, located in the flow channel of the engine. This leads to the increased dynamic stresses in blades and consequently to the blade damage. The goal of the research was to find an acceptable method of reducing the level of gas flow nonuniformity. Two different methods were investigated during this research. Thus, this study gives the ideas about methods of improving the flow structure in gas turbine engine. Based on existing conditions (under development or existing engine) it allows the selection of the most suitable method for reducing gas flow nonuniformity.

On factors influencing air-water gas exchange in emergent wetlands

Science.gov (United States)

Ho, David T.; Engel, Victor C.; Ferron, Sara; Hickman, Benjamin; Choi, Jay; Harvey, Judson W.

2018-01-01

Knowledge of gas exchange in wetlands is important in order to determine fluxes of climatically and biogeochemically important trace gases and to conduct mass balances for metabolism studies. Very few studies have been conducted to quantify gas transfer velocities in wetlands, and many wind speed/gas exchange parameterizations used in oceanographic or limnological settings are inappropriate under conditions found in wetlands. Here six measurements of gas transfer velocities are made with SF6 tracer release experiments in three different years in the Everglades, a subtropical peatland with surface water flowing through emergent vegetation. The experiments were conducted under different flow conditions and with different amounts of emergent vegetation to determine the influence of wind, rain, water flow, waterside thermal convection, and vegetation on air-water gas exchange in wetlands. Measured gas transfer velocities under the different conditions ranged from 1.1 cm h−1 during baseline conditions to 3.2 cm h−1 when rain and water flow rates were high. Commonly used wind speed/gas exchange relationships would overestimate the gas transfer velocity by a factor of 1.2 to 6.8. Gas exchange due to thermal convection was relatively constant and accounted for 14 to 51% of the total measured gas exchange. Differences in rain and water flow among the different years were responsible for the variability in gas exchange, with flow accounting for 37 to 77% of the gas exchange, and rain responsible for up to 40%.

Gas/liquid flow configurations

International Nuclear Information System (INIS)

Bonin, Jacques; Fitremann, J.-M.

1978-01-01

Prediction of flow configurations (morphology) for gas/liquid or liquid/vapour mixtures is an important industrial problem which is not yet fully understood. The ''Flow Configurations'' Seminar of Societe Hydrotechnique de France has framed recommendations for investigation of potential industrial applications for flow configurations [fr

Flow structure in a downward branch pipe with a closed end. Characteristics of flow velocity in the branch pipe

International Nuclear Information System (INIS)

Miyoshi, Koji; Nakamura, Akira; Takenaka, Nobuyuki

2016-01-01

Many pipes branch off from a main pipe in industrial plants. The penetration of hot water into the branch pipe causes thermal stratification. The thermal stratification layer fluctuates and causes thermal fatigue. The characteristics of velocity distributions in the branch pipe for inner diameters from D_b=21 mm to 43 mm were investigated by laser Doppler velocimetry in this paper. As for the flow in the branch pipe at L=4D_b, the mean velocity of the spiral flow was a simple forced vortex which indicated a straight velocity distribution. The maximum circumferential velocity U_θ _m_a_x and minimum axial velocity U_z _m_i_n at L=4D_b were expressed with D_b and main flow velocity. Empirical formulas were proposed for estimating the distributions of U_θ _m_a_x and U_z _m_i_n in the axial direction. (author)

Measuring surface flow velocity with smartphones: potential for citizen observatories

Science.gov (United States)

Weijs, Steven V.; Chen, Zichong; Brauchli, Tristan; Huwald, Hendrik

2014-05-01

Stream flow velocity is an important variable for discharge estimation and research on sediment dynamics. Given the influence of the latter on rating curves (stage-discharge relations), and the relative scarcity of direct streamflow measurements, surface velocity measurements can offer important information for, e.g., flood warning, hydropower, and hydrological science and engineering in general. With the growing amount of sensing and computing power in the hands of more outdoorsy individuals, and the advances in image processing techniques, there is now a tremendous potential to obtain hydrologically relevant data from motivated citizens. This is the main focus of the interdisciplinary "WeSenseIt" project, a citizen observatory of water. In this subproject, we investigate the feasibility of stream flow surface velocity measurements from movie clips taken by (smartphone-) cameras. First results from movie-clip derived velocity information will be shown and compared to reference measurements.

Changes in cerebral artery blood flow velocity after intermittent cerebrospinal fluid drainage.

OpenAIRE

Kempley, S T; Gamsu, H R

1993-01-01

Doppler ultrasound was used to measure blood flow velocity in the anterior cerebral artery of six premature infants with posthaemorrhagic hydrocephalus, before and after intermittent cerebrospinal fluid (CSF) drainage, on 23 occasions. There was a significant increase in mean blood flow velocity after the drainage procedures (+5.6 cm/s, 95% confidence interval +2.9 to +8.3 cm/s), which was accompanied by a decrease in velocity waveform pulsatility. CSF pressure also fell significantly. In pat...

Numerical Analysis of Inlet Gas-Mixture Flow Rate Effects on Carbon Nanotube Growth Rate

Directory of Open Access Journals (Sweden)

B. Zahed

2013-01-01

Full Text Available The growth rate and uniformity of Carbon Nano Tubes (CNTs based on Chemical Vapor Deposition (CVD technique is investigated by using a numerical model. In this reactor, inlet gas mixture, including xylene as carbon source and mixture of argon and hydrogen as  carrier gas enters into a horizontal CVD reactor at atmospheric pressure. Based on the gas phase and surface reactions, released carbon atoms are grown as CNTs on the iron catalysts at the reactor hot walls. The effect of inlet gas-mixture flow rate, on CNTs growth rate and its uniformity is discussed. In addition the velocity and temperature profile and also species concentrations throughout the reactor are presented.

Comparison of Simultaneous PIV and Hydroxyl Tagging Velocimetry in Low Velocity Flows

Science.gov (United States)

Andre, Matthieu A.; Bardet, Philippe M.; Burns, Ross A.; Danehy, Paul M.

2016-01-01

Hydroxyl tagging velocimetry (HTV) is a molecular tagging velocimetry (MTV) technique that relies on the photo- dissociation of water vapor into OH radicals and their subsequent tracking using laser-induced fluorescence. At ambient temperature in air, the OH species lifetime is about 50 micro-s. The feasibility of using HTV for probing low- speed flows (a few m/s) is investigated by using an inert, heated gas as a means to increase the OH species lifetime. Unlike particle-based techniques, MTV does not suffer from tracer settling, which is particularly problematic at low speeds. Furthermore, the flow needs to be seeded with only a small mole fraction of water vapor, making it safer for both the user and facilities than other MTV techniques based on corrosive or toxic chemical tracers. HTV is demonstrated on a steam-seeded nitrogen jet at approximately 75 C in the laminar (Umean=3.31 m/s, Re=1,540), transitional (Umean=4.48 m/s, Re=2,039), and turbulent (Umean=6.91 m/s, Re=3,016) regimes at atmospheric pressure. The measured velocity profiles are compared with particle image velocimetry (PIV) measurements performed simultaneously with a second imager. Seeding for the PIV is achieved by introducing micron-sized water droplets into the flow with the steam; the same laser sheet is used for PIV and HTV to guarantee spatial and temporal overlap of the data. Optimizing each of these methods, however, requires conflicting operating conditions: higher temperatures benefit the HTV signals but reduce the available seed density for the PIV through evaporation. Nevertheless, data are found to agree within 10% for the instantaneous velocity profiles and within 5% for the mean profiles and demonstrate the feasibility of HTV for low-speed flows at moderate to high temperatures.

Outer region scaling using the freestream velocity for nonuniform open channel flow over gravel

Science.gov (United States)

Stewart, Robert L.; Fox, James F.

2017-06-01

The theoretical basis for outer region scaling using the freestream velocity for nonuniform open channel flows over gravel is derived and tested for the first time. Owing to the gradual expansion of the flow within the nonuniform case presented, it is hypothesized that the flow can be defined as an equilibrium turbulent boundary layer using the asymptotic invariance principle. The hypothesis is supported using similarity analysis to derive a solution, followed by further testing with experimental datasets. For the latter, 38 newly collected experimental velocity profiles across three nonuniform flows over gravel in a hydraulic flume are tested as are 43 velocity profiles previously published in seven peer-reviewed journal papers that focused on fluid mechanics of nonuniform open channel over gravel. The findings support the nonuniform flows as equilibrium defined by the asymptotic invariance principle, which is reflective of the consistency of the turbulent structure's form and function within the expanding flow. However, roughness impacts the flow structure when comparing across the published experimental datasets. As a secondary objective, we show how previously published mixed scales can be used to assist with freestream velocity scaling of the velocity deficit and thus empirically account for the roughness effects that extend into the outer region of the flow. One broader finding of this study is providing the theoretical context to relax the use of the elusive friction velocity when scaling nonuniform flows in gravel bed rivers; and instead to apply the freestream velocity. A second broader finding highlighted by our results is that scaling of nonuniform flow in gravel bed rivers is still not fully resolved theoretically since mixed scaling relies to some degree on empiricism. As researchers resolve the form and function of macroturbulence in the outer region, we hope to see the closing of this research gap.

Gas Near a Wall: Shortened Mean Free Path, Reduced Viscosity, and the Manifestation of the Knudsen Layer in the Navier-Stokes Solution of a Shear Flow

Science.gov (United States)

Abramov, Rafail V.

2018-06-01

For the gas near a solid planar wall, we propose a scaling formula for the mean free path of a molecule as a function of the distance from the wall, under the assumption of a uniform distribution of the incident directions of the molecular free flight. We subsequently impose the same scaling onto the viscosity of the gas near the wall and compute the Navier-Stokes solution of the velocity of a shear flow parallel to the wall. Under the simplifying assumption of constant temperature of the gas, the velocity profile becomes an explicit nonlinear function of the distance from the wall and exhibits a Knudsen boundary layer near the wall. To verify the validity of the obtained formula, we perform the Direct Simulation Monte Carlo computations for the shear flow of argon and nitrogen at normal density and temperature. We find excellent agreement between our velocity approximation and the computed DSMC velocity profiles both within the Knudsen boundary layer and away from it.

Velocimetry using scintillation of a laser beam for a laser-based gas-flux monitor

Science.gov (United States)

Kagawa, Naoki; Wada, Osami; Koga, Ryuji

1999-05-01

This paper describes a velocimetry system using scintillation of a laser-beam with spatial filters based on sensor arrays for a laser- based gas flux monitor. In the eddy correlation method, gas flux is obtained by mutual relation between the gas density and the flow velocity. The velocimetry system is developed to support the flow velocity monitor portion of the laser-based gas flux monitor with a long span for measurement. In order to sense not only the flow velocity but also the flow direction, two photo diode arrays are arranged with difference of a quarter period of the weighting function between them; the two output signals from the sensor arrays have phase difference of either (pi) /2 or -(pi) /2 depending on the sense of flow direction. In order to obtain the flow velocity and the flow direction instantly, an electronic apparatus built by the authors extracts frequency and phase from crude outputs of the pair of sensors. A feasibility of the velocimetry was confirmed indoors by measurement of the flow- velocity vector of the convection. Measured flow-velocity vector of the upward flow agreed comparatively with results of an ultrasonic anemometer.

Study on of Seepage Flow Velocity in Sand Layer Profile as Affected by Water Depth and Slope Gradience

Science.gov (United States)

Han, Z.; Chen, X.

2017-12-01

BACKGROUND: The subsurface water flow velocity is of great significance in understanding the hydrodynamic characteristics of soil seepage and the influence of interaction between seepage flow and surface runoff on the soil erosion and sediment transport process. OBJECTIVE: To propose a visualized method and equipment for determining the seepage flow velocity and measuring the actual flow velocity and Darcy velocity as well as the relationship between them.METHOD: A transparent organic glass tank is used as the test soil tank, the white river sand is used as the seepage test material and the fluorescent dye is used as the indicator for tracing water flow, so as to determine the thickness and velocity of water flow in a visualized way. Water is supplied at the same flow rate (0.84 L h-1) to the three parts with an interval of 1m at the bottom of the soil tank and the pore water velocity and the thickness of each water layer are determined under four gradient conditions. The Darcy velocity of each layer is calculated according to the water supply flow and the discharge section area. The effective discharge flow pore is estimated according to the moisture content and porosity and then the relationship between Darcy velocity and the measured velocity is calculated based on the water supply flow and the water layer thickness, and finally the correctness of the calculation results is verified. RESULTS: According to the velocity calculation results, Darcy velocity increases significantly with the increase of gradient; in the sand layer profile, the flow velocity of pore water at different depths increases with the increase of gradient; under the condition of the same gradient, the lower sand layer has the maximum flow velocity of pore water. The air-filled porosity of sand layer determines the proportional relationship between Darcy velocity and pore flow velocity. CONCLUSIONS: The actual flow velocity and Darcy velocity can be measured by a visualized method and the

Influence of slip velocity in Herschel-Bulkley fluid flow between parallel plates - A mathematical study

International Nuclear Information System (INIS)

Sankar, D. S.; Lee, U Sik

2016-01-01

This theoretical study investigates three types of basic flows of viscous incompressible Herschel-Bulkley fluid such as (i) plane Couette flow, (ii) Poiseuille flow and (iii) generalized Couette flow with slip velocity at the boundary. The analytic solutions to the nonlinear boundary value problems have been obtained. The effects of various physical parameters on the velocity, flow rate, wall shear stress and frictional resistance to flow are analyzed through appropriate graphs. It is observed that in plane Poiseuille flow and generalized Couette flow, the velocity and flow rate of the fluid increase considerably with the increase of the slip parameter, power law index, pressure gradient. The fluid velocity is significantly higher in plane Poiseuille flow than in plane Couette flow. The wall shear stress and frictional resistance to flow decrease considerably with the increase of the power law index and increase significantly with the increase of the yield stress of the fluid. The wall shear stress and frictional resistance to flow are considerably higher in plane Poiseuille flow than in generalized Couette flow.

experimental investigation of sand minimum transport velocity

African Journals Online (AJOL)

user

The production of reservoir fluid through long tiebacks/pipelines has emerged as one of ... transport in multiphase flows, the investigation of the ... Nigerian Journal of Technology ... associated with water-gas-oil-solid flow in pipeline in ... The mixture was well agitated using a .... operational conditions the limit deposit velocity.

MR measurement of coronary arterial blood flow velocity. Evaluation of age, stenosis and drugs as factors affecting coronary blood flow

International Nuclear Information System (INIS)

Taoka, Yoshiaki; Harada, Masafumi; Nishitani, Hiromu; Yukinaka, Michiko; Nomura, Masahiro

1998-01-01

Coronary arterial blood flow velocity was measured using MRI. Two types of phase contrast methods were used for the measurements, one of which exhibited good resolving power whereas the other provided more distinct images acquired while the subject patients held their breath. Before measuring coronary arterial blood flow velocity, accuracy of the two phase contrast methods was evaluated using a phantom. The results obtained with both methods largely agreed with the values obtained using the phantom. Using both methods, the patterns of coronary arterial blood flow over one cardiac cycle were essentially identical. A peak was noted in late systole or in early diastole in the right coronary artery, whereas in the left coronary artery, a peak was noted somewhat later in diastole. In healthy volunteers, no significant difference in the maximal flow velocity in the coronary arteries was found from one age group to another. Among patients with coronary arterial stenosis, coronary arterial blood flow velocity central to the area of stenosis was lower than that observed in the healthy volunteers. Coronary arterial blood flow velocity was observed to decrease after administration of isosorbide dinitrate and increased following administration of nifedipine. (author)

Gas Velocities Reveal Newly Born Planets in a Disk

Science.gov (United States)

Kohler, Susanna

2018-06-01

Occasionally, science comes together beautifully for a discovery and sometimes this happens for more than one team at once! Today we explore how two independent collaborations of scientists simultaneously found the very first kinematic evidence for young planets forming in a protoplanetary disk. Though they explored the same disk, the two teams in fact discovered different planets.Evidence for PlanetsALMAs view of the dust in the protoplanetary disk surrounding the young star HD 163296. Todays studies explore not the dust, but the gas of this disk. [ALMA (ESO/NAOJ/NRAO); A. Isella; B. Saxton (NRAO/AUI/NSF)]Over the past three decades, weve detected around 4,000 fully formed exoplanets. Much more elusive, however, are the young planets still in the early stages of formation; only a handful of these have been discovered. More observations of early-stage exoplanets are needed in order to understand how these worlds are born in dusty protoplanetary-disk environments, how they grow their atmospheres, and how they evolve.Recent observations by the Atacama Large Millimeter/submillimeter Array (ALMA) have produced stunning images of protoplanetary disks. The unprecedented resolution of these images reveals substructure in the form of gaps and rings, hinting at the presence of planets that orbit within the disk and clear out their paths as they move. But there are also non-planet mechanisms that could produce such substructure, like grain growth around ice lines, or hydrodynamic instabilities in the disk.How can we definitively determine whether there are nascent planets embedded in these disks? Direct direction of a point source in a dust gap would be a strong confirmation, but now we have the next best thing: kinematic evidence for planets, from the motion of a disks gas.Observations of carbon monoxide line emission at +1km/s from the systemic velocity (left) vs. the outcome of a computer simulation (right) in the Pinte et al. study. A visible kink occurs in the flow

The boundary condition for vertical velocity and its interdependence with surface gas exchange

Directory of Open Access Journals (Sweden)

A. S. Kowalski

2017-07-01

Full Text Available The law of conservation of linear momentum is applied to surface gas exchanges, employing scale analysis to diagnose the vertical velocity (w in the boundary layer. Net upward momentum in the surface layer is forced by evaporation (E and defines non-zero vertical motion, with a magnitude defined by the ratio of E to the air density, as w = E/ρ. This is true even right down at the surface where the boundary condition is w|0 = E/ρ|0 (where w|0 and ρ|0 represent the vertical velocity and density of air at the surface. This Stefan flow velocity implies upward transport of a non-diffusive nature that is a general feature of the troposphere but is of particular importance at the surface, where it assists molecular diffusion with upward gas migration (of H2O, for example but opposes that of downward-diffusing species like CO2 during daytime. The definition of flux–gradient relationships (eddy diffusivities requires rectification to exclude non-diffusive transport, which does not depend on scalar gradients. At the microscopic scale, the role of non-diffusive transport in the process of evaporation from inside a narrow tube – with vapour transport into an overlying, horizontal airstream – was described long ago in classical mechanics and is routinely accounted for by chemical engineers, but has been neglected by scientists studying stomatal conductance. Correctly accounting for non-diffusive transport through stomata, which can appreciably reduce net CO2 transport and marginally boost that of water vapour, should improve characterisations of ecosystem and plant functioning.

Measurement of pressure distributions and velocity fields of water jet intake flow

International Nuclear Information System (INIS)

Jeong, Eun Ho; Yoon, Sang Youl; Kwon, Seong Hoon; Chun, Ho Hwan; Kim, Mun Chan; Kim, Kyung Chun

2002-01-01

Waterjet propulsion system can avoid cavitation problem which is being arised conventional propeller propulsion system. The main issue of designing waterjet system is the boundary layer separation at ramp and lib of water inlet. The flow characteristics are highly depended on Jet to Velocity Ratio(JVR) as well as the intake geometry. The present study is conducted in a wind tunnel to provide accurate pressure destribution at the inlet wall and velocity field of the inlet and exit planes. Particle image velocimetry technique is used to obtain detail velocity fields. Pressure distributions and velocity field are discussed with accelerating and deaccelerating flow zones and the effect of JVR

Doppler-shifted fluorescence imaging of velocity fields in supersonic reacting flows

Science.gov (United States)

Allen, M. G.; Davis, S. J.; Kessler, W. J.; Sonnenfroh, D. M.

1992-01-01

The application of Doppler-shifted fluorescence imaging of velocity fields in supersonic reacting flows is analyzed. Focussing on fluorescence of the OH molecule in typical H2-air Scramjet flows, the effects of uncharacterized variations in temperature, pressure, and collisional partner composition across the measurement plane are examined. Detailed measurements of the (1,0) band OH lineshape variations in H2-air combustions are used, along with single-pulse and time-averaged measurements of an excimer-pumped dye laser, to predict the performance of a model velocimeter with typical Scramjet flow properties. The analysis demonstrates the need for modification and control of the laser bandshape in order to permit accurate velocity measurements in the presence of multivariant flow properties.

Nonlinear vacuum gas flow through a short tube due to pressure and temperature gradients

Energy Technology Data Exchange (ETDEWEB)

Pantazis, Sarantis; Naris, Steryios; Tantos, Christos [Department of Mechanical Engineering, University of Thessaly, Pedion Areos, 38334 Volos (Greece); Valougeorgis, Dimitris, E-mail: diva@mie.uth.gr [Department of Mechanical Engineering, University of Thessaly, Pedion Areos, 38334 Volos (Greece); André, Julien; Millet, Francois; Perin, Jean Paul [Service des Basses Températures, UMR-E CEA/UJF-Grenoble 1, INAC, Grenoble, F-38054 (France)

2013-10-15

The flow of a rarefied gas through a tube due to both pressure and temperature gradients has been studied numerically. The main objective is to investigate the performance of a mechanical vacuum pump operating at low temperatures in order to increase the pumped mass flow rate. This type of pump is under development at CEA-Grenoble. The flow is modelled by the Shakhov kinetic model equation, which is solved by the discrete velocity method. Results are presented for certain geometry and flow parameters. Since according to the pump design the temperature driven flow is in the opposite direction than the main pressure driven flow, it has been found that for the operating pressure range studied here the net mass flow rate through the pump may be significantly reduced.

Nonlinear vacuum gas flow through a short tube due to pressure and temperature gradients

International Nuclear Information System (INIS)

Pantazis, Sarantis; Naris, Steryios; Tantos, Christos; Valougeorgis, Dimitris; André, Julien; Millet, Francois; Perin, Jean Paul

2013-01-01

The flow of a rarefied gas through a tube due to both pressure and temperature gradients has been studied numerically. The main objective is to investigate the performance of a mechanical vacuum pump operating at low temperatures in order to increase the pumped mass flow rate. This type of pump is under development at CEA-Grenoble. The flow is modelled by the Shakhov kinetic model equation, which is solved by the discrete velocity method. Results are presented for certain geometry and flow parameters. Since according to the pump design the temperature driven flow is in the opposite direction than the main pressure driven flow, it has been found that for the operating pressure range studied here the net mass flow rate through the pump may be significantly reduced

Large Eddy Simulation Analysis on Confined Swirling Flows in a Gas Turbine Swirl Burner

Directory of Open Access Journals (Sweden)

Tao Liu

2017-12-01

Full Text Available This paper describes a Large Eddy Simulation (LES investigation into flow fields in a model gas turbine combustor equipped with a swirl burner. A probability density function was used to describe the interaction physics of chemical reaction and turbulent flow as liquid fuel was directly injected into the combustion chamber and rapidly mixed with the swirling air. Simulation results showed that heat release during combustion accelerated the axial velocity motion and made the recirculation zone more compact. As the combustion was taking place under lean burn conditions, NO emissions was less than 10 ppm. Finally, the effects of outlet contraction on swirling flows and combustion instability were investigated. Results suggest that contracted outlet can enhance the generation of a Central Vortex Core (CVC flow structure. As peak RMS of velocity fluctuation profiles at center-line suggested the turbulent instability can be enhanced by CVC motion, the Power Spectrum Density (PSD amplitude also explained that the oscillation at CVC position was greater than other places. Both evidences demonstrated that outlet contraction can increase the instability of the central field.

Mass flow and velocity profiles in Neurospora hyphae: partial plug flow dominates intra-hyphal transport.

Science.gov (United States)

Abadeh, Aryan; Lew, Roger R

2013-11-01

Movement of nuclei, mitochondria and vacuoles through hyphal trunks of Neurospora crassa were vector-mapped using fluorescent markers and green fluorescent protein tags. The vectorial movements of all three were strongly correlated, indicating the central role of mass (bulk) flow in cytoplasm movements in N. crassa. Profiles of velocity versus distance from the hyphal wall did not match the parabolic shape predicted by the ideal Hagen-Poiseuille model of flow at low Reynolds number. Instead, the profiles were flat, consistent with a model of partial plug flow due to the high concentration of organelles in the flowing cytosol. The intra-hyphal pressure gradients were manipulated by localized external osmotic treatments to demonstrate the dependence of velocity (and direction) on pressure gradients within the hyphae. The data support the concept that mass transport, driven by pressure gradients, dominates intra-hyphal transport. The transport occurs by partial plug flow due to the organelles in the cytosol.

Film cooling effects on the tip flow characteristics of a gas turbine blade

Directory of Open Access Journals (Sweden)

Jin Wang

2015-03-01

Full Text Available An experimental investigation of the tip flow characteristics between a gas turbine blade tip and the shroud was conducted by a pressure-test system and a particle image velocimetry (PIV system. A three-times scaled profile of the GE-E3 blade with five film cooling holes was used as specimen. The effects on flow characteristics by the rim width and the groove depth of the squealer tip were revealed. The rim widths were (a 0.9%, (b 2.1%, and (c 3.0% of the axial chord, and the groove depths were (a 2.8%, (b 4.8%, and (c 10% of the blade span. Several pressure taps on the top plate above the blades were connected to pressure gauges. By a CCD camera the PIV system recorded the velocity field around the leading edge zone including the five cooling holes. The flow distributions both in the tip clearance and in the passage were revealed, and the influence of the inlet velocity was determined. In this work, the tip flow characteristics with and without film cooling were investigated. The effects of different global blowing ratios of M=0.5, 1.0, 1.3 and 2.5 were established. It was found that decreasing the rim width resulted in a lower mass flow rate of the leakage flow, and the pressure distributions from the leading edge to the trailing edge showed a linearly increasing trend. It was also found that if the inlet velocity was less than 1.5 m/s, the flow field in the passage far away from the suction side appeared as a stagnation zone.

Real-Time GPU Implementation of Transverse Oscillation Vector Velocity Flow Imaging

DEFF Research Database (Denmark)

Bradway, David; Pihl, Michael Johannes; Krebs, Andreas

2014-01-01

Rapid estimation of blood velocity and visualization of complex flow patterns are important for clinical use of diagnostic ultrasound. This paper presents real-time processing for two-dimensional (2-D) vector flow imaging which utilizes an off-the-shelf graphics processing unit (GPU). In this work...... vector flow acquisition takes 2.3 milliseconds seconds on an Advanced Micro Devices Radeon HD 7850 GPU card. The detected velocities are accurate to within the precision limit of the output format of the display routine. Because this tool was developed as a module external to the scanner’s built...

Simultaneous measurement of particle and fluid velocities in particle-laden flows

International Nuclear Information System (INIS)

Jin, D. X.; Lee, D. Y.

2009-01-01

For the velocity measurement in a particle-laden fluid flow, the fluid velocity and the inherently dispersed particle velocity can be analyzed by using PIV and PTV, respectively. Since the PIV result statistically represents the average displacement of all the particles in a PIV image, it is inevitable that the PIV result includes the influence of the dispersed particles' displacement if a single CCD camera is used to simultaneously measure the fluid velocity and the dispersed particle velocity. The influence of dispersed particles should be excluded before the PIV analysis in order to evaluate the fluid velocity accurately. In this study, the optimum replacement brightness of dispersed particles to minimize the false influence of dispersed particles on the PIV analysis was theoretically derived. Simulation results show that the modification of dispersed particle brightness can significantly reduce the PIV error caused by the dispersed particles. This modification method was also verified in the analysis of an actual experimental case of the particle-laden fluid flow in a triangular grooved channel

High-velocity two-phase flow two-dimensional modeling

International Nuclear Information System (INIS)

Mathes, R.; Alemany, A.; Thilbault, J.P.

1995-01-01

The two-phase flow in the nozzle of a LMMHD (liquid metal magnetohydrodynamic) converter has been studied numerically and experimentally. A two-dimensional model for two-phase flow has been developed including the viscous terms (dragging and turbulence) and the interfacial mass, momentum and energy transfer between the phases. The numerical results were obtained by a finite volume method based on the SIMPLE algorithm. They have been verified by an experimental facility using air-water as a simulation pair and a phase Doppler particle analyzer for velocity and droplet size measurement. The numerical simulation of a lithium-cesium high-temperature pair showed that a nearly homogeneous and isothermal expansion of the two phases is possible with small pressure losses and high kinetic efficiencies. In the throat region a careful profiling is necessary to reduce the inertial effects on the liquid velocity field

Gas-liquid flow filed in agitated vessels

International Nuclear Information System (INIS)

Hormazi, F.; Alaie, M.; Dabir, B.; Ashjaie, M.

2001-01-01

Agitated vessels in form of sti reed tank reactors and mixed ferment ors are being used in large numbers of industry. It is more important to develop good, and theoretically sound models for scaling up and design of agitated vessels. In this article, two phase flow (gas-liquid) in a agitated vessel has been investigated numerically. A two-dimensional computational fluid dynamics model, is used to predict the gas-liquid flow. The effects of gas phase, varying gas flow rates and variation of bubbles shape on flow filed of liquid phase are investigated. The numerical results are verified against the experimental data

CFD study of the minimum bubbling velocity of Geldart A particles in gas-fluidized beds

NARCIS (Netherlands)

Wang, Junwu; Hoef, van der M.A.; Kuipers, J.A.M.

2010-01-01

The minimum bubbling velocity, which demarcates the homogeneous and heterogeneous fluidization regimes, plays a pivotal role in gas fluidization of Geldart A particles. We systematically study the effect of gas and particle properties on the minimum bubbling velocity of Geldart A particles in

A dual-phantom system for validation of velocity measurements in stenosis models under steady flow.

Science.gov (United States)

Blake, James R; Easson, William J; Hoskins, Peter R

2009-09-01

A dual-phantom system is developed for validation of velocity measurements in stenosis models. Pairs of phantoms with identical geometry and flow conditions are manufactured, one for ultrasound and one for particle image velocimetry (PIV). The PIV model is made from silicone rubber, and a new PIV fluid is made that matches the refractive index of 1.41 of silicone. Dynamic scaling was performed to correct for the increased viscosity of the PIV fluid compared with that of the ultrasound blood mimic. The degree of stenosis in the models pairs agreed to less than 1%. The velocities in the laminar flow region up to the peak velocity location agreed to within 15%, and the difference could be explained by errors in ultrasound velocity estimation. At low flow rates and in mild stenoses, good agreement was observed in the distal flow fields, excepting the maximum velocities. At high flow rates, there was considerable difference in velocities in the poststenosis flow field (maximum centreline differences of 30%), which would seem to represent real differences in hydrodynamic behavior between the two models. Sources of error included: variation of viscosity because of temperature (random error, which could account for differences of up to 7%); ultrasound velocity estimation errors (systematic errors); and geometry effects in each model, particularly because of imperfect connectors and corners (systematic errors, potentially affecting the inlet length and flow stability). The current system is best placed to investigate measurement errors in the laminar flow region rather than the poststenosis turbulent flow region.

Study on CFD approach for gas entrainment phenomenon. Evaluation of applicability of finite element flow analysis

International Nuclear Information System (INIS)

Eguchi, Yuzuru

2005-07-01

The report is concerned with the evaluation of applicability of numerical modelling methods for the prediction of gas entrainment in an upper plenum of a sodium-cooled fast breeder reactor (FBR). Special attention was paid to applicability of variational multiscale (VMS) modelling in the context of the Finite Element Method. Two flow problems, which were experimentally shown to induce gas entrainment, are solved by a VMS code (MISTRAL). First, computing a benchmark problem of a gas entrainment swirl flow in a cylindrical vessel has led to the following results; (1) the VMS solution is able to resolve the precise vortex core structure more accurately than the non-VMS solution computed by Smart-fem. The circumferential velocity obtained from VMS computation rises almost double in comparison with the non-VMS solution, though it still underestimates the experimental values. (2) the half-value radius of the negative region of the second invariant of velocity gradient matches well between the VMS solution and non-VMS solution. (3) the negative/positive boundary of the second invariant of velocity gradient obtained from the VMS solution is closer to the vortex core radius observed in the experiment than that of the non-VMS solution, though the vortex dip length computed from the VMS result is shorter than the experimental value. Second, computing a benchmark problem of open channel flow with a square pillar and downstream suction pipe has led to the following results; (4) 2Δx-type spatial oscillation was observed due to lack of mesh subdivisions. (5) the distributional profile of the second invariant of velocity gradient is similar to that of the first problem (swirl flow in a cylindrical vessel), characterized by a strong negative region surrounded by a weak positive region. As a possible future plan, it may be necessary to analyze more precisely the features of unsteady vortices obtained in the second benchmark problem and to identify the difference (if any) from the

Gas-water two-phase flow characterization with Electrical Resistance Tomography and Multivariate Multiscale Entropy analysis.

Science.gov (United States)

Tan, Chao; Zhao, Jia; Dong, Feng

2015-03-01

Flow behavior characterization is important to understand gas-liquid two-phase flow mechanics and further establish its description model. An Electrical Resistance Tomography (ERT) provides information regarding flow conditions at different directions where the sensing electrodes implemented. We extracted the multivariate sample entropy (MSampEn) by treating ERT data as a multivariate time series. The dynamic experimental results indicate that the MSampEn is sensitive to complexity change of flow patterns including bubbly flow, stratified flow, plug flow and slug flow. MSampEn can characterize the flow behavior at different direction of two-phase flow, and reveal the transition between flow patterns when flow velocity changes. The proposed method is effective to analyze two-phase flow pattern transition by incorporating information of different scales and different spatial directions. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Inhalational anaesthesia with low fresh gas flow

Directory of Open Access Journals (Sweden)

Christian Hönemann

2013-01-01

Full Text Available During the inhalation of anaesthesia use of low fresh gas flow (0.35-1 L/min has some important advantages. There are three areas of benefit: pulmonary - anaesthesia with low fresh gas flow improves the dynamics of inhaled anaesthesia gas, increases mucociliary clearance, maintains body temperature and reduces water loss. Economic - reduction of anaesthesia gas consumption resulting in significant savings of > 75% and Ecological - reduction in nitrous oxide consumption, which is an important ozone-depleting and heat-trapping greenhouse gas that is emitted. Nevertheless, anaesthesia with high fresh gas flows of 2-6 L/min is still performed, a technique in which rebreathing is practically negligible. This special article describes the clinical use of conventional plenum vaporizers, connected to the fresh gas supply to easily perform low (1 L/min, minimal (0.5 L/min or metabolic flow anaesthesia (0.35 L/min with conventional Primus Draeger® anaesthesia machines in routine clinical practice.

Flow behind an exponential shock wave in a rotational axisymmetric perfect gas with magnetic field and variable density.

Science.gov (United States)

Nath, G; Sahu, P K

2016-01-01

A self-similar model for one-dimensional unsteady isothermal and adiabatic flows behind a strong exponential shock wave driven out by a cylindrical piston moving with time according to an exponential law in an ideal gas in the presence of azimuthal magnetic field and variable density is discussed in a rotating atmosphere. The ambient medium is assumed to possess radial, axial and azimuthal component of fluid velocities. The initial density, the fluid velocities and magnetic field of the ambient medium are assumed to be varying with time according to an exponential law. The gas is taken to be non-viscous having infinite electrical conductivity. Solutions are obtained, in both the cases, when the flow between the shock and the piston is isothermal or adiabatic by taking into account the components of vorticity vector. The effects of the variation of the initial density index, adiabatic exponent of the gas and the Alfven-Mach number on the flow-field behind the shock wave are investigated. It is found that the presence of the magnetic field have decaying effects on the shock wave. Also, it is observed that the effect of an increase in the magnetic field strength is more impressive in the case of adiabatic flow than in the case of isothermal flow. The assumption of zero temperature gradient brings a profound change in the density, non-dimensional azimuthal and axial components of vorticity vector distributions in comparison to those in the case of adiabatic flow. A comparison is made between isothermal and adiabatic flows. It is obtained that an increase in the initial density variation index, adiabatic exponent and strength of the magnetic field decrease the shock strength.

Effect of flow velocity on the process of air-steam condensation in a vertical tube condenser

Science.gov (United States)

Havlík, Jan; Dlouhý, Tomáš

2018-06-01

This article describes the influence of flow velocity on the condensation process in a vertical tube. For the case of condensation in a vertical tube condenser, both the pure steam condensation process and the air-steam mixture condensation process were theoretically and experimentally analyzed. The influence of steam flow velocity on the value of the heat transfer coefficient during the condensation process was evaluated. For the condensation of pure steam, the influence of flow velocity on the value of the heat transfer coefficient begins to be seen at higher speeds, conversely, this effect is negligible at low values of steam velocity. On the other hand, for the air-steam mixture condensation, the influence of flow velocity must always be taken into account. The flow velocity affects the water vapor diffusion process through non-condensing air. The presence of air significantly reduces the value of the heat transfer coefficient. This drop in the heat transfer coefficient is significant at low velocities; on the contrary, the decrease is relatively small at high values of the velocity.

Propagation velocity of an avalanche along the anode wire in a Geiger-Mueller counter filled with Q-gas at 1 ATM

International Nuclear Information System (INIS)

Matsuda, Kazunori; Sanada, Junpei

1990-01-01

Simple methods were applied to investigate the characteristics of a Geiger-Mueller counter with Q-gas flowing at 1 atm. The propagation velocity of the photon-aided avalanche along the anode wire depends linearly on the strength of the electric field in the counter. Its fluctuation (FWHM) as a function of distance between the source position and the end point is discussed. (orig.)

Simulations of viscous and compressible gas-gas flows using high-order finite difference schemes

Science.gov (United States)

Capuano, M.; Bogey, C.; Spelt, P. D. M.

2018-05-01

A computational method for the simulation of viscous and compressible gas-gas flows is presented. It consists in solving the Navier-Stokes equations associated with a convection equation governing the motion of the interface between two gases using high-order finite-difference schemes. A discontinuity-capturing methodology based on sensors and a spatial filter enables capturing shock waves and deformable interfaces. One-dimensional test cases are performed as validation and to justify choices in the numerical method. The results compare well with analytical solutions. Shock waves and interfaces are accurately propagated, and remain sharp. Subsequently, two-dimensional flows are considered including viscosity and thermal conductivity. In Richtmyer-Meshkov instability, generated on an air-SF6 interface, the influence of the mesh refinement on the instability shape is studied, and the temporal variations of the instability amplitude is compared with experimental data. Finally, for a plane shock wave propagating in air and impacting a cylindrical bubble filled with helium or R22, numerical Schlieren pictures obtained using different grid refinements are found to compare well with experimental shadow-photographs. The mass conservation is verified from the temporal variations of the mass of the bubble. The mean velocities of pressure waves and bubble interface are similar to those obtained experimentally.

Flow regimes in vertical gas-solid contact systems

Energy Technology Data Exchange (ETDEWEB)

Yerushalmi, J.; Cankurt, N. T.; Geldart, D.; Liss, B.

1976-01-01

The flow characteristics in fluidized beds, i.e., gas-solid systems, was studied to determine the flow regimes, the interaction of gas and solid in the various flow regimes and the dependence of this interaction and of transition between flow regimes on the properties of the gas and solid, on the gas and solid flow rates, and on the containing vessel. Fluidized beds with both coarse and fine particles are considered. Test results using high speed photography to view the operation of a 2-dimensional bed are discussed. (LCL)

Experiments on vertical gas-liquid pipe flows using ultrafast X-ray tomography

Energy Technology Data Exchange (ETDEWEB)

Banowski, M.; Beyer, M.; Lucas, D.; Hoppe, D.; Barthel, F. [Helmholtz-Zentrum Dresden-Rossendorf (Germany). Inst. fuer Sicherheitsforschung

2016-12-15

For the qualification and validation of two-phase CFD-models for medium and large-scale industrial applications dedicated experiments providing data with high temporal and spatial resolution are required. Fluid dynamic parameter like gas volume fraction, bubble size distribution, velocity or turbulent kinetic energy should be measured locally. Considering the fact, that the used measurement techniques should not affect the flow characteristics, radiation based tomographic methods are the favourite candidate for such measurements. Here the recently developed ultrafast X-ray tomography, is applied to measure the local and temporal gas volume fraction distribution in a vertical pipe. To obtain the required frame rate a rotating X-ray source by a massless electron beam and a static detector ring are used. Experiments on a vertical pipe are well suited for development and validation of closure models for two-phase flows. While vertical pipe flows are axially symmetrically, the boundary conditions are well defined. The evolution of the flow along the pipe can be investigated as well. This report documents the experiments done for co-current upwards and downwards air-water and steam-water flows as well as for counter-current air-water flows. The details of the setup, measuring technique and data evaluation are given. The report also includes a discussion on selected results obtained and on uncertainties.

High resolution measurement of the velocity profiles of channel flows using the particle image velocimetry technique

International Nuclear Information System (INIS)

Nor Azizi Mohamed

2000-01-01

The high resolution velocity profiles of a uniform steady channel flow and a flow beneath waves were obtained using the particle image velocimetry (PIV) technique. The velocity profiles for each flow were calculated for both components. It is shown that the profiles obtained are very precise, displaying the point velocities from a few millimeters from the bottom of the channel up to the water surface across the water depth. In the case of the wave-induced flow, the profiles are shown under the respective wave phases and given in a plane representation. High resolution measurement of point velocities in a flow is achievable using PIV and invaluable when applied to a complex flow. (Author)

Spatial heterogeneity of biofouling under different cross-flow velocities in reverse osmosis membrane systems

KAUST Repository

Farhat, Nadia; Staal, M.; Bucs, Szilard; Van Loosdrecht, M.C.M.; Vrouwenvelder, Johannes S.

2016-01-01

the spatial heterogeneity of biofilm development over the membrane fouling simulator (MFS) length (inlet and outlet part) at three different cross-flow velocities (0.08, 0.12 and 0.16 m/s). The MFS contained sheets of membrane and feed spacer and simulatedComparison of the inlet and outlet position of the MFS showed a more (i) heterogeneous biofilm distribution and a (ii) higher biological activity at the inlet side (first 2.5 cm) for all cross-flow velocities. The lowest cross-flow velocity had

The effects of non-uniform flow velocity on vibrations of single-walled carbon nanotube conveying fluid

Energy Technology Data Exchange (ETDEWEB)

Sadeghi-Goughari, Moslem [Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of); Hosseini, Mohammad [Sirjan University of Technology, Sirjan (Iran, Islamic Republic of)

2015-02-15

The vibrational behavior of a viscous nanoflow-conveying single-walled carbon nanotube (SWCNT) was investigated. The nonuniformity of the flow velocity distribution caused by the viscosity of fluid and the small-size effects on the flow field was considered. Euler-Bernoulli beam model was used to investigate flow-induced vibration of the nanotube, while the non-uniformity of the flow velocity and the small-size effects of the flow field were formulated through Knudsen number (Kn), as a discriminant parameter. For laminar flow in a circular nanotube, the momentum correction factor was developed as a function of Kn. For Kn = 0 (continuum flow), the momentum correction factor was found to be 1.33, which decreases by the increase in Kn may even reach near 1 for the transition flow regime. We observed that for passage of viscous flow through a nanotube with the non-uniform flow velocity, the critical continuum flow velocity for divergence decreased considerably as opposed to those for the uniform flow velocity, while by increasing Kn, the difference between the uniform and non-uniform flow models may be reduced. In the solution part, the differential transformation method (DTM) was used to solve the governing differential equations of motion.

The effects of non-uniform flow velocity on vibrations of single-walled carbon nanotube conveying fluid

International Nuclear Information System (INIS)

Sadeghi-Goughari, Moslem; Hosseini, Mohammad

2015-01-01

The vibrational behavior of a viscous nanoflow-conveying single-walled carbon nanotube (SWCNT) was investigated. The nonuniformity of the flow velocity distribution caused by the viscosity of fluid and the small-size effects on the flow field was considered. Euler-Bernoulli beam model was used to investigate flow-induced vibration of the nanotube, while the non-uniformity of the flow velocity and the small-size effects of the flow field were formulated through Knudsen number (Kn), as a discriminant parameter. For laminar flow in a circular nanotube, the momentum correction factor was developed as a function of Kn. For Kn = 0 (continuum flow), the momentum correction factor was found to be 1.33, which decreases by the increase in Kn may even reach near 1 for the transition flow regime. We observed that for passage of viscous flow through a nanotube with the non-uniform flow velocity, the critical continuum flow velocity for divergence decreased considerably as opposed to those for the uniform flow velocity, while by increasing Kn, the difference between the uniform and non-uniform flow models may be reduced. In the solution part, the differential transformation method (DTM) was used to solve the governing differential equations of motion.

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-07-01

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

Data adaptive estimation of transversal blood flow velocities

DEFF Research Database (Denmark)

Pirnia, E.; Jakobsson, A.; Gudmundson, E.

2014-01-01

the transversal blood flow. In this paper, we propose a novel data-adaptive blood flow estimator exploiting this modulation scheme. Using realistic Field II simulations, the proposed estimator is shown to achieve a notable performance improvement as compared to current state-of-the-art techniques.......The examination of blood flow inside the body may yield important information about vascular anomalies, such as possible indications of, for example, stenosis. Current Medical ultrasound systems suffer from only allowing for measuring the blood flow velocity along the direction of irradiation......, posing natural difficulties due to the complex behaviour of blood flow, and due to the natural orientation of most blood vessels. Recently, a transversal modulation scheme was introduced to induce also an oscillation along the transversal direction, thereby allowing for the measurement of also...

Thermal-Flow Code for Modeling Gas Dynamics and Heat Transfer in Space Shuttle Solid Rocket Motor Joints

Science.gov (United States)

Wang, Qunzhen; Mathias, Edward C.; Heman, Joe R.; Smith, Cory W.

2000-01-01

A new, thermal-flow simulation code, called SFLOW. has been developed to model the gas dynamics, heat transfer, as well as O-ring and flow path erosion inside the space shuttle solid rocket motor joints by combining SINDA/Glo, a commercial thermal analyzer. and SHARPO, a general-purpose CFD code developed at Thiokol Propulsion. SHARP was modified so that friction, heat transfer, mass addition, as well as minor losses in one-dimensional flow can be taken into account. The pressure, temperature and velocity of the combustion gas in the leak paths are calculated in SHARP by solving the time-dependent Navier-Stokes equations while the heat conduction in the solid is modeled by SINDA/G. The two codes are coupled by the heat flux at the solid-gas interface. A few test cases are presented and the results from SFLOW agree very well with the exact solutions or experimental data. These cases include Fanno flow where friction is important, Rayleigh flow where heat transfer between gas and solid is important, flow with mass addition due to the erosion of the solid wall, a transient volume venting process, as well as some transient one-dimensional flows with analytical solutions. In addition, SFLOW is applied to model the RSRM nozzle joint 4 subscale hot-flow tests and the predicted pressures, temperatures (both gas and solid), and O-ring erosions agree well with the experimental data. It was also found that the heat transfer between gas and solid has a major effect on the pressures and temperatures of the fill bottles in the RSRM nozzle joint 4 configuration No. 8 test.

A custom on-line ultrasonic gas mixture analyzer with simultaneous flowmetry developed for use in the LHC-ATLAS experiment, with wide application in high and low flow gas delivery systems

International Nuclear Information System (INIS)

Bates, R.; Bitadze, A.; Battistin, M.; Berry, S.; Berthoud, J.; Bonneau, P.; Botelho- Direito, J.; Bozza, G.; Crespo-Lopez, O.; DiGirolamo, B.; Da Riva, E.; Favre, G.; Godlewski, J.; Lombard, D.; Zwalinski, L.; Bousson, N.; Hallewell, G.; Mathieu, M.; Rozanov, A.; Boyd, G.; Deterre, C.; Doubek, M.; Vacek, V.; Vitek, M.; Degeorge, C.; Katunin, S.; Langevin, N.; McMahon, S.; Nagai, K.; Robinson, D.; Rossi, C.

2013-06-01

We describe a combined ultrasonic instrument for continuous gas flow measurement and simultaneous real-time binary gas mixture analysis. In the instrument, sound bursts are transmitted in opposite directions, which may be aligned with the gas flow path or at an angle to it, the latter configuration being the best adapted to high flow rates. Custom electronics based on Microchip R dsPIC and ADuC847 micro-controllers transmits 50 kHz ultrasound pulses and measures transit times in the two directions together with the process gas temperature and pressure. The combined flow measurement and mixture analysis algorithm exploits the phenomenon whereby the sound velocity in a binary gas mixture at known temperature and pressure is a unique function of the molar concentration of the two components. The instrument is central to a possible upgrade to the present ATLAS silicon tracker cooling system in which octafluoro-propane (C 3 F 8 ) evaporative cooling fluid would be replaced by a blend containing up to 25% hexafluoro-ethane (C 2 F 6 ). Such a blend will allow a lower evaporation temperature and will afford the tracker silicon substrates a better safety margin against leakage current-induced thermal runaway caused by cumulative radiation damage as the luminosity profile at the CERN Large Hadron Collider (LHC) increases. The instrument has been developed in two geometries following computational fluid dynamics studies of various mechanical layouts. An instrument with 45 crossing angle has been built in stainless steel and installed for commissioning in the ATLAS silicon tracker evaporative fluorocarbon cooling system. It can be used in gas flows up to 20000 l.min -1 , and has demonstrated a flow resolution of 2.3% of full scale for linear flow velocities up to 10 m.s-1 in preliminary studies with air. Other instruments are currently used to detect low levels of C 3 F 8 vapour leaking into the N 2 environmental gas surrounding the ATLAS silicon tracker. Gas from several

Discharge estimation combining flow routing and occasional measurements of velocity

Directory of Open Access Journals (Sweden)

G. Corato

2011-09-01

Full Text Available A new procedure is proposed for estimating river discharge hydrographs during flood events, using only water level data at a single gauged site, as well as 1-D shallow water modelling and occasional maximum surface flow velocity measurements. One-dimensional diffusive hydraulic model is used for routing the recorded stage hydrograph in the channel reach considering zero-diffusion downstream boundary condition. Based on synthetic tests concerning a broad prismatic channel, the "suitable" reach length is chosen in order to minimize the effect of the approximated downstream boundary condition on the estimation of the upstream discharge hydrograph. The Manning's roughness coefficient is calibrated by using occasional instantaneous surface velocity measurements during the rising limb of flood that are used to estimate instantaneous discharges by adopting, in the flow area, a two-dimensional velocity distribution model. Several historical events recorded in three gauged sites along the upper Tiber River, wherein reliable rating curves are available, have been used for the validation. The outcomes of the analysis can be summarized as follows: (1 the criterion adopted for selecting the "suitable" channel length based on synthetic test studies has proved to be reliable for field applications to three gauged sites. Indeed, for each event a downstream reach length not more than 500 m is found to be sufficient, for a good performances of the hydraulic model, thereby enabling the drastic reduction of river cross-sections data; (2 the procedure for Manning's roughness coefficient calibration allowed for high performance in discharge estimation just considering the observed water levels and occasional measurements of maximum surface flow velocity during the rising limb of flood. Indeed, errors in the peak discharge magnitude, for the optimal calibration, were found not exceeding 5% for all events observed in the three investigated gauged sections, while the

Recent progress in the joint velocity-scalar PDF method

Science.gov (United States)

Anand, M. S.

1995-01-01

This viewgraph presentation discusses joint velocity-scalar PDF method; turbulent combustion modeling issues for gas turbine combustors; PDF calculations for a recirculating flow; stochastic dissipation model; joint PDF calculations for swirling flows; spray calculations; reduced kinetics/manifold methods; parallel processing; and joint PDF focus areas.

Experimental Studies of Low-Pressure Turbine Flows and Flow Control. Streamwise Pressure Profiles and Velocity Profiles

Science.gov (United States)

Volino, Ralph

2012-01-01

This report summarizes research performed in support of the NASA Glenn Research Center (GRC) Low-Pressure Turbine (LPT) Flow Physics Program. The work was performed experimentally at the U.S. Naval Academy faculties. The geometry corresponded to "Pak B" LPT airfoil. The test section simulated LPT flow in a passage. Three experimental studies were performed: (a) Boundary layer measurements for ten baseline cases under high and low freestream turbulence conditions at five Reynolds numbers of 25,000, 50,000, 100,000, 200,000, and 300,000, based on passage exit velocity and suction surface wetted length; (b) Passive flow control studies with three thicknesses of two-dimensional bars, and two heights of three-dimensional circular cylinders with different spanwise separations, at same flow conditions as the 10 baseline cases; (c) Active flow control with oscillating synthetic (zero net mass flow) vortex generator jets, for one case with low freestream turbulence and a low Reynolds number of 25,000. The Passive flow control was successful at controlling the separation problem at low Reynolds numbers, with varying degrees of success from case to case and varying levels of impact at higher Reynolds numbers. The active flow control successfully eliminated the large separation problem for the low Reynolds number case. Very detailed data was acquired using hot-wire anemometry, including single and two velocity components, integral boundary layer quantities, turbulence statistics and spectra, turbulent shear stresses and their spectra, and intermittency, documenting transition, separation and reattachment. Models were constructed to correlate the results. The report includes a summary of the work performed and reprints of the publications describing the various studies.This report summarizes research performed in support of the NASA Glenn Research Center (GRC) Low-Pressure Turbine (LPT) Flow Physics Program. The work was performed experimentally at the U.S. Naval Academy

Wind-induced flow velocity effects on nutrient concentrations at Eastern Bay of Lake Taihu, China.

Science.gov (United States)

Jalil, Abdul; Li, Yiping; Du, Wei; Wang, Jianwei; Gao, Xiaomeng; Wang, Wencai; Acharya, Kumud

2017-07-01

Shallow lakes are highly sensitive to respond internal nutrient loading due to wind-induced flow velocity effects. Wind-induced flow velocity effects on nutrient suspension were investigated at a long narrow bay of large shallow Lake Taihu, the third largest freshwater lake in China. Wind-induced reverse/compensation flow and consistent flow field probabilities at vertical column of the water were measured. The probabilities between the wind field and the flow velocities provided a strong correlation at the surface (80.6%) and the bottom (65.1%) layers of water profile. Vertical flow velocity profile analysis provided the evidence of delay response time to wind field at the bottom layer of lake water. Strong wind field generated by the west (W) and west-north-west (WNW) winds produced displaced water movements in opposite directions to the prevailing flow field. An exponential correlation was observed between the current velocities of the surface and the bottom layers while considering wind speed as a control factor. A linear model was developed to correlate the wind field-induced flow velocity impacts on nutrient concentration at the surface and bottom layers. Results showed that dominant wind directions (ENE, E, and ESE) had a maximum nutrient resuspension contribution (nutrient resuspension potential) of 34.7 and 43.6% at the surface and the bottom profile layers, respectively. Total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP) average concentrations were 6.38, 1.5, and 0.03 mg/L during our field experiment at Eastern Bay of Lake Taihu. Overall, wind-induced low-to-moderate hydrodynamic disturbances contributed more in nutrient resuspension at Eastern Bay of Lake Taihu. The present study can be used to understand the linkage between wind-induced flow velocities and nutrient concentrations for shallow lakes (with uniform morphology and deep margins) water quality management and to develop further models.

Axial flow velocity patterns in a normal human pulmonary artery model: pulsatile in vitro studies.

Science.gov (United States)

Sung, H W; Yoganathan, A P

1990-01-01

It has been clinically observed that the flow velocity patterns in the pulmonary artery are directly modified by disease. The present study addresses the hypothesis that altered velocity patterns relate to the severity of various diseases in the pulmonary artery. This paper lays a foundation for that analysis by providing a detailed description of flow velocity patterns in the normal pulmonary artery, using flow visualization and laser Doppler anemometry techniques. The studies were conducted in an in vitro rigid model in a right heart pulse duplicator system. In the main pulmonary artery, a broad central flow field was observed throughout systole. The maximum axial velocity (150 cm s-1) was measured at peak systole. In the left pulmonary artery, the axial velocities were approximately evenly distributed in the perpendicular plane. However, in the bifurcation plane, they were slightly skewed toward the inner wall at peak systole and during the deceleration phase. In the right pulmonary artery, the axial velocity in the perpendicular plane had a very marked M-shaped profile at peak systole and during the deceleration phase, due to a pair of strong secondary flows. In the bifurcation plane, higher axial velocities were observed along the inner wall, while lower axial velocities were observed along the outer wall and in the center. Overall, relatively low levels of turbulence were observed in all the branches during systole. The maximum turbulence intensity measured was at the boundary of the broad central flow field in the main pulmonary artery at peak systole.

Custom ultrasonic instrumentation for flow measurement and real-time binary gas analysis in the CERN ATLAS experiment

Science.gov (United States)

Alhroob, M.; Battistin, M.; Berry, S.; Bitadze, A.; Bonneau, P.; Boyd, G.; Crespo-Lopez, O.; Degeorge, C.; Deterre, C.; Di Girolamo, B.; Doubek, M.; Favre, G.; Hallewell, G.; Katunin, S.; Lombard, D.; Madsen, A.; McMahon, S.; Nagai, K.; O'Rourke, A.; Pearson, B.; Robinson, D.; Rossi, C.; Rozanov, A.; Stanecka, E.; Strauss, M.; Vacek, V.; Vaglio, R.; Young, J.; Zwalinski, L.

2017-01-01

The development of custom ultrasonic instrumentation was motivated by the need for continuous real-time monitoring of possible leaks and mass flow measurement in the evaporative cooling systems of the ATLAS silicon trackers. The instruments use pairs of ultrasonic transducers transmitting sound bursts and measuring transit times in opposite directions. The gas flow rate is calculated from the difference in transit times, while the sound velocity is deduced from their average. The gas composition is then evaluated by comparison with a molar composition vs. sound velocity database, based on the direct dependence between sound velocity and component molar concentration in a gas mixture at a known temperature and pressure. The instrumentation has been developed in several geometries, with five instruments now integrated and in continuous operation within the ATLAS Detector Control System (DCS) and its finite state machine. One instrument monitors C3F8 coolant leaks into the Pixel detector N2 envelope with a molar resolution better than 2ṡ 10-5, and has indicated a level of 0.14 % when all the cooling loops of the recently re-installed Pixel detector are operational. Another instrument monitors air ingress into the C3F8 condenser of the new C3F8 thermosiphon coolant recirculator, with sub-percent precision. The recent effect of the introduction of a small quantity of N2 volume into the 9.5 m3 total volume of the thermosiphon system was clearly seen with this instrument. Custom microcontroller-based readout has been developed for the instruments, allowing readout into the ATLAS DCS via Modbus TCP/IP on Ethernet. The instrumentation has many potential applications where continuous binary gas composition is required, including in hydrocarbon and anaesthetic gas mixtures.

Simulation of gas and particle flow in a circulating fluidized bed; Kaasu- ja kiintoainevirtauksen simulointi kiertoleijukattilassa

Energy Technology Data Exchange (ETDEWEB)

Kallio, S. [Aabo Akademi, Turku (Finland). Inst. of Heat Engineering

1996-12-01

The aim of this work was to study the effects of different parameters on the flow behaviour in a CFB riser by means of empirical models based on measurement data and a computer code based on macroscopic equations for multiphase flow. The effects of primary air velocity and riser geometry have been observed in the results. Simulation of secondary air flow proved to be problematic with the software used. In the project, also analyses of measurement data from cold model experiments has been performed. Moreover, the possibilities to use commercial CFD codes for simulation of gas-solids flow were investigated. The code FLUENT seemed promising. (author)

Lunar ash flow with heat transfer.

Science.gov (United States)

Pai, S. I.; Hsieh, T.; O'Keefe, J. A.

1972-01-01

The most important heat-transfer process in the ash flow under consideration is heat convection. Besides the four important nondimensional parameters of isothermal ash flow (Pai et al., 1972), we have three additional important nondimensional parameters: the ratio of the specific heat of the gas, the ratio of the specific heat of the solid particles to that of gas, and the Prandtl number. We reexamine the one dimensional steady ash flow discussed by Pai et al. (1972) by including the effects of heat transfer. Numerical results for the pressure, temperature, density of the gas, velocities of gas and solid particles, and volume fraction of solid particles as function of altitude for various values of the Jeffreys number, initial velocity ratio, and two different gas species (steam and hydrogen) are presented.

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

Science.gov (United States)

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

2012-03-01

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

Mathematical Model of Two Phase Flow in Natural Draft Wet-Cooling Tower Including Flue Gas Injection

Directory of Open Access Journals (Sweden)

Hyhlík Tomáš

2016-01-01

Full Text Available The previously developed model of natural draft wet-cooling tower flow, heat and mass transfer is extended to be able to take into account the flow of supersaturated moist air. The two phase flow model is based on void fraction of gas phase which is included in the governing equations. Homogeneous equilibrium model, where the two phases are well mixed and have the same velocity, is used. The effect of flue gas injection is included into the developed mathematical model by using source terms in governing equations and by using momentum flux coefficient and kinetic energy flux coefficient. Heat and mass transfer in the fill zone is described by the system of ordinary differential equations, where the mass transfer is represented by measured fill Merkel number and heat transfer is calculated using prescribed Lewis factor.

Lattice Boltzmann method and gas-kinetic BGK scheme in the low-Mach number viscous flow simulations

International Nuclear Information System (INIS)

Xu Kun; He Xiaoyi

2003-01-01

Both lattice Boltzmann method (LBM) and the gas-kinetic BGK scheme are based on the numerical discretization of the Boltzmann equation with collisional models, such as, the Bhatnagar-Gross-Krook (BGK) model. LBM tracks limited number of particles and the viscous flow behavior emerges automatically from the intrinsic particle stream and collisions process. On the other hand, the gas-kinetic BGK scheme is a finite volume scheme, where the time-dependent gas distribution function with continuous particle velocity space is constructed and used in the evaluation of the numerical fluxes across cell interfaces. Currently, LBM is mainly used for low Mach number, nearly incompressible flow simulation. For the gas-kinetic scheme, the application is focusing on the high speed compressible flows. In this paper, we are going to compare both schemes in the isothermal low-Mach number flow simulations. The methodology for developing both schemes will be clarified through the introduction of operator splitting Boltzmann model and operator averaging Boltzmann model. From the operator splitting Boltzmann model, the error rooted in many kinetic schemes, which are based on the decoupling of particle transport and collision, can be easily understood. As to the test case, we choose to use the 2D cavity flow since it is one of the most extensively studied cases. Detailed simulation results with different Reynolds numbers, as well as the benchmark solutions, are presented

Stationary velocity distributions in traffic flows

International Nuclear Information System (INIS)

1997-01-01

We introduce a traffic flow model that incorporates clustering and passing. We obtain analytically the steady state characteristics of the flow from a Boltzmann-like equation. A single dimensionless parameter, R=c 0 v 0 t 0 with c 0 the concentration, v 0 the velocity range, and t 0 -1 the passing rate, determines the nature of the steady state. When R 1, large clusters with average mass left-angle m right-angle ∼R α form, and the flux is J∼R -γ . The initial distribution of slow cars governs the statistics. When P 0 (v)∼v μ as v→0, the scaling exponents are γ=1/(μ+2), α=1/2 when μ>0, and α=(μ+1)/(μ+2) when μ<0. copyright 1997 The American Physical Society

Velocity vector estimation in synthetic aperture flow and B-mode imaging

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt

2004-01-01

A method for determining both velocity magnitude and angle in a synthetic aperture ultrasound system is described. The approach uses directional beamforming along the flow direction and cross-correlation to determine velocity magnitude. The angle of the flow is determined from the maximum normali...... with a precision of 0.36 % (60°) and 1.2 % (90°), respectively. The 60° angle is estimated with a bias of 0.54° and a standard deviation of 2.1°. For 90° the bias is 0.0003° and standard deviation 1.32°....

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)

Contribution to the dynamical study of gas-liquid two-phase flows

International Nuclear Information System (INIS)

Lewi, Joseph.

1975-01-01

A single system of equations valid for two-phase flows at any time and anywhere was searched for. The mathematical theory of distributions was used. The results obtained was applied to the turbulent flow of an emulsion in a canal of constant section. It is shown that the use of distribution conservation equations makes it possible to determine the shapes of the mean velocity profiles, to obtain a relation between the friction coefficient and a Reynolds number introduced in a logical way, and to express the total pressure drop in the canal. Three experiments were carried out to compare the performance of various optical methods used for displaying bubble liquid-gas flows, and, within the limits of these methods, to study the interaction between the bubbles and the sensible end of variable impedance probe, and the granulometry of the emulsion in the vicinity of the probe [fr

Velocity and phase distribution measurements in vertical air-water annular flows

International Nuclear Information System (INIS)

Vassallo, P.

1997-07-01

Annular flow topology for three air-water conditions in a vertical duct is investigated through the use of a traversing double-sensor hot-film anemometry probe and differential pressure measurements. Near wall measurements of mean and fluctuating velocities, as well as local void fraction, are taken in the liquid film, with the highest turbulent fluctuations occurring for the flow condition with the largest pressure drop. A modified law-of-the-wall formulation for wall shear is presented which, using near wall values of mean velocity and kinetic energy, agrees reasonably well with the average stress obtained from direct pressure drop measurements. The linear profile using wall coordinates in the logarithmic layer is preserved in annular flow; however, the slope and intercept of the profile differ from the single-phase values for the annular flow condition which has a thicker, more turbulent, liquid film