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A gas flow unified measurement system (UMS-G) for sequential measurement of gas diffusion and gas permeability of geosynthetic clay liners (GCLs) under applied stress conditions (2 to 20 kPa) is described. Measurements made with the UMS-G are compared with measurements made with conventional experimental devices and are found to give similar results. The UMS-G removes the need to rely on two separate systems and increases further the reliability of the gas properties' measurements. This study also shows that the gas diffusion and gas permeability reduce greatly with the increase of both gravimetric water content and apparent degree of saturation. The effect of applied stress on gas diffusion and gas permeability is found to be more pronounced at gravimetric water content greater than 60%. These findings suggest that at a nominal overburden stress of 20 kPa, the GCL used in the present investigation needs to be hydrated to 134% gravimetric water content (65% apparent degree of saturation) before gas diffusion and gas permeability drop to 5.5 x [10.sup.-11] [m.sup.2] x [s.sup.-1] and 8.0 x [10.sup.-13] m x [s.sup.-1], respectively, and to an even higher gravimetric water content (apparent degrees of saturation) at lower stress. Key words: geosynthetic clay liner, gas flow, diffusion, advection, gravimetric water content. Dans le cadre de cette etude, on decrit un systeme de mesure du flux gazeux unifie (UMS-G) afin de mesurer sequentiellement la diffusion gazeuse et la permeabilite au gaz des membranes geosynthetiques d'etancheite d'argile (GCL) soumises des conditions de contrainte (2 20 kPa). Les mesures prises au moyen de l'UMS-G sont comparees aux mesures obtenues au moyen de dispositifs experimentaux courants et il s'avere que les resultats sont semblables. En utilisant l'UMS-G, il n'est plus necessaire d'avoir deux systemes separes et la fiabilite des mesures des proprietes des gaz augmente davantage. De plus cette etude demontre que la diffusion gazeuse et la permeabilite au gaz diminuent considerablement lorsqu'a la fois la teneur en eau gravimetrique et le degre de saturation apparent augmentent. Lorsque la teneur en eau gravimetrique est superieure 60%, on constate que l'effet de la contrainte appliquee sur la diffusion gazeuse et la permeabilite au gaz est plus prononce. Ces resultats suggerent que sous une surcharge de 20 kPa, la GCL utilisee aux fins de cette investigation doit subir une hydratation jusqu'a une teneur en eau gravimetrique de 134% (degre de saturation apparent de 65%) avant que la diffusion gazeuse et la permeabilite au gaz ne baissent jusqu'a 5.5 x [10.sup.-11] [m.sup.2] x [s.sup.-1] et 8.0 x [10.sup.-13] m x [s.sup.-1], respectivement, et jusqu'a une teneur en eau gravimetrique encore plus elevee (degre de saturation apparent) a des contraintes plus faibles. [Traduit par la Redaction] Mots-cles: membrane geosynthetique d'etancheite d'argile (GCL), flux gazeux, diffusion, advection, teneur en eau gravimetrique., Introduction Evaluation of gas migration is important in engineered cover systems of waste containment facilities to prevent or minimize possible contamination of the environment following their closure due to gas [...]

Measurements of decompression wave speed in conventional and rich natural gas mixtures following rupture of a high-pressure pipe have been conducted A high-pressure stainless steel rupture tube (internal diameter = 38.1 mm and 42 m long) has been constructed and instrumented with 16 high frequency-response pressure transducers mounted very close to the rupture end and along the length of the tube to capture the pressure-time traces of the decompression wave. Tests were conducted for initial pressures of 33-37 MPa-a and a temperature range of 21-68[degrees]C. The experimentally determined decompression wave speeds were compared with both GASDECOM and PIPEDECOM predictions with and without nonequilibrium condensation delays at phase crossing. The interception points of the isentropes representing the decompression process with the corresponding phase envelope of each mixture were correlated with the respective plateaus observed in the decompression wave speed profiles. Additionally, speeds of sound in the undisturbed gas mixtures at the initial pressures and temperatures were compared with predictions by five equations of state, namely, BWRS, AGA-8, Peng--Robinson, Soave--Redlich--Kwong, and Groupe Europeen de Recherches Gazieres. The measured gas decompression curves were used to predict the fracture arrest toughness needed to assure fracture control in natural gas pipelines. The rupture tube test results have shown that the Charpy fracture arrest values predicted using GASEDCOM are within +7% (conservative) and -11% (nonconservative) of the rupture tube predicted values. Similarly, PIPEDECOM with no temperature delay provides fracture arrest values that are within +13% and -20% of the rupture tube predicted values, while PIPEDECOM with a 1[degrees]C temperature delay provides fracture arrest values that are within 0% and -20% of the rupture tube predicted values. Ideally, it would be better if the predicted values by the equations of state were above the rupture tube predicted values to make the predictions conservative but that was not always the case. [DOI: 10.1115/1.4001438] Keywords: gas pipelines, rupture, rich gas, decompression wave speed, GASDECOM, PIPEDECOM, expansion waves, dynamic pressure measurements

The gas-liquid two-phase slug flow regime phenomenon is commonly encountered in the chemical engineering industry, particularly in oil and gas production transportation pipelines. Slug flow regime normally occurs for a range of pipe inclinations, and gas and liquid flowrates. A pipeline operating in the slug flow regime creates high fluctuations in gas and liquid flowrates at the outlet. Therefore, the monitoring of slugs and the measurement of their characteristics, such as the gas void fraction, are necessary to minimize the disruption of downstream process facilities. In this paper, a correlation between gas void fraction, absolute acoustic emission energy, and slug velocities in a two-phase air/water flow regime was developed using an acoustic emission technique. It is demonstrated that the gas void fraction can be determined by measurement of acoustic emission. [DOI: 10.1115/1.4000463] Keywords: acoustic emission, slug flow, gas void fraction, slug velocity, process monitoring

Computational simulations of flow and heat transfer in heat recovery steam generators (HRSGs) of vertical-and horizontal-tube designs are reported. The main objective of the work was to obtain simple modifications of their internal configuration that render the flow of combustion gas more spatially uniform. The computational method was validated by comparing some of the simulation results for a scaled-down laboratory model with experimental measurements in the same. Simulations were then carried out for two plant HRSGs--without and with the proposed modifications. The results show significantly more uniform combustion gas flow in the modified configurations. Heat transfer calculations were performed for one superheater section of the vertical-tube HRSG to determine the effect of the configuration modification on heat transfer from the combustion gas to the steam flowing in the superheater tubes. [DOI: 10.1115/1.2751505]

A preconditioned numerical method for gas-liquid two-phase flows is applied to solve cavitating flow. The present method employs a finite-difference method of the dual time-stepping integration procedure and Roe's flux difference splitting approximation with the MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. The present density-based numerical method permits simple treatment of the whole gas-liquid two-phase flow field, including wave propagation, large density changes and incompressible flow characteristics at low Mach number. Two-dimensional internal flows through a backward-facing step duct, convergent-divergent nozzles and decelerating cascades are computed using this method. Comparisons of predicted and experimental results are provided and discussed. [DOI: 10.1115/1.1777230]

The application of pneumatic metrology to control dimensional accuracy on machined parts is based on the measurement of gas flow resistance through a restricted section formed by a jet orifice placed at a small distance away from a machined surface. The backpressure, which is sensed and indicated by a pressure gauge, is calibrated to measure dimensional variations. It has been found that in some typical industrial applications, the nozzles are subject to fouling, e.g., dirt and oil deposits accumulate on their frontal areas, thus requiring more frequent calibration of the apparatus for reliable service. In this paper, a numerical and experimental analysis of the flow behavior in the region between an injection nozzle and a flat surface is presented. The analysis is based on the steady-state axisymmetric flow of an incompressible fluid. The governing equations, coupled with the appropriate boundary conditions, are solved using the SIMPLER algorithm. Results have shown that for the standard nozzle geometry used in industrial applications, an annular low-pressure separated flow area was found to exist near the frontal surface of the nozzle. The existence of this area is believed to be the cause of the nozzle fouling problem. A study of various alternate nozzle geometries has shown that this low-pressure recirculation area can be eliminated quite readily. Well-designed chamfered, rounded, and reduced frontal area nozzles have all reduced or eliminated the separated recirculation flow area. It has been noted, however, that rounded nozzles may adversely cause a reduction in apparatus sensitivity. [DOI: 10.1115/1.1598991]

A new probe technique is introduced for the measurement of concentration in binary gas flows. The new technique is demonstrated through application of the probe in a Mach 4 nonreacting jet of hydrogen injected into a nominally quiescent air environment. Previous concentration probe devices have mostly used hot wires or hot films within an aspirating probe tip. However, the new technique relies on Pitot pressure and stagnation point transient thin film heat flux probe measurements. The transient thin film heat flux probes are operated at a number of different temperatures and thereby provide stagnation temperature and heat transfer coefficient measurements with an uncertainty of around [+ or -] 5 K and [+ or -] 4% respectively. When the heat transfer coefficient measurements are combined with the Pitot pressure measurements, it is demonstrated that the concentration of hydrogen within the mixing jet can be deduced. The estimated uncertainty of the reported concentration measurements is approximately [+ or -] 5% on a mass fraction basis. [DOI: 10.1115/1.1595671]

Studies of wavy stratified and stratified/atomization two-phase flow in horizontal pipes are outlined. Notable features of this flow regime include the appearance of disturbance waves, the atomization onset and the drastic change of the gas/liquid interface profile from flat to 'concave.' Liquid-to-wall shear stress tends to decrease circumferentially. A computational procedure for predicting main flow characteristics, which takes into account the above results in its design relations, is first assessed with detailed experimental data and is then combined with a CFD code, aiming at enhancing the predictive capability. [DOI: 10.1115/1.1576265] Keywords: Gas/Liquid Flow, Stratified Flow, Horizontal Pipes, Liquid Holdup, Pressure Drop, Shear Stress, Computational Method.

The mechanistic model of Taitel and Dukler [1] has previously been reported to exhibit a region in which three solutions exist for the height of the gas-liquid interface in the stratified/wave flow regime. Most laboratory studies have not dealt with flow rates in the ranges where the multiple solutions occur. An experimental study has been carried out at the University of Calgary to obtain such data. The object of this work is to review the relevant theory, investigate situations where theory suggests that multiple solutions should exist, and attempt to show whether or not such solutions do physically exist. [DOI: 10.1115/1.1521710]

Pressure drop experiments on natural gas flow in 150 mm pipes at 80 to 120 bar pressure and high Reynolds number were carried out for pipes smooth to rough surfaces. The roughness was measured with an accurate stylus instrument and analyzed using fractal methods. Using a similar approach to that of Nikuradse the measured friction factor was related to the measured roughness values. Taking the value of the relative roughness and dividing it by the slope of the power spectrum of the measured roughness, a greatly improved fit with the measured friction factor was obtained. Indeed, a new friction factor correlation was obtained, but now formulated in terms of direct measurement of roughness. [DOI: 10.1115/1.1576264] Keywords: Friction Factor, Turbulent Flow, Wall Roughness, Pressure Drop, Natural Gas

This paper deals with the numerical simulation of two-phase flows based on the solution of the Navier-Stokes equations with a k-[epsilon] turbulence model for the gas phase and a particle tracking model of the disperse phase fulfilling the framework of the Eulerian-Lagrangian (PSI-cell) approach. The numerical procedures for the two phases are based on multigrid and domain decomposition methods applied to a block-structured grid. Due to the enormous numerical effort of such flow simulations the entire solving procedure has been parallelized for computers of MIMD architecture. The paper gives a short description of the applied and developed numerical methods. Furthermore the numerical simulation of a particle laden gas flow through a flow splitter from the area of power engineering is presented as an example for a real world application of the numerical approach.

A gas flow regulator for ion propulsion systems on board small satellites is proposed. The device is fabricated by means of micromachining techniques and is made up of a silicon die and a borosilicate glass cover joined together by means of anodic bonding. The fabrication process of two different versions of the device is described. The gas mass flow dependence on both the inlet pressure and the absolute temperature is measured and discussed.

An image processing technique was designed to be utilized in combination with a Fabry-Perot interferometer for time-resolved velocity measurements in gas flows. The method was employed to obtain the Doppler shift in Mie or Rayleigh scattered light from the measurement volume. The technique minimizes the unwanted effects due to the drifting of laser frequency and interferometer alignment. The scattered light is mixed with unshifted light from the interrogation laser for reference before it is passed through the interferometer.

Research is conducted to examine turbulent heat fluxes in homogeneous curved shear flow. The measurements are performed far downstream of a thermal line source in both destabilized and stabilized curved shear flow. The curvature is observed to affect the heat fluxes due to its impact on the turbulence kinetic energy of the flow. Results are in good agreement with previous findings showing that momentum transport in curved boundary layers are more strongly affected by flow curvature than heat transport.

Application of electrothermal launchers for obtaining powder materials coatings with improved values of density and adhesion requires formation of the gas flow region, immediately following behind the shock wave, where microparticles are being caught into acceleration. A method of such region forming by means of the shock wave space and time shaping is presented. The flow dynamics analysis on the basis of a numerical model which was carried out for the case of two gaps in the launcher discharge unit, has shown that it is possible to accelerate microparticles up to very high velocities (2 km/s and higher) with simultaneous control of their temperature and to increase substantially the launcher efficiency. Measurements with the experimental equipment allowed us to determine dynamic parameters of flows, the velocity and extension of the shock-compressed region as well as velocities of the shock-waves and main flow region. Registration of plasma flows radiation spectra permitted to determine their temperature. The obtained experimental results are in good correlation with computer simulation data. Index Terms - Coating, microparticle, flow, electrothermal launcher

An instrument for the measurement of wall shear stress in two-phase flows is described. The device, termed a Laser Interferometer Skin Friction (LISF) meter, determines the wall shear by optically measuring the time rate of thinning of a thin oil film placed on the wall of the flow channel. The LISF meter has proven to be a valuable tool for measurement of wall shear in single-phase gaseous flows but, to date, had not been applied to liquid or gas-liquid flows. This paper describes modifications to the LISF meter developed to facilitate its use in two-phase flows. The instrument's configuration, governing theory, and data reduction procedure are described. Additionally, results of validation experiments for a single-phase water flow are presented, which demonstrate the instrument's ability to accurately measure wall shear. Measurements are also presented for two-phase, water-air flows in a duct of square cross section at various superficial gas and liquid velocities within the bubbly flow regime. Results of the measurements confirm previous observations that the addition of a very small amount of the gaseous phase increases the wall shear significantly over that in a single-phase water flow. The two-phase wall shear saturates to a maximum and then declines again as the superficial gas velocity is increased. The peak two-phase wall shear increases as the liquid superficial velocity is decreased. These trends are qualitatively in agreement with previous measurements obtained in pipes using an electrochemical technique.

An analytic and experimental investigation into gaseous flow with slight rarefaction through long microchannels is undertaken. A two-dimensional (2-D) analysis of the Navier-Stokes equations with a first-order slip-velocity boundary condition demonstrates that both compressibility and rarefied effects are present in long microchannels. By undertaking a perturbation expansion in [Epsilon], the height-to-length ratio of the channel, and using the ideal gas equation of state, it is shown that the zeroth-order analytic solution for the streamwise mass flow corresponds well with the experimental results. Also, the effect of slip upon the pressure distribution is derived, and it is obtained that this slip velocity leads directly to a wall-normal migration of mass. The fabrication of wafer-bonded microchannels that possess well-controlled surface structure is described, and a means for accurately measuring the mass flow through the channels is presented. Experimental results obtained with this mass-flow measurement technique for streamwise helium mass flow through microchannels 52.25-[[micro]meter] wide, 1.33-[[micro]meter] deep, and 7500-[[micro]meter] long for a pressure range of 1.6-4.2 atmospheres (outlet pressures at atmospheric) are presented and shown to compare favorably with the analysis. [147] Index Terms - Fluid flow measurement, microelectromechanical devices, perturbation methods, rarefied gas dynamics.

The improved design of a gas-injection electronic gas minipermeameter aids field and laboratory research. This design overcomes errors in gas flow rate calculation, flow rate meter calibration and difficulties in calculation of permeability of weathering rinds. This instrument aids the calculation of permeability on fracture surfaces, large hand samples and outcrops.

An experimental procedure was developed for determining both the density and flow rate of a gas from measurements of pressure drops caused by an abrupt flow area contraction in a cylindrical pipe. Experiments were carried out by varying the density and flow rate of a light gas mixture of air and helium, spanning a Reynolds number range from 0.2 x [10.sup.4] to 3.4 x [10.sup.4]. From experimental results, a procedure was then proposed for evaluating the density from pressure change measurements in the scope of light gas extraction experiments. [DOI: 10.1115/1.2953294]

This paper describes a novel in-line sensor that measures the magnitude and direction of gas flow in a tube. The sensor possesses a unique set of performance characteristics: low detection limit, little resistance to flow, and directional sensitivity. The sensor consists of two hot wire anemometers mounted in a U-shaped tube. Differences in the signals between the two hot wires under low velocity conditions are used to determine the direction of the flow. Calibration curves of flow rate versus measured velocity are used to determine the magnitude of the flow. The sensor has applications in systems that are characterized by naturally driven oscillating flows.

An experimental study revealed the velocities of atomic hydrogen and helium in an arcjet thruster to be similar, thereby implying velocity measurements near the exit plane to be representative of the average mass velocity. This suggests that species specific velocity-measurement strategies are versatile in quantifying velocity measures of the related species near the exit plane.

An experiment was conducted to evaluate the use of an adaptation of the electrostatic probe theory to include measurements of mass flows of a dense gas-solid suspension. The ball probe theory was used for accounting for the effects of multiple scattering and sliding of particles over the round surface of dense suspensions.

The thrust measurement of a miniature electrothermal thruster is conducted by using microwave-excited microplasmas. The results have shown that the pressure thrust has contributed to the total thrust at low gas flow rates and that the micronozzles have an isothermal wall rather than an adiabatic.

For the first time, to the best of our knowledge, two-dimensional instantaneous measurements of the flow velocity and the gas temperature have been performed in a turbulent flame with simultaneous use of particle image velocimetry and planar filtered Rayleigh scattering. These single-shot measurements provide simultaneous information on the local flame structure (curvature and temperature gradients) and on the local flow conditions (vortices, flow divergences, and strain rates). The applicability of the technique is demonstrated in a turbulent lean [CH.sub.4]-air V flame. OCIS codes: 120.1740, 120.6780, 290.5850, 290.5870.

Oxygen laser-induced fluorescence was studied experimentally to quantify significant error and uncertainty sources and to evaluate the technique feasibility for gas temperature measurements in the 1-6-atm, 300-500-K regime. The dominant uncertainty source is quantum noise. For low-speed flows, the dominant error source is nonlinear process errors originating from oxygen ion fluorescence and saturation. For flows where the pressure is unknown or variable, collisional quenching may introduce an additional error up to 3 K/atm. For high-speed flows above 300 K, the dominant error source is the slow vibrational relaxation time of oxygen molecules. The optimum experimental conditions are determined by budgeting the allowable temperature inaccuracy to various uncertainty and error sources. In general, the nonlinear process errors limit the laser fluence that may be used, and the quantum noise determines the minimum number of laser shots per measurement.

This paper develops a liquid film symmetry correlation and a liquid film thickness distribution model for horizontal annular gas-liquid pipe flows. The symmetry correlation builds on the work of Williams et al. (1996) (Droplet Flux Distributions and Entrainment in Horizontal Gas-Liquid Flows,' Int. J. Multiphase Flow, Vol. 22, pp. 1-18). A new correlating parameter is presented. The liquid film thickness model is based on the work of Laurinat et al. (1985) (Film Thickness Distribution for Gas-Liquid Annular Flow in a Horizontal Pipe,' PhysicoChem. Hydrodynam., Vol. 6, pp. 179-195). The circumferential momentum equation is simplified to a balance between the normal Reynolds stress in the film's circumferential direction and the circumferential component of the weight of the film. A model for the normal Reynolds stress in the circumferential direction is proposed. The symmetry correlation is used to close the model equations. The model is valid for films with disturbance waves, and is shown to be applicable to air-water flows over a range of conditions from low velocity asymmetric to high velocity symmetric annular flows. [S0098-2202(00)02102-7] Keywords: Two-Phase Flow, Annular Flow, Horizontal Gas-Liquid Flow, Liquid Film Thickness Distribution