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International audience; A vast amount of studies in the literature have been devoted to Bretherton's problem related to the steady-state motion of an elongated gas bubble in a capillary filled with liquid. For a train of bubbles confined in a circular tube, we clearly measured a dependence of the bubble-wall friction force as a function of the liquid volume fraction. This experimental observation may require further theoretical developments.

Based on a mass balance and the behavior of the critical liquid volume fraction, appropriate forms of the rectilinear diameter for coexisting densities are dervied. For the refrigerants R22, R134a, and R124, a single temperature-dependent term in the rectilinear diameter was necessary to fit experimental vapor and liquid coexisting densities to determine the critical density. Internal consistency tests of coexistence density data and critical density values are developed. Critical density values for R22, R134a, and R124 are in good agreement with published values and with values calculated from published coexistence density data. Critical density values found in this study are 523.65 &+- 1.07 kg m 3 for R22, 513.02 &+- 1.98 kg m 3 for R134a, and 559.76 &+- 1.54 kg m 3 for R124.

The potential of application of in-situ neutron diffraction for studies of solidification of Al alloys have been previously reported by the authors for the binary hypereutectic A-Si system. This illustrated the potential of neutron diffraction for high resolution melt analysis at near-liquidus temperatures required for advanced studies of grain refining, eutectic modification, etc. The solid and liquid volume fractions were determined based on the change of intensity of neutron diffraction peaks over the solidification interval. The path of non-equilibrium solidification for the alloy modified with addition of copper and magnesium is very complex. Phase diagrams and FactSage-based computations give only approximate kinetics of solid phase(s) evolution during cooling and solidification. On the other hand, in-situ neutron diffraction, coupled with the results of thermal analysis, provides non-biased experimental data on phase evolution; for example, on formation of FCC Al-Cu-Si and diamond silicon during solidification of hypereutectic Al-Si-Cu alloy., TMS 2011 - 140th Annual Meeting and Exhibition, 27 February 2011 through 3 March 2011, San Diego, CA

Holcomb, C.D., Niesen, V.G., Van Poolen, L.J. and Outcalt, S.L., 1993. Coexisting densities, vapor pressures and critical densities of refrigerants R-32 and R-152a at 300-385 K. Fluid Phase Equilibria , 91: 145-157. Experimental measurements for the vapor pressures and coexisting densities are presented for the refrigerants R-32 (difluoromethane) and R-152a (1,1-difluoroethane) from 300 K to near thier respective critical points. In addition, the coexisting density measurements have been analyzed to determine an internally consistent critical density using the critical liquid volume fraction method. Experimental results have been correlated and are in good agreement with existing literature values for each compound.

International audience; We investigate the capture of particles in soft porous media. Liquid foam constitutes a model system for such a study, allowing the radii of passage in the pore space to be tuned over several orders of magnitude by adjusting the liquid volume fraction. We show how particle capture is determined by the coupling of interstitial liquid flow and network deformation, and present a simple model of the capture process that shows good agreement with our experimental data.

Two of the most important input parameters needed to simulate the processing of continuous fiber laminated composites are the fiber bed permeability and the portion of the autoclave load borne by the consolidating fiber network (compressibility). In this study we have experimentally examined how both these parameter change with resin volume fraction as pressure is applied and consolidation proceeds. For a unidirectional fiber bed, the Kozeny-Carman equation can be used to predict both the transverse (perpendicular to the laminate plies) permeability (Kozeny constant, K′z = 11) and the axial (parallel to the fibers) permeability (Kozeny constant, K′X = 0.57). The axial permeability was found to be dependent on the surface tension of the permeant. For a unidirectionally aligned fiber, the measured transverse permeabilities varied from 1.1 × 10−10 cm2 to 12. × 10−9 cm2 while the axial values varied from 2.1 × 10−9 to 4.4 × 10−8 cm2 for a liquid volume fraction range of 0.25 to 0.5. Axial permeability measurements indicate that the permeability decreases with increasing off-axis angle × (measured from the laminate axial direction). The off-axis permeability behavior can be described by a modified Kozeny-Carman equation. The fiber network compressibility can be described with a logarithmic relation which has been found valid for a large number of consolidated soils.

Aqueous foams continuously age due to fluid drainage and bubble coarsening, which makes it difficult to perform steady-state rheological measurements. Consequently we have developed the foam drainage rheology technique, where perfusion counteracts fluid drainage and bubble replenishment counteracts bubble coarsening during measurement of the shear stresses by a rheometer. We evaluate published power-law and Herschel-Bulkley models and find that parameters derived from emulsion experiments cannot describe our results. We propose a hybrid model, which combines our earlier film-shearing model, where the film thickness depends on liquid volume fraction, with a Herschel-Bulkley shear-rate dependence.

International audience; We present an experimental and numerical study of the osmotic pressure in monodisperse ordered foams as a function of the liquid fraction. The data are compared to previous results obtained for disordered monodisperse and polydisperse concentrated emulsions. Moreover, we report a quantitative investigation of the transition from a bubble close packing to a bcc structure as a function of the liquid volume fraction. These findings are discussed in the context of theoretical models that have been proposed in the literature.

A percolation model of foam mobilization in porous media is developed. This model indicates that there is a minimum pressure gradient or, equivalently, a minimum gas velocity required to initiate mobilization of foam. As a result, for most foam enhanced oil recovery processes, where the surface tension is not low, deep foam penetration depends on propagation of foam formed at a high pressure gradient near the well. Low surface tension makes mobilization of CO2 foams feasible, however, at pressure gradients found throughout much of the formation in a typical field application. The theory further predicts, and data confirm, that the minimum velocity for foam mobilization during steady flow of liquid and gas decreases as injected liquid volume fraction increases. The theory suggests a better strategy for foam generation: alternate injection of small slugs of liquid and gas.

Some two-dimensional (2D) exfoliated zeolites are single- or near single-unit cell thick silicates that can function as molecular sieves. Although they have already found uses as catalysts, adsorbents and membranes precise determination of their thickness and wrinkling is critical as these properties influence their functionality. Here we demonstrate a method to accurately determine the thickness and wrinkles of a 2D zeolite nanosheet by comprehensive 3D mapping of its reciprocal lattice. Since the intensity modulation of a diffraction spot on tilting is a fingerprint of the thickness, and changes in the spot shape are a measure of wrinkling, this mapping is achieved using a large-angle tilt-series of electron diffraction patterns. Application of the method to a 2D zeolite with MFI structure reveals that the exfoliated MFI nanosheet is 1.5 unit cells (3.0 nm) thick and wrinkled anisotropically with up to 0.8 nm average surface roughness. © 2015 Macmillan Publishers Limited.

Gillespie's model for the kinetics of radial spreading of a finite liquid reservoir in a thin porous substrate is corrected to properly account for the time dependence of the position of the advancing meniscus. A similarity solution for the liquid volume fraction within the substrate is obtained using power-law expressions for the dependence of the permeability and the capillary pressure on the liquid volume fraction. It is shown that the asymptotic rate of spreading at long times is independent of the initial conditions.

A new experimental method is presented using fluorescein dye to determine the spatial and temporal variations of the liquid volume fraction in aqueous foams. This method is used for quantitative studies of liquid redistribution (drainage) in three types of experiments: forced, free, and pulsed drainage. Characteristic quantities, such as the drainage velocity, show power-law dependences on experimental parameters that are inconsistent with traditional foam drainage models based on Poiseuille-type flow in the liquid-carrying channels (Plateau borders) of the foam. To obtain a theoretical description, the foam drainage equation is generalized using an energy argument which accounts for viscous dissipation in both the channels and the nodes (or vertices, which are the junctions of four channels) of the liquid network. Good agreement with results for all three types of drainage experiments is found when using this new model in the limit where the dissipation is dominated by the nodes.

A semi-mechanistic model for two phase gas-liquid slug flow proposed recently by Dukler and Hubbard has been modified and extended to apply to the entire intermittent flow regime. Flow predictions of the model proposed in this paper are compared with detailed experimental data recently obtained for an air-oil system. The model requires the use of empirical correlations for the slug velocity and the in situ liquid volume fraction in the slug. In addition, either the slug frequencies or length corresponding to the given design conditions must be known. However, calculated values of average pressure gradient and in situ liquid volume fraction are relatively insensitive to these latter parameters, and in fact, good results are obtained assuming a constant slug length. The paper includes a discussion of the limitations of the proposed model and the expected direction of further study required to extend its mechanistic aspects.

Four correlations for predicting the in situ liquid volume fraction for gas-liquid flow in inclined pipes have been tested against available data from the literature. It is demonstrated that the commonly used correlations of Baker(4) and Flanigan(5) are subject to large errors. It is recommended that the correlation of Guzhov et al(2) be used unless it predicts values of EL less than 0.25. In the latter case, the Lockhart-Martinelli(3) correlation should be used.

Three methods for predicting the in situ liquid volume fraction for the upward flow of gas-liquid mixtures in inclined pipes have been tested against available data from the literature. Combined with the results of an earlier paper, a total of seven methods have been compared. It is demonstrated that for angles of up to 10°, pipeline inclination has little effect on the predicted holdup. Correlations arc recommended for use under specified conditions. On a compare, avec les resultats deja publics, ceux de trois methodes servant a prevoir la fraction du volume de liquide retenu (in situ) lors de l'ecoulement ascendant des melanges de gaz et de liquides dans des tuyaux inclines. Si l'on combine les resultats de la presente etude avec ceux d'un travail precedent, la comparaison embrasse sept methodes. On demontre que, pour des angles allant jusqu'a 10°, l'inclinaison des pipe-lines n'a que pen d'effet sur la retenue prevue. On recommande l'emploi de correlations dans des conditions specifiees.

Experimental data for gas holdup in liquid slugs are reported for two different pipe sizes (2.58 cm and 5.12 cm I.D.). A simple empirical correlation is developed and is shown to be a significant improvement over the only other published correlation proposed by Hubbard (1965). The results of this investigation are important for the development of a mechanistic model for the prediction of pressure drop and holdup for slug flow in pipes.

A basic equation of air-lift pump performance is derived from a simple momentum equation. In the analysis, frictional pressure drop in two-phase flow is expressed by means of liquid volume fraction of the mixture, and slug flow is assumed in order to obtain the relationship between liquid volume fraction and flow rates of both phases. The results predicted by the analysis are compared with experimental data of other investigators as well as of the authors. Good agreement with experimental data is shown in the ranges of 25 mm≤D (inner diameter)≤100 mm, 4 m≤L (length of pipe)≤42 m and 0.4

Using a mechanistic approach, equations are developed to describe the stratified cocurrent flow of gas-liquid mixtures in horizontal pipes. An iterative method is suggested for their solution. Experimental data were collected using air-oil mixtures in a one inch 1. D. by 101 ft. long acrylic pipe. Pressure drop and average in situ liquid volume fraction are presented as a function of the superficial gas velocity and are compared with predicted results from this study and other models reported in the literature. Visual observation of flow patterns and their transitions are indicated on the tentative flow pattern map of Govier and Aziz(1).

The sedimentation of mixtures containing one and two sizes of spherical particles (44 and 62 ..mu..m in diameter) was studied. Radioactive tracing with /sup 57/Co was used to measure the settling velocities. The ratio of the settling velocity U of uniformly sized particles to the velocity predicted to Stokes' law U/sub 0/ was correlated to an expression of the form U/U/sub 0/ = epsilon/sup ..cap alpha../, where epsilon is the liquid volume fraction and ..cap alpha.. is an empirical constant, determined experimentally to be 4.85. No effect of viscosity on the ratio U/U/sub 0/ was observed as the viscosity of the liquid medium was varied from 1x10/sup -3/ to 5x10/sup -3/ Pa.s. The settling velocities of particles in a bimodal mixture were fit by the same correlation; the ratio U/U/sub 0/ was independent of the concentrations of different-sized particles.

The design and proper operation of liquefiers, refrigerators, and equipment incorporating power cycles depend on the knowledge of saturation properties. Accurate saturated liquid densities are also needed for economic storage and custody transfer operations. Also, liquid-vapor density data, including that in the triple point and critical point regions, are important in the development of equations of state originating at the coexistence boundary.