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  • 1
    Electronic Resource
    Electronic Resource
    Simple Lagrangian formulation of bubbly flow in a turbulent boundary layer (bubbly boundary layer flow) (1997)
    Springer
    Journal of marine science and technology 2 (1997), S. 1-11 
    Details
    ISSN: 1437-8213
    Keywords: two-phase flow ; micro-bubble ; turbulent boundary layer ; Monte Carlo method ; mixing length
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract For the theoretical consideration of a system for reducing skin friction, a mathematical model was derived to represent, in a two-phase field, the effect on skin friction of the injection of micro air bubbles into the turbulent boundary layer of a liquid stream. Based on the Lagrangian method, the equation of motion governing a single bubble was derived. The random motion of bubbles in a field initially devoid of bubbles was then traced in three dimensions to estimate void fraction distributions across sections of the flow channel, and to determine local bubble behavior. The liquid phase was modeled on the principle of mixing length. Assuming that the force exerted on the liquid phase was equal to the fluid drag generated by bubble slip, an equation was derived to express the reduction in turbulent shear stress. Corroborating experimental data were obtained from tests using a cavitation tunnel equipped with a slit in the ceiling from which bubbly water was injected. The measurement data provided qualitative substantiation of the trend shown by the calculated results with regard to the skin friction ratio between cases with and without bubble injection as function of the distance downstream from the point of bubble injection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01245932
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of hydrodynamic forces on the pressure-difference equation (1994)
    Springer
    Transport in porous media 17 (1994), S. 133-144 
    Details
    ISSN: 1573-1634
    Keywords: Pressure-difference equation ; immiscible ; two-phase flow ; hydrodynamic forces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Because of the influence of hydrodynamic forces, the difference in macroscopic pressure which exists, at static equilibrium, between two immiscible phases located in a porous medium may be different from that which pertains during flow. In this paper, the concept of relative pressure difference, together with a new pressure-difference equation, is used to investigate the impact that the hydrodynamic forces have on the difference in macroscopic pressure which pertains when two immiscible fluids flow simultaneously through a homogeneous, water-wet porous medium. This investigation reveals that, in general, the equation defining the difference in pressure between two flowing phases must include a term which takes proper account of the hydrodynamic effects. Moreover, it is pointed out that, while neglect of the hydrodynamic effects introduces only a small amount of error when the two fluids are flowing cocurrently, such neglect is not permissible during steady-state, countercurrent flow. This is because failure to include the impact of the hydrodynamic effects in the latter case makes it impossible to explain the pressure behaviour observed in steady-state, countercurrent flow. Finally, the results of this investigation are used as a basis for arguing that, during steady-state, countercurrent flow, saturation is uniform, as is the case of steady-state, cocurrent flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00624729
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  • 3
    Electronic Resource
    Electronic Resource
    Vertical two-phase flow in porous media (1992)
    Springer
    Transport in porous media 8 (1992), S. 99-131 
    Details
    ISSN: 1573-1634
    Keywords: Characteristic ; wavespeed ; shock ; expansion fan ; Rankine-Hugoniot equations ; entropy inequality ; two-phase flow ; counterflow ; saturation ; pressure ; convection ; diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: abstract New concepts are introduced to describe single-component two-phase flow under gravity. The phases can flow simultaneously in opposite directions (counterflow), but information travels either up or down, depending on the sign of the wavespeedC. Wavespeed, saturation and other quantities are defined on a two-sheeted surface over the mass-energy flow plane, the sheets overlapping in the counterflow region. A saturation shock is represented as an instantaneous displacement along a line of constant volume fluxJ Q in the flow plane. Most shocks are of the wetting type, that is, they leave the environment more saturated after their passage. When flow is horizontal all shocks are wetting, but it is a feature of vertical two-phase flow that for sufficiently small mass and energy flows there also exist drying shocks associated with lower final saturations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617113
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  • 4
    Electronic Resource
    Electronic Resource
    An Upgraded Viscous Coupling Measurement Methodology (1997)
    Springer
    Transport in porous media 28 (1997), S. 221-231 
    Details
    ISSN: 1573-1634
    Keywords: viscous coupling ; transport processes ; relative permeablity ; Onsanger relationship ; transport coefficients ; two-phase flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract In this Note, suggestions are presented about simple but usually ignored ways to enhance the reliability and utility of the otherwise interesting procedures recently studied (e.g. by Zarcone and Lenormand), and independently by Dullien and Dong for obtaining needed information about the relative importance of the role played by viscous coupling phenomena during multiphase flow processes that occur in and the interstices of natural porous media systems. This is done now because of the persistence of so many perplexing questions and contradicting opinions about what has been a controversial subject ever since the appearance of Yuster's watershed paper in 1951. Here, the belief held by at least a few of the currently publishing authorities is embraced, namely that viscous coupling issues will never be fully settled until the indications of the underlying theoretical interpretations can be fully confirmed by laboratory observations, hence a disclosure of even modest ways to achieve data acquisition enhancements is the motivation for what is written in what follows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006596830724
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  • 5
    Electronic Resource
    Electronic Resource
    An Alternative Description of Viscous Coupling in Two-Phase Flow through Porous Media (1997)
    Springer
    Transport in porous media 28 (1997), S. 205-219 
    Details
    ISSN: 1573-1634
    Keywords: two-phase flow ; viscous coupling ; Cocurrent flow ; counter current flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A new formalism is developed to describe the viscous coupling phenomena between two immiscible, flowing fluids in porous media. The formulation is based on the notation of ‘two-phase mixture’ in which the relative motion between an individual phase and the mixture in porous media can be described by a diffusion equation. The present formulation is derived from Darcy's law with cross-terms without making further approximations. However, the new formulation requires fewer effective parameters to be determined experimentally, thus offering a more viable tool for the study of two-phase flow dynamics with viscous coupling in porous media. Moreover, it is found that no new term appears in the present model in cases with and without viscous coupling; instead, the incorporation of viscous coupling only modifies the effective parameters. It can thus be concluded that viscous coupling does not represent a fundamentally new phenomenon within the framework of the present formulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006514204336
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  • 6
    Electronic Resource
    Electronic Resource
    On Vaporizing Water Flow in Hot Sub-Vertical Rock Fractures (1997)
    Springer
    Transport in porous media 28 (1997), S. 335-372 
    Details
    ISSN: 1573-1634
    Keywords: heterogeneous fractures ; preferential flow paths ; two-phase flow ; boiling and condensation ; vapor-dominated geothermal reservoirs ; nuclear waste disposal ; numerical simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Water injection into unsaturated fractured rock at above-boiling temperatures gives rise to complex fluid flow and heat transfer processes. Examples include water injection into depleted vapor-dominated geothermal reservoirs, and emplacement of heat-generating nuclear wastes in unsaturated fractured rock. We conceptualize fractures as two-dimensional heterogeneous porous media, and use geostatistical techniques to generate synthetic permeability distributions in the fracture plane. Water flow in hot high-angle fractures is simulated numerically, taking into account the combined action of gravity, capillary, and pressure forces, and conductive heat transfer from the wall rocks which gives rise to strong vaporization. In heterogeneous fractures boiling plumes are found to have dendritic shapes, and to be subject to strong lateral flow effects. Fractures with spatially-averaged homogeneous permeabilities tend to give poor approximations for vaporization behavior and liquid migration patterns. Depending on water flow rates, rock temperature, and fracture permeability, liquid water can migrate considerable distances through fractured rock that is at above-boiling temperatures and be only partially vaporized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006570702193
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  • 7
    Electronic Resource
    Electronic Resource
    The Motion of Long Bubbles in a Network of Tubes (2000)
    Springer
    Transport in porous media 40 (2000), S. 201-218 
    Details
    ISSN: 1573-1634
    Keywords: two-phase flow ; bubbles ; network simulation ; effective permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The motion and interaction of discrete bubbles in porous materials is studied numerically using a network model. The goal is to extend analytical results for the motion of bubbles through a single straight tube to a more ‘realistic’ geometry for porous materials, modeled here as a planar network of straight tubes of different radii. The problem is characterized by two dimensionless parameters, the capillary number (Ca) and the volume fraction of bubbles (φ); results are characterized by determining the effective permeability of the network and the mean residence time of bubbles in the material. The simulations indicate that at low volume fraction most of the bubbles follow a limited number of high-flow pathways through the network. In this case the predictions of our simulations can be approximated by a simple analytical model. Bubbles interact with each other because their presence changes the local resistance to flow in individual tubes. As φ increases, interactions between individual bubbles become important resulting in a wider range of residence times in the porous material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006697532629
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of Precursor Wetting Films in Immiscible Displacement Through Porous Media (2000)
    Springer
    Transport in porous media 38 (2000), S. 291-317 
    Details
    ISSN: 1573-1634
    Keywords: wetting film ; pinch-off ; immiscible displacement ; two-phase flow ; porous media ; oil recovery ; soil remediation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A computer-aided simulator of immiscible displacement in strongly water-wet consolidated porous media that takes into account the effects of the wetting films is developed. The porous medium is modeled as a three-dimensional network of randomly sized unit cells of the constricted-tube type. Precursor wetting films are assumed to advance through the microroughness of the pore walls. Two types of pore wall microroughness are considered. In the first type of microroughness, the film advances quickly, driven by capillary pressure. In the second type, the meniscus moves relatively slowly, driven by local bulk pressure differences. In the latter case, the wetting film often forms a collar that squeezes the thread of oil causing oil disconnection. Each pore is assumed to have either one of the aforementioned microroughness types, or both. The type of microroughness in each pore is assigned randomly. The simulator is used to predict the residual oil saturation as a function of the pertinent parameters (capillary number, viscosity ratio, fraction of pores with each type of wall microroughness). These results are compared with those obtained in the absence of wetting films. It is found that wetting films cause substantial increase of the residual oil saturation. Furthermore, the action of the wetting films causes an increase of the mean volume of the residual oil ganglia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006557114996
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  • 9
    Electronic Resource
    Electronic Resource
    Lattice-Boltzmann simulations of flow through Fontainebleau sandstone (1995)
    Springer
    Transport in porous media 20 (1995), S. 3-20 
    Details
    ISSN: 1573-1634
    Keywords: lattice-Boltzmann simulations ; single-phase flow ; two-phase flow ; Fontainebleau sandstone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We report preliminary results from simulations of single-phase and two-phase flow through three-dimensional tomographic reconstructions of Fontainebleau sandstone. The simulations are performed with the lattice-Boltzmann method, a variant of lattice-gas cellular-automation models of fluid mechanics. Simulations of single-phase flow on a sample of linear size 0.2 cm yield a calculated permeability in the range 1.0–1.5 darcys, depending on direction, which compares qualitatively well with a laboratory measurement of 1.3 darcys on a sample approximately an order of magnitude larger. The sensitivity of permeability calculations to sample size, grid resolution, and choice of model parameters is quantified empirically. We also present a qualitative study of immiscible two-phase flow in a sample of linear size 0.05 cm; simulations of both drainage and imbibition are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616923
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  • 10
    Electronic Resource
    Electronic Resource
    Generalized relative permeability coefficients during steady-state two-phase flow in porous media, and correlation with the flow mechanisms (1995)
    Springer
    Transport in porous media 20 (1995), S. 135-168 
    Details
    ISSN: 1573-1634
    Keywords: two-phase flow ; relative permeabilities ; ganglion dynamics ; viscous coupling ; coupling indices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A parametric experimental investigation of the coupling effects during steady-state two-phase flow in porous media was carried out using a large model pore network of the chamber-and-throat type, etched in glass. The wetting phase saturation,S 1, the capillary number,Ca, and the viscosity ratio,k, were changed systematically, whereas the wettability (contact angleθ e ), the coalescence factorCo, and the geometrical and topological parameters were kept constant. The fluid flow rate and the pressure drop were measured independently for each fluid. During each experiment, the pore-scale flow mechanisms were observed and videorecorded, and the mean water saturation was determined with image analysis. Conventional relative permeability, as well as generalized relative permeability coefficients (with the viscous coupling terms taken explicitly into account) were determined with a new method that is based on a B-spline functional representation combined with standard constrained optimization techniques. A simple relationship between the conventional relative permeabilities and the generalized relative permeability coefficients is established based on several experimental sets. The viscous coupling (off-diagonal) coefficients are found to be comparable in magnitude to the direct (diagonal) coefficients over board ranges of the flow parameter values. The off-diagonal coefficients (k rij /Μ j ) are found to be unequal, and this is explained by the fact that, in the class of flows under consideration, microscopic reversibility does not hold and thus the Onsager-Casimir reciprocal relation does not apply. Thecoupling indices are introduced here; they are defined so that the magnitude of each coupling index is the measure of the contribution of the coupling effects to the flow rate of the corresponding fluid. A correlation of the coupling indices with the underlying flow mechanisms and the pertinent flow parameters is established.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616928
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