Porous media, propagation

Compared with the use of arbitrary grid interfaces in combination with reduced-order flow models, the porous medium approach allows one to deal with an even larger multitude of micro channels. Furthermore, for comparatively simple geometries with only a limited number of channels, it represents a simple way to provide qualitative estimates of the flow distribution. However, as a coarse-grained description it does not reach the level of accuracy as reduced-order models. Compared with the macromodel approach as propagated by Commenge et al, the porous medium approach has a broader scope of applicability and can also be applied when recirculation zones appear in the flow distribution chamber. However, the macromodel approach is computationally less expensive and can ideally be used for optimization studies. 

Biot M. A. (1956) Theory of propagation of elastic waves in a fluid-saturated porous medium. Low frequency range. Journal of Acoustical Society of America 28, 168-191... 

When the mobility ratio is greater than one, the front between the displaced and displacing fluids is unstable if the porous medium is sufficiently wide (> 10 cm) to allow the formation and propagation of viscous fingers. The lower viscosity fluid channels or "fingers" through the displaced fluid, leaving much of it uncontacted. (See... 

Certain dilute lamellar liquid crystalline phases having relatively low apparent viscosities can propagate through this porous medium micromodel without plugging it. Their behavior followed the trends established with isotropic phases. 

A model of filtration combustion in a thin porous layer, immersed in a bath of gaseous reactant, has also been investigated (Shkadinskii et al, 1992a). In this case, only filtration of gas from the surroundings to the sample, normal to the direction of combustion propagation (cross-flow filtration), should be considered. New pulsating instabilities associated with the gas-solid chemical reaction and mass transfer of gas to the porous medium were identified. 

Aldushin, A. P., and Sepliarskii, B. S., Propagation of waves of exothermic reaction in porous medium during gas blow-through. Phys. Dokl., 23,483 (1978b). 

A promising method of controlling and evaluating the structural parameters of plastic foams is the acoustic (ultrasonic) pulse method This method is based on the propagation of elastic waves in a porous medium depending on shape, distribution and volumetric content of the GSE. 

In oil recovery processes, the formation of an oil bank is very important for an efficient oil displacement process in porous media. This was established from studies on the injection of an artificial oil bank followed by the surfactant formulation which can produce ultralow interfacial tension with the injected oil. We observed that the oil recovery increased considerably and the residual oil saturation decreased with the injection of an oil bank as compared to the same studies carried out in the absence of an injected oil bank (54). Figure 17 schematically represents the oil bank formation and its propagation in porous media, which is analogous to the snowball effect. If an early oil bank is formed then it moves through the porous medium accumulating additional oil ganglia resulting in an excellent oil recovery, whereas a late oil bank formation will result in a poor oil recovery. 

To determine the effect of a pressure field, resulting from cavitation bubbles compressing, on the penetration of a melt into a capillary channel of a filter, one should estimate the character of the pressure impulse propagation through the capillary. The mechanism of the flow is somewhat different under conditions of fine filtration of a melt through a porous medium (a filter from multilayer fiberglass with a cell of 0.6 x 0.6 or 0.4 x 0.4 mm in size) with rather short (about several mm) but complexly curved channels, but the main conditions remain. 

Another effect of decreasing the reaction rate should be to make the probability of propagating any one channel more nearly equal. In the transport-controlled case, branching of channels may occur, but one of the channels will quickly dominate at the expense of the other because of the efficiency of reactive flow capture. In the kinetic rate-con trolled case, any one channel will be less able to capture flow from another. Therefore, in a porous medium with a random distribution of permeability, we expect that the degree of branching should be greater in the kinetic rate-controlled case. 

If the porous medium is liquid saturated, the low-frequency, long-wave length PD wave propagates conservatively (low energy losses), just as a tsunami propagates great distances with little energy loss. Furthermore, it is kept within the porous and permeable zone and does not transit into impermeable or low permeability rocks because the liquids cannot move into and out of the pores at a sufficient velocity. 

The motions of a plane wave propagating through a porous medium may be described as follows ... 

Will there be a selective adsorption or chromatographic separation of the surfactant mixture as it propagates through the porous medium ... 

Gelfand, B.E., Gubin, S.A., et al., "Study of Special Features of Propagation and Reflection of Pressure Waves in a Porous Medium," Soviet Phvsics-Applied Mathematics Technical Physics. Vol., No. 6, 1975, pp. 74-77. 

LINEAR STABILITY OF A PLANAR REVERSE COMBUSTION FRONT PROPAGATING THROUGH A POROUS MEDIUM GAS-SOLID COMBUSTION MODEL... 

The model envisions a planar combustion front propagating through an infinite isotropic combustible porous medium. Figure 1 depicts the situation and the assumed temperature, O2 and pressure profiles. Important assumptions in the model are described below, and are discussed in more detail in a later section. 

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