Height Of Medium Research Articles

Experimental Investigation of Matrix Wettability Effects on Water Imbibition in Fractured Artificial Porous Media

Spontaneous water imbibition into the matrix blocks is known as the main mechanism for increased oil recovery from naturally fractured oil reservoirs. The rate of oil recovery and its ultimate value is mostly affected by wettability of the rocks and their pore structure. Oil viscosity also greatly influences the rate of oil recovery.A novel experimental model was utilized to study the imbibition mechanism under different wettability conditions. Matrix blocks made from different grain types and size distributions of glass beads were saturated with two different types of synthetic oil, to mimic the oil-saturated matrixes. The wetting characteristic of the models used in this study were altered by a standard chemical treatment process. Wettability, grain type and size distribution, as well as oleic phase properties, were changed to find the effect of these parameters on oil recovery efficiency.The results revealed that presence of a small fraction of oil-wet grains drastically affects oil recovery by capillary imbibition. A criterion was obtained to describe the effects of wetting property of the matrix blocks on oil recovery efficiency by capillary imbibition. The effect of gravity force, resulting from the density difference between oil in the matrix block and the water in the fracture, was also analyzed using inverse Bond number (NB−1). Application of this dimensionless number was found to be limited by the height of the porous medium. The results also confirm that oil production rate during imbibitions is greatly influenced by oil viscosity.

Effect of drainage height on concentration‐dependent propane dispersion in vapex

AbstractThis article examines the effect of drainage height (i.e. height of saturated porous medium) on concentration‐dependent dispersion coefficient of propane in vapour extraction (Vapex) of heavy oil. For this purpose, Vapex experiments are carried out at 21°C using propane as a solvent at 0.689 MPa pressure for three different drainage heights of the heavy oil medium. Subsequently, the concentration‐dependent dispersion coefficients of propane are determined. The results show that the dispersion coefficient of propane (at all concentrations) in heavy oil increases with the drainage height. © 2011 Canadian Society for Chemical Engineering

Laboratory Investigation of Free Fall Gravity Drainage in Fractured Porous Systems Using Unconsolidated Macromodels

Naturally fractured reservoirs (NFRs) contain a significant amount of the world's oil reserves. Oil recovery by gravity drainage in a NFR strongly depends on the capillary height of the porous medium. Capillarity and gravity forces are usually the major driving forces in NFRs. To address this issue, a series of flow visualization experiments were performed using unconsolidated packed models of rectangular geometry with two fractures on the side. Parametric sensitivity analyses were performed considering effects of different system parameters such as fracture aperture, matrix height and permeability, and fluid viscosity on liquid drainage rate. These experiments enabled us to capture some aspects of the flow communication between matrix block and fracture during gravity drainage. Results from this study showed that the rate of liquid flowing from matrix to fracture is proportional to the difference of liquid levels in the matrix and in the fracture (H f ― H m ). In addition, the characteristic rate and the maximum liquid drainage rate from these fractured models are determined for stable gravity-dominated processes. Also, it was concluded that the characteristic rate depends only on the dimensions of the fracture and properties of the test fluid, and not on the properties of the matrix. For a given fracture―matrix system with different initial liquid saturation conditions, it is observed that the production history can be correlated by plotting the fraction of recoverable liquid as a function of time. Furthermore, ultimate recovery factor and capillary threshold height can be correlated using dimensionless numbers such as the Bond number and the porosity ratio.

Centrifugal compression of soft particle packings: Theory and experiment

An exact method is developed for computing the height of an elastic medium subjected to centrifugal compression, for arbitrary constitutive relation between stress and strain. Example solutions are obtained for power-law media and for cases where the stress diverges at a critical strain--for example as required by packings composed of deformable but incompressible particles. Experimental data are presented for the centrifugal compression of thermo-responsive N-isopropylacrylamide (NIPA) microgel beads in water. For small radial acceleration, the results are consistent with Hertzian elasticity, and are analyzed in terms of the Young elastic modulus of the bead material. For large radial acceleration, the sample compression asymptotes to a value corresponding to a space-filling particle volume fraction of unity. Therefore we conclude that the gel beads are incompressible, and deform without deswelling. In addition, we find that the Young elastic modulus of the particulate gel material scales with cross-link density raised to the power 3.3±0.8, somewhat larger than the Flory expectation.

A Theoretical Study on the 3‐Degree Freedom Geophone Coupling System for Areas with Limestone Outcrops

AbstractThere is a great potential of extremely abundant oil and gas resources in sedimentary basins of marine carbonate in vast areas of South China. However, it is very difficult to make a good geophone coupling in the field work because of large‐area outcrops of hard limestone, which lead to decline of quality of seismic data and serious limit on hydrocarbon exploration there. Now, geophone coupling test is largely blind due to lack of appropriate theoretical guidance. In this paper, in order to understand the transmission mechanism of the geophone‐limestone coupling system, considering that the coupling media such as gesso, clay and so on involved in field seismic data acquisition, we propose a theory of geophone‐limestone 3‐DOF (degrees of freedom) coupling system based on the vibration dynamic concept. The geophone‐limestone coupling system responses are computed with varying parameters of coupling media, geophone spikes and damping. We find that the geophone‐limestone coupling system is a resonance system which has three resonance frequencies. The results show that the resonance frequency can be increased through increasing the elastic modulus of the coupling medium, reducing the area of the underside and the height of the coupling medium, using spikes with lower material density, reducing the height of the spike and increasing the area of the spike's underside. The results also show that the impact of the narrow frequency bands “band pass filtering” can be decreased by increasing the damping of the coupling system properly. Finally, we preliminarily validate the theoretical model of the geophone‐limestone 3‐DOF coupling system through experiments on a shake table.

THREE-DIMENSIONAL SIMULATIONS OF MAGNETIZED SUPERBUBBLES: NEW INSIGHTS INTO THE IMPORTANCE OF MHD EFFECTS ON OBSERVED QUANTITIES

We present three-dimensional magnetohydrodynamic (MHD) simulations of superbubbles, to study the importance of MHD effects in the interpretation of images from recent surveys of the Galactic plane. These simulations focus mainly on atmospheres defined by an exponential density distribution and the Dickey & Lockman density distribution. In each case, the magnetic field is parallel to the Galactic plane and we investigate cases with either infinite scale height (constant magnetic field) or a constant ratio of gas pressure to magnetic pressure. The three-dimensional structure of superbubbles in these simulations is discussed with emphasis on the axial ratio of the cavity as a function of magnetic field strength and the age of the bubble. We investigate systematic errors in the age of the bubble and scale height of the surrounding medium that may be introduced by modeling the data with purely hydrodynamic models. Age estimates derived with symmetric hydrodynamic models fitted to an asymmetric magnetized superbubble can differ by up to a factor of 4, depending on the direction of the line of sight. The scale height of the surrounding medium based on the Kompaneets model may be up to 50% lower than the actual scale height. We also present the first ever predictions of Faraday rotation by a magnetized superbubble based on three-dimensional MHD simulations. We emphasize the importance of MHD effects in the interpretation of observations of superbubbles.

Dispersion of particles by spontaneous interparticle percolation through unconsolidated porous media

We have performed extensive experimental and numerical studies of spontaneous percolation of small beads through an unconsolidated porous media made with large glass beads. In this paper, an experimental setup and a fast "discrete element method" algorithm are presented to deal with large numbers of particles during our interparticle percolation phenomenon studies. In all the experimental and numerical analyses, the size ratio between the moving beads and the stable packing was chosen larger than the geometrical trapping threshold: xi_{c}=(2/sqrt[3]-1);{-1}=6.464... . We measure the longitudinal and transverse dispersion coefficients versus the height of the porous medium or the number of falling small beads. The influence of bead properties such as density, diameter, or restitution coefficients was investigated by using either steel or glass beads. The individual description of these effects and their explanations were made possible by confrontation and coupling between experimental and numerical results. Indeed, with our numerical model, individual analysis of the effects of these mechanical or geometrical parameters were made possible and carried out.

Postharvest Damage of Mangosteen and Quality Grading Using Mechanical and Optical Properties as Indicators

Postharvest damage in fresh mangosteens at wholesale level in Thailand was investigated from April to October 2004. A total of 37.1% of the production yield was rendered inedible by damage during this period; damages included fruit cracking, hardened rinds, rough surfaces, translucent flesh, gummosis and decay. This study focused on a method of predicting damage based on the color of the skin of the affected mangosteen. As a first step, diameter, height, weight, and volume of large, medium, small, and undersize mangosteens were measured. The term, dimension ratio, was introduced as a sizing parameter identifying conventional trade size. The coefficient of static friction of the glossy- and rough-surface mangosteens on plexiglass, plywood, and galvanized steel sheet varied from 0.31 to 0.46. The color of sound and defective fruits was measured in terms of their tristimulus values X, Y, and Z. The corresponding chromaticity coordinates of a mangosteen, x and z, depended on the maturity stage of the fruit while y depended on the type of fruit surface. A ratio was proposed to test the accuracy of predicting internal defects from the color variation between two spots on the surface of the same fruit. The highest percentage of correct prediction was 67.4% with a color ratio of X1 (pink blush color on yellow ground color) to X2 (pink color) that was greater than 1.25.

Developing Nonthermal-Equilibrium Convection in Porous Media With Negligible Fluid Conduction

In certain contemporary technologies, porous media with high solid-phase conductivity are impregnated with low-conductivity fluids, e.g., metal and graphite foam cooled by air. For such cases, an approximate analytical model for the developing heat transfer inside a two-dimensional rectangular porous medium subjected to constant heat flux is presented. The model neglects conduction in the fluid and assumes plug flow. The resulting nonthermal-equilibrium equations are solved for the solid and fluid temperatures by separation of variables. The temperatures decay exponentially as the distance from the heated base increases. The effects of the Biot and Peclet numbers are presented. Fully developed heat-transfer conditions are achieved at an axial distance equal to five times the height of the porous medium, with a constant Nusselt number equal to 3.

Induction of Zone‐Like Liver Function Gradients in HepG2 Cells by Varying Culture Medium Height

In most laboratory-scale mammalian cell cultures, the primary mode of oxygen delivery to cultured cells is by passive diffusion through a thin layer of culture medium, and the height of culture medium chosen may therefore have a significant effect on the phenotype of oxygen-sensitive cell types. Many of the liver functions performed by hepatocytes are thought to be regulated into zones by the local oxygen concentration; of particular interest to in vitro toxicologists, the cytochrome P450 family of detoxification enzymes is known to be preferentially expressed by hepatocytes at low (perivenous) oxygen concentrations. Using an array of different medium heights in a 12-well plate format, we show that the height of culture medium has a significant effect on cytochrome P450 1A1 detoxification activity, glucose metabolism, and cell morphology of HepG2 hepatocellular carcinoma cultures. In particular, cytochrome P450 activity exhibits a maximum at medium heights corresponding to perivenous oxygen concentrations. This work demonstrates that optimizing cell culture performance is not always the same as maximizing oxygen delivery.

Finite Volume Method for Radiation Heat Transfer in Graded Index Medium

Because a ray goes along a curved path determined by the Fermat principle, curved ray tracing is very difficult and complex in a graded index medium. To avoid the complicated and time-consuming computation of curved ray trajectories, a finite volume formulation is developed to solve the radiative-transfer problem in a multidimensional absorbing-emitting-scattering semitransparent graded index medium. Three test problems in radiative transfer are taken as examples to verify this finite volume formulation. The predicted temperature distributions and apparent directional emissivity are determined by the proposed method and compared with data in the references. The results show that the finite volume formulation presented in this paper has a good accuracy in solving the radiative transfer problem in a multidimensional absorbing-emitting-scattering semitransparent graded index medium. Nomenclature A = surface area of cell, m 2 b = asymmetry factor of scattering D = direction cosine integrated over control solid angle Erms = rms error of apparent directional emissivity, defined in Eq. (27) ei = unit outward normal vector at the ith surface of cell volume H = height of medium, m I = radiative intensity, W/m 3 sr Ib = blackbody radiative intensity, W/m 3 sr

Behaviour of torsional Alfven waves and field line resonance on rotating magnetars

Torsional Alfven waves are likely excited with bursts in rotating magnetars. These waves are probably propagated through corotating atmospheres toward a vacuum exterior. We have studied the physical effects of the azimuthal wavenumber and the characteristic height of the plasma medium on wave transmission. In this work, explicit calculations were carried out based on the three-layered cylindrical model. We found that the coupling strength between the internal shear and the external Alfven modes is drastically enhanced, when resonance occurs in the corotating plasma cavity. The spatial structure of the electromagnetic fields in the resonance cavity is also investigated when Alfven waves exhibit resonance.

NOVEL BIOREACTORS FOR OSTEOCHONDRAL TISSUE ENGINEERING

Tissue engineering is a new approach for articular cartilage repair, but the integration of engineered cartilage into the host subchondral bone is a major problem. One approach for solving this problem is to make osteochondral tissue engineering instead of cartilage tissue engineering only. The aim of the present paper was to describe two patented newly designed bioreactors for tissue-engineered osteochondral graft. The first bioreactor is double-chamber bioreactor, which is made of glass and is completely transparent. The whole system consists of one chamber for culture of chondrocytes and the other chamber for osteoblast culture. One important role for this bioreactor is to co-culture osteoblasts and chondrocytes at the same time in a biphasic scaffold. The bioreactor is modified from spinner flasks. The stirring of the magnetic bars provides medium mixing and mechanical stimulations for the cells. The second bioreactor is modified from perfusion chamber. The driven force of the medium flow is produced by siphon phenomenon. The bioreactor is composed with two parts. The first part is a modified siphon tube which can hold the biphasic scaffold for osteochondral tissue engineering. The second part is a medium reservoir bottle, which contains large amount of medium and can connect to multiple siphon tubes at the same time. The medium reservoir bottle is placed higher than the siphon tubes. The gravity will drive medium into the siphon tubes. The siphon phenomenon will make the cell-seeded scaffold covered with the medium. When the height of medium reach the height of outflow tube of the siphon tube, the medium will drain out, and the scaffold will be exposed to the air in incubator, which provides oxygen exposure. Then the gravity will make the medium refill again, the scaffold will be immersed in medium until next cycle of medium drainage out. The curve shape of the siphon tube will prevent backward bacteria contamination. The flow of the medium from reservoir through the siphon tube will produce an effect like traditional perfusion chamber bioreactor; however no power supply is necessary in this system.

Resonant frequency of circular microstrip antennas with and without air gaps

An improved analytical model is presented for calculating the resonant frequency of circular microstrip antennas with and without air gaps. Unlike the previous models, the present one is widely applicable to all patch diameters-from very large to very small compared to the height of the dielectric medium below the patch and also to the substrates covering the entire range of dielectric constants. The computed results for different antenna dimensions and modes of resonance are compared with the experimental values.

Dynamical Evolution and Ionization Structure of an Expanding Superbubble: Application to W4

Recent observations have revealed a superbubble associated with the young stellar cluster OCl 352 near the W4 H II region: a void in H I emission, reported by Normandeau and coworkers, and a bright shell in Hα emission, reported by Dennison and coworkers. We investigate the hypothesis that the bubble is blown by stellar winds from the O-type stars in the association. The Kompaneets approximation is adapted to model a wind-blown bubble in a stratified interstellar medium. We describe some general principles necessary for understanding the dynamics of an expanding bubble and the associated ionization structure in a stratified atmosphere. The Kompaneets model can be used to determine the mean scale height of the ambient medium as well as the age of the bubble. The ionization structure also places constraints on the ambient density near the cluster. We also estimate the surface brightness of the shell and the fraction of ionizing photons that escape the bubble. The prescription we use can be applied to any observed bubble that is blown by the effectively continuous energy output of stellar winds or multiple supernovae. Application to the W4 superbubble shows that the mean scale height of the ambient gas around the cluster is remarkably small, 25 pc for a cluster distance of 2.35 kpc. The age of the bubble is estimated to be about 2.5 Myr, consistent with the notion that the bubble is blown by stellar winds from a very young cluster in which no supernovae have yet occurred.

Propagation of electromagnetic waves in two media separated by a variable interface

The investigation of the propagation of electromagnetic waves in two media separated by a variable interface has required the use of the imaging space of a Hankel transformation. The reversal of such a transformation produces an integral representation, which in this case has proved to be valid for all frequencies. Moreover, no depolarization appears in the field as long as the variation in the interface remains small and is directly dependent on the height of the second medium.

Hypoxia in radiobiology.

The importance of hypoxia in radiobiology and radiotherapy continues to occupy much space in this journal (Littbrand and Revesz, 1969; Berry, Hall and Cavanagh, 1970). In spite of the excellent review by Boag (1969) we feel the pitfalls, namely: (a) variation in height of medium with its subsequent effect on oxygen diffusion and cell numbers; (b) the diffusion and respiration of oxygen dissolved in medium; and (c) the radiation consumption of oxygen, need emphasising further. Chapman, Sturrock, Boag and Crookall (1970) describe some of these difficulties, especially the production of anoxia with cells attached to polystyrene Petri dishes and we, in this laboratory, have encountered similar problems with “K” value estimation for mammalian cells.

On the nature of equatorial spreadF

Ionospheric propagation via scattering from the F region was sought at 50 Mc/s over a transequatorial path (with midpoint near Huancayo, Peru) employing a 2580-km transmitter-receiver separation. Propagation via F scatter was present over this path about 10 per cent of the time, though only at night. A condition closely related to the occurrence of F scatter was the presence of equatorial spread-F configurations on the Huancayo ionograms. The height of the propagation medium supporting this F scatter was usually identifiable with the lowest height of the associated equatorial spread F on the ionograms. On the basis of an interpretation of experimental results, equatorial spread F is shown to arise from scattering by relatively thin sheets of irregularities in electron density which occur at the bottom of the F layer or as much as 100 km lower. The thickness of these patches is estimated at the order of 50 km. The scattering irregularities comprising these patches are found to be elongated along the earth's magnetic lines of force. Electron irregularities of scale 10 meters or smaller measured in at least one dimension transverse to the magnetic field lines, and 1000 meters or longer measured along the magnetic field lines, are shown to exist as high as 450 km in the nocturnal equatorial F region during equatorial spread-F conditions. Equatorial spread-F echoes observed at Huancayo are demonstrated to be arriving at all elevation angles in the magnetic east-west plane. The geographical extension of a given scattering sheet in the magnetic east-west direction was at times as great as 1000 km. An observational procedure is suggested for distinguishing two fundamental varieties of spread-F echoes appearing on the equatorial ionograms. A necessary condition, that the contours of mean electron density be parallel to the magnetic lines of force, is proposed as a controlling factor for the occurrence of spread F in the equatorial ionosphere.