Dissertationen: „Porous jump“

1

Shin, Youn-Ok 1971. „Vapor and liquid equilibria in porous media“. Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21323.

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The alteration of the vapor and liquid equilibrium (VLE) of volatile organic mixtures by using porous media at the liquid-vapor interface was studied. Kelvin, assuming ideal behavior of fluids, first introduced the vapor pressure of liquid over a meniscus as a function of its surface tension and the radius of the curvature. A thermodynamic model (SSmod model) predicting the VLE of non-ideal organic mixtures in porous media was developed as a function of pore sizes based on the pressure equations available in literature. The model was used to predict the VLE of two aqueous alcohol solutions, ethanol-water and propanol-water, and two binary alcohol solutions, methanol-isopropanol and ethanol-octane. Experiments were conducted using sintered metal and fritted glass plates as porous media and compared with the model predictions. The model predictions for the actual pore diameters tested showed good agreement with the experimental results.

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2

Khan, Zafar Hayat. „Modelling moving evaporation fronts in porous media“. Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16850.

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Understanding vertical heat transfer and through flow in porous media such as geothermal reservoirs is of great interest. In a geothermal system, a denser layer of liquid water may overlie a less dense layer of water vapour. Vertical and horizontal thermal diffusion stabilises such configurations, but the buoyancy contrast can cause instability. In this study, the mechanisms contributing to the stability and instability of such systems are analysed using a separate-phase model with a sharp interface be- tween liquid and vapour. The governing equations representing incompressibility, Darcy’s law and energy conservation for each phase are linearised about suitable base states and the stability of these states is investigated. We have considered two different thermal boundary conditions, both with and without a vertical through- flow. In the first case, the boundaries above and below the layer of interest are assumed to be isothermal. We found that due to the competition between thermal and hydrostatic effects, the liquid–vapour interface may have multiple positions. A two-dimensional linear stability analysis of these basic states shows that the Rayleigh–Taylor mechanism is the dominant contributor to instability, but that there are circumstances under which the basic state may be stable, especially when the front is close to one of the boundaries. In the second case, a constant heat flux is imposed at the liquid boundary and a fixed temperature at the vapour boundary. We have shown that competition between the effects of cooling and the viscosity difference between the fluid phases causes multiple liquid-vapour front positions, whether or not gravity is considered. The stability analysis has shown that along with the Rayleigh-Taylor (buoyancy- driven) mechanism, a Saffman-Taylor viscous fingering mechanism can also play an important rule in the transition to instability.

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3

Makris, Aristidis. „The propagation of gaseous detonations in porous media“. Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41700.

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The propagation of a gaseous detonation wave into a porous medium has been studied experimentally and theoretically. The porous medium is composed of inert spheres of equal diameter contained within a detonation tube. The propagation mechanisms were elucidated by means of high-speed Schlieren and open shutter photography of the wave-particle interactions in 2-D obstacle arrays, to simulate the phenomenon in actual porous media. It is found that a Chapman-Jouguet (CJ) detonation can transmit into a porous medium filled with detonable gas and continue to propagate as a quasi-steady combustion wave. There exists a continuous spectrum of averaged combustion wave velocities ($ rm0.3 le V/V sb{CJ} le 1)$ spanning the lean and rich propagation limits and exhibiting a maximum value at the most sensitive composition. A decrease in the particle size of the medium has the effect of narrowing the detonability range and reducing the velocity for a given mixture. It is clearly demonstrated that the propagation phenomenon, and thus the velocity, is governed by the relative length scales of the detonable mixture (critical tube diameter $ rm d sb{c})$ and of the porous medium (average pore size $ rm d sb{p}).$ An empirical correlation was established between the wave velocity (V/V$ sb{CJ})$ and the properties of the system, via the ratio $ rm d sb{c}/d sb{p}.$ The global wave propagation mechanism, for the major part of the possible range of velocities, i.e., $ rm V/V sb{CJ} ge 0.5,$ consists of periodic phases of detonation failure by diffraction around obstacles (i.e., the particles), followed by local reinitiation at detonative Mach stems formed by shock wave-particle interactions. This is essentially identical to the propagation of "quasidetonations" studied by Teodorczyk et al. (1988, 1991), in linear arrangements of obstacles. When local reinitiation of detonation is not possible, ignition transfer in the pores is controlled by the turbulent jetting of hot combustion produc

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4

Foroutan, Rana. „Intake shape factors for transversely isotropic porous media“. Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29536.

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The study of flow of water through porous medium is important in geotechnical and geoenvironmental engineering. For determining the in situ hydraulic conductivity characteristics of porous media, one of the most convenient and popular methods is the cased borehole technique. In this method, water is allowed to enter the excavated region of the cased borehole inserted into the ground. The rate of rise of water in the casing is then used to estimate the hydraulic conductivity characteristics of the porous medium in the vicinity of the entry point. When the porous medium has isotropic hydraulic conductivity characteristics, the "intake shape factor", which influences the flow rate is solely dependent on the geometrical arrangement of the intake region. When the intake region is located in a porous medium with transversely isotropic hydraulic conductivity characteristics, the flow rate is influenced by both the geometrical characteristics of the intake region and the mismatch in the directional hydraulic conductivity. The objective of the thesis is to investigate certain aspects of water flow in porous geomaterials that display hydraulic anisotropy. The thesis also characterizes the flow rate for entry points that are located in soils with transversely isotropic hydraulic conductivity.
This study presents the application of computational procedures, based on finite element techniques, for the determination of the intake characteristics of a cylindrical intake located in a hydraulically transversely isotropic porous medium. Numerical results presented, illustrate the situations where the separate hydraulic conductivities can be estimated by a suitable alteration in the geometrical characteristics of the cylindrical intake. An approximate relationship is developed for estimation of the intake shape factor of cylindrical entry regions without a repeat of detailed finite element computations.

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5

Narayan, Shankar B. „Measurement of diffusion and adsorption in porous adsorbents“. Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73968.

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6

Galbraith, Graham H. „Heat and mass transfer within porous building materials“. Thesis, University of Strathclyde, 1992. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21508.

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The thermal and structural performance of building elements can be significantly impaired by the presence of excess moisture. At present, designers have available only simplistic steady-state techniques to predict such effects, for example that presented by Glaser in 1959. These simple models recognise moisture transport in vapour form only and do not allow information on material moisture content to be obtained directly. They are also based on the assumption that the material transport properties are independent of the prevailing environmental conditions, whereas they are in fact complex functions of parameters such as relative humidity. This research has been carried out to develop a set of model equations which account for both liquid and vapour transfer through porous structures, and which enable material moisture content profiles to be produced. The equations generated in this work are transient and enable the effects of moisture and thermal capacity to be considered. An experimental investigation has also been carried out to produce a methodology which can be used to obtain the required material properties. These equations and material properties have been combined with realistic boundary conditions to produce a finite difference model which enables simple wall structures to be analysed in terms of temperature, vapour pressure, relative humidity, moisture content and moisture flow rate. The use of this FORTRAN 77 computer code is illustrated by application to traditional and timber-framed wall constructions. The results illustrate the applicability and flexibility of such an approach and confirm the importance of its further development in the future.

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7

Corson, Lindsey Thomson. „Geochemical effects on natural convection in porous media“. Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18197.

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We describe a model of buoyancy-driven flow in a saturated reactive porous medium, the porosity and permeability of which evolve through precipitation and dissolution as a mineral is lost or gained from the pore fluid. We consider two scenarios: convection driven solely by solutally induced buoyancy effects with a vertically varying equilibrium solubility, and convection driven by a combination of thermally and solutally induced buoyancy effects where the solubility of the dissolved component depends on the temperature. In both cases we characterise the onset of convection using linear stability analysis, and explore the further development of the coupled reaction-convection system numerically. For solutal convection, at low Rayleigh numbers the effect of the reaction-permeability feedback is shown to be destabilising, while at higher Rayleigh numbers the porosity evolution has a stabilising effect. Over longer timescales, reaction-permeability feedback triggers secondary instabilities in quasi-steady convective circulation, leading to rapid reversals in the direction of circulation. Over very long timescales, characteristic patterns of porosity emerge, including horizontal layering as well as the development of vertical chimneys of enhanced porosity. For thermosolutal convection we find that, when the system is solutally unstable, the behaviour of the system is qualitatively the same as for solutal convection, regardless of whether the system is thermally stable or unstable. However, new, interesting behaviour is seen when the system is solutally stable. The long-term evolution of the porous layer depends on whether the underlying thermal or solutal gradient dominates. When the solutal gradient dominates, the reaction-permeability feedback triggers a secondary instability, resulting in the lateral migration of the concentration and temperature elds and rapid reversals in the direction of circulation. However, when the thermal gradient dominates, the thermal gradient dominates, the reation-permeability feedback tends to suppress the circulation, although it re-emerges after a long quiescent.

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8

McKenzie, Kimberly. „Skeletal distribution of bisphosphonate after elution from porous implants“. Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86584.

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Skeletal attachment to an implant can be enhanced by locally delivering the bisphosphonate zoledronic acid from an implant. The purpose of this study was to map the skeletal distribution of locally delivered zoledronic acid.
A porous tantalum implant coated with hydroxyapatite and 14C-labelled zoledronic acid was implanted into the left femur of three dogs. After one year bone samples were taken from sites near to and distant from the implant. The amount of drug in each sample was determined using liquid scintillation counting and its distribution in peri-implant bone was additionally demonstrated using autoradiography.
All distant skeletal bone samples contained 11.8 ng/g zoledronic acid or less whereas bone immediately adjacent to the implant contained 388 ng/g. There was a 10-fold to 100-fold decrease in zoledronic acid content in bone just 1 or 2 cm away from the implant. Autoradiographs of thin bone-implant sections and bone sections revealed the highest concentration of zoledronic acid within and immediately adjacent to the implant. These data demonstrated for the first time that zoledronic acid eluted from an implant remained mainly local, with minimal systemic distribution.
L'attachement squelettique à un implant peut être amélioré en apportant de l'acide zoledronique de bisphosphonate de façon locale depuis l'implant. Le but de la présente étude était d'évaluer la distribution squelettique de l'acide zoledronique localement généré.
Un implant poreux de tantale enduit d'hydroxyapatite et d'acide 14C zoledronique a été implanté dans le fémur gauche de trois chiens. Après un an, plusieurs échantillons d'os, proches et éloignés de l'implant, ont été prélevés. La quantité de médicament dans chaque échantillon a ensuite été déterminée en utilisant un comptage par scintillation liquide; la distribution dans l'os autour de l'implant a aussi été demontré par autoradiographie.
Tous les échantillons prélevés loin de l'implant contenaient 11.8 ng/g d'acide zoledronique ou moins alors que ceux prélevés immédiatement à côté de l'implant contenaient 388 ng/g. Une diminution de 10 à 100 fois dans la teneur en acide zoledronique a été notée dans l'os situé seulement à 1 ou 2 cm de l'implant. Les autoradiographies des sections minces d'os-implant et des sections d'os ont indiqué que la concentration la plus élevée en acide zoledronique se situait dans l'implant et immédiatement à côté. Ces données démontrent, pour la première fois, que l'acide zoledronique élué d'un implant reste principalement local, avec une distribution systémique minimale.

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9

Burel, Thomas. „Investigation of smooth contact angle treatment in porous media“. Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30826.

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Some of the key challenges faced in the oil/gas extraction and carbon dioxide injection/storage processes are the presence of complex geometries and the significant effect of the capillary forces which arise at low capillary numbers. Therefore, the contact angle needs to be carefully treated. Mesoscopic techniques such as lattice Boltzmann methods are capable of dealing with lower capillary numbers as compared to the Navier-Stokes solvers, which can also implicitly capture the interface between two fluids. To investigate immiscible two-phase ows at low Reynolds and capillary numbers (Re < 1 and Ca < 1), the colour-fluid model is used i.e. the Rothman-Keller model [1]. This model includes two steps: a perturbation operator from Lishchuk et al [2] (the continuum surface force [3]) or Gunstensen et al [4] approaches and a recolouring operator [5]. However, the lattice Boltzmann implementation employs a Cartesian grid for domain discretisation that is unable to conform with curved surfaces. It misinterprets those curved surfaces as a series of stair-like patterns. On those surfaces, a non-physical contact angle could be defined which may lead to a numerically flooding of the wetting fluid inside the droplet for a non-spreading drop or outside for a spreading droplet. To remove this unphysical behaviour and take into account the flow field effect on the contact angle, interpolation techniques are employed to estimate the real contact angle on the 'stairs' boundaries. We also employ extrapolations to obtain more accurate density on concave corners, thus the grid resolution can be reduced. After the code is numerically validated on static droplets, on droplets deformed under a simple shear, and on simple geometries. Finally, we perform simulations on a Berea sandstone sample [6] to understand dynamics behaviour of immiscible fluids in porous media.

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10

Du, Xiangdong 1967. „Scaling laws in permeability and thermoelasticity of random media“. Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102973.

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Under consideration is the finite-size scaling of two thermomechanical responses of random heterogeneous materials. Stochastic mechanics is applied here to the modeling of heterogeneous materials in order to construct the constitutive relations. Such relations (e.g. Hooke's Law in elasticity or Fourier's Law in heat transfer) are well-established under spatial homogeneity assumption of continuum mechanics, where the Representative Volume Element (RVE) is the fundamental concept. The key question is what is the size L of RVE? According to the separation of scales assumption, L must be bounded according to d<L<<LMacro where d is the microscale (or average size of heterogeneity), and LMacro is the macroscale of a continuum mechanics problem. Statistically, for spatially ergodic heterogeneous materials, when the mesoscale is equal to or bigger than the scale of the RVE, the elements of the material can be considered homogenized. In order to attain the said homogenization, two conditions must be satisfied: (a) the microstructure's statistics must be spatially homogeneous and ergodic; and (b) the material's effective constitutive response must be the same under uniform boundary conditions of essential (Dirichlet) and natural (Neumann) types.
In the first part of this work, the finite-size scaling trend to RVE of the Darcy law for Stokesian flow is studied for the case of random porous media, without invoking any periodic structure assumptions, but only assuming the microstructure's statistics to be spatially homogeneous and ergodic. By analogy to the existing methodology in thermomechanics of solid random media, the Hill-Mandel condition for the Darcy flow velocity and pressure gradient fields was first formulated. Under uniform essential and natural boundary conditions, two variational principles are developed based on minimum potential energy and complementary energy. Then, the partitioning method was applied, leading to scale dependent hierarchies on effective (RVE level) permeability. The proof shows that the ensemble average of permeability has an upper bound under essential boundary conditions and a lower bound under uniform natural boundary conditions.
To quantitatively assess the scaling convergence towards the RVE, these hierarchical trends were numerically obtained for various porosities of random disk systems, where the disk centers were generated by a planar Poisson process with inhibition. Overall, the results showed that the higher the density of random disks---or, equivalently, the narrower the micro-channels in the system---the smaller the size of RVE pertaining to the Darcy law.
In the second part of this work, the finite-size scaling of effective thermoelastic properties of random microstructures were considered from Statistical to Representative Volume Element (RVE). Similarly, under the assumption that the microstructure's statistics are spatially homogeneous and ergodic, the SVE is set-up on a mesoscale, i.e. any scale finite relative to the microstructural length scale. The Hill condition generalized to thermoelasticity dictates uniform essential and natural boundary conditions, which, with the help of two variational principles, led to scale dependent hierarchies of mesoscale bounds on effective (RVE level) properties: thermal expansion strain coefficient and stress coefficient, effective stiffness, and specific heats. Due to the presence of a non-quadratic term in the energy formulas, the mesoscale bounds for the thermal expansion are more complicated than those for the stiffness tensor and the heat capacity. To quantitatively assess the scaling trend towards the RVE, the hierarchies are computed for a planar matrix-inclusion composite, with inclusions (of circular disk shape) located at points of a planar, hard-core Poisson point field. Overall, while the RVE is attained exactly on scales infinitely large relative to microscale, depending on the microstructural parameters, the random fluctuations in the SVE response become very weak on scales an order of magnitude larger than the microscale, thus already approximating the RVE.
Based on the above studies, further work on homogenization of heterogeneous materials is outlined at the end of the thesis.
Keywords: Representative Volume Element (RVE), heterogeneous media, permeability, thermal expansion, mesoscale, microstructure.

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11

Parrouffe, Jean-Michel. „Combined convective and infrared drying of a capillary porous body“. Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39371.

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This research has resulted in the design and development of an experimental facility to study the combined convective infrared (I.R.) drying process of a capillary porous material (glass beads) in high temperature flow conditions.
The necessity to decrease the heat transfer coefficient for the effect of high mass transfer flux (when convection is combined with I.R. heating) has been demonstrated. Further, the analogy between the transfer of heat and mass expressed in terms of average heat and mass transfer coefficient ratios has been verified to apply when the surface is not contaminated. Experiments have also showed that there is a link between the evaporation temperature and crust formation at the evaporating surface. Moreover, an increase in the heat transfer coefficient was observed when the surface reaches the boiling point and is higher than that of the flowing air. Lastly, it was observed that the critical moisture content is independent of the convective drying parameters, sample thickness and the overall incident heat flux.
A drying front model is also presented and tested with the experimental results in convection drying and for the combined process. The drying time, the bottom temperature evolution, the surface temperature evolution up to the critical point and the overall shape of the drying rate curve were well reproduced by the model. Simulations have also showed that the effect of the diffusion mass flux on the heat and mass transfer coefficients leads to a decrease of the evaporation rate by a maximum of 8% for both the purely convective and combined processes.

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12

Dong, Wenjun 1969. „Modelling of advection-dominated transport in fluid-saturated porous media“. Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100350.

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The modelling of contaminant transport in porous media is an important topic to geosciences and geo-environmental engineering. An accurate assessment of the spatial and temporal distribution of a contaminant is an important step in the environmental decision-making process. Contaminant transport in porous media usually involves complex non-linear processes that result from the interaction of the migrating chemical species with the geological medium. The study of practical problems in contaminant transport therefore usually requires the development of computational procedures that can accurately examine the non-linear coupling processes involved. However, the computational modelling of the advection-dominated transport process is particularly sensitive to situations where the concentration profiles can exhibit high gradients and/or discontinuities. This thesis focuses on the development of an accurate computational methodology that can examine the contaminant transport problem in porous media where the advective process dominates.
The development of the computational method for the advection-dominated transport problem is based on a Fourier analysis on stabilized semi-discrete Eulerian finite element methods for the advection equation. The Fourier analysis shows that under the Courant number condition of Cr=1, certain stabilized finite element scheme can give an oscillation-free and non-diffusive solution for the advection equation. Based on this observation, a time-adaptive scheme is developed for the accurate solution of the one-dimensional advection-dominated transport problem with the transient flow velocity. The time-adaptive scheme is validated with an experimental modelling of the advection-dominated transport problem involving the migration of a chemical solution in a porous column. A colour visualization-based image processing method is developed in the experimental modelling to quantitatively determinate the chemical concentration on the porous column in a non-invasive way. A mesh-refining adaptive scheme is developed for the optimal solution of the multi-dimensional advective transport problem with a time- and space-dependent flow field. Such mesh-refining adaptive procedure is quantitative in the sense that the size of the refined mesh is determined by the Courant number criterion. Finally, the thesis also presents a brief study of a numerical model that is capable to capture coupling Hydro-Mechanical-Chemical processes during the advection-dominated transport of a contaminant in a porous medium.

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13

Galvin, Robert. „Elastic wave attenuation, dispersion and anisotropy in fractured porous media“. Curtin University of Technology, Department of Exploration Geophysics, 2007. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=17486.

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Development of a hydrocarbon reservoir requires information about the type of fluid that saturates the pore space, and the permeability distribution that determines how the fluid can be extracted. The presence of fractures in a reservoir can be useful for obtaining this information. The main objectives of this thesis are to investigate how fracturing can be detected remotely using exploration seismology. Fracturing will effect seismic data in a number of ways. Firstly, if the fractures are aligned preferentially in some direction, the medium will exhibit long wavelength anisotropy. In turn, if wave propagation is not aligned with one of the symmetry axes of the effective medium then shear wave splitting will depend upon the properties of the fracture filling fluid. Secondly, elastic waves will experience attenuation and dispersion due to scattering and wave-induced fluid flow between the fractures and matrix porosity. This occurs because the fractures are more compliant than the background medium and therefore there will be a pressure gradient formed during passage of the wave, causing fluid to flow between fractures and background. If the direction of shear-wave propagation is not perpendicular or parallel to the plane of fracturing, the wave polarized in the plane perpendicular to the fractures is a quasi-shear mode, and therefore the shear-wave splitting will be sensitive to the fluid bulk modulus.
The magnitude of this sensitivity depends upon the extent to which fluid pressure can equilibrate between pores and fractures during the period of the deformation. In this thesis I use the anisotropic Gassmann equations and existing formulations for the excess compliance due to fracturing to estimate the splitting of vertically propagating shear-waves as a function of the fluid modulus for a porous medium with a single set of dipping fractures and with two conjugate fracture sets dipping with opposite dips to the vertical. This is achieved using two alternative approaches. In the first approach it is assumed that the deformation taking place is quasi-static. That is, the frequency of the elastic disturbance is low enough to allow enough time for fluid to flow between both the fractures and the pore space throughout the medium. In the second approach I assume that the frequency is low enough to allow fluid flow between a fracture set and the surrounding pore space, but high enough so that there is not enough time during the period of the elastic disturbance for fluid flow between different fracture sets to occur. It is found that the second approach yields a much stronger dependency of shear-wave splitting on the fluid modulus than the first one. This is a consequence of the fact that at higher wave frequencies there is not enough time for fluid pressure to equilibrate and therefore the elastic properties of the fluid have a greater effect on the magnitude of the shear-wave splitting. I conclude that the dependency of the shear-wave splitting on the fluid bulk modulus will be at its minimum for quasi-static deformations, and will increase with increasing wave frequency.
In order to treat the problem of dispersion and attenuation due to wave-induced fluid flow I consider interaction of a normally incident time-harmonic longitudinal plane wave with a circular crack imbedded in a porous medium governed by Biot’s equations of dynamic poroelasticity. The problem is formulated in cylindrical coordinates as a system of dual integral equations for the Hankel transform of the wave field, which is then reduced to a single Fredholm integral equation of the second kind. It is found that the scattering that takes place is predominantly due to wave induced fluid flow between the pores and the crack. The scattering magnitude depends on the size of the crack relative to the slow wave wavelength and has its maximum value when they are of the same order. I conclude that this poroelastic effect should not be neglected, at least at seismic frequencies. Using the solution of the scattering problem for a single crack and multiple-scattering theory I estimate the attenuation and dispersion of elastic waves taking place in a porous medium containing a sparse distribution of such cracks. I obtain from this analysis an effective velocity which at low frequencies reduces to the known static Gassmann result and a characteristic attenuation peak at the frequency such that the crack size and the slow wave wavelength are of the same order.
When comparing with a similar model in which multiple scattering effects are neglected I and that there is agreement at high frequencies and discrepancies at low frequencies. I conclude that the interaction between cracks should not be neglected at low frequencies, even in the limit of weak crack density. Since the models only agree with each other at high frequencies, when the time available for fluid diffusion is small, I conclude that the interaction between cracks that takes place as a result of fluid diffusion is negligible at high frequencies. I also compare my results with a model for spherical inclusions and find that the attenuation for spherical inclusions has exactly the same dependence upon frequency, but a difference in magnitude that depends upon frequency. Since the attenuation curves are very close at low frequencies I conclude that the effective medium properties are not sensitive to the shape of an inclusion at wavelengths that are large compared to the inclusion size. However at frequencies such that the wavelength is comparable to or smaller than the inclusion size the effective properties are sensitive to the greater compliance of the flat cracks, and more attenuation occurs at a given frequency as a result.

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14

Ruan, Jianming. „Characterisation and biocompatibility evaluation of calcium phosphate biomaterials in vitro“. Thesis, University of Strathclyde, 2000. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21172.

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Medical applications of calcium phosphate biomaterials are limited because of poor mechanical properties and acute inflammation reactions which take place occasionally in the clinic. To increase the usefulness of calcium phosphate biomaterials it is necessary to improve the mechanical properties and biological character. Processing and characterization of porous hydroxyapatite (HA) and dense composite (HA-Spinel) biomaterials have been performed in the present research. Biocompatibility of these biomaterials has been examined in vitro using human and rat immortalized osteoblast cells, and the advantages and limitations of cell culture biocompatibility tests are discussed. X-ray analysis of material structure demonstrated that after sintering at 1450°C, HA-Spinel was changed into tricalcium phosphate (TCP)-Spinel phase structure. Mechanical properties testing showed that the bending strength and compressive strength of HA may be improved by adding Spinel. Biocompatibility examination demonstrated that both human and rat osteoblast cells anchored to the surface of the porous and dense biomaterials in a short time, and subsequently, grew and proliferated normally on the surface of these biomaterials. Cytotoxicity evaluation in vitro by studying material extracts demonstrated that compared with the control group of cells cultured on polystyrene, HA-Spinel possessed slight toxicity. Cell growth in HA-Spinel first extracts was slightly impaired. Tritium labeling and immunofluorescent analysis proved that human osteoblast cells and rat osteoblast cells have normal expression of collagen synthesis on the above biomaterials. Confocal laser scanning microscopy (CLSM) observation showed that collagen fibers were produced on these materials, and the amount of the collagen synthesized on the materials increased with culture time. Subsequent analysis indicated that both HA and HA-Spinel can strongly adsorb serum and albumin proteins from culture media and the amount of protein adsorption was proportional to the porosity in the materials. Protein adsorption on the material surface was saturated usually in 2-4 hours, and 1/3-1/2 of the total protein adsorption was achieved in several minutes. In vitro assay also confirmed that human and rat osteoblast cells can be applied as an in vitro model to evaluate the biocompatibility, cytotoxicity and other biological characteristics. Compared with human osteoblast cells, rat osteoblast cells have a greater proliferation rate. In normal conditions, the proliferation rate of the rat osteoblast cells is 2-4 times that of the human osteoblast cells and for this reason rat osteoblasts seem more sensitive to material extracts.

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Raychoudhury, Trishikhi. „Transport of surface-modified iron nanoparticles through model subsurface porous media“. Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104765.

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AbstractThe overall objective of this research is to evaluate significant mechanisms for deposition of surface-modified NZVI in granular subsurface media during transport. Although surface-modified NZVI have been shown to transport more easily than bare NZVI, there is a lack of knowledge of how different parameters such NZVI particle concentration, NZVI size, aqueous-phase flow velocity, and sand particle size influence nanoparticle transport. To investigate the effects of these parameters on transport, a number of laboratory experiments were conducted with NZVI synthesized from ferrous sulfate in the presence of polymers that were effective in colloidal stabilization of the particles. The bare and surface modified-NZVI was characterized for size and surface chemistry by a wide array of analytical instruments. The polymer-stabilized NZVI were employed in three different studies to identify parameters that influence deposition of NZVI in model, granular, subsurface media. In the first study, the breakthrough patterns of carboxymethyl cellulose (CMC)- and polyacrylic acid (PAA)- stabilized NZVI eluted from packed sand columns under a range of pore water velocities and NZVI influent concentrations were investigated. The NZVI effluent relative concentrations of both types of particles decreased with decreasing flow velocities and increasing particle concentrations. PAA-NZVI exhibited slower elution from the columns than CMC-NZVI under identical experimental conditions, and this is attributed to more rapid aggregation kinetics of PAA-NZVI. The second study focused on the quantitative evaluation of aggregation kinetics and the possible effects of aggregation on NZVI deposition. Aggregation of CMC-NZVI particles resulted in a change in particle size distribution (PSD) with time, and the changes in particle size were evaluated by nanoparticle tracking analyzer (NTA). The effects of particle concentrations on the transport in porous media were evaluated by comparing the time profiles of elution of CMC-NZVI from packed sand columns. Changes in PSD over time were responsible for a gradual increase in effluent concentration between 1 and 4 pore volumes, and beyond 4 pore volumes particle detachment contributed to non-steady state effluent concentrations. The NZVI elution profiles had a good fit with aggregation kinetics equations coupled to colloid transport equations that account for particle deposition and detachment. The third study focused on assessing the significance of straining of CMC-NZVI particles during transport in model subsurface porous media. Laboratory experiment were conducted to assess the transport of CMC-NZVI in columns packed with four different sized sands and with three different concentrations. . Breakthrough curves (BTC) and retention profiles of CMC-NZVI along the column length were analyzed to characterize CMC-NZVI transport. The breakthrough curves suggest that with decrease in mean sand diameter, the effluent concentrations decrease. Very high CMC-NZVI particle retention towards the inlet, particularly for the finer sands was observed. These observations are consistent with particle retention in porous media due to straining and/or wedging. Two colloid transport models considering 1) particle deposition by attachment only, and 2) particle retention by straining along with particle deposition by attachment were fitted to the experimental data. Comparison of experimental data and the model calculations suggest that in addition to deposition on collector surface, CMC-NZVI particles are removed from the solution by straining in packed sand beds, with straining rate coefficients that decrease with increase in sand diameter.
L'objectif global de cette recherche est d'évaluer les mécanismes importants de déposition des particules NZVI modifiées en surface dans les milieux granulaires subsurfaciques pendant le transport. Bien que les particules NZVI modifiées en surface aient montré un transport plus facile que les particules NZVI nues, il y a un manque de connaissance sur la façon dont des simples paramètres, tel que la concentration des particules NZVI, leur taille, la vitesse d'écoulement de la phase aqueuse et la taille des particules de sable, influencent le transport des nanoparticules. Dans la première étude, on a étudié les modèles des particules CMC- et PAA-ZVI élues des colonnes remplies de sable dans une gamme de vitesses de l'eau des pores, et des concentrations influentes de particules NZVI. . Les concentrations effluentes relatives des deux types de particules NZVI ont diminué avec la diminution des vitesses d'écoulement et avec l'augmentation des concentrations des particules. Les particules PAA-NZVI présentaient une élution plus lente que les particules CMC-NZVI dans des conditions expérimentales identiques, ceci étant attribué à une cinétique d'agrégation plus rapide pour les particules PAA-NZVI. La réduction de la stabilité colloïdale due à l'agrégation des particules CMC- et PAA-NZVI a été vérifiée en utilisant les tests de sédimentation et on a trouvé que les particules PAA-NZVI ont été moins stables que les particules CMC-NZVI. La deuxième étude portait sur l'évaluation quantitative de la cinétique d'agrégation et les effets d'agrégation possibles sur la déposition des particules NZVI. L'agrégation des particules CMC-NZVI a entraîné un changement dans la distribution de la taille des particules (PSD) avec le temps, et les changements dans la taille des particules étaient évalués par l'analyse de suivi des nanoparticules (NTA). Les effets de la concentration des particules dans la gamme sur le transport dans les milieux poreux ont été évalués en comparant les profils de temps d'élution des particules CMC-NZVI dans les colonnes remplies de sable. Les profils d'élution des particules NZVI ont eu un bon ajustement avec les équations cinétiques d'agrégation couplées aux équations de transport colloïdal, qui tiennent compte de la déposition des particules et de détachement. La troisième étude portait sur l'évaluation de l'importance de la filtration des particules CMC-NZVI pendant le transport dans les milieux poreux subsurfaciques modèles. Des expériences de laboratoire ont été effectuées pour évaluer le transport des particules CMC-NZVI dans les colonnes et trois concentrations différentes. Les courbes percées (BTC) et les profils de rétention des particules CMC-NZVI le long de la colonne ont été analysés afin de caractériser le transport. Les courbes BTC suggèrent que les concentrations effluentes diminuent avec la diminution du diamètre moyen du sable. Une très élevée rétention des particules CMC-NZVI a été observée, particulièrement pour les sables plus fins. Ces observations sont en accord avec la rétention des particules dans les milieux poreux due à la filtration et au calage. Deux modèles de transport colloïdal qui considèrent 1) la déposition des particules uniquement par attachement, et 2) la rétention des particules par filtration et déposition par attachement, ont été ajustés aux données expérimentales. La comparaison des données expérimentales avec les calculs du modèle suggèrent qu'en plus de la déposition sur la surface du collecteur, les particules CMC-NZVI sont retirées de la solution par filtration dans les lits remplis de sable, avec des coefficients de filtration qui diminuent avec le diamètre du sable.

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Gurnagul, N. (Norayr). „Some effects of relative humidity on the porous structure of paper“. Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74013.

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Renato, Viola. „Multi-dimensional thermal response & permeability characterization for porous ablative materials“. Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30382.

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In space missions, the atmospheric entries present a critical challenge for the design of spacecraft due to the extreme external environment that they must endure. Thermal protection systems (TPSs) are required to prevent any damage to the spacecraft, its internal components or passengers. A very common and highly reliable TPS type is based on the use of ablative materials. The improvement of the ablator simulation procedure in its entirety, from the fist phases of the design process to the exceptionally accurate modelling of the material behaviour in the final stages, is the focus of the study herein presented. In order to achieve this goal, two activities were completed: the creation of a new simulation tool and the precise characterization of porous material permeability. The simulation tool consists of a novel and low computationally demanding coupled methodology able to simulate the three-dimensional behaviour of ablative TPSs. This tool is composed by the Ablative Response Code (ARC), which was specifically designed for this task, and reduced order aero-thermodynamic models. The property characterization was performed using the DSMC (Direct Simulation Monte Carlo) method. This activity evaluated the changes in permeability, commonly considered constant, caused by the variations in temperature and pressure occurring during a (re-)entry. The combination of the activities generated for this dissertation can be used for both the design of future mission TPSs and the development of next generation ablative materials. Simulation results produced for several test cases with different planets' atmospheres and examples of possible applications are presented as confirmation of the developed methods relevance for ablative design and development.

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Cloete, Maret. „Modelling of non-Newtonian fluid flow through and over porous media with the inclusion of boundary effects“. Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80240.

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Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Different generalized Newtonian fluids (where the normal stresses were neglected) were considered in this study. Analytical expressions were derived for time independent, fully developed velocity profiles of Herschel-Bulkley fluids (including the simplifications thereof: Newtonian, power law and Bingham plastic fluids) and Casson fluids through open channel sections. Both flow through cylindrical pipes (Hagen-Poiseuille flow) and parallel plates (plane Poiseuille flow) were brought under consideration. Equations were derived for the wall shear stresses in terms of the average channel velocities. These expressions for plane Poiseuille flow were then utilized in the modelling of flow through homogeneous, isotropic porous media. Flow through parallel plates was extended and a possibility of a moving lower wall (plane Couette-Poiseuille flow) was included for Herschel-Bulkley fluids (and the simplifications thereof). The velocity of the wall was assumed to be opposite to the pressure gradient (thus in the streamwise direction) yielding three different possible flow scenarios. These equations were again revisited in the study on flow over porous structures. Averaging of the microscopic momentum transport equation was carried out by means of volume averaging over an REV (Representative Elementary Volume). Flow through parallel plates enclosing a homogeneous porous medium (assumed homogeneous up to the external boundary) was studied at the hand of Brinkman’s equation. It was as- sumed (also for non-Newtonian fluids) that the term dominating outside the external boundary layer area is directly proportional to the superficial velocity that is, since only the viscous flow regime was considered, referred to as the ‘Darcy’ velocity if the diffusive Brinkman term is completely neglected. For a shear thinning or shear thickening fluid, the excess superficial velocity term was included in the proportionality coefficient that is constant for a particular fluid traversing a particular porous medium subjected to a specific pressure gradient. For such fluids only the inverse functions could be solved. If the ‘Darcy’ velocity is not reached within the considered domain, Gauss’s hypergeo- metric function had to be utilized. For Newtonian and Bingham plastic fluids, direct solutions were obtained. The effect of the constant yield stress was embedded in the proportionality coefficient. For linear flow, the proportionality coefficient consists of both a Darcy and a Forch- heimer term applicable to the viscous and inertial flow regimes respectively. Secondary averaging for different types of porous media was accomplished by using an RUC (Representative Unit Cell) to estimate average interstitial properties. Only homoge- neous, isotropic media were considered. Expressions for the apparent permeability as well as the passability in the Forchheimer regime (also sometimes referred to as the non-Darcian permeability) were derived for the various fluid types. Finally fluid flow in a domain consisting of an open channel adjacent to an infinite porous domain is considered. The analytically derived velocity profiles for both plane Couette- Poiseuille flow and the Brinkman equation were matched by assuming continuity in the shear stress at the porosity jump between the two domains. An in-house code was developed to simulate such a composite domain numerically. The difference between the analytically assumed constant apparent permeability in a macro- scopic boundary layer region as opposed to a dependency of the varying superficial velocity was discussed. This code included the possibility to alter the construction of the domain and to simulate axisymmetrical flow in a cylinder.
AFRIKAANSE OPSOMMING: Verskeie veralgemeende Newtoniese vloeistowwe (waarvan die normaalspannings ignoreer- baar is) word in hierdie studie beskou. Analitiese uitdrukkings vir tyd-onafhanklike, ten volle ontwikkelde snelheidsprofiele vir Herschel-Bulkley vloeistowwe (wat die vereen- voudigde weergawes daarvan insluit: Newtoniese, magswet- en Bingham-plastiek vloei- stowwe), sowel as Casson vloeistowwe, is afgelei vir vloei deur ‘n oop kanaal. Beide vloei deur silindriese pype (Hagen-Poiseuille vloei) en parallelle plate (vlak-Poiseuille vloei) is oorweeg. Vergelykings vir die skuifspannings op ‘n wand in terme van die gemiddelde snelhede is afgelei. Hierdie uitdrukking wat vir vlak-Poiseuille vloei verkry is, is in die modellering van vloei deur homogene, isotropiese poreuse media ook gebruik. Vloei deur parallelle plate is uitgebrei en die moontlikheid van ‘n bewegende onderste wand (vlak-Couette-Poiseuille vloei) is ondersoek vir Herschel-Bulkley vloeistowwe (en die vereenvoudigings daarvan). Dit word aangeneem dat die snelheid van die wand in die teenoorgestelde rigting as die drukgradiënt georiënteer is (dus in die stroomgewyse rigting) wat dan tot drie verskillende moontlike vloeigevalle lei. Hierdie vergelykings is weer in die studie van vloei oor poreuse strukture gebruik. Die gemiddelde van die mikroskopiese momentum transportvergelyking is bereken oor die volume van ‘n REV (“Representative Elementary Volume”). Vloei deur parallelle plate wat ‘n homogene poreuse medium omsluit (waar die medium homogeen aanvaar word tot by die eksterne grens) is bestudeer aan die hand van Brinkman se vergelyking. Daar is aanvaar (ook vir nie-Newtoniese vloeistowwe) dat die dominante term buite die eksterne grenslaaggebied direk eweredig is aan die oppervlaksnelheid en, aangesien slegs vloei in die viskeuse gebied oorweeg word, daarna verwys word as die “Darcy”- snelheid, indien die diffusiewe Brinkman-term heeltemal weglaatbaar is. Vir ‘n span-ningsverdunnende of -verdikkende vloeistof, word die oortollige oppervlaksnelheidsterm ingesluit by die proporsionaliteitskoëffisiënt wat konstant is vir ‘n spesifieke vloeistof wat deur ‘n sekere poreuse medium, onderhewig aan ‘n spesifieke drukgradiënt, vloei. Vir sulke vloeistowwe kon slegs die inverse funksies opgelos word. As die “Darcy”- snelheid nie binne die betrokke gebied bereik word nie, is daar van Gauss se hipergeometriese funksie gebruik gemaak. Vir Newtoniese en Bingham-plastiek vloeistowwe is egter direkte oplossings verkry. Die effek van die konstante toegeespanning is ingebed in die proporsionaliteitskoëffisiënt. Vir lineêre vloei bestaan die proporsionaliteitskoëffisiënt uit beide ‘n Darcy- en ‘n Forch- heimer-term wat van toepassing is in die viskeuse- en traagheidsvloeigebiede onder- skeidelik. Sekondˆere gemiddeldes vir verskillende tipes poreuse media is verkry; deur gebruik te maak van ‘n RUC (“Representative Unit Cell”) kan interstisiële gemiddelde eienskappe geskat word. Slegs homogene, isotrope media is in oorweging gebring. Uit- drukkings vir die o¨enskynlike deurlaatbaarheid sowel as die deurdringbaarheid in die Forchheimer-gebied (ook soms na verwys as die nie-Darcy deurlaatbaarheid) is afgelei vir die verskillende vloeistoftipes. Ten slotte is vloeistofvloei in ‘n gebied wat bestaan uit ‘n oop kanaal aangrensend aan ‘n oneindige poreuse domein ondersoek. Die analities-afgeleide snelheidsprofiele vir beide vlak-Couette-Poiseuille vloei en die Brinkman-vergelyking is gekoppel deur ‘n kontinu¨ıteit in die skuifspanning by die poreuse-sprong tussen die twee gebiede te aanvaar. ‘n Interne numeriese kode is ontwikkel om so ‘n saamgestelde domein numeries te simuleer. Die verskil tussen die analities konstant-aanvaarde deurlaatbaarheid in ‘n makroskopiese grenslaagstreek, eerder as ‘n afhanklikheid met die veranderende opper- vlaksnelheid, is bespreek. Hierdie kode sluit ook die moontlikheid in om die domein te herkonstrueer, asook om die simulasie van aksiaal-simmetriese vloei in ‘n silinder te ondersoek.

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Zihms, Stephanie Gabriele. „Smouldering and thermal remediation effects on properties and behaviour of porous media“. Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23194.

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Smouldering and thermal remediation processes can achieve rapid removal of organic contaminants from soils but these processes expose soils to high temperatures for extended periods of time. Wild fire research shows changes in soil properties, when exposed to temperatures up to 850°C. Based on temperatures achieved during smouldering, this work aims to investigate how high temperature thermal and smouldering treatments affect soils. Laboratory experiments on simple soils prepared from silica sand and silica sandkaolin show that thermal treatments affect soil particle size distribution, mass, pH, mineralogy, liquid limits, and plastic limits. Properties such as particle density and bulk density remain unchanged after exposure to elevated temperatures. In silica sand, shear strength decreases with increasing temperature and smouldering whereas it increases with increasing temperature in the sand-kaolin soil. High temperatures and smouldering may smooth the sand particle surfaces and reduce interparticle friction. The presence of kaolin may protect the sand grains from this effect and affect the shear strength through mineralogical changes. Kaolin addition has similar effects on hydraulic conductivity. Samples containing 10% kaolin show a relationship between hydraulic history, microstructure and hydraulic conductivity. Samples treated by smouldering have lower saturated hydraulic conductivities compared to furnace treatments. For silica sand no changes in hydraulic conductivity were observed. These changes in dynamic response were linked to changes on a particle scale such as chemistry, mineralogy, and composition.

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Radulescu, Matei Ioan. „The propagation and failure mechanism of gaseous detonations : experiments in porous-walled tubes“. Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84420.

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In order to elucidate the propagation mechanism of detonations, the failure mechanism of detonations propagating in tubes with porous walls is investigated experimentally. Two distinct failure mechanisms were identified depending on the type of detonating mixture. Experiments in mixtures characterized by piecewise laminar reaction zone structures with weak three-dimensional effects revealed that the attenuation and failure is caused by the global mass divergence to the porous, permeable walls. The limits observed in these mixtures agreed very well with the theoretical limiting conditions for the existence of curved ZND detonations subjected to lateral expansions.
Experiments were also conducted in a second class of mixtures, characterized by irregular cellular structures and turbulent reactions zones. When detonations in this class of mixtures are attenuated, transverse waves re-amplify from local instabilities in the reaction zone. This re-amplification permits the detonation wave to continue to propagate and overcome the effects of global mass divergence and transverse wave attenuation at the porous walls. Ultimately, when the rate of transverse wave re-generation is surpassed by the rate of transverse wave damping at the walls, the detonation can no longer be self-sustained and fails. The limits obtained in these irregular structure mixtures were found significantly wider than predicted by the ZND formulation, thus further confirming the important role of the three-dimensional turbulent structure in these detonations in providing a more efficient mechanism of gas ignition and propagation than detonations that exhibit a regular structure.
The implications of the present study are that the ZND model is not valid in describing the reaction zone structure, the ignition mechanism and thus the propagation mechanism in these turbulent detonations. In these mixtures, the ignition mechanism is a combination of the classical mechanism of adiabatic shock compression leading to ignition as well as the intense turbulent mechanism usually attributed to deflagrations only.

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Thompson, Rebecca. „Effect of locally delivered alendronic acid on bone formation around porous titanium implants“. Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116924.

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The purpose of this study was to determine the effects of local delivery ofthe bisphosphonate alendronic acid (AA) on bone formation around, withinand on porous titanium implants. Cylindrical rods 9mm in diameter and90mm in length were coated with either 0.2mg or 1.0mg of AA prior tobilateral surgical implantation into the femoral intramedullary canals of 10experimental canines. Twelve weeks after surgery the femora wereharvested and scanned with micro computed tomography (microCT) prior toprocessing for undecalcified thin section histology and analysis withbackscattered scanning electron microscopy (BSEM). MicroCT analysisshowed that both levels of AA significantly enhanced peri-implant boneformation around the coated implants compared with controls, with the 1.0mg AA dose resulting in a 3.5-fold greater increase than 0.2mg AA. BSEManalysis of peri-implant bone formation correlated very well the microCTanalysis in a direct comparison of matched microCT and histologic sections.BSEM analysis showed no significant effect of either 0.2mg AA or 1.0mg AAon bone-implant apposition or the extent of bone growth into the implantporous coating. This thesis provided valuable guidance on the doseresponse to locally delivered AA and its potential for enhancing the fixationof orthopaedic implants by increasing the amount of bone that forms withinthe immediate peri-implant space.
L'objectif de cette étude était de déterminer les effets d'une administration localedu biphosphonate acide alendronique (AA) sur la formation osseuse sur, autour età l'intérieur d'implants poreux en titanium. Des tiges cyclindriques de 9mm dediamètre et de 90mm de longueur ont été enduites avec 0.2mg ou 1.0mg de AApréalablement à leur implantation chirurgicale bilatérale dans les canaux fémorauxintramédullaires sur 10 canins expérimentaux. Douze semaines après lachirurgie, les fémurs ont été prélevés et scannés par tomodensitométrie (microCT)avant l'histologie de sections minces décalcifiées et l'analyse par microscopie àbalayage d'électrons rétrodiffusés (BSEM). Les analyses microCT ont montréque les deux doses de AA amélioraient significativement la formation osseuse périimplantautour des implants enduits comparativement aux implants contrôles ; ladose de 1.0mg de AA résultant en une augmentation 3.5 fois supérieure à celleobtenue avec la dose de 0.2mg de AA. Les analyses BSEM de la formationosseuse péri-implant ont montré une bonne corrélation avec les analyses microCTpar une comparaison directe des sections correspondantes microCT ethistologiques. Les analyses BSEM n'ont montré d'effet significatif ni de la dose0.2mg ou 1.0mg AA sur l'apposition os-implant ou sur le niveau de croissanceosseuse dans l'implant poreux enduit. Cette thèse a permis de fournir desdonnées utiles sur la dose réponse pour une administration locale de AA ainsi quesur son potentiel pour améliorer la fixation d'implants orthopédiques en accroissantla quantité osseuse qui se forme aux environs immédiats de la zone péri-implant.

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Gao, Changhong. „A network model for capture of suspended particles and droplets in porous media“. Curtin University of Technology, Faculty of Science and Engineering, Department of Petroleum Engineering, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=128222.

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Produced water presents economical and environmental challenges to oil producers. Downhole separation technology is able to separate oil or gas from produced fluid in downhole environment and injects waste water into deeper formations, thus saving energy and reducing waste emission. More than 120 downhole separation systems have been installed worldwide, but only about 60% of the installations achieved success. Most of the failures were due to the injectivity decline under the invasion of impurities in the injected water, such as suspended particles and oil droplets. A reliable model is needed to predict the reaction of reservoir permeability under the invasion of such impurities and serves as a tool to screen appropriate formations for downhole separator installations.
Previous experimental studies on particle-induced permeability damage reveal that high particle concentration, low fluid velocity, large particle size lead to more severe damage. The damage mechanisms are attributed to surface interception, bridging and size exclusion of particles in porous media. While for droplets, the resultant permeability decline is mostly due to surface interception. Empirical correlations with key parameters determined by core flooding data are widely applied to the simulation of permeability decline under invasion of particles and droplets. These correlations are developed based on characteristics of certain rocks and fluids, thus their applications are very restricted.
A more scientific method is to model the flow and capture of particulates at pore level. Reservoir rocks are porous media composed of pores of various sizes. Pore network models employ certain assumptions to imitate real porous media, and have been proved realistic in simulating fluid flow in porous media. In this study, a 2-dimensional square network model is used to simulate capture of particles and droplets in porous media. Pore bodies are represented by globes and pore throats are imitated with capillary tubes. The flow rates in the network are obtained by simultaneously solving mass balance equations at each pore body. The network model is tuned to match the porosity and permeability of a certain rock and serves as the infrastructure where the capture process takes place.
Particles are categorized as Brownian and non-Brownian particles according to size. For Brownian particles, diffusion is dominant and Fick’s law is applied to each pore inside the network to obtain deposition rate. For non-Brownian particles, their trajectories are mainly governed by gravity and drag force acting on them. Besides, the size of each particle is compared with the size of the pore where it is captured to determine the damage mechanism. For particles much smaller than the pore size, surface deposition is dominant and the permeability decline is gradual. For particles with sizes comparable to pore size, bridging and clogging are dominant and the permeability decline is much more severe.
Unlike particles, droplets can not be captured on top of each other. Accordingly, a captureequilibrium theory is proposed. Once the pore surface is covered by droplets, equilibrium is reached and droplets flow freely through porous media without being captured. The simulation on capture of oil droplets reveals that the surface wettability has significant influence on the resultant permeability damage. Most natural reservoirs are neutrally or oil wet. It is thus recommended to apply these surface conditions to future simulations.
The proposed model is validated with test data and reasonably good agreements are obtained. This new mechanistic model provides more insights into the capture process and greatly reduces the dependence on core flooding data.

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Bories, Sylvain. „Modeling of conduction and natural convection in ice-water systems containing porous metal foams“. Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106592.

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A numerical investigation of heat conduction and laminar natural convection in ice-water systems containing porous metal foams, undertaken in the context of computationally convenient two-dimensional steady-state problems, is presented in this thesis. The overall goals of this work are to provide improvements to available cost-effective mathematical models of these phenomena, solve these models numerically, and investigate the influence of the porous metal foam on fluid flow and heat transfer in ice-water systems. The long-term goal (and the motivation for this work) is to contribute to the development of mathematical models and numerical solution methods for simulations of enhanced ice-water seasonal cold-storage systems. The proposed mathematical models are based on the local volume-averaging method. A Darcy-Brinkman-Forchheimer model is used for the momentum equations. For the heat transfer, volume-averaged equations governing two intrinsic phase-average temperature fields are used: one for the metal foam and the other for the water (solid or liquid). The following improvements to available two-temperature models are proposed: novel expressions for the interfacial heat transfer coefficient in both the conduction and convection regimes; and modified effective thermal conductivity models that provide consistency between predictions of one-temperature and two-temperature models in the limit of local thermal equilibrium. A well-established fixed-grid, co-located, finite volume method (FVM) is adapted for the numerical solution of the aforementioned mathematical models. All of the computer simulations are done with rectangular calculation domains, cooled and heated on the opposite side walls, and the adiabatic condition is imposed on the top and bottom walls. The FVM is first validated by the comparing the predicted results to experimental data for steady-state conduction and laminar natural convection in square enclosures containing pure liquid water and ice-water systems (no foam), with temperatures spanning the density inversion point of water. The problem involving natural convection in pure liquid water is solved using a variable-property model (VPM) and also a constant-property model (CPM), with the constant fluid properties evaluated at several reference (or average) temperatures, and the reference (or average) temperature that yields the lowest differences between the results obtained with the VPM and CPM is determined. The FVM is then used to predict laminar natural convection flow fields and average heat transfer rates at the walls in square horizontal enclosures containing liquid water and aluminum foam. The left wall-temperature is fixed at while the right-wall temperature is assigned two different values above the density inversion temperature of water. The effect of changes in the dimensions of the enclosure is investigated with no foam and the results are compared to those of simulations with five different foams. The effects of thermal dispersion and of the Forchheimer drag term on the computed heat transfer rates are quantified. Finally, a demonstration problem involving conduction and laminar natural convection in ice-water-metal-foam systems is investigated, for a representative porous foam made of aluminum, and other parameters in ranges relevant to seasonal cold-storage applications. The rectangular enclosure is maintained in a vertical position with respect to the gravitational acceleration vector. Its width in the horizontal direction is 10 cm, its height is varied between 10 to 50 cm, and the imposed cold and hot wall temperatures are -20°C and 20°C, respectively. The computed streamlines, water-ice interface positions, and wall heat transfer rates are compared to the corresponding results obtained with open domains (no foam). The influence of the aspect ratio of the enclosure is also investigated and the results are presented.
Une étude numérique portant sur la conduction thermique et la convection naturelle laminaire dans des systèmes glace-eau contenant des mousses métalliques poreuses est présentée dans cette thèse. Elle est réalisée grâce à la résolution de problèmes bidimensionnels et stationnaires. Les objectifs principaux de cette étude sont d'améliorer les modèles existants pour ces phénomènes et de les résoudre numériquement afin d'examiner l'influence de l'ajout de mousse métallique sur les écoulements et les transferts thermiques dans les systèmes glace-eau. L'objectif à long terme ayant motivé cette étude est de contribuer au développement de modèles mathématiques et méthodes numériques capables de simuler des systèmes glace-eau optimisés pour le stockage saisonnier de froid. Les modèles mathématiques proposés sont basés sur la méthode de moyenne sur volume représentatif. Un modèle type Darcy-Brinkman-Forchheimer est utilisé pour les équations d'écoulement fluide. Pour les équations gouvernant le transfert de chaleur, on considère deux champs de température moyennés sur chacune des phases : un pour la mousse métallique et un autre pour l'eau (solide ou liquide). Les améliorations suivantes sont proposées pour les expressions semi-empiriques données aux paramètres de ces équations: de nouvelles expressions pour le coefficient de transfert thermique entre les phases sont développées, à la fois dans le régime de pure conduction thermique et dans le régime de convection; des modifications sont apportées aux modèles de conductivité effective afin d'assurer la cohérence des modèles considérant un seul champ de température et ceux en considérant deux. Une méthode de type volume fini (FVM dans le texte) à grille fixe est adaptée et toutes les simulations sont réalisées sur des domaines rectangulaires. Les parois de droite et de gauche sont respectivement chauffées et refroidies et celles du haut et du bas sont adiabatiques. La méthode numérique est tout d'abord validée grâce à une comparaison à des résultats expérimentaux de convection naturelle laminaire dans des cavités carrées contenant de l'eau liquide et des systèmes glace-eau (pas de mousse de métal), dans des conditions stationnaires. Les températures des parois sont choisies de part et d'autre de la température de densité maximale de l'eau. Le problème est simulé avec un modèle à propriétés variables (VPM) et un modèle à propriétés constantes (CPM). Les propriétés sont évaluées à plusieurs températures de référence, et celle qui implique la plus faible différence entre le VPM et le CPM est déterminée. Le code est ensuite utilisé pour prévoir les champs de vitesse liés à la convection naturelle laminaire et le transfert thermique moyen depuis les parois de cavités carrées horizontales contenant de l'eau liquide et de la mousse d'aluminium. La température de la paroi de gauche est fixée à tandis que celle de la paroi de droite prend deux valeurs différentes. L'influence des dimensions de la cavité est examinée en l'absence de mousse métallique et les résultats sont comparés à ceux obtenus avec cinq mousses différentes. Les effets de la dispersion thermique et du terme de traînée de Forchheimer sont quantifiés. Enfin, un problème de démonstration est simulé. La conduction thermique et convection naturelle laminaire dans des systèmes glace-eau-mousse-métallique est étudiée avec une mousse d'aluminium typique, les autres paramètres étant choisis pour correspondre à des situations de stockage saisonnier de froid. La cavité rectangulaire est verticale, sa longueur fixée à 10 cm, sa hauteur comprise entre 10 et 50 cm et les parois froides et chaudes sont maintenues à -20°C et 20°C respectivement. Les résultats des simulations en termes de lignes de courant, positions de l'interface glace-eau et flux thermiques depuis les murs sont comparés aux résultats de simulations sans mousse métallique. L'influence du rapport d'aspect de la cavité est aussi examinée et les résultats sont présentés.

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Chornewich, Cristina. „Bacterial transport in granular porous media: the effects of cell concentration and media pre-coating“. Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=67039.

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Column transport experiments were conducted under saturated conditions to examine the effects of cell concentration and media pre-coating. Two strains of E. coli were used in the study; the commonly studied laboratory organism E. coli K12 D21 and a mutant of the waterborne pathogen E. coli O157:H7. Column experiments were conducted with both clean sand and sand that was pre-coated with bacteria. The influent concentration of the E. coli strains was varied over several orders of magnitude to examine the effect of cell concentration. Concentration dependent removal rates were observed for both organisms in both the clean and media pre-coated sand columns. It was also found that the media pre-coating either does not influence the transport behavior or it decreases the attachment efficiency. Although differences in transport are observed, these differences are not large enough to have a significant influence on the predicted travel distances.
Des expériences de transport par colonne ont été menées afin d'examiner les effets de la concentration des cellules et du pré-revêtement de média. Deux souches de bactéries ont été utilisées: E. coli K12 D12 et une souche mutante E. coli O157:H7. Les expériences par colonne ont été menées avec du sable propre et du sable qui a été préalablement enduit de bactéries. La concentration de l'influent en bactérie a été variée sur plusieurs ordres de grandeur pour examiner l'effet de la concentration cellulaire. Une dépendance du taux d'élimination à la concentration a été observée pour les deux souches de bactéries dans les deux types de sable. De plus, le pré-revêtement de média n'influence d'aucune façon le comportement du transport ni en réduit l'efficacité d'adhésion. Bien que des différences dans le transport ont été observées, celles-ci n'ont eu aucun effet significatif sur la prédiction de la distance à parcourir.

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Stein, Todd. „Quantitative histological comparison of bone growth into titanium and cobalt-chromium porous coated canine implants“. Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56631.

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The purpose of this study was to directly compare bone growth into identical porous coated titanium and cobalt-chromium canine implants. A transcortical screw was chosen as the cortical implant model. A straight cylindrical implant was used in cancellous bone. Quantitative analysis was performed using backscattered electron microscopy (BSEM) and computerized digital analysis. Cortical specimens were analyzed after six and twelve week periods of implantation. Bone ingrowth at six weeks for the cobalt-chromium implants averaged 50.4% $ pm$ 10.4% and for the titanium implants averaged 54.1% $ pm$ 5.1%. At twelve weeks, ingrowth for cobalt-chromium was 55.1% $ pm$ 9.2% and for titanium was 57.3% $ pm$ 9.3%. There was no statistically significant difference between the six and twelve week specimens or between cobalt-chromium and titanium for either time period. Cancellous implants were analyzed after twelve weeks and no difference in bone ingrowth between the two materials was observed.

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Després, Mélissa. „On the evaluation of ductile behaviour of porous nickel-based superalloys using finite element method“. Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83860.

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The present work aims to assess the ductile behaviour of porous Inconel 625 nickel-based superalloys, produced by Metal Injection Moulding (MIM). A qualitative study of the local behaviour was conducted through a series of simple finite element models. Obtained results have been analyzed and compared to more common materials. The following study focuses on the strain localization phenomenon leading to ligament failure between 2 pores relative to their dimensions, their orientation, the distance separating them and the triaxiality ratio. Obtained results demonstrated that the dimensions of the plastic zone in the neighbourhood of pores proportionally increase with pore diameter. Hence, it has been shown that in the case of Inconel 625, the localization was more pronounced between 2 pores whose relative orientation is 0º. Furthermore, it was possible to observe that the critical far-field strain corresponding to the onset of flow localisation between two pores was decreasing as the distance between them was diminishing. By comparing the behaviour of Inconel 625 with that of aluminium 7075-T6, it has been shown that the amplification of the plastic strains was lower in the case of Inconel 625 and consequently the onset of strain localisation (i.e.ligament failure) was found to be delayed in comparison with aluminium. Hence, the high work hardening coefficient of Inconel 625 reduces its sensitivity to the presence of pores. It has thus been shown that Inconel 625 MIM has mechanical properties superior to the equivalent cast material.

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Kay, Andrew Brian. „The effect of non invasive low intensity pulsed ultrasound on bone growth into porous tantalum implants“. Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23279.

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The purpose of this study was to evaluate the effect of non-invasive, low-intensity, pulsed ultrasound on bone growth into tantalum porous implants. Three transcortical cylindrical implants were inserted into both femora of 12 dogs. One leg underwent daily ultrasound stimulation for 40 consecutive minutes with the transducer positioned over the central, or "target" implant, while the contralateral leg served as the control. Six dogs were each treated for periods of two and three weeks. A quantitative analysis was performed to determine the volume fraction of bone ingrowth. At two weeks, there was 12.4 $ pm$ 5.4% bone ingrowth in the stimulated femora compared with 12.7 $ pm$ 6.5% in the controls (p = 0.74). At three weeks, bone growth into the stimulated and control implants was 21.1 $ pm$ 6.5% and 22.7 $ pm$ 7.3%, respectively (p = 0.53). Although a prior study showed that 20 minutes of ultrasound stimulation had a positive effect on bone ingrowth, the results of this study suggest that a treatment of 40 consecutive minutes does not enhance the amount of bone growth into porous metallic implants.

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Li, Jing. „Multi-scale investigations of carboxymethyl cellulose- coated nanoscale zero valent iron particle transport in porous media“. Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123130.

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Subsurface injection of nano scale zero valent iron (NZVI) particles is an emerging technology for in situ remediation of the sites contaminated by toxic contaminants such as chlorinated organic dense non aqueous phase liquids (DNAPLs) and heavy metals. One of the key challenges in applying NZVI particles for remediation at the field scale is that NZVI particles are not readily transported in subsurface porous media. The overall objective of this research is to address this challenge by conducting a number of column experiments and 2-D pilot scale tank experiments as well as by exploring the deposition mechanics of metal nanoparticles theoretically. Although numerous studies have focused the stability and transport of polymer/polyelectrolyte coated NZVI particles, the comparison of the effect of the same type of polyelectrolyte stabilizer with different molecular weight on the stability and transport of the corresponding coated NZVI particles has not been systematically conducted to date. Varying molecular weights of homologous polyelectrolytes can cause changes in viscosity and rheology in free solution, and alter the extent of colloidal stability when coated on the nanoparticles. Furthermore, most of the studies on NZVI particle transport have been conducted in the vertically placed columns, which are not representative with the actual flow orientation in field, leading to a potential difference of transport performance of NZVI particles between the commonly used vertical flow orientation and the horizontal flow model. In addition, the scale-up effects (from laboratory-scale column to pilot-scale or field-scale demonstrations) on NZVI transport are reported. In this study, a thorough investigation on NZVI transport is conducted in a 2-D pilot-scale tank to shed some light on the transport performance of NZVI particles under conditions that are more close to actual circumstances. Finally, to calculate the deposition rate coefficient of metal nanoparticles during transport, a considerable number of studies on NZVI particles transport employed equations for predicting the single collector contact efficiency that are developed on the basis of the numerical calculations for common colloidal particles such as latex particles, which have smaller densities than those of metal particles. Taking the horizontal flow mode and the density effects for metal nanoparticles into consideration, a new methodology is developed in three dimensions (3-D) to more precisely predict the single collector efficiency of NZVI particles.In the first study, the influence of the molecular weight of the polyelectrolyte grafted on NZVI particle on its stability and transport was investigated. Three carboxymethyl celluloses (CMC) with different molecular weights (90,000 Da, 250,000 Da and 700,000 Da) were used to stabilize NZVI particles. The comparison of the results revealed that the stability and transport of NZVI particles were improved significantly by CMC with high molecular weight, due to its high viscosity property. In the second study, the effects of gravity on NZVI particle during its transport were extensively assessed in vertical and horizontal placed columns under different conditions (mean sand diameters and NZVI concentrations). The results indicated that the gravity forces significantly reduced NZVI particles transport in coarse sand and at high NZVI concentration in horizontally placed columns. To thoroughly study the impact of horizontal orientation flow on the transport of NZVI particles at a larger scale, a series of transport experiments were conducted in a pilot-scale 2-D tank. Furthermore, to address the challenges met in predicting the single collector efficiency in horizontal orientation flow mode, a methodology based on trajectory analysis of particles around a Happel sphere-in-cell model for porous media in 3-D was developed.
L'injection souterraine des nanoparticules de fer à zéro valence (NZVI) est une technologie émergente pour l'assainissement in situ des sites contaminés par des polluants toxiques comme les solvants chlorés et les métaux lourds. L'un des principaux défis dans l'application des particules de NZVI à des fins de rémédiation est que les particules de NZVI ne sont pas facilement transportées dans des milieux poreux souterrains. L'objectif général de cette recherche est de relever ce défi en réalisant un certain nombre d'expériences en colonnes et en 2-D sur desbassins à l'échelle pilote ainsi que par l'analyse de la mécanique de dépôt de nanoparticules métalliques en théorie. Bien que de nombreuses études ont porté sur la stabilité et le transport de nanoparticules de fer (NZVI) revêtues de polymère / poly-électrolyte, la comparaison de l'effet du même type de stabilisant en polyélectrolyte ayant des poids moléculaires différents, sur la stabilité et le transport des particules de NZVI enrobées n'ont pas été effectués systématiquement à ce jour. Des poids moléculaires variables des polyélectrolytes homologues peuvent provoquer des variations de viscosité en solution libre et dans l'étendue de la stabilisation colloïdale électrostérique de NZVI en s'attachant sur la surface des nanoparticules. Des études antérieures sur le transport des particules NZVI ont été menées dans les colonnes placées verticalement, qui souvent ne sont pas représentatifs de l'orientation de l'écoulement réel sur le champ, ce qui conduit à une différence de potentiel de performance du transport de particules NZVI entre l'orientation de l'écoulement vertical couramment utilisé et le modèle à flux horizontal. Outre, les effets à l'échelle grandissante (de la colonne à l'échelle de laboratoire, pilote ou des manifestations à l'échelle du champ) sur le transport de NZVI sont rapportés. Dans cette étude, une enquête approfondie sur le transport de NZVI est effectuée dans un réservoir en 2-D à l'échelle pilote afin de faire la lumière sur la performance du transport des particules de NZVI dans des conditions qui sont plus près de la situation réelle. Enfin, pour calculer le coefficient de vitesse de dépôt des nanoparticules de métal en cours de transport, un nombre considérable d'études sur les particules de NZVI ont été effectué en employant des équations de transport à fin de prédire le contact de rendement du capteur unique qui sont mis au point sur la base des calculs numériques pour les particules colloïdales communes moins denses tels que des particules de latex, qui ont des densités plus inferieures que celles des particules de métal. Prenant le mode d'écoulement horizontal et les effets de la densité de nanoparticules métalliques en considération, une nouvelle méthode est développée en trois dimensions (3-D) afin de prédire plus précisément l'efficacité du collecteur unique de particules NZVI .

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Chen, Fu 1960. „Role of solid wettability in two processes : bubble generation from porous media and froth treatment in processing oil sands“. Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38102.

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Solid wettability plays an important role in many industrial processes. Two examples of processes dependent on solid wettability are: Bubble generation from porous media (project one) and the bitumen froth treatment process in the recovery of oil from oil sands (project two).
Project one. Bubble size has a profound effect on flotation efficiency controlling particle collection and froth stability. Models of bubble generation at a rigid sparger usually include a wettability effect (i.e., contact angle). The role of sparger wettability on bubble formation was examined using three rigid spargers exhibiting water contact angles of 0, 64 and >90°. The wettability was varied by heating the sparger, and the contact angle was determined by the Washburn and modified Washburn methods. By measuring permeability, it was determined that heating had no effect on sparger pore structure. The results showed no detectable wettability effect on bubble formation over the practical operating range of column flotation. The lack of wettability effect may be attributed to the highly irregular morphology of the sparger surface. The bubble size, it was shown, can be predicted by using the concept of sparger equivalent pore diameter and active pore number, which are estimated by a back-calculation routine.
Project two. Production of oil from oil sand deposits in northern Alberta involves open pit mining, mixing the ore with water, extraction of bitumen from the slurry by a flotation-related process (Hot Water Extraction Process), removal of water and solids from the froth formed (froth treatment process), and upgrading the heavy bitumen to liquid hydrocarbons. The froth treatment process to remove fine solids and water from the bitumen froth depends on the wettability of the solids. Fine solids were extracted from samples of bitumen froth using heptane. A mixture of heptane and toluene (diluent) was used to study fine solid wettability. The contact angle (sessile drop method) and partition of the fine solids among the aqueous, diluent and interphase regions were determined. The effect of diluent composition, sample drying, and surface washing was examined. The partition of the particles correlated well with their wettability, and the results helped interpret observations from plant practice.

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Pelley, Andrew John. „Effect of particle size and natural organic matter on the transport and fate of latex nanoparticles in saturated porous media“. Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100232.

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Colloid filtration experiments were performed using latex particles (50 nm, 110 nm and 1500 nm) in both the presence and absence of 5.0 mg/L humic acid (HAs). At low ionic strengths (1 -- 10 mM KCl), an increase in attachment efficiency (alpha) with increasing particle size was observed, which contrasts with predictions based on DLVO theory. The presence of HAs generally resulted in a decrease in alpha. Characterization experiments to better understand this behaviour included particle sizing using dynamic light scattering (DLS) and zeta potential using laser Doppler velocimetry (LDV). The particles' hydrodynamic diameters were unchanged in the presence of HAs. HAs lead to an increase in absolute zeta potential for the 50 nm and 110 nm colloids and a decrease in zeta potential for the 1500 nm particles. A discussion of the apparent deviations from Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and explanations for the observed behaviour are provided.

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Medvescek, James. „Experimental investigation of fully developed flows of a Newtonian fluid in straight rectangular ducts with adjacent open and porous-metal-foam domains“. Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119474.

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Over the last two decades, porous metal foams (which have very high values of surface-area-to-volume ratio, of the order of 10,000 square meters per cubic meter; and values of porosity in the range 0.85-0.98) have been increasingly used in devices for heat transfer (ultra-compact heat exchangers and heat sinks; heat pipes; and loop heat pipes), filtration, catalytic conversion, and acoustical control. In computational methods for thermofluid optimization of such devices, cost-effective modeling of fluid flows in adjacent open and porous-metal-foam domains is done using two different, but compatible, sets of volume-averaged governing equations; and at the interface between these domains, the intrinsic-phase-averaged pressure, phase-averaged fluid velocity, and normal stress are assumed to be continuous, and a tangential stress-jump condition, with two adjustable coefficients, is imposed. Accurate experimental data for determining these adjustable coefficients and establishing possible laminar-turbulent transition criteria for the aforementioned flows are urgently needed. In the present work, an experimental investigation of fully developed flows of air in a straight, uniform, rectangular duct of high cross-sectional aspect ratio and containing open and porous-metal-foam domains was undertaken. These flows are akin to those studied in the classical Beavers-Joseph problem. Four different porous metal foams (with nominal pores per inch designations of 20, 40, 60; nominal thickness of 12.7 mm; and porosity in the range 0.85-0.94) were considered. An experimental facility was specially designed and constructed to allow test-section configurations of nominal open-domain heights of 0 (completely filled with porous metal foams), 3.175 mm, 6.35 mm, and 12.7 mm. The nominal width and length of the test section was fixed at 152.4 mm and 457.2 mm, respectively. The top wall of the test section had 64 wall-static-pressure taps and also a wall-shear-stress sensor, which was redesigned (improved) from an earlier version. The airflow rates were measured using a Venturi tube (specially designed, constructed, and calibrated for this work) and a bank of laminar flow elements. An analytical solution for laminar fluid flows in the problems of interest was adapted from other works in the published literature. The results obtained from experiments undertaken for benchmarking tasks, characterization of the porous metal foams (photomicrographs; ligament, pore, and cell effective diameters; and porosity), and calibration of the wall-shear-stress sensor are presented and discussed. Data from experiments undertaken to determine the permeability and dimensionless form-drag coefficient of the porous metal foams were processed using four different approaches, and the results are presented and comparatively discussed. Comprehensive sets of experimental data collected for airflows in adjacent open and porous-metal-foam domains (in the laminar, transitional, and turbulent regimes) are presented and discussed. These experimental data, the analytical solution for such problems with laminar flows, power-spectral-density (PSD) plots of the instantaneous wall-shear-stress measurements, and the requirements for physically tenable values for the laminar-flow results were collectively used to obtain guidance regarding laminar-turbulent transition, and then deduce the two coefficients in the interfacial jump condition on the shear stress. For flows through test sections completely filled with the porous metal foams, the data collected were used to obtain a Darcy friction factor as a function of a Reynolds number (both based on the superficial velocity of the air and the effective diameter of the metal-foam ligaments). The data collected in the experiments on flows in test sections with adjacent open and porous domains were used to obtain the open-domain Darcy friction factor as a function of the corresponding Reynolds number. These results are presented and discussed.
Au cours des deux dernières décennies, les mousses métalliques poreuses, MMP, (ayant des valeurs très élevées de superficie d'échange thermique volumétrique, de l'ordre de 10 000 mètres carrés par mètre cube, et valeurs de la porosité de 0,85 à 0,98) sont devenues de plus en plus commun dans plusieurs domaines: le transfert thermique (échangeurs de chaleur ultracompacts, dissipateurs de chaleur, caloducs et des caloducs en boucle), la filtration; la conversion catalytique; et l'acoustique. Les simulations numériques d'écoulements en domaines ouvert / de MMP adjacents se font en résolvant deux équations différentes (moyennées volumétriquement), correspondant aux deux domaines différents. À l'interface de ceux-ci, la pression intrinsèque (moyennée), la vélocité du fluide (moyenné), et la contrainte normale sont supposées être continues, et une discontinuité de la contrainte tangentielle à l'interface, avec deux coefficients réglables, est imposée. La connaissance de ces coefficients réglables, et l'établissement de critères de transition laminaire-turbulent pour ces types d'écoulements nécessitent urgemment des données expérimentales précises. Le travail ci-inclus comprend une étude expérimentale d'écoulements d'air pleinement développés, en canal rectangulaire et uniforme, de rapport largeur/hauteur élevé, et contenant des domaines ouvert / de MMP adjacents. De tels écoulements ressemblent à ceux étudiés dans le problème Beavers-Joseph. Quatre MMP différentes (ayant des pores de tailles nominaux de 20, 40, 60 pores par pouce, une épaisseur nominale de 12,7 mm, et des porosités allant de 0,85 à 0,94) furent examinées. Un dispositif expérimental fut conçu et construit pour permettre des configurations d'hauteurs du domaine ouvert dans la section de mesure de 0 (complètement rempli de MMP), 3,175 mm, 6,35 mm, et 12,7 mm. La largeur nominale et la longueur de la section de mesure furent fixées à 152,4 mm et 457,2 mm, respectivement. La paroi supérieure de la section de mesure possède 64 prises de pression statique et un capteur de contrainte de cisaillement à la paroi. Les débits d'air furent mesurés en utilisant un tube de Venturi (spécialement conçu, construit, et étalonné pour ce travail) et une banque d'éléments laminaires. Les résultats obtenus des expériences menées pour i) des tâches d'analyse comparative; ii) la caractérisation des mousses métalliques (microphotographes; diamètres effectifs des ligaments, des pores et des cellules; porosité); et iii) l'étalonnage du capteur de contrainte de cisaillement sont présentés et interprétés. Les données provenant des expériences mesurant la perméabilité et le coefficient adimensionnel de traînée de forme des MMP furent déterminées selon quatre approches différentes, et comparées. Des ensembles de données expérimentales recueillies en écoulements d'air en domaines ouvert / poreux adjacents (dans les régimes laminaire, de transition, et turbulent) furent présentés et analysés. Ces données, la solution analytique de tels écoulements laminaires, les densités spectrales de puissance des mesures instantanées de la contrainte de cisaillement à la paroi, et les conditions nécessaires correspondantes au régime laminaire furent collectivement utilisées pour obtenir des indicateurs concernant la transition laminaire-turbulent, et pour déduire les deux coefficients dans la condition de discontinuité de la contrainte de cisaillement à l'interface. Les données provenant des mesures dans lesquelles le canal était complètement rempli de MMP furent utilisées pour calculer un coefficient de frottement de Darcy en fonction du nombre de Reynolds (basé sur la vélocité superficielle de l'air et le diamètre effectif des ligaments de la MMP). Les données recueillies dans les expériences en domaines ouverts / poreux adjacents furent utilisées pour obtenir le coefficient de frottement de Darcy (du domaine ouvert) en fonction du nombre de Reynolds correspondant. Ces résultats sont présentés et interprétés.

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Petosa, Adamo. „Transport, deposition and aggregation of metal oxide nanoparticles in saturated granular porous media: role of water chemistry, collector surface and particle coating“. Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119416.

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As a multitude of engineered nanomaterials (ENMs) are being incorporated into a growing number of consumer products, the potential release of these reactive and potentially toxic constituents into natural aquatic environments and soils is inevitable. Nanosized metal oxides such as cerium dioxide (nCeO2), titanium dioxide (nTiO2) and zinc oxide (nZnO) are examples of ENMs currently appearing in consumer products. Upon the release of such ENMs into natural and engineered aquatic environments, particle aggregation and deposition behavior will determine the particle transport potential and thus the environmental fate and potential ecotoxicological impacts of the released materials. The objective of this research was to examine the transport behavior of select nanosized metal oxides (namely, nCeO2, nTiO2 and nZnO) in saturated granular porous media using laboratory-scale column experiments. The influence of water chemistry (pH, ionic strength (IS) and cation type (Na+, Ca2+, or Mg2+)) and particle coating (uncoated (bare) and poly(acrylic acid) (PAA)-coated ENMs) on particle deposition was examined in quartz sand or loamy sand-packed columns. Select particle transport studies in natural groundwater were also conducted, and PAA-coated metal oxide transport was compared to that of an analogous nanosized PAA polymeric capsule (nCAP). All ENM suspensions were characterized over a range of environmentally relevant water chemistries using dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) to establish aggregate size and laser Doppler velocimetry to determine particle surface potential. To investigate aggregate morphology, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images were obtained under select conditions. Overall, bare ENMs exhibited high retention within water-saturated quartz sand-packed columns at NaNO3 solution IS as low as 0.1 mM for nTiO2 and 0.01 mM for nZnO. Furthermore, bare nTiO2 was found to exhibit extensive aggregation, regardless of pH and IS. At lower salt concentrations, the particle attachment efficiency (α) for the nTiO2 aggregates onto quartz sand increased with increasing IS. At higher IS, α (pH 7) > α (pH 3) > α (pH 9), likely due to enhanced particle aggregation at pH 7 and subsequent physical straining within the granular matrix. Bare nTiO2 and nZnO displayed dynamic (time-dependent) deposition behaviors under selected conditions. In contrast, PAA-coated nTiO2 and nZnO were less prone to aggregation and exhibited significant transport potential at IS as high as 100 mM NaNO3 or 3 mM CaCl2. Likewise, PAA-coated nCeO2 particles suspended in NaNO3 were highly mobile in quartz sand-packed columns. Nonetheless, heightened nCeO2 and nCAP particle retention and dynamic transport behavior was observed with increasing divalent salt concentrations and in natural groundwater. Moreover, enhanced particle retention was encountered in loamy sand in comparison to quartz sand. Finally, the nCAPs proved to be a good surrogate particle for the PAA-coated nCeO2. These findings illustrate the importance of considering the extent and type of particle surface modification when investigating metal oxide contamination potential in granular aquatic environments. Furthermore, the results obtained emphasize the need to consider the nature of the granular medium, along with the water chemistry, when evaluating ENM contamination risks.
Actuellement, des différents types de nanomatériaux manufacturés (NMM) sont intégrées dans un nombre croissant de produits de consommation. Par conséquent, la libération de ces matériaux réactifs et potentiellement toxiques dans le sol et les milieux aquatiques naturels est inévitable. Lors de la décharge dans l'environnement, l'agrégation et la déposition déterminent le potentiel de transport des particules, influencent les éventuels effets écotoxicologiques des matières rejetées. Les oxydes métalliques de taille nanométrique, tels que le dioxyde de cérium (nCeO2), dioxyde de titane (nTiO2) et l'oxyde de zinc (nZnO) ne font pas exception, nécessitant une meilleure compréhension de leur comportement dans les milieux aquatiques naturels et artificiels. L'objectif de cette recherche était d'examiner le comportement de transport de certains oxydes métalliques de taille nanométrique (en particulier le nCeO2, nTiO2 et nZnO) dans les milieux poreux granulaires saturés. Ceci a été réalisé dans le laboratoire en utilisant des expériences contrôlées en colonne. L'influence de la chimie de l'eau (pH, force ionique (FI) et le type de cations (Na+, Ca2+ ou Mg2+)), et le revêtement des NMM (non revêtus ou revêtus de poly(acide acrylique), PAA) sur la déposition des particules a été examiné dans des colonnes remplis de sable de quartz ou de sable loameux. Des études examinent le transport des particules suspendus dans les eaux souterraines naturelles ont également été menées. Finalement, le transport des oxydes de métal a été comparée à celle d'une capsule nanométrique (nCAP) analogue composer de PAA. Dans l'ensemble, les oxydes métalliques non revêtus démontrent une rétention élevé dans les colonnes remplies de sable de quartz et saturées avec des solutions de NaNO3. Avec ces particules, une forte rétention est observée à des FI aussi faibles que 0.1 mM pour le nTiO2 et 0.01 mM pour le nZnO. En outre, le nTiO2 démontre une agrégation extensive, peu importe le pH et la FI. À des concentrations de NaNO3 inférieures, l'efficacité de filtration (α) des agrégats de nTiO2 dans le sable de quartz augmente en augmentant la FI. À des plus hautes FI, α (pH 7) > α (pH 3) > α (pH 9). Ceci est probablement due à une augmentation d'agrégation à pH 7, causant les particules de devenir prises entres les grains de sable de la colonne. Finalement, le nTiO2 et nZnO non revêtus démontrent des comportements de déposition dynamiques (dépendant du temps) dans certaines conditions analysées. En revanche, le nTiO2 et nZnO revêtus de PAA étaient moins enclins à l'agrégation et démontrent un potentiel de transport important à des FI assez élevées (100 mM NaNO3 ou 3 mM CaCl2). De même, les particules de nCeO2 revêtus de PAA suspendus dans des solutions de NaNO3 étaient très mobiles dans le sable de quartz, peu importe la FI. Néanmoins, le nCeO2 et les particules nCAP démontrent une déposition rehaussée, parfois dynamique avec l'augmentation des concentrations de sels divalents et dans les eaux souterraines naturelles. Une déposition rehaussée est également rencontrée dans le sable loameux comparativement au sable de quartz. Enfin, les particules nCAP se sont avérées être un bon substitut expérimental pour les particules de nCeO2 revêtus de PAA. Ces résultats illustrent l'importance de considérer l'étendue et le type de revêtement des NMM en examinant le potentiel de contamination des oxydes métalliques dans les milieux granulaires et poreux saturés. En outre, les résultats obtenus soulignent la nécessité de tenir compte de la nature du milieu granulaire, ainsi que la chimie de l'eau, lors de l'évaluation des risques de contamination des NMM.

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Toms, Julianna J. „Effect of fluid distribution on compressional wave propagation in partially saturated rocks“. Curtin University of Technology, Department of Exploration Geophysics, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=128424.

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Partial saturation of porous rock by two fluids substantially affects compressional wave propagation. In particular, partial saturation causes significant attenuation and dispersion due to wave-induced fluid flow. Such flow arises when a passing wave induces different fluid pressures in regions of rock saturated by different fluids. When partial saturation is mesoscopic, i.e. existing on a length scale much greater than pore scale but less than wavelength scale, significant attenuation can arise for frequencies 10-1000 Hz. Models for attenuation and dispersion due to mesoscale heterogeneities mostly assume fluids are distributed in a regular way. Recent experiments indicate mesoscopic heterogeneities have less idealised distributions and distribution affects attenuation/dispersion. Thus, theoretical models are required to simulate effects due to realistic fluid distributions.
The thesis focus is to model attenuation and dispersion due to realistic mesoscopic fluid distributions and fluid contrasts. First X-ray tomographic images of partially saturated rock are analysed statistically to identify spatial measures useful for describing fluid distribution patterns. The correlation function and associated correlation length for a specific fluid type are shown to be of greatest utility. Next a new model, called 3DCRM (CRM stands for continuous random media) is derived, utilizing a correlation function to describe the fluid distribution pattern. It is a random media model, is accurate for small fluid contrast and approximate for large fluid contrast. Using 3DCRM attenuation and dispersion are shown to depend on fluid distribution.
Next a general framework for partial saturation called APS (acoustics of partial saturation) is extended enabling estimation of attenuation and dispersion due to arbitrary 1D/3D fluid distributions. The intent is to construct a versatile model enabling attenuation and dispersion to be estimated for arbitrary fluid distributions, contrasts and saturations. Two crucial parameters within APS called shape and frequency scaling parameters are modified via asymptotic analysis using several random media models (which are accurate for only certain contrasts in fluid bulk moduli and percent saturation). For valid fluid contrasts and saturations, which satisfy certain random media conditions there is good correspondence between modified APS and the random media models, hence showing that APS can be utilized to model attenuation and dispersion due to more realistic fluid distributions.
Finally I devise a numerical method to test the accuracy of the analytical shape parameters for a range of fluid distributions, saturations and contrasts. In particular, the analytical shape parameter for randomly distributed spheres was shown to be accurate for a large range of saturations and fluid contrasts.

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Darmawan, Hariyanto. „Transport of a pathogenic bacterium and its non-pathogenic variant strain through a granular porous medium: from a simple system to a real system“. Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104768.

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The attachment efficiency of two strains of Escherichia coli O157:H7 – one pathogenic strain and another non-pathogenic strain – was measured over a range of solution ionic strengths and in two different granular systems: a simple system made of clean quartz sand and a real system made of natural subsurface soil. In this study, the relevance of the non-pathogenic strain of E. coli O157:H7 as a potential surrogate for its pathogenic counterpart was investigated. The results suggest that it is not straightforward to find an appropriate surrogate for the pathogenic strain. Different porous media begets different attachment efficiency of the potential surrogate strain relative to the attachment efficiency of the toxigenic strain. A modest attempt was also made to build an artificial system that mimics the natural soil, by coating the clean granular sand with humic acids and adding clay component.
Pour étudier la contamination d'eaux souterraines, l'efficacité d'adhésion de deux variétés d'E. coli O157:H7 – une pathogène et une autre non-pathogène – a été mesurée sur une gamme de force ionique dans deux systèmes granulaires : un système simple fait de sable de quartz propre et un système naturel de sol souterrain. Dans cette étude, la pertinence de la variété non-pathogène (E. coli O157:H7) comme substitut potentiel pour sa contrepartie fut étudiée. Les résultats suggèrent qu'il est très difficile de trouver un substitut approprié de la variété pathogène pour ce type d'études, car différents médias porreaux engendrent différentes efficacités d'adhésion de la variété substitut potentielle. Une tentative a aussi été faite de construire un système artificiel dans le labo qui imite le sol naturel, en enrobant le sable de quartz avec des acides humiques et par l'addition d'un composé d'argile.

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Sýs, Tomáš. „Komplexní analýza funkce distribučního systému typu U“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443219.

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Fluid flow maldistribution plays a key role in equipment used in process and energy industries, although its evaluation is often underestimated or fully neglected. Uneven flow distribution may cause thermal or mechanical load on the tube bundle, and in extreme scenarios, it can also have an adverse effect on the process efficiency. This thesis aims to find the optimal computational tools for flow distribution prediction suitable for the initial stage of the equipment design process and to identify suitable settings of these tools for their subsequent industrial deployment. The results of simplified analytical models, detailed numerical simulations, and experimental measurements were compared for the dividing header and the U-type distribution system. It was found that the results provided by simplified mathematical models, the solution of which is also significantly less time-consuming compared to detailed CFD simulations, best correspond to the measured experimental values in all modeled configurations. For arrangements with higher lateral resistance coefficient, both computational approaches provide approximately equally accurate results. However, for arrangements with lower lateral resistance coefficient, the deviation of the results obtained by CFD calculations from the experimental data is significantly larger.

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Rouchon, Lydie. „Etude cinétique expérimentale et modélisation de la réaction de carbonatation de l'oxyde de calcium“. Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2012. http://tel.archives-ouvertes.fr/tel-00782500.

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Les émissions anthropiques de dioxyde de carbone, gaz à effet de serre, sont considérées comme les principales causes du réchauffement climatique. Le captage du dioxyde de carbone par l'oxyde de calcium, qui s'avère être une masse de captage appropriée, au cours de plusieurs cycles de carbonatation/décarbonatation est une solution à la diminution des émissions industrielles. Néanmoins, la capacité de captage du dioxyde de carbone par l'oxyde de calcium diminue au cours des cycles, soulevant ainsi des problèmes économiques majeurs. Actuellement, cette perte d'efficacité de captage est largement étudiée contrairement à la réaction même de carbonatation de CaO d'un point de vue fondamental.Dans l'optique de mieux comprendre la réaction de carbonatation de CaO, une étude cinétique a été menée par le biais d'expériences de thermogravimétrie sur poudre. L'approche cinétique a été basée sur des tests de cinétiques hétérogènes fondés sur les hypothèses de l'état pseudo-stationnaire et de l'étape limitante. Les courbes cinétiques expérimentales obtenues en conditions isothermes (450-650°C) et isobares (2-30 kPa) ont montré un temps de latence lié au processus de germination de la nouvelle phase, ainsi qu'un fort ralentissement de la réaction à partir d'un certain degré d'avancement. Ce temps de latence et le degré d'avancement correspondant au frein cinétique dépendent de la température et de la pression partielle de CO2. Afin d'en expliquer l'origine, des caractérisations texturales et morphologiques ont été effectuées à différents degrés d'avancement. Les modifications observées à l'échelle des agrégats ont suggéré une limitation de la vitesse de réaction par des phénomènes de transport de matière, susceptibles de bloquer l'accès du gaz au cœur des agrégats. Les décrochements en température réalisées en thermogravimétrie ont mis en évidence un comportement cinétique complexe. Trois domaines ont pu être distingués au cours de la réaction, quelles que soient la température et la pression partielle de CO2. L'interprétation de ces résultats a souligné le rôle de la porosité et de son évolution sur la cinétique, ainsi qu'un effet anti-Arrhenius dans le deuxième domaine.La modélisation cinétique a dû faire intervenir à la fois un modèle proche de la réalité physique à l'échelle des grains denses, mais également les processus de transport de matière et de chaleurs au sein de l'agrégat, afin de rendre compte des courbes expérimentales et de quantifier l'impact des différents paramètres expérimentaux sur la vitesse de réaction. Ce couplage échelle de la population des grains-échelle de l'agrégat a été réalisé à l'aide d'un logiciel de cinétique hétérogène, CIN4, développé au département PRESSIC, en collaboration avec la société ASTEK. Les simulations obtenues ont permis de décrire la réaction jusqu'au freinage cinétique.

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Hsu, Tzu-Hsuan, und 徐子軒. „Electrophoretic Motion of Charged Porous Colloidal Spheres in Stress-Jump Condition“. Thesis, 2013. http://ndltd.ncl.edu.tw/handle/41565520927960222813.

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碩士
國立臺灣大學
化學工程學研究所
101
The boundary condition for the flow field across a porous material-liquid interface has drawn the attention of many researchers. Stress-jump condition, proposed by Ochoa-Tapia and Whitaker, has been introduced to solve this type of problem. In this study, the electrophoretic behavior of a porous particle in stress-jump condition is investigated. The effect of double-layer polarization is taken into account. Brinkman model is adopted to simulate the porous structure, and stress-jump condition is introduced into porous material-liquid interface. We treat the problem by separating the physical region into two domains using spherical coordinates. The coupled electrokinetic equations are linearized assuming the applied electric field is weak. General electrokinetic equations are employed and solved with pseudo-spectral method based on Chebyshev polynomials and Newton-Raphson schemes. Key parameters of electrokinetic interest such as stress-jump coefficient, double layer thickness, friction coefficient of the porous particle, volume fraction, and fixed charge density are examined for their respective effect on the particle motion. We found, among other things, the stress-jump coefficient is a crucial factor in determining the particle electrophoretic behavior. As stress-jump coefficient increases, the electrophoretic motion becomes quicker, due to the friction force decreases. In addition, stress-jump coefficient has a significant influence on the degree of double-layer polarization. These properties make electrophoretic behavior becomes more complicated. Comparison with experimental data available in the literature is excellent, indicating the reliability of this analysis, as well as the importance of using stree-jump condition.

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Dissertationen zum Thema „Porous jump“

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