Fluid flow in porous media

Microcomputed tomography can be used to characterize the geometry of the pore space of a sedimentary rock, with resolu@on that is sufficiently refined for the realis@c simula@on of physical proper@es based on the 3D image. Significant advances have been made on the characteriza@on of pore size distribu@on and connec@vity, development of techniques such as laNce Boltzmann method to simulate permeability, and its upscaling. Sun, Andrade and Rudnicki (2011) recently introduced a mul@scale method that dynamically links these three aspects, which were oUen treated separately in previous computa@onal schemes. In this study, we improve the efficiency of this mul@scale method by introducing a flood--fill algorithm to determine connec@vity of the pores, followed by a mul@scale laNce Boltzmann/finite element calcula@on to obtain homogenized effec@ve anisotropic permeability. The improved mul@scale method also includes new capacity to consistently determine electrical conduc@vity and forma@on factor from CT images. Furthermore, we also introduce a level set based method that transforms poregeometry to finite element mesh and thus enables direct simula@on of pore--scale flow with finite element method. When applied to the microCT data acquired by Lindquist et al. (2000) for four Fontainebleau sandstone samples with porosi@es ranging from 7.5% to 22%, this mul@scale method has proved to be computa@onally efficient and our simula@ons has provided new insights into the rela@on among permeability, pore geometry and connec@vity. .

The Bruggeman approximation has widely been used for estimating the effective conductivity and diffusivity of both the catalyst and gas diffusion layers of polymer electrolyte membrane (PEM) fuel cells. This approximation is based on the Bruggeman's Effective Medium Theory [Bruggeman D. Berechnung verschiedener physikalischer konstanten von heterogenen substanzen. Ann Phys (Leipzig) 1935;24:636-79], which provides empirical correlation for the effective properties of a composite system. Since it is an empirical correlation, a unique correlation based on the Bruggeman approximation does not always hold for the PEM fuel cell effective properties. Rather, the Bruggeman correlation is a cell specific and experiment dependent correlation that depends on structure, phase composition, water saturation, experimental parameters, etc. Further, this correlation needs to be combined with other correlations to estimate the effective diffusivities. In this article, a set of mathematical formulations has been proposed for the effective transport properties in both the catalyst and gas diffusion layers of a PEM fuel cell. The effective conductivity and diffusivity expressions are derived from the mathematical formulations of the Hashin Coated Sphere model [Hashin Z. The elastic moduli of heterogeneous materials. J Appl Mech 1962;29:143-50], which provides an identical mathematical foundation for each of these effective properties rather than an empirical correlation and avoid to use of multiple correlations together. The present model formulations agree well with the results available in literature for the limiting case. Hence, the proposed formulations for the effective transport properties will be a useful estimating tool in the numerical modeling of PEM fuel cells.

The micropolar fluid flow over moving stretching surface in a non-Darcian porous medium with a uniform magnetic field is examined when viscosity and thermal conductivity are vary with temperature. Both the fluid viscosity and thermal conductivity are considered as an inverse linear function of temperature. Mathematical formulation of the problem under consideration is presented and a similarity transformation is applied to reduce the system of partial differential equations and their boundary conditions, describing the problem, into a boundary value problem of ordinary differential equations. The system of equations is solved numerically by shooting technique. The results are presented graphically for velocity, temperature and micropolar distributions for various values of non-dimensional parameters.

Thermoacoustic refrigeration systems use the principles of acoustics and thermodynamics in order to produce cooling effects. These systems are a possible solution to the environmental pollution problems caused by refrigerant gases like Chlorofluorocarbon (CFC),  Hydrochlorofluorocarbons (HCFC) and R-12 as they are spreading Toxicity and damaging the ozone layer. Moreover, these systems have no moving parts which reduce the maintenance costs significantly.

In this report, we are going to discuss both Driven Thermoacoustic Refrigerators (TADTAR) and Thermoacoustic Refrigerators (TAR) systems. However, due to COVID-19 epidemic and shortage of time our focus will be mainly on TAR system. The report contains a brief discussion about TAR and TADTAR systems’ theoretical backgrounds, operating principles, device components, obtained and desired results.

A comprehensive design for TAR system is going to be shown. This design is done using MATLAB code following Tijani’s, Swift’s, Hofler’s and Rott’s equations and standards. Also, it is based on a DELTAEC simulation model which is designed and ran successfully by following
Hofler’s and Tijani’s models with additional variations. Inventor drawings of each part of the design are provided within the report, and a prototype model is built and experimentally investigated.

Accurate descriptions of strength evolution are required in predictive models of fault zone behavior during earthquakes. At low sliding rates, frictional resistance between fault rocks is much higher than the shear stress that is typically inferred to be present during earthquakes. Laboratory experiments confirm that the friction coefficient drops at high sliding rates, and it is suggested that strengthening, possibly related to an increase in the area of viscous melt patches, may occur after this initial weakening stage. Most existing weakening mechanisms do not predict such strengthening, which may exert an important control on the thickness of the shear zone. We propose a micromechanical model of flash heating that describes how shear resistance evolves at the asperity scale as a result of distributed deformation over a weak layer that grows during the brief lifetime of each asperity contact. Beyond a threshold weakening velocity, our model predicts that friction should decrease with slip rate since higher sliding speeds cause the weak layer to thicken more rapidly. A comparison with published experimental data from a range of mineral systems shows good agreement with the model predictions. The parameter choices that ensure good model fits to the laboratory friction data are consistent with a priori estimates for the onset of asperity melting at high contact normal stresses. At higher sliding rates and/or elevated temperatures, our model predicts that the frictional rate dependence should transition from velocity weakening to become velocity strengthening because decreases in the contact lifetime with slip rate cause the average asperity strength to increase.

The study of flow of non-Newtonian fluids in porous media is very important and serves a wide variety of practical applications in processes such as enhanced oil recovery from underground reservoirs, filtration of polymer solutions and soil remediation through the removal of liquid pollutants. These fluids occur in diverse natural and synthetic forms and can be regarded as the rule rather than the exception. They show very complex strain and time dependent behavior and may have initial yield-stress. Their common feature is that they do not obey the simple Newtonian relation of proportionality between stress and rate of deformation. Non-Newtonian fluids are generally classified into three main categories: time-independent whose strain rate solely depends on the instantaneous stress, time-dependent whose strain rate is a function of both magnitude and duration of the applied stress and viscoelastic which shows partial elastic recovery on removal of the deforming stress and usually demonstrates both time and strain dependency. In this article the key aspects of these fluids are reviewed with particular emphasis on single-phase flow through porous media. The four main approaches for describing the flow in porous media are examined and assessed. These are: continuum models, bundle of tubes models, numerical methods and pore-scale network modeling.

ABSTRACT: Accurate measurement of permeability is critical for fluid flow modeling in porous media. Various experimental methods devised to measure permeability as a porous material property in composites are reviewed. Liquid flow and gas flow methods of permeability measurement for in-plane and transverse directions specifically for fiber-reinforced composites are discussed, as well as issues related to these methods and some associated permeability models. Alternative methods of permeability determination based on cross transport phenomenon are reviewed as well.

Spatial confinement in nanoporous media affects the structure, thermodynamics and mobility of molecular soft matter often markedly. This article reviews thermodynamic equilibrium phenomena, such as physisorption, capillary condensation, crystallisation, self-diffusion, and structural phase transitions as well as selected aspects of the emerging field of spatially confined, non-equilibrium physics, i.e. the rheology of liquids, capillarity-driven flow phenomena, and imbibition front broadening in nanoporous materials. The observations in the nanoscale systems are related to the corresponding bulk phenomenologies. The complexity of the confined molecular species is varied from simple building blocks, like noble gas atoms, normal alkanes and alcohols to liquid crystals, polymers, ionic liquids, proteins and water. Mostly, experiments with mesoporous solids of alumina, gold, carbon, silica, and silicon with pore diameters ranging from a few up to 50 nm are presented. The observed peculiarities of nanopore-confined condensed matter are also discussed with regard to applications.
A particular emphasis is put on texture formation upon crystallisation in nanoporous media, a topic both of high fundamental interest and of increasing nanotechnological importance, e.g. for the synthesis of organic/inorganic hybrid materials by melt infiltration, the usage of nanoporous solids in crystal nucleation or in template-assisted electrochemical deposition of nano structures.

Softening at drinking water treatment plants is often realised by fluidised bed pellet reactors. Generally, sand is used as seeding material and pellets are produced as a by-product. To improve to sustainability, research has been carried out to replace the seeding material by re-using grained and sieved calcite pellets as seeding material. An explicit fluidisation model is developed to predict the fluid bed state in fluid bed pellet softening reactors with calcite as seeding material. The fluidisation theory is extended in a model whereby soft sensors are derived and experimentally tested for a wide range of seeding material and pellets. With the soft sensors porosity, particle size and pressure drop can explicitly be calculated. Pilot research has been carried out to calibrate and full-scale experiments to validate the fluidisation models. Four different fluidisation models were reviewed from which the original Richardson-Zaki fluid bed model has been selected as the best explicit fluidisation model to predict the porosity, particle size and pressure drop. Applying a discretisation model for the fluid bed pellet reactor, the current operation of the treatment softening can be improved by estimating the fluidisation, pressure drop behaviour and particle profile. Waternet can apply the Richardson-Zaki fluid bed model in practice for building a soft sensor to achieve optimal bed fluid conditions for the softening process.

Thermoacoustic refrigeration systems use the principles of acoustics and thermodynamics in order to produce cooling effects. These systems are a possible solution to the environmental pollution problems caused by refrigerant gases like Chlorofluorocarbon (CFC), Hydrochlorofluorocarbons (HCFC) and R-12 as they are spreading toxicity and damaging the ozone layer. Moreover, these systems have no moving parts which reduce the maintenance costs significantly.
In this report, we are going to discuss both Driven Thermoacoustic Refrigerators (TADTAR) and Thermoacoustic Refrigerators (TAR) systems. However, due to COVID-19 epidemic and shortage of time our focus will be mainly on TAR system. The report contains a brief discussion about TAR and TADTAR systems’ theoretical backgrounds, operating principles, device components, obtained and desired results.
A comprehensive design for TAR system is going to be shown. This design is done using MATLAB code following Tijani’s, Swift’s, Hofler’s and Rott’s equations and standards. Also, it is based on a DELTAEC simulation model which is designed and ran successfully by following Hofler’s and Tijani’s models with additional variations. Inventor drawings of each part of the design are provided within the report, and a prototype model is built and experimentally investigated.

The unsteady flow can be analysed by Saint-Venant equations. These equations can be solved by characteristics and finite difference methods. The Saint-Venant equations are changed into four complete differential equations in characteristics method and these equations are solved by drawing two characteristics lines. The Saint-Venant equations are changed into set nonlinear equations and are solved using Preissman scheme in finite difference method. This set of equation is changed into linear equation using Newton-Rafson method and can be solved using Sparce method. In this research, the results of the two method were compared and this was shown that: 1) these two methods can draw the surface profiles and flow hydrograph as well; 2) the finite difference method is more accurate than that one; 3) the mesh size in finite difference method can be larger than that one; 4) the difference between two methods are increased by increasing the time and distance.. He is interested in the topics of: groundwater hydrology, irrigation and drainage engineering, sustainable development and environmental assessment, climate and integrated and sustainable water resource management, artificial neural network, and genetic algorithm. He has contributed to more than 80 publications in journals, books, or as technical reports. Currently, he is as a

The mathematical expressions that are used to predict the volumetric performance and pressure behavior of the reservoir vary in forms and complexity depending upon the number of mobile fluids in the reservoir. There are generally three cases of flowing systems:

Prinsloo, G.J. 2011. Inlet Air Flow Meter for an Internal Combustion Engine. Bachelor Engineering Thesis, Mechatronic Engineering, Stellenbosch University, South Africa. doi 10.13140/2.1.3010.4649.
This project focus on the design an Inlet Air Flow Meter for accurate measurement of mass flow rate of atmospheric air into an engine during engine dynamometer tests. The meter will be used to determine the air-fuel ratio and volumetric efficiency of the engine. To determine if an Inlet Air Flow Meter can be designed and constructed to be sufficiently accurate for dynamometer applications, while evaluating the potential for commercial use in high performance engine management systems. The Inlet Air Flow Meter will be used to evaluate new Biofuel formulations and their performance in internal combustion engines, for example non-edible vegetable oils extracted for fatty acid compositions and biodiesel production, and to evaluate the air flow characteristics, engine performance and emissions production of non-edible oils.

A large number of correlations can be found in the literature for the calculation of pressure drop caused by fluid flow through packed beds. New correlations continue to be proposed and there appears to be no general agreement regarding which correlation is the most accurate. In this work, experiments have been carried out with water using glass spheres of nine different sizes, varying from 1.18 mm to 9.99 mm. For each size, experiments were repeated with at least two different porosities. A total of 38 correlations from the literature have been evaluated and a uniform notation was established to facilitate the comparison of the correlations. While the Ergun equation remains the most widely-used correlation, the data collected in this work shows that it should not be used above Rem ≈ 500. A simple new equation (fV = 160 + 2.81Rem^0.904) is proposed to represent the data collected in this work. The new equation yields the smallest mean error among all the correlations considered here. While a substantial amount of the data collected in this work involved D/dP ratios less than 10, the correlations that fit the current data best do not have any wall effect correction terms.

Thermal energy storage technologies can facilitate the transition to an energy system based largely on renewable sources and enable efficiency gains for industrial processes in general. Due to their specific advantages, various concepts of thermo-chemical storage systems are being developed. They share characteristic features of mass and heat transport that are strongly coupled through a variety of physical and chemical phenomena. To facilitate the understanding of the coupled multi-physics processes inside such systems, a versatile conceptual model for directly permeated reactive beds was developed in part 1 of this work. It was based on thermodynamic principles and the Theory of Porous Media. The model was then implemented into OpenGeoSys, a scientific finite element simulation software. In this article, the model is specified to the well-studied calcium hydroxide reaction system to illustrate its practical applicability. Sensitivity analyses reveal the influence of particle diameter, porosity, permeability, mass flux, and reaction rate. Two distinct "reaction waves" are identified to migrate through the reactor. The power required to pump the gas stream was decomposed into parts related to the classical mechanical pressure drop and to the chemical reaction. The results can be used for the optimization of thermochemical heat storage systems.

A B S T R A C T The fluid flow and heat transfer of a nanofluid is numerically examined in a two dimensional microchannel filled by a porous media. Present nanofluid consists of the functionalized multi-walled carbon nanotubes suspended in water which are enough stable through the base fluid. The homogenous mixture is in the thermal equilibrium which means provide a single phase substance. The porous media is considered as a Darcy-Forchheimer model. Moreover the slip velocity and temperature jump boundary conditions are assumed on the microchannel horizontal sides which mean the influences of permeability and porosity values on theses boundary conditions are presented for the first time at present work. To do this, the wide range of thermo physical parameters are examined as like Da ¼ 0.1 to 0.001, Re ¼ 10,100, dimensionless slip coefficient from 0.001 to 0.1 at different mass fraction of nanoparticles. It is observed that less Darcy number leads to more local Nusselt number and also applying the porous medium corresponds to higher slip velocity.

In the present study, heat transfer and fluid flow of a pseudo-plastic non-Newtonian nanofluid over permeable surface has been solved in presence of injection and suction. Similarity solution method is utilized to convert the governing partial differential equations into ordinary differential equations, which then is solved numerically using Runge–Kutta–Fehlberg fourth–fifth order (RKF45) method. The Cu, CuO, TiO 2 and Al 2 O 3 nanoparticles are considered in this study along with sodium carboxymethyl cellulose (CMC)/water as base fluid. Validation has been done with former numerical results. The influence of power-law index, volume fraction of nanoparticles, nanoparticles type, and permeability parameter on nanofluid flow and heat transfer was investigated. The results of the study illustrated that the flow and heat transfer of non-Newtonian nanofluid in presence of suction and injection has different behaviors. For injection and the

The flow around cylinder open the path for studying more complex shape bodies that still keep in their external flow properties the combinations of the flow properties of simpler bodies like flat plates, cylinders, ellipses. The aim of this study is to describe flow around a cylinder based on simulations with Comsol and Ansys Fluent and to make comparisons with the experimental and analytical results. Drag force that appear at flow around cylinders have an important practical impact in applications. Cylinder is a case where because of its simplicity the flow results could be checked broadly in all three ways -analytical, computational and experimental. Describing in exhaustive way the flow around cylinder with all of its flow properties opens the way of studying further more complex shapes like hulls of the ships and submarines.

La pollution d'aquifères par des hydrocarbures est très persistante et difficile à traiter, devenant un enjeu majeur pour l'environnement en raison de l'effet négatif sur la santé humaine. La génération de mousse in situ combinée au lavage de sols est une technique de dépollution innovante, permettant un meilleur contrôle de la mobilité des fluides dans des formations hétérogènes. Le but de cette méthode est de bloquer l'écoulement dans les couches à forte perméabilité pour améliorer l'efficacité de balayage des strates peu perméables.

This paper presents a review of the state-of-the-art on interphase mass transfer between immiscible fluids in porous media with focus on the factors that have significant influence on this process. In total close to 300 papers were reviewed focusing to a large extent on the literature relating to NAPL contamination of the subsurface. The large body of work available on this topic was organized according to the length scale of the conducted studies, namely the pore, meso and field scales. The interrelation of interphase mass transfer at these different scales is highlighted. To gain further insight into interphase mass transfer, published studies were discussed and evaluated in terms of the governing flow configurations defined in terms of the wettability and mobility of the different phases. Such organization of the existing literature enables the identification of the interfacial domains that would have significant impact on interphase mass transfer. Available modeling approaches at the various length scales are discussed with regard to current knowledge on the physics of this process. Future research directions are also suggested.

Carbonate rocks are complex in their structures and pore geometries and often exhibit a real problem in their classification and behavior. Many petrophysical and fluid flow properties remain unexplained and perhaps uncertain because of improper characterization of the reservoir rock. In this research, carbonate rock types were defined from thin-sections based on the structure of the rock together with its pore types. The rock type classifications were improved by incorporating pore-throat size distribution and poro-perm information, and high resolution plug CT images. This would lead to a robust rock typing scheme that should facilitate the understanding of heterogeneity effects on reservoir flow properties. Laboratory-measured imbibition relative permeability (Kr) data were determined on reservoir core samples in two " mixed-wet " carbonate fields from the Middle East region. The Kr curves were explained based on the identified rock types and gave consistent trends. The Kr curves were fitted with Corey exponents, and yielded high " no " and low " nw " for the higher permeability samples, which may be wrongly interpreted as more oil-wet rocks compared to the lower permeability samples. The variations in Kr curves with the different rock types were argued to be the result of different rock structures and pore geometries that control pore accessibility and surface area. The obtained Krw and Kro data from steady state experiments are not abundant in the literature and hence should serve as an important piece of information in mixed-wet carbonate reservoirs with varying rock types.

In this research work, we analysed the various multiphase flow parameters in a porous medium. From the research work it was observed that pressure gradient calculations and flow regimes in multiphase flow are all dependent on these parameters, which are liquid holdup, viscosity, velocity, density, surface tension and these parameters can be determined by using certain correlations and charts as described in chapter three of this research . We also determined the effects of some of these parameters on multiphase flow in a porous medium or in a pipe

The study of flow of non-Newtonian fluids in porous media is very important and serves a wide variety of practical applications in processes such as enhanced oil recovery from underground reservoirs, filtration of polymer solutions and soil remediation through the removal of liquid pollutants. These fluids occur in diverse natural and synthetic forms and can be regarded as the rule rather than the exception. They show very complex strain and time dependent behavior and may have initial yieldstress. Their common feature is that they do not obey the simple Newtonian relation of proportionality between stress and rate of deformation. Non-Newtonian fluids are generally classified into three main categories: time-independent whose strain rate solely depends on the instantaneous stress, time-dependent whose strain rate is a function of both magnitude and duration of the applied stress and viscoelastic which shows partial elastic recovery on removal of the deforming stress and usually demonstrates both time and strain dependency. In this article, the key aspects of these fluids are reviewed with particular emphasis on singlephase flow through porous media. The four main approaches for describing the flow in porous media are examined and assessed. These are: continuum models, bundle of tubes models, numerical methods and pore-scale network modeling.

Spatial confinement in nanoporous media affects the structure, thermodynamics and mobility of molecular soft matter often markedly. This article reviews thermodynamic equilibrium phenomena, such as physisorption, capillary condensation, crystallisation, self-diffusion, and structural phase transitions as well as selected aspects of the emerging field of spatially confined, non-equilibrium physics, i.e. the rheology of liquids, capillarity-driven flow phenomena, and imbibition front broadening in nanoporous materials. The observations in the nanoscale systems are related to the corresponding bulk phenomenologies. The complexity of the confined molecular species is varied from simple building blocks, like noble gas atoms, normal alkanes and alcohols to liquid crystals, polymers, ionic liquids, proteins and water. Mostly, experiments with mesoporous solids of alumina, gold, carbon, silica, and silicon with pore diameters ranging from a few up to 50 nm are presented. The observed peculi...

Thermoacoustic refrigeration systems use the principles of acoustics and thermodynamics in order to produce cooling effects. These systems are a possible solution to the environmental pollution problems caused by refrigerant gases like Chlorofluorocarbon (CFC), Hydrochlorofluorocarbons (HCFC) and R-12 as they are spreading toxicity and damaging the ozone layer. Moreover, these systems have no moving parts which reduce the maintenance costs significantly.
In this report, we are going to discuss both Driven Thermoacoustic Refrigerators (TADTAR) and Thermoacoustic Refrigerators (TAR) systems. However, due to COVID-19 epidemic and shortage of time our focus will be mainly on TAR system. The report contains a brief discussion about TAR and TADTAR systems’ theoretical backgrounds, operating principles, device components, obtained and desired results.
A comprehensive design for TAR system is going to be shown. This design is done using MATLAB code following Tijani’s, Swift’s, Hofler’s and Rott’s equations and standards. Also, it is based on a DELTAEC simulation model which is designed and ran successfully by following Hofler’s and Tijani’s models with additional variations. Inventor drawings of each part of the design are provided within the report, and a prototype model is built and experimentally investigated.

Wettability is a key factor influencing multiphase flow in porous media. In addition to the average contact angle, the spatial distribution of contact angles along the porous medium is important, as it directly controls the connectivity of wetting and non-wetting phases. The controlling factors may not only relate to the surface chemistry of minerals but also to their texture, which implies that a length-scale range from nanometres to centimetres has to be considered. So far, an integrated workflow addressing wettability consistently through the different scales does not exist. In this study, we demonstrate that such a workflow is possible by combining micro-computed tomography imaging with atomic force microscopy (AFM). We find that in a carbonate rock, consisting of 99.9% calcite with a dual porosity structure, wettability is ultimately controlled by the surface texture of the mineral. Roughness and texture variation within the rock control the capillary pressure required for initializing proper crude-oil-rock contacts that allow ageing and subsequent wettability alteration. AFM enables us to characterize such surface-fluid interactions and to investigate the surface texture. In this study, we use AFM to image nano-scale fluid-configurations in situ in 3D at connate water saturation and compare the fluid configuration with simulations on the rock surface assuming different capillary pressures.

In this thesis we implement a numerical model of heat transfer in geothermal reservoirs. We use existing pressure and flow transport solvers as a starting point to investigate discretization techniques for a convection-conduction temperature equation. Then we develop and analyse two dierent heat transfer solvers: explicit and implicit, that have dierent accuracy and onvergence requirements. For the convective part of the energy equation the upwind scheme is implemented and the two-point flux approximation is used to discretize the conductive term. Usually heat transfer simulations require large computational time due to high resolution on a fine scale. For efficient computation we investigate flow-based upgridding techniques, which were used before for fluid transport in porous media. However upgridding and upscaling can lead to less accurate results due to much loss of details in a discrete model. We compare solutions on different types ofgrids such as Cartesian grid and flow-based grids that are generated according to various indicators like permeability, velocity, time-of-flight and thermal conductivity. In this work we simulate an initial-boundary value problem with a heat flow through boundaries and try to investigate, which coarse grid leads to the most accurate results when solving the energy equation.

Several deterministic and stochastic multi-variable global optimization algorithms (Conjugate Gradient, Nelder-Mead, Quasi-Newton, and Global) are investigated in conjunction with energy minimization principle to resolve the pressure and volumetric flow rate fields in single ducts and networks of interconnected ducts. The algorithms are tested with seven types of fluid: Newtonian, power law, Bingham, Herschel-Bulkley, Ellis, Ree-Eyring and Casson. The results obtained from all those algorithms for all these types of fluid agree very well with the analytically derived solutions as obtained from the traditional methods which are based on the conservation principles and fluid constitutive relations. The results confirm and generalize the findings of our previous investigations that the energy minimization principle is at the heart of the flow dynamics systems. The investigation also enriches the methods of Computational Fluid Dynamics for solving the flow fields in tubes and networks for various types of Newtonian and non-Newtonian fluids.

A B S T R A C T Platinised titanium mesh is a common electrode material in industrial electrolytic cells and Ce-based redox flow batteries. In this work, the electrodeposition of platinum on a stack of titanium micromeshes is performed from a flowing alkaline solution in a rectangular channel, divided flow cell. The morphology and distribution of the resulting platinum deposits are studied by SEM, EDS mapping and X-ray computed tomography. The active surface area of the electrode was assessed from the charge transfer current for the reduction of Ce(IV) ions and compared to that of planar and expanded metal mesh electrodes. The surface area was estimated by hydrogen electrosorption relative to that at a planar Pt/Ti electrode. As expected from the potential drop within the electrode channel, the individual micromesh near the cell separator showed a higher platinum content. Pt/Ti micromesh offers an extended surface area and enhanced mass transport compared to planar electrodes and conventional expanded metal mesh anodes. The applications for these and alternative electrode structures are discussed.

We model the transport of fluid through porous media in terms of fractional diffusion equation (FDE) for the pressure (,) p x t. Potential application could be to shale gas recovery in tight porous media. Specifically, we pose the time FDE in a finite domain of length L, 0 (,), 0 , 0 t

Using the method of complex potentials we present the closed form of analytical solution for the stresses and displacements around an elliptical cavity filled with fluid in the permeable poroelastic medium. The far-field pore pressure is different from the pressure inside cavity. The fluid is allowed to diffuse through the cavity's wall towards surrounding medium. The two-dimensional plane-strain and plane-stress models are considered with steady-state distribution of diffusive pore-fluid pressure. The diffusion of fluid is coupled to the deformation of a medium using a linear theory of poroelasticity. Since in the static case the diffusion of pore fluid is controlled by an ordinary Laplace equation, the problem is reduced to elastic problem with distribution of volume forces (known as seepage forces) along gradients of pore pressure. Due to similarity between poroelasticity and thermoelasticity, the present solution is applicable both to the poroelastic and thermoelastic problems with a steady-state distribution of pore pressure and temperature, respectively. Since it is getting more common to model the deformation coupled to Darcy-flow in geosciences and no clear criteria has been suggested for verification of numerical codes, we discuss the possible application of the analytical solution as the benchmark for testing of poroelastic and thermoelastic numerical codes. To stimulate a wider use of the solution for stresses, displacements and pore-fluid pressure around an elliptical cavity are implemented in MATLAB and can be downloaded from the web.

An analysis is presented to study the forced convection in unsteady magnatohydrodynamic boundary layer flow of a nanofluid over a permeable shrinking sheet in the presence of thermal radiation and chemical reaction. A variable magnetic field is applied normal to the sheet. The nanofluid model includes Brownian motion and thermophoresis effects are also considered. The boundary layer equations governed by the partial differential equations are transformed into a set of ordinary differential equations the help of local similarity transformations. The coupled and nonlinear differential equations are solved by the implicit finite difference method along with the Thamous algorithm. We have explained the effect of various controlling flow parameters namely unsteadiness parameter (A), magnetic parameter (M), thermal radiation parameter (R), Prandtl number (Pr), Brownian motion parameter (Nb), thermophoresis parameter (Nt) and Lewis number (Le) on the dimensionless velocity, temperature and nanoparticle volume fraction profiles are analyzed.

The porosity and the pore size have a great effect on the properties of packed beds. There is no doubt that any small change in the porosity of the packed bed leads to a big change in the pressure drop required for the fluid flow through the packed bed.

Proton exchange membrane (PEM) fuel cell Two-phase flow pressure drop PEM fuel cell flow channels a b s t r a c t Water management in proton exchange membrane (PEM) fuel cells has stimulated an extensive research on different aspects of water transport phenomena. As a PEM fuel cell operates, power is produced with water and heat as inevitable byproducts. The water produced during the operation of a PEM fuel cell results in a liquid-gas two-phase flow in flow channels. A successful PEM fuel cell design requires a comprehensive knowledge about different properties of liquid-gas two-phase flow. One such property, that has a dominant impact on the performance of a PEM fuel cell, is the two-phase flow pressure drop within the flow channels. This paper reviews the two-phase flow pressure drop correlations that have been developed for the application of PEM fuel cell. It also reviews the effect of different working conditions on the two-phase flow pressure drop in PEM fuel cell flow channels.