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This paper presents an adaptive mesh refinement (AMR) algorithm to solve the non-isothermal multiphase flows in heterogeneous porous media comprising different rock types. To address the discontinuity coming from different rock types, we found that the ratios of relative permeability and oil-gas capillary pressure are continuous; hence they are chosen as the judging values for the regridding purpose. Moreover, because of the tensorial permeability and the complex topology of the AMR grid, a coupling flux solution based on the multipoint flux approximation was carefully designed. Numerical examples revealed the accuracy and efficiency of the proposed AMR algorithm. [ABSTRACT FROM PUBLISHER]

The waxy crude oil is cooled and the waxy crystals form a grid structure after the shutdown, which leads to a very complicated heat transfer process. The degree of temperature drop of crude oil after shutdown directly determines the formulation of restart plan. How to accurately describe the phase transition heat transfer process of waxy crude oil based on the phase change of wax crystals is a hot issue in the field of crude oil storage and transportation. In this paper, the wax evolution process of crude oil was described, and a new wide phase transition partition model was proposed, with the governing equations being given for each sub-region. In the fuzzy zone of porous media, the Brinkmann-Forchheimer-Darcy seepage model was adopted. The iterative method was used to solve the discrete equations, and the solver adopted strong implicit method. The model and its solution method were verified by experiment. The breaking point was the index to judge the transition of crude oil from liquid phase to porous medium, and different breaking points of different kinds of crude oil correspond to different temperature ranges of porous media, so the influence of different breaking point temperature on heat transfer process was developed. Then, based on the model, the phase change heat transfer process was analyzed by using the change trajectory of the highest temperature point, and the transformation and influence of natural convection heat transfer process were discussed emphatically. [ABSTRACT FROM AUTHOR]

Rock physics models are widely used for reservoir characterisation in seismic studies. By improving the models, especially for reservoir rocks, more realistic characterisations can be achieved. To calibrate such models the elastic properties of reservoir porous rocks have been measured by ultrasonic techniques for many years. In conventional ultrasonic methods the local strain inside the wave is much higher than that in field experiments. Up until now, it has not been clear how the velocity of the ultrasonic wave depends on the strain, however this knowledge is important for interpretation of the results of the experiments. This work is an extension of our previous study on the effect of the strain amplitude on wave velocity. This paper focuses on S-wave velocity and its dependency on strain-amplitude effect for porous media (Bentheimer sandstone) and reference media (aluminium). In this study we: (1) directly measured the particle displacement in the ultrasonic wave using a Laser Doppler Interferometry (LDI) and (2) measured the changes in P and S-waves velocities by variations of increasing amplitudes applied to a source transducer from 43 to 400 volts. We measured the velocity using a conventional ultrasonic method and linked the changes of velocity to the measured local strain in the wave which we measured by LDI. The study indicated that for the unconfined Bentheimer sandstone, increasing the local strain produced by an ultrasonic wave from (3.6) 10−7 to (5.7) 10−6 resulted in the S-wave velocity decreasing by 4.75%. Using the LDI technique we also investigated the strains at different points on the surface produced by an S-wave transducer. [ABSTRACT FROM AUTHOR]

Asphaltene deposits can reduce the productivity of the reservoir as well as foul piping and surface equipment. Current chemical and mechanical methods for treating deposition are only partially effective partly because the deposition process is poorly understood. The most commonly way to asphaltene precipitation reduction is applying an asphaltene inhibitor. In order to investigate the extent of formation damage by asphaltenes in crude oil this work has used electro kinetic technique to study the adsorption of asphaltenes in rock pores. Most researchers investigate the kinetics of adsorption by monitoring changes in the concentration of asphaltene or polymer in a dispersion of adsorbent particles or capillaries. This study is a coherent approach to measure amount of asphaltene adsorption on rock surface and survey effect of asphaltene inhibitors on precipitation reduction in porous media. [ABSTRACT FROM AUTHOR]

A numerical investigation of the flow and behaviour of properties of a water-based Al2O3-nanofluid inside a two-sided lid-driven inclined non-uniformly heated and concentrated porous cavity is made in this paper. The focus of the study is on determining how the buoyancy ratio and the inclination angles influence the unsteady double-diffusive natural convection in a cavity filled with a porous medium, and with non-uniform boundary conditions. We further consider different nanoparticle volume fractions of the nanofluid. It is assumed that the left and right vertical walls are insulated, while the bottom wall is heated and concentrated non-uniformly and the top wall maintained at a constant cold temperature. The top and bottom walls move from left to right and right to left with constant speed, respectively. The governing equations are solved numerically using a staggered grid finite-difference method for streamlines, isotherms, iso-concentrations, average Nusselt number and average Sherwood number for various values of nanoparticle volume fraction, inclination angle and buoyancy ratio. The change in the flow, temperature and concentration profile patterns with respect to time is depicted and described. The results are compared with previously published work and excellent agreement has been obtained. [ABSTRACT FROM AUTHOR]

Porous pavements are used widely worldwide to improve wet-weather driving safety and to reduce tire-pavement noise. A common form of distress that affects these service functions of porous pavements is clogging. The conventional pavement condition survey practices do not perform tests or make measurements to assess the degree of clogging, and the extent it has affected the pavement's functional performance with respect to noise reduction or skid resistance enhancement. There is also no sound engineering basis or guidelines today to guide highway agencies to determine the state of clogged porous pavement condition at which a major maintenance or rehabilitation of porous pavement must be carried out to restore the pavement's noise reduction or skid resistance enhancement performance. This paper focuses on the determination of a porous pavement's skid resistance threshold state at which clogging has led to inadequate skid resistance for safe traffic operations. It presents a rational engineering procedure that applies skid resistance requirements to determine the threshold service state of a clogged porous pavement. A theoretically sound concept and analysis for calculating the wet-weather skid resistance of a porous pavement is developed. Since it is not possible or practical to measure the in situ degree of clogging on site, a permeability measurement is proposed in this study for practical implementation of the proposed procedure. A threshold permeability is determined to define the threshold service state of the porous pavement with respect to wet-weather skid resistance. [ABSTRACT FROM AUTHOR]

Many industrial and natural processes involve flow in highly permeable media, such as exchangers, canopies, urban canyons. Traditional assumptions used for modeling flow equations in low permeability structures may not hold for these systems with very large pores. Reynolds numbers may be too large so that Darcy's law is no longer valid. Large Capillary and Bond numbers may also invalidate the quasistatic assumptions implicit in many empirical formulations and upscaling results. In this paper, we review several approaches developed to handle such cases, basing our analysis on new experimental data and results from upscaling methods. For one-phase flow this has led to various formulations of macro-scale momentum transport including generalized Forchheimer equations and macro-scale turbulent models. For two-phase flows, we discuss possible ways toward deriving macro-scale models from the pore-scale equations and introduce several macro-scale models: generalized Darcy's laws, models with cross terms accounting for the viscous interaction between the flowing phases, formulations capturing inertial, or dynamic effects. Models suitable for describing flow in structured media like chemical exchangers containing structured packings are also introduced. Finally, we present hybrid representations that couple approaches at two different scales, for instance, a meso-scale network approach coupled with dynamic rules obtained from pore-scale numerical simulations or experiments. This approach proved useful in describing the diffusion of impinging jets in packed beds, which is not described properly by capillary diffusion. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on sound absorption performance of aerogel/polymer nonwoven fabrics. Polyester/polyethylene nonwovens embedded with hydrophobic amorphous silica aerogel were chosen for sound absorption measurements. The sound absorption coefficient (SAC) of single and laminated layers of aerogel nonwovens blankets was tested by Brüel and Kjær impedance tube, the noise reduction coefficient (NRC) was used for numerical analysis. A sound absorption index was developed to analyze the effect of aerogel content on sound absorption ability. The effect of air-back cavities on SAC of single-layer aerogel/polymer nonwoven fabrics was investigated. The results show that there is a decrease in SAC with the increase of aerogel content. It is observed that the NRC linearly increased with the increase of layers for all the samples. It was also found that the air-back cavities result in resonance phenomenon, as the increase in thickness of air-back cavities the peak values of SAC shift toward lower frequencies. [ABSTRACT FROM AUTHOR]

This is the second in a series of three papers that studies acoustic waves governed by the linearized compressible Stokes equations in a porous medium. In particular, we want to analyze the simultaneous inviscid and high frequency limits of fluid flows in a porous medium. The presence of time-space boundary layers decouples the flow into an incompressible (that we call microincompressible) and an acoustic part (that we call micro-acoustic) on the microscopic scale. While this paper employs the two-scale methods used in our first paper [10], the present boundary layer phenomenon requires additional weak convergence tools. Using the Bloch decomposition, we introduce modified Helmholtz operators, enabling us to split the flow into its microincompressible and microacoustic parts. Closed equations for the microincompressible flow are obtained using two-scale convergence, while closed equations for the microacoustic flow are given in our forthcoming paper. [ABSTRACT FROM PUBLISHER]

The normal incidence sound absorption coefficient of single-layered porous materials predicted using some prediction models is well known. The published acoustic behaviors prediction models, such as Biot model, Zwikker and Kosten model, Delany and Bazley model, and Champoux and Allard model, can give acceptable prediction results by only taking specific flow resistivity and material thickness as independent variables to estimate the normal incidence sound absorption coefficient. However, the existing literature fails to provide proper knowledge regarding the acoustic characteristics of dual-layered porous nonwoven absorbers. So, the aim of this paper was to propose a theoretical acoustic model for dual-layered porous nonwoven absorber and to verify the proposed model experimentally. In theory aspect, the study focused on the extension algorithm of the Zwikker and Kosten model for dual-layered nonwoven absorber. The theoretical analysis of the impact of thickness and porosity of outer and inner layer on sound absorption coefficient was detailed using numerical simulation method. In experiment aspect, we particularly designed 20 dual-layered nonwoven absorbers with four types of meltblown polypropylene nonwoven materials and five types of hydroentangled E-glass fiber nonwoven materials firstly. Secondly, the calculated sound absorption coefficients using the proposed model were compared with the measured ones of the 20 dual-layered nonwoven absorbers at 250, 500, 1000, and 2000 Hz. Experimental results indicate that the measured and the calculated data have very similar trend with the change of thickness, porosity, and the sound frequency, apart from the obvious difference between them at low frequency. [ABSTRACT FROM PUBLISHER]

Numerous computational and conceptual difficulties are often encountered when conceiving techniques which are effective in detecting damage intensity, localization, and onset. Actually, also when the semi-inverse or the material characterization problems (which are commonly formulated in this context) can be recognized to be well posed, the numerical and computational obstacles which need to be overcome can render useless the conceived methodology. In the present paper we propose to change the paradigm used up to now when addressing the problem of damage assessment in engineering materials. In fact, we propose to conceive a metamaterial the properties of which make more expedite and effective the detection of cracks onset and damage evolution via the study of reflection and transmission of waves. More particularly, porous materials with underlying heterogeneous micro-structure may magnify the effects of reflection and transmission of waves at damaged sites depending on the considered boundary conditions. Materials of this type would make easier the structural health monitoring via nondestructive evaluation of local damage and would permit to detect incipient structural failure in a more efficient way. By analyzing the characteristic patterns of the reflection and transmission properties of surfaces where damage is concentrated, we show that, in the considered metamaterials, slow incident waves can be used to detect the onset and evolution of first gradient macroscopic damage (δe), while fast incident waves can be used to reveal loss of contact at the microscopic level, i.e. to detect the onset of second gradient macroscopic damage (δr). [ABSTRACT FROM AUTHOR]

In the emulsion flooding processes, the flow of the emulsion droplets facilitates the oil recovery. However, there is currently limited insight into the microscopic enhanced oil recovery mechanism of emulsion droplets. It is essential to conduct further research to explore the interactions among the emulsion phase, oil phase, and water phase. In this work, the role of emulsion droplets on the mobilization of residual oil was numerically studied by the phase field method. We have studied the relevant mechanism in a single flow region structure, and a porous media. The results show that droplet radius, interfacial tension, and wettability all affect the flow behavior of the emulsion phase. The flow of emulsion results in much more displacement efficiency and sweep efficiency, which helps recover trapped oil in pore corners and the low permeability areas in the porous medium. In contrast to water flooding, the emulsion flooding elevated the oil recovery from 42.8% to 48.5% in the high-permeability region and from 10.9% to 40.4% in the low-permeability region. [ABSTRACT FROM AUTHOR]

Tolerating the harsh conditions of reservoirs is one of the main challenges for the application of chemicals in field operations. Polymers are one of the chemical agents with extensive utilization in reservoirs. They could be used to control water conformance, though there are some limitations like low thermal tolerance and low chemical stability, which restrict their applications. To overcome these limitations, encapsulation of xanthan gum by silica nanoparticles and lecithin has been investigated in this research. Using the inverse emulsion method, xanthan gum is encapsulated and the stability of capsules at various conditions is assessed. It is illustrated that the stability of silica-shelled capsules is greater than that of lecithin. Based on the results of this study, the encapsulation of xanthan gum improved its thermal resistivity. Besides, formed capsules reflect fair stability against high salinity conditions. Finally, the formed capsules were injected into two artificial Berea sandstone cores and it was found that the lecithin-shelled capsules can reduce the permeability of cores up to 92%. Silica-shelled capsules are also capable of blocking the porous medium partially and reduce the permeability by around 33%. [ABSTRACT FROM AUTHOR]

The paper describes the results of the experimental study of the properties of piezoceramics, ceramic matrix composites "ceramics/crystal," and porous ceramics based on lead-free sodium-lithium niobates (Na, Li)NbO3 and sodium-potassium niobates (Na, K)NbO3 compositions. The measurements of elastic, dielectric and piezoelectric parameters, as well as microstructural studies of experimental samples of lead-free porous piezoelectric ceramics and composites were performed. It was shown that the use of alkali metal niobates in the form of ceramic matrix composites and porous ceramics allows to increase the main functional parameters of these materials and makes them competitive with piezoceramics of the PZT system. The developed lead-free porous and composite materials have a unique combination of parameters and can be used for the manufacture of ultrasonic transducers and devices for a wide range of applications, including medical and nondestructive testing equipment. [ABSTRACT FROM AUTHOR]

When a cementitious material is in contact with ambient air, CO2 enters the material by the porous network and through the cracks, reacts with the CSH hydrates and Ca (OH)2. These carbonation reactions depend on saturation degree of the material, it does not occur in a fully saturated or totally dry material. Thus, knowledge of isotherms, both for water sorption and desorption, is of interest in modelling the long-term behaviour of these materials. The objective of this paper is to obtain desorption and adsorption isotherms in a short time, and to study the influence of carbonation on the isotherms using an accelerated experimental protocol using thin disc materials of 37.5 mm of diameter and 2 mm thick. The results show that isotherms can be obtained in a significantly reduced time, on the basis of near equilibrium state for each relative humidity levels. The analysis of the distribution of pore radii obtained from the isotherms shows that carbonation causes an increase of the volume of capillary pores while dramatically decreasing the connected porosity of hydrates. [ABSTRACT FROM AUTHOR]

This paper presents a new macroscopic mesh-free particle method in which Darcy's and Forchheimer's terms are introduced into the governing equation to ensure the capacity of the particle method in simulating laminar and turbulent porous medium flows. A developed interfacial condition and inflow boundary condition are implemented in the macroscopic particle method to improve the stability of the Particle-based model. The comparisons of channel flow over and within porous bed among the present method, previous mesh-based method, and experimental data show that the macroscopic particle method is capable of simulating flows in both the clear flow region and porous flow region. Finally, two cases of flow over a rigid box and a cylinder lying on porous bed are simulated, and the numerical results are in good agreement with the measured data. The analysis and comparisons indicate that the newly developed particle-based method is reliable and has been successfully extended to macroscopic porous medium simulation. [ABSTRACT FROM AUTHOR]

Porous materials are widely used in porous media filtration, membrane separation, catalyst substrates, solid fuel cells, insulation, and other fields. When the porous material used in the field of insulation, heat transfer characteristics become its most important performance parameters. The heat transfer characteristics of porous material is a complex issue affected not only by solid elements and porosity, it is also affected by composite structures. Therefore, how to optimize the heat transfer properties of porous materials is a problem to be urgently solved. In this paper, the numerical method is used to study the effects of pore size, pore shape, pore connectivity, porosity and so on. It is found that pore shape, pore connectivity and gas conductivity have great impacts on the heat transfer of porous materials. The effect of pore arrangement is very little. The design optimization of porosity is affected by porous material mechanical property. [ABSTRACT FROM AUTHOR]

This paper presents multiscale modeling substantiated with experimental aspects of state, filtration, and motion of the gas-liquid mixtures involving phase transition regions in concentrated volumes applicable to porous media and pipe flows. Based on physics, it is confirmed analytically that actual levels of underpressure in gas-liquids systems are considerably above traditional understanding of saturation pressure at which gas emission from the liquid and its dissolution in the liquid in a form of embryos can occur. It is demonstrated that these processes are not equilibrium processes, and they can also occur on nanoscales and microscales. Thermo-hydrodynamic analyses and experimental investigation of the gas-liquid systems in areas of phase transition presented here have resulted in useful equations governing such flows in filtration in the porous media and in straight pipes. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to theoretically investigate the steady two-dimensional electrical magnetohydrodynamic (MHD) nanofluid flow over a stretching/shrinking sheet. The effects of stretching and shrinking parameter, as well as electric and magnetic fields, thermal radiation, viscous and Joule heating in the presence of slip, heat and mass convection boundary conditions at the surface, are imposed and studied. The mathematical model governing the flow has been constructed which are partial differential equations and then rehabilitated for a system of ordinary differential equations involving the momentum, energy and concentration equations via suitable similarity transformations. Though various conjectures have been put forward to explain the concept of boundary layer flow, the current investigation employed implicit finite difference scheme indicates good agreement with those of the previously published investigation in the limiting sense. Numerical results of the dual solutions for the velocity, temperature, and concentration as well as heat transfer are elucidated through graphs and tables. The velocity, thermal and solutal boundary layer thickness in the first solutions is smaller than that of the second solutions, the first solution is more stable compared to the second solution. Temperature and nanoparticle concentration fields are augmented by the heat and mass convective boundary conditions. [ABSTRACT FROM AUTHOR]

A novel mathematical model and original numerical method for investigating the two-dimensional waves of heterogeneous combustion in porous media are proposed and described in detail. The mathematical model is constructed within the framework of the model of interacting interpenetrating continua and includes equations of state, continuity, momentum conservation and energy for solid and gas phases. Combustion, considered in the paper, is due to the exothermic reaction between fuel in the porous solid medium and oxidiser contained in the gas flowing through the porous object. The original numerical method is based on a combination of explicit and implicit finite-difference schemes. A distinctive feature of the proposed model is that the gas velocity at the open boundaries (inlet and outlet) of the porous object is unknown and has to be found from the solution of the problem, i.e. the flow rate of the gas regulates itself. This approach allows processes to be modelled not only under forced filtration, but also under free convection, when there is no forced gas input in porous objects, which is typical for many natural or anthropogenic disasters (burning of peatlands, coal dumps, landfills, grain elevators). Some two-dimensional time-dependent problems of heterogeneous combustion in porous objects have been solved using the proposed numerical method. It is shown that two-dimensional waves of heterogeneous combustion in porous media can propagate in two modes with different characteristics, as in the case of one-dimensional combustion, but the combustion front can move in a complex manner, and gas dynamics within the porous objects can be complicated. When natural convection takes place, self-sustaining combustion waves can go through the all parts of the object regardless of where an ignition zone was located, so the all combustible material in each part of the object is burned out, in contrast to forced filtration. [ABSTRACT FROM AUTHOR]

Virtually every home in the US has some form of shades, blinds, drapes, or other window attachment, but few have been designed for energy savings. In order to provide a common basis of comparison for thermal performance it is important to have validated simulation tools. This paper outlines a review and validation of the ISO 15099 centre-of-glass thermal transmittance correlations for naturally ventilated cavities through measurement and detailed simulations. The focus is on the impacts of room-side ventilated cavities, such as those found with solar screens and horizontal louvred blinds. The thermal transmittance of these systems is measured experimentally, simulated using computational fluid dynamics analysis, and simulated utilizing simplified correlations from ISO 15099. Correlation coefficients are proposed for the ISO 15099 algorithm that reduces the mean error between measured and simulated heat flux for typical solar screens from 16% to 3.5% and from 13% to 1% for horizontal blinds. [ABSTRACT FROM PUBLISHER]

Implicit schemes have been extensively used in building physics to compute the solution of moisture diffusion problems in porous materials for improving stability conditions. Nevertheless, these schemes require important sub-iterations when treating nonlinear problems. To overcome this disadvantage, this paper explores the use of improved explicit schemes, such asDufort–Frankel,Crank–Nicolson and hyperbolization approaches. A first case study has been considered with the hypothesis of linear transfer. TheDufort–Frankel,Crank–Nicolson and hyperbolization schemes were compared to the classicalEuler explicit scheme and to a reference solution. Results have shown that the hyperbolization scheme has a stability condition higher than the standardCourant–Friedrichs–Lewycondition. The error of this schemes depends on the parameterτrepresenting the hyperbolicity magnitude added into the equation. TheDufort–Frankel scheme has the advantages of being unconditionally stable and is preferable for nonlinear transfer, which is the three others cases studies. Results have shown the error is proportional to. A modifiedCrank–Nicolson scheme has been also studied in order to avoid sub-iterations to treat the nonlinearities at each time step. The main advantages of theDufort–Frankel scheme are (i) to be twice faster than theCrank–Nicolson approach; (ii) to computeexplicitlythe solution at each time step; (iii) to be unconditionally stable and (iv) easier to parallelize on high-performance computer systems. Although the approach is unconditionally stable, the choice of the time discretizationremains an important issue to accurately represent the physical phenomena. [ABSTRACT FROM PUBLISHER]

In this paper, we consider a one-dimensional porous thermoelasticity system with past history, which contains a porous elasticity in the presence of a visco-porous dissipation, a macrotemperature effect and temperature difference. We establish the exponential stability of the system if and only if the equations have the same wave speeds, and obtain the energy decays polynomially to zero in the case that the wave speeds of the equations are different. [ABSTRACT FROM AUTHOR]

In the present investigation, the radiative MHD flow of an incompressible viscous electrically conducting non-Newtonian Casson hybrid nanofluidover an exponentially accelerated vertical porous surface has been considered. Under the influence of slip velocity in a rotating frame, it takes Hall and ion slip impacts into account. Water and ethylene glycol mixture is considered a base Casson fluid. A steady uniform magnetic field is applied under the postulation of a low magnetic Reynolds number. The ramped temperature and time-altering concentration at the surface are considered. First-order consistent chemical reaction and heat absorption are also regarded. Silver and Titania nanoparticles are disseminated in base fluid water and ethylene glycol combination should be formed by a hybrid nanofluid. The Laplace transformation technique is employed on the non-dimensional governing equations to ensure closed-form analytical solutions. The graphical representations scrutinize the effects of physical parameters on the significant flow characteristics. The expression for non-dimensional shear stress, heat transfer rate and mass transfer are also evaluated. They are tabulated with different variations in implanted parameters. For uniform and ramped wall temperatures, the resultant velocity grows by an increase in Hall and ion slip parameters. The resultant velocity increases by an increase in volume fractions of nanoparticles with uniform wall temperature, and a reverse effect is observed with ramped wall temperature. The temperature of Casson hybrid Ag-TiO2/WEG nanofluid is relatively superior to that of Casson Ag-WEG nanofluid. Species concentration of Casson hybrid Ag-TiO2/WEG nanofluid decreases with an increase in Schmidt number and chemical reaction parameters. The heat absorption increases the Nusselt number near the surface, while Ag and TiO2 nanoparticle volume fractions tend to lessen it. [ABSTRACT FROM AUTHOR]

For small-sized structures or devices, size-dependent effect and thermal-induced deformation become the main concerns in guiding their practical applications. To reveal such concerns of porous structures, the dynamic response of a finite porous microrod, subjected to a moving heat source and fixed at both ends, is investigated based on the non-local elasticity theory and the theory for porous materials with thermal relaxation. The corresponding governing equations are formulated and solved using Laplace transform and its numerical inversion. The distributions of the non-dimensional temperature displacement stress and volume fraction are obtained and illustrated graphically. In the simulation, the effects of the non-local parameter, the velocity of the heat source, and the thermal lag factor on the considered quantities are examined and illustrated graphically. Comparisons between the microrod with voids and without voids are shown. [ABSTRACT FROM AUTHOR]

Methylene blue (MB) is a prevalent pollutant in organic wastewater. For this research, eucalyptus wood was used as a template, into which quartz powder dissolved in NaOH was grown, resulting in a low-cost and efficient porous silica adsorbent material (PSAM). This PSAM successfully replaces expensive materials for MB removal from water. Through the application of Scanning Electron Microscopy (SEM) and Brunauer–Emmett–Teller (BET) analysis, it became evident that PSAM displays a porous slit pore structure characterized by numerous active sites, leading to an impressive maximum specific surface area of 88.05 m²/g. The central objective of this research was to investigate the impact of experimental temperature, initial dye concentration, and pH on the adsorption process. The adsorption kinetics were analyzed using the pseudo-first-order and pseudo-second-order models, as well as the Langmuir model. Remarkably, PSAM exhibited a substantial maximum adsorption capacity of 90.01 mg/g at 293 K, achieving an adsorption rate of over 85% within a mere 10-minute timeframe. The thermodynamic analysis revealed that the adsorption of MB onto PSAM was characterized by spontaneity and accompanied by heat absorption. Fourier Transform Infrared (FTIR) and SEM comparisons of PSAM before and after adsorption indicated that MB adsorption primarily occurred through electrostatic gravitational binding. In comparison to other adsorbents, PSAM exhibited exceptional efficacy in removing MB from water. [ABSTRACT FROM AUTHOR]

In this study, an efficient meshfree numerical method is introduced for solving the nonlinear boundary value problems. The method of fundamental solutions (MFS) is one of the most popular among meshfree methods. While traditionally limited to linear and homogeneous problems, this study extends the applicability of the MFS to include nonhomogeneous and nonlinear equations. To achieve this, an extended MFS is combined with a fixed-point iteration scheme. This developed framework is benchmarked to address two different flow problems. The first involves fluid flow through porous media in a channel governed by the nonlinear Brinkman-Forchheimer equation. The second problem pertains to electrohydrodynamic (EHD) flow in a circular conduit. The obtained solutions are compared with the finite element method and the solutions available in the existing literature. [ABSTRACT FROM AUTHOR]

Porous carbon materials have attracted considerable interest and show great potential for various applications because of their remarkable properties, including high specific surface area, unique porous structures, mass transport, easily accessible active sites, controllable surface chemistry, etc. Owing to these properties, porous carbons can be employed in environmental remediation as adsorbents for eliminating pollutants such as carbon dioxide (CO2) from the atmosphere and oil and heavy metal ions from aquatic ecosystems. In this minireview, we grouped porous carbons into three main parts based on their dimensions, and the recent progress in porous carbon application as adsorbents for environmental remediation, including oil-water separation, CO2 capture, and heavy metal ion removal, are discussed according to their dimensions. [ABSTRACT FROM AUTHOR]

Saturated fluid porous media appears complex thermodynamic features. To accurately characterize this phenomenon in nature, it is necessary to take into account variability of the coefficients in the porous medium due to the memory effects. In view of these variations, we introduce a memory formula in the form of tempered fractional derivative. In this formula, the temperature of saturated fluid porous media satisfies a tempered fractional Burgers equation. To avoid solving nonlinear problems, linearized technique is employed to deal with the nonlinear terms. Two approximated formulas, called tempered L1 and tempered $ {\rm L2-1}_{\sigma } $ L 2 − 1 σ formulas, are used in time discretization and the general central difference for the space variable. The corresponding numerical schemes are established and the stability and convergence are strictly analyzed. Finally, various numerical examples are given to intuitively demonstrate the accuracy and effectiveness of the proposed schemes. [ABSTRACT FROM AUTHOR]

The effect of Cattaneo–Christov heat flux on hydromagnetic flow of non-Newtonian (Maxwell, Jeffrey and Oldroyd-B) fluids filled with Darcy–Forchheimer porous medium with thermal radiation, uneven heat source/sink and variable thermal conductivity is studied numerically. The mathematical problem is developed with the help of momentum, and energy equations using the suitable transformation variables. The numerical results for the transformed highly nonlinear ordinary differential equations are presented for Maxwell, Jeffrey and Oldroyd-B fluid cases. For numerical computations, an effective numerical solver namely bvp4c package is used. Effects of various controlling restrictions on the flow, and thermal fields are examined. Numerical computations for the friction factor and local Nusselt number are executed. [ABSTRACT FROM AUTHOR]

Based on the finite volume method, adopting the movement border as a wave generator, a twodimensional numerical wave flume is established. The volume of fluid (VOF) method is used to track the wave surface. After comparison of the numerical results with the theoretical results, the accuracy of the numerical wave flume is verified. In the numerical simulation, the net panel is simplified as porous media entirely. The coefficients of the porous media are determined by the least squares method. In this way, the porous media model will have the same pressure drop as the net panel. In order to validate the numerical model, the numerical results were compared with the data obtained from corresponding physical model tests, and the numerical results and the corresponding experimental data show reasonably good agreement. Using the proposed numerical approach, this paper presents wave propagation through a net panel with different net solidities, different attack angles as well as two nets with different spacing distances. The impacts of the wave height and wavelength on the wave propagation through the net panel are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, we consider a modification to the Darcy equation by taking into account the dependence of viscosity on the pressure. We present a stabilized mixed formulation for the resulting governing equations. Equal-order interpolation for the velocity and pressure is considered, and shown to be stable (which is not the case under the classical mixed formulation). The proposed mixed formulation is tested using a wide variety of numerical examples. The proposed formulation is also implemented in a parallel setting, and the performance of the formulation for large-scale problems is illustrated using a representative problem. Two practical and technologically important problems, one each on enhanced oil recovery and geological carbon-dioxide sequestration, are solved using the proposed formulation. The numerical examples show that the predictions based on the Darcy model are qualitatively and quantitatively different from the predictions based on the modified Darcy model, which takes into account the dependence of the viscosity on the pressure. In particular, the numerical example on the geological carbon-dioxide sequestration shows that the Darcy model over-predicts the leakage into an abandoned well when compared to that of the modified Darcy model. On the other hand, the modified Darcy model predicts higher pressures and higher pressure gradients near the injection well. These predictions have dire consequences in predicting damage and fracture zones, and in designing the seal, whose integrity is crucial to the safety of a geological carbon-dioxide sequestration geosystem. [ABSTRACT FROM AUTHOR]

This paper is concerned with a theoretical interpretation of an abrupt shift from the slow conductive to fast convective burning observed in the combustion of gas-permeable explosives under gradual elevation of the ambient pressure. The paper is a revision of our recent communication on the problem, and is based on the amended heat equation, which meets the requirement of the conservation of energy lacking in the previous model. It appears, however, that both formulations lead (in appropriately chosen units) to a largely similar picture of the transition. The transition is triggered by a localised autoignition in the extended resistance-induced preheat zone formed ahead of the advancing deflagration, provided the pressure difference between hot gas products and gases deep inside the pores of the unburned solid exceed a certain critical level. For moderately high activation energies the critical overpressures are comparable to those observed experimentally. In line with observations, the critical overpressure increases with diminishing permeability. The amended formulation implies the possibility of overpressure-driven gasification waves occurring even in the absence of chemical heat release. [ABSTRACT FROM PUBLISHER]

This paper reviews the evidence on the effects of recessions on potential output. In contrast to the assumption in mainstream macroeconomic models that economic fluctuations do not change potential output paths, the evidence is that they do in the case of recessions. A model is proposed to explain this phenomenon based on an analogy with water flows in porous media. Because of the discrete adjustments made by heterogeneous economic agents in such a world, potential output displays hysteresis with regard to aggregate demand shocks and thus retains a memory of the shocks associated with recessions. [ABSTRACT FROM AUTHOR]

The combinations of acetic acid/water co-solvent and KCl were employed as the eluent to regenerate porous magnetic microspheres (PMMs) during treatment of wastewater containing cationic dyes. The effect of acetic acid/water volume ratio and KCl concentration on desorption percentages were systemically investigated. The results indicated that the carboxyl group in acetic acid could produce weak electrostatic attraction with cationic dyes, which was helpful to weaken the interaction between cationic dyes and sulfonic groups. The saturated solution of KCl in acetic acid displayed excellent regeneration capacity for PMMs including methyl violet. This fact was further demonstrated during desorption of basic fuchsin from PMMs. Overall, the present paper provided a novel and simple route to treat wastewater containing cationic dyes and optimized the combination of acetic acid/water co-solvent and KCl for regeneration of PMMs. [ABSTRACT FROM PUBLISHER]

This paper describes the manufacture of porous polytetrafluoroethylene (PTFE) and fluoroethylenepropylene (FEP) films by pressing PTFE-FEP-PTFE films between metallic meshes to produce a porous ferroelectret material. The influence of uniaxial pressing force and processing conditions (temperature and presence of a vacuum between the polymer films) on the as-formed ferroelectret film are assessed in terms on pore (void) height, distribution of pore height and film quality. The piezoelectric d33 coefficient (charge per unit force) of polarised films is measured and related to pore height and film quality. [ABSTRACT FROM PUBLISHER]

In the present paper, in the context of the linear theory of heat-flux dependent thermoelasticity for micropolar porous media, we derive a uniqueness theorem with no positive definiteness assumption on the elastic constitutive coefficients. Moreover, we prove, under non homogeneous initial conditions, a reciprocal relation and a variational principle. These generalize previous results about inhomogeneous and anisotropic micropolar thermoelastic materials. [ABSTRACT FROM AUTHOR]

This paper reports results on effective piezoelectric properties of advanced composites based on polydomain relaxor-ferroelectric single crystals of 0.67Pb(Mg1/3Nb2/3)O3 - 0.33PbTiO3. Two variants of the single crystal/porous polymer composite with 0-3-0 connectivity are proposed to study the role of microstructural factors in forming high piezoelectric sensitivity. The effective properties of the related 0-3 single crystal/polymer composite are predicted and considered to show ways of increasing the piezoelectric anisotropy and sensitivity. Examples of the volume-fraction and aspect-ratio dependences of the effective piezoelectric coefficients d3j*, g3j*, the hydrostatic piezoelectric coefficient gh*, and squared figures of merit d33* g33* and dh* gh* of composites are analysed to show in which ranges high piezoelectric sensitivity is attained. The presence of single-crystal polydomain inclusions in the porous 3-0 matrix promotes the large effective parameters (g33* ∼ 103 mV · m/N, gh* ∼ 103 mV · m/N, d33* g33* ∼ 10-10 Pa-1, and dh* gh* ∼ 10-10 Pa-1), and the obvious high-performance advantage of the 0-3-0 composites is discussed taking into account features of their microstructure. [ABSTRACT FROM AUTHOR]

An inverse method is presented for the estimation of geothermal reservoir initial temperatures based on a control theory algorithm in which computed well temperatures are fitted to well-logged temperatures. The method and results are presented in a two-part paper. Part I deals with the mathematical model of the well and the formation while Part II presents the inverse control algorithm and results of application. Well temperatures are obtained by simulating the circulation and shut-in processes in the presence of lost circulation using macroscopic balances to describe momentum and energy transport. Transport processes in the formation consider the reservoir as an isotropic porous medium with Darcian flow. Computed well temperatures are fed to the inverse control algorithm to estimate the initial formation temperatures. The method was applied to the estimation of the initial formation temperatures of well LV-3 from the Las Tres Virgenes, Mexico, geothermal field, as described in Part II of this paper. [ABSTRACT FROM AUTHOR]

The material to air equilibrium partition coefficient (Ke ) is often used to represent sorption capacity of building materials. However, it does not represent the sorption dynamics (i.e., the sink effect) of volatile organic compounds (VOCs) inside a porous material, which depends not only on the partition, but also on the in-material diffusion rate and convective mass transfer rate through the boundary layer. Based on fundamental mass transfer theory for VOC sorption by building materials, this paper proposes VOC sorption mass (M(t)) and sorption saturation degree (SSD) as new evaluation indices for sorption capacity and dynamics of building materials under given constant inlet concentration. It is found that SSD can be characterized by dimensionless sorption mass (m*), which is a function of dimensionless air change rate (N*), dimensionless mass capacity (ϴ), and Fourier number for mass transfer (Fom). Two cases, one with constant inlet VOC concentration and the other a hypothetical case under a no-ventilation condition, are simulated to illustrate material sorption capacity. This evaluation method can clarify the difference between air saturation state and material saturation state and would be useful for modeling the impact of material sorption on indoor air quality. [ABSTRACT FROM AUTHOR]

Feasibility of a method for finding flow permeability of porous materials, based on combining computerised X-ray micro-tomography and numerical simulations, is assessed. The permeability is found by solving fluid flow through the complex 3D pore structures obtained by tomography for actual material samples. We estimate overall accuracy of the method and compare numerical and experimental results. Factors contributing to uncertainty of the method include numerical error arising from the finite resolution of tomographic images and the rather small sample size available with the present tomographic techniques. The total uncertainty of computed values of permeability is, however, not essentially larger than that of experimental results. We conclude that the method provides a feasible alternative for finding fluid flow properties of the kind of materials studied. It can be used to estimate all components of permeability tensor and is useful in cases where direct measurements are not achievable. Analogous methods can be applied to other modes of transport, such as diffusion and heat conduction. [ABSTRACT FROM AUTHOR]

This paper deals with the application of a meshless method called element-free Galerkin method (EFGM) for modelling the contaminant transport through the unsaturated porous media with transient flow condition. In EFGM, an approximate solution is constructed entirely in terms of a set of nodes and no elements or characterization of the interrelationship of the nodes is needed to construct the discrete equations. For analysis, the one-dimensional form of advection-dispersion equation with linear first-order degradation is considered. The unknown concentration values are approximated by using moving least square approximants. The weak form of the governing equation is formulated and the Lagrange multiplier method is used for enforcing the essential boundary conditions. The van Genuchten model is used for describing the hydraulic properties of the unsaturated soil. MATLAB code is developed to obtain the numerical solution. Numerical examples representing various phenomena that occur during the migration of contaminants are presented to illustrate the applicability of the proposed method and the results are compared with those obtained from the finite element method and the analytical solution. [ABSTRACT FROM AUTHOR]

This paper concerns with the linear theory of micropolar thermoelasticity for materials with voids. We construct the fundamental solution of the system of differential equations in the case of steady oscillations in terms of elementary functions. Some basic properties of this solution are established. [ABSTRACT FROM AUTHOR]

Among physical characteristics of porous materials, properties related to liquid flow in porous materials play a critical role in the prediction of drying curves. In the present work, a simple experimental method was developed to simultaneously measure the capillary pressure and the relative permeability of particle beds by a simple drainage method. The observed data of permeability at low saturation of less than 70% was in fair agreement with a range of two lines that were predicted from the Campbell model. The purpose of the development of the present drainage method along with the drying method described in a previous paper is to provide a group of physical properties which are needed for prediction of drying curves by use of minimal measurement devices. [ABSTRACT FROM AUTHOR]

In this paper we study the spatial behaviour for a large class of isotropic and homogeneous porous thermoelastic materials for which the constitutive coefficients are supposed to satisfy some relaxed positive definiteness conditions. By using some appropriate measures, we are able to establish results describing the spatial behaviour of transient and steady-state solutions in these enlarged classes of thermoelastic porous materials. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to study an identification problem related to a specific nonlinear model describing the rainfall type infiltration into a porous medium in which saturation can be partially or totally reached after some time. [ABSTRACT FROM AUTHOR]

This paper reviews the recent progress made in the asymmetric synthesis on chiral catalysts in porous materials and discusses the effects of surface and pores on enantioselectivity(confinement effect). This paper also summarizes various approaches of immobilization of the chiral catalysts onto surfaces and into pores of solid inorganic supports such as microporous and mesoporous materials. The most important reactions surveyed for the chiral synthesis in porous materials include epoxidation, hydrogenation, hydroformylation, Aldol and Diels-Alder reactions, etc. The confinement effect originated from the surfaces and the pores turns out to be a general phenomenon, which may make the enantioselectivity increase(positive effect) or decrease(negative effect). The confinement effect becomes more pronounced particularly when the bonding between the catalyst and the surface is more rigid and the pore size is tuned to a suitable range. It is proposed that the confinement in chiral synthesis is essentially a consequence of subtle change in transition states induced by weak interaction in pores or on surfaces. It is also anticipated that the enantioselectivity could be improved by tuning the confinement effect based on the molecular designing of the pore/surface and the immobilized catalysts according to the requirements of chiral reactions. [ABSTRACT FROM AUTHOR]

Experiments on porous material heated by a microsecond laser pulse and the corresponding theoretical analysis are carried out. Some non-Fourier heat conduction phenomena are observed in the experimental sample. The experimental results indicate that only if the thermal disturbance is strong enough (i.e., the pulse duration is short enough and the pulse heat flux is great enough) is it possible to observe apparent non-Fourier heat conduction phenomenon in the sample, and evident non-Fourier heat conduction phenomenon can only exist in a very limited region around the thermal disturbance position. The hyperbolic heat conduction (HHC) equation and the dual-phase lag (DPL) model are employed, respectively, to describe the non-Fourier heat condution process happening in the experimental sample, and the finite-difference method (FDM) is used to solve them numerically. The numerical solutions show that both the HHC equation and the DPL model can predict the non-Fourier heat conduction phenomenon emerging in the experimental sample qualitatively. Moreover, if τ[sub q] and τ[sub T] are assumed to have suitable values, the theoretical result of the DPL model is more agreeable to the experimental result. [ABSTRACT FROM AUTHOR]

This paper presents the mechanical and tribological characteristics of the NiTi shape memory alloy (SMA) fabricated by powder metallurgy. This material has prominent applications in micro-electromechanical systems, medical implants, actuator, space and aerospace industries, etc. In every field, wear characteristics plays a dominating role. In present work dry-abrasion wear behavior is determined for NiTi alloy by varying binder percentage. With increasing binder percentage from 2.5 to 15 %, density decreases from 6.5 to 5.3 g/cm3 while porosity increases from 19 % to 51 %. Increasing rotational speed and binder percentage at a constant load the wear rate increases in the NiTi alloy. Due to the presence of hard particles, NiTi exhibits a very small wear rate. The coefficient of friction is also computed for the alloys in present research work. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction were used for the investigation of surface morphology and phases in the NiTi alloy. [ABSTRACT FROM AUTHOR]

Previous two-fluid lattice Boltzmann (LB) models for multicomponent fluids are limited to mixtures with a low molecular weight ratio (i.e., below 9). In this paper, a finite difference-based two-fluid LB model is developed for mixtures with larger molecular weight ratios, which can be widely found in real applications. The basic idea is to use the finite difference scheme to discretize the discrete velocity LB equations derived from the two-fluid theory. The corresponding macroscopic hydrodynamic and diffusion equations are obtained by multiscale expansions. The adjusting strategy of model parameters significantly influencing the accuracy and stability of the LB model is discussed in detail. It is demonstrated that the present LB method is able to model multicomponent fluids with a high molecular weight ratio (e.g., 32). Further, the present model is applied to the simulation of multicomponent fluids in porous media. [ABSTRACT FROM PUBLISHER]