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In the present work, a comparison of the P–T equilibrium points of gas hydrates formation in bulk phase and porous medium (large particle size natural quartz sand) was studied for three different gas-hydrates: CO2, CH4 and a sample of natural gas. The effect of the large particle size in the P–T equilibrium conditions during the formation of gas hydrates was analyzed. Isochoric method and a cooling-heating rate of 0.7 K/h were used. The experimental results are compared with literature data and with the software CSMHyd and PVTsim. It was found that the P–T equilibrium points obtained in bulk are similar, within the experimental error, to the P–T points obtained in the large particle size natural quartz sand (gas + water + porous medium), in the range of temperature and pressure of 270–285 K and 1–14 MPa. For the systems gas (CO2, CH4) + water, the results were compared with literature data with an average deviation less than 7%. The system natural gas + water + porous medium was compared with similar experiments reported in the literature with smaller porous size silica (6–100 nm). A similar tendency is observed in systems with a porous size greater than 20 nm. Highlights: Porosity and permeability of quartz sand were measured experimentally. Phase equilibria of CH4, CO2, and natural gas hydrates in quartz sand were measured. The methodology is validated for gas hydrates stability in bulk phase and porous media. Experimental results are compared with literature and software CSMHyd and PVTsim. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the entropy production characteristics of two non-miscible fluids in an inclined porous channel with temperature-dependent thermal conductivity and viscosity. The porous region of the channel is divided in two regions. In region-1 and region-2, the Couple stress and Newtonian fluid take place due to constant pressure gradient, respectively, under the influence of a uniform magnetic field. Here, the Darcy–Brinkman model is used for the flow of immiscible fluid through the porous media. In this work, we used a semi-analytical method named as homotopy analysis method (HAM) to solve the coupled nonlinear ordinary differential equations. The goal of the considered problem is to examine the consequences of a variety of thermophysical parameters, including Hartmann number, varying viscosity parameter, varying thermal conductivity parameters, and Grashof number on the characteristics of entropy generation, Bejan number distribution, thermal behavior and flow characteristics of non-miscible couple stress and Newtonian fluid passing through a porous channel. The novel aspect of this study is the formation of entropy and Bejan number as a result of non-miscible Newtonian and couple stress fluids with varying thermal conductivity and viscosity in porous media. In terms of rheological investigation, a semi-analytical simulation for changeable thermal and flow properties in an immiscible Newtonian and couple stress fluid via an inclined porous channel is a brand-new concept, and the behaviors of such flows have not been examined yet. From this study, it is concluded that on raising the variable thermal conductivity, Hartmann number and the permeability of the porous medium, the flow velocity, thermal characteristics and entropy generation number decrease. The authors also come to the significant conclusion that non-miscible Newtonian and couple stress fluids have larger entropy production numbers, flow velocities, and temperature profiles for higher values of Grashof number, variable viscosity parameter, and couple stress parameter. The findings of this work have also been graphically validated through the previously established work. The results of the present analysis can be used in petroleum industry, lubrication theory, etc. [ABSTRACT FROM AUTHOR]

K‐feldspar, which constitutes about 60%$\%$ of the Earth's crust, is crucial for understanding electrical conductivity in porous rocks. Its electrical properties are vital for applications in ceramics, electrical insulation and conductive polymers. In this work, we study the time evolution of electrical conductivity of K‐feldspar‐rich rocks with varying temperatures, at high and low pH, which has been studied through simulation using time domain random walk. Random walkers, mimicking ions in transport, move in accordance with appropriate hydrodynamic equations, dissolution and precipitation kinetics. Electrical conductivity has been calculated considering variations in the parameters of temperature, fluid pH and the abundance of K‐feldspar in rocks. Electrical conductivity is found to increase with temperature up to a critical value, after which it decreases. The sharpness of the rise and fall in electrical conductivity is quantified through a measure defined as the conductivity quality factor Qσ$Q_{\sigma }$. We find that Qσ$Q_{\sigma }$ increases with a decrease in the availability of K‐feldspar mineral. Our simulated results of electrical conductivity show a good match with the experimental trends reported. [ABSTRACT FROM AUTHOR]

Non-Newtonian fluids within heterogeneous porous media may give rise to complex spatial energy and mass distributions owing to non-local mechanisms, the modeling of which remains unclear. This study investigates the natural convection heat and mass transfer of non-Newtonian fluids in porous media, considering the Soret and Dufour effects. A strongly coupled model is developed to quantify the coupled transport of energy and reactive pollutants with the non-Newtonian fluid. The constitutive equation for the non-Newtonian fluid is described by a two-sided Caputo type space fractional velocity gradient. The governing equation, with a symmetric diffusion term, is effectively solved using a stable and convergent shifted Grünwald–Letnikov formula. The influences of three important parameters, which are the average skin friction coefficient, the average Nusselt number, and the Sherwood number, on fluid heat and mass transfer are calculated and analyzed. Numerical results reveal a significant interaction between the fractional derivative and the buoyancy ratio number, both of which affect the average skin friction coefficient. Furthermore, the average Nusselt number increases with the Dufour number while decreasing with the average Sherwood number. These findings enhance our understandings of the dynamics of energy and mass co-transport in non-Newtonian fluids, particularly in relation to their constitutive equation featuring spatial non-local properties. [ABSTRACT FROM AUTHOR]

We report measurements performed to understand the effects of gas (QG) and liquid (QL) flow rates, surface tension (σGL), liquid viscosity (μL), and particle diameter (dp) on dynamics of local liquid spreading, pressure drop, and overall liquid holdup in a pseudo‐2D trickle bed. We show that an increase in the gas‐phase inertia leads to a decrease in the lateral liquid spreading, whereas an increase in the liquid‐phase inertia leads to an increase in the lateral liquid spreading. We also show that an increase in dp causes a reduction in the lateral liquid spreading. Using dimensionless numbers (AB and We), we propose a regime map showing contributions of different forces to the local liquid spreading. We show that the interplay between the inertia and capillary forces governs the liquid distribution near the inlet, whereas the relative contribution of gravitational force increases toward the outlet. Finally, we propose a relation between AB and We for "bed‐scale" liquid spreading. [ABSTRACT FROM AUTHOR]

The combustion technology of hydrogen enriched natural gas can directly apply hydrogen energy to household gas, playing an important role in promoting the development of hydrogen energy. This study designed a domestic burner with porous media for hydrogen enriched natural gas. The effect of hydrogen blending ratio on the primary mix process in the injector was analyzed numerically, and an experiment was conducted to investigate the flame morphology, thermal efficiency and pollutant emissions of the hydrogen-enriched natural gas. The results show that there is a risk of backfire inside the injector when the hydrogen blending ratio exceeds 45%, and the pre-mixing uniformity decreases as the hydrogen doping ratio increases. Corresponding to variable hydrogen doping ratios, two combustion modes appear in the porous medium region, immerged combustion and surface combustion. When a combustion mode transition occurs, CO emissions increase rapidly, while thermal efficiency and NOx emissions show a downward trend. Additionally, the critical hydrogen doping ratio of mode transition drops as the porous density increases. Overall, taking the environmental characteristic and efficiency into considerations, the maximum hydrogen blending ratio should be not exceed 35%. [Display omitted] • A domestic burner with porous media for hydrogen enriched natural gas was designed. • The effect of hydrogen blending ratio on the primary mix process was analyzed. • The combustion performance and emissions of the domestic burner was investigated. • The transition of combustion mode induced by hydrogen doping ratio was observed. [ABSTRACT FROM AUTHOR]

The combined effects of diffusion-thermo and radiative absorption on free convective hydromagnetic heat-generating chemically reactive flow of Cu-water nanofluid past an instantaneously accelerated unlimited vertical plate nested in a porous medium are investigated. A comparative analysis is executed for both isothermal and ramped conditions. The set of transformed domain equations has been obtained using a closed form of the Laplace transform method with the help of the Heaviside step function. Graphical and tabular explanations are provided for the physical characteristics of several flow parameters affecting the problem. Graphs are generated using MATLAB computing software. Findings of the problem manifest that the diffusion-thermo parameter and the radiation absorption parameter intensify the velocity and fluid temperature in the entire fluid area. This augmentation is most prominent for copper nanoparticles. Concentration, temperature, and velocity profiles in the case of ramped conditions are less than in isothermal conditions. Furthermore, the ramped parameter amplifies the heat transfer rate while reversing the mass transfer rate. It is also established that the volume concentration of nanoparticles enhances the heat transfer rate. The present study is of great interest in numerous fields of industry and machine-building applications. [ABSTRACT FROM AUTHOR]

In this article we address the problem of locating point forces within a time-dependent singular Brinkman flow. The context of the study is framed as an approximation of cerebrospinal fluid (CSF) around the central nervous system, with the point forces representing a model for the blood-brain barrier. We approach the problem by reformulating the identification task as an optimization problem, employing a tracking shape functional. A notable challenge in this study arises from the irregularity in the solution of the partial differential equation (PDE), which complicates the exploration of sensitivity analysis. To overcome this issue, we employ a relaxation method and compute the topological derivative of the cost function. The topological derivative, commonly used in shape optimization problems, offers insights into how the cost function responds to small perturbations in the domain. To determine the optimal position of the point forces, we employ a one-shot algorithm based on the derived topological gradient. Finally, we present numerical results that showcase the efficiency of our method in addressing the identified problem. [ABSTRACT FROM AUTHOR]

Particle tracking (PT) is a popular technique in microscopy, microfluidics and colloidal transport studies, where image analysis is used to reconstruct trajectories from bright spots in a video. The performance of many PT algorithms has been rigorously tested for directed and Brownian motion in open media. However, PT is frequently used to track particles in porous media where complex geometries and viscous flows generate particles with high velocity variability over time. Here, we present an evaluation of four PT algorithms for a simulated dispersion of particles in porous media across a range of particle speeds and densities. Of special note, we introduce a new velocity-based PT linking algorithm (V-TrackMat) that achieves high accuracy relative to the other PT algorithms. Our findings underscore that traditional statistics, which revolve around detection and linking proficiency, fall short in providing a holistic comparison of PT codes because they tend to underpenalize aggressive linking techniques. We further elucidate that all codes analyzed show a decrease in performance due to high speeds, particle densities, and trajectory noise. However, linking algorithms designed to harness velocity data show superior performance, especially in the case of high-speed advective motion. Lastly, we emphasize how PT error can influence transport analysis. [ABSTRACT FROM AUTHOR]

• Infiltration rates under low gravities were agreed with 1G based predictions. • The air entrapped little in fine porous media may have prevented the infiltration rate reduction. • The infiltration theory is applicable to fine uniform porous media under low gravities. The applicability of the theory of water infiltration in porous media under low gravities is controversial. We evaluated the hypothesis that infiltration under low gravities can be simulated from horizontal infiltration experiments under 1G. Parabolic flights provided low gravity conditions, assuming in the space station (µG), on the moon (0.19 G), and Mars (0.38 G). We measured infiltration rates in uniform particle-size porous media. No significant differences existed between infiltration rates under low gravities and ground-based predictions, i.e. the 1G condition. The air was entrapped little in this study, which may have prevented the infiltration rate reduction reported in previous studies. We concluded that the current infiltration theory adequately simulated water infiltration in fine uniform porous media under low gravity conditions. [ABSTRACT FROM AUTHOR]

AbstractLarge-scale hot air drying rooms play a crucial role as efficient drying equipment across various industries. The uniform distribution of hot air is a crucial factor influencing the drying quality of large-scale hot air drying rooms. This study focuses on camellia seeds as the drying subject. Building on a porous media model and the drying kinetics of camellia seeds, a CFD model of the drying room was established. Three-dimensional simulations of the internal flow and temperature fields were performed using CFD software, and the simulated results aligned well with experimental data. To improve the uniformity, this study introduced an optimized design featuring a combination of a Type E3 air guide hood with five guiding plates and a fan, selected based on optimized angles (θ1 = 5°, θ2 = 10°). Under the condition of improving the structure without introducing a new heat source, the optimization ensured a significant improvement in flow field uniformity while making the temperature field closer to the desired ideal temperature. This offers a reference for the design and research of hot air drying equipment and hot air drying rooms. [ABSTRACT FROM AUTHOR]

Salt efflorescence is one of the major hazards to cultural heritages, masonries, and highways etc. It is now generally accepted that damages caused by salt efflorescence are mainly due to continuous cycles of salt crystallization/dissolution or hydration/dehydration in confined spaces. The position where salt efflorescence occurs and its type are closely related to the degree of damages caused by salt efflorescence. It is known that water is the key environmental factor determining the salt crystallization position. But influence of the correlation between water supply and evaporation on the position of salt crystallization is still not clearly understood. In this work, a set of experiments are designed to investigate salt efflorescence in porous matrix. It is found that the types and positions of salt efflorescence have little to do with nucleation, but are mainly governed by crystal growth, which is controlled by the rates of water evaporation, water and salt supply, capillary forces and surface properties of the porous matrices. [ABSTRACT FROM AUTHOR]

Yttrium‐stabilized zirconia (YSZ) plays a crucial role in thermal barrier coatings widely used to protect metallic components in gas turbine engines against high‐temperature combustion product gases and harsh environments. The thermal conductivity of these coatings is a critical parameter influencing the gas turbine design, performance, and service life. In this study, a laser temperature gradient method is utilized to measure the thermal conductivity of porous YSZ coatings. The method employs specialized laser energy delivery to create a one‐dimensional temperature gradient through the sample thickness, closely simulating the operational condition. This approach provides an effective, direct means to determine the thermal conductivity of high‐temperature heat‐resistant porous ceramic materials. [ABSTRACT FROM AUTHOR]

System‐scale computational fluid dynamics (CFD) simulations in chemical and process engineering remain limited owing to the complexity of integrating the results obtained at different scales. The present study addresses this issue by correlating the flow behaviors calculated by CFD in porous media at the micro‐scale and the macro‐scale using deep neural network (DNN) technology. The DNN model is trained using a dataset constructed from the results obtained for a large number of particle‐scale CFD simulations that are coupled to macroscopic governing equations. Comparisons with experimental results obtained with a packed bed show that the proposed CFD‐DNN method provides predictions of pressure drop with an accuracy that is 28% greater than that of a method based on the Ergun equation. [ABSTRACT FROM AUTHOR]

When a contaminated liquid evaporates from within a porous material, the impurities or dirt accumulate and deposit within the pore space. This occurs during the cleaning of filters and fouling of textiles, and is related to the 'coffee-ring' problem. To investigate how and where dirt is deposited in the pore space, we present a model for the motion of an evaporation front through a porous material, and the related accumulation, transport, and deposition of dirt, assuming that the liquid remains stationary. For physically relevant parameters, vapour transport out of the porous material is quasi-steady and we derive a single ordinary differential equation describing the motion of the evaporation front in time. Model solutions exhibit spatially non-uniform profiles of the deposited dirt-layer thickness through the porous material. The dirt accumulation and evaporation problems are coupled: deposited dirt hinders vapour transport through the porous material, slowing the evaporation. We identify two scenarios in which the porous material becomes clogged with dirt. Accumulation of suspended dirt at the evaporating interface along with slow dirt diffusion results in the deposited dirt layers clogging the pores at the evaporating interface, halting the drying and trapping liquid in the porous material. Alternatively, slow dirt deposition results in the suspended dirt being pushed far into the porous material by the evaporation, eventually leaving only dirt (with no liquid) in the pore space. We investigate the dynamics of both clogging scenarios, characterising the parameter regimes for which each occurs. Both clogging scenarios must be avoided in practice since they may be detrimental to future filter efficacy or textile breathability. [ABSTRACT FROM AUTHOR]

Biological microorganisms and artificial micro-swimmers often locomote in heterogeneous viscous environments consisting of networks of obstacles embedded into viscous fluid media. In this work, we use the squirmer model and present a numerical investigation of the effects of shape on swimming in a heterogeneous medium. Specifically, we analyse the microorganism's propulsion speed as well as its energetic cost and swimming efficiency. The analysis allows us to probe the general characteristics of swimming in a heterogeneous viscous environment in comparison with the case of a purely viscous fluid. We found that a spheroidal microorganism always propels faster, expends less energy and is more efficient than a spherical microorganism in either a homogeneous fluid or a heterogeneous medium. Moreover, we determined that above a critical eccentricity, a spheroidal microorganism in a heterogeneous medium can swim faster than a spherical microorganism in a homogeneous fluid. Based on an analysis of the forces acting on the squirmer, we offer an explanation for the decrease in the squirmer's speed observed in heterogeneous media compared with homogeneous fluids. [ABSTRACT FROM AUTHOR]

A wide range of environmental, energy, medical and biological processes rely on dispersive transport through complex media. Yet, because of the stagnant and opaque nature of the microscopic system, the role of disordered flow and structure in the dispersive transport of solutes remains poorly understood. Here, we use a circular porous microfluidic system to investigate the radial dispersion in porous media driven by non-Newtonian fluids with strong advection rate (or at high Péclet number) and low-to-moderate Reynolds numbers. We observe for the first time the presence of diffusion 'blind zones' in the microstructure for high solution injection velocities. More specifically, an in-depth analysis uncovers that the circumferential flow frame, coformed by obstacles and vortices especially the 'twin-vortex' with same rotation direction, is responsible for the diffusion 'blind zones' and transport heterogeneity. The vortices are induced by the coupling of microfluidics and porous structures, and correlated to inertial flow-induced instabilities. The trade-off between diffusion efficiency and quality/completeness with respect to the high Péclet number (or high inlet velocity) serves to enhance our comprehension of intricate fluid dynamics and affords a set of principles to aid a diverse range of practical implementations. [ABSTRACT FROM AUTHOR]

An experimental apparatus was designed to study the impacts of wettability on evaporation of water from Ottawa sand. Evaporation rates were measured for: (1) a 5.7-cm-thick layer of hydrophilic Ottawa sand; (2) a 5.7-cm-thick layer with 12% hydrophobic content, consisting of a 0.7-cm-layer of n-Octyltriethoxysilane-coated hydrophobic sand buried 1.8 cm below the surface of hydrophilic sand; and (3) a 5.7-cm-thick layer with mixed wettabilities, consisting of 12% n-Octyltriethoxysilane-coated hydrophobic sand mixed into hydrophilic sand. The sand-water mixtures experienced forced convection above and through the sand layer, while a simulated solar flux (i.e., 112±20 W/m²) was applied. Evaporation from homogeneous porous media is classified into the constant-rate, falling-rate, and slow-rate periods. Wettability affected the observed evaporation mechanisms, including the transition from constant-rate to falling-rate periods. Evaporation entered the falling-rate period at 12%, 20%, and 24% saturations for the all hydrophilic sand, hydrophobic layer, and hydrophobic mixture, respectively. Wettability affected the duration of the experiments, as the all hydrophilic sand, hydrophobic layer, and hydrophobic mixture lasted 17, 20, and 26 trials, respectively. Both experiments with hydrophobic particles lasted longer than the all hydrophilic experiment and had shorter constant-rate evaporation periods, suggesting hydrophobic material interrupts capillary action of water to the soil surface and reduces evaporation. Sand temperatures suggest more evaporation occurred near the test section inlet for higher saturations and the hydrophobic layer experienced more evaporation occur near the outlet. Evaporation fluxes were up to 12× higher than the vapor diffusion flux due to enhanced vapor diffusion and forced convection. [ABSTRACT FROM AUTHOR]

The flow analysis of electrolyte solution in microchannel/capillary is essential in various applications of health care such as dialysis and diagnosis processes of biological fluids/samples. To investigate the flow analysis in a homogeneous and isotropic porous microchannel with two membranes fitted at the upper wall surface, a novel biophysical model is presented mathematically. The lower wall surface is kept stationary and negatively charged to analyse the influence of the electroosmosis mechanism. The membranes have a self-propagating pumping process with varying amplitude and phase lag. The continuity and momentum equations are considered to describe the fluid flow and the Poisson–Boltzmann equation is taken to analyse the distribution of the electric potential for the electrolyte solution in the normal direction to a charged surface. To derive the governing equations, we have considered the approximation of low Reynolds number and Debye-Hückel linearization. Using MATLAB coding, key results like velocity, pressure difference, skin friction, volumetric flow rate, and stream function are computed under the influence of significant parameters. Present study finds that the movement of the electrolyte solution can be driven by membrane-based pumping at a small scale and further regulated by electroosmosis. The resistance due to the porous medium impacts the velocity and volumetric flow rate but this resistance can be mitigated by increasing the strength of the external electric field. This analysis is potentially useful for developing membrane-based microfluidic devices to analyse the biological flow at the micro-scale. [ABSTRACT FROM AUTHOR]

Wettability is a key parameter that determines the distribution and behavior of fluids in the porous media of oil reservoirs. Understanding and controlling wettability significantly impacts the effectiveness of various enhanced oil recovery (EOR) methods and CO2 sequestration. This review article provides a comprehensive analysis of various methods for measuring and altering wettability, classifying them by mechanisms and discussing their applications and limitations. The main methods for measuring wettability include spontaneous imbibition methods such as Amott–Harvey tests and USBM, contact angle measurement methods, and methods based on the characteristics of imbibed fluids such as infrared spectroscopy (IR) and nuclear magnetic resonance (NMR). These methods offer varying degrees of accuracy and applicability depending on the properties of rocks and fluids. Altering the wettability of rocks is crucial for enhancing oil recovery efficiency. The article discusses methods such as low-salinity water flooding (LSWF), the use of surfactants (SAAs), and carbonated water injection (CWI). LSWF has shown effectiveness in increasing water wettability and improving oil displacement. Surfactants alter interfacial tension and wettability, aiding in better oil displacement. CWI also contributes to altering the wettability of the rock surface to a more water-wet state. An important aspect is also the alteration of wettability through the dissolution and precipitation of minerals in rocks. The process of dissolution and precipitation affects pore structure, capillary pressure, and relative permeabilities, which in turn alters wettability and oil displacement efficiency. [ABSTRACT FROM AUTHOR]

The shaft hydropower plant (SHPP) is a novel hydraulic concept for low-head hydropower sites with several environmental and operational advantages over conventional layouts. However, the first two projects implementing this concept have shown comparatively high construction costs and project risks. Therefore, further optimization is required to increase economic attractiveness and enable broader market adoption. Initial model tests recommend a square-shaped shaft inlet with a three-sided approach flow for low-loss and fish-friendly inflow conditions. Yet, this design requires significant space for structural implementation and may be unsuitable for use with multiple shafts or as an extension of non-powered dams and weirs. This research paper presents the application of a computational fluid dynamics simulation setup to evaluate the hydraulic performance of various design configurations, especially alternative design layouts with a one-sided approach flow without further physical model tests. The simulation setup is calibrated against observations including head loss and velocity measurements from the physical model tests, and its satisfactory performance enables the analysis of alternative design layouts. This study aims to derive the most significant design parameters for achieving the desired hydraulic conditions at the intake. Increasing the flow depth before the intake and enlarging the inlet area have the most significant impact, while increasing the overflow of the front gate has the least significant effect. The chosen CFD application is deemed suitable for hydraulic design optimization and provides guidance on the key parameters to focus on for tailored site-specific design development. [ABSTRACT FROM AUTHOR]

The lower effective thermal conductivity of goose down fibres provides an excellent thermal insulator property, which is mainly assumed due to its air-entrapping ability and thus lower diffusive thermal conductivity. Although the effective thermal conductivity of a porous medium is a combination of both diffuse and radiative thermal conductivity, using an alternate approach, the present work attempted to quantify the influence of structural parameters on radiative transmittance, which is directly related to radiative conductivity that affect the overall effective thermal conductivity. A Box–Behnken design was used to study the effect of areal density, thickness of nonwovens, and blend proportion of the goose down fibres in non-wovens on the radiative transmittance. It was found that radiative transmittance does not decrease linearly with an increase in areal density. Also, the model predicted an interaction factor among the thickness of the nonwoven and the blend proportion of the goose down fibers; with an increase in thickness, radiative transmittance showed a decreasing trend; with an increase in goose down blend proportion, radiative transmittance decreased, but the extent of reduction was different for different levels of thickness. So, it was found that the multidirectional orientation of goose down fibres along with their fine barbules are the major factors that contributed to their lower radiative transmittance properties. [ABSTRACT FROM AUTHOR]

Proton Exchange Membrane Fuel Cell (PEMFC) technology has been receiving more attention recently and can play a more expanded role in space missions with low gravity or microgravity. The liquid water generation in the Gas Diffusion Layer (GDL) of a Proton Exchange Membrane Fuel Cell (PEMFC) increases the resistance to oxygen flow toward the catalyst layer. Water flooding inside the GDL can affect the PEMFC performance especially at higher current densities. Therefore, a good understanding of the effect of liquid water amount in the GDL is crucial to water management and, subsequently, to the performance of the fuel cell. The purpose of the present study is to investigate the effect of the microstructure characteristics of the GDL on the water flooding and liquid water distribution inside the GDL. A one-dimensional theoretical model has been developed. Results indicate that the porosity gradient has a significant effect on the liquid water saturation and the performance of the PEM fuel cell. [ABSTRACT FROM AUTHOR]

Porous ionic electrospray emitters have received significant interest for space propulsion due to their performance and operational simplicity. We have developed a diffusion equation for describing the transient flow response in a porous electrospray emitter, which allows for the prediction of the settling time for flow in the porous emitter. This equation accounts for both the change in liquid storage at exposed pores on the emitter with pressure and viscous diffusion through Darcy's law. Transient flow solutions are provided for the most common emitter topologies: pillar, cone, and wedge. Transient flow solutions describe the settling time and magnitude of current overshoot from porous electrosprays, while providing useful guidelines for reducing transient response time through emitter design. Comparing diffusion of pressure to the onset delay model for electrospray emission shows that diffusion is most relevant at higher voltages and when a porous reservoir is used. Accounting for multiple emission sites on the wedge geometry shows that emission sites settle in proportion to emission site spacing to the power − 1.74. Article Highlights: The transient response of porous electrosprays is affected by fluid storage in exposed pores. Pressure diffuses into a porous electrospray through depletion of fluid in exposed pores. Diffusion of pressure complements the existing onset delay model for porous electrosprays. [ABSTRACT FROM AUTHOR]

This study explores hydrogen production via steam methane reforming (SMR) within complex Voronoi catalytic foams. Pioneering pore-scale analysis unveils the intricate interplay between foam geometry and SMR performance, surpassing conventional macro-scale studies. The highly intricate Voronoi foams intrigue due to their maximized surface area and efficient heat transfer. The research meticulously examines the combined effects of various factors like inlet velocity, temperature, foam properties, and steam-to-carbon ratio on hydrogen yield. Employing OpenFOAM's finite volume method, pore-scale simulations were conducted. Each investigated parameter significantly impacted hydrogen production, with temperature boasting the most remarkable influence. A 142.5% surge in hydrogen production was observed when increasing the temperature from 1100 to 1200 K. Lengthening the foam from 5 mm to 10 mm yielded a 90% increase. This groundbreaking study highlights the immense potential of Voronoi foams to revolutionize SMR processes, paving the way for cleaner and more sustainable energy solutions. [Display omitted] • The SMR process is simulated in a catalytic environment with pore-scale perspective. • Effect of velocity, temperature, S/C ratio & porosity on H 2 generation is analyzed. • Temperature has a greater impact on hydrogen mass flow rates. • Voronoi catalytic foam structure can highly affect heat transfer & hydrogen production. • 90% increase in hydrogen production rate observed by doubling the length of the foam. [ABSTRACT FROM AUTHOR]

With their extraordinary ability to conduct heat and their promise to increase heat transfer efficiency, nanofluids have emerged as a major player in the field of fluid technology today. This manuscript delves into the dynamic behavior of time-dependent complex Oldroyd-B nanofluids as they traverse between parallel plates within a porous media. Intriguingly, the study introduces captivating elements, including magnetic fields, convection, diffusion, heat source effects, and chemical reactions, which augment the uniqueness of the research. The designed model exhibits the potential to uncover the inherent characteristics and memory effects of viscoelastic nanofluids, pioneering the utilization of non-integer Caputo fractional derivatives to address this challenge. To tackle the complexities of this problem, we employ a combination of finite difference and finite element methods for the discretization of the governing flow equations. This enables us to flawlessly compute key parameters such as the Nusselt number, Sherwood number, and Skin friction coefficient for the complex fractional viscoelastic model. Our rigorous approach also involves the validation of the numerical scheme for convergence and the provision of error estimates. Our research delves into the realm of heat and mass transfer phenomena in porous media, specifically focusing on the intricate interplay between complex fluid dynamics and nanoparticle suspension. The results are given graphically, providing a picture of the importance of certain fractional and dimensionless physical characteristics. Notably, the flow simulations' application and importance are deepened by the inclusion of chemical processes, especially when considering the chemical sector. [ABSTRACT FROM AUTHOR]

Flow around a solid sphere finds utility in numerous single- and two-phase engineering applications, such as sport balls, combustion systems, silt conveyance in waterways, hydraulic conveying, pneumatic equipment, food and chemical manufacturing. Therefore, this paper aims to examine the Casson nanofluids flow and heat transfer over a solid sphere that is saturated in an isotropic porous material in the presence of Stefan blowing and slip conditions. The forced situation is due to the presence of a stagnation point while the surface of the sphere is subjected to thermal slip conditions. Besides, various significant impacts are taken into account such as Lorentz force, thermal radiation, heat source/sink, and activation energy. The solution technique is based on non-similar transformations and implicit finite difference method with the Blottner algorithm. It is remarkable that, for all values of the activation parameter, the growth of Stefan number reduces the gradients of the velocity, temperature, and nanoparticle concentration. Also, the presence of the thermal slip factor reduces the temperature distributions. Additionaly, an increase in either the Casson parameter or Darcy number enhances the flow while both temperature and concentration are diminishing. Furthermore, there is an improvement in values of the Nusselt number up to 50.57 % when the magnetic parameter is varied from 0 to 6. [ABSTRACT FROM AUTHOR]

The nature and behaviour of the drag coefficient $C_D$ of irregularly shaped grains within a wide range of Reynolds numbers $Re$ is discussed. The morphology of the grains is controlled by their fractal description, and they differ in shape. Using computational fluid dynamics tools, the characteristics of the boundary layer at high $Re$ has been determined by applying the Reynolds-averaged Navier–Stokes turbulence model. Both grid resolution and mesh size dependence are validated with well-reported previous experimental results applied in flow around isolated smooth spheres. The drag coefficient for irregularly shaped grains is shown to be higher than that for spherical shapes, also showing a strong drop in its value at high $Re$. This drag crisis is reported at lower $Re$ compared to the smooth sphere, but higher critical $C_D$ , demonstrating that the morphology of the particle accelerates this crisis. Furthermore, the dependence of $C_D$ on $Re$ in this type of geometry can be represented qualitatively by four defined zones: subcritical, critical, supercritical and transcritical. The orientational dependence for both particles with respect to the fluid flow is analysed, where our findings show an interesting oscillatory behaviour of $C_D$ as a function of the angle of incidence, fitting the results to a sine-squared interpolation, predicted for particles within the Stokes laminar regime ($Re\ll 1$) and for elongated/flattened spheroids up to $Re=2000$. A statistical analysis shows that this system satisfies a Weibullian behaviour of the drag coefficient when random azimuthal and polar rotation angles are considered. [ABSTRACT FROM AUTHOR]

Summary: A new mixed nonlocal finite element framework is developed for nonlinear thermo‐poro‐elasto‐plastic simulation of porous media with multiphase pore fluid flow and thermal coupling. The solid‐fluid interaction is accounted for using the mixture theory of Biot based on the volume fractions concept. Different sources of nolinearities arising from the multiphase fluid flow effects, advective‐diffusive heat transfer, inelastic deformation, fluid flux injection induced mechanical tractions, solid skeleton deformation permeability dependence, and temperature dependent viscosity are included in developing a robust numerical solver for the targeted coupled multiphysics problem. To address the effect of microstructure in inelastic localized deformation behaviour with dilational softening, a nonlocal plasticity model is proposed based on a characteristic length scale which rectifies the non‐physical pathological mesh dependence problem encountered in conventional plasticity. The accuracy and strength of the developed model is shown with comparing the obtained numerical results of a benchmark bilateral compression test with existing published data in the literature. To show the versatility and robustness of the developed computational framework in modelling the geomechanics of real‐case engineering practices, large scale thermo‐hydro‐mechanical (THM) subsurface stimulation processes with applications in enhanced oil recovery (EOR) are effectively simulated and the targeted enhanced recovery and performances are demonstrated. The current formulation does not include phase transformation modelling capability, and therefore, the developed models may not be applicable for simulation of the engineering processes that involve phase change behaviour (e.g., steam injection). [ABSTRACT FROM AUTHOR]

Numerical simulation studies of water–rock interaction mechanisms and pore-scale multiphase flow properties often require high computational efficiency and realistic geometries to enable a fast and accurate description of hydrodynamic behavior. In this paper, we have chosen to use deep learning models to achieve these requirements, firstly by using encoder structures to refine the image segmentation of void-solid structures on complex geometries of scanning electron microscopy (SEM) images of porous media through few-shot learning (FSL), not only obtaining an accuracy of 0.97, but also reducing the amount of annotation work. We then focus on pore-scale three-dimensional (3D) structural reconstruction using the unpaired image-to-image translation method, optimizing the cycle-consistent adversarial network (cycle-GAN) model via sliced Wasserstein distance (SWD) to transfer marine sedimentary sandstone features to the initial image, and the geometric stochastic reconstruction problems are transformed into optimization problems. Subsequently, the computational efficiency was improved by a factor of 21 by implementing the lattice Boltzmann simulation method (LBM) accelerated by GPU through compute-unified device architecture (CUDA). The flow field distribution and absolute permeability of the extracted 2D samples and the reconstructed 3D porous media structure were simulated. The results showed that our method could rapidly and accurately reconstruct the 3D structures of a given feature, ensuring statistical equivalence between the 3D reconstructed structures and 2D samples. We solve the problem of extrapolation-based 3D reconstruction of porous media and significantly reduce the time spent on structure extraction and numerical calculations. [ABSTRACT FROM AUTHOR]

We present a comprehensive theoretical analysis which integrates the Klinkenberg plot into the pulse decay method (PDM) to effectively address the slippage effect on permeability measurement of micro/nanoporous media. Employing an asymptotic perturbation analysis on the Navier–Stokes equation within a capillary model, our work fills a critical gap in the interpretation of PDM experimental data, particularly by considering the influence of Knudsen number on permeability. Our findings substantiate the reliability of the Klinkenberg plot in interpreting PDM data, particularly when the ratio between the pore volume and the upstream or downstream chamber is below 0.1. It is noteworthy that our study underscores the persistent presence of the slippage effect when one chamber is sealed, emphasizing the necessity for careful consideration in permeability measurements under such conditions. The robustness of the theoretical framework is validated through experimental results, providing strong supports for the accuracy and applicability of our approach in heat and mass studies in micro/nanoporous media. [ABSTRACT FROM AUTHOR]

Understanding the environmental drivers of microbial H 2 metabolisms is crucial for evaluating the risks for geological hydrogen storage. This study investigates how mineralogy and temperature affect H 2 consumption kinetics and metabolic activity of a microbial consortium containing methanogens, homoacetogens and sulfate reducers, incubated at 25, 34 and 40 °C under H 2 /CO 2 (80/20, v/v; 2 bars) with different rock powders (basalt, calcite, gypsum, and sandstone). The presence of gypsum favors sulfate reduction over methanogenesis and homoacetogenesis, especially at 25 °C. Methanogenesis is dominant at 34 and 40 °C with all sulfate-free mineralogies. At 25 °C, homoacetogenic bacteria are favored over methanogens and acetate production varies with the mineralogy. This suggests interactions of the microbial community with the rock powders, which may serve as a surface to form biofilms. These metabolic shifts are associated with radical changes in microbial populations, highlighting that ecosystems plasticity towards H 2 also depends on the mineralogical composition of the reservoir. • Both temperature and mineralogy affect H 2 consumption kinetics. • Gypsum powder favors sulfate reduction over methanogenesis and homoacetogenesis. • Low temperature favors homoacetogenesis over methanogenesis. • Proportions of methanogenesis and homoacetogenesis vary with the substrate mineralogy. • Metabolic shifts are associated with radical changes in microbial populations. [ABSTRACT FROM AUTHOR]

This paper deals with the existence of weak solutions of the system that describes the two‐phase two‐component fluid flow in porous media. Both two‐phase and possible one‐phase flow regions are taken into account. Our research is based on a global pressure, an artificial variable that allows us to partially decouple the original equations. As a second primary unknown for the system, we choose the gas pseudo‐pressure, a persistent variable which coincides with the gas pressure in the two‐phase regions while it does not have physical meaning in one‐phase flow regions, when only the liquid phase is present. This allows us to introduce an another persistent variable that is an artificial variable in one‐phase flow regions and a physical variable in two‐phase flow regions—the capillary pseudopressure. We rewrite the system's equations in a fully equivalent form in terms of the global pressure and the gas‐pseudo pressure. In order to prove the existence of weak solutions of obtained system, we also use the capillary pseudo‐pressure. By using it, we can decouple obtained equations on the discrete level. This allows us to derive the existence result for weak solutions in more tractable way. [ABSTRACT FROM AUTHOR]

Under varying flow rate conditions, the transport and retention of polydisperse microplastics (MPls), with an average particle size of 16 ± 6 µm, were investigated in saturated porous media. First-order reversible and irreversible kinetic sorption models were used to describe the sorption kinetics. Sensitivity analyses provided insight into the effects of each sorption parameter. Both numerical modeling and experimental measurements were utilized to evaluate the retention rates of sand filters. The influence of flow rate on sorption was reflected in variations in the distribution coefficient (Kd), the mass transfer coefficient (β), and the irreversible sorption rate (K1). Lower flow rates were associated with higher Kd and β values, indicating increased sorption and reduced mass transfer rates. An increase in Kd resulted in a more gradual sorption process, with a decrease in peak concentration, whereas changes in β had a comparatively smaller impact on sorption rate and peak concentration. Lower K1 values were linked to higher peak concentrations and decreased retention efficiency. Numerical modeling revealed retention rates of 28 ± 1% at a flow rate of 31 mL min−1 and 17 ± 1% at 65 mL min−1. The introduction of MPls into saturated sand environments modifies the transport dynamics within the medium. Consequently, these alterations affect the hydrological characteristics of porous media, impacting groundwater quality and agricultural output. The mean absolute error (MAE) of 6% between the modeled and observed retention rates indicated a high level of accuracy. This study underscores the importance of examining retention efficiency and the accuracy of numerical models in understanding MPl transport in porous media. [ABSTRACT FROM AUTHOR]

The global transition to renewable energy sources such as wind and solar has created a critical need for effective energy storage solutions to manage their intermittency. This review focuses on compressed air energy storage (CAES) in porous media, particularly aquifers, evaluating its benefits, challenges, and technological advancements. Porous media-based CAES (PM-CAES) offers advantages, including lower costs and broader geographical availability compared to traditional methods. This review synthesizes recent advancements in numerical modeling, simulation, and experimental studies, which have enhanced the understanding of air–water–heat flow interactions and improved efficiency in these systems. Field studies demonstrate that using existing idle and abandoned wells can minimize infrastructure costs and environmental impact. This review underscores the potential of CAES in porous media to support the growing demand for sustainable and reliable energy storage solutions. [ABSTRACT FROM AUTHOR]

Salt weathering is a common deterioration phenomenon that affects outdoor cultural properties, and it is important to precisely predict the heat, moisture, and salt transfer in porous materials to suppress salt weathering. Osmosis and osmotic pressure were considered in the field of soil research, especially in clay research, but not in the field of outdoor cultural properties and building materials, which are the main target of salt weathering. Osmosis in clay is supposed to be caused by its surface charge. However, it has been suggested that sandstones and bricks that constitute cultural properties and buildings also have surface charge as clay. Thus, osmosis and osmotic pressure can occur in building materials, which may lead to materials degradation. In this study, we derive basic equations, based on nonequilibrium thermodynamics, for the simultaneous heat, dry air, water vapor, liquid water, cation, and anion transfer in building materials by considering osmosis. This equation was compared with existing model for heat and moisture transfer equations as well as models that considered the salt transfer. Based on the previous research for osmosis in clay, we summarized conditions under which osmosis occurs in building materials and presented an outlook for modeling the physical properties of materials related to osmosis. [ABSTRACT FROM AUTHOR]

In the present research, the stagnation point flow of EMHD Casson nanofluids over a stretchable electromagnetic plate is considered. Flow over the Riga plate is considered to analyze the Electromagnetic influences on fluid flow. Also, permeability, radiation, chemical reaction and heat source attributes are considered in this study. The guiding equations of the problem are transformed to nonlinear ODE using suitable similarity transformations. The numerical investigation of the flow is studied by implementing the Keller Box procedure using MATLAB. Validation of the numerical method is analyzed by comparing it with the previous studies. Also, calculated numerical observations of the local Nusselt and Sherwood parameters are of interest. An increase in the velocity outlines is detected for augmented observations of modified Hartmann number and unlike trends are noted for Casson, permeability, Prandtl number and suction factors. Temperature enhancement is witnessed for radiation, heat source, thermophoresis, Brownian diffusion and Biot number cases. Opposite trends are perceived in the case of suction constant. Concentration profiles are increasing for the alterations of thermophoresis parameter and declined in case of radiation, heat source, Brownian diffusion and Lewis number. [ABSTRACT FROM AUTHOR]

This research aims to enhance convective thermal transport in an inverted T-shaped porous enclosure filled with a water-based hybrid nanofluid, incorporating a circular cylinder at different vertical locations (Case C1-no cylinder, Case C1-cylinder at (0.5, 0.25), Case C2-cylinder at (0.5, 0.5), Case C3-cylinder at (0.5, 0.75)). The numerical investigation employs the penalty finite element technique to simulate the Darcy–Brinkmann–Forchheimer-based mathematical model. Moreover, the complete results of streamlines, isotherms, mean Nusselt number (Num), and thermal enhancement percentage ( En % ) are analyzed at the broad range of flow parameters, including Rayleigh number ( Ra = ( 10 3 − 10 6 ) ), Darcy number ( Da = ( 10 − 5 − 10 − 2 ) ), and porosity value ( ϵ = (0.1 − 0.9) ). Initial comparative investigations of different configurations (C0–C3) at selected Ra values reveal that case C1 exhibits significant potential for enhancing convective heat transport phenomena. Consequently, only case C1 physical domain has been explicitly analyzed for convective heat and fluid flow characteristics at the selected range of flow parameters. Further, it is analyzed that the increasing range of Ra, Da, and ϵ enhances the convective heat and fluid flow phenomena. Furthermore, the comparative study of Num and En % for case C1 against the simple case C0 reveals substantial improvements as Ra, Da, and ϵ increase. The En % for Da and Ra reaches up to 97%, while a maximum of 25% improvement is observed with varying values of ϵ. These findings highlight the promising opportunities to optimize convective thermal transport in the investigated system, mainly through adopting case C1. [ABSTRACT FROM AUTHOR]

The adsorption of cationic water-soluble polymers onto negatively charged porous wood pulp fibers is an essential aspect of papermaking. Adsorption data can be displayed as a direct plot of the amount adsorbed, Γ, versus the amount of polymer added or as an isotherm plot showing the amount adsorbed versus the residual unadsorbed polymer. In either data presentation, the analysis is more transparent if the units of each axis are the same (e.g., mg/g or meq/g), giving dimensionless slopes. Values for Γmax, ΓI, fI, and Γme can be extracted from many isotherms where: Γmax is the maximum capacity of the fibers to adsorb polymer; ΓI is the y-axis isotherm intercept and gives the maximum dose that can be fully adsorbed; fI is the slope of the direct plot at ΓI, and fI is the mass fraction of the added polymer that can access interior (pore) surfaces; and, Γme is the saturated amount of polymer adsorbed on exterior surfaces. Additionally, the molecular weight distribution of the adsorbing polymer in conjunction with the adsorption isotherm can be used to estimate the molecular weight distributions of adsorbed polymer on interior and exterior fiber surfaces as functions of the polymer dose. [ABSTRACT FROM AUTHOR]

In order to leverage on existing scaling methodologies, clinker bed was investigated to evaluate its performance for scaled down sizes. Small-sized clinker bed will provide cheaper and faster means of carrying out performance optimization study of clinker cooling process, which has been a research focus in recent years. Heat transfer mathematical equations were adopted to determine the outlet's temperatures and air pressure drop across the clinker bed, while Buckingham Pi theorem was employed to perform the scaling down of the clinker bed. Findings from the study revealed that for the actual size, predicted air outlet temperature, when compared to the experimental and numerical simulation results from existing literature, produced deviation of -5.46% and +1.65% respectively. For the scaled down-sizes, the air outlet temperature when compared with the actual size of experimental result, yielded deviations of 3.96%, 5.77% and 4.9% because the scaled sizes have 3, 6 and 9 scale factors, respectively. The results further revealed that an increase in mass flow rate of air will improve the heat transfer performance of the clinker bed, but this comes with an increase in pressure drop across the clinker bed heights. Furthermore, an increase in clinker flow rate was observed to be undesirable because the clinker outlet temperature actually being expected to cool down eventually increases, although pressure drop remained unchanged. By adopting a thermal-hydraulic performance factor (ϑ), maximum percentage deviation between ϑ of the actual size and each scaled size was 0.08% which indicates negligible performance deviation. The study therefore reveals that the size of clinker bed can be reduced to enable the development of small-scale prototype, and for numerical simulation to optimize the cooling process, especially when the outlet temperature and air pressure drop are the primary targets of investigation. [ABSTRACT FROM AUTHOR]

The use of thermal energy storage (TES) contributes to the ongoing process of integrating various types of energy resources in order to achieve cleaner, more flexible, and more sustainable energy use. Numerical modelling of hot storage packed bed storage systems has been conducted in this paper in order to investigate the optimum design of the hot storage system. In this paper, the effect of varying design parameters, including the diameter of the packed bed, the storage material, the void fraction, and the aspect ratio of the packed bed, on storage performance was investigated. COMSOL Multiphysics 5.6 software has been used to design, simulate, and validate an axisymmetric model, which was then applied to evaluate the performance of the storage system based on the total energy stored, the heat transfer efficiency, and the capacity factor. In this paper, a novel-packed bed was proposed based on the parametric analysis. This involved a 0.2 void fraction, 4 mm porous media particle diameter, and Magnesia as the optimum storage material with air as the heat transfer fluid. [ABSTRACT FROM AUTHOR]

In this paper, we study the onset and development of three-dimensional convection in a tilted porous layer saturated with a liquid. The layer is subjected to a gravitational field and a strictly vertical temperature gradient. Typically, problems of thermal convection in tilted porous media saturated with a liquid are studied by assuming constant different temperatures at the boundaries of the layer, which prevent these systems from supporting conductive (non-convective) states. The boundary conditions considered in the present work allow a conductive state and are representative of typical geological applications. In an earlier work, we carried out a linear stability analysis of the conductive state. It was shown that at any layer tilt angles, the most dangerous type of disturbances are longitudinal rolls. Moreover, a non-zero velocity component exists in -direction. In the present work, three-dimensional non-linear convection regimes are studied. The original three-dimensional problem is reduced to two-dimensional one with an analytical expression for the velocity -component. It is shown that the critical Rayleigh number values obtained through numerical solutions of the obtained 2D problem by a finite difference method for different layer inclination angles, are in a good agreement with those predicted by the linear theory. The number of convective rolls realized in nonlinear calculations also fits the linear theory predictions for a given cavity geometry. Calculations carried out at low supercriticalities show that a direct bifurcation takes place. With increasing supercriticality, no transitions to other convective regimes are detected. The situation studied in this problem can be observed in oil-bearing rock formations under the influence of a geothermal temperature gradient, where the ensuing fluid convection can affect the distribution of oil throughout the layer. Graphic Abstract [ABSTRACT FROM AUTHOR]

Air filters with pleats of different shapes present intricate manufacturing complications and flow patterns that pose a significant computational challenge. These pleated filters are primarily employed to enhance filtration area and dust-removing efficiency, as the volume of fine particulate matter in the atmosphere continues to escalate. This study examines diverse pleat shapes, such as U-shaped, semi-triangular, triangular, and sine wave triangular pleats, and investigates the effects of different design parameters, including pitch, height, thickness, angle, and amplitude of the pleat at varying inflow velocities. The simulation results using the RNG k-ϵ turbulence model have been compared to the previously documented experimental data and found to be in close agreement, within the inlet velocity range of 0.5–4.5 m/s. The study revealed that the pressure drop across the filter is influenced by both the pleat shapes and design parameters. In comparison to U-shaped, semi-triangular, and triangular pleats, the pressure drop values in rectangular-type pleats are higher by approximately 10%, 42%, and 100%, respectively, for a unit height of pleat and filter medium thickness. Among all the pleats examined, sine wave-type triangular pleats had the lowest pressure drop value. These results can provide valuable insights to industries involved in clean-air environments and automobiles. [ABSTRACT FROM AUTHOR]

Zero-valent iron nanoparticles (ZVINs) as a new environment remediation technology has significant potential for the treatment of contaminated soil and groundwater. In spite of the high efficiency of ZVINs in the removal of various pollutants from porous media, their have some weaknesses such as lack of stability and a strong tendency to rapidly aggregate which limits their application in field scales. The main objectives of this study was to investigate the efficency of guar gum (GG), polyacrylamide (PAM), polystyrene sulfonate (PSS), polyvinylpyrrolidone (PVP) stabilized-ZVINs (GG-ZVINs, PAM-ZVINs, PSS-ZVINs and PVP-ZVINs) and non-stabilized (bare) ZVINs (Bare-ZVINs) on nitrate removal from sand-packed columns. The characteristics of the synthesized ZVINs were characterized by scanning and transmission electron microscopy (SEM, TEM), zeta-potential analyzer and X-ray diffraction (XRD) techniques. A series of transport experimaent on sand-packed column were conducted under different concentrations of ZVINs (1, 2, and 3 g/L) and initial nitrate concentration (150, 250, and 350 mg/L). The CXTFIT code was used to simulate nitrate reduction in the sand columns; and estimating the transport parameters. The results revealed that mechanisms such as straining, ripening and aggregation had a considerable impact on the ZVINs transport in porous media. The results indicated that by increasing nitrate concentration the removal efficiency was decreased and in contrast by increasing concentrations of the ZVINs the nitrate reduction potential showed an enhancing trend. The results also revealed that ZVINs had a potential for nitrate removal from sand columns upon the following order: PAM-ZVINs > GG-ZVINs > PSS- ZVINs > PVP- ZVINs > Bare- ZVINs. [ABSTRACT FROM AUTHOR]

The study presents the development of the Meshless Local Petrov–Galerkin (MLPG) method to model and predict contaminant transport in porous media which is known as an important issue to prevent the pollution propagation in groundwater. The research focuses on the Rafsanjan Plain in southeastern Iran as a real case study, where no studies of meshless methods have been done. Computational models were implemented using MATLAB, integrating Radial Basis Functions (RBF) as the interpolation technique. The process commenced by establishing a groundwater flow model, where hydraulic head served as the foundational parameter for determining seepage velocity under unsteady-state conditions. Subsequently, the contamination transport was simulated within the aquifer for a period of six months. Comparative analysis between observed empirical data and the modeled values in both flow dynamics and contaminant transport revealed a significant and reasonable alignment. Analysis of the parameters showed that the value of the shape parameter ( α c) can have the greatest impact on achieving a more accurate value. In this research, with α c =6 in the contamination transport model, the most reliable outputs were obtained compared to the observed values. Furthermore, the assessment of the coefficient of determination (R2 = 0.97) was conducted to evaluate the acceptability of the calibrated parameters. The high R2 value suggests a robust correlation between the observed and simulated data, indicating that the model's parameters are within an acceptable range. This finding underscores the accuracy and reliability of the developed MLPG method for analyzing contaminant transport in unconfined aquifers, particularly in the context of the Rafsanjan Plain. [ABSTRACT FROM AUTHOR]

This study addresses the critical challenge of excessive water production in mature oil and gas reservoirs. It focuses on the effectiveness of polymer gel injection into porous media as a solution, with an emphasis on understanding its impact at the pore scale. A step-wise Lattice Boltzmann Method (LBM) is employed to simulate polymer gel injection into a 2D Berea sample, representing a realistic porous media. The non-Newtonian, time-dependent characteristics of polymer gel fluid necessitate this detailed pore-scale analysis. Validation of the simulation results is conducted at each procedural step. The study reveals that the methodology is successful in predicting the effect of polymer gel on reducing permeability as the gel was mainly formed in relatively larger pores, as it is desirable for controlling water cut. Mathematical model presented in this study accurately predicts permeability reductions up to 100% (complete blockage). In addition, simulations conducted over a wide range of gelation parameters, TD_factor from 1 to 1.14 and Threshold between 0.55 and 0.95, revealed a quadratic relationship between permeability reduction and these parameters. The result of this research indicates LBM can be considered as promising tool for investigating time-dependant fluids on porous media. [ABSTRACT FROM AUTHOR]

The fine particle liquid–solid flow in porous media is involved in many industrial processes such as oil exploitation, geothermal reinjection and particle filtration. Understanding the migration characteristics of single fine particles in liquid–solid flow in porous media can provide micro-detailed explanations for the fine particle liquid–solid flow in porous media. In this paper, an existing lattice Boltzmann method–discrete element method (LBM-DEM) is improved by introducing a new boundary thickening direct forcing (BTDF) immersed boundary method (IBM) to replace the classical IBM. The new method is used to investigate the migrations of one, two or three fine particles in a flow field in porous media and the reactions of one, two or three fine particles on the flow field. It is found that the movement distance of a fine particle in porous media does not show a linear correlation with the fine particle's density. A fine particle with a higher density may move a shorter distance and then stagnates. Although a fine particle with a smaller diameter has a better following performance in a flow field, it is also likely to be stranded in a low-infiltration area in porous media. Under the same increase ratio, the increase in the diameter of a fine particle causes an increased pressure drop of the liquid–solid flow. In some cases, the increase in the quantity of fine particles can intensify the disturbance of fine particles on the flow field, improving the movement of fine particles. [ABSTRACT FROM AUTHOR]