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The current paper studied the behavior of a triangular cavity occupied with Ag-MgO/water nanofluid under MHD natural convection and provided with a rotating circular barrier, while the right-angled corner is equipped with quarter-circle porous medium and maintained at a fixed hot temperature Th. Several parameters are tested such as Rayleigh number (103 ≤ Ra ≤ 106), Hartmann number (0 ≤ Ha ≤ 80) and Darcy number (10−5 ≤ Da ≤ 0.15). The obtained results depict the enhancing effect of Ra and the controlling role of the magnetic parameter on heat transport. Increasing the characteristics of the porous media such as the porosity and the permeability showed a substantial impact on the heat transport efficiency within the enclosure. Moreover, the novelty findings in this paper are principally illustrated in the boosting impact of raising the porous medium thickness when it is associated with the growing up of the heated parts of the geometry by increasing the dimension of the radius (rp). Also, the rotational velocity (ω) and the radius (rob) of the circular obstacle are tested and showed an important influence on the energy transport within the cavity. Moreover, the obtained results by modifying the length (a) prove its pertinent influence on the heat transfer performance. [ABSTRACT FROM AUTHOR]

In this work, we investigate the yield criterion of nanoporous materials by using homogenization approach and Steigmann–Ogden surface model. The representative volume element is proposed as an infinite matrix containing a tiny nanovoid. The matrix is incompressible, rigid-perfectly plastic, von Mises materials and nanovoids are dilute and equal in size. First, the constitutive of microscopic stress and microscopic strain rate is established based on the flow criterion. Secondly, according to the Hill's lemma, the relationship between the macroscopic equivalent modulus and the microscopic equivalent modulus is established by homogenization approach. Thirdly, the macroscopic equivalent modulus containing the Steigmann–Ogden surface model including surface parameters, porosity and nanovoid radius is derived from the trial microscopic velocity field. Finally, an implicit macroscopic yield criterion for nanoporous materials is developed. For surface modulus, nanovoids radius and porosity studies are developed through extensive numerical experiments. The research results in this paper have reference significance for the design and manufacture of nanoporous materials. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study on quasi-static ductile tearing of thin plates of the aluminium alloy AA6016 in three tempers. Depending on the temper, the main fracture mechanism in the plate tearing tests changes from grain boundary failure to coalescence of voids nucleated at the constituent particles. The experiments are complemented by nonlinear finite element simulations using an enriched Gurson–Tvergaard–Needleman (GTN) model to describe the material response. The onset of accelerated void growth is initiated either by incipient material softening (named the softening model) or by the occurrence of strain localization (named the localization model). It was found that strain localization takes place at a critical porosity f c , which depends on the current hydrostatic and deviatoric stress states. While the failure strain depends on the stress path, the critical porosity appears to be path independent. A third method is proposed (named the f c (T , L) model), where a critical porosity surface f c = f c T , L is used to determine when accelerated void growth starts. The surface is generated beforehand by solving for strain localization under proportional stress states defined by the stress triaxiality T and the Lode parameter L. By comparing the simulations to the experiments, it was found that the localization model performed well for a wide range of stress states. The softening model does not portray dependence on the Lode parameter and is therefore less versatile. The localization model and the f c (T , L) model gave similar predictions, but some minor differences were observed for two of the three tempers. [ABSTRACT FROM AUTHOR]

In this paper, thermo-hydro-mechanically (THM) coupled processes triggered during the construction, operation and closure of a deep geological repository for heat generating, high level radioactive waste are discussed based on a generic disposal concept. For this purpose, we are using the numerical non-isothermal two-phase–two-component flow in deformable porous media (TH2M) implementation (Grunwald et al. in Geomech Geophys Geo-energy Geo-resour, 2022) in the open-source software OpenGeoSys (Bilke et al. in Transport Porous Media 130(1):337–361, 2019, https://doi.org/10.1007/s11242-019-01310-1). THM coupled effects covered in this work focus on single and two-phase-flow phenomena, gas and heat generation as well as poro-elastic medium deformation. A suitable set of benchmarks covering aforementioned THM-effects, devised in the scope of the BenVaSim benchmarking project (Lux et al. in Synthesis report. BenVaSim—International Benchmarking for Verification and Validation of TH2M Simulators with Special Consideration of Fluid Dynamical Processes in Radioactive Waste Repository Systems. Tech. rep., 2021, https://doi.org/10.13140/RG.2.2.28998.34887) is chosen and one additional benchmark is presented, allowing for the demonstration and comparison of the OGS-6 TH2M implementation against results obtained by other well-established codes used in the field. Apart from the code comparison, the benchmarks also serve as means to analyze THM coupled processes in a repository based on very simplified geometries. Therefore, they can help to improve the process understanding, but any quantitative results should not be interpreted as predictions of the behaviour of a real repository. The results obtained in this work agree well with the results presented by the project partners in BenVaSim—both in single phasic, fully liquid saturated cases and in partially saturated two phase regions. Hence, the suitability of the OGS-6 TH2M implementation for the application in the field of radioactive waste management, supporting the safety case and analyzing the integrity of the geological and geotechnical barrier systems is demonstrated. Finally, a detailed discussion of observed phenomena in the benchmarks increases our understanding and confidence in the prediction of the behaviour of TH2M coupled systems in the context of deep geological radioactive waste disposal. [ABSTRACT FROM AUTHOR]

Purpose: To study free vibration and bending analyses of a sandwich microbeam with a functionally graded (FG) porous core and two polymeric face sheets reinforced with graphene nanoplatelets (GPLs). Methods: In this paper, the modified couple stress theory (MCST) and a quasi-3D trigonometric shear deformation beam theory are employed. The resultant material properties are examined using the rules of micromechanical. The equations derived through energy method are solved by Navier's method to obtain the natural frequencies and deflection of the nanobeam for a simply-supported boundary condition. Results: Trueness of the results are justified through comparison with the new recently published materials. Parametric static and dynamic results are presented for investigating effect of significant parameters on the frequencies and deflections of the sandwich microbeam, such as porosity parameter, distribution of the pores, the thickness of the core, volume fraction and distribution pattern of the GPLs, thickness-to-length scale parameter, and foundation coefficients. Conclusions: The results show that the VA distribution type has the biggest deflection and the AV one has the lowest value of static bending. [ABSTRACT FROM AUTHOR]

Ensemble-based data assimilation methods have been extensively investigated for inverse problems of fluid flow in porous media. However, when the permeability field is characterized by fine-scale gridblocks, the problem can be ill-posed and result in non-unique solutions. To address this issue, the principal component analysis with truncation was presented, but it may lead to biased estimation. In this paper, we propose to keep all eigenfunctions without truncation and add an additional sorting step after principal component analysis: sorting the initial samples according to the dimensional variability and assigning the dimensions with large variances to the leading eigenfunctions. The estimation is expected to be more accurate as the subspace spanned by the ensemble favors the dominant components. The proposed method is tested for multiple synthetic flow and transport cases. The results show that it provides more accurate estimation of the permeability fields and generates better history matching and prediction results for the production data (by 10–15%) than the results from the standard ensemble smoother, with the same computational cost. This sorting approach can be readily extended to the ensemble Kalman filter as well, for inverse modeling and estimating reservoir properties. [ABSTRACT FROM AUTHOR]

The current research undertakes the onset and formation of Darcy–Bénard convection within a channel of finite depth filled with fluid-saturated porous medium. The Darcy model of porosity is adopted, and a new family of solutions controlled by two parameters is identified from the governing equations representing the flow and thermal fields. These solutions cover most of the basic states studied so far associated with the Darcy law equations. Overall, they exhibit the relaxed impermeable wall constraints resulting in a linear vertical velocity distribution and with non-uniform lateral velocities. The corresponding thermal fields under different thermal boundary conditions are also evaluated analytically in terms of the error function. Despite the fact of the presence of non-uniform streamwise or spanwise velocities, it is shown that a linear stability analysis is still accessible through successively orienting the vortex perturbation, and hence, the conditions setting the convective instability onset are sought. In the two-parameter space, the pairs of most unstable Rayleigh wavenumber are determined for each thermal cases studied. Their contributions to triggering/delaying of emergence of the Darcy–Bénard cells are illuminated. The impacts of further physical mechanisms on the disclosed family in the present paper are open to new researches. [ABSTRACT FROM AUTHOR]

Foam injections in porous medium were performed throughout various objectives from Enhanced Oil Recovery (EOR) in 1970s to In Situ Environmental Remediation (ISER) in the mid-1980s. Several foam models were developed with the will to reproduce laboratory experiments and then, field applications related to different working conditions. Nevertheless, compressible effects on the gas phase remain sparsely investigated on both experimentation interpretations and foam models. In this paper, we present a compressible interpretation of a 1D core foam injection experiment, showing that gas compressibility has a pronounced effect despite a relative high working pressure. Based on experimental pressure values along the core, a semi-analytical Local Equilibrium (LE) foam model using a Mobility Factor FM was set and variables behaviour along the core were investigated. Then, foam parameters (fmmob, fmdry and epdry) were determined, and the laboratory experiment was successfully simulated using this compressible solver. Numerical simulations were then performed using the incompressible and compressible solvers. ∇ P = f (f g) | U t = c o n s t a n t extrapolated curves for both solvers were plotted and compared to highlight the role of compressibility. Moreover, coupled effects of foam compressibility and foam rheology were discussed. Article Highlights: A large part of foam injections in porous medium are greatly impacted by gas decompression. Foam flowing properties interpretation in a 1D core experiment is updated and discussed. The gas phase compressiblity appears as a key parameter for field applications to counter the radial effect around the wellbore. [ABSTRACT FROM AUTHOR]

The leakage of small holes in the buried CO2 pipeline is not easy to detect, which leads to the problem of the inability to accurately trace the source of the pipeline repair in the later stage. This paper designs and builds an experimental system to simulate the leakage of buried CO2 pipelines and conducts experiments on the leakage of small holes in buried CO2 pipelines to investigate the changes in the surrounding soil temperature when they leak. The results showed that the type of movement of CO2 in porous media after it is released from the leak is "funneling." At a distance of about 50 mm from the horizontal, the temperature difference in the horizontal surface is smallest at the 50 cm closest to the vertical distance of the leak, while at a distance of 225 mm from the horizontal, the temperature difference in the horizontal surface is largest at the 70 cm farthest from the vertical distance of the leak. The research results can provide a theoretical basis for the later development of technologies that can quickly locate the leakage points of buried CO2 pipelines and accurately determine their leakage status. [ABSTRACT FROM AUTHOR]

Oil sludge is the primary pollutant produced by the petroleum industry, which is characterized by large quantities, difficult disposal, and high toxicity. Improper treatment of oil sludge will pose a severe threat to the human living environment. Self-sustaining treatment for active remediation (STAR) technology has a specific potential for treating oil sludge, with low energy consumption, short remediation time, and high removal efficiency. Given the low smoldering porosity, poor air permeability, and poor repair effect of oil sludge, this paper considered coarse river sand as the porous medium, built a smoldering reaction device, conducted a comparative study on smoldering experiments of oil sludge with and without river sand, and studied the key factors affecting smoldering of oil sludge. The study shows that the repair effect is greatly improved by adding river sand, increasing the pore, and improving air permeability, and the total petroleum hydrocarbon removal rate reaches more than 98%, which meets the requirements of oil sludge treatment. When the mass ratio of oil sludge to river sand (sludge–sand ratio) is 2:1, the flow velocity is 5.39 cm/s, and the particle size of the medium is 2–4 mm. In addition, the best conditions for smoldering occur. The average peak temperature, average propagation speed, and average removal efficiency are relatively high. The peak temperature occurs in a short time; the heating time is also short, and the heat loss is low. Moreover, the generation of toxic and harmful gases is reduced, and secondary pollution is hindered. The experiment indicates that the porous media play a crucial role in the smoldering combustion of oil sludge. [ABSTRACT FROM AUTHOR]

The heterogeneity of reservoir micro-pores and the multifractal nature of their geometric morphology control the migration of oil and gas in porous media and affect the characteristics of oil and gas accumulation and productivity at the macro-scale. In this paper, based on high-resolution x-ray microscope computer tomography (XCT), combined with fractal and multifractal analysis, the microscopic pore-throat characteristics of 12 igneous rocks cylindrical core igneous rocks in the Huanghua Depression, China, were analyzed. A new DW interpretation chart (D = box-counting dimension; W = width of multifractal spectrum) based on fractal and multifractal analysis is presented to characterize the complexity of pore-throats in igneous rocks and to describe the influence of secondary transformation behavior on pore-throat microstructure. We found that microscopic pore-throat structures of different types of igneous rocks have significantly different fractal and multifractal characteristics. In addition, the complexity of pore-throat microstructure is indicative of the evolution dynamics of reservoir performance. The permeability of igneous rocks with simple microscopic pore-throat structures and strong heterogeneity is more sensitive to changes in porosity, and it is beneficial to the formation of high permeability oil–gas reservoirs. These results show the effect of igneous rock microstructure on macro-reservoirs and will provide a new perspective for the in-depth study of complex igneous oil–gas reservoirs. [ABSTRACT FROM AUTHOR]

Accurate prediction of the flow characteristics in low-permeable porous media is of great importance for achieving efficient geo-energy development as well as gas geological storage practices. Due to the microscale and complex geometry of the formation structures, mechanistic studies on the flow behavior in low-permeable porous media have arisen as a challenging research topic. In this paper, a pore-scale numerical study is carried out concerning the seepage characteristics in the low-permeable Berea core. After extracting the complex pore structure from the high resolution CT images, a novel methodology is proposed to screen the simulation representative elementary volume (REV), on which the fluid flow characteristics in the low-permeable pore media are scrutinized with help of the comprehensive Computational Fluid Dynamics (CFD) software. The roughness effect, which becomes significant in microscale pore channels, is taken into account for the permeability result corrections. Based on good agreement between the pore-scale simulation and the macroscale measurement results, the capability of the proposed CFD workflow on the study of the seepage characteristics in low-permeable porous media is well demonstrated. [ABSTRACT FROM AUTHOR]

This paper presents a numerical and experimental study of the effect of viscous and capillary forces on the characteristics of a multiphase flow in a pore doublet model, which is one of the most well-known elementary models of a pore space. Numerical simulation is carried out using OpenFOAM. The process of oil displacement by various agents in a pore doublet model is subjected to a multiparametric analysis with varying pore surface wettability, pressure difference, surface tension, and the ratio of the pore doublet channel size. It is shown that the numerical simulation results are in good agreement with experimental data for the pore doublet model in the case of a hydrophobic surface at various capillary numbers. The physical model of the pore doublet is implemented in a microfluidic chip manufactured using soft lithography. The proposed approach based on computational and experimental microfluidics makes it possible to carry out a numerical study of two-phase filtration in porous medium models corresponding to laboratory studies and to scale the results by characteristic sizes of the core. [ABSTRACT FROM AUTHOR]

The purpose of this work is to provide a novel approach for studying the chaos control of hybrid nanoparticles in a porous medium under feedback control and quasiperiodic gravity sinusoidal modulation. We use the powerful tool of Fourier modes to convert the governing flow model PDEs into ordinary ones. Under the combined effect, the properties of hybrid nanofluids a silver–magnesium oxide/water can be used to suppress heat transfer in a variety of industrial applications, i.e., cooling nuclear components. Numerical data comparison with the results presented in the previous literature shows a significant agreement with the present study. On the basis of nonlinear control theory and chaotic dynamics, the equilibrium points of the system are analyzed along with the local stability. As part of the article, different aspects of hybrid nanofluids (Ag–MgO/ H 2 O ) stability are discussed, starting from the preliminary stages to the practical application of hybrid nanofluids. It has been specifically focused on preventing nonlinear conditions from being aggravated by hybrid nanofluids. A pitchfork and inverted bifurcation can occur at various control gain and frequency or amplitude parameters. As a consequence of chaos, the paper proposes the implications of feedback control combined with quasi-gravity modulation to effectively control the chaotic system. [ABSTRACT FROM AUTHOR]

The paper studies the influence of nanomodifying peat-based additive TMT600 on the properties of foam, cement paste, and foam concrete. X-ray computed tomography is used to determine the homogeneity of the porous medium of non-autoclaved foam concrete. X-ray computed tomography provides a qualitative and quantitative assessment of the pore size distribution throughout the concrete volume. [ABSTRACT FROM AUTHOR]

This paper proposes a computational simulation procedure for simulating chemical dissolution-front instability problems, in which radially divergent flow is involved in fluid-saturated porous media. In the proposed computational simulation procedure, a combination of the finite element and finite difference methods is used to simulate a chemical dissolution-front instability problem involving radially divergent flow, while a new algorithm is used to apply a small perturbation to the problem. Particular attention is paid on simulating low-order modes of an unstable circular chemical dissolution-front propagating in a fluid-saturated porous medium, in which dissolvable materials only occupy a small part, so that the final porosity is remarkably smaller than unity when dissolvable materials are completely dissolved in the chemical dissolution system. To verify the proposed computational simulation procedure, analytical solutions for a benchmark chemical dissolution-front instability problem involving radially divergent flow are derived in a purely mathematical manner. The related computational simulation results have demonstrated that: (1) the proposed computational simulation procedure is correct and useful for simulating chemical dissolution-front instability problems, which are associated with both stable and unstable chemical dissolution systems involving radially divergent flow in fluid-saturated porous media; (2) the simulated shapes of the second-order, third-order and fifth-order modes associated with an unstable chemical dissolution-fronts are respectively an ellipse, a star of three angles and a star of five angles in the unstable chemical dissolution system involving radially divergent flow in the fluid-saturated porous medium; (3) although the heterogeneity of a porous medium can affect the propagation speed of a chemical dissolution-front, it does not affect the low-order mode shape in the unstable chemical dissolution system involving radially divergent flow in the fluid-saturated heterogeneous porous medium. [ABSTRACT FROM AUTHOR]

The injection and in situ generation of foam in porous media successfully control gas mobility and improve the fluids' sweep efficiency inside porous media. Mathematical models describing this problem use two phases, foamed gas, and fluid, and usually have a term for foam generation and destruction. Moreover, the non-Newtonian foam behavior is frequently modeled using Hirasaki and Lawson's formula for foamed gas viscosity. In this paper, we detail how the traveling wave analysis can be used to estimate the propagation profiles and velocity for a range of non-Newtonian foam models in porous media at constant total superficial flow velocity. We reformulate Hirasaki and Lawson's formula in an explicit form allowing us to find traveling wave solutions for a foam model with non-Newtonian gas viscosity and a foam generation linearly dependent on the foam texture. Comparing the solution with the one for the Newtonian version allows us to analyze qualitatively and quantitatively the rheology of the foam flow in porous media. [ABSTRACT FROM AUTHOR]

In recent years, biodegradable porous Zn-based scaffolds employed as bone tissue engineering scaffolds to treat large bone defects have attracted attention of many researchers. Although porous Zn-based scaffolds have acceptable biocompatibility in vivo and more reasonable degradation rates than degradable Mg-based and Fe-based scaffolds, there is still a certain distance between the porous Zn-based scaffolds that have been developed and the ideal bone tissue engineering scaffolds. In this paper, the methods that had been used to prepare porous Zn-based scaffolds were summarized, and the advantages and disadvantages of each method were analysed. The mechanical properties of porous Zn-based scaffolds were reviewed, and the compressive, tensile, and fatigue behaviors of the scaffolds were also discussed. The degradation properties of porous Zn-based scaffolds in vitro were summarized, and the degradation rules were found. Comparing the degradation properties of bulk Zn-based materials and porous Zn-based scaffolds, the degradations of porous Zn-based scaffolds were more deeply understood. In addition, the degradation behaviors of porous Zn-based scaffolds in vivo were also reviewed. The antibacterial properties of porous Zn-based scaffolds were summarized. Reviewing the experimental results of the biocompatibility of porous Zn-based scaffolds in vitro and in vivo, the main factor affecting the biocompatibility was identified, and the reasons for the large gap between the biocompatibility results in vivo and in vitro were discussed. At last, the problems faced by the current porous Zn-based scaffolds used as bone tissue engineering scaffolds were proposed, and the potential solutions to these problems were also suggested. [ABSTRACT FROM AUTHOR]

Gas injection can increase oil recovery because the gas–oil interfacial tension is less than the water–oil interfacial tension (IFT) and tends to zero in the miscibility state. However, little information has been provided on the gas–oil movement and penetration mechanisms in the fracture system at the porosity scale. The IFT of oil and gas in the porous medium changes and can control oil recovery. In this study, the IFT and the minimum miscibility pressure (MMP) are calculated using the cubic Peng-Robinson equation of state that has been modified using the mean pore radius and capillary pressure. The calculated IFT and MMP change with the pore radius and capillary pressure. To investigate the effect of a porous medium on the IFT during the injection of CH4, CO2, and N2 in the presence of n-alkanes and for validation, measured experimental values in references have been used. According to the results of this paper, changes in IFT vary in terms of pressure in the presence of different gases and, the proposed model has good accuracy for measuring the IFT and the MMP during the injection of hydrocarbon gases and CO2. In addition, as the average radius of the pores gets smaller, the interfacial tension tends to lower values. This effect is different with increasing the mean size of interstice in two different intervals. In the first interval, i.e. the Rp from 10 to 5000 nm, the IFT changes from 3 to 10.78 mN/m and in the second interval, i.e. the Rp from 5000 nm to infinity, the IFT changes from 10.78 to 10.85 mN/m. In other words, increasing the diameter of the porous medium to a certain threshold (i.e. 5000 nm) increases the IFT. As a rule, changes in IFT affected by exposure to a porous medium affect the values of the MMP. In general, IFT decreases in very fine porous media, causing miscibility at lower pressures. [ABSTRACT FROM AUTHOR]

The paper presents a method of the preparation and functionalization of polymer microspheres consisting of glycidyl methacrylate (GMA) and crosslinking agents: 1,4-dimethacryloyloxybenzene (1,4DMB) and trimethylolpropane trimethacrylate (TRIM). Poly(GMA-co-1,4DMB) and poly(GMA-co-TRIM) microspheres were obtained by seed swelling polymerization. To introduce thiol groups into the microspheres structure, the reaction with thiocarboxylic acids was performed. The chemical structure of parent and modified microspheres was confirmed by FTIR and Raman spectroscopy. Elemental composition of microspheres after functionalization was determined by elemental analysis. The analysis showed the percentage of sulfur in the range of 2.78–4.51%, which corresponds to a concentration of thiol group in the range of 0.87–1.41 mmol g−1. Additionally, the porous structure of the copolymers was investigated using the low-temperature nitrogen adsorption–desorption method. The starting microspheres are characterized by a specific surface in the range of 150–160 m2 g−1, whereas functionalized copolymers indicate slightly lower surface area, of about 130 m2 g−1. The thermal stability of the materials was determined by the method of differential scanning calorimetry and thermogravimetric analysis. The course of the thermal degradation under oxidative conditions of modified microspheres is different from the starting copolymers. The functionalized microspheres showed much higher thermal stability (approximately 270 °C) compared to the starting microspheres (230–250 °C). [ABSTRACT FROM AUTHOR]

According to estimates, between 10 and 25% of the grain crop is lost in the post-harvest. The correct drying of the beans is one of the actions to contain this loss. Drying grains is one of the most critical steps in grain processing for its proper conservation after harvest. As the grain mass is a set of solid and empty spaces (holes) through which a fluid can pass, its drying could be considered a problem of the coupled open-porous medium. In this paper, we propose a mathematical and computer simulation model which describes the convection in a free flow with a porous obstacle applied to the grain drying processing. A computational fluid dynamics scheme was implemented in FORTRAN using Finite Volume to simulate and compute the numerical solutions. The code is parallel implemented using OpenMP (loop and teams approach) and OpenACC programming interfaces. We use three case studies with different mesh sizes to evaluate the implementations. As a result, there was a reduction in processing time in the cases. The total simulation time for a multicore architecture (16 physical cores) was 6,14 times less using parallel loops and 8.5 using parallel teams, and 8.38 using a single GPU (Quadro M5000). [ABSTRACT FROM AUTHOR]

The surface fracture toughness is an important mechanical parameter for studying the failure behavior of air plasma sprayed (APS) thermal barrier coatings (TBCs). As APS TBCs are typical multilayer porous ceramic materials, the direct applications of the traditional single edge notched beam (SENB) method that ignores those typical structural characters may cause errors. To measure the surface fracture toughness more accurately, the effects of multilayer and porous characters on the fracture toughness of APS TBCs should be considered. In this paper, a modified single edge V-notched beam (MSEVNB) method with typical structural characters is developed. According to the finite element analysis (FEA), the geometry factor of the multilayer structure is recalculated. Owing to the narrower V-notches, a more accurate critical fracture stress is obtained. Based on the Griffith energy balance, the reduction of the crack surface caused by micro-defects is corrected. The MSEVNB method can measure the surface fracture toughness more accurately than the SENB method. [ABSTRACT FROM AUTHOR]

In this paper, for the mixed Navier—Stokes/Darcy model with Beavers—Joseph—Saffman's interface condition, we first establish an a priori estimate for possible weak solutions by means of expanding the coupled system. Then we prove the existence of weak solutions without the small data and/or large viscosity restriction, which is required for the existence of the weak solutions in literatures. As a direct corollary, we also get the global uniqueness of the weak solution. [ABSTRACT FROM AUTHOR]

Perfectly incompressible materials do not exist in nature but are a useful approximation of several media which can be deformed in non-isothermal processes but undergo very small volume variations. In this paper, the linear analysis of the Darcy-Bénard problem is performed in the class of extended-quasi-thermal-incompressible fluids, introducing a factor β which describes the compressibility of the fluid and plays an essential role in the instability results. In particular, in the Oberbeck-Boussinesq approximation, a more realistic constitutive equation for the fluid density is employed in order to obtain more thermodynamically consistent instability results. The critical Rayleigh-Darcy number for the onset of convection is determined, via linear instability analysis of the conduction solution, as a function of a dimensionless parameter β ^ proportional to the compressibility factor β , proving that β ^ enhances the onset of convective motions. Article Highlights: The onset of convection in fluid-saturated porous media is analyzed, taking into account fluid compressibility effect. The critical Rayleigh-Darcy number is determined in a closed algebraic form via linear instability analysis. The critical Rayleigh-Darcy number is shown to be a decreasing function of the dimensionless compressibility factor. [ABSTRACT FROM AUTHOR]

In this paper, the effect of boundary slip on the reflection and refraction of elastic waves at the interface of fluid-saturated porous media is investigated based on the virtually enlarged pore (VEP) model. The theoretical formula for the energy reflection and refraction of elastic waves is derived by introducing a potential function. The dependence of energy reflection and refraction coefficients on permeability and pore fluid viscosity is investigated using the VEP model. The numerical results are obtained and displayed graphically. It is observed that boundary slip has a noticeable effect on the energy reflection and refraction coefficients of elastic waves. The boundary slip effect makes the energy reflection and refraction coefficients more sensitive to the permeability and the viscosity of pore fluid. Article Highlights: Reflection and refraction of elastic waves are studied based on the VEP model The influence of boundary slip effect on the reflection and refraction coefficients is investigated. Reflection and refraction coefficients are more sensitive to permeability and viscosity based on the VEP model. [ABSTRACT FROM AUTHOR]

This paper serves as a brief introduction to the longer introduction provided by the book by Nield and Bejan (NB). Attention is focussed on the modelling of the interaction of the heat transfer and the presence of a porous medium. Except for a brief mention, convection in unsaturated media is beyond the scope of this book and hence this review. Our coverage is mainly confined to single phase flow. The effects of radiation considered are confined to a contribution to volumetric heating produced by the absorption of radiation. Topics covered relate to both pore scale (microscale) and macroscale modelling and processes. Both theoretical and experiment studies are considered. Whilst NB contains a section on deformable media, the book is largely constrained to rigid porous media. This review is confined to matters concerning rigid porous media. [ABSTRACT FROM AUTHOR]

This paper proposes the application of capillary and chain random models of pore space structure for determination of limit pore diameter distributions of porous materials, based on the mercury intrusion curves. Both distributions determine the range in which the pore diameter distribution of the investigated material occurs and defines the degree of inaccuracy of the method based on the mercury intrusion data caused by the indeterminacy of the sample shape and its pore space architecture. We derived equations describing the quasi-static process of mercury intrusion into the porous layer and porous ball with a random chain pore space structure and analysed the influence of the model parameters on the mercury intrusion curves. It was shown that the distribution of link length in the chain model of the pore space, random location of chain capillaries in the sample and the length distribution of the capillaries do not influence significantly the intrusion process. Therefore, a simple model of the mercury intrusion into the layer is proposed in which chain links of the pore space have random diameters and constant length. This model is used as a basic model of the intrusion process into a sample of any shape and size and with homogeneous and isotropic chain pore space architecture. The thickness of the layer then represents the mean length of chain capillaries in the sample. It was also proved that the capillary and chain models of pore space architecture are limit models of the network model identified in this paper with the pore architecture of the investigated sample. This justifies the application of both models for determination of limit cumulative distributions of pore diameters in porous materials based on the mercury intrusion data. [ABSTRACT FROM AUTHOR]

The emergence of nanofluids as high-performance thermal transport media has drawn great research attention in the field of heat transfer. Owning to the huge importance of natural convection applications in environmental, agricultural, manufacturing, electronics, aviation, power plants, and industrial processes, heat transfer and flow characteristics of these special fluids in various cavities have been extensively researched. This review paper has paid serious attention to the benefits of controlling the natural convection heat transfer and flow performance of nanofluids in square cavities using magnetic field sources in addition to the aspect ratio, porous media, cavity and magnetic field inclination, hybrid nanofluids, etc. The influence of several variables such as heat distribution methods, thermal and concentration boundary conditions, governing parameters, magnetic field types, numerical schemes, thermophysical correlation types, nanofluid types, slip conditions, Brownian motion, and thermophoresis on the magnetohydrodynamic (MHD) natural convection behaviours of nanofluids in square cavities has been reviewed. The paper focused on the application of numerical and experimental methods to hydromagnetic behaviours of nanofluids in square-shaped enclosures. The concept of bioconvection, bio-nanofluid (green nanofluid), ionic nanofluid, and hybrid nanofluid has also been reviewed in relation to natural convection for the first time. Special cases of MHD natural convection in cavities involving micropolar and hybrid nanofluids are also presented herein. Convective heat transfer in square cavities has been demonstrated to be altered due to the presence of magnetic fields. [ABSTRACT FROM AUTHOR]

In this paper, the entropy generation of natural convection Jeffrey fluid flow through an inclined porous channel is investigated by taking into account the impact of angled magnetic field, Soret parameter, thermal radiation, and Hall current. On the basis of simplified assumptions, the governing equations are transformed into dimensionless equations by using suitable transformations, and the spectral quasi-linearization method (SQLM) is used for the numerical solution. Graphs are utilized to address the effects of new thermophysical parameters. The calculations reveal that increasing the Soret parameter, inclination angle, Hall parameter, magnetic parameter, and Jeffrey fluid parameter induces an increase in entropy generation. Conversely, it decreases as the radiation parameter and channel angle of inclination increase. [ABSTRACT FROM AUTHOR]

In this paper, we consider the complex flows when all three regimes pre-Darcy, Darcy and post-Darcy may be present in different portions of a same domain. We unify all three flow regimes under mathematics formulation. We describe the flow of a single-phase fluid in by a nonlinear degenerate system of density and momentum. A mixed finite element method is proposed for the approximation of the solution of the above system. The stabilit1y of the approximations are proved; the error estimates are derived for the numerical approximations for both continuous and discrete time procedures. The continuous dependence of numerical solutions on physical parameters are demonstrated. Experimental studies are presented regarding convergence rates and showing the dependence of the solution on the physical parameters. [ABSTRACT FROM AUTHOR]

In this paper, the mathematical model of heat and porous media equations being considered in fractional form. The Laplace residual power series method and the Laplace Adomian decomposition technique are used to compare the solutions of the fractional heat transfer and porous media equations. For this reason, a few examples are presented to understand the fractional heat transfer and porous media equations in its more accurate form. The results show the simple and sophisticated procedures of the two proposed analytical approaches, where partial differential equations are considered with fractional derivatives. The outcomes of the described methods demonstrate that they have an accurate algorithm to construct with exceptionally precise cost calculation capabilities. The obtained results are presented through tables and graphs and the approximate results are found in great contact with exact solutions. [ABSTRACT FROM AUTHOR]

In this paper, the coupled linear theory of thermoviscoelasticity for porous materials is considered in which the coupled phenomenon of the following four mechanical principles is proposed: the deformation of the skeleton of a porous solid, the volume fraction concept of the pore network, Darcy's law for the flow of a fluid through a porous medium, and Fourier's law of thermal conduction. The governing systems of equations of motion and steady vibrations are proposed. The fundamental solution of the system of steady vibration equations is presented explicitly by means of elementary functions, and its basic properties are established. By virtue of Green's identity the uniqueness theorems for the classical solutions of the basic internal and external boundary value problems (BVPs) of steady vibrations are proved. Then, the surface and volume potentials are presented and their basic properties are given. Finally, the existence theorems for classical solutions of the above-mentioned BVPs are proved by means of the potential method (boundary integral equation method) and the theory of singular integral equations. [ABSTRACT FROM AUTHOR]

Reservoir modeling consists of two key components: the reproduction of the historical performance and the prediction of the future reservoir performance. Industry-standard reservoir simulators must run fast on enormous and possibly unstructured grids while yet guaranteeing a reasonable representation of physical and chemical processes. However, computational demands limit simulators in capturing involved physical and geochemical mechanisms, especially when chemical reactions interfere with reservoir flow. This paper presents a mathematical workflow, implemented in IORSim, that makes it possible to add geochemical calculations to porous media flow simulators without access to the source code of the original host simulator. An industry-standard reservoir simulator calculates velocity fields of the fluid phases (e.g., water, oil, and gas), while IORSim calculates the transport and reaction of geochemical components. Depending on the simulation mode, the geochemical solver estimates updated relative and/or capillary pressure curves to modify the global fluid flow. As one of the key innovations of the coupling mechanism, IORSim uses a sorting algorithm to permute the grid cells along flow directions. Instead of solving an over-dimensionalized global matrix calling a Newton–Raphson solver, the geochemical software tool treats the species balance as a set of local nonlinear problems. Moreover, IORSim applies basis swapping and splay tree techniques to accelerate geochemical computations in complex full-field reservoir models. The presented work introduces the mathematical IORSim concept, verifies the chemical species advection, and demonstrates the IORSim computation efficiency. After validating the geochemical solver against reference software, IORSim is used to investigate the impact of seawater injection on the NCS Ekofisk reservoir chemistry. Article Highlights: The IORSim sorting algorithm decouples the nonlinear geochemical reaction calculations into recurring one-dimensional problems to assure numerical stability and computation efficiency. To the best of our knowledge, this work presents the mathematical concept, implementation, and application of topological sorting for the first time on (industry) field-scale problems. IORSim combines topological sorting with basis swapping and splay trees to significantly reduce computation times. Moreover, a high-speed forward simulation mode was developed to allow the post-advection of chemical components to visualize species distribution, water chemistry, and mineral interactions. If the geochemical reactions interfere with the fluid flow, the IORSim backward mode uses relative permeability curves to update the global fluid flow at each time step. We validate the implemented topological scheme on a reservoir grid, show the computation efficiency, and compare the impact of explicit, implicit, and grid refinement on numerical dispersion. The decoupled flow simulator and geochemical reaction calculations allow seamless integration of full-field reservoir models that contain complex geological structures, a large number of wells, and long production histories. The computation capabilities of IORSim are demonstrated by simulating and reproducing the impact of seawater injection in the southern segment of the giant Ekofisk field (more than 50 years of injection and production history). IORSim shows that seawater injection changed the Ekofisk mineralogy and impacted the produced water chemistry. In the investigated Ekofisk case, seawater promoted calcite dissolution and led to the precipitation of magnesite and anhydrite. Moreover, surface complexation modeling revealed that sulfate is adsorbed on the calcite surface. [ABSTRACT FROM AUTHOR]

This paper presents and discusses the results obtained by the participants to the benchmark described in de Hoop et al, Comput. Geosci. (2024). The benchmark uses a model for CO2 geological storage and focuses on the coupling between two-phase flow and geochemistry. Several test cases of various levels of difficulty are proposed, both in one and two spatial dimensions. Six teams participated in the benchmark, each with their own simulation code, though not all teams attempted all the cases. The codes used by the participants are described, and the results obtained on the various test cases are compared, as well as the performance of the codes. It is shown that the results obtained are widely consistent, giving a good level of confidence in the outcome of the benchmark. The general complexity of two-phase flow coupled with chemical reactions altering porous media means that some differences between the codes remain. Besides, from the convergence study, it is clear that the two-dimensional problem has a relatively high sensitivity to a spatial resolution which adds to the complexity. [ABSTRACT FROM AUTHOR]

This paper investigates the contact problem of an elastic layer that is perfectly attached to a porous half-space by two rigid flat punches with collinear symmetry. Using integral transformation, the problem is condensed to a singular integral equation of the Cauchy type. Then, the exact expressions for the surface contact stress and surface interface displacement are provided. By using the Gauss–Chebyshev technique, the integral equations are solved numerically, and the variations of the unknown contact stresses and deformations for different parameters are addressed. The results indicate that stress concentration is typically higher on the outer edge of the contact area compared to the inner edge. This also explains why surface damage is more likely to occur on the outer edge in elastic and poroelastic materials. Due to the interaction between the two punches, there will be a superposition of normal displacements at the center. The deformation or bulging at the center can be managed by adjusting the parameter values, allowing the engineered material to fulfill its intended purpose. The potential applications of these research findings encompass safeguarding porous structures against contact-related deformation and damage. [ABSTRACT FROM AUTHOR]

This paper presents an analytical formulation to investigate functionally graded porous beams' nonlinear thermal buckling performance under various boundary conditions. The current model incorporates innovative cinematic techniques with the focus on the stretching effect and the iteration techniques. The material properties of the porous FG beams are temperature-dependent and vary according to a simple power-law distribution. The validity of the present theory' results is confirmed by comparing them with those obtained by other researchers. The findings demonstrate that the critical buckling temperature in TD and TID ranges from 1.03 to 1.27% for a uniform distribution and 1 to 1.47% for linear and non-linear distributions. Conversely, for regular porosity variation, the critical buckling temperatures fluctuate between 0.99 and 1.74%, and between 0.99 and 1.59% for porosity variation. Furthermore, the influence of boundary conditions becomes more pronounced when the nonlinear temperature difference is high. [ABSTRACT FROM AUTHOR]

A new strategy was developed to build a CO2-philic/hydrophilic surfactant by combining the common free radical polymerization and the grafting modification technology, and a brush polymer was synthesized with poly(vinyl acetate)(PVAc) based copolymer as the CO2-philic group (as the main chain) and the methoxy poly(ethylene glycol) (mPEG) as the hydrophilic part (as the branched chain) (PVAc-g-mPEG). The CO2-philic ability can be controlled by adjusting the chain length of the CO2-philic fragment. The results indicate that PVAc-g-mPEG has excellent surfactant activity, and can emulsify the CO2/H2O system to obtain the CO2-in-water (C/W) high interval phase emulsion (HIPE 80%, v/v), which can remain stable for more than 20 h. If using the monomers/crosslinking agent solution instead of water, the highly porous monolithic materials will be obtained after the continuous phase is polymerized. In this paper, polyacrylamide (PAM) and poly(acrylamide/diethyl aminoethyl methacrylate) (PADM)-based porous monolithic materials were prepared. These materials were used to remove bovine serum albumin (BSA, as the model matter) from the solution, and the results indicated that PAM-based porous monolithic materials had almost no enrichment capacity for protein, while PADM-based porous monolithic materials can adsorb BSA up to 129.3 mg/g. [ABSTRACT FROM AUTHOR]

The mechanism of fluid and heat transmission within materials with complex porous structures has not yet been fully explored and understood using basic analytical techniques. Therefore, the lack of advanced equipment and techniques has left an important knowledge gap in explaining the complex mechanisms of fluid motion and heat transfer in complex porous structures. This review provides an overview of how image analysis and processing techniques allow insight into the complex and heterogeneous porous structure of materials and explains the mechanism of heat and mass transfer in these complex porous materials in 3D and 4D observation in different directions. Accordingly, it provides interesting results related to the evaluation of microporous properties of complex porous materials including porosity, distribution and size of pores, distribution and orientation of fibers, tortuosity and mechanism of cracking, and destruction of the porous materials under mechanical tests. It also explains the mechanism of liquid transport in porous materials through 3D/4D observation thanks to image processing techniques. Therefore, this review has completed some limited knowledge in microstructural analysis and helped to understand the physical phenomena of liquid transfer in complex porous materials that were not fully exploited by experimental or simulation work. The paper also provides useful data for physical model simulation of imbibition and drying porous materials. [ABSTRACT FROM AUTHOR]

This paper presents a method for particle tracing in laboratory X-ray micro-computed tomography (µCT) using an adjusted Random Sample Consensus (RANSAC) algorithm combined with least squares ellipse fitting (LSF). For method testing, a setup for the investigation of deep bed filtration (DBF) has been used as an example of a complex process that can be elucidated with such a method. Particle tracking with tomography systems requires high-temporal resolution which can only be achieved with synchrotron radiation computer tomography. Therefore, in this work, it has been demonstrated that instead of particle tracking, particle tracing in opaque systems such as DBF can be performed in laboratory µCT systems. To achieve particle tracing, dynamic µCT scans with a duration between 30 and 110 s combined with an exposure time of 0.13 s/projection were executed and during the scan time the filtration was performed, causing parabola shaped motion artefacts. The developed method exploits the motion artefacts created by the particle motion during the scan. It could be shown that it is possible to trace particles in complex structures within only one 30 s scan. Furthermore, through trace length and time, it is possible to determine the average velocity. Whereby, the accuracy and limits depend on the particle size, particle velocity/data rate and the X-ray attenuation of particle and medium. Article Highlights: A method for the three-dimensional tracing of particles in porous and opaque media was developed using X-ray microtomography. The method was implemented in a way that it can be used under simple laboratory conditions instead of synchrotron facilities. The method was validated experimentally using opaque geometries of different complexities. [ABSTRACT FROM AUTHOR]

The mechanical formation damage induced by pore collapse within production curve depletion-dependent reservoirs significantly influences oilfield development. This paper proposes a new perturbative solution for transient pores collapse hysteresis modeling in depletion-dependent oil reservoirs with compaction effects during alternating loading/unloading cycles. The nonlinear hydraulic diffusivity equation is perturbed through a first-order expansion technique using the depletion-dependent permeability, k(p) as a perturbation parameter, ϵ . The practical uses of the model developed in this work are identifying flow regimes and hysteresis responses in pressure-sensitive reservoirs, estimating buildup pressure, specifying oil flow rate to prevent severe hysteretic behavior, and history matching during reservoir surveillance. The log–log analysis shows that the shut-in pressure has an influence on permeability loss. However, the comparisons between the permeability loss and its partial recovery curves show that this loss represents less than 5 % of the permeability value from the previous drawdown cycle. The derivative was also used to compute the instantaneous permeability loss using the relationship: ∂ m D / ∂ t D = k D (p D) ∂ p D / ∂ t D . The main advantages of the solution derived in this work are the simple implementation, practical graphical analysis of the pores collapse hysteresis effect, the possibility of simulating different boundary conditions and well-reservoir settings, and the requirements of only a few pressure and permeability field data to input in the deviation factor. The solution proposed can be applied to choose the production time to shut the well and monitor the adequate oil flow rate during the production curve. [ABSTRACT FROM AUTHOR]

This paper investigates a non-homogeneous two-dimensional model for reproducing chemotactic bacteria, immersed in a porous medium that experiences non-uniformly imposed flows. It is shown that independently of the form of the fluid velocity field, the compressible/incompressible nature of the fluid significantly shifts the Turing stability-instability transition line. In dry media, Gaussian perturbations travel faster than the hyperbolic secant ones, yet the latter exhibit better stability properties. The system becomes highly unstable under strong flows and high surface tension. Approximated solutions recovered by injecting Gaussian perturbations overgrow, in addition to triggering concentric breathing features that split the medium into high and low-density domains. Secant perturbations on the other hand scatter slowly and form patterns of non-uniformly distributed peaks for strong flows and high surface tension. These results emphasize that Gaussian perturbations strongly modulate the activity of bacteria, hence can be exploited to perform fast spreading in environments with changing properties. In this sense, Gaussian profiles are better candidates to explain quick bacterial responses to external factors. Secant-type approximated solutions slowly modulate the bacterial activity, hence are better alternatives to dive into weak bacterial progressions in heterogeneous media. [ABSTRACT FROM AUTHOR]

This paper develops a new two-dimensional model to estimate the radon exhalation rate of fractured porous media. The fractal discrete fracture network is used to characterize the fracture structure in the model. The finite element method solves the governing equations of radon migrations in fractures and porous matrix. Well-equipped laboratory tests validate the model with reasonable accuracy. The comparison of the model with the traditional radon migration model indicates that the model can simulate radon migration in fractured porous media more effectively than the traditional model. The effects of fracture intensity (P21), seepage velocity, and fracture connectivity on radon migration in fractured porous media are analyzed using the model. The radon exhalation rate increases with the fracture intensity and seepage velocity. There is an exponential relationship between fracture connectivity and radon concentration. The model provides a reliable method to analyze radon migration in fractured porous media and is helpful for radon pollution prevention and control. [ABSTRACT FROM AUTHOR]

This paper deals with the entropy generation for combined convection–radiation heat transfer between two parallel isothermal plates filled with a homogeneous and uniform porous medium. The porous medium is regarded as a gray, emitting, absorbing and scattering medium. Since this medium is a radiating medium, in addition to the contributions of fluid friction (velocity gradients) and conductive heat transfer (temperature gradients) in the amount of entropy generation, the contribution of radiative heat transfer is considered. In fact, the radiative entropy generation rate is the sum of the entropy generation rates due to absorption–emission, scattering and walls effects. The calculations are done for two types of boundary conditions including hot and cold walls and in the absence and presence of the radiative heat transfer mechanism. Also, the influences of shape factor, radiation–conduction parameter and wall emissivity on the values of total entropy generation number are investigated. The results show that the radiative heat transfer mechanism has a significant effect on the magnitudes of entropy generation rates for both types of boundary conditions. Also, the magnitudes of total entropy generation numbers in the case of cold walls are higher than these magnitudes in case of hot walls. [ABSTRACT FROM AUTHOR]

This paper considers the robust numerical methods for solving the time-dependent Stokes-Darcy multiphysics problem that can be implemented by use of existing surface water and groundwater codes. Porous media problem for the groundwater flow is preferable to employ the mixed discretization due to their superior conservation property and the convenience to compute flux on the large domain with relatively coarse meshes. However, the theory of mixed spatial discretizations for the time-dependent problems is far less developed than the non-mixed approaches, even for the one domain problems. Herein, we develop a stabilized mixed discretization technique for the porous media problem coupled with the fluid region across an interface with the physically appropriate coupling conditions. Time discretization is constructed to allow a non-iterative splitting of the coupled problem into two subproblems. The stability and convergence analysis of the coupled and decoupled algorithms are derived rigorously. If the time scale is bounded by a constant which only depends on the physical parameters, we prove the unconditional stability of both schemes. Four numerical experiments are conducted to show the efficiency and accuracy of the numerical methods, which illustrate the exclusive features of the Stokes-Darcy interface system. [ABSTRACT FROM AUTHOR]

Realizing high specific surface area and high heteroatom doping is the main challenge for carbon materials as electrode materials for high energy density supercapacitors. In this paper, edible fungus residue is used as the precursor via an effective carbonization-activation approach to obtain the edible fungi derived hierarchical porous carbons (EFHPCs) and adjust the porosity and heteroatom doping of carbon materials. When the EFHPC was assembled in asymmetric aqueous supercapacitor, the energy density reached to 113.12 Wh/kg at power density of 750.0 W/kg, which is significantly higher than that of commercial activated carbon. Therefore, EFHPCs can be used as ideal negative electrodes for asymmetric supercapacitors. These results indicate that the synthesis strategy adopted to design carbon with good porosity and heteroatom doping is promising for advanced supercapacitors. [ABSTRACT FROM AUTHOR]

There are many nanoscale pores in deep low permeability coal seams. The flow of coalbed methane (gas) in nanoscale pores belongs to the gas flow in porous media with medium and high Knudsen numbers. Its flow mechanism is one of the key unsolved scientific problems. In order to explore the gas transport law in nanopores of coal, a gas transport model based on microscopic boundary restriction was adopted to describe the gas flow law, and its rationality was verified by experimental data. The Field Emission Scanning Electron Microscope was used to scan the nanopores of customized anodized aluminum membrane. Then, the Maximally Stable Extremal Regions (MSER) algorithm of MATLAB and binarization algorithm were employed to quantify the pore structure parameters (equivalent pore size and porosity) of the membrane nanoscale pores. Finally, PMI micro-flow permeability tester was used to carry out different rarefied degree gas penetration experiments through anodized aluminum membranes, and the adopted gas transport model was verified. The results show that the binarization method is more accurate to characterize sample whose theoretical pore sizes are 20–35 nm, while MSER characterizes samples whose theoretical pore sizes are 110–150 nm and 200–300 nm more accurately. In other words, binarization method is more accurate for characterizing mesopores, while MSER algorithm is more accurate for macropores. The results have important reference value for more accurate extraction of nanopore parameters of porous media. Compared with traditional gas transport model, the adopted model considering the microscopic boundary restriction in this paper is closer to the experimental results. Moreover, it is suitable for describing the gas flow law in multiscale nanopores. The study provided important guiding significance for ascertaining the gas migration law in low permeability coal seam, improving the prediction accuracy of gas extraction and taking effective measures to increase production. The research results can further enrich the theoretical system of gas transport in coal, which is conducive to the efficient gas extraction, and is of great significance to promote the realization of carbon peak and carbon neutrality. [ABSTRACT FROM AUTHOR]

In this paper, a two-dimensional, steady, laminar boundary layer analysis is presented to analyze numerically the internal heat generation and Soret–Dufour effects on mixed convection flows of power-law fluids adjacent to a vertical flat plate maintained at variable heat flux and variable mass flux conditions in a Darcy porous medium. The Ostwald–de Waele power-law model is utilized here. The transformed governing equations are solved by the Keller box method. After performing comparisons with previously published results, good agreement is obtained. [ABSTRACT FROM AUTHOR]

In the paper, the fabrication method and characteristics of porous coatings on Ti-Nb-Zr-Sn alloy biomaterial obtained by plasma electrolytic oxidation (PEO) are presented. The PEO process was performed at two voltages of 180 ± 10 and 450 ± 10 V, respectively, during 3 min of treatment in the electrolyte based on orthophosphoric acid with copper II nitrate of initial temperature of 20 ± 2 °C. Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES), X-ray photoelectron spectroscopy (XPS) and 2D roughness measurements were performed on the samples. The study results indicate an enrichment of the porous layer (18 and 21 μm thick, for 180 and 450 V, respectively) in two elements, P and Cu, coming from the electrolyte used. The analysis performed based on the SEM, EDS, GDOES and XPS results obtained shows that after the PEO treatment, three sub-layers of the coating can be distinguished and separated and two models are proposed to fit these findings. It was found that both the contents of copper and phosphorus in the surface layer as well as the thickness of porous coating can be controlled to some extent by the PEO parameters. The greatest achievement of the presented work is the lack of toxic tin inside the top surface layer of the porous coatings as well as the enrichment of the coatings with copper ions up to 2.3 at%. In authors' opinion, the finding of the transition layer enriched within hydrogen and nitrogen ions can be interpreted by the presence of molecules of phosphoric acid and copper nitrate occurring in that sub-layer. This is a great advancement in the field of identification of the layers obtained by PEO. [ABSTRACT FROM AUTHOR]

The bones elastic characterization using the nondestructive technique based on the propagation of the ultrasonic waves well studied in this paper. The elastic properties of materials play a fundamental role in the scientific and medical domains; their measurements give important information on the mechanical properties of these materials. In addition, the ability to measure the elastic properties of bones quickly and accurately can help make sure its structure quality over the life cycle and control its damage throughout the lifetime. This paper mainly concerns the control of osteoporosis. In order to treat this phenomenon, we must first make the diagnosis. This work is important by the fact that it is a characterization (essentially mechanical) of the osteoporosis bones and that it is imperative that the sounding be of the nondestructive type, especially if the examination is be repeated often. First, the work of this study concerns develop new methods for the nondestructive evaluation of mechanical alterations of bone tissue to osteoporosis. In our study, we found the link between the bone elastic properties variation and its porosity, saturation fluid, pores shape, pore radius and trabecular alignment. The technique used in this study has based on measure the ultrasound and elastic parameters as celebrate the porosity. This requires develop of theoretical models to study, the ultrasonic waves propagate in porous bones (Biot model). These criterions have identified experimentally in bovine trabecular bones. The results obtained show that the proposed method is very effective in characterizing the osteoporosis effect on the bones elastic properties, for acoustic characterization purposes. [ABSTRACT FROM AUTHOR]

In Part I of this series, we presented a new theoretical approach for computing the effective permeability of porous media that are under deformation by a hydrostatic pressure P. Beginning with the initial pore-size distribution (PSD) of a porous medium before deformation and given the Young's modulus and Poisson's ratio of its grains, the model used an extension of the Hertz–Mindlin theory of contact between grains to compute the new PSD that results from applying the pressure P to the medium and utilized the updated PSD in the effective-medium approximation (EMA) to estimate the effective permeability. In the present paper, we extend the theory in order to compute the electrical conductivity of the same porous media that are saturated by brine. We account for the possible contribution of surface conduction, in order to estimate the electrical conductivity of brine-saturated porous media. We then utilize the theory to update the PSD and, hence, the pore-conductance distribution, which is then used in the EMA to predict the pressure dependence of the electrical conductivity. Comparison between the predictions and experimental data for twenty-six sandstones indicates agreement between the two that ranges from excellent to good. [ABSTRACT FROM AUTHOR]