Homogeneous Porous Material Research Articles

Problem of Three-Point Bending of an Elastic Beam from Porous Metal

Using numerical methods, we construct a solution to a physically and geometrically nonlinear problem of three-point bending of an elastic beam, made of porous metal, with rectangular cross-section. Unlike the classical version of the problem for a homogeneous beam, the heterogeneity over the cross-section due to material compaction because of the collapse of pores, which occurs in the compression zone at sufficiently large deflections, is taken into account. To describe the elastic state of a porous metal, the stress – strain diagram of a bimodular medium is used. The results of computations of strong bending of a beam, made of the low-porosity aluminum foam, are presented. These results demonstrate the difference between the obtained solution and similar solutions for beams, made of homogeneous porous and compacted material.

Dynamic stress response in reservoirs stimulated by fluctuating fluid pressure during pulsating hydraulic fracturing

Determining the most effective scheme for fracturing operations depends on accurate calculations of reservoir stress. Traditional fracturing theories usually focus on stable fluid injection modes, which employ static assumptions in modelling and analysis. However, pulsating hydraulic fracturing (PHF) introduces fluctuating fluid pressure to stimulate reservoirs, which requires considering dynamic factors and exploring the dynamic stress response within the reservoir. Furthermore, reservoirs are often classified as homogeneous continuous or porous media materials, but the boundaries between these classifications are sometimes apparent. This paper investigated the development of both an elastodynamics model and a poroelastodynamics model for calculating dynamic stress responses during PHF. The staggered grid finite difference method addressed these models, with the outer boundary employing the perfectly matched layer (PML) method to simulate an infinite reservoir. The numerical simulation results were extensively verified and compared with analytical solutions, and the differences between various models and their relevant conditions were thoroughly analyzed. Analyzing fluid pressure fluctuation parameters revealed noteworthy insights into reservoir stress response characteristics. Results indicate that as the Biot coefficient and permeability increase, the disparities between the elastodynamics and poroelastodynamics models become prominent. In practical terms, high Biot coefficient or high permeability reservoirs necessitate using the poroelastodynamics model for accurate reservoir stress analysis. As the frequency of fluid pressure fluctuation increases, the amplitude of response of reservoir circumferential stress also increases, while the response amplitude of radial stress and fluid pressure decreases. These findings offer valuable theoretical guidance for parameter design in engineering applications during PHF.

On the area-averaged effective sound absorption coefficient of porous materials excited by a monopole

The area-averaged effective sound absorption coefficient (SAC) of a rigid-backed homogeneous porous material subjected to a monopole excitation is calculated as the absorbed-to-incident sound power ratio. Using Allard's model to describe the sound propagation above the porous material, an analytical model for this power-based SAC is proposed and proves to give a good approximation of the sound absorption performance under monopole excitation of sufficiently large areas of material. The impact of factors on the power-based SAC, such as monopole height, material radial dimension used to calculate the sound powers, and material properties is discussed. The power-based SAC frequency-dependent behavior is analyzed through sound intensity field assessments at the material surface and is compared to normal incident plane wave and diffuse field SACs. The sound absorption behavior of sound absorbers under monopole excitation exhibits notable distinctions and peculiar results compared to those observed under plane wave and diffuse fields, particularly at low frequencies and for sources close to the material.

Mathematical Analysis on Dispersion Relation of Rayleigh Wave for an Initially Stressed Magneto-Poroelastic Material with Corrugated and Impedance Boundary

This study showcases the Mathematical modelling of elastic surface waves and the analysis of dispersion relations of Rayleigh-type of wave in an initially stressed homogeneous porous magneto-elastic material having corrugated and impedance boundary exhibitions. Adoption of the classical harmonic method of wave analysis, non-dimensionalization of the resulting equations of motion, and corrugated-impedance boundary conditions produced by the modeled problem are also captured. The dispersion equation was analytically and graphically presented. Effects of the contributing physical quantities, such as impedance and corrugated boundary parameters, on Rayleigh waves for the chosen material are analyzed. The magnetic field’s influences and the wavenumber associated with the corrugated boundary surfaces on the material increase the dispersion relations of the Rayleigh wave profile on the material. In addition, we noted that the dispersion relations of the wave increases for increasing phase velocity and some parameters of voids. Also, a void parameter triggered a decrease on the dispersion profile of the Rayleigh wave when increased while noting some uniform exhibitions from other voids coefficients. This work holds the potential to provide more insights into studies involving displacement distributions in earthquake sciences, stress-strain analysis in Structural Engineering materials, among others.

Hydraulically induced fracturing in heterogeneous porous media using a TPM‐phase‐field model and geostatistics

AbstractHydraulically induced fracturing is widely used in practice for several exploitation techniques. The chosen macroscopic model combines a phase‐field approach to fractures with the Theory of Porous Media (TPM) to describe dynamic hydraulic fracturing processes in fully‐saturated porous materials. In this regard, the solid's state of damage shows a diffuse transition zone between the broken and unbroken domain. Rocks or soils in grown nature are generally inhomogeneous with material imperfections on the microscale, such that modelling homogeneous porous material may oversimplify the behaviour of the solid and fluid phases in the fracturing process. Therefore, material imperfections and inhomogeneities in the porous structure are considered through the definition of location‐dependent material parameters. In this contribution, a deterministic approach to account for predefined imperfection areas as well as statistical fields of geomechanical properties is proposed. Representative numerical simulations show the impact of solid skeleton heterogeneities in porous media on the fracturing characteristics, e. g. the crack path.

Breathable MOFs Layer on Atomically Grown 2D SnS2 for Stable and Selective Surface Activation.

2D transition metal dichalcogenides (TMDs) have significant research interests in various novel applications due to their intriguing physicochemical properties. Notably, one of the 2D TMDs, SnS2 , has superior chemiresistive sensing properties, including a planar crystal structure, a large surface-to-volume ratio, and a low electronic noise. However, the long-term stability of SnS2 in humid conditions remains a critical shortcoming towards a significant degradation of sensitivity. Herein, it is demonstrated that the subsequent self-assembly of zeolite imidazolate framework (ZIF-8) can be achieved in situ growing on SnS2 nanoflakes as the homogeneous porous materials. ZIF-8 layer on SnS2 allows the selective diffusion of target gas species, while effectively preventing the SnS2 from severe oxidative degradation. Molecular modeling such as molecular dynamic simulation and DFT calculation, further supports the mechanism of sensing stability and selectivity. From the results, the in situ grown ZIF-8 porous membrane on 2D materials corroborates the generalizable strategy for durable and reliable high-performance electronic applications of 2D materials.

Local discontinuous Galerkin schemes for an ultrasonic propagation equation with fractional attenuation

The goal of this article is to develop local discontinuous Galerkin (LDG) schemes for solving a time fractional equation describing the ultrasonic wave in a homogeneous isotropic porous material. Two novel semi-discrete LDG schemes are designed for the considered model. The semi-discrete LDG schemes are constructed by splitting the original model into a coupled system. The first semi-discrete scheme follows the traditional LDG method by splitting second-order space derivative. The second one splits the original model for both time and space derivatives. The discontinuous Galerkin is used for the spatial discretization. Two kinds of fully discrete LDG schemes are presented by using the Grünwald-Letnikov and L1 approximation formulas for the time fractional derivatives. The $ L^2 $ norm stability and convergence analysis are carried out for both semi-discrete and fully discrete LDG schemes. The stability analysis reveals that the numerical schemes are unconditionally stable in $ L^2 $ norm and convergence with optimal convergence rate. Finally, numerical examples are presented to test the effectiveness of the proposed schemes and the correctness of the theoretical analysis.

Sound absorption performance of helically perforated porous metamaterials at high temperature

A high-temperature theoretical model is established to investigate the sound absorption performance of helically perforated porous metamaterials (HPPM) at high temperature. Finite element simulations are carried out to validate the theoretical model, and good agreements have been achieved. By perforating three-dimensional helical holes in homogeneous porous material, sound waves can enter the porous material matrix more fully through these extended macroscopic helical perforations, thereby obtaining good low-frequency sound absorption at high temperatures. The results show that with the increase of temperature, the impedance matching between the metamaterial and air becomes better, so as to improve the low-frequency sound absorption ability. Compared to homogeneous porous materials, the average absorption coefficient is greatly improved, especially at higher temperatures. The numerical results of sound pressure and energy dissipation at different temperatures show that high-temperature enhances the pressure diffusion effect at off-peak frequencies, resulting in more energy dissipation in high sound pressure regions. The helically perforated porous metamaterials with large helical diameter and low pitch exhibit better sound absorption performance in the low frequency range. The proposed metamaterial can be used for low-frequency sound absorption at high temperature.

Normal incidence sound absorption of an acoustic labyrinthine metal-fibers-based porous metamaterial at high temperature

This work studies the sound absorption performance of acoustic labyrinthine porous metamaterials (ALPM) at high temperature. The proposed metamaterial is constructed by perforating a homogeneous metal-fibers-based porous matrix with folded slits. These macroscopic perforations provide long channels for sound waves to enter the structure, allowing sound waves to enter the porous material due to the pressure diffusion effect, resulting in excellent subwavelength absorption at high temperatures. Based on the double porosity theory and temperature-dependent parameters, we develop a high-temperature theoretical model and validate it by numerical method. The results show that with the increase of temperature, the peak frequency of the ALPM moves to higher frequencies and the half-absorption bandwidth becomes wider. The discussion of sound absorption mechanism based on the pressure distribution results shows that with the increase of temperature, the pressure diffusion effect exists in a wider frequency range, which helps to suppress the propagation of long-wavelength sound waves at high temperature. The study of particle vibration velocity and energy dissipation density shows that the higher the temperature, the stronger the motion of air particles, and more sound energy is dissipated in the porous material, resulting in enhanced sound absorption. The ALPM can be regarded as a combination of homogeneous porous material and space-coiled resonator. Compared to these two components, the ALPM exhibits excellent sound absorption in the frequency range of 200Hz to 600Hz, especially at high temperatures. The proposed porous metamaterials show promising applications in low-frequency sound absorption at high temperature.

High-temperature effect on the sound absorption of cylindrically perforated porous materials

A theoretical model and a finite element (FE) model are proposed to evaluate the effect of high temperature on the sound absorption performance of cylindrically perforated porous materials. The theoretical model is established by applying the double porosity theory, in which the perforated porous material is considered as a combination of the porous material matrix and the cylindrical perforation. The FE model is constructed using the pressure acoustics module of the COMSOL Multiphysics software to verify the theoretical model. In these two models, the temperature effect is accounted for by applying the temperature-dependent physical parameters of the air in the porous material. Several representative examples show that the results obtained by the theoretical model agree well with those obtained by the FE model, and the sound absorption peak moves to higher frequencies as the temperature rises. The analysis of the propagation and dissipation of sound energy at different temperatures shows that the increase in temperature can prevent sound from entering the porous medium, thereby delaying the appearance of the absorption peak along the frequency axis. The perforated porous materials exhibit higher sound absorption performance than traditional homogeneous porous materials and, therefore, have enhanced high-temperature sound absorption potential.

Mathematical Study of the Water-Vapor Permeability of the Surface Layer of a Homogeneous Porous Material

Permeability in relation to gases and liquids is one of the most important characteristics of porous materials. A porous material can interact with gases and liquids flowing through it in different ways that depend on a material’s permeability. Studies of the interaction of water vapor with materials with uniformly distributed pores are of considerable practical interest, since many of these materials are used in building and construction. Interest is also due to the possibility of expanding the study results obtained for an individual pore to a porous medium if this medium can be represented as a structure with uniformly distributed pores with sufficient accuracy. The dependence of the permeability of an individual cylindrical pore on its radius, length, and characteristics of the process of water-molecule interaction with the pore walls is studied.

Numerical identification of temperature dependent thermal conductivity using least squares method

Purpose This paper aims to considered the problem of identification of temperature-dependent thermal conductivity in the nonstationary, nonlinear heat equation. To describe the heat transfer in the furnace charge occupied by a homogeneous porous material, the heat equation is formulated. The inverse problem consists in finding the heat conductivity parameter, which depends on the temperature, from the measurements of the temperature in fixed points of the material. Design/methodology/approach A numerical method based on the finite-difference scheme and the least squares approach for numerical solution of the direct and inverse problems has been recently developed. Findings The influence of different numerical scheme parameters on the accuracy of the identified conductivity coefficient is studied. The results of the experiment carried out on real measurements are presented. Their results confirm the ones obtained earlier by using other methods. Originality/value Novelty is in a new, easy way to identify thermal conductivity by known temperature measurements. This method is based on special finite-difference scheme, which gives a resolvable system of algebraic equations. The results sensitivity on changes in the method parameters was studies. The algorithms of identification in the case of a purely mathematical experiment and in the case of real measurements, their differences and the practical details are presented.

Novel method and its mechanism of reconstruction of commercial alumina to homogeneous porous alumina composite material

Abstract In this study, a novel method for reconstruction of commercial alumina to a homogeneous porous alumina composite material (HPACM) using an alumina powder, boric acid, and Na2SO4 and Na2CO3 additives is proposed for the first time and experimentally evaluated in detail. The properties of the as-prepared porous materials and their formation mechanisms are investigated. Unlike the traditional complex methods for manufacturing of porous alumina including electrochemical anodisation of aluminium and chemical etching, the HPACM can be simply prepared through sintering and dissolution. Scanning electron microscopy and N2 adsorption–desorption isotherm analyses demonstrate the formation of the HPACM with a diameter distribution centred at ∼20 nm after the sintering and decomposition at high temperatures and dissolution at room temperature. Transmission electron microscopy and X-ray diffraction results show that the main components of the as-prepared HPACM are alumina and sodium aluminate. The formation of the HPACM is attributed mainly to the reactions between the alumina powder, boric acid, and Na2SO4 and Na2CO3 additives at high temperatures and dissolution of the intermediate product of sodium aluminate at room temperature. A NaCl additive does not contribute to the formation of the intermediate product during the sintering process, owing to its considerable vapour loss at low temperatures. Moreover, a nanoindentation test shows that the HPACM has a good mechanical strength.

Implementing continuous freeze-casting by separated control of thermal gradient and solidification rate

Ice-templated porous materials from freeze-casting have attracted widespread attentions in many research fields. Several apparatuses based on the freeze-casting have been proposed to fabricate aligned porous materials, where the unidirectional growth of ice is mainly controlled by changing temperatures at the sample ends. The thermal conduction cross the whole sample restricts the freezing process in traditional freeze-casting methods. In this paper, a new approach of freeze-casting is proposed, where the thermal gradient and the solidification rate can be controlled independently for continuous directional freezing. The lateral thermal conduction provides an effective way to produce axially homogeneous porous structural materials with unrestricted length and controllable microstructures. Moreover, the axial homogeneity can also be further improved by adding a small amount of sucrose.

Multi-layered Porous Foam Effects on Heat Transfer and Entropy Generation of Nanofluid Mixed Convection Inside a Two-Sided Lid-Driven Enclosure with Internal Heating

Mixed convection of Cu-water nanofluid inside a two-sided lid-driven enclosure with an internal heater, filled with multi-layered porous foams is studied numerically and its heat transfer and entropy generation number are evaluated. Use of multi-layered porous media instead of homogeneous ones is capable of heat transfer enhancement, by weakening flow where does not impose a pivotal role on heat transfer and amplifying the flow in regions where have more effects on the heat transfer. Eight different arrangements of porous layers are considered and the two-phase mixture model is implemented to simulate nanofluid mixed convection inside the cavity. Results are presented in terms of stream functions, isotherms, Nusselt and entropy generation number for the eight cases considering various Richardson numbers (Ri = 10−4 to 103) and nanofluid concentrations (φ = 0 to 0.04). Results indicate that using the multi-layered porous material can confine flow vortices in the vicinity of the moving walls and could enhance the heat transfer up to 17 percent (with respect to the case using homogeneous porous material with the highest permeability), such that this enhancement is more in lower Ri values (stronger convective effects). Entropy generation number also increases by nanofluid volume fraction increment and Ri decrement. Cases with a higher heat transfer rate also have the higher entropy generation number. In addition, an increase of volume fraction decreases the relative entropy generation number (S*) for low Ri number, while contrary fact observed for high Ri values.

Interfacially Polymerized Particles with Heterostructured Nanopores for Glycopeptide Separation.

Porous polymer materials are extensively used for biomolecule separation. However, conventional homogeneous porous polymer materials cannot efficiently separate specific low-abundance biomolecules from complex samples. Here, particles fabricated by emulsion interfacial polymerization featuring heterostructured nanopores with tunable size are reported, which can be used to realize low-abundance glycopeptide (GP) separation from complex biofluids. The heterostructured surface inside the nanopores allows solvent-dependent local adsorption of biomolecules onto hydrophilic or hydrophobic regions. Low-abundance hydrophilic GPs in complex biofluids can be efficiently separated via the hydrophilic region of nanopores in low-polarity solvent after the hydrophobic region removes high-abundance hydrophobic proteins and non-glycopeptides in high-polarity solvent. It is expected that these particles with heterostructured nanopores can be used for separation of nucleic acids, saccharides, and proteins, and downstream clinical diagnosis.

Three-dimensional modelling and analysis of solar radiation absorption in porous volumetric receivers

This work addresses the three-dimensional modelling and analysis of solar radiation absorption in a porous volumetric receiver using the Monte Carlo Ray Tracing (MCRT) method. The receiver is composed of a solid matrix of homogeneous porous material and isotropic properties, bounded on its side by a cylindrical wall that is characterized through a diffuse albedo. The Henyey-Greenstein phase function is used to model the radiation scattering inside the porous media. The effect of the angle of incidence, optical thickness (porosity, pores size and height of the receiver), asymmetry factor of the phase function and wall properties on the solar radiation absorption in the porous media is studied in order to obtain the receiver efficiency as a function of these parameters. The model was validated by comparing the results for a simple geometry composed of a long slab of finite thickness with the values available in the literature, and then tested with a cylindrical receiver using a parabolic dish as concentration system with a concentration factor of 500. A peak of absorbed solar radiation of 156 MW m−3 and an absorption efficiency of 90.55% were obtained for a phase function asymmetry factor of 0.4 (forward scattering) and scattering albedo and extinction coefficient of 0.54 and 100 m−1, respectively. The results for the diffuse reflectance, diffuse transmittance and absorption are also presented. The model developed in this work is useful to obtain and understand the energy absorption distribution in porous volumetric receivers coupled to solar concentration systems, when different porous structures and geometric parameters are used.

Method and description of dynamic vibration reduction in cabins of gantry cranes

Reduction of vibration in the cabin can be achieved by increasing the area of vibration absorption by placing on the ceiling and floor vibro-absorbing facings. The process of absorption of vibration occurs due to the transition of the energy of oscillating particles to heat due to frictional losses in the pores of the material; therefore, for effective vibration absorption, the material must have a porous structure, the pores must be open from the side of the vibration and join together (unclosed pores) so as not to prevent the penetration of the vibration wave into the thickness of the material. As a vibration-absorbing cladding, we use a construction in the form of a layer of a homogeneous porous material of a certain thickness, reinforced directly on the surface of the fence.

Substantiation of the parameters of vibration systems in the cab of the gantry crane at the workplace of crane operators

Reduction of vibration in the cabin can be achieved by increasing the area of vibration absorption by placing on the ceiling and floor vibro-absorbing facings. The process of absorption of vibration occurs due to the transition of the energy of oscillating particles to heat due to frictional losses in the pores of the material; therefore, for effective vibration absorption, the material must have a porous structure, the pores must be open from the side of the vibration and join together (unclosed pores) so as not to prevent the penetration of the vibration wave into the thickness of the material. As a vibration-absorbing cladding, we use a construction in the form of a layer of a homogeneous porous material of a certain thickness, reinforced directly on the surface of the fence.

Multi-domain boundary element method for axi-symmetric layered linear acoustic systems

Homogeneous porous materials like rock wool or synthetic foam are the main tool for acoustic absorption. The conventional absorbing structure for sound-proofing consists of one or multiple absorbers placed in front of a rigid wall, with or without air-gaps in between. Various models exist to describe these so called multi-layered acoustic systems mathematically for incoming plane waves. However, there is no efficient method to calculate the sound field in a half space above a multi layered acoustic system for an incoming spherical wave. In this work, an axi-symmetric multi-domain boundary element method (BEM) for absorbing multi layered acoustic systems and incoming spherical waves is introduced. In the proposed BEM formulation, a complex wave number is used to model absorbing materials as a fluid and a coordinate transformation is introduced which simplifies singular integrals of the conventional BEM to non-singular radial and angular integrals. The radial and angular part are integrated analytically and numerically, respectively. The output of the method can be interpreted as a numerical half space Green's function for grounds consisting of layered materials.