Longitudinal Permeability Research Articles

Lattice Boltzmann simulation of oxygen removal from anode porous transport layer in proton exchange membrane electrolyzer

The anode porous transport layer (PTL) plays a crucial role in improving the performance of proton exchange membrane (PEM) electrolyzer. However, oxygen accumulation may cover the interface between the anode catalytic layer and PTL, decreasing mass transfer and electrolysis efficiency. In this study, we employed a comprehensive simulation approach, combining lattice Boltzmann simulation with the Immersed Boundary Method (IBM) and Phase Field Model (PFM), to investigate oxygen removal from the anode PTL. The simulation can accurately capture bubble morphology and gas saturation, demonstrating the four stages of gas removal: invasion, exhaust, breakup and retraction. Notably, the invasion stage contributes to approximately 3/4 of the total gas removal time, whereas the invasion time is significantly influenced by the critical throat in PTL. Removing the critical throat may lead to a 20% reduction in the invasion time. To determine the critical throat, we further simulate the breakthrough of a single pore by a bubble. At lower current densities (1.4 A/cm2), reducing interfacial tension facilitates bubble penetration through smaller pores but weakens the longitudinal permeability, leading to a longer invasion stage. However, at higher current densities (14 A/cm2), the breakthrough is predominantly governed by the critical throat. This suggests that optimizing the PTL structure is more effective in mitigating bubble coverage than adjusting interfacial tension under high current density conditions. These findings may provide some guidelines for enhancing the performance of PEM electrolyzer under high current density conditions.

Study of the hygroscopic properties of three Australian wood species used as solid wood and composite products

The use of engineered wood products and mass timber panels such as cross laminated timber (CLT), glued laminated timber (glulam) and laminated veneer lumber (LVL) is becoming more common, as these products have benefits in terms of environmental credentials and resource utilisation and have the potential to provide faster and more economical construction processes. However, timber exposed to moisture for prolonged periods can degrade biologically, leading to a loss of appearance and decreased mechanical properties. Southern pine, radiata pine and shining gum timber are important forest resources for the Australian timber industry. To date, no in-depth studies on the hygroscopic properties of these species have been carried out from a timber wetting point of view. Consequently, existing literature has a knowledge gap regarding the determination of moisture movement properties in these species that are applicable to numerical modelling when used as solid wood or in the production of engineered wood products (EWPs). The work presented herein will help develop a better understanding of moisture ingress and egress in solid timber and EWPs and provide data for future predictive tools (such as numerical modelling) for moisture management in timber buildings. Samples were prepared from solid timber as well as EWP’s to examine the relationships between glue lines and edge gaps in CLT and multiple glue lines in LVL on moisture movement. As expected, longitudinal permeability was higher than radial and tangential permeability for the species tested. Southern pine samples had higher gas and liquid permeability values than radiata pine and shining gum. CLT with end grain sections including an edge gap had higher gas and liquid permeability than similar sections with glue lines only. LVL sections with 1 glue line had slightly lower permeability values than in samples with 2 glue lines. Gas and liquid permeabilities were lower for LVL samples than a two-layered veneer section without a glue line illustrating the barrier posed by the glue line. The moisture loss parameter during the diffusion testing was higher for LVL ends and CLT ends with edge gaps than face and edge sample sections. The results will be used to develop numerical models for moisture behaviour in solid and composite timber panels when exposed to humidity and free water. It is recommended to conduct additional studies to examine the impact of the adhesive layer and its properties on impeding moisture migration or functioning as a moisture barrier.

Air permeability of thermally modified hemlock wood

Western hemlock (Tsuga heterophylla) is a prevalent coastal species in British Columbia (BC). Its wood has a high potential for thermal modification, a process that can affect numerous physical properties, including air permeability. The current study investigates the longitudinal air permeability of hemlock wood modified at three temperature levels, 170 °C, 212 °C, and 230 °C, and a two-hour treatment length. Permeability values obtained using Darcy’s law and the water-falling volume displacement method were positively correlated with treatment temperature up to 212 °C, after which the permeability decreased slightly. ANOVA followed by the Duncan test revealed that thermal treatment at 212 °C and 230 °C significantly increased air permeability, whereas it was insignificant at 170 °C.

Vacuum infusion as a novel method to determine wood permeability

This study aims to propose a novel method, vacuum infusion process, to measure the longitudinal permeability of wood. The vacuum infusion method uses a vacuum bag sealed over the fibrous material, with a vacuum inlet and a vacuum outlet. It can be performed on top of any flat surface, and its process is relatively swift. Six different woods (Pinus elliottii, Araucaria angustifolia, Ochroma pyramidale, Cedrela fissilis, Tectona grandis, and Eucalyptus grandis) and three different fluids (water, soybean oil, and furfuryl alcohol) were selected for the study. After preliminary evaluations of morphology, chemical characteristics, density, porosity, contact angle and capillary pressure, three woods and two fluids were selected for the actual permeability measurements. The highest permeability was obtained for the Ochroma pyramidale wood, being 0.45–7.49 × 10–11 m2. This wood was 58–88% and 18–62% more permeable than the Pinus elliottii and Eucalyptus grandis woods, respectively. The fluid was found to have some influence on the experiment and therefore must be carefully selected. The difference in permeability of the woods was attributed to morphological characteristics, especially the presence of axial vessels, which are 60% larger for Ochroma pyramidale wood compared to Eucalyptus grandis wood, while Pinus elliottii has no vessels. The amount of voids in all woods, nevertheless, was similar, as well as the evaluated chemical characteristics and structural anatomical elements (tracheids and/or fibers). In all, the determination of apparent permeability using the vacuum infusion process is practical and with good accuracy, yielding results similar to those from other methods in the literature.

A study for the longitudinal permeability of fibrous porous media with consideration of electroviscous effects

We investigate theoretically the longitudinal permeability for the electroviscous flow through one-dimensional (1D) fibrous porous media with orderly and disorderly fiber arrays. The structures of fibrous porous media are idealized as circular unit cells. In the cell, the dimensionless net charge density is given by solving the linearized Poisson-Boltzmann equation, and is approximated as 1 by detailed discussions. Based on the approximate value of the net charge density, circular unit cell and Voronoi Tessellation method, we propose mathematical models for the longitudinal permeability with considering electroviscous effects. The effects of the fiber volume fraction, fiber radius and electroviscous resistance number on the longitudinal permeability are analyzed in detail. Moreover, there are good agreements between the present predictions and these results from the literatures.

Comfort related woven fabric transmission properties made of cotton and nylon

The interaction of water and air i.e. moisture regain, water vapor transmission, wicking and air permeability with woven textiles are tested to investigate the comfort of woven fabrics made of nylon, cotton, and cotton–nylon mixtures with different yarn counts. The fabrics porosity (based on equation 1 and 2), woven fabric sett (ASTM D3775-03), fabric thickness (ASTM D1777-96), fabric weight (ASTM D3776M - 20), fabric vapour transmission (ASTM E96-00), transfer wicking, and longitudinal wicking (DIN 53924), moisture regain (ASTM D2495-07), and air permeability (ASTM D737) were examined for investigations based on the standards in the brackets. The experimental results showed that fabric transfer wicking, longitudinal wicking, moisture regain and air permeability properties increase as the yarn goes to coarser for all woven fabric samples but the water vapor transmission property decrease. Additionally, fabric transfer and longitudinal wicking capabilities improved with increased nylon fiber blend ratios within fiber conformation. However, the nylon fiber composition has negative impact on air permeability, water vapor transfer rate, wicking and moisture capabilities of the woven fabrics. Generally, it can be concluded that the existence of nylon fiber, and yarn count coarseness improved wicking properties of the woven fabrics and decreased the air permeability property of woven fabrics.

Mimicking Bone Anisotropic Structure with Modified Gyroid Scaffolds; A Finite Element Analysis

The structure of the bone is very complex and heterogeneous; this causes different mechanical and biological properties in its longitudinal and transverse directions. For example, the modulus of elasticity and the permeability of the trabecular bone in a longitudinal and radial direction can vary up to several times. Therefore, implant design that matches these differences is necessary to maximize compliance with the host bone. Given that, in this study, a gyroid structure that generally is used in bone scaffolds was modified to design anisotropic scaffolds. Therefore, the gyroid triply periodic minimal surface trigonometric function was manipulated, and five different architectures were denoted as G(-50), G(-25), G(0), G(+25), and G(+50) with a constant porosity of 80% were developed. The effective elastic moduli of the models were calculated using finite element analysis. The results showed an anisotropicity rate of 0.21, 0.62, 1.50 and 2.23 in elastic moduli for G(-50), G(-25), G(+25) and G(+50) models respectively. As well, the permeability of the models was calculated using computational fluid dynamics (CFD) analysis. Anisotropic models showed different permeability in longitudinal and transverse directions. Longitudinal permeability to lateral direction rate were 0.67, 0.80, 1.25 and 1.47 for G(-50), G(-25), G(+25) and G(+50) models respectively.

Biodegradation and Micro- Scale Treatability Pattern of Loblolly Pine Heartwood Bioincised by Bacillus Subtilis and Physisporinus Vitreus

One strategy for improving the treatability of refractory wood species is biological incising, and its efficiency depends on how the microorganisms modify the porous structure of the wood. Evaluation of the bioincised wood treatability on a micro-scale can thus help to better understand the treatability enhancing mechanisms. In the present study, the biodegradation pattern and micro-scale treatability of Loblolly pine (Pinus taeda L.) heartwood were determined after bioincising with the white-rot fungus Physisporinus vitreus (Pers.: Fr.) P. Karsten isolate 136 and bacterium Bacillus subtilis UTB22. Oven-dried specimens with dimensions of 50 mm × 25 mm × 15 mm (L × T × R) were incubated with the microorganisms at (23±2) °C and (65±5) % relative humidity for six weeks. The control and exposed wood blocks were then pressure treated by 1 % fluorescent dye (fluorescein)-containing water to study the treatability pattern under a fluorescence microscope. The longitudinal and tangential air permeability and compression strength parallel to the grain of the specimens were also determined at the end of the incubation period. Scanning electron microscopic (SEM) studies showed that degradation by B. subtilis UTB22 was limited to the pit membranes, but the cell walls were also degraded to some extent by P. vitreus. The fungus caused a higher mass loss compared to the bacterium, whereas the permeability enhancing ability of the bacterium was more pronounced. The fluorescent dye tracer also showed that higher treatability with more uniformity was obtained by B. subtilis UTB22. The improvement in treatability by both microorganisms was mainly due to the degradation of the earlywood tracheids.

Enhancing Magnetic Sensor Sensitivity by Grooved Grating Patterned Soft Magnetic Films

Etching the grating on the magnetic film surface is able to increase the film effective longitudinal permeability ( $\mu _{\textit {eL}}$ ) significantly, which has been demonstrated by a magnetic sensor consisting of a solenoid and grooved grating patterned film. The feasibility that the magnetic polarization field generated by the groove end faces compensates for the shape demagnetization field and intensifies $\mu _{\textit {eL}}$ is verified theoretically. After the optimal structural parameters are obtained, the planar and patterned films are manufactured with the microfabrication process. The effects of groove width, sensor dimensions, and excitation frequency on the sensor performance are systematically investigated. For the prototype with the patterned magnetic film of $10~\mu \text{m}$ groove width, the impedance ratio and impedance sensitivity are 4049% and 347 %/Oe at 1 MHz. Compared with the prototype with the same thickness planar smooth magnetic film core, they are improved by 436% and 659%, respectively. It is revealed that the grooved grating patterned films offer the possibility of developing film-based microsensors, making their performance comparable to that of wire-based sensors.

تاثیر باران های اسیدی بر خواص فیزیکی و مکانیکی سنگ تراورتن

One of the problems caused by air pollution is acid rain. The development of urban communities and subsequent use of air polluting vehicles on the one hand and the widespread use of travertine in building facades in Iran on the other hand have doubled the study of the effect of acid rain on the properties of travertine. In this study, three types of travertine (Travertine B, Travertine D and Travertine R) were studied. This paper investigates the effect of the rain at four pH (2.5, 4, 5.5 and 7) on its physical properties including effective porosity, longitudinal wave velocity and permeability, and its mechanical properties including tensile strength and uniaxial compressive strength. The results showed that as the pH decreases, the effective porosity increased and the longitudinal wave velocity, tensile strength and uniaxial compressive strength decreased. The highest increase in effective porosity due to decreasing pH was related to travertine B and the lowest increase was related to travertine R. The highest decrease in longitudinal wave velocity, tensile strength, and uniaxial compressive strength due to decreasing pH was related to travertine B and the lowest decrease was related to travertine R.

Macroscopic permeability of doubly porous solids with spheroidal macropores: closed-form approximate solutions of the longitudinal permeability

The presence of macropores and fractures significantly affects the effective transport properties of porous solids such as concrete and rocks. The dimensions of the fractures are generally large behind that of the initial porosity, so that the problem contains two porosities. The influence of the macroporosity is studied in the homogenization framework by solving at the intermediate scale, that of the macropores, a coupled Darcy/Stokes problem with the Beavers–Joseph–Saffman (BJS) interface condition. We derive analytic expressions of the macroscopic permeability in the case of an isotropic permeable matrix containing spheroidal-shaped macropores. To this aim, we consider a representative volume element (RVE) on which uniform boundary conditions are considered for the velocity and pressure fields. The local problem is written as minimum principles; kinematic and static approaches are developed to derive rigorous bounds for the macroscopic permeability. Closed-form expressions of the longitudinal permeability (along the revolution axe of the spheroid) are determined by considering a simplified RVE constituted of two confocal spheroids. They depend on the volume fraction and the eccentricity of the spheroidal macropores, the scale factor between the two porosities and the slip coefficient of the BJS model. Illustrations show the influence of these parameters.

Transverse and longitudinal fluid flow modelling in fractured porous media with non‐matching meshes

AbstractA new discrete fracture model is introduced to simulate the steady‐state fluid flow in discontinuous porous media. The formulation uses a multi‐layered approach to capture the effect of both longitudinal and transverse permeability of the discontinuities in the pressure distribution. The formulation allows the independent discretisation of mesh and discontinuities, which do not need to conform. Given that the formulation is developed at the element level, no additional degrees of freedom or special integration procedures are required for coupling the non‐conforming meshes. The proposed model is shown to be reliable regardless of the permeability of the discontinuity being higher or lower than the surrounding domain. Four numerical examples of increasing complexity are solved to demonstrate the efficiency and accuracy of the new technique when compared with results available in the literature. Results show that the proposed method can simulate the fluid pressure distribution in fractured porous media. Furthermore, a sensitivity analysis demonstrated the stability regarding the condition number for wide range values of the coupling parameter.

Analytical determination of viscous permeability of hybrid fibrous reinforcements

• Transverse and longitudinal permeability models are developed for hybrid composites. • Permeability models are able to predict values in a wide range of cell porosity. • The model is valid for symmetrical and hybrid type cells and only depends on geometric parameters but not of fluid rheology. • Above 0.6 porosity value the models behave as symmetric. Transverse and longitudinal permeability for hybrid fibrous porous media were determined by solving Stokes and Darcy–Weisbach equations, respectively. A rectangular representative unit hybrid-cell with two sizes of fibre was used for solving one dimensional fluid flow to obtain velocity profile, flux, pressure drop and finally permeability. Both models were validated by using analytical models for permeability in symmetric cells reported in literature. Numerical simulations were performed using computational fluid dynamics to assess the permeability behaviour of several hybrid cells. Interesting results were found for several fibre radii ratios where the permeability changes differently for transverse and longitudinal models, so this model is based on fibre spacing and the change in diameter. It is notorious that for low porosity values and low fibre radii ratios, the transverse permeability decreases with respect to the constant fibre radii cell. It can be concluded that the permeability only depends on geometric variables, and the hybrid effect is more relevant in the permeability for porosities lower than 0.65.

Research and Application of Fine Intelligent Injection Technology of Cable Type in Dagang Oilfield

Dagang oilfield belongs to typical multi-layer system, heterogeneity of complex fault block reservoir, reservoir and the large difference of physical property of crude oil, water, etc, the longitudinal permeability difference is obvious, separate injection interval is not detailed, The existing bridge eccentric note, bridge concentric injection technology can’t meet the needs of the fine water injection, real-time measurement and control because of drift, well depth, pressure and other factors, and there is poor adaptability, measuring problem of long time and low efficiency. Cable type fine intelligent water injection technology in underground intelligent water distributor, the ground controller as the core tools, cable as transmission medium, the computer network communication technology, intelligent control technology combined with oil field water injection demand, developed a new and reliable water injection system, realized the layered injection allocation under different deviation, full automatic control and monitoring data, and direct reading test. The technology in the implementation of 5 Wells in dagang oilfield, the implementation of maximum deviation 80 °, the maximum depth of 3661.52 m, the highest water flooding pressure 25 mpa, construction success rate reaches 100%, downhole test times 5 Wells, inspection accuracy of 100%. The results show that the cable type intelligent water flooding technology can not only realize downhole data real-time monitoring, real-time traffic regulation, and can complete the packer direct reading test, and the measurement process is reliable and efficient, at the same time solve the high Angle well, horizontal well can’t test the technical problem, provides the high Angle well, horizontal well fine water injection technology support.

Numerical Fluid Flow Modelling in Multiple Fractured Porous Reservoirs

This paper compares the fluid flow phenomena occurring within a fractured reservoir for three different fracture models using computational fluid dynamics. The effect of the fracture-matrix interface condition is studied on the pressure and velocity distribution. The fracture models were compared based on the variation in pressure and permeability conditions. The model was developed for isotropic and anisotropic permeability conditions. The results suggest that the fracture aperture can have a drastic effect on fluid flow. The porous fracture-matrix interface condition produces more realistic transport of fluids. By increasing the permeability in the isotropic porous matrix, the pressure drop was significantly higher in both the fracture and reservoir region. Under anisotropic conditions in the 3D fractured reservoir, the effect of the higher longitudinal permeability was found to lower the pressure in the fractured reservoir. Depending on the properties of the fractured reservoir, this study can enhance the understanding of fracture-matrix fluid interaction and provide a method for production optimisation.

A Contribution to the Geological Characterization of a Potential Caprock-Reservoir System in the Sulcis Coal Basin (South-Western Sardinia)

The results provided by this study contribute to the geological characterization of a potential caprock-reservoir system for CO2 storage in the experimental area of the mining district of the Sulcis Coal Basin (south-western Sardinia, Italy). The work is aimed to improve the knowledge of the petrographic and petrophysical characteristics of the siliciclastic and carbonate geological formations that make up the potential caprock-reservoir system. Core samples from a number of wells drilled in the study area for mining purposes were analyzed especially for texture and physical properties (longitudinal velocity, density, porosity, and permeability). The preliminary integrated petrographic and petrophysical characterizations indicate that the Upper Paleocene to Early Eocene potential carbonate reservoir is heterogeneous but presents suitable reservoir zones for CO2. A preliminary analysis of the potential caprock siliciclastic lithologies of the Middle Eocene to Lower Oligocene suggests that they appear suitable for CO2 confinement. Finally, to account for the stability of the investigated area, an accurate geodynamical study of south-western Sardinia was carried out using global navigation satellite system and advanced differential interferometric synthetic aperture radar methodologies in order to estimate vertical and horizontal crustal displacements. The study area results stable, since it is characterized by surface crustal horizontal and vertical velocities smaller than 1 mm/year and few mm/year, respectively.

Dependence of longitudinal magnetic permeability and transverse conductivity on mechanical loads on the shaft

This research deals with transformer type eddy-current transducer connected in differential circuit and it also proposes method for real-time evaluating mechanical tension in metal cylindrical products. The authors have proposed contactless method for estimating product mechanical deformation which is based on utilizing correlation connections between metals’ electromagnetic properties and their structural condition. The authors have introduced a generalized normalized informative magnetic parameter and on its basis obtain basic transform functions aided for determining increments of relative magnetic permeability and specific electric conductivity of product under load comparatively to standard sample. The article shows the possibility of using the differential method to increase the sensitivity of the evaluation of cylindrical products mechanical parameters. The authors have developed a physical model of an electromagnetic transducer with a product that is subjected to torsion, a theoretical justification is given at the level of the domain structure of the material under study and electromagnetic phenomena. The authors have created an experimental setup, the results of experimental studies of the influence of the mechanical moment caused by the torsion of an object on its electromagnetic properties were obtained. The research has proposed amplitude and phase methods for evaluating mechanical stresses. The results of the research allow to conclude, that there is an efficient transducer operating mode in the range 1 ≤ х ≤ 3, in which for η = 0,38 errors of mr and  estimation are less than 1% and 3% correspondingly. It is also noticeable, that in this range of x relative sensitivity of transducer is maximal. This allows us to create industrial devices for contactless multi-parameter evaluation of physical and mechanical parameters of metal products and structures. The obtained results of theoretical and experimental studies do not contradict the previously known laws of theoretical mechanics, which allows them to be widely used in the practice of nondestructive testing.

Effect of Heat Treatment on the Gas Permeability, Sound Absorption Coefficient, and Sound Transmission Loss of Paulownia tomentosa Wood

In this study, the gas permeability, sound absorption coefficient, and sound transmission loss of the Paulownia tomentosa wood were estimated using capillary flow porometry, transfer function method, and transfer matrix method, respectively. The longitudinal specific permeability constant of the Paulownia tomentosa wood with a thickness of 20 mm was 0.254 for the control sample and 0.279, 0.314, and 0.452 after being subjected to heat treatments at 100 °C, 160 °C, and 200 °C, respectively. The gas permeability was observed to be slightly increased by the heat treatment. The mean sound absorption coefficients of 20-mm thick Paulownia tomentosa log cross-section for the control sample and after being subjected to heat treatments at 100 °C, 160 °C, and 200 °C were 0.101, 0.109, 0.096 and 0.106, respectively. Further, the noise reduction coefficients of 20-mm thick Paulownia tomentosa log cross-section of the control sample and after being subjected to heat treatment at temperatures of 100 °C, 160 °C, and 200 °C were 0.060, 0.067, 0.062 and 0.071, respectively. The mean of sound transmission loss of the 20-mm thick Paulownia tomentosa log cross-section was approximately 36.93 dB. Furthermore, the gas permeability and sound absorption coefficient of the heat-treated Paulownia tomentosa discs slightly increased depending on the heat treatment temperature; however, the rate of increase was insignificant.

Specific gas permeability of normal and nanosilver-impregnated solid wood species as influenced by heat-treatment

The effect of heat treatment at 50 and up to 150°C was studied on dowel-shape specimens prepared from beech (Fagus orientalis), poplar (Populus nigra), and fir (Abies alba) wood. Specimens were cut into two diameter sizes (18 and 25mm) to explore the effect of diameter size on permeability. Separate sets of specimens from each size and species were prepared to be first impregnated with a 200 ppm aqueous nanosilver (NS) suspension to investigate the effect of facilitated heat-transfer on permeability at different temperatures. Specimens were heated in five consecutive steps at 50, 75, 100, 125, and 150°C and for 24 hours in each step. High variance was found in the specific gas permeability between each treatment group, thus indicating probable high fluctuation in settlement of extractives at different spots of a log. Heat treatment only affected gas permeability at the first steps of heating (50 and 75°C), where loss of moisture content resulted in a permeability increase in nearly all species. Consecutive steps of heating up to 150°C did not significantly affect the permeability in either normal or NS-impregnated specimens. Keywords: Beech, poplar, fir, longitudinal permeability, wood-modification

Influence of different thermal cycling treatments on the physical, mechanical and transport properties of granite

Two different types of thermal cycling treatments (slow heating followed by slow cooling or rapid quenching) were carried out on the granite samples in the present research. The responses of physical, mechanical and transport properties of the granite after various thermal cycling treatments were compared and analyzed. Non-destructive tests (mass, volume, longitudinal wave propagation and permeability) and destructive tests (uniaxial compression and Brazilian splitting) were utilized to characterize these properties. Variations of all the properties demonstrate that thermal cycling (heating and cooling) can induce damage in the samples. Mass, density, P-wave velocity, UCS, Young’s modulus and tensile strength decrease, whilst volume and permeability increase with rising temperature. Additionally, the results also demonstrate the importance of cooling method. Rapid quenching has a more significant effect on granite samples, showing lower density, P-wave velocity and strength, but greater permeability, which is due to the generation of thermal gradient cracks. Moreover, the difference between P-wave velocity and UCS of slow cooling and those of rapid quenching increases with temperature up to 500 °C, which can be attributed to the more significant thermal shock cracking induced by higher temperature-gradient stress in the samples during rapid quenching. The microstructural analyses from thin sections show that microcracking in granite subjected to thermal cycling treatments was induced in different severity depending on peak temperature and cooling method.