Effect Of Porosity Research Articles

Static Response of Functionally Graded Porous Circular Plates via Finite Element Method

The main purpose of this paper is to investigate the axisymmetric bending response of functionally graded porous (FGP) circular plates. The material properties are changed continuously in the thickness direction of the plate. Three distinct porosity distributions uniform, symmetric and monolithic are employed. The effect of porosity on the axisymmetric bending analysis of circular plates is examined parametrically. In this study, clamped and roller supports which commonly serve to achieve ideal boundary conditions in numerous engineering applications are used. The finite element method is employed for numerical analysis. The principal of the potential energy is used to obtain the governing equations. To generate the model of the FGP circular plates, an eight-node quadratic quadrilateral element with two degrees of freedom on each node is utilized. The results of this study are confirmed by the existing published literature. A good agreement between the results of the presented model and the previous literature has been observed. The results of the present study show that plate deflection increases with the increase of the porosity coefficient and the ratio of radius to thickness of circular plates. By increasing the porosity coefficient, the displacement values of the plates made of uniform porosity distribution is effected more than those of other porosity distributions.

Machine learning backpropagation network analysis of permeability, Forchheimer coefficient, and effective thermal conductivity of macroporous foam–fluid systems

Macroporous materials exhibit outstanding properties in heat and mass transfer due to their high pore volume, high surface area, and high Young's modulus. Consequently, understanding their thermofluidic properties is crucial in the design, synthesis, and optimal application of these materials. Therefore, this study, premieres, the use of a machine learning (ML) backpropagation network to develop and train a series of datasets for permeability, Forchheimer coefficient, and effective thermal conductivity of variable macroporous foam–fluid systems with respect to degrees of interstices, fluid and solid properties. To account for permeability values for flowing fluids in the Darcy regime, numerical simulations of slow–moving fluids were implemented over the materials' interstices. In comparison to similarly substantiated values of permeability in the Forchheimer regime, these values were a bit lower. The ML-based backpropagation algorithm was used to analyze data, which produced predictions (output signals) that are more than 90 % in correlation to CFD datasets. This provided insight into the effect of porosity and reduced mean pore openings on macroporous structures' thermofluidic behaviour. Material porosity was observed to play a dominant role in estimating Forchheimer coefficients and effective thermal conductivities for these foam-fluid systems. However, reduced mean pore openings were observed to be more critical for estimating permeability. The contributory effects of reduced mean pore openings on the effective thermal conductivity for these macroporous foam–fluid systems were determined to vary between 5.8 and 13.2 percent. Furthermore, the effective thermal conductivity of macroporous foam–fluid systems was also evaluated in relation to changes in the interstitial fluid and solid matrix thermal conductivity.

A novel rapid generation algorithm for Representative Volume Element (RVE) in composite materials considering pore geometrical parameters

Pore defects are inevitable in the manufacturing process and significantly affect the mechanical properties of composite materials. In this work, a novel algorithm capable of concurrently generating both ellipsoidal and gourd-shaped pores in composite materials is proposed and the interference detection procedure is optimized for efficient interference detection between the generated geometrical bodies. Besides, the algorithm is integrated with RVE-based finite element (FE) simulation to explore the effects of various pore types, volumes, aspect ratios, and porosity on the elastic properties of unidirectional C/C composites. The present work provides a valuable reference for generating general pore defects and investigating their resulting effects on mechanical properties of related composite structures.

Effects of Porosity and Boron Reinforcement in AISI 316L Stainless Steel for Biomedical Applications

AISI 316L stainless steel (SS) is one of the most widely used biomaterials in the manufacture of implants and biomaterials. It has advantages over equivalent biomaterials such as low cost, good mechanical properties and biocompatibility. The pores found in porous biomaterials provide mechanical interlock, ensuring strong attachment of the implant to the tissue. In this study, 20%, 30% and 40% by volume of polyvinyl alcohol (PVA) and Boron powder were added into 316L powder to obtain porous SS implant. To investigate the effect of porosity and boron effect on the stainless-steel implant material, the samples produced in PVA and Boron added groups, were sintered at 1180 oC under an argon atmosphere. With the evaporation of PVA in the structure, porous and boron added samples were obtained in two groups. Finally, the samples were subjected to Brinell hardness and compression tests and analyzed by SEM, EDS and XRD. As a result of the hardness tests, the highest values were measured as 37.006, 31.32, 25.28 HB. 39.5, 34.5, 26.2 MPa strengths were measured for 20%, 30% and 40% porous samples respectively.

On the free and forced vibrations of porous GPL reinforced composite conical panels using a Legendre-Ritz method

An analysis is conducted in the present investigation to study the free and forced vibration characteristics of composite laminated conical panels. It is assumed that composite panel is reinforced with graphene platelets (GPLs) where the amount of GPLs may be different between the layers which results in a piecewise functionally graded media. In addition, the effect of uniform and non-uniform porosities is also included into the formulation. The elasticity modulus of the media is estimated following the Halpin-Tsai rule while the simple rule of mixtures approach is applied to obtain the mass density and Poisson's ratio on the panel. With the aid of the first order shear deformation theory of shells and Donnell kinematics, definition of strain, kinetic and potential energy of applied loads is given. After that with the general idea of Ritz method suitable for arbitrary types of boundary conditions and Legendre polynomials as the basic functions, the energies are discreted which results in the general form of the equations of motion. While standard eigenvalue solution is applied to obtain the natural frequencies, a Newmark time marching method is implemented to obtain the temporal evolution of displacement of the panel. Results of this study are well-compared with the available data in the open literature and after that novel results on the present study are provided in the form of figures and tables. It is highlighted that type of porosity and graded pattern of GPLs are both important on the frequencies and dynamic deflection of the panel.

A fundamental study on cyclic voltammetry at porous carbon thin-film electrodes

Porous carbons represent an important group of electrode materials for electrochemical applications due to their high specific surface area, good conductivity, and intrinsic porosity. However, the often-neglected influence of the electrode porosity on the electrochemical results may lead to wrong interpretation of data. The aim of this work is therefore to provide comprehensive understanding of the effects of electrode porosity on cyclic voltammetry (CV) – a technique which is frequently used for initial characterization of novel electrode materials. Our approach consists of simulating experimental results, observed for the redox-reactions of [Fe(CN)6]3-/4− at porous CNT thin-film electrodes, with a mathematical model. The results demonstrate that the main difference between planar and porous electrode is the additional charge transferred in the porous electrode domain, which has the decisive contribution to the overall faradaic current at high scan rates. To further verify the applied model, the porosity of the porous CNT film is varied on purpose by changing the Nafion-Carbon-ratio (NCR). We are able to determine the electrochemically available pore volume (ECPV) of the electrode, which is strongly affected by the NCR, and correlate changes in the ECPV with changes in the scan-rate dependent CV. Moreover, we implement an approach for determination of reaction rate constants at porous electrodes, which was verified by simulated CV data. Evaluation of the experimental results shows that the reaction rate constant of the porous CNT material actually has the same order of magnitude as the planar glassy carbon substrate.

Effect of the pore parameters of the perforated baffle on the control of liquid sloshing

The phenomenon of liquid sloshing inside a tank has a significant negative impact on the safety of the vessel. Installing perforated baffles is considered an effective means of mitigating liquid sloshing. This study investigated the influence of pore parameters on the anti-sloshing effectiveness of baffles. The simulations were performed using STAR-CCM+. In the numerical simulation of the tank sloshing, we have adjusted the factors in the k-ε model to obtain more approximate results compared to the experiments. By changing variables such as the porosity, degree of porosity, and pore distribution of the baffles, the results of the numerical simulations were compared to analyze their performance. Different combinations of porosity and porosity degree parameters have varying effects on sloshing factors such as the wave height, pressure, and rolling moment of the liquid tank. The perforated baffle performed well at restraining the slamming load. The findings also indicate that the effects of porosity are greater than those of the pore distribution. In most cases, an even pore distribution is more effective. These results can provide guidelines for the optimal design of vertical porous baffles.

Soft-templating synthesis of hierarchical mordenite as high-performance catalyst for cyclic acetals production via acetylation of glycerol and benzaldehyde

Highly active hierarchical mordenite zeolite with micro/mesoporosity (TM-n) for selective synthesis of cyclic acetals via acetylation reaction is reported. The hierarchical zeolite is synthesized using soft-templating approach with variations in octadecyltrimethoxysilane (OTMS/Al2O3 ratio, n = 0.2, 0.3 and 0.4) in precursor hydrogels. The results reveal that OTMS not only creates secondary mesoporosity in zeolite framework (larger mesopore volume, external surface area, average pore diameter), but also influences the crystallization process, altering the crystal morphology, crystallinity and Si/Al ratios. Among TM-n zeolites prepared, TM-0.3 hierarchical mordenite has the optimum OTMS amount incorporated while further increasing the OTMS amount leads to the formation of ANA/GIS intergrowth. Thanks to the accessible hierarchical porosity, reduced acidity and morphological effects, the TM-0.3 hierarchical mordenite exhibits excellent catalytic performance (84.1% conversion, TOF = 0.087 s−1, 61.5% dioxolane selectivity) in acetylation of glycerol and benzaldehyde (160 °C, 20 min) better than pristine mordenite. The catalyst is reusable for five runs with minimal loss of activity (TOF = 0.087 → 0.084 s−1), making it a promising catalyst for chemical productions involving bulky molecules. In addition, comparative catalytic tests with classical homogeneous and heterogeneous catalysts, including H2SO4, HCl, CH3COOH, H–Y, H-LTL, Na-X, Na-A, were performed.

Study on gas accumulation in polymer electrolyte membrane water electrolyzer considering two-phase flow

In this study, we analyze gas accumulation in a polymer electrolyte membrane water electrolyzer by considering two-phase flows in the porous transport layer on the anode and cathode sides. First, effect of mass flow rate on gas accumulation is analyzed. The transport of liquid water occurred differently on the anode and cathode sides. While the transport of liquid water on the anode side decreased in the high current density region, that on the cathode side increased with current density. The limiting current density increased by 1.2 A/cm2 when the mass flow rate was increased. Next, we study the effect of contact angle of the porous transport layer. When the contact angle was decreased from 75° to 30°, gas saturation decreased by 0.04. The use of a hydrophilic porous layer on the cathode side, however, hindered the transport of liquid water into the channel because the porous transport layer tended to retain liquid water. Finally, we study the effect of porosity of the porous transport layer. When the porosity was 80%, the mass flow rate of liquid water into the porous layer was 0.1 g/s, and gas saturation was approximately 0.25 at 0.8 A/cm2.

Wave reflection and transmission in seawater-unconsolidated-consolidated sediment models based on VGS([formula omitted]) and Biot theories

It proves challenging to accurately describe wave propagation within layers of sediment with significant variations in physical properties and states, using a single sediment acoustic theory. In this paper, we construct a sedimentary wave field model applicable to sedimentary layers containing different physical properties, by combining Biot theory and viscous-grain-shearing theory, and give an analytical solution for the coefficients of the wavefield potential function. The acoustic reflection coefficients of the seafloor surface are obtained accordingly. The comparison against the in-situ test of the Seabed Characterization Experiment shows that our model is better capable to describing wave propagation in structures with multiple sediment types. We give the most suitable model for the New England Mud Patch sediment structure by establishing different assignments of sedimentary acoustic theories, and discuss the effect of porosity and thickness of different layers on the reflection coefficients of waves of different frequencies.

Flow-induced rearrangement of a poroelastic cluster

Although poroelastic clusters in nature, such as bristled wings and plumed seeds, exhibit remarkable flight performances by virtue of their porous structure, the effects of another key feature, elasticity, on aerodynamic loading remain elusive. For a poroelastic cluster, we investigate the aerodynamic effects of elastic deformation that occurs through the collective rearrangement of many elastic components and the fluid-dynamic interactions between them. As a simple two-dimensional model, an array of multiple cylinders which are individually and elastically mounted is employed with diverse values of porosity and elasticity. Under a uniform free stream, the poroelastic cluster enlarges its frontal area and augments the total drag force in the quasi-steady state; this is in contrast to the general reconfiguration of fixed elastic structures, which tends to reduce the frontal area and drag. The rearrangement of the poroelastic cluster is dominated by the virtual fluid barrier that develops in a gap between the elastic components, interrupting the flow penetrating between them. The effects of this hydrodynamic blockage on changes in the frontal area and drag force are analysed in terms of porosity and elasticity, revealing the fluid-dynamic mechanism underlying the appearance of peak drag at an intermediate porosity. Moreover, to represent the coupled effects of porosity and elasticity on the rearrangement, a scaled elastic energy is derived through a consideration of the energy balance.

Effect of solid solution treatment on the kinetics of hydrogen porosity evolution and mechanical properties in Al–Cu–Li alloys

The evolution kinetics of hydrogen porosity during solid solution treatment (SST) of vacuum-cast Al–Cu–Li alloys and the effect of porosity defects on the mechanical properties of the alloys were investigated. It has been found that porosity at 6h SST was dominated by nucleation and its evoluton of fractions has a linear correlation with time, APS = (0.05 ± 0.06)＋(0.11 ± 0.01) t. However, the growth of porosity at 12 h is evidenced by a decrease in the number of pores and an increase in the size of large pores, expanding inter-porosity distance due to Ostwald ripening. Three dimensional quasi-in situ X-ray CT quantification of porosity demonstrate that the hydrogen concentration at the interface in the early stages of the solid solution was not adequate to balance its surface tension and vacancies were created by cross-diffusion, reducing the interficial energy for porosity nucleation. The effects of porosity on the tensile strength satisfies lnσ-lnσ0 = αlnfp, and those detrimental hydrogen porosities can be predicted by a multi-scale model which take into account hdyrogen diffusion during vacuum solution treatment.

Numerical study of solidification and melting behavior of the thermal energy storage system with non-uniform metal foam and active rotation

This paper focuses on the strengthening study of the latent heat thermal energy storage (LHTES) unit and proposes a coupling strengthening method with non-uniform graded metal foam and active rotation. The non-uniform graded metal foams are employed to enhance heat conduction, and the rotation method is selected to make full use of natural convection. The solidification and melting behavior under the coupling effect of non-uniform metal foam and active rotation are numerically analyzed. The aluminum foam is partially concentrated and divided into two parts (concentrated part and diluted part) and is divided into the even-layered or uneven-layered porous structures according to the different regions area. Under the same volume of phase change material (PCM), the effects of layered forms (even-layered and uneven-layered approach), concentrated porosity, concentrated ratio, and rotational speed are performed. It can be concluded that the metal foam should concentrated near the inner tube and the uneven-layered structure can further improve the phase change heat transfer performance compared to the even-layered structure. Moreover, the thermal performance of the LHTES unit improves firstly and then decreases as the concentrated porosity, concentrated ratio, and rotational speed increase. The optimal values are obtained at 0.86 concentrated porosity, 0.3 concentrated ratio, and 0.5 rpm rotational speed. Compared with the static case with uniform metal foam, the melting time, solidification time, and total melting and solidification time can be significantly reduced by 40.30 %, 28.66 %, and 33.18 %, respectively. Similarly, the thermal energy storage rate can be correspondingly increased by 62.57 %, 40.82 %, and 54.11 %, respectively.

Thermal Analysis of a Casson Boundary Layer Flow over a Penetrable Stretching Porous Wedge

This work aims to analyze the Casson thermal boundary layer flow over an expanding wedge in a porous medium with convective boundary conditions and ohmic heating. Moreover, the effects of porosity and viscous dissipation are studied in detail and included in the analysis. The importance of this study is due to its applications in biomedical engineering where the analysis of behavior of non-Newtonian blood flow in arteries and veins is desired. Within the context of blood flow, it is also applicable to many other fields, for instance, radiative therapy, MHD generators, soil machines, melt-spinning, and insulation processes. The modeled problem is a set of PDEs, which is nondimensionalized to derive a nonlinear boundary value problem (BVP). The obtained BVP is solved using the shooting technique, endowed with the order four Runge-Kutta and Newton methods. The impact of different parameters on the momentum and temperature fields is investigated along with two important parameters of physical significance, i.e., the Nusselt number and the surface drag force. Results are validated, and an excellent agreement is seen for the parameters of interest using MATLAB built-in function bvp4c. A significant finding is that by increasing the Casson liquid parameter, the velocity decreases as the wedge expands quicker than the free stream velocity at R=2. However, the velocity increases for the case when R=0.1. A decrease in the Darcy number increases the temperature profile. Furthermore, the convective parameter accelerated the heat transmission rate, and a rise in the Prandtl number thickens the thermal boundary layer. The findings of this investigation contribute to problems in fluid dynamics and heat transfer that involve studying the behavior of a non-Newtonian fluid with Casson rheological properties near a solid porous wedge surface.

Effect of Porosity on the Free Vibration Analysis of a Rotating Pretwisted Sandwich Blade with a Functionally Graded Core in the Thermal Environment

This work deals with the investigation of the effect of porosity on the natural frequencies of the rotating pretwisted sandwich blade with a functionally graded core in the thermal environment. The top metallic and the bottom ceramic surfaces are exposed to ambient temperature and high inlet temperature, respectively. A finite element approach using a layerwise theory is developed. Two different porosity distributions are assumed here. The effect of the volume fraction index, rotational velocity, porosity model and temperature gradient on the natural frequencies of the pretwisted sandwich blade is studied.

MHD flow of the novel quadruple hybrid nanofluid model in a stenosis artery with porous walls and thermal radiation: A Sisko model‐based analysis

AbstractThis study introduces a mathematical model that describes the Magnetohydrodynamics (MHD) flow of blood in a porous stenosis artery, incorporating a new hybrid nanofluid (HNF) model known as ‘Quadruple’ or the tetra‐(HNF) model. An innovative aspect of this study lies in the unexplored combination of tetra‐hybrid nanoparticles with the Sisko rheological model. The conventional Tiwari and Das (HNF) model has been expanded to accommodate the tetra‐(HNFs) case. To transform the governing partial differential equations into ordinary differential equations, a series of variable similarity transformations are employed. The resulting highly nonlinear simultaneous equations are efficiently solved using the shooting method. Numerical computations are conducted to investigate various parametric conditions, and graphs are utilized to visualize notable aspects of flow velocity and temperature. A comprehensive analysis is provided to illustrate the influence of flow parameters on wall shear stress and local Nusselt number, which are depicted through figures and tables. The study shows that the novel tetra‐HNF exhibits enhancements in blood flow when compared to nanofluids with a lower number of hybrids. Increasing the flow power index of non‐Newtonian Sisko model leads to improve convective heat transfer. Furthermore, parameters such as porosity, thermal radiation, and magnetic effects exhibit noticeable impacts on blood flow, temperature, and associated risks in constricted arteries.

Nonlinear low-velocity impact analysis of sandwich plates with titanium face sheets and porous aluminum core reinforced by GPLs

This study examines the nonlinear dynamic response of sandwich plates under low-velocity impacts (LVIs), which consist of a porous aluminum foam core with functionally graded (FG) graphene platelets (GPLs) reinforcement and two titanium alloy face sheets. The finite element method is employed to perform the numerical simulations and the Hertz contact theory is used to model the impact behavior. The generic Halpin-Tsai model, which incorporates the porosity effect, is adopted to estimate the mechanical properties of core made of the FG-GPLRC, based on the experimental data of the closed-cell aluminum alloy foam. The simulation results reveal that the FG-X configuration has the highest impact resistance, and that the addition of GPLs improves the impact performance. Moreover, a thicker core can reduce both the first contact time and the vibration period of plates, while a looser boundary condition can prolong the vibration time after the first impact. Additionally, a higher impactor velocity, mass and radius lead to a higher deflection and contact force. The oblique impact decreases the impact energy. This work provides a lighter and stiffer design for structure engineers when components suffer low-velocity impact.

Impact response of physical analog of Martian regolith

A careful examination of collisional processes occurring on surfaces of Solar System objects requires data on the dynamic properties of porous geological materials. Shock waves traveling in sand with physical properties analogous to those of some types of Martian regolith are studied in a series of uniaxial plate impact experiments. The initial density of the samples and average grain size are 1.30 g cm−3 and 95 μm, respectively. The obtained Hugoniot of this simulant is in general agreement with those of previously studied sands. The effect of porosity and grain morphology on Hugoniots of these geological materials is also highlighted. A laser velocimetry technique is used to observe the structure of propagated waves. Wave fronts with rise times on the order of several hundred or tens of microseconds were recorded in the pressure range of 0.5 to 1.7 GPa. For the simulant, a value of 1.91 was found for an exponent in the relationship between rise time and pressure τ∼p−m. Additionally, exponents for different granular and silica-rich systems studied earlier were also provided. An analysis of wave thickness revealed that in the pressure range of 0.5–1.1 GPa, this parameter can be associated with the grain average size. At the highest pressure (1.7 GPa), the minimum particle size (∼20 μm) turned out to be a more suitable quantity to describe the shock wave structure.

Entropy generation and thermal analysis in quadratic translation of sodium alginate with MHD and porosity effects

Entropy generation and thermal analysis in quadratic translation of sodium alginate with MHD and porosity effects

Molecular dynamics simulations of the effect of porosity on heat transfer in Li2TiO3

Heat transfer is a key consideration in the development of tritium breeder blankets for future fusion reactors. For solid tritium breeder materials there is a fine balance to be struck between high levels of porosity to encourage tritium release and minimising it to maintain the thermal and mechanical properties. Therefore, in this work we employ molecular dynamics simulations to understand how the introduction of porosity influences the thermal conductivity of lithium metatitanate ceramic breeder material. Our simulations predict that increasing the porosity leads to a decrease in the thermal conductivity which is in good agreement with previous experimental observations. By contrast, we do not observe the increase in the thermal conductivity at high temperatures, that is observed in some experiments. We argue that this increase is a consequence of sintering or some other modification of the experimental sample rather than a fundamental change in the heat conduction mechanism in the crystal matrix.