Porosity Of Medium Research Articles

Convective nanofluid flow subjected to variable porosity, inclined magnetic field, and thermal radiations

Nanofluids pique the attention of researchers and scientists because of their excellent thermal transfer rates. They have numerous technological and industrial implementations in daily life. Nonsimilar analysis in this research is performed to study the consequences of nonuniform porosity of a porous medium on the radiative flow of nanofluid across a vertically positioned stretching surface. Moreover, the effects of viscous dissipation and inclined magnetic field are also taken into account. Single phase nanofluid model with latest thermophysical features of nanofluid are considered to devise the physical problem. Hamilton–Crosser model is used to investigate the various shapes of nanoparticles. Titanium oxide (TiO 2), Zirconium dioxide (ZrO2 ), water and Borosilicate ceramic are regarded as nanoparticles, base fluid, and porous media, respectively. The Brinkman–Forchheimer-extended Darcy model is assumed to represent the flow through porous medium. The governing partial differential equations (PDEs) with accompanying boundary conditions are transformed into the dimensionless system by deploying the appropriate transformations. The local nonsimilarity (LNS) approach with MATLAB bvp4c algorithm is executed to solve the dimensionless nonlinear coupled differential system. Results demonstrate that the augmentation in Hartmann number and porosity parameter diminished the velocity profiles of the considered nanofluids. Moreover, maximum temperature profile is noticed for the lamina shaped nanoparticles. Local Nusselt number for considered cases diminishes against the augmented estimations of Richardson number, radiation parameter and nanoparticles shape factor. A comparative study between the current study and previously published results for a specific case is conducted to validate the results, and good agreement is found between them.

The Application of Rayleigh Wave Method in the Underground Void Area Exploration

Underground voiding refers to the phenomenon that abnormal looseness, plate breakage, increase in porosity of underground medium lead to the formation of voids that decrease the stability of stratum and weaken the physical and mechanical properties. For example, road underground voiding will seriously affect the comfort and safety of vehicle driving. At present, the engineering geophysical prospecting technology is mainly used to detect the void area. In this paper, the elastic wave simulation method is used to study the response of the Rayleigh wave method to the underground void of the pavement. The response regularity is explored by adjusting the model parameters. The outdoor experiment is carried out according to the law parameters, and the effectiveness of the elastic wave for the detection of shallow surface voids is verified.

Response of photo-elasto-electric semiconductor porosity medium according to changing thermal conductivity with two-temperature

This study examines a new model for a solid semiconductor porosity medium with variable thermal conductivity under photo-thermoelastic conditions using two-temperature theory. A normal mode analysis is carried out to solve the equations in two dimensions analytically while taking into account the linear relationship between thermal conductivity and temperature. Physical fields, such as carrier density distribution, temperature, stress, and displacement, are then determined. The interaction between plasma and elastic waves is also considered. The simulation is conducted using silicon material, and the numerical calculations are illustrated graphically. This study investigates the effects of different porosity parameters (with and without porosity), thermal variable conductivity, and the two-temperature parameter on the physical field values.

Upcycling of used ceramic membrane as media in upflow biological reactor treating low strength wastewater

This work investigates the feasibility of media prepared from used (fouled) ceramic membrane (CM) in an upflow biological reactor (UBR) treating synthetic low strength wastewater (chemical oxygen demand, COD ∼ 200 mg/L) representative of an urban drain. The UBR was operated over 163 days at different hydraulic retention times (HRTs) of 48 h, 36 h, 24 h, 12 h and 6 h with corresponding upflow velocity between 0.06 m/d and 0.45 m/d. The COD removal was comparable at HRTs between 48 h and 12 h i.e., 83.4 ± 5.2 % (48 h), 80.5 ± 7.5 % (24 h), 76.2 ± 6.7 % (36 h) and 84.7 ± 7.2 % (12 h), followed by a marginal drop at 6 h HRT (69.9 ± 5.6 %). Ammonia removal was observed at HRTs of 48 h (37.6 ± 24.3 %) and 36 h (50.1 ± 20 %) only. Phosphate followed the same trend with removal observed at higher HRTs alone: 48 h (28.9 ± 12.5 %), 36 h (33.2 ± 8.7 %) and 24 h (23 ± 26.8 %). Total suspended solids (TSS) in the treated effluent was the lowest at 12 h HRT (6.2 mg/L). Only ∼ 3 % reduction in media porosity was observed after 163 days of operation. Overall, this media showed the recycling potential of fouled CM in a biological wastewater treatment system.

Mixed bio-convection analysis on MHD Casson hybrid nanofluid flow over a spinning cone/plate embedded in a variable porosity medium: a comparative study

Mixed bio-convection analysis on MHD Casson hybrid nanofluid flow over a spinning cone/plate embedded in a variable porosity medium: a comparative study

Algebraic growth of 2D optimal perturbation of a plane Poiseuille flow in a Brinkman porous medium

The impact of various factors on the stability of a plane porous Poiseuille flow is investigated in detail. Both modal and non-modal linear stability analyses are used to study the effects of the porosity of the porous media and the ratio of effective viscosity to the fluid viscosity. The present analysis includes solving the linearized Navier-Stokes equation in the form of the Orr-Sommerfeld (O-S) type equation by applying the 2D perturbation to the basic mean flow. The Chebyshev collocation method is used to solve the Orr-Sommerfeld equation numerically. Through modal analysis, the accurate values of the critical triplets (αc,Rc,cc), the eigen-spectrum, the growth rate curves, and the marginal stability curves are studied. Then, by using non-modal analysis, the transient energy growth G(t) of two-dimensional optimal perturbations, the ε-pseudospectrum of the non-normal O-S operator (L), and the regions of stability, instability, and potential instability of the fluid flow system are investigated in detail. The collective results of both modal and non-modal analysis show that the porous parameter and the ratio of effective viscosity to the fluid viscosity have stabilizing effects on the fluid system due to the postponement of the onset of stability.

Thermal investigation and parametric analysis of cascaded latent heat storage system enhanced by porous media

Cascaded latent heat storage (CLHS) has become a promising solution to the recovery and utilization of thermal energy. Many studies optimized the inlet temperature and velocity of heat transfer fluid to improve the heat transfer rate for the charging process of CLHS systems with pure phase change materials (PCMs), but the effect is not significant, mainly because the thermal resistance of the system comes from the PCMs side due to the low thermal conductivity of pure PCMs. Porous media composite phase change materials (CPCMs) have been shown to have promising prospects in a single PCM system, but no research precedent has been found for the application of porous media CPCM in the CLHS system. Besides, when CPCMs are encapsulated in the cavities of the CLHS system instead of pure PCMs, the difference in the degree of impact between the porosity of a porous media and boundary conditions on the thermal performance of a CLHS system is still unclear. The purpose of this article is to significantly improve the heat transfer rate by applying the CPCM to the CLHS system and to comprehensively compare the impact of porosity and HTF inlet boundary conditions on the charging/discharging time and energy/exergy charged/discharged rates of a CLHS system with CPCMs through two sensitivity analysis methods. When the porosity reduces from 0.97 to 0.92, the charging time and the discharging time decrease by 74.50 % and 73.39 % respectively; the average energy charge rate and average exergy charge rate increase by about 4.11 times; the average energy and exergy discharge rates increase by 5.76 times and 5.8 times respectively. Sensitivity analysis shows that the porosity of a porous media is the most important factor affecting the charging and discharging rates of a CLHS system, but its impact on energy and exergy charge/discharge rates is not monotonic. The effect of the inlet temperature and velocity of the HTF on a CLHS system is complex, and simply changing a single variable may not be effective in optimizing thermal performance parameters. This study provides a comprehensive performance enhancement strategy for the thermal energy storage and utilization processes of CLHS systems, which have great potential in fields such as solar energy collection, waste heat recovery, and building heating.

Some remarks on simplified double porosity model of immiscible incompressible two-phase flow

The paper is devoted to the derivation, by linearization, of simplified homogenized models of an immiscible incompressible two-phase flow in double porosity media in the case of thin fissures. In a simplified double porosity model derived previously by the authors the matrix-fracture source term is approximated by a convolution type source term. This approach enables to exclude the cell problem, in form of the imbibition equation, from the global double porosity model. In this paper we propose a new linear version of the imbibition equation which leads to a new simplified double porosity model. We also present numerical simulations which show that the matrix-fracture exchange term based on this new linearization procedure gives a better approximation of the exact one than the corresponding exchange term obtained earlier by the authors.

A POROUS MEDIA APPROACH FOR NUMERICAL OPTIMISATION OF THERMAL WHEEL

The experimental investigations of rotating heat exchangers are usually too costly and provide limited understanding for the phenomena of heat and fluid flow within them; hence, a less expensive and more comprehensive method is required to investigate what can affect their overall performance. In the current study, a porous media concept is presented as an alternative way to numerically analyse the fluid flow and heat transport through a rotary thermal regenerator. An aluminum core formed of multi-packed square passages is simulated as a porous medium of an orthotropic porosity in order to allow the counter-flowing streams to flow in a way similar to that inside the regenerator core. The geometric properties of the core were transformed into the conventional porous media parameters such as the permeability and inertial coefficient based on empirical equations; so, the core has been dealt with as a porous medium of known features. Fluid and solid phases are assumed to be in a local thermal non-equilibrium state with each other. A commercial CFD code "STAR CCM+" was used to solve the current problem numerically, where heat is allowed to be exchanged between the two phases and tracked by creating a heat exchanger interface in the core region. The results are presented by means of overall thermal effectiveness, pressure drop, and coefficient of performance COP. Using porous media approach has been found to be sufficient to simulate the current problem, where the currently computed data were found to deviate by up to 2.7% only from the corresponding analytical and experimental data. The data obtained reveal an obvious impact of the core geometrical parameters on both the heat restored and pressure loss; and hence, the overall efficiency of the regenerator system.

Impact of rotation on thermal instability of Darcy–Brinkman porous layer filled with a Jeffrey nanofluid

The novelty of this research lies in its investigation of the initiation of thermal instability within a Darcy–Brinkman porous layer containing a Jeffrey nanofluid under the influence of rotation. While non-Newtonian fluids complex flow patterns and heat transfer enhancements due to thermal gradients are known, this study addresses a specific and previously unexplored aspect, the impact of rotation on Darcy–Brinkman porous layer containing a Jeffrey nanofluid. When a fluid is subjected to rotation, it can induce additional forces and flow patterns within the fluid. The linear stability theory and normal mode analysis method are used to analyze the stability of the system analytically and are computed numerically using the software Mathematica version 11.3. The investigation focuses on understanding the influence of various factors, namely, the Taylor number, the Lewis number, the Jeffrey parameter, the modified diffusivity ratio, nanoparticles Rayleigh number, the Darcy–Brinkman number, and medium porosity on the onset of thermal instability in the physical system. This novel perspective can contribute to a deeper understanding of heat transfer processes in non-Newtonian fluids and has potential applications in improving the efficiency of industrial systems, such as cooling systems, heat exchangers, and microfluidic devices where efficient heat transfer is crucial for performance improvement.

Implementation and validation of effective thermal conductivity model of coal‐rock mass with rough capillary pore structure under CT three‐dimensional reconstruction

AbstractOn the strength of the capillary physical equivalent model and heat transfer law of series‐parallel combined structural unit, the calculation model of effective thermal conductivity of coal‐rock mass is obtained. The model considers the effect of roughness, porosity factor and other factors on effective thermal conductivity. CT digital core technology is applied to reconstruct the 3D model of coal‐rock mass, and one‐way heat transfer numerical simulation is carried out according to the model. It indicates that the internal temperature of coal‐rock mass is non‐uniformly distributed under the influence of pore structure, and the isothermal surface of pore region bulges towards the boundary of heat flux. Comparing the calculated and simulated values under the same conditions, the average error percentage of the theoretical calculation model is 6.95%, and the model has outstanding prediction performance in porous media with medium porosity and regular pore distribution, which provides a reference for predicting the effective thermal conductivity of coal‐rock mass.

Surface motion of P/SV wave scattering by a semicircular canyon in saturated half-space by complex function and conformal mapping

Based on the complex function theory of elastic dynamics, a complex function solution of P/SV-wave scattering by a semicircular canyon in an elastic porous saturated half-space is obtained. Firstly, through Biot theory and Helmholtz decomposition, the wave potential functions with unknown coefficients in the model are obtained based on the wave function expansion method. Secondly, the complex function expressions of stress and displacement in the model are obtained by using the complex function method and conformal mapping. According to the boundary conditions of the horizontal ground surface and semicircular canyon surface, this boundary value problem can be converted into a series of algebraic equations and solved numerically by truncation. Then, the correctness of the complex function solution in this paper is verified by comparing it with the published results through degenerating the scattering problem in the saturated porous elastic half-space in this paper into that in the elastic half-space. Finally, the influence of the boundary drainage conditions, the medium porosity, and the incident angle and frequency of the incident wave on the ground surface displacement is investigated. Although the P/SV-wave scattering problem is a traditional problem, there is currently no accepted analytical solution that strictly satisfies the zero-stress condition on the horizontal ground surface. This paper is an attempt at this problem, which may provide insight into the search for the strictly analytical solution for P/SV-wave scattering.

Homogenization of fluid saturated double porosity media with a new type of the contrast in the Biot mesoscopic model

This paper presents a mathematical model of a double poro-elastic medium derived by the homogenization of a two-component periodically heterogeneous Biot continuum characterized by strong heterogeneities in the permeability and poroelastic coefficients of mesoscopic structure. A new scaling of the mesoscopic material parameters with respect to the small parameter which is involved in the asymptotic analysis is introduced to capture this high contrast quality of the mesoscopic model. It is shown that such a scaling ansatz of the mesoscopic material parameters can be justified using different micromodels associated with the two mesoscopic components. While the “matrix” is a little permeable stiff phase, the “conductive channels” are made of a very soft fibrous structure equivalently represented by an network of helical springs. The unfolding method of the homogenization is employed to derive the macroscopic model involving the frequency-dependent effective parameters. Semipermeable interfaces between hard dual porosity and soft primary porosity are considered. The wave dispersion of two shear wave modes S1,S2, and two pressure wave modes P1,P2, is illustrated in an numerical example and validated, in a part, using the reference dispersion analysis based on the Bloch wave decomposition.

Significance role of dual porosity and interfacial nanolayer mechanisms on hybrid nanofluids flow: A symmetry flow model

The investigation of heat and mass transfer between two porous disks containing porous media is the focus of this paper. In this research, (Ag–Al2O3/water)-based hybrid nanofluid is used. Governing partial differential equations are converted to nonlinear ordinary differential equations by similarity transformations. Numerical solutions to nonlinear systems of equations are achieved using the shooting technique. It is examined how the particle’s diameter and nanolayer thickness affect the thermal conductivity of a hybrid nanofluid. Due to the increment of nanolayer thickness, the Nusselt number increases and vice versa for the radius of the particle. Tables and graphs show how the governing parameters influence velocity, temperature, and mass concentration profiles, as well as physical quantities such as skin friction coefficient and Nusselt number. As the values of the porous medium parameters ([Formula: see text]–13) and nanolayer thickness ([Formula: see text]–12) elevate, the flow of skin friction coefficient and Nusselt number escalate in both porous disks. Moreover, as the values of the particle radius ([Formula: see text]% to 12%) and Reynolds number ([Formula: see text]1 to 2) amplify, the flow of heat transfer rate is diminished in the lower disk. Porous materials have a high surface area, which increases the contact area between the nanofluids and the porous medium. Porous materials can enhance the permeability of the fluid, reducing the pressure drop in the system. This can be advantageous in applications where high flow rates and low-pressure drops are desired, such as in heat exchangers or cooling systems. Porous materials can provide trapping sites or adhesion points for the nanoparticles, enhancing their dispersion and stability within the hybrid nanofluids. The porosity of the flow medium can therefore influence the purification and filtration efficiency of the hybrid nanofluids, ensuring their cleanliness and functionality. Understanding and controlling the porosity can help optimize the flow characteristics of the nanofluids in various applications. Overall this field will focus on refining hybrid nanofluid compositions, improving modeling techniques, validating experimental findings, optimizing system designs, and exploring new applications.

Double stratification impacts on MHD flow of micropolar nanofluid over a stretching surface inserted in porous medium

A comprehensive analysis of double stratification impacts on the MHD flow of a nanofluid produced by a porous stretching sheet has been conducted by using a numerical approach. The convective boundary conditions (CBCs) and Newtonian heating (NH) cases have been particularly considered in this problem. The governing equations defined in partial differential equations (PDEs) form are converted into ordinary differential equations (ODEs) by using appropriate transformations to meet the requirement of the used numerical method which is bvp4c in the MATLAB software package. Moreover, the numerical findings of the ODEs are displayed via graphical and tabular forms. The impacts of different flow parameters used in particular problem are discussed for the profiles of the velocity, temperature and concentration of micropolar nanofluid along the values of coefficient of skin-friction [Formula: see text], Nusselt number [Formula: see text], the Sherwood number [Formula: see text] and in relation with the variation parameters in general, CBC and NH are calculated to get a clear insight into the flow situation. Some of the findings show that the skin friction increases by increase in magnetic, permeability and material parameters in all cases but the skin friction is reduced by increasing the thermophoresis parameter for CBC and NH cases, respectively. Microrotation profile decreases when material parameter increases, whereas microrotation profiles enhance with increase of the magnetic field and porosity of porous medium.

Analysis of slip condition in MHD nanofluid flow over stretching sheet in presence of viscous dissipation: Keller box simulations

In present paper the mathematical study of Slip conditions on electrically conducting nanofluid over a vertically stretching sheet is presented with effects of viscous dissipation, thermal radiation and Soret and Dufor. The state of flow has been explained mathematically with help of partial differential equations. Model equations are made convenient for calculation by suitable transformations. With the help of Kellerbox technique unknown functions are approximated in flow situation. The influence of medium porosity, magnetic field strength, thermal radiation, Soret and Dufour effects, Buoyancy forces, viscous dissipation wall slip parameter, and heat source are investigated in detail. Effects of emerging parameters on velocity, concentration, temperature and profiles are investigated. In relation to the parameters involved, we can observe the rates of momentum, heat, and mass transfer near the stretching surface. It can be concluded from the study that velocity slip parameter accelerates with fluid motion, temperature of nanoparticles is enhanced due to rise in Eckert number and Biot number, while the Soret effect enhances the nanoparticles concentration close to the stretching sheet. Also, under common assumptions, the analytical approximations for the solution of the current model that were produced by using the Keller box approach were shown to be in very excellent agreement with certain early publications.

STUDY ON HYDROGEOLOGICAL ASPECT OF GALANG SUB-DISTRICT, BATAM CITY FOR ACCEPTANCE OF PROSPECTIVE NPP SITES

This is a preliminary study in the selection of Nuclear Power Plant (NPP) site in Batam's Barelang area to support industrial growth in the area in the future. The initial site selection was conducted in 2015 and 2017 in the pre-survey phase, considering hydrogeological aspect. The results of previous research showed four potential areas, namely Pasir Panjang Beach, Tanjung Batu, Dapur 3 and Tanjung Rame. The hydrogeological aspect plays an important role in the consideration of site acceptance. This is related to the consideration of potential flow of radioactively contaminated groundwater seepage in the site area, in the event of a potential release. The acceptance of the NPP site from the hydrogeological aspect is based on the site’s permeable geological formation and porosity condition, where groundwater can be stored. The purpose of the study was to assess the potential site in Galang Sub-district, Batam City based on hydrogeological aspects which include surface geology, groundwater productivity and rock porosity. Research methods include primary and secondary data collection, literature review and ranking analysis. The results showed that Tanjung Batu, Dapur 3 and Tanjung Rame could be chosen as the potential sites for NPP based on the hydrogeological aspect. The three regions have surface geology in the form of sandstone, clay and claystone rock with medium rock porosity level and medium groundwater productivity. Pasir Panjang Beach is less preferable because it has a high porosity of rocks with the productivity of aquifers is being spread widely.

Numerical Study on Heat and Mass Transfer of Evaporated Binary Zeotropic Mixtures in Porous Structure

This study investigates the heat and mass transfer characteristics of a binary mixture (R134a/R245fa) evaporated in a porous medium. The Eulerian model coupled with the multiphase VOF model and species transport equations is employed to establish a multi-component evaporation model. The effects of heat flux ranging from 200 kW/m2 to 500 kW/m2, porosity ranging from 0.4 to 0.6, and mass fraction ratios (R134a/R245fa) of 3:7, 5:5, and 7:3 are explored. The results indicate that an increase in heat flux contributes to an increase in the evaporation rate. For the overall evaporation rate, the evaporation rates of R134a and R245fa improve by 11.3%, 6.9%, and 16.3%, respectively, while the maximum improvement in heat transfer coefficient is only 1.4%. The maximum evaporation rate is achieved at intermediate porosity in the porous medium, and the highest heat transfer coefficient is obtained at a porosity of 0.4. With the increase in mass fraction, the evaporation rate of the corresponding species also increases, while the overall evaporation rate and heat transfer coefficient remain almost unchanged.

Effect of variable gravity on thermal convection in Jeffrey nanofluid: Darcy-Brinkman model

The subject under consideration in this research has various geophysical and astrophysical applications. Specifically, we investigate the impact of variable gravity on the onset of thermal instability within a layer of Jeffrey nanofluid confined in a Darcy-Brinkman porous medium. The solution of the fluid layer, which is positioned between two free-free boundaries, is determined using a linear stability analysis employing the normal mode technique. The Rayleigh number on the onset of convection is derived by using the Galerkin method. For stationary convection, the effects of different variable gravity parameters on the Jeffrey parameter, Darcy-Brinkman number, Lewis number, moderated diffusivity ratio, porosity of porous media and nanoparticle Rayleigh number are analyzed and presented graphically. The choices of using Jeffrey nanofluid as the base fluid for the study add novelty. Non-Newtonian fluids encompass a diverse range of substances, such as engine oils, oil extraction, wallpaper paste, and various biological liquids like blood etc.

Effect of Hump Configurations of Porous Square Cavity on Free Convection Heat Transfer

Free convection is widely used in engineering applications, including solar energy, electronic devices, nuclear energy, and heat exchangers. A computational simulation utilizing Ansys Fluent-CFD was employed to examine the natural convection heat transfer inside a square cavity filled with pure water and saturated metal foam as a porous medium (porosity ɛ =0.9). The enclosure's lower wavy wall exhibits a high temperature (Th), while the side and upper walls have a low temperature (Tc). For different Rayleigh numbers, the study examines hump configuration and the bottom wall hump number (N). The predominant design of heat transmission was improved using the circular hump design parameters of ɛ=0.9, N=4 and Tc= 25C˚ for different Ra. This resulted in significant improvements in heat transfer enhancement and energy enhancement which were enhanced by 1.13 times, for both. The authenticity research included determining the optimal design for the square enclosure. This involved estimating the effects of hump configure and number of humps for bottom wall of enclosure. These parameters have not been studied yet. The optimum case showed the highest heat transfer coefficient (h) at circular hump, N=4 and Ra = 30´103. While the standard case had N=0 and Ra = 5´103. The CFD simulation results indicate that the primary objective of the study was achieved through the optimal design, which resulted in a significant enhancement of hydrothermal performance for both heat transfer enhancement and energy enhancement 1.13 times compared to standard case.