Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
20
5
2017
CONVECTIVE INSTABILITY IN A THROUGHFLOW IMPOSED HEAT GENERATING POROUS MEDIUM WITH A GRAVITY GRADIENT
A dispersion model involving a fluid-saturated porous medium heated from below is considered in the presence of a
varying gravity field. The medium admits volumetric heat sources and a vertical throughflow across its boundaries. The onset of convective instability is discussed for two types of hydrodynamic boundary conditions. Numerical solutions to the resulting differential system are obtained through the shooting method. Results show that increased gravity level along the height always destabilizes the system irrespective of the other factors, whereas the presence of heat generation leaves opposing effects depending on the magnitudes of the throughflow and gravity gradient.
S.
Saravanan
UGC-DRS Center for Fluid Dynamics, Department of Mathematics, Bharathiar University, Coimbatore 641 046, Tamil Nadu, India
N.
Raja
Department of Mathematics, Bharathiar University, Coimbatore 641 046, Tamil Nadu, India
381-388
MODELING THE CONNECTION BETWEEN POROSITY AND PERMEABILITY: AMIXTURE THEORY APPROACH
This work investigates the connection between porosity and permeability and its influence in the flow of a power
law fluid through a porous matrix using a continuum theory of mixtures. Within this framework, both fluid and
porous matrix are considered superimposed continuous constituents of a binary mixture. A complete set of constitutive equations is presented. The proposed expression relating permeability and porosity depends on two positive material parameters only. Special attention is given to the constitutive expression adopted for the interaction force (a momentum source) because it is the key to performing a physically realistic connection between porosity and permeability. To better understand the coupled influence of porosity and permeability on the flow, a dimensionless parameter relating these quantities is proposed. Comparison with experimental data for distinct porous material obtained by several authors attests to the good performance of the proposed equation.
Maria Laura
Martins-Costa
Laboratory of Theoretical and Applied Mechanics, Graduate Program in Mechanical
Engineering, Universidade Federal Fluminense, 24210–240, Niterói, RJ, Brazil
Jesus Alfonso Puente
Angulo
Laboratory of Theoretical and Applied Mechanics, Graduate Program in Mechanical
Engineering, Universidade Federal Fluminense, 24210-240, Niterói, RJ, Brazil; Department of Mechanical Engineering, Federal Center of Technological Education of Rio de
Janeiro, Angra dos Reis, RJ, Brazil
Heraldo S.
da Costa Mattos
Laboratory of Theoretical and Applied Mechanics (LMTA), Graduate Program in Mechanical Engineering (PGMEC), Universidade Federal Fluminense (UFF), Rua Passo da Patria, 156, 24210-240 Niteroi, RJ, Brazil
389-403
CAPACITY OF ENERGY ABSORPTION BY FLICK THROUGH SHOCK IN COOPER FOAMS
The aim of this work is to develop and characterize new materials with height properties, especially foams based on
copper, obtained by powder metallurgy techniques using a NaCl space holder. The shock resistance (impact energy
absorbed) and porosity measurements were carried out. The foams were investigated by optical microscope to show the
pore dimensions and internal structure. Factors like sintering temperature, space holder size, and copper percentage are studied, too, and have an influence on the mechanical properties of open-cell foams. It was also determined that a higher sintering temperature increases the compactness of samples and the amount of impact energy absorbed. By increasing the dimensions of the space holders and the percentage of them in the mixture, a greater absorption of the impact energy results. A higher sintering temperature has a negative influence on the foam porosity - the porosity decreases when the temperature increases. Another factor that directly influenced the porosity is the copper content, namely, with increasing percentage in the mixture, walls become thicker and pores more closed. The impact energy absorption was investigated using a device designed and built specifically for this purpose.
Mihai Alin
Pop
Department of Materials Science, Transilvania University of Brasov, 500036, Brasov, Romania
Virgil
Geaman
Department of Materials Science, Transilvania University of Brasov, 500036, Brasov, Romania
Irinel
Radomir
Department of Mathematics and Informatics, Transilvania University of Brasov, 500036,
Brasov, Romania
Tibor
Bedo
Department of Materials Science, Transilvania University of Brasov, 500036, Brasov, Romania
405-415
IMMISCIBLE DISPLACEMENT OF VISCOPLASTIC WAXY CRUDE OILS: A NUMERICAL STUDY
The displacement of waxy crude oils obeying the Bingham model was numerically investigated in a water-flooding operation. A more accurate bundle-of-tubes model was developed based on the Rabinowitsch correction method to represent a porous medium. The classic Darcy's law was used as the governing equation using the concept of effective viscosity. Owing to the nondifferentiability of the Bingham model, regularized versions of this rheological model were used to calculate the effective viscosity for the Bingham model. Use was made of the implicit-pressure/explicit-saturation numerical method for solving the governing equations for the saturation profiles. Based on the results obtained in the present work, it is concluded that regularized models are well capable of representing displacement flow of Bingham fluids. It is also concluded that the viscosplastic behavior of waxy crude oils has a negative effect on the water-flooding operation.
Ali
Salehi-Shabestari
Center of Excellence in Design and Optimization of Energy Systems (CEDOES), School of
Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
Mehrdad
Raisee
Center of Excellence in Design and Optimization of Energy Systems (CEDOES), School of
Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
Kayvan
Sadeghy
Center of Excellence in Design and Optimization of Energy Systems (CEDOES), School of
Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
417-433
EFFECTS OF MAGNETIC FIELD ON MOLYBDENUM DISULFIDE NANOFLUIDS IN MIXED CONVECTION FLOW INSIDE A CHANNEL FILLED WITH A SATURATED POROUS MEDIUM
The effects of a magnetic field on molybdenum disulfide (MoS2) nanofluid in mixed convection flow in the presence of thermal radiation inside a channel filled with a saturated porous medium are investigated. Molybdenum disulfide nanoparticles are suspended in water chosen as the conventional base fluid. Both of the boundary walls of the channel are oscillating in their own plane. The fluid is flowing in a vertical direction parallel to the channel such that the external magnetic field is applied in a direction perpendicular to the flow. Five different shapes, namely, platelet, blade, cylinder, brick, and spherical, of molybdenum disulfide nanoparticles are used in this work. The problem is modeled in terms of partial differential equations with physical boundary conditions. An analytical solution of the problem is obtained by using the perturbation method. Expressions for velocity and temperature are obtained and discussed graphically for embedded flow parameters. A comparative study for different shapes of molybdenum disulfide nanoparticles is provided graphically. MoS2 nanoparticles with cylinder shapes have shown the highest heat transfer rate as compared to spherical shapes. Furthermore, it was found that the application of a magnetic field increased the friction forces and caused a significant decrease in the momentum transfer. The porous medium behaved in an opposite
manner to that of the magnetic field.
Ilyas
Khan
Majmaah University
Aaiza
Gul
Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia
81310, UTM Skudai
Sharidan
Shafie
Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia
81310, UTM Skudai
435-448
PERTURBATION ANALYSIS OF HEAT TRANSFER AND A NOVEL METHOD FOR CHANGING THE THIRD KIND BOUNDARY CONDITION INTO THE FIRST KIND
Heat transfer phenomena play a vital role in many problems, such as transport of flow through a porous medium.
In this article, a singular perturbation method and Laplace transform are used to solve the one-dimensional heat
transfer problem in semi-infinite porous media divided into inner and outer solutions. To prevent the mistakes of other
researchers' analyses, a new approach for outer and inner matching boundary conditions is suggested. In addition, the
boundary condition of the third kind (Robin boundary condition) at y = 0 is changed into first kind by means of a novel structure. This approach shows a good accuracy with direct use of the first kind of boundary condition. However, when the slop value at y = 0 requires high accuracy of measurement, applying such an approach is not recommended. On the other hand, by applying the new matching idea, results of an asymptotic solution show good agreement with a numerical solution.
M. R.
Shahnazari
Faculty of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran
Z.
Ahmadi
Faculty of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran
L. S.
Masooleh
Faculty of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran
449-460
STUDY OF PERISTALTIC FLOW OF NANOFLUID WITH ENTROPY GENERATION IN A POROUS MEDIUM
An analysis is carried out to study the peristaltic flow of nanofluid in a vertical asymmetric channel. The considered
mathematical model consists of continuity and momentum equations, while a new model is proposed for the nanoparticle concentration. In particular, we focus on Ag−water and Cu−water nanofluids. The effects of entropy generation along with the porous medium are also taken into account. The significant effects of a thermal conductivity model of Brownian motion for nanofluids comprising the effects of particle size, particle volume fraction, and temperature dependence are included. The governing equations are first modeled and then solved analytically. Numerical integration is used to analyze the novel features of volumetric flow rate and porosity parameter. The obtained expressions for pressure gradient, temperature, and velocity profile are described through graphs for various pertinent parameters. The
streamlines are also drawn for some physical quantities to discuss the trapping phenomenon.
R.
Ellahi
Department of Mathematics and Statistics, FBAS, IIUI, Islamabad, Pakistan; Department of Mathematics, Faculty of Science, Taibah University, Al-Madeenah, Saudi Arabia
M.
Raza
Northern University Wattar Walai Ziarat, Kaka Sahib Road Nowshera, KPK Pakistan
Noreen Sher
Akbar
National University of Sciences and Technology, College of E & ME, Islamabad, Pakistan
461-478