Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
19
4
2016
EFFECT OF VARIABLE GRAVITY ON LINEAR AND NONLINEAR STABILITY OF DOUBLE DIFFUSIVE HADLEY FLOW IN POROUS MEDIA
The present study analyzes the influence of variable gravity on the mechanism of instability of the double diffusive Hadley convection in a horizontal porous layer by applying linear and nonlinear stability analysis. This instability is analyzed using three-dimensional normal modes in the linear theory and the nonlinear theory using energy approach. The vertical thermal Rayleigh number is treated as the eigenvalue. The system that constitutes the eigenvalue problem is solved by applying Shooting and Runga−Kutta methods for various modes of instability. The detailed analysis is carried out for both the linear and nonlinear cases. The stability results are graphically presented, and it is notified that the flow undergoes the influence of gravity parameter along with other flow-governing parameters. This study brings out the drawbacks of linear stability theory over energy stability theory by showing the possible occurrence of subcritical instabilities in the flow parameter space.
Anjanna
Matta
Department of Mathematics, Indian Institute of Technology Hyderabad, Hyderabad - 502205, Telangana, India
P. A. Lakshmi
Narayana
Department of Mathematics, Indian Institute of Technology Hyderabad, Hyderabad - 502205, Telangana, India
287-301
EFFECT OF THROUGHFLOW ON DOUBLE DIFFUSIVE CONVECTION IN A POROUS MEDIUM WITH CONCENTRATION BASED INTERNAL HEAT SOURCE
Onset of double diffusive convection in a horizontal fluid saturated porous layer which is subjected to concentration-based internal heat source is studied. Here the flow is induced by vertical temperature and concentration differences across the boundaries. Effect of vertical throughflow is also considered in this investigation. The flow-governing parameters involved in this study are thermal Rayleigh number RaT and solutal Rayleigh number RaS, which are associated with thermal and concentration differences in the vertical direction, along with the Peclet number Pe, Lewis number Le, and measure of concentration-based internal heat source γ. To perform linear stability analysis, an eigenvalue problem is derived for Rayleigh number RaT, and it has been obtained numerically. Critical thermal Rayleigh number RaTC is evaluated for various values of flow-governing parameters. It has been noticed that oscillatory longitudinal modes are preferred modes of instability.
N.
Deepika
Department of Mathematics, Indian Institute Techonology Hyderabad, Kandi, Telangana, 502285 India
Anjanna
Matta
Department of Mathematics, Indian Institute of Technology Hyderabad, Hyderabad - 502205, Telangana, India
P. A. Lakshmi
Narayana
Department of Mathematics, Indian Institute of Technology Hyderabad, Hyderabad - 502205, Telangana, India
303-312
THERMAL RADIATION EFFECTS ON NON-NEWTONIAN FLUID IN A VARIABLE POROSITY REGIME WITH PARTIAL SLIP
The laminar boundary layer flow and heat transfer for multiphysical transport of an optically dense Casson non-Newtonian fluid along an isothermal horizontal circular cylinder embedded in a variable-porosity medium in the presence of thermal and hydrodynamic slip conditions is analyzed. Non-Darcy effects are simulated via a second-order Forchheimer drag force term in the momentum boundary layer equation. The cylinder surface is maintained at a constant temperature. The boundary layer conservation equations, which are parabolic in nature, are normalized into nonsimilar form and then solved computationally with an efficient, implicit, stable Keller-box finite-difference scheme. Increasing velocity slip consistently enhances temperatures and reduces velocity throughout the boundary layer regime. An increase in thermal slip parameter strongly decelerates the flow and also reduces temperatures in the boundary layer regime. Increasing porosity is found to elevate velocities, that is, accelerate the flow, but decrease temperatures, that is, cool the boundary layer regime. Thermal radiation parameter (inversely proportional to radiative flux contribution) is seen to reduce both velocity and temperature in the boundary layer. Local Nusselt number is also found to be enhanced with increasing radiation parameter. Temperatures are, however, very slightly decreased with increasing values of Casson non-Newtonian parameter. The study is relevant to processing of plastics in industry.
A. Subba
Rao
Department of Mathematics, Madanapalle Institute of Technology and Science, Madanapalle,
India
V. Ramachandra
Prasad
Department of Mathematics, Madanapalle Institute of Technology and Science, Madanapalle,
India
K.
Harshavalli
Department of Mathematics, NTR Govt. Degree College, Vayalpadu, Andrapradesh, India
Osman Anwar
Beg
Gort Engovation-Aerospace, Medical and Energy Engineering, Gabriel's Wing House, 15
Southmere Avenue, Bradford, BD73NU, United Kingdom
313-329
STEADY DOUBLE-DIFFUSIVE MIXED CONVECTION BOUNDARY LAYER FLOW PAST A VERTICAL FLAT PLATE EMBEDDED IN A POROUS MEDIUM FILLED BY A NANOFLUID USING BUONGIORNO'S MODEL
The steady double-diffusive mixed convection boundary layer flow past a vertical flat plate embedded in a porous medium filled by a nanofluid is investigated numerically. Using a similarity transformation, the partial differential equations are transformed into ordinary differential equations before being solved numerically by a shooting method and Maple software. The effects of the mixed convection parameter on the flow and heat transfer characteristics are investigated. The results show that it is possible to obtain dual solutions for the opposing flow, while for the assisting flow, the solution is unique. The local Nusselt number, the local Sherwood number, and the local nanoparticle mass flux increase as the mixed convection parameter increases.
Mohd Hafizi Mat
Yasin
School of Mathematical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia
Anuar
Ishak
School of Mathematical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia
Ioan
Pop
Department of Applied Mathematics, Babes-Bolyai University, 400084 Cluj-Napoca, Romania
331-338
DISPERSION OF A NONWETTING LIQUID IN A DISORDERED NANOPOROUS MEDIUM
A dispersion transition in the Fluka 100 C8 and Fluka 100 C18 hydrophobic silica gels close in structural characteristics has been studied. Nonlinear dependences of the volume of the trapped liquid on the degree of filling, which have not yet been observed at the interaction of nonwetting liquids with nanoporous media, have been revealed. Two critical temperatures Tc1 ~ 330 K and Tc2 ~ 340 K have been found for the Fluka 100 C18−water system. At a temperature above Tc1, a transition occurs at a degree of filling of ~0.6 from the state of the system with a linear increase in the volume of the trapped liquid with the degree of filling to the state in which the dispersion transition occurs at ~0.6. At temperatures above Tc2, the fraction of the trapped liquid is small and independent of the temperature and degree of filling. When Fluka 100 C8 is filled with water, no abrupt change in the volume of the trapped liquid with an increase in the degree of filling has been detected in the temperature range under study of T = 300−360 K. In this case, a linear increase in the volume of the trapped liquid with the degree of filling has been observed.
Vladimir
Borman
National Research Nuclear University MEPhI, Kashirskoe sh. 31, Moscow, 115409, Russia
Anton
Belogorlov
1National Research Nuclear University MEPhI, Kashirskoe sh. 31, Moscow, 115409, Russia; A. V. Topchiev Institute of Petrochemical Synthesis RAS, Moscow, Russia
Alexey
Grekhov
National Research Nuclear University MEPhI, Kashirskoe sh. 31, Moscow, 115409, Russia; A. V. Topchiev Institute of Petrochemical Synthesis RAS, Moscow, Russia
Vladimir
Tronin
National Research Nuclear University MEPhI, Kashirskoe sh. 31, Moscow, 115409, Russia
339-346
MIXED CONVECTION HEAT TRANSFER IN A VENTILATED ENCLOSURE WITH AND WITHOUT A SATURATED POROUS MEDIUM
Unsteady mixed convection heat transfer of the laminar fluid flow in a ventilated enclosure with and without a saturated porous medium was studied numerically. The flow outside the porous medium is governed by the Navier−Stokes equation, whereas the Brinkman−Forchheimer−extended Darcy model in which the inertia and boundary effects are taken into consideration governs the flow through the porous medium. The numerical simulations of the fluid flow and heat transfer were investigated with a wide range of Reynolds numbers (50−500) and Richardson numbers (0−10), with Prandtl number, Darcy number, and the porosity fixed at 0.71, 10−5, and 0.9, respectively. The effect of inclination angle on the fluid flow and heat transfer characteristics was studied in a range of angles between 30° and 90°. The results show that the time required to reach the steady state in the case where a porous medium is present is less than that required in the case where a porous medium is absent. Also, there was a major influence of inclination angle and porous materials on the flow and heat distribution in the enclosure.
Ali A.
Mohammed
Department of Mechanical Engineering, University of Mosul, Mosul, Iraq
Amir S.
Dawood
Department of Mechanical Engineering, University of Mosul, Mosul, Iraq
347-366
COMPUTATIONAL SCREENING OF ZEOLITIC MATERIALS FOR CO2 AND H2S SEPARATION
This work presents theoretical molecular computations performed for CO2 and H2S adsorption evaluation on several zeolite molecular structures using density functional theory (DFT). Therefore this work analyzes the feasibility of the studied zeolites, for CO2 and H2S adsorption, to take the adsorption energy as a criterion for adsorption capacities and using transition state theory as a tool for predicting which sorbents are favored after both thermodynamic and kinetic computations. The calculated values predicted that MEL zeolite is the molecular structure that most favors the adsorption of CO2 and H2S. In addition, analysis using frontier orbital theory predicted that the CO2 and H2S adsorption mechanism was performed with zeolites acting as Lewis acids or electron acceptors. For CO2, the interaction took place between one oxygen atom of the CO2 gas and a silicon atom from the zeolite. The interaction mechanism with H2S predicted that it took place between one sulfur atom as a Lewis base and a zeolite silicon atom. It was concluded that this porous material screening, which is based on quantum electronic structure calculations, could be used for CO2 and H2S removal from fluid mixtures mostly found in the oil and gas industry.
F. A.
Lagos
Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas Norte No. 152, Col. San Bartolo Atepehuacan, C.P. 07730, Mexico
Raiza
Hernandez-Bravo
Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas, Mexico City, Mexico
R.
Cuamatzi-Melendez
Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas Norte No. 152, Col. San Bartolo Atepehuacan, C.P. 07730, Mexico
Melchor
Salazar
Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas Norte No. 152, Col. San Bartolo Atepehuacan, C.P. 07730, Mexico
367-378