Begell House Inc.
Computational Thermal Sciences: An International Journal
CTS
1940-2503
7
1
2015
FINITE ELEMENT SIMULATION OF NONLINEAR MAGNETO-MICROPOLAR STAGNATION POINT FLOW FROM A POROUS STRETCHING SHEET WITH PRESCRIBED SKIN FRICTION
1-14
Diksha
Gupta
Department of Mathematics, Jaypee Institute of Information Technology, A-10, Sector-62, Noida-201307, Uttar Pradesh, India
Lokendra
Kumar
Department of Mathematics, Jaypee Institute of Information Technology, A-10, Sector-62, Noida-201307, Uttar Pradesh, India
Osman Anwar
Beg
Gort Engovation-Aerospace, Medical and Energy Engineering, Gabriel's Wing House, 15
Southmere Avenue, Bradford, BD73NU, United Kingdom
Bani
Singh
Department of Mathematics, Jaypee Institute of Information Technology, A-10, Sector-62, Noida-201307, Uttar Pradesh, India
A mathematical model is developed for the steady magnetohydrodynamic stagnation point thermoconvective boundary layer flow of micropolar fluid over a stretching sheet. An isothermal surface stretched with constant skin friction is considered. A uniform magnetic field is applied perpendicular to the porous stretching sheet. Using similarity transformations, the governing partial differential equations are normalized to a system of nonlinear ordinary differential equations, which are solved numerically with a variational finite element method. The influence of the key physical parameters, namely, buoyancy parameter, magnetic parameter, and transpiration parameter, on the evolution of velocity, microrotation (angular velocity), and temperature function are presented graphically. The local Nusselt number has also been computed for these parameters. Under the limiting cases, the results obtained by using the finite element method are compared with the numerical results available from the literature and excellent correlation is demonstrated. Furthermore, to verify the convergence of the finite element method (FEM) numerical solutions, calculations are conducted with increasing numbers of elements. The study finds applications in magnetic materials processing.
ENHANCED MIXED CONVECTION AND HEAT TRANSFER BY NANOFLUID IN VENTILATED SQUARE ENCLOSURE INCLUDING TWO HEAT SOURCES
15-34
Hamdi
Moumni
Thermal Radiation Laboratory, Fac. Sci. of Tunis, University of Tunis El Manar, Tunisia
Ezeddine
Sediki
Thermal Radiation Laboratory, Fac. Sci. of Tunis, University of Tunis El Manar, Tunisia
In the present study, enhanced mixed convection and heat transfer by nanofluid in a ventilated square enclosure including two heat sources was investigated numerically. The governing equations are solved using a second-order accurate finite volume approach with a staggered grid system. The classical projection method is used to handle the velocity-pressure coupling. The effects of monitoring parameters, namely, Richardson number, Reynolds number, and solid volume fraction on the streamline and isotherm contours as well as average Nusselt number along the two heat sources are carried out and discussed in based range for Reynolds number 10 ≤ Re ≤ 500, Richardson numbers 0.1 ≤ Ri ≤ 10, and the solid volume fraction 0 ≤ Φ ≤ 0.1. The results show that by adding the nanoparticles to base fluid and increasing both Reynolds and Richardson number the heat transfer rate is enhanced. It is also found that, regardless of the Richardson number, Reynolds number, and the solid volume fraction of nanoparticles, the highest heat transfer enhancement occurs at the left heat source surface.
ANALYSIS OF ROTATION, ANISOTROPY, AND RELAXATION TIMES ON REFLECTION WAVES IN MAGNETO-ELECTRO-THERMOELASTIC HALF-SPACE
35-49
Rajneesh
Kakar
Department of Physics, Adarsh Gurukul, Jalandhar, India
Shikha
Kakar
Department of Electronics, SBBS University, Padhiana, India
The problem of reflection of electro-magneto-thermoelastic quasi SV-wave in a rotating transversely isotropic solid half-space is investigated with the help of Lord and Shulman's generalized theory of thermoelasticity. The velocity equation is obtained by solving the governing equations of a rotating transversely isotropic electro-magneto-thermoelastic medium. After solving the basic equations, we have obtained the reflection coefficients for quasi P-wave, quasi thermal wave, and quasi SV-wave. With the use of practical values of electric parameter, magnetic parameter, rotational parameter, and thermal coupling parameters, various curves are plotted to show the effect of temperature, anisotropy, rotation, thermal, electric, and magnetic fields on the reflection of incident quasi SV-wave on the solid half-space. Some special and particular cases are also deduced which are in agreement with results given by an earlier researcher.
NUMERICAL STUDY OF NATURAL CONVECTION HEAT TRANSFER PERFORMANCE IN AN INCLINED CAVITY WITH COMPLEX-WAVY-WALL: NANOFLUID AND RANDOM TEMPERATURE
51-64
Hicham
Salhi
LESEI, Department of Mechanical Engineering, University Batna, Algeria
Mohamed
Si-Ameur
LESEI Laboratory, Department of Mechanical Engineering, Technology Faculty, University of Batna 2, Algeria
Djamel
Haddad
LESEI, Department of Mechanical Engineering, University Batna, Algeria
Natural convection of a nanofluid (NF) consisting of water and (Ag or TiO2) in an inclined enclosure cavity has been studied numerically; the left and right walls of the cavity have a complex-wavy geometry and are maintained at a low and high temperature (random temperature, based on the random function), respectively. Meanwhile, the upper and lower walls of the cavity are both flat and insulated. The governing equations are solved numerically using the finite volume. The complex-wavy-surface is modeled as the superimposition of two sinusoidal function approaches. Results are presented in the form of streamlines, isotherms, and average Nusselt number. In addition, a parametric study is carried out to examine explicitly the volume fraction effects of nanoparticles (NPs) (φ = 0.1, 0.2), the Rayleigh number (Ra = 103,104, 105), the inclination angle of the cavity (γ = 0°, 45°, 90°, 135°, 180°), types of temperature (constant, random), types of NF (Ag and TiO2), and the complex-wavy-surface configuration. The results reveal that NPs addition remarkably enhances heat transfer in the cavity, especially for φ = 0.2. Besides, the effect of inclination angle and type of temperature is more pronounced at higher Rayleigh number. Moreover, it is shown that the heat transfer performance can be optimized by tuning the wavy-surface geometry parameters.
STUDY OF CONSERVATION APPLIED TO POINT-IMPLICIT INTEGRATION TECHNIQUES FOR UNSTRUCTURED FINITE VOLUME NAVIER−STOKES SOLVERS
65-79
Carlos
Junqueira-Junior
Instituto Tecnologico de Aeronautica − ITA, Sao Jose dos Campos, SP, Brazil
Leonardo Costa
Scalabrin
EMBRAER S.A., Sao Jose dos Campos, SP, Brazil
Edson
Basso
Instituto de Aeronautica e Espaco − IAE, Sao Jose dos Campos, SP, Brazil
Joao Luiz F.
Azevedo
Instituto de Aeronautica e Espaco − IAE, Sao Jose dos Campos, SP, Brazil
The work is a study of conservation on linearization techniques of time-marching schemes for the unstructured finite volume Reynolds-averaged Navier−Stokes formulation. The solver used in this work calculates the numerical flux applying an upwind discretization based on the flux vector splitting scheme. This numerical treatment results in a very large sparse linear system. The direct solution of this full implicit linear system is very expensive and, in most cases, impractical. There are several numerical approaches which are commonly used by the scientific community to treat sparse linear systems, and the point-implicit integration was selected in the present case. However, numerical approaches to solve implicit linear systems can be nonconservative in time, even for formulations which are conservative by construction, as the finite volume techniques. Moreover, there are physical problems which strongly demand conservative schemes in order to achieve the correct numerical solution. The work presents results of numerical simulations of closed domain concerning the evaluation of the mass conservation on implicit and explicit time-marching methods using constant and variable time steps. The explicit integration, with the use of a constant time step all over the domain, has preserved the conservative characterist of the finite volume formulation whereas the point-implicit integration requires numerical treatement in order to avoid such nonconservation issues.
SLUG FLOW HEAT TRANSFER IN MICROCHANNELS: A NUMERICAL STUDY
81-92
Thilaksiri
Bandara
School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University,Carlton, Victoria 3053, Australia
Sherman C.P.
Cheung
School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Carlton, Victoria 3053, Australia
Gary
Rosengarten
RMIT University, School of Aerospace, Mechanical and Manufacturing Engineering. 115
Queensberry street. 3053. Carlton, Australia
Two-phase microchannel slug flow has attracted significant interest among researchers due to its wide range of applications. This paper will present some as yet overlooked features of slug flow heat transfer in microchannels, using numerical simulation. Numerical simulations are carried out using ANSYS FLUENT with the volume of fluid (VOF) method with a 2D axisymmetric geometry for a 100 µm inner diameter microchannel with constant wall temperature boundary conditions. Effects of slug flow parameters on heat transfer are discussed showing the heat transfer rate follows a similar trend to existing numerical results. Our results show a significant increase in Nusselt number with liquid−liquid two-phase flow compared to single-phase flow, by up to 200%. The study revealed that capillary number, size of the liquid slugs, as well as the liquid film thickness have an important impact on heat transfer.