Begell House Inc.
Computational Thermal Sciences: An International Journal
CTS
1940-2503
6
5
2014
ON A RIEMANN SOLVER FOR THREE-DIMENSIONAL RANS
369-381
Pavel Vladimirovich
Chuvakhov
Central Aerohydromynamic Institute, 1 Zhukovskogo str., Zhukovsky, Moscos reg., 140180, Russia; and Moscow Institute of Physics and Technology (State University), 9 Institutskiy per., Dolgoprudny, Moscow reg., 141700, Russia
The exact analytical expression for a system of both eigenvalues and right/left eigenvectors of a Jacobian matrix for the inviscid part of a two-equations differential closure 3D RANS operator split along a curvilinear coordinate is derived. Two CFD problems are considered, namely, supersonic flow over a flat plate and supersonic flow over a compression corner with separation. It is shown that application of the exact system of eigenvalues and eigenvectors to realization of the Roe approach for approximate solution of Riemann problem results in increase in convergence rate, better stability, and higher accuracy of a steady-state solution in comparison with those in the case of an approximate system.
NUMERICAL EVALUATION OF NATURAL CONVECTION HEAT TRANSFER IN A SUPPLY-AIR PAZIAUD WINDOW
383-395
Abdelillah
Amrani
Université Mohammed Premier, Faculté des Sciences, Laboratoire de Mécanique & Energétique, 60000 Oujda, Maroc
Nadia
Dihmani
Université Mohammed Premier, Faculté des Sciences, Laboratoire de Mécanique & Energétique, 60000 Oujda, Maroc
Samir
Amraqui
Université Mohammed Premier, Faculté des Sciences, Laboratoire de Mécanique & Energétique, 60000 Oujda, Maroc
Ahmed
Mezrhab
Laboratoire de Mécanique & Energétique, Département de Physique, Faculté des Sciences, Université Mohammed 1er, 60000 Oujda, Maroc
This work describes the convective exchanges which occur in a supply-air Paziaud window. The window is composed
of three panes of glass separated by ventilated U-shaped air gaps. The aim of the study is to evaluate the thermal
performance of a building's interior due to heat flow through the window, which contributes also to room ventilation. The study considers the effects of Rayleigh number, aspect ratio, and blind geometry on the convective heat transfer. The governing differential equations are discretized using a finite volume method, and the coupling pressure-velocity problem is carried out using the SIMPLER algorithm. Results are reported in terms of isotherms, streamlines, and average Nusselt number.
MIXED CONVECTION FLOW OF DOUBLY STRATIFIED COUPLE STRESS FLUID WITH HEAT AND MASS FLUXES
397-404
Kaladhar
Kolla
N I T Puducherry
D.
Srinivasacharya
Department of Mathematics, National Institute of Technology, Warangal-506004,
India
In this paper, double-stratification effects on mixed convection heat and mass transfer along a vertical plate embedded in a couple stress fluid with flux distributions has been studied. The nonlinear governing equations and their associated boundary conditions are initially cast into dimensionless form by pseudo-similarity variables. The resulting system of equations is then solved numerically using the Keller box method. The numerical results are compared and found to be in good agreement with previously published results as special cases of the present investigation. The effects of couple stress parameter, mixed convection parameter, and double-stratification parameters on heat and mass transfer rates for different values of governing parameters are tabulated. An analysis of the results obtained shows that the flow field is influenced appreciably by emerging parameters of the present study.
NATURAL CONVECTION HEAT TRANSFER ENHANCEMENT IN A SQUARE CAVITY FILLED WITH NANOFLUIDS AND PERIODICALLY HEATED FROM THE SIDE
405-424
M.
Hati
Cadi AyyadUniversity, Faculty of Sciences Semlalia, Department of Physics, Laboratory of Fluid Mechanics and Energetics (LMFE), Unit affiliated to CNRST (URAC, 27), B.P. 2390, Marrakech, Morocco
Abdelghani
Raji
Sultan Moulay Slimane University, Faculty of Sciences and Technologies, Physics Department, Laboratory of Flows and Transfers Modelling (LAMET), B. P. 523, Béni-Mellal 23000, Morocco
Mohammed
Hasnaoui
University Cadi Ayyad, Faculty of Sciences Semlali
Mohamed
Naimi
Faculty of Sciences and Technologies, Physics Department, Laboratory of Flows and Transfers Modeling (LAMET), Sultan Moulay Slimane University, B.P. 523, Beni-Mellal, Morocco
H.
El Harfi
Faculty of Sciences and Technologies, Physics Department, Laboratory of Flows and Transfers Modeling (LAMET), Sultan Moulay Slimane University, B.P. 523, Beni-Mellal, Morocco
Natural convection within a square cavity filled with Cu-water or Al2O3-water nanofluids is investigated numerically. The temperature of the left vertical surface (cold temperature) is maintained constant, while that of the opposite surface (hot temperature) is varied sinusoidally in time. The horizontal walls are considered adiabatic. The parameters governing the problem are the amplitude (0 ≤ a ≤ 1) and the period (0.001 ≤ τ ≤ 1) of the variable temperature, the Rayleigh number (103 ≤ Ra ≤ 106), and the solid volume fraction (0 ≤ φ ≤ 0.1). By adding nanoparticles to the pure fluid, a substantial enhancement of heat transfer is observed. In comparison with the constant heating conditions, it is found that the variable heating temperature could lead to a drastic change in the flow structure and the corresponding heat transfer, especially at specific low periods of the hot variable temperature. This leads to a resonance phenomenon characterized by an important increase in heat transfer by about 25.5% with respect to the case of a pure fluid subject to constant hot temperature boundary conditions.
OUTFLOW BOUNDARY CONDITION FOR THE UNSTEADY-SATE FLUID FLOW COMPUTATION WITH VARIABLE DENSITY ON A COLLOCATED GRID
425-437
Yohsuke
Matsushita
Research and Education Center of Carbon Resources, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan
Sohey
Nozawa
Research and Education Center of Carbon Resources, Kyushu University, Fukuoka, Japan
Tomoyuki
Katayama
Department of Chemical Engineering, Graduate School of Engineering, Tohoku University, 6- 6-07 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
Tatsuya
Soma
Department of Chemical Engineering, Graduate School of Engineering, Tohoku University, 6- 6-07 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
Yasuhiro
Saito
Department of Chemical Engineering, Graduate School of Engineering, Tohoku University, 6- 6-07 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
Hideyuki
Aoki
Department of Chemical Engineering, Graduate School of Engineering, Tohoku University, Japan
This study applies the outflow boundary condition for the unsteady-state variabledensity fluid flow in the staggered grid arrangement to a similar flow in the collocated grid arrangement This application is based on the finite volume method, which successfully satisfies mass conservation. In the staggered grid arrangement, the outflow boundary condition yields the velocities on the outflow boundary using the Neumann condition to relate them to the velocities on the cell face, which are obtained by solving the discretized momentum equations. Here, the Neumann condition instead relates the outflow velocities to those on the cell center. The velocities on the cell face do not always satisfy the discretized continuity equations. Therefore, the velocities on the cell face are corrected using the summation of the discretized continuity equations over the entire computational domain in the staggered arrangement. Moreover, in the staggered grid arrangement, the summation of the discretized continuity equations can be directly obtained since the velocities are defined on the cell face; whereas in the collocated grid arrangement, the summation is evaluated after the Rhie-Chow interpolation since the velocities are on the cell center. As there are different procedures for evaluating the velocities on the outflow boundary in the different grid arrangements, unsteady-state fluid flow computations with variable density in the heating or cooling problems are performed to investigate the applicability of the outflow boundary condition
to the collocated grid arrangement. It is found that the outflow boundary condition works well in the collocated grid
arrangement and shows excellent mass conservation. Above all, the outflow boundary condition would be applicable to
the boundary fitted coordinate system and the unstructured grid, which can treat complex geometries and require the
collocated grid arrangement.
MHD TRANSIENT NANOFLUID FLOW AND HEAT TRANSFER FROM A MOVING VERTICAL CYLINDER WITH TEMPERATURE OSCILLATION
439-450
V.
Rajesh
Department of Engineering Mathematics, GITAM University Hyderabad Campus, Rudraram, Patancheru Mandal, Medak Dist.-502 329, Andhra Pradesh, India
O. Anwar
Bég
Fluid Mechanics, Nanosystems and Propulsion, Aeronautical and Mechanical Engineering,
School of Computing, Science and Engineering, Newton Building, University of Salford,
Manchester M54WT, United Kingdom
In the present study, the effects of magnetohydrodynamics (MHD) on the transient free convection flow of a viscous,
electrically conducting, and incompressible nanofluid past a moving semi-infinite vertical cylinder with temperature
oscillation is studied. The fluid is water-based nanofluid containing nanoparticles of copper (Cu) with a nanoparticle
volume fraction range less than or equal to 0.04. The Tiwari-Das nanofluid model [Int. J. Heat Mass Transf., 50(9-10):2002-2018 (2007)] is employed. The dimensionless governing partial differential equations are solved by using
a robust, well-tested, implicit finite difference method of Crank-Nicolson type. The obtained results are benchmarked
with previously published work for special cases of the problem in order to access the accuracy of the numerical method and found to be in excellent agreement. In particular, the effect of significant parameters, such as magnetic parameter, phase angle, nanoparticle volume fraction, and thermal Grashof number, on the flow and heat transfer characteristics is discussed. The present simulations are relevant to magnetic nanomaterial thermal flow processing in the chemical engineering and metallurgy industries.
NATURAL CONVECTIVE HEAT TRANSFER FLOW OF A NON-NEWTONIAN SECOND-GRADE FLUID PAST AN ISOTHERMAL SPHERE
451-460
R.
Bhuvanavijaya
Department of Mathematics, Jawaharlal Nehru Technological University Anantapuram, Andhrapradesh-515002, India
V. Ramachandra
Prasad
Department of Mathematics, Madanapalle Institute of Technology and Science, Madanapalle,
India
Bandaru
Mallikarjuna
Department of Mathematics, BMS College of Engineering, Bangalore, Karnataka-560 019, India
O. Anwar
Bég
Fluid Mechanics, Nanosystems and Propulsion, Aeronautical and Mechanical Engineering,
School of Computing, Science and Engineering, Newton Building, University of Salford,
Manchester M54WT, United Kingdom
An analysis is performed to study free convective boundary layer flow of second-grade fluid along an isothermal, impermeable sphere. The Clausius-Duhem inequality is used to describe the second-grade fluid, the presence at stress terms in momentum boundary layer equations. The governing boundary layer equations are transformed into nondimensional
form by using specified nonsimilarity variables. A numerical solution is obtained by employing the validated, efficient,
implicite finite difference method with Keller box scheme. A parametric study of physical parameters, Deborah number,
and Prandtl number involved in the problem is conducted and a representative set of numerical results for velocity
and temperature profiles as well as skin friction coefficient and Nusselt number are illustrated graphically and in tabular form. Comparisons with previously published work for different values of the physical parameter of the problem are reported and the existing results are found to be in excellent agreement. An increasing Deborah number retards the velocity and Nusselt number inside the boundary layer region while accelerating the temperature profile and skin friction coefficient. Increasing Prandtl number results in depreciation in the velocity, temperature profiles, and skin friction coefficient while the Nusselt number increased. Applications of the model arise in polymer processing in chemical engineering as well as metallurgical materials processing.