eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2009-07-01
16
4
3229
Similarity Solution in the Study of Flow and Heat Transfer Between Two Rotating Spheres with Constant Angular Velocities
A. Baradaran Rahimi
rahimiab@yahoo.com
1
A. Jabari Moghadam
prdpzrpa@scientiaunknown.non
2
Faculty of Engineering,Ferdowsi University of Mashhad
Faculty of Engineering,Ferdowsi University of Mashhad
Abstract. The similarity solution of the steady-state motion and heat transfer of a viscous incompressible
uid contained between two concentric spheres, maintained at dierent temperatures and rotating
about a common axis with dierent constant angular velocities, is considered. The resulting
ow pattern,
temperature distribution and heat transfer characteristics are presented for various cases. Aside from the
energy equation, the same results as previous works are obtained for Navier-Stokes equations, but with
less computational complexities.
http://scientiairanica.sharif.edu/article_3229_1e69cb5bdbdf832455bc1802011e188d.pdf
similarity solution
Steady-state ow and heat transfer
Concentric rotating spheres
Constant angular velocities
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2009-07-01
16
4
3230
Effect of Dierent Geometries in Simulation of 3D Viscous Flow in Francis Turbine Runners
B. Firoozabadi
email@email.com
1
R. Dadfar
acviwpjt@scientiaunknown.non
2
A.R.P. Pirali
jnuichhd@scientiaunknown.non
3
G. Ahmadi
ldpqnrji@scientiaunknown.non
4
Department of Mechanical Engineering,Sharif University of Technology
Department of Mechanical Engineering,Sharif University of Technology
Department of Mechanical Engineering,Sharif University of Technology
Department of Mechanical Engineering,Clarkson University
Abstract. Overall turbine analysis requires large CPU time and computer memory, even in the
present days. As a result, choosing an appropriate computational domain accompanied by a suitable
boundary condition can dramatically reduce the time cost of computations. This work compares dierent
geometries for numerical investigation of the 3D
ow in the runner of a Francis turbine, and presents an
optimum geometry with least computational eort and desirable numerical accuracy. The numerical results
are validated with a GAMM Francis Turbine runner, which was used as a test case (GAMM workshop on
3D computation of incompressible internal
ows, 1989) in which the geometry and detailed best eciency
measurements were publically accessible. In this simulation, the
ow is assumed to be steady and the inlet
boundary condition is prescribed using experimental data. The eect of turbulence is considered by the
k ????" model. The present investigation demonstrates that consideration of 2-blade geometry with periodic
boundary conditions is the best choice of computational domain. By 1-blade geometry, convergence of
the numerical simulation is not appropriate, whereas 13-blade geometry leads to a coarse grid that can
increase inaccuracy and computational cost. Finally, this paper presents a qualitative survey to forecast
cavitation region inception which correlates satisfactorily with experimental observations.
http://scientiairanica.sharif.edu/article_3230_f3406c268c8f6abafa1dcd42fddcd056.pdf
numerical simulation
Francis turbine runner
GAMM
Viscous ow analysis
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2009-07-01
16
4
3231
Modeling of Twin-Entry Radial Turbine Performance Characteristics Based on Experimental Investigation Under Full and Partial Admission Conditions
A. Hajilouy-Benisi
email@email.com
1
M. Rad
bpbejyap@scientiaunknown.non
2
M. R. Shahhosseini
shahhosseini@mehr.sharif.edu
3
Department of Mechanical Engineering,Sharif University of Technology
Department of Mechanical Engineering,Sharif University of Technology
Department of Mechanical Engineering,Sharif University of Technology
Abstract. In this paper, the performance of a turbocharger twin-entry radial in
ow turbine is
investigated analytically and experimentally under steady state, full and partial admission conditions. In
this modeling, the mass
ow rate, pressure ratio and eciency of the turbine are assumed unknown. The
turbine geometry and the inlet total pressure and temperature are known, hence, the turbine performance
characteristics can be obtained. In the turbocharger laboratory, performance characteristics of the turbine
are determined, measuring the main parameters for various operating conditions. Comparing the model
and experimental results shows good agreement. Also, considering the eect of test parameters on
performance uncertainty, it shows that the pressure ratio has more in
uence. Finally, the uncertainty of
eciency decreases as the pressure ratio increases.
http://scientiairanica.sharif.edu/article_3231_e204c6e333590777a863225103fbd7ad.pdf
Radial in ow turbine
Full and partial admission conditions
modeling
Turbocharger
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2009-07-01
16
4
3232
Experimental Analysis of Cavitaion Eects on Drag Force and Back Pressure of Circular Cylinder with Free Turbulence
I. Jafari Gavzan
maedeh_eskandari@yahoo.com
1
Department of Mechanical Engineering,Sharif University of Technology
Abstract. The characteristics of a cavitation water tunnel test setup and the experiments of cavitation
around a circular cylinder with free stream turbulence are presented in this paper. The Reynolds number
of
ow is limited in the range of 1:26105 to 3105 and the far upstream
ow has free turbulence. Drag
force, back pressure, location of cavitation inception, length of cavity and appearance of cavitation are
measured or observed and their results are presented here. It was found that the cavitation eects on the
boundary layer and separation of
ow over the cylinder and drag force become minimum at the cavitation
number of 1.94. The cavitation inception occurs in the sub-layer and at an angle of about 105, with
respect to
ow direction (inception location depends on Reynolds number). The back pressure coecient
becomes maximum at the cavitation number of 1.94.
http://scientiairanica.sharif.edu/article_3232_49a1268ac06f4064c02796833d0866fd.pdf
Drag force
Cavitation tunnel
Free turbulence
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2009-07-01
16
4
3233
Some Experimental Studies on the Performance of a Rigid Wing Land Yacht Model in Comparison with VPP
M. Rad
zqsohpdx@scientiaunknown.non
1
M. Khayyat
khayyat@mech.sharif.edu
2
Department of Mechanical Engineering,Sharif University of Technology
Department of Mechanical Engineering,Sharif University of Technology
Abstract. It is important to understand the
ow characteristics and performance of wings for
designers who want to have an ecient thrust in a land yacht. In this paper, a comparison of aerodynamic
forces obtained by testing the land yacht model in a wind tunnel and by the Velocity Prediction Program
(VPP) is presented. The wind tunnel testing of a land yacht is an eective design tool, but at present
it is mainly used for VPP validation, which allows for a faster and more ecient design process. The
rigid wing land yacht model, which is a radio controlled model, is tested in the national open jet wind
tunnel of the Malek Ashtar University of Technology in Iran. The wing data, which is obtained from the
wind tunnel, is used in the VPP as input data and then the parasitic drag and aerodynamic forces that
are measured in the wind tunnel are compared to those in the VPP. Comparison of the results shows a
reasonably good agreement between experimental data and VPP data. So the latter can be used as an
eective tool in the design of a land yacht.
http://scientiairanica.sharif.edu/article_3233_f7043e3deabe9309fcf6c597d663c9e1.pdf
Land yacht
wind tunnel
Aerodynamic
Wing
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2009-07-01
16
4
3234
Eect of Payload Variation on the Residual Vibration of Flexible Manipulators at the End of a Given Path
A. Heidari
qvspyner@scientiaunknown.non
1
M. H. Korayem
hkorayem@iust.ac.ir
2
A. Nikoobin
siywywfs@scientiaunknown.non
3
Department of Mechanical Engineering,Sharif University of Technology
Department of Mechanical Engineering,Iran University of Science and Technology
Department of Mechanical Engineering,Iran University of Science and Technology
Abstract. In rest-to-rest motion, the gripper of the
exible manipulators vibrates not only in the
duration of the tracking but also after reaching the goal point. This vibration, which is called residual
vibration, continues with a specic amplitude and frequency after reaching the goal point. In this paper,
the eect of a carried payload on the residual vibration magnitude is investigated. The nite element
method is employed for modeling and deriving the dynamic equations of the manipulator with
exible
links and joints. Compared with previous works, the assumptions of low frequency and small amplitude of
vibration about the nal conguration are released and all terms in the dynamic equations are taken into
account. Some simulations for a two-link
exible manipulator along two given paths are then performed
for dierent payloads at the end-eector. In the rst state, a polynomial-Fourier function is considered for
joint motion and then a linear path for gripper motion. Finally, a straightforward approach for predicting
the residual vibration amplitude, in terms of the payload, is proposed.
http://scientiairanica.sharif.edu/article_3234_41e8f658968bc8ac18c5cee14f68a77f.pdf
Manipulator
Flexible link and joint
Residual vibration
Finite Element Method
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2009-07-01
16
4
3235
Coordination of Process Integration and Exergoeconomic Methodology for Analysis and Optimization of a Pulp and Paper Mill
B. Farhanieh
bifa@sharif.edu
1
A. A. Mozafari
mozafari@sharif.edu
2
M. Fani
fani@mech.sharif.edu
3
Department of Mechanical Engineering,Sharif University of Technology
Department of Mechanical Engineering,Sharif University of Technology
Department of Mechanical Engineering,Sharif University of Technology
Abstract. By simultaneously applying pinch technology and the exergoeconomic method to a complex
process system, benecial and energy-ecient measures are identied. The three-link-model" exergoeconomic
methodology optimizes the design and operability of a system. In this work, contrary to traditional
exergoeconomic methods, a reversed method is used. The approach proposed for the optimization of
such a complex system is to iteratively optimize subsystems. Since the reversed exergoeconomic method
is used, assumptions considered by Tsatsaronis (based on four assumptions for calculating the costoptimal
exergetic eciency and relative cost dierence) are not applicable and new assumptions are to be
considered. Unlike traditional exergoeconomic methods, the product exergetic specic cost is considered to
be known and the objective will be to maximize the exergetic cost of the fuel. Heat
ows costs are calculated
with the assistance of a Pinch analysis. The strength of the combination of a Pinch analysis and the
exergoeconomic method is elucidated in a case study applied to the Mazandaran wood and paper industry.
Replacement of the pressure valve and Direct Cyclone Contact Evaporation (DCCE) is proposed, while by
selection of the optimum decision variable and applying Pinch technology simultaneously, the recoverable
black liquor could be increased by 7% and energy consumption decreased by 12%.
http://scientiairanica.sharif.edu/article_3235_1089aa06b52949bd88e316d99c56b70c.pdf
Pinch technology
Exergoeconomic methodology
Process system
optimization
Pulp and paper
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2009-07-01
16
4
3236
Numerical Investigation of Fluid Flow and Heat Transfer Characteristics in Parallel Flow Single Layer Microchannels
M.H. Saidi
email@email.com
1
O. Asgari
omidmec@yahoo.com
2
Department of Mechanical Engineering,Sharif University of Technology
Department of Mechanical Engineering,Sharif University of Technology
Abstract. Heat generation from Very Large-Scale Integrated (VLSI) circuits increases with the
development of high-density integrated circuit technology. One of the ecient techniques is liquid
cooling by using a microchannel heat sink. Numerical simulations on the microchannel heat sink in the
literature are mainly two dimensional. The purpose of the present study is to develop a three-dimensional
procedure to investigate
ow and conjugate heat transfer in the microchannel heat sink for electronic
packaging applications. A nite volume numerical code with a multigrid technique, based on an additive
correction multigrid (AC-MG) scheme, which is a high-performance solver, is developed to solve the steady
incompressible laminar Navier-Stokes (N-S) equations over a colocated Cartesian grid arrangement. The
results show that the thermophysical properties of the liquid can essentially in
uence both the
ow and
heat transfer in the microchannel heat sink. Comparison of the numerical results with other published
numerical results and experimental data, available in the literature for Reynolds numbers less than 200,
indicates that the assumption of hydrodynamically fully developed laminar
ow is valid. The accuracy of
the prediction has been veried by comparing the results obtained here with the numerical and analytical
results from the open literature which showed a good agreement. The detailed temperature and heat
ux
distributions, as well as the average and bulk heat transfer characteristics, are reported and discussed.
The analysis provides a unique fundamental insight into the complex heat
ow pattern established in the
channel due to combined convection-conduction eects in the three-dimensional setting.
http://scientiairanica.sharif.edu/article_3236_7d7b8b80111bddd814ed338f89562ffc.pdf
microchannel
Finite volume numerical simulation
Multigrid technique
Colocated grid arrangement
Heat transfer and uid ow
Electronic cooling