eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2311
2328
10.24200/sci.2018.20327
20327
Numerical investigation into natural convection of nanofluids in an inclined square enclosure with non-uniform heated walls
Xiaofeng Wang
1
Weizhong Dai
2
Department of Mathematics, Henan Institute of Science and Technology, Xinxiang, Henan 453003, China
Mathematics & Statistics, College of Engineering & Science, Louisiana Tech University, Ruston, LA 71272, USA
Studying on natural convection of nanofluids in enclosures with non-uniform heated walls is important for many engineering applications such as solar energy collection. In this article, we develop a fully higher-order compact (FHOC) finite difference method to investigate the natural convection and heat transfer of nanofluids in an inclined square enclosure with sinusoidal temperature distributions. Numerical simulations have been performed over a range of amplitude ratio, inclination angles, phase deviation, nanoparticles volume fraction, and Rayleigh number. Results show that heat transfer can exchange significantly by increasing the amplitude ratio and inclination angles in nanofluids. Moreover, elevating the nanoparticles volume fraction doesn't always enhance the heat transfer of nanofluids. When the Rayleigh number is low ( = ), the average Nusselt number decreases as the solid volume fraction parameter increases. On the other hand, elevating has favorable effects on the heat transfer of nanofluids when is high (e.g., , ). When , the total heat transfer rate decreases in the order of nanoparticles arranged as Cu, CuO, Al2O3, and TiO2. Finally, a correlated expression of the total average Nusselt number, the Rayleigh number and the solid volume fraction of nanoparticles is empirically obtained.
http://scientiairanica.sharif.edu/article_20327_aac8f27b123d10fe558fe1ee09283290.pdf
Natural convection
inclined enclosure
nanofluids
sinusoidal temperature
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2329
2341
10.24200/sci.2018.20608
20608
Implementation of curved wall boundary and absorbing open boundary conditions for the D3Q19 lattice Boltzmann method for simulation of in compressible fluid flows
Eslam Ezzatneshan
e_ezzatneshan@sbu.ac.ir
1
Aerospace Engineering Group, Dept. of New Technologies Engineering, Shahid Beheshti University, Tehran, Iran
In this work, a three-dimensional lattice Boltzmann method is developed for numerical simulation of the fluid flows around the arbitrary geometries in the wide range of Reynolds numbers. For efficient simulation of high Reynolds number flow structures in the turbulent regime, a large eddy simulation (LES) approach with the Smagorinsky subgrid turbulence model is employed. An absorbing boundary condition based on the concept of sponge layer is improved and implemented to damp the vorticity fluctuations near the open boundaries and regularize the numerical solution by significantly reducing the spurious reflections from the open boundaries. An off-lattice scheme with a polynomial interpolation is used for implementation of curved boundary conditions for the arbitrary geometries. The efficiency and accuracy of the numerical approach presented are examined by computing the low to high Reynolds number flows around the practical geometries, including the flow past a sphere in a range of Reynolds numbers from 102 to 104 and flow around the NACA0012 wing section in two different flow conditions. The present results are in good agreement with the numerical and experimental data reported in the literature. The study demonstrates the present computational technique is robust and efficient for solving flow problems with practical geometries.
http://scientiairanica.sharif.edu/article_20608_7cec8e2f6feed6f605cefbf0007618af.pdf
3-D lattice Boltzmann method
curved wall boundary condition
absorbing open boundary condition
high Reynolds numbers
arbitrary geometries
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2342
2355
10.24200/sci.2018.20319
20319
MHD PERISTALTIC SLIP FLOW OF CASSON FLUID AND HEAT TRANSFER IN CHANNEL FILLED WITH A POROUS MEDIUM
O. D. Makinde
1
M. Gnaneswara Reddy
2
1Faculty of Military Science, Stellenbosch University, Private Bag X2, Saldanha 7395, South Africa
Department of Mathematics, Acharya Nagarjuna UniversityCampus, Ongole – 523 001, India
We examine the effect of velocity slip on hydromagnetic peristaltic flow of a Casson fluid and heat transfer through an asymmetric channel fluid filled a porous medium.The model governing equations are obtained, simplified using long wavelength and low Reynolds number assumptions and then tackled analytically.Numerical result for effects of embedded parameters on the stream function, axial velocity, pressure drop, temperature, skin friction and Nusselt number are presented graphically and discussed. It is found that thepermeability parameter enhances the size of the trapped bolus while velocity slip diminishes it. A rise in magnetic field intensity and Cason fluid parameters decrease the both velocity and temperature profiles.The present problem is of substantial importance in crude oil refinement and biomedical engineering.
http://scientiairanica.sharif.edu/article_20319_f5e7cda776612508d1d4733fed47d2f3.pdf
Peristaltic flow
MHD
Casson fluid
Heat Transfer
Porous medium
Partial slip
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2356
2368
10.24200/sci.2018.20603
20603
Finite element modeling and design of pH/temperature sensitive hydrogel based biphasic twisting actuators
M.R. Bayat
1
M. Baghani
mbaghani@ut.ac.ir
2
School of mechanical engineering, College of engineering, University of Tehran, Tehran, Iran
School of mechanical engineering, College of engineering, University of Tehran, Tehran, Iran
In this article, a pH/temperature sensitive hydrogel based biphasic twisting actuator is presented and studied in various environmental conditions. The actuator consists of a neutral incompressible elastomeric phase attached to pH/temperature sensitive hydrogel phase which twists, when subjected to pH/temperature variation. The deformation of the actuator depends on the cross-section of the actuator as well as geometrical and environmental parameters. To have a guideline for the design of the biphasic twisting actuator, a finite element model of the mentioned structure is developed. A thermodynamic based constitutive model is used to describe the behavior of the hydrogel. The finite element method is used to resolve the homogeneous and inhomogeneous swelling of the pH/temperature responsive hydrogel to check the validity of the method. Finally, how various parameters affect the torsional behavior of the actuator is discussed in detail. According to the results, to get the maximum twisting angle it is recommended to use the actuator with the square cross-section. Also, the twisting angle can even increase more by decreasing the hydrogel size as well as increasing the length of the actuator.
http://scientiairanica.sharif.edu/article_20603_af711a2b3da4501940890005e0087c0a.pdf
self-twisting
bilayer
pH/temperature sensitive hydrogel
actuator
Finite Element Method
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2369
2381
10.24200/sci.2018.20693
20693
Numerical study of Jet Impingement Subcooled Boiling on the Superheated Surfaces
Kazem Esmailpour
1
Arad Azizi
2
Seyed Mostafa Hosseinalipour
3
Department of Mechanical Engineering, Islamic Azad University, Damavand Branch, Damavand, Iran
Department of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran
Department of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran
Cooling techniques of superheated surfaces by jet impingement with taking advantage of phase change phenomena i.e. boiling heat transfer has proven to be an efficient method because of its high rates of heat transfer. Furthermore, at a specified heat transfer coefficient, flow required for cooling purposes can reduce two orders of magnitude comparing to free-wall parallel flow which is important regarding to energy and water sustainability issues in various industries. This research mainly concerns numerical simulation of hydrodynamics and heat transfer phenomena regarding phase-change jet impingement on nucleate boiling region. Rensselaer Polytechnic Institute wall boiling model based on Eulerian multiphase model and RNG K-ɛ turbulence model were employed. Each interfacial term was considered and selected based on proximity to real physical phenomena. The selected model in this research was validated by a previously done confined jet impingement subcooled boiling experiment (dielectric fluid-PF5060). Minimum error of 4% and maximum error of 15% were reached at stagnation point. As parametric study, the effect of jet Reynolds number based on nozzle hydraulic diameter at Re 2500 to 10000 and the effect of standoff distance of jet nozzle from target surface at H/D 2, 4 and 6 were investigated.
http://scientiairanica.sharif.edu/article_20693_744ccbcc843e466f588125be7c70b4aa.pdf
Jet Impingement
Subcooled Boiling
Eulerian Multiphase Model
Mass Transfer Enhancement
Interfacial terms
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2382
2393
10.24200/sci.2018.20783
20783
Optimization of multiple transmission layouts for minimal energy consumption of a battery electric vehicle
Tahmoores Farjam
1
Mahmoud Saadat Foumani
m_saadat@sharif.ir
2
Mojtaba Delkhosh
m_delkhosh@mech.sharif.edu
3
School of Mechanical Engineering, Sharif University of Technology, Tehran, P.O. Box 11155-9567, Iran
School of Mechanical Engineering, Sharif University of Technology, Tehran, P.O. Box 11155-9567, Iran
School of Mechanical Engineering, Sharif University of Technology, Tehran, P.O. Box 11155-9567, Iran
Battery electric vehicles (BEVs) are a promising solution for reducing the impacts of passenger vehicles on the environment. However, their driving range is restricted due to the limitations of battery technologies. This range can be extended by adoption of multiple-speed transmissions. Most of the comparisons in the related studies are based on non-optimal designs or limited to modal driving cycles. Furthermore, the impact of power-split continuously variable transmission (PS-CVT) layout with type III power flow on the power consumption of BEVs has never been examined. In this paper, single, two and three-speed transmissions along with PS-CVTs with type I and III power flows are optimized for a case study BEV. Furthermore, the effect of push belt and full-toroidal CVTs in construction of PS-CVT are compared. The results demonstrate that a PS-CVT with type I power flow equipped with the full-toroidal CVT has the best performance. However, it reduces the energy consumption by 0.36% compared to the optimal two-speed layout. In addition, its ratio range is more limited which can negatively impact the dynamic performance. Finally, simulation of the optimal designs along a different cycle proves that the obtained results are consistent, regardless of the driving cycle.
http://scientiairanica.sharif.edu/article_20783_50cd7189cde0c07307f54c4d6ce0c152.pdf
Battery electric vehicle
continuously variable transmission
Power-split transmission
energy consumption
particle swarm optimization
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2394
2406
10.24200/sci.2018.5431.1269
21083
Numerical evaluation of the operating room ventilation performance: ultra-clean ventilation (UCV) systems
Behrang Sajadi
bsajadi@ut.ac.ir
1
Mohammad Hassan Saidi
saman@sharif.ir
2
Goodarz Ahmadi
gahmadi@clarkson.edu
3
School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran
School of Mechanical Engineering, Sharif University of Technology, Tehran
Department of Mechanical and Aeronautical Engineering, Wallace H. Coulter School of Engineering, Clarkson University, Potsdam, NY
The surgical site infection (SSI) is one of the most important infectious problems in hospitals which may be happened in 2.6% of all surgeries. According to the literature, the primary source of SSI is the flakes released from the exposed skin of surgical staffs or patients. It is well known that appropriate ventilation strategy is the most effective way to control bacteria-carrying airborne particles responsible for SSI. In this research, the effect of the most dominant design parameter, namely inlet air velocity, on the ultra-clean ventilation (UVC) systems performance is evaluated in detail using the computational fluid dynamics (CFD). The results show an optimum value for the inlet air velocity which is mainly due to formation of a thermal plume over the wound tissue. This thermal plume protects the wound from contaminants deposition like a shield and may be disturbed at too high inlet air velocity. In addition, the effect of critical factors including the particle size the wound temperature, the operating lights boundary condition, and the existence of fixed and removable partitions on the optimum inlet air velocity is also investigated and discussed extensively.
http://scientiairanica.sharif.edu/article_21083_dc7acd0cd6fdf25617a27a29ccb357ec.pdf
Operating room (OR)
Ultra-clean ventilation (UCV) system
Computational fluid dynamics (CFD)
Surgical site infection (SSI)
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2407
2417
10.24200/sci.2018.5525.1325
20432
Modeling and optimization of friction stir welding parameters in joining 5086 H32 aluminium alloy.
Amit Goyal
amit.goyal.san@gmail.com
1
Ramesh Garg
romeshkgarg@gmail.com
2
Department of Mechanical Engineering Deenbandhu Chhotu Ram University of science and Technology, Murthal-131039 Sonepat, India.
Department of Mechanical Engineering Deenbandhu Chhotu Ram University of science and Technology, Murthal-131039 Sonepat, India
The present manuscript focuses on developing a mathematical model to predict the intergranular corrosion rate of friction stir welded AA5086 H32 aluminium alloy joints. Six factors-Five levels central composite design matrix, having 52 experiments, is used for design of experiments. The developed model is used to examine the impact of studied process parameters i.e. rotational speed, welding speed, tool shoulder diameter, tool hardness, tilt angle , and pin profile on intergranular corrosion rate of the welded joints. Response surface methodology is used to optimize the process parameters for minimizing the susceptibility to intergranular corrosion attack. The optimum combination of studied parameters, to have minimum corrosion rate i.e. 3.2 mg/cm2, is obtained as 1296 rpm rotational speed, 79.4 mm/min welding speed, 14.9 mm tool shoulder diameter, 47.4 HRC tool hardness, 2.380 tilt angle, and square pin profile.
http://scientiairanica.sharif.edu/article_20432_be8daa2dd72694da41543efb8d948486.pdf
FSW
RSM
Aluminium alloys
Corrosion rate
optimization
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2418
2430
10.24200/sci.2018.5700.1434
20614
The effect of friction stir welding parameters on the microstructure, defects, and mechanical properties of AA7075-T651 joints
jafar langari
jafar.langari@gmail.com
1
Farhad Kolahan
kolahan@um.ac.ir
2
Department of Mechanical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.
Department of Mechanical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.
This study aims to examine how friction stir welding parameters, such as welding speed and rotational rate, affect the microstructure, defects, and mechanical properties of AA7075-T651 aluminum alloy joints. It also assesses the relation of the defects and microstructure to the mechanical properties. Microstructural investigations using optical microscopy (OM) and scanning electron microscopy (SEM) indicated remarkable grain structure variations among the different welding zones. Especially, it was found out that the interface between welding nugget zone (WNZ) and thermo-mechanically affected zone (TMAZ) is a dominant determinant of the mechanical properties of joints. The importance of the interface comes from the fact that it is the most prone region to cracks, micro-cavities and tunneling defects. WNZ and TMAZ interfaces as well as their grain structures can be influenced by the heat generated from the friction between rotating tool and workpiece material. Therefore, coarser grain structures observed at the WNZ-TMAZ interfaces of the samples welded at higher rotational rates or lower welding speeds is due to the greater heat generated in such cases. Besides, microstructural variations in the weld zone affect the hardness and mechanical properties of weld joints. Thus, samples with coarse-grained structures display lower values of yield stress and microhardness.
http://scientiairanica.sharif.edu/article_20614_15dd388f40480800842fcd4fbd64c8dd.pdf
Friction stir welding
microstructure
mechanical properties
Welding defects
AA7075–T651 aluminum alloy
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2431
2440
10.24200/sci.2018.5707.1433
21012
An Analytical Study on Mechanical Behavior of Human Arteries – A Nonlinear Elastic Double Layer Model
Ali Reza Saidi
saidi@uk.ac.ir
1
Amin Jahanshahi
ajahanshahi@uk.ac.ir
2
Department of Mechanical Engineering, Shahid Bahonar university of Kerman
Department of Mechanical Engineering, Sirjan University of Technology, Sirjan, Iran
The focus of this article is on analytical solution for stress and deformation of human arteries. The artery is considered as a long homogeneous isotropic cylinder. Hyperelastic, incompressible stress-strain behavior is used by adopting a classical Mooney-Rivlin material model. The elastic constants of the arteries are calculated by using the reported results of biaxial test. The analysis is based on both single and double layer arterial wall models and. Radial and circumferential stress distribution on the minimum and maximum blood pressure is calculated. Variation of radii due to internal pressure within the arteries is found which is in a good accordance with the experimental results. The results containing the changes in diameter and thickness together with the stress distribution for both single and double layer models have been plotted. It is shown that the major difference between the single and double layer models is in their stress distributions. The circumferential stress distribution for different human’s ages is plotted which shows that the stress increases by increasing the age due to decreasing the flexibility of the artery. It is also shown that despite the artery’s inner layer is softer than the outer layer, the maximum stresses occur at the inner layer.
http://scientiairanica.sharif.edu/article_21012_11d94e467dfce807ce471ac33fbe595e.pdf
Human Artery
Analytical solution
Non-Linear Elasticity
Large Deformation
Biaxial Test
eng
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
2019-08-01
26
4
2441
2453
10.24200/sci.2018.4959.1008
20496
Size Effect Investigation on Lateral Vibrations of a Micro Drill Subjected to an Axial Load Using the Modified Couple Stress Theory
Abbas Rahi
a_rahi@sbu.ac.ir
1
Assistant Professor, Faculty of Mechanical &amp; Energy Engineering, Shahid Beheshti University, A.C., Tehran, Iran
E-mail: a_rahi@sbu.ac.ir
In this paper, the modified couple stress theory is used to capture size effect on dynamic behavior in a micro drill subjected to an axial load and a concentrated mass which is attached at its free end. Governing equations of lateral vibrations of the system and also associated boundary conditions are derived by obtaining the total kinetic and potential energies of the system and then using Hamilton’s principle. The Assumed Modes method has been applied to transform the governing partial differential equations into a set of infinite ordinary differential equations. Considering two terms of the equations, first two natural frequencies and also instability rotational speeds of the micro drill system are determined semi-analytically. Finally, numerical results of natural frequencies and also the threshold of instability speeds of the system are presented with respect to different values of the system parameters such as rotational speed, axial load, rotor length, concentrated mass, and also material length scale. The results show that the material length scale parameter is extremely effective on natural frequencies and also the threshold of instability speeds of the micro drill.
http://scientiairanica.sharif.edu/article_20496_4df6cad3f0926a856c65f6e9264c0782.pdf
Micro drill
modified couple stress theory
Size-dependency
free vibration
Axial load