Seismic characteristics of tunnel form concrete buildings with irregular plan
S.B.
Beheshti Aval
دانشیار، دانشکده مهندسی عمران، دانشگاه صنعتی خواجه نصیرالدین طوسی، تهران
author
V.
Mohsenian
کارشناس ارشد زلزله، دانشکده فنی و مهندسی، دانشگاه علم و فرهنگ، تهران
author
N.
Nikpour
کارشناس ارشد زلزله، دانشکده فنی و مهندسی، دانشگاه علم و فرهنگ، تهران
author
text
article
2015
per
The necessity of being regular in plan and elevation of concrete tunnel form buildings in spite of accelerating the manufacturing process and high quality assurance, following several limitations in architectural design and puts limits on the application of this system in areas where there is no possibility of symmetrical construction. Loss of R-factor in the current earthquake regulations is a major challenge in design of these structures. In this study, the seismic behavior of two-tunnel form structures with 5 and 10 stories with irregular floor plans is investigated and the demand/ capacity behavior factor, based on seismic demand and capacity of structure have been calculated respectively. The most distinctive feature of this study is multi-level definition of the behavior factors and their extraction with respect to seismic intensity, and accepted damage level as expected performance levels in designing structure. Moreover surveying literature showed that the lack of adequate study of seismic characteristic of this type of tunnel form buildings. Also, uncoupled frequency ratios and fragility curves are determined for studied models by incremental dynamic analysis (IDA). The results show high capacity of the system and flexible torsional behavior of the structures due to their irregularity. Since both structures are placed in the immediate occupancy performance level in design earthquake, it seems that criteria which necessitate tunnel form structures to be regular in plan, are strict and prudent for the studied structures.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
1
15
http://jsfm.shahroodut.ac.ir/article_552_d226fa5afb4af4de979080a586428f7d.pdf
dx.doi.org/10.22044/jsfm.2015.552
Adaptive fuzzy sliding mode control of a robotic manipulator in task-space using voltage control strategy
Mohammad Mehdi
Fateh
Professor of Control Eng., Univ. of Shahrood, Shahrood, Iran
author
H.
Asrari
کارشناس ارشد کنترل، دانشگاه شاهرود، دانشکده برق و رباتیک
author
S.
Khorashadizadeh
دکتری کنترل، دانشگاه شاهرود، دانشکده برق و رباتیک
author
text
article
2015
per
Actuators of robot operate in the joint-space while the end-effector of robot is controlled in the task-space. Therefore, designing a control system for a robotic manipulator in the task-space requires the jacobian matrix for transforming joint-space to task-space. Using an imprecise Jacobian matrix and the presence of uncertainties degrade the control performance. Uncertainties include the parametric uncertainty, unmodelled dynamics and external disturbance. In this paper, a novel decentralized adaptive fuzzy sliding mode control approach in the task-space is presented using the voltage control strategy. The control design is simple, free from model and robust agains uncertainties. These advantages are because of using voltage control strategy instead of commonly used torque control strategy. The case study is an articulated robot manipulator driven by permanent magnet DC motors. The stability analysis, simulation results and comparison with a torque based control method are presented to verify the effectiveness of the control method. Simulation results show the effectiveness of proposed control method.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
17
26
http://jsfm.shahroodut.ac.ir/article_553_589253fd2bb1e5ccd0d3190478e74f57.pdf
dx.doi.org/10.22044/jsfm.2015.553
Robust and Adaptive Controller for Wind Turbine Blade Testing Machine
Hassan
Ghorashi
دانشجوی دوره دکتری، دانشگاه فردوسی مشهد،گروه مهندسی مکانیک
author
Behnam
Moetakef Imani
استاد، دانشگاه فردوسی مشهد، گروه مهندسی مکانیک
author
text
article
2015
per
The wind turbine blades are made of composite materials and subjected to severe operational loadings. The complexity of composite materials behavior along with variable amplitude loadings dictates the need for experimental setups which can conduct real part test as close as possible to in service loadings. In this regard, wind turbine blade manufacturers are obliged to perform standard ultimate and fatigue tests on their products. In this research a cost effective Blade Testing Machine (BTM) is proposed which is capable of conducting ultimate static and fatigue tests according to wind turbine blade standards. A new control unit is designed and implemented to track fatigue block loading in the frequency range of 1 to 3Hz. The main focus is on designing a controller to perform desired block loading fatigue tests with proper performance. PI and robust feedback controllers are designed and analyzed. Due to the poor robust performance, an adaptive feed forward controller is proposed based on the gain scheduling algorithm. The proposed robust controller compensates un-modeled high frequency dynamics and rejects measurement noises while the adaptive controller compensates low frequency uncertainty and improves reference tracking. Extensive experimentations in the desired frequency range confirm proper performance of the developed controller.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
27
38
http://jsfm.shahroodut.ac.ir/article_554_f2d2b02d009ef7f4a72c041ea21f9af2.pdf
dx.doi.org/10.22044/jsfm.2015.554
Modeling the spall in impact of metalic plates, considering the effects of temperature, strain rate and damage
Mostafa
Baghani
Assistant professor in school of mechanical engineering, college of engineering, University of Theran
author
MohammadReza
Zakerzadeh
Assistant professor, School of mechanical engineering, college of engineering, University of Tehran
author
Majid
Baniassadi
School of Mechanical Engineering, College of Engineering, University of Tehran
author
text
article
2015
per
In this article, the high strain rate, dynamic plastic response of materials in the standard plate impact test is numerically studied. To get the closest results to the experimental data available in the literature, different types of hardening as well as dynamic fracture models are employed. With the aid of this standard plate impact test, one can verify the new models in the ideal condition of uniaxial-strain cases. To properly model this test, to discrete the field, von-Neumann Finite-Volume method is utilized. Jonson-Cook and perfectly elastoplastic hardening models as well as the Zerilli-Armstrong model are used beside the dynamic fracture model of modified Tuler-Butcher, to predict the spall phenomenona. In this work, the impact of two plates (the flyer plate and the target plate) is analyzed. Results of the simulation is compared with the experimental data as well as the other numerical results reported in the literature. The results of the present work are in a better correspondence comparing to the experimental data. Among investigated models, employing JC constitutive model, accompanying with the modified Tuler-Butcher fracture model and Steinberg model for the elastic modulus gives the most accurate results compared to other model combinations.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
39
50
http://jsfm.shahroodut.ac.ir/article_555_b83bc4e0b20e48a3c870550d2d15f473.pdf
dx.doi.org/10.22044/jsfm.2015.555
Side panel of B-Class body in white vehicle design and side crash finite element simulation
Mahammad hasan
Shojaie fard
استاد، مهندسی مکانیک طراحی کاربردی، دانشگاه علم و صنعت ایران، تهران
author
Abolfazl
Khalkhali
استادیار، مهندسی مکانیک طراحی کاربردی، دانشگاه علم و صنعت ایران، تهران
author
Rouzbeh
Kalantari
دانشجوی کارشناسی ارشد، مهندسی خودرو، دانشگاه علم و صنعت ایران، تهران
author
text
article
2015
per
Target function in vehicle crash, is about the suitable deformation of vehicle body structure in the case of do not harm occupant’s space. As a consequence the vehicle body structure should be deformed to absorb the impact’s energy and decrease the transmitted forces to occupants. In this paper at design process the vehicle’s body in white has been simulated in CATIA software firstly, and then the element has been created by the Hyper mesh pre-processor software and finally in Pam Crash software, after introducing appropriate materials, standards joints and contacts between vehicle’s parts, and then loads has been created by initial velocity for able to deform barrier toward side panel of vehicle. The vehicle body structure is designed in Vehicle Research Center, based on the style of B-class vehicle platform’s product and the analysis results of this paper is part of new product development process of national platform’s project. As a result, the requirements out puts such as displacement, velocity, acceleration, and energy absorption and section forces have been extracted. After all the results has been compared with the targets which are predicted. Then the suitable thickness for B-pillar illustrated based on the out puts which are extracted.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
51
64
http://jsfm.shahroodut.ac.ir/article_556_e469f5cda4c37b5ddc8a16b41ffc5d83.pdf
dx.doi.org/10.22044/jsfm.2015.556
One-Dimensional Design of Centrifugal Compressor of a Turo-shaft Engine with Optimization of 90-Degree Bend Duct between Radial and Axial Diffuser
M.
Nili-Ahmadabadi
استادیار، دانشگاه صنعتی اصفهان، دانشکده مکانیک
author
H. M.
Maleki
کارشناس ارشد، دانشگاه صنعتی اصفهان، دانشکده مکانیک
author
text
article
2015
per
In this paper, one-dimensional design of centrifugal compressor with inverse design of 90-degree bend duct between radial and axial diffuser is accomplished using an iterative method. In the design procedure, all overall dimensions of the centrifugal compressor including impeller, vanned radial diffuser, 90-degree bend duct and axial diffuser are computed. To evaluate the results, after the geometry modeling and grid generation, 3-D flow field in the whole compressor are numerically analyzed using CFX software. The numerical simulation shows that there is a high loss region through the 90-degree bend between the radial and axial diffuser because of its high curvature. In order to reach a minimum loss in the 90-degree bend duct, the aerodynamic design of the 90-degree bend duct is carried out using an inverse design method. At the first step, the shape modification capability of the 90-degree bend duct is evaluated by linking up the Ball-Spine inverse design algorithm and CFX software. Then, the geometry is modified by improving the hub and shroud pressure distribution and applying it to the inverse design code. Finally, the designed compressor with the modified 90-degree bend duct is analyzed. The results show that, the total pressure ratio and overall efficiency increases about 3 and 4 percent, respectively.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
65
77
http://jsfm.shahroodut.ac.ir/article_557_458859535b178f85d4e7caf39971a3a6.pdf
dx.doi.org/10.22044/jsfm.2015.557
Adaptivity in isogeometric analysis of structures
using error estimation methods based on stress recovery
Aboozar
Mirzakhani
استادیار، دانشکده فنی و مهندسی واحد شاهرود، دانشگاه آزاد اسلامی، شاهرود، ایران
author
B.
Hassani
استاد، گروه مکانیک، دانشگاه فردوسی مشهد
author
Ahmad
Ganjali
استادیار، دانشکده فنی و مهندسی واحد شاهرود، دانشگاه آزاد اسلامی ، شاهرود، ایران
author
text
article
2015
per
In this research, for the first time, the net of control points in the isogeometric analysis has been improved by employing an error estimator based on a stress recovery method. First, an error estimation algorithm based on stress recovery is used to obtain the energy norm for each element. Then, artificial rods are defined between control points and the estimated values of errors in the control points located at the vicinity of a typical point is assigned to each rod as a thermal gradient. Now, by analyzing this hypothetical truss problem under temperature changes a new arrangement of control points and consequently the knot vectors can be obtained. Repeating this process in isogeometric analysis will lead to a better distribution of errors in the domain of the problem and results in an optimal net of control points to calculate the integrals. To evaluate the efficiency of this method, the results of modeling and analysis of two elasticity problem is presented. The obtained results show that this innovative approach has a good performance and can be employed for reducing the analysis errors.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
79
91
http://jsfm.shahroodut.ac.ir/article_574_dc5f12323c0c46913cac162488fed789.pdf
dx.doi.org/10.22044/jsfm.2015.574
Effect of Grid Configuration on Buckling and Vibration Response of Composite Grid Plates
Amir
Ehsani
دانشجوی دکتری، مهندسی مکانیک، دانشگاه فردوسی مشهد
author
J.
Rezaeepazhand
استاد، مهندسی مکانیک، دانشگاه فردوسی مشهد
author
text
article
2015
per
Abstract The present paper investigates the effects of grid configuration on the buckling and vibration behavior of grid structures. Hence, four similar simply supported plates with equal weights and different grid patterns (Ortho grid, Angle grid, Iso grid and orthotropic grid) are considered. Using, bending stiffness matrix, the buckling load and free vibration frequency of the plates are computed. To investigate the effects of the grid orientation on the mechanical behavior, the orientation of the grids is changed in the plates. The Rayleigh–Ritz method is applied to obtain the axial and shear buckling loads and free vibration frequencies. The results are compared with an angle-ply laminated composite plate with similar in-plane dimensions and equal weight. The results show, changing the grid pattern and orientation, will affect bending stiffness and consequently, significantly change the buckling and vibration behaviors of the grid plates. Keywords: Grid Structures, Buckling Load, Free Vibration Frequency, Composite materials
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
93
100
http://jsfm.shahroodut.ac.ir/article_575_b4a2634e4ca6d93828aaa1036f541b22.pdf
dx.doi.org/10.22044/jsfm.2015.575
Evaluation of the stress intensity factor for circumferential cracked cylinders under non-classical thermal shock
O.
Asemi
دانشجوی کارشناسیارشد، دانشکده مکانیک، دانشگاه شاهرود
author
M. B.
Nazari
استادیار، دانشکده مکانیک، دانشگاه شاهرود
author
text
article
2015
per
In this paper, the stress intensity factor for a circumferential crack in a thick-walled cylinder is derived analytically and numerically which is subjected to the non-Fourier (hyperbolic) thermal shock. The uncoupled thermoelasticity governing equations for an uncracked cylinder are solved analytically. The weight function method is implemented to obtain the stress intensity factor. The non-dimensional hyperbolic heat equation is solved using finite Hankel transform and separation of variables method. Results show the different behavior of the crack under hyperbolic thermal shock. For relatively short cracks, the maximum stress intensity factor of Fourier and hyperbolic models is closed. But for longer cracks, the stress intensity factor of the hyperbolic model is significantly greater than Fourier model. Moreover, the maximum stress intensity factor in hyperbolic model occurs for a crack the peak of stress wave reaches to its tip. According to the results, assumption of adequate heat conduction model for structure design under transient thermal loading is critical.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
101
112
http://jsfm.shahroodut.ac.ir/article_576_d4a44ab5e10b4cda4df4a58f438dd19e.pdf
dx.doi.org/10.22044/jsfm.2015.576
A collaborative simulation for active flow-induced vibration control of a circular cylinder
Amir hossein
Rabiee
iran university of science and technology
author
Miad
Jarrahi
کارشناس ارشد، دانشکده مهندسی مکانیک، دانشگاه علم و صنعت، تهران
author
Seyyed Mohammad
Hasheminejad
استاد، دانشکده مهندسی مکانیک، دانشگاه علم و صنعت، تهران
author
text
article
2015
per
In this paper a collaborative simulation between Matlab/Simulink and Fluent softwares is done to active control of an elastically mounted circular cylinder, free to move in in-line and cross-flow directions. The control goal is reduction of the two-dimensional vortex-induced vibrations (VIV) of cylinder. The natural oscillator frequency is complemented with the vortex shedding frequency of a stationary cylinder. A parallel simulation scheme is realized by linking the PID controller employed in Matlab/Simulink to the plant model constructed in Fluent, aiming at calculation of the control force necessary for total annihilation of the transverse cylinder vibrations. The simulation results reveal the high performance and effectiveness of the adopted control algorithm in diminishing the VIV of elastic cylinder. Once the control algorithm is turned on, there is a extreme reduction in the transverse and in-line cylinder oscillation amplitudes as well as lift and drag coefficients values. In particular, it is observed that the coalesced vortices in the far wake region of the uncontrolled cylinder are seprated and displaying wake vortices of weaker strengths.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
113
124
http://jsfm.shahroodut.ac.ir/article_577_81767c51b7a3b521e88d975aa785b76e.pdf
dx.doi.org/10.22044/jsfm.2015.577
Flexural Behavior of High Performance Cementitious Composites Reinforced With Hooked Steel Fibers
E.
Zeighami
دانشجوی دکتری مهندسی سازه، دانشگاه شاهرود
author
F.
Jandaghi Alaee
دانشیار دانشکده عمران و معماری، دانشگاه شاهرود
author
M.
Jamee
کارشناس ارشد مهندسی سازه، دانشگاه شاهرود
author
text
article
2015
per
This research investigates the mechanical properties of High Performance Fiber Reinforced Cementitious Composites (HPFRCC) with two volume fractions of fiber (1% and 2%). Hooked steel fibers were incorporated into a mortar matrix with 49 MPa compressive strength. Four point bending tests were carried out according to ASTM C1018 and ASTM C1609 Standards. Parameters such as: load carrying capacity (equivalent bending strength), energy absorption capacity (toughness) , deflection, and cracking patterns (number of cracks), were evaluated to investigate the flexural behavior of two HPFRCCs. It was found that the increase in fiber volume fraction not only promotes the flexural behavior from deflection softening to deflection hardening, but also improves all mechanical properties. Deflection capacity gains the most from deflection hardening behavior. Besides, substantial increase in load carrying capacity and energy absorption is also achieved. It was observed that HPFRCC with deflection hardening behavior exhibits multiple cracking in the post cracking behavior.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
125
136
http://jsfm.shahroodut.ac.ir/article_581_772a1313dac59db756f0fc0077ebf56e.pdf
dx.doi.org/10.22044/jsfm.2015.581
Optimization of the Initial Blank Shape in hydroforming Double-Stepped Parts
R.
Mousavipoor
استادیار، دانشکده مهندسی مکانیک، دانشگاه صنعتی نوشیروانی بابل
author
A.
Gorji
دانشجوی کارشناسی ارشد، دانشکده مهندسی مکانیک، دانشگاه صنعتی نوشیروانی بابل
author
M.
Bakhshi
استاد، دانشکده مهندسی مکانیک، دانشگاه صنعتی نوشیروانی بابل
author
text
article
2015
per
Hydroforming is a suitable solution method for removing complex parts` forming problems such as stepped rectangular parts with uniform thickness distribution and higher quality .Optimization of the initial dimensions of the sheet in the hydroforming process has a large effect on producing products with lower price but higher quality. In this paper, optimizations of the sheet initial dimensions for two different geometries have been studied through sensitivity method. The same curves of formed sheet and final sheet has been seen at the end of the optimization step. In the optimization step, the ABAQUS software has been used to perform the simulation process. The examined parameters in this study are the effect of optimizing of the sheet initial dimensions on the thickness distribution and the maximum forming pressure. It has been concluded that the maximum thinning occurring in the punch radius and in the wall region is reduced by optimizing of the sheet initial dimensions at each stage. It must be mentioned that, investigating the maximum forming pressure shows that by the optimization step, material flow improves so, the maximum pressure will decrease.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
137
149
http://jsfm.shahroodut.ac.ir/article_582_1979ae69eae4a644c1e114253ac87997.pdf
dx.doi.org/10.22044/jsfm.2015.582
Effect of SiO2/Al to increase microcantilever infrared detectors sensitivity and compare with Si3N4/Au
H.
Abdollahi
استادیار برق-الکترونیک، دانشکده برق، دانشگاه علوم و فنون هوایی شهید ستاری
author
F.
Samaeifar
دانشجوی دکتری برق- الکترونیک، دانشگاه صنعتی مالک اشتر
author
A.
Haghnegahdar
employe
author
text
article
2015
per
In this paper, a high sensitive uncooled microcantilever infrared detector is designed and simulated. The detector consists of absorbing, bi-material and isolator regions, and has two layers suspended structure made of Silicon dioxide (SiO2) and Aluminum (Al) with a 1µm and 200nm thickness, respectively. Absorbing was increased by reflecting IR flux in absorber layer by coting Al under it, and bending of detector was increased by elongating bi-layer legs in absorber layer. Finite element analysis method was used to simulate thermal and mechanical behaviors. Temperature and displacement changes at the end of tip detector (farthest point from the support leg) were 3.651°C and 940nm, correspondingly, at the 100pW/µm2 boundary conditions for constant heat flux on the absorber. In this detector, the calculated heat transfer coefficient, power, temperature, body temperature, displacement and thermo-mechanical sensitivity are 9.7×10-3, 667.2mW-1, 32.8K/(pW.µm-2), 2.75nm/K, 9.34nm/(pW.µm-2) and 284nm/K, respectively. Those parameters are improved 16, 41, 17, 41, 41 and 2.38 times compared to the same Si3N4/Au detector.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
151
163
http://jsfm.shahroodut.ac.ir/article_583_d01970ac629667af03ac5d0a8dcb0c20.pdf
dx.doi.org/10.22044/jsfm.2015.583
Experimental Study on Heat Transfer of Water/TiO2 Nanofluid in a Straight Tube with Twisted Tapes at Constant Wall Temperature
A.
Houshmand
دانشجوی کارشناسی ارشد، دانشگاه صنعتی اصفهان، دانشکده مهندسی مکانیک
author
A.
Sedaghat
دانشیار، دانشگاه صنعتی اصفهان، دانشکده مهندسی مکانیک
author
M.R.
Salimpour
دانشیار، دانشگاه صنعتی اصفهان، دانشکده مهندسی مکانیک
author
A.
Zargoushi
کارشناس ارشد هوافضا، شرکت پالایش گاز ایلام
author
I.
Mohseni
کارشناس شرکت پالایش گاز ایلام
author
text
article
2015
per
One of the methods for increasing convective heat transfer is by utilizing twisted tapes in heat exchangers which increases surface to volume of heat transfer and also improves augmentation of fluid flow. In the past research, the combined effects of nanofluid and twisted tapes were not studied. In this research paper, the heat transfer performance of water/TiO2 nanofluid in a heat exchanger with twisted tape insert is evaluated. The studied parameters are pitch of twisted tape, mass flow rate, and concentration of nanofluid. The constant wall temperature is employed and the range of Reynolds number is from 3000 to 22000. Experiments were performed for the volumetric concentration range of . The results confirm that heat transfer was enhanced by adding nano-particles. Also, the results were repeated by adding twisted tapes with lower pitches. The maximum heat transfer appraisal indicates a 103.45 percent increase for the concentration of 0.5 and the insert of the twisted tape with (H/D=5).
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
165
172
http://jsfm.shahroodut.ac.ir/article_584_1ab170e59b0c9cd0c84bf722953d7318.pdf
dx.doi.org/10.22044/jsfm.2015.584
Experimental investigation of Boundary Layer on an Oscillating (Pitching) Supercritical Airfoil in Compressible Flow Using Multiple Hot Film Sensors
N.
Fallahpour
محقق، مهندسی هوافضا، دانشگاه امیرکبیر، تهران
author
A. A.
Haghiri
دانشجوی دکتری، مرکز تحقیقات آیرودینامیک قدر، دانشگاه امام حسین(ع)، تهران
author
M.
Mani
استاد، مرکز قطب محاسبات عددی، مهندسی هوافضا، دانشگاه امیرکبیر، تهران
author
M. H.
Kalantary
محقق، مرکز تحقیقات آیرودینامیک قدر، دانشگاه امام حسین(ع)، تهران
author
text
article
2015
per
Aerodynamic characteristics of an airfoil are highly affected by the behavior of the boundary layer. This behavior, and the related phenomena, depends on such different parameters as Reynolds number, angle of attack, unsteady motion, local Mach number,and compressibility. In this paper a series of static and dynamic (pitching motion) tests at pre stall angle of attacks were performed in a high speed wind tunnel to study the steady and unsteady behavior of the compressible boundary layer on a Supercritical Airfoil. Some static tests were performed at Mach numbers of 0.4, and 0.5 whit maximum angles of attack of 6⁰ and oscillation amplitudes of 1⁰ and 3⁰ and oscillation frequencies of 3 and 6Hz in Sinusoidal pitching motions. Measurements involved pressure distribution and shear stress variations using multiple hot film. The effects of compressibility, free stream Mach number, mean angle, reduced frequency and oscillation amplitude were investigated. Results show delay in transition in pitching motion with respect to steady conditions, and asymmetry between transition and relaminarization during pitching motion.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
173
184
http://jsfm.shahroodut.ac.ir/article_585_531e900195e7de0a0956a7f83a5200db.pdf
dx.doi.org/10.22044/jsfm.2015.585
Investigating the ground effect on aerodynamic characteristics of airfoil in oscillatory flow
A.
Heydary
استادیار، مرکز تحقیقات راهبردی انرژی و توسعه پایدار، واحد سمنان ، دانشگاه آزاد اسلامی، سمنان، ایران
author
Ahad
Abedini Esfahlani
استادیار، گروه مکانیک، واحد سمنان ، دانشگاه آزاد اسلامی، سمنان، ایران
author
text
article
2015
per
When a wing is placed near a wall surface, two phenomenons occur. The lift force is increased and the drag force is reduced which will finally lead to high lift to drag ratio. This phenomenon is known as the effect of surface or ground effect. In this study, a two dimensional simulation has been developed to investigate the effect of oscillatory flow around a NACA 4412 airfoil near a wall surface. The effect of wing distance from the surface, the amplitude and frequency of the oscillating flow have been analyzed on the aerodynamic coefficients. The lift coefficient is increased due to the air compression and trapping between the underside of wing and the wall. The drag coefficient is reduced because of wall jet at the trailing edge which increases the back pressure. According to the results obtained in the unsteady case, by reducing the amplitude of free-stream velocity, the lift coefficient is enhanced and the drag coefficient is reduced. Also the drag coefficient decreases due to increasing frequency of the oscillating flow.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
185
196
http://jsfm.shahroodut.ac.ir/article_588_7e9236c1fddea6fded8d274fc9dfc754.pdf
dx.doi.org/10.22044/jsfm.2015.588
Experimental investigation of thermal structure and convection heat transfer from an array of perforated fins with one cross opening
M. M.
Tavakol
دانشگاه آزاد اسلامی واحد شیراز، بخش مهندسی مکانیک، دانشکده مهندسی، شیراز، ایران
author
H.
Saadat
دانشگاه آزاد اسلامی واحد شیراز، بخش مهندسی مکانیک، دانشکده مهندسی، شیراز، ایران
author
M.
Yaghoubi
استاد دانشکده مکانیک، دانشگاه شیراز
author
text
article
2015
per
In this study attempt is made to study convection heat transfer from a new type of perforated fins with cross perforations using experimental measurement. Using the present experimental studies, thermal performance of such perforated fins are determined and discussed. Comparison of convection heat transfer from the present array of perforated fins with the previous studies of perforated fins illustrates better heat transfer performance of the new arrangement and its higher convection heat transfer coefficient. Quantitatively, using the present fin arrangement increases the heat transfer coefficient and the fin effectiveness for about 50% with respect to the previous reported perforated arrangement. Comparison of the fins surface temperature measured by thermograph imager depict higher surface temperature for the target fin with respect to other studied perforated arrangements. Futhermore, the present experimental results can be used as bench case to validate numerical simulations of thermal structure and temperature distribution around the perforated fins.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
197
208
http://jsfm.shahroodut.ac.ir/article_589_ba44b402ef33bb253e7f83276f34f545.pdf
dx.doi.org/10.22044/jsfm.2015.589
Simulation of the Convective Heat Transfer in a Nanofluid Composed of Water and FMWNT Carbon Nanotubes in a Microchannel Subjected to a Magnetic Field in the Slip Flow Regime
A.M.
Taghipour
M.Sc. Student, Department of Mechanical Engineering, Faculty of Engineering, Najafabad Branch,
Islamic Azad University, Najafabad, Isfahan, Iran.
author
A.
Karimipour
استادیار، گروه مهندسی مکانیک، دانشکده فنی و مهندسی، واحد نجف آباد، دانشگاه آزاد اسلامی، نجف آباد، اصفهان، ایران.
author
text
article
2015
per
The forced convective heat transfer of a nanofluid composed of water and FMWNT nano-particles in a two-dimensional microchannel was numerically investigated. The bottom wall of the microchannel was fully insulated. The upper wall was insulated only at the entrance, the rest of the upper wall was subjected to a constant heat flux. A constant magnetic field with a strength of B0 was also applied on it. The slip velocity boundary condition was considered along the walls of the microchannel. Navier-Stokes equations were discretized and then solved numerically using a computer code. Results were presented in the form of velocity profiles, temperature, and the Nusselt number. In the present work, the effect of magnetic field on the slip velocity of the fluid adjacent to the microchannel wall was studied for the first time. The use of a nanofluid composed of water and carbon nanotubes (FMWNT), as the working fluid in a microchannel, could be another novelty of the present study. It was seen that stronger magnetic field corresponded to more amount of slip velocity.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
209
222
http://jsfm.shahroodut.ac.ir/article_590_3ad295596f378f50cd359d09e0968f35.pdf
dx.doi.org/10.22044/jsfm.2015.590
Thermodynamics modeling of heat and vapor transfer in the shell- and- tube membrane humidifier: a gas- to- gas type
M.
Baroutie Ardestanie
دانش آموخته کارشناسی ارشد مهندسی مکانیک، دانشگاه بیرجند، بیرجند
author
H.
Hassanzadeh
استادیار مهندسی مکانیک، دانشگاه بیرجند، بیرجند
author
Y.
Ahmadi Brogani
دانشیار مهندسی مکانیک، دانشگاه بیرجند، بیرجند
author
text
article
2015
per
Water management plays an important role in the performance of polymer fuel cells. Humidifying the reactant gases before entering the fuel cell and adjusting the wet content are among the most important ways for water management. In this study, a membrane humidifier of a gas-gas type has been modeled. The governing equations included mass conservation as well as energy and vapor transfer equations solved by numerical methods and validated by experimental data available in relevant scientific articles. Then, the effect of operating parameters such as flow rate, temperature and relative humidity of the inlet gases and geometric parameters such as thickness, diameter and number of tubes on performance of humidifier have been studied. The results show that, in the same inlet mass flow rate in both wet and dry side, outlet wet gas temperature, heat transfer rate and vapor transfer rate in the counter flow are greater than the parallel flow, therefore the results for this humidifier are provided. In counter flow humidifier, by increasing inlet dry gas temperature, the rate of heat transfer and vapor transfer rate will decrease and also increasing relative humidity of inlet dry gas will reduces the vapor transfer rate and has negligible impact on outlet wet gas temperature and heat transfer rate. Finally, increasing the thickness, length and number of membrane tubes can have negligible impact on the heat transfer rate as well.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
223
236
http://jsfm.shahroodut.ac.ir/article_591_79bff882d9276ebd8d2d5c1cc0574e0a.pdf
dx.doi.org/10.22044/jsfm.2015.591
Numerical Study of Carbon Monoxide and Temperature Distribution in Tunnel Fires Employing Air Curtain
A.
Sojoudi
کارشناسی ارشد مهندسی مکانیک، دانشگاه صنعتی شریف
author
H.
Afshin
استادیار مهندسی مکانیک، دانشگاه صنعتی شریف
author
B.
Farhanieh
استاد مهندسی مکانیک، دانشگاه صنعتی شریف
author
text
article
2015
per
Tunnel fires are responsible for many fatalities in recent decades and this field of study has received an extensive effort by researchers. Most of deathes in these events are attributted to inhalation of toxic gases such as CO rather than high temperature of fire which causes 15 to 25 percent of deaths. Removal of the generated plume or its dilution and reduction of high temperature are the great interest of investigators. In the current study, a numerical test has been performed on a rectangular cross section tunnel of 600m length, 10m width and 7m height with a pool fire at the middle part using FDS5.5. Obtained results were compared with previous theoretical and experimental results. After satisfying a good agreement with prior results, single and couple air curtains were used to investigate their efficiency on dilution of the amount of toxic gases and high temperature. Results show that double air curtain is better than a single one and can decay the relevant amounts of CO and temperature below the standard values.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
235
246
http://jsfm.shahroodut.ac.ir/article_716_08e1570477766f7677bfcba1d70c9ef3.pdf
dx.doi.org/10.22044/jsfm.2015.716
Modeling of Microfluidic Capillary Pressure in Microstructures by Surface Evolver Software
H.
Saffari
دانشیار، دانشکده مهندسی مکانیک، دانشگاه علم و صنعت ایران
author
A. M.
Gheitaghy
دانشجوی دکتری ، دانشکده مهندسی مکانیک، دانشگاه علم و صنعت ایران
author
A.
Rahimi
کارشناس، دانشکده مهندسی مکانیک، دانشگاه علم و صنعت ایران
author
text
article
2015
per
The topology, geometry and contact angle of microstructures play a crucial role in determining their capillarity performance. In the present study, the capillary pressure of liquid in microstructure topologies , viz., sphere, circular and square pillars has been investigated numerically. In order to estimate the capillary pressure as the change in interfacial energy per unit volume, the shape of liquid interface in the microstructures are determined using a surface-energy minimization algorithm by coding in a software. Capillary pressure of microspheres in different contact angles are verified with comparision to other results. Capillary pressure presented versus non-dimensional geometrical parameters characterizing the microstructures and the contact angle between the liquid and solid. Based on these performance parameters, packed spheres on a surface are identified to be the most efficient microstructure geometry for capillarity. Also, square pillars are shown to have higher capillary pressure compared with hexagonal arrays of circular pillars with same solid fraction and pitch. The obtained results from microfluidic capillary pressure in microstructures can be used in different science such as agricultural, textile and polymer, petroleum and heat transfer.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
247
255
http://jsfm.shahroodut.ac.ir/article_717_5612a1eda22bf51956bc22b29c7eb37f.pdf
dx.doi.org/10.22044/jsfm.2015.717
Investigation on the effect of using phase change materials in the wall of solar chimney on natural ventilation of a room
A.
Goodarzi
کارشناس ارشد مکانیک، دانشگاه گیلان، رشت
author
A.
Haghighi
استادیار، گروه مکانیک، دانشگاه گیلان، رشت
author
text
article
2015
per
In this study, the usage of phase change materials (PCMs) in the wall of a solar chimney has been investigated analytically and numerically. Effective heat capacity model has been employed to simulate the phase change phenomenon in the PCM. The conservation energy equations for the solar chimney and the storage wall have been written in an unsteady form and solved for 120 hours with a self-developed code. The results show that the latent energy storage provides the 24-hour ventilation by the system even with a poor solar intensity of 350 W/m2. Also it is observed that the usage of PCM instead of concrete in the storage wall reduces the thickness of the wall from 200 mm to 40 mm and also the mass flow rate fluctuation in the channel. In this study, also the effects of the thermophysical properties and the thickness of the PCM on the performance of the system (air change per hour) have been investigated. It is observed that for a particular flux, PCM with lower melting temperature provides more latent heat storage but because of rising surface temperature of the PCM after melting, more fluctuation in the flow rate of the channel is produced. Also the results show that the increasing of the thermal conductivity and the heat of fusion of the PCM for a particular input heat flux, up to specified limit causes better performance of the system but after that the increasing of these parameters, has no influence on the performance of the system.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
257
269
http://jsfm.shahroodut.ac.ir/article_718_b3f3e2bf9fe95005fc76629621ae45c3.pdf
dx.doi.org/10.22044/jsfm.2015.718
Numerical simulation of the dynamic and thermodynamic an MHD micropump by independently changing the lengths of electric and magnetic fields
M.
Dallakehnezhad
دانشجوی دکتری، مهندسی مکانیک، دانشگاه بیرجند، بیرجند
author
Seyed A.
Mirbozorgi
دانشیار، مهندسی مکانیک، دانشگاه بیرجند، بیرجند
author
text
article
2015
per
In this paper the effect of electric and magnetic-field lengths to change independently is simulated on the temperature distribution and flow velocity of a magnetohydrodynamic micropump considering the lateral electromagnetic diffusive regions. The geometry of MHD flow is a two-dimensional channel between two parallel plates and governing equations of both flow and electromagnetic fields have been solved using the finite volume numerical method. The numerical results show that by applying the temperature allegiance of fluid properties, for a flow in a channel of 1000 mm2 cross-section, magnetic field intensity 0.025 Tesla and electric field strength 20 volt/mm, the flow rate reaches 250 mLit/s when the electric and magnetic field length are changed. However in the case of independent change of magnetic field length, the mean cup temperature from 25 0C at entrance, reaches to 45 0C at exit and in the case of independent change of electric the exit temperature reaches to 35 0C. In the situation of constant properties, the maximum flow rate reaches to 70 mLit/s, while the mean cup temperature reaches to 140 0C for the case of independent change of magnetic field length and 50 0C for the case of independent change of electric field length.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
271
287
http://jsfm.shahroodut.ac.ir/article_719_b895c0e2c0043e3c87398e374a67c462.pdf
dx.doi.org/10.22044/jsfm.2015.719
Analytical and numerical solution for steady-state differential conduction equation in a right triangular plate with constant-temperature boundary condition
Sh.
Ghazanfari Holagh
university of tabriz
author
F.
Talati
university of tanriz
author
text
article
2015
per
This article presents, in general, means to acquire analytical and exact solutions for steady-state partial differential conduction equation, and consequently finding the exact distribution of temperature in irregular geometries with one or more edges unparalleled with Cartesian axes(with various boundary conditions) . To get to this goal and to clarify, one specific problem, a steady-state right triangular plate with the right angle on the origin and with constant-temperature boundary conditions has been considered. In the analytical technique used, the importance and strength of complex variables and their applications, such as complex transformations, especially the Schwarz–Christoffel transformation is clearly visible. Finally, to validate the analytical solution acquired, the problem has been solved using the finite element method in COMSOL Multiphysics 5.0. The results has been compared, and the correspondence has confirmed the analytical solution.Keywords: conduction equation ; Cartesian coordinate system ; analytical solution ; irregular geometry ; right triangle ; Schwarz–Christoffel transformation
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
289
302
http://jsfm.shahroodut.ac.ir/article_720_39e4830a5598e9605bf70738713c82dc.pdf
dx.doi.org/10.22044/jsfm.2015.720
Experimental and Numerical Investigation on the Parameters of Ventilated Super Cavitation around 30 degree Conical Cavitator
Seyyed M.
Javadpour
Sistan &amp; Baluchestan
author
S.
Farahat
استاد ، مهندسی مکانیک، دانشگاه سیستان و بلوچستان
author
H.
Ajam
دانشیار ، مهندسی مکانیک، دانشگاه فردوسی مشهد
author
M.
Salari
دانشیار، مهندسی مکانیک، دانشگاه امام حسین (ع)
author
A.
Hossein Nezhad
دانشیار ، مهندسی مکانیک، دانشگاه سیستان و بلوچستان
author
text
article
2015
per
In present study, ventilated super-cavitating flow around cavitator was studied experimentally. In this stage, a 30-degree cone cavitator was tested in open water tunnel. The fluid flow velocity in the test section was between 24 to 37 m/s and rate of injection was constant. Then, ventilated super-cavitating flow was simulated based on condition inlet and injection. Finally, numerical results compared against existing experimental data. Also the 3D multiphase fluid flow over the cavitators within the test section are modeled and analyzed numerically by solving the corresponding governing equationsusing finite volume method and mixture model. Good agreement was observed in two-way comparison. Finally, effect of significant parameters .i.e. cavitation number, inlet velocity on drag coefficient were studied. The results indicate that the maximum cavity diameter and its length increase as the cavitation number decreases. Also, with a decrease velocity flow, the rate of cavity length changes is reduced. the cavity length variation is similar to the results of cavity diameter.
Journal of Solid and Fluid Mechanics
Shahrood University of Technology
2251-9475
5
v.
3
no.
2015
303
314
http://jsfm.shahroodut.ac.ir/article_721_77b0a7989aba103200552adf3edd6c5f.pdf
dx.doi.org/10.22044/jsfm.2015.721