IFC
text
article
2017
per
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
0
0
http://mme-old.modares.ac.ir/article_17613_d21f2da3ae50f6643ba0af3b832d691c.pdf
Online proportional myoelectric control of a humanoid shoulder motions using electromyogram signals
Armin
Ehrampoosh
School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
author
Aghil
Yousefi-Koma
School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
author
Moosa
Ayati
School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
author
Seyed Saeid
Mohtasebi
School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
author
text
article
2017
per
This paper proposes a two phase strategy for proportional myoelectric control of Surena 3 humanoid robot which benefits from strength of two common myoelectric control methods, Pattern recognition base and simultaneous proportional control, for improving joint angle estimation. The aim of this research is to present a human-robot interface to create a mapping between electrical activities of muscles known as electromyogram (EMG) signals and kinematics of corresponding motion. First phase concerns with motion classification using Quadratic Discriminant Analysis (QDA) and Majority Voting (MV). Several common motion classification algorithms and feature vectors including time domain and frequency domain futures were investigated which lead to QDA and a superior feature vector with more than 97% classification accuracy. The second phase concerns with continuous angle estimation of shoulder joint motion classes using Time Delayed Artificial Neural Network (TDANN) with overall accuracy of 90% R2. QDA serves as a high level controller which decides between four TDANN correspond to each shoulder motion classes. QDA and TDANN models trained with several sets of offline data and were tested with online dataset. Online and offline data estimation accuracy and model robustness against disturbances show a significant improvement compared to similar methods in this field.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
1
12
http://mme-old.modares.ac.ir/article_17331_9b9fdf8b14bb8cc66190dbaa2f6ad5a2.pdf
Numerical Analysis on the Effects of Impeller Geometry Parameters for a Centrifugal Pump in Reverse Operation
Dariush
Mohammadipour
School of Mechanical Engineering, University of Tehran, Tehran, Iran
author
Amir Farhad
Najafi
School of Mechanical Engineering, University of Tehran, Tehran, Iran
author
Hamed
Alemi Arani
School of Mechanical Engineering, University of Tehran, Tehran, Iran
author
Alireza
Riasi
School of Mechanical Engineering, University of Tehran, Tehran, Iran
author
text
article
2017
per
Recently, use of PAT (pump as turbine) in mini hydro power plants (< 500 Kw) has increased due to its lower cost, easy installation and maintenance feasibility. Since the overall efficiency of this machine is lower than conventional turbines, the use of these machines in large plants are not economically recommended. In this study, the effect of geometrical parameters of impeller on PAT performance is investigated. In the present research, the geometries of components of an available commercial pump was scanned and modeled. To make the study more feasible, Impeller was redesigned in CFturbo software. Commercial software of ANSYS CFX 15.0 was used to simulate the fluid flow within PAT. Numerical results are in good agreement with existing experimental data. Three main parameters, namely, blade number variations, leading edge shapes and splitter blades were comprehensively investigated. Result shows that using 7 blades, rounding leading edge with suction side chamfer and 20% length splitter blades improve the efficiency. Finally, the most appropriate geometry with parameters of 6 blades, rounded trailing edge with suction side chamfer and 20%splitter blades is recommended for achieving the highest efficiency that can boost it up to 2%.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
13
24
http://mme-old.modares.ac.ir/article_17323_bf91143fa8cebb2cc840167531ac358e.pdf
Trajectory Investigation of a Transonic Spherical Projectile under Hop-Up Mechanism Using Simulation of Turbulent Three-Dimensional Non-Stationary Flow
Seyed Erfan
Salimipour
Ferdowsi university of mashhad
author
Ali Reza
Teymourtash
Mechanical engineering, Ferdowsi University of Mashhad, Mashhad, Iran
author
Mojtaba
Mamourian
Mechanical engineering, Ferdowsi University of Mashhad, Mashhad, Iran
author
text
article
2017
per
Improvement of shooting accuracy with air gun pellets is very important in sport competitions which is always questioned by shooting enthusiasts. In this study, the performance of a transonic spherical projectile as an air gun pellet with 4.5 mm-caliber under a mechanism known as Hop-up is numerically examined. The motion of this projectile is assumed in four degrees of freedom including three translational motions and one transverse rotational motion. Hop-up mechanism is resulted in a rotational motion of spherical projectile, so a Magnus Force is generated which prevents the altitude loss of the projectile. The Navier-Stokes equations are solved in compressible non-stationary turbulent conditions with equations of the pellet motion in a coupled form and in a moving computational grid by a computer program. The present numerical simulation is based on “Roe” scheme with second-order accuracy using a finite volume method and because of the importance of time dependent parameters, second-order time accurate was applied. To validate the computer program operation, the results were compared to valid experimental data. The results obtained from these studies showed that proper rotation of the projectile for a certain distance prevents its height drop when hits the target. A relation was also obtained between the target location, shooting kinetic energy and proper angular velocity which can neutralize the projectile altitude loss at arbitrary distavces. It is also demonstrated that by increasing the angular velocity, the vortex shedding onset is accelerated and the projectile momentum is decreased.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
25
35
http://mme-old.modares.ac.ir/article_17320_6f0c774228327947039366f39415519e.pdf
Thermoelastic buckling of functionally graded rectangular plate based on improved third order shear deformation theory
Hirbod
Ahmadifar
Mechanical Engineering Department, Engineering Faculty, Islamic Azad University, Ahvaz, Iran
author
Amin
Yaghootian
استادیار دانشگاه شهید چمران
author
text
article
2017
per
In this study, an improved third order shear deformation theory is used to analyze the thermoelastic buckling of a functionally graded rectangular plate. The plate is assumed to be under two types of thermal loading, namely, uniform temperature rise across the thickness and linear temperature change across the thickness of the plate. Moreover, the material properties of the functionally graded plate vary linearly through the thickness and simply supported are considered for all edges of the plate. First, the nonlinear strain-displacement relations are considered based on improved third order theory and then the equilibrium and stability equations are derived. In continue, displacements and the pre-buckling forces are calculated using the equilibrium equations. The temperature difference relation of buckling is obtained by solving the stability equations. To obtain the critical temperature difference, the recent relation is minimized with respect to the number of half wave parameters. Resulting equations are compared with the literature. The results show that, the values of temperature difference buckling obtained based on improved third order shear deformation theory, are lower compared with the classical plate theory, first and third order shear deformation theories. Moreover, the value of critical temperature difference under linear temperature change is bigger compared with the uniform temperature rise across the thickness, and the difference between the two values will be bigger with increasing the thickness of the plate.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
36
44
http://mme-old.modares.ac.ir/article_17318_2156f4d35e032a1bd4f729ebdddf5f38.pdf
Designing backstepping controller for position\force tracking of cooperative robot manipulators
Shima
Ahangar
دانشکده مهندسی برق و کامپیوتر
دانشگاه صنعتی نوشیروانی بابل
author
Zahra
Rahmani
Department of Electrical and Computer Engineering, Babol Noshirvani University of Technology
author
Barmak
Baigzadehnoi
دانشکده مهندسی برق و کامپیوتر
دانشگاه صنعتی نوشیروانی بابل
author
text
article
2017
per
Control of multiple robots, whose end-effects grasp an object, involves complex control tasks. First, the multiple robotic system, for a cooperative task, forms closed kinematic chains that impose additional kinematic and dynamic constraints. Second, the interactive actions among the robots through the object lead to the essential need to control position and interactive force, simultaneously. In this paper, the backstepping control method is studied for tracking control problem of cooperative robot manipulator system handling a common rigid object. The error system of coordinated robot manipulators is developed by defining the new variables based on the integral and differential of position and orientation errors. Then by defining the appropriate change of coordinates and using the backstepping design strategy, a backstepping position tracking control scheme is proposed for multi-robot manipulator systems handling a common object. Additional terms, using the properties of internal forces, are also added to the control signals to consider the force tracking problem. It is proved the closed loop system are uniformly ultimately bounded based on Lyapunov stability theory. Finally, the two three-link planar robot manipulators is applied for simulation, and the simulation results show the effectiveness of the proposed method.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
45
54
http://mme-old.modares.ac.ir/article_17317_ba23d01669cdab06056a59525ba22b3f.pdf
Analysis of dimensional errors for metallic bipolar plates in single PEM fuel cell
Pouya
Pashaie
Fuel Cell Research and Technology Group, Department of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Mazadaran, Iran.
author
Mohsen
Shakeri
استاد دانشکده مهندسی مکانیک-دانشگاه صنعتی بابل
author
salman
nourouzi
Babol University of Technology
author
text
article
2017
per
In recent years, development of polymer electrolyte membrane fuel cells (PEMFCs) has been considered to generate electricity and heat. Among main components of PEMFCs, bipolar plates (BPPs) have significant influence on cost and performance of the system. Metallic BPPs, formed using thin sheets, have been developed as alternative to conventional graphite plates because of advantages such as suitable cost, mechanical strength and power density. Flexibility of the sheets and spring back during forming process make dimensional errors inevitable and lead to inappropriate contact pressure distribution between BPPs and gas diffusion layer (GDL), resulting in decrease of fuel cell performance. Excessive accuracy in BPP production leads to increase the final cost and decrease the general usability of the technology. Therefore, to reduce unnecessary costs, managing design process and improving efficiency, analysis of BPP dimensional errors is done using finite element method and Monte Carlo simulation (MCS). First, contact model of the metallic BPP and GDL is developed and heights of each channel and each rib of BPP are fully parameterized due to stochastic variations of dimensional errors with normal distribution. Then, contact pressure distributions of GDL (Pave, Pstd) for different dimensional errors are obtained by MCSs. Increasing dimensional tolerance from 0.015 mm to 0.075 mm, average contact pressure (Pave) has decreased by 11% and standard deviation of contact pressure (Pstd) has increased up to 90%. Namely desirable distribution of GDL pressure is reduced by increasing the dimensional error and suitable dimensional tolerances for BPPs can be determined according to engineering requirements.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
55
64
http://mme-old.modares.ac.ir/article_17329_d13fcd71bc8beba37bd4e6ed03545b42.pdf
Numerical simulation of magnetic nanoparticle delivery at location of abdominal aortic bifurcation using single wire magnetic source
Saber
Yekani Motlagh
هیات علمی دانشگاه صنعتی ارومیه
author
Salar
Deyhim
دانشگاه صنعتی ارومیه
author
text
article
2017
per
In this paper, drug coated magnetic nanoparticle delivery is numerically studied. Specific part of right foot vessel connected to the abdominal aorta is considered as target tissue. Single wire is applied as magnetic source. Buongiorno’s two-phase model is modified by adding the magnetophoresis term to the volume fraction transport equation. Governing unsteady equations with ferrohydrodynamics Kelvin force as a source term is discretized with PISO based finite volume method. Effects of the location of magnetic source and magnitude of current carrying from wire (1000, 2000, 3000, 4000 and 5000 amperes) are investigated on residence time and deposition level of drug on target tissue. Diameter and volume fraction of nanoparticles are 10 nm and 0.002, respectively. From the results, location of wire should be near and upstream the target tissue. Furthermore, by using this method deposition level of drug on target tissue can be increased by 7.5 times. Best drug delivery performance is seen for current magnitude of 2000 amperes.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
65
74
http://mme-old.modares.ac.ir/article_17330_8fc3d6b3e195613acbb809b2a54170e7.pdf
Numerical simulation of wind turbine in Manjil wind farm considering wind regime study
Mohammad Reza
Ghasemi Bousejin
Department of Agricultural Machinery Engineering, University of Tehran, Iran
author
ali
jafari
tehran university
author
Seyed Saeid
Mohtasebi
University of Tehran
author
kobra
gharali
University of Tehran
author
text
article
2017
per
Research on atmospheric boundary layers in wind farms is an important task. Especially, wind effect on wind turbines installed in mountainous area with complex terrain is complicated. In this research, the wake of a wind turbine and wind flow in complex terrain have studied with computational fluid dynamic (CFD) method in OpenFOAM software. Actuator-disk model with introducing forces, based on Blade Element Momentum Theory, on the disk are used. For simulation of wind turbine in wind farm, Reynolds averaged Navier Stokes equation with k-ɛ turbulence model has been used. Structured mesh was used for simulation domain. Also, main wind direction has been determined from North toward south considering wind rose of area. One of wind turbines is studied by detail. The numerical results show an extended wake effect around 5d (five times the rotor diameter). Wind speed deficit is 26% at this distance. Captured wind power from the simulation is close to real data. Also, wind regime has been studied and analyzed for different seasons. For November, December and January, the time period that wind blows in effective speed, is decreased less than %50 which is important in wind farm design and operation.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
75
85
http://mme-old.modares.ac.ir/article_17313_48f0b8ceb695955510539a3db839e9c2.pdf
Thermo-mechanical behavior of polymer composites exposed to fire
Khosro
Lari
دانشگاه تحصیلات تکمیلی صنعتی و فناوری پیشرفته
author
Mohammad
Gholamian
دانشگاه تحصیلات تکمیلی صنعتی و فناوری پیشرفته
author
Amid
Pouraminaei
دانشگاه تحصیلات تکمیلی صنعتی و فناوری پیشرفته
author
Emad
Jomehzadeh
دانشگاه تحصیلات تکمیلی صنعتی و فناوری پیشرفته
author
text
article
2017
per
Nowadays, the use of polymer-based composites has been growing. Composites due to mechanical, chemical and physical properties are widely used, but the inherent combustion of these materials and the lack of strength at high temperatures, especially when exposed to the fire is one of the challenges of using composites in industries. When composites are exposed to fire, matrix of composite decomposed with heat release, smoke, soot and toxic fumes. Due to the influence of fire on the composite structure, several thermal processes occur such as thermal conductivity in the structure, production and escape of the gases from the composite and resin decomposition. The aim of this study is the investigation of the effects of fire on the composite structures. Analysis of composite resistance to fire, determine the amount and duration of the fire-resistant composite as well as the effects of thermal stress in composite structure requires thermo-mechanical analysis of the composite. ABAQUS software is used for solving the problem in this study. Appropriate model for analyzing the thermal and mechanical parts of the problem according to the governing equations is developed and imported to the Abaqus software through Abaqus subroutines. Thermo-mechanical model validated with the results of valid studies. Finally, this model is used for thermo-mechanical analysis of a composite cylindrical structure exposed to the fire. The results showed that by estimating the failure time of the composite, it is possible to determine the amount of load that can be applied to the structure under different conditions of fire.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
86
96
http://mme-old.modares.ac.ir/article_17360_16f731c014beb08aac82034b6f54c915.pdf
A Closed Loop Sub-Optimal Guidance Design for Sub-Orbital Flying Systems
Emad
Jomehzadeh
مدیر گروه دینامیک پرواز و مهندسی فضایی
/ دانشکده هوافضای دانشگاه خواجه نصیرالدین طوسی
author
farhad
tavakoli
دانشجوی دکتری دانشگاه خواجه نصیرالدین طوسی
author
text
article
2017
per
In this paper, a novel closed loop guidance method is provided for sub-orbital systems. The proposed method can be used in the first phase of a flying vehicle system that flies in atmosphere. In this method, sub-optimal integrated solution of control and guidance in closed-loop is developed. This Sub-optimal guidance technique has been named Model Predictive Static Programming (MPSP) that based on nonlinear optimal control theory and derived from combined philosophies of Model Predictive Control and Approximate Dynamic Programming solves a class of finite horizon optimal control problems with terminal constraints. Also because sensitivity matrices that are necessary for obtaining this solution can be computed recursively, this technique is computationally efficient and is appropriate for online implementation. In this paper, the system’s dynamic equations are modeled in the presence of aerodynamic forces and moment and the dynamic servo-mechanism effect is also assumed in the equations. Furthermore, by simultaneously considering the guidance and control loops, an integrated solution of the guidance and control system is proposed by three-degree of freedom spherical earth simulation model. Result show that proposed closed-loop guidance is able to remove modeling errors by flight data update and guide flying vehicle to the desired point.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
97
106
http://mme-old.modares.ac.ir/article_17359_0cfef132dab203412cdadedf2748726d.pdf
Design of Geosynchronous Satellite Flying Formation Based on Translational Dynamics Affected by Attitudinal Situation at Drift Phase
Amir Reza
Kosari
استادیار دانشکده علوم و فنون نوین دانشگاه تهران
author
Mahdieh
Beglari
Graduated from Faculty of New Sciences and Technologies , Tehran, Iran
author
text
article
2017
per
This paper investigates effect of coupling of satellite translational dynamics and rotational kinematic aiming to design of geosynchronous satellite formation flying at drift phase to the determined operational nominal position at the orbital window in the geosynchronous orbit. Firstly, dynamical and kinematical equations of satellite, and then, the interaction of translational and rotational motion at drifting to the final position at the target orbit by considering satellite as a rigid object have been studied. Despite of similar studies utilized simplifications such as circular assumption of target orbit or various linearization methods, presented analysis of this paper are based on the general form of nonlinear translational equations. According to acquired results of investigating the coupled dynamics at the drift phase to the determined position at the orbital window by considering different attitudinal situations, drift considerations and procedure in presents of other satellites at the orbital window have been presented. Position and attitude of satellite have been controlled by utilization of PD control law associated with the optimized gains based of PSO optimization algorithm aiming to minimizing control effort and fuel and consequently minimizing fuel consumption and increasing satellite operational life. Acquired results from simulations represent effectiveness of the proposed methodology.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
107
118
http://mme-old.modares.ac.ir/article_17362_84abcda0ad30def3b59e098a194360ec.pdf
Agility enhancement using an assistive controller for exoskeleton robots
Iman
Kardan
PhD student/ Mechanical Engineering Department, Ferdowsi University of Mashhad, Mashhad, Iran
author
Alireza
Akbarzadeh
Professor-Mechanical Engineering-Ferdowsi University of Mashhad
author
text
article
2017
per
Assistive exoskeletons are a category of wearable robots that provide a portion of the forces, required by users in performing different motions. Hence, the users will be able to perform the motions with less effort. Hitherto, different control algorithms for assistive exoskeletons are proposed and their various effects on the users’ performance are evaluated. Recently, the authors of the present paper have proposed a new control method, called output feedback assistive controller, for compliantly actuated exoskeletons. This method is independent from user’s intent, requires a very low number of sensors and possesses a simple model-free structure. This paper evaluates the effect of the output feedback assistive controller on the agility of the users. A knee physiotherapy robot is considered as a single joint exoskeleton. Connecting a series elastic actuator to the robot and implementing the output feedback assistive controller, the agility of the user is evaluated in a target following experiment. Two markers are displayed on a monitor to represent the actual and desired knee angles for the user. The user is asked to follow the desired angles by moving his/her leg. The accuracy of the user in following the target is measured and compared in two assisted and unassisted cases. The results clearly verify the positive effect of the output feedback assistive controller on increasing the user’s agility.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
119
129
http://mme-old.modares.ac.ir/article_17363_3577bf2ff78d04f37b55a92de0c2beac.pdf
Using of Turkel precondition method for convergence acceleration of compressible flow with low Mach number
mohsen
motamedi
Faculty member
author
saeed
sheikhi
فارغ التحصیل دانشگاه صنعتی شریف
author
text
article
2017
per
The system of compressible equations using upstream numerical methods has convergence problem to analyze low-Mach number flow. In this study precondition method is employed in Euler equations to solve convergence problem in low-Mach number flow and this preconditioned equations are used to analyze flow around a two-dimensional body. The preconditioner modifies the transient behavior of the Euler equations in manner that the stiffness of the eigenvalues is removed and allows for a faster convergence to the steady state. So, Turkel precondition method, one of the useful preconditioner matrices, is applied in system of Euler equations. As majority of solvers use conservative variables, precondition matrix is recalculated for conservative variables and is employed in Euler equations. The upstream finite volume Roe method in an unstructured grid is employed for space discretization of equations. Transient part of equations also is discretized with fourth order explicit Runge-Kutta method. The performance of the proposed approach is vetted through an inviscid tow-dimensional flow around the NACA0012 airfoil with different Mach number and the steady state solution is calculated. Numerical results show that Turkel preconditioner allow for a faster convergence to the steady state solution in low-Mach number. . .
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
130
136
http://mme-old.modares.ac.ir/article_17361_94047476e63fa9262cb9ea2c50b50880.pdf
Evaluation and optimization of drawing depth in electrohydraulic forming
(with bridge wire between electrodes)
Mehdi
Zohoor
University Faculty Member
KNT University of Technology
author
Seyed Meysam
Mousavi
PhD Student, K. N. Toosi University of Technology
author
text
article
2017
per
Nowadays high velocity forming methods have become popular among industrial companies due to their capability at improving formability in various materials in comparison to conventional methods. Electrohydraulic forming (EHF) is a high velocity sheet metal forming process in which two electrodes are positioned in a water ﬁlled chamber and a high-voltage discharge between the electrodes generates a high-pressure to form the sheet metal. In this work, extensive experimental tests have been designed based on design of experiments (DOE) technique to investigate the effective parameters in EHF (with bridge wire between electrodes). Discharge energy, material, length and diameter of bridge wire have been considered as effective input parameters. Response surface methodology (RSM) has been used to model and optimize the EHF performance with respect to drawing depth for Brass 260. Base on the results, it can be stated that maximum drawing depth is obtained when discharge energy is maximum. It was found that the aluminum wire was more efficient than copper and tungsten. There also exists an optimum amount of length and diameter of bridge wire determined according to the process conditions.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
137
144
http://mme-old.modares.ac.ir/article_17364_d6f2a01fbd0d310eda384b381eaaa63f.pdf
A new method to reach high-density ratios and low viscosities based on the Shan-Chen multiphase model in lattice Boltzmann method
Soroush
Fallah kharmiani
faculty of mechanical engineering, ferdowsi university of mashhad
author
Mohammad
Passandideh-Fard
ferdowsi university
author
text
article
2017
per
In this paper, a new method is proposed to reach high density ratios and low viscosities based on the Shan-Chen multiphase model in the lattice Boltzmann Method. In this new method the interaction force and as a result the pressure tensor is modified purposefully so that the density of the phases can be adjusted to coincide the corresponding values from the Maxwell equal area rule in thermodynamics. This leads to higher stability and therefore the mentioned purposes are achieved. This new method takes advantage of simplicity and the same implementing procedure in 2D and 3D problems with single or multi relaxation time collision operators. In order to validate the new method, first the coexistence densities of the phases at different subcritical temperatures are compared with those of the Maxwell rule, then the validity of the Laplace law for a droplet is evaluated, after that the spurious velocities around the droplet are evaluated, and finally the broken dam problem is simulated and its results are compared with an experimental data. Results show that the developed model is properly stable and is capable of simulating different multiphase flows at a wide range of density ratios and viscosities.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
145
152
http://mme-old.modares.ac.ir/article_17365_4b673dd0fefa7f0149ddb51f926d9a17.pdf
A study of fluid media and size effect on dynamic response of microplate
Mahdi
Aghababaie Beni
Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran
author
Mohamad-Reza
Ghazavi
faculti member TMU
author
Ghader
Rezazadeh
Professor of Mechanical Eng. Dept.
author
text
article
2017
per
This paper analyzes the effect of squeeze film and size effect on dynamic response of microplate. The microplate in this work is a clamped-clamped plate, which is excited using electrostatic force. The gap between microplate and substrate filled with air. First order shear deformation theory (FSDT) and couple stress theory (CST) and considering Von Karman’s strains are used to model the equation of motion of microplate. Non-linear Reynolds equation based on Micropolar theorem is deployed to apply the size effect on the fluid. Afterward, Equations are discretized by applying couple finite element method and finite difference method. The first-order differential equations are solved utilizing Newmark’s method. One of the contribution is presenting the influences of size effect and mid-plane stretching on the microplate dynamic behavior, also the influence of different parameters on the quality factor. According to the results, mid-plane stretching effect increases the microplate rigidity. Interestingly, this effect is more dominant for voltages with higher amplitude. This paper emphasizes that considering the plate size effect will increase the rigidity of the system. Moreover, the plate size effect increases the rigidity whereas, the fluid size effect decreases the rigidity of system. Increasing the fluid’s pressure results in decrease the amplitude of oscillations in step voltage excitation which postpones the dynamic pull-in. This paper concludes that increasing the coupling parameter of fluid increases the natural frequency of microplate, whereas increasing the fluid length scale parameter decreases the natural frequency and quality factor of the system.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
153
164
http://mme-old.modares.ac.ir/article_17366_5101db70d484b1d40ee713ecaa40cc2d.pdf
Study of the effect of elastic properties on non-Newtonian drop motion in inertia regime
Amin
Emamian
Mechanical Engineering Department, Shahrood University of Technology, Shahrood, Iran
author
Mahmood
Norouzi
Shahrood University of Technology
author
Mahdi
Davoodi
Department of Engineering, The University of Liverpool, Liverpool, UK
author
text
article
2017
per
In this paper, steady motion of non-Newtonian falling drop through a Newtonian fluid at low Reynolds number is investigated analytically. Here, the Upper Convected Maxwell model (UCM) is used for drop phase and Newtonian model is considered for external fluid. During the past few decades, studies relating to non-Newtonian instabilities especially those involving free surfaces are amongst the most striking. These types of studies can be used to optimize design processes in, for example, the petroleum and medicine related processes, metal extraction, and paint and power-plant related fields. Analytical solution is obtained using the perturbation method. Reynolds and Deborah numbers are used to linearize the equations governing the problem in analytical method. Deborah number indicates the elastic effect of drop. The drag force increases by the growth of the elastic effect of non-Newtonian Drop’s. The non-Newtonian drop loses its shape and exchanges to an oblate form. Increment in Deborah number enhances the dimple at the bottom of the drop and results in an increment in its drag force and as a consequence its terminal velocity decreases. A hole is created at the rear of the drop due to the presence of inertia force and focus of normal component of stress at the rear of the drop. The novelty of this study is to consider the convection (non-linear) term of the momentum equations which was neglected in the previous studies due to the creeping flow.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
165
174
http://mme-old.modares.ac.ir/article_17367_be151e73d90dfacd331b53e89ae4ab0b.pdf
Numerical Simulation of the Unsteady Wake Flow around a Marine Propeller Using URANS Model
Mohammad Reza
Nazari
استادیار دانشگاه یزد- دانشکده فنی و مهندسی- گروه مکانیک
author
amin
talezade shirazi
Mechanical Eng. Yazd University
author
Mojtaba
Dehghan Manshdi
Department of Mechanical and Aerospace Engineering, Malek ashtar University, Shahin-shahr, Iran
author
text
article
2017
per
The flow field investigation around marine propellers is of great importance, due to its applications in vessels identification and hydrodynamic noise prediction. In the present research, the steady and unsteady wake flow field was simulated using the open-source OpenFOAM software and the simple-Foam and Pimple-DyMFoam solvers. The obtained characteristic chart and near propeller wake flow results were validated against available experimental data, which shown to be in a very good agreement. The grid study results in the wake region prove that unlike global quantities, the employed wake grid strongly affects the wake parameters. The results obtained from the present research show that employing the RANS models are suitable for the hydrodynamic coefficients calculation and these models predict the results with a low computational cost against the Unsteady RANS approach. On the other hand, an accurate investigation of the flow fluctuations and the vortex flow instabilities can only be accrued performing unsteady simulations with an appropriate refined grid. In this research, the effect of advance coefficient is also investigated on the vortex flow pattern in the wake region. Qualitative comparison of the obtained results and similar available data of the more accurate DES turbulence model shows that the URANS method has great capabilities in wake flow simulation provided that a suitable grid is applied. This method significantly decreases the required cells number and run time while maintaining the results accuracy.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
175
184
http://mme-old.modares.ac.ir/article_17368_3abb7bee2bb6643c592051cbe79c11a3.pdf
The wall spring constant variation effect on distribution of Lennard-Jones fluid in nanochannel by molecular dynamic simulation
reza
rabani
PhD Candidate, Tarbiat Modares University
author
Ghassem
Heidarinejad
Tehran, Ale Ahmad Ave, Tarbiat Modares University,Faculty of Mechanical Engineering, Room 317
author
ebrahim
shirani
Foolad Institute of Technology
author
text
article
2017
per
In order to simulate the heat transfer process from wall to fluid in nanochannel numerically, extensive range of spring constants with regard to wall material is used. In this paper, the effect of variation in wall spring constant on the heat transfer and distribution of the macroscopic properties of fluid has investigated. In this regard, heat transfer in argon gas between two stationary walls of a 5.4 nm nanochannel with Knudsen number 10 has simulated using the molecular dynamic method. Comparison between the results shows that by reducing the wall spring constant, the amplitude of wall atoms vibration increased so it makes the gas atoms to become closer to the wall surface that results in an increase in the heat flux and thermal conductivity coefficient of the gas. Evaluating the result reveals that while the spring constant reduces from k_s=1100εσ^(-2) to k_s=100εσ^(-2), the thermal conductivity coefficient of the gas changes from 0.11 mW⁄(m-K) to 0.27 mW⁄(m-K). Furthermore, the reduced distance between the gas atoms and wall surface results in a decrease in the temperature jump on the wall so it increases the gas density near the cold wall while it decreases near warm wall. Comparison between temperature, density and pressure profiles in the nanochannel height shows that regardless to the amount of spring constant variation, the maximum of these properties has occurred at σ⁄2 from the walls.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
185
194
http://mme-old.modares.ac.ir/article_17369_fac8e09dd02ed3115adbd97d3699dfd9.pdf
Parametric Analysis of a Nanofluid Based Photovoltaic Thermal System, Using Computational Fluid Dynamic
Mohammad
Hosseinzadeh
Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
author
Ali
salari
Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
author
Mohammad
Sardarabadi
Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
author
Mohammad
Passandideh-Fard
Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
author
text
article
2017
per
In this study, the effects of using pure water and Zinc oxide/water nanofluid as working fluids on the performance of a photovoltaic thermal system are evaluated using computational fluid dynamic approach. Moreover, effects of the parameters that are independent of the system design on the electrical and thermal efficiencies of the photovoltaic thermal system with Zinc oxide/water nanofluid are investigated. The studied parameters are: absorbed solar irradiation, wind speed, ambient temperature, coolant inlet temperature, coolant mass flow rate, and nanoparticles mass fraction in the Zinc oxide/water nanofluid. In this study, using the designed setup, the three-dimensional numerical model is validated by comparing the simulation results with those of the experiments. The experiments are performed on a selected day in August at the Ferdowsi University of Mashhad, Mashhad, Iran (Latitude: 36° and Longitude: 59°). Based on the numerical results, the thermal efficiency of the photovoltaic thermal system with Zinc oxide/water nanofluid is enhanced by increasing the absorbed solar irradiation, ambient temperature, coolant mass flow rate, and nanoparticles mass fraction. However, increasing the wind speed and coolant inlet temperature decreases the thermal efficiency of the system. Moreover, the considered parameters in this study have slight effects on the electrical efficiency of the photovoltaic thermal system. The relative increase of the electrical and thermal efficiencies of the photovoltaic thermal system with Zinc oxide/water nanofluid with 12 % by weight compared to that of pure water is 0.28 % and 12.58 %, respectively.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
195
204
http://mme-old.modares.ac.ir/article_17370_87b1344eebe179f8f4686f16441bf1d5.pdf
Comparison of effects of adding various carbon nanotube concentrations and increase C/H mass ratio of liquid fuels on combustion behavior and flame thermal radiation
Mehdi
Boghrati
Department of Mechanical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
author
Mohammad
Moghiman
استاد عضو هیئت علمی دانشگاه فردوسی مشهد
author
Seyed Hadi
Pourhoseini
Department of Mechanical Engineering, Faculty of Engineering, University of Gonabad, Gonabad, Iran
author
text
article
2017
per
The particles and atoms of carbon significantly affect radiation heat transfer and combustion behavior of flames. Number of carbon particles within the flame is increased by utilizing fuel with higher C/H mass ratio or adding carbon particles into lighter liquid fuel. In this study, the effect of adding various concentrations of multi-walled carbon nanotubes with hydroxyl functional group into hydrocarbon liquid fuel has been measured on temperature distribution and thermal radiation of the flame. Furthermore, the measured results compared with results of combustion behavior of liquid fuels with higher C/H value. The thermopile sensor and the lux meter were utilized to measure the flame thermal radiation (visible and infrared spectrum) and luminosity (visible wavelengths). Thermography technic and IR image were applied to determine the distribution of temperature and soot within the flame. The results showed that adding nanoparticles into liquid fuel increased the rate of chemical reaction kinetics, temperature and thermal radiation and decreased flame length. In addition, a rise in value of C/H of the liquid fuel increased temperature, flame length and thermal radiation and reduced the rate of chemical reaction kinetics. By adding 0.01% mass fraction of nanoparticles into the base fuel with C/H=5.46, thermal radiation increased by 3.4% as same as liquid fuel with C/H=5.52. The increase of nanoparticle concentrations increased the rate of chemical reaction kinetics, maximum temperature, thermal radiation and luminosity. In addition, the position of maximum temperature moved closer to the burner.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
205
213
http://mme-old.modares.ac.ir/article_17379_cee3446218627b677d66117ad6f4d5a5.pdf
Numerical investigation of dynamic crack growth in steel pipes under internal detonation loading
hosein
niasari
phd student of tarbiat modares univercity
author
Gholamhossein
Liaghat
استاد دانشگاه تربیت مدرس
author
text
article
2017
per
This paper reports numerical simulation of deformation and crack growth in steel pipes under internal moving pressure. A systematic method was developed for the determination of the detonation driven fracture problem parameters. The simulations were performed on steel gas pipes. Explosive PETN cords with detonation speed more than 7000 meters per second were used for creating a confined fracture on the pipe shells. Two finite element models were created for calculation of internal moving pressure parameters and simulation of crack growth. The first model was an Eulerian finite element model that was created for calculation of moving pressure parameters that were applied to tube shell. The second model was a Lagrangian finite element model that was created for ductile crack growth simulation with cohesive elements and element deletion methods. The model used the moving pressure parameters, elastoplastic rate dependent and dynamic cohesive element fracture parameters for simulation of deformation and crack growth. In the next step, the results of finite element model were verified using analytical models. The finite element model predicted the axial crack growth length with less than 7 percent error and crack arrest point with less than 10 percent error from experimental results.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
214
224
http://mme-old.modares.ac.ir/article_17380_3187dce3c9316f5ad498f5a001577d42.pdf
Occurrence of parametric resonance in vibrations of rectangular plates resting on elastic foundation under passage of continuous series of moving masses
Ehsan
Torkan
Islamic Azad University, Khomeinishahr branch, Department of Mechanical engineering
author
Mostafa
Pirmoradian
Faculty member- Islamic azad university, Khomeinishahr branch
author
Mohamad
Hashemian
Faculty member- Islamic azad university, Khomeinishahr branch
author
text
article
2017
per
In this paper, instability due to occurrence of parametric resonance in transverse vibration of a rectangular plate on an elastic foundation under passage of continuous series of moving masses is examined as a model of bridge-moving loads interaction. The extended Hamilton’s principle is employed to derive the partial differential equation of motion. Subsequently, the governing partial differential equation is transformed into a set of ordinary differential equations by the Galerkin procedure. Considering local, Coriolis and centripetal acceleration components of the moving masses in the analysis leads to appearance of time-varying mass, damping and stiffness matrices in the coefficients of the governing equation. The passage of continuous series of moving masses along the rectilinear path results in a parametrically excited system with periodic coefficients. Applying incremental harmonic balance method as a semi-analytical method to the governing equations, stability of the system is investigated for a wide range of masses and velocities of the passing loads and different boundary conditions of the plate. Moreover, effect of the foundation stiffness on stability of the plate is examined. Results indicate that using clamped supports for the edges of entrance and departure of masses over the plate’s surface leads to formation of an instability tongue in the parameters plane which does not appear for the case of using simply supports. Also, it is observed that critical velocities of the moving masses will be increased by escalation the foundation stiffness. Numerical simulations confirm the accuracy of the semi-analytical results.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
225
236
http://mme-old.modares.ac.ir/article_17378_ad6b835606ffe6935ab6e112206d5261.pdf
Accuracy Evaluation of Semi-empirical and Numerical Methods in Estimation of Aerodynamic Coefficients for air-launch-to-orbit delta wing
mohammad
aelaei
Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran
author
Fathollah
Ommi
Tarbiat Modares University, Jalal Ale Ahmad Highway, P.O.Box: 14115-111, Tehran, Iran
author
Saeed
Karimian aliabadi
Modares university
author
text
article
2017
per
In this paper, the importance of accurate estimation of the aerodynamic performance of delta wing has been mentioned. Some available and conventional methods of estimating the aerodynamic coefficients composed of CFD methods and industrial and commercial software have been selected and for comparison, a wing similar to delta wing mounted on Pegasus Air-launch-to-orbit missile as a template is being selected. The reason for this selection, mainly is the lack of wind tunnel in design process and flying in a wide range of flow regimes. As many parameters may be utilized in design process such as the aerodynamic force and moment coefficients, stability derivatives, heat transfer coefficient and the structural loading parameters are being required. In this study, the accuracy of the results of different methods in estimating the force and moment coefficients, as the most significant quantities for performance analysis, at any flow regime has been checked and the suitable method has been introduced in terms of the flight condition. With respect to available parallel processing system, different CFD methods are compared together. Then validity of solution of Reynolds-averaged equations (RANS) and Euler method have been evaluated based on the comparison by DES solutions. Therefore, the valid intervals of the subsequent methods have been presented. Results are indicating the advantage of computational methods to industrial and semi-empirical software. Semi-empirical code and industrial software are shown satisfactory for computation in the linear range i.e. the small angle of attacks.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
237
244
http://mme-old.modares.ac.ir/article_17382_1ed0402861d635bb0ffacbec7a2b102d.pdf
An experimental investigation on viscous fingering instability of Newtonian fluid in transparent porous media with compact structure consist of glass beads
Seyed Majid
khatibi
Master student
author
Ali
Khaleghi
Assiss. Prof., Department of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran
author
Mahmood
Norouzi
Shahrood University of Technology
author
text
article
2017
per
In this paper, the viscous fingering instability in miscible Newtonian fluid displacements is studied experimentally. Studying the results of this instability have widely application in oil extraction from ground bed oil reservoirs to the ground surface. In order to be more actualized results, a porous media with transparent walls and compact structure of spherical glass beads is constructed, that have close permeability to ground bed. The main purpose of this study is to investigate the effects of viscosity ratio, flow rate and Blake dimensionless number on the quality of growth and the shape of the fingers, also their effect on important physical parameters including the mixing length, sweep efficiency and noise growth to base state. The results showed that with increasing the viscosity ratio, instability and number of finger branches increases and more tiny fingers are formed. Also, increasing the viscosity ratio increases the mixing length and decreases the sweep efficiency. Likewise, with increasing the flow rate, it was observed that the number of wide fingers Increased and fingertips tend to spread. Furthermore, by studying the results it was found that increasing the flow rate, increases the sweep efficiency, but have No tangible effect on the mixing length. Also, the results show that increasing the Blake decreases the mixing length and increases the sweep efficiency.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
245
253
http://mme-old.modares.ac.ir/article_17384_a6eb8b12ac4015329121c6772c94f929.pdf
Study on the effect of gap pressure on the geometric characteristics of the tungsten carbide powder produced by electrical discharge
Mohammad Reza
Shabgard
دانشیار تبریز-دانشگاه تبریز- ریاست دانشکده فنی مهندسی مکانیک-گروه مهندسی ساخت و تولید- محمد رضا شبگرد
author
Reza
Najati Ilkhchi
Manufacturing , Mechanical Engineering, Tabriz University
author
Farid
Kabirinia
Manufacturing, Mechanical Engineering, Tabriz University
author
text
article
2017
per
The aim of the current research was to investigate the effect of pressure gradient in the gap on morphological and geometrical characteristics of the powder synthesized by electrical discharge method and optimizing it. Electrical discharge is a modern and high performance approach towards yielding ultrafine powder. The pressure gradient was inducted by pulsed flushing using various current flows of deionized water and ethanol and, two rods of graphite and tungsten were used to yield tungsten carbide powder. Scanning Electron Microscope (SEM) images show that the powder contains both electrodes' material and is within nano range. Furthermore, the SEM images demonstrate that with increasing pressure gradient there is a decline in powder agglomeration. Particle Size Analysis (PSA) results reveal that the mean particle size of the powder produced in deionized water and ethanol is approximately 100nm and the particles produced in ethanol are smaller. Moreover, the size of the crystals of the synthesized particle are within 30-44 nm range. X-ray diffraction showed that the dominant phases of the powder in ethanol and deionized water are WC1-x and W2C respectively. Overall, the results prove that causing steep gradient in the gap, it is possible to synthesize geometrically uniform powder with decent production rate.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
254
260
http://mme-old.modares.ac.ir/article_17383_af2a0ea0e72ebec0afa1a2dbf5c12489.pdf
Micromechanical modeling of effective elastic properties of hybrid nanocomposites reinforced by fuzzy fiber containing carbon nanotubes
Mohammad Kazem
Hassanzadeh-Aghdam
Faculty of Mechanical and Energy Engineering, Shahid Beheshti University,Tehran, Iran.
author
MohammadJavad
Mahmoodi
Faculty of Mechanical and Energy Engineering, Shahid Beheshti University, Tehran, Iran.
author
Hooshang
Barkhordari
Faculty of Mechanical and Energy Engineering, Shahid Beheshti University, Tehran, Iran.
author
text
article
2017
per
In this work, the effect of carbon nanotube (CNT) size on the effective elastic properties of a hybrid composite reinforced by fuzzy fiber is investigated using a unit cell-based micromechanical approach. This hybrid nanocomposite is composed of the CNT, carbon fiber, polymer matrix and interphase created due to the non-bonded van der Waals interactions between the CNTs and polymer. The novel constructional feature of this hybrid nanocomposite is that the uniformly aligned CNTs are radially grown on the surface of the horizontal carbon fibers. The CNT and carbon fiber are modeled as a transverse isotropic solid, while the interphase and polymer matrix are assumed to be isotropic. The influence of CNT size on the overall behavior of polymer matrix nanocomposite (PMNC), composite fuzzy fiber (CFF) and hybrid composite reinforced with fuzzy fiber is examined. Results show that size of CNT is more significant for the transverse effective properties of the hybrid nanocomposites reinforced with fuzzy fiber. It has been found that the transverse effective properties of hybrid nanocomposite are improved with increasing the CNT size. The micromechanical model is also used to examine the influence of interphase on the overall behavior of the PMNC, CFF and hybrid composite reinforced with fuzzy fiber. The effective elastic properties of the hybrid composite obtained by the present micromechanical model demonstrate very good agreement with those predicted by the other researches.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
261
272
http://mme-old.modares.ac.ir/article_17385_1c22befa0cedc70ee7b06f1e5cc18e96.pdf
EXPERIMENTAL INVESTIGATIONS ON HEAT TRANSFER IN DOWNWARD COCURRENT TWO PHASE FLOW IN VERTICAL PIPES.
hamid
hemmati
student/Iran Univercity of Science and Technology
author
mansoor
shirvani
Associate Professor /Iran University of Science and Technology
author
omid
vahidi
Assistant Professor /Iran University of Science and Technology
author
salman
movahedirad
Assistant Professor /Iran University of Science and Technology
author
text
article
2017
per
In the present study direct contact heat transfer between hot water and cold air in vertical pipes with cocurrent downward flow is investigated. Experiments are performed in turbulent condition using 1, 1.5, 2 meter pipes lengths with 0.021 meter diameter. The hot water temperature was varied between 35 to 50 degrees of Celsius and the air temperature was varied between 25 to 35˚C. Air velocities were chosen to be 3, 5, 7, 9 and 11 m/s and the rates of flow rate of water was selected as 5, 8 and 10 lit/min. Two phase annular flow pattern of water and air is formed in the vertical pipe. The interface area between water and air was measured by Image Processing taken from shining laser light sheet on the transparent tubes. Over 80 percent of heat was transferred by evaporation and less than 20 percent was transferred by convection. In all three pipes, Nusselt number decreased with increase in flowrate of liquid phase. In all the verified temperatures, Nusselt number was decreasing by increasing pipe length. Experimental values for Nusselt numbers were compered to empirical values for smooth surfaces. Finally, some adjustments were suggested for Nusselt number correlation by fitting experimental data into existing correlations for pipes with smooth surface. Proposed correlations for heat transfer resulted in Nusselt number with ±15.26% average error.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
273
280
http://mme-old.modares.ac.ir/article_17402_3cb46f06b6d81801217ddfa2ff286036.pdf
Experimental investigation of ground effects on aerodynamics characteristics of a delta wing airplane model
Arsalan
Ghajar
پژوهشگاه هوافضا
author
seyyed arash
seyyed shams taleghani
استادیار
author
Mohammad Reza
Soltani
صنعتی شریف
author
Mehran
Masdari
دانشگاه تهران
author
text
article
2017
per
In this research experimental results of 60 degree delta wing airplane that conducted in National Low Speed Wind Tunnel is presented. The wind tunnel is closed type has an opened test section that its dimensions are 2.8 m × 2.2 m. Tests Reynolds number is beyond 1.5 million that achievement of this Reynolds number at low speed is unique in the country. Ground effect is measured using a fixed plane that its height is variable. Tests are conducted at the different height and aerodynamics forces and moments are measured using a sting type six component strain gaged balance. The tests results showed that the maximum lift coefficients increased from 1.29 to 1.38 due to presence of the ground plane. The lift coefficient due to ground plane in all range of angle of attack is increased and induced drag coefficient is decreased and consequently, the overall aerodynamics efficiency (lift to drag ratio) is increased from 8 to 14.5. When the distance between model and ground plane is less than half of the wing span, lift curve slope is increased in high rate from 2.66 per radian to 3.11 per radian. Decreasing this distance is caused the aerodynamic center is shifted backward and consequently longitudinal static stability is increased. Consequently presence of ground plane is caused increasing of airplane static stability.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
281
289
http://mme-old.modares.ac.ir/article_17403_1f5cd5b9e5910d384136f6fbf3c5213d.pdf
Numerical simulation of the characteristic chart and the steady state wake flow past a marine propeller using OpenFOAM
Mohammad Reza
Nazari
استادیار دانشگاه یزد- دانشکده فنی و مهندسی- گروه مکانیک
author
Amin
Talezade Shirazi
Yazd University
author
Mojtaba
Dehghanmanshadi
Malek-Ashtar University of Technology
author
text
article
2017
per
In the present research, numerical simulation of the characteristic chart and steady-state Wakefield flow around a marine propeller is conducted. Solutions were performed using the open-source OpenFOAM software and the steady incompressible simple-Foam solver. The gradients were calculated using the linear Gauss algorithm, and the pressure equation was solved with the multi-grid method. In this research, characteristic chart simulation of the propeller was carried out for the entire operational conditions and the effect of using Realizable-k-ε and k-ε-v^2-f turbulence models on the results was investigated. The results were found to be in good agreement in all conditions except for the near bollard region. In this region, the propeller inlet angle of attack severely increased, and the two equation model predicted the thrust coefficient with 24% error, while implementing the four equation model significantly developed the results and decreased the error to 5%. The wake region parameters were also investigated in the numerical simulations at different longitudinal and radial cross sections behind the propeller which showed good agreement compared with the available experimental data. Wake region investigation showed that the flow behavior in downstream cross sections is similar to the corresponding upstream section with smaller variation ranges and for the swirling flow behind the propeller, the maximum and minimum angular position of the wake components rotates. The obtained results also show that the wake axial velocity component deviation is extremely large at the blade tip.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
290
300
http://mme-old.modares.ac.ir/article_17404_cf4fb4c6551518548ff2a1a5af9f13f2.pdf
Dynamical parameters identification of shear structure using block pulse functions and ARX model
یاسر
حسینی
دانشگاه تبریز
author
حسین
غفارزاده
دانشیار، مهندسی عمران- سازه، دانشگاه تبریز، تبریز
author
text
article
2017
per
System identification with the development of dynamic testing of structures has become one of the useful methods for structural health monitoring and damage detection and also finite element model updating. Identification of structural dynamic parameters is done by using excitation-responses data and includes physical-dynamical parameters such as mass, stiffness and damping matrices and/or modal parameters such as natural frequencies, damping ratios and modal shapes. Block pulse functions (BPFs) are a set of orthogonal functions that are used to approximate the variety of functions. These functions have explicit definition and provide simple formulation of complex problems. In this research, structural dynamic equations have been converted to state space equations and based on input BP coefficients and BP coefficients of displacement responses, a transfer function is extracted for each degree of freedom. Transfer functions include important information such as the eigenvalues of plant matrix. The equalization of transfer functions with ARX model led to estimate the eigenvalues of plant matrix and identification of dynamical parameters of structure is done based on these eigenvalues.To prove the validity and feasibility of proposed method, numerical simulation of the three-story shear frame with determined responses at all degrees of freedom and excited on base level is presented. Also, the accuracy of the identification process by applying noise at different levels to the structure response is investigated. The results reveal the proposed method can be beneficial in structural identification with less computational expenses and high accuracy.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
301
308
http://mme-old.modares.ac.ir/article_17405_d775667ede7584b24716ec379b723cb9.pdf
Vortex Induced Vibration of Simply Supported Visco elastic Beam
Gholam Reza
Zarepour
Mechanical Faculty of Guilan University
author
ilghar
javanshir
PhD candidate, Department of Mechanical engineeing, guilan university, Rasht Iran
author
text
article
2017
per
In this paper, vortex induced vibration of simply supported viscoelastic beam were investigated using semi-analytical method. By applying the general form of the viscoelastic model, the nonlinear partial differential equations of motion based on the Euler Bernoulli beam’s theory and displacement coupling fluid-structure interaction model were obtained via the Newton’s second law. A classical nonlinear van der Pol equation was taken as the governing equation for one component of the vortex shedding force on the beam. Employing the Galerkin discretization method, the equations of motion are reduced to a set of nonlinear ordinary differential equations with coupled terms and then there have been solved numerically by Runge-Kutta method. Finally, the effect of system parameters on the time response, phase plane and maximum amplitude of the beam are investigated. The results indicate that the viscoelastic behavior have a significant influence on the dynamic characteristics of the system and causes to change the Lock-in phenomenon with respect to corresponding elastic system. For example, for E2=10E1 the viscoelastic behavior can change the position of the locking area, and the maximum amplitude of the beam is increased by 45%. Lock-in from of vortex-induced vibrations was considered as a possible source of increased fatigue and damage. Therefore, by using viscoelastic materials the maximum amplitude of the system is reduced and the Lock-in condition can be changed. Additionally, based on the significant influence of viscoelastic behavior on the dynamic characteristics of the system, viscoelastic behavior should be considered in the mathematical model of the systems.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
309
318
http://mme-old.modares.ac.ir/article_17406_3749a25a520962053c367e6c85210dce.pdf
Micromechanical analysis of the effects of adding silica nanoparticles on the elastoplastic behavior of polymeric nanocomposites considering interphase
Mahdi
Hasanzadeh
Department of Mechanical Engineering, Guilan University, Rasht, Iran.
author
Reza
Ansari
دانشیار دانشگاه گیلان
author
mohammad kazem
Hassanzadeh-Aghdam
Department of Mechanical Engineering, Guilan University, Rasht, Iran
author
text
article
2017
per
In this work, an elastoplastic constitutive model is planned to analyze the effects of adding silica nanoparticles on the overall elastic-plastic stress-strain curves of the polymer matrix nanocomposites. The elastic modulus of the nanocomposites are evaluated by the combination of the Mori-Tanaka and Eshelby micromechanical models considering interphase region formed due to the interaction between silica nanoparticles and the polymer matrix. Then, the elastic-plastic stress-strain curves of nanocomposites are extracted by employing a micromechanics-based ensemble-volume averaged homogenization procedure. To prove the validity of the developed method, the predictions are compared to the experimental data existing in the literature. The effects of volume fraction and diameter of silica nanoparticles, thickness and adhesion exponent of the interphase on the polymeric nanocomposite elastic-plastic stress-strain curves are extensively examined. Stiffer elastoplastic behavior is found in the presence of interphase region. The results clearly indicate that the strengthening of the silica nanoparticle-reinforced polymer nanocomposites is improved with (1) increasing nanoparticle volume fraction, (2), decreasing the nanoparticle diameter, (3) increasing the interphase thickness and (4) decreasing the interphase adhesion exponent. Finally, the elastic-plastic stress-strain curves of silica nanoparticle/polymer nanocomposites under biaxial loading is achieved.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
319
326
http://mme-old.modares.ac.ir/article_17407_d1bcce420cd2f702af5ae38433554154.pdf
Experimental Investigation of aero acoustic noise generation process from a wall mounted square cylinder at incidence
Alireza
Movahedi
Yazd University
author
Ali Akbar
Dehghan
دانشیار دانشگاه یزد
author
Mojtaba
Dehghan manshadi
Malek Ashtar University of Technology
author
text
article
2017
per
In the present research aeroacoustic characteristics of flow over a finite height wall mounted square cylinder at different angles of attack is investigated. The aspect ratio of the model and the boundary layer thickness were 7 and δ⁄D=4.27, respectively. The experiments were done in a acoustically improved aerodynamic wind tunnel. The purpose of this study is to identify correlation between the fluid and the acoustic fields. The flow-induced noise was measured using single microphone. The measured noise is related to aerodynamic characteristics of the flow using a single hot wire. The flow-induced noise of the cylinder is characterized in terms of frequency and magnitude. A sharp pick was observed in the far-field pressure at the vortex shedding frequency in which measured with hot wire anemometer. So, one could be concluded that vortex shedding is a source of aerodynamic noise generation. The strouhal number obtained from two devices was almost equal to 0.11 that is in agreement with previous studies. Also, maximum vortex shedding frequency was measured for α=15°. It is observed that sound pressure level is increased with increasing upstream velocity. The overall sound pressure level ranged between 84.2 and 110.95 (dB) for upstream velocities in the range of 5-15 (m/s). The angle of attack has no important effect on overall sound pressure level.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
327
338
http://mme-old.modares.ac.ir/article_17408_867da92798093b69a0b1bcb685806e35.pdf
Fabrication and Thermal Modeling of Unglazed Transpired Solar Air Heater Collectors with metallic (Steel) and non-metallic absorber plates
Fatemeh
Afzali
Department of Energy, Graduate University of Advanced Technology, Kerman, Iran
author
Hossein
Amiri
هیات علمی دانشگاه تحصیلات تکمیلی صنعتی و فناوری پیشرفته
author
Vahid
Nakhaei
Department of Energy, Graduate University of Advanced Technology, Kerman, Iran
author
Mehran
Ameri
Department of Mechanical Engineering, Shahid Bahonar University
author
text
article
2017
per
Unglazed transpired solar air heater collectors are relatively new solar technologies that can be used for air heating or pre-heating ventilation air and drying agricultural and industrial products. Passing air through the perforated plate, which is usually metallic is the main mechanism of heat transfer. The cost of buying and preparing the absorber plate is the dominant share of costs allocated to this type of collector. In the present study, performance of non-metallic absorber plates available in the Iranian market, as an alternative to metal absorber plates are examined experimentally and theoretically. Therefore, three collectors with Metallic, Polycarbonate and Compressed-Plastic are designed, fobricated and tested in real conditions. In addition, a thermal modelbased on the first law of thermodynamic is developed for these collectors. In this model, all mood of heat transfer (including conduction, convection and radiation) are considered. Results show that there is a good agreement between experimental and theorical results (For most test condition, average relative error in estimation of the outlet temperature of the collectors is less than 5%). The results showed that the performance of three collector’s, espisially for low mass flow rates, was not too different. However, for considered condition Steel (metallic) collector has the best performance and the polycarbonate collector the worse performance. The performance of the Compress plastic was close to the Steel collector and given the low cost of non-metallic collectors, it can be used as a convenient alternative to metal collectors.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
339
350
http://mme-old.modares.ac.ir/article_17409_b5f51ee23b5662be9d49bf64480b98da.pdf
Design of decision-making lane change algorithm of truck-semitrailer in real dynamic environment
saeed
shojaei
Department of Mechanical Engineering, Shahid Rajaee teacher training University, Tehran, Iran
author
Ali
Rahmani Hanzaki
Department of Mechanical Engineering, Shahid Rajaee teacher training University, Tehran, Iran
author
Shahram
Azadi
Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran
author
Mohammad Amin
saeedi
Department of Mechanical Engineering, Islamic Azad University, Parand Branch, Parand, Iran
author
text
article
2017
per
The main goal of this study is to extract an algorithm for truck-semitrailer lane change maneuver decision-making in real dynamic environment. In order to accomplish this aim, a new method for determining decision-making constraints is applied based on the kinematics of the truck-semitrailer. In this approach, the various points of the truck-semitrailer are evaluated in different conditions when lane change maneuver is in progress, and the critical points of the truck-semitrailer are defined according to the present method. Critical points are used as the main points of the truck-semitrailer to apply the constraints. In order to enhance the efficiency of the methodology, new offline dynamic realistic method is used based on a four DoF dynamic model of the truck-semitrailer. By this approach, a relation for minimum time of the maneuver is extracted based on the dynamic model of the truck-semitrailer and environment features. Based on the results of the simulation assays, the minimum reliable time for lane change maneuver is chosen and decision-making strategies are proposed for the lane change maneuver of the vehicle in real dynamic environment. To evaluate the algorithm, it applied to a sample of the truck-semitrailers. The results predict the methodology is accurate and applicable.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
351
360
http://mme-old.modares.ac.ir/article_17411_ef2772bed3864d645040f9bbacb41cf1.pdf
Experimental Determination and Numerical Prediction of Necking and Fracture Forming Limit Curves of 2024 Aluminum Alloy Sheet Using Damage Criterion
Ali
Zahedi
Amirkabir University of Technology (Tehran Polytechnic)
author
Bijan
Mollaei-Dariani
Amirkabir University of Technology
author
Mohammadjavad
Mirnia
Department of Mechanical Engineering, Babol Noshirvani University of Technology
author
text
article
2017
per
Forming limit diagram (FLD) is one of the useful tools in the assessment of the sheet formability for designing industrial products. Experimental methods have been developed to determine FLDs. Costly and time-consuming experiments have led to several studies on the use of analytical methods and finite element softwares for predicting FLDs. In the present study, the necking and fracture forming limit curves of AA2024 aluminum alloy sheet were experimentally and numerically obtained through the hemispherical stretching test. Different geometries of the initial blank were considered to create different strain paths. The commercial finite element code Abaqus/Explicit was utilized to simulate experimental tests. Using theoretical equations and experimental results, fracture properties of the aluminum sheet in terms of the equivalent plastic strain at fracture, the stress triaxiality and the Lode angle parameter were captured and implemented in the Abaqus software. In order to capture necking forming limit strains, a numerical criterion based on the major strain variation in the necking zone has been considered. The comparison of the results shows that the numerical model can predict the forming and fracture limit strains with the maximum error of about 6%.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
361
371
http://mme-old.modares.ac.ir/article_17413_7e9a5ba0b0746dd6414de68b7faa97ef.pdf
Analysis of Laser Interfrometry Parameters in the Evaluation of Defects in the Polymer Matrix Composites
Davood
Akbari
Mechanical engineering-tarbiat modares university
author
Hamidreza
Asemani
Mechanical Engineering, Tehran Univ., Tehran, Iran
author
naser
soltani
Mechanical Engineering, Tehran Univ., Tehran, Iran
author
text
article
2017
per
Laser interferometry is one of the most applicable methods of calculating the surface displacement derivatives that can visualize very small displacement gradients, in µm/m level, on a relatively large area of a sample surface at once. This method can be beneficially used in industrial non-destructive tasting of materials, especially composites. However, getting an acceptable result of this inspection method, depends on the identification and properly adjusting the test parameters to a great extent. Shear size and loading amount, are the most important factors affecting crack detection ability in laser interferometry technique, which are both investigated in this paper. In this regard, several composite specimens with several cracks in different lengths have been prepared and tested with different parameters. Various tensile loading are applied to specify the allowable limit load in different shear sizes. Eventually, the effects of the crack inclination relative to the load direction are studied. The test results show that the best responses are observed with a shear size equal to the approximated defect sizes and a limited band of the loading range can be used to reveal the cracks.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
372
380
http://mme-old.modares.ac.ir/article_17412_89c65b80bdfca04207e43e23d0c43491.pdf
Improvement of wearing property of Al/ (SiC+BNh) surface hybrid composite fabricated by friction stir processing
Masoud
Mosallaee
هیات علمی گروه مهندسی مواد دانشکده مهندسی معدن و متالورژی
author
ameneh
daneshgar
university yazd
author
text
article
2017
per
In this study, the microstructural and tribological properties of surface Al/(SiC+BNh) hybrid composite was investigated. Al/(SiC+BNh) hybrid composite was produced on the surface of Al-1050 substrate via friction stir processing to achieve simultaneous high hardness of SiC particle and lubricating property of BNh particles. Microstructural studied revealed that grain refinement and significant reduction of grain size occurred in the stirred zone. Micro hardness evaluation illustrated that friction stir processing (FSP) increased hardness of stirred zone to about 60± 5HV that was 70% more than the hardness of base metal. Wearing and corrosion properties of Al/(SiC+BNh) hybrid composite were investigated and compared with those of base metal, friction stir processed, Al/SiC and Al/BNh surface composite. Evaluation of wearing property indicated that the wear rate of base metal, Al/SiC surface composite, Al/BNh surface composite and Al/(SiC+BNh) surface composite were 0.075, 0.047, 0.046 and 0.039mg/m, respectively which indicated the highest wearing resistance of Al/(SiC+BNh) in comparison to the base metal and mono SiC or BNh surface composite. This could be related to the simultaneous increase of hardness and reduction in the friction coefficient of hybrid surface composite. . Investigations of corrosion properties showed that FSP improved the corrosion resistance of base metal more than 30%.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
381
389
http://mme-old.modares.ac.ir/article_17414_65396b7db06762f0570a40186f614078.pdf
Effect of accumulative roll bonding process on microstructure and hardness of A356/TiC cast composite
Pejman
Momeni
Babol Noshirvani University of Technology
author
Roohollah
Jamaati
عضو هیئت علمی / دانشگاه صنعتی نوشیروانی بابل
author
text
article
2017
per
In this study, the effect of accumulative roll bonding (ARB) process on microstructure and hardness of cast A356/titanium carbide composite produced by semi-solid processing evaluated. ARB process up to 4 cycles on the composite containing 10 vol.% titanium carbide with an average particle size less than 10 μm performed at ambient temperature. Microstructural examination by optical microscope and harness tests including macrohardness and microhardness performed. The results showed that by increasing the number of process cycles, the distribution of the Si and TiC in the aluminum matrix homogenized, the particles became finer and more spheroidal. On the other hand, particle free zones removed and the quality of the bond between the particles and the matrix improved. In addition, the porosity in the casting structure significantly decreased. It was found that the hardness in the first two cycles greatly increased, and then the number of cycles had less effect on the hardness value. In general, the microstructure of the composite after 4 cycles of ARB process considerably refined so that the increased hardness of the composite was 170% compared to the cast. The results showed that by increasing the number of ARB cycles, the amount of fluctuation in the thickness of the composite decreased.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
390
396
http://mme-old.modares.ac.ir/article_17585_141f5dce533d1a9fccca1d846cab785a.pdf
Investigation of the mechanical properties of the porous scaffolds used in bone tissue engineering by means of micromechanical modeling
Sayed Misagh
Imani
دانشجوی دکتری، مهندسی مکانیک، دانشگاه صنعتی نوشیروانی بابل، بابل
author
Sayed Mahmood
Rabiee
دانشیار، مهندسی مکانیک، دانشگاه صنعتی نوشیروانی بابل، بابل
author
Ali
Moazami Goudarzi
استادیار عضو هیئت علمی دانشگاه نوشیروانی بابل
author
Morteza
Dardel
دانشیار، مهندسی مکانیک، دانشگاه صنعتی نوشیروانی بابل، بابل
author
text
article
2017
per
The use of porous scaffolds for repairing the damaged bone tissues has been increased in recent years. As exploration of the mechanical properties of the scaffolds on the basis of experiments is time consuming and uneconomic, mathematical models are increasingly being introduced into the field, but most of them rely on finite element method and theoretical studies are rarely found in the literature. In this paper, different micromechanical models are presented for obtaining the effective elastic properties of bone scaffolds. Using these models, the mechanical properties of different scaffolds, including ceramic and composite bone scaffolds, are investigated. Single scale and multi-scale modeling approaches are used to simulate the ceramic and composite scaffolds, respectively. Furthermore, because of the wide application of hydroxyapatite in fabrication of bone scaffolds, the mechanical properties of hydroxyapatite scaffolds in different porosities are obtained in the current study by means of the presented methods. Results show that Dewey, self-consistent and differential schemes are the best methods in calculation of the value of Young’s modulus of these scaffolds in porosity ranges of less than 30 %, 30 to 60 % and more than 60 %, respectively. Moreover, self-consistent scheme gives good estimation of the value of Poisson’s ratio of hydroxyapatite scaffolds in different porosities. By obtaining the values of the mechanical properties of the scaffolds in different porosities by these models and using the statistical analysis, the mathematical relationship between the porosity and the mechanical properties of this kind of scaffolds (Young’s modulus and Poisson’s ratio) is obtained.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
397
408
http://mme-old.modares.ac.ir/article_17494_b9b2c3dc651cf313d2ed4eca565cadf5.pdf
A Weakly Coupled Scheme for Modelling Bedload Sediment Transport Using an Augmented Riemann Solver
Mina
Barzgaran
Department of Civil Engineering, faculty of Engineering, University of Birjand, Birjand, Iran
author
Hossein
Mahdizadeh
Faculty member of Birjand University
author
Salman
Pouresmaeil
Department of Civil Engineering, Faculty of Engineering, Bojnord University, Bojnord, Iran
author
text
article
2017
per
In this paper a Godunov-type finite volume method is used for the solution of bedload sediment transport dynamics. The utilised equations for this modelling comprise the shallow water equations used for the hydrodynamic phase and also the Exner equation applied for the morphodynamic variations. These set of equations are then solved using a weakly-coupled scheme based on an augmented Riemann solver. In this approach the morphodynamic equation is first solved and the updated bedload changes with the same Riemann structure are used as a source term within the shallow water equations. The proposed numerical model is first used for the simulation of the parabolic sediment layer and the obtained numerical results are validated with the exact solution. Then, a bedload hump propagation with an initial subcritical condition which is able to create both mild and strong sediment and free-surface interactions is considered and the computed results are compared with the reference solution. These numerical results indicate that the defined weakly coupled method developed based on an augmented Riemann technique is able to be used for modelling bedload sediment transport for all flow regimes and exhibits a very good agreement with analytical or reference solutions for the given test cases.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
409
416
http://mme-old.modares.ac.ir/article_17495_87b0d2763070ad1dcae8d20ef28aca01.pdf
A numerical analysis of an active micromixer with the oscillating stirrer at the different aspect ratios by LBM
Hojjat
Khozeymeh-Nezhad
Ferdowsi university of mashhad
author
Hamid
Niazmand
دانشگاه فردوسی مشهد
author
text
article
2017
per
In the present paper, a numerical simulation is performed to analyze aspect ratio effects of a rectangular stirrer along with two other parameters, frequency and amplitude of stirrer on the mixing efficiency inside a straight microchannel by LBM. Results showed that in a low frequency amplitude, AR variations are not effective on the efficiency in low values of St, however, in the intermediate values, the efficiency increases with the increase of AR. Moreover, in high values of St, the rise in AR up to 0.5 leads to the efficiency reduction, but further increase of AR, increases the mixing efficiency too. In a larger amplitude than the previous case, in high values St, increasing AR up to 0.7 rises efficiency, but further increase of AR, decreases the mixing efficiency. In low and intermediate values of St, the mixing performance in low values of AR has been more efficient than high values of AR. Furthermore, it was shown that in a low frequency, the mixing efficiency decreases and then increases with rise in AR for all values of K so that the closer to 1 the AR, the better the mixing efficiency. In a higher frequency, the efficiency decreases and then increases with the growth in AR in small value of K, while this trend become inverse in large values of K. Generally, in intermediate values, the larger and nearer to 1 the AR, the larger the mixing efficiency.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
417
426
http://mme-old.modares.ac.ir/article_17496_67c7253f8254f284bf5a8afc2dfde0ef.pdf
Dynamic analysis of long thick cylindrical shell subjected to dynamic internal pressure using high order shear deformation theory
Sayyed Ali
Azarpazhoo
Department of Mechanical Engineering, University of Guilan, Guilan, Iran
author
Sayyed Roohollah
Kazemi
Department of Mechanical Engineering, University of Guilan, Guilan, Iran
author
text
article
2017
per
Designing explosion of gas pipelines, gun tubes, pulse detonation engine tubes and etc, all related to problem of cylindrical shell subjected to dynamic internal loads. In this paper, dynamic response of the thick cylindrical shell subjected to dynamic internal load with considering the high order shear deformation theory (HODT) is investigated and compared with the first order shear deformation theory of Mirsky- Hermann (FSDT). The effects of transverse shear deformation and rotatory inertia were included in the governing equations of the dynamic system. First, the equations of motion have been derived by using Hamilton’s principle then by changing variables the obtained partial differential equations have been converted to ordinary differential equations. With this method, the problem can be solved for various mechanical moving pressure loads without considering the effect of boundary conditions with long length assumption. The results of the present analytical method have been verified by comparing with finite element results, by using software. The comparison of the results with the finite element method shows that the high order theory and first order Mirsky-Hermann theory can predict the dynamic response of the thick cylindrical shell and the high order theory in areas away from the middle layer is more successful.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
427
438
http://mme-old.modares.ac.ir/article_17497_4c174124c80b18feb11ce91d88f00927.pdf
Effects of suction/injection on flow and heat transfer over a permeable surface in presence of different nanofluids
Hamid
Maleki
Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran.
author
Mohammad
Zolfaghar
Department of Mechanical Engineering, Qom University of Technology, Qom, Iran.
author
Mahdi
Mohseni
Faculty member,
Department of Mechanical Engineering,
Qom University of Technology, Qom, Iran.
author
text
article
2017
per
In this study, flow and heat transfer of some nano-fluids over a permeable surface with convective boundary condition has been investigated. Four types of nano-fluids, i.e. Cu-water, Al2O3-water, TiO2-water and Ag-water are considered for investigation. The governing partial differential equations (PDEs) first transformed to ordinary differential equations (ODEs) using similarity solution method. The obtained equations then, solved numerically by making use of Runge–Kutta–Fehlberg fourth–ﬁfth order’s (RKF45) method. The effects of nanoparticles type, volume fraction of nanoparticles, the type of permeability and convective boundary condition in three cases, i.e. suction, injection and impermeable surface, on the velocity and temperature variations as well as the local Nusselt number and skin friction coefficient are examined. The results show that some of above parameters have different effects in suction and injection states. The effect of nanoparticle volume fraction on velocity and temperature variations and then the local skin-friction coefficient and local Nusselt number are noticeably larger than in injection rather than suction or impermeable surfaces. In all cases, the increase of volume fraction lead to enhancement of local skin friction as well as Nusselt number. In the cases of suction and impermeable surfaces, the maximum friction coefficient was found with Ag-water as nano-fluid while the maximum Nusselt number observed with Cu-water nanofluid in suction.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
17
v.
9
no.
2017
439
449
http://mme-old.modares.ac.ir/article_17584_f4707c678c92697e685ae011016782ac.pdf