Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
Simulations of Particle Filtration and Tracking in Electrical Field
109
118
EN
Ahmad
Sedaghat
Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, 84156-83111, I. R. of Iran
sedaghat@cc.iut.ac.ir
Amir Hossein
Mohammadzadeh
Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, 84156-83111, I. R. of Iran
a.mohamadzadeh@mech.iut.ac.ir
The movement of charged particles in an electrical field is of practical importance in filtration efficiency and in electrostatic coating. In this paper, both of the applications have been investigated computationally. For the case of filtration, a mathematical model is introduced for the electret filter which is made of split type fibers. The filter was assumed to be composed of rectangular fibers arranged in staggered array field. Simulation was conducted to study the filtration efficiency. Single fiber efficiencies under various filtration conditions were calculated and compared with results obtained from semi-empirical expressions. In the electrostatic powder painting, the gas flow and particle flow fields inside a coating booth under given operating conditions are considered and the effects of particle sizes on their trajectories are studied. Steady state turbulent gas flow was simulated by solving incompressible Navier–Stokes equations and the standard k−ε turbulence model. The discrete phase of particles was modeled based on the Lagrangian approach. In both cases studied here, the flow field and the collection mechanisms were accurately simulated experimental observations.
Particle/gas flow,numerical simulation,Electrical filter,Powder coating
http://scientiairanica.sharif.edu/article_3474.html
http://scientiairanica.sharif.edu/article_3474_35e45f539e39f60047fe99653fb68cfe.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
Numerical simulation of oblique impact of a droplet on a surface in the film boiling regime
119
129
EN
P.
Pournaderi
Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156- 83111, Iran
s.pournaderi@me.iut.ac.ir
A. R.
Pishevar
Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
apishe@cc.iut.ac.ir
In this study we focused on the simulation of oblique collision of a water droplet on a superheated surface via a novel algorithm. In this approach vaporization rate of the droplet is computed and is accurately applied in the solution process. High temperature of the surface leads to the formation of a vapor layer between droplet and surface. Mesh clustering near the surface is used to capture the effect of the vapor layer. The level set method in conjunction with the ghost fluid method is used to represent a sharp interface. Available experiments confirmed the validity of the proposed algorithm. The Weber number based on the normal velocity is the dominant parameter in the oblique impact process. Spreading radius and contact time of the droplet are dependent on the normal Weber number. An increase in the initial normal velocity of the droplet enhances the total heat removal from the wall.
oblique impact,Leidenfrost regime,droplet,hot surface,level set,ghost fluid method
http://scientiairanica.sharif.edu/article_3475.html
http://scientiairanica.sharif.edu/article_3475_b7e8ee0f67f29711c3739a82e2d18fd1.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
The Effect of Angle of Attack on Limit Cycle Oscillations for High-Aspect-Ratio Wings
130
146
EN
Morteza
Dardel
Department of Mechanical Engineering, Babol Nooshirvani University of Technology, Babol, Iran
dardel@nit.ac.ir
Keivan
Eskandary
Department of Mechanical Engineering, Babol Nooshirvani University of Technology, Babol, Iran
keivan.eskandary@yahoo.com
Mohammad Hadi
Pashaei
Department of Mechanical Engineering, Babol Nooshirvani University of Technology, Babol, Iran
mpashaei@nit.ac.it
Amir Hossein
Kiaeian Moosavi
Department of Mechanical Engineering, Babol Nooshirvani University of Technology, Babol, Iran
a_kmoosavi@yahoo.com
In this study, the effect of the angle of attack on aeroelastic characteristics of high aspect ratio wing models with structural nonlinearities in unsteady subsonic aerodynamics flows are investigated. The studied wing model is a cantilever wing with flag, lag and torsion vibrations and with large deflection capability in according to Hodges-Dowell wing model. An unsteady low speed incompressible air flow is assumed to include the flow time lags. Variation of the limit cycle amplitudes and frequency with free stream velocity in different angle of attacks are carefully studied. For considered model, angle of attack has little effect on flutter velocity but its effect on limit cycle amplitudes and frequency is considerable. This study shows that the limit cycle amplitudes are very sensitive to variations in angle of attacks.
High aspect ratio wing,flap-lag and torsion,angle of attack,flutter,limit cycle oscillation
http://scientiairanica.sharif.edu/article_3476.html
http://scientiairanica.sharif.edu/article_3476_c33e649be4d50d6a6b366203152ccd4e.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
Modified fixed-grid finite element method in shape optimization problems based on gradientless method
147
161
EN
M.
Heshmati
Department of Mechanical Engineering, Kermanshah University of Technology, Kermanshah, Iran
m.heshmati@kut.ac.ir
F.
Daneshmand
Department of Mechanical Engineering, McGill University, Canada, H3A 2K6, Department of Bioresource Engineering, McGill University, Canada, H9X 3V9
Y.
Amini
School of Mechanical Engineering, Shiraz University, Shiraz, Iran
aminiyaser@shirazu.ac.ir
This paper presents a methodology for solving shape optimization problemswhere the unknown is the shape of the problem domain. The proposed algorithm is based on the minimization of the stress along design boundary calculated by the Modified Fixed Grid Finite Element Method (MFGFEM).
Using MFGFEM eliminates mesh adaptation and re-meshing processes as needed in the standard finite element method and reduces the analysis cost significantly. In this study, a new approach for computing stiffness matrix of boundary intersecting elements is also presented and optimal shape of the problem domain is obtained via a simple optimization algorithm.The performance of the proposed approach is investigated for the shape optimization problems. It is concluded that the results of the present method are in a good agreement with other analytical and finite element solutions.
Shape optimization,Fixed-grid finite element method,gradientless method,Stress concentration
http://scientiairanica.sharif.edu/article_3477.html
http://scientiairanica.sharif.edu/article_3477_140fe1a51edf2b55873c74336b63bcef.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
Tribological Investigation of RBD Palm Olein in Different Sliding Speeds using Pin-on-disk Tribotester
162
170
EN
S.
Syahrullail
Faculty of Mechanical Engineering, Universiti Teknologi Malaysia
syahruls@fkm.utm.my
M.I.
Izhan
School of Graduates Studies, Universiti Teknologi Malaysia
A.K.
Mohammed Rafiq
Faculty of Biomedical Engineering & Health Science, Universiti Teknologi Malaysia
rafiq@biomedical.utm.my
The tribological investigation in term of coefficient of friction and wear resistance of refined, bleached and deodorized palm olein was conducted using a pin-on-disk tribotester. Palm oil was selected as a candidate due to its superior tribological properties and its large production, that can lead to the mass production of bio-lubricant. The material of the pin and the disk is Titanium (Ti6Al4V).The experiments were conducted following the ASTM G99. The normal load was 9.8N and the observation time was 1 hour. The sliding speeds were 0.25m/s and 1m/s. In this research, only 5ml of the test lubricant was applied at the beginning of the experiment to investigate the capability of the lubricant to maintain its function. To make sure the lubricant do not subside due to the centrifugal force from the rotating disk, a groove was crafted on the disk. In this research, coefficient of friction and wear rate were calculated. From the analyses, the coefficient of friction calculated for palm olein was the lowest for both sliding speed conditions, while the wear rate obtained showed that palm olein was an efficient lubricating oil at a low speed and had high wear rate obtained at the high speed.
pin-on-disk,palm olein,wear rate,coefficient of friction,sliding speed
http://scientiairanica.sharif.edu/article_3478.html
http://scientiairanica.sharif.edu/article_3478_149ceb755cd6f2f8356b3c675adad2ab.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
Effect of speed and load on exergy recovery in a water-cooled two stroke gasoline-ethanol engine for the bsfc reduction purposes
171
180
EN
M.
Ghazikhani
Mechanical Engineering Department, Ferdowsi University of Mashhad, Mashhad, Iran
m_ghazikhani@yahoo.com
M.
Hatami
Mechanical Engineering Department, Ferdowsi University of Mashhad, Mashhad, Iran
m.hatami2010@gmail.com
B.
Safari
Mechanical Engineering Department, Ferdowsi University of Mashhad, Mashhad, Iran
behruoz.safari@gmail.com
Most important part of the second law of thermodynamic is described as determining the value and sources of wasting exergy in processes and suggests concepts for reducing the losses in order to enhance the efficiency. So, the main purpose of this paper is to study the effect of alcoholic additives and load and engine speed on combustion irreversibilities and second law efficiency. The mentioned alcoholic fuel is Ethanol which is combined with gasoline in different percentages of 5, 10, and 15%. The experiments have been done for 2500, 3000, 3500 and 4500 rpm and 25%, 50% and 75% full load. The results show that in most of the times that the alcoholic fuel was used, the combustion internal irreversibility increased and second law efficiency decreased, which is due to the increase in temperature difference between burnedcombustionproductsand unburned mixture, but increasing in load and engine speeds, increased the second law efficiency. Another important outcome from present study is demonstrating the brake specific fuel consumption (bsfc) reduction due to using recovered exergy from water which its average value was 14.1%.
Exergy,Irreversibility,Two Stroke Engine,Ethanol,bsfc
http://scientiairanica.sharif.edu/article_3479.html
http://scientiairanica.sharif.edu/article_3479_fb0f8ea8ced2dae6745e0c156d94959a.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
Machining commands generation with the rotational C2 PHquintic curve interpolant for cam profile manufacturing
181
191
EN
Javad
Jahanpour
Department of Mechanical Engineering, Mashhad branch, Islamic Azad University, Mashhad, Iran
jahanpourfr@mshdiau.ac.ir
Hossein
Dolatabadi
Department of Mechanical Engineering,Mashhad branch, Islamic Azad University, Mashhad, Iran
h.dolat@yahoo.com
This paper presents a new method to generate the cam position commands required for manufacturing a cam profile by an open-architecture CNCmachine. At first, the junction points of several connected PH quintic curves as the cam segments are obtained based on the supposed desired follower motion. Consequently, the desired cam curve is represented via multi-segment C2 PH quintic curve. After that, the new interpolation algorithm is proposed to generate the position commands required for machining of the cam. The designed cam-follower mechanism is performed for several case studies to evaluate the effectiveness of the employed curve representation and the proposed interpolation algorithm. The simulation results demonstrate that the proposed interpolation algorithm is capable for providing a smooth transition for all regions of the follower motion and the obtaineddisplacement, velocity, acceleration and jerk profiles match the corresponding desired profiles closely. Therefore, the newly advised interpolation algorithm with the uniform segmentation scheme is not only feasible for generating the cam position commands but also yields satisfactory performance for the follower motion. Also, the non-uniform rotational segmentation of the cam curve causes the amount of the kinematic characteristics of the follower motion are significantly increased compared to the corresponding desired profiles.
Cam profile,C2 PH quintic curve,Junction point,Rotational interpolation,CNC command generation
http://scientiairanica.sharif.edu/article_3480.html
http://scientiairanica.sharif.edu/article_3480_ba9fdeb6a00669a237bdce925040fb2f.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
The Unsteady Behavior of Subsonic Wind Tunnel Wall Pressure during a Pitching Motion of the Model
192
202
EN
Ali R.
Davari
0000-0003-0101-7069
Department of Mechanical and Aerospace Engineering, Islamic Azad University- Science and Research Branch, Poonak, Tehran, Iran
ardavari@srbiau.ac.ir
M. R.
Soltani
Department of Aerospace Engineering, Sharif University of Technology, Azadi Ave., Tehran, Iran
msoltani@sharif.edu
M.
Ghaeminasab
Department of Mechanical and Aerospace Engineering, Islamic Azad University-Science and Research Branch, Tehran, Iran
mghaemi@yahoo.com
Extensive low speed wind tunnel experiments have been undertaken to measure the test section floor wall pressure distribution in presence of a 2D wing inside the test section. The experiments were performed for both static and dynamic pitching motion of the model at different conditions. In these measurements the effects of existence and oscillations of 2D wing on the floor wall pressure at various locations were studied. According to the results, as the oscillation parameters such as mean angle of attack and frequency change, the wall pressure at the points located in the front part of the test section, in the upstream region, exhibit a different behavior than those in the downstream part. Viscosity is shown to be a major contributor in convecting the fluctuations caused by the model oscillations to the flowfield. As the Reynolds number increases, the downstream region receives less disturbances from the pure dynamic motion of the model. It is believed that the static wake is the dominant contributor in the absence of the viscous effects.
Interference Effect- Pitching Oscillation- Reduced Frequency- Upstream- Disturbance Convection
http://scientiairanica.sharif.edu/article_3481.html
http://scientiairanica.sharif.edu/article_3481_b684bbd593480b5f9497e3d862d60c88.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
Magnetohydrodynamic flow in a permeable channel filled with nanofluid
203
212
EN
M.
Sheikholeslami
Department of Mechanical Engineering, Babol University of Technology, Islamic Republic of Iran
mohsen.sheikholeslami@yahoo.com
D.
D. Ganji
Department of Mechanical Engineering, Babol University of Technology, Islamic Republic of Iran
ddg_davood@yahoo.com
In this paper, the problem of laminar Magnetohydrodynamic nanofluid flow in a porous channel is investigated. Optimal Homotopy Asymptotic Method (OHAM) is used to solve this problem.In order to consume CPU time, Galerkin method is used to minimize the residual. This investigation compared with numerical method (four-order Rung-kutte method) and found to be in excellent agreement. The base fluid in the channel is water containing copper as nanoparticle. The effective thermal conductivity and viscosity of nanofluid are calculated by the Maxwell–Garnetts (MG) and Brinkman models, respectively. The influence of the three dimensionless numbers: the nanofluid volume fraction, Hartmann number and the Reynolds number are examined. The results indicate that velocity boundary layer thickness decreases with increase of Reynolds number and nanoparticle volume fraction and it increases as Hartmann number increases.
Nanofluid,Laminar flow,Permeable channel,Uniform magnetic,Optimal Homotopy Asymptotic Method (OHAM),galerkin method
http://scientiairanica.sharif.edu/article_3482.html
http://scientiairanica.sharif.edu/article_3482_f3cf86f183452192313c202b51a09d74.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
Mathematical Modeling and Decomposition of Hydrodynamics-Acoustic Fields Using Perturbation Methods
213
221
EN
Mohammad
Riahi
Department of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran
riahi@iust.ac.ir
Norouz M.
Nouri
Department of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran
mnouri@iust.ac.ir
Ali
Valipour
Department of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran
avalipour@iust.ac.ir
Conservation of mass, momentum, energy and state equations are recognized as basic mathematical models in the analysis of acoustic behavior of cavitation as well as supercavitation. Also, it is known that the order of acoustics effects aren’t as higher as hydrodynamics ones. Therefore, in this paper, initially, for comparing different terms of equations, via using scale analysis, conservation equations are converted into dimensionless. Then by comparing all conditions coupled with weighting terms available in those equations, groups of parameter which are most appropriate with the hydrodynamics and hydroacoustic of the cavitating flow were selected. By regarding acoustic as lower order phenomenon, compared to hydrodynamic of flow and simultaneously using perturbation method, two equations containing leading and first orders and different terms could be attained. Obtained results were indicated that leading order equations represent hydrodynamic of the cavitating flow and first order equations indicate acoustics of cavitation or supercavitation. Acoustic equations of the present study contain terms related to fluid viscosity, density and pressure changes and background flow velocity. As acoustic equations coupled with leading order equations, in order to find noise of cavitation, equations of fluid flow for compressible flow should be resolved.
Mathematics Modeling,Cavitation,Supercavitation,Perturbation method,Scale Analysis
http://scientiairanica.sharif.edu/article_3483.html
http://scientiairanica.sharif.edu/article_3483_41fe54f78c84ec32e18ab89f99a4ba3a.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
Performance Study on Dehumidifier of Packed bed Liquid desiccant System
222
228
EN
Hesamoddin
Salarian
Department of Mechanical Engineering, Nour Branch, Islamic Azad University Nour, Iran
h_salaryan@yahoo.com
Bahram
Ghorbani
Faculty of Mechanical Engineering, K.N.Toosi University of Technology, Tehran, P.O. Box: 19395-1999, Iran
bahram330ghorbani@gmail.com
Majid
Amidpour
Faculty of Mechanical Engineering, K.N.Toosi University of Technology, Tehran, P.O. Box: 19395-1999, Iran
amidpour@kntu.ac.ir
Gholamreza
Salehi
Faculty of Mechanical Engineering, slamic Azad University, Branch of Nowshahr, Nowshahr, Iran
Liquid desiccant evaporation cooling air conditioning system introduced in this paper. The dehumidifier and regenerator play the most important role in this system. For liquid-gas contact, packed towers with low pressure drop provide good heat and mass transfer characteristics for compact designs.The experimental data have been obtained from a built prototype of liquid desiccant system in a packed bed unit with a surface area per unit volume ratio of 125 m2/m3, the liquid desiccant ,viz lithium chloride. The result showed that the mean mass transfer coefficient of the packing dehumidifier was 0.02kg/ m2s Also the absorber characteristic parameter, the packing size or number of transfer units (NTU), and air-to-desiccant solution mass flow rate ratio (ASMR) are crucial parameters. These parameters are affected to humidity effectiveness and enthalpy efficiency, are introduced and defined in this paper. High efficiency could be achieved if proper values of these variables are selected. In this studyenthalpy efficiency from experimental results has been comparedwith theanalytical computation result based on optimumASMR. From analytical solution, an optimum mass flow rate ratio can be deduced for optimal design of both dehumidifiers and regenerators, but in this studybehavior of the absorberhas been considered.
liquid desiccant system,absorber,Experimental model,dehumidifier efficiency,mass transfer coefficient,optimumASMR
http://scientiairanica.sharif.edu/article_3484.html
http://scientiairanica.sharif.edu/article_3484_6fb625792bee477fe28dc4388bdf5a68.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
21
1
2014
02
01
Analytical solution for the generalized Kuramoto-Sivashinsky equation by differential transform method
229
229
EN
Saeideh
Hesam
Department of Mathematics, School of Mathematical Sciences, Shahrood University, P.O.Shahrood University, P.O.Box 3619995161-316, Shahrood, Iran
taranome2009@yahoo.com
Alireza
Nazemi
Department of Mathematics, School of Mathematical Sciences, Shahrood University, P.O.Box 3619995161-316, Shahrood, Iran
nazemi20042003@yahoo.com
Ahmad
Haghbin
Department of Mathematics, Gorgan branch, Islamic Azad University, P.O. Box 4914739975-717, Gorgan, Iran
ahmadbin@yahoo.com
In this paper, the numerical solution of the generalized Kuramoto-Sivashinsky equation is presented by differential transform method (DTM). The DTM is a powerful and efficient technique for nding solutions of nonlinear equations without the need of a linearization process. In this approach the solution is found in the form of a rapidly convergent series with easily computed components. Numerical experiments demonstrate accuracy and robustness of the method for solving a class of onlinear partial differential equations.
Kuramoto-Sivashinsky equation,Differential transform method,exact solution,Closed form solution
http://scientiairanica.sharif.edu/article_3485.html
http://scientiairanica.sharif.edu/article_3485_f0e7f08a6c45f6e2afb58d8b3b276c67.pdf