2018-09-20T15:44:34Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=324
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
Fluid–structure interaction analysis of a piezoelectric flexible plate in a cavity filled with a fluid
Y.
Amini
H.
Emdad
M.
Farid
This study presents a numerical analysis of fluid- structure interaction whose structure is a flexible piezoelectric material. Piezoelectric materials are widely used in aeroelasticity and turbomachinery fields for vibrational, flutter and noise control. In this work a FSI benchmark is revised to contain the piezoelectric materials. The influence of piezoelectricity on the oscillation of the structure and fluid flow is considered. For validation, two benchmark problems are solved and results of the present code are compared with those of the previous works. Current results show that the piezoelectric behavior of a plate significantly influences the oscillation of the plate and the fluid flow properties.
Fluid–structure interaction
piezoelectric actuators
Smart materials
large structural deformations
2016
04
01
559
565
http://scientiairanica.sharif.edu/article_3843_2983ce88a3477b9c43a41300116cead0.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
Improvement of TFT-LCD's polarizer plate bubble problem using a preheating-process
Chern-Sheng
Lin
Jung-Ti
Huang
Pin Yi
Wu
Yun-Long
Lay
Hung-Jung
Shei
In this study, improvement of the polarizer plate bubble in the thin film transistor liquid crystal display process, especially where the polarizer plate is attached to the black matrix area at the end of the glass substrate, is presented. This study proposed temperature control functions during the attaching process using the preheating operations of pressure sensitive adhesives and a pre-existing warp polarizer plate. The polarizer plate is softened evenly, and, then, the bubbles can be discharged smoothly in the attaching process. Three main control factors are used in the polarizer plate attachment process, using an experimental design method, to determine the best combination of parameters. By applying optimal parameters in the experiments, bubble width can be decreased by 60.49%, compared with that of the previous process.
Preheating-process
Black matrix area
Polarizer plate
2016
04
01
566
574
http://scientiairanica.sharif.edu/article_3844_e317ea2ce0b76dec943e37c02c5058b4.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
Investigating the Effects of Ionic Polymer Metal Composite Patches on Aeroelastic Characteristics of a Cantilever Wing in Supersonic Flow
Shahab
Jamshidi
Morteza
Dardel
Mohammad Hadi
Pashaei
This work presents energy harvesting from limit cycle oscillation of low aspect ratio rectangular cantilever wings in supersonic flow. The wing is modeled in according to classical plate theory with Von-Karman strain-displacement relations for modeling large deflections due to mid plane stretching. The aerodynamic pressure is evaluated based on the quasi-steady first-order piston theory. Linear and nonlinear aeroelastic characteristics of the considered model are accurately examined and the effects of ionic polymer metal composite (IPMC) energy harvesting on flutter margin and limit cycle oscillation amplitudes are investigated. It is shown that position of IPMC on the wing has a great effect on the amount of harvested power. Since IPMC induces a high level of strain, it produces static deflection of wing. This static deflection produces stiffness hardening of the entire system, and accordingly can greatly reduce the amplitude of limit cycle oscillation. Obtained results show that IPMC actuator has more influence on limit cycle oscillation of wing, while its effect on flutter instability is negligible.
energy harvesting
IPMC
flutter
limit cycle
supersonic flow
2016
04
01
575
587
http://scientiairanica.sharif.edu/article_3845_7ec25aebfd3f18eef679db5063716e2f.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
First-Order Optimal Line-of-Sight Guidance for Stationary Targets
S. H.
Jalali-Naini
S. H.
Sajjadi
In this paper, a closed-loop optimal line-of-sight guidance law for first-order control systems is derived for stationary targets. The problem is solved for the one-dimensional case using normalized equations to obtain normalized guidance gains and performance curves. Three sets of normalized equations are introduced and discussed using different normalizing factors. The performance of the guidance laws are compared in normalized forms with zero-lag optimal guidance and first-order optimal scheme with steady-state gains using a second-order control system. Normalized miss distance analysis shows that the miss distance of the first-order guidance law is smaller than the two mentioned schemes for small total flight times.
Line-of-Sight Guidance
Optimal Guidance
Normalized Miss Distance Analysis
First Order Control System
2016
04
01
588
599
http://scientiairanica.sharif.edu/article_3846_e753b5fd15fb0cf1b25f083d830a9180.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
An Alternative Mechanism for the formation of High Density Lipoprotein in Peripheral Tissues
B.
Damirchi
M. S.
Saidi
M.
Rismanian
M.
Amininasab
High Density Lipoprotein (HDL) is a lipid-protein complex which is responsible to transport cholesterol and triglyceride molecules due to the inability of these compounds to dissolve in aqueous environment such as bloodstream. Among renowned probable structures, belt like structure is the most common shape which is proposed to this vital bimolecular complex. In this structure, the protein scaffold encompasses the lipid bilayer and a planar circular structure is formed. Several HDL simulations with embedded components in lipid section were performed. Here we applied a series of molecular dynamics simulations using MARTINI coarse grain force field to investigate an HDL model with pore of different radiuses in bilayer section instead of embedding components. The results of such studies revealed the probable structural modes in HDL configurations. In addition, totally 2.5 µs simulations lead to study the ratio of lipids to protein in HDL conformation and determine the structural shape of HDL and stability of each model due to atomic interactions. Furthermore, we proposed new conformation for HDL in its initial steps of constructing outside of cells and in peripheral tissues.
High Density Lipoprotein
Structural modes
Lipid protein complex
assembly
2016
04
01
600
608
http://scientiairanica.sharif.edu/article_3847_e5d00752d31916b9b5ff2a9219e7ceae.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
ESTIMATION OF MECHANICAL PROPERTIES OF WELDED S355J2+N STEEL VIA THE ARTIFICIAL NEURAL NETWORK
Hakan
ATES
Bekir
DURSUN
Erol
KURT
A new estimation study on the material features for the welding processes is reported. The method bases on the artificial neural network (ANN) for the estimation of material features after in the gas-metal arc welding process. Since the welding is a very common process in many engineering areas, this method would certainly assist the technicians and engineers to estimate the material features related to the welding parameters before any welding operation. In the proposed method, the input parameters of welding are defined as various shielding gas mixtures of Ar, O2 and CO2. As the resulting feature, the estimation is made on the mechanical properties such as tensile strength, impact test, elongation and weld metal hardness following ANN. The controller is trained with the scaled conjugate gradient method. It is proven that some estimated values are consistent with the experimental data, whereas some others have relatively higher errors. Thus, this method can be used to estimate especially the yield strength and elongation values, when the shielding gas proportions are ascertained before the welding, thereby the method helps to ascertain the welding gas selection in a very short time for engineers and assists to decrease the welding costs.
Welding
yield strength
impact test
Hardness
elongation
ANN
2016
04
01
609
617
http://scientiairanica.sharif.edu/article_3848_d0d0c1a9f002fb6f3e22f766be77279a.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
Numerical prediction of thermo-aeraulic behavior for a cavity with internal linear heat source
C.
Teodosiu
D.
David
R.
Teodosiu
Computational Fluid Dynamics (CFD) is a promising way, nowadays, to predict the air Flow in enclosures. As a result, the objective of this study is to assess the potential of CFD technique to predict the air Flows driven by buoyancy in heated real-scale rooms. The numerical model is validated using experimental data for fullscale test rooms; therefore, the experimental set-up is rst presented. This is followed by the numerical model description, focusing on its principal elements: computational domain geometry, discretization, turbulence model, radiation model, and thermal boundary conditions. In addition, a simplied approach is proposed to integrate a heat source in CFD models: Term source homogeneously spread all over the volume of the heat source. Comprehensive experimental-numerical comparisons are presented in terms of heat transfer to the walls of the test room, heat source behavior, and plume development. The results show that the model developed in this study leads to realistic predictions. Finally, the simplied CFD description of heat sources developed here can be extrapolated for other congurations - dierent power, heat emission (convection/radiation), dimensions, and shape. Consequently, this method can be applied in detailed studies dealing with thermal comfort, indoor air quality, and energy consumption for heated rooms.
Computational Fluid Dynamics modeling (CFD)
Transition SST k-w turbulence model
DO radiation model
Experimental full-scale room
Buoyancy-driven cavity
Linear heat source
2016
04
01
618
632
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
Forced vibration analysis of a system equipped with the nonlinear displacement-dependent (NDD) damper
Javad
Jahanpour
Mojtaba
Porghoveh
Shahab
Ilbeigi
In this paper, forced vibration analysis of a mass-spring system equipped with a nonlinear displacement-dependent (NDD) damper is elaborated. To this end, the nonlinear governing differential equation of the system is derived for two types of soft- and hard- periodic excitations. In order to obtain the displacement of the excited system, the approximate analytical solution of the governing equation is developed using the multiple scales method (MSM). The proposed analytical formulations are performed for several cases of hard- and soft-excitation and are also verified by the numerical fourth-order Runge-Kutta method. Moreover, the performance of the NDD damper is analyzed and compared with the traditional linear damper used in the both hard- and soft-excited vibration analyses. For a same external periodic force, a comparison has also been carried out between the responses of the hard- and soft-excitations. It is found that the organizing the external force based on its amplitude into two types as soft- and hard- excitation, leads to a better estimated response in the forced vibration analysis. Moreover, the NDD damper has a superior performance in reducing the vibration amplitude thorough tending to the steady-state solution compared to the traditional linear damper.
Nonlinear displacement-dependent (NDD) damper
Forced vibration analysis
Hard- and Soft- excitation
Multiple scales method
Vibration reduction
2016
04
01
633
647
http://scientiairanica.sharif.edu/article_3850_d8ce54b4bf29264e57c9907a7145451e.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
A novel computational framework to approximate analytical solution of nonlinear fractional elastic beam equation
K.
Sayevand
K.
Pichaghchi
In this paper, the generalized travelling solutions of the nonlinear fractional beam equation is investigated by means of homotopy perturbation method. The fractional derivative is described in the Caputo sense. The reliability and potentiality of the proposed approach which is based on joint Fourier-Laplace transforms and homotopy perturbation method will be discussed. The solutions can be approximated via an analytical series solution. Moreover, convergence and stability of the proposed approach for this equation is investigated. The results reveal that the proposed scheme is very effective and promising.
Caputo fractional derivative
Nonlinear elastic beam equation
Fourier transform
Laplace trans- form
Homotopy perturbation method
2016
04
01
648
657
http://scientiairanica.sharif.edu/article_3851_bb4b91c36f7002a710640f39c573fe57.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
Modeling Paramecium swimming in a capillary tube
Ali
N. Sarvestani
Amir
Shamloo
Mohammad Taghi
Ahmadian
In certain types of biomimetic surgery systems, micro robots inspired by Paramecium are designed to swim in a capillary tube for gaining access to internal organs with minimal invasion. Gaining insights into the mechanics of Paramecium swimming in a capillary tube is vital for optimizing the design of such systems. There are two approaches to modeling the physics of micro swimming. In the envelope approach which is widely accepted by researchers, Paramecium is approximated as a sphere self-propelled by tangential and normal surface distortions. Not only this approach is incapable of considering the specific geometry of Paramecium, but also it neglects short range hydrodynamic interactions due to beating cilia. Thus it leads to dissimilarity between experimental data and simulation results. In this study, it is aimed to present a sub layer approach to modeling Paramecium locomotion which is capable of directly applying the hydrodynamic interactions due to beating cilia on Paramecium boundary. In this approach, Paramecium’s boundary is discretized to hydrodynamically independent elements; in each time step of swimming, a specific function is fit to Paramecium boundary. Then, element coordinates are extracted and fluid dynamic equations are solved to model the physics of micro swimming.
Paramecium
swimming
Modeling
modified boundary element
2016
04
01
658
667
http://scientiairanica.sharif.edu/article_3852_5bbb7366ba638226b3c3f918346fdae8.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
A Novel Method for Maximum Lift Prediction in High-Lift Configurations
Mahmoud
Pasandideh Fard
Seyyed Ali
Sahaf
Many decisions in the preliminary design steps of an aircraft are very hard to take, due to a lot of unknown variables at this stage. These early decisions can be made more reliable by testing different configurations by numerical methods repetitively. Therefore it is very important to have a rapid, reliable and particularly easy to implement numerical tool. One of the most important steps in aerodynamic configuration development is design and sizing of the high lift devices. The main criterion for this design is lift increment that a particular configuration can produce. Therefore, it is very important to adequately estimate the maximum lift coefficient for a flapped wing at highly deflected flap configurations.This paper tries to introduce a novel numerical-empirical method for estimation of lift generation capability of a specific high lift device configuration. However, drag production estimation is not in the scope of this paper. In this method the linear portion of the lift curve is derived numerically, while the curved near stall region is estimated through empirical methods. The results are compared with some experimental data to show the method validity.
High Lift Device
Aircraft Design
Maximum Lift
Reynolds Average Navier Stokes
2016
04
01
668
677
http://scientiairanica.sharif.edu/article_3853_a9696c53cb227aa111f93a4cb6540b73.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2016
23
2
Investigation of the Effect of Walkway Orientation on Natural Ventilation
M.
Rismanian
A. F
Forughi
F.
Vesali
M. S.
Mahmoodabadi
Proper orientation of walkways based on regional winds and local shades provides a good control over walkways ventilation. Architectures of the old town of Sirjan had experimentally orientated the city’s walkways in a manner that shadows in walkways produced the maximum possible natural ventilation in this hot and dry town. This study has focused on this optimum design of Sirjan city considering natural ventilation mechanism. At first, a typical walkway with certain geometric parameters is considered. Then, considering the symmetry of the shadows cast in walkways, the natural ventilation rate is investigated at 7 different angles with 15° intervals. The problem is modeled using finite volume method numerically with Sirjan climate conditions. Results show that the present orientation of walkways in this city creates the maximum possible rate of natural ventilation and thermal comfort in a walkway.
Natural Ventilation
Walkway orientation
free convection
Sirjan
Finite volume
2016
04
01
678
684
http://scientiairanica.sharif.edu/article_3854_ceadda300d3bbdcdad42e3e02b5f55f7.pdf