2018-03-18T03:50:27Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=342
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
On a Conceptual Method for the Extraction of Wind Energy Using Airfoil and Linear Generator
Hossein
Darijani
Abbas
Panahi
In this paper, a new conceptual method is introduced in order to extract wind energy using a set of airfoils and a linear generator. Indeed, the idea of this method is inspired from the ocean wave energy extractor, and the linear wind generator. In this method, under wind velocity a mover connected to the airfoils undergoes a linear reciprocating motion such that this motion is converted to electricity using the magnetic field of a linear generator. Moreover, the structure and mechanism of the proposed method is illustrated. Based on this illustration, a perfect kinematics and kinetics analysis of the mechanism including of the displacement, velocity, acceleration, force and mechanical powers is done. Finally, the average generative power based on the proposed method is investigated under different conditions and compared to the output power of the ocean energy extractors in similar situations. The most important advantage of the proposed method in comparison with two mentioned methods is its simplicity, high efficiency and compatibility to all wind situations.
Wind energy
Airfoil
Linear generator
Kinematics and kinetics Analysis
output Power
2017
04
01
597
609
http://scientiairanica.sharif.edu/article_4045_ba6cceb6f51752d0d3f98066018e7ef2.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
Economic and Environmental Evaluations of Different Operation Alternatives of an Aquifer Thermal Energy Storage in Tehran, Iran
Hadi
Ghaebi
M.N.
Bahadori
M.H.
Saidi
Aquifers are underground porous formations containing water. Confined aquifers are surrounded by impermeable layers on top and bottom, called cap rocks and bed rocks. A confined aquifer with a very low groundwater flow velocity was considered to meet the annual cooling and heating energy requirements of a residential building complex in Tehran, Iran. Four different alternatives of aquifer thermal energy storage (ATES) were employed to meet the heating/cooling demands of the buildings. These alternatives were: using ATES for cooling alone, for heating alone by coupling with flat plate solar collectors and for cooling and heating by coupling with a heat pump. For the economic evaluation of the alternatives, a life cycle cost analysis was employed. For the environmental evaluation, Ret Screen software was employed. For the three considered operational alternatives, using ATES for cooling alone had the minimum payback period time of 2.41 year and the life cycle cost of 16000$. In the environmental consideration of the three alternatives, coupling of ATES with heat pump for cooling and heating had the minimum CO2 generation, corresponding to 359 tons/year.
Aquifer thermal energy storage
economic evaluation
environmental evaluation
2017
04
01
610
623
http://scientiairanica.sharif.edu/article_4046_420cab581039e807c0ff8a988844d974.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
Effects of non-equilibrium condensation on aerodynamics of the flow field in a steam turbine cascade
Hamed
Bagheri Esfe
Mohammad Jafar
Kermani
Majid
Saffar Avval
In the present paper an in-house CFD code is developed using Roe scheme to simulate condensing two-phase flow in blade to blade passage of a steam turbine. Effects of condensation on the flow field of steam turbine rotor tip section are investigated for different outlet pressures. Firstly, comparison is performed between results of wet and dry cases. Then effects of outlet pressure variations on the flow field are studied. Finally effects of condensation on different specifications of the flow field (total pressure loss coefficient, entropy generation and deviation angle) are investigated. Also the mechanism of flow deviation in the cascade flow field is described. Condensation has a great influence on the behavior of the flow field based on the numerical results of this paper. It changes the outflow direction and consequently the flow entering to the next blade deviates from its on-design condition, thus additional losses are produced. For example, the value of deviation angle reaches to 7.62for wet case and exit Mach number Me=1.45. Also there are stagnation pressure loss and entropy generation due to non-equilibrium condensation that reduce the efficiency of the steam turbine
Steam turbine
Non-equilibrium condensation
Deviation angle
Stagnation pressure loss
2017
04
01
624
634
http://scientiairanica.sharif.edu/article_4047_e2ce21d98b4eb48e3863e56db3b7f8e6.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
MHD mixed convection boundary layer flow of a Casson fluid bounded by permeable shrinking sheet with exponential variation
S. S. P. M.
Isa
N. M.
Arifin
R.
Nazar
N.
Bachok
F. M.
Ali
I.
Pop
A review was carried out on the exponentially permeable shrinking sheet on how it influenced the magnetohydrodynamic (MHD) mixed convection boundary layer flow of a Casson fluid. The boundary layer equations in the form of partial differential equations have been transformed to the ordinary differential equations, by using the similarity transformation. Subsequently, the numerical technique uses the shooting way to provide solutions for the ordinary differential equations. Different factors related to the flow and heat are indicated by the attained results as well as graphs. Moreover, four solutions are presented graphically. Also, the numerical calculations exhibit that the Casson fluid parameter ε, buoyancy parameterλ and suction parameter s would significantly affect the characteristics of flow and thermal boundary layers of a Casson fluid.
Casson fluid
MHD
mixed convection
Exponentially shrinking sheet
2017
04
01
637
647
http://scientiairanica.sharif.edu/article_4048_f90278967e16e91f91079e6f34306d5d.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
Application of Homotopy Perturbation Sumudu Transform Method for Solving Nonlinear Fractional Heat-like Equations
Mohamed Meabed
Khader
In this paper, we propose an algorithm to find approximate solutions of the proposed system of the fractional heat-like equations. The proposed algorithm basically illustrates how the two powerful algorithms, the homotopy perturbation method (HPM) and the Sumudu transform method (STM) can be combined and used to get exact solutions of fractional partial differential equations. We also present some examples to illustrate the accuracy and the effectiveness of this algorithm.
Fractional heat-like equations
Caputo derivative
Mittag-Leffler functions Homotopy perturbation method
Sumudu transform method
2017
04
01
648
655
http://scientiairanica.sharif.edu/article_4049_e9b70e2a9bca01d00c46fa1289376b3f.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
Fatigue behavior of nano-grained pure copper processed by equal channel angular rolling
Asiyeh
Habibi
Mostafa
Ketabchi
Mohammad
Eskandarzadeh
The equal channel angular rolling process was successfully performed on commercial pure copper. After 4 passes of this process, grains with a diameter of about 70- 500 nm were formed. The fatigue test results showed that the ultra-fine grained copper represents a longer lifetime under stress-controlled fatigue. To clarify the formation process of surface damage, morphological changes in the fractured surface were monitored by scanning electron microscopy.
nano-grained copper
severe plastic deformation
equal channel angular rolling
Fatigue
2017
04
01
656
661
http://scientiairanica.sharif.edu/article_4050_1c69391225f96ceadf859cf581dc24b1.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
Improving Lateral Dynamics of Vehicle Using Direct Yaw Moment Controller Based on Quantitative Feedback Theory
Masoud
Goharimanesh
AliAkbar
Akbari
In this paper a robust controller based on quantitative feedback theory is designed to improve the stability of a four wheel vehicle using direct yaw moment controller. The essential yaw moment is calculated by this robust and applied to the vehicle dynamics model. Quantitative feedback theory controller design is based on a linear model which is assumed as a simple linear handling model, moreover, simulations are carried out based on nonlinear handling dynamics. The results show that the robust controller could overcome the system uncertainties and control the vehicle in various handling maneuvers.
Robust Control
Quantitative Feedback Theory
Direct Yaw Moment
Vehicle stability control
2017
04
01
662
672
http://scientiairanica.sharif.edu/article_4051_f7c4ef5fb661a527e50b37f7b3215256.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
A modified model for stability analysis of narrow-width NEMS tweezers: Corrections due to surface layer, scale dependency and force distributions
Ali
Koochi
Hossein
Hosseini-Toudeshky
Mohamadreza
Abadyan
Stability analysis and modeling the electromechanical response of nanotweezers is crucial for reliable design and manufacturing of these nano-devices. Herein, a modified model is developed for static and dynamic stability analysis of nanotweezers with low width to thickness ration (narrow width). The surface elasticity in conjunction with the strain gradient theory is employed to consider the coupled effects of scale dependency i.e. size-dependency of material characteristics and surface layer. The nonlinear governing equation was solved using analytical Rayleigh-Ritz method (RRM). The influence of various parameters including scale dependency, surface stresses, damping parameter and dispersion forces on the stability of the tweezers is addressed. Furthermore the maximum length and the minimum gap of the tweezers are computed which are of the important design parameters.
Nanotweezers
stability analysis
scale dependency
Surface layer
Strain Gradient Theory
2017
04
01
673
683
http://scientiairanica.sharif.edu/article_4052_435a319abf580da6487183d9c4dfdec9.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
High frequency vibrations of quartz crystals subject to initial thermo-mechanical bias
Mohammad Mostafa
Mohammadi
Mohsen
Hamedi
Hosein
DaneshPajooh
When a quartz resonator is exposed to an initial mechanical bias, its resonance frequency changes. This change in the resonance frequency is called the forcefrequency effect and isquantified by force frequency coefficient. The experimental data suggest that force frequency coefficient may change due to homogenous thermal biases on the quartzcrystal. In this article, we investigate the effect of initial homogeneous thermal strains on the force frequency effect. Then we derive an explicit formula that predicts the resonance frequency shift of the thickness shear mode of AT-cut quartz crystals. The mathematical model is validated on circular AT-cut quartz crystals at 78 using the experimental results. The model leads to a better understanding of quartz crystal behavior which increases accuracy of pressure sensors in applications suchas down-hole pressure measurement in the oil and gas industry.
quartz
force frequency effect
thermal bias
mathematical modelling
2017
04
01
684
697
http://scientiairanica.sharif.edu/article_4053_c7b8f09c8783bc9f98ffcf8cb4a2f1a6.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
Chemical reaction, soret and dufour effects on MHD mixed convection stagnation point flow with radiation and slip condition
H.
Niranjan
S.
Sivasankaran
M.
Bhuvaneswari
The main aim of the present study, the effects of Soret & Dufour on MHD mixed convection flow of a viscous fluid towards a vertical plate embedded in a porous medium in the existence of slip, radiation and chemical reaction. The numerical solutions acquired using shooting method and the governing equations are reformed into ordinary differential equations by similarity transformation. The present results compared with previously presented works are found in good agreement on several distinct cases. The effects of different parameters on velocity, temperature & concentration distributions are illustrated graphically. The variation of diverse parameters on local skin friction, rates of heat and mass transfer are obtainable in tabular arrangement. The velocity, temperature increases on increasing the Dufour parameter and the concentration profiles decreases when chemical reaction parameter increases.
Chemical reaction
MHD
porous medium
Radiation
Slip
Soret/Dufour
2017
04
01
698
706
http://scientiairanica.sharif.edu/article_4054_bf94cca12dd0d2f323d92811a4503feb.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
Multilevel optimization of profile of splitter blades in the impeller of a centrifugal compressor
S.Abolfazl
Moussavi Torshizi
Ali
Hajilouy Benisi
Mohammad
Durali
In this research a multilevel optimization on the profile of splitter blades of a turbocharger compressor is performed using genetic algorithm in order to improve its performance. Successive corrections of profile at hub, midspan and shroud of splitter blades, with the objective of decreasing incidence losses at the leading edge and adjustment of blade loading at shroud, results in an impeller having improved splitter blades. The impeller flow filed analysis shows the optimization has been successful in reducing flow leakage at the shroud region and as well as losses in leading edge region. Although numerical simulations predict0.5% decrease in pressure ratio at design point, but 2.2 points improvement in isentropic efficiency is calculated. Based on the optimization results a new impeller is designed and manufactured and tested on a turbocharger test bed. Experimental results approve the simulation prediction results on the expected improvement in performance
Centrifugal compressor
Optimization
splitter blades
blade profile
incidence loss
2017
04
01
707
714
http://scientiairanica.sharif.edu/article_4055_1c2d15f0270b8dcd88ef11d599d7e22a.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
An analytical method for finding exact solitary wave solutions ofthe coupled (2 1)-dimensional Painlevé Burgers equation
Ahmad
Neirameh
Mostafa
Eslami
In this present study we obtained some new analytical solutions, such as trigonometric function, rational function, and hyperbolic function solutions by using of new extension of the (G'/G)-expansion method to the coupled (2 + 1)-dimensional Painlevé integrable Burgers equation with the aid of the computer software Maple. This method allows to carry out the solution process of nonlinear wave equations more thoroughly and conveniently by computer algebra systems such as the Maple and Mathematica. In addition, some figures of partial solutions are provided for direct-viewing analysis. The method can also be extended to other types of nonlinear evolution equations in mathematical physics
Painlevé Burgers equation
soliton solution
hyperbolic, trigonometric and rational solutions
2017
04
01
715
726
http://scientiairanica.sharif.edu/article_4056_3cc75b6cc877c47c59e93483a6ada63d.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
2
Stress Analyses in Single Deck and Double Deck Floating Roofs Subjected to Earthquake Ground Motions
F.G.
Golzar
R.
Shabani
S.
Tariverdilo
This paper investigates the stress pattern in circular single and double deck floating roofs excited by earthquake ground motion. Variational formulation is employed to derive the governing equations. Response of the floating roofs is evaluated for different classes of ground motions including near field and far field records. Results indicate that far-field earthquakes produce larger wave elevation and different stress patterns emerge in the roof. It is found that the bending stresses in double deck roofs emerge in a smooth and approximately symmetric pattern with a peak around the mid-span. This pattern differs drastically with stress pattern in single deck floating roofs where several unpredictable local stress peaks arise. The results could have practical implications in the design process of floating- roof cylindrical tanks.
Cylindrical tank
Sloshing response
Earthquake
Floating Roof
2017
04
01
727
739
http://scientiairanica.sharif.edu/article_4057_86c6cbdaa72068ca7a6824dc82ee5c14.pdf