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fluid-mechanics
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Air Pollution Modeling, Using AERMOD Model Coupled with OpenFOAM Software
, M.Sc. Thesis Sharif University of Technology ; Tayyebi Rahni, Mohammad (Supervisor) ; Rashidi, Yousef (Supervisor)
Abstract
Over the course of past decade, air pollution has been placed among the top issues chocking capital Tehran. Stationary source of air pollution is among the most important, but, less treated facors. On the year, 2014, Tehran’s air quality company addressed a number of projects in this very field could gain further governmental supports. This announcement could be a sign, showing the importance of this research. These researches in fact, have the potentioal to increase the authority’s decision making abilities in critical situations. As the models prognosticates future with acceptble accuracy, it leads to highly efficient dicissions. The results could also be used in demographic studies as...
The Effect of Radiation Pressure on Dust and Gas Dynamics in Accretion Disks
, M.Sc. Thesis Sharif University of Technology ; Rahvar, Sohrab (Supervisor)
Abstract
The purpose of this study is to investigate the effect of radiation pressure on accretion disks. The radiation density causes the separation of electrons from ions which leads to the creation of an internal electric dipole. In this study Radiation density is calculated using the Eddington limit. Afterwards radiation pressure is calculated with the use of collisions between photons and electrons in the plasma. Collisions are assumed to happen only between photons and electrons, due to the larger cross section of electrons compared to protons. The mentioned assumption causes the creation of an electric dipole and with it an internal electric field. The separation of the charges is assumed to...
Entropy minimization in turbine cascade using continuous adjoint formulation
, Article Engineering Optimization ; Volume 48, Issue 2 , 2016 , Pages 213-230 ; 0305215X (ISSN) ; Mazaheri, K ; Sharif University of Technology
Taylor and Francis Ltd
Abstract
A complete continuous adjoint formulation is presented here for the optimization of the turbulent flow entropy generation rate through a turbine cascade. The adjoint method allows one to have many design variables, but still afford to compute the objective function gradient. The new adjoint system can be applied to different structured and unstructured grids as well as mixed subsonic and supersonic flows. For turbulent flow simulation, the k-ω shear-stress transport turbulence model and Roe's flux function are used. To ensure all possible shape models, a mesh-point method is used for design parameters, and an implicit smoothing function is implemented to avoid the generation of non-smoothed...
General framework for dynamic large deformation contact problems based on phantom-node X-FEM
, Article Computational Mechanics ; Volume 61, Issue 4 , April , 2018 , Pages 449-469 ; 01787675 (ISSN) ; Khoei, A. R ; Sharif University of Technology
Springer Verlag
2018
Abstract
This paper presents a general framework for modeling dynamic large deformation contact-impact problems based on the phantom-node extended finite element method. The large sliding penalty contact formulation is presented based on a master-slave approach which is implemented within the phantom-node X-FEM and an explicit central difference scheme is used to model the inertial effects. The method is compared with conventional contact X-FEM; advantages, limitations and implementational aspects are also addressed. Several numerical examples are presented to show the robustness and accuracy of the proposed method. © 2017, Springer-Verlag GmbH Germany
Multilevel optimization of the splitter blade profile in the impeller of a centrifugal compressor
, Article Scientia Iranica ; Volume 24, Issue 2 , 2017 , Pages 707-714 ; 10263098 (ISSN) ; Hajilouy Benisi, A ; Durali, M ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
In this research, multi-level optimization of the profile of the splitter blades of a turbocharger compressor is performed using genetic algorithm in order to improve its performance. Successive corrections of the profile at hub, mid-span, and shroud of the splitter blades, with the objective of decreasing the incidence losses at the leading edge and adjustment of the blade loading at the shroud, result in an impeller having improved splitter blades. The impeller flow field analysis shows that the optimization has been successful in reducing the flow leakage at the shroud region as well as the losses in the leading edge region. Although numerical simulations predict a decrease by 0.5% in...
Two-dimensional symmetric double contacts of elastically similar materials
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 230, Issue 10 , 2016 , Pages 1626-1633 ; 09544062 (ISSN) ; Adibnazari, S ; Sharif University of Technology
SAGE Publications Ltd
2016
Abstract
The two-dimensional contact problem for an elastic body indenting an elastically similar half plane resulting in double contacts is important for various applications. In this paper, a generic quasi-static two-dimensional symmetric double contact problem with nonsingular end points between two elastically similar half planes, under the constant normal and oscillatory tangential loading, is analyzed. The classical singular integral equations approach is utilized to extract the pressure and shear functions in the contact zones; subsequently boundary conditions at end points are applied and a new side condition is derived and titled "the consistency condition" for symmetric double contacts....
An experimental investigation into a novel small-scale device for energy harvesting using vortex-induced vibration
, Article International Journal of Low-Carbon Technologies ; Volume 16, Issue 2 , 2021 , Pages 317-325 ; 17481317 (ISSN) ; Bijarchi, M. A ; Mohammadi, O ; Shafii, M. B ; Sharif University of Technology
Oxford University Press
2021
Abstract
Renewable energies could be a good solution to the problems associated with fossil fuels. The storage of wind energy by means of small-scale devices rather than large-scale turbines is a topic that has gained lots of interest. In this study, a compact device is proposed to harvest wind energy and transform it into electrical energy, by means of oscillations of a magnet into a coil, using the concept of vortex-induced vibration (VIV) behind a barrier. For a more comprehensive investigation, this system is studied from two viewpoints of fluid mechanics (without magnet) and power generation (with the magnet). For this purpose, an oscillating plate hinging on one side and three barriers with...
Computational intelligence of Levenberg-Marquardt backpropagation neural networks to study the dynamics of expanding/contracting cylinder for Cross magneto-nanofluid flow model
, Article Physica Scripta ; Volume 96, Issue 5 , 2021 ; 00318949 (ISSN) ; Raja, M. A. Z ; Chu, Y. M ; Khan, W. A ; Abbas, S. Z ; Shoaib, M ; Irfan, M ; Sharif University of Technology
IOP Publishing Ltd
2021
Abstract
In the present investigation, design of integrated numerical computing through Levenberg-Marquardt backpropagation neural network (LMBNN) is presented to examine the fluid mechanics problems governing the dynamics of expanding and contracting cylinder for Cross magneto-nanofluid flow (ECCCMNF) model in the presence of time dependent non-uniform magnetic force and permeability of the cylinder. The original system model ECCCMNF in terms of PDEs is converted to nonlinear ODEs by introducing the similarity transformations. Reference dataset of the designed LMBNN methodology is formulated with Adam numerical technique for scenarios of ECCCMNF by variation of thermophoresis temperature ratio...
Transformer components impact on compatibility of measured PDs: Comparison of IEC60270 and RF methods
, Article High Voltage ; Volume 4, Issue 1 , 2019 , Pages 33-40 ; 23977264 (ISSN) ; Vakilian, M ; Toan Phung, B ; Blackburn, T ; Sharif University of Technology
Institution of Engineering and Technology
2019
Abstract
Power transformer partial discharge signal measurement using Radio Frequency method has advantages over IEC 60270 'apparent charge' measurement method for online monitoring due to greater immunity against external interference. However, the lack of a well-defined calibration relationship between the two methods is main disadvantage of RF method. Simultaneous measurements, using these two methods, carried out on various transformer PD source models, in laboratory, to investigate main parameters that affect the relationship of results of these two methods. In this paper, factors that influence this relationship are classified into three groups: (i) type of PD sources, (ii) transformer windings...
A perspective on electrostatics in gas-solid fluidized beds: Challenges and future research needs
, Article 13th International Conference on Fluidized Bed Technology, CFB 2021, 10 May 2021 through 14 May 2021 ; 2021 , Pages 426-431 ; 9781771368506 (ISBN) ; Bi, X. T ; Grace, J. R ; Sharif University of Technology
GLAB Reactor and Fluidization Technologies
2021
Abstract
This paper provides a perspective on the current knowledge and potential areas of future research related to electrostatics in fluidized beds. Aspects addressed include characterization techniques, interplay between electrostatics and hydrodynamics, charge control methods, applications of tribo-electrostatic fluidization systems, and computational simulations which account for electrostatic forces, as well as other forces. This is a complex research field involving fluid mechanics, powders, and electrical physics. © 2021 CFB 2021 - Proceedings of the 13th International Conference on Fluidized Bed Technology. All rights reserved
Aeroelastic instability analysis of a turbomachinery cascade with magnetorheological elastomer based adaptive blades
, Article Thin-Walled Structures ; Volume 130 , 2018 , Pages 71-84 ; 02638231 (ISSN) ; Navazi, H. M ; Haddadpour, H ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Torsional aeroelastic analysis of a turbomachinery cascade comprised of three-layered sandwich blades embedded with Magnetorheological Elastomer (MRE) core layer is carried out in this paper. The MRE material is used as a constrained damping layer between two elastic skins in order to investigate its effects on the aeroelastic stability of a blade cascade. To formulate the structural dynamic of the blades, torsional theory of rectangular laminated plates is used and the unsteady Whitehead's aerodynamic theory is employed to model the aerodynamic loadings. Assumed modes method and the Lagrange's equations are used to derive the governing equations of motion of the coupled aeroelastic system....
Analytical solution for contact problem between a tilted wedge and half-plane under partial slip condition
, Article Materials and Design ; Volume 29, Issue 7 , 2008 , Pages 1291-1299 ; 02613069 (ISSN) ; Naderi, D ; Sharafbafi, F ; Sharif University of Technology
Elsevier Ltd
2008
Abstract
Elastic contact problem of a tilted shallow wedge with a half-plane is considered. The problem is solved analytically in either full slip or partial slip conditions. Closed-form expression is given for the Muskhelishvili's potential function of the contact. In the partial slip condition, the locations of the stick and slip zones were given explicitly in terms of the applied external loads and coefficient of friction. The results have been compared with finite elements modelling results. © 2007 Elsevier Ltd. All rights reserved
A perspective on electrostatics in gas-solid fluidized beds: challenges and future research needs
, Article Powder Technology ; Volume 329 , 2018 , Pages 65-75 ; 00325910 (ISSN) ; Bi, X. T ; Grace, J. R ; Sharif University of Technology
Elsevier B.V
2018
Abstract
This paper provides a perspective on the current knowledge and potential areas of future research related to electrostatics in fluidized beds. Aspects addressed include characterization techniques, charge generation and dissipation mechanisms, interplay between the electrostatics and hydrodynamics, charge control methods, applications of tribo-electrostatic fluidization systems, and computational simulations which account for electrostatic charges. This is a complex research field involving fluid mechanics, powders and electrical physics, with potential rewards in terms of safety, process monitoring and new applications. © 2018 Elsevier B.V
Experimental investigation of mechanical behavior and microstructural analysis of bagasse fiber-reinforced polypropylene (BFRP) composites to control lost circulation in water-based drilling mud
, Article Journal of Natural Gas Science and Engineering ; Volume 100 , 2022 ; 18755100 (ISSN) ; Jafari Behbahani, T ; Ghotbi, C ; Nasiri, A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
During the drilling operation in high-permeability, natural and artificial fractured formations, the lost circulation of drilling mud is a common problem. Various methods have been applied to control lost circulation and among these methods, using Lost Circulation Materials (LCM) is the most common method that blocks the fluid loss channels in the formation by creating structures. In this project, the aim is to develop and use natural fiber-reinforced composites as LCM can be an innovative and technical solution. Natural fiber-reinforced composites have excellent properties such as high specific strength, non-abrasive, eco-friendly, and biodegradability. It seems to be possible that...
Hydrodynamic and electrochemical modeling of vanadium redox flow battery
, Article Mechanics and Industry ; Volume 16, Issue 2 , 2015 ; 22577777 (ISSN) ; Elyasi, S ; Mollazadeh, M ; Sharif University of Technology
EDP Sciences
2015
Abstract
Two and three dimensional modeling of a single cell of vanadium redox flow battery has been done thoroughly according to electrochemical and fluid mechanic equations in this study. The modeling has been done in stationary state and its results have been presented in three chemical, electrical and mechanical sub models. The parametric analysis on some of important factors in cell operation demonstrated that increase in electrode and membrane conductivity and electrode porosity contributes to electric potential increase in cells. Also operational temperature increase leads to decrease in cells' voltage. Better fluid distribution on the electrode surface area results in better cell operation,...
Discharge capacity of conventional side weirs in supercritical conditions
, Article 4th European Congress of the International Association of Hydroenvironment engineering and Research, IAHR 2016, 27 July 2016 through 29 July 2016 ; 2016 , Pages 658-664 ; 9781138029774 (ISBN) ; Jalili Ghazizadeh, M. R ; Kabiri Samani, A ; Nekooie, M. A ; Sharif University of Technology
CRC Press/Balkema
2016
Abstract
Side weirs are widely used for level control and flow regulation in hydraulic engineering applications such as irrigation, land drainage, and sewer systems. These hydraulic structures allow a part of the flow to spill laterally when the surface of the flow in the main channel rises above the weir crest. The supercritical flow over a side-weir is a typical case of spatially varied flow with decreasing discharge. This study is aimed at investigating the variations of specific energy along the side-weir using experimental results. Some diagrams have been presented in terms of dimensionless ratio of diverted discharge to total discharge. These diagrams which can be used in the design of side...
Modeling of thermal pollution in coastal area and its economical and environmental assessment
, Article International Journal of Environmental Science and Technology ; Volume 2, Issue 1 , 2005 , Pages 13-26 ; 17351472 (ISSN) ; Javid, A. H ; Moghimi, P ; Kayhan, K ; Sharif University of Technology
CEERS
2005
Abstract
The Persian Gulf is one of the aquatic ecosystems which has recently faced with different pollutions. Cooling water discharges due to various industries such as power plants can cause important disorders on present ecosystem balance because of its high temperature. Obviously, due to thermal pollution, a great number of aquatic creatures face with a new situation that they can not tolerate. Thermal pollution leads to their migration, creates a potential for new coming species which in turn can thoroughly change the marine ecosystem feature. The other impacts of this phenomenon are: disorders in reproduction, nourishment and other biological habits. In this research, thermal pollution due to...
A note on the resonant interaction between a surface wave and two interfacial waves
, Article Journal of Fluid Mechanics ; Volume 491 , 2003 , Pages 1-9 ; 00221120 (ISSN) ; Lawrence, G. A ; Seymour, B ; Sharif University of Technology
Cambridge University Press
2003
Abstract
Hill & Foda (1998) and Jamali (1998) have presented theoretical and experimental studies of the resonant interaction between a surface wave and two oblique interfacial waves. Despite many similarities between the findings there is one seemingly major difference. Hill & Foda's (1998) analysis indicated that there are only narrow bands of frequency, density ratio and direction angle within which growth is possible. On the other hand, Jamali (1998) predicted and observed wave growth over wide ranges of frequency and direction angle, and for all the density ratios that he investigated. We show that Hill & Foda's (1998) second-order representation of the dynamic interfacial boundary condition is...
Numerical analysis of coherent structures in bidirectional swirl combustion chamber
, Article Computational Thermal Sciences ; Volume 8, Issue 3 , 2016 , Pages 265-289 ; 19402503 (ISSN) ; Keshavarz, P. M ; Saidi, M. H ; Sharif University of Technology
Begell House Inc
Abstract
Analysis and identification of vortex structures and their formation, particularly in swirl flows, have received widespread interest among researchers in the field of fluid mechanics. Due to the importance of vortex structures and their applications in combustion chambers, a special type of combustion chamber, which is called a “bidirectional swirl combustor,” has been investigated in this work. The dependence of vortex structures on the combustion chamber geometry and fuel injection location in cold flow, the effect of hot flow on coherent structures, and the difference between vortex structures in hot and cold flows have been studied as well. A common characteristic which is in combustion...
Experimental works on dynamic behavior of laminated composite beam incorporated with magneto-rheological fluid under random excitation
, Article ACM International Conference Proceeding Series, 8 February 2017 through 12 February 2017 ; Volume Part F128050 , 2017 , Pages 156-161 ; 9781450352802 (ISBN) ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
Association for Computing Machinery
2017
Abstract
Laminated composite structures are widely being used in modern industries particularly robot arms, aerospace and wind turbine blades where the structures mainly exposed to harsh random vibration and in turn, leads to unpredicted failure. Adding Magneto-rheological (MR) fluids in such structures may significantly improve their dynamic response. In the present work, the vibration response of laminated composite beams filled with MR fluids (MR laminated beam) under random loading has been investigated using experimental as well as simulation approaches. Finite Element Model (FEM) has been utilized to simulate the vibration response under random loading. An in-house set-up has been designed to...