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Modeling Saturated Porous Media Using Extended Finite Element Method
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
Soil structures have important roles in civil engineering applications. The most important types of these structures are soil dams and foundations which their damages may cause huge loss. Thus, appropriate analysis of these structures under possible loading conditions is unavoidable. The real behavior of this media can be achieved from the solution of its coupled governing differential equations. In order to solve this set of equations in practical applications, appropriate numerical solutions should be used. The finite element method can be called as one of the most important numerical solutions of differential equations which have been used in analyzing different types of engineering...
Nonlinear Analysis of Vibration of Tapered Piezo Electromagnetic Beam in Presence of External Permanent Magnet in Order to Energy Harvesting Improvement
, M.Sc. Thesis Sharif University of Technology ; Hosseini Kordkheili, Ali (Supervisor)
Abstract
With the increasing development in the field of electronics and information technology, the required dimensions and power of electronic devices and sensors have decreased. The range of applications of these electronic devices is very large, which is the product of technological progress development. There is a problem in the development and application of such devices, the supply of electrical power used in them, especially in the set of wireless sensors, this problem is more significant.The use of piezoelectric materials is one of the methods of converting mechanical energy into electrical energy. The voltage generated by the piezoelectric material can be used to charge the capacitor or...
Recovery of drop in heat transfer rate for a rotating system by nanofluids
, Article Journal of Molecular Liquids ; Volume 220 , 2016 , Pages 961-969 ; 01677322 (ISSN) ; Rashidi, S ; Abolfazli Esfahani, J ; Sharif University of Technology
Elsevier
Abstract
This paper simulates Al2O3-water nanofluid flow and forced convection around a rotating circular cylinder. The governing parameters are Reynolds number (1 ≤ Re ≤ 100), solid volume fraction of nanoparticles (0 ≤ φ ≤ 0.05) and non-dimensional rotation rate (0 ≤ α ≤ 3). The simulations are performed to study the effects of mentioned parameters on the heat transfer rate and fluid flow characteristics. The governing equations including the continuity, momentum, and energy equations are solved with a finite volume method. It is observed that the reduction of heat transfer with increase in rotation rate is in the vicinity of 6.9% and 32% for Re = 5 and 100, respectively at φ = 0.05. Furthermore,...
The dynamic pull-in instability and snap-through behavior of initially curved microbeams
, Article Mechanics of Advanced Materials and Structures ; Volume 19, Issue 6 , Jul , 2012 , Pages 485-491 ; 15376494 (ISSN) ; Sharif University of Technology
T&F
2012
Abstract
In this study, dynamic pull-in instability and snap-through buckling of initially curved microbeams are investigated. The microbeams are actuated by suddenly applied electrostatic force. A finite element model is developed to discretize the governing equations, and Newmark time discretization is employed to solve the discretized equations. The static pull-in behavior is investigated to validate the model. The results of the finite element model are compared with finite difference solutions and their convergence is examined. In addition, the influence of different parameters on dynamic pull-in instability and snap-through buckling is explored
Free vibration analysis of moderately thick trapezoidal symmetrically laminated plates with various combinations of boundary conditions
, Article European Journal of Mechanics, A/Solids ; Volume 36 , 2012 , Pages 204-212 ; 09977538 (ISSN) ; Fallah, A ; Aghdam, M. M ; Sharif University of Technology
2012
Abstract
In this study, free vibration analysis of moderately thick symmetrically laminated general trapezoidal plates with various combinations of boundary conditions is investigated. The governing partial differential equations and boundary conditions for trapezoidal plate are obtained using first order shear deformation theory (FSDT) together with proper transformation from Cartesian system into trapezoidal coordinates. Generalized differential quadrature (GDQ) method is then employed to obtain solutions for the governing equations. Results of the GDQ method are compared and validated with available results in the literature which show accuracy and fast rate of convergence of the method. Effect of...
Nonlinear vibration of a three-dimensional moving gantry crane subjected to a travelling trolley hoisting a swinging object
, Article Transactions of the Canadian Society for Mechanical Engineering ; Volume 34, Issue 3-4 , 2010 , Pages 333-350 ; 03158977 (ISSN) ; Ghafoori, E ; Sadeghpour, M ; Sharif University of Technology
2010
Abstract
Nonlinear vibration of a three-dimensional moving gantry crane carrying a trolley hoisting a swinging object is studied in this paper.A finite element method is used to solve nonlinear coupled governing equations of the structure. A combinational technique (Newmark-Runge-Kutta) is employed for direct integration procedure. To develop a comprehensive parametric study and sensitivity analysis of the coupled nonlinear system, sequence of numerical simulations are carried out. Parametric study is directed to find out how different parameters like speed and acceleration of the trolley and gantry crane as well as the mass of the moving trolley and swinging object may affect the linear and...
Optimal passive vibration control of Timoshenko beams with arbitrary boundary conditions traversed by moving loads
, Article Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics ; Volume 222, Issue 2 , 2008 , Pages 179-188 ; 14644193 (ISSN) ; Kargarnovin, M. H ; Esmailzadeh, E ; Sharif University of Technology
2008
Abstract
Passive control of vibration of beams subjected to moving loads is studied in which, an optimal tuned mass damper (TMD) system is utilized to suppress the undesirable beam vibration. Timoshenko beam theory is applied to the beam model having three types of boundary conditions, namely, hinged-hinged, hinged-clamped, and the clamped-clamped ends, and the governing equations of motion are solved using the Galerkin method. For every set of boundary conditions, a minimax problem is solved using the sequential quadratic programming method and the optimum values of the frequency and damping ratios for the TMD system are obtained. To show the effectiveness of the designed TMD system, simulations of...
Time and space extended-particle in cell model for electromagnetic particle algorithms
, Article Physics of Plasmas ; Volume 19, Issue 3 , 2012 ; 1070664X (ISSN) ; Anvari, A ; Sharif University of Technology
Abstract
A general method for deriving electromagnetic particle in cell (EMPIC) algorithms has been given by Eastwood [Comput. Phys. Commun. 64, 252 (1991)]. This method devises variation of the action-integral to find discrete governing equations. The most important advantage of this method is automatic inclusion of the time coordinate via the action integral into the computational domain. This inclusion is inevitable because electromagnetic algorithms are based on time evolution of the system from its initial state. The drawback of this method is that it is rather abstract. This causes obscurity of particle-mesh interactions and makes it hard to analyze physical treatments of the computational...
A non-isothermal, transient model of a non-catalytic reaction in a packed bed with a multi-component high-temperature gas mixture
, Article 3rd M.I.T. Conference on Computational Fluid and Solid Mechanics, Boston, MA, 14 June 2005 through 17 June 2005 ; 2005 , Pages 1023-1025 ; 0080444814 (ISBN); 9780080444819 (ISBN) ; Saboohi, Y ; Sharif University of Technology
2005
Abstract
A mathematical model has been developed to simulate heterogeneous reactions with a complex set of physicochemical and thermal phenomena in a packed bed. These include the chemical reaction itself, the transport of gaseous species in the pores, the generation or consumption of heat by the reactions, and the transport of heat in the porous domain. Solution of complicated sets of governing equations is based upon the concept of a finite volume fully implicit approach. The model has then been applied to analyze the reduction of a hematite pellet in a moving packed bed reactor. © 2005 Elsevier Ltd
An X-FEM implementation of hydro-fracture growth in naturally fractured saturated porous media
, Article Poromechanics 2017 - Proceedings of the 6th Biot Conference on Poromechanics, 9 July 2017 through 13 July 2017 ; 2017 , Pages 2027-2034 ; 9780784480779 (ISBN) ; Khoei, A. R ; Khalili, N ; Sharif University of Technology
Abstract
In this paper, a coupled hydro-mechanical formulation is developed for the simulation of interaction between hydraulic fractures and natural discontinuities within saturated porous media. The momentum balance equation of the bulk together with the momentum balance and continuity equations of the fluid phase are employed to obtain the fully coupled set of governing equations. The hydro-fracture is modeled for fluid flow using the Darcy law. The natural discontinuity on the other hand is modeled for both opening and closing modes which induce fluid flow and/or contact behavior along the crack edges. The discontinuity in the displacement field is incorporated by using the Heaviside enrichment...
Static analysis of electrically actuated nano to micron scale beams using nonlocal theory
, Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011 ; Volume 7 , August , 2011 , Pages 391-396 ; 9780791854846 (ISBN) ; Pasharavesh, A ; Ahmadian, M. T ; Fallah, A ; Sharif University of Technology
2011
Abstract
In this paper, size dependent static behavior of micro and nano cantilevers actuated by a static electric field including deflection and pull-in instability, is analyzed implementing nonlocal theory. Euler-bernoulli assumptions are made to model the relation between deflection of the beam and bending moment. Differential form of the constitutive equation of nonlocal theory is used to find the revised equation for bending moment and substituting in the equilibrium equation of electrostatically actuated beams final nonlinear ordinary differential equation is arrived. Also the boundary conditions for solving the equation are revised and to analyze the size effect better governing equation is...
Dynamic stability of cantilevered functionally graded cylindrical shells under axial follower forces
, Article Thin-Walled Structures ; Vol. 79, issue , June , 2014 , p. 138-146 ; Kazemi, M. T ; Haddadpour, H ; Mahmoudkhani, S ; Sharif University of Technology
Abstract
Flutter of cantilevered, functionally graded cylindrical shells under an end axial follower force is addressed. The material properties are assumed to be graded along the thickness direction according to a simple power law. Using the Hamilton principle, the governing equations of motion are derived based on the first-order shear deformation theory. The stability analysis is carried out using the extended Galerkin method and minimum flutter loads and corresponding circumferential mode numbers are obtained for different volume fractions, length-to-radius, and thicknesses-to-radius ratios. Two different configurations are considered for the FGM: one in which the metal phase is the outer layer...
Effects of tip mass and interaction force on nonlinear behavior of force modulation FM-AFM cantilever
, Article Journal of Mechanics ; 2016 , Pages 1-12 ; 17277191 (ISSN) ; Zohoor, H ; Habibnejad Korayem, M ; Sharif University of Technology
Cambridge University Press
2016
Abstract
Influences of the tip mass, excitation mode of Frequency Modulated Atomic Force Microscope (FM-AFM) on the resonance frequency shift in force modulation (FM) mode are studied. Governing equations of motion are determined based on Timoshenko beam model with concentrated end mass. Approach point and base amplitude are set such that the FM-AFM remains just in FM mode. Either the linearized and nonlinear Derjaguin-Muller-Toporov (DMT) model are investigated. Then frequency shifts are determined for various interaction force regimes. It is showed the effect of tip mass on frequency shift is significant even for small tips. Nonlinear model shows lower frequency shifts in comparison with linearized...
Effects of tip mass and interaction force on nonlinear behavior of force modulation fm-afm cantilever
, Article Journal of Mechanics ; Volume 33, Issue 2 , 2017 , Pages 257-268 ; 17277191 (ISSN) ; Zohoor, H ; Habibnejad Korayem, M ; Sharif University of Technology
Cambridge University Press
2017
Abstract
Influences of the tip mass, excitation mode of Frequency Modulated Atomic Force Microscope (FM-AFM) on the resonance frequency shift in force modulation (FM) mode are studied. Governing equations of motion are determined based on Timoshenko beam model with concentrated end mass. Approach point and base amplitude are set such that the FM-AFM remains just in FM mode. Either the linearized and nonlinear Derjaguin-Muller-Toporov (DMT) model are investigated. Then frequency shifts are determined for various interaction force regimes. It is showed the effect of tip mass on frequency shift is significant even for small tips. Nonlinear model shows lower frequency shifts in comparison with linearized...
Free vibrations and stability of high-speed rotating carbon nanotubes partially resting on Winkler foundations
, Article Composite Structures ; Volume 126 , 2015 , Pages 52-61 ; 02638223 (ISSN) ; Rahmanian, M ; Firouz-Abadi, R. D ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
In the present study, free vibrations and stability of rotating single walled carbon nanotubes (SWCNT) is investigated by nonlocal theory of elasticity; while the CNT is partially resting on an elastic foundation. The governing equations of motion are presented by using Love's shell assumptions. An exact series expansion method of solution is employed and very accurate results are obtained. Some parameter studies including the effects of rotating speed, foundation stiffness, slenderness ratio and nonlocal parameter on the natural frequency and stability margins of the current model are studied. The studies show that rotation rates and foundation elasticity can contribute significantly in the...
Free vibration analysis of cylindrical shells partially resting on an elastic foundation
, Article Meccanica ; Volume 51, Issue 5 , 2016 , Pages 1113-1125 ; 00256455 (ISSN) ; Firouz Abadi, R. D ; Sharif University of Technology
Springer Netherlands
2016
Abstract
The present study aims at the investigation of free vibration analysis of thin cylindrical shells surrounded by an elastic medium, which is distributed over a particular length of the shell. The Love’s shell theory is utilized along with the Winkler foundation to obtain the governing equations of motion. An exact series expansion method of solution is employed for any arbitrary boundary conditions. The excellent accuracy of the obtained results is validated by comparing to the available literature. Moreover, several case studies are performed to provide an insight into the influence of some practically important parameters on free vibrations of circular cylindrical shells, including...
An experimental-based numerical simulation of two phase flow through porous media: A comparative study on finite element and finite difference schemes
, Article Petroleum Science and Technology ; Volume 31, Issue 18 , 2013 , Pages 1881-1890 ; 10916466 (ISSN) ; Kharrat, R ; Ghazanfari, M. H ; Sharif University of Technology
2013
Abstract
In this study, the nonlinear partial differential equations governing two phase flow through porous media are solved using two different methods, namely, finite difference and finite element. The capillary pressure term is considered in the mathematical model. The numerical results on a 2-D test case are then compared with the experimental drainage process and water flooding performed on a glass type micromodel. Based on the obtained results, finite difference technique needs less computational time for solving governing equations of two phase flow, but findings of this method show less agreement with the experimental data. The finite element scheme was found to be more adequate and its...
Thermal-hydraulic analysis of HPLWR fuel assembly cluster
, Article Journal of Supercritical Fluids ; Volume 77 , May , 2013 , Pages 91-99 ; 08968446 (ISSN) ; Salehi, A. A ; Jahanfarnia, G ; Sharif University of Technology
2013
Abstract
The High-Performance Light Water Reactor (HPLWR) is the European version of the Supercritical-pressure Water Cooled Reactor (SCWR). Light water reactors at supercritical pressure, being currently under design, are the new generation of nuclear reactors. The present article is a thermal-hydraulic analysis of the HPLWR fuel assembly cluster. The existing thermal hydraulic codes are not capable of analyzing and designing the HPLWR fuel assembly. It is necessary to introduce a new thermal-hydraulic code that can incorporate the parameters and specifications of the HPLWR fuel assembly. The governing equations include energy, mass and momentum equations beside thermal-hydraulic equations are...
Size dependent vibrations of micro-end mill incorporating strain gradient elasticity theory
, Article Journal of Sound and Vibration ; Volume 332, Issue 15 , 2013 , Pages 3922-3944 ; 0022460X (ISSN) ; Movahhedy, M. R ; Akbari, J ; Sharif University of Technology
2013
Abstract
In this paper, a size-dependent formulation is presented for vibration analysis of micro-end mill tool. The formulation is developed based on the strain gradient elasticity theory in order to enhance the modeling capability of micro-size structures. Due to stubby geometry of micro-tool, the shear deformation and rotary inertia effects are considered in the derivation of equations. Hence, based on the strain gradient Timoshenko beam theory, the extended Hamilton's principle is used to formulate a detailed dynamical model of the rotating micro-tool. The dynamical model includes a set of partial differential equations with gyroscopic coupling produced due to the spindle rotation. The governing...
Investigation of the effects of process damping on chatter instability in micro end milling
, Article Procedia CIRP ; Volume 1, Issue 1 , 2012 , Pages 156-161 ; 22128271 (ISSN) ; Movahhedy, M. R ; Akbari, J ; Sharif University of Technology
2012
Abstract
In this paper, chatter instability of micro end mill tools is studied by taking into account the process damping effect. The actual geometry of the micro tool including shank, taper part and fluted section is considered in the analysis. Timoshenko beam theory is utilized to consider the shear deformation and rotary inertia effects due to short and thick beam-type structures of each parts of the micro tool. The extended Hamilton's Principle is used to formulate a detailed dynamical model of the rotating micro end mill. The governing equations are solved by assumed mode model expansion. An exact dynamic stiffness method is developed to investigate modal characteristics of the tool including...