Search for: finite-difference-methods
0.014 seconds
Total 161 records

    Dynamics of multi layer microplates considering nonlinear squeeze film damping

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 1096665X (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Ahmadian, M. T ; Moghimi Zand, M ; Borhan, H ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    This paper presents a model to analyze pull-in phenomenon and dynamics of multi layer microplates using coupled finite element and finite difference methods. Firstorder shear deformation theory is used to model dynamical system using finite element method, while Finite difference method is applied to solve the nonlinear Reynolds equation of squeeze film damping. Using this model, Pull-in analysis of single layer and multi layer microplates are studied. The results of pull-in analysis are in good agreement with literature. Validating our model by pull-in results, an algorithm is presented to study dynamics of microplates. These simulations have many applications in designing multi layer... 

    An optimized large-stencil approach for capturing near-PI frequencies

    , Article 12th AIAA/CEAS Aeroacoustics Conference, Cambridge, MA, 8 May 2006 through 10 May 2006 ; Volume 5 , 2006 , Pages 3010-3022 ; 1563478099 (ISBN); 9781563478093 (ISBN) Ghasemi, A ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2006
    Large-stencil schemes which their spectral properties are acceptable in the vicinity of ω = π are analyzed for the first time. A machine independent model for evaluating the efficiency of generalized time-marching finite-difference algorithms over periodic domains is developed. This model which is based on operation count reveals that for small values of Total Computational Cost(TCC), the previous low-order small-stencil schemes are more efficient while for moderate TCC, the efficiency of optimized large-stencil schemes abruptly increases. This important result is the motivation for developing optimized large-stencil schemes. The current schemes are successfully implemented in a full... 

    Transient radiative heat transfer analysis of a polypropylene layer using hottel's zonal method

    , Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) Safavisohi, B ; Sharbati, E ; Aghanajafi, C ; Khatami Firoozabadi, R ; Sharif University of Technology
    Polymer films possess excellent optical properties, such as high transparency, and thermal characteristics, like low heat conductivity, as well as further polymer specific advantages. Consequently, polymer films have an outstanding potential for many solar applications. They are already used for encapsulation of photovoltaic (PV) cells, as convection barrier in solar collectors and as substrate or adhesive layers for glazing. In translucent polymers, energy can be transferred internally by radiation in addition to conduction. Since radiant propagation is very rapid, it can provide energy within the layer more quickly than diffusion by heat conduction. Thus, the transient thermal response of... 

    A study on mutual interaction between atomistic and macroscopic phenomena during electrochemical processes using coupled finite difference - Kinetic Monte Carlo model: Application to potential step test in simple copper sulfate bath

    , Article Journal of Electroanalytical Chemistry ; Volume 588, Issue 2 , 2006 , Pages 267-284 ; 15726657 (ISSN) Saedi, A ; Sharif University of Technology
    Elsevier  2006
    A novel method is used to link a 2D kinetic Monte Carlo code to a 1D finite difference code to construct a more realistic and efficient tool for simulating various electrochemical processes. This multiscale model is able to simulate the long-scale mass transfer of electroactive species in bath along with electrode surface phenomena at atomic scale simultaneously. An embedded atom method (EAM) has been used to evaluate the barrier energies of diffusion and redox reactions on electrode surface. The FD code provides the ion concentration on OHP for KMC code, while the KMC code provides the surface activity and rate constants of redox reactions as an input data for FD code. The electrochemical... 

    Numerical investigation and field monitoring of karun bridge abutment

    , Article 33rd CSCE Annual Conference 2005, Toronto, ON, 2 June 2005 through 4 June 2005 ; Volume 2005 , 2005 , Pages GC-253-1-GC-253-8 ; 1894662091 (ISBN); 9781894662093 (ISBN) Bayat, A ; Sadaghiani, M. H ; Sharif University of Technology
    Karun Bridge is part of a national highway project underway in southern Iran. The bridge is a 336 m steel arch structure that weighs more than 2500 tons and crosses the Karun River 270 meters above the river valley. The bridge will be the largest suspended bridge in the Middle East. Cantilever construction is to be used to construct the bridge from both sides simultaneously. The weight of the bridge is to be carried by two abutments and four piers that are anchored to exposed weathered rock mass. Loads on the abutments and piers include significant cantilever loads and moments during bridge erection and wind loads. Daily rapid temperature changes also will impart significant thermal loads on... 

    Numerical modeling of surface wave motion with a bottom turbulent boundary layer

    , Article 24th International Conference on Offshore Mechanics and Arctic Engineering, 2005, Halkidiki, 12 June 2005 through 17 June 2005 ; Volume 3 , 2005 , Pages 923-926 Jamali, M ; Sharif University of Technology
    An effective numerical technique is presented to model turbulent motion of a standing surface wave in a tank. The equations of motion for turbulent boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to obtain the wave and boundary layer characteristics such as bed shear stress. A mixing-length theory is used for turbulence modeling. Although the technique is presented for a standing surface wave, it can be easily applied to other free surface problems. Copyright © 2005 by ASME  

    Error analysis of finite difference methods for two-dimensional advection-dispersion-reaction equation

    , Article Advances in Water Resources ; Volume 28, Issue 8 , 2005 , Pages 793-806 ; 03091708 (ISSN) Ataie Ashtiani, B ; Hosseini, S. A ; Sharif University of Technology
    In this paper, the numerical errors associated with the finite difference solutions of two-dimensional advection-dispersion equation with linear sorption are obtained from a Taylor analysis and are removed from numerical solution. The error expressions are based on a general form of the corresponding difference equation. The variation of these numerical truncation errors is presented as a function of Peclet and Courant numbers in X and Y direction, a Sink/Source dimensionless number and new form of Peclet and Courant numbers in X-Y plane. It is shown that the Crank-Nicolson method is the most accurate scheme based on the truncation error analysis. The effects of these truncation errors on... 

    Numerical errors of explicit finite difference approximation for two-dimensional solute transport equation with linear sorption

    , Article Environmental Modelling and Software ; Volume 20, Issue 7 , 2005 , Pages 817-826 ; 13648152 (ISSN) Ataie Ashtiani, B ; Hosseini, S. A ; Sharif University of Technology
    The numerical errors associated with explicit upstream finite difference solutions of two-dimensional advection - Dispersion equation with linear sorption are formulated from a Taylor analysis. The error expressions are based on a general form of the corresponding difference equation. The numerical truncation errors are defined using Peclet and Courant numbers in the X and Y direction, a sink/source dimensionless number and new Peclet and Courant numbers in the XY plane. The effects of these truncation errors on the explicit solution of a two-dimensional advection-dispersion equation with a first-order reaction or degradation are demonstrated by comparison with an analytical solution in... 

    Transient heat transfer analysis of a layer by considering the effect of radiation

    , Article Journal of Fusion Energy ; Volume 23, Issue 3 , 2005 , Pages 207-215 ; 01640313 (ISSN) Sharbati, E ; Safavisohi, B ; Aghanajafi, C ; Sharif University of Technology
    The transient heat transfer analysis of a layer has been studied much less than the steady state. However, transient temperature distribution resulted from including radiation and conduction simultaneously, is significantly different from those obtained by considering conduction alone. In order to include the effect of radiation heat transfer, we must insert the gradient of radiative flux in the energy equation. For this purpose, a variety of multi-flux methods have been suggested. A simplified procedure is the two-flux method, which is the one used in the present paper. This paper is focused on one-dimensional transient heat transfer of a layer using Finite Difference Method. To this end, a... 

    Development of a 2-D 2-group neutron noise simulator for hexagonal geometries

    , Article Annals of Nuclear Energy ; Volume 37, Issue 8 , 2010 , Pages 1089-1100 ; 03064549 (ISSN) Malmir, H ; Vosoughi, N ; Zahedinejad, E ; Sharif University of Technology
    In this paper, the development of a neutron noise simulator for hexagonal-structured reactor cores using both the forward and the adjoint methods is reported. The spatial discretisation of both 2-D 2-group static and dynamic equations is based on a developed box-scheme finite difference method for hexagonal mesh boxes. Using the power iteration method for the static calculations, the 2-group neutron flux and its adjoint with the corresponding eigenvalues are obtained by the developed static simulator. The results are then benchmarked against the well-known CITATION computer code. The dynamic calculations are performed in the frequency domain which leads to discarding of the time... 

    Enhanced finite difference scheme for the neutron diffusion equation using the importance function

    , Article Annals of Nuclear Energy ; Volume 96 , 2016 , Pages 412-421 ; 03064549 (ISSN) Vagheian, M ; Vosoughi, N ; Gharib, M ; Sharif University of Technology
    Elsevier Ltd  2016
    Mesh point positions in Finite Difference Method (FDM) of discretization for the neutron diffusion equation can remarkably affect the averaged neutron fluxes as well as the effective multiplication factor. In this study, by aid of improving the mesh point positions, an enhanced finite difference scheme for the neutron diffusion equation is proposed based on the neutron importance function. In order to determine the neutron importance function, the adjoint (backward) neutron diffusion calculations are performed in the same procedure as for the forward calculations. Considering the neutron importance function, the mesh points can be improved through the entire reactor core. Accordingly, in... 

    Comparison of finite difference schemes for water flow in unsaturated soils

    , Article World Academy of Science, Engineering and Technology ; Volume 40 , 2009 , Pages 21-25 ; 2010376X (ISSN) Taheri Shahraiyni, H ; Ataie Ashtiani, B ; Sharif University of Technology
    Flow movement in unsaturated soil can be expressed by a partial differential equation, named Richards equation. The objective of this study is the finding of an appropriate implicit numerical solution for head based Richards equation. Some of the well known finite difference schemes (fully implicit, Crank Nicolson and Runge-Kutta) have been utilized in this study. In addition, the effects of different approximations of moisture capacity function, convergence criteria and time stepping methods were evaluated. Two different infiltration problems were solved to investigate the performance of different schemes. These problems include of vertical water flow in a wet and very dry soils. The... 

    Revealing electrical stresses acting on the surface of protoplast cells under electric field

    , Article European Journal of Mechanics, B/Fluids ; Volume 76 , 2019 , Pages 292-302 ; 09977546 (ISSN) Dastani, K ; Moghimi Zand, M ; Hadi, A ; Sharif University of Technology
    Elsevier Ltd  2019
    When cells exposed to an electric field, localized changes in the distribution of the electric field will be induced and these changes in turn lead to electrical stresses on cell surface. The electrical stresses play a key role in the cell membrane structural changes which leads to important phenomena like hydrophilic pores formation on the cell membrane resulting in the cell permeability. In this work, protoplast cell interaction with direct current (DC) electric field is investigated. The electrical stresses acted on the cell membrane in the presence of electric field are investigated numerically by a modified finite difference method, fast Immersed Interface Method (IIM). Exact solution... 

    Implementation of high-order compact finite-difference method to parabolized Navier-Stokes schemes

    , Article International Journal for Numerical Methods in Fluids ; Volume 58, Issue 6 , 2008 , Pages 659-685 ; 02712091 (ISSN) Esfahanian, V ; Hejranfar, K ; Mahmoodi Darian, H ; Sharif University of Technology
    The numerical solution to the parabolized Navier-Stokes (PNS) and globally iterated PNS (IPNS) equations for accurate computation of hypersonic axisymmetric flowfields is obtained by using the fourth-order compact finite-difference method. The PNS and IPNS equations in the general curvilinear coordinates are solved by using the implicit finite-difference algorithm of Beam and Warming type with a high-order compact accuracy. A shock-fitting procedure is utilized in both compact PNS and IPNS schemes to obtain accurate solutions in the vicinity of the shock. The main advantage of the present formulation is that the basic flow variables and their first and second derivatives are simultaneously... 

    Numerical Analysis of Stresses and Steady State Creep Strain Rates Fields of a Short Fibre Composite

    , M.Sc. Thesis Sharif University of Technology Ghavami, Ali (Author) ; Abedian, Ali (Supervisor)
    A finite difference technique is developed to predict the second stage creep displacement rates and stress analysis of a short fiber metal matrix composite subjecting to a constant axial load. The exponential law is adopted to describe the matrix creep behavior. Also, a method for prediction of interfacial debonding at fiber/matrix interface is developed using a stress based method. The obtained results could greatly help to better understand the flow pattern of matrix material and the load transfer mechanism between fiber and matrix. The stress components and strain rates are also validated by the available FEM and experimental results  

    Localization of a Postulated Noise in VVER-1000 Reactor Core Using Neutron Noise Analysis Methods

    , M.Sc. Thesis Sharif University of Technology Malmir, Hessam (Author) ; Vosoughi, Naser (Supervisor)
    In this thesis, localization of a postulated noise from limited neutron detectors sparsely distributed throughout the core of a typical VVER-1000 reactor is investigated. For this purpose, developing a 2-D neutron noise simulator for hexagonal geometries based on the 2-group diffusion approximation, the reactor dynamic transfer function is calculated. The box-scheme finite difference method is first developed for hexagonal geometries, to be used for spatial discretisation of both 2-D 2-group static and noise diffusion equations. Using the discretised static equations, a 2-D 2-group static simulator (HEXDIF-2) is developed which its results are benchmarked against the well-known CITATION... 

    Development of a model for Hydro-Mechanical Deep Drawing Process to Analyze the Effects of Assumptions and Parameters

    , M.Sc. Thesis Sharif University of Technology Taghipour, Ehsan (Author) ; Assempour, Ahmad (Supervisor)
    It is the goal of this thesis to develop an analytical model for the hydro-mechanical deep drawing (HDD) process of an axisymmetric sheet metal with the fixed gap method to evaluate the effects of some assumptions such as: proportional loading, plane stress, and constant thickness conditions. The effect of parameters on the HDD process is also studied. The main model is developed with considering the normal stress and part thickness change, non-proportional loading, bending and unbending effects at the top of the cup wall. The interrelationships between geometrical and mechanical variables are obtained in the finite difference form based on the incremental strain theory, thereby being solved... 

    Developing a Compact Finite Difference Method for Solving Fluid - Solid Interaction in Incompressible Flow

    , M.Sc. Thesis Sharif University of Technology Parseh, Kaveh (Author) ; Hejranfar, Kazem (Supervisor)
    In this study, fluid-solid interaction (FSI) is simulated computationally by using a high-order accurate numerical method. The two-dimensional incompressible viscous flows are considered in the fluid domain. The primary problem with solutions of the incompressible Navier–Stokes equations is the difficulty of coupling changes in the velocity field with changes in the pressure field while satisfying the continuity equation. Herein, the artificial compressibility method is used to overcome this difficulty. Preconditioning is implemented to reduce the stiffness of the system of equations to increase the convergence rate of the solution. Using preconditioning, physical solutions even at low... 

    Comparison and Evaluation of the Performance of some Fundamental Models for Simulation of Naturally Fractured Hydrocarbon Reservoirs

    , M.Sc. Thesis Sharif University of Technology Mahmoudi, Siamak (Author) ; Taghizadeh Manzari, Mehrdad (Supervisor)
    Fractured reservoirs show a different behavior from common reservoirs because of the existence of a broad network of fractures. This phenomenon makes it necessary to apply special methods for fractured reservoirs in the procedure of reservoir simulation. Since twenty percent of petroleum content in the world is buried in fractured reservoirs, investigating these reservoirs is of great importance.
    The first step in simulation of these kinds of reservoirs is to come up with a geometrical model which can be used to take the fracture network influence into account. In the course for reaching such an objective, various models have been developed which are based on specific assumptions and in... 

    A Multiscale Moving Boundary Model For Cancer Invasion

    , M.Sc. Thesis Sharif University of Technology Mohammad Mirzaei, Navid (Author) ; Fotouhi Firoozabad, Morteza (Supervisor)
    Cancer invasion of tissue is a key aspect of the growth and spread of cancer and is crucial in the process of metastatic spread i.e. the growth of secondary cancers. Invasion consists in cancer cells secreting various matrix degrading enzymes (MDEs) which destroy the surronding tissue or extracellular matrix (ECM). Through a combination of proliferation and migration, the cancer cells then actively spread locally into the surrounding tissue. Thus processes occuring at the level of individual cells eventually give rise to processes occuring at the tissue level. In this thesis we introduce a new type of multiscale model describing the process of cancer invasion of tissue.Our multiscale model...