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    Numerical Simulation Cavitating Flows Using Compact Finite-difference Scheme

    , M.Sc. Thesis Sharif University of Technology Shokri, Maryam (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In the study, the simulation of two-dimensional cavitating flows is performed by applying a high-order accurate numerical method to the preconditioned, homogenous, multiphase Navier-Stokes equations. The baseline differential equations system is comprised of the mixture volume, mixture momentum and constituent volume fraction equations. A coordinate transformation is applied and the resulting system of governing equations in curvilinear coordinates is discretized using a fourth-order compact finite-difference scheme. The high-order accurate numerical scheme employing the suitable linear and nonlinear filters to account for density jumps across the cavity interface is shown to yield an... 

    Numerical Simulation of Incompressible Flows over two Dimensional Geometries by Means of Immersed Boundary Method

    , M.Sc. Thesis Sharif University of Technology Shahmardi, Armin (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    Two-dimensional incompressible flow analysis is one the most important applied issues in engineering and applied science field. Numerical solution of governing equations of flow requires exact computational grid generation.In complex geometries, generation of the grid which is coincident to the body is very difficult and time consuming. Immersed boundary method is an appropriate superseded method of body conformal grid generation in flow field numerical solution. In this method a grid which is not coincidentto bodyis generated and flow field properties are modified on points adjacent to the boundary of the object (Ghost Cell Method) to satisfy boundary conditions.
    The purpose of this... 

    Modeling and Characterizing Transient Behavior of Distillation Columns with Travelling Wave Theory

    , M.Sc. Thesis Sharif University of Technology Hemmati Alam, Narjes (Author) ; Pishvaie, Mahmoud Reza (Supervisor)
    Abstract
    Simulation and controlling nonlinear process is one of the challenging problems in academic and industrial research. Saving data for keeping history of process or arising number of calculation for optimization in control design, is forcing to decrease number of equation or order of system. One of the methods to decrease the order of distillation process is using the travelling wave theory. This solution shows god accuracy for simulation the behavior of distillation column. On the other hand finite difference method as a solver for distillation equation takes some time to converge to steady state condition and the numbers of calculation in this method are high. Finite difference method is... 

    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)
    Abstract
    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  

    Development of a Computer Code for Thermo Hydraulics Analysis of Prismatic High Temperature Gas Cooled Reactors

    , M.Sc. Thesis Sharif University of Technology Naderi, Mohammad Hossein (Author) ; Ghofrani, Mohammad Bagher (Supervisor) ; Jafari, Jalil (Supervisor)
    Abstract
    A prismatic high temperature gas-cooled reactor (HTGR), which is a graphite moderated, helium-cooled reactor, is a promising candidate for next generation nuclear power plant in that it enables applications, such as hydrogen production or process heat for petrochemical by supplying heat with core outlet temperatures as high as 1000°C. A Thermal Hydraulic Analysis Code (THAC) for gas-cooled reactors has been developed. THAC implicitly solves heat transfer equation of fuel, graphite block and helium. Three types of fuel pins were considered; solid fuel pin, fuel pins with inside holes and annular fuels with coolant flow from its inside and outside surfaces. THAC predicts axial and radial... 

    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)
    Abstract
    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)
    Abstract
    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... 

    Design and Implementation of Near Field Excitation System for Spectroscopy of Biological Species

    , Ph.D. Dissertation Sharif University of Technology Sasanpour, Pezhman (Author) ; Rashidian, Bizhan (Supervisor) ; Vossoughi, Manouchehr (Supervisor) ; Shahrokhian, Saeed (Co-Advisor)
    Abstract
    The main goal of this project is analysis, design and implementation of scanning near field optical system for detection of biological species. The activities fall in two main category. Theoretical and experimental. In theoretical part, after studying different models describing near field interaction, we have developed software for computationally analysis of nonlinear interaction of light with nanostructures, considering third order nonlinear susceptibility and dispersion behavior of permittivity for metallic nanostructures. The software implements three dimensional finite difference time domain (FDTD) method for analysis of interaction of electromagnetic wave with matter. In developed... 

    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)
    Abstract
    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... 

    Development of a Computer Code for Thermal Hydraulic Design of a High Temperature Gas Cooled Reactor Core

    , M.Sc. Thesis Sharif University of Technology Khosravi Mirzaee, Morteza (Author) ; Ghofrani, Mohammad Bagher (Supervisor) ; Jafari, Jalil (Supervisor)
    Abstract
    High temperature gas cooled reactors (HTGR) are one of the most promising reactors in the new generation of world commercial reactors. They are divided into two main categories: Prismatic gas cooled reactors and pebble bed gas cooled reactors. These reactors have many advantages, such as inherent safety, high thermodynamic efficiency and the possibility of producing hydrogen. One of the most important challenges in developing these reactors is providing appropriate codes in design and simulating their performance. Two codes have been developed in this thesis. The first, THFAM, is a steady state thermal hydraulic code which helps in analyzing a fuel assembly. The second, named THCM is... 

    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)
    Abstract
    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... 

    Modeling of Liquid-Vapor Two Phase Flow through Nozzle

    , M.Sc. Thesis Sharif University of Technology Varzideh, Mohammad (Author) ; Nouri Borujerdi, Ali (Supervisor)
    Abstract
    This thesis is about modeling of liquid-vapor two phase flows through nozzle. Liquid-vapor two phase flow is very applicable in industries such as boilers, expansion valves, refrigeration and sudden failures in pipelines. Two models are used for modeling of fluid flow through nozzle, transient and steady state. In Both model the solution field is considered as saturated liquid and vapor and the mass, momentum and energy equations as well as equation of state is used for describing of fluid flow properties. Homogeneous equilibrium model is used and for complete modeling of fluid flow heat transfer and friction force is also considered.
    Numerical solutions are used for solving of the... 

    A Multiscale Moving Boundary Model For Cancer Invasion

    , M.Sc. Thesis Sharif University of Technology Mohammad Mirzaei, Navid (Author) ; Fotouhi Firoozabad, Morteza (Supervisor)
    Abstract
    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... 

    Development of Compact Finite-Difference Lattice Boltzmann Method for Solving Two-Phase Flows

    , Ph.D. Dissertation Sharif University of Technology Ezzatneshan, Eslam (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In the present thesis, a high-order compact finite-difference lattice Boltzmann method (CFDLBM) is proposed and applied for an accurate and efficient numerical simulation of liquid-vapor two-phase flows. At first, the stability of the fourth-order CFDLBM is performed by using the von Neumann stability analysis for the D2Q7 and D2Q9 lattices. The stability analysis indicates that the CFDLBM proposed is stable and thus suitable for the simulation of high Reynolds number flows. The high-order CFDLBM is then developed and applied to accurately compute 2-D and 3-D incompressible flows in the Cartesian coordinates. Herein, the spatial derivatives in the lattice Boltzmann equation are discretized... 

    Development of WENO Finite Difference Lattice Boltzmann Method for Simulation of 2D Incompressible Laminar and Turbulent Flows

    , M.Sc. Thesis Sharif University of Technology Saadat, Mohammad Hossein (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In the present study, the numerical simulation of incompressible laminar and turbulent flows using a high-order finite difference lattice Boltzmann method is presented. To handle curved geometries with non uniform grids, the incompressible form of lattice Boltzmann equation is transformed into the generalized curvilinear coordinates and the spatial derivatives of the resulting equation are discretized using the fifth-order WENO scheme. The advantage of using the WENO-LBM developed is that it needs less number of grid points and remains stable even at high Reynolds number flows. For the temporal term, the fourth-order explicit Rung-Kutta scheme is adopted for laminar flow calculations and... 

    Investigation of Dynamic Behavior of Beams with Different Supports under Moving Vehicles

    , M.Sc. Thesis Sharif University of Technology Samanipour, Kianoosh (Author) ; Vafai, Abolhassan (Supervisor) ; Esmaeil Pourestekanchi, Homayun (Co-Advisor)
    Abstract
    With the transportation progress and appearance of transit industry, necessity of modern vehicles redounded to appearance of heavier trucks with higher speeds, moving on the roads. In addition, with the progress in mechanical engineering and automobile industry, appearance of such trucks is growing increasingly. So, bridges as one of the structures that civil engineers design and construct, nowadays are subjected to higher moving dynamic loads in comparison with the past. As a result, lots of investigation and researches in the universities and institutions all over the world are being conducting on the effects of the vehicle speeds on the dynamic stresses of the bridges. Bridge codes... 

    Soil-structure Interaction in Geothermal Foundations

    , M.Sc. Thesis Sharif University of Technology Moradshahi, Aria (Author) ; Khosravi, Ali (Supervisor)
    Abstract
    Regarding the issue that significant amount of energy consumption in the world is dedicated to heating and cooling of the buildings, by using traditional methods of heating and cooling, the environment is facing serious problems like green house gases. There were various techniques for decreasing the amount of contaminants stem from this process. Heat-exchanger energy piles are one of the most common methods that will result in economic usage of energy resources. Assessing the long-term behavior of the energy piles requires comprehensive understanding of the complex interaction between soil and pile subjected to mechanical and thermal loadings. Several numerical and analytical methods have... 

    Numerical Solution of Two-dimensional Compressible Flow Using Immersed Boundary Method with Compact Finite Difference Scheme

    , M.Sc. Thesis Sharif University of Technology Mashayekh, Erfan (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In this study, the viscous compressible flow is simulated over two-dimensional geometries by using the immersed boundary method and applying a high-order accurate numerical scheme. A fourth-order compact finite-difference scheme is used to accurately discretize the spatial derivative terms of the governing equations and the time integration is performed by the fourth-order Runge–Kutta scheme. To regularize the numerical solution and eliminate spurious modes due to unresolved scales, nonlinearities and inaccuracies in implementing boundary conditions, high-order low-pass compact filters are applied. A uniform Cartesian grid that is not coincident with the body surface is used and the boundary... 

    A Parametric Study of Geosynthetic Reinforced Soil (GRS) Low Height Walls with Concrete Block Facing in FLAC Software

    , M.Sc. Thesis Sharif University of Technology Selseleh, Amin (Author) ; Pak, Ali (Supervisor)
    Abstract
    Because of seismic flexibility, aesthetics, economic advantage and rapid construction of reinforced soil walls, application of these walls has raised tremendously since 1970’s. The early reinforced soil retaining walls used metallic srips to reinforce the soil with precast concrete panels as facing, however, since 1990’s using of geosynthetics to reinforce these walls with modular concrete block facing have replaced the old fashion. In this study, a finite difference code was developed in FLAC software. After verification of the numerical modeling procedure, a wall with 3.6m height reinforced by geosynthetics was simulated. In the course of numerical simulations the stage of counstruction,... 

    An Investigation on the Effects of Liquefaction-Induced Lateral Spreading on Deep Foundations Using Finite Difference Method

    , M.Sc. Thesis Sharif University of Technology Afzal Soltani, Sina (Author) ; Haeri, Mohsen (Supervisor)
    Abstract
    Liquefaction is an important phenomenon in geotechnical engineering which can cause severe damages to structures. Liquefaction-induced lateral spreading is defined as the lateral displacement in mild slopes or level grounds ending in free faces (such as quay walls) triggered by liquefaction in subsurface soil layers. During recent years, extensive studies have been conducted around the world documenting liquefaction induced lateral spreading and its effects on deep foundations. In the present study, a series of shaking table experiments which were previously conducted at Sharif University of Technology are numerically simulated using the three dimensional finite difference based program,...