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    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 Characteristic Boundary Conditions with Artificial Compressibility Method by Compact Finite-Difference Discretization

    , Ph.D. Dissertation Sharif University of Technology Parseh, Kaveh (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In the present study, the preconditioned incompressible Navier‐Stokes equations with the artificial compressibility (AC) method formulated in the generalized curvilinear coordinates are numerically solved by using a high‐order compact finite‐difference scheme for accurately and efficiently computing the incompressible flows. A fourth‐order compact finite‐difference scheme is utilized to discretize the spatial derivative terms of the resulting system of equations and the time integration is carried out based on the dual time‐stepping method. The capability of the proposed solution methodology for computing the steady and unsteady incompressible viscous flows in a wide range of Reynolds... 

    Numerical Simulation of 2D Panel Flutter in Compressible Flow using Compact Finite-Difference Method

    , M.Sc. Thesis Sharif University of Technology Vafaei Sefti, Maryam (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In the present study, the numerical simulation of the panel flutter in compressible inviscid flow is performed by the compact finite difference method. For this purpose, the 2D compressible Euler equations written in the arbitrary Lagrange-Eulerian form are considered and the resulting system of equations in the generalized curvilinear coordinates is solved by the fourth-order compact finite-difference method. An appropriate nonlinear filter is applied for the shock capturing and for the solution to be stable. The governing equation for the panel is also numerically solved by using the fourth-order compact finite difference method. The time integration in the flow domain is made by the... 

    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... 

    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... 

    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... 

    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... 

    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... 

    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... 

    Lattice Approximation for Stochastic Partial Differential Equations

    , M.Sc. Thesis Sharif University of Technology Mohammadian, Sogol (Author) ; Zohuri Zangeneh, Bijan (Supervisor)

    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... 

    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... 

    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  

    A Monte Carlo Method for Neutron Noise Calculation in the Frequency Domain

    , M.Sc. Thesis Sharif University of Technology Ghorbani Ashraf, Mahdi (Author) ; Vosoughi, Naser (Supervisor)
    Abstract
    Neutron noise equations, which are obtained by assuming small perturbations of macroscopic cross sections around a steady-state neutron field and by subsequently taking the Fourier transform in the frequency domain, have been usually solved by analytical techniques or by resorting to diffusion theory, but in this thesis, in order to increase of accuracy of neutron noise calculation, has been used transport approximation for neutron noise calculation and the Monte Carlo method has been used to solve transport equation of the neutron noise in the frequency domain. Since the transport equation of the neutron noise is a complex equation, a new Monte Carlo technique for treating complex-valued... 

    Numerical Solution Of One-Dimensional Non-Fourier Bioheat Transfer Through Skin Tissue

    , M.Sc. Thesis Sharif University of Technology Fazel, Zeynab (Author) ; Taghizadeh Manzari, Mehrdad (Supervisor)
    Abstract
    Innovations in laser, microwaves, and similar technologies have significantly advanced thermal treatments for diseases or even injuries concerning skin tissue. For a thorough understanding in the underlying mechanisms of bioheat transfer behavior of skin,a1D unsteady non-dimensional hyperbolic model of heat transfer through this tissue with metabolic heat generation which is subject to specific boundary conditions, is solved numerically using the finite difference method. A thermal shock is generated at the base of the tissue, which moves forward with a finite speed. A Numerical solution for a simple one-layer skin tissue is obtained. Then, the effects of various parameters, time step,... 

    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 Compact Finite Difference Boltzmann Method for Simulating Compressible Rarefied Gas Flow

    , M.Sc. Thesis Sharif University of Technology Alemi Arani, Ali (Author) ; Hejranfar, Kazem (Supervisor) ; Fouladi, Nematollah (Co-Supervisor)
    Abstract
    In this work, a high-order accurate gas kinetic scheme based on the compact finite-difference Boltzmann method (CFDBM) is developed and applied for simulating the compressible rarefied gas flows. Here, the Shakhov model of the Boltzmann equation is considered and the spatial derivative term in the resulting equation is discretized by using the fourth-order compact finite-difference method and the time integration is performed by using the third-order TVD Runge-Kutta method. A filtering procedure with three discontinuity-detecting sensors is applied and examined for the stabilization of the solution method especially for the problems involving the discontinuity regions such as the shock. The... 

    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... 

    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,...