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    Effects of non-dimensional parameters on formation and break up of cylindrical droplets

    , Article 2004 ASME Heat Transfer/Fluids Engineering Summer Conference, HT/FED 2004, Charlotte, NC, 11 July 2004 through 15 July 2004 ; Volume 2 B , 2004 , Pages 1339-1342 Taeibi Rahni, M ; Sharafatmand, S ; Sharif University of Technology
    American Society of Mechanical Engineers  2004
    The consistent behavior of non-dimensional parameters on the formation and break up of large cylindrical droplets has been studied by direct numerical simulations (DNS). A one-fluid model with a finite difference method and an advanced front tracking scheme was employed to solve unsteady, incompressible, viscous, immiscible, multi-fluid, twodimensional Navier-Stokes equations. This time dependent study allows investigation of evolution of the droplets in different cases. For moderate values of Atwood number (AT), increasing Eotvos number (Eo) explicitly increases the deformation rate in both phenomena. Otherwise, raising the Ohnesorge number (Oh) basically amplifies the viscous effects.... 

    Numerical Simulation of Solid-fluid Mixture in Magnetic Field (MRF) Using Smoothed Particle Hydrodynamics (SPH) Method

    , M.Sc. Thesis Sharif University of Technology Dini, Afrand (Author) ; Taghizadeh Manzari, Mehrdad (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
    This work is related to the research in the fields of particulate flow with the presence of external magnetic field and simulating movements of particles till making chain of particles. Using direct numerical simulation method for a two-way coupling of fluid and magnetic governing equations makes a more roboust and precise method. Also, using some assumptions simplified general maxwell equations to set of magnetostatic equations. these eqautions are solved by the boundary element method and the integral equations. Using analytic integrals and calculation of magnetic intensity are some techniques suggested for improving the preciesion of the presented work. the magnetic force and torques can... 

    Multiscale Modeling of Cohesive Crack and Bulk for Softening Materials

    , M.Sc. Thesis Sharif University of Technology Saadat, Mohammad Ali (Author) ; Khoei, Amir Reza (Supervisor)
    Multiscale modeling is performed within the framework of homogenization methods for problems in which the scales are separated. The existence of representative volume element (RVE) is one of the main ingredients of homogenization methods. Due to non-existence of RVE and macroscale mesh sensitivity, the continuous homogenization method is not applicable for softening materials. Despite the non-existence of RVE for softening materials, it has been demonstrated that by performing the average over the active damage zone rather than the entire domain, objective responses with respect to RVE size could be obtained. That is why discontinuous homogenization is used instead of continuous... 

    Computational Homogenization of Inter-Facial Thermal Resistance in Heterogeneous Materials

    , M.Sc. Thesis Sharif University of Technology Akbari, Ramin (Author) ; Khoei, Amir Reza (Supervisor)
    The constitutive modeling of heterogeneous micro-structure of solids based on multi-scale theories has become the subject of intensive research. One of the most important problem at this scale is the interfacial effects of constituents. Investigation of thermal conduction in this area leads to a phenomenon known as Inter-facial Boundary resistance. The general reasons behind this phenomenon are imperfect contact interface and changing in energy carriers properties known as Kapitza resistance. A computational homogenization of conduction tensor by considering inter-facial resistance and effective factors on it, is proposed. In order to capture discontinuous field around this area and its... 

    Multiscale Modeling of Cohesive Crack Growth based on XFEM and Damage Model

    , M.Sc. Thesis Sharif University of Technology Salahi Nezhad, Mohammad (Author) ; Khoei, Amir Reza (Supervisor)
    In this research, multi-scale modeling of mixed-mode failure mechanism of quassi-brittle materials is presented. For modeling a realistic crack growth in heterogeneious media, crack initiation criterion, crack growth orientation and the macroscopic cohesive law are derived from a microscopic sample. As a microscopic crack initiation criterion, acoustic tensor is investigated and scaled acoustic tensor has been proposed by comparison its results with maximum principal tensile stress. For crack growth direction based on micro-scale, acoustic tensor and multiscale aggregating discontinuities has been investigated and multiscale aggregating discontinuities by comparison results of these methods... 

    Direct Numerical Simulation of Heat and Fluid Flow through Porous Channel

    , M.Sc. Thesis Sharif University of Technology Ebrahimi, Behnam (Author) ; Nouri Boroujerdi, Ali (Supervisor)
    In this project, direct numerical simulation of fluid flow inside the porous channel is carried out. The flow channel is containing uniform array of solid blocks with square cross sections in an staggered scheme. Two thermal boundary conditions of constant temperature and constant heat flux of solid blocks were applied to the problem. The Navier-Stokes equations directly applied to the fluid region with no assumption of volume-averaging. Governing equations of two-dimensional flow with constant properties were discretized with control volume method. Energy equations for solid and fluid phases were solved separately. The results show that for solid block lengths over channel height, a/H=0.05,... 

    Design and Simulation of a Spiral Based Microfluidic Device for Separation of Circulating Tumor Cells Using Tunable Nature of Viscoelastic Fluid

    , M.Sc. Thesis Sharif University of Technology Nouri, Mohammad Moein (Author) ; Saeedi, Mohammad Saeed (Supervisor)
    Nowadays, cancer, which has been mentioned as the disease of the century, is the second leading cause of death throughout the world, and its incidence is constantly increasing. Isolation of circulating tumor cells is one of the most critical steps in diagnosing and controlling cancer progression. Due to the rarity of cancer cells compared to other cells in the blood sample, the isolation process requires optimal and high-precision devices. With the advent of inertial microfluidics, the ability to control the particles movement, the processing of blood samples as quickly and accurately as possible, and the viability of cells with a high percentage, introduced microfluidic systems as a... 

    Computer simulation of flocs interactions: Application in fiber suspension

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 292, Issue 2-3 , 2007 , Pages 99-109 ; 09277757 (ISSN) Jafari, A ; Zamankhan, P ; Mousavi, S. M ; Sharif University of Technology
    Elsevier  2007
    The present effort is the development of a multiscale modeling, simulation methodology for investigating complex phenomena arising from flowing fiber suspensions. Specific consideration was given to dynamic simulations of viscoelastic fibers in which the fluid flow is predicted by a method that is a hybrid between Direct Numerical Simulations (DNS) and Large Eddy Simulation techniques (LES), and fluid fibrous structure interactions (FSI) will be taken into account. Numerical results are presented for which focus is on fiber floc deformation by hydrodynamic forces in turbulent flows. Dynamics of simple fiber networks in a shearing flow of water in a channel flow illustrate that the... 

    Direct Numerical Simulation of External In-compressible Flow Using High-order Accurate Finite-difference Lattice Boltzmann Method

    , M.Sc. Thesis Sharif University of Technology Aboutalebi, Mohammad (Author) ; Hejranfar, Kazem (Supervisor)
    In the present study, a high-order finite-difference lattice Boltzmann solver is applied for simulating steady and unsteady three-dimensional incompressible flows. To achieve an accurate and robust flow solver, the incompressible form of the lattice Boltzmann equation in the three-dimensional generalized curvilinear coordinates is discretized spatially based on the fifth-order weighted essentially non-oscillatory (WENO) finite-difference scheme. To ensure the stability and temporal accuracy of the flow solver, the fourth-order Runge-Kutta method is used for the time integration. To examine the accuracy and performance of the flow solver, different three-dimensional incompressible flow... 

    Pore-scale Simulation of the Effect of Pore Geometry and Surface Heterogeneity on Oil Recovery by Low-salinity Water Flooding

    , M.Sc. Thesis Sharif University of Technology Ahmadi Falavarjani, Ali (Author) ; Mahani, Hassan (Supervisor) ; Ayatollahi, Shahabodin (Supervisor)
    Low-salinity waterflooding (LSWF) is a promising EOR approach that decreases the oil-wetness of reservoir rocks, hence increasing the recovery factor. Despite the importance of the pore-geometry on the performance of LSWF, especially in 3D simulations being affected by corner-flow and roughness, it is not yet investigated, thus in this thesis we aim at studying the aforementioned effects on LSWF. According to the preceding studies, during the drainage phase, the brines in the corners of pores cannot be displaced by oil because of requiring very high capillary pressure; thereby rendering a mixed-wet system. Hence considering this type of wettability is necessary for two-phase flow... 

    Turbulence Equation-of-State Interaction Modeling in Large Eddy Simulation

    , M.Sc. Thesis Sharif University of Technology Ghayour, Amir Mohammad (Author) ; Salehi, Mohammad Mahdi (Supervisor)
    In most real combustion systems, flow is turbulent (e.g., diesel engines). Therefore, a reliable turbulence modeling approach is necessary to design and analyze a system with turbulent flow. Direct numerical simulation (DNS), Large eddy simulation (LES), and Reynolds-averaged Navier-Stokes (RANS) are the three most mature Computational fluid dynamics (CFD) methods for turbulent flow simulations. Because of LES’s good accuracy and acceptable computational cost. In this project, LES is chosen to simulate the turbulent flow field.Modeled turbulence subgrid scales' interaction with nonlinear flow parameters, needs modeling. In supercritical and transcritical conditions, Equation-of-state is a... 

    Mechanistic Investigation of Enhanced Oil Recovery by Engineered Water Using Computational Fluid Dynamics at Pore Scale

    , Ph.D. Dissertation Sharif University of Technology Namaee Ghasemi, Arman (Author) ; Ayatollahi, Shahaboddin (Supervisor) ; Mahani, Hassan (Supervisor)
    Despite the proven advantage of the engineered water flooding technique, a coherent and mechanistic understanding of the fundamental phenomena occurring at pore scale is lacking. Most of the available simulation models have a phenomenological approach and have limited predictive capability. One of the key questions is how to justify and relate large (Darcy) scale observations to effects and phenomena that essentially occur at much smaller scales (i.e. pore and molecular level). Furthermore, two-phase flow dynamics and the effect of complex interplay between wettability, capillary number, and ions dispersion in a heterogeneous porous medium on the trapping and mobilization of oil at pore... 

    Mechanistic study of the effects of dynamic fluid/fluid and fluid/rock interactions during immiscible displacement of oil in porous media by low salinity water: Direct numerical simulation

    , Article Journal of Molecular Liquids ; 2020 Alizadeh, M. R ; Fatemi, M ; Sharif University of Technology
    Elsevier B.V  2020
    Low salinity waterflooding (LSWF) is a process in which by lowering the ionic strength and/or manipulation of the composition of the injection water, the long term equilibrium in oil/brine/rock system is disturbed to reach a new state of equilibrium through which the oil production will be enhanced due to fluid/fluid and/or rock/fluid interactions. In spite of recent advances in the simulation of the LSWF at core scale and beyond, there are very few works that have modelled and simulated this process at the pore scale specially using direct numerical simulation (DNS). As a result the effects of wettability alteration and/or Interfacial Tension (IFT) change on the distribution of the phases...