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    Application of coupled lattice boltzmann and Phase-field methods for multiphase flow simulations

    , Article ASME 2013 Heat Transfer Summer Conf. Collocated with the ASME 2013 7th Int. Conf. on Energy Sustainability and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology, HT 2013 ; 2013 ; ISBN: 9780791855492 Premnath, K. N ; Patil, D. V ; Banerjee, S ; Sharif University Of Technology
    Coupling of lattice Boltzmann (LB) and phase-field (PF) methods is discussed for simulation of a range of multiphase flow problems. The local relaxation and shifting operators make the LB method an attractive candidate for the simulation of the single-phase as well as multiphase flows. For simulating interface dynamics, LB methods require to be coupled with an appropriate scheme representing interfacial dynamics. To this end, we have used a model based on the order parameter, which could be either an index function or a phase-field variable, and coupled it with a LB solver for the simulation of various classes of complex multi-physics and multiphase flows. The LB method is used to compute... 

    Multimaterial topology optimization by volume constrained Allen-Cahn system and regularized projected steepest descent method

    , Article Computer Methods in Applied Mechanics and Engineering ; Vol. 276 , 2014 , pp. 534-565 ; ISSN: 00457825 Tavakoli, R ; Sharif University of Technology
    A new computational algorithm is introduced in the present study to solve multimaterial topology optimization problems. It is based on the penalization of the objective functional by the multiphase volume constrained Ginzburg-Landau energy functional. The update procedure is based on the gradient flow of the objective functional by a fractional step projected steepest descent method. In the first step, the new design is found based on the projected steepest descent method to ensure the reduction in the objective functional, simultaneously satisfying the control constraints. In the second step, regularization step, an H1 regularity of the solution is ensured while keeping the feasibility of... 

    Droplet-based flows in serpentine microchannels: chemical reactions and secondary flows

    , Article International Journal of Multiphase Flow ; Volume 97 , 2017 , Pages 186-196 ; 03019322 (ISSN) Madadelahi, M ; Shamloo, A ; Sharif University of Technology
    Mixing is an essential operation in many microfluidic devices. Droplet-based micromixers utilize droplets for mixing enhancement. In the present study, a novel three-dimensional simulation is conducted which has the ability to capture not only the mixing process, but also the chemical reactions inside liquid droplets. This two-phase model is used for simulating the reacting flow inside a serpentine microchannel and explores the effects of droplet size and reaction rate on the production and consumption of species in droplets. It is observed that the chemical reaction in each droplet, begins from its front area. Furthermore, it is shown that the production of species does not depend on water... 

    Experimental and numerical approach to enlargement and determination of performance of primary sedimentation basin

    , Article 2007 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, San Diego, CA, 30 July 2007 through 2 August 2007 ; Volume 2 FORA, Issue PART A , March , 2007 , Pages 265-272 ; 0791842886 (ISBN); 9780791842881 (ISBN) Razmi, A. M ; Firoozabadi, B ; Sharif University of Technology
    In the present study, the presence of a baffle and its effect on the hydrodynamics of the flow in a primary settling tank has been investigated experimentally by ADV (Acoustic Doppler Velocimeter). On the other hand, the characteristics of this flow field were simulated by an unsteady two-phase finite volume method, and VOF (Volume of Fluid) model; and results were evaluated by the experimental data. The numerical calculation performed by using k - ε RNG model agrees well with experiments. It depicts the ability of this method in predicting the velocity profile and flow structure. In addition, the optimum position of the baffle to achieve the best performance of the tank was determined by... 

    Modeling Multiphase Fluid Flow Using SPH

    , M.Sc. Thesis Sharif University of Technology Safdari Shadloo, Mostafa (Author) ; Taghizadeh Manzari, Mehrdad (Supervisor)
    Smoothed Particle Hydrodynamics (SPH) is a Lagrangian method for simulation of fluid flow. Movable particles are used to interpolate fluid properties instead of fixed Eulerian grids in this method. By essence, the aforesaid particles are movable points which carry the fluid properties such as temperature, enthalpy, density, etc. these variables can also be the stress, strain or the rheological properties of the fluid. Thus, this method needs no grids and the fluid properties are calculated using an interpolation mechanism which classifies this method as meshless. A computational code is designed using SPH for the simulation of multiphase flows. Usage of the Lagrangian formulation has made it... 

    Multiscale Finite Volume Method for Simulation of Compressible Multiphase Flow in Porous Media

    , M.Sc. Thesis Sharif University of Technology Hosseini, Sajad (Author) ; Jamshidi, Saeed (Supervisor) ; Masihi, Mohsen (Supervisor)
    Today, due to a massive increase in accuracy of reservoir characterization models, multiphase flow simulation on real permeability fields faces a serious challenge. Using multiscale methods in reservoir flow simulation of a heterogeneous environment has led to huge speed-up of the simulation. In multiscale methods, instead of replacing a heterogeneous medium by an equivalent homogeneous medium, used in upscaling, the problem is solved on the original resolution. In this thesis, multiscale finite volume method (MSFV) has been used to simulate flow and saturation behavior of a black oil model. Unlike the original multiscale finite volume methods that were unable to solve compressible fluid... 

    An ISPH scheme for numerical simulation of multiphase flows with complex interfaces and high density ratios

    , Article Computers and Mathematics with Applications ; Volume 75, Issue 8 , 2018 , Pages 2658-2677 ; 08981221 (ISSN) Rezavand, M ; Taeibi Rahni, M ; Rauch, W ; Sharif University of Technology
    Elsevier Ltd  2018
    Multiphase problems with high density ratios and complex interfaces deal with numerical instabilities and require accurate considerations for capturing the multiphase interfaces. An Incompressible Smoothed Particle Hydrodynamics (ISPH) scheme is presented to simulate such problems. In order to keep the present scheme simple and stable, well-established formulations are used for discretizing the spatial derivatives and a repulsive force is applied at the multiphase interface between particles of different fluids to maintain the interface sharpness. Special considerations are included to overcome the difficulties to model severe physical discontinuities at the interface and surface tension... 

    Simulation of Multiphase Flow in Non-Circular Capillaries Using SPH

    , M.Sc. Thesis Sharif University of Technology Fayazbakhsh, Mohammad Ali (Author) ; Kazemzadeh Hannani, Siamak (Supervisor) ; Taghizadeh Manzari, Mehrdad (Supervisor)
    In this thesis an SPH method is used for simulating multiphase two- and three-dimensional Newtonian fluid flows. The weakly compressible algorithm consists of two steps of prediction and correction. In the prediction step, the velocity field is integrated forward in time without enforcing incompressibility. The correction step consists of enforcing incompressibility by solving the pressure Poisson equation which creates a trade-off between the pressure and density variations. The surface tension force is applied in the linear momentum conservation equation by the divergence of the surface stress tensor. Advanced techniques are applied to achieve better convergence and reduce pressure-related... 

    Synthesis of Several Multiphasic Ionic Liquid-Coated Pt/Al2O3 Catalysts: Selective Synchronous Hydrogenation of C=C and C=O Bond and Modeling of the Ionic Liquid and Solvent Effects

    , M.Sc. Thesis Sharif University of Technology Vatan Meidan Shahi, Reza (Author) ; Gholami, Mohammad Reza (Supervisor)
    In this study various ionic liquids (ILs) and their mixtures were coated on Pt/Al2O3 catalyst and the resulted IL-coated catalyst were used in synchronous hydrogenation of cyclohexene and acetone. The rate constants (k) and seletivities (S) toward C=O hydrogenation were determined for several catalysts in various solvents. The solvatochromic parameters (ETN, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen- bond acceptor basicity; α, hydrogen-bond donor acidity) were determined for used ILs and solvents and all obtained selectivities were modeled based on solvatochromic parameters of IL layer and bulk solvent using Multiparameter Linear Regression (MLR) method for... 

    Effect of multiphase fluid and functionally graded density fluid on the stability of spinning partially-filled shells

    , Article International Journal of Mechanical Sciences ; Volume 140 , 2018 , Pages 109-118 ; 00207403 (ISSN) Sahebnasagh, M ; Nikkhah Bahrami, M ; Dehghani Firouz Abadi, R ; Sharif University of Technology
    Elsevier Ltd  2018
    The effect of a multiphase fluid, including an arbitrary number of liquid phases, and a functionally graded density fluid on the stability of rotating partially-filled cylindrical shells is investigated. The first-order shear shell theory is used for modeling the structural dynamics of the shell and a 2D model is introduced based on the Navier–Stokes equations, for fluid motion. The multiphase and the functionally graded density fluids are arranged according to the mass density in a steady state condition due to centrifugal forces. Using the boundary conditions between liquid phases and the boundary conditions of the fluid on the cylinder wall, the coupled fluid-structure system model is... 

    Development of Optimal Integrated and Intensive Model of Energy Processing and Conversion

    , Ph.D. Dissertation Sharif University of Technology Avami, Akram (Author) ; Saboohi, Yadollah (Supervisor)
    In a single chemical plant, the operation of each unit operation is not independent of each other. In the other hand, the main operations are performed in reactors following by several separation steps including distillation and purification units. The total energy requirements are sullied by the heat exchanger networks. The performance of these systems is improved by integration and intensification of the reactor and distillation column in a single unit. The main objective of the present work is to provide an effective design approach to intensify the reactor and distillation column. In a reactive distillation column, the reaction and separation is done in a single unit. Increasing... 

    Optimum Design Of Wave Mitigating Multi phase FGMs

    , M.Sc. Thesis Sharif University of Technology Zanjirzani, Hadi (Author) ; Tvakkoli, Roohollah (Supervisor)
    Functionally graded materials (FGMs) are categorized in a branch of composite materials in which the local volume fraction of contributing phases are not fixed throughout the spatial domain, but vary gradually as a function of position. This spatial variation leads to the gradual variation of physical and mechanical properties inside the materials. It provides us the opportunity of designing multiple purpose materials by the variation of local volume fractions according to our goal. The optimal distribution of local volume fractions is a function of the spatial domain geometry and loading conditions, and in general situations, due to the complexity of the problem, it is not possible to... 

    Modeling of Dynamic Kill in Gas-Condensate Well

    , M.Sc. Thesis Sharif University of Technology Daneshpajouh, Abouzar (Author) ; Shad, Saeed (Supervisor)
    By exploring huge gas-condensate reservoirs, three-phase transient flow modeling demonstrates its crucial role in designing dynamic kill, relief well parameters and kill procedure of such wells. Controlling gas-condensate well needs robust transient three phase models capable of capturing discontinuities in density, geometry and velocity of phases. In this paper, two phase Advection-Upstream-Splitting-Method hybrid scheme is extended to three-phase model capable of modeling blowout and dynamic kill in gas-condensate-water wells. Density and viscosity changes are calculated using Peng-Robinson equation of state and in according, flow model parameters are corrected.The capability of this model... 

    Numerical Modeling of Liquid Jet Breakup Using SPH Method

    , M.Sc. Thesis Sharif University of Technology Pourabdian, Majid (Author) ; Morad , Mohammad Reza (Supervisor) ; Omidvar, Pourya (Supervisor)
    Smoothed Particle Hydrodynamics (SPH) is a numerical Lagrangian meshless method which has numerous applications in astrophysics, hydrodynamics, free-surface flows, jets and sprays formation. Atomization of continuum liquid to fine droplets or in other words, liquid breakup processes are emerged in many engineering applications such as fuel sprays inside the combustion chamber of internal combustion engines that sizes of produced sprays significantly influence the engine’s efficiency. This research is accomplished to investigate the one-phase and two-phase flows of liquid jet breakup. For this aim, an open source code called SPHysics which solves the flow field by SPH method is utilized. This... 

    Development of a Simulator to Simulate Multi-phase Flow with Asphaltene Precipitation in the Wellbore

    , M.Sc. Thesis Sharif University of Technology Hassanpour Youzband, Aliakbar (Author) ; Taghikhani, Vahid (Supervisor) ; Bozorgmehri, Ramin (Supervisor)
    Asphaltene, the heaviest and most polarizable fraction of crude oil, has a potential to precipitate, deposit and plug pipelines, causing considerable production costs. The main objective of this study is to contribute to the thermodynamic and transport modeling of asphaltene in order to predict its precipitation, segregation and deposition. Potential calculation of some thermophysical properties of asphaltene is also explored. Predicting the flow assurance issues caused by asphaltene requires the ability to model the phase behavior of asphaltene as a function of pressure, temperature and composition. It has been previously demonstrated that the Perturbed Chain form of Statistical Association... 

    Integration of Population Balance Method and Computational Fluid Dynamics for Simulation of Bubble Column Hydrodynamics

    , Ph.D. Dissertation Sharif University of Technology Baghaei, Ali (Author) ; Bastani, Dariush (Supervisor) ; Sarrafi, Amir (Supervisor)
    Different modeling and simulation techniques, new numerical methods and analyzing effects of different parameters on operation of bubble columns are continuously under study for optimized design, scale-up and prediction of industrial bubble columns. Tools for analyzing and developing gas-liquid systems are experimental techniques and computational fluid dynamics (CFD). In order to describe accurately the fluid dynamics of complex gas-liquid systems, more advanced mathematical models are required. To obtain a feasible numerical solution, efficient numerical techniques must be devised. One of such models that considerably reduces the assumptions and consequently increases the accuracy of... 

    Theoretical and Experimental Study of the Influence of Chemical Environments and Investigation of their Effects on the Kinetics of Redox Reactions using Metal and Metal Oxide Nanocatalyst

    , Ph.D. Dissertation Sharif University of Technology Kohantorabi, Mona (Author) ; Gholami, Mohammad Reza (Supervisor)
    Bimetallic nanoparticles with unique structure, synergistic effect between two metals, and the tunable physical/chemical properties have been used for catalysis. Various methods exist for the staibility, and improvement of the catalytic performance of nanoparticles. In this thesis, different co-catalysts were applied to increase tha staibility, and activity of nanoparticles and metal oxides. In this way, Ni-based bimetallic nanoparticles including CuNi, CoNi, and AgNi, and AgPt with different concentrations were synthesized on the cerium oxide nanorods derived from cerium metal-organic frameworks and magnetic graphene oxide nanosheets, respectively and characterized. The catalytic... 

    Simulation of Flow Drag Reduction through Air Injection from the Porous Wall

    , M.Sc. Thesis Sharif University of Technology Boyerahmadi, Amirhossein (Author) ; Moosavi, Ali (Supervisor) ; Sadrhosseini, Hani (Supervisor)
    The effect of using backpressure of air injection in a microchannel on internal flow pressure drop were investigated in this study. Multiphase flows are commonly encountered in gas and oil industries. Flow fields in production operations are often complex and include multiphase flows of gas and liquid. Previously, because of their complex nature, these flow patterns have been mostly investigated only experimentally and empirical correlations based on the experimental data. From another point of view, it is almost impossible to experimentally realize all the flow conditions for each of the flow patterns. Nowadays computer facilities provide the tool to construct and use large-scale... 

    LBM Computational Simulation of Oscillations Caused by Formation and Detachment of Drops

    , M.Sc. Thesis Sharif University of Technology Mardani, Ramin (Author) ; Taeibi Rahni, Mohammad (Supervisor) ; Ebrahimi, Abbas (Supervisor)
    Formation and detachment of drops are of fundamental importance in studying two-phase flows, such as ink jet printing, emulsion, and spray. Drops are formed under the effects of surface tension forces. After formation, forces like gravity detach the drop from the rest of the fluid. The flow rate is varied from dripping to jetting regime. In this project, formation and detachment of drops were simulated, using LBM with phase field model, which can simulate flows with high-density ratios and is a robust method for applying wetting condition on the walls. Results were validated using single-phase and two-phase flows. After code validation, the oscillations caused by formation and detachment of... 

    Simulation of Non-newtonian Flow of Drilling Fluid Around the Drill String with the Olga Software

    , M.Sc. Thesis Sharif University of Technology Sadri, Avazdordi (Author) ; Jamshidi, Saeed (Supervisor)
    Because of the importance of simulations in the oil industry, there are different software applications designed for this purpose. The purpose of the simulation in the oil industry is to reduce operational errors during the operation and to achieve the most ideal mode of operation. However, in the simulation of multiphase fluid flow because of the special circumstance, simulation plays an important role in the oil industry. OLGA multiphase flow simulation software is a strong simulation software for water, oil, Gas wells, wellhead facilities, refineries and pipelines and it is capable of simulating pipelines under various dynamic conditions. Simulation of drilling hydraulic parameters is...