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    Numerical Assessment of Optimum Baffle Configuration and Hydrodynamics of Settling Tanks

    , M.Sc. Thesis Sharif University of Technology Asgharzadeh, Hafez (Author) ; Firoozabadi, Bahar (Supervisor)
    Sedimentation tanks are channels designed for sedimentation of suspended solids in water. These tanks are one of the most important parts of water treatment plants and their performance directly affects the functionality of water treatment plants. Therefore, researchers have tried to find better designs of sedimentation tanks. Among several design methods have been presented, modification of the geometry of tanks by installing baffles is one of the most effective and economic methods. According to the importance of performance improvement of industrial sedimentation tanks as well as the diversity in reported results, development and completion of previous studies seem to be necessary. In... 

    Numerical Study of Turbulent Flows by Finite Volume Approach & Turbulence Model K-e

    , M.Sc. Thesis Sharif University of Technology Khalife Soltani, Ali (Author) ; Seif, Mohammad Saeed (Supervisor) ; Taghizadeh Manzari, Mehrdad (Supervisor)
    High-Speed Crafts’ motion has lots of hydrodynamic complexities, so analytical study of their motion is not feasible. Meanwhile, experimental analysis of their reactions in water is not time-consuming & cost-effective. In spite of code generating & developing problems and complexities in the primary stage of numerical modeling of such problems, this method is the most popular & efficient one. On the other hand, flow around high-speed craft bodies has a turbulent nature and needs special cares to predict reasonable results. In the present study, after representing an introduction about the turbulence modeling, we discissed about governing equation such as momentum, volume fraction and rigid... 

    3Dimentional Numerical Modeling of Air Particle Flow in a Cleanroom

    , M.Sc. Thesis Sharif University of Technology Molaei Manesh, Gholam Reza (Author) ; Saeedi, Mohammad Hassan (Supervisor)
    Nowadays, cleanrooms have a growing application in a broad range of industries, e.g. pharmacy, aerospace, nuclear energy and electronics. So, it seems that numerical modeling of airflow in such spaces becomes more essential. As computational fluid dynamics has become a powerful tool for indoor airflow studies, in this research, influence of effective parameters on the flow and concentration distribution in cleanrooms has been investigated by the use of CFD. To do so, aerosol flow in a 3-D cleanroom has been numerically modeled by Fluent 6.3, using Euler-Euler approach and standard k- turbulence model. Comparison between numerical results and experimental data shows a considerably good... 

    Modeling of Atmospheric Toxic Release and Dispersion Using CFD

    , M.Sc. Thesis Sharif University of Technology Mokhtari, Mojtaba (Author) ; Rashtchian, Davood (Supervisor)
    In this project, ammonia dispersion in the environment have been investigated and the experimental data have been used in order to show accuracy of calculations. Also, the results of CFD have been compared with the results of PHAST software. The results show that when there is no obstacle in the way of gas release, dispersion models will get good results, but due to existence of the obstacle, their error will be increased to 300%. However, the error resulting from CFD is less than 24% even if there are obstacle there. The effects of obstacle’s distance and height on the dispersion of ammonia gas are investigated. This study showed that the concentration of ammonia increase, when the distance... 

    Numerical Simulation of Turbulent Cavitating Flows Using Two-Equation k-ϵ Turbulence Model

    , M.Sc. Thesis Sharif University of Technology Dehghanan, Sara (Author) ; Hejranfar, Kazem (Supervisor)
    In the current study, the numerical simulation of the turbulent cavitating flows is performed by solving the preconditioned, homogenous, multiphase Navier-Stokes equations. For the turbulence modeling, the standard two-equation k-ϵ model is used. The baseline differential equations system is comprised of the mixture volume, mixture momentum and constituent volume fraction equations together with two equations for the turbulence kinetic energy k and the turbulence energy dissipation rate ϵ. For the calculation of the eddy viscosity near the wall boundary, appropriate turbulence damping functions are applied to modify the source terms of the ϵ equation. The system of governing equations is... 

    Numerical Simulation of Secondary Sedimentation Tanks to Increase the Efficiency

    , M.Sc. Thesis Sharif University of Technology Lak, Behzad (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Supervisor)
    Sedimentation tanks are one of the important and costly stages of water treatment process in which remained particles from previous stages settle down due to gravity force. In this research, the hydrodynamics of secondary settling tanks without and in the presence of particles is numerically investigated using VOF method in order to simulate the interphase using RNG k-ε for turbulence modelling. The simulations are performed by means of open-source code OpenFoam, and the code is developed to model particles in the flow. The calculated velocity profiles using VOF method show a reasonable agreement with the experimental data. Comparing the concentration profiles with experiments shows the... 

    Experimental and Numerical Study on Particle-Laden Flows

    , Ph.D. Dissertation Sharif University of Technology Afshin, Hossein (Author) ; Firoozabadi, Bahar (Supervisor) ; Rad, Manouchehr (Supervisor)
    Dense underflows are continuous currents that move down-slope due to their density being heavier than that of the ambient water. This difference between the dense fluid and environment fluid can be due to temperature difference, chemical materials, solved materials or suspend solid particles. In these currents, the effect of buoyancy force is produced by this difference density. In this research, many experiments performed in different flow rates, slopes and concentrations to understand the current structure and turbulence specification of the salt solution density currents and particle-laden density currents. Acoustic Doppler Velocimeter is used to measure the velocity fluctuations. The... 

    Simulation of a Turbulent 3D Offset Jet

    , M.Sc. Thesis Sharif University of Technology Mohammad Aliha, Negar (Author) ; Farahanieh, Bijan (Supervisor) ; Afshin, Hossein (Supervisor)
    An offset jet refers to a flow issuing above a wall offset by a distance h and parallel to the axis of the jet. Asymmetric entrainment on both sides of the jet causes the jet to deflect toward the plate. The flow field of an offset jet is complex and is encountered in many engineering applications. For instance, burners, boilers, combustion chambers and fuel injection system are strongly governed by the behavior of offset jets. The understanding of the flow field properties of offset jet is required to ensure the proper design of systems.
    In this study the mean flow and turbulent properties of 3D offset jet with circular nozzle, developing in a stagnant environment, are studied by means... 

    Evaluation of different k-omega and k-epsilon turbulence models in a new curvilinear formulation

    , Article 17th AIAA Computational Fluid Dynamics Conference, Toronto, ON, 6 June 2005 through 9 June 2005 ; 2005 ; 9781624100536 (ISBN) Darbandi, M ; Zakyani, M ; Schneider, G. E ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2005
    Despite significant progress in unstructured grid generation and employment, the robust employment of body-conforming coordinate systems promotes the workers to consider it as a major alternative to treat relatively complex flow fields in irregular geometries. Contrary to the laminar flow treatment, there are many ambiguities around treating turbulent flow on body-fitted coordinate system. The ambiguities are mainly originated from the curvature on the boundaries. Considering the past taken efforts in improving the results of treating turbulent flow on curvilinear coordinate system, we have extended a new formulation on body-fitted coordinate system using physical covariant velocities as the... 

    Three Dimensional Numerical Simulation of Slinger Combustor

    , M.Sc. Thesis Sharif University of Technology Akhtar Danesh, Mohammad Ali (Author) ; Farshchi, Mohammad (Supervisor)
    Annular combustion chambers used in small turbine motors which incorporate centrifugal (rotary) injectors for injecting fuel, are known as Slinger combustion chambers. The Slinger injector works in such a way that fuel enters from an inner tube in motor shaft and exits with high pressure from the holes on the cylinder connected to the shaft. Because of the high centrifugal force, the fuel is sprayed with high quality after entering the combustion chamber. Type and angle of spray, fuel-air mixing type, combustion phenomena and flame stability makes this different than other annular combustion chambers. The process of combustion in the Slinger chamber of YJ402 motor is numerically simulated in... 

    Performance intensification of turbulent flow through heat exchanger tube using double V-cut twisted tape inserts

    , Article Chemical Engineering and Processing - Process Intensification ; Volume 141 , 2019 ; 02552701 (ISSN) Nakhchi, M. E ; Esfahani, J. A ; Sharif University of Technology
    Elsevier B.V  2019
    This paper aims to present a numerical model for heat transfer intensification in a heat exchanger tube equipped with novel double V-cut twisted tape. The effects of different cut ratios (0.6 < b/c<1.8)on the turbulent flow characteristics and thermal performance of the system are investigated over the Reynolds number range from 5000 to 15,000. The accuracy of (RNG)k-ε turbulence model used in the present study is validated by comparing with experimental results. The tube equipped with double V-cut twisted tape shows improved thermal performance in comparison with conventional twisted tape. This improvement is due to the additional vortex flow induced by the V-cuts which leads to more... 

    Experimental and CFD simulation of slurry flow in the annular flow path using two-fluid model

    , Article Journal of Petroleum Science and Engineering ; Volume 198 , 2021 ; 09204105 (ISSN) Movahedi, H ; Jamshidi, S ; Sharif University of Technology
    Elsevier B.V  2021
    The current study is allocated to experimental evaluation of the multiphase flow of fine solid particles (FSPs) as well as comprehensive numerical study in an annular space under static, laminar, and turbulent flow conditions with consideration of the inner pipe eccentricity and rotation. The experimental investigation was carried out using an annular pipe flow loop. The numerical modeling and simulation of the multiphase flow in the annular space have been performed using the Euler-Euler approach. The unsteady-state multiphase model based on the kinetic theory of granular flow (KTGF) is developed to investigate the particulate flow characteristics in the annular space. Moreover, Standard...