Search for: firoozabadi--bahar
0.015 seconds
Total 64 records

    Role of Non-Dimensional Numbers in Density Current Stability

    , M.Sc. Thesis Sharif University of Technology Nourmohammadi, Zahra (Author) ; Firoozabadi, Bahar (Supervisor)
    Density currents are occurred as a result of the intrusion of a dense fluid into a fluid with a different density. Density differences are typically caused by the difference in temperature, existence of solution or insoluble material and suspended solids. A special kind of density current is called a turbidity current which is a sediment-laden density current. This is a kind of flow which is driven by the force of gravity on suspended sediment particles that causes an excess fractional density with respect to the surrounding ambient fluid. In this work, the 2-D sediment-laden density current on a sloping surface of the channel is investigated through experiments. The channel is 12 m long,... 

    Experimental Investigation of Three Dimensional Turbidity Current

    , M.Sc. Thesis Sharif University of Technology Sheikhi Ahangarkolaei, Javad (Author) ; Firoozabadi, Bahar (Supervisor)
    Dense underflows are continuous currents which move down slope due to the fact that their density is heavier than ambient water. Driven by density differences between the inflow and clear water in the reservoirs, the density current plunges the clear water and moves on the bed. While density currents flowing on a sloping bed, the vertical spreading due to water entrainment plays an important role in determining the propagation rate in the longitudinal direction. These currents are similar to wall-jet currents according to structure of the flows but are complicated relative to wall-jet currents due to the existence of density difference. Characteristics of the density current sometimes are... 

    Experimental and Theoretical Investigation on Entrainment Coefficient in Density Current and Introducing Modified Richardson Number

    , M.Sc. Thesis Sharif University of Technology Maleki Tehrani , Mahdi (Author) ; Firoozabadi, Bahar (Supervisor)
    Dense underflows are continuous currents, caused by interaction of two or more fluids of different density. Density currents move down-slope due their density being heavier than that of the ambient water. In this work, entrainment in 3-D density currents in a straight channel was investigated by a set of experimental studies and Theoretical calculations. Velocity components were measured using Acoustic Doppler Velocimetry (ADV). First of all, the bed shear stress was calculated by the velocity profile method and Reynolds stress method as well and showed a good agreement. By increasing the Richardson number, the bed shear stress decreases. On the other hand, the interface shear stress was... 

    Experimental Study on Deposition Behavior of Turbidity Current

    , M.Sc. Thesis Sharif University of Technology Khavasi, Ehsan (Author) ; Firoozabadi, Bahar (Supervisor)
    Density currents are occurred as a result of the intrusion of a dense fluid into a fluid with a different density. Density difference is the main agent of current’s movement. These currents are observed in nature numerously and they are one of the main reasons of the erosion and transportation of deposition in oceans, seas and rivers. Investigation of these currents is of great importance especially in dams’ reservoir as major cause of deposition and reduction of reservoir’s efficency. Density differences are typically caused by the difference in temperature, existence of solution or insoluble material and suspended solids. In this work, density current is studied experimentally. Density... 

    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... 

    Simulation of Density Currents with SPH Method

    , M.Sc. Thesis Sharif University of Technology Ghasemi Varnamkhasti, Amir (Author) ; Firoozabadi, Bahar (Supervisor)
    Flows which density difference in a gravity field is their driven force are called Density Currents. Such flows are present in both nature and man made environments. Due to their importance, there have been large efforts to analyse them in both experimental and numerical way. In the present thesis, Smoothed Particle Hydrodynamics (SPH) is introduced as a new tool to simulate such flows. As the method is Lagrangian and particle based, simulation of Density Currents with particles can be addressed more naturally that can be accounted as the method preference to traditional mesh based methods. SPH projection method is incorporated to impose incompressibility. To precisely simulate Density... 

    Vorticity-Bases Adaptive Mesh Refinement for Upscaling of Highly Heterogeneous Porous Media

    , M.Sc. Thesis Sharif University of Technology Shahriari, Arjang (Author) ; Firoozabadi, Bahar (Supervisor)
    The results of numerical simulation of underground flows are greatly affected not only by the discretization method of flow equations, but also by the way that the geological domain is upscaled. Including the detailed knowledge of heterogeneous permeability distribution is mostly neither feasible nor computationally efficient. So it is important to develop efficient grid generation and upscaling methods to simplify the fine-scale flow model while still including the impact of the heterogeneities as far as possible. Thus regions where parameters of interest have larger values or higher changes require finer grid blocks and regions with lower values or minor changes should have coarser grid... 

    Reservoir Flow Simulation Using Multi-Scale Uscaling Method

    , Ph.D. Dissertation Sharif University of Technology Ashjari, Mohammad Ali (Author) ; Firoozabadi, Bahar (Supervisor)
    This thesis introduces a fast and accurate two-phase reservoir flow simulation procedure. The speed up is achieved by an upscaling technique where coarsening is applied to the detailed geological reservoir descriptions. This process results to two major error sources affecting the simulation accuracy significantly. The homogenization error is appeared when coarse scale data, such as equivalent permeability, is calculated from the available fine grid model information. It is shown that the error can be reduced adjusting coarse grid (non-uniform Cartesian) distribution. For the first time in this study, the grid distribution optimization is done based on “vorticity” map. In particular, the... 

    Numerical Simulation of Glucose Metabolism and Hepatocyte Viability within a Microfluidic

    , M.Sc. Thesis Sharif University of Technology Nejadnasrollah, Farzam (Author) ; Firoozabadi, Bahar (Supervisor)
    The advent of microfluidics as suitable environments for culturing cells is associated with some challenges such as shear stresses applied on the cells. In fact, hepatocytes lose their function as exposed to high shear stresses similar to other cell types. Moreover, among all factors needed for cell viability, feeding hepatocytes with adequate oxygen is of great importance due to their high demand for oxygen compared the other cells. In this thesis, different types of cultures including 2D and 3D has been used in order that shear stresses would be in allowed range and provision of hepatocytes with sufficient oxygen concentrations has been ensured as well. In addition to supplying hepatocytes... 

    Upscaling and Simulation of Two-Phase Flow in Porous Media

    , Ph.D. Dissertation Sharif University of Technology Khoozan, Davood (Author) ; Firoozabadi, Bahar (Supervisor)
    Advanced reservoir characterization methods can yield geological models at a very fine resolution, containing 1011-1018 cells while the common reservoir simulators can handle much fewer numbers of cells due to computer hardware limitations. The process of coarsening the fine-scale model to simulation models is known as upscaling. There are three fundamental steps in the procedure of upscaling, i.e. defining the coarse grid geometry, calculating the average properties for the generated coarse grid and simulation of the two-phase flow equations on the generated coarse-scale model. In this thesis, the focus will be on investigating the applicability of optimization in the context of coarse grid... 

    Simulation of Competitive Flow in the Coronary Arteries Bypass

    , M.Sc. Thesis Sharif University of Technology Azimi Nejad, Milad (Author) ; Firoozabadi, Bahar (Supervisor)
    Atherosclerosis is one of the most important factors for mortality and morbidity in the world. Coronary artery bypass graft (CABG) is applied for treatment of this disease which in this surgery, the patient vessels, such as internal thoracic artery and saphenous vein, are harvested and grafted to the coronary arteries. The graft success and its performance in short and long-term are depended on the much factors e.g. the severity of stenosis in the coronary artery. It should be noted that the low level of stenosis in the coronary artery causes the creation of undesirable phenomenon of competitive flow in the grafts after the surgery which this phenomenon has been reported as a cause of graft... 

    Three Dimensional Large Eddy Simimulation of Lock-Exchange Density Currents

    , M.Sc. Thesis Sharif University of Technology Mahdinia, Mani (Author) ; Firoozabadi, Bahar (Supervisor) ; Farshchi, Mohammad (Supervisor)
    In this thesis, lock-exchange density currents are investigated using the dynamic large eddy simulation (LES) method. These are flows that occur under the influence of gravity and density gradient. In the lock-exchange type currents, a bulk of heavy fluid is released under an ambient lighter fluid. One charachteristic of such flows is the presence of turbulence at different scales across flow and Kelvin-Helmholtz and lobe and cleft instabilities at the interface, which additionally act to complicate the matter. Although lots of efforts have been devoted to simulate density currents, much of the previous simulations have used Reynolds Average Navier-Stockes (RANS) methods. Practically, these... 

    Effect of Stenotic Carotid Geometry on Flow and Stroke-risk

    , M.Sc. Thesis Sharif University of Technology Amirkhosravi, Mehrad (Author) ; Firoozabadi, Bahar (Supervisor) ; Saeedi, Saeed (Supervisor)
    Carotid bifurcation is one of the most important bifurcations in human body which has a lot of curvature in some people. The common carotid artery bifurcates into an internal carotid artery (ICA) and an external carotid artery (ECA). The incidence of stenosis in carotid bifurcation and in particular in the internal carotid artery is of special importance. In the United States of America by 2006, nearly 700000 strokes occur each year, with about 160000 deaths and 20 to 30% of strokes are caused by stenotic carotid that cost estimated at $160 billion. The purpose of this thesis is to investigate in hemodynamic factors of blood flow such as velocity variation, vortex patterns, shear stress and... 

    Experimental Investigation on the Accelerated Motion of Newtonian and Non-Newtonian Liquid Drops

    , M.Sc. Thesis Sharif University of Technology Aminzadeh, Milad (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Supervisor)
    Motion of liquid drops into another fluid is of central importance in a variety of most commonly used industries. Vast applications of emulsions in food and drug industries as well as using of drops in liquid-liquid extraction processes and direct contact heat exchangers are examples in which dynamics of motion of drops play a significant role in operation and efficiency.
    In present study, we consider the accelerated motion of Newtonian and non-Newtonian liquid drops experimentally. In order to find the effect of bulk fluid on the motion of drops, air and water are used as bulk fluid. The experiments have been done on Water, Ethanol, Ethyl acetate, n-Hexane and Toluene as Newtonian and... 

    Investigation of Two-Fluid Flow Contains Oil and Water in Hydrocyclones

    , Ph.D. Dissertation Sharif University of Technology Maddahian, Reza (Author) ; Farhanieh, Bijan (Supervisor) ; Firoozabadi, Bahar (Co-Advisor)
    Having an efficient and reliable system for oil-water separation especially in offshore oil and gas industry is of crucial importance. Due to the platform movement, space, weight and operating limitations in offshore industries, using common methods, (e.g. gravity based vessels), for oil-water separation is ineffective. On the other hand, producing oil on offshore platforms is often accompanied by large discharge of oil-contaminated water into the sea, resulting in environmental pollution. Therefore a need for high efficiency compact separators capable of operation in various operating conditions arises. One solution to the mentioned problem is the use of hydrocyclone separators. The... 

    Experimental Study on Behavior of Turbidity Currents with Obstacle

    , M.Sc. Thesis Sharif University of Technology Oshaghi, Mohammad Reza (Author) ; Afshin, Hossein (Supervisor) ; Firoozabadi, Bahar (Co-Advisor)
    Turbidity currents are produced when a particle laden fluid flows under the lighter ambient fresh fluid. The streaming of particle laden fluid is called turbidity current and this kind of currents is the major mechanism for sediment transportations in lakes and oceans. In the present research, the main concentration is on the effect of obstacle on the behavior of turbidity current. A series of laboratory experiments were carried out with various obstacle heights, shapes and different inlet densimetric Froude numbers. In each experiment, velocity profiles upstream and downstream of the obstacle were measured, using an ADV (Acoustic Doppler Velocimeter). Kaolin was used as the suspended... 

    Three-Dimensional Large Eddy Simulation of Continuous Density Currents

    , M.Sc. Thesis Sharif University of Technology Najafpour, Nategheh (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Co-Advisor)
    When a fluid moves inside another fluid while they have unequal density, a phenomena occurs which is called density (or gravity) current. Therefore density difference and gravity are key factors of density current generation. Due to application in engineering and geology, it is essential to investigate and analyze the above mentioned phenomena. Dam reservoirs, sandstorm in deserts, snow slide onset and falling, ash clouds produced during eruption of a volcano, and spreading of density current due to the collapsing of reservoirs are some examples of gravity current. There are lots of methods to simulate the turbulence of density current like DNS or RANS. But DNS has high computational cost... 

    Numerical Modeling of Drop Formation and Deformation using the Finite Volume Method

    , M.Sc. Thesis Sharif University of Technology Sadat Salehi, Moloud (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Co-Advisor)
    Drop formation from the tip of a nozzle and its motion in bulk fluid is an interesting and practical process which has widely turned researchers’ attention. Investigation into the governing physics and effective parameters on formation, deformation and motion of a drop increases the efficiency of the related industrial processes. Thus in the present study, in order to simulate this process, full Navier-Stokes equations solved by the Volume of Fluid (VOF) method in an axisymmetric domain using Fluent software as the solver. In this research, the effects of Weber number (the proportion of inertial force to surface tension force) and Ohnesorge number (which refers to the proportion of viscous... 

    Large Eddy Simulation of Continuous Density Current Impinging on Obstacles

    , M.Sc. Thesis Sharif University of Technology Abbaszadeh, Shahabaddin (Author) ; Firoozabadi , Bahar (Supervisor) ; Afshin, Hossein (Supervisor)
    Density currents as a particular form of stratified fluid motion in nature have attracted the interest of many researchers in the past decades. These flows are formed whenever a fluid with specific density begins to move through another fluid with different density called ambient fluid. Prediction of propagation of turbulent density currents, especially because of their remarkable influence on the environment, is one of the researcher’s interests in geophysics and engineering. Density currents have a lot of applications in industry and nature. Sand storm in deserts, turbidity currents in oceans and avalanches are natural examples and leakage of dense gas into the atmosphere due to reservoir... 

    Experimental Investigation of Mass Transfer by Droplet Using Image Processing

    , M.Sc. Thesis Sharif University of Technology Babak, Pirooz Hashemi (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Co-Advisor)
    Wide and varied aspects of droplet motion due to its increasing application in various fields has attracted much attention. Analysis of mass transfer from the liquid drop into the other fluid, such as complex and intriguing problems in fluid mechanics, which is very important. Many experimental and numerical studies have been carried out in this case that the evelopment of laboratory equipment and software, are rapidly growing.
    In this study, given the importance of this issue, experimental study on mass transfer in fluid systems solution droplet liquid - liquid extraction, have been considered. Different methods have been discussed to date. In the present study, using image processing...