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    Experimental and numerical approach to enlargement of performance of primary settling tanks

    , Article Journal of Applied Fluid Mechanics ; Volume 2, Issue 1 , 2009 , Pages 1-12 ; 17353572 (ISSN) Razmi, A ; Firoozabadi, B ; Ahmadi, G ; Sharif University of Technology
    Circulation regions always exist in settling tanks. These regions would result in short-circuiting enlargement of the dead zone and high flow mixing problems and avoid optimal particle sedimentation. Therefore, the main objective of the tank design process is to avoid formation of the circulation zone, which is known as dead zone. Experiments show that the tank performance can be improved by altering the geometry of the tank which leads to a different velocity distributions and flow patterns. In this paper, the presence of a baffle and its effect on the hydrodynamics of the flow field has been investigated in a primary settling tank. Hydrodynamics of the flow field in these basins is... 

    Study of heterogeneity loss in upscaling of geological maps by introducing a cluster-based heterogeneity number

    , Article Physica A: Statistical Mechanics and its Applications ; Volume 436 , October , 2015 , Pages 1-13 ; 03784371 (ISSN) Ganjeh Ghazvini, M ; Masihi, M ; Baghalha, M ; Sharif University of Technology
    Elsevier  2015
    The prediction of flow behavior in porous media can provide useful insights into the mechanisms involved in CO2 sequestration, petroleum engineering and hydrology. The multi-phase flow is usually simulated by solving the governing equations over an efficient model. The geostatistical (or fine grid) models are rarely used for simulation purposes because they have too many cells. A common approach is to coarsen a fine gird realization by an upscaling method. Although upscaling can speed up the flow simulation, it neglects the fine scale heterogeneity. The heterogeneity loss reduces the accuracy of simulation results. In this paper, the relation between heterogeneity loss during upscaling and... 

    Simulation of 2-Phase Fluid Flow on Unstructured Grids Upscaled by Image Segmentation Methods

    , M.Sc. Thesis Sharif University of Technology Gholinezhad, Sajjad (Author) ; Jamshidi, Saeed (Supervisor) ; Hajizadeh, Alireza (Co-Advisor)
    This paper describes the use of Quad-Tree Decomposition for upscaling of absolute permeability 2D geological models. Quad-Tree Decomposition is a data structure and generates an unstructured upscaled model that preserves the heterogeneity of the original geological model. In other words, in high-variability regions of the geological model, the gridblocks of the upscaled model remain small but in other regions that the permeability variation is low, the gridblocks of the upscaled model are coarsened. Quad-Tree Decomposition is a very simple, efficient and robust method that reduces the total number of gridblocks and results to high saving in time and memory required to flow simulation in the... 

    DSMC simulation of subsonic flow through nanochannels and micro/nano backward-facing steps

    , Article International Communications in Heat and Mass Transfer ; Volume 38, Issue 10 , 2011 , Pages 1443-1448 ; 07351933 (ISSN) Darbandi, M ; Roohi, E ; Sharif University of Technology
    In this study, we use direct simulation Monte Carlo method to simulate subsonic flow in nanochannels and micro/nanoscale backward-facing (BF) step considering a wide range of Knudsen number regimes. The nanochannel flow simulation indicates that the nanoscale flow through the nanochannel resembles unique features such as encountering negative pressure deviation behavior and observing flat velocity profiles at higher Knudsen number regimes. On the other hand, the micro/nano BF step flow simulations demonstrate that the length of separation region considerably decreases as the flow becomes more rarefied and approaches the transition regime. Meanwhile, the variations in the flow properties are... 

    Computational Simulation of Turbulent Film Cooling, Using RANS/LES Hybrid Approach and Digital Filter Based Interface Boundary Conditions

    , M.Sc. Thesis Sharif University of Technology Sheikholeslam Noori, Mahdi (Author) ; Taeibi-Rahni, Mohammad (Supervisor)
    Nowadays, hybrid LES/RANS approach is being widely used by many researchers. This approach uses the advantages of both LES and RANS approaches simultaneously. Hybrid approach is as accurate as LES, but its cost is much lower. The biggest problem of hybrid approach is transformation of data between RANS and LES regions. Before, precursor simulation and synthetic methods, such as Fourier series and synthetic eddy methods (SEM) have been used extensively to solve such problems. Precursor simulation is expensive, because of high cost of generation of data. On the other hand, Fourier series method is confined to simple geometries, while SEM has problem of programming. Interface condition in this... 

    Simulation of Flow in Voraxial System Using Fluent

    , M.Sc. Thesis Sharif University of Technology Boromand, Behnam (Author) ; Taghizadeh Manzari, Mehrdad (Supervisor) ; Zabihollah, Abolghasem (Supervisor)
    One of the newest technologies in order to separate oil from water and also oil wastewater is the axial vortex separator technology (with commercial name of voraxial). In the current project, we analyze one of the voraxial (2000) separator systems types. In the modeling of voraxial system, we utilize a 3D model which is developed on the basis of commercial sample of voraxial 2000 technology, and conduct the solution of particles and fluid with Lagrangian Eulerian approach. Considering the k-ɛ turbulence model and an incompressible flow with the input of 30GPM and rotational velocity of 400RPM was another segment of the project. Due to the largeness of 10µ particles diameter, the Brownian... 

    Simulation of Magnetorheological Fluid Flows at Particle Scale

    , Ph.D. Dissertation Sharif University of Technology Hashemi, Mohammad Reza (Author) ; Taghizadeh Manzari, Mehrdad (Supervisor) ; Fatehi, Rouhollah (Co-Advisor)
    Magnetorheological fluids are suspensions of magnetic solid particles suspended in a nonmagnetic matrix fluid. By imposing an external magnetic field, particles are arranged in microstructures aligned with the external field and hence, dramatically affect the fluid flow. Since the strength of the magnetic field determines the resistance of these microstructures against flow, the rheology of the suspension is a function of the intensity of the external magnetic field. The goal of the present work is to study the role of non-gap-spanning magnetic clusters on the rheology of a magnetorheological fluid. Here, first a robust tool for direct numerical simulation of magnetic suspensions is... 

    Simulation of Fluid Aliquoting in Centrifugal Microfluidics

    , M.Sc. Thesis Sharif University of Technology Yousefpour, Mohammad Hossein (Author) ; Moosavi, Ali (Supervisor) ; Arghavani, Jamal (Supervisor)
    In this thesis, a numerical analysis of micro chamber filling in centrifugal microfluidics is investigated. In the development of micro total analysis systems, it is often necessary to achieve complete and uniform filling of relatively large micro chambers. With centrifugal devices, these large micro chambers must often be orientated perpendicularly to the direction of centrifugal force and are usually bounded by materials with varying surface properties. On the other hand, the mixing characterization of two fluid by centrifugal microfluidic method has been also conducted. The multiphase flow analyses based on Eulerian-Eulerian approach have been conducted and the VOF method was used for ... 

    Numerical Investigation of Cavitation Phenomenon in the Turbopump Inducer of Cryogenic Engines

    , M.Sc. Thesis Sharif University of Technology Sedaghi, Reza (Author) ; Farshchi, Mohammad (Supervisor) ; Ebrahimi Chamgardani, Abbas (Supervisor)
    Simulation of the flow inside a turbopump inducer of a cryogenic engine, can help to reduce the number of experimental tests in the design phase. In cryogenic engines, high speed of the turbo pump, engine working at off-design conditions, startup and shutdown of the engine, can cause the pressure to drop below the vapor pressure at the inducer blades. In such circumstances, cavitation bubbles start to grow and collapse as they are washed by the flow to the regions with higher pressure. Cavitation is the rapid formation and collapse of vapour cavities in a liquid.The energy required for evaporation is received from the surrounding liquid which causes the temperature to drop in the... 

    A new method to calculate efficiency of randomly-packed distillation columns and its comparison with the methods utilized in ASPEN Plus

    , Article Fuel Processing Technology ; Volume 96 , 2012 , Pages 65-73 ; 03783820 (ISSN) Sadeghifar, H ; Sadeghifar, A ; Sharif University of Technology
    In this paper, a unique and applicable method was developed for calculation of efficiency (and mass and heat transfer coefficients) of randomly-packed distillation columns. This method has potential advantages; e.g., unlike all the available methods, it can calculate efficiency without using any empirical mass transfer and hydraulic correlations, and without the need to estimate the operational and hydraulic parameters of an operating column. It, therefore, will be free of errors and limitations of such empirical items and can be used for efficiency calculation of any random packing including new ones. Along with an analysis of the proposed method, the paper also presents a thorough analysis... 

    A preconditioned euler flow solver for simulation of helicopter rotor flow in hover

    , Article Computational Fluid Dynamics 2010 - Proceedings of the 6th International Conference on Computational Fluid Dynamics, ICCFD 2010 ; 2011 , Pages 479-484 ; 9783642178832 (ISBN) Hejranfar, K ; Moghadam, R. K ; National Aeronautics and Space Administration; European Office for Aerospace Research and Development ; Sharif University of Technology
    In the present study, a preconditioned Euler flow solver is developed to accurately and efficiently compute the inviscid flowfield around hovering helicopter rotor. The preconditioning method proposed by Eriksson is applied. The three-dimensional preconditioned Euler equations written in a rotating coordinate frame are solved by using a cell-centered finite volume Roe's method on unstructured meshes. High-order accuracy is achieved via the reconstruction of flow variables using the MUSCL interpolation technique. Calculations are carried out for an isolated rotor in hover for different conditions and the computed surface pressure distributions are compared with the experimental data. The... 

    Thermal performance evaluation of domed roofs

    , Article Energy and Buildings ; Volume 43, Issue 6 , June , 2011 , Pages 1254-1263 ; 03787788 (ISSN) Faghih, A. K ; Bahadori, M. N ; Sharif University of Technology
    Domed roofs have been used in Iran and many other countries to cover large buildings such as mosques, shrines, churches, schools. They have been also employed in other buildings like bazaars or market places in Iran due to their favorable thermal performance. The aim of this research is to study about domed roofs thermal performance in order to determine how they can be helpful in reducing the maximum air temperature of inside buildings during the warm seasons considering all parameters like air flow around them, solar radiation, radiation heat transfer with the sky and the ground as well as some openings on the building. The results of the study show that the thermal performance of the... 

    Three-dimensional compressible-incompressible turbulent flow simulation using a pressure-based algorithm

    , Article Computers and Fluids ; Volume 37, Issue 6 , 2008 , Pages 747-766 ; 00457930 (ISSN) Javadi, K ; Darbandi, M ; Taeibi Rahni, M ; Sharif University of Technology
    In this work, we extend a finite-volume pressure-based incompressible algorithm to solve three-dimensional compressible and incompressible turbulent flow regimes. To achieve a hybrid algorithm capable of solving either compressible or incompressible flows, the mass flux components instead of the primitive velocity components are chosen as the primary dependent variables in a SIMPLE-based algorithm. This choice warrants to reduce the nonlinearities arose in treating the system of conservative equations. The use of a new Favre-averaging like technique plays a key role to render this benefit. The developed formulations indicate that there is less demand to interpolate the fluxes at the cell... 

    Numerical study of forced convective heat transfer of nanofluids: comparison of different approaches

    , Article International Communications in Heat and Mass Transfer ; Volume 37, Issue 1 , 2010 , Pages 74-78 ; 07351933 (ISSN) Lotfi, R ; Saboohi, Y ; Rashidi, A. M ; Sharif University of Technology
    Forced convective of a nanofluid that consists of water and Al2O3 in horizontal tubes has been studied numerically. Computed results were validated with existing well established correlation. Two-phase Eulerian model has been implemented for the first time to study such a flow field. A single-phase model and two-phase mixture model formulations were also used for comparison. The comparison of calculated results with experimental values shows that the mixture model is more precise. It is illustrated that the single-phase model and the two-phase Eulerian model underestimates the Nusselt number. Effects of nanoparticles concentration on the thermal parameters are also discussed  

    Unstructured coarse grid generation for reservoir flow simulation using background grid approach

    , Article 16th Middle East Oil and Gas Show and Conference 2009, MEOS 2009, Manama, 15 March 2009 through 18 March 2009 ; Volume 2 , 2009 , Pages 685-697 ; 9781615670123 (ISBN) Evazi Yadecuri, M ; Mahani, H ; Sharif University of Technology
    Reservoir flow simulation involves subdivision of the physical domain into a number of gridblocks. This is best accomplished with optimized grid point density and minimized number of gridblocks especially for coarse grid generation from a fine grid geological model. In any coarse grid generation, proper distribution of grid points, which form basis of numerical gridblocks, is a challenging task. We show that this can be effectively achieved by generating a background grid that stores grid point spacing parameter. Spacing (X) can be described by Poisson's equation (∇2 L = G) where the local density of grid points is controlled by a variable source term (G). This source term can be based on... 

    A comparison of various routing protocols in Mobile Ad-hoc Networks (MANETs) with the use of Fluid flow simulation method

    , Article 4th International Conference on Wireless and Mobile Communications, ICWMC 2008, Athens, 27 July 2008 through 1 August 2008 ; 2008 , Pages 260-267 ; 9780769532745 (ISBN) Salehan, A ; Robatmili, M ; Abrishami, M ; Movaghar, A ; IARIA ; Sharif University of Technology
    One of the most important challenges in mobile Ad-hoc networks is simulation. The simulation of these networks based on the accessible simulation techniques, which are based on packet, is a demanding and time-consuming task. Moreover, with the complexity of the network and the increase in the numbers of the nodes, it is likely to take a long time. This is because these simulators, one by one, regard the acts of all moving packets in one part of the network, and process these acts as a series of events. Since the number of the events is high in this method, the simulation takes time. Nowadays, in wired networks, several methods have been suggested to lessen the time of simulation; one example... 

    Computational simulation of non-Newtonian blood flow in carotid bifurcation for investigation the various rheological blood models

    , Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 2 , 2007 , Pages 263-270 ; 0791842967 (ISBN) Jahanyfard, E ; Firoozabadi, B ; Goodarzvand Chegini, A ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2007
    One of the leading causes for death after heart diseases and cancer in all over the world is still stroke. Most strokes happen because an artery carrying blood from the heart to the brain is clogged. Most of the time, as with heart attacks, the problem is atherosclerosis, hardening of the arteries, calcified build up of fatty deposits on the vessel wall. The primary troublemaker is the carotid artery, one on each side of the neck, the main thoroughfare for blood to the brain. In this study, the fluid dynamic simulations were done in the carotid bifurcation artery for studying the formation of atherosclerosis, and shear thinning behavior of blood as well as Newtonian comportment was studied.... 

    Computational Simulation of Turbulent Endwall Effects in Gas Turbines, Using LES Approach

    , M.Sc. Thesis Sharif University of Technology Ebrahimi, Hossein (Author) ; Tayyebi Rahni, Mohammad (Supervisor) ; Ramezanizadeh, Mahdi (Supervisor)
    The most common three-dimensional flows accuring in axial turbomachineries are endwall flows. These flows, which depend on inner hub and on external surface of airfoils are called secondary flows. In modern turbines, these flows reduce turbine efficiency up to about 3 percent.Many sientists are interested in investigation such flows. In this study, turbulent endwall flows are modeled using large eddy simulation approach. Also, SIMPLE algoritm and Smagorinsky subgrid scale model are used. Non-orthogonal curvilinear coordinate system and structural grid are implemented.To verify the results, they were compared with some existing experimental data which, showed that current numerical results... 

    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)
    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... 

    Simulation of Fluid Flow in Nanotubes by Non-Equilibrium Molecular Dynamics

    , M.Sc. Thesis Sharif University of Technology Khodadadi, Ali (Author) ; Moosavi, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
    One of the critical challenges in droplet based micro- and nanofluidic devices is handling the droplet breakup such that a controllable droplet size is produced. The experimental and numerical investigations at the microscale indicate that the droplet size can be well controlled by T junction geometries. In the present study we use non-equilibrium molecular dynamics (NEMD) simulations to investigate this phenomenon at the nanoscale. In order to generalize the study the Lennard-Jones type potential between the fluids and the walls have been considered and the strength and the effective range of the potential are changed to consider a wide variety of materials. Our results reveal that the...