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flow-simulation
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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 ; Taeibi-Rahni, Mohammad (Supervisor)
Abstract
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...
Computational Simulation of Turbulent Endwall Effects in Gas Turbines, Using LES Approach
,
M.Sc. Thesis
Sharif University of Technology
;
Tayyebi Rahni, Mohammad
(Supervisor)
;
Ramezanizadeh, Mahdi
(Supervisor)
Abstract
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...
Simulation of Flow in Voraxial System Using Fluent
, M.Sc. Thesis Sharif University of Technology ; Taghizadeh Manzari, Mehrdad (Supervisor) ; Zabihollah, Abolghasem (Supervisor)
Abstract
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 ; Taghizadeh Manzari, Mehrdad (Supervisor) ; Fatehi, Rouhollah (Co-Advisor)
Abstract
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 ; Moosavi, Ali (Supervisor) ; Arghavani, Jamal (Supervisor)
Abstract
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 ; Farshchi, Mohammad (Supervisor) ; Ebrahimi Chamgardani, Abbas (Supervisor)
Abstract
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...
Simulation of Fluid Flow in Nanotubes by Non-Equilibrium Molecular Dynamics
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
Abstract
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...
Dynamic Modeling and Experimental Study of Asphaltene Deposition in Wellbore Considering Mechanism of Precipitation, Aggregation and Deposition
,
Ph.D. Dissertation
Sharif University of Technology
;
Ghotbi, Cyrus
(Supervisor)
;
Dabir, Bahram
(Co-Supervisor)
;
Taghikhani, Vahid
(Co-Supervisor)
Abstract
Efforts to identify, predict, and resolve problems linked to asphaltenes and flow assurance have resulted in the development of numerous laboratory and modelling techniques. However, there has been little research on the molecular structure of asphaltenes and how it relates to solubility, stability, aggregation, and deposition behavior. Not only was a thorough structural analysis of asphaltene extracted from three samples of light, medium, and heavy oil performed in this study, but medium oil asphaltene was also fractionated into three sub-fractions based on solubility, with minimum, medium, and maximum solubility, and each subfraction was subjected to a structural analysis. All asphaltene...
Studying and Reviewing the Modification, Completion or Change of the Classical Theories Used in the Simulation of Resin Injection Network for Manufacturing of a Large Composite Structure by Means of Vacuum Infusion Process
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
In recent years, liquid resin injection processes for aviation applications have been considered an alternative to conventional autoclave-based processes. At present, these processes have challenges that have been denied industry trust due to their inability to be objectively reproducible. In the last decade, some software has been developed to simulate the vacuum injection process, but this software does not have enough capability to predict the injection network, and an operator with sufficient empirical knowledge must use this software. In recent years, researchers have used this softwares to simulate the process, but so far no software has been developed that can offer injection...
Evaluation of the Effect of Connected Vehicles Speed and Acceleration Parameters on Freeways Safety and Efficiency
, M.Sc. Thesis Sharif University of Technology ; Nassiri, Habibollah (Supervisor)
Abstract
Autonomous Vehicles have received much consideration in different trends in recent two decades. Autonomous Vehicles refer to vehicles that can drive without a driver and perform all driving tasks automatically, so eliminating the driver's role can affect various aspects. In this research, the effects of Autonomous Vehicles on the improvement of the traffic condition is studied. To this end, freeway’s performance parameters including travel time and traffic speed at the time of a traffic accident in mixed traffic conditions have been simulated. Considering that the braking behavior, acceleration, and speed changes of the Autonomous Vehicle are effective on the evaluation parameters, five...
Simulation of 2-Phase Fluid Flow on Unstructured Grids Upscaled by Image Segmentation Methods
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Saeed (Supervisor) ; Hajizadeh, Alireza (Co-Advisor)
Abstract
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...
Computer simulation of the effect of particle stiffness coefficient on the particle-fluid flows
, Article Particulate Science and Technology ; Volume 40, Issue 2 , 2022 , Pages 233-242 ; 02726351 (ISSN) ; Rajabi, M ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
The Computational fluid dynamics (CFD)–discrete element method (DEM) numerical simulation may be applied to predict the hydrodynamic behavior of dense particle–fluid flows. The main drawback of this simulation is the long computational time required owing to the large number of particles and the minute time-step required to maintain a stable solution. In this work, a new method to improve the efficiency and accuracy of CFD–DEM simulations is presented. The particle stiffness coefficient is used as a flexible parameter to improve the accuracy and efficiency of the model. The particle concentration distribution results are compared with experimental one’s to derive the optimum effective...
New correlative models to improve prediction of fracture permeability and inertial resistance coefficient
, Article Transport in Porous Media ; Volume 121, Issue 3 , February , 2018 , Pages 557-584 ; 01693913 (ISSN) ; Jamshidi, S ; Pishvaie, M. R ; Sharif University of Technology
Springer Netherlands
2018
Abstract
Presence of fracture roughness and occurrence of nonlinear flow complicate fluid flow through rock fractures. This paper presents a qualitative and quantitative study on the effects of fracture wall surface roughness on flow behavior using direct flow simulation on artificial fractures. Previous studies have highlighted the importance of roughness on linear and nonlinear flow through rock fractures. Therefore, considering fracture roughness to propose models for the linear and nonlinear flow parameters seems to be necessary. In the current report, lattice Boltzmann method is used to numerically simulate fluid flow through different fracture realizations. Flow simulations are conducted over a...
Conceptual duct shape design for horizontal-axis hydrokinetic turbines
, Article Scientia Iranica ; Volume 23, Issue 5 , 2016 , Pages 2113-2124 ; 10263098 (ISSN) ; Rad, M ; Khayat, M ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
In the present paper, conceptual duct shape design for kinetic energy extraction with hydrokinetic turbines is discussed. The goal is to find a single-passage axisymmetric geometry that holds stable flow with maximum kinetic energy flux at duct throat. For finding the optimum duct shape, the fluid flow was numerically simulated in a wedge shaped space with Flow-Simulation Software. In a multi-stage conceptual design, tabulated configurations were employed to study each geometrical characteristic separately. These include curvature of profile camber, trailing edge shape, profile tip shape, and duct exit cross sectional area. The revolved profile of each duct consists of a well constrained...
Cooperation within von Willebrand factors enhances adsorption mechanism
, Article Journal of the Royal Society Interface ; Volume 12, Issue 109 , 2015 ; 17425689 (ISSN) ; Mehrbod, M ; Ejtehadi, M. R ; Mofrad, M. R ; Sharif University of Technology
Royal Society of London
2015
Abstract
von Willebrand factor (VWF) is a naturally collapsed protein that participates in primary haemostasis and coagulation events. The clotting process is triggered by the adsorption and conformational changes of the plasma VWFs localized to the collagen fibres found near the site of injury. We develop coarse-grained models to simulate the adsorption dynamics of VWF flowing near the adhesive collagen fibres at different shear rates and investigate the effect of factors such as interaction and cooperativity of VWFs on the success of adsorption events. The adsorption probability of a flowing VWF confined to the receptor field is enhanced when it encounters an adhered VWF in proximity to the...
Simulation of mould filling in lost foam casting process
, Article International Journal of Cast Metals Research ; Volume 16, Issue 6 , 2003 , Pages 554-565 ; 13640461 (ISSN) ; Ashuri, H ; Varahram, N ; Davami, P ; Sharif University of Technology
Maney Publishing
2003
Abstract
In this investigation, an algorithm was developed to calculate the gas pressure at the melt/foam interface (gap) owing to degraded foam during mould filling in the lost foam casting process (LFC). The effect of back-pressure on mould filling was modelled using a new experimental function by the addition of a three-dimensional volume of fluid (3D-VOF) function. The molten flow and free surface were simulated using the solution algorithm-VOF (SOLA-VOF) numerical technique. To simulate the three-dimensional incompressible flow in the LFC, the pressure boundary conditions, heat transfer and foam gas pressure effect were modified. Finally, in order to verify the computational results of...
Utilizing a simulation approach for analysis of patient flow in the emergency department: a case study
, Article 15th Iran International Industrial Engineering Conference, IIIEC 2019, 23 January 2019 through 24 January 2019 ; 2019 , Pages 151-157 ; 9781728117751 (ISBN) ; Haji, B ; Shakhsi Niaei M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Simulation has been shown to be one of the most powerful tools in many areas of the health-care system, a system which attracted the attention of researchers due to its intricacy. The main goal of this study is to evaluate the patients' flow in an emergency department (ED). Discrete event simulation (DES)has been used as the core of this research so that it offers various ways to reduce the length of stay (LOS)of patients in different segments of ED by assessing various scenarios. In particular, a new approach for verification of the simulated model will be discussed. This study reports on the results that extracted from a case study on patient record data in one of the EDs located in Tehran...
Numerical optimization of laboratory combustor geometry for NO suppression
, Article Applied Thermal Engineering ; Volume 102 , 2016 , Pages 1328-1336 ; 13594311 (ISSN) ; Shakeri, A ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In this article, geometry optimization of a jet stirred reactor (JSR) combustor has been carried out for minimum NO emissions in methane oxidation using a combined numerical algorithm based on computational fluid dynamics (CFD) and differential evolution (DE) optimization. The optimization algorithm is also used to find a fairly accurate reduced mechanism. The combustion kinetics is based on a five-step mechanism with 17 unknowns which is obtained using an optimization DE algorithm for a PSR-PFR reactor based on GRI-3.0 full mechanism. The optimization design variables are the unknowns of the five-step mechanism and the cost function is the concentration difference of pollutants obtained...
Investigation of the continuum-rarefied flow and isotope separation using a hybrid CFD-DSMC simulation for UF6 in a gas centrifuge
, Article Annals of Nuclear Energy ; 2020 ; Akbar Salehi, A ; Reza Keshtkar, A ; Mahdi Shadman, M ; Hossein Askari, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
UF6 gas flow in the total regions of a rotor with the radius of 0.1 m and the length of 1 m in axisymmetric and steady states was simulated using a new hybrid CFD-DSMC method in the OpenFOAM framework. Implicit coupled density-based scheme was performed for CFD method, and Variable Hard Sphere (VHS) and diffuse model were employed in DSMC method. Also, as an initial estimation, the local Knudsen number was applied to determine the interface location between the continuum-rarefied regions (r = 0.0855 m). Then it was modified (r = 0.084 m) to reduce the computational cost. The comparison results of pure CFD and CFD-DSMC methods illustrated that there were large differences between the flow...
A robust optimization approach for the production-inventory-routing problem with simultaneous pickup and delivery
, Article Computers and Industrial Engineering ; Volume 143 , May , 2020 ; Akbari Jokar, M. R ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The production routing problem (PRP) merges the lot-sizing problem and the vehicle routing problem, two classical problems that have been the focus of comprehensive studies for over half a century. Solving the PRP is an effort to optimize decisions about the production, inventory, distribution, and routing in an integrated manner. In the literature of the recent decade, due to economic changes and regulatory issues, reverse logistics has become a focal point. Subsequently, the vehicle routing problem with simultaneous pickup and delivery (VRPSPD) has drawn more and more attention for its considerable effect on the reverse logistics problem. In addition, one of the major arguments in supply...