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Total 95 records
Experimental Investigation of Flow Pattern around Pile Groups (two piles)
, M.Sc. Thesis Sharif University of Technology ; Ataie-Ashtiani, Behzad (Supervisor)
Abstract
The occurrence and development of scour hole around bridge pier are the main causes of bridge destruction. To predict manner, occurrence, development and final situation of scour hole around pier is the most important in the hydraulic design of bridges. A large number of studies have been performed to estimate the scour depth around piers at simplified laboratory conditions. The available equations from these studies do partly not present acceptable solutions. This issue is especially of great importance to the pile groups. For accurate determination of scour depth, it is required to get a better understanding of the flow and governing mechanism around pier. Although the flow pattern...
Numerical Analysis of Flow Pattern around Pile Groups (Two Piles)
, M.Sc. Thesis Sharif University of Technology ; Ataie Ashtiani, Behzad (Supervisor) ; Beheshti, Ali Asghar (Co-Advisor)
Abstract
Numerical simulations and large eddy simulations (LES) of turbulent flow around single pile, circular tandem piles, circular and square side-by-side piles at different spacing ratios (centre to centre distance to the pile diameter) with flow Reynolds number of 105 on the fixed flat-bed are presented. The calculations are performed using a computational fluid dynamics model, FLOW-3D, which solves the Navier-Stokes equations in three dimensions with finite volume method. Numerical simulations are validated by comparing the numerical results of time-averaged flow patterns around single and side-by-side piles with that of the experimental measurements. At the downstream of single pile,...
Investigation of bed Stability in Downstream for the Diversion dam under Scour (Mill & Moghan case study)
, M.Sc. Thesis Sharif University of Technology ; Shamsai, Abolfazl (Supervisor)
Abstract
Numerical simulations and large eddy simulations (LES) of turbulent flow downstream of diversion dam , pool-riffle bedform in different geometrical ratios (different lengths of riffle and pool) with flow Reynolds number of 3.0 E+04 to 3.3E+04, downstream of special case study "Mill and Moghan diversion dam" with Froude number of 0.5 are presented The calculations are performed using a computational fluid dynamics model, FLOW-3D, which solves the Navier-Stokes equations in three dimensions with finite volume method. Numerical simulations are validated by comparing the numerical results of time-averaged flow patterns downstream of pool-riffle sequence with that of the experimental...
Flow Control in Vacuum Assisted Resin Transfer Molding
, M.Sc. Thesis Sharif University of Technology ; Shojaei, Akbar (Supervisor) ; Pishvaie, Mahmoud Reza (Supervisor)
Abstract
Vacuum assisted resin transfer molding (VARTM) is one of the most efficient and low cost process in composite industries. In this process, the preform is covered by a flexible vacuum bag and resin flows into the mold with applying vacuum pressure at the vent. The main objective in VARTM process is preventing voids and dry spots formation in final composite part because these defects may significantly deteriorate the mechanical properties of a structure. Flow front is an important parameter in this process which have a high influence on the void formation. Resin flow control is required to prevent dry spots or micro voids during the VARTM process. In general, the flow control is classified...
Experimental Investigation and CFD Simulation of the Flow Pattern of the FCC's Fluidized Bed Regenerator
, M.Sc. Thesis Sharif University of Technology ; Dehkordi, Asghar Molaei (Supervisor) ; Seifkordi, Aliakbar (Supervisor) ; Behjat, Yaghoub (Supervisor)
Abstract
Hydrodynamic behavior of gas-solid fluidization in large-diameter beds like FCC regenerator exhibits complex aspects. To investigate the gas-solid flow pattern of UOP's combustor-style FCC regenerator, a lab-scale regenerator was designed by a downscale factor of 0.045. The regenerator's operation and fluidization of FCC particles through it was examined and pressure axial distributions were measured and analyzed at different superficial air velocities. 3D CFD simulation of the regenerator was performed with Eulerian-Eulerian approach to investigate the effects of operating conditions, including superficial air velocity, catalyst mass flux, presence of recirculated catalyst, and the...
Liquid-Liquid Two Phase Flow in Horizontal Well on Bottom Hole Condition: Creation a Visualized Flow Regime for Two Phase (Liquid-liquid) Flow
, M.Sc. Thesis Sharif University of Technology ; Ghoodarznia, Iraj (Supervisor)
Abstract
The concurrent flow of oil and water is a common occurrence in the field of multiphase flow in different fields including petroleum industry. In such conditions an accurate assessment of pressure loss inside the well plays a vital role in efficient and effective production planning. Changes in well orientation, wellbore diameter, reservoir and fluid properties as well as fluid flow rates are among parameters in which will affect the flow patterns that can occur inside a well during its life time. These flow patterns are created as a result of a competition between viscous, gravity and capillary forces. Due to the fact that the dominant forces vary for different flow regimes, the pressure...
Experimental Study on Two-Phase Flow Characteristics in Micro-Channels
, M.Sc. Thesis Sharif University of Technology ; Nouri, Ali (Supervisor)
Abstract
The present study provids an experimental investigation on two-pase flow characteristics in microchannels. Experiment were conducted with a mixture of air and water in horizontal circular pyrex channel with 400µm inner diameter. The pressure drop and flow rates of the liquid and gas were measured using new method and images of the flow patterns recorded by high shutter speed camera. The gas and liquid superficial velocity ranges were 0.025-12.5m/s and 0.016-3.6m/s, respectively. The flow pattern map is developed from the observed flow patterns based on phases superficial velocity as wel as We numbers of liquid and gas phases. The flow pattern map is compared with those of larger channels....
Investigation of Multiphase Flow in Oil Wells (with Focus on Two Phase Flow), Flow Pattern Recognition and Modeling
, M.Sc. Thesis Sharif University of Technology ; Shad, Saeed (Supervisor) ; Jamshidi, Saeed (Supervisor)
Abstract
The concurrent flow of oil and water is a common occurrence in the field of multiphase flow in different fields including petroleum industry. In oil and gas, production engineers often face a situation in which more than one phase is flowing through the producers. In such conditions an accurate assessment of pressure loss inside the well plays a vital role in efficient and effective production planning. Changes in well orientation, wellbore diameter, reservoir and fluid properties as well as fluid flow rates are among parameters in which will affect the flow patterns that can occur inside a well during its life time. These flow patterns are created as a result of a competition between...
Numerical Simulation and Manufacture of a Proton Exchange Membrane Fuel Cell to Examine Mass and Charge Transport through Micro Porous Layers
, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir (Supervisor) ; Noori, Ali (Supervisor)
Abstract
Fuel cell is a power generator like internal combustion engines, but the first point is that internal combustion engines produce mechanical power while fuel cells produce electrical power. Secondly, internal combustion engines use hydrocarbon derivatives such as gas as fuel and their exhaust fumes are toxic gaseous, but fuel cells use hydrogen as fuel and their exhaust are only water in either vapor or liquid form. One of the most important issues in fuel cells is optimum design of micro channels of bipolar plates which is different regarding the type and application of fuel cells. Optimum designing of micro channels on bipolar plates plays a key role in fluid mass transport through micro...
Experimental Study of the Effect of Interaction of Two Flexible Stems on Diffusion of the Contamination
, M.Sc. Thesis Sharif University of Technology ; Jamali, Mirmosadegh (Supervisor)
Abstract
In this research, the dynamic of flow, dispersion of contaminant and characteristic of wake in the presence of two flexible stems of polyurethane is investigated in a hydraulic flume. The stream velocity of 2.28, 4.47 and 7.58 cm/s are considered, which are equivalent to Reynolds number in stem diameter scale 173, 340 and 576. The spacing ratio of two stems are one, two and three in both transverse and longitudinal direction. Velocity fields are measured using Particle Image Velocimetry (PIV) technique. The size of wake area behind stems is determined using the flow field measurement. The results show that the spacing ratio l/d affects the wake area size and interactions of wakes. The...
Production Well Multi-Phase Flow Measurement Using Ultrasonic Technology
, M.Sc. Thesis Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Sahd, Saeed (Supervisor) ; Amjadi, Ahmad (Co-Supervisor)
Abstract
Flow measurement in both types of single phase and multiphase has a crucial place in a wide variety of industries, specially petroleum industry. for single phase flowmeters, improving their precision using different types of mechanical, mathematical and analytical techniques will be considered as an important step. Using multiphase flow meters will cause no need of volume catching and costly separators and also make us capable of taking well-timed decisions in production management. for making flow meters weather multiphase or single phase, there is a crucial need of a multiphase flow loop. To achieve that, an 8-meter-long flow loop using transparent Plexiglas pipes with inside diameter of...
Hydrodynamic Simulation and Flow Pattern Analysis of Shark Undulation Motions
, Ph.D. Dissertation Sharif University of Technology ; Abbaspour Tehrani Fard, Majid (Supervisor)
Abstract
Many species in nature exist which human can reach the aims of flying and swimming by inspiring from them. Observations show that fish can use their especial undulating motions of body/fins to crusing, increase performance, suddenly acceleration, and maneuvering. To design a robot fish and benefit the characteristics and abilities of a live fish, using its real geometry and kinematics in the robot is vital. Therefore, simulations are essential to better exploiting the fish behavior, which can obtain useful consequences by using computational fluid dynamics. In this thesis, first the kinematics of sharks is investigated. Then, investigations are accomplished by utilizing an unsteady finite...
A Study on Two-Phase Flow in Bottom Hole Conditions in Horizontal Wells
, M.Sc. Thesis Sharif University of Technology ; Shad, Saeed (Supervisor)
Abstract
Considering the importance of oil and gas industries in Iran, issues related to drilling and exploitation of oil and gas fields are among the country's priorities and challenges in industries, research centers and universities, and extensive research is conducted in this field. Since during the process of oil production from oil wells and reservoirs, the formation of multiphase flows, including two-phase fluid flow, is inevitable, investigating the behavior of multiphase fluids, which is a branch of fluid mechanics, is of special importance. In this regard, in continuation of the research conducted in the Faculty of Chemical and Petroleum Engineering of Sharif University of Technology, in...
High frequency oscillatory flow in micro channels
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Vol. 460 , 2014 , pp. 355-360 ; ISSN: 09277757 ; Javadi, A ; Bastani, D ; Miller, R ; Sharif University of Technology
Abstract
This paper deals with computational and experimental studies on the oscillatory flow at high frequencies up to 100. Hz performed with the Oscillating Drop and Bubble Analyzer (ODBA) setup based on the capillary pressure technique. The CFD results are validated considering pressure amplitude experimental data. The simulated results of phase shift between the generated oscillatory flow and the consequent pressure amplitudes show also good agreement with the experimental data. In absence of any compressibility and viscoelasticity effects and assumptions, a complex velocity field during oscillation is the main reason for the observation of a phase shift. The results of velocity profiles at the...
Simulation of mixed electroosmotic/pressure-driven flows by utilizing dissipative particle dynamics
, Article Microfluidics and Nanofluidics ; Vol. 17, issue. 1 , July , 2014 , pp. 199-215 ; ISSN: 16134982 ; Noruzitabar, M ; Mehboudi, M ; Sharif University of Technology
Abstract
In this paper, we present an extension of dissipative particle dynamics method in order to study the mixed electroosmotic/pressure-driven micro- or nano-flows. This method is based on the Poisson-Boltzmann equation and has a great potential to resolve the electric double layer (EDL). Hence, apart from studying the bulk flow, it also provides a strong capability in order to resolve the complex phenomena occur inside the EDL. We utilize the proposed method to study the pure electroosmotic and also the mixed electroosmotic/pressure-driven flow through the straight micro-/nano-channels. The obtained results are in good agreement with the available analytical solutions. Furthermore, we study the...
Numerical investigation on the solid flow pattern in bubbling gas-solid fluidized beds: Effects of particle size and time averaging
, Article Powder Technology ; Vol. 264, issue , September , 2014 , p. 466-476 ; Salehi, M. S ; Molaei Dehkordi, A ; Sharif University of Technology
Abstract
The effects of particle size on the solid flow pattern in gas-solid bubbling fluidized beds were investigated numerically using two-fluid model based on the kinetic theory of granular flow. In this regard, the set of governing equations was solved using finite volume method in two-dimensional Cartesian coordinate system. Glass bead particles with mean sizes of 880. μm, 500. μm, and 351. μm were fluidized by air flow at excess gas velocities of 0.2. m/s and 0.4. m/s. For particle diameters of 880 and 351. μm, the predicted characteristic times for solid dispersion were 0.14. s and 0.15. s, respectively, while characteristic times for solid diffusivity were 1.68. ms and 0.75. ms in the same...
Numerical investigation of the effect of sprue base design on the flow pattern of aluminum gravity casting
, Article Defect and Diffusion Forum ; Volume 344 , October , 2013 , Pages 43-53 ; 10120386 (ISSN) ; 9783037859049 (ISBN) ; Bahmani, A ; Davami, P ; Varahram, N ; Shabani, M. O ; Fisher D. J ; Sharif University of Technology
2013
Abstract
Effects of sprue base size and design on flow pattern during aluminum gravity casting have been investigated by employing different sprue base sizes and using computational fluid dynamics (CFD). Calculations was carried out using SUTCAST simulation software based on solving Navier-Stokes equation and tracing the free surface using SOLA-VOF algorithm. Flow pattern was analyzed with focusing on streamlines and velocity distribution in sprue base, runner and in-gate. Increasing well size was produced a vortex flow at the bottom of sprue base which increased the surface velocity of liquid metal in runner. Using a rather big sprue well could eliminate vena contracta, but in-gate velocity was...
Stream-wise and cross-flow vortex induced vibrations of single tapered circular cylinders: An experimental study
, Article Applied Ocean Research ; Volume 42 , 2013 , Pages 124-135 ; 01411187 (ISSN) ; Tamimi, V ; Saeed Seif, M ; Sharif University of Technology
2013
Abstract
Tapered circular cylinders are employed in a variety of ocean engineering applications. While being geometrically simple, this configuration creates a complex flow pattern in the near wake of the structure. Most previous experimental studies on tapered circular cylinders were dealing with stationary cylinders to explore the wake flow field and vortex shedding patterns past the cylinder. Few studies paid attentions to the vortex induced vibration of the tapered cylinders. This paper reports some results from in-water towing-tank experiments on the vortex-excited vibrations of tapered circular cylinders in a uniform flow. Cylinders with different mean diameters (28 and 78 mm), mass ratios (6.1...
Determination of optimum injection flow rate to achieve maximum micro bubble drag reduction in ships; An experimental approach
, Article Scientia Iranica ; Volume 20, Issue 3 , 2013 , Pages 535-541 ; 10263098 (ISSN) ; Nematollahi, M ; Sharif University of Technology
2013
Abstract
Reduction in ship resistance, in order to decrease fuel consumption and also achieve higher speeds, has been the topic of major research over the last three decades. One of the most attractive ideas in this field is micro bubble drag reduction, which attempts to obtain optimum injection flow rate based on ship specifications. The model test results of a 70 cm catamaran model was used to quantify the effect of air injection rate on drag reduction, and to estimate a simple formulation for calculating an efficient injection rate by considering the main parameters of the ship, such as: length, width and speed. The test results show that excessive air injection decreases the drag reduction...
Flow field around single and tandem piers
, Article Flow, Turbulence and Combustion ; Volume 90, Issue 3 , April , 2013 , Pages 471-490 ; 13866184 (ISSN) ; Aslani-Kordkandi, A ; Sharif University of Technology
2013
Abstract
The present study provides a comparison between the flow pattern around two circular piers in tandem and a single pier set up on a moderately rough flat bed in a laboratory flume. Velocities are measured by an Acoustic Doppler Velocimeter (ADV). The contours of the time-averaged velocity components, Reynolds shear stresses, turbulence intensities and turbulence kinetic energy at different planes are presented. Streamlines and vectors are used to study the flow features. The analysis of power spectra around the piers is also presented. The results show that the presence of downstream pier changes the flow structure to a great extent, particularly in the near-wake region. Within the gap...