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Numerical Simulation of Turbulent Flow in Annulus with Rotation of an Inner Cylinder in High Angular Speed
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor)
Abstract
In this thesis velocity and temperature fields of concentric cylinders with rotation of inner wall have been investigated numerically. Air enters the gap between cylinders and attains fully developed in both velocity and temperature fields after certain lengths. Adiabatic and constant heat flux boundary conditions have been applied and Nusselt number was calculated. In order to analyze the variations of velocity and temperature fields, different angular velocities at constant axial Reynolds number and different axial velocities at constant angular velocity have been investigated. The turbulent stresses were approximated with k ?? ...
The Effect of Second Order Dissipation on the Sound Velocity in Quasi-QCD Plasma Using the Effective Potential of the Linear Sigma Model
, M.Sc. Thesis Sharif University of Technology ; Sadooghi, Neda (Supervisor)
Abstract
The heavy ion collision experiments are in progress in order to investigate how the Universe has evolved after the Big Bang. The recent observations show that a nearly perfect fluid is produced after heavy ion collisions. An appropriate incorporation of the relativistic hydrodynamics and the field theory would help us to describe the dynamics of QCD (Quantum Chromodynamics) matter under extreme conditions, and to survey the expected phase transitions. The majority of efforts to investigate the characteristics of the QCD plasma are devoted to an ideal, non-dissipative one. To get the results which are highly in accordance with the experiment, it is necessary to bring also in mind the role of...
Simulation the Near-Fault Velocity Pulses from Form and Intensity Point of View
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayaz (Supervisor)
Abstract
Near-Field earthquakes have gained so much attention through their catastrophic consequences on structures in the vicinity of seismic sources during recent events. Based on recorded data, it is understood that these kinds of phenomena are often accompanied with a large energy pulse at the first times of record whose impulsive characteristic is primarily caused by “forward directivity”. Incapability of response spectra for depicting great demand for energy dissipation disqualifies this method for utilization. Thus it seems inevitable to analyze the models prone to this kind of hazard using time-history based analysis. Being simple enough in time domain, raises hopes for finding a mathematical...
Analysis of Nonuniform Superconducting Transmission Lines and Microstrips in Microwave Regime
, M.Sc. Thesis Sharif University of Technology ; Mehrany, Khashayar (Supervisor) ; Fardmanesh, Mehdi (Supervisor)
Abstract
Nonuniform superconducting microstrip transmission lines in microwave regime have been investigated. Nonuniform transmission lines provide the capability of controlling line parameters. Photonic structures with subwavelength features can be homogenized and thus be accurately approximated by homogeneous yet spatially dispersive structures. This idea is here applied to nonuniform superconducting transmission lines with subwavelength nonuniformities, i.e. subcentimeter features in the microwave regime. This modelling is quite useful in geometrical and optical control of quasi-TEM wave propagation and dispersion engineering along microwave superconducting lines. This approach has applications...
Phase and Group Velocity of Scalar Waves in One Dimensional Disorderd Media
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
In this thesis we study the dispersion of one-dimensional scalar waves in a random media. We used the finite difference method to obtain the numerical solution of wave equation in this media. Then we were able to find wave signals for different disorder intensities and at different distances from the source. Using the Wavelet Transform, intresting features such as phase and group velocity can be studied. The Morlet function is used as the mother wavelet for decomposing the signals at different places. Cross-correlation functions of Wavlet transforms of the signals at different positions are used to obtain phase velocity and its dependence on frequency. We show how the phase velocity at the...
Study of Dispersed Phase Holdup and Slip Velocity in a Pulsed Disc and Doughnut Extraction Column
, M.Sc. Thesis Sharif University of Technology ; Outukesh, Mohammad (Supervisor) ; Torab Mostaedi, Meisam (Supervisor)
Abstract
Dispersed phase holdup has been measured in a 75 mm diameter pulsed disc and doughnut extraction column for three different liquid-liquid systems. The effects of operational variables such as pulsation intensity and dispersed and continuous phases flow rates on holdup have been investigated and found to be significant. The existence of three different operational regimes, namely mixer-settler, dispersion, and emulsion regimes, was observed when the energy input was changed. The results indicated that the characteristic velocity approach is applicable to this type of extraction column for analysis holdup in transition and emulsion regions. Empirical correlations are derived for prediction of...
Evaluation of Dynamic Properties of Plastic Concrete Using Bending Disk Tests in Small Strain Range
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Evaluation of the compression wave velocity (Vp ) and small strains elastic modulii of various types of plastic concrete specimens in unconfined and triaxial compression tests using piezoelectric transducers was performed in this study. Plastic concrete consists of aggregates, cement, water and bentonite, mixed at a high water cement ratio, to produce a ductile material. It is used for creating an impermeable cut-off wall for seepage control in highly permeable dam foundations. A plastic concrete cut-off wall acts essentially as a barrier to stop or reduce the groundwater flow. In this study the effect of specimen age, water-cement ratio, bentonite-cement ratio, confining pressure, wave...
Investigate of Effective Parameters on Critical Ventilation Velocity in Tunnels
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor)
Abstract
Suitable design of ventilation systems is one of the strategies to deal with phenomenon like fire in tunnels. For design a ventilation system first should recognize fire and effective parameters on it. So we need a good modeling of fire. Whereas the aim of this research is investigate the critical ventilation velocity, we only studying the effects of fire. Two effective parameter of fire is the rate of heat release and rate of smoke release, therefore with studying physics and nature of fire, obtain these parameters. After calculation of fire effects, we should investigate the effective parameters on critical ventilation velocity. The critical velocity is the air flow that helps prevent...
Simulation of Fire in Tunnels Using Fire Dynamics Simulator Code (FDS)
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor)
Abstract
Designing of an efficient emergency ventilation system is one of the main approaches to prevent the perilous fire in tunnel phenomenon. For this purpose, firstly, fire behavior and its heat release rate should be investigated. Knowing about temperature distribution and smoke movement is the second step. One of the most considerable factors in smoke control is critical velocity. It means the minimum velocity to prevent backlayering flow. If longitudinal ventilation velocity were less than this amount, smoke and hot gases originated from the fire can enter the upstream zone. This may cause lack of oxygen and decrease visibility for the passengers when they are escaping from the fire field. In...
Nonlinear Effect Stimulated Brillouin Scattering (SBS) and SBS Slow Light Analysis
, M.Sc. Thesis Sharif University of Technology ; Akbari, Mahmood (Supervisor)
Abstract
Nowadays, ultra-high bandwidths and speed are essential for information processing and transmission. Also, we know optical systems have these properties. Therefore, we use optical systems to provide these essentials. We need optical devices to obtain all optical systems. Optical buffers and memories are examples of optical devices which realization of them is still an unsolved challenge. The slow light is suitable method to realize optical buffers. To realize slow light, different methods have been introduced. One of these methods is slowing down of the group velocity of light pulses in a medium which we use that in this thesis. To realize these, many different methods and material systems...
Simulation of Wave Propagation in the Sea
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor)
Abstract
In positioning and navigation, Sonar with utilization of sound waves in water environments is similar to the role of Radar in not watered (irrigated) environments. In the Sonar field, modeling and simulation of propagation of sound waves in the undersea environment is a fundamental and very important topic. Nowadays simulation is significant tool that allow to the researchers to predict the quality of Sonar function respect to the experimental conditions. For simulation and modeling of sound wave propagation are used two different methods; Wave theory and Ray theory. In the wave theory, because of the large volume of data, the interpretation of the results is hard. Also in this method cannot...
Evaluation of the Damage to Steel MRF Structures Under Near Field Earthquake Pulses Using a Performance-Based Design Approach
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayaz (Supervisor)
Abstract
Research on the characteristics of the near field earthquakes has been very popular in recent years due to the considerable damages they have caused to the structures located within the vicinity of seismic sources. The incapability of response spectra for structural damage assessment has been revealed through recent investigations. The recorded data show that the near field earthquakes are often accompanied by a large energy pulse in the beginning of the records caused by the so-called directivity phenomenon. That has encouraged many researchers to study the possibility of using the velocity pulse of these records to evaluate the imposed seismic demands on structures. Thus, investigating the...
Numerical Study of Ground Vibrations due to Pile Driving and Effect of Trench on Reduction of Amplitude of Vibrations
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor)
Abstract
Ground vibration during pile driving is one the most important factors that limits usage of this kind of piles. It is of great importance to estimate the level of vibration prior to the beginning of pile driving to avoid structural damage or disturbance of building occupants. In this study, an axisymmetric finite element model that utilises an adaptive meshing algorithm has been introduced, using the commercial code ABAQUS, to simulate the full penetration of a pile from the ground surface to the desired depth by applying successive hammer impacts. The model has been verified by comparing the computed particles velocity with those measured in the field. The results indicate that the peak...
An Experimental-Numerical Study of Penetration in Constrained Ceramic-Metal Structures Covered by Polymer Layer
, M.Sc. Thesis Sharif University of Technology ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor)
Abstract
This thesis has been done in two parts. In part I,a rupture disc wasdesigned. The rupture disc is an important part of a gas gun and is used as a fast response valve whichburst at a predefined pressure. Afterdesign,it has been used instead of an electric valve to increase the maximum velocity that can be achieved by the gas gun. Toavoid fragmentation and to have a better control on rupture pressure,a groove isusuallygraved on the disc. Cross and circumferential grooves werestudied in this thesis. It was found that in most cases the discs with a cross groovewere not fully opened because they have four independent failure paths and these paths should be opened simultaneously. However, having...
Development of an Improved Semi-active Damper Based on the Reduction of the Effects of Brace Flexibility
, M.Sc. Thesis Sharif University of Technology ; Ahmadizadeh, Mehdi (Supervisor)
Abstract
Considerable research work has been dedicated to the development of structural control systems to improve the performance of structures and reduce the casualties resulting from earthquakes. It is generally accepted that semi-active control systems result in better structural performance compared to what can be achieved using passive systems. However, it has been observed that the majority of the performance improvement obtained from semi-active control systems stems from the reduction of brace flexibility effects, rather than the control algorithm used. In this study, it is attempted to utilize this fact to improve the performance of passive control systems, or develop simple semi-active...
Numerical Simulation of Saccardo Ventilation System in Tunnel Fire Scenarios
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor) ; Farhanieh, Bijan (Supervisor)
Abstract
While the population of the cities all over the world is increasing, more and more tunnels and underground transportation passages are being constructed. So, there is an urgent need for designing an appropriate ventilation system for these passages, not only in normal conditions but also for emergency scenarios especially in fire incidents.In the present research, the operation of Saccardo ventilation system, especially in emergency fire scenarios is investigated using computational fluid dynamics methods. Studies conducted in this research are classified into five parts.In the first part, the effect of tunnel ventilation flow rate (due to Saccardo system operation) and its interaction with...
Star Formation History in Solar Neighbourhood
, M.Sc. Thesis Sharif University of Technology ; Rahvar, Sohrab (Supervisor)
Abstract
Star Formation History (SFH) is one of the important quantities to constrain galaxy formation and evolution scenarios and star formation models. In this thesis we aim to derive SFH for solar neighbourhood stars. We can use absolute magnitude-color diagram of a stellar system to derive the SFH. The method is to consider different functions for SFH and compare the resulting colormagnitude diagram with observational data. We used HIPPARCOS satellite data in this thesis. Hipparcos has measured astrometric parameters for about 120000 stars very accurately, which enables us to compare the color-magnitude of those stars with theoretical color-magnitudes. In this thesis, using Monte Carlo method, we...
Underwater Navigation by Acoustic Sensors and INS data Fusion
, M.Sc. Thesis Sharif University of Technology ; Salarieh, Hassan (Supervisor)
Abstract
In this study, by INS and auxiliary acoustic sensors data fusion, underwater navigation algorithm is implemented and validated by computer simulations. Extended Kalman Filter based on perturbation analysis is used as combination algorithm. The outputs of the INS forms equations of mechanism. The variational variables are state variables estimated in the Kalman filter. Because of the weakness of the GPS signals due to electromagnetic signals Attenuation in water, acoustic sensors are used as auxiliary sensors in underwater navigation. Here those acoustic sensors that implementing them in this country is impossible or very costly would not be examined.In this research the output of Doppler...
Ultrasound Image Reconstruction using Capacitive Micromachined Ultrasonic Transducers
, M.Sc. Thesis Sharif University of Technology ; Vosoughi Vahdat, Bijhan (Supervisor)
Abstract
In this thesis its considered the characterization of an ultrasound wave in a medium with some obstacles. Derivation of speed of molecules and pressure of the wave is carried out in the Cartesian coordinates system. Simulation is carried out to prove the dependency of wave speed to set up parameters such as the target point (x,y,z) at which the speed value is obtained, the location of the obstacles, the amplitude of original wave emitting from the source, and the propagation speed in different layers of the medium. From the numerical results, it is apparent that the amplitude of the speed wave gets degraded as the wave travels through the medium which is a function of reflection and...
Investigation of the Influence of Geometry and External Field on Fluid Flow Through Carbon Nanotubes by Molecular Dynamics Simulation
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
Water transportation through carbon nanotubes is key for designing nanodevices. The directed transport of water molecules through a rotating charged carbon nanotube (CNT) is investigated by molecular dynamics simulations. It is found that the net flux of continuous unidirectional water flow depended sensitively on the charge distribution, charge density and rotation of the CNT. we find that for a constant charge density, the water flux increases with the increase of the charge difference. Besides, we find that the water flux shows a nonlinear dependence on the angular velocity of the rotation. The rotation of the CNT with low angular velocities, can not generate a continuous water flux. The...