Sharif Digital Repository

In nature, tidal currents are visible in gorges and in saltwater and freshwater collisions. In the study of behavior of different types of flow, it is usually assumed that the pressure is hydrostatic and the equations are solved based on this assumption. In the Approach Controlled regime observed during the double layer in 1993, the modeling performed using the equations derived from this assumption did not fit the results of the experiments. This demonstrates the inability of the hydrostatic pressure assumption to solve this particular regime. Hence, the equations were written on the basis of non-hydrostatic pressure and then the observed results were in accordance with the results of the... 

Local scour around bridge piers is one of the main causes of bridge failures Application of existing equations to complex flow patterns is problematic and often leads to questionable results in the field applications. A lack of understanding of the complex flow field and erosion mechanisms seems to be at least partly responsible for this state. Despite the rapid expansion of the literature on the flow around cylindrical piers, there are still challenges for flow field comprehension and estimating design scour depths around complex bridge piers. Due to geotechnical and economical reasons, bridge designs often leads to a complex foundation. Laboratory studies of local scour around complex... 

Nowadays, applications of the synthetic materials are developing in civil engineering projects and widely used in these projects. Therefore, during previous years; use of the Geotextiles as one of the Geosynthetic materials in order to filtration, drainage, separation, soil protection, etc have developed ever-increasing. The goal of this research is modeling and studies of the Geotextiles application in the downstream filter zone of embankment dams in combination with granular materials using FLAC2D software. Gordeh Bin embankment dam situated in West Azerbaijan province has been chosen as case study. In this matter, different models have been made with changes in thickness of the inclined... 

Flameless combustion in combustion technology is an innovative method with low nox production that few years provided it passes. In this paper the effects of various parameters on flameless combustion chamber with separate fuel and air jets, has been modeled numerically with the help of Fluent 6.3 software. Differences between traditional combustion and flameless combustion were determined and the flame structure has been studied in different scenarios. In numerical modeling, approach were used to modeling turbulence and eddy dissipation concept (EDC) approach use to modeling combustion and turbulence interaction effects. A global Two-step reaction mechanism for propane and a global... 

In recent years, the increase of particulate matter concentration due to frequent dust storms has become one of the most important dilemmas of people around the world. The high concentration of dust particles causes irreparable respiratory diseases, premature death, economic and social damages. Because of placement in the vicinity of the main sources of dust, Iran has been severely affected by the phenomenon of dust storms and damage caused by it.In this research, two dust storms occurred in Tehran are simulated using WRF-Chem and HYSPLIT models. The first event took place on February 2, 2016, and the second event took place on May 22, 2018. In order to determine the empirical parameters of... 

Hydrogen is one of the favorite substitute for fossil fuels due to various properties including the flammability, ubiquity, and easy extraction from plain water. These properties have made it an appropriate alternative source of energy that can be used in internal combustion engines. Compared with fossil fuel energy, in addition to much lower emissions, hydrogen has proved to be much more efficient when applied as a clean source of energy. The main purpose of the present project is to study the effect of applying hydrogen on performance of compression - ignition as internal combustion engines as an alternative fuel. These studies encompass the results derived from the experiment of using... 

Sensitive ecosystem and scarcity of freshwater are the main characteristics of small islands. These islands have small catchments and usually lack tangible surface water resources. As a result these islands are dependent almost entirely on groundwater. Groundwater on small islands usually occurs in the form of a freshwater lens floating on the more dense saline water. The freshwater lens is highly sensitive to various stresses such as drought, pumping, sea tide, etc. Due to the importance of freshwater lens in islands, proper and optimal use of this vital resource should be studied. Kish island`s freshwater lens was three dimensionally simulated using the numerical model SUTRA. The aim was... 

Exchange flows are common physical phenomena in calm river banks and lakes. The sunlight penetrating into water column gradually attenuates due to light absobtion by water column. The light converts to heat energy in water molecules, suspended particles and disssolved matters, and results in warming the water body. Aquatic vegetation enhances the spatial variability in shallower regions of an aquatic system. Heterogeny in light penetration caused by emergent vegetation shading results in a spatial heterogeneity in water temperature. The density of water is dependent on its temperature, but the relation is not linear. As water is heated, it expands to become less dense. Horizontal density... 

Due to the importance of enhanced oil recovery of heavy oil fractured reservoirs, in this work micromodel setup has been used to study the miscible solvent injection in five-spot fractured reservoirs with different fracture geometrical characteristics. Due to the visual nature and flexibility of the micromodel patterns it is a subject of interest to be used in different studies. Different patterns has been constructed by chemical etching and controlled laser etching and saturated with displaced fluid and flooded by constant rate injection of hydrocarbon solvent in abient temperature and pressure. At first, effect of fracture’s length, numbering, orientation, discontinuity and scattering on... 

In this study, a thermo-mechanical model was utilized to investigate the welding residual stresses as well as thermal responses in dissimilar joint of carbon steel to stainless steel. A thermo-elastic-plastic analysis was first developed to assess temperature and deformation fields during and after welding operation. The employed model was capable of considering the effects of various factors such as, dilution, welding parameters and welding sequence on the developed residual stress as well as temperature distribution. In the next stage, the achieved predicted results together with EBSD data were used to correlate micro and macro residual plastic strains in the HAZ of the stainless steel... 

Nowadays, application of ultrasonic wave technology as a novel method of enhancing oil recovery and also gas an oil well stimulation is prevailing. Not only this method is environment friendly, but also it is economic. Although the application of this method is proved to be of outstanding positive influences in field operations, it suffers from lack of knowledge about the main governing mechanisms and also there are few mathematical models describing the process. In this study it is intended to investigate the role of ultrasonic waves on rate of recovery and the total recovery from porous media. A model is proposed which can predict the recovery at different times of operation. The results... 

In this study, single-phase and two-phase, incompressible flow in a non-deformable porous media was modeled and also simulated. The Reynolds numbers have been considered high enough to justify the use of the model including inertial terms. Afterwards, the mass conservative equations were discretized. Then, the numerical model has been developed for heterogeneous porous media. The heterogeneous porous media was comprised by several specified homogeneous regions, each having isotropic transport properties or permeability distribution with applying stochastic methods. The developed numerical model was used for predicting of saturation profile in water flooding process in one, two and... 

This thesis is about modeling of liquid-vapor two phase flows through nozzle. Liquid-vapor two phase flow is very applicable in industries such as boilers, expansion valves, refrigeration and sudden failures in pipelines. Two models are used for modeling of fluid flow through nozzle, transient and steady state. In Both model the solution field is considered as saturated liquid and vapor and the mass, momentum and energy equations as well as equation of state is used for describing of fluid flow properties. Homogeneous equilibrium model is used and for complete modeling of fluid flow heat transfer and friction force is also considered.
Numerical solutions are used for solving of the... 

A large number of structures subjected to the seismic loading have been damaged or have experienced failure in different parts such as the pile structure or even in the entire structure due to unanticipated effects of the soil-pile-structure interaction.The complexity of problems regarding the soil-pile-structure interaction is an influencing factor in prediction of the behavior of structure during the earthquakes. In this study, the effect of the interaction on the dynamic response of bridges was investigated using the finite element software ABAQUS. The primary purpose of this study, as previously described, is to study the effects of the soil-structure interaction on a bridge located on a... 

Troposphere layer includes complex flows which their effects in acoustic sensors are indicated as acoustic wave noise.It is essential to analyze these complex flows to recognize how to reduce the noise. In this thesis we have perused and modeled the sound wave propagation in troposphere layer.Given data are some thermal and velocity profiles of atmospheric flowsthe assumptions are: 1- gravity waves are negligible, 2- air density depends only on altitude, 3- sound waves parabolic equation assumptions are applied. Our goal Is to find the sound pressure level originated from a sound source in troposphere layer.This thesis emphasizes on analysis, recognition and modeling of the problem. Main... 

Single ventricle anomaly is a congenital heart disease which is characterized by anatomical malformations. The main abnormality that a patient faces is desaturated blood flow, which, without any treatment increases the risk of death. The classical treatment is based on a three stage palliative procedure which should begin from the first few days of patient’s life. The final stage is known as Fontan procedure which directly connects inferior vena-cava to pulmonary arteries without going through the ventricle.This connection is known as Total Cavo Pulmonary Connection (TCPC). After surgery, the single ventricle could supply adequate and saturated systemic blood flow for the body, but TCPC... 

Behavior and retrofit methods of buried pipes in slope under dynamics loading are investigated in FLAC 2D. Hysteretic damping is used to represent of soil damping and compared with Rayleigh damping model. Mohr-coloumb and elasto-plastic model are adopted for soil and pipe constitutive model respectively. Young modulus is defined as function of stress level and shear strain. Displacements and accelerations of numerical model was compared with the physical model on the shaking table tests. Influence of different parameters like young modulus, reference shear strain and dilation angel is investigated. Interaction model between soil and pipe is considered as elasto-plastic with separation and... 

Ground water resources are the main source of water supply in many regions. During last decades ground water quality has been deteriorated due to many sources of contamination. Seawater intrusion in coastal aquifers is one of these sources. With development of different numerical models, simulation of seawater intrusion in coastal and island aquifers has been used greatly in analyzing the condition of these aquifers. The first step in performing a numerical modeling is determination of a suitable conceptual model. Considering the complexity of a real problem, a proper conceptual model should show the true condition of the problem as well as lead to a cost and time effective simulation. In... 

Public transit system has become one of the targets of terrorist attacks using explosives, examples of which include the 1995 attack on Paris subway and the 2004 attack on Moscow subway. Under the present context of intense threats of terrorist attacks on subway systems in metropolitan areas around the world, explicit three-dimensional Finite Element method was used to investigate the dynamic response and damage of subway structures under internal blast loading. The study was motivated by the fact that explosion in subway structure may not only cause direct life loss, but also damage the subway structure and lead to further loss of lives and properties. The study used the Mashhadsubway... 

In the present study, the objective was to obtain the forward and backward swimming equation for the fiery eel and the European Eel in the experimental section. Then, by processing the videos, swimming equations were extracted. The obtained equations were used to move the 3D eel geometry of the STAR-CCM + software. The purpose of numerical modeling is to study the effect of body amplitude and wave frequency on the forces applied on the eel body during swimming. Numerical simulations were performed for the three amplitudes of 0.1, 0.115, and 0.138m and four different frequencies of 1, 1.2, 1.2 Hz, and Reynolds number 3857. The results of numerical work show us that the increase in the wave...