Sharif Digital Repository

The objective of this project is numerical simulation of air flow and heat transfer between two horizontal concentric cylinders with rotation of inner cylinder and inertia of outer cylinder grooves on the inner cylinder. In this study, the air, meanwhile rotational motion by the inner cylinder will enter into the annular space between two cylinders with certain flow rate. It can be mentioned to cooling of power plant generators, Electric motors and rotating machines among usages of air flow between two cylinders. In this article the objective is calculation of pressure drop and Nusselt number, temperature distribution on the inner cylinder under conditions of constant temperature of... 

In the present work, the behavior of flow inside the pressure-swirl atomizers (PSA) is studied by the numerical simulation. The pressure-swirl atomizer is widely used in many industrial applications such as fuel injection in gas turbine, internal combustion engine and liquid-fuel rocket, spray drying, spray in firing and agricultural nozzles.
The flow simulation inside the injector (PSA) deals with many complicated considerations due to air core formation in the axial zone of the injector as well as high tangential and axial velocities in the swirl chamber. The two phase flow is modeled by level set methods in the pressure swirl atomizer. Moreover, the explicit algebraic Reynolds stress... 

In this project, direct numerical simulation of fluid flow inside the porous channel is carried out. The flow channel is containing uniform array of solid blocks with square cross sections in an staggered scheme. Two thermal boundary conditions of constant temperature and constant heat flux of solid blocks were applied to the problem. The Navier-Stokes equations directly applied to the fluid region with no assumption of volume-averaging. Governing equations of two-dimensional flow with constant properties were discretized with control volume method. Energy equations for solid and fluid phases were solved separately. The results show that for solid block lengths over channel height, a/H=0.05,... 

In the present study, Nano-fluid natural convection on a constant temperature vertical plate is numerically investigated, following the similarity analysis of transport equations. After changing the governing differential equations to the ordinary differential equations, they were numerically solved by the fourth order Runge-Kutta method.. The analysis shows that all three main profiles, velocity, temperature and concentration in their specific boundary layers, and the Prandtle number, depend on three important additional dimensionless parameters, namely a Brownian motion parameter, a thermophoresis parameter, and a buoyancy ratio parameter. Finally, it was found that the Nusselt number in... 

A gas cyclone is a fixed mechanical device that uses centrifugal force to separate solid particles from gas. Gas containing particles is brought tangentially into the cyclone. This results in the development of a vortex, which applies strong centrifugal forces to the particles. The larger particles move toward the outer wall of the system as a result of centrifugal forces. gases spiral down from a tangential inlet towards the conical section, where the flow is reversed and the particles are collected in a hopper. The gas phase then proceeds upward in an inner vortex towards the gas exit via the vortex finder.
In this study swirling flow of two-phase gas-solid in cyclone separator is... 

In the present study, the thermal behavior of human teeth during laser radiation has been discussed. The high laser power, as well as its low emission, can allow deviations from the Fourier heat transfer model. To overcome this problem, the non- Fourier heat transfer method, dual phase lagged (DPL), has been used. Wisdom considered in this study to evaluate the thermal behavior of tooth. Using the finite volume method, the DPL equations are solved and the thermal response of the teeth is obtained during laser irradiation. The effect of delay times, which are the parameters of the DPL model and depart from the Fourier model, is fully demonstrated on the temperature behavior of the tooth, and... 

In the leading thesis, an attempt is made to improve the evaporation rate by emphasizing the reduction of heat transfer to the fluid bulk. In this study, inspired by the process performed in plants in the transfer of water from the roots to the leaves and especially the function of plant vessels, a kind of evaporator-improving surface was designed. The general function of this surface is to prevent the heat radiated to the surface of the water from being spent on heating the fluid deep in the water, and by concentrating this heat in a thin layer of fluid on the surface, the rate of evaporation increases. This surface consists of three parts: evaporative layer, insulation and water suction... 

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... 

In recent years, many advanced Computational Fluid Dynamics (CFD) methods have been developed for accurate and efficient simulation of fluid flow. The application of these methods shows that for sufficient accuracy, the mesh resolution has to be reasonably high. Unfortunately, conventioanal single-grid Navier-Stokes solvers suffer from poor convergence characteristics. For this problem we used Multigrid method to speed up the convergence rate. In this section a code was developed (based on the conventional CFD algorithm) which can solve Navier-Stokes equations on structured grids. It also simulates the free surface by VOF method. Agglomeration multigrid method is used in present study for... 

In this thesis, we study the effect of cognition and cooperation on two important MAC layer performance metrics, i.e. maximum stable throughput and delay. To this end, we consider a broadband secondary user which interferes with N narrowband primary users. In our study we focus on four transmission protocols as well as two transmission policies, i.e. parallel and non-parallel transmissions. In the cooperative protocols, the broadband transmitter relays the packets of the primary users which have not correctly decoded at the primary receiver. In non-parallel transmission case, the packets of the broadband user are transmitted in the total available bandwidth and in parallel transmission case,... 

One of the most important factors of reducing durability of concrete structures is corrosion of steel reinforcement in concrete. In this paper, corrosion behavior of reinforcing steel in concrete is investigated in two different methods of protection based on neural network. As regard the first method, pozzolanic additives with optimized percentage were added to Concrete mix design (the percentage of these additives are 25% Weight of cement of fly ash, Micro silica with 10 percent of weight of cement and 25% of Blast Furnace slag weight of cement). In the second approach of protection, 0/5 percent weight of cement of ferrogard 901 inhibitor is added to basic mix concrete design and the... 

One of the most important issues among defense is the increasing of the defense power using present facilities. Therefore, optimal setting and arrangement of equipment by considering different air-to-earth attack of enemy without knowing of properties and capabilities of available systems may not be possible. So, using defense equipment considering properties of them, and paying attention to existence restrictions and effective elements can have an effective role with the design of suitable algorithm.The main purposes of this thesis are: maximization of the efficiency of a defense system against. aerial invader targets, achieving the best arrangement of defense equipment based on suggested... 

In this research, an intelligent and integrated system for elderly fall detection monitoring based on CCTV cameras has been designed and implemented. The system consists of three main components: a fall detection device, a central server, and a mobile application. The fall detection algorithm runs in real time on a Raspberry Pi 4B board and combines classical methods with deep learning techniques. Specifically, an SVM model is employed in the classical stage, while Convolutional Neural Networks (CNN) and MoveNet models are utilized in the deep learning stage to enhance accuracy. To ensure security and privacy, the system incorporates end-to-end encryption and secure HTTPS-based... 

In this dissertation we will study the problem of transmitting the information of continuous source over fading channel, especially when the transmitter does not have complete information about the channel status. In this situation we will have a tradeoff between the Quality of received packets and the Reliability in transmissions. To increase the quality of packets, for example, we should increase the quantization, and therefore, the transmission rates at the transmitter. But this will also increase the Error Probability at the receiver. It means that if the receiver gets the transmitted packet, it will have a better estimation of information source, but it is likely that error happens and... 

One of the most heatedly debated issues in Computer Science is Outlier Detection due to its vast and substantial applications such as credit cards, Image Processing,tax fraud detection, and medical approaches. Consequently, Outlier detection has been researched within various domains and knowledge disciplines. On the other hand, the research attempts have not been sufficient to overcome this critical problem considerably inasmuch as nearly all proposed techniques are associated with a special kind of applications or datasets.Firstly, this thesis attempts to provide a precise definition which not only excludes other one’s drawbacks, but also has its distinctive merits. Three essential... 

Tehran Refinery, as an industrial center that has significant water consumption in Tehran, intends to use the flow of water from the treatment plant south of Tehran after final preparation, with the aim of managing water resources and meeting its needs. And it uses a biological activated carbon (BACF) filter to reduce the DOC concentration. In these filters, the removal of organic matter is performed by the adsorption process as well as the biodegradation process by microorganisms grown on activated carbon. The presence of biofilm leads to continuous bio-regeneration of activated carbon during the water treatment process. Therefore, in this study, by examining the performance of these... 

Code clones are similar code snippets in software projects. Code clones, along with their disadvantages and applications, have long been studied by researchers. In recent years, due to the popularity of open source software, using software development ecosystems such as GitHub have increased dramatically. These ecosystems allow their users to perform high-quality software development without the need for physical presence. A number of previous studies have shown that software is being developed or modified repeatedly and many defects in software projects are duplicates. Finding these recurring codes and defects may be useful for software developers. Given that finding and fixing software...