Sharif Digital Repository

Problems of global warming have motivated energy communities to design and develop green power generators. Energy of the ocean waves is one of the most fascinating clean energies which have not been completely explored yet. The present work intends to design and develop a novel efficient system to generate electricity using the power of ocean waves. The proposed device can operate in most ocean situations. The device floats with the buoyancy of the buoy over the ocean surface. Regarding the ocean inputs the device is sinking or floating at the ocean to control and optimize input force. In the proposed system kinetic energy of the ocean wave is converted into force. This force moves the... 

Laparoscopy is a minimally invasive surgical (MIS) procedure specific to the surgical sites within the abdomen. For this surgical method a laparoscope, a camera (endoscope), and a grasping instrument is needed. They all inserted in to the abdomen through openings (5 - 10 mm diameter side port). Currently used grasper heads are small and often with steel material. With respect to these two properties applying large forces that cause damage in the organs is inevitable. The aim of this project is to design a new large laparoscopic grasper head that applies pressure along the length of the lever arms and can take up tissues of large sizes. Based on surveys and estimations SMA, artificial muscles... 

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... 

Based on progress madein industry, considering the essence of human resource health is an inevitable subject. Ventilation is an important matter which affects the quality and efficiency of production due to its coherence with providing a healthy and suitable workplace. In this regard, there are some settings for industrial ventilation systems which are designed to satisfy related health and hygiene standards.Simulation of ventilation systems based on CFD methods is a great contribution to choose anappropriate ventilation system type. In this study, by modeling the proposed ventilation setting in a 3D environment, we are assured that the system is capable of industrial ventilation in welding... 

Numerous applications of Lab on a Chips (LOCs) in chemical/biochemical analyses as well as the emergence of advanced methods for their manufacture attracts many researchers’ attention to these micro instruments. Low sample volume consumption and their high controllability are accounted as the main advantage of LOC systems. Micromixers are among the main components of any LOC in which mixing and/or reaction among two components occur. Micromixers have many potential applications in biological and medical sciences, and so they are repeatedly charged by biofluids. Due to sensibility of biofluids, to avoid disintegration, applying electroosmotic flow instead of pressure-induced flow has priority... 

In recent two decades, several strain gradient models have been developed to investigate size effects seen in small scale structures. However, the physical origin of length scale parameter and gradient terms has received little attention in the literature. On the other hand, stress gradient plasticity has been recently proposed to study size effects. The model attributes the origin of size effects to a dislocation pileup involving stress gradient and has a physical length scale as the mean spacing of dislocation obstacles. However, the stress gradient plasticity model has not included the influence of dislocation source strength which would affect the material strengthening beside obstacle... 

In this research energy and exergy Balance has been studied for a turbocharged three-cylinder engine. Energy balance is a method based on the first law of thermodynamics and based on this method the control volume is selected on the engine and the input and output energies of the control volume are calculated. Exergy balance is also a method based on the second law of thermodynamics which achieves the amount of irreversibility and ability to convert useful work for different energies in the control volume. In the tests performed, the net output power, output exhaust energy, energy transferred to the cooling fluid and other energies, including convection and radiation heat transfer from the... 

The scarcity of potable water is one of the world's challenges. In the Middle East, this crisis is even worse and as a consequence, the most aggregation of desalination plants has been constructed in this area. However, brine effluent discharged from these plants entails serious environmental issues. Despite the extensive studies about the investigation of dilution and the area which faces the brine discharges as submerge jets, there are a few experimental investigations with a focus on the injecting brine discharge into the shallow environment. Whereas the Persian Gulf's coastal environment is shallow. Moreover, there is a huge construction of desalination held in this area. Accordingly,... 

Ferrofluids are used in various fields such as drug delivery systems, heat transfer, biotechnology and separation processes. In this study, the splitting of ferrofluid microdroplets in symmetric and asymmetric T-junctions in the presence of a magnetic field has been investigated numerically and experimentally. These studies have shown that the creation of an asymmetric magnetic field can either affect the phenomenon of ferrofluid microdroplet breakup or the volume of microdroplets that are created after breaking and leaving each branch. Furthermore, more control can be applied to the phenomenon of microdroplet breakup. In the numerical study, the ferrofluid microdroplet breakup at different... 

The solar-driven humidification-dehumidification desalination system with a geothermal dehumidifier (SD-HDH-GD) has been given special attention, for producing drinking water and subsurface irrigation applications. This contribution scrutinizes the performance of the geothermal dehumidifier of the SD-HDH-GD system. To this aim, a comprehensive three-dimensional transient computational fluid dynamics model of the geothermal dehumidifier and the surrounding soil is developed. An experimental setup is established to verify the developed numerical model. At first, the performance of the system in a short-term period of 12 hours is investigated, and the effect of several operation parameters is... 

In the present study, waves maker and its effective parameters has been investigated. Different kind of wave makers have been investigated and compared with each others. Then, according to marine laboratory requirnents such as Dimensions, seakeeping tests, installation place and budget, a proper wave maker is designed. In design procedure, differential equations of waves and paddle wavemaker, wavemaker's power, forces on paddle and mechanical system with servo motor are used. For improving efficiency of system and converting the rotary motion to linear motion, a ball screw is utilized.
 

Limitations of fossil energy resources and environmental factors such as gas emission and global warming, forces human being to tend to apply renewable energies especially solar energy resource. Iran, which is located in yellow belt of the earth, has a high potential to be benefited from solar energy. Since more than 40 percent of energy resources are consumed in the building section, using solar energy I buildings can help the country to reduce the energy consumption. Space Cooling and heating and water heating are some examples of solar energy applications in buildings. Because, there are various types of climates in the world, there is not a unified code and guideline to design and... 

In this work, mathematical models are employed to predict transient temperature field, fluid flow within the melt zone and distribution of thermal and residual stresses during and after GTAW process. At the first step, fluid flow in the weld pool and transient temperature field within the metal being welded are determined by simultaneously solving the equations of conservation of mass, energy and momentum. To do so, a commercial finite volume base-program, FLUENT, is utilized. In the next step, temperature distribution during cooling as well as resulting thermal and residual stresses are predicted by means of a commercial finite element base program, ABAQUS. The employed models are capable... 

Lamniar flow through porous media has been investigated using finite volume staggered grid. In order to study turbulent flow modelling turbulent flow using RANS models with the aid of Fluent software has been done. And the microscopic and macroscopic results are compared with LES results. None of the RANS models used (k-e, RNG, k-wv2f, v2f and RSM) were able to model the flow through porous media properly, although k-e and RSM gave the best microscopic and macroscopic results  

Nowadays, computer simulations have an important role in the investigation of the thermal performance of the systems. In this thesis, a software program was developed for simulation of cooling system of an ER24PC Locomotive diesel engine. For this purpose, the C + + programming language is applied. One of the most important components in the cooling system is the radiator. In order to model the radiator, a relationship must be used to determine the heat transfer coefficient for coolant side and air side of the radiator. This relationship can be based on experimental, analytical, or numerical solutions. Offset strip fins are used in radiator of ER24PC locomotives. With application of... 

The complex nature of the friction welding process (FSW) prevents a useful understanding of this process. The effective and reliable theoretical models can be useful in understanding the physical and mechanical phenomena governing the FSW process. The modeling techniques of FSW process are still under development and more researches to provide a complete model of the process has been done and currently underway. This study presents a thermo-mechanical FSW model of AA5086 and AA6061 aluminum alloys and qualitative and quantitative evaluation of welded samples was done by experimental tests. In order to accomplish the project objects, by simultaneous solving of heat transfer and plastic... 

One of the most important applications of plasma is etching of substrates. This process is the key element of microfabrication. In order to improve the microstructures quality, it is necessary to improve plasma etching process. Therefore different methods have been developed to make etching process more efficient. The latest method is Bosch-process etching method. In this project to understand the effect of input parameters, Bosch-process etching of a PMMA substrate is simulated. Based on the governing equations, the problem is divided to four parts. First, by developing a heuristic approach to solve Maxwell’s equations numerically, electric and magnetic fields in the chamber are determined.... 

Changes in the internal structure of engines for reducing fuel consumption has almost stopped. While changes in powertrain is a better way to reduce vehicle fuel consumption. Recently, infinitely variable transmissions or IVTs have attracted large attention of car manufacturers . In these systems, due to the continuous transmission ratio, engine speed is kept in a range which is the optimum fuel consumption speed range. Designing of these systems for each vehicle must be done according to the requirements of the vehicle and engine abilities. So, an exact model of engine fuel consumption for the design of these systems is required. One way of improving the accuracy of conventional models, is... 

Nowadays, nanotechnology has emerged in many processes; hence the construction of this scale is also important. By reducing the size of equipment, raw material consumption is reduced and less space is needed for equipment. In addition it is economical. LIGA method has the potential to make parts with small dimensions and accurate tolerances, that it is impossible with other methods (chemical vapor deposition, physical vapor deposition, bulk micromachining, surface Machining). It is possible to assemble the pieces by producing micro-molding in LIGA procedure.In this thesis, numerical simulation of electrodeposition that is one of the main steps in the LIGA procedure has been investigated. One... 

In this study, the numerical simulation of turbulent flow using Open Source software OpenFOAM, The impact of air flow around the high-rise buildings and classification based on the height and arrangement of the buildings has been against the flow. Numerical method used, the finite volume method uses a piso algorithm, Navier-Stokes equations are solved and the speed and pressure can be obtained. Large Eddy Simulation model is a simulation model used in this software. In general tall buildings against wind loads has three types of move, move along the wind, prependicular along the wind and the twisting motion that occurs at the same time, they are, but, due to the variable nature and...