Sharif Digital Repository

Scale formation is an unpleasant phenomenon that occurs when the mixed fluids are incompatible. The scales damage the reservoir, wellbore and the surface facilities. They reduce the effective fluid path and increase the pressure drop of the system; so it is necessary to study the precipitation thermodynamics of scale formation, and present a trustable method for banning the scales from precipitation. In this project, it has been tried to study the value of precipitated scale due to the mixing of two incompatible waters (Civand and Sea Water). The results of which are compared with the results of a geochemical software named PHREEQC. Then, the performance of hydro chloridric acid as a scale... 

Due to the suitable performance characteristics and the widespread use of Surface Piercing Propellers (SPPs) in high-speed crafts, many experiments and numerical studies have been conducted in this field. Due to the lack of a comprehensive series similar to conventional propellers in the field of SPPs, in this thesis, it has been tried to personalize the suitable basis by conducting two separate experimental tests in the National Iranian Maritime Laboratory (NIMALA) towing tank and the cavitation tunnel at Sharif University using computational fluid dynamics method and the commercial code STAR-CCM+. For this purpose, a wide range of phenomena and effective parameters on hydrodynamic... 

In this thesis, vibration analysis of multi-walled carbon nanoconesstudied by molecular mechanics approach. In this simulation, atoms of carbon and bondings of them modeled by concentrated mass and structural elements, respectively and then mode shapes and natural frequencies of these structures calculated and effects of height, apex angle, boundary conditions and number of layers on natural frequencies of carbon nanocones studied. Also, critical buckling load of multi-walled carbon nanocones due to axial and in-plane loads obtained and effects of height, apex angle and number of layers on critical buckling loads of carbon nanocones studied. These results validated by molecular dynamics and... 

So far a number of solutions have been proposed to resolve some problems of steel plate shear walls including large induced loads on the surrounding members, late panel’s yielding along with lack of openings. One of the forms that can be considered for steel shear walls is braced shear panels.Regarding to the many advantages of this structural system, in this thesis steel shear panels with concentric or eccentric bracing have been introduced. For this purpose, first a procedure for plastic analysis and design, aiming to develop a predetermined collapse mechanism, is proposed. The results demonstrate that the closed-form analytical equations along with the extension of failure mode control... 

Todays, advances in manufacturing technologies have led to design and production of micro-scale elements, including the elements employed in micro-electro-mechanical systems (MEMS). Micro-rotating systems like the micro-turbines are that kind of systems at which the high rotational speeds and the complexity of design and analysis have led to a special attention in modeling and investigating of their dynamic-vibrational behavior. In addition, in small scales, using the non-classical continuum mechanics theories such as the couple stress theory and the strain gradient theory is required to obtain the high precise results. On the other hand, attention to the torsional deformation of rotors... 

Incapability of the classical continuum mechanics theory to justify the experimental observations of the mechanical response of the small-scale structures and parts motivated the researchers to pursue the introduction and utilization of the non-classical continuum theories for analysis and design of such structures and parts. In this paper, utilizing the modified couple stress theory and the strain gradient theory as well-known and powerful non-classical continuum theories, the mechanical response, including the displacement and stress fields, for micro-rotating disks with angular acceleration is investigated. The governing differential equations of motion and the corresponding boundary... 

Nowadays, water and energy shortage is the main concern of many industries. Every saving that could be done is valuable. In the first step of this project, energy recovery devices that are used in reverse osmosis systems, are reviewed and advantages and disadvantages of each system are investigated. These apparatuses save energy by recovering high-pressure energy from leaving brine and reduce the energy consumption of the device. The main focus of this study is energy consumption of the device that is used for desalination of seawater in reverse osmosis systems and on this basis, different energy recovery devices are compared. According to the investigation, results showed that most of the... 

Strong van der Waals (vdW) potential fields of carbon nanotubes (CNTs) makes them capable to encapsulate some nanostructures inside their hollow space, which leads to the construction of new hybrid nanostructures under specific conditions. Carbon nano-peapods, carbon nanowires and the hybrid of DNA and CNT are the main categories of hybrid nanostructures of CNT. Characteristics of hybrid nanotubes are unique and different from those of CNT. In nanostructures, the lattice spacing between individual atoms is considerable with respect to the structural dimensions. Also, the range of internal characteristic length is relatively close to external ones. So that utilizing the classical continuum... 

Acidizing is one of the common methods of stimulating the well to remove formation damage and Skin factor. In carbonate reservoirs, hydrochloric acid creates permeable channels called wormholes due to the reaction with the porous medium. Previous researches have studied the effect of the main rock and fluid parameters (temperature, pressure, type and concentration of acid and rock lithology) at the core scale. However, wellbore scale will different from core scale due to the difference in the wormhole density, the flow geometry, the amount of acid leakage from wormhole wall and competition. Very limited models predict these effects for large scales. In this research, the geometry of linear...