Sharif Digital Repository

Fully developed fluid flow and heat transfer is numerically investigated in micro-channels. There are many techniques to intensify heat transfer for internal flows, such as: increasing Reynolds number, extending surface area of channel wall and also disrupting the boundary layer thickness on the wall. Among these, extension wall surface area is a common technique. There are several ways to extend surface area including finned, slotted, chemically etched, grooved as well as porous media adhered wall surface. One other method that we work on it is modifying wall cross-section and usage of uniform suction porous media. The governing equations include the momentum equation of the core region... 

Non-uniform laminated beams are being used in many engineering applications as primary elements. Helicopter blades, wind turbine blades and robot arms are examples of applications of these structures, in which the high stiffness-to-weight ratio and the non-uniform geometry are of high importance. Changing the thickness in laminated structures is a big challenge in fabrication view as different tapering configurations may significantly alter the stiffness of the structure. Thus, increasing the stiffness and dynamics characteristics of tapered beams with simple configuration is of high importance. The present work aims to investigate the effect of adding nano particles in resin during the... 

The aim of this research is to consider the effect of geometric changes on pumping performance of two phase gas-fluid flow in a vertical pipe. The idea is to inject a light gas to the bottom of a tube full of fluid so we will obtain an upward flow due to density differences. Potential benefits of this device are numerous such as dredging of river estuaries and harbors, sludge extraction in sewage treatment plant, water treatment and many others. There are almost four distinct flow patterns which occurs in the rise pipe, bubbly flow, slug flow, churn flow and annular flow that each of them require special conditions. heat transfer between two phases, phase changes, mass and volume rate... 

Evolution of electrical devices and the need for wireless sensor and remote control has led to extensive research in field of energy harvesting. Regarding this approach, most studies devoted to use of piezoelectric effect in converting the dissipative vibration energy into usable electrical energy. Despite extensive progress made in this field of engineering, there were no significant growth in analytical solution and implementation of mathematical equations related to dynamic and electricity of piezoelectric harvester of beams with different geometries. The main focus of this thesis is solving constitutive and coupled electromechanical equations of piezoelectric harvester related to a... 

The purpose of this project is to model a rotating beam with variable properties of the cross section and also to present an active control method for suppressing the undesired vibrations due to external loading. The beam is modeled as a cantilever Euler-Bernoulli beam with nonuniform physical and geometrical properties. For a practical example, the characteristics of a wind turbine blade was used to solve the problem. The analyzed blade in this study is NREL 5-MW wind turbine blade. But the method can be extended to be used for other blades as well . First the natural frequencies and modeshapes were computed by MATLAB. Then by applying pole placement method, a control strategy was designed... 

The investigation of the behavior of structures subjected to various kinds of loadings is of considerable importance. In this research, an attempt was made to analyze behavior of beams that a load is moving on them.Most of the existing relevant works in this field are dealt with examination of elastic beams with constant section, while in most cases beams with variable sections are used in order to have the optimum structure and appropriate stress distribution and to maximize strength to weight or cost ratio. While construct analysis is very advantageous, it is very difficult due to the complexities arising from the variable sections. But this design is so advantageous that it dominates...