Sharif Digital Repository

Matrix acidizing aims at bypassing near wellbore damages in typical carbonate reservoirs or enhancing permeability and hydraulic conductivity in naturally fracture ones. The simulation of acidizing process at pore scale and complex geometries by LBM will lead to gain more knowledge about molecular mechanisms that govern rock dissolution, diffusion and advection of reactive fluid and help the evaluation of acidizing efficiency.In this thesis, simulation of acidizing includes the following steps:
• Multicomponent fluid convection
• Fluid diffusion into the solid
• Fluid-rock reaction
• Boundary conditions including periodic, bounceback, non-equilibrium bounceback, Dirichlet,... 

In modelling of large deformations in deformable solids, rate type constitutive equations are of great importance. In order to fulfill the material objectivity conditions it is necessary to choose an objective rate of stress tensor. On the other hand, using corotational rates, because of their special properties (which are resulted of the fact that varaition of parameters are computed from an observer connected to a rotated triad), in rate type non-linear elastic constitutive equations (called hypo-elastic equations) are notable. In this thesis, the necessary conditions for a linear rate type isotropic tensor-valued function of a tensor argument and its rate to be integrable are driven. In... 

The behavior movement of human is fundamentally concerned with the relationship between the central nervous system of motor control، and musculoskeletal system of a human. Optimal control was employed to relate these structures together. Movement is one of the important part of human life، CNS is important because it has the fundamental role in the movement. Investigators believe that CNS is learned by iteration movements from childhood and finally it chooses the movement that makes a cost function minimum value of itself. Researching for CNS modeling grows in recent years on the different part of human body. Because upper body have less difficulty in movements، it is more useful for CNS... 

Research in the field of medical science goes back decades and significant progress has been made in understanding the behavior of organs and living tissues. Consequently, scientists need to work towards identifying how to mathematically model the mechanical behavior of these living organisms. If we consider any living entity, we can see that they are a product of atoms, molecules, cells, tissues, and/or organs. Differential geometry and continuum mechanics indicate that during the growth process these organisms are influenced by the phenomena of aging, remodeling and morphogenesis. The majority of research in this area, i.e. the study of these important phenomena in living tissues, has... 

Today, the world is facing the limited resources of fossil fuels and the pollution caused by them. One of the best alternatives that can be offered to fossil fuels is the use of hydrogen in fuel cell technology. Polymer electrolyte membrane fuel cell is one of the types of fuel cell that has a significant advantage over other types of fuel cell in terms of low working temperature and high performance speed. In order to become more widespread, the fuel cell must be freed from the two problems of uncertainty and short life. These two factors can be improved by using a condition monitoring system in both stationary and transportation applications. By using continuous status monitoring and error... 

The concept of generalized strains is a well-established subject in the classical continuum mechanics. The characteristics and various applications of the generalized strains have been the point of interest of many researchers in the classical continuum mechanics. The aim of this thesis is the introduction of generalized strains in the micropolar theory, as a non-classical continuum theory. A set of generalized strains is suggested for the deformation of macro-elements. Moreover, a set of generalized strains is proposed for the micro-structures. Since the rate of strains possesses a significant importance in the constitutive equations of nonlinear analysis of solids, expressions for the rate... 

In this project, a size-dependent formulation is presented for mechanical analyses of inhomogeneous micro-plates based on the modified couple stress theory. The modified couple stress theory as a non-classical continuum theory has the ability to consider the small size effects in the mechanical behavior of the structures.The material properties are supposed arbitrarily to vary through the thickness of the plate. The governing differential equations of motion are derived for functionally graded plates utilizing variational approach. Based on the derived formulation, the static and free-vibration behaviors as well as buckling analysis of a rectangular functionally graded micro-plate are... 

Stress tensors and their rates are fundamental quantities in modeling the behavior of materials in the field of nonlinear continuum mechanics. One of the most remarkable applications of stress rates is their presence in the rate type constitutive equations of materials.
Co-rotational rates are corresponding to the rates which are measured by an observer who is in a reference rotating coordinate system. In general, under some specific conditions for the spin of a co-rotational rate, the rate of an Eulerian tensor would be objective. In this thesis, the objective co-rotational rates of Eulerian stress tensors for isotropic elastic materials under large deformations are obtained for the... 

The micropolar theory is a nonclassical continuum theory which considers a microstructure associated to each particle. This microstructure has three degrees of freedom and can rigidly rotate in the three dimensional space. Beside the classical or force stress tensor, in the micropolar theory the couple stress tensor is also considered.This research is devoted to deriving energy pair tensors for material strain measures in micropolar continuum. The subject of strains and their conjugate stresses is one of the major topics in the field of solid mechanics which has greatly been dealt with in the literature. This concept was introduced for investigating structural inequalities in solid...