Sharif Digital Repository

This work is related to the research in the fields of particulate flow with the presence of external magnetic field and simulating movements of particles till making chain of particles. Using direct numerical simulation method for a two-way coupling of fluid and magnetic governing equations makes a more roboust and precise method. Also, using some assumptions simplified general maxwell equations to set of magnetostatic equations. these eqautions are solved by the boundary element method and the integral equations. Using analytic integrals and calculation of magnetic intensity are some techniques suggested for improving the preciesion of the presented work. the magnetic force and torques can... 

Multiscale modeling is performed within the framework of homogenization methods for problems in which the scales are separated. The existence of representative volume element (RVE) is one of the main ingredients of homogenization methods. Due to non-existence of RVE and macroscale mesh sensitivity, the continuous homogenization method is not applicable for softening materials. Despite the non-existence of RVE for softening materials, it has been demonstrated that by performing the average over the active damage zone rather than the entire domain, objective responses with respect to RVE size could be obtained. That is why discontinuous homogenization is used instead of continuous... 

The constitutive modeling of heterogeneous micro-structure of solids based on multi-scale theories has become the subject of intensive research. One of the most important problem at this scale is the interfacial effects of constituents. Investigation of thermal conduction in this area leads to a phenomenon known as Inter-facial Boundary resistance. The general reasons behind this phenomenon are imperfect contact interface and changing in energy carriers properties known as Kapitza resistance. A computational homogenization of conduction tensor by considering inter-facial resistance and effective factors on it, is proposed. In order to capture discontinuous field around this area and its... 

In this research, multi-scale modeling of mixed-mode failure mechanism of quassi-brittle materials is presented. For modeling a realistic crack growth in heterogeneious media, crack initiation criterion, crack growth orientation and the macroscopic cohesive law are derived from a microscopic sample. As a microscopic crack initiation criterion, acoustic tensor is investigated and scaled acoustic tensor has been proposed by comparison its results with maximum principal tensile stress. For crack growth direction based on micro-scale, acoustic tensor and multiscale aggregating discontinuities has been investigated and multiscale aggregating discontinuities by comparison results of these methods... 

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,... 

Nowadays, cancer, which has been mentioned as the disease of the century, is the second leading cause of death throughout the world, and its incidence is constantly increasing. Isolation of circulating tumor cells is one of the most critical steps in diagnosing and controlling cancer progression. Due to the rarity of cancer cells compared to other cells in the blood sample, the isolation process requires optimal and high-precision devices. With the advent of inertial microfluidics, the ability to control the particles movement, the processing of blood samples as quickly and accurately as possible, and the viability of cells with a high percentage, introduced microfluidic systems as a... 

In the present study, a high-order finite-difference lattice Boltzmann solver is applied for simulating steady and unsteady three-dimensional incompressible flows. To achieve an accurate and robust flow solver, the incompressible form of the lattice Boltzmann equation in the three-dimensional generalized curvilinear coordinates is discretized spatially based on the fifth-order weighted essentially non-oscillatory (WENO) finite-difference scheme. To ensure the stability and temporal accuracy of the flow solver, the fourth-order Runge-Kutta method is used for the time integration. To examine the accuracy and performance of the flow solver, different three-dimensional incompressible flow... 

Low-salinity waterflooding (LSWF) is a promising EOR approach that decreases the oil-wetness of reservoir rocks, hence increasing the recovery factor. Despite the importance of the pore-geometry on the performance of LSWF, especially in 3D simulations being affected by corner-flow and roughness, it is not yet investigated, thus in this thesis we aim at studying the aforementioned effects on LSWF. According to the preceding studies, during the drainage phase, the brines in the corners of pores cannot be displaced by oil because of requiring very high capillary pressure; thereby rendering a mixed-wet system. Hence considering this type of wettability is necessary for two-phase flow... 

In most real combustion systems, flow is turbulent (e.g., diesel engines). Therefore, a reliable turbulence modeling approach is necessary to design and analyze a system with turbulent flow. Direct numerical simulation (DNS), Large eddy simulation (LES), and Reynolds-averaged Navier-Stokes (RANS) are the three most mature Computational fluid dynamics (CFD) methods for turbulent flow simulations. Because of LES’s good accuracy and acceptable computational cost. In this project, LES is chosen to simulate the turbulent flow field.Modeled turbulence subgrid scales' interaction with nonlinear flow parameters, needs modeling. In supercritical and transcritical conditions, Equation-of-state is a... 

Despite the proven advantage of the engineered water flooding technique, a coherent and mechanistic understanding of the fundamental phenomena occurring at pore scale is lacking. Most of the available simulation models have a phenomenological approach and have limited predictive capability. One of the key questions is how to justify and relate large (Darcy) scale observations to effects and phenomena that essentially occur at much smaller scales (i.e. pore and molecular level). Furthermore, two-phase flow dynamics and the effect of complex interplay between wettability, capillary number, and ions dispersion in a heterogeneous porous medium on the trapping and mobilization of oil at pore...