Sharif Digital Repository

In this study, a novel multi-scale hierarchical method has been employed to explore the role of edge dislocation on Nano-plates with hexagonal atomic structure in large deformation. multiscale hierarchical atomistic/molecular dynamics (MD) finite element (FE) coupling methods are proposed to demonstrate the impact of dislocation on mechanical properties of Magnesium in large deformation. The atomic nonlinear elastic parameters are attained via computing first-order derivation of stress with respect to strain of Representative Volume Element (RVE). To associate between atomistic and continuum level, the mechanical characteristics are captured in the atomistic scale and transferred to the... 

To have a deeper understanding of Hydraulic fracturing operation, in this study four important parts in this field was developed and simulated. In the first part, continuity and momentum equations for a single phase flow in a propagating penny-shaped fracture inside an impermeable matrix was revisited based on a fixed coordinate system. Its correctness was validated against experimental data and its features were compared with the well-known lubrication theory in analytical form. The new derived continuity equation caused the fracture tip to have a positive and finite pressure while, the conventional model predicted negative infinity for that. In the second part, Finite Volume method was... 

Transverse Vortex-Induced Vibration(VIV) and Flow-Induced Vibration(FIV) of a rigid, circular, elastically mounted single degree of freedom cylinder is scrutinized in range 3×104≤ Re ≤12×104 by means of Computational Fluid Dynamics(CFD). ANSYS CFX, based on FV, is employed to simulate VIV and FIV in different system parameters such as stiffness and mass ratio. Firstly, the minimum structured, hexahedron computational cell required to simulate VIV and FIV by means of Finite Volume (FV) method is provided. Then, the appropriate size for computational domain to simulate VIV and FIV accurately is discussed concisely. Approximated amplitude and frequency ratio are compared to experimental data... 

Drop formation is an interesting field of research due to its wide-range of applications, such as drug delivery, biomedical studies, pharmaceutical industry, Lab-On-Chip (LOC) devices, etc. In recent years, researchers have used numerical studies to better understand how the process of forming and carefully examining the factors that affect quality improvement. One of the most effective methods in controlling the size and the process of drop formation is use of external force in microfluidic devices. Among the external force in this study, an electric field with oscillating current was used. Rapid methods for creating, deforming, and breaking up of drops in microfluidic applications are... 

Rapid preparation of a homogeneous mixture is essential for many chemical and biological applications, such as micro-scale biological-chemical agent detection, drug delivery, and DNA hybridization. Some mixing systems have a micro-scale geometry, which results in a very slow mixing process, mainly due to laminar flow in these systems. Mixing in a slow flow is performed only by molecular diffusion. In the absence of any disturbances, increased mixing is not possible simply by diffusion. Accordingly, a suitable and innovative method to improve mixing for such systems is required. Induced charge electro-osmosis is a new field of electro-osmotic flow, which performs better than conventional... 

It is about half century passed from the invention and application of the polymer flooding. Although there are successful reports from the using polymer flooding, but there are problems that in some cases this process fails. For more insight on the problems and in order to improve
the efficiency of this process the conceptual understanding of the process is required. More conceptual understanding from this process, requires investigation in pore scale. In the presenting investigation, the flow of Newtonian and non-Newtonian fluids in the single phase and two phase form and in pore scale are simulated using finite volume method. Because, the finite volume method is used in very... 

Considering the importance of oil and gas industries in Iran, issues related to drilling and exploitation of oil and gas fields are among the country's priorities and challenges in industries, research centers and universities, and extensive research is conducted in this field. Since during the process of oil production from oil wells and reservoirs, the formation of multiphase flows, including two-phase fluid flow, is inevitable, investigating the behavior of multiphase fluids, which is a branch of fluid mechanics, is of special importance. In this regard, in continuation of the research conducted in the Faculty of Chemical and Petroleum Engineering of Sharif University of Technology, in... 

Batteries have always been used as one of the most important sources of electricity storage and supply. Among different types of batteries, lithium-ion batteries are widely used in various fields and engineering applications due to their high-density energy/power, high discharge/charge rate, and long life. The most common of these applications are using these batteries in all-electric and hybrid vehicles, which reduce environmental problems. Due to the high cost of these types of batteries and the environmental issues of battery decomposition, researchers are seeking to discover long-lasting batteries that lithium titanate oxide batteries have the most extended lifespan among lithium-ion... 

In this study a locally mass conservative finite volume method (FVM) is employed to simulate the coupled model of flow and geomechanics for the land subsidence problem. At the first step, a FV numerical method is implemented to solve a Biot consolidation model with discontinuous coefficients one dimensionally. The studies show that the FV scheme leads to a locally mass conservative approach which removes pressure oscillations especially along the interface between materials with different properties and yields higher accuracy for the flow and mechanics parameters. Then this numerical discretization is utilized to investigate different sequential strategies with various degrees of coupling... 

Pulse Tube Refrigerator (PTR) has an exceptional feature among all similar refrigerators, because of its unique characteristics such as long lifetime, compact size and no moving parts in low temperature. Despite of all these advantages because of its low efficiency, many researchers are trying to optimize performance of this refrigerator. Most of these efforts are based on one-dimensional simulation of the system. In this thesis, a two-dimensional analysis is performed to study the nature of flow field in an Inertance Tube Pulse Tube Refrigerator (ITPTR). This analysis is based on a numerical modeling of an entire ITPTR. To reach this purpose the two-dimensional form of mass, momentum and... 

Gorgan Bay and Miankaleh Wetland have been exposed to various environmental risks in the past years due to the decrease in the Caspian water level and the subsequent decrease in the water level of these water bodies. 2 channels, Chapgoli and Ashuradeh, are the only ways connecting the Gulf with the Caspian Sea. If the water level of the Caspian Sea and the Gulf continue to decrease, these 2 channels will be completely blocked and the connection between the Gulf and the sea will be completely closed. Due to the low depth of the bay and high evaporation on this water body, the blockage of these 2 channels will eventually lead to drying up of the bay or changing the flora and fauna of the area.... 

Direct reduction of iron is a process to reduce iron in solid phase. The output of this procedure is direct reduced iron (DRI) that can be used in electric arc furnacewithout further changes. Midrex technology, which is the most important one among direct reduction of iron processes, provides 60% of DRI.
Required synthesis gas for reduction process is gained from reforming of the natural gas,with the major proportion of methane, with water steam and carbon dioxide in a piece of equipment called “reformer”. As a matter of fact, reformer is a type of plug chemical reactors. Input materials (natural gas, water steam and carbon dioxide) enter from the bottom section to the prepared pipes in... 

In this paper, a hierarchical RVE-based continuum-atomistic multiscale framework is established on the basis of the nonlinear finite element method and molecular dynamics simulation in order to model the geometric and material nonlinearities of deformable solids. In this framework, the coarse scale material properties required for nonlinear finite element method are directly exploited via fine scale atomistic simulation of atomic RVEs designated for each coarse scale integration point and required boundary conditions for atomic RVE simulation are achieved from the coarse scale kinematical response. In order to ensure the kinematical and energetic consistency between the two scales, the... 

This thesis is about modeling of liquid-vapor two phase flows through nozzle. Liquid-vapor two phase flow is very applicable in industries such as boilers, expansion valves, refrigeration and sudden failures in pipelines. Two models are used for modeling of fluid flow through nozzle, transient and steady state. In Both model the solution field is considered as saturated liquid and vapor and the mass, momentum and energy equations as well as equation of state is used for describing of fluid flow properties. Homogeneous equilibrium model is used and for complete modeling of fluid flow heat transfer and friction force is also considered.
Numerical solutions are used for solving of the... 

DIRECT reduction is a process for reducing iron ore in the solid state. The product is in the form of sponge iron. This can be used directly as a raw material for steelmaking in an electric arc furnace. MIDREX process produces more than 60 percent of global DRI production. Because of high potential natural gas and iron ore resources in Iran and also lack of scarp, MIDREX direct reduction process is feasible. The main function of the MIDREX shaft furnace is to generate sponge iron from iron ore. The solids flow downwards by gravity and the reducing gases flow upwards in counter current, while the corresponding chemical transformations occur. Physical phenomena in the reactor could be... 

One of the main purposes of this project is to propose an efficient and stable algorithm of a semi-discretized formulation for compositional simulation of oil reservoirs. In this algorithm, all the equations including both mass balances and equilibrium equations are solved simultaneously. The gradient terms are discretized by the Finite Volume Method (FVM). The resulting Differential Algebraic Equation, the so-called DAE, are solved by MATLAB functions. Another novel technique developed, handles each block equations set, separately. In this block-by-block scheme, there are two set of equations; the primary (mass balance) and secondary (equilibrium) equations. In the primary ones, the... 

The ultimate aim of this research is optimizing high- performance Horizontal Axis Wind Turbine (HAWT) associated with using Computational fluid dynamics (CFD) to predict the flow behavior over wind turbine blades. Computational prediction of the flow over wind turbines is a challenging numerical problem because of the complicated aerodynamics and large variation in length scales. Phenomena such as; the unsteady flow, vortex shedding of the blade tips, flow separation, complicated blade geometry due to variable twist and chord and changes in angle of attack, and highly turbulent flow over blade sections makes CFD prediction challenging, as well as interesting. The goal is to gain an in depth... 

In this thesis the oil reservoir simulation is carried out by using a combination of fast Multi-scale finite volume method and Streamline method considering gravity effects. In this simulation, the governing equations for incompressible fluid flow in porous media are solved using the IMPES (implicit pressure- explicit saturation) viewpoint. Multi- scale method is rapid (equivalent on coarse-scale methods) and accurate (equivalent on fine-scale methods) in solving the pressure field. Using the pressure field obtained through this way combined with Darcy equation make us able to extract the conservative velocity field. In this study, analytical and numerical Streamline methods are used to... 

Carbonate Matrix acidizing in order to improve or increase initial permeability, leads to different dissolution patterns under different operating and environmental conditions. In a specific rock / reactive fluid system, when a reactive fluid injects into the system in an optimal velocity, the dissolution pattern proceeds like a finger, names Wormhole. Formation of Wormhole is known as a success in acidizing process, because of its optimum porosity and permeability evolution and minimum pore volume injected of reactive fluid to breakthrough. So prediction of optimum injection velocity and analysis of dissolution patterns variation by change in operational and environmental conditions,... 

Cardiovascular diseases are most common causes of deaths in the whole world. Nowadays, engineers and scientists in various fields become intent on finding solutions for prevention and recovery of these diseases. In this way, it is very important to know about the blood flow in arterial systems and its changes in various diseases. Numerical simulation of the blood flow beside of experimental studies could be very useful in this way. One dimensional simulation among various methods of numerical simulation was chosen to simulate a cardiovascular system since it has smaller computational cost and ability to modeling of whole arterial systems. It also is useful in extraction of medical indexes....