Sharif Digital Repository

In the present study, the computation of the viscous compressible flow over two-dimensional geometries is performed by using the immersed boundary method and applying a second-order finite volume scheme. For the solution of the governing equations, a uniform Cartesian grid that is not coincident with the body surface is used and the boundary conditions on the wall are satisfied by the ghost-cell immersed boundary method. The spatial discretization of the fluid equations is carried out using the second-order central difference finite volume scheme and the time integration is performed by applying the fourth-order Runge-Kutta method. To stabilize the solution algorithm and reduce unwanted... 

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... 

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... 

The goal of this research is to introduce and improve the new multiscale finite volume method for simulation of multiphase flow in porous media. This method has recently presented as an efficient approach in computational fluids dynamics field. This thesis contains the followings: In the first step a brief introduction is presented about petroleum reservoir engineering and different methods of oil production. Then the importance of new simulation methods to anticipate the behavior of these reservoirs with detailed geographical information is discussed. In the second section black-oil formulation in petroleum reservoirs is descritized with the aid of finite volume method. Using general... 

In this work, the combination of a multi-scale finite volume and streamline methods is presented for subsurface flow modeling. The used multi-scale method in this work is the same with the traditional type of it in algorithm and formulation. However, because of using a new mesh structure for implementation of multi-scale finite volume method, the new method named by Staggered Mesh Multi-scale Finite Volume (SMMsFV) method. Using the staggered mesh has some advantages such as reducing the computational cost and increasing the accuracy of the multi-scale method. In the SMMsFV method, first the coarse grid and dual coarse grid are constructed on the underlying fine grid. Then, the basis and... 

Today, due to a massive increase in accuracy of reservoir characterization models, multiphase flow simulation on real permeability fields faces a serious challenge. Using multiscale methods in reservoir flow simulation of a heterogeneous environment has led to huge speed-up of the simulation. In multiscale methods, instead of replacing a heterogeneous medium by an equivalent homogeneous medium, used in upscaling, the problem is solved on the original resolution. In this thesis, multiscale finite volume method (MSFV) has been used to simulate flow and saturation behavior of a black oil model. Unlike the original multiscale finite volume methods that were unable to solve compressible fluid... 

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... 

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,... 

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... 

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... 

Multi-Scale finite volume (MSFV) method have been developed and applied for multiphase flow in porous media. The most important advantage of MSFV method is its computational efficiency. In this thesis we apply and implement this method to porous media simulation. Then, computational parameters such as coarsening ratio, effect of threshold on adaptive computation and different boundary conditions for computing basis functions are investigated. The two difficulties of sMSFV method are problems with high permeability contrast and problems with high course grid aspect ratio which are considered. In standard MSFV (sMSFV) method reduced boundary condition is used to determine the basis and... 

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... 

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 purpose of this study is to numerically investigate the Vortex-Induced Vibration (VIV) around the cylinder, which occurs in many engineering structures, including offshore structures, offshore risers, deep-sea pipelines, bridges, cables, and tall buildings. This phenomenon is non-linear and self-limitting and is the major cause of fatigue and failure in engineering structures. At the same time, it is possible to harvest Aquatic Clean Energy from Vortex-Induced Vibration. This research investigates the single degree of freedom and two degrees of freedom oscillator. The numerical model is validated using an experimental model in the Sharif University of Technology's advanced hydraulics... 

Nowadays, in the world and our country, Iran, sediment transport and the phenomenon of sedimentation are of great importance. The entry of water flow with suspended sediments into the dam reservoir by floods with different return periods during the initial period of dam construction causes a considerable part of the helpful volume of the reservoir to be filled with sediments. As a result, the discharge of these sediments and the methods that exist in this field should be studied so that a large volume of reservoir water is not wasted during the discharge of these sediments. In this research, the opening time and extent of the bottom outlets of Qeshlaq Dam when the flood enters the reservoir... 

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.... 

in this study, turbulent natural convection inside an air filled square cavity with several hot and cold internal bodies in the range of Rayleigh numbers between 1010 and 1012 has been investigated numerically. Vertical walls of the enclosure have been considered isothermal and horizontal walls are insulated in all cases. An appropriate arrangement of internal bodies in which the minimum heat transfer occurs is desired. For this purpose, two dimensional Reynolds-averaged Navier-Stokes equations have been solved with the finite volume discretization method in a staggered grid. In addition, two equation high-Reynolds-number model with standard wall functions is used to simulate the... 

Oil spills in marine environments lead to serious environmental disasters and have significant short-term and long-term effects on the aquatic life cycle, the health of people living on the coasts, the region's ecology, and social and economic activities. Shipping and marine transportation are responsible for many oil accidents. For this reason, harbors- as one of the most important marine transportation infrastructures- are always exposed to oil spills which in addition to economic losses, can lead to disruption of ports' performance.To reduce the environmental and economic damages caused by oil spill incidents, it is necessary to prepare the harbors to deal with and clean up oil pollution... 

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...