Sharif Digital Repository

In this work solid circulation pattern in 2-D gas-solid fluidized beds has been investigated carefully. In this regard TFM approach was used. In addition KTGF was applied along with Gidaspow drag model. A commercial CFD software (ANSYS FLUENT 15.0) was used to simulate the hydrodynamics of the bed. Effects of a number of operating and design parameters on the solid circulation pattern were examined in detail. These parameters were gas velocity, restitution coefficient, pressure, solid density, temperature and vertical plates. The simulation results were validated against experimental data reported in the literature. Furthermore, the solid vertical velocity was investigated carefully  

Aphron drilling fluids or CGA fluids are the wellknown updated drilling fluids in recent years.this kind of drilling fluids can control the mud loss into the formation and thus reduce formation damage and drilling costs. its structure consists of two phase fluid (gas and liquid) that the aphrons are the micro bubbles with 10 to 100 micrometer diameter that have strong stability in liquid phase compared to foamy drilling fluids. Generally aphron drilling fluids are made of base drilling fluid and surfactants, for more stability, mixed surfactant-polymer additive is so beneficial. in the last two decades, the Lattice-Boltazmann method is introduced for computational fluid dynamic area and... 

In this study, a fully coupled thermo-hydro-mechanical model for two-phase fluid flow and heat transport in fractured/fracturing porous media is introduced using the extended finite element method (XFEM) for numerical solution. The subject is important in the environmental and industrial fields such as hydraulic fracturing in petroleum industry, CO2 geo-sequestration, geothermal energy extraction and radioactive waste disposal in unsaturated porous media. In the fractured porous media, there are couplings of traction and heat and mass transfer between the fracture space and the surrounding media. Therefore, consideration of the fracture geometry explicitly in the modeling is important to... 

Understanding of how fluid flow through porous media has many application in industry like Water filters technology and Gravel dams. also it’s very important in oil industry in areas like oil tank engineering. For doing this important thing many peoples tried to find out how fluid flows through the porous media they already invented the various kind of models, .the model used in this thesise is called pipe flow model which people use this model before but what I did have a little difference I used random lattice which people did not paid attention to it so the result of this model will be more trustable and close to what happens in nature. The result of this simulation showed us that the... 

One of the most important factors in global warming is greenhouse gases such as carbon dioxide. Separating carbon dioxide from industrial activities such as fossil fuel power plants and storing it in the underground water can help combat the global warming challenge. In this research, numerical modeling of carbon dioxide sequestration in the aquifers under isothermal conditions is investigated. The process of storing carbon dioxide in aquifers consists of four main stages. In the first stage, the injected carbon dioxide accumulates into the aquifers under the impermeable bed. In the second stage, some carbon dioxide is trapped by the capillary forces inside the porous media's pores. In the... 

Hydraulic fracturing is a process during which a viscous fluid under relatively high pressure and flow rate is injected into a wellbore to induce and propagate a system of cracks in the ground.Hydraulic fracturing of underground formations has been widely used in different fields of
engineering, such as petroleum engineering, geotechnical engineering, environmental engineering, mining engineering,and so on.Despite the technological advances in the techniques of in-situ hydraulic fracturing, the industry lacks a realistic and reliable numerical model to design cost - effective and efficient hydraulic fracturing treatment.This is due to the complex interaction and strong coupling between... 

Researchers have done a lot of studies about the use of CFS in blood flow modeling in order to improve the supplementary devices or find mechanical factors which cause artery to be diseased. Blood is a complex rheological fluid, blood flow is a pulastile flow, and blood flow field interacts with the deformable vessel wall. Thus, blood flow modeling like other biological phenomena has its own complexities such as anisotropy, vsicoelasticity, and nonlinearity in stress-strain relationship of vessel wall. To explore the role of hemodynamics in the initiation and progression of stenosis in carotid artery bifurcation, a 3D Computational Fluid Dynamics (CFD) technique is applied. The effect of... 

Greenhouse gas emissions into the atmosphere have multiplied with the increase in fossil fuel consumption, which directly affects global warming. Global warming has other undesirable consequences such as rising sea water level and declining snow cover. To reduce greenhouse gases in the atmosphere, researchers have studied various ways, one of which is carbon dioxide injection into underground formations, which has a significant effect on reducing the amount of these gases in the atmosphere. Existence of high volume underground reservoirs with suitable conditions for gas injection to prevent gas escape has made it a widely used and effective method. Despite many advantages of this method, it... 

Loop heat pipe (LHP) is a two phase heat transfer device that is mostly used in cooling spacecrafts facilities. In this research a novel LHP is studied analytically and its steady state operating characteristics is analyzed in a one dimensional approach with heat transfer and pressure drop correlations. The novel LHP has a new arrangement in evaporator and reservoir configuration in comparison with conventional LHPs, which results in a different energy and fluid flow. In addition, the novel LHP has a new mechanism for acive control of working temperature. In modeling the proposed LHP the fluid and energy flows are first determined, then proper correltaions for calculationg each energy flow... 

Transport phenomena in porous media play important role in many areas of subsurface hydrology, geo-physics, environment, energy and petroleum. The work in the field of numerical modeling of fractured porous media is yet an open area of research. The classic finite element method (FEM) has some limitations in modeling of discontinuities like fracture. FEM mesh should conform with the geometry of the fracture. Presence of fracture imposes discontinuity in pressure field of fluid phases and displacement field of solid phase (rock). To represent the fractures, the extended finite element method (X-FEM) can be used in which the standard finite element approximation of the field variables is... 

A fully coupled numerical model is developed for the modeling of the cracks in porous media with flow of two fluids using the extended finite element method.The governing equations of two-phase fluid flow in deformable porous media, which account for the coupling between various physical phenomena, are derived within the framework of the generalized Biot theory. The solid phase displacement, the wetting phase pressure and the capillary pressure are taken as the primary variables of the formulation. The other variables are incorporated into the model via the experimentally determined functions that specify the relationship between the hydraulic properties of the porous medium, i.e.... 

Transport of drilling cuttings at the bottom of the well has always been one of the common problems of oil and gas drilling, which causes stock pipe or reduce the penetration rate and other problem. For this reason, the design of drilling fluid is one of the important drilling problems to be considered in order to optimally transfer drilling cuttings to surface. So far, many papers have been devoted to optimizing the drilling fluid for the transport of cuttings, but these papers focus on the state of drilling fluid static and less to model the dynamics and to examine the interaction between the cuttings and drilling fluid. At this end this study will modeling the drilling fluid flow using... 

Polymerase chain reaction, abbreviated as PCR, is a method of amplifying the number of copies of a desired DNA sequence through special protocols. The rapid advance of microfluidic devices and the emerging concept of digital microfluidics has resulted into the development of digital droplet PCR (ddPCR) systems with their significant uses in the detection of rare mutations, cancer diagnosis, and surveillance. A large number of micron-sized droplets are required to perform ddPCR. in this study, To investigate the gradient of confinements induced droplet self-breakup mechanism, we carried out the computational fluid dynamics (CFD) simulations for the two-phase flow using a commercial software... 

Investigation of reservoir performance and long-term production prediction are main goal of numerical simulation. Numerical simulation mainly consists of solving sets of non-linear equations developed by combination of continuity equation, equation of state and Darcy equation. Classical methods such as finite difference method (FDM), finite volume method (FVM) and finite element method (FEM) are widely used for solving sets of fluid flow equations that mentioned above. Researchers have used other methods like boundary element method recently. Each of these methods has their own restrictions. But the main source of error in these methods is due to numerical estimation of spatial derivatives... 

In recent years, application of porous media is highlighted among researchers due to their wider use in micro-scale problems, such as in gas reservoirs, micro-filtering, and heat exchangers. In such applications, accurate description of flow behavior, using governing equations based on continuum assumption, is not valid, since mean free path has the same order as the characteristic length of the problem. In such cases, imposing appropriate slip condition on the fluid-solid interface of porous media (in pore-scale level), based on kinetics theory, is an appropriate approach. For this purpose, pore-scale simulation of flow inside porous media in slippery and transient regimes is carried out... 

There is extensive use of solid-gas fluidized beds in the petrochemical, energy, chemical, and metallurgical industries. They provide fast heat- and mass-transfer because of the good mixing of solids. Tapered fluidized beds (TFBR) are more appropriate for this type of particle because they have axial velocity changes. This feature allows large particles to remain at the bottom of the bed and fine particles near the bed surface. In this work, the process of the solids mixing in a two-dimensional tapered fluidized bed with a bottom diameter of0/07 m and a height of 0.7 m was studied using computational fluid dynamics (CFD) techniques and applying a two-fluid model approach. The solids mixing... 

Considering the wide range of applications of porous media for heat transfer enhancement in various components of industrial machineries, including solar collectors, air dryers, compact heat exchangers, electronic microchips, investigation of heat transfer characteristics in porous media has been a major concern for many researchers. On the other hand, precise understanding of the physics of porous media-flow interaction has been an open research topic for a long time. The present research however, has aimed at developing a computational method to simulate the interaction between fluid flow and porous media to investigate heat transfer from prously covered surfaces. Pore scale modeling of... 

Numerous three-dimensional models of laminar flow and heat transfer in rough microchannels are developed and analyzed numerically to compare the effect of roughness elements on the thermal and hydrodynamic characteristics. In these models, the rough surfaces are configured with rectangular, triangular and sinusoidal roughness elements. Here, the effects of the roughness height, roughness element width, roughness element pitch, channel separation, Reynolds number and both Newtonian and non-Newtonian fluid on pressure drop and heat transfer in rough microchannels are all investigated and discussed.H2 thermal boundary condition is considered for all peripheral walls and power law model also is... 

Real modeling of ceramic foam filters, because of their specific tortuosities is not possible and in case of possibility of real modeling of pores in filters, because of restriction of element’s dimensions, the number of elements increases and model can’t be run in a reasonable time with common computers which are accessible nowadays. The common computer simulation of filters in Computational Fluid Dynamic (CFD) and their effect on fluid flow pattern is done by use of permeability properties of porous media. In this research, ceramic foam filters which are used in casting are simulated by Forchhimer and Darcy models. SUT CAST software is used for simulation, because of its ability for... 

Mass or large-scale storage of hydrogen, as a clean source of energy, should be conducted in underground formations in order to be used as a reliable energy source at the peak of consumption. In this regard, underground formations such as aquifers and depleted hydrocarbon reservoirs are the most favorable and secured media for hydrogen storage. However, detailed understanding of the flow dynamics of hydrogen-water in these media is critical to maximize hydrogen storage and recovery and tackle the existing uncertainities which exist in the flow functions. To fill this gap, this research aims at a detailed pore-scale investigation of the effect of flow regime, hydrogen compressibility, and...