Sharif Digital Repository

Oil production from asphaltenic oil reservoirs has always encountered difficulties, such as plugging and unpredictable fluid properties. To physically recognize the aspects of asphaltene deposition, several dynamic and static asphaltene deposition tests were designed and performed on one of the giant south Iranian oil reservoirs using dead and live crude oil and real core samples. Moreover, the effects of fluid velocity on the extent of damage were investigated. It was found that surface deposition of asphaltene particles is the main source of formation damages in the porous media and the resulting permeability impairment obeys an exponential behavior. All of the experiments confirm that... 

We provide the simulation of electroosmotic phenomenon in nanochannels using the Dissipative Particle Dynamics (DPD) method. We study the electroosmotic phenomenon for both newtonian and non-newtonian fluids. Literature shows that most of past electroosmotic studies have been concentrated on continuum newtonian fluids. However, there are many nano/microfluidic applications, which need to be treated as either non-newtonian fluids or non-continuum fluids. In this paper, we simulate the electroosmotic flow in nanochannel considering no limit if it is neither continuum nor non-nonewtonian. As is known, the DPD method has several important advantages compared with the classical molecular dynamics... 

In this paper, the hydrodynamic drag and lift forces on microparticles in a dilute suspension in low Reynolds number Poiseuille flow in a microchannel is experimentally investigated using microscopic image analysis. An effective technique is applied to manipulate single-particle tracking in order to determine the velocity field and hydrodynamic forces on microparticles with diameter-to-channel height ratio of 0.1 (Formula presented.) in microchannels. The results show that there is a distance near the walls of the channel in which the hydrodynamic coupling between the particles and channel walls is considerable. Also, the magnitude of drag force that is imposed on the particles with... 

In this article, velocity field and settling distribution of microparticles in a dilute suspension in low-Reynolds-number Poiseuille flow in a microchannel is experimentally investigated using microscopic image analysis. An effective technique is applied to manipulate single-particle tracking in order to determine the controlling parameters on transportation and settling of microparticles in microchannels. The results show that the velocities of dispersed phase are affected by the hydrodynamic properties, and this velocity deviation can be significant when the hydrodynamic coupling between particles and channel walls is considerable. Increasing the Reynolds number would result in decrease in... 

The aim of this work is to investigate flow hydrodynamics in porous media. Random non-overlapping spherical particles in a cylindrical geometry were produced as a porous media. Navier-Stokes equations in three-dimensional porous packed bed have been solved and dimensionless pressure drop has been studied for a fluid flow through the porous media at different Reynolds numbers (based on pore permeability and interstitial fluid velocity). The numerical results are in good agreement with those reported by Macdonald (1979) in the range of Reynolds numbers studied. At higher Reynolds numbers turbulent models such as large eddy simulation (LES) and Reynolds stress model (RSM) also have been... 

In this article, mixed-convective heat transfer of nanofluids in a vertical channel partially filled with highly porous medium was studied. In the porous region, the Brinkman-Forchheimer extended Darcy model was used to describe the fluid flow pattern. Different viscous dissipation models were also applied to account for viscous heating. At the porous medium-fluid interface, interfacial coupling conditions for the fluid velocity and temperature were used to derive the analytical solution using a two-parameter perturbation method. The model used for the nanofluids incorporates the effects of Brownian motion and thermophoresis. With constant wall temperature, velocity and temperature profiles... 

Generally speaking, most micro-fluidic mixing systems are limited to the low Reynolds number regime in which diffusion dominates convection, and consequently the mixing process tends to be slow and it takes a relatively long time to have two fluids completely mixed. Therefore, rapid mixing is essential in micro-fluidic systems. In order to hasten the mixing process in micro scale, in this study we come up with a novel scheme for a two dimensional micro-fluidic mixer which encompasses three pairs of electrodes, one pair embedded in the mixing chamber and two pairs located in the micro-channels before and after the mixing chamber. The width of the middle pair is assumed to be twice of the... 

Reservoir flow simulation involves subdivision of the physical domain into a number of gridblocks. This is best accomplished with optimized gridpoint density and a minimized number of gridblocks, especially for coarse-grid generation from a fine-grid geological model. In any coarse-grid generation, proper distribution of gridpoints, which form the basis of numerical gridblocks, is a challenging task. We show that this can be achieved effectively by a novel grid-generation approach based on a background grid that stores gridpoint spacing parameters. Spacing parameter (L) can be described by Poisson's equation (▽2L = G), where the local density of gridpoints is controlled by a variable source... 

Low-crested breakwaters have become more attractive because they do not hinder the beautiful coastal landscape and are more environmentally friendly comparing to traditional breakwaters. The available formulae for design of these types of structures mainly focus on wave transmission, reflection and dissipation aspects. However, stability of the armour blocks are not directly taken into account in the design process. In this study the Lagrangian meshfree method of SPH along with a discrete element method i.e. Polyhedral DEM are used to simulate the interaction between the sea water waves with different characteristics and low-crested breakwaters constructed using cubic armour blocks. SPH is... 

Reservoir flow simulation involves subdivision of the physical domain into a number of gridblocks. This is best accomplished with optimized grid point density and minimized number of gridblocks especially for coarse grid generation from a fine grid geological model. In any coarse grid generation, proper distribution of grid points, which form basis of numerical gridblocks, is a challenging task. We show that this can be effectively achieved by generating a background grid that stores grid point spacing parameter. Spacing (X) can be described by Poisson's equation (∇2 L = G) where the local density of grid points is controlled by a variable source term (G). This source term can be based on... 

In the present research, the rising behavior of air bubble in a viscous liquid is investigated experimentally. Aqueous solutions of glycerol and CMC were used as the Newtonian and shear-thinning non-Newtonian viscous liquids, respectively. The bubble is formed via injection of air by a syringe pump and rises in the quiescent viscous liquid. The process was captured using a high-speed camera (1000 fps) and was post processed to obtain the bubble characteristics such as the center of mass and aspect ratio. The experimental results were verified using the existing literatures and the non-dimensional numbers were reduced to two (Velocity number and Flow number) by lumping the parameters. In... 

In this paper, a fully coupled numerical model is developed based on the X-FEM technique to simulate the reactive acid transport in fractured porous media. The porous medium consists of the solid and fluid phases, in which the fluid phase includes water and acid components, and chemical reactions can be occurred between acid component and solid phase at the solid–fluid interfaces. The governing equations include the mass and momentum conservation laws for fluid phase, and the advective–diffusive transport of acid component that must be solved to obtain the primary unknowns, including the pore fluid pressure, acid concentration, and fluid velocity vector. Applying the... 

Proppants transport is an advanced technique to improve the hydraulic fracture phenomenon, in order to promote the versatility of gas/oil reservoirs. A numerical simulation of proppants transport at both hydraulic fracture (HF) and natural fracture (NF) intersection is performed to provide a better understanding of key factors which cause, or contribute to proppants transport in HF–NF intersection. Computational fluid dynamics (CFD) in association with discrete element method (DEM) is used to model the complex interactions between proppant particles, host fluid medium and fractured walls. The effect of non-spherical geometry of particles is considered in this model, using the multi-sphere... 

In this study, the heat transfer and fluid flow characteristics of a three-dimensional microchannel that is partially filled with a layer of porous medium at its bottom solid wall is investigated. The microchannel is consisted of a clear fluid flow region, solid walls and a porous layer that is attached to its solid bottom wall. A constant heat flux is applied to the bottom wall of the microchannel. Darcy-Brinkman-Forchheimer model is used to simulate the fluid flow inside the porous medium. The novelty of this work is to investigate thoroughly and precisely the effect of using of porous layer configuration in MCHSs on hydraulic and thermal performances. The effect of porous layer thickness,... 

In this study, dynamic modeling of an elbow axially functionally graded (AFG) macro/micro-tube carrying magnetic flow with different cross-sections is considered. Parametric optimization is performed for vibration suppression of such fluid-interaction systems. Implementing computer simulations, passive vibration control procedures, along with the effect of AFG materials and magnetic properties of the fluid as well as precisely manufactured geometry of the system, is investigated. It is assumed that the material characteristics of the system vary in the longitudinal direction based on exponential and power-law distribution profiles. Influence of the downstream inclination angle and... 

Applying upscaling techniques is an undeniable demand in reservoir simulation, considering the difference between level of details in a geological model and level of details that can be handled by reservoir simulators. Upscaling reservoir model involves first constructing a coarse grid by employing gridding algorithms and then computing average properties for coarse grid blocks. Although various techniques have been proposed for each of these steps, one has to be aware of strengths and weaknesses of each technique before attempting to apply them. In this paper, we focus on different gridding methods and evaluate their performances. Three main grid generation techniques are considered:...