Sharif Digital Repository

Two phase slug flow often happens in culvert and water tunnels conveying water from dams and weirs. Having complicated hydraulic properties, little is known about different hydraulic properties of this kind of flow, while most of the previous studies deal with other liquids than water and air, mostly dealing with chemical and mechanical engineering problems. In this paper, the results from experimental study of air/water slug flow due to changing in slope of the conduit from horizontal to 2, 3 and 4% are presented. The conduit has rectangular cross section with dimension cm of Plexiglas material and inclined part. Air is added to the system upstream of the conduit using an air discharge.... 

Vortex engine has shown to be a credible substitute in thermal power and aerospace industries mainly due to their advantages such as better mixing, improved combustion, and considerable cooled walls of combustion chamber. The engine geometry and tangential inlet oxidizer create inner and outer vortices rotating in the same angular direction. The inner vortex moves from head to the end of engine in the axial direction and outer vortex moves in the opposite direction. In the vortex engine, vortices affect spray droplets and force them to have a spiral path and apply a centrifugal force on the droplets to push them towards sidewall. Also axial relative velocity of droplets and flow filed act as... 

Having an efficient and reliable system for oil-water separation is of crucial importance in oil and gas industry. Hydrocyclones have been used for more than a century to separate oil from water as well as sand from liquid or gas. The main objectives of this research are as follows: Determination the hydrocyclone principle of operation, based on computational fluid dynamic simulations. Hydrocyclones, in a spite of simple structure, are widely used in industry such as Petrochemical, Mining, Chemical Industries, Pharmacy, Food and Pulp Industries. The CALC BFC is one phase flow numerical code based on finite volume method and SIMPLEC algorithm. It was extended for simulating the two phase flow... 

Two-phase flows are widely used in petrochemical industry, chemical processes, boilers, nuclear reactors, cooling systems and air conditioning equipment. Since the problem of earth’s ozone layer and global warming, the analysis of flow characteristics in evaporators are necessary to improve performance of refrigerating systems and saving the environment. Most of the researchers have been studied the evaporation of two phase flow refrigerant through experimental studies and numerical analysis has less attention in the literature. In this Thesis, a mathematical model based on the two-phase separated flow model is developed to simulate the evaporation of pure refrigerant under constant heat... 

Based on the air entrainment, the water conveyance tunnels can be categorized as pressurized, two-phase flow. When the flow is controlled by gates, sudden closure of gates would produce unsteady two-phase flow. The most important effect of such an event is the sudden change in the pressure which can be a function of channel slope, air and water inflow and their ratio. In this thesis the pressure change in unsteady two-phase in an experimental set up using rectangular tunnel is studied. About 100 tests were carried out for single and two-phase flow with various water and air discharges causing unsteady flow with different slopes. It was observed that in a defined slope the ratio of the... 

Relative permeability is an important factor that controls the two phase fluid flow in porous media. The use of carbon dioxide in enhanced oil recovery methods is common. But the question is, how does the carbon dioxide affect the relative permeability curves? In this thesis, the CO2-oil relative permeability is measured in CO2 flooding process with unsteady state method. For this purpose, the core flooding apparatus is used and the results are compared with N2-oil relative permeability in N2 flooding. The results of comparison show that oil relative permeability in CO2 flooding is higher than N2 flooding. Reduction of Interfacial tension and oil viscosity, solubility of CO2 in oil and oil... 

Liquid-liquid extraction is one of most important processes in chemical industries. So determination of operating condition effects is very critical. In this thesis we modeled concentration profile in the jet via mathematical equations and compare with experimental data. The major problem in concentration profile and solving equations is lack of knowledge in velocity profile within the jet was formed. Therefore, different flow models such as piston flow model, parabolic flow model, vortex flow model and a cone flow model was used and terminal concentrations inside the jet compared with laboratory values. Results shows the most accurate model to predict the flow concentration along the... 

Reduced-order modeling (ROM) is a novel approach in all realms of computational science including reservoir simulation. Among various ROM methods, Trajectory Piecewise Linearization (TPWL) is on its evolution for reservoir applications. Previous investigations reflect promising future for incorporating TPWL into the next generations of enhanced reservoir simulators. In this work, we employ TPWL to investigate the claimed efficiency, robustness and accuracy of this method as a surrogate simulator for a developed reservoir simulator. The self construction of the used simulator gives us the opportunity to explore this method and to examine previous assertions on the subject. The efficiency of... 

The phenomena of formation and detachment of droplets are of fundamental importance in studying two-phase flows, such as spraying processes, ink jet printing, emulosin, etc. Droplets are formed under the effects of surface tension forces. After formation, forces like gravity detach the droplet from the rest of the fluid. Recent advancements in computational fluid dynamics and computers have made it feasible to have advancement in simulation of complex flows, including two-phase phenomenon. On the other hand, the lattice Boltzmann method (LBM) has been developed into an alternative and promising numerical scheme for simulating multi-component fluid flows.
In this project, formation and... 

Numerical simulation of air-water annular two-phase flow in a tube is carried out by using level set method for determining position of interface between two phases. Governing equations include continuity, momentum and level set equations that considered for each phase. The finite difference scheme is used to discretize the differential equations. The SIMPLE algorithm is adopted to solve the discretized equations for linking continuity and momentum equation. An unequally spaced staggered grid size for flow field is adopted. The Level Set method is used to capture interface position between two phases. To increase the accuracy of solution at level set equation, 5th order finite difference and... 

Designers consider formation of slug flow in pressurized pipes because of hazardous effects of this flow pattern. Therefore, researchers, using different methods, attempt to study formation of slug flow and its effects. For numerical simulation of this phenomenon, In spite of existence of commercial 2D or 3D two-phase models, numerical models used for the slug flow modeling are 1D. In this thesis, a 2D model has been developed to simulate the initiation and formation of slug flow and estimation of the effects in pressurized pipes. Most important assumptions used in this model are existence of turbulence, surface tension and air compressibility. Isothermal condition has been supposed for... 

The phenomenon of vortex flow, is one of the most predominant streams in the nature. This phenomenon yielded by the motion of vortices, produces up to 1000 times acceleration of the Earth’s gravity. The issues of uncontrolled harvesting of oil wells and increase the life of the wells, which cause to increase in the extracted crude salt, reveal the importance of waste management and both handling and refining petroleum. According to global statistics, for every extracted barrel of oil, three barrels of water are yielded. Therefore, 250 million produced water barrels per day is produced.The separator technology with vortex core (brand Voraxial) is one of the latest technologies in waste-water... 

One of the important issues that increasing development of electronic systems has caused is how to transfer the generated heat out of the system. Heat pipes can transfer large amount of heat because of using latent heat of evaporation and condensation. In micro scales using micro heat pipes is popular that in this instrument liquid returns to evaporator by means of surface tension force. So numerical solution is essential for verifying experimental results and increasing performance of this instrument. In this research has been planned to develop a comprehensive model for numerical solution of flow and heat transfer in micro heat pipes. For this reason surface evaporation and …,... 

In this project, a response of a single well in a gas condensate reservoir has been investigated by compositional modeling and implicit numerical method. The most significant goals of this paper are as follows: 1- Examination of the flow produced in a gas condensate reservoir in constant pressure or mass rate. 2- Investigation of variables affecting the productivity of reservoir. 3- The study of effect of injection and gas cycling to the well on the production. A three-zone model has been used in this study as if there is only gas phase in the third and second zones. Condensation occurs since the pressure drops below the dewpoint pressure in the second zone; however, gas phase is only... 

Continuous separation processes in microfluidic devices experienced a steep rise in attention during the last two decades. Among the different separation processes, liquid-liquid extraction especially benefits from the short molecular diffusion distance and large specific interfacial area, as these are advantageous for effective mass transport. In the present study, glass-based microfluidic devices have been fabricated utilizing laser ablation and wet chemical etching methods then experiments and numerical simulation were carried out to investigate hydrodynamic behavior of fluid flow in Y-junction microfluidic. In order to achieve phase separation at the end of the microchannel, a phase... 

In this thesis, two types of two-phase flow are studied in one dimension. The first type is oil-gas two-phase flow which is miscible and compressible. The second one is oil-water two-phase flow which is immiscible and incompressible. Oil wet and water wet conditions are studied in the second type of flow. Two approaches, i.e. double porosity and double porosity-double permeability, are used to study naturally fractured reservoirs. In these approaches, the matrix and fracture are modeled as two separate media that exchange mass via a transfer function. Black oil model is applied to simulate the fluid system. The governing equations consist of the conservation of mass equations for each... 

Study of two-phase flowin porous media forms a basis for investigating various fluid systemsin the nature and industries. In recent years, more and more researchers use pore-scale mod-els to explore various physical phenomena occurring in complex media such as hydrocarbonreservoirs. After solving the flow equations in pore-scale, this approach can be utilized tocalculate some macroscopic values using particular forms of averaged flow field.In this research, Smoothed Particle Hydrodynamics (SPH) is used to simulate two-phaseflow in pore spaces of two- and three-dimensional porous media. The SPH method is a La-grangian meshless method that is suitable for flows with free surfaces, deformable... 

Slug Flow is one of the most important schemes of two-phase air/water flow, which is quite complex and quite different to a single-phase flow. Also one of the common water conveyance systems is a rectangular tunnel which may have adverse slope at some parts of the tunnel. In this study the hydraulic of slug flow in rectangular tunnels with variable slope from horizontal to adverse have been considered using experimental setup. About 150 tests were carried out for different air/water discharge ratios and adverse slopes, and dynamic pressure fluctuations together with the slug period were measured. It was observed that the pressure fluctuations increase as the air to water ratio increases and... 

Fluid flow in porous media is a common phenomenon in the nature, in many fields of science and engineering such as flow of water in the soil, migration of contaminants in the soil, petroleum reservoir engineering, semi?olten magma flow in the crust, water flow in plants, blood flow in body tissues, etc. In many cases, the porous structure of the medium and fluid flow pattern are very complex because of the inherent problems of fluidAluid and fluidsolid interactions. Also, secondary issues such as intrinsic permeability and tortuosity of porous media, and relative permeability of two phase flow, increase the complication of the analyses. Studying these types of phenomena in the nature or even... 

The main purpose of this work is investigation of coolability of a boiling debris bed. The main governing equations are derived using volume averaging technique. From this technique some specific interfacial areas between phases are appeared and proper relations for modeling these areas are proposed. Using these specific areas, a modification for the Tung/Dhir model in the annular flow regime is proposed. The proposed modification is validated and the agreements with experimental data are good. Finally, governing equations and relations are implemented in the THERMOUS program to model two-phase flow in the debris bed in the axisymmetric cylindrical coordinate. Two typical configurations...