Sharif Digital Repository

Since coronary artery diseases are increasing every day, simulation of blood flow in blood vessels and their stenosis is one of the most important topics nowadays. Many efforts have been made to achieve numerical simulations using different methods such as Finite-Difference. In this thesis, an SPH method is used to simulate pulsatile blood flow in arteries. The weakly compressible algorithm consists of two steps of prediction and correction. In the prediction step, the velocity field is integrated forward in time without enforcing incompressibility. The correction step consists of enforcing incompressibility by solving the pressure Poisson equation which creates a trade-off between the... 

The gas flow field geometry influences the transport phenomena inside PEMFCs and hence affecting their overall performance. Radial force and secondary flows resulting from curvature of the spiral channels in PEMFCs can improve mass transport limits and so does to their overall performance. Studying the effects of curvature of spiral channels on fuel cell performance and comparing them with similar designs is the aim of this thesis. The geometries are generated using concentric Archimedes’ spirals and categorized as axial or radial depending on the direction of the vector perpendicular to their MEA . Each category has five geometries which are the result of branching the main channel into... 

In this research, a simple yet efficient two-dimensional model of proton exchange membrane fuel cell (PEMFC) is developed using stream function-vorticity formulation. The model accounts for the fluid flow and masstransport processes in cathode gas channel and gas diffuser layer. The governing equations are decoupled and solved usingtwo efficient approaches, Alternating Direction Implicit (ADI) and False Transient Method (FTM) in a modified geometry to simulate the fully-developed condition consistently. An in-house code was developed to perform a parametric study of fuel cell performance. The results show the variations of important parameters along the cathode channel such as velocity... 

Performance of Polymer Electrolyte Membrane Fuel Cells (PEMFC) at high current densities is limited to transport of reactants and products. Also at high currents, large amounts of water are gener-ated due to electrochemical reactions. Due to low temperature of PEMFC, some of the steam condenses. The amount of water existing in a PEMFC influences its performance. Shortage of water adversely af-fects cell performance by drying out the membrane. On the other hand, an excessive amount of water blocks pores of porous medium and transport of fuel becomes difficult.
In order to predict flooding and its effects on the PEMFC performance, development of a two-phase flow model is necessary. In this... 

In this thesis, an Incompressible SPH (ISPH) method is used to simulate suspensions. A suspension is assumed to be a mixture of solid particles in a Newtonian fluid. First, renormalization tensors are applied to the discretized equations of SPH method. This leads to a higher accuracy in this method. It should be noted that the projection method is used for ISPH. After that, the Immersed Boundary Method (IBM) is used to model and simulate the presence of solid particles in fluid flow. Some modifications were necessary to use IBM with Lagrangian approach. Then, some benchmark problems are solved to validate the presented method. The main objective of the present thesis is simulation of... 

Innovations in laser, microwaves, and similar technologies have significantly advanced thermal treatments for diseases or even injuries concerning skin tissue. For a thorough understanding in the underlying mechanisms of bioheat transfer behavior of skin,a1D unsteady non-dimensional hyperbolic model of heat transfer through this tissue with metabolic heat generation which is subject to specific boundary conditions, is solved numerically using the finite difference method. A thermal shock is generated at the base of the tissue, which moves forward with a finite speed. A Numerical solution for a simple one-layer skin tissue is obtained. Then, the effects of various parameters, time step,... 

In this work, simulation of 3D three-phase naturally fractured reservoirs is studied. Both Dual Porosity and Dual Porosity-Dual Permeability models which are commonly used in commercial softwares such as ECLIPSE and CMG, are utilized. The governing equations include the mass (in Black-oil model) and linear momentum (in Darcy law form) equations, which are converted into pressure equations and a set of transport equations for the saturations and mole fractions of phases. These equations are solved once for the matrix domain and subsequently for the fracture domain. These two set of equations are coupled through transfer functions. The accuracy of computations significantly depends on how... 

The main goal of this study is simulation of the flow-like landslide phenomenon and investigation of the effect of bed material entrainment on its behavior. Debris flows are considered as one of the types of flow-like landslides, and flow of dry granular materials on horizontal and inclined beds as a simple model of these types of flows in nature is numerically simulated. Also, in order to investigate the effect of entrainment on dynamics of flow, a bed containing granular materials is installed on horizontal and inclined beds. The governing equations of the flow are solved in the continuum context using the Smoothed Particle Hydrodynamics (SPH) method and the depth-averaged assumptions are... 

In This work, the performance of a finite volume (FV) numerical method is examined for simulating naturally fractured hydrocarbon reservoir. The dual-porosity approach applied for fracture modeling, and the flow transfer formulated based on a generalized black oil model which is based on matrix formulation, leading to a system of equations prone to degeneracy. This FV high-resolution central scheme numerical method is not sensitive to the choice of CFL number like some of other central schemes and can conveniently handle degenerate equations appearing in the reservoir simulation governing equation. In this effort, one dimension multi phase flow simulated in naturally fractured reservoir and... 

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... 

This study presents an integrated two-dimensional numerical framework for simulating rainfall-induced landslides from instability initiation to post-failure flow. The discrete element method (DEM) is used to establish a rheological model that relates the apparent viscosity of a granular sand to shear rate, normal stress, and water saturation. A theoretical model is developed to determine water distribution and water-induced forces between particles for different saturations. The resulting forces are embedded in a 3D shear cell as a numerical rheometer and a wet sand is sheared between two walls. A power law rheological model is obtained as a function of inertia number and saturation. It was... 

Iran is one of the biggest suppliers of oil in the world. Iran's economy highly depends on its oil. Iran has valuable old reservoirs that need some techniques to optimize their production of it.Determining optimal well placement and control is essential to maximizing production from an oil field. The reservoir optimization problem is an extraordinary complex problem that depends on many factors such as flow pattern, well specification, reservoir properties, and environmental and economic criteria. Finding the locations of injection and production wells and other optimum operational parameters in the oil industry are very important and have a great influence on the operation of the... 

One of the methods of measuring the flow rate in a pipe (channel) is by using the acoustic waves with long wavelenghs in Sonar flowmeters. This flowmeter consists of an array of sensors, mounted on the outer wall of the pipe. These sensors by listening and interpreting the sound waves passing through the fluid, would give a “non-intrusive” measurement of the volumetric flow rate. This means that the flowmeter is not in direct contact with the flow and therefore its repair, relocation or replacement will not disturb the flow. In this project, we will provide a clear understanding of the principles and physics involved in sonar-based acoustic flowmeters, by means of numerical simulation of the... 

Measuring flow rate in various industries is an operational challenge that requires to be accurate and fast to avoid wasting energy and money. Various flowmeters are employed in different industries using different principles and methods. Sonar flowmeters are one of the acoustic methods of fluid flow measurement, which do this by listening to the sound of the flow via arrays of sensors. Sonar flow measurement can be achieved by finding either the convection velocity of eddies or the speed of sound in the fluid. The first method is suitable for measuring single-phase flows, which is the subject of this thesis. This method needs a detailed study of turbulence. In the present work, this is...