Sharif Digital Repository

The goal of this thesis is the development and application of the finite volume method (FVM) with a same solution procedure in the fluid and structure domains for the simulation of fluid-structure interaction (FSI) problems in the compressible fluid flow. The unsteady Euler equations written in the arbitrary Lagrangian–Eulerian (ALE) form are considered as the governing equations of the compressible fluid flow and the moderate/large nonlinear deformation of the elastic structure is considered to be governed by the Cauchy equations in the Lagrangian/total Lagrangian forms. Therefore, the nonlinear phenomena in the unsteady compressible fluid flow and the large deformation of the elastic... 

Helium gas is the working fluid in common Pulse Tube Refrigerators (PTRs) due to its brilliant properties in reaching cryogenics temperature as low as 4 K. Generally ideal gas equation of state has been used to evaluate thermodynamic performance of He. However using ideal gas equation of state for He in 10 bar and 5 K causes considerable error on estimation of density. The objective is to use real gas equation of state for temperatures near zero Kelvin. This approach makes an accurate prediction of PT cooling capacity and COP. In this thesis the objective is to realize the most relevant equations of state describing the proper behavior of He in the regions of operating point of PTR. Later on... 

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 study, the solution of compressible flows is performed using finite volume lattice Boltzmann method (FVLBM). A model associated with 13 discrete velocity vectors and 2 energy levels is used and the Boltzmann transport equation is solved using a cell-centered finite volume on structured meshes. The values of distribution functions on each cell faceare determined by averaging from their values at the two control points located on the center of two neighboring cells. The fourth-order Runge-Kutta time-stepping scheme is applied to discretize temporal derivative term. The second- and fourth-order numerical dissipation termsareadded to the algorithm to stabilize the solution when solving... 

The co-existance of rarefied and near-continuum flow regimes is widelyencountered in analyzing the multiscale flow problems, e.g., micro-and nanoflows. Previous investigations have revealed that the continuum-based simulation methods would suffer from the lack of accuracy to predict the rarefied flow regimes. On the other hand, the molecular simulation methods are not computationally efficient in simulating the near-continuum flow regimes. Therefore, the use of hybrid simulation methods has been recommended as a serious alternative to simulate the multiscale flow problems. These methods apply the molecular methods in solving the rarefied flow regions and the continuum methods in solving the... 

The fabrication of micron-sized instruments MEMS have been in fast progress in different fields of science and technology such as those of chemical processes in chemical engineering, propulsion in aerospace industries, microchip cooling and inkjet printers in electrical industries, and medical appliances in medical and biomedical science. They have forced the manufacturers and researchers to work and think in fabricating such small-scale sizes. However, the complexity of fabricating MEMS with moving parts has also promoted the manufacturers to think of alternative ways. For example the use of moving parts to pump fluid in such devises causes such difficulties and the researchers could adopt... 

In this thesis, a typical dynamic model of syngas fermentation, refered as hybrid method for biofuels production, coupled with a distillation column is developed in SimDFBA. The bioreactor is simulated in MATLAB/Simulink by using Clostridium ljungdahlii acetogenic micro-organism metabolic network. Bioreactor modeling is accomplished with a bubble column reactor in both liquid and gas phases, while the separator was simulated with ASPEN. PDE equiations of bioreactor modeing are dicretized to ODE equation by using QUICK scheme of finite volume method. A new econometric optimization study for outlet gas purification through a pressure swing adsorption unit to recycle relatively pure hydrogen is... 

In recent years, many advanced Computational Fluid Dynamics (CFD) methods have been developed for accurate and efficient simulation of fluid flow. The application of these methods shows that for sufficient accuracy, the mesh resolution has to be reasonably high. Unfortunately, conventioanal single-grid Navier-Stokes solvers suffer from poor convergence characteristics. For this problem we used Multigrid method to speed up the convergence rate. In this section a code was developed (based on the conventional CFD algorithm) which can solve Navier-Stokes equations on structured grids. It also simulates the free surface by VOF method. Agglomeration multigrid method is used in present study for... 

Numerical simulations of participating media need careful solution of the radiation transfer equation (RTE) along the fluid flow governing equations. Evidently, the accuracy of achieved solutions highly depends on the accuracy of radiation transfer calculations. Despite numerous efforts performed in the previous researches, the RTE calculation still faces with several challenges from both accuracy and computational cost perspectives. The main objective of this research is to present new contributions in overcoming such challenges. So, a finite-volume (FV) solver is suitably developed to solve the RTE numerically. This extended solver is then coupled with an existing FV flow solver. The... 

In this study, an arbitrary Lagrangian-Eulerian (ALE) approach is incorporated with a mixed finite- volume-element (FVE) method to establish a novel moving boundary algorithm to simulate unsteady incompressible flow on non-stationary meshes. The method collects the advantages of both finite-volume and finite-element methods as well as the ALE approach in a unified algorithm capable of solving laminar, transient, and turbulent flows in fluid flow problems with moving boundaries. To enhance the robustness of the extended algorithm, we treat the convection terms at the cell faces using a physical influence upwinding scheme, while the diffusion terms are treated using bilinear finite-element... 

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... 

Excited jet flow has many physical and industrial applications, e.g. in aeroacoustics and the combustion instability. Analysis of this type of flow needs an accurate simulation of flow dynamics. This work presents the large eddy simulation of this type of flow. The numerical method used in the large eddy simulation must have low numerical dissipation and high order of accuracy. Compact methods which satisfy these requirements and have high resolution of frequency, are favorable ones for the large eddy simulation. A fourth-order compact finite volume method which had been developed in the MSc thesis of the author is extended and completed in the present work. This extension includes 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... 

In the present study, the thermal behavior of human teeth during laser radiation has been discussed. The high laser power, as well as its low emission, can allow deviations from the Fourier heat transfer model. To overcome this problem, the non- Fourier heat transfer method, dual phase lagged (DPL), has been used. Wisdom considered in this study to evaluate the thermal behavior of tooth. Using the finite volume method, the DPL equations are solved and the thermal response of the teeth is obtained during laser irradiation. The effect of delay times, which are the parameters of the DPL model and depart from the Fourier model, is fully demonstrated on the temperature behavior of the tooth, and... 

Modern technology is accompanied by miniaturized devices. With increasing the use of micro satellites and micro airial vehicles (MAVs), finding new power-generating resources is inevitable. Batteries were always an option however high efficiency, long life-span and environmental consideration have encouraged the researches to focus on micro combustion. On the other hand, hydrocarbon fuel contains about 100 times more energy per unit mass than lithium-ion batteries. Micro combustion is defined as a combustion which is occurred bellow quenching distance and old literatures were uncertain about occurrence of such combustion. In this paper we present the fundamental concepts of micro combustion... 

The idea of using under water vehicles inspired by nature has gained considerable attention during the past few decades. This interest is due to the advantages of swimming and moving by this technique, in comparison with the conventional methods. Benefits are such as increasing speed, improved power, better manoeuvre ability,greater stability, optimal hydrodynamic performance ... etc. The purpose of this study was developing a model to simulate a stingray Manta Ray moving behaviour. Ansys- Fluent software was applied to solve the related equations of viscous laminar flow in 3-D form.Simulation of Manta Ray was performed with the flapping pectoral fin with dynamic mesh. Using this... 

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... 

In this study we investigated the stress effects on the fractured block in formation and its impact on flow through the matrix. At first the effect of various stresses on reduction of sample's pore volume and thereby reduction the permeability have been studied. The equations used to describe the elasticity relations in saturated matrix block is provided by Bayot theory. In this theory, the system of related equations to stress and strain changes have been developed in matrix. We have used finite element method in COMSOL software to solve the equation system created by elasticity relations in formation. After solving the equations, volume and volumetric strain changes which are caused by the... 

Rapid variation in permeability with strong anisotropy are common features in subsurface reservoirs. When formulating a finite-volume pressure equation scheme, continuous normal flux and pressure are key physical constraints that must be imposed at control-volume interfaces, across which strong discontinuities in permeability can occur.
The derivation of algebraic flux continuity conditions for full-tensor discretization operators has lead to families of efficient locally conservative flux-continuous control-volume distributed (CVD) finite- volume schemes for determining the discrete pressure and elocity fields in subsurface reservoirs [5, 9, 11, 13].
When applying these...