Sharif Digital Repository

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... 

In the this study, a numerical simulation of two-dimensional incompressible sloshing flow in a rectangular tank with baffle(s), using Lattice Boltzmann Method (LBM) is presented. Finite difference LBM and two-phase "Lee" model were used. The potential form of intermolecular forces is utilized to guarantee the stability of the numerical scheme and the discretization of the solution domain is performed by a two dimensional structured grid. Two different distribution functions are applied to obtain pressure, momentum, and composition of the particles. Furthermore, the Boltzmann transport equation is discretized, by using standard D2Q9 method. The "dropl" test case is simulated by the present... 

Numerical simulations and large eddy simulations (LES) of turbulent flow downstream of diversion dam , pool-riffle bedform in different geometrical ratios (different lengths of riffle and pool) with flow Reynolds number of 3.0 E+04 to 3.3E+04, downstream of special case study "Mill and Moghan diversion dam" with Froude number of 0.5 are presented The calculations are performed using a computational fluid dynamics model, FLOW-3D, which solves the Navier-Stokes equations in three dimensions with finite volume method. Numerical simulations are validated by comparing the numerical results of time-averaged flow patterns downstream of pool-riffle sequence with that of the experimental... 

In the present work, the experiments were carried out for two types of PAM (3330 and 3630) with three distinct concentrations (25, 40 and 55 ppm) and TiO_2-water nanofluid for four concentrations (1.5, 2, 2.5 and 3 vol. %), and the Nusselt number and friction factor for each of them expressed separately. The Reynolds number was in the range from 11000 to 21000. The steady state turbulent convective heat transfer and friction factor of the combination of TiO_2-water nanofluid and polymer 3330 in the coiled tube were investigated. The effects of the Reynolds number for 2 vol. % nanoparticles which consists of 25 ppm PAM (3330) determined at the constant temperature of 24°C. It was observed... 

This work numerically simulates pressure drop and heat transfer for flow in a pipe with porous wall. Incompressible two dimensional, ax symmetric laminar or turbulence flow with constant mass flow rate is considered. It is assumed that there is no thermal equilibrium in the porous media region between solid and fluid phase. Effect of porous wall thickness and Darcy number on the rate of heat transfer and pressure drop were investigated. The Darcy number varies from to and porous wall thickness can fill entire pipe. the turbulent model is used to calculate the fluid flow and heat transfer characteristics in turbulent flow. Nusselt number can enhance about ... 

Study of fluid flow through the porous fractured media is used in many branches of science such as oil production, environment, water resources, geotechnics and mining, and the results of these researches are useful for industries.The porous fractured media consist of two main parts each having different roles. The first is the fracture networks that act as channels to conduct the fluid in the media, and the second is the porous media that act as a storage space for the fluid. The differences of dimensions and ability of fluid conduction between these two parts would cause the flow analysis to be performed in a heterogeneous and non-isotropic media. Moreover, the irregular networks of... 

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 study, the numerical simulation of turbulent flow using Open Source software OpenFOAM, The impact of air flow around the high-rise buildings and classification based on the height and arrangement of the buildings has been against the flow. Numerical method used, the finite volume method uses a piso algorithm, Navier-Stokes equations are solved and the speed and pressure can be obtained. Large Eddy Simulation model is a simulation model used in this software. In general tall buildings against wind loads has three types of move, move along the wind, prependicular along the wind and the twisting motion that occurs at the same time, they are, but, due to the variable nature and... 

In this thesis, by focusing on the hydraulics of three phase flow in vertical tubing to investigate asphaltene deposition problem, the solid particles behaviors in a turbulent flow is fully studied. Reasonable size distribution for particles (based on previous works and researches) was assumed and a model for 2 sections of a Marrat oil field well to evaluate their asphaltene deposition problem was developed. Three phase liquid-gas-solid flow in the well tubing was simulated. Asphaltene deposition profile on the well tubing, mean and maximum of the deposition rate and particle concentrations in the flow regime were calculated and compared with real field data. Better agreement with field data... 

Research on convective heat transfer coefficient around a rod bundle has several applications in industry. So far, many studies have been conducted in correlations related to internal fully developed flow. By comparing Dittus-Boelter, Sieder-Tate and Petukhov found to be more practical. The present study examines the validity of these frequently applied correlations experimentally. A thermohydraulic loop has been designed and manufactured to test and measuring the convective heat transfer coefficient. Due to its generalizibility, the unique geometry of this test facility (hexagonal arranged, 7 vertical rods in a hexagonal tube) has achieved extensive application. The major deviation factors... 

Vibration is one of the major problems in gas and oil pipelines. Vibrations can cause damage to the pipes, supports, valves and other equipment installed in the system. These vibrations can be caused by equipment installed on pipelines like compressors and pumps or by fluid flow in pipes and fixed equipment like connections and valves. This research investigates the dynamic behavior of fluid flow in pipelines in Karanj and Parsi oil fields located in the southern part of Iran. The pipeline is responsible for injecting gas into the field. Excessive vibrations in the system cause repeatable damage which in turn increases the operating and maintenance cost. First, the vibration of pipelines has... 

In this study, a new finite-element-volume (FEV) arbitrary Lagrangian-Eulerian (ALE) method is suitably extended to simulate the three-phases flows air, liquid water droplets and ice in ice accretion, i.e., over flying object surfaces. This methods benefit from the advantages of both finite-volume and finite-element methods. This method is developed for the first time to simulate three phases turbulent flows. Since the ice formation and growth needs grid movement consistant with ice boundary movement, we have used ALE approach to fulfill this requirment. In this regard, we use the linear spring analogy approach to move the hybrid triangular-rectangular mesh suitably. Facing with a chaotic... 

As a result of fission reaction in a nuclear reactor, the produced high neutron flux would affect the material of Reactor Pressure Vessel (RPV). This neutron radiation has a detrimental impact on the mechanical properties of the RPV material such as hardening (or embrittlement) while neutrons are absorbed by the material. A major concern in embrittled RPVs is propagation of critical flaw causing through-wall cracks. Some transients leading to overcooling of RPV intensify the propagation of theses cracks and result in thermal load on RPV, known as Pressurized Thermal Shock (PTS). Such situation could be created in case of Emergency Core Cooling System (ECCS) actuation which leads to injection... 

In this thesis velocity and temperature fields of concentric cylinders with rotation of inner wall have been investigated numerically. Air enters the gap between cylinders and attains fully developed in both velocity and temperature fields after certain lengths. Adiabatic and constant heat flux boundary conditions have been applied and Nusselt number was calculated. In order to analyze the variations of velocity and temperature fields, different angular velocities at constant axial Reynolds number and different axial velocities at constant angular velocity have been investigated. The turbulent stresses were approximated with k ?? ... 

In the present study, an incompressible smoothed particle hydrodynamics based on the artificial compressibility method is applied for simulating the incompressible turbulent flows. The Reynolds-averaged incompressible Navier–Stokes equations using the artificial compressibility method in the Eulerian reference frame are written in the Lagrangian reference frame to provide an appropriate incompressible SPH algorithm for the turbulent flow computations. Here, the k-L_m turbulence model, which is a simplified k-ϵ turbulence model, is used and formulated in the Lagrangian reference frame. The SPH formulation implemented here is based on an implicit dual-time stepping scheme to be capable of... 

In this thesis the steady state convective heat transfer for turbulent, two-dimensional, incompressible gas flow in a circular microchannel under slip flow and temperature jump conditions is numerically investigated by means of finite volume scheme. The low Reynolds number k-ε turbulence model is employed using a new boundary condition for turbulent kinetic energy at solid surface. To calculate variables at control volume surfaces in the axial direction upwind differencing scheme and in the radial direction central differencing scheme are used. Rhie-Chow interpolation technique is used to prevent pressure field oscillations. The set of discrete equations are solved using SIMPLE Algorithm. In... 

Nowadays, hybrid LES/RANS approach is being widely used by many researchers. This approach uses the advantages of both LES and RANS approaches simultaneously. Hybrid approach is as accurate as LES, but its cost is much lower. The biggest problem of hybrid approach is transformation of data between RANS and LES regions. Before, precursor simulation and synthetic methods, such as Fourier series and synthetic eddy methods (SEM) have been used extensively to solve such problems. Precursor simulation is expensive, because of high cost of generation of data. On the other hand, Fourier series method is confined to simple geometries, while SEM has problem of programming. Interface condition in this... 

Today energy sources, in any kind, have their special situation in human’s life and we must use our knowledge to manage them for effective usage by decreasing losses and finding modern renewable sources. One of the best way to achieve this purpose is increasing efficiency and improve energy generator performances under different environmental conditions. In spite of the fact that wind turbines stall dynamics behavior is under investigation for 6 years, study of dynamic stall phenomenon especially over series blades still needed. By addition to this phenomenon, improper wind turbine arrange decreases efficiency too. As a matter of fact, scrutiny of dynamics stall of wind turbines serial... 

In the present study, the numerical simulation of incompressible laminar and turbulent flows using a high-order finite difference lattice Boltzmann method is presented. To handle curved geometries with non uniform grids, the incompressible form of lattice Boltzmann equation is transformed into the generalized curvilinear coordinates and the spatial derivatives of the resulting equation are discretized using the fifth-order WENO scheme. The advantage of using the WENO-LBM developed is that it needs less number of grid points and remains stable even at high Reynolds number flows. For the temporal term, the fourth-order explicit Rung-Kutta scheme is adopted for laminar flow calculations and... 

In this study, the performance of the Moss-Brooks semi-empirical model in estimating soot for six different diffusion flames with methane, ethylene, and kerosene fuels in laminar and turbulent regimes has been investigated. The results show that the model with the default constants in the laminar ethylene flame has relatively acceptable performance, but in the turbulent ethylene flame as well as the laminar and turbulent flames of methane, has a significant error. In this regard, inspired by past research and performing sensitivity analysis, the constants of oxidation and coagulation sub-models were reviewed and Improved. The results of soot volume fraction were evaluated for values of 0.015...