Sharif Digital Repository

In order to improve the efficiency of atriums, effective parameters in ventilation and acceleration of airflow are numerous. Nevertheless, parameters such as shape and height of atrium, geometry of the inlet and outlets, opening areas and the presence of heat sources in each store play a vital role. In structures higher than one floor, there is no significant airflow in the upper floors and the ventilation of atrium is unpleasant for residents. Air movement in the building is done by buoyancy-driven force and hot air upward movement due to pressure differences.This study attempts to improve the natural ventilation performance with changing mentioned parameters. So for this purpose, 3D... 

In this thesis, we studied the oscillation of neutrino flavors and the measurement of mixing parameters through the detection of cosmic neutrinos at neutrino telescopes. Most of the astrophysical explosions predict the emission of neutrino flux and kilometer-scale detectors are under construction for the observation of these neutrinos. Detection of astrophysical neutrinos opens a new window to understand the neutrino properties and also the properties of astrophysical sources.In this thesis first we review the phenomenology of neutrino flavor oscillation and characteristics of neutrino mass matrix. By introducing a new class of invariants (under general transformation of lepton fields bases)... 

Neutrino flavor oscillations are clear evidence of massive neutrinos. It has been for more than a decade that neutrino physics became one of active topics in the field of particle physics and various experiments started studying the flavor oscillation of neutrinos. Unfortunately, experiments studying the flavor oscillations are only sensitive to the mass square difference, and they are incapable of providing more information about the absolute mass scale of neutrinos. Additionally, sterile neutrinos having non-standard interactions are under vast investigations and studies. Determination of neutrino masses and their effective number is among the most challenging problems by which... 

Today with growth of wireless communications and progress of small and cheap sensors which have capability of communication and calculation, wireless sensor networks are important and useful topic. But due to energy restrictions, efficient use of resources and increasing network lifetime, have been considered as key factors in network design. In this regard, using efficient multicast routing in energy consumption, for an efficient data transmission to specific number of nodes instead of all nodes code updates, information requests, task assignments and etc., is necessary.On the other hand these networks use unlicensed spectrum and suffer from collision due to congestion caused by other... 

Since the Iranian oil terminals company(I.O.T.C.) has been the main and strategic gateway of exporting petroleum in the country and plays an important role in the optimum continuity of national, regional and international energy supply chain and also conducting the needed projects whit a desirable quality and minimum time and cost has a prominent influence on steady continuity of manufacturing, importing and exporting of petroleum and gas production. The main purpose of doing this thesis is diagnosing the process of approval, design and implementation of projects in the I.O.T.C., Thus, whit regarding to the modern needs of implementing projects and the necessity of reviewing the structure... 

In this research, droplet motion in symmetric and asymmetric junctions in micro and nano scales was investigated. Droplets motion in symmetric and asymmetric junctions have many applications in many industries such as chemical and pharmacy. In this research symmetric T-junction in micro and nano sizes was simulated numerically in 2D and 3D formes. Also asymmetric T-junction (with unequal width branches) was simulated numerically in two cases, 2D and 3D. In the asymmetric T-junction, also an analyrical theory was developed. Numerical simulation was performed by using VOF techniqe and analytical theory was developed by thin film theory. For verifying the accuracy of numerical solution, grid... 

We studied dynamics of droplets inside channels under surface forces created by chemicalsteps on the channel walls. A multi-component Shan-Chen lattice Boltzmann method isused for this purpose.The effects of parameters such as the channel height, viscosity anddensity ratios on the results were investigated for homogeneous and grooved substrates. Alsoan analytical solution was developed for droplets under chemical heterogeneities in channels with smooth surfaces. The solution considers a general condition, namely, asymmetry of the contact angles on the top and bottom walls, the viscosity of the gas as the second fluid and the effect of the channel height. Then using Shan-Chen lattice... 

Hydrodynamic mesoscopic equations are solved using boundary integral method to investigate the coarsening dynamics of two dimensional nanodroplets. The dynamics is probed by locating two drops on homogeneous, chemical heterogeneous and physical heterogeneous substrates respectively. For homogeneous substrate, the effect of different parameters like droplets distance, slip boundary condition, surface contact angle and disjoining pressure type on the dynamics is studied. Results reveal that increasing the contact angles to values larger than a critical value may qualitatively change the coarsening process and the profile of the disjoining pressure can appreciably modify the coarsening rate.... 

A droplet placed on the boundary of two solids with different wettabilities will move to the more wettable part. This is a well-known phenomenon and has been extensively used in a variety of processes and applications ranging from biological systems and ink jet printing to the commercial lab-on-a-chip. Because of its importance, many studies are conducted around this phenomenon. The difference between the equilibrium contact angles of the droplet on the two parts gives rise to an interfacial driving force which moves the droplet. Such a motion is not continuous as the droplet slides to the more wettable area, the driving force diminishes and consequently the droplet stops. A non-stop motion... 

Mesoscopic hydrodynamic equations are solved employing a VOF based method to investigate the equilibrium shape of nanodroplets positioned over various topographic geometries of the supporting substrate for three-dimensional systems. By taking into account liquid-liquid and liquid-solid interactions a complex distribution for inter-molecular forces over the substrates (the disjoining pressure) is observed. In this research we show that motion of nanodroplets not only caused by contact angle difference in drplets two sides, but also depend on disjoining pressure parameters.Geometries with increasing complexities, from wedges to three dimensional edges and wedges, were explored with the main... 

This research concerns investigating the behavior of two-phase flow in the inlet and outlet of the microchannels.Both the droplet based and the continuous microfluidics are considered. For the continuous system whenthe minor fluid enters the microchannel, due to ratio of viscosity of two fluids, viscous folding occurs.Viscous folding phenomena is similar to the buckling phenomena in solids.This means that the viscosity of the fluid, which is applied to two sides of the fluid layer, causes folding the fluid layer and changing the shape of it. For the study we employ a VOF based numerical routine. In order to verify numerical results, the grid and the time step independenciesare checked. In... 

Carbon Nanotube webs exhibit interesting properties when used as thermo-acoustic projectors. This work studies thermo-acoustic phenomena of these sound sources both in near and far field regions. Our three-dimensional simulation and experimental data show pressure waves are highly affected by dimensions of sound sources in near field due to interference effects. Although pressure amplitude increases with increasing frequencies, maximum pressure amplitude reached in lower frequencies may become larger than its maximum amount at higher frequencies because of interference effects. Measurement of different surface area sources shows generation of sound waves in far field is independent of... 

Drag reduction on surfaces always has been a great case of study, especially in transport industry. This project discusses the external laminar flow of a single-phase fluid over a flat plate and the effects of making rectangular tiny grooves - in micron or millimeter - on them to reduce total drag. Making grooves with appropriate geometry on surfaces causes the fluid-solid contact area on the groove's surface turn into fluid-fluid and as a result the fluid will not shed into the groove. In other words the flow instead of having a no-slip boundary condition on inner surfaces of the groove, creates vortices in them that causes a remarkable reduction in velocity gradient followed by a skin... 

This project studies the effects of different blade and different velocity fields on reducing drag coefficient. A numerical simulation was set up for a circular cylinder to represent the effects of blade on reducing drag. In this study, velocity, density and the cylinder diameter were constant and different viscosities were selected for different regime flows. The computational fluid dynamic programmer FLUENT was used to simulate results for this project. Arrays of cylinders were set up to see the changes in velocity profiles and drag coefficients for a range of Re. In this study, I studied three cases of setting up blade and concentrated on friction drag coefficient and pressure drag... 

Carbon nanotubes have special thermodynamic properties which makes suitable as a thermo-acoustic sound source. Recently it is shown that by using these nanotubes it is possible to generate strog sound waves in air or water. Experimental analysis of phenomenon can be complicated and expensive. Hence this fact, in this study using molecular dynamic simulation, numerical analysis of sound generation with CNTs in air and water is discussed. For this purpose, the required structue of the system is generated and it has reaced equilibrium. This process has been done for 6 different CNT and for each CNT there are 5 different distances between them. Althogether, 30 different cases has is used for... 

Investigation of transport and deposition of aerosol particles has been of interest to researchers in many branches of science. Various numerical and experimental methods has been utilized in particulate fluid flows studies. In recent relevant researches lattice Boltzmann method has been widely used and is reported to be a robust and efficient method. In present study, numerical investigation of dispersion and deposition of aerosol particles is studies in the channel, containing elliptical obstacles geometry using Lattice Boltzmann Method. Fluid flow simulations are performed using LBM while for the study of particle transport and deposition, tracking and the motion equations of them,...