Sharif Digital Repository

Progress aerodynamic and structural applications has lead to solid-fluid interaction (SFI) engineering. One major application of SFI is to improve of aerodynamic characteristics of airplanes. One option is to use elastic shells.this field of study is so novel and a challenge for future researches. This what current thesis is focused on We use numerical simulation in both fluid and solid parts.In other word, we employ the finite –element method to solve the solid mechanics governing equation and the finite volume element method to treat the fluid dynamics governing equations. The fluid governing equations are 2D navier- stokes equations and the solid part is the 1D Euler – Bernoulli equations... 

With the rapid development of mico-nano propulsion systems in micro-spacecrafts and micro-sattelites, precise investigation of flow field in these devices has become necessary. Micro propulsion systems usually have a thrust in order of mili Newton, and they can be used for maneuvers of spacecrafts with mass of less than 10 kg. Micro propulsion systems are usually classified according to their thrust generation mechanism to different classes like cold gas, and chemical propulsion systems. Cold gas micro propulsion systems obtain their energy from thermodynamic expansion of gas and not by combustion. If the flow fiel dimensionare comparable to mean free path, rarefaction effects are observed... 

Novel manufacturing technologies in micro scales, such as micro machining, guide us through constructing micro scale systems known as MEMS. These systems have a wide range of applications, from fabrication of electrostatic, magnetic, pneumatic sensors and actuators to micro mechanical gears and motors. Also, MEMS applications involve the manipulation of one or more fluids, known as microfluids. Simulation of flow through microchannels over nano particles has important applications in solid particles transport. In this flow, the rarefaction phenomenon will affect the flow behavior and its subsequent impacts such as aerodynamic drag forces. In this work, we use the Lattice Boltzmann method... 

Hydrogen fuel cell is one important choice to supply energy for vehicles in near future. The lack of a safe but inexpensive technology to store hydrogen in a vehicle tank is a serious challenge to commercialize the application of fuel cells. Past experiments have shown that carbon nanostructures, especially single walled carbon nanotubes, have considerable capacity to boost up hydrogen storage. Therefore, many studies have been performed to investigate the possibility of higher hydrogen storage capability using nanostructures for the past decade. Molecular dynamics method which is considered as one of the most important tools in studying nanostructures has shown vast applications in these... 

A global rotating atmosphere with polar vortex and super rotation is simulated using a simplified Venus General Circulation Model (GCM). The polar vortex is maintained strongly by meridional circulation develops in the form of a simple Hadley cell, extending from the equator to the pole in both hemispheres and rotation terrestrial planet. Venus Total Polar Vortex Parameter (PVP) was defined like globally integrated super-rotation but at polar skullcaps (60-90 deg). Venus Polar Vortex Parameter is PVP=1.5 that’s qualitatively similar to observed polar vortex. Then with study in terrestrial planet and Titan modeling, we appointed the Polar Vortex Parameter and critical limit of Polar Vortex... 

With a fast progress in nanotechnology devices and components, e.g., MEMS/NEMS, heat transfer study in micro/nanoscales has become so critical for the systematic design and precise control of such miniaturized devices towards the integration and automation of Lab-on-a-chip devices. Demands in high heat transfer rates have returned the concerns to impinging jet cooling systems. However, studying impinging jets in the micro/nano scales is requires the molecular dynamics knowledge to analyze the true micro/nanoscale flow behavior accurately. According to the importance of this subject, we use direct simulation Monte Carlo (DSMC) method to simulate nano impinging jet gas flows. The thesis is... 

Due to important applications and benefits of mass transfer in engineering and especially in nano-scales engineering, nano-science researchers have focused on this field. Considerably, in classical fluid dynamics applications, the fluid can be transported using differential pressure gradient. But the classical methods require moving components, which are usually expensive and not applicable in nano-sizes. To avoid these problems in nano-size transportation, we can use electro-osmotic process to perform mass transfer in low transfer rates. In electro-osmotic process, we can move electrolyte solvent with the aid of an external electrical field. Due to importance of this process in... 

Nowadays, a wind tunnel is a tool used in aerodynamic research to study the effects of air moving past solid objects. By employing a wind tunnel, we can compeletely control the conditions of aerodynamic testing on specific models. In this research, the design of a diffuser for the subsonic wind tunnel has been taken into account by CFD. The wind tunnel is of suction type and is powered by three axial fans which are manufactured by LTG Inc. The tunnel test section has a 140 cm height and 195cm width which can provide a necessary Mach number. Considering the setting of the three axial fans, located at the end of the diffuser and parallel to each other, it’s necessary to take into consideration... 

Progress of technology and the ability of construction of devices in micro and nano scales, have developed a new field of science that the classical laws of fluid dynamics can not be analyzed in by the well known Navier-Stokes Model. So, research fields in micro and nano scales have been paid attention more. In micro and nano scales, due to small size of characteristic length, the fluid is rarefied and the behavior of the fluid and its interaction with surfaces and walls in such scales is very different from those in large-scale systems. So, the particle-based-methods like Direct Simulation Monte-Carlo (DSMC) method have been considered one of the most interesting fields of researches for... 

This research considers the wind effects on the thermal deficiency of natural draught dry cooling tower (NDDCT) using the CFD tool. To have a realistic study, the NDDCT of Shazand Powerplant, located in Shazand, Iran, is simulated as the sample cooling tower design points. Considering of Shazand NDDCT model, the mal-effects of local wind were studied against its thermal efficiency. As is known, the thermal efficiency of a NDDCT can be affected by local wind in either its upper (i.e., outlet section) or lower (i.e., the radiator section) parts. In this study, a full study is performed to quantify the mal-effects of local wind on either upper or lower parts of one tower. The results show that... 

In this project, we are willing to analyze and design a subsonic wind tunnel WT configuration for the Aerospace Engineering Department in Sharif University of Technology. This WT will be an open-circuit "suck down" type, whose entry is open to the atmosphere (laboratory) and three axial fans downstream of its test section. In addition to three parallel fans, we are expected to design two simultaneous small and large size test sections for it. The small and large sections would have an area about 1.4 and 4 m2and maintain a maximum air velocity of 100 and 50 m/s, respectively. So, our design is faced with two main complexities. In one hand, we are to manage the air flow through these two test... 

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... 

The enviromental wind would cause serious drop in the performance of Heller cooling systems in thermal powerplants working on Rankin cycle. Therfore, it is necessary to consider the wind velocity in the design of such cooling tower systems. We use the computational fluid dynamics (CFD) and simulate the 3D buoyant flow passing through and over a heel cooling tower. We consider three different wind veocities of 0, 5 and 10 m/s in our simulations. In order to consider the low efficiency of the cooling system in efficiency drop of the main rankin cycle, we need to consider actual power generated by the powerplant generator, which is directly affected by the turbine back pressure. To connect the... 

In this study, our objective is to simulate the growth of frost for humid air passing through pressure regulators. The study is carried out in two main stages. First, we use an empirical method to model the formation of frost for a humid-air passing over a flat plate. The model is a semi-2D one and that it is limited to predict the frost growth at a particular station along the plate, considering the local flow heat transfer parameters. We show the validity of results comparing with available experimental data. Second, we numerically simulate the frost formation and growth for a humid air passing between two parallel plates. In this regard, the semi empirical method is suitably coupled with... 

Micro/Nano science has obtained enormous applications in aerospace engineering especially in the propulsion system of micro/nano satellites. The satellite attitude control is a vital part of every space mission. Different thruster systems have been already suggested and utilized to achieve this important mission correctly. Considering the future perspectives of space missions for small satellites, the development of micro/nano thrusters has been attracted more attention since the last decades. The scope of this research is to analyze hybrid hot/cold laboratory supersonic micro-thrusters especially for the micro-satellite implementations. The ultimate goal of the current research is to... 

An aerodynamical model for studying asymmetric and three-dimensional flow fields about wind turbine rotors is presented. The developed algorithm combines a asymmetric and three-dimensional Navier-Stokes solver with a so-called actuator disc technique in which the loading is distributed along lines representing the blade forces. The loading is determined iteratively using a bladeelement approach and tabulated airfoil data. Computations are carried out for a 5MW NREL wind turbine equipped with three blades. The computed power production is found to be in good agreement with measurements. The computations give detailed information about basic features of wind turbine wakes, including... 

According to the climates of the country, using natural draft dry air cooling systems at the power plant is one of the proposed solutions for lower water consumption, but strong wind can make drop in performance of power plant cooling systems based on Rankine Cycle. This means that wind disrupted the order of the normal flow of air intake around the tower by creating areas of low pressure, preventing the flow of air into the cooling system. In the world, many researches and solutions have been proposed to solve the problem. The most common of these solutions is using of windbreaks as aerodynamic devices to compensate for the pressure drop in the cooling tower when the wind blows. But... 

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... 

Nowadays, widespread needs for creating low pressure ambient in various industries make vacuum systems have different research and industrial applications. One of these applications is in cooling system of Rankine power cycle. In this case, the performance of the vacuum system has a direct and significant effect on the cooling performance of the condenser and consequently, power production of the steam turbine. Also, a considerable part of deration in thermal power plants industry is due to the thermal deration of the cooling systems. This is mostly because of malfunction of the condenser due to ambient temperature rise. Therefore, by providing suitable solutions to improve the efficiency... 

Heavy fuel oil (HFO) is usually consumed in large scale furnaces, e.g., those of power plants. Experience shows that its combustion produces large amount of NOx emission. In present study, a large scale heavy fuel oil fired furnace is numerically simulated to investigate different possible solutions for NOx reduction. In this regard, a computational framework is firstly designed benefiting from the researches reported previously in literature. The results of this framework are then compared with available measurements to evaluate the accuracy of current designed computational framework. Second, the influences of a number of different controlling parameters are studied carefully to improve...