Sharif Digital Repository

Electrostatic precipitators (ESPs) are widely recognized for their pivotal role in the collection of dust and particulate matter. ESPs are essential to ensure a particle- and dust-free atmosphere in industrial and non-industrial work environments. With the ever-increasing significance of maintaining air quality at the desired standards, the role of ESPs has gained paramount importance in mitigating airborne pollutants and protecting public health. Achieving higher collection efficiency for particulate matter and attaining cleaner air is of great importance in the design and selection of precipitators. On the other hand, particle collection efficiency is considered as a crucial factor for ESP... 

The present study focus is on finding a new solution to control laminar separation bubble phenomenon by combustion actuators in micro scale, which is investigated in flows with low Reynolds number surface effect and free flows. The main parameters in this problem are classified in three groups of formation location of laminar separation bubble, its length, and transition from laminar to turbulent around airfoil SD8020 in attack angle of 5 and 8 degree. Following that, the new combustion actuators in micro scale method the comparison it with cold (and hot) air jet injection is introduced to control boundary layer flow with separation bubble point of view. Some mechanisms are identified in... 

In this research, aeroelastic model of an elastic flapping wing has been derived in order to be integrated with the flight dynamic model. The model developed in this research well describes the coupled and nonlinear behavior of the passive torsional deformations of the wing during flapping motion. Based on this obtained equations, a precise propulsion model proper for flapping wing vehicles has been introduced. The effect of geometric and mechanical properties of the wing is being accounted. In order to validation of the analytical model several FMAVs as well as an instrumented test stand for online measurements of forces, flapping angle and power consumption have been designed and built... 

In this study, investigated the simulation flow over a double-delta wing. The flow field was simulated by three dimension grid and RANS flow equation by K-ω-SST model. In order to investigate effect of AOA and leading edge flap simulated variable AOA and leading edge flap angle. The results shows created two vortex in inside and outside the wing. The vortex burst at high AOA and the Lift decrease after vortex bursting. The using leading edge flap effect on the vortex power and postpone vortex bursting and increasing wing lift coefficient in the high AOA. Also the leading edge flap effect on the pitch moment coefficient and change the pitch moment coefficient curve slope. The other effects of... 

Experimental determination of aircraft aerodynamic characteristics is of prim importance in evaluation of its trimability and stability requirements. One of the most common tools for experimental identification of aircraft is the wind tunnel equipped with aerodynamic force and moment balance system. Design and development of wind tunnel equipped with such system for measuring aerodynamic forces and moments can affect the accuracy and quality of identifying the aircraft dynamics. However, since procurement of such professional systems is very expensive, the primary goal of this project is focused on initial design of a tabletop wind tunnel with a force and moment balance system. In addition,... 

The purposes of this research are one and three dimensional aerodynamic designs of a twin entry radial-inflow gas turbine's impeller. The GT4082 model Garrett turbocharger was chosen for this purpose. In order to predict existing turbine performance curves one dimensional model was prepared for whole turbine. For validating the 1d-modeling's results, widespread tests were performed on the turbine at Sharif University of Technology turbocharger lab. Comparing the results of 1d-modeling with experimental results, show 4.7% and 4% max difference for efficiency and mass parameter respectively. The wheel designing procedure started from primary design based on the mean line assumption, in 1-d... 

For several decades, turbocharging of internal combustion engines has been a wide spreading technology to increase the engine output power as much as possible. Turbocharger has two main components: compressor, and turbine. Therefore, increasing the efficiency of turbine and compressor has a major role in engine performance improvement. This has been a continuous research goal in 20th century. Considerable advances has been achieved until now. Turbocharger turbine should be matched to engine in a wide range operation conditions with high efficiency. Many researchers have published their achievements considering turbine elements design improvements. This research is focused on the turbine... 

Duct Inverse design problems usually involve finding the wall shape associated with a prescribed distribution of wall pressure or velocity. In this investigation, a novel iterative inverse design method is presented and developed for internal flows. In the proposed method, the duct walls shape is changed under a novel algorithm based on the deformation of a virtual flexible string in flow. The deformation of the string due to the local flow conditions resulting from changes in wall geometry is observed until the target shape satisfying the prescribed wall’s pressure distribution is reached. The flow field at each step is analyzed to obtain the current pressure distribution along the wall.... 

According to the recent researches it has been found that wind can reduce the efficiency of Air Cooled Condensers (ACC) which use for cooling purposes in power plants. Wind affects the natural suction of the cooling air and makes local low pressure area in fan’s inlet results to disrupt its normal performance. Using aerodynamic obstacles inside and around the condensers can compensate this lack of performance when there is strong wind. In this thesis with the aid of computational fluid dynamics, condenser’s behavior with various weather situations is studied. Simulation in no wind situation and different wind speeds is considered and accomplished with Gambit Fluent software. This simulation... 

Wind turbines have been the subject of many researches in recent decades. Optimization and continuous improvement of these systems play a decisive role in the development and exploitation of wind farms. Wind turbines can be studied from several aspects such as structure, dynamics, aerodynamics, electricity and control. In this research, robust power control of the wind turbine has been studied with emphasis on accurate 2 DOF mechanical and aerodynamic modeling. Aerodynamic coefficients of the turbine have been calculated using the numerical methods and the effect of this numerical modeling has been studied in comparison with the analytical methods on the turbine power control. Several new... 

At this project we proceed to aero elastic modelling of a flapping wing using unsteady aerodynamic approach. Solving this model according to aerodynamic and structure coupling needs to simultaneously solve of aerodynamic and wing structure. Left side and right side of wing, each on divided into 18 elements. each element is interacting with sides element in terms of structural force and moment. In this modeling aerodynamic was modeling with unsteady aerodynamic approach (using modify theodersen function), also structure is flexible in to direction, bending and twisting. In the following it is proved that with change in flapping pattern better performance can be achieved. the effect of change... 

Axial compressors are utilized to increase compressible flow pressure in an efficient manner where mass flow rate is high, such as aviation engines and power generation gas turbines. The flow is compressed within this machine through several stages. Each stage consists of a rotor blade row followed by a stator blade row. Energy transfer to the air is performed on the rotor by changing its velocity vector. Then, pressure is recovered from velocity by diffusion, meanwhile turning the flow direction through stator blades. These blades have been designed and optimized with various methods evolved with developing computational and manufacturing facilities. In this thesis the aerodynamic design of... 

Radial inflow gas turbines are widely used in auxiliary power units, small industrial gas turbines and turbocharger of internal combustion engines. They have advantage for low mass flow rate and wide range operation conditions. This research aimed to improve aerodynamic performance of the radial turbine of GT4082 Garret turbocharger. First, performance characteristics of the turbine were obtained experimentally at Turbocharger Laboratory of Sharif University of Technology. Laboratory results are the basis for modeling evaluation. Then, a one-dimensional model was developed to predict the turbine performance characteristics. The model results were compared with experimental results, that... 

In this research, the dynamics, aero-elasticity, and control of an airship with a flexible body hull and fins are investigated. The flexible airship is modeled as a combination of several beams with specific boundary conditions. So that the dynamics and vibration of its body hull and fins can be taken into account regarding the aerodynamic, gravity, aerostatic, and control input forces. The governing equations of motion of the system are derived by using the velocity of an arbitrary point on each component and integration over the component and substituting them into the Euler-Lagrange equations in a body frame. Afterward, the added mass acting on the hull is calculated. Then, a perturbation... 

In recent years design and manufacturing of high speed marine vessels has been developed. to estimate and control dynamics of these vessels the dynamic equation is needed.The aim of this research is Determination of hydrodynamic and aerodynamic coefficients and longitudinal dynamic equation of a high speed catamaran wich is a kind of AAMV. There are three ways to determine these coefficients. Analytical method which is usually not applicable for industrial problems, Experimental method which is too expensive and numerical method which have two parts. The first is softwares that analyse the flow with assumption that the fluid is inviscid and second softwares which solve the full Navier-Stokes... 

In adaptation with nature, Flapping Wing Arial Robots (FWARs) are flying vehicles that use wing flapping motion to produce lift and thrust forces simultaneously. Wing oscillating motion of FWARs in turn creates an unsteady and turbulent flow field around them that makes their aerodynamic modeling and analysis a complex and formidable task. As a result, experimental aerodynamic investigation of FWARs has been the focus of many researchers in the last few years. Inspired by nature, Bird-like FWARs utilize a tail as an augmented aerodynamic surface during their flight motion. In turn the tail aerodynamics that in general plays an important role in flight stability and control is adversely... 

In this thesis, maneuverability enhancement of a given twin engine fighter aircraft with integrated thrust-vector and conventional aerodynamic control surfaces havebeen studied. For this purpose a nonlinear 6DOF simulation program base on a near exact mathematical model has been prepared for the aircraft, and then a thrust vectoring system for producing moments about three body axes, like that used in F/A-18, has been added to the simulation. The control method that is employed to control the aircraft in simulation environment is based on Nonlinear Dynamic Inversion (NDI). Finally the Velocity Vector Roll (VVR) maneuver has been considered as an example tostudymaneuverability enhacement. It... 

Morphing concepts can potentially improve the performance and fuel consumption of modern aircrafts. Smart materials can reduce the weight and complexity, and also are of the best choices to improve efficiency and reliability for realizing morphing wings. Developing of a simple model and optimization of smart piezocomposite actuators position of a thin wing with variable camber is considered. The goal is to gain desired properties in incompressible subsonic regime. Lifting surfaces of a composite wing are simplified using shell model. Keeping the problem simple, a piezocomposite patch is used to change the shell curvature. Basic modes are extracted from FEM software and behavior of bimorph... 

The physics of the flow around the wing in the oscillatory motion of the wing has various patterns, including the leading edge vortex, the tip vortex and trailing edge vortex escape. The interaction of these vortices forms a complex flow structure around the wing, which will have a direct effect on the aerodynamic performance of the wing. Therefore, controlling these structures can be considered as a way to improve the performance of the flapping wing. One of the passive flow control techniques that has recently been taken into consideration is a leading-edge protuberance method. Another type of passive flow control is geometric correction, using corrugation method. According to studies, two... 

The unsteady phenomena occur in rotors of helicopters, wind turbines and compressors. Investigation of the unsteady flow is a very important test, since it can affect and restrict the performance of rotors of helicopters and wind turbine's blades when operating at high angles of attack. Dynamic tests, such as pitching and plunging oscillations are one of the best methods for studying these phenomena due to the complexity of the unsteady flows. In analyzing the results of dynamic tests one must consider the interference effects of wind tunnel walls. Different investigations show that in dynamic tests, the interference effects of flow field around the model, wind tunnel walls and support of...