Sharif Digital Repository

The analysis results of air combat simulations explain fighters succeed at close air combat that are super maneuverable and at high angle of attack controllable. Closed-coupled delta wing/canard configurations play an important role in modern aircraft design. These configurations offer high trimmed lift, improved agility and maneuverability as well, as a potential for increased lift-to drag ratio, all of which make them attractive to study. Experiments were carried out in a subsonic closed circuit wind tunnel over a delta wing model under the influence of canard. Canard was set in two different vertical positions, high and mid, with respect to the wing location. Flowfield measurements were... 

Road network expansion is a well known problem in the world, particularly in developing countries. One approach in financing this development is to charge the users for the services rendered. Recent studies prove the merits of private sector participation in road investment and revenue collection. Public sector may cooprate with private sector in permitting it to build the roads, operate and maintain them for certain period of time, while taking advantage of the revenues collected. The road will, then, be transferred to the public sector when that period of time is over. This study presents an extension to a previous model in this area. It presents a bi-level programming network design... 

There are some problems in calculation of heavy and huge equations which are ill-posed and nonlinear. They need to be solved by the processors. The errors are important in our measurements because this precision is very important in calculation. The Block Method approach solving Forward Problem in Electrical Impedance Tomography (EIT) results produce an exact solution only if the measurements are done with enough accuracy. In this thesis, a 3D model of EIT with Block Method is implemented by means of Digital Signal Processor (DSP) to obtain exact results. In this work it has used a powerful processor called TMS320C6416DSK to reduce the measurement error in equations. It has used Code... 

Wake aerodynamic of plunging airfoils have received less attention than the other unsteady phenomena. An experimental investigation was carried out to study the unsteady characteristics of flow field behind a model of a plunging airfoil in various conditions. The model has 0.25cm chord and is the 16m section of a 660kW wind turbine blade. All tests were conducted in the subsonic closed circuit wind tunnel in Iran. Invariable parameters were plunging amplitude, mean angle of attack and plunging frequency. The Wakes of plunging airfoil can be characterized as drag-producing, neutral, or thrust-producing .Our preliminary results show that the structure of vortex in the wake for the plunging... 

The human speech signal conveys many levels of information ranging from phonetic content to speaker identity and even emotional status. This thesis deals with the task of open-set speaker identification (SI) from an unconstrained telephone conversation between two speakers. The goal is to find at most two speakers among a known set of target speakers that best match the voice samples of the input speech; the input voice samples are not constrained to the target speaker set. The uni-speaker problem is investigated first. The classic GMM-UBM system for text-independent SI and its adapted form are explored. The use of score-space information is advocated as a complementary source to the... 

Wind tunnel experiments are conducted to evaluate surface pressure distribution over a semi span swept wing with sweep angle of 33 degrees. The wing section has a laminar flow airfoil similar to that of NACA 6-series airfoils. The tests were conducted at speeds ranging from 50 to 70m/s with and without surface roughness. Surface static pressure was measured on the wing upper surface at three different chordwise rows located at the inboard station, (section 1, 2y/b=0.2), middle station, (section 2, 2y/b=0.43), and outboard station, (section 3, 2y/b=0.78). The differences between pressure distributions on the three sections of the wing were studied and the experimental results showed that... 

An experimental investigation of unsteady boundary layer over a wind turbine blade conducted in a subsonic wind tunnel. The experiment performed at different positions along the airfoil chord. Model was oscillated with amplitude of ±5 cm. Reynolds number, based on airfoil chord, ranged 3˟105 upto 6.5˟105 and the reduced frequency ranged from 0.0055 to 0.0981. Velocity profile measured with a total pressure rake. The data were reduced via a low-pass filter. Increasing the reduced frequency, the velocity profile increases the level on turbulence fluctuation and becomes more attached to the surface.

 

Supercritical airfoils are designed for transonic flow to reduce the strength of shock and its drag. These type of airfoils are used in design and construction of commercial airplanes because of their low drag in transonic regime and, as a result, a reduction in fuel consumption. Using supercritical airfoils needs accurate investigation of flow field due to several influential factors such as their specific geometry, nonlinear nature of flow phenomena, and compressibility effects. However, the availability of experimental and numerical data for supercritical airfoils is less than that for conventional airfoils. Thus, conducting experimental tests is essential for understanding of flow field... 

In the study of supersonic air intakes, two important issues including performance and stability are considered. In these types of intakes, when inlet mass flow rate is reduced to a specified amount, a self-sustained instability called Buzz phenomenon occurs. During this phenomenon, shocks and expansion waves oscillate ahead of the intake that will degrade the performance considerably due to the periodic pressure fluctuations inside the intake. In the current study, a supersonic axisymmetric air intake with mixed compression which has designed for a free stream Mach number of 2.0 has been tested were conducted for free stream Mach numbers of 1.8, 2.0, and 2.2, and the results were analyzed... 

Transonic flow study is important due to its vast applications. Supercritical airfoils are designed for transonic flow to postpone drag divergence and reduce the strength of shock. This type of airfoils are chiefly used in modern commercial airplanes because of their low drag in transonic regime and, as a result, reduction in their fuel consumption. Using supercritical airfoils needs accurate investigation of flow field due to several influential factors such as specific geometry, nonlinear nature of flow phenomena, and compressibility effects. However, the availability of experimental and numerical data for supercritical airfoils is less than that of the conventional ones. Thus,... 

For supersonic inlets with reduction of mass flow ratio to a specified value self-induced oscillations know as Buzz would occure. Study and suppression of these oscillations are categorized in the field of inlet stability. In this work performance and stability of a supersonic inlet is studied experimentaly. Also a flow control mean is examined for stability and performance improvement. Investigation of the effect of bleed location as a key parameter for this flow control method is the main goal of this study. The model used is an axisymmetric mixed compression inlet. Experiments were done in 3 freestream Mach Numbers of 1.8, 2.0 and 2.2 with application of bleed and in no-bleed condition.... 

An extensive wind tunnel tests were conducted on an axisymmetric supersonic inlet at free stream Mach numbers from 1.8 to 2.2, and at different values of mass flow rates. For each test, pressure distributions over the inlet spike was measured and the flow was visualized by means of the shadowgraph system and a high speed camera to obtain main performance characteristics of the inlet during its stable and unstable operations. As the Mach number is increased the pressure recovery is reduced, but maximum value of the mass flow rate is increased. The results of the stable operation of the inlet showed that, variations of the mass flow affects the surface pressure over the entire surface of the... 

Supercritical airfoils have been designed for transonic flow, however due to different flight conditions, the airfoil behavior during take-off and landing of the aircraft in subsonic flow regime must be known. Experimental and numerical information derived from supercritical airfoils are less than those of conventional airfoils. Because of the special geometry of supercritical airfoils and different phenomena that occurs through flow, using such airfoils even in steady states requires precise study/analysis of the flow. Therefore, one could benefit from experimental tests to better understand flow phenomena. The objective of the present research is the study effect of mean angle of attack... 

Re-entry prediction and control is essential for space research, therefore study of Aerodynamics re-entry is important. Due to the particular configuration of the capsule for thermal protection in the ultrasonic phase capsule becomes unstable at supersonic speeds. The purpose of this study is to establish insight into the behavior of the re-entry in the instability region, for this purpose Fluent software is used to simulate the capsule with Orion configuration in static and dynamic flight. Dynamic simulation was performed using forced oscillation technique to amplitude and frequency of oscillation be examined separately. In zero angle of attack with low frequency, increasing the amplitude... 

Nd:YAG laser is one of the most applicable laser for researches and development where it's basic wavelength and harmonics are used on different laser project. It's basic output has a wide pulse duration and low peak power ,therefore in order to increase the peak power the pulse duration is reduced by Q-switching.In this project by means of passive Q-switch technique an energy equivalent to 500 mj with 10to 20 ns pulse duration is extracted from the oscillator and the output energy is amplified to about 850mj in a single pass through amplifier. In this project we used saturable absorber for Q-switching because it is more optimum and simpler than other Q-switching techniques like... 

Amyloid β (Aβ) peptide is believed to be associated with the progression of Alzheimer's disease. One of the main obstacles in developments of therapeutic agents to combat progression of Alzheimer's disease, is the presence of the blood–brain barrier (BBB), which prevents the penetration of the majority of drugs. However, nanoscale objects are able to cross the BBB at low concentrations. Therefore, it is worthwhile to study the interactions of these peptides at the interface of nanomaterials. In this work we have employed molecular dynamics, and weighted histogram analysis methods in order to study the dynamic behavior and affinity of Aβ25-35 peptide on metallic surfaces of different...