Sharif Digital Repository

Today, the world energy crisis, the need to optimize its consumption and discussion to reduce fuel consumption has become a vital issue. The conventional vehicle air conditioning system due to compressor in refrigeration cycle, which has causes a severe loss in engine useful power, increasing fuel consumption, etc. Therefore, the main goal of this project is the feasibility of the vehicle cooler replacement with the vapor jet refrigeration cycle. In this cycle, the energy required for completing the refrigeration cycle is provided from the heat of the water inside the radiator that is possible with conventional refrigeration cycle. The first stage of this project includes design and... 

Buzz is a phenomenon caused by the self-sustained shock oscillations in most supersonic inlets. When the entering mass flow is reduced below a specific value, inlet buzz occurs and results in variations of both inlet mass flow and pressure. An extensive wind tunnel tests were conducted on an axisymmetric supersonic inlet at Mach numbers from 1.8 to 2.2, at different values of mass flow rates, and at various angles of attack, α=0-10 degrees, to study the inlet buzz phenomenon. For each test, pressure distributions over the inlet cowl and spike were measured and the flow was visualized by means of the shadowgraph system and a high speed camera to obtain main performance characteristics of the... 

Use of micro/nanoelectromechanical systems has become increasingly prevalent in recent years. Therefore, the development of technologies and understanding of fundamental physics associated with them is necessary.In micro-and nano-scale different behavior is often observed and it is due to Knudsen number that forms different types of flow regimes. When the flow is considered to be continuum; for it is in the slip-flow regime, for it is called the transition-flow regime. When , the flow is considered to be free molecular and is sufficiently rarefied to allow molecular collisions to be completely neglected in analysis. For continuum and slip flow regime the Navier-Stokes equations with... 

All supersonic intakes with external compression, having a good level of performance at all the critical poin t. Exhibit a marked instability of flow in subcritical operation below some value of the flow ratio, in the form of an oscillation of the shock system, colloquially known as “buzz", which can lead to thrust loss, engine surge or even structural damages. Therefore the effort to understand the nature and cause of this phenomenon is important in order that the starting of buzz can be predicted and more effectively avoided without losing performance. This phenomenon has been the subject of many studies, mainly experimental. In this research, we design and build an axisymmetric supersonic... 

Application of canard next to the wing have been widely used in military industry for decades. Although it’s most application is in supersonic flying objects, It has to do it’s duty in lower air speeds too. The aim of this study was to investigate the influence on the wing due to the presence of canard in supersonic flow regime. But because of the importance of the issue, significant attempts has been conducted in subsonic flow regime. High research volume, Absence of a comprehensive theory in this branch and the local defense industry demand as a developing country on the other hand, delivers the importance and applicability of the subject. Another issue of importance is that the... 

The receptivity, transition and stability mechanisms of supersonic and hypersonic boundary layers to freestream disturbances are one of the most complex studies in fluid mechanics. It is well known that turbulent flows generate much higher shear forces on the surface of vehicles and hence much higher viscous heating rates than a laminar flow would at the same flight conditions. Therefore, the accurate prediction of boundary layer behavior is a critical part of the aerodynamic design of high-speed vehicles and thermal protection systems. Formation of a bow shock in front of the vehicle makes the receptivity of flow-field more complex than and different from those of low-speed subsonics. Since... 

Today, the world energy crisis, the need to optimize its consumption and discussion to reduce fuel consumption has become a vital issue. The conventional vehicle air conditioning system due to compressor in refrigeration cycle, which has causes a severe loss in engine useful power, increasing fuel consumption, etc. Therefore, the main goal of this project is the feasibility of the vehicle cooler replacement with the vapor jet refrigeration cycle. In this cycle, the energy required for completing the refrigeration cycle is provided from the heat of the water inside the radiator that is possible with conventional refrigeration cycle. The first stage of this project includes design and... 

In this thesis, aerodynamic and aero thermodynamic effects associated with local heat addition into an inviscid steady state high speed flow are studied, numerically. This local heat, can be generated by a C.W laser, has a cylindrical shape and a Gaussian distribution in space. The loctation of the heat source, focal point of the laser, is considered to be upstream of the shock wave generated by a squared obstacle. The free stream Mach is 6 and the angle of attack is zero. Also, the center of this focal point is located on the symmetry line of the square. This kind of heat addition into high speed flow leads to wave drag reduction. Various parameters can affect this kind of flow control.... 

The main aim of this study is to propose a new structure of compression surfaces of a supersonic inlet in order to improve target performance parameter i.e. total pressure recovery ratio. This idea resulted in developing a new type of supersonic inlet, utilizing four ramps and a cone as compression surfaces simultaneously.A prototype of this type of inlet has been designed for Mach 3 and its performance has been studied via numerical simulation in design point and off design conditions. Eventually the new inlet compared to experimental performance survey data from two cases of two-cone inlets and also analytical calculations of ideal performance of some types of supersonic inlets. Results of... 

Flow characteristics analysis over a wing, is one of the pioneer challenges in super and sub-sonic flow near flying objects. Taking into account of growing rate of low aspect ratio utilization, usually called Delta wings, investigation of vortex behavior over this wings is highly noticeable. In addition, the lack of research in this branch of Aerodynamics inside the country, considering it’s critical application, has doubled the importance of doing research in this filled. Experimental researches on super-sonic flow over a Delta wing is limited and there are not much accurate researches about vortexes in this category of wings. In this work, the main effort is to investigate the phenomena in... 

Inlets must decelerate the air with lowest loss and drag together with a given pressure and Mach number with best quality and uniformity to the engine. This is done based on flight Mach number, by an arrangement of shock waves and surfaces gradient in the inlet. Any distortion in the flow field and the inlet geometry parameters may disrupt such arrangement and influence on the inlet performance, in addition, under critical conditions, it might affect the stability of the intakes. Any distortion in the flow field and the inlet geometry parameters may disrupt such arrangement and influence on the inlet performance, in addition, under critical conditions, it might affect the stability of the...