Sharif Digital Repository

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 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... 

Using flapping motions, birds produce aerodynamic forces required to fly. Flapping wing aerodynamics is one of the most complicated problems in unsteady aerodynamic field. Experimental study on the structure, the way of production and growth and the feasibility of controlling the leading edge vortex are the main goals of this research in order to improve the aerodynamic performance of flapping wings. Since leading edge vortex structure appears in both upstroke and downstroke of a complete storke in flapping motion, controlling the structure in one of the half-storkes can provide the possibility of having a better aerodynamic performance. In this research, the wing is designed and... 

The importance of creating a fluid flow with accurate and controllable flow in many industries is undeniable. There are several ways to create this type of flow, and a variety of pumps can be used to create such a flow. The presence of noise, limitations in reducing the flow rate (sometimes in some pumps the flow rate can not be reduced to a minimum), depreciation costs and many other limitations, reduce the attractiveness of using conventional pumps in some applications. The subject of this project is the design and construction of piezoelectric based micro-pumps to solve the above problems. In many applications, the need for fluid flow with very low flow and high quality and accuracy is... 

Network coding as an efficient approach for performance improvement of communication networks has been introduced by Ahlswede et al. Despite simple forwarding schemes, in network coding scenarios, intermediate nodes forward the encoded version of their received packets. In wireless Networks, resource allocation includes routing, network coding, flow control, scheduling and power control.In this dissertation a joint scheduling, routing, flow control and Inter-session NC formulation based on a convex optimization problem is studied. Our formulation integrates the optimal scheduling, flow control and Inter-session network coding with a modified version of minimum delay routing. We propose a way... 

In the present study, the simulation of incompressible Electro-Magneto-hydrodynamic flows is performed using a finite volume lattice Boltzmann method (FVLBM). The Boltzmann transport equation is solved using a cell-centered finite volume method on structured meshes. A central difference scheme is used to discretize the spatial derivatives and the fourth-order numerical dissipation term is added to stabilize the solution. To discretize the temporal derivative, the fourth-order Runge-Kutta time stepping scheme is applied. The standard collision-streaming lattice Boltzmann method has been used to simulate EMHD flows in the literature, however, it has several deficiencies such as the... 

The competition between producers and the contracts issues between the producers and consumers of electrical energy in restructured power systems might cause on unwanted increase in power interchange beyond transmission lines capacity. If the power interchange is not well-managed, it would often cause overloads in specific path. This phenomenon is termed as lines congestion. The major goal of congestion management is to create a set of rules that ensure sufficient control over producers and consumers to maintain an acceptable level of power system security and reliability in the time of limitation of transmission network with maximizing economic market efficiency. As FACTS devices provide... 

The advantages of using solar energy, including absence of environmental pollution, renewability, availability, ease of installation and use, and has attracted much attention of researchers. Expanding the use of solar energy in remote areas where national grid coverage is weak, makes off-grid inverter vital role clear. The swinging nature of solar energy requires the use of electrical energy storage and battery charger for optimum energy extraction in a technically and economically manner. The aim of this project is to develop a Smart Charger in Standalone Solar Inverter. Charger circuit design has been done in order to accommodate a 4kW inverter. Selected Charger topology is the... 

In recent years, there have been a tremendous research performed in the field of sestems containing small scales. However, besides all advantages of such systems, microfluidic systems have extraordinary difficulties and pumping liquid drops as part of some of these systems has been very important issue. An approach related to flow control is use of surface acoustic waves (SAW), which is known as acoustofluidic device. So far, most researches have only qualitatively investigated acoustic flux phenomenon. On the other hand, computational research is ongoing more emphasizing on accuracy, optimization, and obtaining more detailed physical understanding of SAW applications. Investigation of the... 

Transonic flow compressors are widely used today. In these systems, the occurrence of shock waves, interaction of the shock and the boundary layer, thickening of the boundary layer and separation are some challenges which can severely affect the aerodynamic performance. Here we use a numerical analysis and an optimization algorithm to optimize the aerodynamic shape of a transonic axial compressor blade section. The total pressure loss through a cascade of blade sections is selected as the cost function. A continuous adjoint optimization method is used along with a RANS solver to find the new blade section shape. Application of three different geometric modelling of a compressor blade section... 

Flow control means changing the optimal flow behavior of the fluid in accordance with the desired targets, such as decreasing drag force, increasing the lift force or lift to drag ration, as well as manipulating the separation of the flow from the surface. So far, little research has been done on increasing the airflow performance through the active control of the trailing edge flow. Gurney flap is a great tool, and its experimental results show a significant increase lift force in the airfoil. In this study, it is possible experimentally to use plasma actuators to create microtap and garney flap artificial for enhancing the aerodynamic performance of airfoil by controlling the flow field at... 

This thesis investigates the stall control over an airfoil employing dual excitation of separated shear layers with DBD plasma actuators. This research is studied experimentally on the NACA 0015 airfoil at the angle of attack and Reynolds number of 14° and 300000, respectively. Two plasma actuators, one on the suction side just upstream the separation point and the other on the pressure side at the trailing edge, are exploited to control the baseline flow. Surface pressure distribution, as well as the dominant natural frequency associated with flow structures in the wake, are evaluated. Based on the active actuators, three controlled cases are considered in the present study. In the first... 

Available Transmission Capability (ATC) is a measure of remaining capability in the transmission system for future use which is calculated and posted by Independent System Operator (ISO) considering various certain and uncertain power system parameters. ATC can be affected considerably by application of flexible AC transmission system (FACTS) controller among them Unified Power Flow Controller (UPFC) is the most recent one applied in power systems. This thesis is aimed to study the probabilistic ATC assessment incorporating UPFC. It first proposes a probabilistic ATC calculation method which is capable of considering various certain and uncertain parameters of ATC calculation in the...