Sharif Digital Repository

There is a need for renewable energy sources to be more feasible. The purpose of this project is to develop a compact device that is able to harvest wind energy and transform it into electrical energy using the concept of vortex shedding. When calibrated correctly, the vortex shedding will induce resonant oscillation. Electricity would be collected from this oscillation using a magnet and coil assembly. This method was proven to work in water, but has not been applied to air currents. Our group designed and built a small-scale prototype to be tested in closed circuit wind tunnel. The wind harvester works at a moderate wind range of 3 to 5 m/s. Data was collected on the amplitude and... 

Nowadays, the lattice Boltzmann method has been widely used by scientists and engineers as an alternative to conventional numerical solvers for the Naiver-Stokes equations. The drag force decrease on the surfaces in industrial applications special in transport industries has always been of special importance. In the current research, the effects of the drag decrease has been investigated by making some rectangular grooves on the millimeter and micrometer scale on a flat surface that has been under external laminar flow of a single-phase fluid with the uniform type. Making grooves on the surfaces usually lead to change the contact area from the solid-fluid to fluid-fluid in the grooves area.... 

The phenomenon of vortex flow, is one of the most predominant streams in the nature. This phenomenon yielded by the motion of vortices, produces up to 1000 times acceleration of the Earth’s gravity. The issues of uncontrolled harvesting of oil wells and increase the life of the wells, which cause to increase in the extracted crude salt, reveal the importance of waste management and both handling and refining petroleum. According to global statistics, for every extracted barrel of oil, three barrels of water are yielded. Therefore, 250 million produced water barrels per day is produced.The separator technology with vortex core (brand Voraxial) is one of the latest technologies in waste-water... 

The Ranque-Hilsch vortex tube (RHVT) has no moving parts through which a high-pressure fluid gains on rotational velocity by passing radially through the inlet nozzles and then enters the vortex chamber. Subsequently, the high-pressure fluid becomes divided into two relatively distinctive hot and cold axial flows. Today, while RHVT is of great industrial interest due to its simplicity in manufacturing and operation; however, the mechanism of energy dissociation, which is dominated by the complex coupled interaction of the viscous thermo-fluid characteristics and geometrical properties, is not fully understood and no clear theory has been proposed to explain the energy dissociation so far.... 

Energy harvesting is a process in which energies in nature are recycled on a small scale and used to power equipment such as sensors, data recorders and transmitters, IoT monitoring and applications. Recently, energy harvesting from a new model based on movements caused by vortices of wind and water flow has been considered. The fall of unstable vortices behind the body induces aero-hydrodynamic forces into the body. If the body has degrees of freedom of movement, the vortex phenomenon can cause the body to rotate or rotate, resulting in energy extraction. Previous studies show that very little activity has been done so far on energy extraction from the Stall flutter phenomenon. The main... 

In this study, the physic of an unsteady flow surrounding two oscillating airfoils in tandem configuration at low Reynolds-numbers has been simulated in a 2D manner by utilizing the Sliding-mesh approach and K-ω-SST turbulent model in Ansys-Fluent application. The first step in this study is selecting the decent numerical grid and flow solution scheme. After choosing the proper solution for this problem, next is to verify the methodology with respect to the references. In the next step, The tandem configuration and pitching motion of the airfoils is being implemented with existing tools and the flow structure, leading-edge and trailing-edge vortex shedding and blade-vortex interactions is... 

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... 

Wing grids are among devices used for increasing wing performance. Wing grids decrease wing induced drag by breaking the wing main tip vortex to smaller vortices with lower turbulence intensity value. These devices are mostly used in low Reynolds regimes, and their effectiveness decreases as the Reynolds number increases. In most researches around the world, wing grids have simple design configurations, but in this research wing grids are designed in such a way that each grid has a minimum value of induced drag respectively. So, in addition to reducing baseline wing induced drag by breaking the main vortex to smaller vortices by means of wing grid, each grid has a minimum value of induced... 

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... 

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... 

High swirl combustors with circulative structures in the flow field, have a highly flame stability with a wide range of operating conditions. In this study, Sharif Gas Turbine Model Combustor (SGTMC) which is a double high swirl burner, was investigated experimentally and numerically. In experimental studies, SGTMC with different settings of swirlers is investigated in terms of flame lean blow-out(LBO), wall temperature, the exhaust gas composition and pollutant and also flame geometry parameters. Setting of burner are changed by variations in air fraction between inner and outer air inlets or swirlers’ vanes degrees and flow rotation directions. The results indicate that the concentrations... 

The present study is aimed at investigating experimental methods to control and stabilize the oscillatory effects of sheet/cloud cavitation. Two methods were investigated: The use of artificial cavitation generating appendages, which had a two dimensional geometry similar to that of vortex generators. Employing air injection into the cavity from different locations on the chord of the hydrofoil and a comparison of the stability achieved from each case by analyzing pictures captured from a high-speed camera. To conduct these experiments, a cavitation tunnel along with measurement devices were used. Four different appendages were tested as artificial cavitation generators, which were in two... 

The interaction of the vortices and helicopter’s blades is the most significant source of generating the main rotor’s noise, especially in landing and rising. The kind of this noise is broadband and it is produced because of establishing the vortices behind the forward blade, their interaction with backward blade, changing their structures and creating turbulency loading. The known method for modeling of the interaction of the vortices structures and solid surfaces is the simple compounding the rod and airfoil. In this project, by using this method, the noise of the interaction of vortex and blade is modeled in the Reynolds number of 48000 with LES and FW-H Analogy as a hibrid method in... 

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... 

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... 

In present study physics film cooling with two rows fan shape’s holes with RSM turbulence model is simulated. At the first, structure of flow in film cooling with fan shape’s holes is identified, Then effective flow parameters and geometry parameters in film cooling problem with 2 rows fan shape’s holes is investigated. As the result of present study, four transverse arrangements for arrangement is leading to optimum effectiveness is introduced. The continuing effects of trench in cylindrical and fan-shaped holes are investigated. Finally, the efficiency of film cooling cylindrical and fan-shaped holes compared with the anti vortex holes . The results show fan-shaped holes in the high... 

The aim of the present research is to investigate the combustion chamber cooling with vortex method in presence of kerosene and liquid oxygen as propellants. For this purpose, a part of oxidizer is entered into the cylindrical combustion chamber tangentially (from bottem of the chamber), and creates a vortex flow (outer vortex). With motion of created outer vortex along the wall and eventually hit its top wall (the head of the chamber), secondary vortex (inner vortex) occurs along the center line, with a downward direction (opposite to the primary vortex). The fuel and other part of the oxidizer injection is also carried in the head of chamber, so by mixing the fuel and oxidizer that happens... 

Focusing on unsteady flow field over delta wings due to vacuity of researches in this branch on one hand and requiring of modern aircrafts designers to this science on the other hand, expresses necessity of accomplishing present investigation. Scrutiny of pressure distribution of low aspect ratio wings in unsteady state and determination of aerodynamic characteristics of these wings in variant conditions, can be beneficial to plan aircrafts need to fly with high maneuverability in high speeds. This issue becomes important when in supersonic regime, with respect to emerged shock waves and vortices, develop complicated pressure distributions on the wing surface in unsteady state that affect... 

One can use the vibrational energy available in environment to harvest energy via piezoelectric materials, for various applications and this research field has received growing attention by researchers over the last years. This research motivation is, harvesting electrical energy from a fluttering plate in 2D axial flow via piezoelectric materials. For this purpose, a nonlinear Euler-Bernoulli beam model is used to model structure, an incompressible 2D vortex lattice method is used to model the aerodynamics, and coupled linear piezoelectric electro-mechanical equations is used to model piezoelectric materials. The structure is considered into axial flow, and flow speed gradually increases,... 

Aeroelasticity analysis and prediction of wind turbines sturcture deformations are fundamental parts in their design. Increasing the size of wind turbine blades and development of Mega-watt sized wind turbines have enhanced the importance of these studies. In this study, the aeroelasticity analysis of a wind turbine blade has been done based on flexible multibody dynamics method. For this purpose, the modal approach has been used for modeling blade structure which has been considered as a flexible beam with bending and torsion degrees of freedom. The unsteady vortex lattice method has been used to calculate aerodynamic loads in order to combine with wind turbine blade structure model. Using...