Aerospace Science and Technology
Mohammad Reza Hashemi; Seyyed Majid Malek Jafarian; Mojtaba Dehghan Manshadi
Abstract
In this research, the effects of canard flow on a diamond wing equipped with LEX, same as new-generation fighters, have been investigated, using a closed-circuit wind tunnel. All tests were performed at a speed of 12.5 meters per second, which is equivalent to Reynolds number 214000 based on model length. ...
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In this research, the effects of canard flow on a diamond wing equipped with LEX, same as new-generation fighters, have been investigated, using a closed-circuit wind tunnel. All tests were performed at a speed of 12.5 meters per second, which is equivalent to Reynolds number 214000 based on model length. The pressure measurement is conducted by the five-hole probe, which is normalized by the dynamic pressure of the free stream velocity in four cross-sections over the wing. The results showed that at a low angle of attack, a strong vortex is produced at the leading-edge of the wing, called the leading-edge vortex. As the leading-edge vortex moves downstream, the diameter of its core and distance from the wing surface increases. At higher angles of attack, LEX, canard and body vortices are also present, which combine with the leading-edge vortex and cover a large cross-flow area over the wing. At these angles of attack, the movement of the vortical flow downstream leads to an increase in the pressure coefficient of the vortex core, which indicates the beginning of instability and vortex breakdown. The results showed that the pressure increase in the vortex core was not sudden and this results in that the breakdown phenomenon in the diamond wing equipped with LEX and canard occurs slowly.
Aerospace Science and Technology
Sahel Alasvand; Mostafa Kazemi; Mahmood Mani
Abstract
The noise of wind turbines is mainly of aerodynamic origin and is caused by the impact of the flow on the turbine blade. Therefore, improving the behaviour of the flow around the turbine and reducing aeronoise can result in reducing its annoying noise. In the first step of this research, a suitable serration ...
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The noise of wind turbines is mainly of aerodynamic origin and is caused by the impact of the flow on the turbine blade. Therefore, improving the behaviour of the flow around the turbine and reducing aeronoise can result in reducing its annoying noise. In the first step of this research, a suitable serration is selected according to the physics of the flow, and then it is installed on the leading edge of the blade in such a way that it does not cause the power loss of the turbine. All the studies have been done experimentally in the wind tunnel and with the help of power, pressure and air velocity measurements in the wake and in the different free stream velocities. The results showed that the pressure fluctuations in the model equipped with a serrated blade have decreased by 4-9% on average in different areas compared to the simple Savonius. On the other hand, the results of the frequency analysis of the anemometer sensors also showed that in the dominant frequencies, the serration caused the range of phenomena to decrease. These results were obtained in such a way that the power measurement showed that the maximum power value of the turbine equipped with serrated blade experienced an increase of nearly 19%. On the other hand, the velocity profile in the wake also shows a greater deficit in the flow around the modified Savonius, which confirms the decrease in the output momentum from the turbine and consequently the increase in power.
Aerospace Science and Technology
Bahareh Mojarrad; Saeed Oveisi; Mostafa Kazemi; Mahmoud Mani
Abstract
The primary objective of this study was to demonstrate how plasma actuators could be used to discharge a perpendicular dielectric barrier as a virtual Gurney flap. This study utilized wind tunnel experiments on a flat plate airfoil. Each experiment is conducted at two different free flow velocities of ...
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The primary objective of this study was to demonstrate how plasma actuators could be used to discharge a perpendicular dielectric barrier as a virtual Gurney flap. This study utilized wind tunnel experiments on a flat plate airfoil. Each experiment is conducted at two different free flow velocities of ten and twenty meters per second. To study and extract the aerodynamic phenomena generated by plasma actuators and to compare them to the Gurney phenomena of a physical flap, velocity profiles in the model sequence were measured using a hot wire flow meter in two different longitudinal positions relative to the model. All experiments were conducted from five distinct vantage points, 0, 2, 4, 6, and 8, and plasma actuators were activated in two distinct settings to extract concepts under a variety of conditions. Wind tunnel experiments indicate that downward sequence transfer occurs when plasma actuators are used. Additionally, there are two distinct types of vortex shedding on the model's back: one that resembles Karman vortex shedding and another that occurs below the model. The observation of velocity profiles demonstrates that the deformation of the sequence caused by the use of plasma actuators is very similar to that caused by an airfoil sequence equipped with a physical Gurney flap.
A. Hossein Gholami; Mohammad Haeri; Ali Reza Doodman Tipi
Abstract
With the advancement of science and technology, ultra-light drones with electric propulsion hold many applications. In these drones, the electric motor is the primary consumer of energy. Thus, having an accurate model of power consumption of the motor, propeller, and battery set can play an essential ...
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With the advancement of science and technology, ultra-light drones with electric propulsion hold many applications. In these drones, the electric motor is the primary consumer of energy. Thus, having an accurate model of power consumption of the motor, propeller, and battery set can play an essential role in determining the drone's flight duration. This paper aims to model the behavior of two sets of motor and propeller in the wind tunnel. One motor set has a low speed, and the other has a medium speed. Also, after the above modeling, the models of speed-power, thrust-power, and speed-efficiency are extracted. Then, a lithium polymer battery with a minimal voltage drop for the drone is used. In the operating speed, the flight time of the desired drone is obtained. The power consumption, speed, and thrust models are obtained using interpolation. Finally, the motor that consumes less power and has a longer flight time is selected.
M. Manshadi; A. Sharafi; M.H. Soltani
Volume 9, Issue 2 , September 2012, , Pages 15-24
Abstract
An extensive experimental investigation is conducted to study the effect of canard position relative to the fuselage reference line on the aerodynamic forces of a fighter type configuration model. Aerodynamic forces at different flight conditions are measured in a subsonic wind tunnel. The wing and the ...
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An extensive experimental investigation is conducted to study the effect of canard position relative to the fuselage reference line on the aerodynamic forces of a fighter type configuration model. Aerodynamic forces at different flight conditions are measured in a subsonic wind tunnel. The wing and the canard have triquetrous shapes. Experiments are conducted at Reynolds number of 342209 and at 0 to 40 degree angles of attack. The results show that canard increases the lift and drag forces while it decreases the static stability of the model. The canard at itandrsquo;s up position increases the aerodynamic forces and decreases the static stability i.e., superior maneuver capability. Furthermore, when the forward position of the canard is considered, both lift and drag are increased; however, the overall aerodynamic efficiency and also more static stability are improved. The canard at up and forward position respect to the wing-body is an appropriate selection for the best performance at moderate to high angles of attack among the various wing-canard-body configurations.
Bahman Jahromi; M.R. Soltani; M. Masdari
Volume 9, Issue 1 , March 2012
Abstract
The goal of this investigation is to study the effect of wing sweep angle on the horizontal wing-body- tail configurations in subsonic flow. For this purpose, a series of wind tunnel tests were conducted on a model having a moveable horizontal tail and a wing planform with different sweep angles. Tests ...
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The goal of this investigation is to study the effect of wing sweep angle on the horizontal wing-body- tail configurations in subsonic flow. For this purpose, a series of wind tunnel tests were conducted on a model having a moveable horizontal tail and a wing planform with different sweep angles. Tests were performed at different tail deflection angles. Static surface pressure distribution over the suction side of wing was measured for both static and dynamic changes of the tail angles of attack. The strength of the vortices over different wings was compared and the effect of tail deflection on the wing flow field was investigated. It is seen that the wing sweep angle is a dominant factor for the strength of the vortices over the wing and hence the maneuverability of the vehicle.
Mohammad Reza Dr. Soltani; M. Masdari; M. Seidjafari; Kaveh Ghorbanian
Volume 7, Issue 2 , September 2010, , Pages 132-137
Abstract
Extensive wind tunnel tests are conducted to evaluate surface pressure distribution of a semi span swept wing. The wing section has a laminar flow airfoil similar to NACA 6-series airfoils. The investigations are conducted at various speeds and angles of attack. Surface pressure distribution over the ...
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Extensive wind tunnel tests are conducted to evaluate surface pressure distribution of a semi span swept wing. The wing section has a laminar flow airfoil similar to NACA 6-series airfoils. The investigations are conducted at various speeds and angles of attack. Surface pressure distribution over the wing upper surface is measured for both chordwise and spanwise sections. Statistical analyses are performed on the data to realize the transition point at each chordwise section. The 3D pressure profiles are compared to the corresponding 2D results at the same conditions. Calculation of the standard deviation, SD, of time variable pressure data shows that SD increases in the transition area and then decreases again when the flow becomes fully turbulent downstream. The measured transition points are further compared with 2D computational results.