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Analysis of separation control authority of DBD plasma actuator using hot-film sensor array
, Article Journal of Applied Fluid Mechanics ; Volume 14, Issue 5 , 2021 , Pages 1421-1435 ; 17353572 (ISSN) ; Maghrebi, M. J ; Soltani, M. R ; Sharif University of Technology
Isfahan University of Technology
2021
Abstract
The boundary-layer control authority of a DBD plasma actuator using surface mounted hot-film sensors is evaluated. Wind tunnel experiments on a wind-turbine blade section were established at a Reynolds number of 0.27 x 106. Aerodynamic performance of the wind-turbine blade section for both plasma-ON and plasma-OFF modes are evaluated using measurements made by both surface pressure and wake survey behind the model. Two distinct boundary-layer states are recognized. A state which occurs at the onset and in proximity of the deep stall, which is affected by the low-frequency instabilities of the separated flow. In this case, the steady actuation of plasma imparts local momentum on the nearby...
Experimental Investigation of the Effects of Suction and Wall Porosity on the Surface Pressure and Aerodynamic Forces in Transonic Wind Tunnel
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
Transonic speed is one of the most important flight regimes. There are two main significances related to it. First, all of the supersonic air vehicles should pass through this regime to reach to their final speed. Second, nowadays most of the commercial airplanes fly in nearsonic speeds. According to nonlinear nature of the flow through the speeds, the related researchers haven’t been successful in development of a comprehensive theory as well as subsonic and supersonic ones. So, transonic flow is one of the most critical regimes in wind tunnel testing. In order to eliminate the shock-boundary layer interaction and wave cancellation, perforated walls and side suction are used in test section...
Oscillation Frequency and Reynolds Number Effects on a Contaminated Wind Turbine Blade Section
, Article 25th AIAA Applied Aerodynamics Conference, 2007, Miami, FL, 25 June 2007 through 28 June 2007 ; Volume 2 , 2007 , Pages 1203-1207 ; 10485953 (ISSN) ; 1563478986 (ISBN); 9781563478987 (ISBN) ; Birjandi, A. H ; Goreishi, S. M ; Sharif University of Technology
2007
Abstract
A series of unsteady low speed wind tunnel tests on a section of a 660 Kw wind turbine blade which is under construction were conducted to examine the effects of distributed surface contamination on its performance characteristics. Model was tested at three mean angles of attack, 5, 10 and 18 degrees at the fixed oscillation domain of 5 degrees. Results show that contamination decreases the maximum lift coefficient more than 40 percent. However Reynolds number and oscillation frequency increase, have a positive effect on the maximum lift coefficient in the contaminated model and it decreased the difference between maximum lift coefficient in the clean airfoil and the contaminated one
Experimental investigation of effects of mach number on the flow instability in a supersonic inlet
, Article Experimental Techniques ; Volume 37, Issue 3 , 2013 , Pages 46-54 ; 07328818 (ISSN) ; Farahani, M ; Sharif University of Technology
2013
Abstract
An extensive wind tunnel tests were conducted on an axisymmetric supersonic inlet at Mach numbers from 1.8 to 2.2 and at different values of mass flow rates. Frequencies of the buzz were achieved from the pressure data as well as the high speed shadowgraph pictures. For each Mach number, two main frequencies for the buzz were obtained. The inlet at its design condition was stable, but when the mass flow rate was reduced, at first the shock wave started to oscillate with a small amplitude which is matched the Ferri criterion (little buzz). In this situation, both high- and low-frequency oscillations occurred; however, the high frequency one was dominant, but the oscillations seemed to be...
The influence of free stream turbulence intensity on the unsteady behavior of a wind turbine blade section
, Article 45th AIAA Aerospace Sciences Meeting 2007, Reno, NV, 8 January 2007 through 11 January 2007 ; Volume 11 , 2007 , Pages 7611-7618 ; 1563478900 (ISBN); 9781563478901 (ISBN) ; Soltani, M. R ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2007
Abstract
Extensive wind tunnel tests have been conducted to investigate effects of turbulence intensity variations on the behavior of a section of a wind turbine blade in an oscillatory motion. Special emphasize was applied on the aerodynamic characteristics when oscillating the model in the vicinity of its static stall angle of attack and in the post stall condition. The model had 0.25m chord and was pitched about its quarter-chord. Data were acquired at various Reynolds number, and reduced frequency. Results show that turbulent intensity has strong effect on the unsteady load coefficients, hence aerodynamic performance of this model. Furthermore, free stream turbulence has different effect on the...
Design and Development of a Load Alleviation Control System for an Aeroelastic Wing Using Smart Materials
, M.Sc. Thesis Sharif University of Technology ; Pourtakdoust, Hossein (Supervisor)
Abstract
As the aeronautical design evolves, the optimal solutions tend to employ slenderer and aeroelastic wings. These slender wings could help to increase the flight endurance, by decreasing the fuel consumption. However, as a wing becomes slenderer its structural stiffness decreases. The decrease in the stiffness highlights the structural vibrations and aeroelastic behavior in these wings. Atmospheric turbulences induce vibrations that can cause fatigue and structural failures. A possible solution to decrease these oscillations is to use active vibration control and flutter suppression. Conventional control surfaces on a wing can be used to implement the active vibration control. However, given...
Experimental investigation on turbulence intensity reduction in subsonic wind tunnels
, Article Aerospace Science and Technology ; Volume 15, Issue 2 , 2011 , Pages 137-147 ; 12709638 (ISSN) ; Soltani, M. R ; Manshadi, M. D ; Sharif University of Technology
Abstract
Experiments are performed to evaluate the impact of trip wires on the turbulence intensity in a few low speed wind tunnels. Trip wires of different sizes are installed at different positions in the contraction section of four different wind tunnels and measurements are made at various free stream velocities. The results indicate that the pressure distributions are altered compared to the clean condition. Trip wires move the adverse pressure gradient toward the inlet of the contraction section. Consequently, the turbulence intensity in the test section of the wind tunnels is reduced and the flow uniformity is improved considerably. Frequency and statistical analysis are performed and the...
Application of screens and trips in enhancement of flow characteristics in subsonic wind tunnels
, Article Scientia Iranica ; Volume 17, Issue 1 B , 2010 , Pages 1-12 ; 10263098 (ISSN) ; Ghorbanian, K ; Manshadi, M. D ; Sharif University of Technology
2010
Abstract
Subsonic wind tunnel experiments were conducted to study the turbulence level in the test section. Measurements were performed by introducing trip strip and/or damping screens on the flow field. The results indicated that the introduction of trip strips not only reduced the turbulence intensity compared to cases without it, but also flattened the variations. Further, the experiments which investigated the impact of the damping screens indicated a similar reduction in turbulence intensity; the pattern, however, remained the same. Furthermore, the results for cases wherein both trip strips as well as damping screens were placed on the contraction and in the settling chamber, respectively,...
Control of separation in the concave portion of contraction to improve the flow quality
, Article Aeronautical Journal ; Volume 113, Issue 1141 , 2009 , Pages 177-182 ; 00019240 (ISSN) ; Soltani, M.R ; Manshadi, M.D ; Mirzaei, M ; Sharif University of Technology
2009
Abstract
Subsonic wind tunnel experiments were conducted to study the effect of forced transition on the pressure distribution in the concave portion of contraction. Further more, the effect of early transition on the turbulence level in the test section of the wind tunnel is studied. Measurements were performed by installing several trip strips at two different positions in the concave portion of the contraction. The results show that installation of the trip strips, have significant effects on both turbulence intensity and on the pressure distribution. The reduction in the free stream turbulence as well as the wall static pressure distribution varied significantly with the location of the trip...
Effect of amplitude and mean angle-of-attack on the boundary layer of an oscillating aerofoil
, Article Aeronautical Journal ; Volume 112, Issue 1138 , 2008 , Pages 705-713 ; 00019240 (ISSN) ; Bakhshalipour, A ; Sharif University of Technology
Royal Aeronautical Society
2008
Abstract
Extensive experiments were conducted to study the effect of various parameters on the surface pressure distribution and transition point of an aerofoil section used in a wind turbine blade. In this paper details of the variation of transition point on the aforementioned aerofoil are presented. The aerofoil spanned the wind-tunnel test section and was oscillated sinusoidally in pitch about the quarter chord. The imposed variables of the experiments were free stream velocity, amplitude of motion, mean angle-of-attack, and oscillation frequency. The spatial-temporal progressions of the leading-edge transition point and the state of the unsteady boundary-layer were measured using eight...
Surface contamination effects on the 2-D and unsteady wind turbine blade section performance
, Article 25th AIAA Applied Aerodynamics Conference, 2007, Miami, FL, 25 June 2007 through 28 June 2007 ; Volume 2 , 2007 , Pages 795-801 ; 10485953 (ISSN) ; 1563478986 (ISBN); 9781563478987 (ISBN) ; Birjandi, A. H ; Goreishi, S. M ; Sharif University of Technology
2007
Abstract
A series of unsteady low speed wind tunnel tests on a section of a 660 Kw wind turbine blade under construction were conducted to examine the effects of distributed surface contamination on its performance characteristics. Our data shows that the airfoil is very sensitive to the applied surface roughness. Results show that contamination decreases static maximum lift coefficient more than 40 percent. In the dynamic test this effect is the same and is about 38 percent. Contamination decreases the width of the dynamic diagrams loop such and leads to the smooth stall on the airfoil
Symmetric and asymmetric performance investigation of a diverterless supersonic inlet
, Article AIAA Journal ; Volume 60, Issue 5 , 2022 , Pages 2850-2859 ; 00011452 (ISSN) ; Soltani, M. R ; Sharif University of Technology
AIAA International
2022
Abstract
A series of wind-tunnel tests were conducted on a Y-shaped diverterless supersonic inlet (DSI) in order to investigate its performance at various operating conditions. The present DSI was designed for a freestream Mach number of M∞ 1.65. The experiments were performed at supercritical, critical, and subcritical operating conditions and at 0 deg angle of attack and angle of side slip. The results showed that the present DSI had an acceptable performance at its design condition. A symmetric supersonic flow pattern was observed at both supercritical and critical operating conditions. At low subcritical operating conditions, the supersonic flow pattern remained symmetric too. However, at high...
Effects of wing geometry on wing-body-tail interference in subsonic flow
, Article Scientia Iranica ; Volume 18, Issue 3 B , 2011 , Pages 407-415 ; 10263098 (ISSN) ; Soltani, M. R ; Askari, F ; Pajuhande, H. R ; Sharif University of Technology
Abstract
Extensive wind tunnel tests were performed on several wing- body-tail combinations in subsonic flow to study the effects of wing geometric parameters on the flow field over the tail. For each configuration, tail surface pressure distribution, as well as the velocity contour at a plane perpendicular to the flow direction behind the wing was measured. The results show a strong effect of wing to tail span ratio, as well as wing aspect ratio, on the flowfield downstream of the wing. For low sweep wings, as those considered here, wing and body interference effects on the tail are associated with the wing tip vortex and nose-body vortex
Performance study of a supersonic inlet in the presence of a heat source
, Article Scientia Iranica ; Volume 18, Issue 3 B , 2011 , Pages 375-382 ; 10263098 (ISSN) ; Farahani, M ; Sepahi Younsi, J ; Sharif University of Technology
2011
Abstract
The flow over a supersonic inlet has been investigated experimentally and numerically at a free stream Mach number of 2 and a zero degree angle of attack. Wind tunnel tests were performed to obtain the performance parameters of the inlet and were used as a baseline and validation tools for the numerical code. A heat source was added to the flow field at a distance ahead of the inlet. The effect of heat source addition on the main performance parameters of the inlet is investigated numerically. Results show that the heat source considerably reduces drag coefficient; however, its effect on pressure recovery is not favorable. This unfavorable effect was then minimized by controlling heat source...
Experimental investigation of flow instability in a supersonic inlet
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 3 , 2010 , Pages 515-521 ; 9780791849170 (ISBN) ; Farahani, M ; Sharif University of Technology
2010
Abstract
An extensive wind tunnel test series were conducted on an axisymmetric supersonic inlet. The model was tested at Mach numbers from 1.8 to 2.2 and at different values of mass flow rate. Shadowgraph flow visualization was used to capture the external shock structure in front of the inlet. The goal of this study is to find out the general characteristics of the inlet buzz. Frequencies of the buzz have been achieved from the analysis of the pressure data as well as the shadowgraph pictures. The amplitude of the shock waves motion has been measured from the visualization pictures too. In the some large value of mass flow rate, the frequency of shock oscillation increased versus Mach number. Also...
Effects of canard position on wing surface pressure
, Article Scientia Iranica ; Volume 17, Issue 2 B , 2010 , Pages 136-145 ; 10263098 (ISSN) ; Askari, F ; Davari, A. R ; Nayebzadeh, A ; Sharif University of Technology
2010
Abstract
A series of wind tunnel tests were performed to study the effects of a canard and its position on the downstream flowfield over the wing surface. The wing surface pressure was measured for both canard-off and canard-on configurations. In addition, the canard position effects on the wing were investigated at different angles of attack. The canard was installed at three vertical positions and at two different horizontal distances from the wing apex. The results show a remarkable increase in the wing suction peak for the canard-on configurations. At low to moderate angles of attack, among the various configurations examined in the present experiments, the mid-canard configuration developed a...
Effect of an end plate on surface pressure distributions of two swept wings
, Article Chinese Journal of Aeronautics ; Volume 30, Issue 5 , 2017 , Pages 1631-1643 ; 10009361 (ISSN) ; Masdari, M ; Tirandaz, M. R ; Sharif University of Technology
Abstract
A series of wind tunnel tests was conducted to examine how an end plate affects the pressure distributions of two wings with leading edge (LE) sweep angles of 23° and 40°. All the experiments were carried out at a midchord Reynolds number of 8×105, covering an angle of attack (AOA) range from −2° to 14°. Static pressure distribution measurements were acquired over the upper surfaces of the wings along three chordwise rows and one spanwise direction at the wing quarter-chord line. The results of the tests confirm that at a particular AOA, increasing the sweep angle causes a noticeable decrease in the upper-surface suction pressure. Furthermore, as the sweep angle increases, the development of...
Comparison final velocity for land yacht with a rigid wing and cloth sail
, Article International Journal of Engineering, Transactions A: Basics ; Volume 22, Issue 1 , February , 2009 , Pages 59-68 ; 17281431 (ISSN) ; Rad, M ; Sharif University of Technology
Materials and Energy Research Center
2009
Abstract
The powering requirement of a land yacht is one of the most important aspects of its design. In this respect the wind tunnel testing is an effective design tool. In fact, changing the parameters of the vehicle and testing the changes in the wind tunnel will give us a better understanding of the most efficient vehicle, and yet it is time consuming, expensive, and has inherent scaling errors. Another set of design tools are Computational Fluid Dynamics and parametric prediction. Computational Fluid Dynamics (CFD) codes are not yet wholly proven in its accuracy. Parametric prediction is the starting point for most engineering studies. It will be used to calculate the land yacht's performance...
Some experimental studies on the performance of a rigid wing land yacht model in comparison with VPP
, Article Scientia Iranica ; Volume 16, Issue 4 B , 2009 , Pages 291-300 ; 10263098 (ISSN) ; Had, M ; Sharif University of Technology
2009
Abstract
It is important to understand the flow characteristics and performance of wings for designers who want to have an efficient thrust in a land yacht. In this paper, a comparison of aerodynamic forces obtained by testing the land yacht model in a wind tunnel and by the Velocity Prediction Program (VPP) is presented. The wind tunnel testing of a land yacht is an effective design tool, but at present it is mainly used for VPP validation, which allows for a faster and more efficient design process. The rigid wing land yacht model, which is a radio controlled model, is tested in the national open jet wind tunnel of the Malek Ashtar University of Technology in Iran. The wing data, which is obtained...
Flow asymmetry in a y-shaped diverterless supersonic inlet: A novel finding
, Article AIAA Journal ; Volume 58, Issue 6 , 2020 , Pages 2609-2620 ; Soltani, M. R ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2020
Abstract
Extensive wind-tunnel tests were performed on a Y-shaped diverterless supersonic inlet (DSI). All tests were conducted at a free stream Mach number of M∞ 1.65, the design Mach number for this inlet, and at both zero degrees angle of attack (AOA) and angle of sideslip (AOS). The experiments were performed at various inlet operating conditions comprising supercritical, critical, and subcritical conditions that covered almost all ranges of the engine operating for this DSI. The results showed that the DSI had relatively acceptable performance characteristics when operating at its design condition. A symmetric supersonic flow pattern was observed at both supercritical and critical operating...