The Unsteady Pressure Field and Flow State Over a Pitching Airfoil with Leading-edge Suction PDF Download
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Author: Mah'd H. Alrefai
Publisher:
ISBN:
Category :
Languages : en
Pages : 264
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Author: Mah'd H. Alrefai
Publisher:
ISBN:
Category :
Languages : en
Pages : 264
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Author: Luiz M. Lourenco
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 86
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Author: Todd Allen Brown
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 238
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 33
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This research program investigated the physical mechanisms involved in the onset of leading edge separation when airfoils pitch to high angles of attack. Both constant pitch rate and variable pitch rate motions were considered. The highlights of results from a combined experimental and computational effort are described in this report. The conclusions from this research indicate the need for boundary-layer resolved measurements of the flow behavior near the leading edge and the evolution of the reverse flow regions on the suction surface. Furthermore, the deliberate shaping of the pitch trajectory for the purpose of optimization of separation delay is suggested as one way to manage the flow and aerodynamic behavior of an airfoil. Dynamic Stall, Unsteady Separation.
Author: Metwally H. Metwally
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 231
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 560
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Author: Mohamed Gad-el-Hak
Publisher: Springer Science & Business Media
ISBN: 3540696725
Category : Science
Languages : en
Pages : 533
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No be certain it can is not based mathematics. knowledge if upon da Vinci, (Leonardo 1452 1519) the humankind. Thinking is one greatest of Joys of Galilei, (Galileo 1564 1642) Now I think is to be the root all hydrodynamics and is at of physical science, second the to none in its mathematics. present beauty of Thomson (William (Lord Kelvin), 1824 1907) The book contains the lecture notes of of the nine instructors at present eight the short Flow Control: Fundamentals and which held course was Practices, in the week 24 28 June and Carg6se, Corsica, France, during 1996, repeated at the of Notre 9 13 1996. University Dame, Indiana, September Following the week in the course a on same was held. Corsica, 5 day workshop topic Selected from the scheduled to 1998 workshop are papers appear early special volume of the International Journal Heat Thermo of Experimental Transfer, and Fluid All Mechanics. three events were Jean Paul dynamics, organized by Bonnet of Universit6 de Andrew Pollard of Univer Poitiers, France, Queen's at and Mohamed Gad el Hak of the of sity Kingston, Canada, University Notre U.S.A.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 464
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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Experiments were conducted on a NACA-0015 airfoil undergoing low constant pitch rates to study the effects of dynamic stall formation on the airfoil upper surface pressure field. The airfoil was pitched about pivot locations of 0.25c, 05c, and 0.75c at nondimensional pitch rates below 0.2. Lift and drag coefficients were evaluated for all cases, and smoke flow visualization at low pitch rates was studied for the quarter chord pivot location. Results indicate that the greatest increases in lift due to the pitching motion occur prior to the nondimensional pitch rate of 0.1 for all three pivot locations. The effects of pitch rate on the maximum lift and drag values appear similar for the three pivot locations studied. Lift to drag ratios show significant enhancement even at very low nondimensional rates. Flow visualization indicates that the leading edge dynamic stall vortex is present even at very low nondimensional pitch areas. Keywords: Aerodynamic lift/drag; Pitch motion; Airfoils; Leading edges; Stall vortices; Aerodynamic forces; Unsteady flow; Reprints.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722115975
Category :
Languages : en
Pages : 28
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The research was carried out in the Compressible Dynamic Stall Facility, CDSF, at the Fluid Mechanics Laboratory (FML) of NASA Ames Research Center. The facility can produce realistic nondimensional pitch rates experienced by fighter aircraft, which on model scale could be as high as 3600/sec. Nonintrusive optical techniques were used for the measurements. The highlight of the effort was the development of a new real time interferometry method known as Point Diffraction Interferometry - PDI, for use in unsteady separated flows. This can yield instantaneous flow density information (and hence pressure distributions in isentropic flows) over the airfoil. A key finding is that the dynamic stall vortex forms just as the airfoil leading edge separation bubble opens-up. A major result is the observation and quantification of multiple shocks over the airfoil near the leading edge. A quantitative analysis of the PDI images shows that pitching airfoils produce larger suction peaks than steady airfoils at the same Mach number prior to stall. The peak suction level reached just before stall develops is the same at all unsteady rates and decreases with increase in Mach number. The suction is lost once the dynamic stall vortex or vortical structure begins to convect. Based on the knowledge gained from this preliminary analysis of the data, efforts to control dynamic stall were initiated. The focus of this work was to arrive at a dynamically changing leading edge shape that produces only 'acceptable' airfoil pressure distributions over a large angle of attack range. Chandrasekhara, M. S. and Platzer, M. F. Ames Research Center AF-AFOSR-0012-90; AF-AFOSR-0007-91; AF-AFOSR-0004-92; AF PROJ. 2307...
