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Some Recent Research On Airfoil Dynamic Stall With Application To Airfoil Design
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Book Synopsis Some Recent Research on Airfoil Dynamic Stall with Application to Airfoil Design by : Norman D. Ham
Download or read book Some Recent Research on Airfoil Dynamic Stall with Application to Airfoil Design written by Norman D. Ham and published by . This book was released on 1971 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: Some recent research on airfoil dynamic stall tentatively defines the boundary-layer flow processes during dynamic stall and suggests an approach to airfoil design for stall delay. The effect of changes of airfoil leading-edge radius and camber on increments in maximum lift coefficients is estimated, using a simple criterion for leading-edge stall. (Author).
Book Synopsis Airfoil Dynamic Stall and Rotorcraft Maneuverability by :
Download or read book Airfoil Dynamic Stall and Rotorcraft Maneuverability written by and published by . This book was released on 2000 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: The loading of an airfoil during dynamic stall is examined in terms of the augmented lift and the associated penalties in pitching moment and drag. It is shown that once stall occurs and a leading-edge vortex is shed from the airfoil there is a unique relationship between the augmented lift, the negative pitching moment, and the increase in drag. This relationship, referred to here as the dynamic stall function, shows limited sensitivity to effects such as the airfoil section profile and Mach number, and appears to be independent of such parameters as Reynolds number, reduced frequency, and blade sweep. For single-element airfoils there is little that can be done to improve rotorcraft maneuverability except to provide good static clmax characteristics and the chord or blade number that is required to provide the necessary rotor thrust. However, multi-element airfoils or airfoils with variable geometry features can provide augmented lift in some cases that exceeds that available from a single-element airfoil. The dynamic stall function is shown to be a useful tool for the evaluation of both measured and calculated dynamic stall characteristics of singleelement, multi-element, and variable geometry airfoils.
Book Synopsis Review of MIT Research on Airfoil Dynamics Stall, 1964-1971 by : Norman D. Ham
Download or read book Review of MIT Research on Airfoil Dynamics Stall, 1964-1971 written by Norman D. Ham and published by . This book was released on 1971 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research on the dynamic stall of airfoils and helicopter blades is described, beginning with wind tunnel tests and helicopter flight tests which led to the current research. Flutter criteria, tests of two-dimensional airfoils undergoing large transient motions, and a partial theory of airfoil dynamic stall are presented. The application of the two-dimensional results to the loading and motion of rotor blades due to stall is described. Unsteady boundary layer analyses and tests, and their relationship to the development of a complete flow separation model, to airfoil design, and to blade-vortex interaction effects are summarized.
Book Synopsis The Phenomenon of Dynamic Stall by : W. J. McCroskey
Download or read book The Phenomenon of Dynamic Stall written by W. J. McCroskey and published by . This book was released on 1981 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stall and its consequences are fundamentally important to the design and operation of flight vehicles. A certain degree of unsteadiness always accompanies the flow over an airfoil or other streamlined body at high angle of attack, but the stall of a lifting surface undergoing unsteady motion is even more complex than static stall. Dynamic stall remains a major unsolved problem with a variety of current applications in aeronautics, hydrodynamics, and wind engineering. This report summarizes the main physical features of the phenomenon and the attempts that have been made to predict it. The information presented is drawn mainly from recent review articles and investigations by the author and his colleagues. Since a large fraction of the existing knowledge has come from experimental research, the details of dynamic stall are discussed principally in physical terms.
Book Synopsis An Experimental Study of Dynamic Stall on Advanced Airfoil Sections. Volume 1: Summary of the Experiment by :
Download or read book An Experimental Study of Dynamic Stall on Advanced Airfoil Sections. Volume 1: Summary of the Experiment written by and published by . This book was released on 1982 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: The static and dynamic characteristics of seven helicopter sections and a fixed-wing supercritical airfoil were investigated over a wide range of nominally two-dimensional flow conditions, at Mach numbers up to 0.30 and Reynolds numbers up to 4x10 to the 6th power. Details of the experiment, estimates of measurement accuracy, and test conditions are described in this volume. The results of the experiment show important differences between airfoils, which would otherwise tend to be masked by differences in wind tunnels, particularly in steady cases. All of the airfoils tested provide significant advantages over the conventional NACA 0012 profile. In general, however, the parameters of the unsteady motion appear to be more important than airfoil shape in determining the dynamic-stall airloads.
Book Synopsis Dynamic Stall of Small Wind Systems by : Richard B. Noll
Download or read book Dynamic Stall of Small Wind Systems written by Richard B. Noll and published by . This book was released on 1983 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781726196895 Total Pages :62 pages Book Rating :4.1/5 (968 download)
Book Synopsis Airfoil Dynamic Stall and Rotorcraft Maneuverability by : National Aeronautics and Space Administration (NASA)
Download or read book Airfoil Dynamic Stall and Rotorcraft Maneuverability written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-27 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: The loading of an airfoil during dynamic stall is examined in terms of the augmented lift and the associated penalties in pitching moment and drag. It is shown that once stall occurs and a leading-edge vortex is shed from the airfoil there is a unique relationship between the augmented lift, the negative pitching moment, and the increase in drag. This relationship, referred to here as the dynamic stall function, shows limited sensitivity to effects such as the airfoil section profile and Mach number, and appears to be independent of such parameters as Reynolds number, reduced frequency, and blade sweep. For single-element airfoils there is little that can be done to improve rotorcraft maneuverability except to provide good static C(l(max)) characteristics and the chord or blade number that is required to provide the necessary rotor thrust. However, multi-element airfoils or airfoils with variable geometry features can provide augmented lift in some cases that exceeds that available from a single-element airfoil. The dynamic stall function is shown to be a useful tool for the evaluation of both measured and calculated dynamic stall characteristics of single element, multi-element, and variable geometry airfoils.Bousman, William G.Ames Research CenterAERODYNAMIC STALLING; ROTARY WING AIRCRAFT; MANEUVERABILITY; VORTICES; AIRFOIL PROFILES; THRUST; LEADING EDGES; MACH NUMBER; PITCHING MOMENTS; REYNOLDS NUMBER; DRAG; AERODYNAMIC LOADS...
Book Synopsis Airfoil Dynamic Stall and Rotorcraft Maneuverability by : William G. Bousman
Download or read book Airfoil Dynamic Stall and Rotorcraft Maneuverability written by William G. Bousman and published by BiblioGov. This book was released on 2013-08 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: The loading of an airfoil during dynamic stall is examined in terms of the augmented lift and the associated penalties in pitching moment and drag. It is shown that once stall occurs and a leading-edge vortex is shed from the airfoil there is a unique relationship between the augmented lift, the negative pitching moment, and the increase in drag. This relationship, referred to here as the dynamic stall function, shows limited sensitivity to effects such as the airfoil section profile and Mach number, and appears to be independent of such parameters as Reynolds number, reduced frequency, and blade sweep. For single-element airfoils there is little that can be done to improve rotorcraft maneuverability except to provide good static C(l(max)) characteristics and the chord or blade number that is required to provide the necessary rotor thrust. However, multi-element airfoils or airfoils with variable geometry features can provide augmented lift in some cases that exceeds that available from a single-element airfoil. The dynamic stall function is shown to be a useful tool for the evaluation of both measured and calculated dynamic stall characteristics of single element, multi-element, and variable geometry airfoils.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Characterization of Dynamic Stall on 9-15 % Thick Airfoils Using Experiment and Computation by : Phillip B. Davidson
Download or read book Characterization of Dynamic Stall on 9-15 % Thick Airfoils Using Experiment and Computation written by Phillip B. Davidson and published by . This book was released on 2014 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, the blade geometry on wind turbines and helicopters has been optimized for a particular span location. Unsteady flow phenomena like dynamic stall limit these designs and need to be better understood and correctly simulated. Currently, empirical and computational fluid dynamics (CFD) methods are used to simulate rotating wind turbine or helicopter blades, but each of these methods has limitations in predicting unsteady separated flows. To address these needs, the present work investigated oscillating airfoils over a range of conditions with an approach that provided fast, low-cost unsteady pressure data combined with a highly resolved flow field to better understand the physics of dynamic stall. An additional objective was to show how such data may be used to assess CFD simulations. This research has yielded interesting results showing characteristics of thin airfoil stall, leading edge stall, and trailing edge stall that were sorted and classified. Classification of the oscillating airfoil behavior with or without dynamic stall was performed using previous definitions for stall regime, separation characteristics, and other qualitative differences in stall pattern. After classifying the unsteady flow for each of the cases, comparison of experimental results and results obtained using an unsteady Reynolds Averaged Navier-Stokes (URANS) solver was performed to assess the ability of the solver to produce the same unsteady effects. Although both experiment and computation produced similar flow features, the timing and magnitude of the features in the dynamic stall and re-attachment process of the pitching cycle exhibited some significant differences.
Book Synopsis Analysis of the Development of Dynamic Stall Based on Oscillating Airfoil Experiments by : Lawrence W. Carr
Download or read book Analysis of the Development of Dynamic Stall Based on Oscillating Airfoil Experiments written by Lawrence W. Carr and published by . This book was released on 1977 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Aerodynamic Pressure and Flow-visualization Measurement from a Rotating Wind Turbine Blade by : Charles P. Butterfield
Download or read book Aerodynamic Pressure and Flow-visualization Measurement from a Rotating Wind Turbine Blade written by Charles P. Butterfield and published by . This book was released on 1988 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781722115975 Total Pages :28 pages Book Rating :4.1/5 (159 download)
Book Synopsis Compressibility Effects on Dynamic Stall of Airfoils Undergoing Rapid Transient Pitching Motion by : National Aeronautics and Space Administration (NASA)
Download or read book Compressibility Effects on Dynamic Stall of Airfoils Undergoing Rapid Transient Pitching Motion written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-30 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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...
Book Synopsis Evaluation of Airfoil Dynamic Stall Characteristics for Maneuverability by :
Download or read book Evaluation of Airfoil Dynamic Stall Characteristics for Maneuverability written by and published by . This book was released on 2000 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: The loading of an airfoil during dynamic stall is examined in terms of the augmented lift and the associated penalties in pitching moment and drag. It is shown that once stall occurs and a leading-edge vortex is shed from the airfoil there is a unique relationship between the augmented lift, the negative pitching moment, and the increase in drag. This relationship, referred to here as the dynamic stall function, shows limited sensitivity to many parameters that influence rotors in flight. For single-element airfoils it appears that there is little that can be done to improve rotorcraft maneuverability except to provide good static clmax characteristics and the chord or blade number that is required to provide the necessary rotor thrust. The loading on a helicopter blade during a severe maneuver is examined and it is shown that the blade's dynamic stall function is similar to that obtained in two-dimensional wind tunnel testing. An evaluation of three-dimensional effects for flight and an oscillating wing in a wind tunnel suggests that the two problems are not proper analogues. The utility of the dynamic stall function is demonstrated by evaluating sample theoretical predictions based on semi-empirical stall models and CFD computations. The approach is also shown to be useful in evaluating multi-element airfoil data obtained from dynamic stall tests.
Download or read book Rush, Olive written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The folder may include clippings, announcements, small exhibition catalogs, and other ephemeral items.
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781722792268 Total Pages :76 pages Book Rating :4.7/5 (922 download)
Book Synopsis Suppression of Dynamic Stall with a Leading-Edge Slat on a Vr-7 Airfoil by : National Aeronautics and Space Administration (NASA)
Download or read book Suppression of Dynamic Stall with a Leading-Edge Slat on a Vr-7 Airfoil written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-16 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: The VR-7 airfoil was experimentally studied with and without a leading-edge slat at fixed angles of attack from 0 deg to 30 deg at Re = 200,000 and for unsteady pitching motions described by alpha equals alpha(sub m) + 10 deg(sin(wt)). The models were two dimensional, and the test was performed in a water tunnel at Ames Research Center. The unsteady conditions ranged over Re equals 100,000 to 250,000, k equals 0.001 to 0.2, and alpha(sub m) = 10 deg to 20 deg. Unsteady lift, drag, and pitching-moment measurements were obtained along with fluorescent-dye flow visualizations. The addition of the slat was found to delay the static-drag and static-moment stall by about 5 degrees and to eliminate completely the development of a dynamic-stall vortex during unsteady motions that reached angles as high as 25 degrees. In all of the unsteady cases studied, the slat caused a significant reduction in the force and moment hysteresis amplitudes. The reduced frequency was found to have the greatest effect on the results, whereas the Reynolds number had little effect on the behavior of either the basic or the slatted airfoil. The slat caused a slight drag penalty at low angles of attack, but generally increased the lift/drag ratio when averaged over the full cycle of oscillation. Mcalister, K. W. and Tung, C. Ames Research Center...
Book Synopsis Summary of Low Speed Airfoil Data by : Michael S. Selig
Download or read book Summary of Low Speed Airfoil Data written by Michael S. Selig and published by Soartech. This book was released on 1995 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
