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Author :
Publisher :
ISBN 13 :
Total Pages : 28 pages
Book Rating : 4.:/5 (317 download)
Download or read book The Structure of Trailing Vortices Generated by Model Rotor Blades written by and published by . This book was released on 1981 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Kenneth W. Mcalister
Publisher : BiblioGov
ISBN 13 : 9781289270322
Total Pages : 46 pages
Book Rating : 4.2/5 (73 download)
Download or read book Preliminary Study of a Model Rotor in Descent written by Kenneth W. Mcalister and published by BiblioGov. This book was released on 2013-08 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Within a program designed to develop experimental techniques for measuring the trajectory and structure of vortices trailing from the tips of rotor blades, the present preliminary study focuses on a method for quantifying the trajectory of the trailing vortex during descent flight conditions. This study also presents rotor loads and blade surface pressures for a range of tip-path plane angles and Mach numbers. Blade pressures near the leading edge and along the outer radius are compared with data obtained on the same model rotor, but in open jet facilities. A triangulation procedure based on two directable laser-light sheets, each containing an embedded reference, proved effective in defining the spatial coordinates of the trailing vortex. When interrogating a cross section of the flow that contains several trailing vortices, the greatest clarity was found to result when the flow is uniformly seeded. Surface pressure responses during blade-vortex interactions appeared equally sensitive near the leading edge and along the outer portion of the blade, but diminished rapidly as the distance along the blade chord increased. The pressure response was virtually independent of whether the tip-path plane angle was obtained through shaft tilt or cyclic pitch. Although the shape and frequency of the pressure perturbations on the advancing blade during blade-vortex interaction are similar to those obtained in open-jet facilities, the angle of the tip-path plane may need to be lower than the range covered in this study.
Author :
Publisher : DIANE Publishing
ISBN 13 : 142891546X
Total Pages : 148 pages
Book Rating : 4.4/5 (289 download)
Download or read book NACA 0015 Wing Pressure and Trailing Vortex Measurements written by and published by DIANE Publishing. This book was released on with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781720665205
Total Pages : 42 pages
Book Rating : 4.6/5 (652 download)
Download or read book Preliminary Study of a Model Rotor in Descent written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-03 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Within a program designed to develop experimental techniques for measuring the trajectory and structure of vortices trailing from the tips of rotor blades, the present preliminary study focuses on a method for quantifying the trajectory of the trailing vortex during descent flight conditions. This study also presents rotor loads and blade surface pressures for a range of tip-path plane angles and Mach numbers. Blade pressures near the leading edge and along the outer radius are compared with data obtained on the same model rotor, but in open jet facilities. A triangulation procedure based on two directable laser-light sheets, each containing an embedded reference, proved effective in defining the spatial coordinates of the trailing vortex. When interrogating a cross section of the flow that contains several trailing vortices, the greatest clarity was found to result when the flow is uniformly seeded. Surface pressure responses during blade-vortex interactions appeared equally sensitive near the leading edge and along the outer portion of the blade, but diminished rapidly as the distance along the blade chord increased. The pressure response was virtually independent of whether the tip-path plane angle was obtained through shaft tilt or cyclic pitch. Although the shape and frequency of the pressure perturbations on the advancing blade during blade-vortex interaction are similar to those obtained in open-jet facilities, the angle of the tip-path plane may need to be lower than the range covered in this study.McAlister, K. W. and Tung, C. and Sharpe, D. L. and Huang, S. and Hendley, E. M.Ames Research CenterTRAJECTORIES; VORTICES; BLADE-VORTEX INTERACTION; HELICOPTER TAIL ROTORS; HELICOPTER WAKES; FLIGHT CONDITIONS; DESCENT; LOADS (FORCES); PRESSURE; FLOW VISUALIZATION; MACH NUMBER
Author :
Publisher :
ISBN 13 :
Total Pages : 252 pages
Book Rating : 4.:/5 (946 download)
Download or read book The Origin and Structure of Trailing Vortices in Aerodynamics written by and published by . This book was released on 2001 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: The helicopter rotor wake is among the most complex flow-fields in aerodynamics. Despite the fact that a large amount of computational and experimental work on the rotor wake has been published, little of a quantitative nature is known about the origin of the main component of the rotor wake, the tip-vortex, as a function of the rotor speed, rotor blade geometry, and angle of attack. The primary objective of this work is to predict the formation of the rotor tip vortex as a function of physical parameters such as angle of attack, rotor speed, and blade aspect ratio. While the rotor-blade tip-vortex is of primary interest, the techniques developed are applicable to fixed wings as well.
Author :
Publisher :
ISBN 13 :
Total Pages : 230 pages
Book Rating : 4.:/5 (317 download)
Download or read book Devices that Alter the Tip Vortex of a Rotor written by and published by . This book was released on 2001 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: Small devices were attached near the tip of a hovering rotor blade in order to alter the structure and trajectory of the trailing vortex. Stereo particle image velocimetry (PIV) images were used to quantify the wake behind the rotor blade during the first revolution. A procedure for analyzing the 3D-velocity field is presented that includes a method for accounting for vortex wander. The results show that a vortex generator can alter the trajectory of the trailing vortex and that a major change in the size and intensity of the trailing vortex can be achieved by introducing a high level of turbulence into the core of the vortex.
Author : Kenneth W. McAlister
Publisher :
ISBN 13 :
Total Pages : 150 pages
Book Rating : 4.:/5 (31 download)
Download or read book NACA 0015 Wing Pressure and Trailing Vortex Measurements written by Kenneth W. McAlister and published by . This book was released on 1991 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : R. K. Takahashi
Publisher :
ISBN 13 :
Total Pages : 40 pages
Book Rating : 4.F/5 ( download)
Download or read book Preliminary Study of a Wing-tip Vortex Using Laser Velocimetry written by R. K. Takahashi and published by . This book was released on 1987 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : S. Gene Sadler
Publisher :
ISBN 13 :
Total Pages : 132 pages
Book Rating : 4.:/5 (31 download)
Download or read book Development and Application of a Method for Predicting Rotor Free Wake Positions and Resulting Rotor Blade Air Loads written by S. Gene Sadler and published by . This book was released on 1971 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rotor wake geometries are predicted by a process similar to the startup of a rotor in a free stream. An array of discrete trailing and shed vortices is generated with vortex strengths corresponding to stepwise radial and azimuthal blade circulations. The array of shed and trailing vortices is limited to an arbitrary number of azimuthal steps behind each blade. The remainder of the wake model of each blade is an arbitrary number of trailing vortices. Vortex element end points were allowed to be transported by the resultant velocity of the free stream and vortex-induced velocities. Wake geometry, wake flow, and wake-induced velocity influence coefficients are generated by this program for use in the blade loads portion of the calculations. Blade loads computations include the effects of nonuniform inflow due to a free wake, nonlinear airfoil characteristics, and response of flexible blades to the applied loads. Computed wake flows and blade loads are compared with experimentally measured data. Predicted blade loads, response and shears and moments are obtained for a model rotor system having two independent rotors. The effects of advance ratio, vertical separation of rotors, different blade radius ratios, and different azimuthal spacing of the blades of one rotor with respect to the other are investigated.
Author :
Publisher :
ISBN 13 :
Total Pages : 230 pages
Book Rating : 4.:/5 (319 download)
Download or read book NASA Technical Paper written by and published by . This book was released on 1991 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : United States. National Aeronautics and Space Administration
Publisher :
ISBN 13 :
Total Pages : 148 pages
Book Rating : 4.3/5 (91 download)
Download or read book NASA Technical Paper written by United States. National Aeronautics and Space Administration and published by . This book was released on 1991 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 340 pages
Book Rating : 4.3/5 (91 download)
Download or read book NASA Technical Memorandum written by and published by . This book was released on 1992 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 836 pages
Book Rating : 4.:/5 (31 download)
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Gordon J. Leishman
Publisher : Cambridge University Press
ISBN 13 : 9780521858601
Total Pages : 860 pages
Book Rating : 4.8/5 (586 download)
Download or read book Principles of Helicopter Aerodynamics with CD Extra written by Gordon J. Leishman and published by Cambridge University Press. This book was released on 2006-04-24 with total page 860 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by an internationally recognized teacher and researcher, this book provides a thorough, modern treatment of the aerodynamic principles of helicopters and other rotating-wing vertical lift aircraft such as tilt rotors and autogiros. The text begins with a unique technical history of helicopter flight, and then covers basic methods of rotor aerodynamic analysis, and related issues associated with the performance of the helicopter and its aerodynamic design. It goes on to cover more advanced topics in helicopter aerodynamics, including airfoil flows, unsteady aerodynamics, dynamic stall, and rotor wakes, and rotor-airframe aerodynamic interactions, with final chapters on autogiros and advanced methods of helicopter aerodynamic analysis. Extensively illustrated throughout, each chapter includes a set of homework problems. Advanced undergraduate and graduate students, practising engineers, and researchers will welcome this thoroughly revised and updated text on rotating-wing aerodynamics.
Author : S. Gene Sadler
Publisher :
ISBN 13 :
Total Pages : 788 pages
Book Rating : 4.F/5 ( download)
Download or read book Development and Application of a Method for Predicting Rotor Free Wake Positions and Resulting Rotor Blade Air Loads written by S. Gene Sadler and published by . This book was released on 1971 with total page 788 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rotor wake geometries are predicted by a process similar to the startup of a rotor in a free stream. An array of discrete trailing and shed vortices is generated with vortex strengths corresponding to stepwise radial and azimuthal blade circulations. The array of shed and trailing vortices is limited to an arbitrary number of azimuthal steps behind each blade. The remainder of the wake model of each blade is an arbitrary number of trailing vortices. Vortex element end points were allowed to be transported by the resultant velocity of the free stream and vortex-induced velocities. Wake geometry, wake flow, and wake-induced velocity influence coefficients are generated by this program for use in the blade loads portion of the calculations. Blade loads computations include the effects of nonuniform inflow due to a free wake, nonlinear airfoil characteristics, and response of flexible blades to the applied loads. Computed wake flows and blade loads are compared with experimentally measured data. Predicted blade loads, response and shears and moments are obtained for a model rotor system having two independent rotors. The effects of advance ratio, vertical separation of rotors, different blade radius ratios, and different azimuthal spacing of the blades of one rotor with respect to the other are investigated.
Author : Hock-Bin Lim
Publisher :
ISBN 13 :
Total Pages : 162 pages
Book Rating : 4.:/5 (317 download)
Download or read book Numerical Study of the Trailing Vortex of a Wing with Wing-tip Blowing written by Hock-Bin Lim and published by . This book was released on 1994 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781724328755
Total Pages : 368 pages
Book Rating : 4.3/5 (287 download)
Download or read book Perpendicular Blade Vortex Interaction and Its Implications for Helicopter Noise Prediction written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-27 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: Perpendicular blade vortex interactions are a common occurrence in helicopter rotor flows. Under certain conditions they produce a substantial proportion of the acoustic noise. However, the mechanism of noise generation is not well understood. Specifically, turbulence associated with the trailing vortices shed from the blade tips appears insufficient to account for the noise generated. The hypothesis that the first perpendicular interaction experienced by a trailing vortex alters its turbulence structure in such a way as to increase the acoustic noise generated by subsequent interactions is examined. To investigate this hypothesis a two-part investigation was carried out. In the first part, experiments were performed to examine the behavior of a streamwise vortex as it passed over and downstream of a spanwise blade in incompressible flow. Blade vortex separations between +/- one eighth chord were studied for at a chord Reynolds number of 200,000. Three-component velocity and turbulence measurements were made in the flow from 4 chord lengths upstream to 15 chordlengths downstream of the blade using miniature 4-sensor hot wire probes. These measurements show that the interaction of the vortex with the blade and its wake causes the vortex core to loose circulation and diffuse much more rapidly than it otherwise would. Core radius increases and peak tangential velocity decreases with distance downstream of the blade. True turbulence levels within the core are much larger downstream than upstream of the blade. The net result is a much larger and more intense region of turbulent flow than that presented by the original vortex and thus, by implication, a greater potential for generating acoustic noise. In the second part, the turbulence measurements described above were used to derive the necessary inputs to a Blade Wake Interaction (BWI) noise prediction scheme. This resulted in significantly improved agreement between measurements and calculations of the BWI noise spectr...
