Download or read book Unsteady Velocity Measurements Taken Behind a Model Helicopter Rotor Hub in Forward Flight written by and published by DIANE Publishing. This book was released on with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Unsteady Velocity Measurements Taken Behind a Model Helicopter Rotor Hub in Forward Flight written by John D. Berry and published by . This book was released on 1997 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Unsteady Velocity Measurements Taken Behind a Model Helicopter Rotor Hub in Forward Flight written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-09 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: Drag caused by separated flow behind the hub of a helicopter has an adverse effect on aerodynamic performance of the aircraft. To determine the effect of separated flow on a configuration used extensively for helicopter aerodynamic investigations, an experiment was conducted using a laser velocimeter to measure velocities in the wake of a model helicopter hub operating at Mach-scaled conditions in forward flight. Velocity measurements were taken using a laser velocimeter with components in the vertical and downstream directions. Measurements were taken at 13 stations downstream from the rotor hub. At each station, measurements were taken in both a horizontal and vertical row of locations. These measurements were analyzed for harmonic content based on the rotor period of revolution. After accounting for these periodic velocities, the remaining unsteady velocities were treated as turbulence. Turbulence intensity distributions are presented. Average turbulent intensities ranged from approximately 2 percent of free stream to over 15 percent of free stream at specific locations and azimuths. The maximum average value of turbulence was located near the rear-facing region of the fuselage. Berry, John D. Langley Research Center NASA-TM-4738, NAS 1.15:4738, L-17524, ATCOM-TR-97-A-001 RTOP 505-59-36-01...
Download or read book Unsteady Velocity Measurements Taken Behind a Model Helicopter Rotor Hub in Forward Flight Nasa tm 4738 written by and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Unsteady Velocity Measurement Taken Behind a Model Helicopter Rotor Hub in Forward Flight written by and published by . This book was released on 1997 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: Drag caused by separated flow behind the hub of a helicopter has an adverse effect on aerodynamic performance of the aircraft. To determine the effect of separated flow on a configuration used extensively for helicopter aerodynamic investigations, an experiment was conducted using a laser velocimeter to measure velocities in the wake of a model helicopter hub operating at Mach-scaled conditions in forward flight. Velocity measurements were taken using a laser velocimeter with components in the vertical and downstream directions. Measurements were taken at 1 3 stations downstream from the rotor hub. At each station, measurements were taken in both a horizontal and vertical row of locations. These measurements were analyzed for harmonic content based on the rotor period of revolution. After accounting for these periodic velocities, the remaining unsteady velocities were treated as turbulence. Turbulence intensity distributions are presented. Average turbulent intensities ranged from approximately 2 percent of free stream to over 15 percent of free stream at specific locations and azimuths. The maximum average value of turbulence was located near the rear-facing region of the fuselage.
Download or read book Compressible Unsteady Lifting surface Theory for a Helicopter Rotor in Forward Flight written by Harry L. Runyan and published by . This book was released on 1985 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book Compressible Unsteady Lifting surface Theory for a Helicopter Rotor in Forward Flight written by and published by . This book was released on 1985 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Langley Scientific and Technical Information Output 1997 written by and published by . This book was released on 1998 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Steady and Periodic Pressure Measurements on a Generic Helicopter Fuselage Model in the Presence of a Rotor written by Raymond E. Mineck and published by . This book was released on 2000 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: A wind tunnel test of a generic helicopter fuselage model with an independently mounted rotor has been conducted to obtain steady and periodic pressure data on the helicopter body. The model was tested at four advance ratios and three thrust coefficients. The periodic unsteady pressure coefficients are marked by four peaks associated with the passage of the four rotor blades. Blade passage effects are largest on the nose and tail boom of the model. The magnitude of the pulse increases with rotor thrust coefficient. Tabular listings of the unsteady pressure data are included to permit independent analysis. A CDrom containing the steady and unsteady pressure data presented in the report is available from the authors.
Download or read book Experimental Smoke and Electromagnetic Analog Study of Induced Flow Field about a Model Rotor in Steady Flight Within Ground Effect written by Robin B. Gray and published by . This book was released on 1960 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hovering and steady low-speed forward-flight tests were run on a 4-foot-diameter rotor at a ground height of 1 rotor radius. The two blades had a 2 to 1 taper ratio and were mounted in a see-saw hub. The solidity ratio was 0.05. Measurements were made of the rotor rpm, collective pitch, and forward-flight velocity. Smoke was introduced into the tip vortex and the resulting vortex pattern was photographed from two positions. Using the data obtained from these photographs, wire models of the tip vortex configurations were constructed and the distribution of the normal component of induced velocity at the blade feathering axis that is associated with these tip vortex configurations was experimentally determined at 450 increments in azimuth position from this electromagnetic analog. Three steady-state conditions were analyzed. The first was hovering flight; the second, a flight velocity just under the wake "tuck under" speed; and the third, a flight velocity just above this speed. These corresponded to advance ratios of 0, 0.022, and 0.030 (or ratios of forward velocity to calculated hovering induced velocity of approximately 0, 0.48, and 0.65), respectively, for the model test rotor. Cross sections of the wake at 450 intervals in azimuth angle as determined from the path of the tip vortex are presented graphically for all three cases. The nondimensional normal component of the induced velocity that is associated with the tip vortex as determined by an electromagnetic analog at 450 increments in azimuth position and at the blade feathering axis is presented graphically. It is shown that the mean value of this component of the induced velocity is appreciably less after tuck-under than before. It is concluded that this method yields results of engineering accuracy and is a very useful means of studying vortex fields.
Download or read book Aeromechanics Technology Product Design for the 21st Century written by and published by . This book was released on 1995 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Unsteady Subsonic and Transonic Potential Flow Over Helicopter Rotor Blades written by Morris P. Isom and published by . This book was released on 1974 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Differential equations and boundary conditions for a rotor blade in forward flight, with subsonic or transonic tip Mach number, are derived. A variety of limiting flow regimes determined by different limits involving blade thickness ratio, aspect ratio, advance ratio and maximum tip Mach number is discussed. The transonic problem is discussed in some detail, and in particular the conditions that make this problem quasi-steady or essentially unsteady are determined. Asymptotic forms of equations and boundary conditions that are valid in an appropriately scaled region of the tip and an azimuthal sector on the advancing side are derived. The equations are then put in a form that is valid from the blade tip inboard through the strip theory region.
Download or read book An Unsteady Helicopter Rotor written by Peter Frederick Lorber and published by . This book was released on 1988 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Principles of Helicopter Aerodynamics written by J. Gordon Leishman and published by Cambridge University Press. This book was released on 2002-12-23 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt: Helicopters are highly capable and useful rotating-wing aircraft with roles that encompass a variety of civilian and military applications. Their usefulness lies in their unique ability to take off and land vertically, to hover stationary relative to the ground, and to fly forward, backward, or sideways. These unique flying qualities, however, come at a high cost including complex aerodynamic problems, significant vibrations, high levels of noise, and relatively large power requirements compared to fixed-wing aircraft. This book, written by an internationally recognized expert, provides a thorough, modern treatment of the aerodynamic principles of helicopters and other rotating-wing vertical lift aircraft. Every chapter is extensively illustrated and concludes with a bibliography and homework problems. Advanced undergraduate and graduate students, practising engineers, and researchers will welcome this thorough and up-to-date text on rotating-wing aerodynamics.
Download or read book An Unsteady Helicopter Rotor written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computational method was developed to treat unsteady aerodynamic interactions between a helicopter rotor, wake, and fuselage and between the main and tail rotors. An existing lifting line prescribed wake rotor analysis and a source panel fuselage analysis were coupled and modified to predict unsteady fuselage surface pressures and airloads. A prescribed displacement technique is used to position the rotor wake about the fuselage. Either a rigid blade or an aeroelastic blade analysis may be used to establish rotor operating conditions. Sensitivity studies were performed to determine the influence of the wake fuselage geometry on the computation. Results are presented that describe the induced velocities, pressures, and airloads on the fuselage and on the rotor. The ability to treat arbitrary geometries is demonstrated using a simulated helicopter fuselage. The computational results are compared with fuselage surface pressure measurements at several locations. No experimental data was available to validate the primary product of the analysis: the vibratory airloads on the entire fuselage. A main rotor-tail rotor interaction analysis is also described, along with some hover and forward flight. Lorber, Peter F. and Egolf, T. Alan Unspecified Center COMPUTATIONAL FLUID DYNAMICS; CONFIGURATION INTERACTION; INTERACTIONAL AERODYNAMICS; ROTARY WINGS; UNSTEADY AERODYNAMICS; UNSTEADY FLOW; AERODYNAMIC LOADS; FUSELAGES; HELICOPTER WAKES; HORIZONTAL FLIGHT; HOVERING; PRESSURE EFFECTS...
Download or read book Non Steady Velocity Measuremeht of the Wake of a Helicopter Rotor at Low Advanced Ratios written by H. R. Velkoff and published by . This book was released on 1981 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: A system was developed which could measure the instantaneous velocities in the wake of a model helicopter rotor operating at low advance ratios. A three-wire hot film probe was mounted on a traverse and placed at many positions in the wake. The output of the probe was fed into an on-line computer operating in an interactive mode. Computer generated vector plots were made of both time averaged velocities and instantaneous velocities for the case of mu = 0.06. (Author).
