Download or read book Wake Geometry Measurements and Analytical Calculations on a Small Scale Rotor Model 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 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation was conducted in the Langley 14- by 22-Foot Subsonic Tunnel to quantify the rotor wake behind a scale model helicopter rotor in forward level flight at one thrust level. The rotor system in this test consisted of a four-bladed fully articulated hub with blades of rectangular planform and an NACA 0012 airfoil section. A laser light sheet, seeded with propylene glycol smoke, was used to visualize the vortex geometry in the flow in planes parallel and perpendicular to the free-stream flow. Quantitative measurements of wake geometric proper- ties, such as vortex location, vertical skew angle, and vortex particle void radius, were obtained as well as convective velocities for blade tip vortices. Comparisons were made between experimental data and four computational method predictions of experimental tip vortex locations, vortex vertical skew angles, and wake geometries. The results of these comparisons highlight difficulties of accurate wake geometry predictions. Ghee, Terence A. and Berry, John D. and Zori, Laith A. J. and Elliott, Joe W. Unspecified Center...

Download or read book Wake Geometry Measurements and Analytical Calculations on a Small Scale Rotor Model written by Terence A. Ghee and published by . This book was released on 1996 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comparison of Calculated and Measured Model Rotor Loading and Wake Geometry written by Wayne Johnson and published by . This book was released on 1980 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Airloads and Wake Geometry Calculations for an Isolated Tiltrotor Model in a Wind Tunnel written by and published by . This book was released on 2001 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comparisons of measured and calculated aerodynamic behavior of a tiltrotor model are presented. The test of the Tilt Rotor Aeroacoustic Model (TRAM) with a single, 0.25-scale V-22 rotor in the German-Dutch Wind Tunnel (DNW) provides an extensive set of aeroacoustic, performance, and structural loads data. The calculations were performed using the rotorcraft comprehensive analysis CAMRAD II. Presented are comparisons of measured and calculated performance for hover and helicopter mode operation, and airloads for helicopter mode. Calculated induced power, profile power, and wake geometry provide additional information about the aerodynamic behavior. An aerodynamic and wake model and calculation procedure that reflects the unique geometry and phenomena of tiltrotors has been developed. There are major differences between this model and the corresponding aerodynamic and wake model that has been established for helicopter rotors. In general, good correlation between measured and calculated performance and airloads behavior has been shown. Two aspects of the analysis that clearly need improvement are the stall delay model and the trailed vortex formation model.

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.

Download or read book Flow Environment Study Near the Empennage of a 15 Percent Scale Helicopter Model written by Susan Althoff Gorton and published by . This book was released on 2000 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: Development of advanced rotorcraft configurations has highlighted a need for high-quality experimental data to support the development of flexible and accurate analytical design tools. To provide this type of data, a test program was conducted in the Langley 14- by 22-Foot Subsonic Tunnel to measure the flow near the empennage of a 15-percent scale powered helicopter model with an operating tail fan. Three-component velocity profiles were measured with laser velocimetry (LV) one chord forward of the horizontal tail for four advance ratios to evaluate the effect of the rotor wake impingement on the horizontal tail angle of attack. These velocity data indicate the horizontal tail can experience unsteady angle of attack variations of over 30 degress due to the rotor wake influence. The horizontal tail is most affected by the rotor wake above advance ratios of 0.10. Velocity measurements of the flow on the inlet side of the tail fan were made for a low-speed flight condition using conventional LV techniques. The velocity data show an accelerated flow near the tail fan duct, and vorticity calculations track the passage of main rotor wake vortices through the measurement plane.

Download or read book Laser Techniques Applied to Fluid Mechanics written by R.J. Adrian and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 624 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the tradition of its predecessors, this volume comprises a selection of the best papers presented at the Ninth International Symposium on Applications of Laser Techniques to Fluid Mechanics, held in Lisbon in July 2000. The papers reflect the state-of-the-art in laser applications of laser techniques in fluid mechanics describing novel ideas for instrumentation, instrumentation developments, results of measurements of wall-bounded flows, free flows and flames and flow and combustion in engines. The papers demonstrate the continuing interest in the development of an understanding of new methodologies and implementation in terms of new instrumentation.

Download or read book NASA Technical Memorandum written by and published by . This book was released on 1989 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book 04 2326 04 2434 written by and published by . This book was released on 2004 with total page 610 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analytical Model of Rotor Wake Aerodynamics in Ground Effect written by and published by . This book was released on 1983 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rotor Induced Inflow Ratio Measurements and CAMRAD Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics Calculations written by and published by . This book was released on 1990 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comparison of the inflow calculations between an analytical rotor- wake method and rotor-inflow measurements using a laser velocimeter has been presented. The inflow measurements were made above a four-bladed rotor system using rectangular planform blades operating in forward flight at a thrust coefficient of 0.0064 and at rotor advance ratios of 0.15, 0.23, and 0.30. The experimental measurements showed that as the advance ratio u increased, the induced-upflow region moved progressively from the forward 20 percent of the rotor disc at u=0.15 to a point where it covered most of the forward half of the rotor disc at u=0.30. The induced-inflow characteristics at all advance ratios were unsymmetrical about the longitudinal centerline. The comparisons with the analytical method CAMRAD (Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics) show that the region of induced upflow over the rotor disc was effectively modeled only at u=0.15. The importance of the choice of rotor-trim option is examined, and results of two trim selections are detailed. Keywords: Helicopter wake; Helicopter inflow; CAMRAD; Blade-tip vortices; Laser velocimeter.

Download or read book A Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics Part 1 Analysis Development written by and published by . This book was released on 1980 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of a comprehensive analytical model of rotorcraft aerodynamics and dynamics is presented. This analysis is designed to calculate rotor performance, loads, and noise; helicopter vibration and gust response; flight dynamics and handling qualities; and system aeroelastic stability. The analysis is a combination of structural, inertial, and aerodynamic models that is applicable to a wide range of problems and a wide class of vehicles. The analysis is intended for use in the design, testing, and evaluation of rotors and rotorcraft, and to be a basis for further development of rotary wing theories. The analysis is implemented in a digital computer program. (Author).

Download or read book Horizontal axis Wind System Rotor Performance Model Comparison written by and published by . This book was released on 1983 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rotor Induced inflow ratio Measurements and CAMRAD Calculations written by Danny R. Hoad and published by . This book was released on 1990 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aeronautical Engineering written by and published by . This book was released on 1971 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: A selection of annotated references to unclassified reports and journal articles that were introduced into the NASA scientific and technical information system and announced in Scientific and technical aerospace reports (STAR) and International aerospace abstracts (IAA)

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.