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  • 1
    Publication Date: 2011-08-24
    Description: An experimental investigation was conducted in the 14 by 22 ft subsonic tunnel at NASA Langley Research Center to quantify the rotor wake behind a scale model helicopter rotor in forward flight (mu = 0.15 and 0.23) at one thrust level (C sub T = 0.0064). The rotor system used in the present test consisted of a four-bladed, fully articulated hub and utilized blades of rectangular planform with a NACA-0012 airfoil section. A laser light sheet, seeded with propylene glycol smoke, was used to visualize the flow in planes parallel and perpendicular to the freestream flow. Quantitative measurements of vortex location, vertical skew angle, and vortex particle void radius were obtained for vortices in the flow; convective velocities were obtained for blade tip vortices. Comparisons were made between the experimental results and the wake geometry generated by computational predictions. The results of these comparisons show that the interaction between wake vortex structures is an important consideration for correctly predicting the wake geometry.
    Keywords: AERODYNAMICS
    Type: In: AHS, Annual Forum, 48th, Washington, June 3-5, 1992, Proceedings. Vol. 1 (A93-35901 14-01); p. 697-719.
    Format: text
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  • 2
    Publication Date: 2019-06-28
    Description: 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.
    Keywords: Aircraft Design, Testing and Performance
    Type: NASA-TP-3584 , L-17449 , NAS 1.60:3584 , ATCOM-TR-96-A-007
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted in the 14- by 22-Foot Subsonic Tunnel at NASA Langley Research Center to measure the inflow into the scale model helicopter rotor in forward flight (mu sub infinity = 0.15). The measurements were made with a two-component Laser Velocimeter (LV) one chord above the plane formed by the path of the rotor tips (tip path plane). A conditional sampling technique was employed to determine the position of the rotor at the time that each velocity measurement was made so that the azimuthal fluctuations in velocity could be determined. Measurements were made at a total of 146 separate locations in order to clearly define the inflow character. This data is presented herein without analysis. In order to increase the availability of the resulting data, both the mean and azimuthally dependent values are included as part of this report on two 5.25 inch floppy disks in MS-DOS format.
    Keywords: AERODYNAMICS
    Type: NASA-TM-100544 , AVSCOM-TM-88-B-007 , NAS 1.15:100544
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  • 4
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted in the 14- by 22-Foot Subsonic Tunnel at NASA Langley Research Center to measure the inflow into a scale model helicopter rotor in forward flight (micron sub infinity = 0.30). The measurements were made with a two component Laser Velocimeter (LV) one chord above the plane formed by the path of the rotor tips (tip path plane). A conditional sampling technique was employed to determine the azimuthal position of the rotor at the time that each velocity measurement was made so that the azimuthal fluctuations in velocity could be determined. Measurements were made at a total of 180 separate locations in order to clearly define the inflow character. These data are presented without analysis.
    Keywords: AERODYNAMICS
    Type: NASA-TM-100543 , NAS 1.15:100543 , AVSCOM-TM-88-B-006
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  • 5
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted in the 14- by 22-Foot Subsonic Tunnel at NASA Langley to measure the inflow into a scale model helicopter rotor in forward flight (microinf = 0.15). The measurements were made with a two component Laser Velocimeter (LV) one chord above the plane formed by the path of the rotor tips (tip path plane). A conditional sampling technique was employed to determine the azimuthal position of the rotor at the time each velocity measurement was made so that the azimuthal fluctuations in velocity could be determined. Measurements were made at a total of 147 separate locations in order to clearly define the inflow character. This data is presented without analysis. In order to increase the availability of the resulting data, both the mean and azimuthally dependent values are included as part of this report on two 5.25 inch floppy disks in Microsoft Corporation MS-DOS format.
    Keywords: AERODYNAMICS
    Type: NASA-TM-100541 , AVSCOM-TM-88-B-004 , NAS 1.15:100541
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  • 6
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted in the 14- by 22-Foot Subsonic tunnel at NASA Langley Research Center to measure the inflow into a scale model helicopter rotor in forward flight (mu sub inf = 0.23). The measurements were made with a two component Laser Velocimeter (LV) one chord above the plane formed by the path of the blade tips. A conditional sampling technique was employed to determine the position of the rotor at the time that each velocity measurement was made so that the azimuthal fluctuations in velocity could be determined. Measurements were made at a total of 168 separate locations in order to clearly define the inflow character. This data is presented without analysis. In order to increase the availability of the resulting data, both the mean and azimuthally dependenet values are included as part of this report on two 5.25 inch floppy disks in Microsoft Corporation MS-DOS format.
    Keywords: AERODYNAMICS
    Type: NASA-TM-100545 , NAS 1.15:100545 , AVSCOM-TM-88-B-008-VOL-5
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  • 7
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted in the 14- by 22-Foot Subsonic Tunnel at NASA Langley Research Center to measure the inflow into a scale model helicopter rotor in forward flight (mu sub infinity = 0.23). The measurements were made with a two-component Laser Velocimeter (LV) one chord above the plane formed by the path of the rotor tips (tip path plane). A conditional sampling technique was employed to determine the azimuthal position of the rotor at the time that each velocity measurement was made so that the azimuthal fluctuations in velocity could be determined. Measurements were made at a total of 180 separate locations in order to clearly define the inflow character. This data is presented without analysis.
    Keywords: AERODYNAMICS
    Type: NASA-TM-100542 , NAS 1.15:100542 , AVSCOM-TM-88-B-005
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  • 8
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted in the 14- by 22-Foot Subsonic Tunnel at NASA Langley Research Center to measure the inflow into a scale model helicopter rotor in forward flight. The measurements were made with a two component Laser Velocimeter (LV) one chord above the plane formed by the path of the rotor tips (tips path plane). A conditional sampling technique was employed to determine the position of the rotor at the time that each velocity measurement was made so that the azimuthal fluctuations in velocity could be determined. The results of these tests were compared with inflow velocities predicted by a current technology rotor wake analysis program.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 87-1321
    Format: text
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  • 9
    Publication Date: 2019-07-13
    Description: An investigation has been performed to assess methods used for rotor inflow modeling. A key element of this assessment has been the recent acquisition of high quality experimental measurements of inflow velocities taken in the proximity of a lifting rotor in forward flight. Widely used rotor performance predictive methods are based on blade element strip theory coupled with an inflow model. The inflow prediction models assessed in this paper include the uniform inflow based on momentum, a skewed disk model, and two methods based on a vortex wake structure.
    Keywords: AERODYNAMICS
    Type: National Specialists'' Meeting on Aerodynamics and Aeroacoustics; Feb 25, 1987 - Feb 27, 1987; Arlington, TX; United States
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  • 10
    Publication Date: 2019-07-13
    Description: An experimental investigation was conducted in the 14- by 22-foot subsonic tunnel at NASA-Langley Research Center to measure the inflow into a scale model helicopter rotor in forward flight. These inflow measurements were acquired utilizing a two-component laser velocimeter, and the data were processed by a frequency-domain processor (FDP). As a subset of the experiment, a time-domain counter processor was utilized simultaneously with an FDP to make a comparison of the two processors possible. The results indicate that the FDP had a marked improvement in processing capability in conditions of low signal-to-noise ratios and had a reduction in the number of erroneous data points acquired. However, the FDP yielded a lower data rate in comparison to the counter when signal-to-noise ratios were high. Comparison of the data sets shows that the FDP consistantly measures velocities which are 0.7 percent higher than those measured by the counter processor.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ICIASF ''91 - International Congress on Instrumentation in Aerospace Simulation Facilities; Oct 27, 1991 - Oct 31, 1991; Rockville, MD; United States
    Format: text
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