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  • 1
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    A wind tunnel application of large-field focusing schlieren (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A large-field focusing schlieren apparatus was installed in the NASA Lewis Research Center 9 by 15 foot wind tunnel in an attempt to determine the density gradient flow field of a free jet issuing from a supersonic nozzle configuration. The nozzle exit geometry was designed to reduce acoustic emissions from the jet by enhancing plume mixing. Thus, the flow exhibited a complex three-dimensional structure which warranted utilizing the sharp focusing capability of this type of schlieren method. Design considerations concerning tunnel limitations, high-speed photography, and video tape recording are presented in the paper.
    Keywords: ACOUSTICS
    Type: In: DGLR(AIAA Aeroacoustics Conference, 14th, Aachen, Germany, May 11-14, 1992, Proceedings. Vol. 1 (A93-19126 05-71); p. 169-176.
    Format: text
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  • 2
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    Application Focused Schlieren to Nozzle Ejector Flowfields (1999)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The motivation of the testing was to reduce noise generated by eddy Mach wave emission via enhanced mixing in the jet plume. This was to be accomplished through the use of an ejector shroud, which would bring in cooler ambient fluid to mix with the hotter jet flow. In addition, the contour of the mixer, with its chutes and lobes, would accentuate the merging of the outer and inner flows. The objective of the focused schlieren work was to characterize the mixing performance inside of the ejector. Using flow visualization allowed this to be accomplished in a non-intrusive manner.
    Keywords: Aircraft Propulsion and Power
    Type: First NASA/Industry High Speed Research Program Nozzle Symposium; 15-1 - 15-14; NASA/CP-1999-209423
    Format: application/pdf
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  • 3
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    NASA/LaRC jet plume research (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The following provides a summary for research being conducted by NASA/LaRC and its contractors and grantees to develop jet engine noise suppression technology under the NASA High Speed Research (HSR) program for the High Speed Civil Transport (HSCT). The objective of this effort is to explore new innovative concepts for reducing noise to Federally mandated guidelines with minimum compromise on engine performance both in take-off and cruise. The research program is divided into four major technical areas: (1) jet noise research on advanced nozzles; (2) plume prediction and validation; (3) passive and active control; and (4) methodology for noise prediction.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: First Annual High-Speed Research Workshop, Part 2; p 609-644
    Format: application/pdf
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  • 4
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    Dynamic pressure loads associated with twin supersonic plume resonance (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA Journal (ISSN 0001-1452); 26; 954-960
    Format: text
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  • 5
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    Study of external dynamic flap loads on a 6 percent B-1B model (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The origin of dynamic pressure loads on external divergent engine nozzle flaps of the B-1B aircraft was investigated in the NASA/LaRC 16 foot transonic tunnel using a 6 percent full span model with powered engine nacelles. External flap dynamic loads and afterbody drag associated with flap removal were measured using this model. Both dry and max. A/B power nozzles were evaluated in this study. As a result of this study, the principal mechanisms responsible for high dynamic external flap loads were determined along with performance penalty associated with flap removal.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: ASME PAPER 91-GT-236
    Format: text
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  • 6
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    External nozzle flap dynamic load measurements on F-15 S/MTD model (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Dynamic pressure loads were obtained on 1/12 scale models of the F-15B production aircraft and the F-15 S/MTD experimental aircraft with rectangular nozzles and canards. Flight Mach numbers from 0.51 to 1.20 were studied for aircraft angles of attack from 0 to 10 deg and nozzle pressure ratios from 1.00 to 5.09. The results show that dynamic levels are lower in the internozzle region of twin rectangular nozzles than are levels found with twin axisymmetric nozzles. At other locations, the levels associated with both geometries are of the same order of magnitude when normalized by aircraft dynamic Q. At Mach number of 0.51, the loads spectrum is dominated by plume shock noise processes for both geometries. Above Mach 0.51, this mechanism is associated with either vortex bursting from a forward location or turbulent boundary layer separation over the nozzle external flaps. At supersonic speeds both geometries show significantly decreased load levels.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 90-1910
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  • 7
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    Model and full scale study of twin supersonic plume resonance (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper examines the effect of both nozzle geometry and scale on the twin supersonic plume resonance phenomenon associated with aircraft having engine nozzle center-to-center spacings less than two diameters. Exit plane near field dynamic pressures were measured for both single and dual nozzle operation in 4.7 percent model and full scale under static conditions. The frequencies associated with this phenomenon were predicted to within 5 percent for a full scale F-15 aircraft. Amplitude levels associated with this phenomenon were found to dominate the dynamic pressure fluctuations in the inter-nozzle region, and reach a level near the structural design limit for this aircraft. The model scale studies, which involved both axisymmetric and rectangular geometry, indicated that amplitude levels could be expected to be much higher in flight. High amplitude levels would likely occur in the overexpanded region for axisymmetric geometry, and in the underexpanded region for rectangular geometry.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 87-0244
    Format: text
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  • 8
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    Supersonic jet plume interaction with a flat plate (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Supersonic jet plume interaction with a flat plate was studied using a model scaled test apparatus designed to simulate plume/aircraft structure interaction for the cruise configuration. The generic configuration consisted of a rectangular supersonic nozzle of aspect ratio 7, and a large flat plate located beneath the nozzle at various nozzle plate distances; the plate was instrumented to measure surface dynamic pressure and mean wall temperature, with provisions for measurements of acceleration and strain on coupon size panels that could be inserted in the plate. Phase-averaged schlieren measurements revealed the presence of high-intensity acoustic emission from the supersonic plume above the plate, directed upstream; this radiation could be associated with the shock noise generation. Narrow band spectra of surface dynamic pressure show spectral peaks with amplitude levels reaching 1 psi, related to the screech tones. Temperature measurements indicated elevated surface temperatures in regions of high turbulence intensity.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 872361 , International Powered Lift Conference and Exposition; Dec 07, 1987 - Dec 10, 1987; Santa Clara, CA; United States
    Format: text
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