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  • 1
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    Limitations of linear theory for sonic boom calculations (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Keywords: ACOUSTICS
    Type: Journal of Aircraft (ISSN 0021-8669); 30; 3; p. 309-314.
    Format: text
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  • 2
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    Progress in Sonic-Boom Understanding: Lessons Learned and Next Steps (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: In January 1988, representatives from NASA, NOAA, academia, and industry gathered at the NASA Langley Research Center to assess the status of understanding of the sonic boom which accompanies supersonic flight. As a result of that meeting, a research program on sonic boom within the NASA High-Speed Research (HSR) Program was implemented. This paper discusses the elements of the sonic-boom program, progress which has been made since 1988, and the current change in direction for the Sonic-Boom Element of the NASA HSR Program.
    Keywords: Acoustics
    Type: High-Speed Research: 1994 Sonic Boom Workshop. Configuration, Design, Analysis and Testing; 269-292; NASA/CP-1999-209699
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  • 3
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    Assessment and design of low boom configurations for supersonic transport aircraft (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A review is presented of presently utilized sonic boom prediction and minimization techniques. The three-pronged approach - acceptability studies, atmospheric propagation studies, and configuration design and operation, to the sonic boom problem as an element of the High Speed Research Program are discussed. Experimental and theoretical results of concepts designed to validate present minimization methods are given.
    Keywords: ACOUSTICS
    Type: In: DGLR(AIAA Aeroacoustics Conference, 14th, Aachen, Germany, May 11-14, 1992, Proceedings. Vol. 1 (A93-19126 05-71); p. 334-341.
    Format: text
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  • 4
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    Limitations on wind-tunnel pressure signature extrapolation (1992)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Analysis of some recent experimental sonic boom data has revived the hypothesis that there is a closeness limit to the near-field separation distance from which measured wind tunnel pressure signatures can be extrapolated to the ground as though generated by a supersonic-cruise aircraft. Geometric acoustic theory is used to derive an estimate of this distance and the sample data is used to provide a preliminary indication of practical separation distance values.
    Keywords: AERODYNAMICS
    Type: High-Speed Research: Sonic Boom, Volume 2; p 201-220
    Format: application/pdf
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  • 5
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    Design and analysis of low boom concepts at Langley Research Center (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The objective of the sonic boom research in the current High Speed Research Program is to ultimately make possible overland supersonic flight by a high speed civil transport. To accomplish this objective, it is felt that results in four areas must demonstrate that such a vehicle would be acceptable by the general public, by the airframers, and by the airlines. It should be demonstrated: (1) that some waveform shape has the possibility of being acceptable to the general public; (2) that the atmosphere would not totally destroy such a waveform during propagation; (3) that a viable airplane could be built which produces such a waveform; and (4) that any performance penalty suffered by a low boom aircraft would be counteracted by the economic benefit of overland supersonic flight. The work being done at LaRC is in support of the third element listed above--the area of configuration design. The initial part of the paper will give a review of the theory being used for configuration designs and discuss two theory validation models which were built and tested within the past two years. Discussion of the wind tunnel and theoretical results (linear theory and higher order methods) and their implications for future designs will be included.
    Keywords: ACOUSTICS
    Type: First Annual High-Speed Research Workshop, Part 2; p 675-699
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  • 6
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    A study of loudness as a metric for sonic boom acceptability (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A parametric study of loudness levels with respect to weight, altitude, and Mach number for sonic boom signatures generated by two Mach 2.0 conceptual configurations is presented and compared with a similar study for nose shock overpressure. This paper discusses the relative importance of the two sonic boom metrics and the implications of the trends shown. Of the two configurations considered in this study, one was designed for optimum aerodynamic performance and the second was designed to produce a constrained overpressure sonic boom signature at cruise flight conditions. Results indicate that reductions in both loudness and overpressure level are possible when the configuration is shaped to produce a low boom signature. Results also prove that the loudness metric is a more reliable measure of the disturbance due to sonic booms than nose shock overpressure, because the overpressure does not include the sometimes significant effects of embedded shocks which are often present in mid-field low boom signatures.
    Keywords: ACOUSTICS
    Type: AIAA PAPER 91-0496
    Format: text
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  • 7
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    High-Speed Research: Sonic Boom, volume 2 (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A High-Speed Sonic Boom Workshop was held at NASA Langley Research Center on February 25-27, 1992. The purpose of the workshop was to make presentations on current research activities and accomplishments and to assess progress in the area of sonic boom since the program was initiated in FY-90. Twenty-nine papers were presented during the 2-1/2 day workshop. Attendees included representatives from academia, industry, and government who are actively involved in sonic-boom research. Volume 2 contains papers related to low sonic-boom design and analysis using both linear theory and higher order computational fluid dynamics (CFD) methods.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CP-3173 , L-17146-VOL-2 , NAS 1.55:3173
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  • 8
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    Applicability of linearized-theory attached-flow methods to design and analysis of flap systems at low speeds for thin swept wings with sharp leading edges (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Low-speed experimental force and data on a series of thin swept wings with sharp leading edges and leading and trailing-edge flaps are compared with predictions made using a linearized-theory method which includes estimates of vortex forces. These comparisons were made to assess the effectiveness of linearized-theory methods for use in the design and analysis of flap systems in subsonic flow. Results demonstrate that linearized-theory, attached-flow methods (with approximate representation of vortex forces) can form the basis of a rational system for flap design and analysis. Even attached-flow methods that do not take vortex forces into account can be used for the selection of optimized flap-system geometry, but design-point performance levels tend to be underestimated unless vortex forces are included. Illustrative examples of the use of these methods in the design of efficient low-speed flap systems are included.
    Keywords: AERODYNAMICS
    Type: NASA-TP-2653 , L-16151 , NAS 1.60:2653
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  • 9
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    Validation of a pair of computer codes for estimation and optimization of subsonic aerodynamic performance of simple hinged-flap systems for thin swept wings (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Extensive correlations of computer code results with experimental data are employed to illustrate the use of linearized theory attached flow methods for the estimation and optimization of the aerodynamic performance of simple hinged flap systems. Use of attached flow methods is based on the premise that high levels of aerodynamic efficiency require a flow that is as nearly attached as circumstances permit. A variety of swept wing configurations are considered ranging from fighters to supersonic transports, all with leading- and trailing-edge flaps for enhancement of subsonic aerodynamic efficiency. The results indicate that linearized theory attached flow computer code methods provide a rational basis for the estimation and optimization of flap system aerodynamic performance at subsonic speeds. The analysis also indicates that vortex flap design is not an opposing approach but is closely related to attached flow design concepts. The successful vortex flap design actually suppresses the formation of detached vortices to produce a small vortex which is restricted almost entirely to the leading edge flap itself.
    Keywords: AERODYNAMICS
    Type: NASA-TP-2828 , L-16428 , NAS 1.60:2828
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  • 10
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    Effect of milling machine roughness and wing dihedral on the supersonic aerodynamic characteristics of a highly swept wing (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted to assess the effect of surface finish on the longitudinal and lateral aerodynamic characteristics of a highly-swept wing at supersonic speeds. A study of the effects of wing dihedral was also made. Included in the tests were four wing models: three models having 22.5 degrees of outboard dihedral, identical except for surface finish, and a zero-dihedral, smooth model of the same planform for reference. Of the three dihedral models, two were taken directly from the milling machine without smoothing: one having a maximum scallop height of 0.002 inches and the other a maximum scallop height of 0.005 inches. The third dihedral model was handfinished to a smooth surface. Tests were conducted in Test Section 1 of the Unitary Plan Wind Tunnel at NASA-Langley over a range of Mach numbers from 1.8 to 2.8, a range of angle of attack from -5 to 8 degrees, and at a Reynolds numbers per foot of 2 x 10(6). Selected data were also taken at a Reynolds number per foot of 6 x 10(6). Drag coefficient increases, with corresponding lift-drag ratio decreases were the primary aerodynamic effects attributed to increased surface roughness due to milling machine grooves. These drag and lift-drag ratio increments due to roughness increased as Reynolds number increased.
    Keywords: AERODYNAMICS
    Type: NASA-TP-2918 , L-16546 , NAS 1.60:2918
    Format: application/pdf
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