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waveform freezing of sonic booms revisitedNonlinear distortion of sonic booms propagating in the atmosphere is strongly affected by stratification and geometrical spreading. For a downward propagating sonic boom in a standard atmosphere, stratification and spreading cause a slowing down of nonlinear distortion. In certain cases a stage is reached where no further distortion takes place. When this happens, the waveform is said to be frozen. In previous work the authors argued that for most HSCT designs and flight conditions being considered, the sonic boom is not frozen when it reaches the ground. The criterion used was the value of the distortion distance x bar is a measure of the nonlinear distortion suffered by the wave (and is closely related to Hayes's E variable). The aircraft must be at an altitude greater than 27 km (80,000 ft) for x bar at the groun be within 95% of its asymptotic value. However, work reported here demonstrates that the ground waveform is much closer to the frozen state than indicated by the previous analysis. In the new analysis, duration of the sonic boom is used as the criterion for judging closeness of approach tz frozen state. In order for the duration of the sonic boom at the ground to be within 95% of its frozen value, the flight altitude of the aircraft needs to be only 15 km (45,000 ft).
Document ID
19960055051
Document Type
Conference Paper
Authors
Cleveland, Robin O.
(Texas Univ. Austin, TX United States)
Blackstock, David T.
(Texas Univ. Austin, TX United States)
Date Acquired
August 17, 2013
Publication Date
July 1, 1996
Publication Information
Publication: The 1995 NASA High-Speed Research Program Sonic Boom Workshop
Volume: 1
Subject Category
Acoustics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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IDRelationTitle19960055049Analytic PrimaryThe 1995 NASA High-Speed Research Program Sonic Boom Workshop
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