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Acoustic field in unsteady moving mediaIn the interaction of an acoustic field with a moving airframe the authors encounter a canonical initial value problem for an acoustic field induced by an unsteady source distribution, q(t,x) with q equivalent to 0 for t less than or equal to 0, in a medium moving with a uniform unsteady velocity U(t)i in the coordinate system x fixed on the airframe. Signals issued from a source point S in the domain of dependence D of an observation point P at time t will arrive at point P more than once corresponding to different retarded times, Tau in the interval (0, t). The number of arrivals is called the multiplicity of the point S. The multiplicity equals 1 if the velocity U remains subsonic and can be greater when U becomes supersonic. For an unsteady uniform flow U(t)i, rules are formulated for defining the smallest number of I subdomains V(sub i) of D with the union of V(sub i) equal to D. Each subdomain has multiplicity 1 and a formula for the corresponding retarded time. The number of subdomains V(sub i) with nonempty intersection is the multiplicity m of the intersection. The multiplicity is at most I. Examples demonstrating these rules are presented for media at accelerating and/or decelerating supersonic speed.
Document ID
19950020759
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Bauer, F. (New York Univ. New York, NY., United States)
Maestrello, L. (Institute for Computer Applications in Science and Engineering Hampton, VA, United States)
Ting, L. (New York Univ. New York, NY., United States)
Date Acquired
September 6, 2013
Publication Date
May 1, 1995
Subject Category
Fluid Mechanics And Heat Transfer
Report/Patent Number
NAS 1.26:198162
ICASE-95-39
NASA-CR-198162
Accession Number
95N27179
Funding Number(s)
PROJECT: RTOP 505-90-52-01
CONTRACT_GRANT: NAS1-19480
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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