Journal article
Negative group velocity Lamb waves on plates and applications to the scattering of sound by shells
The Journal of the Acoustical Society of America, Vol.113(5), pp.2659-2662
05/2003
Handle:
https://hdl.handle.net/2376/105045
PMID: 12765384
Abstract
Symmetric Lamb waves on plates exhibit anomalies for certain regions of frequency. The phase velocity appears to be double-valued [M. F. Werby and H. Uberall, J. Acoust. Soc. Am. 111, 2686-2691 (2002)] with one of the branches having a negative group velocity relative to the corresponding phase velocity. The classification of the symmetric plate modes for frequencies appearing to have a double-valued phase velocity is reviewed here. The complication of a double-valued velocity is avoided by examining mode orthogonality and the complex wave-number spectra. Various authors have noted an enhancement in the backscattering of sound by elastic shells in water that occurs for frequencies where symmetric leaky Lamb waves (generalized to case of a shell) have contra-directed group and phase velocities. The ray diagram for negative group velocity contributions to the scattering by shells [G. Kaduchak, D. H. Hughes, and P. L. Marston, J. Acoust. Soc. Am. 96, 3704-3714 (1994)] is unusual since for this type of mode the energy on the shell flows in the opposite direction of the wave vector. Circumnavigation of the shell is not required for the leaky ray to be backward directed.
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Details
- Title
- Negative group velocity Lamb waves on plates and applications to the scattering of sound by shells
- Creators
- Philip L Marston - Department of Physics, Washington State University, Pullman, Washington 99164-2814, USA. marston@wsu.edu
- Publication Details
- The Journal of the Acoustical Society of America, Vol.113(5), pp.2659-2662
- Academic Unit
- Physics and Astronomy, Department of
- Publisher
- United States
- Identifiers
- 99900546750001842
- Language
- English
- Resource Type
- Journal article