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Backward waves with double zero-group-velocity points in a liquid-filled pipe.

Cui, H. and Lin, W. and Zhang, H. and Wang, X. and Trevelyan, J. (2016) 'Backward waves with double zero-group-velocity points in a liquid-filled pipe.', Journal of the Acoustical Society of America., 139 (3). pp. 1179-1194.

Abstract

Hollow cylinders often exhibit backward propagation modes whose group and phase velocities have opposite directions, and these exhibit a minimum possible frequency at which the group velocity vanishes at a nonzero wavenumber. These zero-group-velocity (ZGV) points are associated with resonant conditions in the medium. On the basis of ZGV resonances, a non-contact and laser ultrasound technique has been developed to measure elastic constants of hollow pipes. This paper provides a theoretical and numerical investigation of the influence of the contained liquid on backward waves and associated ZGV modes, in order to explore whether this ZGV technique is suitable for in-service non-destructive evaluations of liquid-filled pipes. Dispersion spectra and excitation properties have been analyzed. It is found that the presence of the liquid causes an increased number of backward modes and ZGVs which are highly excitable by a point source. In addition, several guided modes twice undergo a change of sign in the slopes of their dispersion curves, leading to two ZGV points. This phenomenon of double ZGVs in one backward wave, which is caused by strong mode repulsions, has not been found in isotropic hollow cylinders, but it can be observed in a fluid-filled thin-walled pipe.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1121/1.4944046
Publisher statement:© 2016 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America. The following article appeared in Cui, H., Lin, W., Zhang, H., Wang, X. & Trevelyan, J. (2016). Backward waves with double zero-group-velocity points in a liquid-filled pipe. Journal of the Acoustical Society of America 139(3): 1179-1194.
Date accepted:02 March 2016
Date deposited:15 March 2016
Date of first online publication:17 March 2016
Date first made open access:17 September 2016

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