Wave Motion 36 (2002) 23–39 Influence of the cross-section geometry of a cylindrical solid submerged in an acoustic medium on wave propagation Andreia Pereira, António Tadeu ∗ , Julieta António Department of Civil Engineering, University of Coimbra, Polo II-Pinhal de Marrocos, 3030-290 Coimbra, Portugal Received 12 February 2001; received in revised form 28 May 2001; accepted 14 August 2001 Abstract This paper studies wave propagation in the vicinity of a cylindrical solid formation submerged in an acoustic medium generated by point blast loads placed outside the inclusion. The full 3D solution is obtained first in the frequency domain as a discrete summation of responses for 2D problems defined by a spatial Fourier transform. Each 2D solution is computed using the Boundary Element Method, which makes use of two-and-a-half-dimensional Green’s functions. This model is implemented to obtain Fourier spectra responses which make it possible to identify the behavior of both the axisymmetric and non-axisymmetric guided wave modes, when the cross-section of the elastic inclusion changes from circular to smooth oval. When the cylindrical elastic inclusion is submerged in a fluid, thus allowing a dilatational wave velocity greater than the shear wave velocity of the elastic medium (slow formation), our computations show a progressively slower flexural wave and the increased importance of a second flexural mode as the ovality of the inclusion becomes more pronounced. The waves associated with the screw mode become less important as the ovality ratio of the inclusion increases. When the formation is fast (the shear wave velocity of the cylindrical solid inclusion is faster than the pressure wave velocity of the fluid), the responses again indicate a progressively slower flexural wave, as the inclusion becomes more oval. The results computed at the receivers placed on the axis appear to be weakly affected by the ovality ratio of the inclusion. © 2002 Elsevier Science B.V. All rights reserved. 1. Introduction The propagation of acoustic waves in the vicinity of elastic inclusions or formations has been studied for a number of years. Different approaches have been developed to try to reproduce the phenomena involved. Most of the work related to this field relies on research by geophysicists and seismologists into the development of seismic prospecting techniques (acoustic logging, vertical profiling and cross-hole surveying) to predict subterranean characteristics, and by ocean and aeronautical researchers to study the interaction of the fluid with shell-shaped and solid structures. Biot [1] did the first theoretical work on the dispersion equation for guided waves, and their phase and group velocities, along a borehole. Since then, a large number of researchers have addressed the problem of wave prop- agation along fluid-filled boreholes subjected to plane waves and point sources, placed on and away from the axis of the borehole. ∗ Corresponding author. Tel.: +351-239-797-204; fax: +351-239-797-190. E-mail address: tadeu@dec.uc.pt (A. Tadeu). 0165-2125/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0165-2125(01)00117-2