Archives of Acoustics, 11, 4, pp. 339-352, 1986

Acoustical wave propagation in a cylindrical layer system In viscous medium

Anna Grabowska
Institute of Fundamental Technological Research. Polish Academy of Sciences

A problem is considered of an acoustical wave propaga.ting along a hollow J
infinite elastic cylinder filled with air and surrounded by a viscoelastic tissue.
Such a case approximately corresponds t~ a biopsy performed with the application
of a needle introduced to such tissues as liver, kidney, muscles, and tho like.
In the problem under consideration it was proved, that the volume viscosity
is significant, whereas shear viscosity can be neglected.
Basic equations were formulated in terms of displacement potentials, as
well as the boundary conditions. This led to a. characteristic equation of the
problem which were solved numerically.
It wa.s proved that a boundary wave propagates along the needle with
a velocity and attenuation not much smaller than in the surrounding tissue.
Part of tho energy is transfered from the needle into the tissue where the energy
is dissipa.ted. Distributions of tho radial and axia.l stross components and radial
displacement components were found.
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