  The fluid-structure interaction is studied for a system composed of two
coaxial pipes in an annular geometry, for both homogeneous isotropic metal
pipes and fiber-reinforced (anisotropic) pipes. Multiple waves, traveling at
different speeds and amplitudes, result when a projectile impacts on the water
filling the annular space between the pipes. In the case of carbon
fiber-reinforced plastic thin pipes we compute the wavespeeds, the fluid
pressure and mechanical strains as functions of the fiber winding angle. This
generalizes the single-pipe analysis of J. H. You, and K. Inaba,
Fluid-structure interaction in water-filled pipes of anisotropic composite
materials, J. Fl. Str. 36 (2013). Comparison with a set of experimental
measurements seems to validate our models and predictions.
