Elastic wave scattering by an inclusion in a multilayered medium submerged in fluid. II. Three-dimensional model

摘要

Response of plane three-dimensional multilayered medium enclosing an elastic inclusion of arbitrary shape and submerged in fluid is investigated. The system is subjected to an oblique plane incident wave from within the fluid. The steady-state free-field response is modeled by the Thomson-Haskell method using delta-matrix modification and the scattered wave field by a boundary method. The transient response is evaluated using the Fourier synthesis. Numerical results are presented for a single layer plate with an ellipsoidal inclusion.The steady-state results show that the response along the fluid-solid interface is sensitive to the aspect ratio and location of the inclusion, impedance contrast, and the angle of incidence. In addition, the results of the three-dimensional analysis for the nonaxisymmetric problem indicate significant variation of the radial and azimuthal displacement components with the change in the azimuthal angle. Comparison of the two-dimensional and three-dimensional models indicates that for the harder inclusion, both the models show similar qualitative trends in the transient and steady-state responses. However, for a softer inclusion, the steady-state responses of the two models are found to differ significantly from each other. The transient studies clearly indicate the horizontal wave traveling at the solid-fluid interface with the acoustic wave velocity of the fluid. The effect of the scatterer on the vertical displacement is found to be significant only in the vicinity of the inclusion.