Propagation of acoustic waves in buried waveguides: modelling of the forward problem and imaging with sampling methods

Jean-François Fritsch

Nondestructive testing of elongated structures partially or totally buried is important in the industry. Several techniques exist to identify defects in closed waveguides; among them, the Linear Sampling Method (LSM) has given good results in many different configurations. However, there are few works on the modeling of the propagation of waves and on the identification of defects in buried waveguides. These configurations present two main challenges: we can only access one side of the zone to control, and the waves propagating in the structure will partially leak in the surrounding medium. To synthesize measures, the domain is truncated in the transverse direction of the guide with PMLs and in the longitudinal direction with Dirichlet to Neumann operators defined with the transverse modes. A modal formulation of the LSM using the reference fields, which are the responses of the healthy structure to the incident modes, is proposed. First results of imaging are finally presented.