Three dimensional wave scattering by rigid circular pipelines submerged inan acoustic waveguide

The Boundary Element Method (BEM) is used to compute the three-dimensional variation pressure field generated by a point pressure source inside a flat waveguide channel filled with a homogeneous fluid, in the presence of infi nite rigid circular pipelines. The problem is solved in the frequency domai n, using boundary elements to model the pipeline and an appropriate Green's function to simulate the free surface and the rigid floor of the channel. Because of the 2 - 1/2 - D geometry of the problem, the separation of varia bles has been used, and the solution at each frequency is expressed in term s of waves with the varying wavenumber, k(z). Time responses at different p oints in the space domain are computed by applying an inverse (Fast) Fourie r Transform, using a Ricker pulse as the dynamic excitation source. Simulation analyses using this idealized model are then used to study the p atterns of wave propagation in the vicinity of these inclusions, following waves with different apparent wave velocities along the z axis. The amplitu de of the wavefield in the frequency vs, axial-wavenumber domain is present ed, allowing the position of the inclusions to be recognized and identified , providing a basis for the development of non-destructive testing and imag ing methods.