2.5D BEM modeling of underwater sound scattering in the presence of a slippage interface separating two flat layered regions

This paper describes the use of a boundary element formulation in the frequency domain to investigate the 2.5D acoustic wave propagation in an underwater configuration with a bottom irregularity, simulating the effect of a possible slippage between two flat parts of a waveguide. Each part is delimited by a free surface and a flat bottom, which may be built as multilayered fluid structure.The problem is solved using a model which incorporates Green's functions that take into account the presence of flat layers of different thicknesses, computed using the definition of pressure potentials at each flat interface. With this procedure only the bottom irregularity and the slippage interface need to be discretized.The mathematical formulation is presented for the general case in which two multilayered structures are connected via an interface, and then verified and applied to the computation of 3D frequency and time domain pressure responses for the benchmark problem of a rigid bottom with step or slope irregularities. These simulations are used to identify wave propagation features that may help to assess the presence and shape of the bottom irregularities.