ABSTRACT
Underwater acoustic models based on the FW-H equation are considered for the generation and propagation of noise emitted from oscillating lifting surfaces, as in the case of flapping-foil thrusters used for the propulsion of small ships and AUVs. In such cases the study of the 3D field by means of the full wave equation in the inhomogeneous sea environment comes with excessive computational cost, even at low frequencies. Assuming azimuthal symmetry of the environmental parameters, a numerical model is developed based on a FDTD scheme, incorporating free-surface and seabed effects, and variable sound speed profile. For the treatment of the 3D initial – boundary value problem with excitation from point monopole and dipole sources the above scheme is implemented with a PML technique for modelling the radiating field at the open boundaries. Numerical results are presented illustrating the applicability of the present method to simulate fields from time-harmonic acoustic excitation.
