An analysis of the efficiency and accuracy of applying Huygen's principle to acoustic scattering models

Over the last decade, the Target-in-the-Environment-Response (TIER) model has proven to be an efficient simulation tool for computing the acoustic scattering from axisymmetric objects in an underwater environment. The model functions by first computing the free-field scattered pressure via a high-fidelity Finite Element (FE) computation. The scattered pressure is converted into a scattering amplitude and stored in a look-up table. These scattering amplitudes are used in a fast ray model to compute the acoustic scattering from an object on or embedded in a seafloor, for any vehicle path imaginable. Computing the scattered pressure amplitude for the look-up tables via the FE method is a bottleneck of the computation. For monostatic scattering problems, the look-up table historically sampled the azimuthal angle domain with 1-deg resolution. However, this approach is not efficient in time nor disk space when moving to bistatic scattering situations. Here, we present a more efficient alternative, which is based on application of Huygen’s principle. The results from this method are assessed against the original sampling method and validated against additional high-fidelity models including a hybrid 2-D/3-D FE-Propagation model and a fully 3-D Impedance Matrix method, the latter of which is numerically exact and offers a benchmark solution.