Modeling sound propagation through internal waves using a spectral element method

Abstract

Considered here is the problem of low-frequency sound propagation over shallow, shoaling bathymetry in the presence of perturbations to the background sound velocity profile due to internal waves (IW). The question we attempt to answer is: to what degree can heuristic models of IWs coupled to numerical sound propagation models capture the variability in sound propagation observed in the environment? A high-order finite element model is employed to compute the acoustic field as it propagates through these IWs. The generality of the finite element method allows for spatial and temporal sound speed variations, and its convergence properties yield arbitrarily small error as the grid is rened. Simulations in the presence and absence of IWs will demonstrate the degree to which IWs influence sound propagation. Different models of IWs will demonstrate the sensitivity of the sound propagation to the choice of heuristic used for the IWs. Results will be shown for shoaling waveguides of O(100 m) depth and O(10 km) range, and frequencies of O(50 Hz). [Work supported by the NDSEG Fellowship.]