Toward simulation of long-term corrosion effects on acoustic scattering responses of underwater unexploded ordnance

Underwater unexploded ordnance (UXO) remediation faces the challenge of detecting and classifying objects that cannot easily be sensed using optics or electromagnetics. Instead, active sonar can be used to identify these munitions, which may be proud on the seabed, partially or fully buried in sediment. Historically, munitions were fired or discarded into oceans and inland waterways, presenting challenges for identifying ordnance exposed to long-term corrosion and biofouling. A long-term goal is to develop simplified models of corroded UXO with the intention of generalizing the model to expedite remediation efforts for a variety of munitions and environments without the need for physical testing of the many possible outcomes of long-term exposure. Working toward this objective, we are developing finite element (FE) acoustic scattering models to predict UXO acoustic signatures. A preliminary set of models will be presented in this talk with a focus on simplified geometries. Geometries were cylinder and truncated cone shapes with combinations of notches and cylindrical cuts along the axis of rotational symmetry. Free-field acoustic scattering experiments (1–100 kHz) were performed in an underwater test tank facility to examine acoustic effects of individual geometric features and to verify the accuracy of FE models. [Work supported by SERDP.]