Investigation of Alberich Coating to Optimise Acoustic Stealth of Submarines

Abstract

Due to the nature of their deployment, very few people know the location and course of a submarine during its time at sea, including only a handful of the ship’s crew. The possibility of immediate retaliation by the UK and her allies is aided by the submarine’s ability to remain undetected by SONAR at all times. To investigate one method for improving acoustic stealth, a finite element model (FEM) was created on ANSYS to model a unit-cell of an Alberich coating and impeding sound wave representative of SONAR. A simplification of a widely used acoustic impedance equation was adopted into MATLAB code to attain values of impedance that were applied to the model in place of a water loading boundary. Using the results given by five sets of simulations, an optimised Alberich coating was modelled, containing a 26 mm spherical cavity, 40 mm anechoic layer and 30 mm long steel backplate. This optimised model improved the acoustic stealth of submarines by displaying greater acoustic absorption at both ends of the frequency range, compared with other models used, showing that Alberich-style coatings can be used to improve acoustic stealth, to combat new low-frequency SONAR.