CONTRIBUTING GEOMETRIC FEATURES OF SUBMARINE TARGET ECHO STRENGTH

In collaboration with DRDC, Martec Limited has developed the AVAST software commonly used for the prediction of target echo strength (TES) for a variety of underwater targets. Recent improvements to the software include a high-frequency capability based on raytracing methods which require a NURBS surface representation of the target. By using a surface representation of the target, this capability is able to avoid the limitations of discretized methods for predicting the target strength of submarines at torpedo sonar frequencies. Raytracing methods have been validated against theoretical solutions and other numerical methods, but there is a lack of experimental validation data for such methods. This is partly due to the difficulty in performing such experiments, particularly if far-field measurements are desired. One solution to such difficulties is to perform near-field experiments for validation and use the validated numerical methods for far-field predictions. Inherent in the TES predictions is a particular angular dependence which changes with the distance to the target and directly influences the features of the target’s TES pattern. To evaluate how various submarine structures (sail, main hull, fins, etc.) contribute to the high frequency TES, numerical analyses of the submarine structures will be completed and compared in both the nearand farfield. It is also important to understand how anechoic tiles influence the TES prediction in the near-field and far-field. To do so, a generic acoustic tile configuration will be assumed and the influence of anechoic tiles will be examined. The numerical comparison presented in the paper used a generic diesel-electric submarine model as the test platform.