Numerical optimization of sonar arrays using FE/BE methods

Designing high power active sonar arrays may have many conflicting requirements, e.g. optimal projector spacing for acoustic output and overall size constraints to fit a platform. Optimization procedures can potentially be used to aid array design. The optimization process is described in terms of design variables, which are the input parameters, and response variables which are chosen to assess the design. The whole procedure attempts to maximise a multi-dimensional evaluation function having formulated an initial design. Here the acoustic performance of active arrays has been investigated using a combined boundary element (BE) and finite element (FE) method to maximise possible source level over a selected frequency band. The design variables are the relative distances between projectors. This highlights the advantage of the combined boundary element and finite element technique over purely finite element schemes. The relative distances between projectors are described parametrically permitting a simple change of array configuration by the optimization algorithm, while a pure finite element model would require an automatic method to fabricate a new mesh for every change in projector position. The procedure is computationally efficient but still requires careful consideration by the sonar engineer to see whether the evolving design is sensible. The method is demonstrated on an array of ring transducers