Shape optimization of acoustic lenses for underwater imaging

2016 
Shape optimization of two-dimensional lenses for acoustic cameras used in underwater acoustic imaging is presented. To understand elastic shear wave effects of a lens on the pressure field of the medium, we couple two physics models, namely a pressure acoustics model and a linear elastic model and formulate it in the finite element analysis framework. As a result, the focal length of a lens is calculated to be longer than that in the absence of shear effects. The accuracy of our model is tested against experimental results, and compared with finite element analysis of a single physics model as well as the hybrid method - a method using geometrical acoustics and wave acoustics. Pressure at the focal point is optimized using geometric parameters for lens surfaces as design variables. Performance differences due to temperature change or obliquely incident waves are controlled using design constraints. The effectiveness of our optimization formulation is verified by solving single- and dual-lens design problems.
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