Ivansson Sven M
Department of Underwater Research, Swedish Defence Research Agency, SE-164 90 Stockholm, Sweden.
J Acoust Soc Am. 2008 Oct;124(4):1974-84. doi: 10.1121/1.2967840.
Thin rubber coatings with cavities in a doubly periodic lattice are able to reduce reflections of underwater sound by redistributing normally incident energy such that absorption in the surrounding rubber is enhanced. For spherical scatterers, the anechoic effect can be studied numerically by the layer-multiple-scattering (LMS) method. In comparison to more flexible but also more computer intensive methods, such as finite-element method modeling, there are two important advantages. An improved physical understanding of the anechoic effect can be achieved by simplified semianalytical analysis, and the high computational speed allows modern global optimization techniques to be applied for coating design. In this paper, the flexibility of the LMS method is improved by combination with an efficient algorithm for numerical computation of transition matrices for superellipsoidal scatterers. (A superellipsoid is a generalization of an ellipsoid, allowing more box-filling shapes, for example.) Extensions to mixtures of nonspherical scatterers of different types are also considered, in order to enhance the broadband performance. Symmetry properties are used to reduce the size of the pertinent equation systems. Examples of numerical coating design for underwater acoustic applications are presented, using differential evolution algorithms for the optimization.
具有双周期晶格中空腔的薄橡胶涂层能够通过重新分配垂直入射能量来减少水下声音的反射，从而增强周围橡胶中的吸收。对于球形散射体，消声效果可以通过层多重散射（LMS）方法进行数值研究。与更灵活但计算量也更大的方法（如有限元法建模）相比，LMS方法有两个重要优点。通过简化的半解析分析可以更好地从物理角度理解消声效果，并且高计算速度允许将现代全局优化技术应用于涂层设计。在本文中，通过与一种用于超椭球体散射体过渡矩阵数值计算的高效算法相结合，提高了LMS方法的灵活性。（超椭球体是椭球体的推广，例如允许更多填充盒子形状。）还考虑了扩展到不同类型非球形散射体的混合物，以提高宽带性能。利用对称性质来减小相关方程组的规模。给出了水下声学应用的数值涂层设计示例，使用差分进化算法进行优化。
