Abstract
This research shows a fundamental study for the design of acoustic metasurface composed of acoustic media and multi-elastic-material. Topology optimization method that can deal with multi-material distribution is incorporated into two-phase material model that can express acoustic-elastic coupled system uniformly without imposing coupling boundary conditions. The proposed method is applied to the design problem of acoustic metasurface that exhibits negative mass density. First, the two-phase material model is introduced. Next, level-set based topology optimization and topology optimization based on Multi-Material Level Set (MM-LS) method are introduced. The design problem of acoustic metasurface is defined and objective functional, effective mass density of acoustic metasurface, is formulated using Sparameter-based method. Sensitivity analysis is conducted based on the concept of topological derivative and adjoint variable method, and sensitivity of each level set function that are used in MM-LS method is obtained. The optimization algorithm is constructed, and finally two-dimensional numerical example shows that our approach successfully achieves the optimal design of the metasurface.
