Band gap structure of acoustic phononic crystals with cluster primitives in triangular lattices

Abstract

In this study, a two-dimensional steel/gas acoustic phononic crystal with triangular lattices was considered as the model and single cylinder primitives were substituted with cluster primitives, before investigating the energy band structures of the longitudinal sound wave using the plane wave expansion method. The results indicated that energy band extremes were still present at the high symmetry points or symmetry lines in the Brillouin zone, although the range of the irreducible Brillouin zone increased by two times. Compared with single cylinder primitives, double cylinder primitives could achieve excitation in low frequency broad band gaps at relatively low filling rates. Furthermore, sextuple cylinder primitives achieved primary band gap width increases of 7.3 times. The width of the band gap increased with the filling rates of the cluster primitives. Precise control of the band gap location and width at low filling rates can be achieved by varying the primitive orientation or inter-cylinder distance in the primitives.