声波在流固耦合声子晶体中的传播特性

Propagation Properties of Acoustic Wave in Fluid-Solid Phononic Crystals

利用平面波展开方法计算了二维正方晶格钢／水声子晶体的能带结构．在（206．2～280．1）kHz频率范围内存在完全带隙，沿着布里渊区（Brillouin）2个高对称方向FX、ГM的方向带隙分别为（138．5～280．1）kHz和（206．2～287．1）kHz．利用有限元软件Abaqus计算了完美周期和含有缺陷态的声子晶体的传输谱曲线．对完美周期声子晶体，在带隙频率范围内声波有较大衰减；而含有线缺陷的声子晶体的透射幅值在带隙频率范围内增大，导波作用明显；在225．9kHz频率时声波在声子晶体中传播的压力场仿真进一步说明了波沿线缺陷传播形成波导结构．基于超声浸水透射技术，实验测试了声波在声子晶体中传播的带隙及缺陷态特征．结果表明：测试结果与理论计算及有限元方法仿真的结果基本吻合．

Band gap properties of a two-dimensional square lattice steel/water phononic crystal and defect state were investigated both theoretically and experimentally. The band structure was calculated with the plane wave expansion method. An absolute band gap from 206.2 to 280. 1 kHz opened between the first and the second bands. Along the two high symmetry directions （ FX and ГM） of the first Brillouin zone, two part gaps appeared, i. e. , （138.5 - 280.1） kHz and （206.2 - 287.1 ） kHz, respectively. Using finite element method, transmission spectra was computed for phononic crystals with and without line defect. Some strong attenuation peaks appeared for periodic structures, and abrupt increment among the band gaps regions occurred for line defect structure. These results showed that acoustic wave localized in line defect, which were in accordance with the pressure field at 225.9 kHz acoustic wave propagating in water. Based on well-known ultrasonic immersion transmission technique, transmission spectra were measured for periodic and line defect phononic crystals. The measured transmission spectra agrees well with the numerical results.