Key Laboratory of Photonic/Phononic Crystals of Ministry of Education,National University of Defense Technology, Changsha, Hunan, People's Republic of China, 410073.
J Acoust Soc Am. 2011 Sep;130(3):1201-8. doi: 10.1121/1.3621074.
Recently, by introducing locally resonant scatterers with spherical shape proposed in phononic crystals into design of underwater sound absorption materials, the low-frequency underwater sound absorption phenomenon induced by the localized resonances is observed. To reveal this absorption mechanism, the effect of the locally resonant mode on underwater sound absorption should be studied. In this paper, the finite element method, which is testified efficiently by comparing the calculation results with those of the layer multiple scattering method, is introduced to investigate the dynamic modes and the corresponding sound absorption of localized resonance. The relationship between the resonance modes described with the displacement contours of one unit cell and the corresponding absorption spectra is discussed in detail, which shows that the localized resonance leads to the absorption peak, and the mode conversion from longitudinal to transverse waves at the second absorption peak is more efficient than that at the first one. Finally, to show the modeling capability of FEM and investigate shape effects of locally resonant scatterers on underwater sound absorption, the absorption properties of viscoelastic materials containing locally resonant scatterers with ellipsoidal shape are discussed.
最近，通过将声子晶体中提出的球形局域共振散射体引入水下吸声材料的设计中，观察到了由局域共振引起的低频水下吸声现象。为了揭示这种吸收机制，应该研究局域共振模式对水下吸声的影响。本文采用有限元法，通过将计算结果与层状多次散射法的结果进行比较，验证了该方法的有效性，用于研究局域共振的动力学模式和相应的吸声性能。详细讨论了用一个单元的位移轮廓描述的共振模式与相应的吸收谱之间的关系，结果表明，局域共振导致吸收峰的出现，并且在第二个吸收峰处的纵波到横波的模式转换比在第一个吸收峰处更有效。最后，为了展示有限元法的建模能力并研究局域共振散射体的形状效应对水下吸声的影响，讨论了含有椭球形局域共振散射体的粘弹性材料的吸声特性。
