微孔共振腔吸声机理的直接数值模拟研究

DIRECT NUMERICAL SIMULATION OF THE ACOUSTIC DISSIPATION MECHANISM FROM MICRO-RESONATORS

声衬是由大量的微孔共振腔按一定规则排列组成,由于微孔共振腔的小尺寸和流动的复杂性,采用实验和理论方法难以观测其内部及附近的复杂流动情况。本文采用计算气动声学方法对不同频率和声强声波入射下的二维微孔共振腔的吸声过程进行了直接数值模拟.结果表明:(1)腔口处粘性耗散和涡脱落现象是其吸声的主要形式;(2)在不同的频率和声强入射下,微孔共振腔的吸声过程表现出三种不同的模式,分别为无涡脱落、规则涡脱落和不规则涡脱落;(3)微孔共振腔的吸声性能在入射波为共振腔固有频率时最好.

Acoustic liner is composed by an array of micro-resonators. Because of the small dimensions and complex flow, the flow field around the mouth of the micro-resonators has not been directly observed experimentally or predicted theoretically. Direct numerical simulation was used to investigate the acoustic dissipation mechanism of a two-dimensional micro-resonator under the excitation of incident acoustic waves with different frequencies and intensities by a computational aeroacoustics methodology. Numerical results reveal that： （1） Viscous dissipation and the shedding of micro-vortices around the mouth of the resonator play the main role on sound absorption. （2） Under the different frequencies and intensities of the incident sound waves, acoustic dissipation of the micro-resonator exhibits three different modes, i.e. no shedding of micro-vortices, regular shedding of micro-vortices and irregular shedding of micro-vortices, respectively. （3） The acoustic dissipation from a micro-resonator reaches the maximum when the incident sound wave frequency coincides with the characteristic frequency of the micro-resonator.