Direct numerical simulation of the acoustic dissipation mechanism from micro-resonators

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.