Investigation on the normal acoustic impedance of a wire screen bounded to a slit resonator

Linear acoustic liner has come into use in engine nacelles to achieve a linear property of which the acoustic impedance is insensitive to the environmental conditions such as sound pressure level and grazing flow Mach number. In this paper, the normal acoustic impedance of a wire screen bounded to a slit resonator is investigated by direct numerical simulations based on computational aeroacoustic methods. A two-dimensional normal incident impedance tube model is adopted for this investigation. The two-microphone method is deployed to determine the acoustic impedance and absorption coefficient. The wire mesh is modeled as an array of eight identical square cylinders in a parallel arrangement. The size of the square cylinders are 0.1 mm × 0.1 mm and the gaps between two adjacent square cylinders are g=2/15 mm. Tonal waves of different sound pressure levels and frequencies are introduced from the termination of the tube through a PML boundary condition. Numerical results show that the parallel square cylinders play a key role in sound energy absorption. Generally, the wire mesh gives an additional sound energy dissipation. However, the absorption coefficient decreases when the resonator exposing to a high intensity wave at resonance.