Mechanism Analysis and Experiment Study for Wire Mesh-Assisted Ventilated Acoustic Metamaterials Based on the Acoustic Analytical Model and Numerical Acoustic-Flow Coupling Model

Aims In this paper, a wire mesh-assisted ventilation acoustic metamaterial (MVAM) is presented for efficient noise suppression and ensuring ventilation and heat exchange. Method The analytical models of ventilated acoustic metamaterial (VAM) and MVAM in the absence of flow conditions were established based on the wave expansion method and Green's function. The complex frequency planes and transmission coefficients of each resonant part (RP) were obtained, and the bandwidth and the effects of wire mesh on the transmission coefficients were analyzed. The results were compared with numerical models based on the finite element method, which showed excellent agreement. Four RPs were arranged in an artificial array to create VAM and MVAM configurations. Subsequently, the sound transmission losses for both VAM and MVAM were obtained, and experiments were carried out with the quadrupole two-loading method to verify the accuracy of the analytical and numerical models. When considering the effect of the grazing flow, a numerical model of acoustic-flow field coupling was established. The transfer impedance and the flow field distribution at different flow velocities were calculated and analyzed, and the influence law of different flow states on acoustic performance was revealed. Finally, experiments were carried out on the effect of MVAM at a grazing velocity of Ma = 0.01 utilizing a Norsonic acoustic imager. The results show that MVAM can attenuate noise under a certain grazing velocity, which verified the reliability. Results In the absence of flow, the metal wire mesh caused a slight increase in the transmission coefficient of a single RP. Therefore, under this condition, the metal wire mesh harms noise attenuation. The bandwidth of a single RP is negatively correlated with its distance to the center of the duct. By analyzing the results for the VAM and MVAM models in the absence of flow, the wire mesh makes the STL, which still maintains four distinct peaks, decrease overall. The accuracy of the analytical and numerical calculation results was verified experimentally by the quadrupole dual-load method. By the analysis of the coupled acoustic-flow field model, the perturbation of the grazing flow on the sound field and the effect mechanism of the wire mesh are revealed. With the increase in the grazing flow velocity, the mode of the flow field is changed, which suppresses the influence of the pressure perturbation generated by the vortex on the acoustic field. The MVAM can effectively reduce the pressure loss along the path caused by the structure. The experiments on noise reduction performance under the influence of grazing flow in an anechoic chamber were conducted, and MVAM can achieve efficient noise attenuation was verified, ensuring its reliability. Conclusions The analytical and numerical models of the relevant configurations are developed. The acoustic performances of VAM and MVAM in the absence of flow and grazing flow conditions are analyzed and compared, and the accuracy of the calculation results is verified by experiments, which proves that MVAM can effectively control the duct noise under the influence of grazing flow and reduce the pressure loss.