On the Impact of the Orifice Shape in Acoustic Liner Attenuation Under Turbulent Grazing Flow

This work investigates the influence of orifice-edge geometry on the aeroacoustic performance of perforated acoustic liners exposed to turbulent grazing flow. Two liner geometries are compared. They differ only for the shape of the facesheet orifices. One has sharp edge orifices, while the other chamfered edge orifices. The internal diameter, the facesheet thickness and the cavity depth is the same. High-fidelity lattice-Boltzmann very-large-eddy simulations are performed and compared with experimental measurements to assess both the acoustic response and the underlying flow physics. Impedance eduction reveals that the sharp-edged liner exhibits up to 50\% higher acoustic resistance over the investigated frequency range, whereas the reactance remains broadly similar, apart from a shift in resonance frequency from approximately 1.7 to 1.9 kHz. Flow-field analysis indicates that the chamfered geometry promotes stronger momentum exchange and weaker shear layers strength above the orifices, effectively behaving as a more permeable surface. These findings show that small manufacturing-scale variations in orifice-edge shape can significantly alter both the aerodynamic development and the acoustic attenuation of liners under grazing flow, highlighting the need to account for edge geometry in liner design and predictive modeling.