On the Impact of the Orifice Shape in Acoustic Liner Attenuation Under Turbulent Grazing Flow
Angelo Paduano (Politecnico di Torino)
Francesco Scarano (Politecnico di Torino)
D. Casalino (TU Delft - Aerospace Engineering)
Júlio A. Cordioli (Universidade Federal de Santa Catarina)
E.F. Avallone (TU Delft - Aerospace Engineering)
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Abstract
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.
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