[en] The near-orifice aerodynamic response of a single degree of freedom acoustic liner to tonal and multi-tonal excitation with grazing flow was experimentally studied. A high-magnification PIV setup was designed to provide dense 2D velocity field measurements above an orifice of the liner. The resonator near-orifice velocity dynamics near and far from resonance were shown to be significantly different, with dynamic velocity scales well captured by a lumped-element model that was also satisfactorily applied to multi-tonal forcing cases. The effects of varying the forcing acoustic sound pressure level and the tangential flow velocity scale (the friction velocity) were investigated. It was observed that a “rough-wall” analogy was not suited to account for the induced mean aerodynamic effects, but that, under certain conditions, a “transpiration wall” analogy may be of interest. Graphic abstract:

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