Abstract: A linearized potential flow model is developed to study the grazing flow effect on the acoustic impedance of a perforated plate. This model uses the particle velocity continuity boundary condition rather than the widely used displacement continuity to match the unsteady flowfields separated by the orifice shear layer. The underlying sound vortex interaction mechanism is taken into account by applying the Kutta at the leading edge of the orifice. The influences of the finite plate thickness and the orifice shape are also incorporated. Good agreement is obtained between the theoretical prediction and the experimental data both for the acoustic resistance and reactance.

Key words: sound-vortex interaction, perforated liner, shear layer, linear perturbation theory