Numerical investigation of the acoustic behavior of a multi-perforated liner

The acoustic response of a turbulent flow through a multi-perforated liner is computed with incompressible LES. The effect of a large array of apertures is accounted for by simulating a single jet with periodic conditions in both directions tangential to the plate. Flows that are parallel to the plate are included in the regions above and below the aperture, which is tilted in the tangential flow direction as in practical film cooling liners. The mass flow rate through the aperture is forced with a small sinusoidal perturbation superposed on a mean component. The acoustic behavior is determined by measuring the fluctuating pressure difference across the aperture that results from the forcing. In this work, two different forcing frequencies are considered. The transfer function between forcing and response, which represents the acoustic impedance of the liner, is calculated for these frequencies. Good agreement is found when compared with existing theory, when the latter is modified for the thickness and tilting of the aperture.