Bias flow acoustic liner with straight and tapered apertures

Experimental and computational studies are performed on slit resonators, i.e., one aperture with a high aspect ratio that spans through the center of the plate. An impedance tube experiment is conducted to investigate the macroscopic response of slit apertures. The test specimens include straight and tapered apertures. Subsequently, the effect of introducing a bias flow is investigated. The absorption performance increases when the sound pressure level increases to a level that causes a production of shed vortices. When a bias flow is introduced, the absorption coefficient reaches its maximum absorption of the incident sound wave in the region near the resonant frequency for a Mach number close to 9.71× ͳͲ^-3. 2D numerical simulations are performed and validated with the experimental results. Good agreement is obtained for the majority of the simulated cases. Vortex shedding and its effect on the absorption coefficients is also investigated.