Experimental investigations of perforated liners with bias flow based on sound-vortex theory

At first, the reflection coefficient of a perforated liner with bias flow was calculated while considering its real structure on the experimental equipment. By choosing perforated plates of different geometrical parameters, measurements were carried out and the experimental results agree with theoretical results well. Both theory and experiments show that the absorption coefficient of perforated liners with bias flow can reach 1.0, provided that its geometrical parameters and flow velocity are chosen properly. Secondly, perforated liners without and with bias flow were compared with each other in this paper. On the condition that the apertures in the perforations are comparatively large, the former tends to have a narrow absorptive band while the latter has a high absorption coefficient with much wider absorptive band by choosing flow velocity properly. Considering that blowing and suction will have different influence on surface shear flow of perforated liners, the comparative experimental results between blowing and suction were also included.