Micro-perforated panels in interaction with boundary layers in zero pressure gradient flow
* Presenting author
Abstract:
The application of a micro-perforated absorber (MPA) adjacent to an axial fan in duct flows can significantly influence both the effective sound emissions, as well as the fan’s efficiency. These phenomena can be theoretically attributed in part to bias flow, altered blind flow in tip gap clearance, turbulent boundary layer stimulation, and self-excitation of the MPA. In this contribution, we investigate the influence of a zero pressure gradient boundary layer over a MPA flushed mounted in an overflowed plate test rig at low Mach numbers. The alteration of the boundary layer profile due to the presence of the MPA is investigated, as well as, the wall pressure correlation to the self-noise of the MPA. It is found that self-noise and excitation vary strongly with the perforation ratio and slit orientation relative to the mean flow velocity. Furthermore, the flow over the MPA might reduce the sound-absorbing effectiveness in the high-frequency range.