Conference

Jonas Gustavsson and Yang Zhang

Kreitzman, J.R.

2019

Acoustic liners constructed of a perforated facesheet over a honeycomb core attenuate acoustic waves in the design range but also carry a drag penalty as the unsteady transverse jets produced by the perforations interact with the grazing boundary layer. Our research focuses on active liners, where the perforations can be opened and closed as desired to provide acoustic suppression when needed while maintaining low drag during cruise when noise is less of a concern. The current facesheet design consists of two layers of perforated material that can be moved relative to one another to open and close the orifices. Here we present results on the drag penalty in both open and closed configurations. Comparisons between five different liner configurations are tested along with the baseline solid, smooth wall and standard single degree-of-freedom (SDOF) liner configuration as reference cases. The experiments are carried out using precision machines aluminum samples tested in a wind tunnel at Mach numbers of 0.3, 0.5 and 0.6. Measurements show higher pressure drop, about 4%, for the SDOF liner than for the closed liner configuration, while the smooth wall exhibits about 3% lower pressure drop than its closed counterparts. A von Karman integral analysis is performer to estimate the ski friction coefficient. In the present experiments, the of dominant source of drag is boundary-layer growth, while pressure gradients contribute on the order of 10%. The current results are consistent with published data at higher Mach numbers, while M-0.3 has higher skin friction coefficient. At Mach 0.5 and 0.6, the smooth wall sample showed much lower friction, 2.0X10^-3, than the closed liner samples, 3.4-3.9x 10^-3, while the SDOF liner exhibited even higher drag, 4.0x10^-3.

25th AIAA/CEAS Aeroacoustics Conference

Delft, Netherlands

AIAA Paper 2019-2683

5/18/2019

https://arc.aiaa.org/doi/abs/10.2514/6.2019-2683

https://doi.org/10.2514/6.2019-2683