Impedance prediction of three-dimensional honeycomb liners with laminar/turbulent boundary layers using DNS

Acoustic liners usually operate in the presence of a high speed turbulent grazing flow. In this paper, numerous investigations of an acoustically excited flow field inside and outside a conventional honeycomb liner under Mach 0.5 laminar or turbulent boundary layers are performed using DNS, with a focus on the interaction between the orifice and the boundary layer. The numerical simulations were conducted at different incident sound pressure levels (SPLs) and frequencies. Using flow visualization of the boundary layer-orifice interaction, basic flow features near and far away from the liner orifice are presented. A comparison of laminar and turbulent grazing flow conditions are also considered for the same incident acoustic field conditions. Impedance prediction applies the traditional Dean's method and the numerical predicted results are compared with experimental data from NASA Langley. Discussions of the impedance prediction including its precision and accuracy are also provided.