Direct numerical simulation of three-dimensional honeycomb liners with turbulent boundary layer

Resonant acoustic liners are installed in jet engines to reduce noise by converting sound into vorticity-bound fluctuations. This work aims to study the acoustically excited flow field inside and outside a honeycomb liner under a Mach 0.5 turbulent boundary layer using DNS, with a focus on the interaction between the orifice and the boundary layer. The simulations are conducted in three steps: first, a RANS simulation is performed to obtain the basic flow conditions and a reasonable comparison is found between the RANS simulation data and experimental data taken from NASA Langley. The RANS data also serves as guidelines for the incoming turbulent boundary layer generation. Second, a temporally evolving Mach 0.5 compressible turbulent boundary layer is generated over a perfectly flat wall. Since the temporal boundary layer is growing in time, the momentum thickness Reynolds number (Re_θ) varies from 1385 to 2990. Quantitative analyses are performed at Re_θ = 2310 and the simulation data agree well with both the previous experimental and simulation results in several aspects. Finally, acoustic waves at different sound pressure levels (SPLs) are enforced when the turbulent boundary layer is present. Using flow visualization of the turbulent boundary layer and orifice interaction, basic flow features near or far away from the liner orifice are presented. Several flow properties are also quantified. These analysis will be helpful to reveal the behavior of conventional honeycomb liners under turbulent boundary layers.