Two groups of direct numerical simulations were conducted to investigate the interaction of a planar incident acoustic field with a cavity-backed circular orifice in the presence of a boundary layer with freestream Mach number of 0.5. The orifice-cavity geometry and grazing flow properties are extracted from a conventional single degree-of-freedom, locally-reacting liner tested at NASA Langley. This paper splits the discussions into two parts: the first part reports the results of single-orifice interaction with a temporal laminar/turbulent grazing boundary layer under the effect of planar acoustic incident sound. The second part moves to a more complicated but realistic liner model by increasing the number of the orifices over a single cavity and aims to investigate flow interactions between different orifices under a spatially-evolving laminar boundary layer. Both groups of the simulations predicts the impedance value with Dean's two-microphone method. The normalized impedance value were scaled by the porosity of the liner and its validity is discussed.
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