Direct numerical investigation of acoustic liners with single and multiple orifices grazed by a Mach 0.5 boundary layer

Abstract

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, locallyreacting 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 1 . The normalized impedance value were scaled by the porosity of the liner and its validity is discussed.

Scattering to Higher Harmonics for Quarter Wave and Helmholtz Resonators

“…The DNS approach is also pursued by Zhang and Bodony, who study the influence of laminar and turbulent grazing flow 6,15 and the interaction between neighboring cavity openings 16 . Mendez and Eldredge 17 determine the influence of purging flow via large eddy simulations (LES).…”