Production of Sound by Turbulent Flow over an Embedded Strut

An analysis is made of the sound produced during low-Mach-numberturbulent flow over a thin, two-dimensional rigid strut embeddedin a compliant layer. The layer is interposed between the flowand a plane rigid wall, and is modelled by ahomogeneous ‘blanket’of uniform thickness, whose properties are represented by thoseof a fluid of uniform mean density and sound speed. The strutis transverse to the mean flow and projects normally from thewall to an arbitrary distance, but does not make physical contactwith the fluid. Sound is produced by the diffraction by thestrut of the intensive convective pressure fluctuations of theboundary layer. Numerical predictions are made of the radiationinto the fluid, and of the extent to which the diffracted fieldstands out against the background noise of the turbulent boundarylayer.