2021
DOI: 10.1017/jfm.2021.658
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Acoustic-roughness receptivity in subsonic boundary-layer flows over aerofoils

Abstract: The generation of a viscous–inviscid instability through scattering of an acoustic wave by localised and distributed roughness on the upper surface of a NACA 0012 aerofoil is studied with a time-harmonic compressible adjoint linearised Navier–Stokes approach. This extends previous work by the authors dedicated to flat plate geometries. The key advancement lies in the modelling of the inviscid acoustic field external to the aerofoil boundary layer, requiring a numerical solution of the convected Helmholtz equat… Show more

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Cited by 4 publications
(3 citation statements)
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“…While this is the first paper on the receptivity of a multi-fluid flow to acoustic–roughness interaction, one could compare our results with the similar work, such as Raposo et al. (2021). Their numerical studies of acoustic–roughness receptivity in subsonic boundary-layer flow over aerofoils show that the receptivity amplitude varies with the position of a Gaussian-shaped roughness in the absence of a thin film.…”
Section: Discussionsupporting
confidence: 65%
“…While this is the first paper on the receptivity of a multi-fluid flow to acoustic–roughness interaction, one could compare our results with the similar work, such as Raposo et al. (2021). Their numerical studies of acoustic–roughness receptivity in subsonic boundary-layer flow over aerofoils show that the receptivity amplitude varies with the position of a Gaussian-shaped roughness in the absence of a thin film.…”
Section: Discussionsupporting
confidence: 65%
“…The latter was later applied to the roughness–acoustic receptivity in boundary layers over subsonic aerofoils (Raposo et al. 2021). Remarkably, a strong receptivity regime in supersonic boundary layers was reported by Liu, Dong & Wu (2020); namely, if the incident angle of the freestream acoustic wave is around a particular value such that its streamwise phase speed is quasi-zero, then the perturbation velocity of the acoustic signature in the near-wall viscous layer could be amplified by a factor of compared to its freestream value, leading to an extra amplification of the receptivity efficiency in comparison with the Ruban–Goldstein regime, where is the Reynolds number, with the length scale being the distance to the leading edge.…”
Section: Introductionmentioning
confidence: 99%
“…The leading-order contribution to the receptivity of inviscid modes depends on the deformation of the sound-generated Stokes layer by the curved wall. The acoustic receptivity has also been studied in detail using the harmonic linear Navier-Stokes (HLNS) equations in the context of incompressible flow (Raposo, Mughal & Ashworth 2018) and subsonic flow conditions (Raposo, Mughal & Ashworth 2019;Raposo et al 2021), and an acoustic receptivity model is proposed to account for the effects of variances in the freestream acoustic field on the instabilities when localized surface roughness is present.…”
Section: Introductionmentioning
confidence: 99%