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Receptivity mechanisms in three-dimensional boundary-layer flows
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0002-4346-4732
KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control.ORCID iD: 0000-0001-7864-3071
2009 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 618, 209-241 p.Article in journal (Refereed) Published
Abstract [en]

Receptivity in three-dimensional boundary-layer flow to localized surface roughness and free-stream vorticity is studied. A boundary layer of Falkner–Skan–Cooke type with favourable pressure gradient is considered to model the flow slightly downstream of a swept-wing leading edge. In this region, stationary and travelling crossflow instability dominates over other instability types. Three scenarios are investigated: the presence of low-amplitude chordwise localized, spanwise periodic roughness elements on the plate, the impingement of a weak vortical free-stream mode on the boundary layer and the combination of both disturbance sources. Three receptivity mechanisms are identified: steady receptivity to roughness, unsteady receptivity to free-stream vorticity and unsteady receptivity to vortical modes scattered at the roughness. Both roughness and vortical modes provide efficient direct receptivity mechanisms for stationary and travelling crossflow instabilities. We find that stationary crossflow modes dominate for free-stream turbulence below a level of about 0.5%, whereas higher turbulence levels will promote the unsteady receptivity mechanism. Under the assumption of small amplitudes of the roughness and the free-stream disturbance, the unsteady receptivity process due to scattering of free-stream vorticity at the roughness has been found to give small initial disturbance amplitudes in comparison to the direct mechanism for free-stream modes. However, in many environments free-stream vorticity and roughness may excite interacting unstable stationary and travelling crossflow waves. This nonlinear process may rapidly lead to large disturbance amplitudes and promote transition to turbulence.

Place, publisher, year, edition, pages
2009. Vol. 618, 209-241 p.
Keyword [en]
tollmien-schlichting waves, free-stream disturbances, orr-sommerfeld, equation, continuous-spectrum, localized receptivity, pressure-gradient, leading-edge, transition, roughness, vortices
National Category
Fluid Mechanics and Acoustics
URN: urn:nbn:se:kth:diva-9407DOI: 10.1017/S0022112008004345ISI: 000262741500010ScopusID: 2-s2.0-57749172676OAI: diva2:113868
Uppdaterad från in Press till Published 2009 QC 20101022 Available from: 2008-10-30 Created: 2008-10-30 Last updated: 2010-11-23Bibliographically approved
In thesis
1. Receptivity of Boundary Layers under Pressure Gradient
Open this publication in new window or tab >>Receptivity of Boundary Layers under Pressure Gradient
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Boundary-layer flow over bodies such as aircraft wings or turbine blades is characterized by a pressure gradient due to the curved surface of the body. The boundary layer may experience modal and non-modal instability, and the type of dominant instability depends on whether the body is swept with respect to the oncoming flow or not. The growth of these disturbances causes transition of the boundary-layer flow to turbulence. Provided that they are convective in nature, the instabilities will only arise and persist if the boundary layer is continuously exposed to a perturbation environment. This may for example consist of turbulent fluctuations or sound waves in the free stream or of non-uniformities on the surface of the body. In engineering, it is of relevance to understand how susceptive to such perturbations the boundary layer is, and this issue is subject of receptivity analysis.


In this thesis, receptivity of simplified prototypes for flow past a wing is studied. In particular, the three-dimensional swept-plate boundary layer and the boundary layer forming on a flat plate with elliptic leading edge are considered. The response of the boundary layer to vortical free-stream disturbances and surface roughness is analyzed, receptivity mechanisms are identified and their efficiency is quantified.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. vi, 23 p.
Trita-MEK, ISSN 0348-467X ; 2008:08
Leading-edge effects
urn:nbn:se:kth:diva-9379 (URN)978-91-7415-155-8 (ISBN)
2008-10-29, K1, Teknikringen 56, KTH Campus Valhallavägen, Stockholm, 10:15 (English)
76218 VR Receptivity
QC 20101022Available from: 2008-10-30 Created: 2008-10-27 Last updated: 2012-02-23Bibliographically approved

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