Sensitivity of crossflow surfacetransitionroughnessto free-stream conditions and

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The present work is an experimental investigation of stationary crossflow (CF) instability-induced transition of the boundary layer over a 45°swept wing, under varying free-stream turbulence, surface roughness, angle of attack and Reynolds number. Key topological features of the transition front, such as the mean transition location and the jaggedness of the front, are retrieved via IR thermography. Linear Stability Theory (LST) is used to extract the N-factor of the most amplified stationary crossflow mode at the transition location, identified experimentally. Results show clear causality between free-stream turbulence, surface roughness, Reynolds number, angle of attack and transition. Large losses of laminarity and a consistent decrease in the transition N-factor are observed with rising turbulence and roughness. Remarkably, N-factor sensitivity to free-stream turbulence is found to vary significantly and non-linearly with angle of attack for the modest levels of turbulence explored in this campaign, whereas the N-factors scale linearly with the log of the surface roughness level, which is consistent with a receptivity mechanism, which is independent of the angle of attack.
Original languageEnglish
Title of host publicationAIAA Scitech 2019 Forum
Subtitle of host publication7-11 January 2019, San Diego, California, USA
Number of pages10
ISBN (Electronic)978-1-62410-578-4
Publication statusPublished - 2019
EventAIAA Scitech Forum, 2019 - San Diego, United States
Duration: 7 Jan 201911 Jan 2019


ConferenceAIAA Scitech Forum, 2019
Country/TerritoryUnited States
CitySan Diego
Internet address


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