Abstract
A realistic aircraft wing is not expected to be an ideally smooth surface: the influence of junctions or wing panels must be taken into account in the laminar wing design. The presence of these spanwise invariant two-dimensional surface irregularities further amplifies the boundary-layer streamwise instabilities existing on a smooth surface, potentially causing an early transition to turbulence. In the present work, the effect of steps, gaps and humps on the development of Tollmien-Schlichting (TS) waves in an incompressible boundary layer is studied using direct numerical simulations (DNS). For a specific height we investigated several shapes of the geometric irregularity. Depending on their shape the surface imperfections give rise to a local separation bubble which interacts with the oncoming TS waves: for the frequency considered, all the surface irregularities have a destabilizing effect, with the rectangular hump case being the most dangerous one.
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Acknowledgements
The authors acknowledge the financial support of SSeMID: Stability and Sensitivity Methods for Industrial Design funded by European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 675008. F.T. would also like to thank Dr. Hui Xu for providing the data used in the comparison of Fig. 2.
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Tocci, F., Chauvat, G., Hein, S., Hanifi, A. (2022). Direct Numerical Simulations of Tollmien-Schlichting Disturbances in the Presence of Surface Irregularities. In: Sherwin, S., Schmid, P., Wu, X. (eds) IUTAM Laminar-Turbulent Transition. IUTAM Bookseries, vol 38. Springer, Cham. https://doi.org/10.1007/978-3-030-67902-6_70
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DOI: https://doi.org/10.1007/978-3-030-67902-6_70
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