Print Email Facebook Twitter Dynamics of a supersonic transitional flow over a backward-facing step Title Dynamics of a supersonic transitional flow over a backward-facing step Author Hu, W. (TU Delft Aerodynamics) Hickel, S. (TU Delft Aerodynamics) van Oudheusden, B.W. (TU Delft Aerodynamics) Date 2019-10-17 Abstract The transition mechanism and unsteady behavior behind a backward-facing step (BFS) in the supersonic regime at Ma=1.7 and Reδ0=13718 is investigated using large-eddy simulation (LES). The visualization of the flow field shows that the transition process behind the step is initiated by a Kelvin-Helmholtz (K-H) instability of the separated shear layer, followed by secondary modal instabilities of the K-H vortices, leading to Λ-shaped vortices, hair-pin vortices and finally to a fully turbulent state. The separation system features a broadband low-frequency dynamics in the range of fδ0/u∞=0.003∼0.20 as concluded from the spectral and statistical analysis. Dynamic mode decomposition suggests that the medium frequency motions centered around fδ0/u∞=0.06 are related to the interactions between reattaching and the shedding of large coherent shear vortices, while the lower (fδ0/u∞≈0.01) and higher (fδ0/u∞≈0.1) frequency unsteadiness are associated with the periodical expansion and shrinking of the separation system and the convection of upstream K-H vortices, respectively. All these three unsteady mechanisms are coupled to the laminar-to-turbulent transition process in the different stages. To reference this document use: http://resolver.tudelft.nl/uuid:947e28da-9342-44b1-b0ee-0479a7dc4a13 DOI https://doi.org/10.1103/PhysRevFluids.4.103904 Embargo date 2020-01-01 ISSN 2469-990X Source Physical Review Fluids, 4 (10) Bibliographical note Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. Part of collection Institutional Repository Document type journal article Rights © 2019 W. Hu, S. Hickel, B.W. van Oudheusden Files PDF PhysRevFluids.4.103904.pdf 10.34 MB Close viewer /islandora/object/uuid:947e28da-9342-44b1-b0ee-0479a7dc4a13/datastream/OBJ/view