The path of laminar-to-turbulent transition behind a backward-facing step (BFS) in the supersonic regime at Ma = 1.7 and Reδ0 = 13718 is investigated using a very well-resolved large eddy simulation (LES). Five distinct stages are identified in the transition process by the visualisation of instantaneous flow. The transition is initiated by a Kelvin-Helmholtz (K-H) instability of the separated shear layer, followed by secondary modal instabilities of the distorted K-H vortices, leading to Λ-shaped vortices, hair-pin vortices and finally to a fully turbulent state around the reattachment location. Spectral analysis and proper orthogonal decomposition (POD) reveal that the low-frequency breathing dynamics also plays a major role in the transition process.
|Title of host publication||Proceedings of the 11th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2019|
|Subtitle of host publication||30/07/19 - 2/08/19 Southampton, United Kingdom|
|Number of pages||6|
|Publication status||Published - 1 Jan 2019|
|Event||11th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2019 - Southampton, United Kingdom|
Duration: 30 Jul 2019 → 2 Aug 2019
|Conference||11th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2019|
|Period||30/07/19 → 2/08/19|
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