Transition of streamwise streaks in zero-pressure-gradient boundary layers

By Luca Brandt, Dan S. Henningson. Journal of Fluid Mechanics, 2002

164 citations recorded by the source corpus.

A transition scenario initiated by streamwise low- and high-speed streaks in a flat-plate boundary layer is studied. In many shear flows, the perturbations that show the highest potential for transient energy amplification consist of streamwise-aligned vortices. Due to the lift-up mechanism these optimal disturbances lead to elongated streamwise streaks downstream, with significant spanwise modulation. In a previous investigation (Andersson et al. 2001), the stability of these streaks in a zero-pressure-gradient boundary layer was studied by means of Floquet theory and numerical simulations. The sinuous instability mode was found to be the most dangerous disturbance. We present here the first simulation of the breakdown to turbulence originating from the sinuous instability of streamwise streaks. The main structures observed during the transition process consist of elongated quasi-streamwise vortices located on the flanks of the low-speed streak. Vortices of alternating sign are overlapping in the streamwise direction in a staggered pattern. The present scenario is compared with transition initiated by Tollmien–Schlichting waves and their secondary instability and by-pass transition initiated by a pair of oblique waves. The relevance of this scenario to transition induced by free-stream turbulence is also discussed.

Subfields: Computational Mechanics, Global and Planetary Change, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/e7e3f89ccce94ac9b4a5decc0e47180132fbcbab

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Citations in the corpus

On Tollmien–Schlichting-like waves in streaky boundary layers (2004, methodology): “The breakdown is characterised by structures identical to those identified by Brandt and Henningson [27] in the case of a linearly unstable streak.”
Leading-edge effects in bypass transition (2007, background): “Simulations of Andersson et al. (2001), Brandt & Henningson (2002), and Brandt et al. (2003) focused on secondary instabilities of streaks.”
The lift-up effect : The linear mechanism behind transition and turbulence in shear flows (2014, background): “As the streaks grow in strength, they become susceptible to high-frequency secondary instabilities due to the presence of both wall-normal and spanwise inflectional velocity profiles (Brandt and Henningson, 2002; Brandt, 2007).”
SIMSON : A Pseudo-Spectral Solver for Incompressible Boundary Layer Flows (2007, background): “Transition of streamwise streaks in zero-pressure-gradient boundary layers (Brandt & Henningson, 2002) 13.”
Transition in boundary layers subject to free-stream turbulence (2004, methodology): “A similar peculiar decrease of the boundary-layer displacement thickness is observed in the numerical simulations of the breakdown of a single steady streak subject to sinuous instability by Brandt & Henningson (2002).”
Stability of zero-pressure-gradient boundary layer distorted by unsteady Klebanoff streaks (2011, methodology): “These modes were subsequently prescribed as inlet perturbations in the DNS of Brandt & Henningson (2002).”