Oblique Laminar-Turbulent Interfaces in Plane Shear Flows

Duguet, Yohann; Schlatter, Philipp

doi:10.1103/physrevlett.110.034502

Cited by 99 publications

(177 citation statements)

References 27 publications

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“…The oblique patches spread in the spanwise direction and resemble a wedge shape. The scenario is similar to that reported for the growth of the laminar-turbulent interface of a turbulent spot (Duguet & Schlatter 2013;Couliou & Monchaux 2016), featuring oblique velocity streaks. Consequently, the oblique patches are regarded as the preliminary feature of the turbulent wedge in the current condition, contributing to the spanwise growth of turbulent fluctuations.…”

Section: Pod Analysissupporting

confidence: 83%

On Reynolds number dependence of micro-ramp-induced transition

Schrijer

Scarano

2018

J. Fluid Mech.

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The variation of transitional flow features past a micro-ramp is investigated when the Reynolds number is decreased approaching the critical regime. Experiments are conducted in the incompressible flow spanning from supercritical to subcritical roughness-height-based Reynolds number (Re h = 1170, 730, 460 and 320) with tomographic particle image velocimetry. The effect of Re h on three-dimensional flow behaviour is analysed in a domain encompassing 73 ramp heights in the streamwise direction. Above the critical Re h , the primary vortex pair and induced central low-speed region in the mean flow field are active over longer range when decreasing Re h . In the instantaneous flow, at Re h < 1000, the hairpin vortices induced by Kelvin-Helmholtz (K-H) instability progress gradually from close to the micro-ramp into the region where the overall shear layer is destabilized, indicating the correlation between the K-H instability and the onset of transition. The breakdown of K-H vortices as observed at Re h = 1170, does not occur at lower Re h . Decreasing Re h , the secondary vortex structures make their first appearance significantly downstream, postponing the formation of sideward disturbances, which destabilize the local shear layer by ejection events. Two major types of eigenmodes with symmetric and asymmetric spatial distribution of velocity fluctuations in the near wake are clearly identified by proper orthogonal decomposition. The symmetric and asymmetric modes correspond to the presence of vortex shedding and a sinuous wiggling motion respectively. It is found that Re h is the key factor determining the importance of the symmetric mode. At Re h = 1170, the disturbance energy of the symmetric mode decays before the onset of transition, suggesting that it is relatively insignificant in the process. However, decreasing Re h to 730 and 460, the symmetric mode produces continuous growth of high level disturbance energy, leading to transition.

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Section: Pod Analysissupporting

confidence: 83%

On Reynolds number dependence of micro-ramp-induced transition

Schrijer

Scarano

2018

J. Fluid Mech.

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“…In the spanwise direction studies of spots between plates show that the longitudinal vortices at the boundary drive further rolls in their neighborhood [70][71][72]. This process is not monotonic, and some of the rolls that are triggered may decay again, which is consistent with the transient nature of local structures.…”

Section: Localizationsupporting

confidence: 51%

Transition to turbulence in shear flows

Eckhardt

Marzinzik

Schmiegel

A Perspective Look at Nonlinear Media

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Pipe flow and many other shear flows show a transition to turbulence at flow rates for which the laminar profile is stable against infinitesimal perturbations. In this brief review the recent progress in the understanding of this transition will be summarized, with a focus on the linear and nonlinear states that drive the transitions, the extended and localized patterns that appear, and on the spatio-temporal dynamics and their relation to directed percolation.

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“…The mechanism for the growth in the oblique direction is similar to that of PCF, [24][25][26] where the large-scale motions play the key role. At t = 950, a long band is formed (see Fig.…”

Section: -mentioning

confidence: 76%

Turbulent bands in plane-Poiseuille flow at moderate Reynolds numbers

et al. 2015

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In this letter, we show via numerical simulations that the typical flow structures appearing in transitional channel flows at moderate Reynolds numbers are not spots but isolated turbulent bands, which have much longer lifetimes than the spots. Localized perturbations can evolve into isolated turbulent bands by continuously growing obliquely when the Reynolds number is larger than 660. However, interactions with other bands and local perturbations cause band breaking and decay. The competition between the band extension and breaking does not lead to a sustained turbulence until Re becomes larger than about 1000. Above this critical value, the bands split, providing an effective mechanism for turbulence spreading.

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Oblique Laminar-Turbulent Interfaces in Plane Shear Flows

Cited by 99 publications

References 27 publications

On Reynolds number dependence of micro-ramp-induced transition

On Reynolds number dependence of micro-ramp-induced transition

Transition to turbulence in shear flows

Turbulent bands in plane-Poiseuille flow at moderate Reynolds numbers

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