Edge states in a boundary layer

Cherubini, Stefania; Palma, P. De; Robinet, Jean-Christophe; Bottaro, Alessandro

doi:10.1063/1.3589842

Cited by 48 publications

(42 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The situation for the Blasius boundary layer is a step up in complexity, both conceptually and technically: the spatial development implies that the control parameters vary along a trajectory, and the flow is not confined in the wall-normal direction. A recent calculation in a narrow periodic domain demonstrates the applicability of edge tracking in a spatially developing flow [16]. The introduction of a fixed length scale is, however, incompatible with the localization and the spatial spreading of the disturbance which follows from the spatial expansion of the flow.…”

mentioning

confidence: 99%

Self-Sustained Localized Structures in a Boundary-Layer Flow

et al. 2012

View full text Add to dashboard Cite

When a boundary layer starts to develop spatially over a flat plate, only disturbances of sufficiently large amplitude survive and trigger turbulence subcritically. Direct numerical simulation of the Blasius boundary-layer flow is carried out to track the dynamics in the region of phase space separating transitional from relaminarizing trajectories. In this intermediate regime, the corresponding disturbance is fully localized and spreads slowly in space. This structure is dominated by a robust pair of low-speed streaks, whose convective instabilities spawn hairpin vortices evolving downstream into transient disturbances. A quasicyclic mechanism for the generation of offspring is unfolded using dynamical rescaling with the local boundary-layer thickness.

show abstract

mentioning

confidence: 99%

Self-Sustained Localized Structures in a Boundary-Layer Flow

et al. 2012

View full text Add to dashboard Cite

show abstract

“…This type of turbulent band was also reported in the direct numerical simulation by Tsukahara et al 13 In spite of mathematical difficulties, nonlinear analyses of disturbance in the shear flows around the marginal Re were vigorously performed for the last few decades. Recently, a new concept, "edge state" was proposed [14][15][16][17][18][19] and successfully described behavior of the nonlinear disturbances in the transitional pipe flow. [20][21][22] When considering the marginal Re, one can examine the largest vortical scale of turbulent disturbances in the wall unit.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of relaminarizing and transitional channel flows

Seki

Matsubara

2012

Physics of Fluids

View full text Add to dashboard Cite

A hot-wire measurement was conducted in a planar channel flow that originated from a strongly disturbed flow in an entrance channel followed by an expansion channel used to reduce the Reynolds number (Re). From ceasing decrease of the streamwise velocity fluctuation energy and the linear extrapolation of the intermittency factor, the lower marginal Re, which is defined as the minimum Re for partial existence of sustainable turbulence, is estimated around 1400 based on the channel width and the bulk velocity. The upper marginal Re at which the intermittency factor reaches one is about 2600. The flow fields passing a turbulent patch were reconstructed with conditional sampling of the streamwise velocity data based on the time of laminarturbulence interfaces and the reconstructed flow fields indicate a large-scale flow structure across laminar and turbulent parts. This large structure makes it possible for some regions to be at higher Re than the average, so that turbulence can partly survive. The moderate-scale disturbances larger than the turbulent one appear in the non-turbulent parts of the transitional flow, and in these cases the non-turbulent velocity profile is almost identical to the turbulent one. The large-scale fluctuation is observed even over Re = 2600. This leads to the conclusion that a turbulent channel flow close to the upper marginal Re becomes inhomogeneous. C 2012 American Institute of Physics. [http://dx

show abstract

“…Therefore, following the theoretical work of Waleffe (1997), the maximum values of the streamwise and wall-normal components of the velocity are chosen as state variables. Figure 6 provides the trajectories in this reduced phase space (Cherubini et al 2011b) of nonlinear optimal perturbations with different initial energy (the ones also used in figure 3, top frame). The origin (corresponding to zero disturbance velocity with respect to the laminar Blasius solution) is the laminar attractor; the turbulent attractor is localized on the top right, for values of the perturbation velocity components around u ≈ 0.7, v ≈ 0.3; the relative attractor on the edge is the looping trajectory represented by the black thick line and is localized around u ≈ 0.25, v ≈ 0.045 (cf also the inset in the figure).…”

Section: Resultsmentioning

confidence: 99%

A purely nonlinear route to transition approaching the edge of chaos in a boundary layer

et al. 2012

View full text Add to dashboard Cite

The understanding of transition in shear flows has recently progressed along new paradigms based on the central role of coherent flow structures and their nonlinear interactions. We follow such paradigms to identify, by means of a nonlinear optimization of the energy growth at short time, the initial perturbation which most easily induces transition in a boundary layer. Moreover, a bisection procedure has been used to identify localized flow structures living on the edge of chaos, found to be populated by hairpin vortices and streaks. Such an edge structure appears to act as a relative attractor for the trajectory of the laminar base state perturbed by the initial finite-amplitude disturbances, mediating the route to turbulence of the flow, via the triggering of a regeneration cycle of and hairpin structures at different space and time scales. These findings introduce a new, purely nonlinear scenario of transition in a boundary-layer flow.

show abstract

Edge states in a boundary layer

Abstract: is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible.This is an author-deposited version published in: http://sam.ensam.eu Handle

Cited by 48 publications

References 24 publications

Self-Sustained Localized Structures in a Boundary-Layer Flow

Self-Sustained Localized Structures in a Boundary-Layer Flow

Experimental investigation of relaminarizing and transitional channel flows

A purely nonlinear route to transition approaching the edge of chaos in a boundary layer

Contact Info

Product

Resources

About