title: Self-sustained localized structures in a boundary-layer flow.
abstract: 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.
authors.affiliation: LIMSI-CNRS, UPR 3251, F-91403 Orsay, France.
authors.forename: Yohann
authors.initials: Y
authors.lastname: Duguet
authors.forename: Philipp
authors.initials: P
authors.lastname: Schlatter
authors.forename: Dan S
authors.initials: DS
authors.lastname: Henningson
authors.forename: Bruno
authors.initials: B
authors.lastname: Eckhardt
mesh_terms: D003198:Computer Simulation; D008962:Models, Theoretical; D013499:Surface Properties