Recent studies have suggested that in some cases transition can be triggered by some purely nonlinear mechanisms. Here we aim at verifying such an hypothesis, looking for a localized perturbation able to lead a boundary-layer flow to a chaotic state, following a nonlinear route. Nonlinear optimal localized perturbations have been computed by means of an energy optimization which includes the nonlinear terms of the Navier- Stokes equations. Such perturbations lie on the turbulent side of the laminar-turbulent boundary, whereas, for the same value of the initial energy, their linear counterparts do not. The evolution of these perturbations toward a turbulent flow involves the presence of streamwise-inclined vortices at short times and of hairpin structures prior to breakdown.
|Autori interni:||DE PALMA, Pietro|
|Titolo:||Rapid path to transition via nonlinear localized optimal perturbations in a boundary-layer flow|
|Rivista:||PHYSICAL REVIEW E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS|
|Data di pubblicazione:||2010|
|Digital Object Identifier (DOI):||10.1103/PhysRevE.82.066302|
|Appare nelle tipologie:||1.1 Articolo in rivista|