Berlin 2015 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 26: Focus Session: Percolation and turbulent transition

DY 26.2: Hauptvortrag

Mittwoch, 18. März 2015, 10:00–10:30, BH-N 243

Spatio-temporal dynamics in pipe flow and boundary layers — •Bruno Eckhardt — Philipps-Universität Marburg

The transition to turbulence comes in two varieties: in one case, the laminar profile becomes linearly unstable, and a subsequent cascade of instabilities results in the spatially and temporally fluctuating turbulent state. A fluid heated from below (Rayleigh-Benard problem) is the paradigmatic example for this situation. In other cases, turbulence sets in even though the laminar profile remains linearly stable. This `bypass transition' is typically observed in pipe flow, boundary layers and other shear flows. The turbulence is spatially heterogeneous and temporally transient, with the linearly stable laminar state as an absorbing state. Considerable numerical and experimental data support a model for the bypass transition that builds on localized exact coherent structures and their homoclinic and heteroclinic connections, the spatio-temporal dynamics of excitable media, and the statistical mechanics of directed percolation.