Dresden 2009 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 16: Fluid dynamics I

DY 16.5: Vortrag

Mittwoch, 25. März 2009, 15:45–16:00, ZEU 255

Escape from turbulence in shear flows — •Alberto de Lozar and Björn Hof — Max-Planck-Institut für Dynamik und Selbstorganisation, Göttingen, Deutschland

The collapse of turbulence, observable in shear flows at low Reynolds numbers, raises the question if turbulence is generically of transient nature or becomes sustained at some critical point. Recent data have lead to conflicting views with the majority of studies supporting the model of turbulence turning into an attracting state. We have performed lifetime measurements of turbulence in pipe flow spanning eight orders of magnitude in time, drastically extending all previous investigations. We show that no critical point exists in this regime and that in contrast to the prevailing view the turbulent state remains transient. The behavior found here identifies turbulence in pipe flow as a type-II super-transient, which had been conjectured as a potential description of turbulence two decades ago. Additionally we investigate the lifetime behaviour for square duct and plane Poiseuille flow in order to establish in how far this transition behaviour and the collapse of turbulence are general features of shear flows.