Berlin 2015 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 26: Focus Session: Percolation and turbulent transition

DY 26.5: Vortrag

Mittwoch, 18. März 2015, 11:15–11:30, BH-N 243

About discontinuous laminar-turbulent transitions in planar shear flows — •Yohann Duguet — LIMSI-CNRS, Université Paris-Sud, Orsay, France

The suggestion that transitional shear flows with a stable laminar state could be described as stochastic contact processes was formulated almost three decades ago. Recent progresses in pipe flow experiments and simulations have allowed for firmer claims about the universality class to which it belongs, with an emphasis on the university class of directed percolation. In this flow we would like to discuss two planar flows also featuring competition between laminar and turbulent phases, by analysing the mechanisms for the collapse of turbulence from accurate numerical simulations in large domains. For the case of planar Couette flow, the question seems to remain open even judging from recent observations. The case of a parallel boundary layer flow with uniform suction, however, shows a clear example of brutal discontinuous phase transition. We will discuss the crucial differences between the local mechanisms in these two examples. This is joint work with the Mechanics department of KTH (Stockholm, Sweden).