Berlin 2015 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 26: Focus Session: Percolation and turbulent transition

DY 26.6: Talk

Wednesday, March 18, 2015, 11:30–11:45, BH-N 243

Transition to turbulence in Couette-Taylor flow as a directed percolation process ? — •Grégoire Lemoult¹, Shreyas Jalikop¹, Kerstin Avila², and Björn Hof¹ — ¹IST Austria (Institute of Science and Technology, Klosterneuburg, Austria) — ²Institute for Multiscale Simulation at the Friedrich-Alexander Universität Erlangen-Nürnberg

In the counter-rotating regime of Couette-Taylor (CT) flow, turbulence appears abruptly through spatio-temporal intermittency (STI). STI is observed during the sub-critical transition to turbulence in many shear flows, most notably pipe flow and Couette flows. K. Avila et al. (Science 333, 2011) recently characterized the onset of sustained turbulence in pipe flow. Their work suggested that the transition could be a second order non-equilibrium phase transition. The present contribution aims to experimentally characterize the transition to sustained turbulence in CT flow and explore the analogy to a phase transition.

Our CT setup has an aspect ratio and an azimuthal length of more than 600 gap-widths. These large dimensions minimise the finite-size effects, and render the setup suitable to experimentally investigate the spatio-temporal dynamics. We present evidence to support the idea that the transition is a phase transition of second order and provide first estimates of some of the associated critical exponents: laminar gap size distributions and turbulent fraction.