Dresden 2009 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 12: Poster I

DY 12.10: Poster

Dienstag, 24. März 2009, 14:30–16:30, P1A

Interaction of turbulent spots in pipe flow — •devranjan samanta, alberto delozar, and bjorn hof — MPI for dynamics and self organisation Bunsenstrasse 10 gottingen 37073 lower saxony germany

The process of transition from laminar to turbulent regime in shear driven flows is still an unresolved issue. Localized turbulent regions or spots emerge in the laminar turbulent transition regime. A good understanding of these localized structures is crucial for the comprehension of the transition to turbulence. We investigate the interaction of such turbulent spots in pipe flow for Reynolds numbers from 1900 to 2500. Turbulence is created locally by injecting a jet of water through a small hole in the pipe wall. The spacing of the turbulent spots downstream is inversely proportional to the perturbation frequency. It is observed that for distances less than approximately 20 pipe diameters turbulent spots start to interact and annihilate each other. The interaction distance is measured as a function of Reynolds number. This investigation is closely related to spatially turbulent laminar periodic patterns which were earlier observed in other shear driven flows like Taylor-Couette or plane Couette.