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Conference papers
The splitting of a turbulent puff in pipe flow
Abstract : The transition to turbulence of the flow in a pipe of constant radius is numerically studied over a range of Reynolds numbers where turbulence begins to expand by puff splitting. We first focus on the case Re = 2300 where splitting occurs as discrete events. Around this value only long-lived pseudo-equilibrium puffs can be observed in practice, as typical splitting times become very long. When Re is further increased, the flow enters a more continuous puff splitting regime where turbulence spreads faster. Puff splitting presents itself as a two-step stochastic process. A splitting puff first emits a chaotic pseudopod made of azimuthally localized streaky structures at the downstream (leading) laminar-turbulent interface. This structure can later expand azimuthally as it detaches from the parent puff. Detachment results from a collapse of turbulence over the whole cross-section of the pipe. Once the process is achieved a new puff is born ahead. Large-deviation consequences of elementary stochastic processes at the scale of the streak are invoked to explain the statistical nature of splitting and the Poisson-like distributions of splitting times reported by Avila, Moxey, de Lozar, Avila, Barkley and Hof (2011 Science 333 192-196).
https://hal-polytechnique.archives-ouvertes.fr/hal-01044637
Contributor : Denis Roura Connect in order to contact the contributor
Submitted on : Wednesday, July 23, 2014 - 9:40:38 PM
Last modification on : Monday, January 3, 2022 - 4:36:02 PM
Contributor : Denis Roura Connect in order to contact the contributor
Submitted on : Wednesday, July 23, 2014 - 9:40:38 PM
Last modification on : Monday, January 3, 2022 - 4:36:02 PM