https://hal-polytechnique.archives-ouvertes.fr/hal-01044637Shimizu, MasayukiMasayukiShimizuGraduate School of Engineering Science - Osaka University [Osaka]Manneville, PaulPaulMannevilleLadHyX - Laboratoire d'hydrodynamique - X - École polytechnique - CNRS - Centre National de la Recherche ScientifiqueDuguet, YohannYohannDuguetLIMSI - Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur - UP11 - Université Paris-Sud - Paris 11 - UFR 919 - Sorbonne Université - UFR d'Ingénierie - SU - Sorbonne Université - Université Paris-Saclay - CNRS - Centre National de la Recherche Scientifique - Université Paris Saclay (COmUE)Kawahara, G.G.KawaharaGraduate School of Engineering Science - Osaka University [Osaka]The splitting of a turbulent puff in pipe flowHAL CCSD2012Roura, Denis2014-07-23 21:40:382023-03-24 14:52:592014-07-23 21:40:38enConference papers1The 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).