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Session: Instability and Transition 1
Session starts: Tuesday 25 August, 10:30
Presentation starts: 11:45
Room: Room B

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Takahiro Ishida (Tokyo University of Science)
Takahiro Tsukahara (Tokyo University of Science)

Abstract:
Direct numerical simulations are performed for annular Poiseuille flows with various radius ratios η (= rin/rout) ∈ [0.1, 0.8] in subcritical transition regime of Reτ ∈ [48, 150]. Because the flow system of the annular Poiseuille flow can be regarded as the Hagen-Poiseuille flow (when η ≈ 0) and the plane Poiseuille flow (η ≈ 1), the (dis-)similarity and the connection between them are discussed. We found the occurrences of localized structure like the turbulent puff in the Hagen-Poiseuille flow at low η and of helical wave like the turbulent stripe pattern in the plane Poiseuille flow at high η. The switching point between helical wave and localized structure by changing η is caught in the region η ∈ [0.1, 0.3].