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THE MECHANISM OF ENERGY TRANSFER IN TURBULENT POISEUILLE FLOW AT VERY LOW-REYNOLDS NUMVER

Koji Fukudome
Department of Mechanical Engineering, and also Department of Engineering Physics, Electronics and Mechanics, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya 466-8555, Japan

Oaki Iida
Department of Mechanical Engineering, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya 466-8555, Japan

Yasutaka Nagano
Nagoya Industrial Science Research Institute; Department of Mechanical Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan

要約

Direct numerical simulations (DNSs) with a spectral method are performed to study structures of relaminarizing turbulent Poiseuille flow at very low-Reynolds numbers, where a flow, simultaneously including quasi-laminar and turbulent regions, becomes spatially intermittent. Turbulent energy is found to be exchanged between the turbulent and quasi-laminar regions; in the very vicinity of the wall, turbulent energy is transferred from the turbulent to quasilaminar regions, while in the region away from the wall, it is transferred in the opposite direction. This energy exchange is attributed to the inclination of turbulent region with respect to streamwise direction in the plane parallel to the wall, and constant advection velocity of turbulent region over the entire channel. Moreover, we also confirmed generation of a large-scale flow circulating around the turbulent region, whcih continues to appear over the long time.