Extension at the downstream end of turbulent band in channel flow

Journal article (2020)

Authors

Jinsheng Liu Tsinghua University

Yue Xiao Peking University, CAPT-HEDPS and SKLTCS

Linsen Zhang Peking University

Mogeng Li University of Melbourne

Jianjun Tao Peking University

Shengjin Xu Tsinghua University

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Published Date

2020

Language

English

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Abstract

In this Letter, the velocity structures and the extension behavior of localized turbulent bands in channel flows are measured by particle image velocimetry in a plane parallel to the walls and are analyzed by comparing with direct numerical simulations at low Reynolds numbers. It is illustrated that the convection velocity of the band head (band's downstream end) is not determined by the formation and propagation of low-speed streaks but by a high-speed "hat"shaped region near the band head. This "hat"region travels downstream obliquely like a solitary wave and leaves newly generated low-speed streaks to travel slowly in the spanwise direction, leading to the head extension of turbulent bands.