China Ocean Engineering

, Volume 32, Issue 5, pp 614–623 | Cite as

Analysis on Link Between the Macroscopic and Microscopic Air–Water Properties in Self-Aerated Flows

  • Wang-ru Wei
  • Wei-lin Xu
  • Jun Deng
  • Zhong Tian
  • Fa-xing Zhang


Self-aeration in high-speed free surface flows occurs commonly and is of interest to ocean engineering, hydraulic engineering, and environmental engineering. For two-phase air–water flows, macroscopic air–water flow properties develop gradually, accompanied by the change of microscopic air–water structures. In this article, representational experimental studies on macroscopic and microscopic characteristics of self-aerated open-channel flows are summarized and compared. The isolated effect of the flow Reynolds number and air quantity on the differences in air count rate and chord size are analyzed and discussed. The results show that the characterized flow depth y50, affected by the turbulence transfer, is a specific criterion to distinguish the interior air–water structure development. Two distinct linear trends of self-aeration are found, depending on the y50/y90 variation with a breaking point at Cmean = 0.50. The air count rate and size scale in self-aerated flows are affected by the air quantity of self-aerated flows, even with identical flow Reynolds numbers. Thus, a specific parameter is proposed to assess the air–water structures and a series of self-similarity relationships in self-aeration properties are obtained. The link between macroscopic and microscopic air–water properties results in significant scale effect on air–water structures in self-aerated flows.

Key words

self-aeration two-phase flows air concentration air bubble open channel 


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Copyright information

© Chinese Ocean Engineering Society and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Wang-ru Wei
    • 1
  • Wei-lin Xu
    • 1
  • Jun Deng
    • 1
  • Zhong Tian
    • 1
  • Fa-xing Zhang
    • 1
  1. 1.State Key Laboratory of Hydraulics and Mountain River EngineeringSichuan UniversityChengduChina

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