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Mean flow and turbulence structure of open channel flow with suspended vegetation

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Abstract

In combination with a channel bed, suspended vegetationin an open channel can alter flow structure and generate vertically asymmetric flow. This study investigated the mean flow and turbulence structure of an open channel with suspended vegetation through theoretical analysis and laboratory experiments. Three patterns of bionic leaves with different roughness were adopted to imitate suspended vegetation, and three-dimensional velocity field was measured by using an acoustic Doppler velocimeter. The measured data showed that the vertical profile of streamwise velocity obeys a two-power law and that the maximum velocity at the middle depth is close to the smooth boundary (i.e., the channel bed in the experiment) under the combined action of vegetation cover and channel bed. Shear stress is linearly distributed along the vertical axis, and the vertical profile of turbulence intensity obeys an exponential law. Then, a two-power law expression was adopted to predict the vertical profile of streamwise velocity. Theoretical models for the vertical distribution of shear stress and turbulence intensity were also established. The predicted results validated by measurements showed that the different magnitudes of vegetation cover and channel bed boundary roughness exert an obvious impact on flow structure.

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Acknowledgements

This work was supported by the CRSRI Open Research Program (Program SN: CKWV2017503/KY), Hubei Natural Science Foundation (Grant No. 2018CFA010) and the CAS Interdisciplinary Innovation Team, and 111 Project (Grant No. B18037).

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Authors and Affiliations

  1. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, China

    Qian Li, Yu-hong Zeng & Yu Bai

Authors
  1. Qian Li
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  2. Yu-hong Zeng
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  3. Yu Bai
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Corresponding author

Correspondence to Yu-hong Zeng.

Additional information

Project supported by the National Natural Science Foundation of China (Grant Nos. 51879197, 51622905 and 51439007).

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Li, Q., Zeng, Yh. & Bai, Y. Mean flow and turbulence structure of open channel flow with suspended vegetation. J Hydrodyn 32, 314–325 (2020). https://doi.org/10.1007/s42241-020-0020-6

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  • DOI: https://doi.org/10.1007/s42241-020-0020-6

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