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Study on flow characteristics and diversity index of diamond-type boulder cluster with different spacing ratios

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Abstract

The placement of boulder or boulder cluster in rivers can increase or repair the complexity of river structure and the diversity of hydraulic conditions, which is very important for the habitat of many aquatic organisms. In this study, the diamond-type boulder cluster was modeled as four hemispheres exposed to a fully developed turbulent open channel flow. Numerical simulation was conducted to investigate the time-averaged flow characteristics, three-dimensional coherent structures, turbulence characteristics, and flow diversity index at different spacing ratios L/D (the ratio of the distance L to the diameter D, 1.0 ≤ L/D ≤ 3.5, where L is the center-to-center distance between two adjacent hemispheres and D is the diameter of the hemisphere). The results show that with the increase of the spacing ratio, the shear layer on the side of the gap flow gradually strengthens, and the single Karman vortex street in the wake region of the hemisphere array is suppressed. The time-averaged peak velocity in the gap flow gradually decreases with the increase of the spacing ratio, and the single of the recirculation zone behind the hemisphere array transforms into the recirculation zone behind each hemisphere, and the length of the each recirculation zone increases to the same. The turbulence intensity of the array first increases with the increase of the spacing ratio and then gradually decreases to a constant, reaching the peak intensity at L/D = 2. Based on the Shannon entropy concept, the flow diversity index in the zone of influence (ZOI) is calculated by considering the velocity and turbulence kinetic energy. The flow diversity index is the largest in the ZOI at the spacing ratio of 1.5.

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Data availability

The datasets used during the current study are available from the corresponding author on reasonable request.

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Funding

The work was supported by the National Natural Science Foundation of China (Grant Nos. 52020105006 and 51879199) and Major Technology Innovation of Hubei Province (No. 2019ACA154).

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Contributions

Yisen Wang: Conceptualization, methodology, and writing-original draft.

Zhonghua Yang: Conceptualization, supervision, funding acquisition, and writing-review and editing.

Minghui Yu: Writing-review and editing.

Haiyan Zhou: Investigation and supervision.

Dawei Zhang: Supervision.

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Correspondence to Zhonghua Yang.

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The authors declare no competing interests.

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Wang, Y., Yang, Z., Yu, M. et al. Study on flow characteristics and diversity index of diamond-type boulder cluster with different spacing ratios. Environ Sci Pollut Res 29, 34248–34268 (2022). https://doi.org/10.1007/s11356-021-18047-4

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  • DOI: https://doi.org/10.1007/s11356-021-18047-4

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