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455 / 2024-03-21 13:56:14
On the role of Froude number in turbulent flow and sediment transport through boulder arrays
Numerical simulation
Subtheme 3: Eco-hydraulics and Environment > Topic 1: Innovation and Development of Eco-hydraulics Theory
Abstract Accepted
Tang Zhengdao / School
In mountainous rivers, Froude number (Fr) in the vicinity of large boulders varies significantly at low relative submergence, leading to local hydraulic jumps. Yet few studies quantify the turbulent structures within these jumps and elucidate their impact on sediment transport. This research employs large eddy simulations to investigate the free-surface turbulent flow through boulder arrays placed over five layers of spheres. Three identical turbulent structures are observed, i.e., meandering high-speed streaks from the boulder’s corridor with a characteristic length of 3.6 folds of boulder diameter (D) at low Fr, flapping of boulder wakes with a length of 0.9D at intermittent Fr, and a "V"-shaped elongated-titling vortex structure with a length of 0.86D at high Fr. In the former two scenarios, the surface-subsurface flow exchanges govern drag and lift forces on bed spheres. While at high Fr, the "V"-shaped vortices emerge as the primary influencing factor. Considering these two mechanisms, the predicted deposition zones shift from upstream of boulders at low Fr to the flanks of boulders at high Fr. Additionally, the predicted scouring zones transition from the sides of the boulders to the wake region with increasing Fr. The deposition and scouring zones align well with experimental observations published in the literature, providing valuable insights into the inter-connection between sediment transport and flow structures.
Important Date

  • Conference Date

    Oct 14

    2024

    to

    Oct 17

    2024

  • Sep 30 2024

    Draft paper submission deadline

  • Oct 17 2024

    Registration deadline

Sponsored By
International Association for Hydro Environment Engineering and Research Asia Pacific Division
Organized By
Changjiang River Scientific Research Institute
Sichuan University
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