Author(s): Nejib H. Abdullahi; Zulfequar Ahmad

Linked Author(s):

Keywords: Sand mining; bedload transport; pit morphology; aggradation; degradation; bed evolution

Abstract: Sand mining from the river for different purposes is a common cause of the failure of hydraulic structures. Its presence in a river causes intense bedload transport, which is crucial for designing and operating hydraulic structures. The flow characteristics and aggradation-degradation phenomenon in the vicinity of the sand mining pit have been analyzed with experimental and numerical approaches. The bed level evolution in the vicinity of the pit was measured using a pointer gauge for different temporal and equilibrium stage conditions. A numerical simulation was done using a three-dimensional computational fluid dynamics model, Flow-3D, which was used to compute the bedload transport deposited in the pit and to estimate the spacetime dynamics of the bed evolution of the pit. The volume of fluid (VOF) equation is used to confirm the application of boundary conditions at the free surface in a numerical method. The turbulence formed in the vicinity of the pit was predicted using the turbulence model k-ε with re-normalization group (RNG) extensions. Different bedload transport equations and mesh grid sizes were tried to identify the best fit for aggradation-degradation simulation around sand mining pit. The total volume of bedload transported from the upstream section was deposited in a pit since a pit was used as a bedload trap. The experimental and numerical results showed a close agreement which verified the efficiency of the Flow-3D model.

DOI: https://doi.org/10.26077/2c0b-f314

Year: 2022