Fractal dimensions of hydraulic parameters in sand mined alluvial channel

Abstract

Long-term extraction of sand from a river causes large mining pit on the river bed, and these pits change their fluvial processes. In this paper, an experimental study is executed to interpret the turbulence flow structure in a mining pit. This research mainly focuses on the fractal dimension of velocity fluctuations and Reynolds shear stress (RSS) of flow in the longitudinal and vertical plane for a mining pit region. The results show that the magnitude of fractal dimension for velocity fluctuation and RSS is smaller in the mining pit than the upstream and downstream of the pit. The large values of fractal dimensions at the pit downstream show an increase in flow roughness. It is found that the Taylor microscale decreases towards the channel bed, and this is because of increasing turbulence dissipation near the bed region. We have observed a significantly lower value of Taylor microscale in the mining pit. The higher value of the Taylor microscale is found far downstream of the pit. Nondimensional turbulence mixing length shows a decrease in the traversing length of an eddy at the far downstream of the pit. HIGHLIGHTS We calculated the fractal dimension and turbulence scale in a mining pit.; Fractal dimension is less inside the pit as contrast to downstream of the pit.; The study shows that Taylor microscale increases at the pit downstream.; For sustainable management of sand mining operation, a detail understanding of the flow characteristics is required.;

Keywords

• energy dissipation
• fractal dimension
• mining pit
• taylor microscale