Sediment transport capacity of hyperconcentrated flow

Abstract

As one of the most important components of river mechanics, sediment transport capacity of sediment-laden flows has attracted much attention from many researchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow, an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional, steady, uniform, fully-developed turbulent flow. A new structural expression of sediment transport capacity was achieved. Using 115 runs of flume experimental data, which were obtained through two kinds of sediment transport experiments in the state of equilibrium, in combination with the basic rheological and sediment transporting characteristics of hyperconcentrated flow, the main parameters in the structural expression of sediment transport capacity were calibrated, and a new formula of sediment transport capacity for hyperconcentrated flow was developed. A large amount of field data from the Yellow River, Wuding River, and Yangtze River, etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for management of rivers carrying high concentration of sediments. hyperconcentrated flow, turbulent energy equilibrium, efficiency coefficient, sediment transport capacityIn the Yellow River, hyperconcentrated flood occurs frequently during the rainy seasons. Both the historical maximum concentration of 1600 kg/m 3 and the mean annual amount for sediment transport of 1600 million tons are the highest values worldwide. According to the statistical results coming from the sedimentation bulletin of Chinese Rivers and the Yellow River 1)2) , and the analysis of the field data from Tongguan, Huayuankou, and Lijin Hydrological Stations along the

The concept of transport capacity in geomorphology

“…However, at the highest suspended sediment concentrations, a decrease in the bedload‐transport rates was observed and related to macroviscous effects. In a recent paper, Shu and Fei [, p. 973] explicitly state that the sediment‐transport capacity for a hyperconcentrated flow is “the total amount of sediments that water flow can carry” and developed a formula for sediment‐transport capacity of hyperconcentrated flow, in part based on Bagnold 's [] sediment‐transport efficiency model for suspended transport. Based on the equilibrium equation of turbulent kinetic energy for solid and liquid two‐phase flow, they obtained a structural formula for sediment‐transport capacity, which includes the flow viscosity and flowing resistance coefficient for hyperconcentrated flows: where S v * is the sediment concentration at capacity (m 3 m −3 ); p is an empirically determined coefficient (−); μ r is fluid viscosity (Pa s); f m is a coefficient of resistance (−); γ m is the specific gravity of the flow (kg m −1 s ‐2 ); γ s is the specific gravity of the sediment (kg m −1 s −2 ); U is vertical mean flow velocity (m s −1 ); R is hydraulic radius (m); N is an empirically defined coefficient (−). …”

Deposition morphology of non-homogeneous debris flow and its energy characteristics

“…Non-homogeneous debris flows are characterized by a wide grain size gradation, high volumetric weight, and non-uniformity of both the flow resistance and velocity (Fei and Shu 2004). They behave in a way similar to the properties of the solid-liquid two-phase flows with high sediment transport capacity (Shu and Fei 2008). Furthermore, the deposition, cross-flow, scouring and striking of non-homogeneous debris flows cause a great deal of damage to the local resident and surrounding environment.…”

Macroinvertebrates in the bed sediment of the Yellow River

“…The mean annual discharge of the river is 58 billion m 3 and river flows are strongly seasonal: highest in autumn and lowest in winter. The annual distribution of sediment discharge is concentrated in the summer-flood season with a historical maximum load of 1,600 kg m -3 (1958, recorded at Wenjiachuan) and mean annual sediment transport of 1,600 million tones (Shu and Fei, 2008). The mean annual sediment concentration is 35 kg m -3 (recorded at Sanmenxia).…”