Author(s): Yuchuan Bai; Haijue Xu
Keywords: Hyperconcentrated flow; instability; sediment motion; turbulence; Yellow River
Abstract: Sediment concentrations of Chinese rivers are among the highest worldwide. If the sediment concentration exceeds a certain value, the flow dramatically changes exhibiting properties different from low-concentration sediment-laden flows, both in the movement and the pattern of sediment transportation. The hyperconcentrated flow exhibits distinct phenomena, such as “instability flow”, “clogging river”, or “blast flow”. Such flow phenomena are related to the formation, development and break-up of a hyperconcentrated laminar layer, and also reflect the transition from laminar to turbulent and return to laminar flow. The turbulence intensity of the hyperconcentrated flow is normally weak with turbulence largely damped as the sediment concentration becomes sufficiently high. It was found that the instability of hyperconcentrated flows is not only controlled by the critical Reynolds number, but also related to sediment concentration, distribution of the sediment in water, and the size and density of the sediment particles.