Flow Characteristics And Sediment Transport Research Under The Ice Cover

Yellow River sediment problem has been the focus of the study. Recently, mainly due to sediment deposition the riverbed elevation increased, and flow capacity is reduced, it posed serious threat to residents along the river. So the study for the entire period of the Yellow River sediment transport is important.In this thesis, the study on the sediment transport in the Yellow River in Inner Mongolia, to analysis sediment transport in the open water period and ice period. In the open water period, the sediment concentration is proportional to the flow. In the ice period, flow characteristics changed under the ice. The presence of ice cover changed the water level and velocity magnitude and vertical distribution. Through field observations and data from hydrological stations, the sediment transport and the factors are analyzed during ice period of The Yellow River, the following results are obtained:(1) In the open water period, sediment concentration is proportional to discharge. The flow plays a key role on sediment concentration under the water. But in the ice period, for a same discharge, the sediment concentration is very low. The existence of ice and the change of flow velocity and distribution, which determine the sediment concentration in the frozen period;(2) Maximum velocity on the surface in the open water period in Yellow River, it is about2m/s. From the water surface to the river bottom, the velocity decreases gradually. In the ice period, the maximum velocity is located at the middle of the flow depth, it is closer to smaller roughness side of ice and riverbed. The velocity is about0.9m/s, it is, less than the value of the open flow;(3) Water temperature is very different between the open flow and the frozen period, with the decrease of the temperature, resulting in the kinematic viscosity increase, Reynolds number and the particle settling velocity are reduced. To some extent, these changes enhance the ability of flow to carry sediment. Sediment concentration increased slightly in the water, before the frozen-up is more obvious;(4) In winter, sediment concentrations began to decrease with the ice flow. It is lowest in the frozen period, then increases at break-up. It is5-20times smaller than the concentration of the open flow. The amount of sediment transport is small2-15times smaller, and the D50value is larger than the open flow.