Study on the Instability Characteristics of Open Channel Hyper-Concentration Flow

It is widely existed in nature the flow carries with sediment, such as in Changjiang River, Yellow River, Zhujiang River and so on, in which, the flow in the middle and lower reach carries large quantity of sediment and appears to be unique characters of hyper-concentration flow, such as the phenomenon of the suspended river over the ground, the seiche in its lower reach and so on. Aiming at these, the instability characteristics of the hyper-concentration flow is studied in this paper. And it is shown in the analysis that, compared with the instability characteristics of the clear water (that is the single-phase Newtonian fluid), not only Reynolds number is taken as the criterion to judge whether certain kind of flow is stable, but also some other parameters such as the sediment concentration, the suspending index and the particle diameter all become the factors that effects the instability characteristics of the flow, which makes the problem become even more complex. In this paper, three rheologic models are established respectively to study the flow with the coarse sediment (model for Newtonian two-phase flow), the flow with large amount of fine sediment (model for non-Newtonian two phase flow). The results show that the concentration of the sediment and the suspending index will make great influence on the instability characteristics of the flow, and two Newtonian two-phase models give the similar results while the Non-Newtonian two-phase model gives the quite different ones, which are not mentioned in other papers. The results of the research can supply a scientific basis to the explanations of "slurrying river", the turbulence intensity of the flow carries sediment and the variance of the turbulence structure.