Experiment of Suspended Load with Hyperconcentration in Rectangle Open Channel

Abstract

In view of the abnormal phenomenon that a flood peak increased in August 2004 and July 2005 along the lower Yellow River, the experiments of this abnormal phenomenon is studied. It is found that the flood increase was due to the decrease the channel roughness in the propagation of high concentrated flood carrying the extra fine sediment which was discharged from xiaolangdi reservoir. Experiments with hyper-concentration flowing over the rough beds prove that the resistance of the flow may be considerably reduced by suspended sediment. Especially in hyper-concentration, the phenomenon of drag-reducing is more obvious when the sediment contents exceed the flocculation sediment contents. It has the significant value for the flood control and flood prediction of hyper-concentration. It is found that the location of the maximum velocity appears below free surface by a series of experiments on velocity distribution and the distribution of sediment concentration in open channel flows. The classic log law and exponential law can not meet the command of experiment. Because the vertical distribution of sediment concentration is dependent on the velocity distribution, based on the diffusion theory, the deriving equation about the distribution of sediment concentration is got according the corrected the equation of velocity distribution. The results indicate that the deriving equation in this paper is well coincident with those observed data in open channel. The equation has important application value.