Bimodal Bed Load Transport Characteristics under the Influence of Mixture Ratio

The transport of a non-uniform bed load in river is complicated process and has enormous implications on the sediment flux anomalous riverbed evolution. To investigate characteristics related particle interactions, real-time monitoring system was developed to determine instant rate grain composition load. Doppler Velocimetry used synchronously measure fluctuating velocity high frequency. A total 211 cases flume experiments were conducted, focusing with bimodal pattern. experimental results indicate that random fluctuation amount closely depends flow-intensity caused by turbulence burst near bed. When value flow-fluctuation peak bigger than 2.5 σ, coarse sands tend incipient motion probability but are mostly fine sand when less 1.5 σ. particles remains continuous throughout process, while intermittent because mechanism mainly follows three modes. If difference diameter between large, may undergo supernormal effect particles. total, fine, present different trends changes material composition, which presents humped curve terms mixture ratio, optimal corresponding ratio ηc about 3:7. not fixed, it size differential material. With proper higher uniform size. These findings might provide valuable support for predicting evolution rivers.