| The motion characteristics of the non-uniform sediment, especially the impact caused by theinteraction among various diameter particles to the bed load transport, is rather complex. However, therecent researches are still insufficient, which not only prevents the development of the sediment disciplinebut also couldn’t meet the need from the plan, design and management of the river project. Therefore,carrying out the mechanism study of transport of non-uniform sediment is both of great theoreticalsignificance and great value of engineering application.In order to study the effect of the non-uniformity of particle on the bed load transport, we haveconducted series of tests in water channel (8groups,25cases)with different non-uniform sediment,achieving fluent turbulent based on the process，particulate exchange and real-time monitoring of bed loadtransport capacity. We also have designed and produced the related special-purpose measuring instruments(bed load dynamic sampling and measuring system and load dynamic selection of measurement systems);filtering out measurement accuracy of bed load selected measurement frequency, and proposing the methodof particle distribution density based on image recognition technology, non-uniform sediment sortingdegree and bed load sediment transport rate.Series of study show that in the condition of inadequate supply, bed load transport process generallyfollowed the model of early stages of development, gradually stabilizing and slowly decaying in theend.Increments of moving-mass accumulation over time have the characteristics of the four function curve,time-varying characteristics of bed load transport rates are generally reflect the behavior of cubic curves.Comprehensive reflection of surface roughness heterogeneity, clayey bottom characteristics and particleeffects of near-wall flow field, introduces a comprehensive flow intensity function Ψb, characteristics ofFourier: Frb, non-uniform features: β and dimensionless functionΦof the intensity of the bed loadsediment transport. By use of dimensional analysis and fitting of the measured data analysis, we haveestablish the complex dependencies of a non-uniform bed load transport intensity and the integrated flowintensity, which give the corresponding calculation method of reflecting the non-uniformity of sedimentparameters.The volatility of sink near the bed surface flow turbulence structure and bed load transport ratesanalysis shows that the volatility of non-uniform bed load transport rate gets the close related toparoxysmal movement of coarse particles. Put forward2modes of coarse bed particles sports: Turbulencecaused by the burst trigger mode and fine particle collision caused the trigger mode. The coherent flowvelocity pulsation characteristics are related to the intermittency characteristics of bed load transport.The affect of the Particle non-uniform degree to the bed load transport is reflected in the influence ofthe existing of fine particles to the flow structure of bed and the collision to the coarse particle. Generally speaking, when the pulse peak value is greater than2.5σ, plenty of coarse sand may start transporting;However, most of the transport sediments are fine sands in case that the intensity of instantaneous pulsebelow1.5σ, and coarse sand rarely participate in the movement. The motion intensity of the coarseparticles and the total sediment discharge, because of the existence of fine particle of appropriateproportion, will be promoted. Under the same flow conditions, with the ratio increased of the fine particles,the process of transport intensity of the non-uniform bed load presents a humped curve. When the ratio ofthe coarse particles to fine particles is3:7, the transport rate of the non-uniform bed load attains themaximum. That means the high efficient of the bed load transport can be realized by controlling theappropriate heterogeneous degree of the particles (the ratio of the coarse particles to fine particles) duringthe water and sand regulation in the alluvial river. |
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