THE EFFECT OF BED LOAD ON MAXIMUM SCOUR DEPTH AT RIVER CONFLUENCEBehnam Balouchi1 and Mahmood Shafai Bajestan
Local scour at river confluence is an important feature with a complex three-dimensional (3D) flow pattern. At this place, scour and sedimentation occur which can damage the surrounding area, change river morphology and can be harmful to navigation. In the past the effect of many variables which can affect the sedimentation pattern at river confluence has been studied. The main goal of this study is to experimentally investigate the effect of coming sediment from main channel on scour depth. To do so first a general non dimensional relation was developed, and then a sediment feeder was designed and calibrated. Afterwards, series of experimental tests were conducted in various hydraulic conditions and sediment discharge. The results indicate that increasing the amount of bed load, reducing the maximum scour depth ratio up to 35 percent. Also it was observed that bed scour and sedimentation patterns differs from the case of clear water. Finally, an equation was developed to predict the scour depth in terms of live bed. The accuracy of the new relation is within 90 percent. The sensitivity analysis of this equation shows that it is more sensitive to dens metric Froude number.
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