Effects of silt loading on turbulence and sand transport  

作　　者：Daniel G.WREN Roger A.KUHNLE 

机构地区：[1]USDA-Agricultural Research Service-National Sedimentation Laboratory

出　　处：《International Journal of Sediment Research》2012年第4期451-459,共9页国际泥沙研究（英文版）

基　　金：supported by base funding from the USDA-Agricultural Research Service

摘　　要：The transport of bed material and fluid turbulence are affected by many factors, including the fine sediment load being carried in a channel. Current research has focused on sand-sized particles introduced to gravel beds, while the effect of silt load on sand transport has received less attention. Experiments on the effects of silt load, in concentrations 0-26,900 mgl^-1 , on sand transport were performed with a recirculating laboratory flume using three different sand bed configurations： ripples （Fr=0.24）, dunes （Fr=0.34）, and dunes （Fr=0.48）. Three Acoustic Doppler Velocimeters were arranged to measure flow and turbulence quantities simultaneously in one vertical. Sand transport did not change in a consistent manner with increasing silt load, increasing up to 4,000 mg l^-1 for dunes （Fr=0.48） and up to 2,000 mgl^-1 for dunes （Fr=0.34） and then declining to near the clear water case with increasing silt concentrations. Silt addition for the ripple case caused a relatively small change in sand transport, decreasing with added silt up to approximately 2,000 mg l^-1 and then increasing as silt went up to approximately 10,000 mg l^-1. Dunes （Fr=0.48） decreased in length and height as silt increased, while dunes （Fr=0.34） did not show a consistent trend. A clear trend of decreasing Reynolds stress with increasing silt concentration was observed in the ripple case, with a 33% reduction in near-bed Reynolds stress caused by an 8,900 mg l^-1 concentration of silt.The transport of bed material and fluid turbulence are affected by many factors, including the fine sediment load being carried in a channel. Current research has focused on sand-sized particles introduced to gravel beds, while the effect of silt load on sand transport has received less attention. Experiments on the effects of silt load, in concentrations 0-26,900 mgl^-1 , on sand transport were performed with a recirculating laboratory flume using three different sand bed configurations： ripples （Fr=0.24）, dunes （Fr=0.34）, and dunes （Fr=0.48）. Three Acoustic Doppler Velocimeters were arranged to measure flow and turbulence quantities simultaneously in one vertical. Sand transport did not change in a consistent manner with increasing silt load, increasing up to 4,000 mg l^-1 for dunes （Fr=0.48） and up to 2,000 mgl^-1 for dunes （Fr=0.34） and then declining to near the clear water case with increasing silt concentrations. Silt addition for the ripple case caused a relatively small change in sand transport, decreasing with added silt up to approximately 2,000 mg l^-1 and then increasing as silt went up to approximately 10,000 mg l^-1. Dunes （Fr=0.48） decreased in length and height as silt increased, while dunes （Fr=0.34） did not show a consistent trend. A clear trend of decreasing Reynolds stress with increasing silt concentration was observed in the ripple case, with a 33% reduction in near-bed Reynolds stress caused by an 8,900 mg l^-1 concentration of silt.

关 键 词：Turbulence modulation BEDFORMS DUNES Sand transport Silt loading 

分 类 号：TV149[水利工程—水力学及河流动力学]