SECONDARY CURRENTS AND BED SHEAR STRESS IN COMPOUND OPEN-CHANNEL FLOWS WITH SHALLOW FLOOD PLAIN

摘要

The pattern of the secondary currents in compound open-channel flows is affectedrnstrongly by the water depth ratio between the flood plane and main channel. The bedrnshear stress is also affected strongly by the pattern of the secondary currents.rnHowever, almost researchers have estimated the bed shear stress by the log-lawrnwithout detailed verification whether this law is valid or not. In this study, thernturbulence measurements of compound open-channel flows over smooth bed werernconducted by making use of a laser Doppler anemometer(LDA) with high accuracy.rnThe friction velocity was evaluated firstly by a linear formula in the viscous sublayerrnin compound open-channel flows. It was found that the effect of the spanwisernReynolds stress on the bed shear stress is greater than that of the mean secondaryrncurrents in shallower compound open-channel flows.