SECONDARY FLOWS IN OPEN CHANNEL WITH SMOOTH AND ROUGH BED STRIPS

摘要

Secondary flows are artificially generated with a non-uniform lateral distribution of bed roughness in an open channel. The channel bed comprises longitudinal smooth and rough strips; the latter is in the form of densely packed sediment particles. Flow velocities are measured using a two-dimensional LDA system in the streamwise and vertical directions. The time-average velocity in the lateral direction is estimated based on the mass conservation equation. The detailed measurements show that the flow characteristics deviate significantly from those observed in open channel flows without bed strips. The results presented include time-average velocity profiles, distributions of turbulence intensities, high-order moment characteristics, and cross-sectional flow patterns. Influences on sediment transport are also discussed.