CURVED OPEN CHANNEL FLOW ON VEGETATION ROUGHENED INNER BANK

A RNG k - epsilon numerical model together with a laboratory measurement with Micro ADV are adopted to investigate the flow through a 180 degrees curved open channel (a 4 m straight inflow section, a 180 degrees curved section, and a 4m straight outflow section) partially covered with rigid vegetations on its inner bank. Under the combined action of the vegetation and the bend flow, the flow structure is complex. The stream-wise velocities in the vegetation region are much smaller than those in the non-vegetation region due to the retardation caused by the vegetation. For the same reason, no clear circulation is found in the vegetated region, while in the non-vegetation region, a slight counter-rotating circulation is found near the outer bank at both 90 degrees and downstream curved cross-sections. A comparison between the numerical prediction and the laboratory measurement shows that the RNG k - epsilon model can well predict the flow structure of the bend flow with vegetation. Furthermore, the shear stress is analyzed based on the numerical prediction. The much smaller value in the inner vegetated region indicates that the vegetation can effectively protect the river bank from scouring and erosion, in other words, the sediment is more likely to be deposited in the vegetation region.