An Experimental Investigation on Flow Structure in Channel with Consecutive Bends

Abstract

Bend flow has distinct three-dimensional characteristics, such as water surface superelevation and spiral flow. Existing experimental results and numerical simulation studies on bend flow were mostly aimed at simple bends. This paper presents the results of mean-velocity measurements conducted on a multiple-bend channel with 6 consecutive bends. The cross-sectional distribution of depth-averaged longitudinal velocity and vertical distribution of longitudinal velocity are shown and the differences between flow structures at various sections of the 6 consecutive bends are discussed. The results showed that: typical bend flow structure was not fully established in the first channel bend, and the flow structure in the first bend should not be used as a representation of the general condition of bend flows; maximum values of depth averaged velocity were always found near the convex bank for higher flow discharges, and near the concave bank for lower flow discharges, but offset in space to the downstream direction; distribution of longitudinal velocity over depth in the first bend was similar to that in other bends; maximum velocity was found below the free surface except for the central region and the decrease in velocity near the water surface was comparatively large at the convex bank in the first half of bend.