Experimental investigation of flow structures and bed deformation with small width-to-depth ratio in a bend flume

The flow structures and bed formation have been analyzed at typical cross-sections in flat-rigid and inclined beds with small width-to-depth ratio through the observational data in a U-shape bend flume. The results show that the bed configuration strongly affects the variations of the super-elevation of water surface and the intensity of secondary flow. The trend for the intensity of secondary flow shows an increase in the first part of the bend until a maximum value at 60° to the bend, and then decreases in the second part of the bend on flat rigid bed. The analyses also indicate that the water level trend between the outer bank and inner bank inversely varies at the bend entrance and exit in comparison with that on a rigid bed. The intensity of secondary flow shows two peaks of variation exist at sections 60° and 165°, which are associated with the peaks of transverse bed slope on inclined bed. In addition, the maximum deposition in the inner bank and scour in the outer bank associated with the maximum finer and coarsening of bed material occurs at section 60° and 165° related to two peaks of the intensity of secondary flow.