Experimental Study on Bed Variation and Sand Waves in Curved Channels

Abstract

In this paper, the bed variation and sand waves in curved channels are discussed experimentally. In the experiment, the flume is 900 curved open channel and the ratio between width of channel and water depth is less than 10. In this experimental condition, a big sand waves rapidly developed at the outer side in curved channel. The spiral flow occurred behind the wand waves and big scour hole appeared by this spiral flow. Because of this local score, the maximum score depth at the outer side was 1.4 times of the averaged score depth without sand waves condition.In the inner side of the curved channel, the deposition of sand usually occurs. But in this experimental condition, at the downstream region in curved channel, the scour region appeared in the inner side due to the above spiral flow.

Applications of 3d Numerical Model Considering Surface and Seepage Flows in Generalized Curvilinear Coordinate System

“…12 to represent the water levels. According to the simulation results, analogous to the experimental observations 17) at the 30°, 40°, and 50° cross sections, fully developed secondary currents near the outer bank are confirmed in the upstream region of the scouring area around the 55° cross section. On the other hand, the agreement of velocity distributions at the 60° cross section is not deemed satisfactory.…”

“…11 shows the comparisons of water surface profiles and vertical velocity distributions in the streamwise direction. Based on the simulation results, the overall reproduction of streamwise velocity distributions exhibits favorable agreements with the experimental observations 17) . Notably, the nearly stagnant flow patterns observed at the inner bank of the 50°, 60°, and 70° sections, where the flow separation takes place, are reproduced in the numerical simulation.…”

“…Moreover, the Fig. 9 perimental riverbed fomation 17) Fig. low velocity magnitude at the bottom region of the outer bank surpasses that of the experimental measurements.…”

“…10 presents the contour plot of depth-averaged velocity and streamlines around the channel bend. In the experimental study 17) , a separation zone is observed around the 40° section at the inner bank, with the mainstream converging towards the outer bank around the 50° to 55° section, where maximum scouring takes place. The flow diverges gradually towards the inner bank downstream of the 55° section.…”

“…Subsequently, the model is employed to simulate the flows in a curved open channel over a deformed riverbed, aiming to assess the accuracy of reproducing the flow fields, including the complicated velocity of streamwise and secondary flows and water surface profile. Hinokidani et al 17) conducted experiments to investigate bed variations in a curved channel. The experimental channel used in their study has a length of 684 cm and a width of 20 cm, featuring a rectangular cross section.…”