缓变弯道河道冲刷试验研究

Experimental study on scouring in curved open channel bend with transition curves

有关弯道水流及其河道演变特性的研究一直为人们所关注。本文引入了在直线段和单一曲率圆弯道间插入曲率渐变的过渡段这一新的弯道型式,舒缓水流冲击力和离心力作用,以减轻水流对河床及堤身、堤脚的冲蚀破坏。作者首先对这一弯道和圆弯道的水流流速、副流强度进行了数值模拟的计算和比较;又通过变换床沙、流量及放水时间,进行了24组合的动床试验;最后,通过整理分析所有实验数据,对插有缓变曲线的弯道的减蚀作用进行了探讨。结果表明:插有缓变曲线的弯道可以减轻水流对两岸堤身和堤脚的冲蚀破坏;在弯道同一横断上的最大冲深与沙洲波高的比值最终稳定在0.58。

Researches relevant to the characteristics of water flow and river-bed variation in a river bend has been of much importance in river evolution by now. In this study, with the help of transition curve often used in the design of transportation routine, the authors design a experiment flume by inserting transition curve between a straight flume and a circle curve flume in order to decrease the impact force of the current and to prevent scour along the river bed, dike and the feet of dike. In this paper, firstly, the flow velocity and intensity of the secondary flow in the river bend and the semi-circle bend are simulated and analyzed. Secondly, 24 runs of movable bed experiments for different bend types and bed material, different discharge and flow time are carried out respectively. Finally, according to the comparison of the data obtained from 24 runs experiments, the effect of reducing erosion of the flume with transition curve are investigated. As the results： The transition curve flume has a better effect in decreasing the socur of the current along the river bed, dike and the feet of dike than the circle bend ; from the entrance to exit of the river bend, the ratio of the biggest scour depth to bars height at same cross section varies gradually from 0.75 to 0.58.