雨水管道沉积物冲刷特性

Analysis of scouring features of sedimental left-over elements in rainwater pipes

通过试验模拟雨水管道内沉积物的冲刷过程,探索不同水力、沉积物条件下雨水管道内的冲刷规律,结合数学模型拟合,计算特定条件下管道内沉积物的冲刷率和冲刷通量。结果表明,不同条件对管道内沉积物冲刷过程有较大影响,管道内较大的流量、坡度下,水流动能大,冲刷能力强,会带来较高的冲刷通量;而较小的粒径表层易剥离,以悬浮的形式被水流冲刷带走,因此在冲刷的前15 s表现出更高的冲刷通量;沉积厚度较大时,管道末端出水悬浮颗粒物质量浓度较高,也易形成较大的冲刷通量。经过构建数学模型,计算出了特定条件下雨水管道沉积物的冲刷率和冲刷通量。

The paper is inclined to present an analysis of the scouring features of the sedimental left-over elements in the rainwater pipe scouring process of the sediment in such pipes through a simulation research.For the above said research purpose,we have proposed the calculation method of the macroscopic parameters of the scouring process in accordance with the mathematical models and calculated the scouring rate and flux of the sediment.The results of the calculation show that different conditions can have a great effect on the scouring process in the pipe.The actual situation should be that:the higher the flow or the slope has,the greater energy of the water current may produce and in turn stronger capability and higher scouring flux the scouring may be endowed with.For example,in the first 15 s of the scouring,a larger slope can result in a larger scouring flux.However,15 seconds later,the reverse would be true.Analyzing the trend of the scouring rate can let us know that,if the flow rate or the slope degree is large enough or the scouring time is long enough,it would be possible for the scouring rate to reach 100%.On the other hand,smaller particles can be easily peeled off and scoured away by the water flow in the form of suspension.Its starting process can just demand a little shear stress,which implies a higher scouring flux in the first 15 s of the scouring.However,when the sedimentary thickness is greater,the concentration of the suspended particles in the effluent of the pipe should be higher,which also tends to result in a greater scouring flux.Under the different conditions,the difference in the concentration of the suspended particles in the effluent can mainly appear in the initial 30 s of the scouring,with the concentration being closer 120 s later.Hence,the scouring flux under different conditions can help us to deduce the following regulation:that is,it tends to decrease exponentially with the time lasting,and eventually tends to become horizontal.But,in the initial 30 s of the process,the scouring flux tends to decrease most significantly.Therefore,it would be possible for the scouring rate and the flux of the sediment to be calculated and worked out in the rainwater pipe under certain condition by using the mathematical models of the scouring process.