中文摘要：

针对自然界特定且时常遇到的分汊型河道,建立物理模型试验系统,以氯化钠溶液为示踪剂,进行密度大于环境水体的污染物在分汊河道中输移扩散机理的试验研究。首先测量了不同横向位置点源排放下污染物的输移过程。试验结果表明不同的上游流量、支汊宽度比和排放位置对污染物的断面浓度分布有显著影响。当上游流量由大变小时,分汊口前主河道中污染浓度发生分叉现象,对于河道中心排放条件下,污染云团在断面中心处由单一高浓度核心区分裂为两个高浓度区;在左侧岸边排放下,大流量时只存在单一的高浓度核心区,并沿着左侧边壁运动,而小流量时浓度分叉后左侧高浓度区在边壁的反射作用下与右侧的合并,偏离左岸向河道中心输移。然后计算了不同工况下污染物进入支汊的分污比,分析表明中心排放下支汊分污比与支汊宽度比、分流比呈正相关,与上游来流呈负相关;岸边排放时支汊分污比与分流比、支汊宽度比和上游来流量均呈正相关。最后,建立了不同排放位置下污染物分污比与上游来流量、分流比的函数关系式,为掌握污染物在分汊河道中的输移特性提供了科学依据。

英文摘要：

A physical model experiment system was set up for the braided river,a typical river pattern in the nature.The transport mechanism of the denser pollutant in this river was experimentally studied.The tracer was sodium chloride solution.First,the transport process pollutant released at different transverse places of the main channel was measured.The results showed that the concentration distributions were obviously affected by the inflow rate of the river,width ratio of two anabranches and releasing location.When the inflow rate changed from large to small,a concentration bifurcation phenomena occurred in the main channel.For centerline release,the number of high concentration zones changed from one to two.For left bank release,only a single core occurred and moved along the left bank if the inflow rate is large.However,under a small flowrate,the left concentration core was reflected by the left bank and emerged into the right one.The combined cloud drifted off the left bank and moved to the center of the channel.Secondly,the pollutant transport flux ratio of two anabranches was calculated and analyzed.For centerline release,the pollutant transport flux ratio was correlated positively with the width ratio and diversion ratio,and had reverse correlation with the inflow rate.For left bank release,three factors were all positively associated with the pollutant transport flux ratio.Finally,the relationships between the pollutant transport flux ratio,flowrate and diversion ratio were established for different release locations,which provides scientific basis for the transport mechanism in the braided rivers.