摘要
本文利用一个二维的水动力学和泥沙冲淤动力学模式，对河床演变和三角洲的发育过程进行数值模拟研究。动力模式包括水流方程、悬沙输送方程和底床变化（含推移质运动）方程。数值积分格式采用ＩＡＰ平方守恒格式和分解算法，使计算既省时又长期稳定。对一个理想的河湖区域进行了长达５０年的数值积分。模拟结果肯定了曾庆存等以前得到的主要结论，并得到一些新的结论。研究表明：泥沙首先在河流入口处沉积，并逐渐向下游推进和向河槽两边延伸；随着泥沙的沉积，底床逐渐升高，在河槽中形成了一个沙岛；在沙岛上游，原河槽中沉积的泥沙又被冲刷，重新出现深河道；数值积分５０年后，人口处已形成一个巨大的冲积扇（水下三角洲），并不断向下游扩展，三角洲（包括沙岛）的前缘十分陡峭；由于泥沙的沉积，河床抬升，水深变小，水流速度场在整个堆积扇上明显增大，并在三角洲前缘出现明显的绕岛环流和河流分叉现象。模拟结果还表明，在漫滩区泥沙只淤不冲，而在河槽中既有淤积又有冲刷。此外，由于泥沙的淤积，使得湖型水库的水流入口处（库尾）水位明显抬高（即所谓“翘尾巴”现象）。这些结果在定性上与有关湖泊型水库淤积的观测事实是相当符合的。
A two-dimensional sediment transport model was designed to investigate river bed deformation and delta evolution. The dynamic model includes the water now equations,the suspended sediment transport equation and the bed deformation equation.In the model the IAP finite difference scheme of quadratic conservation and a splitting technique are adopted, thus leading to economical and stable computation for a long time. The results of a fifty-year simulation for a simple river-lake region show that sediment first deposited in the vicinity of the river entry and gradually extended downstream and to both sides of the river channel.The thickness of the deposited sediment gradually increased and a sand bar was formed.In the upper reach of the sand bar,the deposited sediment in the river channel was eroded and a deep channel appeared again.After fifty years,a large alluvial sector(submerged delta)was formed and gradually extended downstream.The fronts of the delta and the sand bar are very sharp.The water depth reduced due to deposition, the water flow velocity upon the alluvial sector increased obviously and at the front of the delta exists currents around the sand bar.In addition, only deposition occurs in the shallow beach areas, whereas in the river channel not only deposition but also erosion occur.All the above results agree fairly well in quality with the observations of sedimentation phenomena of lake-type reservoirs and show that the model is suitable for long-term simulation of river morphological processes.
出处
《气候与环境研究》
CSCD
1996年第1期30-34,36-37,共7页
Climatic and Environmental Research
基金
国家科委攀登计划中国科学院院长基金
关键词
泥沙沉积
三角洲
数值模拟
river sedimentation,delta evolution,computational modeling
