葛洲坝水利枢纽下游近坝段二维水沙数值模拟

2D numerical model for water and sediment near the Gezhouba Project

针对长江中游葛洲坝水利枢纽下游近坝段卵石夹沙河床级配分布宽等特点,应用非均匀悬沙、底沙二维数学模型,考虑底沙的不平衡输移及冲淤过程中床沙的级配调整问题,对计算中的关键环节如卵石夹沙河床水流的有效挟沙能力、非均匀沙起动概率及非均匀沙推移质输沙率的计算提出了处理方法,利用水文、泥沙及河床变形资料对该方法进行了葛洲坝水利枢纽运行后、1998年洪水前后及三峡工程运行后水面线、流速分布及冲淤过程的验证.结果表明,该方法可以应用于三峡工程运行初期河床演变预测研究.

According to the characteristics of the middle reaches of the Yangtze River, a wide-size distribution with a gravel and sand bed near the Gezhouba Project, a 2D mathematical model for nonuniform suspended load and bed load was used for numerical simulation, which takes into account the nonequilibrium transport of bed sediment and the gradation changes during the deposition and erosion process. Models for key factors, such as the effective carrying capacity of gravel and sand bed flow, the nonuniform sediment incipient probability and the uniform bed load transport rate, were also developed. The parameters of the models were calibrated using hydrologic data, sediment and riverbed deformation data and the water surface profile. The distribution of flow velocity and the deposition and erosion processes were verified against field data from different periods, such as the impoundment of the Gezhouba, the flood in 1998 and the initial impoundment of the Three Gorges Project （TGP）. Results indicate that the model is applicable to the prediction of the fluvial process during the initial impoundment of TGP.