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基于镇扬江段河势变化剧烈、感潮特性明显、水沙运动复杂的特征,建立了二维非稳态水流、水质及泥沙耦合数学模型,在有限体积法框架下应用通量差分裂(FDS)格式计算模型中各跨单元边界的数值通量,基于实测数据对模型进行了率定验证.运用所建模型对洪季、枯季镇扬江段水沙过程进行数值仿真,结果表明:(1)镇扬江段汛期流速约为0.72—1.98m/s,枯水期流速约为0.33—1.24m/s,汛期平均流速约比枯水期增加了40.6%;(2)汛期水动力条件较好,沿河排污口最大污染带长度约1550m,枯水期总污染带长度约2800m,比汛期增加了46.2%;(3)汛期镇扬江段平均含沙量为0.12—0.20kg/m3,枯水期平均含沙量为0.07—0.11kg/m3,汛期含沙量较枯水期增加了40%;汛期,泥沙浓度从上游至下游沿河长方向基本呈现递减趋势;枯水期,由于径流、潮流双重作用明显,泥沙浓度沿程变化较小.
Based on the characteristics of drastic change of river regime, obvious tidal characteristics and complicated water and sediment movement in Zhenjiang section, a two-dimensional mathematical model of unsteady flow, water quality and sediment coupling was established. In the framework of finite volume method, (FDS) was used to calculate the numerical fluxes of each cross-unit boundary in the model, and the model was validated by the measured data.The numerical simulation of runoff and sediment transport in the Yangjiang section of Hongji and Qunjiizhen by using the model showed that : (1) The flow velocity in flood season in Zhenyang section is about 0.72-1.98m / s, the flow rate in dry season is about 0.33-1.24m / s, the average flow velocity in flood season is about 40.6% more than that in dry season; (2) The hydrodynamic conditions in flood season are better , The length of the largest pollution belt along the river outfall was about 1550m, the total pollution belt length in the dry season was about 2800m, an increase of 46.2% over the flood season; (3) The average sediment concentration in the Zhenyang section during the flood season was 0.12-0.20kg / m3, Sediment concentration in the flood season increased by 40% compared with that in the dry season. During the flood season, the sediment concentration tended to decrease along the river from the upstream to the downstream. In the dry season, due to the double effect of runoff and tidal flow, the mud Sand concentration changes along the smaller.