长江下游及河口区水动力特征

基于EFDC模型，构建长江下游及河口区二维水动力模型，对河流和河口区进行整体模拟，研究长江下游及河口区水动力特征.模型在空间上采用变尺度、拟合边界的矩形网格，在时间上采用动态时间步长，在模拟过程中自动识别干湿网格，更好地保证模拟精度与效率.利用1998年冬季以及2005年夏季和秋季实测资料，对粗糙高度等敏感参数进行参数率定和验证.结果表明，模拟的潮位和流速与实测成果拟合较好，较好地反映了各水期长江下游及河口区的水动力要素的空间分布特征.应用模型模拟2004-2007年不同水期的水动力过程，并对模拟结果进行统计分析.研究显示:从空间来看，河道、河口流态存在显著差异，涨、落潮流场空间分布差异大；受径流和潮差的相互作用，潮流界在河口以上150~450 km之间变动，径流量和潮流界位置具有对数相关关系.从时间来看，径流量丰平枯变化大，对潮流量和径流入海时间都有一定的影响，潮流量、径流入海时间与径流量之间也存在明显的定量关系. 

Hydrodynamics in the Lower Reaches of the Yangtze River and Its Estuary

Abstract:Based on the EFDC model,a two-dimensional hydrodynamic model for the lower reaches of the Yangtze River and the estuary area was constructed.In this model,mutative scale and fitting border rectangular grids were used for space fitting.Dynamic time step and automatic identification of wet and dry grids during the simulation were applied to ensure the simulation accuracy and efficiency.The modeled results matched well with the monitored data including water level and flow direction in 1998 and 2005,and the model was verified to reflect the hydrodynamic characteristics of the research area.The model was used to simulate the hydrodynamics in different water periods from 2004-2007,and results showed that flow state in the reaches and estuary were significantly different,and the water path and tidal flows had large differences in space during periods of the flood and ebb tides.Due to the interactions between runoff and tide range,the tide boundary changed from 150 to 450 km from estuary to upstream of the river,and had a logarithmic relationship between tide boundary distance and runoff amount.The runoff varied largely among different floodings,dry and normal season,and played a significant role in total flow into sea and transport time,and the different quantitative relationships were created.