长江河口波-流共同作用下的全沙数值模拟

Numerical simulation of total sediment under waves and currents in the Changjiang Estuary

针对长江河口地形、水文、泥沙运动等复杂的特点,建立了波-流共同作用下的二维全沙及河床演变模型.在合理计算研究区域流场等的基础上,利用切应力概念确定悬沙扩散方程中的源函数;通过系列数值试验和实测资料的统计分析,在经典的泥沙临界起动速度中引入反映河床底质结构及固结程度的局地系数;选用由流速、盐度、含沙量浓度确定的泥沙颗粒絮凝沉降速度,从而提高长江口悬沙场数值模拟精度.在底沙输运计算中,提出一种较为合理确定有关参数的方法.通过洪、枯季大、中、小潮水文、泥沙资料和典型台风引起航槽冲淤变化的实测资料验证,表明该文提出的模型能较合理地反映长江河口流场、泥沙场及地形的演变.

According to the characteristics of the complicate bathymetry, hydrology and sediment movement in the Changjiang Estuary, a two-dimensional numerical model for total sediment transport and sedbed evolution under waves and currents are developed. Based on the rational calculation of currents in the study area, the method of shear stress is adopted to determine the source function in the suspended sediment diffusion equation. Through a series of the numerical experiments and the statistical analyses of the observed field data, a local coefficient, which can reflect the bottom material and consolidation, is introduced into the classic critical erosion velocity of the sediment. The floc settling velocity of sediment particles is taken as the function of current velocity, salinity and suspended sediment concentration, which can improve the calculation precision of the suspended sediment numerical simulation in the Changjiang Estuary. In the computation of bed-load sediment transport, a rational method for determining the related parameters is developed. The verification of hydrology and sediment data shows that the model can preferably reflect the current field, sediment field and bathymetry evaluation in the Changjiang Estuary.