大江河口三维非线性斜压水流盐度数学模型

A 3-D nonlinear numerical model with inclined pressure in large estuaries

本文建立了河口三维非线性斜压水流盐度数学模型。该模型通过。坐标变换，使整个水域垂直方向可采用相同的分层。基于过程分裂法，将三维流动分成表面重力波（外模式）和内重力波（肉模式）。外模式采用改进型双步全隐有限差分DSI法进行计算，内模式利用欧拉-拉格朗日公式，改进三维垂直方向隐式格式，减小了数值耗数，提高了计算精度及稳定性。该模型应用于长江口三维盐水入侵计算，结果表明水流盐度分布与实测一致。

A 3-D numerical model with inclined pressuare is developed to compute saltwater intrusion in large estuaries. Adopting the a-coordinate transformation in the control equation,the same grids in vertical coordinate direction are used to the local topograph. The model uses mode-splitting method for surface gravity waves (external mode) and internal gravity waves(internal mode). The external mode is sloved by the improved double-sweepimplicit finite difference method. The internal mode utilizes the Eulerian-Lagrangian method,improves the implicit-difference scheme for the vertical direction,and reduces numerical diffusion. The model raises the calculative accuracy and stability. The model has been tested by computing the saltwater intrusion in Changjiang estuary and the results shows the current and Salinity time-space distribution of computation is in agreement with the measured data.