中文摘要：

采用平面无结构网格和垂向直接分层，建立了强潮河口盐度三维斜压力数学模型。无结构网格使模型能够适应河口复杂的边界，并可以根据需要进行局部加密。Casulli的半隐式法离散模型水位梯度和垂项紊动扩散项，克服了水位梯度和垂项紊动扩散对模型稳定性的影响，Semi-Lagrangian法用于模型对流项的离散，使模型具有“无条件”稳定性。采用水池风生流和盐度异重流算例检验了模型，并应用模型模拟了强潮河口（瓯江口）的潮流盐度运动，计算和实测结果进行比较，表明该模型是准确、可靠的。

英文摘要：

One three-dimensional baroclinie flow model is presented for the the strong tidal estuary, in which unstructured grids and unstretched z-coordinates are used. Unstructured grids provide a great amount of flexibility for fitting boundaries and for local mesh refinement. The semiimplicated method developed by Casulli is employed for the free-surface and vertical diffusion, thereby removing stability limitations with the surface gravity and vertical diffusion terms. The semi-Lagrangian method is used for the advection, so the model is ＂unconditionally stable＂. The test cases of wind influence flow and lock exchange flow are used for model＇ s verification, then the model is used for simulating the salt transportation of Onjiang estuary. The numerical results are quite agreeable with the observed, which suggests that the numerical algorithm is robust and reliable.