Numerical Study of Tidal Effects on Seawater Intrusion in Confined and Unconfined Aquifers by Time-Independent Finite-Difference Method
Numerical Study of Tidal Effects on Seawater Intrusion in Confined and Unconfined Aquifers by Time-Independent Finite-Difference Method
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DOI：
10.1061/(asce)0733-950x(2004)130:4(191
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发表时间：
2004-07
期刊：
影响因子：
--
通讯作者：
Bang Chen;S. Hsu
中科院分区：
文献类型：
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作者：
Bang Chen;S. Hsu
本研究提出了一种二维与时间无关的有限差分模型，用于模拟潮汐对承压含水层或潜水层中海水入侵的影响。该模型考虑倾斜的海滩面。将不规则的海滩面和变化的地下水面映射到方形域，并通过适当的坐标变换消除移动边界的时间依赖性。因此，将控制方程的有限差分表达式写在与时间无关的网格系统中，并建立与时间无关的有限差分格式。传统亨利问题和改进亨利问题的报告结果证实了该数值技术。理想化的海水入侵（称为亨利问题）被扩展到模拟倾斜海滩表面的海水入侵，以解释潮汐效应。潮汐效应增强了海水的迁移。承压含水层的主要特征是海水在涨潮时侵入内陆。咸水继续侵入内陆，并在退潮时到达最上游的位置。在无承压含水层中，潮汐波动仅引起垂直方向的侵入剖面的变化。地下水位的波动随着潮汐的波动而波动，但存在一定的滞后性，但潮汐的影响随着距海滩的水平距离而减弱。海水侵入距离的变化也随潮汐振荡，时滞恒定为0.25T，其中T为潮汐周期。含水层的形状也影响盐水的入侵和入侵的速度。海水入侵的速率和海水入侵的距离随着岸坡的增加而增加。
This study presents a two-dimensional time-independent finite difference model to simulate tidal effects on the intrusion of seawater in either a confined or phreatic aquifer. The model considers a sloped beach face. The irregular beach face and varying ground water surface are mapped to a square domain and the time dependence of the moving boundary is removed by an appropriate coordinate transformation. The finite-difference expression of the governing equations is, therefore, written in a time-independent mesh system, and a time-independent finite difference scheme is established. The numerical technique is confirmed by the reported results of the traditional Henry's and modified Henry's problems. Idealized saltwater intrusion, known as Henry's problem, was extended to simulate seawater intrusion on sloped beach faces accounting for tidal effects. Tidal effects enhance the migration of seawater. The dominant feature of a confined aquifer is that seawater intrudes inland during the flood tide. The saltwater continues to intrude further inland and reaches its furthest upstream position at ebb tide. In an unconfined aquifer, the tidal fluctuation causes the variation of the intrusion profile in the vertical direction only. The fluctuation of the water table oscillates according with the fluctuating tide with a time lag, but the influence of the tide is damped out with horizontal distance from the beach. The variation of the distance through which the seawater intrudes also oscillates with the tide, with a constant time lag of 0.25T, where T is the tidal period. The shape of the aquifer also affects the intrusion of saltwater and the velocity of intrusion. The rate of seawater intrusion and the distance through which the seawater intrudes increases with the slope of the bank.