Numerical Modelling of Water Quality Environment in Coastal and Estuarine Waters

本研究的目的是开发多功能、可靠的数值模型，用于预测沿海和河口水域的水质，这些水质严重依赖于盐度和/或水温差异造成的斜压效应。这种水域的水流特征分为三种；一维均匀混合流，垂直二维分层流，三维分层流（其中包括水平二维均匀混合流）。通过将变密度场中随时间变化的空间分布流与水质动态耦合，建立了各类别的模型。本研究取得了丰硕的成果，总结如下：1。采用有限元方法，针对不同类别建立了适用于变密度场的高通用性流动模型，并对其数值特性（稳定性、精度（主要通过钻机试验）和求解效率）进行了研究。对于更多的一维和三维问题，基于描述水质物质变化的对流-色散方程建立了有限元水质模型。通过将水质模型与流量模型耦合，建立了比传统箱形模型精细得多的水质预测模型。对于垂直二维问题，表明该流动模型能够用于研究浮游生物的垂直运动、停滞和浓度，从而有助于理解赤潮的产生机制。为了进一步研究，建立了生物系统的初步模拟模型，并对其基本数值特性进行了测试。提出了河流水质控制模型，并对其有效性进行了验证。作为后续研究，有必要进一步研究所建立模型的解的可重复性，并讨论所涉及的未知参数的估计和识别方法。少

The purpose of this study is to develop versatile, reliable numerical models for perdicting water quality in coastal and estuarine waters that depends heavily on baroclinic effects due to difference in salinity and/or water temperature. The flow in such waters is charactreristically categorized into three ; one-dimensional well-mixed flow, vertically two-dimensional stratified flow, three-dimensional stratified flow (in which horizontally two-dimensional well-mixed flow is included). The model for each category is built by coupling time-dependent spatially distributed flow in variable density field with water quality dynamics. The fruitful results obtained through this study are summarized as follows.1.Flow models of high versatility, applicable to variable density field, were newly developed for the respective categories by employing the finite element method, and their numerical properties (stability, accuracy (mainly by rig-testing) and solution efficiency) were investigated.2.For o … More ne-dimensional and three-dimensional problems, finite element water quality models were developed based on the convection-dispersion equation that describes variation of the water quality substances. By coupling the water quality model with the flow model, water quality prediction models, far refined than the conventional box models, were built.3.For vertically two-dimensional problem, it was shown that the flow model was capable of being used for investigating vertical movement, stagnation and concentration of plankton, and therefore useful for understanding the mechanics of red-tide generation.4.For future perspective of the study, a primary simulation model for biological system was developed and its basic numerical properties were tested. In addition, a water quality control model for rivers was proposed and its validity was demonstrated.As the follow-up study, it is necessary to further investigate solution reproducibility of the models developed, and to discuss the methodology for estimation and identification of the unknown parameters involved. Less