蜿蜒河道水理及污染傳輸之模擬研究

Abstract

水流流經彎道，其水理現象與污染傳輸行為較之直線渠道來得複雜，本研究將沿用謝氏(1992)發展之深度平均二維淺水波模式並加入污染質傳輸子模式，探討彎道中水理與污染質傳輸的問題。而由模擬結果中，可將：1.延散剪應力效應對水理現象2.環流傳輸效應對污染質傳輸3.二次流整體效應對污染質傳輸的影響程度加以分區，區分為I.二次流強度太小--影響程度可忽略II.彎道長度太短--影響程度亦可忽略III.其影響程度不可忽略共三區。另外，於模擬不適用梯度定理之污染傳輸案例時，以Chang(1971)於實驗中量測到之側向污染傳輸係數為基準，再考慮曲率半徑的影響，提出一連續彎污染傳輸係數之修正方法，並獲得良好的模擬結果。

The flow phenomena and behaviors of contaminant transport are more complicated in curved channel than it in straight channel. In this paper, the depth-averaged 2-D shallow water flow model, developed by Hsieh (1992), was used to study the issues of flow and contaminant transport in curved channel. Base on the analysis of bend effect for dispersion stresses in flow simulation and for circulatory transport in contaminant simulation, the influence of bend effect can be distinguished into three types. 1.Secondary intensity is too weak to induce significant influence. 2.Bend length is too short to cause significant influence. 3.Bend effect causes significant influence. Based on Chan7g’s (1971) experimental data, the lateral transport coefficient in the cases of inadequacy of the gradient theorem for contaminant transport was modified by considered the influence of curvature. And the simulated results from the modified model are satisfactory compared with the measured data.