環流傳輸係數對彎道汙染質側向傳輸之影響分析

Abstract

本研究分別採用擬似三維與水深平均二維模式進行彎道汙染傳輸模擬，探討環流傳輸效應對側向傳輸的影響，其中擬似三維模式可利用解得的垂向流場與濃度場自動反應環流傳輸效應，水深平均二維模式則採用在梯度定理假設下所推導而得的Fischer等(1979)環流傳輸經驗公式來反應環流傳輸效應。本研究採用不符合梯度定理假設的Almquist and Holley(1985)連續彎汙染傳輸實驗案例進行模擬，分析不同環流傳輸效應模擬結果的差異性。

A quasi-3D model and a two-dimensional depth-averaged model are adapted in this study to analyze the circulatory-transport effect for the contaminant transport in open-channel bends. The quasi-3D model can provide the vertical velocity and contaminant profiles, so that the circulatory-transport effect can be computed automatically from theknown velocity defect. The two-dimensional depth- averaged model adopts Fischer et al. (1979) circulatory-transport formula, which was derived based on the gradient transport assumption, to empirically reflect the circulatory-transport effect. The contaminant transport test in a meandering channel reported by Almquist and Holley (1985), which does not conform to the gradient transport assumption, is adopted herein to evaluate the difference between the models.