質點法應用於感潮河川污染物傳輸之模擬

SIMULATION OF CONTAMINANT TRANSPORT IN TIDAL RIVERS USING PARTICLE METHODS

林孟郁(Meng-Yu Lin) ； 林彥廷(Yan-Ting Lin) ； 王安培(An-Pei Wang)

《中國土木水利工程學刊》 28卷1期 (2016/03) Pp. 67-76

https://doi.org/10.6652/JoCICHE.201603_28(1).0007

摘要

本研究應用Lagrangian質點法模擬感潮河川污染物之二維傳輸現象，其中擴散／延散作用以質點強度交換法處理。質點法具有無網格且較少數值消散的特性，並可以集中計算資源於汙染物涵蓋的區域。模式建立後以典型的二維濃度擴散問題驗證精確度，包含在單向均勻水流的河川中瞬時注入與持續添加汙染點源，以及具非均勻流速之斜坡海岸的濃度傳輸。驗證成果顯示本模式具良好的準確性。而後模擬兩例不同地形之理想化感潮河川的汙染物傳輸，其潮流速度以解析近似解給定，並忽略河道基流的效應。結果顯示本模式能有效呈現感潮河川中受往返水流驅動之污染物傳輸現象。

關鍵字

質點法 ； 質量傳輸 ； 對流－延散方程式 ； 感潮河川

並列摘要

This study develops a numerical model to simulate two-dimensional mixing in tidal rivers using a Lagrangian particle method with the scheme of particle strength exchange for diffusion term. The major advantage of this model is the essentially grid-free nature of the particle method, which may reduce the numerical dissipation in solving the mass transport equation, and also concentrate the computational resources on the simulation of concentration field. Several benchmark problems of two-dimensional advection-diffusion equation were simulated using this model for validation, such as the impulsive injection and continuous injection of a point source in the uniform flow within a straight channel, and the dispersion on a sloping beach with a non-uniform velocity field. The comparisons between numerical and analytical results show good agreements. To test the capability of the model, two cases of contaminant mixing in a rectangular estuary with simplified geometry caused by a monotonic tidal wave were simulated. The tidal velocity field is given from an analytic solution, and the base flow is ignored. Computational results show that this model is capable of simulating the dispersion of contaminant due to the oscillatory flow in a tidal river.

並列關鍵字

particle method ； mass transport ； advection-dispersion equation ； tidal river