Study of pollutant transport in open channels with storage zones

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Study of pollutant transport in open channels with storage zones

 

Author: Lam, Tat-shing
Title: Study of pollutant transport in open channels with storage zones
Degree: M.Sc.
Year: 1997
Subject: Water -- Pollution
Pollutants -- Transportation
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: [4], 58, [29] leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1250480
URI: http://theses.lib.polyu.edu.hk/handle/200/746
Abstract: To study the complex nature of mixing process in natural channels, a developed computer program was modified and applied in this work. In natural stream, variation in bank geometry dominant channel features, play their strongest role in affecting mixing characteristics of pollutant transportation. Such variation in bank geometry can be simulated by a sequence of pool and riffle structure in the proposed model. A quasi-three-dimensional numerical scheme is adopted to analyze the mixing process. The numerical model is governed by the mass balance equations and momentum equations which are split into three parts in the finite difference solution : advection, dispersion and propagation, for analysis. After studying different cases of channel geometry, roughness and flow velocity, and by comparing the computer and laboratory experimental results, it is noted that the concentration-time curves are significantly skewed with long tails which is different from the conventional one-dimensional Fickian type dispersion analysis. The skew of long tail is known to be caused by the effect of recircular flow at the storage area of the bank and such phenomenon is called "storage effect". In addition, the mass exchange characteristic between the flow zone and storage zone is studied and the mass exchange coefficient is related to the storage configuration and roughness. The proposed model shows significantly improvement over the convention one-dimensional dispersion model in predicting natural mixing process in open channels under low flow condition. It will assist the future water pollution control of natural steam and water resource management programmes.

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