Study of tidal flushing and pollutants transport in two typhoon shelters of Hong Kong using finite element model

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Study of tidal flushing and pollutants transport in two typhoon shelters of Hong Kong using finite element model

 

Author: Ma, Chun-sing
Title: Study of tidal flushing and pollutants transport in two typhoon shelters of Hong Kong using finite element model
Degree: M.Sc.
Year: 1995
Subject: Marine pollution -- China -- Hong Kong
Tides -- China -- Hong Kong
Finite element method
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: 1 v. (various paging) : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1205004
URI: http://theses.lib.polyu.edu.hk/handle/200/1002
Abstract: The tidal flushing and pollutant transport characteristics of Yau Ma Tei and Sam Ka Tsuen typhoon shelters are determined by a developed finite element model, which is based on the numerical solutions of the two-dimensional mass transport and hydrodynamic equations. It is found that the tidal flushing of pollutants is brought about mainly by the tidal exchanges during flood tide and ebb tide. Moreover, it is determined by the types of open boundary condition. The tidal flushing is found mainly at the entrance of each typhoon shelter, and the effect decreases at points farther away from the entrance. Tidal flushing affects the dispersion rate of pollutants in the typhoon shelters. At ebb tide, the pollutants are transported out from the shelters to the open boundary, and hence the amount of pollutants left inside the shelter is then minimized. On the contrary, during flood tide, certain amount of pollutants will be transported back into the shelter through the entrance. The amount of pollutants in the shelter would reach maximum value during this period. For the use of analytical model, concentration of pollutants for both typhoon shelters are found drop to zero value in 8 days. However, for the use of numerical model, pollutants at different position in the shelter are found to have different dispersion pattern. Therefore, the numerical model can be used to reveal a more realistic situation for the typhoon shelters. A single continuous emission source is also included in the study. A plume is found to be continuously developed in the shelter. In addition, decay of pollutants is also considered to simulate the real situation. From this study, we understand the pollution problems of existing typhoon shelters. However, in order to improve its water quality, we suggest that the government should restrict illegal dumping waste to the sea. As a result, we may have a better environment for better living standard.

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