| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系碩士班 === 93 === The objective of this study is to develop a linearized analytical model and solve the diffusion problems of pollutants.
The water quality model includes unsteady discharge equations and continuity equation of concentration. Because the De Saint Venant equations which contain the continuity and momentum equations, and the continuity equation of contraction are nonlinear partial differential equations, it is difficult to obtain the exact solution. In this study, a linearized analytical technique is provided, not only apply to the scheme of the nonlinear differential equations, and also apply to the coefficients of the diffusion terms of the water quality model.
The linearized analytical method has been used in solving regular rectangular cross sections of open channel successfully. Because the circular cross section of the open channel is more complicated than other rectangular or wide rectangular cross sections, the methods used before of obtaining coefficients of the diffusion equations of discharges and concentrations are using Taylor Series expansion which exist the infinite terms of the series. Therefore, it is impossible to obtain accurate solutions. In this study, an unsteady water quality model of open channel with circular cross section is proposed. By using the linearized analytical method to modify the coefficients of the diffusion equations of and concentration, the good results are obtained.
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