Method of determining grid sizes of finite element method of water quality models for geometrically complex river course  

作　　者：Yang Chunping Zhong Yuanyuan Zeng Guangming 

机构地区：[1]Hunan Univ, Dept Environm Engn, Changsha 410082, Peoples R China

出　　处：《Chinese Science Bulletin》1998年第4期345-348,共4页

基　　金：ThisworkwassupportedbytheScienceandTechnologyFoundationfromtheEducationalDepartmentoftheMinistryofMachineryIndustryofChina (GrantNo .95 2 5 1313) .

摘　　要：The method of determining grid sizes of finite element method of water quality models is presented on the basis of characteristics of pollutant distributed in the just downstream grid of discharge. A given length of the grid is applied to calculate the minimum distance for the pollutant to complete mixing in the lateral direction in the just downstream grid of the discharge, and the minimum distance is regarded as the maximum width of the grid. Application of the maximum width of the grid and flow rate per unit width of the river results in the number of flow zones in the lateral direction of the river. Consequently division of grids and numerical calculation of water quality with finite element method can be carried out on the basis of available method and topographic map of the river course. Analysis of sensitivity shows that the effect of the width of the river and the effect of the length of the grids on the minimum number of flow zones in the lateral direction is relatively small, and that the effect of the given lateral mixing degree of the pollutants on the minimum number of flow zones is acceptable, which indicates that the method presented is relatively stable. The method can avoid the blindness and randomness in determining the number of flow zones, and can decrease the amount of computation under the condition that the accuracy requirement is met. The problem that determining the sizes of the grids must rely on empirical knowledge has been solved.The method of determining grid sizes of finite element method of water quality models is presented on the basis of characteristics of pollutant distributed in the just downstream grid of discharge. A given length of the grid is applied to calculate the minimum distance for the pollutant to complete mixing in the lateral direction n the just downstream grid of the discharge, and the minimum distance is regarded as the maximum width of the grid. Application of the maximum width of the grid and flow rate per unit width of the river results in the number of flow zones in the lateral direction of the river. Consequently division of grids and numerical calculation of water quality with finite clement method can be carried out on the basis of available method and topographic map of the river course. Analysis of scnsitivity shows that the effect of the width of the river and the effect of the length of the grids on the minimum number of flow zones in the lateral direction is relatively small, and that the effect of the given lateral mixing degree of the pollutants on the minimum number of flow zones is acceptable, which indicates that the method presented is relatively stable. The method can avoid thc blindness and randomness in determining the number of flow zones, and can decrease the amount of computation under the condition that the accuracy requirement is mct. The problem that determining the sizes of the grids must rely on empirical knowledge has bcen solved.

关 键 词：RIVER water quality model FINITE ELEMENT METHOD numerical calculation grid. 

分 类 号：X11[环境科学与工程—环境科学]