Study On The Generation Method Of Quadrilateral Mesh With Internal Feature Constraints

Finite volume method and finite element method are the most widely used numerical methods. One important step of using these numerical methods is discretization for solving area. That is mesh generation. For two-dimensional flood routing analysis model, computational domain is complex internal with a variety of wading structures, such as roads, railways, dams, buildings, etc. These structures are usually dealt with in the analysis model as internal boundary conditions. When mesh generation, these structures will be treated as feature constraints, so mesh unit side adsorbed on the constraints and mesh unit around the constraints match each other at the constraints. Existing mesh generation technique cannot directly generate mesh in the region internal with feature constraints. Therefore, research automatic quadrilateral mesh generation method internal with feature constraints to meet the special needs of mesh generation for the two-dimensional flood routing analysis model; it has some theoretical significance and application value.This paper presents an algorithm of quadrilateral mesh generation based on Paving method, dealing with internal feature constraints and develops a process of quadrilateral mesh generation dealing with internal feature constraints. It can handle multiple line constraints, point constraints, to meet the requirements of practical engineering models need to deal with internal feature constraints.This paper presents the algorithms of processing feature constraints include line constraints and point constraints. For single line constraint, which is seen as a zero area empty, its discrete nodes form a closed loop, then paving a layer of quadrilateral mesh elements around it. For line constraints intersects forming non-enclosed area, first through the intersection nodes divide line constrains to multiple line constraints, then discrete nodes of each line constraints form a closed loop, and then merge the closed loop to form one or more separate closed loops; For line constraints intersects forming enclosed area, proposes algorithm of automatically determining the boundaries of each sub-region. The discrete nodes form two closed loops as internal loop and external loop. For point constraints, calculate the nearest node on the external loop, the line between the two points as line constraint.Based on the algorithm of quadrilateral mesh generation internal with feature constraints, developed automated quadrilateral mesh generation program, and applied to a two-dimensional flood routing analysis model.