Abstract: This paper shows a method on the indirect quadrilateral mesh generation based on the triangular mesh.In order to solve the defect of remain triangular elements during combining triangular elements，a detailed algorithm for determining side edges is proposed in this paper.This algorithm determines side edges by the edges contained in the triangular background mesh，swapping or splitting the edges of the background mesh according to the position of edges in background mesh and the situation of front edges.This algorithm can avoid the residues of triangular elements.Finally，a grid example is presented to illustrate the validity of this algorithm.

Key words: quadrilateral mesh, combination of triangular elements, front edge

摘要： 研究了基于背景三角网格的四边形网格间接生成算法，并针对三角形合并过程中容易残留三角形的缺陷提出了确定侧边的详细算法，该算法主要是依据背景三角网格中边的位置和前沿边的情形，通过背景三角网格中已存在的边、边交换或边分割确定侧边，以避免在三角形合并过程中残留三角形单元。最后给出实例验证了算法的有效性。

关键词: 四边形网格, 三角形合并, 前沿边