In general, after the automatic merging process is complete, a limited number of triangles will still exist. This ensures that the quadrilaterals which are formed are as close to rectangular as possible. Then, a series of steps are performed, each time lowering the feature angle and checking for elements that can be merged. In order to form quadrilateral elements with the best aspect ratios, SMS starts with a feature angle of ninety degrees and checks for any elements that can be merged. This command uses the Merge triangles feature angle specified in Element Option dialog. If no elements are selected when this command is executed, all triangles in the finite element mesh will be processed. The Merge Triangles command from the Elements menu automatically merges a selected set of triangles simultaneously.

Doing this manually for large numbers of elements takes a lot of time. The Split/Merge tool can be used to merge individual pairs of triangles. These can be merged together using the Split/Merge tool, as shown in the right part of the figure. When the elements are split, triangles are formed. The dotted line in the left part of the figure represents the location of the breakline. This example has some long, skinny quadrilaterals which will be split across the width. All new triangles satisfy the Delauney criterion.Ī breakline example is shown. The elevations of any new nodes are interpolated from the original mesh. When this command is performed, elements are sliced along the nodestring to ensure that the edges will conform to the breakline. This forces element edges along the nodestring line. The Add Breaklines command from the Elements menu can be executed when at least one nodestring has been selected.

Several commands are available to modify the current elements these include:

Surface water modeling system quad9