Once node generation is complete or partially complete, the nodes can be meshed to form triangles (triangulation algorithm using the advancing front technique).

If the global mesh generator is used, triangles are generated starting from the outer contour boundary (according to the best possible angle criteria) until all nodes inside the contour boundary are meshed.

When generating elements locally within a defined region, it is possible to specify the outer generation boundary directly by capturing nodes instead of the outer contour boundary (which does not have to be present for this). Starting from this boundary, triangles are then generated (according to the best possible angle criteria) until all nodes inside the polygon defined in this way are meshed.

The triangulation algorithm automatically takes into account the defined contour sections within the generation polygon when meshing: The element edges must not intersect existing contour lines.

 

Prerequisites for the use of triangulation algorithms:

• All start, end and division contour points of contour lines must be mesh nodes,

• Mesh nodes must not lie on contour lines if they are not division points of the contour lines,

• Contours are optimised,

• There are no duplicate nodes (two or more nodes with the same coordinates).

 

If the contour generation is completed by optimisation before the mesh nodes are generated, the boundary and node grid algorithms provided by SPRING deliver nodes that meet the triangulation requirements. Errors in the triangulation algorithm are caused, for example, by:

• Hand-picked nodes (double nodes, nodes on contours that are not contour points ...),

• Subsequently inserted contours (contour points without nodes, non-optimised contours, ...)

• Moving nodes (double nodes, contour points without nodes.

 

These errors can be recognised or partially rectified by the following operations:

• Optimise the contours

• Boundary node generator with 0 steps (nodes are generated on contour points)

• Checking the node spacing (Mesh Checks…)

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If triangles and quadrilaterals are permitted when creating elements, the triangulation algorithm always creates triangles first. Suitable adjacent triangles are then combined to form quadrilaterals in order to reduce the number of elements, and thus the computing and storage resources required later..

 

Unbending the mesh