Posted Thu, 02 Apr 2015 15:13:52 GMT by Nate Toll Sr. Scientist
Hello Everyone,

I am having trouble with the triangle meshing routine.  I have imported shape files for a model domain polygon and lines representing streams.  I can mesh the model domain fine, but when I convert the stream shapefile into superelement lines and run the meshing routine I get the error "Invalid Topology in Element xxx" 

I haven't been able to locate anything useful to indicate what this error message is telling me about my stream geometry.  I have been successful drastically reducing the complexity of the stream geometry, but I'm hoping someone has some other ideas what this error means. 

Regards, Nate
Posted Fri, 15 May 2015 00:32:31 GMT by
Probably a problem with the shape file you are using to specify super-elements

Posted Wed, 27 May 2015 09:38:37 GMT by Björn Kaiser
An invalid mesh topology may be attributed to geometrical characteristics in the supermesh, which may inhibit the generation of a mesh consistent for the FEM.

Obviously, the line in your supermesh causes the problem. Indeed, problems can arise as a results of lines containing sharp kinks or lines which confluence at sharp angles.

Moreover, inconsistencies in geometrical topologies of the input shapefile may also cause the problem as Pete already indicated. Therefore, you may check the shapefile according to possible overlapping lines. You may also check if one large line is represented by several line segments (e.g. several line features). In that case, please assure the last vertex of one line spatially converges with the first vertex of the subsequent line. Small spatial deviations in the magnitude of several orders after the decimal operator between the last vertex of one line segment and the vertex of the subsequent line segment may trigger invalid topologies in the FE-mesh.

Apart from the input data, the mesh generators provided by FEFLOW have advantages and disadvantages with respect to robustness and capabilities of handling complex geometrical structures. Accordingly, it is worth to try another mesh generator.

Instead of using a line in the supermesh you could also split the polygon into two sub-polygons along the trace of the line enabling the application of the Advancing Front mesh generator which originally does not consider lines in the supermesh.
Posted Mon, 13 Jul 2015 19:56:09 GMT by Nate Toll Sr. Scientist
Thanks for the replies.  Is there anyway to determine from the element number in the error where the problem in the line geometry may be?  I have located the errors, but it can be tedious. 

For others who stumble of this post: Intersections of polylines and complex geometries are a good place to check.  While tedious I have found that creating supermesh lines in feflow has better results than converting shapefiles for complex geometries. 

Posted Tue, 14 Jul 2015 15:35:42 GMT by
I haven't yet found a more efficient way other than close and careful inspection of the supermesh, and I agree, using feflow to do the supermesh is the most efficient editing method.


You must be signed in to post in this forum.