Posted Thu, 20 Dec 2018 14:31:19 GMT by Drake

I have recently been carrying out some excavation modelling and have a relatively simple supermesh.  I understand that vertices might be causing my problems and I'm still exploring those issues.

I have recently tried to mesh using "Triangle" mesh generator.  I am following some guidance documents provided by DHI in a training course offered a couple years back.

-I left the generator running over night and it never finished.
-Generator quickly fills up all 32GB of my RAM
-Clicking on the "stop mesh operation" button does not stop the meshing operation.  Even at the beginning when I still have memory available and my computer is still responsive.
-Advancing front and GridBuilder mesh generators will complete with their default settings.  I haven't experimented with refinement yet.

-What are the advantages of GridBuilder over Triangle (and vice versa)?
-For an open cast excavation scenario, would GridBuilder be suitable?  What would be the potential problems when trying to run the model.  I am using Triangle since that is the method chosen by DHI in the documentation they provided.
-Are there any detailed recomendations on the polygons used for creating supermesh (max / minimum angles, vertices separation, minimum spacing between "nested" or parallel polygon lines, etc.)?

Posted Wed, 16 Jan 2019 06:19:27 GMT by Peter Schätzl
Listing the advantages and disadvantages would lead to a potentially very long list, so I start with a hint on the most likely reason for Triangle failiing. I'd recommend to check your supermesh for vertices that are very close to each other, or lines crossing other lines at small angles, or lines crossing other lines very close to a vertex. You may not visually detect these issues without zooming in close to vertices. In these cases, Triangle tends to infinitely subdivide the borders in order to come up with a valid mesh, and thus fills up the memory without ever reaching its target.
Posted Wed, 16 Jan 2019 17:31:08 GMT by Drake
Thanks again Peter,

I've come to the realization that when I import polygons from QGIS, I'm just better off retracing those polygons inside Feflow.  Makes it a bit laborious since it is easier for me to create nested polygons inside QGIS.  But Im getting used to the Feflow split polygon function. I am a little confused why I normally have to create 3 splits however to get the nesting to work.

So far, this has resulted in a clean triangle operation.

Posted Thu, 17 Jan 2019 06:00:35 GMT by Peter Schätzl
sounds good. I haven't dealt with QGis too much (I mainly use it as a quick visualizer for GIS files), but when using ArcMap, at least some time ago vertices of adjacent polygons were not necessarily at exactly the same location - and sometimes FEFLOW's automatic snapping distance at import wouldn't be enough to merge them. Some process like this would explain the meshing problems. I'm not GIS expert enough to judge what it would take to guarantee identical vertices on the polygons. Does anyone else have an idea?

Best regards,

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