Why does the Triangle mesh generator fail on some geometries?
If your geometry contains intersecting lines that form very small angles, triangle can run into problems meshing in the region of the intersection. The same issue can occur if you have a geometry with a line tangent to an arc, because very small angles can occur at the point of tangency. Sometimes, it is sufficient to change the Min Angle parameter in the Problem Definition dialog (reached by the Problem main menu selection in the preprocessor) so that it is a smaller value than the default 30 degrees (e.g. 20 degrees). In other cases, it may be necessary to redraw the geometry to get it to mesh correctly, e.g. put a small radius instead of a sharp corner; put a small gap between a tangent circle and line, etc.
