Hi Folks,
I found there were bugs in the ElemCutter class in LibMesh. When I run the
example under /subdomains/ex3/, It works fine when the refinement times
below 4, but error comes out when this value is set 5 or above
**---------------------------------------------------------------------------------------------------------
adding cut point (d_star, x_star) = 0.610641 , (x,y,z)=(0.610641, 0,
0)
Inside cut face element!
Error: Input must have at least three input vertices.
**---------------------------------------------------------------------------------------------------------
As another case, even the refinement value is still remains 4, if I changed
the radius from 0.5 to 0.4, it gives rise the same error.
Finally, I checked the source codes and found that it may come from the use
of endpoint_tol in the member function find_intersection_points().
I have two way to fix it. One is just simply remove this tol or use smaller
tol, which works temporarily, but it will generate problems when devising
xfem. The other is to use uniform tol in all the member functions, for
example is_inside(), is_outside(), is_cut(), in addition, this tol must be
set a value dependent of the element size. This is probably more
reasonable. At least it runs well up to now in my codes. I can share it if
it is needed :)
In addition, I personally think this ElemCutter can be further improved if
the element order can be considered. For example, for QUAD9 element, if
only one node at the middle of an edge in the "-" side of the interface,
the others are on the "+" side, then this algorithm cannot find it. In
other words, it is only first order accuracy! One solution is to first
divide the higher order element into subelement according to their nodes,
then do the subtriangulation in each of them.
Xujun
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