Dear Yves,
Thanks a lot for your help. I think the fact that assigning the
integration method by only providing the degree of interpolation is very
useful. That solved my problem now.
Thank you also for your remark about using macro for models. It's really
helpful.
Best regards,
Phuoc
On 18/06/2018 17:32, Yves Renard wrote:
Dear Phuoc,
The main reason is that you use a Newton-Cotes integration methods on
the prism. The Newton-Cotes integration method has Gauss points on the
geometrical nodes which is not convenient at all for the pyramid. You
can use instead
mim = gf.MeshIm(m, 3)
which will select an integration of order at least 3 on each element.
Just an additional remark. You can use the macro system which can give
clearer expressions. For instance
sig_u = "(lambda_para*Trace(Grad_u)*Id(qdim(u)) + mu_para*(Grad_u +
Grad_u'))"
stress_jump_inner = "{sig_u} .... ".format(sig_u=sig_u)
can also be entered has
md.add_macro('sig_u', "(lambda_para*Trace(Grad_u)*Id(qdim(u)) +
mu_para*(Grad_u + Grad_u'))")
stress_jump_inner = "sig_u ... "
or
stress_jump_inner = "Def sig_u :=
(lambda_para*Trace(Grad_u)*Id(qdim(u)) + mu_para*(Grad_u + Grad_u'));
sig_u ..."
you can also define macros with parameters, see
http://getfem.org/userdoc/gasm_high.html#macro-definition
Best regards,
Yves
Le 18/06/2018 à 13:35, Huu Phuoc BUI a écrit :
Dear Yves,
Please find enclosed the smallest python script. I made an mistake
when assigning Lamé coefficients for 3D problems (sorry!). Now the
problem seems to be different than the 'nan' ouput.
By using generic assembly, it says:
"RuntimeError: (Getfem::InterfaceError) -- Error in
bgeot_geometric_trans.cc, line 245 bgeot::scalar_type
bgeot::lu_inverse(bgeot::scalar_type*, bgeot::size_type, bool):
Non invertible matrix
"
Best regards,
Phuoc
On 18/06/2018 10:57, Yves Renard wrote:
Dear Phuoc,
Do you compute some gradient quantities on the finite element nodes
? If not, it should not pose any problem since using the generic
assembly, the computation are located on the Gauss points which are
not located on the nodes.
can you extract the smallest possible program on which the error
occurs ?
Best regards,
Yves
Le 18/06/2018 à 10:35, Huu Phuoc BUI a écrit :
Dear Yves,
Sorry I email you again on this topics. In fact, the generic
assembly did some computation on pyramid elements but the output is
'nan'. On elements of others types (of the mixed mesh), the output
is fine.
Please let me know if you have an idea. Thanks.
Best regards,
Phuoc
On 15/06/2018 16:43, Huu Phuoc BUI wrote:
Dear Yves,
That's great! It's indeed working now. Thank you very much for
your help.
Best regards,
Phuoc
On 15/06/2018 16:38, Yves Renard wrote:
Dear Phuoc,
The problem is indeed the same, to compute the location of gauss
points on a neighbour element, the inversion of the geometric
transformation is called. This inversion used a Newton algorithm
whose starting point is a node of the element ... (function
find_initial_guess in bgeot_geotrans_inv.cc).
I changed a bit the starting point, so it should work now. But
this is clear that the fact that the transformation is singular
at the pyramid tip is a difficulty.
Best regards,
Yves
Le 15/06/2018 à 11:53, Huu Phuoc BUI a écrit :
Dear Yves,
Thank you very much for your help.
Now it worked when computing the outer faces. But I faced
another problem of this mixed mesh. In fact, I'd like to compute
the stress jump at the inner faces using generic assembly, and
GetFEM++ showed an error like this:
"
File
"/usr/local/lib/python2.7/dist-packages/getfem/getfem.py", line
5591, in asm_generic
return getfem('asm', 'generic', mim, order, expression,
region, model, *args)
RuntimeError: (Getfem::InterfaceError) -- Error in
getfem_generic_assembly_compile_and_exec.cc, line 3887 virtual
int getfem::ga_instruction_neighbour_transformation_call::exec():
Geometric transformation inversion has failed in neighbour
transformation
"
So, as you said, this error comes from geometric transformation
of pyramid elements. Do you have an idea how to fix it?
Best regards,
Phuoc
On 15/06/2018 11:10, Yves Renard wrote:
Dear Phuoc,
The problem come from the fact that the test is made on the
mean unit normal vector on a face. This mean unit normal vector
is computed by averaging the unit normal vector on each
geometrical node of a face. Unfortunately, for a pyramid
element, the transformation is singular on the geometrical nodes.
I replaced the mean of normal vector by the normal vector on
the mean of geometrical nodes of the face. It fixes the
problem. (I push the change on the master branch).
Best regards,
Yves
Le 14/06/2018 à 15:40, Huu Phuoc BUI a écrit :
Dear Yves,
Please find the mesh attached.
Thank you for your help.
Best regards,
Phuoc
On 14/06/2018 14:52, Yves Renard wrote:
Dear Phuoc,
No, I see no reason. If you can just send me the mesh in a
format readable by GetFEM, I could check what is wrong.
Best regards,
Yves
Le 14/06/2018 à 10:24, Huu Phuoc BUI a écrit :
Dear Getfem-users,
I have a problem with computing the outer faces when using a
mixed mesh (having tetras, hexa, prisms and pyramids).
The error is:
face_left = m.outer_faces_with_direction([0, 0., -1.0], 0.01)
File
"/usr/local/lib/python2.7/dist-packages/getfem/getfem.py",
line 1372, in outer_faces_with_direction
return self.get("outer_faces_with_direction", v, angle,
CVIDs)
File
"/usr/local/lib/python2.7/dist-packages/getfem/getfem.py",
line 1152, in get
return getfem('mesh_get',self.id, *args)
RuntimeError: (Getfem::InterfaceError) -- Error in
bgeot_geometric_trans.cc, line 381 const base_matrix&
bgeot::geotrans_interpolation_context::B() const:
Non invertible matrix
Please let me know if you have any idea. Thank you.
Best regards,
Phuoc
--
Yves Renard ([email protected]) tel : (33) 04.72.43.87.08
Pole de Mathematiques, INSA-Lyon fax : (33) 04.72.43.85.29
20, rue Albert Einstein
69621 Villeurbanne Cedex, FRANCE
http://math.univ-lyon1.fr/~renard
---------
--
Yves Renard ([email protected]) tel : (33) 04.72.43.87.08
Pole de Mathematiques, INSA-Lyon fax : (33) 04.72.43.85.29
20, rue Albert Einstein
69621 Villeurbanne Cedex, FRANCE
http://math.univ-lyon1.fr/~renard
---------
