Re: Source term

[Konstantinos Poulios]

Hi,

Relying on element numbering for transferring data is not be very reliable because GetFEM may use a different element numbering. I would recommend you to save your values in a text file with 4 columns (or 3 for 2D):

x,y,z,val

where the first 3 columns (2 for 2D) contain the coordinates of the center of the element

Then you can use the following snippet for reading and transferring the values to a model variable/data defined on a discontinuous MeshFem mf:

import numpy as np
from scipy.spatial import KDTree
file = open("source_data.txt", "r") # assuming it contains 4 columns: x,y,z,value
source_data = np.loadtxt(file,dtype=float)
tree = KDTree(source_data[:,0:3])
dd,ii = tree.query(mf.basic_dof_nodes())
md.add_fem_data("source", mf)
md.set_variable("source", source_data[ii,3])

BR

Kostas

On Thu, Jun 2, 2022 at 2:14 PM Bourriche Lahoussaine <lahoussaine.bourriche@etu.toulouse-inp.fr> wrote:

Hello,
No it's  a list of values ( not _expression_).
Do you have an idea how to deal with this

Cordialement

Lahoussaine BOURRICHE
3A, ENSEEIHT , Physique num&eacute;rique
+33 6 20 76 17 12

----- Mail d’origine -----
De: Konstantinos Poulios <logari81@googlemail.com>
À: Bourriche Lahoussaine <lahoussaine.bourriche@etu.toulouse-inp.fr>
Cc: getfem-users <getfem-users@nongnu.org>
Envoyé: Thu, 02 Jun 2022 13:54:57 +0200 (CEST)
Objet: Re: Source term

Hello,

When you say that you have a value for each element, do you have an
analytic _expression_ for that, or do you have something like a list with
element number --> value?

If you have an analytic _expression_ then you can use md.interpolation(....)
to assign your source data to a model variable. Something like this
(assuming that your problem variable is called u):

N = m.dim()
mf = gf.MeshFem(m,N)
mf.set_classical_fem(0) # zero degree fem, i.e. discontinuous
...
md.add_fem_data("source", md.interpolation(".....", mf, RG_ID))
md.add_linear_term(mim, "source.Test_u", RG_ID)

BR
Kostas

On Thu, Jun 2, 2022 at 11:54 AM Bourriche Lahoussaine <
lahoussaine.bourriche@etu.toulouse-inp.fr> wrote:

> Hello
> I want to define a source term in a specific region, the source is a
> vector of values ( for each elemnt i have a source value ).
> How it will be?
> Cordialement
>
> Lahoussaine BOURRICHE
>
>