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Re: Source term

From: Konstantinos Poulios
Subject: Re: Source term
Date: Thu, 2 Jun 2022 14:33:57 +0200


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):


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])


On Thu, Jun 2, 2022 at 2:14 PM Bourriche Lahoussaine <> wrote:
No it's  a list of values ( not _expression_).
Do you have an idea how to deal with this


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

----- Mail d’origine -----
De: Konstantinos Poulios <>
À: Bourriche Lahoussaine <>
Cc: getfem-users <>
Envoyé: Thu, 02 Jun 2022 13:54:57 +0200 (CEST)
Objet: Re: Source term


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)


On Thu, Jun 2, 2022 at 11:54 AM Bourriche Lahoussaine <> 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

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