Dear Anne-Cecile
The syntax of the add_linear_term command is
add_linear_term(*mim*, *expression*, *region=None*, **args*)
<https://getfem.org/python/cmdref_Model.html#getfem.Model.add_linear_term>
and it doesn't depend on whether the term is in a volume or on a surface.
You should just provide the correct region id as the third argument.
One thing that you need to be careful about is that in GetFEM (and in math
in general) there is no left and right hand side of an equation, move all
your terms to one side so that you will have zero on the other side,
otherwise you will end up with wrong signs in your terms.
Best regards
Kostas
On Thu, Apr 21, 2022 at 2:40 AM Lesage,Anne Cecile J <
ajles...@mdanderson.org> wrote:
> Dear all
>
>
>
> In the variational formulation of the poroelastic equations I use
>
> (see attached picture) I have surface integral terms (in purple). When
> there are non zero like
>
> The second one when the normal pressure gradient is non zero because there
> is fluid flux on the surface
>
> What shall I add in my python scrip on top of the volume integral terms
> (see python script below)?
>
>
>
> Thank you
>
> Regards
>
> Anne-Cecile
>
>
>
> # Brain poroelastic with buoyancy term = -(rhot-rhof) g ex
>
> # Equation 1
>
> md.add_linear_term(mimu3b,
> 'smf*Grad(ub):Grad(Test_ub)+smf/(1-2*nub)*Div(ub)*Div(Test_ub)+Grad(pb).Test_ub')
>
> if(buoyancy):
>
> print('Assembling buoyancy term along -ex\n');
>
> md.add_linear_term(mimu3b,
> 'Test_ub(1)*g*(rhot-rhoa*Heaviside(X(1)-csflevel)-rhow*Heaviside(-X(1)+csflevel))')
>
> # Equation 2
>
> md.add_linear_term(mimp3b,
> '1.0/dt*(Div(ub)-Div(ub_prev))*Test_pb+kb*Grad(pb).Grad(Test_pb)') # no
> shrinking
>
> if shrinking==1:
>
> print('Assembling shrinking term kc1 \n');
>
> md.add_linear_term(mimp3b, 'kcsh1*(pb-pcs)*Test_pb')
>
> if shrinking==2:
>
> print('Assembling shrinking term kc2 \n');
>
> md.add_linear_term(mimp3b, 'kcsh2*(pb-pcs)*Test_pb')
>
> if shrinking==3:
>
> print('Assembling shrinking term kc3\n');
>
> md.add_linear_term(mimp3b, 'kcsh3*(pb-pcs)*Test_pb')
>
> #mfouth = gf.MeshFem(meshh)
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