Dear Mustapha,
mixed boundary conditions are removed in Dumux 3.0 because there is no
general way of imposing them for most multiphase-flow problems.
We might try to reimplement this in another way, but AFAIK there is
currently no concrete plan how to achieve this.
So this depends a bit on your equation. For the advective part you can
simply convert Dirichlet to Neumann (flux*x) at the inflow, at the
outflow the advective part doesn't need boundary conditions if using the
(full) upwind scheme. For the diffusive part you have two options:
You can convert Dirichlet to Robin BCs (or "solution-dependent" Neumann
BCs in Dumux language) by computing the resulting flux given the
concentration on the boundary
and adding it to the advective Neumann flux. As Neumann fluxes can be
solution-dependent, i.e. Robin BCs, you use the same problem interface
function "neumann" for that. The boundary conditions are thus imposed
weakly.
Another way of imposing the Dirichlet boundary conditions weakly would
be Nitsche's method (i.e. penalizing the deviation from the boundary
condition). You can add the penalized term also in the "neumann" method
to the residual.
Both solutions are similarly implemented in the 1p2c test
(https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/blob/master/test/porousmediumflow/1pnc/implicit/1p2ctestproblem.hh)
for CCTpfa and Box discretizations, realizing the "outflow" boundary
condition in Dumux <3.0. So this is done for the mass balance equation
and for the advective part of the transport (i.e. it was also imposed
that grad(x)*n is zero on this boundary). But it should work analogously
for the diffusive transport term.
I hope this helps,
Timo
On 21.06.2018 11:06, Mustapha El Ossmani wrote:
Dear DuMuX users,
*In Dumux 3.0*, we did not understand how we can impose a mixed
bounadry conditions of the type neumann and dirichlet.
For example in 1p2c modulehow to use a neumann condition for pressure
and dirichlet for concentration on the same part of the border ?
In this, we get an error that we must use a pure condition. We must
convert Dirichlet BCs to a Robin BCS. There is an example that deals
with this case?
Thank you in advance for your reply.
Best regards
Mustapha
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IWS, Universität Stuttgart fax: +49 711 685 60430
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