Hi Lorenzo,
we consider equations of the form
ds/dt - div(f) = q
by setting Neumann BC it is always meant that f*n is specified on the
boundary, where n is the normal vector on the boundary. Now the boundary
flux f*n can be a constant but it is also allowed to depend on any
variables (solutionDependentNeumann), the assembler will just compute
the derivative for you. So the Neumann BC actually allows you to add
anything to the residual (replacing f*n), so that you can use it to
implement constant boundary fluxes, Robin-type BCs, Dirichlet BCs in a
weak sense, or with a penalty method.
Outflow is (was / removed in 3.0 ) a special kind of such a Neumann BC,
where f*n is approximated using only local information. For Tpfa it was
only implemented for cubes and basically extrapolates the flux from the
opposite face to the boundary (I'm not sure if that is stable). For Box
the flux is assembled just like on an inner control volume face. As it
is not possible to implement such a condition generally for all
discretization and physics/equations it has been removed in 3.0. In the
cases where you are sure that such a BC works, you can just implement it
inside the problem's neumann() function.
In order to answer your question for 2p you have to be more specific.
Which discretization scheme are you using? Which element types? For
which equations to you want to set Outflow in the 2p model? What other
BCs do you set? What do you expect? What do you get?
Timo
On 04.02.19 14:28, lc wrote:
Good afternoon,
after having searched on internet, I didn't find the info which I need.
Could you please explain the details of the implementation of the
Outflow (even if it has been removed in the new release) and Neuman BC
in DuMux and in what they differ, please? In particular, in the case
of porousmedia 2p case.
Kind regards,
Lorenzo
On 03.12.2018 15:11, Martin Schneider wrote:
3) What about asking google about "outflow and Neumann" boundary
conditions?
I am sure you will find a lot of explanations about it.
_______________________________________________
Dumux mailing list
[email protected]
https://listserv.uni-stuttgart.de/mailman/listinfo/dumux
--
_______________________________________________________________
Timo Koch phone: +49 711 685 64676
IWS, Universität Stuttgart fax: +49 711 685 60430
Pfaffenwaldring 61 email: [email protected]
D-70569 Stuttgart url: www.hydrosys.uni-stuttgart.de
_______________________________________________________________
_______________________________________________
Dumux mailing list
[email protected]
https://listserv.uni-stuttgart.de/mailman/listinfo/dumux
