Hi Georg,
sorry for the long silence.
I agree that it should be easier to calculate the fluxes from outside
the local residual. As you suggest, this could be made possible by a
static computeFlux function. We are currently on the way of rethinking
and -working the whole volVars/fluxVars stuff. We see that we can
incorporate your suggestion.
Until then, you can have a look at the function calculateFluxAcrossLayer
in dumux/freeflow/stokes/model.hh:98ff. While this will not work for the
boundary, you can use stuff from there. In particular, after the line
this->localResidual().evalFluxes(element, elemVolVars);
you are safe to calculate the computeFlux function for the boundary faces.
That said, computeFlux for a boundary face in the box method will be
just an approximation by using the finite element gradient on the
boundary. To get the "real" flux in terms of the exact
mass/volume/energy that is flowing out of the domain, one has to
evaluate the residual for the entire control volume _without_ the
boundary terms. That means that one has to add up the contributions from
the subcontrol volumes. For your multidomain scenario and if you want to
calculate the fluxes across a part of the coupling boundary, these
fluxes should be the result of the routine globalResidual found in
dumux/implicit/model.hh where the model is a subdomain model. This
doesn't see the coupling, which means that no boundary terms are
calculated on the coupling boundary, which is what you want
Kind regards
Bernd
On 03/15/2016 03:06 PM, [email protected] wrote:
Hello Dumux,
I tried to calculate the fluxes over a certain part of the boundary of
the model domain. For this purpose I used an ElementIterator to
iterate over the elements of the grid. In each element I iterate over
the intersections and in each intersection over the vertices. With
information from the IntersectionIterator and the vertex index I can
get the boundary face index and the boundary face position. I test
whether I am at the desired location on the grid and then calculate
the local residual of the corresponding element. This works just fine.
The idea was to use the computeFlux-function of the local residual
afterwards with the corresponding boundary face index and
onBoundary=true to get the flux over the boundary. However, this will
not work because the fluidState is not defined when the local
fluxVariables are constructed and this will cause Valgrind to complain.
To me it came as a surprise that it is not possible to use the
computeFlux-function outside the localresidual since this is quite an
important quantity to access when traversing the grid. I see that
several people have tried just the same approach but commented the
code afterwards, probably for the reasons mentioned above. The
workaround which was used instead is to locally construct the
fluxVariables of the element and then do just the same flux
calculation as in the localresidual. This way, one is forced to copy
code and have code which does exactly the same in two different
locations. I think this should be improved and the fluxes over the
interfaces should be readily available when iterating over the grid.
The solution to this problem would be to add a second
computeFlux-function to the local residual. This function would get
all the parameters needed for the flux calculation without the need to
touch the private functions of the local residual. This would be a
public version of computeFlux (the current computeFlux function is
private in nature since it can’t be called outside the local residual
without causing problems and maybe should be set private for consistency).
I believe the problem is the same for all (implicit) models. I
attached my code which is specific to my multidomain/fuel cell model.
The first function is called in the multidomain problem. The
computeFlux-Function is part of the localresidual.
These are just some ideas. Please let me know what you think.
Best regards
Georg Futter
——————————————————————————
*German Aerospace Center *(DLR)
Institute of Engineering Thermodynamics | Computational
Electrochemistry | Pfaffenwaldring 38-40 | 70569 Stuttgart
Dipl.-Ing. *Georg Futter* | Ph.D. student
Telefon 0711/6862-8135 | [email protected] <mailto:[email protected]>
www.DLR.de <http://www.dlr.de/>
_______________________________________________
Dumux mailing list
[email protected]
https://listserv.uni-stuttgart.de/mailman/listinfo/dumux
--
_______________________________________________________________
Bernd Flemisch phone: +49 711 685 69162
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
