Hi Tri Dat,
I checked the velocity computation. There is a comment that says that it
only works for cubes. That being
said, we could compute element velocities by evaluating the pressure
gradient at element center using the P1 ansatz functions.
This is probably not done right now because we currently allow
discontinuous permeabilities per sub-control-volume. So this is why
the current approach uses a weighting of the scv velocities. Which
results as you saw in weird velocities. I don't know if the element
center approach results in better velocities especially when looking at
discontinuous param multi-phase simulation. @all Someone
else might know more than me.
So the problem that you have with both cell- and vertex centered FV is
that your only primary variable is the pressure. So computing the
velocity field is a post-processing step and generally the pressure
gradients are not approximated everywhere in the domain because we
compute fluxes, so you can't just evaluate the velocities everywhere you
want. If you look at 1p cell-centered FV with triangles you also get
weird velocity values.
There might be smarter ways to reconstruct the velocity fields than
currently implemented but they
are going to be more complicated / time consuming.
Do you need good velocities for e.g. particle tracking?
Best wishes
Timo
On 20.10.2016 15:08, NGO Tri Dat wrote:
Hi Dumuxers,
I have just done a simple test of 1p model with a pressure gradient
along X-axis on cube and simplex meshes and using implicit box method.
The simulation parameters:
-Permeability K = 1E-11 (m^2)
-Viscosity of the fluid : mu = 1E-3 (Pa.s)
-Pressure gradient: delta_P = 1E+8 (Pa)
-delta_X = 3 (m)
The velocity along X-axis should be v = K/mu * div p = 1/3 (m/s)
The attached image shows the pressure and velocity field obtained by
Dumux.
Unfortunately, the velocity field on two meshes are quite different.
Concretely, the simulation result on cube mesh is similar to the
theoretical one, but not the test on simplex mesh.
I wonder if there is a bug in the calculation of velocity on simplex
meshes in Dumux.
Could you please check it and confirm me?
Kind regards,
Tri Dat
PS: I also send you the used *.hh/input/mesh files
__________________________
/Avant d'imprimer, pensez à l'environnement ! Please consider the
environment before printing ! /
/Ce message et toutes ses pièces jointes sont confidentiels et établis
à l'intention exclusive de ses destinataires. Toute utilisation non
conforme à sa destination, toute diffusion ou toute publication,
totale ou partielle, est interdite, sauf autorisation expresse. IFP
Energies nouvelles décline toute responsabilité au titre de ce
message. This message and any attachments are confidential and
intended solely for the addressees. Any unauthorised use or
dissemination is prohibited. IFP Energies nouvelles should not be
liable for this message./
__________________________
_______________________________________________
Dumux mailing list
Dumux@listserv.uni-stuttgart.de
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: timo.k...@iws.uni-stuttgart.de
D-70569 Stuttgart url: www.hydrosys.uni-stuttgart.de
____________________________________________________________________
_______________________________________________
Dumux mailing list
Dumux@listserv.uni-stuttgart.de
https://listserv.uni-stuttgart.de/mailman/listinfo/dumux
