Hi Timo, I also saw the comments which indicate that the velocity computation only works for cubes. Indeed, when I was using Dumux 2.7, I was unable to get velocity field for simplex meshes, it worked only for cubes. Now, I am using Dumux 2.9 and it allows me to export velocity output for both simplex and cube meshes but it leads to weird results for simplex meshes.
Nevertheless, for the purpose of the calculation of effective permeabilities and particle tracking, I still need right velocities. Furthermore, considering that I am working on 2d-in-3d non-manifold triangle meshes using Foamgrid, the box-method must be used. Do you have any idea? Best wishes, Tri Dat De : Timo Koch [mailto:[email protected]] Envoyé : jeudi 20 octobre 2016 16:11 À : DuMuX User Forum; NGO Tri Dat Objet : Re: [DuMuX] Wrong velocity field on simplex mesh 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 [email protected]<mailto:[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]<mailto:[email protected]> D-70569 Stuttgart url: www.hydrosys.uni-stuttgart.de<http://www.hydrosys.uni-stuttgart.de> ____________________________________________________________________ __________________________ 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. __________________________
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