Hi Timo, 1. I declared permeability as a scalar. I have not yet tested the case of tensor permeability in world coordinates. I will do that.
2. To simulate advection-diffusion model in Dumux, I simply modified properties of fluid in the file in "dumux/material/fluidsystems/" . Concretely, I desactivated all pressure-dependence of density, viscosity and diffusion coefficient. In the isothermal condition, fluid density, viscosity and diffusion coefficient are constant. The velocity V is computed by Darcy's law, so it will also be constant. 3. I was not clear. Y in "Y = Ymin" or "Y= Ymax" is Y-coordinate. 4. To estimate the velocity, I looked at the concentration front and compute it by hand. Kind regards Tri Dat 2016-12-08 13:56 GMT+01:00 Timo <[email protected]>: > Hi Tri Dat, > > this is interesting. I have a few more questions to narrow it down. > > How did you specify the permeability? In world coordinates as tensor? As > scalar? And why do you need it in your advection-diffusion equation? (maybe > I understood wrongly and you actually compute the velocity using Darcy's > law, so the full 1p2c model?) > > What do you mean by "Y" in your boundary conditions? > > How did you observe the velocity? Did you use the velocity calculation > feature of Dumux? Or did you just look at the concentration front and > compute it by hand? > > Best wishes > > Timo > > On 06.12.2016 14:11, Tri Dat NGO wrote: > > Hi Dumux developers, > > I have just done some simulations of the advection-diffusion equation > (Figure_1, simplified from 1p2c model in Dumux) on three 2D-in-3D grids. > Case (A), the first grid resides on the XOY plane, the mesh (B) and (C) are > obtained by rotating the mesh (A) around Y-axis by an angle \alpha with > cos (\alpha) =1/sqrt(5)) and 90°, repectively. Consequently, the mesh (C) > resides on the YOZ (see the Figure_2, A: white, B: blue, C: yellow). > > */ Initial condition: P=P0, c = 0. > */ Boundary conditions: > - Y = Ymin: P=2P0, c=C0, > - Y = Ymax: P=P0, c=0 (It means that the flow is along Y-axis) > - No-flux Neumann condition for the remaining boundaries. > > Viscosity is constant, gravity is neglected. The diffusion effect is very > smaller than the convection one (V*L/D ~1E7). Since gravity is neglected, > in principle, the result of these three simulations should be the same: the > front of the concentration profile travels with a velocity V. But, > curiously, this is not the case. The travelling velocity of front of the > concentration curve in the case (A) is equal to \sqrt(5) time in the case > (B). Furthermore, in the case (C), there was a convergence problem: Linear > solver did not converge. > > It seems that the permeability in the case (B) Kyy(B) equal to 1/sqrt(5) > of the one in the case (A), Kyy(A), and Kyy(C) = 0. I think that it may be > a bug (?) in the transformation from global to normal vector cooridnate > of the reference element in the box method on 2D-in-3D mesh when using > FoamGrid. Could you please check it and confirm me? > > I'm sorry for this long email and I hope I was clear with that. > Kind regards, > Tri Dat > > > _______________________________________________ > Dumux mailing > [email protected]https://listserv.uni-stuttgart.de/mailman/listinfo/dumux > > > > _______________________________________________ > Dumux mailing list > [email protected] > https://listserv.uni-stuttgart.de/mailman/listinfo/dumux > >
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