Hi Tri Dat,
thank you very much for pointing this out. I just found a bug in the
BoxFVElementGeometry. The normal vector on interior faces was not scaled
by the correct area, thus ending up in wrong fluxes. Could you please
check out the branch fix/boxnetworkgridnormalcomputation and try again?
Hopefully this solves the problem!
Best wishes,
Dennis
On 08.12.2016 14:32, Tri Dat NGO wrote:
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]
<mailto:[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
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