Hi!
I made some progress with the advection problem.
However, I am pretty
sure I didn't understand the formulation of boundary conditions correctly.
Being new to FVM, I first had to realize that there is a distinction between
the values of a cell variable ("sitting at the cell center") and the values of
the faces confining the cells.
I got that the face value between two cells is the arithmetic mean of the
values of the adjacent cells.
How is the situation at the boundary of the domain? I have the impression that
the face value is the same as the cell value there.
However, constraining the face value for "facesLeft" isn't reflected onto the
first cell value.
In my case I am starting with an initial state where the system is in
equilibrium and am interested in its evolution upon a disturbance or excitation
on the left boundary.
So I have the porous material and the air 'above' it at the same temperature
and at a partial vapor pressure that results from those temperatures. Now I
increase the temperature and partial pressure on the left boundary and have the
heat and the water vapor advected along the system. I have tried this by
setting the boundary conditions for the four variables as
X_G_in = 0.01294 # water content of incoming air, corresponds to dewpoint
of 18°C
X_S_in = 0.3484 # eq. water content of sorbent under carrier gas with
given parameters
T_G_in = 20. + 273.15 # temperature of incoming carrier gas
T_S_in = T_G_in # temperature of sorbent at entrance is equal to carrier
gas temperature
# (use ramp when values T_S_init and T_G_in differ a lot)
u1.constrain(X_G_in, mesh.facesLeft)
u2.constrain(X_S_in, mesh.facesLeft)
u3.constrain(T_G_in, mesh.facesLeft)
u4.constrain(T_S_in, mesh.facesLeft)
This of course sets only the face values and doesn't change the value of the
cell on the left boundary.
So when the solver iterates the cell variable it is only iterating equilibrium
values.
Consequently the system doesn't evolve.
What am I doing wrong?
Cheers,
Markus
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