Evgeny,
> I found one problem with inp file - in line "1 0 quad 1 2 3 4". I
> guess the second number should be nonzero here. I have try to set 1 and
> get better results. Now I can see velocity changes around the
> input-output bounds.
Is this an input file you created yourself, or are you saying that there
is a mistake in the input files we distribute as part of step-35?
> I think with cell face iterator I have to use cell quad iterator to
> set all bounds when I create my inp, am I right?
I don't think I understand what you are trying to say here. An iterator
can only point to a cell *or* a face. It can't be a "cell face iterator".
> For input bound I use the same function as in the 35 tutorial. I
> tried to set ConstantFunction() with value about 1 or -1 for the output
> bound. But I stiil got the same error on the 3th step. I can see the
> pressure was about 10^18 before that.
That suggests that you use boundary conditions that are not compatible
with the incompressibility assumption. For example, if you prescribe
velocity boundary values that point inward at every part of the
boundary, you say that you want to have inflow everywhere -- but because
the model assumes that your medium is incompressible and that there are
no interior sinks for the fluids, this clearly can't work.
> I get a good looking flow between input and output bounds when I use
> ConstantFunction() with the same value for both input and output bounds.
> But only for the about 5 steps. And then I can see the pressure grows
> dramatically.
> How I can chooze correct boundary conditions when I have variable
> input boundary?
For one, you have to make sure that the boundary conditions are
compatible with the model. In your case, this means that if you use
Dirichlet or no-flux boundary conditions everywhere, then you need to
have that
\int_{partial Omega} n.u = 0
Best
W.
--
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Wolfgang Bangerth email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/
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