Ah! ok, sure. I actually saw this before but than completely forgot
about it.
Thank you for the explanation; now, it follows my expectations :-)
On 21.11.2017 14:40, David Knezevic wrote:
On Tue, Nov 21, 2017 at 7:10 AM, Tobias Moehle
<tobias.moe...@uni-rostock.de <mailto:tobias.moe...@uni-rostock.de>>
wrote:
Dear all,
I have some problem with Lagrange multipliers: Maybe I
misinterpret my results, but somehow they don't have the effect I
expected.
Looking at the solution of systems_of_equations_ex3, (using
paraview) I see the (real part of) pressure r_p to be 0 at time
step 0 and than it jumps to ~10, where it stays for the rest of
the simulation. But isn't it actually enforced to stay at 0 "forever"?
This is beacuse the following lines:
// We can set the mean of the pressure by setting Falpha. Typically
// a value of zero is chosen, but the value should be arbitrary.
navier_stokes_system.rhs->add(navier_stokes_system.rhs->size()-1, 10.);
So in this case we set the mean pressure to be 10. We do this just for
illustration purposes, to show that the Lagrange multiplier can be
used to set the mean pressure to any value you like (but as mentioned
in the comment normally one would just set it to zero). If you want to
change the value, just change the "10" in the line above.
David
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