[Nek5000-users] issue w/ insulated wall?
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Tue Jul 15 16:28:49 CDT 2014
Hello all,
Following the issue that I have had with temperature field in my
problem (see https://lists.mcs.anl.gov/mailman/htdig/nek5000-users/
2014-June/002883.html), I have been performing several test cases and
trying to solve the issue. I just wanted to share two of these tests,
and wondered if anyone have any comments/thoughts on them.
I have a 3D cylindrical domain with several embedded horizontal holes
in it and an inflow (at the top) and an outflow (at the bottom). I
solved both momentum and heat equations for this problem, but no heat
source was added to the domain.
In the first test, the problem was initialized with a temperature
(equal to the inflow temperature) and all walls were set as no-slip
insulated boundary condition. For this setup, one expects temperature
to remain unchanged forever. However, after around t=200 (of
convective time scales), the temperature starts to grow gradually
leading to NAN value. This usually occurs for elements attached to
the wall and inflow opening.
In the second test, everything is identical to the first test, except
that I changed the walls temperature boundary condition to a constant
value equal to initial temperature. Temperature remains constant so
far (after t = 1000).
Although, these two examples are physically different (in terms of
boundary conditions), but it might raise the question whether there
is any issue with insulated (i.e., 'I ' flag in .rea) boundary
condition. It, however, certainly shows that the issue begins from
walls. I should note that the walls are curved surfaces (i.e., not
parallel to coordinate planes). I searched the users archive and
apparently, similar issue with insulated wall was reported:
https://lists.mcs.anl.gov/mailman/htdig/nek5000-users/2012-February/
001688.html
Regards,
Mohsen
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