[Nek5000-users] symmetry boundary conditions and genmap

[nek5000-users at lists.mcs.anl.gov]

Hi Marco,

It looks maybe like you replaced "W" by "SYM"  ?

In the .rea file, if a line has a character that is read by nek, then the line has to be formatted,
which means that spaces in the line are important.

Thus, you should replace "W  "  ('W-space-space) by "SYM"  , i.e., all bcs are read as 3 character
strings.

Now, concerning SYM, there is another constraint --- namely the following:

Any SYM boundary must be aligned with either X , Y, or Z unit normals, unless you're using the
stress formulation.

The reason is that, say, for a SYM boundary that has unit normal in the Z direction, the velocity
bcs are:

   du/dz = 0 ,  dv/dz = 0,  w=0

That is, Dirichlet for w and Neumann for u and v.

If the SYM bc is not aligned, it ends up being a mixed bc for the 3 velocity components, which
in Nek can at present be handled only with the stress formulation, which means PN-PN-2, and 
not PN-PN.

Best, Paul

________________________________________
From: nek5000-users-bounces at lists.mcs.anl.gov [nek5000-users-bounces at lists.mcs.anl.gov] on behalf of nek5000-users at lists.mcs.anl.gov [nek5000-users at lists.mcs.anl.gov]
Sent: Thursday, June 30, 2016 7:46 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] symmetry boundary conditions and genmap

Hello,

I have two rea files that are exactly identical but for the boundary conditions: one has ‘W’ and the other one has ‘SYM’. If I am not mistaken, the ‘SYM’ boundary type is supported by Nek5000 but is causing problem when I try to generate a map file with genmap. It returns the following error message:
 reading .rea file data ...
  ERROR: error reading    1       79200      299357
  aborting 530 in routine rdbdry.

           1  quit

The rea file with ‘W’ boundary type successfully goes through the genmap script. Is there anything I should be aware when setting SYM bc type in the rea file?

I could not find any related post in the archive of the mailing list.

Thanks,
Marco

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