[Nek5000-users] Rayleigh Benard with symmetry BCs

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

My apologies upfront for any simple misconceptions as I'm new to nek.

I have successfully run the included 2d RB example and thought things looked reasonable.  I then changed the mesh to an aspect ratio 2, 4x8 element mesh and modified the boundary conditions to be 'SYM' sidewalls and 'SYM' (free-slip) for the top and bottom velocity (see attached rea and map file).

Without changing anything else from the example (I did not modify SIZE) the velocities appear to blow up, and I get a series of errors like the following in the logfile:

     1   100 **ERROR**: Failed in HMHOLTZ: TEMP   1.4999E-02   3.7064E+01   2.4836E-03
          1   2.0000E-02  6.0370E-03 Heat done

     1   100 **ERROR**: Failed in HMHOLTZ: VELX   2.8743E-21   1.7086E-16   2.3416E-23
  0.000000000000000E+000  p22            1           1
 New CG1-tolerance (RINIT*epsm) =   1.010379228335448E-010
  2.341589846098494E-023


     1   100 **ERROR**: Failed in HMHOLTZ: VELY   1.0837E-01   1.0104E+03   1.0104E-10
 New CG2-tolerance (RINIT*10-5/10-10) =   2.795810823528297E-003
  3.472834773690102E-025



Do I need to adjust the tolerances because the mesh/BCs are different?


I don't think it matters, but I ran this on 16 procs (there are 16 per node on the machine I'm using).

                                               -Jared

CCS2/CNLS Postdoctoral Research Associate
Los Alamos National Laboratory
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