[Nek5000-users] Using OIFS

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

Alex,

I see that p26 is set to 3 -- this is the target courant number -- which should be 2, no?  You might even make it smaller than that to start with.

Also, for my nondimensionalization, I had

  1.000000E+00 p054: direction of flow rate -- 1-X, 2-Y, 3-Z
  12.56637E+00 p055: volumetric flow rate

whereas you have

   -1.00000     p054 fixed flow rate dir: |p54|=1,2,3=x,y,z
   1.00000     p055 vol.flow rate (p54>0) or Ubar (p54<0)

finally,  I have

  4.000000E+00     p099 dealiasing
  0.050            p103 filter weight of last mode

whereas you have

   3.00000     p099 dealiasing: <0--> off/3--> old/4--> new
  0.100000E-01 p103 weight of stabilizing filter (.01)


Let me know if making those changes helps.

--Mike




On Aug 3, 2011, at 3:41 AM, <nek5000-users at lists.mcs.anl.gov<mailto:nek5000-users at lists.mcs.anl.gov>> wrote:

Hi neks,

I'm trying to simulate a turbulent channel flow like in the presentation "A comparison
of Nek5000 and OpenFOAM for DNS of turbulent channel flow" of Michael A. Sprague from the last
user meeting (http://www.mcs.anl.gov/~fischer/nek5000/sprague_nek5000_dec2010.pdf "mid"-case).
In the presentation it is mentioned that the CFL number is approx. 2 so I have choosen the BDF3/OIFS3
scheme. However the solution blows up and Nek5000 stops the computation after 49 steps.

Are there any parameters I have to set in the rea-file to get it work? TCHAR is true and p026 is
set to 3. Dealiasing is turned on as well, but I'm not sure if the weight of the filter may be wrong.

The files of the case are attached.

Thanks!
Alex
<sprague3D.tar.gz><ATT00001..txt>