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Old   June 21, 2008, 08:29
Default About the divergence when using unstructured mesh
  #1
Shamoon
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HI ALL,

I AM DOING A PROBLEM OF EXTERNAL FLOW ON A CYLINDER AT M=2 AND 10 DEGREE ANGLE OF ATTACK. I HAVE MADE A COMPLETE TET/HYBRID MESH. I KEPT THE CFL NO LOW TO 0.2 BUT AFTER 3000 ITERATIONS IT DIVERGED.

THEN I RAN THE PROBLEM AGAIN AND INCREASED THE CFL NO SO THE DIVERGENCE CAME AT 1600 ITERATIONS.

SECONDLY, BEFORE DIVERGENCE IT GAVE ME SO MANY WARNINGS LIKE TIME-STEP REDUCED IN 3 CELLS TEMPERATURE LIMITED TO 1 IN 2 CELLS IN ZONE 2 (DEFAULT-INTERIOR) ABS PRESSURE LIMITED TO 1 IN 3 CELLS IN ZONE 2

THE PROBLEM IS OF 2 MILLION CELLS SO I RUN IT ON 3 COMPUTERS ON PARALLEL TELL ME HOW THE DIVERGENCE PROBLEM CAN BE SOLVED?
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Old   June 22, 2008, 05:58
Default Re: About the divergence when using unstructured m
  #2
arash
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Hi! you may regulate the underlaxtion factor ,it has a direct effect on convergence, let your problem work at first with the default ,after some iterations , decrease the factor to 0.3 or 0.4 . it may works.
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Old   June 22, 2008, 09:00
Default Re: About the divergence when using unstructured m
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Shamoon
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Arash, Thanks for ur reply but I am running the simulation at Inviscid and coupled(Density based) solver. I do not get any option of Under-relaxation factor in it. It comes only in either a viscous solver or using Seggregated (pr based) solver
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