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Old   July 6, 2010, 05:12
Default ansys12: turning off correction scaling
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Alain
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hey guyz!!
I'm trying to model the diffusion of a gaz (as fluid) through a simple nozzle.
I use a compiled udf and normally every thing is normal: no error, no warining ..
but when iterating, (the used scheme, the boudary conditions, and he under-relaxation factor already set up), it kicks me saying:
Divergence detected in AMG solver: pressure correction -> turning off correction scaling!
Divergence detected in AMG solver: pressure correction -> Increasing relaxation sweeps!


I've already met the second message but I've never paid attention to the first one: "turning off correction scaling!"

could someone explain me more what is it about?
thanks
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Old   March 29, 2011, 05:52
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I encountered the same problem, have you already solved? Thanks for your reply!
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Old   March 29, 2011, 08:35
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Yes and no by the same time,
I mean since the problem is linked with pressure, it's likely linked with density also (because the pressure is a function of the density), ...
So yes because I checked the density and corrected the error so that now it works and there's no warning message anymore, but no because I'm still not aware of what does "turning off correction scaling!" really mean.
I hope it could help you ,
if not tell me more, ..
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Old   March 29, 2011, 08:40
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Thanks a lot!
I'm solving a problem like flow past a oscillating cylinder in 2D plane.
Using LES model with SIMPLEC pressure-velocity couple methods.
I tried to lower the under relaxtion factors, but it didn't work.
I don't know why.
But thanks anyway.
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Old   August 31, 2011, 10:22
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Quote:
Originally Posted by noa_emric View Post
Yes and no by the same time,
I mean since the problem is linked with pressure, it's likely linked with density also (because the pressure is a function of the density), ...
So yes because I checked the density and corrected the error so that now it works and there's no warning message anymore, but no because I'm still not aware of what does "turning off correction scaling!" really mean.
I hope it could help you ,
if not tell me more, ..
What did you correct for density?

and my case is about simulating a twin rotor turbine blade with 180 degree periodic BC. I am simulating at velocities of 7, 10, 15, 20 and 25 m/s. The mesh diverges at 20 and 25 m/s saying divergence detected in AMG solver --> increasing pressure sweep correction,
primtive error at node 0
primtive error at node 1
primtive error at node 2
primtive error at node 3
primtive error at node 4
primtive error at node 5
primtive error at node 6
primtive error at node 7

Initially this error appeared in first few iteration of 20 and 25 m/s but later appeared in other velocity cases as well. I am using default UR factors with Standard pressure and SIMPLE schemes. I also tried with lowering UR factors but didn't work. (However, the mesh was a little bit coarse that time). I have also seen that lowering the UR factors from scratch also diverges the solution.

Any solutions in this regard are welcomed.
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Old   August 31, 2011, 11:05
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Alain
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well, in my case, the goal was to study the behavior of a plasma flow (a free burining arc) out from thermal equilibrium. Since Fluent aint been developed to do that, I created an UDF to adapt the solver. In this UDF, parameters such as density, thermal conductivity, speed of the sound, viscosity, ...

In the previoous talk, I meant the mass density is linked with pressure because both parameters mainly depend on the chemical concentration n[m^-3] of each species in the gas (P = n.k.T, and rho = n.m)
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Old   June 2, 2014, 09:23
Post did you solved your problems?
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i also encountered the error. and i want to know the reason why the error appear? thank you if you can tell me ?




Quote:
Originally Posted by Shamoon Jamshed View Post
What did you correct for density?

and my case is about simulating a twin rotor turbine blade with 180 degree periodic BC. I am simulating at velocities of 7, 10, 15, 20 and 25 m/s. The mesh diverges at 20 and 25 m/s saying divergence detected in AMG solver --> increasing pressure sweep correction,
primtive error at node 0
primtive error at node 1
primtive error at node 2
primtive error at node 3
primtive error at node 4
primtive error at node 5
primtive error at node 6
primtive error at node 7

Initially this error appeared in first few iteration of 20 and 25 m/s but later appeared in other velocity cases as well. I am using default UR factors with Standard pressure and SIMPLE schemes. I also tried with lowering UR factors but didn't work. (However, the mesh was a little bit coarse that time). I have also seen that lowering the UR factors from scratch also diverges the solution.

Any solutions in this regard are welcomed.
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Old   March 8, 2015, 22:17
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Hi~
I encountered the same problem.
Is there any solution?
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