AMG solver divergent

rezarahnama · April 28, 2016, 03:31

Hi everybody
i am working on a case that models sterlization of a fermentor with steam.modeling consitions and setups are listed below:
Density based
Transient and multiphae (wetsteam)
Boundary Conditions are pressure inlet= 2 bar, 233 C and pressure outlet=1.6 bar, 129 C
I used inviscid flow
soloution method is implicit
when i start to calculate and run the case after about 5-15 iteration, solution diverge and i face to listed errors :
# Divergence detected in AMG solver: > Increasing relaxation sweeps!
# Divergence detected in AMG solver: Coupled -> Decreasing coarsening group size!
Divergence detected in AMG solver: WSB-eq
Divergence detected in AMG solver: WSN-eq

can anybody help me to resole this problem?

LuckyTran · April 29, 2016, 18:08

What does inviscid multiphase flow of wet steam even look like?

Anyway, since you are running a transient case and it diverged in 15 or so iterations, does that mean that it diverged on the very 1st iteration?

Most likely, you have incorrect initial conditions or your mesh is really bad. I would check those first. Make sure your initial conditions for all variables are consistent. For transient simulations you often need to generate the initial conditions from another simulation.

Also check your mesh quality. Run the mesh check and see if there are any glaring issues.

April 28, 2016, 03:31	AMG solver divergent	#1
rezarahnama New Member Reza Rahnama Join Date: Apr 2016 Posts: 2 Rep Power: 0	Hi everybody i am working on a case that models sterlization of a fermentor with steam.modeling consitions and setups are listed below: Density based Transient and multiphae (wetsteam) Boundary Conditions are pressure inlet= 2 bar, 233 C and pressure outlet=1.6 bar, 129 C I used inviscid flow soloution method is implicit when i start to calculate and run the case after about 5-15 iteration, solution diverge and i face to listed errors : # Divergence detected in AMG solver: > Increasing relaxation sweeps! # Divergence detected in AMG solver: Coupled -> Decreasing coarsening group size! Divergence detected in AMG solver: WSB-eq Divergence detected in AMG solver: WSN-eq can anybody help me to resole this problem?

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April 29, 2016, 18:08		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,751 Rep Power: 66	What does inviscid multiphase flow of wet steam even look like? Anyway, since you are running a transient case and it diverged in 15 or so iterations, does that mean that it diverged on the very 1st iteration? Most likely, you have incorrect initial conditions or your mesh is really bad. I would check those first. Make sure your initial conditions for all variables are consistent. For transient simulations you often need to generate the initial conditions from another simulation. Also check your mesh quality. Run the mesh check and see if there are any glaring issues.