[RyGuy]

Hello All,

I am using coupled-implicit realizable k-epsilon viscous model with four boundary conditions to model a transonic compressible single phase flow.

The boundary conditions are main_inlet, powder_inlet, outlet and nozzle_walls.

I am using Intensity and Hydraulic diameter option for internal compressible flows along with the ideal-gas law for the density of the gas (air) in the compressible flow and the sutherland law for temperature affected viscosity values.

I get the following error:

Error: Internal error at line 947 in file '..\..\src\rp_mstage.c'.
divergence detected in AMG solver
Error: Object()

Reducing the Courant number does not seem to help...

Has anyone ever seen this error? How do I resolve this issue?

Anxiously awaiting a reply...

[Pfalcon]

Is that in the first iteration?

[RyGuy]

Thanks for the quick reply. No one usually ever replies......

The iterations start out good for the first 5 approximately, but quickly starts to diverge and before about 20 iterations (as well as Fluent automatically reducing the Courant number many times) I receive that error message.

Have you seen the likes of this before?

If you would like more information regarding my process I can gladly make it available to you!

Thanks for your time and effort,
Ryan

[Pfalcon]

Seen this before. Can be difficult to start a calculation. Check all boundary conditions again and make sure that they are defined in the right way. Make sure the mesh has reasonable quality. Also it probably helps to start out with a simpler more robust turbulence model (SA for example), and check the solution strategies in the FLUENT manual.

[RyGuy]

Hello Again,

I have checked my boundary conditions and they seem reasonable to me.

Main_inlet - is a pressure inlet corresponding to the proper edge.
Powder_inlet - is a pressure inlet corresponding to the proper edge.
Nozzle_walls - all edges needed are chosen.
Outlet - is a pressure outlet corresponding to the proper edges.

It seems when I switch to the SA 1-eqn model the residuals do not have as much trouble converging as before. If I can reach convergence with the 1-eqn model I can just switch it back to, say the k-epsilon model and iterate again correct?

I will continue to search in the manual about this topic as well....
Thanks for your time
Ryan

[Pfalcon]

just switch back to k-e after the flow has settled on SA, with a bit of luck k-e runs stable and you reach nice convergence

[shahed.malekipour]

Originally Posted by Pfalcon

Is that in the first iteration?

in my case, I get the error in the first iteration! what should I do?

[shahed.malekipour]

Originally Posted by shahed.malekipour

in my case, I get the error in the first iteration! what should I do?

thank u everyone, I found the reason.

[federicodauria]

hi, I've the same problem.
I am using a density based type to study an ideal gas flow trough a nozzle. k-omega model.
The boundary conditions are pressure farfield inlet, pressure outlet.

I get the following error after about 50000 step:

Error: Internal error at line 1549 in file '..\..\src\rp_mstage.c'.
divergence detected in AMG solver.
what's the problem? what should I change in the settings?

thanks for your attention

[prabha007]

i am facing the following error. my problem type are
supersonic flow through constant cross section. which has one pressure inlet and three pressure outlet. pleas help me, i cannot able to solve this one.My id- prabha.aero@gmail.com

Internal error at line 1549 in file '..\..\src\rp_mstage.c'.
Divergence detected in AMG solver iter continuity x-velocity y-velocity z-velocity energy k epsilon time/iter
1 1.0000e+00 1.0000e+00 1.0000e+00 1.0000e+00 1.0000e+00 4.2860e-01 6.9502e-01 0:23:18 999
2 5.9241e-01 9.3721e-01 9.7271e-01 9.4691e-01 5.9003e-01 2.6348e-01 5.1220e-01 0:25:17 998
3 7.3231e-01 8.7290e-01 9.0639e-01 8.8105e-01 7.2436e-01 1.7387e-01 5.4305e-01 0:30:10 997
4 9.7003e-01 7.9767e-01 8.2500e-01 8.0102e-01 9.4848e-01 1.3600e-01 3.7917e-01 0:30:45 996
5 1.0000e+00 7.3452e-01 7.6763e-01 7.3059e-01 1.0000e+00 1.2598e-01 4.1529e-01 0:34:32 995
6 1.0374e+00 6.7770e-01 7.2468e-01 6.7018e-01 1.0205e+00 1.1571e-01 3.2431e-01 0:34:13 994
# Divergence detected in AMG solver: Coupled -> Decreasing coarsening group size!
# Divergence detected in AMG solver: Coupled -> Increasing relaxation sweeps!

Divergence detected - temporarily reducing Courant number to 0.5
and trying again...

Divergence detected - temporarily reducing Courant number to 0.05
and trying again...

Divergence detected - temporarily reducing Courant number to 0.005
and trying again...

Divergence detected - temporarily reducing Courant number to 0.0005
and trying again...

Divergence detected - temporarily reducing Courant number to 5e-05
and trying again...

Error: Internal error at line 1549 in file '..\..\src\rp_mstage.c'.
Divergence detected in AMG solver
Error Object: #f

[chenxiaohu]

Originally Posted by prabha007

i am facing the following error. my problem type are
supersonic flow through constant cross section. which has one pressure inlet and three pressure outlet. pleas help me, i cannot able to solve this one.My id- prabha.aero@gmail.com

Internal error at line 1549 in file '..\..\src\rp_mstage.c'.
Divergence detected in AMG solver iter continuity x-velocity y-velocity z-velocity energy k epsilon time/iter
1 1.0000e+00 1.0000e+00 1.0000e+00 1.0000e+00 1.0000e+00 4.2860e-01 6.9502e-01 0:23:18 999
2 5.9241e-01 9.3721e-01 9.7271e-01 9.4691e-01 5.9003e-01 2.6348e-01 5.1220e-01 0:25:17 998
3 7.3231e-01 8.7290e-01 9.0639e-01 8.8105e-01 7.2436e-01 1.7387e-01 5.4305e-01 0:30:10 997
4 9.7003e-01 7.9767e-01 8.2500e-01 8.0102e-01 9.4848e-01 1.3600e-01 3.7917e-01 0:30:45 996
5 1.0000e+00 7.3452e-01 7.6763e-01 7.3059e-01 1.0000e+00 1.2598e-01 4.1529e-01 0:34:32 995
6 1.0374e+00 6.7770e-01 7.2468e-01 6.7018e-01 1.0205e+00 1.1571e-01 3.2431e-01 0:34:13 994
# Divergence detected in AMG solver: Coupled -> Decreasing coarsening group size!
# Divergence detected in AMG solver: Coupled -> Increasing relaxation sweeps!

Divergence detected - temporarily reducing Courant number to 0.5
and trying again...

Divergence detected - temporarily reducing Courant number to 0.05
and trying again...

Divergence detected - temporarily reducing Courant number to 0.005
and trying again...

Divergence detected - temporarily reducing Courant number to 0.0005
and trying again...

Divergence detected - temporarily reducing Courant number to 5e-05
and trying again...

Error: Internal error at line 1549 in file '..\..\src\rp_mstage.c'.
Divergence detected in AMG solver
Error Object: #f

hi,do u solve this question???? I have same question...
If you have konwn the reason, please tell me ,THX in advance.

[ashwingm]

I also had the following error, "Error: Internal error at line 1549 in file '..\..\src\rp_mstage.c'. "

If you are doing an axi-symmetric(example:CD nozzle, nose cone, anything that will be rotated along an axis), then make sure that, under BOUNDARY CONDITIONS, your axis of symmetry is set as "AXIS" and not "SYMMETRY".

My solver started solving, once I made this change. Hope this helps.

[mei1018786279]

I am facing the following error. my problem type are gas-solid two-phase flow by DEM-DDPM. one velocity inlet and one pressure outlet. pleas help me,I cannot able to solve this one.My id-1018786279@qq.com
WARNING: 3.9736% of the total discrete phase mass were behind in time by, on mass-weighted average, 0.000107 s, which is 0.0036% of their total age or 53.6834% of the last time step
iter continuity u-air v-air w-air k epsilon time/iter
296580 3.3968e+09 1.8910e-01 9.6527e-02 9.2661e-02 7.9803e-01 1.5212e+02 0:00:34 20
# Divergence detected in AMG solver: mp-x-momentum -> Decreasing coarsening group size!
# Divergence detected in AMG solver: mp-x-momentum -> Increasing relaxation sweeps!
# You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t)

[dong574933]

I don't know your this problem

[rahulmule797@gmail.com]

Originally Posted by shahed.malekipour

thank u everyone, I found the reason.

How you solved it