[mou]

Hello everyone,

I'm currently doing the 2D NACA 0012 Airfoil Validation Case: https://turbmodels.larc.nasa.gov/naca0012_val.html

I created the mesh and set the case according to the website. But when I try to calculate it. Fluent will not calculate due to this error: Divergence detected in AMG solver: temperature

  iter  continuity  x-velocity  y-velocity      energy           k       omega     time/iter
        Stabilizing pressure coupled to enhance linear solver robustness.

Experiencing convergence difficulties - temporarily relaxing and trying again...

Experiencing convergence difficulties - temporarily relaxing and trying again...
        Stabilizing temperature to enhance linear solver robustness.

Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Error at host: floating point exception

Error at Node 0: floating point exception
Error at Node 1: floating point exception
Error at Node 2: floating point exception
Error at Node 3: floating point exception

Error: floating point exception
Error Object: #f

My boundary conditions settings are:

• Inlet: pressure-far field, Mach number:0.15, gauge pressure:1.8e+05

• Outlet: pressure outlet, gauge pressure:1.8e+05

• Operating condition: operating pressure is 0

I used the Hybrid initialization and coupled solution method (pressure-velocity coupling).

I tried different Mach number, and I found out when I used Mach 0.3, the error has new information :turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 10 cells. And when I tried Mach 0.6, the case runs.

So, my questions are:

• What should I do to solve this problem and make it run at Mach 0.15?

• I don't understand why it could calculate when I increased the Mach number.

Do you have any ideas? I will provide more information if it's needed.

Thanks in advance.

Mou

[ngoctm]

Hi Mou,

The most likely cause is that the under-relaxation factor (URF) for that equation is too large. Reduce the URF and repeat the calculation.

Please make sure the minimum orthogonal quality for the mesh is 0.01 (0.15 is better), the maximum skewness reported in Mesh > Quality is less than 0.93-0.95

A final possible cause of AMG divergence is incorrectly defined as boundary conditions.

Hope this help,

[mou]

Hi ngoctm,

Thanks for the advice, after I changed the URF and it runs!

Best regards,

Mou

[antt]

I am currently analyzing the fluid flow field of a multi-nozzle in three dimensions. However, the following error keeps occurring.

Divergence detected in AMG solver: temperature
absolute pressure limited to 5.000000e+10 in 32400 cells on zone 2

turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 2150 cells

Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Error at host: floating point exception

===============Message from the Cortex Process================================

Compute processes interrupted. Processing can be resumed.

================================================== ============================

Error: floating point exception
Error Object: ()

Error at Node 2: floating point exception

Error at Node 0: floating point exception

Error at Node 1: floating point exception

Error at Node 3: floating point exception

Error: floating point exception
Error Object: #f

mesh quality is
------------------------------------------
Skewness min 2.5942e-07/max 0.40638
aspect ratio min1.0015/max 3.346
orthogonal quality min 0.84878/max 1.
------------------------------------------

I need advice. please help me..

thank you