Learning Forum

[abhnv11295]

I am trying to simulate a heat pipe in (3D) which has three sections:

 

Evaporator - Constant heat flux (boundary conditions)
Condensor - Constant temperature (boundary conditions)
Adiabatic section - Zero heat flux (boundary conditions)

I am using VOF multiphase model -> Evaporation - condensation model -> Lee model.

Transient simulation with gravity and implicit body force formulation.

Time step size = 0.0001 (1E-04).

 

The simulation runs well for about 10-12 seconds of flow time but then it stops due to this error

 

"Divergence detected in AMG solver: pressure correction        Stabilizing temperature to enhance linear solver robustness.

        Stabilizing temperature using GMRES to enhance linear solver robustness.

Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: pressure correction"

 Even though the simulation was running well for 10-12 seconds (100,000 time steps). What can be the possible reason for this error?

[SRP]

Hi,

This error message is an indication that equation is diverging. The most likely cause is that the under-relaxation factor (URF) for that equation is too large. Reduce the URF by 10%.

Thank you.

[abhnv11295]

I had already changed the URFs. 

Following are the URFs I have kept in my case:

Pressure - 0.5

Density - 1

Body forces - 1

Momentum - 0.2

Vaporazation of mass - 1

Energy - 0.8

[Rob]

Phase change and VOF currently don't always work well. If you look at the flow field a bit before divergence what is happening?