Learning Forum

[desouzadacosta]

Hi All

I am trying to simulate a tank filling from the bottom, valve opening and emptying .

The filling is going fine, but after the opening of the valve, the emptying operation is showing divergence in the k field :

Global Courant Number [Variable Time Step Criteria] : 7.135128
Updating solution at time levels N and N-1.
 done.
 physical-dt  1.0000e-05
 
  iter  continuity  x-velocity  y-velocity  z-velocity           k       omega    vf-water     time/iter
 
 reversed flow in 259 faces on pressure-outlet 14. 
 
 reversed flow in 259 faces on pressure-outlet 14. 
 
 reversed flow in 259 faces on pressure-outlet 14. 
 
 reversed flow in 259 faces on pressure-outlet 14. 
        Stabilizing k to enhance linear solver robustness.
 
Error: Divergence detected in AMG solver: k
 
Error: Divergence detected in AMG solver: k
Error Object: #f.

I already tried the turbulence damping, k-epsilon, k-omega, implicit/explicit VOF, reduced time step, options without success.

I reproduce below some pictures of the simulation. Any expert advice is very welcome.

[DrAmine]

How is the opening of the valve modeled? Switching boundary condition? When dies divergence occur?

[desouzadacosta]

Thanks for the reply. It is changed from wall to interior using execute commands, after some volume of water is reached.

[DrAmine]

And when does it diverge?

[desouzadacosta]

At t = 3.672 s

[DrAmine]

Ok. What is the boundary condition applied in the bottom? Try with Tait equation for water.

[desouzadacosta]

Sorry. How to use Tait equation?

[DrAmine]

Compressible liquid.