Learning Forum

[javat33489]

Hello everyone. I'm working on a water + gas VOF problem.
I set the water density to 700 so it resembles oil. I'm using methane as the gas.

I'm using a simple flow chart:

My system's total water flow rate is 500 m³/day, gas flow rate is 1000 m³/day, and the outlet pressure is 6 MPa.
I converted everything to a mass flow rate of kg/sec, and the result is 4 kg/sec for water and 0.00773 kg/sec for gas at the inlet.

But when calculating, I get a FLOATING POINT EXEPTION error. Why? I entered everything correctly.
Below are my calculation settings. Please take a look at where I made a mistake.

[Rob]

It's diverged, so start with the mesh and work on from there. Why are you running VOF with a dispersed interface: that's really not a good combination. 

[javat33489]

Sir, the grid is fine.

If I don't enable the VOF model and run the system on water or gas only, everything works fine. But as soon as I enable the VOF and phases, I get an error.

Sir, I also tried SHARP, but it doesn't help.

[Rob]

And the time step size? Given the potential speed difference which flow regime are you working in? And I don't mean laminar/turbulent. 

[javat33489]

sir I have simplified the problem to explicit
and also made a dynamic timestep, I also reduced it a lot
the calculation takes a very long time but it works
sir, tell me this correctly?

 

[Rob]

If it's works then it's probably OK. Whether it's optimal, going to converge well or give a physically meaningful result is an entirely different set of questions.