Learning Forum

[Nicolo]

Hi

I am trying to simulate a two phase flow of air and water in a pip with cross section if a semicircle. the area is about 1mm2.

the fow of water is about .006m/s and flow of air is about 1.5m/s. 

I use Volume of fluid and implicit mode and ticked implicit body force.

I tired case of steady state and transient but both after a couple of thousand of iterations in reaches the errore of floating Point execution.

As I already know this errore can be due to the bad meshing I have reported the mesh for you here.

Min quality is .5 but of of the mesh is above .9

Max skewness is .4 but most of the mesh is below .1.

in case of transient flow I used time steps of .01s and it still diverged

 

What is worthy to mention is that when I use initialize bottom and choose air inlet it suggests a wrong value!

 

Also when I use explicit it keep telling me that 

Global Courant number is greater than 250.00 The

velocity field is probably diverging. Please check the solution 

and reduce the time-step if necessary.   I have to reduce it to .002s so it would not give that errore which is really small!

 

 

I would really appreciate it if you can tell me how I should get convergence from this simulation, or if I should change settings/mesh or... here

 

thanks in advance

 

 

 

 

 

[Rob]

First off read the documentation regarding inlets for the VOF model. Then work out where the free surface ought to be and read how the surface is tracked. 

[Nicolo]

Thanks Rwoolhou for the answer, actually it is a pipe with semi circle cross section so the top part is not a free surface, if that is what you are referring to.

if not and I still need to read it could you please let me know if you are referring to a certain documentation? If not I would appreciate it if you introduce one to me.

Actually the inlets I chose where based on the real physics of my problem.

also I would appreciate it if you let me know if my mesh is ok?!

[Rob]

Are you solving air and water flow?  I'm referring to the Fluent User's Guide. Click on Help and you'll need to navigate a bit to get to it.