Learning Forum

[Esivue Eshilama]

I am trying to simulate a multiphase flow in a straight section of pipe. The end goal is to see the visual flow topology (volume fraction of air phase in water). The air volume fraction at the inlet is 1/3. I have used the transient solver and the mixture model but when I view the contour of the air volume fraction, it appears to be uniform (1/3) across the pipe. I expected it to have contours with regions in the pipe ranging from 0 (no air) to 1 as shown below:

Here is what I get below:

I'd really appreciate some help on this issue.

[SRP]

Hi,

Can you please give more information on the boundary condition you employed for the given problem?

Thank you

Saurabh

 

[Esivue Eshilama]

Inlet velocity: 4.5 m/s; Wall roughness height: 4.7e-4; Surface tension constant (water/air): 7.48e-2; Pipe diameter: 0.052m; Pipe length: 1.3m; air volume fraction:0.3333

[SRP]

Hi,

As the air volume fraction is 0.333, it is better to go for  Multiphase ---> Eulerian----> Multi-Fluid VOF model.

You can go through the theory guide: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v222/en/flu_th/flu_th_sec_ifm.html

Also check this section of user guide: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v222/en/flu_ug/flu_ug_sec_mphase_using_steps_eulerian.html%23flu_ug_sec_use_ifm

Please go through forum discussion: Simulating bubble formation in water container (ansys.com)

Thank you

Saurabh

 

[Rob]

To add, have a look at a Baker Chart to understand when (how) flow regimes are established. With a constant volume fraction on the inlet you may need a lot of pipe before anything interesting happens. You did turn on gravity? 

[Esivue Eshilama]

Yes, I did turn on gravity. I'll try those and relate back to you.