Learning Forum

[i.tamunodienye2]

When i use mass-flow inlet as inlet BC, the volume fraction does not come up to indicate the fraction for the liquid phase. In this case, how do one monitor the volume of gas or liquid?

[aitor.amatriain]

You can modify it in Boundary Conditions - Phase - name of the phase (on the left side of boundary type and ID).

[i.tamunodienye2]

Hi Aitor Please can you provide me with photo shot of what you mean.

[Rob]

[i.tamunodienye2]

When i use "velocity-inlet" as my inlet boundary condition, the volume fraction is indicated in the multiphase tab of liquid-phase or secondary phase. See blow
However, this is not the case when i use mass-flow inlet as my inlet boundary condition. No volume fraction is indicated as the multiphase tab does not comes up yet the volume fraction of the phases are important to me. Please in this case what do i do.
Secondly, i will need to monitor the volume fraction of gas, pressure and velocity. Area-weighted average and mass-weighted average, which of these report definitions are appropriate if mass-flow inlet is used as the inlet BC

[Rob]

You'll need to set the mass flow of each phase rather than the fraction. It's a better solution if you have two phases with very different densities.
Both reports will work, but need to be used with some caution. Area averaged will skew results if the velocity isn't uniform, mass average may skew towards the heavier phase. Both return the correct mathematical values, it's just whether they're useful. For multiphase I tend to track mass of phase at a location and work from there.

[i.tamunodienye2]

Yes, it is two phase, air(gas) and water(liquid).
Ideal gas is selected from the density drop down menu of the air material.
Water(liquid) density is as given in the material property in fluent (998.2kg/m3)
I have set the mass-flow rates as follows for both air(gas) and water.
gas-inlet(mass-flow-inlet)


liquid-inlet

I also want to track the volume fraction based on the set-up shown below. This will help me determine some flow regimes occurring in the domain.
I want to ask which set-up is appropriate if i use mass-flow rate as my inlet BC. Again, could you please help me understand how to set-up the mass fraction and it's usefulness.


Thanks

[i.tamunodienye2]

I also want to track the volume fraction based on the set-up shown below. This will help me determine some flow regimes occurring in the domain.
I want to ask which set-up is appropriate if i use mass-flow rate as my inlet BC. Again, could you please help me understand how to set-up the mass fraction and it's usefulness.
This is a correction of my previous post.

Thanks

[aitor.amatriain]

Set-up in terms of what?

[i.tamunodienye2]

The figure shows a plane surface monitor.
The set-up is to report the volume fraction of the phase 1-gas.
Since i am using mass flow rate as my BC, i wanted to ask the appropriate report type, whether mass-weighted average or area-weighted average.

[Rob]

Check the maths definitions, I think you want area weighted volume fraction and mass weighted for mass fraction. might remember: I've been giving live training to a Uni group and need a lot more tea....

[i.tamunodienye2]

Thank you.
I am interested in the training.
Is it specific or what will benefit all.
Let me have the training link (webex, zoom etc)

[Rob]

It was a live event organised by the University: if you speak to your course leader they can contact the local office to arrange for an equivalent (paid for) event.