[aruelle]

Hello

I am using a VOF model for the simulation of a diphasic flow entering a pipe and then spilled in a tank. The entry of the diphasic flow is defined as a velocity inlet. The volume fraction of the velocity inlet in fixed to 0,3. Convergence is ok. Moreover, i saw different works where the volume fraction of the velocity inlet is different from 1 or 0.
Nevertheless, i read in an Ansys document that for velocity inlet, only one phase can enter; therefore, only one phase can have the inlet volume fraction set to 1 and nonzero inlet velocity.
So, can somebody help me about this? Is it allowed and physically correct to impose a volume fraction of 0,3 to a velocity inlet with the vof model?
Thank you very much for your help,
Amélie

[sega]

Originally Posted by aruelle

Hello

I am using a VOF model for the simulation of a diphasic flow entering a pipe and then spilled in a tank. The entry of the diphasic flow is defined as a velocity inlet. The volume fraction of the velocity inlet in fixed to 0,3. Convergence is ok. Moreover, i saw different works where the volume fraction of the velocity inlet is different from 1 or 0.
Nevertheless, i read in an Ansys document that for velocity inlet, only one phase can enter; therefore, only one phase can have the inlet volume fraction set to 1 and nonzero inlet velocity.
So, can somebody help me about this? Is it allowed and physically correct to impose a volume fraction of 0,3 to a velocity inlet with the vof model?
Thank you very much for your help,
Amélie

For a volume fraction you will need a volume, where a boundary is a face.
So this does not make sense.

You want to set up 30% of the inlet with phase one and 70% of the inlet with phase two? Am I guessing right?

I would split up the inlet into two (30%/70%) and define the VOF-variable to 0 at the one and 1 at the other.

[kkaptan]

I hope this message finds you well. I am reaching out to seek assistance regarding a challenge I am facing while trying to calculate the free surface elevation in Fluent.

My aim is to accurately determine the free surface elevation when a wing moves over the free surface. Initially, I attempted this by utilizing the "Open Channel Flow" option. However, despite setting the pressure inlet boundary conditions, I encountered an issue where the free surface did not deform as expected, even though the iterations proceeded without any apparent problems. I have attached a screenshot illustrating this problem for reference. In this particular simulation, the velocity (U) is set to 10 m/s, and the ratio of the water depth to the wing's chord length (h/c) is 0.2.

Subsequently, I modified the inlet boundary condition to a Velocity inlet. However, I found that there was no option available to define the free surface level in this configuration. My attempt to address this by using a region and patching it after initialization did not yield the desired results, as there still remained a small area where air was present, as evident from the attached screenshot.

In an effort to resolve this issue, I experimented with using two different inlets, namely "inlet_air" and "inlet_water." Unfortunately, this approach resulted in the analysis diverging. I suspect that I may have made an error in defining the boundary conditions.

I would greatly appreciate any insights or guidance you could provide on this matter. Your expertise and assistance in navigating through this challenge would be invaluable to me.

Thank you very much for your time and consideration. I look forward to hearing from you soon.