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leff April 10, 2011 12:34

Filling Tank with Water
I'm dealing with a transient problem of filling a tank with water.
The tank has a hole at the top, through which water leaks into it.
The water then hits a horizontal plate at the middle of the tank and continues to flow to its bottom.

I've used the same guidelines as presented in the "Tank Flushing" example in Ansys workshops.

The problem is solved as 2-phase flow.

Unfortunatly, the boundary between water and air isn't sharp enough at the zone where water hits the horizontal plate inside the tank.

Time steps are small enough, so convergance criterion of 1e-4 is met.
The homogeneous model is used for the multiphase flow, along with k-e turbulence. Free surface model option is set to Standard.

Water-Air surface tension coefficient is set to 0.072 N/m.
Continuum Surface force with water as primary fluid option is chosen for Surface tension model.
Free Surface option is set for the Interphase Transfer.

Please help me out, what could be the problem?

I've attached the following:

CFX file of my model:
CFX file of Tank flush example:
Tank flush workshop presentation:

Thanks in advance!!

ghorrocks April 10, 2011 22:27

Is your mesh fine enough to resolve the surface? I assume there is a thin water film on the horizontal plate. You will need to have several elements through this thickness to resolve the liquid and gas. If you do not resolve this the model will just blur the interface and never recover - which is what you are seeing.

leff April 11, 2011 04:22

Thanks for your fast reply!

I've indeed considered that reason. Although, the element thickness for the water film formed on the horizontal plate is 2 mm. Don't you think it's enough?

Thanks again!!

ghorrocks April 11, 2011 06:20

You have not understood what I said. The element size is determined by the minimum flow feature size you want to pick up. You probably need at least 5 elements to capture the film (and even this is horribly coarse) and if the film is 1mm thick then you need elements about 0.2mm in length.


Don't you think it's enough?

leff April 12, 2011 08:51


I'll give it a shot.. Hope I'll have good news to post next time :D

Thanks a lot for your help!!

rejkin October 1, 2011 09:30

File for the tank flush example
I know this is an old thread but I'm trying to get the Tank Flushing example to work but I can't find the actual flush.cfx5 mesh file to even start the tutorial. Does anyone have the file?
The file uploaded in the OP's post isn't available anymore. It would be a great help thanks! :D

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