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VOF for flow problems with inlet and outlet

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Old   March 21, 2006, 04:34
Default VOF for flow problems with inlet and outlet
  #1
Jannifer
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hello,

Anyone have any experience in using VOF model for flow in a channel before?

Would appreciate it if any one can offer any advice

Thanks
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Old   March 21, 2006, 10:56
Default Re: VOF for flow problems with inlet and outlet
  #2
Charles
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What is it that you are struggling with?

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Old   March 22, 2006, 03:03
Default Re: VOF for flow problems with inlet and outlet
  #3
jannifer
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hello

i am just simulating the flow of a slug bubble flowing in a mini channel. however i cannot get the expected bubble shape.

may i know whats the problems?

thanks for your help

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Old   March 28, 2006, 10:19
Default Re: VOF for flow problems with inlet and outlet
  #4
Dustin
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Well, don't use outflow for one thing, it's not supported (even though you can select it).

Beyond that, use a fine mesh to render the interface well and a small enough time step (I usually have to use one less than the one suggested by the Cr=0.25 value).

Make sure to include surface tension...
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Old   April 4, 2006, 03:38
Default Re: VOF for flow problems with inlet and outlet
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jannifer
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Dustin

Thanks for your help

do you include wall adhesion?

also can u furnish me with more details for the model that i should use?

Do i use geo-reconstruct or implicit scheme. how about the ralaxation factor?

hope u can help me with this
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Old   April 4, 2006, 06:40
Default Re: VOF for flow problems with inlet and outlet
  #6
Dustin
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- Usually, I try to run a simpler case without wall adhesion first, to make sure everything else is kosher, then I add the contact angle info in.

- Most of the time, Euler-Explicit with PISO, PRESTO and 2nd Order Momentum for VF and momentum work well for me.

- And I if I didn't mention before, try using as small a time step as is feasible.

- Relaxation factors should be fine as the default values, but you mayu need to lower momentum to 0.5 or so.

Good luck - Dustin

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Old   April 4, 2006, 10:02
Default Re: VOF for flow problems with inlet and outlet
  #7
jannifer
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Heh thanks alot i will give it a try

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Old   April 6, 2006, 14:15
Default Re: VOF for flow problems with inlet and outlet
  #8
Jannifer
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sorry to bother again

but can i check with you if VOF assumes that there no slip between the liquid and the gas phase.

Thank again
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Old   April 6, 2006, 14:26
Default Re: VOF for flow problems with inlet and outlet
  #9
Dustin
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VOF averages the properties of the fluids over an interfacial region.

I would guess that's not the answer you want

- Dustin
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Old   April 6, 2006, 14:37
Default Re: VOF for flow problems with inlet and outlet
  #10
Jannifer
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ya and a momentum equation is used for the entire domain.

But how can we intreprete the fact that the properties is being averaged? does that means that at the interfacial region the velocity of the gas and liquid phase are the same giving slip flow at the boundary?

Thanks in advance for your help

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Old   April 6, 2006, 14:46
Default Re: VOF for flow problems with inlet and outlet
  #11
Dustin
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I'm shooting from the hip on this one, so it ain't gospel.

I think so (that the same wall slip velocity would be used at the interface). Contact angle/wall adhesion would dominate this process (I think) for most cases.

But, wrong may I be....
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Old   April 6, 2006, 14:56
Default Re: VOF for flow problems with inlet and outlet
  #12
Jannifer
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haha okok thanks for your kind help.
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