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Fluent v15 multiphase flow b.c. failure Non-channel flow

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Old   August 23, 2014, 02:26
Default Fluent v15 multiphase flow b.c. failure Non-channel flow
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mike h
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I have been running v15 for a 2 phase (water-air) flow using channel flow on a body half in the water. answers for Fr<1 are reasonable but for Fr>1 are quite bad in terms of predicted load and resistance.

So tried running w/o channel flow setup.
have been using symmetry for the 4 outer walls of the zone, vel inlet on the upstream and press outlet on the downstream.

using implicit vof, channel flow off/channel flow wave off.

i initialize the water zone using patching from marked cells. all is ok at the start.

In only a few time steps, the upstream plane is 100% air and then starts to contaminate the 3 lower zone planes near the inlet vel plane (the upper was initialized to 100% air so there's nothing to change.) this is weird.

see the attached image after a couple of time steps to see the contamination of air in what should be the water part of the zone

not really a bc failure but more something screwy maybe in the vof implementation. btw explicit vof had no effect on this, same result.

i have tried different outer zone bc's like all vel inlet and slip walls and nothing stops this problem. (evidently there is something in the channel flow option that precludes it but i don't know what)

in the past with starccm+ or numeca this never happened and the no 'channel flow' was used in any case.

anybody ever see anything like this? i have contacted ansys but no answer on it so far.


anybody successfully done vof 2 phase flows w/o channel flow option? if so what did you set?

getting tired of this problem.


THANKS!
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Old   September 22, 2014, 07:41
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Antonio Casas
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Try using inlet mass flow. Check this out: http://youtu.be/y4Sd__Viw-0
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