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Laminar-Two-Phase-Flow - Filling of a Pot

Posted 25 nov. 2012, 08:19 UTC−5 Fluid & Heat, Computational Fluid Dynamics (CFD) Version 4.3 2 Replies

Linda Reuter
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Hi,

I've done a lot of simulations with comsol 4.3 and they worked. My modell is a pot which is filled with water.I'm using the laminar two phase flow in 2D with the phases water and air. i have two boundaries inlet of water and outlet of air. Now I have following problems:
(1) Sumtimes the air turnes its direction and my defined air outlets become inlets. the results are problems with the singularity. i could sometimes handle that by putting an little air inlet next to the air outlet. but this not allways helps.

(2) I change the inflowvelocities in different simulations. Now sometimes the pot is filled much to fast as it shoul. But i haven't changed anything in the settings except the velocity. The flow is incompressible. Does anyone know, why this happens?

I hope anyone can understand me :)
I'm glad for every answer!
2 Replies Last Post 27 nov. 2012, 12:26 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 26 nov. 2012, 00:55 UTC−5
Hi

I cannot explain all of it but I can remind you that an "inlet and outlet are similar BC and an inlet can also be an outlet & vice versa. There is a nice discussion in the KB and in one of the model library models, on how to adapt the in/outlets depending on i.e. gravity, pressure etc

--
Good luck
Ivar
Hi I cannot explain all of it but I can remind you that an "inlet and outlet are similar BC and an inlet can also be an outlet & vice versa. There is a nice discussion in the KB and in one of the model library models, on how to adapt the in/outlets depending on i.e. gravity, pressure etc -- Good luck Ivar
Shawn.F
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Posted: 1 decade ago 27 nov. 2012, 12:26 UTC−5
Linda,

I guess more information is needed to completely understand the problem. However, due to my own experience, you may lose mass! Usually, COMSOL has problem to keep mass conserved in multiphase flow simulations, the mass loss is mainly for the fluid with higher density. Check the mass conservation, also turn your governing equation to conservative form, most likely you will get rid of this issue.

Good luck.

Shawn

PS. are you using Phase-field or Level-set?
Linda, I guess more information is needed to completely understand the problem. However, due to my own experience, you may lose mass! Usually, COMSOL has problem to keep mass conserved in multiphase flow simulations, the mass loss is mainly for the fluid with higher density. Check the mass conservation, also turn your governing equation to conservative form, most likely you will get rid of this issue. Good luck. Shawn PS. are you using Phase-field or Level-set?

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