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Zaktatir January 14, 2010 04:51

domain definition
I am trying to simulate droplets breakup in stratified air water flow: that means i ll have:
-continuous air
-continuous water
-water droplets

which definition is the most convenient for this simulation

stumpy January 14, 2010 13:16

Air and Water would be Eulerian phases (like a free surface simulation) and water droplets would use Lagrangian particle tracking, with a break-up model as necessary. I've never tried to set this up, so there could be limitations in CFX.

Zaktatir January 14, 2010 14:21

unfortunately it doesn't work...

are ther any breakup or separation model based on the KH-theory

Zaktatir July 6, 2010 04:37

I modeled the problem with two continuous phases and one disperse.. but when my droplets become bigger the flow pattern changed and did not suit the normal flow pattern? what shall i do
thx Jessica

Zaktatir July 7, 2010 07:39

okay i think there is no interest or idea.. that s why i change my question...
is it possible to activate a phase while calculating (phase not active till something happen)

ghorrocks July 7, 2010 08:03

Yes, definitely. You can make a source for the volume/mass fraction which is dependent on some condition being met, maybe an elapsed time. It can trigger the source term to start generating the mass/volume fraction.

Zaktatir July 7, 2010 08:21

yeah i made this but i get another flow patter as expected.
I should define a positive source: that means that droplets are being separated leading a negative source for the water phase


ghorrocks July 7, 2010 19:03


yeah i made this but i get another flow patter as expected.
What is a "flow patter"?

Zaktatir July 8, 2010 02:50

sorry flow pattern..

I made a condition: if relative velocity betwwen water/air phase exceeds a critical velocity there will be water stripping and droplet formation. At this point the droplet phase should be activated (in each cell)... I introduced source term (for the droplet phase) and the same source term but negativ for the water phase (is this correct).. The Diameter will be then calculated (capillary waves approach)

The flow pattern should be similar to that without this additionally phase but it does not work??

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