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sajeesh July 8, 2013 09:35

Eulerian VOF method-outlet boundary?????

I am doing a 2D simulation for the movement of a water droplet having Diameter 25 micrometer through a channel of cross scetion 50 micro X 500 micro..
Using Eulerian VOF coupled method to explicitly define the velocity of droplet and oil phase

I patch the droplet phase and assign a volume fraction of 1 to that water droplet patched region

I am using transient case with double precision

Oil as primary phase and secondary phase as droplet
scheme: phase coupled SIMPLE gradient : Least sqaure method Momentum : first order upwind volume fraction: geo construct

Inlet BC: velocity for oil and droplet volume fraction zero and droplet velocity also at inlet

when i am using Outlet boundary condition
I have to define the back flow volume fraction.
initially If i give the back flow fraction as 0 the simulation running fine and give the correct tracking of interface also

For me i want to eject the droplet from the exit.But by this condition after the simulation the droplet is stuck at exit.solution gets stopped by the high courant number

Similarly i tried with outflow that time also simulation perfect upto reaching the outlet then again the simulation stopped and the droplet is not going out.

When i tried outlet boundary condition with back flow volume fraction of droplet as 1 it is showing error ->Solution diverging ..velocity diverging .Global courant number more than 250..

Please help me to eject the droplet from the channel during simulation.For that what BC should i give at outlet...

My email ID

Thanking You


otsigun July 10, 2013 04:34


I am also working on similar Project on wetting Dynamics of an indium droplet. Can you send me your files, so that I can recommend something

sajeesh July 10, 2013 08:25

sir what files you want....

case and data file

otsigun July 10, 2013 09:26

yes please send me case and last data file so that i can look through

sajeesh September 23, 2013 01:38

did you get my mail..have seen the files....pls reply me..if you got it


sajeesh September 23, 2013 01:59

did you get my mail..have seen the files....pls reply me..if you got it


otsigun September 26, 2013 03:34

Hi saajesh:

I think you should try like this:

1 Finer mesh

VOF method instead of Euler

Implicit instead of explicit


Pressure based Coupled

Least square cell based



Small time steps (like 1e-6)

My droplet and tank project with wall adhesion worked like this

Sorry for the late answer, Good luck!

sajeesh September 26, 2013 09:39

Thanks sir for reply

How i can give velocity for the droplet if i select the VOF model

I want to give different velocity for the droplet.

To study the internal external velocity vectors at differnt flow rates of discrete phase


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