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-   -   swak4Foam to calculate bubble velocity (http://www.cfd-online.com/Forums/openfoam/98032-swak4foam-calculate-bubble-velocity.html)

 nimasam March 1, 2012 13:28

swak4Foam to calculate bubble velocity

hi former
i guess, it should be possible to access a bubble velocity with swak4Foam
but i dont know how the procedure can be?
the procedure should be like that:

1) select all cells with alpha < 0.5
2) calculate the gravity center in each time step

any comment or suggestion?

 gschaider March 1, 2012 15:10

Quote:
 Originally Posted by nimasam (Post 347134) hi former i guess, it should be possible to access a bubble velocity with swak4Foam but i dont know how the procedure can be? the procedure should be like that: 1) select all cells with alpha < 0.5 2) calculate the gravity center in each time step any comment or suggestion?
Why use a cutoff? that way you're going to get jumps in your result. Something like

"(pos()*vol()*(1-alpha1))/sum(vol()*(1-alpha1))"

(with an accumulation sum) might give you the center of the "non-fluid".Have a look at my presentation from the last workshop (you'll find it on the swak4Foam-page on the Wiki). Slide 76 has a similar application.

BTW: if you're interested in the velocity of the liquid interface then you might want to have a look at slide 155 where it s demonstrated how to calculate that with sampledSurfaces

 arsalan.dryi May 24, 2016 14:56

Hi Foamers,

I'm doing a 3D simulation of two and three bubble rising using a modified interFoam solver and I need to bubbles centre position, velocity and surface area.

For a single bubble rising I used swak4Foam expressions for example for bubble centre position in Y as follows :
Code:

```    bubbleCentreY     {         type swakExpression;         valueType internalField;         verbose true;     variables (     "Vol= sum (alpha1 < 0.5 ? vol() : 0);"     "VolY= sum (alpha1 < 0.5 ? pos().y*vol() : 0);"        );            expression "VolY/Vol";         accumulations (         min                );         }```
Is there a way to compute two or three bubble properties in this manner?