CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM (http://www.cfd-online.com/Forums/openfoam/)
-   -   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?

Thanks in advance,
Best Regards,
Arsalan.


All times are GMT -4. The time now is 05:39.