# swak4Foam to calculate bubble velocity

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 March 1, 2012, 13:28 swak4Foam to calculate bubble velocity #1 Senior Member   Nima Samkhaniani Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,232 Blog Entries: 1 Rep Power: 18 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?

March 1, 2012, 15:10
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Bernhard Gschaider
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Quote:
 Originally Posted by nimasam 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

 May 24, 2016, 14:56 #3 Member   Arsalan Join Date: Jul 2014 Posts: 72 Rep Power: 5 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. zeynab hoseini likes this.

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