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Calculation of circulatory and rise velocity using level set method

Posted Jun 7, 2012, 1:30 p.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD) Version 4.2a 4 Replies

Anurag Kumar Tiwari
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Dear Invar,
I tried to calculate circulatory using intop1 operator but I failed. I would like to know to calculate circulatory and rise velocity of a bubble rising in a stagnant fluid. Thank you in advance
4 Replies Last Post Dec 28, 2015, 12:10 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jun 8, 2012, 3:45 p.m. EDT
Hi

that is a good remark, the intop() operator only applies to a defined boundary, and in the level set method you have only virtual boundaries

It's not a physics I'm used to work with so I'm not sure what to propose. Have you cheked the models in the model library ?
Perhaps you can define a Results Data Set - cut line/circle and integrate that if this works for a line I'm not sure how to generate a circle, with cylindrical coordinates ?

If nobody ca give you a tip here, probabl the best is then to as "support". If so pls reportack it's an interesting question ;)

--
Good luck
Ivar
Hi that is a good remark, the intop() operator only applies to a defined boundary, and in the level set method you have only virtual boundaries It's not a physics I'm used to work with so I'm not sure what to propose. Have you cheked the models in the model library ? Perhaps you can define a Results Data Set - cut line/circle and integrate that if this works for a line I'm not sure how to generate a circle, with cylindrical coordinates ? If nobody ca give you a tip here, probabl the best is then to as "support". If so pls reportack it's an interesting question ;) -- Good luck Ivar
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Jun 11, 2012, 9:05 a.m. EDT
You should try integrating the quantity of interest multiplied by an operator that represents the volume fraction of the fluid you want to measure. If Vf1 is the volume fraction variable I would try either multiplying by “*(Vf1>0.5)” or even just “*Vf1”.

Nagi Elabbasi
Veryst Engineering
You should try integrating the quantity of interest multiplied by an operator that represents the volume fraction of the fluid you want to measure. If Vf1 is the volume fraction variable I would try either multiplying by “*(Vf1>0.5)” or even just “*Vf1”. Nagi Elabbasi Veryst Engineering
Anurag Kumar Tiwari
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Posted: 1 decade ago Jun 19, 2012, 10:29 a.m. EDT
Dear all
Finally I got the answer that we can integrate(surface) the delta function which is equivalent to perimeter of the bubble. For level set method delta function is 6*abs(phils*(1-phils))*(philsr^2+philsz^2+eps). Similarly, the perimeter or circumference of a circle with equivalent diameter da which has an area equal to that of a bubble can be calculated by (intop1((phils>0.5)*2*pi))^0.5.
circulatory = perimeter of area equivalent circle/perimeter of bubble
For a perfectly circular bubble the circularity is equal to unity and will decrease as the bubble
is deformed.

Terminal velocity can be calculated using following expression
Vt = (intop2((phils>0.5)*w))/(intop3((phils>0.5)))

Once again thank you both Invar and Nagi

Neel
Chemical enginnering
Dear all Finally I got the answer that we can integrate(surface) the delta function which is equivalent to perimeter of the bubble. For level set method delta function is 6*abs(phils*(1-phils))*(philsr^2+philsz^2+eps). Similarly, the perimeter or circumference of a circle with equivalent diameter da which has an area equal to that of a bubble can be calculated by (intop1((phils>0.5)*2*pi))^0.5. circulatory = perimeter of area equivalent circle/perimeter of bubble For a perfectly circular bubble the circularity is equal to unity and will decrease as the bubble is deformed. Terminal velocity can be calculated using following expression Vt = (intop2((phils>0.5)*w))/(intop3((phils>0.5))) Once again thank you both Invar and Nagi Neel Chemical enginnering
Sonali Kulkarni
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Posted: 8 years ago Dec 28, 2015, 12:10 a.m. EST

I am simulating deformation of an water drop due to electric field (outer fluid is oil), using phase filed model. I am getting the volume fraction plot. I want to measure the change in the area of the drop with time. What expression should i plot to see the area change in the water drop?
I am simulating deformation of an water drop due to electric field (outer fluid is oil), using phase filed model. I am getting the volume fraction plot. I want to measure the change in the area of the drop with time. What expression should i plot to see the area change in the water drop?

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