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Overset mesh problem ball falling on liquid surface

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Old   October 12, 2016, 11:35
Default Overset mesh problem ball falling on liquid surface
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avk
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Hello,
I am new to star ccm+ and attempting to learn a overset mesh analysis methodology
Background

I am simulating a free fall of table tennis ball with 40 mm diameter with 2.7 gm mass on liquid surface

For this I modeled a tank 500 mm x 250 mm x 250 mm with VOF flat wave setup to height of 160 mm. Ball domain is 100 mm x 100 mm x 50 mm with center at 190 mm from bottom of tank central to tank if viewed from top

problem is modeled as symmetry on one face of tank with symmetry plane coinciding with symmetry plane of overset mesh of ball. with initial velocity of 0 m/s. Fluid flow is assumed to be laminar

problem experienced
as simulations progress I was expecting liquid level in background mesh and overset mesh to remain same but I am observing that liquid level in overset mesh drops as compared to background mesh because of which I suspect something is not right in my case. I tried to figure this out for quite a long time with no heads-up hence posting here if anyone has seen this sort of behavior and if any one can share any tips for this ?

Referring to boat tutorial has not helped so far

Thanks
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Old   October 13, 2016, 00:58
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Got it resolved, thanks

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Old   July 24, 2017, 14:06
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Can you please explain how you resolved it? Experiencing the same problem.

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Old   July 25, 2017, 03:05
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Well if I remember correctly in my case, I realized that there are 2 separate variables for volume fractions namely Volume fraction of liquid and Volume fraction of heavy liquid for flatVoFWave.

Initially I was using Volume fraction of heavy liquid for flatVoFWave variable to plot contour but it was followed by mentioned experience. Later when I plotted contour with Volume fraction of liquid variable results started making more sense.

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Old   July 25, 2017, 03:24
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This indeed was the case; problem solved.

It's phenomenal that something that trivial can cause bizarre, distorted results - I mean, technically speaking the program should know that the wave doesn't change, and the 'heavy fluid' and the 'liquid' are the same goddamned thing (that's how they were defined!) - but I guess one has to play by the rules to get results here.

Thanks so much for the prompt reply, saved me a lot of time trying to solve a problem which didn't even exist. Cheers!

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Old   October 11, 2019, 03:03
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Quote:
Originally Posted by Jon Faried View Post
This indeed was the case; problem solved.

It's phenomenal that something that trivial can cause bizarre, distorted results - I mean, technically speaking the program should know that the wave doesn't change, and the 'heavy fluid' and the 'liquid' are the same goddamned thing (that's how they were defined!) - but I guess one has to play by the rules to get results here.

Thanks so much for the prompt reply, saved me a lot of time trying to solve a problem which didn't even exist. Cheers!

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Hey there,

I'm facing a similar problem right now, could you further explain your solution on this?
Indeed there are two variables, Volume Fraction of Light (and Heavy) Fluid of Flat Vof Wave and Volume Fraction of Air/Water (user defined).
Which of them should I choose to initialize my simulation and the volume fractions in the inlet/outlet boundaries?

Would be glad to hear from you (=
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