Foam is dying?

[Ivaylo Katev]

And some more explanations
Perhaps you have noticed that usually the size related units are using the scene units, but the velocity threshold is not using the scene units, it's in grid units, that's why changing the cell size changes the foam birth.
apparently it's a bit unexpected for the users, and one may ask why the velocity threshold is not in scene units that will make it cell size independent. The reason is simple - when you run a sim, you have no idea what the threshold must be. But using the preview ranges you can measure what is the liquid velocity in the area that you want to produce foam, and putting the measured value as threshold you have a good starting point for experimenting

[omere]

Thank you for that.
now i have issue with he behavior of the liquid.
as i increase the cell size, the liquid is moving much faster, too fast and it looks like it was speed up.
i tried to increase the SPF but it didn't changed that.
i've attached in this link 3 files:
one is with cell size 0.4 and SPF 4.
one is with cell size 0.2 and SPF 4.
one is with cell size 0.2 and SPF 8.

https://we.tl/ofCkzJLjRt

what am i missing here?

[Ivaylo Katev]

i can't see speed difference in the attached files, in all of them the beer hits the glass bottom in frame 7

[omere]

true, but the splashing is much faster after the hit. looks like fast forward

[omere]

so i have found the problem and it's the scene scale. after increasing it under dynamic from 1 to 3 i got much more smooth simulation and also didn't have holes in the liquid.
i'm attaching a link to the compression that i've did between scale 1 and 3:
https://we.tl/lfZU4elb8R

[omere]

And some more explanations
Perhaps you have noticed that usually the size related units are using the scene units, but the velocity threshold is not using the scene units, it's in grid units, that's why changing the cell size changes the foam birth.
apparently it's a bit unexpected for the users, and one may ask why the velocity threshold is not in scene units that will make it cell size independent. The reason is simple - when you run a sim, you have no idea what the threshold must be. But using the preview ranges you can measure what is the liquid velocity in the area that you want to produce foam, and putting the measured value as threshold you have a good starting point for experimenting

thank you very much.
but i still don't understand the relation between the Cell size and the Vel.Threshold.
am i measuring the potential end result?

[Ivaylo Katev]

the velocity threshold is measured in cells/sec, changing the cell size the meaning of the value is changed too.

[omere]

of course, but i didn't understand how you are doing the estimation of the vel.threshold value.
if my cell size is 0.2, how do i calculate the rough value that i need according to your explanation?

[Ivaylo Katev]

for the estimation you need to run pure liquid sim firs, the preview gives ability to measure the value of certain channel using the visualization range.
each channel has upper and lower boundary of the value with colors assigned of both of them. when you tweak the visualization range by the spinner, the preview responds and you can sere which cells appear/disappear in result of your tweak.
the usual way to measure the velocity is to set the upper boundary to very high value and to tweak the lower boundary. the slower you tweak the value, the preciser is the measurement.

[omere]

i see now.
thank you very much.
what do you think about my solution for the liquid behavior? the one that i changed the scene scale to 3.
do you think that this is the right approach or is there a better way to control the behavior?

[Ivaylo Katev]

many simulations are done in bigger scene scale, it's widely used.

[omere]

good to know.
thank you

[omere]

how can i achieve less of a straight line between the foam and the liquid?
i want the foam and liquid to mix like in the photo that i'm attaching

[Ivaylo Katev]

in general this is hard to achieve, but you can try to play with the size multiplier of the foam shader.
the idea is to increase the size of the bubbles until the underwater bubbles become big enough to be in contact