Hi Dr. Sassi, thanks for the explanation and the time you took for these test
The first one is an approach I already used before, but wasn't happy about the bubbles having no interaction with the surface. Until, I've seen your second test, and realized you can mesh with a volume builder and use a cloner for particle geometry. That could work if I make the bubbles not subtract but add to the builder.
I was playing around with the new liquids, and was wondering if it would be possible to create rising bubbles inside a container with liquid particles (imagine a glass of sparkling water). I was under the impression that liquid particles could interact with other particles, and I wanted the new particles to move organically with the liquid and gather on its surface, so I put an emitter inside the initial liquid volume and set a lower density with the math modifier, but the emitted particles don't move at all. I tried adding a liquify modifier to the emitted particles, and they seem to interact with the liquid particles but won't rise towards the surface despite the lower density. If I move the emitter above the initial liquid volume, the particles fall and stay on the surface as expected, but only if I use the liquify modifier. Playing with Mixture ID didn't work either.
So, my question is: do liquid particles interact only with other liquid particles? If so, is it possible at all to have particles generated from the inside of a (liquid) particle group?
Here's a test file to show the issue.