I want to simulate two fluids shearing past each other, to show that they form a vortex naturally. (That is, I don't want to put an artificial vortex to make the fluids rotate. I want it to happen as a natural result of the physics simulation.) I don't need to render it, but I would like to have it show the velocity of the particles, as done in the tutorial below.
I followed the technique in Maxim Sachs' tutorial on YouTube on how to do Fluid Flow Simulations. I made an emitter of particles and set its physics to "fluid." I duplicated it, flipped it 180 degrees and aimed it at the first emitter. (So that both fluids belong to the same particle system.) But when I animate it, the fluids flow past each other as if neither was there. (That is, no collisions between the two particle systems.)
Can such a simulation be done in Blender and what's the trick to allowing the two fluids to interact?
==== Update: Since asking the question, I've tried another tack. I am using a fluid domain and created two inflow volumes. I get some mixing that way, although I haven't gotten parameters right to get a vortex yet. But even if I get the vortex, I don't see a way to color the two inflows. Blender sees the fluids one (probably related to doing it all in the domain.) I've tried coloring the inflows with red and green materials, but no difference.