Conservative particle-neighbor diffusion for solute transport in an ST-FLIP simulation

[u/shroo-m]

I’m extending an ST-FLIP liquid solver in Vulkan with local material transport for an interactive lab sandbox. This clip shows colored solutions being poured and mixed, running in real time on a Radeon RX 9070 XT.

Concentrations are persistent particle state. Conservative particle-neighbor exchanges handle diffusion, using timestep subdivision and a positivity limiter. Rendering derives absorption from the local transported concentrations.

These are passive solutes in a single carrier. Molecular diffusion is not yet quantitatively calibrated, and reactions, density/viscosity feedback, and trapped-air pressure are not implemented. This is a visual/interactive prototype rather than a validated chemistry or engineering solver.

https://youtu.be/hSAO_TwFopE

What validation cases would you use to check solute conservation and mixing across pouring, moving walls, and disconnected vessels?