Visualization of Nanofiltration and Reverse Osmosis with Lennard-Jones particles

This simulation is a crude attempt to illustrate the processes involved in membrane filtration techniques. This stands in contrast to depth filtration, in which the particles are retained in a complex network in the filter material itself. In membrane filtration, on the other hand, particles that are too large to pass through the pores of the membrane and are thus retained.
However, mebrane filtration is rarely carried out as shown here. (dead-end filtration)
This setup promotes the build-up of a filter cake, whereas in cross-flow filtration and pervaporation, the liquid is pumped tangentially to the membrane until the desired degree of clarification is achieved.
(A video on tangential filtration will hopefully appear soon).
The temperature is kept constant with a Berendsen-thermostat

Particles of two different sizes interacting with a Lennard-Jones(exp, 6) potential are placed on a plane. There are separate LJP model parameters for each particle type, as well as for the interaction of small particles with large particles. The boundaries, on the other hand, have only the exp. repulsion potential.
The gaps between the obstacles are so narrow that a particle needs a certain amount of energy to enter the gap, otherwise it will be repelled. Once it is in, it has no problem getting to the other side (if there is no particle there yet).
The smaller particles are coloured according to the number of neighbouring particles.
In the first clips, the upper and lower wall boundaries are replaced by periodic boundaries so that particles that exit on one side appear on the other side (as soon as the centre of the particle crosses the boundary)

In the first clips, the particles are forced through the "membrane" by acceleration.
The red particles are four times as heavy as the "solvent" particles, except when they are smaller. Then the weight ratio is 1:3
00:00 Acceleration, Radius ~1:5
01:06 Acceleration, Radius ~1:2, Clogging of membrane
02:12 Compression, Radius ~1:4
03:19 Compression, Radius ~1:3
04:19 Compression, Radius ~1:3, 2x Playback Speed
04:52 Compression, Radius ~1:2, Leakage^^
05:59 Compression, Radius ~1:2, with Velocity colormap
07:05 Compression, Radius ~1:5, with Velocity colormap

Видео Visualization of Nanofiltration and Reverse Osmosis with Lennard-Jones particles канала Hali Hammer