The simulation of filter processes with the FilterDict module consists of the following steps:

1. Fluid flow: The flow through the (clean or partially clogged) filter is computed by solving the appropriate equations within the fluid phase.
2. Particle Tracking: Particles are tracked in the calculated flow field. Tracking of particles is based on solving an ordinary differential equation, and includes drag forces, electrostatic attraction between particles and filter surface, as well as diffusive motion. Within one batch, the particles are treated as independent objects. It is always assumed that the particle density is low and that the moving particles have no effect on the flow. Therefore, FilterDict can only be used in applications where these assumptions hold. This is the case in most areas of air and liquid filtration. It does not hold for sludge filtration, where the particles and their interaction determine the properties of the fluid.
3. Particle Collisions (at Surfaces): When a moving particle collides with a solid surface, the collision model decides whether the particle sticks to the surface or bounces off and continues traveling.
4. Particle Capture (in Porous Materials): When a particle moves through a porous material, the particle may be deposited inside of the material. The pass through model decides how probable it is for the particle to move through the material layer. This is only applicable if both the particle and the porous material are unresolved by the voxel grid, i.e. particles and pores are smaller than the voxel length.
5. Filter Clogging: Particles that stick to the surface after a collision and particles that are captured inside a porous material do not continue their movement. Rather, they are considered as deposited particles. These particles clog the filter and increase the flow resistivity locally. The clogging and flow resistivity models describe the relation between the volume of the deposited particle and the increase of the local flow resistivity. Different models are used for particles that are resolved by the voxel grid or particles that are unresolved in the voxel grid.

In filter lifetime simulation, the simulation spans the whole filter life. Therefore, the steps flow computation, particle tracking, particle collision or absorption, and filter clogging are iterated to model the changing filter properties over time.

In this case, one iteration corresponds to a (physical) time interval in an experiment. The amount of particles that is simulated in one iteration is called a batch. The batch size corresponds to the challenged mass of the filter experiment in the simulated time interval.